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Piston
moving component of reciprocating engines that is contained by a cylinder and is made gas-tight by piston rings / From Wikipedia, the free encyclopedia
For the American composer, see Walter Piston.
For the use of the term in optics, see piston (optics).
In general, a piston is a lubricated sliding shaft that fits tightly inside the opening of a cylinder. Its purpose is to change the volume enclosed by the cylinder, to exert a force on a fluid inside the cylinder, to cover and uncover ports, or some combination of these. A rubber seal is sometimes used to keep the lubricate within the shaft. Due to the constant motion of the machine this seal wears quickly and should be replaced with every servicing. If the seal should break during usage there can be disastrous long lasting consequences for the machine.
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