AU697575B2 - Plug/connector moulding system - Google Patents

Description

Plug/Connector Moulding System Field of the Invention The following invention relates to electrical connectors suitable for connecting cables which conduct heavy current, typically from 30 through to 1,000 amps and for voltages from 30 through to 11,000 volts.

Known connectors of the above capacity are often adapted for use in hazardous areas such as underground coal mines, oil refineries, grain handling facilities and other associated industries wherever explosive or flammable gas may occur. Such devices, apart from aiming to prevent dangerous sparks, also aim at isolating the electrical components therein from moisture, high humidity or a corrosive atmosphere.

Known connectors, whether useable in single phase or multiple phase circuitry and incorporating possibly earthing, neutral or signalling type circuitry suffer numerous disadvantages.

For example, the housings for known coupling members are cast in metal such as brass, bronze or cast iron and are expensive to produce. Furthermore, air or gas cavities remain within the housing, thus providing a risk of internal gas explosion. Furthermore, moisture may ingress to the internal cavity of such plugs through the joints, seals and grommets employed in the external casing.

6 Furthermore, there is a risk of shock to personnel using the connectors.

A further problem of such known connectors is their heavy weight, thus rendering the same cumbersome and impractical. Also, the working life of known connectors is short due to wear and tear of the contact pins or sockets.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate at least one or more of the above disadvantages and/or more generally to provide an improved plug/connector and to provide a moulding system by which such an improved S" connector may be manufactured.

S0:, Disclosure of the Invention There is disclosed herein an electrical connector suitable for connecting cables which conduct heavy current, from 30 through 1000 amps, comprising: a plurality of insulated electrical conductors encased by sheathing and each i having a thimble secured to one end thereof and a pin secured to each thimble, and a single molded dielectric casing surrounding a portion of all of the conductors, surrounding the thimbles, and surrounding the pins, which pins do not protrude from said casing, the casing leaving said end of the pin presented for connection to a mating I' fitting.......

[N:\LIBLL]00015:KEH end thereof.

Preferably, three or more said insulated conductors, each conductor having a pin removably secured to one end thereof.

Preferably, a plurality of said insulated electrical conductors within said molded dielectric casing, each conductor having a respective said thimble secured thereto, each thimble having a pin secured thereto.

Preferably, said casing has a front face with which said end of the pin is flush.

Preferably, said end of the pin is recessed into said casing.

Preferably, the respective pins are secured to the respective thimbles by means of a threaded fastener.

There is further disclosed herein a method of manufacturing the above disclosed electrical connector, the method comprising the steps of: providing a mold cavity, attaching a thimble to a respective free end of one of said insulated electrical conductors, providing a jig adapted to fit within the mold cavity to locate the respective thimbles, C attaching the respective thimbles to the jig, placing the jig within the mold cavity, and injecting or pouring a liquid dielectric material around the conductors and thimbles, allowing the dielectric material to set, removing the molded plug from the mold cavity, and removing the jig from the moulded plug, and connecting one of said pins to each encased thimble.

T' Definition "Thimble" as used herein is intended to mean any form of electrical contact element to be secured to a conductor of a cable within the casing of a connector and having for example a threaded end or other means for the receipt of the butt end of an electrical contact pin. A "thimble" may also be a contact pin itself.

Pin" as used herein is intended to mean any form of removable electrical contact element adapted to be fastened to a thimble or directly to a conductor of a cable. A pin may comprise a solid projection, a hollow tube having a recess therein for the receipt of a projection of a mating fitting, or a tab or the like. il aIJI N:\LIBLL]00015:KEH 3 Brief Description of the Drawings A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic perspective view of an end portion of a three wire industrial cable, Fig. 2 is a schematic perspective view of a thimble attached to one wire core, Fig. 3 is a schematic perspective view of the end of a cable having a thimble attached to each wire core, Fig. 4 is a schematic perspective view of one half of a mould cavity, the other half being a mnirror image, though possibly including an injection port, Fig. 5 is a schematic perspective view of a jig section for attachment to the thimbles on the end of the prepared cable of Fig. 3, Fig. 6 is a schematic perspective view of a finished moulded plug, and Fig. 7 ;s a schematic perspective cut-away view of another finished moulded plug.

Description of the Preferred Form of the Invent. n Referring initially to Fig. 1, there is schematically depicted the end of a three wire industrial cable 10. Cable 10 comprises an outer sheath 23 encasing three individual wire cores 13 each insulated by sheathing 11. Supporting the three individual cores 13 within the outer sheathing 23 is some supportive dielectric material.

Referring now to Fig. 2, one of the individual conductive cores 13 is shown attached to a conductive thimble 12. Core 13 might be soldered or otherwise crimped or electrically connected to the thimble 12. Thimble 12 comprises an internally threaded aperture 22 at its remote end.

Fig. 3 depicts the industrial cable 10 having three individual thimbles 12 attached to respective wire cores.

Assembly of the above prepared cable might be undertaken in a cable manufacturing workshop, with the cable ends beig prepared and fitted with the metallic thimbles 12 according to the required current and voltage applications.

Referring now to Fig. 5, a jig 18 is depicted. Jig 18 formed of heat resistant material, typically bronze or the like is provided with three parallel apertures 19, each adapted to receive oaie of three longitudinal bolts 20. That is, bolts 20 extend through the apertures 19 such that their threaded ends penetrate through to the other side of the jig 18. These threaded ends are adapted to engage with the internal thread 22 in each thimble 12. Once threadingly engaged, the cable end is ready for having a dielectric casing moulded therearound.

With reference to Fig. 4, one half of a mould cavity is depicted. This being the bottom half, the top half would be a mirror image adapted to be placed on top of the bottom half. Of course, however, some means of injection such as a radial port or ports I[N:\LIBLL]00015:dss S C. S

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4 might be provided in either mnould. half. The mould cavity 14 comprises a first small aperture 16 of a similar diameter to that of cable 10. The other end of the mould cavity comprises an annular recess 17 adapted to tightly receive the jig 18.

That is, with the jig 18 affixed to the end of the individual cores 11 via thimbles 12, both the jig 18 and cable assembly including outer sheath 10 is placed within the mould cavity. The upper half of mould cavity (not shown) is then placed upon so as to encase the various components.

The internal cavity is then injection moulded or gravity fed with insulative plastics material which would completely surround the cable ends and majority of the thimbles 12. In this regard, it should be appreciated that during moulding, the ends of the thimbles 12 would be flush against the rear face of the jig 18 such that upon removing the moulded plug from the cavity 15, the free ends of the thimbles 12 remain exposed for the threaded connection thereto of electrical contact pieces (not shown).

For workshop or factory production, the following can be taken as more specific steps in the method of producing an electrical connector: Firstly, the end of the cable 10 is prepared according to its type and number of conduct, etc. This preparation would involve the removal of some outer sheath, removal of some dielectric or insulation from each core or conductor.

Then suitable thimbles are fitted to each conductor of the cable.

The thimbles and other hardware is then placed and secured by suitable means to the jig fixture 18 assembly so designed to accurately hold and align the cable cores and conductors in correct alignment and position for the type of plug/connector to be moulded.

IThe cable end and the jig assembly is then located in a hollow moulding 14 or die box.

The hollow tool or die box 14 is then injected and filled with suitable moulding material. Beneficially, this material should be compatible with the material used in the manufacture of the cable itself, and also suitable for the work type and area in which the finished cable and plug combination are to be used.

The moulded plug/connector is then cured or vulcanised or allowed to sit according to the requirements of the material.

.The cable and newly moulded plug may then be removed from the moulding box 14 and the jig assembly 18 may then be removed. The finished article may then be checked and tested.

A connector may also be manufactured in the field or on location.

For example, whilst the above disclosed method steps for workshop or factory prodiction are generally applicable for manufacture in field use or on location, the moulding tool or die box 14 may be lighter and more portable, being constructed for ,example with fibreglass. Furthermore the plastics material to be injected into the [N:\LIBLL]00015:dss

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C 4so 4.6 4 4 O t moulding box 14 may be of a self-curing nature and may be poured or pumped into the cavity Fig. 6 shows a finished plug 21. The plastics material used in moulding the plug 21 is typically rubber or neoprene or an alternative type of electrically non-conductive material.

It should be appreciated that whilst the purpose of the jig 18 and bolts 20 is to accurately position the thimbles 12 within the mould cavity, other means of positioning the thimbles might be adopted. For example, a plastics frame might be adopted which supports the thimbles 12 within the mould cavity, which plastics frame would remain integrally encased within the plug 21.

The molten or liquid material applied to the mould might either be pumped or simply poured into the cavity 15. Neoprene for example might be heated to a molten state prior to being pumped or poured into the cavity, whereas an epoxy resin or the like in liquid form, prior to setting may be pumped or poured into the cavity To facilitate maintenance of the finished plug 21, worn or damaged electrical contact pins threadedly connected to the thimbles may be individually removed and replaced, thus prolonging the working life of the plug. For example, and as depicted in Fig. 7, a replaceable electrical contact pin 24 is removably connected to the thimble 12.

Contact pin 24 may be hollow tubular piece being connected by a bolt 23 to the thimble 12. Contact pin 24 as shown may be recessed into the moulded plug 21. Alternatively, the pin, or thimble, may be flush with the front face of plug 21 or may protrude therefrom. In this embodiment, the distal end of the contact pin 24 does not extend to the extremity of the plug body. Pin 24 is recessed into the plug body to prevent inadvertent contact with other bodies and subsequent shorting.

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond. the scope of the present invention. For example, a mating fitting having recessed electrical contact pieces might similarly be formed. Furthermore, where mating fittings require bolted interconnection, a metal end face or plate having longitudinally extending bolt holes might be integrally moulded with the plug.

Furthermore, typically for underground mining cables, the plastics material adopted might be neoprene, though any other suitable moulding material may be adopted for various applications.

Where a thimble other than the type of thimble 12 depicted in the drawings is to be incorporated into a moulded plug, some other means of fastening the same to the jig 18 might be adopted. For example, where female thimbles are to be moulded into the plug, such might, not necessarily be provided with internal thread capable of being engaged by bolts 20. To this end, special bolts having smooth protrusions capable of interference fit engagement with the female thimbles might be passed through the apertures 19,in jig' 18.

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Claims (8)

1. An electrical connector suitable for connecting cables which conduct heavy current, from 30 through 1000 amps, comprising: a plurality of insulated electrical conductors encased by sheathing and each having a thimble secured to one end thereof and a pin secured to each thimble, and a single molded dielectric casing surrounding a portion of all of the conductors, surrounding the thimbles, and surrounding the pins, which pins do not protrude from said casing, the casing leaving said end of the pin presented for connection to a mating fitting.

2. The electrical connector of claim 1 wherein each conductor has a respective said pin removably secured to one end thereof.

3. The electrical connector of claim 1 comprising three or more said insulated conductors, each conductor having a pin removably secured to one end thereof.

4. The electrical connector of claim 1 comprising a plurality of said insulated electrical conductors within said molded dielectric casing, each conductor having a respective said thimble secured thereto, each thimble having a pin secured thereto. The electrical connector of claim 1, wherein said casing has a front face cct with which said end of the pin is flush. CI* C6. The electrical connector of claim 1, wherein said end of the pin is o, c recessed into said casing.

7. The electrical connector of any one of the preceding claims wherein the o t' respective pins are secured to the respective thimbles by means of a threaded fastener.

8. A method of manufacturing the electrical connector of claim 1, the |i method comprising the steps of: providing a mould cavity, attaching a thimble to a respective free end of one of said insulated electrical conductors, providing a jig adapted to fit within the mould cavity to locate the respective a thimbles, attaching the respective thimbles to the jig, a placing the jig within the mould cavity, and injecting or pouring a liquid dielectric material around the conductors and o: thimbles, a ,allowing the dielectric material to set, i. removing the molded plug from the mould cavity, removing the jig from the moulded plug, and connecting one of said pins to each encased thimble.

9. An electrical connector substantially as hereinbefore described with reference to the accompanying drawings. i 4 [N:LBLL]00015:EH .a [N:\LIBLL] l15:Ki!H i A method of manufacturing an electrical connector, the method being substantially as hereinbefore described with reference to the accompanying drawings.

11. An electrical connector produced by the method of claim Dated 24 August, 1998 L.D. A.D. Macey P/L Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON a cc V tc C C V C V (C V( V V V V C IV t~ t -t C ICC V ~VVV~ V V V V C C CCIC V to V V IC V V CV V V o CC Vt C V.14 C II V 4 1 4I [N:\LEBLL]00015.:KEH I Plug/Connector Moulding System Abstract An electrical connector comprises at least one insulated conductor (11) having a thimble (12) removably secured to one end thereof. A moulded dielectric casing (21) surrounds the conductor leaving the thimble presented for connection to a mating fitting. In manufacture of the connector, the thimbles (12) are aligned by contact with screws passing through a jig The jig and the aligned thimbles to which the electrical conductors are affixed is then placed within a mould cavity (16) and a dielectric material is injected or poured into the cavity about the thimbles and conductors and allowed to set. t. r~C IL I 9 9 *4 Il ii 91 9 II *r C VrII ftlt~ ,i i 1 ii i I r _:I