| 摘要 |
1,034,744. Freeze drying. VICKERS Ltd. May 7, 1965 [May 19, 1964], No. 20691/64. Heading F4G. [Also in Division A2] A method of freeze-drying material, e.g. leafy vegetable, comprises placing in a container or tray 1 frozen material to be dried, subjecting the frozen material to vacuum produced in a chamber (not shown), and sublimating the ice in the material by heat from electrically or fluid-heated heaters 6, 7 and adjusting the extent to which the evolved water vapour flows from the container by throttling the flow to vary the thermal conductivity of the water vapour surrounding the material. The throttling step may be effected by relative movement of the heater 7 and the upstanding flanges 5 which form the sides of the container, which sides may be imperforate as shown, or perforated when the heater 7 can be brought into direct contact with the tray. Measuring devices may automatically control the temperature and movement of the heaters. In a modification, the heater plates are not movable and a throttling valve is formed by a shutter mounted in the connection between the chamber and a vacuum-tight compartment containing condenser plates. |
