GB2179796A - Sequentially broken automatic circuit breaker for mains electrical accessories - Google Patents

Abstract

An automatic circuit breaker for a mains electrical accessory such as a socket or trailing lead comprising a double-break switch link to be thrown out of contact on fault detection, in which one break always precedes the other. A switch member (10) has an associated floating medial pivot (16) between its electrically isolated electrical contacts (20A, 20B), with spring biasing (14) and latch (32). Break of the first contact set (20A, 22A) involves movement of the medial pivot (16) and tipping of the switch member thereon and on the second of said contact sets (20B, 22B), thereby breaking the first contact set (20A, 22A). A further fixed pivot (24) is then encountered to break the second contact set (20B,22B), pivoting continuing until switch member (10) meets a fixed stop 30. The latch (32) is released by an electromagnet, and a spring-urged reset button and test button are provided. Earth leakage and reverse polarity are sensed, in part by using a toroid. <IMAGE>

Description

SPECIFICATION Mains electrical accessories DESCRIPTION This invention relates to mains electrical accessories, such as socket outlets, switches, plugs, adapters, trailing leads etc, that additionally incorporated circuit breakers responsive to abnormal circuit conditions usually including earth leakage.

We have ourselves recently made various proposals for such accessories particularly the circuit breakers thereof whether in terms of their mechanical action, for example combining reset with an extension of normal accessory switch action and/or providing a swing action latch, or their fault detection circuitry, such as additionally detecting polarity reversal and/or loss of neutral.

One aspect of this invention concerns the provision or further provision of a consistent action for a double break switch link to be thrown out of contact in the fault-detected circuit breaker action, and to that end it is specifically proposed that one break is always preceded by the other break of the double-break action.

In a preferred embodiment, the switch member has an associated floating medial pivot between its electrical contacts and further associated spring biassing and latch means such that first break movement for first of said contacts involves movement of the medial pivot and tripping of the switch member thereon and on the second of the said contacts thereby breaking the first thereof, and that further break movement on a further then-encountered pivot later breaks the second of said contacts. A fixed rest may be provided for the switch member on the first contact side of the medial pivot, the further pivot being to the other side of the medial pivot.

Such sequential breaking of the first and second contacts is readily reflected in making of the second of the contacts before the first on resetting, say by a restoration force applied to move the switch member effectively from where it carries the first contact.

It is further preferred that the first and second contacts are electrically separate, each to serve a different one of live and neutral of mains electrical supply, when, of course, the live contact may break before the neutral and make after. Wire connections directly to the first and second contacts can usefully be of a flexible nature and further traverse a toroid to which control circuitry is responsive via a sense winding.

A particular structure may have the floating pivot effectively as a pip cooperating with an helical compression spring. Such structure may have the further pivot as a fixed buttress then usefully offering, via an extension into through or past the switch member, say at a flaring, edge-slotting or other formation therein or thereof, guidance for the switch link. Such structure may have a reset member movable against the switch member and moving the latter by a part of the reset member biassed towards the switch member and having a further relatively fixed part by which it is latched, with the biassed part then serving to assure adequate contact pressure at latching.Where the spring bias to the floating pivot is the only break force applied, as will be specifically described, the biassed part of the reset member requires sufficient spring force for holding the first contact in make position, and the floating pivot spring force is to hold the second contact in make position. A restricted permitted movement of such biassed part, in the break action, ensures throwing off of the reset member as well.

Specific embodiment can be with the reset member operative through an accessory front plate and the switch member biassed at its floating pivot towards that plate, with the first contact breaking towards the plate and the second contact breaking away from the plate as the switch member tips.

Another aspect of this invention concerns provision of fault circuit breaking in a mains electrical accessory having more than one accessory unit or module, for example as in a so-called double-socket when such circuit breaking may be common to two such units or modules.

In a preferred embodiment housing room for at least part of circuit breaking components is afforded by and at least partially in and behind a raised portion of the common front plate, which raised portion may be between two said units or modules, say between two sets of socket entries for a double socket outlet.

Specific implementation of this invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1, 2, and 3 are diagrammatic representations of make, intermediate break, and break conditions; Figure 4 and 5 are sectional and plan views of a particular structure; Figures 6 and 7 are front and side views of a preferred double-socket outlet; and Figure 8 is an outline circuit diagram for fault break control.

Referring first to Figs. 1 to 3, elongate switch member 10 is housed in a mains electrical accessory block affording, below a face plate (not shown) to which it is attached, a seat 12 for a helical compression spring 14 affording at its free end a floating medial pivot for the switch member 10 via locating engagement therewith shown at a pip 16. Extending to opposite sides relative to its medial floating pivot the switch member has first and second contacts 20A and 20B, and the block or associated face plate also affords fixed contacts 22A and 22B below and above the first and second contacts 20A and 20B, respectively. The block or associated face plate further affords a further pivot for the switch member which pivot is fixed at a buttress 24 having an extension 26 through a hole 28 in the switch member 10 for guiding the latter during make and break action.A fork and side-slotting of the member 10 could equally well, possibly advantageously, be used. The pivot buttress 24 is spaced from the medial pivot along the length of the switch member so towards one side thereof and, in the make position, also from the surface of the switch member so to engage the pivot buttress 24 during break action. Lastly, for Figs. 1 to 3, the block or associated face plate provides a rest 30 for the switch member 10 that is spaced from the medial pivot along the length of the switch member in the opposite direction to the pivot buttress 24, and a spring biassed latchable reset mechanism indicated at 32 as to engage the switch member 10 so as to bias its contact 20A against fixed contact 22A when latched (Fig. 1) and release same when not latched (Figs. 2 and 3).In its make position (Fig. 1) with its contact 20A latched and biassed against fixed contact 22A, the switch member 10 is acted upon by its medial pivot spring 14 also into engagement of its second contact 20B with the second fixed contact 22B.

When the latching system 32 releases the switch member 10, the medial pivot spring 14 first tips the switch member 10 about pip 16 and about engagement at contacts 20B, 22B until the switch member 10 engages the pivot buttress 24. That first tipping breakes the contacts 20A 22A (Fig. 2). Thereafter the medial pivot spring 14 further tips the switch member 10 about its pip 16 and about the pivot buttress 24 until the switch link 10 meets the rest 30. That further tipping breaks the contacts 20B, 22B (Fig. 3). Self-evidently, breaking of the first contacts 20A, 22A before the second contacts 20B, 22B at loss of latching by the mechanism 32 is followed at resetting (via such mechanism 32 moving the switch member 10 effectively at its end carrying the first contact 20A) by making of the second contacts 20B, 22B before the first contacts 20A, 22A.

The first and second contacts 20A, 20B of the switch member 10 are indicated as being electrically separate and can serve for mains live and neutral, respèctively, via suitable connections made both to those contacts 20A, 20B, preferably via flexible leads that may be crimped or otherwise connected thereto, and to the contacts 22A, 22B.

During all such actions, the switch member 10 is guided on the buttress extension 26 via its hole 28 that is flared at 34 to accommodate required tipping movements.

Turning to Figs. 4 and 5, like references are used where appropriate with part of an accessory face plate shown at 40 and boundary walling of or for locating an associated housing block 42 is shown at 44. Connector blocks are shown at 46A, 46B for mains live and neutral connections to the fixed contacts 22A, 22B. The switch member 10 is shown generally oblong in a suitable well, see sides 48A, 48B in Fig. 5. Also shown are a toroid 50 which may be traversed by suitable flexible leads from the contacts 20A, 20B, a test button 52, a solenoid 54 and more detail of the latching/reset mechanism 32.

Concerning the latter, a reset button 56 has a hollow stem housing a compression spring 58 acting on a further part 60 guided therein for limited movement, see pin-and-slot formations 62, 64. A swinging latching member 66 is shown pivotted at 68 and with a latch tooth 70 to cooperate with an appropriate formation 72 of the reset button 56. The latching member 66 is shown adjacent the solenoid 54 to be knocked out of latching thereby, and it will be appropriately springbiassed to its latch position.

In operation, then, after a break action, the reset button 56 can be depressed and its part 60 will first engage the adjacent end of the switch member 10, near the contact 20A, and move it through a make operation that is completed after the latch member 66 has been pushed aside and then returned by its spring bias with its latch tooth 70 over the formation 72. The latch mechanism 32 is then ready for the next release operation forced by the solenoid 54 whether in response to detection of a fault condition by suitable control circuitry or by the latter making a forced equivalent response on depression of the test button 52. It is envisaged that suitable control circuitry will be housed via a carrier such as a printed circuit board in the space 74.

An exemplary outline of such control circuitry is shown in the circuit diagram of Fig. 8 having toroid 50 traversed by live and neutral lines L and N, which may be the aforesaid flexible leads from contacts 20A and 20B, and having a sense winding S going to a suitable integrated circuit chip 1C with associated bridge and trimming circuitry B, T. Also shown are solenoid switch 55, a test circuit including button 52 and reverse polarity detection circuitry RP. A double-pole switching action is shown by the solenoid switch 55 on both of live and neutral lines, also a breaking switch link 78 in the test circuit.

Turning particularly to Figs. 6 and 7, face plate 40 and rear body 42 can be seen clearly, and the former has a localised projection 80 at the positions of the test button 52 and reset button 56, the latter being shown in finger-accepting recesses 52R and 56R. In that way, more room is provided for the required movements of the buttons 52 and 56.

Specifically, the projection 80 is shown be tween two accessory units or modules of a double accessory unit, actually a doublesocket, see flat-pin entry sets 82A, 82B with an exemplary outline at 84 in Fig. 7 of a mating plug. Also shown are individual neon tell-tale indicators 86A, 86B for those socket entry sets 82A, 82B, though some might well be replaced with a single neon indicater, then perhaps in the projection 80, where, as is to be expected, the fault-break provisions are common to the two accessory units or modules.

In operation, it is preferred for the reset button to move outward at tripping, but to be flush otherwise, i.e. after resetting and before a fault is detected.

The switch member 10 is shown further guided by a width-wise trammel 90 which assists in restraining the spring 14 and contributes to guidance of the switch member 10.

Flexible leads connected to the switch member 10 may be rivetted, welded or crimped to suitable live and neutral terminal plates fixed thereto.

If desired, resetting could be via a rocker type switch rather than the illustrated pressbutton.

A particularly advantageous aspect of this invention resides in achieving satisfactorily large contact spacings at breaking, and such is contributed to substantially by the nature of the biassing applied to the switch member and its swinging effectively towards the faceplate of the accessory.

Claims (15)

1. A circuit breaker for a mains electrical accessory, comprising a double-break switch link to be thrown out of contact in the faultdetected circuit breaker action, and wherein one break is always preceded by the other break of the double-break action.

2. A circuit breaker as claimed in claim 1 comprising a switch member having an associated floating medial pivot between its electrical contacts and further associated spring biasing and latch means such that first break movement for first of said contacts involves movement of the medial pivot and tipping of the switch member thereon and on the second of the said contacts, thereby breaking the first thereof, and that further break movement on a further then-encountered pivot later breaks the second of said contacts.

3. A circuit breaker as claimed in claim 2 in which a fixed rest may be provided for the switch member on the first contact side of the medial pivot, the further pivot being to the other side of the medial pivot.

4. A circuit breaker as claimed in claim 1, 2 or 3 in which on resetting, the second of the contacts is made before the first by a restoration force applied to move the switch member effectively from where it carries the first contact.

5. A circuit breaker as claimed in any one of claims 1 to 4 in which the first and second contacts are electrically separate.

6. A circuit breaker as claimed in any one of claims 1 to 5 in which wire connections directly to the first and second contacts are of a flexible nature.

7. A circuit breaker as claimed in claim 6 in which the wire connections traverse a toroid to which the control circuitry is responsive via a sense winding.

8. A circuit breaker as claimed in claim 2 or any one of claims 3 to 7 when appendent on claim 2 in which the floating pivot comprises a pip cooperating with an helical compression spring.

9. A circuit breaker as claimed in claim 2 or one of claims 3 to 8 with claim 2 in which the further pivot is a fixed buttress offering guidance for the switch link.

10. A circuit breaker as claimed in claim 9 in which said guidance is afforded via an extension into through or past the switch member, at a flaring, edge-slotting or other formation therein or thereof.

11. A circuit breaker as claimed in any preceding claim provided with a reset member movable against the switch member and moving the latter by a part of the reset member biassed towards the switch member and having a further relatively fixed part by which it is latched, with the biassed part then serving to assure adequate contact pressure at latching.

12. A circuit breaker as claimed in claim 8 or in any one of claims 9 to 11 with claim 8 in which the spring bias to the floating pivot is the only break force applied, the biassed part of the reset member provides sufficient spring force for holding the first contact in make position, and the floating pivot spring force holds the second contact in make position.

13. A circuit breaker as claimed in claim 12 in which a restricted permitted movement of such biassed part, in the break action, ensures throwing off of the reset member as well.

14. A circuit breaker as claimed in claim 11 or any claim appendent thereto in which the reset member is operative through an accessory front plate and the switch member biassed at its floating pivot towards that plate, with the first contact breaking towards the plate and the second contact breaking away from the plate as the switch member tips.

15. A circuit breaker for an electrical accessory constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.