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 pressurized motor port through a groove in
motor when traveling down a slope.
the counterbalance valve (E), to the park brake
pressure reducing valve (B), and then to the park
Servo piston shuttle valve (F) routes supply oil from
brake piston to release the park brake.
the pressurized 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).