Provided is a servovalve system having a fail safe apparatus adapted for
switching the servovalve system between an operating position and a fail safe position.
The servovalve system comprises a housing having a housing bore and a housing chamber,
a spool moveably disposed within the housing, and a stepper motor connected to
the spool and configured to vary the spool position for manipulating the fluid
flowing within a fluid circuit when the servovalve system is placed in the operating
position. A rotary-linear converter converts rotational motion of the stepper motor
into axial motion of the spool. The fail safe apparatus includes a piston slidably
sealed within the housing chamber and mechanically coupled to the rotary-linear
converter. The piston is operative to move the spool from the operating position
to the fail safe position upon a loss of fluid pressure in the housing chamber.
