| 摘要 |
PROBLEM TO BE SOLVED: To prevent a damage caused by a local abrasion on the inner wall surface of a cladding tube. SOLUTION: In a plenum spring 8, a shaft line 15 is formed spirally toward the longitudinal direction. Namely, in the state where a load is not applied to the longitudinal direction of the shaft line 15, a plurality of projection parts 8b projecting to the furthermore outside than an average coil diameter R shown by a two-dot chain line are provided. The spring 8 is formed to satisfy following inequalities: the inner diameter of the cladding tube>R, and the inner diameter of the cladding tube≤the outer diameter of the projection part 8b. COPYRIGHT: (C)2008,JPO&INPIT
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