| 摘要 |
<p>PURPOSE:To ensure safe housing and buckling of the work unit of an excavator equipped with a multiarticulated work linkage by interlocking the operation of a hydraulic circuit for controlling raising and laying-down the base boom and a hydraulic circuit controlling operation of the boom. CONSTITUTION:In raising the work unit, the change-over valve 58 for controlling a base boom raising and laying-down cylinder 13 is set at a-position, the change- over valve 44 for controlling a second boom raising and laying-down cylinder 15 at b-position and an auxiliary change-over valve 74 for controlling the arm cylinder is changed-over to c-position according to the setting of the valves 58 and 44. Consequently, hydraulic fluid supplied by an auxiliary pump 46 flows into the head-side of the cylinder 13 through a circuit 79 so that the base boom is raised. On the other hand, hydraulic fluid supplied by a main pump 32 flows into the rod-side 15a of the arm cylinder 15 through the b-position of the change-over valve 44 so that the second boom is rotated in a clockwise direction. In housing the work unit, the arm is rotated in a clockwise direction according to laying-down the base boom so that the work unit is prevented from contacting the vehicle body.</p> |
