Abstract:
A data storage library for the storage of a plurality of data storage media, the library including a Z-direction mechanism for raising and lowering the media within the library, the Z-direction mechanism comprising support means for a picker mechanism for inserting storage media into and withdrawing them from storage locations within the library, a motor driven rotateable lever arranged to raise and lower the picker mechanism, and a counter-balancing mechanism including a spring which serves to reduce the power required to drive the motor.

Description:
BACKGROUND TO THE INVENTION  
       [0001]     This invention concerns data storage libraries in which a plurality of individual data storage media can be stored at various positions within the libraries.  
         [0002]     So-called libraries in which data is stored in magnetic or optical form on a plurality of individual data storage media are well known in the art. Particular data storage media which have been used include magnetic tape cartridges and cassettes, tape spools, magnetic storage discs, and data stored in optically readable form, for example on a storage disc.  
         [0003]     In general, such libraries store the media in racks, drums or magazines, or on shelves, from which individual media can be extracted by a transport mechanism which conveys them to a data drive where data is read from or written to them, to other positions within the library, or even to another library.  
         [0004]     Unlike conventional libraries for housing books, which fill rooms, magnetic and optical storage media for libraries of the type described are frequently stored in units which are of a size such that they fit within standard 19 inch (approximately 483 mm) racking systems, software residing on a separate computer or computers being used to control the functioning of these units. In addition, space constraints usually dictate that these units also have as small a height as possible based on increments of 1.75 inches (44.45 mm), which is generally the standard height increment for racking systems. There is therefore a desire for storage units which are to be housed within such racking systems to provide storage space for as many individual storage media as possible but also in the smallest rack height possible.  
         [0005]     In addition to storing the data storage media themselves, such storage units also need to house a transport mechanism for transporting individual media within the units, or to another unit, and in general they also have to house data drives for reading from and/or writing to individual data storage media, plus a power supply for the unit.  
         [0006]     Yet further equipment is usually included within these units, for example cooling fans and devices for identifying individual media within them, e.g. bar code readers for reading bar codes on the individual media, so that the transport mechanism can select and move the correct medium. This is clearly essential if the individual storage media are arbitrarily loaded by hand into vacant positions within the unit, and it is highly desirable even where this is not the case in order that control of the positioning and movement of the media within the units can be satisfactorily monitored. This can be particularly desirable where media can be exchanged between adjacent units.  
         [0007]     Bearing in mind the physical requirements of equipment required within each unit, for example power supplies, read/write devices for the stored media and transport mechanisms for transporting the media within the units, plus the overall physical constraints of the storage units themselves, the space within the units which is available to store individual data storage media is itself restricted. Furthermore, the physical dimensions of the data storage media themselves, their individual orientations within the units, for example imposed by racking systems, and the need to insert them into and remove them from individual storage locations within the units, impose constraints as to how many data storage units can be stored in a particular size of unit.  
         [0008]     In general, data storage media used in libraries of the type in question have one dimension which is substantially less than the other two, thereby enabling them to be stored with this minimum dimension either vertical or horizontal, the media themselves then being described as being stored either horizontally or vertically, respectively.  
         [0009]     Both horizontal and vertical storage of data storage media has been used hitherto in an attempt to maximise the number of storage units which can be stored within a particular unit. Storage with the media arranged vertically, that is with their minimum dimension arranged horizontally, has the advantage that individual storage media can be inserted into and removed from storage locations within a library using a transport mechanism operating solely within the X-dimension within the library, that is from front to back of the library. Picking and insertion of individual media from and to their respective storage locations can then be effected without the need for Z-direction movement of the picking mechanism, that is vertically. However, if the data storage media are stored in pluralities of horizontal stacks, that is with their minimum dimension vertical, or if more than one layer of vertically arranged media is housed within a unit, the transport mechanism also has to operate in the Z-direction.  
         [0010]     Various transport mechanisms have been proposed hitherto for providing movement of the mechanism in the Z-direction in data storage libraries, and typically such mechanisms involve the use of drive belts driven by stepping or DC motors. Although satisfactory Z-direction movement can be achieved using such mechanisms, they frequently occupy additional space in the X- and Y-directions within the units compared with mechanisms which only provide movement in the X- and Y-directions. This is a disadvantage because of space limitations within the units caused by the overall physical dimensions of the units themselves and those of the non-storage components such as power supplies and data readers/writers which have to be housed within the units.  
         [0011]     Withdrawal and insertion of data storage media from and into their respective storage locations is generally effected using a picker mechanism which can both translate and rotate the media in a horizontal plane, that is provide both R- and θ-movement. These movements are required, for example, to access data readers/writers placed at 90° to the media storage locations, and to access further storage locations facing the original array. X-Direction movement of the picker mechanism itself within the library unit can thereby be avoided, and as a result the associated space for this movement by the picker mechanism can be avoided.  
       SUMMARY OF THE INVENTION  
       [0012]     According to the present invention there is provided a data storage library for the storage of a plurality of data storage media, the library including a Z-direction mechanism for raising and lowering the media within the library, the Z-direction mechanism comprising support means for a picker mechanism for inserting storage media into and withdrawing them from storage locations within the library, a motor driven rotateable lever arranged to raise and lower the picker mechanism, and a counter-balancing mechanism including a spring which serves to reduce the power required to drive the motor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     An embodiment of transport mechanism for data storage media in data storage libraries in accordance with the present invention will now be described with reference to the accompanying drawings in which:  
         [0014]      FIG. 1  is a perspective view of the embodiment;  
         [0015]      FIG. 2  is a plan view of the embodiment;  
         [0016]      FIG. 3  is a side view of the embodiment;  
         [0017]      FIG. 4  is a perspective view of a part of the embodiment;  
         [0018]      FIG. 5  is a plan view of the part of the embodiment shown in  FIG. 4 ;  
         [0019]      FIG. 6  is a side view of part of the embodiment shown in  FIGS. 1-3  with parts removed;  
         [0020]      FIG. 7  is a plan view of the part of the embodiment shown in  FIG. 4  with parts removed for clarity;  
         [0021]      FIG. 8  is a perspective view of the embodiment seen in the direction of arrow A in  FIG. 4 ;  
         [0022]      FIG. 9  is a perspective view of the embodiment seen in the direction of arrow B in  FIG. 4 ;  
         [0023]      FIG. 10  is a perspective view to an enlarged scale of part of the embodiment shown in  FIGS. 4-8 ;  
         [0024]      FIGS. 11   a - e  are side views of part of the embodiment with parts omitted for clarity; and  
         [0025]      FIGS. 12   a - e  are perspective views corresponding to  FIGS. 11   a - e.   
     
    
       [0026]     The illustrated transport mechanism can be used in a variety of data storage libraries and so only the mechanism is shown in the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     The mechanism shown consists of a substantially horizontal and rectangular platform  1  carrying a picker mechanism  2  which is movable relative to the platform  1  to provide movement of the picker mechanism  2  in the Y-direction, and a vertical motion mechanism  3  for moving the platform  1  up and down to provide the picker mechanism  2  with movement in the Z-direction within the library. The picker mechanism  2  also provides translation of data storage media in the R-direction and angular rotation θ of the data storage media in the X,Y-plane.  
         [0028]     The platform  1  consists of a framework with two long sides  4  and  4 ′ connected together by two short sides  5  and  5 ′. Two pairs of rollers  6  and  6 ′, one roller of each pair being disposed above the other, are respectively located in vertical guides  7  and  7 ′ which are both of channel section. The guides  7  and  7 ′ are secured within the unit to prevent them moving when the mechanism is operated.  
         [0029]     A rod  8  is pivotally mounted in holes in end portions  9  and  9 ′ respectively of the shorter sides  5  and  5 ′ of the platform  1 . Pinions  10  and  10 ′ are fast on the respective ends of the rod  8 , and they engage vertical rack strips  11  and  11 ′ respectively attached to the vertical guides  7  and  7 ′ respectively. A guide roller  12  is pivotally mounted on shorter side  5 ′ of the platform  1  serve to reduce front to back translation of the platform  1 .  
         [0030]     The vertical motion mechanism  3  includes an arm  13  which is rotateable in a vertical plane beneath the rod  8 , and is pivotally connected to the rod  8  by a slider mechanism  14 . As can be seen from  FIGS. 1 and 2 , the slider mechanism  14  consists of a pair of substantially horizontal strips  15  between which, and at a central region thereof, is pivoted an end portion of the arm  13 . Sliders  16  and  16 ′ are attached to end portions of the strips  15  and are slideable on the rod  8  which is also free to rotate within the sliders  16  and  16 ′.  
         [0031]     Arm  13  is connected to a gear wheel  18  by an extension piece  22 , the gear wheel  18  being mounted on a shaft which is rotateable in a suitable hole in the framework of the unit. The gear wheel  18  is dished for reasons which will subsequently be explained.  
         [0032]     An electric motor  17  attached to the framework of the library (not shown) drives the gear wheel  18  via a pinion  19  on the output shaft of a speed reducing gearbox  20  driven by the output shaft of the motor  17 . A “clock” spring  21  is positioned within the dish of the gear wheel  18 , and it is secured at its outer end  23  to the framework of the library and at its inner end  24  to hub  26  the gear wheel  18 , the spring  21  having been pre-wound to provide an upward force which substantially balances the combined downwardly acting weight of the platform  1 , the picker mechanism  2 , the arm  13  and the extension piece  22 . As a result, the electrical power required by the motor  17  to raise and lower the platform  1  with its picker mechanism  2  is relatively low, and so a much smaller motor is required than if it had in particular to raise the platform  1  without this assistance. Not only does this have the advantage of being able to use a lower powered electric motor, which inherently tend to be relatively small, the use of a “clock” spring enables substantial lifting forces to be provided within a relatively small footprint within data storage libraries. Indeed, the “clock” spring can be substantially contained within the thickness of the dished gear wheel  18 .  
         [0033]     By the term “clock” spring we mean a spring made from a strip of metal which is wound in successive turns with one turn on another. Such springs are also known as “power” springs.  
         [0034]     Coil springs are generally not preferred because in order to produce an effect similar to that of a “clock” spring they would, by contrast, have to be substantially larger, and they are unlikely to fit into the space required by a “clock” spring producing the same or similar lifting effect.  
         [0035]     Actuation of the motor  17  causes the pinion  19  to rotate, which rotates the gear wheel  18  which in turn rotates the extension piece  22  and the arm  13 , thereby partially winding or unwinding the pre-wound spring  21 . The slider mechanism  14  is also raised or lowered, and the sliders  16  and  16 ′ slide along the rod  8  as the latter and the platform  1  to which it is attached are also raised or lowered.  
         [0036]     Control of raising and lowering of the platform  1  can be effected in any convenient manner, for example using a magnetically or optically coded strip attached to either of the fixed vertical guides  7  and  7 ′, and an associated magnetic or optical detector on the platform  1  (neither being shown in the drawings).  
         [0037]     As can be seen from  FIG. 2 , the mechanism  3  can be made to occupy relatively little space within the library unit within which it is located, the arm  13  being positioned directly below the rod  8 . The use of a dished gear wheel, which can itself be relatively thin, and a “clock” spring within it, which can also be relatively narrow whilst providing a strong rotational force, also contributes to the small space required by the mechanism  3 . The motor  17  and its associated gear box  20  do project out of the plane of operation of the arm  13 , but they can be relatively small because the motor  17  does not have to move the whole weight of the platform  1  and the picker mechanism  2  to move the latter in the Z-direction.  
         [0038]     The picker mechanism  2  will now be described with reference to  FIGS. 4-12 .  
         [0039]     The picker mechanism  2  consists of a base plate  25  on which is pivotally mounted a substantially “U” section body portion  40  with a lid  41  attached thereto. As can be seen more clearly from  FIG. 7 , the base plate  25  has two pairs of wheels  31  and  31 ′ which run in grooves  30  extending down the lengths of the long sides  4  and  4 ′ respectively of the platform  1 . Shafts for the wheels  31  rotate in bearings  32  mounted in the base plate  25 , and shafts for the wheels  31 ′ rotate in bearings  32 ′ mounted in end portions of arms  33  which are biased by springs (not shown) into the grooves  30 , thereby locating the base plate  25  on the platform  1 .  
         [0040]     The base plate  25 , and therefore the body portion of the picker  2 , is movable along the grooves  30  in the sides  4  and  4 ′ using a motor  42  through a belt drive  43  and a gear box shown generally at  44 . A gear wheel  34  driven by a gear wheel  35  driven from the gear box  44  meshes with a straight rack strip  36  attached to the long side  4  of the platform  1 .  
         [0041]     The gear wheel  35  is rotateable on a large diameter bearing  37  about which the body portion  41  is also rotateable. The large diameter bearing  37  provides space for cables to pass through it for control of the picker mechanism  2 .  
         [0042]     Within the body portion  40  is a gear box actuator mechanism  45  which is slideable within the body portion  40  on grooved tracks  46 ,  46 ′ attached to the lid  41  of the picker  2 , the actuator mechanism  45  having three wheels  47  which run in the grooved tracks  46  and  46 ′.  
         [0043]     Movement of the actuator mechanism  45  along the tracks  46 ,  46 ′ is effected using a motor  48  with a pinion  49  on its output shaft, the pinion  49  engaging a rack strip  50  attached to the underside of the lid  41 . Power to operate the motor  48  is provided via a ribbon cable (not shown).  
         [0044]     Integral with the actuator mechanism  45  is a cartridge picker  51  which is shaped to engage a recess in the underside of standard data storage cartridges. Engagement of the picker  51  with the recess in the underside of a standard cartridge can then be effected by lowering the platform  1  and moving the actuator mechanism  45  away from the gear box  44  so that the picker  51  projects out of the body portion  41  and beneath the cartridge so that the picker  51  is located beneath the aperture in the cartridge. The platform  1  is then raised so that the picker  51  enters the aperture in the cartridge. The cartridge is then supported by two cartridge levellers  52  and  53 , the leveller  52  including the picker  51 .  
         [0045]     Removal of the cartridge from its storage location within the library is then effected by moving the actuator mechanism  45  back into the body portion  40 , the cartridge being pulled over support runners  54  attached to the body portion  40 .  
         [0046]     A probe  55  and actuator members  56  and  57  form part of a gearbox actuator  58  attached to the actuator mechanism  45  on the opposite side from the levellers  52  and  53 . The actuator members  56  and  57  serve to actuate the gear box  44  when a cartridge is drawn sufficiently far along the runners  54  into the body portion  40 . The probe  55  co-operates with a sensor  59  to detect when the actuator members  56  and  57  have entered the gear box  44  sufficiently to actuate the dog-clutch, and also when they have moved out of the gear box  44  sufficiently for the dog clutch to have disengaged.  
         [0047]     The gear box  44  has a horizontal base plate  60  with two vertical side plates  61  and  62  within which is located a vertical input shaft  63  with a pulley  64  fast on its upper end, the pulley  64  being driven by the drive belt  43 . A gear wheel  65  fast on the lower end of the shaft  63  meshes with a gear wheel  66  on a vertical rotateable shaft  67 , the gear wheel  66  being slideable on the shaft  67 . A further gear wheel  68  is fast on the shaft  67 .  
         [0048]     The gear wheel  66  has dog-clutch teeth  69  between it and the gear wheel  68 , and the gear wheel  68  has recesses in it to receive the teeth of the dog-clutch when the latter is engaged. A compression spring  70  between the gear wheels  66  and  68  serves to push the two halves of the dog-clutch apart and out of engagement with each other.  
         [0049]     The gear wheel  65  is permanently meshed with the gear wheel  66 , the gear wheel  66  also being permanently meshed with the gear wheel  35 .  
         [0050]     The gear wheel  68  is permanently meshed with a toothed rack ring  71  secured to the base  25  of the picker  2 .  
         [0051]     Operation of the dog-clutch is effected by the actuator member  56  which on being pushed into the gear box  44  engages a cam  72  mounted on a horizontal shaft  73  which is rotateable in the side plates  61  and  62  of the gear box  44 . The cam  72  has a forked end portion  74  which is disposed around an upper portion of the shaft  67 . The forked end portion  74  of the cam  72  rests on the upper surface of an upward extension  75  of the gear wheel  68 . Insertion of the actuator member  56  into the gear box pushes the cam  72  down, which in turn pushes the gear wheel  68  down, thereby engaging the dog-clutch. Rotation of the shaft  63  then causes the gear wheel  68  to rotate, thereby causing the picker body  40  to rotate about the shaft  36 .  
         [0052]     Withdrawing the actuator member  56  from the gear box  44  allows the cam  72  to rotate upwardly as a result of the upward force provided by the compression spring  70  between the gear wheels  66  and  68 , and the dog-clutch as a result disengages and rotation of the picker body  40  ceases.  
         [0053]     A slideable pin  76  extends downwardly from the gear box  44 , a lower end portion of the pin  76  engaging holes  77  in the base plate  25  to lock the picker body  40  in rotational positions 90° relative to each other.  
         [0054]     The pin  76  can be withdrawn from the holes  77  by actuating a substantially “L” shaped lever  78  which is pivotal about a shaft  79 . A projection on the lever  78  engages a slot in an upper end portion of the pin  76 , rotation of the lever  78  thereby serving to raise or lower the pin  76 .  
         [0055]     The various stages of insertion and withdrawal of the actuator mechanism  58  into the gear box  44  can be seen from  FIGS. 11   a - e  and  12   a - e.    
         [0056]     Normally, without insertion of the actuator member  57 , the pin  76  will be located in one of the holes  77 . However, insertion of the actuator  58  into the gear box  44  results in the actuator member  57  pushing against an extension  80  of the lever  78 , thereby causing the latter to rotate and lift the pin  76  out of the hole  77  in which it was located. This, of course, is necessary to enable the body  41  of the picker  2  to rotate when the dog-clutch described above is engaged.  
         [0057]     When the actuator member  57  is withdrawn from the gear box  44 , the lever  78  rotates, and the pin  76  can then enter one of the holes  77 .  
         [0058]     When the actuator  58  is withdrawn from the gear box  44 , rotation of the shaft  63  results in gear wheel  65  rotating gear wheels  35  and  34 , the latter moving along the straight rack strip  36 . The result is movement of the picker  2  in the plane of the platform  1 .  
         [0059]     The ratios of the numbers of teeth on the gear wheels  35 ,  66  and  65 , and on the toothed ring  71 , are such that if the toothed ring  71  is rotated, the gear wheel  35  remains static. This enables the body portion  40  of the picker mechanism  2  to rotate relative to the base plate  25  whilst the picker mechanism  2  remains stationary relative to the rack strip  36 .  
         [0060]     Insertion of the pin  76  into one of the holes  77  in the base plate  25  serves to prevent movement of the base plate in the Y-direction whilst the body portion  40  is being rotated relative to the base plate  25 .  
         [0061]     Movement of the picker  2  is effected using a single motor, thereby enabling the picker  2  to be made relatively compact compared with pickers using separate drive motors for Y- and θ-direction movement. Furthermore, movement of the individual data storage media into and out of the picker  2  activates the gear box  44  and as a result automatically changes between these directions of movement.  
         [0062]     As will be appreciated, vertical motion mechanisms in accordance with the present invention could be used with any of a variety of picker mechanisms to provide motion in the Z-direction, and not necessarily that shown in the accompanying drawings.  
         [0063]     It will also be appreciated that picker mechanisms in accordance with the present invention could be used in a variety of data storage libraries, including those which do not include mechanisms in accordance with the present invention for providing Z-direction movement.