GB2232608A - Abseiling device - Google Patents

Abstract

An abseiling device for use in emergency escapes has a friction member (13) having a plurality of apertures (18) through which are passed a strap (10). A user of the device controls his rate of descent by holding the strap (10) and applying an appropriate tension thereto. Initial resistance to motion is applied by at least one ablative pad (31) positioned between the friction member (13) and the strap (10). A user is thereby enabled to grasp the strap (10) before his rate of descent becomes too great. <IMAGE>

Description

ABSEILING DEVICE The present invention relates to abseiling devices, for use particularly in escape from structures such as oil rigs.

In many emergency situations where evacuation of tall structures such as oil rigs is required casualties occur as a result of over saturation of communal escape routes. There is, therefore, a need for individual escape devices which will enable individual evacuees to make their own way from a high level to sea (or ground) level.

In a known type of escape device use is made of the principle of abseiling, which is well-known to, for example, mountaineers and pot holers. In this device a strap mounted on a reel within a personal safety pack passes through a friction member, to which is attached a cradle, to an attachment device. A user of the pack attaches the unit to a secure mounting point (such as a guard rail) on the structure from which he wishes to escape, positions himself in the cradle and makes a descent as the strap unrolls from the reel.

The rate of descent is controlled by the user holding the strap below the friction member and manually adjusting the tension of the strap passing through the friction member.

Unfortunately if tension is not applied to the strap in time the rate of descent of a user of the device may rapidly become such that grasping the strap may become impossible, or possible only at the consequence of severe friction damage to the hand. There is therefore a grave risk of serious injury occurring to the user.

Under emergency conditions even trained personnel are liable on occasions to forget the importance of applying tension to the strap at an early stage of their descent.

There is, therefore, a need for regulating the rate of acceleration at the initial stages of a descent. Conventional braking devices could be used, but would require extra complication in what is basically a very simple and effective device, and also generate a great deal of heat which could cause damage to the materials used or to a user of the device.

According to the present invention a friction member, for use in an abseiling device, having a plurality of apertures through which a strap can be passed in zig-zag fashion, includes at least one ablative pad adapted to bear against such a strap.

The strap may pass between an ablative pad and a pressure plate or, preferably, between 2 ablative pads Resilient means,preferrabir adjustable, might be used to adjust the amount of pressure between the or each ablative pad and the strap.

The pad arrangement is preferably positioned at an end of the friction member most adjacent an end of the strap upon which the abseiling device will depend.

A suitable ablative material for use in the pads is brake block rubber of the type used for bicycle brakes. This material has the advantage over other materials in that its coefficient of friction with respect to most other materials is comparatively unaffected by the presence of water.

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, of which Figure 1 is a general view of an abseiling device, of the type to which the invention relates, in use, Figure 2 is an elevation of a friction member as used in the device of Figure 1, Figure 3 is an elevation of a friction member according to the present invention, Figure 4 is an end view, in section along line IV-IV of Figure 3, and Figure 5 is an end view, corresponding to Figure 4, of a detail of an alternative form of the invention.

A known form of abseiling device, usable for escape from high structures, (Figure 1) has a strap 10 extending from a reel 11 rotatably mounted in a storage pack 12. The strap 10 passes through a friction device 13 and terminates at an attachment device 14 which can be attached to a securing point 15 which may be, for example, a guard rail of structure from which escape is desired. A cradle 16 is attached to the friction device 13 by a releasable clip 17.

The friction device 13, shown in more detail in Figure 2, consists of a metal disc having a plurality of apertures 18 through which the strap 10 is passed in zig-zag fashion (see Figure 4). Also in the friction member 13 are a cut out 19 and a hole 20 which receives the releasable clip 17 (not shown in this figure).

When not in use the device is completely self contained within the storage bag 12. In use, a user 21 of the device will remove the end containing the attachment 14 from the bag 12 and attach it to mounting means 15. He will then seat himself in the cradle 16 and so position himself, the bag 12 and the friction member 13 that he can lower himself from structure to which the mounting 15 is secured.

Whilst doing this he must grasp with his hand the strap 10 below the friction member 13 and maintain tension on the strap 10 as it passes through the friction member 13. The amount of tension controls the amount of friction between the strap 10 and the friction member 13, and hence the rate at which the friction member 13, and hence the user 21 moves down the strap 10 which steadily unrolls from the reel 11.

When the user reaches sea (or ground) level he wraps the strap 10 around that part of the friction member 13 exposed by the cut out 19, so taking the loading off the strap 10 and enabling the release clip 17 to be released.

Should the user 21 delay grasping the strap 10 below the friction member 13 and applying tension his speed might easily become dangerously high.

In an improved friction member according to the present invention (Figures 3, 4) a friction member 13 is substantially identical to that shown in Figure 2 apart from a recess 30 beyond that end of the series of apertures 18 most adjacent the end of the strap 10 having the attachment device 14. A first pad 31 of ablative material such as brake block rubber is positioned in the recess 30. The strap 10 is passed in zig-zag fashion through the apertures 18 and over the first ablative block 31. A second ablative block 32 is then positioned against the surface of the strap 10 remote from the first ablative pad 31, being held in position in a recess 33 in a cover plate 34 which is secured to the friction member 13 by bolts 35 passing through holes 36 in the cover plate 34 into tapped bores (not shown) in the friction member 13.

In use an abseiling device including a friction member 13 operates in identical fashion to the device described above with reference to Figures 1 and 2. However friction between the ablative pads 31, 32 and strap 10 results in a reduced rate of acceleration of the user 21. The user 21 therefore has time to collect his thoughts, take hold of the strap 10 below the friction device 13 adjust the tension in the strap 10 as it passes through the friction device 13, and so control his rate of descent before that rate of descent gets too high.

In an alternative form of the invention (Figure 5) the second ablative pad 32 is replaced by a pressure plate 40.

It will be realised that there are many ways in which the invention may be used in order to give varying degrees of control over the rate of acceleration as affected by ablative pads 31, 32.

If the cover plate 34 is a solid member and is secured rigidly with respect to the friction member 13 the friction between the ablative pads 31, 32 and the strap 10 will decrease as the friction member 1.3 moves relative to the strap 10 eroding the material of the pads.

The rate of acceleration of the user 21 will therefore increase.

This effect can be controlled by, for example, using a resilient cover plate 34, or spring washers between the cover plate 34 and the head of the bolts 35. Numerous alternative methods of achieving similar results will be readily apparent to those skilled in the engineering arts. It will also be readily apparent how friction members 13 according to the present invention can be adjusted for use by users of different weights.

Claims (8)

1. What is claimed is: 1. A friction member, for use in an abseiling device, having a plurality of apertures,through which a strap can be passed in zig-zag fashion, and including at least one ablative pad adapted to bear against such a strap.
2. 2. A cascade member as claimed in Claim 1 having 2 ablative pads between which such a strap can be passed.
3. 3. A friction member as claimed in Claim 1 having a pressure plate between which and the ablative pad such a strap can pass.
4. 4. A friction member as claimed in any one of Claims 1-3 wherein the pad arrangement is positioned at an end of the apertures most adjacent an end of such a strap upon which the abseiling device will depend.
5. 5. A friction member as claimed in any one of Claims 1-4 wherein the pressure between the strap and the pad or pads is adjustable.
6. 6. A friction member substantially as herein described.
7. 7. A friction member substantially as herein described with reference to Figures 3-5 of the accompanying drawings.
8. 8. An abseiling device including a friction member as claimed in any one of Claims 1-7.