| 摘要 |
PROBLEM TO BE SOLVED: To materialize a movable pit cover device dispensing with a large space for therein housing it. SOLUTION: In moving a movable stage backward, a worker winds a cover part 81 by a winder 82, in conjunction with this move, to reduce a pit cover portion constituting the cover part 81. Further, in this event, a plurality of beam parts 83 move by being backward pushed in sequence from front beam parts 83 by a moving pit cover part 7 moving in keeping with the move of the movable stage, narrowing their intervals in sequence (a2, b2). Meanwhile, when moving the movable stage forward, the cover part 81, with one end thereof fixed to the movable stage, is drawn out from the winder 82. Further, the plurality of beam parts 83 are drawn out forward in sequence from beam parts 83 at the front by the connection of a wire 84 directly to the cover part 7 or via other beam parts 83, with spaces between them widened up to a prescribed space set by means of a wire length (a1, b1). COPYRIGHT: (C)2007,JPO&INPIT
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