| 摘要 |
PROBLEM TO BE SOLVED: To arrange a new tube by connecting the new tube to a hollow cylinder including a hitting machine via a shock absorber, pressing an existing tube by means of the hitting machine for excavating forward, and at the same time, expanding the hole by means of a tip member for pushing and removing the existing tube outward. SOLUTION: While a hollow cylinder 10 is pulled by means of a towing device via a towing medium 25 passed through an existing tube 30, a tip member 12 is arranged in the tip aperture part of a hollow casing 11, and a hitting machine 21 is fixed inside the tip member 12. When compressed air is supplied through a compressed air tube 44 for actuating the hitting machine 21, the tip member 12 bites inside the ground and excavates the ground in the direction shown by an arrow 20 along the existing tube 30, and at the same time, the existing tube 30 is pushed out and a new tube 50 is installed. The excavated sand is discharged backward via an excavated sand discharging tube 41. Jet water is jetted into the hollow cylinder 10 via a water supply tube 42 so as to easily excavate and discharge the sand. In this way, the existing tube buried underground can be replaced without digging a trench for exposing it.
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