| 摘要 |
PURPOSE:To surely change the advancing direction by connecting a tip diagonal cut head to the tip of a casing surrounding a screw, straightly advancing the casing in the axial direction, and rotating a head via a motion converting means. CONSTITUTION:When the advancing direction of a leading tube 1 is to be changed by 45 deg., for example, a cylinder or the like provided in a vertical shaft is driven to retreat a head 11, and projections P are moved to positions P2 of groove patterns M. When the head 11 is advanced, the direction of the head 11 is changed. When an excavation is conducted in this state, the excavation direction is changed after diagonal cutting. Since the projections P are located at the positions P1 of the grooves M, the rotation angle of the head 11 is maintained as far as the cylinder is not expanded or shrunk. Since the head 11 is rotated in the excavated soil, the required rotating force can be reduced. Since only the longitudinal motion force is applied to a casing 4, the head 11 is not rotated freely, and it can be easily controlled. |
