THREE STEP OIL JACK FOR DIGGING OUT UNDERGROUND

摘要

The present invention relates to a three-stage hydraulic jack for underground excavators for propelling an excavation machine in the excavation of underground tunnels for laying water and sewage pipes, gas pipes, and telecommunication pipes. The purpose is to obtain the maximum propulsion distance with the minimum working length by constructing three stages of hydraulic jack used to propel the semi-shielded machine by the press-fit of.;Since the conventional hydraulic jack is composed of a maximum of two stages, the stroke is short and the propulsion distance cannot be obtained long, resulting in low workability and long construction period.;The present invention has been devised in view of such a point and is designed to obtain the maximum propulsion mechanism by configuring the piston rod in three stages.