JPH09173985A - Powder classifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drop almost the whole powder inside a powder introducing port without carrying the powder outside from the powder introducing port by supplying a high pressure air to an air introducing passage formed by forming a groove in the inside part of a casing and blowing air around the powder introducing port to increase atmospheric pressure. SOLUTION: At the time of charging the powder in a powder classifier 1 from a powder charging port 23, the powder is dispersed in the surroundings on the upper surface of a classifying rotor 4 and drops to the inside of the classifying rotor 4 from the powder introducing port 10 of the upper surface of the classifying rotor 4. In such a case, a partition plate 5 is fitted to the outside of the powder introducing port 10 and air is supplied to the outer periphery of the parting plate 5 to make the pressure higher than that in the inside of the powder introducing port 10. Thereby, the powder is hardly carried outside the parting plate 5, the whole powder drops inside the powder introducing port 10 and the deterioration of classifying accuracy and the clogging of the powder between the classifying rotor and the casing are not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder classifier equipped with a rotatable classifying rotor in a casing and classifying powder by utilizing centrifugal force and air flow, and particularly in a peripheral portion of the classifying rotor. The present invention relates to a powder classifier that controls the flow of powder to improve classification accuracy and prevent clogging and sticking of powder.

[0002]

2. Description of the Related Art A classifier such as that disclosed in Japanese Patent Publication No. 6-61535 is known as one of powder classifiers equipped with a classifying rotor and classifying powder by utilizing the rotation of the classifying rotor and the air flow. ing. This classifier rotates a classifying rotor, which has a number of classifying blades around it, at high speed in the casing, forms an air flow from the periphery to the center in the classifying rotor, and the air flow and the centrifugal force generated by the rotation of the powder. Is applied to select powders with a desired reference value as a boundary.

Specifically, a plurality of classification blades are provided inside the outer peripheral portion of the classification rotor as described above, and an air introduction path is formed therein, and further, the classification blade portion is powdered on the upper outer periphery of the classification rotor. The powder inlet is formed along the circumference so that the powder falls, while the casing is provided with a powder inlet at the center of the upper part for injecting the powder. While being dispersed in four directions on the upper surface of the, the powder is introduced into the classification blades in the classification rotor, that is, the classification chamber. Then, the powder that has entered the classification chamber is subjected to centrifugal force by the classification blades and is carried from the periphery to the center by the air flow flowing inward of the classification rotor,
Small diameter powder that is greatly affected by air viscosity resistance is carried to the center by the air flow and taken out from the fine powder outlet provided in the center, and large diameter powder that is greatly subjected to centrifugal force is classified by the centrifugal force. The particles are flown outward and collected at a coarse powder outlet provided around the particle, and the powder is classified with a predetermined particle size as a boundary.

[0004]

However, in the conventional powder classifier, the charged powder may be carried toward the outer end of the classifying rotor without being entirely dropped into the powder introduction port. Then, since the powder enters the classification chamber from the outer circumference of the classification rotor, classification is not performed accurately in the classification chamber, and fine powder is included in the coarse powder side or coarse powder is classified into the fine powder side. There was a problem that it decreased. Also, the space between the classification rotor and the casing is narrowed because it is necessary to keep airtightness originally,
Furthermore, since it has a labyrinth structure, if powder enters this gap, it will solidify and become clogged. When the body flows in, the frictional heat due to the rotation of the classification rotor may cause the powder to be melted and adhered to the gap to cause a rotation failure of the classification rotor.

[0005]

In order to solve the above-mentioned problems, the present invention rotatably includes a classification rotor having a vertical rotation axis in a casing, and the centrifugal force generated by the rotation of the classification rotor and the classification rotor In a powder classifier that classifies powder according to the balance with an air flow, the classifying rotor causes air to flow from the circumference to the axial center direction between two discs of substantially the same diameter which are arranged in parallel vertically. Equipped with an air circulation cavity,
Providing a plurality of classification blades on the outer peripheral portion of the air circulation cavity,
A powder introduction port communicating with the classification blade is circumferentially arranged on the upper disc, and the powder introduced through a powder introduction port provided at the center of the upper part of the casing is squared on the upper surface of the classification rotor. After being dispersed into the air-flowing cavity through the powder introduction port, the casing has a rounded portion between the powder introduction port and the outer peripheral end of the classification rotor. A powder classifier was constructed by forming a high-pressure portion for increasing the atmospheric pressure of the above to the atmospheric pressure in the powder introduction port. Therefore, when high-pressure air is sent to the high-pressure portion, for example, an air introduction path formed by forming a groove in the inner side of the casing, and air is blown out around the powder introduction port to raise the atmospheric pressure, the powder is introduced into the powder introduction port. It is possible to drop almost all the powder into the powder introduction port without being carried further outward.

Further, the powder classifier is constructed by circumferentially providing a partition plate for partitioning the powder introduction port and the outside of the powder introduction port. The partition plate is provided along the outer periphery of the powder introduction port and holds the opening area of the powder introduction port by a predetermined amount. As a result, the powder charged from the charging port in the central portion smoothly falls into the powder introducing port. The partition plate is attached to the casing and a predetermined amount of clearance is provided between the partition plate and the classification rotor. However, the partition plate may be provided along the outer peripheral edge of the powder introduction port of the classification rotor.

A partition plate is provided from the casing toward the classification rotor, a ring-shaped air introduction path is formed outside the partition plate, and high-pressure air is sent to the air introduction path to supply the powder introduction port. The powder classifier was configured so that the atmospheric pressure in the radially outer peripheral portion was made higher than the atmospheric pressure in the powder introduction port. A surface of the air introduction path facing the rotor is made of a porous member, and air is sent into the casing through the porous member.

With this arrangement, the high-pressure air can be jetted uniformly along the circumference and the pressure can be evenly applied.
Further, instead of a porous member, a large number of nozzles may be arranged circumferentially, or slit-like gaps may be opened in the rotor direction to blow air uniformly.

According to such a powder classifier, when the powder is introduced into the powder classifier from the powder inlet, the powder is dispersed around the upper surface of the classifying rotor and the powder is introduced on the upper surface of the classifying rotor. It falls from the mouth into the classification rotor. At that time, a partition plate is provided outside the powder introduction port, and air is sent to the outer peripheral side of the partition plate to increase the pressure inside the powder introduction port. Therefore, the classification accuracy is not lowered and the powder is not clogged between the classification rotor and the casing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the powder classifier according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the powder classifier 1, and FIG. 2 is a plan view of the powder classifier 1 in which a part of the classifying rotor 4 is cut away.

First, a description will be given with reference to FIG.

The classifier 1 includes a casing 2 and a casing 2.
The casing 2 comprises a classification rotor 4 and the like rotatably housed therein. A powder inlet 23 connected to a powder supply device (not shown) is provided at the center of the upper surface of the casing 2, and air is provided at the sides. An inlet 24 is formed. The casing 2 has a circular shape as a whole, and has a partition plate 5 and an air introduction path 6 inside as shown in FIG.
Etc. are provided.

The partition plate 5 is circumferentially provided near the outer circumference of the casing 2, and its tip is located outside the powder introduction port 10 of the classification rotor 4 described later. The air introduction path 6 is formed on the outer side of the partition plate 5 in a circular shape like the partition plate 5, and is connected to an air compressor (not shown) via a connection port 17. Further, a porous member 9 having fine holes is attached to the lower part of the air introduction path 6, and the air sent from the air compressor is jetted into the casing 2 through the porous member 9.

The classification rotor 4 comprises two discs (upper plate 4a,
A rotary shaft which is a disk-like shape in which lower plates 4b) are combined in an upper and lower direction and which is provided with a cavity portion 26 communicating from the outer peripheral portion to a lower portion of the shaft center portion and which is vertically attached to the shaft center portion of the casing 2 by bearings 25, 25. It is fixed to the upper end of 36.

In the cavity 26 of the classifying rotor 4, as shown in FIG. 2, a plurality of outer classifying blades 7 and inner classifying blades 8 are radially arranged at equal intervals along the circumference. This forms a classification chamber 11. Upper plate 4a of classification rotor 4
A powder introduction port 10 is formed in a ring shape facing the classification blade gap 37 between the outer classification blade 7 and the inner classification blade 8 and communicating with the inside of the classification chamber 11. On the lower surface of the lower plate 4b of the classification rotor 4, a large number of auxiliary blades 12 are radially arranged at equal intervals, and when the classification rotor 4 rotates, the auxiliary blades 12 give a flow of air to the rotation direction, Classroom 11
The air is swirled in the direction of.

A space 15 is formed between the upper plate 4a of the classification rotor 4 and the top plate of the casing 2, and connects the powder charging port 23 and the powder introducing port 10 of the classification rotor 4 to each other. In this space 15, a large number of powder dispersion blades 16 extending from the axial center to the outer peripheral direction are radially provided on the center side of the upper plate 4a of the classification rotor 4, and the radial ends of the dispersion blades 16 and the powder are dispersed. The upper plate 4a between the body introduction ports 10 is flattened, and a dispersion gap 28 for secondarily dispersing the powder is continuously formed.

Reference numeral 18 denotes a disk-shaped balance rotor having a cavity 27 communicating with the shaft center portion from the circumferential portion in the same manner as the classification rotor 4. The balance rotor 18 is the classification rotor 4.
The hollow portion 27 is integrally fixed to the rotating shaft 36 in the casing 2 so as to be vertically symmetrical with the hollow portion 27 so as to communicate with the hollow portion 26 of the classification rotor 4. Further, a large number of blades 2 are provided in the cavity 27 around the opening of the balance rotor 18.
Zeros are radially provided, and a spiral casing 21 that surrounds the balance rotor 18 is integrally and airtightly attached to the casing 2 so as to surround the balance rotor 18. A collecting device such as a cyclone and a bag filter, a fan, and a blower, which are not shown, are connected to the spiral casing 21.

Next, the operation of the powder classifier 1 will be described.

First, the classifying rotor 4 and the balance rotor 18 are rotated at a predetermined speed by an electric motor (not shown),
An air flow is generated inside the powder classifier 1 by the suction action of the blower connected to the outside. As a result, the air that has flowed in from the air inlet 24 of the casing 2 is converted into a flow in the rotational direction by the auxiliary blade 12, enters the classification chamber 11 in a swirling state, and in the classification chamber 11, the classification blades 7 and 8 cause the classification rotor 4 to rotate. And the air passing through the balance rotor 18 flows into the cyclone through the spiral casing 21. Further, the air compressor is operated to send air into the air introduction path 6.

In this state, when the powder to be classified is charged through the powder charging port 23, the powder rides on the air flow from the powder charging port 23 and passes between the dispersing blades 16 while passing through the space between the dispersing blades 16. The powder is divided almost uniformly in the radial direction around the axis, and the powder is subjected to primary dispersion. The powder emerging from the end of the dispersion blade 16 is radiated in the radial direction of the arrangement circle of the dispersion blade 16 as the classification rotor 4 rotates, and the dispersion gap 28
Is secondarily dispersed within.

The sufficiently dispersed powder falls into a classification chamber 11 from a powder introduction port 10 provided in a ring shape on the outer peripheral portion of the classification rotor 4. At that time, since the partition plate 5 is formed in a circumferential shape outside the powder introduction port 10, the powder falls into the powder introduction port 10 and is further ejected from the air introduction passage 6 by the air. Since the atmospheric pressure on the outer peripheral side of the body introduction port 10 is increased, the powder is not carried over the partition plate 5 to the outer peripheral end of the classification rotor 4. Therefore, the powder does not enter the narrow gap with the casing 2 at the outer peripheral end of the classification rotor 4, and the classification accuracy is not deteriorated or adhered.

Then, each particle of the powder that has fallen into the classification chamber 11 is subjected to the centrifugal force due to the rotation of the classification rotor 4 and the drag force due to the air flow in the axial direction. The air is transported to the outside of the powder classifier 1 through the balance rotor 18 and the spiral casing 21 while riding on the air flow in the radial direction, and is collected by a collector such as a cyclone or a bag filter. On the other hand, coarse particles satisfying the relationship of centrifugal force> drag force are blown to the outer periphery of the classifying rotor 4 and taken out of the powder classifying machine 1 from the coarse powder taking-out port 14 while being air-sealed using a rotary valve or the like.

[0024]

EXAMPLES Next, experimental examples of the powder classifier 1 according to the present invention will be described.

The classifier used in the experiment has a classification rotor having an outer diameter of 15 cm and a classification rotor rotation speed of 10,000 rp.
m, the air volume of the blower was 2.5 m ³ / min, and a porous sintered metal was used for the air introduction path.

The classified powder is an epoxy-based powder coating having a median diameter of 5 μm, and the supply amount per hour is 1.0 kg / h,
The values were 1.7 kg / h, 2.5 kg / h, and 3.1 kg / h.

The air pressure from the air compressor is 0 kg.
f / cm ² (flow rate 0m ³ /min),0.5kgf/cm ² (flow rate 0.2
0m ³ /min),1.0kgf/cm ² (flow rate 0.41m ³ / min),
2kgf / cm ² (flow rate 0.83m ³ / min), 3kgf / cm ² (flow rate 1.23m ³ / min), 4kgf / cm ² (flow rate 1.64m ³ / mi)
n), 5 kgf / cm ² (flow rate 2.05 m ³ / min), and classification was performed for 10 minutes under each condition.

The results are shown in FIG. From this result, the classification operation was stopped due to the fusion of the powder at the conventional air pressure of 0 kgf / cm ² , but when the air pressure was 0.5 kgf / cm ² when the air was sent to the air introduction path. Except for the above, no fusion was observed. Further, as shown in FIG. 5, the classification accuracy k is
Improved between ^{0.5kgf / cm 2 ~1.0kgf / cm 2} , it was possible to obtain good results. The classification accuracy index is the particle diameter DP ₂₅ and the partial classification efficiency of 75, which correspond to the partial classification efficiency of 25%.
% Of particle size DP ₇₅ , ie DP ₂₅ / DP ₇₅
Is an index indicating that the closer to 1 the accuracy is.

[0029]

According to the present invention, the atmospheric pressure on the outer peripheral side of the powder introduction port is set higher than that of the powder introduction port, and the partition plate is provided outside the powder introduction port. The powder is not carried to the outer circumference of the powder introduction port, and all the powder falls inside the powder introduction port, which lowers the classification accuracy and reduces the powder in the gap between the casing and the classification rotor. Inconvenience such as sticking does not occur.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a powder classifier according to the present invention.

FIG. 2 is a partially cutaway plan view of the powder classifier shown in FIG.

FIG. 3 is a partially enlarged sectional view of the powder classifier according to the present invention.

FIG. 4 is a graph showing experimental results.

FIG. 5 is a graph showing experimental results.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder classifier 2 Casing 4 Classification rotor 5 Partition plate 6 Air introduction path 7 Outer classification blade 8 Inner classification blade 9 Porous member 10 Powder introduction port 11 Classification chamber 12 Auxiliary blade 14 Coarse powder extraction port 15 Vacancy 16 Dispersion Blade 17 Connection Port 18 Balance Rotor 20 Blade 21 Spiral Casing 23 Powder Inlet Port 24 Air Inlet Port 25 Bearing 26, 27 Cavity 28 Dispersion Gap 36 Rotation Shaft 37 Classification Blade Gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Okabe, inventor Hideo Okabe, 5-3-1 Tsurugaoka, Oi-cho, Iruma-gun, Saitama Nisshin Flour Milling Co., Ltd. (72) Hideyuki Iijima Oi-cho, Iruma-gun, Saitama Prefecture 5-3-1 Tsurugaoka Nisshin Flour Milling Co., Ltd. Production Technology Laboratory (72) Inventor Yukio Iwata 5-3-1 Tsurugaoka Tsurugaoka Iruma-gun Saitama Prefecture Nisshin Milling Co., Ltd.

Claims (4)

[Claims] 1. A powder classifier that rotatably includes a classifying rotor having a vertical rotation axis in a casing, and classifies powder by a balance between a centrifugal force generated by the rotation of the classifying rotor and an air flow in the classifying rotor. In the above, the classifying rotors are arranged in parallel in the vertical direction and have a diameter of 2
An air circulation cavity portion for circulating air from the circumference to the axial center direction is provided between the circular plates, and a plurality of classification blades are provided on the outer peripheral portion of the air circulation cavity portion, and powder that communicates with the classification blades. The powder introduced through the powder introduction port provided in the upper disk in the circumferential direction of the upper disc and in the upper center of the casing is dispersed in four directions on the upper surface of the classification rotor, and then the powder introduction It is formed so as to fall through the mouth into the air circulation cavity, and the casing is configured such that the air pressure of the conical portion between the powder introduction port and the outer peripheral end of the classification rotor is on the powder introduction port side. A powder classifier characterized by forming a high-pressure portion that is higher than atmospheric pressure. 2. The powder classifier according to claim 1, wherein a partition plate that partitions the powder introduction port and the outside of the powder introduction port is provided in a circumferential shape. 3. The partition plate is provided from the casing toward the classification rotor, and an air introduction path is formed outside the partition plate, and high pressure air is sent to the air introduction path to supply the powder introduction port. The powder classifier according to claim 1, wherein the atmospheric pressure in the radially outer peripheral portion is made higher than the atmospheric pressure on the powder introducing port side. 4. A porous member is provided in the air introduction passage,
The powder classifier according to any one of claims 1 to 3, wherein air is sent into the casing through the porous member.