| 摘要 |
An outer peripheral cylindrical surface 13, 17, which is a non-engagement outer peripheral surface, is formed in an outer periphery of an annular portion 3 and a portion 15 of each of pillar portions 4, while an engagement portion formed of an edge 9 is formed on an outer periphery of the other annular portion 2 and another portion 14 of each of the pillar portions 4. The outer peripheral cylindrical surface 13, 17 is formed inside a circle smaller by a specified size than a circumcircle of the edges 9.
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