| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability of fluid interruption and prevent actual deteriora tion of strength of a conduit by forming a long hole through at least three punching steps showing cutouts linearly arranged on a longitudinal direction of the conduit. SOLUTION: Cutouts serving as longitudinal both ends of a long hole 90 are formed, and in addition, a new cutout is formed therebetween. Leading ends of a pair of projections are cut by the new cutouts near an intersection of the arcuate cutout on both ends. An effective opening in a direction of short axis of the long hole 90 is enlarged. It is thus possible to largely set separation width between a main shaft 20 and a pressure receiving plate 30 of an interruption closer 10 inserted into a conduit 200 from the long hole 90, that is, length L of a connection shaft without limitation. After insertion and turning by 90 degrees inside the conduction pipe, accordingly, pushing spacing of a seal rubber 50 in an axial direction of the pipe is sufficiently secured. The separation spacing between the edge of the long hole and seal rubber 50 is sufficiently large after interruption. |
