Abstract:
A fully mechanical gripper for grasping and releasing data cassette cartridges is disclosed. The gripper may be built into a robotic picker, or may be implemented as an adapter to be fitted to an existing robotic picker. When used as an adapter, the present invention provides the added functionality of allowing a single robotic picker to carry different sized tapes by connecting and disconnecting itself to the adapter.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is directed generally toward gripping mechanisms for handling magnetic tape cartridges. More specifically, the present invention is directed toward a passive (completely mechanical) apparatus for gripping a data cassette within a robotic media storage library.  
           [0003]    2. Background of the Invention  
           [0004]    Robotic media storage libraries are devices for providing automated access to a large collection of data stored on multiple physical storage media, such as magnetic tape cartridges or compact discs. Robotic media storage libraries generally contain a plurality of storage locations for physical media, one or more media drives for reading or writing physical media and a manipulator or “picker” for moving physical media from a storage location to a drive and back. Robotic media storage libraries may have special storage locations designated for certain purposes, such as serving as a temporary storage location while two pieces of media are being swapped or for adding or removing physical media from the library.  
           [0005]    When magnetic tape cartridges are used in a storage library, there are basically two commonly employed methods by which the robotic picker grasps a tape cartridge for manipulation. One method is to use an electric motor, actuator, or solenoid to operate some kind of gripping mechanism. Another method to use a hook and channel, where a hook on the robotic picker engages a channel in the tape cartridge and drags the tape out of its storage location.  
           [0006]    Both of these methods have definite disadvantages. Although electric grippers are effective, they are expensive, and the small electric motors used can burn out. Hook and channel systems do not provide positive locking with a tape cartridge; thus, hook and channel systems often drop tapes. within the library.  
           [0007]    What is needed then, is a gripping mechanism for grasping tape cartridges that does not rely on expensive electric motors or solenoids.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a fully mechanical gripper for grasping and releasing data cassette cartridges. The gripper may be built into a robotic picker, or may be implemented as an adapter to be fitted to an existing robotic picker. When used as an adapter, the present invention provides the added functionality of allowing a single robotic picker to carry different sized tapes by connecting and disconnecting itself to the adapter.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0010]    [0010]FIG. 1 is an external view of a robotic tape library in accordance with a preferred embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a cutaway view of a robotic tape library in accordance with a preferred embodiment of the present invention;  
         [0012]    [0012]FIG. 3 is diagram of a subassembly of a robotic picker in accordance with a preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 4A is an exploded view of an adapter module in accordance with a preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 4B is an enlarged view of a gripper cam in accordance with a preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 5 is a side profile view of the operation of an adapter module in accordance with a preferred embodiment of the present invention;  
         [0016]    [0016]FIG. 6 is a transparent top view of an adapter module with loaded data cassette in accordance with a preferred embodiment of the present invention;  
         [0017]    [0017]FIG. 7 is a partial transparent top view of an empty adaptor module in accordance with a preferred embodiment of the present invention; and  
         [0018]    [0018]FIG. 8 is a partial transparent view of an adapter module with loaded data cassette in accordance with a preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    [0019]FIG. 1 depicts a typical data cartridge library  100  for automated storage and use of data cassettes. The model shown is a rack-mount type enclosure holding 100 data cassettes and 4 data cassette recorders. FIG. 2 provides an internal cutaway view of library  100 . Chassis  200  provides a framework for cassette recorders  202 , cassette storage cells  204 , and robotic picker assembly  206 . Robotic picker assembly  206  loads cassettes from cassette storage cells  204  to cassette recorders  202  for reading and writing. Likewise, when cassettes are no longer being read or written, robotic picker assembly  206  returns the cassettes to cassette storage cells  204 . Robotic picker assembly  206  is capable of rotating about a vertical axis and moving up or down along vertical shaft  208  using servo motors  210  and related control circuitry.  
         [0020]    [0020]FIG. 3 is a diagram of a subassembly  302  of robotic picker assembly  206  (in FIG. 2). Subassembly  302  contains a servo motor  304  and belt drive  306  to extend or retract a reach carriage  307  in a radial direction with respect to vertical shaft  208  (in FIG. 2). Reach carriage  307  can be driven into contact with a data cassette  308  or into contact with cassette adapter module  310  as required. A large cassette may be grasped directly using reach carriage  307 , while smaller cassettes may be grasped using adapter module  310 . Thus, both large- and small-sized cassettes may be stored in the same library, with subassembly picking up and holding adapter module  310  to use with smaller tapes only when necessary, and storing adapter module  310  in some location in the library when not in use.  
         [0021]    In an alternative embodiment of the invention, the mechanism of adapter module  310  may be built directly and permanently into subassembly  302 , so that no adapter module is necessary. Thus, the mechanism described herein may be embodied in either an adapter module for use with an existing robotic picker or in the robotic picker directly.  
         [0022]    [0022]FIG. 4A is an exploded view of adapter module  310 . Module  310  is contained by housing  400 , which is designed to be the same size in width and height as a large data cassette, so that the adapter will fit into the aperture of reach carriage  307 . A pair of gripper fingers  402 A and  402 B are actuated by gripper cam  404  to grasp a smaller data cassette. Gripper cam  404  is actuated by applying pressure against gripper cam lever  405 , which protrudes from the rear of the gripper cam  404 .  
         [0023]    To grip a data cassette, robotic picker subassembly  302  (in FIG. 3) extends reach carriage  307  until adapter module  310  strikes against one of cassette recorders  202  or cassette storage cells  204 . When adapter module  310  makes contact, adapter housing  400  is prevented from moving forward, and a special boss (not shown) attached to reach carriage  307  applies pressure to gripper cam lever  405 .  
         [0024]    Applying pressure to gripper cam lever  405  causes gripper cam  404  to rotate around center pin  420 , locking pins  408 A and  408 B to move out of a locked position within locking channels  444 , and gripper cam followers  406 A and  406 B on gripper fingers  402 A and  402 B to engage cam surfaces in gripper cam  404  to drive gripper fingers  402 A and  402 B to hinge about pivot pins  430 A and  430 B. This causes gripper fingers  402 A and  402 B to make a gripping or ungripping motion with respect to data cassette  308 .  
         [0025]    Whether gripper fingers  402 A and  402 B grip or ungrip is determined by the position of shifter plate  412 . Shifter plate  412  is configured to rotate up and down shift screw  416 . Doing so causes gripper cam  404  to shift up and down center pin  420 , because gripper cam  404  is connected to shifter plate  412  through mounting flange  417  (FIG. 4B) When reach carriage  307  is retracted, stop pin  431  catches on a surface of robotic picker subassembly  302  (in FIG. 3). This causes top plate  418  to slide forward relative to housing  400 .  
         [0026]    If no cassette is loaded into adapter  310  and reach carriage  307  is retracted, stop pin  417  will make contact with stationary peg  422 . This contact with stationary peg  422  will cause shifter plate  412  to rotate counter-clockwise when reach carriage  307  is retracted, moving gripper cam  404  downward so that gripper cam  404  enters into contact with gripper cam followers  406 A and  406 B on grip cam surfaces  440 A and  440 B (FIG. 4B). When reach carriage  307  is then extended, adapter housing  400  strikes storage cell  204 , lever  405  is actuated, gripper cam  404  begins to rotate, and gripper fingers  402 A and  402 B close in to grasp data cassette  308 .  
         [0027]    If data cassette  308  is loaded in adapter  310 , stop pin  419  will be in contact with data cassette  308 . Thus, when reach carriage  307  is retracted, shifter plate  417  will rotate clockwise, and gripper cam  404  will move upward and enter into contact with gripper cam followers  406 A and  406 B on ungrip cam surfaces  442 A and  442 B (FIG. 4B). When reach carriage  307  is then extended into contact with storage cell  204 , top plate  418  slides forward, gripper cam  404  begins to rotate, and gripper fingers  402 A and  402 B release their grasp of data cassette  308 .  
         [0028]    [0028]FIG. 5 is a diagram of a side view of a preferred embodiment of the present invention. Data cassette  308  is held in adapter module  310 . The mechanisms of adapter module  310  are actuated by stop pin  431 , which protrudes from the bottom of adapter module  310  and gripper cam lever  405 , which protrudes from the rear of adapter module  310 . Reach carriage  307  applies force  500  to adapter module  310  at gripper cam lever  405 , when extending adapter module  310  to pick up or release data cassette  308 . Picker subassembly  302  includes a stationary boss  502 , which applies force  504  to stop pin  431  when reach carriage  307  is retracted.  
         [0029]    [0029]FIG. 6 is a transparent top view of adapter module  310  in accordance with a preferred embodiment of the present invention, shown releasing data cassette  308  into tape drive  600 . Gripper cam lever  405 , when actuated by reach carriage  307 , rotates gripper cam  404  in a counterclockwise direction. Gripper cam followers  406 A and  406 B, which engage ungrip cam surfaces  442 A and  442 B, are moved by the rotated gripper cam  404  so as to cause gripper fingers  402 A and  402 B to open and release data cassette  308 . When gripper cam followers  406 A and  406 B engage grip cam surfaces  440 A and  440 B instead, gripper fingers  402 A and  402 B close when gripper cam lever  405  is actuated by reach carriage  307 .  
         [0030]    [0030]FIG. 7 is a partial transparent top view of adapter module  310  in accordance with a preferred embodiment of the present invention, depicting the operation of shifter plate  412 , when no cassette is loaded into adapter module  310 . When adapter module  310  is retracted, top plate  418  slides forward in relation to the frame of adapter module  310 . Stop pin  417  then engages stationary peg  422 . Stop pin  417  is part of shifter plate  412 , which is itself attached to top plate  418 . As top plate  418  continues to shift forward, this causes shifter plate  412  to rotate counter-clockwise around screw shaft  416 , thereby causing gripper cam  404  (FIG. 4A) to shift downward to engage grip cam surfaces  440 A and  440 B against gripper cam followers  406 A and  406 B, thereby causing adapter module  310  to enter into a “grip mode” of operation.  
         [0031]    [0031]FIG. 8 is a partial transparent top view of adapter module  310  in accordance with a preferred embodiment of the present invention, depicting the operation of shifter plate  412  when data cassette  308  is in the grip of adapter module  310 . When data cassette  308  is loaded into adapter module  310 , adapter module  310  is retracted, and top plate  418  slides forward, stop pin  419  comes into contact with the edge of data cassette  308 . Thus, when top plate  418  slide forward, shifter plate  412  is rotated in a clockwise direction. This causes gripper cam  404  (FIG. 4A) to be shifted upward so as to engage gripper cam followers  406 A and  406 B on ungrip cam surfaces  442 A and  442 B (FIG. 4B), thereby causing adapter module  310  to enter into an “ungrip mode” of operation.  
         [0032]    The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.