| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of rust in use on a beach or the like, and to improve workability in forming a preservation layer on a piston rod at the manufacturing time. SOLUTION: A piston rod 7 is composed by dividing into two parts, namely, a main rod 18 and a sub-rod 20 formed integrally with a rod head 19 for external connection. The preservation layer 21 is formed on the circumferential surface of the sub-rod 20 and welded on the same axis as the head of the main rod 18, to form the piston rod 7 composed integrally of the main rod 18, the sub-rod 20 and the rod head 19.
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