GB2193389A

GB2193389A - Cable clamp

Info

Publication number: GB2193389A
Application number: GB08618069A
Authority: GB
Inventors: Peter Lyndon Vickery Vetquoy
Original assignee: MERITLINK Ltd
Current assignee: MERITLINK Ltd
Priority date: 1985-07-24
Filing date: 1985-07-24
Publication date: 1988-02-03
Also published as: GB8618069D0

Abstract

A three-pin plug includes a cable clamp in which the cable is clamped by two clamping members (10) each having lateral serrations 11 interrupted by a sharply defined longitudinal line of discontinuity 14 in the form of a rectangular cross- section channel whose sharp edges engage the insulating sheath of the flex to prevent the flex from being rotated in the clamp during the application of torsion to the flex. The serrations themselves engage the sheath to resist tension on the flex. <IMAGE>

Description

SPECIFICATION Flex clamp This application relates to a flex clamp for electrical appliances.

It is often desirable to provide means for clamping flex to electrical equipment, for example when attaching a plug to the power flex to an electical appliance, in such a way that not only are the individual conductor strands (live and neutral, and optionally earth) anchored to the respective terminals, but also the outer insulating sheath is clamped so that the flex will be able to withstand an axial pull without imposing strain on the electrical connections to the conductor strands.

In accordance with the present invention we provide a flex clamp comprising means for supporting a flex, a serrated member for engaging the flex to clamp it in position in engagement with said supporting means to resist withdrawal of the flex in the event of tension on the flex, wherein the serrations have tip loci extending generally perpendicular to the direction of flex tension and the clamping member includes a sharply defined line of discontinuity along a direction parallel to the line of flex tension, whereby the edges of the serrations bordering the line of discontinuity resist rotation of the flex in the even of torsion being applied to the flex, in use.

Preferably the flex supporting means may be a second such clamping member co-operating with the first-mentioned one so that their serrations are adjacent one another at a location of maximum flex clamping. In that case, it is possible for both of the clamping members to be provided with the above-mentioned line of discontinuity of the serrations.

By providing a sharply defined discontinuity, for example in the form of a channel extending parallel to the line of flex tension, it is possible to guard against any torsion in the flex resulting in strain on the electrical connections, thereby providing protection against both tension and torsion in the flex.

The present invention also provides an electrical connector plug having terminals for conductor strands of a flex, and a flex clamp as defined above arranged to engage the insulating sheath of the flex.

In order that the present invention may be more readily understood the following description is given, merely by way of example, with reference to the accompanying drawing in which: Figure 1 is a plan view of a 13 amp plug in accordance with British Standard BS 1363A, adapted to incorporate the flex clamp of the present invention; Figure 2 is an enlarged view of one of the two serrated clamping members to be incorporated in the plug body shown in Fig. 1; and Figure 3 is a side elevational view of the clamping member of Fig. 2, seen along the arrow Ill thereof.

Fig. 1 shows the conventional layout of 13 amp plug as comprising a moulded plastic plug body 1 having a flange 2 which, together with a similar flange on the cover (not shown) of the plug defines a recess down each side of the plug to enable a user to grip the plug without risk of contacting the live and neutral terminals of the plug. For this purpose the flange 2 helps to shield to user's hand as the plug is offered up to a socket.

The plug body further comprises recesses 3, 4 and 5 of rectangular shape to receive the conventional metallic earth, neutral and live pins of the plug. A flex inlet opening 6 at the end of the plug opposite the recess 3 for the earth pin allows the flex to be inserted along the direction of arrow 7 in Fig. 1 between two cruciform posts 8 and 9 intended to support serrated clamping members to co-operate to grip the flex (not shown) between them.

Fig. 2 shows a view of the flex clamping member 10 intended to fit on the post 8 of Fig. 1. As shown, the clamping member 10 has a plurality of serrations 11 each having a tip locus 12 (Fig. 3) which extends in a direction perpendicular to the plane of the paper in Figs. 1 and 2 and is therefore generally perpendicular to the direction of tension on the flex, in use of the plug. This direction of tension will of course be exactly in the opposite direction to the arrow 7 shown in Fig. 1.

The clamping member 10 includes a spring leaf 13 having a tip 13a to engage in a recess 13b defined on the plug body of Fig. 1.

As shown in Fig. 3, the clamping member 10 has a channel 14 extending perpendicular to the directions of the serration tip loci 12 i.e. parallel to the direction of flex tension when the plug is in the assembled condition and this represents a sharply defined line of discontinuity in the serrations in that the edge 15 of each serration bordering on the channel 14 is a right angle.

When a length of flex is in position in the flex inlet opening 6 of the plug body 1, the clamping member 10 has the sharp side edges 15 of its serration tips pressed against the insulating sheath of the flex to prevent the flex from rotating in the event of torsion being applied to the flex. To effect this engagement the flex is supported by the opposite clamping member and the opposite side wall of the flex inlet opening 6. Any such torsion will thus be unable to disturb the electrical connections between the live and neutral connector strands of the flex, and optionally the earth strand in the case of a three core flex.

It is possible for the channel 14 to be incorporated in an alternative embodiment of plug where only one such clamping member 10 is provided (the flex being supported by a suitable counter surface on the opposite side of the inlet opening 6), and even where two such members are provided it is not essential for the channels 14 to be formed in both of them.However, in the preferred arrangement where there are two serrated members each having a channel 14, the operation of opening the flex clamp to allow insertion of the flex (after removal of the plug cap which is not shown in the drawings) is facilitated in that a screwdriver can be placed between the two channels with the opposite ends of the screwdriver blade tip in respective ones of the two channels 14 and the screwdriver can then be urged along the direction of arrow 7 in order to open the flex clamp and to allow the flex to be placed on top simply by lateral movement of the flex in a direction perpendicular to the plane of the paper in Fig. 1. Subsequent withdrawal of the screwdriver blade tip will then allow the two flex clamp members to spring together to grip the flex.

The arrangement of the flex clamp members is such that the serration tips near the end 10a of the clamping member 10 are closer together than those near the end 10b, and any tension on the flex will, in a known manner, pull the serrations 11 even more securely into contact with the flex sheath.

In order to limit rotation of the flex clamping member 10 in the event of such tension, the cruciform support post 8 has one (8a) of its four limbs extending further in a radial direction than the others, to engage in a recess 16 at one end of the bore 17 of the clamping member 10 which receives the post (in this case the end furthest from the observer in Fig. 2) to define a rotation stop.

Claims

1. A flex clamp comprising means for supporting a flex, a serrated member for engaging the flex to clamp it in position in engagement with said supporting means to resist withdrawal of the flex in the event of tension on the flex, wherein the serrations have tip loci extending generally perpendicular to the direction of flex tension and the clamping member includes a sharply defined line of discontinuity along a direction parallel to the line of flex tension, whereby the edges of the serrations bordering the line of discontinuity resist rotation of the flex in the even of torsion being applied to the flex, in use.

2. A flex clamp according to claim 1, wherein said flex supporting means includes a second serrated member such that the flex seats between the first-mentioned and the second serrated member.

3. A flex clamp according to claim 2, and including means resiliently biasing the serrated members into engagement with the flex even in the absence of flex tension.

4. A flex clamp according to claim 2 or claim 3, wherein both of said serrated clamping members are provided with a said sharply defined line of discontinuity.

5. A flex clamp according to any one of the preceding claims, wherein the or each said sharply defined line of discontinuity comprises a rectangular cross-section channel extending parallel to the line of flex tension.

6. A plug according to any one of the preceding claims, wherein the or each said serrated clamping member is mounted on a pivot which limits the degree of rotation in the direction towards a flex being clamped thereby.

7. A flex clamp substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

8. An electrical connector plug including terminals for conductor strands of a flex, and a flex clamp according to any one of the preceding claims arranged to engage the flex sheath.