by Remundo » 04/10/09, 18:46
1. State of the art of valve techniques
1a) The oldest valve technology is the sliding drawer, used in steam engines. But at the end of the XNUMXth century, the development of steam engines and the first internal combustion engines generated greater pressures: friction increased and compromised the tightness and longevity of the sliding drawers. This will lead to the "modern" valve.
1b) The poppet valves appeared at the end of the XIXth century for advanced steam engines (for example US339809 in 1886), then their evolutions improved the breathing of the combustion engines for the admission and the exhaust. They solve the problems of friction and sealing by the metal assembly integral with a rod and a "tulip", which presses on a bearing surface (the valve seat), thanks to a return spring and / or to gas pressure in the combustion chamber. The rod is guided axially in translation by the cylinder head of the engine and opened by an intermittent thrust in the upper part by various mechanical means (camshaft, crankshafts, rockers, rollers, etc.) driven by the machine (MAC).
Even before the twentieth century, engine manufacturers already offered specific cylinder head layouts with 'poppet' valves, as in GB189519735A dating from 1895 from DE DION & BOUTON. These valves induce significant progress in the efficiency of internal combustion engines, which allow from 1900 until today the full development of motorized vehicles, especially automobiles.
This historical reminder is not without interest because the 'poppet' valves have geometrically changed little. They are almost universally used for engines.
1 C) During the XNUMXth century, many engineers and inventors wished to explore another path: rotary valves. It seems mechanically ill-advised to convert the rotational movement of the engine (generally with pistons, connecting rods and crankshaft) into a translational movement, which is further away since it is placed in the upper part of the engine while the crankshaft is in the lower part.
Thus rotary valves develop and are tested in two different ways:
- Rotary shaft valves, with axis parallel to the motor shaft, typically well described by the patents of Roland Claude CROSS (1923 to 1963, for example CA370900A), but with numerous variants, notably earlier such as those of the MINERVA BOURNONVILLE valve (1920s), or of FRAYER & HOWARD (1909), or else that of BUTLER (1904). We can cite as other related works: MUELLER (1914), FRANCIS (1921), FREYLER (1927), MELLORS (1944), NORTON rotary valves (1960s), LOTUS 2 stroke rotary valve (1990s), spherical rotary valves by Georges J. COATES (1990s, for example US4944261A, still in development).
- Rotary shaft valves, axis orthogonal to the motor shaft, and well described by the patents of Franck ASPIN(1935 to 1975, for example FR931056A), with many other later variants like that of Walter FROEDE (1950s), but also earlier like that of Léonard VALLILEE (1911) or Fernand FOREST (1881). Other related works include: Marcel ECHARD (1920), DENNISSON (1921), Frank W. OFELDT (1924), CRAWFORD (1925), PEACY (1926), Walter F. ISLEY (1942), TJAARDA for BRIGGS (1942) to 1943), GERNANDT for BRIGGS (1944), and a recent elastic approach WO2008129392A1 by THYSSENKRUPP METALURGICA.
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