US3241776A - Fine granulator - Google Patents

Description

March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULAIOR Filed April 29, 1963 5 Sheets-Sheet l INVENTOR. 4 WILLIAM M. SHELDON wfwew ATTORNEY March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULATOR Filed April 29, 1963 5 Sheets-Sheet 2 INVENTOR WILLIAM M. SHELDON ATTORNEY March 22, 1966 w. M. SHELDON 3,241,776

FINE GRANULA'IOR Filed April 29, 1965 5 Sheets-Sheet 3 INVENTOR.

WILLIAM M. SHELDON March 22, 1966 w. M. SHELDON FINE GRANULATOR 5 Sheets-Sheet 4 Filed April 29, 1963 ATTORNEY March 22, 1966 w. M. SHELDON FINE GRANULATOR 5 Sheets-Sheet 5 Filed April 29, 1963 INVENTOR. WILLIAM M. SHELDON ATTORNEY United States Patent 3,241,776 FKNE GRANULATOR William M. Sheldon, Elizabeth, N.J., assiguor to Pulverizing Machinery Division of Slick Industrial Company, Washington, D.C., a corporation of Delaware Filed Apr. 29, 1963, Ser. No. 276,645 6 Claims. (Cl. 241-55) This invention relates to the comminution of material and particularly to an improved apparatus for effecting comminution of suspended material by cutting impact on a shearing edge in the presence of a selectively directed gaseous carrier.

Comminution of material by impact pulvenization is Widely employed in the commercial arts and widely varying types of apparatus are utilized in accord with the type of material to be comminuted and the desired particle size range of the resulting comminuted .product. Cornminuting apparatus of the so called hammer mill types are Widely used for effecting impact pulverization of materials to a particle size range of about 5000 to 40 microns. Such hammer type mills are generally characterized by a high speed rotating shaft having mounted thereon a .plurality of hammerlike members. Most, if not all, mills of this type effect reduction by impact, while the material is in suspension, in conjunction with an associated breaker surface usually constituted by a part of the housing surrounding the rotating elements. Such mills, however, are usually characterizedby the production of what for many end uses is an unacceptable amount of ultra fines and an undue amount of heat generation. The development of such ultna fines is usually objectionable as, for example, when the comminuted material is to be used in forming tablets or for injection molding. The development of undue amounts of heat is particularly objectionable in the handling of materials that tend to agglomerate, either by release of Water of combination or hygroscopicity or by reason of sensitivity to temperature.

This latter problem has become of increasing importance with continually expanding use of synthetic resins and so called plastics and other polymerization products, many of which are somewhat resilient in nature and/or have a tendency to become soft and plastic beyond certain temperatures. In the attempted handling of materials of the types above noted in conventional hammer mill type apparatus various expedients, such as the prereduction of product temperature or of ambient air temperature by the utilization of Dry Ice or other refrigerants have been employed to limit the degree of temperature rise and to limit the maximum temperatures attained during comminution. Such expedients, however, are palliative in nature at best and, apart from the additional expense involved, have been characterized with a marked lack of commercial utility due to necessarily reduced production, increased cost and in some instances, the necessity of removing, by a subsequent drying operation, atmospheric moisture condensation that becomes incorporated in the comminuted material.

This invention may be briefly described as an improved apparatus for effecting comminution of suspended material by cutting impact with rapidly moving acute angle shearing edges in a rotor induced selectively directed gaseous carrier which conveys heat or other agglomeration inducing factors away from the locus of material deformation and serves to rapidly reduce the temperature of the comminuted product.

Among the advantages of the subject invention is the permitted comminution, at ambient air temperatures and with a markedly decreased temperature rise, of an extended range of materials including many, if not most,

Patented Mar. 22, 1966 of those whose comminution is effected only with difficulty, if at all, in convention-ally constructed impact pulverization apparatus even with the expedients above noted. Other advantages of the subject invention include a marked increase in induced flow of gaseous carrier into and through the locus of deformation, an improved control of particle size range of the resulting product and the avoidance of the production of undue amounts of ultra-fines characteristic of impact pulverizat-ion operations. Still other advantages include the provision of greatly extended effective lengths of cutting edge markedly improved yields per unit power input and a simplicity of construction that permits appreciable economies both in initial cos-t and maintenance of apparatus embodying the subject invention,

The primary object of this invention is the provision of an improved apparatus for effecting comminution of suspended material by cutting impact with a rapidly moving shearing edge in a rotor induced selectively directed gaseous carrier which serves to convey heat or other agglomeration inducing factors away from the locus of material deformation and rapidly reduces the temperature of the comminuted material.

Another object of this invention is the provision of improved apparatus for effecting comminution of agglomerative materials.

Other objects and advantages of the invention will be set forth in the following specification and claims and will be ascertainable from the appended drawings which illustrate, by way of example, the principles of the invention as the same are incorporated in a presently preferred embodiment of a oomminuting apparatus.

Referring to the drawings:

FIGURE 1A is an oblique view, partially broken away, of a mill (wth the housing cover removed) incorporating the principles of this invention;

FIGURES 1B and C are side elevational and plan views, respectively, of the mill illustrated in FIGURE 1A and with the housing cover in place;

FIGURE 2 is a schematic and somewhat idealized plan view of the essentials of the comminution chamber and rotor assembly contained therein as the same would be viewed with the housing cover portion thereof removed;

FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a side elevation, in enlarged scale, of a presently preferred configuration for a fan blade type spacer element;

FIGURE 5A is a schematic representation of an air injector type of material feed which may be utilized in conjunction with the subject mill;

FIGURE 5B is an enlarged oblique view of a preferred configuration for the saw teeth on the rotor assembly.

Referring to the drawings, there is provided a housing assembly, generally designated 1 and formed of a base member 4 and a substantially semi-cylindrically shaped upper or cover member 6 removably securable thereto. The base and cover members 4 and 6 are shaped to generally define an internally disposed comminution chamber 3, a material feed channel 5 communicating therewith and a dependent receiving chamber 7 for the comminuted material after the same passes through the semicylindrically shaped screen member 32 which also serves to cooperatively define the above mentioned comminution chamber 3. As best illustrated in FIGURE 1B, the cover member 4 is provided with a plurality of particularly located circular air inlet apertures 16, suitably three, in each of the side Wall portions 26, 28 thereof, as well as a material entry aperture 8 in alignment with the feed channel 5 to accommodate material entry into the comminution chamber 3 by a worm type feed mechanism generally designated 10. The air inlet apertures 16 are preferably screened with a coarse screen or mesh of suitable size as to prevent egress of uncomminuted material therethrough but yet not impede air flow therethrough into the comminution chamber.

The base housing member 4 is suitably shaped to terminally support the extending arms 12 of a pair of suspended rotor supporting journals or bearing assemblies 14. A rotor shaft 22 is rotationally supported in the journals 14 and is provided with an extension end 24 extending beyond one side of the housing for facilitating a drive connection thereto. As best shown in FIGURES 2 and 3, the internally disposed comminution chamber 3 is essentially of cylindrical configuration being defined by the apertured and essentially planar wall portions 26, 28, an upper curved wall 30 of essentially semi-cylindrical configuration and a lower curved wall formed by the perforate and removable plate or screen 32 of complemental semi-cylindrical configuration. As will be apparent to those skilled in this art, the removable lower screen 32 is provided with apertures of predetermined size to determine the maximum particle size of the comminuted material that is permitted to exit from the comminution chamber.

Disposed within the comminuation chamber 3 is a rotor assembly formed of a plurality of circular saw-like blades or serrated periphery disc-like members 34 fixedly mounted on said rotor shaft 22 and maintained in close parallel spaced relation by interposed spacer washers 36. As illustrated in FIGURES 1A, 2 and 3, the disc-like members 34 are peripherally saw toothed so as to present a succession of cutting edges in the direction of rotation and, for most applications are preferably collectively mounted in a slightly skewed or offset relation as indicated by the angle A (FIGURE 2) to a plane normal to the axis of rotation of the shaft 22 to minimize, if not prevent, undesired tracking of material introduced through the feed channel 5. As best illustrated in FIGURE B the saw teeth on the periphery of the blade members 34 are preferably shaped to provide a chisel-like, acute angle cutting edge 35 disposed substantially parallel to the axis of the rotor shaft 22. As illustrated, the trailing edge of each tooth declines so as to completely expose the cutting edge on the succeeding tooth. The provision of the above-described chisel-like cutting edge disposed substantially parallel to the rotor shaft axis results, when the number of available teeth per blade and number of blades are considered, in a greatly increased effective length of cutting edge all localized within and operatively displaceable through the locus of material deformation. Secured to the undersurface of the upper curved wall 30 and disposed remote from the material feed aperture 8 is a deflector type liner member 31 having a surface configuration disposed in facing relation with the rotor periphery and of suitable contour to deflect material in a more or less radial direction back into contact with the cutting edged periphery of the saw toothed rotor.

As will be apparent from the foregoing, the saw tooth configuration of the periphery of the disc or blade members provides a plurality of successive selectively positively cutting edges, which, upon engagement with the material, effect comminution primarily by a cutting impact with a rapidly moving chisel-shaped shearing edge, as distinguished from the so-called pure impact principle of grinding or comminution.

Referring again to FIGURES 2 and 3, each of the saw blade members 34 is provided with a plurality of apertures 38, suitably four in number, preferably arranged in equiangular relation and disposed substantially tangent to the periphery of the interposed spacer element 36 and in substantial radial alignment with the screened air inlet apertures 16 disposed in the opposite side wall portions of the cover member 6. Although discrete circular air inlet apertures 16 are preferred, a single elongate arcuate aperture in each side wall subtending an arc of about degrees would also be suitable. As illustrated, the blade members 34 are mounted on the rotor shaft 22 in such manner as to preferably dispose the blade apertures 38 in substantially axial longitudinal alignment. In the specifically illustrated embodiment wherein ambient air inlet apertures 16 to the comminution chamber are disposed on both side Walls of the cover member 6, a balanced bidirectional air flow toward the center of the rotor is obtainable by preferential utilization of an unapertured or imperforate central blade member 34a and by beveling or tapering the apertures in the blades on either side thereof so as to be divergent in the direction of the desired air flow, as best shown in FIGURE 2. The inclusion of the beveled or tapered apertures 38 in the saw blade members 34 and the alignment thereof in the manner described thus provides a plurality of channels for selectively directed gas flow, specifically a flow of ambient air, longitudinally of the rotor 22. In addition thereto, the interposition of the spacer members 36 intermediate adjacent blade members serves to separate the same and thereby define a plurality of radially disposed channels for selectively directed gas flow, each having a plurality of common junctions with the aforedescribed longitudinal channels.

It is to be understood that while the presently preferred embodiment is constructed as above set forth, a balanced bidirectional gas flow will also be obtained by utilization of an apertured but preferably unbeveled central blade 34a. Also, as now will be apparent to those skilled in this art, other arrangements as to degree or selective direction of bevel, and size and location of the saw blade apertures may be made as desired to obtain optimum results with a particular machine and/ or particular material to be comminuted, for example, un beveled apertures 38 in association with interposed spacer washers 36 of the fan blade type configuration, as illustrated in FIGURE 4, will also result in the desired and selectively axially directed flow of the gaseous carrier. In addition thereto, other expedients, such as an injector type material feed, as illustrated in FIGURE 5A may be employed.

In operation of the subject unit, unidirectional high speed rotation of the rotor assembly effects a positively induced and greatly increased primary bi-directional flow of ambient air or other gaseous carrier into the commiution chamber through the ambient air inlet apertures 16 on each side of the housing, longitudinally of the rotor shaft 22 through the tapered or beveled apertures 38 therein and, intermediate each pair of blades 34, a secondary flow radially outward into and through the locus of comminution, such radial flow being accelerated and reinforced by the action of the fan type spacer members 36 when the same are employed as heretofore described.

Although the mechanics of the above described rotor induced air flow pattern are not fully understood at the present time, it is believed that it serves, in addition to maintaining the material to be comminuted in suspended and separated condition in the vicinity of the chisel-shaped blade cutting edges, to uniformly convey heat away from the locus of deformation and to markedly and rapidly reduce the temperature of the comminuted product prior to the necessary intersurface contact thereof required for agglomeration.

The effect of maintaining the material to be comminuted in suspended and separated condition and uniformly conveying heat away from the locus of deformation has resulted, as shown in tests, with a saw tooth rotor embodying this invention, in the (1) production of granular grinds with a minimum of ultra-fines, (2) marked increased in the production rate per H.P./hr., (3) comminution, at satisfactory commercial rates, of many materials heretofore reduceable only at reduced rates and/or with the expedients referred to earlier in conventional equipment, (4) reduction in grind temperatures, (5) avoidance of the need, in many cases, of the expedients referred to earlier.

By way of example, in a recent comparative test on polystyrene having Dry Ice necessarily mixed herewith, a conventional machine incorporating a standard stirrup type rotor produced 33 lbs. per hour of comminuted product at 3 /2 H.P. A saw tooth rotor unit embodying the principles of the subject invention operating on the same material produced an equivalent comminuted product at a rate of 60 lbs. per hour at 1. H.P. Other operative tests on varying materials have shown as much as a 4 to 1 capacity ratio in favor of the subject invention over conventional and commercially available equipment.

In another comparative test on cellulose propionate (a fibrous material similar to cellulose acetate), a conventional machine with a bar hammer rotor produced 12.5 lbs. per H.P. hour of 92.6% through 40 mesh product with a .039 Rd.Pt. screen. The production obtained by the unit embodying the subject invention and with an equivalent speed and screen, was 20 lbs. per H.P. hour and of an average analysis of 94% through a 40 mesh and with a grind temperature about 25 F. lower than that produced in the conventional machine.

In still another comparative test, pure gum nitrol rubber (Hycar) could not be satisfactorily comminuted in a conventional bar hammer rotor machine due to a rapid rise in temperature, softening of the material in the grinding chamber and smoking of the material. The same material was processed satisfactorily in a unit embodying the subject invention with A and A Rd.Pt. screens at respective capacities of 18.5 and 27 lbs. per H.P. hour.

In other tests on a polyester resin having a melting point of 235 F. and a softening point of between 110 F. and 115 F. an unsuccessful attempt was made to produce a screened product of 100%, +40 mesh and maximum, --140 mesh using liquid CO as a coolant, on a bar type conventional machine. Using applicants device on the same material and without coolant there was obtained a screen product analysing 100%, 40 mesh and 140 mesh when grinding the resin with an anti-caking agent and 100%, 40 mesh and 11.1% 140 mesh when no anti-caking agent was added. The temperature of the ground material never exceeded 98 F.

6 with a F. feed material and R. atmospheric temperature.

In general, and apart from the specific advantages delineated above, tests to date indicate that units incorporating the subject invention produce satisfactory results in about 80% of those cases wherein it has been tested on materials which could not be satisfactorily processed by conventional equipment. Also, tests have shown that it is generally possible to operate the subject unit at appreciably higher mill temperatures than can be tolerated with conventional pulverizing machines. For example, it has been found possible with applicants device to process low density polyethylene at outlet temperatures as high as 200 F. without any fusing in the comminution chamber. Nitrol rubber has been suc cessfully run without fusing at outlet temperatures of 160 F. This feature is of extreme importance in increasing capacity and reducing the size of required equipment to do a particular job. It is also indicative of the fact that something more than a simple reduction of heat rise is responsible for the unexpected beneficial and new results that have been obtained from the subject construction to date.

In addition to the above mentioned comparative test results, the subject invention has been found to be particularly advantageous in the production of high density powdered sugar (47 /2 lbs. per cubic foot packed density) and which after comminution has been remarkably free from lumping, even though no starch was added before grinding. Tests have been run on lots of sugars from different refineries, and comminution has been performed under a wide range of relative humidities with no apparent difference in the non-lumping storage characteristics.

Applicant is unable to explain this highly advantageous result except to suggest that it may be due tothe combined features of maintaining the material to be comminuted in suspended condition and uniformly passing air through the suspended material while it is being comminuted, combined possibly with the additional fact that the material is being comminuted by a fast acting shearing action, on an acute angle cutting edge.

The following is a list of random test results on various materials which to date have been found to be particularly adapted to comminution by apparatus incorporating the subject invention:

Material Character Mill Lbs. per Grind temp.,F. HP-hr.

Cellulose propionate Fibrous and mod- 148 19. 0 49%, -40.

erately tough. Coconut, stripped Britt1e Egg Coilee, roasted beans d0 1 6 I Licorice extract Very brittle 1. 300 'i b PVC, chlorinated type #1 Tough 140 7. 5 Polyester, pigmented resin--. do 146 3.3 Ptgyethyleile, and d0 7. 5 91%, -16.

ar ion ac Polyethylene and pigment Fine, granular 84 200 Excellent color witht2%% pigdispersion. men Polyethylene, L.D. reactor Tough 200 8 51%, -40.

flake.

Polystyrene 90 {1.3% +12.

16.6 -40. Polystyrene, pigmented, 5. 5 {47%,3-40. 50:50 T10 80. Potatoes, dried sliced, raw 200 {1%7, +10.

20 40. Resin, misc., A.C.X Moderately touglL 120 22.0 +40.

, -140. Rice Hard 210 +10.

49 (1, 10+50. -50+200. Rt i bberfiqitrol (crude) Tough, resilient." 4 {Dig/b, +10

ype 36 R%bber,fiNitrol (crude) do 100 18 {4.0%, +20

ype '2. 51 5 Rubber, silicone flashiugs Tough 1.5 {4.5%, +20.

(cured). 82%, 20+50.

Material Character Mill Lbs. per Grind temp.,F. HP-hr.

Sugar Brittlc 104 190 {99.8%, 70.

88.3%, 200. Teflon and Fibre Glass, So1lt, fibrous 60 70:30 mix. umps. Vinyl scrap Tough 104 12 g fla r 0y -8- Wlir at Hard 4.10 13% Other materials which have also been found to be particularly suited for comminution by apparatus incorporating the subject invention include:

Elastomers Leather scraps Nylon pellets Polyurethane Scrap rubber Synthetic crude rubber Vinyl resins.

Having thus described my invention, I claim:

1. A comminuting apparatus comprising housing means shaped to define a substantially cylindrically shaped comminution chamber having a material entry aperture, comminuted material egress means and a generally axially disposed gaseous carrier entry aperture therein,

a rotor assembly disposed within said chamber including an axially disposed rotatable shaft having a plurality of peripherally serrated disc like blade members with acute angle cutting edges mounted in spaced relation thereon and said blade members having apertures therein disposed remote from the serrated peripheries thereof for providing, upon rotation of said rotor assembly,

a selectively directed primary flow of a gaseous carrier from said gaseous carrier entry aperture longitudinally of said shaft intermediate said shaft and the periphery of said blade members and diverted secondary flows of said gaseous carrier radially outward intermediate said disc like :blade members int-o and through a locus of deformation for said material to be comminuted as defined by the path of travel of the serrated peripheries of said blade members.

2. The comminuting apparatus as set forth in claim 1 wherein said acute angle cutting edges of said peripherally serrated disc like blade members are disposed substantially parallel to the axis of said rotor assembly shaft and are advanceable in the direction of rotation thereof.

3. The comminuting apparatus as set forth in claim 1 including spacer means disposed intermediate said disc like blade members to assist in the radially outward displacement of said secondary flows of gaseous carrier.

4. The comminuting apparatus as set forth in claim 1 wherein said disc like blade members are mounted in skewed relation upon said shaft.

5. A comminuting apparatus comprising housing means shaped to define a substantially cylindrically shaped comminution chamber having a generally axially disposed gaseous carrier entry aperture therein,

a rotor assembly disposed within said chamber including an axially disposed rotatable shaft having a plurality of peripherally serrated disc like blade members with acute angle cutting edges mounted in spaced relation thereon,

said blade members having apertures therein disposed intermediate said shaft and the peripheries thereof for producing, upon rotation of said rotor assembly,

a selectively directed primary flow of gaseous carrier through said gaseous carrier entry aperture and longitudinally of said shaft intermediate said shaft and the periphery of said blade members and diverted secondary fiows of said gaseous carrier radially outward intermediate said disc like blade members to cooperatively confine,

with said housing means, suspended material to be comminuted within a comminuting zone of generally hollow cylindrical configuration which envelopes the locus of displacement of the serrated peripheries of said disc like blade members.

6. The comminuting apparatus as set forth in claim 5 wherein said acute angle cutting edges of said peripherally serrated disc like blade members are disposed substantially parallel to the axis of said rotor assembly shaft and are advanceable in the direction of rotation thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,764,020 6/1930 Hopkins 241-242 X 2,165,946 7/1939 Smith 24ll8 2,226,741 12/1940 Randolph 241-51 X 2,293,728 8/ 1942 Freund 241-17 2,468,337 4/1949 Lykken et a1. 241-55 2,601,953 7/1952 Savage 241-18 2,726,045 12/ 1955 Hinerfeld 241l6 2,981,487 4/1961 Davis 241-242 X ROBERT C. RIORDON, Primary Examiner.

WILLIAM W. DYER, 111., I. SPENCER OVERHOLSER,

Examiners.

Claims (1)

1. A COMMUNICATING APPARATUS COMPRISING HOUSING MEANS SHAPED TO DEFINE A SUBSTANTIALLY CYLINDRICALLY SHAPED COMMINUTION CHAMBER HAVING A MATERIAL ENTRY APERTURE, COMMINUTED MATERIAL EGRESS MEANS AND A GENERALLY AXIALLY DISPOSED GASEOUS CARRIER ENTRY APERTURE THEREIN, A ROTOR ASSEMBLY DISPOSED WITHIN SAID CHAMBER INCLUDING AN AXIALLY DISPOSED ROTATABLE SHAFT HAVING A PLURALITY OF PERIPHERALLY SERRATED DISC LIKE BLADE MEMBERS WITH ACUTE ANGLE CUTTING EDGES MOUNTED IN SPACED RELATION THEREON AND SAID BLADE MEMBERS HAVING APERTURES THEREIN DISPOSED REMOTE FOR THE SERRATED PERIPHERIES THEREOF OF PROVIDING, UPON ROTATION OF SAID ROTOR ASSEMBLY, A SELECTIVELY DIRECTED PRIMARY FLOW OF A GASEOUS CARRIER FROM SAID GASEOUS CARRIER ENTRY APERTURE LONGITUDINALLY OF SAID SHAFT INTERMEDIATE SAID SHAFT AND THE PERIPHERY OF SAID BLADE MEMBERS AND DIVERTED SECONDARY FLOWS OF SAID GASEOUS CARRIER RADIALLY OUTWARD INTERMEDIATE SAID DISC LIKE BLADE MEMBERS INTO AND THROUGH A LOCUS OF DEFORMATION FOR SAID MATERIAL TO BE COMMINUTED AS DEFINED BY THE PATH OF TRAVEL OF THE SERRATED PERIPHERIES OF SAID BLADE MEMBERS.

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