US3015391A

US3015391A - Classification process and apparatus

Info

Publication number: US3015391A
Application number: US10596A
Authority: US
Inventors: Thomas D Sharples
Original assignee: Sharples Corp
Current assignee: Sharples Corp
Priority date: 1960-02-24
Filing date: 1960-02-24
Publication date: 1962-01-02
Anticipated expiration: 1979-01-02

Description

1952 T. D. SHARPLES 3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 SheetsSheet 1 7 35 52 INVENTOR.

THOMAS D. SHARPLES l4 BY/%GGW ATTORNEY Jan. 2, 1962 T. D. SHARPLES 3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 Sheets-Sheet 2 INVEN TOR. THOMAS D. SHARPLES ATTOR N EY Jan. 2, 1962 T. D. SHARPLES CLASSIFICATION PROCESS AND APPARATUS 5 Sheets-Sheet 3 Filed Feb. 24, 1960 -\-------------\\-\\&

INVENTOR. THOMAS D. SHARPLES ATTORNEY Jan. 2, 1962 T. D. SHARPLES 3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 Sheets-Sheet 4 I03 I- a l I |0| lol 97 102 /5 Q u? 120 T m [6 IRS 16 .1 "1:1 |2| INVENTOR.

THOMAS D. SHARPLES ATTORNEY Jan. 2, 1962 T. D. SHARPLES CLASSIFICATION PROCESS AND APPARATUS 5 Sheets$heet 5 Filed Feb. 24, 1960 INVENTOR. THOMAS D. SHARFfLES BY ATTORNEY United States Patent 3.915.391 CLASSIFECATIQN PRGCESS AND APPARATUS Thomas D. Sharoles, Plymouth Meeting, Pa.. assignor to The Sharples Corporation. a corporation of Delaware Filed Feb. 24', 196i). Ser. No. 10,596 14 Claims. (Cl. 209144) This invention pertains generally to the classification of finely divided solids on the basis of size and density to produce fractions of different degrees of fineness, and pertains more particularly to an improved method and means for the control of fluid flow into the classifying zone.

There are various types of classifiers that operate on the principle of subjecting finely divided solids, hereinafter referred to for convenience as powder, to opposing forces comprised of an outwardly directed centrifugal force and an inwardly directed drag force, the latter resulting from the inward flow through the classification zone of a fluid, e.g. liquid or gas, hereinafter referred to for con 'cnience in description as air. In the operation of such classifiers, particles having a relatively lower ratio of surface area to mass, i.e. the larger particles, are thrown outwardly by centrifugal force, whereas particles having a relatively higher ratio of surface area to mass, i.e. the smaller particles, are carried inwardly by the air, the drag of the air on the smaller particles offsetting or overcoming the centrifugal force imposed thereon.

The invention is particularly adapted for the control of the flow of air into classifiers of the vortex type. In the operation of a vortex classifier, air is introduced at the periphery of the classifying zone, and the direction of flow is controlled by mechanism, e.g. a volute or spaced vanes, so as to set up a spiral flow which proceeds inwardly through the classifying zone, the air leaving the classifying zone centrally thereof. A particle introduced into the spiral flow, whether at the periphery of the classifying zone or intermediate its inner and outer boundaries, will have a radially outward centrifugal force acting on it because of its tangential velocity, and a radial inward drag force acting on it caused by the inwardly spiralling air.

The centrifugal force acting on the particle varies as the square of the tangential velocity whereas the radially inward drag force on the particle varies directly with the radial component of air velocity. These forces for a particle of a given size are equal at some point in the classifying zone of vortex classifiers generally, and at all points in the classifying zone, within at least practical approximation, in classifiers of the type described and claimed in US. Patents 2,616,563 and 2,796,173, and in co-pending application Serial No. 665,426, filed June 13, 1957, now Patent 2,943,735.

From the foregoing it will be seen that, with all else remaining the same including the velocity of inwardly flowing air, the greater the tangential velocity of air flow, the greater will be the centrifugal force acting upon a particle carried along by that air flow, and since the centrifugal force varies as the square of the tangential velocity, whereas the drag force is directly proportional to the radially inward flow of air, the smaller Will be the particles in the fine fraction.

it follows that, since classifying zones employed in vortex classifiers are annular in shape, the tangential component of air velocity in a spiral may be varied .between, as a maximum, the tangential introduction of the inwardly flowing air into the annular classifying zone, and, as a minimum, the direct radial introduction of the incoming air.

Thus in the case of any given classifier operating on the vortex principle, irrespective of design and construc- Patented Jan. 2, 1962 "ice tion, and with the same volume of incoming air, the nature of the two fractions may be varied, the fine fraction being generally finer or coarser depending upon the angle from tangential to radial that the incoming air enters the classifying zone.

In classifiers of commercial design, the direction of air fiow into a classifying zone is customarily controlled by vanes which may be adjustable or fixed. In the case of adjustable vanes, construction difficulties are such as to greatly increase the cost of manufacture. In the case of classifiers with fixed vanes on the other hand, in order to vary the direction of air fiow into the classifying zone it is necessary to manufacture replaceable units, each having vanes positioned at a diiferent angle from that of the other units. A set of such interchangeable units, while less expensive to manufacture, have limited utility because of necessity they must be limited in number. Then too, no adjustment as to air angle can be made while the machine is in operation.

The present invention is directed to the control of the angle of introduction of air into an annular classifying zone which is highly versatile in that any desired angle may be obtained quickly and easily with apparatus of relatively low cost of manufacture.

In the practice of the invention, the infiowing air is introduced into the classifying zone in a plurality of directions, hereinafter referred to, for convenience, as angles, the direction tangential to the classifying zone being regarded as of zero angle, and the direction radially inwardly of the classifying Zone being regarded as of angle. Thus when air streams of two di erent angles are employed, one may be tangential and the other radial to obtain the desired resultant angle of entry of air into the classifying zone through adjustment of the velocity and volume of the two component flows with respect to each other. On the other hand, the two component air flows may be directed into the classifying zone at any other two difierent angles between the zero or tangential angle and the plus 90 or radially inward angle, i.e. the angle which a line directed radially inwardly defines with respect to the tangential line. The angle which a radially outwardly directed line defines with respect to the tangential line, in light of the foregoing explanation, would have a value of minus 90.

Further features of the invention will become apparent to persons skilled in the art as the specification proceeds in connection with the accompanying drawings in which:

FIGURE 1 is an elevation partly in section of an embodiment of the invention;

FIGURE 2 is an enlarged section shown broken of'a left-hand portion of FIGURE 1;

FIGURE 3 is an enlarged section shown broken of a right-hand portion of FIGURE 1;

FIGURE 4- is a view shown broken taken on line P4 of FIGURE 1;

FIGURE 5 is a plan view shown broken of vane adjusting mechanism;

FIGURE 6 is an exploded view of vane rings;

FlGURES 7, 8, 9 and 10 show the air control vanes in difierent adjusted positions with respect to each other, being views partly in section taken on lines 77, 8-8, 9-9, and 1010 of FIGURE 4;

FIGURE 11 is an elevation shown broken and largely in section illustrating another embodiment of the invention;

FIGURE 12 is a view taken on line 1212 of FIG- URE 11;

FIGURE 13 is an elevation shown broken of the vane rings of FIGURES l1 and 12;

FIGURE 14 is an elevation shown broken and largely in section of a further embodimentof the invention;

FIGURE 15 is a plan view shown broken taken on line 15-15 of FIGURE 14;

FIGURE 16 is a View taken on line 16-16 of FIG- URE 14;

FIGURE 17 is an elevation shown broken and largely in section of a still further embodiment of the invention;

FIGURE 18 is a section shown broken of an air inlet of FIGURE 17 in different adjusted position;

FIGURE 19 is a view shown broken on line 19-19 of FIGURE 17; and

FIGURE 20 is a view shown broken and largely in section of an additional embodiment of the invention.

Referring now more particularly to FIGURES 1 to 3, note is made of the fact that the method and means shown and described herein for feeding powder into the classifying zone are more particularly described and claimed in my co-pending application Serial No. 10,762, filed of even date herewith. At is shown a base or support upon which is mounted a cylindrical casing 11 having an inwardly projecting upper rim 12 which supports and to which is attached, e.g. by welding, an annularring 13 having a rounded inner circular edge 14 which functions as the inner edge of an annular classifying zone 17. Resting upon and attached to ring 13, e.g. by bolts or screws, is an annular structural member 15 shown as having a flat inner bottom surface which serves as the lower end surface or wall of classifying zone 17.

. The inner bottom and side wall of member 15 is shown lined with wear-resisting material, illustrated at 16, which may be of ceramic tile, e.g. of tungsten carbide, cemented in position.

Since the various parts may be secured together in any desired manner, such as by bolts, screws, Welding and the like, the particular manner of attaching parts to one another for purposes of brevity, will ordinarily not be referred to.

Member 15 has an upwardly projecting annular portion 18 which supports annular member 19 attached thereto.

Projecting inwardly from member 19 are a plurality of circumferentially spaced pins 20 which project into and support an annular plate 21, the spacing between member 19 and plate 21 being such as to provide an annular inlet 22 leading to classifying zone 17, said inlet containing a pair of cooperating air directing vane rings 23 to be hereinafter more particularly described, since it is to the generic and specific features involved that this invention is directed.

Resting upon and secured to plate 21 is a cylindrical support 24 for feed funnel 25 having a downwardly projecting feed tube 26 surrounded by

filler members

27 and 28.

Positioned within casing 11, and encased within an interior casing 30, is housing 31 in which is journaled, in bearings not shown, a spindle 32 having a pulley 33 attached to'its lower end. Mounted on the upper end of spindle 32 is a circular plate 34 shown shaped about its peripheral under portion in a manner to define a surface of revolution 35 of curved cross section, i.e. a surface generated by revolving a curved line, having a shape as illustrated, around the axis of the machine. Surface 35 which, as illustrated, is rotatable, comprises the inner part of the upper end surface or wall of the classifying zone. The rest of the upper end surface or wall is supplied by surface 36 on ring 37, the latter being attached to the under surface of plate 21, as illustrated at 38. Surface '36 also is asurface of'revolution.

Positioned on top of plate 34 is an annular member 41 which is provided with a plurality of circumferentially spaced radial channels 42, preferably lined with wear-resistant tubes, e.g. ceramic tubes, say of tungsten carbide, as illustrated at 43. Superimposed upon member 41 is an annular member 44 secured to plate 34 by any desired means, such as by circumferentially spaced screws as illustrated at 45, thus holding member 41 in position. Member 44 has an inwardly projecting inner circular edge which together with the upper central portion of plate 34 forms a powder feed chamber 47, plate 34, as shown, being provided with a central wear-resistant disc 48, e.g. of tungsten carbide, resting upon a somewhat larger disc provided at the center of plate 34. It will be noted that feed tube 26 leads into feed chamber 47, and that radial channels 42 lead outwardly from feed chamber 47. It will also be noted that plate 34,

members

41 and 44, spindle 32, and pulley 33 are joined together and comprise the rotor, whereas the rest of the parts remain stationary.

Spaced radially outwardly from the outer ends of channels 42 in a manner to form an annular gap 51 is a wear ring 52 mounted on ring 37. Ring 52 is so positioned with respect to channels 42 as to intercept the powder fed outwardly through channels 42 upon rotation of the rotor.

While the surface of ring 52' facing gap 51 may be made parallel to the outer periphery of the rotor which in turn may be made parallel to the axis of rotation of the rotor, it is preferred, and as described and claimed in my above-mentioned co-pending application, that such inner surface 55 of ring 52, quite apart from the shape of the'outer periphery of the rotor, define an angle a with respect to the axis of rotation of between 5 and 15 for highly efiicient delivery of the powder into classifying zone 17, although values of angle a up to but less than 45 are contemplated, i.e. directions of lateral flow into the classifying zone in which the axial component exceeds the radial component. Ring 52 is preferably wear-resistant, and conveniently may be of ceramic tile,

e.g. of tungsten carbide, cemented in position on ring 37.

Any desired means may be employed for effecting the flow of air through classifying zone 17 inwardly through annular irflet 22, and outwardly through annular chamber 56 between casing 11 and casing 30, e.g. blower 57 positioned in conduit 58, the latter leading from bag filter 59 in which the fine fraction is collected, filter 59 being connected to chamber 56 by conduit 60.

In the operation of the classifier shown in FIGURES 1 to 3, upon the functioning of blower 57, fluid, such as air, flows into annular inlet 22 and acquires an inwardly spiralling flow by virtue of the functioning of vane rings 23 to be hereinafter more particularly described, said vane arrangement affording the desired shape to the spiralling flow.

The unitary structure comprised of spindle 32 and the parts mounted thereon being in rotation, the powder is fed into chamber 47 through funnel 25 and pipe 26. From chamber 47 the powder flows outwardly through channels 42, thereby acquiring a rotary motion, and is projected against ring 52. The relative rotational movement between member 41 and ring 52 develops a relatively high degree of sheer in the powder to deagglomerate any agglomerated particles present, and also uniformly distribute the powder circumferentially in gap 51 from which the powder enters annular classifying zone -17 laterally thereof, in the form of a rotating annulus comprised of substantially uniformly distributed powder.

The rotation of the annulus of powder entering classifying zone 17 is in the same direction as that of the spiralling air, and for best results the speed of rotation of powder and the speed of rotation of the air at the place or circular area of entry of powder laterally into the air are preferably substantially evenly matched at least within practical approximation.

The powder, upon laterally entering the inwardly spiralling flow of air, is acted upon by the centrifugal force resulting from its rotation, and also by the radial component of flow of air through the classifying zone. The result is that the larger particles, having a relatively lower ratio of surface area to mass, are thrown outwardly by centrifugal force, whereas the smaller particles having a relatively higher ratio of surface area to mass, are carried inwardly by the inwardly spiralling air.

The air, bearing the fine fraction, after passing around circular edge 14, enters annular chamber 56, and passes out through filter 59 wherein the fine fraction is collected, the air, free from fines, passing out through blower 57.

The coarse fraction, being thrown outwardly in rotating condition, slides around the inner periphery of member and passes out through a tangential opening 61 leading into a circular chamber 62 from which it is withdrawn through outlet 63.

Classifying zone 17 may be of any desired shape with end surfaces or walls stationary or rotating, or stationary in part and rotating in part, such as those more particularly described and claimed in U.S. Patents 2,616,563 and 2,796,173, and in co-pending application Serial No. 665,426, filed June 13, 1957, now Patent 2,943,735. The invention, however, is particularly suitable for use wit classifying zones adapted for free vortex flow of inwardly spiralling fluid. In the preferred classifying zone, the axial distance, designated for convenience h, between the opposing end surfaces or walls at any radial distance, designated for convenience r, from the axis of rotation bears, within at least practical approximation, the following relationship:

where h is the axial spacing between the end surfaces or Walls at the outer boundary of the classifying zone, and r is the radius from the axis of rotation to the outer boundary of the classifying zone.

Classifying zone 17 is considered as having an outer periphery beginning at an imaginary circular line 64 on surface 36 and an inner periphery at circular edge 14, and even though the lower end surface or wall may be fiat, its spacing with respect to

surfaces

35 and 36, in the preferred embodiment, conforms within practical approximation to the above equation, the feed of powder into the classifying zone being intermediate its inner and outer boundaries.

It is to be understood, however, that the classifying Zone may have any other shape and that the point or area of feed of powder may be intermediate the inner and outer boundaries of the classifying zone as illustrated, or outwardly from the outer boundary thereof, or otherwise, as desired.

A multiplicity of methods and means may be provided for carrying out the invention of the present application, and various alternatives are illustrated in the drawings.

Referring now more particularly to FIGURES 4 to 10, as well as to FIGURES 1 to 3, it will be noted that vane rings 23 are comprised of upper ring 71 and lower ring 72, the former superimposed upon the latter with their inner peripheral edges positioned in an annular groove 73 in ring 37, said groove being positioned directly under plate 21. Ring 72 is held against rotation by means of a pin 74 secured in plate 21 and which extends downwardly into bore 75 positioned in the inner edge of ring 72, pin 74 passing through a longitudinal notch 76 in ring 71. Notch 76 is of sufiicient length to permit rotational movement of ring 71 with respect to ring 72 for purposes to he hereinafter more particularly described.

To facilitate rotational movement of ring 71 with respect to ring 72, ring 72 is provided with a plurality of circumferentially spaced notches 77, each of which is provided with a spring member 78 which presses against ring 71 tending to spread the rings apart. After the desired adjustment of ring 71.with respect to ring 72 is made, the rings are held in adjusted position by the tightening of a pluraiity of circumferentially spaced screws, one screw being illustrated at 81 in FIGURE 2. The tightening of screws 31 compresses spring 78 and secures

rings

71 and 72 together.

To facilitate the movement of ring 71 with respect to ring 72, ring 71 may be provided with handle 82 which passes downwardly through a longitudinal notch 83 in 6 plate 21, better seen in FIGURE 4. If desired, a fixed gauge member 84 may be secured to plate 21, the dis tance from edge 85 of which to edge 86 on handle 82 may be utilized as an indicator of the rotational position of ring 71 with respect to ring 72. A set of gauge blocks of different widths for insertion between

edges

85 and 86, each gauge block indicating a different relative rotational position of ring 71 with respect to ring 72, is very useful for the purpose.

That portion of ring 72 which is positioned in annular inlet 22 is provided with two sets of circumferentially spaced grooves or slots, one set of grooves 37 being of greater angle with respect to the axis of the classifying zone than the second set of grooves 88. If desired, grooves 87 may be so positioned as to direct incoming air passing therethrough tangentially with respect to the classifying zone, whereas the grooves 38 may be so positioned as to direct incoming air radially into the classifying zone. On the other hand,

grooves

87 and 88 may direct the incoming air in any other desired different directions into the classifying zone, e.g. between the tangential and radial directions. -The use of the tangential direction for one set of grooves and the radial direction for the other set of grooves provides a high degree of versatility in obtaining the desired resultant direction of air flow into the classifying zone.

From what has been said, it will be seen that ring 72 may be employed independently of ring 71 in the practice of the invention, in which case the resultant direction of air flow would be fixed, no adjustment being provided, except by making ring 72 interchangeable. For purposes of versatility, therefore, the use of ring 71, having a plurality of circumferentially spaced shutter members 91, is preferred.

Shutter members 91 preferably have the shape com parable to that indicated in FEGURE 7, for when in the position shown

grooves

87 and 88 are fully open, the ends of shutter members 91 being shaped appropriately for the purpose.

When ring 71 is shifted to the position shown in FIG- URE 8, grooves 87 are left fully open but grooves 83 are partially closed, the result of which is that the resultant direction of air how is shifted toward the tangential.

When ring 71 occupies the position shown in FIG- URE 9, grooves 88 are completely closed, and the resultant direction of air flow into the classifying zone has been shifted the maximum amount, with the grooves in question, toward the tangential.

In FIGURE 16 ring 71 is illustrated in a position in which grooves 87 are completely closed, leaving grooves 88 for the most part unobstructed. With the shutter blocks 91 in the position shown in FIGURE 10, the resultant direction of air flow into the classifying zone is moved the maximum amount toward the radial that is possible with the particular vane rings illustrated. It will be recognized that a lesser shift of ring 71 clockwise in FEGURE 10 would leave grooves 87 partially open, the degree to which being adjustable by movement of ring 71.

From the foregoing it will be seen that shutter blocks 91 may be so shaped and positioned with respect to

grooves

87 and 88 as to obtain any desired resuitan; direction of, air flow into the classifying zones.

Another embodiment of the invention is shown in F 1G- URES 11 to 13 wherein the air entering classifying zone 92 is fed downwardly through an annular space 93 between spaced

concentric walls

94 and 95, the resultant angle of flow being controlled by vane rings 96 and 97, the former being movable and the latter remaining stationary. The feed of powder into classifying zone 92 is through a feed tube 98, and the air leaves the classifying zone centrally thereof up through a tube 99, the structure being as indicated.

Stationary ring 97 as seen in FIGURES l2 and 13 is provided with a series of diagonal grooves 101 and a series of transverse grooves 102.

Air passing downwardly through grooves 101 has imparted to it a circumferential component of flow which has a tangential component with respect to the classifying zone 92, whereas air passing down through grooves 102 has imparted to it a longitudinal component of flow which is radial with respect to the classifying zone 92. The resultant of the two flows determines the angle at which the spiralling flow enters the classifying zone 92, analogous for all purposes to the resultant or air flows through

grooves

87 and 88 as above described.

While stationary ring 97 may be employed alone in the practice of the invention, it is preferred to provide adjustment such as by vane ring 96 which is provided with a plurality of circumferentially spaced shutter blocks 103. For adjustment purposes ring 96 is pro vided with a handle "104 which passes through longitudinal slot 105 in shell 94 and engages one shutter block 103 as illustrated.

Assuming that

grooves

101 and 102 are both closed by shutter blocks 103, movement of shutter blocks 103 to the right as seen in FIGURE 13 would gradually open grooves 101 to permit diagonal flow of air through ring 97. Further movement of shutter blocks 103 to the right would gradually uncover grooves 102 to permit longitudinal flow of air through ring 97 along with the diagonal flow through grooves 101. The reverse order of opening of

grooves

101 and 102 would occur upon movement of shutter blocks 1103 to the left. Thus the desired relative flows may be obtained by adjustment of the relative rotational position of ring 96 with respect to ring 97.

Another embodiment of the invention is illustrated in FIGURES 14 to 16 wherein air flow into classifying zone 106 is controlled by vane rings 107 and 108.

Vane ring 107 is provided with blocks 111 which mesh with blocks 1 12 on vane ring 108, the spacing of blocks 111 and 112 with respect to each other being such that, when in the position shown in FIGURE 16, a plurality of circumferentially spaced diagonal channels or grooves 113 and a plurality of circumferentially spaced radial channels or grooves 114 are provided.

As shown, vane ring 108 is fixed, and vane ring 107 is made adjustably circumferentially to move blocks 111 counterclockwise as seen in FIGURE 16 to narrow or close channels 114 and at the same time enlarge channels 113. On the other hand, movement of blocks 111 clockwise as seen in FIGURE 16 narrows or closes channels 113 while at the same time enlarging channels 114. Thus the volume of diagonal (less angular) flow with respect to the volume of radial (more angular) flow is made adjustable to arrive at the desired final resultant flow of air into classifying zone 106.

Movement of vane ring .107 is accomplished by lossening screws 115 which pass down through longitudinal slots 116 in top plate 117. A two-part vernier scale 118 may be provided if desired to indicate the relative position of vane rings 107 and 108 with respect to each other, part 119 being fixed to plate 117 and part 120 being movable with screws 115 which engage vane ring 107. When the desired adjustment is obtained screws 115 are tightened to hold vane rings 107 and 108 in the desired adjusted position.

Flow of air into classifying zone 106 is inwardly through annular chamber 121 which surrounds vane rings 107 and 108, the flow being to the left as seen in FIG- URE 14, the air picking up the desired spiralling flow upon passage through channels 113 and/or 114.

Feed of powder intoclassifying zone 106 is through feed pipe 122 and a plurality of circumferentially spaced radial channels 123 positioned in rotating plate 124. In

the particular classifier of FIGURE 14, bottom plate 125 also rotates. The inwardly spiralling air carrying the fine fraction therewith leaves classifying zone 106 through annular opening 126, and the heavy traction after being thrown outwardly drops down through outlet 127.

Another embodiment of the invention is shown in FIGURES 17 to 19, wherein the circumferential air inlet structure shown at 131 and leading into classification zone 132 (shown broken) is comprised of two

branches

133 and 134, each set at an angle with respect to classifying zone 132.

Air inlet structure 131 and its branches 133 and 13d surround classifying zone 132 which may be annularly shaped, e.g. as in Patent 2,796,173.

Each

branch

133 and 134 has an annular air inlet 135 which is bordered on each of opposite sides with an inwardly extending annular grooved member 136, the grooves being diagonal as illustrated at 137 in FIGURE 19.

Secured to the face of one grooved member 136 of each pair, such as by the use of a suitable cement, is a flexible tube 138, e.g. of rubber, natural or synthetic, which is inflatable much the same as the tube of an automobile tire. Tube 138 is shown deflated in FIG- URE 17 to provide a gap 141 between opposed members 136, and inflated in FIGURE 18 to close gap 141. It is understood that tube 138 extends completely around its associated member 136 so as to be endless and completely circular.

In the operation of the embodiment shown in FIG- URES 17 to 19, air drawn into inlet 135 has a diagonal component of flow imparted to it upon passing through grooves 137, and a longitudinal or radial component of flow upon passing through gaps 141, the maximum longitudinal or radial flow occurring when tube 138 is completely deflated. The longitudinal or radial component of flow decreases with increase in inflation of tube 138 until such time that tube 138 is sufliciently inflated to completely close gaps 141 as illustrated in FIGURE 18. Flow through grooves 137 continues at all times. Thus the resultant of air flow is variable at Means for inflating and deflating tubes 13% is illustrated in FIGURE 17 as being comprised of tubes 142 connected to a source of air not shown, the entrance and exit of air being controlled by a valve or a pressure regulator 143. A gauge 144 might be provided in air supply line 145 to be used as a guide in the inflation and deflation of tubes 138.

A still further embodiment of the invention is illustrated in FIGURE 20 in which 146 is a stationary casing having an annular air inlet 147 in which is positioned a plurality of circumferentially spaced diagonal vanes 148 which impart a rotary or diagonal movement to the air upon entering classifying chamber 150. An annular opening 151 in which is disposed a circular tube 152 permits air to enter longitudinally or radially, the volume of the last-mentioned air being controlled by inflating or deflating tube 152. It will be understood that upon complete inflation of tube 152, gap 153 is closed, and that upon complete deflation of tube 152, gap 153 is open to its greatest extent. It will be obvious that any intermediate opening of gap 153 may be obtained upon control of the inflation of tube 152 to vary the resultant of air flow at will.

154 is a rotor which may be much the same as that illustrated in FIGURE 1, powder to be classified being delivered through a plurality of outwardly extending tubes 155, the powder striking surface 156 to be delivered into the classifying zone much the same as already described in connection with FIGURES 1 to 3.

Experiments with classifiers embodying the invention cogently demonstrate the outstanding contribution to the art that has been made, it being possible to adjust the resultant angular entry of the inwardly flowing spiral of air into the classifying zone at will with excellent precision and with the classifier in full operation. This is of very considerable advantage for it makes possible 9 variation in air flow while observing the classifying operation and to immediately adjust in accordance with the desired results.

As has been brought out above, the invention is applicable to classifiers and classifying operations without limitation in which an inwardly spiralling flow of fluid, whether or liquid or gas, e.g. of water or air, takes place. The construction and operation of vortex classifiers in general, whether employing liquid or gas as a medium, are in a rather highly developed state, to which this invention makes a major contribution. Several embodiments of the invention have been shown and described, and others will occur to persons skilled in the art upon becoming familiar herewith. For instance, the resultant angle of the spiral may be varied, i.e. moved toward the tangential by the peripheral application of reduced pressure between any of the various multiple air directing means shown and described and the classifying zone, or other means for accomplishing such purpose may be devised. Also, the inwardly flowing fluid may be directed inwardly toward the classifying zone at any other desired number of angles, e.g. three or four, if desired for any reason, to obtain the desired resultant of air flow, as will become obvious to persons skilled in the art upon becoming familiar with the above description. Wear-resistant material may be placed at any point of wear and While reference has been made to tungsten carbide, other materials act excellently, e.g. the ceramic aluminum oxide.

it is, therefore, to be understood that the above particular description is by way of illustration and not of limitation, and that changes, omissions, additions, sub stitutions and/ or other modifications may be made without departing from the spirit of the invention. Accordingly, it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty that reside in the invention.

I claim:

1. The method of classifying finely divided material on the basis of size and density which comprises directing a fluid in a plurality of directions toward an annular classifying zone positioned between spaced walls to bring the body of fluid between said walls into an inwardly spiralling flow, one of said directions relative to said classifying zone being different from that of another of said directions, feeding said finely divided material into said classifying zone for classification therein, withdrawing from an inner boundary of said zone a fine fraction of said finely divided material, withdrawing from the periphcry of said zone a coarse fraction of said finely divided material, and controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

2. The process of claim 1 in which the inward spiral flow of said air is in the form of a free vortex.

3. The process of claim 1 in which the ends of said classifying zone are at least in part rotating, and in which said spiral rotates in the same direction.

4. The process of claim 1 in which said finely divided particles are fed into the inwardly spiralling flow while rotating in the same direction and within practical approximation at a matched speed of rotation.

5. Theprocess of claim 3 in which said finely divided particles are fed into the inwardly spiralling flow while rotating in the same direction and within practical approximation at a matched speed of rotation.

6. A classifier for finely divided material comprising boundary means including first and second opposing wall structures forming between them an annular classifying zone, inlet means including a plurality of fluid-directing means adjacent the outer limit of said zone for producing within said zone an inwardly spiralling vortex, one said fluid-directing means directing fluid in a direction relative to said classifying zone which is different from that of another said fluid-directing means, inlet means for said finely divided material, outlet means communicating with the inner boundary of said annular classifying zone, means for producing a differential in pressure between said first-mentioned inlet means and said outlet means for the flow of fluid into said classifying zone directed by said plurality of fluid-directing means and out of said classifying zone through said outlet means, and means for controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

7. The combination of claim 6 which includes means for adjusting the fluid-directing magnitude of the plurality of fluid-directing means with respect to each other.

8. The combination of claim 7 in which the means for adjusting the relative magnitude of said fluid flows takes the form of grooved rings movable relative to each other.

9. The classifier of claim 6 in which the axial distance h between the opposing wall structures of the classifying zone at any radial distance r from the axis of rotation bears within practical approximation the following relationship:

where h is the axial spacing between the wall structures at the outer boundary of the classifying zone and r is the radius from the axis of rotation to the outer boundary of the classifying zone.

10. The method of classifying finely divided material on the basis of size and density which comprises directing air in a plurality of directions toward an annular classifying zone positioned between spaced walls to bring the body of air between said walls into an inwardly spiralling flow, one of said directions relative to said classifying zone being more tangential than radial and another of said directions relative to said classifying zone being more radial than tangential, feeding said finely divided material into said classifying zone for classification therein, withdrawing fr'om an inner boundary of said zone a fine fraction of said finely divided material, withdrawing from the periphery of said zone a coarse fraction of said finely divided material, and controlling the velocity and volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

11. A classifier for finely divided material comprising boundary means including first and second opposing wall structures forming between them an annular classifying zone, inlet means including fluid-directing members adja cent the outer limit of said zone for producing within said zone an inwardly spiralling vortex, said fluid-directing members being divided into at least two groups with the members of one said group being inter-spersed between members of another said group and with the fluid-directing members of said one group having means for directing fluid in a direction relative to said classifying zone which is different from that of said another group, inlet means for said finely divided material, outlet means communicating with the inner boundary of said annular classifying zone, means for producing a differential in pressure between said first-mentioned inlet means and said outlet means for the flow of fluid into said classifying zone directed by said fluid-directing members and out of said classifying zone through said outlet means, and means for controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

12. A classifier for finely divided material comprising boundary means including first and second opposing wall structures forming between them an annular classifying zone, inlet means including a plurality of fluid-directing means adjacent the outer limit of said zone for producing within said zone an inwardly spiralling vortex, one said fluid-directing means directing fluid in a direction relative to said classifying zone which is different from that of another said fluid-directing means, inlet means for said finely divided material carried byione of said wall structures and extending into communication with said zone at a feed point intermediate its inner and outer limits, saidiboundary means being in part stationary and in part rotatable, said rotatable part including said inlet means, means for feeding finely divided material to said lastmentioned inlet means, means for driving said rotatable part, outlet means communicating with the inner boundary of said annular classifying zone, means for producing a differential in pressure between said firstmentioned inlet means and said outlet means for the flow of fluid into said classifying zone directed by said plurality of fluid-directing means and out of said classifying zone together with a fine fraction through said outlet means, outlet means for a coarse fraction communicating with the outer boundary of said annular classifying zone, and means for controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

13. A classifier for finely'divided material comprising boundary means including first and second opposing Wall structures forming between them an annular classifying zone, inlet means including a plurality of fluid-directing means adjacent the outer limit of said zone for producing within said zone an inwardly spiralling vortex, one said fluid-directing means directing fluid in a direction relative to said classifying zone which is dilferent from that of another said fluid-directing means, inlet means for said finely divided material carried by one of said wall structures and extending into communication with said zone at a feed point intermediate its inner and outer limits, said boundary means including said inlet means being rotatable, means for feeding finely divided material to said lastmentioned inlet means, means for rotating said boundary means, outlet means communicating with the inner boundary of said annular classifying zone, means for producing a differential in pressure between said firstmentioned inlet means and said outlet means for the flow of fluid into said classifying zone directed by said plurality of fluid-directing means and out of said classifying 12 zone together with a fine fraction through said outlet means, outlet means for a coarse fraction communicating with the outer boundary of said annular classifying zone, and means for controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling flow.

14. A classifier for finely divided material comprising boundary means including first and second opposing wall structures forming between them an annular classifying zone, inlet means including a plurality of fluid-directing means adjacent the outer limit of said zone for producing within said zone an inwardly spiralling vortex, one said fluid-directing means directing fluid in a direction relative to said classifying zone which'is different from that of another said fluid-directing means, inlet means for said finely divided material carried by one of said wall structures and extending into communication with said zone at a feed point intermediate its inner and outer limits, said boundary means being stationary, means for feeding finely divided material to said last-mentioned inlet means, outlet means communicating with the inner boundary of said annular classifying zone, means for producing a differential in pressure between said firstmentioned inlet means and said outlet means for the flow of fluid into said classifying zone directed by said plurality of fluid-directing means and out of said classifying zone together with a fine fraction through said outlet means, outlet means for a coarse fraction communicating with the outer boundary of said annular classifying zone, and means for controlling the volume of the component fluid flows with respect to each other to obtain the desired shape of the spiral in the inwardly spiralling fiow.

References Cited in the file of this patent UNITED STATES PATENTS