| 摘要 |
PROBLEM TO BE SOLVED: To achieve quality stabilization and cost reduction by accomplishing the elimination of the need for leak inspection, an improvement in production accuracy, the prevention of cut and damage of an engaging claw, an improvement in production efficiency, etc. SOLUTION: A tubular part 18 having a male screw 23 on its upper part is provided. An engaging claw 24 is provided in the upper end of the tubular part 18. Steps 19 and 20 are provided on internal annular portions of its intermediate part, and a vale seat 21 is provided on an internal annular portion of its lower part. The main body 16 of a bush 8 having at its lower end a sandwiching face 22 for a seal ring is formed based on the process of casting a metal material. The upper end of a metal skirt 17 having holes in its periphery is joined to the lower end of the main body 16 by a weld 30.
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