Patent ID: 7849876

Claim:
A valve assembly comprising a valve body and a valve member; the valve body comprising a supply port, a delivery port, and a supply chamber communicating with the supply port; the valve member being at least partially positioned within the supply chamber and being movable in an axial direction between a supply position, whereat the supply chamber communicates with the delivery port, and, a nonsupply position, whereat the supply chamber is sealed from the delivery port; and the valve member comprising radial surfaces; wherein the radial surfaces are radially sized and axially situated so that 1) when the valve member is in the supply position, the sum of fluid forces imposed on the radial surfaces, including the anti-interface force imposed on the seated radial surface(s), is positive towards the supply position, and 2) when the valve member is in the nonsupply position, the sum of fluid forces imposed on the radial surfaces, including the anti-interface force imposed on the seated radial surface(s), is positive towards the nonsupply position.