from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A valve that slides back and forth over ports, especially one in the cylinder wall of a steam engine that permits the intake and outflow of steam to move the piston.

from the GNU version of the Collaborative International Dictionary of English

  • n. A particular kind of sliding valve, often used in steam engines for admitting steam to the piston and releasing it, alternately, having a cuplike cavity in its face, through which the exhaust steam passes. It is situated in the steam chest, and moved by the valve gear. It is sometimes called a D valve, -- a name which is also applied to a semicylindrical pipe used as a sliding valve.

from The Century Dictionary and Cyclopedia

  • n. In steam, hydraulic, and pneumatic engineering, a valve which slides over and upon its seat without lifting in opening or closing a port or ports formed in the seat; specifically, a flat-faced plain slide working, or adapted to work or slide, upon a flat-faced seat which includes a port or ports to be alternately opened and closed by the reciprocation of the slide.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. valve that opens and closes a passageway by sliding over a port


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