Abstract: A foldable wheelchair includes a cross brace assembly having first and second brace members pivotally secured to one another. First ends of the brace members are clamped to respective side frames of the wheelchair. Second ends of the brace members are removably secured to respective seat rails so that the cross brace assembly can be adjustably positioned forwardly and rearwardly along the side frames and seat rails. This provides for ease of seat depth adjustment that accommodates growth of the wheelchair user without having to purchase additional components.

Abstract: A closure apparatus for a subsurface pit for servicing an aircraft located beneath an aircraft servicing surface across which aircraft travel is provided with an improved spring biasing arrangement. The system employs separate springs interposed between the hollow body of the pit and the lid so as to urge the pit lid from its horizontal seated position toward a fully raised position. Obstructions are provided for separately intercepting and disengaging the springs from acting against the pit lid as the pit lid is opened through intermediate angular positions between the horizontal seated position and the fully raised position. By sequentially isolating the pit lid from the action of each of the springs, one at a time, the moment of spring force opposing closure of the lid more closely follows the moment of the force of gravity tending to close the lid. This substantially reduces the maximum manual force that is thereby required to overcome gravity in opening the pit lid.

Abstract: A subsurface chamber formed by a pit and buried beneath a surface across which aircraft travel is provided with an effective sealing system at its opening. The opening to the chamber is formed by a mounting frame adapted to receive and seat a lid therewithin. The mounting frame is formed with a frustoconical wall tapering downwardly and inwardly toward the opening into the chamber. The lid is provided with a peripheral rim having a plurality of flexible, resilient, annular, water impervious sealing flaps that extend outwardly from the lid an which are vertically spaced from each other. As the lid is lowered into position, the sealing flaps do not scrape or slide against the frustoconical wall of the mounting frame. Rather, they establish contact with the frame only as the lid approaches to within one quarter inch of its fully seated position.