Komatsu Galeo PC800-8 Shop Manual page 197

10 Structure, function and maintenance standard
1-3 Parking brake
The parking brake is a hydraulic release, wet
type, multiple disc negative brake. The release
pressure employs a self-pressure release
method using the travel motor drive pressure
through the oil passage in the counterbalance
valve spool of the travel brake valve.
When the machine is traveling, the drive pres-
sure is sent to port P of the parking brake circuit,
acts on the piston in the brake cylinder chamber,
overcomes the force of the spring and releases
the brake.
When the machine is parked or stopped, the
counterbalance valve spool returns to neutral,
and the oil in the cylinder chamber is released to
the tank through the counterbalance valve
spool, so the brake is applied by the force of the
spring to mechanically lock the motor shaft and
hold the machine in position.
When parking brake is ON
When the travel lever is placed in neutral, the
counterbalance valve spool returns to the neu-
tral position and parking brake circuit P is
closed.
The pressurized oil in chamber e of the brake
piston passes through the counterbalance valve
spool, is drained to the tank, and brake piston
(18) is pushed fully to the left by force Fs of
spring (19), and the brake is applied.
When parking brake is OFF
When the travel lever is operated, the pressur-
ized oil from the pump actuates the counterbal-
ance valve spool, opens the circuit to the
parking brake, and flows into chamber e of
brake piston (18). It overcomes the force of
spring (19), and pushes brake piston (18) to the
right.
When this happens, the force pushing plate (17)
and disc (16) together is lost, so the plate and
disc separate and the brake is released.
PC800, 850-8
SEN00384-02
35