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Related to poppet valve: Sleeve valve
poppet valve[′päp·ət ‚valv]
A cam-operated or spring-loaded reciprocating-engine mushroom-type valve used for control of admission and exhaust of working fluid; the direction of movement is at right angles to the plane of its seat.
A mushroom-shaped valve in reciprocating engines for controlling the flow of gas in and out of cylinders. The valves are pushed open by cams on a rotating camshaft and closed by strong springs. In aircraft engines, the valves are generally located on the top of the cylinders.