| 摘要 |
A projection part 33 is formed on an end face 32 of a first turnable member 3 . A short recess 43 and a long recess 44 are formed in an end face 43 of a second turnable member 4 . The short recess 43 is provided at both end parts thereof with lock faces 43 a , 43 b which are abutted with both end parts of the projection part 33 to prohibit the first and second turnable members 3, 4 from making a relative turn with force of a predetermined magnitude. The long recess 44 is provided at one end part thereof with an inclination surface 44 a which is abutted with one end part of the projection part 33 to turn bias the first turnable member in one direction with respect to the second turnable member and at the other end part with an inclination surface 44 b which is abutted with the other end part of the projection part 33 to turn bias the first turnable member in the other direction with respect to the second turnable member. The inclination surfaces 44 a , 44 b are symmetrically arranged with respect to a line passing through a center between the lock faces 43 a , 43 b and orthogonal to an axis of the second turnable member 4.
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