Patent ID: 8028968

Claim:
A variable orifice gas flow modulating valve comprising: an orifice hood with a wall defining a recess and an outlet orifice, the recess including a tapered section that narrows from a wide portion to a narrow portion, the outlet orifice extending from the narrow portion of the recess through the wall to an outer surface of the orifice hood; a metering pin including— a central portion extending along a length of the metering pin, and a plurality of fins, each fin extending radially outwardly from the central portion and extending only along a portion of a length of the metering pin, the fins and central portion being tapered at an end of the metering pin such that the tapered portion of the metering pin conforms to the tapered section of the recess, the metering pin including a passage for allowing gas to pass through the metering pin to the outlet orifice, the fins being spaced apart along a circumference of the metering pin with an elongated four-sided opening between each pair of fins allowing gas to flow from the recess to the passage, each opening extending approximately half the length of the fins; and an actuator comprising an electric motor mechanically linked to the metering pin and operable to rotate a threaded rod that is substantially parallel with a longitudinal axis of the metering pin for moving the pin between an open position where the metering pin is separated from the tapered section of the recess by a first distance and allows gas to flow around an outer surface of the tapered portion of the pin to the outlet orifice, at a first rate, an intermediate position where the metering pin is separated from the tapered section of the recess by a second distance and allows gas to flow around an outer surface of the tapered portion of the pin to the outlet orifice at a second rate, and a closed position where the tapered portion of the metering pin is seated against the tapered section of the recess and restricts substantially all gas flow to the passage of the metering pin and the outlet orifice, wherein the second distance is less than the first distance and the second rate is less than the first rate, wherein the actuator is operable to move the metering pin without removing the orifice hood and the actuator is operable to continuously adjust a flow of a gas through the outlet orifice.