GB2042817A

GB2042817A - Strain relief device for terminating a cable

Info

Publication number: GB2042817A
Application number: GB7906840A
Authority: GB
Original assignee: Cannon Electric Great Britain Ltd
Current assignee: Cannon Electric Great Britain Ltd
Priority date: 1979-02-27
Filing date: 1979-02-27
Publication date: 1980-09-24

Abstract

Strain relief for an electrical or fibre optics cable having a layer of lengthwise strands between the outer sheath and the conductors, is effected by trapping the strands between a male and a female member, each of which has a conical surface. In one form the male member (1) and the female member (2) have coarse, rounded screw threads, so that the strands (3) are trapped by screwing. In another form the male member (5) and female member (6) have plain conical surfaces, and are held together by screwing into an outer member (7). <IMAGE>

Description

SPECIFICATION Strain relief device for terminating a cable The present invention relates to a strain relief device for an electrical or fibre optics cable.

Such devices are useful where a cable is terminated in a connector or in an equipment unit to protect the actual connection made from the conductors, whether electrical or optical, to the connector or equipment unit. An object of the invention is to provide a simple device to achieve the above purpose.

According to the invention, there is provided a strain relief arrangement for anchoring a cable of the type in which the conductor or conductors, whether electrical or fibre optic conductors, is or are separated from the outer sheath of the cable by a layer of strands extending along the cable, which strain relief arrangement includes a male member of substantially conical form through which the conductors(s) is (are) threaded after removal of the outer sheath, the strands being fanned out over the conical surface of the male member, and a female member having an inner surface of a conical form suitable to receive the outer conical surface of the male member, the cable being threaded through the female member, and in which after the strands have been fanned out over the male member the latter is received in the female member with the strands trapped between the conical surfaces of the two members and with the end of the outer sheath of the cable within at least the female member.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a cross-section of a first strain relief device embodying the invention.

Fig. 2 is an exploded view of the device of Fig. 1 with a fibre optics cable in place.

Fig. 3 is a cross-section of a second strain relief device embodying the invention.

Fig. 4 is an end-on view of the device of Fig. 3, looking in the direction of the arrow A.

Fig. 5 is an exploded view of part of a connector with which a strain relief device embodying the invention is used.

In the first embodiment, see Figs. 1 and 2, the strain relief device consists of two parts, of which part 1 is a bush with a conical portion while part 2 is a hollow nut with an internal conical portion of similar shape to that of the bush 1. The bush 1 has on its outer conical surface a tapered thread of rounded form, i.e. rather like a bottle thread, and the part 2 has an internal thread for co-operation with the thread on the bush 1. As can be seen from Fig. 1, when the bush 1 is screwed into the nut 2, there is a small gap between the engaging screw threads.

In use, the cable is threaded through the nut 2, and the outer sheath removed, leaving the conductors, of which there are two in the present case, exposed. The cable has, between its outer sheath and the conductors, a layer of strands which extend generally longitudinal of the cable, in the present case the strands being of the material sold under the Registered Trade Mark Kevlar. The strands are teased out, as shown at 3 and laid over the threaded portion of the bush 1. The nut is then engaged so that the strands are trapped between the nut and the bush. Thus the cable is anchored in the bush and nut assembly. The rounded thread used does not cut into or weaken the material of the strands 3.

If the male thread is initially wrapped with a self-amalgamating tape, additional grip is provided, as well as enhanced protection for the strands. The cable with strain relief device in place is then fitted within a connector (or an entry to an equipment box designed to receive it).

The basic idea used in the device of Figs. 1 and 2 can also be employed where the male threaded portion is integral with a connector body, or is integral with an equipment container. In this case the use of the self-amalgamating tape contributes to the environmental sealing of the connector or equipment unit.

In the second embodiment, shown in Figs. 3 and 4, we use a sub-assembly trapped within a connector body or equipment unit part. In this case the sub-assembly consists of a perforated conical member 5 with another member 6 having a conical inner surface whose shape matches that of the outer surface of the member 5. Here the conical surfaces are plain, i.e. not screw-threaded.

The outer member 6 has a male screw thread so that it can be screwed into a bush 7 which traps the smaller member within it. The cable arrangement is somewhat different from that of Figs. 1 and 2 as the strands are turned across the bore of the member 5 and then down the slope of the cone, as shown at 8. The member 6 also has driving slots 9 on the outer end to facilitate the screwing.

Fig. 5 shows part of a connector with which the strain relief devices may be used. This has an outer casing in two portions 10, 1 which have internal recesses 12, 13, to receive ferrules on the ends of the cable cones 14. Note that the cable is a fibre optics cable. At the other end the portions 10, 11 have recesses 1 5, 16, into which the strain relief device 1 7 fits. The connector is assembled with the cable's ferrule in the recesses 12, 1 3 and the strain relief device in the recesses 1 5, 1 6 and the outer portions 10, 11 are then fastened together in any suitable manner.

1. A strain relief arrangement for anchoring a cable of the type in which the conductor or conductors, whether electrical or fibre optic conductors, is or are separated from the outer sheath of the cable by a layer of strands extending along the cable, which strain relief arrangement includes a male member of substantially conical form through which the conductor(s) is (are) threaded after removal of the outer sheath, the strands being fanned out over the conical surface of the male member, and a female member having an inner surface of a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Strain relief device for terminating a cable The present invention relates to a strain relief device for an electrical or fibre optics cable. Such devices are useful where a cable is terminated in a connector or in an equipment unit to protect the actual connection made from the conductors, whether electrical or optical, to the connector or equipment unit. An object of the invention is to provide a simple device to achieve the above purpose. According to the invention, there is provided a strain relief arrangement for anchoring a cable of the type in which the conductor or conductors, whether electrical or fibre optic conductors, is or are separated from the outer sheath of the cable by a layer of strands extending along the cable, which strain relief arrangement includes a male member of substantially conical form through which the conductors(s) is (are) threaded after removal of the outer sheath, the strands being fanned out over the conical surface of the male member, and a female member having an inner surface of a conical form suitable to receive the outer conical surface of the male member, the cable being threaded through the female member, and in which after the strands have been fanned out over the male member the latter is received in the female member with the strands trapped between the conical surfaces of the two members and with the end of the outer sheath of the cable within at least the female member. Embodiments of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a cross-section of a first strain relief device embodying the invention. Fig. 2 is an exploded view of the device of Fig. 1 with a fibre optics cable in place. Fig. 3 is a cross-section of a second strain relief device embodying the invention. Fig. 4 is an end-on view of the device of Fig. 3, looking in the direction of the arrow A. Fig. 5 is an exploded view of part of a connector with which a strain relief device embodying the invention is used. In the first embodiment, see Figs. 1 and 2, the strain relief device consists of two parts, of which part 1 is a bush with a conical portion while part 2 is a hollow nut with an internal conical portion of similar shape to that of the bush 1. The bush 1 has on its outer conical surface a tapered thread of rounded form, i.e. rather like a bottle thread, and the part 2 has an internal thread for co-operation with the thread on the bush 1. As can be seen from Fig. 1, when the bush 1 is screwed into the nut 2, there is a small gap between the engaging screw threads. In use, the cable is threaded through the nut 2, and the outer sheath removed, leaving the conductors, of which there are two in the present case, exposed. The cable has, between its outer sheath and the conductors, a layer of strands which extend generally longitudinal of the cable, in the present case the strands being of the material sold under the Registered Trade Mark Kevlar. The strands are teased out, as shown at 3 and laid over the threaded portion of the bush 1. The nut is then engaged so that the strands are trapped between the nut and the bush. Thus the cable is anchored in the bush and nut assembly. The rounded thread used does not cut into or weaken the material of the strands 3. If the male thread is initially wrapped with a self-amalgamating tape, additional grip is provided, as well as enhanced protection for the strands. The cable with strain relief device in place is then fitted within a connector (or an entry to an equipment box designed to receive it). The basic idea used in the device of Figs. 1 and 2 can also be employed where the male threaded portion is integral with a connector body, or is integral with an equipment container. In this case the use of the self-amalgamating tape contributes to the environmental sealing of the connector or equipment unit. In the second embodiment, shown in Figs. 3 and 4, we use a sub-assembly trapped within a connector body or equipment unit part. In this case the sub-assembly consists of a perforated conical member 5 with another member 6 having a conical inner surface whose shape matches that of the outer surface of the member 5. Here the conical surfaces are plain, i.e. not screw-threaded. The outer member 6 has a male screw thread so that it can be screwed into a bush 7 which traps the smaller member within it. The cable arrangement is somewhat different from that of Figs. 1 and 2 as the strands are turned across the bore of the member 5 and then down the slope of the cone, as shown at 8. The member 6 also has driving slots 9 on the outer end to facilitate the screwing. Fig. 5 shows part of a connector with which the strain relief devices may be used. This has an outer casing in two portions 10, 1 which have internal recesses 12, 13, to receive ferrules on the ends of the cable cones 14. Note that the cable is a fibre optics cable. At the other end the portions 10, 11 have recesses 1 5, 16, into which the strain relief device 1 7 fits. The connector is assembled with the cable's ferrule in the recesses 12, 1 3 and the strain relief device in the recesses 1 5, 1 6 and the outer portions 10, 11 are then fastened together in any suitable manner. CLAIMS

1. A strain relief arrangement for anchoring a cable of the type in which the conductor or conductors, whether electrical or fibre optic conductors, is or are separated from the outer sheath of the cable by a layer of strands extending along the cable, which strain relief arrangement includes a male member of substantially conical form through which the conductor(s) is (are) threaded after removal of the outer sheath, the strands being fanned out over the conical surface of the male member, and a female member having an inner surface of a conical form suitable to receive the outer conical surface of the male member, the cable being threaded through the female member, and in which after the strands have been fanned out over the male member the latter is received in the female member with the strands trapped between the conical surfaces of the two members and with the end of the outer sheath of the cable within at least the female member.

2. An arrangement as claimed in claim 1, in which the threaded male member has on its conical surface a coarse screw thread which is of rounded form, the female member having a corresponding screw thread, and in which the reception of the male member within the female member is effected by screwing.

3. An arrangement as claimed in claim 2, and in which the threads on the male member are wrapped with a self-amalgamating tape prior to the spreading of the strands over those threads.

4. An arrangement as claimed in claim 1, in which the male and the female members each have plain conical surfaces, in which each of the strands is, after the cable has been threaded through the male and the female members, bent back across the base of the male member and then over its conical surface, in which the female member has a screw thread on its outer surface which co-operates with a zero thread on the inner surface of a third member, and in which to secure the arrangement the female member is screwed into the third member with the male member in place, thus trapping the strands between the conical surfaces.

5. A strain relief arrangement for anchoring a cable, substantially as described with reference to Figs. 1,2 and 5, or Figs. 3, 4 and 5 of the accompanying drawings.