GB2232712A - Clip - Google Patents

Abstract

A clip for securing strip form lightning conductors comprises a base (10) for fixing to a wall or the like adapted to receive a cover (14) comprising a body portion (16) and spaced resilient legs (19) having latches (21). Spaced apertures (23) in the base (10) receive the legs (19) such that when the clip is assembled with the legs (19) in the apertures (23) and the latches (21) are resiliently urged into retaining engagement with shoulders (25) of the base (10). A channel (28) between the apertures (22) is provided in which a lightning conductor tape (26) can be secured. The legs (19) are substantially enclosed by the base (10) to prevent access. The clip is readily assembled, firmly secures the tape (26) against lightning strike forces, and is resistant to tampering when assembled. <IMAGE>

Description

CLIP This invention relates to clips and especially to clips suitable for use in securing electrical conductors of strip form to mounting surfaces, for example the walls of buildings or the outer surfaces of chimneys.

In lightning protection systems flat metal strips, commonly known as tape, of a suitable metal e.g. copper or aluminium are used to provide conductors from an air terminal e.g. a spike at the top of a building or chimney to earth, for example an earth rod or plate in the ground.

The tape is secured to a wall or the outer surface of the chimney by a number of suitably spaced clips.

Suitable two-part clips are described in our Patents Nos. 1208437 and 2127889. These clips rely largely on an interference fit between two parts and have been found to perform very satisfactorily. However, they have been somewhat awkward to install because of the forces necessary to insert the spaced studs provided on one part of these known clips into the spaced complementary apertures in the other part of the known clips. It has usually been necessary to apply sufficient force to insert the studs into the complementary apertures by hitting the outer part of the clip, after leading end portions of the studs have been introduced into the two apertures, with a hammer.Not only is this difficult to achieve in the circumstances under which most clips of this type are used, for example the installer may be suspended a considerable distance above the ground in a freely swinging cradle, but also the use of a hammer has raised the possibility that damage may be caused to either the tape or to the mounting surface when installing the clips.

Furthermore, there is of course the possibility that the hammer will be lost from the cradle or that the parts of the clip may be dropped.

It is essential in clips for this purpose that the engaging force between the two parts of the clip be sufficiently high to prevent the conductive tape being torn from the clip by separation of the two parts of the clip, when lightning strikes. The forces which may be generated when a lightning strike is discharged by way of the conductive strip may be considerable. It has therefore been necessary in the known clips, for example, of the type shown in our Patent Nos. 1208437 and 2127889 to ensure that the two parts are sufficiently firmly secured together and it is this requirement for a considerable resistance to separation that has led to the need to secure the two parts together by using a hammer.Even when using a hammer, there remains a possibility that the blow struck by the hammer will be inadequate, so that the parts of the clip will not remain engaged when subjected to a lightning strike.

One of the various objects of the present invention is to provide an improved clip suitable for use in holding an electrical conductor of strip form.

In one aspect the invention provides a clip comprising a base adapted to be fixed to a mounting surface and a cover comprising a body portion and two spaced resilient projections each having latch portions remote from the body portion, the latch portions facing inwardly towards one another, the base comprising two spaced apertures adapted to receive the resilient projections and having shoulders, the construction and arrangement being such that when the clip is assembled the resilient projections are received in the apertures with the latch portions resiliently urged into retaining engagement with the shoulders, the clip providing a channel between the apertures adapted to retain an electrical conductor of strip form.

Preferably both the base and the cover are moulded of a suitable plastics material with adequate strength and resilience.

Preferably in a clip in accordance with the invention the resilient projections are provided by legs, preferably positioned at opposite end portions of the body portion of the cover. Preferably the latch portions have leading end portions with cam faces inwardly inclined from the remote tip of the leading end portion towards the body portion adapted, when the cover is assembled with the base to engage walls of the base (suitably angled) defining the apertures whereby to urge the legs outwardly away from one another, the base allowing the legs to spring together when the legs have been sufficiently inserted thus urging the latch portions into retaining engagement with the shoulders.

The configuration of such a preferred clip in accordance with the invention is such that the force generated by a lightning strike tends to urge leading end portions of the projections inwardly and thus the latch portions more firmly into engagement with the shoulders.

The preferred clip is thus substantially as secure against lightning strikes as many known clips. Furthermore, the cover can be assembled with the base, in firm, locking engagement, merely by finger pressure thus avoiding the problems arising when using a hammer to assemble the previously known clips.

The base may comprise a central opening in the recess adapted to receive a fastener e.g. a screw by which the base may be attached to the mounting surface. The base may, however, be secured to a mounting surface by any suitable means, for example an appropriate adhesive.

There now follows a detailed description to be read with reference to the accompanying drawings of clips embodying the invention. It will be realised that these clips have been selected for description to illustrate the invention by way of example.

In the accompanying drawings: Figure 1 is a view in side elevation showing a clip embodying the invention; Figure 2 is a plan view with part of a cover broken away showing the clip in assembled condition; and Figure 3 is a side view, partly in section, showing the illustrative clip in assembled condition.

The illustrative clip comprises a base 10 and a cover 14 having a body portion 16 provided with spaced resilient legs 19 at opposite end portions of the cover. The legs 19 are substantially parallel, but in their rest condition diverge very slightly from the body portions 16 to their leading end portion. The legs 19 of the illustrative clip, however, are provided with inwardly facing latch portions 21 remote from the body portion 16.

The base 10 of the illustrative clip comprises two spaced apertures 23 at opposite end portions of the base 10 and shoulders 25 in the apertures. Each shoulder 25 has an under surface portion 27 which is inclined slightly upwardly from the outer edge of the shoulder 25 towards the centre of the base (considering as a lower surface that surface 17 of the base 10 which is adapted to engage a mounting surface S for the clip); the angle may conveniently be about 3O to the plane of the lower surface.

The construction and arrangement of the illustrative clip is such that the legs 19 are snugly received between parallel walls 29 defining the apertures 23 when the cover 14 is assembled with the base, the latch portions 21 being in retaining engagement with the shoulders 25 with a lower surface 15 of the cover 14 in engagement with an upper surface 11 offthe base parallel with the lower surface 17.

In this position ends of the legs 19 remote from the cover 14 are spaced only a small distance from the mounting Surface S (about 2mm or, preferably, less). The assembled illustrative clip provides a channel 26 (Figure 3) positioned between the apertures 23 defined by walls 28 of the base in which an electrical conductor of strip form can be retained by the cover.

Both the base 10 and cover 14 of the illustrative clip are moulded of a suitable plastics material having adequate strength and resilience, for example polypropylene.

The latch portions 21 have leading end portions provided with inner cam faces 33 which are inwardly inclined from the tip towards the body portion 16; suitably the cam faces are disposed at an angle of between 400 and 650 to the lengthwise direction of the legs, more preferably about 600. The faces 33 are arranged, as the cover 14 is assembled with the base 10, to engage cam surfaces 35 defining, in part, the apertures 23 thus to urge the legs 19 outwardly to permit the projections 21 to slide over the surfaces 35 and snap into engagement with the shoulders 25 on completion of assembly, the projections being accomodated in recesses 37 in the base 10. The cam surfaces 35 are outwardly inclined from the upper surface 11 of the base 10 towards the lower surface at an angle of between 1050 and 1250 to the upper surface 11, preferably about 1200.The flexibility of the legs and the caming action provided by the faces 33 and surfaces 35 is such that the cover 14 can be pressed into locking engagement with the base 10 merely by finger pressure.

The illustrative clip also has a countersunk central opening 40 for receiving a fastener, e.g. a screw, by which the base may be secured in engagement with the mounting surface S which may be, for example, a wall or an outer surface of a chimney.

The base 10 and cover 14 may, if desired, be connected by a flexible strip which is moulded integrally with the base 10 and cover 14 as they are moulded. The flexible strip acts as a hinge allowing the cover to be hinged into its operative position in relation to the base 10 but holds the cover 14 in an out of the way position whilst the base 10 is being secured to a mounting surface.

The strip ensures that there is no possibility of the cover 14 becoming lost whilst a user is attempting to insert the legs 9 into the apertures 23. If desired, however, the flexible strip may be removed either before the clip has been assembled or afterwards.

The rigidity of the body portion 16 and of the base 10 militates against distortion under the forces arising in a lightning strike and helps to retain the clip closed, holding the conductor tape in place.

Furthermore, engagement of the latch portions 21 with the shoulders 25 retains the cover 14 in engagement with the base 10 with sufficient force to withstand the striking pulses arising when the conductor 26 discharges a lightning strike.

As the force, of a lightning strike places a heavy load, applied by the conductor, to a central region of the cover 14 this central region tends to be bowed outwardly.

Whilst the rigidity of the plastics resists this bowing to some extent, the bowing actually tends to urge the leading end portions of the legs 19 inwardly and thus the latch portions 21 more firmly into engagement with the shoulders 25. The slight angle of the surfaces 27 allows latching surfaces 31 of the latch portions 21 also to move about the outer edges of the shoulders 25 towards the surfaces 27, reduce the possibility of the latch portions 21 being forced out of engagement with the shoulders 25.

When the illustrative clip is assembled, with the legs 19 in the apertures 23, as described above, portions of the base 10 adjacent the apertures 23 prevent access between the latch portions 21 and shoulders 25, thereby militating against removal of the cover 14. Should an attempt be made to prise the body portion 16 of the cover 14 from the base 10 any flexing of the body portion 16 will tend to urge the latch portions 21 more firmly into engagement with the shoulders thus to retain the cover 14 in place (as with a lightning strike).

The design of the illustrative clip is thus such that separation of the cover 14 from the base 10, once the clip is installed in an operative position, is extremely difficult without destruction of part, at least, of the illustrative clip.

The illustrative clip is more secure and tamper resistant than some clips in common use and is simple to manufacture and thus relatively inexpensive.

Whereas the illustrative clips comprise an opening 40 in the base 10 for a fastener by which the base 10 may be attached to a mounting surface, it will be realised that the base may be secured to the mounting surface S by other means, for example adhesive. In some instances it may be desired to spread the load of attachment over a wider mounting surface area: this may be achieved by providing a mounting flange projecting outwardly from the base conveniently coplanar with the lower surface of the remainder of the base. Such a mounting flange may be moulded integrally with the remainder of the base or provided as a separate sheet to which a base generally similar to the bases 10 shown in the drawings may be attached by suitable means, e.g. adhesive.

Claims (9)

1. A clip comprising a base adapted to be fixed to a mounting surface and a cover comprising a body portion and two spaced resilient projections each having latch portions remote from the body portion, the latch portions facing inwardly towards one another, the base comprising two spaced apertures adapted to receive the resilient projections and having shoulders, the construction and arrangement being such that when the clip is assembled the resilient projections are received in the apertures with the latch portions resiliently urged into retaining engagement with the shoulders, the clip providing a channel between the apertures adapted to retain an electrical conductor of strip form.

2. A clip according to Claim 1 wherein the resilient projections are provided by legs at opposite end portions of the body portion.

3. A clip according to either one of Claims 1 and 2 wherein the latch portions have leading end portions with cam faces inwardly inclined from the tip of the leading end portions towards the body portion and adapted, when the cover is assembled with the base, to engage walls of the base defining the apertures whereby to urge the projections outwardly away from one another, the base allowing the projections to spring together when the projections have been sufficiently inserted, thus urging the latch portions into retaining engagement with the shoulders.

4. A clip according to any one of the preceding claims whereing the latch portions are enclosed by portions of the base adjacent the apertures so as to prevent access between the latch portions and shoulders.

5. A clip according to any one of the preceding claims wherein the base and cover are connected by a flexible hinge portion to retain the cover and base together whilst in an unassembled condition but of sufficient length to permit the cover and base to be readily assembled.

6. A clip according to any one of the preceding claims wherein the base and the cover are integrally moulded of plastics material.

7. A clip according to any one of the preceding claims wherein the base comprises a central opening adapted to receive a fastener by which the base may be attached to the mounting surface.

8. A clip according to any one of Claims 1 to 6 wherein the base comprises an outwardly directed flange portion adapted to be secured to a mounting surface whereby to attach the base to the mounting surface.

9. A clip suitable for use in securing electrical conductors of strip form constructed arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.