GB2453362A

GB2453362A - System for lining railway arches

Info

Publication number: GB2453362A
Application number: GB0719407A
Authority: GB
Inventors: Steven Caffall Finch
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-10-03
Filing date: 2007-10-03
Publication date: 2009-04-08
Also published as: GB0719407D0; GB2453362A8

Abstract

A system for lining arched structures, particularly railway arches (1), provides a plurality of elongate, flexible frame elements (70), each preferably protected by an elastomeric shield (149) and engaged frictionally against the curved soffit (5) by hoop stress applied at either end, preferably by a pair of installation tools (300) mounted on supports, preferably posts (40). Each tool includes a pivoting ratchet which allows the flexible frame element (70) to be formed into an arched shape on the ground and then raised into a vertical plane prior to installation. The frame elements (70) are fixed to the posts (40) to support them at either end in their installed position, providing a self-supporting, arched framework which relies upon the masonry soffit (5) for its shape and stability. Each frame element (70) may comprise a unitary "top-hat" profile with deformable hinges, each hinge having an associated deformation structure which distributes bending forces evenly during installation. The framework is installed from ground level, and the posts preferably support a temporary mezzanine floor which provides access to the soffit for installation of cooperating, flat lining panels, each panel comprising a foamed plastics body with downwardly directed channels and angularly adjustable, interlocking upper and lower edges. Independent claims are included for the system, methods, flexible frame elements, posts, shield material, panel, and installation tool.

Description

System for lining railway arches This invention relates to systems and methods for lining arched structures, in particular railway arches.

Railway arches are the spaces defined between the adjacent piers of an arched viaduct supporting a railway line, and are commonly used for light industrial, storage and other purposes. Other arched structures include tunnels, vaults and the like.

A viaduct comprises a plurality of spaced-apart, usually parallel piers, each being a masonry structure extending transversely across the width of the viaduct and upwardly from a foundation, with an arched masonry structure known as a barrel supported between each adjacent pair of piers so that its soffit or intrados (the downwardly facing, curved surface) meets each pier along a usually horizontal line, not always visually discernible, known as the spring.

The width of the arch is thus defined as the horizontal distance between the respective piers in the transverse direction of the arch, which is typically parallel with the longitudinal axis of the viaduct; and the length of the arch as the length of the piers in the longitudinal direction of the arch, corresponding to the width of the viaduct. The overall height of the arch is the vertical distance between the arch floor or ground surface and the crown, which is an imaginary line extending along the length of the arch at the uppermost part of the soffit, typically equidistant between the respective piers.

The inwardly facing surfaces of the piers (i.e. the surfaces facing inwardly into the arch) thus define the generally vertical sides of the arch, while the two ends of the arch are often closed by freestanding walls defining a front entrance and, optionally, windows. Where the height of the arch permits, a additional floor (herein termed a mezzanine floor) may also be provided. Railway arches are usually damp and dirty and are often severely affected by rainwater which penetrates through the masonry and drips continuously from the soffit. The whole interior surface of the arch (piers and soffit) must therefore be lined so as to intercept the water and divert it, typically to narrow soakaways formed between the base of each pier and the adjacent edge of a concrete floor slab.

Railway arches vary widely in their dimensions and in the geometry of the soffit, which for example may conform to a cylindrical surface, or may be flattened at the crown, or may be ellipsoidal with the minor radius at the crown. The spring may range in height from below ground level to many tens of metres above ground level, although for most commercially usable arches it is likely to be of the order of about I m - 1 5m above ground level.

In order to maximise the available space within the arch, it is important that the lining should conform as closely as possible to the surface of the soffit and piers while providing a continuous downward fall to carry water from the crown to the ground. Conventionally, the lining comprises overlapping corrugated plastics sheets which are screwed or nailed to horizontal battens fixed at spaced intervals to the soffit and piers. Each fixing passing through the corrugated sheets must be sealed to prevent water penetration.

In order to ensure their structural integrity, railway arches are subject to regular inspections, and in the United Kingdom a major inspection is typically carried out every ten years. This requires the sheets, battens and any interior structure to be entirely removed so that the masonry can be inspected and repointed or replaced as required. The arch is then re-lined with new materials. Over the years, thousands of fasteners are inserted into the soffit and piers, and the repeated drilling damages the masonry while the fasteners corrode to leave voids which weaken the barrel and encourage water penetration.

The size and geometry of a railway arch often poses significant access problems when lining the soffit. For example, an average lined arch might be six metres in width and seven metres in height at the crown, with a height of four metres at the spring.

Since the soffit curves away on either hand, it is impossible to support an ordinary ladder to safely reach the crown, while a tall scaffolding tower erected in the centre of the floor may be dangerously unstable when pressure is applied to a tool while fixing into the soffit. The tower must also be repeatedly moved as the work progresses. For this reason, more expensive and sophisticated powered access equipment (such as a hydraulic cherry picker or scissors lift) is usually required.

Even with such equipment, it is very tiring to drill multiple holes into the soffit overhead when fixing the battens. Moreover, it is difficult to accurately align the fixings with holes in the battens. Masonry is a heterogeneous material, comprising bricks and mortar joints of varying hardness as well as old, corroded fasteners and localised voids. It is therefore likely that the drill will wander or will need to be repositioned so as to avoid local obstructions. Similar difficulties may be experienced when using a nail gun.

GB 2 383 804 discloses an arch lining system comprising a plurality of overlapping tiles supported on a framework. The framework comprises a central, galvanized steel water deflection plate, which is fixed along the crown of the arch, and a set of spaced-apart frame elements, each comprising an outer, galvanized steel water deflection plate and an inner, aluminium extrusion, which are arranged in pairs to extend downwardly along the curve of the soffit in opposite directions from the central deflection plate on either side of the crown.

The deflection plates are fixed to the soffit by means of expanding bolts. Once the framework is in place, the tiles are fixed in horizontal rows between the aluminium extrusions, so that the central portion of the lower edge of each tile extends downwardly behind the upper edge of the tile below, forming a continuous surface which sheds water. The ends of each tile are sealed against the aluminium mouldings by means of neoprene gaskets, while any water falling S onto the zone above the tile ends is diverted by the galvanized steel deflection plates to the central portion of the tiles on either side.

The system of GB 804 advantageously provides for inspection of portions of the brickwork by selective removal of the tiles, but it is not clear whether the system is able to accommodate variations in the curvature of the soffit without compromising the waterproof seal between the tiles and the aluminium extrusions.

Moreover, the system of GB 804 relies on gaskets to seal the penetrations of the expanding bolts through the deflection plates, so that the integrity of the waterproof lining depends on the waterproof seal provided by each of the gaskets. Since each expanding bolt necessarily penetrates the deflection plate, it is presumably also necessary to drill holes in the soffit in accurate alignment with the holes in the deflection plate, which may be difficult.

It is the object of the present invention to provide a system for use in lining arched structures, particularly railway arches, which overcomes some or all of the above mentioned difficulties.

Accordingly In its several aspects the present invention provides a system for lining an arched structure and corresponding methods and apparatus, as variously defined in the claims.

The novel framework comprising a plurality of elongate, flexible frame elements, which may be supported by posts at either side of the arch, is easily installed within an arched structure without inserting any fixings into the soffit or piers, so that the attendant problems of water penetration and structural damage are entirely avoided.

The invention recognises that it is possible to provide a framework which is entirely self supporting -which is to say, a framework which is capable of transferring its own weight, plus the load imposed upon it by lining panels, lighting fixtures and the like, to the ground -but which nevertheless relies upon the pre-existing masonry structure to provide it with rigidity and stability.

Since each flexible frame element does not need to be inherently rigid after installation, it may consequently be surprisingly long and small in profile, making it light in weight and cheap to manufacture. By engaging each flexible frame element pressingly against the soffit, the whole lining may be accommodated within an envelope of no more than about, say, 50mm -75mm from the inner surface of the arch, maximising the available space in the lined arch.

The long, narrow, flexible frame elements are preferably supplied, bound together in pairs so as to form a rigid assembly which is easy to transport, and are easily installed without specialist access equipment by means of the novel installation tools which permit the majority of the installation work to be carried out at ground level. Once in place, the novel framework may be used to support a working platform or mezzanine floor which affords easy access for attachment of the lining sheets or panels beneath the soffit. After installation, the frame elements and panels provide conduits and attachment points for wiring, small diameter pipework, lighting and power fixtures, and the like.

Many further features and advantages will be understood from the following description in which some illustrative embodiments of the various elements of the invention are set forth, purely by way of example and without limitation to the scope of the invention, and with reference to the accompanying drawings, in which: Figs. 1 -12 illustrate sequential steps in the installation of a first embodiment of the novel system in a railway arch; Figs. 1 3A -1 3C are respectively front, top and side views of a first baseplate; Figs. 14A -14C are end views respectively of a first post, a first, unitary frame element incorporating a first, plastic deformation element, and the first frame element attached to the first post; Fig. 14D is an end view of two first frame elements strapped together as supplied for transportation; Fig. 15 is a front view of part of the first post; Figs. 16A and 16B are respectively a rear view and a side view of one end of the first frame element; Fig. 17 is a side view of part of the first post; Fig. 18 is a front view of part of a second, unitary frame element incorporating a second, plastic deformation element, slidingly engaged with a second post; Figs. 1 9A and 198 are respectively a rear view and a side view of one hinge portion of the first frame element of Fig. 16A, showing the first, plastic deformation element after a first stage of deformation; Figs. 19C and 19D correspond to Figs. 19A and 19B and show the first frame element after a second stage of deformation; Figs. 20A -20D show views corresponding to those of Figs. 19A -190 of the second frame element of Fig. 18 after respectively first and second stages of deformation; Figs. 21A 21 E are respectively front, rear, side, first end and second end views of one rigid section of a third, articulated frame element incorporating a third, resilient deformation element, prior to assembly; Figs. 22A and 22B are respectively a side view and an end view of a spacer of the third frame element; Figs. 23A and 238 are respectively a side view and an end view of a pivot of the third frame element; Figs. 24A -24C are respectively rear, front and side views of one hinge portion of the third frame element after assembly, showing the third, resilient deformation element; Fig. 24D corresponds to Fig. 24C and shows the third frame element during installation; Figs. 25A and 25B are respectively a front view and a side view of a jointing bar for use in joining together two short frame elements to form a longer frame element; Figs. 26A and 26B are cross-sections of a first shield, repectively before and after attachment to a frame element; Figs. 27, 29 and 30 are cross-sections respectively of second, third and fourth shields; Fig. 28 is a cross-section of a cap for use with the third shield of Fig. 29; Figs. 31A and 31 B are respectively a front view and an end view of one end of a crown lining sheet; Figs. 32A and 32B are respectively a front view and an end view of a bracing strut; Figs. 33A and 33B are respectively a side view and a front view of a bracket for use with the bracing strut; Fig. 34A is a rear view of a first panel, in which the central portion is cut away to show both of its ends; Fig. 34B is a longitudinal section through the first panel at B -B in Fig. 34A; Fig. 34C is a lower end view of the first panel as shown in Fig. 34A; Figs. 35A -35C are enlarged views of the lower end of the first panel as shown respectively in Figs. 34A -34C; Figs. 36A and 368 are enlarged views of the upper end of the first panel as shown respectively in Figs. 34A and 346; Figs. 37A -37C are cross sections showing the cooperating upper and lower ends of two first panels after installation respectively near the crown, near the spring line, and on posts adjacent the piers of a railway arch; Figs. 38A and 38B are respectively a front view and an end view of part of a replacement mounting flange for attachment to a cut end of the first panel; Fig. 39 is a section through part of an installed lining at the crown of a railway arch, parallel with the longitudinal axis of the arch; Fig. 40 is a section through part of another installed lining lower down on the soffit of another railway arch, parallel with the longitudinal axis of the arch; Figs. 41A and 41B show a first releasable mounting mechanism of a first installation tool, respectively before and after attachment to a third post; Figs. 42A and 428 are respectively plain and cut-away side views of the first releasable mounting mechanism in the disengaged position as shown in Fig. 41A; Fig. 43 is a section at X43 - X43 in Fig. 41 B, showing the lower end of the first releasable mounting mechanism in the engaged position; Figs. 44 is a front view of a first movement mechanism of the first tool with the front cover removed, showing the ratchet drive pawis in the disengaged position; Fig. 45 is a longitudinal section through the first movement mechanism at X45 -X45 and X45' -X45' in Fig. 44, with the front cover in place, showing the first tool mounted on the third post of Fig. 41B; Fig. 46 shows the right-hand ratchet mechanism of Fig. 45 with the drive pawl in the engaged position; Figs. 47A and 47B are respectively a front view and a side view of the right hand drive pawl of the first movement mechanism; Figs. 48A and 488 are respectively a front view and a side view of the right hand pawl control lever of the first movement mechanism; Figs. 49A and 49B are respectively a front view and a side view of the intermediate cluster gear assembly of the first movement mechanism; Figs. 50A and 50B are respectively a front view and a side view of the left-hand ratchet wheel of the first movement mechanism (both ratchet wheels are identical); Figs. 51A and 51B are respectively a front view and an oblique end view of the right-hand drive lever of the first movement mechanism; Fig. 52 is a front view showing the frame element attachment mechanism of the first tool in use, in which the first tool is mounted on the first post of Fig. 15 and the first frame element of Fig. 16A is attached to the tool and raised into the vertical position, with the detent mechanism in the locked position; Fig. 53 shows the view of Fig. 52 with the front casing of the first tool cut away and the detent mechanism shown in scrap view in the locked position; Fig. 54 is a side view of the first tool in use as shown in Fig. 52, showing the detent mechanism in the locked position; Fig. 55 is an enlarged side view of the detent and ratchet mechanisms of the first tool as shown in Fig. 54; Figs. 56A and 56B are side views of the detent mechanism of the first toot respectively in the actuated (release) position and the disengaged position; Fig. 57 is a front view showing the first tool attached to the first post, in which the detent mechanism is in the actuated (release) position and the pivot assembly is partially rotated prior to attachment of the first frame element; Fig. 58 is a front view corresponding to Fig. 57 in which the pivot assembly has been fully rotated, the detent mechanism has returned to the disengaged position, and the first frame element has been attached to the tool prior to raising it to the vertical position as shown in Fig. 52; Fig. 59 is an enlarged side view of the frame element attachment mechanism as shown in Fig. 54, with the pivot mechanism and the first frame element in the vertical position; Fig. 60 is a side view corresponding to Fig. 54 but showing the first tool after actuation of the separation adjustment mechanism, with the first frame element fully engaged with the first post; Fig. 61A is a cut-away side view showing the frame element attachment mechanism with most of its components removed, in which the detent housing is sectioned at line A -A of Fig. 61C; Fig. 61B is a section through the detent housing at B -B in Fig. 61A; Fig. 61C is a top view of the detent housing of Fig. 61A; Fig. 62 is a front view corresponding to Fig. 61A, in which the front casing is cut away to reveal the pivot frame assembly, and the detent mechanism is shown in scrap view; Fig. 63 shows the pivot frame assembly of Fig. 62, with the front protection plate removed; Fig. 64 shows the rear mounting plate of the pivot frame assembly housing of the first tool; Figs. 65 -74 show various components of the detent, ratchet and separation adjustment mechanisms of the first tool, in which:-Figs. 65A, 65B and 65C are respectively side, top and front end views of the detent bolt; Figs. 66A and 66B are respectively a side view and an end view of the roll pin; Figs. 67A -67C are respectively front, side and top views of the wedge; Figs. 68A -68C are respectively front, top and end views of the slide key; Fig. 69A is a front view of the left hand pawl assembly; Fig. 69B is a side view of the left hand pawl assembly together with its pivot pin and spacers; Figs. 70A -70C are respectively front, open end and top views of the retaining clip for the left hand pawl assembly; Figs. 71A and 71 B are respectively a front view and a side view of the left hand pawl control lever and its washer; Fig. 72A is a front view of the right hand pawl assembly; Fig. 72B is a side view of the right hand pawl assembly together with its pivot pin and spacers; Fig. 72C shows the pivot pin and spacers of Fig. 72B in end view; Figs. 73A -73C are respectively front, open end and top views of the retaining clip for the right hand pawl assembly; and Figs. 74A and 748 are respectively a front view and a side view of the right hand pawl control lever and its washer; Fig. 75 is a front view of the clamp mechanism of a second releasable mounting mechanism partially engaged with a fourth post; Fig. 76 is a top view corresponding to Fig. 75; Fig. 77 is a top view of the lateral adjustment mechanism and fixed rollers of the second releasable mounting mechanism in position on the fourth post; Fig. 78 is a side view corresponding to Fig. 77 after removal of the second releasable mounting mechanism from the post; Fig. 79 is a top view of the rotary cam of the lateral adjustment mechanism of Figs. 77 and 78; Fig. 80 is a front view of the body portion of a second movement mechanism for use with the second post of Fig. 18, without its moving parts; Fig. 81 is a front view corresponding to Fig. 80, showing the toggle mechanism frame in position; Fig. 82 is a rear view corresponding to Fig. 81; Fig. 83 and 85 are longitudinal sections respectively at X83 -X83 and X85 -X85 of Fig. 80; Fig. 84 is a longitudinal section at X84 -X84 of Fig. 81; Figs. 83A and 84A are longitudinal sections respectively at X83A -X83A and X84 -X84 of Fig. 81, showing the various moving parts in their assembled positions; Fig. 85A is a longitudinal section at X85 -X85 of Fig. 80, showing the various moving parts in their assembled positions; Figs. 86A and 86B are respectively a front view and a side view of the toggle mechanism frame of Fig. 81; Fig. 86C is a cross-section at C -C of Fig. 86A; Fig. 87 is a longitudinal section at X89 -X89 of Fig. 81; Fig. 88 is an enlarged view of the toggle mechanism frame as shown in Fig. 84A; Fig. 89 is a longitudinal section at X89 -X89 of Fig. 81, corresponding to Fig. 87, with the moving parts in place and the front wall of the frame cut away to show their relative positions; Figs. 90A and 90B are respectively front and side views of the catchplate assembly of Fig. 89; and the remaining figures show the various moving components of the second movement mechanism, in which:-Figs. 91A and 91 B are respectively a side view and a top view of the drive lever; Figs. 92A and 92B are respectively a side view and an end view of the drive lever pivot pin; Figs. 93A and 93B are respectively a side view and a top view of the up/down selector lever; Fig. 94 shows the selector lever pivot pin; Figs. 95A and 95B are respectively a side view and a top view of the ratchet selector lever; Figs. 96A and 96B are respectively a left side view and a front view of the left leg; Figs. 97A and 97B are respectively a left side view and a front view of the right leg; Figs. 98A -98C are respectively a front view and two side views of the right hand control arm; Figs. 99A -99C are respectively a front view and two side views of the left hand control arm; Figs. 1 OOA and 1 COB are respectively a top view and a side view of the ratchet toggle lever; Figs. 1 O1A and 101 B are respectively a side view and a top view of the ratchet pawl; Figs. I 02A and 1 02B are respectively a side view and an end view of the ratchet pawl pivot pin; Figs. 103A and 1 03B are respectively a front view and a side view of one up/down toggle lever (both up/down toggle levers are identical in form); Figs. 104A and 104B are respectively a front view and a side view of the left hand bias arm; Figs. 1 05A and 1 05B are respectively a front view and a side view of the right hand bias arm; Fig. 106A is an exploded side view of the upper pawl assembly; Figs. 106B -106D are front views respectively of the upper pawl, its washer and its spacer; Figs. 1 07A and I 07B are respectively a front view and a side view of the pawl link bar; Figs. 1 08A -1 08C are respectively front, top and side views of the rotary bracket of the upper pawl; Fig. 1 09A is an exploded side view of the lower pawl assembly; Figs. 1098 -109D are front views respectively of the lower pawl, its washer and its spacer; Figs. 11 OA and 11 OB are respectively a front view and a side view of the toggle mechanism drive bar; Figs. lilA and ill B are respectively a front view and a side view of the toggle bar assembly of the toggle mechanism; Figs. ii 2A -11 2C are respectively front, side and lower end views of the catchplate of the catchplate assembly of Figs. 90A and 90B; and Figs. 11 3A and 11 3B are respectively a front view and a side view of the slide plate of the catchplate assembly.

It should be noted that small, repetitive details such as fixing apertures and hinge components are not shown in the views of Figs. 1 -12, and for full understanding, reference should be made to the individual component drawings in which these details are depicted.

Corresponding parts are indicated by the same reference numerals in each of the figures.

Referring to Fig. 1, a brickwork railway arch I comprises a barrel 2 which is supported by two parallel piers 3, 3' whose respective opposite, inwardly facing vertical surfaces 4, 4' are spaced apart by about 5.5 metres in the transverse (width) direction W of the arch to define the two sides of the arch. The lower surface of the barrel forms an arched soffit 5 which intersects the sides 4, 4' of the arch to define two horizontal spring lines 6, 6' at a height of about 3.5 metres above the arch floor 7.

The soffit curves upwardly and inwardly as shown from the spring lines on either side of the arch towards an imaginary horizontal crown line 8 at its uppermost part, which extends longitudinally along the arch, parallel with the piers and equidistant between the two sides 4, 4' at a height of about 6 metres above the floor. The arch extends for a length of about 11 metres in its longitudinal direction L to a freestanding wall 9 at its rear end, and is open at its front end so that we can see what's happening. (Normally the front end would be closed with a corresponding wall or shutter.) The floor 7 comprises a concrete slab which is spaced from each pier by a narrow soakaway 10, 10'.

Baseplates Installation commences by spacing out a series of flat attachment plates or baseplates 20 on the floor along the base of each pier. The baseplates are set out in pairs, one on either side of the arch and aligned in the transverse direction of the arch, at a spacing which corresponds to the length of a panel plus the width of a post, as further described below. Conveniently, these components are dimensioned so that the baseplates are spaced apart by an easily measured distance, which in the example shown is 2 metres. The first pair of baseplates are arranged adjacent the front end of the arch, and the final (seventh) pair are arranged adjacent the rear wall 9 so that the spacing between the last two baseplates on each side is reduced to correspond to the length of the arch.

Referring to Figs. I 3A -1 3C, each baseplate 20 comprises a flat steel plate 21 which is bent upwardly to form an angled portion 22 at its rear edge. A hole 23 is formed in each corner of the angled portion for attachment of bracing wires as further described below. A short bracket 24 is welded to the plate 21 so that its rear wall 25 extends for a short distance beyond the angled portion 22, and its two side walls 26 are provided with fixing holes 27 and slots 28 which correspond respectively to the rear apertures 47 and front fixing holes 48 in the posts 40, as further described below.

The plate 21 is provided with fixing holes 29, and each plate is bolted to the floor slab 7 by means of two small expanding bolts inserted (preferably via the central pair of fixing holes 29) into holes dnuied in the floor, so that the rear wall is spaced about 5mm from the inner surface 4, 4' of the respective pier and overhangs the soakaway 10, 10'. The plates need only light fixing sufficient to locate the base of the respective post adjacent the pier and to support the post in an upright position during installation, as will now be described. Once the framework is in place, the fixings do not play any part in supporting it.

The initial fixing of the baseplates is the only stage at which any drilling is required, and also the only stage at which the arch needs to be measured so as to accurately locate components, since subsequent steps in the installation are all dependent on the position of the baseplates. Since the principal measurement and all of the drilling is carried out on the floor, it is a very easy task compared with the conventional method of lining in which most of the work is done high up under the soffit.

Once the baseplates are in position, support means are attached to the baseplates along each side of the arch for supporting the flexible frame elements. Posts

Referring to Figs. 14A -17, the support means comprise a plurality of first, rolled steel posts 40, each formed from a unitary length of mild steel plate farmed into an elongate "top hat" profile comprising a central, U-shaped portion with a pair of oppositely directed lateral flanges 41.

Referring particularly to Fig. 15, each flange 41 is perforated with an array of panel fixing holes 42, 42' which receive self-tapping fixing screws for the attachment of lining panels 200 to the post, as further described below. The panel fixing holes 42 are arranged in groups, the groups being spaced apart in the vertical (longitudinal) direction of the post by a distance di. The corresponding groups of fixing holes 208 and slots 209 in the panel flanges 205 are spaced apart in the vertical direction by a repeat distance d2 (Fig. 36A), in which d2 = (d1 -(d1 / n)) wherein n is a factor of d1. This provides a fixing system in which the vertical position of each p anel is finely adjustable according to the principle of a Vernier scale in increments of (d1 / n) with one coincidence (providing a pair of aligned fixing holes) occurring at a distance of (d2.n), i.e. every (n -1) groups of holes 42.

The four fixing holes 42 within each group are spaced apart in the horizontal or transverse direction and in the vertical or longitudinal direction of the post 40 by small distances, which in the vertical direction are not a factor of the increment (di I n) and so provide for still finer vertical as well as horizontal adjustments in the position of the panels 200 between the increments (di I n). Each panel can thus be fixed in any required vertical position.

In addition to the panel fixing holes, each flange 41 is provided with a series of regularly spaced rectangular apertures 43, and a further series of regularly spaced elongate apertures 44 with rounded ends.

The rectangular apertures 43 receive the projecting teeth 471 of the drive pinion 470 of the first installation tool 300, as further described in due course, so as to form a rack, while the flanges 41 provide an installation tool mounting structure which receives the mounting mechanism 301 of the installation tool so as to releasably mount the installation tool for sliding movement up and down the post 40.

The elongate apertures 44 provide windows which are so dimensioned and positioned that at least one of each diagonal pair of panel fixing holes 78 in the corresponding flange 71 of a first frame element 70 (visible in Fig. 16A and further described below) when attached to the first post 40 (as shown in Fig. 14C) coincides, either with a rectangular aperture 43 or with an adjacent elongate aperture 44. The longitudinal spacing d3 between alternate panel fixing holes 78 in the first frame element also corresponds to the spacing between the fixing holes in the panel flanges according to the Vernier principle, so this arrangement ensures that every respective coincidence between the corresponding fixing holes in the frame element flange and in the panel flange is available for attachment of the panel to the frame element, with the fixing screw passing through the corresponding aperture 43 or 44 in the post, when theY frame element is attached to the post as shown in Fig. 14C.

Referring particularly to Fig. 17, the central, U-shaped portion of the first post comprises a rear waIl 45 and two side waUs 46, each side wall being provided with a series of rear apertures 47 adjacent the rear wall 45, and with frame element attachment means comprising two series of front fixing holes 48, 49 adjacent the respective flange 41.

The rear apertures 47 provide fixing points for the attachment of bracing wires and bracing struts as well as for attaching the post to the baseplate, as will shortly be described. They are spaced apart from the flanges 41 by a sufficient horizontal (transverse) distance to avoid the corresponding U-shaped portion of the first frame element when it is inserted into the post, as most clearly seen in Fig. 60.

The front fixing holes 48, 49 of each series are spaced apart in the vertical (longitudinal) direction by a distance d4, corresponding to the longitudinal spacing d5 of two corresponding series of fixing holes 79 in each corresponding side wall 76 of the first frame element 70 (Fig. 16B), wherein d4 = (d5 -(d5 / n)) and n is a factor of d5.

This provides another fixing system on the Vernier principle, such that one fixing hole in each series 48, 49 is brought into alignment with a corresponding fixing hole 79 in the first frame element 70 to define a through-hole for receiving a bolt (Fig. 140) for attaching the frame element to the post, at each of a series of incremental displacements of the first frame element 70 axially along the first post 40 through the distance (d5 / n).

Whereas the corresponding two rows of apertures 79 in each side wall 76 of the first frame element 70 are aligned in parallel, the corresponding front apertures 48, 49 of the first and second series of the first post are spaced apart by a longitudinal (vertical) distance d6 = (d5 I 2). This doubles the number of repeat coincidences between corresponding apertures in the first frame element 70 and first post 40, providing one coincidence alternately in the first series 48 and second series 49 of front fixing holes for every ((n -1) /2) fixing holes 79 of the first frame element 70, i.e. spaced apart by a distance ((d4.n) / 2), for any given incrementally displaced position of the first frame element 70.

Of course, the relative spacings d4 and d5 could be reversed.

Enough already.

Installation of posts Referring to Fig. 2, each post 40 is first cut to length as required using an angle grinder or the like so that it extends in its installed position to just below the spring line 6, 6'. A length of shield material 149 (further described below) is then attached to the rear wall 45 of the post so that it extends from the bottom of the post to about half a metre above the top of the post, and the post is then placed over the bracket 24 of the respective baseplate 20 (which fits slidingly between the side walls 46) and attached by means of bolts passing via the rear apertures 47 and front fixing holes 48 through the fixing holes 27 and slots 28 respectively. Once mounted on the baseplate, the rear wall of the post extends into the small gap between the rear wall 25 of the bracket and the inner surface of the pier, so that the post is supported in a vertical position just above the upturned rear edge 22 of the bracket with the flanges 41 facing inwardly into the arch and the shield sandwiched between its rear wall 45 and the pier. This allows water to run down between the inner surface 4, 4' of the pier and the shield 149, behind the rear edge 22 of the bracket and straight into the soakaway 10, 10'.

Once An position, each post (other than those at the front and rear of the arch) is braced against rotational movement about its base parallel with the plane of the pier (i.e, prevented from toppling over in the longitudinal direction of the arch) by means of two small galvanised steel tension cables 67, one on either side of the post, each being attached at its upper end to one of the rear apertures 47 close to the top of the post and at its lower end to a galvanised tumbuckle 68 fixed to one of the holes 23 in the baseplate of the adjacent post. The turnbuckles are tightened to tension both cables, while the post is checked for verticality by means of a plumb-bob or, conveniently, a spirit level with a vertical vial. Any water running down the cable will drip off the turnbuckle into the soakaway at its base.

Referring also to Figs. 32A -33B, the front and rear posts on either side of the arch are braced to their respective adjacent posts by means of a horizontal bracing strut 60, 60'. Each bracing strut comprises a tubular body 61 with a long internal thread 62 at each end, the rear bracing struts 60' having a shorter body.

A series of external collars 63 are spaced apart near each end so as to prevent water from running horizontally along the strut in front of the shields. One end of the strut 60 is attached loosely to the upper end of the post 40 by means of a bolt passing through one of the rear apertures 47 to engage the thread 62. The other end of the strut is attached to an elongate stud 64 which is welded to a bracket 65 having elongate fixing slots 66 which are dimensioned to allow it to be bolted to any adjacent pair of rear apertures 47 of the adjacent post in any axial position along the post. Once the bracket is attached and the thread 62 is engaged with the stud 64, the body 61 is rotated to advance it along the stud and adjust the spacing between the two posts, and once the end post is upright, the bolt at the other end of the strut is tightened.

After the installation of lining panels as further described below, the panels will also support the posts in vertical alignment.

The posts 40 are now restrained in the longitudinal direction L by the bracing wires and struts and outwardly in the width direction W by the piers, so their only freedom of movement is now by rotation of the upper ends of the posts inwardly in the width direction W, away from the piers and into the arch. This movement is resisted prior to installation of the flexible frame elements by the small expanding bolts at the base of each post. Once the flexible frame elements are fixed to the posts as will now be described, and during the process of installing them, their load (including the hoop stress applied during installation, and the load placed on them after installation by the lining, lighting fixtures etc.) braces the upper ends of the posts 40 outwardly in the width direction W towards the piers, so that the entire framework is stabilised and rigidified without attachment to the masonry of the arch at any point. It is then impossible for the framework to collapse under load, provided that its component parts are of adequate strength.

Flexible frame elements Each flexible frame element may comprise a continuous, flexible metal or plastics section or profile (i.e. an elongate element with a uniform cross-sectional profile), such as an I-beam, a top-hat section, a square or rectangular hollow section, or the like, which has sufficient resistance to axial compression that it is capable of flexing to conform to the curvature of the soffit without collapsing axially under load. Alternatively, it may comprise a flexible series of rigid, non-compressible portions joined end-to-end by hinge portions. The rigid portions and hinge portions may comprise integral parts of a unitary length of material, in which case the frame element may be manufactured at relatively low cost (conveniently in mild steel by laser cutting) and may be suitable for one-time installation or, with care, for re-use for a limited number of times.

Alternatively, a fully re-usable element may be assembled from individual, jointed sections. Long frame elements may also be cut to make shorter elements, and short lengths may be joined together to make longer elements.

Referring to Figs. 14B -17, a first flexible frame element 70 comprises a unitary length of rolled mild steel utop hat" section, having a central, U-shaped portion with a pair of oppositely directed lateral flanges 71, in which the central, U-shaped portion is divided by means of a laser cutter to define a flexible series of rigid portions 72 joined end-to-end by the flanges 71, which are left intact so that they form a plastically deformable hinge portion 73 adjacent each cut.

The laser cutter produces cut lines of minimal thickness, so that the adjacent cut surfaces 74 which define the ends of each respective pair of rigid portion remain substantially in abutment to limit the range of pivotal movement at each hinge portion 73 to define a maximum angle e of about 1800 between the respective adjacent rigid portions on the inner side of the frame element, i.e. the side which faces away from the soffit. This substantially prevents the formation of a reflex angle on the inner side of the frame element, which ensures that the arched configuration of the frame element cannot fail by localised buckling inwardly and downwardly away from the soffit. The maximum angle e of 1800 also allows two frame elements 70 to form a rigid straight-line configuration when they are bound together flange-to-flange for dispatch from the factory, which makes them easy to handle prior to installation. Moreover, it allows adjacent rigid sections 72 to be vertically aligned along each post below the spring line in their installed position.

Of course, rather than laser cutting, the frame element could be manufactured by conventional cutting or stampinglpressing. In order to bring the cut surfaces 74 into closer abutment, part of the rear wall 75 or side walls 76 which together comprise the central, U-shaped portion can be pressed or stretched to form a slight bulge at each cut line prior to cutting and then pressed back again afterwards, or local portions of the cut surfaces can simply be pressed together after cutting. It is also possible to press localised areas of adjacent rigid portions together so as to define a maximum angle e of less than 180°.

The central, U-shaped portion of the frame element is adapted to be slidingly received in the central, U-shaped portion of the first post 40 during assembly so that once the frame element 70 reaches its installed position, in which the rear wall 75 is pressingly engaged against the soffit (adjacent each hinge portion) for at least some or, preferably, most or all of the length of the frame element, it can be bolted directly to the upper part of the first post 40 as shown in Fig. 14C, with the flanges 71 lying against the flanges 41 of the post.

Each pair of adjacent rigid portions 72 are pivotable during installation about their respective hinge portion 73 through a range of movement which is preferably limited in the outward direction by the abutment of the cut surfaces 74 and both restrained and limited in the inward direction by a plastic deformation element as further described below, so as to define an obtuse angle 8 between them on the inner side of the frame element. This permanent flexibility allows the frame element 70 to be raised into its installed position beneath the soffit 5 so that, once it contacts the soffit, it may be urged against the soffit so as to conform to its upward and inward curvature, defining a self-supporting arched configuration which transfers the load of the frame element to its respective first and second ends 77, which in turn are supported by the respective posts 40 extending upwardly from the ground on either side of the arch. Once in its installed position, the frame element 70 does not need to be supported at any point other than at its respective ends 77, although it may be further ngidified and stabilised in the longitudinal direction of the arch by the attachment of bracing struts and/or panels between adjacent frame elements as further described below.

The rigid portions 72 are independent of each other so that they can adopt a different angle at each hinge portion 73, enabling the frame element 70 to conform to the curvature of any soffit, irrespective of its shape, and also to adopt a more acute angle at the spring line where it departs from the post.

Since each flexible frame element 70 is stabilised and rigidified by compressive hoop stress and by frictional contact with the soffit, it is unnecessary and undesirable (although possible) to provide means for locking each of its rigid portions 72 in fixed angular or rotational relationship to the next. This permanent flexibility simplifies the frame element and also makes it easy to remove it and re-use it, as well as enabling it to conform to the curvature of the soffit as it is installed.

The novel frame element is thus only suitable for use in contact with an existing, arched soffit, and would not provide the rigidity required for a freestanding structure, independent of an existing arch or tunnel.

The flanges 71 form the inner side of the first frame element 70 which faces away from the soffit in the installed position, and each flange is provided with panel attachment means comprising two rows of panel fixing holes 78, which are adapted to receive self-tapping screws and are arranged in diagonal pairs as shown so as to cooperate with the corresponding fixing holes in the panel flanges according to the Vernier principle as discussed above with reference to the first post.

Each rigid portion is provided with support attachment means comprising two rows of post fixing holes 79 in each of its side walls 76, which are adapted to cooperate with the corresponding front fixing holes 48, 49 of the first post forming an adjustable attachment system according to the Vernier principle as described above. This enables the first and second ends 77 to be slidingly adjusted in very small increments relative to the posts during installation so as to bring the rear wall 75 pressingly into abutment with the soffit, and then to be attached to the post 40 so as to support the frame element 70 in the installed position.

Since post fixing holes 79 are provided in each rigid portion, rather than just at the ends 77, the frame element 70 may be divided by cutting it with an angle grinder or the like so as to form two shorter frame elements, and the cut ends of each frame element may thereafter be attached to the support means.

Preferably, the cutting (and joining of shorter elements, as described below) is done in the centre of a rigid portion, so that for reliability the hinge portions are always formed at the factory and not by the user. Indicia 80 are provided on the outer surface of the rear wall 75 of each rigid portion 72 to indicate the correct cut line.

The rear wall 75 of each rigid portion 72 is also provided with means for releasably attaching the frame element to an installation tool, comprising two oppositely directed pairs of keyhole slots 81, 81'. When the rigid portion is cut by the user, one pair of slots 81 or 81' is left on each cut half, which then forms the end 77 of the frame element for attachment to the tool. In the example of Fig. 16A, the end 77 of the frame element terminates at a position corresponding to one of the cut lines, proving a terminal rigid portion 72' half the length of the others, which is attached to the tool during installation. Each frame element is supplied from the factory with one such half length terminal rigid portion 72' at each end, so that the frame element can either be cut to length or used as supplied.

It is important to ensure that the frame element is able to bend at each respective hinge portion 73 as it engages the soffit, so as to avoid straight portions which depart from the curvature of the soffit.

One way of achieving this would be to resiliently bias each pair of adjacent rigid portions away from a straight line configuration, i.e. towards an inwardly bent configuration. However, to facilitate easy handling and transportation, it is preferable for each frame element to be biased towards (or supplied in) a straight tine configuration in its rest position.

In order to achieve both of these objectives, preferably each hinge portion is provided with means which readily permits a first, small degree of bending inwardly into the arch, but which resists further bending until a substantially greater torque is applied to the joint. This means that as the frame element is progressively bent into its installed configuration (such as during attachment to the installation tools), as each hinge portion reaches its first extent of bending, it S begins to transfer torque to the rigid portions on either side, so that all of the hinge portions are bent to the first, small extent, before the applied torque increases to the extent necessary to bend any of them further. Since all of the hinge portions are thus placed in an initially bent configuration when they contact the soffit, they are more readily bent to a further extent necessary to bring all of the rigid portions into abutment at their ends with the soffit.

Of course, it is not essential for every one of the rigid portions to abut the soffit after installation, since the load on the framework will bring each frame element progressively into contact with the soffit at its outer ends, ensuring that it remains stable even as it flattens slightly at the crown to accommodate any slight settling or movement after installation.

Referring to Figs. I 9A -190, rather than cutting completely through the central, U-shaped portion at each hinge portion, the cut is preferably interrupted to define a plastic deformation element 87 in the rear wall 75 which forms the outer side of the first frame element 70 in the installed position, attached to the respective rigid portions 72 at each end and adjacent and spaced apart from the respective hinge portion 73.

(For the avoidance of doubt, in this specification the term "plastic deformation element" means "plastically deformable element", and not "a deformation element made from plastics material"; whereas the term "plastics" or "plastics material" refers to polymer material. Preferably, the plastic deformation element is made integrally with the frame element, e.g. from mild steel.) In the first frame element 70, the plastic deformation element 87 comprises a pattern of cuts (conveniently made by a laser cutter) similar to that used when forming the diamond shaped steel mesh commonly known as "expanded metal".

S Each plastic deformation element is progressively plastically deformed by elongation during installation as the obtuse angle 8 between the respective adjacent rigid portions reduces. The cut lines in the centre of the plastic deformation element are closer together than those at the ends, defining a weaker, initial deformation region 88 which is deformed to a first, minor extent as shown in Figs. I 9A -1 9B by application of relatively little torque to the respective hinge portion. The remainder of the plastic deformation element is deformed to a second, relatively greater extent as shown in Figs. 19C -19D, only by application of relatively greater torque.

In its maximally deformed condition (perhaps slightly beyond the position shown in Figs. 1 9C and 190), the plastic deformation element 87 prevents further bending and so defines a minimum, limiting angIe 8. Once deformed, the plastic deformation element 87 will readily collapse (although of course it will not return to its original configuration) to permit the adjacent rigid portions 72 to be straightened again.

Referring to Figs. 18 and 20A -200, a second unitary, flexible frame element is formed similarly to the first frame element 70 from a unitary length of mild steel utop hat" section. Each flange 91 has two rows of panel fixing holes 98, which (unlike those of the first element 70) are spaced apart by a distance d7 which is a factor of the length of each rigid portion 92, so as to form a continuous pattern from one rigid portion 92 to the next. As described above, the distance d7 is related to the spacing d2 between adjacent fixing holes in the corresponding flange of the panel 200 to form an adjustable panel attachment system on the Vernier principle.

In Fig. 18, the second frame element 90 is shown with its central U-shaped portion slidingly engaged in the corresponding central U-shaped portion of a second post 100. Each flange 101 of the second post has a series of rectangular apertures 102 spaced apart by a distance d8, which are adapted to be engaged by the movement mechanism of a second, alternative installation tool as further described below. Each flange 101 also has a row of outer fixing holes 103 and a row of inner fixing holes 104, the holes in each row being spaced apart by the same distance d7 as the panel fixing holes 98 in the second frame element so as to receive self tapping screws for attachment of the panels to the post.

The second frame element 90 is narrower than the second post 100 so that the outer fixing holes 103 on each flange of the post are exposed when the second frame element 90 is attached to it in the position shown. The vertical panels can thus be fixed to the outer row of fixing holes 103 in this region, and to the outer fixing holes 103 or inner fixing holes 104 over the rest of the post.

A second plastic deformation element 94 is arranged adjacent each hinge portion 93 of the second frame element 90, and functions similarly to that of the first frame element. It is formed by continuous, interlaced cuts in the outer wall 95 defining a relatively smaller, weaker central region 96 which deforms to a first, small extent as shown in Figs. 20A -20B on application of a first, small torque, while the remainder of the deformation element 94 is relatively larger so that it is substantially deformed to a second, greater extent only on application of substantially greater torque, as shown in Figs. 20C -20D. Deformation increases proportionately to the applied force.

In alternative embodiments, the plastic deformation element can be arranged as a crumple portion which is compressed as the angle 0 reduces. It can also be a separate element, e.g. wrapped around the pivot pin of each discrete rigid portion of an articulated, re-usable flexible frame element, one embodiment of which will now be described.

Referring to Figs. 21A -240, a third, fully re-usable flexible frame element 110 comprises an articulated assembly of individual rigid portions 112 joined end-to-end by pivots 113.

Similarly to the first and second flexible frame elements, each rigid portion 112 comprises a short length of galvanised or passivated zinc plated mild steel formed into an elongate "top hat" section comprising a rear waIl 115 and two opposed side walls 116, which together form a central U-shaped portion, and two oppositely directed lateral flanges 111. The rear wall 115 forms the outer side of the frame element which engages the soffit, while the flanges 111 form the inner side of the frame element which faces away from the soffit in use. The end walls 114 of each rigid portion cooperate to form abutment surfaces which limit the obtuse angle e formed between each pair of adjacent rigid portions on the inner side of the frame element to a maximum of 1800 as shown in Fig. 24G.

Panel fixing holes 118 are provided in each of the flanges 111, while post fixing holes 119 are provided in each side wall 116 so that the frame element can be attached to one of the posts 40 as already described above. Two oppositely directed pairs of keyhole slots 121, 121' are provided in each rear wall, and indicia 120 indicate the correct position at which the rigid section 112 may be cut to define two separate, half length terminal sections, each of which may subsequently be attached to the first installation tool and thereafter to one post as one end of a separate frame element. Similarly to the first and second frame elements, each third frame element 110 is supplied with two half length terminal rigid sections (not shown) so that it is ready for use.

The side walls 116 of each rigid portion 112 are joggled inwards to form an outer pair of hinge brackets 122 at one end of the rigid portion and an inner pair of hinge brackets 123 at the other. The rigid portions are assembled together at the factory by means of a steel rivet 124 which passes through the respective outer and inner hinge brackets to form a pivot pin about which the two sections can pivot. The pivot pin 124 passes through a spacer 125 (made for example from plastics material) which maintains the separation between the inner pair of brackets 123 so as to rigidify the resulting pivot or hinge portion 113.

After assembly, the ends of the pivot pin or rivet 124 lie flush with or slightly inward of the side walls 116 as shown, so that the assembled frame element can be slidingly engaged in the post 40 in the same way as the first and second frame elements already described.

The rear wall 115 of each rigid portion 112 is cut at each end to define a bracket 126 which is bent inwardly towards the flanges 111. A resilient deformation element, comprising a helical steel tension spring 127, is attached between each pair of adjacent brackets 126 so that it extends between the two adjacent rigid portions 112 in spaced relation to the hinge 113. The spring is accommodated by a cutout 128 in the rear wall so that it can be positioned as far as possible from the hinge portion 113.

As the adjacent rigid portions 112 pivot about the hinge 113 during installation (Fig. 240), the spring 127 elongates proportionately to the applied torque, so that it transfers torque from one rigid portion to the next in a similar way to the plastic deformation elements already described, ensuring that each hinge portion is angled during installation.

Preferably , the spring 127 is arranged so that, in the 180° or rest condition of the respective hinge portion, its coils are almost or completely closed and it is only lightly engaged with the brackets 126, as shown in Fig. 24G. This means that relatively little torque is required to pivot the rigid portions 112 to a first, minor extent, before the spring more strongly resists further deformation until substantially greater torque is applied. Each resilient deformation element 127 thus biases the third frame element lightly towards a straight line configuration in its rest condition, as shown in Fig. 24C.

The tension spring 127 or hinge portion 113 or rigid portions 112 may be provided with an extension limiting arrangement (for example, a short steel cable or bar inside the spring, or a sleeve around the spring, or an arm which extends from one rigid portion to abut against the other) which defines a minimum, limiting angle 0 and so prevents over-extension of the spring. Instead of a tension spring, the resilient deformation element might comprise a helical compression spring arranged between two abutting surfaces of the respective adjacent rigid portions 112-for example, between the rear wall of one rigid portion and a projecting arm of the other rigid portion -in which case the compression spring will define a minimum, limiting angle Oat the point at which its coils are fully closed. A resilient, rubber or plastics spring could be used instead of or in addition to a coil spring. Afternatively, the resilient deformation element could comprise a leaf spring, or any other type of spring, such as a torsion spring arranged around the pivot pin or spacer so that its projecting ends engage the respective rigid portions 112. Of course, the articulated, third frame element 110 could also be made without resilient deformation portions.

Instead of resilient or plastic deformation portions, each separate pivot or integral hinge portion could include some other means providing a reaction force or resistance to pivotal movement -for example, a friction device arranged at the pivot.

Of course, if preferred, the pivots 113 could be arranged to permit the user to divide the frame element and re-join it at each hinge. Preferably however the hinges are permanent and are made in the factory so as to avoid any risk of incorrect assembly, and the frame element is divided if required by cutting through a rigid portion where indicated (120).

The pivots 113 allow the third frame element to be installed, removed and re-installed as many times as necessary, so it can be re-used each time the framework is removed for renovation of the arch.

In contrast, where the first and second, unitary frame elements are made from mild steel or perhaps from aluminium, they must be treated with care so as to avoid repeatedly stressing their unitary hinge portions, which could result in metal fatigue and ultimately failure of the hinges. The relatively great length and small profile of each frame element may make it difficult to install it without repeated flexing; however, this difficulty is ameliorated by the presence of the deformation elements which limit angular displacement at each joint, and is preferably overcome by use of the novel installation tool, as further described below.

It is envisaged that articulated frame elements (assembled from separate sections) will be preferred for long term use in arches which are frequently inspected, whereas unitary frame elements (which can be manufactured at low cost, for example, by re-working a roll formed or pressed, top hat section with a production laser cutting machine) will be preferred in one-time installations which are not likely to be disturbed, or in situations where economy is more important.

It is also envisaged that those using the novel system on a regular basis will keep a stock of frame elements and divide and re-join them as necessary for each job.

Referring to Figs. 25A and 25B, a jointing bar 130 comprises a rigid, U-shaped section having a rear wall 131 and two side walls 132, each side wall having a series of holes 133 which correspond to the fixing holes (79, 119) in the side walls of each rigid section of the first, second and third frame elements. Two frame elements may be joined end-to-end to form a longer frame element by arranging the jointing bar 130 inside the central, U-shaped portions of the respective, half-length terminal rigid sections of the two shorter frame elements so that they abut in the centre of the jointing bar, and bolting the two frame elements respectively to the jointing bar via the cooperating holes.

Shields Referring to Fig. 26A, 26B and 40, a first flexible, waterproof shield 140 comprises an extruded, elongate elastomeric profile having a central attachment portion 141 and two lateral water shedding portions 142. Each water shedding portion is longitudinally corrugated so as to define parallel water shedding channels 143 on its outer surface, and is provided with elongate drip grooves 144 on its inner surface which discourage water from running laterally between the corrugations. In its installed position (Fig. 40), any water falling on the shield is thus channeled downwards to the ground or onto the rear, water shedding surface of the panel 200 on either side, so that the shield protects the frame element beneath.

The shield is extruded from a die which is so shaped that in its relaxed condition it tends to curl in on itself. When it is mounted on a frame element 70 during installation of the framework, as shown in Fig. 266, it tends to wrap itself around the frame element so that the central corrugations abut resiliently against the side walls of the frame element as shown to retain the shield in position.

In addition, an adhesive band 145 protected by a releasable paper strip 146 is stuck to the inner surface of the attachment portion, so that it can be adhered to the rear wall of the frame element as shown for easier assembly.

When the frame element 70 is raised into an installed position beneath the soffit as shown in Fig. 40, the attachment portion of the shield is thus positioned between the rear wall of the frame element and the soffit. Elongate compression portions 147 are arranged to cushion the frame element 70 against the soffit 5, so that the shield is not damaged as the ends of each rigid section of the frame element press upwardly and outwardly against the soffit. The corrugated water shedding portions 142 are spread out on each side during installation of the panels 200 so that they are urged resiliently into engagement with the channeled rear surfaces of the panels as shown, providing a dry zone beneath the shield.

(For the avoidance of doubt, references in this specification to the frame element being engaged against or in contact with the soffit are to be construed as including this arrangement, in which a shield is interposed between the frame element and the soffit.) Preferably, the shield material is supplied with the water shedding portions spread out (as shown in Fig. 26A) as a continuous length on a large diameter roll, so that as it is unrolled it naturally adopts a curved configuration which helps it to conform to the curvature of the frame element.

It will be noted that the shields and panels do not rely on any compressive seal for their effectiveness, but rather on the respective downwardly oriented water channelling surfaces which prevent water from travelling laterally towards the frame element. This provides great tolerance between the various system elements so that the system remains effective, irrespective of the accuracy of installation or the curvature of the soffit. Of course, compressive seals or the like could be provided if preferred.

A similar shield element 149 is shown in the installed position at the crown of the arch in Fig. 39.

Referring to Fig. 27, a second shield 150 comprises an elongate profile extruded from a fairly hard, high density polyethylene, comprising a resilient central attachment portion 151 with a rounded external surface 152 and incurved edges 153 from which lateral water shedding portions 154 extend outwardly on either side. Each water shedding portion is slightly curved inwardly away from the soffit so that as each panel is installed, the outer edge 155 resiliently engages the rear surface of the panel. Elongate ribbing or drip grooves might be provided on the outer and/or inner surfaces of the lateral portions 154, similarly to those of the first shield.

The central attachment portion 151 is adapted to be fitted over the central, U-shaped portion of a frame element so that its edges 153 resiliently embrace the side walls of the frame element, holding the shield in position. The rounded external surface 152 tends to deflect the frame element and shield away from any old fixings projecting from the soffit as the frame element is raised into position, while the wide flanges on the panels 200 accommodate any resulting displacement of the frame element Once installed, the rounded profile of the attachment portion 151 cushions the ends of each rigid section of the frame element against the soffit.

Referring to Fig. 29, a third, very simple shield element 160 comprises a length of waterproof, elastomeric or flexible plastics material, similar for example to a polyester damp proof course as used in building construction, or alternatively a thin, flexible metal sheet (e.g. aluminium, zinc or galvanised steel).

Referring to Fig. 28, if the third shield element 160 is sufficiently thin and flexible, it can be folded over the rear surface of the frame element and clipped in place by means of a springy cap 161 (Fig. 28). The cap is formed in sections, or alternatively in a continuous length, from galvanised steel or hard plastics material, and has a rounded central attachment portion 162 with incurved edges 163 and outwardly extending flanges 164 which are slightly longer than the corresponding flanges of the frame element. In use, the central attachment portion 162 is clipped over the central, U-shaped portion of the frame element with the shield element 160 in-between, so that its incurved edges 163 resiliently retain the shield element 160 in position against the side walls of the frame element. The hard, rounded central portion 162 deflects the whole assembly away from any obstructions which may be projecting from the soffit, which are further diverted by the flanges 164 past the flanges of the frame element so that they do not puncture the shield 160.

Referring to Fig. 30, a fourth shield 170 is extruded similarly to the first shield element from elastomeric material, and has a thickened central attachment portion 171 comprising resilient wings 172 which grip the frame element to hold it in position. The water shedding portions 173 comprise deep elongate corrugations with drip grooves 174, whose inner and outer extremities 175, 176 respectively contact the rear surfaces of the panels and the soffit. Each water shedding portion 173 is thus compressed between the soffit and the panels during installation, which extends it outwardly away from the frame element and retains it positively in its installed position.

Installation of flexible frame elements The nominal required length L1 for each flexible frame element can be calculated roughly, based on the width W of the arch according to the formula L1 = ((irW)/2) + 1 m, which resolves to L1 = (1.57W) + 1 m. This gives the correct length to span a semi-cylindrical soffit with a O.5m overlap for fixing at each end.

Alternatively or additionally, a table can be supplied in which the columns are headed by representations of the arch configuration (egg-shaped, cylindrical, flattened, etc.), the rows correspond to the width of the arch, and the body of the table gives the required length of the flexible frame element for each combination.

In the example shown in Figs. 1 -12, each unitary, flexible frame element 70 is about I Om in length, about 50mm deep (between its rear wall and its flanges) and about 110mm in width (between the outer edges of its flanges). It is relatively rigid in its width direction, but due to its length it is quite floppy in its depth direction, which presents a potential difficulty in transporting it and raising it into its installed position, several metres above ground level, while avoiding uncontrolled movements which could cause unnecessary flexing and weakening of its integral hinge portions.

Referring to Fig. 14D, this problem is avoided prior to installation by supplying the flexible frame elements 70 in pairs which are arranged front to front (flanges together) and banded together by plastics ties 178. Since each frame element is preferably constrained to form a maximum angle on its inner face (facing away from the soffit in use) of 180° at each joint, the two elements together thus form a substantially rigid, straight assembly in which they are easily handled and transported to the point of use without damaging them.

Referring to Figs. 3 -8, each frame element 70 is then preferably installed by means of a pair of first installation tools 300, by which means each frame element 70 is easily raised into pressing engagement with the soffit and then secured in its installed position while avoiding any unnecessary flexing of its integral joints.

Referring particularly to Fig. 3, each first installation tool 300 comprises a releasable mounting mechanism 301 for mounting the tool for controlled movement towards the soffit; a frame element attachment mechanism (302, Fig. 5) for releasably attaching one end of the flexible frame element 70 to the tool; and a movement mechanism 303 for controlling the movement of the tool up and down towards and away from the soffit. In the embodiment shown, the releasable mounting mechanism 301 is adapted for releasably mounting the tool in sliding engagement with the flanges 41 of one of the posts 40, while the movement mechanism 303 comprises a mechanism for manually raising and towering the toot up and down the post.

In addition, each tool 300 preferably includes a separation adjustment mechanism 304 for moving the respective end of the attached frame element 70 towards and away from the respective post 40; and a pivot mechanism 305 controlled by a releasable ratchet mechanism, which permits the frame element to be raised from a substantially horizontal orientation to a substantially vertical orientation after attachment to the tool while restraining the frame element 70 against downward movement.

The various features of the first tool 300 are described in more detail in due course.

Once all the posts 40 are in place and the bracing struts 60 and bracing cables 67 have been installed, each of the two installation tools 300 is mounted on the base of a respective one of a first pair of posts 40 on opposite sides of the arch, the ratchet is released by pulling the detent ring 423, and the pivot mechanism 305 is pivoted in whichever direction offers more room, so that each respective frame element attachment mechanism 302 extends horizontally or, preferably, slightly downwardly towards the floor of the arch. The separation adjustment mechanism 304 is adjusted by means of its removable handle 396 to provide a gap between each end of the frame element and the respective post 40, which accommodates the ends of the shield 149 as the frame element is raised as further described below.

A first pair of frame elements 70 are then placed on the ground and separated by cutting the ties 178. One frame element 70 is then attached at a first one of its ends 77 to the attachment mechanism 302 of a first one of the tools, so that it extends along the ground away from the respective post 40 (Fig. 3).

The installer then walks with the second end 77 of the frame element in a wide arc towards the second tool, so that the frame element is progressively bent into an arched configuration while it lies on the ground, and attaches the second end 77 to the attachment mechanism 302 of the second tool 300 as shown in Fig. 58. Bending at each hinge portion is controlled by the respective plastic deformation elements as described above.

Once the two ends 77 of the frame element 70 are attached to the two respective tools 300, the midsection of the frame element is raised a short distance off the ground and supported on building blocks 11 or the like. A length of shield material 149 is then cut from the roll and fitted over the outer (ie. the soffit-engaging) face of the frame element 70, so that it extends along the whole length of the curved frame element between its two ends. (Fig. 4.) The frame element 70 is then raised to a substantially vertical plane as shown in Fig. 5, while the attachment mechanism 302 of each tool pivots about its pivot mechanism 305. The ratchet mechanism cooperates with the pivot mechanism 305 to allow upward movement while preventing the frame element from falling back downwards in either direction, and cooperates with a safety detent bolt 421 (further described below) to automatically lock the pivot mechanism 305 of each tool when the frame element 70 reaches its vertical position.

This makes it relatively straightforward for two people to raise the flexible frame element 70 by pushing it upwards, one at each end, or even for a single person to raise it by pushing it initially as close to the middle as they can reach, then closer to one end, relying on the two ratchets to hold it up once it reaches a more upright position. The maximum 180° angle e between adjacent rigid portions 72 prevents the frame element 70 from bending outwardly to contact the posts 40, so that it settles into a stable, fairly even, arched configuration in which it is safely supported in a vertical plane, clear of the posts, as shown in Fig. 54.

Alternatively, for installation by one person, the midsection of the frame element can first be raised as high as possible off the ground and supported on a short freestanding ladder. A rope or plumb-bob cord 12 is then passed through the two centre keyhole slots 81, 81' in the rear wall 75 of one rigid portion 72 nearest to the middle of the frame element 70, and the frame element is raised to the vertical position by pulling the rope or cord 12 in the longitudinal direction of the arch. This can also be accomplished without effort by passing the rope 12 through a block which is fixed between the upper ends of two distant posts, or by using two ropes passing through two blocks fixed respectively to the upper ends of two distant posts.

Of course, if preferred, each tool could also be adapted to provide a geared mechanism or the like for raising the frame element to an upright position, although the applied torque will then be substantial.

Once the frame element is locked in the vertical position by the detent bolts, with the shield 149 extending down between the frame element and the post at each end, a handle 550, comprising a short steel tube with a threaded inner end and a hole in its outer end, is screwed into the left-hand (upward) drive socket 522' of the movement mechanism 303 of each tool. In the example shown, a short length of cord 13 is also attached to the hole in the outer end of each handle so that the handle can be operated from the ground against the restoring force of its return spring 535' (further described below). (Fig. 5.) The two handles 550 are then operated (either simultaneously by two people or alternately by the same person) by pulling on the cords 13 to raise each tool 300 carrying the frame element 70 up the two posts 40, until the outer face of the rear wall 75 of the frame element (cushioned by the shield 149) contacts the soffit 5.

The ends of the shield material 149 attached to the frame element 70 are thus removed progressively from the gap between the frame element and the post by the upward movement of the tools. They are then trimmed as necessary, and the upper end of the shield matenal 149 previously captured behind each post 40 is led up beneath the shield material 149 on the frame element 70 as shown, so that the two lengths overlap to provide a water-shedding joint. (Fig. 6.) The removable handle 396 of each separation adjustment mechanism 304 is then operated to move each respective frame element attachment mechanism 302 carrying the respective end 77 of the frame element 70 outwardly, so that the central U-shaped portion of each end of the frame element is slidably engaged in the central U-shaped portion of the corresponding post 40, with the flanges 71 of the frame element abutting against the flanges 41 of the post, as shown in Fig. 60.

If necessary, each frame element 70 can now be adjusted for verticality by means of a plumb-bob 14 suspended on the cord 12 which is attached to the midpoint of the frame element. A second cord 15 is stretched between the respective supporting columns 40 beneath the frame element. The position of the frame element is simply adjusted by pulling on the plumb-bob cord 12 in the required longitudinal direction of the arch until the plumb-bob 14 is in alignment with the bottom cord 15. (Fig. 6.) The handles 550 are then operated again so as to raise the tools 300 and the frame element 70 slidingly upwardly relative to the posts 40, forcing the frame element pressingly upwardly and outwardly against the soffit 50 into its final, installed position. This upward movement induces a compressive hoop stress between the ends 77 of the frame element, forcing each rigid portion 72 of the frame element outwardly against the soffit 5 and sandwiching the shield 149 between the frame element and the soffit along its whole length while urging the upper ends of the posts outwardly against the piers.

Each end 77 of the frame element 70 is then attached by bolts 50 to the upper end of the post 40 above the tool, as shown in Fig. 14C, so that the residual hoop stress is maintained by the posts acting in compression. Due to the adjustable attachment system already described, based on the Vernier principle, the frame element 70 is attachable in virtually any vertical position on the post 40, and the degree of overlap is of little significance, so the system is very tolerant of errors in measurement or calculation. (Fig. 7.) If the plumb-bob cord 12 was looped through the keyhole slots in the frame element, it can now be recovered by pulling on one end so as to be re-attached to the next frame element. Alternatively, it could be looped through a small wire or plastics widget (not shown) attached to the keyhole slots, so as to make it easier to recover.

S The frame element attachment mechanism 302 of each tool is then detached from the frame element and the handle 550 is engaged in the right-hand (downward) drive socket and operated to bring the tool back down the post 40, after which the mounting mechanism 301 is released and the tool is removed from the post. The remaining frame elements 70 are then installed in the same way. In its installed position, each of the frame elements 70 is thus jammed up tightly against the brickwork of the soffit so that it conforms flexibly to the curvature of the soffit 5, forming a self supporting arched configuration in which it is supported only by the two posts 40 on opposite sides of the arch, while being rigidified and also restrained against movement in the longitudinal direction of the arch by frictional contact with the soffit. (Fig. 8.) By use of the novel tool, the flexible frame element may thus be handled and installed simply and efficiently while avoiding unnecessary flexing of the joints.

Moreover, there is very little need to work above ground level during installation of the framework. All that is required is a relatively short ladder which gives access to the upper end of each column for fixing the bracing struts and cables, overlapping the lengths of shield material, bolting the frame element to the column and operating the tool, which is preferably operable mostly from ground level as described. Thus (apart from a few bolts and a spanner) there is no need to carry tools or materials up or down the ladder.

Of course, the tools are equally suitable for use in installing the articulated frame elements 110.

Joists The posts may be used to support horizontal joists, providing a mezzanine floor, in which case the posts are dimensioned accordingly and the joists and floor are installed once the framework is in place and before the lining panels are attached, so that the floor provides a working platform which affords easy access to the whole of the soffit up to the crown.

Alternatively, where it is not intended to install a mezzanine floor, smaller posts are used, and lightweight temporary joists 181 may be releasably attached to the posts to support a temporary working platform giving access to the soffit.

Referring to Fig. 9, for installation of a floor or working platform, a bracket 180 is preferably first bolted to the upper end of each post 40. Each bracket 180 may comprise a flat plate which is inserted into the central U-shaped portion of the frame element 70 inside the post 40 and is bolted through corresponding holes in the two abutting side walls 76, 46 (Fig. 14C). It may be installed at the same time as the frame element 70 is bolted to the post, so that all three elements are fixed together simultaneously by the bolts 50. The bracket 180 may provide adjustable attachment holes, both for attachment of the bolts 50 and for attachment of the joist 181, so that the bracket 180 can be adjustably positioned on the post 40 and/or the joist 181 can be adjustably positioned on the bracket 180. Alternatively, a two-part bracket can be used which provides positional adjustment between its parts.

Conveniently, each temporary joist 181 comprises a telescopic assembly comprising two hollow, box section or inverted, U-section or top-hat section aluminium end portions 182, in which an aluminium centre portion 183 is telescopically received. The centre portion 183 has slots 184, and the three parts are retained in sliding, adjustable relation by bolts 185 which pass through the slots. Each end portion 182 has a fixing hole 186 at its outer end, closer to its base than to its upper (horizontal) wall.

Each temporary joist 181 is first lifted at one end and slid over one of the brackets 180, which is received between the side walls of the joist so that the upper wall of the joist sits on the bracket, and then pivotably attached to the bracket by means of a bolt via the fixing hole 186. (Fig. 9.) The other end of the joist is then raised off the ground (either by lifting it directly or, perhaps, by a modified attachment to the installation tool) and attached at its second end to the corresponding bracket 180 on the upper end of the opposite post 40. The assembly telescopes to accommodate the changing length of the joist. By fixing two or three joists side by side and then laying boards or planks across them, a stable working platform or floor 187 is quickly created which affords easy access to the soffit up to the crown. (Fig. 10.) The framework (comprising principally the flexible frame elements 70 and posts 40) can be used to support panels 200 or sheeting to form a waterproof lining, and can also be used either with or without a lining or shield elements to support lighting fixtures, pipework, racking and the like.

Finishing the crown Where it is intended to install lining materials, preferably a crown shield 190 is now attached between the frame elements 70 along the crown line, with its edges lying beneath the shields 149 on the flanges 71 of the frame elements, so as to intercept water falling from the crown of the arch and channel it downwards onto the panels 200 on either side.

Referring to Figs. 31A -31B, the crown shield 190 comprises a corrugated plastics sheet, the corrugations being arranged to run in the transverse (width) direction of the arch so that they channel water downwards along the curve of the soffit.

Preferably, a bracing strut 60 or 60' is also arranged between each pair of adjacent frame elements 70 at the crown, so as to additionally s tabilise the frame elements in the longitudinal direction of the arch. (Where panels are to be attached to the frame elements, the panels will also provide stability.) Each S bracing strut 60 is installed underneath the crown shield 190 along the crown line so as to support the centre of the crown shield, and the crown shield is optionally attached to the bracing strut by cable ties 191 passing through holes in its edges, beneath the protective shield 149, as shown in Fig. 10 and in cross-section in Fig. 39.

In a development, the bracing strut can be adapted to define a cable channel for retaining cables, pipework and the like running between the adjacent frame elements at the crown line, in which case the adjoining longitudinal panel edges can be spaced apart along the crown line to leave a space for the cabling, which is finished by a longitudinal cover strip.

Panels Referring to Figs. 34A -37C, a first panel 200 comprises a body portion 201 made from waterproof, rigid, closed cell foamed plastics material (e.g. polyurethane, polyisocyanurate or expanded polystyrene), which is bonded to a substantially flat, planar front board 202 with bevelled upper and lower longitudinal edges 203, 222, whose substantially flat front surface 204 faces inwardly into the arch in the installed position. The board 202 can be made from cementitious material, calcium silicate, polypropylene, polyethylene or other fairly rigid plastics material, fibreglass, powder coated sheet steel, compressed cellulose or mineral particles, or any other fairly rigid material which is adequately strong and resistant to damp and which presents an acceptable internal surface 204.

Two steel flanges 205 are bonded, one at each end of the panel, between the body portion 201 and the front board 202 so as to extend in the transverse direction of the panel between the upper longitudinal edge 210 of the panel and the lower longitudinal edge 222 of the front board 202, which is spaced apart from the lower longitudinal edge 211 of the panel, which edges 210, 211, 222 will generally be horizontal in the installed position. The outwardly extending portion of each flange 205 forms an attachment portion 206 which is perforated with a diagonal pattern of fixing holes 208 and slots 209, which are spaced apart in the transverse direction of the panel by a distance d2 so as to cooperate with the corresponding fixing holes in the respective flange of the post 40 or frame element 70 according to the Vernier principle as discussed above, providing a positionally adjustable fixing system. The attachment portions 206 of the flanges are wide enough in the longitudinal direction of the panel to tolerate substantial variations in the spacing of the posts 40 and frame elements 70, so that each panel may overlap the respective flange of the frame element or post to a greater or lesser extent as illustrated for example in Figs. 39 and 40.

The inwardly extending portion 207 of each flange may also be provided with second perforations, so that the front board 202 and flanges 205 can all be arranged in a mould before the body portion 201 is formed by injecting a pre-mixed plastics compound into the mould, which then expands through the second perforations to bond the front board 202 and flanges 205 together.

The rear, water shedding surface 212 of the body portion 201 is divided into a plurality of channels 213 which extend in parallel in the transverse direction of the panel to guide water falling from the soffit 5 or shields 149 onto the panel, downwardly from its upper edge 210 to its lower edge 211, while preventing it from travelling laterally beneath the shields 149. The base of each channel 213 (forming part of the rear, water shedding surface 212) diverges outwardly from the front surface 204 as shown and downwardly in the installed position towards the lower edge 211 of the panel, where it curves back, inwardly into the arch and towards the front surface 204 to form the outer, water shedding surface 214 of a lower wall 215, whose opposite (inwardly facing) surface 216 also curves inwardly (away from the soffit) in the installed position of the panel to define an elongate recess 221 between the lower edge 211 of the panel and the lower edge 222 of the front board 202.

The lower wall 215 is so arranged that its outer surface 214 and inner surface 216 are both inclined downwardly, irrespective of the angle of inclination of the panel in its installed position, as will be seen by comparing the relative position of the lower wall 215 in its installed position close to the crown of the arch (Fig. 37A) and in a vertical orientation adjacent one of the piers (Fig. 37C).

This ensures that water running down the water shedding surface 212 of the channel 213 will always drip vertically downwardly from the tip 217 of the lower wall 215. In order to prevent water from running laterally along the tip 217 of the lower wall in the longitudinal direction of the panel, each of the lands 218 which separate the channels 213 extends around the tip 217 of the lower wall to provide a nose 219 which always lies at the lowermost point of the lower wall 215 (cf. Figs. 37A, 37C).

The overall depth of the panel between each of its flanges 205 and the rear surface 220 of each of the lands 218 is slightly less than the depth of the frame element 70 between its flanges 71 and its rear wall 75, so that the body portion 201 can be accommodated adjacent the soffit 5 in the space between the frame elements 70 (depending of course on the angular position of each panel relative to the frame elements) and only the relatively thin front board 202 extends outwardly of the flanges 71 of the frame element at the top and bottom of the panel. This allows the whole lining to be arranged very close to the masonry of the arch, maximising the usable space within.

The rear, water shedding surface 212 of each channel 213 terminates at its upper end in a shallow recess 223 which extends longitudinally for the whole length of the panel, proximate its upper edge 210 and generally horizontally in the installed position. Each land 218 tapers at its upper end to meet a shallow, faceted hump 224 which divides the floor of the recess 223 between each pair of adjacent channels 213. This ensures that water falling into the recess 223 will not travel laterally along it, but will rather be shed to one side or the other of each hump 224 and thus directed into the nearest channel 213. (The humps 224' at the ends of the panel face towards the centre of the panel.) The upper wall 225 of the recess 223 extends generally in the outward direction towards the soffit (which is to say, outwardly towards the soffit rather than inwardly towards the arch) in the installed position of the panel to define an elongate protuberance 226 which (together with the channels 213, lands 218 and recess 223) also forms an integral part of the moulded body portion 201.

Referring particularly to Figs. 37A -37C, the attachment portions 206 are attached by self-tapping screws respectively, either to the flanges of two adjacent posts or to the flanges of two adjacent flexible frame elements, so as to support the panel 200 in an installed position in which it is inclined downwardly from its upper edge 210 to its lower edge 211, with its rear, water shedding surface 212 facing in an outward direction towards the soffit 5 or the adjacent pier 3, 3', as illustrated for example in Fig. 40.

Preferably, installation commences with the bottom panels. Each panel is attached to the framework above the one below so that the flanges 205 of each panel abut the flanges of the post or frame element adjacent the respective upper and lower bevelled longitudinal edges 203, 222 of the front boards 202, which edges respectively abut each other to define, either a wide groove (Figs.

37A, 37C) or a narrow interstice (Fig. 37B) or a groove of intermediate width, depending on the angle 82 defined between the inwardly facing surfaces 204 of the two panels 200.

The rear surface 220' of each of the lands 218 at the lower edge 211 of the panel is radiused about an axis defined by the bottom edges 221 of the flanges 205, so that the second panel may be installed by inserting its lower edge 211 behind the upper edge 210 of the panel below, before rotating its respective upper edge 210 towards the soffit into its installed position, the radiused surface allowing it to clear the soffit at its lower edge as it rotates. Since the front board 202 of the upper panel then rests on the front board 202 of the lower panel, it is easy to support the upper panel during installation, and if preferred, it may be secured by means of only two fasteners, one at each end either at mid-height or near to its upper edge.

Referring to Fig. 37A, two panels 200 are shown in their installed positions, close to the crown line 8 of a wide arch with a gently curving, flattened soffit, with their respective front surfaces 204 substantially aligned and their respective rear, water shedding surfaces 212 both inclined downwardly at a shallow angle e3 of only 2° below a nominal horizontal line H. is (In Figs. 37A -37C, the upper panel 200 is denoted by the reference numeral 200' and the lower panel 200 by the reference numeral 200", purely to distinguish their relative positions.) The respective upper and lower walls 225, 215 of the two panels are so configured (as already described) that, even in this position, they interlock to shed water from the rear surface 212 of the upper panel 200' to the rear surface 212 of the lower panel 200", such that the respective rear surfaces 212 of the two panels form an effectively continuous water shedding surface, with the upper wall 225 and protuberance 226 of the lower panel 200" being received in the corresponding recess 221 of the upper panel 200' and the lower waIl 215 of the upper panel 200' extending downwards into the recess 223 of the lower panel 200" as shown. In this configuration it is impossible for water to travel up out of the interlocking joint thus produced between the panels.

Referring to Fig. 37B, the two panels may be attached at any point adjacent the soffit or piers so that they are inclined downwardly at different angles of inclination as shown, whilst their respective upper and lower walls 225, 215 still cooperate to shed water from the rear surface 212 of the upper panel 200' to the rear surface 212 of the lower panel 200".

In the position shown in Fig. 37B, the rear, water shedding surface 212 of the upper panel 200' is inclined downwardly at a relatively shallow angle 83 of about 5° below a nominal horizontal line H, representing the position of the upper panel if it were attached, just above the spring line of an arch in which the soffit departs from the spring line at an exceptionally shallow angle. The lower wall 215 of the upper panel 200' is positioned vertically above and behind the rear, water shedding surface 212 of the lower panel 200", so that even in this extreme position, water dripping from the lower wall 215 will fall downwardly, behind the protuberance 226, upper wall 225 and rear water shedding surface 212 of the lower panel, so that the two panels again form an effectively continuous, water shedding surface.

In the position shown in Fig. 37B, the obtuse angle 82 between the upper and lower panels is about 102°, while in the example of Fig. 37A, the corresponding angle 82 is about 177°, giving an angular variation between the two illustrated positions of about 750 Preferably, the upper and lower walls 225, 215 of each panel are so configured that the obtuse angle 82 may be varied by at least 15° while still forming a continuous, water shedding surface between the two panels, which degree of variation allows the panels to be adapted for use in most positions on reasonably evenly curved soffits.

More preferably, the obtuse angle 82 may be varied by at least 70° as shown; and most preferably, the aforesaid angular variation is possible, even where the rear, water shedding surface of the upper panel lies at a relatively shallow angle of only a few degrees below the horizontal, as shown, which permits each pair of panels to be installed at virtually any point on the internal surface of virtually any arch, irrespective of its geometry.

Referring to Fig. 37C, the upper and lower walls 225, 215 are so configured that the two panels may also be installed one above the other on the posts adjacent the pier at one side of the arch, with their rear surfaces facing the internal surface 4 or 4' of the pier and their respective front surfaces 204 in vertical alignment as shown, to form a vertical wall. In this position, the lower wall 215 is accommodated in the recess 223 with its tip 217 lying just above the shallow humps 224 (which is why they are shallow), while the protuberance 226 is received in the recess 221, so that once again, the respective rear surfaces 212 of both panels cooperate to form an effectively continuous water shedding surface.

In order to facilitate attachment of the panels to the posts adjacent each pier so as to form a vertical wall, as well as to the frame elements around the soffit so as to form a curved ceiling, the front surface 204 of each panel is preferably flat and planar as shown; of course, if preferred, each panel could be curved for use exclusively beneath the soffit. The foamed plastics body portion 201 and lands 218 provide a light weight, rigid structure which also thermally insulates the front surface 204, reducing condensation.

The panels 200 can be attached to any supporting framework, and are not limited to use with the novel flexible frame elements. Instead of self tapping screws, the respective flanges may be adapted if preferred to receive special fasteners, designed for example so that they require only a quarter turn to install or release them. Such adaptations will be within the purview of those skilled in the art.

In alternative embodiments, the front board 202 could simply be a thin layer or coating attached to the body portion 201. It is also possible to make the panel in a single, unitary piece, without either flanges or a front board. The two flanges could be combined into a single, embedded supporting structure, or they could be integral with the front board.

Rather than being deep grooves moulded into the rear surface of the body portion as shown, the channels could be defined by shallow ribs or the like S which are formed on the rear, water shedding surface; the body and attachment portions of the panel could then be made for example as a unitary plastics moulding, or from a single sheet of steel which is joggled at its top and bottom edges to form the upper and lower walls.

Of course, the rear, water shedding surface of the panel could also be formed without channels. Alternatively, the channels could be slanted, for example, in a chevron pattern, downwardly and inwardly towards the vertical centre line of the panel, so as to channel water away from the edges of each panel towards the centre of the panel beneath. However, the parallel channels of the illustrated embodiment advantageously allow the panel to be cut along its transverse (top to bottom) direction to virtually any required length, so as to fit between the final pair of posts or frame elements; whereas, if the channels were inclined towards the centre of the panel, the panel could not be cut to less than half of its original length without the channels then directing water towards the cut end.

Referring to Figs. 38A -388, in order to allow each panel 200 to be cut to length along its transverse dimension if required, a replacement mounting flange 230 is formed from a single, folded sheet of mild or spring steel, having an attachment portion 231 similar to that of the panel 200 which extends from a pair of resilient, spaced walls 232, 233, which are arranged to embrace the cut end of the panel 200 with the front wall 232 lying over its front surface 204 and the rear wall 233 lying over the rear surfaces 220 of the lands 218, so that the double thickness attachment portion 231 then lies in the same position as the original flange 205 which has been cut away from the panel.

After cutting the panel 200 to length, a thin scrap steel sheet (not shown) is first laid against the rear surfaces 220 of the lands 218 along the cut edge of the panel. The front wall 232 and rear wall 233 are then resiliently pulled apart (assisted by the separation of the two halves of the folded attachment portion 231) and forced over the cut edge of the panel, with the scrap steel sheet protecting its rear surface. Once the aligned end walls 234, 235 abut the cut end of the panel, the scrap steel sheet is pulled out and the rear wall 233 is tapped with a hammer so that sharp, inturned points 236 formed integrally with the rear wall 233 penetrate the rear surfaces 220 of the lands 218, locking the flange to the panel. Small screw holes (not shown) may also be provided so that the front wall 232 can be screwed to the front board 202 for added security.

Finishing the lining Referring to Figs. 11 -12, the panels 200 are attached to the flanges of the posts 40 and frame elements 70, starting from the floor and working up towards the crown between the joists in a continuous sequence, so that each panel is interlocked with the one below. The final set of panels are cut to length and then fitted with replacement flanges as described above before being attached between the rear pair of posts and frame elements on either side of the arch.

Once the final rows of full panels have been placed on either side of the crown, the remaining longitudinal gap at the crown can be filled by a row of panels cut to fit along their longitudinal axes, or with two rows of cut panels which meet at the crown, with the lands being cut away if necessary to accommodate the bracing strut. Alternatively, a gap can be left to accommodate cables and the like, in which case it is preferably covered by a removable cosmetic cover strip (not shown). Once lighting fixtures and other fittings are in place, the temporary joists can finally be removed.

After installation, each frame element 70 is kept dry by its shield 149, so that any water falling on the area above the frame element is diverted downwardly along the shield or sideways onto the rear, water shedding surfaces 212 of the overlapping panels 200, whose channels 213 prevent water from running back beneath the protective shields. The shields 149 extend around the end posts to cover the corners of the rear wall 9 (as well as the front wall, which is not shown), so that the front and rear walls can be finished, either conventionally or by means of another set of panels 200 supported if required on vertical, top hat section brackets screwed to the walls or attached at their upper ends to the rearmost frame element 70, to provide a complete, waterproof lining.

By providing an upper fastener and a lower fastener on each side of each panel 200, which are attached to the respective flanges 71 of the frame elements 70 on either side, each panel 200 acts as a rigidifying element or cross-brace which prevents movement of the respective frame elements in the longitudinal direction of the arch. Once all the panels are in place, the lining forms an extremely stable structure. The panels can be removed one by one for inspection and maintenance of the masonry, and when a major inspection is necessary, the entire lining and framework can be removed and replaced by reversing the installation procedure.

If required, the interstices or grooves between the longitudinal edges of the panels can be filled with mastic or with a compressible rubber or foam profile, but this should be unnecessary as long as they are arranged in close abutment, which is made possible by the adjustable attachment system described above.

Advantageously, the continuous U-shaped channels defined by the nested frame elements and posts and protected by the shields can be used as conduits to carry wiring and small diameter flexible pipework around the inside of the arch, while the flanges of the frame elements, posts and panels provide mounting points for sockets, lighting fixtures and the like. The gaps between adjacent panels at each frame element are preferably covered by cosmetic, plastics or metal cover strips (not shown) which provide access to the cabling beneath, the cover strips preferably being resiliently retained so that their outer edges are pressed outwardly against the inner surfaces 204 of the panels, providing an even finish at each joint which covers variations in spacing between the posts, frame elements and panels. Of course, if preferred, the panels could be arranged to abut at their vertical joints as well.

If preferred, the novel framework can be lined with ordinary corrugated sheets or any other suitable sheets or panels instead of the panels 200, in which case each edge of the corrugated sheet or panel will form an attachment portion which is placed over the flanges of the frame element or post and then drilled or screwed through to fix it in position.

First releasable mounting mechanism Referring to Figs. 41A -43, the releasable mounting mechanism 301 of the first installation tool 300 is adapted to mount the tool as shown on the flanges of a post, and is shown in Figs. 41 B and 43 attached to a third post 40' which is similar to the first post 40, having flanges 41' with regularly spaced rectangular apertures 43' which are adapted to receive the projecting teeth 471 of the drive pinion 470 of the tool 300.

The mechanism 301 comprises two pairs of waisted rollers 310, 310' mounted in bearings 311 on the ends of pivoted arms 312, 312', the two pair of arms being arranged respectively at the lower and upper ends of the tool 300 so that they can be extended and retracted via apertures 313 in the side walls 351, 352 and backplate 306 of the tool body.

The corresponding arms of each pair are linked by bars 314 so that both pairs of rollers are drawn together simultaneously by a screwthread mechanism at the lower end of the tool from their disengaged position (Fig. 41A) into their engaged position (Figs. 41 B, 43) so as to engage the tool with the flanges of the post. In the engaged position, the backplate 306 of the tool body is spaced apart from the post by fixed rollers 315 which extend respectively through apertures 316 in the backplate so that their external surfaces are slightly proud of the backplate.

The screwthread mechanism comprises a screwthread 317 rotatably mounted between the lower wall 318 and an inner wall 319 of the body of the tool in parallel with a fixed guide bar 320. The screwthread 317 is rotated by a handwheel 321 so as to advance a traveller 322, comprising a block with a threaded bore for receiving the screwthread and a plain bore for slidably receiving the guide bar, towards the base of the tool. Links 323 pivotably connected between the traveller 322 and the lower arms 312 draw each respective pair of arms 312, 312' together, causing the rollers 310, 310' to converge behind the flanges 41' so that their waisted surfaces ride up the flanges, drawing the backplate 306 towards the post 40' so that the fixed rollers 315 are engaged against the external surfaces of the flanges as shown (Figs.

41 B, 43). The tool 300 is thus captured on the post 40' so that it can move up and down but cannot be rotated or detached. The handwheel 321 is rotated in the opposite direction to dismount the tool.

The retractable rollers adapt to posts of different widths, so that the tool can be attached to larger posts intended to support a mezzanine floor, or to smaller posts where only a lining is to be installed.

Second releasable mounting mechanism Referring to Figs. 75-79, in a second, alternative embodiment of the installation tool a second releasable mounting mechanism comprises a clamp mechanism 330 (Figs. 75-76) together with a lateral adjustment mechanism 340 and a pair of fixed rollers 315' (Figs. 77 -79), the fixed rollers (one of which is visible in the drawings) being similar to the fixed rollers 315 of the first releasable mounting mechanism described above. The second releasable mounting mechanism is shown in use on a fourth post 100' similar to the second post 100, having flanges 101' with rectangular apertures 102' which are adapted to be engaged by the movement mechanism of the second tool.

The clamp mechanism 330 comprises a pair of clamp arms 331, each clamp arm being mounted at one end for both rotational and translational movement on a fixed, round guide bar 332 which extends transversely across the tool body in front of the backplate 306'. The opposite end of each clamp arm is provided with a threaded bore which receives a stud having a knob 333 at its outer end.

A U-shaped arm 334 extends laterally from the centre of each clamp arm to support a roller 335 which can be moved in and out of engagement behind the respective flange 101' of the post by sliding the clamp arm 331 along the guide bar 332.

In use, the clamp arms 331 are positioned so that the rollers 335 lie behind the post flanges 101' before the knobs 333 are rotated to advance their threaded studs towards the backplate 306'. As each stud engages the backplate, it forces the distal end of the respective clamp arm 331 outwardly away from the backplate 306', drawing the rollers 335 into engagement with the rear surfaces of the post flanges 101' so as to clamp the tool to the post. The backplate 306' is spaced apart from the post flanges 101' by the fixed rollers 315' so that the second tool can slide axially up and down the post 100'.

The second tool is restrained against rotational and lateral movement in the plane of the post flanges by the lateral adjustment mechanism 340, which comprises a pair of pivotably mounted lateral adjustment arms 341 whose distal ends project from an aperture 342 in the centre of the backplate 306' so that their respective guide rollers 343 are positioned between the sidewalls 106' of the post. The lateral adjustment arms are biased resiliently together by a spring 344 and can be moved apart by a rotary cam 345 which bears against a cam follower 346 on each arm. The cam is rotated by a pair of spur gears 347, 347', which are linked by a shaft 348 to a corresponding pair of lateral adjustment arms (not shown) at the upper end of the second tool and driven by a handwheel 349 via a worm gear 350. In use, the handwheel 349 is rotated to urge the guide rollers 343 outwardly into abutment with the sidewalls 106' of the post.

Both the clamp mechanism and the lateral adjustment mechanism are inherently adaptable for use on posts of various different sizes.

Frame element attachment mechanism The frame element attachment mechanism 302, separation adjustment mechanism 304 and pivot mechanism 305 which together form the upper part of the first tool 300 will now be described with reference to Figs. 52 -74B.

Referring firstly to Figs. 52-54, 59 and 61A, the frame element attachment mechanism 302 comprises a rigid, upstanding parallelepipedal mounting base 360 with rectangular sides and a relatively narrow front profile as seen in Figs. 52 and 53, which is adapted to be received into the central, U-shaped portion of the frame element 70 between its side walls 76 so that the flat, rear wall 361 of the mounting base 360 abuts the rear wall 75 of the frame element. The mounting base 360 is sufficiently narrow to allow it to be received in frame elements of various sizes, selected according to the size of the arch and the load that they are intended to carry.

A pair of threaded shafts 362 with knobs 363 at their front ends extend through threaded bores in the mounting base 360 and terminate beyond its rear wall 361 in round mushroom-shaped retaining studs 364. A fixed stud 365 iS attached to the rear wall 361 in spaced relation to each retaining stud, Referring also to Fig. 1 6A, the retaining studs 364 and fixed studs 365 respectively are spaced apart by a distance corresponding to the distance between each pair of keyhole slots 81, 81'.

In use, the separation adjustment mechanism 304 is operated by rotating the handle 396 to position the mounting base 360 in spaced relation from the post 40, the ratchet mechanism (described below) is released, the mounting base is pivoted as shown in Fig. 57 towards its initial, downwardly inclined position, and the knobs 363 are rotated to advance the retaining studs 364 outwardly away from the rear wall 361.

The half-length terminal rigid portion 72' of the frame element 70 is then placed over the mounting base so that the retaining studs pass respectively through the round apertures 82 or 82' of the keyhole slots in its rear wall 75.

The frame element is then slid towards the bottom of the mounting base so that the neck portions 83 or 83' of the keyhole slots are captured beneath the retaining studs 364, until the round apertures 82 or 82' are aligned with the fixed studs 365. The retaining studs are then tightened by means of the knobs 363 to clamp the neck portions 83 or 83' of the keyhole slots to the rear wall 361 of the mounting base, the fixed studs 365 extending through the round apertures 82 or 82' to locate the frame element firmly in position as shown most clearly in Fig. 59. Once the frame element is securely mounted on the mounting base 360, it is raised to the vertical position as shown in Fig. 54.

When the frame element 70 has been attached to the post 40, the retaining studs 364 are slackened off and the mounting base 360 is retracted by operating the separation adjustment mechanism 304 so as to withdraw the fixed studs 365 from the round apertures 82 or 82' of the keyhole slots. The tool is then lowered for a short distance until the retaining studs 364 are aligned with the round apertures, before the mounting base is retracted again to withdraw it from the frame element 70, the retaining studs passing out via the apertures 82 or 82'. The tool can then be reversed down the post and removed.

Referring to Figs. 16A and 59, it will be noted that the neck portion 83 or 83' of each keyhole slot is slightly longer by a distance d9 than the distance between the corresponding retaining stud 364 and fixed stud 365. This permits the attachment mechanism to be used alternatively in a second tool which has a second, alternative movement mechanism as described below, by accommodating the short upward movement which is required to release the upper or lower pawl of the second movement mechanism (as further described below) from engagement with the corresponding aperture 102 of the second post 100 before the second tool can be reversed down the post. The first movement mechanism of the first tool (further described below) does not require any initial upward movement before it is reversed down the post, so the neck portions 83, 83' may be shortened by the distance dg for use with this tool, making it slightly easier to locate the studs in the correct position.

Pivot mechanism and separation adjustment mechanism Referring particularly to Fig. 61A, the mounting base 360 is mounted for axial movement on the pivot mechanism 305, which is mounted for pivotal movement about a threaded shaft 390 which in turn forms part of the separation adjustment mechanism 304.

The shaft 390 is mounted for rotation in a fixed axial position between a small rear bearing 391 and a front bearing 392. The front bearing 392 is pressed into a housing 393 which extends from the rear face of the front casing 308 of the tool, and is retained by an internal circlip 394 seated in an annular groove in the front casing 308. The splined distal end 395 of the shaft extends from the front of the tool to receive a removable rotary hand'e 396.

The pivot mechanism 305 comprises a pivot frame 380 whose movement is controlled by a combined detent and ratchet mechanism 400, further described below, the ratchet mechanism including a pair of front and rear ratchet plates 401, 402 and a front protection plate 403, all three plates being laminated together and fixed to the front end of the pivot frame 380 to form a unitary assembly (Fig. 62; cf. Fig. 63). The assembled pivot frame 380 and plates 401, 402, 403 are pivotably mounted on the shaft 390 on the rear shaft bearing 391, which is pressed into an annular housing 383 fixed to the rear endplate 384 of the pivot frame 380, and a front bearing 382, the front bearing 382 being pressed into an axial bore in the front plates 401, 402, 403.

The external surface of the annular housing 383 is mounted in turn within a large rear bearing 381, which is received in a recess in a rear mounting plate 307 (Fig. 64), which is screwed to the upper end of the backplate 306 of the tool body. The shaft 390 is thus mounted at its rear end in two concentric, inner and outer bearings 391, 381, and at its front end in two coaxial, axially spaced bearings 392, 382, which allow the pivot frame 380 and the shaft 390 to rotate coaxially but independently of each other.

In practice, the shaft 390 will most likely be provided with a thread of smaller pitch than that illustrated, which will minimise the small amount of axial movement of the mounting base which may occur as the pivot mechanism is rotated.

It will be noted that the shaft diameter progressively reduces towards its rear end. This allows the various components to be assembled by first pressing the small rear bearing 391 into the annular housing 383 of the pivot frame 380, and then pressing together the annular housing 383, the large rear bearing 381, and the rear mounting plate 307. These assembled components are then inserted together into the tool body, the mounting plate being screwed to the backplate 306. The shaft is then inserted axially from the front of the tool (rotating it as necessary to engage the threaded bore of the mounting base 360) into the rear bearing 391, after which the front bearings 382 and finally 392 can be pressed in axially around the shaft, one after the other, separated by a washer.

The assembly is dismantled by pressing the shaft out in the reverse direction, an aperture 309 being provided for this purpose in the backplate 306. The front bearings 382 and 392 are seated in front of a shoulder on the shaft so that they retain the shaft axially in position and (after removal of the circlip 394) are pressed out together with the shaft. Finally, the rear mounting plate 307 is unscrewed from the backplate 306 so that it can be removed together with the pivot frame 380 from between the backplate 306 and the front casing 308, after which the mounting plate 307 and pivot frame 380 can be separated.

Referring particularly to Fig. 61A, a guide groove 366 extends along each side of the mounting base 360, which receives a slide key 367 (Figs. 68A -68C) screwed to the upper edge of the pivot frame 380. The rear wall 361 of the mounting base is cut away just below the guide groove so that the upper part of the mounting base forms an ovethang at its rear end which can be extended axially from the pivot frame, over the top of the rear mounting plate 307, to engage the attached frame element slidingly with the post as shown in Fig. 60.

The overall length of the overhanging portion of the mounting base 360 is sufficient to allow it to be used with frame elements and posts of various depths, while providing enough clearance between the post and the frame element in its fully retracted position (Fig. 54) to accommodate the end of the shield material 149 during installation.

The pivot frame 380 defines a slide channel which slidingly receives the rear support portion 368 of the mounting base 360, which is slidably retained in the channel by a bottom key 369 in addition to the upper slide keys 367 so as to form a rigid assembly which resists twisting forces exerted by the frame element. The threaded shaft 390 engages in a threaded block 370 at the base of the support portion 368, to which the bottom key 369 is screwed, so that the mounting base 360 is driven axially along the pivot frame 380 by rotation of the handle 396 and shaft 390.

Detent and ratchet mechanism Referring particularly to Fig. 55 and Figs. 61A -C, the front casing 308 is extended to form a detent housing 410 with front and rear walls 411, 412, the S rear wall 412 having a guide block 413 fixed to its rear surface, both walls and the guide block being provided with axially aligned, square apertures 414.

The detent housing also has upper and lower horizontal walls 415, 416, each having a longitudinal guide slot 417, 418. The lower wall 416 also has a pair of transverse guide slots 419 which define abutment surfaces 420 at their inner ends.

Referring also to Figs. 65A -67C, the detent assembly comprises a square bolt 421 having a chamfered rear end 422 and a ring 423 at its front end, and a transverse aperture 424 intersected by a round bore 425; and a wedge 426 which has a stem 427 with a corresponding transverse bore 428 close to its front edge.

During assembly of the tool, a compression spring 429 is first arranged in the housing 410. The bolt 421 is then inserted into the spring through the square aperture in the front wall 411, and the stem 427 of the wedge is passed up through the lower guide slot 418 behind the compressed spring and through the aperture 424 in the bolt so that its upper end is received in the upper guide slot 417. A roll pin 430 is then inserted through the aligned bores 425, 428 so that it projects from either side of the bolt. The roll pin 430 and stem 427 cooperate to form an abutment for the spring 429, which biases the chamfered end 422 of the bolt into engagement with a corresponding aperture 404 in the protection plate 403 and ratchet plates 401, 402, locking the pivot frame 380 in its vertical position.

Referring to Fig. 61A and particularly to Fig. 63, the edge of the front ratchet plate 401 defines an arcuate ratchet 405 which extends from the 180° or bottom dead centre position B for about 105° in a clockwise direction to its upper extremity A, and a smooth, arcuate surface 406 which extends from the bottom dead centre position B for about 105° in an anticlockwise direction to its upper extremity C. The edge of the rear ratchet plate 402 defines an oppositely directed arcuate ratchet 407 which extends from B to C, and a smooth, arcuate surface 408 which extends from B to A. (Fig. 63.) Referring now to Figs. 53 and 55, the front ratchet 405 is engaged by the paw! 441 of a right-hand pawl assembly 440, which is mounted behind the front casing 308 between front and rear spacers 457, 458 on a pivot pin 459 which extends through corresponding front and rear apertures (of which the rear aperture 433 can be seen in Fig. 62) formed respectively in the front casing 308 and in an internal wall 431. The rear ratchet 407 is engaged by the corresponding paw! 441' of a corresponding, left-hand paw! assembly 440', which is mounted between front and rear spacers 457', 458' on a pivot pin 459' in corresponding apertures 432', 433' (visible in Figs. 61A and 62).

Each pawl assembly is controlled by a respective, right-hand or left-hand paw! control lever 460, 460' mounted respectively on a fixed pivot 434, 434' which extends from the rear face of the front casing 308.

Referring also to Figs. 69A -74B, the right-hand paw! assembly 440 comprises a flat plate 442 which is fixed solidly in spaced relation to its paw! 441 by a short spacer 443, so that the paw! 441 engages the front ratchet 405. The corresponding pawl 441' and flat plate 442' of the left-hand pawl assembly 440' are joined by a long spacer 443', so that the left-hand pawl 441' engages the rear ratchet 407.

Each flat plate 442, 442' defines a thin, arcuate guide arm 444, 444' whose distal end 445, 445' is separated from the body of the plate, for example by laser cutting, to define a socket 446, 446' in which it is frictionally retained.

During assembly, the guide arm is bent sideways out of the plane of the plate, and two identical helical compression springs 447, 448 (447', 448') are fed onto it, followed by a spring steel retaining clip 456, 456'. The distal end of the guide arm is then pressed back into the socket, and the clip 456, 456' is forced over the plate to secure the joint as shown in Figs. 53 and 55.

Each control lever 460, 460' comprises an arcuate lower limb 461, 461' which extends around the front bearing housing 393, having at its lower end a flat plate 462, 462' with a slot 463, 463' which is interposed between the two springs on the respective guide arm 444, 444' so that the guide arm passes slidingly through the slot.

The upper end of each control lever is cranked so that it extends fowards through a window 435 in the front casing 308 to terminate in a tab 464, 464' which extends upwardly through the respective guide slot 419 in the lower wall of the detent housing.

A tension spring 465 is arranged between the upper ends of the guide arms, which biases the two tabs towards a rest position in which they abut respectively against the abutment surfaces 420, as shown in Fig. 53. In this position, the compressive force exerted against the plate 462 or 462' by each of the paired springs 447, 448 (447', 448) on the corresponding pawl assembly is equalised to urge the respective pawl 441 or 441' into engagement with its corresponding ratchet.

The ratchet mechanism is released by pulling the ring 423 in the direction of the arrow as shown in Fig. 56A, which retracts the bolt 421 from the aperture 404 and advances the wedge 426 so that it urges the tabs 464, 464' apart, as shown in Fig. 57. This urges the plates 462, 462' inwardly so as to bias the pawls 441, 441' out of engagement with the ratchets and into abutment with stop pins 436, 436' fixed to the internal wall 431. (The inner springs 447, 447' provide lost motion which permits delayed disengagement of the pawis from the ratchets.) The mounting base 360 cart then be rotated in either direction until it is angled obliquely downwardly towards the ground, ready to receive the frame element as shown in Fig. 58.

The ring 423 is then released so that the chamfered end 422 of the bolt is urged against the front face of the protection plate 403 (Fig. 56B). In this position of the bolt, the wedge 426 is disengaged from between the tabs 464, 464' so that the tabs return to their rest position as shown in Fig. 58 and the pawis are urged into engagement again with the ratchets.

As the mounting base 360 is rotated upwards towards the vertical position, the chamfered end of the bolt slides along the front face of the protection plate 403 and one of the two pawls is deflected against the oblique surfaces of the teeth of the corresponding ratchet while the other pawl slides along the corresponding smooth surface 406 or 408. Once the mounting base reaches the vertical position (Fig. 53), each of the pawis abuts against the radial surface of the last tooth of its respective ratchet, preventing further rotational movement in either direction, while the bolt 421 engages in the aperture 404 to provide additional security against inadvertent release.

During disassembly of the framework, a cord may be tied between the rings 423 of the respective bolts of Iwo corresponding installation tools arranged on opposite sides of the arch, so that by pulling on the cord, both pivot mechanisms can be released simultaneously to allow a frame element mounted between the tools to be lowered to the ground, preferably controlled by a rope attached to its uppermost point.

First movement mechanism Referring to Figs. 44-51 B, the movement mechanism 303 of the first installation tool 300 comprises a drive pinion 470 having rounded teeth 471 which extend through a slot 357 in the backplate 306 of the tool body so as to engage the rectangular apertures 43 or 43' in the right-hand flange of the first post 40 or third post 40', forming a rack-and-pinion mechanism. (Both posts are symmetrical, with corresponding apertures in each flange, so that they can be cut to length and installed either way up.) For clarity, the section of Fig. 45 is taken at X45 of Fig. 44 through the mechanism, but at X45' of Fig. 44 through the corresponding apertures of the backplate and the post.

The drive pinion 470 provides a positive, infinitely adjustable, reversible drive both up and down the post, and is driven by a worm 480 which engages a worm wheel 472. The worm prevents the tool from slipping back down the post until it is driven in the reverse direction. The drive pinion 470 and worm wheel 472 are formed as a unitary component or solid assembly and mounted coaxially on a bearing 473, the bearing being mounted between spacers 474, 474' on a first shaft 475 which is supported in the side wafls 351, 352 of the tool body.

The side walls 351, 352 are extended to form arcuate portions 353, 353', and a front cover 490 comprising a flat web 491 and two lateral, forwardly projecting arcuate flanges (of which the right-hand flange 492 can be seen in Fig. 45) is screwed to the front casing 308 of the tool between the arcuate portions 353, 353' of the sidewalls so that a slot is defined between each flange and the corresponding arcuate portion of the sidewall.

The worm 480 is fixed to a second shaft 481 (or formed integrally with it), which is mounted for rotation in a rear bearing 482, the rear bearing being pressed into a housing 483 on the backplate 306, which housing is cut away at its lower right hand edge to accommodate the teeth of the pinion. The forward end of the worm shaft 481 carries a small spur gear 484 (either keyed to the shaft 481 or cut integrally with it) and is supported at its extremity in a bearing 485, which is pressed into a housing 493 on the flat web 491 of the front cover and retained by a plate 494.

A third shaft 476 is mounted in parallel with the first shaft 475 between the side walls 351, 352, and carries a pair of ratchet wheels 500, 500' together with a right-hand (downward) drive lever 520 and a left-hand (upward) drive lever 520', each component being mounted on a bearing for rotation about the shaft 476, the left-hand components being retained axially in position by a spacer 477.

Each ratchet wheel is a unitary component or solid assembly comprising a circular ratchet 501, 501' and a bevel gear 502, 502', both parts being arranged coaxially on their respective bearing 503, 503', both ratchets 501, 501' being arranged so that their teeth face upwards at the front of the tool.

An intermediate cluster gear assembly 504 comprising a spur gear 505 and a bevel gear 506, both gears being formed as a unitary component or assembled solidly together, is mounted for rotation about a bearing 507 on a fourth shaft 508 so that the spur gear 505 engages the small spur gear 484 on the worm shaft 481, and the bevel gear 506 engages the inwardly facing bevel gears 502, 502' of the two ratchet wheels 500, 500', which rotate together in opposite directions. The fourth shaft 508 is mounted non-rotatably in parallel with the worm shaft 481 between a mounting block 510 on the backplate 306 and a corresponding mounting block 495 on the flat web 491 of the front cover, and has a tubular structure 509 in its centre which provides a transverse aperture through which the third shaft 476 can pass and also functions as a spacer to separate the bearings of the two ratchet wheels.

Each drive lever 520, 520' comprises a flat, generally triangular plate 521, 521' which extends through the respective slot defined between one flange 492 of the front cover and the corresponding arcuate portion 353, 353' of the side wall of the tool body, with a second, curved cover plate (not shown) being arranged to cover the gap between the left-hand side wall and drive lever. Each plate 521, 521' has a drive socket 522, 522' at one corner, a spool and bearing assembly 530, 530' at its second corner, and a ratchet assembly 540, 540' at its third corner.

The right-hand drive lever 520 will now be described in detail, the corresponding parts of the left-hand drive lever 520' being similar. Referrin9 particularly to Figs. 51A -51B, the drive socket has an internally threaded portion 523 at its base, which is adapted to receive a corresponding external thread at the inner end of the tubular drive handle 550 (Figs. 5 -7). This allows the drive handle to be screwed into the socket so that it can be operated safely from ground level by a cord 13 tied through a hole at its outer end.

The spool and bearing assembly comprises a narrow spool 531 with a bevelled retaining flange 532, arranged coaxially with the bearing 533 which receives the shaft 476. Referring to Fig. 44, a small steel cord 534 (534') is attached at its upper end to the spool, and at its lower end to a tension spring 535 (535') which is fixed under tension to the tool body. As the respective lever is depressed to its fully actuated position (shown in dotted lines 520", Fig. 45), the steel cord 534 (534') is wound onto the spool, tensioning the spring 535 (535'), which returns the handle to its rest position as shown in Figs. 44 and 45 after each stroke. Downward movement of the lever is limited by abutment with an upper edge 354 of the front casing 308.

The drive lever plate 521 is provided with a pair of fixed pivot pins 524, 525, a small stop pin 526 and a large stop pin 527. The ratchet assembly 540 comprises a drive pawi 541 (541') with a short tab 542 extending from its proximal end, which is mounted on the pivot 524 and biased into contact with the corresponding circular ratchet 501 (501') by a pawl control lever 543 mounted on the second pivot 525. The pawl control lever 543 has an elongate limb with a hole at its distal end 544, and a short, cranked limb 545 which defines an abutment surface 546 extending radially from its pivot axis. A tension spring 547 is arranged between the hole in the distal end 544 of the pawl control lever and a corresponding hole in the tab 542 of the drive pawl.

The elongate limb of the pawl control lever is biased into abutment with the small stop pin 526 by a torsion spring 548 so that as the drive lever 520 is depressed, the elongate limb of the pawl control lever 543 moves away from the ratchet 501 and the tension spring 547 urges the drive pawl 541 into engagement with the ratchet, as shown in Fig. 46.

The return spring 535 provides a heavier spring force than the tension spring 547 and torsion spring 548 of the ratchet assembly. As the drive lever 520 is returned to its rest position by the return spring 535, the abutment surface 546 of the pawl control lever contacts a fixed web 355 extending from the backplate 306, rotating the short limb 545 until it abuts against the large stop pin 527 to define the rest position of the drive lever. In this position, the tension spring 547 urges the drive pawl 541 out of engagement with the ratchet 501, as shown in Fig. 45. The tension spring 547 provides lost motion, allowing delayed release of the drive pawl 541 from the ratchet.

The mechanism is assembled by first installing the drive pinion 470 by passing the first shaft 475 through the side walls of the tool body, and then inserting the second and fourth shafts 481, 508, carrying their respective components, into their respective rear mountings on the backplate. The ratchet wheels 500, 500' and drive levers 520, 520' are then installed by passing their mounting shaft 476 through the side walls of the tool body and through the central tubular structure 509 of the fourth shaft, before the front cover 490 is fixed in position with the forward ends of the second and fourth shafts 481, 508 being received respectively in the housing 493 and mounting block 495.

The bearing 485 is then pressed into the annular space between the forward end of the worm shaft 481 and the housing 493, and its retaining plate 494 is screwed to the housing. Finally, the second curved cover plate (not shown) is fixed over the gap between the left-hand sidewall 352 and the flat plate 521' of the left-hand drive lever.

To dismantle the assembly, the front cover 490 is pulled away from the tool body together with the bearing 485.

To drive the tool 300 up the post, the handle 550 is inserted in the left-hand (upward) drive socket 522' and repeatedly pulled down in a pumping action against the return force of the tension spring 535'. The corresponding right-hand drive lever 520 is biased to its rest position by the return spring 535 so that its drive pawl 541 is held in the disengaged position (Fig. 45), allowing the right-hand ratchet wheel to rotate in the reverse direction as the left-hand ratchet wheel 500' is driven round by the corresponding left-hand ratchet mechanism.

The gears transmit the drive force from the drive lever to the pinion wheel, providing an upward movement through approximately one aperture 43, 43' of the post for every downward stroke of the handle. The tool is reversed down the post by inserting the handle into the right- hand (downward) drive socket 522 and operating the right-hand drive lever in a similar way.

In the example illustrated, the apertures 43' of the third post 40' are arranged at a pitch d10 of about 33mm. In practice, it may be preferred to adapt the gear ratio to provide more rapid movement and less mechanical advantage.

In an alternative embodiment, the manually operated gear train may be replaced by a reversible electric motor arranged to rotate the drive pinion through suitable reduction gearing, which may also incorporate a worm gear so that the tool is safely supported at all times against inadvertent downward movement. Such adaptations are within the purview of those skilled in the relevant art.

On sites without a mains electricity supply, two such motorised tools may then be powered by a small portable generator which also provides power for a drill and an angle grinder as well as a circular saw for cutting the panels.

Preferably, the motors of both of the tools are adapted to be controlled via extension leads or wireless transceivers from a common control box, so that both tools can be simultaneously advanced up or down their respective posts on either side of the arch while the operator observes the operation from a convenient position.

The movement mechanism of the tool can be any mechanism suitable for controlling the movement of the tool up and down towards and away from the soffit, and need not be adapted to drive the tool up and down. The releasable mounting mechanism of the tool can be any mechanism suitable for releasably mounting the tool for controlled movement towards the soffit.

For example, instead of being adapted for mounting on a post which forms part of the finished framework, the tool may be adapted to be mounted on the structural lining (e.g. concrete or cast iron segments) of a tunnel, or on a rack attached to the structural lining. Alternatively, the movement mechanism may incorporate a straight or curved rack which is releasably mounted at the side of an arch or tunnel by the releasable mounting mechanism so that the tool can move up and down on the rack.

The installation tool attachment means of the frame elements need not compnse apertures in the frame elements, and the frame element attachment mechanism of the tool can comprise any means suitable for attaching one end of the flexible frame element to the tool; for example, it could grip the flexible frame element externally, or could present an aperture into which the end of the flexible frame element is inserted.

Second movement mechanism Referring to Figs. 80 -11 3B, in a second, alternative embodiment of the installation tool, a second movement mechanism 600 is adapted to engage the rectangular apertures 102 in the left-hand flange of the second post 100 of Fig. 18.

For clarity, the post 100 is shown sectioned through the apertures 102 of its left-hand flange in each of Figs. 83A, 84A, 85A and 88, and the respective sidewalls 351', 352' are omitted from all of the side (sectional) views.

Fixed parts Referring to Figs. 80 -85A, the mechanism comprises various moving components which are mounted respectively on a left-hand wall 601, a right-hand wall 602, and a right-hand upper wall 603. A separator wall 604 is fixed at its upper and lower ends mid-way between the left-hand and right-hand walls 601, 602. All four walls 601, 602, 603, 604 are mounted in parallel on the backplate 306' of the tool body between the left-hand sidewall 352' and the right-hand sidewall 351'.

A lower aperture 605 is formed in the backplate 306' between the left-hand and right-hand waIls 601, 602, the centre portion of the separator waIl 604 being cut away adjacent the aperture. First and second upper apertures 606, 607 are formed in the backplate 306' between the left-hand wall 601 and the right-hand upper wall 603.

A window 608 is also formed in the backplate 306' and covered by a thin steel plate 609 fixed to the rear surface of the backplate, so as to provide clearance for the moving parts of the toggle mechanism.

An upper pawl stop 610 and lower pawl stop 611 are fixed between the left-hand wall 601 and right-hand upper wall 603, respectively adjacent the first and second upper apertures 606, 607. A lower drive lever stop 612 is fixed to the backplate, above the separator wall and between the left-hand and right-hand walls 601, 602, and an upper drive lever stop pin 613 is fixed between the left-hand and right-hand walls 601, 602.

A right-hand leg stop pin 614 is fixed between the separator wall 604 and the right-hand wall 602, and a left-hand leg stop pin 615 is fixed between the separator wall 604 and the left-hand wall 601. A ratchet pawl stop pin 616 is fixed between the left-hand and right-hand walls 601, 602.

The right-hand wall 602 is provided with a notch 617 (a similar notch is formed in the left-hand wall), and with a cutout which provides an abutment surface 618 at its upper edge.

The left-hand wall 601 is also provided with fixed, upper and lower stop pins 619, 620; a fixed spring mounting post 621; three fixed pivot pins 622, 623, 624; and two short, arcuate slots 625, 626 which are radiused respectively about the pivot pins 623 and 624.

The right-hand wall 602 is provided with corresponding fixed, upper and lower stop pins 627, 628; a fixed spring mounting post 629; three fixed pivot pins 630, 631, 632; and two short, arcuate slots 633, 634 which are radiused respectively about the pivot pins 631 and 632.

In addition, the right-hand wall has a round mounting hole 635 and two short stop pins 636, 637.

The left-hand and right-hand walls 601, 602 are also provided with three pairs of aligned round mounting holes 638, 639; 640, 641; and 642, 643, the right-hand mounting hole 641 being countersunk. Both walls are radiused about the mounting holes 642, 643. Corresponding holes 648, 649, aligned with the mounting holes 642, 643, are formed respectively in the right-and left-hand side waIls 351', 352'.

Two pairs of aligned round mounting holes 644, 645; and 646, 647 are formed in the left-hand wall 601 and the right-hand upper wall 603, both of the right-hand mounting holes 645, 647 being countersunk.

Referring also to Figs. 86A -87, a pressed and welded steel frame 650 with rear mounting flanges 651 defines a slideway comprising a pair of parallel grooves 652, with a slot 653 midway between the grooves. A circular mounting plate 654 is positioned to the left of the slideway (when viewed from the front of the tool, i.e. looking towards the post), with a round mounting hole 655 in its centre. The flanges 651 are spot-welded or riveted to the backplate 306' as shown in Fig. 81 so that the mounting plate 654 lies in front of the window 608.

The portion 658 of the frame supporting the mounting plate forms two, upper and lower right-hand abutment surfaces 656, 657, and two corresponding upper and lower left-hand abutment surfaces 656', 657'.

Pawl assemblies Referring to Figs. 1 06A -1 09D and to Fig. 88, an upper pawl 660 comprises a steel plate with a central mounting hole 661; an outwardly extending triangular portion which defines an abutment surface 662; a radial stop surface 663; a short pivot pin 664; and a post 665 with a second pivot pin 666 extending from its flat distal end. It is mounted between a washer 667 and a spacer 668 on a pivot pin 669 between the upper pair of mounting holes 644, 645, with the countersunk head of the pivot pin 669 lying flush with the right-hand upper wall 603, and secured (like most of the other pivotally mounted components disclosed herein) with an external circlip and washer, the circlip engaging in an annular groove close to the distal end of the pivot pin. In its installed position, the post 665 extends past the radiused edge of the right-hand upper wall 603 50 that the pivot pin 666 extends between the right-hand upper wall 603 and the frame 650.

A lower pawl 670 comprises a steel plate with a central mounting hole 671; an outwardly extending portion which defines an abutment surface 672; a stop surface 673; and a short pivot pin 674. It is mounted between its washer 675 and spacer 676 on a pivot pin 677 between the second pair of upper mounting holes 646, 647, with the countersunk head of the pivot pin 677 again lying flush with the right-hand upper wall 603.

The two pawis are linked by a link bar 680 which is pivotably mounted between the respective pivot pins 664, 674. The link bar synchronises the pivotal movement of the two pawis between a first position (Fig. 88) and a second position (not shown).

In the first position, the lower pawl 670 is rotated to its inoperative position while the abutment surface 662 of the upper pawl 660 is extended to engage in an aperture 102 of the post. The stop surface 663 abuts against the upper pawl stop 610, preventing further rotation of the pawl 660 and thus supporting the weight of the tool on the post.

In the second position, the upper pawl 660 is rotated to its inoperative position while the abutment surface 672 of the lower pawl 670 is extended to engage in an aperture 102 of the post. The stop surface 673 abuts against the backplate 306' and the lower pawl stop 611, preventing further rotation of the lower pawl 670 and thus supporting the weight of the tool on the post.

The two pawis are moved alternately between the first and second positions by a toggle mechanism, which will now be described.

Toggle mechanism A rotary, angled bracket 681 having a mounting hole 682 and a larger, circular aperture 683 is pivotably mounted via its mounting hole 682 on the pivot pin 666 of the upper pawl so that it rotates freely on the flat end surface of the post 665.

Referring to Figs. 11 OA -11 3B and to Figs. 88 -90B, a catchplate assembly comprises a catchplate 690 pivotably mounted on a slide plate 700. It should be noted that in Fig. 89, the frame 650 is partially cut away to show the positional relationship between the moving parts.

The slide plate 700 comprises a flat steel plate 701 having a seat 702 with a central mounting hole 703, a spring mount 704, and a fixed post 705 with a pivot pin 706 extending axially from its flat distal end.

The catchplate 690 comprises a flat steel plate 691 having an elongate pivot pin 692 extending from its reverse surface and a spring mounting hole 693 at its lower end. The upper end of the catchplate is shaped to form a spear point with symmetrical, smoothly curved edges, each edge supporting a thin, flat spring steel strip 694, 694'. Each strip is spot-welded at its proximal end 695, 695' to the plate 691 so that it is resiliently biased into contact with its respective curved edge, and terminates at its distal end in a rounded end 696, 696'. Two recesses 697, 697' are formed in the opposite edges of the plate, each recess having a slightly narrowed neck defined by a small protuberance 698, 698' opposite the rounded end 696, 696' of the respective strip.

The catchplate is mounted via its pivot pin 692 in the mounting hole 703 of the slide plate so that it is free to rotate on the flat surface of the seat 702, and biased by a tension spring 699 mounted between the respective spring mounts 693, 704 into a rest position in which it is aligned with the longitudinal axis of the slide plate (Figs. 90A, 90B).

S The slide plate is slidably mounted for reciprocal movement in the grooves 652 of the frame 650, so that the circlip on the distal end of the pivot pin 692 is accommodated by the slot 653.

A toggle bar assembly 710 comprises a flat bar 711 with a first, central pivot pin 712 extending in parallel with two posts 713, 713' from one side, and a second pivot pin 714 extending from its other side at one end. A straight, round section toggle bar 715 carrying a telescopic compression spring 716 is fixed to a base portion 717, which is pivotably mounted on the second pivot pin 714 so that the toggle bar 715 can freely rotate in the same plane as the flat bar 711.

The first pivot pin 712 is pivotably mounted in the central mounting hole 655 of the circular mounting plate 654 of the frame 650, so that the bar 711 lies flat agains the mounting plate 654 with the posts 713, 713' extending past the mounting plate 654 towards the slideway. The bar 711 is thus free to rotate between a first (clockwise) position as shown in Figs. 88 and 89, in which the posts 713, 713' abut respectively against the lower right-hand and upper left-hand abutment surfaces 657, 656'; and a second (anticlockwise) position (not shown), in which the two posts 713, 713' abut respectively against the upper right-hand and lower left-hand abutment surfaces 656, 657'.

The distal end of the toggle bar 715 is received in the circular aperture 683 of the rotary bracket 681 so that the spring 716 is compressed between the bracket 681 and a flat seat formed on the base portion 717.

In the first (clockwise) position of the toggle bar assembly, the upper pawl 660 is thus biased by the spring 716 towards its first (operative) position as shown; while in the second (anticlockwise) position of the toggle bar assembly, the upper pawl is biased by the spring 716 towards its second (inoperative) position, simultaneously rotating the lower pawl 670 towards its respective operative position. The upper pawl 660 and the toggle bar 715 and spring 716 thus form a bistable system in which the spring 716 provides lost motion, biasing either one or the other of the two pawis into engagement with the apertures 102 of the post white resiliently compressing to allow the pawl to be deflected by the flange 101 of the post as the tool slides upwards.

The slide plate 700 is driven up and down in the slideway by a drive bar 707 which is mounted at its distal end on the pivot pin 706 so that it extends out through the open side of the frame 650, between the left-hand portion 658 and the slideway. The proximal end of the drive bar is attached to the drive lever as described below.

As the drive lever returns to its rest position, the slide plate travels up the slideway of the frame, and the spear pointed upper end of the catchplate intercepts the uppermost of the two posts 713 or 713' of the toggle bar assembly, deflecting the catchplate to one side or the other against the restoring force of its tension spring 699 until the respective post 713 or 713' passes the rounded end 696 or 696' of the respective spring steel strip. As the motion of the slide plate is reversed with the downward stroke of the drive lever, the post 713 or 713' is captured in the recess 697 or 697', so that the catchplate pivots outwards against its tension spring 699 as the slide plate descends, rotating the flat bar 711 of the toggle bar assembly as it goes. The toggle bar 715 rotates about the pivot 714 as the bar 711 rotates, so that the spring 716 is compressed telescopically against the rotary bracket 681, which rotates at the same time about its pivot pin 666.

The bistable toggle mechanism reaches its dead centre point as the three pivots 712, 714, 666 move into alignment. As it passes this rotational position, the spring 716 flips the mechanism into the opposite, stable state, in which the spring 716 biases the two pawls 660, 670 towards their opposite state. As soon as the movement of the toot brings the operative pawl into alignment with an aperture 102 of the post, the pawl is rotated by the spring 716 so that its respective abutment surface extends through the post flange to support the tool.

The drive lever can then be returned to its rest position, ready for the next downward stroke, as described below.

The length of the drive bar 707 is approximately 60mm between its two pivot axes, and is adjusted during prototyping so that the toggle mechanism flips just before the drive lever 720 reaches its lowest position.

As the slide plate 700 begins to move back up the slideway, the post 713 or 713' is released from the respective recess 697, 697' in the catchplate against the light spring pressure of the spring steel strip 694 or 694', and the catchplate 690 is returned to its axially aligned, rest position by the tension spring 699.

The spring steel strips 694, 694' provide a light retaining force which retains the post 713 or 713' in its respective recess if the action of the drive handle should be reversed half-way through a stroke, so as to avoid the danger of the toggle mechanism being marooned in its dead-centre (metastable) position. The catchplate 690 is located close to the backplate 306' of the tool, so the window 608 is provided to give it sufficient clearance as it rotates.

The apertures 102 in the post are arranged at a pitch d8 (Fig. 83A), while the upper and lower pawls 660, 670 are spaced apart in the longitudinal direction of the post by a distance (d8 / 2). As the tool moves up or down the post, each successive aperture is thus engaged consecutively by one, then the other of the pawis, so that the respective inoperative pawl lies mid-way between two apertures.

In the example shown, the distance d8 is about 100mm.

The respective downwardly facing abutment surfaces 736, 736' of the two legs are also spaced apart in their respective active positions in the longitudinal direction of the post by a distance (d8 I 2) and, like the pawis, engage the apertures 102 alternately, so that the tool is lifted or lowered in incremental steps, each time through a distance of (d8 I 2), as will now be described.

Lift mechanism I0 Referring to Figs. 91A -926 and 96A -97B, the tool is lifted incrementally up the post by a drive lever assembly comprising a drive lever 720, a right-hand leg 730 and a longer, left- hand leg 730'.

iS The drive lever comprises a flat plate 721 with a round pivot hole 722, right-and left-hand fixed pivot pins 723, 723', and an elongate post 724 which has a small pivot pin 725 extending axially from its flat, distal end. The front edge of the plate (i.e. the edge facing the front of the tool, away from the backplate) forms an arcuate ratchet 726 with upwardly facing teeth, which is radiused about the pivot hole 722. A cylindrical socket 727 having an internal thread 728 at its base and a spring mounting tab 729 on its upper edge is mounted above the ratchet.

Each leg compnses a flat plate 731, 731' with a round pivot hole 732, 732' at its upper end and a shorter, offset foot portion 733, 733' at its lower end. Each foot comprises a first, rearwardly facing abutment surface 734, 734', arranged below a rearwardly extending heel 735, 735' which defines a second, downwardly facing abutment surface 736, 736'.

Each plate 731, 731' is provided as shown with an elongate, curved slot 739, 739', while the lower portions of its front and rear edges are contoured as shown to define front and rear, outer guide surfaces 737, 737' and 738, 738'.

Each slot 739, 739' defines a rear inner guide surface 740, 740'; an upper front surface 741, 741'; a front transition surface 742, 742'; and a lower front guide surface 743, 743'.

The right-and left-hand legs 730, 730' are mounted respectively on the right-and left-hand pivot pins 723, 723' via their pivot holes 732, 732', and the drive lever 720 is mounted between the left-hand and right-hand walls 601, 602 on a pivot pin 719 which extends through the mounting holes 638, 639 and pivot hole 722. In their installed position, the respective foot portions 733, 733' of the two legs lie, one above the other behind the cut-away central portion of the separator waIl 604 so that the plates 731, 731' are slidingly received between the separator wall 604 and, respectively, the right-and left-hand walls 602, 601, and the heels 735, 735' extend from the rear of the backplate via the lower aperture 605.

The post 724 extends through the notch 617 in the right-hand wall to terminate in the same longitudinal plane as the drive bar 707, whose proximal end is pivotably mounted on the pivot pin 725 so that the catchplate assembly 690, 700 is driven up and down by the drive lever 720.

The drive lever is biased upwardly by a return spring 718 (fixed between the tool body and the tab 729) towards its rest position, in which its upper edge abuts against the drive lever stop pin 613 as shown. This allows the drive lever handle (similar to that of the first embodiment) to be screwed into the socket 727 and operated by a cord from ground level against the restoring force of the spring. In its lower position (not shown), the rear edge of the drive lever abuts against the lower stop 612.

The outer rear guide surfaces 738, 738' cooperate respectively with the stop pins 614, 615 to limit the rearward extension of the legs through the full arc of rotation of the drive lever, so that neither of the legs can fall out of the lower aperture 605 and get damaged as the tool is dismounted and transported.

Referring to Figs. 104A -105B, each leg is rearwardly biased (i.e. towards the backplate 306' and post 100) respectively by a right-or left-hand bias arm 750, 750', which is mounted on its respective pivot pin 632, 624 so that its post 751, 751' extends through the arcuate slot 634, 626 to engage the corresponding outer front guide surface 737, 737' of the leg. Each bias arm is biased towards the backplate 306' by a tension spring 752, 752' attached between its spring mounting tab 753, 753' and the respective spring mounting post 629, 621.

The front guide surfaces 737, 737' of the two legs are shaped to define an inoperative and an operative condition of each bias arm 750, 750' as follows: Inoperative condition As the drive lever approaches its upper position as shown, the post 751, 751' of the bias arm abuts against the rear end of the arcuate slot 634, 626 while the respective leg is free to move between an extended position (the heel being extended via the lower aperture 605 to engage the flange 101 of the post) in which the front guide surface 737, 737' departs from the post 751, 751' of the bias arm; and a retracted position (the heel being retracted to clear the flange 101 of the post) in which the front guide surface 737, 737' lies loosely against the post 751, 751' of the bias arm.

Operative condition As the drive lever approaches its lower position (not shown), the front guide surface 737, 737' comes slidingly into contact with the post 751, 751' of the bias arm, so that both legs are resiliently biased by the springs 752, 752' into engagement with the flange 101 of the post or (if the tool is dismounted from the post) with the fixed stop pins 614, 615.

In use, the rearwardly facing abutment surfaces 734, 734' engage the flange 101 of the post to limit the depth of penetration of the heel 735, 735' into the respective aperture 102.

Up/down selector mechanism The mechanism for selecting the direction of motion of the tool up or down the post will now be described.

Referring to Figs. 98A -99C and Figs. 1 03A -B, a pair of right-and left-hand control arms 760, 760' are mounted, each on its respective pivot pin 631, 623 so that a post 761, 761' at one end of each control arm extends through the corresponding arcuate slot 633, 625 in the right-or left-hand wall 602, 601 to engage the corresponding elongate, curved slot 739, 739' of the respective right-or left-hand leg. An oppositely directed, spring mounting tab 762, 762' is provided on the opposite end of each control arm from the post.

A corresponding pair of right-and left-hand toggle levers 770, 770' (both identical in form) are mounted, each on its respective pivot pin 630, 622. Each pivot pin extends respectively through a mounting hole 771 with a spacer 772, so that the toggle lever is spaced apart from the corresponding right-or left-hand wall 602, 601. Each toggle lever is thus pivotable in an arc towards the backplate 306', outside the corresponding control arm 760 or 760' (and outside the bias arm 750, 750'), between an "IJID" position (illustrated), in which it abuts its lower stop pin 628, 620; and a "DOWN" position (not shown), in which it abuts its upper stop pin 627, 619.

A spring mounting collar 773 is arranged at the distal end of each toggle lever, with a post 774, 774' extending axially from the distal end of each collar. A tension spring 775, 775' ts mounted between each collar 773 and the spring mounting tab 762, 762' of the corresponding control arm 760 or 760', so that each toggle lever 770, 770' cooperates with its corresponding control arm 760 or 760' to form a second, "up/down" bistable toggle mechanism.

U(J1077 position In the "UP" position of the up/down toggle mechanism (illustrated), the post 761, 761 l of each control arm is resiliently biased towards the backplate 306' by the spring 775, 775', which also biases the toggle lever 770, 770' into abutment with its respective lower stop pin 628, 620.

This causes the post 761, 761' to resiliently engage the rear inner guide surface 740, 740' of the respective right-or left-hand leg through the whole arc of rotation of the drive lever, urging each leg into abutment with the flange 101 of the post.

Like the upper and lower pawis, the downwardly facing abutment surfaces 736, 736' of the two legs are spaced apart in the longitudinal direction of the post by a distance (d8 / 2), so that when the tool is resting on the upper pawl 660 (engaged in an aperture 102 of the post) with the drive lever 720 in its uppermost (rest) position, the heel 735 of the right-hand leg 730 will engage in a corresponding, lower aperture 102, as shown.

As the drive lever handle (not shown) and drive lever 720 are moved downwards by the user, the tool body and its attached frame element are jacked up on the right-hand leg until the bistable toggle mechanism (mounted on the frame 650) passes its dead-centre point and the state of the two pawls 660, 670 is reversed. The lower pawl 670 now engages in the aperture 102 just vacated by the upper pawl 660. As the drive lever begins to return towards its rest position on the upstroke of its handle, the weight of the tool is transferred from the right-hand leg 730 to the lower pawl 670. As the drive lever approaches its rest position, the heel 735' of the left-hand leg 730' then engages in the aperture 102 just vacated by the heel of the right-hand leg, ready for the next downstroke of the handle, while the heel of the right-hand leg slidingly abuts the flange 101 of the post between the adjacent apertures.

"DO WN" position In the UDOWNn position (not shown) of the up/down toggle mechanism, the post 761, 761' of each control arm is resiliently biased away from the backplate 306' by the spring 775, 775', which also biases the toggle lever 770, 770' into abutment with its respective upper stop pin 627, 619.

As the drive lever 720 begins to descend from its rest position, the post 761, 761' of each control arm resiliently engages the lower front guide surface 743, 743' of its respective leg, urging the leg forwards, away from the backplate 306' and out of engagement with the post 100. The leg which initially lies adjacent the respective aperture 102 thus passes by the aperture without engaging in it.

(It will be recalled that in the upper position of the drive lever, the bias arm 750, 750' is in its inoperative condition, so that the leg is free to move forwards, away from the post.) As the drive lever 720 continues to move downwards, each bias arm 750, 750' enters its operative condition as it begins to engage the corresponding outer front guide surface 737, 737', biasing each respective leg into sliding contact with the flange 101 of the post. At the same time, the post 761, 761' of the corresponding control arm passes across the front transition surface 742, 742', during which time the leg is biased both rearwardly by the bias arm, and forwards (away from the backplate 306') by the control arm.

As the drive lever moves towards its lower position, the post 761, 761' of the control arm contacts the forward end (i.e. the end remote from the backplate 306') of its arcuate slot 633, 625, which restrains the post against further forward movement. Continued downward movement of the drive lever 720 brings the transition surface 742, 742' of each leg away from the respective post 761, 761', and as the drive lever nears its lower position, the upper front surface 741, 741' of the upper, widened portion of the curved slot 739, 739' provides sufficient clearance for the heel 735 of the other one of the legs (which initially lay mid-way between two adjacent apertures 102) to enter into the aperture 102 which initially lay immediately below it.

The various components are dimensioned so that the total range of movement of the downwardly facing abutment surfaces 736, 736' of the two legs in the longitudinal direction of the post over the full arc of rotation of the drive lever is slightly greater than the incremental lift distance (d8 I 2). The tool is thus lifted slightly as the downwardly facing abutment surface 736 or 736' of the said, other one of the legs engages the base of the aperture 102 and the drive lever moves towards its maximally depressed position. This slight lifting frees the respective pawl 660 or 670 from engagement with the post, so that the bistable toggle mechanism (mounted on the frame 650), which flips state just before the dnve lever bottoms out, again reverses the state of the two pawls 660, 670.

The pawl which was previously supporting the weight of the post is now disengaged from the post flange, leaving the other pawl 660 or 670 mid-way between two apertures 102. As the drive lever returns to its rest position, the tool and its attached frame element therefore descend under gravity through the incremental distance (d8 I 2) until the said, other one of the pawis engages in the aperture immediately below it. The handle is operated again in the same way to produce further, incremental downward movement.

As noted above with reference to Figs. 16A and 59, th e pawls 660, 670 require a slight upward movement of the tool in order to release them from the flange 101 of the post. In order to allow this small upward movement to occur when the frame element is attached to the post, the keyhole slots in the frame elements are elongated by a small distance dg.

Referring to Figs. 93A -94, the up/down direction of movement of the tool is selected by means of an up/down selector lever 780, comprising a pair of arms 781, 781' joined by a front bar 782 with a knob 783. Each arm has a corresponding pivot hole 784, 784' which receives a pivot pin 789, the pivot pin being passed through all four mounting holes 649, 642, 643, 648 and fixed with a circlip on the outer surface of the right-hand side wall 351'.

In the installed position, the two arms 781, 781' embrace the right-and left-hand walls 602, 601, with the left-hand arm 781' lying just inside the left-hand side wall 352', and the front bar 782 lying just in front of the respective radiused edges of the right-and left-hand walls 602, 601.

A ratchet selector lever 790 is also mounted on the pivot pin 789 beside the up/down selector lever 780, as further described below.

The distal end of each arm 781, 781' has a slot 785, 785' which receives the distal end of the post 774, 774' of the respective right-or left-hand toggle lever 770, 770'. Each up/down toggle mechanism is reversed by moving the knob 783 up (for the "UP" condition, as shown) or down (for the DOWN"conditiofl, not shown), causing the post 774, 774' to slide reciprocally along the slot 785, 785' as the mechanism passes its dead-centre position and reverses. The spring 775, 775' thus also functions to retain the lever 780 in the "UP" or "DOWN" position.

Ratchet Since the second movement mechanism provides incremental rather than infinite positional adjustment, a ratchet mechanism is provided for applying final pressure to the frame element, prior to attaching it to the post. The ratchet is only engaged after sufficient pressure has been exerted against the frame element to prevent any further full increment of upward movement of the tool through the distance (d8 / 2), and provides fine adjustment of the position of the drive lever 720 and hence of the tool body, supported on one or other of the two legs 730, 730'.

Referring to Figs. 100A-102B, the ratchet pawl 800 has a pivot hole 801 with a pair of spacers 802, 802', and an elongate post 803 with a spring mounting collar 804 at its distal end. The pawl is mounted on a pivot pin 805 with a countersunk head between the mounting holes 640, 641 in the left-and right-hand walls 601, 602, so that the post 803 extends through the cutout in the right-hand wall 602. In its engaged condition (not shown), the pawl engages the ratchet 726 on the drive lever, and is restrained by abutment with the stop pin 616. In its disengaged condition as illustrated, the post 803 abuts against the abutment surface 618 of the said cutout.

The position of the ratchet pawl is controlled by a ratchet toggle lever 810 which is mounted in the mounting hole 635 in the right-hand waIl 602 by means of its pivot 811. The toggle lever is pivotable between an engaged position (not shown) in which it abuts against the lower stop pin 637, and a disengaged position in which it abuts against the upper stop pin 636 as shown.

The distal end of the ratchet toggle lever is provided with a spring mounting collar 812, and an elongate post 813 which extends axially from the distal end of the collar. A tension spring 814 is mounted between the collar 812 of the ratchet toggle lever and the corresponding collar 804 of the ratchet pawl, forming another bistable toggle mechanism which resiliently biases both components into the selected position while providing lost motion to allow the ratchet pawl to be deflected by the teeth of the ratchet as the drive lever 720 is depressed.

Referring lastly to Figs. 95A and 95B, the ratchet selector lever 790 comprises a left-hand selector arm 791' and a right-hand support arm 791 joined by a front bar 792 with a knob 793. Pivot holes 794, 794' are formed respectively in the two arms, and the lever is mounted on the pivot pin 789 so that the selector arm 791' lies close to the right-hand arm 781 of the up/down selector lever, and the support arm 791 lies just inside the right-hand side wall 351'.

The selector arm 791' has a slot 795 which receives the distal end of the post 813, so that the ratchet toggle mechanism is disengaged by moving the knob 793 into the downward position as shown, and engaged by moving it up, the post 813 sliding reciprocally along the slot 795 and the spring 814 functioning to retain the ratchet selector lever 790 in the selected position.

Summary

In summary, a preferred embodiment provides a plurality of elongate, flexible frame elements, each protected by an elastomeric shield and engaged frictionally against the curved soffit by hoop stress applied at either end, preferably by a pair of installation tools mounted on posts. Each tool preferably includes a pivoting ratchet which allows the flexible frame element to be formed into an arched shape on the ground and then raised into a vertical plane prior to installation. The frame elements may be fixed to the posts to support them at either end in their installed position, providing a self-supporting, arched framework which relies upon the masonry soffit for its shape and stability. Each frame element may comprise a unitary utop..hatn profile with deformable hinges, each hinge having an associated deformation structure which distributes bending forces evenly during installation. The framework can be installed without specialist access equipment, and the posts may be used to support a temporary mezzanine floor which provides access to the soffit for installation of cooperating, flat lining panels, each panel preferably comprising a foamed plastics body with downwardly directed channels and angularly adjustable, interlocking upper and lower edges.

Instead of the baseplates first described, a single steel beam or the like could alternatively be fixed horizontally along the base of each pier, each post being attached at its base to the beam; alternatively, each pair of posts may be attached, one at either end of a beam arranged transversely across the floor of the arch, so that a suspended floor may be laid across the beams, in which case the beams and posts need not be bolted to the floor. The entire installation may then be accomplished without the use of a drill or nail gun.

Instead of or additionally to the use of shield material, each frame element and/or each column might be made with an integral shield portion which diverts water downwards to the ground and/or to the panels on either side. In the frame elements, the shield portion might also form the integral, plastically deformable hinge portions, which may then be located on the outer side of the frame element. For example, each frame element might comprise a flat strip of steel, aluminium or plastics material arranged adjacent the soffit, with a series of short, rigid box sections extending (integrally or in fixed relation) from its inwardly facing surface. The box sections may be flanged and may provide attachment means (e.g., screw holes or channels) for receiving the lining sheets or panels, which may have flanges as illustrated or alternatively for example may simply slot into the channels. The ends of the box sections may be spaced apart by a sufficient distance that they abut to define a minimum obtuse angle at each hinge portion. The whole frame element (or just the strip) may be galvanised, and the strip may be bent along each edge, inwardly into the arch and/or outwardly towards the soffit, so as to prevent water from running back along its inner surface. Such an integral frame element made from aluminium or plastics material may be very light in weight, and depending on the length and design of the flexible frame element and the availability of access equipment, it may be preferred to install the flexible frame element in low arches or tunnels without using the novel installation tools. Alternatively, the element can be attached at one end and then engaged against the soffit by using just one tool at the other end.

Of course, if the framework is to be used without panels, or if (unusually) the arch is inherently dry, no shields are required.

The invention may be applied to low arches in which the soffit curves upwardly from the ground or from a short distance above the ground, as well as to round, egg-shaped or horseshoe-shaped tunnels and the like in which the soffit and the sides of the structure form a continuous curve, the width of the floor being less than the width of the tunnel at its horizontal diameter. In such cases, the support means may simply comprise steel plates bolted to the floor, or a beam laid transversely across the floor, or alternatively brackets or the like attached above floor level to the inner surface or structural lining of the tunnel, so that the flexible element extends part way around the soffit from side to side of the tunnel or alternatively right around the curve of the tunnel to terminate at the floor at either end.

All of these support means may incorporate or accommodate a screwthread or other adjustment mechanism for forcing the ends of the frame element apart or together (depending on how far the frame element extends around the circumference of the tunnel) so as to induce a compressive hoop stress which urges it outwardly against the inner surface of the tunnel into its installed position. Two frame elements may also be coupled together end-to-end by an expander which induces hoop stress. Such arrangements may be suitable for use for example in installing a waterproof inner lining in underground railway tunnels and station platforms.

The novel framework may also be installed in inclined tunnels, such as escalator (moving staircase) tunnels in underground railway stations, in which case the posts and frame elements may be arranged, either vertically in stepped relation or inclined normally to the axis of the tunnel, and may be supported additionally against downward movement by attachment to the structural lining of the tunnel and/or by additional bracing struts.

Wherever means are disclosed herein for performing a function, that means may comprise any arrangement which is capable of performing that function in its essential aspects as defined by the claims, and is not limited to the specific means described.

The support means can be any arrangement which supports the ends of the frame element securely in the installed position.

In very simple installations, such as in low arches without a hard floor, each of the support means may simply comprise a steel stake driven into the ground, or a hole in the ground into which the respective end of the flexible element is placed (supported in its installed position hard up against the soffit) before the hole is filled with concrete. If preferred, the flexible element may be attached at one or both ends to a bracket which is bolted or otherwise secured directly to the structural lining which forms the inner surface of a tunnel, or to the masonry of a pier or soffit, in which case the brackets may be left permanently in position when the lining and framework are removed for maintenance of the structure. A post or rack may be secured adjacent one or both brackets to receive the installation tool during installation of the flexible element.

The frame element attachment means of the post, and the corresponding attachment means of the frame element, can be any holes, flanges, slots, lugs, portion of the post or frame element or other feature whatsoever, whether limited to that function or providing that function in combination with another essential or inessential function, which facilitates the attachment of the frame element to the post or other support means. Preferably, the attachment means should allow the frame element to be vertically adjusted relative to the post or support means during installation and prior to attachment.

The panel attachment means need not comprise cooperating holes for receiving screws or other fasteners. For example, each frame element could provide a channel into which the edges of the panels or corrugated lining sheets can be inserted; alternatively, the frame elements could be adapted to allow the panels to be hooked on without the use of fasteners.

Claims

1. A system for lining an arched structure; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; the system including a framework for installation within the structure, the framework including a plurality of elongate frame elements, each frame element having first and second ends; charactensed in that each frame element is flexible, such that as it is raised pressingly against the soffit into an installed position, the frame element conforms flexibly to the curvature of the soffit so as to form a self supporting arched configuration; and in that support means are provided respectively at the first and second sides of the structure, the frame element being attachable respectively at its first and second ends to the support means so as to support it in the installed position.

2. A system according to claim 1, characterised in that the support means comprise first and second posts, the posts extending upwardly from the floor respectively at the first and second sides of the structure.

3. A system according to claim 2, characterised in that each frame element is adjustably attachable to the posts such that during installation the frame element may be raised relative to the posts into the installed position, and then may be attached to the first and second posts to support it in the installed position.

4. A system according to claim 3, characterised in that the frame element is adapted to be slidingly engaged with the posts during installation.

5. A system according to claim 2 or claim 4, characterised in that each frame element comprises a series of rigid portions joined end-to-end by hinge portions, and in that each post and each rigid portion comprises an elongate profile having a central, U-shaped portion with oppositely directed lateral flanges, such that the central, U-shaped portion of the rigid portion is adapted to be received in the central, U-shaped portion of the post.

6. A system according to claim 3 or claim 4, characterised in that each frame element is provided with a first series of first apertures and each post is provided with a second series of second apertures, the apertures of one of the series being spaced apart by a distance x, and the apertures of the other series being spaced apart by a distance (x -(xln)), wherein n is a factor of x, such that corresponding ones of the first and second apertures are brought into alignment to define fixing holes for attachment of the frame element to the post at each of a series of incremental displacements of the frame element axially along the post through the distance (x/n).

7. A system according to claim 3 or claim 4, characterised in that at least one installation toot is provided for installing the frame element; the tool including a post engagement mechanism for releasably mounting the toot in sliding engagement with one said post, a frame element attachment mechanism for attaching one end of a frame element to the tool, and a movement mechanism for controlling the movement of the tool up and down the respective post.

8. A system according to claim 7, characterised in that the tool includes a pivot mechanism which permits the frame element to be raised from a substantially horizontal orientation to a substantially vertical orientation after attachment to the tool.

9. A system according to claim 7 or claim 8, characterised in that the tool includes a separation adjustment mechanism for moving the respective end of the frame element towards and away from the respective post.

10. A system according to claim 1, characterised in that each frame element is provided with a flexible, elongate, waterproof shield, the shield being adapted for mounting on the frame element such that after installation the shield extends between the frame element and the soffit.

11. A system according to claim 1, charactensed in that a plurality of panels are provided, each panel having a front surface, an opposite rear, water shedding surface, and at least one attachment portion; and each frame element includes panel attachment means, the panel attachment means being adapted to receive the respective attachment portions of the panels so as to support the panels in an installed position in which each panel is inclined downwardly from an upper edge of the panel to a lower edge of the panel, and in which the rear surface of each panel faces in an outward direction towards the soffit and the front surface faces in an inward direction away from the soffit such that the respective rear surfaces of the panels cooperate to form an effectively continuous water shedding surface.

12. A system according to claim 11, charactensed in that the support means comprise first and second posts, the posts extending upwardly from the floor respectively at the first and second sides of the structure; and each post includes panel attachment means, the panel attachment means being adapted to receive the respective attachment portions of the panels so as to support the panels in an installed position in which the rear surface of each panel faces in an outward direction towards an adjacent inner vertical surface of the structure and the front surface of each panel faces in an inward direction away from the inner vertical surface of the structure, such that the respective front surfaces of the panels are substantially vertically aligned and the respective rear surfaces cooperate to form an effectively continuous water shedding surface.

13. An elongate frame element for installation in an installed position beneath a soffit of an arched structure, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; the frame element having first and second ends, an outer side which contacts the soffit in the installed position, and an opposite, inner side which faces away from the soffit in the installed position; chararacterised in that the frame element is adapted to be supported, only at its first and second ends at respectively the first and second sides of the structure; and in that the frame element comprises a flexible series of rigid portions joined end-to-end by hinge portions, each rigid portion being pivotable during installation about a respective hinge portion through a limited range of movement so as to define an obtuse angle with a respective adjacent rigid portion on the inner side of the frame element, such that the frame element may be raised into its installed position beneath the soffit and upon contacting the soffit may conform to the curvature thereof.

14. An elongate frame element according to claim 13, characterised in that the range of pivotal movement at each hinge portion is limited to prevent the formation of a reflex angle between respective adjacent rigid portions on the inner side of the frame element.

15. An elongate frame element according to claim 14, characterised in that the range of pivotal movement at each hinge portion is limited to define a maximum angle of 180° between respective adjacent rigid portions on the inner side of the frame element.

16. An elongate frame element according to claim 15, characterised in that the frame element adopts a straight line configuration in a rest condition prior to installation.

17. An elongate frame element according to any of claims 13 -15, characterised in that the rigid portions may form a different angle at each hinge portion in the installed position.

18. An elongate frame element according to claim 13, characterised in that each rigid portion comprises an elongate profile having a central, U-shaped portion with oppositely directed lateral flanges.

19. An elongate frame element according to claim 13, characterised in that each frame element includes panel aftachment means, the panel attachment means being adapted to receive respective attachment portions of a plurality of panels so as to support the panels in an installed position in which each panel is inclined downwardly from an upper edge of the panel to a lower edge of the panel, and in which a rear surface of each panel faces in an outward direction towards the soffit and an opposite, front surface faces in an inward direction away from the soffit such that the respective rear surfaces of the panels cooperate to form an effectively continuous water shedding surface.

20. An elongate frame element according to claim 19, characterised in that each rigid portion comprises an elongate profile having a central, U-shaped portion with oppositely directed lateral flanges, and the flanges comprise the panel attachment means.

21. An elongate frame element according to claim 13, characterised in that the frame element comprises a unitary length of material, the unitary length of material comprising an elongate profile having a central, U-shaped portion with oppositely directed lateral flanges, and a plurality of said rigid portions are defined by divisions in the central, U-shaped portion such that each hinge portion comprises a plastically deformable region of the flanges.

22 An elongate frame element according to claim 13, characterised in that the rigid portions are defined in at least one unitary length of material such that each hinge portion comprises a plastically deformable region of the material.

23. An elongate frame element according to claim 21 or claim 22, characterised in that the rigid portions are defined by laser cutting' so as to form adjacent cut surfaces which limit the range of pivotal movement at each hinge portion to define a maximum angle of about 1800 between the respective adjacent rigid portions on the inner side of the frame element.

24. An elongate frame element according to claim 13, characterised in that a plastic deformation element is arranged adjacent each respective hinge portion, each plastic deformation element being spaced apart from the respective hinge portion such that the plastic deformation element is progressively plastically deformed during installation as the obtuse angle between the respective adjacent rigid portions reduces.

25. An elongate frame element according to claim 21 or claim 22, characterised in that a plastic deformation element is formed integrally with the frame element adjacent each respective hinge portion, each plastic deformation element being spaced apart from the respective hinge portion such that the plastic deformation element is progressively plastically deformed during installation as the obtuse angle between the respective adjacent rigid portions reduces.

26. An elongate frame element according to claim 24 or claim 25, characterised in that the plastic deformation element plastically elongates as the obtuse angle between the respective adjacent rigid portions reduces.

27. An elongate frame element according to claim 24, 25 or 26, characterised in that each plastic deformation element is deformable to a first, minor extent by application of relatively little torque to the respective hinge portion, and to a second, relatively greater extent only by application of relatively greater torque.

28. An elongate frame element according to claim 13, characterised in that the frame element is assembled from a plurality of individual rigid portions joined by pivots.

29. An elongate frame element according to claim 13 or claim 28, characterised in that a resilient deformation element is arranged adjacent each respective hinge portion, such that each resilient deformation element is progressively resiliently deformed dunng installation as the respective adjacent rigid portions pivot about the respective hinge portion.

30. An elongate frame element according to claim 29, characterised in that the resilient deformation element is progressively resiliently deformed as the obtuse angle between the respective adjacent rigid portions reduces.

31. An elongate frame element according to claim 29, characterised in that the resilient deformation element is a metal spring.

32. An elongate frame element according to claim 30, characterised in that each resilient deformation element is arranged such that the obtuse angle may be reduced by a first, minor extent by application of relatively little torque to the respective hinge portion, and to a second, relatively greater extent only by application of substantially greater torque.

33. An elongate frame element according to claim 13, characterised in that each hinge portion is formed on the inner side of the frame element.

34. An elongate frame element according to claim 13, characterised in that the frame element includes installation tool attachment means for releasably attaching the first and second ends of the frame element respectively to first and second installation tools such that the frame element may be mounted on the installation tools so as to raise it pressingly against the soffit into the installed position.

35. An elongate frame element according to claim 34, characterised in that each rigid portion is provided with installation tool attachment means such that the frame element may be divided by cutting, and the cut ends may thereafter be mounted on the installation tools.

36. An elongate frame element according to claim 13 or claim 34, characterised in that the frame element includes support attachment means for adjustably attaching the first and second ends of the frame element to support means provided respectively at the first and second sides of the structure.

37. An elongate frame element according to claim 13 or claim 35, characterised in that each rigid portion is provided with support attachment means for adjustably attaching the first and second ends of the frame element to support means provided respectively at the first and second sides of the structure, such that the frame element may be divided by cutting, and the cut ends may thereafter be attached to the support means.

38. A post for use in supporting a flexible, elongate frame element in an installed position beneath a soffit of an arched structure, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; the post being adapted for installation in a substantially vertical position at one side of the structure, and including frame element attachment means for attachment of one end of the flexible frame element in a selected vertical position on the post, and an installation tool mounting structure for releasably mounting an installation tool for sliding movement up and down the post, such that during installation the flexible frame element may be raised by the installation toot relative to the post into the installed position, and then may be attached to the frame element attachment means to support the flexible frame element in the installed position.

39. A post according to claim 38, characterised in that the post includes panel attachment means, the panel attachment means being adapted to receive corresponding attachment portions of a plurality of panels so as to support the panels in an installed position in which a rear surface of each panel faces in an outward direction towards an adjacent inner vertical surface of the structure and an opposite, front surface of each panel faces in an inward direction away from the inner vertical surface of the structure, such that the respective front surfaces of the panels are substantially vertically aligned and the respective rear surfaces cooperate to form an effectively continuous water shedding surface.

40. A post according to claim 38 or claim 39, characterised in that the post comprises an elongate profile having a central, U-shaped portion with oppositely directed lateral flanges.

41. A panel for use in lining an arched structure with an internal framework; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line, the framework being installed within the structure and extending beneath the soffit; the panel having a front surface, an opposite rear, water shedding surface, and at least one attachment portion, the attachment portion being adapted for attachment to the framework so as to support the panel in an installed position in which the panel is inclined downwardly from an upper edge of the panel to a lower edge of the panel, and in which the rear surface faces in an outward direction towards the soffit and the front surface faces in an inward direction away from the soffit; charactensed in that the panel includes an upper wall and a lower wall, the upper wall extending generally in the outward direction proximate the upper edgeofthepanel and the lower wall extending generally in the inward direction proximate the lower edge of the panel, such that a first said panel may be attached to the framework above a second said panel, the first panel and the second panel being inclined downwardly at different angles of inclination so as to define an obtuse angle between the first and second panels, such that the lower wall of the first said panel cooperates with the upper wall of the second said panel to shed water from the rear surface of the first said panel to the rear surface of the second said panel, such that the respective rear surfaces of the first and second panels form an effectively continuous water shedding surface; and in that the upper and lower walls are so configured that the said obtuse angle may be varied by at least 15 degrees.

42. A panel according to claim 41, characterised in that the front surface is substantially flat, and the upper and lower walls are so configured that the first and second panels may be installed one above the other such that their respective front surfaces are substantially vertically aligned, such that the respective rear surfaces of the first and second panels form an effectively continuous water shedding surface.

43. A panel according to claim 41, characterised in that the upper and lower walls are so configured that they interlock to shed water from the rear surface of the first said panel to the rear surface of the second said panel, such that the respective rear surfaces of the first and second panels form an effectively continuous water shedding surface, when the first and second panels are installed such that their respective front surfaces are substantially aligned and their respective rear surfaces are both inclined downwardly at an angle of 2° below horizontal.

44. A panel according to claim 41, characterised in that the said obtuse angle may be varied by at least 70 degrees.

45. A panel according to claim 41, characterised in that the rear surface diverges from the front surface downwardly in the installed position towards the lower edge of the panel.

46. A panel according to claim 41, characterised in that an elongate recess is formed adjacent the lower wall, such that the upper wall of the second said panel may be received in the recess of the first said panel.

47. A panel according to claim 41, characterised in that the rear surface is divided into a plurality of channels.

48. A panel according to claim 41, charactensed in that the panel includes a body portion made from rigid foamed plastics material.

49. A panel according to claim 48, characterised in that the rear surface is divided into a plurality of channels, the channels being formed in the body portion.

50. A flexible, waterproof shield for installation together with an internal framework within an arched structure; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; the framework including a plurality of elongate, flexible frame elements; the shield comprising an elongate profile having a central, attachment portion and two lateral water shedding portions, the attachment portion comprising means for attaching the shield to a said flexible frame element so as to retain the shield on an outer side of the frame element as the frame element is raised into an installed position beneath the soffit.

51. A shield according to claim 50, characterised in that the shield is made from plastics material.

52. A shield according to claim 50, characterised in that the shield is made from elastomeric material.

53. A shield according to claim 50, charactensed in that the shield is adapted to be formed into a roll.

54. An installation tool for use in installing a framework within an arched structure; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; the framework including a plurality of elongate, flexible frame elements, each frame element having first and second ends; the tool comprising a releasable mounting mechanism for mounting the tool for controlled movement towards the soffit, a frame element attachment mechanism for attaching one end of a flexible frame element to the tool, and a movement mechanism for controlling the movement of the tool up and down towards and away from the soffit.

55. An installation tool according to claim 54, charactensed in that the releasable mounting mechanism comprises a post engagement mechanism for releasably mounting the tool in sliding engagement with a post, the post being adapted to support a respective end of the flexible frame element in an installed position.

56. An installation tool according to claim 55, characterised in that the post engagement mechanism is adapted to engage a pair of opposite'y directed lateral flanges of the post.

57. An installation tool according to claim 54, charactensed in that the tool includes a separation adjustment mechanism for moving the respective end of the frame element towards and away from the respective post.

58. An installation tool according to claim 54 or claim 57, characterised in that the tool includes a pivot mechanism which permits the frame element to be raised from a substantially horizontal orientation to a substantially vertical orientation after attachment to the tool.

59. An installation tool according to claim 58, characterised in that the pivot mechanism includes a releasable ratchet which restrains the frame element against downward movement.

60. A method of installing a framework within an arched structure; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; characterised by the steps of A) providing a plurality of flexible, elongate frame elements, each frame e'ement having first and second ends; B) providing support means respectively at the first and second sides of the structure; C) raising each frame element into an installed position in which the frame element is pressingly engaged against the soffit, such that a hoop stress is induced in the frame element and the frame element flexibly conforms to the curvature of the soffit; and D) attaching the first and second ends of the frame element to the support means, respectively at the first and second sides of the structure so as to support the frame element in the installed position.

61. A method according to claim 60, characterised in that the support means comprise a plurality of first and second posts arranged respectively at the first and second sides of the structure, and in that step B) includes the steps of B i) attaching a plurality of first and second attachment plates to the floor in spaced positions, respectively at the first and second sides of the structure; and B ii) attaching each of the first and second posts respectively to a respective one of the first and second attachment plates.

62. A method according to claim 60, characterised by the additional steps of A i) providing a plurality of flexible, elongate, waterproof shields; and A ii) attaching each shield to a frame element, so as to retain the shield on an outer side of the frame element as the frame element is raised into the installed position at step C), such that the shield extends between the frame element and the soffit when the frame element is pressingly engaged against the soffit.

63. A method according to claim 60, characterised in that step A) includes the steps of A I) providing a pair of said frame elements, the frame elements being detachably bound together so as to form a rigid assembly for transportation; and A ii) separating the said frame elements prior to installation.

64. A method according to claim 60, characterised in that step C) includes the steps of C i) providing a pair of installation tools, each installation tool comprising: a releasable mounting mechanism for mounting the tool for controlled movement towards the soffit, a frame element attachment mechanism for attaching one end of the frame element to the tool, and a movement mechanism for controlling the movement of the tool up and down towards and away from the soffit; S C ii) mounting the tools respectively at the first and second sides of the structure for controlled movement towards the soffit; C iii) attaching each end of a frame element to a respective one of the tools; and C iv) raising the tools towards the soffit until the frame element is in the installed position.

65. A method according to claim 64, characterised in that the support means comprise a plurality of first and second posts arranged respectively at the first and second sides of the structure, and at step C ii) the tools are mounted respectively on corresponding first and second posts.

66. A method according to claim 64, characterised in that each installation tool includes a pivot mechanism which permits the frame element to be raised from a substantially horizontal orientation to a substantially vertical orientation after attachment to the tool; and in that step C iii) includes the steps of C iii a) attaching the first end of the frame element to a first one of the tools; C iii b) attaching the second end of the frame element to the other one of the tools; and C iii c) raising the frame element to a substantially vertical orientation.

67. A method according to claim 65, characterised in that each installation tool includes a separation adjustment mechanism for moving the respective end of the frame element towards and away from the respective post; and in that step C iv) includes the step of C iv a) moving each respective end of the frame element into engagement with the respective post.

68. A method according to claim 67, characterised by the additional steps of A I) providing a plurality of flexible, elongate, waterproof shields; A ii) attaching each shield to a frame element such that first and second end portions of the shield extend respectively between the frame element and corresponding first and second posts, so as to retain the shield on an outer side of the frame element as the frame element is raised into the installed position at step C), such that the shield extends between the frame element and the soffit when the frame element is pressingly engaged against the soffit; and in that at step C iv a), each end of the shield is removed from between the frame element and the respective post before moving the respective end of the frame element into engagement with the post.

69. A method according to claim 60, characterised in that the support means comprise a plurality of first and second posts arranged respectively at the first and second sides of the structure, and by the additional steps of I0 E i) providing a plurality of joists, E ii) supporting each of the joists between corresponding first and second posts, and E iii) supporting a floor on the joists.

70. A method of lining an arched structure; the structure having a floor and a soffit, the soffit curving upwardly and inwardly from opposite, first and second sides of the structure to a crown line; characterised by the steps of A) providing a plurality of flexible, elongate frame elements, each frame element having first and second ends; B) providing support means respectively at the first and second sides of the structure; C) raising each frame element into an installed position in which the frame element is pressing engaged against the soffit, such that the frame element flexibly conforms to the curvature of the soffit; D) attaching the first and second ends of the frame element to the support means, respectively at the first and second sides of the structure so as to support the frame element in the installed position; and F) attaching a plurality of panels to the frame elements so as to support the panels in an installed position in which each panel is inclined downwardly from an upper edge of the panel to a lower edge of the panel, and in which a rear surface of each panel faces in an outward direction towards the soffit and an opposite, front surface faces in an inward direction away from the soffit such that the respective rear surfaces of the panels cooperate to form an effectively continuous water shedding surface.

71. A method according to claim 70, charactensed in that the support means comprise a plurality of first and second posts arranged respectively at the first and second sides of the structure, and by the additional steps of E I) providing a plurality of joists, E ii) supporting each of the joists between corresponding first and second posts, and E iii) supporting a floor on the joists, such that the floor provides access to the soffit for attachment of the panels at step F).

72. A method according to claim 70, characterised in that the support means comprise a plurality of first and second posts arranged respectively at the first and second sides of the structure, and by the additional step of 0) attaching a plurality of second panels to the posts so as to support the second panels in an installed position in which a rear surface of each second panel faces in an outward direction towards an adjacent inner vertical surface of the structure and an opposite, front surface of each second panel faces in an inward direction away from the inner vertical surface of the structure, such that the respective front surfaces of the second panels are substantially vertically aligned and the respective rear surfaces cooperate to form an effectively continuous water shedding surface.