GB2150967A

GB2150967A - Collapsible ladder

Info

Publication number: GB2150967A
Application number: GB08333016A
Authority: GB
Inventors: Patrick Brophy
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-12-10
Filing date: 1983-12-10
Publication date: 1985-07-10
Also published as: GB8333016D0

Abstract

A collapsible ladder has rungs extending between side members each of which consists of successive pairs of crossed links arranged in the manner of lazy tongs. Extension of the ladder is limited by a chain 8, 9 which interconnects the outer pivot points of adjacent pairs of links so as to serve additionally as a hand rail. Locking levers 10, 18 are provided to wedge adjacent pairs of rungs apart at the top and bottom of the ladder so as to prevent collapse of the ladder in use. <IMAGE>

Description

SPECIFICATION Improvements in or relating to collapsible ladders This invention relates to collapsible ladders.

Generally speaking ladders may be of rigid or flexible construction. A rigid ladder has fixedly spaced rungs interconnected by side elements of metal or timber construction. A disadvantage of such a ladder is that it may be inconveniently long for storage purposes. It is known to make rigid ladders in two or more sections that slide over each other to reduce the overall length but the length is nevertheless too great for certain applications. A flexible ladder has flexible side elements made, for example, of rope or chain. While it can readily be stowed in a confined space, albeit with some risk of entanglement, such a ladder suffers from the disadvantage that it is awkward to climb because it hangs vertically from a suspension point and is liable to flex considerably during use.

The invention is particularly, but not exclusively, concerned with ladders for use as fire escapes. Rigid ladders or stairs may be permanently mounted on the outside walls of industrial and commercial premises but are not generally acceptable for domestic premises. The ordinary householder often has no effective means of escape from the upper floors of his property but an enlightened minority do store flexible ladders at a convenient location, e.g. beside an upstairs window. In addition to the general disadvantage mentioned above, a flexible ladder fire escape has the drawback that it hangs close to the outside wall of the house thus bringing a user uncomfortably near the building that is on fire.

It is an object of the present invention to provide a collapsible ladder in which the above disadvantages are obviated or mitigated.

According to the present invention there is provided a collapsible ladder comprising rungs extending between side members each consisting of an arrangement of rigid links pivotally interconnected with each other and the rungs so as to be foldable together and apart to collapse and extend the ladder.

Preferably, locking means are provided for automatically locking the ladder in the extended position.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a perspective view of one embodiment of ladder according to the invention in use as a fire escape, the inset showing a fragment of the ladder to an enlarged scale, and Figure 2 is a view from inside the building of Fig. 1, showing the manner of stowage and suspension of the ladder.

Referring now to the drawings, the exemplary ladder comprises rungs 1 interconnected by side members 2, 3 each of which consists of successive pairs of crossed links 4, 5 and 6, 7 of equal length arranged in the manner of lazy tongs in that, taking for example the side member 2, all the links 4 are parallel to each other and all the links 5 are parallel to each other, the links of each pair being pivotally interconnected at their mid-points with each other and the associated rungs 1 and at their ends with an adjacent pair so as to form a parallelogram linkage therewith. The side member 3 is of identical construction and will not be described.

Chains 8, 9 are connected to respective side members 2, 3 at the outer pivot points 10, 11 between the links 4, 5 and 6, 7. The chains 8, 9 limit the spreading movement of the links 4, 5 and 6, 7 during extension of the ladder and thus define the extended length of the ladder. They also serve as handrails to facilitate climbing of the ladder. Shorter lengths of chain 1 2 are connected between adjacent inner pivot points 13, 1 4 of the side members 2, 3 in spaced staggered relationship along the ladder.

The upper ends of the side members 2, 3 are connected to heavier duty chains 8a, 9a which are used to anchor the ladder to floor joists of an upper floor of a building adjacent a window 1 5. The free lengths of chain 8, 9 between the anchorage points and the top of the ladder must be such that when the ladder is thrown out of the window it will automatically, or with only minimal adjustment, assume the position shown in Fig. 1, namely sloping downwardly and outwardly with respect to the outer wall of the building with its lower end resting firmly on the ground and its upper end securely positioned on the window frame. The anchorage points of the chains 8a, 9a are concealed and protected by a window box 1 6 in which the ladder is stored when in the folded, out-of-use condition. The box 1 6 has a cover 17.

Locking means are provided at the top and bottom of the ladder for locking the ladder in the extended position. The top locking means is shown in the inset of Fig. 1 and comprises a lever 1 8 pivoted on the top rung 1 and having at its free end a fork formation 1 9 slidably engaging the next lower rung 1. A spring 20 biases the lever 18 into the locking position illustrated, i.e. substantially at right angles to the rungs 1. The bottom locking means is of similar construction.

Normally the ladder is stored in the box 1 6 which is closed by the cover 17. The links 4, 5 and 6, 7 of the side members 2, 3 are folded together and the rungs 1 are brought into close proximity so that the levers 18 of the top and bottom locking means lie at a small angle to the rungs 1 on which they are pivoted. To use the ladder the window 1 5 is opened or broken using the cover 17, the ladder is lifted out of its box 16 and thrown out of the window 1 5. It automatically extends into the position shown in Fig. 1 and the levers 1 8 of the locking means move into the locking position. Slightly adjustment may be required to stabilise the ladder but this should be minimal and the ladder will be ready for use almost immediately.The cover 1 7 of the box 1 6 may be replaced in order to provide a step from which to mount the ladder. The ladder may be folded again by reaching out of the window, moving the lever 1 8 of the top locking means out of the locking position against spring pressure and then hauling the ladder in by pulling on successive rungs until the bottom of the ladder is reached when the lever 1 8 of the bottom locking means is released.

Alternatively, the chains 8a, 9a may be released from their anchorages (to which they may be connected for example, by snap-links) and the top locking means is then released to allow the ladder to collapse into the folded condition under its own weight.

It will be appreciated that numerous modifications may be made to the above described design without departing from the scope of the invention. For example, the anchoring chains 8a, 9a may be replaced by hooks which simply engage the window frame to secure the upper end of the ladder. This has the advantage that fitting costs are reduced because no anchorage points need be provided.

Claims

1. A collapsible ladder comprising rungs extending between side member each consisting of an arrangement of rigid links pivotally interconnected with each other and the rungs so as to be foldable together and apart to collapse and extend the ladder.

2. A ladder as claimed in claim 1 wherein each side member comprises successive pairs of cross links arranged in the manner of lazy tongs with the links of each pair being pivotally interconnected at their mid-points with each other and the associated rung and at their ends with an adjacent pair so as to form a parallelogram linkage therewith.

3. A ladder as claimed in claim 2, wherein the outer pivot points of adjacent links are interconnected by a chain serving to limit the spreading movement of the links and to provide a hand rail facilitating climbing of the ladder.

4. A ladder as claimed in any one of the preceding claims, wherein locking means are provided for automatically locking the ladder in the extended position.

5. A ladder as claimed in claim 4, wherein the locking means comprises a locking lever pivotally mounted on an upper rung of the ladder and biased into a locking position in which it engages with a free end thereof against an adjacent rung so as to wedge said two rungs apart.

6. A collapsible ladder substantially as herein described with reference to the accompanying drawings.