US2951648A - Milling apparatus - Google Patents

Description

Filed June 27, 1955 2 Sheetsf-Sheet l n Ei f 3% .fm n. i ffw V l V/ n4 .a ew wf. f m il 7 u s f .ww MM/ WW am www am Mmfmm/ 3 W 4 M/aw mwa 5 4 M, f IJW. 4 L 5 MM .p 8 W 0 /6 M 3 ....wlf

7' TOR/VE Y Sept. 6, 1.960

M. D. lssr-:RLIS v 2,951,648

MILLING APPARATUS Filed June 27, 1955 2 Sheets-Sheet 2 A. INVENTOR.

' MORRIS Q [55.55515 SMQ@ United States Patentl MILLING APPARATUS Morris D. Isserlis, 117 Riverview Ave., Highland Park, N J.

Filed June 27, 1955, ser. No. 518,138

8 claims. (ci. 241-55) application SerialA No; 503,915 ledt April l 26;` 19,55, now

abandoned.

-Inone knowntype of milling machine, high velocity;

Z force generated bythe rotating air mass; classification is achieved.

If desired, the above-described machine may be enrployed as a hammer mill which provides particle classi* iication by making. the impeller blades of suiiicient length that-they can. make direct physical contact with the mate'- rial to be pulverized.

Milling -apparatus embodying the principles of the in'- ventionmay also include inlet and outlet pipes at the center of the housing and axially aligned. In this constructipnof a milling machine, the impeller which has its blades lyingY in planes which extend radially from the axis on which the inlet and outlet are aligned,A is. provided with afsolid disk secured to the impeller 'approxi-v mately midway between. the inlet and outlet and. orie` ented in a pl-ane transverse to the oniwhich the Thus, efficient inlet and outlet pipes are oriented` Thus,` in effect,

jetsof 'afiiuid are employed to'pulverize `solid-materials t to a ne state. IIn order to achieve the requiredtfluid velocity, t extremely high` fluid pressuresrnust be provided andcornparatively complex and expens-ive auxiliary apparatus is required for this purpose. The cost of such auxiliary apparatus is prohibitive. In addition, other knownitypesof milling apparatus dolnot readily provide milling 4to iine particle size and, concurrently, iine particle size classification.

Accordingly, the principles andobjects-of this invention. are-v directed to providing milling 'apparatus of new and novel form `capable of pulverizing solid` materials to. substantially any desired particle size and, at the same time, providing useful classification in the fine particle range. The objects of thetinvention are also concerned with providing an improved milling apparatus which is comparatively inexpensive whilev being comparatively simple and rugged in construction.

` III general, `the principles and objects ofV this-invention are accomplished by the provisionof milling apparatus including a stationary housing having aslarge volume at` the center thereof `and tapering to a minimum volume` ab the periphery thereof.A Thus, the housing may comprise a pairof generally conical members or sections off spheres orwthe `like coupled together attheir bases.A

An impeller is provided at the center of thehousing andA l iiaving comparatively shortA blades sothatthe diameterof-theimpelleris smaller than the diameterl ofthe housing-, along its long axis.` Means are providedu `for intro`` ducingmaterial. to be` pulverized at the periphery. of.` the liousingand `for withdrawing` the pulverized` particles at thercenter of the housing..

t In order to` achieve the desired pulverizing.operation;- the impeller is rotated -at high speedv whereby. the large volume of air at thecenter of the housingfis rotated the direct flow path between the inlet and outlet pipes is-'bl-ockedy by the soliddisk and the material introduced into the. housing is forced to the periphery and cannot reach the outletl before it has been pulverized. In this way, the classifying action of the apparatus is improved.

The. invention is described in greater detail by refer, encetoithedrawing wherein:

Fig. 1V is a sectional elevational view of milling apparatus embodying the principles of the invention andV al schematic:` representation of auxiliary apparatus employed therewith;

Fig. 2` is atsectional view-along the line 2--2 in Fig. 1; Fig. 3 is asectional elevational view of a por-tionof; another embodiment of theinvention;

Fig.w4 -is a sectional elevational View of still another embodiment ofy the invention and auxiliary apparatusemployed therewith; and Fig.5 is` a perspective View of the impeller employed with the apparatus of Fig: 4f

Referring to the drawing `and particularly to-Figs. 1 and 2, `milling-.apparatus embodying the principles of the invention: includes a housing 12 comprising a pair oft similar dished members 14 and 16 in the form of cones orsections of spheres or the like. Thedished members are Vshown as sections of spheres. 'The/(lished` member 14ihas an apex or center 18 and ar-im 20 and the dishedV member- 16 has an apex or center 22 and a rim 241. Thedishedlmembers are secured together at their rimsw by means of bolts 26 or the like with a gasket- 2S of rubber or the 'like interposed between the rims. The dished. members, thus, are widely spaced at their centers offaplices and theA spacingbetween them decreases-to a minimum: at. the region of `contact'` between the rims 20 and 24'.A Thus, `as one. important feature of` the invenfA t tionsztlie. housing 12 -encornpassesV a` large volume atits and'- energy is transferredthroughout the volume of.

tlie housing to the periphery thereof where a small volume of` air is rotated at high speed. The frictional forces generatedV by they rapidly m'ovingnair mass,.par tcularlyatthe periphery of the liousingadjacent-to the wall thereof, create extreme` turbulence and eddy. currents. Thus, the solid material introduced into the hous-` ing at the periphery is retainedatthe periphery due to centrifugal -force and the eddy `currents cause-violent collisions of the particles so that they pulverize each other due to self-impact; A suction force applied at the outlet. from" the. housing at the center thereof draws the iine particles out of the housing with the size of tlie par-t ticles` removed being determined by the resultant of the4 flow of airlin-to the. housing througlitle inlet'andout of housing through the outlet andhof` the.centrifuga.l 5,

center'between the apices of thew dished: members and: the volume `decreases to a minimum at the.- periphery ther'eof; The dished members may be of cast iron, steel` onthelike. t

A shaft 3'0 is suitably rotatably jo-urnaliedinthevwall ofthe dished member 14 and aligned with the' centers 18-and221'of the dished members 14 and 16, respectively.'` The. shaft extends Iinto the interiorr ofthe `housing` 12. `Within` theV housing, the shaft 3i]` carries anirnpeller 32' including a plurality of varies or blades` 34p which lie in planes which extend radially from the shaft 30 as `shownin Fig. 2. Outside the housing, theshaft 305 is coupled to a suitable motor drive apparatus 364 which may. comprise a motor yal-'one or a motor `and belt` couplingl arrangement or the like.

The impeller blades 34, have edges 38 and 40 which, prefrably,. followthe contour of the in'ner walls of the housing and extend closely adjacent to said walls. Thus, the width W of the blades is` as large `as possible. to. provide maximum`` impeller capacity. The length 112.

of the impeller blades is such that the diameter of the impeller is smaller than the diameter of the housing at the rims of the dished members by such an amount that theimpeller blades donot contact the material which is pulverized at the periphery of the housing. A favorable ratio Vof housing diameter to impeller diameter is of the order of two to one.V

With the housing vertically disposed as shown in Fig. 1, an inlet pipe 42 is coupled to the periphery of the housing at the bot-tom thereof and secured to the wall of one of the dished members, for example the dished member 16. The pipe 42 may be disposed at substantially any desired angle with respect to the housing and is open to the atmosphere to allow air to enter with the charge of material to be pulverized. A hopper 43 which carries the material to be fed into the housing is coupled by a pipe 44 to the inlet pipe 42. The pipe 44vmay contain apparatus for feeding material such as ascreW conveyor or the like. Y

The dished member -16 is provided with an outlet opening 46 at the apex thereof which comprises an outlet for the pulverized material. Thus, the outlet of the milling apparatus is positioned at the center of the housing l2. An outlet pipe 48 is coupled directly to the outlet opening 46 and a screw conveyor driven by a motor 52 is disposed within the pipe 48. A conventional material separator 54 which separates the ai1 and the pulverized particles which fall into the screw conveyor 50 is coupled to the outlet pipe 48, preferably, immediately adjacent to the outlet opening 46 in the housing 12 and a suction fan 56 is suitably coupled to the dust collector through an lair line 55 controlled by a damper 57. A rotary valve 58, driven by the motor 52 and adapted to withdraw pulverized particles without disturbing the air ilow in the outlet line, is coupled to the outlet pipe 48 and pulverized material is collected therefrom.

In operation of the milling apparatus 10, the impeller 32 is first set into rotation at high speed, for example at about 20,000 feet per minute top speed. Thus, the air within the housing is set into rotation and large centrifugal forces lare generated therein. Then, the suction fan 56 is turned on an-d the feeding of solid materials 'and air (or steam or the like) from the source 44 is begun. As the solid materials are fed into the housing, they are swept to the periphery thereof Where they are pulverized due to self-impact. The theory of operation is that the impeller sets the large mass of air at the center of the housing into rotation at high speed and the rotational energy thus developed is transferred throughout the volume of the housing to the periphery thereof. At the periphery of the housing, the rapidly moving air generates large frictional forces which create extreme turbulence and eddy currents and the solid materials swirled about in these eddy currents are pulverized due to self-impact.

As the solid material is pulverized, the resulting particles which 'are of many dilferent sizes tend to become classified according to size along the diameter of the housing with the iinest particles oriented toward the center of the housing in the vicinity of the outlet pipe 48 and the larger particles retained near the periphery due to the centrifugal force of the rot-ating air. The particles thus classied which are too large to leave the housing also fact as a grinding medium on the incoming material. The ground particles are withdrawn from the housing 12 by the air flowing through the housing from the inlet pipe 42 and out of the outlet opening 46. The suction force `applied to the system by the suction fan 5.6 under the control of the damper 57 determines the air flow through the system and through the housing and the resultant force of this air ilow and the centrifugal force of the mass of rotating air determines the size of the particles Vwithdrawn from the housing. If very fine Vparticles are desired, the suction force is made small and the grinding time is thus made comparatively long and if larger particles are desired, the suction force is increased and the grinding time is thereby reduced.

In operation of the milling yapparatus 10, the impeller 32 may be rotated in a counterclockwise direction as viewed in Fig. 2 such that the flow of air rotated thereby is opposed to the flow of solid material and air entering the housing through the inlet pipe 42. This arrangement provides increased turbulence at the point of entry of solid material and promotes the attrition thereof. yIn addition, if the feeding of solid material into the housing is discontinued, the counterclockwise rotation of the air within the housing may be employed to clean out the housing by driving the contents thereof out through the inlet pipe. Alternatively, the rotation of the impeller may be in a clockwise direction and in the same direction, substantially, as the ow of air and solid materials into the housing through the inlet v pipe.

, As described above, the classification of the milling Iapparatus 110 depends on the centrifugal force within the housing and the ow of air therethrough. In addition, classification is effected by the reduction in velocity of the air which enters Ithe housing at comparatively small volume and expands at the center of the housing to a larger volume.

Effective pulverizing is promoted in the milling apparatus of the invention by the considerable energy input to the system in the large mass of air rotated at high speed at the center of the housing. In addition, since the grinding action is performed by particles of solid material colliding with each other and not with portions of the apparatus, there is substantially no wear on the component parts thereof. The apparatus described herein may be employed to pulverize many different types of materials, for example, pigments, abrasive dusts, ceramics, waxy materials and the like. Y

Another embodiment of the invention shown in Fig. 3 employs all of the features of the apparatus shown in Fig. l except that an impeller 60 is employed which h-as blades 62 which extend close to the periphery of the housing. Thus, the material to be pulverized which is retained at the periphery by centrifugal force is pulverized by direct impact with the blades 62 of the impeller and the ow of air through the housing as described above provides classiiication and removal of the particles of the desired size. The tips of the blades comprise, or yare coated with, a wear-resistant material such as Stellite which is an alloy of cobalt, chromium, tungsten, carbon, and silicon.

Referring to Fig. 4, a modification of the invention includes a housing 70 of the general form described above and comprising a dished member 72 having an opening 74 at its center and a dished member 76 having an opening 78 at its center. The dished members 72 and 76 are secured together at their peripheries with their concavities opposed and with the center openings 74 and 78 aligned. Thus, the dished members are widely spaced at their centers and the spacing between them decreases toward the periphery of the housing.

A shaft 80 having one end connected to a motor extends through the opening 74 in the dished member 72 into the `housing interior. The shaft 80 is in axial alignment with the two center openings 74 and 78. The shaft 80 has a smaller diameter than the opening 72 and is suitably supported, for example in bearing blocks 84, positioned outside the housing 70 suitably supporting themselves in any convenient manner. A protective sleeve or the like (not shown) may be provided over the shaft in the vicinity of the opening 74. Within the housing, the shaft carries an impeller 86 of the general type described above. The impeller includesV a plurality of'blades 88, for example four blades, which, in effeet, lie in planes Vsubstantially perpendicular to the shaft 80. AEdges 90 and 92 of the-impeller blades followrtliefcontour ofthe housing alongtheir length. The impeller. blades arepreferably substantially as wide as the, distance..` between the wallsof the housing along their entirelength so that only the minimum clearance ispresentbet'ween the edges of the ,blades and the walls ofthehousing. The clos'e spacingofthe blades tothe housing walls is designed to promote the building up of pressurebetween the blade. edge and the wall so that pulyerized material is substantially prevented from flowing-` therebetween. lThe impeller blades-may be of any desired length depending Ion whether or not it is desired to make direct contactwith the; material being pulverized. f

According-to the invention, a.metallic disk or plate 94 is` secured. to the impeller. The disk` is disposed substantially midway between the' edges 90 and 92 of the impeller blades v$8 and along the long axis of the housing substantially perpendicular to the shaft 80. The disk diameter is not critical and may be equal to, slightly smaller than, or slightly larger than the diameter of the impeller. Thus, the disk, in effect, blocks the direct iiow path between the central openings 74 and 78 in tzhe dished members 72 and 76. Disk 94 is seen in In addition, in this embodiment of the invention, material is to be pulverized is fed into the housing at the center thereof and through the central opening 74 in the member 72. To this end a lpipe 96 is secured to the opening 74 surrounding the shaft 80 and is coupled to a hopper 98 or some other suitable reservoir of material to be fed to the housing to be pulverized. The outlet system employed with the 'apparatus shown in Fig. 4 may be the same as that shown in the apparatus of Fig. l

. with the outlet pipe 48 coupled to the central opening 78 in the dished member 76.

One advantage of the apparatus shown in Fig. 4 derives from the fact that the material inlet is at the center of the housing where there is substantially no pressure and substantially no energy is expended in feeding material into the housing. Another advantage arises from the presence of the disk 94 on the impeller which promotes the classifying action of the apparatus. Classification is improved because when material is fed into the housing even the finest particles therein cannot flow directly into the outlet pipe 48 due to .the presence of the disk. Thus, as the material is fed in, some of it strikes the disk as it flows to the periphery of the housing due to the centrifugal force generated by the impeller. During the movement to the periphery of the housing, the material is struck by the blades 'and pulverizing is beg-un. When the material is properly pulver-ized and it is drawn out of the housing by the applied suction force and by the ow of air therethrough, it passes upwardly between the impeller blades which strike the material and provide an additional pulverizing action. The outgoing material is directed through the blades and is prevented from passing between the edges of the blades and the wall of the housing due to pressure generated in that area by the rotating impeller.

What is claimed is:

1. Milling apparatus which operates by means of air turbulence comprising a stationary housing consisting of two walls Widely spaced at their centers and becoming gradually more closely spaced up to their peripheries Where they are secured together, an impeller shaft at the center of said housing and extending between said walls, and a plurality of impeller blades secured to said shaft, said impeller blades being adapted to be rotated at highv speed so that material being milled is retained at the periphery of said housing in la region of considerable air turbulence in which the material in elfect mills itself, said blades having a width substantially equal to the width of said housing, the edges of said blades adjacent to said walls following the contour of said walls, the length of said blades being smaller than the radius of said housing so,thatsaidblades are remotefromme periphery of` the.

housing ,where materialA is milled and'said blades are substalntially, outof. direct contactwith the material` being mi led.

2. Milling appanatus comprising. a, stationary housing consisting oftwo,` generally concavemembers positioned with their centers aligned and widely spaced at their. centers and in contact with each other at their peripheries, an impeller shaftat thecenter. of said housing, impeller blades secured to said shaft, said blades being substantially as wide as saidfhousing and ,having theiredges following the contour of the walls of said housing', the length of saidblades being smaller than the radiusof said housing so that `saidrblades are remote from the periphery ofi the housingzwhereimateri-alis milled and saidbladesare substantially` -out fdirect' contact with the material? being milled, and a'disk secured'atA its center to said'sliaft' and lying in a plane perpendicular to said shaft substantially midway between the centers of said walls.

3. The apparatus defined in claim 2 and including a inlet opening at the center of one of said walls and an outlet opening at the center of the other of said walls.

4. Milling apparatus which operates by means of air turbulence comprising a stationary housing consisting of two generally dish-shaped members oriented with concave surfaces facing each other and having their peripheries secured together, an impeller within said housing having an impeller shaft oriented transversely between the centers of said dish-shaped members, said impeller having at least two sets of impeller blades, and a disk secured to said impeller shaft and lying in a plane perpendicular to said shaft, said disk having a diameter substantially equal to the diameter of said impeller, the diameter of said impeller being of the order of half the diameter of said housing so that said blades are remote from the periphery of the housing where material is milled and said yblades are substantially out of direct contact with the material being milled.

5., Milling apparatus comprising a stationary housing consisting of two generally spherical wall members positioned with their concave surfaces facing each other and with their peripheries secured together, an impeller within said housing and having an impeller shaft oriented transversely between the centers of said walls, the ratio of the diameter of said housing to the diameter of said impeller being of the order of two to one, and a solid disk secured to said impeller shaft and oriented in a plane perpendicular to said impeller shaft, the plane in which said disk lies being approximately midway between the edges of said impeller blades.

6. Milling apparatus which operates by means of air turbulence comprising a stationary housing consisting of a pair of walls having centers and spaced apart with their centers aligned, material inlet means at the center of one wall and material outlet means at the center of the other wall, an impeller shaft at the center of said housing, impeller blades secured to said shaft, said blades being substantially as wide as said housing and having their edges following the contour of the walls of saidhousing, the length of said blades being smaller than the radius of said housing, so that the tips of the blades are remote from the material being ground at the periphery of the housing, and -a disk secured at its center to said shaft and lying in a plane perpendicular to said shaft and substantially midway between the centers of said walls, said impeller blades being adapted for rotation at high speeds to cause air turbulence at the periphery of said housing.

7. The apparatus defined in claim 6 and including a suction fan coupled to said material outlet means for selectively withdrawing ground material from said housing, the speed of said fan being variable to provide a classifying action on the material withdrawn.

8. Milling apparatus comprising a stationary housing consisting of .two generally spherical wall members positioned with their concave surfaces facing each other and with their peripheries secured together, an impeller within said housing and having an impe11er shaftoriented transversely between the centers of said walls, the natio of the diametenof said housingto the diameter of said impeller being of the order of two to one, and a solid disk secured to said impeller shaft andoriented in a plane perpendicular to said impeiler shaft.

References Cited in the le of this patent UNITED STATES PATENTS 427,228 Finney May 6, 1890 617,345 Mitchell Jan. 10, 1899 669,897 Day Mar. 12, 1901 1,656,862 Loy Jan. 17, 1928 A1,753,936 Moore Apr. 8, 1930

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