HYDRAULIC CIRCUIT FOR HYDRAULIC EXCAVATOR

摘要

PURPOSE:To control the running speed and the traction of an excavator equipped with a multiarticulated working linkage in steps by providing two main pumps and two auxiliary pumps for the hydraulic circuit of the excavator. CONSTITUTION:In the running mode, hydraulic fluid is supplied to running hydraulic motors 34 and 40 by main pumps 31 and 32 and auxiliary pumps 45 and 46 through the operation of running change-over valves 35 and 41 and running acceleration change-over valves 49 and 50. Hydraulic circuits connected to the running hydraulic motors 34 and 40 can be connected with each other in series or in parallel by changing-over series-parallel change-over valves 70 and 71 through operating a pilot valve 67. Thus the hydraulic circuit is capable of controlling the running speed and the traction of the excavator in steps.