JP2011224423A - Classifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a classifier removable of fine powder of raw material powder without degrading productivity.SOLUTION: The classifier is constituted of: arranging a plurality of classifying rotors each having a plurality of classifying vanes, coaxially in a casing; and providing the outer peripheral part of the classifying rotor with a plurality of guide vanes communicating with gas lead-in ports, at predetermined spaces to form an annular classifying space. Fine powder is allowed to flow into the classifying rotor together with gas supplied through a guide vane ring, and coarse powder is allowed to flow into a coarse powder storage chamber provided below the guide vanes, and discharged. The classifying space between the respective classifying rotors adjoining each other is provided with annular protrusions each having an opening with a diameter smaller than the inner diameter of the guide vane ring, over the whole periphery of the inner surface. The retention of powder in the classifying space is thereby adjusted, and the flow of the powder is guided into the vicinity of the classifying rotor to efficiently remove fine powder, thus attaining improvement in classifying accuracy.

Description

  The present invention relates to a classifier that separates powder into fine powder and coarse powder, and more specifically, removes fine powder smaller than a predetermined particle size to obtain a product having a predetermined particle size range. .

  Conventionally, as a classification means for classifying powder into fine powder and coarse powder, centrifugal force is applied to the powder by a cylindrical classification rotor that rotates around a central axis extending in the vertical direction in a cylindrical casing, and classified. The raw material powder is supplied to the classification space formed around the rotor, the gas is allowed to flow from the radially outer side to the inner side of the classification rotor, only the fine powder is transported into the classification rotor together with the gas, and the coarse powder is discharged downward. Vertical axis classifiers that are discharged from the outlet for sorting are used in the manufacturing field of toners, powder coatings, and the like. For example, in the toner manufacturing process, in recent years, in order to realize high-speed printing and high resolution, a toner having an average particle diameter of 5 μm to 7 μm and no fine powder of 4 μm or less is required.

In such classification, in order to remove fine powder efficiently, the dispersion of the raw material powder in the classifier is strengthened, and the residence time of the powder swirling around the classification rotor by increasing or decreasing the residence time Optimal adjustment of the amount is an effective method.
As such a classifier, for example, since the dispersion state of the powder in the classification space greatly affects classification accuracy and product yield, a plurality of classification rotors having the same rotation axis direction are provided in one casing. Therefore, a tandem classifier described in Patent Document 1 with improved dispersibility in the classification space is also known.

  And in the said patent document, in order to improve dispersibility, a plurality of guide vanes communicating with the gas inlet are provided outside the outer peripheral surface of the classifying rotor with a slit-shaped gap, and from this slit-shaped gap, By injecting gas into the classification space, the raw material powder around the classification rotor is dispersed. There has also been reported an apparatus that adjusts the residence time of the raw material powder by providing a spiral member on the inner peripheral portion of the guide vane and reliably discharging the raw material powder along the spiral member.

  However, also in the classifier, when the amount of raw material powder charged from the raw material inlet increases, the mixing of fine powder of 4 μm or less into the coarse powder (product) increases. On the other hand, when the rotational speed of the classification rotor is reduced to reduce the fine powder of 4 μm or less into the coarse powder (product), the product having a particle size that should be the product is discharged together with the fine powder. , The coarse powder (product) yield will decrease. Thus, in either case, productivity was not sufficient.

JP 2000-157934 A

  In view of the above problems, an object of the present invention is to provide a classifier that can prevent the mixing of fine powder into coarse powder (product) without reducing productivity.

  A first feature of the present invention is that a plurality of classification rotors having a plurality of classification blades are coaxially arranged in one casing, and communicated with the gas inlet at a predetermined interval on the outer periphery of each classification rotor. A guide blade ring composed of a plurality of guide blades is provided to form an annular classification space, and fine powder is caused to flow into each classification rotor together with the gas supplied through the guide blade ring, and coarse powder is placed below the guide blade ring. In the classifier configured to flow into and out of the coarse powder storage chamber provided in the ring, an annular protrusion having an opening having a smaller diameter than the inner surface of the guide blade ring in the classification space between the adjacent classification rotors Is provided over the entire inner surface.

By providing an annular protrusion having a small-diameter opening in the classification space, the powder cannot move directly from the upper partial space to the lower partial space, and is temporarily dammed by the protrusion, and then the protrusion. Is guided to the classification space of the outer peripheral portion of the classification rotor connected to the lower side of the opening. Therefore, the residence time of the powder in the classification space can be increased. Then, when passing through the protruding portion, the powder is drawn toward the center side along the protruding portion and passes near the next classification rotor. As a result, the powder is agglomerated and dispersed by collision with the classification blades of the classification rotor, so that the fine powder in the coarse powder easily flows into the classification rotor, and the classification accuracy is improved.

Further, by providing the protrusion, a narrow gap is generated between the protrusion and the classification rotor. Therefore, the velocity of the gas flow flowing through the gap is increased. Furthermore, the powder moving from the upper partial space to the lower partial space by the swirling airflow generated by the rotation of the classifying rotor is agglomerated by the swirling airflow and improves dispersibility when passing through the gap. In addition, fine powder is efficiently removed, and classification accuracy is improved.

The second feature of the present invention is that the annular projection is formed on the inner surface of the guide blade ring.

By forming the annular protrusion on the inner surface of the guide blade ring, the powder can be reliably dammed. That is, the powder moves from the upper partial space to the lower partial space while rotating on the inner surface of the guide blade ring. After being dammed once by the part, it moves to the vicinity of the classifying rotor along the protruding part, so that it receives both actions of dispersion and classification by collision with the classifying blade.

According to a third aspect of the present invention, the annular protrusion is formed by sandwiching a disc having an opening smaller in diameter than the inner diameter of the guide blade ring between each classification rotor and the corresponding guide blade ring. It is characterized by that.

  By constructing the annular projection with a disc, the projection can be easily manufactured, and also when changing the aperture diameter of the projection for each raw material or for each operating condition, the disc has a different aperture diameter. By replacing it, the opening diameter of the protrusion can be easily changed.

  According to a fourth aspect of the present invention, the opening of the annular protrusion is smaller in diameter than the outer diameter of the classification rotor.

  By making the opening of the annular projection smaller than the outer diameter of the classification rotor, the upper partial space and the lower partial space are more reliably partitioned, and the powder stays in the upper partial space better. Can be adjusted to. In addition, when the powder moves from the upper subclass space to the lower subclass space, it will pass near the classifying rotor, and the number of collisions with the classifying blades will increase, so that the aggregation will be loosened and dispersed. For this reason, the fine powder in the coarse powder easily flows into the classification rotor, and the classification accuracy is improved.

  According to a fifth aspect of the present invention, a spiral member is further attached to the inner peripheral surface of the guide blade ring.

  By providing a spiral member on the inner peripheral surface of the guide blade ring, the powder in the classification space descends along the spiral member. Therefore, by selecting the gradient of the spiral member, the annular shape is selected. In addition to the damming action by the protrusions, the residence time and amount of the powder can be adjusted effectively.

Vertical section of the classifier of this embodiment Sectional drawing showing other embodiment of the formation method of a projection part Sectional drawing showing other embodiment of the formation method of a projection part Perspective view of spiral member

This embodiment is shown below.
The classifier shown in FIG. 1 is composed of upper and lower casings 1a and 1b that can be swung up and down via a hinge 28. Inside the upper casing 1a and the lower casing 1b, classifying rotors 2 are respectively provided. Contained. The figure shows a state in which both casings 1a and 1b are closed.

In the lower casing 1b, there are provided a discharge rotor 4 coaxially coupled to the lower portion of the classification rotor 2, and a drive shaft 3 that pivotally supports the discharge rotor 4 and rotates the classification rotor 2 and the discharge rotor 4. On the outer peripheral side of 2, a guide blade ring 5 having a plurality of guide blades arranged annularly at intervals from the classifying rotor 2 is provided. The classification rotor 2 in the upper casing 1a is obtained by vertically inverting the classification rotor 2 of the lower casing 1b, and both are arranged symmetrically on the same axis.

The classification rotor 2 in the lower casing 1 b is driven by a drive motor 29, and this drive motor 29 is connected to the classification rotor 2 via the drive shaft 3. Similarly, the classification rotor 2 in the upper casing 1 a is driven by a drive motor 29, and this drive motor 29 is connected to the classification rotor 2 via the drive shaft 3.

The classification rotor 2 is supported in a cantilever manner, and includes an upper disk 6, a lower disk 7 that is spaced from the upper disk 6, and an upper disk 6 and a lower disk 7. The discs 6 and 7 are connected to each other, and are formed from a plurality of classification blades 8 arranged radially on the outer peripheral side of the discs 6 and 7. In each classification rotor 2, a drive shaft 3 and a fine powder storage chamber 17 are arranged symmetrically.

The classifying blades 8 are radially arranged at equal intervals along the outer peripheral surface of the classifying rotor 2, and the shape and orientation of the cross section thereof can be arbitrarily selected from the forms of known classifying blades, The slit-shaped gap formed between the two classification blades 8 adjacent to each other is designed so as to have a shape suitable for the gas flow.

  The discharge rotor 4 includes an annular top plate 9 having the same opening as that of the lower disk 7, a circular bottom plate 10 that is spaced from the top plate 9, and a space between the top plate 9 and the bottom plate 10. A plurality of blades 11 that connect the two blades 11 are arranged radially at equal intervals by providing an interval between adjacent blades 11. A drive shaft 3 is connected to the bottom plate 10 to rotatably support the discharge rotor 4 and the classification rotor 2. The discharge rotor 4 also functions as a member for rotating and supporting the classifying rotor 2, and the blade 11 is composed of a material, a width, a thickness, a length, etc. that have sufficient strength as a support member. ing.

Here, the classification rotor 2 and the discharge rotor 4 are communicated with each other through an opening 13 formed in the lower disk 7 of the classification rotor 2. By making the diameter of the opening 13 smaller than the inner diameter of the discharge rotor 4, it becomes difficult for the gas in the classification rotor 2 to flow into the discharge rotor 4, and the flow of the gas trying to flow into the classification rotor 2 is suppressed. This makes it difficult for coarse powder to enter the classification rotor 2. Further, by reducing the diameter of the opening 13, the gas flowing into the discharge rotor 4 is accelerated, and the discharge of fine powder in the discharge rotor 4 is also promoted.

  The guide vane ring 5 is arranged at equal intervals along the outer peripheral surface of the classifying rotor 2 with a plurality of guide vanes extending in the vertical direction, and the direction of the gap between the guide vanes swivels in the classifying spaces 14a and 14b, for example. In order to enhance the dispersion effect on the flowing powder, it is arranged tangentially toward the outer peripheral surface of the classification rotor 2. The number and shape of the guide vanes and the interval between the guide vanes can be changed as appropriate, and by adjusting them, the passage speed of the air passing through the guide vanes can be changed. Dispersibility can be made good.

  A gas introduction chamber 16 for supplying classification air to the classification spaces 14 a and 14 b through the guide blade ring 5 is provided on the outer periphery of the guide blade ring 5. The gas introduction chamber 16 is formed coaxially with the guide vane ring 5 in the casing 1 outside the guide vane ring 5, and the gas introduction chamber 16 is provided with a gas introduction port 19.

  The raw material powder is supplied to the upper partial space 14 a from the raw material supply port 12 provided in the upper casing 1 a, and the powder supplied to the upper partial space 14 a is a guide vane disposed on the outer peripheral portion of the classification rotor 2. By the centrifugal force formed by the gas flowing in from the ring 5 and the rotation of the classification rotor 2, the powder is classified into coarse powder and fine powder.

  Between the guide blade ring 5 in the upper casing 1a and the guide blade ring 5 in the lower casing 1b, a disc 26 having a circular opening at the center is attached, and the opening of this disc 26 is It is smaller than the inner diameter of the guide blade ring 5. The circular plate 26 forms a protrusion between the adjacent classification spaces 14a and 14b. Here, since the opening of the disk 26 is smaller than the inner diameter of the guide blade ring 5, the powder repelled by the classification blade 8 is directly in the upper partial space along the inner peripheral surface of the guide blade ring 5. The powder cannot be moved from 14a to the lower partial space 14b and descends along the inner peripheral surface of the guide blade ring 5 in the upper casing 1a. That is, by attaching the disk 26, the disk 26 becomes a partition plate that separates the upper partial space 14a and the lower partial space 14b, and the residence time can be adjusted. The residence time in the powder classification space can be adjusted by changing the size of the opening of the disk 26. That is, if the opening is made smaller, the residence time becomes longer, and conversely, if the opening is made larger, the residence time becomes shorter.

  Further, the powder once dammed is then guided to the classification space 14b in the lower casing 1b along the protruding portion. When passing through this protruding portion, the powder moves along the protruding portion. It is attracted to the center side and passes through the vicinity of the classification rotor 2, and easily collides with the classification blade 8 of the classification rotor 2. Then, the powder colliding with the classification blade 8 is loosened and becomes excellent in dispersibility, and the fine powder easily flows into the classification rotor 2, so that the classification accuracy is improved.

The classification rotors 2 in the upper casing 1a and the lower casing 1b may be operated at the same rotational speed, but may be operated at different rotational speeds. Conventionally, since it has been difficult to adjust the residence time of the powder in each classification space, when each classification rotor 2 is operated at a different rotational speed, sufficient classification is not performed in each classification space. As a result, it was difficult to obtain products with different particle sizes according to the rotation speed of each classifying rotor. However, as described above, by providing the disk 26, the upper classification space 14a and the lower classification space 14b can be partitioned. As a result, a product having a particle size corresponding to a predetermined rotation speed can be obtained in each classifying rotor 2. For example, when the operation is performed with the rotational speed of the classification rotor 2 in the upper casing 1a being faster than the rotational speed of the classification rotor 2 in the lower casing 1b, the powder that has flowed into the classification rotor 2 in the upper casing 1a The body becomes fine powder, the powder flowing into the classification rotor 2 in the lower casing 1b becomes an intermediate powder having a particle size between the fine powder and the coarse powder, and the powder repelled by the classification rotor 2 in the lower casing 1b is The coarse powder is discharged from the coarse powder outlet 21.

Further, by attaching the disk 26, a narrow gap is formed between the disk 26 and the classification rotor 2, and as a result, the velocity of the gas flow flowing through the gap is increased. Further, the powder moving from the upper partial space 14a to the lower partial space 14b by the swirling airflow generated by the rotation of the classifying rotor 2 is aggregated and dispersed by the swirling airflow even when passing through the gap. As a result, fine powder is removed and classification accuracy is improved.

In the present embodiment, the protrusion 26 is formed by attaching the disc 26 between the upper casing 1a and the guide blade ring 5 in the lower casing 1b. However, as another embodiment, for example, FIGS. As shown in FIG. 4, instead of attaching the disc 26, the annular ring is directly attached to the inner peripheral surface of either the lower end portion of the guide blade ring 5 in the upper casing 1a or the upper end portion of the guide blade ring 5 in the lower casing 1b. The protrusion 27a or 27b may be formed.

Also, the size of the opening is not particularly limited, but it needs to be large enough for the powder to move. If the opening is too small, it becomes difficult for the powder to move from the upper partial space 14a to the lower partial space 14b, so that the amount of residence in the upper partial space 14a increases, and as a result, the dispersibility of the powder decreases. However, the fine powder may be mixed in the coarse powder while it is agglomerated, or the powder concentration in the classification space 14a becomes too high due to an increase in the retention amount, and the coarse powder may easily flow into the fine powder. Comes out.

As a means for adjusting the residence time of the powder in the classification spaces 14a and 14b, it is also effective to provide the spiral members 15 shown in FIG. 4 in the classification spaces 14a and 14b.

The helical member 15 is formed by processing a belt-like member into a spiral shape, and is fixed to the inner peripheral surface of the guide blade ring 5 and extends over the entire length in the height direction of the classification spaces 14a and 14b. A minute gap is formed between the inner peripheral surface of the spiral member 15 and the outer peripheral surface of the classifying rotor 2 so as not to contact.

By providing a spiral member 15 in the classification spaces 14a and 14b and appropriately selecting the inclination gradient, the residence time of the powder in the classification spaces 14a and 14b can be adjusted. That is, increasing the gradient shortens the residence time, and decreasing the gradient increases the residence time.

The spiral member 15 may be composed of a plurality of strip-shaped members. In this case, the plurality of the spiral members 15 are attached to the inner peripheral surface of the guide blade ring 5 so as to be spiraled over substantially the entire circumference by attaching the plurality of strip members with a gap in the circumferential direction. The shaped member 15 can be attached, and the choice for forming a desired gradient can be expanded. The spiral member 15 does not necessarily extend over the entire length in the height direction of the classification blade 8, and may be provided only in a part of the partition region in the height direction of the classification blade 8. When the portion is provided, it is preferable that the lower end of the portion is extended to the surface of the protruding portion in order to prevent the powder from staying around the protruding portion. Further, the spiral member 15 may be directly attached to the guide blade ring 5 and integrated.

A passage for discharging fine powder and coarse powder sorted by the classification rotor 2 is formed in the upper casing 1a. The fine powder flows into the classification rotor 2 and is discharged from the fine powder discharge port 20 through the annular fine powder storage chamber 17 provided on the outer periphery of the discharge rotor 4.

The powder sent from the upper partial space 14a to the lower partial space 14b is classified into fine powder and coarse powder by the classification rotor 2, and the fine powder flows into the classification rotor 2 and the outer periphery of the discharge rotor 4 Is sent to the annular fine powder storage chamber 17 provided at the outlet and discharged from the fine powder discharge port 20. The coarse powder is sent to an annular coarse powder storage chamber 18 disposed in communication with the lower partial space 14 b and discharged from the coarse powder discharge port 21.

A seal portion 22 is provided between the lower surface of the lower disk 7 and the lower casing 1b. By feeding pressurized gas from the passage 25 into the seal portion 22, air sealing is performed to prevent the fine powder storage chamber 17 and the coarse powder storage chamber 18 from leaking fine powder and coarse powder. This pressurized gas is called rinsing air, and flows out from the seal portion 22 to the fine powder storage chamber 17 and the coarse powder storage chamber 18, respectively.

Inside the coarse powder storage chamber 18, an annular disk 23 having an L-shaped cross section called a centrifugal ring is provided. The annular disk 23 is formed in a shape along the inner side surface and the bottom surface of the coarse powder storage chamber 18, and the upper end thereof is attached to the lower disk 7 of the classification rotor 2 and rotates integrally with the classification rotor 2. . A gap between the annular disk 23 and the inner side surface and the bottom surface of the coarse powder storage chamber 18 serves as a passage for the rinsing air. As a result, the rinsing air that enters the coarse powder storage chamber 18 from the passage 25 flows out into the coarse powder storage chamber 18 through the inner side surface and bottom surface of the coarse powder storage chamber 18 and the passage below the annular disk 23.

A plurality of discharge blades 24 are arranged on the upper surface of the annular disk 23. By rotating the discharge blade 24 integrally with the classification rotor 2, a strong centrifugal force can be applied to the coarse powder in the coarse powder storage chamber 18, and in the coarse powder storage chamber 18 and around the coarse powder discharge port 21. It is possible to prevent clogging and stagnation, and to quickly discharge the coarse powder out of the classifier.

Thus, the coarse powder in the coarse powder storage chamber 18 is fluidized by being rolled up by the outflow of the rinsing air when it is pushed out in the centrifugal direction by the annular disk 23, and the aggregation and adhesion of the coarse powder are effectively suppressed and coarse. The discharge from the powder storage chamber 18 is performed smoothly. In addition, by pulverization of the agglomerates and separation of the fine powder and coarse powder mixed in the coarse powder by fluidization, mixing of the fine powder into the coarse powder can be prevented and an effect of improving classification accuracy can be expected.

In the above configuration, the raw material powder is supplied to the upper partial space 14 a from the raw material supply port 12 provided in the upper casing 1 a, and the powder supplied to the upper partial space 14 a is applied to the outer peripheral surface of the classification rotor 2. The first classification is performed by the centrifugal force generated by the gas flowing in from the arranged guide blade ring 5 and the rotation of the classification rotor 2. The fine powder flows into the classification rotor 2, is discharged from the discharge rotor 4 through the fine powder storage chamber 17, is discharged from the fine powder discharge port 20, and is collected by a well-known collector or cyclone not shown.

On the other hand, the coarse powder moves downward along the spiral member 15 provided in the upper partial space 14 a between the guide blade ring 5 and the classification rotor 2, and is attached between the guide blade ring 5. It passes through the opening of the disk 26 and is sent to the lower partial space 14b.

In the lower partial space 14b, the second classification is performed in the same manner as in the upper partial space 14a, and the fine powder flows into the classification rotor 2, passes through the fine powder storage chamber 17 from the discharge rotor 4, and flows into the fine powder discharge port 20. And is collected by a well-known collector or cyclone (not shown). The coarse powder moves downward along the spiral member 15 provided in the lower partial space 14b between the guide blade ring 5 and the classification rotor 2, and is arranged in communication with the lower partial space 14b. After being sent to the annular coarse powder storage chamber 18, the fluid is fluidized by the annular disk 23 and rinsing air in the coarse powder storage chamber 18, and centrifugal force is applied by the discharge vanes 24, from the coarse powder discharge port 21. It is discharged outside and collected.

Toner classification was performed using a tandem classifier (200TTSP, manufactured by Hosokawa Micron Corporation) in which the classification rotor 2 shown in FIG. In the upper casing 1a and the lower casing 1b, guide blade rings 5 having an inner diameter of 220 mm were attached. A color toner having an average particle size of 5.1 μm (weight basis) and a fine powder content of 4 μm or less of 65.2% (number basis) was used as the raw material toner. In addition, coarse powder becomes a product also in the following Examples 1 and 2 and Comparative Example 1.

Example 1
A disc 26 having an opening diameter of 200 mm was attached between the guide blade ring 5 in the upper casing 1a and the guide blade ring 5 in the lower casing 1b. Each classifying rotor 2 was operated at a rotational speed of 5000 rpm. The feed rate of the raw material was 80 kg / h. As a result, the coarse powder yield was 53.0%, the average particle size was 5.9 μm (weight basis), and the content of fine powder of 4 μm or less contained in the coarse powder was 6.5% (number basis).

(Example 2)
A disc 26 having an opening diameter of 180 mm was attached between the guide blade ring 5 in the upper casing 1a and the guide blade ring 5 in the lower casing 1b. Otherwise, the operation was performed under the same conditions as in Example 1. As a result, the yield of coarse powder was 57.0%, the average particle size was 6.1 μm (weight basis), and the content of fine powder of 4 μm or less contained in the coarse powder was 4.2% (number basis).

(Comparative Example 1)
The toner powder was classified using a tandem classifier to which the disk 26 was not attached. The operation was performed at a feed rate of 60 kg / h. As a result, the yield of coarse powder was 56.0%, the average particle size was 5.6 μm (weight basis), and the content of fine powder of 4 μm or less contained in the coarse powder was 12.5% (number basis). Although the feed rate of the raw material is lower than those in Examples 1 and 2, there are many fine powders mixed in the coarse powder, the dispersion is insufficient, and good classification results are not obtained.

Thus, by attaching the disk 26 between the guide blade ring 5 in the upper casing 1a and the guide blade ring 5 in the lower casing 1b, the content of fine powder of 4 μm or less contained in the coarse powder is greatly increased. Could be reduced. In particular, in Example 2, although the raw material supply rate was increased as compared with Comparative Example 1, the coarse powder yield was high and the content of fine powder of 4 μm or less was low. Moreover, as a result of comparing Example 1 and Example 2, Example 2 had a higher coarse powder yield and a lower content of fine powder of 4 μm or less. This is because the attachment of the circular plate 26 having a smaller opening diameter than that of the first embodiment in the second embodiment extends the residence time of the powder and causes the powder to swirl in the vicinity of the classification rotor. It is thought that the fine powder decreased due to both dispersion and classification.

The classifier of the present invention removes fine powder from the powder after removing coarse particles, and classifies various powder materials in addition to toners, powder coatings, minerals, foods and feeds that use the coarse powder as a product. It can be done efficiently.

DESCRIPTION OF SYMBOLS 1a Upper casing 1b Lower casing 2 Classification rotor 3 Drive shaft 4 Discharge rotor 5 Guide blade ring 6 Upper disk 7 Lower disk 8 Classification blade 9 Top plate 10 Bottom plate 11 Blade 12 Raw material supply port 13 Opening 14a Upper partial space 14b Lower Partial class space 15 Spiral member 16 Gas introduction chamber 17 Fine powder storage chamber 18 Coarse powder storage chamber 19 Gas introduction port 20 Fine powder discharge port 21 Coarse powder discharge port 22 Seal member 23 Annular disk (centrifugal ring)
24 discharge blade 25 passage
26 Disc (projection)
27a Protrusion (protrusion)
27b Protrusion (protrusion)
28 Hinge 29 Drive motor

Claims (5)

A plurality of classification rotors having a plurality of classification blades are coaxially arranged in one casing, and a guide blade ring comprising a plurality of guide blades communicating with the gas inlet at a predetermined interval on the outer periphery of each classification rotor. An annular classifying space is formed to allow fine powder to flow into the classifying rotor together with the gas supplied through the classifying rotor and the guide blade ring, and coarse powder is provided below the guide blade ring. In the classifier configured to flow into and out of the powder storage chamber, an annular protrusion having an opening smaller in diameter than the inner diameter of the guide blade ring is provided in the classification space between the classification rotors adjacent to each other. A classifier characterized by   The classifier according to claim 1, wherein the annular protrusion is formed on an inner surface of the guide blade ring.   2. The annular protrusion is formed by sandwiching a disc having an opening smaller in diameter than the inner diameter of the guide blade ring between each classification rotor and the corresponding guide blade ring. The classifier described.   The classifier according to any one of claims 1 to 3, wherein the opening of the annular protrusion has a smaller diameter than the outer diameter of the classifying rotor.   The classifier according to any one of claims 1 to 4, wherein a spiral member is attached to an inner peripheral surface of the guide blade ring.