Abstract:
A tape cartridge and cartridge drive system for controlling the compatibility of first and second tape cartridges having the same form factor in first and second tape drives. The system permits backward compatibility of the first tape cartridge in the second tape drive, while prohibiting the second tape cartridge from being used in the first tape drive. The second tape cartridge includes a tab projecting distally from a recess. The tab is positioned to contact the door actuator surface on the first tape drive so as to prevent insertion of the second tape cartridge into the first tape drive. The tab defines a cross-sectional area perpendicular to the insertion direction smaller than a gap in the door actuator assembly of the second tape drive to permit the second tape cartridge to be inserted into the second tape drive, whereby the second tape cartridge is compatible only with the second tape drive.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to a system for mechanically distinguishing between two tape cartridges of the same form factor that contain magnetic tape having different recording characteristics. 
     BACKGROUND OF THE INVENTION 
     Tape cartridges configured to meet certain minimum physical requirements are said to have a particular “form factor.” In the tape cartridge arts, form factor generally defines the peripheral dimensions of the cartridge and the interface characteristics with the tape drive. For a variety of economic and manufacturing reasons, it may be desirable to provide a tape cartridge for a different type of tape drive that has the same form factor as existing tape cartridges. If there are different recording and dimensional characteristics of the magnetic tape for the different tape drive, however, such a tape cartridge must be distinguishable from existing tape cartridges of the same form factor. 
     Current techniques for distinguishing between different tape cartridges having the same form factor typically rely either on the read/write head assembly to magnetically detect a non-conforming tape format, or on some type of interaction between a physical feature of the tape cartridge and a sensing circuit in the tape drive. European Patent Application 0 389 121, for example, describes a data protection feature for a tape cartridge that enables sensing circuitry within the tape drive to distinguish between two different types of tape cartridges in otherwise identical form factors. 
     U.S. Pat. No. 5,480,103 (Gerfast et al.) discloses mutually incompatible mechanical cartridge lockout mechanisms incorporated into tape cartridges of the same form factor to mechanically distinguish between tape cartridges containing magnetic tape with different recording characteristics. In operation, the first tape cartridge can not be inserted into the tape drive for reading the second tape cartridge. Conversely, the second tape cartridge can not be inserted into a tape drive for reading the first tape cartridge. 
     Digital linear tape drives of the type sold under the “DLTtape” trademark are the most popular backup drives on the market today. As the drive and cartridge technology evolves to incorporate magnetic tapes with different recording characteristics, it is desirable for the new drives to be backwardly compatible with the enormous number of existing digital linear tape cartridges in use. In some circumstances, however, a fail-safe mechanical incompatibility is necessary to prevent new tape cartridges with magnetic tape having different recording characteristics for the new tape drive from being inadvertently used in an older style tape drive that might destroy data written on the tape by a newer drive. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a system for controlling the compatibility of first and second tape cartridges having the same form factor in first and second tape drives. The present system permits backward compatibility of the first tape cartridge in the second tape drive, while prohibiting the second tape cartridge from being used in the first tape drive. 
     In one embodiment, the first and second tape cartridges each include a housing with an access door extending across a portion of a front face, and a recess along a portion of a side face and a door latch positioned adjacent to the recess and a pivot axis of the door. The first and second tape drives each have a door actuator assembly positioned in a cartridge interface. Each of the door actuator assemblies includes a ramp to unlock the door latch on the first and second tape cartridges and a door actuator surface to open the doors on the first and second tape cartridges as tape cartridges are inserted along an insertion direction, such that the first tape cartridge is compatible with the first and second tape drives. The door actuator assembly on the second tape drive has a gap extending along the insertion direction between the ramp and the door actuator surface. The second tape cartridge comprises a tab projecting distally from the recess. The tab is positioned to contact the door actuator surface on the first tape drive so as to prevent insertion of the second tape cartridge into the first tape drive. The tab defines a cross-sectional area perpendicular to the insertion direction smaller than the gap to permit the second tape cartridge to be inserted into the second tape drive, whereby the second tape cartridge is compatible only with the second tape drive. 
     In one embodiment, the first and second tape cartridges contain magnetic tape with different recording characteristics. The second tape drive typically distinguishes the first tape cartridge from the second tape cartridge by recording characteristics on magnetic tape contained therein. The tab can be integrally molded into the housing of the second tape cartridge. 
     The present invention is also direct to a housing for a second tape cartridge having the same form factor as a housing for a first tape cartridge. The first and second housings each include an access door extending across a portion of a front face and a recess along a portion of a side face. A door latch is positioned adjacent to the recess and a pivot axis of the door. The housing for the second tape cartridge comprises a tab projecting distally from the recess. The tab is positioned to contact a door actuator assembly on a first tape drive so as to prevent insertion of the second tape cartridge into the first tape drive along an insertion direction. The tab defines a cross-sectional area perpendicular to the insertion direction smaller than a gap in a door actuator assembly of the second tape drive to permit the second tape cartridge to be inserted into the second tape drive, whereby the first tape cartridge is compatible with the first and second tape drives and the second tape cartridge is compatible only with the second tape drive. 
     In another embodiment, the system for controlling the compatibility of first and second tape cartridges having the same form factor in first and second tape drives includes a first tape drive having a drive clutch with a first diameter and the second tape drive having a drive clutch with a second diameter smaller than the first diameter. The first and second tape cartridges each include a housing containing a hub with magnetic tape. The housing of the first tape cartridge has an opening larger than the first diameter to permit mechanical coupling of the hub in the first tape cartridge with the drive clutch in the first and second tape drives. The housing of the second tape cartridge comprises an opening larger than the second diameter and smaller than the first diameter to permit mechanical coupling of the hub in the second tape cartridge with the drive clutch in the second tape drive, but not the first tape drive, whereby the second tape cartridge is compatible only with the second tape drive. 
     In another embodiment, the system for controlling the compatibility of first and second tape cartridges having the same form factor in first and second tape drives includes the first tape drive having a drive clutch with a plurality of teeth and the second tape drive having a drive clutch with a plurality of teeth and at least one flat region at or below a plane defined by valleys of the teeth. The first tape cartridge includes a housing containing a hub with magnetic tape. The hub of the first tape cartridge has a plurality of teeth capable of meshing with the teeth on the drive clutch of the first and second tape drives. The second tape cartridge includes a housing containing a hub with magnetic tape. The hub of the second tape cartridge has a plurality of teeth and at least one flat region located above a plane defined by valleys of the teeth and corresponding to the flat region on the drive clutch of the second tape drive, whereby the second tape cartridge is compatible only with the second tape drive. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a schematic illustration of a prior art tape drive assembly. 
     FIG. 2 is perspective view of a prior art tape cartridge. 
     FIG. 3 is a perspective view of a prior art tape cartridge interface. 
     FIG. 4 is a perspective view of a tape cartridge in accordance with the present invention. 
     FIG. 5 is a perspective view of a cartridge interface in accordance with the present invention. 
     FIG. 6 is a top plan view of the tape cartridge of FIG. 4 after engagement with the tape cartridge interface. 
     FIG. 7A is a schematic illustrations of the door actuator assembly illustrated in FIG.  3 . 
     FIG. 7B is a schematic illustrations of the door actuator assembly illustrated in FIG.  5 . 
     FIG. 8 is a schematic illustration of a prior art interface between the tape cartridge and a drive clutch. 
     FIG. 9 is a schematic illustration of a tape cartridge interfaced with a drive clutch in accordance with the present invention. 
     FIG. 10 is a schematic illustration of the incompatibility of the present tape cartridge with a prior drive clutch. 
     FIG. 11 illustrates a cartridge hub and drive clutch in accordance with the present invention. 
     FIG. 12 illustrates the incompatibility of a cartridge hub in accordance with the present invention with prior drive clutches. 
     FIG. 13 illustrates the compatibility of a prior cartridge hub with a drive clutch in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a prior art tape drive assembly  10  such as disclosed in U.S. Pat. No. 5,790,337, entitled “Tape Cartridge Qualified by Location, and Identified by Geometry, of Type Aperture”. The assembly  10  includes a tape head  12 , an internal take-up reel  14  driven by a take-up reel drive motor  15 , and a tape cartridge receiver  16 . These elements are contained within a housing  18 . Magnetic recording tape  20  of a predetermined type is provided to tape drive assembly  10  by insertion of a cartridge  22  into the tape cartridge receiver  16 . The tape cartridge receiver  16  includes a supply reel drive motor  25  that engages and drives supply reel  24  when the cartridge  22  is loaded into the cartridge receiver  16 . After being engaged by a buckling mechanism, such as for example as described U.S. Pat. No. 4,720,913 entitled “Mechanism for Joining Tape Leaders”, the tape  20  is spooled-off of a cartridge supply reel  24 , with an outermost tape leader being wound onto the internal take-up reel  14 . 
     FIGS. 2 and 3 are perspective views of a prior art first tape cartridge  30  and a corresponding first tape cartridge interface  50  for a first tape drive  80 , such as the tape drive assembly  10  of FIG.  1 . Housing  32  includes a door  34  that rotates about an axis  36  in the direction  38  when the first tape cartridge  30  is inserted into the tape cartridge interface  50 . The door  34  includes a door latch  40  having a cut out  42 . Side surface  44  of the cartridge  30  includes a recess  46  that cooperatively engages with first door actuator assembly  48  on a first tape cartridge interface  50  (see FIG.  3 ). 
     In operation, a user grasps a gripping surface  52  near rear face  54  of the first tape cartridge  30 . The front face  56  of the first tape cartridge  30  is inserted into the first tape cartridge interface  50  of the first tape drive  80  along an insertion direction  58 . Side guide surface  60  and top guide surface  62  engage with the side surface  44  and top surface  64  of the first tape cartridge  30 , respectively. As the first tape cartridge  30  progresses along the insertion direction  58 , ramp  70  penetrates cutout  42 . Further insertion causes the ramp  70  to lift the door latch  40 . Surface  72  on the door  34  engages with the door actuator surface  74  of the first tape cartridge interface  50  to rotate the door  34  in the direction  38 , thereby exposing the magnetic recording tape  20  (see FIG.  1 ). 
     FIGS. 4 and 5 are perspective views of a second tape cartridge  130  and a corresponding second tape cartridge interface  150  for a second tape drive  180  in accordance with the present invention. Door latch  140  includes a cut out  142 . Door  134  on the front face  156  of the second tape cartridge  130  rotates about an axis  136  in a direction  138  to expose the magnetic tape (see FIG.  1 ). The first tape cartridge  30  has substantially the same form factor as the second tape cartridge  130 , except that recess  146  includes a tab or stop  110 . The tab  110  may be integrally formed with the recess  146  or attached with an adhesive. The second tape cartridge interface  150  of the second tape drive  180  includes a door actuator assembly  148  having a ramp  170  and a door actuator surface  174 . Gap  112  is formed between the ramp  170  and the door actuator surface  174 . 
     FIG. 7A is a schematic illustration of the door actuator assembly  48  in the first tape drive  80  shown in FIG.  3 . Tape cartridge  130  is illustrated schematically with only the tab  110  shown in detail. As the second tape cartridge  130  slides along the tape cartridge interface  50 , the tab  110  engages the door actuator surface  74  to block complete insertion into the first tape drive  80 . Therefore, the second tape cartridge  130  can not be used with the first tape drive  80 . 
     FIG. 7B is a schematic illustration of the door actuator assembly  148  in the second tape drive  180  shown in FIG.  5 . As the second tape cartridge  130  slides along the tape cartridge interface  150 , the tab  110  slides through the gap  112  so that the second tape cartridge  130  can be completely inserted into the second tape drive  180 . The door actuator surface  174  engages with the surface  172  on the second tape cartridge  130  to open the door  134  (see FIG.  4 ). In this way, second tape cartridges  130  having magnetic tape with different recording characteristics can only be used in the second tape drive  180  shown in FIG.  5 . On the other hand, the door actuator surface  174  is positioned to engaged with the surface  72  on the first tape cartridge  30  so that both of the tape cartridges  30 ,  130  can be used with the door actuator assembly  148  provided in the second tape drive  180 . 
     In operation, front face  156  of the second tape cartridge  130  is inserted into the second tape drive  180  at the cartridge interface  150  along the insertion direction  158 , so the ramp  170  engages with the cutout  142  and lifts the door latch  140 . The door actuator surface  174  engages with the surface  172  to rotate the door  134  it about the axis  136  in the direction  138  to expose the magnetic tape. The tab  110  in the recess  146  is aligned with the gap  112  and slides above the ramp  170  and below the door actuator surface  174 . The tab  110  does not interfere with the insertion of the second tape cartridge  130  into the second tape drive  180  (see FIG.  7 B). FIG. 6 is a top plan view of the second tape cartridge  130  with the door  134  in the open position. 
     Similarly, front face  56  of the first tape cartridge  30  can be inserted into the second tape drive  180  so the ramp  170  engages with the cutout  42  and lifts the door latch  40 . The door actuator surface  174  engages with the surface  72  on the door  34  to rotate it about the axis  36  in the direction  38  to expose the magnetic tape. The tab  110  is not necessary for the tape cartridge  30  to operate correctly with the second tape drive  180 . On the other hand, if a user attempts to insert the second tape cartridge  130  into the first tape drive  80  shown in FIG. 3, the tab  110  will contact the door actuator surface  74  on the first tape cartridge interface  50  and prevent complete insertion of the second tape cartridge  130  into the first tape drive  80  (see FIG.  7 A). 
     FIGS. 8 through 10 illustrate an alternate embodiment for achieving backward compatibility of the first tape cartridge  200  with the second tape drive, while preventing the second tape cartridge  220  from being used in the first tape drive. FIG. 8 is a schematic illustration of a first tape cartridge  200  having a cartridge housing  202  and a hub  204  containing magnetic tape (see FIG.  1 ). The hub  204  is biased in a direction  206  toward an opening  208  in the bottom of the cartridge housing  202 . The bottom of the hub  204  includes a surface  210  configured to mechanically couple with a surface  212  on the top of a drive clutch  214 . A supply reel drive motor (see FIG. 1) drives the drive clutch  214  in the first tape drive  218 . The opening  208  has a first diameter  216  larger than the diameter  219  of the drive clutch  214 . 
     FIG. 9 illustrates a second tape cartridge  220  in accordance with the present invention having an opening  222  with a diameter  232  smaller than the diameter  219  of the drive clutch  214  on the first tape cartridge  200 , but larger than a diameter  242  of drive clutch  224  on second tape drive  240 . The drive clutch  224  mechanically couples with the hub  221 . Since the drive clutch  224  has a diameter smaller than the diameter  216  of the opening  208  of the first tape cartridge  200 , the first tape cartridge  200  is backwardly compatible with the second tape drive  240 . 
     On the other hand, as illustrated in FIG. 10, the opening  222  on the second tape cartridge  220  has a diameter  232  is smaller than the diameter  219  of the drive clutch  214  on the first tape drive  218 , thereby preventing a user from inadvertently using the second tape cartridge  220  in the first tape drive  218 . 
     FIGS. 11 through 13 illustrate an alternate embodiment for achieving backward compatibility of first tape cartridge  290  with the second tape drive  264 , while preventing the second tape cartridge  252  from being used in the first tape drive  280 . FIG. 11 is a schematic illustration of the compatibility of the second tape cartridge  252  with a second tape drive  264  in accordance with the present invention. Hub  250  on second tape cartridge  252  includes a toothed regions  254  and one or more flat regions  256 . The flat region  256  is located above a plane  258  defined by valleys  260  on the toothed regions  254 . In the illustrated embodiment, the flat regions  256  are located in a plane defined by the peaks  255  of the tooth region  254 . Drive clutch  262  in the second tape drive  264  includes a corresponding pattern of teeth  266  and one or more flat regions  268 , except that the flat regions  268  are located at or below a plane  270  defined by valleys  272  on the toothed region  266 . Consequently, the toothed hub  250  is compatible with the drive clutch  262 . In the event of a tooth mismatch (clutch teeth  266  resting on fill regions  256  of the hub  250 ), the second tape drive  264  includes a motor shuffle algorithm to assure proper tooth engagement. 
     FIG. 12 illustrates an attempt to engage the second tape cartridge  252  of FIG. 11 with the first tape drive  280 . Drive clutch  282  includes a plurality of teeth  284 . The flat regions  256  on the hub  250  prevent the teeth  254  from engaging with the teeth  284  on the drive clutch  282 . That is, the filled in regions  256  on the hub  250  prevent the teeth  284  from mechanically coupling with the second tape cartridge  252 . Consequently, the second tape cartridge  252  can not be used with the first tape drive  280 . 
     FIG. 13 is a schematic illustration of the compatibility of the first tape cartridge  290  with a second tape drive  264  in accordance with the present invention. Hub  292  on first tape cartridge  290  includes a toothed regions  294 . Drive clutch  262  in the second tape drive  264  includes a pattern of teeth  266  and one or more flat regions  268 . Since the flat regions  268  are located at or below a plane  270  defined by valleys  272  on the toothed region  266 , the toothed hub  292  is compatible with the drive clutch  262 . Consequently, the flat regions  268  on the drive clutch  262  do not prevent a first tape cartridge  290  from coupling with the second tape drive  264 .