AU744118B2 - Electrical plug - Google Patents

Description

21/12/01 11:41 21/12/1 11:1 HEW SYDNEY 4 0262837999#1813NO49 04/9 NO.439 P004/019 TITLE: ELECTRICAL PLUG TECHNICAL FIELD The present invention relates to an electrical plug.

The invention has been primarily developed for medium to high voltage and/or medium to high current multi-core power supply cables such as those used in the underground mining industry and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to that partic ular field of use.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Known electrical plugs for power supply cables used in underground mines have generally included an axially extending cylindrical body which is configured at one end for insertion into a complimentary receptacle having a number of connector pins. The other end of the body is configured to receive a multi-core cable. Within the body the ends of' the cable cores are electrically connected to respective internal contacts which, in turn, selectively electrically engage with the connector pins within the receptacle.

As it is necessary to insulate the ends of the various cores in the multi-core cable from each other the body generally includes a one piece moulded insulator which surrounds the internal contacts and allows them to contact only a respective connector pin. An example of a known electrical plug is illustrated in Figures 1 and 2 and will be described below in more detail.

21/12/01 11:42 21'1201 1:42 SA SYDNEY 026283799914813NO49 P0/1 NO.439 P005/019 -2- The known plugs are particularly disadvantageous as they are heavy and the insulator is prone to damage and is difficult to replace without at the same time replacing all the internals of the body. In a mine environment where operating conditions are harsh the known plugs are particularly undesirable as they are expensive to maintain in safe working condition.

DISCLOSURE OF THE INVENTIQN It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

According to a first aspect of the invention there is provided an electrical cable coupling assembly including: a body having a first end configured for receiving a complementary coupling assembly and a second end configured for receiving an electrical cable having a plurality of cores; a plurality of conductive connectors each adapted to receive a corresponding one of the cares at one end and a corresponding conductive connector member associated with the complementary coupling assembly at the other end to allow electrical connection between the corresponding core and the corresponding connector member, and releasable electrical connection between the corresponding core and a corresponding core in the complementary coupling assembly; a plurality of substantially tubular insulators each captively retained at least partially in the body and at least partially enveloping a corresponding one of the connectors; 21/12/01 11:42 BSW SYDNEY 4 02628379994813 NO.439 P006/019 -3a first plate disposed at the first end of the body and coupled to the body and having a plurality of apertures each of which is in axial alignment with one of the insulators; and a second plate spaced from the first plate and disposed between the first and second ends of the body and coupled to the body and to the first plate and having a plurality of apertures each of which is in axial alignment with one of the insulators, each of the insulators being clamped at least partially between the first and second plates.

Preferably the coupling assembly further includes a coupling member extending and captively retained between the two plates.

Preferably the coupling member is a conductive phase barrier.

Preferably the coupling member is coupled to the two plates to selectively clamp each insulator at least partially in between the two plates.

Preferably each insulator is substantially cylindrical.

Preferably the insulators and connectors are substantially equally angularly spaced about a longitudinal axis of the coupling assembly.

Preferably each insulator is at least partially enveloped by a corresponding outer tubular insulator.

Preferably each insulator is separated from the corresponding outer insulator by an air gap.

Preferably each connector is metallic.

Preferably each insulator includes a plastics sleeve.

According to a second aspect of the present invention there is provided an electrical cable coupling assembly comprising: 21/12/01 11:42 BSW SYDNEY 4 0262837999#813 NO.439 P007/019 -4a body having a first end configured for receiving a complementary coupling assembly and a second end configured for receiving an electrical cable having a plurality of cores; a plurality of conductive connectors each adapted to receive a corresponding one of the cores at one end and a corresponding conductive connector member associated with the complementary coupling assembly at the other end to allow electrical connection between the corresponding core and the corresponding connector member, and releasable electrical connection between the corresponding core and a corresponding core in the complementary coupling assembly; a plurality of substantially tubular insulators each captively retained at least partially in the body and at least partially enveloping a corresponding one of the connectors; and two captive fittings coupled to the body and captively retaining each insulator, each fitting including an aperture in axial alignment with a corresponding one of the insulators located at least partially in between the two fittings, the two fittings being coupled to each other to selectively locate and clams each insulator at least partially between the two fittings, each fitting including a solid conductive core and each aperture being defined by an axially extending passage in the conductive core through which the corresponding insulator at least partially extends.

Preferably at least one of the conductive cores is generally cylindrical.

Preferably at least one of the conductive cores is earthed.

Preferably at least one of the conductive cores is metallic.

21/12/01 11:42 21/1201 1142 W SYDNEY 0262837999#813N.49P8/1 NO.439 Pooe/oig Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

BRIEF DESCRIPTION OF THE DRAWINGS Some preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure I is an end view of a known electrical plug; Figure 2 is a cross section taken along line 2-2 of Figure 1; Figure 3 is an end view of an electrical plug according to the invention; Figure 4 is a cross section taken along line 4-4 of figure 3; Figure 5 is an end view of an alternative electrical plug according to the invention; Figure 6 is a cross section taken along line 6-6 of Figure Figure 7 is an exploded cross sectional view of the plug of Figure 6; Figure 8 is an end view of another electrical plug according to the invention; Figure 9 is a cross section taken along line 9-9 of Figure 8; and Figure 10 is a cross sectional view of an adaptor for the plug of Figure 8; Figure I I is an exploded cross sectional view of the plug of Figure 9.

MODES FOR CARRYIN OUT THE INVENTION Reference is made to the prior art electrical plug I of Figures I and 2. The plug includes a generally cylindrical body 2 extending between a first end 3 and a second end 4 which are configured respectively for insertion into a corresponding receptacle WO 98115037 PCT/AU97/00651 (not shown) and receiving a multi-core electrical cable (not shown). As is well known to those in the art, multi-core cables generally include three equally spaced apart medium or high voltage mains conductors and one or more pilot cores for carrying communication signals. Body 2 includes a single piece moulded interior insulator which extends from end 3 and terminates at end 6, which lies intermediate ends 3 and 4. Insulator 5 surrounds two differently sized sets of three connectors 7 and 8 which, at one end, receive the cores of the cable and, at the other end, receive the connector pins that are located within the receptacle. Accordingly, electrical connection is selectively provided between the cores in the cable and the connector pins within the receptacle. One such receptacle is described and illustrated in Australian Patent Application No. 21600/95, the disclosure of which is incorporated herein by way of cross reference.

The end of the cable is received in an aperture 9 at end 4 of body 2 and subsequently secured by clamping means 10. The cores of the cable are separated in internal chamber 11 and inserted into respective cylindrical bores 12 in insulators and secured to connectors 7 or 8, as appropriate.

Connectors 7 and 8 each include at one end a thimble 13 for receiving the free end of a respective cable core, as is known to those skilled in the art. The end of the core is soldered or otherwise connected to thimble 13. Each connector also includes, at its other end, a socket 14 for receiving a respective connector pin located within the receptacle. That is, the connector pins are received into engagement with respective sockets 14 when plug 1 is inserted into the receptacle. The respective pairs of thimble 13 and contact 14 are maintained in abutting electrical engagement by bolts WO 98/15037 PCT/AU97/00651 -6- Insulator 5 also encases a phase barrier 16 which is a centrally located metal structure having three legs which extend radially outwardly between adjacent mains conductors. Barrier 16 is earthed via lead 17 and reduces the risk of phase to phase faults. In alternative embodiments barrier 16 includes a different number of legs.

Referring now to Figures 3 and 4, there is illustrated an electrical plug 21 according to the invention. The features of plug 21 which correspond with those of plug 1 are denoted by corresponding reference numerals.

Plug 21 includes six equally angularly spaced axially extending tubular insulators 22 which, best shown in Figure 4, have a central internal annular ridge 23 against which thimble 13 and socket 14 are collectively secured by the operation of bolt 15. It will be appreciated that thimble 13 and socket 14 provide the same function as described above with respect to prior art plug 1.

Although in this embodiment insulators 22 are made from polyester, other insulating materials are used in other embodiments, for example, rubber, reinforced resin or ceramics. Moreover, in very high voltage applications each insulator 22 extends within a co-axially disposed additional insulator (not shown) to ensure greater electrical isolation between the cores and connectors 7 and 8. Preferably, the internal diameter of the additional insulator is sufficiently greater than the external diameter of insulator 22 to provide an air gap therebetween.

Each insulator 22 includes at opposed ends annular shoulders 25 and 26 for abutting a complementary formation to retain the insulators in a fixed configuration with respect to body 2. At end 3 of body 2, that complementary formation is defined by the combination of a circular apertured plate 27 and an annular lip 28 which WO 98/15037 PCT/AU97/00651 -7inwardly extends from end 3. Plate 27 includes a plurality of apertures which receive the ends of insulator 22, whereby plate 27 abuts against shoulder At the other end of insulators 22, the complementary formation is defined by a circular plate 29 which includes apertures corresponding to those in plate 27. These apertures in plate 27 interact similarly with shoulders 26 of the insulators.

Both plates 27 and 29 are secured to body 2 by way of circumferentially spaced rivets 30. Moreover, these plates are structural members and provide additional strength to plug 21 and, accordingly, increase the useful lifetime of the product.

Moreover, plug 21 provides this additional strength while being lighter than the prior art plug 1.

In this embodiment barrier 16 is also a structural member being engaged at opposed ends 31 and 32 by respective plates 27 and 29. The plates are forced toward each other and into clamping engagement with insulators 22 by the action of bolts 33 which are threadedly engaged within complimentary bores in barrier 16.

In other embodiments only the cores in the cable carrying supply voltages are within insulators 22, the pilot lines being of sufficiently low voltage that the intermediate air gap is adequate to prevent arcing therebetween.

In some embodiments, once the cable is installed within cavity 11, that cavity is filled with an expandable compound via a filling aperture (not shown). The compound stress relieves the cable termination and reduces the possibility of water ingress from outside the cable and plug, or through water entrapment within the cable (a function of the cable manufacturing process).

I i -1, WO 98/15037 PCT/AU97/00651 -8- Plate 27 is produced from a metal or hard plastics material and, accordingly, is resistant to damage from inadvertent contact with other objects. In the event plate 27 is damaged it can be easily replaced.

Reference is now made to an alternative electrical plug 41 according to the invention which is illustrated in Figures 5, 6 and 7. Where appropriate corresponding features have been denoted by corresponding reference numerals. More particularly, plug 41 includes a body 2 which extends between a first end 3 and a second end 4.

These ends 3 and 4 are respectively configured for engagement with a complementary electrical plug (not shown) and receiving an electrical cable (not shown) having four cores. Plug 41 also includes four spaced apart connectors 42 for receiving at respective first ends 43 the cores and at respective second ends 44 a connector formation associated with the complementary plug to allow releasable electrical connection between the cores and the connector formations. Four insulating sheaths extend about respective connectors 42 for electrically isolating connectors 42 from each other.

Connectors 42 are metallic and, as plug 41 is intended for low to medium voltage applications, sheaths 45 are plastics sleeves. In higher voltage applications, sheaths 45 are defined by a layer of ceramic material which is deposited on the outside of connectors 42. This arrangement effectively eliminates any air gap between the connectors 42 and the respective surrounding insulating sheaths 45 and thereby prevents corona discharge about those connectors.

Body 2 includes a generally cylindrical solid conductive nose cone 46 which extends along an axis 47 and which has four spaced apart parallel axially extending i c- WO 98/15037 PCT/AU97/00651 -9passages through which sheaths 45 extend. In this embodiment cone 46 is both metallic and earthed. Accordingly, cone 46 functions not only as a mechanical support for plug 41 but also as a phase barrier.

Cone 46 includes, at one end, shoulders 48 which extend across the periphery of the adjacent passages to provide an abutment for one end of sheaths 45. Cone 46 also includes, at its other end, a removable end cap 49 which also extends across the periphery of the passages to provide an abutment for the other ends of sheaths 45. The combination of shoulders 48 and cap 49 captively retains sheaths 45 within cone 46.

In this embodiment, cap 49 is retained to cone 46 by a bolt 50 which is offset from the passages. In other embodiments different attachment means are used.

Body 2 includes a hollow cylindrical housing 51 which extends along axis 47 between a first end 52 and a second end 53 which are respectively threaded internally and externally. End 52 also includes an abutment formation 55 for receiving a coupling nut 56. Moreover, cone 46 includes an abutment formation 57 and an external thread 58. When thread 58 is engaged with end 52, as shown in Figure 6, nut 56 is captively retained between formations 55 and 57 for rotation about axis 47. Nut 56 includes an internal thread 59 for selectively engaging with a complementary thread of the electrical plug or receptacle.

End 53 is received within the complementary internally threaded end 65 of a backnut 66. Sandwiched between end 53 and backnut 66 is a rubber grommet 67 and a washer 68. As will be appreciated by those skilled in the art, as the threaded engagement between backnut 66 and end 53 is increased, grommet 67 is compressed WO 98/15037 PCTAU97/00651 and therefore moves into a more intimate sealing and clamping engagement with the cable extending into housing 51.

Another electrical plug 71 according to the invention is illustrated in Figures 8 to 11 where, for convenience, corresponding features are denoted by corresponding reference numerals. In this embodiment plug 71 includes connectors 72 having four spaced apart axially extending pins 73 for engaging within complementary apertures of an adjacent plug, such as plug 41. Connectors 72 are housed within sheaths 45 and, as such, are insulated from each other. Moreover, the connector and sheath combinations are located within respective axial passages of a generally cylindrical conductive former 75. Former 75 is threaded to a tubular first and second body portions 76 and 77 and functions similarly to nose cone 49.

Plug 71 also includes a second tubular body portion 81 which extends between a Sfirst end 82 and an axially spaced apart second end 83. End 83 is, in use, captively engaged with a respective backnut 84, washer 85 and grommet 86, similarly to end 53 of housing 51.

Former 75 includes a shoulder 91 adjacent one end, and an end cap 92 adjacent the other end, for providing opposed abutments for sheaths 45. These abutments retain sheaths 45 and connectors 42 within the passages in former Preferably, cone 46 and former 75 are cast from copper and machined to include the respective passages.

A plug produced in accordance with the preferred embodiments of the invention offers a more durable and cost effective product which provides the necessary WO 98/15037 PCT/AU97/00651 -11insulation between the cores at a weight significantly less than corresponding prior art plugs. By way of example, plug 21 is approximately 20% lighter than prior art plug 1.

Although the invention has been described with reference to a particular example it will be appreciated by those skilled in the art that it may be embodied in many other forms.

I

Claims (15)

1. 2. The coupling assembly according to claim I further including a coupling member extending and captively retained between the two plates. ,i/ld/Ui 11:45 tJW bYUNLY U b^S(5Ya 9Ulj NU.439 P010/019 -13-
2. 3. The coupling assembly according to claim 2 wherein the coupling member is a conductive phase barrier,
3. 4. The coupling assembly according to claim 2 wherein the coupling member is coupled to the two plates to selectively clamp each insulator at least partially in between the two plates. The coupling assembly according to claim I wherein each insulator is substantially cylindrical.
4. 6. The coupling assembly according to claim 1 wherein the insulators and connectors are substantially equally angularly spaced about a longitudinal axis of the coupling assembly.
5. 7. The coupling assembly according to claim 1 wherein each insulator is at least partially enveloped by a corresponding outer tubular insulator.
6. 8. The coupling assembly according to claim 7 wherein each insulator is separated from the corresponding outer insulator by an air gap.
7. 9. The coupling assembly according to claim 1 wherein each connector is metallic. The coupling assembly according to claim 8 wherein each insulator includes a plastics sleeve.
8. 11. An electrical cable coupling assembly comprising: a body having a first end configured for receiving a complementary coupling assembly and a second end configured for receiving an electrical cable having a plurality of cores; a plurality of conductive connectors each adapted to receive a corresponding one of the cores at one end and a corresponding conductive connector member associated I di/±I/ui 11:'43 =W ZTUNtLT -t dbdUS(aaIrdij NU.qsj t-t11/U1th -14- with the complementary coupling assembly at the other end to allow electrical connection between the corresponding core and the corresponding connector member, and releasable electrical connection between the corresponding core and a corresponding core in the complementary coupling assembly; a plurality of substantially tubular insulators each captively retained at least partially in the body and at least partially enveloping a corresponding one of the connectors; and two captive fittings coupled to the body and captively retaining each insulator, each fitting including an aperture in axial alignment with a corresponding one of the insulators located at least partially in between the two fittings, the two fittings being coupled to each other to selectively locate and clams each insulator at least partially between the two fittings, each fitting including a solid conductive core and each aperture being defined by an axially extending passage in the conductive core through which the corresponding insulator at least partially extends.
9. 12. The coupling assembly according to claim 11 wherein at least one of the conductive cores is generally cylindrical.
10. 13. The coupling assembly according to claim 11 wherein at least one of the conductive cores is earthed.
11. 14. The coupling assembly according to claim 11 wherein at least one of the conductive cores is metallic. The coupling assembly according to claim I wherein each insulator includes a shoulder at each of its ends which abuts against one of the plates to restrain the insulator. dl/l/Ul 11:45 bSbW bYUN-Y k)b~.BSyt 31J NU.439 P012/U1:9
12. 16. The coupling assembly according to claim I wherein each plate is detachably secured to the body.
13. 17. The coupling assembly according to claim 1 wherein the first plate closes off an end of the body.
14. 18. The coupling assembly according to claim I wherein each of the insulators is spaced from an interior of the body by an air gap,
15. 19. The coupling assembly according to claim 3 wherein the plates abut against the phase barrier. An electrical cable coupling assembly substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. DATED this 21 st Day of December, 2001 METAL MANUFACTURES LIMITED Attorney: RUSSELL J. DAVIES Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS