Abstract:
An apparatus for mixing a liquid in a container in order to provide a homogeneous solution or suspension of the liquid in the container. In particular, the apparatus of this invention can be used to provide a homogenous dispersion of particulate material in a liquid medium.

Description:
[0001]     This application claims priority to U.S. Provisional Application No. 60/623,273, filed on Oct. 29, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to the field of mixing liquids to form a homogenous suspension or solution. More particularly, this invention further relates to the field of mixing liquids containing particulate material in order to obtain a homogeneous suspension of particulate material in the liquid.  
         [0004]     2. Discussion of the Art  
         [0005]     Automated instrumentation has been developed for performing assays in clinical laboratories. Automated instrumentation has been used in the area of immunoassays. In the area of immunoassays, certain reagents known as solid-phase reagents are used in heterogeneous immunoassays. In heterogeneous immunoassays, the solid-phase reagent can include paramagnetic particles, while another reagent, the labeled reagent, can include a chemiluminescent label. In order to obtain accurate and precise assays results, the solid-phase reagent must exist as a uniform, homogeneous dispersion as particles in a dispersing medium. One problem encountered when using solid-phase reagents is that over a period of time, the particulate material in the reagent tends to settle out of the dispersion. Therefore, there is a need to re-disperse the particulate material of the solid-phase reagent in the dispersing medium. In an automated system, the solid-phase reagent must be re-dispersed by the apparatus, without manual shaking by an operator. Many references in the prior art indicate apparatus and methods for maintaining solid particulate material in a uniform, homogeneous dispersion.  
         [0006]     U.S. Pat. No. 5,104,807 describes an apparatus in which a train of containers is provided on a movable holder. The train is conveyed such that it passes through a container rotating area and a container non-rotating area. The motion of the movable holder driven by a driving source is transmitted to the containers located in the container rotating area as a rotational force of the containers on their own axes. In the container non-rotating area, a light beam of a photometer is formed so that light measurement can be performed to measure the test solutions in the containers which arrived at the non-rotating area.  
         [0007]     U.S. Pat. No. 3,848,796 discloses a sedimentation rate centrifuge comprising a centrifuge head, a driven shaft mounting the head for rotation therewith and a drive motor coupled to the driven shaft for imparting rotative motion thereto about the axis of the each in intermittent periods of predetermined duration to generate centrifugal force applicable in a direction generally normal to its axis of rotation. The centrifuge head comprises a body, a sample tube holder carried by the body near the periphery thereof, the sample tube holder constructed and arranged to receive elongate sample tubes each containing a thin column of blood and each vertically arranged and oriented substantially parallel to the axis or rotation of the body so that the centrifugal force is applied laterally to the long axis of the sample tubes, means for causing periodic rotation of the sample tube holder and the associated sample tube about its own long axis between each application of centrifugal force and when the body is substantially at rest.  
         [0008]     UK Patent Application GB 2 081 118 describes the simultaneous mixing of the contents in each of a plurality of containers each including a liquid. The mixing is effected by simultaneously causing the containers each to be rotated about its own axis first in one direction and then in another. In one embodiment the test tubes are mounted in a turntable with a disc-shaped drive member frictionally engaging each tube and rotatable (independently of turntable) to cause each tube to be rotated about its own axis to mix the contents therein. The turntable assembly is particularly suitable for use with automated analysis machines.  
         [0009]     U.S. Pat. No. 6,436,349 describes a reagent transport apparatus for use on a clinical analyzer. The reagent transport apparatus comprises a base, a reagent tray mounted on the base for rotation about a primary vertical axis of rotation; a drive motor for rotating the reagent ray about the primary vertical axis of rotation; a control unit in the form of a computer circuit for operating the drive motor to selectively position a selected one of the reagent containers at the reagent aspiration point; a plurality of mounting assemblies disposed in a first circle on the reagent ray, concentric with the primary vertical axis of rotation; a plurality of agitating assemblies disposed in a second circle on the reagent ray, concentric with the primary vertical axis of rotation, each of the agitating assemblies having a respective secondary vertical axis of rotation; and agitating motor for rotating each of the plurality of agitating assemblies about the respective secondary vertical axis of rotation, each agitating assembly comprising a first reagent container holder mounted on the reagent tray for rotation about the respective secondary vertical axis of rotation, the reagent transport assembly further comprising a ring gear, concentric with the primary vertical axis of rotation and coupled to the agitating motor, in driving engagement with each of the satellite gears wherein rotation of the ring gear by the agitating motor about the primary vertical axis causes each of the satellite gears to rotate about the respective secondary vertical axis.  
       SUMMARY OF THE INVENTION  
       [0010]     This invention provides an apparatus for mixing a liquid in a container in order to provide a homogeneous solution or suspension of the liquid in the container. In particular, the apparatus of this invention can be used to provide a homogenous dispersion of particulate material in a liquid medium.  
         [0011]     In one aspect, the apparatus comprises a plurality of rotatable seats, each seat capable of supporting a container that contains a liquid. Each rotatable seat comprises a platform for supporting the container. The platform has a top major surface and a bottom major surface. The platform of each rotatable seat is preferably cylindrical in shape, wherein the top major surface and the bottom major surface preferably have circular geometry. A shaft projects from the bottom major surface of the platform of each rotatable seat, and, attached to the shaft are at least one sprocket wheel and at least one bearing. A chain, which chain is driven by a different sprocket wheel, i.e., the drive sprocket wheel, causes the sprocket wheel attached to the shaft shaft projecting from the bottom major surface of the platform of the rotatable seat to rotate. The shaft of the rotatable seat rotates in the bearing(s), whereby the platform of the rotatable support rotates. A container seated upon the top major surface of the platform of the rotatable seat is thus enabled to rotate, whereby the contents of the container can be agitated.  
         [0012]     In one embodiment, the plurality of rotatable seats can be arranged in a circle on a carousel, and the chain can engage the sprockets of the sprocket wheels attached to the shafts associated with the rotatable seats. By this arrangement, the rotatable seats can be rotated when the chain is driven by the drive sprocket wheel.  
         [0013]     The use of a chain and a drive sprocket wheel for rotating rotatable seats for supporting reagent containers exhibits numerous benefits. One benefit involves reduction of the weight of the carousel, thereby decreasing the rate of wear of the components that support the carousel. Another benefit involves reduction of acoustic noise relative to that produced by a gear-driven agitating system. A third benefit involves reduction of cost relative to that of a gear-driven agitating system. A fourth benefit involves reduction of the inertial load on the agitating motor relative to that of a gear-driven agitating system. A fifth benefit involve the elimination of the need for a lubricant, as is required in a gear-driven agitating system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1A  is a schematic view of an immunoassay apparatus of the prior art that can employ the reagent transport apparatus of this invention. The schematic view is a top plan view.  
         [0015]      FIG. 1B  is a perspective view of the carousels of the immunoassay apparatus of  FIG. 1A . Also shown in  FIG. 1B  are motors that drive the carousels and the motor that drives the mechanisms that agitate the reagent containers.  
         [0016]      FIG. 2  is a perspective view of a carousel showing placement of seats for holding containers that are to be agitated and placement of seats for containers that need not be agitated.  
         [0017]      FIG. 3  is a top plan view of the carousel of  FIG. 2 .  
         [0018]      FIG. 4  is a bottom plan view of the carousel of  FIG. 2 .  
         [0019]      FIG. 5  is a schematic view, in cross-section, showing the carousel, the rotatable seat, the chain, the sprocket wheel attached to the shaft of a rotatable seat, and bearings attached to the shaft of a rotatable seat.  
         [0020]      FIG. 6  is a schematic view, in cross-section, showing the carousel, a fixed seat, and a retention element for securing oversized containers.  
         [0021]      FIG. 7A  is a perspective view of a seat suitable for a rotatable seat.  
         [0022]      FIG. 7B  is a perspective view of a seat suitable for a fixed seat.  
         [0023]      FIG. 8  is a side view in elevation of the rotatable seat of  FIG. 7A .  
         [0024]      FIG. 9  is a side view in elevation of the fixed seat of  FIG. 7B .  
         [0025]      FIG. 10  is a side view in elevation of a retention element for securing oversized containers.  
         [0026]      FIG. 11  is a perspective view of a drive sprocket wheel.  
         [0027]      FIG. 12  is a perspective view of a sprocket wheel associated with a rotatable seat.  
         [0028]      FIG. 13  is a perspective view illustrating the chain, the drive sprocket wheel, the sprocket wheels attached to the shafts of rotatable seats, bearings attached to the shafts of rotatable seats, rotatable seats, and fixed seats.  
         [0029]      FIG. 14  is a perspective view of a cam assembly for engaging the drive sprocket wheel and the chain and disengaging the drive sprocket wheel from the chain.  
         [0030]      FIG. 15  is a top plan view of the cam assembly of  FIG. 14 .  
         [0031]      FIG. 16  is a bottom plan view of the cam assembly of  FIG. 14 . 
     
    
     DETAILED DESCRIPTION  
       [0032]     As used herein, the term “carousel” means a tray capable of holding a plurality of containers. The expression “reagent container” generally means a container that contains a solid-phase reagent or a labeled reagent, also known as a tracer reagent. However, the expression “reagent container” can also include containers for diluents and for reagents other than the types mentioned previously. The expression “sprocket wheel” means a wheel rimmed with sprockets, used to engage the links of a chain in a pulley or drive system. The expression “drive sprocket wheel” means a sprocket wheel that causes the chain in a pulley or drive system to move. The term “sprocket” means any of various toothlike projections arranged on the rim of a wheel to engage the links of a chain. The expression “diametric pitch” means pitch diameter divided by the number of sprockets.  
         [0033]     An immunoassay can be used to determine the presence or concentration of an item of interest in a sample. In the article described in U.S. Pat. No. 6,562,298, incorporated herein by reference, to perform an immunoassay (as shown in  FIG. 1A  herein), a reaction container (not shown) is moved into a process lane  10  at a first position. At the first position, a known quantity of sample, e.g., 50 μL of blood, is deposited in the reaction container by a filling system  14 . The filling system comprises a pipette (not shown), which may be mounted on an arm for vertical movement and angular movement. After the reaction container is indexed to arrive at a second position, a known quantity of a first reagent is deposited into the reaction container by a second filling system  18 . The first reagent can contain magnetically responsive microparticles coated with antibodies or other binding substances that specifically bind to the item of interest in the sample. The first reagent may be added with an assay specific diluent. In some cases, the first reagent and a conjugate can be added at the second position.  
         [0034]     At a third position, a mechanical device (not shown) is provided to mechanically move the reaction container and cause mixing of the contents in the container. Further treatment of the reaction mixture and performance of the immunoassay are described in U.S. Pat. No. 6,562,298, previously incorporated herein by reference. U.S. Pat. No. 6,562,298 also shows a reaction container suitable for use with this invention, a process lane suitable for use with this invention, and a mechanical device for moving the reaction container that is suitable for use with this invention.  
         [0035]     Referring now to  FIGS. 1A, 1B ,  2 ,  3 ,  4 ,  5 , and  6 , a reagent transport apparatus  100  provides a carousel  102  for a plurality of reagent containers. Reagent containers that are suitable for this invention are described in U.S. Pat. No. 6,562,298, previously incorporated herein by reference. In particular, see column  13 , line  35  through column  14 , line  37  and  FIGS. 22, 23A ,  23 B,  23 C,  24 A,  24 B, and  25  of U.S. Pat. No. 6,562,298. At least some of the reagent containers contain solid-phase reagents. These containers are periodically agitated to maintain homogeneous dispersions of the solid-phase reagents. The reagent containers have at least one agitator fin, and preferably a plurality of agitator fins, molded into their inner walls. The reagent containers can also have machine-readable labels, e.g., bar code labels, attached thereto. A bar code reader can be used to record such data as the loaded position of each particular reagent in a reagent container, the identity of each particular reagent in a reagent container, the lot number of each particular reagent in a reagent container. Containers for tracer or labeled reagent can be used with the carousel  102  described herein, with carousels adjacent to and concentric with the carousel  102  described herein, or with some other type of reagent transport component. These containers can be loaded onto designated positions on the carousel  102  described herein, onto carousels adjacent to and concentric with the carousel  102  described herein, or onto some other type of reagent transport component. Reagent containers can be loaded directly from a storage area.  
         [0036]     A bar code reader, e.g., a laser bar code reader, records various data relating to the reagent containers, such as, for example, the loaded position of each particular reagent in a reagent container, the identity of each particular reagent in a reagent container, the lot number of each particular reagent in a reagent container. Such recordation of data enables random loading of the reagent containers.  
         [0037]     Probes for aspirating reagents from reagent containers and dispensing reagents into reaction containers are described in U.S. Pat. No. 6,562,298, previously incorporated herein by reference. Volumes of reagent used depend upon the particular assay, and specific reagents can be added to the reaction container by an appropriate reagent probe. Probes for dispensing reagents are preferably thoroughly washed with deionized water between dispensings.  
         [0038]     In addition to the carousel  102 , the reagent transport apparatus comprises a base (not shown) and at least one motor  106 , e.g., a stepper motor, fixed to the base by suitable fasteners for driving the carousel  102  about the central axis of the carousel  102 .  
         [0039]     The carousel  102  is supported by a plurality of v-wheels  108 , typically three in number, secured by bolts, e.g., shoulder bolts, to the base of the reagent transport apparatus. In the embodiment described herein, two v-wheels are in fixed locations, while the position of a third v-wheel relative to the carousel  102  can be varied by a biasing element, e.g., a spring. When the carousel  102  is positioned for rotation about its central axis, all three v-wheels  108  engage a v-shaped projection located near the bottom of the inner wall  110  of the carousel  102 .  
         [0040]     In the embodiment shown in  FIGS. 2 and 3 , the carousel  102  has an inner ring  120  of seats and an outer ring  122  of seats. In addition, the carousel  102  has a plurality of projections  124  for displaying machine-readable labels  126 , e.g., bar code labels. The machine-readable labels  126 , when read by a reader, such as, for example, a bar code reader, notify the system as to the absence of a container in the inner ring  120 . This notification accelerates initialization of the system.  
         [0041]     The inner ring  120  of seats is concentric with the outer ring  122  of seats. Each seat  128  in the inner ring  120  can contain a reagent container. In this embodiment, these seats  128  are designed to be rotated in order to agitate the contents of a reagent container mounted thereon. Each seat  130  in the outer ring  122  can also contain a reagent container. However, these seats  130  are not designed to be rotated in such a manner as to agitate the contents of a container mounted thereon. The rotatable seats  128  on the inner ring  120  are supported by at least one bearing, which will be described later.  
         [0042]     As shown in  FIGS. 2 and 3 , there are a total of  50  positions for containers on the carousel  102 . Twenty-five of these positions are located on the inner concentric ring  120  and another twenty-five are located on the outer concentric ring  122 .  
         [0043]     Referring to  FIG. 1B , which depicts a carousel system of the prior art, the carousel  102 , which is also shown in  FIG. 1A , is shown in the operating environment that is used in the ARCHITECT i2000/i2000SR apparatus, manufactured by Abbott Laboratories.  FIG. 1B  also shows rotatable seats  128  and fixed seats  130  of the type suitable for use in the present invention. In  FIG. 1B , the containers seated on the rotatable seats  128  are agitated by means of movement of a ring gear “R”, which is driven by a satellite gear “S 0 ”, which is driven by a motor “M”. The ring gear “R” causes the satellite gears “S 1 , S 2 , . . . , S n ” to rotate about their own axes. Both the carousel  102  and a second carousel “C” are driven by the motor  106 , which motor is of the type suitable for use in the present invention. The motors  106  and “M” are mounted on the base (not shown). The operating environment of the ARCHITECT i2000/i2000SR apparatus can be used in the present invention, without the ring gear “R”, and without the satellite gears “S 0 ” and “S 1 , S 2 , . . . , S n ”.  
         [0044]     The carousel  102  further contains a plurality of resiliently biased retention elements  132 . See also  FIG. 10 . These retention elements  132  help retain oversized test kit containers when they are used. One material suitable for forming the retention element  132  is a polyimide thermoplastic resin, which is commercially available under the trademark “Ultem 2300.” 
         [0045]     In addition, the carousel  102  has a target  140  for positional calibration of the filling systems with respect to the carousel  102  (see  FIG. 3 ). A further addition to the carousel  102  is the pin  142  at the home location (see  FIG. 4 ). This pin  142  trips a home sensor (not shown) in order to enable location of the home position of the carousel  102 .  
         [0046]     Referring to  FIGS. 2, 3 ,  4 ,  5 ,  6 ,  7 A,  7 B,  8 ,  9 ,  11 ,  12 , and  13 , the carousel  102  contains a plurality of rotatable seats  128  for reagent containers. Each rotatable seat  128  comprises a platform  144  having a top surface  146  and a bottom surface  148 . A reagent container can be mounted on the top surface  146  of the platform  144  of the seat  128 . In general, the mounting procedure is shown in  FIGS. 24A and 24B  of U.S. Pat. No. 6,562,298, previously incorporated herein by reference. Each rotatable seat  128  has a shaft  150  projecting from bottom surface  148  thereof. Upon the shaft  150  is mounted at least one sprocket wheel  152 , which contains a plurality of sprockets  154 . Attached to the end of the shaft  150  by a fastener  162 , e.g., a screw, is a sprocket wheel  152 . In one embodiment, the sprockets  154  can be placed in a single row. In alternative embodiments, two or more rows of sprockets  154  can be placed on the sprocket wheel  152 . The sprockets  154  are designed to engage the links of a chain  156 . When the drive sprocket wheel  158  is actuated by a motor so as to be caused to rotate about its own axis, the drive sprocket wheel  158  causes the chain  156  to move, whereby the chain  156 , in turn, causes the sprocket wheels  152  to rotate about their respective axes. Rotation of the sprocket wheels  152  causes rotation of the shafts  150 , which cause the rotatable seats  128  to rotate about their respective axes. In this manner, the contents of the containers containing the solid-phase reagent can be agitated to bring about homogeneity of the solid-phase reagent. The drive sprocket wheel  158  is similar to the sprocket wheels  152  in that the drive sprocket wheel  158  contains a plurality of sprockets  154 ′, but the drive sprocket wheel  158  is not associated with a rotatable seat  128  for supporting a reagent container. At least one bearing  160 , which is located on the shaft  150  of the sprocket wheel  152 , is employed to allow the rotatable seat  128  to be easily rotated. As shown in  FIG. 5 , the rotatable seat  128  is supported by two ball bearings  160 . In the embodiment shown in  FIG. 5 , it can be seen that the bearing  160  is supported on the carousel  102  by a flange  160   a.  A single rotatable seat  128  can be a unitary piece and be made from a bar of stainless steel as shown in  FIGS. 7A and 8 . Rotatable seats  128  can also be formed from an assembly of individual components, e.g., platform, shaft, ring-shaped projection. Each of the seats  128  is adapted to receive a reagent container that contains a reagent that requires agitation.  
         [0047]     The carousel  102  is shown to contain a plurality of fixed seats  130  arranged in a circle concentric with the rotatable seats  128 . These fixed seats  130  can be used to support reagents that do not need to be agitated (tracer or labeled) or assay specific diluents that do not need to be agitated. Each fixed seat  130  comprises a platform  164  having a top surface  166  and a bottom surface  168 . A reagent container can be mounted on the top surface  166  of the platform  164  of the fixed seat  130 . In general, the mounting procedure is shown in  FIGS. 24A and 24B  of U.S. Pat. No. 6,562,298, previously incorporated herein by reference. Each fixed seat  130  has a shaft  170  projecting from bottom surface  168  thereof. The fixed seat  130  is press fitted to the carousel  102  by means of the shaft  170 . A single fixed seat  130  can be a unitary piece made from a bar of stainless steel as shown in  FIGS. 7B and 9 . Fixed seats  130  can also be formed from an assembly of individual components, e.g., platform, shaft, ring-shaped projection. Each of the seats  130  is adapted to receive a reagent container that does not require agitation.  
         [0048]     In the embodiment shown in  FIGS. 2 through 6 , inclusive, and  13 , a motor  172 , separate from the motor  106  for driving the carousel  102  about the central axis of the carousel  102 , is employed to cause the drive sprocket wheel  158  to rotate about the axis of the drive sprocket wheel  158 . This motor  172  is shown in  FIGS. 1B, 14 , and  16 . In  FIG. 1B , the motor  172  is designated by the reference character “M”. In the present invention, the motor  172  drives a drive sprocket wheel  158  and does not drive a satellite gear “S 0 ” that rotates a ring gear “R” that causes other satellite gears “S 1 , S 2 , . . . , S n ” to rotate.  
         [0049]     The particular dimensions of the foregoing components are not critical. However, certain dimensions will be disclosed to indicate the order of magnitude of the components of one embodiment of this invention.  
         [0050]     A suitable nominal diameter of the carousel  102  can range from about 18 to 24 inches. The nominal height of the carousel  102  can range from about two to four inches.  
         [0051]     Nominal dimensions of a typical seat for a reagent container can range from 0.9 to 1.0 inches in diameter for the ring-shaped projection that mates with gripping fingers at the base of the reagent container; one to two inches in diameter for the platforms  144  and  164 ; 0.7 to 0.9 inche for the length of the drive shaft  150  and 0.9 to 1.1 inches for the length of the drive shaft  170 . However, the foregoing dimensions are merely examples, and one of ordinary skill in the art can select alternative dimensions for carrying out the intended purpose of the invention.  
         [0052]     The drive sprocket wheel  158  is mounted over the motor  172 . The number of sprockets  154 ′ on the drive sprocket wheel  158  is not critical. The actual number of sprockets is specific to a particular design and depends upon link spacing in the chain, diametric pitch, space available for locating the sprocket wheel, availability of commercially available and customized components, diameter upon which the centerlines of the rotatable seats  128  are located, stretchability of the chain, operating temperature, coefficient of thermal expansion of the materials used, and the like. One having ordinary skill in the art can readily specify these features without undue experimentation. Similarly, the number of sprockets  154  on the sprocket wheels  152  is not critical and is dependent upon the same factors described previously for determining the actual number of sprockets  154 ′ on the drive sprocket wheel  158 .  
         [0053]     At least one row of sprockets  154 ′ on the drive sprocket wheel  158  is required. More than one row of sprockets  154 ′ can be used. Additional rows of sprockets  154 ′ can be added. The use of additional rows is dependent upon space constraints and design needs. As more rows are utilized, chain wear is reduced. Similarly, at least one row of sprockets  154  on the sprocket wheel  152  is required. More than one row of sprockets  154  can be used. Additional rows of sprockets  154  can be added. The use of additional rows is dependent upon space constraints and design needs. As more rows are utilized, chain wear is reduced  
         [0054]     The primary difference between the drive sprocket wheel  158  and the sprocket wheels  152  is the manner in which they are attached to components to which they are adjacent. In the embodiment described herein, the drive sprocket wheel  158  is attached to the shaft of the motor  172  by a press fit. A sprocket wheel  152  associated with a rotatable seat  128  is attached to the shaft  150 , which is typically an elongated element having a D-shaped cross-section, by means of a fastener  162 , e.g., a screw (see  FIG. 5 ). The drive sprocket wheel  158  is set at a different height from the sprocket wheels  152  attached to the shafts  150  projecting from the bottom surfaces  148  of the platforms  144 , in order to prevent interference. The diametric pitches of the drive sprocket wheel  158  and the sprocket wheels  152  are typically the same; however the diametric pitches of the drive sprocket wheel  158  and the sprocket wheels  152  can vary by multiples of 2.  
         [0055]     The number of strands in the chain  156  is not critical. The number of strands in the chain  156  can be specified by the designer, and the material of the chain  156  can be specified by the designer. Of course, the designer is one of ordinary skill in the art. The chain  156  shown in  FIGS. 6 and 13  has three strands. Some materials require no reinforcing strands. Other materials call for reinforcing strands.  
         [0056]     The length of the chain  156  is not critical. The actual length is dependent upon design parameters and is specified on the basis of diametric pitch, pitch diameter of the sprockets, diameter upon which the centerlines of the sprocket wheels are located, chain stretchability, operating temperature, coefficient of thermal expansion of the materials used, etc. Ultimate tensile strength, temperature range, operating load, operating speed, and weight can be specified by one of ordinary skill in the art. Dual ladder chains can be used.  
         [0057]     The number of drive pins on the chain  156  is not critical. The actual number of drive pins is specific to a particular design and depends upon link spacing in the chain, diametric pitch, space available for locating the sprocket wheel, availability of commercially available and customized components, diameter upon which the centerlines of the sprocket wheels  152  are located, stretchability of the chain, operating temperature, coefficient of thermal expansion of the materials used, and the like. One having ordinary skill in the art can readily specify these features without undue experimentation.  
         [0058]     Chains  156  suitable for use for this invention are commercially available under the trademark PIC® Design and are commercially available from W. M. Berg, Inc., East Rockaway, N.Y. One type of chain has a stainless steel core having a coating of molded polyurethane. The number of drive pins can vary. The length of the chain can vary. See, for example, No-Slip Positive Drive Belt data sheet, from PIC® Design, incorporated herein by reference, and MIN-E-PITCH® Dual Ladder Chain data sheets from W. M. Berg, Inc. The foregoing data sheet discloses chains having from 30 to 440 drive pins, spliced lengths of from 4.712 inches to 69.115 inches, bulk lengths of from 5 to 100 feet. These chains can have either an Aramid fiber Kevlar core(s) (FLA-Series) or a stainless steel core(s) (FLS-Series) and a molded polyurethane coating. The Aramid fiber core provides highest flexibility and speed; the stainless steel core provides lowest stretch. Typical dimensions for a chain designated as a triple core belt (F20TS-Series, F20TS-XX-Series (PIC® Design)) are 0.15708 inch circular pitch, three strands, width of 0.375 inch, 0.070 pin diameter, 1/16 inch between strands. Design specifications from W. M. Berg, East Rockaway, N.Y. are substantially similar to those from PIC® Design. For the carousel  102  described herein, the chain  156  typically has chains having from 360 to 370 drive pins and a spliced length of from 56.548 inches to 58.119 inches. However, these parameters can vary, based on the circumference of the carousel  102 , the number of sprocket wheels  152 , and other design factors.  
         [0059]     The chain  156  can provide smooth and quiet operation. The chain need not be lubricated. A linked chain, such as, for example, a bicycle chain, could conceivably be used in place of the coated chains commercially available from PIC® Design and from W. M. Berg, East Rockaway, N.Y.  
         [0060]     Selection of motors is determined by the designer and is dependent on choices made about the manner desired for the chain  156  and the carousel  102  to be driven. Suitable motors can readily be selected by one of ordinary skill in the art. The drive sprocket wheel  158  can be driven by means of a motor  172 , e.g., a stepper motor. A typical motor suitable for use in this invention has a coil resistance of 0.38±10% ohms, 1.8 degree±3% step angle, operates off 36 volt power, is pulse width modulated, rated at 2.5 amps per coil, and has an encoder mounted to it. Such a motor is manufactured by Pacific Scientific and has the designation P/N P22NSXA-LSS-SS-07. The encoder can be a HP encoder P/N HEDL-5600-H06.  
         [0061]     The stepper motor  172  is reversible and controlled by a central processing unit (not shown). The stepper motor  172  functions to cause the drive sprocket wheel  158 , the chain  156 , and the sprocket wheels  152  to rotate the drive shafts  150  of the rotatable seats  128  at specified intervals of time. The rotation imparted to the drive shafts  150  of the rotatable seats  128  provide the necessary motion to rotate the reagent containers for enabling the fins to agitate the dispersions of solid-phase reagents within the reagent containers and thereby maintain uniform concentrations of the solid-phase reagents within the dispersions in the reagent containers.  
         [0062]     Actuation of the motor  172  causes the drive sprocket wheel  158  to drive the chain  156 , which causes the sprocket wheels  152  to rotate, which ultimately causes the rotatable seats  128  to rotate about their respective axes.  
         [0063]     The motor  106  for the driving the carousel  102  is fixed to a motor mount (not shown) on the base. The motor  172  for driving the chain  156  is fixed to a motor mount (not shown) on the base.  
         [0064]     Both motors  106  and  172  are located beneath the carousel  102 , as they are in ARCHITECT i2000/i2000SR apparatus. See  FIG. 1B . The centerline of the motor  172  for driving the drive sprocket wheel  158  is located in such a way as to cause the drive sprocket wheel  158  to engage the chain  156  when a handle enables a cam to be positioned so that the chain  156  is engaged with the drive sprocket wheel  158 .  
         [0065]     A cam  180  can be employed to engage and disengage the chain  156  from the drive sprocket wheel  158 . The cam  180  is operated by a handle  182  and is supported by an interface plate  184  and a mounting plate  186 . When the cam  180  rotates, it presses against a motor mounting plate  188 . The motor mounting plate  188  is spring loaded against the interface plate  184 . As the cam  180  rotates, the motor mounting plate  188  slides laterally, and the springs  190  are further compressed. The motor  172  is attached the motor mounting plate  188 , and the drive sprocket wheel  158  is attached to the motor  172 . The action of the cam  180  disengages the drive sprocket wheel  158  from the chain  156 . Moving the handle  182  back allows the springs  190  to push the motor mounting plate  186  to a position whereby the springs  190  are uncompressed, thereby re-engaging the drive sprocket wheel  158  with the chain  156 . One fastener, e.g., a screw, attaches the handle  182  to the cam  180 . Four fasteners, e.g., screws, attach the motor  172  to the motor mounting plate  186 . Four additional fasteners, e.g., screws, attach the interface plate  184  to the motor mounting plate  186 . The handle  182  is operated by hand.  
         [0066]     Operation  
         [0067]     The operator loads required assay reagents, in machine-readable labeled containers, into the appropriate seats (rotatable for solid-phase reagents or fixed for labeled or tracer reagents) on the carousel in any order. The analyzer will read all labels before initiating a run, identifying each reagent, its position, its lot number, and expiration date. U.S. Pat. No. 6,562,298 describes how an assay can be performed. With respect to the reagent transport apparatus, when it is desired to agitate the contents of the reagent containers seated in the rotatable seats  128 , the drive sprocket wheel  158  is engaged with the chain  156 . The motor  172  is then actuated to impart oscillating motion to the chain  156 , which in turn imparts oscillating motion to the sprocket wheels  152 , which cause the rotatable seats  128  to rotate, thereby agitating the contents of the reagent containers seated on the rotatable seats  126 . The motor  172  is reversible, so that the rotatable seats can be rotated both clockwise and counter-clockwise, thereby rotating the contents of the reagent containers seated on the rotatable seats clockwise and counter-clockwise.  
         [0068]     Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.