Temperature responsive viscous fan drive

Claim 1

A viscous drive comprising: a housing member having an annular peripheral surface; a clutch member rotatable relative to the housing member and disposed within the housing member to define an operating chamber, the clutch member having a pair of axially spaced generally radially extending annular surfaces and an outer peripheral surface spaced from the peripheral surface of the housing member; a fluid storage chamber separate from and adjacent to the operating chamber; an opening between the operating chamber and the storage chamber for providing fluid flow communications between the chambers, the opening being carried by the housing member; valve means effecting selective fluid communication via the opening between the storage chamber and the operating chamber temperature responsive means controlling the valve means; fluid disposed within the storage chamber and being selectively displaced into the operating chamber when the valve means is in a fluid communication position whereby the fluid is positioned in the operating chamber to transmit energy via the fluid from one of the members to the other of the members; pump means comprising an impeller element carried by one of the members in the operating chamber and being effective to pump fluid from the operating chamber to the storage chamber, the impeller element being located radially outwardly from the rotational axis substantially along the outer periphery of the clutch member; and a notch for improving pump-out time in the peripheral surface of one of the members extending parallel to the axis between the axially spaced surfaces of the clutch member and opening radially toward the peripheral surface of the other member.