| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an overlapping excavation area and to control cutters, independent from one another. SOLUTION: A plurality of first cutters 2a, 2b adapted to be rotated for excavating a working face, are arranged in one and the same plane with a predetermined space therebetween, and a swingable second cutter 3 is provided in a place other than rotating areas of the first cutters 2a, 2b. The second cutter 3 is provided so as to be axially movable from a position in a plane the same as the plane of the first cutters 2a, 2b. When the second cutter 3 is axially shifted with respect to the first cutters 2a, 2b, its swingable range is widened or is rotationally driven. |
