| 摘要 |
PROBLEM TO BE SOLVED: To provide an excavation enlarging head capable of enlargedly excavating by surely expanding a plurality of enlarging edges and preventing the eccentricity of the rotation of an enlarging head. SOLUTION: The excavation enlarging head is constituted by providing the expansible enlarging edges 3a and 3b inside of 7a and 7b slantly crossing a rotational shaft (s) at a different position on the rotational shaft (s) of an enlarging head body 1a to the outer circumference of the enlarging head body 1a connected to the front end of an excavation rod 2. COPYRIGHT: (C)2003,JPO
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