GB1315545A - Methods of and apparatus for continuous freeze-drying - Google Patents

Abstract

1315545 Freeze-drying Y SAHARA 14 May 1970 23346/70 Heading F4G Frozen objects 40 of food or medical stuff are freeze-dried in containers 11 moving round a circular path, each container 11 (and object 40) as it moves around the path being successively evacuated of air, maintained under vacuum while it is passed through a heating tunnel B containing high frequency or infra-red radiators, connected to a source of gas at atmospheric pressure, and unloaded. In Fig. 1, the objects 40 are loaded on to holders 8 secured to conduits 4 branching from from a central conduit 3 which is rotated at a variable speed by means of a motor A1, the containers 11 being raised for loading but lowered for evacuation on to the open ends 6 of the conduits 4 by means of a guide rail 39. Initial evacuation of air from each container 11 is effected by one of five vacuum pumps C2, C5 &c. selected by operation of electromagnetic valves spaced around the circular path. The rotatable conduit 3 is connected via a fixed conduit 20 to alternative vapour traps 21 and 21<SP>1</SP> containing refrigerated cooling coils 35 and 35<SP>1</SP> and evacuated by a vacuum pump 23 which maintains the containers under vacuum. A turntable 2 (supporting the branch conduits 4) is provided with microswitches 12 (the same number as containers 11) spaced around its periphery and operable by microcontacts 15- 18 Each microswitch 12 controls the condition of a four-way relay which successively opens the electromagnetic valve to effect initial evacuation of the container 11, opens a further electromagnetic valve 5 to effect the maintaining of the vacuum in the container, closes the valve 5, and opens another electromagnetic valve to leak clean dry air or nitrogen to the container 11. The tunnel B comprises high-frequency radiators B3 and is lined with radiation-reflecting thermally-insulating shields B2, further shields being provided on the rod 7 at 30 and around the slit B1, and in the form of self-closing doors at the ends of the tunnel B. The temperature of the object 40 is raised to - 20‹ or - 25‹ C., and the strength of the electromagnetic field increases along the tunnel. In another embodiment, Figs. 9 and 10 (not shown), medical stuff or bacterial strains are placed in glass ampoules (which constitute the containers 11) which themselves are loaded on to the turntable 2 and sealed to the downwardlyfacing ends of the branch conduits 4 by means of connectors. Heating is by infra-red (or high frequency) radiators, and the ampoules are sealed after drying by being rotated by a belt while heated by a burner.