Patent ID: 7963380

Claim:
A method for improving pumping efficiency in a viscous fan drive during operation, the viscous fan drive including an output-coupling member including a housing member coupled to a cover member, an actuator shaft partially disposed within said output-coupling member, an input-coupling assembly coupled to said actuator shaft and including an input-coupling member, said input-coupling-assembly and said actuator shaft capable of rotating at a given input speed, a fluid operating chamber including a shear space defined by said input-coupling member and said cover member, at least one fill hole contained in said input coupling member fluidically coupling said fluid reservoir chamber to said fluid operating chamber; and a scavenge hole including an opening contained in said cover member fluidically coupling said fluid operating chamber to said fluid reservoir chamber, the method comprising: forming a wiper element of a molded plastic material comprising a pair of spaced apart arms coupled to and extending from a radial tang member, said arm members both extending in the same direction and positioned substantially perpendicular to said tang member and the longitudinal length of said arm members being substantially the same and the longitudinal length being substantially greater than the longitudinal length of said tang member; introducing a notch to a cover wall portion of a cover member; and introducing said wiper element between said cover wall portion and an outer periphery of an input coupling member such that said radial tang member is contained within said notch and such that the radial outer surface of said pair of spaced apart arm members have a similar radius as said cover wall portion and such that the radial inner surfaces have a similar radius as an outer periphery portion of said input coupling-member along said length and such that said opening of said scavenge port is contained between said pair of spaced apart arm members; wherein dynamic fluid sealing and pumping efficiency are improved.