US3483831A - Rotary-type compact tablet making machine - Google Patents

Description

Dec. if@ 3%@ mYQz-m ms 5TM @g ROTARY-TYPE COMPACT TBLET MAKING MACHINE Filed June 29, 1957 3 Sheets-Sheet l fr HHUHHM/@MWWUH if ii! -iii G Hm L Vf. zal! ,il fil ec. -f, ffwQHs @uw Erm. g

ROTARY-TYPE COMPACT TBLET MAKING MACHINE Filed June 29. 1967 3 Sheets-Sheet 2 Dec. 3&5, i969 KwosHi FUJH Erm. 3,483,331

ROTARY-TYPE COMPACT TABLET MAKNG MACHINE 3 Sheets-Sheet 3 Filed June 29, 1967 United States Patent O 3,483,831 RUTARY-TYPE CMPACT TABLET MAKING MACHlNE liyoshi Fujii, Okayama, Kitakawachi-gun, Tatuo Asogawa, Kishiwada, Yoshio Yamaguchi, Takatsuki, Chikaaki Fujii, Fuse, Yukihide Noguchi, Kishiwada, and Yoshiro Funakoshi, Kyoto, `ll'apan, assignors to Takeda Chemical Industries, Ltd., Osaka, Japan Filed .lune 29, 1967, Ser. N o. 650,122 Claims priority, application Japan, July 2, 1966, 41/43,395 Int. Cl. Bb 1.7/08

lU.S. Cl. 107--17 2 Claims ABSTRACT OF THE DISCLOSURE A rotary-type compressive tablet making machine which has a plurality of pressed units each comprising a die with cooperating upper and lower punches. The punches are slidable into and out of a die opening adapted to receive the material to be pressed into a solid compact body Iby the punchers. A pair of stationary upper and lower rollers are positioned so that they are opposed to each other, and a space is left between them through which the press units are moved in a continuous line. The arrangement is such that as each press unit passes through the space between the rollers, the upper punch engages the periphery of the upper roller and is urged downwardly into the die opening, -while the lower punch engages the periphery of the lower roller and is urged upwardly within the die opening to compress the mate rial in the die opening into a solid compact body. The punches are disengaged from the respective rollers and urged upwardly so that the lower punch pushes the compacted body upwardly to discharge it out of the die opening. Means are also provided to keep the upper and/or lower punches engaged with the compacted body so as to continuously press the compact body at least for a short distance after the press unit has passed between the rollers.

The present invention relates to a rotary-type compressive tablet forming machine and more particularly to an improvement in such tablet forming machine, the improvement being in the provision of means to prevent the formation of capping and cracks in the resulting tablet.

A rotary-type compressive tablet forming machine is well known in the art and has widely been used in compressively compacting powder, granular and the like material into tablet and the like compact bodies. The materials to be formed into solid bodies are pharmaceutical preparations, food agricultural chemicals and the like.

As is well known in the art, a rotary-type compressive tablet forming machine comprises a series of a plurality of press units, each comprising a stationary die with cooperating upper and lower punches, the upper punch being slidable into and out of the die opening within which the lower punch is guided. These press units are continuously moved along a predetermined path. Typically, these units are supported on a turn table which is rotated so that the press units will be continuously moved along a circular path. In the path of travel of these press units, there are arranged a pair of stationary upper and lower rollers counter-facing to each other with a space therebetween. As each press unit passes through the space between the upper and lower rollers, the upper punch engages the curved periphery of the upper roller and is thereby downwardly guided to slide into the die opening while the lower punch engages the curved periphery of the lower roller and is thereby up- TCC? wardly guided to slide within the die opening, so that the material within the die opening is subjected to compaction forming a solid tablet. As soon as the press unit has passed through the space between the rollers the punches are disengaged from the respective rollers and the compression pressure on the compact body by the punches is released, and the upper punch is gradually guided upwardly so as to leave the die, while the lower punch is also guided upwardly to push the solid compact body upwardly and to discharge the same out of the die opening. Thereafter, the die opening is charged again with new material and the press unit is further moved to the position of the upper and lower stationary rollers where the same operation as explained above is repeated. Since the general construction and operation of a rotary-type compressive tablet forming machine is well known in the art, no further detailed explanation thereof will be necessary here.

It will be noted from the above that the material as contained in the die is most compressed by the punches when they most fully engage the respective rollers. This state of compression is referred to as main compression. It will also be noted that, after the main compression, no positive pressure is exerted -by the punches on the compart body.

Conventional compressive tablet forming machines of the type described above have drawbacks that there often occurs a phenomenon called capping or the formation of laminar cracks or the like defect in the resulting solid compact body. This is caused by a delamination tendency at such weakened area in the compact body where there has been a local stress concentration during the compaction or compression. When the weakened area is visible, the defective compart body can easily be rejected. However, when the defect is within the compact body and accordingly not visible, it is impossible to distinguish the defective ones from good ones. Such a defective compact body is less stable and tends to crack, break or collapse when encountering vibration, shock or the like during transportation, handling, etc.

We have found unexpectedly that the capping crack is liable to occur in the course of upward discharging the compact body by the lower punch after the main compression stage rather than in the compressive forming stage, so that, if any measure is to be taken in order to prevent the formation of a capping crack, it should be at the stage subsequent to the main compression but before ejection of the compact body from the die.

It has further been found that the formation of cappingy crack or the like defects in a compact body can be prevented if the compact body in the die is continuously pressed under a certain pressure between the upper and lower punches even after the main compression stage and the die with the so-pressed compact body therein is moved at least a certain distance from the main compression position.

Thus, according to the present invention a proper means is associated with the upper and/or lower roller to cooperate with the upper and/ or lower punch in order to enable travelling of the die for a certain distance from the main compression position while maintaining a certain axial pressure on the compact body within the die as explained above. The said means may be in the form of a roller, block or the like which is capable of lifting the lower punch upwardly and/ or of pushing the upper punch downwardly to apply the required axial pressure on the compact body within the die during a predetermined length of travel of the die immediately after leaving the main compression position. lt is important that a pressure is not completely released just after the main compression stage. Thus, for example, when the pressure applied to the compact body within the die is completely released immediately after the main compression stage and the die is moved for more than 100 mm. and then the compact body is pressed, the formation of capping, crack or the like can not be prevented.

The pressure to be continuously exerted on the compact body within the die after the main compression stage should be not higher than about 250 kg. per square cm. of the cross sectional area of the compact body as mentioned before. Preferably, the pressure should be not less than about 2 kg./cm.2. During the travel after the maincompression stage the pressure on the compact body may be gradually decreased but should not be completely released during the travel of at least l mm., preferably 50 mm. After the post-pressurization for a predetermined distance of travel of the die the compact body within the die may be discharged from the die in a conventional manner by upwardly lifting the lower punch.

The present invention will 4be further described by "referring to the accompanying drawings wherein;

FIG. l is a schematic side elevation of a pertinent portion of a conventional rotary-type compressive compact body forming machine,

FIG. 2 is a view similar to FIG. 1 but showing the present invention,

FIG. 3 is a plan view of FIG. 2,

FIG. 4 is a view similar to FIG. 2 but showing a modication thereof,

FIG. 5 is a schematic side elevation of a portion of another embodiment of the invention, and

FIG. 6 is a schematic side elevation of a portion of still another embodiment of the invention.

Referring to the drawings, particularly to FIG. 1 which shows a schematic side elevation of pertinent portion only of a typical conventional rotary-type compressive cornpact forming machine, there are a series of press units P each comprising a die D which is stationary or fixed on the periphery of a turn table (not shown) which is rotated at a speed of about 10-50 r.p.m. in the direction indicated with an arrow. The diameter of the turn table is -90 mm., usually about 40-45 mm. Each die D is associated with an upper punch A and lower punch B, the upper punch A being adapted to slide into and out of a die opening 1 during the travel of the die D. In the path of travel of these press units P there are arranged a pair of rollers, a stationary upper roller R1 and a lower roller R2 which are opposed to each other with a space therebetween as shown. The press unit is guided by a turn table into and then out of the space between the rollers R1 and R2. This arrangement is such that as the press unit P reaches the position of the rollers R1 and R2 the upper punch A engages the upper roller R1 and is thereby pushed downwardly into the die opening 1 while the lower punch B engages the lower roller R2 and is thereby lifted upwardly within the die opening 1, so that the material M within the die opening 1 is pressed by the upper and lower punches into a solid compact body. When the punches A and B are closest to each other (on the line X-X in FIG. 1) the material is most compressed (eg. about 2 tons per cm.2 of the compact cross section). The position X-X is referred to as the main compression position or stage. Immediately after the main compression position the punches are disengaged from the respective rollers. The upper punch is guided gradually upwardly as shown by means of a guide GG and guide elements AA while the lower punch B is also guided upwardly by means of a guide rail G so that the solid compact body C is discharged upwardly out of the die D. Due to disengagement of the punches A and B from respective rollers lR1 and R2 so that the pressure exerted on the compact body C by these punches are completely released and sometimes there is even formed a space S below the compact body C within the die opening as shown. As pointed out before, this complete release of pressure has been found to cause the formation of capping, crack or the like in the resulting compact body.

A machine of the present invention is the same in the ybasic: construction and operation as any conventional rotary-type compact forming machine of the kind described above by referring to FIG. l. The important feature or this invention is in the provision of a suitable means in order to continuously press the compact body by the punches even after the main compression stage X-X within a predetermined instance of travel of the press unit P.

Referring to FIG. 2 and FIG. 3 which schematically show one embodiment of the invention, there is provided a guide block 2 adjacent to the lower roller R2 and guide rail G. The upper surface of the guide block 2 is so curved that the lower punch B, after the main compression position X-X, will be transferred onto the surface of the block 2 and continuously guided thereby upwardly on to the upper face of the guide rail G. The upward inclination is so selected in the relation to the curved periphery of the upper roller or the locus of the upper punch A which is guided upwardly by guide means G/G that the compact body C within the die will be placed under a predetermined pressure by the two opposing punches A and B for a predetermined distance (at least about l0 mm.) of travel of the press unit P from the main compression stage X-X. Indicated with the numeral 3 is a holder for the block 2. The gradient and length of the block 2 may be varied depending upon the particular machine, material to be compacted, and other factors involved and can readily be determined by experiments.

FIG. 4 shows a slight modification of the apparatus shown in FIGS. 2 and 3. Thus, a wedge 4 is provided within the holder 3 but below the block 2, said wedge 4 being operated by a handle 5 to adjust the position of the block 2.

FIG. 5 shows another embodiment of the invention. This embodiment is same as that shown in FIGS. 2 and 3 except that the block 2 of the FIGS. 2 and 3 is replaced by a roll 6. In the embodiment shown, the lower punch B, after the main compression position, will ride on the guide roll 6 and is upwardly guided on to the surface of the guide rail G so that the punch B will not descend after leaving the main compression stage and will cooperate with the upper punch A to continue to press the compact body within the die under a predetermined pressure for a predetermined distance of travel of the press unit.

FIG. 6 shows still another embodiment of the invention, which is same as the embodiment shown in FIG. 5 except that another guide roll 7 is arranged adjacent the upper roller R1 so that the upper punch A, after leaving the main compression stage X-X, will engage the surface of the roll 7 and the movement of the punch A is so controlled in relation to the movement of the lower punch B as to exert a desired pressure on the compact body C.

In any case, the important feature of the invention is in that the pressure exerted by the two opposite punches on the compact body within the die is not completely released even after the main compression stage and in that a measure is taken to continuously press the compact body by these punches during a further travel of the press unit, while allowing the upward movement of the punches to discharge the compact body from the die by pushing the same upwardly by the lower punch. By this postpressurization, it has been found that the formation or' capping, crack and the like defects in the resulting compact body is prevented.

The following experiments demonstrate surprising advantages of the invention. All parts are by weight.

Experiment 1 ln this experiment, a commercial standard rotary-type compression tablet forming machine (Model No. 8F-

Type 3, made by Kikusui Seisakusho, Japan) was employed with or without the block 2 as shown in FIGS. 2 and 3. The turn table (44 cm. in diameter) was rotated at r.p.m. The surface of the block was curved with a gradient of 5/100 and the length was 100 mm. After the main compression, the compact was post-pressed (50 kg./cm.2) for 70 mm.

By this machine there were produced tablets (each 8 mm. in diameter, curvature 6 mm. R, Weight about 200 mg.) from a granular mixture of 1 part 0f sulpyrin, 1 part of pyrabital, 0.2 part of milk sugar, 0.2 part of starch, 0.2 part of ethyl cellulose and 0.3 part of talc.

The resulting tablets were tested in respect of friability and hardness. The results are as follows:

Hardness (kg.)

Friability (min.)

Experiment 2 In this experiment the machine same as in Experiment 1 was employed, except that the roll 6 shown in FIG. 5 was used in place of the block 2. The roll 6 was 200 mm. in diameter. The gradient of a tangent line common to the roll 6 and roller R2 was 4/100 and the tangent line between these rolls was 40 mm. in length. After the main compression the compact was continued to be pressed under 20 kg/cm.2 for about 40 mm.

By this machine there were produced tablets (each 9 mm. in diameter, curvature 7.5 mm. R, weight about 285 mg.) from a granular mixture of 1 part of milk sugar, 0.09 part of corn-starch, 0.08 part of water, 0.03 part of talc and a trace amount of magnesium stearate.

The properties of the resulting tablets are as follows:

Friability (min.)

Hardness (kg.)

Experiment 3 In this experiment, a commercial high-speed rotarytype compressive tablet forming machine (made by Kikusui Seisakusho, Japan) with the turn-table (42 cm. in diameter) rotated at 36 r.p.m. was employed with or without the rolls 6 and 7 shown in FIG. 6. The dimension and arrangement of the roll 6 was same as those in Experiment 2B. The roll 7 was 180 mm. in diameter. The gradient of a tangent line common to the roll 7 and roller R1 was 5/100 and the tangent line between these rolls 7, R1 was 11.0 mm. in length. After the main compression the compact was post-pressed under 100 kg./ cm.2 for about 30 mm.

By this machine there were produced tablets (each 7.5 mm. in diameter, 5.5 mm. R in curvature, 200 mg. in weight) from a granular mixture of 1 part of milk sugar, 0.09 part of corn-starch, 0.08 part of water, 0.03 part of talc and a trace amount of magnesium stearate.

The properties of the resulting tablets are as follows:

Experiment 4 Frability (min.) Hardness (kg.)

Without rolls 6, 7 3. 8 1. 19 With rolls 6, 7 30 6. 16

In all these experiments the friability was expressed in terms of a period of time (minutes) which has been taken in breaking at least one among live tablets in a friability testing machine (55 cm. in inner diameter) rotated at a speed of 50 r.p.m. The hardness was measured by Erweka 0 hardness tester.

What we claim is:

1. A rotary-type compressive compact tablet making machine comprising a plurality of press units each having a die with a die opening and cooperating upper and lower punches, the upper punch being slidable into and out of the die opening and the lower punch being slidable in the die opening to press a material in the die opening into a solid compact body between said punches, a pair of stationary upper and lower rollers opposed to each other with a space therebetween, means for moving the press units through said space in succession so that when each press unit passes through said space the upper punch engages the periphery of the upper roller and is thereby downwardly guided to slide into said die opening while the lower punch engages the periphery of the lower roller and is thereby guided upwardly to slide within said die opening so as to compress the material in the die opening into a solid compact body, and then the upper punch is disengaged from the upper roller and guided upwardly in such a manner that the upper punch leaves the die opening and the lower punch pushes the compact body upwardly to discharge the same out of the die opening and a curved block placed adjacent at least one of the upper and lower rollers and acting on at least one of said punches to control the movement of the punch by the curved surface of the block after it has disengaged from the roller in order to continuously press the compact body between the punches at least for a certain distance after the press unit has passed the main compression position in the space between the pair of rollers.

2. A machine as claimed in claim 1 wherein the curved block is in the form of a rotatable roll in a lixed position.

References Cited UNITED STATES PATENTS 2,027,915 1/1936 Kux. 2,043,085 6/1936 Westin et al. 107-17 FOREIGN PATENTS 321,748 11/1929 Great Britain.

WALTER A. SCHEEL, Primary Examiner ARTHUR O. HENDERSON, Assistant Examiner U.S. Cl. X.R 18-20

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