Shear type fluid coupling

Claim 1

A COUPLING APPARATUS COMPRISING A PAIR OF RELATIVELY ROTATABLE COUPLING MEMBERS, ONE BEING A HOUSING MEMBER HAVING A CHAMBER AND THE OTHER BEING A ROTOR MEMBER OPERABLE IN SAID CHAMBER, COOPERATIVE PORTIONS ON SAID HOUSING AND ROTOR MEMBERS INCLUDING AXIALLY SPACED OPPOSED SHEAR SURFACES IN A SIDE-BY-SIDE RELATION AND RADIALLY SPACED OPPOSED SHEAR SURFACES IN AN OVERLAPPING RELATION, A VISCOUS SHEAR FLUID IN SAID CHAMBER INCLUDING FLUID IN THE SPACE BETWEEN SAID AXIALLY AND RADIALLY SPACED SHEAR SURFACES AND COOPERABLE WITH SAID AXIALLY AND RADIALLY SPACED SURFACES TO TRANSMIT TORQUE THEREBETWEEN, ONE MEMBER OF SAID PAIR BEING AXIALLY SHIFTABLE RELATIVE TO THE OTHER MEMBER FOR SIMULTANEOUSLY VARYING THE DISTANCE BETWEEN THE AXIALLY SPACED SHEAR SURFACES AND THE AMOUNT OF OVERLAPPING OF THE RADIALLY SPACED SHEAR SURFACES AND THEREBY VARYING THE TORQUE TRANSMITTED BY SAID SHEAR SURFACES, AND MEANS FOR EFFECTING AXIAL SHIFTING OF SAID ONE MEMBER AXIALLY AWAY FROM THE OTHER MEMBER IN RESPONSE TO A TORQUE OVERLOAD CONDITION TO EFFECT SIMULTANEOUSLY A WIDENING OF THE GAP BETWEEN SAID AXIALLY SPACED SHEAR SURFACES AND A DECREASE IN THE AREA OF OVERLAP OF SAID RADIALLY SPACED SHEAR SURFACES WHEREBY THE TORQUE TRANSMITTED BY SAID SHEAR SURFACES AND THUS THE TORQUE OUTPUT IS DECREASED.