| 摘要 |
PURPOSE:To prevent the occurrence of high pressures in a rod chamber by connecting a tank through a valve opening or closing only when discharge is made on the rod side chamber and a low-pressure relief valve to the connecting open path of the rod side chamber of a bucket-opening and closing oil-pressure cylinder. CONSTITUTION:The bucket-opening and closing oil-pressure cylinder 10 of a bottom damp type bucket 5 has a pilot operation control valve 30 between oil-pressure pumps 28. Pipelines 33 and 34 connecting the bottom side chamber 27 of the cylinder 10, the rod side chamber 26, and the control valve 30 are connected to a tank 39 through relief valves 35 and 37. The pipeline 42 is branched from the midway of the pipeline 33 and connected to the tank 39 through a pilot operation type valve 43 and a low-pressure relief valve 44. The valve 43 is so set that it can open only when the discharge of the rod chamber 26 is made. The anomalous rise of internal pressure of the rod chamber 26 of the oil-pressure cylinder 10 can thus be prevented. |
