JP3733349B2 - Airflow classifier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an airflow classifier that classifies powder into a plurality of classified products, in particular, a powder having an average particle size of about 4 to 10 μm into three classified products by air flow.
[0002]
[Prior art]
When powders such as glass, silicon carbide, and color toner are classified into various industrial raw materials using an airflow classifier, they must have a particle size within the required range excluding fine powder as well as so-called coarse powder. Is done. For example, silicon carbide or silicon nitride is mixed with resin and used as an abrasive. However, if fine powder is mixed, the polishing performance is lowered, and the toner is melted by heat and adheres to paper, but the fine powder is mixed. If it is, the fine powder will melt first, and the letters will become unclear.
[0003]
For this reason, those powders are classified into medium powder having a particle size within the above-mentioned required range, coarse powder having a larger diameter, and fine powder having a smaller diameter than that, and the medium powder is used as a product. As the classification method, the simplest method is to arrange two airflow classifiers in series and classify the powder into coarse powder and other powders with the first classifier, and then classify the next classifier. The other powder is classified into medium powder and fine powder.
[0004]
In general, airflow classification is a method in which powder is sent together with an air stream to a rotating classification blade, and the powder is spun off by the classification blade, and the classification efficiency (accuracy) is higher as the powder has a higher mass. For this reason, for example, when classifying into coarse powder, medium powder, and fine powder, the classification accuracy decreases as the latter side is reached. Moreover, since the ratio (solid-gas ratio) between the powder and the air flow is more likely to be splashed off by the classification blade as the amount of the powder is smaller, the classification accuracy is higher. That is, the smaller the solid-gas ratio, the higher the classification accuracy.
[0005]
For this reason, the method using the above two classifiers has good classification accuracy and can easily change the classification point, but there is a problem that the installation space becomes large because two classifiers are used. For this reason, it has been proposed to provide a plurality of classification rotors in one classifier and classify the powder into three types.
[0006]
For example, as shown in FIG. 6, when classifying rotors 25 and 26 are provided vertically in casings 23 and 24 that can be divided into two parts, and powder a is introduced into the casing from powder inlet 27, this powder a Among these, the fine powder a ₃ passes through the upper classification rotor 25, the medium powder a ₂ passes through the lower classification rotor 26, and the coarse powder a _{1 that} does not pass through both the classification rotors 25, 26 is The gas is discharged from the outlet short pipe 28 below the casing 24 (see Patent Document 1).
[0007]
[Patent Literature]
Japanese Patent Laid-Open No. 2001-293438
[Problems to be solved by the invention]
However, the above prior art first removes the finest (lighter) fine powder a ₃ in the upper classification chamber (classification rotor 25), which has a high solid-gas ratio and poor classification accuracy. It is bad. The powder from which the fine powder a ₃ has been removed by the upper classification rotor 25 is further classified by the lower classification rotor 26, but the outer sides of the upper and lower classification rotors 25, 26 are in communication with each other. The concentration and the particle size distribution affect each of the classification rotors 25 and 26. For this reason, the fine powder a ₃ cannot be reliably separated by the upper classification rotor 25 and the middle powder by the lower classification rotor 26, and the classification accuracy is poor.
[0009]
This invention makes it a subject to be able to classify from coarse powder to fine powder in order, such as coarse powder, medium powder, and fine powder, in one casing.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a plurality of classification rotors in a casing, allows powder raw materials to pass through each of the classification rotors one after another, and the coarse powders are obtained by the classification rotors in the passing order. In order to classify from fine powder to fine powder.
[0011]
Specifically, a plurality of classifying rotors are provided in order in a cylindrical casing closed at both ends, with the rotational axis centered on the cylindrical axis of the casing, and each classifying rotor is partitioned by a partition wall in the casing. A plurality of classification chambers are formed, a raw material input port is provided at one end of the casing, an intake port is provided at the other end, a powder discharge port is provided on the side of the casing facing each classification rotor, and the partition wall Forms a hole that connects the classification rotor in the previous classification chamber on the raw material input side to the classification chamber in the next stage, and feeds the raw material into the casing from the raw material input port, and sucks in the air from the intake port to input the raw material. Mouth, classification chamber, classification rotor, next-stage classification chamber, classification rotor, air flow is formed as an intake port, and fine powder is classified in order by each classification rotor along the air flow. Like Than it was.
[0012]
The classification degree adjustment is performed by controlling the rotation speed of the classification rotor, and each classification rotor is rotated by an individual driving machine or rotated by one driving machine via a transmission to control the rotation speed. .
[0013]
As in the past, it is preferable to send secondary air for classification into each classification chamber. For example, a secondary air chamber for classification is formed around the entire casing wall around the classification rotor. The classification rotor communicates with the entire circumference of the peripheral wall of the secondary air chamber through holes provided at equal intervals, and secondary air is sent from each hole toward the classification rotor.
[0014]
Further, secondary air can be ejected from the periphery of the hole communicating with the classification chambers before and after the partition wall toward the outside of the previous classification rotor (see the ejection port 10a and the annular slit 16 in the embodiment). . In this way, the blown air plays the role of separating the air curtain between the front and rear classification chambers and the coarse and fine zones of the powder, and exhibits a sealing effect.
[0015]
Furthermore, if the classifying rotor is provided with dispersing blades that rotate together with the rotor to disperse the powder before classification, the classification effect is increased. At this time, if the classifying rotor is such that classifying blades are provided radially between a pair of parallelly spaced discs, the dispersing blades are provided on the surface of the disc.
[0016]
In the classifier having the above-described configuration, since there are a plurality of classifying rotors, classification can be performed at least in three stages. In the case of the three stages (coarse powder, medium powder, fine powder), the classification chamber has 2 The coarse powder is classified in the preceding classification chamber, the medium powder is classified in the subsequent classification chamber, and the fine powder is taken out together with the intake air from the intake port.
[0017]
Embodiment
1 and 2 show an embodiment, in which 1 is a casing, which is divided into an upper partial chamber 1a, a lower partial chamber 1b, and a fine powder discharge chamber 1c by annular partition plates 2a and 2b. Yes. In the casing 1, two classification rotors 3a and 3b are provided up and down, and each is rotated by motors 4a and 4b provided outside the casing 1. In addition, a powder supply port 12 is provided in the upper partial chamber 1a. The rotational directions of both rotors 3 may be opposite, but the same direction is desirable.
[0018]
Each of the classification rotors 3a and 3b includes a top plate 5 and a bottom plate 6 which are separated in parallel, and a plurality of circumferential radial blades 7 sandwiched therebetween, and are connected to the motors 4a and 4b by a rotating shaft 8. ing. Further, the bottom plate 6 is formed with a through-hole 20 through which powder passes, and the outer edge portion thereof rotates close to the inner edge portion of the through-hole 21 of the partition plate 2.
[0019]
An annular passage 10 for sealing air is formed in the partition plates 2a and 2b, and air b is ejected through the annular passage 10 through a plurality of jet outlets 10a provided at equal intervals around the annular passage 10 and the partition plates 2a and 2b. Intrusion of powder from the gap between the base plate 6 and the bottom plate 6 is prevented. In general, since the coarse powder a ₁ is splashed by the classification blade 7, it does not move to the lower classification chamber 1 b through the holes 20 and 21, but enters through a short path from the gap between the partition plates 2 a and 2 b and the bottom plate 6. There is a fear. However, the short path is prevented by the ejection of the air b from the ejection port 10a.
[0020]
An annular partition wall 9 is provided in both the classification chambers 1a and 1b, and an annular space formed by the partition wall 9 and the inner surface of the casing 1 is used as secondary air introduction chambers 11a and 11b. The secondary air introduction chambers 11a and 11b are provided with an air inlet 15 and powder outlet pipes 13a and 13b, and the fine powder discharge chamber 1c is provided with a fine powder outlet pipe 13c. A plurality of vertical slits (holes) 14 are formed at equal intervals around the annular partition wall 9 at the position facing the classifying blades 7, and the secondary air b is uniformly introduced into the entire circumference of the classifying chambers 1a and 1b from the slits 14. Is done. For this reason, the introduction air b is uniformly ejected from the slit 14 to the classification rotors 3a and 3b. Thereby, there is little disturbance of the air current around the classification rotors 3a and 3b, and the classification accuracy is good.
[0021]
Next, the operation will be described. The air exhaust device F connected to the fine powder outlet pipe 13c is started, and the powder a is introduced together with air from the powder supply port 12. Of the powder a, the coarse powder a ₁ is splashed by the classification blade 7a that rotates at a high speed in the upper partial chamber 1a, rotates inside the partition wall 9, and has a large opening formed in the partition wall 9. 17 and the cylindrical lead-out path 17a are discharged from the coarse powder outlet pipe 13a.
[0022]
The intermediate powder a ₂ and fine powder a ₃ that have passed through the classification blade 7a of the upper partial chamber 1a are transferred to the lower partial chamber 1b through the hole 20 of the bottom plate 6 and the hole 21 of the partition plate 2a of the classification rotor 3a. The In its lower part classifying chamber 1b, the medium powder a _2, which classifying blades 7b bouncing skipped in the opening 17, is discharged from the intermediate powder outlet tube 13b through the outlet passage 17a. The fine powder a _{3 that} has passed through the classification blade 7 b enters the fine powder discharge chamber 1 c, is discharged from the fine powder outlet pipe 13 c together with air, and is captured by the collector 30.
[0023]
In this classification, since the coarse powder a ₁ is first separated, the solid-gas ratio in the lower partial classification chamber 1b is lowered, and the classification accuracy of the fine powder a ₃ is good. Further, since there is no coarse a ₁ on the lower portion classifying chamber 1b, the powder a ₂ is improved dispersibility easily classified accuracy. Further, since the coarse powder a ₁ and the medium powder a ₂ are dispersed and classified, wear of the airflow classifier based on the coarse powder a _{1 and the} like is reduced. Moreover, since the classification chambers 1a and 1b are partitioned by the partition plate 2a, it is easy to adjust the powder concentration in each of the classification chambers 1a and 1b. Further, since the upper and lower classification chambers 1a and 1b are not directly connected, there is no possibility that the coarse powder a ₁ is mixed into the lower partial classification chamber 7b.
[0024]
3 to 5 show another embodiment. In this embodiment, first, the secondary air b is drawn from the gap (annular slit 16) between the outer edge of the bottom plate 6 of the classification rotor and the inner edges of the partition plates 2a and 2b. It is a eruption. This secondary air b also acts as sealing air. In general, in the classification chamber, the air flow velocity around the classification rotor is large, and the flow velocity decreases as it approaches the partition wall 9 of the casing 1. That is, there are many fine powders around the classification rotor 3, and there are many coarse powders around the partition wall 9 away from the classification rotor 3. For this reason, if secondary air is introduced from the annular slit 16 between the two, it becomes easy to separate into a fine powder zone and a coarse powder zone, and only fine powder enters the classification rotor. Cheap. At this time, as shown in FIG. 5, the position L2 of the annular slit 16 is desirably about half (40 to 60%) of L1, and if close to the center position, a fine powder zone and a coarse powder zone It becomes easier to separate.
[0025]
Furthermore, it has established a dispersion blade 18 in the classifying rotor, in the opposite dispersion blade 18, the upper and lower dispersion rotor 3a, the relative velocity effect of 3b, to prevent aggregation of fine powder a _3. At this time, the secondary air b is introduced into the classification chambers 1a and 1b mainly through the annular slit 16 and supplementarily through the vertical slit 14. It is not necessary to introduce the secondary air b from the vertical slit 14.
[0026]
In each embodiment, the classifying rotors 3a and 3b have two stages, but it is needless to say that the present invention can be adopted even with three or more stages.
[0027]
【The invention's effect】
According to the present invention, as described above, classification is performed in order from coarse powder to fine powder in one casing, so that the classification accuracy is high.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of one embodiment. FIG. 2 is a plan view of the same. FIG. 3 is a schematic cross-sectional view of another embodiment. Cut front view [Fig. 6] Schematic sectional view of conventional example [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Casing 1a Upper partial chamber 1b Lower partial chamber 1c Fine powder discharge chamber 2a, 2b Partition plate 3a, 3b Classification rotor 4a, 4b Motor 5 Top plate 6 Bottom plate 7, 7a, 7b Classification blade 8 Rotating shaft 9 Partition wall 10 Ring Paths 11a, 11b Secondary air introduction chamber 12 Powder supply port 13a Coarse powder outlet pipe 13b Medium powder outlet pipe 13c Fine powder outlet pipe 14 Slit (hole)
15 Secondary air inlet 16 Annular slit 18 Dispersion blade 20, 21 Through hole a Raw material a ₁ Coarse powder a ₂ Medium powder a ₃ Fine powder b Air

Claims (6)

A plurality of classifying rotors (3a, 3b) are arranged in the vertical direction so that the rotation axis is on the cylindrical axis of the casing (1) in the cylindrical casing (1) with both ends closed and the cylindrical axis in the vertical direction. Each classification rotor is partitioned by a partition wall (2) to form a plurality of classification chambers (1a, 1b) in the casing (1), and one end of the casing (1) A raw material input port (12) communicating with the classification chamber (1a), an intake port (13c) communicating with the lowermost classification chamber at the other end, and a casing (1) facing each classification rotor (3a, 3b) Powder discharge ports (13a, 13b) are provided on the side surfaces, respectively , and the partition wall (2) includes an inside of a classification rotor (3a) in a previous classification chamber (1a) on the raw material input port (12) side. Form holes (20, 21) that communicate with the next-stage classification chamber (1b) Then, the raw material (a) is fed into the casing (1) from the raw material inlet (12), and sucked from the inlet (13c), and then the raw material inlet (12), the classification chamber (1a), the classification rotor (3a) In the next classification chamber (1b) ... Finally, an air flow called an inlet (13c) is formed, and these are arranged in the order of coarse powder to fine powder along the air flow. Airflow classifier that takes out and classifies.   An annular partition wall (9) is provided around the classification rotor (3a, 3b), and a secondary air chamber for classification is formed by an annular space formed by the annular partition wall (9) and the inner surface of the casing (1). The secondary air chamber and the classification rotor communicate with each other through holes (14) provided at equal intervals on the entire circumference of the annular partition wall (9), and the secondary air chambers are directed from the holes (14) toward the classification rotor. 2. The airflow classifier according to claim 1, wherein air is fed. Secondary from the circumference of the holes (20 , 21 ) communicating the classification rotor (3a) in the previous classification chamber (1a) and the classification chamber (1b) in the next stage toward the outside of the classification rotor (3a) in the previous stage The airflow classifier according to claim 1 or 2, wherein air is jetted out.   Dispersion blades (18) co-rotating with the rotor are provided on the outer surface of the classification rotor, and the powder entering the classification rotor is dispersed by the dispersion blades (18). 4. The airflow classifier according to any one of 3.   The classifying rotor has classifying blades (7) extending radially between a pair of parallelly separated discs (5, 6), and the dispersing blades are arranged on the outer surface of the discs (5, 6). The airflow classifier according to claim 4, further comprising (18). The classification chambers are two chambers (1a, 1b), the coarse powder (a ₁ ) is taken out from the powder discharge port (13a) of the previous classification chamber (1a), and the powder discharge port of the subsequent classification chamber (1b). The airflow type classification according to any one of claims 1 to 5, wherein medium powder (a ₂ ) is taken out from (13b), and fine powder (a ₃ ) is taken out together with intake air from an air inlet (13c). Machine.

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