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slide valve[′slīd ‚valv]
a movable element in a system for controlling a thermal or mechanical process; directs the flow of a working fluid or gas into the proper channel by displacement relative to ports in the surface over which it slides. Slide valves are used in piston steam engines, where they distribute the steam; in control systems for regulating steam turbines; in pneumatic mechanisms; and hydro-automated systems.
A D-slide valve is an inverted box that is alternately displaced by the slide valve rod to the right or left along the valve seat, which has rectangular ports. Depending on the position of the slide valve, the ports communicate with a closed space, which surrounds the valve and is filled with the working body, or with a cavity that is connected to the atmosphere or a condenser. A shortcoming of a D-slide valve is an imbalance, as a result of which the working body presses the valve strongly against the seat, causing wear of the working surfaces and necessitating considerable force to move the valve.
A piston valve is similar to a D-slide valve in its principle of operation but is completely balanced. Such a slide valve has two pistons that are mounted on a common stem and move in a bushing equipped with ports. In high-precision hydraulic control systems piston valves are sometimes given a continuous rotary motion about their axis or an oscillatory motion along the axis to increase the system’s sensitivity by substituting friction of motion for static friction.
A tap valve is essentially a D-slide valve bent around its axis, which is perpendicular to the direction of its movement. The valve is set into a cylindrical bushing with two ports. As it rocks around its fixed axis, the valve connects or disconnects the ports and chambers.
The one-way air valve of an automobile tire is also called a slide valve.
REFERENCESLemberg,M. D. Sistemy gidroavtomatiki. Moscow-Leningrad, 1965.
Veller, V. N. Avtomaticheskoe regulirovanie parovykh turbin. Moscow, 1967.
S. M. LOSEV