Mechanical joint with torque limiter comprising a containment body, a first rotary part and a second rotary part, said first rotary part and second rotary part being supported by said body so as to be able to rotate about a respective predetermined rotation axis (Y-Y) and defining motion input part or motion output part into/from said mechanical joint, wherein: - said first rotary part comprises locking cylinders projecting transversally to the respective rotation axis (Y-Y); - said locking cylinders are supported by said first rotary part so as to be able to move between an operative engagement position, in which said locking cylinders engage the second rotary part so as to make it rotate as a unit with the first rotary part, and an operative disengaged position in which substantially said locking cylinders do not engage said second rotary part making said second rotary part substantially free in rotation with respect to said first rotary part; - said joint comprises means for pushing said locking cylinders with a predetermined elastic load towards said operative engagement position, wherein said means for pushing said locking cylinders with a predetermined elastic load towards said operative engagement position comprise: - hydraulic actuation means in which a hydraulic circuit contains a hydraulic working liquid that acts on said locking cylinders to push said locking cylinders towards said operative engagement position; - gasket means to prevent pressurised liquid from leaking from said hydraulic circuit and - pressing means to place the hydraulic working liquid in said hydraulic circuit under pressure with a predetermined pressure value, characterised in that said pressing means to put the hydraulic working liquid in said hydraulic circuit under pressure comprise a gas spring in which a mobile piston comes out from a body containing pressurised gas acts on the hydraulic working liquid of said hydraulic circuit to keep it under pressure with a predetermined load. - said first rotary part comprises locking cylinders projecting transversally to the respective rotation axis (Y-Y); - said locking cylinders are supported by said first rotary part so as to be able to move between an operative engagement position, in which said locking cylinders engage the second rotary part so as to make it rotate as a unit with the first rotary part, and an operative disengaged position in which substantially said locking cylinders do not engage said second rotary part making said second rotary part substantially free in rotation with respect to said first rotary part; - said joint comprises means for pushing said locking cylinders with a predetermined elastic load towards said operative engagement position, wherein said means for pushing said locking cylinders with a predetermined elastic load towards said operative engagement position comprise: - hydraulic actuation means in which a hydraulic circuit contains a hydraulic working liquid that acts on said locking cylinders to push said locking cylinders towards said operative engagement position; - gasket means to prevent pressurised liquid from leaking from said hydraulic circuit and - pressing means to place the hydraulic working liquid in said hydraulic circuit under pressure with a predetermined pressure value,