JP3388610B2 - Powder classifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder classifier, and more particularly to a powder classifier which prevents powder particles from adhering to a classifying blade.

[0002]

2. Description of the Related Art A powder classifier is used to select powders having a certain particle size or less from powders having various particle sizes and to separate powders having a narrow particle size distribution width.

Although there are various types of classifiers utilizing the air flow, for example, a classifying rotor equipped with classifying blades is provided, and the classifying rotor is rotated at a high speed and a centrifugal force is applied to the powder by a rotor. There is a method of classifying the powder by utilizing the balance between the force and the drag force caused by the air flow introduced from the periphery of the rotor.

By the way, in this type of powder classifier, a radial blade whose direction of the classifying blade is directed to the center of the classifying rotor is the mainstream (for example, Japanese Patent Publication No. 57-11269), but thereafter, the direction of the classifying blade is the classifying rotor. A tilted blade that is offset from the center of the blade by a certain angle has been proposed (Japanese Patent Publication No. 4-62).
794). The use of the classification rotor having the inclined blade has an advantage that the classification point becomes small even at low speed.

[0005]

However, the present inventors have found that when particles having adhesiveness are classified with a powder classifier having an inclined blade of this kind, the powder particles tend to adhere to the inside of the blade. I realized that there is. This phenomenon has been confirmed experimentally.

When this phenomenon is observed in detail, it is recognized that the particles that have jumped inward from the classification chamber collide with the inside of the blade in order to enter the other classification chamber again. This is because the air velocity in the circumferential direction of the air is faster than that of the radial vane because the vanes are inclined inside the classification vane, and therefore particles are accelerated in the circumferential direction and collide with the inside of the vane. Conceivable.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a powder classifier which does not adhere to the inside of the blade even when the powder particles having adhesion are classified.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a large number of classification blades formed in a classification chamber in the circumferential portion of a classification rotor and extending in a radial direction.
Fold the blade and the end of the radial blade on the outer edge of the disk.
Toward the outer edge of the curved disc with respect to the rotation direction of the classification rotor
Formed by connecting with inclined blades that extend so as to retract
I decided to do it.

[0009]

With the above construction, the powder particles that have flown out of the classification chamber do not swirl over a long distance because the radial flow velocity of the classification blade suppresses the flow velocity in the circumferential direction.
As a result, even adherent powder particles will not adhere to the inside of the classification blade, that is, the radial direction blade section.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of a powder classifier according to the present invention with a part of a classification rotor cut away, and FIG. 2 is a vertical sectional view of the powder classifier.

First, referring to FIG. 2, reference numeral 1 denotes a powder feeding port 2a which is connected to a powder feeding device (not shown) at the center of the upper surface.
And a disk-shaped casing having an air inlet 2b on its peripheral side, the casing 1 having a circumferential portion and a cavity portion 3 communicating from the circumferential portion to a lower portion of the axial center portion. The classifying rotor 4 is arranged, and the classifying rotor 4 is integrally fixed to the upper end of a rotary shaft 6 which is vertically attached by bearings 5 and 5 to the axial center of the casing 1 in the vertical direction. Further, as shown in FIG. 1, a large number of classification blades 7 each having a radial blade portion 7a on the inner side and an inclined blade portion 7b on the outer side are arranged on the circumferential portion of the open peripheral edge portion of the classification rotor 4. A ring-shaped powder introduction port 10 communicating with the classification chamber 11 is formed in the upper plate 4a of the classification rotor 4 facing the specific point a (see FIG. 3) of the inclined blade portion 7b of the classification blade 7. With such a classifying blade structure, a classifying chamber 11 having a wide forced vortex corresponding to the coarse powder side and the fine powder side is formed in the classifying blade 7.

On the lower surface of the classification rotor 4 facing the classification blade 7, a large number of auxiliary blades 12 are arranged at equal intervals so as to intersect with the radial direction. A flow in the direction of rotation is applied to the air, and the air is introduced into the classification chamber 11 in a swirled state. Reference numeral 13 denotes a void formed on the outer periphery of the classification rotor 4, and a coarse powder outlet 14 communicating with the void 13 is formed in the casing 1.

FIG. 3 shows two classification blades 7 of the classification rotor 4.
Is shown enlarged.

The angle φ formed by the inclined blade portion 7b of the classification blade 7 with the radial direction is 20 to 70. It is good to choose in the range of
Especially 45. The front and back are the most effective. This angle φ is 2
0. Below, the effect of providing the inclined blade portion 7a is not so great and 70. If it exceeds the range, the dispersibility of the powder to be supplied deteriorates.

Returning to FIG. 2 again, 15 is a powder charging port 2a formed between the upper plate 4a of the classification rotor 4 and the lower surface of the upper plate of the casing 1 and the ring-shaped powder introduction opening 10 of the classification rotor 4. A large number of powder dispersion blades 16 extending in the outer peripheral direction from the axial center portion are radially provided on the central side of the upper plate 4a of the classification rotor 4 located in the empty space 15 and The upper plate 4a of the classification rotor 4 between the radial ends of the dispersion blades 16 and the ring-shaped powder introduction opening 10 is flattened, and the flat surface and the casing 1 facing it.
A dispersion gap 17 for secondarily dispersing the powder is formed between the inner surfaces of the.

Numeral 18 is a disk-shaped balance rotor having a cavity portion 19 which communicates from the circumferential portion to the axial center portion in the same manner as the classification rotor 4, and the balance rotor 18 is arranged symmetrically with the classification rotor 4. In addition, the cavity portion 19 is integrally fixed to the rotating shaft 6 in the casing 1 so that the cavity portion 19 communicates with the cavity portion 3 of the classification rotor 4, and the cavity portion 19 in the opening peripheral edge portion of the balance rotor 18 is A lot of feathers 20
Are radially provided, and a spiral casing 21 surrounding the opening of the balance rotor 18 is attached to the casing 1 integrally and secretly. In addition, a collecting device such as a cyclone and a bag filter and a fan (not shown) are provided in the spiral casing 21.
Blower etc. are connected.

Next, the operation of the powder classifier thus constructed will be described.

First, the classifying rotor 4 and the balance rotor 18 are rotated at a desired speed by an electric motor (not shown),
A negative pressure air flow is generated inside the classifier by the suction action of the balance rotor 18 and a blower connected to the outside. Along with this, the air flowing in from the air inlet 2b of the casing 1 is converted into a flow in the rotational direction by the auxiliary blade 12, enters the classification chamber 11 from the void 13 in a swirling state, and then the classification blade 7 in the classification chamber 11. As a result, an air flow having the same peripheral speed as the classification rotor 4 is produced. At the same time, since air is sucked by the balance rotor 18 and the blower in the classifying chamber 11, the air on the circumferential surface of the classifying chamber 11 flows in the radial direction. The air passing through the balance rotor 18 is connected to the cyclone blower via the spiral casing 21. The flow of air at this time is shown by an arrow in FIG.

In this state, the powder raw material charged from the powder charging port 2a rides on the air flow, and while passing between the dispersing blades 16, it is substantially uniform in the radial direction around the axis of the classification rotor 4. It is divided and the primary dispersion of the powder is performed. The powder emerging from the end of the dispersion blade 16 is radiated in the tangential direction of the dispersion blade array circle as the classification rotor 4 rotates, and is secondarily dispersed in the dispersion gap 17.

The powder which has been sufficiently dispersed by the above operation is supplied to the classification chamber 11 through the ring-shaped powder introduction opening 10. Here, each particle of the powder is rotated by centrifugal force and radial flow. Receive a resistance by. Of these particles, the coarse particles satisfying the relationship of centrifugal force> drag force are blown into the space 13 around the outer periphery of the classification rotor 4, and are air-sealed from the coarse powder outlet 14 by using a rotary valve or the like and outside the classifier. Taken out. Further, the fine particles for which the relationship of centrifugal force <drag is established are pneumatically transported to the outside of the classifier through the balance rotor 18 and the spiral casing 21 while being carried by the airflow in the radial direction, and are collected by a collector such as a cyclone or a bag filter. To be collected.

Now, the operation of the classification blade will be considered.

In FIG. 3, the distance from the center O of the classification rotor 4 to the bending point B of the classification blade 7 (the bending position between the radial blade portion 7a and the inclined blade portion 7b) is R _M, and the center of the classification rotor 4 is The distance from O to the radial position (the position corresponding to the above-mentioned specific point a) where the powder particles are charged onto the classification rotor 4 is R ₀ .

4 (a), (b), and (c), the distances R _M to the bending position of the classification blade 7 when the radius of the classification rotor 4 is 1 are 0.724, 0.770, respectively. 0.8
28 shows a locus when the powder particles are set to 28 and jump out of the classification chamber. FIG. 4A shows a case in which the classification blade 7 has only the inclined blade portion 7b having no radial blade portion 7a (that is, the inclined blade itself of the conventional powder classifier). In this state, the powder particles are inclined blades. In order to swirl the inside of the classification chamber at the portion 7b, the adherent powder adheres to the inside of the classification blade (the inclined blade portion 7b).

However, as shown in FIG. 4 (b), if the classification blade has even a few radial vanes 7a, the radial vanes 7a suppress the flow velocity in the circumferential direction of the powder particles, so that the powder particles are spread over a long distance. Since it does not turn, it does not adhere to the inside of the classification blade, that is, the radial blade portion 7a.

When the radial vane portion 7a is further lengthened as shown in FIG. 4 (c), the circumferential flow velocity of the powder particles can be further suppressed by the radial vane portion 7a, so that the radial vane portion 7a does not swirl. It will be collected as fine powder in a short trajectory.

Next, when the classification diameter by such a classification blade is examined, it becomes as shown in FIG. The inclination angle φ of the inclined blade portion 7b in this case is 30 °.

FIG. 5 shows the distance R _M to the bending position of the classification blade.
Shows the classified diameter when the value is changed, and the classified diameter hardly changes halfway even if the distance R _M is increased, but increases discontinuously when R _M exceeds the particle feeding position R _0. To do. This is because the shape of the blade with which the powder particles come into contact first with this point as the boundary is from the inclined blade portion 7b to the radial blade portion 7b.
It is thought that this is because it changes to a. In other words, it is considered that the shape of the blade portion with which the powder particles first come into contact greatly affects the classification diameter. Furthermore, the position of R _M is the particle feeding position R
It is noticed that the classification diameter is particularly large near ₀ . From this, it is considered desirable to design the classifying blade so that R _M and the particle feeding position R ₀ are not so close to each other.

[0029]

As described above, according to the present invention,
The powder particles that have jumped out of the classification chamber do not swirl over a long distance because the radial velocity of the classification blade 7a suppresses the flow velocity in the circumferential direction, and as a result, even the powder particles having adhesiveness are classified in the classification blade, that is, the radial direction. It does not adhere to the inside of the blade 7a. The longer the radial blade portion 7a has, the greater the function of suppressing the flow velocity of the powder particles in the circumferential direction, but the bending position of the inclined blade portion of the classification blade and the radial blade portion is the outer circumference of the classification rotor rather than the powder introduction port. Since the classification diameter suddenly increases toward the side, it is preferable not to make the radial blade portion too long in order to secure a small classification diameter which is a characteristic of the conventional inclined blade.

[Brief description of drawings]

FIG. 1 is a plan view showing a powder classifier according to the present invention with a part cut away.

2 is a vertical cross-sectional view of the powder classifier shown in FIG.

FIG. 3 is an enlarged view of a classification blade of the powder classifier according to the present invention.

FIG. 4 is a diagram showing the operation of the classification blade of the powder classifier according to the present invention.

FIG. 5 shows a classification diameter when a classification blade according to the present invention is used.

[Explanation of symbols]

1 Casing 2a Powder Inlet 2b Air Inlet 4 Classifying Rotor 6 Rotating Shaft 7 Classifying Blade 7a Radial Blade 7b Inclined Blade 10 Powder Introducing Opening 11 Classifying Chamber 12 Auxiliary Blade 14 Coarse Powder Outlet 16 Dispersing Blade 18 Balance Distance to the bending position of the rotor R ₀ classification blade

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B07B 1/00-15/00

Claims (2)

(57) [Claims] 1. A disk outer edge is provided between two disks by placing two disks having the same diameter horizontally and in parallel in a casing having a powder inlet in the center of the upper surface and an air inlet in the side surface. From yen
Classification rotor with a cavity that allows air to flow toward the center of the plate
A rotatably by the vertical shaft, the circumferential portion near the space constitutes a classification chamber in the cavity of the classification rotor, to form a large number of blades on the classification chamber, the upper disc between該分class vanes in the powder classifying device formed by providing a powder introduction apertures, the classification vanes, the radial vanes extending along the radial direction, the disc outer edge bent from the end portion of the disc outside edge of the radial blade section The powder classifier is characterized in that it is formed so as to be connected to an inclined blade portion extending so as to retract toward the rotation direction of the classification rotor. From the vertical rotation axis center of 2. A classification rotor a distance to the bending position of the inclined blade portion and the radial vanes of said classifying blades, from the vertical rotation axis center of the classifying rotor until the powder introduction apertures The powder classifier according to claim 1, which is smaller than the distance.