Patent Abstract:
The sheath flow forming device includes: a container for storing sample fluid and having a supply port for supplying the sample fluid; a second container for storing sheath fluid and having a supply port for supplying the sheath fluid; a flow cell having a sample fluid inlet for receiving sample fluid supplied from the supply port of the first container, a sheath fluid inlet for receiving the sheath fluid from the supply port of the second container, and an outlet for discharging the mixture of the sheath fluid and the sample fluid; a first pump for supplying a sheath fluid to the sheath fluid inlet; a second pump for suctioning fluid within the flow cell through the outlet of the flow cell; and a first drive source for driving the first pump and second pump.

Full Description:
This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 2003-346023 filed in Japan on Oct. 3, 2003, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheath flow forming device and sample analyzer provided with same. 
     2. Background 
     A particle analyzer (refer to Japanese Laid-Open Patent Publication No. 9-288053) is a known prior art related to the present invention and includes a container for accumulating a sample liquid containing particles to be analyzed and having a nozzle extending downward from the bottom part, a flow cell into which the tip of the nozzle is inserted, a first pump for injecting into the flow cell a first flow quantity Q1 of a sheath fluid which encapsulates a sample fluid flow injected from the nozzle, and an imaging means for imaging particles in the sample fluid encapsulated in the sheath fluid flowing through a transparent container formed on the downstream side of the flow cell, wherein the top part of the sample fluid container is open to the air, and a second pump is provided for suctioning fluid in the flow cell downstream from the transparent tube path of the flow cell, such that the sample fluid flow quantity Qs is determined by (Q2−Q1) when the injection quantity of the first pump is designated Q1 and the suction quantity of the second pump is designated Q2. 
     In this conventional device, the sample fluid flow quantity Qs is determined by the difference in the flow quantities of the pumps (Q2−Q1). When one flow quantity changes due to a change in the drive sources of the first and second pumps, the flow quantity Qs fluctuates greatly since the flow quantity Qs is quite small (for example, 1/100) compared to the flow quantities Q1 and Q2. Accordingly, problems arise when this occurs inasmuch as the particle flow in the sample fluid becomes unstable, the measurement accuracy is reduced, and at times measurement becomes impossible. 
     SUMMARY OF THE INVENTION 
     In view of these problems, the present invention provides a sheath flow forming device and sample analyzer provided with same, which are capable of normally maintaining a constant flow quantity Qs even when the flow quantities Q1 and Q2 change due to the influence of the drive source of the pumps. 
     The sheath flow forming device embodying features of the present invention includes: (a) a container for storing sample fluid and having a supply port for supplying the sample fluid; (b) a second container for storing sheath fluid and having a supply port for supplying the sheath fluid; (c) a flow cell having a sample fluid inlet for receiving sample fluid supplied from the supply port of the first container, a sheath fluid inlet for receiving the sheath fluid from the supply port of the second container, and an outlet for discharging the mixture of the sheath fluid and the sample fluid; (d) a first pump for supplying a sheath fluid to the sheath fluid inlet; (e) a second pump for suctioning fluid within the flow cell through the outlet of the flow cell; and (f) a first drive source for driving the first pump and second pump. 
     The sample analyzer embodying features of the present invention includes: (a) a first container for storing sample fluid and having a supply port for supplying the sample fluid; (b) a second container for storing sheath fluid and having a supply port for supplying the sheath fluid; (c) a flow cell having a sample fluid inlet for receiving sample fluid supplied from the supply port of the first container, a sheath fluid inlet for receiving the sheath fluid from the supply port of the second container, and an outlet for discharging the mixture of the sheath fluid and the sample fluid; (d) a first pump for supplying a sheath fluid to the sheath fluid inlet; (e) a second pump for suctioning fluid within the flow cell through the outlet of the flow cell; (f) a first drive source for driving the first pump and second pump; (g) a light source for irradiating with light the sample fluid in the flow cell; (h) detection unit for detecting optical information from the sample fluid; and (i) analysis unit for analyzing the detected optical information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the flow system and optical system of an embodiment of the sample analyzer; 
         FIG. 2  shows the essential structure of the embodiment of the sample analyzer; 
         FIG. 3  is a block diagram of the control system of the embodiment of the sample analyzer; 
         FIG. 4  is a timing chart showing the test result of the embodiment of the sample analyzer; 
         FIG. 5  is a timing chart showing the test results of the embodiment of the sample analyzer; and 
         FIG. 6  shows the flow system of a modification of the embodiment of the sample analyzer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the sample analyzer of the present invention are described hereinafter based on the drawings. In the following embodiments, a particle image analyzer is described as an example of the sample analyzer of the present invention. The present invention is not limited to the given examples. 
     Flow System and Optical System of the Particle Image Analyzer 
       FIG. 1  shows the flow system and optical system of an embodiment of the sample analyzer of the present invention. 
     As shown in  FIG. 1 , a sheath flow cell FC is provided with a sheath fluid inlet  1 , sample fluid inlet  2 , and outlet  3  for discharging the mixture of the sheath fluid and sample fluid. A sample container C 1  stores sample fluid through an open top, and an outlet provided in the bottom part is connected to a sample fluid inlet  2  through a flow path. An electromagnetic valve (hereinafter referred to as “valve”) SV 1  is provided in the flow path between the outlet of the sample container C 1  and the sample fluid inlet  2 . Furthermore, a mixing device  12  is provided for mixing the sample fluid within the sample fluid container C 1 . 
     A syringe pump CL 1  has a discharge port  4 , and a sheath fluid supply port  5 . The discharge port  4  is connected to the sheath fluid inlet  1  of the sheath flow cell EC through a flow path. A valve SV 4  is provided in the flow path between the discharge port  4  and the sheath fluid inlet  1 . A sheath fluid container C 2  stores sheath fluid in its interior, an outlet provided in the bottom part of the container is connected to a sheath supply port  5  through a flow path. A valve SV 6  is provided in the flow path between the outlet of the sheath fluid container C 2  and the sheath fluid supply port  5 . 
     A syringe pump CL 2  is provided with a suction port  5   a , and a syringe pump CL 3  is provided with two suction ports  6 , and a sheath fluid supply port  7 . The discharge port  4   a  of the syringe pump CL 2  is connected to the suction port  6  of the syringe pump CL 3 . 
     The outlet  3  of the sheath flow cell FC is connected to the suction port  5   a  of the syringe pump CL 2  through a flow path, and is connected to the opening on the open top part of the discharge fluid container C 3 . Valves SV 2  and SV 5  are provided in the flow path between the outlet  3  and the suction port  5   a . Valves SV 2  and SV 3  are provided in the flow path between the outlet  3  and the opening of the discharge fluid container C 3 . 
     The sheath fluid supply port  7  of the syringe pump CL 3  is connected to the outlet of the sheath fluid container C 2 . A valve SV 7  is provided in the flow path between the sheath fluid supply port  7  and the outlet of the sheath fluid container C 2 . 
     The syringe pumps CL 1  and CL 2  are driven in linkage with a single first drive source  8 , and the syringe pump CL 3  is driven by a second drive source  9 . The first drive source  8  is provided with a stepping motor SM 1 , and a transmission mechanism  10  for converting the rotational movement of the motor SM 1  to linear movement and transmitting the linear movement to the syringe pumps CL 1  and CL 2 . The transmission mechanism  10  includes a drive pulley attached to the drive shaft of the stepping motor SM 1 , and a driven pulley about which is reeved a timing belt, and converts the rotational movement of the stepping motor SM 1  to linear movement. 
     The second drive source  9  is provided with a stepping motor SM 2 , and a transmission device  11  for converting the rotational movement of the stepping motor  2  to linear movement and transmitting the linear movement to the syringe pump CL 3 . The transmission mechanism  11  includes a drive pulley attached to the drive shaft of the stepping motor SM 2 , and a driven pulley about which is reeved a timing belt, and converts the rotational movement of the stepping motor SM 2  to linear movement. 
     Furthermore, A light source LS for irradiating with light the sample fluid flow which is severely constricted as it is surrounded in the sheath fluid, and an objective lens OL and CCD camber VC for imaging the particles in the sample fluid flow are provided in the sheath flow cell FC. The light source LS is a strobe lamp. 
     Syringe Pump and Drive Source Structures 
       FIG. 2  shows details of the structure of the first drive source  8  shown in  FIG. 1 . As shown in the drawing, the syringe pumps CL 1  and CL 2  have the same structure and dimensions, and are fixedly attached to the surface of a support plate  13  in series and in mutually opposing directions. The syringe pump CL 1  is provided with a cylinder  14 , piston  15  the tip of which is inserted into the cylinder  14 , packing  16  for providing an airtight seal of the gap between the cylinder  14  and piston  15 , discharge port  4 , and nipples  17  and  18  respectively provided at the sheath fluid supply ports  5 . 
     Furthermore, the syringe pump CL 2  is provided with a cylinder  14   a , piston  15   a  the tip of which is inserted into the cylinder  14   a , packing  16   a  for providing an airtight seal of the gap between the cylinder  14   a  and piston  15   a , discharge port  4   a , and nipples  17   a  and  18   a  respectively provided at the suction ports  5   a . The pistons  15  and  15   a  have mutually identical diameters. 
     The respective back ends of the pistons  15  and  15   a  are linked by a linkage  19  such that both have the same axis. The stepping motor SM 1  is fixedly attached to the back surface of the support plate  13  such that the output shaft of the motor extends from the surface of the support plate  13 , and an output shaft drive pulley PL 1  is provided. 
     Furthermore, a corresponding driven pulley PL 2  is provided on the front surface of the support plate  13 , and a timing belt TB is reeved between the drive pulley PL 1  and the driven pulley PL 2  so as to be tensioned parallel to the pistons  15  and  15   a . The timing belt TB and linkage  19  are connected by a connecting member CM. 
     When the stepping motor SM 1  rotates, the connecting member CM moves linearly in the axial direction (arrow A or arrow B direction) of the pistons  15  and  15   a  by the timing belt TB. That is, the drive force and driven pulley PL 1 , PL 2 , and the timing belt TB from a transmission mechanism for converting the rotational movement of the stepping motor SM 1  to linear movement in the arrow A or arrow B direction, and transmit the this linear movement to the syringe pumps CL 1  and CL 2  at the same time. 
     When the pistons  15  and  15   a  move in the arrow A direction, the syringe pump CL 1  performs a discharge operation, and the syringe pump CL 2  performs a suction operation. When the pistons  15  and  15   a  move in the arrow B direction, the syringe pumps CL 1  and CL 2  performs the respectively opposite operations. 
     Control System 
       FIG. 3  is a block diagram of the control system of the sample analyzer shown in  FIG. 1 . A personal computer  20  is provided with an image processing unit  21  for acquiring image signals from a CCD camera VC and performing image processing to generate particle image data, analysis unit  22  for recognizing the particles from the particle shape and coloration, counting the particles and statistically analyzing the particles, and control unit  23  for controlling a driver circuit unit  24 . The analysis result of the analysis unit  22  is output from an output unit  25 . The driver circuit unit  24 , which is controlled by the control unit  23 , is provided with driver circuits for the valves SV 1  through SV 7 , stepping motors SM 1  and SM 2 , and light source LS, respectively. The output unit  25  is a CRT. The driver circuit which drives the light source LS is controlled such that the light source LS emits light at predetermined periods. 
     Analysis Operation 
     The analysis operation of the sample analyzer having the previously described structure is described below. 
     In  FIG. 1 , the syringe pump CL 1  is set in the state in which the piston  15  is drawn from the cylinder  14  (discharge operation enabled state), and the syringe pump CL 2  is set in the state in which the piston  15   a  is pushed into the cylinder  14   a  (suction operation enabled state). Furthermore, the syringe pump CL 3  is also set in the state in which the suction operation is enabled. 
     Then, the valves SV 2 , SV 3 , SV 4 , and SV 6  are opened. 
     Since a positive pressure is applied beforehand to the sheath fluid container C 2 , the sheath fluid is discharged from the container C 2  to the discharge fluid container C 2  through the valve SV 6 , syringe pump CL 1 , valve SV 4 , sheath flow cell FC, and valves SV 2  and SV 3 . 
     Then, the valves SV 2 , SV 3 , SV 4 , and SV 6  are closed. 
     In this way the sheath fluid is loaded into the syringe pump CL 1 . 
     Then, the valves SV 3 , SV 5 , and SV 7  are opened. 
     The sheath fluid is discharged from the container C 2  to the discharge container C 3  through the valve SV 7 , syringe pump CL 3 , syringe pump CL 2 , and valves SV 5  and SV 3 . 
     Then, the valves SV 3 , SV 5 , and SV 7  are closed. 
     In this way the sheath fluid is loaded into the syringe pumps CL 2  and CL 3 . 
     Then, the valves SV 1 , SV 2 , SV 4 , and SV 5  are opened, the stepping motors SM 1  and SM 2  are driven, and the syringe pump CL 1  performs an operation of discharging a flow quantity Q, the syringe pump CL 2  performs an operation of suctioning a flow quantity Q, and the syringe pump CL 3  performs an operation of suctioning a flow quantity Qs. 
     In this way a flow quantity Q of sheath fluid flows from the syringe pump CL 1  to the sheath flow cell FC, and a flow quantity Qs of sample fluid also flows from the sample container C 1  into the sheath flow cell FC. After the sample fluid is converted to a narrow sample fluid flow surrounded in a sheath fluid flow in the sheath flow cell FC, the mixed fluid of the flow quantity (Q+Qs) mixed with the sheath fluid is discharged from the sheath flow cell FC. 
     Within the discharged mixed fluid, a mixed fluid of flow quantity Q is suctioned by the syringe pump CL 2 , and a mixed fluid of flow quantity Qs is suctioned by the syringe pump CL 3 . 
     At this time, the sample fluid flow formed in the sheath flow cell FC is irradiated by light emitted from the light source LS, and the particles contained in the sample fluid are imaged by the CCD camera VC. 
     The personal computer  20  shown in  FIG. 3  receives the imaging signals from the CCD camera VC and subjects the signals to image processing, recognizes the type and number of particles based on the obtained particle image and performs statistical analysis, and outputs the analysis result to the output unit  25 . 
     Sample Fluid Flow and Stability 
     The following tests were conducted to confirm the stability of the sample flow quantity relative to changes in the flow quantity of the sheath flow in the particle image analyzer of the present embodiment. 
     In  FIG. 1 , with the valves SV 1 , SV 2 , SV 4 , and SV 5  in the open state, the syringe pump CL 1  was driven by the first drive source  8 , and the second syringe pump CL 2  was independently drive by the third drive source which is independent from the first drive source  8 , and the flow quantity of the syringe pump CL 1  was periodically changed by the first drive source  8 . 
     In  FIG. 1 , at this time the change over time of the flow quantity Q at point P 1  in the flow path between valve SV 4  and the discharge port of the syringe pump CL 1  is shown in part (a) of  FIG. 4 . 
     Furthermore, the change over time of the flow quantity Q at point P 2  in the flow path between valve SV 5  and the suction port  5   a  of the syringe pump CL 2  is shown in part (b) of  FIG. 4 . Finally, the change over time of the flow quantity Q at point P 3  in the flow path between valve SV 1  and the sample fluid inlet  2  is shown in part (c) of  FIG. 4 . 
     As shown in part (a) of  FIG. 4 , the flow quantity Q at point P 1  changed about a center of 100 mL/sec with an amplitude of 1 mL/sec and a period of 4 sec. 
     The flow quantity at point P 2  held constant at 100 mL/sec, as shown in part (b) of  FIG. 4 . 
     The flow quantity Q at point P 3  changed about a center of 100 mL/sec with an amplitude of 1 mL/sec and a period of 4 sec, as shown in part (c) of  FIG. 4 . 
     That is, when the flow quantity of either of the syringe pumps CL 1  or CL 2  changes, the flow quantity Q of the sample fluid is changed only by the amount of the change in the flow quantity. Thus, it can be understood that when the flow quantity of the sheath fluid changes by 0.5%, the flow quantity of the sample fluid changes by ±50%. 
     In contrast, the syringe pumps CL 1  and CL 2  were driven by the same drive source  8 , and the flow quantities of the syringe pumps CL 1  and CL 2  changed simultaneously via the drive source  8 , as in the specification of the present invention. In this case, the results corresponding to parts (a), (b), and (c) of  FIG. 4  are shown in parts (a), (b), and (c) of  FIG. 5 . 
     The flow quantity Q at points P 1  and P 2  changed about a center of 100 mL/sec with an amplitude of 1 mL/sec and a period of 4 sec, as shown in parts (a) and (b) of  FIG. 5 . 
     In this case, the flow quantity Q at point P 3  held constant at 100 mL/sec, as shown in part (c) of  FIG. 5 . 
     That is, since the syringe pumps CL 1  and CL 2  are driven by a single drive source  8  in the present invention, even if the flow quantities of the syringe pumps CL 1  and CL 2  change via a change by the drive source, the change is mutually equal for both, such that the flow quantity of the sample fluid flow remains constant. 
     Furthermore, since the open topped sample fluid container can be connected to the sample fluid inlet of the sheath flow cell, a mixing device can be inserted so as to easily perform the mixing and dispersion operation of the sample even when the specific gravity of the particles is large and the particles readily precipitate in the sample fluid. 
     In the above embodiment, analysate particles include tangible components such as are contained in body fluids of humans and lactating animals, organic powders such as food additives, and inorganic powders such as toner and pigments. 
     Although the rotational movement of the stepping motors is converted to linear movement by a timing belt in the above embodiment, the rotational movement of the stepping motor also may be converted to linear movement by a ball screw or wire. 
     Although the light source in the above embodiment is a strobe lamp, a white light source, laser light source or the like also may be used. Furthermore, although the strobe lamp is controlled by a driver circuit so as to emit light at a predetermined period, the strobe lamp also may be controlled for continuous light emission via the driver circuit. 
     A CCD camera is used in the above embodiment imaging particles to detect particles in the sample fluid, however, a camera such as a video camera, or light sensor such as a photodiode, phototransistor, photomultiplier tube and the like also may be used. 
     The present invention has been described using an example when applied to a particle image analyzer in the above embodiment, however, the present invention is not limited to this example, inasmuch as the present invention also may be applied to flow cytometers which optically or electrically measure various types of particles having diameters from the submicron level to several hundred micron level. 
     A modification of the above embodiment is described below in an example using a syringe pump CL 4  which has a diameter larger than the syringe pump CL 1 , and which replaces the syringe pump CL 2  and syringe pump CL 3 , as shown in  FIG. 6 . In  FIG. 6 , the piston of the syringe pump CL 4  has a diameter which is larger than the diameter of the piston of the syringe pump CL 1 , and the syringe pumps CL 1  and CL 4  are driven in linkage by a single drive source  8 . In other aspects the construction is identical to that of  FIG. 1 . In this modification, the stepping motor SM 1  is driven, and the syringe pump CL 1  performs an operation to discharge a flow quantity Q and the syringe pump CL 4  performs an operation to suction a flow quantity (Q+Qs), such that the difference in the flow quantities of the syringe pump CL 1  and the syringe pump CL 4  is the constant suction quantity Qs.

Technology Classification (CPC): 5