GB2057780A

GB2057780A - Strain relief device for terminating a cable

Info

Publication number: GB2057780A
Application number: GB7929040A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1979-08-21
Filing date: 1979-08-21
Publication date: 1981-04-01

Abstract

Where an electrical or fibre optics cable is terminated at a connector or in an equipment unit, it is desirable for there to be a strain relief arrangement to prevent tugs on the cable from damaging the conductors themselves. In the present arrangement this is effected, when the cable has a layer of lengthwise strands 9 between the outer sheath and the conductors, by trapping, the strands between a male 1 and a female 4 member, each of which has a conical surface. By pulling the strands a self-locking of the two members occurs. The cable has been found to withstand greater tensions before breaking in this particular device. The device could also be used with ropes. <IMAGE>

Description

SPECIFICATION Strain relief device for terminating a cable This 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 whose outer surface is of generally conical form and which has a central bore through which the cable is threaded, the outer sheath being then removed and the strands fanned out across the base of the male member and along the outer conical face of the male member, and a female member whose inner surface is of generally frusto-conical form which matches the outer surface of the inner member, so that its thickest area is adjacent the thinnest area of the male member, wherein in use the strands of a cable after having been fanned out over the outer face of the male member are turned and spread across the end face of the female member at its thicker end, and wherein securing means surrounding the cable urges the female and the male member together when the arrangement is in use.

Attention is directed to Cannon Electric (Great Britain) Limited's application No.

7906840 (M. A. Matthews-M. J. Cook 12-1) in which a similar strain relief arrangement is disclosed. The present invention has an advantage over the afore-mentioned application in that it is a self-locking device which does not involve the screwing of the strands surrounding the conductors, in between the male and the female parts of the device, as disclosed in one aspect of that application.

There is a risk that the strands in that application may break at the point where they are turned across the bore of the male member and where they are passed over the screw threads.

The cable in the strain relief device of the present application, described below has been found to withstand, without breaking about twice the tension a cable in the afore-mentioned application can withstand.

An embodiment of the invention will now be described with reference to the accompanying drawing in which is shown a crosssection through the strain relief device embodying the invention.

The drawing shows a funnel-shaped male member 1 with an axial bore extending the length of the member, which member has a conical portion 2 and a cylindrical portion 3.

The male member 1 is inside a female member 4 which has a conical inner surface whose shape matches that of the outer conical surface of the male member 1. The conical surfaces are plain. The cylindrical portion 3 of the male member 1 has a screw thread along the length of its outer surface. A locking nut 5 and a sealing nut 6 are provided with internal threads for co-operation with the thread on the male member as shown in the diagram.

In use the cable 7 is threaded through the sealing nut 6, the locking nut 5 and the female member 4. The outer sheath of the cable is removed exposing the conductors 8.

The cable has, between its outer sheath and the conductors, a layer of strands 9 which extend generally longitudinally along the cable, in the present case the strands being of the material sold under the Registered Trade Mark Kevlar. The cable is threaded through the male member 1, and is a press fit in the bore of the male member 1. A rubber O-ring (not shown) or a rubber compression seal 10 may be located in a groove in the male member to provide an airtight seal, and a compression grip on the outer sheath of the cable. The strands are teased out and are turned across the bore of the male member 1.

They are then led down the outer conical surface of the male member 1, and threaded through the bore of female member 4. The female member is then pushed into contact with the male member. By pulling the strands tightly a self-locking of the male and female members occurs.

The edge of the end face of the female member at its thicker end adjacent the male member is rounded so that when the strands are pulled across this edge tearing of the strands does not occur.

When the male and female members are tightly together the locking nut 5 is screwed into place. The ends of the strands are then trimmed. The sealing nut 6 is then screwed tight to make the assembly air-tight, and give a good compression grip on the outer sheath of the cable.

A film of, for example, a silicone compound could be applied to the conical surfaces of the male and the female members, so that when the strands are pulled under tension, they embed themselves in the silicone, so increasing the friction between the strands and the conical surfaces of the device.

The assembled device may be part of a connector body or equipment unit part where it is necessary that the strain is taken by this device rather than at another point in the connector body, in particular at the actual coupling of the conductors.

The strain relief arrangement as described above could be used for ropes where strands forming at least the outside of a rope are fanned out and are turned across the bore of the male member. The strands are then trapped between the male member and the female member as described above.

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 whose outer surface is of generally conical form and which has a central bore through which the cable is threaded, the outer sheath being then removed and the strands fanned out across the base of the male member and along the outer conical face of the male member, and a female member whose inner surface is of generally frusto-conical form which matches the outer surface of the inner member, so that its thickest area is adjacent the thinnest area of the male member, wherein in use the strands of a cable after having been fanned out over the outer face of the male member are turned and spread across the end face of the female member at its thicker end, and wherein securing means surrounding the cable urges the female and the male member together when the arrangement is in use.

2. A strain relief arrangement as claimed in claim 1 wherein the edge of the end face of the female member at its thicker end adjacent to the male member is rounded.

3. A strain relief arrangement as claimed in claim 1 or 2 wherein the securing means includes a locking nut and a sealing nut with a rubber compression seal.

4. A strain relief arrangement for anchoring a cable, substantially as described herein with reference to the accompanying drawing.

5. A strain relief arrangement substantially as hereinbefore described with reference to the accompanying drawing.

5. A strain relief arrangement for anchoring a rope, which strain relief arrangement includes a male member whose outer surface is of generally conical form and which has a central bore through which the rope is threaded, strands forming at least the outside of the rope being fanned out across the base of the male member and along the outer conical face of the male member, and a female member whose inner surface is of generally frusto-conical form which matches the outer surface of the inner member, so that its thickest area is adjacent the thinnest area of the male member, wherein in use the strands after being fanned out over the outer face of the male member are turned and spread across the end face of the female member at its thicker end, and wherein securing means surrounding the rope urges the female and the male member together when the arrangement is in use.

CLAIMS (7 Feb 1980)

1. A strain relief arrangement for anchoring a cable of the type in which the conductor or conductors, whether electrical or fibre optic conductors, 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 having at one end a smoothly rounded surface joining an axial bore through the member with the large end of an externally conically tapered portion of the member beyond the small end of which is located an attachment portion of the member, wherein the cable threads the bore of the male member and, a portion of the cable outer sheath having been removed from the cable in the region beyond the large end of the tapered portion of the male member, the cable strands thereby exposed are splayed over the rounded surface and the conical portion and are trapped between the conical portion and the complementary tapered bore of a co-operating female member advanced over the attachment portion of the male member and held in position on the male member by securing means engaging the attachment portion of the male member.

2. A strain relief arrangement for anchoring a rope, which arrangement includes a male member having at one end a smoothly rounded surface joining an axial bore through the member with the large end of an externally conically tapered portion of the member beyond the small end of which is located an attachment portion of the member, wherein the rope threads the bore of the male member and strands from at least the outside portions of the rope are splayed over the rounded surface the conical portion and are trapped between the conical portion and the complementary tapered bore of a co-operating female member advanced over the attachment portion of the male member and held in position on the male member by securing means engaging the attachment portion of the male member.

3. An arrangement as claimed in claim 1 or 2 wherein the attachment portion is provided by a screwthreaded shank.

4. An arrangement as claimed in claim 3 when appended to claim 1 wherein the securing means is provided by a first nut engaging the screw-threaded shank and a second nut also engaging the screw-threaded shank longitudinally compresses a tubular seal housed in the male member so as to effect a seal between its bore the cable sheath.