Abstract:
A rib of an airplane wing is prevented from deforming due to a machining load when machining a rivet hole in parts where the rib and a skin are joined. With regard to a rib that provides a connection between first and second spars of the airplane wing, the rib is formed with mounting flanges secured to a skin via a rivet, a stringer through hole for a stringer to be positioned through, and first and second cutouts facing parts where the first and second spars and the skin are connected. Since reinforcing beads are formed along the mounting flanges and reinforcing flanges are formed so as to extend in the span direction from the edges of the stringer through hole and the first and second cutouts and be connected integrally to the mounting flanges, the stiffness of the rib toward a load in the vertical direction when drilling a rivet hole can be enhanced.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an airplane wing structure having first and second spars extending in the span direction; a plurality of stringers disposed between the first and second spars and extending in the span direction; a rib extending in the chord direction and providing a connection between the first and second spars; and a skin covering the first and second spars, the stringer, and an upper face and a lower face of the rib. 
         [0003]    2. Description of the Related Art 
         [0004]    An airplane wing structure is disclosed in Japanese Patent Application Laid-open No. 2002-302097 or Published Japanese Translation (PCT) No. 2000-506816. 
         [0005]    In general, a rib for defining the airfoil of an airplane wing is formed by press forming a thin plate material in order to lighten the weight. In addition, a stringer through hole is formed in an upper edge and a lower edge of the rib with a stringer fixed to an inner face of a skin of the wing and positioned through the stringer through hole via a gap. The wing is formed as a box structure that is resistant to bending or twisting by joining a spar, the stringer, the rib, and the skin, but when lift or drag acts on the wing, there is a possibility that the rib, which is formed from a thin plate material, will buckle due to the shear load. In the arrangements disclosed in Japanese Patent Application Laid-open No. 2002-302097 and Published Japanese Translation (PCT) No. 2000-506816, when press forming the rib, a bead extending in the vertical direction (wing thickness direction) is formed integrally with the rib, thereby enhancing the buckling strength of the rib toward a shear load. 
       SUMMARY OF THE INVENTION 
       [0006]    In an embodiment of the present invention, a rib and a skin are joined by superimposing the skin on a mounting flange formed by bending over a peripheral part of the rib and, in a state in which they are positioned, machining a rivet hole in the skin and the mounting flange with a drill and crimping a rivet inserted into the rivet hole. 
         [0007]    However, when drilling a rivet hole while positioning by superimposing a skin S on a mounting flange F of a rib R, the entire rib R might be curved due to the drilling load as shown in  FIG. 6A , or the mounting flange F of the rib R might be curved due to the drilling load as shown in  FIG. 6B . In addition, problems exist with respect to the rivet hole not being formed as a true circle, thus degrading the machining precision, or the rib R deforms, thus requiring a repair operation. 
         [0008]    It is an object of an embodiment of the present invention, to prevent a rib of an airplane wing from deforming due to a machining load when machining a rivet hole in the parts where the rib and a skin are joined. 
         [0009]    In order to achieve the object, according to an embodiment of the present invention, there is provided an airplane wing structure having first and second spars extending in the span direction; a stringer disposed between the first and second spars and extending in the span direction; a rib extending in the chord direction and providing a connection between the first and second spars; and a skin covering the first and second spars, the stringer, and an upper face and a lower face of the rib. A mounting flange is formed on at least one of an upper edge and a lower edge of the rib and being secured to the skin via a rivet. A stringer through hole is formed by cutting out the mounting flange with the stringer positioned through the stringer through hole. First and second cutouts are formed in the front end and the rear end of at least one of the upper edge and the lower edge of the rib and facing parts where the first and second spars and the skin are connected. The rib comprises a reinforcing bead formed along the mounting flange, and a reinforcing flange that extends in the span direction from edges of the stringer through hole and the first and second cutouts and is integrally connected to the mounting flange. 
         [0010]    In accordance with the arrangement of an embodiment of the present invention, with regard to the rib that provides a connection between the first and second spars of the airplane wing, the rib includes the mounting flange secured to the skin via the rivet, the stringer through hole for a stringer to be positioned through, and the first and second cutouts facing the parts where the first and second spars and the skin are connected, since the reinforcing bead is formed along the mounting flange and the reinforcing flange is formed so as to extend in the span direction from the edges of the stringer through hole and the first and second cutouts and be connected integrally to the mounting flange, the stiffness of the rib toward a load in the vertical direction can be enhanced. When drilling a rivet hole with the skin superimposed on the mounting flange of the rib, not only is it possible to prevent the machining precision of the rivet hole from being degraded due to deformation of the rib or its flange by a machining load, but it is also possible to eliminate the need for a jig for preventing deformation of the rib and eliminate the necessity for an operation to repair a deformed rib, thus reducing the machining cost. 
         [0011]    According to an embodiment of the present invention, the reinforcing bead comprises a main body portion and a bent portion that bends from an end part of the main body portion along the stringer through hole or the first or second cutout. 
         [0012]    In accordance with the arrangement of this embodiment of the present invention, since the reinforcing bead of the rib is provided with the bent portion, which bends from the end part of the main body portion along the stringer through hole or the first and second cutouts, the effect of the reinforcing bead in reinforcing the rib can be further enhanced. 
         [0013]    A main spar  13  of embodiments corresponds to the first spar of the present invention, a front spar  14  of the embodiments corresponds to the second spar of the present invention, an upper skin  19  and a lower skin  20  of the embodiments correspond to the skin of the present invention, a front rib  21  of the embodiments corresponds to the rib of the present invention, and first and second reinforcing beads  23 A and  23 B of the embodiments correspond to the reinforcing bead of the present invention. 
         [0014]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0016]      FIG. 1  is a top view of a left main wing of an airplane. 
           [0017]      FIG. 2  is an enlarged sectional view along line  2 - 2  in  FIG. 1 . 
           [0018]      FIG. 3  is a sectional view along line  3 - 3  in  FIG. 2 . 
           [0019]      FIG. 4  is a partially cutaway perspective view of the main wing;  FIG. 5  is a view corresponding to  FIG. 2  and related to a second embodiment. 
           [0020]      FIGS. 6A ,  6 B, and  6 C are views showing problems of a conventional example. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    As shown in  FIG. 1  and  FIG. 2 , a main wing  12  supported on a fuselage  11  of an airplane includes a main spar  13  extending in substantially the span direction, a front spar  14  disposed in front of the main spar  13 , and a rear spar  15  disposed to the rear of the main spar  13 . A front edge member  16  is fixed to the front of the main spar  13 , a flap  17  is swingably supported on the inside, in the span direction, of a rear edge part of the main wing  12 , and an aileron  18  is swingably supported on the outside, in the span direction, of the flap  17 . 
         [0022]    An upper skin  19  defining an upper surface of the main wing  12  includes a plurality of stringers  19   a  integrally formed therewith along a lower face in the span direction, and a lower skin  20  defining a lower surface of the main wing includes a plurality of stringers  20   a  integrally formed therewith along an upper face in the span direction. 
         [0023]    The main spar  13  is formed from an I-form cross-section member that includes a web  13   a  and a pair of upper and lower flanges  13   b  and  13   c , and the front spar  14  is formed from a channel-form cross-section member that includes a web  14   a  and a pair of upper and lower flanges  14   b  and  14   c . Although not illustrated, the rear spar  15  is also formed from an I-form cross-section member in the same manner as for the main spar  13 . 
         [0024]    The main spar  13  and the front spar  14  are connected via a plurality of front ribs  21  disposed in the chord direction, and the main spar  13  and the rear spar  15  are connected via a plurality of rear ribs  22  disposed in the chord direction. The front rib  21  and the rear rib  22  are members formed by press forming a metal plate, and have a shape that defines the airfoil of the main wing  12 . Since the front rib  21  and the rear rib  22  have substantially the same structure with slightly different shapes, the structure of the front rib  21  is explained below as being representative thereof. 
         [0025]    The front rib  21  is a substantially rectangular plate-shaped member having a slightly lower height on the front edge side, two weight-cutting holes  21   a  and  21   b  are formed in its front and rear parts for the purpose of lightening the weight, and first and second reinforcing beads  23 A and  23 B extending in the fore-and-aft direction are integrally press-formed beneath the two weight-cutting holes  21   a  and  21   b . The first reinforcing bead  23 A on the front side includes a bent portion  23   b  that bends upward and forward from the front end of a main body portion  23   a  extending in the fore-and-aft direction, and the second reinforcing bead  23 B on the rear side includes a bent portion  23   b  that bends upward and rearward from the rear end of a main body portion  23   a  extending in the fore-and-aft direction. These first and second reinforcing beads  23 A and  23 B are formed integrally when the front rib  21  is press formed. 
         [0026]    Furthermore, a stringer through hole  21   c , through which the stringer  19   a  formed on the lower face of the upper skin  19  is positioned, is formed in a central part of the upper edge of the front rib  21 . A stringer through hole  21   d , through which the stringer  20   a  formed on the upper face of the lower skin  20  is positioned, is formed in a central part of the lower edge of the front rib  21 . Furthermore, formed on opposite front and rear sides of the lower edge of the front rib  21  with the stringer through hole  21   d  interposed therebetween are a pair of front and rear mounting flanges  21   e  and  21   f  that are bent toward the inside in the span direction. 
         [0027]    A mounting portion  21   g  at the front end of the front rib  21  is fixed via rivets  24  to a plate-shaped mounting portion  14   d  that connects the web  14   a  and the pair of upper and lower flanges  14   b  and  14   c  of the front spar  14 , and a pair of front and rear mounting portions  21   h  and  21   i  at the upper edge of the front rib  21  are fixed via rivets  25  to mounting portions  19   b  and  19   c  formed on the lower face of the upper skin  19 . 
         [0028]    Moreover, a mounting portion  21   j  at the rear end of the front rib  21  is fixed via rivets  26  to a plate-shaped mounting portion  13   d  that connects the web  13   a  and the pair of upper and lower flanges  13   b  and  13   c  of the main spar  13 , and the pair of front and rear mounting flanges  21   e  and  21   f  at the lower edge of the front rib  21  are fixed via rivets  27  to the lower skin  20 . 
         [0029]    Furthermore, a first cutout  21   k  is formed between the mounting portion  21   g  and the mounting flange  21   e , which are on the front side of the front rib  21 , and a second cutout  21   m  is formed between the mounting portion  21   j  and the mounting flange  21   f , which are on the rear side of the front rib  21 . 
         [0030]    As is clear from  FIG. 4 , a reinforcing flange  21   n  is formed on an edge part of the stringer through hole  21   d  that faces the lower skin  20  by bending the edge part in the span direction, and reinforcing flanges  21   o  and  21   p  are formed on the first and second cutouts  21   k  and  21   m  respectively by bending them in the span direction. The reinforcing flange  21   o  of the first cutout  21   k  is integrally continuous with the front end of the mounting flange  21   e , the reinforcing flange  21   n  of the stringer through hole  21   d  is integrally continuous with the rear end of the mounting flange  21   e  and the front end of the mounting flange  21   f , and the reinforcing flange  21   p  of the second cutout  21   m  is integrally continuous with the rear end of the mounting flange  21   f.    
         [0031]    More specifically, the reinforcing flange  21   o , the mounting flange  21   e , the reinforcing flange  21   n , the mounting flange  21   f , and the reinforcing flange  21   p  are continuously connected without interruption. In addition, the height, in the span direction, of the reinforcing flange  21   o , the reinforcing flange  21   n , and the reinforcing flange  21   p  is lower than the height of the mounting flanges  21   e  and  21   f  in the span direction. 
         [0032]    As hereinbefore described, since the reinforcing flanges  21   n ,  21   o , and  21   p , which are integrally continuous with the mounting flanges  21   e  and  21   f , are formed on the stringer through hole  21   d  and the first and second cutouts  21   k  and  21   m  of the front rib  21 , and the first and second reinforcing beads  23 A and  23 B, which are formed from the main body portions  23   a  and  23   a  that follow the mounting flanges  21   e  and  21   f  and the bent portions  23   b  and  23   b  that follow the reinforcing flanges  21   o  and  21   p  of the first and second cutouts  21   k  and  21   m , are formed on the lower part of the front rib  21 , the synergistic effects thereof greatly enhance the stiffness of the front rib  21  against a vertical load and, in particular, the stiffness of the lower part of the front rib  21 , to which the lower skin  20  is joined. 
         [0033]    In particular, since the edges on the lower side of the first and second reinforcing beads  23 A and  23 B are positioned in proximity to and immediately above the bend lines of the mounting flanges  21   e  and  21   f , when a vertical load acts thereon, flexing of the front rib  21  between the first and second reinforcing beads  23 A and  23 B and the bend lines of the mounting flanges  21   e  and  21   f , or flexing of the bend lines of the mounting flanges  21   e  and  21   f , can be suppressed yet more effectively. 
         [0034]    As a result, as explained by  FIG. 6 , when a rivet hole is drilled by superimposing the lower skin  20  on the mounting flanges  21   e  and  21   f  of the front rib  21 , without using a special jig J (see  FIG. 6C ) that supports the mounting flanges  21   e  and  21   f  from beneath, it is possible to solve the problem of the front rib  21  flexing due to the vertical load and thereby preventing the hole from becoming a true circle, or the front rib  21  deforming and thus requiring repair, thereby improving the machining precision and reducing the machining cost. 
         [0035]    A second embodiment of the present invention is explained now by reference to  FIG. 5 . 
         [0036]    The first and second reinforcing beads  23 A and  23 B of the front rib  21  of the first embodiment include the bent portions  23   b  and  23   b  extending from one end of the main body portions  23   a  and  23   a  along the first and second cutouts  21   k  and  21   m , but first and second reinforcing beads  23 A and  23 B of the second embodiment further include bent portions  23   c  and  23   c  extending from the other end of main body portions  23   a  and  23   a  along a stringer through hole  21   d . In accordance with this second embodiment, compared with the first embodiment, the stiffness of the front rib  21  can be further enhanced. 
         [0037]    Embodiments of the present invention are explained above, but the present invention can be modified in a variety of ways as long as the modifications do not depart from the spirit and scope thereof. 
         [0038]    For example, in the embodiments, the front rib  21  is explained in detail, but the present invention may be applied to the rear rib  22  in the same manner. Furthermore, the rib of the present invention may be integrally continuous from a front edge part to a rear edge part without being divided. 
         [0039]    Furthermore, in the embodiments, the part where the front rib  21  and the lower skin  20  are joined is explained, but the present invention may be applied to a part where a front rib  21  and an upper skin  21  are joined. 
         [0040]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.