GB2292782A

GB2292782A - Shock absorber

Info

Publication number: GB2292782A
Application number: GB9417751A
Authority: GB
Inventors: Kevin Mark Holroyd
Original assignee: MARLING LEEK Ltd
Current assignee: MARLING LEEK Ltd
Priority date: 1994-09-02
Filing date: 1994-09-02
Publication date: 1996-03-06
Also published as: GB9417751D0

Abstract

A shock absorber comprises a tearable member 23 such as a woven textile piece having a pair of limbs 35, 37. The limbs are attached to first and second attachment members 5, 7; 11, 13. The tearable member 23 has a main section 29 which tears when the attachment members 5, 7; 11, 13 are pulled apart with an impulsive force above a predetermined magnitude. <IMAGE>

Description

SHOCK ABSORBER The present invention relates to a shock absorber for absorbing an impulsive shock force. It is especially, although not exclusively, suited to application in a safety line of the kind used to protect persons working on high buildings or the like.

It is common practice for building workers or window cleaners to be protected by attaching a safety line (lanyard) to a secure point on the structure on which they are working. The other end of the line is attached to a safety harness worn by the worker. In the event of a fall, however, the tensioning of the safety line as it breaks the fall can impart a great impulsive physical shock to the person. Although the line may prevent death or serious injury which would have resulted from the fall itself, the impulsive shock can nevertheless cause injuries. The shock absorber of the present invention can be incorporated into such a safety line for absorbing much of this impulsive shock.

The shock absorber of the present invention may be used in other situations where it is desired to absorb the force of an impulsive shock, for example in a lifeline such as worn by yachtsmen or in a vehicle seat belt arrangement. Other applications will be apparent to persons skilled in the art upon reading this description.

Therefore, the present invention now provides a shock absorber comprising a tearable member having a pair of limbs respectively attached to first and second attachment members and said tearable member further having a main section which tears when said attachment members are pulled apart with an impulsive force above a predetermined magnitude.

The tearable member may comprise any material capable of tearing when the attachment members are pulled apart in the aforementioned manner. It may for example be partly or wholly made of a tearable polymer material, e.g. in the form of a strip or sheet. It may also partly or wholly comprise a fabric or textile material such as a non-woven fabric or textile.

However, in a preferred embodiment the tearable member comprises a woven textile piece. In the context of the present invention, the term "textile" means a textile made of natural or synthetic fibres or a mixture of both.

Although a single strip or sheet may be used as the tearable member, a plurality of strips or sheets may be employed, e. g. laid over one another.

Most preferably, the woven textile piece comprises a plurality of lengths of woven textile. Conveniently, these are laid over one another.

Preferably also, the first and second attachment members are respectively joined to first and second ends of a lanyard and the limbs of the tearable member are joined to the lanyard at respective first and second positions, between the first and second ends.

Conveniently, such attachment may be effected by stitching. However, other means of attachment, e. g.

adhesive bonding, may also be used, additionally or in the alternative.

The lanyard may for example be formed with a loop portion and the first and second positions where the tearable member is joined at respective ends of the loop. In that case, the main section of the tearable member may be located inside the loop.

When the tearable member is a woven textile piece, its limbs may be arranged with respect to its main section, such that when the main section tears, either the weft or catch or lock threads tear and the majority of the warp yarns remain unbroken.

The present invention will now be explained in morse detail by the following non-limiting description of a preferred embodiment and with reference to the accompanying drawings in which Figure 1 shows a safety line incorporating a shock absorber according to the present invention, prior to use; Figure 2 shows a detail of the means of attachment of the woven textile piece to the lanyard in the direction of the arrow indicated by II in Figure 1; and Figure 3 shows the shock absorber and safety line of Figure 1, after use and tearing of the textile piece.

Figure 1 shows a safety line generally designated by numeral 1, comprising a lanyard 3. The lanyard 3 consists of a strip of strong woven material having a first end 5 and a second end 7 and is formed into a loop 9 in its central portion, between the first and second ends.

The first and second ends 5, 7 are respectively attached to first and second securement rings 11, 13 by means of respective closed loops 15, 17 formed of those lanyard ends. These loops 15, 17 are closed by means of stitching portions 19, 21.

A woven textile piece 23 is formed of a plurality (e.g. four) of webbing strips 25, 27, etc. of woven textile, overlaid on one another. The woven textile piece 23 consists of a main portion 29 with a free end, inside the loop 9 of the lanyard. The other end 33 of the woven textile piece 23 is divided into a pair of limbs 35, 37 respectively. As seen better from Figure 2, these limbs are formed by a lateral split in the end 33 of the woven textile piece. These limbs 35, 37 are respectively attached to the ends 39, 41 of the looped portion 9 of the lanyard, by means of respective sections of stitching 43, 45.

In use, the rings 11, 13 are respectively attached to a secure point of attachment and the safety harness of the user. In the event of a fall, an impulsive pull-apart force is imparted to the safety line as indicated by the arrows 47, 49. This pulls the limbs 35, 37 of the woven textile piece in opposing directions, corresponding to the arrows 47, 49, since the limbs are attached to the ends 39, 41 of the looped portion 9 of the lanyard. This causes a ripping or tearing along the length of the webbing strips 25, 27 of the woven textile piece 23, as seen in Figure 3. As shown in the latter drawing, the strips 25, 27 have torn along part of the length of the woven textile piece 23.

However, depending upon the severity of the force, the strips could tear all the way or substantially all the way along the length of the woven textile piece.

The loose fibres 51 resulting from the tearing are shown in Figure 3, hanging from the limbs 35, 37 of the woven textile piece, which limbs are of course extended by virtue of the tearing.

As indicated previously, it is preferable to arrange the strips to tear either the weft or the catch or lock threads, yet such that the majority of the warp yarns remain unbroken.

Experimental results have demonstrated an improved smoothness and consistency of force absorption, compared with conventional arrangements.

In the light of this disclosure, modifications of the described embodiment, as well as other embodiments, all within the scope of the present invention as defined by the appended claims will now become apparent to persons skilled in this art.

Claims

CLAIMS:

1. A shock absorber comprising a tearable member having a pair of limbs respectively attached to first and second attachment members and said tearable member further having a main section which tears when said attachment members are pulled apart with an impulsive force above a predetermined magnitude.

2. A shock absorber according to claim 1, wherein the tearable member is made of textile.

3. A shock absorber according to claim 2, wherein the tearable member is a woven textile piece.

4. A shock absorber according to claim 3, wherein the woven textile piece comprises a plurality of lengths of woven textile.

5. A shock absorber according to any preceding claim, wherein the first and second attachment members are respectively joined to first and second ends of a lanyard and the limbs of the tearable member are joined to the lanyard at respective first and second positions between said first and second ends.

6. A shock absorber according to claim 5, wherein said lanyard is formed with a loop portion and said first and second positions where the tearable member is joined are at respective ends of the loop.

7. A shock absorber according to claim 5 or claim 6, wherein the main section of the tearable member is located inside the loop.

8. A shock absorber according to claim 3 or claim 4, wherein said limbs are arranged with respect to the main section of the woven textile piece such that when the main section tears, either the weft or catch or lock threads tear and the majority of the warp yarns remain unbroken.

9. A shock absorber substantially as hereinbefore described with reference to any of the accompanying drawings.