| 摘要 |
PURPOSE: A hydraulic system for a cargo crane and a hydraulic valve for selectively controlling the same are provided to prevent the damage of an actuator due to excessive hydraulic pressure and to change a hydraulic circuit according to each purpose. CONSTITUTION: A hydraulic system for a cargo crane comprises a crane boom, a master cylinder(30), a slave cylinder(40), and a hand lever(231). The master cylinder is connected to the hand lever through a first branch pipe(241) and a second branch pipe(242). The first and second branch pipes are connected to a relief valve(260) and first and second three-way control valves(251,252) are connected between the hand lever and the first and second control valves. The first and second control valves are connected to an outlet(261) of the relief valve through a third branch pipe(243). The outlet is connected to an oil tank(210). The relief valve is connected to the slave cylinder through third and fourth three-way control valves(271,272). The three and fourth control valves are connected between the hand lever and the first and second control valves by fourth and fifth branch pipes(283,284). |
