An actuator comprising a reversible electric motor, which over a gearing, drives an activation element which can move back and forth. The activation element is of the non-self-locking type. Furthermore the motor and gearing are of a non self locking type. A brake holds the activation element in any position, when the electric motor is inactive, said brake can be released by means of a release mechanism. The motor is used as generator when the brake is released and the generator voltage from it is used to adjust the velocity of the activation element. Thus, a quick release is provided, where the activation element can be disengaged and adjusted evading gear and motor, and where the movement of the activation element, during the disengagement, occurs with a controlled velocity.