Patent ID: 7100544

Claim:
An on/off fan drive system of an engine comprising: a drive pulley coupled to and rotatable with an engine crankshaft, said engine crankshaft rotating at a given engine speed, said drive pulley having a hub, said hub having an internal threaded portion; a translatable clutch housing coupled to a fan; a drive shaft having an external threaded portion positioned within said translatable clutch housing, said external threaded portion coupled within said internal threaded portion of said hub; a friction liner residing between and engageable with said translatable clutch housing and said drive shaft; a clutch spring positioned between said drive shaft and said cone clutch element, said clutch spring biasing said translatable clutch housing into an engaged position with a clutch engagement force, said engaged position defined wherein said friction liner is fully engaged with said drive shaft to rotate said translatable clutch housing as a function of a rotational rate of said drive shaft; and a fluidic control circuit coupled to said translatable clutch housing and capable of moving said translatable clutch housing between said engaged position and a disengaged position, said disengaged position defined wherein said friction liner is disengaged from said drive shaft and prevents rotation of said translatable clutch housing as a function of said rotational rate of said drive shaft.