JP2006133103A - Sample circulating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample circulating device capable of considerably reducing the amount of a medium used for measurement and capable of precisely carrying out particle size measurement with small amount of a sample and the medium. <P>SOLUTION: The sample circulating device which circulates a sample suspension to a particle size measuring section, comprises a reservoir section 22 made up in a hollow conic shape whose upper section is opened as a pouring section for the sample suspension and whose vertex side faces downward; an impeller chamber 240 which is disposed in communication with the lower section of the reservoir section; an impeller 23 which is disposed inside the impeller chamber; an impeller drive shaft 25 which is disposed so as to pass from the upper section of the reservoir section through the lower head section of the reservoir section and reach the inside of the impeller chamber, and whose lower end side is fixed to the impeller; a drive section which drives the upper end side of the impeller drive shaft so as to rotate; an outlet which is disposed in communication with the impeller chamber; an inlet which is disposed in communication with the inner face of the reservoir section; a sample supply pipe which is connected to the outlet and supplies the particle size measuring section with the sample suspension; and a sample collecting pipe which collects the sample suspension from the particle size measuring section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a particle size measuring apparatus for measuring the particle size of sample particles by introducing a sample suspension in which sample particles are dispersed in a liquid medium such as water or an organic solvent into the measurement field. More specifically, the present invention relates to a sample circulator that can greatly reduce the amount of sample suspension used for measurement and can perform highly accurate measurement with a small amount of sample and medium.

  In general, a method for measuring the particle size (particle size distribution) of a powder sample using a particle size measuring device is widely used as a means for confirming the quality of a powder product during development or manufacture. In particular, in the powder product manufacturing process, by measuring the particle size at each stage (each step) in the process, the quality of the powder product can be improved and the quality can be maintained, or Monitoring is conducted.

  As a means of particle size measurement, a laser scattering type or laser diffraction / scattering type particle size analyzer is most widely used from the viewpoint of simplicity, rapidity, and data reproducibility, and the range of use is increasing. It is a fact. The measurement of particle size distribution using a laser diffraction / scattering particle size analyzer is based on the calculation formulas based on the diffraction theory of Fraunhofer or Mie's scattering theory (the relational expression mathematically analyzing the physical phenomenon of scattered light, Based on the relational expression, the actual scattering phenomenon is performed using a relational expression in the case of detecting with a fan-shaped detector having a small opening angle. With such a particle size analyzer, the particle size of the powder product sample collected from each stage of the powder product manufacturing process is measured.

  The particle size measurement of the powder product as described above is a wet measurement in which a sample is collected from the powder product, dispersed in a liquid medium (dispersion medium) to form a sample suspension, and measurement is performed using the sample suspension. Generally done well. In such wet measurement, a sample suspension is passed through a flow cell arranged at a measurement position, and the particle size of the sample particles is measured while the sample suspension flows in one direction in the flow cell. There is a method in which a batch type cell is detachably disposed at a measurement position, and the particle size of sample particles is measured by a sample suspension accommodated in the batch type cell.

  In the method using the flow cell, a sample circulator for supplying the sample suspension into the flow cell from the outside of the flow cell and recovering the measured sample suspension from the flow cell is required. The method using a batch cell does not require a sample circulator, but it requires a mechanism to stir the sample suspension so that the sample particles are uniformly dispersed in the sample suspension contained in the batch cell. It becomes. In the absence of a stirring mechanism, the distribution of sample particles becomes non-uniform due to particle settling and the like, resulting in poor measurement accuracy. In addition, since the sedimentation speed increases as the particles become larger or heavier, the particle size distribution in the measurement results becomes uneven.

  The measurement method using the batch type cell has an advantage that the amount of the sample suspension used for the measurement is small. Therefore, the amount of the sample and the dispersion medium is also reduced, and the cost of waste liquid treatment and the purchase cost of the dispersion medium can be reduced. However, the measurement method using a batch type cell has the following problems.

  It is necessary to stir the sample suspension in the cell to perform high-accuracy measurement using a batch cell, but if the stirring mechanism such as a stirring blade is provided in the cell, the stirring mechanism operates. Therefore, the thickness of the cell cannot be reduced below a certain level, which is not preferable from the viewpoint of measurement accuracy of the particle size. In general, in a laser diffraction / scattering particle size analyzer, the smaller the thickness of a sample suspension in the direction in which laser light is transmitted, the higher the accuracy of measurement possible.

  Next, since the laser beam is transmitted through the central portion of the cell, the stirring mechanism cannot be disposed, and the stirring mechanism must be disposed at a peripheral position away from the central portion. For this reason, the sample suspension at the center of the cell may not be sufficiently uniformly dispersed, or there may be a problem that some particles settle and the particle size distribution becomes uneven. .

  Moreover, it is difficult to sufficiently increase the stirring capacity of the stirring mechanism provided in the batch type cell due to limitations on position and dimensions. For this reason, only small-sized particles that are easy to disperse are selectively dispersed, and large-sized particles and heavy particles cannot be sufficiently dispersed, resulting in uneven particle size distribution. There was a problem.

  In addition, since the batch type cell does not have a structure in which the sample suspension flows in one direction unlike the flow cell, even if the sample suspension is stirred by the stirring mechanism, a circulating flow or vortex is generated in the cell. In other words, selective sedimentation or deposition of particles may occur at positions where these stream lines do not pass. For this reason, an error may occur in the measurement result of the particle size and particle size distribution.

  In order to perform highly accurate particle size measurement, it is effective to perform measurement using only a medium not including a sample as background measurement before actually measuring the sample suspension (main measurement). Then, the measurement value of the background measurement is subtracted from the measurement value of the main measurement to obtain the intensity distribution of the diffracted / scattered light only by the sample particles, and the measurement result of the high precision particle size without the influence of the medium can be obtained. .

  In a batch type cell, only the medium is contained in the cell and the background measurement is performed, but when performing the main measurement with the next sample suspension, the cell is once taken out of the measurement position and the medium in the cell is removed. After replacing the sample suspension, it is necessary to set it again at the measurement position. For this reason, the measurement conditions of the background measurement and the main measurement slightly change due to a slight deviation in the orientation and position of the cell at the measurement position or a shift in the optical axis adjustment of the laser beam. As a result, even if the measurement value of the background measurement is subtracted from the measurement value of the main measurement, the intensity distribution of the diffracted / scattered light only from the sample particles from which the influence of the medium has been completely removed cannot be obtained. There was a problem that the results could not be used to the maximum.

  Further, in the batch type cell, the concentration of the sample cannot be continuously adjusted. That is, it is necessary to remove the cell from the measurement position, adjust the concentration by adding a powder sample or medium, and set it again at the measurement position. For this reason, adjusting the sample concentration of the sample suspension to an optimum value from the intensity of transmitted light or the like is a laborious operation.

  Since the batch type cell has a different structure from a commonly used flow cell, the measurement result may be different even when the same sample is measured. For this reason, the result measured by the flow cell cannot be directly compared with the result measured by the batch type cell. In order to use not only the flow cell but also the batch type cell, a structure for detachably fixing the batch type cell to the particle size measuring device and a mechanism for changing the optical path of the laser beam are added. Therefore, there is a problem that the cost of the particle size measuring device increases.

  The batch type cell needs to be removed from the measurement position and cleaned after the measurement. Since this cleaning operation is performed by removing the cell from the measurement position, it is difficult to automate the operation and is a labor-intensive operation. Moreover, in the case of a batch type cell, since the cells are independent, there is a problem that it is difficult to use for cooperation work in combination with other devices.

In the particle size measurement using the flow cell, various problems of the batch cell as described above can be solved. The following Patent Document 1 is known as a method for performing particle size measurement using a flow cell and a sample circulator. Patent Document 1 describes a particle size distribution measuring device in which a sample suspension is stored in a dispersion bath (4), and the sample suspension is supplied and circulated to a flow cell (20) by a pump (6). Yes.
JP 2000-155088 A

  In the conventional particle size measurement using a flow cell and a sample circulator as described in Patent Document 1, a large amount of sample suspension is required for the dispersion bath and the sample circulation path. A volume of 200 mL or more was required. In addition, the dispersion bath and the circulation path must be cleaned after the measurement is completed, but a medium having a volume 2 to 4 times the amount of the sample suspension is required for cleaning. For this reason, the amount of the whole medium used for the measurement becomes large, and there has been a problem of an increase in waste liquid treatment cost and an adverse effect on the environment.

  If the measurement using the batch cell as described above is performed without using the flow cell, the amount of medium used for the measurement can be reduced. However, in the measurement using a batch cell, various problems as described above occur.

  Therefore, the present invention is a sample circulator that circulates a sample suspension in a particle size measuring apparatus using a flow cell, and can greatly reduce the amount of medium used for measurement, with a small amount of sample and medium. An object of the present invention is to provide a sample circulator capable of performing highly accurate particle size measurement.

  In order to achieve the above object, the sample circulator of the present invention provides a sample circulation for circulating a sample suspension in which sample particles are dispersed in a liquid medium in a particle size measurement unit for measuring the particle size of the particles. A storage part comprising a conical cavity whose upper part is opened as the input part for the sample suspension and whose apex side is directed downward, and an impeller chamber provided in communication with the lower part of the storage part And an impeller that is rotatably disposed inside the impeller chamber, and is provided so as to reach the impeller chamber from above the reservoir through the lower tip of the reservoir, and the lower end side is fixed to the impeller An impeller drive shaft, a drive unit that rotationally drives the upper end side of the impeller drive shaft, an outflow port provided in communication with the impeller chamber, and an inflow port provided in communication with the inner surface of the storage unit And at the outlet And a sample supply pipe for supplying the sample suspension to the particle size measurement unit, and a sample recovery pipe connected to the inlet and for collecting the sample suspension from the particle size measurement unit. is there.

  In the sample circulator, it is preferable that the storage portion is arranged so that a conical center axis is inclined from a vertical direction.

  In the sample circulator, the storage portion may be arranged such that the inclination angle at which the conical central axis is inclined from the vertical direction is approximately ½ of the apex angle of the conical shape. preferable.

  In the sample circulator, it is preferable that the impeller drive shaft is disposed such that a central axis thereof forms a predetermined angle with a conical central axis of the storage portion.

  In the sample circulator, the inlet is preferably arranged so that the inflow direction of the sample suspension is substantially in contact with the curved surface of the inner surface of the reservoir.

  Since this invention is comprised as mentioned above, there exist the following effects.

  Since the shape of the reservoir is conical with the apex side down, even a small amount of sample suspension can be circulated through the entire liquid without any retention and sample suspension required for particle size measurement. Can be greatly reduced.

  Since the central axis of the conical shape is inclined forward from the vertical direction, the sample suspension can be easily introduced even though the storage portion has a small capacity.

  Since the inclination angle of the central axis of the conical shape is arranged to be approximately ½ of the apex angle, the impeller drive shaft can be arranged in the vertical direction through the storage portion, and the upper end of the storage portion The open surface becomes large and the sample suspension can be charged easily.

  Since the central axis of the impeller drive shaft is arranged at a predetermined angle with the conical central axis of the reservoir, the open surface at the upper end of the reservoir is large, and the sample suspension can be easily introduced. Become.

  Since the inflow port is arranged so that the inflow direction of the sample suspension is substantially in contact with the curved surface of the inner surface of the reservoir, the sample suspension flows smoothly along the conical surface of the reservoir, The suspension can be smoothly circulated without involving air or the like.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a particle size measuring apparatus using a sample circulator 2 of the present invention. The sample circulator 2 is for circulating the sample suspension to the flow cell 12 in the particle size analyzer 1. The sample circulator 2 of the present invention can greatly reduce the amount of sample suspension required for particle size measurement compared to the conventional one, and is a small amount of 20 to 25 mL, which is less than or equal to the amount used in a batch type cell. Can be circulated efficiently.

  In the sample circulator 2, a circulation part 21 is disposed on the base 20, and a drive part 26 is disposed above the rear part of the circulation part 21. The powder sample is dispersed in a liquid medium (dispersion medium) such as water or an organic solvent, and a storage unit 22 (FIG. 2) is a conical cavity formed in the circulation unit 21 of the sample circulator 2 as a sample suspension. 3 and FIG. 4). The sample suspension is supplied from the storage unit 22 to the flow cell 12 of the particle size analyzer 1 through the outlet 241 and the sample supply pipe 242, and further from the flow cell 12 through the sample recovery pipe 222 and the inlet 221. It is returned to the storage unit 22. The configuration and operation of the sample circulator 2 will be described in detail later.

  It is desirable to arrange the sample supply pipe 242 and the sample recovery pipe 222 to be as short as possible. In addition, the sample supply pipe 242 is disposed so as to have a monotonous upward slope so that the outlet 241 side is at the lowest position and local minimum points are eliminated. As a result, the volume of the sample circulation system can be reduced, and all the samples can be circulated smoothly without stagnation.

  The particle size of the powder particles of the sample is measured by a particle size analyzer 1. The particle size analyzer 1 determines various measurement data relating to the particle size of the powder in the sample suspension. The measurement data is sent from the particle size analyzer 1 to the computer 3. The computer 3 performs aggregation processing of these measurement data and graphic processing such as graphs, etc., obtains data such as a particle size distribution and its change over time, and outputs the data to the display unit 31 or a fixed disk device. Record / save in auxiliary storage device.

  Connected to the computer 3 are a display unit 31 for displaying characters and images, and an input unit 32 for an operator to input data and the like. As the display unit 31, a CRT, a liquid crystal display panel, or the like can be used, and as the input unit 32, a keyboard, a pointing device, or the like can be used.

  A switching valve 243 is provided near the outlet 241 in the middle of the sample supply pipe 242, and a discharge pipe 244 is connected to the switching valve 243. At the time of measurement, the output of the switching valve 243 is switched to the particle size analyzer 1 side, and as described above, the sample suspension is discharged from the reservoir 22 of the sample circulator 2 to the outlet 241, the sample supply pipe 242, and the particle size analyzer. The sample 1 is circulated with the sample collection pipe 222, the inlet 221, and the storage unit 22. When the measurement is completed, the output of the switching valve 243 is switched to the discharge pipe 244 side, and the sample suspension is discharged from the discharge pipe 244 as waste liquid. Then, after the sample circulation system is washed, the output of the switching valve 243 is switched to the particle size analyzer 1 side, the next sample suspension is thrown into the storage unit 22, and the next particle size measurement is performed.

  FIG. 2 is a diagram showing the configuration of the particle size analyzer 1. A laser light source 10 having a collimator 11 is arranged in the particle size analyzer 1, and parallel laser light is output from the laser light source 10. A sample suspension for measuring the particle size is introduced into the flow cell 12 to cause diffraction and scattering by the sample particles in the parallel laser light. The condensing lens 13 is for condensing the scattered light scattered by the sample particles in the flow cell 12. The photodetector 14 is for detecting the intensity distribution of scattered light, and includes a plurality of detection elements.

  The intensity distribution of the scattered light detected by the plurality of detection elements of the photodetector 14 is multiplexed by the multiplexer 15 with respect to the time axis. The data of the intensity distribution is further amplified by the amplification amplifier 16 and converted into digital data for each detection data of each detection element by the A / D converter 17. The output of the A / D converter 17 is sent to the arithmetic control unit 18, and the detection data of each detection element is stored in an internal memory. Then, the arithmetic control unit 18 performs processing for averaging the detection data over a predetermined time interval and processing for obtaining the particle size distribution of the sample from the detection data, and outputs the measurement data to the data communication unit 19. .

  The data communication unit 19 transmits measurement data to the computer 3 via a communication cable or the like. Further, the data communication unit 19 receives a control signal from the computer 3 and outputs the control signal to the arithmetic control unit 18. The control signal includes a signal indicating a measurement start timing and a signal indicating a time interval for performing the averaging process. The calculation control unit 18 performs calculation processing of the detection data according to this control signal, and creates measurement data.

  Next, the configuration of the sample circulator 2 will be described with reference to FIGS. FIG. 3 is an enlarged side view of the main part of the sample circulator 2. FIG. 3 is a side view of the sample circulator 2 as viewed from the right in FIG. FIG. 4 is a cross-sectional view in which the circulation part 21 is further enlarged. FIG. 4 is a cross-sectional view of the circulating portion 21 as viewed from the same direction as FIG. FIG. 5 is a cross-sectional view of the circulating portion 21 cut along a horizontal plane at the position of the inlet 221. FIG. 6 is a view showing the configuration of the impeller chamber 240 and the impeller 23 in the lower member 24. FIG. 6 is a view of the lower member 24 as viewed from above.

  A circulation unit 21 is disposed on the base 20 of the sample circulator 2. A drive unit 26 is disposed above the rear portion of the circulation unit 21. FIG. 3 shows a state where a part of the cover of the drive unit 26 is removed. Inside the circulation part 21, a storage part 22 is formed as a hollow part opened upward. The storage portion 22 is a conical hollow portion, and the apex side is directed downward. The upper part of the storage unit 22 is opened to serve as a sample suspension charging unit.

  A lower member 24 is fixed to the lower side of the circulation portion 21, and an impeller chamber 240 is provided inside the lower member 24 so as to communicate with the storage portion 22. The impeller chamber 240 has a substantially cylindrical shape, and the impeller 23 is rotatably disposed inside the impeller chamber 240. The impeller 23 has a central portion fixed to the impeller drive shaft 25 and is rotationally driven by the impeller drive shaft 25. The circulation part 21 and the lower member 24 are connected and fixed in a liquid-tight state so that the sample suspension does not leak from these connection parts.

  Further, as shown in FIG. 6, the outlet 241 is provided so as to communicate with the impeller chamber 240. The sample suspension stirred and energized by the impeller 23 rotating in the impeller chamber 240 flows out from the outlet 241 in the direction of the arrow. The impeller 23 has four rotating blades arranged in a cross shape. The sample suspension is urged to flow out of the outlet 241 by the rotation of the impeller 23 and is sufficiently stirred to uniformly disperse the sample particles in the dispersion medium.

  A lower end portion of the impeller drive shaft 25 is fixed to the center portion of the impeller 23. The impeller drive shaft 25 is rotatably supported by a bearing 27 above the circulation portion 21 and is arranged in a vertical direction so as to pass through the inside of the storage portion 22 and reach the impeller chamber 240 from the lower end of the storage portion 22. Yes.

  The drive unit 26 is provided with a bearing 27, a drive motor 28, a transmission mechanism 281, and a drive circuit 29. A transmission mechanism 281 including a toothed pulley and a toothed belt is provided between the output shaft of the drive motor 28 and the upper end portion of the impeller drive shaft 25 supported by the bearing 27. The output is increased and transmitted to the impeller drive shaft 25. The drive motor 28 is driven by a drive circuit 29, and the rotational speed of the output shaft can be adjusted to an arbitrary value by the drive circuit 29. Further, the drive circuit 29 is disposed at an upper position where the sample suspension is not easily applied.

  As shown in FIG. 4, the storage portion 22 formed in the circulation portion 21 is a conical hollow portion whose apex side is directed downward. The apex angle α of the cone is about 30 degrees, for example. Further, the conical center axis 22c is inclined by an angle β from the vertical direction to the front side. If it does in this way, the upper end of storage part 22 will spread greatly toward the operator's near side (front side), and it will become easy to throw in sample suspension from the upper part of storage part 22. The inclination angle β is preferably about ½ of the apex angle α.

  Since the shape of the storage portion 22 is a conical shape with the apex side directed downward, even a small amount of sample suspension can be smoothly circulated without any retention portion. Since the conical central axis 22c is inclined forward from the vertical direction, the sample suspension can be easily introduced even though the storage portion 22 has a small capacity.

  The sample suspension whose particle size is measured in the particle size analyzer 1 is returned from the flow cell 12 to the storage unit 22 through the sample recovery pipe 222 and the inlet 221. That is, the sample suspension flows into the reservoir 22 from the inlet 221 as indicated by the arrows in FIG. The inflow port 221 is disposed so that the inflow direction of the sample suspension is in a direction in contact with the conical surface of the storage unit 22. As a result, the sample suspension flows smoothly along the conical surface of the reservoir 22 and falls in a spiral shape along the conical surface and joins the liquid reservoir without involving air or the like.

  In addition, the inner surfaces of these sample circulation systems are finished to have a smooth surface so that sample adhesion and deposition do not occur. In addition, in order to make it possible to use acidic and alkaline media, organic solvents, and the like as the dispersion medium, the material of the sample circulation system is a material having corrosion resistance and insolubility with respect to these media (for example, stainless steel or fluorine). Resin).

  According to the sample circulator 2 configured as described above, the amount of the sample suspension required for the particle size measurement can be reduced to 20 to 25 mL, which is the same as or less than that of a normal batch type cell. Even with such a small amount of sample suspension, there is no staying portion, and the entire liquid can be circulated smoothly and efficiently.

  As described above, according to the sample circulator of the present invention, the amount of the sample suspension required for the particle size measurement can be greatly reduced, and a highly accurate particle size measurement can be performed with a small amount of sample and medium. it can. For this reason, the purchase cost of a dispersion medium and the waste liquid processing cost can be reduced, and the bad influence with respect to an environment can also be reduced significantly. Moreover, the various problems of the particle size measurement using the batch type cell as described above can be solved.

  That is, it is possible to perform high-precision particle size measurement under the same measurement conditions using a common cell, when a normal volume sample circulator is used and when a small volume sample circulator of the present invention is used. In addition, all sample suspensions can be circulated smoothly and uniformly without selectivity, and measurement results with high reliability and stability can be obtained. Further, the sample circulation system can be easily cleaned, and the operator is less likely to touch the medium as compared with the batch type cell. Even when the sample contains an expensive substance such as a noble metal, it can be easily recovered from the discharge pipe. And since the sample input part is outside the optical system of the particle size analyzer, it becomes easy to automate the measurement by combining with other equipment.

  According to the present invention, the amount of sample suspension required for particle size measurement can be greatly reduced, and even a small amount of sample suspension can be circulated smoothly and efficiently without any stagnation. High precision particle size measurement can be performed with the medium.

It is a figure which shows the whole structure of the particle size measuring apparatus using the sample circulator 2 of this invention. 1 is a diagram illustrating a configuration of a particle size analyzer 1. FIG. FIG. 3 is an enlarged side view of a main part of a sample circulator 2. It is sectional drawing which expanded and displayed the circulation part 21 further. It is sectional drawing which cut | disconnected the circulation part 21 by the horizontal surface. FIG. 3 is a diagram showing the configuration of an impeller chamber 240 and an impeller 23.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Particle size analyzer 2 Sample circulator 3 Computer 10 Laser light source 11 Collimator 12 Flow cell 13 Condensing lens 14 Photo detector 15 Multiplexer 16 Amplifying amplifier 17 A / D converter 18 Operation control part 19 Data communication part 20 Base 21 Circulation part DESCRIPTION OF SYMBOLS 22 Storage part 23 Impeller 24 Lower member 25 Impeller drive shaft 26 Drive part 27 Bearing 28 Drive motor 29 Drive circuit 31 Display part 32 Input part 221 Inlet 222 Sample collection pipe 240 Impeller chamber 241 Outlet 242 Sample supply pipe 243 Switching valve 244 Discharge pipe 281 Transmission mechanism

Claims (5)

A sample circulator (2) for circulating a sample suspension in which sample particles are dispersed in a liquid medium, to a particle size measuring unit (1) for measuring the particle size of the particles,
A reservoir (22) consisting of a conical cavity whose upper part is opened as the input part for the sample suspension and whose apex side is directed downward;
An impeller chamber (240) provided in communication with the lower part of the storage part (22);
An impeller (23) rotatably disposed inside the impeller chamber (240);
Impeller drive provided so as to reach the impeller chamber (240) from above the storage part (22) through the lower tip of the storage part (22) and having a lower end fixed to the impeller (23) An axis (25);
A drive section (26) for rotationally driving the upper end side of the impeller drive shaft (25);
An outlet (241) provided in communication with the impeller chamber (240);
An inlet (221) provided in communication with the inner surface of the reservoir (22);
A sample supply pipe (242) connected to the outlet (241) and supplying the sample suspension to the particle size measuring unit (1);
A sample circulator having a sample recovery pipe (222) connected to the inlet (221) and recovering the sample suspension from the particle size measurement unit (1). The sample circulator according to claim 1,
The reservoir (22) is a sample circulator in which the conical center axis is arranged so as to incline from the vertical direction. The sample circulator according to claim 2,
The reservoir (22) is arranged so that the inclination angle (β) at which the central axis of the conical shape is inclined from the vertical direction is approximately ½ of the apex angle (α) of the conical shape. vessel. The sample circulator according to any one of claims 1 to 3,
The impeller drive shaft (25) is a sample circulator arranged such that the central axis thereof forms a predetermined angle with the conical central axis of the reservoir (22). The sample circulator according to any one of claims 1 to 4,
The inflow port (221) is a sample circulator arranged so that the inflow direction of the sample suspension is substantially in contact with the curved surface of the inner surface of the reservoir (22).

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