| 摘要 |
PURPOSE:To excavate a tunnel having a rectangular section, in spite of simple formation. CONSTITUTION:A rotary shaft member 8 is rotatably held at the inside of a through hole 4 on a cylindrical, rotary member 5, which hole 4 is horizontally formed in a shield main body 1 and at its eccentric position, and a cutter head 9 is attached to the front end part of the rotary shaft member 8. A ring gear 18 engaged with a rotary gear 17 provided rotatably at the side of the shield main body 1 is attached to the rear end part of the rotary shaft member 8. The number of teeth on the rotary gear 17 and that on the ring gear 18 are settled at the ratio of 2 to 3. The cylindrical, rotary member 5 and the rotary gear 17 are allowed to rotate at the same speed through a gearing mechanism 21 and are allowed to rotate at a threefold speed as compared with the rotary shaft member 8. Futhermore, a front view of the cutter head 9 is formed in the same shape as Reuleaux's triangle. |
