OIL-PRESSURE CIRCUIT FOR OIL-PRESSURE SHOVEL

PURPOSE:To prevent the great lowering of the operating speed of an arm even when concurrently operating a bucket and a boom during the operation of the arm by providing a parallel circuit with a throttle to an oil-pressure circuit for an oil-pressure shovel. CONSTITUTION:When arm switch valves 15 and 22 are positioned at A and an arm is crowded by sending pressure oils in an oil-pressure pumps 8 and 9 into the bottom chamber 6a of an arm cylinder 6, part of the pressure oil in the oil- pressure pump 9 is sent through parallel circuit 23 and a throttle 24 to the bottom chamber 6a even when a circuit 21 is intercepted by operating a bucket switch valve 17 concurrently for example. Thus, no great variation occurs in the action of the arm. Also, even when the bucket switch valve 17 is operated under the condition that bucket switch valves 15 and 22 are positioned at B and the arm 3 is damped, part of the pressure oil in the oil-pressure pump 9 is sent to the bottom chamber 6a without passing through the throttle from the parallel circuit 23.