GB2204192A - Electrical devices provided with circuit breakers - Google Patents

Abstract

An electric plug-in adaptor or switch or socket assembly is provided with a residual current circuit breaker (RCCB) and a reset device whose operation is prevented when a plug is inserted in the device by locking means having a locking member (20, 67) which engages with a reset button to prevent it being depressed. The locking means is moved by the earth pin (64) of the plug engaging with a cam surface (36, 63) provided thereon. The locking means can be a one-piece locking lever (61) or it can comprise a linkage (30, 31). The device also includes a spring loaded safety shutter which covers the live and neutral socket openings. The locking means operates completely independently of the shutter. <IMAGE>

Description

ELECTRICAL DEVICES PROVIDED WITH CIRCUIT BREAKERS DESCRIPTION This invention relates to electrical devices and more particularly, but not exclusively, to plug sockets and/or adaptors or switches provided with a circuit breaker intended to cut off the current supplied if an electrical fault arises in the circuit to which current is supplied.

One of the essential requirements of a socket or switch incorporating a circuit breaker and associated reset button is that it must not be possible to operate the reset button while current is being supplied to the appliance plugged into the socket. In one known adaptor, this requirement is met by positioning the reset button on the face of the adaptor which abuts the front face of the socket when the adaptor is plugged into it. If the circuit breaker is triggered due to a fault arising, it can only be reset by removing the adaptor from the socket to expose the reset button.

Thus, the electrical supply to the appliance plugged into the adaptor is cut off and the reset button can be actuated to complete the circuit again.

In another known arrangement, the mandatory shutter which normally covers the live and neutral socket openings includes a blocking member which cooperates with the reset button to prevent it being depressed when a plug is inserted in the socket openings. Thus, the reset button can only be used when the plug is removed from the socket or switch and the shutter returns to its normal position in which it blocks entry to the live and neutral socket openings and cuts off the electrical supply to the appliance plugged into the socket or switch.

It is an object of the present invention to provide a switch, socket and/or adaptor in which the reset button is prevented from operation by means which operate independantly of the mandatory shutter.

According to the invention, there is provided an electrical device such as a switch, socket and/or adaptor for supplying electric current comprising a normally closed circuit breaker which is operable to disconnect the supply of electric current to the device, a safety shutter normally covering the live and neutral socket openings but movable by the pins of a plug on insertion therein, a reset device operable to close the circuit breaker and locking means operable independantly of the safety shutter and movable to a first position, on insertion of a plug in said socket openings, in which operation of the reset device is prevented and a second position permitting actuation of the reset device when the plug is removed from said sockets openings.

Conveniently, the circuit breaker is a relay and the reset device comprises a spring loaded push button which- closes the relay when pushed against the action of its spring. In a preferred embodiment, the locking means includes a locking member shaped to cooperate with the reset button to prevent its depression.

In one embodiment, the reset button has a portion of reduced width which provides a shoulder on the underside of the bottom, the locking member having an open ended fork portion of substantially the same width as said reduced width button portion so that the fork of the locking member can engage under the shoulder on the reset button and prevent its depression. In another embodiment, the open ended fork portion fits directly under the reset button which has no such portion of reduced width.

The locking means includes a part, preferably a cam surface, engagable by a pin on a plug when inserted in a socket opening to move the locking member into engagement with the reset button and prevent its depression. This cam surface can be provided on a linkage connected to the locking member, the linkage comprising a first link member pivotally mounted at one end on the socket or switch housing, its other end being pivotally or slidingly attached to a second link member releasably attached to the locking member.

Alternatively, the cam surface can be provided on a one-piece locking lever havin-g the locking member provided at one end thereof. The locking lever can be pivotted about a point intermediate its ends or at its end remote from that provided with the locking member, the part engagable by the plug pin being located intermediate the locking member and the pivot point.

It is an important feature of the preferred embodiments that the locking means for the reset button is resiliently biassed into its second position as this ensures that when a plug is removed from the socket openings, the locking means is disengaged from the reset button thereby leaving it free to be depressed to reset the relay.

Conveniently, the reset button cooperates directly with one of a pair of contacts of the relay and is operable to close them, the movement of said one of the relay contacts by the button causing a flag member pivotally mounted on the relay to move to a second position in which an indicator part thereof aligns itself with a window in the socket or switch housing to indicate that the reset button has been actuated. Preferably, the flag member is resiliently biassed to return to a first position in the event that the relay contacts open whereby another portion of said indicator part aligns with said window to indicate that the reset button cannot be depressed.

Several embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front view of a 3 pin plug-in adaptor of the invention; Figure 2 is a side view of the adaptor shown in Figure ; Figure 3 is a rear view of the invention of the adaptor shown in Figure 1; Figure 4 is a cross sectional view of the adaptor of Figures 1-3 with some parts omitted to more clearly illustrate the shutter mechanism and reset button locking means; Figure 5 is a schematic perspective view of the reset button locking means for the reset button; Figure 6 is a simplified view of the relay used in the adaptor of Figure 4 showing its indicator flag; Figure 7 is a plan view of the relay shown in Figure 6; Figure 8 is a schematic illustration showing a one-piece locking means; ; Figure 9 is a schematic illustration of an alternative one-piece locking means to that shown in Figure 8, and Figure 10 is a schematic illustration of a still further alternative locking means to those shown in Figures 8 and 9 with a single link member connected to a separate locking member.

Referring to the drawings, there is shown in Figures 1 and 2 a 13 amp 3 pin plug-in adaptor L having an earth pin 2, and live and neutral pins 3 projecting from its rear face. The front face is provided with a socket opening 2a to receive the earth pin 2 and openings 3a and 3b to receive respectively the live and neutral pins 3. A panel 4 has a reset button 5 and a tester button 6 on it together with a window 7 in which an indicator portion 44 of indicator flag 43 is visible.

The pins 2 and 3 are fitted in a mounting assembly 8 which is attached to casing half 19. The end of each pin 2, 3 is connected via a double pole relay to a live and neutral socket outlet to make an electrical connection therewith.

The pins 2, 3 are connected to an appropriate electrical circuit board (not shown) designed to enable the adaptor to perform its required electrical function. As the electrical parts of the adaptor do not form a part of the invention, they have been omitted from the drawings and will not be described with the exception of relay 9 which forms part of the circuit and breaks the circuit should a fault arise.

The relay includes a pair of contacts 10 spring loaded into the open position (see Figure 4) and engagable by the reset button 5. It will be seen that when the reset button 5 is depressed, it will close the contacts 10 to complete the circuit again, the spring loaded contacts being kept in engagement with the fixed contacts under the action of coil spring 11 which will have become energised again on completion of the circuit.

It is a mandatory requirement that electrical plugs or switches include a safety shutter to prevent access to their live terminals when a plug is not inserted therein. The adaptor illustrated includes such a safety shutter 12 which has a lower part with feet 13 and 14 to cover socket openings 3a, 3b. Its upper part has a chamfered finger 15 on it which protrudes into the earth socket 2a when the shutter is in its normal rest position illustrated in Figure 3 i.e. normally covering the socket openings 3a, 3b. The shutter 12 is biassed into its illustrated rest position by means of spring 16.It will be appreciated, that when a plug is inserted into the socket openings 2a, 3a, 3b, its longer earth pin will engage the chamfered finger 15 and cause the shutter 12 to slide downwardly thereby exposing the socket openings 3a, 3b which can then receive the live and neutral pins of the plug on it being pressed further into the adaptor socket openings.

The shutter arrangement just described is well known so will not be described further.

In appliances including a residual current circuit breaker (RCCB), it is anticipated that it will become a mandatory requirement that the reset button for the RCCB must not be capable of being used while the circuit is still live, the reason for this being that it could be dangerous for a person to press the button while the fault which originally caused the RCCB to break the circuit is still present. The present invention complies with this requirement by providing a locking mechanism for the reset button 5 which prevents the button being depressed when a plug is inserted in the socket openings 2a, 3a, 3b, but releases the button so that it can be reset as soon as the plug is removed. This locking mechanism is shown in Figures 3-5 and will now be described more fully.

Referring to Figures 3 and 5, it can be seen that the locking mechanism comprises a locking member 20 having a fork 21 at one end. The locking member is slidable along a channel 23 defined between walls 22. The free end of reset button 5 protrudes into the channel 23 and includes a first portion 24 of reduce-d diameter (see Figure 5) and a second portion 25 reduced still further in diameter. A shoulder 26 is provided on the button immediately adjacent the first portion 24 of reduced diameter. As can be seen more clearly in Figure 4, the shoulder 26 limits the outward movement of the button 5. The button is spring biassed by means of a forked leaf spring (not shown) fitted around the button 5 between the shoulder 26 and the rear face of the front casing half 19. The free end 27 of the button 5 protrudes through a hole in the casing for the relay 9 to engage with its co-ntact 10.

The width of the fork 21 on the locking member 20 is sufficient to allow the second portion 25 of the button 5 to pass through it but not the wider first portion 24. Thus, when the locking member 20 is moved into engagement with the reset button 5 in a manner to be described hereafter, the fork 21 engages under the shoulder 26 and prevents depression of the button 5.

The locking member 20 is moved by means of a linkage system including primary and secondary link members 30 and 31. The primary link member 30 is pivotally mounted at one end 32 and pivotally connected at 33 to the secondary link member 31. The pivotal connection can be replaced by a cooperating pin and slot arrangement of desired or any other form of connection which will provide compliance in the linkage system.

Similarly, a compliant connection is provided between the free end of the secondary link member 31 and the locking block 20. In the illustrated embodiment, this comprises providing the free end of the link member 31 with a T-piece 34 which is a loose fit in a slot provided in the end wall of the locking member 20, a cavity 35 being formed in the member 20 immediately behind the slot 34.

The primary link member 30 is formed intermediate its ends with a cam surface 36 which projects into the earth pin socket opening 2a as can be clearly seen in Figures 1, 3 and 4. The link 30 is biassed into its rest position shown in Figures 1, 3 and 4 by means of a leaf sping 37 which acts between the link 30 and a post 38. Other arrangements can be used to provide the required biassing if required.

The locking member 20 and its associated linkage 30, 31 operates as follows. When a plug is inserted in the socket openings 2a, 3a, 3b, the longer plug earth pin 40 (see Figure 5) first engages the chamfered finger 15 of the shutter 12 and the cam surface 36 of the primary link member 30. As a result, the shutter 12 is depressed to fully expose the socket openings 3a, 3b and thereby allow the live and neutral pins 41, 42 of the plug to be fully inserted therein to make electrical contact with the metal forked connectors (not shown)- at the ends of the adaptor terminal pins 2, 3. Simultaneously, the plug earth pin 40 raises the primary link member 30 which pivots about pin 32. This causes the secondary link 31 to move upwardly and the locking member 20 to slide upwardly in channel 23 until bottom 39 of fork 21 abuts the edge of the second button portion 25 of reduced diameter when in this position, the fork 21 is located beneath the shoulder 26 so the button cannot be depressed. Thus, it is impossible to "make on to a fault" by pressing the reset button 5.

Once the plug is removed, the shutter 12 and the primary link member 30 are returned to their rest position shown in Figures 1, 3 and 4 under the action of their respective return springs 16 and 37 and the locking member is withdrawn from engagement with the collar 26 on the reset button 5 so it can be depressed to re-complete the circuit.

The relay 9 is of known type and preferably has attached to it an indicator flag 43 which has an indicator portion 44 which is visible in the window 7.

The indicator portion 44 has a white segment 45 and a red segment 46 and the flag is pivotally attached to the relay at 47 so that when the button 5 is depressed, movement of the contact 10 moves a lever 48 attached to the indicator flag whereby it is pivotted to show the red segment 46 in the window 7 thereby indicating that the circuit is complete and the adaptor is fully operational. When the relay contacts 10 open due to a fault, the indicator flag 43 is pivotted to its other position under the action of a return spring 49 mounted between locating pins 50, 51 and 52 and the white segment 45 shows at the window to indicate a fault which can only be overcome by removing the plug from the adaptor and then depressing the reset button 5.

The following description should be read in conjunction with the foregoing description as the principle of operation of the further embodiments to be described shortly is exactly the same. The main changes made are that the 3-part locking mechanism is formed in one or two pieces and the pivot points of the locking member and the way in which it is resiliently biassed are.

different.

Referring to Figure 8, there is shown a locking mechanism comprising a locking member 61 having a fixed pivot 62 intermediate its ends. A cam surface 63 is provided at one end of the locking member and is positioned behind the earth socket opening 64. The live- and neutral socket openings 65 and 66 would be covered by the normal safety shutter arrangement (not shown) The other end of the locking member 61 is formed with a forked end 67 which is movable into engagement with reset button 68 which has a narrowed down portion 69 to provide a collar 70.

The locking member 61 is biassed by means of a compression spring 71 which may be located to the left of the pivot point 62 as illustrated or, alternatively, above and to the right of the pivot point 62.

With the illustrated arrangement, it will be appreciated that when a three pin plug is inserted in the socket openings 64, 65, 66, the earth pin will engage with the cam surface 63 on the locking member 61 which will pivot about the pivot point 62 against the action of the compression spring 61 to bring the forked end 67 into engagement with the reset button 68, thereby placing the forked end 67 under the collar 70 so that the button cannot be depressed.

The arrangement shown in Figure 9 is very similar to that shown in Figure 8 except that the locking member 61a pivots about a fixed pivot point 62a located at one end thereof. The locking member 61a has a forked end 67a which engages with the reset button 68 as before.

Cam surface 63a is provided intermediate the pivot point 62a and the forked end 67a and lies behind the socket opening 64 as before. A compression spring 71a acts on the locking member 61a at a point located between the cam surface 63a and the forked end 67a.

It will be seen that the arrangement shown in Figure 9 operates as follows. When a three pin plug is inserted into the socket opening 64, 65, 66, the earth pin will initially engage with the cam surface 63a to pivot the locking member 61a upwardly against the action of the compression spring 71a. As a result of this movement, the forked end 67a will engage with the push-button 68 to prevent it being depressed. On removal of the plug from the socket, the locking member 61a is returned to its initial position shown in Figure 2 under the action of the spring 71a and the reset button can again be depressed.

The arrangement shown in Figure 10 is different from those described with reference to Figures 8 and 9 in that the locking mechanism is formed in two parts.

The first part is lever 72 which pivots at one end about fixed pivot 62b. An upstanding stud 77 is provided near its other end and a cam member 63b is integrally attached to the lever 72 intermediate the pivot 62b and the stud 77 and has a cam surface 73 which protrudes into earth opening 64 in the socket.

The second part of the locking mechanism is the locking member on slider 20a which comprises a body having a forked portion 67b at one end and a slot 80 adjacent its other end aligned with the space between the aperture in the forked end portion 67b. An upstanding spring locating leg 74 is integrally formed with the slider 20a and is provided at its free end with a peg 75 to locate a coil spring 71b which acts against abutment 76 provided on the socket body (not shown).

The operation of the Figure 10 arrangement illustrated is as follows : the stud 77 of the lever 72 is normally located in the opening 80 of the locking member 20a and the compression spring 71b urges the locking member 20a and the lever 72 so that cam surface 73 obtrudes into the earth socket opening 64 in the socket body (not shown). In this condition, the reset push button is free to be depressed as its travel is not obstructed by the forked portion 67b of the locking member 20a.

However, when the earth pin of a plug is inserted in the earth socket opening 64, it engages cam surface 73 and the lever 72 is thereby forced to move in an arc around its pivot point 62b. The stud 77 on the lever 72 engaged in slot 80 in the locking member, forces the locking member 20a to move in the direction of arrow A against the action of the coil spring 71b whereby the forked portion 67b engages with the reset button 68, and its first diameter 69 passes through the U-shaped part of the locking member but not shoulder 70. As a result, the reset button cannot be depressed to an on position until such time as the plug is removed from the earth opening 64 and the forked portion 67b is disengaged from the reset button 68 under the action of the spring 71b and returns to the reset portion shown in Figure 3.

Although the arrangements illustrated in Figures 8-10 rely on compression springs being used, it will be appreciated that the design would operate equally well using tension springs suitably repositioned.

As an alternative to the U-shaped part of the locking member engaging with a portion of the reset button of a reduced diameter as in the described embodiments, the button can have a spindle extending therefrom around which its biassing spring is fitted, the U-shaped part being positioned under the button but around the return spring to prevent depression of the button.

It will be appreciated that although the described embodiment is a plug-in adaptor, the invention can apply equally well to a switch or socket assembly.

Similarly, although the described preferred embodiment is a 3 pin electrical device, the invention could equally well be applied to a 2 pin device.

Claims (21)

1. An electrical device such as a switch, socket and/or adaptor for supplying electric current comprising a normally closed circuit breaker which is operable to disconnect the supply of electric current to the device, a safety shutter normally covering the live and neutral socket openings but movable by the pins of a plug on insertion therein, a reset device operable to close the circuit breaker and locking means operable independantly of the safety shutter and movable to a first position, on insertion of a plug in said socket openings, in which operation of the reset device is prevented and a second position permitting actuation of the reset device when the plug is removed from said sockets openings.

2. A device as claimed in claim 1 wherein the circuit breaker is a switching means and the reset device comprises a spring loaded push button which closes said switching means when pushed against the action of its spring.

3. A device as claimed in claim 2 wherein said switching means is a relay.

4. A device as claimed in claim 2 wherein the locking means includes a locking member shaped to cooperate with the reset button to prevent its depression.

5. A device as claimed in claim 4 wherein the reset button has a portion of reduced width which provides a shoulder on the underside of the bottom, the locking member having an open ended fork portion of substantially the same width as said reduced width button portion so that the fork of the locking member can engage under the shoulder on the reset button and prevent its depression.

6. A device as claimed in claim 4 or claim 5 wherein the locking means includes a part engagable by a pin on a plug when inserted in a socket opening to move the locking member into engagement with the reset button and prevent its depression.

7. A device as claimed in any one of claims 1-6 wherein the locking means comprises a one-piece locking lever.

8. A device as claimed in claim 7 wherein the locking member is provided at one end of the locking lever.

9. A device as claimed in claim 8 wherein said part engagable by the plug pin is provided at the opposite end of the locking lever, said lever being pivotable about a point intermediate its ends.

10. A device as claimed in claim 9 wherein the locking lever is pivotable about a point at its end remote from that provided with the locking member, the part engagable by the plug pin being located intermediate the locking member and the pivot point.

11. A device as claimed in any one of claims 7-10 wherein the locking lever is pivotally movable against the action of a compression spring.

12. A device as claimed in any one of claims 7-10 wherein the locking lever is pivotally movable against the action of tension spring.

13. A device as claimed in any one of claims 6-12 wherein said part is a cam surface.

14. A device as claimed in claim 6 wherein said part is a cam surface provided on a linkage connected to the locking member.

15. A device as claimed in claim 14 wherein the linkage comprises a first link member pivotally mounted at one end on the socket or switch housing, its other end being pivotally attached to a second link member releasably attached to the locking member.

16. A device as claimed in claim 14 or claim 15 wherein the cam surface is provided in the first link member immediately adjacent the earth socket opening.

17. A device as claimed in any one of the preceding claims wherein the locking means is normally resiliently biassed into its second position.

18. A device as claimed in any one of claims 3 to 17 wherein the reset button cooperates directly with one of a pair of contacts of the relay and is operable to close them.

19. A device as claimed in claim 18 wherein movement of said one of the relay contacts by the button causes a flag member pivotally mounted on the relay to move to a second position in which an indicator part thereof aligns with a window in the socket or switch housing to indicate that the reset button has been actuated.

20. A device as claimed in claim 19 wherein the flag member is resiliently biassed to return to a first position in the event that the relay contacts open whereby another portion of said indicator part aligns with said window to indicate that the reset button cannot be depressed.

21. A device substantially as herein described with reference to the accompanying drawings.