Planar torsional spring

A torsional spring comprising a body and connection means of said body to an actuating element and to an actuated element to elastically react to a torsional load exchanged around a transmissive axis (Z),

• wherein said body is a unitary body with a planar structure, that is mainly developing on plane (XY) orthogonal to said transmissive axis (Z), and substantially delimited in said plane by a circular or polygonal imaginary outline (c1) circumscribing the outer periphery of said body, centered in said transmissive axis (Z), a number of cavities being formed in said body by removal of material, defining on the same body a beam-like pattern comprising an even number n of modules, each module occupying a sector delimited by said outline (c1) and by two radiuses (r1, r2) forming a central angle of 2·π/n, each module comprising:
• two main radial members arranged along respective radiuses (r1, r2) and shared among adjacent modules, each main radial member having a radially internal end and a radially external end and forming a single elongate shape aligned along the respective radiuses (r1, r2);
• and
• a linking portion evolving between, and only linked with, two internal or external ends of the two main radial members of the module so as to be circumferentially spaced and separate from the two main radial members, symmetrically between two adjacent modules with respect to either radius (r1, r2) that separates them, and such that in each main radial member one only and the same internal end or external end be shared between two linking portions of respective adjacent modules,
• wherein said connection means are provided at free ends of said main radial members opposite with respect to the ends from which the linking portions evolve, said free ends being all radially external ends or radially internal ends;
• wherein said linking portions evolve in a serpentine fashion and each linking portion comprises first and second secondary radial members spaced apart by a circumferential member.