Valve closure seating method and apparatus

摘要

A micro-mass flow controller (10) has a sonic choked flow restriction (28) with an oscillatable valve (26) for repetitiously opening and closing the sonic choked flow restriction (28) in a time-modulated sequence to set or vary mass flow rate of gas through the sonic choked flow restriction (28) over a period of time to something between no flow and maximum mass flow rate. A bimorph piezoelectric actuator (40) is coated in a sputtered dielectric layer (78) and then encapsulated in stainless steel or other metal cladding (80). A closure member (46) on the actuator (40) is registered to a valve seat (70) by actuating the actuator (40) to force the closure member (46) in a puddle of adhesive (86) against the valve seat (70) until the adhesive (86) cures.