Accessory drive mechanism

Claim 1

IN A VEHICLE ENGINE COOLING SYSTEM, A FAN UNIT FOR COOLING SAID ENGINE, SAID FAN UNIT COMPRISING A POWER INPUT MEMBER DRIVEN BY SAID ENGINE AT SPEEDS PROPORTIONAL TO ENGINE SPEED, A FAN SUPPORT HOUSING ROTATABLE AT VARIABLE SPEEDS OF ROTATION WITH RESPECT TO SAID POWER INPUT MEMBER, FAN BLADE CARRIED BY SAID HOUSING FOR ROTATION THEREWITH, SAID HOUSING ENCLOSING A CHAMBER, A ROTATABLE MEMBER DISPOSED IN SAID CHAMBER AND DRIVEN BY SAID POWER INPUT MEMBER, A U-SHAPED PERMANENT MAGNET RING DISPOSED WITHIN SAID CHAMBER FOR TRANSMITTING TORQUE FROM SAID ROTATABLE MEMBER TO SAID HOUSING IN RESPONSE IN ROTATION OF SAID ROTATABLE MEMBER BY SAID POWER INPUT MEMBER, A MAGNET SHUNTING RING CARRIED BY SAID PERMANENT MAGNET RING AND EXTENDING BETWEEN THE ARMS OF SAID U-SHAPED PERMANENT MAGNET RING, SAID SHUNTING RING BEING FORMED OF A TEMPERATURE SENSITIVE MAGNETIC MATERIAL CHARACTERIZED BY ITS ABILITY TO VARY ITS PERMEABILITY WITH CHANGES IN TEMPERATURES NORMALLY ENCOUNTERED IN THE NORMAL OPERATION OF SAID ENGINE, SAID SHUNTING RING BECOMING INCREASINGLY MAGNETIC WITH A DROP IN TEMPERATURE AND LESS MAGNETIC WITH A RISE IN TEMPERATURE, SAID PERMANENT MAGNET RING BEING FORMED OF MAGNETIC MATERIAL CHARACTERIZED BY ITS ABILITY TO MAINTAIN A SUBSTANTIALLY CONSTANT FLUX DENSITY WITHIN THE NORMAL RANGE OF TEMPERATURE ENCOUNTERED IN OPERATION OF SAID ENGINE.