An actuation device comprises a driving member, a driven member and an actuator device. The driven member has a seat, in which there is operatively inserted, with possibility of relative movement, an engagement part of the driving member. According to the invention also the driving member has a seat, which, in at least one position of the actuation system, at least partially faces the seat of the driven member. The actuation system further comprises a floating body, displaceable in a controlled way between the two seats when said seats at least partially face one another.