| 摘要 |
PURPOSE:To permit safe and efficient operations of an oil-pressure shovel by using a system in which the pressure of the pilot oil chamber of an oil pressure switch valve for operating an oil-pressure motor is raised, the pilot pressure is taken out by a shuttle valve and a slewing-free valve is closed. CONSTITUTION:A slewing operating lever is actuated to raise the oil pressure of a pilot oil path 25 or 26. As soon as an oil-pressure switch valve 4 is switched from C-position to A- or B-position, only the pressure signal on the side where the oil pressure of the oil path 25 or 26 rises is taken out by a shuttle valve 16 and a slewing free valve 14 is closed to stop the pressure oil of the oil path 32. An oil-pressure motor 5 is actuated by pressure oil coming through the switch valve 4, and an upper slewing part is turned. When the lever is positioned at neutral and the oil pressure of the oil paths 25 and 26 is lowered to the pressure of tank, the valve 4 is set to C-position, and sending of oil to the motor 5 is stopped for free rotation.
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