ISOLATED PROPORTIONAL VALVE

Herein is provided an improved proportional fluid control valve. The proportional valve includes a fluid valve that controls the flowrate of an output fluid. The fluid valve is coupled to a pressure chamber of the control valve. The position of the fluid valve, and the corresponding flowrate of the output fluid, can be varied by changing the pressure of a working fluid within the pressure chamber. The pressure within the pressure chamber can be increased by a piston that pumps working fluid from a reservoir to the chamber. The piston is coupled to a first solenoid and a spring that move the piston in a reciprocating pumping motion. The pressure of the working fluid within the pressure chamber can be decreased by opening a bleeder valve that allows working fluid to flow from the pressure chamber back to the reservoir. The bleeder valve is coupled to a second solenoid and a spring that open and close the valve. The first and second solenoids are connected to a controller that generates digital signals which energize the solenoids and move the piston and bleeder valve, accordingly. The controller can move the fluid valve and vary the output fluid flowrate by energizing the solenoids and either increasing or decreasing the pressure within the pressure chamber.