| 摘要 |
PURPOSE:To bend the whole leading body unforcedly and correct the direction of a leading hole easily by connecting the head section and succeeding section of an internal casing by a universal joint composed of a spherical contacting section and the engaging section of a polygon. CONSTITUTION:A head section 73 is rotated and driven from a succeeding section 7b by universal axial bond in the head section 7a and succeeding section 7b of an internal casing, and the head section 7a and the succeeding section 7b are turned mutually under the state, in which both sections 7a and 7b are inclined at a specified angle, according to the conditions of excavation. A guide boring rod 20 is revolved and driven apart from the internal casing 7 first, and a guide hole is dug while the guide boring rod 20 is propelled forward. When the direction of excavation is corrected by a leading body 5, four pairs of cylinders 11 are used, length, in which the piston rods 12 of two bodies in four bodies are elongated and the rods of other two bodies are shortened, is controlled, and the internal casing 7 is turned and driven while hydraulic force, where the leading body 5 is directed at an arbitrary angle within the range of a practically sufficient solid angle, is applied to the leading body 5. |
