Drive system with full surface drive contact
A drive system with full surface drive contact. The drive system tends to maximize the surface contact pattern or area at typical bit-recess reaction (drive) torque values, thereby tending to minimize bit-recess surface contact stresses, coating damage, recess ream and premature bit fatigue failure. The drive system comprises a fastener and/or bit having drive surfaces formed of either polygon involutes or a single arc construction. A punch is also provided for forming a recess in either the fastener or the bit, wherein the punch has corresponding surfaces.
1. A fastener comprising at least one of an external drive profile and a recess; drive surfaces on at least one of the external drive profile and the recess, each of said drive surfaces extending from an inner to an outer diameter formed of polygon involutes comprising a plurality of continuous tangent arcs, wherein each arc has a radius pointing toward a center of the fastener, wherein the arcs are concave relative to the center of the fastener, wherein each radius is constant but different, and wherein each radius has a center located on locus points of a radius at the center of the fastener.
2. A fastener as recited in claim 1 , wherein at least one of the external drive profile and the recess comprises a plurality of lobes, wherein each lobe is formed of polygon involutes.
3. A fastener as recited in claim 2 , wherein each lobe is formed of polygon involutes comprised of two arcs.
4. A fastener as recited in claim 3 , wherein each arc has a different radius, and each arc has a constant radius where in each is a segment of a circle.
5. A fastener as recited in claim 3 , further comprising a wall between each lobe, said wall being flat.
6. A fastener as recited in claim 3 , further comprising a wall between each lobe, said wall being at least one of concave circular, convex vertex and concave vertex.
7. A fastener as recited in claim 1 , wherein a top surface of said external drive profile is at least of flat and curved.
8. A fastener as recited in claim 7 , wherein the top surface of said external drive profile has a recess formed therein.
9. A fastener as recited in claim 7 , wherein the top surface of said external drive profile has a hexagon-shaped recess formed therein.
10. A fastener as recited in claim 1 , wherein each of the lobes is truncated.
11. A fastener as recited in claim 1 , further comprising walls between the lobes, wherein the walls taper at least one of inwardly and outwardly.
12. A fastener as recited in claim 1 , further comprising a center post within said recess.