Spool valve and seal having zero leakage

摘要

A spool valve and seal having zero leakage includes a spool valve member having a hollow interior translatable within a bore in a valve body with inlet pressure connected through ports to the hollow interior of the spool valve member. A series of radial orifices axially displaced from the inlet ports communicate the interior with the exterior surface of said spool valve member, the outlets of said orifices terminating in chamfered edges. A seal is positioned adjacent the spool valve member in an annular groove formed in the surface of the bore within which the spool member is translated, the seal being positioned to prevent leakage between the inlet pressure passages and an outlet chamber in said valve body. The preferable seal for this purpose consists of a rubber O-ring in the groove with a Teflon sealing ring overlying the O- ring adjacent the surface of the spool member such that high fluid pressure on the inside of the spool member which is communicated through said orifices to the surface of the sealing ring forces the sealing ring and O-ring into the groove so that when the orifice edges pass the sealing ring they do not abrade the surface of the sealing ring. To avoid having the seal involved in the metering function of the valve, the maximum diameter of the chamfered edges is less than the length of the bore between the seal groove edge nearest the outlet chamber and the outlet chamber in said valve body.