| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To solve a problem with a conventional diversion cover joint with a mounted-in drilling cutter which has a cylindrical drilling edge attached to a threaded portion or a rubber packing mounted directly on a step formed therebetween, in which the rubber packing runs out when the peripheral pressure of a fitted portion is applied to a distortion between a drilled portion formed in the outer curved surface of a diversion main pipe and a stepped portion, thus producing insufficient water tightness or pressure contact force. <P>SOLUTION: At the lower part of a threaded portion 2a of a drilling cutter, a seal portion 2b is provided which has a diameter smaller than that of the threaded portion and somewhat larger than that of a diversion hole drilled in a diversion main pipe. A cylindrical drilling edge 2c is attached to the front end thereof. The upper end of a cylindrical elastic body 25 is fitted into an annular fitting groove drilled in the bottom face of the lower end base of the threaded portion to cover the upper end base of the seal portion and its peripheral face. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
