Abstract: A linear actuator comprises a piston and a rotary electric motor together with means which are interposed between the electric motor and the piston to define a mechanical system for transforming rotary movement of the motor into linear displacement of said piston, the actuator is characterized in that the electric motor is a vibration type motor comprising at least a stator and a rotor together with excitation means for deforming said stator and/or said rotor in modes of vibration combining tangential vibration and normal vibration for driving said rotor in rotation, and in that the means interposed between the electric motor and the piston include means for mechanically decoupling said piston from said electric motor in the event of the electrical power supply to the elector motor being interrupted.

Abstract: A linear actuator comprises a piston and a rotary electric motor together with means which are interposed between the electric motor and the piston to define a mechanical system for transforming rotary movement of the motor into linear displacement of said piston, the actuator is characterized in that the electric motor is a vibration type motor comprising at least a stator and a rotor together with excitation means for deforming said stator and/or said rotor in modes of vibration combining tangential vibration and normal vibration for driving said rotor in rotation, and in that the means interposed between the electric motor and the piston include means for mechanically decoupling said piston from said electric motor in the event of the electrical power supply to the elector motor being interrupted.