JP6205928B2 - Magnetic contactor - Google Patents

Description

  The present invention relates to an electromagnetic contactor including a contact device in which a movable contact is detachably arranged with respect to a fixed contact, and an electromagnet unit that moves the movable contact of the contact device.

  In an electromagnetic contactor that opens and closes a current path, a movable contact is driven by an excitation coil and a movable plunger of an electromagnet unit. That is, when the exciting coil is in a non-excited state, the movable plunger is urged by the return spring, and the movable contact is released from the pair of fixed contacts arranged at a predetermined interval. . By exciting the exciting coil from this released state, the movable plunger is moved against the return spring, and the movable contact is brought into contact with the pair of fixed contacts (see, for example, Patent Document 1). ).

Japanese Patent No. 3107288

By the way, in the conventional example described in Patent Document 1, a housing that covers the sealing contact portion and the driving portion is provided, and a box-shaped lower housing in which the upper end that covers the driving portion is opened, The upper housing covers the sealing contact portion joined to the upper end of the side housing.
Here, the drive unit has, for example, a rectangular frame-shaped yoke whose front and rear end surfaces are open so as to surround the exciting coil, and both side plates of the rectangular frame-shaped yoke are accommodated in the lower housing, and the sealing contact portion is The fixed contact is protruded from the upper surface and accommodated in the upper housing.

However, in the conventional example described in Patent Document 1, the sealing contact portion and the drive portion are accommodated in the housing, but when a large impact is applied to the housing, the joint portion between the upper and lower housings There is an unsolved problem that all the stresses are generated, and the sealing contact part and the drive part may be scattered due to disconnection.
Further, when vibration is applied to the housing in a certain frequency band, resonance occurs at the joint between the sealed contact portion and the drive portion and the upper housing and the lower housing. There is an unresolved problem that may be scattered.

In order to solve this unsolved problem, it is conceivable to integrate the drive unit and the lower housing by enclosing an adhesive or resin in at least the lower housing that houses the drive unit. However, in this case, since an adhesive or resin is sealed between the drive unit and the lower housing, there are new problems such as an increase in product weight, an increase in manufacturing cost, and poor assembly workability. is there.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and can be reliably performed without increasing the weight between the outer case and the electromagnet unit serving as the drive unit. The purpose is to provide a contactor.

In order to achieve the above object, one aspect of a current detection device for an electromagnetic contactor according to the present invention includes a contact device in which a movable contact is arranged so as to be able to contact and separate from a fixed contact, an electromagnet unit for moving the movable contact, and a lower case for housing the pre-Symbol electromagnet unit, and a outer casing and an upper casing for housing the contact device, either of the opposed portion of the lower case and the electromagnet unit A locking recess is formed on one side, a locking projection is formed on the other side, and one of the locking recess and the locking projection of the lower case is formed on the upper case. An engagement plate portion is formed to clamp the open end portion of the formed side surface from the outside.

  According to the present invention, at least the relatively heavy electromagnet unit is locked to the locking recess formed in one of the electromagnet unit and the outer case in the outer case, and the locking protrusion formed in the other is locked. Even when a large impact is applied to the case or when resonance occurs, the electromagnet unit can be reliably held without being detached from the outer case.

It is a perspective view which shows an example of the electromagnetic contactor which concerns on this invention. It is a perspective view of the state where the exterior case of the magnetic contactor concerning the present invention was removed. It is AA sectional view taken on the line of FIG. It is sectional drawing which shows the lower case which integrated the contact apparatus and the electromagnet unit, and the upper case with which this is mounted | worn. It is a reference figure which shows the case where an electromagnet unit is integrated with a lower case part by resin sealing. It is sectional drawing which shows the lower case which integrated the contact apparatus and electromagnet unit which show the modification of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a first embodiment of an electromagnetic contactor according to the present invention, FIG. 2 is a perspective view of a state where an exterior case is removed, and FIG. 3 is a cross-sectional view taken along line AA of FIG.
In the figure, reference numeral 10 denotes an electromagnetic contactor. As shown in FIG. 2, the electromagnetic contactor 10 is an electromagnetic in which a contact device 100 having a contact mechanism and an electromagnet unit 200 for driving the contact device 100 are integrated. The contactor body 300 and an exterior case 400 that covers the electromagnetic contactor body 300 are configured.

  As shown in FIG. 3, the specific configuration of the contact device 100 constituting the electromagnetic contactor main body 300 includes a contact storage case 101 having a lower end surface opened. The contact storage case 101 includes a metal rectangular tube body 102 whose upper and lower end surfaces are opened, a ceramic top plate 103 that closes the upper end surface of the rectangular tube body 102, and an inner peripheral surface of the rectangular tube body 102. It is comprised with the bottomed square cylinder 104 which open | released the arrange | positioned upper end.

A contact mechanism 105 is stored in the contact storage case 101. The contact mechanism 105 includes a pair of left and right fixed contacts 106a and 106b, and a movable contact 120 arranged so as to be able to contact and separate from the contacts of the fixed contacts 106a and 106b.
Each of the pair of left and right stationary contacts 106a and 106b is joined to the contact portions 107a and 107b formed in a U-shaped cross section and arranged on the left and right objects at a predetermined interval, and the upper ends of these contact portions 107a and 107b. And external connection terminals 108a and 108b. The inner peripheral surfaces of the side plate portion and the upper plate portion excluding the lower plate portion of the contact portion 107a are covered with insulating covers 109a and 109b.

  The movable contact 120 has a contact plate 121 supported by a connecting shaft 131 fixed to a movable plunger 215 of the electromagnet unit 200 described later, and the left and right ends of the contact plate 121 are fixed contacts 106a and 106b. The contact portions 107a and 107b are inserted between the upper plate portion and the lower plate portion. The connecting shaft 131 has a flange portion 131a that protrudes outward at the upper end. The contact spring 132 is inserted into the connecting shaft 131 from the lower end side, and then the through hole 133 of the movable contactor 120 is inserted, and the upper end of the contact spring 132 is brought into contact with the flange portion 131a. The movable contact 120 is positioned by, for example, a C-ring 134 so as to obtain a force.

  In the released state, the movable contact 120 is in a state where the contact portions 120a at both ends and the contact portions 107a and 107b of the fixed contacts 106a and 106b are separated from each other with a predetermined interval. In addition, the movable contact 120 has a predetermined position by a contact spring 132 at a closing position, with a contact portion 120a formed on the lower surfaces of both ends being connected to a contact 110a on the lower plate portion 118 of the contact portions 107a and 107b of the fixed contacts 106a and 106b. It is set to contact at a contact pressure of.

As shown in FIG. 3, the electromagnet unit 200 has a U-shaped magnetic yoke 201 that is flat when viewed from the side, and a cylindrical auxiliary yoke 203 is fixed to the center of the bottom plate portion 201 a of the magnetic yoke 201. Yes. A spool 204 is disposed outside the cylindrical auxiliary yoke 203.
The spool 204 includes a central cylindrical portion 205 that passes through the cylindrical auxiliary yoke 203, a lower flange portion 206 that protrudes radially outward from the lower end portion of the central cylindrical portion 205, and a radial direction from the upper end of the central cylindrical portion 205. The upper flange portion 207 protrudes outward. An exciting coil 208 is wound around a storage space formed by the central cylindrical portion 205, the lower flange portion 206, and the upper flange portion 207.

The upper magnetic yoke 210 is fixed between the upper ends of the magnetic yoke 201 serving as the open end. The upper magnetic yoke 210 is formed with a through hole 210 a facing the central cylindrical portion 205 of the spool 204 at the central portion.
In addition, a movable plunger 215 having a return spring 214 disposed between a bottom portion and a bottom portion of a cap, which will be described later, is disposed in the central cylindrical portion 205 of the spool 204 so as to be slidable up and down. The movable plunger 215 is formed with a peripheral flange portion 216 protruding outward in the radial direction at an upper end portion protruding upward from the upper magnetic yoke 210.

Further, on the upper surface of the upper magnetic yoke 210, for example, a permanent magnet 220 having an annular shape having a square outer shape and a circular through hole 220 a is fixed so as to surround the peripheral flange portion 216 of the movable plunger 215. The permanent magnet 220 is magnetized so that the upper end side is, for example, an N pole and the lower end side is an S pole in the vertical direction, that is, the thickness direction.
An auxiliary yoke 225 having a through hole 224 having the same outer shape as the permanent magnet 220 and having an inner diameter smaller than the outer diameter of the peripheral flange portion 216 of the movable plunger 215 is fixed to the upper end surface of the permanent magnet 220. The peripheral flange 216 of the movable plunger 215 is in contact with the lower surface of the auxiliary yoke 225.

The shape of the permanent magnet 220 is not limited to the above, and can be formed in an annular shape. In short, if the inner peripheral surface matches the shape of the peripheral flange portion 216, the outer shape is circular. It can be made into arbitrary shapes, such as a square.
A connecting shaft 131 that supports the above-described movable contact 120 is screwed to the upper end surface of the movable plunger 215.
The movable plunger 215 is covered with a cap 230 made of a non-magnetic material and formed in a bottomed cylindrical shape, and a flange portion 231 formed to extend radially outward from the open end of the cap 230 has an upper magnetic yoke. The lower surface of 210 is sealed and joined. Further, the bottom surface of the rectangular tube body 102 of the contact housing case 101 is sealed and joined to the upper surface of the upper magnetic yoke 210.

As a result, the contact device 100 and the electromagnet unit 200 are integrated, and an airtight chamber 240 is formed in which the contact housing case 101 and the cap 230 communicate with each other via the through hole 210a of the upper magnetic yoke 210. A gas such as hydrogen gas, nitrogen gas, a mixed gas of hydrogen and nitrogen, air, or SF ₆ is sealed in an airtight chamber 240 formed by the contact housing case 101 and the cap 230.

  Further, the magnetic yoke 201 is formed in a flat U shape by a bottom plate portion 201a and side plate portions 201b and 201c bent at a right angle upward from front and rear end portions of the bottom plate portion 201a. As shown in FIG. 2, the side plate portions 201b and 201c include a narrow portion 201d connected to the bottom plate portion 201a and a wide portion 201e formed wider than the narrow portion 201d connected to the upper end of the narrow portion 201d. It is configured.

  And the latching recessed part 201f is each formed in the right-and-left end surface of the wide part 201e, ie, the end surface facing the inner peripheral surface of the lower case 400a. As shown in FIGS. 2 and 4, the locking recess 201f is formed at a position close to the lower end of the wide portion 201e. The locking recess 201f includes a bottom part 201g perpendicular to the end face, a vertical side part 201h extending upward from the inner end of the bottom part 201g, and an inclined side part 201i extending obliquely upward from the vertical side part 201h to the end part. It consists of and.

On the other hand, as shown in FIGS. 2 and 4, the outer case 400 includes a lower case 400 a that opens the upper end that accommodates the electromagnet unit 200, and an upper case 400 b that is attached to the upper end of the lower case 400 a. Yes.
The lower case 400a is formed in a bottomed rectangular tube shape having an open upper end surface. As shown in FIG. 1, the lower case 400a is formed with a mounting plate 401 having a screw insertion hole formed in the longitudinal direction of the lower case 400a at the lower part of the front end surface of the outer surface. As shown in FIG. 2, locking projections 402 that are locked to the locking recesses 201f are formed at positions facing the end surfaces of the side plate portions 201b and 201c of the magnetic yoke 201 of the electromagnet unit 200, respectively. The locking projection 402 includes a bottom 402a that protrudes at a right angle inward from the inner peripheral surface locked to the bottom 201g of the locking recess 201f and shorter than the bottom 201g of the locking recess 201f, and the bottom A vertical side 402b that extends upward from the protruding end of 402a to be shorter than the vertical side 201h of the locking recess 201f, and an inclined side 402c that extends diagonally upward from the upper end of the vertical side 402b to the inner peripheral surface. Has been.

Further, an elastic sheet 403 as a sheet elastic body that is in contact with the bottom surface of the bottom plate portion 201a of the magnetic yoke 201 of the electromagnet unit 200 is disposed on the upper surface of the bottom plate portion of the lower case 400a. Further, four engagement holes 405 are formed at positions near the front and rear end portions on the upper end side of the left and right side plate portions 404a and 404b.
When the electromagnet unit 200 in which the contact device 100 is integrated is inserted from the upper side of the lower case 400a, the electromagnet unit is placed on the inclined side portions 402c of the pair of left and right engaging projections 402 formed on the inner peripheral surface of the lower case 400a. The corner of the lower end surface of the wide portion 201e in the 200 magnetic yoke 201 abuts.
In this state, when the electromagnet unit 200 is pushed further downward, the side plate portions 404a and 404b of the lower case 400a move outward as indicated by an arrow X in FIG. 4 as the lower end surface of the wide portion 201e of the magnetic yoke 201 moves downward. The wide portion 201e of the magnetic yoke 201 is allowed to move downward.

  Further, when the electromagnet unit 200 is pushed downward, the corner portion of the wide portion 201e of the magnetic yoke 201 is lowered while being in contact with the vertical side portion 402b of the locking projection 402. Thereafter, while the elastic sheet 403 is elastically deformed, when the bottom portion 201g of the locking recess 201f formed in the wide portion 201e of the magnetic yoke 201 is positioned opposite the bottom portion 402a of the locking projection 402, the lower case 400a The engagement is such that the outward elastic deformation is eliminated and the locking projection 402 is inserted into the locking recess 201f. When the downward pressing of the electromagnet unit 200 is released in this engaged state, the bottom plate portion 201a of the magnetic yoke 201 of the electromagnet unit 200 is biased upward by the elasticity of the elastic sheet 403, and the bottom side portion 201g of the locking recess 201f is The upward movement of the electromagnet unit 200 is stopped by coming into contact with the bottom side portion 402a of the locking projection 402, and the locking state is brought about. In this locked state, the upward release of the electromagnet unit 200 from the lower case 400a is reliably prevented.

  On the other hand, as shown in FIG. 4, the upper case 400b is formed in a rectangular tube shape with the lower end opened, and the upper plate portion 411a has a through-hole that allows the external connection terminals 108a and 108b of the contact device 100 to be externally desired. 412 is formed, and the left and right side plate portions 411b and 411c are formed with engagement plate portions 413 protruding downward at positions close to the front and rear ends. As shown in FIG. 4, the engaging plate portion 413 is formed with a hook portion 414 projecting inwardly on the inner surface on the lower end side.

  Then, as shown in FIG. 4, the upper case 400 b is attached from above to the lower case 400 a in which the electromagnet unit 200 in which the contact device 100 is integrated is fixed. At this time, the external connection terminals 108a and 108b of the contact device 100 are projected to the outside through the through hole 412, and the hook portion 414 of the engagement plate portion 413 is engaged with the engagement hole 405 of the lower case 400a, thereby The case 400b can be fixed to the lower case 400a.

Next, the operation of the first embodiment will be described.
Now, the external connection terminal 108a connected to the contact 107a of the fixed contact 106a is connected to, for example, a power supply source that supplies a large current, and the external connection terminal 108b connected to the contact 107b of the fixed contact 106b is loaded. It is assumed that it is connected to
In this state, it is assumed that the exciting coil 208 in the electromagnet unit 200 is in a non-excited state and the electromagnet unit 200 is in a released state in which no exciting force for lowering the movable plunger 215 is generated. In this released state, the movable plunger 215 is urged upward by the return spring 214 away from the upper magnetic yoke 210. At the same time, the attractive force due to the magnetic force of the permanent magnet 220 is applied to the auxiliary yoke 225, and the peripheral flange 216 of the movable plunger 215 is attracted. For this reason, the upper surface of the peripheral flange 216 of the movable plunger 215 is in contact with the lower surface of the auxiliary yoke 225.

When the exciting coil 208 of the electromagnet unit 200 is energized from this released state, an exciting force is generated by the electromagnet unit 200 and the movable plunger 215 is resisted against the biasing force of the return spring 214 and the attractive force of the annular permanent magnet 220. Lower. The lowering of the movable plunger 215 is stopped when the lower surface of the peripheral flange portion 216 comes into contact with the upper surface of the upper magnetic yoke 210.
As described above, when the movable plunger 215 is lowered, the movable contact 120 connected to the movable plunger 215 via the connecting shaft 131 is also lowered, and the contact portion 120a thereof becomes the contact 110a of the fixed contacts 106a and 106b. Contact is made with the contact pressure of the contact spring 132.

Therefore, a closed state is reached in which a large current from the external power supply source is supplied to the load through the fixed contact 106a, the movable contact 120, and the fixed contact 106b.
When the current supply to the load is interrupted from the closed state of the contact mechanism, the excitation of the excitation coil 208 of the electromagnet unit 200 is stopped.
As a result, the exciting force that moves the movable plunger 215 downward by the electromagnet unit 200 disappears, so that the movable plunger 215 rises by the urging force of the return spring 214, and the annular permanent magnet 216 as the peripheral flange 216 approaches the auxiliary yoke 225. The suction force of 220 increases.

  As the movable plunger 215 rises, the movable contact 120 connected via the connecting shaft 131 rises. In response to this, the movable contact 120 is in contact with the stationary contacts 106a and 106b while the contact pressure is applied by the contact spring 132. Thereafter, when the contact pressure of the contact spring 132 disappears, the movable contact 120 is in an open state in which it is separated upward from the fixed contacts 106a and 106b.

When this contact opening start state is reached, an arc is generated between the contact 110a of the fixed contacts 106a and 106b and the contact 120a of the movable contact 120, and the current conduction state is continued by this arc. At this time, since the insulating covers 109a and 109b covering the upper and side plates of the contact portions 107a and 107b of the fixed contacts 106a and 106b are mounted, the arc is movable in contact with the contacts 110a of the fixed contacts 106a and 106b. It can be generated only between the contact 120a of the child 120. For this reason, it is possible to reliably prevent the arc from moving on the upper plate portion and the side plate portion of the contact portions 107a and 107b of the stationary contacts 106a and 106b, thereby stabilizing the arc generation state and improving the arc extinguishing performance. Can be made. In addition, by covering both the upper and side plates of the contact portions 107a and 107b of the fixed contacts 106a and 106b with the insulating covers 109a and 109b, it is possible to reliably prevent the arc tip from being short-circuited. .
The arc is stretched to the left and right sides of the contact portions 107a and 107b of the stationary contacts 106a and 106b and extinguished.

The operation of the electromagnetic contactor 10 is as described above, and an impact force is applied to the electromagnetic contactor 10 from the outside or resonance occurs, and a force that pulls upward from the lower case 400a is applied to the electromagnet unit 200. Shall be.
At this time, the locking convex portion 402 formed on the inner peripheral surface of the lower case 400a is locked to the locking concave portion 201f formed in the wide portion 201e of the side plate portions 201b and 201c of the magnetic yoke 210 of the electromagnet unit 200, The bottom side 201g of the locking recess 201f is in contact with the bottom side 402a of the locking projection 402.

Therefore, it is possible to reliably prevent the electromagnet unit 200 from separating upward from the lower unit 400a.
In addition, when the electromagnet unit 200 is pulled out from the lower case 400a, the latching projection 402 formed on the inner peripheral surface of the lower case 400a is latched into the latching recess 201f formed in the magnetic yoke 201 of the electromagnet unit 200. This can be surely prevented. Therefore, no new parts are added or the weight is increased in order to prevent removal, and the whole can be reduced in size and weight.

  Further, an elastic sheet 403 is disposed on the bottom surface of the lower case 400a, and the elastic sheet 403 causes the electromagnet unit 200 to urge upward so that the bottom side portion 201g of the locking recess 201f and the locking projection 402 of the lower case 400a. It is possible to prevent the generation of noise due to the vibration transmitted to the lower case 400a without causing the bottom portion 402a to come into contact with each other and causing play between the lower case 400a and the electromagnet unit 200.

  Furthermore, when the upper case 400b is attached to the upper end of the lower case 400a, the engaging plate portion 413 formed on the upper case 400b engages the outside of the lower case 400a. To the outside is suppressed. For this reason, it can prevent reliably that the latching convex part 402 remove | deviates outside from the latching recessed part 201f because the lower case 400a bends outside.

  Incidentally, in the case where the locking recess 201f and the locking projection 402 are not provided, the electromagnet unit 200 and the lower case 400a are connected as shown in FIG. 5 in order to connect the electromagnet unit 200 and the lower case 400a. It is necessary to fill the part with a filler 450 such as a synthetic resin material or an adhesive, and it takes time and effort to fill the filler 450, the assembly work cannot be performed efficiently, and the weight also increases. It cannot be reduced in size and weight.

However, in the present embodiment, as described above, it is only necessary to lock the locking projections 402 of the lower case 400a in the locking recesses 201f formed in the electromagnet unit 200, and the electromagnet unit 200 and the lower portion can be simply configured. The case 400a can be firmly integrated.
In the above embodiment, the case where the elastic sheet 403 is arranged on the bottom surface of the lower case 400a has been described. However, the present invention is not limited to this, and the bottom surface of the lower case 400a is elastic as shown in FIG. The elastic curved portion 460 that has an upward convex shape may be integrally formed. In short, an elastic body that can bias the electromagnet unit 200 upward may be disposed.

Moreover, in the said embodiment, only an example was demonstrated about the contact apparatus 100 and the electromagnet unit 200, and the internal structure of the contact apparatus 100 and the electromagnet unit 200 can be made into arbitrary structures.
Moreover, in the said embodiment, although the board part 401 for attachment was formed in the lower side of the front-back direction of the lower case 400a, and the lower case extended in the direction at right angles with respect to an attachment surface, it limited to this. Instead, the screw insertion hole may be formed in a direction perpendicular to the longitudinal direction of the lower case 400a.

Moreover, in the said embodiment, although the latching recessed part 201f was formed in the electromagnet unit 200 and the latching convex part 402 was formed in the lower case 400a, it was not limited to this, The electromagnet unit 200 A locking projection may be formed on the lower case 400a, and a locking recess may be formed on the lower case 400a.
Moreover, in the said embodiment, although the airtight chamber 240 was comprised with the contact storage case 101 and the cap 230 and gas was enclosed in this airtight chamber 240, it was not limited to this, It interrupts | blocks Gas filling may be omitted when the current is low.

  In the first and second embodiments, the case in which the outer case 400 is divided into the lower case 400a and the upper case 400b has been described. However, the present invention is not limited to this, and the lower case 400a and the upper case are not limited thereto. 400b may be integrated into a rectangular tube shape with the upper end surface or the lower end surface opened, and a closing plate portion that closes the upper end surface or the lower end surface may be provided.

  DESCRIPTION OF SYMBOLS 10 ... Electromagnetic contactor, 100 ... Contact apparatus, 101 ... Contact storage case, 106a, 106b ... Fixed contact, 107a, 107b ... Contact part, 120 ... Movable contact, 200 ... Electromagnet unit, 201 ... Magnetic yoke, 201f ... Locking recess, 203 ... cylindrical auxiliary yoke, 204 ... spool, 208 ... excitation coil, 210 ... upper magnetic yoke, 214 ... return spring, 215 ... movable plunger, 220 ... permanent magnet, 225 ... auxiliary yoke, 400 ... exterior case , 400a ... lower case, 400b ... upper case, 401 ... mounting plate, 402 ... locking projection

Claims (6)

A contact device in which the movable contact is arranged so as to be able to contact and separate from the fixed contact;
An electromagnet unit that moves the movable contact of the contact device;
And a lower case for housing the pre-Symbol electromagnet unit, and a outer casing and an upper casing for housing the contact device,
A locking recess is formed in one of the lower case and the opposing portion of the electromagnet unit, and a locking protrusion is formed on the other, and is locked in the locking recess.
The upper case is formed with an engagement plate portion that clamps an open end portion of a side surface on which one of the locking concave portion and the locking convex portion of the lower case is formed from the outside. Magnetic contactor to do. The electromagnet unit has a magnetic yoke formed in a U-shape from a bottom plate portion surrounding a magnetizing coil constituting the electromagnet and a pair of side plate portions, and an end surface facing the inner peripheral surface of the exterior case of the side plate portion 2. One of a locking recess and a locking projection that engage with each other is formed, and the other of the locking recess and the locking projection is formed on an inner peripheral surface of the exterior case. The electromagnetic contactor as described in. The pair of side plate portions includes a narrow portion connected to the bottom plate portion and a wide portion formed on an upper end side of the narrow portion, and one of the locking concave portion and the locking convex portion is formed on the wide portion. The electromagnetic contactor according to claim 2, wherein:   The electromagnetic contactor according to any one of claims 1 to 3, wherein an elastic body is interposed between a bottom portion of the exterior case and a bottom portion of the electromagnet unit.   The electromagnetic contactor according to claim 4, wherein the elastic body is integrally formed on a bottom portion of the exterior case. The electromagnetic contactor according to any one of claims 1 to 5 , wherein a hook portion that is engaged from an outside is formed in an engagement hole formed in the lower case on a distal end side of the engagement plate portion .

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