Patent Publication Number: US-3880566-A

Title: Apparatus for forming spheroidal particles

Description:
United States Patent 11 1 Komarek et al.  
 &#39; 14 1 Apr. 29, 1975 l l APPARATUS FOR FORMING SPHEROIDAL PARTICLES ]75] Inventors: Ronald J. Komarek. Rochester;  
 Gordon L. Hume. Alhion both of N.Y.  
 [73] Assignee: Eastman Kodak Company,  
 Rochester. N.Y.  
 ]22] Filed: June 7., I974 ]2l] Appl. No.: 477.388  
 I52] [1.5. CI. 425/362. 425/222; 425/331; 425/324 ]5l Int. Cl B30h 3/00; B3(lh 9/28; 82% 3/00 [58] Field of Search 425/l94. 222 33L 332. 425/335, 336. 362, 360, 324  
 I56] References Cited UNITED STATES PATENTS 3.58L67ll l/l97l Landers .i 425/33l X 3.7l3 l87 l/l973 Quartarone et al 425/333 X 3.792.655 2/1974 Caddell ct al 425/33] X 3.801822 4/l974 Harhison i a i w i 425/222 3.807.926 4/1974 Morse U 425/33] 3.84l 6l7 Ill/I974 Moldenhauer et al i. 425/33] Primary E.\&#39;umin0rJ. Howard Flint, Jr. Almrncy. Agent. or Firm.lohn F. Stevens; Daniel B. Reece, Ill  
 ]57] ABSTRACT An apparatus and method are described for forming generally spheroidal particles from plastic material. The apparatus includes a molding ring which passes between the nip of a pair of cooperating rolls. Plastic material is pressed into holes in the forming ring at the nip to form cylindrical particles having a height approximately equal to the diameter. and ejected into a rounding chamber for rounding the particles into generally spheroidal particles.  
 12 Claims, 7 Drawing Figures PmENIEmPnzems SHEET 10? 2 APPARATUS FOR FORMING SPHEROIDAL PARTICLES This invention relates in general to the production of generally spheroidal particles of solid material, and more particularly, this invention relates to the molding of particles of predetermined shapes and subsequently tumbling the particles to thereby shape the particles in a generally spheroidal manner.  
  This invention is particularly applicable to the production of solid particles from plastic material. While such material will be referred to herein as plastic material, it is understood that this term is used in a broad sense and includes such materials as dough, paste, etc.  
  Various forms of particle forming devices are known in the art. Conventionally, such devices are a form or variation of the device illustrated in U.S. Pat No. 2,208,905 where particles are molded from a plastic mass using cooperating devices such as molding rolls, or a molding roll and a belt. Other forms of particle forming devices include extruders. Furthermore, it is known in the art that the particles so formed may be rounded or smoothed by various types of tumbling apparatus.  
  The particle forming apparatus of the present invention provides a convenient way of making generally spheroidal particles by apparatus designed to first form particles from a plastic mass in a generally cylindrical shape in which the cylinder height is approximately the same as the diameter, and second, round the edges of the so-formed particles by tumbling.  
  It is therefore an object of this invention to provide apparatus for forming generally spheroidal particles from a plastic mass.  
  It is another object of this invention to provide apparatus for forming generally spheroidal particles in an efficient and economical manner.  
  It is a further object of this invention to provide apparatus for forming particles of a shape which requires a minimum of coating material, where the particles are to be coated, because of their high volume to surface area ratio.  
  Other objects and advantages of this invention will appear herein.  
 In the drawings:  
  FIG. 1 is a schematic side elevation view of one form of the apparatus according to my invention;  
  FIG. 2 is an enlarged partial view of the particle forming element of my invention;  
  FIG. 3a is an enlarged view of a particle which has just been ejected from the particle forming apparatus;  
  FIG. 3b is an enlarged view of a particle which has been nearly made spheroidal;  
  FIG. 3c is an enlarged view of a generally spherodial particle made by the apparatus according to this invention; and  
  FIG. 4 is an enlarged partial section view of the particle ejecting device.  
  FIG. 5 is a plan view of the apparatus shown in FlG.  
  Referring to the drawings, FIGS. 1 and 2 illustrate a preferred embodiment of the invention wherein a mass of plastic material to be made into particles is supported by means of movable molding ring 12, retaining plate 14, and conventional end plates (not shown) which retain the sides of the plastic mass to the extent necessary. Molding ring 12 is positioned for movement between the nip of axially parallel rolls l6 and 18, and is supported by an additional guide member 20. Additional guide members may be used and placed at suitable locations on the forming ring. One, or both, of the rolls l6 and 18 are driven by conventional power means (not shown) and in turn operate to frictionally rotate molding ring 12 about an imaginary axis, at for example point 20. Molding ring 12 is thus supported by rolls l6 and 18, and guide member 20.  
  Rolls 16 and 18 are provided with shafts 22 and 24 which are suitably supported in bearings. Roll 16, roll 18, or both, may therefore be gear driven by suitable meansv Roll 16 is placed near the bottom of plastic mass 10 to provide bottom support therefor. Rolls l6 and I8 rotate in opposite directions as indicated by the arrows.  
  Molding ring 12 is preferably of a diameter at least twice that of rolls l6 and 18, and most preferably about two or four times the diameter of rolls l6 and 18. lt may be fabricated from a relatively rigid or selfsupporting material such as metal. lt is provided with a multiplicity of cylindrical holes 26. For a desired size of particle to be formed, the thickness of the ring is chosen to be approximately the same as the diameter of holes 26.  
  An air jet is provided at a point along the periphery of molding ring 12 to discharge formed particles from holes 26. The arrangement shown in the drawing is particularly suitable because an air jet 30 is provided on the inside periphery of the molding ring and discharges in a radially outward direction. The air jet 30 is conveniently positioned adjacent the inner surface of molding ring 12. Suitable air pressure is provided from an air compressing source (not shown) and operates in a continuous manner to discharge formed particles into rounding chamber 32.  
  Rounding chamber 32 is circular in structure, and is provided with high, rounded side walls 34 and 36 which serve to retain the particles in the rounding chamber during tumbling. The particles are given a circular movement in rounding chamber 32 by means of spaced air nozzles 38 (one illustrated) which are directed tangentially with respect to rounding chamber 32. Additional air nozzles are preferably placed in the rounding chamber 32 in a similar manner to further aid the particles in their swirling motion. Rounding chamber 32 is provided with a discharge point 40 located in the sidewall 36 for allowing rounded particles to exit therefrom.  
  Other types of rounding chambers are known in the art and may be used in place of the particular one illustrated. A chamber in the form of a spiral having several turns, preferably about 4 or 5 turns. wherein particles enter one end and travel around the spirals to be tumbled, and exit at the other end, is also particularly desirable.  
  FIGS. 40, 4b, and 4c illustrate the formed particles 50a, 50b and 50c in progressive stages of development. The particle 50a is generally cylindrical, having a height 52 about equal to its diameter 54. This is the shape of the particle 50 as it is formed and as it is ejected from the molding ring. FIG. 4b illustrates particle 50b in an intermediate stage of development, such as after travelling around the rounding chamber several times. Particle 50c is in a finished shape afte&#39; several more revolutions around the chamber. As illustrated, this particle is generally spheroidal.  
  In operation, plastic mass is positioned between molding ring 12 and retaining plate 14, resting partially on roll 16. Plastic mass 10 may be maintained by a continuous feed, if desired. One, or both, of the rolls l6 and 18 are driven for rotation in the direction indicated. Molding ring 12, being in frictional engagement with rolls 16 and 18 is thereby moved in the direction indicated by the arrow. Some of the plastic mass 10 trapped in the nip between roll 16 and molding ring 12 is packed into holes 26 thereof to form particles. The so-formed particles travel in the molding ring 12 until they reach the position of air jet 30. The particles are ejected here by action of the air pressure from air jet 30 into rounding chamber 32. Air nozzles provide the particles with a uniform rotary and tumbling movement around the periphery thereof. As the particles become rounded and lighter, they migrate up the sides of rounding chamber 32 and eventually reach exit port 40 where they are collected for packaging or subsequent operations.  
  In a typical use of the invention described herein, generally spheroidal particles of methionine approxi mately two mm. in diameter are made in the following manner. Methionine is mixed with microcrystalline cellulose and safflower oil in an l8:l:l ratio. Water is added to this mixture until the material reaches a cookie dough&#34; consistency, ie, forms easily but does not adhere to a dry surface. The dough is converted into generally spheroidal particles by processing through the forming ring and rounding vessel. The velocity of the air used in the rounding vessel isjust sufficient to keep the particles moving and tumbling. After the particles are removed from the rounding vessel they are further dried at ambient temperatures.  
  In other examples, this basic procedure may be used to make generally spheroidal particles of lysine and sodium sulphate.  
  Material which is to be prepared into spheroidal par ticles must be capable of being made into a plastic mass which will have cookie dough&#34; texture, i.e., can be forced into the forming ring yet will not adhere to the ring firmly enough to cause a large amount of distortion when ejected from the ring with a jet of air. Particles smaller than one mm. are more difficult to round be&#39; cause it is more difficult to adjust the air flow for proper movement and tumbling. Spheres are large as ten mm. and larger may also be made.  
  Forming rings can be made with any choice of holes about the same length (thickness of the ring) as the diameter. Forming ring width and diameter may vary according to the production capacity desired. The rounding vessel can be modified for continuous production by insuring uniform air flow and by placing an exit port on the upper portion of the outer wall. The uniform air flow will allow stratification of the particles according to the density of the particles. The particles will partially dry in the air flow reducing their density as they are rounded.  
  By generally spheroidal,&#34; it is meant to include particles which are spherical, as well as particles which may not, in the strict sense of the word, be rounded suf flciently to be called spheroidal. The majority of particles, however, will be spheroidal.  
  Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention.  
 We claim:  
  1. Apparatus for preparing particles of solid material comprising a7 a movable molding ring having a multiplicity of generally cylindrical openings extending through said ring, the diameters of said openings being approximately equal to the depths thereof,  
 bv a pair of cooperating rolls positioned on opposite sides of said molding ring and adapted to rotate in unison, the surfaces thereof being spaced apart an amount sufficient for said molding ring to pass within the nip of said rolls,  
 0. means for holding a mass of plastic material in the nip between said ring and one of said rolls whereby said plastic material is compressed into the openings of said ring during movement through said nip to form generally cylindrical particles, and  
 (1. means for ejecting said cylindrical particles from said openings.  
 2. Apparatus according to claim 1 wherein the mold ing ring is substantially self-supporting.  
  3. Apparatus according to claim 1 wherein said mold ing ring is of a substantially greater diameter than said cooperating rolls.  
  4. Apparatus according to claim 1 wherein both of said cooperating rolls are in frictional engagement with said molding ring.  
  5. Apparatus according to claim 1 which includes a receiving chamber for said cylindrical particles having means to cause tumbling of said particles until they become generally spheroidal.  
  6. Apparatus according to claim 1 wherein said means for ejecting said particles is an air jet.  
  7. Apparatus for preparing generally spheroidal particles of solid material comprising a. a movable molding ring having a multiplicity of generally cylindrical openings extending through said ring, the diameters of said openings being approximately equal to the depths thereof,  
 b. a pair of cooperating rolls positioned on opposite sides of said molding ring and adapted to rotate in unison, the surface thereof being spaced apart an amount sufficient for said molding ring to pass within the nip of said rolls,  
 c. means for holding a mass of plastic material in the nip between said ring and one of said rolls whereby said plastic material is compressed into the openings of said ring during movement through said nip to form generally cylindrical particles,  
 d. means for ejecting said cylindrical particles from said openings, and  
 e. a receiving chamber for said cylindrical particles having means to cause tumbling of said particles until they become generally spheroidal.  
  8. Apparatus for rounding particles of solid material comprising a circular chamber having a sidewall which curves upwardly and inwardly defining a generally smooth path for particles orbiting within said chamber, means for imparting a circular movement to said particles within said chamber, and exit means in said sidewall spaced from the bottom thereof for allowing said particles to exit from said chamber.  
  9. Apparatus according to claim 7 wherein said sidewall is substantially semicircular.  
 10. Apparatus according to claim 7 wherein said chamber has a raised center portion.  
 11. Apparatus according to claim 7 wherein said particles are given movement by means of an air stream.  
 12. Apparatus for preparing generally spheroidal particles of solid material comprising a. a movable molding ring having a multiplicity of generally cylindrical openings extending through said ring, the diameters of said openings being approximately equal to the depths thereof,  
 b. a pair of cooperating rolls positioned on opposite sides of said molding ring and adapted to rotate in unison, the surfaces thereof being spaced apart an amount sufficient for said molding ring to pass within the nip of said rolls,  
 c, means for holding a mass of plastic material in the nip between said ring and one of said rolls whereby said plastic material is compressed into the openings of said ring during movement through said nip to form generally cylindrical particles,  
 d. means for ejecting said cylindrical particles from said openings, and  
 e. a receiving chamber for said cylindrical particles having means to cause tumbling of said particles comprising a circular chamber having a sidewall which curves upwardly and inwardly defining a generally smooth path for particles orbiting within said chamber, means for imparting a circular movement to said particles within said chamber, and exit means in said sidewall spaced from the bottom thereof for allowing said particles to exit from said chamber.