US Patent 10342292 Sole for footwear

A sole having respective forefoot, midfoot and backfoot parts, which are contiguous in a longitudinal direction running from toe to heel, and including a stiffening shank extending in the longitudinal direction from toe to heel. The shank extends over a predominant portion of the longitudinal development from the backfoot part to the forefoot part, and has areas of different flexibility alternating along the longitudinal development, the flexibility of these areas being progressively variable in a substantially continuous manner between one area and the contiguous areas.