Abstract:
An apparatus and methods for dispensing sample holders for use in an automated sample analyzer is disclosed herein. The apparatus for dispensing sample holders includes a rotating carousel for housing stack of sample holders. Stacks of sample holders from the rotating carousel are fed into a chute where sample holders contact a set of rotating members having helical threads thereon. The helically threaded rotating members engage the sample containers and separate each sample holder from the remaining sample holders in the stack by rotation of the helically threaded rotating members. The sample holder can then be transferred for use in an automated sample analyzer.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional of application U.S. Ser. No. 12/756,608, filed on Apr. 8, 2010, now granted U.S. Pat. No. 8,480,954 which is a continuation application and claims priority to and the benefit of U.S. Ser. No. 11/704,080, filed on Feb. 8, 2007, now granted U.S. Pat. No. 7,731,899, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to devices and methods for storing and dispensing cuvettes for use in an automated clinical sample analyzer. 
     BACKGROUND OF THE INVENTION 
     Automatic clinical sample analyzers are common in hospitals and research institutions for analyzing large quantities of samples. For example, environmental specimens, such as water, or patient specimens, such as blood, urine or other biological samples, can be tested using automated sample analyzers to determine concentrations of contaminants or analytes, for example. 
     Automated sample analyzers have a variety of component systems that work in concert to manipulate patient samples. For example, an automated sample analyzer may have one or more reagent dispensing components, sample holder dispensing components, sample and reagent probes, washing stations, detecting mechanisms, and automated arms, carousels, or conveyors for moving samples from one station to another. 
     Automated sample analyzers reduce time taken to perform assays on the samples, improve output, and reduce human error and contamination, thereby providing cost effective sample analysis. However, despite the automated functioning of such analyzers, operator intervention is often required if a component malfunctions, or if consumables, such as reagents and sample holders, need replacing. Therefore, there is a need in the art for an automated sample analyzer that reduces the need for operator intervention, thereby further improving efficiency, accuracy of testing, and throughput. 
     SUMMARY OF THE INVENTION 
     The invention is related to an apparatus and methods for dispensing sample holders for use in an automated clinical sample analyzer. In one aspect, the invention is directed to a device for separating a sample holder from a stack of sample holders. The device includes a support member for receiving a stack of at least two sample holders and at least one releasing member, preferably two releasing members. The support member is positioned to introduce at least one of the sample holders in the stack of sample holders between a first releasing member and a second releasing member. The first and second releasing members each include a helical thread. The first releasing member is operatively connected to a first rotator capable of rotation in a clockwise direction. The second releasing member is operatively connected to a second rotator capable of rotation in a counter-clockwise direction. The first and second rotators rotate the first and second releasing member thereby releasing one of the at least two sample holders from the stack of sample holders. In a further embodiment, the first rotator is further capable of rotation in a counter-clockwise direction while the second rotator is further capable of rotation in a clockwise direction. The rotator may comprise an oscillating motor in one embodiment. 
     According to the invention, in one embodiment, the releasing members are threaded. For example, in one embodiment, the first releasing member has a right hand oriented helical thread and the second releasing member has a left hand oriented helical thread. In one embodiment, the pitch of the right-hand helical thread is the same as the pitch of the left hand helical thread. Alternatively, the pitch of one helical thread differs from the pitch of another helical thread. The pitch is in the range of about 6.9°-7.3° in one embodiment, while in another embodiment, the pitch is in the range of about 9.2°-9.6°. In a further embodiment, the pitch is about 9.4°, while in another embodiment, the pitch is about 7.1°. 
     In yet another embodiment, the first releasing member has a right hand oriented helical thread and a left hand oriented helical thread. The second releasing member also has a right hand oriented helical thread and a left hand oriented helical thread. According to one embodiment, the pitch of the right hand helical thread of the first releasing member differs from the pitch of the left hand helical thread of the first releasing member. For example, the pitch of the right hand helical thread is in the range of about 6.9°-7.3° while the pitch of the left hand helical thread is in the range of about 9.2%9.6°. In a further embodiment, the pitch of the right hand helical thread is about 7.1° while the pitch of the left hand helical thread is about 9.4°. 
     In a further embodiment, the first releasing member is substantially cylindrical and has the same diameter as the second releasing member. In another embodiment, the diameter of the first releasing member is different than the diameter of the second releasing member. In yet another embodiment, the releasing member is tapered with the widest portion at the top, or alternatively, the widest portion is at the bottom. 
     The device according to the invention also includes a sample holder receiver, according to one embodiment of the invention. For example, the sample holder receiver receives the sample holder following separation of the first sample holder from the second sample holder. 
     In another embodiment, the support member for receiving a stack of at least two sample holders is a tube, while in another embodiment, the support member comprises at least two walls, each wall having a C-shaped cross-section. 
     The device, according to one embodiment, further comprises a rotating module, for example, a wheel, disc, or cylinder, having a plurality of openings for supporting stacks of sample holders. In one embodiment, each of the plurality of openings is positioned equidistant from the center of the carousel and equidistant from each other. In yet another embodiment, the plurality of openings are positioned around the circumference of the rotating carousel. 
     According to another aspect, the invention includes a method for separating a sample holder from a stack of sample holders. The method includes positioning a stack of at least two sample holders adjacent a first releasing member comprising a helical thread, rotating the first releasing member in a first direction, engaging said sample holder; disengaging the first sample holder from the stack of sample holders; rotating the first releasing member in a second direction; and releasing the sample holder from the stack of sample holders. 
     In a further embodiment, the method includes positioning the stack of sample holders adjacent a second releasing member. The releasing member, for example, includes a helical thread, in one embodiment, the first releasing member has a right hand oriented helical thread, and the second releasing member has a left hand oriented helical thread. In a further embodiment, the first releasing member also includes a left hand oriented helical thread, while the second releasing member also includes a right hand oriented helical thread. 
     In one embodiment, the method includes rotating said second releasing member in a second direction while performing the step of rotating said first releasing member in a first direction. In another embodiment, the method includes rotating said second releasing member in a first direction while performing the step of rotating said first releasing member in a second direction. In one embodiment, the first direction is a clockwise direction and the second direction is a counter-clockwise direction. In another embodiment, the step of releasing the sample holder from the first releasing member while simultaneously releasing the sample holder from the second releasing member. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of an automated sample analyzer having a cuvette dispensing station, according to an illustrative embodiment of the invention. 
         FIG. 2  is a perspective view of a cuvette for holding a sample and for dispensing from a cuvette dispensing station, according to an illustrative embodiment of the invention. 
         FIG. 3A  is a plan view of a cuvette dispenser of an automated sample analyzer including a cuvette loading module on the top portion to receive stacks of cuvettes, according to an illustrative embodiment of the invention. 
         FIG. 3B  is a perspective view of the cuvette dispenser of an automated sample analyzer as shown in  FIG. 3A , with the cuvette loading module removed to reveal an engagement piece for engaging and rotating the cuvette loading module, according to one illustrative embodiment of the invention. 
         FIG. 4  is a perspective view of a cuvette dispenser of an automated sample analyzer including several sensors for activating movement of cuvettes through the cuvette dispenser, according to one illustrative embodiment of the invention. 
         FIG. 5A  is a cross-sectional view of a cuvette loading module housing a stack of cuvettes prior to the cuvettes being released into the cuvette dispense chute for distribution, according to one illustrative embodiment of the invention. 
         FIG. 5B  is a cross-sectional view of a cuvette dispenser including the cross-sectional view of the cuvette loading module of  FIG. 5A , wherein the stack of cuvettes shown in  FIG. 5A  has been released into the cuvette dispense chute, according to one illustrative embodiment of the invention. 
         FIG. 5C  is a cross-sectional view of the cuvette dispenser shown in  FIG. 5B , wherein a cuvette from the stack of cuvettes has been released from the cuvette release members to the cuvette transfer position, according to one illustrative embodiment of the invention. 
         FIGS. 6A-C  are successive perspective views of a releasing member, according to one embodiment of the invention, as it rotates in a clockwise direction. 
         FIGS. 7A-C  are successive perspective views of a releasing member, according to one embodiment of the invention, as it rotates in a counter-clockwise direction. 
         FIGS. 8A-C  are perspective views of cuvette release members for releasing a cuvette from a stack of cuvettes in the cuvette dispense chute, wherein the cuvette release members are threaded and rotate to engage the cuvette to remove it from the stack and dispense it at the cuvette transfer position according to an illustrative embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Automated sample analyzers are used for detecting a substance, such as a contaminant or an analyte, in a sample. For example, a sample may be an environmental sample such as a soil or water sample, or the sample may be from a human or animal patient, such as a blood or urine sample. An automated sample analyzer can analyze a sample according to a predetermined protocol that may include, for example, providing a sample holder, providing a sample, adding reagents, aspirating the sample, and detecting the contents of a sample. 
     The invention, as described herein, discloses a cuvette dispenser for use with an automated sample analyzer. A cuvette dispenser, according to the invention, dispenses sample holders in a manner that reduces operator intervention with the dispenser. According to the invention, after an operator loads the cuvette dispenser with sample holders, the cuvette dispenser manages the task of distributing individual sample holders to the automated sample analyzer as needed, which reduces the need for operator intervention. Furthermore, the cuvette dispense mechanism is designed to reduce malfunction, thereby improving the efficiency of the cuvette dispenser and the automated sample analyzer. 
     Automated Sample Analyzer 
       FIG. 1  is a top view of an automated sample analyzer having a cuvette loading station, according to an illustrative embodiment of the invention. According to one illustrative embodiment of the invention, the automated sample analyzer  11  has a cuvette dispensing station  10  positioned adjacent a cuvette transport carousel  1 . The cuvette dispensing station  10  dispenses empty cuvettes  12  (not shown) for retrieval by a cuvette transfer arm  14  (not shown), which transfers cuvettes  12  from the cuvette dispensing station  10  to the cuvette transport carousel  1 . 
     An exemplary sample cuvette  12  according to the invention is shown in  FIG. 2 . According to one embodiment, the cuvette  12  is a container that has two side walls  56  and two end walls  58 . In a further embodiment, cuvette  12  has a lip or flange  50  extending around the opening  51  of the cuvette  12 . For example, the lip  50  protrudes at approximately 90° from the side walls  56  in one embodiment, while in another embodiment, the lip  50  protrudes at approximately 90° from the end walls  58 . Alternatively, the lip  50  extends around the perimeter of the opening  51 . 
     With continued reference to  FIG. 2 , in a further embodiment, the cuvette  12  has a projection  52  on a side wall  56  for engaging a groove, hole or recess  54  in another cuvette  12 . In yet another embodiment, the cuvette  12  has a first projection  52  on a first side wall  56  and a second projection  52  on a second side wall  56 . In another embodiment, the cuvette  12  has a groove, hole or recess  54  on a side wall  56  for being engaged by a projection  52  from another cuvette  12 . In yet another embodiment, the cuvette  12  has a first recess  54  on a first side wall  56  and a second recess  54  on a second side wall  56 . For example, when a first cuvette  12  is inserted into a second cuvette  12 , the first projection  52  of the first cuvette engages a groove  54  on a first side wall  56  of the second cuvette  12  and a second projection  52  on the first cuvette  12  engages a groove  54  on a second side will  56  of the second cuvette  12  to releasably secure the first cuvette  12  to the second cuvette  12  to form a stack of cuvettes  120 . 
     As used herein, a stack of cuvettes  120  means at least two cuvettes  12  that are releasably joined to one another. Releasably joined means that the earth&#39;s gravitational forces alone are not sufficient to separate a bottom cuvette  12  from a top cuvette  12  when the two cuvettes are joined, but that the addition of an external force to separate the bottom cuvette, the first cuvette, from the top cuvette, i.e., the second cuvette is necessary. The number of cuvettes in a stack may be 2-500, preferably 10, 20, 25, 30, 50, or 100, for example. 
     In another embodiment, the cuvette  12  has a projection  52  on the end wall  58 , while in a further embodiment, the cuvette  12  has a groove, hole or recess  54  on the end wall  58 . In a different embodiment, the cuvette  12  has a first projection  52  and first recess  54  on a first end wall  58  and a second projection  52  and a second recess  54  on a second end wall  58 . 
     Referring again to  FIG. 1 , the cuvette transport carousel  1  has a series of slots  2  for receiving a cuvette  12 . According to one embodiment of the invention, the cuvette transport carousel  1  rotates in both the clockwise and counter clockwise directions in order to position cuvettes  12  held in the slots  2  at different stations adjacent to the cuvette transport carousel  1  in the automated sample analyzer. For example, in one embodiment, cuvette transport carousel  1  rotates to position a cuvette  12  near the sample pipette robot  5  so that the sample pipette robot  5  can dispense a sample from a sample carousel (not shown) into the cuvette  12 . 
     In another embodiment, the cuvette transport carousel  1  rotates to position a cuvette  12  at a reagent dispensing station  7 . At the reagent dispensing station, according to one embodiment of the invention, one or more reagents (not shown), such as buffers or magnetic particles having antigens or antibodies bound thereto, for example, are dispensed into the sample cuvettes  12  by one or more reagent pipettes (not shown). 
     In a further embodiment, the cuvette transport carousel  1  rotates to position a cuvette  12  at a magnetic particle washing station  4 . Cuvettes  12  are removed from the cuvette transport carousel  1  wherein the magnetic beads added to the cuvette  12  at the reagent dispense station  7  are washed according to methods described in the concurrently filed U.S. patent application entitled “Magnetic Particle Washing Station”Ser. No. 11/704,138. 
     In yet another embodiment, the cuvette transport carousel  1  rotates to position the cuvette  12  near an analysis station  6 . For example, in one embodiment according to the invention, the analysis station is a luminometer  6 . The cuvettes  12  are removed from the cuvette transport carousel  1  and positioned inside the luminometer  6  one at a time. In one embodiment, the luminometer  6  provides a sealed environment free from outside light for performing chemiluminescent assays which measure, for example, target molecules in the sample. 
     Cuvette Dispenser 
       FIG. 3A  is a perspective view of a cuvette dispenser of an automated sample analyzer, including a cuvette loading module for receiving stacks of cuvettes, according to an illustrative embodiment of the invention, while  FIG. 3B  is a perspective view of the cuvette dispenser of an automated sample analyzer as shown in  FIG. 3A , but with the cuvette loading module removed to reveal an engagement piece for engaging and rotating the cuvette loading module according to one illustrative embodiment of the invention. 
     As shown in  FIGS. 3A-B , according to one embodiment, the cuvette dispenser  10  includes a cuvette loading module  14 , a cuvette dispense chute  20 , one or more cuvette release members  30 ,  32 , and a cuvette transfer position  36 . The cuvette loading module  14  has a plurality of slots  16  for holding stacks of cuvettes  120 . The cuvette dispense chute  20  receives stacks of cuvettes  120  from the cuvette loading module  14  and provides them to the one or more cuvette release members  30 ,  32 . Cuvette release members  30 ,  32  separate individual cuvettes  12  from the stack of cuvettes  120 , depositing individual cuvettes  12  one at a time to the cuvette transfer position  36 . 
     According to one embodiment of the invention, the cuvette loading module is positioned above the cuvette dispense chute  20  and the cuvette release members  30 ,  32 . In one embodiment, the cuvette loading module  14  is circular, for example, a wheel, disc, or cylinder. In a further embodiment, the cuvette loading module  14  has a plurality of vertically oriented slots  16  extending from the top  13  of the module  14  to the bottom  24  of the module  14  for receiving stacks of cuvettes  120 . The module  14  has, for example, 15, 20, or 25 slots  16 . Each slot  16  includes two side walls  18 . The side walls  13  of the slot  16  abut a rear wall  21 . According to one embodiment of the invention, each slot  16  is spaced an equal distance from the center of the circular module  14 . In a further embodiment, each slot  16  is equally distributed around the perimeter of the module  14 . 
     In a further embodiment of the cuvette loading module  14 , each side wall  18  has a lip  17  for securing the stack of cuvettes  120 . In another embodiment, between lip  17  of the first side wall and lip  17  of the second side wall  18 , there is a gap  23 . The gap  23  allows an operator to see whether or not a slot  16  is empty or filled with cuvettes  12 , thus improving ease of operation. In a further embodiment, rear wall  21  includes a window  19  for allowing a sensor (not shown) to detect the presence or absence of a cuvette  12 . 
     According to one embodiment, the cuvette loading module  14  rotates about a central axis. The module  14  sits on a base plate  360  and engages a central pin  34 . The pin  34  is operatively connected to a motor (not shown), for example, by an axle or shaft. The pin  34  rotates causing the module  14  to rotate to position a stack of cuvettes  120  above a cuvette shutter  22 . In one embodiment, while the module  14  rotates, the base plate  360  remains stationary. In a further embodiment, the base plate  360  supports the base of the cuvette stack  120 . 
       FIG. 4  is a perspective view of a cuvette dispenser of an automated sample analyzer showing several sensors for activating movement of cuvettes through the cuvette dispenser, according to one illustrative embodiment of the invention. In one embodiment, a cuvette stack sensor  400  is fixed to the base plate  360 . According to another embodiment of the invention, the cuvette stack sensor  400  detects the presence or absence of a stack of cuvettes  120  in the slots  16 . For example, in one embodiment, the cuvette stack sensor  400  detects the presence or absence of a cuvette stack  120  via the window  19  in the rear wall  21  of the slot  16 . For example, if a cuvette is not detected in the slot  16 , the sensor  400  detects the absence of the cuvette stack  120  and the cuvette loading module  14  rotates to position a stack of cuvettes  120  over the cuvette shutter  22 . 
       FIG. 5A  is a cross-sectional view of a cuvette loading module housing a stack of cuvettes prior to the cuvettes being released into the cuvette dispense chute for distribution, according to one illustrative embodiment of the invention. Once the cuvette stack  120  is positioned over the cuvette shutter  22 , as shown in  FIG. 5A , the cuvette stack sensor  400  detects a cuvette, activating the cuvette shutter  22  to open. In one embodiment, the cuvette shutter  22  pivots in the plane of the base plate  360  to open and close over a cuvette chute  20 , described below in greater detail. In another embodiment, the cuvette shutter  22  pivots in a plane not parallel to the base plate  360 . For example, the cuvette shutter  22 , in one embodiment, is a door that opens from a plane parallel to the base plate  360  to a plane that is substantially perpendicular to the base plate  360 . 
       FIG. 5B  is a cross-sectional view of the cuvette dispenser. The stack of cuvettes shown in  FIG. 5A  has been released into a cuvette dispense chute, according to one illustrative embodiment of the invention. Once the cuvette shutter  22  opens, the cuvette stack  120  drops from the cuvette loading module  14  into cuvette dispense chute  20 , for example. At this point, the cuvette  12  at the bottom of the stack rests on a first cuvette release member  30  and a second cuvette release member  32 , while the remaining cuvettes are supported by the chute  20 . 
     According to one embodiment of the invention, the chute  20  is a tube, for example, a rectangular tube, a square tube or a cylindrical tube, sized and shaped to receive a plurality of cuvettes  12 , e.g., a stack of cuvettes  120 . In a further embodiment, the tube  20  is open on the front portion  60 , while in another embodiment, the tube is closed over the front portion  60 . In another embodiment, the chute  20  includes a first parallel wall  28  and a second parallel wall  29  to support cuvettes  12 , thereby permitting visibility of the cuvettes  12  in the chute. For example, in one embodiment, the cuvette dispense chute  20  is a pair of parallel walls, each shaped in cross-section like a square bracket ([ ]) providing a hollow passage between the walls to support a stack of cuvettes  120 . 
     Referring again to  FIG. 4 , once the stack of cuvettes  120  is present in the cuvette dispense chute  20 , a cuvette dispense sensor  56 , positioned for example, at the base of the cuvette dispense chute  20 , detects the presence of the cuvette stack  120 , according to one embodiment of the invention. Upon detecting the presence of a cuvette stack  120 , the first cuvette release member  30  and second cuvette release member  32  rotate to release a cuvette  12  from the cuvette stack  120 . The cuvette dispense chute  20  supports the cuvettes  12  until they are removed from the stack  120  by the first cuvette release member  30  and second cuvette release member  32 . 
       FIGS. 6A-C  and  FIGS. 7A-C  are perspective views of a first cuvette release member and a second cuvette release member respectively. As shown in  FIGS. 6A-C  and  FIGS. 7A-C , the first cuvette release member  30  and the second cuvette release member  32  are cylindrical in shape. In one embodiment, the first cuvette release member  30  has the same diameter as the second cuvette release member  32 . In another embodiment, the first cuvette release member  30  has a diameter that is different from the diameter of the second cuvette release member  32  (not shown). In an alternate embodiment, however, the first cuvette release member  30  and the second cuvette release member  32  are tapered (not shown). For example, in one embodiment, the widest part of the tapered first cuvette release member  30  is the bottom of the cuvette release member  30 , while in another embodiment, the widest part of the tapered cuvette release member  30  is the top of the cuvette release member  30 . 
     With continued reference to  FIGS. 6A-C  and  FIGS. 7A-C , according to one embodiment of the invention, the cuvette release members  30 ,  32  are threaded, for example, like the windings on a screw. According to one embodiment, the first cuvette release member  30  has a helical thread  31  that is in a first orientation while the second cuvette release member  32  has a helical thread in a second orientation  33 . For example, in one embodiment, the first cuvette release member  30  has a right hand oriented helical thread  31  disposed on the cuvette release member  30 , while the second cuvette release member  32  has a left hand oriented helical thread  33  disposed on the cuvette release member  32 . In a further embodiment, the first cuvette release member  30  has a right hand oriented thread  1135  as well as a left hand oriented helical thread  1131  disposed on the cuvette release member  30 . In a further embodiment, the second cuvette release member  32  has a left hand oriented helical thread  1136  as well as a right hand oriented helical thread  1132  disposed on the cuvette release member  32 . 
     In an alternate embodiment, the first cuvette release member  30  has a helical thread  31  that is in the same orientation as the helical thread  33  of the second cuvette release member  32 . For example, the first cuvette release member  30  and the second cuvette release member  32  each have a helical thread  31 ,  33  with a right hand orientation, while in another embodiment, the first cuvette release member  30  and the second cuvette release member  32  each have a helical thread  31 ,  33  with a left hand orientation. In one embodiment, a cuvette release member  30 ,  32  has only one thread, while in another embodiment, a cuvette release member  30 ,  32  has two or more threads. 
     With continued reference to  FIGS. 6A-C  and  FIGS. 7A-C , in a further embodiment, the first cuvette release member  30  has a thread  1131  of a first orientation at the top end  131 . The orientation of the thread  1131  reverses direction on the cuvette release member  30  to become a thread of a second orientation  1135 . The thread  1131  reverses direction at a reversal point  1133  which is about 5-45% along the length of the axis of the cuvette release member  30 , the axis running from the top end  131  of the cuvette release member  30  to the bottom end  231  of the cuvette release member. Preferably the thread  1131  reverses direction at a reversal point  1133  which is about 10-35%, about 15-30%, or more preferably at a point about 25% along the length of the axis of the cuvette release member  30 . For example, in one embodiment, the first cuvette release member  30  has a left hand oriented thread  1131  originating from or near the top portion  131  of the first cuvette release member  30 . In one embodiment, after making approximately a full turn (360 degrees) around the cuvette release member  30 , the left hand orientation  1131  of the thread is reversed to a right hand orientation  1135  at a point  1133 . 
     In a further embodiment, the second cuvette release member  32  has a thread  1132  of a first orientation at the top end  132 . The orientation of the thread  1132  reverses direction on the cuvette release member  32  to become a thread of a second orientation  1136 . The thread reverses direction at a reversal point  1134  which is about 5-45% along the length of the axis of the cuvette release member  32 , the axis running from the top end  132  of the cuvette release member  32  to the bottom end  232  of the cuvette release member. Preferably the thread  1132  reverses direction at a reversal point  1134  which is about 10-35%, about 15-30%, or more preferably at a point about 25% along the length of the axis of the cuvette release member  32 . For example, in one embodiment, the first cuvette release member  32  has a right hand oriented thread  1132  originating from or near the top portion  132  of the first cuvette release member  32 . In one embodiment, after making approximately a full turn (360 degrees) around the cuvette release member  32 , the right hand orientation of the thread  1132  is reversed to a left hand orientation  1136  at a reversal point  1134 . 
     With continued reference to  FIGS. 6A-C  and  FIGS. 7A-C , in a further embodiment, the pitch of the helical thread  31  of the first cuvette release member  30  is the same as the pitch of the helical thread  33  of the second cuvette release member  32 . In a further embodiment, the pitch of the helical threads  31 ,  33  on the first and second cuvette release members  30 ,  32  is between about 6° and 10°, and in a further embodiment, the pitch is about 7°. 
     With reference to  FIGS. 6A-C , in a further embodiment, the first cuvette release member  30  has a first portion of a helical thread in a first orientation  1131  having a first pitch and a second portion of the helical thread in a second orientation  1135  having a second pitch. The first portion of the helical thread  1131 , after making approximately a full turn (360 degrees) around the cuvette release member  30 , reverses orientation at a reversal point  1133  and a second portion of the helical thread  1135  having a second pitch continues turning around the cuvette release member from the reversal point  1131 . For example, the second portion  1135  makes one, two, three, or four full turns around the cuvette release member  30 . In one embodiment, the first pitch is between about 9.2° and 9.6° and the second pitch is between about 6.9° and 7.3°. In a further embodiment, the first pitch is about 9.4° and the second pitch is about 7.1°. 
     With reference to  FIGS. 7A-C , in another embodiment, the second cuvette release member  32  has a first portion of a helical thread in a first orientation  1132  having a first pitch and a second portion of the helical thread in a second orientation  1136  having a second pitch. The first portion of the helical thread  1132 , after making approximately a full turn (360 degrees) around the cuvette release member  30 , reverses orientation at a reversal point  1134  and a second portion of the helical thread  1136  having a second pitch continues turning around the cuvette release member from the reversal point  1134 . For example, the second portion  1136  makes one, two, three, or four turns around the cuvette release member  30 . In one embodiment, the first pitch is between about 9.2° and 9.6° and the second pitch is between about 6.9° and 7.3°. In a further embodiment, the first pitch is about 9.4° and the second pitch is about 7.1°. 
     As used herein, the pitch of a helical thread  31 ,  33  means the angle formed between the helical thread and a plane that intersects the helical thread  31 ,  33 , the plane being perpendicular to the longitudinal axis of the cuvette release member  30 ,  32 . 
     As shown in  FIGS. 3A-3B , the first cuvette release member  30  and the second cuvette release member  32  rotate in an axis parallel to the axis of the cuvette stack  120 , according to one embodiment of the invention. In another embodiment, first cuvette release member  30  and the second cuvette release member  32  rotate around an axis perpendicular to the cuvette stack  120 . 
     Referring again to  FIGS. 3A-B , cuvette release members  30 ,  32  are each connected to a rotating member  42 . For example, in one embodiment, an exemplary rotating member is a gear wheel  42  as shown in  FIGS. 3A-B . The gear wheel  42  is operatively connected to a motor (not shown), for example, an oscillating motor, capable of effecting the rotation of the gear wheels  42 , and thereby the rotation of the cuvette release member  30 . For example, in one embodiment, the first cuvette release member  30  is connected to a first rotating member  42  by axle  46  and the second cuvette release member  32  is connected to a second rotating member  44  by axle  48 . 
     The first rotating member  42  and the second rotating member  44 , in one embodiment, are each capable of rotating in both the clockwise or counter-clockwise direction to effect the rotation of the first cuvette release member  30  and the second cuvette release member  32 , respectively. For example, in one embodiment, the first cuvette release member  30  and the second cuvette release member  32  each rotate in the same direction, for example, clockwise, or alternatively, counter-clockwise. 
     In yet another embodiment, the first cuvette release member  30  rotates in a direction opposite from the second cuvette release member  32 . For example, the first cuvette release member  30  rotates in a clockwise direction while the second cuvette release member  32  rotates in a counter-clockwise direction. Alternately, in another embodiment, the first cuvette release member  30  rotates in a counter-clockwise direction while the second cuvette release member  32  rotates in a clockwise direction. 
     In an even further embodiment, the first cuvette release member  30  rotates in a first direction, e.g., clockwise, for a first period of time, while the second cuvette release member  32  rotates in a second direction, e.g., counter-clockwise, for a first period of time, after which the first cuvette release member  30  reverses to rotate in a second direction for a second period of time and the second cuvette release member  32  simultaneously reverses to rotate in a first direction for a second period of time. 
       FIGS. 8A-C  are perspective views of cuvette release members for releasing a cuvette from a stack of cuvettes in the cuvette dispense chute. The exemplary first cuvette release member  30  and second cuvette release member  32  are threaded and rotate to engage, the cuvette  12  to remove it from the stack  120 . Once the cuvette  12  has traveled fully through the cuvette release member  30 ,  32 , the cuvette  12  is dispensed at the cuvette transfer position  36  according to an illustrative embodiment of the invention. As discussed above, once the cuvette shutter  22  opens, a stack of cuvettes  12  moves downward until the bottom cuvette  12  in the cuvette stack  120  comes to rest on the first cuvette release member  30  and the second cuvette release member  32 , according to one embodiment of the invention. The cuvette dispense sensor  58  detects the presence of the cuvettes  12 , the bottom cuvette  12 , and the first cuvette release member  30  and the second cuvette release member  32  begin to rotate to release the cuvette from the stack  120 . 
     As shown in  FIG. 8A , according to one embodiment of the method of the invention, the first cuvette release member  30  and the second cuvette release member  32 , described above with respect to  FIGS. 6A-C  and  FIGS. 7A-C , rotate to engage the lip  50  of the cuvette  12  to effect the cuvette&#39;s  12  separation from the stack of cuvettes  120 . Alternately, in one embodiment, the first cuvette release member  30  rotates while the second cuvette release member  32  is stationary; when the first cuvette release member  30  stops rotating, the second cuvette release member  32  rotates. In yet another embodiment, the first cuvette release member  30  rotates simultaneously with the second cuvette release member  32 . 
     In a further embodiment, the first cuvette release member  30  rotates in a first direction, e.g., clockwise, while the second cuvette release member rotates in a second direction, e.g., counter-clockwise, in order to engage the lip  50  of the cuvette  12  and to separate it from the stack  120 . In yet another embodiment, the first cuvette release member  30  rotates in a first direction, e.g., clockwise, both to engage the lip  50  of the cuvette  12  and to release the cuvette  12  into the cuvette transfer position  36 , while the second cuvette release member  32  rotates in a second direction, e.g., counter-clockwise, both to engage the lip  50  of the cuvette  12  and to release the cuvette  12  into the cuvette transfer position  36 . In a further embodiment, the first cuvette release member  30  rotates in a first direction e.g., clockwise, while the second cuvette release member rotates in a second direction, e.g., counter-clockwise, in order to engage the lip  50  of the cuvette  12  and to separate it from the stack  120 ; the first cuvette release member  30  and the second cuvette release member  32  then each reverse their direction of rotation in order to release the cuvette  12  into the cuvette transfer position  36 . 
     With continued reference to  FIG. 8A , according to one embodiment of the invention, the first cuvette release member  30  has a helical thread  31  having a first portion of a first orientation (e.g., left-handed)  1131  beginning at the top portion  131  of the first cuvette release member  30 . The second cuvette release member  32  also has a helical thread  33  having a first portion of a second orientation (e.g., right handed)  1132  beginning at the top portion  132  of the second cuvette release member  32 . The first cuvette release member  30  rotates in a first direction (e.g., clockwise) and the left cuvette release member  32  rotates in a second direction (e.g., counter-clockwise) to engage the cuvette  12  and to release it from the stack  120 . 
     According to one embodiment, once the cuvette  12  is released from the stack  120 , the rotation of the first cuvette release member  30  and the second cuvette release member  32  is reversed. In one embodiment, the rotation of the first cuvette release member  30  and the second cuvette release member  32  is reversed when the cuvette  12  engages a reversal point  1133  between the first-orientation (e.g., left handed) helical thread portion  1131  and the second-orientation thread (e.g., right handed) portion  1135  on the first cuvette release member  30 , and the reversal point  1134  between the second-orientation (e.g., right handed) thread portion  1132  and the first orientation (e.g., left handed) thread portion  1136  on the second cuvette release member  32 . At that point, for example, the first cuvette release member  30  changes direction to rotate in a second direction (e.g., counter-clockwise) and the second cuvette release member  32  changes direction to rotate in a first direction (e.g., clockwise). The change in rotation prevents a second cuvette  12  from being dispensed prior to the first cuvette  12  being delivered to the cuvette transfer position  36 . 
     As shown in  FIG. 8B , the helical threads  31  of the first cuvette release member  30  and the helical threads  33  of the second cuvette release member  32  continue to engage the lip  50  of the cuvette  12  after the cuvette  12  releases from the stack of cuvettes  120  and while the cuvette  12  moves in a downward direction via the cuvette release members  30 ,  32  toward the cuvette transfer position  36 , in one embodiment, the first cuvette release member  30  and the second cuvette release member  32  engage the lips  50  of the side walls  56  of the cuvette  12 , while in another embodiment, the first cuvette release member  30  and the second cuvette release member  32  engage the lips  50  of the end walls  58  of the cuvette  12 . 
     With continued reference to  FIG. 8A , according to a further embodiment, the force exerted on the cuvette  12  by the helical threads  31  of the first cuvette release member  30  and the helical threads  33  of the second cuvette release member  32  causes the projections  52  on cuvette  12  to disengage from the stack of cuvettes  120 . For example, in one embodiment, the downward force exerted by the rotating first orientation (e.g., left hand) helical thread portion  1131  of the first cuvette release member  30  and the second orientation (e.g., right hand) helical thread portion  1132  of the second cuvette release member  32  causes the recesses  54  on the walls of the cuvette  12  to disengage from the projections  52  on the adjacent cuvette  12  in the stack  120 . 
     With reference to both  FIGS. 8A and 8B , as the first rotating member  30  and the second rotating member  32  continue to rotate, the cuvette  12  moves along the helical thread  31  of the first rotating member  30  and the helical thread  33  of the second rotating member  32  in a downward direction, as indicated by the directional arrow in  FIG. 8A . For example, in one embodiment, once the cuvette  12  is released from the stack  120 , the first cuvette release member  30  and the second cuvette release member  32  reverse rotational direction to further facilitate the cuvette traveling in a downward direction. 
     With continued reference to  FIGS. 8A and 8B , in one embodiment, the first cuvette release member  30  has a helical thread  31  having a top portion  1131  and a bottom portion  1135 . The top portion  1131  has a first orientation (e.g., left hand) and the bottom portion  1135  has a second orientation (e.g., right hand). The first orientation reverses to the second orientation at reversal point  1133 . The second cuvette release member  32  also has a helical thread  33  having a top portion  1132  and a bottom portion  1136 . The top portion  1132  has a first orientation (e.g., right hand) and the bottom portion  1136  has a second orientation (e.g., left hand). The first orientation reverses to the second orientation at reversal point  1134 . When the rotational direction of the first cuvette release member  30  and the second cuvette release member  32  reverses, the cuvette  12 , in one embodiment, then travels along the bottom portion  1135  of the first cuvette release member  30  helical thread  31  and the bottom portion  1136  of the second cuvette release member  32  helical thread  33  in a downward direction toward the cuvette transfer position  36 . 
       FIG. 5C  is a cross-sectional view of the cuvette dispenser shown in  FIG. 5B , while  FIG. 8C  shows a perspective view of the cuvette dispenser. A cuvette from the stack of cuvettes has been released from the exemplary cuvette release members to the cuvette transfer position, according to one illustrative embodiment of the invention. According to one embodiment of the invention, the cuvette transfer position  36  is located directly below and between the first cuvette release member  30  and the second cuvette release member  32 . As shown in  FIG. 3A , the cuvette release members  30 ,  32  rest on a platform  38 . In one embodiment, the cuvette transfer position  36  includes a first projection  39  and a second projection  40  from the platform  38 . A space  37  separates the first projection  39  from the second projection  40 . For example, the space  37  receives the body of the cuvette  12 , while the lips  50  of the cuvette  12  rest on the first projection  39  and the second projection  40  according to one embodiment of the invention. 
     Referring again to  FIG. 4 , once the cuvette  12  is positioned in the cuvette transfer position  36 , a cuvette transfer sensor  48  detects the presence of the cuvette  12 , and stops the first cuvette release member  30  and the second cuvette release member  32  from rotating. This prevents another cuvette  12  from occupying the cuvette transfer position  36 , until the cuvette  12  currently occupying the cuvette transfer position  36  is removed. In a further embodiment, once a cuvette  12  is present at the cuvette transfer position  36 , the cuvette transfer sensor  48  signals to a robotic arm (not shown), for example, to remove the cuvette  12  from the transfer position  36  and to place it on the cuvette transport carousel  1 . 
     According to one embodiment of the invention, once the cuvette  12  is removed from the cuvette transfer position  36 , the cuvette transfer sensor  48  detects the absence of a cuvette  12 , signaling the first cuvette release member  30  and the second cuvette release member  32  to rotate and provide another cuvette  12  to the cuvette transfer position  36 . Once the stack of cuvettes  120  in the cuvette dispense chute  20  has been dispensed, the cuvette dispense sensor  56  detects the absence of cuvettes  12 , causing the cuvette loading module  14  to rotate until the cuvette stack sensor  400  detects a stack of cuvettes  120 , at which point the process of dispensing cuvettes  12  proceeds as previously discussed. 
     In another aspect, the invention is a method for automatically loading a plurality of cuvettes  12  onto a conveyor, such as a rotating cuvette carousel  1 , in an automated clinical sample analyzer. For example, in one embodiment, an operator first loads stacks of cuvettes  120  into the slots  16  of the cuvette loading module  14 . The module  14  rotates until the cuvette stack sensor  400  detects the presence of a stack of cuvettes  120  over the cuvette shutter  22 . 
     Once a stack of cuvettes  120  is positioned over the cuvette shutter  22 , the cuvette shutter  22  opens and the stack of cuvettes  120  falls into the cuvette chute  20 , with the bottom cuvette  12  of the stack  120  resting on the first cuvette releasing member  30  and the second cuvette releasing member  32 . Cuvette dispense sensor  56  detects the presence of the cuvette stack  120  and causes the first cuvette release member  30  and the second cuvette release member  32  to rotate to engage and release a cuvette  12  from the stack  120 , and to deliver the cuvette to the cuvette transfer position  36 . 
     In one embodiment, the first cuvette release member  30  rotates in a first direction, e.g., clockwise, while the second cuvette release member  32  rotates in a second direction, e.g., counter-clockwise to engage the cuvette  12 ; the first cuvette release member  30  then switches direction to rotate in a second direction while the second cuvette release member  32  switches direction to rotate in a first direction to release cuvette  12  to the cuvette transfer position  36 . In another embodiment, the first cuvette release member  30  rotates in a first direction, e.g., clockwise, both to engage the cuvette  12  and to release the cuvette  12  at the cuvette transfer position  36 , while the second cuvette release member  32  rotates in a second direction, e.g., counter-clockwise, both to engage the cuvette  12  and to release cuvette  12  at the cuvette transfer position  36 . 
     Once the cuvette  12  rests in the cuvette transfer position  36 , cuvette transfer sensor  58  signals to a robotic arm (not shown), for example, to remove the cuvette  12  from the transfer position  36  and to place it in a slot  2  of the cuvette transport carousel  1 . 
     Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is not to be defined by the preceding illustrative description but instead by the spirit and scope of the following claims.