SWING CIRCUIT OPERATION SWING MOTOR DEVICE SH BRAKE OFF AU PG BRAKE ON DR BRAKE RELEASE VALVE PARKING BRAKE MAKE UP VALVE MB MAKE UP PORT (MU) MOTOR BRAKE VALVE ANTI-INVERSION VALVE (CW)VB VA(CCW) TO/FROM MAIN CONTROL VALVE 220S3HC15A 1) MOTOR BRAKE VALVE Motor brake valve for the swing motor limits to cushion the starting and stopping pressure of swing operation and controls the swing motor operating pressure to 300 kgf/cm 2 (4270 psi ). 2) MAKE UP VALVE The make up valves prevent cavitation by supplying return oil to the vacuum side of the motor. 3) PARKING BRAKE This is function as a parking brake only when the swing control lever and arm in control lever are not operated.
PARKING BRAKE "OFF" OPERATION The parking brake is released by the pilot pressure oil from the pilot pump. When the swing control lever or arm in control lever placed in the operating position, the pilot oil flows into SH port through the MCV. This pressure transferred to the brake release valve and the brake release valve is change over. Then the pilot oil pressure PG lift the brake piston and release the parking brake. PARKING BRAKE "ON" OPERATION When the swing control lever and arm in control lever placed in the neutral position, the pressure of the pilot oil passage down.
Then the brake release valve returned to the neutral position and the oil is returned from the brake piston to the tank. And the brake is set to "ON". 4) ANTI-INVERSION VALVE This anti-inversion valve absorbs shocks produced as swing motion stops and reduced oscillation cause by swing motion. 3-21 R/G