Screw and screw driver coupling

Claim 1

A COUPLING FOR JOINING TWO ELEMENTS WITH THIER CENTRAL AXES ALIGNED SO THAT TURNING ONE ELEMENT AROUND ITS CENTRAL AXIS WILL TURN THE OTHER ELEMENT, SAID COUPLING COMPRISING A RECESS ON AN END OF ONE ELEMENT AND MATING CONVEX SURFACES ON THE OTHER OF SAID ELEMENTS ADAPTED TO ENTER INTO AND ENGAGE WITH SAID RECESS, SAID RECESS COMPRISING A PLURALITY OF PROJECTIONS, EACH PROJECTION BEING BOUNDED BY A PAIR OF PROJECTION SIDEWALLS WHICH LIE IN PLANES THAT ARE SUBSTANTIALLY PARALLEL TO SAID CENTRAL AXIS, EACH PAIR OF ADJACENT PROJECTIONS BEING SEPARATED BY AN INTERVENING FLUTE, THE SIDEWALL OF EACH ADJACENT PROJECTION FORMING A SIDEWALL OF EACH FLUTE, THE SIDEWALLS OF EACH FLUTE THEREBY BEING SUBSTANTIALLY PARALLEL, EACH FLUTE HAVING AN OUTER WALL INCLINED AT AN ACUTE ANGLE WITH THE CENTRAL AXIS AND EACH FLUTE HAVING A BOTTOM SURFACE WHICH INTERSECTS THE SIDEWALLS AND OUTER WALL, SAID OUTER WALLS AND BOTTOM SURFACES BEING NON-CONVEX RELATIVE TO THE OPENING OF THE RECESS, THE INTERSECTION OF THE BOTTOM SURFACE WITH THE OUTER WALL LYING FARTHER FROM THE CENTRAL AXIS THAN THE PORTION OF THE ADJACENT PROJECTIONS NEAREST THE CENTRAL AXIS, SAID OUTER WALL DIVERGING OUTWARDLY FROM THE SAID INTERSECTION AND THE LONGITUDINAL AXIS, SAID CONVEX SURFACES COMPRISING A PLURALITY OF RADIALLY EXTENDING BLADES, EACH OF SAID BLADES HAVING A PAIR OF SIDEWALLS WHICH ARE SUBSTANTIALLY PARALLEL TO EACH OTHER AND TO THE CENTRAL AXIS, AND WHICH ARE SPACED APART BY SUBSTANTIALLY THE SAME DISTANCE THAT THE SIDEWALLS OF THE FLUTES ARE SPACED APART, EACH BLADE ALSO HAVING AN OUTER WALL AND AN END WALL WHICH BEAR THE SAME ANGULAR RELATION TO THE CENTRAL AXIS AS THE RESPECTIVE OUTER WALL AND BOTTOM SURFACE OF THE FLUTES, THE OUTER WALLS AND END WALLS OF THE CONVEX SURFACES BEING RESPECTIVELY CONGRUENT TO AND ADAPTED TO MAKE FULL SURFACE CONTACT WITH PORTIONS OF THE OUTER WALLS AND BOTTOM SURFACES OF THE RECESS, WHEREBY THE BLADES ARE ADAPTED TO ENTER INTO THE FLUTES WITH THE RESPECTIVE SIDEWALLS IN ENGAGEMENT FOR EFFECTING A TORQUE DRIVING CONNECTION BETWEEN THE TWO ELEMENTS AND WITH THE ELEMENTS HELD IN ALIGNMENT BY THE ENGAGEMENT OF THE OUTER WALLS AND BOTTOM SURFACES OF THE RECESS WITH THE OUTER WALLS AND END WALLS OF THE CONVEX SURFACES, THE BLADES BEING SPACED APART BY GROOVES, THE BOTTOMS OF SAID GROOVES BEING CIRCULAR ARCS, THE INNERMOST PORTIONS OF THE PROJECTIONS BEING TOROIDAL CONVEXLY TOWARD THE CENTRAL AXIS.