US2294920A

US2294920A - Pulverizing machine

Info

Publication number: US2294920A
Application number: US110732A
Authority: US
Inventors: Henry G Lykken
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-11-13
Filing date: 1936-11-13
Publication date: 1942-09-08
Anticipated expiration: 1959-09-08

Description

Sept. 8, 1942. H. G. LYKKEN PULVERIZING MACHINE 3 Sheets-Sheet 1 Filed Nov. 13. 1936 R. m V m SePt- 8, 1942- r H. G. LYKKEN 2,294,920

PULvERuING MACHINE Filed Nov. 13, 1936 s sheets-sheet 2 sept. s, 1942.

H. G. L .YKKEN PULVERIZING MACHINE Filed NOV.` 1.3, 1936 3 Sheets-Sheet 3 Patented Sept. 8,1942 o einen s Henry' Ggrsue i nppuesuonlsovember laisse, serial 17 Claims.

The present invention relates tomachines for' reducing particle size, or pulverizing materials, oi the type wherein the reduction in size is accomplished in the dry state, and further to thev classification of thepulverized materials, and to the processes of reduction in size and of classiaccesso PULVERIZING i' i which is fed the material to be pulverized. The

particles of material ted into the machine are carried about in theyiair currents and become y part oi the vortex, and are `thus caused to conication whereby material of aI predetermined size may be delivered from said machine.

In the present-machine the energy imparted to the air or other gaseous media, such as steam, carbon dioxide, nitrogen, hydrogen or mixtures tact with and rub upon each other, producing an abrading action resulting in the reduction in particle size or pulverization.

When thematerial is reduced lto the desired l degree of iineness in those machines, the mate- -rial laden air rises from the pulverization zone v and ultimately reaches a place of collection or of these and other gaseous uids, constitutes the force for moving the particles of material upon each other to cause the reduction .in size -by this attrition' action, as weil as to provide the reducing atmosphere.' In additionK'reduction in size is caused by the erosion of the particles bythe high speed moving air onzas, and the'gasecus media, including air, may be heated or refrigerated depending upon the materials to be reduced. For convenience in the following specification this method of reduction willbe referred to as air attrition andthe reduction in size use; While the centrifugal force of' the vortex .action referred to causes a classification of the -materials due-to the diilerencesin mass of they different particle sizes of materials in the pulverizing zone, in4 the machine of- Patent No. 1,753,437 there is a further classifier of` pulverized material interposed vahead of the place of collection or use and into which the material laden air passes.

over-size material is separated from that of the will be referred to as pulverization, but this is to' y be understood as not limiting the denition of the actual conditions. f

The machine of this application is useful for the reduction of material even tovery small par. ticle size, and the classincation and separation of the pulverized ,material for either coarse or.

tine sizes, i. e., from ten mesh screen size on the one hand to one micron size on the other hand.

Furthermore, the machine of this application embodied in so-called pulverizing or reducing' `apparatus, as shown forexample-in my Patents Numbers 1,753,437 issued April 8, 1930,1756253 and 1,756,254 issued April 29, 1930. These are cited as examples of types of machines.'

In Patents Nos. 1,753,437 and 1,756,253 a high 'speed rotor is used toproduce high velocity, sub- ."stantially unidirectional, circulating air currents y creating what will be termed a vortex about the 'of the rotor. `In such a vortex the air curnecessarily travel at diiferent rates of desired size, the over-size returning to the pulverizing zone and' the correctly sized material passing from the machine.y

In the. machine of Patent No. 1,756,254 the same character of vortex action is set up to eiv rect airattrition, but by the use of high pressure air ejected through tangential nom'les, the ma.-l

terial being reduced and classified in the one casing. and the? material of proper particle size being removed from the center or the chamber.

The machine of the present invention is an improvement upon' the aforementioned machines in the method-and the apparatus of pulver-ization, as will be more fully pointed out hereinafter. There isalso provided in this machine a new and-improved -classiner which may be used either in conjunction with machines lof my '.former patents or of the present invention, Aor

of othert'ypes, or separately as a classifier in any case'where it is desired to classify materials pneumatically.

One of the objects of the present invention is to provide a new method of'securing reduction in particle size of materials in a dry state.

. Among other objects of myv invention are to provide a machine in which there are major and minor attrition vortices: in which there is'an outer vortex and a plurality of inner vortices; in which there 'are vortices of dierent speeds, or of dinerent'radii having different centers of rotation: in which coarser grinding is done in one vortex'and finer grinding is done in another vor- .tex fed from the first vortex; and in which there speed. This occurs in a closed chamber into` 55 is a rapidly moving annulus of material laden air In this. latter chamber any in which aided by centrifugal force the particles muil upon each other to reduce themselves, and

within the annulus are a plurality of smaller whirling masses in which there is a more intense muiling of the particles upon themselves.

It is another object of my invention to provide a new method of classifying materials in a dry from the classifier is a function of' the height of the classifier; which will select material of small particle size, as ne as one micron in size; and a classifier which may be used with any pulverized material or pulverizer.

Stili another. object of my invention is to provide a machine' for effecting reduction in particle size of either or both friable and non-friable materials to substantially equal degree.

A further object of my invention is to provide a machine in which within reasonable limits materials of different specific gravity may be simultaneously reduced and classified and removed from the machine without disturbing the proportions of the materials as fed into the machine. (As a matter of fact the machine of this invention will more thoroughly mix and uniformly distribute the various components of the mixture passing through the same so that the delivered material is improved in this respect over the material fed into the machine.)

A further object of my invention is to provide a machine for accomplishing the aforementioned objects wherein the apparatus comprises one unit.

Still further objects of my invention are to provide a machine for accomplishing the aforementioned objects in an emcient and economical manner'as to both .space and power consumption; and a compact machine voi simple construction and of few parts and freedom from wear, which machine'is adaptable to easy, assembly and replacement of parts, and rapid and thorough cleaning.

It is a further object of my invention to provide a machine in which reduction of particle size is obtained for all practical purposes without contamination of the materials composing the y machine.

Even further objects of my invention are to provide an arrangement for feeding va. uniformy amount ofmaterial into the reducing chamber and to control the feed of .air into the machine; to remove from the machine materials of substantially uniform particle size; to provide a classifier in which the particle size of the material delivered from the machine is readily and easily controllable; and to provide an economical method of grinding to a definite particle size by promptly removing fromthe reducing zone material which has attained the desired particle size.

Other and further objects and advantages of my invention will be understood from the following specification taken in conjunction with the accompanying drawings,wherein Figure 1 is a vertical cross sectional view of a device constructed in accordance with my invention;

elo

Fig. 2 is a horizontal cross sectional v'iew taken in the plane of line 2-2 of Fig. 1;

Fig. 3 is a horizontal cross sectional view taken in the plane of line 3-3 of Fig. l;

Fig. 4 is a diagrammatic illustration of a for- Amula for the spacing lof the rotor blades according to my invention. y

Fig. 5 is a diagrammatic illustration of a portion of a rotor and showing another method of calculating blade spacings according to the present invention; and

Fig. 6 is a diagrammatic illustration of a portion of the classifier showing the classifier action.

The machine of the present invention comprises a cylindrical casing mounted on a hollow base and carrying on top of the casing a hollow discharge chamber. Extending through the cylinder is a shaft connected to a motor mounted outside the casing. On the shaft adjacent the base is a rotor and extending upwardly from the rotor adjacent the top of the machine is a smooth cylinder or drum which is also mounted on the shaft. Both the rotor and the drum are of smaller diameter than the casing, leaving annular zones therebetween. The lower part or that zone opposite the rotor is the attrition or pulverizing zone and the upper part, opposite the drum, is the classifier zone.

Material to be reduced is continuously fed into the attrition zone from a hopper, the feed being at a uniform rate to maintain eiricient baly anced operating conditions in the machine in which it is neither underloaded nor overloaded.

In one embodiment of a machine for continu` ous production, air, or other gaseous media, is introduced into the machine from the hollow base through an appropriate annular opening at the bottom edge of the rotor. In either case, the air inlet is adjustable to control the volume of air admitted, which is one of the factors controlling the particle size of the finished product.

in this zone and, due to centrifugal forces, the

material in the annulus will 'segregate itself with the finer particles adjacent the rotor and the coarser, larger particles adjacent the casing. The layers of material will necessarily move at different rates ofy speeds because of the different distances thereof from the axis of the rotorl and this will of itself produce a muiling of the particles upon each other and bring'about attrition or abrading or reducing action.

Ordinarily, between each pair of rotor blades there is. in effect, a closed end depression or pocket which may be closedat the bottom without communication with adjoining pockets or may be opened at the bottom so that all pockets communicate with each other. Air is drawn into each pocket by the partial vacuum formed at the back of the forward or leading blade and air is forced out along the front side of the trailing blades sothat there is merely a iiowing in and out movement of the air in each pocket.

'This air movement is merely incidental to the blade faces and extending partially into the inner surface of-the outer vortex, which vortices very materially aid and speed up the attrition action, and allow of obtaining reduction of all of the material to very fine particle sizes, even to one f micron size or lower, -and in substantial vol' ume. It is not altogether certain, but I- believe that the coarsergrinding takes placev in the outer or larger annulus cr vortex, while only .the finer particles are picked up in theV inner,

smaller, higher speed vortices, and that the lntense mulling action occurring inl these smaller vortices produces the very nely ground material which I have been able to obtain in machines constructed according to my invention. By reason of the high rotative speed of the rotor, causing proportionately high speeds of both the o'uterand inner vortices, there occur an innumerable number of collisions of the particles moving at these very high speeds, which materially aids in the reduction of particle size, as

will be now fully explained.

The material ground to the predetmmined size being entrained in the air currents rises from the attrition zone into the classification zone. I have discovered that by controlling the amount of air introduced into the machine, there is carried from the attrition zone notv only the par' v in size can be successfully produced and success-L fully classied in and delivered fcommercially,

ticular particle size desiredbut also some material of larger particle sizes. However, this action promptly and quickly removes from the attrition zone substantially all that material which has already attained the desired particlev size, and that results in the following advantages: The finished material is maintained a somewhat uniform desired size substantially free l .ted into the hollow base In through the air-inlet Y of particles smaller than that size; there is a substantial saving of power because .the `nely pul.

verized material is removed from Jthe mass of material yet to be ground; and the further attrition action of the larger and heavier particles is not cushioned by the presence of the smaller particles, all so that active work of reducing particle size goes forward continuously, efiiciently and economically. These results are further aided by the removal'continuously of the fine material (mostly of intermediate over-size) from the outer vortex by the inner vortices, and the latter promptly giving up that material which is reduced in size.

The classifying zone is desirably of such a height that the ner particles of the selected size can be removed from the to'p of the classifying zone, and the larger particles fall by gravity back to the attrition zone to be there further reduced.

s In the classifying zone, the vortex motion ofthe material laden air entering the classifier is maintained above that level at which such vortex of itself would be effective. This vortex movement is maintained by the rotation of the smooth, imperforate-walled drum which is mounted coaxially with the rotor. Because this drum is imperforate and has no outwardly extending projections there is no agitation or beatthe reducing zone.

ther lattrition. There is, however, not suiiicient force in the whirling air-in the classifier zone to support the heavier and larger particles, and hence under the action of gravity they return to losses and the energy expended in maintaining the vortex action, the air progressively loses,-its velocity as it ascends in the classifier .chamber to the discharge opening, and during this progressive reduction in air velocity the larger par,- ticles drop out, progressively as to their size, as

-the gravitationalforce-overcomes the vortex in-'l uence upon the particles. Accordingly, the

height of the classifier is determined by the desired particle size of the `material'to be delivered from, the machine. v

The outlet `chamber is provided with a `fan iwhich' dischargesthe classified material radially from. the machine to the place of collection or use.

The fact that material as-srriall as one micron from apparatus constructed according to my in'- vention shows ,the eftlcacy ofthe methods of and apparatus for pulverization and classification..

Referring to the drawings, and more particuy larly to Figs. l,"2and 3, the machine comprises a hollowbase I0, two superimposed cylinders I2 and I4, a discharge casing I8, and a cover plate i8. The material to be reduced in size is fed into the machine by the feeding mechanism indicated generally at 20, is reduced or pulverized by my new method in the lower chamber denedby the cylinder I2, is classified by my new method in the upper chamber, defined by the cylinder I4,

. enters the discharge chamber I6, and is removed from the machine through the discharge outlet L22. Air, used in the pulverizing and classifying operations in the indicated embodiment, is admitmultiplication mechanisms, such as gearings, pul-l The attrition chamber I2 has a rotor mounted on the shaft 28, comprising upper and lower spider frames 36 and 88 respectively having

centrai hubs

40 and 42 and outer cylindrical walls 31 ing of the dust-laden air, and the movement of the material laden air is maintained only suf.-

and I9. It will be understood that'it is not essential to have the rotor divided into sections, also that the rotor may comprise more than two sections, and may be constructed in a variety of forms. Secured to the bottom of the frame 38 isan annularplate 44, mounted between the frames 88 and 38. is an annular plate 46, and upon the top of the frame 36,is another annular plate 48, all of which terminate a fixed distance from the surrounding wall I2. The frames and plates are secured together by a multiplicity of bolts 50, only one of which is shown for clarity of the illustration.

Mounted between the plates of the rotor and spaced equal distances therearoundare a plurality of fan blades 52, which may b of any suitable That is, due to the frictional to the projecting upper end thereof which tubes Y screw into appropriate openings in the upper plate 62, to be hereinafter morefully referred to. The upper ends of the tube 60 are exposed from above the plate 62 and have fastened therein a block 84 that is internally screw-#threaded as shown. When it is desired to remove the rotor blades for cleaning, or for replacement, an appropriate screw-threaded tool` is inserted into the block 64, to unscrew the tube from the plate 62, the insertion being made through opening 66, which'is covered by cap B0 bolted to cover plate I8. The tube 60 and attached pin 58 is removed through opening 66, thus making it possible to lift out the rotor blades through a. side door 10 provided in the wall of the -chamber I2. One or more doors I may be provided to permit ready cleaning of the attrition chamber I2.

It will be noted that the fan blades 52 are spaced from the interior of the outer Wall of the attrition chamber I2 and that they are also spaced from the walls 31 and 89 of the center frames, although this latter spacing is not essential.

Air, as stated above, enters `the machine through the opening 24 in the hollow base I0, which opening is surrounded by a collar I2 that is slotted to receive a gate 'I4 adapted to be appropriately adjusted and set tol regulate the size of the air intake opening and thereby control the amount of air admitted -to the machine. 'I'his control is of importance in connection with determining the degree of iineness of the nished product and also permits of variations in accordance with the mass or the specific gravity of the material being ground. In instances where the reduction in size is accomplished in atmosphere other than air, as is sometimes done, this regulation of the amount of the gaseous medium entering the machine becomes important from other angles, such as eliminating wasting of the gases, and other advantages readily perceived by those skilled in the art.

On-the interior of the base and arranged on a level above the air inlet opening 24 is an annular plate 1.6, supported upon brackets 18, through the central opening of which the air is drawn by a plurality of air-impellers '80 riveted to the underside of the lower rotor plate 44. These impellers 80 are equally spaced about the plate and direct the air into the air-seal 26 'formed'j by a fiat ring 82 extending inwardly a suiilcient distance to overlie the projecting edge of the lower rotor plate I4 and yet spaced a short distance above the top thereof, thus providing a narrow passage for the entrance of air into the attrition chamber at high velocity to prevent material being forced out through this opening during the operation of the rotor, and also preventing the air from entering the grinding chamber in a direct path. The ring 82 has a vertical flange 84 bolted to the'interlor of the outer wall of the attrition chamber |2 by botls 83, the holes for which are enlarged to permit adjustment of the air-seal ring 82, and are covered by plate 85 fitting under the bolt head. The bars 56 of the fan blades are recessed as shown at 88 to provide clearance for the ring 82 if necessary, and also to avoid setting up forceful currents to interfere with the 'current of incoming air.

However, should any of the material fall below the ring 82, as for example if the machine should be overloaded or if the machine should be shut down before all of the'material in the attrition chamber was reduced and had passed out of the machine, such .material would accumulate on top of the plate '16, will be/carried around by the pressure of the air impellers 80 until the material r'eaches opening 90 when the material will drop into the pocket 88 provided at one side of trition chamber from a hopper indicated generally at 94 as communicating with a feed tube 96 which registers with a feed opening 98 in the outer wall of the attrition chamber I2. A feed screw |00 rotates in the tube 96 and is driven by a worm wheel I 02 mounted on the shaft |04 of the feed screw. The shaft is mounted in bearing plates |06 and |08, which are respectively of a size to close the end of the feed tube 96 and to enclose the worm wheel. The worm wheel |02 is driven by a. worm ||0 mounted on the shaft of a driving motor ||2. As will be understood in this art, the rotation of the feed screw |00 will positively feed the material into the attrition chamber at a steady and denite rate of speed depending entirely upon the speed of the motor ||2 which may be controlled in any desired manner. The feed opening 98 is shown as located near the top of the attrition chamber I2, but in some instances it may be desirable to locate this feed opening at a lower level, or even at the bottom of the attrition chamber.

When the machine is started in operation the rotor is brought up to speed and through the action of the air impellers 80 air is introduced into the attrition chamber. The rotor blades 52 take up'the air and whirl it around the attrition chamber, setting up a vortex beyond the tips of the rotor blades, which will be hereinafter referred to as the outer vortex, and indicated by the heavy arrows in Fig. 2. The feeding of the material 'through the feed opening 88 is begun.

of material entering the machine are picked up may, be explained as follows:

by this outer vortex and' generally are of comparatively large mass and weight. The centrifugal action of the whirling -mass of particles and constantly eroded by the high speed air currents and reduced in size by collision ,with other particles in its paths. Thus the particles have three paths, one, a somewhat circular path, a second path substantially in the plane of its circular motion and 'at right angles toward the center of the machine as it is reduced in size, and a third path as a result of the component of these two terial against the inner surface of the outer wall of the attrition chamber will retard and practically stop the speed of rotation of the air and material at that point and thus cause a slowly traveling layer of material at the outer surface of the vortex. In some cases it may be desirable to line the inner wall of the attrition chamber l2 with a plurality of rods iid, or the wall may be provided with some other form of corrugated liner. The presence of these rods or thecorrugated liner will cause the accumulation of a layer-of material with very little duid movement at this outer surface 'of thevortex, but either using a corrugated surface or a plain surface there will be aslowly moving layer of material and air adjacent the outer wall of the chamber past which other layers of material and air arel moving.y The referred to retardation of the outer surface of the outer vortex is reflected assenso l. 5

-1 of the rotor. The irl-rush. from the three directions notedabove of mate-ffrial-iaden air to ll the vacuum created behind each blade-causes innumerable high speed imgravity. 'I'he friction of the mass of air and ma progressively inwardly through the vortex toward the inner surface thereof, -while the innermost surface is travelims at substantially the peripheral speed of the rotor. These differences in speed contribute to the mulling of the particles upon each other and the causing of collision between particles to speed upthe further reduction of the, mass o f the particles.

A The rotor ofy thedescribed machine operates at a high peripheral speed o@ the order oi', for example, 150 miles per hour. although lower and higher speeds are entirely successful.

I have discovered that by properly spacing the rotor blades t2 vortices will be set up between the blades, which will be termed inner vortices. These inner vortices are formed in the following manner: The forward travel of each blade creates a vacuum immediately behind the blade. There is an immediate in-rush of air to ijlll the vacuum. That air is taken in part from the inner edge of the outer vortex and such air is laden with finely pulverized material. Air to ll the vacuum is also partly obtained from about the tip of the blade which air slips from in front of the l blade and around its tip. The following blade,

advancing toward the vacuum, compresses the air directly in front of it and this air also rushes in to 'fill the vacuum at very high speed due to its increased pressure. The result of these several forces will be to produce a somewhat circular `high speed vorticose movement between each set of opposing faces of the fanblades.

As the particle size is reduced, greater and greater intensity of impact is required to effect further reduction. It is not practical to provide adequate Iperipheral velocity, sufficient 'for very flne grinding, as. the practical mechanical and economic limit is reached at or near 300 feet per second. In these closed circuit vortices between the blades, however, velocities many times the peripheral velocity of the rotor obtain, due to the high intensity of the dual forces inducing same.

These inner vortices are inherently high speed vortices with respect to the outer vortex, and their speed is rendered even higher by reason of the mots and collisions of the particles upon each other which, together with the pull against thel inertia of the particles inthe vortices and the very high speed of the vortical air currents. re= suits in a rapid attrition of the particles to rapidly produce large quantities of very particles, of the order of one micron ,and fractional micron sizes, if particles that 4small aredesired. The inner vortices referredto are-indicated by the light arrows in Fig. 2.

An eifective spacing of the blades to obtain the inner vortices has been found to be vaccording to the :followingwformula (see Fig. 4): A line H8 is drawn on the radius running from the` center of the shaft through the center of the rotor blade MX. Then draw a line IIS tangent to the upper outside surface of the following rotor blade @ZY and at right angles to the line IIS. 'Ihen draw a line i2@ parallel to line H8 from the top of blade BZK at the point |22 Aof the intersection of the cincumferenne and the radius of the blade. The distance between lines H8 and i2@ isknown. as the distance A". A distance "B is measured along the extension of the radius line of blade 52X from the point l22 to a point las on the in ner surface of the cylinder wall i2. (If a liner, either orf the rod or a corrugated lining type is used, then point |24 is chosen as on the line intersecting the inner surface of the rods or cor rugations.) A distance C" is. the spacing between the opposed faces of the blades 52X and EZY along the dash line iZ. Within the limits hereinafter noted, when the distances A plus B equal C, then the inner vortices will be set rupzas described above. In so far as I have yet determined with a definite maximum and minimum relationship between A and B in determining the distance C" are: minimum; A equals 0.25 B; and

nii'iizirnum-l A equals 0.75 B. I have found that if A plus B equals 1.3 C effective inner vortices will not be set up.

Figure s illustrates a section of the rotor cham-` ber and rotor, and an alternate method of computing the spacing ofthe blades. The blades areI shown at 52N and EEP; the individual vorticesby l' In operation, a layer or concentric cylinderof material forms ongthe wall held in place by*th'e centrifugal pressure of the rotating outer or unidirectional vortex. While this layer may befmore or less iuid, it is slowmoving and in part, stationary, due to the massfrlction upon the wall and its corrugations. If the corrugations are not used there is neverthelessja nlm or layer of material on the wall of the cylinder, as explained above. It forms in` a definitev thickness, depend ing upon the initial clearance between the rotor and wall, the nature of the material, the ratev of feed relative to the rate of reduction, and the speed of the rotor. Between this layer and the outer or uni-directional vortex zoneE-E, there4 is a distinct slippage plane D-D. i 0n one sidel of .this slippage plane is a mass of more or less closely spaced particles with slow relative motion. On the other side is thinly dispersed airsuspended material in high state of agitation and vortex motion. f

` The arrows in leach case indicate the direction of motion and flow of air." A line F-F drawn tangent to the inside of the concentric cylinder of material D-D. A line G-G is drawn tangent to the tip of the blade 52N and parallel to the rst line. A line H-H is drawn parallel to these two lines contacting the tip of the blade -52P and perpendicular to the blade 62N.

The distance between the lines F-F and G-G V is the depth of the free vortex zone. 'Ihe distance between the lines G-G and-H-H is the depth of the radial exposure of the blade or its effective vacuum producing surface. It is maintaining the proper relationship between these two factors that I find desirable to obtain the closed circuit effect. In this figure, the free vortex zone E is indicated as 21/2 times the radial'blade exposure K. Again, in so far as I have determined, this ratio should not be less than 2:1- nor more than 3:1-for the maximum efliciency with a large range of materials, but I do not limi myself within such narrow margins.

If the ratio falls materially below the proper limits, a closed circuit vortex is no longer effected between the blades and merely an in-and-out movement of the air is obtained. If the ratio is materially higher, the unit Avortices become small and less effective, due to the inadequate radial blade exposure.

In the event pulverizing to very fine sizes is not desired, the above spacing of the' rotor blades need not be followed strictly; or if the upwardly traveling air current is so regulated that the time the material is in the attrition chamber is shortened, as when larger particle sizes are desired, the use of inner vortices will speed up the reduction to whatever size is desired.

It should be noted that the diameter ofthe inner vortices is such that they extend into the outer vortex so that the material therein is deposited beyond the edge of the rotor .so that when the material has been sufficiently pulverized in the outer and inner vortices as described, the air ladened with the sufficiently ground material will readily pass upwardly through the open top of the attrition chamber I2 directly into the classifier chamber I4.

The classifier operates on the pneumatic principle' and has a rotor comprising 'an imperforate cylindrical shell |26 which rests upon the top plate 48 of the rotor and is welded to a ringshaped plate |28 which is adapted to be bolted to the rotor by means of the bolts 50. Intermediate its top and bottom the shell |26 may be provided on its interior with one or-more stiiening rings |30 which may be welded thereto. At its upper end the shell |26 fits into an appropriate groove on the under sidel of the upper plate 62, and the shell may be welded to that plate.

The shell |26 has a smooth outer surface, which may or may not be polished, and is of less diameter than the outer cylinder of the classifier chamber I4, providing an elongated classification space. The inner surfacel of the outer cylinder is likewise smooth, it may or may not be polished-and may or may not be covered with a polished liner |32. The classification-space may be of the same width as the space between the rotor blades and the outer wall of the attrition chamber. or such space may be wider or narrower than the space in the attrition chamber. v

At the upper end of the classifier, whichI is the outlet end thereof, the space between the shell |26 and the outer cylinder wall is partially closed by a ring |34, the ring being of such a size as to leave an opening |36 between the shell |26, which passes through the opening, and the inner edge of the ring las. The ring m is 'shown in the present embodiment as fastened between the flange |38 of the outer cylinder of the classifier chamber I4 and the flange I 40 of the discharge chamber I6 at which places the flanges are bolted together, as shown. As 'will be hereafter explained, it may be desirable to vary the size of the opening- |36 by the use of different size rings |34, or the ring may be of a construction whereby the size of the opening |36 may be readily varied.

One or more doors may be provided in the casing I4 to permit of easy examination and Y of the plate 62 I may provide a plurality of fan' blades |42 which may be riveted or otherwise secured to the plate 62. The cover lplate 62 Is 'secured toa sleeve bushing |44 on the shaft 28.

In the operation of the classifier, the materialladened air current, already moving in a, unidirectional spiral path from the attrition chamber I2, enters the classifier chamber I4 at the bottom thereof and progresses upwardly therein toward thedischarge outlet |36. This air current contains the material of desired particle size with considerablev material of larger particle size.l It is difficult to state definitely just what the actions are that occur in the classifier, but

apparently, based on theoretical considerations and 4my observations I believe that the following does occur.

In the classifier there are two rotating bodies, one, the rotating cylinder |26 and the other, the rotating current or vortex of material-ladened air. As explained, this current of air contains particles of varying mass. As is well known, centrifugal force depends partly on mass and the centrifugal force developed will therefore tend to throw the larger and heavier particles of material to the outside of this swirling current of air, with the smaller particles at the inner surface of thevortex formed by the swirling current.

In the classifier of this application, the novel arrangement of having a rotating smooth cylinder on the inside of the vortex supplies the necessary impetus to the smaller and lighter particles of material to continue the classification thereof during the upward movement of the material-ladened air by continuing the vortex action thereof until the air currents reach the discharge outlet |36. Hence with the proportions and action in the attrition chamber adjusted so that the minimum particle size produced is the particle size wanted, then with the classifier of this application, that minimum particle size can be segregated and delivered from the machine without particles of other sizes.

The moving particles are kept in suspension 'against the forces of gravity by the centrifugal of the drum |28 and passing through the outlet more counteracting force due to gravity. At the same time centrifugal force is much stronger in the case of the larger particle tending to divert it to the wall of the chamber. As a resultvin this classification zone a larger particle will move upwardly at a slower rate than a smaller One.

As previously explained, because of the larger mass of the larger particles, those particles will be thrown to the outer surface of the moving mass of air. The inner wall of the cylinder It is stationary and there is considerable friction between it and the current of air passing the inner surface of this cylinder wall. This 'friction results in what is known as the skin-core eiect, which is the progressive reduction of speed of the moving air as the air approaches this stationary surface, an eiiect created because the'l frictional engagement of the air on the inner surface of vthe stationary wall not only retards that air but also progressively retards the next adjacent films or currents of air toward the center of the vortex. At the very inner surface of the outer wall i4, because of this skin-core effect, the air has lost practically all of its velocity and is substantially dormant. Since centrifugal force is dependent on mass and velocity, the centrifugal force acting on the larger particles of material as they approach the inner surface of cylinder It slowly grows smaller and smaller until the particles reach the point where the centrifugal force does not exceed the pull of gravity, and hence these larger particles must fall. AIn the present construction the larger particles are returned to the attrition chamber i3. This latter action continues progressively throughout the height of -the classification chamber with the larger particles being progressively smaller in size as the topy of the chamber is approached.

With no turbulence in the ascending rotating column of material laden air in the classifier, for a given set of conditions of speed of rotation, volume of aspirating air, the effect of the three forces noted above, etc., the separation of the particles occurs along somewhat definite lines according to size, an indication of which is diagrammatically illustrated in Fig. 6. For particles of 100 screen mesh, for example, there is' a point on the outer edge of the vortex (the wall of the cylinder It) where centrifugal forces upon such particles, either individually or when massed together, are not suiiicient to maintain the particle in suspension against the pull of gravity, and hence the particles will fall, back into the attrition chamber in the present machine. `The same action occurs for particles of 200 screen mesh size and of 50 micron size, but of course the points of equilibrium of forces for these other sizes are at higher levels in the elongated classification chamber. In so far as I can now determine, I believe that the location of the point of equilibrium may be computed by considering a particle of a given size under the given set of conditionsat thebase of the The` point S indicates approximately the point at which centrifugal pressure no longer overcomes the pull of gravity on a particle of l00 screen mesh size, the point S' a like condition for the particle 100 screen mesh size, etc., and also the point above which the respective particles are not likely to be lifted.

Because. of their smaller mass and resulting lower centrifugal effect the smaller particles move toward the inner surface of the vortex and toward the outer surface of the rotatingcylinder |26. The skin-core effect also obtains at the surface of the rotating cylinder |28, but in this case, because of its high velocity it isspeeding up the film of air adjacent to its surface. This contact of the material ladened air with the surface of the rotating cylinder imparts energy to both the air and its contained particles of material. This added energy to the inner surface ofthe vortex enables the inner portion of the vortex to continue without substantial abatement for the entire height of the chamber.

It is this additional energy that is imparted to these nner particles on the inner surface of the vortex that enables them to withstand the pull of gravity throughout the length of their yjourney up the chamber to the discharge outlet |35. Since in the v:dual zone of classification the larger particles have been eliminated from the interior of the vortex of moving air, as ex plained above, they are not lifted to the discharge outlet.

As will be seen from the foregoing there are present what appear to be two conicting forcee that apparently nevertheless contribute cumulatively to the successful operation of the classi ler, namely, the slowing down of the outer surface of the vortex by the stationary wall of the cylinder id and the speeding up of the inner surface of the vortex by the cylinder 26.

It is to be noted that the two conflicting forces just described are not dying forces which dissipate themselves, but are virulent forces active throughout the lengthof the classifying cham ber and so contribute constantly to the classicarotating drum or cylinder |26 of the classifier,

particle the line H2; a -400 mesh particle the line Rrr-S3; a 50 micron particle the line R-S, and so on progressively, with the particle of the desired size following closely the circumference tion of -the material passing through the chamber. The brake eiect of the stationary wall is vconstantly present and the centrifugal force is constantly being augmented by the energy imparted by the rotating cylinder |26, so that both forces are at all times Working toward continuous classification of material.

All conditions being equal, in the this invention, the height of the classifier chamber is determined by the maximum particlev size it is desired to deliver from the machine and the time needed to eliminate particles of larger sizes from the vortex in the classifier` thereof. Thus. by extending the height of the classifier, particles of only the smallest size produced in the attrition chamber can be successfully segregated and delivered from the machine. On the other hand, if mixtures of particle sizes are desired, as is sometimes the case, the location of the discharge outlet |36 will be fixed at some lowerlevel in the classier chamber consonant with the largest of e the particle sizes desired in the mixture.

When the air current enters the classifier chamber from the attrition chamber, it is' heav ily laden with a great mass of material, much of which is over-size. As centrifugal force acts to' machine of material laden air progresses spirally up the classiiler chamber, the larger particle sizes at the outer surface'of the vortex will be progres` sively smaller and the amount of the volume of of less diameter than the Icasing for causing at- V trition of particles upon each other by movement of the gaseous medium in which they are suspended, a smooth cylinder mounted concentrically of but of less diameter than the casing for causing classification of the pulverizedmaterial,`

the spacing betweenthe rotor and the casing and between the cylinder and the casing being substantially alike with the spaces opening into each other, and means for rotating the rotor and cylinder. f

' 2. A machine for delivering pulverized mate- 1 f rial of predetermined sizes, comprising a casing,

which may remain in the vortex, causing them to lose their energy, and fall. y

The air current, carrying the desired material, entering the outlet opening |36 is picked up. by

a rotor spaced from the walls of the casing and comprising a plurality of radial, substantially imi perforate blades extending longitudinally of the the fan blades |42 and impelled through the discharge outlet 22 of the machine, from whence it may be taken to a place of use or to a collector (not shown). It will be understood that a separate ow inducing means may be substituted for the fan |42, and need`not be .a part of this machine.

As an example of classier size, I have been able to successfully classify material o f less than 5 micron size in a classifier where the outer cylinder I4 is thirty-six inches in diameter and thirty-one and one-half inches high, with the rotating drum |26 concentric therewith and twenty-eight inches in diameter and with the drum rotating at a speed of 1800 R. P.'M. The discharge opening |36 is one and one quarter inches in width. With other size machines it has been practical on a commercial scale to classify materials one micron in size.

While one example has been given, it is obvious that to deliver any given particlel size, it is only a matter of varying vthe height of the classier zone, making same high for very ne material and proportionately lowe'i` for coarser material. However, varying the quantity of air, hence its velocity, or the rotative speed of the air column, or the width of the annular space to suit requirements, also aiect the ilneness of the material.

With proper proportioning of the height of the classier zone, Vair velocities, rotative speed and clearance, commercial classication very exactly While one physical embodiment of my invention has been described, it will be understood that various changes in construction could be r'nade without departing from the principles herein outlined. Accordingly, modifications may be made in the arrangement and location ofparts within the spirit and scope of my invention, and such modifications are intended to be covered by the appended claims.

I claim:

1. A machine for delivering pulverized matel rial of predetermined sizes comprising a casing,

means for supplying a gaseous medium to said machine, a rotor mounted concentrically of but rotor, the blades being spaced apart a distance substantially equal to the distance between the tip of a blade and the wall 0f the casing plus the distance between parallel lines extending from the tips of adjacent blades when the line drawn from the-tip of one blade intersects the radius of the preceding blade at right angles.

3. A machine for delivering pulverized mate?- rial of predetermined sizescomprising a stationary casing, a rotor spaced from the walls'of the casing and comprising a plurality of radial blades extending longitudinally of the rotor, the

blades being spaced apart, according to the for-f mula C equals A plus B where B is the distance from the tip of the blade to the inner surface of a surrounding stationary element, where A is the distance from the tip of the blade to the point of intersection of a line drawn at right angles tov the radius of the blade and touching the tipv of the following blade, and C is the distance between opposing faces of the blades near the tips thereof. Y

4. A machine vaccording to claim 3 wherein the distance A is not less than 0.25 B, and not greater than 0.75 B.

5. A'machine according to claim 3 wherein the distance A plus Bis not greater than 1.3 C.

6. A classiierr comprising a cylindrical`caslng, a cylinder having a smooth wall concentric with and spaced from the casing, a rotatable shaft on which the cylinder is mounted, means for introducing a vortex of material-laden gaseous medium into the lower end ofthe space between the cylinder and the casing, the smooth wall cylinder acting upon the material and gaseous medium to eiect classification of the material according to particle size, and a discharge outlet at the upper endof said space.

7. A classifier comprising acylindrical casing, a cylinder having a smooth wall concentric with and spaced from the casing, a rotatable shaft on which the cylinder is mounted, means for introducing a vortex of material-laden gaseous medium into the lower end of the space between the cylinder and the casing', the material being of a variety of particle sizes, the smooth wall cylinder acting upon the3material and gaseous medium to effect classification of the material according to particle size, the discharge outlet located above the lower end of said space a distance determined by the selected particle size to be classified and delivered from the machine, and a return for oversize particles.

8. A machine for pulverizing material comprising` a casing, a rotor mounted therein having a projecting portion at thebase thereof, means to rotate the rotor to createa vortexabout the periphery of the rotor,an inlet for admitting air to the casing nearthe bottom of said rotor, means ing mounted co-axially.

1 2. A machine for delivering pulverized mate-I medium and material into the space between the rotor and the casing, the rotorcausing attrition uponeach other of the particles of material suspended in said medium by movement of the medium and suspended particles, an imperforate tubular element mounted concentrically of 'said casing. andv of substantially the same diameter as said rotor and arranged to receive the pulverized material inthe space between the element and the casing, an outlet for the selected material, said tubular element extending substantially the entire distance'between the rotor and the outlet, and means for rotating the rotor and the tubular element.

10.' A machine for delivering pulverized material of predetermined sizes comprising a casing,

means for supplying a gaseous medium to said y machine at low' pressure, a driven shaft mounted for rotation in said casing, a rotor for causing attrition of particles upon each other by movement of the gaseous medium; a hollow cylinder for causing ,classification of the pulverized materials, the rotor and the cylinder being mounted upon said shaft, and an outlet for the classified material located at one end of the casing, the

cylinder extending from adjacent the outlet in'- v wardly a substantial distance toward said rotor.-

11. A machine for delivering pulverized mate'- rial of predetermined sizes comprising a casing, means for supplying a gaseous medium to said machine, a rotor mounted concentrically of 'but of less diameter than the casing vfor causing attrition of particles upon each other by movement of the gaseous'medium in the casing, means for continuously feeding material into the space between the rotor and the-casing, a hollow cylindrical member mounted concentrically of but of less diameter than the casing for causing Glassification of the pulverized material by centrifugal action upon the material between 'the member and the casing; fan means for directing the gaseous medium into the space between the rotor and' the casing, an outlet for classified pulverized material, the outlet being concentric'with the cylindrical member, a dischargeoutlet from themachine, and fanV means for moving the classied pulverized material through the discharge outlet, the rotor, cylindrical member and fan means beelement at substantially the same peripheral speeds. I

13. A classifier comprising a cylindrical casing, an imperforate classifying cylinder mounted 'in said casing, the cylinder being coaxial with and spaced from thev casing, means for rotating the cylinder, means for feeding material suspended ina gaseous medium directly into one end of the space between said cylinder and said casing, and a discharge outlet located adjacent the opposite end of the cylinder.

14. A classifier comprising a cylindrical casing, a cylinder having a smooth wall concentric with and spaced from the casing, a rotatable shaft on which the cylinder is mounted, means for rotating the shaft, means for feeding a suspension of material and a gaseous medium into one end of the space between the cylinder and the casing, the smooth Wallcylinder acting upon the material and gaseous medium to effect classification of the material according to particle size, a return for oversize particles of material, and an outlet concentric with the'cyli'nder and of less area thanthe space between the Vcylinder wall and the casing. f

l5. A classifier comprising a cylindrical casing, a cylinder having a smooth wall concentric with and spaced from the casing, a rotatable shaft on which the cylinder is mounted, means for rotating the shaft, means for feeding a suspension of material and a-gaseous medium into one end of the space between the cylinder and the casing, the smooth wall cylinder being operated at such speed as to act upon'the material and gaseous medium to effect classification of the material according to particle size, a return for oversize particles of material, a discharge outlet from the casing, and a plate-extending at least partially across the space between the cylinder wall and the casing andlocated between that space and the discharge outlet.

16. A classifier comprising a cylindrical casing,

a cylinder having a smooth wall concentric with and spaced from thecasing, -a rotatable shaft on which the cylinder is mounted, means for' rotating the shaft, means forjfeeding a suspension of material' and a gaseousmedium into one end of the space between the cylinder and the casing, the smooth wall cylinder being operated at such speed as to act upon the material and gaseous medium to effect classification of the material according to particle size, a'return for oversize particles of material, and a ring-shaped plate vrextending from vthe casing inwardly to a position adjacent the cylinder but spaced therefrom, the cylinder extending into the opening of said I plate, A

rial o f predetermined sizes comprising. a casing,' 'A means for supplying a gaseous medium to said machine, a rotor mounted concentrically of but of less diameter than the casing for causing attrition of particles upon each other b y movement by -movement of `the gaseous medium in the casing, means for directing the gaseous medium into the space between the rotor and the casing, and

means for operating the rotor and the cylindrical j 17. A classifier comprising a cylindrical casing,

' a cylinder having a smooth wall concentric with and spaced from the casing, a, rotatable shaft on which the cylinder is mounted, means for rotating the shaft, means for feeding a suspension of material and a gaseousmedium into onel end ofthe space between the cylinder and the casing,

vthe smooth wall cylinder acting upon the mate- 'rial and gaseous' medium to eect classification of the .material according toparticle size, aretum for"'ove rsize particles of material, a ringshaped platel occupying a position betweenthe casing and the cylinder but spaced therefrom, a discharge casing communicating with the'last mentioned space and having a. discharge outlet, and a fan mounted in the discharge casing.

HENRY G. LYKKEN.