GB2063566A - Automatic circuit breaker - Google Patents

Abstract

An electromagnetically and thermally responsive circuit-breaker has a trip electromagnet 17 arranged so that its cone armature 16 is attracted on heavy faults to strike a rocker 23 so as to separate the contacts 4, 5 and release the operating mechanism 7, 11, 12, 13 which is also released when the bimetallic strip 9, heated by overload, acts on the rocker 23 to open the contacts. An arc runner 24 directs the arc into a chute 6 having metal quenching strips 34. Adjacent similar circuit-breakers have interconnected handles 7 and interconnecting insulators in their casings for connecting tripping shafts together. <IMAGE>

Description

SPECIFICATION A solenoid-thermal switch This invention refers to a solenoid-thermal switch preferably suitable for use with both three-phase industrial systems and household systems. In industrial applications, a plurality of switches may be used, one connected in each phase, with appropriate linkages between them so that even if the current increases in only one phase, all of the phases will be switcned off. In household systems, the switch may be used as a general protection device, for example to protect one subscriber independently of others occupying the same building, and can be applied both as an automatic current limiter switch and a power control switch. The broad range of its field of application is apparent from the foregoing.

The present invention reiates to a switch of solenoid-thermal type, which name is used to describe those switches which operate when the current flowing in the circuit in which they are connected exceeds a given value, with the actuation being possible in two completely different ways: by means of the heat generated in a component through which the current flows, which, for example, results in deformation of the shape of the component, or by induction, according to the strength of the current.

The present invention provides a solenoidthermal switch comprising terminals, a bimetallic strip connected to one of the terminals through a support, which strip, when a current of predetermined strength greater than the rated current of the circuit flows through it, is deformed by the heat generated and acts on a part connected to a moving contact in such a way that the latter separates from the static contact, while at the other end it forces an actuation arm to shift to a break position, and at the same time any resulting arc is directed by appropriately shaped metal plates to an extinction chamber in which are fitted a number of metal strips arranged to form narrow compartments in which are arc is quenched; and coil means whereby when a large increase of current occurs, the switch functions electromagnetically as the coil attracts its moving core, causing the shaft running through it to strike a rocker to cause the moving contact to separte from the static contact, any arc being directed to the extinction chamber.

Preferably the rocker connected to the moving contact has two surfaces on which a screw of the bimetallic strip and the end of the moving core shaft strike respectively, the rocker being held by a drive spring and another one surrounding a shaft which positions it, while it rocks on another shaft parallel to the latter, and said part connected to the moving contact also has an aperture through which passes a third shaft for selectively connecting a plurality of like parts in adjacent switches together in a poly-phase application, together with a fourth shaft on which turns the trigger which through a ring causes the actuation arm to move, the arm being held in position by a spring around the shaft on which it turns.

Preferably said switch may be connected with other like switches in a polyphase application so that all switches break even though the increase of current occurs in only one of them by means of a shaft which is fastened to each rocker connected to each moving contact which shaft passes through an opening provided in each cover of the switches, each causing an insulating part to move which is connected at its other end to another shaft fastened in the same way to said rocker of the next adjacent switch.

Preferably also said switch may, in combination with like switches in a polyphase application be connected together so that the actuation arms are linked together by a projection from one side of each in the form of a narrow cylinder which corresponds to a recess of the same shape in the other side of the next adjacent arm, so that by fitting each projection into the recess of the adjacent arm all are interconnected.

Preferably any arc may be directed by the configuration of the static and moving contacts, one being part of the static core of the relay and the other located diagonally opposite it, the arrangement being such as to make the arc enter the extinction chamber in the shortest possible time, to prevent the case from being burnt by the high temperature produced.

The switch of the preferred embodiment possesses notable advantages over those existing on the market, since it is of extremely sturdy construction and can be used even for currents of more than 50 amperes. In addition, it can be actuated not only automatically as described in previous paragraphs, but also manually by direct action on the actuation arm on occasions when it is desired to cut off the current to make a repair in the system or for any other purpose.

A further preferred characteristic is the linkage system of the arms used in polyphase current applications, for which purpose the cranked arms have a projection of generally cylindrical shape on one side and a recess of appropriate shape, with the assembly positioned so that the projection of each arm fits into the recess of the one immediately to the right, so that all are linked without need of rivets or any other type of external fastening, with resulting considerable simplification of this task.

To facilitate explanation, this specification is accompanied by drawings showing by way of illustrative example without limiting effect a preferred design of a solenoid-thermal switch in accordance with the principles of the invention.

Figures 1 and 2 show elevation and end elevation views respectively of the interior of a solenoid-thermal switch according to the invention, with one of the side covers removed.

Figures 3 and 4 are part sectional and end elevation views respectively, of two cranked arms of the switch of Figs. 1 and 2, from which can be seen the manner of their interconnection, Figure 5 is a view of the cover removed in Figs. 1 and 2 to make the interior of the switch visible. It shows the linkage system between the various switches in a polyphase circuit application, and, Figures 6 and 7 are end views of the linkage system, the latter sectional.

Referring to the drawings, the switch comprises a case 1 with respective input and output terminals 2 and 3, together with a static contact 4 and a moving contact 5, as well as an extinction chamber 6 inside which the spark produced when the arc form between the contacts is put out. Also provided are an actuation arm 7 for manual actuation of the switch, a support 8 for the action, and a bimetallic strip 9 with an adjustment screw 10. The moving contact 5 has a rocking trigger 11 connected by a ring 1 2 to the actuation arm 7, behind which is an overlap platform 13.

From the moving contact runs a flexible lead 14 with appropriate insulation 15, while above it can be seen a moving core 1 6, an induction coil 1 7 and a spring 1 8 which holds the moving core 1 6 out of the coil while it is at rest. At the back is also a spring-loaded device 1 9 whose function is to allow fastening of the switch to a rail of the standard type used for mounting the cases of electrical apparatus.

In the part connected to the moving contact is a bore 20 to mount a shaft which interconnects various switches fitted side by side in polyphase circuits. The extinction chamber assembly 6 is surrounded by insulation 21, and there is a ceramic part 22 to protect the switch from the action of the arc. There is also provided a rocker 23 on the end of the removing contact to enable the switch to function both by heat and electromagnetically.

A metal strip 24 will direct the arc into the interior of the extinction chamber 6, together with part 25 of the static core 26 of the electromagnetic relay. A part 27 effects electromagnetic tripping when it strikes part 23 and causes the moving contact to retract. On the moving contact is provided a spring-retainer shaft 28, a shaft 29 connecting the moving contact 5 to the overlap platform 1 3 and a rocker shaft 30 around which the rocking trigger 11 turns.

The bimetallic strip 9 is mounted on a support 31. Part 32 connects terminal 3 to the bimetallic strip and is fastened to 31 with a screw 33. A set of quenching strips 34 is provided to break the arc and assist its extinction ihside the chamber 6.

The switch mechanism is closed by a cover 35 (see Figs. 5 and 6) pierced by an opening 38 in which is fitted an insulating moving part 36. Through the latter are passed the connecting shafts 37 which are fitted in the bores 20 of each of the solenoid-thermal switches connected in a polyphase circuit.

Furthermore, in a polyphase circuit application, connection of the various actuation arms 7 is facilitated by the fact that one end of each arm has a projection 40 of generally cylindrical shape, which corresponds to a recess 39 of similar characteristics on the opposite side of the arm. It is thus possible by inserting each projection 40 into the recess 39 of the arm to its right to achieve interconnection of the various arms 7 without the need of rivets or other separate part.

In operation, for the switch to function thermally, all that is needed is a minor overload of the order of two to three times the rated current, for the heat generated by the current increase to deform the bimetallic strip 9 enough for its screw 10 to act on the rocker 23. This forces the moving contact to separate from the fixed contact 4 and makes the arm 7 trip, breaking the circuit.

The switch functions electromagnetically in cases of large overload, since the substantial increase of turn amperes in the coil 1 7 will cause it to attract the moving core 1 6 by induction. This forces the shaft 27 to move down and strike the rocker 23 connected to the moving contact 5 making it move away from the static contact 4 to trip the arm 7 and likewise break the circuit.

In both cases (ie thermal or electromagnetic switching), when this happens in a switch connected in a polyphase circuit and linked to others acting on the various phases, the breaking of the circuit will be transmitted through the shaft 37 to the switches in the other phases, so that even though only one switch cuts out, the other phases will be automatically disconnected, preventing possible damage to machines or other devices connected to the circuit from overload of the remaining phases when only one is disconnected, as would happen without this automatic cutout.

There has been described a switch of more compact size that those available on the market. In addition, its design makes possible a much higher breaking capacity than that of which switches available on the market are capable. This high capacity is due to the precise aiming of the arc into the extinction chamber, into which it is directed with extreme rapidity. Inside the chamber the strips 34 break up the arc into small fragments, which prevents the case.from being burnt by the high temperature.

The invention is not restricted to the details of the foregoing example.

Claims (6)

1. A solenoid-thermal switch comprising terminals, a bimetallic strip connected to one of the terminals through a support, which strip, when a current of predetermined strength greater than the rated current of the circuit flows through it, is deformed by the heat generated and acts on a part connected to a moving contact in such a way that the latter separates from the static contact while at the other end it forces an actuation arm to shift to a break position, and at the same time any resulting arc is directed by appropriately shaped metal plates to an extinction chamber in which are fitted a number of metal strips arranged to form narrow compartments in which the arc is quenched; and coil means whereby, when a large increase of current occurs; the switch functions electromagnetically as the coil attracts its moving core, causing the shaft running through it to strike a rocker to cause the moving contact to separate from the static contact, any arc being directed to the extinction chamber.

2. A solenoid-thermal switch as claimed in claim 1, in which the rocker connected to the moving contact has two surfaces on which a screw of the bimetallic strip and the end of the moving core shaft strike respectively, the rocker being held by a drive spring and another one surrounding a shaft which positions it, while it rocks on another shaft parallel to the latter, and said part connected to the moving contact also has an aperture through which passes a third shaft for selectively connecting a plurality of like parts in adjacent switches together in a polyphase application, together with a fourth shaft on which turns the trigger which through a ring causes the actuation arm to move, the arm being held in position by a spring around the shaft on which it turns.

3. A solenoid-thermal switch as claimed in claim 1, connected with other like switches in a polyphase application so that all the switches break even though the increase of current occurs in only one of them, by means of a shaft which is fastened to each rocker connected to each moving contact which shaft passes through an opening provided in each cover of the switches, each causing an insulating part to move which is connected at its other end to another shaft fastened in the same way to said rocker of the next adjacent switch.

4. A solenoid-thermal switch as claimed in claim 1, in combination with other like switches in a polyphase application connected together so that the actuation arms are linked together by a projection from one side of each in the form of a narrow cylinder which corresponds to a recess of the same shape in the other side of the next adjacent arm, so that by fitting each projection into the recess of the adjacent arm all are interconnected.

5. A solenoid-thermal switch as claimed in claim 1 in which any arc is directed by the configuration of the static and moving contacts, one being part of the static core of the relay and the other located diagonally opposite it, the arrangement being such as to make the arc enter the extinction chamber in the shortest possible time, to prevent the case from being burnt by the high temperature produced.

6. A solenoid-thermal switch as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawings.