OIL-PRESSURE CIRCUIT FOR OIL-PRESSURE SHOVEL

PURPOSE:To prevent the meandering running of an oil-pressure shovel by using a system in which left and right-handed running motors are connected in parallel with independent oil-pressure pumps, the discharge pipeline of each oil-pressure pump is connected to the other through an electromagnetic communication valve, and the valve is opened or closed by a switching valve. CONSTITUTION:Since an electromagnetic communication valve 23 is closed when operating left and right-handed running switch valves 14 and 18, the pressure oils of oil- pressure pumps 12 and 13 are supplied to each of left and right-handed running motors 6 and 7, whereupon the speeds of the left and right-handed motors 6 and 7 become values corresponding to the operation amounts of the valves 14 and 18. Under the condition, when operating a turning switch valve 16, for example, the communication valve 23 is opened. Therefore, part of the pressure oil of the oil-pressure pump 12 is supplied to the turning motor 8 and part of the pressure oil of the pump 13 is supplied to the left-handed motor 6 through the communication valve 23 even when the amount of pressure oil to be supplied to the left-handed motor 6 is reduced. By this, the reduction rate of the speed of the left-handed motor 6 is lessened, the amount of pressure oil to be supplied from the pump 13 to the right-handed motor 7 is reduced, and the speed of the right-haded motor 7 is also reduced.