US2258901A - Classifier - Google Patents

Description

H. G. LYKKEN 2,258,901

Oct. 14, 1941.

. CLASSIFIER Filed May 29*. 1957 s Sheets-Sheet 1 Oct. 14, 1941. H. G. LYKKEN 2,258,901

CLASSIFIER Filed May 29, 1937 3 Sheets-Sheet 2 INVENTOR. Henry 6. Ay/f/ferp ATTORNEY. I

Oct. 14, 1941. H. a. LYKKEN CLASS IFIER F-iled May 29; 1937 5 Shets-Sheet 3 INVENTOR. H 227 6 Ay/f/fen BY// ATTORNEY.

Patented Oct. 14, 1941 CLASSIFIER Henry G. Lykken, Minneapolis, Minn. Application May 29, 1937, Serial No. 145,496

19 Claims.

This invention concerns improved machines and methods for classifying the particles of a mass of previously pulverized material, whereby material of a predetermined particle size may be segregated from the mass and delivered from the machine, or material of several different particle sizes may be delivered from the machine separately and concurrently. The machine is not intended to have any pulverizing action, although it is recognized in some of the suggested forms minor and incidental pulverizing will occur.

In the present machine the mass of pulverized material after being introduced into the machine is caught in a rising vortex of gaseous media, such as air, and is whirled around in a classifying compartment at high speed, care being exercised to prevent any disturbing forces, eddyor other currents. The gaseous media and pulverized material may enter the classifying compartment in many different ways and thereafter, ac-

cording to the present invention, is maintained in the vortex state by a high speed, smooth rotor which, together with an oppositely disposed concentric, stationary wall of the machine, defines a narrow, vertical, annular classifying space.

The centrifugal force of the vortex action on the particles effects the classification or sorting of the material in accordance with the differences in size and corresponding mass velocities of the various moving particles in the classifying zone. That is, the finer particles being of small mass are less affected by the centrifugal forces set up by the vortex action, and consequently rise at and near the inner periphery of the vortex to a place ofexit adjacent the top of the machine. The larger particles are projected outwardly toward the outer periphery of the vortex during their rise in the classifying space between the rotor and the opposite wall, and the respective sizes rise to define heights or places along the outer wall according to their sizes, as will be more fully explained hereafter. Consequently, in addition to the very fine particles, it is possible to take out of the classifying chamber and collect particles of any larger size, or of different graded sizes, by suitably locating a tapping zone or zones verticallly of the circumferential wall of the classifier. It is, ac-

' cordingly, one object of this invention to provide means for efiiciently effecting any or all of the abovepurposes.

The machine of this invention is capable of classifying various kinds of pulverized materials whether they be of uniform chemical charactertrained material. classified may also enter the machine with the aggregates, etc. Furthermore, the classifier of this application may be used with various types of pulverizing machines.

The air or other gaseous media may be let into the machine from a place beneath the rotor, or near the bottom of the machine, and may also be induced to rise through the classifying chamber by means of a suitable fan adjacent the'top of the machine, or by appropriate exhaust means connected to an outlet from the classifying chamber. However, care should be exercised that such devices do not disturb or agitate the smooth movement of the rising currents of air and en- If desired, the material to be air. As another instance, the material may be fed tangentially through the wall of the classifying chamber either with or without the necessary air to form the carrier. As a further example, a suitable mechanical feeding means, such as a screw conveyor may be used, in which case the air may be fed into the classifying chamber from the bottom or tangentially, or both,

. as may be found advisable in accordance with operating conditions and the particular materials to be dealt with.

By whatever means thematerial and air en- I ter the classifying chamber, unless thematerial enters the machine with a sufliciently vortical motion and in substantial suspension in the air, it is quickly put into suspension and the air and mass of suspended particles caused to Whirl by the action of the high speed rotor. In the drawing the rotor is provided at its lower end only with spaced apart vertical fins or other suitable means for originating the vortex.

It is another object of this invention to pro vide a classifier with, vanes or similar means to initiate a vortex action, and a smooth rotor element for maintaining the vortex action.

It is still another object of this invention to provide a classifier of the above indicated character wherein the-classification zone has uninterrupted, smooth, continuous currents of air and entrained material. v

In some industries abrasive materials having particles of uniform size-are required. This is the case in the manufacture of brake bands where the abrasive particles in some instances must approximate 30 microns. In other fields it is important that the material have no metal contamination as for example the cosmetics or food industries. In handling all these materials the parts of the machine may be protected as by istics, or are compounds, or various forms of having the moving and stationary walls of the classifying chamber covered with resilient-material such as rubber. The rubber increases what might be termed a skin-drag effect on the air with two results, first, reducing the wear on the walls and rotor parts, and, second, the rubber covered rotor will move more air, thereby increasing the vortex action, without setting up undesired undulating or eddy currents, all ofwhich is conducive to speedy and accurate classification. Furthermore, the rubber facing of the stationary wall has a retarding action on the particles moving therealong and slows or stops their motion somewhat definitely, and also preventing the deflection and return of the particles to the vortex.

It is, therefore, a further object of this invention to provide rubber or other similar walls along the classification zone.

At times, to obtain accurate classification it may be desirable to connect two or more classifiers in series relation so that the material is returned one or more times through classifying zones for further grading. With this arrangement, the oversize and undersize particles are both eliminated to obtain a substanially uniform final product. Hence, it is a still further object of this invention to provide a method and arrangement of apparatus for accomplishing the abovementioned result.

Various other objects and advantages of the invention will appear as the description proceeds, reference being made to the accompanying drawings, illustrating several practical embodiments of the invention, and in which Figure 1 is a vertical sectional view of a classifying machine" constructed in accordance with the invention, parts being broken away to facilitate the illustration;

Fig. 2 is a horizontal cross sectional view taken in the planeof line2--2 of Fig. 1;

Fig. 3 is a fragmentary view in vertical section of a classifying machine illustrating a modified form of device having a plurality of tapping points at the side of the machine, and also showing the application of rubber linings to the classifying chamber;

Fig. 4 is-a'view in vertical section of a portion of a classifying machine illustrating a modified form of tapping arrangement at the side of the classifler andalso showing one form of conveyor-for feeding pulverized material to the machine; a

Fig. 5 is a fragmentary view of a classifier constructed according to the invention and illustrating the approximate paths taken along the classification chamber by the various sizes of particles, the spiral portion of the paths being omitted; and

Fig. 6 is a diagrammatic illustration of apparatus for and method of subjecting the particles one or more times to the action of a classifying zone for further gradation.

Referringto the drawings, and more particularly to Figs; 1 and 2, the machine comprises-in general a-stationary, vertical, generally "cylindrical casing or housing It], a drum-like rotor ll mounted on a vertical shaft I2 for concentric rotation in the housing at high speed, the shaft being mounted in top and bottom bearings l3 and I4 respectively. The elongated space l5 defined between the rotor II and the oppositewall of the casing 10 forms a classifying chamher or zone for the pulverized material, which may be continuously fed to this chamber in a variety of ways.

If desired, the pulverized material, together annular space about the rotor H. Air also may be fed into the classifying chamber I 5 at the bottom of the rotor H through a central opening in a base plate [8 and through an annular air-seal opening l9 which communicates with the air supply through an inlet opening 20 in the base of the machine.. The rotor ll revolving at high speed sets up, or continues as the case may be, a vortex in the material-laden air. A fan I! mounted at the upper end of the shaft l2, or an exhaust fan (not shown) connected to the machine outlets also may induce the particles of thematerial and the supporting air currents to rise in the chamber l5 during the whirling action of the vortex. In cases where the bottom feed of air is used the air will rise through the classification zone, and the fan l1 may be considerably reduced in proportions or eliminated.

In cases where pulverized material is fed into the classifier with insufficient force, etc., it becomes necessary to initiate the vortex action quickly and in sufficient intensity, and in other cases where it is desired to more quickly set up the vortex action in the classifying chamber, the lower portion of the rotor H may be provided with spaced blades or fins 2|. These blades are secured to the face of the drum or rotor, and are tapered with the wide portion moving very close to the bottom 18.

In all of the embodiments of the invention described in this application the details of construction of the apparatus may be substantially the same as that shown in Fig. 1. There the casing I0 is provided with a cover plate 31, to which is fastened the upper bearing member l3,

. and a base 38 which also supports the lower bearing l4. The rotor ll may be mounted on the shaft l2 through the medium of upper and lower annular heads 39 and 40 the upper head 39 beingbolted at 4! to a collar 42 keyed as at 43 to the shaft l2; The rotor l I is of sheet metal, such as polished Monel metal, and is mounted between the plates 39 and 40 so as' to form a smooth unbroken surface, especially in the upper portion. The fan or air impeller I! is also secured to the collar 42 by the bolts 4|.

The shaft l2 may be driven by a -pulley and belt drive 44 from a motor 45, or may be directly connected to the motor. For ordinary purposes a speed of about 300 feet per second at the periphery of the rotor has been found satisfactory, but this as well as the rate of air input and the feed of the material may be varied according to the material and sizes being classified and can be regulated readily to bring about the desired results hereinafter described.

The fan I] is mounted in a discharge chamber separated from the classification chamber l5 by an annular plate 23 having 'a central opening 22 of less diameter than the rotor, the arrangement being such that undulations or irregular movements of the air due to the rotation of the fan bllades will not be felt in the classification zone 5.

The plate 23 is spaced above the rotor top plate Accordingly, owing to the confined'space and the ing on the particle.

; horizontal direction,

a vertical direction, of gravity and the .rising component resulting from Thus the larger particles are the other factors, a uniform classification can be had of the smallest of the pulverized .particles supplied to the classifier, or, if desired, of all particles below a certain size.

Considering the bottom portion in more detail, the air-seal opening I8 is formed between the bottom edge of .the annular head 40 and the base plate l8. Adjacent the opening l9'is a set of air-impeller blades 41- which function somewhat like an air pump to supply air evenly and under pressure all around the bottom of the classification chamber at .the base of the fins 2|. The number and spacing and shape of the blades 41 may be varied without affecting the efficient operation of the machine, and in some cases they may be eliminated, for instance, if the air were forced into the machine under pressure through the inlet 20.

The lower portion of the classification chamber below the major classification zone may be characterized by an outer wall inclinedoutwardlytoward the bottom of the chamber as indicated at 48. This inclined wall cooperates with the outer edges of the blades 2| arranged at a. slightly greater inclination to form a tapered annular space the effect width of which becomes narrower as it approaches the bottom. With this arrangement, the centrifugal forces acting on the particles are increased at the bottom of the chamber due to the narrowed chamber and also the increased peripheral speed of the, bottom of the tapered blades 2|. Hence, the larger or oversize particles of material, falling to the bottom by gravity, are more quickly eliminated from the vortex by being swept around adjacent the base plate Hi to the outer wall '48 of the classification chamber and thence out of the machine through the exit port 26. It may be noted that the somewhat conical wall 48 also tends tov deflect downwardly the heavier particles thrown outwardly by the mid and upper portions of the blades 2|, thereby further aiding theprocess of eliminating those particles from the machine. A reason for the taper and height of the blades M is to gradually reduce and finally eliminate from the classification zone elements producing disturbing pulsations in the material-laden air, after which .final classification begins, as will now be described.

The approximate path of the particles is spirally upwardly while the classified position of a particle of given size is approximately represented by the vector line computed from the forces act- Such forces include the mass-velocity of the particle according to the well known formula (MW), which is a force in a and the opposed forces, in

the lifting action of the gaseous media on the particles in the vortex.

.During revolution of the rotor II the pulverized particles of material to be classified are set in rapid whirling motion and. are thrown outwardly toward the casing cording to their mass tion of the air or of particles toward the (MV while the lifting actop of the classifying cham- III with different velocities acagainst the pull of gravity,

the fans tends to raise the.

'particle along' the line R-S, along the line R-S selected fifty micron size her, and the force of gravity tends to draw the particles downwardly. For a given set of .conditions of speed of rotation, volume of aspirating air, and the effect of theforces noted above, the separation or Stratification of the particles occurs along somewhat definite lines corresponding to different heights, along the inner wall of the casing [0 apparently determined by the vector line or resultant of the forces named above. This is diagrammatically illustrated in Fig. 5 for a number of particles of different microscopic sizes. For particles of screen mesh, for example, there is a point on the outer edge of the vortex adjacent the wall of the casing where centrifugalforce upon such particles is not sufficient to maintain the particle in suspension and hence particles of that size will quickly mass and fall from that height.

The s'ame action occurs for particles of 200 screen mesh size, and of 50 micron size for further examples, but the points of equilibrium of the forces for these and other smaller sizes are at higher levels along the wall of the classification chamber.

Insofar as it has been possible to determine'at the present time it is believed that the various points of equilibrium and Stratification of the particles may be computed by considering a particle of a given size under a definite set of conditions at the lower portion of .the major classification zone, which point is designated bythe letter R. A 100 screen mesh particle will move substantially along the path of line R-S, a 200 mesh particle along the line R-S a 300 mesh a fifty micronparticle the line R,S and 'so on progressively with the smaller particles following closely the periphery of the rotor II and passing through opening 22 in plate 23 and out of the machine through a port 24. A collector of any suitable constructioncan be connected to port 24 to collect the particles discharged therefrom.

It is apparent that at any one or more of the circumferential areas S, S etc., the particles of the respective sizes may be taken out of the machine by providing suitable tapping ports around the casing I0. Accordingly, as illustrated in Figs. 1 and 5 a ring oftapping ports 25 (obviously shown exaggerated in size) may be provided to take out the particles at the S level which, in this example, are of the order of fifty microns.

With the exception of the smaller particles, at times termed fines, which leave the machine through the port 24, the other sizes than the particles fall toward the bottom of the classification chamber, and are swept out of the machine through the tan- 'gentially disposed outlet 25.

material may be removed from the classifier sia 400, mesh size multaneously. One arrangement therefor is by providing a repetition of tapping ports 25 at different levels as shown in Fig. 3. It is clear that any suitable number of circles of such ports may be provided and that with this arrangement a number of different particle sizes may be collected at the same time from a single machine.

In Fig. 4 is shown a slightly different form of tapping construction involving the same general principles. In this example, the diameter of the upper part of the casing I is enlarged as indicated at 21. This increase in the width of the classifying space enables the particles to travel outwardly where gravity has asmaller MV force to overcome, thus the desired particles more readily gravitate and find their way substantially straight downward and out of the machine through the port openings 29 to a place of collection or use at the outside of the machine. It will be seen that with this form of device all particles between the smallest, which escape through opening 22, and the size determined by the height of the lip 28, will be collected so that a mixture of graduated sizes will be available. Such mixtures are usable in a number of industries, of which the cement industry is one.

product. Unit A in Fig. 6, operating as any of the machines described above, has a circle of tapping ports I25 which discharge into the lower portion of 'the classifying zone of unit B. The particle size at ports I25 may be fifty microns as assumed above, but some particles of smaller size also'may be ejected through ports I25. However, when that discharged material enters the B unit the desired fifty micron particle has now become the largest particle size in the B unit. That particle size may now be discharged and collected through bottom outlet I26 while the lighter material rises and is taken off at the top opening I35 or through an intermediate tap I31 as indicated.

While several practical embodiments of the invention have been illustrated 'and described, it is to be understood that various other modifications There is also shown in Fig. 4 a screw feed conveyor 30, provided with a suitable feed opening 3| and driven by any desirable means such as a belt and pulley 32, which is one arrangement that may be used for feeding the pulverized material to the classifier. This form of feed may be substituted for that described in connection with Fig. 1.

Returning to Fig. 3, it has been found advantageous in some instances to provide the rotor and the opposite wall of the classification chamber with facings of suitable material such as rubber. These facings are indicated in the drawing by the numerals 33 and 34. respectively. The lower portion of the rubber faced rotor also may be provided with rubber impellers or fins 35. The relatively rough surface (as compared to polished metal) thus provided on the rotor wall H has an increased skin-drag efiect and sets more air in motion than the polished metal surface consequently increasing the vortex action and the centrifugal throw-out of the various particles ac-' cording to their mass characteristics, while the stationary rubber facing 34 has a damping effect tending to stop the travel of the projected particles at the rubber surface, so that the desired stratification becomes sharply defined. The rubber facings also protect the parts of the classifler from wear and lengthen the life of the classifier, in which the increased skin-drag effect probably plays an important part.

Although not shown, it will be understood that any suitable form of regulator may be inserted in the air inlet opening 20 to thus control the amount of aspirating air admitted at the bottom of the machine. By so controlling the air the particle side delivered and collected can be determined because varying this factor varies the upward force acting against gravity, and the time 'the material remains in the classifier chamber.

To obtain a high degree of uniformity in particle size with-material required in some industries, Fig. 6 illustrates diagrammatically one method and arrangement of apparatus for continuously obtaining accuracy in classificationof materials. A pair of classifiers, of the general kind described above, are connected together in a manner such that oversize and underslze particles are definitely eliminated from the final and changes may be made without departing from the fundamental principles outlined. Accordingly, it is not intended to impose limitations in the scope of the invention, except as defined in the appended claims.

I claim: i

1. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying chamber therebetween which is narrow as compared to the diameter of said rotor, means for feeding the material .and a gaseous medium to the classifying, chamber, means for driving said rotorat high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifying chamber during'the vortex action, and a tapping port at a definite level along the side of the casing through which particlw of the suspended material of a predetermined size pass from said chamber.

.2. A machine for classifying pulverized material containing particles of diiferent sizes, comprising a cylindrical casing, a cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying chamber therebetween which is narrow as compared to the diameter of said rotor, means for' feeding the material and a gaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension,. means for causing thesuspended material to rise in the classifying chamber during the vortex action, and tapping ports at different levels along the side of the casing through which particles of said material of predetermined different sizes pass from said chamber.

3. A machine for classifying pulverized material containing particles of diflerent sizes, comprising a cylindrical casing, a cylindrical rotor within said casing and. concentric with and spaced from said casing to form a classifying chamber therebetween which is narrow-as compared to the diameter of said rotor, means for feeding the material and a gaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex of said material ingaseous suspension, means for causing the suspended material to rise in the classifying chamber during the vortex action, an outlet at the top of the casing for removal of collectible flne particles of said material rising in said chamber adjacent the peripheral face of the rotor, and a tapping port at a definite level along the side of the casing through which classified particles of said material of a size larger than said fine particles pass from said chamber.

4. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying chamber'therebetween which is narrow as compared to the diameter of said rotor, means for feeding the material and a gaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex'of said material in gaseous suspension, means for causing the suspended material to rise in the classifying chamber during the vortex action, an outlet at the top of the casing for removal of collectible fine particles of said material rising in said chamber adjacent the peripheral face of the rotor, and tapping ports at different levels along the side of the casing through which classified particles of said material of larger sizes pass from the classification chamber.

5. A machine for classifying pulverized material containing particles of diiferent sizes, comprising a cylindrical casing,. a cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying chamber therebetween which-is narrow as compared to the diameter of said rotor, means for feeding the material and a gaseous medium to the classifying chamber at one end thereof, means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifying chamber during the vortex action, and a tapping port at a definite level along the side of the casing through which classified particles of material pass from said chamber, the classifying rotor being provided with impeller blades extending part Way along said rotor adjacent said feeding means only.

6. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying chamber therebetween which is narrow as com pared to the diameter of said rotor, means for feeding the material and a gaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifyi ing chamber during the vortex action, and a tapping port at a definite level along the side of the casing through which classified particles of said material pass from said chamber, said feeding means including an opening through the casing beneath said tapping port and a connecting conduit substantially tangential to said classifying chamber.

7., A machine for classifying pulverized material containing particles of different sizes, comprising a casing, a rotor concentric with and spaced from said casing to form therewith a classifying chamber, means for feeding the material and a gaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex of said materialin gaseous suspension, means for causing the suspended material to rise in the classifying chamber during th vortex action, a tapping port at a definite level along the side of the casing through which classified particles of material pass from said chamber, said feeding means including an opening through the casing beneath said tapping port and a connecting conduit substantially tangential to said classifying chamber, and an exit opening in the periphery of said chamber and adjacent the lower end thereof from which gravitated material is swept from the machine by the action of the rotor.

8. A machine for classifying pulverized material containing particles of different sizes, comprising a casing, a rotor concentric with and spaced from said casing to form therewith a classifying chamber, means for feeding the material and a gaseous medium tothe classifying chamber, means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifying .chamberduring the vortex action, tapping ports at different levels along the side of the casing through which stratified particles of said material of predetermined different sizes pass from said chamber, said feeding means including an opening through the casing beneath all of said tapping ports and a connecting conduit substantially tangential to said classifying chamber, and an exit conduit substantially tangential to said chamber and beneath the plane of said other opening.

9. A machine for classifying pulverized material containing particles of different sizes, comprising a .casing, a rotor concentric with and spaced from said casing to form therewith a classifying chamber, means for feeding the ma terial and a gaseous medium to the classifying chamber, .means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifying chamber during the vortex action, tapping ports at different levels along the side of the casing through which stratified particles of said material of predetermined difierent sizes pass from said chamber, said feeding means including an opening through the casing beneath all of said tapping ports and a connecting conduit substan- 1 tially tangential to said classifying chamber, and

'an exit conduit substantially tangential to said chamber and beneath the plane of said other opening.

10. A machine for classifying pulverized material containing particles of different sizes, comprising a casing, a smooth rotor having a smooth surface concentric with and spaced from said and a port at the side of the casing communicatcasing to form therewith a classifying chamber,

an inlet for a gaseous medium at one end of said rotor, means communicating with the other 'end of the rotor so constructed and arranged that said medium rises through the classifying chamber, means for feeding the pulverized material to the chamber, means for driving the rotor at high speed to maintain a vortex action and to intermix said material with the gaseous medium to form a suspension of dispersed particles, and

ports at the side of the casing at different levels along the classifying zone so that stratified particles of predetermined particle sizes respectively may be removed from the classifying chamber.

12. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a'vertical, cylindrical rotor within said casing and concentricwith and spaced from said casing to form a classifying chambentherebetween which is narrow as compared to the diameter of said rotor, an inlet for a gaseous medium at one end of said rotor and means communicating with the other end of the rotor arranged so that said medium rises through the classifying chamber, means forfeeding the pulverized material to the chamber, means for driving the rotor at high speed to maintain a vortex action and to intermix said material with the gaseous media to form a suspension of dispersed particles, a port at the side of'the casing communicating with the classifying chamber,

said port being located at a point intermediate the ends of said rotor and being adapted for the 'withdrawal from said chamber of stratified material of a predetermined particle size, said casing having an outlet port above the rotor, and a plate adjacent the top of the rotor interposed between said outlet port and the classifying chamber, said plate having an opening for passage of relatively small and collectible particles.

chamber therebetween which is narrow as compared to the diameterv of said rotor, an inlet for a gaseous medium at one end of said rotor, means communicating with the other end of the rotor arranged so that said medium rises through the classifying chamber, means for feeding the pulverized material to the chamber, means fordriving the rotor at high speed to produce and maintain a vortex action and to intermix said material with the gaseous media to form a suspension of dispersed particles, the lower peripheral portion only of' said rotor'being provided. with impeller blades to initiate the vortex action, the lower portion of the casing adjacent said blades being inclined inwardly and upwardly.

14. A machine for classifying pulverized material containing particles of different sizes, com- "prising a cylindrical casing, a vertical, cylindrical rotor within said casing and concentric with and spaced from said casing to form a classifying ch mber therebetween which is narrow as compa ed to the diameter of said rotor, an inlet for a gaseous medium at one end of said rotor, means communicating with the other end of the rotor arranged so that said medium rises through the classifying chamber, means for feeding the pulverized material to the chamber, means for drivingthe rotor at high speed to produce and maintain-a vortex action and to intermix said material with the gaseous media to form a suspension of dispersed particles, the lower portion only of said rotor having inwardly and upwardly tapered impeller blades, and the lower portion of said casing being similarly tapered.

15. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a vertical, cylindrical rotor'within said casing and concentric with and spaced'from said casing to form a classifying chamber therebetween which is narrow as compared to the diameter of said rotor, an inlet for a gaseous medium at one end of said rotor, means communicating with the other end of the rotor arranged so that said medium rises through the classifying chamber, means for feeding the pulverized material to the chamber, means for driving the rotor at high speed to produce and maintain a vortex action and to intermix said material with the gaseous media to form a suspension of dispersed particles, the lower portion only of said rotor having upwardly and inwardly tapered impeller blades, the lower portion of said casing being also upwardly and inwardly tapered to cooperate with said blades, and a discharge opening opposite said blades.

16. A machine for classifying pulverized material containing particles of different sizes, comprising a cylindrical casing, a vertical, cylindrical rotor within said casing and concentric with and spaced from said casing to forma classifying chamber therebetween which is narrow as compared to the diameter of said rotor, means for feeding the material and agaseous medium to the classifying chamber, means for driving said rotor at high speed to maintain a vortex of said material in gaseous suspension, means for causing the suspended material to rise in the classifying chamber during the vortex action, and a tapping port at a definite level along the side of the casing through which stratified particles of material pass from said chamber, the portion of said casing above the level of said port being enlarged and communicating therewith.

17. A machine for classifying pulverized material comprising a stationary cylindrical casing, a concentric smooth walled cylindrical rotor within said casing and spaced therefrom a distance which is small as compared to the diameter of the rotor, resilient covering material upon opposed faces of said casing and rotor, means for feeding a gaseous medium and pulverized material to the space between the casing and rotor, outlets respectively for material of selected size and for oversize material, and blades constructed at least in part of resilient material cooperating with said rotor to produce and maintain a vortex action in the pulverized material and gaseous medium and to eject oversize particles of matehaving a smooth wall except for a bladed portion at one end thereof, a rubber covering for the inner surface of the casing and for the opposed surface of the rotor, nieans for feeding material to the space between the rotor and casing, an 'outlet from said space adjacent the end of the rotor opposite said bladed portion, and means for producing a current of air through substantially the entire extent of said space and through said outlet.

19. A machine for classifying pulver d material comprising a stationary cylind cal casing having a smooth rinner surface, a concentric cylindrical rotor within said casing and spaced radially therefrom a distance which is small as bladed portion, and means for producing a current of air through substantially the entire extent of said space and through said outlet.

' HENRY G. LYKKEN.

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