GB1581663A

GB1581663A - Internal insulating cover for incorporation in an electrical plug

Info

Publication number: GB1581663A
Application number: GB2471/79A
Authority: GB
Original assignee: Ward and Goldstone Ltd
Current assignee: Volex PLC
Priority date: 1977-08-17
Filing date: 1977-08-17
Publication date: 1980-12-17

Description

(54) IMPROVEMENTS IN OR REALTING TO AN INTERNAL INSULATING COVER FOR INCORPORATION IN AN ELECTRICAL PLUG (71) We, WARD & GOLDSTONE LIMI TED, a British Company of Sampson Works, Frederick Road, Salford, Manchester, M6 6AP, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an internal insulating cover for incorporation in an electrical plug for attachment to an electrical appliance and for use in coupling such an appliance into the electricity mains supply.

The risks involved in the wrongful connection of an electrical plug to an electrical appliance by an unskilled or ignorant person are well known since they often result in damage to property and/or death. As a result there is an increasing demand for moulded-on electrical plugs, i.e. plugs which are fitted onto the appliances in the factory and which can only be detached by cutting them off the electrical cable or lead wired to the appliance.

With such moulded-on plugs it is essential to ensure their complete electrical safety during manufacture and assembly since less than 100% safety would not be apparent to the purchaser of an appliance having such a moulded-on plug.

It is an object of the present invention to provide an internal insulating cover for incorporation in an electrically safe mouldedon plug.

According to the present invention there is provided an internal insulating cover for incorporation in a moulded-on domestic electrical plug comprising an insulating base insert mounting metal pins for insertion in an electrical socket and to which are electrically connected the conductors of an electrical cable and an insulating body integrally moulded with the base insert wholly to enclose the connections of the conductors to terminals of the plug, the internal insulating cover comprising a flexible plastics casing adapted to be resiliently clipped over the base insert prior to moulding of the insulating body on to the insert, and having an integral pip or projection which is visible in the finished moulded-on plug to indicate its presence to the manufacturer, This insulating cover provides insulation additional to the plug body thus preventing any risk of exposure to the surface of live parts.

Preferably, the casing is formed with formations adapted to cooperate with com- plementary formations on the base insert to effect the clipping securement of the casing over the latter.

Preferably, the formations in the casing comprise at two opposed sides windows adapted to snap fit around complementary noses on the base insert.

Preferably, the casing has two spaced side-by-side indicator pips or projections at one side thereof which are visible in the finished plug.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a rear view of a moulded-on plug incorporating an internal insulating cover according to the invention; Figs. 2 and 3 are respectively sectional views on the line II--II and III--III of Fig.

1; Fig. 4 is an exploded view of the plug of Figs. 1 to 3 with the external moulded body omitted and showing the insulating cover according to the invention; Figs. 5 to 7 are respectively a front view, a rear view and a side view sectional view on line VIl-VIl of Fig. 5 of the base insert; Fig. 8 is a perspective view of the assembled base insert and insulating cover according to the invention.

Reference is made to the accompanying drawings which show one non-limitative shape of moulded-on domestic plug.

The plug body 20 is, for example, a polyvinylchloride moulding strong enough to resist cracking if subjected to inadvertent mechanical shocks. It has an integral hollow neck 21 recessed as indicated at 22 to give a degree of flexibility thereto and through which extends a cable 23.

Within the plug body 20 is a base insert 24 formed with three elongate passages 25 to receive live, neutral and earth pins 26A, 2613, and 26C. Also, in the rear face, it has a recess 27 in which are rivetted two fuse clips 28A and 28B. Fuse clip 28A is connected by a fuse link strap 29 to the live pin 26A. The fuse link strap 29 is, at one end, rivetted to the live pin 26A, while its other end is rivetted through a shoulder 30 of the base insert 24 to the fuse clip 28A.

The base insert 24 has alongside shoulder 30 another shoulder 31 spaced from one another by a channel 32. The latter leads to a flange 33. Below and adjacent to shoulder 31 is a flange 34.

The upper surface of shoulder 31 is formed with a recess 35 with a lead-in groove 36.

Neutral pin 26B is connected to the base insert 24 at a platform 34A on flange 34, earth pin 26C to base insert 24 at flange 33 and live pin 26A as indicated above to the fuse link strap 29 at a platform 34B which is alongside platform 34A on flange 34.

Flange 33 is at a lower level than the platform 34A when the plug is viewed with its pins depending.

Conductors 38A, 38B, 38C of cable 23 each terminate in a ring terminal 39 and are secured to neutral and earth pins 26B and 26C and the other fuse clip 28B by rivetting or peening.

It will clearly be seen from Figs. 4 and 5 that conductor connections are as aforesaid, at different levels on the base insert 24 and are spaced along substantially a straight line.

Earth conductor 38C passes through and is located by channel 32, its ring terminal 39 being disposed on flange 33 between ramps 30A, 31A of shoulders 30, 31. Neutral conductor 38B has its ring terminal 39 located between shoulder 31 and a locating and shielding wall 40, and the ring terminal 39 of live conductor 38A is located in recess 35 of shoulder 31, the conductor being located by lead-in groove 36. A wall 41 shields fuse link strap 29 from the conductors 38A, 38B, 38C and ring terminals 39.

To provide insulation additional to that provided by the plug body 20 there is provided an internal insulating cover 42.

With the pins 26, conductors 38A, 38B, 38C fuse link strap 29 and fuse clips 28 secured together through the intermediary of the base insert 24 as aforesaid, the insulating cover 42 is then fitted over the latter. To facilitate such fitment the base insert 24 has on two opposed edges projecting noses 43 of somewhat bevelled shape.

The cover 42 is a flexible thin walled casing or shell formed of a relatively flexible plastics material and has at two opposed ends a pair of windows 44 (only one pair shown).

The cover 42 generally follows the shape of the base insert 24. It is simply clipped on over the latter until the noses 43 protrude through the windows 44 (see Figs. 2 and 8).

This assembly is then located in an appropriately configured mould and the plug body 20 moulded therearound and around the cable 23.

The method of clipping the base insert and insulating cover together prior to the final moulding stage can also be varied to suit requirements.

One or more sides of the insulating cover 42 has an indicator pip or projection which in the finished moulded-on plug will be visible thus indicating to the manufacturer that the supplementary cover is incorporated in the plug and has not been inadvertently omitted. In the present embodiment a pair of such indicator pips 42A are provided.

The electrical plug construction is completed for the provision of a fuse 45 which clips into the fuse clips 28. This fuse 45 is supported in a carrier 46 comprising a plate 47 for releasably closing recess 27 and an integral sleeve 48 through which extends the fuse 45. The plate 47 has a window 49 (see Fig. 1) through which the fuse 45 can be viewed.

It will be manifest that the external configuration of the plug can be of any convenient shape, for example the front and rear faces may be substantially parallel, or the front face wholly sloping instead of just partially as in the described embodiment.

Reference is made to our copending Patent Applications Nos. 35448/76 (Serial No.

1,581,661) and 2469/79(Serial No.1,581,662), the former of which discloses and claims the moulded-on electrical plug disclosed herein, while the latter discloses and claims the insulating base insert of the domestic electrical plug disclosed herein.

WHAT WE CLAIM IS:- 1. An internal insulating cover for incorporation in a moulded-on domestic electrical plug comprising an insulating base insert mounting metal pins for insertion in an electrical socket and to which are electrically connected the conductors of an electrical cable and an insulating body integrally moulded with the base insert wholly to encose the connections of the conductors to terminals of the plug, the internal insulating cover comprising a flexible plastics casing adapted to be resiliently clipped over the base insert prior to moulding of the insulating body on to the insert, and having an integral pip or projection which is visible in the finished moulded-on plug to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. neck 21 recessed as indicated at 22 to give a degree of flexibility thereto and through which extends a cable 23. Within the plug body 20 is a base insert 24 formed with three elongate passages 25 to receive live, neutral and earth pins 26A, 2613, and 26C. Also, in the rear face, it has a recess 27 in which are rivetted two fuse clips 28A and 28B. Fuse clip 28A is connected by a fuse link strap 29 to the live pin 26A. The fuse link strap 29 is, at one end, rivetted to the live pin 26A, while its other end is rivetted through a shoulder 30 of the base insert 24 to the fuse clip 28A. The base insert 24 has alongside shoulder 30 another shoulder 31 spaced from one another by a channel 32. The latter leads to a flange 33. Below and adjacent to shoulder 31 is a flange 34. The upper surface of shoulder 31 is formed with a recess 35 with a lead-in groove 36. Neutral pin 26B is connected to the base insert 24 at a platform 34A on flange 34, earth pin 26C to base insert 24 at flange 33 and live pin 26A as indicated above to the fuse link strap 29 at a platform 34B which is alongside platform 34A on flange 34. Flange 33 is at a lower level than the platform 34A when the plug is viewed with its pins depending. Conductors 38A, 38B, 38C of cable 23 each terminate in a ring terminal 39 and are secured to neutral and earth pins 26B and 26C and the other fuse clip 28B by rivetting or peening. It will clearly be seen from Figs. 4 and 5 that conductor connections are as aforesaid, at different levels on the base insert 24 and are spaced along substantially a straight line. Earth conductor 38C passes through and is located by channel 32, its ring terminal 39 being disposed on flange 33 between ramps 30A, 31A of shoulders 30, 31. Neutral conductor 38B has its ring terminal 39 located between shoulder 31 and a locating and shielding wall 40, and the ring terminal 39 of live conductor 38A is located in recess 35 of shoulder 31, the conductor being located by lead-in groove 36. A wall 41 shields fuse link strap 29 from the conductors 38A, 38B, 38C and ring terminals 39. To provide insulation additional to that provided by the plug body 20 there is provided an internal insulating cover 42. With the pins 26, conductors 38A, 38B, 38C fuse link strap 29 and fuse clips 28 secured together through the intermediary of the base insert 24 as aforesaid, the insulating cover 42 is then fitted over the latter. To facilitate such fitment the base insert 24 has on two opposed edges projecting noses 43 of somewhat bevelled shape. The cover 42 is a flexible thin walled casing or shell formed of a relatively flexible plastics material and has at two opposed ends a pair of windows 44 (only one pair shown). The cover 42 generally follows the shape of the base insert 24. It is simply clipped on over the latter until the noses 43 protrude through the windows 44 (see Figs. 2 and 8). This assembly is then located in an appropriately configured mould and the plug body 20 moulded therearound and around the cable 23. The method of clipping the base insert and insulating cover together prior to the final moulding stage can also be varied to suit requirements. One or more sides of the insulating cover 42 has an indicator pip or projection which in the finished moulded-on plug will be visible thus indicating to the manufacturer that the supplementary cover is incorporated in the plug and has not been inadvertently omitted. In the present embodiment a pair of such indicator pips 42A are provided. The electrical plug construction is completed for the provision of a fuse 45 which clips into the fuse clips 28. This fuse 45 is supported in a carrier 46 comprising a plate 47 for releasably closing recess 27 and an integral sleeve 48 through which extends the fuse 45. The plate 47 has a window 49 (see Fig. 1) through which the fuse 45 can be viewed. It will be manifest that the external configuration of the plug can be of any convenient shape, for example the front and rear faces may be substantially parallel, or the front face wholly sloping instead of just partially as in the described embodiment. Reference is made to our copending Patent Applications Nos. 35448/76 (Serial No. 1,581,661) and 2469/79(Serial No.1,581,662), the former of which discloses and claims the moulded-on electrical plug disclosed herein, while the latter discloses and claims the insulating base insert of the domestic electrical plug disclosed herein. WHAT WE CLAIM IS:-

1. An internal insulating cover for incorporation in a moulded-on domestic electrical plug comprising an insulating base insert mounting metal pins for insertion in an electrical socket and to which are electrically connected the conductors of an electrical cable and an insulating body integrally moulded with the base insert wholly to encose the connections of the conductors to terminals of the plug, the internal insulating cover comprising a flexible plastics casing adapted to be resiliently clipped over the base insert prior to moulding of the insulating body on to the insert, and having an integral pip or projection which is visible in the finished moulded-on plug to

indicate its presence to the manufacturer.

2. An internal insulating cover as claimed in claim 1 in which the casing is formed with formations adapted to cooperate with complementary formations on the base insert to effect the clipping securement of the casing over the latter.

3. An internal insulating cover as claimed in claim 2, in which the formations in the casing comprise at two opposed sides windows adapted to snap fit around complementary noses on the base insert.

4. An internal insulating cover as claimed in any one of claims 1 to 3 in which the casing has two spaced side-by-side indicator pips or projections at one side thereof which are visible in the finished plug.

5. An internal insulating cover for incorporation in a moulded-on domestic electrical plug comprising an insulating base insert mounting metal pins for insertion in an electrical socket and to which are electrically connected the conductors of an electrical cable and an insulating body integrally moulded with the base insert wholly to enclose the connections of the conductors to terminals of the plug, the internal insulating cover being substantially as hereinbefore described with reference to the accompanying drawings.