JP2013125635A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit breaker of high breaking capacity, which is suitable for automatic assembling, while being a thermal electromagnetic overcurrent tripping device.SOLUTION: A circuit breaker is equipped with an opening/closing mechanism portion 51; an overcurrent tripping device 52; a movable contact 13 provided on a cross bar 12 rotating with the opening/closing mechanism portion 51; and a breaking portion stored in a base 3 and including an arc-extinguishing device 53 for cutting an arc; a middle base 2; the base 3; and a cover 1 for covering each component stored in the middle base 2. On the middle base 2, a first hole 2d is provided so as to oppose to the breaking portion on a surface orthogonal to an insertion direction of the middle base 2 into the base 1. The first hole 2d is pasted by a yoke 7 of the overcurrent tripping device 52. In the circuit breaker, the cover 1 has a projecting portion for locking the overcurrent tripping device of a pole on which the opening/closing mechanism portion 51 is not placed, and an insulation member 54 is arranged between the opening/closing mechanism portion 51 and the overcurrent tripping device 52.

Description

  The present invention relates to a circuit breaker such as a circuit breaker for wiring or an earth leakage breaker, and more particularly to a configuration in which an overcurrent tripping device and the like are arranged so as to be suitable for automatic assembly.

  The circuit breaker has a function to open and close the electric circuit by operating the operation handle provided in this circuit breaker, that is, not only the switch function, but also prevent the electric wire and load equipment from being burned out due to overcurrent flow. In order to do so, it plays a big role of cutting off the electric circuit. It is well known that the overcurrent detection is roughly classified into the thermal type, electromagnetic type and electronic type, and the automatic circuit breaker can be obtained relatively easily. However, there is a demerit that the product cost is high. Therefore, although it is the above-mentioned thermal electromagnetic circuit breaker, it is suitable for automatic assembly and circuit breaker that prevents adhesion of metal melt generated due to short circuit breakage to the switching mechanism and overcurrent trip device There is a vessel.

  In this circuit breaker, the open / close mechanism part provided between the frame plates that have an operation handle and are opposed to each other, and the overcurrent trip device that detects the overcurrent and rotates the open / close mechanism part are housed in the middle base. And a breaker including an arc extinguishing device for cutting an arc generated between the movable contact provided on the crossbar that rotates in conjunction with the opening / closing mechanism and the fixed contact that repeats contact and separation with the movable contact. The part is stored in the base. A middle base is placed on the upper part of the base, and a circuit breaker is configured by covering the base and each component housed in the middle base with a cover. Further, the middle base has a first hole formed in the bottom surface, and the first hole is pasted by a yoke constituting the overcurrent tripping device. The overcurrent tripping device is press-fitted into the middle base, and is firmly fixed to the middle base by fitting a bent portion provided in the yoke into a second hole provided in the middle base. And as above-mentioned, it can be assembled | attached sequentially from an upper direction and becomes a structure suitable for automatic assembly (for example, refer patent document 1).

JP 2011-134570 A

In the conventional circuit breaker, the breaker including the arc extinguishing device and the opening / closing mechanism are partitioned by the middle base. A first hole is formed. Therefore, at the time of interruption, the yoke receives an increase in the pressure of the interruption part due to the generation of the arc through the first hole, and the overcurrent tripping device needs to be firmly fixed to the middle base.
On the other hand, in order to further improve the interruption performance, it is necessary to further increase the pressure of the interruption portion due to arc generation. For this purpose, it is necessary to firmly fix the overcurrent tripping device to the middle base. However, in order to support automatic assembly, there is a problem that the overcurrent tripping device cannot be secured by screwing or the like. .
In addition, the overcurrent tripping device that is the energization part and the opening and closing mechanism part that is the non-energization part are installed at a fixed interval so that the overcurrent tripping device is pressed into the middle base At this time, for example, even if the bent portion of the yoke is not fitted into the second hole of the middle base and the overcurrent tripping device floats in the cover direction, it may be assembled without any problem. There was also a point.

  The present invention has been made to solve the above-described problems, and provides a circuit breaker having a high breaking capacity suitable for automatic assembly while being a thermal electromagnetic overcurrent tripping device. .

  The circuit breaker according to the present invention includes an opening / closing mechanism portion disposed between frame plates having an operation handle and facing each other, an overcurrent tripping device for detecting an overcurrent and rotating the opening / closing mechanism portion, A mechanism base and a middle base on which the overcurrent tripping device on which the opening / closing mechanism section is mounted are fixed; a movable contact provided on a crossbar that rotates in conjunction with the opening / closing mechanism section; and the movable contact And a breaker including an arc extinguishing device that cuts an arc generated between the stationary contact member and the stationary contact member that repeats contact and separation, a base in which the breaker is stored, a middle base, a base, and a middle base The middle base is provided with a first hole so as to face the blocking portion on a surface orthogonal to the direction in which the middle base is inserted into the base. One hole is overpowered In the circuit breaker pasted by the members constituting the tripping device, the overcurrent tripping device of the pole on which the switching mechanism is not mounted is locked by a cover, and the switching mechanism and overcurrent tripping An insulating member is disposed between the device and the removing device.

  According to the present invention, since the overcurrent tripping device is locked by the insulating member and the cover, a circuit breaker having a high breaking capacity suitable for automatic assembly can be provided.

It is an external appearance perspective view which shows the circuit breaker in Embodiment 1 of this invention. It is the figure which showed accommodation of the member to the middle base in FIG. It is the figure which showed the overcurrent tripping apparatus in FIG. It is a perspective view which shows the back surface of the cover in FIG. It is an expansion perspective view which shows the state which mounted | wore the insulating member with the overcurrent tripping device of the center pole in FIG. FIG. 2 is a plan view and a cross-sectional view showing a middle base in FIG. 1. FIG. 2 is a plan view and a cross-sectional view showing a base in FIG. 1. It is sectional drawing at the time of making the middle base fit to the base in FIG. It is the figure which showed the interruption | blocking part in FIG.

Embodiment 1 FIG.
FIG. 1 is a perspective view of a circuit breaker in a trip state according to Embodiment 1 of the present invention. FIG. 1A is an external view, and FIG. 1B is an exploded view of a cover, a middle base, and a base from FIG. Is shown. 2 is a diagram showing the housing of the member in the middle base in FIG. 1B, FIG. 3 is a diagram showing an overcurrent tripping device and a yoke for one pole from FIG. 2, and FIG. FIG. 5 is an enlarged perspective view showing a state in which an insulating member 54 is attached to the overcurrent tripping device 52 at the center pole. 6 and 7 show a middle base and a base, respectively, (a) is a plan view corresponding to the X view in FIG. 1 (b), (b) is a sectional view, and FIG. 8 is a middle base. 8 is a cross-sectional view (corresponding to (b) of FIG. 6 and FIG. 7) when the are fitted. FIG. 9 is a diagram showing the housing of the member in the base in FIG.

  In FIG. 1, the insulating casing of the circuit breaker 101 for three poles includes a cover 1, a middle base 2, and a base 3. Among them, the middle base 2 includes an opening / closing mechanism 51 having an operation handle 4, an overcurrent tripping device 52 for the number of poles (in this case, three), an overcurrent tripping device 52 for the central pole, and an opening / closing. Insulating members 54 interposed between the mechanism portions 51 are accommodated, and arc-extinguishing devices 53 corresponding to the number of poles are accommodated in the base 3. Further, with respect to the middle base 2, the side plates 2 a and 2 a of the middle base 2 are fitted into the recesses 3 a and 3 a of the base 3 in order to prevent damage due to an internal pressure increase due to an arc generated at the time of interruption. Therefore, the side plates 2a and 2a form a part of the insulating housing. The operation handle 4 protrudes from the handle window hole 1a of the cover 1 so that the operation handle 4 can be operated in the ON direction (on the paper in FIG. 1, clockwise) or the OFF direction (on the paper in FIG. 1, counterclockwise). From the positional relationship between the arc-extinguishing device 53 and the arc-extinguishing device 53, it is well known that 5 is a power supply side terminal and 6 is a load side terminal.

  As shown in FIG. 2, the overcurrent tripping device 52, the opening / closing mechanism 51, and the arc extinguishing device 53 (see FIG. 1B) are also well known. That is, a fixed contact 9 having a fixed contact 8 at one end and fixed to the yoke 7 is connected to the power supply side terminal 5 through a flexible copper wire 10 and has a movable contact 11 at one end. Contact and separation are repeated between the movable contact 13 held by the cross bar 12 that rotates in conjunction with the portion 51, and the contact between the fixed contact 8 and the movable contact 11 is particularly caused by the separation. The arc generated between them is cut by the arc extinguishing device 53.

  The opening / closing mechanism 51 includes a handle arm 15 pivotally supported on a frame 14 formed by a pair of opposed frame plates 14A and 14B, an operation handle 4 fixed to the handle arm 15, and a frame. 14, which is pivotally supported by a pivot 14, and which is rotated by an operation of an overcurrent tripping device 52, which will be described later, and a latch 17. Similarly, a so-called unit is formed by a crossbar 12 pivotally supported by the frame 14. The frame plate 14A (14B) has foot portions 14A1 and 14A2 on the front and rear sides in the power source / load direction, and these foot portions 14A1 and 14A2 are inserted into the middle base 2 through the insertion holes 2b (FIG. 6A). The opening / closing mechanism 51 is fixed to a predetermined position in the insulating housing. Here, details of the toggle link mechanism, that is, manual operation (on to off, off to on) of the circuit breaker 101, trip operation, or reset operation after trip are not essential parts of the present invention. The above detailed explanation is omitted (for the explanation of each operation, see Japanese Patent Application No. 2008-317552, which is a prior application by the same inventor).

  As shown in FIG. 3, the overcurrent tripping device 52 is electrically connected to the fixed contact 9 having a fixed contact 8 at one end when viewed in the current path (hereinafter simply referred to as connection). Connected to the coil 18, the relay terminal 19 connected to the coil 18, the bimetal 20 connected to the relay terminal 19, and an arbitrary location for obtaining a desired bending amount due to the heat generation of the bimetal 20. The flexible copper stranded wire 21 (see also FIG. 2) and the load-side terminal 6 connected to the flexible copper stranded wire 21 are used. 9, the fixed iron core 22 fixed together with the yoke 7, the insulating pipe 23 covering the fixed iron core 22 and positioned at the inner diameter of the coil 18, and positioned at the inner diameter of the insulating pipe 23 and moving against a biasing spring (not shown). It is constituted by a movable core 24 that. In other words, the overcurrent tripping device 52 is a thermodynamic electromagnetic type, and the thermal portion is connected to the yoke 7, the coil 18, the fixed iron core 22, the insulation by the relay terminal 19, the bimetal 20, and the flexible copper strand 21. The electromagnetic parts are formed by the pipe 23, the urging spring, and the movable iron core 24, respectively.

As shown in FIG. 4, an accommodation space 1a for accommodating the coil 18 of the overcurrent tripping device 52 is provided on the back surface of the cover 1, and the cover 1 is mounted on the base at the end of the accommodation space 1a. In some cases, a projecting portion 1b for locking the yoke end 7b of the yoke 7 is provided.
As shown in FIG. 5, the insulating member 54 is formed in a substantially U-shape, and the yoke end 7b of the overcurrent tripping device 52 at the center pole is mounted in a groove provided in the recess. After the overcurrent tripping device 52 is press-fitted into the middle base 2, the convex portions 54 a of the insulating member 54 are loosely fitted on the pair of frames 14 of the overcurrent tripping device 52, and the opening / closing mechanism 51 is placed on the insulating member 54. Is placed. Since the insulating member 54 is provided in the vicinity of the fixed contact 8, if it is made of a material that emits an arc extinguishing gas when the short circuit is interrupted, it contributes to an increase in gas pressure due to the occurrence of an arc at the time of interruption. In addition, if the material is blended with a ceramic fiber or metal hydroxide using a nylon resin as a base material as a filler, it is possible to promote insulation recovery immediately after the short circuit is cut off.

  The operation of the overcurrent tripping device 52 is well known as described above. That is, as shown in FIGS. 2 and 3, when the overload current flows for a predetermined time or more, the bimetal 20 moves in the right direction on the paper. The adjustment screw portion 20a rotates the trip bar 16, and the latch 17 in contact with the trip bar 16 is rotated by this rotation, so that the opening / closing mechanism portion 51 is tripped and movable contact is made. The child 13 is separated from the fixed contact 9. On the other hand, when a short-circuit current flows, a large magnetic force is generated in the coil 18, and the movable iron core 24 moves rightward against the spring force of the biasing spring, thereby rotating the latch 17 directly. Similarly, the opening / closing mechanism 51 is tripped. The overcurrent tripping device 52 is housed in the insulating housing by inserting the load side terminal 6 into the base 3 and the yoke 7 and the relay terminal 19 into the middle base 2 respectively. Explained.

As shown in FIG. 6 and FIG. 7, the load side terminal 6 and the power source side terminal 5 described above are respectively inserted groove 3b (load side terminal 6) and insertion groove 3c (power source) from the viewpoint of a relay point of the current path. It is not necessary to fix it so firmly only by inserting it into the side terminal 5).
On the other hand, the relay terminal 19 is fitted into the insertion hole 2c provided in the middle base 2 by press fitting. As described above, in the overcurrent tripping device 52, the yoke end portion 7b to which the fixed contact 9 is fixed is connected to the opening / closing mechanism 51 via the insulating member 54 at the pole where the opening / closing mechanism 51 is mounted. Since the other poles are locked by the protruding portion 1b of the cover 1, the yoke 7 tries to rotate with the yoke end 7b as a fulcrum when a force in the direction of pulling out the relay terminal 19 is applied. Since the relay terminal 19 is fitted in the insertion hole 2c, the relay terminal 19 cannot rotate and does not come out of the insertion hole 2c.

  Further, with respect to the yoke 7, in view of the point that there is a movable part called a movable iron core 24, and the point that there is a bimetal 20 that is mechanically coupled (via the fixed contact 9, the coil 18, and the relay terminal 19), Since the movement (curvature) of the movable iron core 24 and the bimetal 20 affects the current characteristics of the circuit breaker 101, the fixing due to the insertion must be strong.

  Therefore, in this embodiment, the yoke 7 is provided with two bent portions 7a, and the middle base 2 is provided with a second hole 2e into which the bent portion 7a is fitted. The dimensional relationship between the bent portion 7a and the second hole 2e will be described in detail. The inner dimension B between the partitions of the middle base 2 at the portion where the yoke 7 is inserted is slightly smaller than the both end size A including the bent portion 7a. (A> B). On the other hand, the inter-partition wall inner dimension C of the second hole 2e is made the same as A (A = C), and the area of the inner dimension C is matched with the surface area D of the bent portion 7a. In this way, when the yoke 7 is inserted, the partition wall made of thermoplastic resin opens slightly outward, and when the bent portion 7a reaches the inner dimension C, the partition wall opened outward returns to its original shape and is bent. The movement of the part 7a is prevented. That is, once the overcurrent tripping device 52 is inserted, it is difficult to pull it out, coupled with the fact that the overcurrent tripping device 52 is fixed to at least one of the poles. This means that it is firmly fixed at the position, and thus contributes to stabilization of current characteristics.

  In this way, it is not necessary to fix the overcurrent tripping device 52 to the insulating housing by, for example, screw tightening or the like, and as is clear from FIGS. Since the circuit breaker 101 is formed by so-called lamination, automatic assembly is possible, and the manufacturing cost can be suppressed. The second hole 2e literally penetrates as a “hole” in the mold production of the middle base 2, but is not necessarily limited to this form. If the yoke 7 does not float, “ The “hole” may be closed.

  However, in view of the manufacturing cost of the mold, it is preferable to penetrate the mold as a “hole”. Incidentally, an arc extinguishing device 53 is placed under the middle base 2 where the overcurrent tripping device 52 is fixed, as shown in FIG. On the other hand, although the 2nd hole 2e is obstructed to some extent by the bending part 7a, it is not perfect. Therefore, it is expected that the arc gas generated in the arc extinguishing device 53 at the time of short circuit interruption will reach the opening / closing mechanism 51 through the second hole 2e, which is not preferable. Therefore, in the first embodiment, the protrusion 3e is provided in the power source-load direction of the base 3 including the position of the second hole 2e (see FIG. 7B). Thus, as is apparent from FIG. 8, when the middle base 2 is fitted to the base 3, the second hole 2e is completely closed by the protrusion 3e, so that the blocking performance is particularly improved. be able to. Moreover, the protrusion 3e is provided in advance to ensure insulation between the poles, particularly a creepage distance. However, the automatic assembly described above, stabilization of characteristics, and improvement of the shut-off performance are also provided. There is no increase in cost such as the addition of parts in realizing the above.

  Now, with respect to the improvement of the interruption performance, the arc travel interruption method (also described in the background art section) is adopted in this embodiment. In this arc travel interruption method, an arc generated at the time of short-circuit interruption is guided to the arc extinguishing device 53 by using an electromagnetic repulsive force, and finally the arc extinguishing device 53 secures a current path by the arc. The arc is cut. Specifically, the arc generated between the contacts 9 and 13 is transferred to the yoke 7 on the stationary contact 9 side and to the arc runner 25 (see FIG. 9) on the movable contact 13 side. Due to this transition, the current path becomes the power source side terminal 5 to the arc runner 25 to the grid 53 a of the arc extinguishing device 53 to the yoke 7 to the coil 18 to... To the load side terminal 6. The repulsive force of the magnetic field generated when the direction of the electric current of the arc runner 25 (arrow E) and the direction of the electric current from the lower side to the upper side (arrow F) on the paper surface of the grid 53a are different directions, and the arrow F Then, the direction of the current toward the fixing point of the yoke 7 with the fixed contact 9 (arrow G, see FIG. 3) is also different from the direction of the magnetic field, and the arc is caused to the arc extinguishing device 53. Led. The guided arc is cut, and as a result, the large current accompanying the occurrence of this short circuit is quickly cut off.

  As is apparent from the above description, it is necessary to expose the yoke 7 with respect to the stationary contact 9 and the grid 53a, which is realized by the following measures. That is, the first hole 2d is formed in the bottom surface of the middle base 2 to which the overcurrent tripping device 52 is fixed, and the first hole 2d is formed into the yoke 7 by the fixing of the overcurrent tripping device 52. In other words, the uppermost grid 53a of the arc extinguishing device 53 and the yoke 7 are opposed to each other without any inclusions therebetween. The first hole 2d has a narrow portion extending on the right side (FIG. 6 (a) on the paper surface, the lower side). Both contacts 9 and 13 are inserted into the narrow portion. It is ensured as a turning locus of the movable contact 13. Reference numeral 26 denotes a reflection plate as a pressure receiving part that promotes the opening operation of the movable contact 13 by receiving the expansion pressure of the arc gas, and 27 is a core that promotes the electromagnetic repulsive force. The “blocking portion” indicates, for example, a region constituted by the arc extinguishing device 53 and the arc runner 25 in addition to the reflector 26 and the core 27.

  Another measure concerning the above-mentioned “assistance of the opening operation” will be described here. In FIG. 3, if the hollow portion 22a is provided in the fixed iron core 22 and the rod 28 is provided in contact with or close to the movable iron core 24 in the hollow portion 22a, the movable portion can be moved as described in the background art section. Since the rod 28 strikes the movable contact 13 by the movement of the iron core 24, the contacts 9 and 13 can be quickly separated without waiting for the opening / closing mechanism 51 to operate. In addition to this, in the arc travel interruption system of the first embodiment, as described above, the coil 18 is included in the current path by the arc, so that the movable iron core 24 and, consequently, the rod 28 are still moved by the magnetic force of the coil 18. Since the movable contact 13 remains moving in the direction of opening, the movable contact 13 can be prevented from rotating in the contact direction (so-called swaying back), and high arc voltage can be maintained, that is, rapid arc transfer. Can be planned. Reference numeral 29 denotes a barrier laid between the yoke 7 and the coil 18, and the barrier 29 prevents an appropriate current (arc current) from bypassing the coil 18 not only during current detection but also during arc maintenance. It generates magnetic force.

When the circuit breaker 101 is short-circuited, a high-pressure gas is generated between the fixed contact 8 and the movable contact 11, that is, by an arc generated at the breaking portion. The pressure of the high-pressure gas is A force that pushes up the yoke 7 exposed to the blocking portion from the first hole in the direction of the cover 1 is generated.
According to the present embodiment, since the insulating member 54 and the protruding portion 1b of the cover 1 lock the yoke end portion 7b, the yoke 7 does not move in the direction of the cover 1 and the pressure at the time of interruption is reduced. The circuit breaker having a high breaking capacity suitable for automatic assembly can be obtained.

  Further, in the overcurrent tripping device 52, the relay terminal 19 is press-fitted into the insertion hole 2c provided in the middle base 2, so that the parts can be assembled from one direction and the yoke 7 is directed in the direction of the cover 1. Since there is no risk of floating, automatic assembly can be realized at the same time while satisfying the basic performance essential for circuit breakers such as stabilization of characteristics and improvement of breaking performance. This can contribute to a significant profit improvement, especially for small circuit breakers with high cost competitiveness.

  In addition, the yoke 7 is press-fitted into the middle base 2, and the overcurrent tripping device 52 is fixed to the middle base 2 so that the overcurrent tripping device 52 is not moved in the direction opposite to the press-fitting direction. Since the second hole 2e is formed, the yoke 7 is more firmly fixed to the middle base 2, and the characteristics can be stabilized and the blocking performance can be improved.

  Further, the insulating member 54 is formed in a substantially U shape, and a groove for attaching to the yoke end portion 7 b is provided in the concave portion, and the convex portion 54 a is loosely fitted to the pair of frames 14 of the opening / closing mechanism portion 51. In addition, since the overcurrent tripping device 52, the insulating member 54, and the opening / closing mechanism 51 are assembled together in automatic assembly, the positional relationship between them is assured and the structure is suitable for automatic assembly.

  Further, since the insulating member 54 is formed of a material that emits arc extinguishing gas when the short circuit is interrupted, the effect of promoting arc extinction of the arc generated between the fixed contact 8 and the movable contact 11 when the short circuit is interrupted. There is also.

  Further, since the insulating member is formed of a material in which a nylon-based resin is used as a base material and a ceramic fiber or a metal hydroxide is blended as a filler, there is an effect of promoting the insulation recovery immediately after the short circuit is cut off.

  In this embodiment, the example in which the insulating member 54 is attached only to the overcurrent tripping device of the pole on which the opening / closing mechanism 51 is mounted has been described. However, the protruding portion 1b of the cover 1 is eliminated or The height of the installation part 1b may be adjusted, and a locking member may be disposed between the overcurrent tripping device of the pole on which the cover 1 and the opening / closing mechanism part 51 are not placed. At this time, if the locking member is formed of a material that emits arc extinguishing gas when the short circuit is interrupted, the arc generated between the fixed contact 8 and the movable contact 11 is interrupted when the short circuit is interrupted. Can be encouraged. Furthermore, if this locking member is formed of a material in which a nylon-based resin is used as a base material and a ceramic fiber or a metal hydroxide is blended as a filler, insulation recovery immediately after interruption of a short circuit can be promoted.

1 cover, 1b protruding portion, 2 middle base, 2d first hole, 2e second hole,
3 Base, 3e Protruding part, 4 Operation handle,
7 Yoke, 7a Bend, 7b Yoke end, 9 Fixed contact,
12 crossbars, 13 movable contacts, 14 frames,
51 Opening / closing mechanism, 52 Overcurrent tripping device, 53 Arc extinguishing device, 54 Insulating member,
101 Circuit breaker.

Claims (6)

An opening / closing mechanism having an operation handle and disposed between mutually opposed frame plates, an overcurrent tripping device for detecting an overcurrent and rotating the opening / closing mechanism, the opening / closing mechanism, and the opening / closing mechanism A middle base on which the overcurrent tripping device is mounted, a movable contact provided on a crossbar that rotates in conjunction with the opening / closing mechanism, and contact with and separation from the movable contact are repeated. A blocking portion including an arc extinguishing device for cutting an arc generated between the stationary contact, a base in which the blocking portion is stored, the middle base, the base, and each component stored in the middle base. And a cover to cover,
In the middle base, a first hole is formed so as to face the blocking portion on a surface orthogonal to a direction in which the middle base is inserted into the base. In the circuit breaker pasted with the members constituting the overcurrent tripping device,
The overcurrent tripping device of the pole on which the switching mechanism is not mounted is locked by the cover, and an insulating member is disposed between the switching mechanism and the overcurrent tripping device. A circuit breaker characterized by that.   The circuit breaker according to claim 1, wherein the relay terminal on the side where the fixed contact is not provided in the overcurrent tripping device is press-fitted into an insertion hole provided in the middle base.   The member of the overcurrent tripping device is press-fitted into the middle base, and the overcurrent tripping device is opposite to the press-fitting direction in order to fix the overcurrent tripping device to the middle base. The circuit breaker according to claim 1 or 2, wherein a second hole is formed so as not to float in the direction.   4. The overcurrent tripping device for a pole on which the opening / closing mechanism portion is not placed is locked by the cover via a locking member. Circuit breaker described in.   5. The circuit breaker according to claim 4, wherein the insulating member and the locking member are made of a material that generates an arc extinguishing gas when touched by an arc generated when the circuit breaker is interrupted.   6. The circuit breaker according to claim 5, wherein the insulating member and the locking member are made of a material in which a nylon-based resin is used as a base material and ceramic fibers or metal hydroxide is blended as a filler.

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