US Patent 7322375 High bandwidth rotary servo valves

A valve includes a rotating, substantially pressure-balanced spool that selectively aligns openings within the spool with openings within a sleeve to selectively connect ports of a manifold for gas or liquid routing. A valve may also include a stem, a needle coupled to the stem. a seat configured to receive the needle, a reservoir, an outlet coupled to the reservoir, and a servo motor coupled to the stem. The servo motor rotates the stem to raise or lower the needle relative to the seat to variably restrict or allow matter flowing from the reservoir to the outlet.