Abstract:
The invention relates to an airframe having a substantially circular cross section in a lateral direction (Y) and which extends in the longitudinal direction (X). The airframe comprises, a plurality of rails for supporting seats, each rail being parallel to the longitudinal direction (X) of the airframe, a plurality of beams parallel to the rails; and a plurality of crossmembers aligned, in use, in the lateral direction (Y) of the airframe. Each crossmember supports only some of the successive rails, each crossmember being supported by only some of the successive beams in the lateral direction (Y) of the airframe with the beams forming part of a wing box and/or a main landing gear well of the airframe. Each crossmember comprises at least one connection to each of the beams that support it where each connection comprises at least one articulation about at least one axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT/FR2010/050128, filed Jan. 27, 2010, and claims the benefit of and priority to French Patent Application No. 0950556, filed Jan. 29, 2009, the entire disclosures of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention concerns airframes, notably aircraft. It concerns more specifically the architecture of the fuselage. 
       TECHNICAL BACKGROUND 
       [0003]    It is desirable for the cabin arrangements of a civil airliner to have some flexibility. Accordingly, the passenger seats being supported by longitudinal rails, it is advantageous to be able to modify the transverse position of the rails relative to the median vertical longitudinal plane of the cabin. 
         [0004]    In an ordinary section of the fuselage, this does not give rise to any particular difficulty. The rails conventionally rest on crossmembers that extend perpendicularly to the longitudinal direction of the fuselage and are supported on lateral portions of the fuselage. Thus whatever the position required for the seat rails, the rails rest on the crossmembers. 
         [0005]    Things are different in some particular sections of the fuselage. This is the case of the wing box that lies in the fuselage aligned with the wings. This is also the case of the main landing gear well accommodating the main landing gear supporting the fuselage directly. In these two particular areas, the structure of the fuselage includes beams extending in the longitudinal direction of the fuselage: these are beams in the case of the wing box and gantries in the case of the main landing gear well. In these two areas, the architecture of the fuselage and transverse deformations to which it is liable to be exposed prohibit fitting the aforementioned crossmembers. This is why, in these areas, the rails are carried by links themselves carried by the longitudinal beams. It is therefore the position of the latter that conditions the position of the rails in the transverse direction, which therefore cannot be chosen at will. 
         [0006]    This architecture also prohibits subsequent modification of the position of the rails. Thus customers such as the airlines are not able to customize the cabin in these areas. 
         [0007]    An object of the invention is therefore to improve the flexibility of the cabin arrangements, notably at the level of the wing box and the main landing gear well. 
       SUMMARY OF THE INVENTION 
       [0008]    To this end, the invention provides an airframe having a substantially circular cross section in a lateral direction (Y) and which extends in the longitudinal direction (X), the airframe comprising, a plurality of rails for supporting seats, each rail being parallel to the longitudinal direction (X) of the airframe, a plurality of beams parallel to the rails; and a plurality of crossmembers aligned, in use, in the lateral direction (Y) of the airframe, each crossmember supporting only some of the successive rails, each crossmember being supported by only some of the successive beams in the lateral direction (Y) of the airframe, the beams forming part of a wing box and/or a main landing gear well of the airframe, characterized in that each crossmember comprises at least one connection to each of the beams that support it where each connection comprises at least one articulation about at least one axis. 
         [0009]    It is therefore a question of partial crossmembers or “mini-crossmembers” that have a low inertia. 
         [0010]    Accordingly, in the areas featuring the mini-crossmembers, the seat rails may occupy many transverse positions as they continue to bear on the mini-crossmembers. This therefore imparts great flexibility to the cabin arrangements, including in these areas. Thus it is possible to offer airlines versions of the airframe having an increased seating density, for example an additional passenger per row. For example, this solution makes it possible to offer on a long-haul aircraft with two cabin aisles a three-four-three configuration, i.e. ten seats in the transverse direction, or a three-five-three configuration, i.e. eleven seats in that direction. Thus airlines can be offered at low cost a payload optionally increased by 10%. 
         [0011]    Unlike the aforementioned known crossmembers, the mini-crossmembers have multiple bearing points on the beams, notably when they are positioned in the wing box or the main landing gear well, making it possible to have a crossmember the length of which is very much less than the transverse dimension of the fuselage. Accordingly, differing in this respect from the aforementioned known crossmembers, it is not necessary for these mini-crossmembers to bear on lateral portions of the fuselage structure. 
         [0012]    In return, these mini-crossmembers make it possible to optimize the position of the longitudinal beams that support them since it is no longer necessary to choose their position allowing for the future position of the seat rails. This therefore optimizes the mass of the fuselage structure, especially in the wing box. 
         [0013]    The mini-crossmembers further preserve the transverse flexibility of the fuselage at the level of the wing box and the main landing gear well, in particular in bending about an axis parallel to the longitudinal axis of the fuselage. This preserves the flexibility initially imparted by the links in known aircraft. 
         [0014]    At least two of the crossmembers are advantageously aligned in the longitudinal direction of the crossmembers. 
         [0015]    Each crossmember advantageously includes a connection to each of the beams that support it, the or each connection including at least one articulation about at least one axis parallel to the direction of the crossmember, preferably two articulations about respective axes parallel to the direction of the crossmember. This flexibility in the direction of the longitudinal axis of the fuselage enables improved distribution of the forces applied to the floor in the structure of the airframe. 
         [0016]    It is moreover known that, because of the effect of pressure on the one hand and of flexing of the wings on the other hand, the gantries are entrained by the beams of the wing box and because of this tend to be deformed by pivoting about the longitudinal axis X of the fuselage and moving toward each other. The connection between the beams and each mini-crossmember transmits vertical forces but should not transmit forces caused by unwanted movements such as rotation of the beam. In the aforementioned prior art aircraft, this problem does not arise because the seat rails extend along the axis X and are connected to the beams of the wing box which themselves extend along the axis X. There can therefore be no transmission of flexing torque between the two elements about this axis. Thus it is desirable for the connection between the crossmembers and the underlying structure to transmit vertical forces from the floor to this structure but not to transmit bending movements about the axis X to the floor. 
         [0017]    To this end, the connection includes at least one articulation about an axis parallel to the longitudinal direction of the airframe. 
         [0018]    Accordingly, the articulation of the connection enables a satisfactory response to this problem by preventing transmission of bending moments about the axis X from the beams to the crossmembers. 
         [0019]    The connection advantageously comprises a ball-joint. 
         [0020]    Moreover, there are severe overall size constraints for accommodating the landing gear and preserving the volume of the cabin. This is why the height of the assembly formed by the seat rails, the crossmembers, the connections and the beams is limited. It is therefore desirable to render this assembly as compact as possible without compromising the functions and the characteristics of these components, in particular the inertia of the beams and the mini-crossmembers. 
         [0021]    To this end, the connection is such that the axis or each axis is below an upper face of the beam. 
         [0022]    Faced with the same problem, in another embodiment of the invention the connection is such that the crossmember is connected to the beam by way of an upper wall of the crossmember, the connection lying inside the crossmember. 
         [0023]    The connection preferably includes two intermediate parts facing respective opposite faces of the beam and rigidly fixed together by means of two articulations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Other features and advantages of the invention will become more apparent in the course of the following description of four embodiments of the invention given by way of nonlimiting example and with reference to the appended drawings, in which: 
           [0025]      FIG. 1  is a side view of an airframe of the invention; 
           [0026]      FIG. 2  is a view of the fuselage of the airframe from  FIG. 1  in vertical section perpendicular to the longitudinal axis of the fuselage; 
           [0027]      FIG. 3  is a perspective view of part of the internal structure of the fuselage of the airframe from  FIG. 1  at the level of the wing box and the main landing gear well  5 ; 
           [0028]      FIG. 4  is a view in elevation of the detail C of the airframe from  FIG. 3  showing the arrangement of the mini-crossmembers on the beams in a first embodiment of the invention; 
           [0029]      FIG. 5  is a view to a larger scale of the detail D in  FIG. 4 ; 
           [0030]      FIG. 6  is a perspective view of the elements of the detail D forming the connection; 
           [0031]      FIGS. 7 ,  8  and  9  are respectively analogous to  FIGS. 4 ,  5  and  6  and illustrate a second embodiment of the invention; 
           [0032]      FIG. 10  is a perspective view of the connection between a mini-crossmember and a beam in a third embodiment of the invention; 
           [0033]      FIG. 11  is a partial view in elevation of the elements from  FIG. 10 ; 
           [0034]      FIGS. 12 and 13  are views of the elements from  FIG. 11  in section taken along the lines XII-XII and XIII-XIII, respectively; and 
           [0035]      FIGS. 14 to 17  are respectively analogous to  FIGS. 10 to 13  and illustrate a fourth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]      FIG. 1  shows an airframe  2  of the invention that here is an aircraft including a fuselage  4 , landing gear  5  and two wings  3 . 
         [0037]      FIGS. 2 and 3  show the structure of the fuselage at the level of the wing box  6 , lying between and in line with the wings, and the main landing gear well  8  aft of the wing box  6 . 
         [0038]    The conventional system of axes XYZ is used hereinafter in which X designates the longitudinal direction of the aircraft and the fuselage, Y the horizontal transverse direction, and Z the vertical direction. 
         [0039]    The fuselage of the aircraft  2  includes rails  10  supporting passenger seats  12 . The rails are parallel to each other and to the direction X in a common plane parallel to the directions X and Y. The rails of the same section in a plane parallel to the plane YZ are spaced from each other. 
         [0040]    The wing box  6  comprises beams  14  parallel to each other and to the direction X in a common plane parallel to the directions X and Y. The beams of the same section in a plane parallel to the plane YZ are spaced from each other. 
         [0041]    The main landing gear well  8  comprises flat stiffeners  16  consisting of the assembly of a vertical beam  18  and a horizontal beam  19  each lying in a plane parallel to the plane XZ and together forming a gantry. The beams  19  are parallel to each other in the longitudinal direction X. They lie in the same horizontal general plane parallel to the directions X and Y so that each beam  19  has a height in the direction Z greater than its thickness in the direction Y. The beams  19  of the same section in a plane parallel to the plane YZ are spaced from each other. 
         [0042]    The rails  10  and the beams  14  and  19  are straight. 
         [0043]    The fuselage structure comprises straight crossmembers  20  formed here by parallel beams that are elongate in the transverse direction Y. The crossmembers are all in the same horizontal plane parallel to the directions X and Y. The crossmembers  20  form aligned rows of crossmembers, the rows extending in the longitudinal direction X. In each row, the crossmembers  20  are also aligned in the longitudinal direction of the crossmembers. Thus in the section of the fuselage shown in  FIG. 2 , there are two successive crossmembers in the direction Y. Of course, the number of successive crossmembers, i.e. the number of rows, could be higher, for example equal to three, four, five, etc. The crossmembers are spaced from each other in the longitudinal direction X and in the transverse direction Y. The crossmembers are also spaced from the lateral extremities of the fuselage and its structure. Here, the crossmembers are therefore not carried by lateral portions of the fuselage structure. 
         [0044]    Each crossmember  20  supports some of the successive rails  10  in the same section in the transverse direction Y but not all of the successive rails. 
         [0045]    For example, it can be seen in  FIG. 2  that if the number of successive rails in the transverse direction is six, each of the two crossmembers  20  supports only three of the six rails. Moreover, each of the rails  10  in a given section is supported by one and only one crossmember. The rails supported by the same crossmember are spaced from each other. 
         [0046]    In a similar way, each crossmember  20  is supported by some of the successive beams  14 ,  19  in the direction Y in the section concerned but not all of the beams in that section. Here, in the section shown in  FIG. 2 , each crossmember rests on only two of the beams  14 ,  19  of the four successive beams in the transverse direction Y. The number of beams supporting each crossmember could be greater than two, for example equal to three, four or five, etc. Each of the beams  14 ,  19  in the same section supports only one of the crossmembers  20  in the section. 
         [0047]    In the more detailed illustration of  FIG. 3 , each of the two mini-crossmembers  20  in a section supports five of the ten rails  10  in the section and is supported by three of the six beams  19  in the section. 
         [0048]    A more detailed first version of the  FIG. 2  arrangement is described in next with reference to  FIGS. 4 to 6 . The arrangement of this and subsequent versions is described considering a beam  19  as part of a gantry. The same description would nevertheless apply to a beam  14 . 
         [0049]    Each of the crossmembers  20  has a mechanical connection to each of the beams  19  on which it rests, which is made up as follows: The connection includes an intermediate part  122  that here is a fork. The lower part of the fork has an inverted “U” or “V” shape so that it forms two branches  124  facing respective opposite main faces of the beam  19 . 
         [0050]    The connection includes a shaft  126  that passes through the beam  19  and the two branches  124  to form an articulation between the beam  19  and the fork  122  about an axis  28  parallel to the transverse direction Y. The upper end of the fork  122  is also divided into two branches  130  but its width in the transverse direction Y is very much less than that of the lower end of the fork. The two branches  130  lie on respective opposite sides of the lower end of a yoke  132  including an upper plate  134  rigidly fixed to a horizontal wall of the crossmember  20  at a location approximately halfway up the height of the crossmember. A shaft  136  passes through the two branches  130  and the yoke  132  to constitute an articulation between these two parts about an axis  38  that is also parallel to the transverse direction Y. The two rotation axes  28  and  38  allow the yoke  132  to move relative to the associated beam  19  in the longitudinal direction X. The section Y 0  that corresponds to the median vertical longitudinal plane of symmetry of the fuselage is shown in the right-hand part of  FIG. 4 . 
         [0051]    The second version shown in  FIGS. 7 to 9  features a more elaborate version of the connection between each crossmember and each beam that supports it. There is seen again the fork  222  which has a lower end fixed to the beam  19  in the same way as in the first version, defining an articulation about the axis  28 . However, the fork is not connected directly to the yoke  232  this time. In this version, the connection includes an intermediate part formed here by a link  240 . The link has a lower end articulated to the upper end of the fork  222  to define an articulation or pivot about an axis  242  parallel to the longitudinal direction X. The link  240  has an upper end articulated to the yoke  232  in the same way that the fork  122  is articulated to the yoke  132  in the first version. The link therefore forms an articulation about an axis  38  parallel to the transverse direction Y. Furthermore, the link  240  is articulated to the yoke  232  by means of a ball-joint connection situated between the shaft on the axis  38  and the yoke, for example. 
         [0052]    In this second version, the two axes  28  and  38  still allow movement of the yoke  232  relative to the beam  19  in the longitudinal direction X. In this arrangement, however, the link  240  further allows movement of the yoke  232  in the transverse direction Y relative to the beam  19  and its rotation about the axis X. This arrangement allows the mini-crossmember to move in the transverse direction Y, parallel to the upper section of the beam. Accordingly, if the pressure in the cabin generates an effect known as the accordion effect or if certain movements occur at the level of the wing box, it is possible for the beams  19  situated underneath to move toward each other in the direction Y, as indicated by the arrow  244  in  FIG. 7 . Angular movement of the beam  19  about the axis X relative to the mini-crossmember  20  (and vice versa) is also allowed. The ball-joint connection allows angular movement of the yoke relative to the beam  19  about the axis X. The whole of this connection ensures centering of the forces on the beams  18 ,  19  and prevent transmission from the beams  18 ,  19  to the crossmembers  20  of forces tending to deform the beams by causing them to pivot about the axis X and to move toward each other. 
         [0053]    A third version that is close in spirit to but more compact than the first version described above is described next. In this version, the fork is divided into two spaced separate parts  322  which here are shackles. Each shackle  322  has a shape close to that of a link, generally flat and plane in the plane XZ, the thickness of the shackle extending in the transverse direction Y. Each of the two shackles  322  has a lower orifice  350  coinciding with an upper orifice  352  of the beam  19 . A common shaft that is not shown passes through the three orifices  350  and  352  and defines the axis  28 . 
         [0054]    Each of the two shackles also has an upper orifice  354 . The general shape of the profile of the yoke  332  is that of an inverted “U” defining two branches  356  each of which has an orifice  358 . The four orifices  354  and  358  are coaxial and receive a common shaft defining the axis  38 . The shaft passes through a cylindrical spacer  360  between the two shackles and coaxial with the orifices  354 . It maintains the correct spacing between the two shackles at this level. The two shackles being mobile about the same two rotation axes  28  and  38 , they are immobile relative to each other and rigidly fixed to each other indirectly. 
         [0055]    The plate  334  forming the base of the “U” at the top of the yoke is rigidly fixed to the crossmember  20  as before, here to its lower wall. Six fixing points are provided here, as shown in  FIG. 13 , although this number is not limiting on the invention. 
         [0056]    The two shackles  322  lie entirely facing respective opposite faces of the beam  19  under its upper wall  362  that forms the top thereof, in particular under the upper and lower faces of this wall. The two axes  28  and  38  are therefore under the two faces of this wall. The two branches  356  of the yoke  332  extend downwards facing the edges of the wall  362  and the external lateral faces of the upper ends of the respective shackles. The lower face of the plate  334  faces and is parallel to the wall  362 , there being a gap between them. 
         [0057]    Thus it may be seen that replacing the fork  122  by the two parts  322  makes it possible to dispose the two axes  28  and  38  at the level of the beam  19  and to reduce the overall height of the connection between the beam and the crossmember. 
         [0058]    Finally, a fourth version of this connection is described with reference to  FIGS. 14 to 16 . 
         [0059]    In this version, the orifice  452  of the beam  19  is produced in its upper wall  462  but is nevertheless at a distance from the upper face of this wall. Only the lower part of each shackle  422  faces the corresponding lateral wall of the beam  19  as this time the shackles lie above the beam. 
         [0060]    The single yoke of the first three versions is replaced this time by two separate yokes  432  that are spaced from each other and associated with the respective shackles  422 . Moreover, the upper end of each shackle has a forked shape this time into which the lower end of each yoke  432  is inserted. All six orifices comprising the two upper orifices of each shackle and the orifice of each yoke are coaxial to receive one or two common shafts defining the axis  38 . 
         [0061]    Moreover, in this version, the crossmember  10  has a section that is open downward. It may be an inverted “U” shape section, but here it is an “a” shape section. The upper plate of each of the yokes  432  is fixed directly to the upper wall  460  forming the top of the crossmember  20 , against its internal face. It is therefore clear that the yokes  432  lie below this wall  460 . They extend inside the section of the crossmember  20  facing its internal faces. The shackles  422  lie under the yokes and the beam  19  extends under the yokes and partly under the shackles. 
         [0062]    Each of the two yokes  432  is itself formed here by two identical parts  453 . Each of the parts  453  consists of three walls perpendicular to the directions X, Y and Z, respectively, forming a corner angle bracket with a projecting corner. The horizontal wall  454  is in surface contact with the upper wall  460  of the crossmember  20 . The wall  456  lies in the plane YZ and is rigidly fixed to one of the vertical flanks of the crossmember  20 . The third wall  458  is parallel to the plane XZ and is fixed to the homologous wall  458  of the other part  453  forming the same yoke so that together they form the lower part of the yoke received in the associated shackle. 
         [0063]    The two parts  453  forming the same yoke  432  are fixed to the wall  460  and to respective lateral flanks of the crossmember. They are disposed so as to be mirror images of each other by virtue of a rotation of 180° about the axis Z. On the other hand, the two yokes  432  are disposed to be images of each other by virtue of their symmetry with respect to a plane parallel to the directions X, Z and situated halfway between the two yokes. This version of the yokes enables complex shapes to be imparted to them starting from a common part of simple shape, four of which are used. 
         [0064]    Thus the connection lies inside and under the crossmember, but not above it. This version makes it possible to save space by accommodating the connection partly inside the mini-crossmember  20 . This is a particularly simple, lightweight and economic solution. For example, it makes it possible to retain for the beam  19  a height of 340 mm, which is a preferred height given the presence of the landing gear wheels beneath and the floor of the cabin above. The open section of “Ω” shape has as much inertia about the axis X as an “I” section and sufficient inertia about the axis Z to take up any shear stress between the rails. This simplification of the fixing of the crossmembers to the beams makes it possible in return to fix stabilizer webs  70  shown in  FIGS. 3 and 4  in the vicinity of the connection and in particular in vertical alignment with and below it. Such an arrangement of the webs has the advantage of reducing the machining to be effected and the mass of the beams. 
         [0065]    Naturally the third and fourth versions do not impede the movement functions described more generally for the first and second versions. Furthermore, each of the four versions gives rise to no fatigue problems affecting the parts of the fuselage structure. 
         [0066]    Of course, many modifications may be made without departing from the scope of invention. Mini-crossmembers could be provided in other areas of the airframe than the wing box and the main landing gear well.