Abstract: The invention relates to an electro-mechanical force motor device for converting a controlled electrical input signal into a mechanical movement, particularly for actuation of a hydraulic pilot or servo device. The basic component of the invention is a linear electric force motor with its principal components coaxially disposed and arranged to achieve linear mechanical displacement in accordance with an applied signal of voltage. The armature or coil element of the linear force motor is coupled to a double-acting bellows, which not only serves as a double-acting return spring, but also totally isolates the magnetic and electro magnetic elements of the force motor from the controlled system.