Abstract: A fluid coupling (1) with a sealed casing (2) including two mutually communicating chambers (21, 23) and traversed by a driven shaft (10) connected to a user, one of said chambers (21) containing a pair of rotors (15, 17) provided with radial blades (16, 18), a driving first rotor (17) being operationally connected to a driving shaft and the driven second rotor (15) being associated with the driven shaft (10), the other chamber (23) acting as a delay chamber, the casing (2) containing a fluid arranged to transfer motion from the driving rotor (17) to the driven rotor (15). Within the sealed casing (2) there is provided at least one further chamber or reservoir (22) connected to said two chambers (21, 23) such as to feed the fluid contained in it to the delay chamber (23) with a delay subsequent to the starting of the motor, said fluid being transferred with a further delay to the working chamber (21) containing the rotors (15, 17).