Valve construction

摘要

The invention relates to a valve having a housing in which there is a passage having at least two spaced ports. A slide is accommodated in the passage for to and fro movements between at least two positions in one of which at least one of the ports is open and in the other of which such port is closed. A slide actuator effects movements of the slide and the slide carries a seal which effects a seal of the closed port when the slide is in the port-closing position. The seal has a sealing actuator operable separately from the slide actuator to apply a sealing force to the seal. The force applied to the seal is neutralized in response to actuation of the slide.