US3255285A - Granulation and apparatus - Google Patents

Description

June 7, 1966 F. cHlLsoN 3,255,285

GRANULATION AND APPARATUS Filed Dec. 9, 1960 mvswroa FPA/vas CHM so/V ATTORNEY 3,255,285 GRANULATION AND APPARATUS Francis Chilson, East Chatham, N.Y. (40 Park Ave., New York, N.Y. 10016) Filed Dec. 9, 1960, Ser. No. 74,874

' 14 Claims. (Cl. 264-109) This application is a continuation-in-part of my application, Serial No. 314,398, filed October 11, 1952, and now abandoned.

This invention is that of a method `and also of an apparatus for making granulations from an individual substance or a mixture of'substances directly from any such material, which method involves merely subjecting such material in its otherwise untreated free-flowing disintegrated state simply to an adequate required pressure.

Granulations, or what also conveniently can be called granulates, are normally or ordinarily haphazardly irregularly shaped and variedly sized aggregates, generally individually stably holding together, of smaller sized particles (such as described immediately below) of an individual substance or mixture of substances.

By free-flowing disintegrated state of a material is meant the material powdered, or finely divided, or disintegrated into otherwise relatively small subdivided form, say, at least smaller in size than the granulates or granulations to be madefrom it.

Thus, more specifically the method of the invention is in essence a continuous process for making such granulations (or granulates) simply by feeding such material in its -ordinary free-flowing disintegrated state, and without any prior preparatory treatment, directly into and through the nip provided by burnished concave surfaces of opposed elongated grooves on the respective peripheralA surfaces of oppositely disposed compression rolls rotating in opposite directions (which grooves have certain required features and relation to one another); and thus merely subjecting that material between these rolls to a pressure high enough to compact its particles adequately for them to hold together when the 4thus compacted material after leaving the grooves and thus being released from pressure, breaks away as granulates.

In various industries, such as notably the pharmaceutical, explosive, fertilizer, and animal feed making, relatively finely divided materials have to be converted into granulesV vor granulates of them as one stage of a multistage or multi-step process in the manufacture of such end products as medicinal tablets, or tablets of ammunition, fertilizer or some animal feed.

The requirement of the several preliminary steps with accompanying consumption ofnecessary treating materials, power, drying heat, use of additional labor, extra equipment andy the space for it, in the heretofore employed granulating -of materials for use in the preparation of compressed tablets of medicaments especially, and of other products, are well known. All of the foregoing for generations have been an extensively serious disadvantage not only because of the greatly increased cost but also in the delay necessitated for carrying out the series of preliminary steps and also in the danger of loss in material and also in activity of the essential constituents.

The separate ingredients to be incorporated, for example, in medicinal tablets are usually in a state of fine subdivision. As a result, the mixtures of such ingredients to be included in compressed tablets do not flow smoothly and evenly through the small orifices that feed such mixtures into the small dies of the tableting press, so as to retain their original uniformity, and likewise similarly do not flow readily and with uniformity into the small dies. This results from the fact that such finely divided powders bridge over the discharge outlet of the feeding line or United States Patent C) 3,255,235 Patented June 7, 1966 lCe some earlier location in the line and their iiow becomes irregular and often even stops.

In the manufacture of explosives such as ammunition, it is equally important that finely divided explosive powders be granulated so that the weight of explosive charges placed in gun cartridges can be controlled accurately and uniformly.

Also in the manufacture of many fertilizers and animal feeds, it is highly desirable that the finely divided product be granulated so as to reduce loss of material by the scattering of fine dust particles in hand-ling.

Accordingly, it long has been the practice to convert such mixtures of finely divided powders into suitably sized granulates or granules, for in that form they iiow smoothly, `uniformly and continuously through the feeding orifices and into the tableting dies. Heretofore, two methods of producing granulations generally have been used. In one of them a moistening agent or binder is added to finely divided powders subjected to a tumbling step toform moist agglomerates. Then these are forced through a metallic screen, extruded through small holes of a perforated container, or rolled into akes. These Wet flakes or extruded large granulations must first be dried by the application of heat.

' The dried agglomerates then are passed through a grinder or tumbling mill to be ground or broken down into granules -of the desired size, before they may be compressed into tablets or made into some other form of manufactured product.

An example of that procedure is disclosed in U.S. Patent 2,167,432 to Cox, July 25, 1939. This granulating method is time consuming, requires much costly apparatus and extra fioor space. It has the further objection that it cannot be used with many pharmaceutical substances which deteriorate or change upon the addition of a moistening agen-t or the application of heat.'

Furthermore, the difficulty of thoroughly cleaning-all the apparatus of Cox, and other prior art granulation processes after granulating one composition, to avoid contamination of other materials to be granulated thereafter, is so great aspractically to restrict use of the apparatus to the processing of merely one composition.

This is aparticularly serious limitation on -the use of such prior art processes, for example, in the pharmaceutical industry where manufacture of small batches of different pharmaceuticals is common and not the exception,

and where minute traces of previously processed sub stances can cause a contamination of odor, color or taste to spoil a subsequent batch of different material. Without complete removal of such traces of contamination an explosive combination even may result, for example,`

when granulation of potassium permanganate follows that of some other substance having only a trace of starch.

The only method available heretofore for making granulations of pharmaceutical powders which cannot stand wetting or heating has been the so-called slugging process. In it the mixed powdered chemicals are fed int'o the large dies of the slugging machine, similar to an over-size tableting press, to be compressed into large slugs generally of the order of from 5A; to 1 inch in diameter and from 1A to 11/2 inches long.

While such slugs may be uniform in dimensions, they most rarely are uniform in weight or density. That follows from the impossibility of accurately controlling the flow of finely powdered materials even into such large size dies. Therefore, the slugs must be ground up into granulations which are fed to tableting machines for making tablets wherein the weight of each table has to be accurately controlled.

An embodiment of a slugging process is exemplified bythe apparatus of Patent 2,252,900 to E. W. Shafer,

August 19, 1941, which is one for forming such pellets from moist or organic materials such as animal feeds.

One serious disadvantage of the slugging process with dry slugs is that approximately 60% or more of their Weight invariably is reduced to line powder when grinding them to produce granulations. Such large quantity of fines then must be separated by sifting off from the granules and thereafter must be re-slugged and the new slugs ground to be converted into granules. Each repetition of this operation yields only 40% or less of the material handled converted into useable granular form.

Another disadvantage of the slugging method ils that it is not-an overall continuous operation, and neither the output of the slugging machine nor of the grinder` can be fed directly into a tableting press. Also, slugging machines are diicultly cleaned so that contamination also is a serious problem. j

The foregoing disadvantages and others of the prior art, i.e. so-called wet granulating and slug-granulating, methods and the excessive costs they involve are overcome by the method of the invention and also by the apparatus it embraces.

Considered broadly, the method of the invention involves directly engaging the ordinary otherwise untreated free-flowing relatively nely divided starting material under pressure between smoothly burnished concave surfaces of opposed elongated grooves on the circular surfaces of oppositely disposed compression rolls rotating in opposite directions. While the material is being compressed between the grooves, it is subjected to a pressure of at least 2,000 pounds per square inch by the rolls. That compresses the material to a much denser state wherein its particles physically adhere together and so that, upon separting opposed grooves and releasing the pressure on the thus compacted material, it disengages from the grooves and breaks into haphazardly irregularly shaped and varied sized granulates or granulations.

It is advantageous that the transverse cross-section of .the groove to be oval in shape with its depth being along the shorter diameter of the oval and never greater. than half of the shorter diameter.

It is also advantageous that the grooves be continuous about their respective rolls, for example, parallel complete circles, and further advantageous that they be in the form of a helix spiralling around the cylindrical surface of the roll.

It is significantly advantageous that the rim of one groove overlap at least in part the open top of its opposing groove on the other roll. Such grooves even may intermesh to a large extent.

The foregoing broad indication of the nature of the process of the invention and references to the rolls and the character of the grooves shows that broadly the apparatus of the invention comprises a pair of oppositely disposed and correspondingly grooved compression rolls each mounted for rotation on its respective shaft carried on suitable bearings. The grooves on each roll are elongated, with their concave surfaces smoothly burnished and positioned so that the grooves on one roll cooperate with those on the other, when the rolls are rotated, to engage in succession and hold between respectively corresponding opposed portions of the grooves successive portions of material to be formed into granulations. The rolls are associated with means to rotate them in opposite directions in close enough proximity to engage material to be compressed between opposed grooves and with means to enable them to impress at least about 2,000 pounds per square inch on the material thus engaged by the grooves.

A feature of the invention is the provision of a simple compact apparatus that enables carrying out a process of making granulates directly from otherwise untreated freeowing material simply by the application of a required minimum amount of pressure on it.

A second feature of the invention is the provision of a' process for making granulates without any need for adding any moistening or binding agent to the material to be granulated :and without any pretreatment other than reduction in size.

Another feature of the invention is the provision of a direct continuous process for making granulations from otherwise untreated free-flowing material.

A further feature of the invention is the provision of a process of making granulates that is much less costly, much more rapid, and considerably more efficient than prior processes.

Still another feature of the invention is the provision of a method and apparatus that enables making granulations from materials that cannot be granulated by the wet granulation method.

Yet another feature of the invention is the availability of a method and apparatusthat enables making granulates even from moist free running material.

Another feature of the invention is the provision of granulating apparatus that can be cleaned readily easily and thoroughly to enable granulating by it material of a different cornpostion without fear of contamination from residues of material treated previously.

Still a further feature of the invention is the provision of an apparatus that is not restricted to any particular size of granulates that can be made on or to any specific size of starting material to be granulated.

Other features of the method and apparatus of the invention can be seen from the detailed description below of a merely illustrative embodiment of the apparatus and of the operation of the process, as exemplied by the accompanying drawings wherein:

FIG. l is a top plan view of the apparatus;

FIG. 2 is an end elevational view of the structure of FIG. 1 with parts broken away and showing the cooperative relation between a pair of compression rolls and a powder containing hopper disposed above them;

FIG. 3 is a fragmentary detail horizontal sectional view showing the inter-relation between right hand and left hand helical grooves of the opposed compression rolls seen in FIG. l and FIG. 2.

FIG. 4 is a diagrammatic view of another embodiment in which two pairs of compression rolls are disposed one above the other for forming granulates of a selected size, which may be either larger or smaller than what is obtained from one of the pairs of rolls alone;

FIG. 5 is a fragmentary detail view showing another embodiment of compression rolls having parallel circular grooves;

FIG. 6 is a perspective view of still another embodiment of compression roll having parallel straight line grooves each parallel to the axis of the roll; and

FIG. 7 is a fragmentary detail view of one means for adjusting the pressure between the rolls either to enable granuating different free-flowing materials which require different pressures to granulate them or to make a more or less dense granulate of the same material.

FIG. 1 discloses a pair of opposed compression rolls 11 and 12 mounted horizontally on their respective shafts 13 and 14, with each separately journaled at its opposite ends lin its pair of sturdy bearings 15 and 17 and 16 and 18 respectively. Compression springs 19 and 20, whose compression can be varied by means of adjusting nuts 22 and 23, serve to maintain constant the selected high pressure between all opposing points of contact along the rolls 11 and 12 within the limits set by the bolt clearance slots 24 and 25 in bearings 1S and 17 (FIGS. 2 and 7).

For successful operation of the process of the invention, the pressure maintained between compression rolls 11 and 12 must be at least about 2,000 pounds per square inch, and advantageously of the order of about 3,500 to about 4,000 pounds per square inch. To granulate very hard materials the pressure can be increased above that and even to 10,000 pounds per square inch, or higher if needed.

Compression rolls 11 and 12 are formed from a sufiior a suitable one of its alloys. Their peripheral cylindrical surfaces are grooved (as in FIGS. 1 and 6) with oppositely spiraling helical grooves 27 which ca n be cut on a screw turning lathe and burnished also by use of such lathe, by substituting the proper tools.

As seen more clearly in FIG. 2, a powder retaining device such as hopper 28 is disposed above the converging portions of rolls 11 and 12. Spur gears 29 and 30v of appropriate pitch diameter, a separate one of them being rigidly affixed to the same end'of shafts 13 and 14 of rolls 11 and 12 in cooperation with the driving pinion gear 31, assure continuous rotation of rolls 11 and 12 each in its respective direction as indicated by the arrows. Pinion gear 31 can be driven by an electric motor or e by other suitable power means not shown.

FIG. 3 shows in greater detail the inter-relation between the right hand helical grooves 27 of one roll and the oppositely cut left hand helical grooves of the other roll. Both helices must have the same pitch and the same width across parallel to the axis, so that by the operation of the adjustable compression means 19 and 20, the abutting surfaces of the groove rolls are maintained in proper contact at all points. As part of the invention, particularly for use with the most nely divided powders, these grooves should be burnished or ground and polished by a lapping operation to form very smooth surfaces that are free of crevices that could retain theY compacted material treated.

example, the small granulatesvformed between the firstl or upper pair of rolls are gravity fed directly into the lower or second pair of rolls. Therein a larger number of the initially smaller granulates from the upper rolls are compressed into a smaller. number of larger aggregates. This arrangement of plural compression vstages is advantageous particularly in granulating finely powdered materials, or Where unsually large granular aggregate of the materials may be needed.

This arrangement of multiple pairs of compression rolls can be used also for granulating softer materials, whose granulates may come from the upper pair of rolls in the form of irregularly VA.shaped aggregates larger than desired for the tableting, In such case, the pressure between any lower pairY of rolls can be reduced so that a smaller number of larger aggregates are broken down between them and discharged in the form of a larger number of smaller granules, as may be desired. Alternatively, if the granulates formed by one pair of compression rolls are found to be too large to be used directly in the very small dies'of some tableting presses, these aggregates may be passed through a reciprocating granulator of the type commonly used in wet granulation.

The diagrammatic representation in FIG. 4 does not show supporting means for the rolls, .driving shafts and hopper. It is understood that these structural arrangement details can be devised by anyone skilled in the art in a manner best to suit his particular needs.

FIG. 5 shows parallel circular grooves provided on the compression rolls, that can be used in place of the helicalv grooves shown in the embodimentof FIGS. 1 and 3. Use of parallel circular grooves provides another possible variation in structure shown by the use of differently sized spur gears to drive one roll at a different rate from that of its cooperating opposed roll. Thus, for example, in FIG. 4 gear 38 axed to the end of the shaft of roll 32 can be smaller in diameter than gear 39 affixed to the end of the shaft of roll 33. Similarly, driving gear 40 which drives roll 35 can be smaller in dameter than driven gear 41 which drives roll 36.

The same relative motion between differentially driven rolls can be obtained by using compression rolls of different diameters and driving them at the same speed axially. With some types of material, particularly in granulating organic materials such as fertilizer substances, trictional engagement between compression rolls driven at different circumferential speedsappear advantageous. When using parallel circular grooves for granulating organic or moist materials,`it sometimes may be necessary or desirable to use doctor combs such as shown by 42 and 43 in F-IG. 4, to prevent adhesion of the granulated material to the grooves of the compression rolls.

FIG. 5 illustrates the inter-relation between opposed parallel circular grooves such as can be used with either the combination of FIG. 4 or that of FIGS. `1 and 2.

i FIG. o showsin perspective a compression roll 44 with parallel straight elongated grooves 45, parallel to the shaft 46 of the roll.

FIG. 7 discloses in greater detail an effective arrangement for adjusting the pressure to be applied between opposed compression rolls. In it a manually adjustable nut 23 can be brought to bear against the compression 'spring 20 in such manner as to force rod 48 to advance bear- `either gases or liquids therethrough for regulating the surface temperature of the grooves. Ordinarily, the very high pressures used have a tendency to cause the heating up of the rolls after a period of operation varying with the pressure. Thus, in some operations it is desirable to remove this excess heat to avoid overheating with consequent discoloration or scorching of the granulated mate? rial. This can be done most economically by passing cold water through the cores in the rolls.

Alternatively, for granulating some biologicals or pharmaceuticalsubstances requiring constant refrigeration, a suitable refrigeration liquid can be circulated through those cores. Otherwise, when granulating moist materials, the ordinary heat developed in the usual oper-ation of the rolls ordinarily is suliicient to dry out the granulation formed from them. Should more heat be needed, it is simple to h eat the rolls further, by passing `hot water or gases through those cores..

Thus, by controlling the temperature within and the pressure between the rolls, granulates of any desired size can be produced by this continuous process on the apparatus of the invention and from materials that ordinarily cannot be granulated by the earlier methods.

The inclusion of the smoothly burnished or polished grooves is a very significant part of the invention. An`- other such part is the fact thatthe transverse section of the grooves should be oval with the shorter diameter in the radial direction and with its radial depth no greater than the shorter diameter of the oval.

While the invention has been explained by giving detailed description of certain specific embodiments of it exemplified in the accompanying drawings, it is understood that various modifications and substitutions can be made in -any of such embodiments within the scope of the appended calims which are intended to include effective equivalents thereof.

Wh-at is claimed is: v

1. Inan apparatus for continuously preparing granulates from free-owing relatively finely divided starting material in its ordinary free-flowing disintegrated state, by feeding said material into it, and which apparatus has opposed axially parallel rolls, and on the cylindrical peripheral surface of each of them a series of correspond` ingly opposed parallel elongated grooves, means for rotat'- ing said rolls in oppos-ite directions, said rolls being mounted and positioned relative to one another with their assay/:ss

grooves so disposed on'efach of them respectively that the individual opposed members of each pair of opposed grooves approach one another as they descend during said rotation of the rolls, and near enough to engage between them successive portions of said material fed thereto;

the improvement which comprises (a) the concave surfaces of said grooves being smoothly burnished, and (b) means for applying pressure on at least one of said rolls toward the other to enable a pressure of at least a ton per square inch to be impressed successively on successive portions of said starting material as said successive portions of it are nipped and engaged between said rolls during their said rotation in opposite directions to one another.

2. Apparatus as claimed in claim 1, wherein the transverse cross-section of the individual grooves is oval with its shorter diameter extending radially and with its depth along its shorter radius being no greater than its shorter radius.

3. Apparatus as claimed in claim 1, wherein the grooves of each separate roll constitute a continuous helical groove about its respective roll.

4. Apparatus as claimed in claim 1, wherein each of the grooves is circular and each of its rims is in a plane perpendicular to the axis of its respective roll.

5. Apparatus as claimed in claim 1, wherein the individual grooves extend lengthwise from one end of the roll to the other.

6. Apparatus as claimedin claim 5, wherein the individual grooves are parallel to the axis of their respective roll.

7. Apparatus as claimed in claim 1, wherein the rims of the grooves on one roll overlap part of the respective open tops of the correspondingly opposed grooves on the other roll.

8. In a continuous method of making granulations from free-flowing relatively finely divided starting material by feeding it in its ordinary untreated free-flowing disintegrated state into a zone of diminishing cross-section and successively engaging successive portions of said material within the plurality of nips presented between the respective pairs of opposed elongated concave surfaces of two separate pluralities of respectively oppositely facing converging elongated concave surfaces, each of said separate pluralities of concave surfaces being correspondingly arranged in cylindrical form around its own relatively horizontal axis with both axes parallel to one another, while both of said pluralities of said concave surfaces are rotated in opposite directions so that the successiveportions of each such pair of opposed concave surfaces approach one another as they descend and thereby successively engage between them successive portions of said material;

the improvement which comprises (a) the operating conditions that the converging oppositely facing concave surfaces are smoothly burnished so that the successively engaged successive portions of said starting material thereby are engaged between smoothly burnished said elongated concave surfaces of said separate plurality of oppositely facing converging elongated concave surfaces while each of said separate plurality thereof is rotated in opposite direction to the other; and (b) during said engagement of said successive portions of said material within said plurality of nips subjecting said material while it is being engaged between said converging oppositely facing smoothly burnished concave surfaces to a pressure of at least 2,000 pounds per square inch by forcing at least one of said smoothly burnished concave surfaces toward the other, thereby compacting said materialto a much denser state wherein its particles physically substantially adhere to one another; and then diverging said oppositely facing concave surfaces from one another thereby releasing the pressure on the thus compacted material, whereupon said compacted material is disengaged from said concave surlfaces and breaks into haphazardly irregularly shaped and varied sized granulates.

9. The method as claimed in claim 8, wherein the pressure being impressed on the material being engaged between said burnished concave surfaces is from at least 2000 to about 10,000 pounds per square inch.

10. The method as claimed in claim 8, wherein the transverse cross-section of each such burnished concave surface is oval in shape with its depth along thev shorter diameter of the oval and never greater than half of the shorter diameter.

11. The method of preparing medicinal tablets, which comprises the steps of claim 8, and then feeding the re sulting granulates obtained thereby to the hopper of a tableting machine for feeding them directly to the tableting machine for feeding them directly to the tableting dies.

12. The method as claimed in claim 8, wherein the elongated individual smoothly burnished concave surfaces of each plurality of them are parallel to its respective axis.

13. The method as claimed in claim 8, wherein the concave surfaces form a series of parallel circles each in a plane perpendicular to the axis of its respective plurality of them.

14. The method as claimed in claim 8, wherein the elongated concave surfaces of each separate plurality thereof constitute a continuous helical elongated concave surface about its respective axis.

References Cited by the Examiner UNITED STATES PATENTS 5 4 309,117 12/1884 Wilcox 18-21 XR 1,164,718 12/1915` Hill 65-143 1,756,328 4/1930 Andelin 18-9 1,761,623 6/1930 Early 1 65-143 1,993,235 3/1935 Adams et al 65-142 2,090,669 8/1937 Dreyfus et al. 18-9 2,297,505 9/1942 Schmidberger 18-48 2,485,128 10/\1949 Adams 18-9 2,514,616 7/1950 Adams 18-9 2,623,243 12/1952 Jean et al. 18-47.5 l2,662,247 12/1953 Klugh et al 18-21 2,874,604 2/ 1959 Diels et al 18--9 XR 2,958,903 11/1960 Decker '18-21 3,091,012 5/1963 Bell i 25-75 XR FOREIGN PATENTS 170,052 1/1952 Austria.

WILLIAM J. STEPHENSON, Primary Examiner.

R. J. DOHERTY, C. N. SHANE, Assistant Examiners.

Claims (2)

1. IN A APPARATUS FOR CONTINUOUSLY PREPARING GRANULATES FROM FREE-FLOWING RELATIVELY FINELY DIVIDED STARTING MATERIAL IN ITS ORDINARY FREE-FLOWING DISINTEGRATED STATE, BY FEEDING SAID MATERIAL INTO IT, AND WHICH APPARATUS HAS OPPOSED AXIALLY PARALLEL ROLLS, AND ON THE CYLINDRICAL PERIPHERAL SURFACE OF EACH OF THEM A SERIES OF CORRESPONDINGLY OPPOSED PARALLEL ELONGATED GROOVES, MEANS FOR ROTATING SAID ROLLS IN OPPOSITE DIRECTIONS, SAID ROLLS BEING MOUNTED AND POSITIONED RELATIVE TO ONE ANOTHER WITH THEIR GROOVES SO DISPOSED ON EACH OF THEM RESPECTIVELY THAT THE INDIVIDUAL OPPOSED MEMBERS OF EACH PARI OF OPPOSED GROOVES APPROACH ONE ANOTHER AS THEY DESCEND DURING SAID ROTATION OF THE ROLLS, AND NEAR ENOUGH TO ENGAGE BETWEEN THEM SUCCESSIVE PORTIONS OF SAID MATERIAL FED THERETO; THE IMPROVEMENT WHICH COMPRISES (A) THE CONCAVE SURFACES OF SAID GROOVES BEING SMOOTHLY BURNISHED, AND (B) MEANS FOR APPLYING PRESSURE ON AT LEAST ONE OF SAID ROLLS TOWARD THE OTHER TO ENABLE A PRESSURE OF AT LEAST A TON PER SQUARE INCH TO BE IMPRESSED SUCCESSIVELY ON SUCCESSIVE PORTIONS OF SAID STARTING MATERIAL AS SAID SUCCESSIVE PORTIONS OF IT ARE NIPPED AND ENGAGED BETWEEN SAID ROLLS DURING THEIR SAID ROTATION IN OPPOSITE DIRECTIONS TO ONE ANOTHER.

8. IN A CONTINUOUS METHOD OF MAKING GRANULATIONS FROM FREE-FLOWING RELATIVELY FINELY DIVIDED STARTING MATERIAL BY FEEDING IT IN ITS ORDINARY UNTREATED FREE-FLOWING DISINTEGRATED STATE INTO A ZONE OF DIMINISHING CROSS-SECTION AND SUCCESSIVELY ENGAGING SUCCESSIVE PORTIONS OF SAID MATERIAL WITHIN THE PLURALITY OF NIPS PRESENTED BETWEEN THE RESPECTIVE PAIRS OF OPPOSED ELONGATED CONCAVE SURFACES OF TWO SEPARATE PLURALITIES OF RESPECTIVELY OPPOSITELY FACING CONVERGING ELONGATED CONCAVE, SURFACES, EACH OF SAID SEPARATE PLURALITY OF CONCAVE SURFACES BEING CORRESPONDINGLY ARRANGED IN CYLINDRICAL FORM AROUND ITS OWN RELATIVELY HORIZONTAL AXIS WITH AXES PARALLEL TO ONE ANOTHER, WHILE BOTH OF SAID PLURALITIES OF SAID CONCAVE SURFACES ARE ROTATED IN OPPOSITE DIRECTIONS SO THAT THE SUCCESSIVE PORTIONS OF EACH SUCH PAIR OF OPPOSED CONCAVE SURFACES APPROACH ONE ANOTHER AS THEY DESCEND AND THEREBY SUCCESSIVELY ENGAGE BETWEEN THEM SUCCESSIVE PORTIONS OF SAID MATERIAL; THE IMPROVEMENT WHICH COMPRISES (A) THE OPERATING CONDITIONS THAT THE CONVERGING OPPOSITELY FACING CONCAVE SURFACES ARE SMOOTHLY BURNISHED SO THAT THE SUCCESSIVELY ENGAGED SUCCESSIVE PORTIONS OF SAID STARTING MATERIAL THEREBY ARE ENGAGED BETWEEN SMOOTHLY BURNISHED SAID ELONGATED CONCAVE SURFACE OF SAID SEPARATE PLURALITY OF OPPOSITELY FACING CONVERGING ELONGATED CONCAVE SURFACES WHILE EACH OF SAID SEPARATE PLURALITY THEREOF IS ROTATED IN OPPOSITE DIRECTION TO THE OTHER; AND (B) DURING SAID ENGAGEMENT OF SAID SUCCESSIVE PORTIONS OF SAID MATERIAL WITHIN SAID PLURALITY OF NIPS SUBJECTING SAID MATERIAL WHILE IT IS BEING ENGAGED BETWEEN SAID CONVERGING OPPOSITELY FACING SMOOTHLY BURNISHED CONCAVE SURFACES TO A PRESSURE OF AT LEAST 2,000 POUNDS PER SPQUARE INCH BY FORCING AT LEAST ONE OF SAID SMOOTHLY BURNISHED CONCAVE SURFACES TOWARD THE OTHER, THEREBY COMPACTING SAID MATERIAL TO A MUCH DENSER STATE WHEREIN ITS PARTICLES PHYSICALLY SUBSTANTIALLY ADHERE TO ONE ANOTHER; AND THEN DIVERGING SAID OPPOSITELY FACING CONCAVE SURFACES FROM ONE ANOTHER THEREBY RELEASING THE PRESSURE FACES FROM ONE ANOTHER THEREBY RELEASING THE PRESSURE ON THE THUS COMPACTED MATERIAL, WHEREUPON SAID COMPACTED MATERIAL IS DISENGAGED FROM SAID CONCAVE SURFACES AND BREAKS INTO HAPHAZARDLY IRREGULARLY SHAPED AND VARIED SIZED GRANULATES.

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