Patent Publication Number: US-6911609-B2

Title: Grip type switch device and controller for industrial machinery using the switch device

Description:
TECHNICAL FIELD 
   The present invention relates to a grip type switch device including a switch case configured to be held by one hand and provided with a push-button switch adapted to be switched OFF or ON according to the amount of push-button depression, and to a controller for industrial machinery employing the grip type switch device. 
   BACKGROUND ART 
   In factories or the like, a controller for industrial machinery  201  provided with an industrial machinery, such as a robot, has an arrangement, as shown in  FIG. 17 , wherein a dangerous zone around the industrial machinery (the industrial robot)  203  is enclosed by a safety fence (partitioning means)  207  having a doorway  205  freely opened or closed whereby an operator is prevented from being involved in trouble that the operator is caught in the operating industrial machinery  203 . In the case of normal operation of the industrial machinery  203 , the operator standing outside the safety fence  207  controls the machinery  203  via a control panel  209  attached to an outside surface of the safety fence  207 . 
   From the standpoint of safety, emergency stop switches  211  are provided at the control panel  209  and at plural places inside and outside of the safety fence  207 . In the event of a dangerous state of the industrial machinery  203 , any one of the emergency stop switches  211  inside and outside of the safety fence  207  may properly be manipulated to cut off power to a main circuit of the controller  201 , thereby driving the whole controller  201  into emergency stop. 
   From the standpoint of safety, as well, a safety switch  215  is also provided at the doorway  205  of the safety fence  207  so as to deactivate the industrial machinery  203  when a door  213  in the doorway  205  is not fully closed. 
   The safety switch  215  is electrically connected with the industrial machinery  203  installed at place inside of the safety fence  207  and comprises, as shown in  FIG. 18 , a switch body  217  containing contacts, and an actuator  219  adapted to close or open the contacts in the switch body  217  when inserted into or extracted from the switch body  217 . The switch body  217  is secured to the safety fence  207  at place around the doorway  205 , whereas the actuator  219  is secured to the door  213 . The actuator  219  is positioned at place corresponding to an insertion hole  221  of the switch body  217  so that the actuator may enter an operation section  223  of the switch body  217  when the door  213  is closed. 
   The inserted actuator  219  closes the contacts contained in a switch section  225  of the switch body  217 , so that the industrial machinery  203  inside of the safety fence  207  is supplied with power and ready to operate. When, on the other hand, the actuator  219  is extracted from the operation section  223  by opening the door  213 , the contacts in the switch section  225  are opened to cut off the power to the industrial machinery  203 , so that the industrial machinery  203  does operate unless it is manually operated. Thus, the industrial machinery  203  does not operate when the door  213  is open. This leads to the prevention of the occurrence of trouble that the operator working inside of the safety fence  207  is caught in the operating industrial machinery  203 . 
   In cases where the operator enters the zone inside of the safety fence  207  to manually operate the industrial machinery  203  or to carry out maintenance service for the industrial machinery  203 , the operator uses a teaching pendant  227  equipped with a push-button switch, a so-called enable switch (deadman switch) in order to obviate an accident associated with contact with the operating industrial machinery  203  during the work. 
   As shown in  FIG. 19 , the teaching pendant  227  is a portable unit which is connected with the control panel  209  via a cable  229 , thereby enabled to teach a program to the industrial machinery  203  or to operate the industrial machinery  203 . The teaching pendant  227  includes an input keyboard  231  disposed on a main surface thereof, and a push-button switch (enable switch)  233  disposed on one side surface thereof. The push-button switch  233  is adapted to be switched from a first OFF state to an ON state, and then to a second OFF state according to the amounts of push-button depression. In some cases, the push-button switch  233  may be disposed on a back side of the teaching pendant  227 . 
   When the teaching pendant  227  is in the first OFF state where a push button  235  of the push-button switch  233  is undepressed, key entry is not effected even though the keyboard  231  is manipulated. When the operator of the teaching pendant  227  teaches a program to the industrial machinery  203 , the operator performs the key entry through the keyboard  231  while holding the push-button switch  233  in the ON state by depressing the push button  235 . If, at this time, the operator releases the push button  235  recognizing potential danger of contact with any moving part of the manually operated industrial machinery  203 , the push-button switch  233  is returned to the initial or first OFF state so that the industrial machinery  203  is deactivated. 
   In the event of an imminent danger panicking the operator into pressing further down on the push button  235 , the push-button switch  233  in the ON state is shifted to the second OFF state, thereby deactivating the industrial machinery  203 . 
   Thus, the teaching pendant  227  permits the key entry via the keyboard  231  thereof only when the push-button switch  233  thereof is in the ON state. Furthermore, the push-button switch  233  can be set to any of the three positions (the first OFF state, the ON state and the second OFF state) according to the amounts of push-button depression  235 . Accordingly, the teaching pendant provides for a tangible indication of intent of the operator manually operating the machinery so that the safety of the operator is ensured. 
   In the manual operation of the industrial machinery  203  as described above, there may be a case where, in addition to the above operator, a plural number of assistant operators enter the zone inside of the safety fence  207  for assisting this main operator manipulating the teaching pendant  227 . In this case, these assistant operators individually carry with them a grip type switch device for safety purpose when entering the zone inside of the safety fence  207 , the grip type switch device equipped with a three-position type push-button switch of a similar configuration to that of the above push-button switch  233 . That is, the industrial machinery  203  can also be deactivated by any of the assistant operators that shifts the grip type switch device to the second OFF state. 
   A specific example of the grip type switch device is shown in FIG.  20 . As seen in the figure, the grip type switch device  239  includes a switch case  241  designed to be held by one hand, and a push-button switch  243  operable as depressed by the hand gripping the switch case  241 . The switch device  239  is electrically connected with the aforesaid control panel  209  via a cable  245  connected with contacts in the switch case  241  by soldering and unified with the switch case  241 . 
   The operators inside of the safety fence  207  perform their jobs with one hand thereof while gripping their grip type switch devices  239  in the other hand thereof, respectively. In a case where a program is taught to the industrial machinery  203 , the program teaching to the industrial machinery  203  is not effected unless not only the push-button switch  233  of the teaching pendant  227  but also the push-button switches  243  of all the grip type switch devices  239  are shifted to the ON state. This ensures an even more enhanced safety during the work. 
   Another specific example of the grip type switch device is arranged such that an essential configuration and function of the switch device are substantially the same as those of the above grip type switch device and that a watertight connector is used for removably connecting the contacts in the switch case and the cable. 
   Since such grip type switch devices  239  are connected with the control panel  209  via the respective cables  245 , the operators inside of the safety fence  207  usually carry out their jobs while trailing the cables  245  behind them. Therefore, the cable  245  may be damaged due to sliding contact with the floor or otherwise, a connection portion between the cable  245  and the switch case  241  may be so frequently twisted as to be broken. 
   Unfortunately, the specific example of the switch device shown in  FIG. 20  has the configuration wherein the switch case  241  is unified with the cable  245 . Therefore, even though only the cable  245  is damaged, it is impossible to replace the damaged cable alone. Hence, the whole grip type switch device  239  must be changed for the sake of cable replacement. This results in an extremely high maintenance cost. 
   In the other specific example of the switch device, the cable is connected with the contacts in the switch case via the watertight connector so that the cable alone can be replaced if it is damaged. However, the cable replacement also requires the watertight connector to be replaced. Since the watertight connector itself is quite expensive, a high maintenance cost results, as well. 
   When the operator performs his job inside the safety fence  207 , the door  213  in the doorway  205  is held open whereby the contacts of the safety switch  215  are opened to cut off the power to the industrial machinery  203 . However, there may be contemplated a case where the door  213  is inadvertently closed while the operator is working inside the safety fence  207 . In such a case, a fear exists that the actuator  219  of the safety switch  215  enters the switch body  217  thereby inadvertently resuming the power supply to the industrial machinery  203 . 
   In view of the foregoing, it is an object of the present invention to provide a grip type switch device wherein, in the case of damage to the cable, the damaged cable alone can be readily replaced at low cost. 
   It is another object of the present invention to ensure that the industrial machinery is positively maintained in cutoff even if the doorway of partitioning means, such as the safety fence, is inadvertently closed. 
   DISCLOSURE OF THE INVENTION 
   According to the present invention for achieving the above objects, a grip type switch device comprises a switch case configured to be held by one hand and including a push-button switch capable of being switched OFF or ON according to the amount of push-button depression, and is characterized in that connection means contained in the switch case establishes removable electrical connection between an end of a cable introduced into the switch case and contacts of the push-button switch. 
   According to this arrangement, the cable is removably held in electrical connection with the push-button switch by means of the connection means contained in the switch case. Hence, in the case of damage to the cable, for example, the damaged cable alone can be removed from the grip type switch device for replacement. In contrast to the conventional example where the damaged cable requires the replacement of the whole grip type switch device, the present invention does not require such a replacement nor require the provision of an expensive connector, such as a watertight connector. Thus, a maintenance cost associated with the cable replacement can be reduced. 
   In another aspect of the present invention, the grip type switch device is characterized in that the connection means comprises a base contained in the switch case, and a terminal block formed on the base and including a plurality of conductive connection portions, on one side, electrically connected with the contacts of the push-button switch, and that conductive connection portions, on the other side, attached to individual leading ends of plural cores of the cable are removably fitted with the corresponding conductive connection portions on the one side, thereby establishing electrical connection of the cable. 
   According to the arrangement, the conductive connection portions, on the one side, of the terminal block electrically connected with the push-button switch are removably fitted with the conductive connection portions, on the other side, attached to the leading ends of the cores of the cable. In order to replace the cable, therefore, the cores of the cable only need be disengaged from the terminal block, so that the cable replacement is facilitated. In addition, the push-button switch and the cable are interconnected by way of the less costly terminal block which contributes to a simple configuration. Thus, the maintenance cost for the grip type switch device can be reduced. 
   In another aspect of the present invention, the grip type switch device is characterized in that the connection means comprises a connector including a connector portion for the switch which is contained in the switch case and electrically connected with the contacts of the push-button switch, and a connector portion for the cable which is electrically connected with leading ends of plural cores of the cable introduced into the switch case and is removably fitted with the connector portion for the switch. 
   According to the arrangement, the connector portion for the switch in electrical connection with the push-button switch is removably fitted with the connector portion for the cable in connection with the leading ends of the cores of the cable. In order to replace the cable, therefore, the fitted connector portions only need be disengaged from each other, so that the cable replacement is facilitated. In addition, the push-button switch and the cable are interconnected by way of the less costly connector, which contributes to the simple configuration. Thus, the maintenance cost for the grip type switch device can be reduced. 
   In another aspect of the present invention, the grip type switch device is characterized in that the push-button switch is shifted from a first OFF state to an ON state and then to a second OFF state according to the increased amounts of push-button depression, and that the push-button switch includes an auxiliary contact in the switch case, the auxiliary contact designed to be opened or closed when the push-button switch is in the first OFF state and to be closed or opened when the push-button switch is in the second OFF state. 
   According to the arrangement, the push-button switch of the grip type switch device is adapted to be shifted from the first OFF state to the ON state and then to the second OFF state with increase in the amount of push-button depression. Hence, the push-button switch in the ON state can be returned to the first OFF state by releasing the pressure thereon, or otherwise be shifted to the second OFF state by further depressing the push-button switch. Thus is ensured the safety of the operator. 
   In addition, the auxiliary contact assuming different open/close positions in the first OFF state and the second OFF state is disposed in the switch case. Therefore, whether the push-button switch is in the first OFF state or in the second OFF state can be determined by monitoring the open/close position of the auxiliary contact. 
   In another aspect of the present invention, the grip type switch device is characterized in that the switch case is provided with an emergency stop switch to be manipulated for bringing an external system into emergency stop. 
   According to the arrangement, the emergency stop switch is provided at the switch case. Therefore, in the case of a dangerous situation involving the operator, the operator can bring the external system into emergency stop by manipulating the grip type switch device rather than directly manipulating the external system. This provides for a quick reaction to the emergency situation, leading to an enhanced safety during the work. 
   In another aspect of the present invention, the grip type switch device is characterized in that the switch case is provided with an actuator removably inserted in a safety switch provided at the external system, and that the external system is shifted to an enable mode for control via a control panel of the external system upon insertion of the actuator in the safety switch, whereas the external system is shifted to a disable mode for control via the control panel thereof upon extraction of the actuator from the safety switch. 
   According to the arrangement, the external system is disabled for control by extracting the actuator provided at the grip type switch device from the safety switch. Therefore, the external system can be disabled to control the machinery when, for example, the machinery is subjected to the teaching operation via the manipulated grip type switch device. This obviates an accident wherein the machinery is externally operated by mistake during the execution of the teaching operation. Thus, the safety during the work can be enhanced. 
   In another aspect of the present invention, the grip type switch device is characterized in that the actuator is disposed in the switch case in a manner to be freely projected or retracted. 
   According to the arrangement, in a case where the actuator is extracted from the safety switch before the teaching operation to the machinery is carried out, for example, the projected actuator can be retracted into the switch case. Therefore, the operator may retract the actuator projected from the switch case thereinto before the operator carries out his job as holding the grip type switch device in his hand, whereby the actuator is prevented from contacting the machinery or the like. 
   In another aspect of the present invention, the grip type switch device is characterized in that a guard member for partially covering a push button of the push-button switch is removably fixed to the switch case. 
   According to the arrangement, the guard member partially covers the push button so as to interfere with winding an adhesive tape about the push-button switch for holding the push-button switch in the ON state, for example. The guard member is effective to prevent a wrong use of the push-button switch that the push-button switch is held ON by winding the adhesive tape thereabout rather than by gripping the switch device by hand. 
   In another aspect of the present invention, the grip type switch device is characterized in that indication means indicative of the ON and OFF states of the push-button switch is provided at the switch case. 
   According to the arrangement, the indication means is provided for indication of the ON and OFF states of the push-button switch. Therefore, the operator of the grip type switch device can recognize the state of the push-button switch at a glance. 
   In another aspect of the present invention, the grip type switch device is characterized in that a drive switch for another device is provided at the switch case. 
   According to the arrangement, the drive switch for another device is provided at the switch case and hence, the another device can be operated by manipulating the drive switch at the grip type switch device. Therefore, the grip type switch device may also be used as operation means for another device, contributing to the increased efficiency of the work. 
   In another aspect of the present invention, the grip type switch device is characterized in that the switch case is provided with watertight means at a lead-in portion thereof, through which the cable is introduced into the switch case. 
   According to the arrangement, the switch case is provided with the watertight means at its lead-in portion for the cable and hence, the grip type switch device is prevented from suffering failure caused by water invasion. This ensures a trouble-free use of the grip type switch device even in an environment requiring a watertight measure. 
   In another aspect of the present invention, the grip type switch device is characterized in that a push button of the push-button switch projects from a periphery of the switch case, and that the switch case is formed with projections at places on opposite sides of the push button, the projections projecting further outward than the push button. 
   According to the arrangement, the projections projecting further outward than the push button are formed on the opposite sides of the push button, so that the push button is guarded by the projections sandwiching the push button therebetween. Thus, the projections prevent the push-button switch from being inadvertently depressed ON in cases where, for example, the grip type switch device is placed on a flat plane. 
   According to the present invention, a controller for industrial machinery comprises: partitioning means partitioning a zone around an industrial machinery and including a doorway freely opened or closed; and a control panel for the industrial machinery disposed near the doorway and switched between a disable mode for control and an enable mode for control in association with the ON state and the OFF state of the push-button switch of the grip type switch device, respectively. 
   According to the arrangement, the control panel for the industrial machinery is disabled for control when the push-button switch of the grip type switch device is ON. Therefore, the industrial machinery is prevented from being inadvertently activated by someone outside the partitioning means who manipulates the control panel when the program teaching to the industrial machinery is carried out by manipulating the grip type switch device. Thus, the safety of the operator can be ensured during the teaching operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a first embodiment of the present invention; 
       FIG. 2  is a side elevation in section showing the first embodiment hereof; 
       FIG. 3  is a group of diagrams explaining operations of the first embodiment hereof; 
       FIG. 4  is a fragmentary perspective view showing a part of the first embodiment hereof; 
       FIG. 5  is a sectional view showing one state of another part of the first embodiment hereof; 
       FIG. 6  is a sectional view showing another state of the above part of the first embodiment hereof; 
       FIG. 7  is a sectional view showing still another state of the above part of the first embodiment hereof; 
       FIG. 8  is a fragmentary perspective view showing a part of an exemplary modification of the first embodiment hereof; 
       FIG. 9  is a side elevation showing the exemplary modification of the first embodiment hereof; 
       FIG. 10  is a side elevation showing another exemplary modification of the first embodiment hereof; 
       FIG. 11  is a sectional view showing one state of a part of a second embodiment of the present invention; 
       FIG. 12  is a sectional view showing another state of the above part of the second embodiment hereof; 
       FIG. 13  is a sectional view showing still another state of the above part of the second embodiment hereof; 
       FIG. 14  is a side elevation showing a third embodiment of the present invention; 
       FIG. 15  is a sectional view taken on the line A—A in  FIG. 14 ; 
       FIG. 16  is a diagram illustrative of how the third embodiment hereof is used; 
       FIG. 17  is a perspective view showing a controller for industrial machinery according to the background art of the present invention; 
       FIG. 18  is a fragmentary perspective view showing a part of the controller for industrial machinery of  FIG. 17 ; 
       FIG. 19  is a fragmentary perspective view showing another part of the controller for industrial machinery of  FIG. 17 ; and 
       FIG. 20  is a perspective view showing a conventional example. 
   

   BEST MODE FOR CARRYING-OUT THE INVENTION 
   (First Embodiment) 
   Now referring to  FIGS. 1  to  7 , the present invention will be described by way of a first embodiment thereof wherein the present invention is applied to a grip type switch device for use with a controller for industrial machinery such as an industrial robot.  FIGS. 1 and 2  are a perspective view and a side elevation in section.  FIG. 3  is a group of diagrams illustrative of how the grip type switch device is gripped.  FIG. 4  is a perspective view showing a terminal block disposed in a switch case, whereas  FIGS. 5  to  7  are sectional views each showing a different state of a push-button switch disposed in the switch case. 
   In this embodiment, an essential configuration of a controller for industrial machinery  201  employing the grip type switch device is substantially the same as that shown in  FIGS. 17  to  19  and therefore, the following description is made with reference to these figures as well, so that the redundancy is obviated. 
   As shown in  FIGS. 1 and 2 , a grip type switch device  1  according to the embodiment comprises a switch case  3  designed to be held by one hand; a push-button switch  5  disposed in the switch case  3 ; a multicore cable  7  including a plurality of cores, one end  6  of which is removably attached to the switch case  3  and the other end of which is connected with the control panel  209  (see FIG.  17 ); and a terminal block  9  as connection means which is disposed in the switch case  3  for electrically connecting contacts of the push-button switch  5  with the cable  7 . 
   As shown in  FIGS. 1 and 2 , the switch case  3  comprises a cover member  11  and a case body  13 , the cover member  11  removably attached to the case body  13 . 
   The case body  13  is formed with a lead-in aperture  15  at one end thereof, through which the one end  6  of the cable  7  is inserted. The lead-in aperture  15  is provided with a cylindrical watertight packing  17  which closes gap between the one end  6  of the cable  7  and the case body  13  thereby preventing water invasion. A protective member  19  of an elastic material, such as rubber, is spirally wound around an outside surface of the one end  6  of the cable  7 . The protective member  19  protects the one end  6  of the cable  7  from a direct external force applied thereto during the use of the grip type switch device  1 , whereby the cable  7  is prevented from being bent or twisted heavily. 
   As inserted into the case body  13 , the one end  6  of the cable  7  is removed of sheath thereof for exposing multiple cores  21  thereof, leading ends  23  of which are removed of jacket for exposing conductors in the individual cores  21 . The exposed conductor portions are removably connected with the terminal block  9 . It is noted here that the exposed conductor portions at the leading ends  23  of the cores  21  constitute conductive connection portions on the other side according to the present invention. 
   On the other hand, a guard member  27  such as formed of a hard resin material is removably attached to the switch case  3  for partially covering a push button  25  of the push-button switch  5 . One end  29  of the guard member  27  is fixed to a bottom of the case body  13  by way of a screw  31 . In a case where an operator grips the switch case  3  in his right hand in order to manipulate the grip type switch device  1 , the guard member  27  may be fixed to the switch case  3  as shown in FIG.  3 A. In a case where the switch case  3  is gripped by the left hand, as shown in  FIG. 3B , the guard member  27  may be fixed to the switch case  3  in the opposite orientation to that shown FIG.  3 A. 
   The guard member  27  thus fixed makes it impossible to hold the push-button switch  5  in the ON state by wrapping an adhesive tape around the switch case, for example, because the guard member  27  prevents the adhesive tape from pressing down on the push button  25 . That is, the guard member  27  obviates a wrong use of the switch device wherein the adhesive tape is wrapped around the switch case to hold the push-button switch  5  in the ON state while the operator neglects to hold the push-button switch depressed. 
   On the other hand, the cover member  11  is centrally formed with an elongate hole  33  for insertion of the push button  25  such that the push button  25  of the push-button switch  5  in the switch case  3  projects outwardly from the elongate hole  33 . The cover member  11  is further formed with projections  35   a ,  35   b  at longitudinally opposite ends thereof, the projections projecting further outward than the push button  25 . The projections  35   a ,  35  are so formed as to guard the opposite ends of the push button  25 , thereby preventing the push-button switch  5 , which is placed on a flat plane for example, from being accidentally depressed ON. 
   Two LEDs  37   a ,  37   b  as indication means are provided at an end face, on the other side, of the cover member  11  or at an end face of the projection  35   a , the LEDs emitting lights of different colors (red and green, for example) for indicating the ON and OFF states of the push-button switch  5 , respectively. For instance, the LED  37   a  is ON during the OFF state of the push-button switch  5 , whereas the other LED  37   b  is ON during the ON state of the pus-button switch. 
   As shown in  FIGS. 2 and 4 , the terminal block  9  comprises a board  41  connected with terminal pieces  71 ,  81  forming contacts of the push-button switch  5  (described herein later) via conductors  39 ; a base  43  of an L-shape in section which is mounted on the board  41  and includes an upper stage  45  and a lower stage  47 ; and cylindrical conductive connection portions  51   a ,  51   b , on the one side, which are disposed in plural insertion holes  49   a ,  49   b  formed in the base  43 . 
   The conductor portions of the cores  21  of the cable  7  are inserted in the conductive connection portions  51   a ,  51   b , on the one side, disposed in the insertion holes  49   a ,  49   b , respectively. On the other hand, screws  53   a ,  53   b  extended from individual top surfaces of the upper stage  45  and the lower stage  47  are threadedly engaged with the insertion holes  49   a ,  49   b , respectively. The screws  53   a ,  53   b  are tightened thereby pressing the conductor portions at the leading ends  23  of the cores  21  against the conductive connection portions  51   a ,  51   b  on the one side, respectively. The conductive connection portions  51   a ,  51   b  on the one side are electrically connected with the board  41 , so that an ON or OFF signal of the push-button switch  5  is transmitted to the cores  21  of the cable  7  via the conductive connection portions  51   a ,  51   b  on the one side. 
   The push-button switch  5  is a three-position type switch adapted to be shifted from the first OFF state to the ON state and then to the second OFF state according to the amounts of push-button depression  25 . As shown in  FIG. 5 , for example, the push-button switch  5  comprises a switch case  55  having a rectangular shape in plan; a push button  25  depressibly supported by the switch case  55 ; a pair of c-contacts  59  adapted to switch ON or OFF the push-button switch  5  and a normally close contact  61 , as an auxiliary contact; and a pair of switching mechanisms  63  operatively associated with pressing-down on the push button  25  for switching the c-contacts  59  between an open position and a close position. As seen in the figure, the push-button switch  5  has a symmetrical configuration and therefore, the following description discusses a configuration of only a right half thereof while the explanation of a left half thereof is dispensed with. 
   As shown in  FIG. 5 , the normally close contact  61  is disposed centrally downwardly of the switch case  55 , whereas the pair of c-contacts  59  having a snap action configuration are disposed at opposite ends of the switch case as sandwiching the normally close contact  61  therebetween. 
   The normally close contact  61  comprises a movable member  65  disposed in the switch case  55  and projecting toward the push button  25  (upwardly) as urged upward by a helical spring  64  disposed therebelow; a pair of movable terminals  67  attached to the movable member  65 ; and a pair of stationary terminals  69  brought into or out of contact with the movable terminals  67 . In an initial state, the movable member  65  is urged upward by the helical spring so that the normally close contact  61  is closed with the movable terminals  67  thereof contacting the stationary terminals  69  thereof. The stationary terminals  69  are electrically connected with the terminal pieces  71  projected downwardly from the switch case  55 , the terminal pieces  71  connected with the board  41  of the terminal block  9  via the conductors  39 . 
   The c-contact  59   a  has the snap action configuration, comprising a movable terminal  73 ; a normally close stationary terminal  75  and a normally open stationary terminal  77  disposed above and below the movable terminal  73 ; an operative member  79  for moving the movable terminal  73  between the normally close stationary terminal  75  and the normally open stationary terminal  77 ; and a helical spring  80  anchored to the operative member  79  and to the movable terminal  73 . 
   When the c-contact  59  is in the initial state or in the first OFF state, the movable terminal  73  thereof is in contact with the normally close stationary terminal  75  as spaced away from the normally open stationary terminal  77  thereof. The movable terminal  73 , the normally close stationary terminal  75  and the normally open stationary terminal  77  are electrically connected with the individual terminal pieces  81  projected downwardly from the switch case  55 , the terminal pieces  81  connected with the board  41  of the terminal block  9  via the conductors  39 . 
   The switching mechanism  63  is disposed in an accommodating portion  83  defined in the push button  25 . The switching mechanism  63  comprises a pressing piece  85  for pressing the operative member  79  of the c-contact  59 ; a slide block  87  operatively associated with pressing-down on the push button  25  for depressing the pressing piece  85 ; and a pressing shaft  89  engaged with the slide block  87 . 
   The pressing shaft  89  is formed with a pair of flanges  91   a ,  91   b  at an upper end thereof. One  91   a  of the flanges is formed with a slope  93 . The pressing shaft  89  has a hollow structure such that a helical spring  95  anchored to an upper inside surface of the accommodating portion  83  is anchored to place in the pressing shaft  89 . 
   The slide block  87  is formed with a cavity  97  vertically extended therethrough, whereas the pressing shaft  89  is inserted through the cavity  97 . The slide block  87  is formed with a slope  101  at an inside wall of one end  99  thereof, the slope  101  engaged with the slope  93  of the pressing shaft  89 . A helical spring  103  is interposed between the one end  99  of the slide block  87  and a side wall of the accommodating portion  83 , the helical spring  103  serving to urge the slide block  87  toward the center of the push button  25 . The other end  105  of the slide block  87  is adapted to abut against an upper end of the pressing piece  85 . 
   When the push button  25  of the push-button switch  5  in the initial or first OFF state shown in  FIG. 5  is depressed, the pressing piece  85  pushes down the operative member  79  of the c-contact  59  as operatively associated with pressing-down on the push button  25 , as shown in FIG.  6 . Thus, the movable terminal  73  is moved away from the normally close stationary terminal  75  to be brought into contact with the normally open stationary terminal  77 , so that the push-button switch  5  is shifted to the ON state. 
   When the push button  25  of the push-button switch  5  in the ON state is further depressed, the slope  101  of the slide block  87  slides on the slope  93  of the pressing shaft  89 , so that the slide block  87  is moved outwardly relative to the push button  25 , as shown in FIG.  7 . The movement of the slide block  87  releases the other end  105  thereof from the engagement with the upper end of the pressing piece  85  which, in turn, is allowed to move upwardly to release the pressure on the operative member  79 . This causes the movable terminal  73  to move away from the normally open stationary terminal  77  and to come into contact with the normally close stationary terminal  75 . Thus, the push-button switch  5  in the ON state is shifted to the second OFF state. 
   At this time, the movable member  65  of the normally close contact  61  in the push-button switch  5  is pushed down by the push button  25 , so that the movable terminals  67  are moved away from the stationary terminals  69  to open the normally close contact  61 . That is, the normally close contact  61  is closed in the first OFF state and is opened in the second OFF state. Therefore, whether the push-button switch  5  is in the first OFF state or in the second OFF state can be readily determined by monitoring the state of the normally close contact  61 . 
   In a case where a part of the cable  7  is damaged so that the grip type switch device  1  requires the replacement of the cable  7 , the cover member  11  of the switch case  3  is first removed. Subsequently, the individual screws  53   a ,  53   b  at the upper stage  45  and the lower stage  47  of the terminal block  9  are loosened to release the pressure on the conductive connection portions  51   a ,  51   b , on the one side, of the conductor portions of the cable  7 . This state allows the conductor portions of the cable  7  to be extracted from the insertion holes  49   a ,  49   b  in the terminal block  9 . Subsequently, the cable  7  with the cores  21  is drawn out from case body  13  to be replaced by a new cable. 
   On the other hand, the new cable may be mounted to the switch case  3  by performing the above steps in the reversed order. Specifically, the cores  21  are first drawn out from the one end  6  of the cable  7 . The one end  6  of the cable  7  is inserted through the lead-in aperture  15  via the watertight packing  17 . Then, the sheath of the cable  7  is removed to expose the cores  21 , the leading ends  23  of which are also removed of the jacket thereof to expose the conductor portions. The exposed conductor portions are individually inserted in the insertion holes  49   a ,  49   b  of the terminal block  9 . Subsequently, the screws  53   a ,  53   b  are tightened to press the conductor portions against the conductive connection portions  51   a ,  51   b  on the one side thereby establishing the electrical connection. Finally, the cover member  11  is fixed to the case body  13  to finish the replacement of the cable  7 . 
   Next, description is made on the operations of the industrial machinery  203  operated by means of the grip type switch device  1 . In a case where the industrial machinery  203  is subjected to program teaching or manually operated, the operator responsible for the program teaching brings the teaching pendant  227  with him into the zone inside of the safety fence  207  whereas the other assistant operators bring the grip type switch devices  1  with themselves into the zone inside of the safety fence  207 . At this time, the door  213  in the doorway  205  of the safety fence  207  is held open. Thus, the actuator  219  fixed to the door  213  is extracted from the switch body  217  of the safety switch  215  and hence, the industrial machinery  203  is deactivated to be placed in a mode to be manually operated by way of the teaching pendant  227  or any of the grip type switch devices  1 . 
   When the program is taught to the industrial machinery  203 , the teaching operation or the like is carried out in a state where the operator holds the push-button switch  233  of the teaching pendant  227  in the ON state while at the same time, the assistant operators hold the push-button switches  5  of the grip type switch devices  1  in the ON state. 
   While the push-button switch  5  is ON, the LED  37   a  of the switch case  3  goes out whereas the LED  37   b  comes on. Therefore, the assistant operator can visually determine that the push-button switch  5  is in the ON state where the teaching operation is permitted. On the other hand, the push-button switch  233  of the teaching pendant  227  is also enabled for teaching to the industrial machinery  203  when shifted to the ON state. 
   In a case where any of the assistant operators is aware of abnormality such as contact with the industrial machinery  203 , the assistant operator can press further down on the push button  25  of the push-button switch  5 , thereby shifting the push-button switch  5  in the ON state to the second OFF state. Thus, the manual operation of the industrial machinery  203  is disabled irrespective of the manipulation of the teaching pendant  227 . 
   According to the first embodiment described above, the leading ends  23  of the cable  7  introduced into the switch case  3  are removably held in electrical connection with the c-contacts  59  of the push-button switch  5  by means of the terminal block  9 . Even in the case of damage to the cable  7 , therefore, the damaged cable  7  may be readily replaced by removing the cores  21  thereof from the terminal block  9  and then removing the cable  7  from the switch case  3 . That is, the cable  7  alone can be replaced when the cable  7  is damaged. This results in a lower maintenance cost than the conventional example wherein the damaged cable  7  requires the replacement of the whole grip type switch device. 
   In addition, the less costly terminal block  9 , as the connection means, is used for connecting the cable  7  with the c-contacts  59  of the push-button switch  5 . Accordingly, the grip type switch device  1  can be constructed in a simple structure at low cost which results in the reduction of maintenance cost. 
   Although the embodiment described above employs the terminal block  9  as the connection means for interconnecting the cable  7  and the contacts of the push-button switch  5 , the present invention is not limited to this. For instance, an arrangement shown in  FIG. 8  may be made. 
   Instead of using the terminal block  9 , the arrangement shown in  FIG. 8  may be made such that a connector portion  107  for the cable is connected with the exposed conductor portions of the cores  21  of the cable  7  whereas a connector portion  109  for the switch is connected with the leading ends of the conductors  39  connected with the c-contacts  59  of the push-button switch  5 , and that the connector portion  107  for the cable is removably fitted with the connector portion  109  for the switch thereby electrically connecting the c-contacts  59  of the push-button switch  5  with the cable  7 . It is noted here that a connector comprising the connector portion  107  for the cable and the connector portion  109  for the switch constitutes the connection means of the present invention. 
   Likewise to the first embodiment described above, such an arrangement also provides the easy and removable connection between the cable  7  and the push-button switch  5 . Furthermore, the connection means is constituted by the less costly connector consisting of the connector portions  107 ,  109  and hence, the maintenance cost for the grip type switch device  1  can be reduced. 
   In addition, the switch case  3  may be further provided with a drive switch  111  for another device at the other end thereof, which is opposite to the one end thereof through which the cable  7  is introduced. The device activated by the drive switch  111  may be exemplified by an alarm (not shown) disposed in a factory, for example. The drive switch  111  integrated with the grip type switch device  1  may be manipulated to activate the alarm which outputs a buzzer sound or the like. The buzzer sound or the like ensures that any person outside of the safety fence  207  is informed of an emergency inside of the safety fence  207  even in the noises of the factory. 
   Another example of the device to be activated by the drive switch  111  may be the industrial machinery  203  itself. Specifically, an arm of the industrial machinery  203  may be manually driven for teaching, whereby in addition to the operator of the teaching pendant  227 , the assistant operator with the grip type switch device  1  is also permitted to perform the teaching operation to the industrial machinery  203 . This leads to an increased efficiency of the work. It is noted that the drive switch  111  is not limited to the above and may be designed to activate any other device. 
   Furthermore, as shown in  FIG. 10 , the switch case  3  may be provided with an emergency stop switch  113  for the controller  201  (see  FIG. 17 ) at the other end thereof which is opposite to the one end thereof through which the cable  7  is introduced. The provision eliminates the need for the operator to rush to any of the emergency stop switches  211  inside and outside of the safety fence  207  and to manipulate it, in the event of abnormal conditions of the industrial machinery  203 , for example. The controller  201  can be brought into an emergency stop by manipulating the emergency stop switch  113  at the grip type switch device  1 . 
   Therefore, the embodiment provides for a quick emergency stop of the controller  201  in case of abnormal conditions of the industrial machinery  203  or the like, thus ensuring the safety during the work. Such an emergency stop switch  113  may preferably be of a push-lock and turn-reset system, for example. 
   In the first embodiment described above, the two LEDs  37   a ,  37   b  indicating the ON and OFF states of the push-button switch  5  may not necessarily be provided. Further, the drive switch  111  shown in  FIG. 9  or the emergency stop switch  113  shown in  FIG. 10  may not necessarily be provided. 
   (Second Embodiment) 
   A second embodiment of the present invention will be described with reference to  FIGS. 11  to  13 , which are sectional views each showing a different state of a push-button switch disposed in a switch case. Since essential configurations of the switch case  3 , cable  7  and connection means of the grip type switch device  1  of the embodiment are substantially the same as those of the first embodiment, the following description principally discusses differences from the first embodiment with reference to  FIGS. 1  to  4  as well, so that the redundancy is obviated. 
   In the grip type switch device of the embodiment, a configuration of the push-button switch disposed in the switch case  3  differs from that of the first embodiment. Specifically, the first embodiment employs the push-button switch  5  of the snap action type, whereas this embodiment employs the push-button switch of a slow action type. 
   As shown in  FIG. 11 , a push-button switch  131  comprises a switch case  132  having a rectangular shape in plan; a push button  133  depressibly supported by the switch case  132 ; two pairs of pressing elements  134  for producing additional load on the push button when the push-button switch  131  in the ON sate is shifted to the second OFF state; and a pair of switch elements  135  for switching ON or OFF the push-button switch and a normally close contact  136  as an auxiliary contact. As seen in the figure, the push-button switch  131  has a symmetrical configuration and therefore, the following description discusses a configuration of only a right half thereof while the explanation of a left half thereof is dispensed with. 
   Inside of the push button  133 , there are disposed a first pressing member  139  operatively associated with pressing-down on the push button  133  for depressing the switch element  135 , and a second pressing member  140  operatively associated with pressing-down on the push button  133  for depressing the normally close contact  136 . The normally close contact  136  is located centrally of the switch case  132 , whereas the pair of switch elements  135  having the slow action configuration are located at opposite ends of the switch case as sandwiching the normally close contact  136  therebetween. 
   The normally close contact  136  is essentially configured the same way as the normally close contact  61  of the first embodiment described above. Specifically, as shown in  FIG. 11 , the normally close contact  136  comprises a movable member  138  disposed in the switch case  132  and projecting toward the push button  133  (upwardly) as urged upward by a helical spring  137  disposed therebelow; a pair of movable terminals (not shown) attached to the movable member  138 ; and a pair of stationary terminals (not shown) brought into or out of contact with the movable terminals. In an initial state, the movable member  138  is urged upward by the helical spring  137 , while the movable terminals and the stationary terminals are in contact with each other to establish a closed state. The stationary terminals are electrically connected with a terminal piece  141  projecting downwardly from the switch case  132 , the terminal piece  141  connected with the board  41  of the terminal block  9  via the conductor  39  (see FIG.  4 ). 
   The switch element  135  comprises a case portion  142 ; a depression member  143  depressibly supported by the case portion  142 ; a pair of stationary terminals  145  each attached to one end of a leaf spring  144  disposed in the case portion  142 ; a pair of movable terminals  147  attached to a bracket  146  and brought into or out of contact with the stationary terminals  145 ; and a switching mechanism  148  operatively associated with pressing-down on the depression member  143  for bringing the movable terminals  147  into contact with the stationary terminals  145 , but adapted to move the movable terminals  147  away from the stationary terminals  145  when the depression reaches a predetermined amount. Each of the leaf springs  144  is formed of a conductive member, the other end of which projects downwardly from the switch case  132  to define a terminal piece  149 , which is connected with the board  41  of the terminal block  9  via the conductor  39 . It is noted here that the movable terminal  147  and the stationary terminal  145  of the switch element  135  constitute an a-contact. 
   An accommodating portion  151  of a rectangular shape in plan is defined in the depression member  143 , and is formed with slopes  152  at opposite side walls thereof. On the other hand, a pair of projections  150  for pressing down on the leaf springs  144  are provided at a bottom of the depression member  143 . 
   The switching mechanism  148  comprises an insertion member  154  disposed in the accommodating portion  151  of the depression member  143  and formed with a pair of cavities  153 ; a pair of slide blocks  155  disposed in the individual cavities  153  of the insertion member  154  as allowed to move horizontally (lateral directions as seen in FIG.  11 ); a helical spring  156  coupling the insertion member  154  with the bracket  146  for urging the movable terminals  147  downwardly; and a shaft member  157  projecting downwardly from the bracket  146 . 
   The slide blocks  155  are urged toward opposite ends of the depression member  143  by means of helical springs  158  disposed in the cavities  153  of the insertion member  154 . The slide blocks  155  are each formed with a slope  161  at one end thereof, the slope  161  engaged with each corresponding slope  152  of the depression member  143 . 
   The shaft member  157  has its lower part inserted in a hole  162  formed at a bottom of the case portion  142 . The hole  162  receives a return spring  163 , an upper end of which is anchored to a lower end of the shaft member  157 . The shaft member  157  is constantly urged upward by means of an urging force of the return spring  163 . 
   When the push button  133  in the first OFF state (undepressed) is pressed down, the first pressing member  133  of the push button  133  presses down on an upper surface of the depression member  143 , as shown in FIG.  12 . Thus, the switching mechanism  148  operatively associated with the depression member  143  is moved down to push down the movable terminals  147 , which come into contact with the stationary terminals  145 . In this state, the push-button switch  131  is shifted to the ON state, enabled for teaching operation to the industrial machinery  203  (see FIG.  17 ). 
   At this time, pressing forces from the slopes  152  of the accommodating portion  151  act on the slopes  161  of the slide blocks  155  to move the slide blocks  155  inwardly. However, the urging force of the helical spring  156  urging the slide blocks  155  upwardly overcomes the pressing forces, so that the slide blocks  155  are not moved, maintained in the engaged relation with the depression member  143 . 
   When the operator, being aware of any potential danger, presses further down on the push button  133  in the ON state, the urging force of the helical spring  156  overcomes the forces urging the slide blocks  155  outwardly, so that the slide blocks  155  with their slopes  161  sliding on the slopes  152  of the accommodating portion  151  are moved inwardly of the insertion member  154  against the helical springs  158 . As a result, the slide blocks  155  are released from the engaged relation with the depression member  143  so that the switching mechanism  148  is moved upward by means of the return spring  163 , as shown in FIG.  13 . This also moves up the movable terminals  147 , which go out of contact with the stationary terminals  145 , so that the push-button switch  131  is shifted to the second OFF state where the industrial machinery is deactivated. At this time, the projections  150  of the depression member  143  push down the leaf springs  144 , thereby forcefully moving the movable terminals  147  away from the stationary terminals  145  even if the movable terminals  147  are fused to the stationary terminals  145 , for example. Thus is ensured that the push-button switch  131  in the ON state is positively shifted to the second OFF state. 
   On the other hand, when the push-button switch  131  in the ON state is shifted to the second OFF state, the movable member  138  of the normally close contact  136  is pushed down by the second pressing member  140  of the push button  133 . Therefore, the movable terminals of the normally close contact  136  go out of contact with the stationary terminals thereby to open the normally close contact  136 . Thus, the normally close contact  136  is closed in the first OFF state, and is opened in the second OFF state. Accordingly, the push-button switch  131  can be readily determined to be in the first OFF state or in the second OFF state by monitoring the normally close contact  136 . 
   In this embodiment wherein the push-button switch  131  of the slow action type is employed in place of the push-button switch  5  of the snap action type, it goes without saying that the cable  7  can be readily replaced at low cost just as in the first embodiment. The push-button switch  131  can be set to any of three positions (the first OFF state, the ON state and the second OFF state) according to the amounts of push-button depression  133 . The push-button switch  131  provides for a tangible indication of intent of the operator, such that the safety of the operator is ensured. 
   (Third Embodiment) 
   A third embodiment will be described with reference to  FIGS. 14  to  16 .  FIG. 14  is side elevation showing a grip type switch device, whereas  FIG. 15  is a sectional view taken on the line A—A in FIG.  14 .  FIG. 16  is a diagram illustrative of how the grip type switch device is used. 
   In this embodiment, an essential configuration of a controller for industrial machinery  201  employing the grip type switch device is substantially the same as that shown in  FIGS. 17  to  19  and therefore, the following description is made with reference to these figures as well, while obviating the redundancy. In this embodiment, essential configurations of the push-button switch  5 , the connection means and the cable  7  of a grip type switch device  181  are substantially the same as those of the first embodiment, as shown in  FIGS. 17  to  19  and therefore, the following description principally discusses differences from the first embodiment while obviating the redundancy. 
   The grip type switch device  181  of this embodiment differs from that of the first embodiment in the configuration of a switch case  183 . Furthermore, this embodiment differs from the first embodiment in that the controller  201  is provided with a safety switch  184 . 
   As shown in  FIG. 14 , the switch case  183  is provided with a receiving portion  187  for receiving an actuator  185  at the other end thereof which is opposite to the one end thereof through which the cable  7  is introduced. The actuator  185  is retractably disposed in the receiving portion  187 . 
   As shown in  FIGS. 14 and 15 , the receiving portion  187  is formed with an aperture  189  at an end face thereof. An operation lever  191  fixed to one surface of the actuator  185  projectingly extends through the aperture  189 . The actuator  185  may be projected from the receiving portion  187  or retracted into the receiving portion  187  by manipulating the operation lever  191 . In this case, a lock mechanism (not shown) is provided such that the actuator  185  in the projected position is less prone to be retracted into the receiving portion  187  or that the actuator  185  in the retracted position is less prone to be projected from the receiving portion  187 . 
   The safety switch  184  is electrically connected with the control panel  209  (see  FIG. 17 ) disposed on the safety fence  207 , as shown in FIG.  16 . The safety switch  184  is essentially configured the same way as the safety switch  215  shown in FIG.  17  and comprises a case body  193  and c-contacts (not shown) disposed in the case body. A main difference from the safety switch  215  shown in  FIG. 18  is that the actuator  185  is mounted to the switch case  183  rather than to the door  213 . The safety switch  184  is fixed to the outside surface of the safety fence  207  in adjoining relation with the control panel  209 . 
   As shown in  FIG. 16 , the case body  193  is formed with an insertion hole  195  on one surface thereof, the insertion hole  195  adapted to receive the actuator  185 . In a case where the grip type switch device  181  is not used or where the industrial machinery (industrial robot)  203  is externally controlled via the control panel  209  (see FIG.  17 ), the grip type switch device  181  is mounted to the safety switch  184  by inserting the actuator  185  in the insertion hole  195 . 
   The c-contacts of the safety switch  184  is electrically connected with the control panel  209  (see  FIG. 17 ) and hence, the contacts of the safety switch  184  are closed when the actuator  185  is inserted in the safety switch  184  whereby the industrial machinery  203  can be controlled only through the control panel  209 . When, on the other hand, the actuator  185  is extracted from the safety switch  184 , the c-contacts of the safety switch  184  are opened, so that the control panel  209  is disabled to control the industrial machinery  203  while the industrial machinery  203  can be manually operated only through the teaching pendant  227  (see  FIG. 19 ) or the grip type switch device  181 . The safety switch  184  also differs from the safety switch  215  shown in  FIG. 17  in that the safety switch  184  functions to switch the control panel  209  between an enable state for control of the industrial machinery  203  and a disable state for control of the same. 
   In the grip type switch device  181 , the cable  7  is connected by way of the terminal block  9  or the connector similarly to the first embodiment described above. Therefore, the cable  7  can be readily replaced by taking the same procedure as in the first embodiment. 
   Next, description is made on operations of the grip type switch device  181  of the above configuration. In the manual operation of the industrial machinery  203 , the grip type switch device  181  is dismounted to extract the actuator  185  from the safety switch  184 . This switches the c-contacts in the safety switch  184  so as to disable the control panel  209  to control the industrial machinery  203 . Thus, the industrial machinery  203  inside of the safety fence  207  is placed in a mode to be taught only through the teaching pendant  227  or the grip type switch device  181 . 
   Then, while the door  213  in the doorway of the safety fence  207  held open, the operators with the grip type switch devices  181  enter the zone inside of the safety fence  207 , where the operators manually operate the industrial machinery  203  or perform the program teaching via the teaching pendant  227 . That is, by opening the door  213  of the safety fence  207 , the contacts in the safety switch  215  are opened so that the power to the industrial machinery  203  is cut off while only the manual operation is effective. 
   After the actuator  185  is extracted from the safety switch  184 , the operation lever  191  may be manipulated to retract the actuator  185  into the receiving portion  187 . This prevents the actuator  185  from contacting the machinery or any other operator during the work. 
   In the third embodiment, it goes without saying that the cable  7  can be readily replaced at low cost just as in the first embodiment described above. In addition, when the actuator  185  is extracted from the safety switch  184 , the c-contacts in the safety switch  184  are shifted so that the control panel  209  is disabled to control the industrial machinery  203 , which can be operated only by the grip type switch device  181 . Therefore, if anyone outside the safety fence  207  should mistakenly manipulate the control panel  209  during the execution of manual operation of the industrial machinery  203  inside of the safety fence, for example, the industrial machinery  203  is never activated and the safety during the work can be enhanced. 
   Even if the door  213  of the safety fence  207  is inadvertently closed while the industrial machinery  203  is manually operated, the power supply to the industrial machinery  203  can be inhibited so that the industrial machinery  203  is prevented from being activated. This results in the enhanced safety during the work. 
   In the third embodiment described above, the grip type switch device  181  may be provided with the indication means such as the two LEDs for indicating the ON and OFF states of the switch. The switch device may be further provided with the drive switch  111  as shown in  FIG. 9  or with the emergency stop switch  113  as shown in FIG.  10 . 
   Needless to say, the push-button switch  131  of the slow action type illustrated in the second embodiment may be used as the push-button switch disposed in the grip type switch device  181 . 
   Although the three-position type push-button switches are employed as the push-button switches disposed in the grip type switch devices of the foregoing embodiments, the present invention is not limited to this. The present invention may employ a two-position type push-button switch which is switched between ON and OFF by push-button depression. 
   The foregoing embodiments illustrate the examples where the push-button switch includes the two c-contacts or a-contacts. It goes without saying that the push-button switch may include one contact or three or more contacts. 
   It is noted that the watertight means and the indication means of the present invention are not limited to the watertight packing  17  and the LEDs  37   a ,  37   b  illustrated in the foregoing embodiments. As a matter of course, the configuration of the guard member  27  is not also limited to that illustrated by the above embodiments. In short, the guard member may be so configured as to permit the push-button switch to be manipulated and to cover a part of the push button thereby to prevent the push button from being depressed by the adhesive tape wound therearound. 
   In an alternative arrangement, a sensor for detecting a human hand gripping the switch case may be provided in place of the guard member  27 . The arrangement is made such that the push-button switch can be switched ON or OFF only when the sensor detects the human hand gripping the switch case. In this manner, the grip type switch device is prevented from being used with the adhesive tape wound therearound. As this sensor, an electrostatic condenser type sensor is preferred, which provides an easy and reliable detection of the human hand gripping the switch case based on the variations of capacitance. 
   It is to be noted that the present invention is not limited to the foregoing embodiments and various changes and modifications may be made thereto within the scope of the invention. 
   INDUSTRIAL APPLICABILITY 
   As mentioned supra, the grip type switch device according to the present invention is arranged such that the cable is removably held in electrical connection with the push-button switch by way of the connection means contained in the switch case. In the case of damage on the cable, for example, the cable alone can be removed from the grip type switch device for replacement. In contrast to the prior art, the present invention does not require the whole grip type switch device to be replaced by a new one when the cable is damaged. Furthermore, the present invention does not require an expensive connector such as the watertight connector. Thus, the maintenance cost associated with the cable replacement can be reduced. 
   In addition, the grip type switch device according to the present invention features the terminal block as the connection means, wherein the conductive connection portions, on the one side, at the terminal block electrically connected with the push-button switch are removably fitted with the conductive connection portions, on the other side, attached to the leading ends of the cores of the cable. Therefore, the cable can be replaced by releasing the cores of the cable from the terminal block. Furthermore, the less costly terminal block provides for the connection between the push-button switch and the cable and hence, a simple connection structure results. Thus, the maintenance cost for the grip type switch device can be reduced. 
   In addition, the grip type switch device according to the present invention features the connection means which consists of the connector including the connector portion for the switch and the connector portion for the cable. In order to replace the cable, therefore, the fitted connector portions only need be disengaged from each other, so that the cable replacement is facilitated. In addition, the push-button switch and the cable are interconnected by way of the less costly connector, which contributes to the simple configuration. Thus, the maintenance cost for the grip type switch device can be reduced. 
   In the grip type switch device according to the present invention, the push-button switch thereof is adapted to be shifted from the first OFF state to the ON state and then to the second OFF state according to the increased amounts of push-button depression. Thus, the push-button switch in the ON state can be returned to the first OFF state by releasing the push button, or conversely to the second OFF state by pressing further down on the push button. Thus, the safety of the operator can be enhanced. 
   The auxiliary contact assuming different open/close positions in the first OFF state and the second OFF state is provided in the switch case. Therefore, whether the push-button switch is in the first OFF state or in the second OFF state can be readily determined by monitoring the open/close position of the auxiliary contact. 
   The controller for industrial machinery employing the grip type switch device according to the present invention is arranged such that the control panel for industrial machinery is disabled when the push-button switch of the grip type switch device is ON. This prevents the industrial machinery from being inadvertently activated by someone outside the partitioning means that manipulates the control panel when the industrial machinery is subjected to the program teaching via the grip type switch device. Thus, the safety of the operator performing the teaching operation can be ensured.