GB2426029A

GB2426029A - Adjustable staircase

Info

Publication number: GB2426029A
Application number: GB0513655A
Authority: GB
Inventors: Robert Howlett
Original assignee: MERLIN SERVICES Ltd
Current assignee: MERLIN SERVICES Ltd
Priority date: 2005-05-10
Filing date: 2005-07-04
Publication date: 2006-11-15
Anticipated expiration: 2025-07-04
Also published as: GB2426029B; GB0513655D0; GB0509458D0

Abstract

A scaffolding staircase comprising two pairs of stringers 10,12,14 and 16 spaced apart to define the two parallel sides of a flight of steps with a plurality of treads 18 equally spaced apart along the stringers and hingedly joined at their ends near their front and rear edges respectively to each of the two stringers in each pair. One of the sets of stringers securable to at least one scaffolding pole 31 forming part of the lift to which the staircase is to give access, and the stringers are locked so that the treads remain at a fixed orientation. The locking is by a rigid link 24 between one pair of stringers, or by rigid links 24,26 between the stringers in both pairs of stringers. Alternatively the or each rigid link comprises part of a generally horizontal scaffolding tie which extends between the lower end of the staircase and the scaffolding, or is part of a generally vertical scaffolding pole secured to each of the stringers and to the scaffolding, to fix the lower ends of the stringers. The scaffolding pole to which the stringers are attached may be either generally vertical or horizontal. A spirit level in one of the treads facilitates the adjustment of the stringers to render them generally horizontal. A handrail structure fitted to one side of the staircase comprises generally vertical spaced apart scaffolding poles attached to the stringers and a scaffolding pole attached thereto so as to extend parallel to the stringers but spaced therefrom to serve as a handrail. A similar handrail structure is attachable to the other side of the staircase.

Description

Title: Adjustable staircase

Field of invention

This invention concerns staircases and in particular staircases for use with scaffolding which give access from the ground to the first working platform (generally referred to as a lift) or from one lift to another in a multiple lift scaffold.

Background

Hitherto it has been commonplace to secure ladders between the ground and the first lift, and between one lift and the next. However ladders are not convenient or safe when carrying building materials or tools.

It is an object of the present invention to provide a staircase for use in place of a ladder.

It is a further object of the invention to provide a scaffolding staircase which complies with scaffolding industry standards EN 12811.

It is a further object of the invention to provide a staircase as aforesaid which can be inclined at more than one angle to the horizontal so as to span a range of different heights between ground and first lift, or between one lift and the next.

Summary of the invention

According to one aspect of the present invention, a scaffolding staircase comprises: (a) two pairs of stringers spaced apart to define the two parallel sides of a flight of steps, (b) a plurality of treads equally spaced apart along the stringers and hingedly joined at their ends near their front and rear edges respectively to each of the two stringers in each pair thereof, thereby permitting lengthwise displacement of the two parallel spaced apart stringers attached near the front of each tread relative to the two parallel stringers attached near the rear of each tread, (c) attachment means at the end of one of the sets of parallel spaced apart stringers by which they are securable to at least one scaffolding pole, forming part of the lift to which the staircase is to give access, and (d) means for locking the stringers so that the treads remain at a fixed orientation relative to the stringers.

The locking means may comprise a rigid link between the two stringers making up one pair of stringers, or rigid links between the stringers making up both pairs of stringers.

According to another aspect of the invention, when fitted to scaffolding so that the staircase gives access thereto, the locking means may comprise a scaffolding tie attached at one end to one of the stringers on one side of the staircase and at its other end to the scaffolding to which the staircase gives access, so as to extend generally horizontally therebetween and form a triangulation with the stringer and an upright scaffolding pole part of the said scaffolding.

Typically, the tie is attached near the lower end of the stringer.

Preferably a second parallel generally horizontal scaffolding tie joins one of the stringers on the other side of the staircase to the scaffolding.

In order to lock the stringers in position, at least one rigid link can be fitted so as to join the two stringers of at least one of the pairs of the stringers whereby the stringers are rigidly locked relative to each other.

Preferably rigid links are fitted so as to join the two stringers in both pairs of stringers so that both pairs of stringers are rigidly locked relative to each other.

Where a rigid link is/are provided, the or each rigid link may comprise part of the generally horizontal scaffolding tie which extends between the lower end of the staircase and the scaffolding to which it gives access.

In an alternative arrangement of a staircase when fitted to scaffolding to give access thereto, wherein the rigid link between stringers in the (or each) pair may comprise part of a generally vertical scaffolding pole which is secured by scaffolding couplers to each of the stringers and to the scaffolding, so that the lower ends of the stringers are fixed relative to the scaffolding.

In a combination of a staircase fitted to scaffolding as aforesaid, the scaffolding pole to which one of the sets of parallel stringers is to be attached may be either generally vertical or horizontal.

After securing one set of stringers to scaffolding, the treads of the staircase may be adjusted so as to be horizontal by moving the two stringers of the other set lengthwise relative to said one set, until the desired inclination of the treads is achieved, and thereafter locking at least one of the pairs of stringers, so as to prevent further relative movement therebetween, so as to maintain the treads in the desired inclination.

In general, the treads will be horizontal in the desired inclination.

To assist the levelling, spirit level means may be provided in at least one of the treads to facilitate the adjustment of the stringers relative to the scaffolding, to render them generally horizontal.

When a staircase as aforesaid is fitted to a scaffolding which exists upwardly over two or more lifts so as to give access to an upper lift from the one below, the stringers may be attached at their upper ends to a generally horizontal scaffolding pole of the upper lift and at their lower ends to at least one generally horizontal scaffolding pole forming part of the lift below, and at least one generally horizontal pole is employed to tie the lower end of at least one of the stringers from each pair to the scaffolding.

It is a function of a staircase constructed in accordance with the invention that the locking means unlocked or removed, one stringer is slidable relative to the other by means of the pivoting joints between treads and stringers, and by sliding one set of stringers relative to the other the angle between the treads and the stringers is altered such that when the stringers are slid apart to the full extent permitted by the links formed by the treads, the latter will be substantially flattened so as to be generally parallel to the run of the stringers.

Locking means or clip means may be provided to prevent relative movement of the stringers when the treads are generally flattened, so that the flattened structure is more convenient for storage and/or transportation.

In general the treads will overlap one another when flattened.

The stringers may be formed from extruded aluminium tubing, and also may the treads.

Alternatively the treads may be formed from a rigid plastics material, and typically are formed by moulding.

Plastics treads may be stiffened and/or reinforced by integral ribs and/or by struts.

In a preferred embodiment, each tread is joined at each end to the stringers by means of metal brackets, each of which includes a first flange by which it is pivotally joined to the pair of stringers on one side of the staircase and a second flange at right angles to the first, by which it is fixed to one end of the tread.

Preferably the second flange of each bracket is secured to the underside of the tread, and the brackets may be bolted or riveted to the treads to form an integral assembly.

The pivoting joints between brackets and stringers may be provided by rivets or bolts.

According to another aspect of the invention, a handrail structure for fitting to one side of a staircase as aforesaid, comprises generally vertical scaffolding poles adapted to be attached to the stringers near the top and bottom of the staircase on the said one side thereof, and a scaffolding pole attachable thereto by pivoting scaffolding couplers, so as to extend therebetween, generally parallel to the stringers of the staircase, but spaced therefrom by a convenient distance as to be at an appropriate height relative to the treads to serve as a handrail for a person ascending or descending the staircase.

Typically a second similar handrail structure may be provided which is attachable to the other side of the staircase.

The invention also lies in a staircase as aforesaid in combination with a handrail assembly therefor which comprises two upright poles secured to the staircase and a handrail pole which in use is fitted by scaffold couplers to the uprights so as to extend therebetween generally parallel to the stringers of the staircase to which the handrail is fitted.

- In a combination of staircase and handrail as aforesaid, scaffold couplers may be mounted on both of the stringers in the pair of stringers to which the handrail assembly is to be fitted, one pair near the top and the other pair near the bottom of the flight, the couplers being positioned on the stringers so that when the latter are mounted to scaffolding so as to extend at an angle thereto, the two couplers in the pair at the top and the two in the pair at the bottom of the flight are generally aligned one above the other, to allow the poles forming the uprights of the handrail assembly to be pushed therethrough and secured therein, to extend upwardly beyond the upper stringer.

When the upright poles are secured in the couplers, they also serve as rigid links between the stringers by which the treads can be locked at a desired angle.

Preferably the pair of couplers attached to the stringers are rotatable relative thereto, so that when the staircase is in position they can be aligned, to receive the poles which are to form the handrail uprights, but are adapted to be clamped in any selected position to prevent subsequent pivoting of the couplers relative to the stringers.

A second handrail assembly also comprising upright and handrail poles may be attached to the other side of the staircase.

In a staircase and handrail assembly as aforesaid, a second parallel scaffolding pole may be secured by further couplers to the uprights to extend between the or each handrail and the stringers therebelow, to reduce the risk of a person using the staircase from falling sideways through the gap between the handrail and the stringers.

The invention also lies in a kit of parts from which a staircase as aforesaid can be constructed.

The invention also lies in a kit of parts from which a staircase and handrail combination as aforesaid can be constructed.

The invention will now be described by way of example with reference to the accompanying drawings in which: - Fig 1 is a perspective view of a scaffolding staircase embodying the invention, Fig 2 is a similar view of the staircase albeit set at a different angle, Fig 3 is a perspective view of one of the treads of the staircase of Figs 1 and 2, Fig 4 is a diagrammatic side elevation of the staircase shown in Fig 2, Fig 5 is a diagrammatic side elevation of the staircase shown in Fig 1, Fig 6 is a diagrammatic side view of the staircase of Figs 1 and 2 in which the stringers have been adjusted so that the assembly is in a generally flattened condition, for storage or transportation, Fig 7 is an exploded perspective view of a tread, sections of the stingers between which it extends and angle brackets by which the tread is secured to the stringers, Fig 8 is a true side elevation of the staircase of Figs 1 and 2 shown attached to give access to a first scaffolding lift at a height of 1.6m, Fig 9 is a true similar view of the staircase giving access to a scaffolding lift at a height of 2.lm, Fig 10 is a true side elevation to a larger scale than Figs 8 and 9, showing the means of attachment between the top of the staircase and an upright of the scaffolding, Figi 1 is a true side elevation to a larger scale showing the means of attachment between the lower end of the staircase and the scaffolding, Fig 12 is a diagrammatic side elevation of a staircase showing an alternative means of locking the stringers by using an upright scaffolding pole attached to the stringers by

adjustable clamps,

Fig 13 is a diagrammatic scrap view of one end of a tread and part of a stringer to which it is pivotally attached, which shows one of the adjustable clamps for securing to a pole such as shown in Fig 12, Fig 14 is a diagrammatic side elevation of a staircase fitted with adjustable clamps as shown in Fig 13, with two upright poles shown attached to the stringers and a handrail and guard rail formed by further scaffolding poles, attached by adjustable clamps to the uprights to form a complete staircase and handrail assembly which can be attached at its upper end to a transverse scaffolding pole as shown, or two upright poles by suitable clamps, Fig 15 is a scrap true side elevation to an enlarges scale of part of the stringers and two of the treads with associated clamps for attaching the upright poles shown in Figs 12 and 14, and Fig 16 is a scrap side elevation showing how the inclination of the treads can be adjusted and maintained by the adjustment means.

In the drawings a staircase is shown comprising two pairs of stringers each formed form an aluminium scaffolding pole, denoted 10, 12, 14 and 16 separated by plastics scaffolding treads one of which is denoted by reference numeral 18.

Each tread is attached at each end to an angle bracket 20, 22 best seen in Fig 7. Bolts or rivets secure the brackets to the treads and the brackets to the stringers, attachments to the latter allowing pivoting of the treads to the stringers, such that the treads and stringers can be generally flattened as shown in Fig 6, or by adjusting the relative positions of the stringers. In this way the treads can occupy a range of inclinations relative to the stringers, so that the treads can be adjusted so as to be generally horizontal irrespective of the angle subtended by the lower stringers 12, 16 and the ground, between two extremes of inclination such as for example 30 and 430 as shown by comparing Figs 4 and 5.

The stringers 10, 12 and 14, 16 can be locked in different ways.

In Figs 1 and 2 short poles 24, 26 are shown coupled to the stringers by standard couplings or brackets such as 28, 30.

In Figs 8 and 9 the stringers are shown attached to longer upright scaffolding poles 32, 34 and the former is coupledby 28, 30 to the nearside stringers 10, 12. A similar upright pole (not shown) is coupled to the stringers 14, 16 at the end of the treads.

At its upper end, the lower stringer 12 can be coupled to a transverse scaffolding pole such as 31 in Figs 1 and 2 or is coupled by coupler 36 to the upright pole 34. Although not shown the other lower stringer 16 on the other side of the staircase is similarly coupled to another similarly placed upright pole (not shown).

Figs 10 and 11 show the couplings 28, 30 and 36 in more detail, and also show how the lower end of upright 32 is coupled by coupling 38 to a horizontal scaffolding tie pole 40 the other end of which is tied to uprights such as 3and 42 (as shown in Figs 8 and 9).

Figs 8 and 9 also show how a handrail (pole) 44 can be attached by couplings 46, 48 to uprights 32 and 34 and how a guard rail (pipe) 50 can also be attached by couplings 52, 54 to the uprights 32 and 34. Additional guard rails 56, 58 associated with the first lift are also shown attached to uprights 34, 42 in Figs 8 and 9.

The staircase can be supplied complete with one or more upright grabposts (poles) such as as shown in Fig 12, which in some circumstances may be deemed sufficient for safety reasons. The lower end of each such post 60 is coupled by couplings 62, 64 to two of the stringers 10, 12 and once secured in place serve to lock the stringers and therefor the treads 18 in position.

Alternatively the staircase may be supplied with a handrail assembly for one (or both) sides as shown in Fig 14, each comprising two upright poles 66, 68, a handrail 70 and optionally a guard rail 72, each attached to the uprights 66, 68 by couplings 74, 76 and 78, 80. The lower ends of the uprights are attached to both stringers by couplings 82, 84 and 86, 88. As with simple grab posts such as 60, once secured the, or each, upright 66, 68 locks the stringers and treads in position.

Also shown in Fig 14 is a coupling 90 for securing the lower stringer 12 to a transverse scaffolding pole 92 forming part of the lift to which the staircase gives access.

Where the staircase is to give access from the ground to the first lift of a scaffolding assembly, the lower end of stringers 12 and 16 can rest on the ground and may be tied to the scaffolding assembly by poles such as 40 as shown in Figs 8 and 9.

Where the staircase is to give access between one lift and another in a multiple lift scaffolding assembly, the lower ends of stringers 12 and 16 may be attached by couplings (such as 90 as shown in Fig 14) secured at their lower ends to join the stringers to a transverse pole (not shown) of the lower lift or may be attached by couplings such as 28, to upright poles such as 32 (see Figs 8 to 11) which form part of, and extend up from, the lower lift, to provide anchoring points for the lower ends of the stringers 10, 12 etc., and optionally anchoring points for handrails and guard rails (such as 44, 50 in Figs 8 to 11), if not forming part of the staircase assembly as shown in Fig 14.

If handrails and guard rails 70, 72 and dedicated uprights such as 66, 68 are provided as part of the staircase assembly (as shown in Fig 14), they are all preferably constructed from aluminium tube to reduce the weight of the staircase.

In Fig 16 an adjuster generally designated 94 has a cross-bar handle 96 welded to a shank section 98 which is threaded over part of its length as shown at 100. The threaded region is threadedly engaged in an internally threaded coupling 102 which is pivotally joined to the lower stringer 12. The remote upper end 104 of the shank is not threaded but is rotatably received in a coupling 106 which is pivotally joined to the upper stringer 10. The unthreaded portion of the shank is freely rotatable within the upper coupling 106 but is prevented from axial movement relative to the coupling by two radially extending pins 108,110 or two annular rings (not shown) which like the pins cannot pass through the coupling.

In use the lower stringers of the staircase are secured in position and the upper stringers can then be raised or lowered while remaining parallel to the lower stringers by rotating the shank 94 by turning the handle 94, so that the shank unscrews downwardly from, or screws upwardly into the coupling I 02. This is continued until the treads are generally horizontal. The screw threaded engagement of the shank in the lower coupling 102 ensures that the spacing between the stringers is maintained.

Claims

1. A scaffolding staircase comprising: (a) two pairs of stringers spaced apart to define the two parallel sides of a flight of steps, (b) a plurality of treads equally spaced apart along the stringers and hingedly joined at their ends near their front and rear edges respectively to each of the two stringers in each pair thereof, thereby permitting lengthwise displacement of the two parallel spaced apart stringers attached near the front of each tread relative to the two parallel stringers attached near the rear of each tread, (c) attachment means at the end of one of the sets of parallel spaced apart stringers by which they are securable to at least one scaffolding pole, forming part of the lift to which the staircase is to give access, and (d) means for locking the stringers so that the treads remain at a fixed orientation relative to the stringers.

2. A staircase as claimed in claim 1, wherein the locking means comprises a rigid link between the two stringers making up one pair of stringers.

3. A staircase as claimed in claim 1, wherein the locking means comprises rigid links between the stringers making up both pairs of stringers.

4. A staircase as claimed in claim 1 when fitted to scaffolding to give access thereto, wherein the locking means comprises a scaffolding tie attached at one end to one of the stringers on one side of the staircase and at its other end to scaffolding to which the staircase gives access, so as to extend generally horizontally therebetween and form a triangulation with the stringer and an upright scaffolding pole part of the said scaffolding.

5. A staircase as claimed in claim 4, wherein the tie is attached near the lower end of the stringer.

6. A staircase as claimed in claim 4 or 5, wherein a second parallel generally horizontal scaffolding tie joins one of the stringers on the other side of the staircase to the scaffolding.

7. A staircase as claimed in claim 4, 5 or 6, wherein at least one rigid link joins the two stringers of at least one of the pairs of the stringers whereby the stringers are rigidly locked relative to each other.

8. A staircase as claimed in claim 4, 5 or 6, wherein rigid links join the two stringers in both pairs of stringers so that both pairs of stringers are rigidly locked relative to each other.

9. A staircase as claimed in claim 7 or 8, wherein the or each rigid link comprises part of the generally horizontal scaffolding tie which extends between the lower end of the staircase and the scaffolding to which it gives access.

10. A staircase as claimed in claim 2 or 3 or 7 or 8 when fitted to scaffolding, wherein the rigid link between stringers in the (or each) pair comprises part of a generally vertical scaffolding pole which is secured by scaffolding couplers to each of the stringers and to the scaffolding, so that the lower ends of the stringers are fixed relative to the scaffolding.

11. A staircase when fitted to scaffolding as claimed in any of claims 2 to 10, wherein the scaffolding pole to which one of the sets of parallel stringers is to be attached is either generally vertical or horizontal.

12. A staircase as claimed in any of claims 1 to 11, wherein after securing one set of stringers to scaffolding, the treads are adjusted so as to be horizontal by moving the two stringers of the other set lengthwise relative to said one set, until the desired inclination of the treads is achieved, and thereafter locking at least one of the pairs of stringers, so as to prevent further relative movement therebetween, so as to maintain the treads in the desired inclination.

13. A staircase as claimed in claim 12, wherein the treads are generally horizontal in the desired inclination.

14. A staircase as claimed in claim 13, wherein spirit level means is provided in at least one of the treads to facilitate the adjustment of the stringers relative to the scaffolding, to render them generally horizontal.

15. A staircase as claimed in any of claims 1 to 15, when fitted to a scaffolding which exists upwardly over two or more lifts, wherein the stringers are attached at their upper ends to a generally horizontal scaffolding pole of an upper lift and at their lower ends to at least one generally horizontal scaffolding pole forming part of the lift below the said upper lift, and at least one generally horizontal pole is employed to tie the lower end of at least one of the stringers from each pair to the scaffolding.

16. A staircase as claimed in any of claims 12 to 15, wherein with the locking means unlocked or removed; one stringer is slidable relative to the other by means of the pivoting joints between treads and stringers, and by sliding one set of stringers relative to the other the angle between the treads and the stringers is altered such that when the stringers are slid apart to the full extent permitted by the links formed by the treads, the latter will be substantially flattened so as to be generally parallel to the run of the stringers.

17. A staircase as claimed in claim 16, wherein further locking means or clip means is provided to prevent relative movement of the stringers when the treads are generally flattened, so that the flattened structure is more convenient for storage and/or transportation.

18. A staircase as claimed in claim 16 or 17, wherein the treads overlap one another when flattened.

19. A staircase as claimed in any of claims 1 to 18, wherein the stringers are formed from extruded aluminium tubing.

20. A staircase as claimed in any of claims 1 to 20, wherein the treads are also formed from aluminium.

21. A staircase as claimed in any of claims 1 to 19, wherein the treads are formed from a rigid plastics material.

22. A staircase as claimed in claim 21, wherein the treads are formed by moulding.

23. A staircase as claimed in claim 20, 21 or 22, wherein the treads are stiffened and/or reinforced by integral ribs and/or by struts.

24. A staircase as claimed in any of claims 1 to 23, wherein each tread is joined at each end to the stringers by means of metal brackets, each of which includes a first flange by which it is pivotally joined to the pair of stringers on one side of the staircase and a second flange at right angles to the first, by which it is fixed to one end of the tread.

25. A staircase claimed in claim 24, wherein the second flange is secured to the underside of the tread.

26. A staircase as claimed in claim 24 or 25, wherein the brackets are bolted or riveted to the treads to form an integral assembly.

27. A staircase as claimed in any of claims 24 to 26, wherein pivoting joints between brackets and stringers are provided by rivets or bolts.

28. A handrail structure for a staircase as claimed in claims 1 to 27, for fitting to one side of the staircase comprising generally vertical scaffolding poles adapted to be attached to the stringers near the top and bottom of the staircase on the said one side thereof and a scaffolding pole attachable thereto by pivoting scaffolding couplers, so as to extend therebetween, generally parallel to the stringers of the staircase, but spaced therefrom by a convenient distance as to be at an appropriate height relative to the treads to serve as a handrail for a person ascending or descending the staircase.

29. A handrail structure claimed in claim 28, wherein a similar handrail structure is also provided which is attachable to the other side of the staircase.

30. A staircase as claimed in any of claims 1 to 27, in combination with a handrail assembly therefor which comprises two upright poles secured to the staircase and a handrail pole which in use is fitted by scaffold couplers to the uprights so as to extend therebetween generally parallel to the stringers of the staircase to which the handrail is fitted.

31. A staircase as claimed in claim 30, wherein scaffold couplers are mounted on both of the stringers in the pair of stringers to which the handrail assembly is to be fitted, one pair near the top and the other pair near the bottom of the flight, the couplers being positioned on the stringers so that when the latter are mounted to scaffolding so as to extend at an angle thereto, the two couplers in the pair at the top and the two in the pair at the bottom of the flight are generally aligned one above the other, to allow the poles forming the uprights of the handrail assembly to be pushed therethrough and secured therein, to extend upwardly beyond the upper stringer.

32. A staircase as claimed in claim 31, wherein when the upright poles are secured in the couplers, they also serve as rigid links between the stringers by which the treads can be locked at a desired angle.

33. A staircase and handrail assembly as claimed in claim 32, wherein the pairs of couplers attached to the stringers are rotatable relative thereto, so that when the staircase is in position they can be aligned, to receive the poles which are to form the handrail uprights, but are adapted to be clamped in any selected position to prevent subsequent pivoting of the couplers relative to the stringers.

34. A staircase as claimed in claim 30 or 33, wherein a second handrail assembly also comprising upright and handrail poles is attached to the other side of the staircase.

35. A staircase and handrail assembly as claimed in any of claims 30 to 34, wherein a second parallel scaffolding pole is securable by further couplers to the uprights between the or each handrail and the stringers therebelow, to reduce the risk of a person using the staircase from falling sideways through the gap between the handrail and the stringers.

36. A kit of parts from which a staircase as claimed in claim 1, 2 or 3 can be constructed.

37. A kit of parts from which a staircase and handrail combination as claimed in any of claims 30 to 35 can be constructed.

38. A staircase as claimed in claim 1 and handrail combination therefor constructed, arranged and adapted to he secured to scaffolding, substantially as herein described with reference to and as illustrated in the accompanying drawings.

38. A staircase constructed, arranged and adapted to be secured to scaffolding substantially as herein described with reference to and as illustrated in the accompanying drawings.

39. A staircase and handrail combination therefor constructed, arranged and adapted to be secured to scaffolding, substantially as herein described with reference to and as illustrated in the accompanying drawings. r1

Amendments to the claims have been flied as follows

I. A scaffolding staircase when fitted to scaffolding to give access thereto, comprising: (a) two pairs of stringers spaced apart to define the two parallel sides of a flight of steps, (b) a plurality of treads equally spaced apart along the stringers and hingedly joined at their ends near their front and rear edges respectively to each of the two stringers in each pair thereof, thereby permitting lengthwise displacement of the two parallel spaced apart stringers attached near the front of each tread relative to the two parallel stringers attached near the rear of each tread, (c) attachment means at the end of one of the sets of parallel spaced apart stringers by which they are securable to at least one scaffolding pole, forming part of the lift to which the staircase is to give access, (d) means for locking the stringers so that the treads remain at a fixed orientation relative to the stringers, and wherein the locking means comprises a scaffolding tie attached at one end to one of the stringers on one side of the staircase and at its other end to the scaffolding to which the staircase gives access, so as to extend generally horizontally therehetween and form a triangulation with the stringer and an upright scaffolding pole forming part of the said scaffolding.

2. A staircase as claimed in claim I, wherein the locking means also comprises a rigid link between the two stringers making up one pair of stringers.

3. A staircase as claimed in claim 1, wherein the locking means also comprises rigid links between the stringers making up both pairs of stringers. 2o

4. A staircase as claimed in claim 1, 2 or 3, wherein the tie is attached near the lower end of the stringer.

5. A staircase as claimed in claim 3 or 4, wherein a second parallel generally horizontal scaffolding tie joins one of the stringers on the other side of the staircase to the scaffolding.

6. A staircase as claimed in claim 3, 4 or 5, wherein at least one rigid link joins the two stringers of at least one of the pairs of the stringers whereby the stringers are rigidly locked relative to each other.

7. A staircase as claimed in claim 3, 4, or 5, wherein rigid links join the two stringers in both pairs of stringers so that both pairs of stringers are rigidly locked relative to each other.

8. A staircase as claimed in claim 6 or 7, wherein the or each rigid link comprises part of the generally horizontal scaffolding tie which extends between the lower end of the staircase and the scaffolding to which it gives access.

9. A staircase as claimed in claim 2 or 3 or 6 or 7 when fitted to scaffolding, wherein the rigid link between stringers in the (or each) pair comprises part of a generally vertical scaffolding pole which is secured by scaffolding couplers to each of the stringers and to the scaffolding, so that the lower ends of the stringers are fixed relative to the scaffo]ding.

10. A staircase. when fitted to scaffolding as claimed in any of claims 2 to 9, wherein the scaffolding pole to which one of the sets of parallel stringers is to be attached is either generally vertical or horizontal.

11. A staircase as claimed in any of claims I to 10, wherein after securing one set of stringers to scaffolding, the treads are adjusted so as to be horizontal by moving the two stringers of the other set lengthwise relative to said one set, until the desired inclination of the treads is achieved, and thereafter locking at least one of the pairs of stringers, so as to prevent further relative movement therebetween, so as to maintain the treads in the desired inclination.

12. A staircase as claimed in claim 11, wherein the treads are generally horizontal in the desired inclination.

13. A staircase as claimed in claim 12, wherein spirit level means is provided in at least one of the treads to facilitate the adjustment of the stringers relative to the scaffolding, to render them generally horizontal.

14. A staircase as claimed in any of claims I to 14, when fitted to a scaffolding which exists upwardly over two or more lifts, wherein the stringers are attached at their upper ends to a generally horizontal scaffolding pole of an upper lift and at their lower ends to at least one generally horizontal scaffolding pole forming part of the lift below the said upper lift, and at least One generally horizontal pole is employed to tic the lower end of at least one of the stringers from each pair to the scaffolding.

15. A staircase as claimed in any of claims Ii to 14, wherein with the locking means unlocked or removed, one stringer is slidable relative to the other by means of the pivoting joints between treads and stringers, and by sliding one set of stringers relative to the other the angle between the treads and the stringers is altered such that when the stringers are slid apart to the full extent permitted by the links formed by the treads, the latter will be substantially flattened so as to be generally parallel to the run of the stringers.

I 6. A staircase as claimed in claim 15, wherein further locking means or clip means is provided to prevent relative movement of the stringers when the treads are generally flattened, so that the flattened structure is more convenient for storage and/or transportation.

17. A staircase as claimed in claim 15 or 16, wherein the treads overlap one another when flattened.

18. A staircase as claimed in any of claims I to 17, wherein the stringers are formed from extruded aluminium tubing.

19. A staircase as claimed in any oIclaims I to 18, wherein the treads are also formed from aluminium.

20. A staircase as claimed in any of claims 1 to 19, wherein the treads are formed from a rigid plastics material.

21. A staircase as claimed in claim 20, wherein the treads are formed by moulding.

22. A staircase as claimed in claim 19, 20 or 21, wherein the treads are stiffened and/or reinforced by integral ribs and/or by struts.

23. A staircase as claimed in any of claims I to 22, wherein each tread is joined at each end to the stringers by means of metal brackets, each of which includes a first flange by which it is pivotally joined to the pair of stringers on one side of the staircase and a second flange at right angles to the first, by which it is fixed to one end of the tread.

24. A staircase claimed in claim 23, wherein the second flange is secured to the underside of the tread.

25. A staircase as claimed in claim 23 or 24, wherein the brackets are bolted or riveted to the treads to fbrm an integral assembly.

26. A staircase as claimed in any of claims 23 to 25, wherein pivoting joints between brackets and stringers are provided by rivets or bolts.

27. A handrail structure for a staircase as claimed in claims 1 to 26, for fitting to one side of the staircase comprising generally vertical scaffolding poles adapted to be attached to the stringers near the top and bottom of the staircase on the said one side thereof, and a scaffolding pole attachable thereto by pivoting scaffolding couplers, so as to extend therebetween, generally parallel to the stringers of the staircase, hut spaced therefrom by a convenient distance as to he at an appropriate height relative to the treads to serve as a handrail for a person ascending or descending the staircase.

28. A handrail structure claimed in claim 27, wherein a similar handrail structure is also provided which is attachable to the other side of the staircase.

29. A staircase as claimed in any of claims 1 to 26, in combination with a handrail assembly thcrefor which comprises two upright poles secured to the staircase and a handrail pole which in use is fitted by scaffold couplers to the uprights so as to extend therebetween generally parallel to the stringers of the staircase to which the handrail is fitted.

30. A staircase as claimed in claim 29, wherein scaffold couplers are mounted on both of the stringers in the pair of stringers to which the handrail assembly is to be fitted, one pair near the top and the other pair near the bottom of the flight, the couplers being positioned on the stringers so that when the latter are mounted to scaffolding so as to extend at an angle thereto, the two couplers in the pair at the top and the two in the pair at the bottom of the flight are generally aligned one above the other, to allow the poles forming the uprights of the handrail assembly to be pushed therethrough and secured therein, to extend upwardly beyond the upper stringer.

31. A staircase as claimed in claim 30, wherein when the upright poles are secured in the couplers, they also serve as rigid links between the stringers by which the treads can be locked at a desired angle.

32. A staircase and handrail assembly as claimed in claim 31, wherein the pairs of couplers attached to the stringers are rotatable relative thereto, so that when the staircase is in position they can he aligned, to receive the poles which are to form the handrail uprights, but are adapted to be clamped in any selected position to prevent subsequent pivoting of the couplers re]ative to the stringers.

33. A staircase as claimed in claim 29 or 32, wherein a second handrail assembly also comprising upright and handrail poles is attached to the other side of the staircase.

34. A staircase and handrail assembly as claimed in any of claims 29 to 33, wherein a second parallel scaffolding pole is securable by further couplers to the uprights between the or each handrail and the stringers therebelow, to reduce the risk of a person using the staircase from falling sideways through the gap between the handrail and the stringers.

35. A kit of parts from which a staircase as claimed in claim 1 can be constructed.

36. A kit of parts from which a staircase and handrail combination as claimed in any of claims 29 to 34 can be constructed.

37. A staircase as claimed in claim 1 constructed, arranged and adapted to he secured to scaffolding substantially as herein described with reference to and as illustrated in the accompanying drawings.