US2304264A - Apparatus for pulverizing and classifying materials - Google Patents

Description

H. G. LYKKEN APPARATU$ FOR PULVERIZING AND CLASSIFYING MATERIAL Filed Jan. 16, 1959 4 Sheets-Sheet l FIG].

INVENTOR.

. LY KEN 3 B 2 R I o 4 M 4 .Q m 4 4 3 3 .M 72 l O 7 9 l. M X I M I. n |l.vl W 7 u an Y M n w d J 2w M QM 4 M I. 5 N1 2 a I] A 5 5 J a 5 6 J 4 HENRY ATTORNEY.

H. G. LYKKEN Dec. 8, 1942.

APPARATUS FOR PULVERIZING AND CLASSIFYING MATERIAL Filed Jan. 16, 1939 4 Sheets-Sheet 2 FIG FIG.-3

INVENTOR. HENRY G. LYKKEN ATTORNEY.

H. G. LYKKEN Dec. 8, 1942.

APPARATUS FOR PULVERIZING AND CLASSIFYING MATERIAL Filed Jan. 16, 1939 4 Sheets-Sheet 5 INVENT OR.

. VK K E N ATTORNEY.

HENRY c; BY 7 H. G. LYKKEN 2,304,264

Fi led Jan. 16, 1959 '4 Sheets-Sheet 4 APPARATUS FOR PULVERIZING AND CLASSIFYING MATERIAL Dec. 8, 1942.

INVENTOR. HENRY KE I I v ATTORNEY.

Patented Dec. 8, 1942 UNITED STATES PATENT OFFICE APPARATUS FOR PULVERIZING Ann cmssmrmo MATERIALS Henry G. Lykken, Minneapolis, Minn. Application-January 16, 1939, Serial No. 251,062

' .14 Claims.

.My invention relates tonew and improved apparatus for pulverizing and for classifying friable material, i. e., so as to deliver from the apparatus all particles of pulverized material smaller than a determinable particle size. a

More specifically, my invention relates to such apparatus wherein pulverization and classification each occurs in a vortex of air and suspended material. Throughout this specification and classification apparatus can be part of the same housing or they may be separate, interconnected units.

In the pulverization of friable materials, there are manyfactors which adversely affect the emciency of pulverization per unit of power input. Of course, the chemical nature and physical structure of the material, its specific gravity, the ratio of mass to weight of particles of material, the size of the material fed to the pulverizing chamber, and the degree and amount of pulverization desired all must be considered in the design of the apparatus. Additionally, some factors affecting efilciency are adequate and even distribution of material to be pulverized throughout the vortex, the prompt and complete removal therefrom of all material that is sufficiently pulverized, the return thereto of any oversize particles that escape from the pulverizing vortex so as not to interfere with the'pulverizing action'or-the rgoval of the sufficiently pulverized material, e

In the classification of pulverized material, it has heretofore been proposed to use the vortex action for classification because, in a vortex, material is acted upon according to-its mass and the velocity of the vortex, and the oversize material thus will be thrown to the outside of the vortex and the material of desired size will remain in or find its way to the center of the vortex, from-which it can be removed while the oversize is returned tothe pulverizing chamber for further pulverization.

Also, means heretofore have been provided for maintaining the velocity of the vortex with or without creating turbulence in the vortex. Again, many of the same factors, referred to above,

adversely affect the efilciency of the "classifier action. Usually the deslderatum is to deliver as much pulverized material as possible of the selected particle size, i. e., with a very small amount of fines therein, and, for many purposes,

it is essential that no particles larger than the selected size escape from the classification chambet with the finished material.

Broadly speaking, it is the object of my invention to provide pulverization and classification i5 apparatus of the indicated character which will operate efilciently in handling large quantities of material with any desired selected size delivered from the machine, even with extremely fine particles.

It is another object of my invention to provide apparatus of the above indicated character in which changes and adjustments can be quickly and simply made so as to accommodate the machine to handling diflerent types of material or to deliver different selected particle sizes.

It is still another object of my invention to provide pulverizing apparatus of the indicated character with an improved form of rotor for creating the pulverizing vortex.

It is still another object of my invention to provide a classification chamber in which there is an upwardly spiralling vortex feeding into an open end type of rotor.

It is a further object of my invention to provide a machine in which pulverization and classification occur wherein the material is pulverized in a vortex of air and suspended material, the vortex passes into a free vortex zone for preliminary classification and then into a zone having a centrifugal action at a right angle to the axis of the vortex to remove the remaining particles above a pre-determined size.

. It is a still further object of my invention to provide an apparatus for classifying pulverized accurate classification is obtained efiiciently with relatively low speed whirling action. It is a still further object of my invention to provide a pulverizing and classifying machine slfication chamber while maintaining emcient material to extremely fine particle sizes in which ble, in which it is easy to clean or replace parts,

and which is simple and eilicient in operation.

Other and further objects and advantages of my invention will appear from the following specification taken in conjunction with the ac-- companying drawings, in which- Figure 1 is a vertical longitudinal section of a pulverizing and classifying machine, showing one embodiment of my invention;

Fig. 2 is a cross section of such apparatus taken on the line 2-2 of Fig. 1, showing the rotor of the pulverizingchamber;

Fig. 3 is also a cross section of such apparatus, taken on the line 3-4 of Fig. 2, showing the rotor in the upper classification zone:

Fig. 4 is a longitudinal section of a classifier, showing a modified form of rotor: and

Fig. 5 is a longitudinal section of a further modified form of classifier.

The embodiments of my invention shown in the drawings have been successfully operated, but they are shown here purely by way of illustration of the principles involved, my invention not being limited to such forms.

Referring to Figs. 1, 2 and 3, the combined pulverizing and classifying machine comprises a base I l, upon which is mounted a cylindrical casing l2, the casing being closed at its top by a plate l3. A rotatable shaft l4, driven by any suitable source of power, is mounted in bearings l5 and i6, respectively located in the base and top plate. Secured within the casing "and spaced above the base ii is a dish-shaped bottom plate l1 having a central opening l8 therein. The casing has an air inlet opening l9, communicating with the space between the base H and bottom plate I1. Either the opening l8 or the opening I9 is to be provided with suitable means for controlling the amount of air which can be drawn into the machine, as hereinafter described, one such means being illustrated by the slide 2i movable in'guides MA to vary the size of opening I8.

A pulverizing rotor is carried by the shaft M adjacent the plate I1, and is of the closedend type. The rotor frame comprises a hub 22, fast upon the shaft It, to which are secured upper and lower discs 23 and 24 and between which are mounted a plurality ofradially extending supports 25. The disc 241s of larger diameter than the upper disc 23 and these discs are slotted to receive the radial supports 25, which extend beyond the bottom of the plate 24 to form fan blades 21 between the disc 24 and plate II. The lower edges of the blades 21 are shaped to conform to the inclination of the bottom plate II. It will be noted that the supports 25 do not extend beyond the edges of the plates 23 and 24. Bolted to each of the supports 25 are removable blades 28 which constitute the blades of the pulverizing rotor. The outer edges of the blades 28 are inclined as indicated at 29, so as to form a tapered rotor. As explained above, various materials require diflerent degrees of pulverizing templated in this connection blades 28 having other angles of inclination may be interchanged upon the rotor frame as may be best adapted for the particular use of the machine, or that the positions of the blades 28 upon the radial supports 25 may be varied so as to vary the angle of inclination of the rotor blades. In Fig. 1, the blades 28 are wider than the radial supports, and extend slightly beyond the outer edges of the discs 23 and 24. This projection may be more or less than indicated, both for the entire blade, or for either end thereof. However, I prefer to have the rotor function as a closed end rotor to produce a violent vortex action almost entirely in the annular zone around the rotor, and neither the air or material passes through the rotor.

. In this latter connection, air is fed to the vortex area through the opening 3i, and material is fed directly to the vortex zone through the opening 32. Any suitable feeding means may be used, there being illustrated in the drawing a conventional screw feed mechanism 33. Preferably, the feed mechanism will be such that the rate of feed will be controllable in accordance with the requirements of the particular machine.

The inner surface of the casing i2 has at the lower portion thereof, in the pulverizing zone, a corrugated liner ll, which is shown as removable. For most purposes I prefer to use such a liner to retard thematerial circulating in the outer portion of the annular vortex so as to create a greater differential of movement between the particles of suspended material circulating therein. To this end the depth of the corrugations may vary with different materials, but in all cases, the corrugated liner may be omitted entirely and in some cases it may even be preferable to omit it.

In the operation of the pulverizer as described, the material is fed into the vortex of air created by the rotor, and is carried in suspension in that vortex while being whirled around at high speed. The centrifugal forces acting upon the particles will cause a rubbing of particles upon each other as well as an impact between particles with a corresponding shifting of the particles about in the vortex as they are reduced in size, thus creating further impacts and further attrition, all as is well known.

However, the upwardly inclined rotor will pro duce' a more violent vortex in the narrow space toward the bottom of the pulverizing zone where vortex action created by the rotor and it is conthere is atendency for the greatest concentra-' tion of material to be pulverized, and as the area of the vortex zone increases, by reason of the taper of the rotor, the vortex action is a little less violent and more space is provided for the material as it becomes pulverized'.- Furthermore, the component of the forces produced by the upwardly inclined roto'r are such as to cause a more I complete and equal distribution of the material throughout the vortex zone. "Additional advan-' tages arising from use of the inclined rotor occur with respect to the return of the oversize material from the classification zone or chamber. the prompt inter-mingling of the returned material with the vortex, and in the thorough, complete and prompt removal from the pulverizing zone of the sufficiently pulverized material, all of which matters will be more fully discussed hereinafter. v r

In the embodiment shown in Figs. 1 and 3, the classification chamber is defined by a smoothsurfaced inner casing II which is of less diameter than the outer casing l2 and is held spaced therefrom by any suitable means, such as the spacing rings 40. The chamber comprises a free zone 4| at one end thereof, in which there is no mechanism, and a zone 42 at the other end of the chamber in which is located a rotor 43. The upper end of the classification chamber is closed by a ring shaped plate 44 having a central opening 45 therein which constitutes the outlet from the classifier.

This outlet communicates with the chamber 45 between the ring shaped plate 44 and the top plate I3 from which is a discharge opening into an outlet pipe 41 for the finished material.

The rotor in the classification chamber consists of a lower disc 48 having a central inlet opening 49 therein, a top disc having a central outlet opening 52 therein, and a plurality of radially disposed blades 53 which are mounted upon a hub 54. The discs 48 and 5| and blades 53 are secured together in any appropriate manner, as by welding, and the hub 54 is fast upon the shaft l4 so as to rotate therewith.

The top disc 5| of the rotor 43 larger in separation by the vortex rotor 43 during all of which time t or removal of the oversize particl is continuing progressively so that by thetime the material-laden air in the vortex reaches the opening 49, the greater portion if not all of the oversize material has been thrown out toward the outside of the casing and beyond the limits of the opening 49. The air and the remaining material carried therein enters the opening 49 where the air and material is given a whirling motion by the rotor 43 and is subjected to the centrifugal forces. generated by the rotating fan blades 53.

. The action and proportioning of the various the additional centrifugal force imparted by the diameter than the bottom disc 48 and extends very close to the inner casing 39 as well as close to the ring-shaped plate 44. In order to prevent any leakage of air and material to the outlet 45 through the space between the plate 44 and disc 5|, the top surface of the disc may be provided with small radial ribs 55 to act as fan blades exerting a centrifugal pressure outwardly toward the inner casing 39.

The.chamber-48 is, in this embodiment, a fan chamber as well as an outlet chamber. The chamber has two fans therein, the fan 55 and the fan 51. The fan 56 has a plurality of blades 53 which, in the structure indicated in Fig. 1,

are reduced extensions of the blades 53 of the classifier rotor, the hub 54 also being extended upwardly to carry the blades 58. At the upper end of the blades 58 is a top disc 59 to which the blades are secured in any suitable manner.- The fan 51 comprises a plurality of blades 5| mounted radially upon a ring shaped plate 62 which in turn is secured to the disc 59. .{ I'he fans 55 and 51 act as suction fans to draw the air and the material suspended therein through the pulverizing and classifying chambers, but such suction apparatus need not be located in the casing at all, and may be a suitable suction device entirely separate and distinct from the pulverizing or classifying mechanism as shown, for example, in my prior Patent No. 1,760,245, issued May 27, 1930, the showing of the drawings being a present preferred arrangement that is satisfactory for most materials.

The operation of the classifier can be described as follows: The high speed vortex created by the pulverizing rotor discharges or spirals upwardly from the annular pulverizingzone into the lower chamber 4| carrying with it pulverized and some partially pulverized ,or oversize material. In the rotor 43 to be thrown outwardly toward the inner casing 39 at right angle to the normal path through the rotor. Furthermore, the proportioning is such that most of the air leaves the classifierthrough the outlet 52 of the rotor.

, Such air as is thrown laterally by the rotor passes around the edge of the bottom disc 48 and recirculates through the opening 49. Hence any sumciently pulverized material which may have been thrown out accidentally by the rotor 43 is carried back into the opening 49 and finds its way out of the machine with the upwardly rising currents of air. In this connection, it will be noted that the blades 53 of the rotor do not extend to the edge of the disc 48, which arrangement I prefer so as to overcome any tendency for turbulences at the edge of the rotor. Also,-

the size of the disc 48 may be different, which will vary the amount of recirculation, and is a desirable control. However, since the action of the rotor 43 is in the same direction as the vortex in the free zone 4|. the air and material discharged radially from the rotor is receiving an impetus from the fan blades in the direction of the vortex thus tending to maintain the vortex action in the classification chamber.

The discharge pipe 41 of the machine may be connected either to a collector, such as a cyclone collector, or directly to some point of use for the pulverized material.

The classifier action and operation has been described in connection with the mechanism as shown, in which the inlet opening 49 to the rotor 43 is approximately the same size as the outlet openings 52 and 45. The velocity of the material laden air moving through the fan 43 can be controlled by controlling the relationship of these inlet and outlet openings from a relationship where the inlet opening is considerably smaller than the outlet, to the relationship where the vertical vortex type of machine shown in Fig. 1, 4

' 4| toward the eye or inlet opening 49 of the inlet would be considerably smaller than the opening 49. In this latter case the air and material might even enter the rotor 43 principally at the top of the pulverizing chamber so that there is a wide space for the entrance of the re- Jected material. This wide space is likewise useful to allow ready removal of the pulverized material from the vortex zone without being impeded by-the returning rejected material. Furthermore, this permits of aeration of the retuming material by the upwardly moving air so that any completely pulverized particles which may be clinging to the oversize material will be removed and carried back into the classification chamber. Additionally, the inclination'of the rotor blades permits of a better distribution of the returning material in the pulverizing vortex because it will be subjected to the action of a larger part of the blades than if the rotor were of uniform diameter.

In'the arrangement and proportioning of this entire apparatus large volumes of air may be carried through both the pulverizing chamber and the classification chamber so that the material that is sufficiently pulverized is promptly carried out of the pulverizing chamber, through the classification chamber, and out of the machine with the result that the delivered product zontal rotor type of machine shown for example.

in my Patent No. 1,838,560, issued December 29, 1931, or in conjunction with a machine where a vortex is created by air jets as shown in my prior Patents Nos. 1,756,254 and 1,768,621, issued respectively April 29, 1930, and July 1, 1930, or with any other pulverizer mechanism. Also, the air-suspended material may be caused to whirl in the classifier by other means than the pulverizing rotor as, for example, being introduced into the classifier mechanism in such direction as to create a vortex in the free zone 4|, as indicated in my prior Patent No. 1,753,437, issued April 8, 1930.

The; casing of the apparatus illustrated in Figs. 1, 2 and 3 is approximately fifty-four inches high and twenty-four inches in diameter, and pulverizes several hundred pounds of materials -per hour using a rotor speed of approximately twenty-two hundred revolutions per minute. The

free zone 4| is shown as having considerable height, but I have used successfully a machine of this construction having twelve inches less height, as well as machines of greater dimensions. Likewise, the drive for the shaft l4 may be either through the top or the base of the machine, as indicated in the co-pending application of Lykken and Lykken, Serial No. 285,484, filed July 20, 1939. I prefer to drive the shaft through belts and pulley, such as pulley 65 shown in Fig. 1, as will be understood. It will be evident that any other form of drive and method of speed variation could be. used. Also, in some instances the inner casing 39 may be omitted.

Also, the pulverizing rotor is shown with eight blades and the classifier rotor as having four blades but the number of blades used on each of these rotors may be varied as may be found necessary or desirable for the particular problem in hand.

It should be pointed out that the present in vention contemplates a drive for the classifica-' tion rotor that is independent of the drive for the pulverizing rotor so that the speed of the classifier rotor may be varied from the speed of the pulverizing rotor as one means of regulating the degree of'classification or separation in accordance with the requirements of the particular case in hand.

Fig. 4 illustrates a classifier such as may be used with other types of pulverizing mechanisms than the vertical rotor type shown in Fig. 1, although, of course, the principles may also be used in that construction also. In this case there is shown a modified form of classification rotor.

The classification apparatus comprises a casing ll having a lower entrance portion 12, with an inlet opening 13 at the bottom thereof, and a top plate I4. closed by a ring-shaped plate 19, corresponding to the ring-shaped plate 44, and is spaced from the top plate 14 so as to form a combined fan and outlet chamber 16. The classification chamber has a free vortex zone 11 at the lower end thereof, and an upper zone 19 in which is located the rotor 19. The rotor 19 is mounted upon a shaft M which is driven by any suitable source of power (not shown). Air-suspended pulverized material enters the classification chamber through the opening 13 and preferably in a manner to produce a vortex in the air and material. 1

In the lower portion of the free zone 11 a rotor in the form of a fiat disc 92 may be mounted .upon the shaft 9| so as to be rotated therewith. The disc 92 performs two omces, first, it prevents a direct entrance of the air-suspended material into the opening or eye 94 of the rotor 79 and, secondly, it imparts an impetus to the vortex of air and material so as to increase or maintain the speed thereof in the zone Il without imparting any turbulence thereto. I

The rotor 19 comprises a lower disc 99, in which is the inlet opening 84, and an upper disc 86, in which is an outlet opening 91 that com- 'municates with the outlet opening 99 from the classification chamber to the fan and outlet chamber 16. It will be noted that the bottom disc 85 of the rotor 19 extends more closely to the inner surface of the casing ll than does the bottom disc 48 of the rotor shown in Fig. 1. The rotor I9 has a plurality of radial blades 99 which are mounted upon a hub 9| and to which the discs 95 and 96 are secured. Again in this structure a reduced portion of the blades. 99 extend through the openings 91 and 99 into the fan chamber 19 to form the fan 92. The fan chamber also has a fan 93 corresponding to the fan 51 shown in Fig. 1. i

In the form shown in Fig. 4, the rotor blades 89 are slotted horizontally for the reception of a fiat disc 94 which is secured to the blades and also to the hub 9|. The disc 94 extends transversely of and a substantial distance across the openings 94, 91 and 99. The material to be delivered from the classifier enters the chamber 16 through the opening 99 and is delivered from the machine through the outlet 99 to a collector or to a place of use as the case may be.

The operation of the classifier is somewhat similar to the operation of the classifier described in Fig. 1, in that there is a free vortex zone 11 in which the primary classification takes place and the coarser material is thrown outwardly, while th finer material and air enters the eye 94 of the rotor 19 where it is subjected The classification chamber itself is to the centrifugal throw-out action of the blades 89 to remove any oversize particles which may not be eliminated in the vortex action in the free zone 11. However, in the modification shown in Fig. 4, the purpose of the disc 94 is to force all of the air and material away from the axis of the fan I9 so as to be subject to the greater centrifu-' gal force exerted by the outer ends of the fan that obtained with much higher speeds of rotation with the type of classifier rotor shown in Fig. l for example, or by other forms of vortex classifiers heretofore used in the art. Addltionally, there is even less likelihood of any stray particles of oversize material escaping from the classification. chamber through the outlet 00.

Conversely, by the addition of such a disc as illustrated at 94 in Fig. 4 to the higher speed rotors, such as shown in Fig. 1, it is possible to deliver from the classifier practically impalpable powder free of any oversize particles.

Fig. 5 illustrates a further modification of the arrangement in the classification chamber, the same being shown applied to a classifier similar to that shown in Fig. 4, and duplicate parts of operation and use will not be described. In the form shown in Fig. 5, the classifier rotor comprises a bottom disc IOI having an inlet opening I02 therein, a top' disc I03, and a plurality of radial blades I 04 mounted upon ahub I05 that is fast upon the rotatable shaft I06. Mounted below the bottom disc I M of the classifier rotor is a disc I01 carried by a hub I08 which is fast upon the shaft I08, as by means of a set screw, but which may be adjusted vertically along its length to be closer to or more removed from the inlet I02. The purpose of this disc I01 is three-fold in that (1) it prevents a direct vertical entrance of the air-suspended material into the rotor blades I04 along the shaft I06, and for a considerable distance laterally thereof, (2) it imparts a higher rotative speed to the vortex as it is about to enter the eye I02 of the classifier rotor so as to reject oversize material just prior to entering that rotor; and (3) it controls the amount of air entering the classifier rotor and hence the amount of air that is recirculated between the zone III of that chamber and the free zone II2. That is to say, the less amount of air that is permitted to enter the classifier rotor. the less there will be discharged laterally therefrom and recirculated, because of the demands of the suction fan II3 which corresponds in operation to the fan 56 of Fig. l and 92 of Fig. 4.

This recirculation can be controlled from the instance where the disc I0! is very close to the bottom disc IN, to the condition where it is so far removed therefrom that substantially the full quantity of air and material can enter the eye I02 of the fan. The use of this disc I0'I also enables the obtaining of desired fine classification with relatively low speeds of rotation of the classifier rotor, and controlling the recirculation of air be- Other and further modifications may be made in the arrangement and location of parts within the spirit andscope of my invention, and such modifications are intended to be covered by the appended claims.

I claim:

1. A pulverizing and classifying chamber comprising a casing, air and material inlets thereto. a closed end rotor operating adjacent one end of the casing to produce a pulverizing vortex of airsuspended material. the rotor having radial blades arranged to form a tapered rotor, an out-. let at one end of the casing. means for drawing air and pulverizing material through said casing and outlet, and a classifying zone having two communicating portions, one having a substantially smooth wall in which the vortex of air and pulverized material rotates substantially free from turbulence, and the other receiving the air suspended material from the first portion and having therein adjacent the outlet means for subjecting the air and pulverized material to a further centrifugal action on its passage to the outlet, to reject oversize material and return the same to the casing for further pulverization.

2. A pulverizing and classifying chamber comprising a tubular casing, air and material inlets .thereto, a closed and rotor operating adjacent one end of the casing to producea pulverizing vortex of air-suspended material, the rotor having radial blades arranged to form a tapered rotor, an outlet at one end of the casing, means for drawing air and pulverized material through saidcasing and outlet, and a classifier for the pulverized material having a bladed rotor mounted adjacent the outlet end of said casing, said rotor having axial inlet and outlet openings, there being a substantially uninterrupted portion of said casing between said rotors in which portion the vortex of air and pulverized material rotates, the classifier rotor communicating at its periphery with the intermediate portion of the casing.

3. A pulverizing and classifying machine comprising a casing, air and material inlets thereto. a closed end rotor operating adjacent one end of the casing to produce a pulverizing vortex of airsuspended material, the rotorv having radial blades arranged to form a tapered rotor, an outlet at one end of the casing, means for drawing air and pulverized material through said casing and outlet, and a classifying zone having a substantially uninterrupted portion into which the vortex of air and pulverized material is introduced and rotates substantially free from turbulence, and a second portion having therein a rotor mounted adjacent the outlet, said rotor comprising spaced apart top and bottom discs having axial openings therein, a hub, and radial blades extending between said discs, the blades having a shorter radius than the bottom disc.

4. A pulverizing and classifying chamber comprising a casing, air and material inlets thereto, a closed end rotor operating adjacent one end of the casing to'produce a pulverizing vortex of airsuspended material, the rotor having radial blades arranged to form a tapered rotor, a plate dividing the casing into a classifying zone and a fan-containing zone, the plate having a central outlet opening therein, and a rotor mounted adjacent the outlet opening and having a hub and a plurality of blades mounted thereon extending through saidoutlet opening and both above and below said plate.

5.-A classifier for pulverized material comprising a cylindrical casing of substantial height,

means for producing in the lower part thereof a vortex of air-suspended pulverized material, an

into the casing beneath the rotor and into the inlet opening.

6. A classifier for pulverized material comprising a casing, means admitting air and material thereto for classification of the material, an outlet therein, a hub mounted in the casing,-and a rotor mounted on said hub, said rotor comprising bottom and top discs respectively having axial inlet and outlet openings, and a plurality of blades extending across the openings and between the discs, the rotor communicating about its periphery with the interior of the casing. and a plate mounted in said casing and operatively associated with said rotor, said plate extending transversely of said openings.

7. A classifier for pulverized material comprising a casing, means admitting air and material thereto for classification of the material, an outlet therein, a hub mounted in the casing, and a rotor mounted on said hub, said rotor comprising bottom and top discs respectively having axial inlet and outlet openings, a plurality of blades extending across the openings and between the discs, the rotor communicating about its periphery with the interior of the casing, and a plate mounted between the top and bottom discs and extending a substantial distance transversely of said openings;

8. A classifier for pulverized material comprising a casing, means admitting air and material thereto for classification of the material, an outlet therein, a hub mounted in the casing, and a rotor mounted on said hub, said rotor comprising bottom and top discs respectively having axial inlet and outlet openings, a plurality of blades extending across the openings and between the discs, the rotor communicating about its periphery with the interior of the casing, and means cooperating with the rotor to divert material a, substantial distance toward the periphery of the rotor as it passes through the openinga 9. A classifier for pulverized material comprising a casing, means admitting air and material -thereto for classification of the material, an outlet in the casing, a hub mounted in the casing, and a rotor mounted on said hub, said rotor comprising bottom and top discs respectively having axial inlet and outlet openings, a plurality of blades extending across the openings and between the discs, the rotor communicating about its periphery with the interior of the casing, and an adjustable plate positioned to control admission of air and material to said inlet opening.

10. A classifier for pulverized material comprising a casing, means admitting air and material thereto, an outlet therein, and a rotor mounted in the casing, said rotor comprising bottom rial thereto for classification of the material, an

outlet in the casing, a hub mounted in the casing, and a rotor on said hub, said rotor comprising bottom and top discs respectively having axial inlet and outlet openings, a plurality of blades extending across the openings and between the discs, the rotor communicating about its periphery with the interior of the casing, and means cooperating with the inlet and outlet openings of the rotor to control the amount of air discharged into the casing peripherally of the rotor andrecirculated to the inlet opening.

l2.-A classifier for pulverized material comprising a casing, means for producing a vortex of air-suspended pulverized material in the lower portion thereof, an outlet in the casing, 'means for drawing air and material through said outlet, a rotor mounted adjacent the outlet, said rotor having radialv blades, an axial inlet communicating with the center portion of the vortex. and an outlet opening, and means mounted adjacent the rotor inlet for increasing the speed of the vortex as it is about to enter the rotor inlet and to control the amount of air admitted to said inlet.

13. A classifier for pulverized material comprising a tubular casing, an outlet therefrom, a hub mounted .for rotation in said casing, and a rotor carried by the hub near said outlet and of lessdiameter than said casing, said rotor comprising a bottom disc having'an axial opening. and a plurality of blades extending radially from said hub across said outlet opening in proximity thereto and a substantial distance along said hub forming pockets communicating with said outlet and said opening, the undesired material entering therotor through said opening and being discharged peripherally of said rotor.

14. 'A classifier for pulverized material comprisinga tubular casing having two zones therein, means for producing a vortex of air-suspended pulverized material in one of said zones, the zone being substantially unobstructed so that the vortex operates therein substantially fee from turbulence, 'a rotor mounted in said second zone, the rotor having a bottom disc with a central .opening therein forming an axial inlet communicating with the center portion of said vortex the rotor also having an axial outlet and communicating with said zone about its periphery, and an outlet from said casing for pulverized material.

' HENRY G. LYKKEN.

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