| 摘要 |
<p>A crane hydraulic circuit for operating both the cross-pull preventing control of a boom turning device and winch control with one hand manipulation of a winch control lever. A brake unit (24) having a check valve (9) and a pilot type crossover relief valve (10) is provided in a boom turning hydraulic circuit X also including a pump (1) and a boom turning motor (2); and a pressure control valve (12) for setting the pressure to lower than a pressure control valve (7) and an electro-magnetic control valve (8) are provided in a pilot tube. The valve (8) is opened or closed by the operation of a switch (31) provided at a manipulating lever (38) of a change-over valve (37) in a winch hydraulic circuit Y having a pump (35) and a winch motor (36). When a load is lifted by operating the valve (37), if the end of the boom is not located directly above the lifting load, the boom is forcibly turned due to the cross-pull load. Accordingly, when the switch (31) is closed at this time, the relief valve (6) is opened as the pressure in the oil passage (22) is raised up to the set pressure of the control valve (12). Consequently, the braking force of the motor (2) becomes weak, and the boom can accordingly turn freely at a smooth speed, eliminating the cross-pull load. </p> |
