| 摘要 |
PROBLEM TO BE SOLVED: To fully open a sheathing board by spring-up operation of the sheathing board even when it is built in a channel so as to prevent obstruction for traffic. SOLUTION: Guides 3, 3 for maintaining a vertical posture by a locking action until a sheathing board 2 reaches an upper limit are provided on both sides of a sheathing board 2 risen and fallen by turning operation of a screw shaft 5. When the sheathing board 2 reaches the upper limit and the locking action to the guides 3, 3 is released, the sheathing board 2 is sprung up so as to become a horizontal posture by pulling a chain 8 to fully open the sheathing board.
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