| 摘要 |
When a worm wheel is in a first stop position a locking surface of a first projecting portion and a locking surface of a second projecting portion, which is provided back to a pressing surface of a first projecting portion adjacent to the locking surface of the first projecting portion, are situated along concentric arc-shaped rotational loci of the rotational end faces of a first engagement arm and a second engagement arm, while when the worm wheel is in a second stop position a locking surface of the second projecting portion and the locking surface of the first projecting portion, which is provided back to a pressing surface of the second projecting portion adjacent to the locking surface, are situated along the concentric arc-shaped rotational loci of the rotational end faces of the first engagement arm and the second engagement arm. |
