| 摘要 |
PROBLEM TO BE SOLVED: To prevent the abrasion of the second portion of the cemented carbide tip of a circular casing and prolong the life of the tip at least until the excavation of one vertical shaft is completed by fitting a hard block at the front in the advancing direction of the cemented carbide tip, and discharging excavated soil not to enter between the tip and the natural ground. SOLUTION: A cemented carbide tip 1 has an outer blade cutting the outer periphery and bottom of a casing 11 and an inner blade cutting the inner periphery and bottom, and a block 4 is arranged at the front in the excavating direction to protect the tip 1. The block 4 is located at the position for protecting the second portion of the cemented carbide tip 1 from the excavation chips of the natural ground. Several feed water pipes 5 are cut into a casing shell 12 and welded. The feed water pipes 5 are located at positions uniformly dividing the circumference to prevent the casing 11 from being formed into an elliptical shape by welding strain. The size of the outer shape of the feed water pipes 5 is made not to protrude outward from the thickness of the shell 12. The second portion of the semented carbide is not abraded, and the life of the expensive tip 1 is prolonged.
|
