PISTON DISPENSING APPARATUS

摘要

2103140 9222478 PCTABS00018 A valve assembly (13) has a depressable stem (17) extending into a pressurized container (11) of liquid. Valve assembly (13) has a first passage (39) through stem (17) to a metering chamber (31) and a second passage (43) from metering chamber (31) to container (11). Chamber (31) has a slideable piston (19) one side of which defines an end of the chamber (31) and the other side of which is subjected to pressure in the container. When stem (17) is not in the depressed position, first passage (39) is closed and chamber (31) fills with liquid which enters through second passage (43). When the stem is depressed, first passage (39) is opened and second passage (43) is closed, and the pressure in the container moves piston (19) to expel liquid. Stem (27) has threads (53) such that rotation thereof will increase or decrease the size of the chamber (31).