| 摘要 |
PROBLEM TO BE SOLVED: To prevent a cover member from slipping out by forming the cover member so as to be fitted in an opening of a steel pipe, providing an expanded portion made of a rubber material, on part of the cover member, and forming a communication hole capable of communicating with the inside and outside of the steel pipe. SOLUTION: A boardlike member having a semilunar periphery in a plan view is formed of water-expandable rubber such as EPDM, which member conforms to an opening 6 at the edge of a steel pipe 4 and is slightly smaller in shape than the opening 6 and almost similar to the same. Then, a collar 12 is integrally formed over the entire of the circular arc portion of the boardlike member, and a rib 14 is integrally formed at a frontward portion of the collar 12. Further, a depression is formed in a central portion of the boardlike member, and a disk-shaped expanded portion 20 having a pinhole 22 is formed in the depression, to thereby form a cover member 10. At the time of construction, an adhesive is applied to the periphery of the cover member 10 except for the collar 12, and a portion opposite to the collar 12 is inserted into the opening 6, whereby the cover member 10 is fitted into the edge of the steel pipe 4. Thus, the cover member 10 can be prevented from slipping out due to change in pressure in the steel pipe 4.
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