| 摘要 |
A boom-holding control device brings an excavator boom into a holding condition or a release condition. The device includes a boom-holding valve provided on a fluid pressure line for preventing boom deadweight-caused drainage of a hydraulic flow from a boom cylinder to thereby keep a boom in a holding condition, a boom release valve for releasing the boom from the holding condition in response to at least one of a boom-down pilot signal pressure supplied from a boom cylinder remote control valve and a travel signal pressure fed from a travel control operator-interface device and a solenoid-actuated changeover valve provided on a travel signal line for selectively opening and blocking off the travel signal line. The changeover valve is normally kept in a closing position and will be shifted to an opening position at the time of simultaneous activation of a travel selection switch and a boom release switch.
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