Valve having fast and slow acting closure elements

Abstract

A first valve portion and a second valve portion are arranged in series in a flow passage within a valve casing to open and close the flow passage. The first valve portion includes a first valve seat, a first valve element supported to a first valve shaft and adapted to make an axial reciprocating movement into contact with or away from the first valve seat, and an opening and closing drive unit composed of a motor and a motion converting mechanism that converts a rotary motion into a linear motion, the opening and closing drive unit causing the first valve shaft to make a reciprocating movement and capable of effecting a flow rate control and slow valve-opening for the flow passage. The second valve portion includes a second valve seat, a second valve element adapted to move into contact with or away from the second valve seat, a compression spring that urges the second valve element into contact with the second valve seat, and an electromagnetic valve-opening unit for moving the second valve element away from the second valve seat by an electromagnetic force and capable of effecting quick valve-closure for the flow passage.