| 摘要 |
PROBLEM TO BE SOLVED: To make the excavating length of one edge of a polygonal shaft half of the conventional length by supporting two drum cutter rotating horizontal rotating shafts by one frame, bending the frame in the bearing parts of the rotating shafts, and providing an angle regulating mechanism capable of regulating the bending angle. SOLUTION: Two side frames are arranged adjacently to a center frame 1, and connected through angle regulating mechanisms 20 provided on the upper stage, middle stage and lower stage of the center frame 1. A rotating shaft is provided on the lower end part of the side frame 2 so as to be extended from the front side to the reverse side, and disc-like drum cutters 6 are provided on both ends thereof. When the bending angle of the frame 2 is regulated, the space between excavating inside nuts is narrowed, and the space between excavating outside nuts is extended. The angle formed by the vertical lines of the two side frames 2 isαdeg., and theαis properly set, whereby the frames 2 are bent to form various excavated holes. Thus, the excavating length of one edge of a polygonal shaft can be set to half of the conventional length.
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