Lubrication – Lubricators – Drip pans
Reexamination Certificate
2000-08-01
2001-04-17
Fenstermacher, David (Department: 3682)
Lubrication
Lubricators
Drip pans
C277S598000
Reexamination Certificate
active
06216823
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a fluid-tight drip pan, and more specifically to a fluid-tight drip pan for the engine compartment of a helicopter.
BACKGROUND OF THE INVENTION
Helicopters, in general, have the same basic configuration or layout. For instance, a typical helicopter will have a cabin section which is used to transport people, cargo or both. In addition, the helicopter will have an engine compartment which is located typically above and to the rear of the cabin section. The engine compartment will house two primary components, at least one engine and a rotor transmission with a corresponding transmission housing.
Both the engine and the rotor transmission contain numerous fluids, such as petroleum-based lubricants, that are critical to the operation of the engine and the transmission. These fluids inevitably leak from various locations in the engine and the transmission during both the operation and storage of the helicopter. Because the engine compartment is generally oriented above the cabin section, any leaking fluids eventually seep or drip into the cabin section, unless proper sealing mechanisms are in place. The inflow of these leaking fluids spoil, stain or damage the cabin's interior materials such as seat covers and acoustic linings. In addition, the leaking fluids can severely damage or destroy sensitive electronic equipment that may be placed in the cabin section of, for instance, a BLACKHAWK™ helicopter.
Moreover, the exterior of the helicopter around the engine and transmission compartment is not completely watertight, allowing water to leak from these areas into the cabin with similar adverse effects.
During routine inspection and maintenance it is necessary to have ready access to the engine and the rotor transmission. Such access is required to check critical fluid levels, to replace worn or damaged parts, or to adjust mechanical systems. Typically, various access panels in or around the engine compartment provide the requisite openings to achieve ready access to the engine and the rotor transmission. In some helicopters, such as the BLACKHAWK™ helicopter, a forged airframe structure forms an access opening which is located below the rotor transmission housing and above the cabin section. The opening is thus accessible through the cabin's ceiling. This access opening, however, must be sealed by a cover against the inevitable oil and fluid drippings which the engine and the rotor transmission will produce, as well as against water leakage.
The access opening below the engine compartment in the BLACKHAWK™ helicopter is defined by both the aircraft structural forgings and a flexible or yieldable downwardly-turned skirt which is riveted onto the helicopter's forged structure. The skirt is thin and many times more flexible relative to the helicopter's forged structure.
Prior drip pan designs attached a covering plate directly to the flexible skirt with a hollow seal sandwiched therebetween. One hollow seal used in prior designs resembled the flexible, hollow door seals used around car doors or refrigerator doors. However, the skirt contains surface aberrations, such as the protruding rivet heads from the rivets securing the skirt to the forged helicopter structure. When the seal engaged both the skirt and the rivet heads, it could be upset enough so that leakage occurred. Accordingly, the hollow seal traversing these aberrations while sandwiched between the skirt and the covering plate is unable to provide a suitable, consistent, long-term fluid seal. Moreover, flexing of the flexible skirt could also cause leakage.
Also, the geometry of the cover cannot be such that it protrudes significantly into the interior of the cabin section. Headroom in the cabin section typically is limited and any additional protrusion from the ceiling of the cabin section is undesirable. In addition, because weight is critical to the operation of any aircraft, heavy cover constructions are undesirable.
Accordingly, one objective of this invention is to provide an improved cover and seal for the interior access opening of helicopters such as the BLACKHAWK™ helicopter and those of similar structure.
Another object of this invention is to provide a drip pan that will effectively and consistently seal fluid from passage from an engine or transmission compartment to a cabin section of a helicopter.
Another object of this invention is to provide a drip pan which permits quick access to the engine or transmission compartment of a helicopter without requiring modification to the existing aircraft structure.
Another objective of the invention is to more effectively seal a drip pan to the skirt defining a transmission access opening in a BLACKHAWK™ helicopter.
Still another object of this invention is to provide a drip pan that can be attached to the existing structure of a BLACKHAWK™ helicopter without modification of the existing airframe structure and with minimal intrusion into the helicopter's cabin section.
SUMMARY OF THE INVENTION
These and other objects of the invention are provided for by a helicopter drip pan apparatus which covers and effectively seals a structural opening in the helicopter defined by a flexible skirt and without leakage at aberrations of the skirt surface. According to one embodiment of the invention, a fluid tight seal is achieved by redefining an aberration-free surface with which a sealing mechanism can be used. To this end and in accordance with one aspect of the present invention, a relatively rigid adapter plate, many times more rigid than that of the flexible skirt, is attached and sealed to the flexible skirt surface but around and not including the rivets holding the skirt in place. Interposed between the flexible skirt and the rigid adapter plate is a gasket to both sides of which a sealant is applied, providing an effective and consistent fluid seal at that interface. Moreover, a further sealing surface can now be formed in the adaptor plate for the cover plate described below. By using an adapter plate sealed to the flexible skirt, an aberration-free, planar sealing surface can be defined in parts other than the skirt. To this end, a cover plate constitutes a frame having an inner lip upon which a drip pan member conforms and rests. An O-ring is oriented in a groove in either the adapter plate or cover plate, and the cover plate frame is attached to the aberration-free surface of the rigid adapter plate to cover and seal the structural opening. Thus a more permanent leak-free seal is produced between the adaptor plate and skirt while a sealing surface for the cover plate is defined on the adaptor plate.
In accordance with another aspect of the present invention, access holes in the drip pan apparatus provide ready access to the rotor transmission during routine servicing. Removable covers sealingly engage the access holes each of which contain an O-ring. Furthermore, the fluid collected by the drip pan member is carried away by a drain tube attached to a drain hole located in the drip pan.
Accordingly, the drip pan apparatus is more permanently sealed to the opening defining skirt and a more effective seal is oriented between components of the drip pan (i.e. adaptor plate and cover plate), to produce an effective and consistent long-life seal without the afore-mentioned vagaries of the less consistent hollow seal alone acting on the flexible skirt and its aberrations.
REFERENCES:
patent: 2475836 (1949-07-01), Henricksen et al.
patent: 3971511 (1976-07-01), Casey
patent: 4394853 (1983-07-01), Lopez-Crevillen et al.
patent: 5018407 (1991-05-01), Hoecht
patent: 5411116 (1995-05-01), Kish et al.
patent: 5544632 (1996-08-01), Choate
Fenstermacher David
Wood Herron & Evans L.L.P.
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