WO2019122463A1

WO2019122463A1 - Self-compensating mechanism for circuit breaker

Info

Publication number: WO2019122463A1
Application number: PCT/EP2019/054500
Authority: WO
Inventors: Naresh KODELA; Hari KONKA; Vinod MANNARU
Original assignee: Eaton Industries (Austria) Gmbh
Priority date: 2017-12-22
Filing date: 2019-02-22
Publication date: 2019-06-27
Also published as: GB2569669A; GB201810489D0; GB2569669B

Abstract

For a circuit breaker (1) comprising a housing (2), a first contact (3) positional fixed in the housing (2), and a movable contact bridge (4) with a second contact (5) located at a first end (6) of the contact bridge (4), which second contact (5) is associated with the first contact (3), the circuit breaker (1) further comprising a knob (7) articulately fastened to the housing (2), a connecting part (8) articulately fastened to the knob (7), and a latch (16) pivot-mounted to the housing (2), with an engagement-part (17) of the latch (16) being hook-shaped for engaging a latch seat (18) of the circuit breaker (1), with the latch seat (18) being arranged on the connecting part (8), it is suggested that the connecting part (8) is rigidly fastened to the contact bridge (4), and that at least one first resilient spring-area (9) providing a contact force between the first contact (3) and the second contact (5), when the first contact (3) and the second contact (5) are in a closed state, is arranged between the latch seat (18) and the first end (6) of the contact bridge (4).

Description

Self-compensating mechanism for circuit breaker

The present disclosure relates to a circuit breaker according to the generic part of claim 1.

Circuit breakers for an automatic interruption of an electric line are well known for many years. One of the most important parts of a circuit breaker is the latching mechanism. A latching mechanism enables the circuit breaker to rapidly open the contacts under pre definable conditions. Such known latching mechanisms comprise a lot of different parts, which have to be manufactured with high accuracy. This makes the latching mechanism one of the most critical parts of a circuit breaker.

A further aim of the latching mechanism is to provide a constant contact force between the movable contact and the fixed contact. Contacts change their geometry with each switching event, especially under high currents, like over currents and short circuit currents due to wear. The latching mechanism has to compensate such changes in the geometry of the contacts along with the process and material property variations. This makes common latching mechanisms even more complex.

It is an object of the present invention to overcome the drawbacks of the state of the art, and to describe a circuit breaker with a simple latching mechanism with a lower number of parts and low demand on accuracy of the parts, and a high capability for compensating changes in geometry of the switching contacts of the circuit breaker.

According to the invention, this is achieved by a circuit breaker presenting the features of claim 1.

As a result, the circuit breaker has a lower number of parts. Especially the latching mechanism comprises lower number of parts, which additionally have a lower demand for manufacturing accuracy compared to conventional latching

mechanisms. Such a latching device and such a circuit breaker is easy to assemble and to manufacture. As a consequence of a lower price of such circuit breakers even poor people, which could not afford common circuit breakers, can benefit from the advantages of electrical safety.

The actual circuit breaker further has a longer life over a lot of emergency switch off situations. As an effect of the spring area, it is possible to keep the contact force high over a high number of switching operations. This further keeps the self warming effect of the switching device low and also keeps the temperature in the fuse box low. High contact force and low temperatures minimize the risk of self welding of the contacts.

Dependent claims describe further preferred embodiments of the invention.

The wording of the claims is incorporated by reference as additional part of the claims.

The invention is described with reference to the drawings. The drawings are showing only preferred embodiments.

Fig. 1 shows the contact bridge and the connecting part of a first preferred embodiment;

Fig. 2 shows the contact bridge and the connecting part of a second preferred embodiment;

Fig. 3 shows the contact bridge and the connecting part of a third preferred embodiment;

Fig. 4 shows the contact bridge and the connecting part of a fourth preferred embodiment;

Fig. 5 shows the contact bridge and the connecting part of a fifth preferred embodiment; and

Fig. 6 shows a view of the second preferred embodiment of a circuit breaker with open housing and closed contacts. Fig. 1 to 6 show parts of preferred embodiments of circuit breakers comprising a housing 2, a first contact 3 fixed in the housing 2, and a movable contact bridge 4 with a second contact 5 located at a first end 6 of the contact bridge 4, which second contact 5 is associated with the first contact 3, the circuit breaker 1 further comprising a knob 7 articulately fastened to the housing 2, a connecting part 8 articulately fastened to the knob 7, and a latch 16 pivot-mounted to the housing 2, with an engagement-part 17 of the latch 16 being hook-shaped for engaging a latch seat 18 of the circuit breaker 1 , with the latch seat 18 being arranged on the connecting part 8. It is provided that the connecting part 8 is rigidly fastened to the contact bridge 4, and that at least one first resilient spring-area 9 providing a contact force between the first contact 3 and the second contact 5 when the first contact 3 and the second contact 5 are in a closed state, is arranged between the latch seat 18 and the first end 6 of the contact bridge 4.

As a result, the circuit 1 breaker has a lower number of parts. Especially, the latching mechanism comprises a lower number of parts, which additionally have a lower demand for manufacturing accuracy compared to conventional latching mechanisms. Such a latching device and such a circuit breaker 1 is easy to assemble and to manufacture. As a consequence of a lower price of such circuit breakers 1 even poor people, which could not afford common circuit breakers, can benefit from the advantages of electrical safety.

The actual circuit breaker 1 further has a longer life over a lot of emergency switch off situations. Hereby the latch 16 pulls the latch seat 18, and therefore also the connecting part in the direction of the first contact 3 in the closed state. As an effect of the first spring area 9, it is possible to keep the contact force high over a high number of switching operations. This further keeps the self-warming effect of the circuit breaker 1 low and also keeps the temperature in the fuse box low. High contact force and low temperature minimize the risk of self-welding of the contacts 3, 5.

The actual circuit breaker 1 is a low voltage circuit breaker 1 , especially a so- called miniature circuit breaker or MCB. The circuit breaker 1 has a housing 2 made of an insulating material, especially a thermosetting resin. The circuit breaker 1 further comprises at least two connection terminals 24, 25 for connecting the circuit breaker 1 with electric lines.

In the housing 2 a first and a second contact 3, 5 are arranged, which, when in contact to each other, which is called closed state or closed position, close an electric line through the circuit breaker 1 from one connection terminal 24 to the other connection terminal 25. In Fig. 6 a preferred embodiment of the circuit breaker 1 with an opened housing 2 in the closed state is shown.

The first contact 3 is positionally fixed in the housing 2, and preferably connected to an arc extinguishing chamber 26. The second contact 5 is located at a first end 6 of a movable contact bridge 4. The movable contact bridge 4 is able to move inside the housing.

The circuit breaker 1 further comprises a knob 7 for manual operation of the circuit breaker 1 , which knob 7 is articulately fastened in the housing 2, wherein articulately fastened meaning that there is at least one degree of mobility between the components. A connecting part 8 is articulately fastened to the knob 7, but rigid fastened to the contact bridge 4 and connects the movable contact bridge 4 with the knob 7.

According to the preferred embodiment, the circuit breaker 1 comprises two trigger mechanisms 22, 23. A first trigger 22 is embodied as an electromagnetic trigger for releasing the circuit breaker 1 in case of a short circuit. A second trigger 23 comprises a bimetal strip for releasing the circuit breaker in case of an overcurrent event.

The circuit breaker 1 comprises a latching mechanism with a latch 16 and a latch- seat 18. The latch 16 is pivot-mounted in the housing 2. A part of the latch is embodied as engagement-part 17 and has the form of a hook for engaging the latch seat 18. The latch 16 further comprises an oblong hole, in which a trigger guard is engaged for connecting the latch 16 with the second trigger 23.

The latch seat 18 is arranged at the connecting part 8 and is formed as a cylindrical pin 19. When the latch 16 engages the latch seat 18, the latch seat 18 acts as a fulcrum for the system of connecting part 8 and contact bridge 4. The contact bridge 4 and the connecting part 8 is biased with a spring 20 in a direction to open the contacts 3, 5. An opening for the spring 20 can be arranged on the contact bridge 4, as shown in the fig. 1 to 3, or on the connecting part 8, as shown in fig. 4. In case of manual operation of the circuit breaker 1 as a switch without an emergency shut down, the latch 16 is engaged with the latch seat 18 and is also connected to the contact bridge 4 during the opening of the contacts 3, 5 with the knob 7. In case of an emergency shut down, the latch 16 is moved either by the first trigger 22 or the second trigger 23, around the pivot point of the latch 16, so that the latch 16 gets out of engagement of with the latch seat 18. Independent of the position of the knob 7, the spring 20 moves the contact bridge 4 and the connecting part 8 away from the fixed first contact 3.

According to the preferred embodiments, the connecting part 8 is the only part to link the knob 7 with the contact bridge 4.

According to the preferred embodiments, the connecting part 8 is formed as a single polymer part. This makes the construction durable and easy to manufacture.

At least one first resilient spring-area 9 is arranged between the latch seat 18 and the first end 6 of the contact bridge 4. At least one first resilient spring-area 9 provides the contact force between the first contact 3 and the second contact 5 when the first contact 3 and the second contact 5 are in a closed state. Since the connecting part 8 is fastened to the contact bridge 4 in a rigid way, especially with a rigid contact bridge link part 15 of the connection part 8, the second contact 5 can bend with a given force relative to the latch seat 18. Therefore the number of movable pieces inside the housing 2 can be further reduced, thus making the circuit breaker 1 easier to manufacture.

It can further be provided, that a second resilient spring-area 27 is arranged between a knob link part 14 of the connecting part 8 and the latch seat 18. The second spring area 27 is preferably arranged between the knob link part 14 of the connecting part 8 and the latch seat 18. The knob link part 14 is preferable to be substantially straight, and further embodied more rigid than the spring-areas 9,27.

The second resilient spring area 27 is preferably formed substantially in the form of a circle segment 13, especially as a semiring segment. The first resilient spring-area 9 can preferably be a part of the connecting part 8. Hereby the connecting part 8 can be formed to have substantially rigid parts, like the knob link part 14 and the contact bridge link part 15, and resilient parts, like the spring areas 9,27.

Alternatively the first resilient spring-area 9 can be a part of the contact bridge 4.

According to the preferred embodiments, the first spring-area 9 is formed as a pre- definable curved part 12 of the connecting part 8. Such a first spring-area 9 is shown in fig. 1. The second spring-area 27 can be formed as a pre-definable curved part 12 of the connecting part 8 too.

Especially the spring area 9 can be formed substantially in the form of a circle segment 13 or as a semi ring segment.

In another embodiment, the first resilient spring-area 9 can be formed as a constriction 21 of the cross-section. This can be a constriction 21 of the cross- section of the connecting part 8, as shown in the preferred embodiments in the fig. 2 to 4, or a constriction 21 of the cross-section of the contact bridge 4, as shown in the preferred embodiment in the fig. 5. In the constriction 21 of the cross section the connecting part 8 and/or the contact bridge 4 is less rigid than in other parts of a larger cross-section.

According to the preferred embodiment in fig. 3 it can be provided, that the first resilient spring-area 9 is arranged in a forked part of the connecting part 8.

Further, it can be provided that a gap 10, especially in form of a notch 11 , is formed between the contact bridge 4 and the connecting part 8. The gap 10 helps to ensure the resilient effect of the spring areas 9,27 in that way.

Claims

1 . Circuit breaker (1 ) comprising a housing (2), a first contact (3) positional fixed in the housing (2), and a movable contact bridge (4) with a second contact (5) located at a first end (6) of the contact bridge (4), which second contact (5) is associated with the first contact (3), the circuit breaker (1 ) further comprising a knob (7) articulately fastened to the housing (2), a connecting part (8) articulately fastened to the knob (7), and a latch (16) pivot-mounted to the housing (2), with an engagement-part (17) of the latch (16) being hook-shaped for engaging a latch seat (18) of the circuit breaker (1 ), with the latch seat (18) being arranged on the connecting part (8), characterised in that the connecting part (8) is rigidly fastened to the contact bridge (4), and that at least one first resilient spring-area (9) providing a contact force between the first contact (3) and the second contact (5), when the first contact (3) and the second contact (5) are in a closed state, is arranged between the latch seat (18) and the first end (6) of the contact bridge (4).

2. Circuit breaker (1 ) according to claim 1 , characterised in, that a second resilient spring-area (27) is arranged between a knob link part (14) of the

connecting part (8) and the latch seat (18).

3. Circuit breaker (1 ) according to claim 1 or 2, characterised in, that the second resilient spring area (27) is formed substantially in the form of a circle segment (13), especially as a semi-ring segment.

4. Circuit breaker (1 ) according to one of the claims 1 to 3, characterised in, that the connecting part (8) is formed as a single polymer part.

5. Circuit breaker (1 ) according to one of the claims 1 to 4, characterised in, that the first resilient spring-area (9) is a part of the connecting part (8).

6. Circuit breaker (1 ) according to claim 5, characterised in, that the at least one first resilient spring-area (9) is formed as a pre-definable curved part (12) of the connecting part (8).

7. Circuit breaker (1 ) according to one of the claims 1 to 4, characterised in, that the first resilient spring-area (9) is a part of the contact bridge (4).

8. Circuit breaker (1 ) according to one of the claims 1 to 7, characterised in, that the first resilient spring-area (9) is formed as a constriction (21 ) of the cross-section.

9. Circuit breaker (1 ) according to one of the claims 1 to 8, characterised in, that a gap (10), especially in form of a notch (1 1 ), is formed between the contact bridge (4) and the connecting part (8).

10. Circuit breaker (1 ) according to one of the claims 1 to 9, characterised in, that the latch seat (18) is formed as a cylindrical pin (19).

11. Circuit breaker (1 ) according to one of the claims 1 to 10, characterised in, that, when the latch (16) engages the latch seat (18), the latch seat (18) acts as a fulcrum for the system of connecting part (8) and contact bridge (4).

12. Circuit breaker (1 ) according to one of the claims 1 to 11 , characterised in, that the contact bridge (4) and the connecting part (8) are biased with a spring (20) in a direction to open the contacts (3, 5).