US2623700A

US2623700A - Disintegrating device

Info

Publication number: US2623700A
Application number: US77518A
Authority: US
Inventors: Scherer Robert Pauli
Original assignee: Catalent Pharma Solutions Inc
Current assignee: Catalent Pharma Solutions Inc
Priority date: 1949-02-21
Filing date: 1949-02-21
Publication date: 1952-12-30
Anticipated expiration: 1969-12-30

Description

Dec. 30, 1952 R p, SCHERER 2,623,700

DISINTEGRATING DEVICE Filed Feb. 2l, 1949 JNVENTOR. 0 be rZjCL'/z ere/1 fm1 ya Patented Dec. 30, 1952 UNITED STATES DISINTEGRATING DEVICE Application February 21, 1949, Serial No. 77,518

1 Claim.

V This invention relates to method and apparatus for the disintegration of granular solid material. More particularly, the invention relates to means and methods in which moving granular solid material is shattered or disintegrated by being subjected to sudden reversals in direction of movement, as by repeated violent impacts against a hard surface or even against a gaseous cushion.

ln the past, impact mills such as hammer mills have been employed to reduce granular or pulverulent material to finer particle size. Mills of this general type operate basically by hurling the material being ground back and forth between a rapidly rotating set of strikers and a stationary set of strikers. The ability `of mills of this type to reduce solid material to smaller particle size is limited by the rate at which the rotating strikers c-an be revolved which is determined by factors such as strength of materials of construction, speeds tolerated by bearings, and the like.

I have now provided a disintegration device having twice the eiciency of hammer mills or like mills having one moving and one stationary set of strikers. My novel device reaches this high efliciency without increase in rotational speed, for my device includes two counter-rotating sets of strikers so that the relative velocity of these two sets of strikers with respect to each other is equal to the sum of the actual velocities of the two sets of strikers. Further, my novel disintegration device meets all other requirements for a practically satisfactory mill with respect to points such as methods of feeding material to be ground into the mill, method of discharging ground material from the mill, method for effecting repeated impacts on a single particle, method of adjustment or modification to determine the extent of disintegration, simplicity of construction, and the like.

My novel disintegration device comprises two facing discs rotatable in opposite directions on a common axis. The opposed cooperating faces of the two discs are each provided with one or more rings of axially projecting vanes so spaced radially that the innermost ring of one disc is closely surrounded by a ring of the other disc which again is closely surrounded by a ring of vanes on the first disc, and so on so that a suitable number of rings, say, three rings, are arranged on the Afaces. of the two discs in the indicated overlapping `and closely spaced relationship. The two opposed faces of the two discs are closely spaced .so that a vplane normal to the axis of rotation at PATENT OFFICE 2 the mid-point between the two disc faces will substantially bisect all the vanes of both discs. This plane will represent the median plane along which the particles being disintegrated will travel.

The material to be disintegrated may be fed into the central region between the two discs according to several methods. Thus, one or both of the shafts on which the two discs rotate may be hollow. Or, one disc may be apertured near its shaft at a plurality of locations (to define short spokes in the disc), and the outside of the disc may be'flanged around the apertured area to dene a region into which the material to be ground may ybe fed. In either construction, the material to be ground can be fed into a region from which the material thereafter passes between the vanes in a manner disclosed hereinbelow. Most suitably, the material to be ground is suspended in air or other gas flowing into the mill and thereby carried through the feed passage (the hollow shaft or disc apertures and the space immediately outside thereof) into the space between the two discs inside the innermost ring of vanes. From this space the particles move into the slots between the innermost ring of vanes under the influence of gravity and/ or centrifugal force. When the particles have moved into these slots, the particles are carried along by the vanes andthereby accelerated tothe rotative velocity of the innermost ring of vanes. Under the influence of centrifugal force, the particles will then migrate radially outwardly along the leading faces of the vanes until the particles reach the outer ends of the vanes when the particles are thrown olf tangentially into the narrow clearance space between the two innermost rings of vanes of the two discs. Since these two rings of vanes rotate in opposite directions, the result is a violent reversal in the direction of movement ofthe particle with consequent fragmentation of. the particle. This process is repeated at each interface or clearance space between counter-rotating rings of vanes and becomes progressively more violent because the lineal velocity of succeeding rings increases as the diameters of the rings increase. i

The particles are nally thrown clear of the vane system at the periphery of the outermost ring of vanes. lThe particles are then either swept 'out by way of a scroll and tangential discharge opening or are discharged directly into a plenum chamber from which they are later recovered or are discharged otherwise.

The clearance between the overlapping counter-rotating rings of vanes should preferably be kept at a minimum, to reduce the length of the tangent particle path from one ring to another whereby violence of reversal and resultant impact are increased. However, the clearance should. be at least three or four times the diameter of the particles traversing the clearance to prevent packing or jamming with material being ground.

The vanes are preferably shaped to present edges to the surfaces over which the vanes sweep. Surfaces against which centrifugal force urges material being ground are preferably inclined radially outwardly. Thus lodging or packing of material being ground is reduced or eliminated.

The above described device is characterized by an air pumping action when operated. Thus, an air-sweep is automatically provided for feeding the solid material into and through the device. To reduce the power consumption due to this pumping action, a vacuum may be applied to the device to reduce the amount of air present therein. Operation under partial vacuum not only reduces power consumption but also lessens the cushioning effect of the air on particle impact and therefore brings about finer disintegration.

It is, therefore, an important object of the present invention to provide means and methods for fine disintegration of granular solid material involving radial migration of solid granules from a central point along a path in which the material is repeatedly subjected to violent impacts against radially spaced annular series of vanes projecting into said path from closely spaced counter-rotating discs.

Other and further objects and features will become apparent from the following description and appended claim and from the accompanying drawings which show, diagrammatically and by way of example, a disintegration device according to the present invention together with modifications thereof. More particularly:

Figure 1 is a fragmentary longitudinal vertical cross-sectional view, with parts shown in elevation, of a disintegrating device according to the present invention;

Figure 2 is a fragmentary cross-'sectional View taken along the line 2 2 of Figure 1;

Figure 3 is an enlarged fragmentary View similar to Figure 1; and

Figure 4 is an enlarged fragmentary View taken along the line 4 4 of Figure 2.

The device shown in Figures l through 4 includes a housing comprising a left half it and a, right half ||2, each flanged, as at lita and ||2d and held together by bolts i4. The two housing halves define an inner chamber H5 accessible through a central aperture |l8 in the left housing half il@ and a central `aperture l2@ in the right housing half 2. .A tubular sleeve |22 is seated in the aperture H8 while another tubular sleeve |213 is seated in the aperture |29.

The two discs l@ and lfl` are centrally reces`ed to define therebetween a central chamber its. The ends of the two shafts |32 and |35 may be threaded and may project into the central chamber' M8. Nuts |5t and |52 maybe threaded, respectively, over the threaded ends of the shafts |32 and it. The opposed faces of the two nuts |555 and |52 may be spaced very closely or may even contact each other over a limited area, to prevent or limit displacement of the discs it@ and It toward each other.

The opposed faces of the two discs and i3d, outside the central recesses therein, may be recessed to define therebetween an annular space his communicating with the chamber llt through slots |53 formed in the disc lili) and defining spokes |58 in the latter extending from the hub |42. The space |54 is limited peripherally by convergent radially outwardly sloping walls E@ and |52 formed, respectively, in the discs i3@ and |32. Further, the outside of the disc |33 is form-ed with an annular flange |54 aligned with the Wall |653 so that the radially inner wall of the flange is flush with the wall |55. The inside of the housing H9 is annularly recessed, as at |565, to clear the end of the flange |66 and to dene an annular space |58 limited peripherally by the flange Hifi and inwardly by the hub |52. The space i 63 thus extends between the bottom of the recess ta and the outsides of the spokes ist. A tube |10 pierces the bottom of the recess ist and projects past the outer edge of the flange 5&5'. The tube llc serves to feed into the space i material to be disintegrated.

Outside the wall |6, the disc |33 is formed with three radially spaced annular grooves and with three radially spaced annular ribs lii each arranged radially outside one of the grooves |12. Vanes |16 project from each of the ribs lill and define slots |18 therebetween. The radially outside walls |12a of each groove |12 slope radially inwardly and aiially outwardly, as shown in Figures l and 3. The right disc |36 is formed with three radially spaced annular grooves i3d opposed tc the ribs |14 and with three radially spaced annular ribs |82 opposed to the grooves |12. vanes Hillv project from each of the ribs |82 and denne slots |86 therebetween. The radially outside walls |82a of each groove lili) slope radially inwardly and axially outwardly, as shown in Figures l and 3.

The disc |39 is rotated clockwise, while the disc |315 rotates counterclockwise. The vanes |15 project past the ribs |82 into the grooves lSl and the vanes HM project past the ribs |11! into the grooves |12. The leading edges of the vanes |15 conform to the generally V-shaped contour of the grooves |33 and the leading edges of the vanes |84 similarly conform to the generally V- shaped contour of the grooves |12. Thus, the leading edges of the end surface i'liicz of the vanes |16 extend parallel to and closely spaced from the sloping groove walls lila, while the leading edges of the end surfaces lita of the vanes mit extend parallel to and closely spaced from the sloping groove walls |12c. Further, said vane end surfaces |16 and Ilflc slope both away from their leading edges and from the opposed groove walls laila and |12a, so that said leading edges may be compared to knife edges sweeping the sloping wall surfaces ltllc and |1241. In other words, while the vanes |15 and |84 overlap each other, the terminal vane portions outside the overlap project into the grooves |80 and |12, respectively, and are characterized by leading edges conforming closely to the shapes of said grooves. Thus, the grooves |12 and |80 are continuously swept clean on rotation of the discs |30 and |34.

The leading surfaces |1619 and |641) of the vanes |16 and |84 are raked backwardly. In other words, these surfaces slope away from the leading edges thereof, the direction of slope being the opposite to the direction of rotation, and the radially outermost edges of the leading surfaces |1617 and |8419 being considered as the leading edges thereof. Further, the inside surfaces |16c and |84c slope away radially outward- 1y from their leading edges. The trailing surfaces |16d and |8401 extend at a diverging angle from the opposed, leading surfaces |16?) and |042) so that the slots |18 and |66 will taper radially outwardly. As a result, any-particles traversing the gaps between the rings of vanes |16 and |84 will be subject to direct impact with the leading surfaces of each vane with a minimum impacting against the inner vane surfaces and entry of the particles into the slots between the vanes will be facilitated.

Only the outsides |16e and |04e of the vanes |16 and |84 extend in concentric relationship in parallelism with the axes of the discs |30 and |34.

The above described slope of the walls |60 and |62 and of the groove walls |12a and |B0a aids in preventing packing material being comminuted against the walls in question, for the said slope permits centrifugal force to contribute its influence toward radially outward movement of the material passing from the tube into and through the space |60, through the slots |56, through the space |54 and between the vanes |16 and |84 and out through a tangential discharge conduit |00.

It should be understood that different numbers of vane series and grooves may be provided in each disc and that the number of vanes in each series may be varied. Further, the number of rings of vanes in the two discs need not be the same. Resonance can be effected when the two rotors have each the same number of rings of vanes.

between the next ring of vanes |16 which is rotating in reverse direction. Thus, the particles will be forced .to reverse their direction of movement very suddenly. Such a reversal is repeated as many times as there are gaps bounded by counter-rotating rings of vanes |84 and |16. The centrifugal force generated by the two rotating discs causes the particles to migrate continuously through the whole system of counter-rotating vanes, discharging the disintegrated particles` at the periphery of the two discs. The effectiveness of the device may be increased by partially or completely evacuating the interior of the device, as through the conduit |90. Such evacuation reduces power consumption and heat generation caused by churning of the enclosed air, and further serves to reduce or eliminate the cushioning effect of the air layers moving with the counter-rotating annular series of vanes as well as to prevent accumulation of material within the housing. Thus, the particles will impinge more sharply on the vanes with resultant improved disintegration.

The force exerted on the individual particles passing through this device may be computed. By way of example, I give hereinbelow such a computation. Let us assume, for instance, that the two discs |30 and |34 each have a diameter of 4 inches; that each disc rotates at 12,000 R. P. M.; that the vanes of each ring have a radial depth of 1A, inch; that eachdisc has three rings of vanes; and that the central chamber |48 has a diameter of 1 inch. Then five gaps will be defined between the vane series, and these gaps will have the following diameters: 3%, 3, 21/2, 2 and 11/2 inches. The radial clearance between the counter-rotating rings of vanes may be asw sumed to be 0.020 inch. It will further assume the most unfavorable operating conditions by considering the particles as being completely decelerated but not accelerated by air friction as the particles leave the outer end of one ring of vanes, so that the particles will have zero speed in the middle of the gaps between the rings. Then the particles are accelerated in the opposite direction from zero speed as the particles enter the next outer ring of vanes. On the previous assumptions, a computation of the resulting forces gives the values tabulated as follows:

Radius to interface in inches Lineal Speed of One Disc at Interface in Feet/ Second 78. 5 104. 7 132 157 183 Length of Tangent Traversiug 0.020l radial Clearance in Inches 0. 0. 201 0. 224 0. 2466 0.265 Tangent Length 1n Inches.- 0.087 0.1005 0.112 0.123 0.133 Vl Tangent Length, 1n Feet. 0. 00725 0.00 0.009 0.010 0.011 Stopping Time in Seconds." 0 000184 0.000161 0.00137 0.000130 0.00012 Acceleration in Feet/Second. 426, 000 652, O00 965, 000 l, 210, 000 1 525, 000 Acceleration in Terms of Gravity 3, 25 20, 300 30, O00 37, 600 47, 500

The following discussion will clarify the action of the devices above described. When material to be disintegrated is introduced into the central chamber |48, the individual particles will come under the iniiuence of the centrifugal forces generated by the two discs |30 and |34 and will migrate radially outwardly until the particles enter the slots |86 between the first ring of vanes |84. The particles are then forced to rotate with this ring of vanes. The centrifugal force will now move the particles radially outward through the slots |86, and thereafter the particles will be thrown off tangentially from These figures show that even when it is assumed that the particle is decelerated to zero velocity by the air at the exact middle of the gaps between the counter-rotating rings or series of vanes, there is nevertheless generated at the outermost interface between the counter-rotating rings of vanes, a condition of acceleration or deceleration comparable to that generated when a 0.22 caliber short rie bullet strikes a steel plate. As is well known, the muzzle velocity of a rie bullet 1A; inch long is approximately 900 feet per second. The stopping distance is therefore 1A inch, resulting in a spattering of the ball upon the ring of vanes |84 and enter the slots |18 75 striking the steel plate.

aceavoo If the device is operated in rvacuum so that the particles are not completely checked, and reversed by'air friction, the particles impinge on the next outer vanes with a force greater than that indicated hereinabove. Further, if air friction checks and reverses the particles more quickly than assumed, the particles are subjected to forces greater than those indicated. Actually, when the above disclosed apparatus is operated under vacuum, and when 1-lb. per minute of material capable of clearing the 0.020l gaps is passed through the device, the total power required for rotating both discs amounts to about 1/5 H. P.

Many details of construction and operation may be varied Within a wide range without departing from the principles of this invention and it is vtherefore not my purpose to limit the patent on this invention otherwise than necessitated by the scope of the appended claim.

I claim as my invention:

A device for disintegrating granular solid material comprising two spaced opposed discs each formed with radially spaced annular generally wedge-shaped grooves each having an inner wall parallel to the axes of said discs and an outer wall inclined with respect to said inner wall, said discs being further formed with radially spaced annular ribs alternating with said grooves, the ribs of one disc being opposed to the grooves of the other disc and said ribs having vanes projecting therefrom, the ends of said vanes being bounded by planar surfaces and extending withn in said grooves, said vane ends each being formed with an outside surface opposed to said inclined outer groove surfaces and having a leading edge inclined to conform with the inclination of said outside walls of said grooves, said outside vane surface sloping from its leading edge so as to diverge from said outside groove walls, said vane ends further each being formed with an inside surface opposed to said inner groove walls and 8 having a leading edge parallel With the axes of said discs, said inside vane surface sloping away from its leading edge so as to diverge from said inside groove walls, said outside and inside vane end surfaces of each vane intersecting to denne an edge having a leading point located in close proximity to the thereto opposed groove bottom, said edge sloping away from its leading point to diverge from said groove bottom.

ROBERT PAULI SCHEREB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 16,191 Poueyetal Oct. 27, 1925 160,884 Davids Mar. 16, 1875 250,125 Bennett Nov. 29, 1831 777,228 Upton Dec. 13, 1904 812,737 Halstead Feb. 13, 1906 967,042 Ogden et al Aug. 10, 1910 1,215,424 Spensely Feb. 13, 1917 1,221,952 Adams Apr. 10, 1917 1,235,030 Higginson July 31, 1917 1,515,798 Spensely Nov. 18, 1924 1,624,037 Butler Apr. 12, 1927 1,666,640 Cunniil Apr. 17, 1923 1,755,037 Tamen Apr. 15, 1930 1,947,953 Otto Feb. 29, 1934 2,084,227 Swanson June 15, 1937 2,226,429 Hall Dec. 24, 1940 2,306,857 Behnsen Dec. 29, 1942 2,321,599 Hofmann June 15, 1943 2,328,950 Brant Sept. 7, 191%3 FOREIGN PATENTS Number Country Date 16,627 Great Britain of 1890 17,357 Great Britain of 1891 8,066 Great Britain of 1904.