US3566806A - Rotary tabletting machines - Google Patents

Abstract

In a rotary tabletting machine, the annular space occurring between the die table and the usual flange thereabove is enclosed as a material feed chamber for containing material to be tabletted, so that such material moves continuously with the die table and is involved in the minimum of directional change for filling the dies.

Description

United States Patent Inventors Eric Forster;

Ernest Frederick Sumner, Liverpool, England App]. No. 844,525 Filed July 24, 1969 Patented Mar. 2, 1971 Assignee Manesty Machines Limited Liverpool, England Priority July 25, 1968 Great Britain 35505/68 ROTARY TABLE'l'llNG MACHINES 7 Claims, 5 Drawing Figs.

Int. Cl 83% 11/02 Field oiSearch 107/17, l6, 15; 18/ 16.5

References Cited UNITED STATES PATENTS 1,289,570 12/1918 Stokes 107/17 3,029,470 4/1962 Frank 107/ 1 7X 3,460,487 8/ 1969 Kibbe l07/ l 7 Primary Examiner-Price C. Faw, Jr. Attorneys-Kenwood Ross and Chester E. Flavin ABSTRACT: In a rotary tabletting machine, the annular space occurring between the die table and the usual flange thereabove is enclosed as a material feed chamber for containing material to be tabletted, so that such material moves continuously with the die table and is involved in the minimum of directional change for filling the dies.

PATENTED m 2|s7| SHEET 1 OF 3 \I M I INVENTORS ERIC FORSTER ERNEST F. SUMNER ATTORNEYS PATENTEBMR m SHEET 3 OF 3 INVENTORS ERIC FORSTER ERNEST F. SUMNER ATTORNEYS.

ROTARY TABLETTWG MACHINES This invention concerns rotary tabletting machines of the type (hereinafter referred to as of the type-described comprising a turret rotatable about a vertical axis and shaped to provide a horizontal circular die table having a plurality of dies arranged in a circle therearound with a lower punch projecting upwards into each said die from below, and to provide a flange about the die table in which flange are slidably located upper punches aligned with respective ones of the dies, the punches being adapted, upon rotation of the turret, to move relative the dies to compress particulate, granular or like material therein into tablets, and then to eject the tablets.

In the known constructions of such machines, the material to be tabletted is usually supplied to the dies by means of one or more stationary filling shoes which rest on the die table and under which the successive dies pass upon rotation of the turret, openings being provided in the bottom of the or each shoe for the material to fall through into the dies.

Proposals have been made for rotors, agitators or the like to be provided in the feed shoes to ensure mobility of the material and to contribute to proper filling of the dies, but practical experience shows that the known stationary material feeding arrangements are generally only satisfactory for slow speed machines and that increase of the rotational speed of the turret is accompanied by incorrect or insufficient filling of the dies and consequently unsatisfactory or inconsistent tabletting occurs.

We believe that this unsatisfactory operation arises at least partly from the fact that the dies sweep beneath the material in the filling shoe whilst such material is stationary or effectively stationary, and each die is in register with the shoe for only a short period of time insufficient for the material both to achieve the rotational movement of the table and, under the influence of gravity, to flow rapidly down into the die. The present invention is based upon the appreciation that better and more satisfactory die fillingcan be achieved if the materia] is able to move continuously with the die table in its rotation in a horizontal plane, so that upon entering into the dies there is a minimum of change of direction of the movement of the material.

With this object in view, the present invention provides a rotary tabletting machine, of the type described, characterized in that the annular space occurring between the die table and the flange thereabove is enclosedas .a material feed chamber for occupation by material to be tabletted, which material can move with the die table, a deflector being provided within said chamber to cause at least some of the material in the chamber to follow a path above the dies in the die table, in the region of a die filling sector of the table.

Conveniently, the said annular space is enclosed by a circular wall provided at top and bottom with resiliently-loaded sealing strips engaging with the upper surface of the table and the under surface of the flange.

The circular wall is conveniently composed of arcuate sections.

In a preferred embodiment, the machine is a two-station machine wherein each die has a tablet formed therein during each successive half-revolution of the table, and each section of the wall is approximately semicircular and mounted upon a respective stationary part of the machine by a respective mounting.

Each such mounting is preferably adjacent a respective die filling sector of the table, and is conveniently in the form of a hollow feed block whereby material for tabletting can be introduced into the feed chamber in the regions of the filling sectors.

The arrangement of the invention preferably also includes, above the table at the or each filling sector, a downwardly inclined deflector the function of which is to tend to deflect tabletting material into the dies as the latter pass through the filling sector.

In order that the invention may be fully understood, it will be described further, by way of example, with reference to the accompanying drawings which illustrate a preferred embodiment of the machine in the form of a two-station machine.

In the drawings:

FIG. l is a cross-sectional elevation of the entire machine;

FIG. 2 is an enlarged fragmentary detail of part of the machine of PEG. 1',

FIG. 3 is a fragmentary sectional plan corresponding to FIG. 2, the position of the section having been indicated by the lines IIIIII in FIGS. I and 2;

FIG. 4 is a fragmentary section, as indicated by the line IV-IV of FIG. 3, to a more enlarged scale, showing further details of the machine; and

FIG. 5 is a detached elevation showing part of FIG. 4 when viewed as indicated by the arrow V.

The illustrated machine, in general overall constructions, resembles known two-station rotary tabletting machines in that it comprises a supporting framework 10 wherein is journaled a vertical turret shaft 11 on which a turret 112 is secured, an appropriate drive motor 13 being provided for driving the turret 12, by way of a drive belt 14, pulley l5, worm shaft 16, worm wheel 17, drive shaft 18 and drive pinion 19 which meshes with a gear ring 20 set into an annular recess in the underside of the turret 12, and thereby rotating the turret 12 about a vertical axis.

The turret I2 is shaped to provide a substantially horizontal circular die table 21 having an array of die holes 22 vertically therethrough, these die holes 22 being arranged on a circle around the rotational axis of the turret 12 (see FIG. 3) and each accommodating a respective tabletting die 23 which is in the form of a hard metal sleeve of short axial length. A respective lower punch 24 projects upwards from below the die table 21 into each of the dies 23, such punches 24 being accommodated for vertical sliding movement in respective holes in an annular skirt 25 of the turret 12.

The turret i2 is also shaped to provide, above the die table 2i, a flange 26 which overhangs the circle of dies 23 and has therethrough upper punch holes each of which accommodates a respective upper punch 27 which is axially aligned with a respective one of the dies 23.

Cam tracks 28 and 29 are provided for engagement by enlargements or protrusions 30 and 31 on the lower ends of the lower punches 24 and on the upper ends of the upper punches 27, for causing axial up and down movement thereof and effecting the necessary punch movements associated with tabletting operations and at each of two diametrically opposed positions (which correspond to two tabletting stations of the machine) there are upper and lower pressure rolls 32,33 between which the corresponding pairs of punches 27 and 24 pass so that endwise pressure is applied to the successive pairs of punches 27,24 to apply tabletting pressure to tabletting material in the corresponding die 23.

The parts as so far described are comparable with prior known machines. The machine of the invention differs from the known machines, however, in the means provided for supplying tabletting material to the dies 23.

With the turret construction as above discussed, there is, naturally, an annular gap 34 occurring in the turret l2 between the undersurface of the flange 26 and the upper surface of the die table 2ll. In the machine of the invention, this gap or space 34 is employed as a tabletting material feed chamber, and this is achieved by enclosing the space concerned, making provision for feeding tabletting material thereto, and making provision for ensuring that at least part of any material in such space 34, upon rotation of the die table 21, is constrained to move over the dies 23 for filling the latter.

To achieve this, two feed chamber wall sections (of which one is illustrated in its entirety and is indicated generally by reference numeral 35 in FIG. 3) are provided, and since these sections are substantially identical one thereof needs to be described in detail. The wall section 35 comprises two side- byside metal strips 36 and 37 of width just less than the vertical spacing between the die table 21 and the flange 26, which strips are curved to approximately semicircular form so that each resembles one-half of a cylinder of short axial length. The radii of curvature of the strips are somewhat less than the radius of the circle in which the dies 23 are arranged around the die table 21.

The two side-by- side strips 36 and 37 are rigidly secured to one another, at appropriate intervals, by rivets 38 with the result that the wall section 35 may be regarded as being l-I- shaped in cross section, providing narrow upper and lower channels each of which accommodates a respective nylon scraper blade 41,42. A sinuous spring 43, accommodated between the strips 36,37 and abutting against the confronting edges of the blades 41 and 42, serves to load such blades 41,42 so as to protrude from their respective channels in the wall section 35. As can be seen from FIG. 3, the blades 41,42 may be composed of a plurality of sections.

The wall section 35, is secured, by way of the strip 36, to a curved open side 44 of a saddle-shaped hollow feed block 45 the general shape of which can best be seen from FIG. 3. This feed block 45 is flat on its underside for mounting on a mounting plate 46 in turn mounted upon a respective appropriate support column 47 provided on the frame of the machine and to project a short distance over the die table 21, as can be seen from FIGS. 1 and 3, so that the curved side 44 of the feed block 45 follows, but just lies inside the path of movement of the dies 23 therepast. As already mentioned, the feed block 45 is hollow; it has an inlet connection 48 joining with its top and an outlet opening 49 in its bottom, such outlet opening 49 being generally of arcuate form and overlying a number of the dies 23 in the die table 21 as can be seen in FIG. 3.

The lower scraper blade 42 and the lower parts of the strips 36,37 are relieved or gapped in register with the outlet opening 49, as indicated at 50 in FIG. 1, to permit material to flow from the interior of the feed block 45, through the open side 44 thereof and the gap 50, into the annular gap 34 which forms the feed chamber of the machine. Secured within the feed block 45, by screws 51 is an inclined deflector plate 52 which projects through the gap 50 into the feed chamber 34 and is formed therein with a lead-in tongue 53, the edge 56 of such plate 52 remote from the tongue 53 being close to the upper surface of the die table 21.

The two wall sections 35, of which one has just been described, are appropriately mounted by their feed blocks 45 being secured on their mounting plate 46, which are at diametrically opposed positions, relative to the turret 12, so that the feed blocks 45 are in advance of their corresponding pressure roll pairs 32,33, and the upper and lower edges of the wall sections 35 seal respectively with the lower surface of the flange 26 and the upper surface of the die table 21 by their scraper blades 41,42. Each of the wall sections 35, together with its feed block 45, extends around one-half of the turret 12. A finished tablet deflector 54- is provided on one side of each feed block 45, and these are associated with respective tablet takeoff chutes 55 the positions of which are indicated diagrammatically in FIG, 1.

Each feed block 45 has a funnellike hopper 56a secured to its inlet connection 48 and material (not shown) to be tabletted is supplied to the feed chamber 34 between the flange 26 and the die table 21 by being filled into the hopper 56a to fall into the interior of the feed block 45 and pass through the curved open side 44 thereof. Material present in the block 45 can also rest on the die table 21 by way of the outlet opening 49.

Assuming the hoppers 56a to have been filled with tabletting material and the turret 21 being driven, material from the hopper 56a and falling onto the die table 21 both above the dies 23 and in the feed chamber 34 is entrained by the die table 21 and with continued running of the machine the feed chamber 34 becomes substantially full of tabletting material which is largely constrained to move with the table 21, so that the tabletting material, once it has entered the feed chamber 34 may be regarded as having no substantial relative movement in relation to the die table 21 so far as the rotation of the latter in a horizontal plane is concerned,

For understanding the actual operation of the machine, it is most convenient to consider one only of the dies 23 during a complete revolution of the turret 12, the other dies 23 following successively and correspondingly.

At the commencement of the entire tabletting cycle, the upper punch 27 is raised clear of the die 23 and the lower punch 24 is raised to a position wherein its top face is just flush with the top surface of the die table 21, this position of the lower punch 24 being necessary for the removal of a previously formed tablet. As the turret 12 rotates, the die 23 moves towards a first die filling sector of the table 21, which sector corresponds to the outlet opening 49 in a first one of the feed I blocks 45 and during this movement the upper punch 27 is retained in its raised disposition, whilst the lower punch 24 effects slight downward movement. As it approaches the filling sector of the first feed block 45, the die 23 moves beneath the deflector plate 52 thereof and with continued movement the deflector plate 52 and the tongue 53 thereof deflect tabletting material carried on the die table 21 firstly radially outwards of the die table 21 the path of the die 23 and then down into the die 23, at the same time as the lower punch 24 is moved downwards to encourage the die 23 to fill. The die 23 accordingly passes the lower edge 56 of the deflector plate 52 at least partially filled with tabletting material, and now moves past the bottom of the inlet connection 48 where the latter connects with the feed block 45. At this position, the space above the die 23 is partly unoccupied by tabletting material by reason of the die 23 having been partially filled, and fresh tabletting material can enter the feed block 45 through the inlet connection 48 to flow into the die 23 as it passes and/or to cause movement of material already in the feed block 45 into the die 23 to fill the latter, the lower punch 24 by now being fully lowered.

With continued movement of the die 23, and whilst still in the region of the feed block 45, the lower punch 24 now moves upwards slightly to reduce the filled volume of the die 23, thereby effecting so-called weight-adjustment by ejecting upwards out of the die 23 any tabletting material exceeding a predetermined amount. The die 23 now passes towards the respective end of the first feed block 45 adjacent which scrapers 57 and 58 project inwardly over the die table 21 to sweep inwards of the die table 21 any (jected or other tabletting material overlying the die 23 or disposed between the die 23 and the outer edge ofthe die table 21.

The die 23 then passes under a tail plate 59 which projects from the respective end of the feed block 45, and the upper punch 27 commences moving downwards. As the die 23 (which is now disposed, relative to the die table 21, outside the feed chamber 34) emerges from under the tail plate 59, the upper punch enters the die 23 from above and slight initial pressure is applied to the tabletting material from above and below, by way of the two punches 24,27 under the influence of their cam tracks 28,29. With continued rotation of the turret 12, the two punches 24,27 now move between the pressure rolls 33,32 whereat considerable endwise pressure is applied to the punches 24,27 to tend to move them towards each other and compress the material in the die 23 into a coherent tablet 60 (FIG. 4).

This having been done, the upper punch 27 is raised by continued movement of the turret 12, until it is back at the position occupied at the beginning of the cycle and the lower punch 24 is similarly raised to bring the tablet 60 to an ejection position as shown in FIG. 4 wherein its lowermost surface is flush with or just above the upper surface of the die table 21.

The die 23 and tablet 60 are now moving towards the feed block 45 of the second station of the machine, the table 2t having performed half a revolution, for the commencement of a second tabletting cycle which is identical with that just described during the second half of the complete revolution of the turret. As the die 23 approaches the second feed block 4-5 'deflector plate 52 of the second feed block 45 at the commencement of the second tabletting cycle.

We have found that with such an arrangement, it is possible to increase the speed of the tabletting machine, as compared with the running speeds of prior known comparable rotary tabletting machines, as much as two fold, whilst still achieving satisfactory reliable and consistenttabletting and without experiencing the deficiency in die-filling which has been encountered when attempts have been made materially to increase the running speeds of the prior known machines having shoelike or similar feeders. We attribute this achievement to the fact that the arrangement of the invention provides for substantially all, or at least a large proportion, of the tabletting material present in the feed chamber 34 and available for filling the dies 23 to be constrained to move with the die table 21 as compared with the known stationary feed arrangements wherein the tabletting material is effectively initially stationary relative to the die table and has to catch up with the speed of rotation of the die table at the same time as falling into the dies, for filling the latter.

The invention is not confined to the precise details of the foregoing example and variations may be made thereto. For instance, if desired, radial vanes or the like may be provided in the feed chamber (e.g. projecting outwardly from a ring surrounding the hub or center of the turret) to ensure that the tabletting material is positively caused to follow the rotation of the die table rather than reliance being placed upon the fric- 1. A rotary tabletting machine comprising a turret rotatable about a vertical axis shaped to provide-a horizontal circular die table above which is a flange, said flange and said die' table defining between them an annular space around said turret, a plurality of dies arranged in a circle around said horizontal die with each of said dies, wall means enclosing said annular space as a material feed chamber for occupation by material to be tabletted, whereby said material will move with said die table upon rotation of said turret, deflector means in said material feed chamber to cause at least some of tabletting material therein to follow a path over the dies in said die table, in the region of a die filling sector of said table, actuating means constraining said upper and lower punches to move relative to said dies so as to cause each said upper punch to be raised clear. of its said die upon its said die approaching said filling sector, to cause each said lower punch to be lowered as its said die moves in said filling sector for tabletting material to fill into said die, to bring said upper punch down into its said die upon the latter moving out of said filling sector, to apply endwise pressure to said upper and lower punches to compress said material in said die to form a tablet, to raise said upper punch and said lower punch to eject said tablet from said die.

2. A machine as set forth in claim 1 wherein said wall means comprises a circular wall provided at top and bottom with resiliently loaded sealing strips engaging respectively with the upper surface of said die table and the lower surface of said flange.

3. A machine as set forth in claim 2 wherein said circular wall is composed of a plurality of arcuate wall sections.

4. A machine asset forth in claim 3 which is a two-station machine wherein each said die has a tablet formed therein during each successive half-revolution of said die table, characterized in that each said arcuate wall section is semicircular.

5. A machine as set forth in claim 4 further including, for each said wall section, a mounting located at the respective said filling sector,

6. A machine as set forth in claim 5 wherein each said mounting comprises a hollow feed block, supply means, whereby tabletting material may be supplied to said feed block, being connected to said feed block.

7. A machine as claimed in claim 6 further including, con nected to said feed block, a downwardly-inclined deflector disposed to deflect material, in said feed block downwards table, a lower punch projecting upwards into each of said dies, into said dies as P through Said filling Sectoran upper punch slidably located in said flange in alignment

Claims (7)

1. A rotary tabletting machine comprising a turret rotatable about a vertical axis shaped to provide a horizontal circular die table above which is a flange, said flange and said die table defining between them an annular space around said turret, a plurality of dies arranged in a circle around said horizontal die table, a lower punch projecting upwards into each of said dies, an upper punch slidably located in said flange in alignment with each of said dies, wall means enclosing said annular space as a materiaL feed chamber for occupation by material to be tabletted, whereby said material will move with said die table upon rotation of said turret, deflector means in said material feed chamber to cause at least some of tabletting material therein to follow a path over the dies in said die table, in the region of a die filling sector of said table, actuating means constraining said upper and lower punches to move relative to said dies so as to cause each said upper punch to be raised clear of its said die upon its said die approaching said filling sector, to cause each said lower punch to be lowered as its said die moves in said filling sector for tabletting material to fill into said die, to bring said upper punch down into its said die upon the latter moving out of said filling sector, to apply endwise pressure to said upper and lower punches to compress said material in said die to form a tablet, to raise said upper punch and said lower punch to eject said tablet from said die.

2. A machine as set forth in claim 1 wherein said wall means comprises a circular wall provided at top and bottom with resiliently loaded sealing strips engaging respectively with the upper surface of said die table and the lower surface of said flange.

3. A machine as set forth in claim 2 wherein said circular wall is composed of a plurality of arcuate wall sections.

4. A machine as set forth in claim 3 which is a two-station machine wherein each said die has a tablet formed therein during each successive half-revolution of said die table, characterized in that each said arcuate wall section is semicircular.

5. A machine as set forth in claim 4 further including, for each said wall section, a mounting located at the respective said filling sector.

6. A machine as set forth in claim 5 wherein each said mounting comprises a hollow feed block, supply means, whereby tabletting material may be supplied to said feed block, being connected to said feed block.

7. A machine as claimed in claim 6 further including, connected to said feed block, a downwardly-inclined deflector disposed to deflect material, in said feed block downwards into said dies as they pass through said filling sector.

Images