Theory of Operation
control valve is blocked by a valve spool (H). The dig
The function of park brake release valve spool (F) is to
pilot pressure signal increases and shifts the park
route pilot oil (I) to the piston (B) releasing the brake
brake release valve spool (F). Pilot pressure oil from
pack when a dig or swing function is actuated.
the solenoid valve manifold (D) flows through the spool
to piston (B) chamber. The pilot pressure oil pushes
Swing Motor Park Brake Released (K): When swing
the piston up against the spring releasing the brake
or a dig function is actuated, the flow of pilot oil
pack. The upperstructure is now free to turn.
through dig pilot pressure signal passage (E) in the
Continued on next page