Tabletting machines

Abstract

A tabletting machine having continuous cam tracks to operate the punches, and including means for "in motion" adjustment of one of the cam tracks to control the dose of powdered material which is compressed by the punches in the dies to form the tablets and also the thickness of the tablets so produced. To assist in feeding the powdered material into the dies, a concave cylindrical die table is used, the punches operating radially with respect to the axis of rotation of the die table.

We claim: 
     
       1. In a tabletting machine in which the powdered or granulated material to be tabletted is fed from a feed frame onto the surface of a rotating die table so as to fill dies in the die table and be compressed into a tablet in each die, between a pair of punches individual to the die, and which enter the die from opposite ends, one of the punches being subsequently withdrawn from the die and the other punch being pushed through the die to eject the tablet from the die, .[.the improvement wherein:.]. .Iadd.and in which .Iaddend. .[.a..]. the punches are arranged for movement relative to the die table, radially with respect to the axis of the die table, .Iadd.the improvement comprising: .Iaddend.   .[.b..]. a flexible hoop .[.is provided.]. which rotates with the die table and which is constrained and guided by abutments so as to assume a non-circular shape, and   .[.c..]. means .[.is provided.]. .Iadd.coupled to said punches .Iaddend.for moving corresponding ones of each pair of punches under the control of radial deflections of said flexible hoop, one at least of said abutments being adjustable radially with respect to the axis of rotation of the die table thereby to adjust the movement of said corresponding ones of said punches.     
     
     
       2. A tabletting machine as claimed in claim 1 in which the hoop rotates with the die table in contact with the heads of said corresponding ones of said punches. 
     
     
       3. A tabletting machine as claimed in claim 1 in which said corresponding ones of said punches are the radially outer one of each pair of punches. 
     
     
       4. A tabletting machine as claimed in claim 3 in which the heads of the radially outer ones of each pair of punches are held in engagement with the hoop by a spring wire ring engaging the underside of the heads, the ring being confined between the punch heads and a retaining plate carried round with the die table. 
     
     
       5. A tabletting machine as claimed in claim 1 in which the abutments comprise rolling means which roll in contact with the hoop. 
     
     
       6. A tabletting machine as claimed in claim 5 in which the rolling means are freely rotatable, so as to be driven only by contact with said flexible hoop. 
     
     
       7. A tabletting machine as claimed in claim 1 in which said corresponding ones of said punches are moved under the control of said flexible hoop to eject the tablets from the dies. 
     
     
       8. A tabletting machine as claimed in claim 7 in which two of the abutments are adjustable radially with respect to the axis of rotation of the die table, one to adjust the weight of the tablets and the other to adjust the thickness of the tablets produced in the machine. 
     
     
       9. A tabletting machine as claimed in claim 8 in which the abutment for adjusting the weight of the tablets comprises a pair of rollers of equal diameter and having their axes parallel to, and equi-spaced from, the axis of rotation of the die table in all positions of their adjustment. 
     
     
       10. A tabletting machine as claimed in claim 8 comprising not more than three of said abutments, and which includes a circular cam track eccentrically disposed with respect to the axis of rotation of the die table the other punch of each pair being moved by said circular cam track. 
     
     
       11. A tabletting machine as claimed in claim 10 in which the heads of said other punches engage in said circular cam track. 
     
     
       12. A tabletting machine as claimed in claim 10 in which the circular cam track is formed between two freely rotatable, concentric, circular parts. 
     
     
       13. A tabletting machine as claimed in claim 1 in which the axis of rotation of the die table is disposed at an angle to the vertical. 
     
     
       14. A tabletting machine as claimed in claim 13 in which the axis of rotation of the die table is disposed horizontally. 
     
     
       15. A tabletting machine as claimed in claim 1 in which the die table presents a concave cylindrical surface to receive the powdered or granulated material from the feed frame. 
     
     
       16. A tabletting machine as claimed in claim 15 in which the feed frame is arranged to feed the powdered or granulated material to be tabletted onto the surface of the die table, to one side of the dies, to be carried round with the die table, stationary deflector means being provided to move such powdered or granulated material being carried round with the die table inside the feed frame, relative to the die table, over the dies to fill them. 
     
     
       17. A tabletting machine as claimed in claim 16 in which stationary deflector means is provided to move excess powdered or granulated material deflected by said first said stationary deflector means and being carried round with said die table, inside the feed frame relative to the die table, to the other side of said dies, the excess material then leaving the feed frame and entering a part annular channel defined in part by the surface of the die table and in part by a stationary part circular powder retaining band, a still further stationary deflector means being provided for move powdered or granulated material carried round in said channel and re-entering the feed frame, back over the dies to fill them. 
     
     
       18. A tabletting machine as claimed in claim .[.16.]. .Iadd.17 .Iaddend.in which the feed frame comprises an outer wall, an intermediate wall and an inner wall, the inner wall having a wall portion disposed generally in the plane of said powder retaining band, and on said other side of said dies, the intermediate wall being disposed on said one side of said dies and the outer wall having a portion disposed on the side of said intermediate wall remote from the dies, and a hopper for powdered or granulated material to be tabletted is arranged to supply fill material onto the surface of the die table between said outer wall portion and said intermediate wall, such material being deflected passed one end of said intermediate wall by said first said stationary deflector means and excess fill material being deflected passed one end of said inner wall by said second said stationary deflector means, said still further stationary deflector means deflecting surplus fill material re-entering the feed frame into the space between said inner wall portion and said intermediate wall. 
     
     
       19. A tabletting machine comprising a rotatable die table presenting a concave cylindrical surface, a stationary feed frame for feeding powdered or granulated material to be tabletted onto said surface, .Iadd.to be carried around with the die table, a part annular channel being defined in part by the surface of the die table and in part by a stationary part circular powder retaining band for receiving excess powdered or granulated material from one end of the feed frame and for conducting excess material round, on the die table, to re-enter the feed frame at its opposite end, .Iaddend.a ring of dies in the die table, the dies opening.[.,.]. at one end.[.,.]. in said surface .Iadd.in positions to move through the feed frame .Iaddend.to receive powdered or granulated material fed onto said surface by said frame.[.,.]. .Iadd.and moving with said surface, whereby the action of centrifugal force generated by rotation of the die table on the powdered or granulated material feeds the material into the dies .Iaddend.and for each die, a pair of punches individual to the die and rotatable with the die table, means for entering the punches into the die, from opposite ends of the die, thereby to compress powdered or granulated material in the die and form a tablet, and means for subsequently withdrawing one of the punches from the die and for advancing the other punch to eject the tablet from the die.