Abstract: A rotary positive displacement blower (10) of the Roots-type having inlet and outlet vents recess (60,62) for reducing fluid pressure build up in spaces between meshing, helical lobes (34a, 36a) on rotating rotors of the blower.

Abstract: A viscous fan drive having a clutch member with a plurality of restricted fluid flow paths of a given cross sectional area communicating at one end with an element to pump fluid from the restricted flow path to a reservoir and at the other end with radially extending fluid flow paths having a greater cross sectional area than the restricted flow paths and transversing the shear area of the clutch. The restricted flow paths reduce the fluid flow outwardly of the shear area of the clutch member to reduce high speed pumpout and thus increase the speed of the fan when the drive is engaged. The flow paths have a constant cross sectional area, are circumferentially spaced about the clutch member, and transverse the lands and grooves area. The restricted flow paths have a stepped configuration radially outwardly of the flow paths to reduce fluid flow. Each restricted fluid flow path communicates with an axially extending opening transversing the clutch member radially outwardly of the stepped configuration.

Abstract: A fluid coupling device of the type including a rotatable input coupling member, a cover associated therewith to define a fluid chamber, a valve plate separating the fluid chamber into an operating chamber and a reservoir chamber, and an output coupling member disposed in the operating chamber and rotatable relative to the input coupling member. The valve plate defines a discharge orifice permitting the flow of fluid from the operating chamber to the reservoir chamber and a generally flat valve member is located within the reservoir chamber and disposed to move in a plane substantially parallel to the plane of the valve plate to vary the flow area of the discharge orifice. The movement of the valve member defines a valve operating area and the cover includes a portion coextensive with the valve operating area and oriented substantially parallel to the plane of movement of the valve member.