Abstract:
A library apparatus is adapted to write to and read from a plurality of cartridges each housing a tape wound around a reel. The tape has a leader block attached to a tip thereof for pulling the tape out of its cartridge and adapted to be seated in a leader block latch provided on the cartridge. The apparatus includes a cell unit having a plurality of cells for storing the tape cartridges, a threader unit for writing data to and/or reading data from a selected cartridge. The threader unit has a pin for engaging the leader block and pulling the tape out of the cartridge for writing and/or reading data on the tape. A loading unit is connected to the threader unit for holding the cartridge in a first position where the pin is prevented from engaging the leader block of the cartridge, and a second position where the pin is allowed to engage the leader block and write and/or read from the tape. An accessor transfers the cartridge between the cell unit and the first position of the loading unit.

Description:
[0001]    The present invention relates to a library apparatus that reads and writes data from and to a magnetic cartridge tape used as the recording medium, and particularly to a library apparatus adapted to correct the alignment of a leader block attached to the leading end of a recording tape, so that the tape can be pulled out of its cartridge by the leader block.  
         BACKGROUND OF THE INVENTION  
         [0002]    Some computer systems include at least one library apparatus which stores a plurality of magnetic tape cartridges in the racks of its cell units. In this type of library apparatus, after the desired cartridge is ejected from a rack in response to a command from the computer and is set in a magnetic tape apparatus, backup data are written to or read from the cartridge.  
           [0003]    [0003]FIG. 21 is a schematic of the structure of a conventional library apparatus. In this drawing, auto cartridge loader (ACL)  10  includes a cell unit (not shown in FIG. 21) for storing a plurality of cartridges  300  shown in FIGS. 22 and 23, and an accessor mechanism (ACC) (not shown in FIG. 21) that automatically transfers a cartridge  300  to the cell unit or a magnetic tape unit (MTU)  20 , to be described later, in response to commands from the computer (not shown).  
           [0004]    The cell unit described above is constructed from a plurality of racks called cells. The cartridges  300  are stored in these cells. The ACC ejects a cartridge  300  from the desired cell in the cell unit in response to commands from the computer and automatically transfers it to the MTU  20 . In addition, the ACC ejects a cartridge  300  from the MTU  20  and automatically transfers it to a cell in the cell unit.  
           [0005]    [0005]FIG. 22 is a perspective view showing the structure of the cartridge  300  in an upright state. FIG. 23 is a perspective view showing the structure when the cartridge  300  has been turned over. A cartridge case  301  of the cartridge  300  has a generally box shape and accommodates a tape  302 , which is the magnetic recording medium, wound around a tape reel  304 . Data is written to or read from this tape  302  by the MTU  20 .  
           [0006]    A cartridge top  301   c  of the cartridge case  301  is formed from a transparent resin. Thus, the tape  302  wound around the tape reel  304  can be checked from the outside through the cartridge top  301   c . A leader block latch  301   b  is an opening formed on the left side of a side surface  301   a  and functions as a leader port to pull out the tape  302  from the cartridge  300  and to latch or hold a leader block  303  to the cartridge case  301 .  
           [0007]    The leader block  303  is attached to a tip  302   a  of the tape  302  and is the member that engages a threader pin  234  (shown in FIG. 24A) when the tape  302  is pulled out of the cartridge  300  and when the pulled out tape  302  is stored back in the cartridge  300 . The tape tip  302   a  is attached and fixed to a tape tip mount  303   a . The threader pin latch  303   b  is formed to have a nearly hook-shaped cross-section to engage the threader pin  234 .  
           [0008]    In the above structure, in response to commands from the computer, the ACC of the ACL  10  ejects a cartridge  300  from the desired cell in the cell unit and automatically transfers it to a transfer position on the MTU  20 . The threader pin  234  is positioned at the initial position in the MTU  20  as shown in FIG. 25A. Then the MTU  20  loads the cartridge  300  from the transfer position to a read/write position, where the threader pin latch  303   b  of the leader block  303  engages the threader pin  234  as shown in FIG. 25A. Next, as shown in FIG. 25B, under the control of the MTU  20 , the tape reel  304  is rotated forward by a motor (not shown), and the tape  302  is pulled out of the cartridge  300  by the motion of the threader pin  234  in the X+ direction. Then the MTU  20  reads from or writes to the tape  302 .  
           [0009]    When the reading or the writing process on the tape  302  is finished, the tape reel  304  is rotated backwards by a motor (not shown), and the tape  302  is wound back inside the cartridge  300  by the motion of the threader pin  234  in the opposite direction to the X+ direction.  
           [0010]    Next, the MTU  20  unloads the cartridge  300  from the read/write position to the transfer position. The ACC in the ACL  10  ejects the cartridge  300  from the MTU  20  and automatically transfers it to the desired cell of the cell unit in the ACL  10 . Thus, the cartridge  300  is stored in a cell.  
           [0011]    At times, the leader block  303  separates from the tape  302  in a conventional library apparatus because of pressure applied from the outside or deterioration over time. Usually, the leader block  303  can be reattached to the tape  302  by using a special tool. Often, however, the leader block  303  may be attached improperly at an incline with respect to the tape  302  as shown in FIG. 24A.  
           [0012]    Consequently, the leader block  303  could slip and separate from the threader pin  234  while the tape  302  is being pulled out of the cartridge  300  by the threader pin  234 . Typically, when this occurs, after the tape  302  is temporarily stored back in the cartridge  300  and the cartridge is unloaded from the MTU  20 , then the cartridge  300  is reloaded and a retry of the read or write process is performed. That is, when a leader block slip occurs, the tape reel  304  is rotated to store the tape  302  back in the cartridge  300 . As shown in FIG. 24C, however, the leader block  303  does not fully latch to the leader block latch  301   b  (best shown in FIG. 22) because the leader block is mounted at an incline with respect to the tape  302 . Next, the threader pin  234  moves towards the leader block  303  in the X− direction. As shown in FIG. 24D, the threader pin  234  does not properly engage the leader block  303  because the leader block has not engaged the leader block latch  301   b  properly. As a result, the threader pin  234  and its supporting parts could become damaged when the threader pin collides with the leader block  303 , requiring not only the threader pin  234 , but other related parts to be replaced, which increases maintenance costs.  
           [0013]    In the properly attached state, if a retry is performed with the leader block  303  attached to the tape  302 , the leader block will be fully latched to the leader block latch  301   b . Therefore, the threader pin  234  will not collide with the leader block  303 .  
           [0014]    Another problem associated with a conventional library apparatus is that the driving force of the motor (not shown) that rotates the tape reel  304  backwards becomes weaker over time due to deterioration. As a result, the leader block  303  incompletely latches to the leader block latch  301   b  when the tape  302  is wound in the cartridge  300 . In this case, since the leader block  303  of the cartridge  300  is stored in a cell in an incompletely latched state, the leader block  303  must be pushed into the leader block latch  301   b , which is a serious problem in maintenance management.  
           [0015]    Accordingly, one object of this invention is to provide improved library apparatus which prevents a threader pin from colliding with and damaging the leader block of a tape cartridge.  
           [0016]    Another object of this invention is to provide improved library apparatus having a magnetic tape unit which holds a cartridge in a position where the threader pin is prevented from colliding with and damaging the leader block of the cartridge.  
           [0017]    Yet another object of this invention is to provide improved library apparatus having a pressing device which is adapted to push the leader block into a latch provided on the cartridge.  
         SUMMARY OF THE INVENTION  
         [0018]    In keeping with one aspect of this invention, a library apparatus is adapted to write to and read from a plurality of cartridges each housing a tape wound around a reel. The tape has a leader block attached to a tip thereof for pulling the tape out of its cartridge and adapted to be seated in a leader block latch provided on the cartridge. The apparatus includes a cell unit having a plurality of cells for storing the tape cartridges, a threader unit for writing data to and/or reading data from a selected cartridge. The threader unit has a pin for engaging the leader block and pulling the tape out of the cartridge for writing and/or reading data on the tape. A loading unit is connected to the threader unit for holding the cartridge in a first position where the pin is prevented from engaging the leader block of the cartridge, and a second position where the pin is allowed to engage the leader block. An accessor transfers the cartridge between the cell unit and the first position of the loading unit. Also included in the apparatus is a feature for determining whether the pin has properly engaged the leader block of the cartridge in the second position, and a pressing device for pushing the leader block into proper alignment when it is determined that the pin has not properly engaged the leader block.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The above-mentioned and other features of this invention and the manner of obtaining them will become more apparent, and will be best understood by reference to the following description, taken in conjunction with the accompanying drawings in which:  
         [0020]    [0020]FIG. 1 is a block diagram of a library apparatus of the present invention.  
         [0021]    [0021]FIG. 2 is a perspective view of an automatic cartridge loader shown in FIG. 1.  
         [0022]    [0022]FIG. 3 is a side view of the structure of the automatic cartridge loader of FIG. 2.  
         [0023]    [0023]FIG. 4 is of the structure of the automatic cartridge loader of FIG. 3 with parts removed for clarity.  
         [0024]    [0024]FIG. 5A is a plan view showing the structure of a pressing member of the present invention.  
         [0025]    [0025]FIG. 5B is a side view of the pressing member of FIG. 5A along direction B.  
         [0026]    [0026]FIG. 5C is a side view of the pressing member of FIG. 5A along direction C.  
         [0027]    [0027]FIG. 5D is a cross-sectional view of the pressing member along line A-A shown in FIG. 5B.  
         [0028]    [0028]FIG. 5E is a back view showing the structure of the pressing member of FIG. 5A.  
         [0029]    [0029]FIG. 6 is a perspective view of a magnetic tape unit shown in FIG. 1.  
         [0030]    [0030]FIG. 7 is a perspective view of a loader of the present invention.  
         [0031]    [0031]FIG. 8A is a side view of a threader of the present invention shown in FIG. 6.  
         [0032]    [0032]FIG. 8B is a plan view of the threader of FIG. 8A.  
         [0033]    [0033]FIG. 9 is a plan view of the threader of FIG. 8A, with parts removed for clarity.  
         [0034]    [0034]FIG. 10 is a flow chart illustrating a cartridge loading operation of the present invention.  
         [0035]    [0035]FIG. 11 is a flow chart illustrating the pressing operation described in FIG. 10.  
         [0036]    [0036]FIG. 12 is a flow chart illustrating a cartridge unloading operation.  
         [0037]    [0037]FIG. 13 illustrates a catcher closing operation of the present invention.  
         [0038]    [0038]FIG. 14 illustrates a catcher opening operation of the present invention.  
         [0039]    [0039]FIG. 15 illustrates the catcher closing operation of the embodiment shown in FIG. 14.  
         [0040]    [0040]FIG. 16 illustrates the catcher opening operation of the embodiment shown in FIG. 15.  
         [0041]    [0041]FIG. 17 illustrates the catcher centering operation of the present invention.  
         [0042]    [0042]FIG. 18 illustrates an operation for transferring a cartridge to a pressing member.  
         [0043]    [0043]FIG. 19 illustrates an operation for transferring a cartridge to the magnetic tape unit.  
         [0044]    FIGS.  20 A- 20 E illustrate the relative positions of a threader and a leader block when the leader block disengages from the threader in the present invention.  
         [0045]    [0045]FIG. 21 is a block diagram of a conventional library apparatus.  
         [0046]    [0046]FIG. 22 is a perspective top view of a cartridge used in the library apparatus.  
         [0047]    [0047]FIG. 23 is a perspective bottom view of the cartridge shown in FIG. 22.  
         [0048]    FIGS.  24 A- 24 D illustrate the problems associated with a conventional library apparatus.  
         [0049]    FIGS.  25 A- 25 B illustrate an operation for pulling the tape out of a cartridge.  
         [0050]    FIGS.  26 A- 26 C illustrate the problem that could occur when the leader block is not properly attached to the tape.  
     
    
     DETAILED DESCRIPTION  
       [0051]    Referring to FIGS. 1 and 2, an automatic cartridge loader (ACL)  100  includes a cell unit  120  that stores a plurality of cartridges  300  (shown in FIG. 22) and an accessor unit (ACC)  130  that automatically transfers the cartridges  300  to the cell unit  120  or a magnetic tape unit (MTU)  200  in response to commands from a host device such as a computer (not shown).  
         [0052]    The cell unit  120  is constructed from a plurality of racks called cells  121  that are arranged at prescribed intervals in the vertical direction. The cartridge  300  is adapted to be stored in each cell  121 . The ACC  130  ejects one cartridge  300  from the desired cell  121  of the cell unit  120  in response to commands from the computer and automatically transfers the cartridge to a loader  220  in the MTU  200  (shown in FIG. 6). The ACC  130  also ejects the cartridge  300  from the loader  220  and automatically transfers it to a selected cell  121  in the cell unit  120 .  
         [0053]    Referring now to FIG. 3, a drive source is provided for raising or lowering the ACC  130  along the shaft  140  installed vertically in the cabinet  110 . A pair of catcher hands  132  are installed one on both sides of the ACC  130  (best shown in FIG. 13). These catcher hands  132  open (shown in FIG. 14) and close (shown in FIG. 15) with the center of rotation axis as the center of rotation to grasp and release the cartridge  300 , and are driven by a catcher motor  131 .  
         [0054]    Referring now to FIG. 4, a pressing member  150  is attached to the side member  110   a  of the cabinet  110 . The pressing member  150  is adapted to press the leader block  303  against the leader block latch  301   b  when the leader block of the cartridge  300  (shown in FIG. 22A) is not completely latched to the leader block latch  301   b , or the leader block  303  has slipped off the leader block latch  301   b . The installation height of the pressing member  150  is the same height as a specified cell  121 B as shown in FIG. 18.  
         [0055]    Referring now to FIGS. 5A to  5 E, the pressing member  150  includes a plate  151  and a generally convex member  152  formed in the center of the plate. A pair of holes  153 ,  153  for installing the pressing members  150  to the side member  110   a  (shown in FIG. 4) are formed on both sides of the plate  151 . The pressing member  150  is attached to the side member  110   a  by inserting screws in the holes  153 ,  153 .  
         [0056]    Turning now to FIG. 18, a first cell side sensor  500  and a second cell side sensor  510  are provided in the ACC  130  for detecting the presence or absence of a cartridge  300  in the ACC. In FIG. 18, the reference numbers of cell  121 A and cell  121 B are used to specify particular cells from the plurality of cells  121 . An unload sensor  520  is provided in each cell  121  to detect whether the cartridge  300  has been unloaded (ejected) from the cells  121 .  
         [0057]    Turning to FIG. 6, the MTU  200  is comprised of a cabinet  210 , the loader  220 , and a threader  230 . The loader  220  is housed in the cabinet and loads the cartridge  300  transferred by the ACC  130  from a transfer position to the threader  230 . The loader  220  also unloads the cartridge  300  from the threader  230  to the transfer position. As shown in FIG. 18, the height of the loader  220  is the same as the height of the specified cell  121 A.  
         [0058]    As shown in FIG. 7, the loader  220  includes a cabinet  221  that houses the drive mechanism to load and unload the cartridge  300 , and a loader opening  222  as the delivery opening for the cartridge  300 . A cartridge sensor  530  (shown in FIG. 18) is installed in the loader  220  to detect the presence or absence of the cartridge  300  in the loader  220 . As shown in FIG. 6, the threader  230  is placed close to the loader  220  in the cabinet  210 . After the tape  302  is pulled out of the cartridge  300  loaded by the loader  220 , the threader  230  reads from or writes to this tape  302 .  
         [0059]    Referring to FIGS. 8A, 8B and  9 , the threader  230  includes a threader groove  232  formed in a path almost entirely around the threader surface  231 . The tape  302  of the cartridge  300  is moved in the forward direction F or the backward direction B along the threader groove  232  (best shown in FIG. 9). A threader arm  233  is moved in the forward direction F or the backward direction B by a drive mechanism (not shown) along the threader groove  232 . The threader pin  234  is installed vertically at the end of this threader arm  233 .  
         [0060]    The threader pin  234  engages the leader block  303  when the tape  302  is pulled out of the cartridge  300  (shown in FIGS. 25A and 25B) or when the pulled out tape  302  is accommodated back in the cartridge  300 . That is, the tape  302  is moved in the forward direction F or the backward direction B along the threader groove  232  accompanying the motion of the threader pin  234 . A flange  235  is provided next to the forward end of the threader groove  232 . A screw  236  is installed nearly in the center of the threader surface  231  to fix each part in place.  
         [0061]    Next, a cartridge load operation in accordance with the present invention is described. The control of the operation described below is performed by a controller (not shown) that manages the control of the ACL  100  and the MTU  200 . When a command is received from the computer, the ACC  130  of the ACL  100  is raised (or lowered) along the shaft  140  (shown in FIG. 3) and stops at the position of the desired cell  121  in the cell unit  120 . Next, the catcher hands  132 ,  132  (shown in FIG. 13) are placed in a “catcher closed” state (closed on the cell unit  120  side) by the forward rotation drive of the catcher motor  131  to grasp a cartridge  300  with the catcher hands  132 ,  132 .  
         [0062]    By rotating the feeder belt (not shown), a frictional force acts between the feeder belt and cartridge  300 , and the cartridge  300  is transferred in the XA direction, i.e., in the direction of the loader  220  (as shown in FIG. 13). The presence or absence of a cartridge  300  in the ACC  130  is detected by the first cell side sensor  500  and the second cell side sensor  510  (shown in FIG. 18). Unloading or ejection of the cartridge  300  from inside the cell  121  (for example, cell  121 A) is detected by the unload sensor  520 .  
         [0063]    As shown in FIG. 14, when the cartridge  300  is transferred to the position close to the loader  220 , the catcher hands  132 ,  132  enter a “catcher open” state (open on the cell unit  120  side) by the backward rotation drive of the catcher motor  131 . Then the cartridge  300  is inserted in the loader opening  222  of the loader  220  (shown in FIG. 6) and is detected by the cartridge sensor  530  (shown in FIG. 18).  
         [0064]    Referring back to FIG. 9, the threader pin  234  is positioned initially at the initial position P 1 . The loader  220  in FIG. 6 performs a “loader down” operation in which the cartridge  300  is loaded from a transfer position to a read/write position of the threader  230 . The read/write position (the position indicated by the dashed line in FIG. 20D) is a lower position than the transfer position (the position indicated by the solid line in FIG. 20D). In the loader down operation, the cartridge  300  is lowered down at an incline to the right from the transfer position to the read/write position and is set in the threader  230 . As a result, the threader pin latch  303   b  (shown in FIG. 22) of the leader block  303  engages the threader pin  234  as shown in FIG. 25A.  
         [0065]    Referring now to FIG. 10, the threader arm  233  along with the threader pin  234  are driven forward (step SA 1 ). It is then determined whether errors such as the leader block  303  slipping off as described earlier or no movement of the threader arm  233  have occurred in the forward drive (step SA 2 ). If no error has occurred, the threader arm  233 , and the threader pin  234  are moved in the forward direction F along the threader groove  232  (shown in FIG. 9). Thus, the threader pin  234  is moved from the initial position P 1  to position P 2 . Accompanying this motion, the tape  302  is pulled out of the cartridge  300 , and data is read from or written on the tape.  
         [0066]    If an error has occurred, it is determined whether a leader block has slipped off the threader pin  234  (step SA 3 ). This sometimes occurs when the leader block  303  is attached at an incline with respect to the tape  302  as shown above in FIG. 20A. If the distance of movement of the threader pin  234  and the number of rotations of the tape reel  304  are inconsistent, then it is determined that a leader block slippage has occurred. If a slippage has not occurred, then in step SA 18 , the computer is notified of the generation of the error.  
         [0067]    On the other hand, if a leader block slippage or “leader block slipping error” has occurred, the number “i” of generated leader block slipping errors (initial value of 0) is incremented by one (step SA 4 ). Then, it is decided whether the number “i” of leader block slipping errors generated exceeds some threshold value, for example, 3 (step SA 5 ). If the decision is “Yes,” the process in step SA 18  (error notification) is executed. If the decision in step SA 5  is “No,” the ACC  130  is driven to a position in front of the loader  220  in preparation for retrieving the cartridge  300  from the loader (step SA 6 ). It is then decided whether an error has occurred in the drive of the ACC  130  (step SA 7 ). If this decision is “Yes,” the process in step SA 18  (error notification) is executed.  
         [0068]    If the decision in step SA 7  is “No,” then a “loader up” operation is executed in which the cartridge  300  is unloaded from the read/write position to the transfer position as shown in FIG. 20D, after the tape  302  is wound back in the cartridge  300  as shown in FIGS. 20A to  20 C (step SA 8 ). In the loader up operation, the cartridge  300  is raised up at an incline to the left from the read/write position (position indicated by the dashed line in FIG. 20D) to the transfer position (position indicated by the solid line).  
         [0069]    Specifically, the tape reel  304  (shown in FIG. 23) is rotated backwards by the motor (not shown) to wind the tape  302  in the cartridge  300  (best shown in FIG. 20A to FIG. 20C). Because the leader block  303  is attached at an incline with respect to the tape  302  as shown in FIG. 20D, the leader block  303  does not latch completely to the leader block latch  301   b  (shown in FIG. 22) and protrudes in the direction of the threader pin  234  from the proper position. Next, the loader  220  raises the cartridge  300  at an incline to the left from the read/write position (position indicated by the dashed line in FIG. 20D) to the transfer position (position indicated by the solid line in FIG. 20D).  
         [0070]    Then, it is decided whether errors have occurred in the loader up operation (step SA 9 ). If this decision is “Yes,” the process in step SA 18  (error notification) is executed. If the decision in step SA 9  is “No,” the threader arm  233  in FIG. 9 is driven backwards (step SA 10 ).  
         [0071]    Further, a determination is made as to whether an error has occurred during the backward drive, such as no movement by the threader arm  233  (step SA 11 ). If the decision is “No,” the threader arm  233  (also the threader pin  234 ) is continued to be moved in the backward direction B along the threader groove  232  (best shown in FIG. 9). Therefore, the threader pin  234 , for example, is moved from position P 2  to the initial position P 1 . If the decision in step SA 11  is “Yes,” the process in step SA 18  (error notification) is executed.  
         [0072]    In the state with the threader pin  234  positioned at the initial position P 1  (see FIG. 9) as shown in FIG. 20E, the threader pin  234  does not collide with the leader block  303  because the cartridge  300  is positioned in the transfer position. As a result, this embodiment does not have the problem of the leader block  303  colliding with the threader pin  234 , as in the conventional library apparatus and shown in FIG. 24D. Subsequently, a pressing operation is performed to press the leader block  303  against the pressing member  150  in FIG. 18 (step SA 12 ).  
         [0073]    The pressing operation is described in more detail with reference to FIG. 11, where in step SB 1 , the catcher hands  132 ,  132  enter the “catcher open” state (open on the cell unit  120  side) as shown in FIG. 16 by the backward drive of the catcher motor  131  (see FIG. 2). The cartridge  300  in the loader  220  is then grasped by the catcher hands  132 ,  132 .  
         [0074]    A determination is then made as to whether an error has occurred when opening the catcher (step SB 2 ). If the result is “Yes,” the computer is notified about the generation of errors (step SB 17 ). If the decision in step SB 2  is “No,” then in step SB 3 , the rotation of the feeder belt (not shown) causes a frictional force to act between the feeder belt on the catcher hands and the cartridge  300  to feed the cartridge towards the cell unit  120 . After the cartridge  300  is transferred in the XB direction (the direction of the cell unit  120 ) from the loader  220  as shown in FIG. 18, it is held in the ACC  130 .  
         [0075]    In step SB 4 , if a decision about the generation of errors during the transfer of the cartridge  300  is “Yes,” the process in step SB 17  (error notification) is executed. If the decision in step SB 4  is “No,” then in step SB 5 , the ACC  130  is moved in the Y direction (downward) as in FIG. 18 along the shaft  140  (see FIG. 3) and stopped at the position opposite the pressing member  150 . In step SB 6 , if a decision about the generation of errors during the motion of the ACC  130  is “Yes,” the process in step SB 17  (error notification) is executed.  
         [0076]    If the decision in step SB 6  is “No,” then in step SB 7 , the feeder belt is driven to transfer the cartridge  300  in the XA direction (from the position indicated by the solid line to the position indicated by the dot-dashed line in FIG. 18). Thus, the leader block  303  of the cartridge  300  is pressed against the pressing member  150  to completely latch the leader block  303  to the leader block latch  301   b . In step SB 8 , if a decision about the generation of errors related to the pressing motion is “Yes,” the process in step SB 17  (error notification) is executed.  
         [0077]    If the decision in step SB 8  is “No,” then in step SB 9 , the feeder belt is driven to transfer the cartridge  300  in the XB direction away from the pressing member  150 , as shown in FIG. 19 (from the position indicated by the solid line to the position indicated by the dot-dashed line) and held in the ACC  130 . In step SB 10 , if a decision about the generation of errors during the transfer of the cartridge  300  is “Yes,” the process in step SB 17  (error notification) is executed.  
         [0078]    If the decision in step SB 10  is “No,” then in step SB 11 , the ACC  130  is moved in the Y direction (upward) as shown in FIG. 19 along the shaft  140  (shown in FIG. 3) and stopped at the position opposite the loader  220 . In step SB 12 , if a decision about the generation of errors in the motion of the ACC  130  is “Yes,” the process in step SB 17  (error notification) is executed.  
         [0079]    If the decision in step SB 12  is “No,” then in step SB 13 , the feeder belt is driven to transfer the cartridge  300  in the XA direction towards the loader  220  (from the position indicated by the dot-dashed line to the position indicated by the solid line in FIG. 19). This inserts the cartridge  300  back into the loader opening  222  of the loader  220  (shown in FIG. 6) by the feeder belt and is detected by the cartridge sensor  530 . The threader pin  234  (shown in FIG. 9) is positioned at the initial position P 1 .  
         [0080]    In step SB 14 , if a decision about the generation of errors in the transfer of the cartridge  300  is “Yes,” the process in step SB 17  (error notification) is executed. If the decision in step SB 14  is “No,” then in step SB 15 , the catcher motor  131  (see FIG. 2) is activated to execute a “catcher centering” operation for making the catcher hands  132 ,  132  parallel, as shown in FIG. 17. In step SB 16 , if the decision about the generation of errors in catcher centering is “Yes,” the process in step SB 17  (error notification) is executed.  
         [0081]    If the decision in step SB 16  is “No,” then going back to step SA 13  in FIG. 10, it is decided whether an error was generated in the pressing operation. If the decision is “Yes,” the process in step SA 18  (error notification) is executed. If the decision in step SA 13  is “No,” then the “loader down” operation is executed in which the loader  220  loads the cartridge  300  from the transfer position to the read/write position of the threader  230  (step SA 14 ).  
         [0082]    In the loader down operation, the cartridge  300  is lowered at an incline to the right from the transfer position (position indicated by the solid line in FIG. 20D) to the read/write position (position indicated by the dashed line in FIG. 20D) and set in the threader  230 . Thus, the threader pin latch  303   b  (shown in FIG. 22) of the leader block  303  now properly engages the threader pin  234  (shown in FIG. 25A), because the leader block  303  is completely latched to the leader block latch  301   b.    
         [0083]    In step SA 15 , if a decision about the generation of errors in the loader down operation is “Yes,” the process in step SA 18  (error notification) is executed. If the decision in step SA 15  is “No,” then in step SA 16 , the ACL  100  enters the loading possible state. Specifically, the catcher hands  132 ,  132  of the ACC  130  are placed in the “catcher closed” state (shown in FIG. 15). In step SA 17 , if a decision about the generation of errors in the step SA 16  process is “Yes,” the process in step SA 18  (error notification) is executed.  
         [0084]    If the decision in step SA 17  is “No,” the process goes to step SA 1  described earlier, where a retry operation is performed to repeat reading from and writing to the cartridge  300 . In step SA 5 , if the number “i” of generated leader block slipping errors exceeds a threshold value of 3, for example, the process in step SA 18  (error notification) is executed.  
         [0085]    Next, a cartridge unload operation of the embodiment is described with reference to the flow chart of FIG. 12. The unload operation unloads the cartridge  300  in the MTU  200  into the ACL  100  side after the read/write process to the tape  302  ends normally. If the read/write process to the tape  302  ends normally in the state with the cartridge  300  set in the threader  230  as shown in FIG. 25B, a take-up operation in which the tape reel  304  (shown in FIG. 23) is rotated backwards by the motor (not shown) to wind the tape  302  in the cartridge  300  is executed (step SC 1 ). In step SC 2  it is decided whether errors are generated in the take-up operation. If this decision is “Yes,” then in step SC 25 , the computer is notified of the generation of the error.  
         [0086]    If the decision in step SC 2  is “No,” then a backward drive is executed to drive the threader arm  233  (and the threader pin  234 ) in the backward direction B along the threader groove  232  to a pressing position located slightly before the position P 1  (shown in FIG. 9) (step SC 3 ). In step SC 4 , if a decision about a generation of an error in the backward drive is “Yes,” the process in step SC 25  (error notification) is executed.  
         [0087]    If the decision in step SC 4  is “No,” the threader pin  234  is moved from the pressing position to the initial position P 1 . This moves the threader pin  234  in the opposite direction to the X+ direction and winds the tape  302  in the cartridge  300  as in FIG. 25A. The threader pin  234  is stopped at the pressing position, and the motor (not shown) that drives the rotation of the tape reel  304  (shown in FIG. 23) also stops. Strongly pressing the leader block  303  with the threader pin  234  against the cartridge  300  (as shown in FIG. 25A) fully latches the leader block  303  to the leader block latch  301   b  (shown in FIG. 23).  
         [0088]    Thus, this embodiment solves the conventional problem of the driving force of the motor (not shown) for driving the tape reel  304  being weakened by deterioration over time. The pressing position is set at a position where a force which will not bend the threader pin  234  or damage the part fixed to the threader pin  234  acts on the leader block  303 .  
         [0089]    In step SC 5 , the ACC  130  is moved in the Y direction (upward) as in FIG. 19 along the shaft  140  (shown in FIG. 3) and stopped at the position opposite the loader  220 . In this case, the cartridge  300  is not held in the ACC  130 . In step SC 6 , if a decision about a generation of errors during ACC  130  motion is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 6  is “No,” a catcher centering operation is executed to make the catcher hands  132 ,  132  parallel, as in FIG. 17, by rotating the catcher motor  131  (step SC 7 ). In step SC 8 , if a decision about a generation of errors in the catcher centering operation is “Yes,” the process in step SC 25  (error notification) is executed.  
         [0090]    If the decision in the step SC 8  is “No,” then similar to step SA 8  (see FIG. 10), a “loader up” operation which unloads the cartridge  300  from the read/write position to the transfer position is executed (step SC 9 ). In step SC 10 , if a decision about a generation of errors in the loader up operation is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 10  is “No,” a home position drive is executed to move the threader pin  234  from the pressing position described earlier to the initial position P 1  (home position) by driving the threader arm  233  (best shown in FIG. 9) (step SC 11 ).  
         [0091]    In step SC 12 , if a decision about a generation of errors in the home position drive is “Yes,” the process of the step SC 25  (error notification) is executed. If the decision in step SC 12  is “No,” then in step SC 13 , a reverse rotation drive by the catcher motor  131  places the catcher hands  132 ,  132  in the catcher open state (open on the cell unit  120  side) as in FIG. 16, and the cartridge  300  in the loader  220  is grasped by the catcher hands  132 ,  132 .  
         [0092]    In step SC 14 , if a decision about a generation of errors in opening the catcher is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 14  is “No,” then in step SC 15 , the rotation of the feeder belt (not shown) causes a frictional force to act between the feeder belts and the cartridge  300 . As a result, the cartridge  300  in the loader  220  is transferred in the XB direction (the direction of the cell unit  120 ) as in FIG. 16 and held in the ACC  130 .  
         [0093]    In step SC 16 , if a decision about a generation of errors in the transfer of the cartridge  300  is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 16  is “No,” then in step SC 17 , the ACC  130  is moved in the Y direction (downward) as in FIG. 18 along the shaft  140  (shown in FIG. 3) and is stopped at the position opposite the target cell  121 B, for example.  
         [0094]    In step SC 18 , if a decision about a generation of errors in the motion of the ACC  130  is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 18  is “No,” then in step SC 19 , the catcher motor  131  is driven to rotate forward to place the catcher hands  132 ,  132  in the catcher closed state (closed on the cell unit  120  side) as in FIG. 15.  
         [0095]    In step SC 20 , if a decision about a generation of errors in closing the catcher is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 20  is “No,” then in step SC 21 , the drive of the feeder belt transfers the cartridge  300  in the opposite direction to the XA direction (cell  121 B side) as shown FIG. 18. This stores the cartridge  300  in the cell  121 B.  
         [0096]    In step SC 22 , if a decision about a generation of errors in the transfer of a cartridge  300  is “Yes,” the process of the step SC 25  (error notification) is executed. If the decision in step SC 22  is “No,” then in step SC 23 , the reverse rotation drive by the catcher motor  131  (shown in FIG. 2) places the catcher hands  132 ,  132  in the catcher open state (open on the cell unit  120  side) as in FIG. 16 to release the cartridge  300  from the catcher hands  132 ,  132 .  
         [0097]    In step SC 24 , if a decision about a generation of errors when opening the catcher is “Yes,” the process in step SC 25  (error notification) is executed. If the decision in step SC 24  is “No,” the sequence of processes ends.  
         [0098]    While the principles of the invention have been described above in connection with specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.