EP0120580A1

EP0120580A1 - Improvements relating to circuit breakers

Info

Publication number: EP0120580A1
Application number: EP84300936A
Authority: EP
Inventors: Peter Rowan Adams; Alan Godfrey
Original assignee: Keyswitch Varley Ltd
Current assignee: Keyswitch Varley Ltd
Priority date: 1983-02-26
Filing date: 1984-02-14
Publication date: 1984-10-03
Also published as: GB8305401D0

Abstract

A circuit breaker in which the armature (25) of an electromagnet (26) is carried on electrically conductive contact member (24) which is urged by a coil spring (27) into an extreme position bridging a pair of electrically conductive contact element (11) (12) arranged to be connected in series with an electrical circuit. The electromagnet responds to a control pulse by urging the armature in a direction opposing to coil spring. The electrically conductive member is latched releasably in a retracted position without consumption of power by means of a permanent magnet (40). Mechanical latching arrangements are also described.

Description

This invention relates to circuit breakers and it relates especially, although not exclusively to circuit breakers used to interrupt the mains power supply.
According to-the invention there is provided a circuit breaker comprising a pair of electrically conductive contact elements for connection in series with an electrical circuit, an electromagnet including an armature carrying an electrically conductive member capable of assuming an extreme position bridging the contact elements, wherein the electromagnet responds to a control signal to urge the-armature in a sense opposing the action of a first resilient biassing means to effect a change in the axial position of said electrically conductive member, and means are provided to releasibly latch the electrically conductive member without consumption pf power, at a retracted position-remote from the extreme position.
By bridging contact elements in this way the need for discrete leads from a remote switch or the like, as tends to have been used in the past, is obviated. The circuit breaker may have either a magnetic or mechanical latching arrangement.
The magnetic latching arrangement may comprise a permanent magnet arranged to hold-the armature when urged, so as to latch the electrically conductive member at said retracted position and the electromagnet is capable of responding to another control signal to temporarily overcome the field of the permanent magnet and release the armature from said hold whereby the electrically conductive member is returned to the extreme position. Thus if a control pulse of the appropriate polarity is applied to the electromagnet the armature is urged towards a position, in which the electrically conductive member is latched at said retracted position. If a control pulse of the opposite polarity is then applied, the field of the electromagnet overcomes the field of the permanent magnet and the armature is urged back by the first resilient biassing means so that electrically conductive member can complete the electrical circuit. In the case of a mechanical latching arrangement said armature is provided with a sleeve capable of axial and angular displacement relative to the armature, said electrically conductive member is capable of axial displacement relative_"to the armature and is urged against the sleeve by further resilient biassing means, and said armature is provided with a first abutment surface having a first longitudinal position and a second abutment surface having a second longitudinal position, the abutment surfaces being distributed at different angular positions on the armature, said sleeve being caused by the action of said further biassing means on the electrically conductive member to bear against said first or second abutment surfaces in dependence on the angular position of the sleeve on the armature whereby said electrically conductive member assumes respectively said extreme or retractable positions, and said sleeve being arranged to undergo a respective angular displacement so as to bear against said first and second abutment surfaces alternately in response to an axial displacement of the armature.
Alternatively said means for releasably latching the electrically conductive member may comprise a pin mounted on the armature and a plate provided with a channel in which the pin can move in response to movement of the armature, the channel being shaped to provide a stop against which the pin may bear so as to prevent movement of the armature unless the armature is caused first to move in a direction opposing the action of'the first biassing means.
In order that the invention may be more readily understood and carried into effect three embodiments thereof are now described, by way of example only, and by reference to the accompanying drawings of which,

Figures la and lb show respectively plan and side elevation views of one embodiment of a circuit breaker.
Figure 2 shows a plan, part sectional view of another embodiment of a circuit breaker,
Figures 3a to 3d show component parts of the embodiment of Figure 2,.
Figures 4a to 4e illustrate schematically operation of the latching arrangement of Figure 2,
Figures 5a and 5b show respectively plan and side elevation views of yet another embodiment of a circuit breaker, and
Figure 6 shows a mechanical latching arrangement used in operation of the circuit breaker of Figure 5.

Referring initially to Figures la and.lb, the circuit breaker,10 has two electrically conductive contact elements in the form of metal studs 11, 12 typically of silver mounted in spaced apart relationship on an electrically insulating support block B. The support block is fixed to a base plate 13.
The studs 11, 12 are connected electrically to respective terminals 14, 15 which may be connected electrically in series with the mains power supply. It will be understood that while the embodiments described herein in relation to the drawings are intended primarily to interrupt the mains power supply, breakers constructed in accordance with the present invention may be useful in other applications requiring interruption of an electrical circuit. As shown in Figures la and lb the circuit breaker is provided with an electrically conductive member 20 in the form of two further studs 21, 22 mounted in spaced apart relationship on a common metallic strip 23, typically of copper. The strip is set into an electrically insulating mounting 24, formed of a plastics material for example, which is carried at one end of the armature 25 of an electromagnet 26. A coil spring 27 urges the armature in the direction of arrow A so that member 20 assumes the extreme position illustrated in Figure 1; in this position member 20 bridges studs 11, 12 and completes the mains supply circuit. The coil spring may be positioned between the electromagnet and member 20, as shown, or alternatively it may be positioned within the bore of the electromagnet.
In this example, the electromagnet is energised by control pulses applied along leads L₁, _L2. When a control pulse of the appropriate polarity is applied the electromagnet urges the armature, and so member 20, in the opposite direction to that of arrow A thereby interrupting the mains supply. A latching arrangement in the form of a permanent magnet 40 is provided to hold the armature in a retracted position. If a pulse of the opposite polarity, and sufficient magnitude, is then applied to leads L, and L₂ the field of the permanent magnet can be temporarily overcome, allowing the armature to be urged in.the opposite direction (that of arrow A) by the-coil spring 27. The armature will then move back to the position illustrated in Figure 1, under the action of the coil spring thereby allowing member 20 to complete the mains circuit and restore the supply of power.
Permanent magnet 40 may be positioned behind the electromagnet, as illustrated, so as to hold the end of the armature in the retracted position or alternatively it may be positioned in front of the electromagnet, relatively close to member 20, in which case the permanent magnet is arranged to latch a metal plate attached to the back face of mounting 24.
The circuit breaker shown in Figures 2 to 4 operates in a manner similar to that of the circuit breaker shown in Figures la and lb but has a mechanical, rather than a magnetic, laching arrangement. Components common to both embodiments are given the same reference numerals and part of the drawing is shown as a section in the horizontal plane, containing the longitudinal axis of the armature, to illustrate more clearly the latching mechanism used. More detailed views of components of the latching mechanism are shown in Figures 3a to 3d.
Referring to Figure 2, latching is provided by means of a rotary indexing cam mechanism in three parts. The first part comprises the armature which is provided with an axial extension member 30 having four projections in the form of longitudinally extending ribs 31 spaced apart at regular intervals around the axis of the armature and alternately long and short. Clearly the extension member could be formed integrally with the armature, or alternatively it may comprise a separately formed part. The extension member is received in, and can move axially within, a hole 32 in block B. Side views of the extension member, in-two orthogonal directions are shown in Figures 3a and 3b. The second part of the mechanism comprises a plastics material sleeve 33 mounted on the armature and having two diametrically opposite fingers 34. The sleeve also is shown in two orthogonal -directions in Figures 3c and 3d. The third part of the latching mechanism comprises four longitudinally extending channels formed in -the wall of hole 32 to define four guideways for the ribs on the extension member. For clarity the channels are not shown in Figure 2 but they are illustrated, schematically in Figures 4a-4e which demonstrate how the latching arrangement of this embodiment operates. - As shown in Figures 3a-3d the tip of each rib and finger is chamfered to define two cam surfaces (e.g. 31', 31") and also each land portion, between adjacent channels in hole 32, is provided with a chamfered tip. Both the sleeve 33 and bridging member 23 are capable of axial movement relative to the extension member and are urged by a further coil spring 35 to the left in Figure 2. As will be described in greater detail by reference to Figures 4a-4e the fingers on the sleeve can, in dependence on the angular position of the sleeve on the armature, abut a respective pair of ribs, either both long or both short. In the position illustrated in Figure 2 the fingers abut the relatively short ribs and this allows member 23 to assume an extreme axial position bridging the contact studs 11, 12. This position is illustrated schematically in Figure 4a wherein one of the relatively short ribs is shown at R_S in channel C, one of the fingers is shown at F and the two land portions defining channel C are shown at P', P". When the electromagnet 26 in Figure 2 is energised by application of a suitable control signal at L1 and L2 the armature and extension member are caused to move to the right in the drawings and so interrupt the mains supply. During an initial part of this movement each finger F is guided by its respective channel C. However, as shown in Figure 4b the finger emerges eventually from the channel and the chamfered surface S_F of the finger tends to slide past surface S_R of the rib (as illustrated by the arrow) under the influence of coil spring 35 causing the sleeve to rotate. The finger moves through the position shown in Figure 4c until the position in Figure 4d is reached and further rotation of the finger is prevented by the next, relatively long rib R_L on the sleeve.' The finger then abuts the cam surface on land portion P". When the electromagnet is deenergised the armature and extension member move back under the influence of coil spring 27 and this allows the finger to slide past the cam-surface on portion P" as shown in Figure 4e. Rotation of the sleeve continues until the finger is within the next channel C'. The fingers on the sleeve are thus brought into register with, and abut the relatively long ribs on the extension member and so the bridging member 23 is latched at a retracted position remote from the extreme position and the mains supply is interrupted. The supply can be restored if the electromagnet is re-energised causing further retraction of the armature and rotation of the sleeve so that the fingers are brought again into register with and abut the relatively short ribs thus allowing the electrically conductive member to assume the extreme position bridging the contact elements 11, 12. Although it is preferred that the tip of each finger, rib and land portion has two inclined cam surfaces as shown, this need not necessarily be-the case and alternatively one cam surface may suffice.
A further embodiment having a mechanical latching arrangement is shown in Figures 5a and 5b and the mechanical Latching arrangement illustrated generally at 50 in Figure 5 is shown in greater detail in the plan view of Figure 6. Again components common to the embodiments already described are given the same reference numerals. So as to show the latching arrangement more clearly coil spring 27 has been omitted from Figure 5a but, as before, may be located between the back face of mounting 24 and the electromagnet. The latching arrangement 50 comprises a flat plate 51 which is mounted pivotally on the base plate 13 for rotation about vertical axis XX.
The plate is provided with a closed channel 52 within which a pin 53, mounted fixedly on the armature, may move. The form of the channel is shown in greater detail in Figure 6. It comprises two substantially straight portions S, S' which are inclined to one another and meet- at an apex A, and a re-entrant portion R, relatively close to the electromagnet. The re-entrant portion R defines a stop P. When the armature is retracted, in response to a control pulse applied to the electromagnet, the pin deflects the plate to one side or the other and moves along a respective channel portion S or S'. When the control pulse is removed the electromagnet becomes de-energised and the armature moves back again under the action of coil spring 27. The pin then moves into the re-entrant portion R of the channel where it bears against stop P preventing further movement to the left in the drawing and so latching the armature. To unlatch the armature a control pulse of the same polarity is applied to the electromagnet. This causes the armature to retract so that when the pulse is removed the pin may return to apex A along one or other of the channel portions S, S'.
As shown in Figures la and 5a, mounting 24 has a projection 28 which is received in a complementary slot 29 in support block B. The slot contains a microswitch 30 which is closed by the projection when member 20 makes contact with studs 11, 12. When the microswitch closes an electrical signal is generated providing confirmation that the mains supply circuit is complete. The confirmation signal may be fed to a controlling circuit, such as a microprocessor for example. In an alternative arrangement the microswitch may be positioned at the rear of the electrcmagnet and closed by a spindle protruding from the end of the armature. The controlling circuit may be used also to generate the control pulses applied to electromagnet 26. Control pulses may be generated in this way when, for example, a fault is detected in the mains circuit necessitating interruption in the supply. Clearly similar arrangements can be used in the embodiment of Figure 2. It will be appreciated that the circuit breakers described herein are designed for manual as well as remote operation, the conductive member 20 being pulled back by hand against the action of coil spring 27 to effect a break in the mains supply.

Claims

1. A circuit breaker comprising a pair of electrically conductive contact elements for connection in series with an electrical circuit, an electromagnet including an armature carrying an electrically conductive member capable of assuming an extreme position bridging the contact elements, wherein the electromagnet responds to a control signal-to urge the armature in a sense opposing the action of a first resilient biassing means to effect a change in the axial position of said electrically conductive member, and means are provided to releasibly latch the electrically conductive member without consumption of power, at a retracted position remote from the extreme position.

2. A circuit breaker according to Claim 1 wherein said armature is provided with a sleeve capable of axial and angular displacement relative to the armature, said electrically conductive member is capable of axial displacement relative to the armature and is urged against the.s1eeve by further resilient biassing means, and said armature is provided with a first abutment surface having a first longitudinal position and a second abutment surface having a second longitudinal position, the abutment surfaces being distributed at different angular - positions on the armature, said sleeve being caused by the action of said further biassing means on the electrically conductive member to bear against said first or second abutment surfaces in dependence on the angular position of the sleeve on the armature whereby said electrically conductive member assumes respectively said extreme or retractable positions, and said sleeve being arranged to undergo a respective angular displacement so as to bear against said first and second abutment surfaces alternately in response to an axial displacement of the armature.

3. A circuit breaker according to Claim 2 wherein said sleeve is provided with a formation arranged to cooperate, in response to axial displacement of the armature, with a respective said abutment surface and also with a respective further formation fixed in relation to said armature and said sleeve whereby the sleeve undergoes, as a result of said cooperation, a respective angular displacement.

4. A circuit breaker according to Claim 4 wherein each said abutment surface comprises a chamfer on a respective rib which extends longitudinally on said armature and is guided in a respective channel within guide means fixed in relation to the armature, and said respective further formation comprises a surface interconnecting adjacent channels in the guide means.

5. A circuit breaker according to any one of Claims 2 to 4 wherein said armature is provided with more than one said first abutment surface and more than one said second abutment surface, said abutment surfaces being distributed at different angular positions on the armature.

6. A circuit breaker according to Claim 1 wherein the means for releasably latching the electrically conductive member is a permanent magnet arranged to hold the armature, when urged, so as to latch the electrically conductive member at said retracted position and the electromagnet is capable of responding to another control signal to temporarily overcome the field of the permanent magnet and release the armature from said hold whereby the electrically conductive member is returned to the extreme position.

7. A circuit breaker according to Claim 1 wherein said means for releasably latching the electrically conductive member comprises a pin mounted on the armature and a plate provided with a channel in which the pin can move in response to movement of the armature, the channel being shaped to provide a stop against which the pin may bear so as to prevent movement of the armature unless the armature is caused first to move in a direction opposing the action of the first biassing means.

8. A circuit breaker according to Claim 7 wherein said plate is arranged to pivot about an axis parallel to that of the pin and the channel is in the form of a closed loop having a re-entrant portion, relatively close to the electromagnet, which forms said stop.

9. A circuit breaker according to Claims 1 to 8 including means responsive to the position of the armature to provide an indication when the electrically conductive member bridges the contact elements.

10. A circuit breaker according to Claim 9 wherein the means for providing the indication comprises a switch which is arranged to assume the closed condition when the armature assumes said extreme position.