Importance

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Abstract

A fluid valve device for on-off control of fluid flow through a passage extending between two fluid ports (12, 15) and including a valve seat (17A) comprises a hollow valve member (21) which is movable into and out of sealing engagement with the valve seat and defines a valve chamber (20). The valve chamber (20) communicates with one of the fluid ports (15) through the valve seat (17A) and is associated with a valve member actuating device (A) which translates the pressure of the fluid received in the valve chamber (20) from an inlet (12/14) for the fluid flow into a force acting on the valve member to displace it relative to the valve seat (17A). The valve member actuating device in one embodiment includes a thrust surface (A) on the valve member (21) which is directed away from the valve seat and forms part of the wall of the valve chamber (20). A second thrust surface (C) on the valve member (21) is directed oppositely and defines a chamber (V) which is isolated from the valve chamber and the flow passage. A positive-displacement pump includes the fluid valve device as an inlet valve for controlling the admission into the pump chamber (20) of the fluid being pumped.

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First Claim