valve

valve

1. any device that shuts off, starts, regulates, or controls the flow of a fluid

2. Anatomy a flaplike structure in a hollow organ, such as the heart, that controls the one-way passage of fluid through that organ

3. Electronics an evacuated electron tube containing a cathode, anode, and, usually, one or more additional control electrodes. When a positive potential is applied to the anode, electrons emitted from the cathode are attracted to the anode, constituting a flow of current which can be controlled by a voltage applied to the grid to produce amplification, oscillation, etc.

4. Zoology any of the separable pieces that make up the shell of a mollusc

5. Music a device on some brass instruments by which the effective length of the tube may be varied to enable a chromatic scale to be produced

6. Botany

a. any of the several parts that make up a dry dehiscent fruit, esp a capsule

b. either of the two halves of a diatom cell wall

7. Archaic a leaf of a double door or of a folding door

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

valve

[valv]

(anatomy)

A flat of tissue, as in the veins or between the chambers in the heart, which permits movement of fluid in one direction only.

(botany)

A segment of a dehiscing capsule or legume.

The lidlike portion of certain anthers.

(electronics)

electron tube

(invertebrate zoology)

One of the distinct, articulated pieces composing the shell of certain animals, such as barnacles and brachiopods.

One of two shells encasing the body of a bivalve mollusk or a diatom.

(mechanical engineering)

A device used to regulate the flow of fluids in piping systems and machinery.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Valve

A flow-control device. Valves are used to regulate the flow of fluids in piping systems and machinery. In machinery the flow phenomenon is frequently of a pulsating or intermittent character and the valve, with its associated gear, contributes a timing feature.

The valves commonly used in piping systems are gate valves (Fig. 1), usually operated closed or wide open and seldom used for throttling; globe valves, frequently fitted with a renewable disk and adaptable to throttling operations; check valves, for automatically limiting flow in a piping system to a single direction; and plug cocks, for operation in the open or closed position by turning the plug through 90° and with a shearing action to clear foreign matter from the seat. Safety and relief valves are automatic protective devices for the relief of excess pressure. See Safety valve

For hydraulic turbines and hydroelectric systems, valves and gates control water flow for (1) regulation of power output at sustained efficiency and with minimum wastage of water, and (2) safety under the inertial flow conditions of large masses of water.

To control the kinematics of the cycle, steam-engine valves range from simple D-slide and piston valves to multiported types. Many types of reversing gear have been perfected which use the same slide valve or piston valve for both forward and backward rotation of an engine, as in railroad and marine service. See Steam engine

Poppet valves are used almost exclusively in internal combustion reciprocating engines because of the demands for tightness with high operating pressures and temperatures (Fig. 2). Two-cycle engines utilize ports, alternately covered and uncovered by the main piston, for inlet or exhaust. See Cam mechanism, Internal combustion engine, Valve train

In compressors, valves are usually automatic, operating by pressure difference on the two sides of a movable, springloaded member and without any mechanical linkage to the moving parts of the compressor mechanism. Like those for compressors, pump valves are usually of the automatic type operating by pressure difference.

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.

valve

A device which regulates or closes off the flow of a fluid.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

valve

(electronics)

UK term for a vacuum tube.

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

vacuum tube

An electronic device that controls the flow of electrons in a vacuum. It is used as a switch, amplifier or display screen (CRT). Used as on/off switches, vacuum tubes allowed the first computers to perform digital computations. Although tubes made a comeback in high-end stereo components, they have long since been abandoned for TVs and computer monitors. See vacuum tube types, audiophile, tube amplifier and Vintage Radio Museum.

Early Vacuum Tube

Early vacuum tubes were used to amplify signals for radio and other audio devices. This one was made in 1915. Tubes were not used as switches in calculating machines until 1939. (Image courtesy of AT&T.)

Tubes in the 21st Century

Many audiophiles claim vacuum tubes amplify music better than transistors. These high-end Model One amplifiers (collectively weighing 212 pounds) were designed by legendary audio engineer Mark Levinson.

All Kinds

Vacuum tubes have come in myriad shapes and sizes over the years, and the Vintage Radio and Communications Museum has one of the finest collections. (Images courtesy of Vintage Radio and Communications Museum of Connecticut, www.vrcmct.org)

Amazing - A Tube Could Be This Small

This image is from an article in the October 1947 issue of Mechanix Illustrated that highlighted the huge reduction in vacuum tube size. The article's author could not have imagined that in the future several trillion transistors could fit inside the small vacuum tube. (Image courtesy of Mechanix Illustrated.)

Copyright © 1981-2025 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Valve

 

a part or device used to control the flow of a gas or fluid in machines and piping by altering the cross-sectional dimensions of the passage.

In internal combustion engines, pumps, compressors, and blowers, a valve is a part of the distribution mechanism or of the gas or fluid flow-control mechanism. As a variety of pipe fitting, a valve is used to control the flow of gas, vapor, or liquid.

Valves are made up of a housing, which is incorporated into the piping, and a gate, which moves within the housing and alters the dimensions of the bore (and, thereby, the transmissive capacity). Valves are used to develop a pressure differential (throttle valves), to prevent the reverse flow of a fluid (check valves), to release a certain amount of gas, vapor, or liquid when the pressure exceeds a set value (safety valves), to control pressure or flow rate (regulating valves), and to reduce pressure and keep it at a constant level (reducing valves). Valves are also used as stopper fittings to seal off piping, in engineering equipment, and in heat-and-power engineering facilities.

Depending on the design of the housing, valves are classed as pass, angled, three-way, and multipath. In terms of the nature of attachment to the piping, they may be flanged or coupled. The gate may be moved manually, electrically, pneumatically, or hydraulically.

G. G. MIRZABEKOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.