GB2197017A - Adjustable legs for a ladder - Google Patents

Abstract

Telescopic adjustable ladder legs either incorporated as part of the integral design of the ladder or for use as auxiliary fittings on an existing metal or wooden ladder. Each leg is provided with a means of limiting the amount of the leg extension and the means of locking it firmly at the selected height. The use of rung- collars in box section ladder styles is required to allow free movement of the inner leg when they are incorporated in the initial production of the ladder. The fitting of a spirit level in one of the lower rungs is optional. <IMAGE>

Description

SPECIFICATION Adjustable legs for a ladder This invention relates to a set of adjustable legs for stabilising a ladder on sideways sloping or uneven surfaces.

The problems of securing a firm footing for ladders on such slopes or uneven surfaces (e.g. stairs) is commonly dealt with by underpacking one leg with 'ad hoc' blocks of wood or brick. This solution is very insecure and is the cause of many accidents when working on the ladder.

According to the present invention, the solution has two main components: 1. Provision of a telescopic form of adjustment with safe locking devices to both legs of the ladder so that steps or slopes down, either on the right or left of the ladder, can be accommodated.

2. Provision of -a means of securely attaching the lower rungs to the styles of the ladder in such a way that free movement of the adjustable inner legs is not obstructed.

Four alternative examples of locking the inner leg at the height selected are offered.

Some of these use well known principles adapted for use in this invention. Two alternative methods of fitting the lower rungs of the ladder are also offered.

This invention has the added advantage of increasing the possible overall height of the ladder by at least 35 cm. This increase will vary according to the length of the inner leg adopted in the design in conjunction with the positioning of the locking device and the retaining bolt or bolts.

There is another aspect in solving the problem that is not immediately apparent. viz. The solution must not only be safe but in the opinion of the user it must both look and feel safe. This present invention addresses itself to this more discreet aspect.

The fitting of a spirit level in the third or fourth rung to indicate the vertical plane error while stooping to set the height of the legs is an additional option.

A specific embodiment of the invention will now be described by way of examples, with reference to the accompanying drawings in which: Figure 1 shows the dangerously unstable condition of an ordinary ladder with one leg typically packed to accommodate a sloping surface.

Figure 2 shows the general solution offered by this invention with the inner leg extension locked so that there can be no unintentional alteration to the length of the ladder leg.

Figure 3 shows the ladder with the length of one leg commodate its use on a stair-way.

Figure 4 details the first suggested arrangement for securing the inner leg by using a dog on an eccentric clamp handle ('A-A'). It also details the method by which the rungs are fitted directly to the ladder styles ('B-B') so that. there is no obstruction within the box section style to the free movement of the inner leg.

Figure 5 details the arrangement of grooves cut into the inner leg which will engage the dog on the sprung clamp and the bolt retaining groove limiting the amount of extension of the inner leg.

Figure 6 details a suggested simpler arrangement for securing the inner leg by inserting a toggle bolt at the required height setting.

Figure 7 shows the general principle by which an infinitely variable adjustment can be achieved by means of a worm and wheel attachment.

Figure 8 details the pistoi-grip and sprung dogs arrangement for holding the inner leg at the required height.

Figure 9 details an alternative method to the one detailed in Figure 4 for attaching the rung to a separate style-plate rather than directly to the style itself.

Figure 10 shows a typical arrangement for fitting adjustable legs to an existing ladder without any such provision.

Figure 11 shows how a 'H' section ladder style can be adapted for the same purpose.

Figure 12 details a typical design for an infinitely variable fine adjustment to the foot of the ladder.

Referring to the drawings: Figure 2 shows the main components of the ladder used in the invention. The styles are typically of 2.5" x 1" (63 x 25 mm) moulded box section alloy metal 1/8" (3 mm) thick in section (1).

The styles are suitably connected at 9" (228 mm) centres by rungs or treads (2) that go -right through the styles. The rungs are usually attached by welding, bevelling or similar.

Fitted into the bottom of each style of the ladder is an inner moulded or pressed steel leg (3) 26" (661 mm) in length reaching up to the third rung. It must make a comfortable slide fit inside the ladder style. The length of this inner leg can be increased by steps of up to 9" (228 mm) if so desired.

A foot (4) of suitable non-slip hard wearing material is provided at the bottom of each inner leg. As an alternative, this foot can be of the adjustable type as detailed in Figure 12.

The two lower sets of rungs (5) and (6) are joined only to the inside faces of the styles by means of moulded metal collars (7). This leaves the insides of the styles free of any obstructions that could impede the movement of the inner legs. The arrangement shown in Figure 2 provides a maximum extension of 11.5" (292 mm) on either leg.

Figure 4 'A-A' shows the 4' x 1.25" (102 x 32 mm) moulded alloy clamp housing (1) fitted to the ladder style (2) with the inner leg inside it (3).

Two holes are drilled through the ladder style to take the two 1/4" (6 mm) bolts (4).

The inner leg has a slot (5) to allow movement past the bolts inside the style.

The clamp fixing bolts are also utilised to limit the extent of travel downwards by the inner leg thereby preventing it from from falling out of the upright. Removal of the clamp fixing bolts allows the inner leg to be withdrawn.

The clamp release lever (6) is attached to an eccentric bearing (7) to provide a positive snap closing. When closed, a flat dog (8) is engaged with slots (9) cut into the front edge of the inner leg to hold it at the selected position. The greater the downward pressure on the ladder the tighter the dog is forced against the bearing surfaces of the clamp housing and ladder style (10 and 11) by the upward force of the inner leg. The clamp handle being pressed against the style when under load acts as an additional clamp lock.

The 2" (50 mm) diameter by 5/8" (16 mm) moulded steel rung-collar (12) shown at 'B-B' in Figure 4 is attached by drilling and bevelling the inner face of the style (13) over the inner face of the collar (14). The ends of the rung (15) have two flat surfaces ground on them to fit against the flats in the rung collar (16) to prevent the rungs from turning when in use.

Figure 5 shows the general arrangement of the inner leg allowing extension by steps of 1/2" (13mm) at a time. It is made of moulded box section steel 1/8" (3 mm) thick to fit snugly inside the ladder style.

Its length is 26" (661 mm) in this instance to give a total extension of the ladder leg of 11.5" (292 mm). This extension is determined by the distance from the top bolt of the clamp housing to the end of the slot at the top of the inner leg. [Further 9" (228 mm) extensions (the distance between the rungs) can be obtained using additional pairs of rungcollars.] Starting 1" (25 mm) from the top of the inner leg there are a total of twenty three 5/16" (8 mm) grooves (1) cut at 1/2" (13 mm) centres. These grooves engage the flat dog on the clamp bearing. Alternatively a round 1/4" (6mm) dog can be used in which case the grooves will be 5/16" (8mm) holes drilled at 1/2" (13 mm) centres.

The 5/16" (8mm) inner leg retaining slot (2) is cut through the centre line of both faces starting 1/2" (13mm) from the top and extending 1/2" (13 mm) below the bottom groove.

Figure 6 is a simpler and less expensive alternative to the clamp arrangement of Figure 4. It will again require the use of the rungcollars to allow the moulded steel inner legs to move freely inside the ladder styles.

A hole 5/16" (8 mm) diameter (1) is drilled through the ladder style 2" (51 mm) up from the bottom rung. The 1/4" (6 mm) toggle bolt (2) goes through these holes and through the holes at the selected position of the inner leg when the swivel end of the bolt (3) is turned down to prevent it from accidental removal.

The toggle bolt is attached to the ladder by a suitable length of chain to prevent misplacing it. The top end of this chain is connected to the inner leg 1/4" (6mm) retaining bolt (4) with a chain lug (5). The 5/16" (8 mm) wide retaining slot in the inner leg (6) uses this retaining bolt to prevent the inner leg from falling out.

Figure 7 shows how an infinitely variable adjustment to the length of the ladder leg can be obtained with the use of a worm and wheel principle. In this the use of the rungcollars is again required. The grooves cut into the moulded steel inner leg are at a suitable angle and of a suitable width to engage with the teeth of the worm operated by turning the handle. It is a way of jacking up (or down) the inner leg.

The option of a quick release mechanism for lowering or raising the inner leg manually is also suggested in dotted outline. In this the worm is released by swinging about fulcrum point A. The retaining clip at B locks the assembly in gear and prevents accidental release of the worm assembly.

Figure 8 shows the pistol-grip clamp which is operated with a pump action to release or lock the inner leg. In this instance it is used in conjunction with the rung-collars attached to a style-plate (1) as detailed in Figure 8. The pistol-grip assembly consists of: A 4" x 1.75" (102 x 44 mm) tough moulded plastic handle (2) with a groove (3) to limit the movement.

An 8" (203 mm) long 1/16" (1.75 mm) thick pressed steel box section (4) to fit tightly over the ladder style. There is a 5/8" (16 mm) extension to the top front face of this box section (5) to prevent the trigger catching.

Two 3" x 1/2" (76 x 13 mm) 1/16" (1.75 mm) thick steel spring strips (6) attached 3.75" (95 mm) up from the bottom of the box section and with 1/4" (6 mm) dogs (7) welded 5/16" (8 mm) up from the bottom of the spring strips.

A 1" (25 mm) sprung loaded trigger release (8) attached at the top of the pistol-grip handle.

A 1.25" (32 mm) long counter sunk 1/4" (6 mm) bolt with flush fitting nut (9).

A 2" (50 mm) long 1/4" (6 mm) bolt and nut (18).

The rung-collars as described previously will again be needed. The alternative method of attaching them is described below with Figure 9.

The inner legs are also as described previously with 5/16" (8 mm) holes (11) drilled at 1/2" (13 mm) centres on both front and back faces to engage the dogs on the spring strips.

These holes begin 1" (25 mm) from the top and extend down to a further 12.5" (31 8 mm). 8imilar holes (1 2 and 1 3) are drilled through the two narrow faces of the ladder style and the pressed steel box section such that they will line up allowing the dogs to engage in the holes in the inner leg (14).

A suitable groove (15) is left inside the front and back faces of the pistol-grip to accommodate the steel spring strips. A hole (16) is cut into the front face of the ladder style to take the tip of the trigger release thus locking the pistol-grip in place. To set the length of the ladder leg, hold the pistol-grip and with the thumb release the trigger. 8lide the pistol-grip up to its full extent. This will allow the spring strips to extract the dogs holding the inner leg in position. Position the inner leg at its required height and slide the pistol-grip down again pressing the dogs firmly into the newly selected holes of the inner leg. At the same time the trigger will engage in its hole preventing further movement.

Figure 9 shows the style-plate (1) with the rung-collars attached. These are attached in the same way as previously described or in a similar suitable manner. In this instance the clamp handle mechanism is given to show the final arrangement.

The steel style-plate measures 13" x 2.5" (330 x 63 mm) to match the side of the ladder style dimensions. It is 1/8" (3 mm) thick. It has rounded edges to prevent snagging the hands. It is positioned by 1/4"- screws (2) top and bottom. The main fixing is through the retaining bolt or bolts (3).

While all the above refer to the adjustable legs being incorporated in the intial design and fabrication of the ladder, Figure 10 shows how these adjustable telescopic ladder legs can be adapted for use as separate auxiliary components on an ordinary ladder without any such provision.

The unit shown in this instance is of the clamp type. The working parts are made up in the same way as described above. The outer casing replaces the ladder style. This 'box' is then attached with suitable bolts to the existing ladder.

Figure 11 shows how a similar facility can be achieved with a 'T' section ladder rather than a box section ladder. It consists of an outer steel pressing (1) 1/8" (3 mm) thick and grooved to conform to the basic section of the ladder style (2) for strength.

5/16" (8 mm) holes (3) are drilled at 1/2" (13 mm) centres in the outer extension leg. A single hole (4) is drilled through the front edge of the ladder style between the first and second rungs. Through these holes a 1/4" (6 mm) toggle bolt (5) is inserted to keep the outer leg at the position selected.

A suitable length of chain or chord attaches the toggle bolt to the nearest rung by means of a circlip.

The retaining bolt (6) with its spacer washer (7) engages in the slot of the outer leg preventing it from dropping off.

Figure 12 shows the principle in which an infinitely variable adjustment to the foot of the ladder can be included to overcome the coarse 1/2" (1 3 mm) gradations allowed by all the alternative designs except the worm and wheel.

It consists of a 1/2" (13 mm) threaded stud (1) welded into a steel cup-plate (2). The cupplate has a 3/16" (5 mm) bevel (3) at the bottom on the front and rear faces. When inserted at the bottom, the inner leg is pinched over the bevel (4) and above the cupplate (5) to hold it firmly in position.

A 1.75" (44 mm) diameter steel disc (6) 1/8" (3 mm) thick is welded to 1/2" (13 mm) nut (7) which in turn is welded to another 2" (51 mm) diameter by 1/8" (3 mm) thick steel disc (8).

The tough non-slip tight-fitting moulded foot (9) is forced over the 1.75" disc and the whole assembly is screwed onto the end of the 1/2" stud protruding from the end of the cup-plate. The end of the stud is then bevelled to prevent the foot from being removed.

Once the length of the ladder leg has been set to the nearest 1/2" (13 mm) the foot can be turned to make up or lose any additional height as required.

Claims (6)

1. Adjustable legs for a ladder with box section styles, comprising, telescopic inner legs with the means of limiting the amount of extension and provided with the means of locking the inner legs at the selected height by suitable safe means and incorporating rungcollars attached to the ladder styles directly or to a style-plate which is then attached to the ladder styles to allow unimpeded movement of the telescopic inner leg.

2. Adjustable legs for a ladder with 'H' section styles, comprising telescopic outer legs with the means of limiting the amount of extension and provided with a safe locking device for the outer legs at the selected height.

3. Adjustable legs for a ladder as claimed in Claim 1. to be incorporated as an integral part of the ladder in its intial design and production.

4. Adjustable legs for a ladder as claimed in Claim 1. but omitting any reference to rungcollars for an existing wooden or metal ladder without any such provision and to which they can be attached by suitable means as auxiliary fittings.

5. Adjustable legs for a ladder as claimed in Claims 1, 2 and 3 incorporating a spirit level fitted in one of the appropriate lower rungs.

6. Adjustable telescopic ladder legs as substantially described herein and with reference to Figures 1-12 of the accompanying drawings.