GB2095922A - Electric plugs - Google Patents

Abstract

An electric plug comprises a base member (6) and a cover member (8), each of which is provided with a hook formation (24, 26) to enable the cover member to be mounted on the base member. On the end opposite to that on which the hook formation (26) is provided, the cover member (8) is provided with fixing apertures (30), through each of which when the cover and base members are in their relative closed positions a steel fixing pin (36) may be inserted, to engage with a formation (32) on the interior of the base member, to hold the base and cover members fixedly in their closed positions. The terminals (15) of the plug are provided with apertures (40) which, on assembly of the plug, a conductive wire is inserted. The terminal is then deformed to trap the wire between surface portions thereof bounding the aperture. <IMAGE>

Description

SPECIFICATION Improvements relating to electric plugs This invention is concerned with improvements relating to electric plugs. By the term "electric plug" as used herein, we mean a device comprising a hollow body of insulating material, and electrically conductive pins extending through the body into the interior thereof, conductive wires of a two or three core electric cable extending through an inlet aperture into the interior of the plug, which wires are connected to the terminals of the plug. Such plugs are adapted to be inserted into an electric socket, to bring the pins into conductive contact with terminals of the socket, whereby a conductive path is established to the conductive wires of the cable, and to an electric appliance connected to the other end of the cable.

A conventional electric plug comprises a body member and a cover member releasably secured together, enabling the plug to be connected to and disconnected from the cable by a user of the appliance.

It is however becoming increasingly recognised that it is desirable to provide an electric appliance with a plug of the non-rewirable type, that is to say a plug of the type which is permanently attached to the cable, so that a user of the plug cannot interfere with the interior of the plug, and in particular with the connection of the conductive wires of the cable to the terminals of the plug.

Difficulties have however been encountered in the provision of non-rewirable plugs, by the construction and arrangement of the plugs, which in general require either that the cable be secured to the interior terminals, around which the plug body is then provided by an injection moulding operation, or that the plug body is made of two parts which, subsequent to the connection of the cable to the plug terminals are permanently secured together by welding, heat sealing, gluing or similar methods, which are not always satisfactory.

It is therefore one of the objects of this invention to provide a non-rewirable plug which avoids difficulties currently encountered.

According to this invention there is provided a kit of parts for use in the assembly of an electric plug of the non-rewirable type, comprising a base member, a cover member, mounting means on the base and cover members which enable them to be connected together for arcuate movement to relative closed positions in which a fixing aperture in one ofthe base and cover members is in alignment with abutment means on the other of the base and cover members, and fixing means which may be inserted into said fixing aperture and into engagement with said abutment means to prevent relative arcuate movement of the base and cover members from said relative closed positions.

By such insertion of the fixing means into said fixing aperture, it may readily be arranged that such fixing means is difficult to remove, as would be necessary to interfere with the internal connections of the plug terminals.

Preferably said mounting means is provided on the base and cover members at one end of the plug, and said fixing aperture is provided at the other end of the plug. Preferably said mounting means is provided by hooked formations which are interengageable, one with the other, to permit, when so engaged, relative pivotal movement between the base and cover members.

Preferably said mounting means is provided at the end of the plug at which an earth pin is provided.

Preferably there are two such fixing apertures, and the fixing means comprises two stakes which may be force-fitted into the fixing apertures to protrude into the interior of the plug, into engagement with said abutment means. Most conveniently, such stakes are provided by steel pins.

Preferably the fixing aperture or apertures are located adjacent to an inlet aperture of the plug, conveniently between the base and cover members, through which a cable extends into the plug. Preferably the construction and arrangement is such that interior formations of base and cover members, when the base and cover members are in their relative closed positions, engage with and clamp against such a cable extending through the inlet aperture, to prevent relative separative movement between that part of the cable which is inside the plug and the interior terminals of the plug. In this manner, the means utilised to prevent relative movement between the base and cover members from their closed positions is also effective to restrain undesired movement of the cable relative to the plug.

Most conveniently the cover member has a periphery larger than that of the base member, and is fitted over the base member, the fixing apertures being provided in the cover member and the fixing means on insertion into the fixing apertures, when the base and cover members are in their relative closed positions, engaging with a part of the base member of the interior of the plug, to prevent relative separative movement of the cover member relative to the base member.

This invention also provides a non-rewirable plug, produced by assembly of a kit of parts of the kind set out above.

Difficulty is also encountered in non-rewirable plugs, in permanently connecting the conductive wires of the cable to the interior terminals of the plug.

Thus according to another aspect of this invention, there is provided a method of connecting a conductive wire to an interior terminal of an electric plug, in which an aperture is provided in a part of the terminal which, on assembly, will be inside the plug, the conductive wire is inserted into the aperture and said end portion is deformed to trap the wire between surface portions bounding the aperture.

In this manner, particularly where the wire is multi-strand, a contact is provided between the wire and the terminal which extends over a larger area than is easily provided by the use of conventional connecting techniques.

Preferably such deformation of said end portion of the terminal does not cause fracture thereof, as could cause unreliability in the integrity of the connection. Preferably deformation is effected by causing movement of said surface portions bounding the aperture together, preferably surface portions on opposite sides of the aperture moving inwardly towards the centre of the aperture. Thus the aperture may be in the form of a bore into which the wire is inserted, such deformation being effected by a compression to produce radial inward movement of the surface portions bounding the bore.

Such a bore may conveniently be provided by forming a hollow sleeve at one end portion of the terminal, preferably integrally therewith.

Alternatively the aperture may be in the form of a slot provided in said end portion of the terminal, between the surfaces bounding which the wire is inserted. In such circumstances, most conveniently the slot is afforded by cutting said terminal and opening the cut by a wedging operation.

It has been found that closing the aperture by effecting deformation without fracture requires less force than is necessary to effect deformation with fracture, particularly where deformation is effected by causing movement of surface portions on opposite sides of the aperture towards one another, and produces a highly reliable connection.

This aspect of the invention may be utilised in the connection of conductive wires to terminals provided on the inner end portions of plug pins, or in the connection of conductive wires to fused terminals.

This invention also provides an electric plug of the non-rewirable type comprising terminals, particularly an electric plug of the non-rewirable type manufactured from a kit of parts as described hereinabove, at least one of the terminals of which is connected to electric wiring in accordance with the method set out above.

In the provision of non-rewirable plugs of the kind described, dificulty is also encountered in retaining the conductive pins of the plug in position, and preferably in one or more of the various aspects of this invention hereinabove defined, preferably the base is provided with means adjacent to at least one of the pin apertures thereof adapted to insertion of the pin into the aperture to engage with the pin to prevent or restrain movement of the pin relative to the base from a desired operative position.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of an electric plug which is a preferred embodiment of this invention, and two modified forms by which electric wiring may be connected to terminals of the plug. It is to be appreciated that the preferred embodiment, and said modified forms have been selected for the purposes of illustrating the invention by way of example, and not by way of limitation thereof.

Figure lisa plan view of the plug which is the preferred embodiment of the invention, a cover memberthereof having been removed; Figure 2 is a sectional view of the plug, taken on the lines 2-2, with the cover in position; Figure 3 is a further, part sectional view, taken on the line 3-3 of Figure 1; Figure 4 is a part sectional view, taken on the lines 4-4 of Figure 1; Figure 5 is an enlarged view, illustrating the connection of an conductive wire to the earth terminal ofthe plug; and Figures 6and 7 are views corresponding to Figure 3, showing alternative methods of connection of a conductive wire to the earth pin.

The electric plug which is the preferred embodiment of this invention comprises a housing of electrically insulating material, comprising a base member 6 and a cover member 8. Extending from the base member are live, neutral and earth pins 10, 12 and 14 respectively, which pins 12 and 14 are provided on their interior end portions with terminals 13, 15 respectively. However the interior end portion of the live pin 10 is connected to a fuse assembly 16, the fuse Fofwhich being accessible for replacement from the exterior of the base member, said fuse assembly 16 comprising a terminal 17.

At the two sides 18 ofthe plug, and at the end 20 at which the earth pin is provided, the side walls of the base and cover members are rebated, as shown at 22 (Figures 3 and 4). Also at said end 20 the side wall of the base member is provided with mounting means, afforded by two spaced, outwardly-turned lips 24 (Figure 2) whilst the cover member comprises mounting means afforded by two spaced in-turned lips 26. The lips 26 of the cover may be engaged behind the lips of the base, projecting short distances into apertures 25 provided beneath said lips 24, to enable the cover to be moved arcuately, specifically pivotally, relative to the base from an open position to a closed positon, shown in Figure 2.

The cover member is also provided with two fixing apertures 30, which, when the cover member is in its relative closed position, are in alignment with abutment means on the interior of the base, said abutment means comprising abutment apertures 32.

Thus when the cover member is in its closed position relative to the base member, the fixing means afforded by steel pins 36 may be force-fitted into the fixing apertures 30, so as to projct into the abutment apertures 32, to prevent subsequent separative movement between the base and cover members.

In this manner, after the assembly of the plug, as will be described hereinafter, including the connectin of conductive wires of a cable to the terminals within the plug body, the base and cover members may be secured together in a manner such as to make their subsequent separation very difficult.

In the plug which is the preferred embodiment of this invention, the terminals of the neutral and earth pins, and the terminal block of the fuse assembly, are provided with apertures 40 afforded by cutting the terminal, in the case of the neutral and earth pins, in a plane extending generally parallel to the longitudinal axia of the pin, and in the case of the fuse terminal in a similar plane. A wedge is then inserted into the cut, as shown by the arrow W, in Figure 5, and portions of the terminal on either side of the cut are deformed outwardly (Figure 5) to provide the aperture 40, into which the bared end of a conductive wire may be inserted, as shown.

A clamping force is then applied to the separated portions of the terminal, as indicated by the arrows C, to cause surface portions on either side of the aperture to close, to trap the wire in position. Where a thin wire is used, it may be preferable to use a U-shaped foil liner, inserted into the apertue 40 before the wire.

In this manner, the wires of a three-core cable extending through the inlet aperture into the plug may be secured to the terminal of the neutral and earth pins and to the fuse assembly, in a manner which ensures a satisfactory and permanent connection.

As an alternative method of providing such an aperture in the end portion of the terminal, the terminal (such as the terminal of the earth pin 14 Figure 6) may be provided by a hollow tubular sleeve 15', afforded by a machining operation on the end portion of the pin, the aperture 40' of the terminal being afforded by a central bore of the sleeve which extends parallel to the longitudinal axis of the pin 14.

The conductive wire may be inserted into the aperture 40', and the sleeve crimped, the radial inward movement of the surface portions bounding the bore of the sleeve clamping the wire in position.

As a second alternative, shown in Figure 7, the aperture 40" in the terminal 15" may be provided by a transverse bore into which the wire is inserted, the terminal being subsequently deformed by the application of a force along the line C, to effect deformation of the terminal 15", and closure of the aperture 40" as is shown, to clamp the wire in position. By effecting such deformation of the terminal 15", in a manner which is not accompanied by fracture of the terminal, a highly reliable connection between the terminal and the wire may be obtained, which will remain secure throughout the life of the plug.

As is shown in Figure 2, axial movement of the pin 12 in a direction inwardly of the plug is prevented, when the cover is secured to the base, by engagement of a shoulder 44, which extends inwardly from the outer wall of the plug, with the terminal 13 of said plug 12.

Where wiring is connected to a terminal in the manner illustrated in Figure 6, such a method of preventing axial movement of the pin in a direction inwardly of the plug cannot be conveniently utilised.

In the plug which is the preferred embodiment of this invention, at least the earth pin 14 is provided, extending into the pin through the faces thereof of smallest dimension, with two apertures 48. The base is provided with corresponding lips 50 extending into the aperture 52 provided in the base member for the reception of the pin 14. Inner faces of the lips 48 are inclined, permitting the wall portions of the base bounding the aperture 52 to be deformed as the pin is inserted through the aperture 52 from the inner side of the base member, until the lips 50 enter the apertures 48. When in this position (as shown in Figure 3) forces acting on the pin 14, tending to move the pin towards the interior of the plug, are taken by abutting planar faces of the lips and pin, effectively preventing such movement.

Whilst this construction is utilised with the earth pin for the reasons set out above, there may well be other reasons why a pin cannot conveniently be restrained against axial movement towards the interior of the plug by engagement with a formation on the cover member, such as engagement of the pin 12 with the formation 44. Hence, the pin 14 (Figure 3) is retained in position by the lips 50, albeit in a construction in which the wiring is connected to the terminal of the pin in a way which does not in itself prevent the use of a formation for the pin 14, similar to the formation 44.

In the assembly of the plug which is the preferred embodiment of this invention, the wiring of a three-core cable is connected to the terminals of the neutral and earth pins, and to the terminal of the fuse assembly, which are then inserted into the apertures and recesses provided in the base member 6 for reception thereof, a base plate 52 of the fuse assembly 16 momentarily outwardly deforming upwardly extending ribs 44, on movement of the fuse assembly into the position shown in Figure 4. A sleeve 56 is inserted over the cable, a flange 58 on said sleeve being pressed into a semi-circular channel on the base member. The lips 26 of a cover member are inserted through the apertures 25 of the base member, allowing the lips 26 of the cover member to engage beneath the lips 24 of the base member, as shown in Figure 2. The cover member is then moved arcuately relative to the base member, until the cover member is in a closed position relative to the base member, in which the apertures 30 and 32 are in alignment. Steel pins 36 are then forced through the apertures 30 so as to project into the apertures 32, preventing relative arcuate movement between the base and cover members.

By the use of the invention as herein described, the conductive wires of a multi-core cable may readily be connected permanently to the terminals of an electric plug, and the plug may be assembled and then closed in a manner such as to prevent opening thereof, with great simplicity.

Claims (25)

1. A kit of parts for use in the assembly of an electric plug of the non-rewirable type, comprising a base member, a cover member, mounting means on the base and cover members which enable them to be connected together for arcuate movement to relative closed positions in which a fixing aperture in one of the base and cover members is in alignment with abutment means on the other of the bse and cover members, and fixing means which may be inserted into said fixing aperture and into engagement with said abutment means to prevent relative arcuate movement of the base and cover members from said relative closed positions.

2. A kit of parts according to Claim 1 wherein said mounting means is provided on the base and cover members at one end of the plug, and said fixing aperture is provided at the other end of the plug.

3. A kit of parts according to one of Claims 1 and 2 wherein said mounting means is provided by hooked formations which are inter-engageable, one with the other, to permit, when so engaged, relative pivotal movement between the base and cover members.

4. A kit of parts acording to any one of the preceding claims wherein said mounting means is provided at the end of the plug at which an earth pin is provided.

5. A kit of parts according to any one of the preceding claims wherein there are two such fixing apertures, and the fixing means comprises two stakes which may be force-fitted into the fixing apertures to protrude into the interior of the plug, into engagement with said abutment means.

6. A kit of parts according to Claim 5 wherein said stakes are provided by steel pins.

7. A kit of parts according to any one of the preceding claims wherein the fixing aperture or apertures are located adjacent to an inlet aperture of the plug, through which a cable extends into the plug.

8. A kit of parts according to any one of the preceding claims wherein interior formations on the base and cover members, when the base and cover members are in their relative closed positions, engage with and clamp against such a cable extending through the inlet, to prevent relative separative movement between that part of the cable which is inside the plug and the interior terminals of the plug.

9. A kit of parts according to any one of the preceding claims wherein the cover member has a periphery larger than that of the base member, and is fitted over the base member, the fixing apertures being provided in the cover member and the fixing means on insertion into the fixing apertures, when the base and cover members are in their relative closed positions, engaging with a part of the base member on the interior of the plug, to prevent relative separative movement of the cover member relative to the base member.

10. A non-rewirable plug, produced by assembly of a kit of parts according to any one of the preceding claims.

11. A method of connecting a conductive wire to an interior terminal of an electric plug, in which an aperture is provided in a part of the terminal which, on assembly, will be inside the plug, the conductive wire is inserted into the aperture and said end portion is deformed to trap the wire between surface portions bounding the aperture.

12. A method according to Claim 11 wherein such deformation of said end portion of the terminal does not cause fracture thereof.

13. A method according to one of Claims 11 and 12 wherein deformation is effected by causing movement of said surface portions bounding the aperture together, surface portions on opposite sides of the aperture moving inwardly towards the centre of the aperture.

14. A method according to Claim 13 wherein the aperture is in the form of a bore into which the wire is inserted, such deformation being effected by a compression to produce radial inward movement of the surface portions bounding the bore.

15. A method according to Claim 14 wherein the bore is provided by forming a hollow sleeve at one end of the terminal, integrally therewith.

16. A method according to Claim 11 wherein the aperture is in the form of a slot provided in one end portion of the terminal, between the surfaces bounding which the wire is inserted.

17. A method according to Claim 16 wherein the slot is afforded by cutting said terminal and opening the cut by a wedging operation.

18. An electric plug of the non-rewirable type comprising terminals, at least one of which is connected to electric wiring by a method according to any one of Claims 11 to 17.

19. An electric plug according to Claim 18 comprising a base member, a cover member, means by which the base and cover member may be connected together, and electrically conductive pins extending through the base member into the interior of the plug.

20. A kit of parts according to any one of Claims 1 to 10 wherein at least one of the terminals is adapted to be connected to electric wiring by a method accoring to any one of Claims 11 to 17.

21. The invention according to any one of Claims 1 to 11, 19 and 20, wherein the base is provided with means adjacent to at lest one of the pin apertures thereof adapted on insertion of the pin into the aperture to engage with the pin to prevent or restrain movement of the pin relative to the base from a desired operative position.

22. A kit of parts for use in the assembly of an electric plug, constructed and arranged substantially as herein before described with reference to the accompanying drawings.

23. An electric plug constructed and arranged substantially as herein before described with reference to the accompanying drawings.

24. A method of connecting a conductive wire to an interior terminal of an electric plug, when carried out substantially as hereinbefore described with reference to the accompanying drawings.

25. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.