Form No. 29703
SWING BRAKE RELEASE VALVE
The swing brake release valve, located in the valve tray, deactivates the swing parking brake and holds it released
during the swing cycle. It is pressurized any time the upperstructure engine is running.
Whenever swing right/left is selected at the joystick, pressure is directed to the swing pump controls. A portion of
this fluid is routed to the shuttle valve in the swing brake release valve. The shuttle shifts, (blocking opposite
right/left joystick port) directing fluid to the sequence valve, opening it to the swing brake port. With the sequence
valve shifted, pressurized fluid posses through it to the swing brake, releasing it. The swing brake should release
before the swing motor starts turning. When the swing joystick is returned to neutral, the swing deactivates. Pilot
fluid pressure to the shuttle valve drops to zero. The sequence valve shifts to a neutral position. Pressure fluid from
the brake is directed to tank. The fluid flows through a predetermined sized orfice valve which restricts flow until
the upperstructure stops swinging. This restricted flow keeps the swing parking brake pressurized until
approximately 3 seconds after swing stops.
The swing brake release valve contains three cartridges. They are:
Shuttle Valve:
Sequence Valve:
Orifice Valve:
XI. Swing Circuit
(continued)
FIGURE 41
SWING BRAKE RELEASE VALVE
Directs fluid to the sequence valve. Shifts to block unpressurized right/left joystick port in swing
brake release valve.
Directs pilot pressure fluid to the swing parking brake. It is activated by joystick pressure
through the shuttle valve.
Delays fluid from exhausting to rapidly from the swing parking brake whenever the joystick is
returned to neutral. It is connected to the tank port of the sequence valve. The orifice size is
not adjustable.
Shuttle Valve
Swing Brake
Supply Port
Sequence
Valve
Swing Right and Left Pilot Parts
Shuttle Valve
Pressure Port
Orifice Valve
Tank Port
38
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