Abstract:
The invention relates generally to an apparatus for acquiring, holding, and enabling the movement of a cassette-shaped article, such as a reagent or sample cassette, which may be part of an automated diagnostic analyzer, such that the apparatus can tolerate a significant degree of cassette misplacement and/or misalignment during the acquisition maneuver. The invention provides simultaneous two-dimensional movement of the acquiring gripper jaws such that the inter-jaw distance decreases at the same time as movement in an upward vertical direction is provided while the jaw movement is adequately smooth so as not to disturb the physical state of the sample.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to an apparatus for gripping a cassette-shaped article, particularly for acquiring, holding, and enabling the movement a reagent or sample cassette as part of an automated diagnostic analyzer. 
       BACKGROUND OF THE INVENTION 
       [0002]    Diagnostic clinical analyzers continue to become more sophisticated especially with respect to the handling and movement of patient samples and associated reagents between multiple locations. A plethora of increasing complex pick and place transports have evolved into robotic systems capable of two-dimensional, and in some cases, three-dimensional movement of patient sample containers. However, the evolution of apparatuses to physically acquire and hold such containers has not advanced especially when such containers are not simple test tubes, such as, for example, foil sealed cassettes for agglutination reactions as shown in U.S. Pat. No. 5,780,248 incorporated herein by reference in its entirety. Furthermore, such patient sample container acquisition relies upon a small number of fundamental mechanisms. Cam driven machines offer the smoothest motion and control of acceleration and deceleration. They can run at high cyclic rate, however, they are big, heavy and not suitable for applications where space is limited. Hydraulic/pneumatic driven machines are more compact and easier to use, but because they usually use hydraulic/pneumatic pressure to drive the components against hard stops, they create impact (which is particularly important in handling cassettes containing whole blood components) and result in noisy machines of low cyclic rate. Servo motor/stepper motor driven machines are usually slower, can be higher in cost, but have more flexible operation. U.S. Pat. No. 5,681,530 relates to a transport system for fluid analysis instruments that includes a cassette gripper and conveyor, incorporated herein by reference in its entirety. 
         [0003]    With respect to acquisition of the patient sample container, existing mechanisms tend to be specific to test tubes and are mechanically complex with many parts. In addition to having very limited capability to acquire and hold misplaced patient sample containers because of a limited motion function, these units are expensive to manufacture and often have reduced reliability. Furthermore, most mechanisms impart significant inertial forces to the patient sample container which is very undesirable and potentially can result in altering the sample&#39;s physical properties. A number of these systems are noted as follows: U.S. Pat. No. 4,002,247 entitled “Machine for picking up, transferring, turning and placing parts,” U.S. Pat. No. 4,411,576 entitled “Pick and place mechanism,” U.S. Pat. No. 4,975,018 entitled “Linear unit for transferring objects,” U.S. Pat. No. 5,249,663 entitled “Apparatus to load workpieces,” U.S. Pat. No. 5,333,720 entitled “Apparatus to manipulate workpieces,” U.S. Pat. No. 5,467,864 entitled “Dual purpose apparatus to manipulate workpieces,” U.S. Pat. No. 5,564,888 entitled “Pick and place machine,” U.S. Pat. No. 6,264,419 entitled “Robot arm,” U.S. Pat. No. 6,293,750 entitled “Robotics for transporting containers and objects within an automated analytical instrument and service tool for servicing robotics,” U.S. Pat. No. 6,374,982 entitled “Robotics for transporting containers and objects within an automated analytical instrument and service tool for servicing robotics,” U.S. Pat. No. 6,843,357 entitled “Two-axis robot for specimen transfer,” U.S. Pat. No. 6,889,119 entitled “Robotic device for loading laboratory instruments,” U.S. Pat. No. 7,131,361 entitled “Workpiece-transfer device,” U.S. Pat. No. 7,448,294 entitled “Robotic devices,” U.S. Pat. No. 7,563,067 entitled “Robot,” PCT Publication No. WO2008067847 entitled “Container transfer apparatus with automatic positioning compensation,” and U.S. Publication No. 2010/0150688 entitled “Workpiece transfer system.” 
         [0004]    None of the prior references noted above disclose an apparatus capable of operating in a confined space, having a minimal number of parts, having the ability to acquire patient samples in cassettes with significant misalignment, and imparting a movement of the apparatus particularity conducive to the acquisition and holding of non-test tube-shaped patient sample containers. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the invention is to solve or at least improve upon the deficiencies of prior art noted above. 
         [0006]    One aspect of the present invention is directed to an apparatus for gripping a cassette-shaped article. The apparatus includes: a support housing; a linear actuator movable along an x-axis relative to the support; a set of jaws for gripping the cassette-shaped article, each jaw having a proximal end and a distal end, the distal end being adapted for gripping the cassette-shaped article; a movable node located at the proximal end of each jaw for connecting each jaw to the linear actuator; a fixed node relative to the support located between the proximal and distal end of each jaw for connecting each of the jaws to the support, wherein the fixed node is indirectly located on the jaws and is connected to the jaws via linkage and a movable node on the jaws; and wherein movement of the linear actuator provides motion to the movable node in an x- and y-axis thereby rotating the jaws around the fixed node resulting in the jaws opening and closing. 
         [0007]    Another aspect of the present invention is directed to an apparatus for gripping a cassette-shaped article. The apparatus includes: a support housing; a linear actuator movable along an x-axis relative to the support; a set of jaws for gripping the cassette-shaped article, each jaw having a proximal end and a distal end, the distal end being adapted for gripping the cassette-shaped article; a movable node located at the proximal end of each jaw for connecting each jaw to the linear actuator; a fixed node relative to the support located between the proximal and distal end of each jaw for connecting each of the jaws to the support, wherein the fixed node is directly located on the jaws; a drive linkage connected to the linear actuator at the center thereof, the drive linkage having elongated slots on either side of the center, the movable nodes being slidably engaged in the slots, whereupon movement of the linear actuator moves the drive linkage which imparts linear motion to the movable node in a direction perpendicular to the motion of the slide thereby rotating the jaws around the fixed node resulting in the jaws opening and closing; a set of registration dowels attached to the bottom of the housing near the distal end of each of the jaws which are positioned to be capable of being abutted by the cassette-shaped article once the cassette-shaped article has been acquired, a compliance block is located at the upper end of the housing; and a spring is placed under the compliance block, enabling the housing to slightly tilt, wherein acquisition of the cassette is guided by the registration dowels and the movement of the cassette-shaped article is guided by the compliance block and spring allowing for possible misalignment of the apparatus relative to the cassette-shaped article. 
         [0008]    Still, another aspect of the invention is directed to a method for gripping a cassette-shaped article. The method includes: providing a support housing; providing a linear actuator movable along an x-axis relative to the support; providing a set of jaws for gripping the cassette-shaped article, each jaw having a proximal end and a distal end, the distal end being adapted for gripping the cassette-shaped article; providing a movable node located at the proximal end of each jaw for connecting each jaw to the linear actuator; providing a fixed node relative to the support located between the proximal and distal end of each jaw for connecting each of the jaws to the support, wherein the fixed node is indirectly located on the jaws and is connected to the jaws via linkage and a movable node on the jaws; positioning the housing to be located above the cassette-shaped article to be gripped; moving the linear actuator which provides motion to the movable node in an x- and y-axis thereby rotating the jaws around the fixed node resulting in the jaws closing and acquiring the cassette-shaped article. 
         [0009]    Yet another aspect of the invention is directed to a method for gripping a cassette-shaped article. The method includes: providing a support housing; providing a linear actuator movable along an x-axis relative to the support; providing a set of jaws for gripping the cassette-shaped article, each jaw having a proximal end and a distal end, the distal end being adapted for gripping the cassette-shaped article; providing a movable node located at the proximal end of each jaw for connecting each jaw to the linear actuator; providing a fixed node relative to the support located between the proximal and distal end of each jaw for connecting each of the jaws to the support, wherein the fixed node is directly located on the jaws; providing a drive linkage connected to the linear actuator at the center thereof, the drive linkage having elongated slots on either side of the center, the movable nodes being slidably engaged in the slots; providing a set of registration dowels attached to the bottom of the housing near the distal end of each of the jaws which are positioned to be capable of being abutted by the cassette-shaped article once the cassette-shaped article has been acquired; providing a compliance block at the upper end of the housing, and a spring under the compliance block, enabling the housing to deflect; positioning the housing to be located above the cassette-shaped article to be gripped; moving the linear actuator which moves the drive linkage which imparts linear motion to the movable node in a direction perpendicular to the motion of the slide thereby rotating the jaws around the fixed node resulting in the jaws closing and acquiring the cassette-shaped article; wherein acquisition of the cassette is guided by the registration dowels and the movement of the cassette-shaped article is guided by the compliance block and spring allowing for possible misalignment of the apparatus relative to the cassette-shaped article. 
         [0010]    In a preferred embodiment of the invention the apparatus has the ability to accurately acquire and securely hold diagnostic cassettes even in the presence of moderate misalignments. 
         [0011]    Still, another preferred embodiment of the invention provide simultaneous two-dimensional movement of the acquiring jaws of the gripping apparatus such that the inter-jaw distance decreases at the same time while providing movement in an upward vertical direction thus using a minimum of space. 
         [0012]    Yet, another preferred embodiment of the invention provides an apparatus having a minimal number of parts and is therefore inexpensive to manufacture while having high reliability. 
         [0013]    In another preferred embodiment, the apparatus is constructed of a combination of gears, racks, and mechanical linkage which provides a smooth movement superior to cams, pneumatic, or hydraulic driven devices and is particularity adept at not disturbing the physical characteristics of sensitive patient samples. 
         [0014]    In a preferred embodiment, the invention incorporates a spring-loaded vertical drive movement such that the apparatus can tolerate a significant degree of cassette misplacement and/or gripper misalignment during the cassette acquisition maneuver. The movement of the mechanical parts acquiring the cassette is such that physical state of the sample is not disturbed and that the mechanical act of cassette acquisition takes place in a minimum of space. 
         [0015]    In another preferred embodiment, the invention incorporates a Hoeken linkage. 
         [0016]    In yet another preferred embodiment, the invention registers the patient sample container against a set of registration dowels enabling optical sensor or other feedback indicating that the patient sample container has been positively acquired. Further objects, features, and advantages of the present application will be apparent to those skilled in the art from detailed consideration of the embodiments that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic front view of the gripping and holding apparatus in the open position according to Configuration  1  of a preferred embodiment of the present invention. The apparatus, also known as the cassette gripper unit, is contained within a housing  102  which holds a linear actuator, for example, an electric servo motor  104  coupled to or configured as a leadscrew  105 . The servo motor  104  has a shaft configured as a lead screw  105  which is threaded into a rack nut  103  or, alternatively coupled to the leadscrew with a rotating coupling. A sector gear linkage  106  is rotatably attached to the housing  102  and is configured as a Hoeken linkage  107  containing a set of jaws  109 . The end of the set of jaws  109  attached to the sector gear linkage  106  is designated as the proximal end and the end of the set of jaws  109  that grips the diagnostic cassette  110  is designated as the distal end. The upward movement of a cassette  110  is constrained by a set of registration dowels  108 . A compliance block  100 , such as an elastomeric block, and spring  101  allow the cassette gripper unit to acquire and place cassettes with a degree of misalignment. The presence or absence of a cassette  110  securely pressed against the registration dowels  108  is sensed by an optical sensor  111 . 
           [0018]      FIG. 2  is a schematic front view of the gripping and holding apparatus, also known as the cassette gripper unit, in the closed position according to Configuration  1  of a preferred embodiment of the present invention. The apparatus is contained within a housing  102  which holds a linear actuator, for example, an electric servo motor  104  coupled to or configured as a leadscrew  105 . The servo motor  104  has a shaft configured as a lead screw  105  which is threaded into a rack nut  103  or, alternatively coupled to the leadscrew with a rotating coupling. A sector gear linkage  106  is rotatably attached to the housing  102  and is configured as a Hoeken linkage  107  containing a set of jaws  109 . The upward movement of a cassette  110  is constrained by a set of registration dowels  108 . A compliance block  100  and spring  101  allow the cassette gripper unit to acquire and place objects with a degree of misalignment. The presence or absence of a cassette  110  securely pressed against the registration dowels  108  is sensed by an optical sensor  111 . 
           [0019]      FIG. 3  is a schematic front view of the gripping and holding apparatus, also known as the cassette gripper unit, in the open position according to Configuration  2  of a preferred embodiment of the present invention. The apparatus is contained in a housing  102  which holds a linear actuator, for example, an electric servo motor  104  coupled to or configured as a leadscrew. The servo motor  104  has a shaft  301  configured as a lead screw which is threaded into a drive link  300  or, alternatively coupled to the leadscrew with a rotating coupling. A set of jaws  302  is provided where the upper end of the set of jaws  302  which is attached to the drive link  300  is designated as the proximal end and the lower end of the set of jaws  302  which grips the diagnostic cassette is designated as the distal end. The set of jaws  302  is attached to the drive link  300  such that the proximal end of the jaws  302  is allowed to slide horizontally within the drive link  300 . The upward movement of a cassette  110  is constrained by a set of registration dowels  108 . A compliance block  100  and spring  101  allow the cassette gripper unit to acquire and place objects with a degree of misalignment. The presence or absence of a cassette  110  securely pressed against the registration dowels  108  is sensed by an optical sensor  111 . 
           [0020]      FIG. 4  is a schematic front view of the gripping and holding apparatus in the closed position apparatus, also known as the cassette gripper unit, according to Configuration  2  of a preferred embodiment of the present invention. The apparatus is contained in a housing  102  which holds a linear actuator, for example, an electric servo motor  104  coupled to or configured as a leadscrew. The servo motor  104  has a shaft  301  configured as a lead screw which is threaded into a drive link  300  or, alternatively coupled to the leadscrew with a rotating coupling. A set of jaws  302  is attached to the drive link  300  such that the proximal end of the jaws  302  is allowed to slide horizontally within the drive link  300 . The upward movement of a cassette  110  is constrained by a set of registration dowels  108 . A compliance block  100  and spring  101  allow the cassette gripper unit to acquire and place objects with a degree of misalignment. The presence or absence of a cassette  110  securely pressed against the registration dowels  108  is sensed by an optical sensor  111 . 
           [0021]      FIG. 5  is a schematic diagram of the details of the Configuration  1  linkage. A motor shaft configured as a lead screw  105  is threaded into a rack nut  103 . The sector gear linkage  500  rotating about a joint denoted by node A 1  is engaged into the rack nut  103  such that a set of jaws  501  moves in response to the rotation of the lead screw  105  via primary joints at nodes B 1  and B 2 , and a secondary joint at node A 2  associated with a link arm  502 . The movement of the distal end of the set of jaws  501  is indicated by arrows  503 . Joints denoted by nodes A 1  and A 2  are link-to-housing rotationally pinned and joints denoted by nodes B 1  and B 2  are link-to-link pinned. 
           [0022]      FIG. 6  is a schematic diagram of the details of the Configuration  2  linkage. A motor shaft configured as a lead screw  301  is threaded into a drive crossbar slider  300 . The upper end of a set of jaws  302  is engaged into the drive crossbar slider  300  such that the proximal end of the set of jaws  302  slides horizontally left or right within the drive crossbar slider  300  in response to the rotation of the lead screw  301 . The movement of the distal end of the set of jaws  302  is circular and is indicated by arrows  600 . Joints denoted by node D are link-to-housing rotationally pinned and joints denoted by node C are link-to-crossbar slider pinned (such that horizontal left or right movement is allowed). 
           [0023]      FIG. 7  is a diagram of the Hoeken Linkage coupler curve. The movement of the distal end of the link arm  701  is indicated by a dotted curve  700 . The proximal end of the link arm  701  is connected to the sector gear link  703  at the joint denoted by node B 1 . The sector gear link  703  is rotationally attached to the housing  102  at the joint denoted by node A 1 . A connecting link  702  is attached to the link arm  701  at the joint denoted by node B 2  and is rotationally attached to the housing at the joint denoted by node A 2  is the third component of the Hoeken linkage. Rotation of the sector gear link  703  imparts movement to the distal end of the link arm  701 . Joints denoted by nodes A 1  and A 2  are link-to-housing rotationally pinned and joints denoted by nodes B 1  and B 2  are link-to-link pinned. 
           [0024]      FIG. 8  is a schematic diagram of the details of the left element of the set of jaws  109  as shown in  FIGS. 5 and 6 . A profile of this element is shown in the front view, and in the side view of this element, a tapering notch  800  is shown in the distal portion of the set of jaws  109 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    While the present invention is described with respect to the preferred embodiments described below and shown in the figures, the present invention is limited only by the metes and bounds of the claims that follow. 
         [0026]    The apparatus and methods described herein enable the rapid and secure acquisition of diagnostic cassettes in a diagnostic clinical analyzer for subsequent movement within or removal from the analyzer. Examples of known diagnostic analyzers include immunodiagnostic analyzers such as the Vitros® ECi immunodiagnostic analyzer or the Vitros® 3600 immunodiagnostic analyzer, or clinical chemistry analyzers such as the Vitros® 5,1 FS, or Vitros® 5600 all sold by Ortho-Clinical Diagnostics, Inc. Representative systems are disclosed, for example, in U.S. Published Patent Application No. 2003/0026733 and in U.S. application Ser. No. 11/091,283 filed Mar. 28, 2005, both of which are incorporated herein by reference in their entireties. Other examples include blood immunohematology analyzers used in blood typing operations, such as those disclosed in U.S. Pat. Nos. 5,681,530 and 5,594,808, and blood donor screening apparatus, such as those sold under the Ortho Summit System™ sold by Ortho-Clinical Diagnostics, Inc. As used herein, all such analyzers are collectively called “diagnostic analyzers.” 
         [0027]    The benefits of the apparatus may include the ability to acquire the diagnostic cassette in the presence of minor misplacement or misalignment of the cassette&#39;s position, the ability to acquire the cassette while transmitting a minimal amount of force to the patient sample, the ability to acquire the cassette in a minimal amount of space, the ability of the acquiring mechanism to have a minimal number of parts with subsequent high reliability, and the ability to register acquisition of the cassette and to signal that acquisition via optional feedback sensors. 
         [0028]    For a general understanding of the disclosed technology, reference is made to the drawings. In the drawings, like reference numerals have been used to designate identical elements. In describing the disclosed technology, the following term(s) have been used in the description. 
         [0029]    The term “housing” refers herein to a supporting structure, frame, cage, enclosure, encompassment, or substrate to which various other structural elements are attached providing a measure of rigidity such that the cassette gripper apparatus can be used and moved as a unit. 
         [0030]    The term “link” refers herein to a rigid body which contains at least two nodes which are points for attachment to other links or a support. A “binary link” has two nodes; a “ternary link” has three nodes, etc. 
         [0031]    A “node” refers herein to positions on a link where other links may be attached resulting in a joint. 
         [0032]    A “joint” refers herein to a connection between two or more links (at their nodes), which allows some motion, or potential motion, between the connected links. Joints may be of the form of a “rotating pin joint” which allows one degree of freedom for movement or of the form of a “translating slider joint” which also allows one degree of freedom of movement, among others (see Robert L. Norton,  Design of Machinery,  3 rd  edition, McGraw-Hill Book Company, 2003, which is hereby incorporated by reference). 
         [0033]    The term “lead screw” refers herein to a mechanism designed to translate rotational motion into linear motion. This is accomplished by the rotation of a threaded rod that has been inserted into a nut such that when the threaded rod is rotated the nut is moved a specified linear distance (depending upon the pitch of the threads in the rod). 
         [0034]    The term “rack nut” refers herein to a lead screw nut having female threads, threaded into a lead screw, and held in a fixed orientation such that rotation of the lead screw produces linear motion in the rack nut. Furthermore, at least one side of the rack nut has a rack structure which engages a circular pinion or gear such that linear motion of the rack nut causes rotational motion of the pinion or gear. 
         [0035]    One aspect of the invention is directed to an apparatus for gripping a cassette-shaped article, such as a gripping apparatus for acquiring and holding a diagnostic cassette  110  while operating in a highly confined space.  FIGS. 1 and 2  show Configuration  1  of the cassette gripper unit. This unit may be attached to a system, such as a diagnostic analyzer, by an arm (not shown) connected to the compliance block  100 . Raising and lowering of the arm provides z-axis movement to the cassette gripper unit. The arm also provides movement in the x-axis and y-axis directions to appropriately place the cassette  110 . Other suitable mechanisms to secure the unit to the analyzer and provide movement to the unit may also be used. The cassette gripper unit when being lowered may not be perfectly square with the top of the cassette being acquired and the compliance block  100  in cooperation with the spring  101  allows the cassette gripper unit to tilt at a slight incline or gimbal slightly such that the top of the cassette is in light contact with both registration dowels  108 . Hence, the mechanism has the ability to accommodate a degree of misalignment between the cassette  110  and the bottom of the cassette gripper unit. The cassette gripper unit as denoted by Configuration  1  includes a set of jaws  109  that while closing both reduce the inter-jaw gap and at the same time provide vertical movement. The exact movement profile is governed by the mechanical configuration of a Hoeken&#39;s linkage  107 , described more fully below in connection with  FIG. 7 . A set of jaws  109  that operates in the aforementioned manner initially move downward and inward toward the cassette  110  being acquired subsequently providing lift in the vertical direction  503 . Ultimately the vertical movement causes the top of the diagnostic cassette  110  to be pushed securely against the registration dowels  108 . These registration dowels  108  may be composed of compliant materials such as rubber or soft, flexible polymer which deforms upon contact with the diagnostic cassette  110 . The deformation of the registration dowels  108  provides a tension between the diagnostic cassette  110  and the jaw  109  insuring a firm and secure grip on the cassette  110 . Also, the tapered notch  800  cut into the arm of the set of jaws  109  tends to center the cassette in the set of jaws  109  allowing for an additional degree of misalignment. The presence of the cassette  110  in the proper position is sensed by an optical sensor  111  such that an acquisition signal is sent terminating the application of electromotive force. Alternatively, the deformation of the registration dowels may cause pressure to be applied to a micro-switch or strain gauge-like sensor enabling the sending of a signal that the diagnostic cassette  110  has been acquired and is held in the proper position. Note that the use of a Hoeken linkage  107  enables movement of the set of jaws  109  using a very small amount of space, but at the cost of some mechanical complexity. 
         [0036]      FIG. 1  is a schematic front view of a preferred embodiment of the gripping apparatus, also known as the cassette gripper unit, denoted as Configuration  1 . The various components of Configuration  1  are located within a housing  102  featuring a compliance block  100  and a spring  101  to allow for slight positional misalignments between the registration dowels  108  and the top edge of the cassette  110  as the cassette gripper unit is lowered. A servo motor  104  having a shaft configured as a lead screw  105  is attached to the upper portion of the housing  102 . Alternatively, the shaft of the servo motor  104  may be connected to a separate lead screw by several commonly known mechanisms including a rotating coupling. The lead screw  105  is threaded into a rack nut  103  having racks on both the left and right sides. Sector gear links  106  are engaged into the rack nut  103  in a rack-and-pinion configuration and comprise an essential component of the Hoeken linkage  107 . In operation, the application of electromotive force to the servo motor  104  imparts a forward rotation of the shaft subsequently turning the lead screw  105  causing the rack nut  103  to move linearly in a downward direction. This downward movement of the rack nut  103  causes the sector gear links  106  to rotate in a counter-clockwise manner, imparting movement to the Hoeken linkage  107  resulting in simultaneous downward and inward movement followed by an upward motion  503  of the distal end of the set of jaws  109 . The distal end of the set of jaws  109  contact the diagnostic cassette  110 , center the cassette into the tapered notch  800 , and move it slightly upwards such that the top of the cassette is forced against the registration dowels  108 . The presence of the cassette  110  in the proper position is sensed by the optical sensor  111  such that an acquisition signal is sent terminating the application of electromotive force. Alternatively, the compression of the registration dowels causes a micro-switch or strain gauge-like sensor to trip, or alternatively, a load exceeding a specific threshold on the servo motor is reached, and, in either case, an acquisition signal is sent terminating the application of electromotive force. At this point the cassette  110  has been acquired and is securely held for further movement by the diagnostic clinical analyzer. 
         [0037]      FIG. 2  shows Configuration  1  in the closed position with the diagnostic cassette  110  in the fully acquired and held position. 
         [0038]    Another aspect of the invention is directed to a gripping apparatus having a minimal number of parts and, therefore, being less expensive to manufacture, having high reliability, and having precise movements. Referring to  FIGS. 3 and 4 , the cassette gripper unit denoted by Configuration  2  includes a set of jaws  302  that while closing both reduce the distal inter-jaw gap and at the same time providing vertical movement. However, unlike the Hoeken linkage of Configuration  1 , each side of the set of jaws  302  is rotationally pinned to the housing  102  at a single point near their mid-section. This only provides for the distal end of the set of jaws  302  to be able to close inwardly in a circular motion. The distal end of a set of jaws  302  that operates in the aforementioned manner move inward toward the cassette  110  being acquired, centers the cassette  110  in the tapered notch  800 , and provides lift in the vertical direction. The limited number of parts comprising the linkage (three) results in a mechanism having greater precision than Configuration  1  in that mistakes in manufacturing and mounting are multiplied by the number of members of the mechanism (see Robert L. Norton,  Design of Machinery,  3 rd  edition, McGraw-Hill Book Company, 2003, which is hereby incorporated by reference). Ultimately the vertical movement causes the top of the diagnostic cassette  110  to be forced securely against the registration dowels  108 . In a manner similar to Configuration  1 , the presence of the cassette  110  in the proper position is sensed by the optical sensor  111  such that an acquisition signal is sent terminating the application of electromotive force. Alternatively, the compression of the registration dowels causes a micro-switch or strain gauge-like sensor to trip, or alternatively, a load exceeding a specific threshold on the servo motor is reached, such that an acquisition signal is sent terminating the application of electromotive force. At this point the cassette  110  has been acquired and is securely held for further movement by the diagnostic clinical analyzer. 
         [0039]      FIG. 3  is a schematic front view of a preferred embodiment of the gripping apparatus, known as the cassette gripper unit, denoted Configuration  2 . The various components of Configuration  2  are located within a housing  102  featuring a compliance block  100  and a spring  101  to allow for positional misalignments between the gripper apparatus and the position of the cassette during the initial downward movement to acquire the cassette in a manner similar to that of Configuration  1 . A servo motor  104  having a shaft configured as a lead screw  301  is attached to the upper portion of the housing  102 . Alternatively, the shaft of the servo motor  104  could be attached to a lead screw by a number of commonly known mechanisms including a rotating coupling. The lead screw  301  is threaded into a drive link  300  to which the proximal portion of the set of jaws  302  have been pinned in a configuration known as a translating slider joint such that sliding movement in the horizontal direction is enabled. The set of jaws  302  have been rotationally pinned to the housing  102  at about mid-length and are only capable of circular movement. In operation, the application of electromotive force to the servo motor  104  imparts a forward rotation of the shaft and subsequently turns the lead screw  301  causing the drive link  300  to move linearly in an upward direction. This causes the proximal ends of the set of jaws  302  to move outward via the translating slider joints. The distal end of the set of jaws  302  then move inwardly in a circular motion. The distal ends of the set of jaws  302  contact the diagnostic cassette  110  and move it slight upwards such that the top of the cassette is forced against the registration dowels  108 . In a manner similar to Configuration  1 , the presence of the cassette  110  in the proper position is sensed by the optical sensor  111  such that an acquisition signal is sent terminating the application of electromotive force. Alternatively, the compression of the registration dowels causes a micro-switch or strain gauge-like sensor or, alternatively, a threshold exceeding load on the servo motor, such that an acquisition signal is sent terminating the application of electromotive force. At this point the cassette  110  has been acquired and is securely held for further movement within the diagnostic clinical analyzer. Note that the use of a drive link  300  coupled with a set of jaws  302  capable of only circular movement requires greater space in which to operate relative to Configuration  1 , but results in a simpler mechanism having less cost and greater reliability. 
         [0040]      FIG. 4  shows Configuration  2  in the closed position with the diagnostic cassette  110  in the fully acquired and held position. 
         [0041]      FIG. 5  shows further details of Configuration  1 . Here the shaft configured as a lead screw  105  is shown threaded into the rack nut  103  with the sector gear link  500  which is rotationally connected to a joint formed by node A 1  and the housing  102 , engaged into the rack (not shown) of the rack nut  103 . As previously noted, the shaft of the servo motor  104  could be simply connected to a lead screw. In particular, the components of the Hoeken linkage  107  are detailed as (1) a sector gear link  500  rotationally connected to a joint formed by node A 1  and the housing  102 , (2) an arm link (or one-half of the set of jaws)  501  having two joints the first joint formed by node B 1  which connects the sector gear link  500  and the arm link  501  and the second joint formed by node B 2  which connects the connecting link  502  and the arm link  501 , and (3) a connecting link  502  which has two joints the first joint formed by node B 2  connecting the arm link  501  and the connecting link  502  and the second joint formed by node A 2  which rotationally connects the connecting link  502  to the housing  102 . It is important to note that the joints of the Hoeken linkage  107  components are of two types (1) the type designated as A 1  or A 2  has the link rotationally pinned to the housing  102  and (2) the type designated as B 1  or B 2  has one link rotationally pinned to another link. Hence, the sector gear link  500  and the connecting link  502  being rotationally pinned to the housing  102  can only rotate in a circular manner about the point at which they are connected. Whereas, the arm link  501  is free to move such that the distal end of the arm link  501  (or alternatively, the distal end of one component of the set of jaws  501 ) traces the Hoeken movement  503 . 
         [0042]      FIG. 6  shows further details of Configuration  2 . Here the servo motor shaft configured as a lead screw  301  is threaded into the drive link  300 . As previously noted, the shaft of the servo motor  104  could be simply connected to a lead screw. In particular, note that this mechanism is composed of only three mechanical parts. The proximal end of the arm link  302  (or one-half of the set of jaws) is connected to the drive link  300  by a translating slider joint formed by node C and the arm link  302  is rotationally connected to the housing  102  by a joint formed by node D. Furthermore, it is important to note that the above joints are of two types (1) the type designated as D has the link rotationally pinned to the housing  102  and (2) the type designated as C has one link pinned to another link such that the connection is free to slide in one-dimension. Hence, the arm link  302  can only rotate about the joint formed by node D in response to upward or downward movement of the drive link  300  where the translating slider joint formed by node C to the arm link  302  is allowed to slide one-dimensionally in the horizontal direction. 
         [0043]      FIG. 7  shows a schematic diagram of the Hoeken&#39;s Linkage Coupler Curve. The Hoeken curve  700  is traced by distal end of the arm link  701  (or alternatively for the present invention, the distal end of one of the components of the jaws) through rotation of the sector gear link  703  as coupled to the arm link  701  and the connecting link  702 . Connections between the links are of two types; a type A 1  or A 2  connection is where the link component is rotationally pinned to the housing  102  and a type B 1  or B 2  connection is where one link is connected to another link. Note that in the present invention that only the left most portion of the Hoeken curve is utilized. 
         [0044]      FIG. 8  shows details of the one component of the set of jaws  109 . Note that in the side view that there is a notch  800  cut into the distal end of the jaw. This notch  800  gently tapers such that upon closing of the set of jaws  109 , the notch  800 , which is larger than the thickness of the wall of the cassette  110 , has a tendency to center the position of the cassette while it is being held. 
         [0045]    In a particularly preferred embodiment, the apparatus according to the present invention is particularly suited for systems that detect and quantify agglutinates formed in response to immunological agglutination reactions, i.e., immunohematology blood analyzers. In such systems, gel or glass bead micro particles are contained within a small column, referred to as a microcolumn. A reagent such as anti-IgG is dispensed in a diluent in the microcolumn and a test red blood sample is placed in a reaction chamber above the column. The column, which is typically one of a multitude of columns formed in a transparent cassette, is then centrifuged. The cassette is handled by the cassette gripper according to the present invention. Such systems are described in U.S. Pat. Nos. 5,681,530, 5,905,808 and 5,911,000, all of which are incorporated herein by reference in their entirety. A typical cassette used in column agglutination technology (CAT) is described in U.S. Pat. No. 5,780,248, described above. 
         [0046]    In such systems, a cassette  110  stored in a storage unit is moved into a dispensing condition below an opening in the unit. The cassette gripper unit, which is attached to a movable arm, moves in the direction the storage unit until superimposed over the cassette  110  which is to be removed from the storage unit. Thereafter, gripper unit contacts the cassette as described above, which is then clampingly engaged by gripper unit jaws  109 . Thereafter, the cassette  110  is lifted outwardly of the storage unit and may be passed by an adjacent bar code reader which will ascertain information as to the proper orientation of the cassette, that the desired cassette has been removed from the storage unit, that the cassette has not reached its expiration dating, and miscellaneous information as to the sequence number and lot number of the cassette, all of which information may then be transmitted to the memory of a computer and stored therein. 
         [0047]    The cassette gripper unit then transports the cassette  110  to an incubator. At this point, a piercer punches one or more apertures through the foil covering on the cassette. Blood and reagents may then be dispensed into the cassette  110 , which may then be incubated. 
         [0048]    The gripper unit then transports the cassette to a centrifuge, which spins; for instance, initially for two minutes at  55   g  and for three minutes at  199   g,  so as to provide for suitable admixing of the blood sample and reagent in each of the respective wells. Upon completion of the centrifuging action, the gripper member engages the centrifuged cassette and transfers it to a read station. Upon completion of the read, the cassette is disposed of. 
         [0049]    The foregoing is adapted to be computer program-controlled by a computer which is well known to those skilled in the art. 
         [0050]    It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and processes of this invention. Thus, it is intended that the present invention cover such modifications and variations, provided they come within the scope of the appended claims and their equivalents. 
         [0051]    The disclosure of all publications cited above is expressly incorporated herein by reference in their entireties to the same extent as if each were incorporated by reference individually.