| 摘要 |
PURPOSE:To excavate a horizontal hole having a square cross section. CONSTITUTION:A support plate 3 is fixed inside of a skin plate 1 having a square cross section. A rotary partition wall 4 is supported rotatably freely with this support plate 3. A rotary shaft 15 is fitted rotatably freely in a position being eccentric to the center of the skin plate 1 of this rotary partition wall 4. A cutter head 20 is fixed to one end of the tip of this rotary shaft 15, and an external teeth gear 31 is fixed to the other end, and an internal teeth gear 32 is meshed with the external teeth gear 31. The rotary partition wall 4 is rotated by an electric motor 42 through an external teeth gear 5a and a driving gear 41 of the third cylinder part 5. The external teeth gear 31 and the rotary shaft 15 perform planetary motion according to rotation of this rotary partition wall 4, and the cutter head 20 performs also planetary motion. Thereby, an excavating part constituting an equilateral triangle of this cutter head 20 draws a locus whose envelope is a square shape, so that a horizontal hole having a square cross section can be excavated according to an external shape of the skin plate l. |
