Field of the Invention

The present invention relates to a sheet material securing fastener which is able to secure sheet material.

Disclosure of the Invention

In accordance with one aspect of the present invention there is provided a sheet material securing fastener comprising:

fork means having at least two arm members extending from junction means and spaced apart at a region spaced from said junction means and at least one of said arm members having engagement means spaced from said junction means; and

keeper means being substantially resilient and insertable into said fork means to hold a portion of said sheet material between said keeper means and said fork means, and said keeper means is retainable in said fork means to hold said portion of said sheet material, said keeper means arranged to abut said engagement means of one of the arm members, said keeper means able to apply a fastening force to said portion of said sheet material due to said sheet material applying a torsional force to said keeper means in response to a tensile force applied to said sheet material, and the fastening force applied by said keeper means to fasten said portion of said sheet material is in proportion to the tensile force which is applied to the sheet material,

wherein said keeper means is provided with extension means arranged to be positioned exterior of said fork means when said keeper means is retained in said fork means, said extension means able to be used to move said keeper means out of abutment with said engagement means such that said keeper means is removable from said fork means.

Preferably, said extension means has a portion to receive a force to remove said keeper means from said fork means.

Preferably, said extension means is provided with frictional means.

Preferably, said extension means extends from said keeper means substantially proximate a location of said keeper means at which said keeper means is able to abut said engagement means of said fork means

Preferably, gripping means is provided on said keeper means to grip said sheet material.

Preferably, said gripping means comprises serrations.

Preferably, said keeper means is substantially wedged-shaped having an apex region and said keeper means is able to abut said engagement means of said fork means at a location of the keeper means spaced from the apex region such that said keeper means is retainable in said fork means.

Preferably, said gripping means is provided at said apex region of said keeper means.

Preferably, said keeper means comprises at least two arms joined by junction means.

Preferably, the arms of the keeper means are biased away from each other.

Preferably, one of said arms of said keeper means abuts with said engagement means.

Preferably, said extension means extends from an arm of said keeper means.

Preferably, said extension means comprises at least one portion that extends substantially longitudinally and is substantially planar.

Preferably, said arm members of said fork means and said arms of said keeper means extend substantially longitudinally and are substantially planar.

The arm members of the fork means and the arms of the keeper means are arranged such that the spacing apart of the arms of the keeper means is sufficient such that the keeper means is retainable between the arm members of the fork means.

In at least one embodiment of the present invention, said extension means is able to bear a force to insert said keeper means into said fork means.

In at least one embodiment of the present invention, a portion of said extension means contacts a portion of said keeper means remote from said apex region and said third portion is able to slide over said portion of said keeper means.

In at least one embodiment of the present invention, a said arm of said keeper means is articulated and has at least two portions that are moveable relative to one another.

Preferably, said at least two portions of said arm of said keeper means are moveably connected by a joint.

Preferably, one of said at least two portions of said arm of said keeper means abuts with said engagement means of said fork means.

Preferably, said extension means extends from said portion of said arm of said keeper means that abuts with said engagement means.

Preferably, said engagement means comprises a shoulder provided at a distal location of one of said arm members of said fork means and spaced from said junction means.

The sheet material securing fastener applies a retaining force to the sheet material in proportion to the tension applied to the sheet material. For example, the sheet material retained by the fastener may be subject to external tensile

forces, and the retaining force applied to the sheet material by the fastener will be in proportion to the tensile force so applied.

Brief Description of the Drawings

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a first embodiment of a sheet material securing fastener in accordance with the present invention showing the keeper member in the process of being inserted into the fork member;

Figure 2 is an end view of the sheet material securing fastener shown in Figure 1 ;

Figure 3 is perspective view of the first embodiment of a sheet material securing fastener, showing the keeper member retained in the fork member;

Figure 4 is an end view of the sheet material securing fastener shown in Figure 3;

Figure 5 is a perspective view of the keeper member of the sheet material securing fastener shown in Figure 1 ;

Figure 6 is an end view of the keeper member shown in Figure 5;

Figure 7 is a perspective view of an embodiment of another keeper member;

Figure 8 is an end view of the keeper member shown in Figure 7;

Figure 9 is a perspective view of another embodiment of a sheet material securing fastener.

Figure 10 is an end view of a further embodiment of a sheet material securing fastener showing the keeper member in the process of being inserted into the fork member;

Figure 11 is an end view of the sheet material securing fastener shown in Figure 10, showing the keeper member at a further stage in the process of being inserted into the fork member;

Figure 12 is an end view of the sheet material securing fastener shown in Figure 10, showing the keeper member retained in the fork member.

Best Mode(s) for Carrying Out the Invention

In the following description, like reference numerals are used to identify like parts of the embodiments.

Figures 1 , 3, 5, 7 and 9 to 12 are perspective views whilst figures 2, 4, 6 and 8 are end views. Thus, it is to be understood that figures 2, 4, 6 and 8 show end profile views, with the sheet material securing fasteners extending in a longitudinal manner in a direction transverse to the plane of the page on which they are drawn.

The following description and the accompanying drawings use the same reference numerals (though sometimes appended with a reference letter) to denote the same, or corresponding, features in the various embodiments.

Accordingly, the description of such features is not repeated for each embodiment. It is to be understood that the description of such features in relation to one embodiment applies in a corresponding manner, including their manner of use and operation, to other embodiments having similar features.

In Figures 1 to 4, there is shown a sheet material securing fastener 2 comprising a fork member 4 and a keeper member 6. The fork member 4 and keeper member 6 are of a length (shown by the arrow L in Figure 1 ) appropriate for the sheet material 28 to be secured. The fork member 4 is arranged to be mounted to a fixture (not shown). The fork member 4 has two substantially planar arm members 8 and 10. The arm members 8 and 10 are joined by a junction 12 and are spaced apart from each other at a region 14 near their respective distal ends. The arm members 8 and 10 diverge from the junction 12.

The arm member 8 has an engagement member, in the form of a shoulder 20, provided at a location of the arm member 8 spaced from the junction 12. The shoulder 20 is turned inwardly, i.e., toward the arm member 10.

The junction 12 has a portion 9 that extends at substantially a right angle from the arm member 10 to the arm member 8. The arm member 8 has a portion 11 that extends from the portion 9 in an offset manner. The shoulder 20 is provided at the end of the portion 11 of the arm member 8. In this way, the arm member 10, the portion 9 and the arm member 8 of the fork member 4 form a channel.

In the embodiment shown, the arm members 8 and 10 diverge from the junction 12 over their entire lengths. However, as an alternative, the arm members 8 and 10 may diverge from the junction 12 for a portion of their lengths and extend substantially parallel over another portion of their lengths.

The arm 10 of the fork member 4 is provided with an outwardly turned lip 13 to provide a smooth curved surface for the sheet material 28. However, as an alternative, the lip 13 may be omitted.

The keeper member 6 is substantially wedge-shaped and resilient.

The keeper member 6 has an apex region 19. The apex region 19 acts like a hinge such that when the keeper member 6 is depressed, e.g. squeezed, in the region spaced from the apex region 19, the resilience of the keeper member 6 returns it to the undepressed condition. Additionally, the keeper member 6 has an in-built bias which acts to keep apart the ends of the keeper member 6 that are spaced from the apex region 19.

The keeper member 6 has a pair of substantially planar arms 22 and 24 which are joined by a junction 26 at the apex region 19.

The arm 22 of the keeper member 6 has an extension portion 23, having substantially planar portions, extending therefrom near the end 25 of the arm 22. The extension portion 23 has a short transverse portion 27 that extends from the

arm 22 on the inner side (i.e. the side facing the arm 24) of the keeper member 6 and a further portion 29 extending from the short transverse portion 27. The further portion 29 has a first leg 30 extending from the short transverse portion 27 in a direction away from the junction 26 of the keeper member 6 and optionally (as shown) a second leg 31 extending from the first leg 30. When the first and second legs 30 and 31 are both present, the portion 29 is substantially L shaped in end profiled.

The second leg 31 may extend from the first leg 30 on either or both sides thereof, i.e. on the right side (as shown in Figures 2, 4 and 6) on the left side (not shown), or on both the right and left sides (not shown). This is also the case with the keeper members 6a and 6b to be later herein described.

Serrations 32 are provided on the outer face of the leg 31. The serrations 32 extend longitudinally and form a frictional surface for a user to manipulate the keeper member 6. The second leg 31 may be curved (as shown) such that the serrations 32 are provided in a slight depression for ease of handling by the user.

The apex region 19 of the keeper member 6 is provided with serrations 33 on the outer surface thereof. The serrations 32 extend longitudinally. The serrations 33 are provided in the form of teeth, or barbs, that are biased in a direction away from the arm 24 and toward the arm 22. The serrations 33 form a gripping means to grip a sheet material 28 as will be later herein described.

However, in alternative embodiments of the keeper member 6, one or both of the serrations 32 and serrations 33 may be omitted from the keeper member 6. The extension portion 23 facilitates insertion of the keeper member 6 into the fork member 4 as well as removal of the keeper member 6 from the fork member 4. Pressure, i.e. a force, may be exerted on the second leg 31 , or on the edge of the first leg 30 when the second leg 31 is not present, to facilitate insertion of the keeper member 6 in the fork member 4. The second leg 31 , or the first leg 30 when the second leg 31 is not present, can be deflected in the direction shown by arrow A in Figure 4 to disengage the end 25 from the shoulder 20 for removal of the keeper member 6 from the fork member 4.

The serrations 33 on the apex 19 of the keeper member 6 grip the fabric during insertion of the keeper member 6 into the fork member 4. Once the keeper member 6 is in position in the fork member 4 to retain the sheet material 28, the serrations 33 gripping the sheet material 28 also facilitate adjustments that can be made to the tension in the sheet material 28 using the keeper member 6 as will be later herein described.

Figures 7 and 8 show an alternative embodiment of a keeper member 6a. The keeper member 6a shown in Figures 7 and 8 is substantially similar to the keeper member 6 shown in Figures 1 to 6 except that it has an additional leg 34 that extends from the second leg 31 of the extension section 23 and that the second leg 31 is straight (rather than curved as it is in the keeper member 6). However, as an alternative, the second leg 31 may be curved. The keeper member 6a may also be provided with Serrations 32 and/or 33. The additional leg 34 is provided to enable the end 28a of the sheet material 28 to be concealed when the keeper member 6a is in place in the fork member 4.

Either or both of the serrations 32 and 33 may also be provided on the keeper member 6a shown in Figures 7 and 8.

The keeper member 6b of the further embodiment of a sheet material securing fastener 2a shown in Figure 9 is substantially similar to the keeper member 6 shown in Figures 1 to 6 except that it has a longer transverse portion 27a that extends past the first leg 30. The longer transverse portion 27a of the keeper member 6b shown in Figure 9 extends as an arc and abuts the end of the arm 24 of the keeper member 6b. This arrangement enables a greater force to be applied to the first or second leg 30 or 31 for insertion of the keeper member 6 into the fork member 4. Such force may, for example, be applied by hand or by a mallet.

The keeper member 6b shown in Figure 9 may also be provided with either or both of the serrations 32 and 33.

Figures 10 to 12 show a further embodiment of a sheet material securing fastener 2b.

The sheet material securing fastener 2b comprises a fork member 4a and a keeper member 6b. The fork member 4a is similar to the fork member 4 of the embodiments previously described herein except that in the fork member 4a, the portion 9a extends, substantially at a right angle, from the substantially planar arm member 8a to the substantially planar arm member 10a. The arm member

10a has a portion 42 that extends from the portion 9a in an offset manner.

Additionally, the mounting flange 36 projects from the junction 12a adjacent the arm member 8a.

The keeper member 6c is similar to the keeper member 6 previously herein described and illustrated with reference to the embodiment shown in Figures 1 to 6, except that the substantially planar extension portion 23a and the substantially planar arm 22a of the keeper member 6c are different from the extension 23 and the keeper arm 22 of the keeper member 6.

The arm 22a of the keeper member 6c is articulated having a first portion 22b and a second portion 22c that are pivotally or hingedly connected by a joint 40. The joint 40 is provided in the mid region of the arm 22a of the keeper member 6c, though nearer the end 25c than the junction 26 of the keeper member 6c. The portion 22b is the one that is adjacent the junction 26. The portion 22c is the one having the end 25a that abuts with the shoulder 20.

The extension portion 23 extends from the portion 22c of the arm 22a. The extension portion 23a has a short extension portion 27b that extends from the portion 22c on the inner side (i.e. the side facing the arm 24) of the keeper member 6c and a leg 30a that extends from the short transverse portion 27b in an offset manner.

The fork member 4 and keeper member 6 may be manufactured by an extrusion process.

Thθ keeper member 6 is insertable into the fork member 4 to retain, or hold, a portion of the sheet material 28 between the keeper member 6 and the fork member 4. The sheet material 28 is flexible and may be in the form of film or fabric. The sheet material 28 is sandwiched between and in contact with the keeper member 6 and the fork member 4 on its respective faces.

When the keeper member 6 is inserted into the fork member 4, the end 25 of the arm 22 will abut against the shoulder 20 to retain the keeper member 6 in the fork member 4.

The in-built bias in the keeper member 6 is sufficient such that in the free condition of the keeper member 6, i.e. when the keeper member 6 is exterior of the fork member 4, the spacing between the ends of the arms 22 and 24 of the keeper member 6 is greater than the maximum spacing between the shoulder 20 of the arm member 8 and the outwardly turned lip of 13 of the arm member 10 of the fork member 4. This ensures that the end keeper member 6 engages with the shoulder 20 in the fork member 4. The keeper members and fork members of the embodiments described herein with reference to Figures 7, 8 and 9 are similarly arranged.

The length of the keeper member 6 from the apex region 19 to the end 25 that abuts with a shoulder 20 is less than the distance from the junction 12 to the shoulder 20. This ensures that the keeper member 6 is able to engage with the shoulder 20.

A mounting flange 36 projects from the junction 12, adjacent the arm member 10. The mounting flange 36 enables the fork member 4 to be mounted to a fixture (not shown), e.g. a framework for a sign. Apertures (not shown) may be provided in the mounting flange 36 to enable the fork member 4 to be mounted to the fixture by a conventional fastener, e.g. screws 38 (shown in Figure 9). The mounting flange 36 projects from the junction 12 in a direction substantially opposed to the portion 9 of the arm member 8. However, the mounting flange 36 may be provided in any suitable manner such that the fork member 4 can be mounted to the fixture, e.g. the mounting flange 36 may, alternatively, be provided such that it

extends at substantially a right angle to the portion 9 of arm member 8 of the fork member 4.

The manner of use and operation of the sheet material securing fastener of the present invention shall now be described.

The following description is with particular reference with figures 1 - 6 of the accompanying drawings.

Once the fork member 4 has been mounted in position on a fixture by the mounting flange 36, the sheet material 28 to be secured is positioned to overlie the region 14 between the arm members 8 and 10 of the fork member 4. This is generally done using the portion of the sheet material 28 near an end 28a thereof.

The keeper member 6 is then positioned at the region 14 with the apex region 19 directed into the fork member 4 such that the sheet material 28 is positioned between the fork member 4 and the keeper member 6. The keeper member 6 is then pushed into the fork member 4, i.e. between the arm members 8 and 10 of the fork member 4. This condition is illustrated in Figures 1 and 2. The keeper member 6 may be pushed into the fork member 4 by exerting pressure, i.e. a force, on the second leg 31 , or on the edge of the first leg 30 when the second leg 31 is not present, of the extension portion 23 in the direction of the arrow B shown in Figure 2. Thus, the second leg 31 , or the edge of the first leg 30 when the second leg 31 is not present, are able to bear, i.e. receive, a force to insert the keeper member 6 into the fork member 4. As the keeper member 6 is inserted into the fork member 4, the end of the shoulder 20 of the fork member 4 bears against the arm 22 of the keeper member 6. This causes the keeper member 6 to pivot at the junction 20 such that the arms 22 and 24 are moved toward one another.

With the further insertion of the keeper member 6, the end 25 of the arm 22 of the keeper member 6 will pass the end of the shoulder 20 and, due to the resilience of the keeper member 6, the arms 22 and 24 will then spring outwardly away from each other. The sheet material 28 will then lie adjacent the outer surfaces of the

arms 22 or 24 of the keeper member 6. The arm 24 of the keeper member 6 bears against the arm member 10 of the fork member 4, with a portion of the sheet material 28 between the arm 24 and the arm member 10. The end 25 of the arm 22 of the keeper member 6 engages and abuts with the shoulder 20, with a portion of the sheet material 28 therebetween. In this secured position, the keeper member 6 is locked in place in the fork member 4 and cannot escape therefrom. This condition is illustrated in Figures 3 and 4.

In this way, the keeper member 6 is retained in the fork member 4 and the sheet material 28 is held between the keeper member 6 and the fork member 4.

Accordingly, as shown in Figures 3 and 4, the sheet material 28 enters the fork member 4 over the outwardly turned lip 13 of the arm member 10 such that it is sandwiched between the arm member 10 of the fork member 4 and the arm 24 of the keeper member 6. The sheet material 28 extends around the apex region 19, arm 22 and end 25 of the arm 22 of the keeper member 6. The sheet material 28 is sandwiched between the end 25 of the arm 22 of the keeper member 6 and the shoulder 20 of the arm member 8 of the fork member 4.

The part of the sheet material 28 that is subject to tensioning is the part that is outside the fork member 4, i.e., the part that does not enter the fork member 4 over the outwardly turned lip 13.

If any outwardly directed exterior tensioning, or tensile, force is applied to the sheet material (as represented by arrow C in Figure 4), an effective moment, also referred to as a torsional force, will be applied to the keeper member 6 by the sheet material 28. This causes the end 25 of the arm 22 of the keeper member 6 to engage more forcefully against the shoulder 20 of the arm member 8 and also causes the region of the arm 24 adjacent the apex 19 to engage more forcefully against the arm member 10 of the fork member 4. If the tensioning force applied to the sheet material 28 (arrow C) increases, the moment applied to the keeper member 6 (by the tensioning force) will be increased causing an even greater forceful engagement between the end 25 of the arm 22 and the shoulder 20 of the arm member 8 and between the region of the arm 24 adjacent the apex 19

and the arm member 10. This causes the sheet material 28 to be forcefully gripped between the end 25 of the arm 22 and the shoulder 20 and between the arm 10 of the fork member 4 and the arm 24 of the keeper member 6 adjacent the apex region 19.

Conversely, a decrease in the tensioning force applied to the sheet material 28 causes a decrease in the fastening force or, the gripping force, applied to the sheet material 28 by the keeper member 6 engaging with the fork member 4 to retain the sheet material 28 between the fork member 4 and the keeper member 6.

Consequently, the fastening or gripping force applied to the sheet material 28 by the keeper member 6 engaging with the fork member 4 increases/decreases with an increase/decrease in the tensioning force applied to the sheet material 28. That is to say, the fastening or gripping force applied to the sheet material 28 by the keeper member 6 engaging with the fork member 4 to fasten the sheet material 28 is in proportion to the tensile force which is applied to the sheet material 28.

The serrations 33 are provided at the apex region 19 of the keeper member 6 to grip the sheet material 28 and provide reduced slippage between the sheet material 28 and the keeper member 6 during insertion of the keeper member 6 into the fork member 4. Furthermore, the serrations 33 enable the tension in the sheet material 28 to be increased once the keeper member 6 is in its secured position inside the fork member 4. This can be done by holding the loose end 28a of the sheet material 28 and tapping on the extension portion 23. Due to the serrations 33 being biased in the direction away from the arm 24 and toward the arm 22, the serrations 33 act in a ratchet-like manner such that tapping of the extension portion 23 causes the sheet material 28 to gradually move around the apex 19, in the direction shown by arrow D in Figure 4. This results in the tension in the sheet material 28 being increased and also removes any local wrinkles in the sheet material 28 thereby improving aesthetic appearance of the installed sheet material 28.

The sheet material 28 may be released from tension by the sheet material securing fastener 2 by removing the keeper member 6 from the fork member 4. This can be done by exerting a force on the second leg 31 , or on the first leg 30 when the second leg 31 is not present, of the extension portion 23 in the direction shown by arrow A such that the arm 22 pivots at the junction 26 so that the arm 22 moves toward the arm 24 and clears the shoulder 20, of the arm member 8, against which the end 25 abuts. Once the end 25 of the arm 22 clears the shoulder 20, the sheet material 28 will be released from the sheet material securing fastener 2 and the keeper member 6 can be removed from the fork member 4. Thus, the second leg 31 , or the first leg 30 when the second leg 31 is not present, is able to bear, i.e. receive, a force to remove the keeper member 6 from the fork member 4.

The embodiment of the keeper member 6a shown in Figures 7 and 8 has a further leg 34. In addition to the leg 34 acting as a hood to cover the loose end 28a of the sheet material 28, it may also be used as a surface which can be struck using a mallet, or similar tool, to pivot the arm 22 at the junction 26 to thereby remove the keeper member 6 from the fork member 4 and release the sheet material 28 from the sheet material securing fastener 2. Thus, the leg 34 is able to bear, i.e. receive, a force to remove the keeper member 6 from the fork member 4. Insertion of the keeper member 6a into the fork member 4 may be achieved using the second leg 31 as previously herein described with reference to the embodiment shown in Figures 1 to 6.

The embodiment of the keeper member 6b shown in Figure 9 enables the second leg 31 , or edge of the first leg 30 when the second leg 31 is not present, to be struck with a mallet, or similar tool, during the insertion process of the keeper member 6b into the fork member 4. Since the longer transverse portion 27a of the extension portion 23 bears against the end of the arm 24 of the keeper member 6b, the leg 31 can be struck with a greater force to insert the keeper member 6b into the fork member 4. Thus, the second leg 31 , or the edge of the first leg 30 when the second leg 31 is not present, are able to bear, i.e. receive, a force to insert the keeper member 6 into the fork member 4. When the arm 22 is pivoted toward the arm 24 to remove the keeper member 6b from the fork

member 4, the longer transverse portion 27a slides over the end of the arm 24. In other respects, removal of the keeper member 6b from the fork member 4 may be achieved as previously herein described with reference to the embodiments shown in Figures 1 to 8.

The Figures 10, 11 and 12 show, in sequence, the stages of insertion of the keeper member 6c into the fork member 4a.

The manner of use and operation of the sheet material securing fastener 2b has been previously described in detail with reference to other embodiments. Accordingly, the following description of the manner of use and operation of the sheet material securing fastener 2b will be primarily in relation to the manner of use and operation rising from the articulation provided in the arm member 22a of the keeper member 6c. It will be understood that other aspects of the use and operation of the sheet material securing fastener 2b are similar to that previously herein before described with reference to the other embodiments.

The sheet material 28 is positioned between the fork member 4a and the keeper member 6c. The arm 22a is bent at the joint 40 such that the portion 22c is folded back over toward the portion 22b on the side opposed to the arm 24. The keeper member 6c is then pushed into the opening of the fork member 4a at the region 14. This may be done by pressing down with a force on the joint 40 and pushing the end 25a of the arm 22a beyond the edge of the shoulder 20. Thus, the joint 40 is able to bear, i.e. receive, a force to insert the keeper member 6c into the fork member 4a. This stage is shown in Figure 10.

Once the keeper member 6c has entered the fork member 4a, as above described, the portion 22c of the arm 22a engages the shoulder 20. A force is exerted on the leg 30a of the extension portion 23a to rotate it in the direction of arrow D shown in Figure 11 toward the arm 24 of the keeper member 6c. This causes the end 25a of the arm 22a to bear against the shoulder 20 such that the keeper member 6c is pushed into the fork member 4a. Thus, the leg 30a is able to bear, i.e. receive, a force to insert the keeper member 6c into the fork member 4a. This stage is shown in Figure 11.

Since the sheet material 28 is effectively trapped between the shoulder 20 and the end 25a of the arm 22a, the sheet material 28 is pulled further into the fork member 4a, thereby tightening the sheet material 28. Continued exertion of a force on the leg 30a of the extension portion 23a rotates the extension portion 23a in the direction of arrow D to cause the arm member 22a to pass through a condition in which the portions 22b and 22c are linearly aligned and subsequently reach a condition in which the joint 40 moves to an over-centre condition. This condition is shown in Figure 12. In this over-centre condition, the portions 22b and 22c are no longer linearly aligned and the portion 22c lies adjacent the arm member 8a of the fork member 4a.

The end 25a of the arm 22a of the keeper member 6c engages and abuts with shoulder 20, with the portion of sheet material 28 therebetween . In this secured position, the keeper member 6c is locked in place in the fork member 4a and cannot escape therefrom. This condition is illustrated in Figure 12.

In this way, the keeper member 6c is retained in the fork member 4a and the sheet material 28 is held between the keeper member 6c and fork member 4a.

The sheet material 28 may be released from tension by the sheet material securing fastener 2b by removing the keeper member 6c from the fork member 4a. This can be done by exerting a force on the leg 30a of the extension portion 23a in the direction shown by arrow E in figure 12. Thus, the leg 30a is able to bear, i.e. receive, a force to remove the keeper member 6c from the fork member 4a. Exerting force in this direction will cause the joint 40 to move out of the over- centre condition, pass through the condition illustrated in Figure 11 and then the keeper member 6c will disengage from the fork member 4a as shown in Figure 12. Thus, the sequence of steps in removal of the keeper member 6c is the reverse of the steps for insertion of the keeper member 6c into the fork member 4a.

The serrations 32 and 33 may be provided on the keeper members 6a, 6b and 6c shown in the embodiments illustrated in Figures 7, 8 and 9, and 10 to 12 and so their operation will not be again described.

Similarly, the further leg 34 of the keeper member 6a shown in Figures 7 and 8 may also be incorporated into the keeper members 6a and 6b illustrated in the embodiments of Figures 1 to 6 and 9.

Modifications and variations such as those apparent to a skilled addressee are deemed to be within the scope of the present invention.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.