(under subclass 318) Subject matter wherein the valve head is a cylinder fitted for slidable reciprocation within or telescopically on a cylindrical seat, which seat provides a guiding and sealing surface for the head substantially throughout the girth thereof so that the head is guided and sealed in all of its positions, there being a port or ports in the cylindrical wall of either the head or seat which will be opened or closed upon reciprocation of the piston.
SEE OR SEARCH THIS CLASS, SUBCLASS:
157+, especially subclasses 190+ for piston valves with means to increase the head and seat contact pressure to reduce the wear upon operation.
SEE OR SEARCH CLASS
137, Fluid Handling,
288, for piston type valves of the hydrant type, subclasses 538+ for line condition change responsive piston valves and subclasses 625.37+ for piston valves where the flow is divided and recombined.
