Face driving chucks for machine tools

Claim 1

A DRIVING CHUCK, COMPRISING A CYLINDRICAL BODY HAVING A REAR CENTRAL BOSS, AN AXIAL HOLE AND A CYLINDRICAL RECESS ENCLOSING SAID BOSS, SAID BOSS HAVING A CIRCULAR SHOULDER IN SAID HOLE; A COVER CLOSING SAID RECESS AND ENGAGING SAID BOSS, SAID BODY FURTHER HAVING A PLURALITY OF HOLES EQUIDISTANT FROM AND PARALLEL TO SAID AXIAL HOLE AND ANGULARLY DISPOSED RELATIVELY TO EACH OTHER, DRIVING PINS IN THE LAST-MENTIONED HOLES, EACH OF SAID PINS HAVING A FRONT CHISEL-SHAPED END DISPLACED IN RELATION TO THE PIN AXLE AND A REAR ANGULAR END WITH TWO PLANE WALLS FORMING AN INCLINED DIHEDRAL; A RING FREELY MOUNTED IN SAID RECESS AND HAVING AN INNER DIAMETER WHICH IS LARGER THAN THAT OF SAID BOSS, BALLS MOUNTED IN SAID RECESS EXTERNALLY OF SAID RING IN CORRESPONDENCE WITH SAID PINS, SAID BALLS BEING LOCATED BETWEEN THE REAR DIHEDRALS OF SAID PINS, SAID COVER AND THE OUTER SURFACE OF SAID RING, A CENTERING PIN SLIDABLE IN SAID AXIAL HOLE AND HAVING A WORKPIECE-CENTERING FRONT TIP AND A REAR END HAVING A PROJECTION ADAPTED TO ENGAGE SAID SHOULDER, AND A COILED SPRING ENGAGING SAID COVER AND THE REAR END OF SAID CENTERING PIN.