Abstract:
A library apparatus includes: a storage rack configured to be capable of storing a plurality of recording media; a recording-and-reproducing device configured to perform a recording operation and a reproducing operation on the recording media; a robot configured to deliver the recording media between the storage rack and the recording-and-reproducing device using a hand mechanism; an elevator platform configured to carry the hand mechanism; a pair of toothed belts, provided between a driving pulley and a driven pulley, configured to move the elevator platform vertically; a pair of belt-connecting portions configured to couple one of ends of the elevator platform to one of the pair of toothed belts respectively; and a disconnecting mechanism configured to release at least one of connections at the pair of belt connecting portions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-106086 filed on May 7, 2012, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a library apparatus. 
       BACKGROUND 
       [0003]    A library apparatus, which serves as an external mass storage device, stores several hundreds of magnetic tapes or optical disks, which serve as recording media, in a housing called a “locker” and performs automatic writing and reading of recording data. In the locker of a library apparatus, a recording-and-reproducing device that writes data into and reads data from the recording media, a loading-and-ejecting device that loads and ejects the recording media, a storage rack on which the recording media are stored, and a transport device that transports the recording media. The recording-and-reproducing device may be called a “drive”, the loading-and-ejecting device may be called a “CAS”, the storage rack may be called a “slot”, and the media transport device may be called a “robot”. The robot transports the recording media from the slot to the drive or to the CAS. 
         [0004]    Related art is disclosed in Japanese Laid-open Patent Publication No 2011-42463. 
       SUMMARY 
       [0005]    According to one aspect of the embodiments, a library apparatus includes: a storage rack configured to be capable of storing a plurality of recording media; a recording-and-reproducing device configured to perform a recording operation and a reproducing operation on the recording media; a robot configured to deliver the recording media between the storage rack and the recording-and-reproducing device using a hand mechanism; an elevator platform configured to carry the hand mechanism; a pair of toothed belts, provided between a driving pulley and a driven pulley, configured to move the elevator platform vertically; a pair of belt-connecting portions configured to couple one of ends of the elevator platform to one of the pair of toothed belts respectively; and a disconnecting mechanism configured to release at least one of connections at the pair of belt connecting portions. 
         [0006]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0007]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1A  is an exemplary perspective view of a library apparatus; 
           [0009]      FIG. 1B  is an exemplary perspective view of a robot and an elevator mechanism; 
           [0010]      FIG. 1C  illustrates an exemplary state in which a recording medium has been transported to a drive; 
           [0011]      FIG. 2A  illustrates an exemplary elevator mechanism; 
           [0012]      FIG. 2B  illustrates an exemplary example of belt-connecting portion; 
           [0013]      FIG. 3A  illustrates an exemplary belt-connecting portions; 
           [0014]      FIG. 3B  illustrates an exemplary elevator mechanism; 
           [0015]      FIGS. 3C and 3D  illustrate an exemplary timing belt and an exemplary base member; 
           [0016]      FIGS. 4A and 4B  illustrate an exemplary belt-connecting portion; 
           [0017]      FIGS. 5A and 5B  illustrate an exemplary disconnecting mechanism; 
           [0018]      FIGS. 6A and 6B  illustrate an exemplary belt-connecting portion; 
           [0019]      FIG. 7  illustrates an exemplary recovery processing; 
           [0020]      FIG. 8  illustrates an exemplary recovery processing; 
           [0021]      FIGS. 9A to 9J  illustrate an exemplary inclination-correcting process; 
           [0022]      FIG. 10  illustrates an exemplary disconnecting mechanism; 
           [0023]      FIGS. 11A and 11B  illustrate an exemplary disconnecting mechanism; 
           [0024]      FIG. 12  illustrates an exemplary disconnecting mechanism; and 
           [0025]      FIGS. 13A to 13F  illustrate an exemplary disconnecting mechanism. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    In a library apparatus, a robot is moved by two belts that are operably associated with each other. In the library apparatus, when an elevator platform, for example, a base member of the robot, is vertically moved, the ends of the elevator platform are coupled to driving-force transmitting members, such as timing belts (toothed belts), whereby the elevator platform is maintained in a horizontal position by forces simultaneously applied to the ends. Two driving pulleys are coupled to each other via a shaft or the like, so that the two timing belts are simultaneously moved. 
         [0027]    In a driving mechanism using the timing belts, a tooth-jumping phenomenon, in which a belt is instantaneously separated from a driving pulley and a tooth of the belt jumps over a tooth of the driving pulley, may occur owing to lowering of the tension of the belts caused by aging or due to a high impact applied during transportation. In a driving mechanism in which two driving pulleys are coupled to each other by a rotation shaft, if a tooth-jumping phenomenon occurs in one belt, the heights of coupling portions, at which the belts and the base member are coupled, may become different from each other, for example, a phase shift between the belts may occur, and hence, the base member may be inclined, causing an erroneous movement of the robot. 
         [0028]    When a phase shift between the belts is to be corrected, a maintenance person may work after the library apparatus is stopped. The maintenance person decreases the tension of a belt to reduce the meshing force between the belt and the driving pulley, returns the displaced tooth to the original position, then increases the tension to stretch the belt and align the phase. 
         [0029]    For example, in a large-capacity carrying device that moves a horizontal tray carrying sheets up and down, tooth-jumping between timing belts, which move the horizontal tray up and down, and pulleys, which drive the timing belts, is detected and corrected, so that the inclination of the horizontal tray is reduced. Two of four timing belts that move the horizontal tray up and down are driven by pulley-driven belts stretched between the pulleys. When the horizontal tray is inclined, the tension of a pulley-driven belt is reduced, so that tooth-jumping is caused between the pulley-driven belt and the pulley. By causing tooth-jumping to occur between the pulley and the pulley-driven belt that are not the pulley and the pulley-driven belt between which the first tooth-jumping occurs previously, the horizontal tray is returned to a horizontal state, after which the tension of the pulley-driven belt is increased. 
         [0030]      FIG. 1A  is an exemplary perspective view of a library apparatus. A locker  10 , which is a housing of a library apparatus  1 , may include slots  2  that store a plurality of recording media, a drive  3  that records data into and reproduces data from the recording media, and a robot  4  that transports the recording media between the slots  2  and the drive  3 . A control unit (not illustrated) may be provided in the locker  10 . The slots  2  may be provided above the drive  3 . 
         [0031]      FIG. 1B  is an exemplary perspective view of the robot and an elevator mechanisms. In  FIG. 1B , the slot  2  on the near side, for example, on the right side as viewed from the front of the library apparatus, is removed from the library apparatus  1  illustrated in  FIG. 1A .  FIG. 1C  illustrates an exemplary state in which a recording medium has been transported to a drive. In  FIG. 1C , the robot  4  illustrated in  FIG. 1B  may transport the recording medium to the drive  3 . For example, a cartridge tape, such as a linear tape-open (LTO) cartridge tape, may be used as the recording medium. The LTO cartridge tape accommodates, inside a casing, a reel hub on which the magnetic tape is wound. The tape is led out with a leader pin provided at an end of the magnetic tape. For example, a known LTO cartridge tape may be used. 
         [0032]    The robot  4  includes a base member  5 , a hand mechanism  6  that moves the base member  5  in an arrow D direction, for example, a device depth direction, and the elevator mechanisms  7  that move the base member  5  up and down in an arrow H direction, for example, a height direction, along guide posts  9 . The elevator mechanisms  7  move the base member  5  up by timing belts  14 , which are toothed belts stretched between driving pulleys  11  and driven pulleys  12 . Since the hand mechanism  6  is rotatable in arrow R directions, a cartridge tape may be taken out of either of the right and left slots  2  and ma be transported to the cartridge tape to the drive  3 . For example, the robot  4  transports the cartridge tape between the slot  2  and the drive  3  and between the slot  2  and the CAS (not illustrated) with straight-line motions along two axes and a rotational motion about one axis. A first flag F 1  and a second flag F 2  are provided at the lower end portions of the slots  2  of the library apparatus  1 . The first flag F 1  and the second flag F 2  may be read by a camera (not illustrated) mounted on the hand mechanism  6  so as to be used to adjust the levelness of the base member  5  or to correct the reference position of the hand mechanism  6 . 
         [0033]      FIG. 2A  illustrates an exemplary elevator mechanism  7 .  FIG. 2A  may illustrate the elevator mechanisms  7  of the robot  4  illustrated in  FIG. 1B .  FIG. 2B  illustrates an exemplary belt-connecting portion.  FIG. 2B  may illustrate a partial enlarged perspective view of belt-connecting portions  15  that couple the base member  5  of the robot  4 , illustrated in  FIG. 1A , and the timing belts  14  that moves the base member  5  up and down. The driving pulleys  11  have teeth T on the outer circumferential surfaces thereof. The structure of the driven pulleys  12  may be substantially the same as or similar to that of the driving pulleys  11 . Teeth t provided on the inner circumferential surfaces of the timing belts  14  mesh with the teeth Ton the driving pulleys  11  and the driven pulleys  12 . 
         [0034]    The elevator mechanisms  7  are provided on both sides of the base member  5 , and the two driving pulleys  11  are coupled to each other by a rotation shaft  17 . The rotation shaft  17  that rotates the driving pulleys  11  is rotated by a driving belt  16  stretched between the rotation shaft  17  and a motor  13 .  FIG. 2B , illustration of the guide posts  9  may be omitted. The guide posts  9  pass through guide holes  19  provided at both ends of the base member  5 . In the elevator mechanisms  7 , the timing belts  14  and the base member  5  may be coupled by the belt-connecting portions  15 . 
         [0035]      FIG. 3A  illustrates an exemplary belt-connecting portion  15 . The picture on the left side in  FIG. 3A  illustrates, in detail, the connecting portion  15  between the timing belt  14  and the base member  5 . The belt-connecting portions  15  each include a fixed portion  15 B provided integrally with the base member  5 , and an engaging piece  15 A that is attached to the fixed portion  15 B via a screw or the like. By securely attaching the engaging pieces  15 A to the fixed portions  15 B, the timing belts  14  and the base member  5  are coupled by the belt-connecting portions  15 . When the timing belts  14  are vertically moved by the driving pulleys  11 , the base member  5  moves vertically. If, for some reason, the driving pulleys  11  do not rotate and only the timing belts  14  move, tooth-jumping may occur, resulting in a situation illustrated on the right side in  FIG. 3A . The heights of the positions of the belt-connecting portions  15  may become different from each other by a height h owing to tooth-jumping. The tooth-jumping may be called a phase shift between the timing belts  14 . 
         [0036]      FIG. 3B  illustrates an exemplary elevator mechanism.  FIGS. 3C and 3D  illustrate an exemplary belt and an exemplary base member. In  FIG. 3B , the elevator mechanisms  7  illustrated in  FIGS. 1 and 2  may be viewed from view point. For example, when there is no phase shift between the timing belts  14  as illustrated in the picture on the left side in  FIG. 3A , as illustrated in  FIG. 3C , the base member  5  may be horizontal with respect to the timing belts  14 . For example, as illustrated in the picture on the left side in  FIG. 3A , when there is a phase shift between the timing belts  14  as illustrated in the picture on the left side in  FIG. 3A , as illustrated in  FIG. 3D , the base member  5  may be inclined with respect to the timing belts  14 . The inclination of the base member  5  due to a phase shift between the timing belts  14  like this may be returned to a horizontal state. 
         [0037]      FIGS. 4A and 4B  illustrate an exemplary belt-connecting portions.  FIG. 4A  may be a partial perspective view of the belt-connecting portions  15 , as viewed from the front of the library apparatus.  FIG. 4B  may be a partial perspective view of the belt-connecting portions  15 , as viewed from the back of the library apparatus. A disconnecting mechanism  20  may be provided on one of the belt-connecting portions  15  coupling the timing belts  14  and the base member  5 . The belt-connecting portion  15  with the disconnecting mechanism  20  may be called a “movable belt-connecting portion  15 M”, and the belt-connecting portion  15  without the disconnecting mechanism  20  may be called a “fixed belt-connecting portion  15 F”. 
         [0038]      FIGS. 5A and 5B  illustrate an exemplary disconnecting mechanism.  FIG. 5A  may illustrate a state in which the movable belt-connecting portion  15 M, illustrated in  FIG. 4B , is coupled to the timing belt.  FIG. 5B  may illustrate a state in which the movable belt-connecting portion  15 M, illustrated in  FIG. 5A , is disconnected from the timing belt. 
         [0039]    As illustrated in  FIG. 5A , a solenoid  21  with a plunger  22  is provided near the movable belt-connecting portion  15 M of the base member  5 . When the solenoid  21  is deenergized, the plunger  22  protrudes from the solenoid  21 , and when the solenoid  21  is energized, the plunger  22  is retracted into the solenoid  21 . A bracket B 1  is attached to the base member  5  at a position immediately below the plunger  22 . A rotation shaft A 1  is supported by the bracket B 1  in a rotatable manner. Base portions of a lever L 1  and a lever L 2  are fixed to the rotation shaft A 1 . A distal end of the lever L 1  is coupled to a distal end of the plunger  22  in a rotatable manner. 
         [0040]    The movable belt-connecting portion  15 M is provided at an end of a guide block  8  having the guide hole  19 , through which the guide post  9  passes. A bracket B 2  is provided on the guide block  8 , at a position adjacent to the movable belt-connecting portion  15 M. A rotation shaft A 2  is supported by the bracket B 2  in a rotatable manner. The rotation shaft A 2  is provided with a lever L 3  at an end near the solenoid  21  and a lever L 4  at the other end. A distal end of the lever L 2  and the distal end of the lever L 3  are coupled to each other by an intermediate link LM. A distal end of the lever L 4  is coupled, in a rotatable manner, to a bracket B 3  provided on the back surface of the engaging piece  15 A of the movable belt-connecting portion  15 M. 
         [0041]      FIGS. 6A and 6B  illustrate an exemplary belt-connecting portion. A spring  23  that biases the lever L 3  in an arrow P 1  direction is provided at a base portion of the lever L 3 , which is attached to the rotation shaft A 2  supported by the bracket B 2 . When the lever L 3  is biased in the arrow P 1  direction, a rotational force that causes the rotation shaft A 2  to rotate in an arrow P 2  direction is applied from the lever L 3  to the rotation shaft A 2 . When the rotation shaft A 2  is subjected to an urging force that causes the rotation shaft A 2  to rotate in the arrow P 2  direction, an urging force in an arrow P 3  direction is applied from the lever L 4  to the third bracket B 3 . As illustrated in  FIG. 6A , the timing belt  14  is sandwiched and firmly fixed between the engaging piece  15 A and the fixed portion  15 B of the movable belt-connecting portion  15 M owing to the urging force in the arrow P 3  direction. 
         [0042]    When the timing belt  14  is disconnected from the movable belt-connecting portion  15 M, as illustrated in  FIG. 5B , the solenoid  21  is energized. The energized solenoid  21  draws the plunger  22  in an arrow Q 1  direction. When the plunger  22  moves in the arrow Q 1  direction, the rotation shaft A 1  is rotated in an arrow Q 2  direction via the lever L 1 . When the rotation shaft A 1  is rotated in the arrow Q 2  direction, the lever L 2  is rotated in an arrow Q 3  direction, causing the ever L 3  to rotate in an arrow Q 4  direction via the intermediate link LM while overcoming the urging force exerted by the spring  23 . Because the lever L 3  is rotated in the arrow Q 4  direction, the rotation shaft A 2  is rotated in an arrow Q 5  direction, causing the lever L 4  to rotate in an arrow Q 6  direction. 
         [0043]    When the lever L 4  is rotated in the arrow Q 6  direction, the bracket B 3  engaged with the distal end of the lever L 4  moves in an arrow Q 7  direction. As a result, as illustrated in a picture on the left side in  FIG. 6B , the engaging piece  15 A of the movable belt-connecting portion  15 M, to which the bracket B 3  is attached, is moved in the arrow Q 7  direction, thus disconnecting the engaging piece  15 A from the timing belt  14 . For example, when the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F, the movable belt-connecting portion  15 M falls by gravity in an arrow Q 8  direction, as illustrated in a picture on the right side in  FIG. 6B . When the base member  5  is inclined, control to disconnect or connect the movable belt-connecting portion  15 M may be performed depending on the direction in which the base member  5  is inclined, because the movable belt-connecting portion  15 M may not be higher than the fixed belt-connecting portion  15 F. 
         [0044]      FIGS. 7 and 8  illustrate an exemplary recovery processing. When an error, including an inclination error of the base member  5 , occurs in the library apparatus, the control unit may perform the recovery processing illustrated in  FIGS. 7 and 8 .  FIGS. 9A to 9J  illustrate an exemplary inclination-correcting process.  FIGS. 9A to 9J  may illustrate the inclination-correcting process to correct the inclination of the base member  5 . 
         [0045]    When an error occurs in the library apparatus, an LTO cartridge tape may not be inserted into a slot or a drive. Thus, when an error occurs in the library apparatus, retry is performed to insert the LTO cartridge tape again into the slot or the drive in an operation  701 . In an operation  702 , it is determined whether or not retry is succeeded. When retry is succeeded (YES), the flow proceeds to an operation  711 , where the operation of the library apparatus is restarted, and then the flow ends. When retry fails (NO), the flow proceeds to an operation  703 , where it is determined whether or not the number of times retry is performed is within a predetermined value. When the number of times retry is performed is within a predetermined value (YES), a series of the operations from  701  to  703  is repeated. When the number of times retry is performed exceeds the predetermined value (NO), the flow proceeds to an operation  704 . 
         [0046]    Errors of the library apparatus include improper insertion of the cartridge tape, which may occur when the base member  5  carrying the hand mechanism  6  is inclined. Thus, in the operation  704 , the inclination of the base member  5  is measured, and the measured value is compared with the value obtained when the base member  5  is not inclined. Whether or not the base member  5  is inclined may be determined by reading position-correction flags with the robot  4 . For example, whether or not the base member  5  is inclined is determined by comparing a previously measured correction flag value with the latest measured value. The position-correction flags may be read by using a known technique. The first flag F 1  and the second flag F 2  illustrated in  FIG. 1B  may correspond to the position-correction flags. 
         [0047]    In an operation  705 , whether or not the base member  5  is inclined is determined based on the measurement in operation  704 . When the base member  5  is inclined, because it may be caused by tooth-jumping (phase shift) occurring between the timing belt and the driving pulley, whether or not a phase shift occurs is determined in the operation  705 . When it is determined that no phase shift occurs in the operation  705  (NO), the flow proceeds to an operation  712 . In the library apparatus, an error other than the error caused by the inclined base member  5  may be serious. Hence, in the operation  712 , the error is reported to a management company to request recovery by a maintenance person, and then the flow ends. The operation of the library apparatus may be temporarily stopped. 
         [0048]    When it is determined that a phase shift occurs in an operation  705  (YES), the flow proceeds to an operation  706 , where the phase shift is corrected.  FIGS. 9A to 9E  illustrate a correction operation performed when a phase shift between the timing belts  14  occurs, the base member  5  is inclined, and the movable belt-connecting portion  15 M is located below the fixed belt-connecting portion  15 F.  FIGS. 9F to 9J  illustrate a correction operation performed when a phase shift between the timing belts  14  occurs, the base member  5  is inclined, and the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F. 
         [0049]    A circle mark (◯) on the movable belt-connecting portion  15 M in  FIGS. 9A to 9E  indicates that the movable belt-connecting portion  15 M is not energized, and the base member  5  is coupled to the timing belt  14 . A cross mark (×) on the movable belt-connecting portion  15 M in  FIGS. 9A to 9E  indicates that the movable belt-connecting portion  15 M is energized, and the base member  5  is not connected to the timing belt  14 . 
         [0050]    In an operation  801  in  FIG. 8 , it is determined which of the movable belt-connecting portion  15 M and the fixed belt-connecting portion  15 F is located above the other, based on the inclination of the base member  5  of the robot  4 .  FIG. 9A  illustrates that the fixed belt-connecting portion  15 F is located above the movable belt-connecting portion  15 M.  FIG. 9F  illustrates that the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F. In  FIGS. 9A to 9J , the driving pulleys  11  that drive the timing belts  14  may be located above a bottom surface Y of the library apparatus. 
         [0051]    In an operation  802  in  FIG. 8 , the driving pulleys  11  are rotated to lower the base member  5  until one of right and left ends of the base member  5  of the robot  4  comes into contact with the bottom surface Y of the library apparatus. For example, the driving pulleys  11  may be stopped by monitoring the pulses of an encoder provided on the motor. As illustrated in  FIG. 9B , when the fixed belt-connecting portion  15 F is located above the movable belt-connecting portion  15 M, the end of the base member  5  provided with the movable belt-connecting portion  15 M may come into contact with the bottom surface Y of the library apparatus first. As illustrated in  FIG. 9G , when the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F, the end of the base member  5  provided with the fixed belt-connecting portion  15 F may come into contact with the bottom surface Y of the library apparatus first. 
         [0052]    In the operation  802 , when one of the right and left ends of the base member  5  comes into contact with the bottom surface Y of the library apparatus and the rotation of the driving pulleys  11  is stopped, in an operation  803 , the movable belt-connecting portion  15 M is energized to disconnect the movable belt-connecting portion  15 M from the timing belt  14 .  FIGS. 9C and 9H  illustrate a state in which the movable belt-connecting portion  15 M is disconnected from the timing belt  14 . The mark indicating the state of the movable belt-connecting portion  15 M is changed from “◯”, which indicates a connected state, to “×”, which indicates a disconnected state. 
         [0053]    In an operation  804 , it is determined whether or not the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F. When the movable belt-connecting portion  15 M is located below the fixed belt-connecting portion  15 F (NO), the flow proceeds to an operation  805 . When the movable belt-connecting portion  15 M is located above the fixed belt-connecting portion  15 F (YES), the flow proceeds to an operation  806 . 
         [0054]    In the operation  805 , as illustrated in  FIG. 9D , the driving pulleys  11  are rotated to lower the base member  5  until the fixed belt-connecting portion  15 F of the base member  5  comes into contact with the bottom surface Y of the library apparatus. Although the timing belts  14  on both sides of the base member  5  are move in a direction to lower the base member  5  owing to the rotation of the driving pulleys  11 , because the base member  5  and the timing belt  14  are not coupled at the movable belt-connecting portion  15 M, only the timing belt  14  moves. Thus, the end of the base member  5  provided with the fixed belt-connecting portion  15 F also comes into contact with the bottom surface Y of the library apparatus. 
         [0055]    In an operation  806 , because the base member  5  is disconnected from the movable belt-connecting portion  15 M, the base member  5  falls by gravity. Then, the movable belt-connecting portion  15 M is lowered to the level of the bottom surface Y of the library apparatus.  FIG. 9I  may illustrate a state after the base member  5  falls by gravity. 
         [0056]    Upon completion of the operation  805  or  806 , the flow proceeds to an operation  807 , where the movable belt-connecting portion  15 M is deenergized, and the movable belt-connecting portion  15 M is coupled to the timing belt  14 .  FIGS. 9E and 9J  illustrate a state in which the movable belt-connecting portion  15 M and the timing belt  14  are coupled. The mark indicating the state of the movable belt-connecting portion  15 M is changed from “×”, which indicates a disconnected state, to “◯”, which indicates a connected state. Thus, processing in the operation  704  ends. 
         [0057]    In an operation  707  in  FIG. 7 , similarly to the operation  704 , the inclination of the base member  5  is measured, and the measured value is compared with the value when the base member  5  is not inclined. In an operation  708 , it is determined whether or not the inclination of the base member  5  is corrected, based on the measurement in the operation  707 . When the inclination of the base member  5  is corrected (YES), the processing returns to an operation  711 , the operation of the library apparatus is restarted, and then the flow ends. When the inclination of the base member  5  is not corrected (NO), the flow proceeds to an operation  709 , where it is determined whether or not the number of times the recovery processing is performed in the operation  706  is within a predetermined value. 
         [0058]    When the number of times the recovery processing is performed in the operation  706  is within a predetermined value (YES), the processing returns to the operation  704 , and a series of the operations from  704  to  709  is repeated. When the number of times the recovery processing is performed in the operation  706  exceeds a predetermined value (NO), the flow proceeds to an operation  710 . In the operation  710 , because the error due to the inclination of the base member  5  of the library apparatus is not corrected, a serious error may happen. Hence, in the operation  710 , the error is reported to a management company to request recovery by a maintenance person, and then the flow ends. The operation of the library apparatus may be temporarily stopped. 
         [0059]    An error occurring in the library apparatus is caused by a phase shift due to tooth-jumping between the timing belts  14  and the driving pulleys  11 , the positional shift may be automatically corrected by the structure of the movable belt-connecting portion  15 M. Because tooth-jumping does not occur during disconnection and re-connection at the movable belt-connecting portion  15 M, no damage may be given to the timing belts  14 . 
         [0060]      FIG. 10  illustrates an exemplary disconnecting mechanism.  FIG. 10  illustrates a partial perspective view of the disconnecting mechanism  30  of the movable belt-connecting portion  15 M, as viewed from the front of the library apparatus. In the disconnecting mechanism  30  illustrated in  FIG. 10 , components that are substantially the same as or similar to those of the above-described library apparatus will be denoted by the same reference numerals. The disconnecting mechanism  30  may be provided at an end of the guide block  8  having the guide hole  19 , through which the guide post passes. A motor  32  is provided on the guide block  8  via the bracket  31 , at a position adjacent to the movable belt-connecting portion  15 M. A bracket B 3  is provided on the engaging piece  15 A of the movable belt-connecting portion  15 M, and the lever L 4  is provided on the bracket B 3 . 
         [0061]    The lever L 4  is directly coupled to a rotation shaft  33  of the motor  32 . Thus, when the motor  32  is energized and rotated clockwise, the lever L 4  is rotated and the engaging piece  15 A of the movable belt-connecting portion  15 M separates from the fixed portion  15 B. A spring (not illustrated) that biases the engaging piece  15 A toward the fixed portion  15 B may be provided on the lever L 4 , so that the engaging piece  15 A of the movable belt-connecting portion  15 M is pressed against the fixed portion  15 B when the motor  32  is deenergized. 
         [0062]      FIGS. 11A and 11B  illustrate an exemplary disconnecting mechanism.  FIG. 11A  may illustrate an exploded perspective view of the disconnecting mechanism  40  of the movable belt-connecting portion  15 M, as viewed from the front of the library apparatus.  FIG. 11B  is a perspective view illustrating a state in which a solenoid  42 , which is also illustrated in  FIG. 11A , is attached. In  FIGS. 11A and 11B , components that are substantially the same as or similar to those of the above-described library apparatus will be denoted by the same reference numerals. The disconnecting mechanism  40  may be provided at an end of the guide block  8  having the guide hole  19 , through which the guide post passes. The bracket B 3  is provided on the engaging piece  15 A of the movable belt-connecting portion  15 M. The lever L 4  is provided on the bracket B 3 , and the rotation shaft A 2  provided at a base portion of the lever L 4  is held by the bracket B 2  in a rotatable manner. A spring  45  that presses a distal end of the lever L 4  toward the engaging piece  15 A is provided on the base portion of the lever L 4 . 
         [0063]    In the disconnecting mechanism  40  illustrated in  FIGS. 11A and 11B , the solenoid  42 , from which a plunger  43  projects and into which the plunger  43  is retracted, may be attached to the guide block  8  or the base member  5  with a bracket  41 . When the bracket  41  is attached to the guide block  8 , a hole through which the timing belt passes may be provided in the bracket  41 . A distal end of the plunger  43  is coupled to a connecting plate  44  provided above the bracket B 3 . By causing the plunger  43  to be retracted into the energized solenoid  42 , the engaging piece  15 A of the movable belt-connecting portion  15 M is separated from the fixed portion  15 B. When the solenoid  42  is deenergized, the engaging piece  15 A of the movable belt-connecting portion  15 M is pressed against the fixed portion  15 B owing to an biasing force exerted by the spring  45 , whereby the movable belt-connecting portion  15 M is coupled to the timing belt  14 . 
         [0064]      FIG. 12  illustrates an exemplary disconnecting mechanism.  FIG. 12  may be a perspective view of the disconnecting mechanism  20  that disconnects the movable belt-connecting portions  15 M from the timing belts  14 , as viewed from the front of the library apparatus. The movable belt-connecting portions  15 M are provided on both sides of the base member  5 . The disconnecting mechanism  20  includes disconnecting mechanisms  20 A and  20 B that are attached to the movable belt-connecting portions  15 M. The configuration of the disconnecting mechanism  20  may be substantially the same as or similar to that of the above-described disconnecting mechanisms. A phase shift occurring in either of the two timing belts is corrected. 
         [0065]      FIGS. 13A to 13F  illustrate an exemplary disconnecting mechanism.  FIG. 13A  is a perspective view of the disconnecting mechanism  50  of the movable belt-connecting portions  15 M, as viewed from the front of the library apparatus.  FIG. 13B  is an exploded perspective view of the disconnecting mechanism  50  of the movable belt-connecting portions  15 M, illustrated in  FIG. 13A .  FIG. 13C  is a side view illustrating a belt-connecting operation in the disconnecting mechanism  50  of the movable belt-connecting portions  15 M, illustrated in  FIG. 13A .  FIG. 13D  is an enlarged view of a part D in  FIG. 13C .  FIG. 13E  is a side view illustrating a belt-disconnecting operation in the disconnecting mechanism  50  of the movable belt-connecting portions  15 M, illustrated in  FIG. 13C .  FIG. 13F  is an enlarged view of a part F in  FIG. 13E . 
         [0066]    The configuration of the disconnecting mechanism  50  of the movable belt-connecting portions  15 M, illustrated in  FIGS. 13A to 13F , may be different from that of the engaging piece  15 A of the movable belt-connecting portions  15 M illustrated in  FIGS. 11A and 11B . In  FIGS. 13A to 13F , the other configurations may be substantially the same as or similar to those illustrated in  FIGS. 11A and 11B . In  FIGS. 13A to 13F , the components that are substantially the same as or similar to those illustrated in  FIGS. 11A and 11B  are denoted by the same reference numerals. In  FIGS. 11A and 11B , the engaging piece  15 A of the movable belt-connecting portions  15 M is pressed against or moved away from the fixed portion  15 B by the movement of the solenoid  42  and the plunger  43 . 
         [0067]    In  FIGS. 13A  to  FIG. 13F , an engaging frame  51  may be provided instead of the engaging piece  15 A. The engaging frame  51  is biased against the fixed portion  15 B by, for example, the lever L 4  having substantially the same configuration as the lever illustrated in  FIGS. 11A and 11B . Projections  52  that mesh with teeth t of the timing belt  14  is provided in the engaging frame  51 , and Holes  53  are provided in recesses between the projections  52 . A comb-like member  54  that projects from and is retracted into the holes  53  in the recesses is attached to the distal end of the plunger  43  that projects from and is retracted into the solenoid  42 . The comb-like member  54  has projections  55 . When the solenoid  42  is not energized, the projections  55  of the comb-like member  54  may be located at the bottoms of the holes  53 . 
         [0068]    In the disconnecting mechanism  50 , when the plunger  43  is retracted into the deenergized solenoid  42 , the projections  52  provided in the engaging frame  51  mesh with the teeth t of the timing belt  14 , thus coupling the base member  5  and the timing belt  14 . When the solenoid  42  is energized, the plunger  43  projects from the solenoid  42 . As a result, the projections  55  of the comb-like member  54  provided at the distal end of the plunger  43  protrude from the holes  53 , and, as illustrated in  FIG. 13F , tips of the projections  55  are located at substantially the same positions as tips of the projections  52  provided in the engaging frame  51 . Because the gaps between the tips of the projections  55  of the comb-like member  54  and the tips of the projections  52  provided in the engaging frame  51  is small, it may be difficult for the projections of the teeth of the timing belt  14  to enter the gaps. 
         [0069]    Because the timing belt  14  is sandwiched between the fixed portion  15 B of the movable belt-connecting portions  15 M and the engaging frame  51  only by an biasing force exerted by the spring  45 , when the timing belt  14  is driven by the driving pulley  11 , the timing belt  14  may pass between the fixed portion  15 B and the engaging frame  51 . 
         [0070]    The connecting portions between the base member  5  and the timing belts  14  are provided in a movable manner. Thus, even if tooth-jumping between the driving pulleys  11  and the timing belts  14  occurs, a phase shift between the timing belts  14  may be automatically reduced, without damaging the timing belts  14 . At least one of the two connecting portions between the base member  5  and the timing belts  14  is movable and performs disconnection and re-connection of the connecting portion. Thus, the phase shift between the timing belts  14  is automatically reduced. When a phase-shift recovery operation is performed immediately after the library apparatus is turned on, a phase shift caused by an impact applied during transportation may be corrected before the library apparatus is operated, and hence, a highly reliable library apparatus may be provided. 
         [0071]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.