| 摘要 |
PURPOSE:To prevent increase of a load and rolling of a head main body for propulsion caused by receiving rotational resistance from an inwall of an underground hole at the time of rectilinear propagation-while being capable of compensating for shortage of steering capacity at the time of changing directions. CONSTITUTION:A head 1 for propulsion consisting of a head main body 1A for propulsion, a drive shaft 12 and a guiding body 3 is connected to a propulsive pipe 2, and an inclined pressure receiving surface F to direct the propulsive direction of the head 1 for propulsion to the direction receiving earth pressure is formed on the guiding body 3. The guiding body 3 is constituted of a guiding body main body 3A furnished with a first inclined pressure receiving surface F1, and a tongue piece type guiding body front part forming member 3B furnished with a second inclined pressure receiving surface F2 by dividing the inclined pressure receiving surface F in the front and rear directions. The guiding body front part forming member 3B is pivotally supported and connected on to the guiding body main body 3A free to oscillate in the back side direction of the second inclined pressure receiving surface F2, and the guiding body front part forming member 3B is formed free to push its head end part to the outward side in the diametrical direction rather than the outer peripheral part of the guiding body main body 3A in the oscillating state. |
