Patent ID: 7581627

Claim:
A viscous fluid clutch for a fan assembly, said viscous fluid clutch being movable between an engaged position and a released position, said viscous fluid clutch comprising: a clutch input portion; a clutch output portion rotatably supported with respect to said clutch input portion, said clutch output portion being adapted to transfer torque to said fan assembly, said clutch output portion cooperating with said clutch input portion to defining a working area; a viscous fluid disposed within said working area when said viscous fluid clutch is in said engaged position, said clutch input portion transmitting driving torque to said clutch output portion by shearing said viscous fluid within said working area when said viscous fluid clutch is in said engaged position; and a drain-back mechanism defining at least a portion of a viscous fluid storage chamber, said drain-back mechanism disposed to permit viscous fluid flow from said storage chamber to said working area, wherein the viscous fluid flow is a selected amount, and permit substantially the same amount of viscous fluid to flow from said storage chamber to said working area when said viscous fluid clutch is in said released position regardless of the angular orientation of said viscous fluid clutch.