GB2072738A - A releasable encircling device - Google Patents

Abstract

A releasable encircling device integrally moulded from a resiliently deformable plastics material comprising hook and clip members, the principal axes of which are located in the same plane, one of the said members 300 including a double ended element 302 and the other member including a cavity 304 adapted to receive the double ended element, the cavity having undercut portions transverse to the plane of the device, and an integrally moulded formation 306 associated with one of the members adapted to abut the other member or a formation associated therewith to restrain transverse disengagement of the elements. <IMAGE>

Description

SPECIFICATION A releasable encircling device This invention relates to a releasable encircling device and in particular to a snap hook by means of which a line, which is attached to the hook, may be hooked or clipped on to something else, such as another line, a pole, a ring or the like.

A good example of such a fastener is that described in French Patents Nos. 2 059 879 and 2 118 254 to Maillocheau, upon which United States Patent No 3748703 and British Patent No 1 328720 are based. The patents described a snap hook with a clip formation adapted to close the mouth of the hook, the ends of the clip formation and the hook being provided with formations which are interengageable to form a closed loop. The snap hook is attached to the end of an elastic cord orthe like by means of a truncated conical sleeve within which the end of the elastic cord is received.

The interengaging formations are essentially clip formations which are self-coupling when the snap hook is subjected to tension and the clip formation is biassed in such a mannerthatthe interengaging formations are held in their closed position to prevent accidental opening of the hook.

While such a fastener is extremely useful for many purposes there are certain applications where it is necessary to prevent disengagement of the hook and clip as a result of intermittent compressive forces acting on the hook and lateral forces acting across the hook to twistthe hook and clip apart.

A solution to this problem was suggested in the present applicants' British patent application no.

80/06019 upon which the applicants elaborated in British Patent Applications Nos. 80/13130 and 80/18955.

The reieasable encircling device described in the patent applications is particularly suitable for dynamic loading situations such as certain tetherball games, where the line carrying the ball is attached to a fixed member across a snap hook. In the nature of such games, varying tensile loads are applied to the hook which, in recovering as a result of its own resilience after a load, may place a compressive or even lateral load on the engagement formations thereof.

Accordingly the invention provides a releasable encircling device integrally moulded from a resiliently deformable plastics material comprising hook and clip members, the principle axes of which are located in the same plane, one of the said members including a double ended element and the other member including a cavity adapted to receive the double ended element, the cavity having undercut portions transverse to the plane of the device, and an integrally moulded formation associated with one of the members adapted to abut the other member or a formation associated therewith, to restrain transverse disengagement of the elements.

Whether a releasable encircling device of this construction is subjected to tensile or compressive loading, one of the ends of the double ended element will abut a corresponding re-entrant portion of the double undercut groove preventing the opening of the clasp.

It will be appreciated that the resilient deformability of the material from which the releasable encircling device is moulded can be utilised to the full by properly dimensioning the double ended element and the double undercut groove to provide a clip-fit for the double ended element in the groove.

In the preferred form of the invention the cavity is formed in the hook member and comprises a double undercut groove, the principle axis of which extends transversely across the plane of the device, while the double ended element is mounted on a pair of arms integrally moulded to extend from the free end of the clip member, the arms and the double ended ele menttogether defining a stirrup adapted to accept at least partoftheterminal portion of the hook member, the arms being located on the terminal portion when the double ended element is engaged with the groove, abutting the terminal portion to restrain transverse disengagement of the elements.

In a further form of the invention the cavity is formed in the hook member and comprises a double undercut groove, the principle axis of which extends transversely across the plane of the device, while the double ended element is "T"-shaped in cross section, the ends of the cross bar of the "T" constituting the ends of the double ended element and the stem of the "T" being adapted to abut the edges of the groove when the double ended element is engaged therein, an integrally moulded rib being disposed parallel to the plane of the releasable encircling device across the groove and a complementary slot being formed in the double ended element which is adapted to accept the rib when the double ended element is engaged with the groove, the rib abutting the sides of the slot to restrain transverse disengagement of the elements.

In both the above mentioned instances, the double ended element may be movable, along with the member in which it is formed, in the plane of the device for insertion into the groove, the entrance of which is narrower than the dimension across the ends of the double ended element which is insertable in the groove by a force sufficient to overcome the resilience of the material.

The encircling device may conveniently include means for the attachment of an elongate tension member to the releasable encircling device, the double ended element may be mounted on a pair of arms in the manner described above to provide a stirrup adapted to accept a complementally shaped protrusion provided on the termainal portion of the hook member, the one end of the protrusion constituting an undercut edge of the groove and the arms of the strirrup being located on either side of the protrusion when the double ended element is engaged with the groove, abutting the protrusion to restrain transverse disengagement of the elements.

In yet a further form of the invention in which the cavity is formed in the hook member and comprises a double undercut groove, the principal axis of which extends transversely across the plane of the device, a channel may conveniently be formed in the terminal portion of the hook member, the channel extending from the free end of the hook member to the edge of the groove adjacent the free end, while the terminal portion of the clip member may be arranged, in a zone directly adjacent and inwardly of the double ended element, to be received in the channel, the double ended element being receivable in the groove in the manner of a toggle located in a cradle.

A description of specific embodiments of the invention is given by way of examples, with reference to the accompanying drawings in which: Figure 1 is an isometric view of a preferred clasp for a releasable encircling device according to the invention; Figure 2 is a sectional side elevation of a snap hook embodying the clasp of figure 1; Figure 3 is a side elevation of a releasable encircling device attached to a wire forming a part of a helix of a tetherball game apparatus.

Figure 4 is a side elevation of the terminal portion of the hook member of the releasable encircling device of Figure 1 in which the cavity or double undercut groove is formed; Figure 5 is a front elevation of the terminal portion shown in Figure 4; Figure 6 is a side elevation of a "T"-shaped double ended element; Figure 7 is a front elevation of the double ended element of Figure 6; Figure 8 is a front elevation of an alternative double ended element; Figure 9 is a front elevation of an alternative double undercut groove; Figure 10 is a perspective view of an alternative clasp for a releasable encircling device according to the invention; Figure 11 is a side elevation of the clasp of Figure 10 showing the operation thereof.

In Figure 1 a pair of elements are shown joined to form a clasp 402 which is part of a snap hook 400 shown in Figure 2. The snap hook 400 is integrally moulded in a resiliently deformable plastics material and comprises a flexible hook member 404 and a clip member 406. The hook member 404 comprises an elongate shank which, like the clip member 406, is rhomboid in cross section so that it is easily bent.

The snap hook 400 or releasable encircling device is provided with a separately curved, outer end 408 which is thicker than the rest of the device so that it is more rigid. The opposite end of the device is formed with an aperture located in a truncated conical sleeve through which a line 410 is threaded and secured by means of a knot 412.

The hook member 404 and the clip member 406 terminate in inter-engageable formations or ele ments which comprise, in the hook member 404, a double undercut groove 414 extending transversely across the end of the hook member, and, in the clip member, in a double ended element 416 located stirrup-like on the end of a pair of arms 418.

The double undercut groobe 414 on the end of the hook member 404 is defined by a lip forming part of the hook member 404 at its upper end 420 and, at its lower end, by a protrusion 422 located on an extend sion 424 of the hook member. The double ended element 416 is adapted to abut, with its upper end 426, against an upper re-entrant portion of the dou ble undercut groove 414 under compressive loading of the snap hook 400 and, with its lower end428, against a lower re-entrant portion of the groove 414, under tensile loading of the device 400. The actual working the device will be described below with reference to the further embodiments of the invention, the difference between the devices described there and device shown in Figures 1 and 2 being in the insertion procedure of the double ended element into the groove 414.In the snap hook 400 the outer surface 430 of the double ended element 416 slides on the upper edge 420 of the groove 414when the opened device is being closed, the lower edge 428 of the double ended element being inserted into the lower re-entrant portion of the groove 414 first. This allows the passage of the upper end 426 of the double ended element 416 past the upper end 420 of the groove. The dimension across the ends of the double ended element 416 is, of course, larger than the entrance to the groove 414 so that, even afterthe lower end 428 of the double ended element 416 has been inserted into the lower re-entrant portion of the groove 414, a certain amount of force is required to snap the upper end of the double ended element past the upper edge 420 of the groove.The double ended element 416 is withdrawn from the groove 414 with the lower edge 428 being withdrawn first in the manner described below.

The snap hook 10 shown in Figure 3 is formed as a unitary, one-piece structure of injection moulded plastics material, such as nylon, and comprises a flexible hook member 12 and an elongate clip member 15 which, together form a closed loop encircling a wire 16 which forms part of the helix of tetherball game apparatus. The wire 16 is shown in cross section. The hook member 12 comprises an elongate shank 18 which, like the clip member 14, is rhomboid in cross section so that it is easily bent.

The snap hook is provided with a separately curved, outer end 20 which is thicker than the rest of the loop and rectangular in cross section to be more rigid.

The opposite end of snap hook 10 is formed with an aperture 22 through which a line 24 is threaded and is secured by means of a knot 26.

As can be seen more clearly in Figures 4 to 7 the terminal portions 28 and 30 of the hook member 12 and the clip member 14 respectively are provided with a groove 32 extending transversely across the plane of the loop 1 and a complemental double ended element 34, which is capable of engaging with the groove 32 to close the loop. The double ended element 34 is constituted by a "-shaped moulding on the end of the clip member 14, the ends 36 and 38 of the cross bar of the "T" defining the ends of the double ended element and the stem 40 of the "T" providing an abutment formation for the edges 42 and 44 of the groove 32.

The groove 32 is undercut on both edges thereof defining a cavity 46 with a constricted mouth, being provided with re-entrant portions 46a and 46b.

To close the open snap hook 10 the leading edge 38 of the double ended element 34 is advanced towards the upper edge 44 of the groove 32, the upper surface of the "T" sliding in the manner of a cam, over the lower edge 42 of the groove. If compression is now applied across the snap hook 10 or an outward pressure is exerted on the clip member 14,the resilience of the material allows the leading edge 38 of the "T" to enter the re-entrant portion 46a untii the stem 40 of the "T" abuts the upper edge 44 of the groove 32 at which point the lower edge 36 of the double ended element should be allowed past the lower edge 42 of the groove 32. Proper dimensioning of the double ended element 34 and the groove 32 should ensure that the passage of the lower edge 36 of the double ended element 34 past the lower edge 42 of the groove 32 requires a certain amount of pressure.It should, in other words, be a clip fit.

To open the closed loop of the device 10, it is necessary to move the clip member 14 inwardly with respect to the hook member 12, forcing the leading edge 38 of the double ended element into the reentrant portion 46a, and the lower end 36 of the double ended element out of the re-entrant portion 46b and past the lower edge 42 of the groove. This enables the upper end 38 of the double ended ele mentto slide out of the groove on the re-entrant slope undercutting the upper edge 44 of the groove.

To ensure that the closed loop is not inadvertently opened when it is moved along the wire 16 and into accidental engagement with an adjacent coil of the helix (shown in section as a wire 48), the terminal portion 28 of the hook member 12 is provided with an extension 30 which projects beyond the clasp so as to shield the clip member 14 thereby preventing independent movement of the clip member with respect to the hook member 12. In this manner disengagement of the clasp under all but excessive pressures, is obviated. The rigid, curved outer end 20 of the hook member 12 can, of course be dimensioned so that the wire 16 itself will prevent such excessive movement of the terminal portion of the hook 12 and the clip member 14.

As shown in Figure 5, the double undercut groove 32 is separated by a central rib 52 into two cavities 46c, 46d each having the double undercut cross section as described above. The double ended element 30 on the other hand, is divided by a central groove 54 into two portions of "T"-shaped cross section as is shown in Figures 6 and 7, the slot 54 being capable of receiving the rib 52 when the double ended element 34 is engaged with the double undercut groove 32. The engagement of the groove 54 with the rib 52 prevents the lateral movement of the double ended element with respect to the double undercut groove and therefore the lateral disengagement of the clasp.

Itwill be appreciated that, under compressive loading of the device 10 the upper end 38 of the double ended element 34 will abut the re-entrant portion re-entrant portion 46a of the cavity 46 and under tensile loading of the device 10, the lower end 36 of the double ended element 34 will abut the lower re-entrant portion 46b of the cavity 46.

In the embodiment shown in Figures 8 and 9, instead of being equal in width, one portion 202 of the double ended element 200 is widerthan the other portion 204 thereof, the slot 206 being disposed off-centre with respect to the central axis of the clip member 208. Similarly the rib 210 disposed across the groove formed in the terminal portion of the hook member212, is located off-centre with respect to the central axis of the hook member 212, so that two unequal cavities 214 and 216 are formed.

The wide portion 202 of the double ended element is, of course, accommodated in the wider cavity 216, while the narrow portion 204 is accommodated in the narrow cavity 214. This arrangement facilitates the insertion and withdrawal of the double ended element into and from the groove, the narrow portion 204 being inserted or withdrawn first. The slot 206 is extended into the terminal portion of the clip member to allow the independent movement of the portions 202 and 204.

It was the present Applicants' experience that excessive tractive forces caused breakages in the ends of the double ended element and to obviate this problem the clasp was improved by providing a cradle and toggle arrangement, an example of which is shown in Figures 10 and 11.

In the clasp shown in Figure 10 the terminal portion of the clip member 300 has been provided with a "T"-shaped ending in elevation by means of a cross bar 302 connected to the end of the clip member 300.

The double undercut groove 304 has been modified by the formation therein of a slot 306 in the lower edge 308 thereof, the slot 306 being adapted to accommodate the shank adjacent the terminal portion of the clip member 300.

It will be appreciated that in this arrangement the tractive force acts directly on the cross bar 302 and no moments of force can be set up as was the case in the stem 40 of the "T" described above with reference to Figures 3 to 9. This situation also prevails in the cross bar of the stirrup-type clasp shown in Figures 1 and 2. The cross bar 302 is enlarged to define the double ended element described above, by having two discrete ends 310 and 312. Atab 314 is provided and arranged to project from the mouth of the groove 304 when the double ended element 302 is engaged with the groove 304. When a compressive force is applied across the closed device, the upper surface of the tab 314 abuts the upper edge 316 of the double undercut groove 304. (shown in dotted outline in Figure 11).

By virtue of the acute angle between the tab 314 and the upper end 312 of the double ended element 302 the removal of the cross bar or double ended element 302 from the groove, is prevented, the upper edge 316 of the groove catching in the nick 318 between the upper end 312 of the double ended formation 302 and the tab 314.

It will be appreciated that, in the clasp shown in Figures 10 and 11, the lower re-entrant portion of the groove acts as a cradle for the toggle.

Claims (10)

1. A releasable encircling device integrally moulded from a resiliently deformable plastics mat erial comprising hook and clip members, the princi ple axes of which are located in the same plane, one of the said members including a double ended ele ment and the other member including a cavity adapted to receive the double ended element, the cavity having undercut portions transverse to the plane of the device, and an integrally moulded formation associated with one of the members which is adapted to abut the other member or a formation associated therewith to restrain transverse disengagement of the elements.

2. A releasable encircling device according to claim 1 in which the cavity is formed in the hook member and comprises a double undercut groove, the principal axis of which extends transversely across the plane of the device, while the double ended element is mounted on a pair of arms integrally moulded to extend from the free end of the clip member, the arms and the double ended element together defining a stirrup adapted to accept at least part of the terminal portion of the hook member, the arms being located on either side of the terminal portion when the double ended element is engaged with the groove, abutting the terminal portion to restrain transverse disengagement of the elements.

3. A releasable encircling device according to claim 2 in which the stirrup is adapted to accept a complementally shaped protrusion provided on the terminal portions of the hook member, the one end of the protrusion constituting an undercut edge of the groove and the arms being located on either side of the protrusion when the double ended element is engaged with the groove, abutting the protrusion to restrain transverse disengagement of the elements.

4. A releasable encircling device according to claim 3 in which the protrusion is provided on an extended portion on the end of the hook member, the inner edge of the protrusion defining the outer undercut edge of the double undercut groove.

5. A releasable encircling device according to claim 1 in which the cavity is formed in the hook member and comprises a double undercut groove, the principle axis of which extends transversely across the plane of the device, and in which a channel is formed in the terminal portion of the hook member, the channel extending from the free end of the hook member to the edge of the groove adjacent the free, while the terminal portion of the clip member is arranged, in a zone directly adjacent and inwardly of the double ended element, to be received in the channel, the double ended element being receivable in the groove in the manner of a toggle located in a cradle.

6. A releasable encircling device according to any one of claims 2,3,4 or 5 in which the double ended element is provided with a tab adapted to extend from the groove when the double ended element is engaged therewith, the tab being adapted to abut the edges of the groove under load.

7. A releasable encircling device according to claim 1 in which the cavity is formed in the hook member and comprises a double undercut groove, the principle axis of which extends transversely across the plane of the device, while the double ended element is "T"-shaped in cross section, the ends of the cross bar of the "T" constituting the ends of the double ended element and the stem of the r being adapted to abut the edges of the groove when the double ended element is engaged therein, an integrally moulded rib being disposed parallel to the plane of the releasable encircling device across the groove and a complementary slot being formed in the double ended element which is adapted to acceptthe rib when the double ended element is engaged with the groove, the rib abutting the sides of the slot to restrain transverse disengagement of the elements.

8. A releasable encircling device according to claim 7 in which the rib and the slot are located offcentre with respect to the centre line of the device.

9. A releasable encircling device according to any one of the preceding claims in which the cavity comprises a double undercut groove, the principle axis of which extends transversely across the plane of the device, while the double ended element is movable, along with the member in which it is formed, in the plane of the device for insertion into the groove, the entrance of which is narrower than the dimension across the ends of the double ended element, which is insertable in the groove by a force sufficient to overcome the resilience of the material.

10. A releasable encircling device substantially as described in the specification with reference to Figures 1 to 11 of the accompanying drawings.