JPS5616736A - Hydraulic circuit for hydraulic power shovel - Google Patents

Abstract

PURPOSE:To accomplish speeding up in a single travelling operation, smooth and accurate actions individually in the simultaneous slewing and travelling operation and to obtain higher efficiency for each working in the modes of operation other than travelling. CONSTITUTION:Equal delivery pumps of large capacity are used for the first and the fourth pumps 1 and 4 while equal delivery pumps of small capacity are used for the second and the third pumps. In a single travelling operation, alone, the fluids discharged from the first and the second pumps 1 and 2 flow together to the travelling motor 84 and those from the third and the fourth pumps 3 and 4 flow together to the motor 85 separately whereby the travelling speed is increased. In the simultaneous slewing and travelling operation, the fluid discharged from the fourth pump flows to the tank 18 while the fluids from the first, the second and the third pumps 1-3 are fed to the slewing motor 81 and right and left motors 84 and 85 independently. In other mode of operation, fluids from four pumps 1-4 is effectively utilized in the low pressure range to speed up the actuator, and in the high pressure range, with the unloading of the forth pump 4, the fluids discharged from the other three pumps are adequately utilized.