Two-stage closed center electro-hydraulic valve

A two-stage servovalve comprising:

• a motor having a stator and a rotor having a rotor null position and configured and arranged to rotate about a motor axis under the effect of a magnetic field generated by said stator;
• a bias mechanism configured and arranged to bias said rotor to said rotor null position;
• a first stage valve having a first valve member movably mounted in a first chamber along a first valve axis, and adapted to be moved from a first null position to a first off-null position along said first chamber axis to selectively meter fluid flow from at least one port defined between said first valve member and said first chamber;
• a second stage valve in fluid communication with said port of said first valve and having a second valve member movably mounted in a second chamber along a second valve axis, and adapted to be moved from a first position to a second position along said second valve axis as a function of movement of said first valve member, to selectively meter the flow of fluid from at least one port between said second valve member and said second chamber;
• said first stage valve and said second stage valve configured and arranged such that said second stage valve member is at a pressure equilibrium and does not move when said first stage valve member is in said null position;
• a transfer link acting between said first valve member and said second valve member;
• an eccentric drive member acting between said rotor and said transfer link and having a first eccentric axis that is off-set a distance from said motor axis and arranged such that selective rotation of said rotor about said motor axis causes said transfer link to move;
• said transfer link and said drive member configured and arranged such that selective movement of said rotor from said rotor null position to a second rotor position causes said drive member and said transfer link to move said first valve member from said first null position to said first off-null position;
• movement of said first valve member from said first null position to said first off-null position causes said second valve member to move from said first position to said second position;
• and
• said movement of said second valve member to said second position causes said transfer link to move said first valve member from said first off-null position back to said null position.