| 摘要 |
PROBLEM TO BE SOLVED: To provide an excavation head capable of consecutively forming a bulb section of a diameter widening hole in an underground hole excavated by an earth auger with simple operation. SOLUTION: When lock shafts 15 and 15 are moved upward while forward rotating a main shaft 1, diameter widening vanes 5 and 5 consisting of second lever sections 10 combined with first lever sections 8 and 8 having excavating edges 7 and 7 and third lever sections 11 are widely opened to the outside of a diameter of spiral vanes 2 and 2 with oscillating shafts 6 and 6 as the center. The second lever sections 10 have circular arc holes 12 through which the lock shafts 15 and 15 pass, and the third lever sections 11 have open-holes 13 through which the lock shafts 15 pass. When the main shaft 1 is reverse rotated, the diameter widening vanes 5 and 5 are stored inside of the diameter of the spiral vanes 2 and 2.
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