| 摘要 |
PROBLEM TO BE SOLVED: To surely replenish a bit with a simple constitution, without having adverse influence on an excavation mechanism. SOLUTION: The replenishing bit 25 is made to stand by in an inner peripheral part of a cutter head 4 having the required number of bits, and only the replenishing bit 25 standing by in the inner peripheral part of the cutter head 4 is made movable to an outer peripheral part to the cutter head 4 in response to abrasion of the bits. COPYRIGHT: (C)2007,JPO&INPIT |
