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Title:
ELECTRICAL CIRCUIT BREAKERS
Document Type and Number:
WIPO Patent Application WO/2001/009908
Kind Code:
A1
Abstract:
An electrical circuit breaker comprises at least one pair of electrical contacts (52) adapted for connection to an electrical circuit through which electrical current flows, at least one insulating element (54), and an actuator (55) which, on operation, drives the insulating element (54) between the pair of contacts (52) to interrupt the flow of electrical current between the contacts. The electrical circuit breaker may comprise a conducting member (60) displaceably located between the pair of electrical contacts (52) for flow of electrical current between the contacts (52). The insulating element (54) may be attached to or cooperate with the conducting member (53), such that on operation of the actuator (55) the insulating element (54) is driven between the pair of contacts (52) in place of the conducting member (53).

Inventors:
GREW WARWICK JOHN STUART (GB)
GREW WALLACE DOUGLAS (GB)
Application Number:
PCT/GB2000/002939
Publication Date:
February 08, 2001
Filing Date:
July 31, 2000
Export Citation:
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Assignee:
W W GREW & COMPANY LTD (GB)
GREW WARWICK JOHN STUART (GB)
GREW WALLACE DOUGLAS (GB)
International Classes:
H01H9/32; H01H39/00; H01H73/18; (IPC1-7): H01H9/32
Foreign References:
US2254347A1941-09-02
DE19542690A11997-05-22
US3264438A1966-08-02
US3274363A1966-09-20
FR2269181A11975-11-21
EP0450104A11991-10-09
Attorney, Agent or Firm:
Barker, Brettell (138 Hagley Road Edgbaston Birmingham B16 9PW, GB)
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Claims:
CLAIMS
1. An electrical circuit breaker comprising at least one pair of electrical contacts (2,3; 21,22; 41,42; 52) adapted for connection to an electrical circuit through which electrical current flows, at least one insulating element (9,28,46,54,72), and an actuator (4,23,43,55) which, on operation, drives the insulating element between the pair of contacts to interrupt the flow of electrical current between the contacts.
2. An electrical circuit breaker according to claim 1 characterised in that the insulating element (9,28) is provided with a chamfered end.
3. An electrical circuit breaker according to any preceding claim characterised by being provided in a housing (1,20,40,51).
4. An electrical circuit breaker according to claim 3 characterised in that the housing is sealed.
5. An electrical circuit breaker according to any preceding claim characterised in that a conducting member (45,53,70) is displaceably located between the pair of electrical contacts (41,42; 52) for flow of electrical current between the contacts.
6. An electrical circuit breaker according to claim 5 characterised in that the insulating element (46,54,72) is attached to or cooperates with the conducting member (45,53,70), such that on operation of the actuator (43,55) the insulating element is driven between the pair of contacts 52) in place of the conducting member.
7. An electrical circuit breaker according to claim 6 characterised in that the conducting member (53,70) is carried by the insulating element (54,72), being housed in an aperture or recess in the insulating element.
8. An electrical circuit breaker according to claim 6 characterised in that the conducting member (45) and insulating element (46) are not physically connected, the insulating element being positioned to abut against the conducting member to displace the member from between the contacts (41,42) when the actuator (43) is operated.
9. An electrical circuit breaker according to any of claims 6 to 9 characterised in that the insulating element provides an air space between the electrical contacts when the conducting member has been displaced from between the contacts.
10. An electrical circuit breaker according to any of claims 5 to 9 characterised in that the conducting member (53) is normally held between the electrical contacts (52) by frictional engagement with them.
11. An electrical circuit breaker according to claim 10 characterised in that the electrical contacts (52) are spring urged into the frictional engagement with the conducting member (53).
12. An electrical circuit breaker according to claim 11 as dependent from claim 3 or claim 4 characterised in that spring loading of the contacts (52) is provided by the housing (51) of the electrical circuit breaker.
13. An electrical circuit breaker according to claim 12 characterised in that the housing (51) has inherently resilient opposed walls (57) to which the electrical contacts (52) are attached and between which the conducting member (53) is located.
14. An electrical circuit breaker according to claim 13 characterised in that the housing (51) is made of a suitable material, such as a plastics or rubber material, which has some inherent resilience and provides the required spring loading of the contacts (52).
15. An electrical circuit breaker according to claim 14 characterised in that the housing (51) is of a plastics material having some resilience, the electrical contacts (52) comprise externally screwthreaded elements which are screwed into complementary threaded holes (57') in opposed walls (57) of the housing and into bearing engagement with opposite parts of the conducting member (53) so as to locate the conducting member in position between the contacts, and the opposed walls of the housing flex as the screwthreaded elements are tightened onto the opposite parts of the conducting member, thereby enhancing the frictional engagement between the contacts and the conducting member.
16. An electrical circuit breaker according to any of claims 6 to 15 characterised in that the conducting member (53) relocates between further electrical contacts (65) when it has been displaced from the said one pair of electrical contacts (52) by operation of the actuator (55).
17. An electrical circuit breaker according to any of claims 5 to 16 characterised in that there is more than one pair of electrical contacts between which the conducting member displaceably locates.
18. An electrical circuit breaker according to any of claims 5 to 16 characterised in that there is more than one conducting member displaceably located between more than one pair of contacts.
19. An electrical circuit breaker according to any of claims 6 to 18 characterised in that the conducting member (45,53,70) is arranged to be moved linearly by the insulating element on operation of the actuator (43,55).
20. An electrical circuit breaker according to any of claims 6 to 19 characterised in that the conducting member is resettable between the contacts to reestablish the flow of electrical current between the contacts.
21. An electrical circuit breaker according to claim 20 characterised in that the conducting member has a resetting device attached, or attachable, to it by which the member can be moved back into its original location between the contacts.
22. An electrical circuit breaker according to claim 21 characterised in that the resetting device is a chord, rod or link which is manually operated, from a position remote from the circuit breaker, to move the conducting member into position between the contacts.
23. An electrical circuit breaker according to any of claims 1 to 19 characterised in that the circuit breaker is arranged to prevent flow of electrical current being reestablished in the electrical circuit.
24. An electrical circuit breaker according to claim 23 characterised by comprising a nonreturn device.
25. An electrical circuit breaker according to claim 24 characterised in that the nonreturn device is provided on the insulating element, to prevent the element from being removed from between the electrical contacts.
26. An electrical circuit breaker according to claim 25 in characterised in that the nonreturn device comprises a shoulder or serrations (12) on the insulating element (9).
27. An electrical circuit breaker according to any preceding claim characterised in that the actuator (43) comprises a member which, on operation of the actuator, is impelled away from the actuator to drive the insulating element (46).
28. An electrical circuit breaker according to any of claims 1 to 26 characterised in that the actuator (4,23) comprises a member (9,28) which acts as the insulating element and, on operation of the actuator, is impelled away from the actuator.
29. An electrical circuit breaker according to claim 27 or claim 28 characterised in that the member is a pin or a plunger.
30. An electrical circuit breaker according to claim 29 characterised in that the pin or plunger is impelled from one end of a body of the actuator.
31. An electrical circuit breaker according to claim 30 characterised in that the member is impelled by an explosion in the actuator.
32. An electrical circuit breaker according to any preceding claim characterised in that the actuator (4,23,43,55) is activated by an electrical signal.
33. An electrical circuit breaker according to claim 32 characterised in that the electrical signal causes an explosion in the actuator (4,23,43, 55).
34. An electrical circuit breaker according to claim 32 or claim 33 characterised in that the electrical signal is provided by an inertia switch.
35. An electrical circuit breaker according to claim 34 characterised in that the switch operates to provide the electrical signal in the event of impact of, and above, a predetermined force on a vehicle or aircraft to which the electrical circuit breaker is attached for use.
36. An electrical circuit breaker according to any preceding claim characterised by being attached to the electrical circuit of a battery of a vehicle.
37. An electrical circuit breaker according to any of claims 1 to 35 characterised by being adapted to form part of a terminal of a battery of a vehicle.
38. An electrical circuit breaker according to any preceding claim characterised by comprising two or more pairs of contacts, each pair of contacts being adapted for connection to an electrical circuit through which electrical current flows, two or more insulating elements, and an actuator which, on operation, drives an insulating element between each pair of contacts to interrupt the flow of electrical current between the contacts.
39. An electrical circuit breaker comprising at least one pair of electrical contacts adapted for connection to an electrical circuit through which electrical current flows, a conducting member displaceably located between the electrical contacts for flow of electrical current between the contacts, at least one insulating element, and an actuator which, on operation, causes the conducting member to be displaced from between the contacts to interrupt flow of current between the contacts and the insulating element to be positioned between the pair of contacts in place of the conducting member.
Description:
ELECTRICAL CIRCUIT BREAKERS This invention relates to electrical circuit breakers, and particularly to breakers in which the flow of electrical current in an electrical circuit is interrupted by separating electrical contacts in the circuit.

There are a number of applications in which it is desirable to provide at least one electrical circuit breaker in an electrical circuit, to interrupt the flow of electrical current in the circuit. For example, in the automotive or aeronautical industries, if a vehicle is involved in an accident it is desirable to interrupt the flow of current from the battery to, for example, the fuel pump or the alternator etc., thereby reducing the risk of fire and/or explosion in the engine of the vehicle.

According to a first aspect of the present invention there is provided an electrical circuit breaker comprising at least one pair of electrical contacts adapted for connection to an electrical circuit through which electrical current flows, at least one insulating element, and an actuator which, on operation, drives the insulating element between the pair of contacts to interrupt the flow of electrical current between the contacts.

The insulating element may be provided with a chamfered end. This may facilitate insertion of the insulating element between the pair of contacts.

The electrical circuit breaker may be provided in a housing. The housing may be sealed. This helps prevent tampering with the electrical circuit breaker. If the electrical circuit breaker comprises an explosive actuator, this will also help to prevent pieces of the actuator from escaping from the housing, and any sparking caused by the explosion to remain in the housing.

A conducting member may be displaceably located between the electrical contacts for flow of electrical current between the contacts. The insulating element may be attached to or co-operate with the conducting member, such that on operation of the actuator the insulating element is driven between the pair of contacts in place of the conducting member. In one embodiment the conducting member is carried by the insulating element, being housed in an aperture or recess in the insulating element.

In another embodiment the conducting member and insulating element are not physically connected, the insulating element being positioned to abut against the conducting member to displace the member from between the contacts when the actuator is operated.

The insulating element may provide an air space between the electrical contacts when the conducting member has been displaced from between the contacts.

Preferably the conducting member is normally held between the electrical contacts by frictional engagement with them. The force of the actuator acting on the conducting member when the actuator is operated overcomes the friction to release the conducting member from the contacts.

The electrical contacts may be spring urged into the frictional engagement with the conducting member. Spring loading of the contacts may be provided by the housing of the electrical circuit breaker. For example, the housing may have inherently resilient opposed walls to which the electrical contacts are attached and between which the conducting member is located. The housing may conveniently be made of a suitable material, such as a plastics or rubber material, which has some inherent resilience and provides the required spring loading of the contacts. In a preferred embodiment in which the housing is of a plastics material having some

resilience, the electrical contacts comprise externally screw-threaded elements which are screwed into complementary threaded holes in opposed walls of the housing and into bearing engagement with opposite parts of the conducting member so as to locate the conducting member in position between the contacts. The opposed walls of the housing flex as the screw-threaded elements are tightened onto the opposite parts of the conducting member, thereby enhancing the frictional engagement between the contacts and the conducting member.

The conducting member may re-locate between further electrical contacts when it has been displaced from the said one pair of electrical contacts by operation of the actuator. Thus although the electrical current between the latter contacts is interrupted by the operation of the actuator, an electrical current path is established at the further contacts to complete another circuit. For example, the completed circuit may cause a visual or audible alarm to be operated to signal that the electrical circuit breaker has been operated.

There may be more than one pair of electrical contacts between which the conducting member displaceably locates. There may be more than one conducting member displaceably located between more than one pair of contacts. First and second conducting members may be provided. The first conducting member may be displaceably located between a first pair of contacts and activation of the actuator may cause the first conducting member to be displaced from between the first pair of contacts and the second conducting member to be placed between a second pair of contacts.

Preferably the conducting member is arranged to be moved linearly by the insulating element on operation of the actuator. It may, however, possibly be moved non-linearly. For example the conducting member may be arranged to move angularly as it is displaced from between the contacts.

The conducting member may be re-settable between the contacts to re-establish the flow of electrical current between the contacts. Thus the conducting member may, for example, have a re-setting device attached, or attachable, to it by which the member can be moved back into its original location between the contacts. The re-setting device may simply be a chord, rod or link which is manually operated, possibly from a position remote from the circuit breaker, to move the conducting member into position between the contacts.

The electrical circuit breaker may be arranged to prevent flow of electrical current being re-established in the electrical circuit. The electrical breaker circuit may comprise a non-return device. The non- return device may be provided on the insulating element, to prevent the element from being removed from between the electrical contacts. The non-return device may comprise a shoulder or serrations on the insulating element. The non-return device may be provided by the housing of the electrical circuit breaker. The non-return device may prevent the conducting member from being relocated between the pair of electrical contacts once the actuator has operated.

The actuator may comprise a member which, on operation of the actuator, is impelled away from the actuator to drive the insulating element. The actuator may comprise a member which acts as the insulating element and which, on operation of the actuator, is impelled away from. the actuator.

The member may be a pin or a plunger, which may be impelled from one end of a body of the actuator. The member may be impelled by an explosion in the actuator.

The actuator may be activated by an electrical signal. The electrical signal may cause an explosion in the actuator. The electrical signal may be provided by an inertia switch. The switch may operate to provide the electrical signal in the event of impact of, and above, a predetermined force on a vehicle or aircraft to which the electrical circuit breaker is attached for use. The actuator may be an ICI METRON (registered trade mark) actuator.

The electrical circuit breaker may be attached to the electrical circuit of a battery of a vehicle. The electrical circuit breaker may be adapted to form part of a terminal of a battery of a vehicle.

The electrical circuit breaker may comprise a pair of contacts adapted for connection to an electrical circuit through which electrical current flows, an insulating element, and an actuator which, on operation, drives the insulating element between the pair of contacts to interrupt the flow of electrical current between the contacts. Alternatively, the electrical circuit breaker may comprise two or more pairs of contacts, each pair of contacts being adapted for connection to an electrical circuit through which electrical current flows, two or more insulating elements, and an actuator which, on operation, drives an insulating element between each pair of contacts to interrupt the flow of electrical current between the contacts. The pairs of contacts may be connected to different electrical circuits or to the same electrical circuit.

According to a second aspect of the present invention there is provided an electrical circuit breaker comprising at least one pair of electrical contacts adapted for connection to an electrical circuit through which electrical current flows, a conducting member displaceably located between the electrical contacts for flow of electrical current between the contacts, at least one insulating element, and an actuator which, on operation, causes the conducting member to be displaced from between the contacts to interrupt flow of current between the contacts and the insulating element to be positioned between the pair of contacts in place of the conducting member.

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 schematic representation of an electrical circuit breaker according to a first embodiment of the present invention; Figure 2 is a schematic representation of an electrical circuit breaker according to a second embodiment of the present invention; Figure 3 is a schematic representation of an electrical circuit breaker according to a third embodiment of the present invention; Figure 4 is a simplified plan view of an electrical circuit breaker according to a fourth embodiment of the present invention; Figure 5 is a perspective view of the electrical circuit breaker of Figure 4;

Figure 6 shows an enlarged perspective view of another arrangement of a conducting member and insulating element for use with the electrical circuit breaker of Figures 4 and 5, and Figures 7 and 8 are simplified plan views of an electrical circuit breaker according to a fifth embodiment of the present invention, and Figure 9 is a simplified plan view of an electrical circuit breaker according to a sixth embodiment of the present invention.

Figure 1 shows a first embodiment of an electrical circuit breaker, shown in a partially operated position. This comprises a housing 1, a first electrical contact 2, a second electrical contact 3, and an actuator 4. Each contact is connected via a wire 5 to an electrical circuit (not shown).

Each contact comprises a spring 6. In normal conditions, the springs 6 are in contact at junctions 7, and current flows through the electrical circuit. The actuator is of the known METRON, or similar, type having a cylindrical body 8 by which it is fixed with respect to the housing 1, and an axial pin 9 of insulating material projecting co-axially from one end of the body 8. The pin 9 has a chamfered end 10. An electrical signal is received via wire 11 to operate the actuator. A controlled explosion is initiated in the body 8 by the electrical signal, and the pin 9 is caused to be rapidly impelled to project further from the body 8. The electrical signal may come from an inertia switch, not shown. When the actuator is actuated the resultant movement of the pin 9 forces the chamfered end 10 of the pin between the springs 6 of the contacts 2,3, forcing them apart.

The pin acts as an insulating element between the contacts, and interrupts the flow of current through the electrical circuit. The pin further

comprises a serrated portion 12 which comes to rest between the springs 6. The serrations prevent the pin from being dislodged from this position, maintaining a break in the electrical circuit.

Figure 2 shows a second embodiment of an electrical circuit breaker, shown in an unoperated position. This comprises a housing 20, a first electrical contact 21, a second electrical contact 22, and an actuator 23.

Each contact is connected via a wire 24 to an electrical circuit (not shown). Each contact comprises an arm 25 and, in normal conditions, these are in contact at tips 26, and current flows through the electrical circuit. The actuator is of the known METRON, or similar, type having a cylindrical body 27 by which it is fixed with respect to the housing 20, and an axial pin 28 of insulating material projecting co-axially from one end of the body 27. The pin 28 has a chamfered end 29. An electrical signal is received via wire 30 to operate the actuator. A controlled explosion is initiated in the body 27 by the electrical signal, and the pin 28 is caused to be rapidly impelled to project further from the body 27.

The electrical signal may come from an inertia switch, not shown. When the actuator is actuated the resultant movement of the pin 28 forces the chamfered end 29 of the pin between the arms 25 of the contacts 21,22, forcing them apart. The pin acts as an insulating element between the contacts, and interrupts the flow of current through the electrical circuit.

Figure 3 shows a third embodiment of an electrical circuit breaker, shown in an unoperated position. This comprises a housing 40, a first electrical contact 41, a second electrical contact 42, and an actuator 43. Each contact is connected via a wire 44 to an electrical circuit (not shown). A conducting member 45 is positioned, in normal conditions, between the contacts, and an electrical current flows through the electrical circuit via the conducting member. The conducting member is attached to an

insulating element 46. The actuator is of the known METRON, or similar, type having a cylindrical body 47, and an axial pin housed within the body 47. An electrical signal is received via wire 48 to operate the actuator. A controlled explosion is initiated in the body 47 by the electrical signal, and the pin is caused to be rapidly impelled to project from the body 47 to cooperate with the insulating element 46. The electrical signal may come from an inertia switch, not shown. When the actuator is actuated the resultant movement of the pin forces the insulating element 46 between the contacts 41,42, taking the place of the conducting member 45 and thus interrupting the flow of current through the electrical circuit.

Referring to Figures 4 to 6 of the drawings, an electrical circuit breaker is shown which comprises a housing 51, a pair of electrical contacts 52, a conducting member 53, an insulating element 54 and an actuator 55.

The housing 51 is of rectangular box form comprising a body 56, with opposed side walls 57, and a lid, not shown, which is fixed over the body by screws, not shown. The body 56 and lid are made of a suitable insulating plastics material, for example a nylon. At least the material of the body 56 has some inherent resilience whilst, nevertheless, affording the body substantial firmness of its form.

Each contact 52 comprises an externally screw-threaded rod of electrically conductive material, for example brass. The contacts 52 are screwed into complimentary co-axial holes 57'in the side walls 57 of the body 56 of the housing 51 and are fitted with pairs of nuts 58,58'outside the side walls by which wires 59 of an electrical circuit, not shown, are secured to the contacts.

The conducting member 53 and insulating element 54 are provided as a unit slidably contained inside the housing, in the body 56. The insulating element 54 is a parallelepiped block of a suitable insulating plastics material, for example a nylon, and is a sliding fit in the body for movement longitudinally of the housing. Conducting member 53 is located firmly in a transverse bore 60 in, and extends the full width of, the insulating element 54. It may be moulded into the insulating element.

The conducting member is a rod of an electrically conductive material, for example brass, of similar diameter to the rods of the contacts 52, and is so positioned in the insulating element that by appropriate longitudinal location of the element in the body 56 the conducting member aligns with the two contacts. For use of the electrical circuit breaker the insulating member is so aligned and the contacts are screwed into tight frictional engagement with the opposite ends of the member, thereby positively holding the conducting member in position between the contacts. Because of the inherent resilience of the material of the body 56, the side walls 57 holding the contacts are flexed outwardly as the contacts are screwed against the ends of the conducting member, thereby affording spring loading on the contacts which enhances the frictional engagement between the contacts and the conductive member. Those nuts 58 on the contacts which are adjacent to the side walls are tightened against the side walls to secure the contacts in their set positions, engaging the conducting member.

By selection of the electrical conductive material of the contacts and conducting member high currents can be passed through the circuit breaker.

The actuator is of the known METRON, or similar, type having a cylindrical body 61 which is fixed to an end wall 62 of, the housing

body 56, and an axial pin 63 of an insulating material projecting co-axially from one end of the body 61 into the housing body, towards the insulating element. With the contacts set in engagement with the conducting member, as described, the pin 63 of the actuator actually or almost abuts the adjacent end of the conducting member.

When the electrical circuit breaker is installed for use the actuator 55 has a wire 64 connected to it to receive an electrical signal for operating the actuator. A controlled explosion is initiated in the body when the signal is received, for example from an inertia switch, not shown. The explosion causes the pin 63 to be rapidly impelled to project further from the body 61 of the actuator. The impelling force is such that the pin drives the insulating element along the body and the conducting member is moved out of engagement with the contacts, so interrupting the flow of current through the electrical circuit containing the contacts.

Once the insulating element has been driven past the contacts, the side walls 57 of the housing body 56 return to their normal unflexed condition and the inner ends of the contacts project into the return path of the insulating element, so that the conducting member cannot accidentally be re-engaged with the contacts.

Instead of being held in a bore of the insulating element 54, the conducting member 53 may be positioned at the end of the insulating element remote from the pin of the actuator, as shown in Figure 6. The conducting member may be positively located on the insulating element, for example by bonding, a screw or stake, or it may simply abut against the end of the insulating element. The insulating element is still set in engagement with the contacts in similar manner to that described above.

It is possible that the electrical circuit breaker may include a further set of contacts 65, as shown in Figures 7 and 8, connected by wires 66 into another electrical circuit. When the actuator 55 is operated, the insulating element 54 is driven to a position in which the conducting member 53 aligns with, and is engaged with, the further set of contacts 65 to complete that other electrical circuit, for example to activate an alarm or other signal to indicate that the circuit breaker has been operated.

Figure 9 shows a further embodiment of the invention. This also includes a further set of contacts 65, connected by wires 66 into another electrical circuit. Two conducting members 70,71 are provided, moulded into the insulating element 72. Initially, the conducting member 70 is located between the contacts 52. When the actuator 55 is operated, the insulating element 72 is driven to a position in which the conducting member 70 is displaced from between the contacts 52, the conducting member 71 aligns with, and is engaged with, the further set of contacts 65 to complete that other electrical circuit, and the portion 74 of the insulating element locates between the contacts 52.

The electrical circuit breaker may be used in a variety of applications, including automotive and aeronautical uses. It may be used, for example, in conjunction with an air bag safety system. Another of many examples, is perhaps use in a vehicle to react to an overload current in an electric circuit so as to prevent the possibility of fire occurring.