Patent Publication Number: US-7212375-B2

Title: Automated storage library gripper apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is related to co-pending U.S. patent application Ser. No. 10/642,038 entitled “AUTOMATED STORAGE LIBRARY CARTRIDGE GRIPPER WITH CARTRIDGE DETECTOR,” filed on Aug. 15, 2003, and U.S. patent application Ser. No. 10/642,032 entitled “AUTOMATED STORAGE LIBRARY GRIPPER WITH FINGER POSITION DETECTOR”, filed on Aug. 15, 2003, both of which are hereby incorporated by reference herein in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to automated storage library gripper mechanisms, and more particularly to gripper mechanisms and methods for detecting and handling storage cartridges, e.g., magnetic tape cartridges, in automated storage libraries. 
     2. Description of the Related Art 
     Magnetic tape cartridges have proven to be an efficient and effective medium for data storage in computer systems. Large computer systems may utilize numerous cartridges for data storage purposes as well as a plurality of tape drives for inputting and outputting data to and from storage cartridges in a timely manner. Typically, as the number of storage cartridges grows they are organized in automated storage libraries. Automated storage libraries including magnetic tape cartridges may improve access speed and reliability of data storage systems having large numbers of magnetic tape cartridges. 
     Automated cartridge libraries generally include a plurality of storage bins or slots for storing library tape cartridges, a robotic cartridge gripping mechanism (often referred to as a “picker”), and one or more tape drives. The robotic picker may be controlled to select a specific storage tape cartridge from the library and transfer the tape cartridge between a storage slot and a tape drive within seconds. The robotic picker typically includes a gripper or hand mechanism positioned on the robotic picker. The robotic picker may position the gripper near a desired tape cartridge and activate the gripper to engage or grip the tape cartridge to remove the cartridge from the storage bin. The robotic arm may move the gripper and tape cartridge to a location to load the tape cartridge into a tape drive, load port (for adding or removing tapes from the library), and the like. 
     Storage cartridges are typically stored in storage slots stacked within the automated library. The storage cartridges are generally stacked with high density within a storage library housing to increase or maximize the storage capacity for a given size library housing. The density at which the cartridges may be arranged relies, at least in part, on the size and configuration of the gripper mechanism and clearance required to pick a storage cartridge. Typically, a gripper mechanism engages a storage cartridge with opposing gripper fingers on the top and bottom major surfaces of the cartridge. In this instance, storage slots are separated by sufficient distance or clearance for the gripper mechanisms to navigate between neighboring storage cartridges and storage slots during a picking process. The clearance between storage slots results in lower cartridge packing density within the storage library. 
     Gripper mechanisms may also include protrusions that interact with slots or notches on the cartridge housing. The protrusions may pull (or push) a cartridge in one dimension to remove (or insert) a cartridge from a storage bin or media drive. For example, a storage cartridge is pulled from a storage bin by a protrusion on the gripper mechanism to rest on a platform associated with the robotic picker mechanism for transfer to a media drive or the like. 
     Generally it is desired that a controller of the gripper mechanism be able to determine at a given time the state of the gripper fingers, e.g., open, closed, properly closed on a cartridge, or partially closed on a cartridge. For example, when a system is initially powered on, the location of the gripper fingers is desirably known so that actuators are directed to position the gripper fingers appropriately. One method for determining the state of gripper fingers includes moving an actuator slowly until it reaches a command current level, e.g., a spike in the current level associated with being in an open or closed position. This method, however, may be incorrect if the gripper fingers or system become jammed mid stroke. Further, the potential for damaging the gripper mechanism increases. Devices, such as limit switches may also be included in the gripper mechanisms, but generally add cost and complexity to the gripper mechanism. 
     Therefore, what is desired is a gripper mechanism for picking cartridges that allows for increased packing density of storage cartridges within an automated storage library. Further, a system and method for providing information to a gripper positioning controller associated with the state of the gripper mechanism, e.g., open, closed, properly closed on a cartridge, or partially closed on a cartridge, are desired. 
     BRIEF SUMMARY OF THE INVENTION 
     In one exemplary embodiment a mechanical gripper mechanism for transporting and handling storage devices is provided. The gripper mechanism includes a pair of opposing gripper fingers rotatably mounted to a picker frame, each having a distal end adapted to engage opposite minor side surfaces of a storage device. The opposing gripper fingers are further interconnected by corresponding geared surfaces such that the gripper fingers rotate together. 
     In another exemplary embodiment a method for transporting and handling storage devices including opposing gripper fingers is provided. The method includes rotating a pair of opposing gripper fingers to engage opposing minor side surfaces of a storage device, wherein the pair of opposing gripper fingers are rotated together through corresponding geared surfaces associated with each gripper finger. 
     The present invention and its various embodiments are better understood upon consideration of the detailed description below in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary automated storage library system; 
         FIG. 2  illustrates an exemplary gripper assembly adjacent a column of storage slots; 
         FIGS. 3A–3C  illustrate an exemplary gripper assembly having opposing geared surfaces in a closed position, open position, and engaging a cartridge respectively; 
         FIG. 4  illustrates an exemplary gripper mechanism having interconnected gripper fingers and a cartridge detector in greater detail; 
         FIGS. 5A–5B  illustrate an exemplary gripper assembly having optically detectable indicia associated with the position of opposing gripper fingers; and 
         FIG. 6  illustrates an exemplary gear having optically detectable indicia disposed thereon. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is presented to enable any person skilled in the art to make and use the invention. Descriptions of specific materials, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the examples described and shown, but is to be accorded the scope consistent with the appended claims. 
     In one example, a gripper mechanism is provided for handling and transferring storage cartridges by gripping a cartridge housing by opposing minor side surfaces. The gripper fingers are rotatably attached to a picker frame and are coupled with each other through geared surfaces to open and close together through a single actuator. In another example, the gripper mechanism includes optically detectable indicia associated with opposing gripper fingers, where movement of the gripper fingers moves the optically detectable indicia, e.g., optically detectable indicia attached to a gear of the drive train for opening and closing the gripper fingers. An optical sensor may be used to determine the position of gripper fingers, e.g., open, closed, properly closed on a cartridge, or partially closed on a cartridge based on the optically detectable indicia. 
       FIG. 1  is a schematic illustration of an exemplary automated storage library system  100  for the storage and retrieval of a plurality of storage cartridges  114  stored therein. Library system  100  includes one or more media drives  112 , a plurality of storage tapes or cartridges  114  stored in bins or storage slots  116 , and a transport mechanism  118  that may be equipped with a picker mechanism (not shown) for transporting a selected cartridge  114 , for example, between a drive  112  and a storage slot  116 . Storage library system further includes a library controller  104  that communicates with a host processor or computer network to control the actions of transport mechanism  118  and drives  112  to retrieve and/or store data. 
     Library controller  104  may include a single general purpose computer, microprocessor, microcontroller, and the like. Alternatively, a separate cartridge loader controller and a library system controller may be included. A general library controller  104 , tape cartridge loader controller, or library system controller may include any programmable general purpose computer or processor and preferably will have a suitably programmed microprocessor or microcontroller. The input-output connections between the library controller and various other components of the library system  100  may include well-known industry standard cabling and communication protocols. For example, Ethernet, Inter Integrated Circuit bus (I2C), Small Computer System Interface (SCSI), ultra-wide SCSI, fast SCSI, fibre channel, and the like. 
     Library controller  104  operates to coordinate movements and actions of media drives  112 , robotic transport mechanism  118 , and the like. The controller  104  may include a suitable processor as described above and is typically interconnected with a host processor, which sends access commands to controller  104 . In this example, information recorded to or read from one or more of the cartridges  114  is transmitted between one of the drives  112  to the host or a storage area network through a second data path connection, e.g., a fibre channel bridge or the like. 
     Media drives  112  may include, for example, magnetic tape drives and/or optical disk drives, and cartridges  114  may include, for example, magnetic and/or optical storage devices. An exemplary drive includes the SDLT™ 320 magnetic tape drive, and an exemplary storage cartridge includes the Super DLTape™ Type I storage cartridge both sold by Quantum Corporation. The examples described herein are generally described as a magnetic tape library including multiple magnetic tape cartridges. It should be understood, however, that the various embodiments are contemplated with use for other types of storage media and storage media libraries. For example, a storage library may include optical media devices alone or in combination with magnetic media storage devices and the like. 
     Automated storage library system  100  may further include various other features such as load ports for manually adding and removing cartridges to and from the library, various access doors, control panels, power supplies, and the like as are known in the art. For clarity, however, such additional features have been omitted from the description. 
       FIG. 2  illustrates a detailed view of an exemplary robotic transport mechanism having a gripper assembly  200  adjacent a column of storage slots  216  including cartridge  214 . A storage library may include any number of storage slots  216  arranged in various manners. For example, storage slots  216  may be angled down from a front opening to the back to more securely hold cartridges  214 . One or more columns of storage slots  216  may be arranged along an interior cabinet of a library system that has flat or curved interior surfaces. 
     Gripper fingers  210  are attached to a picker frame  230  that may translate along support  232  towards cartridge  214 . As gripper assembly  200  approaches a cartridge  214 , gripper fingers  210  are in an open position such that cartridge  214  may fit between opposing surfaces of gripper fingers  210 . Gripper assembly  200  may further include a cartridge detector  220  that contacts the opposing face of cartridge  214  and depresses or moves linearly relative to gripper fingers  210  and picker frame  230 . In this example, cartridge detector  220  serves as a plunger with a large distal end configured to engage and be resilient against tape cartridge  214 . Depressing cartridge detector  220  indicates to a controller, e.g., a system controller or gripper controller, the position of cartridge  214  relative to gripper fingers  210  and more generally gripper assembly  200 . Cartridge detector may include several trip points, e.g., indicating a cartridge is approaching and a stop point where cartridge  214  is in suitable position for gripper fingers  210  to engage cartridge  214 . Further, various non-contact cartridge detectors may also be used, such as optical or acoustical sensors, as known in the art. 
     In this example, gripper fingers  210  are arranged to engage the opposing minor side surfaces of cartridge  214 , rather than the major (top and bottom) surfaces of cartridge  214 . Gripper fingers  210  may include opposing planar surfaces to grip and frictionally hold cartridge  214  therebetween against gravity and acceleration during movements within a library system. This allows for storage cartridges to be stacked more densely within a storage library system because clearance above and below each cartridge may be reduced compared to conventional grippers that engage and support the bottom and/or top of cartridge  214  for transportation. The engagement of gripper fingers  210  on the opposing minor side surfaces of cartridge  214  is desirably sufficient to hold and transfer cartridge  214  in two or more dimensions without additional structures such as platforms or supports located below and supporting cartridge  214 . In one example, however, a support platform is positioned below gripper fingers  210 . 
     As described in greater detail below, gripper fingers  210  are coupled to each other through corresponding geared surfaces and may be driven by a single motor  215  acting to rotate a single gripper finger  210 . Further, it is generally desired to know that gripper fingers  210  are in an open position prior to moving in to pick cartridge  214  to reduce the potential for damage to the gripper assembly  200  or cartridge  214 . A sensor (not shown) may be used to indicate to a controller the position of gripper fingers  210 , e.g., closed, open, or partially closed. 
     Gripper assembly  200  may further have various features known in the art such as a barcode scanner  250  and calibration camera  236 . Barcode scanner may be used to read barcode labels affixed to cartridges  214  and calibration camera may be used to determine and store locations of storage bins  216  relative to gripper assembly  200 . Additionally, further mechanisms such as pulleys, motors, and the like for vertical and horizontal translation may be included to move gripper assembly  200  within a storage library system. 
     With reference to  FIGS. 3A–3C  and  4 , an exemplary gripper mechanism  300  is illustrated.  FIGS. 3A–3C  illustrate exemplary gripper assembly  300  including a motor  315  and gripper fingers  310  coupled through corresponding geared surfaces in a closed position, open position, and engaging a cartridge respectively.  FIG. 4  illustrates the interaction between proximal ends of gripper fingers  310  in greater detail. 
     Preferably, gripper fingers  310  are rotatably attached to frame  330  such that distal ends thereof open and close to secure a tape cartridge  350  by engaging the cartridge housing on the opposing minor side surfaces  352 . One of the gripper fingers  310  may further include a protrusion  312  extending from the generally planar surface to engage a corresponding notch or groove included in tape cartridge  350 . Gripping a cartridge  350  by its minor side surface  352 , or its shortest dimension, may reduce space lost in a library housing to allow a gripper mechanism access when picking a cartridge. For example, a gripper mechanism that grips a cartridge by the top and bottom surfaces will generally need clearance above and below the cartridge to move in above and below cartridge  350 . Reducing the clearance above and below cartridges may increase the packing density of cartridges within the storage library. 
     Gripper fingers  310  are interconnected to a single actuator or motor  315 . The proximal end of gripper fingers  310  may rotate and interact through toothed or geared surfaces  314  (seen more clearly in  FIG. 4 ). Motor  315  rotates at least one of the gripper fingers  310  about rotation point  313  such that gripper fingers  310  rotate open or closed together through the geared surfaces  314 . The proximal end of one of gripper fingers  310  may include a larger geared surface than the opposing gripper finger  310 . The additional geared surface not coupled to the opposing gripper finger  310  may be coupled to and driven by motor  315  through one or more gears thereby rotating gripper fingers  310  together. 
     Alternatively, motor  315  may drive at least one of the gripper fingers  310  by other suitable methods. For example, motor  315  may move linearly to rotate gripper fingers  310 . Motor  315  may include any suitable motor to create the rotational motion of gripper fingers  310 . For example, a stepper motor, solenoid motor, or the like may be coupled through opposing gears to drive one gripper finger  310 , which through geared surfaces  314 , operates to open and close both gripper fingers  310  together. An exemplary stepper motor that may be used includes stepper motor PK224PA manufactured by Oriental Motors Corporation. 
     Gripper fingers  310  are preferably motor driven open and spring loaded or biased closed, e.g., by spring  374 . This allows for a loss of system power, anticipated or unanticipated, while gripper fingers  310  hold a cartridge with the force provided by spring  374  or other biasing member(s) coupled to gripper fingers  310 . Further, the cartridge may be manually removed without restoring power to the library system. In contrast, conventional gripper mechanisms often include a lead screw operable to open and close gripper fingers; however, such devices generally do not allow for manually opening the gripping fingers in the absence of power. Additionally, lead screw type gripper assemblies are generally slow in opening and closing processes compared to the present example and increase library access time. 
     Gripper fingers  310  may include integrally formed portions, e.g., injection molded pieces or the like, as well as multiple portions coupled together to interact during opening and closing processes. Various sized and shaped geared surfaces  314  are contemplated as well as various curvatures depending on the particular application. In this example, the geared surfaces  314  are on a curved surface of relatively high radius. In other examples, larger or smaller curved surfaces, or no curve at all, may be used in a similar fashion. Further, other similar interacting portions are possible such that gripper fingers  310  are rotatable together. The interaction between gripper fingers  310  through geared surfaces  314  may allow for a relatively lower profile gripper mechanism than conventional gripper mechanisms. 
     Gripper assembly  300  may further include a cartridge detector such as a physical or non-physical sensor. In one example, gripper assembly  300  has a cartridge detector  320  including a plunger or linearly translating member having a distal end  322  with a larger cross-sectional area measured perpendicular to the direction cartridge detector  320  extends than proximal end  324 . Cartridge detector  320  may be included in a detector subassembly  360  (see  FIG. 4 ) having one or more optical sensors configured to detect optical indicia disposed on the proximal end  324  of cartridge detector  320 . Other sensors, such as a potentiometer and the like may also be used with a cartridge detector  320 . Subassembly  360  may thereby determine when a cartridge is in a given position relative to gripper assembly  300  or gripper fingers  310 . 
       FIGS. 5A and 5B  illustrate an exemplary gripper assembly having optically detectable indicia  584  associated with the position and movement of gripper fingers  510 , and  FIG. 6 , which may be referred to in conjunction with  FIGS. 5A and 5B , illustrates an exemplary sensor ring  580  having optically detectable indicia  584  disposed thereon in greater detail. 
     In this example, optically detectable indicia  584  are included on a portion of an elliptical or curved ring with a castellated profile mechanically coupled or associated with gear  580  within the gripper mechanism  500  drive train. One or more optical sensors  590  are disposed such that the castellated profile forming optically detectable indicia  584  of gear  580  interrupts the optical beams of optical sensors  590  as gear  580  rotates. The configuration and relative position of the profile and sensors  590  allows sensors  590  to create signals for a processor or controller to determine, for example, the position, speed, and direction at which gripper fingers  510  are opening or closing, as well as whether the gripper fingers are in an open, closed, properly closed on a cartridge, or partially closed on a cartridge position. 
     A motor (not shown) rotates gear  532  coupled to gear  580 . In this instance, gear  580  is coupled to or includes a geared surface to interact with the larger geared surface of gripper finger  510  (to the right in  FIG. 5A ). Different gear ratios may be used between the motor and gear  580  and between gear  580  and gripper fingers  510  depending on the particular application and design. Additionally, a motor may interact directly with gear  580  or gripper finger  510 . 
     Gear  580  may also include a continuous ring with optically detectable indicia such as a pattern of reflective and non-reflective portions or transmissive and nontransmissive portions. An optical sensor may be positioned with a light source and detector on opposite sides (detecting transmission) of the sensor ring or on the same side (detecting reflection). Alternatively, one or more optical sensors may be disposed to detect the teeth of gear  580  directly to indicate position and/or velocity of gear  580 . A portion of the teeth may further include reflective or non-reflective material. 
     In this example, gripper assembly includes two sensors  590  disposed adjacent each other to provide quadrature signals to a controller. Quadrature signals may provide the position of the sensor ring  580  as well as both the magnitude and direction of the movement of sensor ring  580  and gripper fingers  510 . Optical sensors  590  are spaced approximately twice the pitch of the optical detectable indicia  584  to provide the quadrature signals, i.e., signals that are approximately 90° out of phase. 
     In this example, gear  580  rotates less than 180 degrees from a fully open position to a fully closed position. The optical indicia  584  are disposed to span a portion of gear  580 , i.e., less than 360 degrees. A controller may initially rotate gear  580  back and forth a distance greater than the spacing of optical indicia  584  to determine the location of gear  580  and gripper fingers  510 . For example, by determining that in one direction optical indicia  584  are no longer detected and the sensor  590  is near one end of the optical indicia  584 , the system may determine that gripper fingers are fully open or closed. If sensors  590  are near the middle of the indicia, firmware or the like may issue an open or closed command to continue rotation in one direction until optical indicia  584  are no longer detected. If optical sensors  590  do not detect optical indicia  584  upon initial searching, the system may determine that an error has occurred, e.g., gripper fingers  510  are open or closed beyond desired limits. It should be recognized that in other applications and designs, optical indicia  584  may completely encircle gear  580 . 
     In another example, an optical sensor  592  may be included to serve as a home sensor indicating when gripper fingers  510  are in the full open (or closed) position. For instance, a third optical sensor  592  (or first or second optical sensor depending on the particular application) may be included to serve as a home sensor indicating when the position of gripper fingers  510  and gear  580  are in a known position. For example, if gear  580  is found with optical indicia  584  located at optical sensors  590 , i.e., near the middle of optical indicia  584 , the system may be unsure of the position of gripper fingers  510 . Firmware may issue an open command to rotate clockwise until the third or home optical sensor  592  detects an optical indicia  584  indicating to the system that the gripper fingers  510  are open. 
     Optical sensors  590  and  592  may be attached to a common structure, e.g., a circuit board, located above gripper fingers  510 . Any suitable optical sensors, including separate optical sources and detectors are contemplated. An exemplary optical sensor includes a Transmissive Optical Sensor with Phototransistor Output (model TCST1030) manufactured by Vishay Intertechnology, Inc.; however, other suitable optical sensors may be used. It should be recognized that any number of optical sensors, e.g., one or more, may be used in conjunction with an optically detectable pattern associated with the position or movement of gripper fingers  510 . 
     The above detailed description is provided to illustrate exemplary embodiments and is not intended to be limiting. It will be apparent to those skilled in the art that numerous modification and variations within the scope of the present invention are possible. Accordingly, the present invention is defined by the appended claims and should not be limited by the description herein.