Thermostatically controlled fan clutch

A thermostatically controlled clutch assembly comprising a non-rotatable support shaft, an annular output member journaled for rotation about said support shaft, an annular input member journaled for rotation about said shaft and said output member, one of said members defining an annular chamber, an annular piston housing having an annular groove in one face thereof, said piston housing being positioned within said annular chamber and journaled for rotation about said support shaft and connected for rotation with said input member, an annular piston received in said groove, clutch driving plates connected for rotation with said output member means defining a first passage within the support shaft for conducting pressurized fluid from an external source to the annular piston housing and piston assembly means for defining a second passage within the support shaft for conducting a supply of cooling and lubricating fluid from said external source to the clutch driving and driven plates, and means for commonly draining both the actuating fluid and the cooling and lubricating fluid from the clutch assembly for return to the external source, a control valve and a temperature sending element arranged to open the valve to admit pressurized fluid to said first passage means at and above a predetermined temperature ambient to said sending element whereby to actuate the clutch and establish a driving connection between the input and output members and to close the valve when the temperature ambient to the sensing element is below said predetermined temperature to deactuate the clutch.