Patent ID: 8215329

Claim:
A current to pressure converter (CPC), comprising: a housing defining a control port, a supply port, and a drain port fluidly coupled therethrough; a digital controller enclosed within said housing; a 3-way rotary valve configured to alternatively couple the control port with the drain port, the supply port, or neither the drain port or supply port; a limited angle torque rotary actuator operatively coupled to the digital controller and drivably coupled to the 3-way rotary valve; and a pressure transducer in fluid communication with the control port, the pressure transducer providing pressure feedback to the digital controller; and wherein the digital controller is configured to control the pressure supplied by the control port in proportion to an input analog control signal of 4-20 mA; wherein the 3-way rotary valve comprises: a hydraulic control bushing in fluid communication with each of the control port, the supply port, and the drain port; a hydraulic control shaft rotatably positioned within the hydraulic control bushing to control valving of the control port; and redundant dynamic sealing system operably positioned between the hydraulic control bushing and the hydraulic control shaft, the redundant dynamic sealing system having an inboard dynamic seal and an outboard dynamic seal and an intermediate passage positioned between the inboard and the outboard dynamic seals, the intermediate passage in fluid communication with the drain port to reduce pressure drop across the outboard dynamic seal.