GB2081793A - Improvements in or Relating to Ladders - Google Patents

Abstract

The invention provides a ladder with adjustable legs so that it can be used on uneven surfaces. Each leg (1, 2, 4, 5) consists of a fixed part consisting of C-shaped aluminium and a sliding part (11, 12, 15, 16). Various forms of locking means for securing the sliding parts within the fixed parts are described. Where the ladder is a step ladder, it also includes a top platform (9) having an adjustable bar (10) which enables the angle between the legs to be adjusted. An adaptor (Fig. 8) is also disclosed for fixing to a conventional ladder stile to provide length adjustment. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Ladders This invention relates to ladders and it is an object of the present invention to provide a ladder which is capable of being used in situations in which it would be difficult or impossible to use a known ladder.

According to one aspect of the invention, there is provided a ladder comprising at least one pair of legs and a plurality of steps, wherein the length of at least one of said legs is continuously adjustable within predetermined limits.

Preferably, the or each adjustable leg comprises a fixed part and a sliding part and means for locking the sliding part relative to the fixed part.

Preferably, in the or each adjustable leg the fixed part and the sliding part each consists of metal having a C-shaped cross-section.

Preferably, said sliding part is slidable and lockable within the fixed part.

In one embodiment, said sliding part is lockable in position by wedging means located between two relatively inclined planes, one plane being provided on the associated fixed part, and the other being provided on said sliding part.

Teach sliding part may be lockable in position by means of a pair of wedging means each wedging means being located between a respective pair of inclined planes.

The or each wedging means may be constituted by a roller.

Preferably, the or each roller is mounted for rotation.

Where a pair of broilers is provided, they are preferably mounted on a common bracket.

In another embodiment, said sliding part is lockable in position by means of a plate fixed longitudinally with respect to the fixed part or sliding part and provided with means for urging it against the sliding or fixed part.

The urging means may be a threaded boss on a manually operable knob.

Alternatively, the urging means may be a pivoted lever having an eccentric cam in the region of one end thereof.

There may be provided a second pair of legs mounted for pivotting relative to said first pair of legs, thus producing a so-called "pair of steps".

Expediently, the legs of said second pair are each hingedly attached on a common hinge axis to a respective one of the other pair of legs.

Preferably, the length of each of said legs is continuously adjustable within predetermined limits.

According to a further aspect of the invention, there is provided an adaptor for use with a conventional ladder to form the ladder of said one aspect oF the invention, the adaptor comprising two leg parts secured together for attachment to respective legs of conventional ladder, wherein the length of at least one of said leg parts is continuously adjustable within predetermined limits.

Preferably, the or each adjustable leg part comprises: a first portion for attachment to a leg of a conventional ladder; a second portion mounted for sliding relative to said first portion; and means for locking the second portion relative to the first portion.

Each leg part may be provided with securing means for securing to a respective leg of a conventional ladder.

Expediently, said securing means comprises a bracket.

Embodiments of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of one embodiment of the invention: Figure 2 is a front elevation partly in section of one form of locking means for use in connection with the embodiment of the invention illustrated in Figure 1: Figure 3 is a cross-sectionai view of the locking means shown in Figure 2 taken on the line 3:3 looking in the direction of the arrows; Figures 4 and 5 are side views partly in section of alternative locking means; and Figures 6 and 7 show a modified form of lockingmeans using the same principle as that shown in Figures 2 and 3; Figure 8 shows an adaptor unit; and Figures 9 to 12 show an additional locking device.

The embodiment illustrated in Figure 1 includes two legs 1 and 2 with seven steps 3 extending therebetween. Two further legs 4 and 5 are hingedly connected to respective ones of the legs 1 and 2, the axis of the hinge points 6 and 7 being common. The two legs 4 and 5 are maintained in parallel relationship by means of a plurality of bracing members 8. In the particular embodiment illustrated, all the legs consist of extruded or pressed metal, such as aluminium, having a generally C-shaped cross-section. As shown, the channels in C-shaped cross-section of the front legs 1 and 2 open inwardly, while the channels of the rear legs 4 and 5 open outwardly.

However, it is to be understood that both channels may open outwardly, or both open inwardly, if so desired.

The lengths of all the steps are equal so that the legs 1 and 2 are maintained substantially parallel. However, the length may increase progressively from the top step to the bottom step so that the legs are at an acute angle to one another. The two legs of the second pair are interconnected by bracing members which may again be arranged to hold the second pair of legs parallel or at an acute angie.

A platform 9 is hingedly mounted between two legs 1 and 2 and includes a bar 10 which engages with the topmost one of the bracing members which is indicated by the reference 8'. The bar 10 is provided with upstanding threaded rods which pass through slots 35 in the platform and receive wing nuts 36. Thus the position of the bar 10 below the platform 9 can be adjusted by slackening the wing nuts 36. This, of course, enables the angle between the front and rear pairs of legs to be adjusted as required.

It will be understood that the device so far described constitutes a substantially conventional pair of domestic steps which will fold together or which can be maintained in the open position illustrated by engagement of the bar 10 with the bracing member 8'. However, the embodiment illustrated differs from conventional steps in that the lengths of the legs are all continuously adjustable, within predetermined limits.

An alternative method of adjusting the platform position and the angle between the front and rear pairs of legs is as follows. A longitudinally extending slot may be provided in each of legs 4 and 5 at their upper ends and further elongate slots may be provided in respective side flanges of platform 9. Then, at each side of the platform, a bolt may be passed through the slot of the platform and the slot in the relevant leg 4 or 5 and tightened with a flynut to set a desired angle between the front and rear pairs of legs. This method allows the platform 9 to be level at all angles between the leg pairs, improves the rigidity of the steps, and results in automatic lifting of platform 9 to a vertical position upon closing up the pair of steps.

So far as the legs 1 and 2 are concerned, continuous adjustment is provided by two sliding parts 11 and 12 which are slidable relative to fixed upper parts of the respective legs. Locking means 13 is provided in each case, said locking means being, for example, in the form of a screw clamp which is slidable in the slot 14. It is to be understood that the particular locking means illustrated is only by way of example and that any other desired form of locking means may be used.

In particular, said locking means may be replaced by any of the locking means to be described hereinafter in connection with the rear legs 3 and 4. Furthermore, it is to be understood that, if desired, the length of the sliding parts 11 and 12 may be considerably greater than that shown. For example, the arrangement for extending the front legs of the steps may be precisely the same as that illustrated for the rear legs.

Extension of the rear legs 4 and 5 is provided by means of sliding parts 15 and 16 which are slidable within the C-section of the respective fixed upper parts of legs 4 and 5. The sliding parts consist of C-shaped aluminium generally similar to, but slightly smaller than, the material used for the upper parts of legs 4 and 5, Figure 1 shows how these sliding parts provide adjustment to allow the step ladder to stand on stairs at different levels.

It is to be understood that the illustrated step ladder to be used, for example, on stairs having risers of any height where it would be impossibie or unsafe to use a known type of step ladder. The illustrated step ladder can also be used on uneven floors or ground, or between different floor or ground levels.

It will be appreciated that the extruded or pressed metal, preferably aluminium, must be of sufficient gauge to give strength and rigidity to the legs when extended.

The preferred method of locking the sliding parts 1 5 and 1 6 with respect to the fixed parts is based on the principle of a roller located between two relatively inclined planes. Two inclined planes are provided on each fixed part, and two on each sliding part, and rollers are located between the two. In one form, the inclined planes are provided on the sides of the sliding parts and fixed parts, two rollers being used in each case. Preferably, each pair of rollers are mounted on a carrier including a handle and two extending arms having rigid shafts on which the rollers are rotatable.

Slots are cut to receive the bracket, and the side walls of the inner unit in each case are cut and bent to form one of the inclined planes. The cut portions are strengthened by addition of side and top pieces. This embodiment is illustrated in Figures 2 and 3.

These figures show, for example, the sliding part 1 5 slidable within the fixed part of leg 4.

Portions of each side wall of the sliding part 15 are cut out and bent in to make two wedgeshaped apertures as illustrated at 1 7 and 18. Two rollers 1 9 and 20 are located in respective ones of these wedge-shaped apertures and are rotatably mounted on a carrier 21. It is to be understood that the inwardly sloping walls of the wedgeshaped apertures may be constituted by the material of the sides of the sliding part, but that the top portion as indicated, for example, at 22, is added to give the necessary strength.

In operation, any force tending to move the sliding part 15 upwardly within the fixed part of leg 4 (as seen in Figure 2) will force the rollers 19 and 20 into the narrower parts of the wedgeshaped apertures 17 and 18. Accordingly, the rollers will provide a jamming action between the inclined parts of the apertures and the side walls of the fixed part of leg 4. However, if an upward force is applied to the carrier 21, the rollers 19 and 20 will be moved towards the wider parts of the apertures and, under these circumstances, relative movement between the sliding and fixed parts of the leg may be accomplished without difficulty in either direction. Thus to release the lock, it is only necessary to move the carrier 21 upwards by means of the handle so that the rollers are freed and the sliding part can be move in the respective fixed part of the leg.

In the alternative locking arrangement shown in Figure 4, plate 24 is provided between the side wall 23 of the fixed part of leg 4 and the corresponding side wall 25 of the sliding part 15.

Part of the side wail 25 is built up as shown at 26, and a threaded hole is formed in the built-up part.

A thumb wheel 27 has a threaded boss 28 engaging in the threaded hoie. Thus, if the thumb wheel 27 is rotated, the plate 24 can be forced against the side wall 23, thus providing frictional restraint between the sliding and fixed parts of the leg. As shown, the plate 24 is attached to the side wall 25 by means of rivets 29 which are slidable within holes in the side wall 25.

The locking arrangement shown in Figure 5 is generally similar to that shown in Figure 4 except that the plate 24 is forced against the side wall 22 by means of cam action instead of by screw action. The cam is provided on a handle 30 which is pivotally mounted at 31 on a bracket 32 formed on, or fitted to, the side wall 25. As can be seen, the hinge axis of the handle 30 is eccentric with regard to the cam surface 33 and, accordingly, movement of the handle from the horizontal position to the position illustrated in Figure 5 forces the plate 24 against the side wall 22 and provides the required locking auction. - Figure 6 shows a further locking arrangement which utilises the same principle as does the arrangement shown in Figures 2 and 3, i.e. the principle of a roller located between two relatively inclined planes.Figure 6 shows a portion of one leg 4 of a ladder, including a portion of a fixed part and a portion of a sliding part 1 5.

In this embodiment, the channel in the fixed part of the leg 4 opens outwardly whilst the channel in the sliding part 1 5 opens inwardly so that in combination the two parts form a box section. At its upper end, the sliding part 1 5 is provided with a moulded or machined component 41 which is shown more clearly in Figure 7.

Extending transversely of component 41 is a wedge-shaped recess 42 which accommodates a roller 43. The two relatively inclined planes between which the roller 43 operates are constituted by the inclined wall of recess 42 and the inner surface of the wide rear wall 44 of the C-shaped section of the fixed part of leg 4. In order to allow the roller 43 to engage with wall 44 over its full width, the side flanges of sliding part 15 are partially cut-away as shown at 45.

Roller 43 is preferably formed as a metal cylinder or rod coated with natural or synthetic rubber or provided with a sleeve of natural or synthetic rubber. A wire 46 ending in a finger ring 47 is attached to the roller 43 at its centre. The wire 46 passes through a slot 48 in component 41 and thereby is accessible via the open channel of the fixed part of leg 4. Roller 43 may be fixed, or rotatably mounted. If rotatably mounted, it may be formed as two equal parts disposed at respective sides of the crossbsectional plane where wire 4B is attached.

For attachment to the roller, the wire 46 is formed into a loop which encircles the roller 43 at its central point. The rubber layer or coating is here absent to allow the wire 46 to grip the inner metal part of the roller where a circumferential groove may be provided to receive the wire 46.

Since it is not essential for the roller to be rotatable, it will be apparent that use of a roller is not essential. In fact, any suitably shaped member capable of wedging between two relatively inclined planes may be utilised if required.

It will be understood that, in use, any upward force on the sliding part 15 tending to move the sliding part 1 5 upwards within the fixed part will force the roller 43 into the narrow end of the wedge-shaped cavity formed between wall 44 and component 41. The roller 43 will become firmly jammed in this position, and any increase in upwards force on sliding part 1 5 will tighten the locking action. To release the lock, it is only necessary to lift the roller 43 by means of an upward pull on finger using 47.

Component 41 may be manufactured from wood, synthetic plastics material or metal, and is attached to sliding part 1 5 by means of screws or any other suitably attaching means.

The invention has hitherto been described in detail only in relation to step ladders, such as illustrated in Figure 1. However, it should be understood that the invention is not limited to use with such ladders, but has application to virtually any type of ladder, including known types of multiple section ladder. For example, a ladder formed from two side members supporting a plurality of rungs therebetween may be provided with means for allowing extension of at least one of the side members, to allow for placement on uneven ground or side ways on a staircase. It is possible to envisage a ladder in which adjustment means is provided in only one leg, either by so constructing the rungs that the ladder is reversible or by making the adjustment means such as to allow the adjustable leg to be made longer or shorter than the non-adjustable leg.However, the latter arrangement would require an unusually large gap between ground level and the lowest step or rung if any significant amount of adjustment were to be provided. Furthermore, ladders having rungs constructed to allow reversing of the ladder are less comfortable in use. It is therefore preferred, in the case of a ladder having a single pair of legs, to provide adjustment means in each legs.

Similarly, in the case of the step ladder shown in Figure 1, it is preferred to provide adjustment means in all four legs, although it is not inconceivabie that adjustment could be provided in only one pair of legs, as this would still allow use on a staircase as illustrated, or possibly only in one leg to allow for use on uneven ground.

Figure 8 shows an adaptor unit for providing a conventional ladder or step ladder with adjustment of leg length in one leg. With two or four of these units, as required, a conventional ladder or step ladder may be provided with adjustment in each leg.

An outer part 51 having a C-shaped crosssection is provided with flanges 52 and 53 for screwing or bolting onto a conventional ladder. A sliding part 54 is provided within part 51. Any of the locking arrangements hereinbefore described may be used, but the unit is illustrated with the arrangement of Figures 6 and 7.

Although any of the forms of locking arrangement hereinbefore described is perfectly adequate in operation, it may in certain circumstances be desirable to provide additional securing device for additional safety.

Figures 9 to 12 illustrate such an additional device. As shownin Figure 8, the inner sliding part 1 5 of a leg 4 is made slightly less wide (by about 1/16" or 1.5 mm). Provision of flat springs 61 (Figure 10) will provide smooth sliding in operation.

Figure 11 shows the additional device in its disengaged position. It consists of a wedge 62 of an appropriate material (such as synthetic plastics material or wood) secured by a short chain 63 near the base of each adjustable leg. As shown in Figure 12, following locking in position of the sliding part by the main locking arrangement. the auxiliary wedge may be placed in the gap between the outer side wall of the sliding part and the inner side wall of the fixed part andpressed firmly in position by hand. For release, the sliding part is pressed in a downward direction to disengage both the main and auxiliary locking mechanisms.

Claims (23)

Claims

1. A ladder comprising at least one pair of legs and a plurality of steps wherein the length of at least one of said legs is continuously adjustable within predetermined limits.

2. A ladder as claimed in claim 1, whernin the or each adjustable leg comprises a fixed part and a sliding part and means for locking the sliding part relative to the fixed part.

3. A ladder as claimed in claim 2, wherein in the or each adjustable leg the fixed part and the sliding part each consists of metal having a Cshaped cross-section.

4. A ladder according to claim 2 or 3 wherein said sliding part is slidable and lockable within the fixed part.

5. A ladder as claimed in any one of claims 2 to 4 wherein said sliding part is lockable in position by wedging means located between two relatively inclined planes, one plane being provided on the associated fixed part and the other being provided on said sliding part.

6. A ladder as claimed in claim 5, wherein each sliding part is lockable in position by means of a pair of wedging means each wedging means being located between a respective pair of inclined planes.

7. A ladder according to claim 5 or 6 wherein the or each wedging means is constituted by a roller.

8. A ladder according to claim 7 wherein the or each roller is mounted for rotation.

9. A ladder as claimed in claim 7 or 8 when dependent on claim 6 wherein each pair of rollers is mounted on a common bracket.

10. A ladder as claimed in any one of claims 2 to 4 wherein said sliding part is lockable in position by means of a plate fixed longitudinaily with respect to the fixed part or sliding part and provided with means for urging it against the sliding or fixed part.

1 A ladder as claimed in claim 10, wherein said urging means is a threaded boss on a manually operable knob.

12. A ladder as claimed in claim 10 wherein said urging means is a pivotted lever having an eccentric cam in the region of one end thereof.

13. A ladder according to any one of the preceding claims wherein there is provided a second pair of legs mounted for pivotting relative to said first pair of legs.

14. A ladder according to claim 1 3 wherein the legs of said second pair are each hingedly attached on a common hinge axis to a respective one of the other pair of legs.

15. A ladder according to any one of the preceding claims wherein the length of each of said legs is continuously adjustable within predetermined limits.

1 6. A ladder substantially as hereinbefore described with reference to, and/or as illustrated in the accompanying diagrammatic drawings.

17. A ladder as claimed in claim 16 having locking means substantially as illustrated in Figures 2 and 3, or Figure 4, or Figure 5 or Figure 6 of the accompanying diagrammatic drawings.

1 8. An adaptor for use with a conventional ladder to form the ladder of any one of the preceding claims, the adaptor comprising two leg parts secured together for attachment to respective legs of a conventional ladder wherein the length of at least one of said leg parts is continuously adjustable within predetermined limits.

1 9. An adaptor according to claim 1 8 wherein the or each adjustable leg part comprises: a first portion for attachment to a leg of a conventional ladder: a second portion mounted for sliding relative to said first portion; and means for locking the second portion relative to the first portion.

20. An adaptor according to claim 18 or 19 wherein each leg part is provided with securing means for securing to a respective leg of a conventional ladder.

21 An adaptor according to claim 20 wherein said securing means comprises a bracket.

22. An adaptor for use with a conventional ladder substantially as hereinbefore described with reference to Figure 8 of the accompanying drawings.

23. Any features of novelty, taken singly or in combination, of the embodiments of the invention as hereinbefore described with reference to the accompanying diagrammatic drawings.