JP2715338B2 - Airflow classifier and airflow classification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention particularly efficiently classifies a powder containing 50% by number or more of particles having a volume average particle size of 20 μ or less to have a predetermined particle size. The present invention relates to an airflow classifier and an airflow classifier for obtaining particles.

[Prior Art] With respect to powder classification, pneumatic classifiers of various methods have been proposed. Among them, there are a classifier using a rotary blade and a classifier having no movable part. Among them, there are fixed-wall centrifugal classifiers and inertial force classifiers as classifiers without moving parts, but Lffler.F.
and K Maly: Symp on Powder Technology D2
(1981), an elbow jet classifier commercialized as Nippon Steel Mining, and Okuda.S.and Yasukuni.j.Pr.
oc.Inter.Symposium on powder Technology '81, 77
1 (1981) has been proposed as an inertial force classifier capable of classifying in the fine powder region.

As shown in FIG. 4, as a preferable condition, the powder is ejected into the classification area together with the airflow at a high speed from the supply nozzle port 16 which opens into the classification machine, and a Coanda block 26 is provided in the classification chamber. Introducing an airflow that intersects with the escaping airflow, separates it into coarse powder and fine powder by the centrifugal force of the curved airflow flowing along Coanda, and coarse and fine powder, Classification such as multi-partitioning such as fine powder of coarse powder and medium powder.

However, these are instantaneously introduced into the classifier from the supply nozzle, classified and discharged out of the classifier system, so that the powder introduced into the classifier is sufficiently supplied to the supply nozzle port and the vicinity of the inlet in the classifier. It is important that the particles are dispersed in individual particles. In particular, dispersion in or before the supply nozzle opening is important. Also, the opening to the classifier is introduced with a certain opening height from the surface of Coanda,
If it is too narrow, there will be blockage due to coarse particles, and if it is wide, the dispersion will be worse due to the decrease in flow rate, and different locus will be drawn depending on the introduction site into the classifier, and coarse powder will disturb the locus of fine powder Therefore, there is a limit to the improvement of the classification accuracy, and the classification tends to be remarkably reduced in the classification of a powder having a large number of coarse particles of 20 μ or more.

This is particularly noticeable when the height of the supply nozzle opening is high.
Although it is generally used in the range of m to 10 mm, it is still not sufficient for the reasons described above. This phenomenon becomes more remarkable as the dust concentration increases. If sufficient dispersion is performed and sent to the classification room, ideal classification will be performed.However, dispersion will not be sufficient for high dust concentration, and when fine powder is removed due to reduced classification accuracy. This causes a reduction in the yield of the product and an increase in fine powder, and has a problem in that the processing capacity of the product must be suppressed and used. In particular, such a problem is remarkable when manufacturing a toner used for a copying machine, a printer, or the like.

Generally, many different properties are required for a toner, and in order to obtain such required properties, it is often determined not only by the raw materials used but also by the manufacturing method. In the toner classification process, the classified particles are required to have a sharp particle size distribution. It is also desired to efficiently and stably produce high quality toner at low cost.

Generally, a binder resin having a soft or low melting point, a low softening point and a low Tg is used as a binder resin. A toner composition or a resin composition using such a resin is classified into a classifier. In this case, a problem due to the properties of the resin, that is, adhesion or fusion to the inside of the apparatus main body is likely to occur.

On the other hand, in recent years, the performance required for the toner has become more severe. For example, as an energy saving measure of a copying machine, in order to fix a recording material by pressure, a soft binder such as wax is used as a binder resin, and a fixing speed is increased even in the case of heating type fixing. In order to reduce power consumption required for fixing and to perform fixing at a low temperature, a binder resin having a low Tg or a low softening point has been used.

Further, in order to improve image quality in copying machines and printers, toner particles are gradually moving toward finer particles. In general, as the material becomes finer, the function of the interparticle force increases, but the same applies to resin and toner. When the size of the material becomes fine, the cohesion between particles increases.

When an external force such as an impact force or a frictional force acts on such an aggregated state, the toner and the particles are fused to the main assembly. Therefore, the occurrence of the fusion in the main body as described above is increasing. When such a phenomenon occurs, not only does the operation time of the apparatus decrease, which increases the cost for toner production, but also because the apparatus does not operate in a stable state at all times, it becomes impossible to obtain a classified product having stable performance. Would. In particular, when fusion occurs in the powder material supply section, the powder cannot be supplied to the classification region, and the operation of the apparatus becomes impossible. In an inertial classifier of the type shown in FIG. 5, there is a method in which an injection nozzle 33 is attached to a raw material supply pipe and raw material powder is sent to a classification zone together with compressed air. This method has the effect of dispersing the powder by compressed air and the effect of reducing the load on the blower located downstream of the classification zone.

However, in the supply method using the injection nozzle, when powder having a low Tg or a low softening point is used, there is a problem that fusion occurs in an injection portion, and stable supply cannot be performed. Therefore, there is a method of supplying the raw material to the classification zone only by the suction force of the blower on the downstream side of the classification zone without using the injection nozzle (FIG. 4). In this case, it is necessary to enlarge the blower. Initial investment increases and costs increase. If the size of the blower is not increased, the classification efficiency is reduced.

In view of such a point, there is a demand for an airflow classifier and a classification method for stably and efficiently classifying fine powder, particularly resin fine powder such as toner.

[Problems to be Solved by the Invention] That is, the object of the present invention is to
It is intended to solve the above-mentioned various problems in a classifier and a classifying method of a powder containing 50% by number or more of particles having a particle size of 20 μ or less, and enables a powder having a fine particle size distribution to enable more accurate classification. An object of the present invention is to provide an airflow type classifier and an airflow type classification system which are efficiently generated.

Another object of the present invention is to provide a gas flow classifier and a gas flow classification method for a resin composition which can be stably produced without causing fusing or the like and without causing clogging in the apparatus body. .

It is a further object of the present invention to provide an airflow classifier and an airflow classification method for fine powder toner that can be stably produced by eliminating the generation of fused material.

[Means and Actions for Solving the Problems] The present invention relates to an air flow classifier provided with a powder supply pipe having a powder supply port for supplying powder and a supply nozzle port opened in a classification area. The flow rate of the particles is 2 at a flow rate of 50 m / sec to 300 m / sec by the gas flow flowing in the powder supply pipe.
A powder containing 50% by number or more of particles having a particle size of 0 μm or less is supplied to the classification region through the supply nozzle port, and at least the coarse powder region is generated by the inertia force of the particles in the airflow and the centrifugal force of the curved airflow due to the Coanda effect. A first discharge port for discharging each powder classified into a medium powder region and a fine powder region, and a second discharge port.
In an airflow classifier having an outlet and a third outlet,
The powder supply pipe has, at an end opposite to the opening of the supply nozzle port, air control means for controlling an air flow flowing in the powder supply pipe, and the first discharge port By reducing the pressure in the classification area through at least one of the second outlet and the third outlet, a new airflow is naturally introduced into the powder supply pipe from the air control means, The powder is supplied into the powder supply pipe from the powder supply port located between the supply nozzle opening of the powder supply pipe and the air control means to perform classification. The invention relates to an airflow classifier characterized by the following.

Further, the present invention provides a powder supply pipe having a powder supply port for supplying powder and a supply nozzle port opened in a classification area, wherein 50 particles having a particle diameter of 20 μm or less are supplied from the powder supply port. % Or more, and the powder is supplied to the classification area through the supply nozzle port at a flow rate of 50 m / sec to 300 m / sec by an air current flowing in the powder supply pipe. Then, each powder classified into at least a coarse powder region, a medium powder region, and a fine powder region by a centrifugal force of a curved airflow due to an inertial force of particles in a gas flow and a Coanda effect is a first discharge port, a second discharge port, and a third discharge port, respectively. In the airflow classification method of discharging from an outlet, an air control means for controlling an airflow flowing through the powder supply pipe is provided at an end of the powder supply pipe opposite to the opening of the supply nozzle port. The first outlet, the second outlet, and By reducing the pressure in the classification area through at least one of the third discharge ports, a new airflow is naturally introduced into the powder supply pipe from the air control means, and the supply of the powder supply pipe is performed. The present invention also relates to an air flow type classification method, wherein the classification is performed by introducing the powder into the powder supply pipe from the powder input port located between the opening of the nozzle port and the air control means. is there.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As an example of the airflow classifier of the present invention, a classifier shown in FIG. 1 (cross-sectional view) and FIG. 2 (solid view) is illustrated.

1 and 2, the side wall has a shape indicated by 22, 23, 24, the lower wall has a shape indicated by 25,
Knife edge type classification edges on 23 and lower wall 25 respectively
The classification zone is divided into three by the classification edges 17,18. A supply nozzle port 16 that opens to a classification chamber (classification area) is provided below the side wall 22, and a Coanda block 26 that is bent downward with respect to the extension direction of the bottom tangent line of the nozzle to draw a long elliptical arc is provided. Classification room upper wall 27
A knife edge type inlet edge 19 is provided in the lower part of the classifying chamber, and furthermore, in the upper part of the classifying chamber, air inlet pipes 14 and 15 opening to the classifying chamber are provided.
Is provided. The inlet pipes 14 and 15 are provided with first and second gas introduction adjusting means 20 and 21, such as dampers, and static pressure gauges 28 and 29, respectively. The positions of the classification edges 17, 18 and the inlet edge 19 differ depending on the type of the raw material to be classified and the desired particle size. In addition, discharge ports 11, 12, and 13 that open into the room are provided on the bottom of the classifying chamber, corresponding to the respective separating areas.
The outlets 11, 12, and 13 may be provided with opening and closing means such as valve means, respectively.

The supply nozzle port 16 is composed of a right-angled cylinder portion and a pyramidal cylinder portion, and the ratio of the inner diameter of the right-angled cylinder portion to the inner diameter of the narrowest portion of the pyramidal cylinder portion is 20: 1 to 1: 1, preferably 10: 1. To 2: 1 from
Good introduction speed is obtained.

An air control means 31 such as a valve is provided at the end of the powder supply pipe 34 on the side opposite to the opening of the supply nozzle port 16 to allow secondary air to naturally flow in from outside air.

The classification operation in the multi-division classification region configured as described above is performed, for example, as follows. That is, the outlets 11, 12,
The pressure in the classification area is reduced through at least one of the 13 and the velocity of the flow velocity of 50 m / sec or 300 m / sec by the air flow flowing through the powder supply pipe 34 having the supply nozzle port 16 opening into the classification area by the reduced pressure. The raw material is supplied to the classification area via the raw material supply nozzle 16 at

The supplied raw material moves along the curved line 30 by the action of the Coanda block 26 due to the Coanda effect and the action of a gas such as air flowing in at that time, and according to the size of each particle, large particles (coarse). Particles) are fractions outside the airflow, that is, outside the classification edge 18, and intermediate particles are classification edges.
The fraction between 18 and 17, small particles are divided into fractions inside the classification edge 17, large particles from the outlet 11, intermediate particles from the outlet 12, and small particles from the outlet 13. Is discharged.

In order to carry out the above-mentioned method, it is usual to use an integrated device system in which mutual devices are connected by a communication means such as a pipe, and a preferable example of such a device is shown in FIG. The integrated device shown in FIG. 3 is a three-divider classifier 1 (having the shape shown in FIGS. 1 and 2; details are as described above), a fixed-quantity feeder 2, a vibration feeder 3, The collecting cyclone 4, the collecting cyclone 5, and the collecting cyclone 6 are connected by communication means.

In this apparatus, the so-called powder raw material is fed into the fixed quantity feeder 2 by an appropriate means, and then the powder feed pipe 34 is connected to the feed nozzle port 16 through the vibrating feeder 3 by the feed nozzle port 16.
It is introduced into the split classifier 1. For introduction, 50-30
The pulverized material is introduced into the classifier 1 at a flow rate of 0 m / sec.
The size that composes the classification area of classifier 1 is usually [10-50cm]
× [10 to 50 cm], the pulverized material can be classified into three or more kinds of particles in an instant of 0.1 to 0.01 seconds or less. Then, it is divided into large particles (coarse particles), intermediate particles and small particles by the three-division classifier 1. Then the large particles are discharged
After passing through 11, it is sent to the collecting cyclone 6 and collected. The intermediate particles are discharged out of the system via the discharge conduit 12 and collected by the collection cyclone 5. The small particles are discharged out of the system through the discharge conduit 13 and collected by the collection cyclone 4.
The collection cyclones 4, 5, and 6 function as suction pressure reducing means for sucking and introducing the powdery material into the classification area via the supply nozzle port 16.

In the classifier and the classification method of the present invention, when supplying the powdery raw material to the classification area, it is important to introduce the powdery raw material in a sufficiently dispersed state. When introducing the powder into the classification area,
The outside air is secondarily supplied through the air control means 31 provided at the end opposite to the opening of the supply nozzle port 16 at 34.
That is, by naturally introducing the new airflow, the raw material can be introduced into the classification region in a state where the powder in the powder supply pipe 34 is more dispersed. For this reason, the dispersion of the powder in the classification region is further improved, good classification accuracy is obtained even at a higher dust concentration, and a decrease in product yield can be prevented. Further, at the same dust concentration, better classification accuracy and improvement in product yield can be achieved.

In addition, when sucking the raw material powder and the outside air by the negative pressure of the classification chamber, it is generally necessary to increase the capacity of the blower downstream of the classification chamber, but in the method of the present invention, the negative pressure in the classification chamber is reduced. However, since the amount of airflow flowing through the supply pipe can be maintained by taking in the secondary air, not only good classification accuracy can be obtained by the dispersion effect of the present invention, but also the negative pressure of the blower can be reduced, and as a result, It is possible to use a smaller device than in the past, thereby enabling a significant power saving.

In the present invention, the amount of external air introduced through the air control means 31 may be appropriately adjusted by the air control means 31 such as a valve depending on the properties of the powder to be classified, the classification point, and the like. It is not limited by area. Also, as shown in FIG.
If the airflow meter 32 is attached and the amount of inflow air is measured, more stable classification can be performed.

The apparatus and method of the present invention are particularly effective when classifying toner or toner colored resin powder used in an image forming method by electrophotography. In particular, it is effective when classifying a toner composition comprising a binder resin having a low melting point, a low softening point, and a low Tg. When a toner composition using such a resin is supplied to a conventional classifier, fusion occurs at the injection portion, and stable operation is difficult (in the case of the apparatus shown in FIG. 5), and the capacity of the blower is large. As a result, the initial investment and running cost increase (in the case of the apparatus shown in FIG. 4). There is also a method in which the supply part of the classifier is made a closed system and the whole system is pressurized and supplied. However, in this case, since the airtightness of the system is strictly required, the apparatus is undesirably increased in size.

However, in the present invention, the supply nozzle port of the powder supply pipe 34
Secondary air is spontaneously introduced from the air control means 31 provided at the end opposite to the opening 16 to improve the dispersibility of the powder in the powder supply pipe 34 and improve the classification yield. This is advantageous in that no fusion occurs near the powder inlet 35 of the powder supply pipe 34 and the load on the blower can be reduced.

The effect of the present invention is more remarkable as the particle diameter of the powder is smaller, and is particularly preferable when producing a powder having a volume average diameter of 10 μm or less.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples. still,
The particle size values in the examples and comparative examples are all measured by the following measuring apparatus.

In other words, the Coulter Counter TA is used as a measuring device.
-Type II (manufactured by Coulter, Inc.) is connected to an interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution, and a CX-1 personal computer (manufactured by Canon). Prepare a% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample was suspended was treated with an ultrasonic
After a dispersion treatment for minutes, the Coulter Counter TA-II
According to the mold, the particle size distribution of the particles of 2 to 40 μm was measured on the basis of the number by using a 100 μm aperture as the aperture, and then the value according to the present invention was obtained.

Example 1 After the above materials were mixed well in a blender, they were kneaded with a twin screw extruder set at 120 ° C. The obtained kneaded material was cooled, coarsely pulverized to a particle diameter of 1 mm or less by a cutter mill, and then finely pulverized by a jet mill to a volume average diameter of 7.8 μm to obtain a classified raw material.

The obtained classified material was classified by the flow shown in FIG. 3 using the airflow classifier shown in FIGS. 1 and 2. When introducing the classified material into the classification zone, discharge ports 11, 12, 13
The material is sucked and introduced from the powder inlet 35 of the powder supply 34 by the suction force (18 m ³ / min) derived from the pressure reduction in the system by the suction decompression of the collection cyclones 6, 5 and 4 communicating with the did.

The supply nozzle port 16 was 30 mm wide and 6 mm high, and the air control valve 31 was fully opened. The classified raw material is supplied at a rate of 50 kg per hour, and as a medium powder, a volume average particle diameter of 8.5 μm (particles having a particle diameter of
The inlet edge 19 and the classification edges 17 and 18 were adjusted so as to obtain particles having 5% by number and containing 3.0% by volume of particles having a particle size of 12.7 μm or more.

As a result, the total amount of supplied classification material (100)
In contrast, 2.0 was obtained for the coarse powder, 78 for the medium powder, and 20 for the fine powder, and the medium powder was suitable as a toner. The fusion of the toner near the powder inlet 35 of the powder supply pipe 34 was not observed at all even after the continuous operation for 24 hours.

Example 2 A kneaded product obtained in the same composition as in Example 1 was cooled, coarsely pulverized to a particle size of 1 mm or less by a cutter mill, and then finely pulverized by a jet mill to a volume average diameter of 11.7 μm to obtain a classified material. .

The obtained classified material was classified by the flow shown in FIG. 3 using the airflow classifier shown in FIGS. 1 and 2. When introducing the classified material into the classification zone, discharge ports 11, 12, 13
The raw materials are sucked and introduced from the powder inlet 35 of the powder supply pipe 34 by the suction force (18 m ³ / min) derived from the reduced pressure in the system due to the reduced pressure of the collecting cyclones 6, 5 and 4 communicating with the collecting cyclones 6. did.

The supply nozzle port 16 was 30 mm wide and 6 mm high, and the air control valve 31 was fully opened. The classified raw material is supplied at a rate of 60 kg per hour, and as a medium powder, a volume average diameter of 12.7 μm (particles with a particle diameter of 6.35 μm or less
13% by volume, 1.0% by volume of particles with particle size of 20.2μm or less
The inlet edge 19 and the classification edges 17 and 18 were adjusted so as to obtain particles of (containing).

As a result, the total amount of supplied classification material (100)
On the other hand, coarse powder was 3.0, medium powder was 80.0, and fine powder was 17.0
And the medium powder was suitable as a toner. The fusion of the toner near the powder inlet 35 of the powder supply pipe 34 was not observed at all even after the continuous operation for 24 hours.

Example 3 After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. After cooling the obtained kneaded material and coarsely pulverizing it to 1 mm or less with a cutter mill,
It was pulverized with a jet mill to a volume average diameter of 6.3 μm to obtain a classified raw material.

The obtained classified material was classified by the flow shown in FIG. 3 using the airflow classifier shown in FIGS. 1 and 2. When introducing the classified material into the classification zone, discharge ports 11, 12, 13
The raw materials are sucked and introduced from the powder inlet 35 of the powder supply pipe 34 by the suction force (18 m ³ / min) derived from the reduced pressure in the system due to the reduced pressure of the collecting cyclones 6, 5 and 4 communicating with the collecting cyclones 6. did.

The supply nozzle port 16 was 30 mm wide and 6 mm high, and the air control valve 31 was fully opened. The classified raw material is supplied at a rate of 100 kg per hour, and as a medium powder, particles having a volume average diameter of 6.7 μm (particles having a particle diameter of 4.0 μm or less)
23.0% by volume and 2.0% by volume of particles having a particle size of 10.08 μm or more).
Classification edges 17, 18 were adjusted.

As a result, the total amount of supplied classification material (100)
In contrast, coarse powder is 2.0, medium powder is 75.0, fine powder is 23.0
And the medium powder was suitable as a toner. The fusion of the toner near the powder inlet 35 of the powder supply pipe 34 was not observed at all even after the continuous operation for 24 hours.

Comparative Example 1 In this comparative example, a pulverized product having a volume average diameter of 7.8 μm obtained in the same manner as in Example 1 was used as a classification raw material.

The classified raw material was classified according to the flow shown in FIG. 3 using the airflow classifier shown in FIG. When introducing the classified material into the classification zone, the suction force derived from the pressure reduction in the system by the suction pressure reduction of the collecting cyclones 6, 5, and 4 communicating with the outlets 11, 12, 13 and the suction force from the injection nozzle Powder supply tube 3 with raw material by compressed air (3.0 kg / cm ² pressure)
Suction was introduced from the powder input port 35 of No. 4.

As a result, fusion began to appear at the injection nozzle portion after about one hour of operation, and the injection nozzle portion was blocked by three hours of operation, making it impossible to continue the operation.

Comparative Example 2 Also in this comparative example, a ground material having a volume average diameter of 7.8 μm obtained in the same manner as in Example 1 was used as a classification raw material.

The classified raw material was classified according to the flow shown in FIG. 3 using the airflow classifier shown in FIG. When introducing the classified raw material into the classification zone, a suction force (18 m ³ / min) derived from the reduced pressure in the system by the reduced suction pressure of the collecting cyclones 6, 5, and 4 communicating with the outlets 11, 12, and 13 As a result, the raw material was sucked and introduced from the powder input port 35 of the powder supply pipe 34.

As the supply nozzle port 16, a nozzle having a width of 30 mm and a height of 6 mm was used. The classified raw material is supplied at a rate of 50 kg per hour, and as a medium powder, particles having a volume average diameter of 8.7 μm (27% by number of particles having a particle diameter of 5.04 μm or less and particles having a particle diameter of 12.7 μm or more are contained
The inlet edge 19 and the classification edges 17, 18 were adjusted so as to obtain particles having a volume of 4.0% by volume.

As a result, the total amount of supplied classification material (100)
On the other hand, a coarse powder was obtained at a ratio of 4.0, a medium powder was obtained at a ratio of 70, and a fine powder was obtained at a ratio of 26. No fusion of toner was observed near the powder inlet 35 of the powder supply pipe 34. However, the particle size distribution of the medium powder obtained in comparison with Example 1 was broad, and the yield was low. Was inferior.

[Effects of the Invention] As described above, according to the airflow classifier and the airflow classification method of the present invention, fusion near the powder input port 35 of the powder supply pipe 34 is prevented, and The rate can be improved.

Furthermore, the capacity of the blower downstream of the classifying chamber can be reduced, and significant power savings can be achieved.

The present invention is particularly effective when classifying resin powder such as toner, and is more effective when classifying powder having a volume average diameter of 10 μm or less.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are a schematic sectional view and a three-dimensional view of an airflow classifier of the present invention. FIG. 3 is an explanatory diagram showing an example of a classification process using the present invention. FIG. 4 and FIG. 5 are schematic sectional views of a conventional airflow classifier. DESCRIPTION OF SYMBOLS 1 ... Solid particle multi-division classification apparatus 2 ... Quantitative feeder 3 ... Vibration feeder 4 ... Collection cyclone 5 ... Collection cyclone 6 ... Collection cyclone 11, 12, 13 ... Discharge port 14 , 15 ... inlet, 16 ... supply nozzle port 17,18 ... classification edge, 19 ... inlet edge 20 ... first gas introduction adjusting means 21 ... second gas introduction adjusting means 22,23, 24 ... side wall, 25 ... lower wall 26 ... Coanda block, 27 ... upper wall 28, 29 ... static pressure gauge 30 ... solid particle scattering direction 31 ... air control means 32 ... air flow meter 33 ... injection Nozzle 34 ... Powder supply tube 35 ... Powder inlet

Continuation of the front page (72) Inventor Yasuhide Goseki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-62-264065 (JP, A) JP-A-62-266185 (JP, A)

Claims (2)

(57) [Claims] An air-flow classifier provided with a powder supply pipe having a powder supply port for supplying powder and a supply nozzle port opened in a classification area, wherein the powder flows through the powder supply pipe. Flow rate of 50m / sec to 300m / sec depending on
A powder containing 50% by number or more of particles having a particle size of 0 μm or less is supplied to the classification region through the supply nozzle port, and at least the coarse powder region is generated by the inertia force of the particles in the airflow and the centrifugal force of the curved airflow due to the Coanda effect. A first discharge port for discharging each powder classified into a medium powder region and a fine powder region, and a second discharge port.
In a gas flow classifier having a discharge port and a third discharge port, the powder supply pipe is provided at an end opposite to the opening of the supply nozzle port to control an air flow flowing through the powder supply pipe. The air control means includes a first discharge port, a second discharge port, and a third discharge port. The pressure in the classification area is reduced through at least one of the first discharge port, the second discharge port, and the third discharge port. The powder is supplied from the powder input port located between the opening of the supply nozzle port of the powder supply pipe and the air control means while the natural airflow is naturally introduced into the powder supply pipe. An air-flow classifier, wherein the classification is performed by being introduced into a body supply pipe. 2. A powder supply pipe having a powder supply port for supplying powder and a supply nozzle port opened in a classification area,
A powder containing 50% by number or more of particles having a particle size of 20 μm or less is charged from the powder inlet, and the powder is supplied at a flow rate of 50 m / sec to 300 m / sec by an airflow flowing in the powder supply pipe. Each powder is supplied to the classification area through the supply nozzle port, and classified into at least a coarse powder area, a medium powder area, and a fine powder area by centrifugal force of a curved airflow due to an inertial force of particles in a gas stream and a Coanda effect. In a gas flow classification method for discharging a body from a first outlet, a second outlet, and a third outlet, respectively, the powder supply pipe is provided at an end of the powder supply pipe opposite to the opening of the supply nozzle port. Providing an air control means for controlling an air flow flowing through the pipe, by reducing the pressure in the classification area through at least one of the first outlet, the second outlet, and the third outlet. , From the air control means While the air stream is naturally introduced into the powder supply pipe, the powder is supplied from the powder input port located between the supply nozzle opening of the powder supply pipe and the air control means. A pneumatic classification method, wherein the classification is performed by charging the mixture into a supply pipe.