GB1203213A - Methods and apparatus for coating small bodies - Google Patents

Abstract

1,203,213. Coating method. E. R. SQUIBB & SONS Ltd. 2 Nov., 1967 [9 Sept., 1966], No. 40481/66. Heading A2A. [Also in Divisions A5 and B2] A method of coating small bodies (e.g. pharmaceutical tablets, sweets, seeds, metal magnets, wood chippings, pesticides and fertilisers) by tumbling them in a liquid or semi-liquid coating material (e.g. solution, suspension, emulsion or melt) in a tumbler pan, comprises bringing the bodies to a predetermined temperature before applying coating material thereto and then substantially maintaining the bodies at the said temperature during the application of coating material. The coated bodies may be dried whilst being tumbled and maintained at the said temperature. The bodies may be coated with more than one layer and the bodies may be dried between successive coating applications. The bodies may be heated before and during coating and during drying by means of warm air, steam coils, infrared radiation or ultrasonic vibration. The coating material is preferably preheated. Pharmaceutical bodies may be precoated with a sealing material (e.g. shellac or polyvinyl acetate phthalate), coated with a plurality of sugar layers and finally coated with a layer which can be waxed or polished. A suitable apparatus comprises a rotating tumbler pan 1, a hot water jacketed tank 6 for supplying coating material to the pan 1 via pump 8 and nozzle 9 and a nozzle 36 for directing warm air into the pan 1. Fan 33 supplies air to the nozzle 36 via steam heat exchanger 34, filter 35 and heater 2, the heater 2 being under the control of thermosensitive element 5 in pan 1 to maintain the air at the desired temperature to maintain the bodies at a substantially constant temperature. Thermosensitive element 4 overrides element 5 to switch off heater 2 if the air temperature becomes excessive. A pressure responsive member may be present in conduit 62 for indicating the failure of supply of coating material from tank 6. The pan 1 may be provided with baffles extending along an intermediate zone of the pan 1. The baffles may be of V-shaped cross-section and taper from their centres to their ends. The pan may be only intermittently rotated during drying. The fan 33 may supply air to more than one pan. The apparatus may be provided with control means including timers so that all the operations are carried out automatically. In another embodiment (Fig. 2, not shown), the warm air supplied to the pan may be a mixture of cold and hot air, the proportions of hot and cold air being controlled by a valve under the control of a thermosensitive element in the pan.