| 摘要 |
<p>PURPOSE:To enable to effect a slewing motion even if a load for an arm is light when a hydraulic motor for slewing and a hydraulic cylinder for the arm are operated at the same time and to obtain power for slewing more than specified level despite the load for the arm. CONSTITUTION:A hydraulic circuit for a hydraulic shovel is consisting of switching valve groups 10, 20, having a plurality of switching valves 11-13, 21-24, connected to pumps 1,2 driven by a prime mover 4, and a hydraulic cylinder 40 for an arm, a hydraulic motor 50 for slewing and a hydraulic cylidner 60 for a bucket are connected to those switching valve groups. In this case, an additional pump 3a is provided and an additional switching valve group 30a having a plurality of additional switching valves 31a, 32a is connected thereto. The additional switching valve 31a is constituted so as to be cooperative with the switching valve 21 for slewing by a dual drawing mechanism Z and the additional switching valve 32a for the arm is constituted so as to be switch-controlled by a pressure difference between pressures before and after a squeeze E.</p> |
