Patent GB-891634-A (GB)
Title: Improvements in or relating to methods and apparatus for coating tablets
Inventor: DOEPEL WALLACE ARTHUR
IPC: B30B11/34
Filed: 1960-01-01
Abstract: 891,634. Tablet-coating machines. COLTON CO., ARTHUR. Jan. 1, 1960, No. 75/60. Class 87(2). A compression tablet coating machine embodies a die pocketed rotary compression table having complementary top and bottom punches, a bottom spanulation feed, a core feed and a top granulation feed, the core feed comprising a pick-up rotary feeder table revolving near the compression table, a flexible endless member moving in peripheral contact with both tables and means on the flexible endless member to pick up cores from the core feeder table and impress them into a metered bottom charge within die pockets of the compression table while both tables are moving. Tablet feeding. Tablets pass from a hopper 20 along a vibrating feeder screen 22, stepped at 24 to turn the tablets over and shake the dust off, on to a feeding disc 26 which carries them to its periphery where they enter notches 68 in the periphery of a pick-up rig 40. The drum 30 on which the disc 26 is mounted is vibrated from a vibrator unit 32. Broken tablets escape through extensions 72 from the notches 68. A retaining ring 60, preferably of transparent material, covers the feeding disc 26 and the notches 68 position the tablets below openings 61 in the ring 60. Nozzles 128 enter the openings 61 and pick up the tablets one by one by suction. A manifold is mounted on the top of a column 90 and comprises a fixed top portion 102 and a rotating bottom portion 104. The nozzles 128 project from hollow bodies 126 which are connected through flexible tubes 108 with the rotating portion 104. Vacuum is supplied through the column 90 (which is gear-driven to rotate the portion 104) to the fixed portion 102 which is semi-circular, whereby suction is applied through the tubes 108 when the portion 104 is passing under the portion 102. The hollow bodies 126 are guided for vertical movement on rods 134 which are extensions of the link-connecting pins of the chain 120 which drives the tablet feeding mechanism. Cams 142, co-operating with springs 136, raise and lower each nozzle 128 in required synchronism. The chain 120 is guided round a sprocket 80 to the periphery of the rotating guide table 160, the nozzles 128, holding the tablets, moving with it. Powder feeding. Powder is fed on to the rotating die table 160 by a shoe 260, which has a pocket 264 supplied from a hopper 262, and is levelled off by a blade 278, leaving the bottoms of the die cavities 170 filled. Powder to fill the tops of the die cavities and to cover the deposited tablets is supplied from a hopper 286 through a shoe 284 which has a pocket 288. In this case the amount of powder is metered by pockets 282 in a rotating feed plate 280, the pockets 282 dwelling over the cavities 170 where the arcs of movement of the feed plate 280 and die table 160 coincide. Coating operation. At the position, Fig. 2, where the die cavities are below the feed pocket 264 the lower punch 178 in a die cavity is lowered by a cam 226 to an extent sufficient for the required charge of powder, which is determined by a cam 230, the position of which can be regulated by a nut 232. The punch 178 is then lowered slightly before being raised by a cam 236 to tablet-depositing position, to prevent dislodgment of the tablet when deposited. At position 10, Fig. 2, the nozzle 128 is lowered, by a cam 144, Fig. 4, and the vacuum is cut off by the movement of the portion 104 of the manifold out of the vacuum portion 102, so that the tablet is released. The lower punch is supported by the cam 236 as the nozzle presses the tablet on to the powder. After the tablets have left the nozzle the tube 108 leading thereto is brought, by the continued movement of the portion 104, below a pressure chamber 116 supplied through a pipe 114, Fig. 5, so that dust and chips are blown off the fingers 130, at the end of a nozzle, which have functioned to centre the tablets. The quantity of powdered material metered by the feed table 280 is then deposited in the die on top of the tablet. The lower punch is then positioned preparatory to the powdercompressing operation by an adjustable cam 240 and a cam 206 causes the upper punch to descend and compact the powder, after which the bottom punch engages a level bar 244. Both punches are then moved towards one another by rollers 210, 250, so compressing the powder round the tablet. The upper punch is then raised by a cam 202 and an ejector cam 220 then moves the tablet to the surface of the die table, where it is removed by a blade 270 and deflected to a shoot 272 leading to a hopper 274 and vibrating duster screen 276. The lower punches are restrained against dropping due to gravity by friction plungers 194, Fig. 4. If a tablet becomes jammed in a nozzle, increased pressure in the pipe 114 acts on a diaphragm 300 to operate a micro-switch 302 which causes a solenoid brake-clutch 304 to stop the machine immediately. A feeler finger 306, Fig. 1, similarly operates supplementary safety control. If a tablet has not been deposited it will be ejected off the nozzle 128 by air pressure. If a tablet is not picked up from the ring 40 the suction through the nozzle 128 will draw the lower powder charge out of the die cavity and it will crumble at the ejection point and be dusted off at the vibratory screen 276.