Coupling structure between screw head and tightening tool
A coupling structure between a screw head and a tightening tool includes a recess ( 3 ) with a curved concave surface on the free base of the head ( 1 ) of the screw ( 2 ) and a protuberance ( 6 ) with a curved convex surface finishing the end of the tool ( 5 ). The recess has axial projections ( 4 ) internally and the protuberance ( 6 ) has meridional grooves ( 7 ).
1. A tightening tool having an end comprising:
a protuberance with a substantially spherical surface, which is complementarily coupleable in a recess on a free base of a screw head; the recess has axial projections extending from inside the recess and an edge of a wall with a curved convex surface and transverse section decreasing towards the inside of the recess; wherein said axial projections are configured to transmit torque of the tightening tool on the screw; and the protuberance of which has meridional grooves, which couple on the axial projections, wherein said grooves start from the base of said protuberance, and reach areas close to a pole thereof, the grooves having a curved concave transverse section and a curved longitudinal section between opposed grooves, both the curved transverse section and the curved longitudinal section decreasing towards the pole of said protuberance, and being separated from one another by spherical lunes, which start from the base of the protuberance and reach the areas close to the pole, the spherical lunes having a curved convex external surface which is coincident with the protuberance.
2. Tightening tool according to claim 1 , wherein the spherical lunes are separated from one another with a maximum width smaller than a separation between consecutive axial projections of the recess of the screw head.
3. A tightening tool according to claim 1 , the screw head comprising a recess on the free base of the screw head, the recess has inside, axial projections extending from inside the edge of the wall with a curved convex surface and transverse section decreasing towards the inside of the recess wherein the axial projections do not reach the bottom of the recess and are circumferentially separated from one another by a distance greater than a maximum width of said axial projections.