US2306161A - Pelleting machine - Google Patents

Description

' Dec. 22, 1942. e. A; FRENKEL PELLETING MACHINE Filed Jan. 17, 1942 2 Sheets-Sheet l Dec.- 22; 1942. e. A. FRENKEL 2,306,161

PELLETING momma Filed Jan. 17, 1942 ZSheets-Sheet 2 Patented Dec. 22, 1942 2,306,161 PELLE'I'IN G MACHINE Gustav Adolf Frenkel, Oakland,

Calif., assignor to Shell Development Company, San Francisco, Calla, a corporation of Delaware Application January 17, 1942, Serial No. 427,155

sclaims. (01.45477) The present invention relates to an improved machine for forming materials into' pellets. More specifically, the present invention relates to an improved machine of the rotary moldcompression type suitable for rapidly forming large quantities of tablets or the like of optimum density from powdered materials. v

In the various chemical arts it is often necessary to produce large quantities. of relatively small pellets from dry, powdered material. For example, certain medicinal preparations are prepared as dry formulae and then pelleted prior to packaging. As another example, catalyst car-, rier bodies are often prepared by pelleting dry materials, such as pipe clay, bentonite, bauxite, majolica, etc., the formed pellets then being impregnated with a catalytic material. In the above cited examples and in many analogous instances, it is desirable to produce a pellet which is sufliciently strong structurally to resist crushing during handling and at the same time retains as great a degree of porosity as possible in order to dissolve rapidly in a liquid, absorb a maximum quantity of catalytic material, or f other similar purposes. It is an object of the present invention to pro-- vide a pelleting machine of the rotary compression mold type wherein large quantities of pelletsof uniform porosity and density may be rapidly formed. Further, it is an object of the invention to provide such a machine wherein sticking of formed pellets within the molds is completely avoided. Still further, it is an object of the present invention to provide a pelleting machine of the above type wherein removal of formed pellets from the pressure mold is accomplished with a minimum of abrasion and degradation of the pellets. Other objects, together with some of the advantages to be derived in utilizing the present invention, will become apparent from the following detailed description thereof, reference being had to the accompanying drawings, which constitute a part of this specification, and wherein:

Figure I is a side elevation of the machine; Figure II is a plan view with the feed hopper removed; Figure III is an enlarged sectional plan view of the compression molds through III-III of Figure IV; Figure IV is an enlarged elevation through IV-IV of Figure III, showing one mold in elevation and the other in crosssectional elevation.

Referring to the drawings, a variable speed motor 3 is mounted on a platform frame I. A pair of frame uprights 2, 6 and cross members 5, 1, 8, and 9 are also provided as shown. The compression molds are mounted on cross members 8 and 9 as will be described in detail below. Gear I9 is driven by motor 3 through flexible coupling 4 and in turn drives gear l8. A pulley wheel 44 is also driven by motor 3 and in turn drives pulley wheel 32 through drive belt 33.

A vertical stirrer 50, the blades of which have a slight pitch in order to induce a slight downward pressure on material in contact therewith, is provided within hopper 25, which is mounted on frame cross member I. of stirrer 50 is rotated by gear 30, mounted on frame cross member 5, enmeshing gear 3| which is driven by pulley 32. A vibrating screen 31 is disposed beneath the compression molds and supported on sensitive springs as at 38, 39, 52 which, are inturn supported by rods as at 4|, 42, 5| attached to frame cross members 8 and 9.

Referring particularly to Figures 111 and IV,

the rotary compression molds are basically of the conventional type, i. e. circular in form and provided wtih peripheral pockets, as at 60. In the present instance, however, each mold is formed of a pair of disk halves, as at I2, 34, one of each pair of disk halves being formed of two elements as at 16 and 34. The annular peripheral element I6 is adjustably attached to inner disk half 34 by means of bolts, as at 6|. Disk half 34 is mounted on shaft 20 which is in turn rotatably mounted in bearing housing 14, which is mounted on cross member 8. Disk half l2, which opposes disk half 34, is mounted on shaft 63 winch is in turn rotatably mounted in bearing housing II, mounted on cross member 9. Shafts 20 and G3 are disposed in slightly offset positions, 1. e. they are so arranged that contact between the periphery of disk half l2 and peripheral element It of disk half 34 is made at the point of contact between the two rotary molds. Thus there is always a minute gap between disk I2 and peripheral element I6, except at that point whereat contact is made with the second rotary mold, this gap between any given pair of adjacent peripheral pockets increasing to a maximum at a point around the circumference from the contact point and then gradually decreasing again as the mold is revolved and the contact point approached.

Disks l3 and 35, including an adjustable peripheral element, ll attached to disk 35, are mounted on a shaft rotatably mounted in bearing housing [0 and on shaft 2|, rotatabiy mounted in bearing housing l5, respectively. These disks are also set slightly offset in the manner described in detail with relation to disks 34 and I2.

Shafts 20 and II l9 respectively. Since the distance between each pair of disks forming a rotary mold ,is constantly changing during operation, a flexible drive coupling between each pair of disks. is necessary. A suitable arrangement embodies a to concentric ring of semi-sockets in the inner face The drive shaft 26 are driven by gears l8 and will be rather loose in their sockets, dueto the wedge shaped gap between the disk halves. This, however, has no deleterious effect since the disks are at all times kept in proper radial alignment by those balls which are in the close fitting position. Although eachiball is constantly changing from a close to a loose back again, a sufficient number are provided to prevent any serious misalignment of the disks. By means of the described arrangement; each driven disk half serves to drive its opposing disk half.

A pair of snugly fitting stripper plates 24, 23 are mounted on frame uprights 6 and 2 respectively and are inserted in the wedge shaped openings between the disk halves away from the contact point of the disk halves, as shown in,

Figure IV. These stripper plates serve to remove any pellets which may stick in the molds. They fitting position and also serve to remove small quantities of powdered material which may at times find entrance to the interface between each pair of disk halves.

A pair of prongs'fl, 29 formed as extensions of hopper 25 and of a material having spring-like characteristics, flt snugly against the rims of the molds and extend "at least to the contact point of the two molds. These prongs serve to prevent loss of material around the throat of hopper 25 and to guide material from the hopper into the pressure molds.

machine, although plastic material which is com-,

may also be utilized, is supplied The material falls and/or is urged paratively dry to hopper 25. by vertical stirrer hopper into the compression zone between the rotating molds, spillage being prevented by prongs 21 and 29.

The greatest pressure on the material being pelleted is applied at that point whereat the two rotating molds are in contact with each other and, simultaneously, each of the disk halves is in contact with its opposing disk half at the same point. Pressure is thus gradually applied to material leaving hopper 25 until a maximum pressure point is reached. After the maximum pressure point the rotating molds begin to separate from each other and at the same time each of the disk halves begins to separate from its opposing disk half. As a result the formed pellets fall freely from the molds and are directed by an apron 65 into the screen I! wherein the pellets and any finesthat may pass through the machine are separated in the usual 'manner.

If for any reason'a pellet does adhere to part of one of the peripheral mold pockets, it will be removed by one of the stripper plates 24, 23 as the disk halves revolve.

I claim as my invention:

1. In a pelleting machine of the class described the combination comprising a pair of rotary compression molds including peripheral pockets therein, said rotary molds being mounted to pro- 50 from the throat of the -means between each vide peripheral contact therebetween, each of said rotary molds beingformed as a pair of disk halves, each of said pairs of disk halves beins mounted to provide peripheral contact therebetween only at the peripheral contact point of said rotary molds and ball and socket connecting of said pairs of disk halves whereby radial alignment of said disk halves is maintained.

2. In a pelleting machine of the class described the combination comprising a pair of rotary compression molds including peripheral .pockets therein, said rotary compression molds being mounted to provide peripheral contact therebetween, each of'said rotary molds being formed of a pair of disk halves, each'of said pairs of disk halves being mounted to provide peripheral contact therebetween only at the peripheral contact point of saidrotary molds, one of each of said pairs of disk halves being provided with an annular peripheral element adjustably attached thereto and means arranged and adapted to maintain the radial alignment of each of said pairs of disk halves.

3. In a pelleting machine of the class described the combination comprising a frame member, a pair of rotary compression molds including peripheral pockets therein mounted on said frame member in peripheral contact with each other, said rotary molds being disposed in a common vertical plane and the axes of said rotary molds being disposed in a common horizontal plane, each of said rotary molds being formed of a pair of disk halves, each of said pairs of disk halves being mounted to provide peripheral contact therebetween only at the peripheral contact point of said rotary molds, means arranged and adapted to maintain the radial alignment .of each of said pairs of disk halves and a stripper. plate disposed between each of said pairs of disk halves at a point removed from the peripheral contact point of said rotary molds.

4. Apparatus according to claim 5 including a feed hopper mounted on said frame member and disposed above said rotary compression molds and an extension to said feed hopper enclosing the area between the feed hopper throat and the peripheral contact point between said rotary compression molds. 1

5. In a pelleting machin of the class described the combination comprising a frame member, a pair of rotary compression molds including peripheral pockets therein mounted on said frame member in peripheral contact with each other, said rotary molds being disposed in a common vertical plane and the axes of said rotary molds being disposed in a common horizontal plane, each of said rotary molds being formed of a pair of disk halves, one of each pair of disk halves being mounted in an offset position whereby peripheral contact between each pair of disk halves is provided only at the peripheral contact point of said rotary molds, an annular series of ball and socket connections between each of said pairs of disk halves whereby radial alignment of said disk halves is maintained and a.

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