Tri State Hydraulics

9 Summary of Conclusions

The hydraulic servo valve has made tremendous improvements in reliability and life expectancy from the first introduction in 1951.  The technological refinements have not changed the fundamental mechanical design of the servo valve.  A multitude of refinements have led to theses improvements.  The selection of carbide material as ball on the feedback mechanism, the  introduction of the "ball-in-hole" in the spool, and brazing used to bond the ball to wire are innovations that are the core to Moog's high performance servo valves.

Extensive test results demonstrate that carbide is as durable as sapphire, but has the advantage that it can be bonded to the feedback mechanism wire with a brazing process.  Brazing bond between the wire and ball of the feedback mechanism enables this critical component to withstand deterioration from hydraulic fluid chemicals and high temperatures.  However, the ball-in-hole further extended the life of the servo valve by eliminating wear in the spool, ensuring that the servo valve will maintain reliable, accurate performance for a very long time while being resistant to deterioration and high temperatures in critical machine applications.

Critical Specifications of Servo Valves

  • Carbide material as ball on the feedback mechanism

  • The ball-in-hole in the spool

  • Brazing used to bond the ball to wire

PUMPS, VALVES & MOTORS MOOG Valves Design of Long Life... 9 Summary of Conclusions