JPH10228855A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability for the operation by restricting thermal deformation of an arc extinguishing grid built in a main body case by arc heat and preventing interference between a movable contactor and the arc extinguishing grid at the time of closing operation after electric current is shut off. SOLUTION: This circuit breaker is constituted by installing an arc extinguishing grid 12 on the opposite to a movable contactor 7 and a fixed contactor in a main body case 1 having a separate structure composed by superposing a cover 3 on a case 2, engaging and holding one end of the arc extinguishing grid 12 whose plate face is formed into approximately a U-shape, and pinching the other end by the cover 3. In this case, as a grid holding member to restrict free thermal deformation by restricting the end part of the arc extinguishing grid 12 inside the cover 3, a rib-like projected part 3a is formed near the end part 12a as to projected out of the inner wall face of the cover 3, so that thermal deformation of the arc extinguishing grid 3 toward the switching movement line of the movable contactor due to arc heat can be restricted by the rib-like projected part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small circuit breaker for a circuit protector or the like, and more particularly, to a support structure for an arc-extinguishing grid incorporated in a main body case of the circuit breaker.

[0002]

2. Description of the Related Art First, a conventional structure of a circuit breaker to which the present invention is applied is shown in FIGS. In the figure,
1 is a case 2 and a cover 3 made as a resin molded product
The main body case 4 is an operation handle, and 5 and 6 are external lead-out terminals. A movable contact 7, a fixed contact 8, and a movable contact opening / closing mechanism 9 are provided inside the main body case 1. A trip mechanism 10 of an electromagnetic solenoid type is incorporated, and an arc-extinguishing grid 12 is mounted in an arc-extinguishing chamber 11 in a case defined in an opening and closing movement path portion of the movable contact 7.

Here, the arc-extinguishing grid 12 has a substantially U-shaped plate surface, and a plurality of arc-extinguishing grids 12 are inserted at one end into concave grooves 2a formed on the inner wall surface of the case 2 and locked in place. It is held between the case 2 and the cover 3 by pressing the other end against the inner wall surface of the cover 3. In consideration of the assemblability of the main body case 1, the cover 3 has a flat inner wall surface.
The end face of the arc-extinguishing grid 12 is pressed by the cover 3.

The operation of such a circuit breaker is well known. When the contact 7a of the movable contact 7 is separated from the contact of the fixed contact 8 by a tripping operation due to an overcurrent, an arc generated between the movable contact and the fixed contact is generated. Is driven toward the arc-extinguishing grid 12 by the magnetic force of the arc current, extinguishes as a small gap arc in series between the grids, and the current is interrupted. When turning on the circuit breaker after the current is cut off,
Is manually switched from the trip (OFF) to the ON position to close the movable contact 7.

[0005]

By the way, in the circuit breaker having the conventional structure described above, when closing by the handle, the movable contact 7 is caught on the arc-extinguishing grid 12 when closing by the operation of the handle after the current is cut off. As a result, there may be a problem that the contact cannot be closed properly. The inventors have investigated the cause of this problem and found that the cause is as follows. That is, as shown, the plate surface is U
The arc-extinguishing grid 12 having a deformed shape becomes deformed due to arc heat when it comes into contact with a high-temperature arc. In particular, the tip (free end) 12 a of the arc-extinguishing grid 12 facing the inner wall of the cover 3.
Are curved inward as indicated by the chain line in FIG. 3 (c). On the other hand, the movable contact 7 may be assembled at a position slightly offset from the position indicated by the dashed line in FIG. In addition, in a small circuit breaker, the play gap between the movable contact 7 and the arc-extinguishing grid 12 is small, so that the thermally deformed arc-extinguishing grid 12 interferes with the opening / closing movement locus of the movable contact 7. As a result, when closing the movable contact 7 by operating the handle, an unexpected trouble occurs such that the movable contact 7 is caught on the arc-extinguishing grid 12 and cannot be closed smoothly.

In order to reduce the amount of thermal deformation of the arc-extinguishing grid itself due to arc heat, it is conceivable to increase the thickness of the grid to increase the heat capacity.
It is difficult in practice to increase the thickness of the grid due to the dimensional restrictions of the main body case incorporating the 2. The present invention has been made in view of the above points, and an object of the present invention is to improve a mounting structure of an arc-extinguishing grid, thereby solving the above-mentioned problems and improving reliability in operation. Is to provide.

[0007]

According to the present invention, in order to attain the above object, according to the present invention, a movable contact and a fixed contact are provided on a main body case having a split structure in which a case and a cover of a resin molded product are overlapped. In the circuit breaker in which the arc extinguishing grid is incorporated and one end of the arc extinguishing grid whose plate surface is substantially U-shaped is locked and held at a predetermined position on the case side and the other end is sandwiched by the cover, A grid holding member for restricting free thermal deformation by restraining the arc-extinguishing grid at a fixed position shall be provided on the inner side. Specifically, the grid-holding member is attached to the inner wall surface of the cover in close proximity to the end of the arc-extinguishing grid. And is formed as a rib-shaped projection integrally molded so as to protrude therefrom.

According to this configuration, the other end of the arc-extinguishing grid positioned and held at a fixed position by locking one end to the case side, has a grid holding member (rib-like projection) formed on the inner wall surface of the cover. Are in close proximity to each other. Therefore,
Even if the arc-extinguishing grid is about to be thermally deformed by the heat of the arc generated at the time of current interruption, the arc-extinguishing grid is restricted from free thermal deformation by being restrained by the grid holding member. As a result, there is no possibility that the movable contact and the arc-extinguishing grid will interfere with each other, and even if there is some variation in the assembly accuracy of the movable contact, the closing operation of the movable contact is not hindered and reliability on the operation surface is improved. The performance is improved.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A description will be given based on FIG. In the drawings of the embodiment, the same members corresponding to FIG. 3 are denoted by the same reference numerals. In the structure of the illustrated embodiment, a vertical rib-like projection 3a is newly provided as a restraining member of the arc-extinguishing grid 12 on the inner wall surface of the cover 3 as compared with the conventional structure. Similarly, a concave groove 2a having one end formed in the case 2 (FIG. 3)
(See (d))) and locked in place.

Here, the rib-shaped projections 3a are arranged at the upper and lower stages so that the two arc-extinguishing grids 12 locked and held by the case 2 are restrained at a fixed position.
is molded integrally with the cover 3 so as to protrude from the inner wall surface of the cover 3 in the vicinity of a. With such a configuration,
Fig. 3 (c) The heat generated by the arc between the contacts when the current is interrupted.
When the arc-extinguishing grid 12 is going to be thermally deformed inward of the cover 3 as shown by the dashed line in FIG.
The free thermal deformation is restricted by the contact of a with the rib-shaped projection 3a. Thereby, a space between the arc-extinguishing grid 12 and the contact portion of the movable contact 7 is ensured. Therefore, even if the position of the movable contact 7 is slightly deviated left and right due to the variation in assembly accuracy, the movable contact 7 interferes with the arc-extinguishing grid 12 and closes when closing the handle by operating the handle after the current is cut off. It is possible to avoid the occurrence of operational troubles such as inability to operate.

The provision of the rib-shaped projections 3a on the inner wall surface of the cover 3 does not have any adverse effect on the workability of assembling the cover 3 on the case 2 in the process of assembling the circuit breaker. .

[0012]

As described above, according to the configuration of the present invention, the amount of thermal deformation of the arc-extinguishing grid deformed by the heat of the arc generated at the time of current interruption is restricted, and the circuit breaker is operated by operating the handle after the current interruption. The movable contact can be prevented from interfering with the arc-extinguishing grid when the power supply is turned on, thereby improving the operational reliability of the circuit breaker.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an arc-extinguishing chamber portion of a circuit breaker according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of FIG. 1;

FIG. 3 is a configuration diagram of a conventional circuit breaker, and FIG.
Is an end view of the main body case, (b) is a front view together with the internal mechanism, (c) is a cross-sectional view of the arc extinguishing chamber portion in FIG.
(d) is an exploded perspective view of the assembly structure of the case and the arc-extinguishing grid in (c).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body case 2 Case 3 Cover 3a Rib-shaped protrusion (grid restraining member) 7 Movable contact 12 Arc extinguishing grid

Claims (2)

[Claims] 1. A circuit breaker in which an arc-extinguishing grid is mounted opposite to a movable contact and a fixed contact in a resin main body case having a two-part structure in which a case and a cover are overlapped, and a plate surface is substantially U-shaped. A grid that locks and holds one end of the arc-extinguishing grid to the case and clamps the other end with a cover, restricting the end of the arc-extinguishing grid to a fixed position inside the cover and restricting free thermal deformation A circuit breaker having a holding member. 2. The circuit breaker according to claim 1, wherein the grid holding member is a rib-shaped projection integrally molded so as to protrude from an inner wall surface of the cover in proximity to an end of the arc-extinguishing grid. A circuit breaker characterized by the above.