Digital servo valve system

A digital servo valve system for controlling a displaceable actuator, comprising:

• a valve body having an interior longitudinal cavity with a plurality of ports spaced there along, said ports being in fluid communication with a pressurized fluid source, a fluid pressure return and said actuator;
• a valve spool displaceable within said cavity along a longitudinal axis, said valve spool having a plurality of substantially cylindrical lands alternately spaced with a plurality of recessed regions, said valve spool cooperatively configured with said valve body to regulate fluid flow through said ports in dependence on said valve spool axial position;
• motor means having a drive shaft, said motor means establishing rotational positions of said shaft in response to position command signals;
• rotary-to-linear translation means within said valve body and coupling said drive shaft and said valve spool for converting rotational positions of said shaft to linear positions of said valve spool;
• a controller coupled to said motor means for generating said position command signals;
• and
• null adjustment means for establishing a rotational null position of said shaft and a null position of said valve spool within the cavity of the valve body at which null position said valve spool cuts off fluid flow through said valve body, said null adjustment means comprising:
• an index coupled to said shaft for rotation with said shaft,
• shaft stop means mounted in said valve body and located at a null position,
• a torsion spring mounted coaxially of said shaft and engaging said index and said shaft stop means such that said torsion spring exerts a force urging the index toward said shaft stop means, and
• shaft stop adjustment means for adjusting the position of said shaft stop means.