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The word poppet shares etymology with "puppet": it is from the Middle English popet ("youth" or "doll"), from Middle French poupette, which is a diminutive of poupée.The use of the word poppet to describe a valve comes from the same word applied to marionettes, which, like the poppet valve, move bodily in response to remote motion transmitted linearly.
A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring. The valves in a typical four-stroke engine allow the air/fuel mixture into the cylinder at the beginning of the cycle and exhaust spent gases at the end of the cycle.
Most modern engines use poppet valves, although sleeve valves, slide valves and rotary valves have also been used at times. Poppet valves are typically opened by the camshaft lobe or rocker arm, and closed by a coiled spring called a valve spring. Valve float occurs when the valve spring is unable to control the inertia of the valvetrain at ...
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Poppet valve and sleeve valve: commonly used in piston engines to regulate the fuel mixture intake and exhaust; Pressure regulator or pressure reducing valve (PRV): reduces pressure to a preset level downstream of the valve; Pressure sustaining valve, or back-pressure regulator: maintains pressure at a preset level upstream of the valve
A camless or free-valve piston engine is an engine that has poppet valves operated by means of electromagnetic, hydraulic, or pneumatic [1] actuators instead of conventional cams. Actuators can be used to both open and close valves, or to open valves closed by springs or other means.
Double-beat poppet valves became widely used during the nineteenth century. Francis Stevens invented the Stevens valve gear, a double beat poppet valve, in 1839. It was used throughout the nineteenth century and in the early years of the 20th, on side-wheel paddle steamer engines, including the grasshopper engine, in the United States. [ 4 ]
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