AU652241B2

AU652241B2 - Electrical plug

Info

Publication number: AU652241B2
Application number: AU15147/92A
Authority: AU
Inventors: Peter Simon
Original assignee: HPM Industries Pty Ltd
Current assignee: HPM Industries Pty Ltd
Priority date: 1991-06-05
Filing date: 1992-04-24
Publication date: 1994-08-18
Anticipated expiration: 2012-04-24
Also published as: AU1514792A

Description

1- P/00/0o11 Regulation 3.2

AUSTRALIA

Patents Act 1 990 652241

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: ELECTRICAL PLUG

C,

tie,

C.

C

eCe C tee,,, t C. C C SC The following statement is a full description of this invention, including the best method of performing it known to me/us:

C

C i* GH&CO REF: 0421 0-PI RW/SMcL 2 This invention relates to a plug for attachment to an electric cord and, in particular, to a plug which incorporates an ancillary device which may be used for isolating or protecting apparatus which is connected to an electrical supply by way of the plug.

The invention has been developed from the concept of incorporating a device in the form of a surge protection circuit in a plug and the invention is hereinafter described in such context. However, it will be understood that other ancillary devices may be incorporated in the plug, for example a switch, a fuse or an earth leakage protection circuit.

Electrical plugs are available in some countries in forms which include replaceable cartridge fuses.

However, the fuses are contained in the main body of the plugs and bare wiring to the plug pins is exposed when the plugs are disassembled for the purpose of replacing damaged fuses. In contrast with these known arrangements, the present invention is directed to a plug in which an ancillary device is housed within a compartment which is separate from the wiring to the plug pins.

That is, the present invention provides an electrical plug which comprises a first moulding 25 component and contact pins located in and projecting from the first moulding component. A second moulding component is assembled to the first moulding component in a manner so as to cover terminal ends of the contact pins, and a recess is formed in the second moulding component. The recess is separated from the terminal ends of the contact pins by a wall portion of the second moulding component. A third moulding component is secured to the second moulding component and covers the recess to form a closed compartment. An ancillary electrical device is located within the compartment and is electrically connected with electrical wiring in the first moulding component. The ancillary device includes 1OPI/428 o 5o

S

C

S.

*0 S S *5 ~Li i Wv I i i c :iL- 3 both a surge voltage protection circuit and an indicator lamp, and a lens is located in the third moulding component for transmitting light radiation by the lamp.

The third moulding component may be secured to the second component by either a permanent or removable interconnection. That is, the third moulding component may be welded, adhered or mechanically interconnected to the second moulding component, or the connection may be made by way of one or more removable screws. As a further alternative, the third moulding component may be removably connected to the second moulding component by way of an interfering frictional or snap fitting interconnection.

The second moulding component may be screw connected or otherwise removably connected to the first moulding component, so that the plug may be disassembled for wiring and rewiring purposes. Alternatively, the second moulding component may be assembled to the first moulding component in a permanent manner to form, in effect, a non-rewirable plug.

The invention will be more fully understood from the following description of a preferred embodiment of a plug as illustrated in the accompanying drawings. In the drawings: 25 Figure 1 shows a rear view of the plug, Figure 2 shows a similar view of the plug but with second and third moulding components removed to expose wiring within the rear of the plug, Figure 3 shows a side view of the plug as seen in 30 the direction of a cord entry to the plug, Figure 4 shows a sectional elevation view of the plug as seen in the direction of section plane 4-4 in Figure 1, Figure 5 shows a sectional elevation view of the plug as seen in the direction of section plane 5-5 in Figure 1, '4C~t V CC C...r 0r Cr 0 *e 4* Cr

'S.C

1C i 9* 0 C 9 *0 44 -4- Figure 6 shows an enlarged detailed view of the portion of the encircled region of the plug of Figure and Figure 7 shows a diagram appropriate to a surge protector circuit which is located within the plug.

As illustrated, the plug assembly comprises a first moulding component 10, a second moulding component 11 assembled to the first component 10, and a third moulding component 12 which is secured to the second component 11.

Electrical contact pins 13 extend through apertures within the first moulding component 10 and are held in place by the wall 14 of a recess 15 in the second moulding component 11. Terminal ends 16 of wire 17 of a cord 18 are located within a cavity 19 within the first moulding component 10 and normally are concealed by the second moulding component 11. The wire ends 16 are crimped or soldered to respective ones of the contact pins 13.

The first moulding component has a generally cylindrical configuration but includes a laterally S• projecting neck 19 through which the cord 18 extends.

The neck is formed with a generally U-shaped channel for receiving the cord and the open side of the channel e* 0 S°is closed by a laterally extending portion 21 of the 25 second moulding component 11.

Sie walls of the channel 20 within the first o,: moulding component 10 are formed with recesses 22 which receive complementary projections 23 of the second 3 moulding component 11, and a laterally extending portion 30 21 of the second moulding component is held in snapfitting engagement within the open side of the channel Also, two inwardly projecting nibs 20a are located at the entrance to the recess 19, the nibs being shaped and sized to act as barbs and to anchor the end of the cord 18 within the first moulding component.

The first moulding component 10 is formed with a peripheral recess 24 having a seating surface 25 and a surrounding lip 26, and the second moulding component 11 S:04210P1/428 ai is formed with a complementary peripheral rim 27. When the second moulding component 11 is finally fitted to the first moulding component 10, the outer margin of the rim 27 seals against the seating surface 25 and, as can best be seen in Figure 6, a clearance angle 8 is present between the seating surface 25 and the mating surface of i the rim 27. As will be hereinafter described, the clearance angle 8 closes during assembly of the first and second moulding components 10 and II.

As can be seen from Figure 4, the first moulding component 10 has a peripheral wall 28 which is formed at angularly spaced locations with four inwardly directed ledges 29. Each of the ledges is aligned with an aperture 30 and each ledge is confronted by an integrally moulding barrier 31. Also, the second moulding component 11 is formed integrally with four downwardly extending S0*"0 projections 32 which incorporate outwardly directed ledges 33. The moulded projections 32 are resiliently deformable so that the outwardly directed ledges 33 may 20 move past the inwardly directed ledges 29 when the omoulding components are being fitted together, and when one ledge has moved past the other the outwardly directed ledges 33 snap-lock into the interlocking relationship which is illustrated in Figure 4.

S 25 When forcing the second moulding component 11 into the first moulding component 10 to an extent such that the ledges 29 and 33 in the respective mouldings can move °past one another, the clearance angle 8 (Figure 6) between the recess and the rim of the moulding components 30 closes to zero. Thereafter, when the interlocking relationship has been established between the ledges 29 and 33 and the assembling force is removed, the cover moulding 11 tends to resume its initial shape so that the clearance angle 8 opens slightly and a reactive force is thereby established between the interlocking ledges 29 and 33.

A circuit board 34 is located within the recess in the second moulding component and carries the circuit S:04210P1/428 6 elements which are shown in Figure 7 of the drawings.

Thus, the circuit board carries a metal oxide varistor (MOV) 35, a neon lamp 36, which is connected in series with a resistance 37, and a fuse element 38.

The circuit elements of Figure 7 form a surge S".rotector circuit and such circuit is connected to the Sictive and neutral pins 13 of the plug by wires which' r extend through apertures (not shown) in the wall 14 of the recess A light transmitting lens 39 is located in the third moulding component 12 and is positioned to transmit light from the neon indicator 36.

The surge protection circuit is provided in the plug to protect apparatus which is connected to an electrical supply by the plug. The surge protector circuit functions to protect the apparatus against high voltage surges resulting from lightening strikes or switching faults in the mains supply and, in the event of a 2 ransient high voltage, the metal oxide varistor 35 will function effectively as a short circuit and, with high current flow between the active and neutral lines, the fuse 38 will melt and the lamp 36 will extinguish to provide indication that a high voltage surge condition has existed in the supply. The plug may be used after 25 the fuse has been melted but without providing surge voltage protection.

1- As shown in the drawings, the third moulding •component 12 is secured to the second moulding component 11 by ultrasonic welding and is thus affixed permanently f to the second moulding component. However, if it is S° required that the surge protector or such other device as is located within the recess 12 should be accessible, the third moulding component may be secured to the second moulding component in a detachable manner.

S:0421 0PI/428

Claims

1. An electrical plug which comprises a first moulding component, contact pins located in and projecting from the first moulding component, a second moulding component assembled to the first component in a manner so as to cover terminal ends of the contact pins, a recess formed in the second moulding component and separated from the terminal ends of the contact pins by a wall portion of the second moulding component, a third moulding component secured to the second moulding component and covering the recess to form a closed compartment, an ancillary electrical device located within the compartment, the ancillary electrical device being electrically connected with electrical wiring in the first moulding component and including both a surge voltage protection circuit and an indicator lamp, and a lens located in the third moulding component for transmitting light radiated by the lamp.

2. The electrical plug as claimed in claim 1, wherein the surge voltage protection circuit includes a metal oxide varistor in series with a fuse, both of which are connected electrically across active and neutral contact pins in the first moulding component of the plug.

3. The electrical plug as claimed in claim 1 or 25 claim 2, wherein the third moulding component is removably secured to the second moulding component. l

4. The electrical plug as claimed in claim 1 or claim 2, wherein the third moulded component is welded to the second moulding component. 30

5. The electrical plug substantially as shown in the accompanying drawings and substantially as hereinbefore described with reference thereto. "DATED this 15th day of June 1994 H.P.M. INDUSTRIES PTY LIMITED By their Patent Attorneys S L GRIFFITH HACK CO. 11PI/428 h j j- 1