| 摘要 |
PURPOSE:To perform curved propulsion with a small turn and reduce the propulsion load force concentrated at one time for propulsion when the propulsion load force is larger than the limit of a propulsion facility applying the propulsion force or the strength of a propulsion body and normal propulsion can not be performed. CONSTITUTION:Propulsion pipes 2 are flexibly connected, a propulsion head main body 5 is connected to the top propulsion pipe 2, and a lead section 6 having a pressure receiving face 11 rotatable around the axis X is protrudably provided at its tip section to form a propulsion body 1. During normal propulsion, the whole propulsion body 1 is thrust from the base end side for underground propulsion, and the lead section 6 is protruded from the propulsion head main body 5 for pressure-tightness only when the propulsion load force received from the ground is increased to a fixed value or above as the whole propulsion body 1 is thrust from the base end side and propelled. When the propulsion load force is decreased to the fixed value or below, the whole propulsion body 1 is again propelled under the ground while being merely thrust from the base end side. |
