FIELD OF THE INVENTION

This invention relates to an electrical plug particularly suited for domestic or general use.

BACKGROUND TO THE INVENTION

In a typical dwelling the number of electrical wall sockets is often inadequate and has to be supplemented by adaptors which will permit a plurality of electrical plugs to be connected to a single wall socket.

Electrical plugs also do not always indicate whether power is on and available and do not always have surge protection.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an electrical plug which it is believed will, at least alleviate some of the abovementioned difficulties.

SUMMARY OF THE INVENTION

According to the invention an electrical plug unit comprises a housing from which a number of pin-type connectors project, the plug being adapted to be

coupled to an appliance by means of an electrical cord and charaterised in that the plug includes a socket arrangement in electrical contact with the pin connectors.

Preferably the socket arrangement will be opposed to and aligned with the pin connectors. Thus for example, a socket may be formed as an extension of each pin connector.

Further features of the plug member of the invention include gripping means for the electrical cord, a shutter for shielding the live socket formations, and optionally the provision of a fuse in a pin connector or between pin connectors.

The plug may also have a light for indicating the availability of electrical power.

These and other features of the invention will appear more clearly from the embodiment which is described below.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described by way of example only with reference to the accompanying drawings wherein:

Figure 1 is a perspective view of a plug member in accordance with a first embodiment of an electrical plug the invention;

Figure 2 is a sectional elevation of the plug member of figure 1 ;

Figure 3 is a top view of a second embodiment of an electrical plug;

Figure 4 is a top view of a third embodiment of an electrical plug;

Figure 5 is a top view of a fourth embodiment of an electrical plug;

Figure 6 is a side view of two fifth embodiments of an electrical plug;

Figure 7 is a top view of a sixth embodiment of an electrical plug;

Figure 8 is a cross sectional side view of a seventh embodiment of an electrical plug;

Figure 9 is a perspective view of a second embodiment of a pin for the plug member.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, in which like features are indicated by like numerals, an electrical plug in accordance with the invention includes a housing 10 from which pin contacts 11 , 12, project, the latter being adapted to mate with a corresponding wall socket, not shown. The earth pin is shown at 11 and the current carrying pins at 12. The pin contacts 11 , 12, extend into the interior of the housing 10 and are coupled or adapted to be coupled to an electrical cord 13 in a conventional manner, for example by means of grub screws 14 or the like which project into apertures 11a, 12a, passing through the pins 11 , 12.

It is a feature of the invention that each pin connector 11 , 12 is coupled to or integrally formed with an axially aligned socket formation 15, 16, which is adapted to receive a pin connector 11 , 12, of a similar plug unit. Preferably each socket formation 15, 16, will be adapted to be slightly expanded when a pin connector 11 , 12, is inserted therein to ensure a gripping action and proper electrical contact. Thus for example one or more longitudinal slots 15a, 16a, could be provided in the walls of the socket formations 15, 16, to provide resilient expansion thereof. It will be noted that apertures 17, 18, are provided in the upper side of the body 10 for pin connectors 11 , 12, of another plug to extend into the interior of the body and into the socket formations 15,

16. It is further envisaged that the apertures 18 could be closed by means of shutters 19 which are movable to open the apertures 18 when the earth pin connector 11 enters the aperture 17. Thus for example the earth connector 11 of another plug could engage a trigger mechanism which will act to move the shutters 19 to the open position.

In an alternative embodiment of a pin for the plug, shown in figure 9, the pin 11 or 12 includes the hole 102 and screw 101 combination for receiving conductive exposed strands on the end of an electrical wire and a bent sheet metal formation extending from a top end of the pin to form an open socket 100 having two opposed upright socket jaws. A round spring (not shown) may be located over the top ends 103 of the two formations of the open socket.

It is envisaged that the electrical cord 13 could either be removably or permanently secured to the pin formations 11 , 12. In the former case the body member will preferably be divided into a lid portion 10a and base portion 10b and capable of being disassembled to provide access to the interior of the body 10. One or more threaded screws 22 could for example be provided to hold the body 10 in its assembled condition. Alternatively, the base and lid sections could engage one another in snap on fashion. Where the cord 13 is removable, gripping means will preferably also be provided to clamp the cord relative to the housing 10. Such gripping means could comprise pivotally mounted jaw elements, not shown, or a clamping cone 21 or the like. The clamping cone 21 passes through a tapered aperture 10c in the body 10 so that when the cone 21 is drawn outwardly through the aperture 10c, it is

compressed to clamp the electrical cord 13. If required one or more longitudinal slits 21a could be provided in the cone 21 to assist with compressibility.

It is further envisaged that one or both of the current carrying pin connectors 12 will include fuse means 23 to prevent current overloading. Such fuse means 23 could for example comprise an interrupted zone in the pin connector which is coupled together by an insulating link 23a in screw thread fashion and includes a fuse 23b which will melt when current flow exceeds a predetermined value.

If desirable the plug unit 10 of the invention could further include a light emitting diode, not shown, which will be coupled across the pin connectors 12 with a suitable resistor to provide a visual indication of a live electrical condition.

It has been found that the plug member 10 of the invention has the advantage that a plurality of appliances can be coupled to a single wall socket or the like without the need for adaptor units. Thus each plug unit provides a socket for a subsequent plug.

The socket formations 15, 16 may also be jaw-like upright formations. The jaws may be resilient to snugly receive the pin of the second plug therein.

The plug may also be configured in two-pin configuration or a combination thereof.

Figure 3, 4 and 5 show plugs 29, 30 and 32 having a light 24 which is illuminated when mains power is available to provide a visual indicator. It will be appreciated that such lights may also be included with the plugs shown in figures 1 , 2, 6, 7 and 8.

The light may be embedded in the housing or in a receptacle in the housing filled with clear or transparent resin.

The plug shown in figure 3 includes three pin connector holes 26, as well as 2 pin connector holes 27.

The plug shown in figure 4 includes a two pin connector 25 at its top. The plug shown in figure 5 has two pin connectors 25.

The plug shown in figure 6 (plugs 32 and 33) have pin connectors 26 and 27 that have a flattened surface. A correspondingly shaped hole at the top of plug 32 (as shown in figure 7) and/or 33 allows for the use of another plug having a pin which a flattened surface. These plugs are normally used in wall- outlet sockets on a separate electrical circuit for computers or other important equipment.

Figure 8 shows a side cut-away view of a plug such as plug 32 showing the grub screws 14 securing the cores 35 of a cable 36 in the holes 12a in the pins 12. A circuit breaker 37 may be included between pins 12 or between a pin 12 and pin 11.

It will be appreciated by those skilled in the art that many embodiments of the invention are possible without departing from the scope thereof. Any two or three pin configurations may be used as long as the plug has a hole in its body for receiving cable and attaching the cable cores to the pins and a further socket or holes for receiving a further two or three pin plug therein as well as a light for providing a visual power-on indicator and/or an electrical fuse.