GB2205686A - Circuit breaker - Google Patents

Abstract

A circuit breaker for opening the circuit to an electrical socket comprises a relay (6) having an armature (10), carrying contact arms (12) which are engageable with contacts (14). A tripping mechanism is operative normally to retain the armature in an operative position but in the event a current overload and/or defection of residual current, it permits the armature to be moved by a spring 16 to an inoperative position. When the relay is closed pivotable movement of a latch member (18) under the action of a spring (20) is prevented by abutment of the latch member with the armature, but on opening of the relay, and movement of the armature (10) to its inoperative position, the latch member (18) moves across the armature (10) to prevent it reclosing. The latch member (18) is reset by removing the plug from the socket to cause a shutter (24) to be moved by a spring and to cam the latch member (18) back to its inoperative position where it is retained by the shutter (24). In this manner if the relay trips and is then subjected to an inpact whilst a plug is in the socket, there is no possibility of momentary application of power to the plug. <IMAGE>

Description

Title: "Improvements relating to circuit breakers" Description of Invention This invention is concerned with improvements relating to circuit breakers, particularly of the kind (hereinafter referred to as being of the kind specified) comprising terminals by which a power supply may be connected thereto, a socket by which the plug of an electric appliance may be connected thereto, a power circuit between the terminals and contact members defining pin-receiving apertures of the circuit, and a relay in the power circuit adapted to open the circuit in the event of a current overload and/or detection of residual current.

In many conventional circuit breakers of the kind specified, the relay comprises an armature which is spring loaded to its open position (which it adopts when the relay is tripped) and which may be moved (such as by a solenoid) against the spring loading into a latched position in which the relay is reset.

A problem in such circumstances is that, with the latch tripped and with the circuit open, it is possible for an impact on the circuit breaker (such as may occur when the circuit breaker is dropped or bumped) to cause the armature to move under its inertia against the action of the spring loading momentarily to close. This can be dangerous.

According to this invention there is provided a circuit breaker of the kind specified comprising latch mechanism which when the relay trips and when a plug is in the socket moves from an inoperative to an operative position to prevent closing of the relay, but which when there is no plug in the socket does not so move.

In this manner if the relay trips and is then subjected to an impact whilst a plug is in the socket, there is no possibility of momentary application of power to the plug.

In addition whilst the plug is retained in the socket the relay cannot be reset, and hence closing of the relay under load, with the possible consequences of welding of the relay contacts is avoided.

Preferably the construction and arrangement is such that when the plug is removed from the socket, the latch mechanism is moved to its inoperative position allowing the relay to be reset.

Preferably the latch mechansim comprises a latch member which is urged (such as by a spring) to its operative position but which is prevented from moving to its operative position when the relay is closed and when a plug is in the socket.

Preferably the latch mechansim also comprises an operating member movable between a first position in which it is operatively separated from the latch member and a second position in which it prevents the latch member moving to its operative position.

Preferably, when the latch member is in its operative position, movement of the operating member from its first to its second position is effective to move the latch member to its inoperative position.

Preferably the operating member is urged (such as by a spring) to its second position and is moved to its first position by the insertion of a plug into the socket.

Preferably the operating member affords a shutter which in its second position extends across at least the live and neutral apertures of the socket, and is moved to its first position by movement of a pin of the plug (such as the earth pin) into its aperture.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of a circuit breaker which has been selected for the purposes of illustrating the invention by. way of example.

In the accompanying drawings: FIGURE I is a schematic perspective view of internal parts of the preferred embodiment, showing the relay thereof closed and a plug inserted into the socket; FIGURE 2 is a view similar to Figure I showing the relay tripped; and FIGURE 3 is a view similar to Figure 2, showing the position adopted of various parts when the plug has been removed.

The circuit breaker which is the preferred embodiment of this invention is specifically of the kind specified, comprising a casing (not shown) having an aperture by which an electric cable may be inserted therethrough, and a socket by which the plug of an electric appliance may be connected to the casing, a power circuit extending between the terminals of the circuit breaker and contact members defining the pin-receiving apertures of the socket.

Located within the casing and interposed within the power circuit is a relay 6 comprising a relay housing 8 carrying an armature 10, from which contact arms 12 extend towards contacts 14. The armature 10 is urged by a spring 16 from an operative position, shown in Figure 1, to an inoperative position shown in Figure 2, the relay comprising tripping mechanism operative normally to retain the armature in its operative position but which in the event of overload conditions is delatched to permit the armature to be moved by the spring 16 to its inoperative position.

The circuit breaker comprises latch mechanism comprising a latch member 18 pivotally mounted to the relay housing 8, and urged by a spring 20 from an inoperative position, shown in Figure I, to an operative position shown in Figure 2.

When the relay is closed (i.e. the armature 10 is in its operative position) movement of the latch member 18 under the action of the spring 20 is prevented by abutment of the latch member with the armature base, but on opening of the relay, and movement of the armature 10 to its inoperative position (shown in Figure 2), the latch member 18 moves across the armature 10 to prevent subsequent movement thereof back towards its operative position. In this position of the latch member the relay cannot be reset, despite operation of the resetting means, conveniently a solenoid to urge the armature against the action of the spring 16.

As will be seen from Figure 2, pivotal movement of the latch member IS is limited by engagement of a leg 19 with the armature base.

The circuit breaker comprises a shutter 24 urged by a spring (not shown) from a first position (Figures I and 2) to a second position (Figure 3) and is moved against the action of the spring to its first position by the insertion of a plug into the socket, a cam face 25 of the shutter being engaged by the earth pin and cammed in the direction of the arrow A shown in Figure 2 to uncover the live and neutral pin apertures.

The shutter 24, together with an operative portion 26 thereof, affords an operating member of the latch mechanism, which when the shutter is in its first position is separated from the latch member 18, but which when the shutter is in its second position prevents the latch member moving to its operative position. In addition, from the position shown in Figure 2, on removal of the plug from the socket, the consequent upward movement of the shutter 24 causes a cam face 27 of the operative portion 26 to engage a complementary cam face 28 of the latch member, to cause the latch member to be moved against the action of the spring 20 to its inoperative position, thus permitting movement of the armature 10 against the action of the spring to its operative position.

It will thus be appreciated that with no plug in the socket (the Figure 3 position) the operative portion 26 will prevent movement of the latch member 18, allowing free movement of the armature 10 between its operative and inoperative positions.

Conversely when there is a plug in the socket, the latch member is free to move under the action of the spring to prevent return movement of the armature 10 to its operative position, until the plug is removed from the socket and the shutter 24 is moved to return the latch member to its inoperative position.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (9)

1. CLAIMS:

   I. A circuit breaker of the kind specified comprising latch mechanism which when the relay trips and when a plug is in the socket moves from an inoperative to an operative position to prevent closing of the relay, but which when there is no plug in the socket does not so move.
2. 2. A circuit breaker according to Claim I wherein the construction and arrangement is such that when the plug is removed from the socket, the latch mechanism is moved to its inoperative position allowing the relay to be reset
3. 3. A circuit breaker according to one of Claims I and 2 wherein the latch mechansim comprises a latch member which is urged to its operative position but which is prevented from moving to its operative position when the relay is closed and when a plug is in the socket.
4. 4. A circuit breaker according to any one of the preceding claims wherein the latch mechansim also comprises an operating member movable between a first position in which it is operatively separated from the latch member and a second position in which it prevents the latch member moving to its operative position.
5. 5. A circuit breaker according to Claim 4 wherein when the latch member is in its operative position, movement of the operating member from its first to its second position is effective to move the latch member to its inoperative position.
6. 6. A circuit breaker according to one of Claims 4 and 5 wherein the operating member is urged to its second position and is moved to its first position by the insertion of a plug into the socket.
7. 7. A circuit breaker according to any one of Claims 4 to 6 wherein the operating member affords a shutter which in its second position extends across at least the live and neutral apertures of the socket, and is moved to its first position by movement of a pin of the plug into its aperture.
8. 8. A circuit breaker constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.
9. 9. Any novel feature of novel combination of features hereinbefore described and/or as shown in the accompanying drawings.