GB2188795A - Electrical connection between two conductors - Google Patents

Abstract

A connection between first and second cable conductors such as a conductor of a mains cable 100 and conductor of a service cable 102 is established by two elements 104, 106 each having a saddle portion 110, 118 for engagement with the second conductor 102 and a jaw 112, 120 for engagement with the first conductor 100 with a tooth 126 on one of the jaws biting into the first conductor. However, whereas in the conventional arrangement, the jaws of the connector elements engage on opposed corners of the first conductor, in the arrangement according to the invention, the jaws engage on adjacent faces of the first conductor at positions spaced apart by appreciably less than the maximum width of the conductor. Use of the invention reduces the size of the connector as compared with conventional connectors, and moreover, enables a single size of connector to be used with a relatively wide range of sizes of electrical conductor. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electric cable connections The invention is concerned with an electrical cable connection between two cable conductors, such as a conductor of a mains cable and a conductor of a service cable. Mains cables may have two, three or four core conductors and the conductors themselves can be solid, standed or compacted stranded metal. A known type of cable core to which the invention is particularly applicable, has a solid shaped aluminium conductor, the aluminium having a high purity (of the order of more than 99%) for good electrical conductivity properties.In the case of a two core cable, the two solid conductors are substantially semi-circular or "D" shaped; in the case of a three core cable, the solid conductors each subtend an angle slightly less than 120" about the cable axis - to allow for the twisting of the cores around each other and in the case of a four core cable, the solid conductors each subtend an angle slightly less than 90" about the cable axis. The single core conductor of a service cable is generally circular in cross-section.

It is to be understood that the invention is not restricted to connecting the conductors of mains cables to those of service cables. It can for example, be used to connect two similar conductors, as where two cables are to be joined one in continuation of the other. Nor is to restricted to the connecting of conductors of any particular cross-section, aithough, as mentioned above, it is particularly well adapted to the connecting of solid aluminium conductors as used in two, three and four core cables.

Further, it is to be understood that the invention comprehends a cable connecting arrangement; the method of making the cable connection and a cable connector which can be used to make the cable connection.

A known cable connector which is frequently used for connecting a solid mains cable conductor to a conductor of a service cable is in the form of a clipon connector device having a pair of electrically conducting metal (e.g. aluminium) elements, each of which comprises a saddle portion adapted to seat on the conductor of the service cable, and a jaw adapted to seat on one of the corners of the shaped metal conductors of the mains cable, there being a screw-and-nut arrangement for drawing the two elements towards each other. The two saddle portions engage on opposite sides of the service cable conductor and two corners of the shaped main cable conductor are received respectively in the jaws of the two elements. Thus, the clip-on device straddles the main cable conductor.When the screw-and-nut is tightened, the saddle portions grip on the service cable conductor, and further tightening of the screw-and nut causes each of the two connector elements to pivot on the fulcrum provided by the service cable conductor, until the jaws grip tightly on to the corners of the mains cable conductor. It will be understood that the gripping effect must provide both adequate mechanical connection and the necessary electrical connection.

This type of cable connector has proved quite satisfactory, but it is necessary to provide a range of sizes of connector to accommodate the various possible cable connections, due to the variations in the width of the shaped solid conductors. Clearly for instance, the distance across the corners of the conductors of a three core 300 square millimetres cable is much greater than the equivalent distance across the corners of the conductor of a three core 70 square millimetres cable, and it is impracticable to manufacture one size of clip-on connector which will fit on to both sizes of cable.

According to a first aspect of the invention a cable connection between a first cable conductor and a second cable conductor includes a cable connector comprising two electrically conductive metal elements, each having a saddle portion and a jaw, at least one of the jaws being formed with a tooth, the two saddle portions engaging on opposite sides of the second cable and the jaws engaging with the surface of the first cable conductor at position5 spaced apart by appreciably less than the maximum width of the conductor, there being mechanical means for drawing the two connector elements towards each other, these means causing the elements to pivot about their positions of engagement with the second conductor to an extent which causes the jaws to engage tightly with the first conductor and the said at least one tooth to bite into the first conductor.

In one cable connection in accordance with this aspect of the invention, the first conductor is a shaped solid conductor with a cross-section which subtends no more than 1 80" about the cable axis (probably less than 1800) so that it has corners, and the jaws of the connector elements engage with adjacent faces of the first conductor adjacent to one of the corners. Thus, instead of the connector straddling the first cable conductor and gripping on its two corners, it is engaged around only one corner. Consequently, the connector does not have to be designed to straddle the conductor and hence its cross-sectional dimensions need not be related to the width of the conductor, or to grip on to a wide range of sizes of conductor.At this point, it should be mentioned that a basis for the invention is the realisation that for any particular shape of conductor (D: < 1 20" or < 90 ) the angle subtended by the adjacent faces at the corner remains constant for different sizes of conductor. Since the gripping effect of the jaws of the connector is related to this angle, it follows that virtually the same gripping effect can be obtained with a single size of connector over a wide range of sizes of conductor.

In a preferred connection, where the connector is fitted around the corner of a shaped solid cable conductor, a shoulder of one of the elements located on a first face of the conductor; the jaw of that element engages on the adjacent face of the conductor, and the jaw of the second element engages on the first face of the conductor. The engagement of the shoulder of the one element on the conductor locates that element relative to the corner of the conductor. According to another preferred feature of this aspect of the invention each of the saddle portions has a V-block type engagement on the second conductor. This locates the two elements of the connector relatively to each other.If the one element is located on the first conductor by the shouider, then the location of the two elements relatively to each other provides location of the other element on the first face of the first conductor. The location of the positions at which the jaws of the connector elements engage with the adjacent faces of the first conductor plays an important part in obtaining adequate gripping of the connector on the first conductor.

In the preferred construction, the mechanical connection comprises a screw-and-nut device; this may take the form of a setscrew passing through a clearance hole in one element and engaging in a screw-threaded hole in the other element.

According to a second aspect of the invention a method of effecting a connection between a first cable conductor and a second cable conductor using a cable connector comprising two electrically conductive metal elements and mechanical means for drawing the two elements together, comprises: engaging saddle portions of the two elements on opposite sides of the second conductor; engaging jaw portions of the two connector elements with the surface of the first conductor at positions spaced apart by appreciably less than the maximum width of the conductor and operating the mechanical means to draw the two connector elements towards each other so that they pivot on the second conductor and at least one of them bites into the first conductor According to a third aspect of the invention a cable connector for connecting first and second electrical conductors comprises two electrically conductive metal elements each comprising a saddle portion adapted to rest on the second conductor but to subtend less than 180" around the longitudinal axis of the second conductor so that the two saddle portions of the connector can be brought into engagement with opposite sides of the second conductor and a jaw at the opposite end of the element to the saddle, the two jaws being adapted for localised engagement with the first conductor at spaced apart positions, at least one of the jaws having a sharp edge for biting into the first conductor at its positions of localised engagement with the first conductor, at least one of the elements also having a shoulder inboard of its position of localised engagement with the first conductor, this shoulder providing a location for that element on the conductor and mechanical means for drawing the two elements towards each other.

It is to be understood that various preferred features of construction of the conductive metal elements described with reference to the first aspect of the invention may be utilised in the construction of a cable connector in accordance with the third aspect of the invention. Furthermore, various preferred features of the first aspect of the invention, may be obtained by carrying out preferred forms of the method of the second aspect of the invention.

A cable connector, a method of effecting a connection between a first cable conductor and a second cable conductor and a cable connection in accordance with the three aspects of the invention, will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a cable connection employing a known type of cable connector, Figure 2 is a cross-section through a connection in accordance with the present invention, and Figure 3 is a cross-section through another cable connection in accordance with the invention.

The cable connection shown in Figure 1 is effected between a solid aluminium conductor 10 forming part of a three core mains cable (the other two cores are not shown) and a solid aluminium conductor 12 of a single core service cable. Connections of this type occur wherever a service cable has to be attached to a mains cable. In the connection which is illustrated, the service cable conductor 12 is of circular cross-section, but the mains conductor 10 subtends just under 1200 about the axis of the mains cable and is in the form of a sector of a circle.

The connection is effected by a connector comprising two identical aluminium elements 14 and 16 drawn together by a bolt 18 and a nut 20, with a locking washer 22. The elements 14 and 16 have to be electrically conductive, and are therefore made, for example, of aluminium alloy. Each of the conductive elements has a saddle portion 24, with a V groove 26 to receive the service conductor 12 and a jaw 28 formed with a notch 30 which is intended to receive one of the corners of the mains conductor 10 where the part circular face of that conductor joins one of the flat faces.

The bolt 18 passes through clearance holes in the two elements 14 and 16 between the saddle portions and the jaws, and it will be apparent from Figure 1, that when the nut 20 is tightened on the bolt, the two conductive elements 14 and 16 are drawn towards each other and grip on both the service conductor 12 and the mains conductor 10.

The cable connection shown in Figure 1 is widely used and is effective, but it suffers from the disadvantage that different sizes of connectors have to be stocked to accommodate different sizes of cable conductors. For the most part, it is variations in the size, and shape, of the mains conductors which bring about this requirement for different connector sizes, since the service conductors vary only within a limited range of diameters and one size of saddle portion 24 can be used with most sizes of service conductor. However, the size of the main conductor can vary from 50 square millimetres to 300 square millimetres, and therefore the distance across the two corners of this conductor varies greatly, thus giving rise to the necessity for differing sizes of connector.

The connector illustrated in Figure 1 is referred to as a "clip-on" connector and it grips the mains conductor by straddling it and clipping on to the two corners which are received in the notches 30.

Turning now to Figure 2, which illustrates a connection in accordance with the invention, again there is a solid aluminium mains conductor 100, which is of the same construction as the conductor 10 shown in Figure 1, and a circular cross-section service conductor 103 which is similar to the conductor 12 shown in Figure 1. Indeed, the joint of Figure 2 is for the same situation as that of Figure 1, although the mains conductor 100 is intended to represent one of the conductors of a 70 square milli metres three core mains cable, and the service conductor 102 is intended to illustrate a 35 square millimetres service cable conductor.

An electrically conductive connector is provided, which comprises two conductive elements 104 and 106 and a setscrew 108. The setscrew passes through a clearance hole in the element 104 and engages in a screw-threaded hole in the element 106, so that by turning the setscrew 108, the element 106 can be drawn towards the element 104. It will be appreciated that a bolt and nut such as those illustrated in Figure 1 could be substituted for the setscrew 108, particularly if the connector is of a relatively large size. However, one of the advantages of the invention is that a single size of connector, which in itself can be of quite small dimensions is useable with a wide variety of sizes of mains cable conductors.

The connector element 104 is made of, for example, an aluminium alloy, and generally comprises a central portion through which the clearance hole is formed, with a saddle portion 110 at one side of the clearance hole, and a jaw 112 at the opposite side of the clearance hole. In practice, as will be apparent from Figure 2, the saddle portion 110 and jaw 112 are identical with each other, and therefore the element 104 is not handed. In each of the saddle portion 104 and the jaw 112 there is a recess 114 having a sharp edge 115 and a serrated gripping face 116. It will be seen that the recess 114 in the saddle portion 104 effectively provides a V block effect for receiving part of the periphery of the service cable conductor 102. When resting in the recess 114, the conductor 102 is engaged buy a corner of the saddle portion and by the serrated face 116.

The electrically conductive element 106 is also made of, for example, an aluminium alloy, and is somewhat similar in general shape to the element 104. In fact, it has a central portion with the screwthreaded bore for receiving the screw-threaded portion of the setscrew 108 and a saddle portion 118 and a jaw 120 located on opposite sides of the centre portion. The saddle portion 118 is constructed in similar fashion to the saddle portion 110 of the element 104 in that it has a recess 122 with a serrated face 124 which recess provides a V block effect for receiving the conductor 102 of the service cable. It will be apparent therefore, that the connector can be clamped on to the conductor 102, by engaging the two saddle portions V block fashion on opposite sides of the conductor 102 and tightening the setscrew 108.

The jaw 120 has a sharp edge 126 at the outer end of a recess 128, and a shoulder 130 is formed at the inner end of the recess 128. In the case of the jaw 120, instead of the serrated face, the recess is undercut on the inside of the sharp edge 126. This edge extends across the full width of the element 106.

In forming the cable connection illustrated in Figure 2, the setscrew is slackened, so that the elements 104 and 106 are spaced apart sufficiently to allow the respective saddle portions to pass on opposite sides of the conductor 102. The shoulder 130 of the element 106 is then brought into engagement with the arcuate face of the mains conductor 102, and the sharp edge 126 of the jaw 120 is brought into engagement with the flat face of the conductor 100 adjacent to the part of the arcuate face which is engaged with the shoulder 130. In other words, one of the corners of the conductor 100 where the arcuate face joins a flat face is received in the recess 128 of the element 106.

The setscrew 108 is then turned to draw the two elements 104 and 106 towards each other. Initially, the saddle portions 110 and 118 engage with the service conductor 102, and thereafter, further tightening of the setscrew causes the element 104 to rock on the conductor 102, bringing the extremity of its jaw 112 into engagement with the arcuate face of the conductor 100 at some distance from the corner which is received in the jaw 120 of the other element 106. The corner portion of the conductor 100 between the points of engagement of the two jaws with that conductor is then straddled by the connector, and further tightening of the setscrew 108 causes the sharp edges 115 and 126 to be pressed into the conductor 100 as illustrated in Figure 2.Once the sharp edges 115 and 126 have penetrated the conductor 100 even to a small extent, the connector is very firmly attached to the conductor 100, and a good electrical connection between the conductor 100 and the two elements of the connector is established.

It will be appreciated from the foregoing description, that the connection which is formed as illustrated in Figure 2, is quite similar in overall effect to the conventional joint illustrated in Figure 1, but the significant difference is that the points of engagement of the jaws of the two connector elements 104 and 106 with the conductor 100 are spaced apart by a distance which is much shorter than the minimum distance between the two corners of the conductor 100 which would be bridged by a connector of the known type illustrated in Figure 1.

The advantage of the connector in accordance with the invention, will be apparent from a consideration of Figure 3. In that Figure, there is illustrated a single conductor 200 of a three core mains conductor of 300 square millimetres. There is also illustrated the conductor 202 of a 16 square millimetre service cable. Thus, whilst in Figure 2, there is illustrated a connection between conductors 100 and 102 which are respectively 70 square millimetres and 35 square millimetres in Figure 3, there is illustrated a connection between a large mains conductor 200 and a much smaller small service conductor 202. Nevertheless, a cable connector identical with that illustrated in Figure 2 is utilised to form the joint between the conductors 200 and 202.

For purposes of identification, the major components 104,106 and 108 have been referenced in Figure 3.

The procedure for forming the connection of Figure 3 is exactly the same as that described for forming the connection illustrated in Figure 2.

However, because the conductor 202 is of smaller diameter than the conductor 102, the two saddle portions 110 and 118 of the elements 104 and 106 are drawn closer to each other, though each of them still engages V block fashion on to the conductor 202, and in this way, the conductor 202 is effectively clamped.

Also, the arcuate surface of the conductor 202 adjacent to one corner is located against the shoulder 130, and the sharp edge 126 is engaged with the flat face of the conductor 200 adjacent to that corner. Further, the sharp edge 115 of the jaw 112 of the element 104 is engaged with the arcuate surface of the conductor 200, and when the setscrew 108 is tightened, the sharp edges bite into the conductor, and an effective mechanical clamping effect is obtained as well as an adequate electrical connection.

It is to be noted however, that whereas in the arrangement illustrated in Figure 2, the end of the saddle portion 112 engages with the arcuate face of the conductor 100 approximately midway between the two corners of the conductor 100, in the arrangement illustrated in Figure 3, the end of the jaw 112 engages with the arcuate face of the conductor 200 at a position which is about one quarter of the distance from the corner of that conductor which engages with the shoulder 130, to the opposite corner. From this, it will be appreciated that whereas the clip-on connector illustrated in Figure 1 completely straddles the width of the conductor 10, the connector which is shown in Figures 2 and 3 only engages around one corner of the mains conductor.It is by virtue of this, that it is possible to use a single size of connector to accommodate a wide variety of conductors, so that it is unnecessary to stock a range of differently sized connectors. This is of course of greater advantage, where many thousands of the connectors have to be stocked for servicing a cable network.

It is to be understood of course, that the connector illustrated in Figures 2 and 3 could be employed to effect electrical connections between other types of conductor. For instance, it could be used to connect two mains conductors of the general shape illustrated at 100 and 200. In the construction illustrated all the four extremities of the two elements 104 and 106 are formed with sharp edges, so that all of these bite into electrical conductors when the connection is effected. It is to be understood however that it is not essential to provide sharp edges at all four extremities. Indeed it might be possible to provide only a single sharp edge on one of the two jaws 112 and 120. The design of the connector elements could also be modified to enable the sharp edges to penetrate any insulation present on the conductors. As an alternative to forming serrations in the recess of the connector elements, they could be formed with any other kind of asperity or roughened formation which will assist in gripping onto and making electrical contact with a conductor located in a position similar to that of the conductor 102 illustrated in Figure 2.

A one piece plastics insulating shroud can be provided for totally enclosing the connector illustrated in Figures 2 and 3. Since only a single size of connector is utilised, only a single size of insulating shroud would be required, and therefore the production of such a shroud becomes economical.

Claims (13)

1. A cable connection between a first cable conductor and a second cable conductor including a cable connector comprising two electrically conductive metal elements, each having a saddle portion and a jaw, at least one of the jaws being formed with a tooth, the two saddle portions engaging on opposite sides of the second cable and the jaws engaging with the surface of the first cable conductor at positions spaced apart by appreciably less than the maximum width of the conductor, there being mechanical means for drawing the two connector elements toward each other, these means causing the elements to pivot about their positions of engagement with the second conductor to an extent which causes the jaws to engage tightly with the first conductor and the said at least one tooth to bite into the first conductor.

2. A cable connection as claimed in Claim 1, in which a shoulder of one of the elements locates on a first face of the conductor; the jaw of that element engages on the adjacent face of the conductor, and the jaw of the second element engages on the first face of the conductor.

3. A cable connection as claimed in either of Claims 1 and 2, in which each of the saddle portions has a V-block type engagement on the second conductor.

4. A cable connection as claimed in any one of Claims 1 to 3, in which the mechanical connection comprises a screw-and-nut device.

5. A cable connection as claimed in Claim 4, in which and screw-and-nut device comprises a setscrew passing through a clearance hole in one element and engaging in a screw-threaded hole in the other element.

6. A method of effecting a connection between a first cable conductor and a second cable conductor using a cable connector comprising two electrically conductive metal elements and mechanical means for drawing the two elements together comprising: engaging saddle portions of the two elements on opposite sides of the second conductor; engaging jaw portions of the two connector elements with the surface of the first conductor at positions spaced apart by appreciably less than the maximum width of the conductor and operating the mechanical means to draw the two connector elements towards each other so that they pivot on the second conductor and at least one of them bites into the first conductor.

7. A method of effecting a connection between a first cable conductor and a second cable conductor as claimed in Claim 6, further comprising; engaging a shoulder of one of the connector elements on a first face of the conductor; engaging the jaw of the element with the adjacent face of the first conductor, and engaging the jaw of the second connector element with the first face of the conductor.

8. A cable connector for connecting first and second electrical conductors comprising two electrically conductive metal elements each comprises a saddle portion adapted to engage on the second conductor but to subtend less than 180 around the longitudinal axis of the second conductor so that the two saddle portions of the connector can be brought into engagement with opposite sides of the second conductor and a jaw at the opposite end of the element to the saddle, the two jaws being adapted for localised engagement with the first conductor at spaced apart positions, at least one of the jaws having a sharp edge for biting into the first conductor at its positions of localised engagement with the first conductor, at least one of the elements also having a shoulder inboard of its position of localised engagement with the first conductor, this shoulder providing a location for that element on the conductor and mechanical means for drawing the two elements towards each other.

9. A cable connector for connecting first and second electrical conductors as claimed in Claim 8, in which the mechanical connection comprises a screw-and-nut device.

10. A cable connector for connecting first and second electrical conductors as claimed in Claim 9, in which the screw-and-nut device comprises a setscrew passing through a clearance hole in one element and engaging in a screw-threaded hole in the other element.

11. A cable connection between a first cable conductor and a second cable conductor constructed and arranged substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.

12. A method of effecting a connection between a first cable conductor and a second cable conductor using a cable connector comprising two electrically conductive metal elements and mechanical means for drawing the two elements together substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.

13. A cable connector for connecting first and second electrical conductors constructed and arranged substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.