Abstract: Viscous magnetic clutch for a radiator cooling fan which is electrically energized on closure of thermoswitch mounted within coolant of engine radiator. The clutch plate serves as a fluid pump to feed the viscous sheer area of the clutch so that conventional pump plate construction is eliminated. A drain hole within the clutch plate is controlled by magnetically operated valve mechanism on thermoswitch signal to provide for the retention or exhaust of fluid from the sheer area to provide for the selective hydraulic clutching or declutching of the fan and the drive.

Abstract: Electro-viscous fan clutch having an electromagnet carried by a rotatable pump plate within the confines of the clutch housing. The electromagnet controls a spring arm valve element which is deflected to a spring loaded position by the generated magnetic field so that viscous clutch operation is terminated. On deenergization of the electromagnet, the valve element springs back to a position in which the fluid gate is opened to allow viscous operation of the clutch for engine cooling.

Abstract: Engine cooling fan with viscous-magnetic clutch which is electrically energized on closure of thermal switch mounted within engine coolant. As fan coil housing is driven on engagement of the magnetic clutch, silicone fluid is centrifugally displaced into working area of viscous clutch for fluid drive of fan body. Because of slippage in the fluid drive, fan speeds will gradually increase from minimum to maximum speeds. With progressive increase in speed, conventional fan blading can be employed without excessive fan generated noise.