Abstract: Electro-pneumatic positioner with a pneumatically driven dual-chamber actuator having a pneumatic main air intake valve and a pneumatic main air discharge valve attached to a pressure pipe of the actuator. The positioner may also include a further main air intake valve and a further main air discharge valve attached to a further pressure pipe of the actuator. Each main valve has an actuating element, with the actuating element for the one and the further main air intake valves each being formed by a corresponding main valve. To manufacture an electro-pneumatic positioner of this type comparatively economically, the actuating element of the one main air discharge valve is formed by a feed pipe which connects the pressurized side of the one main air discharge valve to the interior of the reversing valve of the further main air intake valve.

Abstract: A servo-valve includes a tongue-like piezo-ceramic flexible transducer, which is firmly clamped at one end and can be moved at the other by the application of an electric voltage from a position blocking an air inlet nozzle into one that blocks an air outlet nozzle. To design such a servo-valve in such a way that the effects of distortions of the flexible transducer caused by mechanical and thermal effects can be automatically compensated, one end of the tongue-like flexible transducer is firmly secured to a spindle extending transversely to the flexible transducer. The spindle has a controllable securing device which is released once the voltage is no longer being applied during the return movement of the free end of the flexible transducer towards the air inlet nozzle.