EP0206249B1

EP0206249B1 - Circuit breaker

Info

Publication number: EP0206249B1
Application number: EP86108334A
Authority: EP
Inventors: Shinji Mitsubishi Denki K.K. Yamagata; Takuo Mitsubishi Denki K.K. Takatsuka; Hitoshi Mitsubishi Denki K.K. Sato
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1985-05-10
Filing date: 1986-06-19
Publication date: 1991-09-11
Anticipated expiration: 2006-06-19
Also published as: EP0206249A2; EP0206249A3

Description

1. FIELD OF THE INVENTION

The present invention relates generally to a circuit breaker, and particularly concerns a circuit breaker for a power line which is of a type comprising an insulation barrier for isolation between power source side and load side, and is improved for prevention of undesirable decrease of insulation characteristic due to deposition of fine granules of conductive substance around the insulation structure around fixed contact and fixed conductor.

2. DESCRIPTION OF THE RELATED ART

A typical example of the conventional circuit breaker (see for example US-A- 3,599,130, figure 1) having pressure reflectors both for a fixed contact and a moving contact is shown in FIG.3 and FIG.4. As shown in these figures, a fixed contact 1 of power source side comprises a fixed conductor 1a and a fixed contact point 1b which is provided on end tip part of the fixed conductor 1a. An arc runner 2 which is made of a metal is provided at a vicinity of the fixed contact point 1b. A fixed pressure reflector 3, which is usually made of an insulative material, such as phenol resin or PBA (polybuthylenetelephtalate) resin or a high resistivity substance (e.g. tungsten-containing metal) which has a higher specific resistance than the fixed conductor 1a is provided to surround the fixed contact point 1b and also to cover the fixed conductor 1a.
A moving contact 4 comprises a moving conductor 4a and a moving contact point 4b connected to a near end part of the moving conductor 4a. The other end of the moving contact 4 is connected to a known moving mechanism for making circuit breaking operation and circuit interrupting operation. Such known mechanism is disclosed in detail, for instance, in the United States Patent No. 3,599,130. Since the mechnism and operation of the moving contact 4 is not the gist of the present invention, the detailed description of the moving mechanism is omitted. A moving pressure reflector 5 is provided so as to surround the moving contact point 4b, and also to cover the moving conductor 4a. The moving pressure reflector 5 is made of an insulative substance or a high resistance substance which has higher specific resistance than the moving conductor 4a. An insulation barrier 6 is disposed on the fixed pressure reflector 3, so as to isolate a space P of power source side wherein the fixed contact 1 and a known arc extinguisher 7 are disposed from a space L of load side wherein moving mechanism of the moving contact 4 is disposed. The insulative barrier 6 is made of, for instance, a glass-fiber-reinforced polyesther, or the like, insulative sheet and has a vertically oblong hole 6b wherein the moving contact 4 moves. Furthermore, the insulation barrier 6 has, at its lower foot part or base, an indent 6a in which the fixed pressure reflector 3 is to be inserted when a circuit breaker is assembled. By such configuration, the insulation barrier 6 separates the power source side space P in the right side of FIG.3 and the load side space L in the left side thereof.
In the above-mentioned circuit breaker of the prior art, which comprises the fixed pressure reflector 3 on the fixed contact 1 and a moving pressure reflector 5 on the moving contact 4, cross-section of the arc A produced at an opening of the moving contact 4b from the fixed contact 1b is limited small, by the function of the pressure reflectors 3 and 5, and that, the arc resistance is increased. That is to say, the arc current is limited low, thereby producing a current limiting state. In this way, the provision of the pressure reflectors 3 and 5 can improve the current limiting characteristic at breaking of circuit, especially at shortcircuiting. In addition to this, the insulation barrier 6 further improves the insulation characteristics between the power source side space P and load side space L. That is, by provision of the insulation barrier 6, even in the circuit breaking operation with the above-mentioned high arc voltage, break-down of insulation can be prevented. In other words, the insulation characteristic of the circuit breaker is improved, and stable and safe circuit breaking is assured.
In the above-mentioned circuit breaker, there has been a problem such that powder or fine granules of conductive substance generated at each opening of the moving contact point 4b from the fixed contact point 1b, flows along the surface of the fixed pressure reflector 3 and is deposited on the surface, since the surface is formed in a simple face, and such deposited fine granules of the conductive substance are liable to cause breakdown of insulation between the power source side space P and the load side space L.

OBJECT AND SUMMARY OF THE INVENTION

The present invention is made to solve the above-mentioned problem of the prior art circuit breaker, by providing a circuit breaker which is capable of improving insulation characteristic between the power source side space and load side space by preventing breakdown of the insulation due to deposition of powder or fine granule of conductive substance on the surface of the fixed pressure reflector.
The above-mentioned object is accomplished by providing at least one oblong protrusion on the surface of the fixed pressure reflector in a manner to be parallel along or at the vicinity of the foot part of an insulation barrier provided on the fixed pressure reflector.
A circuit breaker in accordance with the present invention comprises
a fixed contact, having a fixed conductor and a fixed contact point disposed at one end part of the fixed conductor,
a fixed pressure reflector disposed to surround the fixed contact point and to cover the fixed conductor,
a moving contact having a moving conductor and a moving contact point disposed at one end part of the moving conductor,
a moving pressure reflector disposed to surround the moving contact point and to cover the moving conductor,
an insulation barrier disposed above the fixed pressure reflector to isolate power source side space and load side space, wherein the improvement is that
the fixed pressure reflector has at least one oblong protrusion provided protruding parallelly along the foot part of the insulation barrier.
By the above-mentioned provision of the oblong protrusion parallely along the foot part of the insulation barrier, powder or fine granules of conductive substance generated at every opening of the moving contact point from the fixed contact point are not deposited on the surface of the fixed pressure reflector, at least at the part where the foot part of the insulation barrier and the oblong protrusion are disposed adjacent each other. Besides, by the provision of the oblong protrusion the creeping distance is elongated, and therefore, insulation characteristic at the surface of the fixed pressure reflector is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a partly sectional side view of a principal part of a circuit breaker embodying the present invention.
FIG.2 is a perspective view showing a principal part of the embodiment of FIG.1.
FIG.3 is the partly sectional view of the conventional circuit breaker.
FIG.4 is the perspective view of the conventional circuit breaker of FIG.3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention is shown in FIG.1 and FIG.2.
As shown in these figures, a fixed contact 1 of power source side comprises a fixed conductor 1a and a fixed contact point 1b which is provided on end tip part of the fixed conductor 1a. An arc runner 2 which is made of a metal is provided at a vicinity of the fixed contact point 1b. A fixed pressure reflector 3, which is usually made of an insulative material, such as phenol resin or PBA resin or a high resistivity substance (e.g. tungsten-containing metal) which has a higher specific resistance than the fixed conductor 1a is provided to surround the fixed contact point 1b and also to cover the fixed conductor 1a. The fixed pressure reflector 3 is provided with at least one oblong protrusion. In the embodiment of FIG.1, two oblong protrusions are provided. An insulation barrier 6 is provided above the fixed pressure reflector 3, in a manner to isolate a space P of power source side wherein the fixed contact 1, the fixed contact point 1b and a moving contact point 4b and a known arc extinguisher 7 are disposed from a space L of load side wherein moving mechanism for a moving contact 4 is disposed. The insulative barrier 6 is made of, for instance, a glass fiber-reinforced polyesther, or similar insulative sheet and has a vertically oblong hole 6b wherein the moving contact 4 moves. Furthermore, the insulation barrier 6 has, at its lower foot part or base 6c, an indent 6a in which the fixed pressure reflector 3 is to be inserted when a circuit breaker is assembled. The two oblong protrusions 8a and 8b are provided substantially in parallel with the foot part 6c of the insulation barrier which is mounted on the fixed pressure reflector 3 at the part of the indent 6a. Therefore, the foot part 6c of the insulation barrier 6 is easily disposed between the two oblong protrusions 8a and 8b.
The moving contact 4 comprises a moving conductor 4a and the moving contact point 4b connected to a near end part of the moving conductor 4a. The other end of the moving contact 4 is connected to a known moving mechanism for making circuit breaking operation and circuit interruption operation. Since the mechanism is known and not the gist of the present invention, description and illustration of the details thereof are omitted. A moving pressure reflector 5 is provided so as to surround the moving contact point 4b and also to cover the moving conductor 4a. The moving pressure reflector 5 is made of an insulative substance or a high resistance substance which has higher specific resistance than the moving conductor 4a.
The operation of the above-mentioned embodiment is elucidated as follows. As a result of the provision of the oblong protrusions 8a and 8b substantially in parallel with and along the foot part of the insulation barrier 6, overwrapping part of the oblong protrusion 8b, the foot part 6c of the insulation barrier 6 and the oblong protrusion 8a form obstacle means against the flow of powder or fine granules of conductive substance generated at the opening of the moving contact point 4b from the fixed contact point 1b. Therefore the hitherto depositing undesirable conductive powder or fine granules are not deposited on the surface of the fixed pressure reflector 3 any more. Furthermore, since the creeping distance along the surface of the fixed pressure reflector 3 is elongated by the provision of the oblong protrusions 8a and 8b, the insulation characteristic of the surface of the fixed pressure reflector itself is improved.
Furthermore, by the provision of two oblong protrusions 8a and 8b, at the mounting of the foot part 6c of the insulation barrier 6 therein, accurate positioning and mounting of the insulation barrier 6 becomes easy.
Though the embodiment shows provision of two oblong protrusions 8a and 8b, the gist of the invention is not limited thereto. That is, provision of only one oblong protrusion is still effective in improving the insulation characteristic to a considerable extent.

Claims

A circuit breaker comprising:
a fixed contact (1), having a fixed conductor (1a) and a fixed contact point (1b) disposed at one end part of the fixed conductor,
a fixed pressure reflector (3) disposed to surround said fixed contact point (1b) and to cover said fixed conductor (1a),
a moving contact (4) having a moving conductor (4a) and a moving contact point (4b) disposed at one end part of the moving conductor,
a moving pressure reflector (5) disposed to surround said moving contact point (4b) and to cover said moving conductor (4a), and
an insulation barrier (6) having a base (6c) mounted on said fixed pressure reflector (3) to isolate power source side space (P) and load side space (L),
characterised in that
said fixed pressure reflector (3) has at least one oblong protrusion (8a) provided protruding parallel to the base (6c) along the whole width of the fixed pressure reflector (3).
A circuit breaker in accordance with claim 1, wherein a pair of said oblong protrusions (8a,8b) are provided substantially parallelly on both sides of said foot part (6c) of insulation barrier (6).
A circuit breaker in accordance with claim 1 or 2, wherein said insulation barrier (6) has
an oblong hole (6b) wherein said moving conductor (4a) moves in longitudinal direction thereof for opening and closing of said moving contact point with said fixed contact point, and
an indent (6a) in which said fixed pressure reflector (3) is to be inserted.