Positive shut-off metering valve with axial thread drive

A sonic venturi valve for metering fuel from a fuel supply to a combustion chamber of a scramjet engine, the valve having a housing defining a fuel chamber in communication with an inlet port coupled to the fuel supply and an outlet port coupled to the combustion chamber via a venturi passageway having a throat through which fuel flows at sonic velocity, the valve comprising:

• (A) a pintle extending along a pintle axis concentric with the venturi passageway, the pintle having a stem connected to a contoured head containing a circumferential seal sized to seal with the throat of the venturi passageway, the pintle stem having an axially extending transverse slot in which is disposed a pin fixed to the housing for preventing the pintle from rotating;
• (B) a pintle guide having an axial bore concentric with the pintle axis in which the pintle stem is disposed and a transverse bore aligned with the transverse pintle stem slot in which the pin is disposed, the pintle guide being fastened to the housing within a drive chamber and sealed to the housing by an annular seal, the axial bore being sized to contact a pintle stem seal throughout the stroke of the pintle;
• (C) a pintle drive mechanism including:
• (i) a servo motor contained within a motor housing connected to the valve housing so that a shaft extends into the housing along the pintle axis;
• (ii) a drive nut mounted at one end to the motor shaft and having a central bore in which the pintle stem is disposed for engaging the pintle stem at mating threads;
• and
• (D) a force distribution assembly comprising:
• (i) a pair of annular thrust bearings disposed about the drive nut, one on each side of an annular drive nut flange;
• (ii) a pair of annular thrust washers disposed about the drive nut, one on each side of each thrust bearing;
• (iii) an annular sleeve disposed about the outer diameter of the thrust washers, the thrust bearings and the drive nut flange, the sleeve being held fixed by an interference fit between the pintle guide and a retaining nut fixed to the housing such that the retaining nut and pintle guide cannot separate from the housing by vibration;
• whereby the motor rotates the drive nut which in turn engages the pintle stem causing translation of the pintle along the pintle axis between an open position allowing media to exit the outlet port and a closed position in which the pintle seal positively engages with the venturi passageway to prevent media from exiting the outlet port.