GB1581661A

GB1581661A - Electrical plugs

Info

Publication number: GB1581661A
Application number: GB35448/76A
Authority: GB
Original assignee: Ward and Goldstone Ltd
Current assignee: Volex PLC
Priority date: 1976-08-26
Filing date: 1976-08-26
Publication date: 1980-12-17
Also published as: ZA775058B

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRICAL PLUGS (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 electrical plugs for attachment to electrical appliances and for use in coupling such appliances 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 resuIt 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 orleadwiredtothe 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 electrically safe moulded-on plug.

According to the present invention a moulded-on domestic electrical plug com- prises 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 conductor connections, which, prior to moulding on of the integral body, are shielded by an insulating cover.

The cover provides additional insulation which prevents any risk of exposure to the surface of live parts.

Preferably this cover is a thin-walled, clipon plastics shell which may be apertured in areas other than the conductor connection areas.

Preferably, the connections of the pins and conductors are housed in recessed areas of the base insert so as not to stand proud of the surface thereof.

Preferably, the connections of the live and neutral pins and their corresponding conductors are at different levels of the base insert when the plug is viewed with the pins depending.

Preferably, the earth conductor passes between two shoulders of the base insert, the connection between the earth conductor and its pin being at a different level to the live and neutral connections when the plug is viewed with the pins depending.

These shoulders may be roughened ortoothed so as to bite into the insulation of the earth conductor when the latter is pressed between the shoulders during assembly so that any tendency for disconnection between the earth conductor and its pin to occur during moulding on of the insulating body is prevented.

The base insert may be recessed between the pins to accommodate a pair of fuseholding clips one of which is connected to the live pin, via a fuse link strap while the other is connected to the live conductor and the recess being closeable by fuse holder and cover.

Preferably, the fuse holder and cover is pivotted at one of its ends to the base insert to facilitate fuse replacement. It may be alternatively completely detachable by sliding or lifting.

The fuse holder and cover is preferably apertured to permit viewing of the fuse and has an integral sleeve or loop adjacent to the aperture to receive and hold a cartridge-type fuse.

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 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 Figs. 5 to 7 are respectively a front view, a rear view and a side view sectional view on line VII-VII of Fig. 5 of the base insert; Fig. 8 is a perspective view of the assembled base insert and cover of Fig. 4; 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 moulded strong enough to resists 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 of urrea (phenolic type). This base insert 24 is formed with three elongate passages 25 to receive live, neutral and earth pins 26A, 26B 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, or alternatively the end of the latter is peened over the strap, 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 the 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. Flange 33 is at a lower level than the platform 34A.

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 as aforesaid.

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.

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, there is then fitted over the latter an insulating cover 42.

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 thin walled shell formed of a relatively flexible plastics material, for example a polyamide 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 appro- priately configured mould and the plug body 20 moulded therearound and around the cable 23.

The insulating cover 42 is shaped according to the shape of the base insert and the method of clipping or otherwise securing them together prior to the final moulding stage can also be varied to suit requirements.

One or more sides of the insulating cover 42 may have 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 is to be noted, inter alia, that the heads of the rivets are preferably spun to ensure proper electrical connection between ring terminals 39 and pins 26.

The above described moulded-on electrical plug ensures no unwanted electrical contact between any of the conductor terminals and dte to the layout of the terminals the conductor runs are smooth and curved without any acute bends.

The moulded-on electrical plug may incorporate a neon indicator lamp.

The fitment of the neon indicator lamp may be effected by providing on the base insert at an appropriate location prior to the integration of the base insert and body a pre-wired neon indicator lamp housed within a flexible enclosure of thermoplastics material, which enclosure projects a predetermined distance above the top of the body when same is moulded on to the base insert, the enclosure partially collapsing at body moulding-on stage and the top of the enclosure forming the wndow through which the neon indicator lamp can be viewed.

Th height which the enclosure projects above the top of the body and the inherent resilience of the enclosure, or a separate resilience given thereto by, for example, a rubber cushion, determines the extent of collapse of the enclosure and ensures nonshattering thereof under pressure. The window of the enclosure in the finished moulded-on plug is preferably flush with the top surface of the plug body but alternatively the window may stand proud of the body top surface or be recessed relative thereto.

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 ofjust partially as in the described embodiment.

In a modification, each pin may, adjacent its end to which a wire or conductor will be secured, be formed with an outwardly extending shoulder preventing its passage through the base, which shoulder is forced into intimate contact with the inner surface of the base insert during manufacture.

Each pin at its wire-receiving end may have two projections between which a bared portion of its corresponding wire is disposed, the projections then being crimped or otherwise pressed together to secure the pin to the wire conductor.

Reference is made to our copending Patent Applications Nos. 2469/79 (Serial No.

1581662) and 2471/79 (Serial No. 1581663) the former of which discloses and claims the insulating base insert of the domestic electrical plug of the present invention, while the latter discloses and claims the insulating cover of the domestic electrical plug of the present invention.

WHAT WE CLAIM IS: 1. 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 conductor connections, which, prior to moulding on of the integral body are shielded by an insulating cover.

2. A plug as claimed in claim 1, wherein the insulating cover comprises a thin-walled, clip-on plastics shell.

3. A plug as claimed in claim 2, in which the shell is apertured in areas other than the conductor connection areas.

4. A plug as claimed in any one of claims 1 to 3, in which the connections of the pins and conductors are housed in recessed areas of the base insert.

5. A plug as claimed in any one of claims 1 to 4, in which the connections of the live and neutral pins and their corresponding conductors are at different levels of the base insert when the plug is viewed with the pins depending.

6. A plug as claimed in claim 5 in which the earth conductor passes between and is located by two shoulders of the base insert, the connection between the earth conductor and its pin being at a different level to the live and neutral connections when the plug is viewed with the pins depending.

7. A plug as claimed in claim 6, in which the surfaces of the shoulders contacting the earth conductor are roughened or toothed so as to bite into the insulation of the latter to prevent disconnection between the conductor and its pin during the final moulding stage.

8. A plug as claimed in any preceding claim in which the base insert is recessed between the pins to accommodate a pair of fuse-holding clips, one of which is connected to the live pin via a fuse link strap while the other is connected to the live conductor, the recess being closable by a fuse holder and cover.

9. A plug as claimed in claim 8, in which the fuse holder and cover is pivoted to the base insert or is removable therefrom to facilitate fuse replacement.

10. A plug as claimed in claim 8 or 9 in which the fuse holder and cover is apertured to permit viewing of the fuse and has an integral sleeve or loop adjacent the aperture to receive and hold a cartridge-type fuse.

11. A plug as claimed in any preceding claim, in which the insulating cover has at least one indicator pip or projection which, in the finished moulded-on plug, will be visible thus indicating the presence of the cover.

12. A plug as claimed in any preceding claim, in which the base insert has walls or barriers which isolate adjacent conductors one from another.

13. A plug as claimed in any preceding claim in which each pin adjacent its end to which a conductor is secured has an outwardly extending shoulder preventing its passage through the base insert, which shoulder is forced into intimate contact with the surface of the base insert during manufacture.

14. A plug as claimed in any one of the preceding claims, in which each pin at its conductor-receiving end has two projections between which a bared portion of its corres

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

Claims

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

moulded on to the base insert, the enclosure partially collapsing at body moulding-on stage and the top of the enclosure forming the wndow through which the neon indicator lamp can be viewed.

Th height which the enclosure projects above the top of the body and the inherent resilience of the enclosure, or a separate resilience given thereto by, for example, a rubber cushion, determines the extent of collapse of the enclosure and ensures nonshattering thereof under pressure. The window of the enclosure in the finished moulded-on plug is preferably flush with the top surface of the plug body but alternatively the window may stand proud of the body top surface or be recessed relative thereto.

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 ofjust partially as in the described embodiment.

In a modification, each pin may, adjacent its end to which a wire or conductor will be secured, be formed with an outwardly extending shoulder preventing its passage through the base, which shoulder is forced into intimate contact with the inner surface of the base insert during manufacture.

Each pin at its wire-receiving end may have two projections between which a bared portion of its corresponding wire is disposed, the projections then being crimped or otherwise pressed together to secure the pin to the wire conductor.

Reference is made to our copending Patent Applications Nos. 2469/79 (Serial No.

1581662) and 2471/79 (Serial No. 1581663) the former of which discloses and claims the insulating base insert of the domestic electrical plug of the present invention, while the latter discloses and claims the insulating cover of the domestic electrical plug of the present invention.

WHAT WE CLAIM IS: 1. 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 conductor connections, which, prior to moulding on of the integral body are shielded by an insulating cover.
2. A plug as claimed in claim 1, wherein the insulating cover comprises a thin-walled, clip-on plastics shell.
3. A plug as claimed in claim 2, in which the shell is apertured in areas other than the conductor connection areas.
4. A plug as claimed in any one of claims 1 to 3, in which the connections of the pins and conductors are housed in recessed areas of the base insert.
5. A plug as claimed in any one of claims 1 to 4, in which the connections of the live and neutral pins and their corresponding conductors are at different levels of the base insert when the plug is viewed with the pins depending.
6. A plug as claimed in claim 5 in which the earth conductor passes between and is located by two shoulders of the base insert, the connection between the earth conductor and its pin being at a different level to the live and neutral connections when the plug is viewed with the pins depending.
7. A plug as claimed in claim 6, in which the surfaces of the shoulders contacting the earth conductor are roughened or toothed so as to bite into the insulation of the latter to prevent disconnection between the conductor and its pin during the final moulding stage.
8. A plug as claimed in any preceding claim in which the base insert is recessed between the pins to accommodate a pair of fuse-holding clips, one of which is connected to the live pin via a fuse link strap while the other is connected to the live conductor, the recess being closable by a fuse holder and cover.
9. A plug as claimed in claim 8, in which the fuse holder and cover is pivoted to the base insert or is removable therefrom to facilitate fuse replacement.
10. A plug as claimed in claim 8 or 9 in which the fuse holder and cover is apertured to permit viewing of the fuse and has an integral sleeve or loop adjacent the aperture to receive and hold a cartridge-type fuse.
11. A plug as claimed in any preceding claim, in which the insulating cover has at least one indicator pip or projection which, in the finished moulded-on plug, will be visible thus indicating the presence of the cover.
12. A plug as claimed in any preceding claim, in which the base insert has walls or barriers which isolate adjacent conductors one from another.
13. A plug as claimed in any preceding claim in which each pin adjacent its end to which a conductor is secured has an outwardly extending shoulder preventing its passage through the base insert, which shoulder is forced into intimate contact with the surface of the base insert during manufacture.
14. A plug as claimed in any one of the preceding claims, in which each pin at its conductor-receiving end has two projections between which a bared portion of its corres

ponding conductor is disposed, the projections then being crimped or otherwise pressed together to secure the conductors to the pin.
15. A moulded-on domestic electrical plug, substantially as hereinbefore described with reference to the accompanying drawings.