MECHANICAL JOINT WITH SELECTABLE TRANSMISSION MODE

A rotational joint (100) arranged to operate selectively at least two modes of transmission of a rotational movement between an input, arranged to carry out a rotation having angular acceleration ω about a longitudinal axis y, and an outlet (190), arranged to carry out a rotation having angular acceleration ϑ about longitudinal axis y. The rotational joint (100) comprises a driving plate (110) integrally connected to the inlet and arranged to carry out a rotation having angular acceleration ω about longitudinal axis y, said driving plate (110) comprising a plurality of radial housings (111,112). The rotational joint (100) also comprises a transmission ring (121,122) connected to the outlet (190) and co-axial to the driving plate (110), said transmission ring (121,122) arranged to carry out a rotation having angular acceleration φ about longitudinal axis y. The rotational joint (100) comprises then a plurality of connection elements (131,132) subjected to the resilient force of a plurality of springs (141,142), said resilient force arranged to push the connection elements (131,132) towards a plurality of slots (A1,A2) located between the driving plate (110) and the transmission ring (121,122), said connection elements (131,132) being configured, when they are located in the slots (A1,A2), to come into simultaneous contact with the driving plate (110) and the transmission ring (121,122), generating by friction a constraint of fixed joint adapted to generate the condition ω = φ. The rotational joint (100) comprises also a plurality of selectors (151,152) arranged to slide radially in the radial housings (111,112) between a free position, where the selectors (151,152) are adapted to counteract the resilient force and to remove the connection elements (131,132) by the slots (A1,A2), and a constrained position, where the connection elements (131,132) are located in the slots (A1,A2). A cam (160) is also provided equipped with a plurality of elongated holes (161,162). The selectors (151,152) comprise a plurality of maneuvering portions (151', 152') constrained to slide in the plurality of elongated holes (161,162). The cam (160) is configured arranged to carry out a rotation, relatively to the driving plate (110), about longitudinal axis y, said rotation generating a sliding of the maneuvering portions (151', 152') in the elongated holes (161,162) causing the movement of the selectors (151,152) between the free position, where the acceleration φ is independent fr