GB2506143A

GB2506143A - Electrical terminal having concave element

Info

Publication number: GB2506143A
Application number: GB201216877A
Authority: GB
Inventors: Lee Farler
Original assignee: BRENCHAM 1988 Ltd
Current assignee: BRENCHAM 1988 Ltd
Priority date: 2012-09-21
Filing date: 2012-09-21
Publication date: 2014-03-26
Anticipated expiration: 2032-09-21
Also published as: GB2506143B; GB201216877D0

Abstract

An electrical terminal comprises a block 1, a conducting element 2 and clamping means 5. The block has a hole 4 for receiving a cable conductor. The conducting element has a concave face 11 and is configured to be received in the hole, and the clamping means are operable to clamp the cable conductor in electrical engagement with the concave face of the conducting element. The clamping means may be one or more grub screws 3. The hole may have a slot 13, which may be tapered or straight-sided (see Fig 6), to accommodate the tang 12 of the conducting element. The block may be brass or may be non-conductive.

Description

Electrical terminal The present invention relates to an electrical terminal.

Electrical terminals are used to connect wires or cables to electrical apparatus, and typically comprise a clamping means by which the conducting core of the cable is held in contact with a conducting element of the terminal, which in turn may make electrical contact with further elements of the electrical apparatus. An example application for an electrical terminal is in connecting a mains cable (from an electricity meter) to a consumer unit. Such cables are often referred to by electricians as "tails".

The applicant has identified that existing electrical terminals are prone to becoming loose! particularly when cables have been disturbed. In the UK, electricity meters are increasingly being replaced by upgraded smart meters, with a range of improved functionality. During the installation process it is necessary to disconnect the old electricity mater, and reconnect the new electricity meter to the consumer unit.

Typically, the installer will simply re-use the existing tails to connect the meter to the consumer unit, and will not disturb the existing connections to the terminals of the consumer unit. However, due to the relatively large sectional area and high flexural stiffness of such cables, significant levels of force may be required to manipulate the cable during installation, The applicant has identified that prior art electrical terminals, such as the type shown in Figure 1 of the appended drawings, are prone to becoming loose during such manipulation. Where the conducting core of the cable comprises a plurality of strands, manipulation of the cable may result in shifting of these strands, which can be the cause of such problems. Loosening of the clamping of the cable to the terminal may result in an increased contact resistance, giving rise to hotspots and a risk of fire, and may further risk the cable being accidentally withdrawn from the terminal, with a consequent risk of electrical short circuits and electrical shock.

The terminal 10 of Figure 1 is widely used in switchgear applications, and comprises a block 1 with a substantially rectangular aperture for receiving a cable (not shown). A conducting element 2 is provided for making an electrical connection from the terminal 101 having an outwardly extending terminal arm 9 to which switchgear may be connected. The conducting element 2 extends through the aperture, and is laterally moveable therein to close the aperture and thereby clamp the cable in electrical engagement with the conducting element 2. A screw 3 is provided which exerts a clamping force on the conducting element 2 to close the aperture. The block I is provided with transverse ridges 7, to improve the clamping engagement between the cable and the block 1. The lower surface 8 of the conducting element, which engages with the conductors of the cable during cEamping, is substantially smooth and flat.

It is desirable to provide an electrical terminal with improved security of connection between the cable and terminal.

According to the present invention, there s provided an electrical terminal comprising a block, a conducting element and clamping means, wherein: the block comprises a hole for receiving a cable conductor, the conducting element has a concave face and is configured to be received in the hole, and the clamping means are operable to clamp the cable conductor in electrical engagement with the concave face of the conducting element.

The hole may be a through hole.

The hole may have a substantially circular profile.

The conducting element may be configured so that the concave face is substantially concentric with the profile of the hole when the conducting element is clamped in engagement with the cable conductor.

The conducting element may have an opposed face which at least partly conforms with the profile of the hole.

The hole may be provided with a slot for receiving the conductor element.

The slot and conducting element may have corresponding dimensions so as to provide a substantially continuous surface comprising the inner profile of the hote and the concave face of the conducting element when the conducting element is received in the hole.

The slot may be configured to: accept insertion of the conducting element in a direction substantially parallel with the direction of cable insertion, and to retain the conducting element against movement that is transverse to this direction.

S The slot may taper outwards from the centre of the hole, and the conducting element may taper outwards from the concave face.

The conducting element may comprise copper or aluminium.

The block may comprise brass.

Rho block may comprise a non-conducting materiaL The clamping means may comprise a plurality of clamping elements, The clamping means may comprise a screw which cooperates with a threaded hole in the block.

The screw may be operable to impinge directly on the cable conductor during clamping.

Two screws may be provided, and their respective threaded holes spaced apart along the axis of the hole for receiving the cable conductor.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a prior art electrical terminal; Figure 2 is an exploded diagram of a first embodiment of the invention; Figure 3 is an isometric view of the first embodiment; Figure 4 is a front and side view of the first embodiment; Figure 5 is an exploded diagram of a second embodiment of the invention: Figure 6 is an isometric view of the second embodiment; Figure 7 is a front and side view of the second embodiment: Figure 8 is an exploded diagram of a third embodiment of the invention; Figure 9 is an isometric view of the third embodiment; and Figure 10 is a front and side view of the third embodiment.

Referring to Figures 2 to 4, a terminal 20 is shown, comprising a block 1, conducting element 2 and clamping means 5.

The block 1 comprises brass, and is a rectangular cuboid with a first dimension that is larger than a second dimension, and a third dimension that is smaller than the second dimension. The block I includes a through hole 4 for receiving a cable conductor (not shown), the through hole 4 extending parallel to the first dimension of the cuboid. The block I further comprises two threaded holes 6, extending from an external face of the cuboid, that is normal to the second dimension thereof, into the through hole 4. The two threaded hoJes 6 are spaced apart along the axis of the through hole 4. The block I may, for example, be formed by machining processes carried out on a solid block of brass -The conducting element 2 comprises copper, and may be produced by a sequence of forming processes carried out on a sheet of material. The conducting element 2 comprises a terminal arm 9 that extends outwards from the terminal 20 when it is assembled, to which switchgear may be electrically connected, and a blade or tang 12 which is for insertion into the through hale 4 of the block 1. The tang 12 extends substantially straight in a first direction, with a cross section that substantially corresponds with the profile of the through hole 4, being substantially dish or arc shaped. When the tang 12 is received in the hole 4, it has a lower face that conforms substantially to the profile of the hole 4, and a concave upper face 11 that in this example is substantially concentric with the hole & The lower conformal face improves the support of the tang 12 by the block 1, increasing the contact area therebetween.

When the clamping means are 5 engaged, and pressure is exerted on the conducting element 2, the conformal lower face means that the tang 12 is not deformed and flattened by the clamping means 5, which might otherwise flatten the concave upper surface.

In use, the cable conductor is clamped against the concave upper face 11 by the clamping means 5. The concave face 11 of the conductor means that the cable conductor tends to be forced by the clam ping means 5 into the bottom of the face 11.

In the case of a cable conductor comprising multiple strands, this arrangement is particularly advantageous.

The clamping means 5 comprises a pair of hexagonal dre grub screws 3, which are received in the threaded holes 6, and are operable to directly engage with the cable conductor, thereby clamping it into electrical engagement with the underlying concave face 11 of the conducting element 2. The screws are formed from steel, and are consequently a harder material than a typical cable conductor. They therefore readily deform the material of the cable conductor as they engage therewith, helping to provide improved security of clamping.

Figures 5 to 7 show a second embodiment of a terminal 20, which is broadly similar to that of the first embodiment, However, in this second embodiment, the hole 4 of the block I is provided with a recess or slot 13, for receiving the tang 12 of the conducting element 2, and with a shape corresponding substantially to that of the tang 12. The conducting element 2 remains substantially the same as for the first embodiment, and tile depth of the slot 13 is selected to be equal to the thickness of the conducting element 2. The tang 12 of the conducting element 2 again has an arc shaped cross section corresponding with that of the slot 13, such that the concave upper surface 11 has a radius of curvature that corresponds with that of the hole 4. This means that when the conducting element 2 is disposed in the slot 13, (he concave surface 11 and the profile of the hole 4 together form a substantially continuous cylindrical profile. This substantially cylindrical profile may be selected to correspond with a particular bable geometry. For example, where the terminal is Intended for use with a particular cable (such as a cable with a 25mm2 conductor), the radius of the hole 4 and concave surface 11 may be selected to provide a relatively close clearance fit with the cable conductor. After clamping pressure is exerted on the cable conductor by the clamping means 5. the individual conductors of a stranded cable conductor are thereby less able to shift as the cable is manipulated, since there is no spare space in the hole 4 into which they can shift. This is in contrast to prior art terminals with a substantially square hole, in which strands of a substantially circular cable conductor are able to move toward the corners of the hole under manipulation of the cable, even after it is clamped into place.

The slot 13 has a lower wall that Is curved to conform with the arc shaped section of the tang 12, and has substantially vertical sidewalls 14 that are parallel to a face of the cuboidal block 1. The slot 13 thereby does not taper with depth, and the conducting element 2 may be inserted into the slot 13 in a direction that is transverse or longitudinal to the axis of the hole 4.

Figures 8 to 10 show a third embodiment which is similar to the second embodiment! but in which the slot 13 tapers outwards with increasing depth, the sidewalls 14 of the slot 13 converging as they near the axis of the hoie 4. The tang 12 of the conducting element 2 again has an arc shaped cross section, and substantially corresponds with the shape of the slot 13. The tang 12 can thereby be inserted into the slot 13 in a direction that is substantially longitudinal to the axis of the hole 4, but cannot be inserted or withdrawn from the slot 13 in a direction that is transverse to the axis of the hole 4. The slot 13 thereby partially retains the conducting element 2 in the slot 13.

This prevents the conducting element 2 from inadvertently shifting during installation and manipulation of the terminal, without the need for the clamping mechanism to be engaged therewith. Again, the concave surface 11 and the profile of the hole 4 together form a substantially continuous cylindrical surface.

Although embodiments have been described in which the clamping means comprises a pair of hexagonal drive grub screws, other types of clamping means are envisaged within the scope of the invention. For example, a single screw may be used, or more than two screws may be used. In other alternatives, the drive means for the screw(s) may be different, for example a torx, slot, posi or Philips drive.

Although embodiments have been described in which the block comprises brass, other materials are possible. In some embodiments, the block may be a non-conductive material such as an engineering plastics material, since the cable conductor directly engages with the conducting element of the terminal.

Although the invention has been described with reference to the particular appiication of connecting tails between meters and consumer units, it will be appreciated that the invention Is applicable to any electrical terminal, including both very small terminals for printed circuit boards, End larger terminals for industrial power distribution.

Whilst specific embodiments of the invention are described hereinbetore, it wilr be appreciated that a number of modifications and alterations may be made thereto without departing from the scope of the invention.

A terminal has been disclosed that addresses the problem of cables becoming loose when they are manipulated. The disclosed terminal provides an improvement in the security and reliability of the connecthn between the cable and the terminal. This is particularly advantageous given the current changes to electrical metering that are taking place in the UK. Given that the potential consequences of a failed connection to a consumer unit are relatively serious, and the installer and their organEsation are typically traceable, these improvements are highly advantageous both for the end user and the installers.

Claims

CLAIMS: 1. An electrical terminal comprising a block, a conducting element and clamping means, wheein: the block comprises a hole for receiving a cable conductor, the conducting element has a concave face and Es configured to be received in the hole, and the clamping means are operable to clamp the cable conductor Ifl electrical engagement with the concave face of the conducting element.
2. The terminal of claim 1, wherein the hole is a through hole.
3. The terminal of claim 1 or 2, wherein the hole has a substantially circular profile.
4. The terminal of claim 3. wherein the conducting clement is configured so that the concave face is substantially concentric with the profile of the hole when the conducting element is clamped in engagement with the cable conductor.
5. The term{nal of any preceding claim, wherein the conducting element has an opposed face which at least partly conforms with the profile of the hole,
6. The terminal of any preceding claim, wherein the hole is provided with a slot for receiving the conductor element.
7. The terminal of claim 6, wherein the slot and conducting element have corresponding dimensions so as to provide a substantially contThuous surface comprising the inner profile of the hole and the concave face of the conducting element when the conducting efement is received in the hole. -
8. The terminal of claim 6 or 7, wherein the slot is configured to: accept insertion of the conducting element in a direction substantially parallel with the direction of cable insertion, and to retain the conducting element against movement that is transverse to this direction.
9. The terminal of claim 8 wherein the slot tapers outwards from the centre of the hole, and the conducting element tapers outwards from the concave face.
10. The terminal of any preceding claim, wherein the conducting element comprises copper or a!uminium.
11. The terminal of any preceding claim, wherein the block comprises brass.
12. The terminal of any preceding claim, wherein the block comprises a non-conducting material.
13. The terminal of any preceding claim, where the clamping means comprise a plurality of clamping elements.
14. The terminal of any preceding claim, wherein the clamping means comprise a screw which cooperates with a threaded hole in the block.15. the terminal of claim 14, wherein the screw is operable to impinge directly on the cable conductor during clamping.16, The terminal of claim 15, wherein two screws are provided, and their respective threaded holes are spaced apart along the axis of the hole for receiving the cable conductor.17. An electrical terminal substantially as hereinbefore described, with reference to Figures 2 to 10 of the accompanying drawings.