Patent GB-739711-A (GB)
Title: Improvements in or relating to machines for compressing a coating upon tablets, pills and like cores
IPC: B30B11/34
Filed: 1952-05-02
Abstract: 739,711. Rotary-mould-table moulding machines. MERCK & CO., Inc. May 2, 1952 [May 4, 1951], No. 11116/52. Class 87 (2). A tablet-coating machine comprises a horizontal continuously rotating table 52 having circumferentially arranged die-pockets 51, a top punch and a lower punch for each pocket and, spaced apart in the path of the die-pockets, bottom powder-feeding means for delivering coating material to each die-pocket, tablet-feeding means for depositing a tablet upon the coating material in each die-pocket, top powder-feeding means for delivering coating material upon the tablets in the die-pockets, actuating means for reciprocating the punches in each die-pocket for compressing the coating material around the tabler therein; and means for ejecting the coated tablets, the tablet-feeding means comprising a rotary member 31 for carrying a succession of tablets to an injection point above the path of the die-pockets and an adjustable feed support-plate 41 interposed between the table 52 and the rotary member 31 to prevent contact of the tablet upon the table until the tablet has been deposited in a die-pocket. The upper punches reciprocate in a rotary head 55 above the rotary table 52. The means for feeding the powder, actuating the punches and ejecting the tablets are known, the important steps, with which the invention is concerned, being the deposition, on the bottom fill, of the tablet to be coated so that it is centred in the die, and the immediate removal of the tablet from contact with the rotary feed member 31. A complete cycle can be described with reference to Fig. 3, which shows a development of the cam track 77 in and on which the lower punches travel. (i) The lower punch moves downwards in the cam. rail 71 to allow the bottom fill of coating powder to be placed by known means in the die cavity. (ii) The lower punch is raised by a cam 72 to a level at which excess bottom fill is stripped off by known means. (iii) A cam 73 raises the lower punch till the level of the bottom fill is correct in relation to the surface of the table 52 for the reception of the tablet to be coated, and, as the tablet is deposited the cam 73, by means of its upper rail, pulls the lower punch downward to prevent the tablet from being further acted upon by the rotary feed member 31. (iv) As the lower punch follows the cam track 77 the top fill of coating powder is added. (v) Excess top fill is stripped off as the lower punch passes over a cam 74. (vi) Compression wheels 75, 76 act to bring the upper and lower punches towards one another and compress the coating powder on the tablet. (vii) As the lower punch passes along the cam track 77 it rises to eject the tablet. The tablets are introduced at a convenient point on the circumference of a ring-shaped member 49 supporting the plate 41, such as F, to which they may be supplied direct from a rotary press which produces them, and each one is carried along in a pocket 32 in the wheel 31. The feed support plate 41 comprises a thin arcuate sheet 43 stiffened by a rail 42, which also prevents the escape of the tablets, and extends over the rotary table 52 nearly as far as the point where the line passing through the centres of the dies 51 and the line passing through the centres of the tablets in the pockets 32 touch one another, this point being the injection point. The adjustment of the plate 41 is derived from arcuate slots 45 through which the bolts 44 pass that hold it down on the member 49, and the plate should be adjusted so that its end is at a distance from the injection point equal to the radius of the tablet being coated, this condition ensuring its smooth transference. The feed wheel 31 is driven from the shaft of the rotary table 52 through gearing 61, 62, 66 so that the peripheral speeds of the above centre lines are equal. To ensure that these centre lines are tangential means may be provided for adjusting the position of the shaft 34. Interposed between the shaft 34 and the feed wheel 31 is an element to which the wheel 31 is fixed by bolts 36 passing through slots 37, these means providing adjustment to ensure that the pockets 32 are in proper alignment with the dies 51. It is also stated that the time during which the tablet has minimum motion relative to a die can be increased by reciprocating the axis of the shaft 34 along the line between it and the axis of the bed 52.