Abstract: A valve actuation system with cooperating pneumatic and hydraulic control features. Compressed pneumatic fluid is generated in a pneumatic fluid supply, and flows in response to requirements between a predetermined command signal and an existing position of a working fluid valve. Hydraulic fluid is pressurized by a pump, and stored within the system by an accumulator. A servo valve comprising a pneumatic fluid flow path and a hydraulic fluid flow path is included to facilitate the flow of hydraulic fluid through the servo valve hydraulic fluid path and a downstream actuator for the working fluid valve in proportion to changes in pneumatic fluid flow through the servo valve pneumatic fluid flow path. A saturated fluid feedback circuit is included to shut off the flow of pneumatic and hydraulic fluid during select periods, such periods typically coincident with static conditions within the actuator of the working fluid valve, thereby reducing pump duty cycle.

Abstract: A valve actuation system with cooperating pneumatic and hydraulic control features. Compressed pneumatic fluid is generated in a pneumatic fluid supply, and flows in response to requirements between a predetermined command signal and an existing position of a working fluid valve. Hydraulic fluid is pressurized by a pump, and stored within the system by an accumulator. A servo valve comprising a pneumatic fluid flow path and a hydraulic fluid flow path is included to facilitate the flow of hydraulic fluid through the servo valve hydraulic fluid path and a downstream actuator for the working fluid valve in proportion to changes in pneumatic fluid flow through the servo valve pneumatic fluid flow path. A saturated fluid feedback circuit is included to shut off the flow of pneumatic and hydraulic fluid during select periods, such periods typically coincident with static conditions within the actuator of the working fluid valve, thereby reducing pump duty cycle.