| 摘要 |
<p>PURPOSE:To simplify the structure while reducing the cost and to facilitate maintenance by providing a linear part formed to move in parallel with the expanding shaft of an expansive cover and supports the cover body under a state being expanded by a predetermined angle, and a bent part extending from the linear part to the rear side of the cover body. CONSTITUTION:When a bridge type crane is run in the direction of an arrow A along a running path, a feeder cable 15 is connected with a preceding cable 48 at the a feeding point in a pit 14. The bent part 39 of a plow 35 is inserted, at the forward end in the running direction, into the underside of a closed pit cover 13a before the running is started. The pit cover 13a is scooped up by the bent part 39 as the crane runs and opened sequentially in front of cable guide rollers 16, 17 while being pressed by an auxiliary guide 36 and then held at a maximum expansion angle by the linear parts 37, 38. This structure allows sequential opening/closing of the cover body through a simple mechanism.</p> |
