Locking differential transmission

Claim 1

IN A GEARED DIFFERENTIAL ASSEMBLY HAVING A POWER INPUT SHAFT AND TWO OUTPUT SHAFTS, GEAR ELEMENTS FORMING A DRIVING CONNECTION BETWEEN SAID INPUT SHAFT AND EACH OF SAID OUTPUT SHAFTS, A FRICTION CLUTCH ASSEMBLY COMPRISING A DRIVING MEMBER CONNECTED TO ONE GEAR ELEMENT, A DRIVEN MEMBER CONNECTED TO ANOTHER GEAR ELEMENT, A FIRST FRICTION CLUTCH ELEMENT CARRIED BY SAID DRIVING MEMBER, A SECOND FRICTION CLUTCH ELEMENT CARRIED BY SAID DRIVEN MEMBER, AND SPRING MEANS FOR URGING SAID FRICTION CLUTCH ELEMENTS INTO CLUTCHING ENGAGEMENT, SAID SPRING MEANS COMPRISING AN ANNULAR DISHED SPRING ELEMENT, ONE PERIPHERY OF SAID SPRING ELEMENT BEING ANCHORED AND THE OTHER BEING ADAPTED TO APPLY A FORCE TO ONE OF SAID CLUTCH ELEMENTS, SAID SPRING ELEMENT COMPRISING BI-METALLIC PORTIONS WITH ONE PORTION HAVING A COEFFICIENT OF THERMAL EXPANSION THAT DIFFERS FROM THE CORRESPONDING COEFFICIENT OF THE OTHER PORTION WHEREBY THE SPRING FORCE APPLIED BY SAID SPRING ELEMENT IS CHANGED IN RESPONSE TO A TEMPERATURE BUILD-UP DUE TO SLIPPING OF THE CLUTCH ELEMENTS UNDER LOAD.