GB2250051A

GB2250051A - Ladder wedge

Info

Publication number: GB2250051A
Application number: GB9122312A
Authority: GB
Inventors: Richard Leslie Newman
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-10-23
Filing date: 1991-10-21
Publication date: 1992-05-27
Anticipated expiration: 2011-10-21
Also published as: GB9022967D0; GB9122312D0; GB2250051B

Abstract

A ladder wedge comprises a flat base (2) having a sloping upper surface (3) carrying a central channel (6) adapted to receive a ladder leg. Stop means, adapted to block the channel, restricts any downward movement of the leg. The stop means preferably comprises a rigid plate and the sides of the channel carry a series of slots (7) adapted to receive the edges of the plate; the slots may be extended into the base of the channel. The plate extends above the surface of the channel and is preferably bent to provide a substantially vertical upper portion extending above the surface of the channel. In use one leg of a ladder is placed on the surface of sloping ground and the other in the channel. The leg in the channel is moved until the ladder is vertical. The stop is placed in an appropriate pair of slots to retain the leg. The stop means can take the form of frame with a central portion displaced from the frame, preferably by a quarter of the distance between the slots. <IMAGE>

Description

LADDER WEDGE.

This invention relates to ladder wedges which allow a ladder to be used safely on inclined and uneven surfaces.

It is well known that a ladder resing against a wall or other upright surface is only stable when the legs are on the same plane. To improve stability and safety when a ladder is used on an inclined surface a brick, stone or wooden block is often placed under one leg to support it.

This procedure is unsatisfactory as the object used is seldom of the correct size and frequently there is inadequate friction between the base of the ladder and the improvised support; there is similarly a lack of friction between the ground and the support. As a result when the ladder is climbed movement of the climber can easily cause the ladder to topple resulting in injury to the climber.

It is often the practice to stabilise a ladder by tying or otherwise attaching the upper part to the surface against which it rests. However in most situations at least one hazardous climb has to be made before attachment can be effected.

In W088/00669 a ladder base is described for use on an uneven foundation surface. The base is complex mechanically and must be fixed to the ladder before the latter is erected.

The object of the present invention is to provide a support for a ladder which enables the ladder to be used safely on a variety of otherwise dangerous surfaces. The support is not attached to the ladder and is simple to use.

According to the present invention there is provided a ladder wedge ladder wedge comprising a flat base having a sloping upper surface carrying a central channel adapted to receive a ladder leg and stop means adapted to block the channel and restrict any downward movement of the leg along the channel.

In one embodiment the upper surface has a flat portion in addition to the sloping portion. The central aperture in the flat portion includes an aperture extending through the base. This form of the wedge is most suitable in applications where the surface on which the wedge rests has only a small incline. The flat portion must have sufficient length to accomodate the foot of the ladder with which it is to be used. The aperture extending through the base accomodates the foot of the ladder and allows it to rest partially or completely on the surface beneath the base.

Preferably the stop means comprises a rigid plate and the sides of the channel carry a series of slots adapted to receive the edges of the plate. The channel may be rectangular or U-shaped. The base of the channel may also carry slots adapted to receive the lower edge of the plate.

In a most preferred embodiment the plate extends above the surface of the channel and the plate is bent to provide a substantially vertical upper portion when inserted in the ladder wedge. The upper portion of the plate may carry inwardly directed wings and a circular aperture or similar means to assist in its insertion into and withdrawal from the slots in the ladder wedge body.

The body of the wedge preferably has a flat base with a ridged, studded or otherwise irregular surface to provide good frictional contact with any surface on which it is placed. To maximise such frictional contact the body of the wedge, or at least the lower surface, should be made of a resilient material.

The body of the wedge may be fabricated from wood, metal, rubber or, most preferably a synthetic polymer material.

Such a material may comprise a thermoplastic resin such as polystyrene, polyethylene, polypropylene, polycarbonate, an acrylic acid polymer, polyacetal, polyurethane or copolymers such as ABS and mixtures of such resins. The synthetic resin may include fillers, pigments, anti-oxidants, anti-ozonants, etc. in known manner. The resin may be reinforced with glass or carbon fibres. While it is advantageous that the lower surface of the body of the central portion of the body should be rigid so that it does not deform under the pressure from the leg of a loaded ladder. These conflicting requirements may be overcome by moulding the main body of the wedge from a suitable synthetic resin mixture leaving a hollow central portion.

The hollow portion is then filled with a rigid material such as metal, wood, stone, concrete or a synthetic resin having less resilient properties such as a glass fibre reinforced thermosetting resin.

The stop is preferably formed as a rigid metal plate fitting in slots in the body of the wedge. The metal may be an aluminium alloy, stainless steel or galvanised steel.

The metal must have sufficient ductility to be bent and wings formed but sufficient rigidity that it will not fold or buckle when subject to pressure from the leg of a loaded ladder.

In use the wedge is placed across a slope on which it is desired to erect a ladder and the stop moved to the slot which ensures that the base of the ladder leg placed against it will be at the same height as the other leg placed directly on the ground.

In alternative embodiments the position of the stop may be continuously variable. The stop may be moved along the channel by means of a threaded driving shaft turning in a threaded tube formed in the body of the wedge or a nut contained within the body.

The wedge according to the invention is primarily designed for use with ladders. However the wedge may also be used with a variety of other load bearing devices which need to be safely erected on uneven ground such as steps, scaffold poles and towers, tripods and tables.

The sides and ends of the ladder-wedge may be vertical but in a preferred form slope inwardly forming a truncated pyramid. In a practical example the base of a wedge has a length in the range 200 to 400 mm and a width in the range of 150 to 200 mm at the high end tapering to 80 to 120 mm at the lower end, e.g. a length 365 mm and a base tapering from 185 to 110 mm. The angle between the upper sloping surface and the base preferably lies in the range 10 to 50 degrees, e.g. 20 degrees.

The central channel is preferably capable of containing the the base of any ladder leg it is to support and may lie in the range 35 to 80 mm. The stop in the form of a plate should be 4 to 8 mm thickness depending upon the material, e.g. 4.5 mm aluminium alloy sheet. The stop must be firmly held by the slots in the central channel of the wedge so that at least 5 mm on each side are enclosed within the slots. A wedge 70 mm width having a 35 lower portion inserted in the slots and a 37 mm winged upper portion has proved satisfactory.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-section of a ladder wedge according to the invention, Figure 2 is an upper plan view of the ladder wedge shown in figure 1, Figure 3 is a cross-section of a stop for use with the ladder wedge shown in figure 1, Figure 4 is a plan view of the stop shown in figure 3, Figure 5 is a schematic view of a ladder wedge according to the invention supporting the leg of a ladder.

Figure 6 is a cross-sedion of an alternative embodiment of a ladder wedge according to the invention, Figure 7 is an upper plan view of the ladder wedge shown in figure 6, Figure 8 is a cross-section of a stop for use with the ladder wedge shown in figures 1 and 6, and Figure 9 is a plan view of the stop shown in figure 8.

A ladder wedge according to the invention, see figure 1, consists of a solid core 1 having a flat base 2 and an upper surface 3 sloping between a higher end 4 and a lower end 5. The surface 3 carries a U-shaped channel 6 cut through its central portion into the body 1. The sides of the channel 6 carry a series of slots 7 which are continued downwards into its base. The opposite side of the channel 6, not shown, carries a series of slots corresponding to the slots 7. The higher end 4 and the lower end 5 of the ladder wedge slope inwardly from the base 2 to the surface 5. The sides 8 and 9, see Figure 2, of the ladder wedge also slope inwardly from the base 2 to the surface 3 so that the wedge takes the form of a truncated pyramid.

A stop 11, see figures 3 and 4, is formed from metal sheet.

The stop 11 has a lower portion 12 adapted to fit into a pair of slots 7 and an upper portion 13 containing a circular aperture 14 and a pair of wings 15. The angle between the portions 12 and 13 is such that the upper portion 13 points substantially in a vertical plane when the wedge is placed on a horizontal surface and the lower portion 12 is inserted into a pair of slots 7. The wings 15 are bent inwardly forming a guide for a ladder leg or other object supported by the wedge.

In use, see Figure 5, one leg of a ladder 21 is placed on an inclined surface 22 while the other leg 23 is placed in the channel 6 of a ladder wedge according to the invention.

The leg 23 is moved along the channel 6 until the ladder is vertical. The stop 11 is then inserted into a pair of the slots 7 to prevent slippage. The ladder may then be safely climbed.

In an alternative embodiment, see figure 6, the ladder wedge consists of a solid core 31 having a flat base 32 and an upper surface 33 sloping between a higher end 34 and a lower end 35. The surface 33 carries a U-shaped channel 36 cut through its central portion into the body 1. The sides of the channel 36 carry a series of slots 37 which are continued downwards into its base. The opposite side of the channel 36, not shown, carries a series of slots corresponding to the slots 37. The higher end 34 and the lower end 35 of the ladder wedge slope inwardly from the base 32 to the surface 35. The sides 38 and 39, see Figure 7, of the ladder wedge also slope inwardly from the base 32 to the surface 33 so that the wedge takes the form of a truncated pyramid.

The surface slopes smoothly between the higher end 34 and the lower end 35 where the surface has a substantially flat portion 40. The flat portion 40 includes an aperture 41 extending through the central channel 36 and the base.

The aperture can accomodate one foot of a ladder when the flat portion is in use. In other respects the mode of operation of the embodiment of the ladder wedge shown in figures 6 and 7 is the same as that described with respect to figures 1 and 2.

A modified stop 51, see figures 8 and 9, is formed from metal sheet. The stop 51 has a frame portion 52 adapted to fit into a pair of slots 7 or 37 and extend upwardly to enclose a central portion 53. The portion 53 is displaced from the plane of the frame and contains a circular aperture 54 assists removal of the stop from the slots.

The displacement of the central portion 53 is about one quarter of the spacing between the slots 7 or 37. By removing the stop, rotating it through 1800 and replacing it in a slot it is possible to move the surface against which a ladder rests by half the slot spacing. The modified stop thus provides a convenient means of adjusting the stop position without having an excessive number of stops in the wedge and weakening the structure.

Claims

1. A ladder wedge comprising a flat base having a sloping upper surface carrying a central channel adapted to receive a ladder leg and stop means adapted to block the channel and restrict any downward movement of the leg.

2. A ladder wedge as claimed in claim 1 in which the stop means comprises a rigid plate and the sides of the channel carry a series of slots adapted to receive the edges of the plate.

3. A ladder wedge as claimed in claim 2 in which the base of the channel carries slots adapted to receive the lower edge of the plate.

4. A ladder wedge as claimed in claim 2 or claim 3 in which the plate extends above the surface of the channel.

5. A ladder wedge as claimed in claim 4 in which the plate is bent to provide a substantially vertical upper portion extending above the surface of the channel.

6. A ladder wedge as claimed in claim 4 or claim 5 in which the upper portion of the plate carries inwardly directed wings.

7. A ladder wedge as claimed in any of the preceding claims in which the upper surface has a flat portion and in addition to the sloping portion.

8. A ladder wedge as claimed in claim 7 in which the central aperture in the flat portion includes an aperture extending through the base.

9. A ladder wedge as claimed in any of the preceding claims which has a hollow central portion containing a rigid material and an outer portion formed from a resilient synthetic polymer.

10. A ladder wedge as claimed in any of the preceding claims in which the sloping upper portion forms an angle with the base between 10 and 30 degrees.

11. A ladder wedge as claimed in claim 10 in which the sloping upper portion forms an angle with the base of 20 degrees.

11. A ladder wedge as claimed in any of the preceding claims in which the stop means comprises a plate adapted to fit into one of a series of slots cut in the central channel of the wedge.

12. A ladder wedge as claimed in claim 11 in which the stop means comprises a frame with a central portion displaced from the frame.

13. A ladder wedge as claimed in claim 12 in which the the central portion is displaced from the frame by a quarter of the distance between the slots.

14. Ladder wedges as claimed in claim 1 and as herein described.

15. Ladder wedges as herein described with reference to the accompanying drawings.