GB2201716A

GB2201716A - Collapsible builders' staging for roofs

Info

Publication number: GB2201716A
Application number: GB08805075A
Authority: GB
Inventors: Edward Terry Reynolds; Ian Alexander Dean Angell
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-03-03
Filing date: 1988-03-03
Publication date: 1988-09-07
Anticipated expiration: 2008-03-03
Also published as: GB8805075D0; GB2201716B; WO1988006667A1; AU1369688A

Abstract

A collapsible builders' staging is provided for use on a pitched roof to eliminate the need for complex scaffolding erected about a chimney stack in need of repair. A staging unit comprises a base member (1), an upright (12), and a slidable collar (8) pivotally connecting an end of the upright (12) to base (1). A tie (15) connects the base (1) and the upright (12). Each end of the tie (15) is pivotally connected to a respective one of the base (1) and upright (12). The staging unit can be moved between a collapsed configuration in which the base (1), tie (15) and upright (12) are substantially parallel and an erect configuration in which, with the base (1) extending down the pitch of the roof, the tie (15) is substantially horizontal.

Description

COLLAPSIBLE BUILDERS' STAGING This invention relates to a collapsible builders' staging for use on a pitched roof to eliminate the need for complex scaffolding erected about a chimney stack in need of repair.

In U.K. Patent Specification No. 1592372 there is disclosed a collapsible builders' stage, for erection and use on a pitched roof or at a window opening of a building.

Such builders' stages have been widely used in recent years but they are relatively expensive and hence usually are purchased by larger building companies or by hirers of equipm.ent.

It is an object of the present invention to provide a collapsible staging unit, for use in erecting a collapsible staging qn a pitched roof, which is adapted for easy operation by a single user and which is relatively inexpensive to manufacture.

According to the present invention there is provided a staging unit comprising at least two elongate members, and coupling means for pivotally coupling said elongate members together, and stabilising means carried by a first one of said elongate members, said stabilising means being arranged to extend outwardly of said first elongate member on either side thereof.

The invention also provides a staging unit comprising first, second and third members, and coupling means for coupling said elongate members together, wherein said coupling means are movable along respective elongate members such that the elongate members may be pivoted between a folded position in which said elongate members extend substantially parallel and an erect position in which said first elongate member forms a single base member.

The present invention also provides a staging unit which comprises: (i) a first elongate member to lie across a pitched roof and serve as a base; (ii) a second elongate member, to serve as an upright; (iii) first coupling means pivotally connecting a first end of the second elongate member to the first elongate member; (iv) a third elongate member, to serve as a tie connecting the first and second elongate members; (v) second coupling means pivotally connecting the third elongate member to the second elongate member;; (vi) third coupling means pivotally connecting the third elongate member to the first elongate member, and (vii) engagement means on the first elongate member for use in securing the unit to a roof ridge or to a chimney stack, and at least two of said coupling means being slidable along a respective elongate member and securable at predetermined positions therealong whereby the staging unit can be moved between a collapsed configuration in which the three elongate members are substantially parallel and an erect configuration in which, with the first elongate member extending down the pitch of the roof, the third elongate-member is substantially horizontal.

Preferably, the second elongate member is substantially vertical in the erect configuration of the staging unit.

In another aspect, the invention provides a staging unit which comprises: (i) a first elongate member to lie across a pitched roof and serve as a base, (ii) a second elongate member, to serve as an upright, (iii) first coupling means connecting a first end of the second elongate memebr to the first elongate member at any one of a number of predetermined positions along the first elongate member, (iv) a third elongate member, to serve as a tie, pivoted by one of its ends to the first elongate member, (v) second coupling means connecting the other end of the third elongate member to the second elongate member at any one of a number of predetermined positions along the second elongate member, and (vi) engagement means on the first elongate member at or adjacent the first end thereof, for use in securing the unit to a roof ridge or to a chimney stack, whereby the staging unit can be moved between a collapsed configuration in which the three elongate members are substantially parallel and an erect configuration in which, with the first member extending down the pitch of the roof, the second and third elongate members are respectively substantially vertical and substantially horizontal.

Further according to the invention, a staging comprises two of the units set forth above, and a rigid demountable linkage connected to the respective upright second members.

The coupling means may comprise, for example, collars or sleeves slidable along the respective elongate members and securable by a fastening pin passed through them.

The first elongate member may be extensible, eg.

telescopically, and securable in any selected condition of extension.

Means may be provided, on the first elongate member, to extend laterally from it for stabilising the member against rotation about its own longitudinal axis. Such stabiliser means may conveniently be one or an opposed pair of arms extending laterally from the member, and conveniently such arms are pivotable to a stored condition substantially parallel to the member.

The engagement means may be, for example, a hook to engage over the ridge of a roof, or a bracket structure to receive a frame member positioned behind a chimney stack. 67hen the engagement means is a hook, suitably there is provided a wheel forwardly of the hook to permit an end of the first member to be wheeled across the roof without restricting the engagement of the hook with the roof ridge.

In an embodiment, at least one of said elongate members is provided with a spigot which is adjustable longitudinally of the respective elongate member to enable towers of various sizes to be received thereon.

Embodiments of the present inventon will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a stage unit, of a first embodiment, seen on a roof and in conjunction with a conventional ladder; Figures 2a-2f show in perspective, a series of positions in which the stage unit is placed during erection of a stage to support a platform; Figure 3 is a perspective view of a second embodiment of a stage unit in its folded position; Figure 4 is a perspective view of the stage unit of Figure 3 in its erected position; Figure 5 is an exploded perspective view of a coupling for use with a stage unit of the invention; Figure 6 shows a scaffolding tower received on a stage unit using couplings as in Figure 5;; Figure 7 shows a staging for engagement with a hipped roof chimney stack using stage units in accordance with a further embodiment; and Figure 7a shows a frame member for use in the staging of Figure 7.

Referring to Figure 1, the stage unit comprises a single base member 1 constituted by an inner tube 2 of box section which is telescopically slidable within an outer tube 3. The outer tube is of circular section but has an end plate with a square hole to slidably receive the inner tube. The outer tube 3 has a pair of aligned openings 4 through which is inserted a fastening pin 5 which passes through a selected one of a number of transverse openings 6 distributed along the length of the inner tube 2, for locking the tubes 2 and 3 at a desired condition of elongation. In Figure 2a, the tubes 2 and 3 are telescoped to their shortest relative position.

On the outer tube 3, there is positioned a collar 7 which is slidable along the tube 3 and which can be locked in a desired position thereon by insertion of a fastening pin 8 through any selected one of several pairs of opposed openings 9 in the tube 3.

On the collar 7, there is provided a lug 10 which carries a pivot pin 11 serving to mount a swingable upright 12 which can pivot freely about the axis of the pin 11.

At the other end of the tube 3, there is provided a fixed lug 13 which carries a pivot pin 14 serving to mount a swingable tie 15. The other end of the tie 15 is secured by a pivot pin 16 to a lug 17 on a collar 18 which can slide freely along the upright 12 but which can be secured in any one of a number of selected positions by engagement of a locking pin 19 through an opposed pair of openings in the collar and through any selected one of a series of openings 20 in the upright 12.

Intermediate the ends of the tube 3, there is provided a collar 21 which carries a pair of stabiliser arms 22 which can be pivoted into a storage position, parallel to the tube 3 as seen in Figure 2a, and into an operative extended position as seen in Figures 2c-2f.

Suitably, all tubes and fittings with the exception of the inner tube 2 are provided by, or adapted from, standard scaffolding poles and fittings.

The operation is as follows: tiith the stage unit in the folded condition seen in Figure 2a, the user climbs up a roof by using a conventional ladder wLw which is hooked over the ridge of the roof, and then engages a hook 23, secured on the free end of the tube 2, over the ridge of the roof.

Referring now to Figure 2b, the fastening pin 5 is withdrawn to enable the tube 2 to slide further out of the tube 3, and is then reinserted to lock the two tubes in the extended condition, see also Figure 1.

The stabiliser arms 22 are then pivoted out of their storage positions to extend substantially transversely of the base member 1. If required, the collar 21 may be slidable along the tube 3 so that the position of the stabiliser arms 22 can be adjusted.

Referring now to Figure 2c, the fastening pin 8 is temporarily removed to permit the collar 7 to be slid along the tube 3 to a desired new position, and the pin 8 is reinserted through the selected openings 9. At the same time, the locking pin 19 is removed temporarily from the collar 18 which is slid down the upright 12 and then locked in position by reinserting the pin 19. The positions of the collar 7 and of the collar 18 are selected such that, whilst allowing for the pitch of the roof, the upright 12 is substantially vertical. This can be done by trial and error, or more easily, by using indicators 30 as described more fully below.

Referring now to Figure 2d, the user lifts up and manipulates the structure to roll the hook 23, by its wheel 24, over the roof to hook over the ridge thereof at the far side of the chimney stack.

Referring now to Figure 2e, another exactly similar unit is prepared, in the same manner as described with reference to Figures 2a-2c, and is engaged over the roof ridge at the near side of the chimney stack. A cross-member 25 has at one end a collar 26 which is engaged slidably on the remote upright 12 and is then fastened in position by a transverse locking pin 27. Once engaged on the remote upright 12, this cross-member 25 can be used to guide that unit from its position of Figure 2e to the position illustrated in Figure 2f. Another similar collar 26 is then engaged on the nearer upright 12 and is similarly fastened in position by a locking pin, thereby resulting in the symmetrical parallel structure seen in Figure 2f.

The two ties 15 are arranged to be substantially horizontal, and scaffolding planks or the like (not shown) can be laid across them to provide a working platform.

The two stage units can be disconnected from each other, and then collapsed to their handling position of Figure 1, by simple reversal of the series of movements described.

It will be apparent from the above that the whole of the operations can be quickly and easily carried out by one person without assistance. In this respect, the erection of each stage unit as illustrated in Figures 2c and 2d is facilitated by the stabilising effect of the extended arms 22.

Furthermore, staging can be positioned on both sides of a chimney stack by the one person without it being necessary to move the ladder "L". Again, the stabilising effect of the extended arms 22 can help in the manipulation of one of the stage units to the far side of the chimney stack.

Two stage units can be erected as described to support a working platform at the front of a chimney stack. By similarly positioning two additional stage units at the back of the chimney stack, a staging surrounding the stack can quickly and easily be assembled, again by one person.

Figures 3 and 4 show a modified embodiment of a stage unit, and also illustrate the structure and operation of each indicator 30 more clearly. In Figures 3 and 4 those features which are similar to features of the unit of Figures 1 and 2 have been accorded the same reference numbers.

Figure 3 shows the modified stage unit in its fully folded position, for example, for carrying up to a roof and it will be appreciated that the modified version of Figure 3 folds more compactly than the embodiment of Figure 1. In this respect, in the modified embodiment, the lower end of the upright 12 is curved, as indicated at 31. This enables the tie 15 to be received between the upright 12 and the base member 1 in the fully folded position. Of course, the pivot connections at each end of the tie 15 to the upright 12 and the tube 3 have to pivot in the opposite directions as compared to the embodiment of Figure 1 to allow the folding and erection of the modified stage unit as indicated in Figures 3 and 4.

The modified stage unit is also provided with a pair of wheels 24 carried by its hook 23. The provision of two wheels 24 further enhances the stability of the stage unit and also makes it easier to roll one stage unit to the far side of a chimney stack, for example, as illustrated in Figure 2d.

It will be seen from Figures 3 and 4 that the hook 23 is comprised of two spaced hook members 32 joined at their outer end by a substantially transverse strut 33. The wheels 24 are journalled onto the hook members 32 such that their axes of rotation are outwardly of the axis of the strut 33.

Thus, the wheels 24 can be brought into contact with the roof surface by lifting the free end of the outer tube 3 away from the surface. In this way, the stage unit can be positioned as required by "wheeling" it across the roof surface. XJhen the hook 23 is hooked over a roof ridge, it is the strut 33 which contacts the roof surface to engage the stage unit in position on the roof.

It will be seen that the hook members 32 each carry a respective one of a pair of lugs 34 which have aligned holes therein for the receipt of a pin 35. As is shown in Figure 3, in the folded position, the upper end of the upright 12 is received between the hook members 32 and retained by the engagement of the pin 35 through the lugs 34.

The detail A of Figure 3 shows the indicator 30 to be a freely swingable indicator arm mounted on the pivot pin 14 mounting the end of the tie 15 to the outer tube 3. This indicator arm 30 falls under gravity to indicate a position on an arcuate scale 36 marked on the adjacent end of the tube 3. It will also be seen that the openings 9, 20 in the tube 3 and in the upright 12 are marked with numbers corresponding to those of the arcuate scale. then the folded stage unit is hooked onto a roof to extend down the roof, for example, as shown in Figure 2a, the pitch of the roof determines the number on the scale 36 to which the indicator arm 30 points.If the stage unit is then erected such that the collars 7 and 18 are fixed to the tube 3 and the upright 12 by pins engaged in the correspondingly numbered openings, the upright 12 will extend substantially vertically and the tie 15 will be substantially horizontal.

Preferably, a respective indicator arm 30 and corresponding arcuate scale 36 is provided on each side of the tie 15 so that the scale can be read from either side of the stage unit.

Figures 3 and 4 show that the tie 15 has been provided with two couplings 103 for the receipt of the uprights of a scaffolding tower. Figure 5 shows a detailed view of one of these couplings 103 which comprises a casting 106 and a spigot 107. Each casting 106 has a generally cylindrical body portion through which a cylindrical bore 108 extends. The diameter of this bore 108 is slightly larger than the external diameter of the tie 15 such that the casting 106 is slidable along the tie 15 and rotatable around the tie 15. One of the castings 106 has a pair of opposed, axially extending slots 109 formed in the body portion, whilst the other of the castings has a pair of opposed, substantially aligned holes 1091 therein.

The body portion of each casting 106 is integrally formed with two opposed, spaced wall members which define an upwardly open channel 126 in which a respective spigot 107 is to be received. A pair of substantially aligned through holes 110 are provided in the wall members.

Each spigot 107 is a substantially cylindrical tube with two pairs of diametrically opposed through holes 111, 112 proximate its lower end. In use, the spigot 107 is received within the channel 126 and is rotated about its own axis to align the holes of one of the pairs 111, 112 with the casting holes 110.

A retention pin (not illustrated) is passed through the casting holes 110 and the aligned pairs of holes 111 or 112 of the spigot to retain the spigot 107 on its casting. The positioning of the holes 111, 112 in the spigot and of the holes 110 in the casting 106 is chosen such that the spigot 107 is pivotable relative to the casting 106 about the axis of the retention pin.

In the folded position of the stage unit, as shown in Figure 3, the spigot 107 has been pivoted such that its axis extends substantially parallel with respect to the axis of the cylindrical bore and hence to the tie 15. Furthermore, each casting 106 has been rotated around the tie such that the channel 126 faces to one side. The castings may be retained in this position by a pin (not shown) extending through appropriately positioned holes in the castings 106 and in the tie 15. In this respect, the tie 15 is provided with holes 104, 105 for positioning the castings 106 on erection, and the castings are preferably held in their rotated, folded position by a pin extending through the casting and into one of the holes in the tie.This pin extends through an additional hole (not shown) formed in the casting to extend substantially radially from the lowest point, as seen in Figure 5, of its cylindrical body to the cylindrical bore 108.

Once the folded stage unit of Figure 3 has been erected to the position shown in Figure 4, the pins retaining the castings 106 on the tie 15 are removed and these castings are rotated around the tie such that their channels 126 open upwardly. The left hand casting as shown in Figure 4 has the aligned holes 1091 and these are aligned with a selected pair of aligned holes in the tie such that a pin 115 can be passed through the holes to retain the casting 106 in position. The spigot 107 is then pivoted to extend upwardly.

The right hand casting, as seen in Figure 4 is similarly secured to the tie via a pin 116 which passes through the slots 109 and a selected one of the pairs of through holes 104, the holes being chosen depending on the width of the tower. The presence of a plurality of holes 104 and the use of slots 109 enables any width of tower, within a given range, to be accommodated. The spigot is then pivoted to extend upwardly.

The upstanding spigots 107 receive the uprights 101 of a scaffolding tower 100 as is indicated in Figure 6. It will be noticed that in this figure the casting 106 with the holes 1091 is shown on the right.

As is conventional, the uprights 101 of the tower terminate in tubular castings 102 which are each slid over a respective spigot 107 until the lower end of each casting 102 abuts the upper surfaces of the upstanding wall members of a respective casting 106.

Each casting 102 is secured to the respective spigot 107 by way of a single pin (not shown) which extends through a hole in the casting 102 and through an aligned hole in the spigot 107. The pin is held in position by an external retention band (not shown) and by gravity.

To enable the spigot 107 to be used with conventional towers it is provided with a number of holes 113, 114 therein. If none of these holes will line up with the hole provided in the casting 102, the spigot can be rotated through 900 by removing its retention pin and then reinserting the pin through the other of its pairs of holes 111, 112.

Figure 6 illustrates the reception of a double width tower 100 on the tie 15. A single width tower can be supported by utilising the intermediate holes 105 on the tie 15.

Figure 7 shows an embodiment of a stage unit which can be used to engage behind a chimney stack "C" when the roof ridge is not conveniently placed for engagement by a hook.

In this embodiment, the hook 23 and wheels 24 are replaced by a simple tubular structure 50, illustrated in Figure 7a, having a tube 51 to each end of which an adjustable triangular member 52, formed of three interconnected tubes, is adjustably mounted. As previously, the adjustments are made by way of slidable collars to be pinned in a selected position.

The tube 51 with the attached triangular members 52 is positioned at the back of the hipped roof chimney stack and then a collar 54 at the end of each base tube 53 of a respective one of the triangular members is releasably secured on a respective tube 2 of a corresponding stage unit. Each base tube 53 telescopically receives therein an adjustment rod 55 carrying a clamping plate 56. The projection of the rods 55 relative to their respective base tubes 53 is adjusted such that the plates 56 clamp against the chimney stack. As previously, scaffold boards (not shown) may be placed across the ties 15 to provide a working platform for a man to stand on, or a tower may be received on the spigots 107 provided.

The embodiment of Figure 7 can be used in an inverted configuration to provide access to a chimney stack close to the lower edge of the roof (ie. a wall end stack). In particular, outer tube 3 can be directly secured to the frame 50 with the fixed lug 13 (see Figure 1) lowermost and the collar 7 (see Figure 1) above the frame member 50. The tube 15, which previously constituted a tie now becomes a strut supporting the previous "upright" 12 in a substantially horizontal attitude. Alternatively, the "upright" 12 can now be regarded as constituting a tie and the "tie" 15 regarded as constituting an upright.

In fact, the tube 15 usually will be inclined outwardly from the vertical in the erect condition, approximately perpendicularly to the roof slope.

It will be appreciated that the invention is not restricted to the constructional details described above with reference to the drawings but that numerous modifications and variations can be made without departing from the scope of the invention. For example, an extension tube can be provided to permit greater extension of outer tube 3 down the roof to provide, for example, access to a dormer window. This extension tube suitably is of box section similar to inner tube 2 but having an enlargement at its upper end to receive the lower end of the inner tube 2 and also appropriately located openings to receive pins passing through the lowermost pair of openings 6 to secure the inner tubes. Openings are distributed along the extension tube in similar manner to the openings 6 in inner tube 2 to permit locking of the outer tube 3 at a desired condition of elongation.

Claims

1. A staging unit comprising at least two elongate members, and coupling means for pivotally coupling said elongate members together, and stabilising means carried by a first one of said elongate members, said stabilising means being arranged to extend outwardly of said first elongate member on either side thereof.

2. A staging unit as claimed in Claim 1, wherein said stabilising means comprises a collar surrounding said first elongate member, and a pair of stabiliser arms connected to said collar to extend outwardly thereof.

3. A staging unit as claimed in Claim 2, wherein said stabiliser arms are pivotally connected to said collar.

4. A staging unit comprising first, second and third elongate members, and coupling means for coupling said elongate members together, wherein said coupling means are movable along respective elongate members such that the elongate members may be pivoted between a folded position in which said elongate members extend substantially parallel and an erect position in which said first elongate member forms a single base member.

5. A staging unit as claimed in any of Claims 1 to 3, further comprising a third elongate member pivotally connected by further coupling means to at least one of said two elongate members, wherein said coupling means are movable along respective elongate members such that the elongate membes may be pivoted between a folded position in which said elongate members extend substantially parallel and an erect position in which said first elongate member forms a base member.

6. A staging unit as claimed in Claim 4 or 5, in which in said erect position, one of said elongate members extends substantially horizontally.

7. A staging unit as claimed in Claim 4, 5 or 6, in which in said erect position, one of said elongate members extends substantially vertically.

8. A staging unit as claimed in any of Claims 4 to 7, wherein said third elongate member is an intermediate member, and further comprising first coupling means for pivotally connecting a first end of said intermediate member to said first elongate member, and second coupling means for pivotally connecting the second end of said intermediate member to a second elongate member.

9. A staging unit as claimed in Claim 8, wherein at least one of said first and second coupling means is slidable along a respective elongate member.

10. A staging unit as claimed in Claim 9, wherein said second coupling means is slidable along said second elongate member, and further comprising securing means for securing said second coupling means in predetermined positions along said second elongate member.

11. A staging unit as claimed in any of Claims 8 to 10, further comprising third coupling means for pivotally connecting one end of said second elongate member to said first elongate member.

12. A staging unit as claimed in Claim 11, wherein said third coupling means is slidable along said first elongate member, and further comprising means for securing said third coupling means in predetermined positions along saidfirst elongate member.

13. A staging unit as claimed in any preceding claim, further comprising engagement means on said first elongate member for securing the unit to a roof ridge or chimney stack.

14. A staging unit comprising: (i) a first elongate member to lie across a pitched roof and serve as a base; (ii) a second elongate member, to serve as an upright; (iii) first coupling means pivotally connecting a first end of the second elongate member to the first elongate member; (iv) a third elongate member, to serve as a tie connecting the first and second elongate members; (v) second coupling means pivotally connecting the third elongate member to the second elongate member;; (vi) third coupling means pivotally connecting the third elongate member to the first elongate member, and (vii) engagement means on the first elongate member for use in securing the unit to a roof ridge or to a chimney stack, and at least two of said coupling means being slidable along a respective elongate member and securable at predetermined positions therealong whereby the staging unit can be moved between a collapsed configuration in which the three elongate members are substantially parallel and an erect configuration in which, with the first elongate member extending down the pitch of the roof, the third elongate member is substantially horizontal.

15. A staging unit comprising: (i) a first elongate member to lie across a pitched roof and serve as a base, (ii) a second elongate member, to serve as an upright, (iii) first coupling means connecting a first end of the second elongate member to the first elongate member at any one of a number of predetermined positions along the first elongate member, (iv) a third elongate member, to serve as a tie, pivoted by one of its ends to the first elongate member, (v) second coupling means connecting the other end of the third elongate member to the second elongate member at any one of a number of predetermined positions along the second elongate member, and (vi) engagement means on the first elongate member at or adjacent to the first end thereof, for use in securing the unit to a roof ridge or to a chimney stack, whereby the staging unit can be moved between a collapsed configuration in which the three elongate members are substantially parallel and an erect configuration in which, with the first member extending down the pitch of the roof, the second and third elongate members are respectively substantially vertical and substantially horizontal.

16. A staging comprising two units as claimed in Claim 15, and a rigid demountable linkage connected to the respective upright second members.

17. A staging unit as claimed in any of Claims 13 to 16, wherein said engagement means comprise a hook to engage over the ridge of a roof.

18. A staging unit as claimed in Claim 17, further comprising a pair of wheels mounted outwardly of the hook to permit an end of the first member to be wheeled across a roof without restricting the engagement of the hook with the roof ridge.

19. A staging unit as claimed in any of Claims 13 to 16, wherein said engagement means is a bracket structure to receive a frame member.

20. A staging unit as claimed in any preceding claim, wherein said coupling means comprise collars or sleeves slidable along the respective elongate members and securable by a fastening pin passed through them.

21. A staging unit as claimed in any preceding claim, wherein the first elongate member is extensible, for example telescopically, and is securable in any selected condition of extension.

22. A staging unit as claimed in any preceding claim, in which at least one of said elongate members is provided with a spigot which is adjustable longitudinally of the respective elongate member to enable towers of various sizes to be received thereon.

23. A staging unit as claimed in any of Claims 4 to 12, or 14 to 19, further comprising at least two spigots mounted on said third elongate member.

24. A staging unit as claimed in Claim 22 or Claim 23 wherein the or each spigot is a tubular member pivotally mounted in a casting member carried by said elongate member.

25. A staging unit as claimed in Claim 24, wherein a plurality of holes are provided in said spigot.

26. A staging unit as claimed in any preceding Claim, further comprising 3angle indicator means having a freely swingable arm mounted to be movable relative to a scale.

27. A staging unit as claimed in any of Claims 4 to 12, 14 to 19 or 23 to 25, further comprising angle indicator means having a freely swingable arm carried by said third elongate member and arranged to be movable relative to a scale on another of said elongate members.