TRAVEL CIRCUIT OPERATION TRAVEL CIRCUIT OPERATION OVERLOAD RELIEF VALVE TRAVEL MOTOR DEVICE RH LH Dr REG Ps Ps REG Dr MB MA MB MA VA(BW) VB(FW) VA(FW) VB(BW) A B D G F E COUNTER BALANCE VALVE C TO/FROM MAIN CONTROL VALVE 480A3HC19 Valves are provided on travel motors to offer the following functions. 1) 1) COUNTER BALANCE VALVE COUNTER BALANCE VALVE When stopping the motor of slope descending, this valve to prevent the motor over run. 2) 2) OVERLOAD RELIEF VALVE OVERLOAD RELIEF VALVE Relief valve limit the circuit pressure below 360 kgf/cm 2 (5120 psi ) to prevent high pressure generated at a time of stopping the machine.
Stopping the motor, this valve sucks the oil from lower pressure passage for preventing the negative pressure and the cavitation of the motor. 3-23 3-23