JP3625554B2 - Powder classifier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder classifier that includes a rotatable classification rotor in a casing and classifies powder using centrifugal force and air flow, and in particular, controls the flow of powder at the periphery of the classification rotor. The present invention relates to a powder classifier that improves classification accuracy and prevents powder clogging and sticking.
[0002]
[Prior art]
A classifier as disclosed in Japanese Patent Publication No. 6-61535 is known as one of powder classifiers that include a classifying rotor and classify powder using the rotation of the classifying rotor and air flow. This classifier rotates a classification rotor provided with a large number of classification blades around it at high speed in the casing, forms an air flow from the periphery to the center in the classification rotor, and generates an air flow and rotational centrifugal force on the powder. Is used to select powders at the desired reference value.
[0003]
Specifically, as described above, a plurality of classification blades are provided inside the outer peripheral portion of the classification rotor, an air introduction path is formed inside, and the powder falls on the classification blade portion on the upper outer periphery of the classification rotor. The powder inlet is formed along the circumference, while the casing is provided with a powder inlet at the center of the upper part, and the powder introduced from the powder inlet is placed on the upper surface of the classification rotor. While being dispersed in all directions, the powder enters the classification blade in the classification rotor, that is, the classification chamber from the powder inlet. The powder entering 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 in the internal direction of the classification rotor. Coarse powder collection that is carried to the center by the air flow and taken out from the fine powder extraction outlet provided in the central part, and is blown out of the classification rotor by centrifugal force, and receives large centrifugal force. The powder is collected at the outlet, and the powder is classified at a predetermined particle size.
[0004]
[Problems to be solved by the invention]
However, in the conventional powder classifier, all of the charged powder does not fall into the powder inlet, and is sometimes conveyed toward the outer end of the classification rotor. Then, since the powder enters the classification chamber from the outer periphery of the classification rotor, classification is not performed accurately in the classification chamber, and classification accuracy such as fine powder is included on the coarse powder side or coarse powder is classified on the fine powder side. There was a problem that decreased. In addition, the gap between the classification rotor and the casing is originally narrow because it is necessary to maintain airtightness, and since a labyrinth structure is adopted, if powder enters this gap, the powder becomes hard and clogs. Furthermore, when a powder having melting properties such as a resin material is classified, if the powder flows into this part, the powder is melted by frictional heat due to the rotation of the classification rotor and fixed in the gap, and the rotation of the classification rotor is performed. Defects may occur.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is provided with a classification rotor having a vertical rotation shaft in a casing so as to be rotatable, and powder is distributed by balancing the centrifugal force generated by the rotation of the classification rotor and the air flow in the classification rotor. In the powder classifier that classifies,
The classification rotor includes an air circulation cavity that circulates air from the circumference toward the axial center between two disks having substantially the same diameter arranged in parallel in the vertical direction, and an outer peripheral portion of the air circulation cavity A plurality of classification blades are provided, a powder introduction port communicating with the classification blades is arranged circumferentially on the upper disk, and the powder charged from the powder injection port provided in the upper center of the casing is After being dispersed in all directions on the upper surface of the classification rotor, it is formed so as to fall into the air circulation cavity through the powder inlet,
The casing is configured with a high-pressure portion in which a pressure in a return-shaped portion between the powder inlet and the outer peripheral end of the classification rotor is made higher than an air pressure in the powder inlet. did. Therefore, when high pressure air is sent to an air introduction path formed by providing a groove in the high pressure portion, for example, the inner portion of the casing, and air is blown out around the powder introduction port to increase the atmospheric pressure, the powder becomes the powder introduction port. Almost all the powder can be dropped into the powder introduction port without being conveyed outward.
[0006]
Further, a powder classifier was configured by providing a powder introduction port and a partition plate that divides the outside from the powder introduction port in a circumferential shape. The partition plate is provided along the outer periphery of the powder inlet and holds a predetermined amount of the opening area of the powder inlet. As a result, the powder charged from the central inlet smoothly falls into the powder inlet. 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 end of the powder inlet of the classification rotor.
[0007]
A partition plate is provided from the casing toward the classification rotor, and an air introduction path is formed in a ring shape outside the partition plate, high-pressure air is sent to the air introduction path, and the radial direction from the powder introduction port A powder classifier was constructed by increasing the air pressure in the outer peripheral portion above the air pressure in the powder inlet. The air introduction path has a surface facing the rotor as a porous member, and air is sent into the casing through the porous member.
[0008]
If it does in this way, high pressure air can be ejected uniformly along a circumference, and pressure can be applied uniformly. Furthermore, instead of a porous member, a large number of nozzles may be arranged circumferentially, or a slit-like gap may be opened in the direction of the rotor to uniformly blow out air.
[0009]
According to such a powder classifier, when powder is introduced into the powder classifier from the powder inlet, the powder is dispersed around the upper surface of the classification rotor and classified from the powder inlet on the upper surface of the classification rotor. It falls into the rotor. At that time, a partition plate is provided outside the powder inlet, and air is sent to the outer periphery of the partition plate to increase the pressure from the inside of the powder inlet. Therefore, the classification accuracy is not lowered and powder clogging between the classification rotor and the casing does not occur.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a powder classifier according to the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a cross-sectional view of the powder classifier 1, and FIG. 2 is a plan view of the powder classifier 1 with a part of the classifying rotor 4 cut away.
[0012]
First, it demonstrates using FIG.
[0013]
The classifier 1 includes a casing 2 and a classifying rotor 4 housed in the casing 2 so as to be rotatable. A powder supply device connected to a powder supply device (not shown) is connected to the center of the upper surface of the casing 2. An opening 23 is formed on the side and an air inlet 24 is formed on the side. The casing 2 has a circular shape as a whole, and a partition plate 5, an air introduction path 6 and the like are provided therein as shown in FIG.
[0014]
The partition plate 5 is provided in a circumferential shape near the outer periphery of the casing 2, and a tip portion thereof is located outside a 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 the same manner as the partition plate 5 and is connected to an air compressor (not shown) via the connection port 17. Further, a porous member 9 having fine holes is attached below the air introduction path 6, and the air sent from the air compressor is jetted into the casing 2 through the porous member 9.
[0015]
The classifying rotor 4 has a disk shape in which two disks (upper plate 4a and lower plate 4b) are vertically combined, and includes a hollow portion 26 that communicates from the outer peripheral portion to the lower portion of the axial center. It is fixed to the upper end of a rotary shaft 36 that is vertically attached to the center by bearings 25 and 25.
[0016]
In the cavity portion 26 of the classification rotor 4, as shown in FIG. 2, the outer classification blades 7 and the inner classification blades 8 are radially arranged at equal intervals along the circumference. 11 is formed. In the upper plate 4a of the classification rotor 4, a powder inlet 10 that communicates with the classification chamber 11 is formed in a ring shape so as to face the classification blade gap 37 between the outer classification blade 7 and the inner classification blade 8. It is. A large number of auxiliary blades 12 are radially arranged at equal intervals on the lower surface of the lower plate 4b of the classifying rotor 4. When the classifying rotor 4 rotates, the auxiliary blades 12 give the air a flow in the rotational direction. Air is introduced in the state of swirling air toward the classification chamber 11.
[0017]
Reference numeral 15 denotes a space formed between the upper plate 4 a of the classification rotor 4 and the top plate of the casing 2, and communicates the powder inlet 23 with the powder inlet 10 of the classification rotor 4. In this void 15, a large number of powder dispersion blades 16 extending radially from the axial center to the center of the upper plate 4 a of the classification rotor 4 are provided radially, and the radial ends of the dispersion blades 16 and the powder The upper plate 4a between the body inlets 10 is flattened to continuously form a dispersion gap 28 for secondary dispersion of the powder.
[0018]
18 is a disk-shaped balance rotor having a hollow portion 27 that communicates from the circumferential portion to the shaft center portion in substantially the same manner as the classification rotor 4. The balance rotor 18 is symmetric with respect to the classification rotor 4 and is empty. The body 27 is integrally fixed to the rotary shaft 36 in the casing 2 so as to communicate with the cavity 26 of the classifying rotor 4. Further, a large number of blades 20 are provided radially in the cavity portion 27 at the peripheral edge of the opening of the balance rotor 18, and a spiral casing 21 surrounding the balance rotor 18 is provided around the outer periphery of the opening of the balance rotor 18. It is attached to the unit in an airtight manner. The spiral casing 21 is connected to a collecting device such as a cyclone and a bag filter (not shown), a fan, a blower, and the like.
[0019]
Next, the operation of the powder classifier 1 will be described.
[0020]
First, the classifying rotor 4 and the balance rotor 18 are rotated at a predetermined speed by an electric motor (not shown), and an air flow is generated inside the powder classifier 1 by the suction action of a blower connected to the outside. As a result, the air flowing in from the air inlet 24 of the casing 2 is converted into a flow in the rotational direction by the auxiliary blades 12, enters the classification chamber 11 in a swirled state, and in the classification chamber 11 by the classification blades 7 and 8, the classification rotor 4. The air passing through the balance rotor 18 flows into the cyclone via the spiral casing 21. Further, the air compressor is operated to send air into the air introduction path 6.
[0021]
When the powder to be classified in this state is charged from the powder inlet 23, the powder rides on the air flow from the powder inlet 23 and moves the axis of the classification rotor 4 while passing between the dispersion blades 16. The powder is divided almost uniformly in the center radial direction, and primary dispersion of the powder is performed. The powder coming out from the end of the dispersion blade 16 is radiated almost in the radial direction of the array circle of the dispersion blades 16 as the classification rotor 4 rotates, and is secondarily dispersed in the dispersion gap 28.
[0022]
The sufficiently dispersed powder falls into the classification chamber 11 from the powder inlet 10 provided in a ring shape on the outer periphery of the classification rotor 4. At that time, since the partition plate 5 is formed in a circumferential shape outside the powder inlet 10, the powder falls into the powder inlet 10 and is further blown out by the air blown out from the air introduction path 6. Since the air pressure on the outer peripheral side of the body introduction port 10 is increased, the powder does not go over the partition plate 5 to the outer peripheral end of the classification rotor 4. Therefore, the powder does not enter a narrow gap with the casing 2 at the outer peripheral end of the classification rotor 4, so that the classification accuracy is not deteriorated or fixed.
[0023]
Each particle of the powder falling into the classification chamber 11 is subjected to a centrifugal force due to the rotation of the classification rotor 4 and a drag due to the air flow in the axial direction, and fine particles satisfying the relationship of centrifugal force <drag are in the radial direction. The air is transported to the outside of the powder classifier 1 through the balance rotor 18 and the spiral casing 21 while being in an air flow, 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 are blown to the outer periphery of the classification rotor 4 and are taken out of the powder classifier 1 from the coarse powder outlet 14 in an air-sealed state using a rotary valve or the like.
[0024]
【Example】
Next, an experimental example of the powder classifier 1 according to the present invention will be described.
[0025]
The classifier used in the experiment has an outer diameter of the classification rotor of 15 cm, the rotation speed of the classification rotor is 10,000 rpm, the air volume of the blower is 2.5 m ³ / min, and a porous sintered metal is used for the air introduction path. It was.
[0026]
The classified powder was an epoxy-based powder paint having a median diameter of 5 μm, and the supply amount per hour was 1.0 kg / h, 1.7 kg / h, 2.5 kg / h, 3.1 kg / h. .
[0027]
The air sent from the air compressor, the air pressure 0 kgf / cm ² (flow rate ^0m 3 ^{/min),0.5kgf/cm 2} (flow rate 0.20m ³ /min),1.0kgf/cm ² (flow rate 0.41m ³ / min), 2 kgf / cm ² (flow rate 0.83 m ³ / min), 3 kgf / cm ² (flow rate 1.23 m ³ / min), 4 kgf / cm ² (flow rate 1.64 m ³ / min), 5 kgf / cm ² (flow rate 2.05 m ³ / min), and classification was performed for 10 minutes under each condition.
[0028]
The results are shown in FIG. From this result, although the classification operation stopped due to powder fusion at the conventional air pressure of 0 kgf / cm ² , the case where the air pressure was 0.5 kgf / cm ² when the air was fed into the air introduction path. Except for the fusion, there was no occurrence. Furthermore, classification accuracy k as shown in Figure ^5, improves between ^{0.5kgf / cm 2 ~1.0kgf / cm 2} , it was possible to obtain good results. The classification accuracy index is a ratio of the particle size DP ₂₅ corresponding to the partial classification efficiency of 25% to the particle size DP ₇₅ corresponding to the partial classification efficiency of 75%, that is, DP ₂₅ / DP _75. An index that represents good things.
[0029]
【The invention's effect】
According to the present invention, since the air pressure on the outer peripheral side of the powder inlet is higher than that of the powder inlet, and the partition plate is provided outside the powder inlet, the powder introduced into the powder inlet is Without being carried to the outer periphery of the powder inlet, all powder falls into the powder inlet and the classification accuracy is lowered, or the powder is fixed in the gap between the casing and the classification rotor, etc. Inconvenience 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 plan view showing a part of the powder classifier shown in FIG.
FIG. 3 is a partially enlarged cross-sectional view of a 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 inlet 11 Classification chamber 12 Auxiliary blade 14 Coarse powder outlet 15 Space 16 Dispersion blade 17 Connection port 18 Balance rotor 20 Blade 21 Spiral casing 23 Powder inlet 24 Air introduction port 25 Bearings 26 and 27 Cavity 28 Dispersion gap 36 Rotating shaft 37 Classification blade gap

Claims (4)

In a powder classifier that comprises a classification rotor having a vertical rotating shaft in a casing so as to be rotatable, and classifies powder by balancing the centrifugal force generated by the rotation of the classification rotor and the air flow in the classification rotor.
The classification rotor includes an air circulation cavity that circulates air from the circumference toward the axial center between two disks having substantially the same diameter arranged in parallel in the vertical direction, and an outer peripheral portion of the air circulation cavity A plurality of classification blades are provided in the powder, and a powder introduction port communicating with the classification blades is circumferentially formed in the upper disk, and a powder charged from a powder injection port provided at an upper center of the casing is the classification. After being dispersed in all directions on the upper surface of the rotor, it is formed so as to fall into the air circulation cavity through the powder inlet,
The powder classification is characterized in that the casing is formed with a high-pressure portion that makes the pressure of the annular portion between the powder inlet and the outer peripheral end of the classification rotor higher than the pressure of the powder inlet. Machine. A partition plate that partitions the powder introduction port and the outside from the powder introduction port is provided so as to extend from the upper part of the casing toward the classification rotor and in a circumferential shape. Item 2. A powder classifier according to Item 1. An air introduction path is formed on the outside of the partition plate at the upper part of the casing , high-pressure air is sent to the air introduction path, and an annular portion between the powder introduction port and the classification rotor outer peripheral end is formed . The powder classifier according to claim 1 or 2 , wherein the air pressure is higher than the air pressure at the powder inlet. The powder classifier according to any one of claims 1 to 3, wherein a porous member is provided in the air introduction path, and air is sent into the casing through the porous member.

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