Abstract:
A gripper for clutching cartridges for transport in a computer information storage library. The library includes storage locations for the data cartridges, a transporter with the gripper for moving the cartridges between the storage locations and a read/write cartridge drive. The gripper provides a positive grip on the end of the cartridge by providing a positive retention finger to hook into the centrally located lip provided on the bottom of the cartridge and at least one opposing finger to contact the top of the cartridge to balance the mechanical forces between the positive retention finger and the opposing finger.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to an information storage library and more specifically to a robotic picker for data cartridges having a positive gripper for holding the cartridges. 
     BACKGROUND OF THE INVENTION 
     An information storage library for a data processing system typically includes at least a media storage system for computer information data cartridges, a drive mechanism for placing the data onto the cartridges and removing the data from the cartridges, a picker also called a gripper or engagement mechanism for inserting cartridges into the drives or the storage locations or for extracting the cartridges from the drives or storage locations, and a transport mechanism for moving the picker and the cartridge between the drives and the storage locations. Computer information storage libraries include a removable media which, for example, could be disk cartridges, either magnetic or optical, and magnetic tape cartridges. Media storage systems include, for example, carousels, cylindrical silos, and slotted magazines or racks. A wide variety of pickers are included in the storage library systems. For example, frictional grippers with multiple fingers may be used or the cartridges may be simply pushed or pulled. In general, for any robotic picker, it is desirable to reduce complexity, weight and number of parts. In particular, it is desirable to reduce the number of electrically active devices to eliminate potential sources for malfunction and to eliminate problems associated with moving electrical connections. Typically the present day picker includes a grip mechanism which holds the cartridges through friction. 
     An example of such a mechanism is shown in the IBM Technical Disclosure Bulletin of August 1993 at pages 265-268 and titled “Automated Cartridge Tape Library Grip Mechanism”. The gripper in the mechanism of the Technical Disclosure Bulletin is opened by activating a solenoid. The gripper grasps cartridges by means of a stationary finger and a pivoting thumb. The thumb is forced closed by grip springs. The thumb is pivoted open by energizing the solenoid. The solenoid is activated to place the gripper mechanism adjacent to the cartridge and then the solenoid is deactivated to grip the cartridge through friction applied through the springs. The grip springs cause the thumb to pivot closed thereby causing the cartridge to be squeezed between the thumb and finger. The problem with a frictional gripping mechanism is that the cartridge could be dislodged from the picker by contact with another mechanism or by an overactive cartridge holding mechanism in the storage system or drive mechanism. 
     It is, therefore, an object of the present invention to provide a picker mechanism that includes a gripper for positively gripping the cartridge. 
     Another picker for data cartridges is described in U.S. Pat. No. 5,687,039 issued on Nov. 11, 1997 to Paul Coffin, et al and assigned to the Hewlett-Packard company. This patent provides a dual fixed finger picker for gripping the cartridges. The fingers are fixed with regard to the picker and the picker must move vertically down to first allow the fingers to pass under the cartridge before engagement and then the picker must move vertically upward to engage the fingers with the cartridge. The picker can then draw the cartridge in and move to the next cartridge location. The picker can disengage the fingers from the cartridge with the similar combination of motions. The picker of this patent does not have a positive finger to provide a positive grip on the cartridge and relies mainly upon gravity to hold the cartridge on the fingers as the cartridge is drawn from the storage location or the drive. 
     Another object of the present invention, therefore, is to provide a positive gripper mechanism on a robotic picker that positively holds the cartridge without involved motions of the picker with regard to the cartridge. 
     There is an ongoing need for improved grippers for the pickers for computer information cartridges that provides a positive grip to hold the cartridge during transport between the storage area and the drives. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a picker assembly having an enhanced gripping mechanism for holding cartridges while transporting the cartridges between the storage area and the drive mechanism of a computer library system. 
     It is another object to provide a gripper mechanism that positively hooks into the cartridge. 
     It is a further object of the invention to provide a gripper that positively interacts with the end of the cartridge while including balancing fingers to prevent the cartridge from disengaging with the gripper mechanism. 
     It is a further object of the present invention to provide a gripper that does not solely depend upon a frictional grip to hold a cartridge for transport in the library system. 
     These and other objects are achieved in this invention by providing an automated storage library having a media storage system for a plurality of data cartridges, at least one drive mechanism, a transport mechanism for moving the cartridges between the drives and the storage areas, the transport mechanism including a positive picker or gripper mechanism that includes a hooking finger for interacting with an end of the cartridge through a positive retention finger to hook into a centrally located lip provided on the bottom of the cartridge and at least one opposing finger to contact the top of the cartridge to balance the mechanical forces between the positive retention finger and the opposing finger. A solenoid may be used to open the fingers for locating the gripper adjacent to the cartridge, as shown in one embodiment. When the solenoid is deactivated, springs place the positive retention finger positively hooking into the lip of the cartridge and further springs positively bring the opposing fingers to contact the top of the cartridge to firmly grip the cartridge. 
     In a second embodiment, the transport mechanism includes a casing that surrounds the cartridge during transporting. At least the positive retention bearing spring is loaded open when the gripper mechanism is positioned to accept or release the cartridge located and closed to hook into the centrally located lip as the gripper mechanism loads the cartridge into the casing. 
     The foregoing and other features and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B are perspective views of an automated storage and retrieval data processing library employing an embodiment of the cartridge holding mechanism of the present invention; 
     FIG. 2 is a perspective illustration of a gripper in proximity to a bank of storage cells of the library; 
     FIG. 3 is a perspective view of a prior art gripper mechanism which includes the positive retention design of the present invention; 
     FIG. 4 is an exploded view of the gripper mechanism in association with a cartridge and storage area according to the present invention; 
     FIG. 5 is an exploded view of the underside of the storage area and cartridge showing the hooking mechanism of the gripper with respect to the present invention; and 
     FIG. 6 is perspective view of an alternative gripper design encompassing the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the illustrations, like numerals correspond to like parts depicted in the figures. The invention will be described as embodied in an automated magnetic tape library storage subsystem for use in a data processing environment. Although the invention shown uses magnetic tape cartridges, one skilled in the art will recognize that the invention equally applies to optical disk cartridges or other removable storage media. Furthermore, the description of an automated magnetic tape storage system is not meant to limit the invention to data processing applications as the invention herein can be applied to magnetic storage and cassette handling systems in general. 
     FIGS. 1A and 1B are views of an automated information storage and retrieval library  10  employing one embodiment of a picker mechanism which can include the present invention. The library  10  includes one or more data recorder modules or drives  12 , a plurality of cartridges  14  stored in a bank of cells  16  forming a storage module, an accessor  18  for transporting a selected cartridge  14  between a storage cell  16  and a drive  12 . The accessor  18  includes the picker mechanism with a cartridge gripper  20  of the first embodiment design. The second embodiment design of a picker mechanism will be discussed later. The drives  12  can be optical disk drives or magnetic tape drives and the cartridges can contain optical or magnetic media, respectively. The library  10  also includes a library data directory or controller  24  that interconnected with, and controls the action of, the drives  12  and the accessor  18 . The controller  24  which includes at least one computing processor is further interconnected with a host processor (not shown) from which it receives access commands. Information to be recorded on, or to be read from, selected cartridges  14  is transmitted between the drives  12  and the host  26  through the library controller  24  or directly between the drives  12  and the host. 
     FIG. 2 is an illustration of the picker mechanism  11  in front of the bank of storage cells  16 . The library  10  may have many such banks of cells and each bank may have any number of cells. The arrangement of the cells  16  shown in FIG. 2 is for illustrative purposes only and it is not necessary for the present invention that the bank of cells have a particular configuration, or even that the cells be grouped into defined banks. A more detailed drawing of the picker mechanism  11 , including the cartridge gripper  20  is shown in FIGS. 3A and 3B. 
     Referring now to FIG. 3A, the accessor  18  moves the picker mechanism  11  forward in the direction such that the cartridge gripper  20  which includes a positive retention finger  30  shaped like a hook and an opposing finger  32  move on opposite sides, i.e., the top and bottom, of the target cartridge. The picker mechanism  11  selects one cartridge from the plurality of cartridges  14  as shown in FIG.  2 . The front end of an eject bar  34  contact the rear end of the target cartridge. This forces the eject bar pads to move away from a cartridge presence sensor thereby notifying the grip controller (not shown) that the cartridge gripper  20  is aligned properly with the cartridge  14 . The picker mechanism  11  continues to move forward until the eject bar contacts the front of the cartridge gripper  20 , thereby triggering a reach complete sensor  38 . 
     The reach complete sensor  38  signals the grip controller that the cartridge  14  is fully seated in the cartridge gripper  20 . The grip controller then stops the forward motion of the cartridge gripper  20  and thereby to de-energize a solenoid  40 . 
     Still referring to FIGS. 3A and 3B, the cartridge gripper  20  grasps the cartridges  14  by means of the positive retention finger  30  in the shape of a hook and the pivoting opposing finger  32 . Both the positive retention finger  30  and the opposing finger  32  are forced closed by grip springs (not shown). The positive retention finger  30  and the opposing finger  32  are pivoted open by energizing the solenoid  40 . The positive retention finger  30  and the opposing finger  32  are as thin as material strength will allow to permit insertion between the closely spaced cartridges in the library storage cells  16 . The positive retention finger  30  has a hook to engage a cavity and lip of the cartridge  14  as will be described later in FIG.  5 . The opposing finger  32  contacts the top of the cartridge to capture the cartridge  14  between the opposing finger  32  and the positive retention finger  30 . 
     The picker mechanism  11  employs an eject bar which translates in the X direction guided by linear bearings and is biased in the X direction by eject springs (not shown). The eject bar  34  serves three purposes. First a cartridge present sensor  36  senses the forward end of travel of the eject bar  34  and notifies the gripper controller that a cartridge is present. A reach complete sensor  38  senses the rear position of the eject bar  34  and notifies the gripper controller that the cartridge  14  is fully seated in the cartridge gripper  20  and deactivates the solenoid  40  to close the gripper by moving the positive retention finger  30  and the opposing finger  32  in the Z direction towards each other. After the picker mechanism  11  arrives at its destination with a cartridge, the solenoid  40  is activated thereby compressing the springs and removes the positive finger  30  and the opposing finger from contact with the cartridge. The spring loaded eject bar  34  then ejects the cartridge from the cartridge gripper  20 . A sensor flag  42  senses that the fingers are open. The sensor flag  42  confirms to the grip controller that the fingers are open and rotated fully in the THETA Y direction. The cartridge gripper then proceeds to move the gripper mechanism forward in the X direction over the cartridge. 
     The picker mechanism  11  is supported by two parallel shafts extending from the accessor  18 . The picker mechanism  11  rides on linear bearings and is permitted to translate in the X direction on the shafts. The picker mechanism  11  is biased in the positive X direction by two compliant springs  44 . The compliant springs  44  causes the cartridge gripper to be held against seats on the cartridge gripper body and against a compliance sensor  46 . The compliance sensor  46  senses the gap between the top and the cartridge grip body to notify the grip controller that the picker mechanism  11  has stepped forward in the positive X motion. 
     The solenoid front  40  is fixed to a mount that permits the solenoid and the mount to rotate in the THETA Y direction on pins and bushings held in journals on the picker mechanism  11  body. The purpose of this is to permit the solenoid  40  to conform to the rotational motion of the fingers  30  and  32  which are attached to the plunger of the solenoid  40 . 
     In order to have the picker mechanism  11  select a cartridge  14 , the library accessor  18  receives a command from the library controller. The accessor  18  moves the picker mechanism  11  in close proximity to the target cartridge. The solenoid is then energized causing the positive retention finger  30  and the opposing finger  32  to rotate open. The sensor flag  42  confirms that the fingers are open. The accessor  18  then moves the picker mechanism  11  forward in the positive X direction such that the positive retention finger  30  and the opposing finger  32  move on opposite sides of the target cartridge with a positive retention finger  30  facing the bottom of the cartridge. A front end of the eject bar  34  contacts the rear end of the target cartridge. This forces the eject bar stop to move away from the cartridge present sensor  36  thereby notifying the grip controller that the cartridge gripper  20  is aligned properly with the cartridge. The cartridge gripper  20  continues to move forward until the eject bar  34  contacts the front of the picker mechanism  11  body to trigger the reach complete sensor  38 . 
     The reach complete sensor  38  signals the controller that the cartridge is fully seated in the cartridge gripper  20 . The controller stops the forward motion of the picker mechanism  11  and de-energizes the solenoid  40 . The grip springs cause the positive retention finger and the opposing fingers to pivot closed causing the cartridge to be squeezed between the fingers. The accessor  18  reverses motion in the negative X direction, thereby extracting the cartridge from its storage cell. 
     The picker mechanism  11  ejects a cartridge to place it into its storage cell  16  or into the drive  12  by having the accessor  18  move the picker mechanism  11  and the cartridge it is carrying near the loader of a tape drive unit  12  such that the remaining motion is only in a forward positive X direction. The accessor  18  moves the picker mechanism  11  and the cartridge forward such that the cartridge begins to move into a tape drive  12 . The controller then energizes the solenoid causing the positive retention finger  30  and the opposing finger  32  to pivot open (in the negative THETA Y rotation). The eject springs push the eject bar  34  forward thereby ejecting the cartridge from the cartridge gripper. The cartridge presence sensor  36  changes state, signaling the controller that the cartridge is free of the fingers  30  and  32 . The cartridge gripper  20  is then moved in a negative x direction to remove the picker mechanism  11  from contact with the cartridge and the tape drive unit. The controller then de-energizes the solenoid permitting the grip springs to rotate the positive retention finger  30  and the opposing finger  32  to a closed position. Restoring the cartridge from the drive unit  12  to its storage cell  16  is performed in the reverse order. The interaction of the positive retention finger  30  and the opposing finger  32  of the cartridge gripper  20  with the cartridge  14  and its storage cell  16  is shown in FIGS. 4 and 5. 
     Referring now to FIG. 4, the interaction of the positive retention finger  30  and the opposing finger  32  of the cartridge gripper  20  with the top side of a cartridge  14  and its interaction with its storage cell  16  is shown. Only one storage cell  16  and one cartridge  14  is shown to more easily describe the interaction with the cartridge gripper  20 . The cartridge  14  is held within its cell  16  by spring fingers  50  and  52 . These spring fingers  50  and  52  interact with notches in the cartridge  14  with only one notch shown at  54 . The spring fingers  50  and  52  positively hold the cartridge into its cell  16 . These spring fingers prevent an easy withdrawal of the cartridge from its cell which could cause the cartridge  14  to drop to the floor of the library and thus prevent any further use of the library until the cartridge was retrieved. The picker mechanism  11  could be a sleeve-like casing enveloping the cartridge  14 . Reference is made to U.S. Pat. Nos. 5,659,444, 5,631,785, and 5,680,377, all issued to C. H. Dang, et al and assigned to the assignee of the present invention for a more complete description of a sleeve casing cartridge picker mechanism. 
     In FIG. 5, the cartridge  14  is shown with a notch  56  that interacts with the spring finger  52  of the cell  16  to hold the cartridge in place. The cartridge  14  also includes a cavity  58  centrally located at the rear of the cartridge  14  with a cavity lip  59  covering the cavity  58  at the rear of the cartridge  14 . The positive retention finger  30  of the cartridge gripper  20  is placed into the cavity  58  with the cavity lip  59  interacting with the positive retention finger  30  to firmly grip the cartridge  14  when the cartridge gripper is activated to grip the cartridge as previously mention for FIG.  3 . The opposing finger  32  contacts the top of the cartridge as the positive retention finger  30  contacts the cavity  58  and the lip  59  on the bottom of the cartridge. With this motion, the cartridge  14  is firmly held by the cartridge gripper  20  and when the cartridge gripper  20  is activated to pull the cartridge  14  from its cell  16 , the grip by the fingers  30  and  32  is such that the tension against the cartridge by the spring fingers  50  and  52  are easily overcome without dropping the cartridge. Another embodiment performing the positive retention finger  30  and the opposing finger  32  for the gripper  20  is shown in FIG.  6 . 
     Referring now to FIG. 6, the cartridge gripper  20  includes a single positive retention finger  60  opposite two opposing fingers  62  and  64 . For this embodiment, the positive retention fingers  60  acts in a similar manner to the positive retention finger  30  of FIG. 5 to interface with the cavity  58  and the lip  59  of the cartridge  14 . The opposing fingers  62  and  64  contact the top side of the cartridge  14  in the same manner as described in FIG.  5  and provide a positive holding action to withdraw the cartridge from its cell  16  in a manner as described for FIG.  5 . 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.