GB2068652A - Electric plug - Google Patents

Abstract

An electric plug has, projecting from and integral with a moulded body of insulating material, at least two line pins of electrically insulating material (1), each of which line pins has an elongate electric conductor (2) wholly embedded in and extending along the length of the pin and electrically connected to a cable. A contact (3), electrically connected to the conductor (2), has at least one exposed surface for effecting electrical contact with a socket outlet and is bonded to and/or partially embedded in the pin at or near its free end. <IMAGE>

Description

SPECIFICATION An improved electric plug This invention relates to electric plugs and is especially, but not exclusively, concerned with electric plugs for use in domestic and similar wiring systems.

When an electric plug is electrically connected in a socket outlet but faces of the plug and outlet do not abut, there is a substantial risk that a child or other person will introduce a finger or other object between the faces, will touch a live pin, and will receive an electric shock. To reduce this risk it has been proposed and is sometimes the practice to provide on at least each line pin of the plug an insulating protective covering which extends around and along a substantial part of the length of the pin projecting from the insulating plug body. Such insulating protective pin coverings may be integral parts of the plug body but more recently it has been proposed to use, for each insulating pin covering, a separate sleeve of insulating material which fits over a part of the length of a pin or a separate body of insulating material which is moulded in situ on a pin.

It is an object of the present invention to provide an improved electric plug having insulated line pins, which electric plug is simpler in construction and less expensive to manufacture than electric plugs having insulated line pins hitherto proposed and used.

According to the invention the improved electric plug comprises a moulded body of electrically insulating material and, projecting from and integral with the moulded body, at least two line pins of electrically insulating material, each of which line pins has an elongate electric conductor wholly embedded in and extending along the length ofthe pin and electrically connected to, or adapted to be electrically connected to, a conductor of a flexible electric cable, and has, bonded to and/or partially embedded in the line pin at or near its free end, at least one electrically conductive contact which is electrically connected to the embedded elongate electric conductor and which has at least one exposed contact surface for effecting electrical contact with a socket of a socket outlet.

Where, as is preferred, each line pin is of substantially rectangular overall cross-section - as is the case in an electric plug for use in a "13 amp" domestic wiring system - preferably, the electrically conductive contact of each line pin has exposed contact surfaces partially embedded in at least the opposed major faces of the pin. Alternatively, for pins of rectangular or any other overall cross-section, the electrically conductive contact of each line pin may have a contact surface which extends continuously around the pin.

The present invention is applicable both to non rewireabie electric plugs, that is to say an electric plug in which the electrical connections between the conductors of a flexible electric cable and the plug pin terminals are wholly embedded in the moulded body and the moulded body is bonded to the electric cable, and to rewireable electric plugs, that is to say an electric plug in which the plug pin terminals by the moulded body are exposed and the conductors of a flexible electric cable can be electrically connected to or disconnected from the pin terminals after removal of a separately formed cover.

In the case of a non-rewireabie electric plug, the elongate electric conductors embedded in and extending along the lengths of the line pins may each be a rigid or semi-rigid rod or other elongate member carrying at its end remote from the electrically conductive contact, terminal means to which a cable conductor is electrically connected; said terminal means may take any convenient and/or conventional form. Aiternatively, the elongate conductors embedded in the line pins may each be constituted by a length of one of the conductors of the electric cable to which the plug is to be bonded, the cable conductor being electrically connected directly to the electrically conductive contact of the pin and the connection being wholly embedded within the moulded pin.In this latter case, preferably, apart from the extreme end of the conductor from which its insulation is removed to facilitate making of the electrical connection, the length of cable conductor extending along and embedded in the pin retains its insulating covering which serves to improve the bond between the insulated conductor and the moulded material of the pin.

In the case of a rewireable electric plug, the elongate electric conductors embedded in the line pins are each preferably a rigid or semi-rigid rod or other elongate member which carries at its end remote from the electrically conductive contact, terminal means to or from which a cable conductor can be electrically connected or disconnected, the terminal means being detachably or permanently mounted in an exposed position on the moulded body. The terminal means may take any conventional form.

Where regulations require that the electric plug incorporates means for electrically connecting a cartridge fuse between the live pin and its associated conductor terminal, the moulded body may be moulded with a recess in the face of the body from which the pins protrude and may have partially embedded in the recess appropriate spring contacts for reception of a cartridge fuse. The cartridge fuse recess may be closed by a separately formed cover.

The electric plug of the present invention has the important advantage in that, in all cases, the quantity of metal required on each line pin to effect electrical connection to a socket may be substantially no greater than the amount necessary to avoid overheating of the plug occurring when the plug is connected to a source of voltage supply; a substantial saving in metal can therefore be made. In addition, the area of exposed contact surface on each line pin can aiso be kept to the minimum necessary to effect an efficient electrical connection with a socket, thereby substantially reducing the risk that a child or other person might receive an electric shock if a finger or other object is inserted between the neighbouring faces of a plug and socket outlet.

Furthermore, in the case of a non-rewireable electric plug, risk that astray wire of an end of one of the cable conductors might protrude through the moulded body can be substantially reduced by enclosing the connections between the cable conductors and the pin terminals by a preformed cover or preformed covers before moulding of the body takes place or by effecting the electrical connection between each cable conductor and its associated electrically conductive contact of the associated line pin within the line pin itself, so that, if a stray wire from the end of the connector should protrude through the line pin, it will be in a position where risk of electric shockto a user is a minimum.

The invention is further illustrated by a description, by way of example, of a preferred nonrewireable electric plug with reference to the accompanying drawings, in which: Figures land 2 show fragmental isometric views of one pin of the non-rewireable plug.

The non-rewireable plug comprises a moulded body (not shown) of plastics insulating material which is bonded to the plastics sheath of a flexible cable (not shown) whose conductors are electrically connected to three conductor terminals wholly embedded in the moulded body and which has, projecting from one face of and integral with the moulded body, three pins of electrical insulating plastics material, two of the pins being line pins (of which one only is shown) and the other pin constituting an earth pin. The three pins are of substantially identical construction.

The line pin illustrated has, wholly embedded in and extending along the length of, the moulded insulating material 1 of the pin an elongate conductor 2 which, at one end, is electrically connected to the associated conductor terminal embedded in the plug body and, at the other end, is electrically connected to a separately formed electrically conductive contact 3 bonded to and partially embedded in the moulded material 1 of the pin. The electrically conductive contact 3 is made from a single strip 4 of metal which is so folded that it is of approximately U-shape, with the base of the U positioned at the free end of the pin. One limb of the U-shaped contact 3 is extended to form a ferrule 5 and the other limb of the U-shaped contact is extended to form a tongue 6. In effecting the electrical connection between the elongate conductor 2 and the U-shaped contact 3, an end of the conductor and the tongue 6 are positioned side by side within the ferrule 5 and the ferrule is crimped to lock the conductor and the tongue in electrical contact.

Claims (3)

1. An electric plug comprising a moulded body of electrically insulating material and, projecting from and integral with the moulded body, at least two line pins of electrically insulating material, each of which line pins has an elongate electric conductor wholly embedded in and extending along the length of the pin and electrically connected to, or adapted to be electrically connected to, a conductor of a flexible electric cable and has, bonded to and/or partially embedded in the line pin at or near its free end, at least one electrically conductive contact which is electrically connected to the embedded elongate electric conductor and which has at least one exposed contact surface for effecting electrical contact with a socket of a socket outlet.

2. A plug according to Claim 1,wherein each line pin is of substantially rectangular overall crosssection and the electrically conductive contact of each line pin has exposed contact surfaces partially embedded in at least the opposed major faces of the pin.

3. A plug substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.