GB2164507A - Sleeved plug pins - Google Patents

Abstract

The current carrying pins (5) of an electric plug are fitted with respective insulating sleeves (6), each sleeve being secured on the pin by a bridging piece which interconnects parts (8) of the sleeve located on opposite sides of the pin and extends through an opening (10) e.g. a hole or edge recess in the pin. <IMAGE>

Description

SPECIFICATION Sleeved plug pins This invention relates to electric plugs, and in particular to plugs for connecting electrical appliances to a mains electricity supply system.

It is known for the current carrying pins of an electric plug to be provided with insulating sleeves which cover the portions of pins protruding from the body of the plug. The sleeves reduce the risk of electric shock due to a person handling the plug touching inadvertently the pins as the plug is pushed into or withdrawn from an electric socket.

According to one prior proposal, each sleeve is made in two equal halves which are secured together around the pin by welding together their abutting edges which extend along the pin. A drawback with this construction is that the sleeve halves and the portion of the pin onto which the sleeve is fitted must be made to close tolerances. If the sleeve is too small relative to the pin the edges will not abut and a satisfactory weld will not be obtainable, whereas if the sleeve is too big it will be loose on the pin. Thus, the sleeve halves must make a good fit with the pin.

Furthermore, the welding operation is complicated due to the relatively long and narrow shape of the surfaces which are welded together.

In accordance with the present invention there is provided an electric plug having a body and at least one contact pin fitted with a sleeve of insulating material covering a portion of the pin protruding from the body, wherein the sleeve comprises parts located on opposites sides of the pin and a bridging piece interconnecting said opposed parts and extending through an opening in the pin.

Conveniently, where the contact pin is rectangular in cross-section, the opposed parts of the sleeve are channel-shaped. The sleeve parts may be made a separate element and be secured directly together on the pin, or alternatively they can be joined by an integral hinge and be held closed together around the pin by the bridging piece.

In one embodiment each sleeve part is formed with a projection which defines a portion of the bridging piece, the projections being fixed together, e.g. by welding within the pin opening. According to another embodiment the bridging piece is defined by a projection formed integrally on one sleeve part and fixed to the other sleeve part.

The opening in the contact pin may be a notch or recess in a side edge of the pin, or a hole passing transversely through the pin. The sleeve parts are preferably fastened together, through a bridging piece, by ultrasonic welding, to fix the sleeve to the pin. Other fastening techniques are also possible, such as solvent welding, adhesive bonding or snap connections.

As the sleeve edges are not connected directly together it is not essential for them to abut and a small gap can be tolerated. Consequently, it is not necessary to maintain close tolerances when making the pins and sleeves.

In addition, when a welded construction is used, production of the weld is simplified because it is confined to the relatively small compact area of the bridging piece.

A full understanding of the invention will be had from the following detailed description of some embodiments, reference being made to the accompanying drawings in which: Figure 1 is a perspective view of an electric plug embodying the invention; Figure 2 is an enlarged scale side view showing a section of one sleeve pin; Figure 3 is a front elevation of one sleeve half before attachment to the pin; Figure 4 is an end elevation of the sleeve half; and Figures 5-11 illustrate some alternative forms of sleeve embodying the invention.

The electric plug illustrated in Fig. 1 is of generally known construction inasmuch that it includes a hollow body of insulating material made up by a base 1 and a cover 2. The cover includes a cable entry 3 and the base carries the contact pins, namely an earth pin 4 and two current carrying pins 5 arranged in the conventional manner of a standard 13 amp plug. The pins 5 are fitted with insulating sleeves 6 which cover the portions of the pins protruding from the body. The sleeves are positioned within recesses in the pins so that their outer surfaces are flush with the exposed pin surfaces, whereby the sleeves will not impede movement of the pins into or out of the apertures of an electric socket.

Each sleeve is formed of two parts which in the embodiment of Figs. 1 to 4 are the same and comprise a channel-shaped element 8 with a central connecting post or stud 9. The pin is provided with a through hole 10 at the centre of its recessed portion to allow the two sleeve halves to be located on opposite sides of the pin with their posts 9 extending through the hole 10 into abutment with each other. The posts 9 are made slightly higher than the side walls of the channel, as may be seen in Fig. 4, to ensure that the posts will abut when the sleeve elements are assembled onto the pin, and to assist assembly of the elements 8 onto the pin the side walls of the channel are chamfered on the inner surfaces at their free edges. When the sleeve elements have been positioned onto the pin the abutting surfaces of posts 9 are fixed together by ultrasonic welding.The fact that the longitudinal edges of the sleeve elements may not meet in the completed sleeve is not a serious disadvantage since the gap will be very small and will not allow the pin to be touched with a finger.

Although one connecting post is adequate, two or more could be used if preferred. In addition the post could be provided on one element only to pass through the hole in the pin for connection to the other element. It is not essential for the connection post to be located through a hole in the pin and it may pass instead through a noch or recess formed at the side of the pin, for example as in the embodiment shown in Figs. 5 to 7. In this case two posts 19 are provided on one sleeve element 18 and pass through a pair of notches 20 provided in the opposite edges of the pin for their end faces to be welded to the other sleeve element 17.

The modified construction shown in Figs. 8 to 10 is basically similar to that of Figs. 5 to 7, but differs in that one post 29 is provided on each element 28 so that the two elements are the same, and the posts are located adjacent the ends of the sleeve rather than at the middle.

Another sleeve design embodying the invention is shown in perspective view in Fig. 11, and is intended for use with a pin having a central hole as in Figs. 1 to 3. The sleeve consists of two parts, with one part 38 including an integral connecting post 39 of sufficient length to pass through the hole in the pin and enter a hole 40 formed in the second sleeve part 37. The sleeve is fixed on the pin by staking over the end of the post 39 by ultrasonic welding or bonding techniques. Ideally, in the completed assembly the end of post 39 is substantially flush with the outer surface of the sleeve parts 37.

Other forms of sleeve are of course possible without departing from the scope of the invention.

While the invention has been described with specific reference to two-part sleeves, it is also applicable to sleeves on which the two parts connected through an opening in the pin are integrally hinged at one edge.

Another advantage of the invention is that the bridging piece connecting the sleeve parts together through an opening in the pin serves to retain the sleeve against movement longitudinally of the pin. Consequently, the sleeve is not required to fit exactly between opposed shoulders on the pin to prevent such movement, and hence greater tolerances are acceptable in the length of the pin recess.

Claims (13)

1. An electric plug having a body and at least one contact pin fitted with a sleeve of insulating material covering a portion of the pin protruding from the body, wherein the sleeve comprises parts located on opposite sides of the pin and a bridging piece interconnecting said opposed parts and extending through an opening in the pin.

2. An electric plug according to claim 1, wherein contact pin is rectangular in crosssection, and the opposed parts of the sleeve are channel-shaped.

3. An electric plug according to claim 1 or 2, wherein the opposed sleeve parts are made as separate elements and are secured directly together on the pin.

4. An electric plug according to claim 1 or 2, wherein the opposed sleeve parts are connected by an integral hinge and are secured together on the pin by the bridging piece.

5. An electric plug according to any one of the preceding claims, wherein the bridging piece is defined by projections integral with the respective sleeve parts and fixed together within the pin opening.

6. An electric plug according to any one of claims 1 to 4, wherein the bridging piece is defined by a projection found integrally with one sleeve part and fixed to the opposed sleeve part.

7. An electric plug according to claim 6, wherein said opposed sleeve part is provided with a hole and said projection is received and fixed in the hole.

8. An electric plug according to claim 6, wherein each sleeve part is formed with an integral projection, the projections defining separate bridging pieces extending through respective openings to secure the sleeve parts together.

9. An electric plug according to any one of claims 1 to 5 or 8, wherein the opposed sleeve parts are of substantially the same form.

10. An electric plug according to any one of claims 1 to 7, wherein the opening in the contact pin is a hole passing transversely through the pin.

11. An electric plug according to any one of claims 1 to 6, or 8, wherein the opening in contact pin comprises a recess in a side edge of the pin.

12. An electric plug according to claim 11, wherein recesses are provided in opposed side edges of the pin and define openings receiving respective bridging pieces interconnecting the opposed sleeve parts.

13. An electric plug substantially as herein described with reference to the accompanying drawings.