Control apparatus in equipment for freeze-drying liquid, semi-liquid or granulated material

摘要

1,073,152. Freeze drying. VICKERS Ltd. Feb. 18, 1965 [Feb. 26, 1964], No. 8049/64. Heading F4G. [Also in Division G3] A temperature control system for freeze drying materials in a vacuum chamber comprises electric heaters 3, 4, each in contact with thermocouples 5, connected in parallel or series to an indicating galvanometer-phototransistor type controller 12 which disconnects the heaters or reconnects them from parallel to series at a determined temperature. A further set of thermocouples 6 also in parallel or series in contact with the material act on a further controller 14 to switch the heaters off or reconnects them from parallel to series if this has not already been done. The arrangement may be controlled by a programme cam which varies the set temperature with time. The controllers 12, 14 may be replaced by transductors, the thermocouples by temperature sensitive resistors, and the electric heaters by steam or hot water heat exchangers. A freeze drying tunnel is described in the Specification wherein the heaters and trays of material are moved stepwise through a series of stations which provide heat to the material. Additional thermocouples deeply embedded in the material may terminate the drying cycle.