| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To smoothly discharge buoyant material with low cost and simple structure. <P>SOLUTION: When a new pipe 2 is connected and inserted in order in a sheath pipe 1 laid under ground, both ends of the sheath pipe 1 are blocked and buoyancy is given to the new pipe 2 by buoyancy material "a" in the sheath pipe 1 to reduce friction between the new pipe 2 and the sheath pipe 1. A covered cylindrical body 23 is fitted in another end of the sheath pipe 1, the buoyancy material "a" is made over flow from a long hole 26 long in a cylindrical shaft direction of the sheath pipe 1 of the side surface to keep a level of the buoyancy material "a:" in the sheath pipe 1 constant. An over flow structure has a simple structure and cost thereof is low. If a hole for overflow is the long hole 26, an edge of the overflow is elongated and discharge is made smooth. If the buoyancy material is discharged smoothly, the new pipe does not impinges on a sheath pipe inner surface and the new pipe is jacked smoothly. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
