| 摘要 |
A joint unit comprises a lock mechanism in which a ball-like joint section provided at the base end of an arm is housed in a holder formed at an end of a cylindrical case. As the joint section is brought into pressed contact against an inner surface of the holder, the lock mechanism locks a pivotal angle. In the lock mechanism, in response to a manual operation of a knob, a bolt is caused to project into the case and this pressing force is transmitted to a roller-like first pressing body and then to a second pressing body placed in contact therewith. Further, the pressing force from the first pressing body is transmitted to a pressure block and then the pressing force from this pressure block brings the joint section into pressed contact against the holder inner surface.
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