Patent Publication Number: US-7584946-B2

Title: Electric positioning and clamping apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Applicant hereby claims foreign priority benefits under U.S.C. § 119 from Japanese Patent Application No. 2007-196300 filed on Jul. 27, 2007, the contents of which are incorporated by reference herein. 
   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates to an electric positioning and clamping apparatus for positioning and fixing a panel material using a locating pin. 
   BACKGROUND OF THE INVENTION 
   An automobile body is formed by joining a plurality of panel materials by spot welding, and it is necessary to position and clamp various panel materials configuring the automobile body in performing the spot welding. Therefore, in order to position and clamp the panel materials, a plurality of positioning and clamping apparatuses are attached to a welding stage arranged in an automobile manufacturing line. On a conveying truck which conveys the panel materials, as described in Patent Documents 1 (Japanese Patent Application Laid-Open Publication No. 2003-159617) and 2 (Japanese Patent Application Laid-Open Publication No. 2003-165037), the plurality of positioning and clamping apparatuses are mounted in order to clamp the panel materials. Further, positioning and clamping of the panel materials by the positioning and clamping apparatus are performed by mounting the positioning and clamping apparatus to a tip of a robot arm to operate and move the robot arm. 
   In each of above cases, the conventional positioning and clamping apparatus has the locating pin which is fitted in a positioning hole formed in the panel material as a workpiece, and the panel material is intended to be positioned by fitting the locating pin into the positioning hole. A clamp arm is assembled in a slit formed in the locating pin in order to clamp the panel material, so that when the panel material is clamped, the clamp arm is caused to protrude from an interior of the slit. 
   SUMMARY OF THE INVENTION 
   When a clamping apparatus for clamping the panel materials is equipped with the conveying truck for conveying the panel materials, as described in Patent Documents 1 and 2, a driving source such as an electric motor or pneumatic cylinder is not equipped with the conveying truck in order to miniaturize the clamping apparatus, and the clamp arm is intended to be driven by the driving source provided to a stage for conveying-in or conveying-out of the panel material after the conveying truck stops. Meanwhile, when the clamping apparatus is disposed on the welding stage arranged in the automobile manufacturing line or is attached at a tip of the robot arm, the driving source must be provided to the clamping apparatus. 
   For example, when the clamping apparatus is disposed on the welding stage, one panel material is positioned using a plurality of, for example, three locating pins in order to enhance position accuracy of the panel material. Further, in the automobile manufacturing line, the plurality of panel materials are conveyed into a single welding stage in order to manufacture a plurality of vehicle types or plurality of vehicle models in a mixing manner. For example, when a plurality of kinds of panel materials are conveyed into the single welding stage, positions through which the locating pin passes are different among respective kinds of panel materials, so that the plurality of kinds of clamping apparatuses must be provided to the single welding stage so as to correspond to the kinds of the panel materials. For this reason, even when each panel material is positioned at its three locations, twenty-four clamping apparatuses are disposed on the welding stage in which eight kinds of panel materials are conveyed. 
   In the conventional positioning and clamping apparatuses, the clamp arm is intended to be driven by pneumatic pressure or an electric motor. Therefore, in order to drive the clamp arm, when compressed air is supplied from a pneumatic-pressure supplying source to a piston, compressed air is branched from a compressed-air supplying source such as a compressor and is supplied to the respective positioning and clamping apparatuses. When the positioning and clamping apparatuses are actuated by compressed air, a distance between a solenoid valve for controlling supply of compressed air and a piston of the positioning and clamping apparatus is different per positioning and clamping apparatus. In addition, since there is a limit to a flow rate of compressed air, when the positioning and clamping apparatuses are a pneumatic pressure actuation type utilizing compressed air as a driving medium, there is the problem that a difference in actuated timing occurs mutually among the plurality of positioning and clamping apparatuses. 
   Meanwhile, as described in above Patent Documents, the positioning and clamping apparatus in which the clamp arm is driven by an electric motor has been applied to a type of separating the electric motor from the positioning and clamping apparatus, similarly to a positioning and clamping apparatus mainly equipped with the conveying truck, since the electric motor must be made larger for obtaining a clamping force. 
   In order to assemble the electric motor serving as a driving source into the positioning and clamping apparatus, as described in above Patent Documents, a spring member for locking is disposed between a cam and a driving rod, and a spring force which has been converted via a cam pin and a cam groove is transmitted as a clamping force caused by the clamp arm. For this reason, a structure of a driving section of the clamp arm is apt to be large, so that the positioning and clamping apparatus cannot be miniaturized. 
   An object of the present invention is to provide an electric positioning and clamping apparatus in which an electric motor is assembled. 
   Another object of the present invention is to provide a small-sized electric positioning and clamping apparatus. 
   An electric positioning and clamping apparatus according to the present invention comprises: a workpiece supporting stand having, at its tip, a workpiece supporting face contacting with a panel material; a locating pin attached to the workpiece supporting stand so as to protrude from the workpiece supporting face, and fitted into a positioning hole formed in the panel material; a clamp arm accommodated in a slit, which is formed in the locating pin so as to be open in a diametrical direction of the locating pin, the clamp arm being swingable between a clamp position where the clamp arm protrudes from the slit to clamp the panel material between the workpiece supporting face and the clamp arm and an escape position where the clamp arm enters into the slit; a driven rod mounted to the workpiece supporting stand so as to be reciprocable axially between a retreat-limit position corresponding to the clamp position of the clamp arm and an advance-limit position corresponding to the escape position of the clamp arm, a tip of the driven rod being coupled to the clamp arm; a driving rod mounted in a gear box attached to the workpiece supporting stand so as be reciprocable axially between the retreat-limit position and the advance-limit position, the driving rod being coupled to a rear end of the driven rod; a spring member mounted between the driven rod and the driving rod, and applying a clamping force to the clamp arm via the driven rod when the driving rod is at the retreat-limit position; a cam block assembled in the gear box so as to be reciprocable in a direction of intersecting the driving rod, having a cam face contacting with an engagement cam attached to the driving rod, and causing the driving rod to be driven between the retreat-limit position and the advance-limit position; and an electric motor assembled in the gear box, and causing the cam block to reciprocate, via a reduction gear mechanism, between a clamp position corresponding to the retreat-limit position and an unclamp position corresponding to the advance-limit position. 
   The electric positioning and clamping apparatus according to the present invention further comprises a lock face formed in the cam block, the lock face restricting movement of the engagement cam when the cam block drives the driving rod up to the retreat-limit position. 
   In the electric positioning and clamping apparatus according to the present invention, the spring member is a compression coil spring assembled between an accommodating box fixed to the driving rod and a flange provided to an end portion of the driven rod inserted into the accommodating box. 
   In the electric positioning and clamping apparatus according to the present invention, the reduction gear mechanism is plural-stage reduction gear pairs for reducing rotation of the electric motor. 
   The electric positioning and clamping apparatus according to the present invention is such that a rack gear meshing with a pinion gear provided at a final stage among the plural-stage reduction gear pairs is attached to the cam block. 
   According to the present invention, the electric motor is used as a driving source to convert its rotation to a reciprocating motion of the cam block via the reduction gear mechanism, the clamp arm is opened and closed via the driven rod by the driving rod driven by the cam block, and the spring member for applying a clamping force to the clamp arm is mounted between the driven rod and the driving rod. Therefore, a portion of the cam block can be simply configured, and simultaneously the clamp arm can be fixed at the clamp position. For this reason, without making the positioning and clamping apparatus large, the electric motor assembled in the positioning and clamping apparatus is used as a driving source to clamp the panel material, whereby the clamping force can be applied to the panel material via the clamp arm. 
   The spring member is provided between the driven rod and the driving rod, and when the driving rod is at the retreat-limit position, a spring force is applied to the clamp arm. Therefore, the present invention can reliably maintain a state where the clamp arm clamps the panel member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing an entire electric positioning and clamping apparatus; 
       FIG. 2  is an enlarged sectional view of  FIG. 1 ; 
       FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 ; and 
       FIG. 4  is an exploded perspective view showing a locating jig and a workpiece supporting ring. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the present invention will be described in detail below with reference to the drawings.  FIG. 1  is a perspective view showing an entire electric positioning and clamping apparatus;  FIG. 2  is an enlarged sectional view of  FIG. 1 ; and  FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 . 
   The electric positioning and clamping apparatus has a workpiece supporting stand  10  supporting a panel material P. The workpiece supporting stand  10  includes a cylindrical fixing pedestal  11  integrated with a rectangular pedestal plate  11   a  at a base end portion of the fixing pedestal  11 , and a cylindrical coupling case  12  fixed to the pedestal plate  11   a , wherein a locating jig  13  is disposed at a tip of the fixing pedestal  11 . The locating jig  13  is attached to the fixing pedestal  11  via a workpiece supporting ring  14 , and a workpiece supporting face  15  with which a panel member P contacts is provided to the workpiece supporting ring  14 . In order to attach the workpiece supporting ring  14  to the fixing pedestal  11 , as shown in  FIG. 1 , a plurality of attaching holes  14   a  are formed in the workpiece supporting ring  14 , and the workpiece supporting ring  14  is fixed to the fixing pedestal  11  by bolts (not shown) assembled in the respective attaching holes  14   a.    
     FIG. 4  is an exploded perspective view showing the locating jig  13  and the workpiece supporting ring  14 . The locating jig  13  includes a circular flange  16  clamped between a tip face of the fixing pedestal  11  and the workpiece supporting ring  14 , and a locating pin  17  integrated with the flange  16 , wherein attaching holes  16   a  are formed in the flange  16  so as to correspond to the attaching holes  14   a  of the workpiece supporting ring  14 . Accordingly, when the locating jig  13  is disposed at the tip of the fixing pedestal  11  by the workpiece supporting ring  14  to attach the workpiece supporting ring  14  and the locating jig  13  by bolts, the locating pin  17  becomes in a state of projecting from the workpiece supporting face  15  located at the tip of the workpiece supporting stand  10 . By fitting, to the locating pin  17 , a positioning hole H formed in the panel member P, the panel member P is positioned by the locating pin  17 . 
   A slit  18  is formed in the locating pin  17  so as to be open in a diametrical direction of the locating pine  17 , and the slit  18  reaches a portion of the flange  16  from a portion of the locating pin  17 , as shown in  FIG. 4 . 
   As shown in  FIG. 2 , a clamp arm  21  is accommodated in the slit  18 , and the clamp arm  21  becomes swingable between a clamp position as shown by a solid line in  FIG. 2  and an escape position as shown by a double-dot line in  FIG. 2 , the clamp position being a position where a clamp piece  22  which is at a tip of the clamp arm  21  protrudes from the slit  18  to clamp the panel material P between the clamp arm  21  and the workpiece supporting face  15 , and the escape position being a position where the clamp piece  22  enters into the slit  18 . 
   A driven rod  24  is assembled axially reciprocably in a through hole formed in a partition wall  23  fixed in the coupling case  12  configuring the workpiece supporting stand  10 , and a base end of the clamp arm  21  is linked to the driven rod  24  by a coupling pin  25  fixed to a tip of the driven rod  24 . The driven rod  24  reciprocates between a retreat-limit position corresponding to the clamp position of the clamp arm  21  and an advance-limit position corresponding to the escape position of the clamp arm  21 . A cam groove  26  is formed in the clamp arm  21 , and a cam pin  27  penetrating the cam groove  26  is fixed to the fixing pedestal  11 . The cam groove  26  includes a straight section  26   a  formed in parallel with a longitudinal direction of the clamp arm  21 , and an incline section  26   b  formed so as to incline from a base end portion of the straight section  26   a . Accordingly, when the straight section  26   a  slides along the cam pin  27  according to the driven rod  24  moving toward the retreat-limit position, the clamp piece  22  protrudes from the slit  18  to the outside. For this reason, as shown by the double-dot line in  FIG. 2 , as the driven rod  24  moves toward the advance-limit position, the incline section  26   b  approaches the position of the cam pin  27  so that the clamp arm  21  is at the escape position of entering into the slit  18 . 
   A gear box  31  formed into a rectangular solid shape as a whole is attached to the base end of the coupling case  12  configuring the workpiece supporting stand  10 , and the gear box  31  includes a main body portion  31   a , a bottom wall portion  31   b  fixed to a bottom face of the main body portion  31   a , and a top wall portion  31   c  fixed to an upper face of the main body portion  31   a . In the gear box  31 , a driving rod  32  is coaxial with the driven rod  24  so as to be mounted axially reciprocably between the advance-limit position and the retreat-limit position, and simultaneously a cam block  33  is reciprocably mounted in a direction approximately perpendicular to the driving rod  32  and in a direction of intersecting the driving rod  32 . The cam block  33  reciprocates so as to be guided, as shown in  FIG. 2 , by two roller bearings  34  with which an upper face of the cam block  33  in shown  FIG. 2  contacts and by two roller bearings  35  with which a lower face of the cam block  33  in  FIG. 2  contacts, and simultaneously so as for both side faces of the cam block in  FIG. 3  to contact with and be guided by inner faces of the gear box  31 . Incidentally, the driving rod  32  and the driven rod  24  are coaxial with each other, but if both the rods reciprocate in the same direction, their centers may be deviated from each other. 
   A slit  36  is formed, as shown in  FIGS. 2 and 3 , in the cam block  33  so as to penetrate vertically, and the driving rod  32  is provided with a holder  37  assembled in the slit  36 . Engagement cams  39  with roller shapes are rotatably mounted on both end portions of a supporting pin  38  fixed to the holder  37 . The engagement cam  39  is assembled in a cam groove  40  formed in the cam block  33  so that the cam groove  40  penetrates the cam block  33  in a width direction of the cam block  33 , whereby an inner peripheral face of the cam groove  40  serves as a cam face  41  contacting with the engagement cam  39 . The cam groove  40  is inclined along a moving direction of the cam block  33  and the cam block  33  moves between a clamp position shown by a solid line in  FIG. 2  and an unclamp position shown by a double-dot line in  FIG. 2 . When the cam block  33  is at the clamp position, the engagement cam  39  is, as shown in  FIG. 2 , at the farthest position separated from the driven rod  24 , and the driving rod  32  is driven to the retreat-limit position at this time. Meanwhile, when the cam block  33  is at the unclamp position, the engagement cam  39  is at the nearest position approaching to the driven rod  24 , and the driving rod  32  is at the advance-limit position. Formed in the cam face  41  is a lock face  41   a  for stopping movement of the driving rod  32  when the cam block  33  is at the clamp position. The lock face  41   a  is directed in a direction approximately perpendicular to the axial direction of the driving rod  32 . When the engagement cam  39  contacts with the lock face  41   a , movement of the engagement cam  39  is restricted so that the driving rod  32  becomes in a locked state. 
   A cylindrical box body  42  is assembled axially movably in the coupling case  12 , and a tip of the driving rod  32  is fixed to a bottom wall portion of the box body  42 . A lid member  43  is fixed to the box body  42  by screws, so that an accommodating box  44  is formed by the box body  42  and the lid member  43 . A rear end portion of the driven rod  24  penetrating the lid member  43  enters into the accommodating box  44 , and a compression coil spring  45  serving as a spring member is assembled in the accommodating box  44  so that its both end portions contact with a flange  24   a  provided at the rear end of the driven rod  24  and with the lid member  43 . 
   A reciprocating stroke of the driving rod  32  driven by the cam block  33  is set slightly longer than a reciprocating stroke of the driven rod  24  coupled to the driving rod  32 . Therefore, before the cam block  33  reaches the clamp position as shown in  FIG. 2 , the clamp piece  22  of the clamp arm  21  contacts with the panel material P, and the driven rod  24  is at the retreat-limit position. Subsequently, when the driving rod  32  moves up to the retreat-limit position, retreating movement of the driven rod  24  is restricted due to contact between the clamp arm  21  and the panel member P, so that the driven rod  24  moves in a direction of being separate relatively to the driving rod  32 . That is, only the driving rod  32  moves axially, and the compression coil spring  45  is contracted. In  FIG. 2 , a stroke where only the driving rod  32  moves axially to contract the compression coil spring  45  is denoted by the numeral reference “S”. 
   Thereby, when the driving rod  32  is at the retreat-limit position, the engagement cam  39  contacts with the lock face  41   a  so that the driving rod  32  is held by the cam block  33 . At this time, a clamping force is applied to the clamp arm  21  by the compression coil spring  45  via the driven rod  24 . Further, since the compression coil spring  45  has a contraction stroke which is the stroke S in magnitude, a plurality of kinds of panel members P different in thickness can be clamped reliably. Incidentally, when a tensile coil spring is used as a spring member to be mounted between the driving rod  32  and the driven rod  24 , the driving rod  32  and the driven rod  24  can be coupled to each other without using the accommodating box  44 , and simultaneously a clamping force can be applied to the clamp arm  21  via the driven rod  24  when the driving rod  32  is at the retreat-limit position. 
   A rack gear  46  is attached to the cam block  33  by a pin  47 , and the rack gear  46  extends, as shown in  FIG. 3 , in a moving direction of the cam block  33 . As shown in  FIG. 3 , guide rollers  48  rotatably mounted on the gear box  31  contact with a back face of the rack gear  46  so that movement of the rack gear  46  is guided by the guide rollers  48 . A teeth face of the rack gear  46  meshes with a pinion gear  49 , so that the rack gear  46  is driven by the pinion gear  49 . An electric motor  50  is assembled in the gear box  31  in order to drive the cam block  33  via the rack gear  46  between the clamp position and the unclamp position, so that rotation of a main shaft  52  of the electric motor  50  is transmitted to the pinion gear  49  via a reduction gear mechanism  51  provided with three-stage reduction gear pairs. 
   The reduction gear mechanism  51  has a small gear  52   a  attached to the main shaft  52  of the electric motor  50 , and a large gear  53   a  of a gear shaft  53  rotatably mounted to the gear box  31  via a bearing meshes with the small gear  52   a , so that the reduction gear pair is configured by the small gear  52   a  and the large gear  53   a . A small gear  53   b  provided on the gear shaft  53  meshes with a large gear  54   a  of a gear shaft  54  rotatably mounted to the gear box  31  via a bearing, so that a second-stage reduction gear pair is configured by the small gear  53   b  and the large gear  54   a . A small gear  54   b  provided on the gear shaft  54  meshes with a large gear  55   a  of a gear shaft  55 , which is rotatably mounted to the gear box  31  via a bearing and is provided with a pinion gear  49 , so that a final-stage reduction gear pair is configured by the small gear  54   b  and the large gear  55   a . The electric motor  50  is a pulse motor, and when the pinion gear  49  is rotated while the rotation of the electric motor  50  is reduced using the reduction gear mechanism  51  provided with the three-stage reduction gear pairs by driving the electric motor  50 , the cam block  33  is reciprocated between the clamp position and the unclamp position via the rack gear  46  meshing with the pinion gear  49 . A reciprocating stroke of the cam block  33  is set according to the number of pulses supplied to the electric motor  50 . 
   The respective large gears  53   a ,  54   a , and  55   a  are disposed, as shown in  FIG. 3 , in the gear box  31  so as to be shifted in a longitudinal direction of the gear box  31 , so that the three-stage reduction gear pairs can be assembled in the gear box  31  without enlarging a width dimension of the gear box  31 . 
   When the cam block  33  is at the clamp position by driving the electric motor  50 , the engagement cam  39  is engaged with the lock face  41   a . Therefore, application of a clamping force to the panel material P can be continued via the clamp arm  21  without supplying electric power to the electric motor  50 , so that energy efficiency can be improved in comparison with a case where the clamping force is applied by motor torque. Even if power supply is stopped, the clamping force can be maintained. Accordingly, when the positioning and clamping apparatus is equipped with the conveying truck to convey the panel materials by the conveying truck, the panel materials can be each put in a clamped state without supplying electric power to the conveying truck from the outside. 
   Two photo sensors  56  and  57  are provided to the gear box  31  in order to detect arrival of the cam block  22  at the clamp position and arrival thereof at the unclamp position. Each of the photo sensors  56  and  57  detects a sensor dog  58  provided to the cam block  33  to find the position of the cam block  33 . In  FIG. 2 , the sensor dog  58  is at a position of the photo sensor  57 , and the photo sensor  57  detects that the cam block  33  has arrived at the clamp position. 
   The main shaft  52  of the electric motor  50  is such that its tip portion is attached to the small gear  52   a;  its rear end portion opposite to the tip portion protrudes from a motor case; and the rear end portion protrudes into a through hole  61  formed in the top wall portion  31   c  of the gear box  31 . For this reason, the rear end portion of the main shaft  52  is exposed to the outside via the through hole  61 . A tool engagement groove  62  is formed in the exposed rear end portion, so that the main shaft  52  can be manually rotated by causing a rotating tool such as a slotted screwdriver to be engaged with the tool engagement groove  62 . Similarly, a base end portion of the gear shaft  53  protrudes into a through hole  63  formed in the bottom wall portion  31   b  of the gear box  31 , and is exposed to the outside via the through hole  63 . A tool engagement groove  64  is formed in the exposed base end portion, so that the gear shaft  53  can be manually rotated by causing the rotating tool to be engaged with the tool engagement groove  64 . 
   A description will be made of a clamping procedure of the panel materials P using the above-mentioned electric positioning and clamping apparatus. When this positioning and clamping apparatus is attached to the welding stage of the automobile manufacturing line to position and clamp the panel materials P configuring an automobile body, the positioning and clamping apparatus is equipped with the welding stage by bolts attached to the attaching holes  59  formed in the pedestal plate  11   a . The plurality of positioning and clamping apparatuses are equipped with the welding stage, and the positioning holes H fitted into the locating pins  17  are formed in the panel material P in advance so as to correspond to the locating pins  17  of each of the positioning and clamping apparatuses. 
   Before the panel material P is conveyed into the welding stage, the cam block  33  is set at the unclamp position as shown by the double-dot line in  FIG. 2  by the electric motor  50 . Under such a situation, the clamp arm  21  is, as shown by the double-dot line in Figure, at the escape position of entering into the slit  18  of the locating pin  17 . At this situation, the panel material P is conveyed into the welding stage and is placed on the workpiece supporting face  15  of the workpiece supporting stand  10 . Thereby, the locating pins  17  are fitted into the positioning holes H of the panel material P. In  FIG. 2 , a state where two panel materials P have been positioned is shown. 
   When the electric motor  50  is driven in a state of contacting the panel material P with the workpiece supporting face  15 , the rack gear  46  is driven via the reduction gear mechanism  51  so that the cam block  33  is driven from the unclamp position to the clamp position in a direction of intersecting the driving rod  32 . Thus, when the cam block  33  is driven up to the clamp position, the driving rod  32  is driven by the cam face  41  from the advance-limit position to the retreat-limit position via the engagement cam  39 , whereby the driven rod  24  coupled to the driving rod  32  is driven from the advance-limit position to the retreat-limit position. Thereby, the clamp piece  22  of the clamp arm  21  coupled to the driven rod  24  protrudes from the locating pin  17  to the outside so that the panel material P is clamped by the workpiece supporting face  15  and the clamp piece  22 . 
   When the driving rod  32  is moved near the retreat-limit position, the clamp piece  22  contacts with the panel material P so that the clamp arm  21  is at the clamp position, and the driven rod  24  is at the retreat-limit position. Subsequently, when the driving rod  32  is driven up to the retreat-limit position which is a distance corresponding to the stroke S, the accommodating box  44  is moved by the driving rod  32  so that the compression coil spring  45  is contracted and deformed. Thereby, a spring force of the compression coil spring  45  is transmitted to the clamp arm  21  via the driven rod  24  so that the clamping force is applied from the clamp arm  21  to the panel material P. When the driving rod  32  is at the retreat-limit position, the engagement cam  39  contacts with the lock face  41   a  of the cam face  41 , so that the driving rod  32  is maintained in a fixed state without assembling any brake member in the electric motor  50  and without supplying electric power to the electric motor  50 . However, the present invention may have a structure in which a small current is supplied to the electric motor  50  so that an external force for holding the cam block  33  at the clamp position is applied by the electric motor  50 . 
   Thus, welding work is carried out to the panel material P under a state where the panel material P has been clamped by the clamp arm  21 . After the welding work is terminated, the clamp arm  21  is returned back to the escape position shown by the double-dot line in  FIG. 2  by reversing the electric motor  50 , and the panel material P is conveyed to the next step. 
   As described above, a case where the electric positioning and clamping apparatus is disposed on the welding stage in the automobile manufacturing line has been explained, but the positioning and clamping apparatus may be equipped with the conveying truck or be attached to a tip of a robot arm. 
   The present invention is not limited to the above-mentioned embodiment, and may be variously modified and altered within a scope of not departing from the gist of the present invention. For example, a worm, a worm wheel, and the like may be used as the reduction gear mechanism  51 . The electric motor  50  is not limited to a pulse motor, and may be a DC motor or the like.