Editing Piston (section)

{{Short description|Machine component used to compress or contain expanding fluids in a cylinder}}
{{other uses}}
{{More citations needed|date=September 2013}}
[[File:Piston of DAT engine.jpg|thumb|Pistons within a sectioned [[petrol engine]]]]
[[File:Piston.gif|thumb|upright|Animation of a piston system.]]
A '''piston''' is a component of [[reciprocating engine]]s, reciprocating [[pump]]s, [[gas compressor]]s, [[hydraulic cylinder]]s and [[pneumatic cylinder]]s, among other similar mechanisms. It is the moving component that is contained by a [[cylinder (engine)|cylinder]] and is made gas-tight by [[piston ring]]s. 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 [[Porting (engine)#Two-stroke porting|ports]] in the cylinder.
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