LATCHABLE ELECTROHYDRAULIC SERVOVALVE

摘要

An electro-hydraulic servovalve (EHSV) ( 10 ) that includes a nozzle ( 16 ), a motor ( 12 ) operably connected to the nozzle ( 16 ) for controlling the position of the nozzle ( 16 ) based on current provided to the motor ( 12 ), a spool ( 18 ) having first and second ends ( 22,26 ) slidably mounted in a sleeve ( 34 ) having first and second ends ( 31,33 ) and a first land ( 21 ) near the first end ( 22 ), a first passage ( 40 ) extending from near the nozzle ( 16 ) to the first end ( 31 ) of the sleeve ( 34 ), a second passage ( 42 ) extending from near the nozzle ( 16 ) to the second end ( 33 ) of the sleeve ( 34 ), the spool ( 18 ) shifting to a first fail-safe position when the current is below a first predetermined level and latching in a second fail-safe position different than the first fail-safe position when the current exceeds a second predetermined level greater than the first predetermined level.