JPS5917395Y2 - Centrifugal wind classifier - Google Patents

Description

[Detailed description of the invention] The present invention relates to a centrifugal wind classifier, and more specifically, the present invention relates to a centrifugal wind classifier. In a centrifugal wind classifier equipped with a particle discharge port, the top wall of the classification chamber is a conical wall that is concentric with the bottom wall and has a larger slope than the bottom wall, and the coarse particle discharge edge of the classification chamber is attached to the top wall. A conveying mechanism that arranges a powder inlet in a circumferential manner at a position between the fine particle discharge edge and supplies the powder and granule to the powder inlet in a circumferential direction by placing the powder on a conveying air flow. This invention relates to a centrifugal wind classifier characterized by being equipped with.

Conventionally, a centrifugal wind classifier is known, which has a conical bottom wall and has an air and fine particle outlet in the center, and a coarse particle outlet on a part of the outer periphery of the classification chamber. In such a known centrifugal wind classifier, the powder and granules are introduced into the classification chamber at one point, so the distribution of the powder and granules in the classification chamber becomes uneven, and this results in an increase in the input amount. The increase causes a decrease in classification accuracy, and only with a very small amount of input,
The drawback is that sufficient classification accuracy cannot be obtained.

Furthermore, in this type of known classifier, the powder is introduced into the classification chamber with no or very little momentum in the circumferential direction, and the powder is accelerated to the circumferential velocity of the wind. Until now, the momentum of the air in the circumferential direction is increased, which has the disadvantage that the classification point varies depending on the amount of powder and granules input.

In this type of centrifugal wind classifier, the present inventors designed the top wall of the classification chamber to be a conical wall that is concentric with the bottom wall and has a larger slope than the bottom wall, and the coarse particle discharge end of the classification chamber is attached to the top wall. Powder and granule inlets are arranged in a circumferential manner at a position between the edge and the fine particle discharge edge, and the granules are placed on the conveying airflow and supplied to the powder and granule in the circumferential direction. When installing a conveyance mechanism, it is necessary to make the distribution of the powder and granules uniform in the classification chamber and to perform the classification operation of the powder and granules with sufficiently high classification accuracy even when the input amount is larger than that of conventional classifiers. In addition, it was found that accurate classification operations are possible without substantially changing the classification point, that is, the cut point between fine particles and coarse particles, even when the amount of powder and granules supplied is increased. I found it.

The present invention will be explained in detail below based on specific examples shown in the accompanying drawings.

In Figures 1 and 2 of the accompanying drawings, the top of the hopper 1 is provided with a conical bottom wall 2, in the center of which air and fines discharge [ ] 3 flows through the conical bottom wall 2. Annular coarse particle discharge ports 4 are arranged on the outer periphery of the bottom wall 2, respectively, and the coarse particles are discharged into the hopper 1 through the discharge ports 4.

In the specific example shown in the attached drawing, this coarse particle discharge port 4 extends over the entire circumference of the conical bottom wall 2 in order to eliminate air turbulence during coarse particle discharge and to make the classification chamber as homogeneous as possible. However, it is of course also possible to provide the coarse particle outlet only on a part of the circumference of the conical bottom wall 2, as in centrifugal wind classifiers known per se.

A top wall 5 is arranged above the conical bottom wall 2 at a distance from the bottom wall, and a space surrounded by the conical bottom wall 2 and the top wall 5 serves as a classification chamber 6.

In the present invention, the top wall 5 is a conical wall that is concentric with the bottom wall 2 and has a larger slope than the bottom wall 2.
The distance between the particles, and therefore the air passage cross-sectional area, increases from the outer periphery toward the center, and as will be described in detail later, the powder and granules are placed on the conveying airflow and distributed in a circumferential manner in the classification chamber 6. Even in the case of supplying the classification chamber 6, disturbances in the flow of air from the periphery to the center of the classification chamber 6 are effectively prevented.

A discharge pipe 7 that extends downward within the hopper 1 and communicates with the outside of the hopper is connected to the air and particulate discharge port 3 .

A primary air flow path 8 is provided on the outer periphery and upper side of the classification chamber 6 to supply wind power for classification, that is, primary air.

In the specific example shown in the accompanying drawings, an annular air passage 8 is provided along the entire outer circumference of the classification chamber 6 in order to supply primary air from the entire outer circumference of the classification chamber 6 and to equalize the flow of air within the classification chamber 6.
However, it is also possible to provide the primary air flow path only in a part of the outer periphery of the classification chamber 6, as in a centrifugal wind classifier which is known per se.

This primary air passage 8 is connected to a suitable air supply source (not shown) via an air supply pipe 9', while an air flow circle is provided on the inner circumference of this primary air passage 8. A distribution rectifying plate 9 is provided for controlling the minute velocity in the circumferential direction.

Furthermore, in the specific example shown in the accompanying drawings, the primary air flow path 8
An annular flow path 10 for auxiliary air is provided on the lower side and on the outer circumference side, and a control plate 11 for directing a large number of air flows in the radial direction is arranged on the inner circumference side of this annular flow path 10. There is.

A supply 12 connected to the annular flow path 10 is provided with an air amount adjusting damper or valve 13 .

This damper or valve 13 makes it possible to adjust the amount of auxiliary air flowing into the classification chamber 6 through the openings between the control plates 11, that is, the minute velocity of the air in the radial direction.

Another important feature of the present invention is that, as clearly shown in FIG. The purpose is to arrange the granule inlets 14 in a circumferential manner.

That is, according to the present invention, by supplying the powder and granules into the classification chamber 6 through the circumferential inlet 14, it is possible to make the distribution of the powder and granules in the classification chamber 6 uniform. At the same time, centrifugal force and centripetal force from the wind are effectively applied to the powder and granules supplied into the classification chamber 6, and even when the input amount is larger than that of conventional classifiers, a sufficiently high classification can be achieved. Capable of classifying powder and granular materials with precision.

Another important feature of the present invention is the above-mentioned circumferential inlet 14.
The purpose is to supply the powder and granules on a conveying air stream into the classification chamber through the air flow.

This feature makes it possible to apply velocity to the powder in the circumferential direction, allowing accurate classification operation without substantially changing the classification point even when a large amount of powder is supplied. becomes possible.

When the granular material inlet 14 is provided at a position between the coarse particle discharge edge and the fine particle discharge edge of the classification chamber 6, the granular material is placed on the conveying gas through the granular material inlet 14. When supplying powder or granules, the flow of air from the periphery to the center of the classification chamber is likely to be disturbed.

In the present invention, as described above, the distance between the bottom wall 2 and the top wall 5 is increased from the outer periphery toward the center, and the powder and granular material inlet ports are distributed, so that such defects are effectively eliminated. Ru.

For this purpose, in the specific example shown in the accompanying drawings, a conveyance mechanism, particularly an ejector 16, is provided for supplying the powder and granular material supplied from the hopper 15 on a conveying air stream.

Between the ejector 16 and the circumferential inlet 14, the powder and granules carried by the conveying airflow are evenly distributed to the circumferential inlet 14.
and is provided with an annular distribution chamber 17 for uniform distribution;
The annular distribution chamber 17 and the circumferential inlet port 14 are connected by a powder inlet pipe 18 .

It is also important that the powder feed pipe 18 extends circumferentially and downward from the distribution chamber 17 in order to introduce the powder into the classification chamber 6 while imparting momentum to the powder in the circumferential direction. It is.

Thus, in the classifier of the present invention, the ejector 16
The powder and granules placed on the conveying airflow are transferred to the annular distribution chamber 1.
7 and is given momentum in the circumferential direction, and in this state is supplied into the classification chamber 6 via the inlet pipe 18 and inlet 14, and the inside of the classification chamber 6 due to the supply of powder and granules. This makes it possible to significantly reduce turbulence in the airflow.

In addition, the circumferential speed of the powder and granular material during feeding is determined by the ejector.
It can be adjusted by adjusting the amount of conveying airflow with a valve 19 attached to 16.

The top wall 5 may have a plurality of circumferential inlets provided at intervals in the circumferential direction as shown in FIG. 3, or one or more circumferential inlets may be provided in the circumferential direction as shown in FIG. It can also be provided as a plurality of slit-like open CIs.

In this latter case, the end edge of the annular distribution chamber 17 may open directly into the classification chamber 6 to form an inlet 14.

The circumferential velocity of the granular material at the time of supply is the same as the circumferential velocity of the air flow, or approximates it (1, preferably no velocity, and its adjustment is performed by the above-mentioned valve 19.
This can be easily done by

The effects of the present invention will be explained with the following example.

A pulverized toner used for electrophotographic J-two-component developer is loaded into a classifier shown in Figures 1 to F4 with an outer diameter of 35 cm at a rate of 1 kg per hour.
amount was charged and centrifugal air classification was performed.

At this time, various conditions were set so that the center diameter of the coarse particles to be recovered was 10 microns and the particle size distribution was 5 to 30 microns.

For comparison, centrifugal air classification was also performed on a classifier having the same structure as above except that the top wall of the classification chamber was made flat.

The input amount of toner crushed product is 2 times, 5 times, 10 times the above input amount.
For the case of changing the amount by 2 times and 20 times, the content (wt%) of fine particles smaller than 5 microns contained in the recovered coarse particles was measured using a Coulter Counter TA-II model,
It is shown in Table 1 below.

Further, the variation accuracy of the center particle diameter is shown in Table 2 below.

Table 1 Input amount Comparative example 13.0% 23.1 56.2 10 10, 4 20 Unclassifiable example 1.5% 1.4 1.9 3.2 5.1 Table 2 Input amount Comparative example Example 1 10±0.5μ 10 f=0.2μ2
±0.5 ±0.25
±1.3 ±0.310
±282 ±0.520 Poor accuracy and unclear ±0.5 From the above results, in the classifier of the present invention, even when the input amount is significantly increased, the cut point between fine particles and coarse particles is substantially It is understood that a highly accurate classification operation is possible without any upward fluctuation.

[Brief explanation of drawings]

FIG. 1 is a partially sectional side view of the centrifugal wind classifier of the present invention, FIG. 2 is a top view of the classifier of FIG. 1, and FIG.
The figure is a layout diagram showing an example of the arrangement of circumferential inlets provided on the top wall, and FIG. Conical bottom wall, 3 is an air and fine particle outlet, 4 is a coarse particle outlet, 5 is a top wall, 6 is a classification chamber, 14 is a powder inlet arranged in a circumferential manner, 16 is a powder particle outlet A mechanism 17 for placing the air on the carrier airflow is an annular distribution chamber, and 18 is an inlet pipe.

Claims (3)

[Scope of utility model registration request] (1) In a centrifugal wind classifier that has a conical bottom wall and a coarse particle discharge port on the outer periphery of a classification chamber with an air and fine particle discharge port in the center, the top wall of the classification chamber is connected to the bottom wall. The conical wall is concentric with the bottom wall and has a larger slope than the bottom wall, and a powder inlet is provided in a circumferential manner on the top wall at a position between the coarse particle discharge edge and the fine particle discharge edge of the classification chamber. What is claimed is: 1. A centrifugal wind classifier, characterized in that the centrifugal wind classifier is provided with a conveying mechanism for placing the powder and granules on the conveying airflow and supplying the powder and granules in the circumferential direction at the powder and granule inlet. (2) Between the transport mechanism and the powder/granular material inlet, there is a distribution device with a substantially circumferential outer periphery in order to uniformly distribute the powder/granular material carried by the conveying airflow to each powder/granular material inlet. The classifier according to claim (1) of the utility model registration, characterized in that the classifier is provided with a chamber. (3) The circumferential distribution chamber and the granular material inlet are connected via an inlet pipe extending circumferentially and downwardly. Classifier.