Abstract:
A switch device includes an operation unit having a pushbutton for performing a pushing operation; a switch unit separably joined to the operation unit, the switch unit including an opening-closing contact mechanism opened or closed in conjunction with the pushing operation of the pushbutton of the operation unit, and a rotary drive plate rotating between a standby position and a usage position; and an engagement portion engaging the operation unit to the rotary drive plate to rotary-drive the rotary drive plate from the standby position to the usage position when the operation unit is attached to the switch unit. The operation unit is detached from or attached to the switch unit to set the opening-closing contact mechanism in respectively predetermined opening-closing states.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This is continuation application of a PCT International Application No. PCT/JP2013/083155 filed Dec. 11, 2013, which claims priority of Japanese Application No. 2013-019361 filed Feb. 4, 2013, the disclosure of which is incorporated herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a switch device, in which an operation unit used in a state of attachment to a panel, or the like, and a switch unit, in which an opening-closing contact is opening-closing operated by the operation unit, are structured to be separable from each other. 
       BACKGROUND ART 
       [0003]    For example, Patent Literature 1 describes a known switch device in which an operation unit and a switch unit operated by the operation unit are structured to be separable. 
         [0004]    A conventional switch device  1  described in Patent Literature 1 is depicted in  FIGS. 12 to 14 . 
         [0005]    A switch device  100  is provided with an operation unit  110  and a switch unit  120  which are structured mutually attachable and detachable. The operation unit  110  transmits a pushing operating force, which is applied from the outside, to the switch unit  120 . The switch unit  120  receives the operating force from the operation unit  110  and opens/closes a plurality of opening/closing contact portions on the basis of the operating force. 
         [0006]    The operation unit  110  is provided with an operation unit main body  111  and a pushbutton  113 . The pushbutton  113  has a substantially round columnar shape, and the upper end surface of the pushbutton  113  receives the operating force from the outside in the axial direction. A protrusion  114  having a round columnar shape is provided in a protruding condition at the side surface on the lower end side of the pushbutton  113 . Two guide grooves  112  having a substantially inverted L-shape are provided facing each other on the lower side of the side surface of the operation unit main body  111  for allowing the operation unit main body  111  to be rotated and fitted into the switch unit  120 . 
         [0007]    The pushbutton  113  of the operation unit  110  is supported by the operation unit main body  111  such that the pushbutton can move in the axial direction and cannot rotate in the rotation direction. As depicted in  FIG. 14 , a lock pin  116  which is caused by the urging force of a spring  115  to protrude from the inner wall of the operation unit main body  111  is provided at the operation unit main body  111 , and a locking protrusion  117  which is to be engaged with the lock pin is provided in a protruding condition at the side surface of the pushbutton  113 . As a result, when the upper surface of the pushbutton  113  is pushed down along a central axial line X by an operating force equal to or greater than a predetermined value, the lock pin  116  of the main body  111  is pushed in by the locking protrusion  117  against the urging force of the spring  115 , and the pushbutton  113  moves downward to release the engagement of the locking protrusion  117  and the lock pin  116 . When the locking protrusion  117  rides over the lock pin  116 , the lock pin  116  protrudes and engages with the locking protrusion  117  again, and the pushbutton  113  is locked at a pushing position shown by a dot line ( FIG. 14 ). 
         [0008]    The switch unit  120  is provided with a partition wall  123  partitioning the inner space of a switch unit main body  121  in the horizontal direction, and a through hole  124  passing through along the central axial line X is provided in the central portion of the partition wall. Two engagement protrusions  122  to be engaged with the guide groove  112  of the operation unit  110  are integrally formed on the inner wall of the switch unit main body  121  above the partition wall  123 . 
         [0009]    A contact shaft  125  is inserted into the through hole  124  such that the contact shaft can move in the direction of the central axial line X, but cannot rotate about the central axial line X. A tubular pushbutton receptacle  126  into which the lower end portion of the pushbutton  113  is to be inserted from above is provided at the upper end of the contact shaft  125 . A helical cut-out guide  127  which extends downward, while turning about the central axial line X, as shown in the figure, is provided in the circumferential side surface of the pushbutton receptacle  126  in order to engage with the protrusion  114  of the pushbutton  113 . 
         [0010]    An opening-closing contact mechanism  130  is accommodated in a space below the partition wall  123  in the switch unit main body  121 . The opening-closing contact mechanism  130  is provided with a pair of fixed contactor pieces  132 , each movable contactor piece being provided with a fixed contact  133 , and a movable bridging piece  134  provided with a pair of movable contacts  135  at both ends. A distal end of the contact shaft  125  is joined to the central portion of the movable bridging piece  134 , and a contact spring  131  that urges the movable bridging piece  134  in the direction of separating from the fixed contactor pieces  132  is attached to the contact shaft  125  between the movable bridging piece  134  and the partition wall  123 . An external connection terminal piece  136  is drawn out to the outside of the main body  121  from each of the fixed contactor pieces  132 . The fixed contact  133  of the fixed contactor piece  132  and the movable contact  135  of the movable bridging piece  134  are provided facing each other to enable contact and separation thereof. 
         [0011]    The operation unit  110  is mounted on a panel (not shown in the figure). 
         [0012]    In a state in which the switch unit  120  is separated from the operation unit  110 , as depicted in  FIG. 12 , the movable bridging piece  134  is pulled apart from the fixed contactor pieces  132  by the contact spring  131 , so that the contact shaft  125  moves downward, and the movable contacts  135  and the fixed contacts  133  are in a state (switch-off) separated from each other. 
         [0013]    When the switch unit  120  is to be joined to the operation unit  110  from this state, initially, the switch unit  120  is fitted from below into the operation unit  110  so that the engagement protrusion  122  of the switch unit  120  is inserted into an inlet port of the guide groove  112  of the operation unit  110  and the protrusion  114  is inserted into an inlet port of the cut-out guide  127  of the switch unit. 
         [0014]    Then, the switch unit main body  121  is turned in the direction of an arrow R (to the right) about the central axial line X. Since the pushbutton  113  is arranged to be incapable of rotating with respect to the operation unit main body  111 , when the switch unit main body  121  is turned in the direction of arrow R, the protrusion  114  moves inside the helical cut-out guide  127 . As a result, the protrusion  114  moves the pushbutton receptacle  126  upward, and following this movement, the movable contact  135  also moves upward, but when the switch unit main body  121  is stopped from turning, the movable contact  135  becomes a state (switch-on) contacting the fixed contact  133  (see  FIG. 13(   a )). The switch unit  120  is thus joined and fixed to the operation unit  110 . 
         [0015]    To detach the switch unit  120  from the operation unit  110 , a procedure reversed to the procedure used to attach the switch unit  120  to the operation unit  110  is implemented. Thus, in a state in which the switch unit  120  depicted in  FIG. 13(   a ) is attached to the operation unit  110 , the switch unit  120  is turned in the direction of arrow L (to the left) about the central axial line X, the units are disconnected, and the switch unit  120  is detached from the operation unit  110  by further pulling downward (see  FIG. 12) . In this state, the movable contacts  135  and the fixed contacts  133  are urged by the contact spring  131  in the separation direction and separated from each other, and the open (switch-off) state is maintained. 
         [0016]    With the switch device  100  having such an arrangement, in a standby state, the movable contacts  135  and the fixed contacts  133  are closed at all times and the switch-on state is maintained, as depicted in  FIG. 13(   a ). 
         [0017]    When the pushbutton  113  of the operation unit  110  is pushed down in this state, the movable bridging piece  134 , which is linked to the pushbutton through the pushbutton receptacle  126  and the contact shaft  125 , is lowered. Therefore, the movable contacts  135  are separated from the fixed contacts  133  and become the switch-off state (see  FIG. 13(   b )). As a result, when the switch device is used as an emergency switch, a stop command can be applied to the control object. In this case, since the pushbutton  113  is locked by the lock pin  116  at a position in which the locking protrusion  117  rides over the lock pin  116  at the pushing operation position shown by a dot line in  FIG. 14 , the pushbutton is held at the pushing operation position and maintained in the OFF state in which the movable contacts  135  are separated from the fixed contacts  133 . 
         [0018]    When an accident occurs such that the switch unit  120  joined to the operation unit  110  is detached from the operation unit  110 , the movable contacts  135  of the switch unit  120  are urged by the return spring  131  in the separation direction and automatically separated from the fixed contacts  133  that have been in a closed state at all times, becoming a switch-off state (the state identical to the operation state). Therefore, when the switch device is used as an emergency stop switch, an accident causing the switch unit  120  to detach from the operation unit  110  results in a switch-off state. As a result, a stop command is issued to the control object and safety of the control object can be maintained.
   Patent Literature 1: Japanese Patent Application Publication No. 2004-103363   
 
       DISCLOSURE OF THE INVENTION 
       [0020]    In the aforementioned conventional switch device, the movable contacts of the opening-closing contact mechanism are urged at all times by the contact spring that urges in the direction such that the opening-closing state of the opening-closing contact is the opening-closing state at the time of the operation state, that is, in the direction in which the movable contacts and the fixed contacts are separated from each other in the case of a normally closed contact arrangement, or in the direction in which the movable contacts and the fixed contacts are closed in the case of a normally open contact arrangement. 
         [0021]    Therefore, the problem associated with a switch device having a normally closed contact arrangement such that the opening-closing contacts are closed in the standby state is that when a slight impact force is applied to the switch unit  120 , or the joined state of the switch unit  120  and the operation unit  110  becomes loose, the contact shaft  125  and the movable bridging piece  134  supporting the movable contacts  135  are pushed downward by the contact spring  131 , the movable contacts  135  are separated from the fixed contacts  133 , and an erroneous operation such as a switch-off operation can be temporarily performed. 
         [0022]    In the switch device having a normally open arrangement such that the opening-closing contacts are open in the standby state, an impact force can erroneously close the fixed contacts with the movable contacts, regardless of the operator&#39;s intentions, thereby causing a switch-on state. 
         [0023]    The invention is provided to resolve the aforementioned problems, and it is an objective of the invention to provide a switch device with a high operation reliability in which opening-closing contact portions are not erroneously opened or closed even when an impact is applied to the switch device from the outside. 
         [0024]    In order to resolve the problems, the invention provides a switch device including an operation unit having a pushbutton for performing a pushing operation, and a switch unit detachably attached to the operation unit and equipped with an opening-closing contact mechanism opened or closed in conjunction with the pushing operation of the pushbutton of the operation unit. 
         [0025]    The switch unit is provided with a rotary drive plate which rotates between a standby position and a usage position. In the standby position, the switch unit drives the opening-closing contact mechanism to be in an opening-closing state where the operation unit is in an operation state, and in the usage position, the switch unit drives the opening-closing contact mechanism to be in an opening-closing state where the operation unit is in a standby state. The operation unit is provided with an engagement portion engaged to the rotary drive plate to rotary-drive the rotary drive plate from the standby position to the usage position when the operation unit is joined and attached to the switch unit. The operation unit is attached to or detached from the switch unit to set the opening-closing contact mechanism to respectively predetermined opening-closing states. 
         [0026]    In the embodiment, the opening-closing contact mechanism may be provided with a contact spring that urges an opening-closing contact of the opening-closing contact mechanism in a direction to be in an opening-closing state where the operation unit is in the standby state. 
         [0027]    The rotary drive plate can be provided, at one end thereof, with a cam piece that drives the opening-closing contact mechanism. 
         [0028]    Further, the rotary drive plate of the switch unit can be also provided with a return spring that returns the rotary drive plate from the usage position to the standby position when the switch unit is separated from the operation unit. 
         [0029]    Further, the engagement portion engaging the rotary drive plate with the operation unit includes an engagement groove provided at the operation unit or the rotary drive plate and inclined in an axial direction and an engagement protrusion provided at the rotary drive plate or the operation unit so as to be engaged with the engagement groove. 
         [0030]    According to the invention, the switch unit, which is separably joined to the operation unit, is provided with a rotary drive plate which rotates between a standby position and a usage position, operates the opening-closing contact mechanism in the standby position to an opening-closing state where the operation unit is in an operation state, and operates the opening-closing contact mechanism in the usage position to an opening-closing state where the operation unit is in a standby state. The operation unit is arranged to be engaged with the rotary drive plate and rotary-drive the rotary drive plate from the standby position to the usage position when the operation unit is joined and attached to the switch unit. Therefore, the opening-closing contact mechanism can be set to a respective predetermined opening-closing state by detaching or attaching the operation unit from or to the switch unit. As a result, if by any chance an accident occurs such that causes the operation unit to separate from the switch unit, the opening-closing state of the opening-closing contact mechanism can be obtained as the opening-closing state where the operation unit is in the operation state. The switch device thus can be used as an emergency safety device. 
         [0031]    Further, the opening-closing contacts of the opening-closing contact mechanism are urged at all times in the direction to be in the opening-closing state at the time the operation unit is in the standby state, that is, in the direction in which the movable contacts and the fixed contacts are closed in the case of a normally closed contact structure and in the direction in which the movable contacts and the fixed contacts are separated from each other in the case of a normally open contact structure. Therefore, even when an impact is applied to the switch device in the standby state, the movable contacts are unlikely to move. As a consequence, erroneous operation is prevented and operation reliability of the switch device can be increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is a partially cut-out perspective view illustrating the entire structure of the switch device of a present embodiment. 
           [0033]      FIG. 2(   a ),  2 ( b ) depict the structure of the pushbutton portion of the present embodiment, wherein  FIG. 2(   a ) is a partially cut-out exploded perspective view and  FIG. 2(   b ) is a partially cut-out perspective view of the assembled state. 
           [0034]      FIG. 3  is a partially cut-out exploded perspective view of the structure of the operation unit main body of the present embodiment. 
           [0035]      FIG. 4  is a partially cut-out exploded perspective view of the structure of the operation unit of the present embodiment. 
           [0036]      FIG. 5(   a ),  5 ( b ) illustrate the operation of the operation unit of the present embodiment, wherein  FIG. 5(   a ) is a partially cut-out perspective view illustrating the locked state at the standby position, and  FIG. 5(   b ) is a partially cut-out perspective view illustrating the locked state at the pushing operation position. 
           [0037]      FIG. 6  is an exploded perspective view of the switch device of the present embodiment. 
           [0038]      FIG. 7  is an exploded perspective view of the switch unit of the switch device of present embodiment. 
           [0039]      FIG. 8  is a front view of the rotary drive plate used in the switch device of the present embodiment. 
           [0040]      FIGS. 9(   a )- 9 ( d ) illustrate the process of joining the operation unit and switch unit of the switch device of the present embodiment. 
           [0041]      FIG. 10(   a ),  10 ( b ) illustrate the joined state of the operation unit and switch unit of the switch device of the present embodiment, wherein  FIG. 10(   a ) depicts the state in which the operation unit and switch unit are separated, and  FIG. 10(   b ) depicts the state in which the operation unit and switch unit are joined together. 
           [0042]      FIG. 11  is a partially cut-out perspective view illustrating the operation state of the switch device of the present embodiment. 
           [0043]      FIG. 12  is a diagram of the conventional switch device. 
           [0044]      FIG. 13(   a ),  13 ( b ) are explanatory drawings of the operation state of the conventional switch device. 
           [0045]      FIG. 14  is a diagram illustrating the operation unit of the conventional switch device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0046]    An embodiment of the invention will be explained hereinbelow in detail with reference to the drawings. 
         [0047]      FIGS. 1 to 11  depict an example of the switch device to be used as a pushbutton switch for emergency stop in accordance with the present embodiment. 
         [0048]    In  FIG. 1 , the reference numeral  1  refers to a switch device provided with an operation unit  10  and a switch unit  20  which are arranged to be joinable to each other and separable from each other. 
         [0049]    The operation unit  10  transmits an external operating force to the switch unit  20  and opens/closes an opening/closing contact mechanism located inside the switch unit  20 . The operation unit includes a pushbutton  12  and an operation unit main body  11  that supports the pushbutton. 
         [0050]    As shown in detail in  FIG. 2 , the pushbutton  12  is assembled with a push rod  13  through a pushbutton return spring  14  constituted by a twisted coil spring. 
         [0051]    When the aforementioned components are assembled, initially, a bent portion  14   a  at one end of the return spring  14  is inserted in and engaged with an engagement groove  12   b  of the pushbutton  12 . A distal end portion of the push rod  13  is inserted into the spring  14  engaged with the pushbutton  12 , and a bent portion  14   b  at the other end of the spring  14  is inserted in and engaged with a fixing hole  13   e  of the push rod  13 . In this state, the pushbutton  12  is rotated rightward, a pair of engagement protrusions  12   c  located inside the pushbutton  12  is aligned with a pair of L-shaped engagement grooves  13   d  on the outer circumference of the distal end portion of the push rod  13 , and then the push rod  13  is inserted into the pushbutton  12 , and the engagement protrusions  12   c  and the engagement grooves  13   d  are engaged with each other. As a result, the pushbutton  12  and the push rod  13  are joined through the return spring  14  so as to be rotatable relative to each other within a predetermined angular range, as depicted in  FIG. 2(   b ). 
         [0052]    The operation unit  10  is formed by joining the operation unit main body  11  to the pushbutton  12  of the above-described structure. As shown in detail in  FIG. 3 , a lock holder  17  provided with a pair of holding grooves  17   b  is inserted into the operation unit main body  11 . A lock pin  15  and a lock spring  16  are inserted into the respective holding grooves  17   b  of the lock holder  17  and held therein. The lock holder  17  inserted into the operation unit main body  11  is pushed in until the engagement protrusion  17   a  is engaged with an engagement hole  11   h  provided in the inner wall of a cylindrical upper body portion  11  of the operation unit main body  11 , thereby fixing the lock holder  17  to the operation unit main body  11 . The lock pin  15  held in the lock holder  17  which has been fixed inside the operation unit main body  11  is elastically pushed by the lock spring  16 , and the distal end of the lock pin  15  protrudes toward the inner side of the lock holder  17 , as depicted in  FIG. 4 . 
         [0053]    The assembly of the pushbutton  12 , the push rod  13 , and the return spring  14  is inserted from above into the operation unit main body  11 . In this case, the lock pin  15  which is pressed inward by the lock spring  16  on the main body side pushes the push rod  13  such as to ride over the receding-protruding section on the outer circumference of the push rod  13  and be locked in a first recess  13   a  for locking. Then, a trigger spring  18  and a push body  19  are inserted from below into the operation unit main body  11 , an engagement hole  19   a  in the push body  19  is engaged with an engagement protrusion  13   f  at the lower end side of the push rod  13 , the main body  11  and the pushbutton  12  are integrally joined, and the operation unit  10  is formed. 
         [0054]    The operation unit main body  11  and the pushbutton  12  are joined to be capable of moving in the axial direction and rotation direction with respect to each other. However, since two rotation suppressing protrusions  11   j  are provided with a spacing of angle C on the inner side of the upper portion of the operation unit main body  11 , and a rotation suppressing protrusion  12   d  corresponding thereto and located on the pushbutton  12  is fitted between the two protrusions  11   j , the range of rotation of the pushbutton  12  relative to the operation unit main body  11  is restricted to the range of angle C. Further, when the push rod  13  is inserted into the operation unit main body  11 , a rotation preventing protrusion  11   k  provided inside the operation unit main body  11  correspondingly to a rotation preventing groove  13   g  provided in the axial direction on the outer circumference of the push rod  13  engages with the rotation preventing groove  13   g , thereby preventing the push rod  13  from rotating relative to the operation unit main body  11  and allowing only the vertical (axial) movement. 
         [0055]    The engagement of the engagement protrusion  12   c  of the pushbutton  12  with the L-shaped engagement groove  13   d  of the push rod  13  allows the pushbutton  12  to be rotated within a range of a rotation angle D (see  FIG. 4 ) relative to the push rod  13 , but in a range of angle C in which the rotation relative the operation unit main body  11  can be performed, the pushbutton  12  is stopped by the L-shaped engagement groove  13   d  of the push rod  13 . 
         [0056]    In the operation unit  10  having such a structure, in a standby state before the pushbutton  12  is pushed, the return spring  14  pushes up the pushbutton  12 , and the lock pin  15  is engaged with the first recess  13   a  provided on the outer circumference of the intermediate portion of the push rod  13 , thereby locking the push rod  13  in this position. Therefore, the pushbutton  12  is held, this position serving as a standby position. The lock pin  15  is supported by the lock holder  17  through the lock spring  16  to be radially retractable inside the operation unit main body  11 . 
         [0057]    When the pushbutton  12  is pushed axially by a predetermined force or a stronger force, the push rod  13  receives this force and the inclined upper wall of the recess  13   a  pushes the lock pin  15  in the outer circumferential direction against the lock spring  16 , thereby releasing the engagement of the recess  13   a  and the lock pin  15 , and pushing the push rod  13  over the lock pin  15 . The lock pin  15  that came out of the recess  13   a  engages with a second recess  13   b  in the upper portion of the recess  13   a  and holds the pushbutton  12  and the push rod  13  in the pushing operation position thereof. 
         [0058]    The push rod  13  is arranged to push down the push body  19 , which is linked to a movable contactor holder  22  of the switch unit through the trigger spring  18 , by such a pushing operation. The lower end of the push body  19  hits the upper end of the movable contactor holder  22  of the switch unit  20 , pushes the movable contactor holder down, and opens/closes the opening-closing contact mechanism of the switch unit  20  (see  FIG. 1 ). 
         [0059]    Further, a fixing thread  11   d  is provided on the outer circumference of the body portion  11   c  below a flange portion  11   b  of the operation unit main body  11 . A fastening nut  11   e  is screwed onto the thread  11   d  to fasten and fix the operation unit  10  to a panel such as a control panel. An axial engagement groove  11   f  (see  FIG. 6 ) for connecting and engaging the operation unit  10  and the switch unit  20  is provided on the outer circumference on the lower end side of the body portion  11   c  of the operation unit main body  11 . As shown in detail in  FIGS. 9(   a )- 9 ( d ), the engagement groove  11   f  is provided with an axial inclined portion  11   f - 1  which rises obliquely from a lower end to the upper left side, a horizontal portion  11   f - 2  which is connected at the upper end of the inclined portion  11   f - 1  and extends in the horizontal direction, and a vertical portion  11   f - 3  that is connected at the right end of the horizontal portion  11   f - 2  and extends slightly upward in the vertical direction. 
         [0060]    An engagement groove  11   g  for engagement with an engagement ridge  21   b  extending axially at the inner circumference of a cylindrical portion  21   a  of a switch unit main body  21  of the switch unit  20  is additionally provided at the outer circumference of the lower body portion  11   c  of the operation unit main body  11  (see  FIG. 6 ). 
         [0061]    The switch unit  20  that is detachably connected to such an operation unit  10  is explained below. 
         [0062]    As depicted in  FIGS. 1 and 6 , the switch unit  20  is provided with the rectangular box-shaped switch unit main body  21 . The main body  21  is provided with at least one pair of fixed contacts  25 - 1   a ,  25 - 2   b  integrally connected to each pair of output terminals  25   a ,  25   b  that is fixedly disposed at the lower end side of the main body. The references with the letter (a) attached thereto represent normally open contacts which are usually open, that are, the contacts constituting the so-called (a) contacts, and the references with the letter (b) attached thereto represent normally closed contacts which are usually closed, that are, the contacts constituting the so-called (b) contacts. 
         [0063]    Further, as shown in detail in  FIG. 6 , the movable contactor holder  22  that holds movable contactors  26   a ,  26   b  in the form of bridging pieces provided with a pair of movable contacts  26 - 1   a ,  26 - 2   b  at the two ends is accommodated movably in the vertical direction inside the main body  21  through a contact spring  27  imparting an urging force to the contacts. The normally open movable contact  26 - 1   a  and the normally closed movable contact  26 - 2   b  held by the movable contactor holder  22  are disposed facing the normally open fixed contact  25 - 1   a  and the normally closed fixed contact  25 - 2   b , and form the opening-closing contact mechanism. In this case, the contact spring  27  is formed from a compressive coil spring and generates an urging force in the direction pushing the movable contactor holder  22  upward. As a result, when the pushbutton  12  is in the usual standby state (state in which the pushbutton  12  is not pushed), as depicted in  FIG. 1 , the normally open movable contact  26 - 1   a  which is held by the movable contactor holder  22  is placed in a state of separation from the fixed contact  25 - 1   a , and the normally closed movable contact  26 - 2   b  is placed in a state of contacting the fixed contact  25 - 2   b . This is the opening-closing state of the opening-closing mechanism at the time the operation unit is in the standby state. 
         [0064]    Further, as depicted in  FIGS. 6 and 7 , the cylindrical portion  21   a  having cut-out portions  21   c  in parts thereof, the cut-out portions  21   c  facing each other, is formed protruding at the upper portion of the switch unit main body  21  in order to join a rotary drive portion  30 . 
         [0065]    The rotary drive portion  30  is provided with a rotary cover  31 , a rotary drive plate  32 , and a rotary drive spring  33 . Engagement protrusions  32   b  formed at the inner circumferential side of the rotary drive plate  32 , which is formed to be split in two substantially semicylindrical portions, are inserted in and engaged with a pair of semicircular-arc grooves  21   d  formed at the outer circumference of the cylindrical portion  21   a  of the switch unit main body  21 , thereby rotatably supporting the rotary drive plate  32  with the cylindrical portion  21   a . A cam piece  32   a  having a cam surface inclined in the circumferential direction is partially formed at the lower end of the rotary drive plate  32 . As shown in  FIG. 8 , the cam piece  32   a  has at the lower end thereof an inclined cam surface which connects together a position with a larger height Hh and a position with a smaller height Hl from the upper end of the rotary drive plate  32 . The cam piece  32   a  penetrates into the main body through a through hole  21   e  (see  FIG. 7 ) in the upper wall of the switch unit main body  21 , and the cam surface is joined to the upper surface of a pressure-receiving piece  22   b  that is formed in a protruding condition on the outer circumferential side of the movable contactor holder  22  that holds the movable contacts  26 - 1   a ,  26 - 2   b  (see  FIGS. 1 and 6 ). 
         [0066]    The rotary drive plate  32  supported by the cylindrical portion  21   a  of the switch unit main body  21  is covered from above with the rotary cover  31 . The rotary drive spring  33  formed from a twisted coil spring is inserted between the rotary cover  31  and the rotary drive plate  32 , and the two ends of the rotary coil spring are engaged. For this purpose, a round fitting hole  31   a  that fits the cylindrical portion  21   a  of the switch unit main body  21  is provided in the central portion of the rotary cover  31 , and a fitting hole  31   b  that fits the upper protrusion  32   d  of the rotary drive plate  32  is provided outside the round fitting hole  31   a . Further, a protrusion  31   c  engaging with the engagement groove  11   f  provided in the lower body portion  11   c  of the operation unit main body  11  is formed protruding at a position facing the inner circumference of the fitting hole  31   a.    
         [0067]    When the rotary cover  31  is covered on the rotary drive plate  32 , the distal end portion of the cylindrical portion  21   a  of the switch unit main body  21  is loosely fitted to the fitting hole  31   a  of the rotary cover  31 , and the rotary cover  31  is rotatably supported on the switch unit main body  21 . Further, at this time, the protrusion  32   d  at the upper portion of the rotary drive plate  32  is fitted to the fitting hole  31   b  of the rotary cover  31 , and the rotary cover  31  and the rotary drive plate  32  are joined integrally together. Therefore, the rotary cover  31  and the rotary drive plate  32  are integrally rotatably supported by the cylindrical portion  21   a  of the switch unit main body  21 . The rotary drive spring  33  mounted between the rotary cover  31  and the cylindrical portion  21   a  of the switch unit main body  21  is locked at one end to the cylindrical portion  21   a  and locked at the other end to the rotary cover  31 , whereby elastic restoration forces are applied in the axial and rotation directions to the rotary cover  31  and the rotary drive plate  32 . 
         [0068]    When the operation unit  10  and the switch unit  20  arranged in the above-described manner are separated from each other, as depicted in  FIG. 10(   a ), the rotary drive portion  30  located on the switch unit main body  21  is rotated rightward, as shown by an arrow R, by the restoration force of the rotary drive spring  33  and placed at a standby position which is slightly shifted from the position of alignment with the switch unit main body  21 . As a result, the rotary drive plate  32  located inside the rotary drive portion  30  is also placed at a standby position, and the cam piece  32   a  formed in a protruding state at the lower end of the rotary drive plate is joined to the pressure-receiving piece  22   b  of the movable contactor holder  22  at a position with the larger height Hh (see  FIGS. 7 and 8) . As a consequence, the movable contactor holder  22  is pushed deeply downward according to the height Hh of the cam piece  32   a  against the urging force of the contact spring  27 . Therefore, in the opening-closing contact portion of an (a) contact arrangement, the normally open movable contact  26 - 1   a  contacts the normally open fixed contact  25 - 1   a  and becomes a switch-on state. In the opening-closing contact portion of a (b) contact arrangement, the normally open movable contact  26 - 2   b  separates from the normally open fixed contact  25 - 2   b , and becomes a switch-off state. Such an opening-closing state of the opening-closing contact portion is the same as the opening-closing state at the time of the standby state of the operation unit in a state in which the operation unit  10  is joined to the switch unit  20 . 
         [0069]    The procedure by which the operation unit  10  is thus joined to the switch unit  20 , in which the rotary drive portion  30  is placed at the standby position, to obtain the usage state will be explained hereinbelow with reference to  FIGS. 9(   a )- 9 ( d ). 
         [0070]    The lower body portion  11   c  of the main body  11  of the operation unit  10  is inserted from above into the cylindrical portion  21   a  of the switch unit  20  in which the rotary drive portion  30  is placed at the standby position. For this purpose, initially, as depicted in  FIG. 9(   a ), the protrusion  31   c  of the rotary cover  31 , which protrudes inward of the cylindrical portion  21   a  of the switch unit main body  21 , and the second protrusion  32   c  of the rotary drive plate  32  are fitted into the engagement groove  11   f  on the outer circumference of the lower body portion  11   c  of the operation unit main body  11 . Then, the operation unit  10  and the switch unit  20  are aligned such that the ridge  21   b  provided at the cylindrical portion  21   a  of the main body  21  of the switch unit  20  is inserted into the engagement groove  11   g  of the operation unit main body  11 . 
         [0071]    Once such an alignment is attained, the lower body portion  11   c  of the operation unit main body  11  is inserted from above into the cylindrical portion  21   a  of the switch unit  20 , in which the rotary drive portion  30  is placed at the standby position, and pushed down while the protrusions  31   c ,  32   c  are fitted to the engagement groove  11   f , and the engagement ridge  21   b  is fitted to the engagement groove  11   g  ( FIG. 9(   b )). As the operation unit  10  is pushed, the protrusion  31   c  of the rotary cover  31  and the protrusion  32   c  of the rotary plate  32 , which are fitted with the engagement groove  11   f , are pushed by the inner wall of the inclined portion  11   f - 1  of the engagement groove  11   f  and moved leftward, as shown by an arrow L. Therefore, the rotary cover  31  and the rotary plate  32  are rotated to the left while twisting the rotary drive spring  33 . 
         [0072]    When the protrusion  31   c  of the rotary cover  31  and the protrusion  32   c  of the rotary plate  32  reach the horizontal portion  11   f - 2  of the engagement groove  11   f , as shown in  FIG. 9(   c ), the protrusions are rotated rightward, as shown by the arrow R, by the restoration force of the rotary drive spring  33  twisted by the rotation of the rotary cover  31  and the rotary plate  32 . As a result, the protrusions  31   c  and  32   c  move to the right end of the horizontal portion  11   f - 2  of the engagement groove  11   f . Further, since the rotary cover  31  is also driven upward by the axial restoration force of the rotary return spring  33 , the rotary cover  31  rises and only the protrusion  31   c  of the rotary cover  31  moves into the vertical portion  11   f - 3  of the engagement groove  11   f , as depicted in  FIG. 9(   d ). As a result, the protrusion  31   c  of the rotary cover  31  is locked to the vertical portion  11   f - 3  of the engagement groove  11   f  of the operation unit  11 . Therefore, the rotary drive portion  30  is fixed and cannot rotate with respect to the body portion  11   a  of the operation unit main body  10 . 
         [0073]    The operation unit  10  is thus inserted to the very end into the rotary drive portion  30 , and becomes the usable state when the operation unit  10  is joined to the switch unit  20 , as shown in  FIG. 10(   b ). In this state, the rotary drive portion  30  is fixed in alignment with the usage position of the main body  21  of the switch unit  20 . When the rotary drive portion  30  is placed at this position, the rotary plate  32  located inside thereof rotates leftward, as shown by the arrow L, together with the rotary drive portion  30 . Therefore, the joining position of the rotary drive plate  32  and the pressure-receiving piece  22   b  of the movable contactor holder  22  of the switch unit  20  becomes a low position with the height Hl of the cam piece  32   a , and the movable contactor holder  22  is pushed up to the position with the height Hl of the cam piece  32   a  by the contact spring  27 . As a result, the normally open movable contact  26 - 1   a  held by the movable contactor holder  22  separates from the normally open fixed contact  25 - 1   a , the normally closed movable contact  26 - 2   b  and the normally closed fixed contact  25 - 2   b  are closed, and the opening-closing contact portion becomes an opening-closing state at the time of the standby state. 
         [0074]    When the switch unit  20  and the operation unit  10  are separated from each other from the joined state thereof, the operations may be performed according to a procedure reversed with respect to the joining procedure illustrated by  FIG. 9(   a )- 9 ( d ). However, unless the rotary cover  31  is pushed down to a position at which the protrusion  31   c  overlaps the protrusion  32   c  of the rotary drive plate  32  in the state shown in  FIG. 9(   d ), the rotary cover  31  cannot be rotated, therefore, it is necessary to perform the operation of pushing down the rotary cover  31 . 
         [0075]    In the switch device  1  depicted in  FIG. 1 , the operation unit  10  is thus joined to the switch unit  20  and placed in the standby state. In this state, the rotary drive plate  32  of the rotary drive portion  30  pushes the pressure-receiving piece  22   a  of the movable contactor holder  22  of the switch unit  20  at a position with a small height Hl of the cam piece  32   a . Therefore, the rotary drive plate  32  is in a standby position at which the movable contactor holder  22  is pushed up. As a result, the normally open movable contact  26 - 1   a  and the normally open fixed contact  25 - 1   a  are separated from each other and become the switch-off state, and the normally closed movable contact  26 - 2   b  and the normally closed fixed contact  25 - 2   b  are closed and become the switch-on state. 
         [0076]    When the pushbutton  12  of the operation unit  10  is pushed in the direction of an arrow P, as depicted in  FIG. 11 , the push rod  13  is pushed down in response thereto. Therefore, the lock pin  15  rides over a step  13   c  located between the two recesses of the push rod  13  joined to the pushbutton  12 , engages with the upper recess  13   b , and holds the pushbutton  12  at the pushing operation position. In response to the downward pushing of the push rod  13 , the push body  19  is pushed down through the trigger spring  18 . As a result, the upper end of the movable contactor holder  22  of the switch unit  20  abutting against the push body  19  is pushed down against the urging force of the contact spring  27 . Therefore, the normally open movable contact  26 - 1   a  and the normally open fixed contact  25 - 1   a  are closed and become the switch-on state, and the normally closed movable contact  26 - 2   b  and the normally closed fixed contact  25 - 2   b  are separated from each other and become the switch-off state. This is the opening-closing state of the opening-closing contact mechanism at the time the operation unit  10  is in the pushing operation state. 
         [0077]    In order to return the switch device  1  in such an operation state to the standby state such as depicted in  FIG. 1 , the pushbutton  12  is turned in the direction of the arrow displayed on the surface of the pushbutton  12  and the locked state caused by the lock pin  15  is released. 
         [0078]    In order to facilitate such an operation of releasing the locked state, as shown in  FIG. 5 , cam portions  11   m  and  12   e  having inclined surfaces that rise from right to left along the circumference are provided facing each other on the inner circumference of the operation unit main body  11  of the operation unit  10  and the outer circumference of the inner wall of the pushbutton  12  facing thereto. 
         [0079]    In the standby state before the pushing operation of the pushbutton  12 , the lock pin  15  is engaged with the recess  13   a  in the lower part of the push rod  13  joined to the pushbutton  12 , as depicted in  FIG. 5(   a ), and the locked state is maintained. Therefore, the pushbutton  1  is at the push-up position, and the cam portion  11   m  of the operation unit main body  11  is separated from the cam portion  12   e  of the pushbutton  12 . 
         [0080]    In the operation state in which the pushbutton  12  has been pushed, the lock pin  15  engages with the recess in the upper part of the push rod  13  and the locked state is maintained. Therefore, the pushbutton  12  is at the push-down position, the cam portion  12   e  of the pushbutton  12  approaches the cam portion  11   m  of the operation unit main body  11 , and practically no gap is present therebetween. 
         [0081]    When the pushbutton  12  is rotated from this state to the right in the preset range of rotation angle C described hereinabove, the cam surface of the cam portion  12   e  of the pushbutton  12  comes into contact with the cam surface of the cam portion  11   m  of the operation unit main body  11  and is pushed up along this cam surface. The push rod  13  rises accordingly, and the recess  13   a  located in the lower part thereof engages with the lock pin  15  and returns to the original standby position. 
         [0082]    When the locked state at the operation position created by the lock pin  15  is thus released, the movable contactor holder  22 , the push rod  13 , and the pushbutton  12  are pushed by the restoration forces of the contact spring  27  and the trigger spring  18 , and returned to the position of the standby state. The pushbutton  12  is returned to the original rotation position by the twisted return spring  14  and becomes the standby state depicted in  FIG. 1 . 
         [0083]    If by any chance an accident occurs such that the switch unit  20  of the switch device  1  separates from the operation unit  10 , as depicted in  FIG. 10(   a ), since the operation unit  10  and the rotary drive portion  30  are not joined together anymore, the rotary drive portion  30  is rotated to the right, as shown by the arrow R, by the restoration force of the internal rotary return spring  33  and returns to the standby position depicted in  FIG. 10(   a ). At the same time, the rotary drive plate  32  located inside the rotary drive portion  30  is also rotated. Therefore, the cam piece  32   a  applies pressure to the pressure-receiving piece  22   a  of the movable contactor holder  22  at a position with a large height Hh of the cam piece  32   a . As a result, the movable contactor holder  22  is pushed downward. Therefore, the normally closed movable contact  26 - 2   b  and the normally closed fixed contact  25 - 2   b  are separated from each other and become the switch-off state, the normally open movable contact  26 - 1   a  and the normally open fixed contact  25 - 1   a  are closed and become a switch-on state, and the opening-closing contact mechanism becomes the state same as the opening-closing state at the time the operation unit is in the operation state. Therefore, the switch device can be used as an emergency safety switch. 
         [0084]    In the switch device  1  of the invention, in a state in which the rotary drive portion  30  is placed at the usage position and the pushbutton  12  is in the standby state, as depicted in  FIG. 1 , the movable contacts of the opening-closing contact portion of the switch unit  20  are urged by the contact spring  27  in the direction of separating the opening-closing portion of the (a) contact and in the direction of closing the opening-closing portion of the (b) contact. Therefore, even when an impact force is applied to the switch device in this state, an erroneous operation such that closes the opening-closing portion of the (a) contact and separates the opening-closing portion of the (b) contact cannot occur. As a result, the operation reliability can be increased. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0000]    
       
         
           
               1 —switch device,  10 —operation unit,  11 —operation unit main body,  12 —pushbutton,  13 —push rod,  20 —switch unit,  21 —switch unit main body,  22 —movable contactor holder,  25 - 1   a —normally open fixed contact;  25 - 2   b —normally closed fixed contact,  26 - 1   a —normally open movable contact,  26 - 2   b —normally closed movable contact,  27 —contact spring,  30 —rotary drive portion,  31 —rotary cover,  32 —rotary drive plate,  32   a —cam piece,  33 —rotary return spring