| 摘要 |
A double lid assembly is provided for a pre-fabricated pit designed for installation below the surface of an aircraft docking and refueling area. A first, heavier lid is mounted by hinges on the pre-fabricated pit for rotation about a horizontal axis. A second, lighter lid is seated within the confines of the first lid and is rotatable about a second axis parallel to the first. When the second, lighter lid is opened, it reduces the force necessary to open the first, heavier lid by reducing the torsional moment holding the heavier lid shut. As the heavier lid is opened, the lighter lid serves as a counter-balance to facilitate opening the heavier lid.
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