GB2427643A

GB2427643A - An adjustable stair enabling variation in tread angle

Info

Publication number: GB2427643A
Application number: GB0513379A
Authority: GB
Inventors: Robert David Black; John Alexander Black
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-06-30
Filing date: 2005-06-30
Publication date: 2007-01-03
Also published as: GB0513379D0

Abstract

An adjustable stair with longitudinal side members 12, 13 each having a longitudinal axis 12L, 13L, where the stair comprises a plurality of treads T1, T2, T3, T4 located between the side members, each tread having a working surface S1, S2, S3, S4. Each tread extends between the two side members, with each tread having a pivot means 14, 15, 16, 17 linking the tread to each side member to provide for the tread to pivot about a tread axis A1, A2, A3, A4 lying in a plane P common to the longitudinal axis of both side members, each tread axis being parallel with the other tread axes. An angling means (23, Fig 3) for simultaneously rotating each tread in the plurality about its tread axis relative to the plane to provide for the working surface of each tread to be simultaneously positioned at the same angle relative to the plane; the angling means providing for the positioning of the plurality and also for the plurality of the treads to be locked in a given working position when in use.

Description

ADJUSTABLE STAIR

TECHNICAL FIELD

This invention relates to an adjustable stair. It is particularly, but not exclusively, concerned with a temporary stair for use in a building being constructed or modified in some way. Typically in such a building there is a need for operatives to be able to readily move between floors when apertures through floors exist but before permanent stairs, ramps or walkways have been installed.

BACKGROUND ART

A temporary need to move between floors can be met by a conventional ladder.

However from a safety standpoint a conventional ladder does not necessarily suit a user for example one who is carrying a load which is heavy or bulky or both. A conventional ladder is provided with rungs of circular, or substantially circular, cross section. Such a cross sectional shape ensures that amount of the support presented to the foot of a user does not alter regardless of the inclination of the ladder. However a relatively narrow rung provide a relatively limited contact area between the rung and the foot of a user. This can be inconvenient whether to somebody going up or down the ladder or to somebody working in a way which requires them to stand on the ladder for a period.

Ladders can be equipped with treads rather than rungs. A tread of flat section provides a larger working surface to a foot of a user enabling the weight of the user to be distributed over a larger area than that afforded by a rung. However for safety reasons each tread needs to be disposed substantially horizontally (say within a range of 50 to the horizontal) so the range of angles in which the ladder with a fixed tread configuration can be set up is limited.

In our co-pending application 0508132.8 there is described a ladder with: longitudinal side members each having a longitudinal axis and each having a treads located between the side members, each tread having a working surface and extending between the side members, pivot means linking each tread to each side member to provide for the tread to pivot about a tread axis perpendicular to the longitudinal axis of each side member; and an angling member having a longitudinal working axis and a working end, the working axis being parallel to the longitudinal axis of each side member; and pivot means whereby the angling member is pivotably attached to each tread so that- in a working configuration the working ends of the side members and the working end of the angling member when placed on a plane surface, act in combination, to cause the working surface of each tread to lie parallel to the plane surface; and in a storage configuration the working surface of each tread is disposed by means of the angling member to lie substantially parallel to the longitudinal axis of each side member.

In the present context a tread is taken to be a member with a working surface for standing on by a user the member being of indefinite width (from side to side) and whose depth (from front to back) is greater than its thickness (from top to bottom).

This contrasts with a rung whose depth is similar to its thickness.

DISCLOSURE OF INVENTION

According to the present invention there is provided an adjustable stair with: longitudinal side members each having a longitudinal axis and each having a a plurality of treads located between the side members; each tread having a working surface to receive a foot of a user; each tread in the plurality extending between the side members, each tread having pivot means linking the tread to each side member to provide for the tread to pivot about a tread axis lying in a plane common to the longitudinal axis of both side members, a given tread axis being parallel to a corresponding tread axis of at least some of the remaining treads; and angling means for simultaneously rotating each tread in the plurality about its tread axis relative to the plane (by means off-set from the tread axis) to provide for the working surface of each tread to be simultaneously positioned at the same angle relative to the plane; the angling means providing for the positioning of the plurality: at a first working position where the working surface of each tread is substantially parallel with the plane; at a second working position where the working surface of each tread is at a limiting angle relative to the plane long; and at any intermediate position between the first and second positions; the angling means providing for the plurality of steps to be locked in a given working position when in use.

According to a first preferred version of the present invention the angling means includes a longitudinal member extending along, or within, one of the side members; the longitudinal member being linked by pivotal means to each tread in the plurality thereof so that displacement of the longitudinal member relative, to the side member provides for movement of the plurality at the first working position or the second working position or at any intermediate position there between; and working means for displacing the longitudinal member relative to the side member.

According to a second preferred version of the present invention or of the first preferred version thereof wherein the working means includes a lead screw for displacing the longitudinal member.

According to a third preferred version of the present invention or of any preceding preferred version thereof the longitudinal member is housed within a side member.

According to a fourth preferred version of the present invention or of any preceding preferred version thereof the stair is equipped with means for attaching the stair to an external support to inhibit unintended displacement of the ladder or a component thereof.

BRIEF DESCRIPTION OF DRAWINGS

An exemplary embodiment of the present invention wifi now be described with reference to the accompanying drawings of a prototype of an adjustable stair of which: Figure 1 is a side view of the stair from above with the steps in a first working configuration; Figure 2 is a front view of the stair shown in Figure 1; Figure 3 is a side view detail of a part of the stair of Figures 1 and 2 showing relative position of movable components in the first working configuration; Figure 4 is a is an end view of the stair from beneath with the steps in a second Figure 5 is a side view detail of a part of the stair of Figure 4 showing relative position of movable components in the second working configuration.

MODE FOR CARRYING OUT THE INVENTION

Figures 1 to 5 variously show a stair 11 with hollow side members 12, 13 having, respectively, longitudinal axis 12L, 13L In this case the side members 12, 13 are parallel to one another.

A plurality of treads Ti to T4 is located between the side members 12, 13. The treads Ti to T4 are identical in form and function.

Tread Ti has a working surface Si to receive a foot of a user. Each of treads Ti to T4 in the plurality extend between the side members 12, 13. The right hand side of each tread Ti to T4 is pivotably linked to side member 13 by a pivot pin (respectively pins 14 - 17). The left hand side of each tread TI to T4 is similarly pivotably connected to side member 12 by a pivot pin (not shown). The right and left hand pivot pins for each tread serve to define a tread axis, namely: tread axis for tread Al Ti A2 T2 A3 T3 A4 T4.

Collectively the tread axis lie in a plane P parallel to towards leading edges i2L, i3L of, respectively, side members 12, 13.

Towards the rear end of each tread Ti to T4 there is provided a projection by means of which the tread is positioned to lie in a working configuration. Figure 3 shows projection 19 from the side of tread T4 extending slidably through arctuate slot 20 in inner side wall 21 of side member 12. Projection 19 has an outer end 22 which is rotatable within a bore 30 in angling member 23 whose function will be described hereafter.

The angling member 23 can be displaced backwards and forwards relative to side member 12 in direction of arrow A-A' by means of a lead screw 24 which is rotatable, by means of head 25, in threaded block 24B secured to side membervl2. On rotating the cap 25 (as shown in Figure 3) in a clockwise direction the angling member 23 is moved in the direction A' causing the projection 19 of tread 14 to be driven along arctuate slot 20 and, simultaneously, the remaining treads Ti to 13 to be driven upwardly along their respective arctuate slots 27-29. If this clockwise rotation is allowed to continue each tread projection reaches the upper end of its corresponding arctuate slot as shown in Figure 4. In this configuration the working surfaces Si -S4 are aligned to lie in plane P. In this configuration the stair ii can be used as a ramp or gangway.

From the configuration shown Figure 4 if the lead screw 24 (Figure 3) is now rotated in an anti-clockwise direction the treads Ti to 14 are caused to move out of the common horizontal plane P typically until reaching a required intermediate configuration as shown in Figures 1, 2 and 3 in which the treads Ti to 14 (and so their working surfaces Si to S4) occupy a position so that the stair ii can be used in a location in which, with the stair ii in place, the working surface Si to S4 are horizontal. The use of lead screw 24 in threaded block 24B ensures a mechanical advantage such that, regardless of the chosen configuration, any credible load on the stair ii cannot result in the lead screw 24 being caused to rotate by the action of the block 24B upon it. Thus the mere action of ceasing to rotate the lead screw 24 once the desired configuration of the treads Ti to 14, and so of the working surfaces Si to S4 has been achieved, results in the safe maintenance of the resulting configuration to be achieved without the need for further securing action.

Figure 5 shows the components of Figure 3 when the angling means 23 has been drawn by means of lead screw 24 to a position which the projection 19 is approaching end 32 of arctuate slot 20 at which location the working surfaces Si to S4 of the treads Ti to T4 are at about 600 to the plane P. In further embodiments means can be provided to positively secure the ladder in a given location to a suitable fixture to prevent inadvertent alignment or removal of the ladder. The ladder in the prototype described is of metal (aluminium alloy). However for other applications wood, plastics or composite materials could be used or combinations of some or all of these. A ladder according to the present invention is readily coated or signed to a greater or lesser extent with distinctive materials, instructions, signs of ownership or origin, testing procedures or whatever.

INDUSTRIAL APPLICABILITY

The adjustable ladder of the present invention provides a readily used means for moving vertically between levels by providing for the ready and simultaneous alignment of the treads automatically by a operation of a linkage providing for the pivoting of the tread relative to the plane of side members of the ladder. Such a ladder is applicable to a wide range of industries including constructional, building and equipment installation amongst many others.

Claims

An adjustable stair with: longitudinal side members each having a longitudinal axis and each having a working end; a plurality of treads located between the side members; each tread having a working surface to receive a foot of a user; each tread in the plurality extending between the side members, each tread having pivot means linking the tread to each side member to provide for the tread to pivot about a tread axis lying in a plane common to the longitudinal axis of both side members, a given tread axis being parallel to a corresponding tread axis of at least some of the remaining treads; and angling means for simultaneously rotating each tread in the plurality about its tread axis relative to the plane (by means off-set from the tread axis) to provide for the working surface of each tread to be simultaneously positioned at the same angle relative to the plane; the angling means providing for the positioning of the plurality: at a first working position where the working surface of each tread is substantially parallel with the plane; at a second working position where the working surface of each tread is at a limiting angle relative to the plane long; and at any intermediate position between the first and second positions; the angling means providing for the plurality of steps to be locked in a given working position when in use.
2 An adjustable stair as claimed in Claim 1 wherein the angling means includes a longitudinal member extending along, or within, one of the side members; the longitudinal member being linked by pivotal means to each tread in the plurality thereof so that displacement of the longitudinal member relative, to the side member provides for movement of the plurality at the first working position or the second working position or at any intermediate positlion there between; and working means for displacing the longitudinal member relative to the side member.
3 An adjustable stair as claimed in any preceding claim wherein the working means includes a lead screw for displacing the longitudinal member.
4 An adjustable stair as claimed in any preceding claim wherein the longitudinal member is housed within a side member.
An adjustable stair as hereinbefore described with reference to the accompanying drawings.
6 An adjustable stair as claimed in any preceding claim equipped with means for attaching the ladder to an external support to inhibit unintended displacement of the ladder or a component thereof.