SWING CIRCUIT OPERATION PP SWING MOTOR R E D DR PARKING BRAKE MOTOR BRAKE VALVE B(CW) A(CCW) T MAKE UP VALVE TO/FROM MAIN CONTROL VALVE 1) MOTOR BRAKE VALVE Motor brake valve for the swing motor limits to cushion the starting and stopping pressure of swing operation. 189AK3HC20 2) MAKE UP VALVE The make up valves prevent cavitation by supplying return oil to the vacuum side of the motor. 3) PARKING BRAKE PARKING BRAKE "ON" OPERATION When the safety solenoid lever is moved to upward, the oil in the parking brake is drained to the tank. So, parking brake is applied. PARKING BRAKE "OFF" OPERATION The parking brake is released by the pilot pressure oil from pilot pump.
When the safety solenoid lever is moved to downward, the pilot pressure from the P4 pilot pump is flow into parking brake through safety solenoid valve. Then the pilot pressure lift the brake piston and release the parking brake. 3-18