GB2278740A

GB2278740A - Electrical plug assembly

Info

Publication number: GB2278740A
Application number: GB9311220A
Authority: GB
Inventors: J Obee
Original assignee: KAINSTAR Ltd
Current assignee: KAINSTAR Ltd
Priority date: 1993-06-01
Filing date: 1993-06-01
Publication date: 1994-12-07
Also published as: GB9311220D0

Abstract

A pre-wired three pin plug comprising a base 1 carrying the pins and other components, a first moulding 9 immersing the internal components and a second moulding 10 enveloping the first moulding. Either the first or second moulding may be extended to provide a strain relieving block 11 for the power cable. An interference suppression filter 5 can be included in the plug. <IMAGE>

Description

Electrical Plug Assembly This invention relates to electrical plug assemblies and in particular it relates to pre-wired, three pin plugs commonly known as 13 amp plugs The increasing demand for pre-wired electrical plugs has focused attention on manufacturing techniques. For the manufacture of plugs, high speed and ease of production must be consistent with high standards of safety and reliability.

It is an object of the present invention to provide a prewired three pin plug that is safe and reliable while being capable of relatively simple manufacture.

According to the invention there is provided a three pin plug assembly comprising a base carrying the three pins, said pins connected on one side of said base, the inside, to a power cable; a first moulding to immerse the electrically conducting components and at least part of the wiring carried on the inside of the base and a second moulding to envelope said first moulding and to form the body of the plug.

An interference suppression filter may be included as one of the components of the plug.

By way of example one embodiment of the invention will now be described with reference to the accompanying figures in which: Figure 1 is a plan view of the base from the inside of the plug when an interference suppression filter is included.

Figure 2 illustrates the extent of the mouldings Figure 3 is a plan view of the base from the inside of the plug when an interference suppression filter is not included.

With reference to the figure 1 a plan view of a plug base is shown. The base 1 is a single piece moulding of polyamide to which the various internal components are added and then electrically connected to the power cable. The base 1 has no side walls and the only internal walls are those providing the fuse holder 8 and surrounding the filter 5.

Live 2, neutral 3 and earth 4 pins are inserted into the base 1 and the pins are retained by pairs of clips 7. An interference suppression filter 5 is attached to the base by means of clips 6. The details and operation of these clips 6 and 7 are described in our co-pending applications. A fuseholder section 8 allows access to a fuse from the front of the plug. The interconnecting wiring between components and to the power cable is as shown in figure 1. With all of the electrically conducting components in place and wired the plug base is secured in a moulding jig. The limits 9 of the mould are shown in cross-section in figure 2. Hot melt PVC is admitted under pressure into the moulding jig and the PVC immerses the electrically conducting components. This first moulding (9) immerses all of the components and interconnecting wiring on the inside of the plug and part of the wiring from the power cable. Exceptionally some stray wiring may not be completely immersed and will project from the first moulding.

A dwell time is allowed after the first moulding operation and the plug is then removed to a second moulding jig. The second mould defines the limits of the shape of the completed plug.

With the plug secured in the second moulding jig a further injection of hot melt PVC is made and the second mould defines the body of the plug as shown at 10 in figure 2. In this embodiment the second moulding incorporates a strain relieving block 11 around the power cable. The strain relieving block may be produced as part of the first moulding instead of the second moulding in some cases where this is required.

Both first and second moulding may be produced by using a single jig in which case the plug remains in the jig for both moulding processes. This would require a slightly more sophisticated jig capable of defining different volumes as required but is well within the state of the art.

When a filter is not required to be included within the plug the fuseholder section may be located more conveniently e.g.

more centrally as shown in figure three.

Extension of both first and second mouldings to the front of the plug may be achieved by providing suitable holes in the base and redefining the moulding jig.

Claims

1. A three pin plug assembly comprising a base carrying the three pins, said pins connected on one side, the inside, of said base to a power cable, a first moulding immersing the electrically conducting components and at least part of the wiring carried on the inside of the base and a second moulding enveloping said first moulding and forming the body of the plug.

2. A three pin plug assembly as in claim 1 where said first moulding is formed by injection of hot melt PVC into a moulding jig wherein said base is secured.

3. A three pin plug assembly as in claim 1 or 2 where said second moulding is formed by injection of hot melt PVC into a moulding jig wherein said base is secured.

4. A three pin plug assembly as in claims 1 to 3 where said first moulding is extended to form a strain relieving block surrounding the power cable for a short distance from the plug.

5. A three pin plug assembly as in claims 1 to 3 where said second moulding is extended to form a strain relieving block surrounding the power cable for a short distance from the plug.

6. A three pin plug assembly as in claims 1 to 5 incorporating an interference suppression filter.