US 3670886 A
A powder classifier having a housing, a rotary member within the housing having two sets of fins separated by a conical member and means for supplying powder to be classified into the bottom of said rotor whereby certain particles will be carried upwardly through the rotor and exhausted while other particles will fall downwardly into a suitable hopper.
Description (OCR text may contain errors)
United States Patent Hosokawa et al.
[5 1 POWDER CLASSIFIER  Inventors: Masuo Hosokawa; Tohei Yokoyama;
Fumlo Nakagawa, all of Osaka, Japan 7 3 Assignee: Hosokawa Funtaikogaku Kenkyusho,
Osaka, Japan  Filed: Aug. 5, 1970 ] Appl. No.2 61,223
(52] 0.5.0. ..2o9/1a9 A,'209/144,20 9/148 511 lm. Cl ..B07b 7/083 [58} Field of Search ..209/13s,139,144,14s,14s
 References Cited- UNITED STATES PATENTS 1,367,636 2/1921 Sturtevant ..209/l39A [451 June 20, 1972 3,040,888 6/1962 Hosokawa etal ..209/ 144 7 3,371,782 3/1968 Meyer et a1 ..209/l44 Primary Examiner-Frank W. Lutter Assistant Examiner-Ralph J. Hill AttomeyEugene E; Geofirey, Jr.
[ ABSTRACT A powder classifier having a housing, a rotary member within the housing having two sets of fins separated by a conical member and means for supplying powderto be classified into the bottom of said rotor whereby certain particles will be carried upwardly through the rotor and exhausted while other particles will fall downwardly into a suitable hopper.
4 Claims, 2 Drawing Figures POWDER CLASSIFIER This invention relates to a powder classifier and more particularly to a novel and improved powder classifier utilizing air for effecting the separation of particles of difi'erent sizes and for the separation of particles of different densities wherein the particles of the powdered material may be substantially uniform in size. v
Prior known classifiers have not been found satisfactory because of relatively low classifying efficiency. With such devices the powdered material was insufi'rciently dispersed and did not exist as individual particles in the air flow. Accordingly, it was diificult toimpart uniform speed of rotation to all particlesand furthermore the air flow was disturbed by secondary flows such as turbulence which prevented proper particle operation.
One object of the invention resides in the provision of a novel and improved powder classifier which will effectively disperse the particles and impart uniform rotation and steady flow to all of the particles and thus effectively and efficiently separate particles of different size or density as the case may be According to the invention the powder classifier is provided with an outer housing and a classifying rotor disposed within the housing. The classifying rotor includes a disk member having a central inlet portfor powder and air, a conical member coaxially aligned with the disk and having its base facing the disk member, a first group of rotating fins radially disposed between the disk member and the base of the conical member and a second group of fins radially disposed about and extending upwardly from the conical member. The air containing the powdered material enters the inlet port of therotating disk member, passes between the first group of radially disposed fins and outwardly into the housing where it then enters the rotor by passing the second group of rotating fins and is then exhausted through an axially disposed rotor opening. During this operation the particles are classified and separated with the fine particles being exhausted with the air upwardly through the rotor opening while the coarse particles will fall and be discharged from the bottom of the housing. In operation the classifying rotor in accordance with the invention imparts rotating motion to the air containing the powdered material with the. result that a centrifugal force is imparted to the particles in accordance with the size or density of each of the particles. The interaction of this centrifugal force and the aerodynamic resistance of the air flow causes the particles to be separated into two groupsas for instance coarse and fine particles size and particles having large and small density.
The above and other objects of the invention will become more apparent from the following description and accompanying drawings forming part of this application.
In the drawings:
FIG. 1 is a vertical cross-sectional view of one embodiment of a powder classifier in accordance with the invention; and
FIG. 2 is a cross-sectional view of FIG. 1 taken along the line II-Il thereof.
The powder classifier in accordance with the invention includes a cylindrical housing and a classifying rotor generally denoted by the numeral 20. The rotor is coaxially disposed within the housing and is rotated by a drive shaft 21 the upper end being connected to suitable means not shown for effecting rotation of the shaft. The rotor 20 includes a frustoconical member 22 fixed to the shaft 21, a lower disk member 24 having a central inlet port 25 and an upper ring member 26. As will be observed more clearly in FIG. 2, a plurality of radially disposed fins 27 are carried between the conical surface of the frustoconical member 22 and the upper ring member 26. A plurality of radial fins 28 are disposed between the base of the frustoconical member 22 and the lower disk member 24. An inverted cone 23 is concentrically fixed to the underside of the base of the frustoconical member 22, the latter being shown as a hollow body through it may of course be fonrled of a solid material in order to provide a fly-wheel effect. The space 12 between the rotor and the cylindrical housing 10 serves as the classifying cavity.
An inverted conical member 14 is disposed within the housing 10 and immediately below the rotor 20 and the upper edges of the conical member are fixed to the inner wall of the housing 10. This conical member forms the lower classifying means as will be described. 7
The lower portions 18 of the housing 10 forms a hopper for removal of the coarse particles. An air inlet pipe 16 connects with the housing 10 at a point adjoining the lower edge of the inverted conical member 14. As will be observed in FIG. 2, the inlet 16 extends tangentially from the housing 10 which imparts a circular motion to the air entering the housing 10. The top of the housing 10 has a cover 30 which includes an outlet port 32, the latter being connected to a suitable particle collector not shown which may comprise a cyclone or bag filter and an exhaust fan. A feeder pipe 34 enters the bottom of the housing 10 and is disposed coaxially with the rotor 20. The air and powdered material flows through the feeder pipe and upwardly into the rotor 20. To facilitate an explanation of the operation of the structure as described above, the solid arrows indicate the flow of air while the dotted arrows indicate the flow paths of the powdered material. Though the solid arrows are shown on one side of the structure and the dotted arrows on the other side of the structure, this procedure has been followed for purposes of simplification and in practice it is to be understood that the paths of both the air and the particles are intermixed.
The rotor is driven at a predetermined speed by means of the shaft 21 and air is exhausted through the'outlet 32 at a preselected rate by an exhaust fan not shown connected to the outlet port 32. The rate of flow is also controlled by the air flow provided by the inlet pipe 16; Powdered material to be classified is carried by air flowing through the pipe 34 and fed into the inlet port of the rotor 20. The air and the powder are directed horizontally by the guide cone 23 and then passes outwardly between the fins 28 and impinges upon the inner wall of the housing 10. When the powder strikes the inner wall, groups of particles of the powder will be effectively,
broken up. Thus during this portion of the operation, the powdered material is effectively separated into discrete particles.
The separated particles then flow upwardly by reason of the revolving air flow and of the large or heavy particles falling downwardly through the inverted cones 14 by reason of the cavity. There is a tendency for these heavier particles to again enter the rotor 20, but only the smaller or lighter particles will enter the rotor and be carried upwardly to the outlet port 22. Some of the large and heavy particles receive substantial centrifugal force imparted by the rotor 20 and thus overcome the sucking force of the exhaust fan. These particles settle on the wall of the housing and then fall downwardly in the hopper l8.
i The coarse particles which fall downwardly through the inverted cone l4 encounter a second flow of air provided by the pipe 16 which serves as a secondary separating function. At this point the lighter or smaller particles which may be carried by the heavier or coarser particles will again be blown upwardly into the space between the rotor and the housing, and they are ultimately exhausted through the outlet 22. Thus only the purely coarse particles will fall in the hopper l8 and may be removed by any suitable means.
The conical surface of the frustoconical member serves as a so-called rectifying function in that it prevents eddy currents and turbulence near the lower portion of the radial fins 27 and thus causes the air to flow smoothly in an upward direction. A
similar function is obtained by the guide cone 23.
With the invention as described above, the powdered material is effectively separated into discrete particles and is repeatedly and cyclically processed in two stages, one being in the rotor 20 and the other being in the inverted cone 14. Thus the particles are separated with a high degree of accuracy and efficiency. This is particularly the case when separating coarse and fine particles. For example, when powdered heavy calcium carbonate is classified by apparatus in accordance with the invention and it is desired to separate particles greater than 25 microns from particles smaller than 25 microns, the percentage of particles smaller than 25 microns remaining with the coarse particles is less than 5 percent by weight and the.New-
tonian classification efficiency is as high as 85 percent.
The foregoing embodiment of the invention has been shown and described for illustrative purposes and various modifications and changes can be made without departing from the spirit and scope of the invention. For example, the radial fins 27 and 28 may be inclined with respect to the radii of the rotor 20 or may be curved. In addition, the 'speed or rotation or rotor 20 and the flow rate of the air flow and the content of the powder in the air can be selected in accordance with the particle size to be classified in order to obtain optimum classifying efficiency.
What is claimed is:
l. A powder classifier comprising a substantially upright cylindrical housing having a fines outlet in the top thereof and a coarse outlet in the bottom thereof, a classifying rotor having a rotating disk member and an inlet port in the center, a rotating conical memberarranged coaxially with said disk member and having a base plane facing said disk member, a
first group of rotating fins radially arranged between 'said disk member andthe base plane of said'conical'member and a second group of rotating fins radially arranged on the conical surface of said conical member said second group of rotating fins radiating from and defining a central space in direct comwall of said housing.
4. A powder classifier, in accordance with claim 1 wherein said cylindrical housing is provided with an air inlet port extending horizontally and tangentially from said housing.
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