US3029470A

US3029470A - Tablet making machine

Info

Publication number: US3029470A
Application number: US826700A
Authority: US
Inventors: Raymond G Frank
Original assignee: FJ Stokes Corp
Current assignee: FJ Stokes Corp
Priority date: 1959-07-13
Filing date: 1959-07-13
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

April 17, 1962 R. G. FRANK 3,029,470

TABLET MAKINGMACHINE' 3 Sheets-Sheet 1 Filed July 15, 1959 Fig.

INVENTO v RAYMOND 3. FR

GAIL HW ATTORNEY fl April 17, 1962 R. G. FRANK 3,029,470

TABLET MAKING MACHINE Filed July 13, 1959 3 Sheets-Sheet 2 Fig. 4

56b 53b 58b 7- I 60 IO!) 47b 98 9 I2 INVEN TOR.

RAYMOND G. FRANK By M KW ATTORNEY April 17, 1962 R. G. FRANK TABLET MAKING MACHINE 3 Sheets-Sheet 3 Filed July 13, 1959 I Is M MA TR NF E G m ATTORNEY United States Patent G 3,ti29,470 TABLET MAKING MACHINE Raymond G. Frank, Ambler, Pa., assignor to F. J. Stokes Corporation, Philadelphia, Pa., a corporation Filed July 13, 1959, Ser. No. 826,700 7 Claims. (Cl. 18-20) The present invention is directed to a tablet making machine, and more particularly to a tablet making machine for forming tablets from fine powders.

The use of automatic tablet making machines has become widespread, and machines for producing tablets of closely regulated size and shape at very high speeds have been developed. However, since virtually all automatic tablet making machines measure the granular material to be tabletted volumetrically, they are dependent upon the free flow of the granular material to the die table.

A fairly substantial variety of powders cannot readily be tabletted by automatic tablet making machinery because the same do not flow freely under the influence of gravity. Thus, with many forms of powdered materials resort must be had to either wet granulating processes or dry granulating processes, commonly called slugging, to render the powders sought to be tabletted into a granular state in which they may be tabletted by present-day high speed tablet making machinery. As both wet granulating techniques and dry granulating techniques are deendent upon a plurality of operations, each involving a variety of types of equipment, the same are expensive both in terms of equipment and labor, and materially add to the cost of the tablet.

This invention has as an object the provision of a novel tablet making machine.

This invention has as another object the provision of a tablet making machine which may be utilized to form tablets from fine powders which are generally classified at the present time as being non-free-flowing.

This invention has as another object the provision of a tablet making machine in which closely regulated volumetric charges of fine powders may be delivered to the dies.

This invention has as yet another object the provision of a tablet making machine which can operate at far higher tabletting speeds with free flowing granular material than the speeds of present-day conventional tabletting equipment.

This invention has as still another object the provision of a tablet making machine which may be used to form tablets from materials which tend to entrain air to such a degree that while they may be free flowing, satisfactory tablets may not be made therefrom without special processing using present-day tabletting equipment.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is 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 vertical sectional view through one embodiment of the tablet making machine of the present invention.

FIGURE 2 is a horizontal sectional view taken on line 2-2 of FIGURE 1.

FIGURE 3 is a sectional view taken on line 3-3 of FIGURE 2.

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 2.

FIGURE 5 is a fragmentary elevational view revealing another embodiment of the tablet making machine of the present invention.

FIGURE 6 is a fragmentary sectional view revealing Patented Apr. 17, 1962 ice another embodiment of the tablet making machine of the present invention.

FIGURE 7 is a fragmentary elevational view of still I another embodiment of the tablet making machine of the present invention.

FIGURE 8 is a sectional view taken on line 8-8 of FIGURE 7.

Referring to the drawings, and initially to FIGURES l through 4, there is shown therein a rotary tablet making machine of the present invention with many of the commonly known elements which are non-essential to the operation of the present invention being omitted.

The tablet making machine of the present invention is designated generally as It and comprises a fixed base 12 which comprises the frame of the machine 10. The rotary portion of the machine comprises a lower driven punch block 14 which is fixedly connected to an upper punch block 16. I

The upper punches 18 are guided in the upper punch block 16, with each upper punch 18 having a flared head which engages the upper fixed cam means 2t).

The die table 22 includes a plurality of dies 24 which are disposed circularly on the die table 22 at a fixed radial distance from its center. The upper punches 18 and the lower punches (not shown) are in vertical alignment with the dies 24 as will be evident to one having skill in this art.

The rotation of the rotary portion of the tablet making machine it) is effected through the gear 26.

The removal of finished tablets from the die table 22 is effected through the chute 28 which is provided with the deflecting knock-off 30 The portion of the rotary tablet making machine 10 set forth above is of standard construction, and no claim of invention is made to the same independent of the portion of such machine set forth below. Accordingly, a wide variety of tablet making machine embodiments incorporating the elements set forth above may be utilized in the tablet making machine 10 of the present invention, since no claim is made to any particular type of element of the type specified above.

The feeding means specified below will be described in detail as a single unit. However, it isto be understood that the present invention includes tablet making machines comprising a plurality of feed units of the type specified below. I

The feed unit designated hopper means consisting of a pair of telescoped hoppers, namely the upper hopper 34 and the bottom hopper 36. As seen from FIGURE 1 the outer wall surface of the upper hopper 34 is radially spaced from the juxtaposed inner wall surface of the bottom hopper 36 so as to provide a ring-shaped gap 38 between the

hoppers

34 and 36. If desired, a spider or other support means may be provided between the

hoppers

34 and 36. However, the hopper 34 may be supported independently of the hopper 36 as will be explained below.

Vibratory means designated generally as 40 are fixedly ecured, as by a metallurgical bond, to the outer wall surface of the upper hopper 34. Such vibratory means 40 are independently supported, and may serve to independently support the hopper 34 in respect to the hopper 36. While one vibratory means 40 is shown in FIGURE 1, it is to be understood that the present invention also;

comprehends a plurality of vibratory means secured to the upper hopper 34, as for example two or more such vibratory means radially spaced about the periphery of the hopper 34.

"In the illustrated embodiment the vibratory means 40 comprises a transducer diagrammatically indicated as 42, a coupler 44 and a tip 46, which tip 46 is secured generally as 32 comprises as by welding or brazing to the outer wall surface of the hopper 34.

I have found that the vibratory energy should be of high frequency, namely above about 10,000 cycles per second, and preferably of an ultrasonic frequency, namely upwards of about 16,000 cycles per second. In order to obtain this vibratory energy of high frequency a variety of known types of transducers may be used in the vibratory means of the tablet making machine of my invention. For example, the transducer 42 may comprise a magnetostrictive transducer, as for example a laminated core of nickel, nickel-iron alloy, Permendur (an iron-cobalt alloy), or an aluminum-iron alloy, or other magnetostrictive material, properly dimensioned to insure axial resonance with the frequency of the alternating current applied thereto so as to cause it to change in length according to its cocfficient of magnetostriction. As will be understood by those skilled in the art, the rnagnetostrictive transducer should comprise both a polarizing means, such as a polarizing coil, and an excitation means, such as an excitation coil. The desirability of magnetically polarizing a magnetostrictive transducer by means of polarizing means in order for the metal laminations in such transducer to efiiciently convert applied R.F. energy from the excitation coil to vibratory energy will be readily understood by those skilled in the art.

In place of a magnetostrictive transducer, other forms of transducing means for producing vibratory energy may be used, such as a transducer stack of laminated strips of metal associated with a permanent magnet and a source of applied R.F. energy, or piezoelectric, electrostrictive, or other types of transducers, such as transducers formed from the piezoceramic material barium titanate.

The coupler 44 preferably comprises a tapered member which is metal-to-metal bonded at its larger end in endto-end contact with the transducer 42, and metal-to-metal bonded in end-to-end contact at its smaller end with the tip 46. The taper is preferably an exponential taper, which may, but need not necessarily, satisfy the equation set forth at page 163 of Piezoelectric Crystals and Their Application to Ultrasonics, by Warren P. Mason, published in 1950 by Van Nostrand Company, namely a curved coupler whose taper is an exponential function of its length and satisfied the relation:

where S equals the original area, S equals the reduced area, T equals the taper constant, and 1 equals the length of the tapered section.

The bottom hopper 36 comprises a throat 47 which discharges into the feed foot 48. The feed foot 48 comprises a fioorless extension of the throat 47 spaced above the fiat upper surface of the die table 22 by a small distance, such as a distance of the order of three thousandths of an inch. Such distance between the bottom edge of the feed foot 48 and the top surface of the die table 22 should be suificiently great to avoid appreciable destruction of the powders being fed to the die table 22 by friction between the bottom edge of the feed foot 48 and the top of the die table 22, but should not be so large as to result in appreciable leakage of the powders from within the feed foot 48 onto the top surface of the die table 22 through the gap between the top surface of the die table 22 and the bottom edge of the feed foot 4-8.

The feed foot 48 is open at its mouth 49 which is spaced from and juxtaposed to the knock-off 30. The remainder of the feed foot 48 is provided with upright walls, and the width of the interior of the feed foot 43 is substantially uniform for its entire length.

However, the height of the chamber within the feed foot 48 may be varied by means of its adjustable ceiling 50, so that the rear portion of the chamber within the feed foot 48 is of lower height than the portion adjacent the mouth 49. Thus, the adjustable ceiling 56 may comprise a flat leaf spring fixedly secured to the underside of the top surface of feed foot 48 adjacent the mouth 49 by the rivets 51. The free rear portion of the adjustable ceiling 50 is engaged with the screw 52 which enters through the top of the feed foot 48. By lowering the rear portion of the adjustable ceiling 50 by downwardly adjusting the screw 52, the pressure on granular material within the rear portion of the feed foot 48 may be greatly increased due to the resultant packing. By this technique positive assurance of uniform volumetric loading to the dies 24 may be obtained.

A vibratory means designated generally as 53 may be coupled to the throat 47 of the hopper 36, as at the bend of such throat 47 as shown in FIGURE 1. The vibratory means 53 may comprise a transducer 54, a coupler 56, and a tip 58.

The transducer 54 may be of the same type as transducer 42 of vibratory means 40. Similarly, the coupler 56 may be of the same type as the coupler 44 of vibratory means 40. e

The tip 53 is secured to the coupler and to the throat 47, thereby effecting the coupling of the transducer 54 to the throat 47.

The throat 47 is provided with a pair of

horns

60 and 60 which serve to balance the throat and facilitate positive engagement between the hopper 36 and its support, as will be set out below.

The hopper 36 and its associated vibratory means 53 are supported by the support 62 which may be fixedly secured to a flange 63 on the housing of the transducer 54. The support 62 is removably secured to the fixed base 12 of the tablet making machine 10 by the bolts 64.

In the illustrated embodiment, the support 62 comprises a pair of members, namely a fiat plate 66 carried on the bolts 64 by the spacers 68, and an offset arm 70 which is secured to the flange 63 of the housing of the transducer 54.

The housing for the transducer 54 may be vibratorily insulated so that leakage or loss of vibratory energy from the flange 63 to the support 62 can be substantially avoided, as by conventional means.

It is desirable to buttress the hopper 36 against lateral movement without losing an appreciable amount of the vibratory energy delivered to it by the vibratory means 40. This can be accomplished by the pins '72 which connect each of the horns 60 to the flat plate 66 of the support 62. The pins 72 are preferably thin resilient members which are dimensioned to be out of resonance with the operating frequency of the vibratory means 53. The pins 72 will therefore serve as vibratory insulators and will not deliver appreciable amounts of vibratory energy from the horns 60 to the hat plate 66. In this manner a high elliciency of delivery of vibratory energy from the vibratory means 53 to the hopper 36 may be achieved while at the same time providing secure support for the hopper 36.

In order to facilitate replacement of the pins 72, such pins 72 may be received within sockets, and held in place by set screws.

While but a single vibratory means 53 is shown secured to the bottom hopper 36 it is to be understood that a plurality of such vibratory means 53 may be utilized.

The scrape-off designated generally as 74 is spaced from the rear of feed foot 48. The scrape-off 74 includes the scrape-off blade 76 which is supported on the bracket 78, which bracket 78 is fixedly secured to the post 80 carried by the base 12. While the scrape-off blade 76 is restrained from lateral motion in respect to the bracket 78 by the bolts 82 thereof which pass through oversize openings in the bracket 78, it is free to move vertically in respect to the bracket 78, and is spring urged downwardly by the leaf spring 84. Thus, the leaf spring 84 is fixed at its outer end to the post 80, and its inner end engages the top surface of the scrape-off blade 76. This insures that the scrape-off blade 76 rides on the uppermost surface of the die table 22.

As seen particularly in FIGURE 2, the scrape-off blade 76 is angularly disposed to the radii of the circle forming the die table 22, and moreover its innermost end 86 is spaced from the shoulder 88 of the die table 22.

The knock-off 30 is provided with a blade 90 which extends angularly from closely adjacent the shoulder 88 of the die table 22 to a point closely adjacent the mouth 49 of the feed foot 48 as seen in FIGURE 2.

From the relationship between the scrape-off blade 76 to the blade 90 of the knock-01f 39 it will be seen that powder which escapes from the feed foot 48 by passing under its undermost edge will be carried by the die table 22 to the scrape-01f blade 76 where it will be deflected to closely adjacent the shoulder 88 of the die table 22. Such powder may during the course of the rotation of the die table 22 spread out a bit, but notwithstanding the same, it will be deflected by the blade 90. of the knock-off 30 so that it is fed into the mouth 49 of the feed foot 48. In this fashion, powder may be fed onto the die table 22 and thence into the mouth 49 of the feed foot 48.

The operation of the embodiment shown in FIGURES 1 to 4 is as follows:

Powder material may be charged to the tablet making machine 10 through the feed unit 32. Such powder material may be successfully charged using the tablet making machine invention of the present invention notwithstanding that such material is normally considered nonfreely-flowable. In addition, powder materials, which are prone to entrain air, and therefore which normally do not form satisfactory tablets, may be debulked of entrained air so as to produce satisfactory tablets. Alternatively, normally freely-flowable powder material may be fed to the tablet making machine It) at a higher rate than could heretofore be effected so that such tablet making machine may be operated at higher tabletting speeds than heretofore.

The provision of the vibratory means 40 as well as the vibratory means 53 enables vibratory energy to be delivered to the powder passing through the

hoppers

34 and 36 into the feed foot 48 throughout substantially the entire height of such column of descending powdered material.

The ring-shaped gap 38 intermediate the hopper 34 and the hopper 36 permits entrained air from the bottom port-ion of the descending colmn of powdered material flowing through the feed unit 32 to be vented to the atmosphere, and prevents such air which is released from the powdered material by the vibration thereof from interfering with the facile flow of the powdered material down the

hoppers

34 and 36. The release of such entrained air effects debulking. Furthermore the vibration of the feed unit 32 including the feed foot 48, as aforesaid, prevents adherence of powdersto the feed unit 32 including the feed foot 48.

From the feed foot 48 the powdered material is charged to the dies 24 which come into registry with the feed foot 48, following which the powdered material is tabletted by the conventional operation of the upper punches 13 and the lower punches (not shown) upon the powdered material received within the dies 24. The confined volume of the feed foot 48, which may be adjusted as explained above, coupled with the movement of the die table 22 insures the desired degree of pressurization of the powdered material just prior to the charging thereof into the dies 24, and thereby facilitates satisfactory volumetric delivery of the powder material to the dies 24 from the feed unit 32.

The embodiment of the tablet making machine 100 of the present invention shown in FIGURE generally resembles the tablet making machine shown in FIGURES 1 through 4 except that in place of a pair of

hoppers

34 and 36 separated by a ring-shaped gap 38, there is provided a single hopper 36a having one or more air vent 6 ducts 92. Alternatively, the hopper 36a may be used in conjunction with an upper hopper which may be in spaced relationship to it in precisely the same fashion as the

hoppers

34 and 36 are spaced apart in the embodiment of FIGURES 1 through 4.

The air vent ducts 92 provide for the release of en trapped air and gases from within the powders in the hopper 36a. The machine 10a has special utility for particular fine size powder ranges, where there may be a rela tively disporportiona-te large amount of gas release from the powders in the region of the throat of the hopper 36a.

Except for the provision of the air vent duct 92, the embodiment shown in FIGURE 6 is identical to the embodiment shown in FIGURES 1 through 4, and accordingly no further description thereof is necessary. It is understood, of course, that the a r vent duct 92 is of such design that loss of powder from the descending powder in hopper 36a is prevented.

The embodiment of the tablet making machine 10b of the present invention shown in FIGURE 6 generally resembles the tablet making machine 10 shown in FIGURES 1 through 4 except that the hopper 36 is supported by three triangularly spaced pins, namely the pin 94 in addition to the

pins

72 and 72 which are carried in the horns 60 and 6t}, and the vibratory means 53b is horizontally mounted and is supported on an external support 96 rather than being secured to the plate 66b.

Thus the throat 47b of the hopper 36b is provided with a horn 98 perpendicularly disposed to the horns 6i and 66. Such horn 98 is engaged with the pin 94 which depends from it to the plate 66!). This construction enables a three point support to be achieved independent of'the support provided by the vibratory means 53b.

The vibratory means 53b is horizontally disposed and hence applies vibratory energy to the feed unit comprising the hopper 36b in a plane parallel to the plane of the uppermost surface of the die table 22. In many situations the application of vibratory energy in a plane horizontal to the plane of the die table is the optimum mode for the application of such energy.

The vibratory means 53b is provided with a coupler 5615, which generally resembles the coupler 56 of the tablet making machine lit of FIGURE 1 through 4. Tip 58b which joins the coupler 56b to the hopper 36b is spaced above the horn 98.

The embodiment of the tablet making machine 100 of the present invention shown in FIGURES 7 and 8 generally resembles the tablet making machine lilb shown in FIGURE 6 except that a plurality of vibrating means 530(1), 530(2), and 530(3) are provided on the hopper 360, and the feed foot 480 is provided with its own vibrating means 106.

Thus, the bottom hopper 360 is provided with three vibrating means 530(1), 530(2), and 530(3), which are preferably uniformly spaced about the bottom hopper 360, as at a relative disposition of degrees about such bottom hopper 360. Each of such vibrating means 530(1), 530(2), and 530(3) may be of the identical construction heretofore set forth for the vibrating means 53 of the tablet making machine 10 of FIGURES 1 through 4. By the use of a plurality of vibrating means, a relatively high amount of vibratory energy may be delivered to the bottom hopper 360. Furthermore, the offset spacing of the vibrating means 530(1), 530(2), and 530(3), assures that dead spots will not be present in the bottom hopper 360. While in the illustrated embodiment 100 the vibrating means 530(1), 530(2), and 530(3) are each shown horizontally disposed at a uniform height above the die table 22, it is to be understood that this invention comprehends the use of a plurality of vibrating means spaced at various heights in respect to the feed unit.

Each of the vibrating means 530(1), 530(2), and 530(3), may be separately supported by brackets to external means (not shown), and the vibrating means may provide reinforcement support for the bottom hopper 360.

The feed foot 48c is provided with its own vibrating means 100 which is supported by the bracket 102 secured to the base 12 of the machine 100.

It is desirable in many cases, particularly when there is high pressure packing within the feed foot 480, to introduce vibratory energy directly to the feed foot 480, and preferably in a plane parallel to the upper surface of the die table 22. Thus, notwithstanding the extensive packing of powder within the feed foot 48c it will be freely delivered to the die table 22 when the feed foot 480 is vibrated, particularly when the feed foot 486 is vibrated in the aforesaid horizontal plane.

The vibrating means 100 may generally resemble the various vibrating means which have heretofore been described, such as the vibrating means 40, 53, etc. in terms of structure of its transducer 104, coupler 106, and tip 108. However, since it is necessary for the coupler to traverse an appreciable portion of the machine, it may be desirable to dimension the coupler somewhat longer than the couplers of the other vibrating means. Thus, if the couplers of the vibrating means 53c(1 53c(2), and 535*(3) are each one-half wavelength long, then it may be desirable to have the coupler 106 one wavelength long.

The transducers of each of the vibrating means 53c(1), 530(2), 530(3), and 100 in the machine embodiment 100 should each be operating at the same frequency and in phase with each other so that maximum vibratory energy is delivered to the powder being fed through the bottom hopper 36c into the feed foot 480.

The tablet making machine of the present invention enables powders to be tabletted without the need of either wet granulating, or dry granulating pretreatments. In the case of freely-flowable powders, the same may be fed to the tablet making machine at a higher rate than could heretofore be etfected. In the case of powders which form tablets that are subject to capping, namely splitting into layers after the tablet is ejected from the die, the same may be eliminated as a problem if the capping is due to the entrapment of air within the powder.

A wide variety of modifications may be made in the tablet making machine of the present invention, which are to be comprehended within the appended claims. For example, the present invention comprehends tablet making machines having means for varying the internal chamber wtihin the feed foot 43 as has been described, other means for varying the internal chamber of the feed foot, and also includes the use of a feed foot having a uniform internal cross-section. Furthermore, the present invention comprehends the use of a feed foot which is closed at both ends, as well as the feed foot shown in the drawings which lacks a vertical wall at its upstream end or mouth 49.

A wide variety of means may be used to eifect vibration of the feed unit, and to magnify and to isolate such vibration.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. In a tablet making machine for forming tablets comprising a rotatable die table having a plurality of circumferentially spaced dies, a feed means having an inventory of pressurized powder for providing a positive assurance of uniform volumetric loading of said dies, said feed means comprising a generally domeshaped floorless feed foot contiguous to the upper surface of said die table, said feed foot having a longitudinal axis lying in a plane substantially parallel to the plane of said dies, a hopper means connected to said feed foot for delivering powder thereto, said feed foot extending from said hopper means in the direction of rotation of said die table with said feed foot extending over a plurality of dies.

2. In a tablet making machine for forming tablets comprising a rotatable die table having a plurality of circumferentially spaced dies, a feed means for providing a positive assurance of uniform volumetric loading of said dies, said feed means comprising a generally domeshaped fioorless feed foot contiguous to the upper surface of the die table, said feed foot being in communication with a throat of a hopper, said feed foot extending from said throat along said die table over said dies in the direction of rotation of said die table, said feed foot including means for selectively varying at least a portion of its internal cross-section, and a vibrating means operatively disposed for vibrating said feed foot.

3. in a tablet making machine for forming tablets comprising a rotatable die table having a plurality of circumferentially spaced dies, a feed means for providing a positive assurance of uniform volumetric loading of said dies, said feed means comprising a generally dome-shaped fiooriess fecd foot contiguous to the upper surface of the die table, said feed foot being in communication with a throat of a hopper, said feed foot being provided with an open month which lacks a vertical wall at its up stream end, said feed foot extending from said throat along said die table over said dies in the direction of rotation of said die table, and a vibrating means operatively disposed for vibrating said feed foot.

4. A tablet making machine in accordance with claim 3 which includes means for directing powder toward the open mouth of the feed foot.

5. In a tablet making machine for forming tablets comprising a rotatable die table having a plurality of circumferentially spaced dies, a feed means for providing a positive assurance of uniform volumetric loading of said dies, said feed means comprising a generally dome-shaped floorless feed foot contiguous to the upper surface of said die table and extending over a plurality of dies in the direction of rotation of said die table, the upstream end of said feed foot being open and the downstream end of said feed foot being closed, with said feed foot being in communication with the throat of a hopper remote from its downstream end.

6. In a tablet making machine for forming tablets comprising a rotatable die table having a plurality of circumferentially spaced dies, a feed means for providing a positive assurance of uniform volumetric loading of said dies, said feed means comprising a generally dome-shaped fioorless feed foot contiguous to the upper surface of said die table and extending over a plurality of dies in the direction of rotation of said die table, the downstream end of said feed foot being closed, with said feed foot being in communication with the throat of a hopper remote from the feed foots downstream end.

7. A tablet making machine in accordance with claim 6 including vibrating means for vibrating said feed means.

References Cited in the file of this patent UNITED STATES PATENTS 785,802 Bacldey Mar. 21, 1905 2,260,456 Johnson Oct. 28, 1941 2,541,899 Wellrnan Feb. 13, 1951 2,555,638 Flam June 5, 1951 2,846,723 Frank Aug. 12, 1958 2,944,493 Bailey et al. July 12, 1960 FOREIGN PATENTS 69,829 Netherlands Nov. 15, 1951