Aeronautics and astronautics – Landing field arrangement
Reexamination Certificate
2003-07-14
2004-04-06
Eldred, J. Woodrow (Department: 3644)
Aeronautics and astronautics
Landing field arrangement
C220S319000, C016S289000, C049S379000, C049S371000, C049S381000, C049S387000, C049S398000
Reexamination Certificate
active
06715715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a self-sealing gravity assisted pit lid mounting system for an access lid to a subsurface chamber for servicing aircraft.
2. Description of the Prior Art
At modern aircraft terminals the servicing of aircraft on the ground is frequently performed using subsurface pits, which are often prefabricated structures. Such aircraft servicing pits are installed at aircraft docking, fueling, and loading areas beneath the surface of the tarmac across which aircraft travel during docking and departure maneuvers. The pits forming a subsurface chamber are typically constructed of fiberglass, steel, concrete, or aluminum. These pits are typically fabricated as complete enclosures with surrounding walls, a floor, and an access lid at the top seated within a frame disposed at the mouth of the prefabricated pit. When the lid is closed it lies substantially flush with the surface of the tarmac. Such pits are installed below the surface of loading and refueling aprons at aircraft terminals, remote parking locations, and aircraft maintenance bases.
The purpose of such pits is to allow ground support functions to be carried out from subsurface enclosures. These ground support functions include the provision of fuel, the provision of electricity to the aircraft while it is in the docking area, the provision of air for cooling the aircraft interior, the provision of pressurized air for starting the aircraft engines, and for other aircraft support activities on the ground. The use of subsurface pits eliminates the need for mobile trucks, carts, and other vehicles which are otherwise necessarily present in the loading area and which interfere with the arrival and departure of aircraft in the vicinity of a loading gate.
The use of subsurface pits also allows the provision of fuel, power, cooling and pressurized air, and other supplies from a central location. The necessary fluid supplies and electrical power can be generated or stored with greater efficiency at a central location, as contrasted with mobile generating or supply vehicles.
The pits located below the aircraft terminal area house valves, junction boxes, cooling air terminations, and other terminal equipment that is temporarily connected to an aircraft that has been docked. Umbilical pipes and lines, otherwise housed within the pits, are withdrawn from them through hatches therein and are coupled to a docked aircraft to supply it with fuel, air for cooling the aircraft interior, pressurized air for starting the engines, electrical power, and other ground support functions.
The pits are constructed with either hinged or totally removable lids that can be moved between open positions allowing access to the pits and closed positions which are flush with the surfaces of the docking, loading, or refueling areas across which aircraft travel and beneath which the pits are mounted. To ensure that the pit lids remain flush with the surrounding surfaces it is desirable to employ a latching mechanism.
The pit access lids in such aircraft servicing pits are extremely heavy, since they must be able to withstand the weight of the wheels of a large aircraft traveling thereacross. Therefore, it is often very difficult to open such access lids without assistance.
Conventional pit access lid mounting systems sometimes employ lift assisted springs that are interconnected to the pit lid in such a way as to act in opposition to gravitational force on the lid, thereby aiding the service personnel in opening of the lid. One such spring-loaded mechanism is described, for example, in U.S. Pat. No. 5,950,368. As illustrated in that prior patent, the pit lid is mounted relative to the mouth of the pit in such a way as to be movable from an open position completely clear of any contact with the mouth of the pit, and a closed position in which a gasket about the periphery of the pit lid provides a liquid-tight seal completely about the perimeter of the mouth opening to the pit. This ensures that rain and melting snow cannot wash dirt and other debris down into the pit.
Spring assisted pit lid mounting systems have certain disadvantages, however. With age and exposure to the elements the springs can rust and break. Consequently, in some applications a gravity assisted pit lid mounting system is preferable. One such gravity assisted system that employees counterweights that are coupled to the pit lid through a system of meshed gears has been used very successfully for many years. This system is described in U.S. Pat. No. 4,467,932. However, one disadvantage of existing gravity assisted pit mounting systems is that it has not heretofore been possible to provide a liquid-tight seal for lids mounted in this manner about their entire periphery. As a consequence, there can be leakage into the pits from rain and melting snow that seeps into the mouth of the pit at the hinge opening. This is because the mounting systems for conventional gravity assisted pit lids have not heretofore provided a complete seal at the top of the pit.
SUMMARY OF THE INVENTION
The present invention provides a unique pit access lid mounting system that not only aids the user in opening the pit lid using a system of counterweights, but also a system that allows a liquid-tight seal to be established about the complete perimeter of the pit lid when the pit lid is rotated about its hinge axis to its closed position, and which provides a complete watertight seal at the top of the pit. Thus, the system of the present invention enables the use of counterweights mounted on a pair of counterweighted arms and coupled to move in counterrotation relative to a hinged pit lid and also provides such a system with a complete watertight seal at the mouth of the opening to the subsurface chamber of the pit.
One primary object of the present invention is to provide a subsurface aircraft servicing pit for use in servicing aircraft while they are on the ground which avoids the use of springs to assist the user in opening the pit lid, but which still provides the pit lid with a continuous, watertight seal about its peripheral edge when it is seated atop the mouth of the buried pit. By employing these features the disadvantages associated with the use of springs to offset the weight of the lid are avoided, but while providing a pit lid hinging arrangement that does not have a break in the watertight seal at the pit lid hinge axis. This latter feature is a disadvantage of conventional counterweighted pit lid systems.
A related object of the invention is to provide an improved subsurface aircraft servicing pit of the type used with conventional counterweighted pit lid assist systems that will accommodate an improved mounting mechanism according to the invention without changing the structure of the pit itself. Rather, the same pit that is utilized to accommodate the gearbox of a conventional gravity assisted pit lid lift mechanism is employed in the system of the present invention, but is provided with a lid seating rim assembly at the mouth of the pit with flanges that extend over the gearbox areas of the pit and seal it in watertight fashion.
To permit the pit lid to be both gravity assisted by counterweights and sealed throughout at its top, the pit lid lifting arms are reconfigured from conventional designs. Specifically, they are constructed with central U-shaped intermediate portions between their ends so as to permit them to be hinged underneath the pit rim, rather than set into upwardly facing, exposed pockets in the frame surrounding the pit lid.
A further object of the invention is to provide a counterweighted pit lid that avoids damage to the structure of the pit by the counterweights if the lid is thrown open in a violent manner. In conventional counterweighted pits it is possible for the counterweights to strike the upright wall of the pit at which the meshed counterweight gears are located with a very large force. The impact can damage the structure of the pit, if the pit lid is thrown or blown open. This can occur either due to
Eldred J. Woodrow
Petersen Craig A.
Thomas Charles H.
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