JP3555302B2 - Laser diffraction particle size distribution analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser diffraction / scattering type particle size distribution measuring apparatus, and more particularly, to a laser diffraction type particle size distribution capable of performing a measurement in which a group of particles to be measured is dispersed in a gas to form an aerosol, a so-called dry measurement. It relates to a measuring device.
[0002]
[Prior art]
Conventionally, in a laser diffraction / scattering type particle size distribution measuring apparatus, the intensity of diffraction / scattered light obtained by dispersing a group of particles to be measured in a medium and irradiating the group of particles to be measured in a dispersed state with laser light. The distribution is measured, and the particle size distribution of the particle group to be measured is obtained from the measurement result by a calculation based on the Fraunhofer diffraction theory or the Mie scattering theory. Using air as a medium, the particles of the powder sample are conveyed by the air flow and ejected from an ejector nozzle or the like to form an aerosol, which is irradiated with laser light to measure diffraction / scattered light. There is a so-called dry measurement.
[0003]
As an apparatus for such a dry measurement, as shown in FIG. 1, a powder sample S supplied from a sample tank 1 is blown out from an ejection port at the tip of an ejector 2, and is located at a position slightly away from the ejection port. By arranging the suction port of the dust collector 12, the sample S is caused to fly once in the air and then sucked into the dust collector 12. Then, the laser light source 13 is arranged so that the laser light for measurement is irradiated from a predetermined direction to the aerosol of the sample S flying in open air, and the measuring optics of the condenser lens 15 and the ring detector 16 are arranged on the opposite side. The system is arranged and the diffraction / scattered light by the sample S is measured.
[0004]
Further, as shown in FIG. 5, the sample tank 1 is provided with a sieve 4 to which vibration is repeatedly given by the vibrating means 5, and the sample S passing through the sieve 4 is naturally dropped and supplied to the ejector 2. Was.
[0005]
[Problems to be solved by the invention]
However, in such a method, since the sample S passes through the sieve 4 depending on the own weight of the sample S together with the strength of the vibration by the vibration means 5, if the own weight of the powder sample S is lighter than a predetermined value, The amount of the powder sample S passing through the sieve 4 becomes smaller than a predetermined amount required for measurement. When the amount of the powder sample S placed on the sieve 4 decreases, the force applied to the powder sample S immediately before passing through the sieve 4 decreases, and the amount of the sample S passing through the sieve 4 decreases. As a result, the amount of the powder sample S supplied to the ejector 2 becomes smaller than a predetermined amount necessary for measurement.
[0006]
As described above, when the supply amount of the powder sample S is not stable, the concentration (density) of the sample passing through the laser irradiation portion varies, so that the reproducibility of measurement is deteriorated, and the data comparison between different types of samples becomes difficult. become unable. If the amount of the powder sample S passing through the laser irradiation part is smaller than a predetermined amount, the diffraction / scattered light incident on the ring detector 16 becomes too weak, and the detection sensitivity is reduced. Conversely, if the amount of the powder sample S passing through the laser irradiation part exceeds a predetermined amount, the diffraction / scattered light incident on the ring detector 16 becomes too strong, and the detection signal becomes saturated.
[0007]
Therefore, conventionally, according to the particle size of the sample S, it is replaced with a sieve 4 having a mesh of a size suitable for the size of the sample S, or the vibration intensity of the vibrating means 5 is adjusted so that the drop amount of the sample S, The supply amount to the irradiated part was adjusted. However, such a sieve 4 not only adjusts the supply amount of the sample S but also functions to disperse the aggregated sample. For example, if the sieve 4 having a large mesh is simply used to increase the supply amount, Then, the aggregated sample S is supplied to the laser irradiation part without being dispersed. Even if the necessary mesh sieve 4 suitable for the dispersion (particle size) of the powder sample S is set, if the vibration necessary for dispersing the aggregated sample S is simply given, this vibration is too strong. Then, when the vibration is suppressed to supply the sample S at a predetermined amount or more, or conversely, to set the supply amount of the sample S to an appropriate amount, the aggregated sample S is not dispersed, and the sample S can be sufficiently supplied. become unable.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems in a laser diffraction type particle size distribution measuring apparatus for powder, and it is intended to make the amount of powder supplied to a laser irradiation part constant and to perform diffraction / scattering. Provided is a laser diffraction type particle size distribution measuring apparatus in which light intensity falls within a predetermined range suitable for measurement and has little fluctuation.
[0009]
[Means for Solving the Problems]
The present invention vibrates the sieving means on which the powder sample is placed in the sample supply unit, and presses the powder sample in the dropping direction by the pressing means to pass the sieved powder sample through the airflow transport pipe. The laser beam is emitted to the sample through the air, the diffraction / scattered light of the laser beam by the sample particles is detected, and the particle size distribution is measured. For example, as the pressing means, there is a means for placing a weight on a sample or applying a biasing force of a spring.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a schematic configuration of a particle size distribution measuring apparatus according to an embodiment of the present invention, and FIG. 2 shows a schematic configuration of a sample tank.
[0011]
Reference numeral 1 denotes a sample tank main body, which is connected to an ejector 2 via a sample supply pipe 3. Reference numeral 4 denotes a sieve for sifting the sample S placed thereon, and the sieve 4 is provided with a vibrating means 5. The sieve 4 has a function of adjusting the supply amount of the powder sample S and dispersing the aggregated powder sample S. After selecting a sieve 4 having a mesh suitable for the particle size of the sample S, the sieve 4 is placed in the sample tank 1. It is configured so that it can be set. The vibration means 5 has a variable vibration intensity, and is set to a vibration intensity suitable for the supply amount of the sample S and the dispersion of the aggregated sample. Further, a pressure F is applied to the sample S placed on the sieve 4 in the falling direction by the pressurizing means, and the amount of the sample 4 passing through the sieve 4 increases depending on the pressure F. As means for pressing the sample S, specifically, as shown in FIG. 3, means for placing a weight 6 on the sample S, or as shown in FIG. There is a means to energize.
[0012]
The structure of the sample tank of FIG. 4 will be described. A screw rod 10 is screwed into a lid 9 that can be attached to and detached from the sample tank 1, and a holding plate 11 is attached so as to be rubbed around the screw rod 10. The pressing plate 7 is attached via a spring 8 attached to the holding plate 11. These are integrally formed, and by removing the lid 9 from the sample tank 1, the pressure plate 7 can be simultaneously removed from the sample tank.
[0013]
The ejector 2 mixes the powder sample S supplied from the sample tank 1 with a carrier airflow from a carrier airflow supply device (not shown) to form an aerosol, and blows it out from a jet port at the tip. A dust collector 12 is disposed at a position slightly away from the ejection port of the ejector 2, and sucks the powder sample S that has exited from the ejection port of the ejector 2 after flying in open air.
[0014]
Reference numeral 13 denotes a laser light source, and the laser light generated from the laser light source 13 passes through a collimator 14 and irradiates the aerosol of the powder sample S flowing in the open air from a predetermined direction. The diffraction / scattered light of the laser light by the powder particles is measured by the measuring optical system of the condenser lens 15 and the ring detector 16 arranged on the opposite side.
[0015]
Next, the operation of the particle size distribution measuring device of FIG. 1 will be described. It is assumed that the sample tank 1 has the structure shown in FIG. First, prior to the particle size distribution measurement, the pressure plate 7 is removed from the sample tank 1 together with the lid 9, and the powder sample S to be measured is put in the sample tank 1. Then, the lid 9 is attached to the sample tank 1 together with the pressure plate 7, the head 10 </ b> A is rotated, and the screw rod 10 is lowered in the direction of the pressure plate 7. Then, the holding plate 11 is lowered, the pressing plate 7 is urged downward by the spring 8, and the sample S placed on the sieve 4 is pressed downward.
[0016]
When the measurement is started, the vibration means 5 is operated, and at the same time, the transport airflow supply device (not shown) is activated to feed the transport airflow to the ejector 2. Then, when the sieve 4 starts to vibrate, the powder sample S starts to fall through the sieve 4. At this time, the aggregated sample S is dispersed by the screen of the sieve 4, falls through the sieve 4, and is sent to the ejector 2 through the sample supply pipe 3.
[0017]
Then, in the ejector 2, the powder sample S mixed into the transport airflow is blown out from the ejection port at the tip of the ejector 2. Then, the laser light emitted from the laser light source 13 and passed through the collimator 14 is applied to the sample S flowing in the open air from a predetermined direction, and the diffracted / scattered light of the sample S is passed through the condenser lens 15. It is measured by the ring detector 16 arranged on the opposite side.
[0018]
In addition, the following aspects are also included as modifications of the present invention.
[0019]
(1) The sieving means on which the powder sample is placed is vibrated, and the sieved powder sample is jetted into the air by a carrier airflow, and the jet sample is irradiated with laser light to diffract the laser light by the sample particles. A laser diffraction type particle size distribution measuring device for detecting scattered light, comprising a pressing weight for pressing a powder sample placed on the sieving means in a falling direction. That is, since the sample is pressed in the falling direction only by the pressing weight, the powder sample can be stably dropped through the sieve by an extremely simple method.
[0020]
(2) Vibrating the sieving means on which the powder sample is placed, injecting the sieved powder sample into the air by a carrier airflow, irradiating the ejected sample with laser light, and diffracting the laser light by the sample particles. In a laser diffraction type particle size distribution measuring device for detecting scattered light, a laser diffraction type particle size distribution device is provided, wherein pressing means for pressing a powder sample placed on the sieving means in a falling direction by a biasing force of a spring is provided. Distribution measuring device. That is, since the sample is pressed in the falling direction by the urging force of the spring, the powder sample can be stably dropped through the sieve with an extremely lightweight structure.
[0021]
【The invention's effect】
The laser diffraction type particle size distribution measuring apparatus of the present invention applies an external pressure to the sample placed on the sieve in the sample tank and allows the sample to pass through the sieve, so that the amount of the sample supplied to the ejector is stabilized, and this ejector is used. In this way, the amount of sample required for the measurement can be properly and without fail flying to the laser-irradiated portion, the sample concentration (density) passing through the laser-irradiated portion is stabilized, the reproducibility of the measurement is improved, and the accuracy is extremely improved. . Also, the agglomerated sample is sufficiently dispersed by the vibrating sieve, and can be passed through the sieve.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a particle size distribution measuring device of the present invention.
FIG. 2 is a diagram showing a schematic configuration of a sample tank of the particle size distribution measuring device of the present invention.
FIG. 3 is a view showing an embodiment (1) of a sample tank of the particle size distribution measuring device of the present invention.
FIG. 4 is a view showing an embodiment (2) of a sample tank of the particle size distribution measuring device of the present invention.
FIG. 5 is a diagram showing a schematic configuration of a sample tank of a conventional particle size distribution measuring device.
[Explanation of symbols]
S ... Powder sample 1 ... Sample tank 2 ... Ejector 4 ... Sieve 5 ... Vibration means 6 ... Weight 7 ... .... Pressing plate 8 ... Spring 9 ... Lid 10 ... Screw rod 11 ...

Claims (1)

The sieving means on which the powder sample is placed is vibrated, and the sieved powder sample is ejected into the air by a carrier airflow, and the ejected sample is irradiated with laser light to diffract / scatter the laser light by the sample particles. 1. A laser diffraction type particle size distribution measuring apparatus, wherein a pressing means for pressing a powder sample placed on the sieving means in a falling direction is provided in the sieve means.

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