A liquid dispensing system and packaging apparatus which includes such a system

摘要

A liquid dispensing system and a packaging apparatus which includes such a system has a chamber 6 of a chryogenic vessel 2 containing a reservoir of liquid gas 1 (such as nitrogen, oxygen or argon) which is to be dispensed in doses 26 through an outlet port 12 which is in constant communication with a sub-chamber 17. The sub-chamber 17 is part of a piston 16 and cylinder 15 device in which the piston is reciprocated by means 21 and 24 to expand and contract the sub-chamber. When the sub-chamber 17 is expanded, liquid gas enters from the reservoir 1 through flow ports 18 which are closed by the piston 16 during contraction of the sub-chamber to dispense a dose 26. Mounted beneath the outlet port 12 is a tubular skirt 25 having internal passages 30 through which purging gas is directed into the region 29 adjacent to the outlet port 12. The region 29 is purged of air to alleviate ice build-up at the outlet port 12. The purging gas liquifies at a temperature not greater than the temperature of the liquid gas at the outlet port and provides a back-pressure at the outlet port to restrain flow of liquid gas therethrough prior to the contraction of the sub-chamber 17 to dispense a dose. The doses 26 are dispensed into open topped containers 34 that are moved successively beneath the outlet port 12 and means 50 is provided for sensing the containers and controlling the devices 21 and 24 to maintain synchronisation between the dispensing and the movement of the containers.