Patent ID: 7650974

Claim:
A viscous fan drive assembly used on an internal combustion engine comprising: an output-coupling member including a housing member coupled to a cover member, said cover member including cover wall portion having an axial-extending notch; 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 shalt 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; a fluid reservoir chamber; at least one fill hole contained in said input coupling member fluidically coupling said fluid reservoir chamber to said fluid operating chamber; a scavenge hole including an opening contained in said cover member fluidically coupling said fluid operating chamber to said fluid reservoir chamber; and a wiper element coupled within said notch and contained between said cover wall portion and an outer periphery of said input coupling member; said wiper element including only one pair of spaced apart arm members extending from a radially extending tang member, said arm members extending in a circumferential direction and both extending in the same direction, wherein said opening is disposed between said pair of spaced apart arm members; wherein each of said pair of spaced apart arm members includes a radial outer surface that has a similar radius as said cover wall portion along the entire length of said arm members and a radial inner surface that has a similar radius as the outer periphery of said input coupling assembly along the entire length of said arm members.