The actuator unit includes a hollow body defining a sliding chamber within; a piston mounted sliding inside said sliding chamber such to provide an actuation force and operated by a fluid fed from the outside; a body having one transmission end for the transmission of said actuation force prolonged outside said sliding chamber and one hooking end hooked to said piston, amplification means being interposed between said body and said piston to amplify said actuation force so as to obtain an amplified actuation force.