GB2268843A

GB2268843A - A connecting clamp

Info

Publication number: GB2268843A
Application number: GB9314534A
Authority: GB
Inventors: Jean-Pierre Genelot
Original assignee: GEC Alsthom Equipements Basse Tension SA
Current assignee: GEC Alsthom Equipements Basse Tension SA
Priority date: 1992-07-16
Filing date: 1993-07-13
Publication date: 1994-01-19
Anticipated expiration: 2013-07-13
Also published as: GB2268843B; GB9314534D0; FR2693843A1; ES2078156A2; DE4323426C2; DE4323426A1; ES2078156B1; FR2693843B1; ES2078156R

Abstract

A connecting clamp for connecting an electricity distribution busbar to a plug of an electrical apparatus, characterized in that it comprises two identical elements (6), each element (6) being made from a metal plate of generally elongate shape, the end portions each having a rounded and silver-plated edge and being coplanar, said end portions being interconnected by a plane intermediate portion that is extended laterally on one side only by a projection having an opening and two facing lugs, said connecting clamp being made by juxtaposing two elements of the above-specified type that are held together by means of a spring (20). <IMAGE>

Description

1 2268843 A CONNECTING CLAMP The present invention relates to a connecting

clamp intended, for example, for electrically connecting an electrical busbar to a plug of a connectable apparatus 5 such as an electrical circuit breaker.

Several types of connecting clamp are already known.

Figure 1 shows a first type.of clamp comprising a metal part having two branches 1 and 2 which are urged towards each other by a metal spring 3. Reference 4 designates a plugged-in busbar and reference 5 designates the plug of the apparatus to be connected. Such a clamp suffers from several drawbacks:

the clamp must necessarily be plugged onto a busbar in a set of busbars, thereby reducing the range of possible uses; since the deflection of the branches 1 and 2 is negligible, a plugging operation may cause the elastic limit of these parts to be exceeded; thus giving rise to a major loss of contact pressure; the force required for plugging is high; the spring is a part whose cost price is high; short circuit behavlor is not good; and itIs necessary to cover all of the parts with a layer of silver.

The present invention aims to overcome at least some of the known drawbacks and to provide a generally improved connecting clamp.

According to an embodiment of the present invention there is provided a connecting clamp for electrically connecting a busbar to an apparatus plug, which clamp includes two cooperating elongate elements, respective end portions of each element providing electrically conductive clamping surfaces, the clamping surfaces of each element being electrically connected to each other and the elongate elements being linked to one another such that respective clamping surfaces of one of the elongate elements face respective clamping 2 surfaces of the other elongate element, the clamp further including resilient means mounted between respective portions of the elongate elements intermediate the end portions thereof for resiliently biasing adjacent clamping surfaces together.

A connecting clamp, for connecting an electricity distribution busbar to a plug of an electrical apparatus, which embodies the present invention is characterised in that it comprises two identical elements, each element being made from a metal plate and being generally elongate in shape, having a first plane end portion connected to a second plane end portion that is coplanar with the first by a plane intermediate portion situated in a plane parallel to the plane of the end portions but offset therefrom by an amount equal to about one-half the thickness of the plate, the intermediate portion extending laterally on one side only in the form of a projection having an opening and two facing lugs, one side of the first end on the same side as the projection being rounded and silver-plated on its edge, one side of the second end on the same side as the projection being rounded and silver-plated on its edge, said connecting clamp being made by juxtaposing two elements of the above type, one of the elements being turned over relative to the other, the elements being placed so that their respective projections and lugs coincide, a spring being engaged in the opening and bearing against the two opposite ends thereof, the ends of the spring surrounding the lugs. 30 Advantageously, the projection of each element is closer to its end for co-operating with the busbar than to its end for co-operation with the connection to the apparatus. According to another characteristic of the invention, within eachielement, the radius of the rounded end for co- operating with the busbar Is greater than the 3 radius of the rounded end for co-operat ng with the apparatus.

Reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a plan view of a prior art connecting clamp; Figure 2 is a front view of one of the component elements of the connecting contact of the invention; Figure 3 is a side view of the same element; Figure 4 is a plan view of a connecting clamp of the invention constituted by means of two elements as shown in Figures 2 and 3; and Figure 5 shows how connecting clamps of the invention may be used.

Figure 1 has already been described above.

Figures 2 and 3 show one of two Identical elements included in a connecting clamp of the invention.

This element, given overall reference 6, Is made from a plane metal plate of brass or copper, and is elongate in shape. It has two coplanar end portions 11 and 12 interconnected by a plane Intermediate portion 13 by means of two folds 14 and 15 and occupying a plane that is parallel to but different from the plane of the portions 11 and 12. The distance between the plane of the end portions 11 and 12 and the plane of the intermediate portion 13 Is equal to about half the thickness of the plate.

The intermediate portion 13 is extended on one side by a rectangularshaped projection 15 internally defining a substantially rectangular opening 16 with two lugs 17 and 18 that face each other and that are in alignment on the perpendicular to the long direction of the part.

It may be observed that the rectangular projection 15 is not disposed level with the middle of the part, but 4 is closer to the end 11 than to the end 12; the reason for this is explained below.

One side 11A of the end 11, on the same side as the projection 15, is rounded and receives a coating of silver. One side 12A of the end 12, on the same side as the projection 15, is rounded and receives a coating of silver.

To make a connecting clamp, two parts 6 are superposed, with one of the parts being turned over relative to the other so that their projections 15 and lugs 17 and 18 overlap.

A spring 20 is then engaged in the recess with the ends of the spring surrounding the lugs and bearing against the corresponding sides of the recesses. The spring serves to hold the two parts 1 together and also to provide contact pressure.

The shorter branch of the contact (ends 11) is intended to co-operate with a busbar 21 in a set of electricity distribution busbars. The longer branch co- operates with a plug of the apparatus. While nominal current is flowing, or short circuit current in the event of a fault, said disposition ensures that the electrodynamic force that urges the parts 6 towards each other is exerted more strongly on the contacts 11A at the busbar end (the forces are represented by arrows FA) than on the other contacts 12A (arrows FA') such that the busbars are not in danger of being damaged by the appearance of electrical arcing.

It may be observed that the radius of the rounded portion 11A at the busbar end is greater than the radius of the rounded portion 12A at the apparatus end. The contact zone or mark is greater at the busbar end, having the same safety effect. The clamp of the invention is cheap to manufacture: 35 the shape of the elements 6 is such that there Is little waste on stamping; once the elements 6 have been made, they can be stacked and only the portions corresponding to the contacts 11A and 12A need be silver-plated; this provides a major saving in silver plate since only a small fraction of the area of each element is silver-plated; it is easy to automate the assembly of a connecting clamp in which two elements and a spring are united, thereby providing savings in labor costs for assembly; and the simplicity of manufacture by stamping makes it possible to provide elements that have repeatable dimensions, such that the dispersion of pressures applied by the clamps is small.

The connecting clamp of the invention may be placed in a cassette of Insulating material as Is well known in low voltage applications, and as can be seen in Figure 5.

In this figure, reference 30 designates a molded block that acts as a support for busbars 31, 32, and 33 which constitute branches from a three-phase set of busbars 35. The molded block is fixed to a metal frame shown In part at 36.

The connecting clamps of the Invention 41, 42, and 43 connect respective busbars 31, 32, and 33 to plugs 51, 52, and 53 of an apparatus 50 such as a circuit breaker, shown in part.

As can be seen, and in compliance with the technique shown in French patent No. 84 12 472 filed 7 August 1984, the connecting clamps are placed in rectangular molded boxes having openings through which the connection parts pass. When the connecting clamps are plugged onto the busbars, the cassettes provide "electrical finger" protection.

The connecting clamps of the invention may be made in various sizes depending on the nominal current of the apparatus to be connected.

An embodiment of the present invention can therefore provide a connecting clamp at a reduced cost, in particular by using a small number of parts which may be produced by a stamping process which gives rise to little waste, and which have small silver plated areas that can be assembled quickly by, for example, an automated process.

An embodiment of the present invention can also provide a connecting clamp which behaves well when subjected to short circuit currents by, for example, the pressure force being mostly at the busbar end rather than at the equipment end which generally avoids damage to the set of busbars.

Claims

CLAIMS 1. A connecting clamp for electrically connecting a busbar to an

apparatus plug, which clamp includes two cooperating elongate elements, respective end portIons of each element providing electrically conductive clamping surfaces, the clamping surfaces of each element being electrically connected to each other and the elongate elements being linked to one another such that respective clamping surfaces of one of the elongate elements face respective clamping surfaces of the other elongate element, the clamp further including resilient means mounted between respective portions of the elongate elements intermediate the end portions thereof for resiliently biasing adjacent clamping surfaces together.
2. A connecting clamp for connecting an electricity distribution busbar to a plug of an electrical apparatus, the clamp being characterized in that it comprises two identical elements (6), each element (6) being made from a metal plate and being generally elongate in shape, having a first plane end portion (11) connected to a second plane end portion (12) that Is coplanar with the first by a plane intermediate portion (13) situated in a plane parallel to the plane of the end portions but offset therefrom by an amount equal to about one-half the thickness of the plate, the intermediate portion (13) extending laterally on one side only in the form of a projection (15) having an opening (16) and two facing lugs (17, 18), one side (11A) of the first end (11) on the same side as the projection being rounded and silverplated on its edge, one side (12A) of the second end (12) on the same side as the projection being rounded and silver-plated on its edge, said connecting clamp being made by juxtaposing two elements of the above type, one of the elements being turned over relative to the other, the elements being placed so that their respective projections (15) and lugs (17, 18) coincide, a spring (20) being engaged in the opening (16) and bearing against the two opposite ends thereof, the ends of the spring (20) surrounding the lugs (17, 18).
3. A connecting clamp according to claim 2, characterized in that the projection of each element (6) is closer to its end (11) for co-operating with the busbar than to its end (12) for co- operation with the connection to the apparatus.
4. A connecting clamp according to claim 2 or 3, characterized in that, within each element (6), the radius of the rounded end (11) for co-operating with the 9 busbar is greater than the radius of the rounded end (12) for co- operating with the apparatus.

- A connecting clamp for connecting an electricity distribution busbar to a plug of an electrical apparatus, substantially as herein described with reference to and as illustrated in Figures 2 to 5 of the accompanying drawings.

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