AskDefine | Define piston

Dictionary Definition



1 United States neoclassical composer (1894-1976) [syn: Walter Piston]
2 mechanical device that has a plunging or thrusting motion [syn: plunger]

User Contributed Dictionary




From piston.


  1. A solid disk or cylinder that fits inside a hollow cylinder, and moves under pressure (as in an engine) or displaces fluid (as in a pump)
  2. A valve device in some brass instruments for changing the pitch


solid disk or cylinder that fits inside a hollow cylinder
valve of brass instruments
Translations to be checked

Derived terms






from pistone.



fr-noun m

Extensive Definition

For other uses see Piston (disambiguation).
A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall.

Piston engines

Main article: Reciprocating engine

Internal combustion engines

There are two ways that an internal combustion piston engine can transform combustion into motive power. These are the two-stroke cycle and the four-stroke cycle. A single cylinder two-stroke engine produces power every crankshaft revolution, while a single cylinder four-stroke engine produces power once every two revolutions. Older designs of small two-stroke engines produced more pollution than four stroke engines. However, modern two-stroke designs, like the Vespa ET2 Injection utilise fuel-injection and are as clean as four-strokes. Large diesel two-stroke engines, as used in ships and locomotives, have always used fuel injection and produce low emissions. One of the biggest internal combustion engines in the world, the Wärtsilä-Sulzer RTA96-C is a two-stroke; it is bigger than most two-story houses, has pistons nearly 1 metre in diameter and is one of the most efficient mobile engines in existence. In theory, a four-stroke engine has to be larger than a two-stroke engine to produce an equivalent amount of power. Two-stroke engines are becoming less common in developed countries these days, mainly due to manufacturer reluctance to invest in reducing two-stroke emissions. Traditionally, two-stroke engines were reputed to need more maintenance (despite exceptions like the Ricardo Dolphin engine, and the Twingle engines of the Trojan car and the Puch 250 motorcycle). Even though the simplest two-stroke engines have fewer moving parts, they could wear out faster than four-stroke engines. However fuel-injected two-strokes achieve better engine lubrication, and cooling and reliability should improve considerably.
image:piston.jpg|A piston and its connecting rod.

Steam engines

Steam engines are usually double-acting (i.e. steam pressure acts alternately on each side of the piston) and the admission and release of steam is controlled by slide valves, piston valves or poppet valves.

Air cannons

There are two special type of pistons used in air cannons: close tolerance piston and double piston. While in close tolerance piston, O-rings are used as valve but in double piston, O-rings are not used.
There are some features of close tolerance piston mentioned below:
  1. Piston can swell and stick.
  2. Fits tightly in the cylinder.
  3. Tight Tolerance fit.
  4. Properties alter due to atmospheric change.
  5. Backlash may such,some of the bin material into the valve which also can cause the piston to stick.
Common features of double piston:
  1. Cannot swell and stick.
  2. Fits loosely in the cylinder.
  3. No tight tolerance fit.
  4. Properties are not altered due to atmospheric change.
  5. Even if foreign material enters the valve,the double piston does not stick.


piston in Azerbaijani: Porşen
piston in Bulgarian: Бутало
piston in Catalan: Pistó
piston in Czech: Píst
piston in Danish: Stempel (motordel)
piston in German: Kolben (Technik)
piston in Estonian: Kolb
piston in Spanish: Pistón
piston in Esperanto: Piŝto
piston in French: Piston
piston in Galician: Pistón
piston in Croatian: Klip stroja
piston in Indonesian: Piston
piston in Italian: Pistone (meccanica)
piston in Hebrew: בוכנה
piston in Latvian: Virzulis
piston in Hungarian: Dugattyú
piston in Dutch: Zuiger
piston in Japanese: ピストン
piston in Norwegian: Stempel
piston in Polish: Tłok
piston in Portuguese: Pistão do motor
piston in Romanian: Piston
piston in Russian: Поршень
piston in Simple English: Piston
piston in Slovak: Piest
piston in Finnish: Mäntä
piston in Swedish: Kolv (maskindel)
piston in Turkish: Piston
piston in Ukrainian: Поршень
piston in Chinese: 活塞
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