Rotary Vane Valves
Rotary Vane Valve having a cylindrical housing with a pair of opposed end bells and an interior axial shaft. A pair of spaced shroud structures are fixed to the shaft at the ends of the vanes to generally separate the interior of the cylindrical housing from the end bells. These shroud structures are spaced from the cylindrical housing at their outer peripheral edges, but an annular throttle plate is spaced axially outwardly at a close distance from these shrouds and adjacent at its outer edge to the cylindrical housing to increase the velocity of purge gas flowing inwardly between the cylindrical housing and the outer peripheral edge of the shroud so that the escape of gas from the interior of the cylindrical housing is effectively prevented. The inner lateral surface of the annular throttle plate is divided into a low pressure zone adjacent the inlet opening and a high pressure zone adjacent the outlet opening in situations where the inlet opening is at a lower pressure than the outlet opening. The low pressure zone is roughened or has a plurality of radially spaced, concentric arcuate grooves while the high pressure zone is recessed with the result that frictional resistance to the flow of purge gas will be greater in the low pressure zone than in the high pressure zone so that the flow of purge gas will tend to be uniformly distributed at all points along the periphery of the throttle plate.
