| 摘要 |
First and second hinge members 23A, 23B are turnably disposed at an end part on an internal opening side of an outer case 11. The first and second hinge members 23A, 23B are non-turnably provided with first and second gears 24A, 24B, respectively, which are meshed with each other. A movable member 25 is disposed at the inside of the outer case 11 such that the movable member 25 is non-turnable but movable in directions toward and away from the first and second hinge members 23A, 23B. First biasing means for turn biasing the first hinge member 3A in one direction are disposed between the first hinge member 23A and the movable member 25 and between the second hinge member 23B and the movable member 25 respectively.
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