Patent ID: 7455075

Claim:
A servo valve, comprising: a chamber having first and second end caps with first and second pilot valve seats with openings to first and second ports; a force motor comprising a stator having a stator coil and forming a cylindrical portion of said chamber, wherein said force motor further comprises: an armature assembly moveable inside said chamber in response to a current in said stator coil, wherein said armature assembly is held on either end of said chamber with elastic members, wherein said armature assembly comprises: a plurality of pilot valves formed by interfacing with said chamber, wherein each of said plurality of pilot valves is formed when a pilot interfaces with one of said first and second pilot valve seats; a plurality of guide/stops in contact with said armature assembly, wherein said plurality of guide/stops forms a portion of said stator of said force motor; an armature base, and a plurality of magnets attached to said armature base, wherein said plurality of magnets are magnetically polarized axially in opposing directions; a third port coupled to said chamber and configured to receive fluid under pressure; and surface features located on said armature base and on one of said plurality of guide/stops, wherein said surface features are sloped to modify a magnetic path of first and second air gaps and leakage paths between said one of said plurality of guide/stops and said armature base whereby the linearity of a magnetic force to an applied input current can be adjusted by adjusting said surface features, wherein a surface feature of at least one of said plurality of guide/stops comprises: a stepped surface configured to approximate a concave shape, wherein the length of the concave shape can be adjusted to lengthen the proportional stroke and the linearity of said proportional stroke can be adjusted by the degree the stepped surface approximates the concave shape, said at least one of said plurality of guide/stops further comprises a corresponding surface radially oppositely spaced apart from said stepped surface and having a slope matching said stepped surface.