| 摘要 |
In an insertion hole (82) formed in an adapter (70), a side wall (84) which presses an insertion piece (104) of a stopper (100) with an urging force of a spiral spring (74) has a wall surface parallel to a virtual straight line (L1) passing a center of the adapter (70) and positioned on the virtual straight line (L1). Thus, a direction which the wall surface of the side wall (84) presses the insertion piece (104) of the stopper (100) is along a facing direction which the side wall (84) and another side wall (82) face each other, and is not inclined outward in a radial direction of the adapter (70) with respect to the facing direction. Thereby, a pressing force (F) applied from the wall surface of the side wall (84) to the insertion piece (104) of the stopper (100) does not cause the insertion piece (104) to be extruded from the insertion hole (82). Thus, insertion state of the insertion piece (104) to the insertion hole (82) can be satisfactorily maintained.
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