AU648168B2 - Improved cable compression connector - Google Patents

Description

P/00/01l1 Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 6 8 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

ame of Applicant: :.:-Actual Inventor(s): Address for Fzrvice: TO BE COMPLETED BY APPLICANT 1f-1F- W0O:ZAN C e ~CffN~1pc DULNISON LTD.

Geoffrey Thomas Glasson CALLINAN LAWRIE, 278 High Street, Kew, 3101, Victoria, Australia Invention Title: "IMPROVED CABLE COMPRESSION CONNECTOR" The following statement is a full description of this invention, including the best method of performing it known to me:- The present invention relates to cable connectors of the compression type used for connecting an electrical conductor to another part of an electrical circuit.

One of the major types of cable presently used for underground electricity distribution comprises a set of four multi-strand insulated conductors, each having across sectional shape approximately a 90 sector. These conductors are housed within a protective outer sheath to form a composite cable of substantially circular cross section. Various types of connectors are used to connect respective ends of the conductors to other parts of the distribution circuit.

However, these connectors have been found to be inadequate in several respects.

The most common type of known connector includes a flattened end portion incorporating one or more holes permitting the connector to be bolted to an adjacent electrical fitting. The other end of the connector incorporates a generally tubular sleeve into which the bare end of a conductor is inserted. In order to achieve the requisite electrical conductivity and mechanical engagement, the outer surface of the tubular sleeve is then compressed with a suitable tool so as to dcampingly engage the end of the conductor. In most such prior art connectors, the tubular sleeve is circular in internal cross section which requires the end of the conductor to be preformed into a corresponding circular cross sectional shape following removal of the insulation, to permit insertion into the connector. Special tools have been developed for this purpose. However, this operation nevertheless requires a considerable degree of skill and can be relatively difficult and time consuming in practice, particularly since it is usually required to be performed in a confined space, "uch as within an electrical distribuition turret or an underground pit. Moreover, it has been found that conductors which have been unsatisfactorily prepared in this way can lead to electrical or mechanical failure once the connector has been attached.

In an attempt to ameliorate this problem, an alternative type of connector was developed, in which the tubular sleeve is formed with a sector shaped cross sectional configuration corresponding closely in cross sectional size and shape to the conductor. This eliminated the need for a separate preforming -2 1 step but was, however, found to posses other significant inherent limitations. In practice, it is usually necessary for the flat portion of the connector to be disposed in a particular orientation to permit attachment to an adjacent electrical fitting.

However, the tubular sleeve can only be installed in one specific orientation, corresponding to the orientation of the associated conductor. This frequently requires the conductor to be subsequently twisted on its axis up to 180 which can be difficult to achieve in the restricted spaces where such connectors are normally used. Even more importantly, however, such twisting can cause damage to the conductor, or permit the individual strands to become loose within the connector, leading in turn to inefficient electrical conduction and inadequate mechanical engagement, particularly where a number of connectors are compactly housed within a junction box, for example.

It is therefore an object of the present invention to provide an improved cable connector, which overcomes or substantially ameliorates at least some of :l5 these disadvantages of the prior art.

Accordingly, the invention provides a cable connector of the compression type for use with an electrical cable comprising a set of conductors each having a cross sectional shape approximating a sector, said cable connector including a generally tubular sleeve adapted to receive an end of one of said conductors, and beingj.d-ated- fois-fl.. to an adjacent fitting thereby to connect said conductor to another part of an electrical circuit, said tubular sleeve defining a substantially regular polygon in internal cross section thereby to getingiy accommodate the end of said conductor in any selected one of a number of possible orientations corresponding to the number of sides of said polygon. In each such orientation, tfa respective radial faces of the conductor closely abut a corresponding pair of adjacent internal surfaces within the tubular sleeve, In the preferred embodiment, the connector is adapted for use with a cable having a set of four conductors, each conductor having a cross sectional shape approximating a 90' sector, and the tubular sleeve is generally square in internal cross section, thereby to nestingly accommodate the end of the conductor in any selected one of four orientations. Preferably, the side lengths of the -3polygon correspond substantially to the radial cross sectional dimensions of the conductor.

Preferably also, the conductor includes a flattened end portion disposed adjacent the tubular sleeve and incorporating one or more holes permitting the connector to be bolted to an adjacent complementary fitting.

After compression, the tubular sleeve is preferably hexagonal in external cross section and the conductor is preferably retained in intimate contact with the connector within the sleeve.

The conductors may be solid-core or multi-stranded, but are preferably of the multi-strand type.

A preferred embodiment 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 sectional view showing a typical insulated conductor forming part of a four core stranded sector type electrical cable; .45 Figure 2 is a side elevation view showing the conductor of Figure 1 ready for engagement with a suitable connector; Figure 3 is a series of views showing a typical prior art connector in which the tubular sleeve is circular in internal cross section; Figure 4 is a series of views similar to Figure 3, showing a second prior art connector in which the tubular sleeve is substantially sector-shaped in internal cross section; Figure 5 is a series of views showing a connector according to the present invention; Figure 6 is a cross sectional view of the connector of Figure 5 with the bare end of the conductor inserted into the tubular sleeve, prior to compression; and Figure 7 is a cross sectional view of the connector and conductor of Figure 6, following compression.

Referring firstly to Figures 1 and 2, the most common type of cable presently used for underground electricity distribution comprises a set of four multi-strand insulated conductors 1, each having a cross-sectional 3hape -4approximately a 90' sector. The four conductors are housed within a protective outer sheath (not shown) to form a composite cable (also not shown) of substantially circular cross section. Various connectors are used to connect the ends of the conductors to other parts of the distribution circuit.

Figure 3 shows a first type of prior art connector 4 incorporating a flattened end portion 5 having a series of holes 6 permitting the connector to be bolted to an adjacent electrical fitting. The other end of the connector 4 incorporates a generally tubular sleeve 7 into which the bare end of a conductor 1 is inserted. The outer surface of the sleeve is then compressed to dclampingly engage and retain the end of the conductor in a manner well known and understood by those skilled in the art. However, in this design, the tubular sleeve is circular in internal cross section, requiring the end of the sector-shaped conductor to be preformed into a complementary cross-sectional shape prior to insertion into the connector, as discussed above. This operation is difficult and time consuming to perform, and often results in subsequent failure of the connection.

Figure 4 shows another prior art device incorporating a tubular sleeve 7 having a complementary sector-shaped cross-sectional configuration e• corresponding closely to the shape of the conductor. As previously discussed, this arrangement frequently requires the conductor to be twisted on its axis up to 180", which is difficult to achieve in practice, and which can cause damage to the conductor as well as loosening of the connection.

Referring now to Figure 5, wherein corresponding features are denoted 4 by corresponding reference numerals, the present invention provides a connector 10 incorporating a flattened end portion 5 adapted for attachment to a complementary electrical fitting, and a generally tubular sleeve 7 adapted to receive the bare end of one of the conductors 1. In this configuration, however, the sleeve 7 is generally square in internal cross section. In this way, the sleeve is adapted to nestingly accommodate the end of the sector-shaped conductor in any selected one of four possible orientations in which the radial faces 11 (Figure 1) of the conductor respectively abut a corresponding pair of adjacent internal surfaces 12 within the tubular sleeve. In the case of a cable having other than four sectors, the sleeve can be appropriately formed to define in internal cross section a regular polygon having a corresponding number of vertices and sides. For example, a connector sleeve of pentagonal cross section can be used in conjunction with a complementary five sector cable.

With the conductor in place within the sleeve, for example as shown in Figure 6, the outer surface of the sleeve is compressed in the conventional manner into a substantially hexagonal shape whereby the conductor is clampingly engaged and firmly retained in intimate contact with the connector, as shown in Figure 7.

It will be appreciated that this configuration enables the conductor to be inserted into the connector in the position which most closely corresponds to the correct orientation required for the particular application. The flattened attachment end 5 of the connector can then be conveniently adjusted to the precise 4"15 orientation required with a maximum axial twist in the conductor of 45". This relatively small amount of twist can generally be accommodated with minimal difficulty, even in confined spaces, without damage to the conductor and without the tendency for the individual strands to work loose, following compression.

Thus, the present invention can be used without the need for a separate preforming step on the conductor, and without the need for excessive twisting of the conductor to achieve correct orientation, Unexpectedly, it has also been found that it is not necessary to orient the compression dies at any particular S angle relative to the conductor. Satisfactory compression and clamping engagement is obtained without any special skill or technique, with the compression dies in any orientation. The invention therefore represents a commercially significant improvement over the prior art.

Although the Invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, the invention is also applicable to cables having solid rather than multi-strand conductors.

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Claims (9)

1. A cable connector of the compression type for use with an electrical cable comprising a set of conductors each having a cross sectional shape approximating a sector, said cable connector including a generally tubular sleeve Ucx.- c\cx\te adapted to receive an end of one of said conductors, and beingadaF d fur aonnvreet# to an adjacent fitting thereby to connect said conductor to another part of an electrical circuit, said tubular sleeve defining a substantially regular polygon re-c-e-\ve. C.'r<s in internal cross section thereby to.iAestiny accommodate the end of said conductor in any selected one of a number of possible orientations corresponding to the number of sides of said polygon.

2. The cable connector of claim 1, wherein fe respective radial faces of the conductor closely abut a corresponding pair of adjacent internal surfaces within the tubular sleeve when said end of said conductor is inserted into said sleeve.

3. The cable connector of claim 1 or 2, wherein the connector is adapted for use with a cable having a set of four conductors, each conductor having a cross sectional shape approximating a 90' sector, and the tubular sleeve is generally square in internal cross section, thereby to tagl accommodate the C end of the conductor in any selected one of four orientations.

4. The cable connector of any one of the preceding claims, wherein the side lengths of the polygon correspond substantially to the radial cross sectional dimensions of the conductor. o:

5. The cable connector of any one of the preceding claims, wherein the conductor includes a flattened end portion disposed adjacent the tubular sleeve and incorporating one or more holes permitting the connector to be bolted to an adjacent complementary fitting.

6. The cable connector of claim 3, wherein after compression, the tubular sleeve is hexagonal in external cross section and the conductor is retained in intimate contact with the connector within the sleeve.

7. The cable connector of any one of the preceding claims, wherein the conductors are solid-core or multi-stranded. -7-

8. The cable connector of claim 1, wherein said tubular sleeve is generally pentagonal in internal cross section.

9. A cable connector substantially as hereinbefore described with reference to Figs 5, 6 and 7 of the accompanying drawings. DATED this 20th day of May 1992. .T.MIS N PTY. LTD..L..\ ThE MORQPSQ^CioClhu£ CORAA^ pk By their Patent Attorneys: CALLINAN LAWRIE S 0 6~ix 5 S. -8- 1 ABSTRACT The invention provides a cable connector (10) of the compression type for use with a set of conductors having a sector cross section shape. The connector (10) comprises a generally cylindrical sleeve which has a substantially regular polygon in internal cross section whereby the number of possible orientations of the conductors within the sleeve corresponds to the number of sides of the polygon. .oA a a o •o -9-