GB2250643A - An electrical plug - Google Patents

Abstract

An electrical plug comprises at least one plug pin (16) having a head (52) larger than the aperture (17) in the plug base (4) into which the pin is fitted. The head is secured to the base by a retaining member (50) inserted into the base from the inside of the plug outwardly. This provides a quick and simple method of securing the plug pin. The retaining member or members can be coloured to match the colour of the insulation of individual wires of the supply cable to ensure correct connection of wiring. Retention of the supply cable may be by means of a pair of vanes secured by extensions of the vanes fitting into holes in the base (4). <IMAGE>

Description

An electrical plug The present invention relates to an electrical plug of the kind having two or more pins fitted into a base component of the plug and a cover securable to the base.

It is a requirement of any such plug that the pins are secured against forces tending to push the pins through the cover from the outside of the base. This may be resisted by strengthening the cover, strengthening the securing of the cover to the base or by fixing by various means the pins to the base. This latter method is preferred since it reduces the need for a heavy cover moulding, and furthermore ensures that pins do not fall out of the bases when wiring up the supply cable.

Assembly of pins in the base during manufacture is another problem. Pins must be readily and easily inserted into the base moulding whilst ensuring that the pins are securely retained in the base against inward pressure on the pins.

An electrical plug according to the invention comprises a base, two or more apertures in the base through each of which a plug pin extends outwardly from its head and a cover securable to the base characterised in that at least one of the plug pins comprises an extend part of portion on or adjacent its head larger than the aperture into which the pin fits and in that a retaining member is insertable into the base in a direction from the interior of the plug outwardly to engage with the base so as to cooperate with the pins and retain the pin in the plug base.

The location of the or each plug pin in an appropriate aperture in the base such that it is prevented from outward movement by the head of the pin enables easy insertion during manufacture. The provision of the retaining member insertable into the base from inwards in an outward direction enables a quick simple method of securing the pin.

Preferably the retaining member is provided with a protrusion and this protrusion is arranged to snap fit into an aperture in the base. This enables the retaining member to be quickly secured during manufacture.

In a preferred embodiment the head of the pin has an extension which forms an abutment for the retaining member. This enables the retaining member to be located in a sufficiently offset position relative to the pin axis so as to provide a secure fixing of the retaining member in the base and this also assists access for an assembly tool.

Preferably both the neutral and line pins of a three pin plug each have a retaining member as previously described. In this arrangement a single assembly tool can be used to secure both pins simultaneously.

In the preferred embodiment two of the retaining members are each formed with heads of a colour coding corresponding to the colour coding of the pin which they retain, each head being shaped differently to fit into a corresponding recess in the base. This ensures only the appropriate pin can be indentified clearly by the correct colour code which matches the colour of the individual insulated wire of the supply cable. Correct connection of wires in the plug can thereby be easily indicated. The retention of the supply cable in the base can be assured by means of a pair of vanes forming retention means mounted within slots either side of a cable entry in the base. These vanes are mainly of a known form but are improved by having extensions which each fit and plug into an appropriate hole in its slot in the base.In this way the vanes do not fall out when wiring up the cable which has previously been a problem with vane type cable retainers. The vanes advantageously are given a limited pivotal movement.

An electrical plug according to a different aspect of the invention has a base with cover, and a supply cable retention means in the base; the retention means comprising a pair of vanes mounted within slots either side of a cable entry, each vane being secured in each slot by means of an extension of the vane fitting into a hole in the base.

A preferred embodiment of an electrical plug according to the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of the cover of the plug of the invention seen from the inside, Figure 2 is a plan view of the base of the plug of Fig. 1 seen from the inside without pin retainers, Figure 3 is a cross-section of the neutral pin of the plug of Fig. 2 taken at III-III showing the fitting of the pin in the base and a retainers about to be inserted, Figure 4 shows the pin of Fig. 3 with the retainer inserted and the pin secured, Figure 5 is a plan view of the retainer of Fig. 3 seen from direction A indicated in Fig. 3, Figure 5A is a plan view of a similar retainer to that shown in Fig. 5 but with a different shaped head used for the line pin of Fig. 2, Figure 6 is an elevation of the retainer of Fig. 3 seen from direction B indicated in Fig. 3, Figure 7 is a plan view of the base of the plug shown in Fig. 2 as seen from the outside, Figure 8 is a plan view of the base of the plug shown in Fig. 7 as seen from the inside with the pin retainers and cable securing vanes in place, and Figure 9 is an elevation of one of the cable securing vanes shown in Fig. 8.

The plug shown in Figures 1 to 9 has a cover 2 shown in Fig. 1 and a base 4 shown wholly in Fig.s 2,7 and 8 and partly in Fig.s 3 and 4. The cover 2 is secured to base 4 by means of a screw 6 located in the base and screwing into a threaded metal insert 8 in the cover (Fig.1). The cover 2 has a cable entry 10 formed as a semi circular portion and the base has a corresponding cable entry 12 also formed as a semi circular portion. Three pins are provided being respectively a line pin 14, a neutral pin 16 and an earth pin 18 which fit in apertures 15, 17 and 19 in the base.

The earth pin 18 is secured in the base in a known way by means of a brass tab 20 crimped onto a threaded shank 22 of pin 18. A terminal screw 80 screws on shank 22 (Fig.8) The line pin 14 having a fuse clip 24 rivetted on an axial protrusion 26 on its head has an extension 28 which locates in a rectangular recess 30 in the base which extends into a semi circular recess 32. Recess 32 has a hole 34 in its bottom which extends to the outside of the base as seen in Fig. 7. A second fuse clip 36 is plugged into a recess 38. Clip 36 has a brass extension 40 with a threaded terminal shank 42. When assembled a fuse 43 is clipped between clips 24 and 36. A line terminal 41 screws on shank 42. Line pin 14 is retained in its aperture 15 by means of a retaining member or retainer 44 which plugs into hole 34 so as to abut on the extension 28.Retainer 44 can be formed of brown coloured plastics material to indicate the correct connection with a supply cable wire (not shown). Retainer 44 is similar to retaining member or retainer 50 which will be described in detail except it has a different shaped head which ensures it is correctly located in its recess 32.

The neutral pin 16 has a shank 51 extending towards its outer extremity having a constanct cross section corresponding to the aperture 16 into which it fits and in that respect is similar tp pin 14. As shown in Fig.s 3 and 4 pin 16 has a head 52 with a minor extension 54 and a major extension 56 formed with a surface 57 facing the interior of the plug perpendicular to the axis X of the pin. Surface 57 provides an abutment for retainer 50. The head 52 fits into a circular recess 58 in the base. The major extension 56 laps over into a recess 60 which extends from recess 58 which is shaped to receive retainer 50. The head 52 has a threaded extension 53 which receives a terminal screw 55. A hole 62 in the bottom of recess 60 extends through base 4 to a larger part 64 of hole 62 which can be seen in Fig. 7 and is similar to hole 34.

Retainer 50 shown in Figures 3 to 6 is provided with a flat upper surface 66 on a head 68 and a lower abutment surface 70 from which extends a protrusion 72.

Protrusion 72 has an end portion 74 larger in diameter than a shank portion 76 so that the end portion 74 snap fits into the larger part 64 of hole 62 as shown in Fig.

4. Retainer 50 may be coloured blue appropriate to the colour coding of the insulation on the proper wire of the supply cable.

Retainer 44 is the same as retainer 50 except it has a different shaped head ensuring it can only fit into its own recess.

The protrusion 72 of the retainers 44 and 50 and corresponding holes 34 and 64 in the base are axially centred on line Z (see Fig.s 7 & 8) so that when assembling the plug a single tool can strike the retainers into snap fit engagement with their respective holes In order to secure the supply cable in the plug a pair of vanes 90 and 90' (see Fig.s 8 and 9) are mounted in slots 92, 92s adjacent cable entry 12. The vanes forming retention means are plugged into the base and secured thereto by means of extension 94 of each vane which each snap fits into a respective hole 96 and 96'.

Claims (9)

1. An electrical plug comprising a base, two or more apertures in the base through each of which a plug pin extends outwardly from its head and a cover securable to the base characterised in that at least one of the plug pins comprises an extended part or portion on or adjacent its head larger than the aperture into which the pin fits and in that a retaining member is insertable into the base in a direction from the interior of the plug outwardly to engage with the base so as to cooperate with the pins and retain the pin in the plug base.

2. A plug as claimed in claim 1 wherein the retaining member is provided with a protrusion and wherein the protrusion is arranged to snap fit into an aperture in the base.

3. A plug as claimed in claim 1 or 2 wherein the head of the or each pin comprises a shank extending towards the outer extremity of constant cross section corresponding to the base aperture into which it fits and a head having one or more extensions formed with a surface facing the interiror of the plug perpendicular to the axis of the pin which provides an abutment for the retaining member.

4. A plug as claimed in any of claims 1 to 3 wherein two retaining members are provided for retaining a pair of pins in the base in neutral and line positions.

5. A plug as claimed in claim 4 wherein the retaining members each have a colour corresponding to the colour coding of the pin which the retain and wherein the heads are shaped differently each fitting with a corresponding recess in the base.

6. A plug as claimed in any one of the claims 1 to 5 having a supply cable retention means in the base the retention means comprising a pair of vanes mounted within slots either side of a cable entry, each cable being secured in each slot by means of an extension of the vane fitting into a hole in the base.

7. A plug as claimed in claim 6 wherein the extension of the vane is fitted into the hole in the base so as to allow a limited pivotal movement.

8. An electrical plug having a base with cover and a supply cable retention means in the base; the retention means comprising a pair of vanes mounted within slots either side of a cable entry, each vane being secured in each slot by means of an extension of the vane fitting into a hole in the base.

9. An electrical plug substantially as herein described with reference to the accompanying drawings.