First (3) and second (5) elements are mutually connected by a hinge pin (7). A transmission element (44) is interposed between the second element (5) and a cradle (53) end and includes elastic means (27) having an end connected to the cradle (53) end opposite to transmission element (44). An elongated first box member (41) contains, at least partially, the transmission element (44), the connected cradle (53) and the elastic means (27) whose end opposite to the cradle (53) is fixed to the first box member (41) transmitting the elastic closing force of the elastic means (27) to the second element (5). The cradle (53) contains a damper (57), each end of which has a respective transverse pin (58) whose ends slide in respective slots (54) formed in the cradle (53) and in respective slots (42) formed in the first box member (41).