Abstract:
A parallel gripper for handling multiwell plates in an automated analysis system, moves individual multiwell plates between a plate storage array unit (i.e., plate hotel) and an imaging station. More particularly, the gripper has two parallel plate-gripping arms that move in equal, but opposite linear directions and are controlled using a stepper motor. Each of the arms has a shelf that provides support for the corresponding side edge of a multiwell plate.

Description:
BACKGROUND OF THE INVENTION 
     Multiwell analysis plates used in automated analytical equipment, including automated biological assay, are widely used. These plates are standardized for use in various instruments, such as epifluorescence multiwell imaging analysis, protein crystal detection and ELISA (Enzyme-Linked ImmunoSorbent Assay). Typically, plastic 96-well plates, having an 8×12 array of wells, are used; however, 6-, 384- and 1536-well plates, and other array arrangements are also used. 
     US Patent Application Publication No. 2004/0256963 filed by Afflick et al. published Dec. 23, 2004, is directed to an automated sample analysis system capable of handling a large number of multiwell plates. As shown in FIGS. 6-8 and discussed at paragraphs 51 and 89-99, this system uses a robotically operated plate handler. In particular, as stated at paragraph 93, the plate handler in this system does not grasp and lift the plates. 
     U.S. Pat. No. 6,496,309 issued to Bliton et al. on Dec. 17, 2002 discloses an automated CCD-based micro-array imaging system, but appears to be silent regarding any sample plate handler, e.g., handlers for the gene chip arrays. 
     U.S. Pat. No. 5,609,381 issued to Thom et al. on Mar. 11, 1997, U.S. Pat. No. 4,808,898 issued to Pearson on Feb. 28, 1989, U.S. Pat. No. 4,699,414 issued to Jones on Oct. 13, 1987, and U.S. Pat. No. 4,579,380 issued to Zaremsky et al. on Apr. 1, 1986, all exemplify parallel grippers that can be used with transporting robots. However, none of these teach or disclose the parallel gripper structure of the present invention using the stepper motor. 
     During gripping, the plastic plates can be unnecessarily squeezed by the prior gripping devices, causing the plates to buckle and adversely affecting the contents of the well. This can result in inaccurate analyses. Also, the prior gripping devices can grip the sides of the plates at uneven positions, which can adversely affect the analysis. 
     It is an object of the present invention to provide a parallel gripper usable with a multi-well plate handling robot to grip a multi-well plate that maintains the plate in a horizontal orientation, avoids disruptive squeezing of the plates during gripping, and minimizes or eliminates sudden movements that can disturb the contents of the plate wells. 
    
    
     
       LIST OF DRAWINGS 
         FIGS. 1A ,  1 B, and  1 C show perspective, elevation and plan views of a system using the inventive gripper. 
         FIG. 2  shows a perspective view of the inventive gripper holding a multi-well plate. 
         FIGS. 3A ,  3 B and  3 C show perspective, plan and exploded views of the inventive gripper. 
         FIGS. 4A ,  4 B and  4 C show a perspective, front and plan view of an individual plate housing. 
     
    
    
     PARTS/FEATURES LIST 
     
         
         
           
               10  Multi-well plate 
               100  Overall automatic analysis system 
               110  Plate hotel 
               120  Individual plate housing (in hotel) 
               150  Plate housing shelf (detached) 
               152  Notch 
               156  Raised center surface of plate housing shelf 
               158  rear panel of plate housing 
               160  Housing shelf 
               162  Housing shelf hole 
               164  Connecting rod 
               166  Housing shelf spacer 
               200  Gripper 
               202  Stepper motor (fixed to back support plate  210 ) 
               204  Motor mount (fixed to back support plate  210 ) 
               206  Coupling (connects stepper motor pin  212  to respective threaded shaft  215 ) 
               208  Movable arm mount guide rail (fixed to back support plate  210 ) 
               210  Back support plate 
               212  Stepper motor rotating pins 
               214  Bearing holder 
               215  Threaded shaft 
               220  Laterally movable arm mount 
               221  Movable arm mount support (moves laterally along rail  208 ) 
               222  Threaded lead nut (fixed to respective arm mount  220 ) 
               230  Fixed end mount (fixed to back Support plate  210 ) 
               240  Fixed intermediate mount (fixed to back support plate  210 ) 
               250  Gripper arm (laterally movable) 
               252  Arm shelf (fixed to respective gripper arm  250 ) 
               260  Arm cushion (fixed to respective gripper arm  250 ) 
               300  Analysis station 
               310  Safety platform 
               320  Microscope/imager 
               330  Illumination source 
               410  X-axis guide rails 
               412  X-axis adjustment motor 
               420  X-axis adjustment shaft 
               422  X-axis movable mount 
               430  Y-axis adjustment shaft 
               432  Y-axis movable mount 
               434  Y-axis adjustment motor 
               440  Vertical support for robot 
               450  Movable plate stage 
           
         
       
    
     DETAILED DESCRIPTION 
     The inventive gripper and its use in an automated analysis system is shown in the drawings. 
       FIG. 1A  shows a perspective view of an automated sample analysis system  100  with an X-Y-Z transporting robot. The X-Y-Z robot is computer controlled to move the gripper  200  along three orthogonal directions. A multiwell plate  10  held by the gripper  200  is movable by the robot along a vertical (i.e., Z-axis) support  440 . The vertical support  440  is attached to a movable plate stage  450 , which is moved along an X-axis on rails  410  by a mount  422  that moves in response to rotation by an X-axis adjustment shaft  420  that, in turn, is controlled by a computer. The plate stage  450  is movable in a Y-axis by movable mount  432  by rotation of Y-axis adjustment shaft  430 . 
     The analysis station  300  includes a safety platform  310  (to prevent a plate from falling below), an imager  320  (such as a microscope and/or CCD camera) and an optional illuminator  330 . During analysis, movement of the multiwell plate  10  over the analysis platform  310  is performed by the computer controlled robot, while holding the plate  10  with the gripper  200 . The plate is moved incrementally to align successive individual wells in the imaging region, e.g., in the light path between the illuminator  330  and imager  320 , thereby imaging each well individually. Upon completion of imaging, the plate  10  is returned by the gripper to its housing shelf in the plate hotel  110 . 
     Alternatively, the plate  10  can be placed by the gripper  200  onto a computer controlled X-Y movable platform instead of the safety platform  310 . The X-Y movable platform can perform the necessary incremental movements to align each successive well in the imaging area, such as the light path between the illuminator  330  and the imager  320 . In this case, after all wells have been imaged, the plate can be removed with the gripper and returned to the plate hotel  110 . Each multiwell plate in the plate hotel that requires analysis is transported to and from the analysis station by the gripper in the same manner. 
     It is noted that any analytical devices can be used in the analysis stage that permits multiwell plate analysis. In some analytical techniques, the illuminator is not necessary, such as those in which the samples in the wells emit light. 
       FIG. 1B  shows an elevation view of the automated analysis system  100 . An individual plate housing  120  is shown assembled with neighboring housings in the plate hotel. The analysis/imaging station  300  is shown behind the plate hotel  110 . The Y- and Z-directions are clearly visible in this view. 
       FIG. 1C  shows a plan view of the system, including X- and Y-directions and the relative arrangement of the plate hotel  110 , the movable plate stage  450  and the analysis stage  300 . 
       FIG. 2  shows a perspective view of the gripper  200  holding a multiwell plate  10 . Also, as shown in  FIGS. 3A-C , the pair of gripper arms  250  are movable by rotation of the stepper motor  202  through its respective threaded adjustment shaft  215 . When the stepper motor is actuated, it rotates two shafts ( 215 ), each shaft having oppositely oriented threads, that cause the mounts  220  to move in simultaneous but opposite linear directions. This causes the pair of arms  250  to move either towards or away from each other, thereby gripping or releasing a multiwell plate, respectively. During rotation of the stepper motor  202 , the arm mounts  220  are moved on respective supports  221 ,  FIG. 3B , linearly along a guide rail  208 . Intermediate mounts  240  and end mounts  230  acts as holders for bushings or bearings, e.g.,  214 , for shaft  215 . It is noted that stepper motors, per Se, are well known in the art. 
     More particularly, as shown in  FIG. 3C , threaded lead nuts  222 , having internal threads that correspond to the threads of the respective shaft  215  on each side of the stepper motor, moves along a linear path by rotation of the shaft  215  by the stepper motor  202 . The threaded lead nuts  222  do not rotate during the linear movements. The lead nuts are attached to the respective movable arm mounts  220 , that, in turn, move the arms,  250 . Movable arms  220  are fixed to respective movable supports  221 , that move laterally along rail  208  in response to rotation of the stepper motor, 
     The arm drive mechanism includes all structural elements that enable the arms to grip and release multiwell plates in a controlled manner. The computer, control system and electrical wires that provide communication and power for the various motors in the system are considered known in the art and are not shown. 
     A cushion  260 , such as an adhesively applied resilient foam pad, attached to each of the arms  250  above the respective shelves  252 , provides resiliency and a lateral force to hold the multiwell plate securely when the gripper grasps the sides of the multiwell plate  10 . The arm shelves  252  ensure that the individual plates are held in a level orientation during transport to the analysis station, and during imaging, thereby ensuring accurate analysis. 
     A single housing unit  150  is shown in  FIGS. 4A-C  in perspective, front elevation and plan views, respectively.  FIGS. 4A and 46  show a multiwell plate  10  resting on a raised portion  156  of a housing shelf  160 . Each housing shelf has a front opening through which a multiwell plate can be inserted or removed by the gripper, and a rear panel. Rods  164  pass through holes  162  to connect a stack of housing shelves  160  together, and spacers  166  separate the shelves along the vertical direction. 
     As shown more particularly in  FIG. 4C , the front of the housing shelf  160  has a notch  152  to allow a user to manually insert or remove a plate without tilting the plate. When a plate is contained in the housing  150 , it rests on the raised portion  156  of the housing shelf, so that the side edges of the plate extend over the sides of the raised portion  156 . When the gripper is extended into the housing to grip a plate ( FIG. 4B ), the cushions  260  of the gripper arms  250  contact the sides of the plate and the shelves  252  lift the side edges of the plate in a level manner, thereby avoiding unwanted tilting that can adversely affect the contents of the wells. 
     It is noted that the plate hotel and any or all of its parts can be formed as a molded plastic structure. 
     The gripper arm components, such as the mounts, supports, arms, bushings, etc. can be machined from aluminum stock, and can be given a protective coating. The attached components can be held together by mechanical means, e.g., screws, and by soldering, welding, and other types of bonding, such as adhesive.