HYDRAULIC CIRCUIT FOR OPERATING CYLINDER OF WORKING MACHINE

摘要

The hydraulic circuit for operating the cylinder of a working machine in such an arrangement that the working machine is lowered by weight at the time of a compaction operation using the bucket and and, at the time of other operations, part of pressure oil in a chamber on the lifting side of a working cylinder in addition to pressure oil discharged from the pump is fed to a chamber on the lowering side so as to increase contracting speed of the cylinder of the working machine. The hydraulic circuit for operating the cylinder is provided with a spool inserted into a hole inside an operating valve body to be displaceable to a first operation position (I), at which a second port (21) of the operating valve (2) communicating with the chamber (3b) on the lowering side communicates with a second tank port (22). A first port (15) of the operating valve communicates with the chamber (3a) on the lifting side and communicates with a first pump port (17). In a second operation position (II) the second port and second pump port (20) communicate with each other. @(21pp Dwg.No.2/7)@.