| 摘要 |
PURPOSE: A boom descending speed controller of an excavator is provided to control ground tamping as well as excavation effectively by controlling the speed of a boom cylinder selectively according to operation characteristics. CONSTITUTION: A boom descending speed controller of an excavator comprises a main pump(1), a boom cylinder(2), a boom-controlling spool(3) controlling the direction and flow rate of the pressure oil of the main pump supplied from the boom cylinder, a remote control valve(4) changing the direction of the boom-controlling spool by applying pilot pressure oil to both water pressure parts of the boom-controlling spool selectively, a parallel line(5) communicating primary and secondary oil pressure lines(11,12) respectively connected to a piston head side chamber(2a) and a piston rod side chamber(2b) of the boom cylinder and an oil groove opening and shutting instrument installed to the parallel line to open and shut an oil groove selectively.
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