| 摘要 |
PROBLEM TO BE SOLVED: To lessen a frictional force between a natural ground and an excavation machine body to be useful even if the capacity of a jacking device is small by opening a solenoid valve to intermittently supply hydraulic oil to respective propulsive jacks. SOLUTION: When a hydraulic pump P is driven and hydraulic oil 30 is supplied to the piston side, each changeover valve 19 is switched over from i-position to ii-position and retained therein. Then, each high speed solenoid valve 20 is repeatedly changed over between a normal position and an offset position at a specified period to repeatedly turn-on and off. As a result, the hydraulic oil 30 is intermittently supplied to the piston side of a shield jack device 9 and hence a rod is intermittently projected and the excavation machine body advances little by little while vibrating along the excavation direction. Accordingly the frictional force between the natural ground and the excavation machine body can be lessened and hence, the capacity of each propulsive jack device can be also lessened.
|
