DRILLING HEAD USABLE FOR BOTH HARD AND SOFT STRATA

摘要

PROBLEM TO BE SOLVED: To continue drilling without replacement of a drilling head even in the case of ground where soft and hard strata coexist and to ensure an excellent efficiency of drilling the hard stratum. ;SOLUTION: A drilling head 1 includes an auger 2, which consists of helical blades 12A, 12B secured to at least the lower end of a head shaft 11 along the contour of the head shaft 11 and a drilling claw 4 provided at the lower ends of the helical blades 12A, 12B, and a roller cutter 3 supported against the lower end of the head shaft 11 rotatable about an axis crossing the core of the head shaft 11 and provided with a number of drilling bits 33, 33... on its peripheral surface. The drilling claw 4 of the auger 2 has its end supported oscillatable upward while using as its center of rotation a pivot 19 at the rear end of the claw, with the lower end position of the roller cutter 3 also relatively projecting downward by Δh. The oscillating movement of the drilling claw 4 enables the end of the drilling claw 4 to recede to a position upward of the end position of the roller cutter 3.;COPYRIGHT: (C)2000,JPO