Abstract: A self-locking drive, for use in door/gate operators is disclosed. The method/means incorporates an electric motor, which has a rotor assembly that can slide axially in its casing. A brake cone is fixed to the rotor-shaft, which can engage a complimentary brake cone that is attached to the motor casing. At rest these brake cones are very lightly engaged due to an axially mounted spring. The components of the system are designed and configured that any attempt to open the closed door/gate results in the brake cones being forced tighter together. This results in further engagement of the of the brake cones which further resist opening of door/gate. The forcing of the cones together is achieved by helical spur gearing. During motorized closing, the stator's centering pull on the rotor at full load, just balances the axial thrust due to the meshing helical gearing. Consequently, the brake cones do not engage during closing of door/gate.