What is "valve"

Valve \Valve\, n. [L. valva the leaf, fold, or valve of a door: cf. F. valve.]

1. A door; especially, one of a pair of folding doors, or one of the leaves of such a door.

   Swift through the valves the visionary fair Repassed.
   --Pope.

   Heavily closed, . . . the valves of the barn doors.
   --Longfellow.

2. A lid, plug, or cover, applied to an aperture so that by its movement, as by swinging, lifting and falling, sliding, turning, or the like, it will open or close the aperture to permit or prevent passage, as of a fluid.

   Note: A valve may act automatically so as to be opened by the effort of a fluid to pass in one direction, and closed by the effort to pass in the other direction, as a clack valve; or it may be opened or closed by hand or by mechanism, as a screw valve, or a slide valve.

3. (Anat.) One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or retard the flow in the opposite direction; as, the ileocolic, mitral, and semilunar valves.

4. (Bot.)

   1. One of the pieces into which a capsule naturally separates when it bursts.

   2. One of the two similar portions of the shell of a diatom.

   3. A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, as in the barberry.

5. (Zo["o]l.) One of the pieces or divisions of bivalve or multivalve shells. Air valve, Ball valve, Check valve, etc. See under Air. Ball, Check, etc. Double-beat valve, a kind of balance valve usually consisting of a movable, open-ended, turban-shaped shell provided with two faces of nearly equal diameters, one above another, which rest upon two corresponding seats when the valve is closed. Equilibrium valve.

   1. A balance valve. See under Balance.

   2. A valve for permitting air, steam, water, etc., to pass into or out of a chamber so as to establish or maintain equal pressure within and without. Valve chest (Mach.), a chamber in which a valve works; especially (Steam Engine), the steam chest; -- called in England valve box, and valve casing. See Steam chest, under Steam. Valve face (Mach.), that part of the surface of a valve which comes in contact with the valve seat. Valve gear, or Valve motion (Steam Engine), the system of parts by which motion is given to the valve or valves for the distribution of steam in the cylinder. For an illustration of one form of valve gear, see Link motion. Valve seat. (Mach.)

      1. The fixed surface on which a valve rests or against which it presses.

      2. A part or piece on which such a surface is formed.

         Valve stem (Mach.), a rod attached to a valve, for moving it.

         Valve yoke (Mach.), a strap embracing a slide valve and connecting it to the valve stem.

late 14c., "one of the halves of a folding door," from Latin valva (plural valvae) "section of a folding or revolving door," literally "that which turns," related to volvere "to roll" (see volvox). Sense extended 1610s to "membranous fold regulating flow of bodily fluids;" 1650s to "mechanical device that works like an anatomical valve;" and 1660s in zoology to "halves of a hinged shell." Related: Valved.

n. 1 A device that controls the flow of a gas or fluid through a pipe. 2 A device that admits fuel and air into the cylinder of an internal combustion engine, or one that allows combustion gases to exit. 3 (context anatomy English) One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or retard the flow in the opposite direction; as, the ileocolic, mitral, and semilunar valves. 4 (context British English) A vacuum tube. 5 (context botany English) One of the pieces into which certain fruits naturally separate when they dehisce. 6 (context botany English) A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, as in the barberry. 7 (context biology English) One of the pieces or divisions of bivalve or multivalve shells. 8 (context biology English) One of the two similar portions of the shell of a diatom. vb. (context transitive English) To control (flow) by means of a valve.

1. n. a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it

2. device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone

3. control consisting of a mechanical device for controlling the flow of a fluid

A valve is a device that regulates the flow of fluids.

Valve may also refer to:

A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.

The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.

Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on / off and pressure control to dish and clothes washers and taps in the home. Even aerosols have a tiny valve built in. Valves are also used in the military and transport sectors.

Valve is an anatomical term applied to the shell of those molluscs that have a shell. Although in theory any mollusc shell can be termed a "valve", the word is now most commonly applied to members of two classes of molluscs: the Bivalvia (clams) and the Polyplacophora (chitons), in other words, to those molluscs whose shells are normally composed of more than one articulating part, each one of which is known as a valve (and also, in the case of chitons, as a "plate".)

Species within one family of very unusual small sea snails, marine opisthobranch gastropods in the family Juliidae, also have two articulating shells or valves, which resemble those of a bivalve. This exceptional family is commonly known as the bivalved gastropods. Gastropods in general are sometimes called "univalves", because in those that have a shell, the shell is usually in one part.