US3337915A

US3337915A - Tablet press

Info

Publication number: US3337915A
Application number: US412993A
Authority: US
Inventors: Jr John M Alexander
Original assignee: Pennsalt Chemical Corp
Current assignee: Pennwalt Corp
Priority date: 1964-11-23
Filing date: 1964-11-23
Publication date: 1967-08-29
Anticipated expiration: 1984-08-29
Also published as: DE1502303A1; GB1125163A

Description

1967 J. M. ALEXANDER, JR 3,337,915

TABLET PRESS 5 Sheets-Sheet 1 Filed Nov. 25, 1964 O 3 l E /IVVNTOR 4 JOHN M. HLEXH/VDE/QJR.

c c C ATTORNEYS.

1967 J. M. ALEXANDER. JR 3,337,915

TABLET PRESS 3 Sheets-Sheet 2 Filed Nov. 23, 1964 lNVE/VTOR JOHN M. IqLEXH VDER /R.

ATTORNEYS.

Aug. 29, 1967 J. M. ALEXANDER, JR

TABLET PRESS Filed Nov. 23, 1964 5 Sheets-Sheet 3 INVENTOR JOHN M. HLEXHNDER, JR.

"MFM

ATTORNEYS.

United States Patent 3,337,915 TABLET PRESS John M. Alexander, Jr., Philadelphia, Pa., assignor to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 23, 1964, Ser. No. 412,993 4 Claims. (Cl. 1816.5)

This invention relates to tablet presses and more particularly, to presses adapted to manufacture tablets from powdery or granular materials.

Rotary tablet presses employ travelling tool assemblies with opposed upper and'lower punches which cooperate in a die to form tabletted products between them as they are passed between upper and lower pressure rolls. In the use of such presses for manufacturing tablets, it has been found that certain tablet forming materials have the property of sticking or clinging to the punch surfaces after the tablet material has been pressed into a tablet. This will spoil the smooth finish of the completed tablet or rupture it when the completed tablet is ejected from the press.

It has been found that by rotating or twisting the punches after the tablet has been compressed by the punches, the problem referred to above is eliminated. The formed tablet will not stick or cling to the punches as they are separated and the tablet is ejected.

Accordingly, it is an object of this invention to pro: vide a tablet press having means for twisting the punches after a tablet has been formed in order to prevent the sticking or clinging of the-tablet material to the punches. Another object of this invention is to provide a tablet press including means for twisting the punches of the press in the easiest and most economical manner.

A still further object of this invention is to provide a tablet press including means for twisting the punches after the punches have been subjected to maximum compressive pressure to form the tablet, whereby the need to develop large twisting forces to twist the punches is eliminated as well as the possibility of rupture of the formed tablet.

Other objects will appear from the disclosure which follows hereinafter.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a fragmentary view in elevation, partly in cross section, of a rotary tablet machine constructed in accordance with the principles of the present invention.

3,337,915 Patented Aug. 29, 1967 FIGURE 7 is a cross-sectional view of a portion of the press illustrated in FIGURE 1 with a slightly modified type of punch.

Referring now to the drawings in detail, wherein like numerals indicate like elements, the reference numeral 10 indicates a rotary tabletting press. Generally, the tabletting press 10 includes a rotary die table 12 which is rotatable about a central vertical spindle 28 which projects upwardly through a fixed support .16. The spindle 28 also mounts an upper annular disk 14 for rotation and synchronization with the die table 12.

The upper disk 14 is provided at arcuate intervals adjacent its periphery with a series of vertical openings 15 which receive upper punches 18. The die table 12 is also provided at arcuate intervals with a series of vertical die openings 22 which are vertically aligned with the openings 15 in the disk 14. The die table 12 is also provided at arcuate intervals with a series of vertical openings 19 aligned with openings 22 and 15, for receiving the lower punches 20.

The fixed support 16 is provided with a series of cams, which will be referred to hereinafter, which cooperate with the heads 32 of the lower punches 20 to move the lower punches up and down. A stationary cam rail 34 secured to the stationary frame of the press is provided above the upper disk 14 for cooperating with the heads 30 of the upper punches 18 to move the upper punches 18 up and down.

As is well-known in such rotary tablet presses, punches 18 and 20 oppose each other in die opening 22 to form tabletted products between their ends. The general operation commences in a fill position in which the upper punch 15 is withdrawn from the die opening 22 by a raised portion of the cam rail 34 as illustrated in the center of FIGURE l. The lower punch 20 is lowered slightly in die opening 22 from the position shown in FIGURE 1. In the fill position, the powdered or granular material which is to be tabletted is placed into die opening 22 above the lower punch 20. Thereafter as the die table 12 rotates from the fill position, the cam rail 34 lowers the upper punches 18 into the die opening 22, thus preparing the punches for compression.

The pair of opposing punches 18 and 20 are then passed between vertically aligned upper and lower pressure rolls mounted upon the frame of the press. Upper pressure roll 24 is positioned so that the head 30 of the upper punch 18 passes under the upper pressure roll which forces the punch 18 down further into die opening 22. At the same moment, the head 32 of lower punch 20 passes over lower pressure roll 26 which forces lower punch 20 up further into the die cavity 22, opposing the FIGURE 2 is a schematic plan view taken along the I FIGURE 4 is a schematic plan view taken substantially along the plane indicated by the line 44 of FIG- URE 1 and illustrating several positions of the lower punches as they are moved around the press.

FIGURE 5 is a cross-sectional view taken substantially along the plane indicated by the line 5-5 of FIGURE'4 and illustrating the mechanism for twisting the lower punches.

FIGURE 6 is an enlarged detailed view of a lower portion of the press illustrated in FIGURE 1 and particularly showing part of the ejection mechanism for a formed tablet.

downward movement of punch 18. The movement of the punches causes the powdery or granular material in the die cavity 22 to be compressed between the punches. In this manner, a tablet is formed.

The tablet press 10 is also provided with means for twisting the punches 18 and 20 after they leave the upper and lower pressure rolls 24 and 26 respectively, or after the point of maximum compression. The twisting of the punches after maximum compression not only prevents the clinging or sticking of tablet material to the punches, but substantially reduces the twisting force which must be applied to the punches so that they may be freely twisted.

The twisting operation is effected by providing the upper punches 18 with a cam 36 intermediate its ends above the upper disk 14. Similarly, the lower punches 20 are provided with cams 38 intermediate their ends and below the die table 12. With specific reference to FIG- URES 2 and 3, it will be observed that a twisting roller 62 is provided outside-ofthe cams 36 in their path of travel. As the cams 36 pass the twisting roller 62, they will be rotated in a counterclockwise direction as viewed in FIGURE 2, thereby causing the upper punches 18 to twist. With specific reference to FIGURES 4 and 5, it will be observed that a lower twisting roller 98 is mounted upon the fixed support 16 on the inside of the cams 38 in their path of travel. As the earns 38 make contact with the roller 98, they are rotated in a clockwise direction as viewed in FIGURE 4, thereby causing the punches 20 to twist. The punches 18 and 20 are twisted in opposite directions thereby insuring that the tablet is freed from the punch surfaces within the die opening 22.

The punches 18 and 20 must be subjected to some compressive force as they are twisted in order to prevent the formed tablet from sticking to one of the punches and rotating with it as it is twisted. Therefore, an upper compression cam assembly 42 and a lower compression cam assembly 40 are provided in the path of travel of the upper and lower punches, respectively, for applying a compressive force to the punches as they are twisted. The compressive forces applied by the compression cam assembly 42 and 40 are substantially less than the compressive force applied by the upper and lower pressure rolls 24 and 26.

The upper compression cam assembly 42 is mounted upon a bracket 48 secured to the frame 66 of the press 10. The compression cam assembly 42 includes a spacer block 50 mounted by means of a stud 64 on the bracket 48. Bores 52 are provided in the spacer block 50. A plurality of pins 54 extend through the bores 52 and are fixed to the spacer block 50. Placed around each pin 54 within the bores 52 is a spring 56. The pins 54 extend through a compression block 58. The springs 56 space the compression block 58 from the spacer block 50 and mount it for deflection against the bias of the spring 52. Nuts 60 threaded on the end of each pin 54 retain the connection between the spacer block 50 and the compres sion block 58. The twisting roller 62 also depends from the bracket 48 and is rotatably mounted thereon for contact with the earns 36.

The lower compression earn assembly 40 is similar in construction and includes a spacer block 70 mounted Within a recess 68 within the fixed support 16. The spacer block 70 includes a plurality of bores 72. Extending through the bores 72 are pins 74. Coil springs 76 are placed around the pins 74 in the bores 72. The pins 74 extend through a lower compression block 78 which is resiliently urged upwardly under the bias of the springs 76. Nuts 80 threadedly connected to the upper ends of the pins 74 maintain the connection between the compression block and spacer block 70.

As the lower punch 20 leaves the lower pressure roll 26, it is engaged by a repositioning cam 44 on the fixed support 16 to prepare it for the twisting operation. The lower punch then moves on to the compression block 78 Where it is resiliently urged upwardly under the bias of the springs 76 towards the upper punch 18. Simultaneously compression block 78 is the positioningof the head 30 of the upper punch 18 on the compression block 58. The compression block 58 under the urging of the springs 52 biases the upper punch 18 downwardly toward the lower punch 20. Hence, a slight compressive force is placed upon the tablet between the punch ends.

As the punches move along the compression blocks 58 and 78, the cam 36 associated with the upper punch 18 makes contact with the twisting roller 62 and is rotated. Similarly, the cam 38 associated with the lower punch 20 makes contact with the twisting roller 98 and is rotated in an opposite direction. The punches 18 and 20 are thus twisted under a slight compressive force to free the tablet from the ends of the punches. Limit stops could be provided on the frame of the press to limit the amount of twist imparted to the punches.

Continued rotation of the disk 14 and die table 12 will cause the head 30 of the upper punch 18 to follow with positioning of the lower punch 20 upon the the fixed cam rail 34. This will raise the punch 18 from 20 leaves the compression block 78, it is engaged by an ejector cam 46 and pushed upwardly slightly. The slight raising of the lower punch 20 has the etfect of pushing the tablet above the die table 12 out of the die opening 22. As shown in FIGURE 1 and schematically in FIG- URE 4, the raised tablet is adapted to be engaged by an ejector arm 88 and pushed into a chute 90 for collection. This mechanism is conventional in the art and forms no part of the present invention.

At the ejection station, the head 32 of the lower punch 20 rides on plate'84 mounted on the fixed support 16.

Passing through plate 84 is an adjustable threaded stud 82 having a handle 86 at one end. By provision of the stud 82, adjustments may be made to insure that the tablet is pushed from the die opening 22 a suificient amount so as to clear the opening and be positioned for removal. 7

After ejection, the lower punch 20 is returned to its fill position by means of a pull down cam 92.

Further downstream, the punches 18 and 20 are adapted to be recocked to their original position by means of a lower punch reset cam 94 and an upper punch reset cam 96. The lower reset cam 94 is secured to the fixed support 16 and contacts the'cam 38 or the lower punch 20 to recock it by rotating it in a counterclockwise direction as viewed in FIGURE 4. The upper reset cam 96 is mounted on the frame of the tablet press 10 on the inside of the cams 36. The cam 96 is adapted to contact the cams 36 of the upper punches 18 and rotates the cams 36 in a clockwise direction as viewed in FIGURE 2 to recock the upper punches 18 and return them to their original positions.

The adjusting stud 64 associated with the upper compression cam assembly 42 is adapted to raise and lower the compression block 58. This is useful in compensat respectively keyed to them. The bushings extend through suitable aligned vertical openings in the disk 14 and die table 12. The upper end of the bushing 100 has a cam l'04 similar to the cam 36 secured to. it and the cam 104 operates in identical manner to the cam 36. Secured to the lower end of the bushing 102 is a cam 106 which is identical in all respects and mode of operation to the cam 38.-

The bushings 100 and 102 are free to rotate with punches 18' and 20', but do not move in an axial direction. The punches can slide relative to their respective bushings from a vfill to a compress position. In this manner, the cams 104 and 106 remain in the same plane. This is desirable in a tablet press wherein movement of the cams would interfere with adjacent portions of the press.

It should be understood that the sequence of operation illustrated in FIGURE 1 is repeated during a single revolution of the die table 12 and annular disk 14. Hence, a plu rality of mechanisms similar to that illustrated in FIG URE 1 are provided around the frame and fixed support of the tablet press 10. Itshould also be understood that The present invention may, be embodied in other spe- V cific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be 1 made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

What is claimed is as follows:

1. In a tablet press, a movable die table, at least one vertical die opening in said table, a lower punch positioned beneath said table with its upper end extending into the die opening, a lower pressure roll mounted below said die table in alignment with the path of travel of said lower punch to move it upwardly into maximum compressive pressure, an upper punch mounted above said die table with its lower end in axial alignment with the die opening, means for moving the lower end of said upper punch into the die opening, an upper pressure roll mounted above said die opening in alignment with the path of travel of said upper punch to move it downwardly into maximum compressive pressure simultaneously with the compressive movement of said lower punch to form a tablet, and a pair of movably mounted punch contact surfaces downstream from said upper and lower pressure rolls and independent thereof, one of said punch contact surfaces being above said upper punch and the other of said punch contact surfaces being below said lower punch for applying to said punches compressive pressure substantially less than the maximum pressure applied by said pressure rolls but sufiicient to hold said punches in contact with the tablet, means adjacent at least one of said punch contact surfaces for twisting one of said punches relative to the other so that sticking of the tablet to said punches is eliminated and twisting of said punches is.effected with a minimum force.

2. In a tablet press in accordance with claim 1, wherein at least one of said punch contact surfaces is vertically adjustable with respect to said die table.

3. In a tablet press in accordance with claim 1, wherein said twisting means effects twisting of each of said punches and comprises a cam surface on each of said punches, rollers adjacent said punch contact surfaces for engaging the cam surfaces on said punches, and means for twisting said punches so that they return to their original positions, said last mentioned means including fixed camming surfaces downstream from said punch contact surfaces and adapted to contact said carn surfaces on said punches.

4. In a tablet press in accordance with claim 1, wherein said contact surfaces are resiliently biased towards each other.

References Cited UNITED STATES PATENTS 2,068,619 1/1937 Bailey 18-20 X 2,573,365 10/1951 Scholes et a1 18-20 X 2,875,471 3/ 1959 Crowther 18-20 3,118,183 1/1964 Gex et a1 18-16.5 X

FOREIGN PATENTS 123,706 1959 Russia.

J. SPENCER OVERHOLSER, Primary Examiner. E. MAR, Assistant Examiner.

Claims

1. IN A TABLET PRESS, A MOVABLE DIE TABLE, AT LEAST ONE VERTICAL DIE OPENING IN SAID TABLE, A LOWER PUNCH POSITIONED BENEATH SAID TABLE WITH ITS UPPER END EXTENDING INTO THE DIE OPENING, A LOWER PRESSURE ROLL MOUNTED BELOW SAID DIE TABLE IN ALIGNMENT WITH THE PATH OF TRAVEL OF SAID LOWER PUNCH TO MOVE IT UPWARDLY INTO MAXIMUM COMPRESSIVE PRESSURE, AN UPPER PUNCH MOUNTED ABOVE SAID DIE TABLE WITH ITS LOWER END IN AXIAL ALIGNMENT WITH THE DIE OPENING, MEANS FOR MOVING THE LOWER END OF SAID UPPER PUNCH INTO THE DIE OPENING, AN UPPER PRESSURE ROLL MOUNTED ABOVE SAID DIE OPENING IN ALIGNMENT WITH THE PATH OF TRAVEL OF SAID UPPER PUNCH TO MOVE IT DOWNWARDLY INTO MAXIMUM COMPRESSIVE PRESSURE SIMULTANEOUSLY WITH THE COMPRESSIVE MOVEMENT OF SAID LOWER PUNCH TO FORM A TABLET, AND A PAIR OF MOVABLY MOUNTED PUNCH CONTACT SURFACES DOWNSTREAM FROM SAID UPPER AND LOWER PRESSURE ROLLS AND INDEPENDENT THEREOF, ONE OF SAID PUNCH CONTACT SURFACES BEING ABOVE SAID UPPER PUNCH AND THE OTHER OF SAID PUNCH CONTACT SURFACES BEING BELOW SAID LOWER PUNCH FOR APPLYING TO SAID PUNCHES COMPRESSIVE PRESSURE SUBSTANTIALLY LESS THAN THE MAXIMUM PRESSURE APPLIED BY SAID PRESSURE ROLLS BUT SUFFICIENT TO HOLD SAID PUNCHES IN CONTACT WITH THE TABLET, MEANS ADJACENT AT LEAST ONE OF SAID PUNCH CONTACT SURFACES FOR TWISTING ONE OF SAID PUNCHES RELATIVE TO THE OTHER SO THAT STICKING OF THE TABLET TO SAID PUNCHES IS ELIMINATED AND TWISTING OF SAID PUNCHES IS EFFECTED WITH A MINIMUM FORCE.