Abstract:
A helicopter drip pan apparatus for covering and sealing a structural opening in a helicopter. The drip pan apparatus includes a frame member adapted to mount to the structural opening of the helicopter. The frame member has an inwardly-facing peripheral surface extending around the frame member. The frame member and thus the surface have at least one linear portion. A drip pan is selectively affixed to the frame member. The drip pan includes an outwardly-facing peripheral groove which extends around the outside edge of the drip pan. Like the surface of the frame member, the groove has at least one linear portion. The perimeter of the drip pan conforms to the surface of the frame member. A seal member is disposed in the groove of the drip pan to sealingly engaging the surface of the frame member against fluid leakage therethrough.

Description:
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 or transmission 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&#39;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 fluidtight, allowing fluid such as 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&#39;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&#39;s forged structure. The skirt is thin and many times more flexible relative to the helicopter&#39;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. 
     The drip pan design disclosed in copending U.S. patent application Ser. No. 09/069,920, filed Apr. 30, 1998, which is fully incorporated herein by reference, provided improvements to prior drip pan designs. However, even this drip pan design can be improved upon further, particularly in the area of the seal and the attachment of the drip pan to its attachment frame. 
     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&#39;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 without leakage. According to one embodiment of the invention, the drip pan apparatus includes a frame member adapted to mount to the structural opening of the helicopter. Unlike prior drip pan designs, the frame member may mount directly to the forged structure of the helicopter or to a flexible skirt required by prior designs. The frame member has an inwardly-facing peripheral surface extending around the frame member. The frame member and thus the surface have at least one linear portion. A drip pan is selectively affixed to the frame member. The drip pan includes an outwardly-facing peripheral groove which extends around the outside edge of the drip pan. Like the surface of the frame member, the groove has at least one linear portion. The perimeter of the drip pan conforms to the surface of the frame member. A seal member is disposed in the groove of the drip pan to sealingly engaging the surface of the frame member against fluid leakage therethrough. 
     In one aspect of the invention, the frame member also has spaced apart slots opening inwardly to an opening defined by the frame member. The drip pan has a plurality of resilient members resiliently engaging the slots to detachably secure the drip pan to the frame member. These resilient members provide a quick and convenient way to install or remove the drip pan without using any hand or power tools. 
     In another aspect of the invention, the drip pan includes a plurality of access openings to provide ready access to mechanical linkages and fluid level indicators. Removable access covers have peripheral seal members which sealingly engaged the access openings against fluid leakage therethrough. The access covers include resilient members which resiliently engage grooves located in the access openings. These resilient members provide a quick and convenient way to install or remove the access covers without using any hand or power tools. 
     In still another aspect of the invention, the opening defined by the frame member is transversely disposed or shifted to one side of the frame member. As a result the four frame rails forming the frame member have varying widths. The shift of the opening provides improved access to an oil filter on particular helicopters. To provide even further access, a specific corner section of the frame member is machined or milled down so that the oil filter can be removed along a line not perpendicular to the drip pan. 
     The drip pan apparatus of the present invention maintains its sealing integrity more effectively than prior drip pan apparatuses. Specifically, the peripherally located seal member continues to sealingly engage the surface of the frame member even when the structural opening and the frame member flexes out of the plane of the drip pan apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic elevational illustration in partial cross section showing orientation of a helicopter, engine, transmission, rotor, and cabin of the type with which the invention is used; 
     FIG. 2 is a perspective disassembled view of the helicopter drip pan apparatus of the invention shown attaching to the skirt around the structural opening; 
     FIG. 3 is a top plan view of the assembled helicopter drain pan apparatus in partial cross section; 
     FIG. 4 is a cross-sectional view taken along lines  4 — 4  of FIG. 3 showing the drain pan apparatus in one assembled mode; 
     FIG. 5 is a cross-sectional view taken along lines  5 — 5  of FIG. 3 showing the drain pan apparatus in an assembled mode; and 
     FIG. 6 is a cross-sectional view similar to that view shown in FIG. 5 illustrating the insertion of a filter from the engine compartment of the helicopter. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a widely known configuration of a typical helicopter  10 . While the typical helicopter  10 , for example, in this description is a Blackhawk™ helicopter as manufactured for the United States by Sikorsky Aircraft Company, Stratton, Conn., it will be appreciated that the invention is useful for numerous aircraft and helicopter configurations of other makes and models. In this configuration the helicopter  10  has a cabin  12  (dashed outline) in which passengers, equipment and cargo can ride during operation. Located just above the cabin  12  is at least one engine  14  which supplies power to a rotor transmission  16 . The rotor transmission  16  is connected to a shaft  18  which imparts rotary motion to the main rotor  20 . The rotor transmission  16  is also connected via a drive shaft (not shown) to a tail rotor  22 . 
     It will be appreciated the rotor transmission  16  requires frequent inspection and maintenance to ensure proper operation of the transmission. To facilitate easy and ready access to the rotor transmission, rotor transmission access openings are provided on both the exterior and interior of the helicopter. For example, structural opening  24  is located within the cabin  12 , providing the requisite access to the rotor transmission  16  situated directly above the cabin. Structural opening  24  generally has some type of removable covering to seal the transmission area  16  from the cabin area  12 . To accommodate attachment of a removable covering, a flexible skirt  26  (FIG. 2) is fixedly secured around the periphery of structural opening  24  by rivets  28 . Skirt  26  is many times more flexible than the structural opening  24  to which it attaches. 
     As can be further appreciated the rotor transmission  16  as well as the engine  14  require various fluids during their respective operations. Generally, these fluids provide the rotor transmission  16  and the engine  14  with lubrication, cooling, and the like. During operation these fluids may leak and drip from either the engine  14  or rotor transmission  16  or both. To prevent leakage of fluid into the cabin  12  via structural opening  24 , a drip pan apparatus  30 , as shown in FIG. 2, is used to cover and seal the structural opening  24 . 
     With specific reference to FIGS. 2-6, the drip pan apparatus  30  according to one preferred embodiment of the invention has a frame member  32 , a drip pan  34 , and a seal member  36  cooperating together to provide a fluid tight sealing arrangement for structural opening  24 . Frame member  32  has a plurality of lugs  38  disposed about the exterior periphery of frame member  32 . Four lugs  38  are disposed on two sides of the frame member  32  and three lugs  38  are disposed on the other two sides of the frame member  32 . Fasteners  40  cooperating with lugs  38  and threaded retention members  42  (FIG. 4) secure frame member  32  to skirt  26  attached to structural opening  24 . Once installed, frame member  32  typically remains in place and is not routinely removed from structural opening  24 , although it could be readily removed by simply extracting fasteners  40 . Frame member  32  is many times more rigid than the flexible skirt  26 . 
     Drip pan  34  has a plurality of resilient members  50  which serve to hold drip pan  34  in sealing engagement with frame member  32 . Each resilient member  50  has elongated arms  52  with curved portions  54 . Resilient members  50  are free to pivot about brackets  58 . Curved portions  54  selectively engage slots  56  opening toward and located about the interior periphery of frame member  32 . To secure drip pan  34  to frame member  32 , the drip pan  34  is pushed into the interior of frame member  32  until the drip pan  34  contacts lip  60  (FIG. 4) which extends around frame member  32  and acts as a stop for drip pan  34 . Only part of the curved portions  54  are resiliently inserted into slots  60 . The installation and the removal of the drip pan  34  can be accomplished rather quickly using the resilient members  50  because no tools such as screwdrivers or wrenches are required. Equally important, resilient members  50  are permanently secured to the drip pan  34  by brackets  58 , so the resilient members  50  cannot be lost or misplaced when the drip pan  34  is removed to gain full access to the engine  14  and rotor transmission  16 . 
     Seal member  36  is disposed in an outwardly-facing groove  62  which extends around the outer periphery of drip pan  34 . In this application, outwardly-facing represents a direction substantial parallel to the plane of the drip pan  34  and extending away from the drip pan  34 . As illustrated in FIGS. 2 and  3 , the outer periphery of drip pan  34 , which has four straight edges or side  35   a,    35   b,    35   c,    36   d  connected by curved portions  37   a,    37   b,    37   c,    37   d,  conforms to frame member  32  which is comprised of four straight sides or rails  39   a,    39   b,    39   c,    39   d  connected by curved portions  41   a,    41   b,    41   c,    41   d.  When drip pan  34  is installed into frame member  32 , seal member  36  sealing engages inwardly-facing surface  64  of frame member  32  to achieve a fluid tight sealing arrangement between drip pan  34  and the frame member  32 . In this application, inwardly-facing represents a direction substantial parallel to the plane of the frame member  32  and extending toward the interior of the frame member  32 . Unexpectedly, seal member  36  provides the necessary sealing engagement between outwardly-facing seal member  36  and inwardly-facing surface  64  despite the fact that groove  62  and surface  64  respectively run along straight sides  35   a,    35   b,    35   c,    36   d  and  39   a,    39   b,    39   c,    39   d.  Typically, peripheral seals are used in cooperation with annular or curved sealing surfaces such as those defined by curved portions  37   a,    37   b,    37   c,    37   d  and  41   a,    41   b,    41   c,    41   d.  It was previously felt that peripheral seals used along straight sealing surfaces would provide unacceptable sealing integrity. 
     In one prior drip pan design, a seal was located in a groove opening in a direction perpendicular to the plane of the drip pan. The seal would engage a surface which was parallel to the plane the dip pan. With this arrangement, flexure of the helicopter frame associated with structural opening  24  may breach the seal integrity between the drip pan and the attachment frame causing fluid to leak into the helicopter cabin. Seal member  36  of the present invention, however, is a peripheral seal located in outwardly-facing groove  62  to form a fluid seal between the periphery of the drip pan  34  and the inwardly-facing surface  64  of frame member  32 . With this arrangement, flexure of the helicopter frame associated with structural opening  24  does not breach the integrity of the sealing arrangement between the drip pan  34  and the frame member  32 . It can be appreciated that while the sealing member  36  could be any suitable cross-sectional geometry, seal member  36  is preferably an O-ring. 
     Routine maintenance and inspection of the rotor transmission  16 , does not ordinarily require removal of the entire drip pan  34 . To accommodate limited access for routine maintenance or inspection, a plurality of small, removable access covers  70  are provided in drip pan  34  to allow access through access openings  72  to mechanical linkages in and around the rotor transmission and to allow inspection of the fluid levels associated with the rotor transmission  16 . An access cover  70  for each access opening  72  is removably disposed in sealing engagement covering the access opening  72 . To secure access cover  70  to the access opening  72  in drip pan  34 , each access cover  70  has a resilient member  74  which functions much like resilient member  54  which secures the drip pan  34  to the frame member  32 . 
     Access opening  72  has an annular groove  76  for resiliently receiving curved portion  78  of resilient member  74  to sealingly secure access cover  70  to access opening  72 . Advantageously, no tools are required to operate the resilient members  74  to install or remove the access covers  70 . In addition, brackets  80  permanently secure resilient member  74  to access covers  70  so resilient members  74  cannot be lost or misplaced. Each access cover  70  is attached to the drip pan  32  by a suitable attachment device such as a cable or chain  82  so when an inspection procedure is complete the access cover  70  is readily retrieved and positioned into access opening  72 . Each access cover  70  includes a seal member  84  disposed in an annular groove  86  extending around the outer periphery of access cover  70 . When access cover  70  is placed into access opening  72 , seal member  84  sealing engages surface  88  of drip pan  34  which forms part of access opening  72 . Like seal member  36 , seal member  84  forms a peripheral seal between the access cover  70  and the surface  88 . This arrangement improves on prior sealing arrangements which located the seal member between an access cover surface parallel to the plane of the access cover and the drip pan, i.e., a face seal. As discussed above, the peripheral seal arrangement provides improved seal integrity even if the drip pan  34  flexes. Preferably, seal member  84  is an O-ring. 
     To facilitate the removal of accessing covers  70  from access openings  72 , pull handles  90  are attached to access covers  70 . Fasteners  92  fixedly secured pull handles  90  to access covers  70 . Preferably, pull handles  90  are cable or chain. 
     During the preflight procedure of a helicopter, critical filters must be checked and determined operational before the helicopter is allowed to fly. To facilitate this inspection process, at least one of the access covers  70  has a transparent cover member  94  (FIG. 5) so that a bypass button or valve associated with a particular filter can be checked visually through the access cover  70  without physically removing the access cover  70  from the access opening  72 . A seal member  96  is dispose between the transparent cover member  94  and access cover  70  to prevent fluid leakage therebetween. Preferably, the transparent cover member  94  is made from acrylic such as Plexiglass™. 
     With reference to FIGS. 2-4, drip pan  34  has a drain hole  100  to drain fluid collected by the drip pan  34 . Drain hole  100  includes strainer members  102  to keep foreign objects that may come to rest on the drip pan  34  from clogging the drain hole  100 . A drain tube  104  may be attached to the drain hole  100  to direct the collected fluid to a catch basin (not shown) or to the exterior of the helicopter. The drain tube  104  is made preferably from metal tubing having a diameter of about 0.625 inches. Alternatively, a removable stopper could be used with drain hole  100  for selective drainage. 
     In at least one application, the drip pan apparatus  30  may be used on helicopters having carrousel bars added to the interior of the helicopter cabin  12  to support, for example, litters used for transporting patients in need of medical attention. Typically, at least one carrousel bar passes directly under the drip pan apparatus  34 . To accommodate a carrousel bar  108  (phantom), elongated recesses  110  are provided in frame member  32  s o that the frame member  32  does not interfere with the installation and operation of the carrousel bar  108 . 
     In still another application, the drip pan apparatus  30 , and more specifically the frame member  32 , may interfere with access to an oil filter associated with the rotor transmission  16  when the drip pan apparatus  30  is installed. To provide for removal of an oil filter  112  (FIG. 6) from the rotor transmission  16 , a portion of frame member  32  is machined away as shown by numeral  114  so that the oil filter  112  can be removed along a line not perpendicular to the drip pan apparatus  30 . During the removal or installation of oil filter  112 , the drip pan  34  is removed to provide even greater access to the oil filter  112 . Frame member  34  is machined just enough to permit removal of oil filter  112 , and maintain sealing engagement between seal member  36  and surface  64  of frame member  34 . 
     To provide further access to the oil filter  112 , the geometry of frame member  32  can be modified. More specifically and with reference to FIG. 3, frame member  32  is comprised of four straight sides or rails  39   a,    39   b,    39   c,    39   d  connected by curved portions  41   a,    41   b,    41   c,    41   d,  where each rail  39   a,    39   b,    39   c,    39   d  has a respective width indicated by W 1 , W 2 , W 3 , W 4 . To provide imporved access to the oil filter  112 , the opening defined by rails  39   a,    39   b,    39   c,    39   d  is shifted to the left in FIG. 3 such that the respective widths W 1 , W 2 , W 3 , W 4  of rails  39   a,    39   b,    39   c,    39   d  are not all equal to one another. Specifically, W 1  equals W 3 , W 4  is greater than W 1  and W 3 , and W 4  is less than W 1  and W 3 . Preferably, the difference between W 2  and W 4  is about one quarter of an inch. This transverse shift of the opening helps to accommodate removal of the oil filter  112  which is generally located in the compartment above the drip pan apparatus  30  near the upper left hand corner of the drip pan apparatus  30  shown in FIG.  3 . 
     Accordingly, the invention provides an improved cover and seal for the interior access opening of a helicopter such as the Blackhawk™ helicopter. As such, the drip pan apparatus of the invention seals against fluid passage from the engine or transmission compartment to the cabin section of a helicopter. In addition, the drip pan apparatus of the invention permits quick access to the engine or transmission compartment of a helicopter, such as the Blackhawk™, without requiring modification to the existing aircraft structure. 
     These and other embodiments and modifications will become readily apparent to those of ordinary skill in the art without departing from the scope of this invention and the applicant intends to be bound only by the claims appended hereto.