Patent Publication Number: US-8536961-B2

Title: Reversible electromagnetic contactor

Description:
RELATED APPLICATIONS 
     The present application is National Phase of International Application No. PCT/JP2010/005586 filed Sept. 13, 2010, and claims priority from Japanese Application No. 2010-018288, filed Jan. 29, 2010. 
     TECHNICAL FIELD 
     The present invention relates to a reversible electromagnetic contactor that mechanically and electrically interlocks simultaneous closing of two electromagnetic contactors of two electromagnetic contactors disposed adjacently, by using a reversible unit. 
     BACKGROUND ART 
     For example, a device in which a reversible unit is mounted across two adjacently disposed electromagnetic contactors and the reversible unit is mechanically interlocked so as to prevent the two electromagnetic contactors from being closed simultaneously (simultaneous ON operation) is known as a reversible electromagnetic contactor that is connected to the control circuit of an induction motor and performs direct-reverse operation control of the induction motor (for example, Patent Document 1). 
       FIGS. 11 and 12  illustrate the conventional reversible electromagnetic contactor similar to that described in Patent Document 1. In an electromagnetic contactor  1   a  shown in  FIG. 11 , a fixed iron core (not shown in the figure), a movable iron core (not shown in the figure) disposed opposite the fixed iron core, and a coil (not shown in the figure) disposed on the outer circumference of the main leg of the fixed iron core are housed in the lower portion inside a case  5 , and when the coil is energized and the movable iron core is attracted to the fixed iron core, a movable contact (not shown in the figure) fixed to a movable contact support  4  and a fixed contact are opened and closed. A display window  3   a  is formed in an arc-extinguishing cover  2   a  provided on top of the electromagnetic contactor  1   a , and an operation indication piece  4   a  fixed to the movable contact support  4  protrudes into the display window  3   a.    
     Another electromagnetic contactor  1   b , which is disposed adjacently to the electromagnetic contactor  1   a , has the same structure, and when the coil thereof is energized and the movable iron core is attracted to the fixed iron core, a movable contact fixed to a movable contact support  4  and a fixed contact are opened and closed. A display window  3   b  is formed in an arc-extinguishing cover  2   b  provided on top of the electromagnetic contactor, and an operation indication piece  4   b  fixed to the movable contact support (not shown in the figure) protrudes into the display window  3   b.    
     As shown in  FIG. 11 , the reversible unit  6  comprises a unit bottom plate  6   a  connected to arc-extinguishing covers  2   a ,  2   b  in a state of being laid across the two electromagnetic contactors  1   a ,  1   b  and a unit cover  6   b  that is engaged by the circumferential edge thereof with the circumferential edge of the unit bottom plate  6   a . A first interlock plate  6   c , a second interlock plate  6   d , and a lock piece  6   e  constituting a lock mechanism are rotationally connected to each other in the inner space formed by these unit bottom plate  6   a  and the unit cover  6   b . Tubular connection bridges  6   f ,  6   g  are formed at the rear surface of the first interlock plate  6   c  and the second interlock plate  6   d  at the end side thereof and protrude to the outside through openings  6   h ,  6   i  formed in the bottom plate  6   a.    
     When the connection bridges  6   f ,  6   g  of the reversible unit  6  are connected in the respective fitting state thereof to the head portions of the operation indicating pieces  4   a ,  4   b  of the two electromagnetic contactors  1   a ,  1   b  in a state in which the unit bottom plate  6   a  abuts on the air-extinguishing covers  2   a ,  2   b , the lock piece  6   e  causes the rotation of either of the first interlock plate  6   c  and the second interlock plate  6   d , restricts the rotation of the other of the interlock plates, and enables the movement of only one of the operation indication pieces  4   a ,  4   b , thereby performing mechanical interlock such that makes it impossible to close the two electromagnetic contactors  1   a ,  1   b  simultaneously. 
       FIG. 13  shows an example of a control circuit for an induction motor provided with an electrical interlock in addition to the mechanical interlock performed by the reversible unit  6 . 
     In  FIG. 13 , a first switch-on push-button  11  and a second switch-on push-button  12  are connected in parallel to a push-button  10 , and these first and second switch-on push-buttons  11 ,  12  and auxiliary contacts  13 ,  14  of normally-closed contacts (contacts (b)) of the two electromagnetic contactors  1   a ,  1   b  are connected in series. 
     Further, a coil C 1a  and a coil C 1b  of the two electromagnetic contactors  1   a ,  1   b  and the auxiliary contacts  13 ,  14  of contacts (b) are connected in series, the coil C 1a  is connected to the auxiliary contact  13  of the contact (b), the coil C 1b  is connected to the auxiliary contact  14  of the contact (b), and the electrical interlock is performed such that when an exciting circuit of either of the coil C 1a  and the coil C 1b  is closed, the exciting circuit of the other of the coil C 1a  and the coil C 1b  is open. 
     The first switch-on push-button  11  and the second switch-on push-button  12  are provided with respective normally-open contacts  11   a ,  12   a  and normally-closed contacts  11   b ,  12   b  and have the configuration such that the normally-open contact  11   a  is mechanically interlocked with the normally-closed contact  11   b , and the normally-open contact  12   a  is mechanically interlocked with the normally-closed contact  12   b.    
     Patent Document 1: Japanese Patent Application Publication No. H3-266325. 
     As shown in  FIG. 13 , the normally-closed contacts (contacts (b)) are necessary to ensure electrical interlock. Therefore, in the case of the two electromagnetic contactors  1   a ,  1   b  which incorporate only one pole of the auxiliary contacts of the normally-open contacts (contacts (a)), an additional auxiliary contact unit should be connected because the normally-closed contacts (contacts (b)) are necessary. When the auxiliary contact unit is thus connected to ensure electrical interlock, outer dimensions are increased and problems are associated in terms of size reduction. In addition, the device cost can be increased since the auxiliary contact unit is used. 
     DISCLOSURE OF THE INVENTION 
     Meanwhile, in the case of the two electromagnetic contactors which incorporate only one pole of the auxiliary contacts of the normally-closed contacts (contacts (b)), since the auxiliary contacts of the incorporated normally-closed contacts (contacts (b)) are used for the electrical interlock, when another additional circuit such as an auto-holding circuit and a signal circuit is wished to be connected, an auxiliary contact unit is required, and the problems are associated with the reduction in size due to the increase in the outer dimensions and with the increase in the device cost caused by the use of the auxiliary contact unit. 
     Accordingly, the present invention has been created to resolve the abovementioned unsolved problems associated with the related art, and it is an object of the present invention to provide a reversible electromagnetic contactor that makes it possible to connect an additional circuit, without using an auxiliary contact incorporated in the electromagnetic contactor, when performing mechanical and electrical interlock in order to prevent two electromagnetic contactors from being closed simultaneously, and also enables size and cost reduction. 
     In order to attain the abovementioned object, the present invention in one embodiment thereof provides a reversible electromagnetic contactor in which a pair of electromagnetic contactors is disposed adjacently so that respective operation indication pieces protruding on upper surfaces move in the same direction in a closing operation and a reversible unit is mounted across the upper surfaces of the pair of electromagnetic contactors, wherein the reversible unit comprises a pair of interlock plates detachably connected to the respective operation indication pieces of the pair of electromagnetic contactors and moving in the same direction as a moving direction of the operation indication pieces; a lock piece which connects the pair of interlock plates, a first normally-closed contact, a second normally-closed contact, and a unit case that accommodates the pair of interlock plates, the lock piece, and the first and second normally-closed contacts and that is mounted across the upper surfaces of the pair of electromagnetic contactors. In a closing operation of one of the electromagnetic contactors, the lock piece rotates in a first direction as one of the interlock plates moves to prevent the other of the interlock plates from moving, and maintains a release operation of the other of the electromagnetic contactors. In a closing operation of the other of the electromagnetic contactors, the lock piece rotates in a second direction, which is different from the first direction, as the other of the interlock plates moves to prevent the one of the interlock plates from moving, and maintains a release operation of the one of the electromagnetic contactors. The first normally-closed contact is connected in series in a power supply circuit to an exciting coil of the other of the electromagnetic contactors, and the one of the interlock plates comprises a first opening operation engagement portion that performs an operation of opening the first normally-closed contact when the one of the interlock plates moves. The second normally-closed contact is connected in series in a power supply circuit to an exciting coil of the one of the electromagnetic contactors, and the other of the interlock plates comprises a second opening operation engagement portion that performs an operation of opening the second normally-closed contact when the other of the interlock plates moves. 
     With the reversible electromagnetic contactor according to this embodiment, in the closing operation of one of the electromagnetic contactors, the lock piece rotates in the first direction as one of the interlock plates moves to prevent the other of the interlock plates from moving, and maintains the release operation of the other of the electromagnetic contactor. Further, in the closing operation of the other of the electromagnetic contactors, the lock piece rotates in the second direction, which is different from the first direction, as the other of the interlock plates moves to prevent the one of the interlock plates from moving, and maintains a release operation of the one of the electromagnetic contactors. The present invention thus enables mechanical interlock of simultaneous closing of the two electromagnetic contactors. 
     Further, in the closing operation of the one of the electromagnetic contactors, the first opening operation engagement portion provided at the one of the interlock plates performs the operation of opening the first normally-closed contact that is connected in series in a power supply circuit to an exciting coil of the other of the electromagnetic contactors and cuts off power supply to the exciting coil of the other of the electromagnetic contactors. In the closing operation of the other of the electromagnetic contactors, the second opening operation engagement portion provided at the other of the interlock plates performs the operation of opening the second normally-closed contact that is connected in series in a power supply circuit to an exciting coil of the one of the electromagnetic contactors and cuts off power supply to the exciting coil of the one of the electromagnetic contactors. In this manner, the reversible electromagnetic contactor according to one embodiment also enables electrical interlock to prevent simultaneous closing of the two electromagnetic contactors. 
     The first opening operation engagement portion and the second opening operation engagement portion provided at the pair of interlock plates that are constituent members of the mechanical interlock serve as members that directly perform the operation of opening the first normally-closed contact and the second normally-closed contact. Therefore, the electrical interlock can be simplified. 
     Further, the normally-closed contacts are necessary to ensure the electrical interlock, but in the reversible electromagnetic contactor according to one embodiment, the first normally closed contact and the second normally closed contact are provided inside the reversible unit. Therefore, it is not necessary to connect additional auxiliary contact units to the auxiliary contacts of the normally-open contacts incorporated by one pole thereof in the two electromagnetic contactors. Since the connection of the auxiliary contact units is thus unnecessary, the external dimensions of the reversible electromagnetic contactor are not increased and expenses on the auxiliary contact unit are unnecessary. Therefore, the contactor can be reduced in size and cost. 
     In the reversible electromagnetic contactor according to one embodiment, the first normally-closed contact comprises a first fixed contact and a first movable contact including a spring member, and is disposed along a moving direction of the one of the interlock plates. When the one of the interlock plates moves, the first opening operation engagement portion moving toward the first normally-closed contact elastically deforms the first movable contact in a direction withdrawing from the first fixed contact to establish an open state. 
     With such a reversible electromagnetic contactor according to this embodiment, a simple structure is used in which the first opening operation engagement portion provided at one of the interlock plates elastically deforms the first movable contact including a spring member and performs the operation of opening the first normally-closed contact. Therefore, the electrical interlock can be further simplified. 
     Further in the reversible electromagnetic contactor according to one embodiment, the first opening operation engagement portion is a protrusion engageable with the first movable contact and formed integrally with the one of the interlock plates positioned at the first normally-closed contact side. 
     With the reversible electromagnetic contactor according to this embodiment, the first movable contact provided at the one of the interlock plates is a zone having a protruding shape. Therefore, the production cost of the one of the interlock plates can be reduced. 
     In the reversible electromagnetic contactor according to one embodiment, the second normally-closed contact comprises a second fixed contact and a second movable contact including a spring member, and is disposed along a moving direction of the other of the interlock plates. When the other of the interlock plates moves, the second opening operation engagement portion moving toward the second normally-closed contact elastically deforms the second movable contact in a direction withdrawing from the first fixed contact to establish an open state. 
     With such a reversible electromagnetic contactor according to this embodiment, a simple structure is used in which the second opening operation engagement portion provided at the other of the interlock plates elastically deforms the second movable contact constituted by a spring member and performs the operation of opening the second normally-closed contact. Therefore, the electrical interlock can be further simplified. 
     Further, in the reversible electromagnetic contactor according to one embodiment, the second opening operation engagement portion is a protrusion engageable with the second movable contact and formed integrally with the other of the interlock plates positioned at the second normally-closed contact side. 
     With the reversible electromagnetic contactor according to this embodiment, the second movable contact provided at the other of the interlock plates is a zone having a protruding shape. Therefore, the production cost of the other of the interlock plates can be reduced. 
     Furthermore, in the reversible electromagnetic contactor according to one embodiment, unit connection terminals for connection to the first normally-closed contact and the second-normally closed contact are provided at an end portion of the reversible unit. 
     With the reversible electromagnetic contactor according to this embodiment, the operation of connecting the first normally-closed contact and the second normally-closed contact of the reversible unit to the pair of electromagnetic contactors can be facilitated. 
     With the reversible electromagnetic contactor in accordance with the present invention, mechanical and electrical interlock can be performed such that two electromagnetic contactors cannot be closed simultaneously. Further, the first opening operation engagement portion and the second opening operation engagement portion provided at the pair of interlock plates that are constituent members of the mechanical interlock serve as members that directly perform the operation of opening the first normally-closed contact and the second normally-closed contact. Therefore, the electrical interlock can be simplified. Further, the normally-closed contacts are necessary to ensure the electrical interlock, but in the present invention the first normally closed contact and the second normally closed contact are provided inside the reversible unit. Therefore, it is not necessary to connect additional auxiliary contact units having normally-closed contacts, for example, to the auxiliary contacts of the normally-open contacts incorporated by one pole thereof in the two electromagnetic contactors. Since the connection of the additional auxiliary contact units is thus unnecessary, the external dimensions of the reversible electromagnetic contactor are not increased and expenses on the auxiliary contact unit are unnecessary. Therefore, the contactor can be reduced in size and cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating the two electromagnetic contactors and the reversible unit constituting the present invention. 
         FIG. 2  shows the control circuit of the induction motor provided with the reversible electromagnetic contactor in accordance with the present invention. 
         FIG. 3  shows the reversible unit in accordance with the present invention from the bottom plate side. 
         FIG. 4  shows the reversible unit in accordance with the present invention from the front surface side. 
         FIG. 5  shows the internal structure of the reversible unit in accordance with the present invention. 
         FIGS. 6(   a ) and  6 ( b ) show the mechanism of mechanical interlock inside the reversible unit in accordance with the present invention. 
         FIG. 7  shows a state in which the reversible unit is mounted to as to be laid across the upper surfaces of the two electromagnetic contactors constituting the present invention. 
         FIG. 8  illustrates the operation of the reversible unit when the two electromagnetic contactors are in the released state. 
         FIG. 9  illustrates the operation of the reversible unit when one of the two electromagnetic contactors is in the closed state. 
         FIG. 10  illustrates the operation of the reversible unit when the other of the two electromagnetic contactors is in the closed state. 
         FIG. 11  shows the devices constituting the conventional reversible electromagnetic contactor. 
         FIG. 12  illustrates the principal components of the conventional reversible electromagnetic contactor. 
         FIG. 13  shows the control circuit of the induction motor using the conventional reversible electromagnetic contactor that is not provided with normally-closed contacts in the reversible unit. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The best mode (referred to hereinbelow as “embodiment”) for carrying out the reversible electromagnetic contactor in accordance with the present invention will be explained in detail hereinbelow with reference to the appended drawings. Structural components identical to those shown in  FIGS. 1 and 12  are assigned with same reference numerals and the explanation thereof is herein omitted. 
       FIG. 1  illustrates an embodiment of the reversible electromagnetic contactor.  FIG. 2  shows an embodiment of the control circuit of an induction motor provided with the reversible electromagnetic contactor shown in  FIG. 1 . 
     As shown in  FIG. 1 , the reversible electromagnetic contactor according to the present embodiment has two electromagnetic contactors  1   a ,  1   b  disposed adjacently, and a reversible unit  20  is mounted across these electromagnetic contactors  1   a ,  1   b.    
     In the electromagnetic contactor  1   a  shown in  FIG. 1 , a fixed iron core (not shown in the figure), a movable iron core (not shown in the figure) disposed opposite the fixed iron core, and a coil (reference numeral  6   a  in  FIG. 2 ) disposed on the outer circumference of the main leg of the fixed iron core are housed in the lower portion inside a case  5 , and when the coil  6   a  is energized and the movable iron core is attracted to the fixed iron core, a movable contact fixed to a movable contact support  4  and a fixed contact are opened and closed. A plurality of power-supply-side main circuit terminals  7   a  and load-side main circuit terminals  7   b , auxiliary contact terminals  8   a ,  8   b , and coil terminals  9   a ,  9   b  are provided on top of the case  5 . A display window  3   a  is formed in an arc-extinguishing cover  2   a  provided on top of the electromagnetic contactor  1   a , and an operation indication piece  4   a  fixed to the movable contact support  4  protrudes into the display window  3   a.    
     In the electromagnetic contactor  1   a , as shown in  FIG. 2 , a normally-open contact (contact (a)) is provided between the mutually opposite power-supply-side main circuit terminal  7   a  and the load-side main circuit terminal  7   b , and an auxiliary contact  10  of the normally-open contact (contact (a)) is provided between the auxiliary contact terminals  8   a ,  8   b . Therefore, the auxiliary contact  10  of the normally-open contact (contact (a)) is one-pole incorporated in the electromagnetic contactor  1   a.    
     Another electromagnetic contactor  1   b , which is disposed adjacently to the electromagnetic contactor  1   a , has the same structure, and when a coil (reference numeral  6   b  in  FIG. 2 ) is energized and the movable iron core is attracted to the fixed iron core, a movable contact fixed to a movable contact support  4  and a fixed contact are opened and closed. The auxiliary contact  10  of the normally-open contact (contact (a)) is one-pole incorporated in this electromagnetic contactor. 
     As shown in  FIG. 5 , the reversible unit  20  comprises a first interlock plate  21  and a second interlock plate  22 , a lock piece  23  that causes only one of the first interlock plate  21  and second interlock plate  22  to move in the closing operation direction, a first normally-closed contact  24  that performs an opening operation when the first interlock plate  21  moves in the closing operation direction, and a second normally-closed contact  25  that performs an opening operation when the second interlock plate  22  moves in the closing operation direction. 
     As shown in  FIGS. 3 and 4 , the reversible unit  20  has a rectangular bottom plate  20   a  that is connected to the arc-extinguishing covers  2   a ,  2   b  (see  FIG. 1 ) when the reversible unit is mounted across the two electromagnetic contactors  1   a ,  1   b , a unit frame  20   b  in the form of an open-lid box that is integrally mounted on the circumferential edge of the bottom plate  20   a , and unit connection terminals  26 ,  27  integrally formed with one end of the unit frame  20   b  in the longitudinal direction. 
     As shown in  FIG. 3 , rectangular openings  20   c ,  20   d  are formed in the bottom plate  20   a  at positions set apart in the longitudinal direction. As shown in  FIG. 4 , a pair of display windows  20   e ,  20   f  opened in rectangular shape is formed at positions set apart in the longitudinal direction, these positions corresponding to the openings  20   c ,  20   d  of the bottom plate  20   a.    
     As shown in  FIG. 5 , the first interlock plate  21  comprises a bent portion  21   b  formed by bending an elongated portion  21   a  in an L-like shape at one end thereof in the longitudinal direction, a pin engagement orifice  21   c  formed in the distal end of the bent portion  21   b , a tubular connection bridge  21   d  formed to protrude at one surface at the other end side of the elongated portion  21   a  in the longitudinal direction, and a reversible unit operation indication piece  21   e  formed at the other surface at the other end side of the elongated portion  21   a . The reversible unit operation indication piece  21   e  is not shown in  FIG. 5  and is shown as a member positioned inside the first display window  20   e  in  FIG. 7 . 
     The second interlock plate  22  is a member of the same shape as the first interlock shape  21  and provided with a bent portion  22   b  formed by bending an elongated portion  22   a  in an L-like shape at one end thereof in the longitudinal direction, a pin engagement orifice  22   c  formed in the distal end of the bent portion  22   b , a tubular connection bridge  22   d  formed to protrude at one surface at the other end side of the elongated portion  22   a  in the longitudinal direction, and a reversible unit operation indication piece  22   e  formed at the other surface at the other end side of the elongated portion  22   a . The reversible unit operation indication piece  22   e  is not shown in  FIG. 5  and is shown as a member positioned inside the first display window  20   f  in  FIG. 7 . 
     As shown in  FIG. 6(   a ), the lock piece  23  is a member provided with a plate-shaped main body  23   a  of a substantially triangular shape in the plan view thereof and rotation pins  23   d ,  23   e  protruding in the same direction from the side surface close to a first apex  23   b  and a second apex  23   c  of the plate-shaped main body  23   a . The lock piece is disposed in the accommodation recess  20   b   2  provided between the unit frame  20   b  and the bottom plate  20   a , so that the first apex  23   b  and the second apex  23   c  are positioned in the short side direction of the unit frame  20   b.    
     The inner wall of the accommodation recess  20   b   2  that is opposite a third apex  23   f  of the lock piece  23  is formed to protrude in a peak-like form toward the third apex  23   f  and has a shape such that a first tilted circumferential wall  20   g   2  and a second tilted circumferential wall  20   g   3  extend at a substantially the same tilt angle toward a circumferential wall apex  20   g   1 . The circumferential surface in the thickness direction of the third apex  23   f  serves as a lock surface  23   g  that is engaged with the first tilted circumferential wall  20   g   2  and the second tilted circumferential wall  20   g   3 . 
     Further, as shown in  FIG. 6(   b ), the first interlock plate  21  and the second interlock plate  22  connected by the lock piece  23  are arranged in the longitudinal direction inside the unit frame  20   b  by pin joining the rotation pin  23   d  of the lock piece  23  disposed in the accommodation recess  20   b   2  and the pin engagement orifice  21   c  of the first interlock plate  21  and by pin joining the rotation pin  23   e  of the lock piece  23  and the pin engagement orifice  22   c  of the second interlock plate  22 . 
     As shown in  FIGS. 5 and 8 , the first normally-closed contact  24  comprises a first fixed contact  24   a  and a first movable contact  24   b  constituted by a plate spring, the first fixed contact  24   a  is connected to a flexible first extending connection wire  29  protruding outward of the reversible unit  20  by an inner connection wire  28  extending around the moving direction of the first interlock plate  21 , and the first movable contact  24   b  is connected to the unit connection terminal  27  by an inner connection wire  30 . 
     The second normally-closed contact  25  comprises a second fixed contact  25   a  and a second movable contact  25   b  constituted by a plate spring, the second fixed contact  25   a  is connected to a flexible second extending connection wire  32  protruding outward of the reversible unit  20  by an inner connection wire  31  extending around the moving direction of the second interlock plate  22 , and the movable contact  24   b  is connected to the unit connection terminal  26  by an inner connection wire  33  extending around the moving direction of the first interlock plate  21  and the second interlock plate  22 . 
     In this case, as shown in  FIGS. 5 and 8 , a first opening operation engagement portion  34  of a protruding shape is formed in the first interlock plate  21 . The first opening operation engagement portion  34  engages with the first movable contact  24   b  when the first interlock plate  21  moves in the closing operation direction, elastically deforms the first movable contact  24   b  in the direction of withdrawing from the first fixed contact  24   a , and sets the first normally-closed contact  24  to the open state. 
     Further, a second opening operation engagement portion  35  of a protruding shape is also formed in the second interlock plate  22 . The second opening operation engagement portion  35  engages with the second movable contact  25   b  when the second interlock plate  22  moves in the closing operation direction, elastically deforms the second movable contact  25   b  in the direction of withdrawing from the second fixed contact  25   a , and sets the second normally-closed contact  25  to the open state. 
     Further, the reversible unit  20  is assembled by positioning the reversible unit operation indication pieces  21   e ,  22   e  of the first interlock plate  21  and the second interlock plate  22  inside the display windows  20   e ,  20   f  formed in the unit frame  20   b , as shown in  FIG. 4 , passing the connection bridges  21   d ,  22   d  of the first interlock plate  21  and the second interlock plate  22  through the openings  20   c ,  20   d  formed in the bottom plate  20   a  and allowing the connection bridges to protrude outside, as shown in  FIG. 3 , and integrally mounting the bottom plate  20   a  and the circumferential edge of the unit frame  20   b.    
     With the reversible unit  20  of the above-described configuration, where the connection bridges  21   d ,  22   d  of the first interlock plate  21  and the second interlock plate  22  protruding to the outside from the openings  20   c ,  20   d  of the bottom plate  20   a  are connected in the fitting state thereof to the respective head portions of the operation indication pieces  4   a ,  4   b  (see  FIG. 1 ) of the two adjacently disposed electromagnetic contactors  1   a ,  1   b , a reversible electromagnetic contactor is configured in which, as shown in  FIG. 7 , the reversible unit  20  is mounted across the upper surface of the electromagnetic contactors  1   a ,  1   b.    
     One electromagnetic contactor in accordance with the present invention corresponds to one of the reverse-rotation electromagnetic contactor  1   a  and the direct-rotation electromagnetic contactor  1   b , the other electromagnetic contactor in accordance with the present invention corresponds to the other of the reverse-rotation electromagnetic contactor  1   a  and the direct-rotation electromagnetic contactor  1   b , the exciting coils in accordance with the present invention correspond to coils  6   a ,  6   b , and the unit case in accordance with the present invention corresponds to the bottom plate  20   a , the unit case in accordance with the present invention corresponds to the unit frame  20   b , and the interlock plates in accordance with the present invention correspond to the first interlock plate  21  and the second interlock plate  22 . 
     The control circuit of an induction motor  37  provided with the reversible electromagnetic contactor is connected as shown in  FIG. 2 . 
     Thus, the power-supply-side main circuit terminals  7   a  and the load-side main circuit terminals  7   b  of the two electromagnetic contactors  1   a ,  1   b  are connected in parallel, the main circuit power source (R, S, T) is connected to the power-supply-side main circuit terminals  7   a , the induction motor  37  is connected by a thermal relay  36  to the load-side main circuit terminals  7   b , and the coil terminals  9   b ,  9   b  of the two electromagnetic contactors  1   a ,  1   b  are connected together. 
     A control button  38  provided with a direct-rotation, reverse-rotation, and stop push-buttons is connected to the auxiliary contact terminals  8   a ,  8   b  of the two electromagnetic contactors  1   a ,  1   b , one electromagnetic contactor  1   a  is taken as a direct-rotation electromagnetic contactor and the other electromagnetic contactor  1   b  is taken as a reverse-rotation electromagnetic contactor (referred to hereinbelow as direct-rotation electromagnetic contactor  1   b  and reverse-rotation electromagnetic contactor  1   a ). 
     Further, the first extending connection wire  29  connected to the first normally-closed contact  24  incorporated in the reversible unit  20  is connected to the coil terminal  9   a  of the direct-rotation electromagnetic contactor  1   b , and the unit connection terminal  27  connected to the first normally-closed contact  24  is connected to the auxiliary contact terminal  8   b  of the direct-rotation electromagnetic contactor  1   b.    
     Further, the second extending connection wire  32  connected to the second normally-closed contact  25  incorporated in the reversible unit  20  is connected to the coil terminal  9   a  of the reverse-rotation electromagnetic contactor  1   a , and the unit connection terminal  26  connected to the second normally-closed contact  25  is connected to the auxiliary contact terminal  8   b  of the reverse-rotation electromagnetic contactor  1   a.    
       FIG. 9  illustrates the operation of the reversible unit  20  performed when the direct-rotation push-button of the control button  38  is pushed and the direct-rotation electromagnetic contactor  1   b  is closed.  FIG. 10  illustrates the operation of the reversible unit  20  performed when the reverse-rotation push-button of the control button  38  is pushed and the reverse-rotation electromagnetic contactor  1   a  is closed. 
     First, the operation of the reversible unit  20  performed when the direct-rotation electromagnetic contactor  1   b  is in the closed state will be explained. 
     With the direct-rotation electromagnetic contactor  1   b  in the closed state, the movable contact support  4  is moved in the closing operation direction by energizing the coil  6   b , and the operation indicating piece  4   b , which is integrated with the movable contact support  4 , moves from the right side to the left side of the display window  3   b . Therefore, the second interlock plate  22  of the reversible unit  20  that is connected to the operation indication piece  4   b  by the connection bridge  22   d  moves in the closing operation direction shown by a broken line in  FIG. 9 . With the reverse-rotation electromagnetic contactor  1   a  in the released state, the operation display piece  4   a  is positioned at the right side of the display window  3   a  and therefore, the first interlock plate  21  of the reversible unit  20  that is connected to the operation indication piece  4   a  by the connection bridge  21   d  does not move. 
     In this case, the second apex  23   c  side of the lock piece  23  of the reversible unit  20  rotates together with the second interlock plate  22  in the closing operation direction about the rotation pin  23   d  engaged with the pin engagement orifice  21   c  of the first interlock plate  21 , and the lock surface  23   g  abuts on the second tilted circumferential wall  20   g   3 . 
     Since the rotation pin  23   d  side of the lock piece  23  is prevented from rotating to the closing operation direction because of the abutment of the lock surface  23   g  on the second tilted circumferential wall  20   g   3 , the first interlock plate  21  cannot move together with the second interlock plate  22  in the closing operation direction. 
     Further, when the second interlock plate  22  of the reversible unit  20  moves in the closing operation direction, the second opening operation engagement portion  35  formed at the second interlock plate  22  elastically deforms the second movable contact  25   b  of the second normally-closed contact  25  and withdraws the second movable contact from the second fixed contact  25   a . As a result, the second normally-closed contact  25  assumes the open state. When the second normally-closed contact  25  is in the open state, an exciting circuit to the coil  6   a  of the reverse-rotation electromagnetic contactor  1   a  is in a cut-off state. 
     The operation of the reversible unit  20  performed when the reverse-rotation electromagnetic contactor  1   a  is in the closed state will be explained below. 
     With the reverse-rotation electromagnetic contactor  1   a  in the closed state, the movable contact support  4  is moved in the closing operation direction by energizing the coil  6   a , and the operation indicating piece  4   a , which is integrated with the movable contact support  4 , moves from the right side to the left side of the display window  3   a . Therefore, the first interlock plate  21  of the reversible unit  20  that is connected to the operation indication piece  4   a  by the connection bridge  21   d  moves in the closing operation direction shown by a broken line in  FIG. 10 . With the direct-rotation electromagnetic contactor  1   b  in the released state, the operation display piece  4   b  is positioned at the right side of the display window  3   b  and therefore, the second interlock plate  22  of the reversible unit  20  that is connected to the operation indication piece  4   b  by the connection bridge  22   d  does not move. 
     In this case, the first apex  23   b  side of the lock piece  23  of the reversible unit  20  rotates together with the first interlock plate  21  in the closing operation direction about the rotation pin  23   e  engaged with the pin engagement orifice  22   c  of the second interlock plate  22 , and the lock surface  23   g  abuts on the first tilted circumferential wall  20   g   2 . 
     Since the rotation pin  23   e  side of the lock piece  23  is prevented from rotating to the closing operation direction because of the abutment of the lock surface  23   g  on the first tilted circumferential wall  20   g   3 , the first interlock plate  21  cannot move together with the second interlock plate  22  in the closing operation direction. 
     Further, when the first interlock plate  21  of the reversible unit  20  moves in the closing operation direction, the first opening operation engagement portion  34  formed at the first interlock plate  21  elastically deforms the first movable contact  24   b  of the first normally-closed contact  24  and withdraws the first movable contact from the first fixed contact  24   a . As a result, the first normally-closed contact  24  is in the open state. When the first normally-closed contact  24  is in the open state, the exciting circuit to the coil  6   b  of the direct-rotation electromagnetic contactor  1   b  is in a cut-off state. 
     The effects of the reversible electromagnetic contactor provided with the reversible unit  20  of the above-described configuration will be explained below. 
     When the direct-rotation electromagnetic contactor  1   b  is in the closed state and the second interlock plate  22  of the reversible unit  20  moves in the closing operation direction, the lock piece  23  restricts the movement of the first interlock plate  21  in the closing operation direction and maintains the released state of the reverse-rotation electromagnetic contactor  1   a , and mechanical interlock is performed such as to prevent the two electromagnetic contactors  1   a ,  1   b  from being closed at the same time. Further, in the second interlock plate  22  of the reversible unit  20 , the second opening operation engagement portion  35  that has moved in the closing operation direction sets the second normally-closed contact  25  to the open state and the exciting circuit to the coil  6   a  of the reverse-rotation electromagnetic contactor  1   a  is cut off. Therefore, electrical interlock is performed such as to prevent the two electromagnetic contactors  1   a ,  1   b  from being closed at the same time. 
     Conversely, when the reverse-rotation electromagnetic contactor  1   a  is in the closed state and the first interlock plate  21  of the reversible unit  20  moves in the closing operation direction, the lock piece  23  restricts the movement of the second interlock plate  22  in the closing operation direction and maintains the released state of the direct-rotation electromagnetic contactor  1   b , and mechanical interlock is performed such as to prevent the two electromagnetic contactors  1   a ,  1   b  from being closed at the same time. Further, in the first interlock plate  21  of the reversible unit  20 , the first opening operation engagement portion  34  that has moved in the closing operation direction sets the first normally-closed contact  24  to the open state and the exciting circuit to the coil  6   b  of the direct-rotation electromagnetic contactor  1   b  is cut off. Therefore, electrical interlock is performed such as to prevent the two electromagnetic contactors  1   a ,  1   b  from being closed at the same time. 
     Thus, with the reversible electromagnetic contact provided with the reversible unit  20  according to the present embodiment, mechanical and electrical interlock can be performed such as to prevent the two electromagnetic contactors  1   a ,  1   b  from being closed at the same time. 
     The normally-closed contacts (contacts (b)) are necessary to ensure the electrical interlock, but in the present embodiment the first normally closed contact  24  and the second normally closed contact  25  are provided inside the reversible unit  20 . Therefore, it is not necessary to connect auxiliary contact units for adding the normally-closed contacts (contacts (b)) to the auxiliary contacts  10  of the normally-open contacts (contacts (a)) incorporated by one pole thereof in the two electromagnetic contactors  1   a ,  1   b . Since the auxiliary contact units are thus not connected, the external dimensions of the device are not increased and expenses on the auxiliary contact unit are unnecessary. Therefore, the device can be reduced in size and cost. 
     The first normally-closed contact  24  incorporated in the reversible unit  20  is configured to be open when the first opening operation engagement portion  34  provided at the first interlock plate  21  moving in the closing operation direction elastically deforms the first movable contact  24   b  constituted by a plate spring and withdraws the first movable contact from the first fixed contact  24   a . The second normally-closed contact  25  is also configured to be open when the second opening operation engagement portion  35  provided at the second interlock plate  22  moving in the closing operation direction elastically deforms the second movable contact  25   b  constituted by a plate spring and withdraws the second movable contact from the fifth fixed contact  24   a . Because of a simple structure in which the first normally closed contact  24  or the second normally-closed contact  25  is in an open state when the first opening operation engagement portion  34  engages with the first interlock plate  21  moving in the closing operation direction or the second opening operation engagement portion  35  engages with the second interlock plate  22  moving in the closing operation direction, the production cost of the reversible unit  20  can be reduced. 
     Industrial Applicability 
     As described hereinabove, the reversible electromagnetic contactor in accordance with the present invention is suitable for connecting other additional circuits, without using auxiliary contacts incorporated in the electromagnetic contactor, when performing mechanical and electrical interlock to prevent two electromagnetic contactors from being closed at the same time, and also enables size reduction and cost reduction. 
     EXPLANATION OF REFERENCE NUMERALS 
       1   a  . . . reverse-rotation electromagnetic contactor;  1   b  . . . direct-rotation electromagnetic contactor;  2   a ,  2   b  . . . arc-extinguishing covers;  3   a ,  3   b  . . . display windows,  4   a ,  4   h  . . . operation indicating pieces;  5  . . . case;  6   a ,  6   b  . . . coils;  7   a  . . . power-supply-side main circuit terminal;  7   b  . . . load-side main circuit terminal;  8   a ,  8   b  . . . auxiliary contact terminals;  9   a ,  9   b  . . . coil terminals;  10  . . . auxiliary contact;  20  . . . reversible unit;  20   a  . . . bottom plate;  20   b  . . . unit frame;  20   b   2  . . . accommodation recess;  20   c ,  20   d  . . . openings;  20   e ,  20   f  . . . display windows;  20   g  . . . circumferential wall apex;  20   g   2  . . . first tilted circumferential wall;  20   g   3  . . . second tilted circumferential wall;  21  . . . first interlock plate;  21   a  . . . elongated portion;  21   b  . . . bent portion;  21   c  . . . pin engagement orifice;  21   d  . . . connection bridge;  21   e  . . . reversible unit operation indication piece;  22  . . . second interlock plate;  22   a  . . . elongated portion;  22   b  . . . bent portion;  22   c  . . . pin engagement orifice;  22   d  . . . connection bridge; 
       22   e  . . . reversible unit operation indication piece;  23  . . . lock piece;  23   a  . . . plate-shaped main body;  23   b  . . . first apex;  23   c  . . . second apex;  23   d ,  23   e  . . . rotation pins;  23   f  . . . third apex;  23   g  . . . lock surface;  24  . . . first normally-closed contact;  24   a  . . . first fixed contact;  24   b  . . . first movable contact;  25  . . . second normally-closed contact;  25   a  . . . second fixed contact;  25   b  . . . second movable contact;  26 ,  27  . . . unit connection terminals;  28 ,  30 ,  31 ,  33  . . . inner connection wire;  29  . . . first extending connection wire;  32  . . . second extending connection wire;  34  . . . first opening operation engagement portion;  35  . . . second opening operation engagement portion;  36  . . . thermal relay;  37  . . . induction motor;  38  . . . control button