GB1227678A - - Google Patents

Abstract

1,227,678. Drying apparatus. NEW BRUNSWICK SCIENTIFIC CO. Inc. 29 Aug., 1969, No. 43095/69. Headings F4G and F4S. Freeze drying.-In a freeze drying apparatus, Fig. 1, having a vapour removal system comprising a vacuum manifold 10, two condensing trap means 1, 2, a refrigerating means 42, and a vacuum creating means 32, an automatic control means connects one trap means with the vapour removal system while shutting off the other for a first period of time, and shuts off the one trap means while connecting the other for a second period of time subsequent to the first, and repeats the cycle alternately. Material to be freeze dried is contained in flasks 22 connected to the vacuum manifold 10 through valves 20. The vacuum manifold is connected to the vacuum pump 32 through two parallel paths, each passing through one of the condensers 1, 2. The paths are controlled by valves which may be of the motor controlled pinch type, the motors being controlled by the timers 54, 56. Each condenser is supplied with coolant from a refrigerator 42 through conduits controlled by valves which are also controlled by the timers 54, 56. On the first cycle of operation V2, V4, V8 are closed manually, thus coolant flows to the first condenser 1 which is open to the vacuum manifold 10 and pump 32. When condenser 1 is almost frosted up the timer 56 opens valve V8 to precool condenser 2, after which valves V1, V3, V7 close and V2, V4 open, switching operation from condenser 1 to condenser 2. The heaters inside condenser 1 are then switched on and valve V5 opened to drain away the defrosted condensate. When condenser 2 is almost frosted up, the procedure is repeated to switch operation from condenser 2 to condenser 1. Liquid cooled condensers.-Each condenser, Fig. 3, has an inner enclosure 60, having a slightly sloping bottom 62 and is sealed by a cover 64 through which a tube 66 passes to communicate with the conduit 26 from the vacuum manifold 10. The outlet pipe 30 to the vacuum pump 32 also passes through the cover 64 which also forms the seal of an external enclosure 68 surrounding the inner enclosure 60. In the gap between the enclosures 60, 68 and spaced apart from both is wound a coil 36 through which coolant flows to and from the refrigerator 42 through conduits 40, 44. The coil is submerged in a heat exchanging fluid, ethylene glycol, which is introduced into the chamber through a filling tube 74. Around the outside of the condenser is a layer of insulation 70. A thermostat 80 controls the refrigerator 42 to regulate the temperature of the coolant. Electrical resistance heaters 86 are provided to defrost the inner enclosure 60, and a valved outlet 50 allows the defrosted condensate to drain away.