GB2299716A

GB2299716A - Non-rewirable plug

Info

Publication number: GB2299716A
Application number: GB9507083A
Authority: GB
Inventors: Chi-Wing Fok
Original assignee: On Tat Bakelite Electric Works Ltd
Current assignee: On Tat Bakelite Electric Works Ltd
Priority date: 1995-04-05
Filing date: 1995-04-05
Publication date: 1996-10-09
Also published as: GB9507083D0

Abstract

A 3-pin electrical plug and power cord assembly comprises moulded top and bottom plug elements 72 and 10 permanently securable together after the wire ends of the power cord 30 have been permanently secured by rivetting to respective electrical terminals in the bottom plug element. The bottom plug element includes apertures for receiving the connector pins and fuse retainer terminals to which respective wire ends are rivetted. The bottom plug element 10 also includes bores 32 within which cooperating spigots 78 on the top plug element 72 are receivable and fuseable to retain the plug elements permanently secured together.

Description

ELECTRICAL PLUG AND POWER CORD ASSEMBLY This invention relates to an electrical plug for permanent connection with an end of an electric power cord and to an assembly of such a plug and power cord and to a method of manufacturing same.

There is an increasing and often statutory requirement for domestic electrical items such as for example vacuum cleaners, toasters, heaters, televisions etc. to be fitted with an electrical plug before the item is supplied to the end user. Although it is the practice in some territories for the retailer to fit a detachable plug to the power cord before supply of the item in question to the user, it is becoming more common for the power cord to be fitted with a non-detachable plug during manufacture or assembly of the item. The item is thus supplied from the manufacturer to the end user ready for immediate connection to a power source and the end user cannot readily interfere with the electrical connections in the plug.

One means of establishing a permanent assembly of plug and power cord is to mould at least part of the plug in situ about the electrical connector pins (i.e. the pins which engage in a power socket) or about a sub-assembly containing such pins, after the wires of the power cord have been electrically connected to the pins. Plugs of the type used for example in North America and continental Europe are relatively small and usually comprise only live and neutral electrical connections with the longitudinal axes of the connector pins being parallel to the axis of the power cord.To produce such a plug and power cord assembly, the wires of the power cord are electrically connected to inner ends of the respective connector pins and a plug body is then moulded about the inner ends of the pins and their electrical connections with the power cord to leave the outer ends of the pins projecting parallel to one another out of the end of the moulded body. In the United Kingdom and certain other territories it is common practice to use a relatively large plug having live, neutral and ground connector pins all of which project from the plug body parallel to one another but normal to the longitudinal axis of the power cord.A plug and power cord assembly of this type is described in GB-A-1581661 wherein a 3-wire power cord has its wires connected to respective connector pins in a sub-assembly, a plastic sheath being located over at least the electrical connections in the sub-assembly, and a plug body being moulded about the subassembly and sheath.

It is an object to the present invention to provide a new and improved electrical plug for permanent connection with a power cord, an assembly of such a plug and power cord and a method of manufacturing same.

In accordance with the invention there is provided an electrical plug for permanent connection with a power cord comprising moulded top and bottom plug elements securable together to form said plug, said bottom plug element having two or more apertures therein for the reception of electrical connector pins for engagement in a plug socket, said bottom plug element having a recess in an outer face thereof for the reception of a fuse element, said outer face comprising the, in-use, face of the plug from which said connector pins project, said plug elements having mutually co-operating formations permanently engageable with one another to secure said plug elements together.

Also in accordance with the invention there is provided an electrical plug and power cord assembly in permanent connection with one another comprising a plug formed from moulded top and bottom plug elements permanently secured together to form said plug, said bottom plug element including two or more apertures through which electrical connector pins project from an outer face of said element for engagement in a plug socket, a recess being provided in said outer face of the bottom plug element containing a fuse element electrically connected between two fuse retainers in said recess, a power cord having a pair of wires non-detachably secured to a respective terminal on one of said connector pins and to one of said fuse retainers, said power cord extending out of said plug through an aperture provided between said top and bottom plug elements.

The invention also provides a method of manufacturing an electrical plug and power cord assembly as described in the preceding paragraph comprising the steps of forming said top and bottom plug elements by moulding, installing electrical connector pins and fuse retainers in said apertures and in said recess respectively, installing an electrical connection between one of said fuse retainers and one of said connector pins, non-detachably securing wires of the power cord to respective electrical terminals of the other electrical connector pin and the other fuse retainer, assembling the top and bottom plug elements together with mutually co-operating formations on said elements in engagement with one another with the power cord extending out of an aperture provided between the assembled top and bottom plug elements, and treating said cooperating formations to cause them to remain in permanent engagement with one another thereby to retain the plug elements in permanent assembly with one another on said power cord.

The said mutually co-operating formations on the top and bottom plug elements are conveniently fuseable one with another to secure said plug elements together and conveniently comprise spigot and socket formations provided on respective ones of said plug elements.

Preferably each of said fuse retainers extends through the base of said recess providing an electrical terminal within the plug, one of said terminals having a said wire nondetachably secured thereto and the other said terminal being permanently electrically connected to the other of said connector pins. All of the said non-detachable electrical connections are conveniently provided by rivetting. The said electrical connection between said other terminal and said other connector pin conveniently comprises a rigid electrically conductive strap connected by rivetting.

The electrical plug and power cord assembly of the invention finds particularly advantageous application in the aforesaid 3-wire power systems of the United Kingdom and certain other territories. Thus an electrical plug and power cord assembly for use with such a 3-wire system may have three said connector pins received within three respective apertures in the bottom plug element comprising live, neutral and ground connector pins, with the power cord comprising live, neutral and ground wires, the live wire being connected to one of the fuse retainer terminals, the neutral wire being connected directly to the neutral connector pin and the ground wire being connected directly to the ground connector pin.

Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawings wherein Figure 1 is a top plan view of the inside of the bottom plug element in its as-moulded condition; Figure 2 is a similar top plan view to that of Figure 1 but with the ends of the power cord shown connected to the respective terminals; Figure 3 is a perspective view showing the bottom plug element and connected power cord of Figure 2 adjacent to the top plug element prior to the securing together of the two elements; Figure 4 is an underneath plan view of the assembled top and bottom plug elements and power cord with the fuse element removed to show the fuse retainers; Figure 5 is a perspective view from the outer face of the assembled plug and power cord with the fuse element installed;; and Figure 6 is a perspective view from the top of the assembled plug and power cord.

The embodiment described and illustrated herein by way of example is with reference to the production of an electrical plug and power cord assembly for use in a 3-wire electrical system having the so called "square pin" power sockets of the type utilized in the United Kingdom and certain other territories. In such systems it is usual for the electrical plug to be provided with a replaceable fuse element of the cartridge type, the power rating of the fuse element usually being from 3 amps to 13 amps dependent upon the item with which it is used.

Referring particularly to Figures 1 to 3 of the drawings, the as-moulded bottom plug element 10 includes three apertures 12, 14, 16 within which are receivable respectively live, neutral and ground connector pins 18, 20, 22 for engagement with a power socket. The plug element 10 includes a boundary wall 24 of uniform height throughout except at a rear end thereof where it is provided with a semi circular recess 26 for the reception of a protective collar 28 adjacent the end of a power cord 30 to be connected electrically to the bottom plug element 10. A base portion of the element 10 includes four bushes providing through bores 32 of an axial height approximating the height of the boundary wall 24.A pair of opposed flexible cord grips 34 are moulded integral with the bottom plug element 10 conveniently in a manner substantially as described in GB-A-2280551 the contents of which are incorporated herein by reference.

The bottom plug element 10 is also formed with a platform 36 having a height extending above that of the boundary wall 24 and being provided at each of its ends with respective through apertures 38 and 40. The top of the platform 36 as viewed in Figure 1 provides the base of a recess 42 formed in the outer planar face 44 of the plug element 10 which is visible more clearly in Figure 4 of the drawings.

With respect to the orientation of the bottom plug element shown in Figure 1, the left hand aperture 38 in the platform 36 is provided with a guide channel 46 and the right hand aperture 40 has a guide wall 48 moulded therearound.

In Figure 2 of the drawings, the electrical connector pins 18, 20, 22 are shown installed in their respective apertures 12, 16 and 18 and the ends of the wires of the power cord are shown connected to respective electrical connections. The inner end of each connector pin is provided with a terminal portion which is connected by rivetting to respective apertured electrical connectors.

Thus the neutral connector pin 18 is connected directly by rivetting to a ring connector 50 crimped to the end of the neutral wire 52 of the power cord. Similarly, the earth connector pin 22 is connected by rivetting to a ring connector 54 at the end of the earth wire 56 of the power cord.

Within the two apertures 38 and 40 in the platform 26, there are installed terminals 58 and 60 having respective fuse retainer clips 62 and 64 within the recess 42 (see Figure 4), said terminals being for connection respectively to the live connector pin 20 and the live wire 66 of the power cord. The electrical connection between the live connector pin 20 and the fuse retainer clip 60 comprises a rigid electrically conductive strap 68 riveted at each of its ends respectively to the pin 20 and the terminal 60.

The other fuse retainer grip terminal 58 is connected by rivetting to a ring connector 70 at the end of the live wire 66 of the power cord. The stem of the connector 70 is located in the guide channel 46 and the ground wire 56 lies in a channel defined between the two ends of the platform 26.

Referring to Figure 3 of the drawings, there is shown the as-moulded top plug element 72 adjacent to the electrically connected bottom plug element 10 and power cord 30. The top plug element 72 includes a body 74 having a peripheral wall 76 configured and dimensioned to fit snugly over the exterior surface of the boundary wall 24 of the bottom plug element 10 when the elements are assembled and secured together. The top plug element 72 includes four parallel spigot members 78 each receivable within a respective said bore 32 in the bottom plug element 10 when the two elements are assembled together. The peripheral wall 76 of the top plug element 72 also includes a semi circular recess 80 at its rear end for cooperation with the said recess 26 in the bottom plug element around the protective collar 28 of the power cord.Said collar 28 includes an end portion 82 of generally square configuration receivable as shown in Figure 2 between the cord grips 34 and the inner face of the boundary wall 24. As shown in Figure 3, the portion 82 is also receivable between an inner face of the peripheral wall 76 of the top plug element 72 and a cord retainer portion 84 projecting from the inner face of the top plug element body 74.

The top plug element 72 also includes three further spigot members 86, 88, 90 which, when the plug elements are assembled together, overly the inner ends of the respective connector pins 18, 20, 22 in extremely close proximity thereto thereby to prevent any inadvertant axially inward movement of the respective connector pins when the plug is inserted in a socket.

In Figures 4 to 6 of the drawings the top plug element 72 is shown assembled to the bottom plug element 10 with the spigot portions 78 received within the cooperating bores 32, the top and bottom plug elements being permanently secured to one another by means of the said spigot portions 78 being fused within their cooperating bores 32. Such fusion may be accomplished by any means suitable to the electrically insulating plastics material from which the plug elements are moulded e.g. by heat or by ultrasound.

Also in Figure 5, a fuse holder 92 is shown installed in a readily accessible position on the outer face 44 of the bottom plug element 10. Such a fuse holder 92 is of conventional form comprising a flat base having a hollow cylindrical formation on its inner face within which the cartridge fuse is receivable. Thus when the fuse holder 92 and fuse are pressed into the recess 42, the conductive ends of the fuse are received within the fuse retainer clips 62 and 64. Such an arrangement in the assembly of the present invention provides an additional safety feature in that the fuse is only accessible when the plug is removed from its socket.

Claims

CLAIMS:-

1. An electrical plug for permanent connection with a power cord comprising moulded top and bottom plug elements securable together to form said plug, said bottom plug element having two or more apertures therein for the reception of electrical connector pins for engagement in a plug socket, said bottom plug element having a recess in an outer face thereof for the reception of a fuse element, said outer face comprising the, in-use, face of the plug from which said connector pins project, said plug elements having mutually co-operating formations permanently engageable with one another to secure said plug elements together.

2. A plug as claimed in Claim 1 wherein said formations are fuseable one with another to secure said plug elements together.

3. A plug as claimed in either one of Claims 1 or 2 wherein said co-operating formations comprise spigot and socket formations provided on respective ones of said plug elements.

4. A plug as claimed in any one of the preceding claims wherein the base of said recess in the outer face of the bottom plug element is provided with a pair of spaced-apart apertures therein within each of which is securable an electrical connector extending through the base of the recess to provide fuse retainers within the recess on an outer face of said base and electrical terminals on an inner face of the base.

5. A plug as claimed in Claim 4 wherein one of said electrical terminals is connectable to a wire of a said power cord and the other of said terminals is electrically connectable to a said connector pin.

6. A plug as claimed in Claim 5 wherein three said apertures are provided in the bottom plug element for the reception respectively of live, neutral and ground connector pins, the said one of said terminals being electrically connectable to a said live connector pin.

7. An electrical plug and power cord assembly in permanent connection with one another comprising a plug formed from moulded top and bottom plug elements permanently secured together to form said plug, said bottom plug element including two or more apertures through which electrical connector pins project from an outer face of said element for engagement in a plug socket, a recess being provided in said outer face of the bottom plug element containing a fuse element electrically connected between two fuse retainers in said recess, a power cord having a pair of wires non-detachably secured to a respective terminal on one of said connector pins and to one of said fuse retainers, said power cord extending out of said plug through an aperture provided between said top and bottom plug elements.

8. An assembly as claimed in Claim 7 wherein each of said fuse retainers extends through the base of said recess providing an electrical terminal within the plug, one of said terminals having a said wire non-detachably secured thereto and the other said terminal being permanently electrically connected to the other of said connector pins.

9. An assembly as claimed in either one of Claims 7 or 8 wherein each of said wires is secured to a respective said terminal by rivetting.

10. An assembly as claimed in any one of Claims 7 to 9 wherein the electrical connection between said other terminal and said other connector pin comprises a rigid electrically conductive strap.

11. An assembly as claimed in any one of claims 7 to 10 wherein three said connector pins are received within three respective apertures in the bottom plug element comprising live, neutral and ground connector pins, and the power cord comprises live, neutral and ground wires, the live wire being connected to one of the fuse retainer terminals, the neutral wire being connected directly to the neutral connector pin and the ground wire being connected directly to the ground connector pin.

12. A method of manufacturing an electrical plug and power cord assembly as claimed in any one of Claims 7 to 11 comprising the steps of forming said top and bottom plug elements by moulding, installing electrical connector pins and fuse retainers in said apertures and in said recess respectively, installing an electrical connection between one of said fuse retainers and one of said connector pins, non-detachably securing wires of the power cord to respective electrical terminals of the other electrical connector pin and the other fuse retainer, assembling the top and bottom plug elements together with mutually cooperating formations on said elements in engagement with one another with the power cord extending out of an aperture provided between the assembled top and bottom plug elements, and treating said co-operating formations to cause them to remain in permanent engagement with one another thereby to retain the plug elements in permanent assembly with one another on said power cord.

13. A method as claimed in Claim 12 wherein said cooperating formations are fused together into permanent engagement with one another.

14. A method of manufacturing an electrical plug and power cord assembly substantially as hereinbefore described with reference to the accompanying drawings.

15. Moulded top and bottom plug elements securable together to form an electrical plug for permanent connection with a power cord constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

16. An electrical plug and power cord assembly in permanent connection with one another constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.