AU724871B2 - Power line cable connector - Google Patents

Description

WO 97/28577 PCT/IB97/00042 -1- POWER LINE CABLE CONNECTOR The present invention relates to junctions or splices for connecting power line cables, for example medium voltage electric cables incorporating a circular core wire. Such junctions may be used for the permanent connection of cables of overhead or underground networks.

Up to the present time, such connections have been made by means of a sleeve or tube, in the longitudinal bore of which are inserted opposite ends of two cables to be connected. Once these ends are inserted in the tube, the tube is crushed at certain points by means of a hydraulic press or the like, in order to assemble the two cables permanently.

It will be readily appreciated that this process of assembly involves the use of a hydraulic installation for supplying pressure to the deep stamping crushing tool.

Such an installation comprises an electric motor or the like for driving the hydraulic pump. Moreover, it is necessary to adapt the stamping tool to the type of junction used as a function of the diameters of the cables to be connected. It is therefore possible, on the one hand, for errors to be made in the choice of the appropriate tool and, on the other hand, for this tool or the hydraulic installation to deteriorate, as all of this equipment is used on open land and sometimes in mud or sand. The junctions are therefore sometimes defective, which is extremely detrimental, particularly when the cables are buried.

The means of solving the above problem is to provide a junction or splicing connector with shear head bolts as shown in GB 2 174 851 and GB 2 272 586. The bare conducting strands of cables are inserted into channels of these connectors, and clamped therein by a pressure pad that is clamped down on the cable by means of bolts. The bolt heads shear off once the torque limit is achieved, thereby limiting the clamping pressure of the cable. A permanent connection without crushing of the tube is thus WO 97/28577 PCT/IB97/00042 -2provided.

One of the problems of such designs is that many of the conducting strands of the power cable may not be in good electrical contact with each other and the connector.

Due to the high currents used in power distribution, and the need for good electrical connection, a reduction in performance of the electrical interconnection of spliced cables may be critical. In addition, many cables used in the industry are of an aluminum alloy, which forms a thin but resistant oxide layer that impairs electrical conductivity. It would be desirable to overcome these problems and improve such splicing connection systems.

Power line conductors come in many sizes and configurations, some being multi-stranded aluminum alloy cables with an insulating jacket therearound, and in certain instances hollow tubes of aluminum alloy or copper. For large diameter cables it may be desirable to remove the insulating jacket prior to interconnection of cable ends via a splicing connector in order to ensure the lowest contact resistance. On the other hand, in certain applications, rather than removing the insulating jacket it would be desirable to have an insulation piercing connector that allows connection without removing a portion of the insulating jacket. This may have the advantage of limiting corrosion of the cable by preventing ingress of water beneath the insulating jacket, or simplify the connection procedures. EP 239 428, for example, shows an insulation piercing connection system for interconnecting cables.

As many different types of cables and different cable sizes are used in the power transmission industry, it would be desirable to have a splicing connector that is easily adaptable for interconnection with a large variety of different cables, in order to reduce manufacturing and handling costs thereof. It would also be desirable for such splicing connectors to be able to interconnect two different cables in as cost effective a manner as possible.

Summary of the Invention In accordance with a first aspect, the present invention provides a power line splicing connector including a tubular body having a cavity extending therethrough in a longitudinal direction for receiving ends of insulated cables therein, the connector further including clamping members moveable transversely into the cavity for clamping the cable ends against a bottom wall of the tubular body opposed to the clamping members, the bottom wall having a plurality of pointed ribs extending longitudinally and directed radially towards a central area around a longitudinal axis of the S 10 cavity, the tubular body being prismatically shaped such that its longitudinal profile is extrudable, the ribs being transversely cut such that individual teeth are formed, the ribs having a height greater than the thickness of the insulation surrounding the cables to be received therein, characterised in that the tubular body is an integral part and the teeth are formed by cutting transverse grooves by screw machining.

Embodiments of the present invention may provide a junction which does not require the use of considerable, sophisticated equipment to make the permanent connection.

Other embodiments of this invention may provide a versatile junction 20 or splicing connector for interconnecting a large variety of different cables, for S* example, where the conducting strands are bared or with an insulating jacket, in a cost-effective and reliable manner.

Embodiments of the invention may provide a power line splicing connector comprising a tubular body extending in a longitudinal direction and having a longitudinal cavity extending therethrough for receiving cable ends therein, further comprising clamping means extending transversely to the cavity for clamping and electrical connection of the cable ends to the splicing connector, wherein the connector comprises a plurality of pointed ribs extending longitudinally along a bottom portion of the tube cavity opposed to the clamping means, the ribs extending along substantially the whole length of the body, the teeth having a depth sufficient for piercing through insulation of conductors received therein. The ribs can be cut transversely at a certain pitch and depth to increase the contact pressure for piercing through insulation, or for breaking through the oxide layer of bared conducting strands of a conductor. The transverse cuts can be made in a screw machining operation that is particularly rapid and cost-effective, 3a whereby the body of the connector is extruded and cut to the desired length.

Advantageously therefore, the connector is particularly cost-effective to manufacture and extremely versatile in that a plurality of different conductor sizes and types can be connected thereto. For a piercing conductor, the transverse cuts can be made very deep and with a large pitch in order to increase the piercing pressure of the teeth. For bare o WO 97/28577 PCT/IB97/00042 -4conductors, a very fine pitch and low depth of the transverse cuts provides a contacting surface with many little pyramidal points that dig into the bare strands, thereby breaking through the oxidation layers, increasing the contact surface area, and frictionally holding the conductors in place for an effective electrical connection thereto.

It is also possible to provide the connector with longitudinal ribs of different heights, whereby the longer teeth could either serve as insulation piercing teeth, or to prevent movement of strands of a bare conductor, the shorter teeth serving to improve the connection with bare conductors.

Embodiments of this invention will now be described by way of example, with reference to the Figures, whereby; Figure 1 is a longitudinal cross-sectional view of a splicing connector according to this invention; Figure 2 is a cross-sectional view through lines 2-2 of Figure 1; Figure 3 is a schematic isometric view of a body of the connector of Figure 1; Figure 4 is a similar view to that to Figure 3 but with different sized transverse cuts through longitudinal ribs; Figure 5 is a partial isometric view of another embodiment of this invention where teeth of different height are provided; Figure 6 is a similar view to that of Figure 5 but with transverse cuts through the teeth.

Referring first to Figure 1, a splicing connector 2 comprises a tubular body 4 having a cavity 6 extending longitudinally therethrough for receiving conductor ends therein, and clamping members 8 extending transversely to the cavity 6 for clamping the conductors therein. The clamping members 8 are threaded bolts 10 received in threaded bores 12 extending through the tubular body 4 into the cavity.

The bolts 10 have a torque limiting head 14 that can WO 97/28577 PCT/IB97/00042 either be integral with the bolt 10 or a separate part fixed thereto and being shearable when excessive torque is applied. Inthis manner the compression force of the bolt that clamps a cable received in the cavity 6 is precisely delimited. The bolt 10 has a clamp surface 16 with a recess 18 in a central portion thereof for increasing the crushing pressure of the clamping surface against a conducting wire. The latter also ensures that a portion of the cable being clamped enters into the recess 18 enabling secure lateral and longitudinal retention of the cable, to prevent movement thereof.

The splicing connector 2 can be further provided with an outer sealing body 20 enclosing the tubular body and having elastomeric cap members 22 at either end that have a funnel shaped entry portion 24 extending longitudinally and aligned with the cavity 6, and having a radial sealing lip 26 that snugly and elastically fits around a cable inserted therethrough for sealing purposes. For sealing the connection interface, gel sealant 28 can be provided within the cavity 6 beneath the clamping members 8.

Referring now to Figures 1-4, the tubular body 4 is in this embodiment an extruded metal part that is cut to the desired lengths, and comprises a plurality of long pointed ribs 28 along a bottom portion 30 of the body opposed to the clamping surfaces 16 of the bolt 10. The ribs 28 are directed radially inwards towards the central axis A of the cavity 6. The ribs 28 have a depth sufficient to pierce through the insulating layer of conventional power line conductors for electrical connection with inner a conducting strands thereof.

As can be seen in Figures 1 and 3, the ribs 28 are cut transversely by grooves 32 that can be made by screw machining in much the same way as machining of a thread for screw connections. The combination of the ribs 28 and grooves 32 form a plurality of teeth 34. In the event that the connector is for connection to insulated conductors, the depth of the groove 32 and the width of the groove can be adjusted to make more or less sharp WO 97/28577 PCT/IB97/00042 -6pointed teeth 34 for providing the requisite pressure for piercing through the insulation layer and into the conducting strands of the conductor. It is also possible to provide one end 3 of the tubular body 4 with teeth that are screw machined differently than the teeth at the other end 5 such that two different conductors can be connected at either end and clamped together by means of the respective clamping members The depth of the grooves 32 can also be varied in order to adjust to conductors with different insulation thicknesses, thereby insuring that the correct depths are achieved and avoiding cutting through strands of the conductor unnecessarily.

As can be seen in Figure 4, if a pressure surface is required for contacting conductors which do not have an insulating layer or where the insulating layer has been removed, very small transverse cuts 32' at a very small pitch can be screw machined across the ribs 28' for digging into the conductor. The latter ensures that the oxide layer is broken through, and a large contact surface area with high contact pressure is achieved.

The above design enables extrusion of the body, which is a particularly cost-effective method of producing large quantities of such connectors, which are then cut to the desired length. Screw-machining is a further very effective manufacturing procedure where tools can be easily exchanged to provide transverse cuts of different depths and pitches.

Referring now to Figures 5 and 6, it is also possible to provide a splicing connector 102,202' provided with a through cavity 106 and clamping members 108 similar to that described for the previous embodiment, with the connector also being provided with longitudinal ribs 128, 128'. Some of the ribs 128' can be much longer than the other ribs 128. The longer ribs can either serve to provide insulation piercing teeth 228' as shown in Figure 6, or if a bare conductor is positioned therein, the ribs 128' or teeth 228' serve to prevent lateral movement of the conducting strands to prevent relaxation of the WO 97/28577 PCT/IB97/00042 -7contact pressure between strands and between the connector when the clamping bolts are tightened thereagainst. The small ribs 128,228 ensure increased contact pressure and piercing of the oxidation layer of the pair conductor strands. As in the previous embodiment, the depth and pitch of the teeth that are provided by transverse cutting of the ribs, can also be modified as a function of the conductor size and type for connection thereto.

Claims (8)

1. A power line splicing connector including a tubular body having a cavity extending therethrough in a longitudinal direction for receiving ends of insulated cables therein, the connector further including clamping members moveable transversely into the cavity for clamping the cable ends against a bottom wall of the tubular body opposed to the clamping members, the bottom wall having a plurality of pointed ribs extending longitudinally and directed radially towards a central area around a longitudinal axis of the cavity, the tubular body being prismatically shaped such that its longitudinal profile is extrudable, the ribs being transversely cut such that individual teeth are formed, the ribs having a height greater than the thickness of the insulation surrounding the cables to be received therein, characterised in that the tubular body is an integral part and the teeth are formed by cutting i transverse grooves by screw machining.

2. The connector of claim 1 wherein the tubular body has an oval cross- sectional profile with long side walls and short top and bottom walls.

S3. The connector of any preceding claim wherein the transverse grooves have a V-shaped profile.

4. The connector of any preceding claim wherein one or more ribs are higher than adjacent ribs.

5. The connector of any one of the preceding claims wherein the grooves have a depth sufficient to enable piercing of the teeth through the thickness of said insulation jackets.

6. The connector of any one of claims 1-4 wherein the depth of the transverse grooves is less than the thickness of said insulation jackets, such that the teeth are adapted for connection to bare conductor strands.

7. The connector of any one of the preceding claims wherein the tubular body is provided with teeth at one end thereof that are different to teeth at another end thereof such that two different conductors can be connected, one at each end.

8. A power line splicing connector substantially as herein described and with reference to the accompanying drawings; Dated this twentieth day of July 2000 The Whitaker Corporation Patent Attorneys for the Applicant: F B RICE CO