Abstract of
GB957869
957,869. Tablet presses. PROCTER & GAMBLE Ltd. Dec. 29, 1960 [Dec. 31, 1959], No. 44668/60. Heading B5A. A press for making tablets e.g. detergent tablets, comprises a drum 17 rotatably mounted in a frame with its axis horizontal, and having a plurality of radially extending bores 34, each with a piston 35 located so as to leave a die cavity 83 in the drum, a hopper 82 to fill the die cavities, and a plurality of outer dies 89 mounted to close the die cavities during compression of the material therein, the pressure being applied by outward movement of the pistons 35 caused by engagement of cam rollers 42 on a stationary central cam 46, the pistons and outer dies being rotated slightly, about the axes of the bores 34, during and after compression to free the moulded tablet. The drum of Fig. 4 is rotated in a clockwise direction on a hollow shaft 14, and starting from position A the end of the piston 35, which is fitted with a die 36, is held below the outer surface 29 of the drum 17 by a return cam roller fitted in an inward extension (not shown) of the piston and engaging on the inside of a cam 53 and a cam link 54. The die cavity 83 is filled with powdered material G as it passes under the hopper 82, a wall 85 preventing escape of material which works back under the wall 84. The piston is raised slightly as it passes under a wall 85a of the hopper by engagement of the roller 42 with a slidable cam piece 58, to level off the charge in the die cavity. The cam piece 58 is adjustable vertically to control the size of the die cavity 83 by rotation of a hand wheel (not shown) fixed to the end of a shaft 72, which causes rotation of a screw threaded sleeve on the inside of a gear-wheel 74 through a worm 71, which in turn'moves a shaft 76 up or down. The return cam roller then engages a cam 59 which retracts the piston 35 slightly and excess material is removed by a suction pipe (not shown). A plurality of outer dies 89 are mounted on roller chains 90, passing round sprockets (not shown), the path of the chains being shown in Fig. 4. An outer die engages with each die cavity 83 and is held in contact therewith by engagement of rollers 98 with a fixed plate 101. The material in the die cavity 83 is compressed, as the cavity passes between positions B and C of Fig. 4, by radial outward movement of the piston 35 on the cam 46. The compression pressure may be adjusted by rotation of a hand wheel (not shown) attached to the end of a shaft 64, causing rotation of a threaded shaft 67, through a worm 63 and a gear-wheel 66, which moves the part 48 of the cam 46 about a pin 49. The tablet T is ejected on to a conveyer (not shown) by a hump on the cam 46 at the position D of Fig. 4. Just before reaching position C of Fig. 4 the piston 35 is rotated slightly about its axis by engagement of a shaft 45 fitted at its lower end (Fig. 6) with a cam 111 on the shaft 14. The piston is returned to its original position by a cam 113, just after passing the position C of Fig. 4. The outer dies 89 are rotatable in their carriages, rotation being effected by cams (not shown) fixed to the plate 101, at the same time as but in the opposite direction to the rotation of the pistons 35 (Figs. 7 and 8, not shown). The roller chains 90 are driven by sprockets fitted on each side of the drum 17 (Fig. 1, not shown). Specification 957,868 is referred to.
in which means are provided so that each tablet, after having been formed as described, is discharged from the die cavity in which it was formed, by radial outward movement of the corresponding piston caused by the control cam, such radial outward movement taking place while the die cavity is uncovered by an outer die.
3 A tablet press according to Claim 1 or 2 comprising means for adjusting the distance along which the pistons move in the radial bores.
4 A tablet press according to Claim 3 in which the central cam is adjustable to vary said distance.
A tablet press according to any of the preceding claims in which a hopper is provided from which the die cavities are filled with particulate material by gravity.
6 A tablet press according to any of the preceding claims comprising means for rotating each piston after said piston has compressed particulate material to form a tablet and before said piston has discharged the tablet from the corresponding die cavity.
7 A tablet press according to any of the preceding claims in which means are provided for varying the volumes of the die cavities.
8 A tablet press substantially as hereinbefore described with reference to the drawings.
For the Applicants, CARPMAELS & RANSFORD, Chartered Patent Agents, 24 Southampton Buildings, Chancery Lane, London, W C 2.
The rotating member 115 is reset by the stationary cam 118 attached to the support plate 101 Thus, as the outer die approaches the point of maximum compression at position C, rotation in a direction opposite to the rotation of its co-operating piston 35 is initiated until the point of maximum compression is reached The die is then reset for the next rotative cycle and the outer die 89 is withdrawn from the die cavity 83 so that the ejection of the finished tablet can commence as the piston 35 moves to position D.
As heretofore described, the tablet press has a single row of pistons 35 and a single central cam 46 It is possible to increase the capacity of the press by a multiple of any number greater than one merely by providing two or more circular banks of pistons 35 in the drum 17 and by providing an equal number of central cams 46 and flights of outer dies 89.
WHAT WE CLAIM IS: 1 A tablet press comprising a frame, a drum rotatable on said frame and having a plurality of radial bores, a piston slidable in each of said bores, a stationary central cam controlling the movement of the pistons along said bores as the drum rotates, the outer end of each of said pistons being spaced inwardly from the drum periphery so that the outer portion of each of said bores forms a die cavity, a plurality of outer dies mounted for synchronous movement with said cavities so that each cavity is covered by an outer die during part of the rotation of the drum, means for filling said die cavity with particulate material prior to the covering of said cavity by said outer die so that said particulate material is compressed into a tablet by the radial outward movement of said piston caused by the control cam, such radial outward movement taking place in the case of each piston while the corresponding die cavity is covered by an Abingdon: Printed for Her Majesty's Stationery Office, by Burgess & Son (Abingdon), Ltd -1964.
Published at The Patent Office, 25 Southampton Buildings, London, W C 2, from which copies may be obtained.
957,869
Description
PATENT SPECIFICATION 9
DRAWINGS ATTACHED.
Date of Application and filing Complete Specification:
Dec 29, 1960 No 44668/60.
Application made in United States of America (No 2088) _ A d bon Dec31, 1959.
/w/ sy Complete Specification Published: May 13, 1964.
Crown Copyright 1964.
Index at Acceptance:-B 5 A(l Bl AI, 2 Dl X).
International Classification: -B 29 d.
COMPLETE SPECIFICATION.
Tablet Press.
We, PROCTOR AND GAMBLE LIMITED, a British Company, of Hedley House, Gosforth, Newcastle upon Tyne 3, (formerly Thomas Hedley & Co Limited, of Phoenix Buildings, Collingswood Street, Newcastle upon Tyne, 1, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-
This invention relates to presses and, more particularly, to a press for manufacturing tablets from powdery and/or granular materials at comparatively low compression pressures.
Several different types of tablet press are used for briquetting coal and for making medicinal tablets However, most prior art presses for these purposes are designed to operate at high compression pressures, which may be twenty thousand pounds per square inch or more, and therefore they are difficult to operate efficiently when compressing powdery or granular materials at substantially lower compression pressures.
Presses designed specifically for making medicinal tablets are usually limited to making small tablets, less than one-half inch in diameter, and are difficult, if not impossible, to adapt properly and economically to the manufacture of substantially larger tablets.
A need for the present invention arose when a press was sought for making detergent tablets of the character described in our Application No 44667/60 (Serial No.
957,868) Such presses are not available commercially, and it was soon discovered that present day commercial equipment is not economically suited for conversion to this task The manufacture of detergent tablets is usually carried out at pressures of lPrice 4 s 6 d l 3,000 pounds per square inch or less and the preferred size of the tablets is about 2 " in diameter and about 1 " in thickness.
To meet these requirements efficiently and economically, it became apparent that a new type of press had to be devised.
It is to be understood, of course, that the invention as herein described is limited neither to the production of detergent tablets nor to the making of tablets of the specific size and at the pressure heretofore indicated These conditions are merely exemplary and indicate the preferred conditions of manufacture They are mentioned to give a better understanding of the problem solved by the invention.
The prime object of this invention is the provision of a press to produce tablets by compressing powdery and/or granular materials, e g detergents, into a unified mass at relatively low pressures in the range up to three thousand pounds per square inch.
Another object of this invention is the provision of a tablet press of the character described which can be adjusted to vary the size of tablets being produced or to control the pressure at which the tablets are compressed.
Another object of this invention is the provision of a tablet press in which means are provided to prevent sticking and caking of the granular or powdery material to the dies and die cavities.
Another object of this invention is to provide a tablet press with high production rates without unduly increasing the physical size of the press or the floor space needed to mount the press.
According to the invention, there is provided a tablet press comprising a frame, a drum rotatable on said frame and having a plurality of radial bores, a piston slidable in each of said bores, a stationary central C C p 57,869 cam controlling the movement of the pistons along said bores as the drum rotates, the outer end of each of said pistons being spaced inwardly from the drum periphery so that the outer portion of each of said bores forms a die cavity, a plurality of outer dies mounted for synchronous movement with said cavities so that each cavity is covered by an outer die during part of the rotation of the drum, means for filling said die cavity with particulate material prior to the covering of said cavity by said outer die so that said particulate material is compressed into a tablet by the radial outward movement of said piston caused by the control cam, such radial outward movement taking place in the case of each piston while the corresponding die cavity is covered by an outer die, and means for rotating each of said pistons and/ or the outer die co-operating therewith relatively to each other as they compress the particulate material, said rotation taking place about the direction of compression.
Briefly stated, in accordance with one embodiment of the invention, the tablet press is composed of a rotating drum with a substantially horizontal axis mounted on a suitable frame and having a plurality of radially movable pistons therein The ends of the pistons are located inwardly of the outer drum surface in order to provide a plurality of die cavities in the drum periphery A hopper is provided for gravity filling successive die cavities with powdery or granular material as the drum rotates through the upper portion of its cycle A plurality of outer dies are mounted on suitable carriages in order to coact with and close the die cavities through the compression portion of the drum rotative cycle The pistons are moved outwardly to compress the material in the die cavities while the latter are closed by the outer dies The finished tablets are removed at the bottom of the rotative cycle of the drum due to radial outward movement of the pistons after the outer dies have been withdrawn from the die cavities Means are provided for rotating each of the pistons and/or the outer die co-operating therewith relatively to each other to prevent adherence of the tablet material to the pistons, die cavities and outer dies.
N While the Specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings in which:Figure 1 is a side elevation, partially broken away, of the entire tablet press; Figure 2 is a cross-section taken along the line 2-2 of Figure 1 showing one die cavity and the mechanism for rotating the dies; Figure 3 is an end elevation, partially broken away, of the entire tablet press; Figure 4 is a cross-section taken along 70 the line 4-4 of Figure 3 showing the radial pistons at four stations in the compression cycle with relation to the central cam; Figure 5 is an enlarged view of the central cam and the mechanism for adjusting same; 75 Figure 6 is a view taken along the line 6-6 of Figure 2 showing the cams for rotating the radial pistons; Figure 7 is a view taken along the line 7-7 of Figure 2 showing one outer die 80 carriage and the mechanism for rotating the outer die; and Figure 8 is a cross-section of the outer die and carriage taken along the line 8-8 of Figure 7 85 Referring to the drawings and especially to Figures 1-4, the tablet press is shown mounted on a base plate 11 A frame composed of the members 12 and 13 is mounted on the base plate 11 A hollow non-rotating 90 axle 14, extends between the members 12 and 13 and is held in place by the flanged supports 15 and 16.
A rotatable drum, generally indicated at 17, is supported on two bearings 18 (only 95 one shown) which is held in place by the locknut 19 threaded on the axle 14 as at 21 Large sprockets 22 and 23 are attached to either side of the drum 17 and a drive gear 24 is secured to the side of the sprocket 100 23 The drum 17 is rotated by the motive power source 25 through the output shaft 26 and drive pinion 27 which engages the drive gear 24 When the press is in operation, the drum 17 is continuously rotated 105 by the motive power source 25.
A better understanding of the structure of the drum 17 can be obtained by referring to Figure 2 and Figure 4 The drum structure is composed of an inner ring 28, an 110 outer ring 29 and the side plates 30 and 31.
Spaced around the drum are a plurality of radial cylinders 33 having their ends extending through the inner ring 28 and the outer ring 29 Each cylinder 33 is held in 115 place by the member 33 a A radial bore 34 extends through each cylinder 33.
For convenience, Figure 4 illustrates cylinders 33 at four positions in the press cycle, as will hereinafter be explained These 120 positions are marked A, B, C and D In actual practice, a plurality of equally spaced cylinders 33 are preferably used In one design a total of 25 equally spaced cylinders 33 has been employed with very good 125 results.
A piston 35 is slidable in each of the bores 34 Each piston 35 has a die insert 36 at its outer end attached by means of the elongated rod 37 The pistons are slotted 130 957,869 ber 76 engages the sleeve 75 and has its outer end attached to the slidable member 58 Rotation of the hand wheel 73 will result in rotating the sleeve 75 through the worm and worm gear combination This 70 will result in upward or downward movement of the member 58 depending upon the direction in which the hand wheel 73 is rotated.
Referring now again to Figure 4, the 75 granular material G to be compressed is supplied to the hopper 81 (Figures 1 and 3) from where it flows into the tilling chamber 82 which overlies the periphery of the drum 17 at the upper portion of the cycle The 80 granular material G may be in the form of detergent granules where a detergent tablet is to be manufactured The granular material flows by gravity into each successive die cavity 83 as it moves under the 85 chamber 82 The die cavity as defined herein is that portion of the bore 34 immediately beyond the face of the die insert 36 when the piston is retracted as at position B in Figure 4 A baffle 84 is provided at the fill 90 ing chamber 82 so that any granular material flowing under the baffle 84 when the drum 17 has been stopped will be retained by the wall 85 rather than be spilled To provide positive inward movement of the 95 piston 35 to fill each die cavity 83, the return cam roller 43 engages the bottom sur-e face of the return cam 53 as each piston 35 approaches the filling chamber 82 This initiates rodial inward movement of each 100 die 35 relative to the drum 17 The dies 35 are gradually drawn inwardly as they pass under the chamber 82 by the return cam 53 and the cam link 55 until the roller 42 strikes the outer surface of the member 58 105 At that point the piston 35 is moved slightly upwardly so that the lower edge of the wall a levels off the granules in the cavity 83.
As the cavity 83 passes beyond the wall 85 a, the piston 35 is again drawn downwardly by 110 the return cam 59 acting on the roller 43 so that the level of granules in the die cavity 83 is slightly below the outer surface of the drum.
Thus, as the pistons 35 move from posi 115 tion A to position B, the die cavities 83 are filled with granular material It will be appreciated, of course, that the quantity of granules to be compressed can be controlled by upward or downward movement of the 120 member 58 by turning the hand wheel 73.
Any excess granular material spilled on the drum surface is removed by the vacuum manifold 86 which is connected by a tube 87 to a conventional vacuum source The 125 opening in the vacuum manifold 86 is small enough and the vacuum low enough so that none of the granules are drawn out from the die cavities 83.
Means are provided for closing each die 130 as at 38 and a guide 39 rides in the slot 38 to prevent turning of each piston However, the slot 38 is wider than the guide 39 to allow some turning which is desirable as will hereinafter be explained A main cam roller 42 is attached at the inner end of each piston 35 A return cam roller 43 is attached to each piston 35 by the arm 44 A piston rotating member 45 is also attached to each piston.
A central cam is provided for controlling the radial movement of the pistons as they are rotated with the drum as it turns about its axis The central cam 46 is fastened to the axle 14 by means of the flange 47.
As seen in Figure 5, an adjustable cam arm 48 is pivoted at 49 to the cam 46 The other end of the cam arm 48 is retained by the pin 51 projecting through the slot 52 The pin 51 is attached to the central cam 46.
A stationary return cam 53 projects laterally outwardly from the central cam 46 in order to contact the cam roller 43 and urge the pistons 35 radially inwardly as, they enter that portion of the cycle A return cam link 45 is pivoted at 55 to the central cam 46 The other end of the link 54 is slotted at 56 A pivot pin 57 is secured to the vertically slidable member 58 and projects through the slot 56 A movable return cam 59 is attached to the slidable member 58 The pin 61 which is attached to the central cam 46 maintains alignment of the slidable member 58.
A mechanism is provided whereby the position of the cam arm 48 and the slidable member 58 can be adjusted from an external location on the press A bracket 62 is mounted on the internal surface of the axle 14 The bracket 62 supports a worm 63 attached to a shaft 64 which extends through the support 16 A hand wheel 65 (Figures 1 and 3) is attached to the outer end of the shaft 64 The worn 63 engages a worm gear 66 which is slidably keyed to the shaft 67 The outer end of the shaft 67 is threaded at 68 and engages a threaded sleeve 69 which is attached to the axle 14 Thus, by turning the hand wheel 65, the shaft 67 can be moved inwardly or outwardly through the worm and worm gear combination Outward movement of the shaft 67 will, of course, cause the cam arm 48 to pivot outwardly about the pivot 49, and; likewise, inward movement of the shaft 67 will allow the arm 48 to pivot inwardly due to the pressure of cam rollers 42 moving over the arm 48.
A worm 71 is attached to the shaft 72 whbich extends through the flanged support 16 and has a hand wheel 73 (Figures 1 and 3) attached thereto The worm 71 drives a worm gear 74 which is secured to the threaded sleeve 75 which, in turn, is rotatable in the bracket 62 A threaded mem957,869 4 957,869 cavity 83 to permit radial outward movement (relative to the drum 17) of the pistons to compress the granular material A plurality of carriages 88 each having an outer die 89 attached thereto are affixed to a pair of spaced endless roller chains 90 and 91 (see Figures 3 and 7) A plate 89 a (Figure 8) is provided to prevent granular material from entering the clearance between the periphery of the die 89 and the bore in the carriage 88 The roller chain 91 runs over the sprockets 92, 93 and 94 as shown in Figure 1 The sprockets 92, 93 and 94 are fixed on shafts 95, 96 and 97 which are in turn supported by bearings (not shown) mounted in the members 12 and 13 A similar set of sprockets are provided for the roller chain 90 and are also mounted on shafts 95, 96 and 97, of which only the sprocket 92 a is visible in Figure 3 The roller chains 90 and 91 engage the large sprockets 22 and 23 and are driven thereby so that the carriages 88 move in the circuitous path followed by the chains as shown in Figure 1 The carriages 88 are spaced so that each of the outer dies 89 will close successive die cavities 83 by engaging the outer end of the bores 34 as the pistons approach the compression portion of the cycle Each carriage 88 is provided with a pair of rollers 98 which bear against the surface 99 of the support plate 101 The support plate 101 is rigidly attached to the frame between the members 12 and 13.
Thus, as the drum 17 is rotated it drives the chains 90 and 91 and the carriage 88 so that each of the die cavities 83 will be closed during the compression portion of the press cycle.
As the pistons 35 move from position B to position C they are moved radially outwardly (relatively to the drum 17) by the cam arm 48 gradually to compress the granular material until tile point of maximum compression is reached at position C The outward movement of the pistons transforms the granular material into a unified mass or solid because the outer dies 89 are constrained by the support plate 101 so that radial outward movement of the pistons 35 decreases the volume of each die cavity 83 until position C is reached A satisfactory compression pressure is achieved by adjusting the position of the cam arm 48 It will be noted that the compression pressure can be adjusted by turning the hand wheel 65 which results in movement of the arm 48 about the pivot 49 When the arm 48 is pivoted counterclockwise about the pivot 49, as viewed in Figure 5, the compression pressure is increased This pressure is decreased, of course, when the arm 48 is pivoted clockwise It is, therefore, possible to control the quantity of granules being compressed (and thus the weight of the finished tablet) through rotation of the hand wheel 73, and the compression pressure (and thus the density of the finished tablet) through rotation of the hand wheel 65 An indication of the compression pressure can 70 be obtained by the use of a well known, properly calibrated strain gauge mounted on the support plate 101 at or near the point of maximum compression at position C Other types of pressure measuring de 75 vice can also be used.
As each piston 35 moves from position C to position D, it is moved outwardly by the central cam 46 until the finished tablet T is ejected at position D A sudden rise 80 in the cam 46 at position D as at 102 (Figure 5) helps to effect removal of the finished tablet T The finished tablets are removed by the conveyor 103 (Figures 1 and 3) which is driven from a sprocket 104 attached to 85 the shaft 97, by a chain 105 and a sprocket 106.
It has been found to be important to rotate the pistons 35 and the outer dies 89 in opposite directions about the direction of 90 compression in the latter stages of compression, until the point of maximum compression at position C is reached This has been found very helpful in preventing sticking of the granular material to the dies and 95 in allowing clean removal of the finished tablet from the die cavity 83 As seen in Figures 2 and 6, the pistons 35 are rotated in one direction prior to reaching the point of maximum compression at position C by a 100 cam surface 111 engaging the rotating member 45 The cam surface 111 is formed on the bracket 112 which is attached to the axle 14 After going beyond the point of maximum compression, a cam surface 113 acts 105 on the member 45 to return the piston 35 to its previous position and to simultaneously make a sliding break between the finished tablet and the outer surface of the die insert 36 to initiate discharge of the finished 110 tablet The cam surface 113 is formed on the bracket 114 which is secured to the axle 14.
Similarly, means are provided for rotating the outer dies 89 prior to reaching the 115 point of maximum compression and then returning them to their original position.
Referring to Figures 2, 7 and 8, the rotating mechanism consists of a rotating member 115 secured on the outer end of the die 120 89 A spacer member 116 is interposed between the rotating member 115 and the carriage 88.
As shown in Figures 2 and 7, a cam 117 is secured to support plate 101 to rotate the 125 outer die 89 by engaging the rotating member 115 as the carriage 88 of each outer die 89 approaches the point of maximum compression at position C This rotation may be opposite to the rotation of the piston 130 957,869 outer die, and means for rotating each of said pistons and/or the outer die co-operating therewith relatively to each other as they compress the particulate material, said rotation taking place about the direction of compression.
