OIL-PRESSURE CIRCUIT FOR CIVIL WORK AND CONSTRUCTION MACHINERY

PURPOSE:To allow the straight running of a civil work and construction machine using plural oil-pressure pumps as driving sources by using a contrived circuit constitution to uniformly supply pressure oil left and right-handed running motors when operating various actuators during the running period. CONSTITUTION:For an oil-pressure shovel, direction switching valves 21, 28, and 23 to operate a bucket cylinder 13, a boom cylinder 11, and a right-side running motor 7 are connected in parallel to the first oil-pressure pump 20. Also, direction switching valves 26, 29 and 25 to operate a turning motor 3, the boom cylinder 11, and an arm cylinder 12 are connected in parallel to the second oil-pressure pump 24, and a direction switching valve 27 to for a left-side running motor 5 is connected in tandem to the downstream side of the arm direction switching valve 25. The input portion of the direction switching valve 27 and the discharge oil supply circuit of an oil-pressure port are connected with a circuit 33 having a load check 31c and throttle 34 on its midway.