GB2432623A

GB2432623A - A scaffold stair unit which uses scaffolding tubes as stringers

Info

Publication number: GB2432623A
Application number: GB0702821A
Authority: GB
Inventors: Lewis Alberto Grijo Dos Santos; John Michael Dyke; Keith Ronald Groom
Original assignee: ACORN CORPORATE SERVICES Ltd
Current assignee: ACORN CORPORATE SERVICES Ltd
Priority date: 2005-06-27
Filing date: 2005-06-27
Publication date: 2007-05-30
Anticipated expiration: 2025-06-27
Also published as: GB2428729A; GB2432623B; GB2432623A8; GB0513043D0; GB0702821D0; GB2428729B

Abstract

A scaffold stair unit 10 comprises a plurality of substantially mutually equidistant and parallel treads 20 pivotally secured to first and second stringers 12,14 at a first side of each tread and third and fourth stringers 16, 18 attached at a second side of each tread. This permits the height of the unit to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads. At least one of the first and second stringers and at least one of the third and fourth stringer are standard diameter scaffold tubes. Preferably, the unit comprises a locking means in the form of a strap assembly 72 which extends from a stringer on a first side of the unit and includes an elongate slot, the strap engaging with a clamping device secured to the other stringer to selectively clamp the strap in a desired position, as shown in Figure 8. Also defined is a scaffold staircase beam 310 for supporting scaffold stair unit as shown in Figure 12.

Description

1 2432623 A Scaffold Stair Unit The present invention relates to a

scaffold stair unit and a method of erecting such a unit.

Scaffold systems are employed on construction sites to provide platforms giving temporary access to structures during construction, or they are used to provide temporary access to existing structures for maintenance. They fail generally into two categories.

Tube and fitting scaffold systems are the "classic" means of providing such temporary access. They are built up using standard diameter tubes joined together by fittings or couplers to provide a framework that can in turn support a working platform for the users of the scaffold. The advantage of tube and fitting scaffolds is the degree of flexibility that may be afforded in terms of varying the height of the working platform, spacing of upright supports etc. However, the downside of such systems is the amount of time required for erection and dismantling thereof, and the amount of skill needed to do so.

On the other hand, proprietary scaffold systems such as CUPLOKR TM and HAK1RT offer less flexibility, since the sizing of components and spacing of connections is standardised. However, the standardised modular components mean they are generally quicker to erect. This is acceptable provided working platforms are required at height increments of, say. I. 5m or 2.Om. However, it is common for bricklayers to prefer, for example, l.8m height increments for working platforms, a size not available in such proprietary systems.

The traditional way of accessing elevated working platforms of scaffolding is by way of ladders. However, due to increasingly strict safety regulations and standards regulations such as, in the UK, the Work at Height Regulations 2005 and British Standard and European Norm BS EN 12811-1:2003, construction firms are increasingly being forced to provide access to elevated working platforms by way of staircases. This standard provides maximum and minimum values for various aspects of stairs. For example, where the "rise" (the height from tread-to-tread) is denoted u and the "going" (the horizontal distance from the front edge of the one tread to the front edge of an adjacent tread) is denoted g, the combination of these dimensions should conform to the expression 2u +g = 600 +1-60mm. Furthermore, the angle of the flight of stairs should lie within the range of 30 to 55 .

It is known for staircases compliant to this standard to be provided for fitment to proprietary scaffold systems. Such staircases are straightforward to fit within such systems in view of the standardised bay widths and lift heights between consecutive platform levels. However, they cannot be used with tube and fitting scaffold systems, because of incompatibility of the fittings and the variability in dimensions.

It is also possible to construct staircases using tube and fitting components by attaching individual stair treads to tubular "stringers" provided at the ends of the treads. However, such staircases are highly time-consuming to assemble and dismantle. At the same time it is virtually impossible to adjust each tread to be level and for treads to be evenly spaced, in order to meet the safety regulations.

Furthermore, it is difficult to plan in advance of erection how many individual tread components would be needed for a particular site, causing problems with logistics.

Scaffold stair units differ from conventional stairs by virtue of the requirement for rapid erection and dismantling. Only if this is case, will the use of such structures be viable on structures that are inherently temporary. They also differ by virtue of the need for the units to interface with other parts of scaffolds, such as scaffold tubes of standard diameter.

The present invention seeks to overcome or at least mitigate the problems of the prior art.

Accordingly, a first aspect of the present invention provides a scaffold stair unit comprising a plurality of substantially mutually equidistant and parallel treads pivotally secured to first and second stringers at a first side thereof and third and

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fourth stringers at a second side thereof in a parallelogram-like fashion, so as to permit the unit height to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads.

A second aspect of the invention provides a method of erecting a scaffold Stair unit comprising a plurality of substantially mutually equidistant and parallel treads pivotally secured to first and second stringers at a first side thereof and third and fourth stringers at a second side thereof in a parallelogram-like fashion, so as to permit the unit height to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads, the method comprising the steps of: securing the top of the unit to an elevated structure; and resting the bottom of the unit on the ground or a lower structure.

A third aspect of the present invention provides a kit of parts comprising a scaffold 1 5 stair unit comprising a plurality of substantially mutually equidistant and parallel treads pivotally secured to first and second stringers at a first side thereof and third and fourth stringers at a second side thereof in a parallelogram-like fashion, so as to permit the unit height to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads, and a staircase beam configured for attachment to a scaffold structure and configured to support the stair unit at an elevated position.

A fouth aspect of the present invention provides a scaffold staircase beam for supporting scaffold stair units, the beam comprising: a first coupler arrangement including a first and second spaced couplers at a first end for connection to a first scaffold column of a scaffold structure; a second coupler arrangement at a second end for connection to a second scaffold column; and a projection provided on the beam proximate the first coupler arrangement to contact a horizontal scaffold member secured to the first scaffold column, in use; wherein the beam is configured such that, when coupled to the first scaffold column with the projection contacting the horizontal member, the top of the beam is at substantially the same level as the horizontal member.

Embodiments of the present invention described, by way of example only, with reference to the accompanying drawings in which: Figs. I and 2 are perspective views of a scaffold stair unit according to a first embodiment of the present invention; Fig. 3 is a side view of the unit of Figs. I and 2; Figs. 4 and 5 are enlarged side views of the top and bottom respectively of the unit of Figs. I and 2; 1 0 Figs. 6, 7, 8 and 9 are perspective views of various components of the unit of Figs. and 2; Fig. 1 0 is a cross-sectional view through a tread of the unit of Figs. I and 2; 1 5 Fig. 11 is a perspective view of a unit according to a second embodiment of the present invention; Fig. 12 is a beam adapted for use with the staircase unit of Figs I and 2 and Fig. 11.

Fig. 13 is a schematic perspective view of a scaffold construction incorporating a stair unit of Fig. I and beam of Fig. 12 With reference to Figs. 1, 2 and 3, a scaffold stair unit according to a first embodiment of the present invention is indicated generally by the numeral 10. When viewed from the standpoint of climbing the stair unit 10, the unit comprises first and second stringers 12 and 14 on the left-hand side of the unit, mounted in a vertically-spaced, parallel relationship. The unit 10 further comprises third and fourth stringers 1 6 and 1 8 positioned on the right-hand side of the unit 10 with the same vertical spacing therebetween, again in a parallel relationship. All of the stringers are made from identical standard diameter scaffold tubes. The length of the first and third tubes 12 and 16 is identical and the length of the second and fourth tubes 14 and 18 is also identical, but somewhat shorter than that of the first and third tubes, as is most readily apparent in Fig. 3.

A plurality of treads 20 (in this case nine) are equally spaced horizontally and vertically along the length of the stringers 12, 14, 16 and 18. The treads 20 are arranged so that when the stair unit 10 is erected, the treads lie in a plane that is substantially horizontal (assuming the surface supporting the bottom of the unit is also horizontal).

With reference to Fig. 1 0, in this embodiment, each tread is formed from a metal (e.g. steel or aluminium) sheet that is bent to form an upper flat tread surface 22, and front and rear vertical webs 24 and 26. The webs terminate with inwardly facing lip 1 0 portions 28 and 30 to improve the rigidity of the treads 20. The tread surface 22 is formed with a high-grip texture or treatment such as checkerplate. At the corners between webs 24 and 26 and flanges 28 and 30 respectively, short lengths of tubing 32 and 34 are welded proximate the left and right-hand side edge of each tread. Thus, two lengths of tubing 32 and 34 are provided at each side of each tread 20.

To secure each tread 20 to each of the stringers 12, 14, 16, 1 8, horizontal holes (not visible) are drilled transversely through each stringer at the same height for each tread. Bolts 36 are inserted inwardly through the holes in the stringers and the tubes 32 and 34 in the treads and are secured by suitable fasteners such as clips, washers, pins or nuts (not visible) inboard of the tubes 32 and 34.

With reference to Figs. 5, 6 and 7, two stand assemblies are provided in order to provide a stable support for the bottom of the unit 1 0. Pivot bushes 40 are inserted into the bottom opening of each stringer 12, 14, 16 and 18 via cylinder portion 42.

The bushes 40 are welded in place around a collar 44 that abuts the end of each stringer. An arm portion 46 extends downwardly and a bore 48 through the arm extends in a transverse, substantially horizontal, orientation.

A base plate 50 comprises a ground engaging portion 52 having first and second upright brackets 54 and 56 extending upwardly therefrom in a parallel spaced relationship. Each bracket 54, 56 is provided with first and second aligned holes 58 and 60. To secure the adjacent pairs of stringers 12 and 14, 16 and 18, to a base plate 50, the arm portions 46 are positioned between the brackets 54, 56 and bolts (not shown) are inserted through the aligned holes 48, 58 and 60, and are secured in place by nuts (not shown).

In this way, the stringers 12, 14, 16 and 18, treads 20 and base plates 50 essentially form a parallelogram-type structure capable of pivoting, so that the tread surface 22 of each tread remains substantially parallel to the ground engaging portions of the base plates 50. Thus, assuming the base plates 52 rest on a horizontal surface, the top surface 22 of each tread is also automatically horizontal, in compliance with safety regulations Furthermore, as the spacing between the bores drilled through the stringers is equidistant for each tread 20, the going and rise distance for each tread is also identical to further comply with regulations.

The unit further comprises first and second top brackets 62 as shown mostly clearly in Figs. 4 and 9. The top brackets 62 are configured to releasably secure the unit 1 0 to a landing or platform to which the unit 10 is intended to provide access. The brackets 62 comprise a sleeve 64 dimensioned so as to snugly fit over the first and third stringers 12 and 16. To securely fix the bracket 62 to the stringers 12 and 16, bores 66 are provided in the sleeve 64. Rivets (not shown) are inserted through the bores 66 and corresponding bores in the stringers 12 and 16. In other embodiments, bolts or other suitable fasteners may be used, or the brackets may be welded to the stringers.

A hook 68 formed from a bent section flat metal bar is welded to the underside of the sleeve 64 and extends away from stringers 12 and 16. As can be seen from Fig. 4, the hook 68 is shaped so as to be seated snugly on a scaffold tube 370 that extends transverse to the stair unit 10, in use. The scaffolding tube 370 forms part of a staircase beam of a staircase, or part of a scaffolding platform support. Although the hook 68 provides a dependable connection to a platform or landing, it may be augmented by additional clips or fasteners (not shown).

The top tread 20 is positioned at an appropriate spacing with respect to the hook 68, so the step from the top tread to a landing or platform has the same rise and going as between the treads of the unit 10 itself. This further enhances the safety of the stairs, and avoids the need for additional components to bridge any gaps. The configuration of a landing is discussed in more detail below.

A locking strap assembly 72 is shown in more detail with reference to Figs. 4 and 8, the strap assembly 72 comprises a strap 74 formed from a metal plate having an elongate slot 76 provided near the bottom end thereof. Two such straps 74 are secured by a bolt 78 and nut 80 arrangement to the first and third stringers 12 and 16 via holes (not visible) in the strap 74, and transversely through the stringers. A second bolt 82 extends through holes (not visible) in the second and fourth stringers 14 and 18, and through the slot 76 of the strap 74. A first semi-circular washer 84 is provided proximate to the head of the bolt 82, and is fixed relative to it A second washer 86 is provided intermediate the slot 76 and a nut 88. The first washer 84 engages the around the stringer 16 and prevents the head of bolt 82 from rotating when the nut is tightened.

Once the stair unit 10 has been placed in the desired position, the nut 88 may be 1 5 tightened so as to prevent any relative movement between the first and second, and third and fourth stringers respectively. This in turn prevents any unwanted movement of the stair unit 10 under load. A further advantage of this arrangement is that the length of slot 76 may be adjusted to either prevent the stair unit 10 being lowered to a suflicient extent that fingers may be trapped between adjacent treads, or, alternatively, that the stair unit may not be adjusted outside the range of going to rise values that are permitted by safety and standards regulations.

Referring to Fig. 11, a second embodiment of the present invention is shown in which like parts are denoted by like numerals with the addition of the prefix "I".

The scaffold stair unit 110 functions in generally the same manner as the unit 10 of the first embodiment, but differs in the following key respects: 1. The second and fourth stringers 114 and 118 are the same length as the first and third stringers 112 and 116.

2. An additional tread 120 is provided at the very top of the stringers.

3 The top brackets 1 62 are secured to the second and fourth stringers 114 and 118 proximate the top thereof, rather than to the first and third stringers This arrangement enables the additional top tread 120 to be provided at the same level as the landing or platform surface to which the stair unit 110 provides access.

Surfaces of such platforms are generally made from wooden boards. If the scaffolding is left erected for a number of months and is exposed to heavy traffic during this period, the wooden surface of the platform or landing near the top of the stair unit tends to become worn away and uneven. By providing an additional metal tread at the top of the unit, this problem of wear can be minimised.

Fig. 12 illustrates a beam to assist in the erection of a staircase using stair units of the first and second embodiments of the invention The beam is hereinafter referred to as staircase beam 310. The staircase beam 310 comprises a top tube 370 that may be engaged by the hooks 68 and 168 of the stair units 10 and 110. It further comprises a bottom tube 372, connected to the top tube 370 by vertical tubes 374, 376 and 378.

Gaps are provided between the top tube 370 and vertical tubes 374 and 378. These gaps are bridged by gusset plates 380 and 382 respectively. Couplers 384 are provided on the connecting tubes 374, 376 and 378 to enable these tubes to he connected to upright tubes or "standards" 386 of a scaffold structure (see Fig. 13).

Further couplers 388 are secured to the top tube 370 to enable transverse or "transom" scaffold tubes 390 (see Fig 13) to be fitted thereto. Wings 395 project outwardly from the upper ends of connecting tubes 374 and 378 to assist with self-levelling as described below.

Referring to Fig. 13, the erection of scaffolding incorporating stair units of the present invention is illustrated schematically, with a number of components omitted for clarity. A scaffold platform 350 is first erected using standards 386, ledgers 390 and transoms 392, in order to support the boards forming the platform (not shown). A pair of staircase beams 310 are then secured to two standards 386 spaced one bay apart, in a direction away from the structure adjacent to which the platform is erected. The staircase beams 310 are first loosely secured using the couplers 384 and are slid up the standard 386 so that the outer most ledger 390 of the platform 350 is seated near the gap between top tube 370 and connecting tube 374 and abuts "wings" 395 as shown in Fig. 12. The couplers 384 are then tightened. The abutting relationship with the wings provides automatic self-levelling of the staircase beams 3 10 to speed the erection process.

Further standards 386 are secured to the outermost tubes 378 using further couplers 384. Three further transoms 393 are then secured to the couplers 388 so as to extend between the two staircase beams 3 10 and tie them together. Additional bracing tubes (not shown) are secured to the structure to increase its stability A stair unit 10 according to the present invention (illustrated without all treads for 1 0 clarity) can then be secured to the staircase beam 310 by placing hooks 68 over the top tube 370 The base plates 50 of the unit are able to rest parallel with the ground due to the ability of the unit to adjust using a parallelogram motion to the particular height of the landing formed by transoms 393. This parallel relationship of the base plates (and resultant self-levelling of the treads) may simply be achieved by a scaffolding erector standing on the bottom tread so that the base plates 50 are brought into contact with the ground along their length. The locking strap may then be secured so that no further movement of the stair unit may occur Boards (not shown) may then be placed over the transoms 393 forming the landing and the process repeated for the next flight of stairs formed from a second stair unit 10. In the case of this second unit 10 (partly shown) the feet 50 thereof rest on the landing adjacent to top of the first unit, and the stair unit extends in the opposite direction to the first unit 10.

Additional standards 386 are provided at centre of beam 310 (parallel to and connected with tube 376). Single or double guardrails (not shown) may be secured directly to the standards adjacent the stair unit 1 0 and further standards (not shown) at the base of the unit for improved safety when climbing the stair unit 10. The guardrails may be assembled from standard scaffolding poles and couplers. The configuration of the stair unit 10 and staircase beam 3 10 means that if guardrails are assembled as described above, the position of the guardrails will also be compliant with the relevant safety regulations.

Dismantling is performed in the opposite way to the method described above.

It will be appreciated that the present invention offers numerous improvements over the prior art in terms of speed of erection and dismantling, the ability to accommodate variations in scaffolding platform height, and in ternis of improved safety for scaffolding users, by ensuring that the treads of the stair unit are level and uniformly spaced within parameters provided by safety regulations. At the same time, erection requires no additional training for erectors familiar with tube and fitting systems, and mmimiscs the risk of components being in over-or undersupply on a particular project.

1 0 it should be appreciated that terms such as "top", "bottom" "left" and "right" should not be regarded as limiting unless explicitly claimed, but are merely used for ease of explanation. The term stringer" should not be regarded as being limiting to the tubular poles disclosed above. Various elongate components of differing profiles may be used instead.

Numerous changes may be made within the scope of the present invention For example, alternative base plates and means of attachment to a landing may be used.

For example, the base plate could be adjustable to compensate for uneven ground.

The tread construction may be adjusted to any suitable form capable of providing connections to the stringers on each end. For example, a complete box-section may be used. The length of the stringers may be altered in order to provide for stair units operable over a varying range of heights. For example, a unit having a nominal height of 2m may be adjustable between 1.8m and 2.2m whilst satisfying safety regulations, whereas a unit having longer stringers and a greater number of treads may provide a nominal height of 2.5m and may be adjustable between 2.7 and 2.3m whilst satisfying the safety regulations. Furthermore, the stair units may be modular in nature. So, for example, additional sections could be added to the stair units by means of push-fit connections at the ends of the stringers, to add additional height to a stair unit. The stringers may not be made from identical tubes. For example, on each side of the unit, a tube may carry the majority of the load from the treads, with a second stringer in the form of a thinner, weaker bar merely being present to maintain the parallelism of the treads. The stair units may be provided with end fittings to enable them to connect to proprietary scaffold systems such as the CUPLOKRTI or HAKIRTM systems mentioned above.

Claims

Claims I. A scaffold stair unit comprising a plurality of substantially

mutually equidistant and parallel treads pivotally secured to first and second stringers at a first side thereof and third and fourth stringers at a second side thereof in a parallelogram-like fashion, so as to permit the unit height to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads, wherein at least one of the first and second stringers and at least one of the third and fourth stringers are standard diameter scaffold tubes.

2. A unit according to claim I wherein the top of the unit comprises fixing means for releasable securement to a scaffold platform.

3. A unit according to claim 2 wherein the releasable securement is achieved by 1 5 means of gravity.

4. A unit according to claim 2 or claim 3 wherein the fixing means comprises a hook.

5. A unit according to any one of claims 2 to 4 wherein the fixing means is configured for releasable securement to scaffold tubing.

6. A unit according to claim 5 when dependent upon claim 4, wherein the hook is dimensioned for engagement around standard scaffold tubing.

7 A unit according to any preceding claim wherein the bottom of the unit comprises surface engaging means configured to drive the treads into substantially parallel alignment with the surface on which the unit rests, in use.

8. A unit according to any one of claims I to 6 wherein the bottom of the unit comprises surface engaging means adjustable to maintain the treads in a substantially level plane in the event that the surface on which the unit rests, in use, is uneven.

9 A unit according to aiiy preceding claim wherein the treads are formed having a substantially inverted U-shaped profile.

10. A unit according to claim 9 wherein connecting means to provide pivotal securernent to the stringers is provided proximate the free ends of U-shaped profile at each side of the tread.

11. A unit according to any preceding claim further comprising releasable locking means configured to maintain the spatial relationship between the stringers on one side of the unit 12. A unit according to claim 11 wherein the locking means comprises a strap extending from a stringer on a first side of the unit and provided with an elongate slot, and wherein a clamping device is secured to the other stringer on the first side and extends through the slot to selectively clamp the strap in a desired position.

13. A unit according to any preceding claim wherein the unit configured to have a top tread arranged at substantially the same level as the platform to which it is to be attached, in use.

14. A unit according to any preceding claim wherein the first, second, third and fourth stringers are standard diameter scaffold tubes.

1 5. A method of erecting a scaffold, stair unit according to claim 1, the method comprising the steps of: I) securing the top of the unit to an elevated structure; and 2) resting the bottom of the unit on the ground or a lower structure.

16. The method of claim 15 further comprising the step of locking the unit into positIon with locking means.

1 7. A method according to claim 15 or claim 16, wherein the step of resting the bottom of the unit on the ground or a lower structure automatically brings the treads into substantially parallel alignment with the surface of the ground or lower structure.

18. A kit of parts comprising a scaffold stair unit according to claim I and a staircase beam configured for attachment to a scaffold structure and configured to support the stair unit at an elevated position 19. A scaffold staircase beam for supporting scaffold stair units, the beam comprising.

a first coupler arrangement including a first and second spaced couplers at a first end for connection to a first scaffold column of a scaffold structure; a second coupler arrangement at a second end for connection to a second scaffold column; and a projection provided on the beam proximate the first coupler arrangement to contact a horizontal scaffold member secured to the first scaffold column, in use; wherein the beam is configured such that, when coupled to the first scaffold co]umn with the projection contacting the horizontal member, the top of the beam is at substantially the same level as the horizontal member.

20. A scaffold stair unit comprising a plurality of substantially mutually equidistant and parallel treads pivotally secured to first and second stringers at a first side thereof and third and fourth stringers at a second side thereof in a parallelogram-like fashion, so as to permit the unit height to be adjusted whilst maintaining the equidistant spacing and parallelism of the treads.