Patent Publication Number: US-8123914-B2

Title: Electrode plate transportation apparatus

Description:
FIELD 
     The present invention generally relates to an electrode plate transportation apparatus, and more particularly, to an electrode plate transportation apparatus in which many electrode plates are horizontally moved to a position above an electrolytic bath and lifting and lowering the electrode plates so that the electrode plates can be placed in and drawn from the electrolytic bath. 
     BACKGROUND 
     Conventional electrolytic refining of nonferrous metal such as copper or zinc alternately arranges anode plates and cathode plates (electrode plates) in an electrolytic bath having an aqueous solution of salt of a target metal. The electrode plates are energized for a predetermined time, and are lifted to leave the electrolytic bath. The electrolytic refining may be implemented by an electrode plate transportation apparatus. This apparatus is capable of horizontally moving the electrode plates in a suspended state to the position above the electrolytic bath. Further, the electrode plate transportation apparatus is capable of lifting and lowering the electrode plates after the horizontal transportation, so that the electrode plates can be placed in and drawn from the electrolytic bath. 
     The electrode plate transportation apparatus has multiple holding members (hooks) arranged in parallel. The hooks hold the electrode plates in the suspended state. This kind of apparatus is described in, for example, Japanese Examined Patent Application Publication No. 55-36277 (Document 1) or Japanese Patent No. 3579802 (Document 2). 
     An electrode plate transportation apparatus described in Document 1 (named automatic electrode plate replacement apparatus in Document 1) has rails provided at opposite sides of the electrolytic bath. The electrode plates may be moved along the rails and may be stopped. The apparatus is equipped with an electrode plate suspending platform capable of moving up and down. An electrode plate transportation apparatus described in Document 2 has a mechanism for placing and drawing the suspended cathode plates in and from the electrolytic bath, in which the mechanism can move along a guide rail. 
     In the suspended type apparatus as described in Document 2, a shock may occur when the electrode plates (cathode plates) shifts to the stationary state from the moving state, and the cathode plates may swing greatly. Document 2 proposes to use a swing blocking bar for mechanically preventing the cathode plates from swing. 
     However, the mechanical blocking may deform the electrode plates and may cause faulty electrodeposition due to deformation of the electrode plates. 
     When wires are used to suspend the electrode plates, the electrode plates may lose balance. This may cause the member for holding the electrode plates to be horizontally rotated and may make it difficult place the electrode plates in the electrolytic bath. 
     SUMMARY 
     The invention has been made in view of the above circumstance and provides an electrode plate transportation apparatus capable of restraining swinging of electrode plates and changing the attitudes of the electrode plates. 
     According to an aspect of the present invention, there is provided an electrode plate transportation apparatus that lifts and lowers electrode plates moved to a position above an electrolytic bath and places and draw the electrode plates in and from the electrolytic bath, including: a stationary frame that is suspended from an upper position in a vertical direction; a rotary unit that is composed of hold members for holding the electrode plates in a suspended state and is held so as to rotate in a rotational direction about the vertical direction by the stationary frame; and a drive mechanism that is provided between the stationary frame and the rotary unit and applies drive force along an one-axis direction in a plane perpendicular to the vertical direction to the rotary unit to thus drive the rotary unit in the rotational direction. 
     The electrode plate transportation apparatus may be configured so that the rotary unit includes: a rotary frame that is provided above the stationary frame and is rotated about the vertical direction in response to the drive force by the drive mechanism; a base frame that is provided below the stationary frame and supports the hold members; and joint members that join the rotary frame and the base frame. 
     The electrode plate transportation apparatus may further include: a motor attached to the stationary frame; a screw that is attached to a rotary shaft and extends in the one-axis direction; a nut engaged with the screw; and a transfer member that transfers driving force of the nut that is moved along the rotary shaft of the motor by rotation of the screw to a position that is offset from a center of gravity of the rotary unit in the plane in a direction crossing the one-axis direction. 
     The electrode plate transportation apparatus may further include an overload protection mechanism that prevents driving force of the motor from being transferred to the screw when a load exceeding a threshold level is applied. 
     The electrode plate transportation apparatus may further include another driving mechanism that is paired with said driving mechanism and is symmetrical with said driving mechanism about a center of gravity of the stationary frame, wherein said another driving mechanism has a configuration identical to that of said driving mechanism. 
     The electrode plate transportation apparatus may further include a guide mechanism that is provided between the stationary frame and the rotary unit and guides the rotary unit in the rotational direction about the vertical direction. 
     The electrode plate transportation apparatus may be configured so that the guide mechanism includes: a guide member that is fixed to the stationary frame and is formed in an arc shape; and a slider member that is fixed to the rotary unit and slide on the guide member. 
     The electrode plate transportation apparatus may be configured so that the guide mechanism has a stopper that limits a range of movement of the slider member. 
     The electrode plate transportation apparatus as claimed in claim  1 , may further include: a detecting part that detects a relative angle between the rotary unit and the electrolytic bath; and a drive control part that controls the drive mechanism on the basis of the relative angle detected by the detecting part to thus drive the rotary unit in the rotational direction. 
     The electrode plate transportation apparatus may be configured so that the detecting part includes: a marker that indicates an angle of the electrolytic bath; an image taking part that is attached to the rotary unit and takes an image of the marker; and a calculation part that calculates the relative angle on the basis of the image of the maker taken by the image taking part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates an electrode plate transportation apparatus in accordance with a first embodiment of the present invention; 
         FIG. 2  is a plan view of a stationary frame and a rotation drive mechanism of the electrode plate transportation apparatus illustrated in  FIG. 1 ; 
         FIG. 3  is a view of hangers illustrated in  FIG. 1  viewed from an X direction; 
         FIG. 4  is a perspective view of a rotation drive mechanism  40 A; 
         FIG. 5  illustrates the electrode plate transportation apparatus in which a rotary unit is slightly rotated from the state depicted in  FIG. 2 ; 
         FIG. 6  is a block diagram of a control system in accordance with a second embodiment; 
         FIGS. 7A through 7C  illustrate cameras and markers for detecting the orthogonality of the rotary unit; 
         FIGS. 8A through 8C  illustrate exemplary images taken by the cameras; and 
         FIG. 9  illustrates a way to calculate a corrected distance. 
     
    
    
     DETAILED DESCRIPTION 
     A description is now given of embodiments of the present invention with reference to the accompanying drawings. 
     First Embodiment 
       FIGS. 1 through 5  illustrate an electrode plate transportation apparatus in accordance with a first embodiment. In the following description, for the convenience sake, an X direction is defined as a horizontal direction on the drawing sheets, and a Y direction is defined as a direction perpendicular to the drawing sheets, while a Z direction is defined as a vertical direction on the drawing sheets. 
     Referring to  FIG. 1 , an electrode plate transportation apparatus  100  in accordance with the first embodiment is equipped with a stationary frame  10 , that is held in a suspended state by a ceiling travel crane (not shown), and a rotary unit  12  that is rotatably held about the vertical direction (the Z-axis direction) with respect to the stationary frame  10 . The center of gravity of the stationary frame  10  and that of the rotary unit  12  coincide with each other (see symbol G in  FIG. 2 ). 
     As illustrated in  FIG. 2 , the stationary frame  10  has a pair of first beams  14   a ,  14   b  running in the Y-axis direction, and a pair of second beams  16   a  and  16   b  running in the X-axis direction. The stationary frame  10  has a rectangular shape as a whole. Two engagement portions  13  are provided on the upper surface of each of the first beams  14   a  and  14   b . Hooks  11  of the ceiling travel crane are engaged with the engagement portions  13 , so that the stationary frame  10  can be suspended. 
     As illustrated in  FIG. 1 , the rotary unit  12  has a rotary frame  18 , a base frame  20 , and multiple joint members (steel members)  22 . The rotary frame  18  is provided above the stationary frame  10 . The base frame  20  is provided below the stationary frame  10 . The multiple joint members  22  join the rotary frame  18  and the base frame  20 . 
     The rotary frame  18  has a member of a rectangular plate having the longitudinal sides running in the X-axis direction, and is supported by the stationary frame  10  from the lower side of the rotary frame  18  so that the rotary frame  18  can be rotated about the Z axis with respect to the stationary frame  10 . 
     The base frame  20  includes a pair of main beams running in the X-axis direction, and multiple sub beams that join the pair of main beams at multiple positions and run in the Y-axis direction. These beams are not illustrated for the sake of simplicity. There are many hangers  26  (for example, 50 to 60 hungers) attached to the lower side of the base frame  20  and used for holding the electrode plates in the suspended state. As can be seen from  FIG. 3  in which the hangers  26  are viewed from the −X side, each of the hangers  26  has a hook hold member  28 , a pair of hooks  30  for suspending an anode plate A, and a pair of hooks  32  for suspending a cathode plate C. The hook hold member  28  runs in the Y-axis direction. The two hooks  30  are respectively provided on opposite ends of the hook hold member  28  in the Y-axis direction. The hooks  32  are provided further in than the hooks  30 . The pair of hooks  30  holds the anode plate A in the suspended state, and the pair of hooks  32  holds the cathode plate C in the suspended state. The hooks  30  and  32  are allowed to rotate about the Z axis by a driving mechanism (not illustrated). By rotating the hooks  30  and  32 , the hooks  30  may be engaged with and disengaged with the anode plate A, and the hooks  32  may be engaged with and disengaged with the cathode plate C. 
     Turing to  FIG. 1  again, there are rotation drive mechanism  40 A and  40 B between the stationary frame  10  and the rotary frame  18 . These mechanisms  40 A and  40 B rotate the rotary unit  12  with respect to the stationary frame  10 . 
     As illustrated in the perspective view of  FIG. 4 , the rotation drive mechanism  40 A is equipped with a linear drive mechanism  42 , a transfer member  44 , and a guide mechanism  46 . The linear drive mechanism  42  is mounted on the surface of the stationary frame  10  on its +X side (more particularly, the first beam  14   a ). The transfer member  44  transfers the driving force of the linear drive mechanism  42  to the rotary frame  18 . The guide mechanism  46  guides the rotary frame  18  in the rotational direction about the Z axis. 
     The linear drive mechanism  42  has a drive motor  50 , a screw  52 , a nut  54  and a T-shaped moving member  56 . The screw  52  may be a trapezoidal screw connected to the rotary shaft of the drive motor  50 . The nut  54  may be a trapezoidal nut that is penetrated through the moving member  56  and is screwed onto the screw  52 . The moving member  56  is fixed to the nut  54  so as to form a single piece and has a T shape viewed from the +Z direction. 
     The drive motor  40  generates rotating force about the Y axis, and is fixed to the stationary frame  10  (more specifically, the first beam  14   a ) by screws. The drive motor  50  is connected to a motor control circuit (not illustrated). An input or man-machine interface such as a joystick is connected to the motor control circuit, which controls the rotation of the drive motor  50  in accordance with an instruction from the operator applied via the input interface. 
     The ends of the screw  52  are held by a pair of hold members  58 A and  58 B fixed to the stationary frame  10  by welding. The hold members  58 A and  58 B are provided with ball bearings into which the screw  52  is inserted. Thus, the screw  52  is allowed to rotate about the Y axis. The screw  52  is rotated by the rotating force of the drive motor  50 . The nut  54  engaged with the screw  52  may be moved in the +Y or −Y direction based on the rotating direction and speed of the screw  52 . The screw  52  and the nut  54  form a feed screw mechanism. 
     As illustrated in  FIG. 4 , an overload protection mechanism (torque limiter)  62  is provided between the drive motor  50  and the screw  52 . The torque limiter  62  prevents the rotating force of the drive motor  50  from being transferred to the screw  52  when a load that exceeds a threshold level is applied on the drive motor  50 . 
     The moving member  56  has a first plate member  56   a  and a second plate member  56   b . The second plate member  56   b  is engaged with a guide member  60 , which is welded to the stationary frame  10  and is formed into a C-shape viewed from the −Y axis. The second plate member  56   b  is an un-refuel slide plate and is slidable along the guide member  60  in the Y-axis direction. 
     In the linear drive mechanism  42  thus configured, the motor control circuit adjusts the rotating direction and revolution of the drive motor  50 , so that the moving member can slide in the Y-axis direction. 
     As illustrated in  FIG. 4 , the transfer member  44  has an about π shape, and engages a +X-side end of the moving member  56  (first plate member) in a recess  44   b  defined by arm-shaped portions formed in the lower side of the transfer member  44 . In  FIG. 4 , the transfer member  44  and the moving member  56  are separate from each other for the convenience&#39;s sake. The transfer member  44  and the first plate member  56   a  are not fixedly attached to each other. Thus, the transfer member  44  can slide on the first plate member  56   a  in the X-axis direction. In other words, the transfer member  44  can change the relative position in the X-axis direction. The distance between the two arms of the lower portion of the transfer member  44  in the Y-axis direction is set slightly greater than the width of the first plate member  56   a  in the Y-axis direction. 
     As illustrated in  FIG. 1 , the transfer member  44  of the rotation drive mechanism  40 A has an upper surface  44   a  fixed to the lower surface of the rotary frame  18  by screws. Thus, as illustrated in  FIG. 5 , the driving force F 1  in the Y-axis direction generated by the motors  50  of the rotation drive mechanism  40 A is transferred, via the transfer member  44 , to a position that is offset from the center of gravity G of the rotary frame  18  in the +X direction. 
     Turning back to  FIG. 4 , the guide mechanism  46  has a guide member  64 , and a pair of slider members  66   a  and  66   b . The guide member  64  is fixed to the upper surface of the first beam  14   a  of the stationary frame  10  and has an arc shape. The slider members  66   a  and  66   b  are slidable on the guide member  64 . The upper surfaces of the slider members  66   a  and  66   b  are fixed to the lower surface of the rotary frame  18 . In the first embodiment, as illustrated in  FIG. 5 , the guide mechanism  46  changes the driving force (F 1 ) transferred to the rotary frame  18  from the linear drive mechanism  42  to driving force (F 2 ) in the rotating direction about the Z axis. 
     As depicted in  FIG. 2 , the other rotation drive mechanism  40 B is structurally the same as the rotation drive mechanism  40 A and is symmetrical with the rotation drive mechanism  40 A about the center of gravity G of the stationary frame  10 . Thus, in the following, the structural elements of the rotation drive mechanism  40 B will be described with the same reference numerals as those of the structural elements of the rotation drive mechanism  40 A. 
     When identical currents are supplied to the drive motors  50  of the rotation drive mechanisms  40 A and  40 B, the respective driving forces F 2  illustrated in  FIG. 5  are exerted on positions that are symmetrical about the center of gravity G. Thus, the rotary unit  12  (more specifically, the base frame  20 ) are slightly rotated about the Z axis located at the center of gravity G. The range of slight rotation may be set approximately equal to the range of vibration of the stationary frame  10  or the range of variation of the attitude of the stationary frame  10 . For example, the range of slight rotation may be set equal to 3 degrees ranging between 1.5 degrees in the counterclockwise direction from the neutral position and 1.5 degrees in the clockwise direction therefrom. In the present embodiment, the range of slight rotation may be defined by stoppers  68  that limit the movements of the slider members  66   a  and  66   b . The stopper members  68  may be pin-like members, which may be driven to the upper surface of the stationary frame  10 , more specifically, the upper surfaces of the first beams  14   a  and  14   b.    
     Referring to  FIG. 1 , in the electrode plate transportation apparatus  100  configured as described above in accordance with the first embodiment, the cathode plates C that are held in the suspended state by the hangers  26  are moved to the position above an electrolytic bath  90  by the ceiling travel crane (not illustrated). At this time, the anode electrodes A are already placed and arranged in an electrolytic bath  90 . After the cathode plates C are positioned, the ceiling travel crane lowers the entire electrode plate transportation apparatus  100  into the electrolytic bath  90  so that the cathode electrodes C and the anode electrodes A can be interleaved. When the electrode plate transportation apparatus  100  is placed (stopped) above the electrolytic bath  90 , reaction force caused by stoppage may rotate the entire apparatus  100  about the Z axis, or unbalance of holding the stationary frame  10  by the ceiling travel crane may vary the horizontal attitude of the stationary frame  10 . 
     The present embodiment is capable of restraining swing and/or attitude variation of the electrode plate transportation apparatus  100 . For example, the operator visually confirms swing and/or attitude variation of the electrode plate transportation apparatus  100 , and manipulates the input interface (such as a joystick) in directions opposite to the directions in which the apparatus  100  swings and varies in attitude so as to cancel swing and/or attitude variation. The instructions given by the operator via the input interface are processed by the motor control circuit, which slightly rotates the rotary unit  12  (more specifically, the base frame  20 ) to restrain swing and/or attitude variation. 
     Our experiments and computer simulation show the following. In the conventional mechanism without the rotary unit  12 , the electrode plates swing in a range of 50 mm when the electrode plate transportation apparatus is stopped. In contrast, the present embodiment has a reduced swing range of 10 mm or less due to the presence of the rotary unit  12  that is slightly rotated with respect to the stationary frame  10 . It is to be noted that the cathode plates C are allowed to be placed in spaces defined by the adjacent anode plates A after the swing of the cathode plates C is manually stopped. In contrast, according to the present embodiment, the cathode plates C may be placed in spaces without manually stopping the swing of the cathode plates C. Even when the cathode plates C vary in the horizontal attitude, this variation can easily be removed by slightly rotating the rotary unit  12 . It is thus possible to easily position the cathode plates C in place. 
     According to the first embodiment, the rotary unit  12  having the hangers  26  for holding the cathode electrodes C in the suspended state is held so as to rotate about the vertical direction (the Z axis) with respect to the stationary frame  10 . The rotation drive mechanisms  40 A and  40 B provided between the stationary frame  10  and the rotary unit  12 , in other words, the linear drive mechanisms  42  apply the driving forces to the rotary unit  12  in the Y-axis direction to thus rotate the rotary unit  12  slightly. Thus, even when the stationary frame  10  vibrates, the rotary unit  12  is slightly rotated to correct the attitudes (directions) of the electrode plates easily. It is thus possible to easily place the cathode plates C in position so that the cathode plates C and the anode plates A can be interleaved. Further, even if the attitude of the stationary frame  10  in the horizontal plane varies, the rotary unit  12  is slightly rotated to correct the positions and attitudes of the cathode plates C. It is easy to place and draw the cathode electrodes in and from the electrolytic bath  90 . 
     In the first embodiment, the rotary frame  18  that is slightly rotatable to the stationary frame  10  is arranged above the stationary frame  10 , and the base frame  20  is arranged below the stationary frame  10 . It is thus possible to coincide the center of gravity of the stationary frame  10  with the center of gravity of the rotary unit  12  including the rotary frame  18  and the base frame  20 . With this structure, it is possible to realize good weight balance between the stationary frame  10  and the rotary unit  12 . 
     In the first embodiment, the linear driving forces in the longitudinal direction (Y-axis direction) of the screws  52  generated by the rotation drive mechanisms  40 A and  40 B are transferred, via the transfer members  44 , to the positions that are offset in the X direction from the center of gravity G of the rotary unit  12 . With this simple structure, the rotary unit  12  can be rotated in the horizontal plane (XY plane). In this case, the engagements of the transfer members  44  and the first plate members  56   a  do not prevent the rotating operation of the rotary unit  12 . This is because the transfer members  44  are slidable in the X-axis direction with respect to the first plate members  56   a  to change the relative position in the X-axis direction, and the widths of the recesses  44   b  of the transfer members  44  in the Y direction are slightly greater than the widths of the first plate members  56   a  in the Y direction. 
     The first embodiment is equipped with the torque limiters  62  that prevent the rotating forces of the drive motors  50  from being transferred to the screws  52  when a torque greater than the threshold level is applied to the motors  50 . It is thus possible to prevent the rotation drive mechanisms  40 A and  40 B from being damaged due to overload. 
     In the first embodiment, the single pair of rotation drive mechanisms  40 A and  40 B are symmetrical about the center of gravity G of the stationary frame  10 . When the mechanisms  40 A and  40 B generate identical driving forces, the rotary unit  12  can be rotated about the center of gravity G of the stationary frame  10 . The guide mechanisms  46  function to reliably rotate the rotary unit  12  about the Z axis. 
     In the first embodiment, the stopper members  68  for limiting the movements of the slider members  66   a  and  66   b  are provided in the vicinity of the guide members  64 . It is thus possible to prevent excessive rotation of the rotary unit  12 . 
     The first embodiment may be varied so that one of the pair of rotation drive mechanisms  40 A and  40 B is omitted. One of the linear drive mechanisms  42  of the rotation drive mechanisms  40 A and  40 B may be omitted. The first embodiment may be varied so that the stopper members  68  are replaced with different stopper members that are ached to the screws  52  and limit the moving ranges of the nuts  54 . 
     Second Embodiment 
     A description is now given, with reference to  FIGS. 6 through 9 , of a second embodiment of the present invention. The second embodiment differs from the first embodiment in that the rotary unit  12  is automatically driven to rotate. Thus, the following description will focus upon the above difference, and the same structural elements of the second embodiment as corresponding elements of the first embodiment will not be described here. 
       FIG. 6  is a block diagram of a control system that realizes automatic control in accordance with the second embodiment. The control system includes a pair of cameras  102 , a control unit  106 , and a linear encoder  108 . In the following, it is assumed that only one of the drive motors  50  is provided for the convenience&#39;s sake. The other drive motor  50  is controlled similarly. The control unit  106  processes pictures taken by the cameras  102  to control the drive motor  50 . The linear encoder  108  detects the amount of movement of the nut  54  in the Y-axis direction. 
     As illustrated in  FIG. 7A , one of the two cameras  102  is placed in the proximity of one of the corners of the rotary unit  12  on the −X and +Y sides thereof (more specifically, the base frame  20 ). The other camera  102  is placed in the proximity of the corner of the rotary unit  12  on the +X and −Y sides thereof. Further, a marker  104  for detecting the orthogonality of the rotary unit  12  is provided on the upper surface of the electrolytic bath  90  and is located in the proximity of the corner on the −X and +Y sides. Another marker  104  is provided on the upper surface of the electrolytic bath  90  and is located in the proximity of the corner on the +X and −Y sides. The markers  104  run in the Y-axis direction. Images of the markers  104  can be taken by the cameras  102  in the state in which the electrode plate transportation apparatus  100  is positioned in place above the electrolytic bath  90 .  FIGS. 8A through 8C  illustrate exemplary images taken by the cameras  102 . 
     Turning back to  FIG. 6 , the control unit  106  has an image processing part  112 , a deviation angle calculation part  114 , a corrected distance calculation part  116  and a drive motor control part  118 . 
     The image processing part  112  processes the images taken by the pair of cameras  102 . The deviation angle calculation part  114  calculates the angle of deviation of each marker  104  with respect to the coordinate (Y axis) of the camera  102  on the basis of the images processed by the image processing part  112 . The deviation angle calculation part  114  may detect the boundary (edge) between the marker  104  and the background (the upper surface of the electrolytic bath  90 ) from the images taken by each of the cameras  102  ( FIGS. 8A through 8C ), and calculates the angle (relative angle) between the edge (boundary) and the coordinate of the camera  102  (Y axis). For example, as illustrated in  FIG. 7A , there may be a case where the entire electrode plate transportation apparatus  100  rotates clockwise with respect to the electrolytic bath  90 , the deviation angle calculation part  114  calculates the angle +θ° shown in  FIG. 8A . For a case illustrated in  FIG. 7B  where the entire electrode plate transportation apparatus  100  rotates counterclockwise with respect to the electrolytic bath  90 , the deviation angle calculation part  114  calculates the angle −θ° shown in  FIG. 8B . For a case of  FIG. 7C  where the entire electrode plate transportation apparatus  100  is positioned at the correct angle, the deviation angle calculation part  114  calculates an angle of 0° because the edge of the marker  104  is aligned with the Y axis. 
     Turning back to  FIG. 6 , the corrected distance calculation part  116  obtains a corrected distance on the basis of the angle calculated by the deviation angle calculation part  114 . The corrected distance may be equal to the distance by which the nut  54  should be moved in the Y-axis direction for adjusting the angle. For example, when the deviation angle calculation part  114  calculates the angle +θ°, as illustrated in  FIG. 9 , the entire electrode plate transportation apparatus  100  is rotated and positioned at the angle +θ° that deviates from the reference angle O. Thus, assuming that the distance to the screw  52  from the center of gravity G is r, the corrected distance a of the nut  54  is obtained by expression (1):
 
 a=r ·(+θ)  (1)
 
     Turning back to  FIG. 6 , the drive motor control part  118  controls the revolution of the motor  50  so as to move the nut  54  in the Y-axis direction by the corrected distance a (absolute value of a) obtained by the corrected distance calculation part  116 . In the rotation drive mechanism  40 A illustrated in  FIG. 9  the nut  54  is moved in the +Y direction. In the rotation drive mechanism  40 B, the nut  54  is moved in the −Y direction. The drive motor control part  118  monitors the moving distance of the nut  54  by using the linear encoder  108  in order to control the revolution of the drive motor  50 . The linear encoder  108  may be composed of a linear scale and an encoder main body that is composed of a light-emitting part and a light-receiving part. The linear scale extends in the Y-axis direction. The light-emitting part projects light onto the linear scale, and the light-receiving part receives the light through the linear scale. 
     When the deviation angle calculation part  114  calculates the angle −θ°, the corrected distance calculation part  116  results in a=r·(−θ), the drive motor control part  118  controls the revolution of the motor  50  so as to move the nut  54  in the Y-axis direction by the corrected distance a (absolute value of a) obtained by the corrected distance calculation part  116 . In the rotation drive mechanism  40 A illustrated in  FIG. 9  the nut  54  is moved in the −Y direction. In the rotation drive mechanism  40 B, the nut  54  is moved in the +Y direction. 
     The cameras  102 , the markers  104 , the image processing part  112 , and the deviation angle calculation part  114  form a detection unit. The corrected distance calculation part  116 , the drive motor control part  118  and the linear encoder  108  form a drive control unit. 
     As described above, according to the second embodiment, the deviation angle calculation part  114  calculates the angle of deviation from the images taken by the pair of cameras  102 , and the corrected distance calculation part  116  calculates the corrected distance a from the angle of deviation by using expression (1). The drive motor control unit  118  controls the drive motor  50  on the basis of the corrected distance a and the output of the linear encoder  108  (the moving distance of the nut  54 ). The second embodiment always or constantly executes the above-mentioned control to automatically correct the swing and/or attitude variation of the electrode plate transportation apparatus  100 . 
     The above-described linear encoder  108  may be replace with a rotary encoder that detects revolution of the drive motor  50 . In this case, the number of revolutions is associated with the corrected distance a in the corrected distance conversion part  116 . 
     The makers  104  may be aligned in the X-axis direction. The markers  104  may have a cross shape. 
     Only one camera  102  and only one marker  104  may be used. Three or more cameras  102  and three or more markers  104  may be used. 
     The present invention is not limited to the specifically disclosed embodiments, but other embodiments and variations may be made without departing from the scope of the present invention.