TM 5-3805-280-24-1
Theory of Operation
oil flows through the dig pilot pressure signal passage
The function of swing motor park brake release valve
to the return passage causing the pressure signal to
(L) is to route pilot oil pressure (D) to the piston
decrease. The release valve spool (F) is shifted by the
releasing the brake pack when a dig or swing function
spring blocking the flow of pilot oil pressure to the
is actuated.
piston (B) chamber. The oil in the piston chamber
flows through the orifice (C) to return as the springs
Park Brake Released (I):
push the piston down applying the park brake. The oil
When a swing or dig function is actuated, the flow of
is metered through the orifice to slow engagement to
pilot oil through dig pilot pressure signal passage in
ensure that park brake is only fully applied after the
the control valve is blocked by a valve spool (H). The
upperstructure has stopped. The orifice and check
dig pilot pressure signal (A) increases and shifts the
valve is located in the swing motor housing adjacent to
swing motor park brake release valve spool (F). Pilot
the swing motor park brake release valve.
pressure oil (D) from the solenoid valve manifold flows
through the spool to piston (B) chamber. The pilot
Pilot oil pressure (D) is maintained at the release valve
pressure oil pushes the piston up against the spring
spool (F) as long as the pilot shutoff valve is ON. The
releasing the brake pack (K). The upperstructure is
circuit for pilot oil pressure is from the pilot pump (E),
now free to turn.
through the pilot shutoff valve, solenoid valve manifold,
and then to the release valve spool.
Park Brake Applied (J):
When the valve spool (H) is returned to neutral, pilot
TX,05,GG2197 1920MAY982/2
9025
05
70
6-66
