Abstract:
A magnetic tape cartridge loader and unloader includes a platform positionable in front of a storage slot of a storage magazine and having a pivotable gripper that releases the cartridge from the storage slot, engages and pulls the cartridge from the slot onto the platform with a hook, engages a back edge of the cartridge with a second hook, and pushes the cartridge into a tape streaming device. The reverse operation is performed to unload the cartridge from the tape streaming device and store it in the storage magazine. The platform includes a locking device to hold the cartridge in position during movement of the platform. The gripper has two oppositely directed spring loaded hooks to engage the cartridge. The gripper is driven laterally by a threaded nut on a lead screw and is pivoted between engaging and disengaging positions of the cartridge engaging hook by a spur gear and gear segment arrangement on a guide along which the gripper slides. Sensors sense the position of the gripper to determine if a cartridge is engaged and to calibrate the automatic operation of the apparatus.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to a cartridge transport and loading apparatus and method and, in particular, to a device for transporting tape cartridges in a cartridges transport system for transport between a storage magazine and a tape streaming device and for loading the cartridge into the tape streaming device, unloading the cartridge from the tape streaming device, and loading the cartridge into the storage magazine and unloading the cartridge therefrom.  
           [0003]    2. Description of the Related Art  
           [0004]    Date storage and data backup on magnetic tape often requires the use of multiple tape cartridges. These multiple tape cartridges are selectively inserted into and removed from tape streaming device, also referred to as tape recording and playback devices. The utilization of multiple tape cartridges is required for expanded data storage and/or storage of the data from different data backup events. For example, a data backup plan may provide for the use of a different tape for each day of the seek.  
           [0005]    Implementation of multiple tape cartridge storage has required a service technician to change the cartridges from the tape streaming device, store the cartridges, and log the event to ensure that the proper cartridge is used at the proper time. Failure on the part of the service technician to change the cartridge at the right time or to use the correct cartridge can result in a failure of the data storage or backup plan.  
           [0006]    The increase in data file size and the increased numbers of data files to be stored on a data storage system along with the increased dependance on data is an electronic format has lead to a greater need for reliable high capacity data storage and backup.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides automatic loading and unloading of cartridges, such as magnetic tape cartridges into and out of a tape streaming device.  
           [0008]    The present invention also provides transport of cartridges between tape streaming devices and a storage magazine.  
           [0009]    The invention also provides a compact device for transport of cartridges which occupies little space.  
           [0010]    These and other advantages of the present invention are provided in a cartridge transport apparatus having a cartridge support platform movable into alignment with a tape streaming device and/or a storage magazine, a gripper having first grip portions for engagement with a leading edge of the cartridge to pull the cartridge from the tape streaming device or a storage magazine, second grip portions for engagement with a trailing edge of the cartridge to move the cartridge along the platform, and a third engagement portion for contact with a trailing edge of the cartridge to push the cartridge into position in the tape streaming device or a storage magazine. The gripper of the present invention preferably has a latch release portion that releases a latch on the storage magazine to permit the cartridge to be  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a cartridge storage magazine and tape streaming devices between which is a tape transport and loader device according to the present invention;  
         [0012]    [0012]FIG. 2 is a perspective view of a cartridge storage magazine and tape streaming devices between which is a tape transport and loader device of FIG. 1 from the other direction;  
         [0013]    [0013]FIG. 3 is an enlarged perspective view of the storage magazine with a tape cartridge stored therein;  
         [0014]    [0014]FIG. 4 is a perspective view of the cartridge transport and loading apparatus according to the principles of the present invention;  
         [0015]    [0015]FIG. 5 is a perspective view of the gripper and drive system of the cartridge transport and loading apparatus;  
         [0016]    [0016]FIG. 6 is an end view of the gripper and the gripper rotation drive;  
         [0017]    [0017]FIG. 7 is a perspective view of the gripper rotation drive and a hook switch;  
         [0018]    [0018]FIG. 8 is a perspective view of the hook switch in a blocked rotation position;  
         [0019]    [0019]FIG. 9 is a perspective view of the gripper and gripper nut;  
         [0020]    [0020]FIG. 10 is a perspective view of the gripper housing of the present apparatus;  
         [0021]    [0021]FIG. 11 is a perspective view of the gripper;  
         [0022]    [0022]FIG. 12 is a perspective view of the sensor arrangement for the gripper housing;  
         [0023]    [0023]FIG. 13 is a perspective view of the sensor plates on the gripper housing;  
         [0024]    [0024]FIG. 14 is a top perspective view of the calibration of the gripper and magazine;  
         [0025]    [0025]FIG. 15 is a perspective view of the step of pushing the cartridge into the storage magazine;  
         [0026]    [0026]FIG. 16 is a perspective view of the step of releasing the cartridge from the storage magazine;  
         [0027]    [0027]FIG. 17 is a perspective view of the step of pulling the cartridge from the storage magazine;  
         [0028]    [0028]FIG. 18 is a perspective view of the step of engaging the cartridge for pushing along the platform;  
         [0029]    [0029]FIG. 19 is a perspective view after the cartridge has been pushed across the platform toward the tape streaming device;  
         [0030]    [0030]FIG. 20 is a perspective view of the step of pushing the cartridge into the tape streaming device;  
         [0031]    [0031]FIG. 21 is a perspective view after the cartridge has been pushed into position in the tape streaming device;  
         [0032]    [0032]FIG. 22 is a side cross section of a tape cartridge engaged by the latch in the storage slot;  
         [0033]    [0033]FIG. 23 is a side cross section of the latch of FIG. 22 being released;  
         [0034]    [0034]FIG. 24 is a side cross section of the hook pulling the cartridge from the slot after release of the latch;  
         [0035]    [0035]FIG. 25 is a perspective view of the present loading and transport apparatus with cooperating lateral and vertical transport apparatus; and  
         [0036]    [0036]FIG. 26 is a second perspective view of the apparatus of FIG. 25. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    [0037]FIG. 1 shows a cartridge storage magazine  10  in which tape cartridges  12 , such as magnetic tape cartridges, are stored. Multiple storage locations are provided for a plurality of cartridges  12 . Tape streaming devices  14 , also referred to as tape recording and playback drives, are also provided, these being disposed opposite the storage magazine  10 . Between the storage magazine  10  and the tape streaming devices  14  is the cartridge transport and loading device  16  of the present invention. The transport and loading apparatus  16  is shown in the position to move the cartridge  12  between a lower, left storage position in the storage magazine  10  and a left-most tape streaming device  14 . Further devices are provided to move the transport apparatus  16  in a lateral direction as indicated by arrow  18  and for moving the transport apparatus vertically. Devices to move the apparatus laterally are well known and may include a threaded nut on a rotationally driven lead screw, for example. Further disclosure of such well known devices is unnecessary. The mechanism for moving the transport apparatus  16  vertically is disclosed in co-pending U.S. Patent Application attorney docket number P01, 0373, which is incorporated herein by reference.  
         [0038]    [0038]FIG. 2 shows the transport and loading apparatus  16  of the present invention in relation to the loading slots of the tape streaming devices  14 . Two such tape streaming devices  14  are provided in side-by-side relation, although other arrangements of tape streaming devices are envisioned. As mentioned above, the transport and loading apparatus  16  may be moved in the direction of the arrow  18  to load and unload the cartridge  12  from either of the two tape streaming devices  14 .  
         [0039]    Referring to FIG. 3, the tape cartridge  12  is stored in a slot  18  in the storage magazine  10 . Other storage slots  20  and  22  are provided above the slot  18  and can be accessed by moving the transport and loading apparatus  16  vertically, as disclosed in the co-pending Application attorney docket number P01,0373. The storage slot  18  has a latch  24  biased toward a locking position by a locking spring  26 . The latch  24  engages the cartridge  12  to prevent inadvertent dislodging of the cartridge  12  from the slot  18 . The cartridge  12  can be removed from the slot  18  only by lifting of the latch  24 . The storage magazine  10  also has a calibration notch  28 , as will be described later.  
         [0040]    Each slot of the storage magazine has a spring (not shown) at the back wall that pushes the cartridge  12  outward. This causes a secure engagement of the cartridge by the latch  24  and permits easy removal upon lifting of the latch  24 . All of the storage slots are provided with the back wall springs and the latches  24 .  
         [0041]    As can be seen in FIG. 3, the cartridge has a recess  30  along the side. An undercut is provided at the edge  32 , as will become apparent later from the description of FIG. 22.  
         [0042]    In FIG. 4, the cartridge  12  is on the transport and loading apparatus  16 , and specifically is resting on a support platform  34  having side walls  36  and  38  to define a sliding channel along which the cartridge  12  is moved. The support platform  34  has a bracket  40  for holding a nut of a lifting apparatus, as described in the co-pending application, and a locking device  42  to selectively restrict movement of the cartridge  12 . In particular, the locking device  42  is a solenoid which activates a roller stop  44  that selectively engages a roller  46 . The roller  46  mounted on the side wall  36  contacts the cartridge  12  as the cartridge  12  is on the platform  16 . The roller  46  rolls as the cartridge  12  moves along the sliding channel. By activating the solenoid  42 , the roller stop  44  prevents movement of the roller  46  and as a result also stops movement of the cartridge  12 . The cartridge  12  is thus prevented from being dislodged during movement of the platform  16 .  
         [0043]    On the opposite side of the platform  16  from the locking device  42  is a gripper  48  on a gripper guide  50 . The gripper  48  is mounted for movement under control of a lead screw  52 . Compartments  54  and  56  are provided in the platform  16  in which are mounted a lead screw motor  58  and a gripper rotation motor  60 , respectively. Also provided in the platform  16  are passageways  62  and  64  for the vertical lifting apparatus and a compartment  66  for sensors.  
         [0044]    In FIG. 5, the gripper  48  and gripper drive apparatus are shown separately. Specifically, the gripper has a gripper body  68  on which are mounted two gripper hooks  70 . The base of the gripper body  68  has a threaded nut portion that encircles the threaded lead screw  52 . Rotation of the lead screw  52  causes the gripper  48  to move axially along the length of the lead screw  52 . The lead screw  52  is mounted for rotation in the gripper guide  50  and has a cog wheel  72  at the end thereof. A timing belt, or cog belt,  74  extends about the cog wheel  72  and also about a second cog wheel  76  that is driven by the lead screw motor  58 . The lead screw motor  58  is a DC motor, such as a motor with a tach-generator feedback.  
         [0045]    The gripper rotation motor  60  drives a spur gear  78  that in turn drives the rotation of the gripper guide  50  to rotate the gripper  48  between gripping and non-gripping positions. Sensor plates  80  are provided on the gripper guide  50  as well.  
         [0046]    Turning to FIG. 6, an end view of the gripper guide  50  shows the spur gear  78  in engagement with a gear segment  82  on the gripper guide  50 . The gripper guide  50  rotates about an axis  84  when the spur gear  78  is driven, so that the gripper  48  rotates between a lifted and a lowered position. The gripper hook  70  at the distal end of the gripper body  68  undergoes the greatest vertical movement when rotated.  
         [0047]    [0047]FIG. 7 shows the rotated position of the gripper guide  50 . The gear segment  82  extends from a guide channel  86  in which it is permitted to move when driven by the spur gear  78 . A plate  88  extends laterally from the gear segment and into a sensing space of a sensor  90 . The sensor  90  is a force sensor that senses the whether the gripper hook is free to move upward. The sensor  90  is used for feedback during the loader operation. For example, the weight of the cartridge is sensed during gripping of the cartridge by the gripper hook to determine if the cartridge is engaged or whether it has been lost and needs to be re-gripped. The sensor is also utilized during the calibration sequence to sense the rigid inner wall of the cartridge slot. rotated position of the gripper guide  50 .  
         [0048]    The gripper guide  50  is in its non-rotated position in FIG. 8, wherein the gear segment  82  is moved to an opposite end of the guide channel  86  compared to FIG. 7. The plate  88  is in a blocking position of the photo-interrupter sensor  90 . The present autoloader apparatus is thereby able to sense the position of the gripper guide  50  as it is rotated.  
         [0049]    [0049]FIG. 9 shows the gripper  48  including the gripper body  68  with the gripper hooks  70  at opposite ends of the distal end. The gripper hooks  70  are formed of spring metal or other flexible material and shaped with a cartridge hook  92  at the end most part. The gripper body  68  connects the gripper hooks  70  to a gripper nut  94  which is mounted on the lead screw  52 . The gripper nut  94  has a guide portion  96  extending in a generally opposite direction of the gripper body  68  and a guide flange  98  is provided on the guide portion  96 .  
         [0050]    In FIG. 10, the gripper body  50  has a pair of bores  100  through which the lead screw  52  extends and a channel  102  extending parallel to the axis of the lead screw  52  along which the guide portion  96  slides as it is moved along the lead screw  52 . The guide portion  96  moves due to the threaded gripper nut (FIG. 9) being threadably engaged on the lead screw  52 . A gear housing  104  in which the gear segment  82  is mounted is provided on the gripper guide  50 , the gripper guide thereby being rotated by driving the spur gear  78  under control of the motor  60 . To ensure that the gripper  48  and the gripper housing  50  rotate as one, the gripper housing has a guide slot  106  into which the guide flange  98  fits. The guide flange  98  slides along guide slot  106  as the gripper  48  is moved in the gripper housing  50 .  
         [0051]    [0051]FIG. 11 illustrates the shape of the cartridge hooks  92  on the hook portions  70 . The distal end of each cartridge hook  92  is turned up at  108 . The hooks  92  have a down turned portion  110  that provides both a pulling surface for the cartridges. The hook portions  70  are flexible and are anchored at  112 . The support for the hook portions  70  is provided by arms  114  of the gripper body  48  on which the hook portions  70  rest and a central portion  116  under which the central part of the hook portions  70  is secured.  
         [0052]    The sensors for the gripper guide  50  are shown in FIG. 12, wherein the sensor plates  80  are shown with sensors  118  and  120  positioned thereon. The sensors  118  and  120  are photo-interrupters that detect transmission or blockage of light between the two parts thereof. The sensor  90  is shown as well, with the plate  88  of the gear segment  82  therein.  
         [0053]    [0053]FIG. 13 illustrates the defined rotation positions that are sensed by the sensor plates  80  using the sensors  118  and  120 . The first of the sensor plates  80 , in particular, the sensor plate  122  has an opening with a lower edge  124  defining a gripper endstop. The second of the sensor plates  80 , in particular, the sensor plate  126  has two openings with edges defining four gripper positions  128 ,  130 ,  132  and  134 . The significance of these positions will become apparent in the following.  
       Operation of the Cartridge Transport Apparatus  
       [0054]    The challenge that led to the present invention was to pick up a data storage cartridge  12  from a slot in a magazine  10  and deliver it to a tape streamer  14  on the other side of the device. It had to be possible to pick up a cartridge  12  at one side and deliver it on the other side, and then pick it up again and deliver it on the initial side. In other words, the cartridge  12  had to pass through the device in both directions. The whole device should fit inside a 19-inch rack. The height in the system is critical, and it was a demand that the mechanism used as little height as possible.  
         [0055]    Standard cartridges  12  should be used, and no new design or changes to the existing cartridges should be performed. The cartridges  12  are rectangular and have only one undercut edge on each side. This limits the possibilities for gripping and handling the cartridges.  
         [0056]    The environment in which the present invention is used includes the following:  
         [0057]    The cartridges  12  are stored horizontally in a magazine  10 . They are held in place by the latch  24 , preventing them from falling out. Additionally there is a spring in the inner end of each cartridge slot  19 ,  20  or  22 , which is compressed when a cartridge  12  is in the slot and presses the cartridge  12  towards the latch  24 .  
         [0058]    As shown in FIG. 22, to release a cartridge  12  from a magazine slot  19 , for example, the latch  24  at the slot opening must be lifted. Then the compressed spring in the back of the slot  19  which exerts the force P 1  will push the cartridge  12  outwards, out of the slot  19  as shown in FIG. 23. The latch  24  must be lifted long enough for the cartridge front edge to come out in order to get the cartridge  12  out of the slot  19  as shown in FIG. 24.  
         [0059]    On the other side of the device one or two tape streamers  14  or additional magazines are placed. Each streamer  14  has a horizontal slot for a cartridge. To load a cartridge  12  in a drive  14 , the cartridge  12  must be pushed into the slot far enough for the feed mechanism in a the drive  14  to start.  
         [0060]    When a cartridge  12  is to be picked up from the drive  14 , the feed mechanism in the drive pushes the cartridge  12  partially out of the slot, and releases it. It is then free to be picked up.  
         [0061]    The multi-position gripper device  48  of the present invention uses very little space. It is based on a gripper device  48  mounted on a nut  94 that runs along a lead screw  52 . The gripper device  48  has a hook  70  in each end, which is used to pull the cartridge  12 , as shown in FIG. 17, out from the magazine slot  19  or the slot on a drive  14 , by hooking under the undercut edge of the cartridge  12  as shown in FIGS.  22 - 24 . The hook  70  can be lifted/lowered to given positions to enable gripping or releasing the cartridge  12 . The same hooks  70  are also used to push the cartridges  12  into the slots  19  in the magazine  10  and the drives  14 , as shown in FIGS. 20 and 21. When a cartridge  12  is to be picked up from a slot  19  in the magazine  10 , the gripper hook  70  first pushes the cartridge  12  a small amount further into the slot  19  as denoted by F 1  in FIG. 22. This is to ensure that the latch  24  is easy to lift. Then the hook  70  is lifted as denoted by F 2  to grip the cartridge  12  as shown in FIG. 23. The gripper hooks  70  are formed in such a way that the latch  24  (that prevents the cartridge  12  from falling out) is lifted simultaneously as the hook  70  grips the undercut edge on the cartridge  12 . In this way the cartridge  12  is released from the magazine slot  19  at the same time it is hooked onto the gripper hook  70 . When moving the gripper hook  70  out of the slot  19  as shown by F 3  in FIG. 24, the cartridge  12  is pushed against the hook  70  due to the spring in the back, and thus preventing the latch  24  from falling down in front of the cartridge  12  and locking it in the slot  12 . In this way the gripper hook  70  serves several a functions in one operation.  
         [0062]    The gripper device  48  is moved linearly by rotating the lead screw  52 . Rotation of the lead screw  52  is achieved by using a DC motor  58 . To prevent the nut  94  from rotating when the lead screw  52  runs, it has the flange  98  running in the slot  106  along the total length of movement. The slot  106  is in a housing  50 , which also works as the tilting device (height positioning) for the gripper hook  48 . The housing  50  can rotate about the center axis of the lead screw  52 , and a DC motor  60  is used to rotate the housing  50 . When the housing  50  rotates, the gripper device  48 , and also the hooks  70 , is rotated along an arc.  
         [0063]    The lead screw assembly is mounted along a platform  16 , over which the cartridge  12  is moved. The gripper hook  70  drags the cartridge  12  out of the magazine slot  19  and as far across the platform  16  as possible, as shown in FIG. 17. It then releases the cartridge  12 , tilts up and moves across to the other side of the cartridge  12 . The hook  48  is then tilted down on top of the cartridge  12 , as shown in FIG. 18. One of the edges  110  on the hook  70  will touch the backside of the cartridge  12 , the other hook  70  is flexed upwards, and when the gripper device  48  is moved, the cartridge  12  is pushed across the platform  16 . When the cartridge  12  is moved to the end of the platform  16  as shown in FIG. 19, the gripper  48  tilts up and moves away from the cartridge  12 . There it tilts down and pushes the cartridge  12  completely off the platform  16  and into the drive  14  as shown in FIGS. 20 and 21.  
         [0064]    When the cartridge  12  is to be removed from the drive  14  and placed in the magazine  10 , the gripper hook  48  works in the same way, but in the opposite direction. It drags the cartridge  12  out of the drive slot, moves back and pushes it as far across the platform  16  as possible. It then releases the cartridge  12  and moves to the other end. There it tilts down and pushes the cartridge  12  into a magazine slot  19 .  
         [0065]    Positioning and tilting of the gripper hook  48  is based on feedback pulses from tacho-generators on the DC motors  58  and  60 . But this method is inaccurate due to backlash in the system. It is not much of a problem for moving the gripper  48  along the lead screw  52 , but the tilting of the gripper hook  70  is critical and needs better positioning. To get an exact rotation of the gripper hook 70 , the system uses the sensors and photo-interrupters  90 ,  118  and  120  at given positions, which gives a discrete positioning which is independent from the backlash in the system. The photo-interrupters  118  and  120  operate in combination with sensor plates  80 . The plates  80  have holes at certain points, which allows light to pass through. By monitoring the signals from the photo-interrupters one will know when the gripper hook  48  is tilted to an exact position.  
         [0066]    There are several slots in the magazine  10 , and the device has to be positioned relative to them. This is taken care of by other mechanisms. The present application is directed to the device that picks up a cartridge  12 , stores it on the platform  16  and delivers it when told. While the device is moved to be positioned in front of a slot  19 , the cartridge is held in place on the platform by a locking mechanism  42 . This is necessary to prevent the cartridge from falling off the tray during transportation if a shock in the longitudinal direction should occur. Also while the gripper hook  48  moves from one side of the cartridge  12  to the other the cartridge  12  is locked from moving.  
         [0067]    The gripper hook feedback system utilizes a control system to know whether the gripper hook  48  holds a cartridge  12  or not. This is necessary to have control of the gripper  48  when errors occur or when power is cut uncontrolled, and to check that the gripper  48  actually grips a cartridge  12  when it is supposed to. In other words, it is necessary to have a feedback signal from the gripper  48  when it holds a cartridge  12 . This is solved using a sensor system  90  on the gripper housing  50 , also called a hook switch.  
         [0068]    The sensor system detects whether the gripper hook  48  is prevented from rotating freely or not. The rotation can be blocked by the following reasons:  
         [0069]    1) The hook  48  is gripping a cartridge  12  and is thereby prevented from further rotation because the mass of the cartridge  12  is higher than the spring force in the hook switch  
         [0070]    2) The hook  48  is touching underneath a flange on the calibration slot  28  in the magazine  10  (self-calibration mode. See description of calibration routine below).  
         [0071]    The sensor system uses a spur gear  78  with a preloaded spring in a slider path  86 , and a photo-interrupter  90  for sensing. The spring preload keeps the gripper device  48  in one position as long as it is unloaded. In this position the photo-interrupter  90  is open and light passes through from the LED to the receiver. If the gripper hook  48  is prevented from rotation, the spur gear  78  is moving relative to the gripper housing  50 . This movement causes a plate  88  to move into the photo-interrupter  90  and prevents light from passing through. Hence the signal from the sensor  90  changes, and the control system “knows” that something is hooked on the gripper  48 .  
         [0072]    As shown in FIG. 14, the present invention is capable of self calibration of three axes by using one sensor. Calibration of the sensor system is based on positioning the gripper hook  48  relative to the slot  28  in the magazine  10 . This relative positioning is used to calibrate three axis of movement in the complete autoloading system. All axes are calibrated using the signal from the hook switch sensor  90  as the calibration signal.  
         [0073]    An initial calibration of the height of the gripper hook  70  is performed. The gripper hook  70  height relative the base in the cartridge sliding surface  34  is calibrated in the production of the system. In production, the position of the sensors  118  and  120  on the platform  16  is carefully adjusted relative the sensor plates  80  with the discrete positions to give exact positioning of the gripper hook  70  relative to the platform  16 . One of the positions determined by the sensor plates  80  is the gripper calibration position.  
         [0074]    Calibration of the elevator is performed by the elevator being moved to a position a small distance below the presumed calibration position. The gripper hook  70  is moved underneath the inner top wall of the magazine and rotated to the gripper hook calibration position. Because the elevator is a bit lower than the estimated calibration position, the gripper hook  70  can rotate freely to this position, and no signal is sensed from the hook switch sensor  90 . Then the elevator is moved upwards while monitoring the signal from the hook switch  90  until the gripper hook  70  touches the top of the top inner magazine wall. The signal from the hook switch sensor  90  will then change, and when it does the position of the elevator relative to the magazine slot is known. It is thereby possible to align the height of the platform, and in particular the cartridge slider surface in the control system and the cartridge sliding surface in the magazine slot.  
         [0075]    Calibration of the traverse is performed when the elevator is moved to the nominal calibration position, while the traverse is moved a small distance off the expected calibration position. The gripper hook  48  is rotated to the lowest position (Position B 5 ) and moved into the calibration slot in the magazine. Then the gripper hook  48  is tilted upwards to the calibration position, so the signal from the hook switch sensor  90  changes. The traverse is then moved slowly while the signal from the hook switch sensor  90  is monitored. When the hook is completely free from the top inner magazine wall, the signal from the hook switch sensor  90  changes, and the exact position of the gripper hook  48  relative to the magazine slot in the traverse direction is known.  
         [0076]    Calibration of the lead screw  52  is performed by the elevator and the traverse (shown in FIGS. 25 and 26) being moved to their nominal calibration positions. The gripper hook  48  is tilted to the lowest position (Position  135 ) and moved into the calibration slot in the magazine. The gripper hook  48  is rotated upwards to the calibration position. When the gripper hook  48  is in this position, the hook switch sensor  90  will give a signal that the gripper hook  48  is blocked by the top inner magazine wall. Next step is to move the gripper hook  48  slowly out of the slot while monitoring the signal from the hook switch sensor  90 . When the hook switch sensor signal changes and tells that the gripper hook  48  is free, the position of the gripper hook  48  relative to the magazine and the cartridges is known.  
         [0077]    The sequence of operation is as follows:  
         [0078]    The operation of the device is based on three sequences, called Fetch, Flip Side and Shove. These three sequences are executed every time a cartridge is to be picked up and delivered. The sequences are basically the same regardless of whether the cartridge  12  is picked up from a magazine slot  19  and delivered to the drive  14 , picked up from a drive  14  and delivered to a magazine slot  19 , or moved from a magazine slot to a magazine slot. The three sequences carried out by the lead screw motor  58  and the tilting motor  60  are independent from which slot the cartridge  12  is to be delivered to or picked up at. This makes the programming of the shuttle and gripper operations very easy.  
         [0079]    Below are described the operation and sequences the device executes when picking up a cartridge  12  in a magazine  10  and delivering it to a drive  14 . This is one of the standard operations the device will perform, and illustrates the working principle of the device. It is assumed that the moving of the other mechanisms is finished before any of these sequences are executed.  
         [0080]    The Fetch Operation: Fetch from Front of the Magazine  
         [0081]    The gripper hook is tilted to the position B 5  shown in FIG. 15 to push the cartridge center. A close up view is shown in FIG. 22. The gripper nut  94  is moved to a position Y 5  to start pushing the cartridge  12 , and the moved further onto a position Y 1  for maximum push in toward the magazine side. As shown in FIG. 16, the gripper hook  70  is tilted up to a position B 4  to grip the cartridge  12 . This is shown in the enlarged view of FIG. 23 as well. Then the gripper nut  94  is moved back to a position Y 5  to start pushing the cartridge  12  and further onto a position Y 9  to hook the released cartridge  12  and move it towards the drive  14  as shown in FIG. 17.  
         [0082]    The Flip Side Operation: Back to Front  
         [0083]    The gripper hook  48  is tilted down to the position B 5 . Then the gripper nut  94  is moved to a position Y 10 . The gripper hook  48  is tilted up to a position B 1  to pass over the cartridge  12  and the gripper nut  94  is moved to the position Y 5 . The gripper hook  48  is tilted to a position B 3  to push on the cartridge top as shown in FIG. 18 and the gripper nut  94  is moved to a position Y 7  to push the cartridge  12  towards the drive  14  as shown in FIG. 19. The gripper hook  48  is tilted to position B 1 , the pass over position, and the gripper nut  94  is moved to the position Y 5 . The hook  48  is tilted down to the position B 5  and the gripper nut  94  is moved to a position Y 6  as shown in FIG. 20.  
         [0084]    The Shove Operation: Shove to Drive  
         [0085]    The gripper nut  94  is moved to the position Y 10  and the gripper hook  48  is tilted to the position B 5  of FIG. 20. Then, the gripper nut  94  is moved to a position Y 16 , which is the load cartridge in drive position. The gripper nut  94  is then moved to the position Y 5  as shown in FIG. 21. The cartridge  12  is thereby shoved into the drive  14 .  
         [0086]    The reverse operation to removed the cartridge  12  from the drive  14 , move it to the storage magazine  10  and shove it in to a slot will be readily apparent to the person of skill in the art after review of the foregoing.  
         [0087]    The overall device in which the present transfer apparatus is provided is shown in FIGS. 25 and 26. In particular, the transfer apparatus is lifted by a lifting apparatus  200  including brackets  202  which support vertically disposed threaded lead screws  204  that are threadably engaged with threaded nuts  206  in the platform, as disclosed in further detail in co-pending patent application attorney docket number P01,0373. This permits the transfer apparatus to access the upper slots of the storage magazine  10 , in the illustrated example, or to access stacked tape streaming devices.  
         [0088]    The transfer apparatus  16  is moved laterally by a drive apparatus  210  including a motor  212 , a gear train  214 , and a timing belt  216  and pulleys. The timing belt  216  is connected to the base  218  of the lifting device  200  so that when driven through the gear train  214  and motor  212 , the lifting device  200  and the platform  16  mounted thereon are moved laterally. The transfer apparatus is thereby able to access side-by-side slots of the storage magazine  10  or side-by-side tape streaming devices  14 .  
         [0089]    As described above the gripper hook  48  needs to be positioned at a number of positions to ensure accurate and complete operation. Still this is no problem because the motion along each axis is easily controlled.  
         [0090]    The present apparatus uses a minimum of height. In addition to the height of the cartridge  12  and the thickness of the platform  16 , it only requires enough height to let the gripper hook  48  pass over the cartridge  12 .  
         [0091]    Of course, an appropriate electronic control circuit, preferably including a microprocessor, is utilized to control the operation of the various motors and to sense the output of the sensors so as to effect operation of the autoloader.  
         [0092]    The present device has a low structural height and is compact in size. In a preferred embodiment, it will fit into a standard 19 inch rack. The present device also utilizes standard tape cartridges  12 .  
         [0093]    Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.