Abstract:
The invention relates to an aircraft comprising a force transmission element which detachably connects a cabin structural segment to an aircraft primary structure and which comprises a cabin bearing element and a structure bearing element, the cabin bearing element being connected to the cabin structural segment and the structure bearing element being connected to the aircraft primary structure. The force transmission element is designed in such a manner that a force transmission can take place between the cabin structural segment and the aircraft primary structure with at least one degree of freedom of movement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/EP2009/053301, filed Mar. 20, 2009, published in German, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/123,866, filed Apr. 10, 2008, and of German Patent Application No. 10 2008 018 249.4, filed Apr. 10, 2008, the entire disclosures of which applications are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to an aircraft with a force transmitting element that separably connects a cabin element to a primary aircraft structure and to an aircraft with a sealing element for a cabin module. 
     BACKGROUND OF THE INVENTION 
     In today&#39;s commercial aircraft, cabin fixture elements that form an interior cabin such as, for example, luggage compartments, paneling sections or other interior structural elements are directly mounted on the primary aircraft structure such as, for example, frames, stringers or other supporting elements of the aircraft fuselage. The primary aircraft structure is continuously subjected to deformations due to various structural stresses caused, for example, by the pressurization of the aircraft interior that leads to swelling of the fuselage at high altitudes, thermal stresses that may be the result of expansions caused by a temperature difference of up to 100° C. or stresses that are related to flight mechanics, particularly during the takeoff and landing phase, and lead, for example, to a distortion of the aircraft in its longitudinal axis. This deformation of the primary aircraft structure inevitably leads to a change in the position of the cabin fixture elements relative to one another. In order to ensure that the individual cabin fixture elements do not damage one another during this constant deformation of the primary aircraft structure, sufficiently wide gaps are provided between the individual cabin fixture elements and these gaps need to be elaborately sealed for aesthetic reasons, as well as noise and temperature reasons. 
     DE 10 2006 048 376.6, the applicant of which is also the applicant of the present application, describes how cabin structure segments such as, for example, ceiling elements or lateral (i.e. side) sections that may be fitted with cabin fixture elements such as luggage compartments can be prefabricated in the form of a cabin structure unit. In order to form a passenger cabin, several cabin structure units are arranged behind one another and interconnected. The cabin structure unit is realized in a self-supporting fashion and has a shape similar to that of half a barrel without bottom. The side walls of such a self-supporting cabin structure unit are anchored to the aircraft floor structure. 
     It was now determined that the cabin structure units may move relative to one another and relative to the primary aircraft structure, for example, due to stresses resulting from flight maneuvers, and that the own weight, as well as the possible load in the luggage compartments, leads to bulging of the cabin structure segments of the cabin structure unit, namely of the two side walls. 
     SUMMARY OF THE INVENTION 
     The invention is based on the first objective of disclosing a device that effectively supports a cabin structure unit. The invention furthermore is based on the second objective of disclosing a device that prevents individual cabin structure units from damaging one another. 
     The first objective is attained with an aircraft with a force transmitting element that separably connects a cabin structure segment to a primary aircraft structure and features a cabin bearing element, as well as a structure bearing element, wherein the cabin bearing element is connected to the cabin structure segment and the structure bearing element is connected to the primary aircraft structure. According to the invention, the force transmitting element is designed in such a way that a force transmission between the cabin structure segment and the primary aircraft structure can take place with at least one degree of freedom of motion. Consequently, the force transmitting element is able to transmit a force in no more than two translatory directions. The transmission of a force in a third translatory direction is not possible. When the cabin structure segments, particularly the side walls, of a cabin structure unit mounted in an aircraft bulge due to their own weight and the load in the luggage compartments, they can only deform until the side of the side wall that faces the primary aircraft structure abuts on the frames of the primary aircraft structure. The force transmitting element makes it possible to purposefully introduce a force into the frames and stringers of the primary aircraft structure via the side walls of the cabin structure unit. The frames and stringers therefore are only subjected to the forces, for which they are designed, namely lateral and longitudinal forces. 
     Takeoffs or landings cause acceleration forces to be exerted upon the cabin structure segment along the longitudinal axis of the aircraft. The force transmitting element makes it possible to introduce part of the acceleration forces into the primary aircraft structure via the side walls of the cabin structure unit. Consequently, the floor structure does not have to absorb all occurring acceleration forces, as well as the torques resulting thereof. The torques occur because the acceleration forces engage over the entire height of the cabin structure unit and therefore form a lever arm referred to the floor structure. The position of the force transmitting element can be chosen such that the torques are minimized. 
     In one advantageous embodiment, the primary aircraft structure features frames and stringers that are designed for absorbing forces in one direction only. The force transmitting element is arranged on the frames and/or stringers and transmits forces in this direction only. Frames are designed for absorbing forces acting thereupon in the radial direction only. Forces that act transverse to the frames, for example forces along the longitudinal axis of the aircraft, may cause the frames to buckle and thusly severely weaken the primary structure. This applies analogously to the stringers. They are designed for absorbing forces that occur along the longitudinal aircraft axis. If transverse forces such as, for example weight forces are introduced into a stringer, it may buckle and also severely weaken the primary structure. Since the force transmitting element advantageously transmits forces in one translatory direction only, it is possible to respectively subject the stringer and the frame to exactly the force that the stringer or the frame is respectively designed to absorb. Consequently, only forces that occur along the longitudinal aircraft axis are introduced into the stringer. Accordingly, only forces that act perpendicular to the frame are introduced into the frame. 
     In another advantageous embodiment of the invention, a friction-reducing insert is situated between the structure bearing element and the cabin bearing element. This insert can prevent frictional forces that act transverse to the direction, in which a force can be respectively introduced into the frames and stringers, from reaching a magnitude that can have damaging effects on the primary aircraft structure. Frictional forces can be created if a relative motion between the aircraft structure and the cabin fixture element or, more specifically, between the structure bearing element and the cabin bearing element occurs during the operation of the aircraft. Plastics such as PTFE or PVDF may be used as inserts. The insert naturally may also be realized in the form of a coating. If the frame consists of aluminum and is realized in the form of a Z-frame, in particular, it would be possible to coat the limb that may form a structure bearing element. One suitable process in this respect involves, for example, hard-anodizing of this limb. This coating already has a significant friction-reducing effect. However, this layer may also be provided with PTFE in order to additionally reduce the friction. 
     This insert also makes it possible to reduce or prevent a noise that could possibly result from the relative motion between the cabin bearing element and the structure bearing element. 
     A spring damping element may be advantageously arranged between the structure bearing element and the cabin bearing element. During the operation of the aircraft, not only relative motions between the cabin structure unit and the aircraft structure may occur, but also oscillations that are caused, for example, by the engines. If these oscillations or vibrations are directly transmitted from the aircraft structure to the cabin structure unit and the cabin structure unit has insufficient internal damping, these oscillations may lead to a background noise in the passenger cabin. In addition, the vibrations of the aircraft structure would also lead to vibrations of the cabin structure unit. Both influences, namely the background noise and the vibrations, contradict the aspirations of airlines to make the stay aboard the aircraft as comfortable as possible for the passengers. The spring damping element reduces these negative influences. The characteristics of the spring and of the damper naturally need to be adapted such that no resonances can occur between the cabin structure unit and the aircraft structure. Such a spring damping element also makes it possible to dampen transverse forces, the cause and harmful effect of which on the primary structure were already explained above, to at least a harmless level. In addition, a uniform surface pressure between the cabin bearing element and the structure bearing element can be achieved with such a spring damping element. Locally occurring punctual load peaks that otherwise could result in damages to the cabin structure unit, the frame and/or the stringer can be avoided in this fashion. Such a spring damping element is furthermore suitable for compensating manufacturing tolerances. The spring damping element naturally may also be used for at least largely preventing a heat transfer due to the contact between the cabin structure unit and the aircraft structure. 
     It is preferred that the spring damping element is either rigidly connected to the cabin bearing element or the structure bearing element. Due to this mounting, the spring damping element is prevented from leaving its assigned location, i.e., from “migrating,” during relative motions between the cabin structure unit and the aircraft structure. This mounting also provides the option of sectionally arranging the spring damping element at predetermined positions only. The size of the sections needs to be chosen in accordance with the occurring loads. It would naturally also be possible to continuously arrange a spring damping element, for example, in the form of an elastomer over the entire height or length of the cabin structure unit or the aircraft structure. 
     Since the spring damping element is only connected to one of the components, i.e., either to the cabin structure unit or to the aircraft structure, the spring damping element is only subjected to compressive stresses, but not to tensile stresses. This opens up a broad selection of spring damping elements because there are certain types, for example, of elastomers that are destroyed under tensile stresses. 
     A one-sided mounting also makes it possible for the cabin structure unit to completely separate from the frames and stringers, i.e., for these components to no longer contact one another. 
     In another advantageous embodiment of the invention, the cabin structure unit respectively features, referred to the longitudinal direction of the aircraft, one right and one left side wall with an upper end and a lower end, between which the cabin bearing element extends in an at least partially continuous fashion and is rigidly connected to the side wall. It is practical to mount the spring damping element on the side wall, in particular, if the side wall is braced against the frame. The cabin bearing element therefore may be designed in such a way that it automatically fixes the spring damping element. Since the side walls are sensitive to bulging, a continuous cabin bearing element that is rigidly connected to the side wall may simultaneously serve as a reinforcement. 
     In another advantageous embodiment of the invention, the lower end of the side wall is spaced apart from the primary aircraft structure by a greater distance than the upper end and the cabin bearing element is realized such that the distance of the cabin bearing element from the structure bearing element is essentially constant. Since the cabin bearing element is designed in such a way that the distance between the cabin bearing element and the frame is constant, it is possible to use identical spring damping elements. On the rear side of the side wall, the cabin bearing element consequently has a greater height at the lower bearing point than at the upper bearing point. 
     A stabilizing rib advantageously is integrally moulded onto the cabin bearing element. As a rule, the side walls are manufactured of fiber-reinforced plastic. In this case, the shape produced approximately corresponds to that of a tube segment. When a force is introduced accordingly, these curved walls only have a low resistance to bulging that may be reduced further by openings, e.g., for windows. For example, if weight forces act upon the side walls of the self-supporting cabin structure unit, the side walls have a tendency to bulge. If the cabin bearing elements extend continuously from the upper to the lower end, it is particularly advantageous to design these cabin bearing elements in a U-shaped fashion such that the limbs extend perpendicularly on the side wall, enormously increase the resistance to bulging in this way and thusly stabilize the side wall. 
     In one advantageous embodiment of the invention, the cabin bearing element is realized in the form of a brace with an extension that is rigidly connected to a sliding element. This extension engages into a U-shaped structure bearing element that is rigidly connected to the stringer. The structure bearing element may be provided with a likewise U-shaped spring damping element that preferably consists of an elastomer. 
     The structure bearing element is arranged such that only forces acting in the longitudinal axis of the aircraft can be introduced into the stringer. The limbs of the U-shaped structure bearing element encompass the extension such that forces acting in and opposite to the direction of flight can be transmitted. It would also be possible to provide one brace with several extensions so as to realize a better force distribution and therefore a lower load per extension. 
     In order to ensure that the respective extensions can be easily inserted into the U-shaped structure bearing element or the spring damping element during the installation, the structure bearing element, the spring damping element and/or the extension may be provided with an insertion bevel, on which the two components to be engaged can slide during the installation until they reach their final position. A certain self-positioning of the components can be achieved during the installation in this way. 
     In another advantageous embodiment of the invention, the sliding element is adjustably arranged in a rail that is rigidly connected to the cabin structure segment. The cabin structure unit needs to be aligned relative to the aircraft structure in the longitudinal direction of the aircraft due to manufacturing tolerances. Since an adjustment option is provided, the individual cabin structures segments can be realized such that the joints between the individual cabin structure segments have the same width. When the cabin structure unit is unfolded in the aircraft fuselage, it is still possible to access the sliding element situated on the side of the cabin structure segment that faces the aircraft structure through the window openings. In order to achieve a smooth adjustability of the sliding element, a friction-reducing insert may be placed between the sliding element and the rail. The adjustment itself may be realized, for example, with a screw that engages on a front side of the sliding element. The adjustment may also be realized with a snap lock. This snap lock engages once the correct position is reached. The adjustment to be carried out manually is automated in this fashion. 
     In another advantageous embodiment of the invention, the rail is arranged in the direction, in which the force transmitting element can transmit a force. Due to this arrangement of the rail, all forces engaging on the rail on the longitudinal axis of the aircraft can be introduced into the stringer. Consequently, force components that otherwise would have to be introduced into the frame are prevented due to the position of the rail, namely parallel to the stringer. 
     The second objective is attained with an aircraft with a sealing element for a cabin structure unit featuring at least two cabin structure segments that are spaced apart from one another by a gap, wherein the gap is at least partially closed with an elastic sealing element. According to the invention, the sealing element is realized in the form of a hollow chamber defined by a pair of opposite longitudinal walls that bridge the gap and a pair of opposite lateral walls that abut on the cabin structure segments, wherein the pair of longitudinal walls buckles toward one another in accordance with a predetermined spring constant when the gap becomes smaller, and wherein the spring constant changes when the pair of longitudinal walls contact one another. 
     Due to this design, relative motions between the individual cabin structure segments that are successively arranged, for example, in the longitudinal axis of the aircraft as they may occur, for example, during takeoffs and landings can be dampened until the longitudinal walls of the sealing element contact one another. Such a sealing element may be arranged within a cabin structure unit, i.e., between the individual adjacent cabin structure segments that form a cabin structure unit, as well as between two adjacent cabin structure units. Consequently, the sealing element can be arranged longitudinally referred to the longitudinal axis of the aircraft, as well as transverse thereto. Such a sealing element naturally may also extend between the floor structure and the lateral section mounted thereon. Until the longitudinal walls contact one another, no forces or only low forces are respectively transmitted to the adjacent cabin structure segment or the adjacent cabin structure unit. Unless both longitudinal walls of the sealing element contact one another and the cabin structure segments and/or cabin structure units continue to move toward one another, the force created during this process cannot be introduced into the adjacent cabin structure segment and/or the adjacent cabin structure unit. The spring characteristic of the sealing element plotted in the form of a force-path diagram therefore may feature a sharp bend or progress unsteadily. This realization of the sealing element consequently provides the advantage that the individual cabin structure segments cannot contact one another or the adjacent cabin structure unit due to the occurring relative motions, and that the occurring forces even can be purposefully introduced into the adjacent cabin structure segment once a critical point is reached. 
     One longitudinal wall of the sealing element may furthermore be designed in a colored fashion. For example, the longitudinal wall that is visible to the passengers may be adapted to the interior of the cabin with respect to its colors. It would naturally also be possible that the longitudinal wall of the sealing element facing the passenger compartment does not extend flush with the cabin structure segment, but the sealing element rather is set back relative to the cabin structure segment. This would result in a shadow joint. 
     In one advantageous embodiment of the invention, a medium is enclosed in the hollow chamber of the sealing element. This medium may be gaseous, liquid or even solid. However, the medium needs to have a certain compressibility. The incorporation of the medium makes it possible to influence of the spring characteristic of the sealing element. The medium should also have adequate noise-insulating properties such that wind and engine noises are largely unable to reach the passenger cabin. In addition, the medium should provide adequate thermal insulation such that the extremely cold temperatures prevailing at high altitudes cannot be transferred into the passenger cabin via this sealing element. When using a liquid or gaseous medium, the hollow chamber would have to be sealed in a fluid-tight or gas-tight fashion on both of its ends. This can be realized, for example, by means of vulcanizing, welding or bonding. 
     In another advantageous embodiment of the invention, the lateral wall of the sealing element features a spring that engages into a groove provided in the cabin structure segment such that the position of the lateral wall is fixed relative to the cabin structure segment. Consequently, the lateral walls remain in contact with the cabin structure segments when the individual cabin structure segments shift relative to one another transverse to the longitudinal axis of the aircraft and, for example, create an offset between the individual cabin structure segments during this process. Due to the stationary arrangement of the lateral wall relative to the cabin structure segment, no gap can form between the lateral wall of the sealing element and the cabin structure segment. Cold temperatures and noises could reach the passenger cabin through these gaps and therefore significantly impair the physical comfort of the passengers in the passenger cabin. 
     According to another aspect of the present invention, a cabin structure unit is proposed for mounting cabin fixture elements in an aircraft, particularly an aircraft of the type described above or in DE 10 2006 048 376.6, wherein the cabin structure unit is designed in such a way that a cabin fixture element can be installed, wherein the cabin structure unit is realized in a self-supporting fashion, wherein the cabin structure unit can be mounted on an aircraft structure, wherein the cabin structure unit features cabin structure segments, and wherein the cabin structure segments are connected to one another in a collapsible fashion by means of hinges. 
     Each cabin structure unit may be divided into a number of segments. The segments may consist of longitudinally extending stiffening ribs, stiffening screens, air ducts or another segment that provides suitable static properties for use as a cabin structure unit. All of the cabin structure segments may form the cabin structure unit, for example, in the circumferential direction. 
     Since the cabin structure unit and, in particular, the structure segments are connected by means of hinges, the volume of the entire unit can be reduced such that the installation of the unit may be simplified. The cabin structure unit may be transported into the installation position in a collapsed state and unfolded into its functional shape at this location. It is also possible to prefabricate the cabin structure unit with its cabin fixture elements outside the aircraft fuselage and to subsequently transport the prefabricated and collapsed cabin structure unit to the installation position in the aircraft fuselage. The hinge is arranged in such a way that the axis, about which the at least one cabin structure segment of a cabin structure unit can be pivoted, extends essentially parallel to the longitudinal axis of the aircraft. The prefabricated and collapsed cabin structure unit can be transported through small openings such as aircraft doors such that it is also easier to change the cabin layout when the fuselage is assembled. In addition, fewer assemblers may be required within the aircraft fuselage at the same time if the cabin structure unit is prefabricated outside the aircraft such that the impairments between the assemblers caused by the small installation space in the fuselage can be reduced. In this way, the assembly of the cabin structure unit, as well as the entire assembly of the aircraft, can be accelerated and realized in a less complicated fashion. 
     According to another exemplary embodiment, the cabin structure unit furthermore features adaptation elements. The adaptation elements are designed in such a way that they connect the cabin fixture elements to the aircraft structure or to the floor structure. 
     In order to connect the cabin fixture elements to the aircraft structure, it would be possible to provide, for example, several standardized connecting elements so as to reduce the complexity and the time required for the installation process. If the cabin fixture element consists, for example, of a window, the window needs to be connected to the opening in the aircraft structure. In this case, it is necessary to provide an adaptation element that seals the inner wall of the aircraft relative to the cabin fixture element. The adaptation element may consist of a simple plug and snap connection that features a window sealing elements, etc. The adaptation element may also provide compensation properties in order to compensate relative motions between the cabin structure unit and the fuselage structure that result, for example, from different temperature or pressure levels. The adaptation element may also be selected from the group consisting of electric connecting elements, air duct connecting elements or data link connecting elements. 
     According to another exemplary embodiment, the cabin structure unit is designed in such a way that it supports the aircraft structure. As already mentioned above, the cabin structure unit is self-supporting such that the cabin structure unit can carry its own weight. In addition, the cabin structure unit may be designed in such a way that it dampens forces and torques that originate, for example, from the fuselage structure. This is the reason why the aircraft structure can be realized with less weight such that the overall weight of the aircraft can also be reduced. The cabin structure unit therefore may have static properties in order to support the aircraft structure. 
     According to another aspect of the invention, a method is proposed for assembling a cabin structure unit for an aircraft of the type described in DE 10 2006 048 376.6. The cabin structure unit is prefabricated outside an aircraft structure. The prefabricated cabin structure unit is transported into the aircraft structure through an opening thereof. The prefabricated cabin structure unit is furthermore placed at a predetermined position in the aircraft structure. The prefabricated cabin structure unit is mounted on the aircraft structure at the predetermined position. 
     If this installation method is used, it is possible to prefabricate the cabin structure unit outside the aircraft such that the assembly processes for the aircraft can be carried out separately and simultaneously. In this way, it is possible, for example, to install the insulation of the aircraft structure while the cabin structure unit can be simultaneously fabricated outside the aircraft. In a next step, the complete cabin structure unit can be transported into the aircraft fuselage through the open fuselage sections and then installed in the aircraft structure at a predetermined position. The logistic complexity can be reduced in this fashion because all equipment parts such as cabin fixture elements can be stored and fabricated outside the aircraft fuselage. The number of assemblers who simultaneously work in the fuselage can also be reduced because the assemblers of the cabin structure unit can assemble the cabin outside the aircraft fuselage. Consequently, the assembly sequences can also be realized more economically becomes more space may be available for the assemblers. In this way, the assembly sequences for the fuselage, the cabin and the entire aircraft can be carried out faster and in a more relaxed fashion. 
     According to the exemplary embodiment of the method, the prefabricated cabin structure unit is realized in a collapsible fashion. In this way, the prefabricated cabin structure unit can be collapsed before it is transported through the opening of the aircraft structure. The prefabricated cabin structure unit is unfolded at the predetermined position in the aircraft structure. 
     Due to the ability to collapse the cabin structure units or the prefabricated cabin structure units, respectively, it is possible to provide small openings in the aircraft fuselage in order to transport the cabin structure unit to the predetermined mounting points in the fuselage. The cabin structure unit can be unfolded in the aircraft fuselage and mounted at the predetermined position. In this way, smaller openings such as doors make it possible to transport the collapsed, prefabricated cabin structure unit into the fuselage. This furthermore makes it possible to install cabin structure units in a disassembled state, namely also after the aircraft is completely assembled or work on the fuselage is completed, respectively. If it is preferred, for example, that passenger aircraft have flexible cabin layouts, it is possible to quickly change the cabin layout by collapsing the cabin structure units, removing the cabin structure units from the aircraft fuselage through the door and installing a different type of cabin structure unit. 
     According to another exemplary embodiment of the method, the cabin fixture element is installed into the prefabricated cabin structure unit outside the aircraft structure. In this way, the cabin fixture elements can be mounted on the cabin structure unit that, in turn, can be simultaneously mounted on the aircraft structure. The overall production time can be reduced. 
     According to another exemplary embodiment of the method, the opening of the aircraft structure is selected from the group consisting of fuselage doors, openings of fuselage segments and hatchways. 
     According to another exemplary embodiment of the method, the cabin structure unit features cabin structure segments, wherein the cabin structure segments are connected to one another in a collapsible fashion by means of hinges. The cabin structure unit may also be divided into cabin structure segments that are connected to one another by means of hinges such that several options can be provided for collapsing a cabin structure unit. In this way, a very small volume of a collapsed and prefabricated cabin structure unit can be realized such that even the smallest openings in the fuselage structure can be used for transporting this cabin structure unit to the intended installation site within the fuselage. 
     Other details and advantages of the invention result from the dependent claims in connection with the description of exemplary embodiments that are elucidated below with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective representation of several cabin structure units in an aircraft fuselage; 
         FIG. 2  shows a cross section through a cabin structure unit under a weight load; 
         FIG. 3  shows a schematic representation of a force transmitting element; 
         FIG. 4  shows a perspective representation of a lateral section with a continuous cabin bearing element; 
         FIG. 5  shows a schematic representation of a cabin bearing element with stabilizing rib; 
         FIG. 6  shows a schematic representation of a force transmitting element that is arranged between a side wall and a stringer; 
         FIG. 7  shows a side will with an adjustable cabin bearing element; 
         FIG. 8  shows a cross section through a sealing element that is not subjected to a load and connected to two cabin segments; 
         FIG. 9  shows a cross section through a sealing element that is subjected to a load in the form of longitudinal forces and connected to two cabin segments; 
         FIG. 10  shows a cross section through a sealing element that is subjected to a load in the form of transverse forces and connected to two cabin segments; 
         FIGS. 11 to 14  show exemplary illustrations of collapsible cabin structure units according to one exemplary embodiment of the present invention; 
         FIGS. 15 to 17  show schematic representations of a method for installing a cabin structure unit according to one exemplary embodiment of the present invention; 
         FIGS. 18 and 19  show schematic representations of a method for mounting a cabin structure unit that consists of several cabin structure segments according to one exemplary embodiment; 
         FIG. 20  shows a schematic representation of a cabin structure unit that contains several cabin fixture elements according to one exemplary embodiment; 
         FIG. 21  shows a schematic representation with first and second cabin structure units that form a fuselage cabin according to one exemplary embodiment; 
         FIG. 22  shows a schematic representation of an aircraft fuselage with first and second cabin structure units that are connected by means of compensation elements according to one exemplary embodiment; and 
         FIG. 23  shows a schematic representation of an adaptation element that connects cabin fixture elements to the aircraft structure according to one exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Identical or similar components in the different figures are identified by the same reference symbols. The figures show schematic representations that are not true-to-scale. 
       FIG. 1  shows a cabin section in a primary aircraft structure  5  that is composed of several cabin structure units  1 . The primary aircraft structure  5  consists of frames  100 , a floor structure  6  and an aircraft skin  102 . The longitudinal braces or stringers are not shown in this figure in order to provide a better overview. The individual cabin structure units  1  are separated from one another by sealing elements  200 . A cabin structure unit  1  is composed of several cabin structure segments  16 , the bottom two of which are referred to as lateral sections  104 . The lateral sections  104  are connected to a movable bearing  3  on one side and to a fixed bearing  4  on the opposite side. The two bearings  3 ,  4  in turn are rigidly connected to the floor structure  6 . Cabin fixture elements  2  in the form of luggage bins are mounted on the cabin structure segments  16  that form the ceiling of the cabin structure unit  1 . Force transmitting elements  106  are mounted between the frames  100  and the lateral sections  16  and introduce the forces generated by the cabin structure units  1  into the frames  100 . 
       FIG. 2  shows a cross section through a cabin structure unit  1 . One can clearly see how the original shape  108  of the cabin structure unit  1  illustrated in the form of a broken line deforms under the force G that originates at the center of gravity of the cabin illustrated in the form of a dot and acts upon the cabin structure unit  1  in the direction of the arrow. The force G is composed of the own weight of the cabin structure unit  1  that may be additionally increased by a load in the cabin fixture elements  2 , as well as a force component in the vertical axis of the aircraft as it is generated, for example, during climbout. The bulging of the side walls  104  is clearly visible. In order to largely prevent this bulging, the force transmitting elements  106  are arranged at the locations, at which the most significant bulging occurs, namely above and below the center of gravity referred to the vertical axis of the aircraft. These force transmitting elements  106  are able to introduce the forces Q generated by the lateral sections  104  into the frame with at least one degree of freedom of motion. 
       FIG. 3  shows a schematic representation of the force transmitting element  106 . In this case, a cabin bearing element  110  is inseparably connected to the side wall  104 . In this figure, the frame  100  is realized in the form of a Z-frame, of which only part of the web  112  and one limb are visible. The limb simultaneously serves as structure bearing element  114 . The surface that faces the lateral section  104  is provided with a friction-reducing insert  116  that is rigidly connected to the structure bearing element  114 . This insert  116  may also be realized in the form of a coating. A spring damping element  118  is situated between the structure bearing element  114  or the insert  116 , respectively, and the cabin bearing element  110  and realized in the form of a flat elastomer in this case. This spring damping element  118  is rigidly connected to the cabin bearing element  110 .  FIG. 3  furthermore shows the force Q that represents the component of the force Q acting upon the frame  100 . 
     The side wall  104  introduces the force Q into the spring damping element  118  realized in the form of a flat elastomer with a progressive characteristic via the cabin bearing element  110 . The force Q predominantly consists of the force Q that acts upon the frame  100  in the radial direction, but also has components that result from motions relative to the primary aircraft structure  5  that can be caused by vibrations and deformations during the operation of the aircraft. The spring damping element  118  dampens these components in order to ensure that they are not introduced into the frame  100 . In addition, the insert  116  prevents adherence between the spring damping element  118  and the frame  100 . Consequently, the spring damping element  118  only introduces forces into the frame  100  that the frame  100  is designed to absorb, namely purely radial forces. In addition, the force is introduced into the frame flatly due to the described design of the spring damping element  118 . Local stress concentrations are prevented in this fashion. 
     Due to this design, the frame  100  is not subjected to forces that it is not designed to absorb. The introduction of such forces could lead to buckling of the frame  100  and therefore significantly weaken the primary aircraft structure  5   
       FIG. 4  shows a perspective representation of a side wall  104  that is provided with window openings  120 . This figure furthermore shows three frames  100 , between which the window openings  120  are positioned. The side wall  104  has an upper end  122  and a lower end  124 . One can clearly see that the lower end  124  is spaced apart from the frame  100  by a greater distance than the upper end  122 . In order to allow the use of largely identical spring damping elements  118  for cost and inventory reasons, the cabin bearing element  110  that is rigidly connected to the side wall  104  is designed such that the distance between the structure bearing element  114  of the frame  100  and the cabin bearing element  110  is at least identical at the locations, at which the spring damping element  118  is installed. The cabin bearing element  110  is furthermore designed continuously between the upper end  122  and the lower end  124 . This continuous design of the cabin bearing element  110  stiffens the side wall  104 . 
       FIG. 5  shows a cross section through the arrangement described with reference to  FIG. 4 . The cabin bearing element is additionally expanded with two stabilizing ribs  126 . The stabilizing ribs  126  are arranged in front of and behind the frame  100  referred to the longitudinal direction of the aircraft and rigidly connected to the cabin bearing element  110  in this case. Consequently, the cabin bearing element  110  is realized in a U-shaped fashion, wherein the stabilizing ribs  126  perpendicularly stand on the side wall  104  and point in the direction of the frame  100 . The distance between the stabilizing ribs  126  needs to be so large that the stabilizing ribs  126  can under no circumstances come in contact with the frames  100  during flight operations because this would cause forces acting along the longitudinal axis of the aircraft to act upon the frames  100 . This could lead to buckling of the frames  100  and therefore significant damages to the primary aircraft structure  5 . The web  128  that connects the stabilizing ribs  126  may also be realized in the form of a hollow chamber profile, in which the hollow chamber itself may also be reinforced by means of webs. The stabilizing ribs  126  significantly stiffen the side walls  104 . This makes it possible to realize the side walls with a weaker cross section and therefore with less materials and less weight. 
       FIG. 6  schematically shows a force transmitting element  106  that is arranged between the side wall  104  and a stringer  130 . The cabin bearing element  110  connected to the side wall  104  is realized in the form of a brace with two extensions  132 , wherein the extension  132  has the contour of a cuboid. The extension  132  engages into a spring damping element  118  of U-shaped design in such a way that two opposite surfaces of the extension  132  contact the limbs of the spring damping element  118  without being connected thereto. These surfaces of the extension  132  are provided with a friction-reducing insert  116  that may also consist of a coating. In addition, the U-shaped spring damping element  118  features insertion bevels  119  on the ends that face away from the connecting web. The angle included by the two opposite limbs of the spring damping element  118  is smaller than 90° and amounts to 60° in the example shown. This U-shaped spring damping element  118  is rigidly connected to a U-shaped structure bearing element  114  in such a way that the limbs of the spring damping element  118  are congruent with the U-limbs of the structure bearing element  114 . The structure bearing element  114  is rigidly connected to the stringer  130 . In this case, the U-limbs of the structure bearing element  114  perpendicularly stand on the stringer  130 , as well as perpendicular to the longitudinal axis of the aircraft. 
     A force generated by the side wall  104  is introduced into the structure bearing element  114  via the extension  132  of the cabin bearing element  110  and the spring damping element  118 , wherein the structure bearing element in turn introduces the force into the stringer. Due to this arrangement, primarily the force component that extends along the longitudinal axis of the aircraft and is identified by the reference symbol L in the illustration can be introduced into the stringer. A rotational motion of the extension  132  can theoretically create another force component that is introduced into the stringer. However, this force component is, if it occurs at all, so small that it cannot cause damages to the stringer  132  due to buckling The spring damping element  106  therefore can only transmit forces with at least one degree of freedom of motion. 
       FIG. 7  shows the cabin bearing element  110  that is arranged such that it can be adjusted relative to the side wall  104 . For this purpose, the cabin bearing element  110  is rigidly connected to a sliding element  134 . The sliding element  134  runs in a rail  136  that is rigidly connected to the side wall  104  or another cabin structure segment  16 . A friction-reducing insert  138  is situated between the rail  136  and the sliding element  134 . In order to adjust the sliding element  134  relative to the side wall  104  or the cabin structure segment  16 , actuators  140  in the form of screws are arranged on the ends of the rail  136  and make it possible to respectively displace and fix the sliding element  134  or the cabin bearing element  110 . The rail  126  is respectively aligned on the side wall  104  and on the cabin structure segment  16  such that it extends parallel to the stringer  130 . 
     Due to manufacturing tolerances, it may occur that the cabin bearing element  110  described with reference to  FIG. 6  does not engage into the structure bearing element  114  rigidly connected to the stringer  130  with its extension  132  during the installation of the cabin structure unit  1  on the aircraft structure  6 , but that the two bearing elements  110 ,  114  rather are shifted relative to one another. Due to the adjustment option, the cabin bearing element  110  can be adjusted such that the two bearing elements  110 ,  114  engage into one another without any problems. An assembler can carry out this adjustment by reaching through a window opening in the fuselage. The insertion bevels  119  that were described above with reference to  FIG. 6  and may be alternatively or additionally arranged on the extension  132  simplify the adjustment to the effect that the extensions  132  do not absolutely have to be positioned exactly in the region between the limbs of the U-shaped spring damping element  118  in order to insert the extensions  132  into the U-shaped spring damping element  118 . The insertion bevels  119  also guide the extension  132  into the U-shaped spring damping element  118  if it is offset relative thereto such that an exact adjustment/positioning is simplified. 
       FIG. 8  shows a cross section through a sealing element  200  that is not subjected to a load. The sealing element  200  is arranged between two adjacent cabin segments  16  and closes a gap between these segments. The adjacent cabin segments  16  may form part of a common cabin structure unit  1 . In this case, the gap normally extends parallel to the longitudinal axis of the aircraft. However, the adjacent cabin segments  16  may also form part of adjacent cabin structure units  1 . In this case, the gap normally extends transverse to the longitudinal axis of the aircraft. The cabin segments  16  may also be realized in the form of side walls  104  that are arranged behind one another referred to the longitudinal axis of the aircraft. The sealing element  200  consists of two opposite longitudinal walls  202  that extend parallel to one another and two opposite lateral walls  204  that extend parallel to one another. The longitudinal walls  202  and the lateral walls  204  enclose a hollow chamber  206 . The hollow chamber  206  is defined by a shape that resembles that of a rectangle, in which the narrow sides were replaced with a semicircle that points in the direction of the lateral walls  204 . The hollow chamber  206  may be closed by means of vulcanizing, welding or bonding on its ends that are not visible in this figure. The outer sides of the longitudinal walls  202  look as if a segment of a circle  208  was removed from their originally rectangular cross section. In other words, the outer sides of the longitudinal walls  22  are concavely curved in the direction of the hollow chamber  206 . Consequently, the material thickness continuously increases from the center of the longitudinal wall  22  toward the lateral walls  204 . Each lateral wall  204  features a central spring  210  that engages into a groove  212  of the lateral section  104 . Due to this symmetric arrangement of the sealing element  200 , there is no preferred installation direction. The spring  210  and groove  212  arrangement is designed such that the lateral walls  204  abut on the side walls  104  in a plane fashion. The spring  210  also cannot be moved relative to the groove  212  under the influence of a force acting in the longitudinal direction of the sealing element  200 . Consequently, it is ensured that no passages are formed during the operation of the aircraft, through which heat could escape from the passenger cabin or noises from outside could be transmitted into the passenger cabin. The hollow chamber  206  may also be filled with a gaseous, liquid or solid medium. The medium should be compressible such that the sealing element can fulfill its function. The medium naturally may also boost or entirely fulfill the functionality of the sealing element  200  with respect to heat insulation and noise reduction. It is also possible to adapt the entire sealing element  200  or only the outer sides of its longitudinal walls  202  to the interior of the passenger cabin with respect to its colors. 
       FIG. 9  shows a cross section through a sealing element  200  that is connected to two cabin segments  16  and subjected to forces occurring along the longitudinal axis of the aircraft. One can clearly see how the longitudinal walls  202  have moved toward one another due to the reduction of the gap and now contact one another in the center. This causes the hollow chamber  206  to be divided into two hollow chambers  214  that collectively have a smaller volume than the original hollow chamber  206 . One can also clearly see that the height of the segment of a circle  216  has increased relative to the segment of a circle  208 , i.e., that buckling of the longitudinal walls  202  has taken place. Once the longitudinal walls  202  contact one another, the force introduced into the sealing element  200  is no longer absorbed by the sealing element  200 , but rather transmitted to the adjacent side wall  104 . This changes the spring constant of the sealing element  200 . This measure prevents the side walls  104  from contacting one another and therefore possible damages thereto. 
       FIG. 10  shows a cross section through a sealing element  200  that is connected to two cabin segments  16  and subjected to forces occurring transverse to the longitudinal axis of the aircraft. This arrangement can be distinguished from the arrangement described with reference to  FIG. 8  in that the side walls  104  are offset transverse to the longitudinal axis of the aircraft. One can clearly see that the design of the sealing element  200  causes the lateral walls  204  to abut on the cabin segments  16  in a plane fashion despite the offset. 
       FIGS. 11 and 12  show an exemplary embodiment of a cabin structure unit  1  with several cabin structure segments that are connected to one another by means of hinges. In this exemplary embodiment, each side of the cabin structure unit  1  is provided with a hinge  18  such that the cabin structure unit  1  can be collapsed as illustrated in  FIG. 12 . With reference to  FIGS. 13 and 14 , a cabin structure unit  1  may also feature a plurality of cabin structure segments  16 , each of which is connected to the other cabin structure segment by means of a hinge. With reference to  FIG. 12 , small units of a cabin structure unit may already be positioned in the collapsed state. 
       FIGS. 15 to 17  show one option for manufacturing a collapsible cabin structure unit. All cabin structure segments  16  can be installed before the cabin structure unit is transported into the fuselage segment. According to  FIG. 15 , the structure unit  1  and the cabin fixture element  2  may be preassembled outside the aircraft structure  5 . The preassembled cabin structure unit  1  therefore has a small volume in the collapsed state. According to  FIG. 16 , the collapsed cabin structure unit  1  can be steered to the predetermined mounting position on the aircraft structure  5 . After the predetermined mounting position on the aircraft structure  5  is reached, the cabin structure segment  16  is unfolded and mounted on the aircraft structure  5  as shown in  FIG. 17 . A simple and fast option for installing a cabin structure unit is provided in this way. 
       FIGS. 18 and 19  furthermore show an option for mounting the cabin structure unit  1  on an aircraft structure  5 . The cabin structure unit  1  may also feature several cabin structure segments  16  that are separately transported to the predetermined position in the aircraft structure  5 . Next, the cabin structure segments  16 ,  16 ″ are connected to one another in order to produce the cabin structure unit  1 . In this way, at least a few components of the cabin structure unit can be preassembled outside the aircraft such that the assembly sequence is accelerated. 
       FIG. 20  shows a schematic representation of a cabin structure unit  1  that consists of several cabin structure segments  16  and several cabin fixture elements  2 . For example, cabin fixture elements  2  such as air ducts and luggage bins can be installed into the cabin structure unit  1  outside. Consequently, adaptation element  21  such as window adaptation units can be installed outside the aircraft structure. A prefabricated cabin structure unit that contains all functional elements such as cabin fixture elements  2 , connecting elements  7  and adaptation elements  21  consequently can be preassembled outside the aircraft fuselage such that a faster and simpler installation can also be realized within the aircraft structure  5 . 
       FIG. 21  shows an aircraft cabin that consists of several interconnected cabin structure units  1 ,  10 ,  10 ′,  10 ″,  10 ′″. According to  FIG. 21 , the entire aircraft cabin may have a modular design with several cabin structure units  1 ,  10 ,  10 ′,  10 ″,  10 ′″. Each cabin structure unit may be preassembled outside the aircraft and ultimately installed into the aircraft structure together with the cabin structure unit  10 . Each cabin structure unit  1 ,  10  may consist, for example, of reinforcing screens  9 , support frames  10 , cabin structure segments  16  or connecting elements  7 . 
     The cabin structure units  1 ,  10  can be easily mounted on one another by means of mounting elements. A compensation element  20  may be inserted between the cabin structure units in order to compensate motions of each individual cabin structure unit  1 ,  10 . Each cabin structure unit  1 ,  10  may be designed in such a way that the compensation element  20  is not visible to the passengers. The gap between the cabin structure units  1 ,  10  can be reduced in comparison with conventional aircraft cabins due to the decoupling of the inner cabin structure units from the aircraft structure such that changes in the volume of the aircraft structure  5  due to pressure or temperature cannot have an influence on the inner cabin structure units  1 ,  10 . 
       FIG. 22  shows an exemplary design of an aircraft fuselage that contains several cabin structure units  1 ,  10 . The so-called door clearance line may also be used as compensation element  20  for compensating motions between each cabin structure units  1  and  10  in this case. Consequently, each cabin structure unit  1 ,  10  can move relative to the other cabin structure units without increasing the load acting upon on each cabin structure unit  1  due to these relative motions. 
     The cabin structure unit  1  may be arranged on the aircraft structure  5  by means of a movable bearing  3  or a fixed bearing  4 . The cabin fixture elements  2  may also consist of monuments such as galleys, toilets or other functional units within a cabin. The cabin fixture elements  2  are integrated into the self-supporting cabin structure units  1 ,  10  and also decoupled from the aircraft structure  5 . This is the reason why the cabin fixture elements  2  also move in the same direction and not in opposite directions in case of a deformation of the cabin structure unit  1 . This makes it possible to lower the risk of damages that are caused by opposed motions of each cabin structure unit  1 , particularly each cabin fixture element  2 . The motion in the vertical direction according to the Z-axis can also be reduced by utilizing a combination of a movable bearing and a fixed bearing  3  and  4  such that only motions along the longitudinal direction of the fuselage can occur. 
       FIG. 23  shows a schematic representation of an adaptation element  21  that connects cabin fixture elements  2  of the cabin structure unit  1  to an aircraft structure  5 . For example, air ducts need to be connected to the installations of the aircraft structure  5  just like window units. With respect to the window panel  2 ,  22 , it is necessary to provide an adaptation element  21  for the window opening  23  of the aircraft structure  5 . The adaptation element  21  produces a connection between the window panel  22  and the window opening  23 . The adaptation element  21  may provide several components that may have sealing properties and flexible properties. The adaptation element  21  needs to be movable because relative motions between the aircraft structure and the cabin structure unit  1  can occur. 
     The adaptation element  21  may produce, for example, a plug and snap connection such that the cabin fixture elements  2  can be easily connected to the functional elements of the fuselage structure  5 . The assembly time can be shortened due to the utilization of plug and snap connections for connecting the cabin fixture elements  2 . 
     As a supplement, it should be noted that “comprising” or “featuring” does not exclude other elements or steps, and that “an” or “a” does not exclude a plurality. It should furthermore be noted that characteristics or steps that were described with reference to one of the above exemplary embodiments can also be used in combination with other characteristics or steps of other above-described exemplary embodiments. Reference symbols in the claims should not be interpreted in a restrictive sense. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Cabin structure unit 
           2  Cabin fixture element, window panel 
           3  Movable bearing 
           4  Fixed bearing 
           5  Aircraft structure 
           6  Floor structure 
           7  Connecting element 
           9  Screen 
           10  Cabin structure unit, support frame 
           16  Cabin structure segment 
           18  Hinge 
           20  Compensation element 
           21  Adaptation element 
           22  Window panel 
           23  Window opening 
           100  Frame 
           102  Aircraft skin 
           104  Side wall 
           106  Force transmitting element 
           108  Original shape 
           110  Cabin bearing element 
           112  Web 
           114  Structure bearing element 
           116  Insert 
           118  Spring damping element 
           119  Insertion bevel 
           120  Window opening 
           122  Upper end of side wall 
           124  Lower end of side wall 
           126  Stabilizing rib 
           128  Web 
           130  Stringer 
           132  Extension 
           134  Sliding element 
           136  Rail 
           138  Friction-reducing coating 
           140  Actuator 
           200  Sealing element 
           202  Longitudinal wall 
           204  Lateral wall 
           206  Hollow chamber 
           208  Segment of a circle 
           210  Spring 
           212  Groove 
           214  Hollow chamber 
           216  Segment of a circle 
         G Force 
         Q Force 
         Q′ Force 
         L Force