Theory of Operation
Counterbalance valve (E) is used for smooth starting
Park brake release shuttle valve (A) routes supply oil
and stopping and helps prevent overrunning of the
from the pressurize motor port through a groove in the
motor when traveling down a slope.
counterbalance valve (E), to the park brake pressure
reducing valve (B), and then to the park brake piston
Servo piston shuttle valve (F) routes supply oil from
to release the park brake.
the pressurize motor port to the servo piston. (For
operation of servo piston and speed selector valve,
Park brake pressure reducing valve (B) reduces the
see Propel Motor Slow Speed Operation and Propel
supply oil pressure routed to the park brake to prevent
Motor Fast Speed Operation in this group.)
sudden brake application.
Crossover relief valves (C) protect the motor circuit
Check valves (D) ensure smooth starts and stops, and
prevent motor cavitation by working together with the
counterbalance valve (E).