| 摘要 |
PURPOSE:To raise the efficiency of operation by a method in which the rise of the circuit pressure on the discharge side of an oil-pressure pump to more than a given pressure value is detected, the rise of a boom is stopped, the ending of the scooping action of a bucket is detected, and the stoppage of rising action of the boom is released. CONSTITUTION:A boom cylinder 5, a bucket cylinder 8, and electromagnetic valves 13 and 14 for controlling are provided to an oil-pressure circuit. The valve 13 is provided with solenoids 15 and 16 for raising and lowering a boom, and the valve 14 is provided with solenoids 17 and 18 for dumping and scooping. For the valves 13 and 14, the oil-pressure circuit is made up to be in series during the concurrent actions of the boom and the bucket. A pressure switch 22 connected to the oil-pressure circuit is turned ON under more than a given circuit pressure value to stop the rising action of the boom. A limit switch 23 to detect the scooping action of the bucket is turned ON when the stroke of the cylinder 8 is minimized, and the rising action of the boom is restarted.
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