| 摘要 |
PURPOSE: A boom control system of an excavator is provided to prevent the accident or the damage of equipment by preventing the unintended descent of a boom. CONSTITUTION: The boom control system of an excavator contains: a boom control valve(5) controlling the direction of pressure oil of a hydraulic pump(1), then supplying to a head chamber(4a) or a rod chamber(4b) of a boom cylinder(4) selectively through a boom ascending hydraulic line(2) and a boom descending hydraulic line(3); a pilot control valve(6) sending boom ascending and descending pilot signals to each hydraulic unit(5a,5b) of the boom control valve(5); a rod holding valve(10) letting the pressure oil of the hydraulic pump(1) flow to the head chamber(4a) of the boom cylinder(4), but discharge with the approval of the boom descending pilot signal of the pilot control valve(6) only; and a locking valve installed on a boom descending signal line(6b) between the pilot control valve(6) and the rod holding valve(10), and provided with hydraulic units, wherein one of the hydraulic units is connected with hydraulic lines(2a) diverged from the boom ascending and descending hydraulic lines(2,3) of the boom cylinder(4) and the other is supported elastically by a spring(22).
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