Abstract:
An aircraft incorporates a lift system for guiding a lift cabin. The lift cabin  21  is capable of servicing several decks in the aircraft. A guiding structure is mounted inside the aircraft fuselage  1  by mounting it to the floor and deck structures, while allowing for strains between the floor and the deck in the vertical direction. The lift cabin is capable of travelling down to the ground if a door in the underside of the fuselage is provided. The lift cabin is arranged on the guiding structure using a bogie truck mounted on the lift cabin, and the bogie truck may be actively connected with profile rails of the guiding structure via roll blocks. The part of the bogie truck carrying the roll blocks or other guiding element may remain within the fuselage, when the cabin is positioned on the ground.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/631,335 filed Nov. 29, 2004 and of German Patent Application No. 10 2004 046 146.5 filed Sep. 23, 2004, the disclosures of which are hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to lift systems for aircraft, particularly to aircraft with multiple decks. 
    
    
     BACKGROUND 
     The steady rise in air traffic is being accompanied by the increased use of double-decker aircraft. The use of onboard lifts to transport cargo between the decks in such airplanes is known from WO 00/30422, for example. In addition, it is desirable in such aircraft that the lift also be able to approach another lower level and service the landing strip level. This document here provides for a scissor lift to lower cargo comprised of boxes, which directly handles the payload. Such a system does not enable passenger transport. Another mentioned solution involves a telescoping device, wherein an additional independently driven carriage travels out and down, lowering or raising the transport container with cargo. The additional independently driven carriage greatly increases the complexity, which adversely impacts maintenance and the weight of the lift system. 
     Given a lift capable of navigating at ground level, it is desirable to convey both cargo and passengers from the ground directly to the respective cabin deck, for which the conventional cargo area loading equipment are hardly suited. 
     U.S. Pat. No. 4,653,707 proposes an onboard lift that services various decks in the aircraft along with the landing strip level. The lift cabin exits through an opening in the fuselage and travels downward, transporting passengers or goods. The structure consists of a guide shaft secured in the aircraft, which envelops the actual cabin on all sides. In light of the guide function, the shaft must be able to traverse at least the distance to the ground. Since the shaft completely envelops the cabin as a force-conveying structural element, it must also be expected to be heavy. In addition, the drive consists of ropes and pulleys, making it complicated and high-maintenance. 
     RH:ar 
     SUMMARY 
     An aircraft according to the present invention incorporates a lift. The aircraft may include a plurality of decks, a fuselage having an opening on an underside and a hatch or door capable of closing the opening. A guiding structure having profile rails is mounted within a shaft through the plurality of decks, which may be aligned with the opening in the underside of the fuselage. A lift system is mounted on the guiding structure. The lift system includes a bogie truck mounted on a cabin and coupled to the guiding structure by guiding elements. For example, the bogie truck may be mounted to the lift cabin roof. A portion of the bogie truck is arranged such that the guiding elements remain within the fuselage, when the cabin is lowered to the ground and the cabin is completely free of the fuselage. 
     A lift according to the present invention is configurable to enable lowering of the lift to ground level. Embodiments have less weight and require less maintenance than known lifts using in aircraft. The lift may have a compact structure and may avoid complexity in the design and functioning of the lift. An embodiment may be designed without the need for telescoping systems and cable winches, for example. 
     The lift offers many other advantages as described in the detailed description. For example, an aircraft incorporating the lift of the present invention is capable of being serviced rapidly from the ground without interfering with cleaning, maintenance and security operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings provide some examples and should not be used to limit the present invention. 
         FIG. 1  illustrates a longitudinal section through an aircraft fuselage with a lift system; 
         FIG. 2  is a cross section through the aircraft fuselage with a lift system; 
         FIG. 3  is a section in the vertical plane of the lower lift area; 
         FIG. 4  is a section in the horizontal plane of the lower lift area. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description and drawings provide some examples of the present invention, which should not be used to limit the scope of the present invention. Instead, the present invention should be limited only to the claims that eventually issue. 
     In  FIG. 1  an aircraft is illustrated having a fuselage  1  with three levels: a cargo area floor  11 , a main deck  12  and an upper deck  13 . A lift cabin  2 . 1  may be lowered to the landing strip  4 . For use by wheelchair-bound persons, a small ramp  22  may be provided. The lift cabin  21  travels into a guide structure  3  by way of a bogie truck  24  secured to the cabin roof  23 . The bogie truck  24  may be detachably secured with connecting elements  57 , as shown in  FIG. 3 , or by any other fasteners or joining mechanism, such as adhesive bonding, welding, slide locking or a combination of these. 
     In one embodiment, when the lift cabin  21  travels into the lowest position, guide elements  25  of the bogie truck  24  are situated completely inside profile rails  31  in the fuselage  1 , while the cabin  21  is completely exposed. This arrangement of the guide structure  3  and lift cabin  21  with mounted bogie truck  24  allows the cabin  21  to have any height, while still allowing the cabin  21  to reach the ground. For example, it may have a height sufficient for use by passengers, crew and servicing personnel. The bogie truck  24  may be designed to have a light weight compared to the weight of the cabin. The bogie truck  24  is guided via the guiding elements  25 . 
     In the drawing of  FIG. 2 , one embodiment of an aircraft according to the present invention is illustrated having dimensions of a large capacity double-level aircraft. The cabin  21  has a height H. In one example, the height H is about 2 meters, which is selected as a height capable of accommodating the height of passengers in the cabin  21 . The height of the bogie truck  24  may be defined as the distance between the upper and lower guiding elements  25 . The height of the bogie truck  24  may be selected based on the distance to the ground and the space available within the fuselage shell  1  in the top lift position  21 . In one example, the distance between the guiding elements  25  is selected to be at least large enough to compensate for the forces generated by the tilting moment of the cabin  21 , when the cabin  21  travels out of the fuselage  1 . The distance between the guiding elements provides a lever arm that reduces the load and may be designed such that the loads are substantially less than the maximum loads supportable by the guiding elements  25 . 
     Since transverse forces are also encountered during flight, as opposed to ground operations, additional guiding elements  26  are provided as needed to provide additional support during operation while in flight solely within the fuselage shell  1 . These additional guiding elements  26  may exit the guiding structure  3  during egress of the cabin  21  from the fuselage  1 . Upon entry into the fuselage  1 , these additional guiding elements  26  provide additional guidance, so that the cabin  21  rests on a wider base as it traverses the interior of the fuselage  1 . This feature offers an additional advantage of preventing any substantial impact with the lift shaft  27 , even if the gap between the cabin  21  and the lift shaft  27  is small. 
     The guiding structure  3  may comprise two profile rails  31 , in which the guiding elements  25 ,  26  run, roll and/or slide. The rails  31  may be rigidly interconnected. The guiding structure  3  may constitute the driving structure for movement of the cabin  21 . In one example, the lift is driven via low-noise toothed belts  55 , which are coupled to the bogie truck  24  as illustrated in  FIGS. 3 and 4 . 
     For example, the guiding structure  3  may be designed as a torsionally resistant box, as illustrated in  FIG. 4 . In one embodiment, to ensure that lift operation is unaffected by fuselage deformation, the guiding structure  3  is secured by a fixed bearing  14  and a movable bearing  15  connected to the fuselage  1  in a statically defined manner. The fixed bearing  14  is capable of absorbing forces in each of the x, y, and z directions, while the movable bearing  15  is capable of countering forces only in the xy plane. Thus, the lift shaft  27  may be comprised of cladding and may have a comparatively light structure due to the absence of substantial contact between the components of the lift and the cladding of the shaft  27 . 
     On the fuselage underside a door  16 , also referred to as a flap, may be provided for ensuring lift egress and pressure tightness when closed, as shown in  FIG. 2 . The lift shaft  27  may be centered, such that the shaft is located between two isles, or may be disposed off-center, as shown in  FIG. 2 , such that the shaft may be located adjacent to a central aisle, whichever offers advantages in terms of lift access and seating arrangement. The shaft  27  has doors  28  on each deck. The door in the cargo area may have a shorter height than the height of the doors in the passenger compartments, for example. 
     The lower lift area, as illustrated in  FIG. 3 , has profile rails  31 , bogie truck  24 , lift cabin  21 , fixed bearings  14  and drive  5 . The drive motor  51  with coupling-braking unit  52  coupled thereto sits on a bearing block  53 , which may be directly coupled with the guiding structure  3 . For example, the drive  5  may form a single unit with the guiding structure  3 , which has the advantage of remaining unaffected by any fuselage cell deformation, which may occur during flight operations. 
     In the example shown, two toothed belts  55  are driven by drive elements and by two driving wheels  54  each secured laterally to the structure  3 . These have deflection pulleys above in the fuselage, which allow adjustment of belt tension. The two toothed belts  55  are connected by coupling elements  56  with the bogie truck  24 . Since the guiding elements  25  absorb the transverse forces or the counter forces from the cabin moment, only longitudinal forces, in a z-direction, act on the toothed belts  55  at the coupling elements  56 . The guiding elements  25  are depicted as roller pairs in the drawing; however, other solutions may be used, such as sliding blocks made of plastic and any other mechanism that provides low friction raising and lowering of the cabin  21 . The bogie truck  24  is mounted to the cabin roof  28  by screws or bolts  57  inserted through a flange; however any other fastener or bonding agent may be used to secure the bogie truck  24  to the cabin  21 . Preferably, the bogie truck is removably secured, enabling a separation for maintenance-related disassembly. The bogie truck  24  may also be detached via the coupling elements  56  from the toothed belts  55 , which may be changed out periodically, as required by a maintenance schedule or upon inspection. In this example, the toothed belts  55  are particularly easy to assemble, because they lie outside the guiding structure  3 . 
     In an alternative embodiment, the fixed bearing  14  may be formed as gimbals, if needed. This is denoted on the drawing by an additional rotational axis  17 . The forces acting on the guiding structure  3  are in this way partially absorbed by the spars of the aircraft structure, e.g., the cargo area floor  11 . The remaining forces are released on the movable bearing  15  located further up. To better thread the additional guiding elements  26  as the cabin  21  ascends, the profile rails  31  are somewhat conical at the lower end, denoted here as an inclined profile catch  33 . 
     Drive solutions other than the one described for driving the toothed belts  55  may be used. For example, individual drive elements could be flanged directly to the guiding structure  3  without a bearing block  53 , wherein the connecting shaft  510  could under certain conditions come to lie inside the profile rails  31 . The guiding elements  25  lying below (track rollers in the drawing) may have to edge higher on the bogie truck  24  in order for this alternative arrangement to fit in the space provided. 
       FIG. 4  shows a section of  FIG. 3  in a horizontal projection. The lift shaft  27  envelops the lift cabin  21  without any contact. Since all forces emanating from the lift movement are absorbed by the guiding structure  3  and/or the profile rails  31 , the lift shaft  27  can be merely designed as a light cladding. The profile rails  31  together with the webs  32  and cover plates  34  form the integral guiding structure  3 . The guiding elements  25 , which are here depicted as track rollers, move in the profile rails  31 . These may be hinged to the bogie truck  24 , which may be made of light metal or plastic, and may only negligibly increase the weight of the entire cabin unit. The toothed belts  55  may be arranged to the side of the guiding structure  3 , which facilitates assembly and disassembly. The connection to the bogie truck  24  is established via coupling elements  56 . 
     For example, the drive motor  51  acts by way of a coupling-braking unit  52 , e.g., via driving belt  58 , on a gear transmission  59 , which moves a driving wheel  54 . The gear transmission  59  ensures that the opposing toothed belt  55  is driven by the connecting shaft  510 . All drive units and shafts may be secured to the bearing block  53 , which is in turn screwed to the guiding structure  3 . This ensures that lifting operations can take place independently of the elastic deformations of the fuselage  1 , which may be encountered in flight operations. 
     The drive train from the motor  51  to the gear transmission  59  may be realized as self-inhibiting gearing or some other configuration, as requirements warrant. The toothed belts  55  may be arranged in any other way, such as having one half of the belt run inside the guiding structure  3 , while the other half is connected outside with the bogie truck  24  via the coupling elements. This solution has the advantage of yielding a more compact design. However, this solution may not be as easy to assemble and disassemble. Trade-offs between easy assembly and disassembly and compactness are allowed by the design of the drive system shown in  FIG. 4 . 
     Many other systems may be used or combined with the systems described for achieving desired performance requirements and will be readily apparent based on the examples of lift systems described and illustrated herein. 
     REFERENCE LIST 
     
         
           1  Aircraft fuselage
         11  Cargo area floor     12  Main deck     13  Upper deck     14  Fixed bearing     15  Movable bearing     16  Fuselage flap     17  Rotational axis     
           2  Lift
         21  Cabin,  21 ′—top position     22  Ramp     23  Cabin roof     24  Bogie truck     25  Guiding elements     26  Additional guiding elements     27  Lift shaft     28  Shaft door     
           3  Guiding structure
         31  Profile rails     32  Connecting webs     33  Inclined profile set     34  Cover plates     
           4  Landing strip 
           5  Driving block
         51  Drive motor     52  Coupling-braking unit     53  Bearing block     54  Drive wheel     55  Toothed belt     56  Coupling element     57  Connecting elements     58  Driving belt     59  Gear transmission     510  Connecting shaft
 
H Dimensional measure=about 2 m