Fan clutch

Claim 1

A FRICTION DRIVE COMPRISING AN ENGINE DRIVEN DRIVE SHAFT, A DRIVE UNIT HAVING A HUB SUPPORTED FOR ROTATION UPON SAID DRIVE SHAFT, MEANS DRIVEN BY SAID HUB SUBJECTING SAID HUB TO AN INCREASING LOAD AS THE SPEED OF ROTATION OF SAID HUB INCREASES, FRICTION ENGAGING MEMBERS WITHIN SAID DRIVE UNIT FOR TRANSMITTING TORQUE FROM SAID DRIVE SHAFT TO SAID HUB, A TEMPERATURE RESPONSIVE POWER ACTUATOR CARRIED BY SAID DRIVE UNIT AND HAVING AN ACTUATOR ELEMENT EXTENDING INTO SAID UNIT, SAID ACTUATOR ELEMENT BEING MOVABLE THROUGH A LIMITED RANGE OF MOTION IN RESPONSE TO VARIATION OF TEMPERATURE OF SAID ACTUATOR, MEANS FOR TRANSMITTING FORCE FROM SAID MOVABLE ELEMENT TO SAID FRICTION ENGAGING MEMBERS, SAID FORCE TRANSMITTING MEANS BEING NORMALLY EFFECTIVE TO BIAS SAID ACTUATOR ELEMENT TO A RETRACTED POSITION TO RELEASE SAID FRICTION ENGAGING MEMBERS, SAID FORCE TRANSMITTING MEANS BEING EFFECTIVE IN A FIRST RANGE OF MOTION OF SAID MOVABLE ELEMENT TO TRANSMIT FULL FORCE FROM SAID MOVABLE ELEMENT TO SAID FRICTION ENGAGING MEMBERS, SAID FORCE TRANSMITTING MEANS COOPERATING WITH SAID MOVABLE ELEMENT IN A SECOND RANGE OF MOVEMENT OF SAID MOVABLE ELEMENT TO APPLY A LIMITED FORCE TO SAID FRICTION ENGAGING MEMBERS, SAID FRICTION MEMBERS BEING RETAINED IN NON-SLIPPING ENGAGEMENT WHEN THE SPEED OF SAID DRIVE SHAFT IS BELOW A PREDETERMINED MAXIMUM SPEED OF ROTATION AND IN SLIPPING FRICTIONAL ENGAGEMENT WHEN THE SPEED OF ROTATION IS GREATER THAN SAID PREDETERMINED MAXIMUM SPEED OF ROTATION TO LIMIT THE MAXIMUM SPEED OF ROTATION OF SAID HUB TO SAID PREDETERMINED MAXIMUM SPEED.