US3371136A - Detergent tablet forming machine - Google Patents

Description

Feb. 27, 1968 F. H. JOHANNSEN 3,371,136

DETERGENT TABLET FORMING MACHINE Filed July 28, 1965 4 Sheets-Sheet l INVENTOR. #2070 H. JO/lA/V/VSEA/ fan 4 61?, [#0555 5 6144456544 Feb. 27, 1968 JOHANNSEN 3,371,136

DETERGENT TABLET FORMING MACHINE Filed July 28, 1965 4 Sheets-Sheet 2 TW/ST INVENTOR. FLO/0 1 JOHA/VA/SEA/ Fall/451?, 441/0555 ,4 6411451664 4 1968 F. H. JOHANNSEN 3,371,136

DETERGENT TABLET FORMING MACHINE Filed July 28, 1965 4 Sheets-Sheet 5 E6: HNXRMJ/ 4' UPPER 0/5 PUNCH I L. r 2

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Feb. 27, 1968 F. H. JOHANNSEN 3,371,136

DETERGENT TABLET FORMING MACHINE Filed July 28, 1965 4 Sheets-Sheet 4 Ma? in BY Fan/4 2, 1/1/0555 1 a 63444519624 United States Patent 3,371,136 DETERGENT TABLET FORMING MACHINE Floyd H. Johannsen, Upland, Calif., assiguor to United States Borax & Chemical Corporation, Los Angeles, Calif, a corporation of Nevada Filed July 28, 1965, Ser. No. 475,488 Claims. (Cl. 264-109) ABSTRACT OF THE DISCLOSURE To prevent a detergent tablet from sticking to opposing tablet forming punch surfaces, the punches are provided with gear operated cam followers which twist the punches as the detergent is being compressed and untwist the punches just as they are being withdrawn. A pair of cams adjustably mounted on the machine displace the cam followers at the desired preselected points.

This invention relates to apparatus for manufacturing tablets and, more particularly, to an improvement in the means for preventing detergent tablets from sticking to the die surfaces during the course of their formation.

Coated and uncoated tablets of many types have been marketed over the years, particularly in the medicinal field, and the apparatus used to produce detergent tablets does not depart in major respects from the prior art apparatus used to produce these conventional tablets. However, certain unique problems do arise when detergent tablets are formed. It is to these problems that this invention is directed.

Many coated and uncoated tablets are formed in rotary presses which comprise a horizontally disposed rotating die head having a plurality of vertical die cavities extending therethrough at spaced-apart circumferential points. Aligned with and cooperating with each die cavity is a pair of die punches disposed above and below the die head. These are generally mounted in guide blocks for rotation in fixed relation to the die head and cooperate with fixed upper and lower cam tracks to perform the sequence of operations required to produce a finished tablet.

Where coated tablets are to be formed, as the die head and guide blocks are rotated through each revolution, a die cavity is filled with a layer of granular coating material, a core tablet is delivered to the center of the die cavity, the die cavity is again filled with granular material overlying the core tablet, the upper and lower punches are closed to form a coated tablet and the tablet is ejected. Rotary presses of this general type are well understood. For example, US. Patent 2,700,038, which was issued to W. F. Wyatt, Jr. and John R. Brownell on Mar. 31, 1959. describes a tablet coating machine of this sort, and Patent 3,000,331, which issued to R. G. Frank on September 19, 1961, relates to a coated tablet press.

More recently, dual rotary presses have been joined with a. rotary transfer mechanism to provide unitary apparatus which can form the core tablet and the coating or outer layer. In the following discussion, the tablet will refer to the inner or core tablet and the coating to the outer coating or layer. One such dual rotary tablet press and transfer mechanism has been developed by Kux Machine Company, which is described in an article printed in the October, 1963 issue of Precision Metal Magazine entitled Clad Parts by Powder Metallurgy. The Kux rotary tablet press, and similar ones, utilize a pair of rotary tablet presses and a transfer mechanism therebetween, all of which are tied together by a common drive.

The first of the two tablet presses forms the core tablet of the two-part product and the second press provides a coating thereabout. While there are a number of sophis 3,371,136 Patented Feb. 27, 1968 ice ticated problems which must be solved in synchronizing the moving parts of such tablet presses, and particularly in depositing the core tablet in the center of the die cavity of the coating press, the present invention constitutes an improvement over single or dual rotary presses of the general type described in the aforementioned article and patents.

To form detergent tablets at commercially feasible production rates creates a number of problems which are either not present when conventional coated pills are formed or which, at least, can be overcome without too much difiiculty. For one thing, in forming detergent tablets it is necessary to use relatively low pressures and to intentionally build into the detergent tablets a desired rate of disintegration so that the tablets will dissolve sufficiently rapidly when placed in their operating environment. Not only is it necessary to build in void spaces that are predominantly inter-particulate in order to obtain predictable rates of disintegration, but it is necessary to find some means of breaking the detergent tablets away from the die punches after they are fully compressed at these low pressures inasmuch as heavy duty detergents have a strong tendency to adhere to the die surfaces. Failure to clear the die surfaces can not only create imperfect products, but cause breakdowns in the rotary presses due to the excessive wear of the rapidly moving parts. In the past, CO generators, starch and the like have been employed as disintegration accelerators so that higher pressures can be used but they have not solved the problem.

Many of the problems involved, their solutions and specific compositions of detergent tablets found to be satisfactory are discussed in Patent 3,081,267 which issued on March 12, 1963 to Richard P. Laskey for Detergent Tablet and Process for Making Same. Laskey and some other prior art references suggest that it is helpful to twist or rotate the die punches after the detergent tablet has been formed to clean the faces of the punch and prevent the build-up of material which would degrade the product or interfere with the operation of the press or both. It has been found helpful even when fatty foods, waxes and heavy chemicals are involved.

While the general concept of twisting the die punches in opposite directions is known, one of the difficulties with many prior art efforts in this direction is that the devices have lacked the versatility for selecting the desired quantum of twisting and for being able to select the point in the compression stage when the twisting is started and the time at which the punches are returned to their unrotated state. Because different detergent compositions cause different degrees and different kinds of smearing and sticking, each requires a different solution.

The present invention provides means for selectively twisting the upper and lower die punches in different directions whereby the angle of twist and the point of beginning and of termination of the twist may be easily selected and controlled. It has been found that careful control of these factors provide a better and more useful detergent tablet inasmuch as a small degree of twist at the proper time is far more beneficial and less harmful than the substantial twisting that many prior art machines employ.

Therefore, an object of this invention is to selectively twist the upper and lower die punches of a rotary tablet press at pre-selected points in the compression cycle to break the detergent tablet cleanly away from the surfaces of the die punches and cavity so that the working surfaces are not subject to excessive wear.

Other objects of the invention are to select the desired amount and speed of the circumferential twisting and to select the release point for the twisting mechanism.

A feature is means for rotating each of the die punches to attain these objects directly connected to the die punches so that they need not be synchronized with other moving parts. Specifically, a movable cam follower assembly having a rack formed thereon is provided to mesh with the teeth cut on a part of the die punch so that a positive interconnection between the parts is provided when the punch is twisted.

Another feature of the invention pertains to the means for adjusting the cam means mounted on the frame of the press so that the twist begins and terminates at preselected points in the rotating position of the die head, taking into account the particular detergent being used in the rotary press and the forming pressures.

Yet another feature of the invention is the means for returning the upper and lower punches to their normal equilibrium or non-axially rotated positions just as the die punches break away from the detergent tablet and die cavity so that any flaking or filming on the surface of the detergent tablet is, in most cases, repaired by the reverse twisting of the die punches as the die punches separate from their die cavity.

Still another feature of the invention pertains to the means for preventing the rotation of the upper die punches as each moves interior of the die cavity under the influence of its pressure roll. By this preventive, the amount and timing of the twisting of the punches can be accurately controlled.

The product produced by the combination of these various features is a detergent tablet which will stand up well under routine handling and yet has the properties required to distintegrate in a reasonable short period of time upon being placed in water or another dissolving liquid.

These and other objects, advantages and features of the present invention will be more fully understood when the following detailed description is read with reference to the drawings, in which:

FIG. 1 is a perspective drawing of a dual rotary press with an integrated transfer mechanism embodying the present invention;

FIG. 2 is a plan view of the dual rotary tablet press of FIG. 1 with certain of the parts omitted to more clearly show the die heads and station positions;

FIG. 3 is an enlarged perspective of a detergent tablet formed with the apparatus of the present invention;

FIG. 4 is an enlarged rectilinear expansion of the rotary die head, punches, guide blocks and stationary cams of a rotary press constructed in accordance with the present invention to apply a coating to core tablets;

FIG. 5 is a section view taken along lines 5-5 of FIG. 4 to illustrate the novel twisting mechanism of the present invention which is associated with each upper die punch;

FIG. 6 is a section view taken along lines 6-6 of FIG. 4 to illustrate the novel twisting mechanism of the present invention which is associated with each lower die punch;

FIG. 7 is an enlarged perspective of the pressure rolls, upper and lower die punches and twisting mechanisms as they cooperate when the punches are at the compression station;

FIG. 8 is an enlarged plan section of a portion of the rotary die head and frame of the coating rotary press of FIGS. 1 and 2 taken through the head of the upper die punch (as at line 88 of FIG. 7) with certain parts cut away to more clearly illustrate the construction and cooperation of the cam follower assemblies and earns which provide the selective twisting of the upper and lower die punches in timed relation to the compression stage of operation;

FIG. 9 is a partial end section view taken along line 99 of FIG. 8 to illustrate the adjustable means for each cam which permit them to selectively operate their associated cam follower assemblies; and

FIG. 10 is an enlarged perspective of the upper and lower die punches at the compression station with part of the detergent tablet and upper die punch cut away to show a formed tablet and the cooperative relation of the surfaces of the die.

Referring to FIGS. 1 and 2, there is illustrated rotary tablet press apparatus including a pedestal or frame 11 having a tablet bed 12, a core tablet rotary press 14, a coating rotary press 16 and a tablet transfer mechanism 18 therebetween. The rotary presses 14 and 16 and rotary transfer mechanism 18 are rotatably mounted on parallel shafts projecting from the bed 12 and synchronized so that the core tablets formed by the rotary core press 14 are transferred by the fingers 19 of the rotary transfer mechanism 18 to the center portion of each die cavity 35 of the rotary coating press 16 as it rotates past the transfer mechanism 18.

Looking more particularly to FIG. 2, it can be seen that the core tablet rotary press 14 has a circular die head 21 rotatably mounted on a shaft 22. A plurality of die cavities 24 (fifteen in the die head of the exemplary embodiment) are circumferentially spaced around the die head 21 and with other equipment (similar to parts of the coating press 16 but not shown in detail) produce a core tablet each time the die head 21 is fully rotated be ginning at a location adjacent fill hopper 26 and terminating at the junction of the transfer mechanism 18 and the die head 21. The formation of the core tablet is not described in detail since it essentially duplicates the operation of rotary press 16.

The transfer mechanism 18 is rotatably mounted on shaft 28 and has a plurality of fingers 19 which are coordinated with the rotation of die head 21 to engage each core tablet as it is finished and carry it off of the upper surface of the die bed 21 around to the die cavities 35 associated with the coating press 16.

The coating rotary press 16 is similar to the core tablet press 14 and includes a die head 34 having fifteen die cavities 35 circumferentially formed through it. The die head 34 is rotatably mounted on the pedestal 11 by shaft 29. It is rotated in timed sequence with the transfer mechanism 18 so as to receive a core tablet 9 in the center area of each of its die cavities 35 as the fingers 19 move over the upper surface of the die head 34. The instant positions of the fifteen die cavities 35 of the coating die press 16 have been numbered S1 through S- as shown, with the compression station being located at 8-13, for ease of explanation. These station locations of FIGS. 1 and 2 are correlated with the rectilinear layout illustrated in FIG. 4.

Forming a part of the rotary press 16 and carried in rotationally fixed relation to the die head 34 are guide blocks 34a and 34b which support upper die punches 36 and lower die punches 37, respectively, for vertical movement with respect to their associated die cavities of die head 34. These guide blocks may actually be a part of the die head proper. Each die cavity 35 has an upper and lower die punch 36 and 37 cooperating therewith and is controlled by a series of stationary cams (FIG. 4) as the die head and guide blocks rotate, as hereinafter explained.

Also associated with the rotary press 16 illustrated in FIGS. 1 and 2 are fill hoppers 41 and 42 which are arranged with respect to positions S-1 through S15 to provide the granular material forming the coating supplied at the proper point in the process.

To coat tablets delivered by the transfer mechanism 18, the coating die press 16 rotates so that each die cavity 35 passes in sequence by the fill hopper 41 where it is charged with coating material in pulverant form to provide a bed for the core tablet which is thereafter delivered to the die cavity by the transfer mechanism 18. After the core tablet 9 is deposited in the die cavity 35, a second filling operation (from hopper 42) provides an overlay of pulverant material needed to form the finished coating of the tablet.

Following these operations, the die cavity 35 and its cooperating upper and lower die punches 36, 37 reach the compression station S13 where a pair of compression rolls 44 and 45 force the upper and lower die punches 36 and 37 together to fully form the coating on the core tablet. The pressure rolls 44 and 45 are rotatably mounted on the frame 11 of the press and act to cam the upper and lower die punches 36, 37 into close juxtaposition interior of their associated die cavity 35.

There is also provided a discharge chute 48 adjacent the position S-15 where means (not shown) deflect the finished coated tablets 10 onto the discharge chute for movement out of the press for storing or packaging.

The two rotary presses 14 and 16 and the transfer mechanism 18 are synchronously rotated through a common drive 51 which is, in turn, rotated by motor 42 through the belt drive identified as 53.

Looking to FIG. 4, the sequence of operations of the rotary press 16 can be most easily understood. In FIG. 4 there is illustrated the rotating die head 34, die punches 36 and 37, and upper and lower guide blocks 34a and 341) which support the upper die punches 36 and the lower die punches 37 for vertical movement in cooperation with their respective die cavities 35.

A series of stationary earns 61, 62 and 63 cooperate with the lower ends of the lower die punches 37 to move them in timed sequence with the filling and other operations of the rotary press. Similarly, stationary cam 66 cooperates with the upper parts of upper die punches 36 to control their movement with respect to their die cavities 35.

Starting at the beginning of a cycle marked (360), which is identified by line 55, a lower die punch 37 is moved downwardly through stations S1 and S-2 as pulverant material from fill hopper 41 is deposited in the die cavity 35 on top of the face of lower die punch 37. As the lower die punch 37 moves from station 34 to S3, the punch is moved upwardly and means (not shown) scrape off the excess pulverant material so that a measured charge of the pulverant material, as illustrated at station position S4, is provided. Thereafter, as the die cavity and die punches We are following in this sequence reach station -5, the lower die punch 37 has moved downwardly fully capturing the first charge of pulverant material in preparation for receiving a core tablet 9, which is shown resting on the upper surface of the rotating die head 34 adjacent station S6. As the die cavity and punches reach station S-6, the transfer mechanism 18 deposits the core tablet 9 on top of the first charge of pulverant material and the lower die punch 37 is moved downwardly so that the second charge of pulverant material from fill hopper 42 may be deposited on top of the core tablet 9 through the positions illustrated as stations S-7 and S- 8.

Following this, as the lower die punch 37 moves from K station S-8 to station 5-9, the die punch 37 moves upwardly to push the excess pulverant material out of the die cavity 35 and means (again not shown) scrapes off the excess to provide a measured amount above and below the core tablet 9, as depicted at station S-ll.

During the first eleven stations of rotation of the die head 34 and its associated die punches 36 and 37, the upper die punch 36 has been held in a retracted position by the stationary cam 66 on which the shoulders 67 of the upper die punch 36 rides.

At the beginning of station 8-11, the stationary cam 66 permits the upper die punch 36 to move downwardly under the force of gravity preparatory to moving under the upper pressure roll 44 at station S-13. As the die punches and their die cavity reach station 8-13, upper and lower punches 36 and 37 fully compress the pulverant material about the core tablet 9. Immediately past station S13, the upper die punch 36 begins to move away from the die head 34 following the stationary cam track 66. Just past the station 843, the die punches 36, 37 break away from each other, the coated tablet is slowly moved toward the upper surface of die head 34 where means adjacent station S- (not shown) direct the tablet onto the conveyor discharge chute 48.

Also shown in FIG. 4 are the cam follower assemblies 70 which are associated with each upper die punch 36 and cam follower assemblies 91 which are associated with each lower die punch 36. These cam follower assemblies and the cams with which they cooperate can be more clearly understood by looking to FIGS. 5-9.

Looking first at FIG. 5, there is depicted a cross-section view along line 5-5 of FIG. 4 which illustrates the cooperative relation between the cam follower assembly 70 and its associated upper die punch 36. The upper die punch 36 is rotatably and slideably supported in the guide block 34a which rotates in fixed relation to the rotating die head 34, and the cam follower assembly 70 is slideably but non-rotatably mounted in the cylindrical recess 73, the axis of which is generally along the radial axis D and at right angles to the axis A of the die punches 36 and 37.

The cam follower assembly 78 cooperating with a central portion of the upper die punch 36 has a cylindrical body member 71 having a series of teeth 74 in the form of a rack formed on one side. A coil spring 78 is disposed between the back of the radial aperture 73 and a hollowed rear portion 72 of the body assembly 71 to normally urge the cam follower body 71 radially outward as illustrated by the solid line drawing of FIG. 5. A screw or vertical pin 79 depends through a radial slot 81 in the cam follower body 71 to hold the body 71 slideably but non-rotatably inside its radially oriented housing 73. The pin 79 may be pressed or threaded into the die head block 340.

A cam follower or roller 83 is rotatably attached to the outer end of the cam follower body 71 and is adapted to cooperate with a stationary cam 86 which is aflixed to the frame 11 of the press 16 in the manner hereinafter described.

The dotted outline of the cam follower assembly 70 illustrated in FIG. 5 depicts the position of the cam follower assembly at its fully retracted position just before the cam roller 83 moves beyond the cam surface 86a. Thereafter the cam follower assembly may return the upper die punch 36 to its normal, non-rotated position following the clockwise rotation of the punch at the compression station about its own axis A. This will occur when the compressive forces are relieved enough to allow the compressed spring 78 to force the assembly outward to its normal position. The angle of rotation a of the upper die punch 36 is determined, of course, by the relative displacement of the cam follower assembly 70 which, in turn, depends upon the vertical distance h of the cam 86 which controls it. The rate of twisting depends upon the angular distance between the beginning of cam surface 86a (at 86b) and its maximum point (at 860).

Looking to the cam follower assembly 91 associated with the lower die punch 37, it is similar in construction (see FIG. 6). It differs only in that it is positioned with respect to the lower die punch 37 so that the punch 37 is rotated counterclockwise when the cam follower assembly 91 is moved to its fully retracted position by its fixed cam 92. The assembly 91 is movable along axis C, which it will be noted is on the opposite side of punch axis A from the axis D of cam assembly 70. This is so that the upper die punch 36 is rotated clockwise and the lower die punch 37 is rotated counterclockwise to twist the die punch surfaces with respect to the tablet 10 being formed therebetween. Again, the angle of rotation 11;, of the lower die punch 37 is a function of the radial displacement of the cam follower assembly 91 which, in turn, depends upon the displacement height 11 of cam 92. Again, the rate of twisting depends upon the angular distance between the points 92b and 920, which define the cam surface 92a.

As shown in FIG. 5, the dotted outline of the cam follower assembly 91 in FIG. 6 illustrates the fully retracted position of the cam follower assembly 91 after the die punch 37 has been fully rotated counterclockwise.

The cooperative rotation of these upper and lower twisting mechanisms may be seen more clearly in FIGS. 7 and 8. FIG. 7 illustrates in perspective the relationship between the cam follower assemblies 70 and 91 which are disposed on opposite sides of their respective upper and lower die punches 36 and 37. The cams shown in phantom provide opposite twists as the outer ends of the punches 36 and 37 are cammed inwardly by the respective pressure rollers 44 and 45. The axes B and B of the pressure rolls 44 and 45, it will be noted, intersect the axis of rotation of the upper and lower die punches A. It has been found that a circumferential rotation of approximately 3 of an inch permits the advantages of the present invention to be obtained.

FIG. 7 also illustrates generally the means provided to prevent the upper die punch 36 from rotating before its cam follower 83 actually contacts the inclining surface 86a of fixed cam 86. The plate 94 is affixed to the frame 11 (see FIG. 8) of the press 16 and has an outer edge 95 which rides along the fiat inner surface 96 defined by the shoulder 67 on the upper die punch 36. The die punch cannot twist in either direction until the flat surface 96 clears the tip of the fixed plate 94.

In the case of the upper die punch 36, it is necessary to provide plate 94 since the upper die punch 36 will tend to pivot in a clockwise direction as it is moved under the pressure roller 44. On the other hand, no such preventive is needed for the lower die punch 37 since it will tend to rotate clockwise as it is compressed by pressure roll 45. Since this tendency is exerted only against the fully extended position of the cam follower assembly 91, it will not cause the lower punch 37 to rotate.

It is necessary to prevent premature rotation of the die punches 36 and 37 so that the amount and timed beginning of the rotation can be controlled to provide the necessary twisting to effect a cleaning of the die cavity surfaces and die punch surfaces, and yet not an excessive amount which would cause the tablets to flake or put such a hard surface on the coated tablet that a desired rate of disintegration cannot be obtained.

The manner of mounting the cams 86 and 92 on the frame 11 is more clearly depicted in FIGS. 8 and 9. Both are mounted similarly so cam 86 may be taken as exemplary. Cam 86 has a pair of radially oriented slots 101 formed through it and is mounted on an inverted T-shaped member 102 by screws 103 which depend through the slots and can be turned to bind the cam 86 against the side of the T-member 102. The rigid member 102 is horizontally oriented and is, in turn, slideably supported along a T-track 106 which is afiixed to the frame 11 of the press 16. A thumb screw or similar device 107 is provided to lock the member 102 at a desired transverse position between the front and rear sides of the rotary press (based on the orientation of the apparatus of FIG. 1).

By this technique of mounting the earns 86 and 92, means are provided for changing the slope of the cam 86 and the point at which its cam follower assembly 71 first contacts the inclined surface 86a thereof. These simple adjustments permit the point in the cycle at which the twisting begins to be adjusted in accordance with the best results for the composition of the detergent being used.

Moreover, it is possible by this means to arrange each cam follower assembly and its actuating cam so that the cam roller just clears the cam surface before the die punches break away from the tablet. Thus, a reverse shearing force occurs at the tablet surface due to the returning of the die punches to their normal unrotated positions. This latter shearing force compensates for any excessive smearing of the detergent that may have occurred during the initial twist in the early part of the compression stage and permits the coated tablet 10 to be extracted without harming the surface of the tablet and without gumming up the die surfaces.

While this invention has been described with reference to an exemplary embodiment involving the coating of tablets, it should be apparent to those skilled in the art that certain modifications, including the formation of core tablets only, can be carried out without departing from the spirit and scope of the invention. For this reason, the invention should only be limited to the extent of the appended claims.

I claim:

1. In detergent tablet forming apparatus of the type having a rotatable die head with a plurality of die cavities and upper and lower punches cooperating therewith, the improvement in means for selectively rotating each set of upper and lower punches comprising, in combination,

(a) rotating means associated with each die punch operable to rotate said punch;

(b) controlling means mounted on the frame of the tablet forming press to initiate the operation of said rotating means as the die punch with which it is associated moves through the compression station with the die head; and

(c) means to adjust the controlling means so that each punch is rotated a preselected circumferential distance during a preselected portion of the co1npression stage of the rotary press.

2. An improvement in tablet forming apparatus in accordance with claim 1 wherein the rotating means are directly connected to their die punches, and means are included to reverse the operation of the rotating means at a preselected angular point in said compression stage so that said die punches are returned to their normal unrotated positions.

3. In tablet forming apparatus of the type having a rotatable die head with a plurality of die cavities and upper and lower punches lying in common axes cooperaling therewith, the improvement in means for selectively rotating each set of upper and lower punches comprising, in combination,

(a) a cam follower assembly for each die punch operable to rotate said punch;

(b) cam means mounted on the frame of the press to operate each cam follower assembly as it moves past the compression station during the rotation of the the die head, die punches and cam follower assemblies; and

(c) means to adjust the operating relationship of said cam follower assemblies and said cam means to provide angular rotations of preselected magnitudes and preselected points of operation and release with respect to the compression stage of the press.

4. An improvement in tablet forming apparatus in accordance with claim 3 and including means mounted on the frame of said press adjacent the compression stage thereof to prevent each successive die punch from rotating until its cam follower assembly is operated by said cam means.

5. An improvement in tablet forming apparatus in accordance with claim 3 and including (a) means for mounting each of said cam follower assemblies slideably interior of said die head for movement in a radial direction; and

(b) gear means directly connecting each cam follower assembly to its associated die punch.

6. An improvement in tablet forming apparatus in accordance with claim 3 wherein (a) the cam follower assemblies for the upper and lower punches which cooperate with a given die cavity are mounted on opposite sides of the axes of the die punches to cause the punches to rotate in opposite directions, and

(b) said adjusting means is a pair of cams mounted on the frame with each having at least two degrees of freedom so that the angle of twist for each die punch of a pair and the circumferential points of commencement and termination of the twisting can be preselected.

7. In tablet forming apparatus of the type having a rotatable die head with a plurality of die cavities formed therethrough at circumferentially spaced-apart locations, upper and lower punches cooperating with each die cavity, and cam means for preselectively moving the sets of upper and lower punches interior of their respective die cavities, the improvement involving means for selectively rotating each set of upper and lower punches at times comprising, in combination,

(a) a cam follower assembly for each die punch slideably mounted in the die head adjacent its die punch;

(b) means directly connecting said cam follower assembly to its die punch so that movement of said assembly causes the punch to rotate;

(c) means urging said cam follower body radially outward whereby the cam follower assembly projects outwardly beyond the periphery of said rotatable die head; and

(d) a pair of cams adjustable mounted on the frame of said press in staggered circumferential relation to move the cam follower assemblies associated with the respective lower and upper die punches selectively to rotate said upper and lower die punches preselected angular distances during the compression stage.

8. In tablet forming apparatus in accordance with claim 7 wherein said cams are positioned with respect to said compression stage and the axes of said die punches to initiate the rotation after the compression of a tablet begins and to permit the cam follower assemblies to return their associated punches to their normal non-rotated positions just as the die punches separate whereby the coated tablet therebetween is cleanly sheared from the sides of said die cavity and the faces of said die punches.

9. An improvement in tablet forming apparatus in accordance with claim 8, and including means mounted on the frame of said machine adjacent the compression station thereof to cooperate with the upper punch as it approaches said compression station to prevent it from rotating until its cam follower assembly operatively contacts the stationary cam with which it is designed to cooperate.

10. In tablet forming apparatus of the type having a rotatable die head with a plurality of die cavities formed therethrough at circumferentially spaced-apart locations, upper and lower punches cooperating with each die cavity, means for moving preformed core tablets to positions coincident with the centers of successive die cavities as the die head is rotated, means for filling the die cavities with granular material to form a coating about the core tablets, and means for preselectively moving the sets of upper and lower punches interior of their respective die cavities; the improvement in means for selectively rotating each set of upper and lower punches at times comprising, in combination,

(a) a cam follower assembly for each die punch having a body mounted in the die head adjacent its die punch for generally radial movement with respect to the axis of rotation of the die head and having rack teeth cut therein;

(b) a series of gear teeth formed about at least a part of the periphery of an intermediate section of each die punch to act as a pinion for the rack formed on said body;

(c) Spring means intermediate a part of the die head and the end of said cam follower body urging said body radially outward so that the outer end of said cam assembly projects outwardly beyond the periphery of said rotatable die head;

(d) a pair of cams adjustably mounted on the frame of the tablet forming press adjacent the compression station thereof in staggered circumferential relation to displace the respective cam follower assemblies as sociated with the lower and upper die punches of each pair as they move past the compression station during the rotation of the die head;

(e) said cams being proportioned to cause the upper and lower cam follower assemblies to move radially inward compressing said springs to rotate said upper and lower die punches simultaneously preselected angular distances, and said cams positioned with respect to said compression stage of the press and the axes of said die punches to initiate said rotation after the compression of a tablet begins and to permit the cam follower assemblies to return said punches to their normal non-rotated positions by the forces of said springs as the die punches separate whereby the coated tablet therebetween is cleanly sheared from the sides of said die cavity and the faces of said dic punches.

11. An improvement in tablet forming apparatus in accordancc with claim 10 and including a fiat plate mounted on the frame of said machine adjacent the compression station thereof to bear against a flat formed on the upper punch as it approaches said compression station to prevent said die punch from rotating until its cam follower assembly operatively contacts the stationary cam with which it is designed to cooperate.

12. An improvement in tablet forming apparatus in accordance with claim 11, and including means for mounting each of said cam follower assemblies slideably interior of said die head so that the racks thereon are maintained in proper engagement with the teeth on the intermediate section of their associated die punches and said assemblies cannot extend radially outward beyond a preselected distance.

13. An improvement in tablet forming apparatus in accordance with claim 10, and including adjustable means mounting each of said cams on the frame of the press whereby the angle of twist for each die punch of a pair and the circumferential points of commencement and termznation of the twisting can be selected to accommodate the multifold characteristics of tablets formed of different detergent compositions.

14. A process for preventing tablets formed by compressing granulated detergent between a pair of die punches from sticking to the surfaces thereof, comprising the steps of:

(a) twisting the die punches in opposite directions as a tablet is being formed with the initial twisting of the punches being after the beginning of the compression of the granulated detergent; and

(b) reverse twisting the punches to their original posit on ust as they separate following the full compression of the granulated detergent to form a tablet.

15. A process for preventing tablets formed by compressing granulated detergent between a pair of die punches from sticking to the surfaces thereof in accordance with claim 14, and including initially twisting the punches approximately three-sixteenth of an inch at their periphery.

References Cited UNITED STATES PATENTS 3,118,183 1/1964 Gex et a1 107-17X FOREIGN PATENTS 724,746 2/1965 Great Britain.

WALTER A. SCHEEL, Primary Examiner. J. SHEA, Assistant Examiner.

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