PURPOSE: To reduce the number of pipes by a method in which the discharge oil of the first oil-pressure pump is sent through the second confluence control valve provided in a communication circuit to an arm control valve, and the discharge oil of the second oil-pressure pump is sent through the first confluence circuit provided in the communication circuit to a boom control valve.
CONSTITUTION: A control valve 7 for traveling, a control valve 8 for bucket, and a control valve 9 for boom are connected in parallel to the first oil-pressure pump P1. Also, a control valve 10 for traveling, a control valve 11 for slewing, and a control valve 11 for arm are connected in parallel to the second oil- pressure cylinder P2. The pressure oil of the pump P1 is led from upstream to the confluence path 51 through a connection path 56 and a check valve 60 in the second confluence control valve 57 and then joined to the control valve 12 for arm. The discharge oil of the second oil-pressure pump P2 is led from upstream of the valve 12 to upstream of the control valve 9 for boom through the path 51 and the check valve 55 of the first confluence valve 52. The confluence circuit having lesser number of pipes can thus be obtained.
KAWASAKI HARUHIKO
ASAOKA MASAHARU
SHINOHARA HIDEAKI
