| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit which avoids accidental movement of a counterweight lifting cylinder without depending on an operator's manual operation, thereby improving reliability. <P>SOLUTION: A direction control valve 18 is provided on the way of a center bypass duct 14 between a hydraulic pump 9 or a tank 10 and a counterweight lifting cylinder 11. At the neutral position (A) of the direction control valve 18, feeding of pressure oil via a pair of main pipelines 19A and 19B to the cylinder 11 is stopped, while one main pipeline 19B connected to a bottom side oil chamber B of the cylinder 11 is made to communicate with the tank via a low pressure pipeline 17 through a return passage 18C provided in the direction control valve 18. On the way of the center bypass pipeline 14, a switching valve 26 switchable between interruption position (a) and communication position (b) according to operation signals from a pilot operation valve 23 is provided between the hydraulic pump 9 and the direction control valve 18. <P>COPYRIGHT: (C)2012,JPO&INPIT |
