Abstract:
A fuselage element including a first fuselage segment including a skin, and a junction device for connecting the first segment to a second adjacent fuselage segment is disclosed. The first segment extending along the longitudinal axis of the fuselage element includes stiffening elements extending along the axis. The end of at least one stiffening element extends beyond a free edge of the skin by a predetermined length.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a fuselage element, as well as to a fuselage portion comprising such an element and an adjacent section. 
     More particularly, it relates to a fuselage element comprising a fuselage section and junction means able to connect the fuselage section to an adjacent section. 
     2. Brief Summary of the Invention 
     The fuselage of an aircraft comprises in particular a skin and stiffener elements for this skin. The stiffener elements are arranged either in a longitudinal direction (known as stringers), or in a plane transverse to the axis of the fuselage (known as frames). 
     The fuselage generally comprises several fuselage sections assembled with each other. These fuselage sections are assembled by means of junctions. The purpose of the junctions is in particular to transfer mechanical loads between adjacent sections, in particular longitudinal stresses. 
     In general, the fuselage, as well as the junctions, has a cylindrical shape, although other shapes may be considered. 
     There are junctions that are designed so as to ensure the continuity of the stringers. The document FR 2 910 874 describes junctions designed in this way. 
     These junctions comprise mechanical junction elements such as a ferrule and stringer joint plates. The ferrule makes it possible to connect the skins of the two adjacent sections and the stringer joint plates make it possible to connect the stringers or longitudinal stiffeners. 
     An example of such a design is shown on  FIG. 1 . This Figure shows a part of two adjacent fuselage sections  2   a ,  2   b . The fuselage has a cylindrical shape and comprises a skin  30 , as well as stringers  50  situated in a longitudinal plane. A cylindrical junction  40  is arranged between these two cylindrical fuselage sections  2   a ,  2   b  at frame  80 . This junction  40  comprises a ferrule  70 , situated on the inner surface of skin  30  of the fuselage and connecting skins  30  of the two sections  2   a ,  2   b , as well as stringer joint plates  90  situated respectively on stringers  50  and connecting stringers  50  of the two sections  2   a ,  2   b.    
     When the stresses to be transmitted between fuselage sections  2   a ,  2   b  are high (typically, greater than 600 N/mm), the use of stringer joint plates  90  is necessary. 
     Nonetheless, the installation of stringer joint plates in the junction element poses problems of fitting of the various elements. Thus, positioning tolerances of the various elements of the junction may become evident. For example, when the stringers of two fuselage sections are not precisely opposite one another, the use of shims between the stringers and the stringer joint plates may be necessary. 
     Moreover, the installation of stringer joint plates requires an access to the junction element of the interior of the fuselage. This makes automation of assembly of the sections difficult. Consequently, assembly time is considerable. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention has the purpose of resolving the aforesaid drawbacks and proposing a fuselage element comprising a fuselage section and junction means between this section and an adjacent section, having a good stability at the junction between the sections, while minimizing the complexity of the assembly. 
     To this end, this invention applies to a fuselage element comprising a fuselage section comprising a skin, and junction means able to connect the said section to an adjacent section, the said section extending along the longitudinal axis of the fuselage, the fuselage element comprising stiffener elements extending along the said axis, characterized in that the end of at least one stiffener element extends beyond a free edge of the said skin by a predetermined length. 
     In this way, the presence of stringer joint plates is not necessary, since certain stiffeners allow the transmission of stresses directly onto the adjacent section. 
     In addition, in the absence of a joint plate, the relative positioning differences between the stringers of one section and of the adjacent section do not pose any problem. 
     Moreover, access to the interior of the fuselage after assembly of the sections no longer is necessary, and automation is simpler to implement. 
     According to a second aspect, this invention applies to a fuselage portion comprising a fuselage element as described above and a second fuselage section adjacent to the first fuselage section and extending along the longitudinal axis of the fuselage, the skin of the second fuselage section being connected to the skin of the first fuselage section of the fuselage element, the second fuselage section comprising stiffener elements extending along the axis over more or less the entire length of the second fuselage section and being arranged with an angular offset around the longitudinal axis in relation to the said at least one stiffener element of the first fuselage section extending beyond the free edge of the skin of the first fuselage section. 
     In this way, the stresses pass from the stringers of the first fuselage section to the stringers of the second fuselage section, and vice versa. This limits the stresses to be passed from the skin of one section to the skin of the other section. 
     Consequently, since the skin is less acted upon, the thickness can be less than in the prior art, thus minimizing the increase in mass. 
     Moreover, by virtue of the angular offset of the stiffener elements of the second fuselage section in relation to the stiffener elements of the first fuselage section, there is no problem of arrangement of the said at least one stiffener element projecting out of the first fuselage section during assembly of the sections. 
     According to one contemplated solution, the stiffener elements of the first fuselage section extend beyond the free edge of the skin of the first fuselage section and the stiffener elements of the second fuselage section extend beyond the free edge of the skin of the second fuselage section, each stiffener of the first fuselage section being inserted between two stiffeners of the second fuselage section. 
     According to one embodiment, the fuselage sections comprise at least a first portion situated at the end of the junction means having a skin thickness greater than the thickness of the skin of a second portion situated at the center of the said fuselage sections. 
     By virtue of its allowances at the junction means, the skin is reinforced locally, being more stable during passage of the stresses from one section to the adjacent section. 
     These allowances are less than those of the prior art by virtue of the extension of the longitudinal stiffeners beyond the free edge of the skin of the first section. 
     It further may be provided that the junction means of the stiffener element comprise a ferrule able to connect the skin of the first fuselage section and of the second adjacent fuselage section. 
     In this way, the skin at the junction means is all the more reinforced, and consequently the junction between sections is all the more stable. 
     Furthermore, the junction means may comprise a second stiffener element of the fuselage (hereinafter referred to as frame) comprising a body extending in a plane transverse to the longitudinal axis of the fuselage, and a base plate extending along the longitudinal axis of the fuselage. 
     In one embodiment, the ferrule is arranged on the outer surface of the skin and the said base plate is fastened onto the inner surface of the skin of the first portion of the said first fuselage section. 
     By virtue of the second stiffener element, the junction is even more stable. 
     In another embodiment, a second stiffener element of the fuselage comprises a body extending in a plane transverse to the longitudinal axis of the fuselage, the fuselage element comprises a ring part extending from the skin to the longitudinal axis of the fuselage, in a plane transverse to the said longitudinal axis of the fuselage, adapted for fastening the said body of the said second stiffener element. 
     In this embodiment the second stiffener element has no cut-outs for passing the stiffener elements extending beyond the free edge of the skin of the first section. 
     This avoids the presence of possible instabilities in the second stiffener element. 
     According to a third aspect, this invention applies to an aircraft fuselage comprising at least one fuselage portion in accordance with the invention. 
     According to a fourth aspect, this invention applies to an aircraft comprising a fuselage in accordance with the invention. 
     This fuselage portion, this aircraft fuselage and this aircraft have characteristics and advantages similar to those described above with reference to the fuselage element. 
     Other features and advantages of the invention also will become apparent in the description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       On the attached drawings, provided by way of non-limitative examples: 
         FIG. 1  is a diagram illustrating a fuselage element part connected to a second fuselage element belonging to the prior art; 
         FIG. 2  is a diagram illustrating fuselage sections of an aircraft; 
         FIG. 3  is a diagram illustrating a fuselage element part connected to a second fuselage element according to a first embodiment in accordance with the invention; and 
         FIG. 4  is a diagram illustrating a fuselage element part connected to a second fuselage element according to a second embodiment in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  shows several fuselage sections  2   a ,  2   b.    
     These fuselage sections  2   a ,  2   b  are assembled with each other so as to form the fuselage of an aircraft. Two fuselage sections  2   a ,  2   b  are assembled by junction means (not shown on  FIG. 2 ) as will be described below. 
     The fuselage sections extend along a longitudinal axis X. 
     Here, the shape of the fuselage sections is cylindrical, and consequently the junction means have the same shape (or are adapted to this shape). 
     Nevertheless, the fuselage sections, as well as the junction means, may have different shapes. 
     Next, a first embodiment of a fuselage element in accordance with the invention is going to be described with reference to  FIG. 3 . 
       FIG. 3  shows a part of a fuselage element  1  seen from the interior of the fuselage. 
     Fuselage element  1  comprises a first fuselage section  2   a  and junction means  4  able to connect first section  2   a  to a second adjacent section  2   b.    
     A part of each section  2   a ,  2   b  is shown here. 
     Thus, only one end of each section  2   a ,  2   b  is shown. 
     In this example, junction means  4  comprise a ferrule  8  which is adapted for connecting skins  3   a ,  3   b  of each section  2   a ,  2   b.    
     Here, ferrule  8  is arranged on outer surface  30   a ,  30   b  of skin  3   a ,  3   b  of fuselage sections  2   a ,  2   b . Nevertheless, as a variant, ferrule  8  may be arranged on inner surface  31   a ,  31   b  of skin  3   a ,  3   b.    
     Fuselage sections  2   a ,  2   b  comprise stiffeners that extend in longitudinal planes or stringers  5 , and stiffeners that extend in transverse planes or frames  9 . 
     Here, frame  9  is situated at junction means  4 . It is shown partially so as to leave the other elements of  FIG. 3  visible. 
     Frame  9  comprises a body  9   a  extending in a plane transverse to longitudinal axis X of the fuselage, and a base plate  9   b  extending along a longitudinal axis X of the fuselage. 
     In this embodiment, the base plate rests on inner surface  31   a  of skin  3   a  of first fuselage section  2   a.    
     In this embodiment, end  5   a   1  of at least one stiffener element  5   a  of first section  2   a  extends beyond the circumference situated at the end of skin  3   a  of first fuselage section  2   a  or free edge  7 . 
     In this way, end  5   a   1  of this at least one stiffener element  5   a  is offset longitudinally in relation to end  5   a   1 ′ of the other stiffener elements of the same section  2   a.    
     Consequently, a portion of this stiffener element  5   a  thus is situated at second fuselage section  2   b . Stiffener element  5   a  extends beyond free edge  7  of skin  3   a  of first fuselage section  2   a  by a predetermined length L. 
     By way of example in no way limitative, this predetermined length L may have values belonging to a bracket of values from 300 mm to 600 mm. 
     Of course, these values for predetermined length L may be different, in particular according to the size and the type of fuselage. 
     It is noted that frame  9  has cut-outs to allow passage of stiffener element  5   a.    
     In one embodiment, first section  2   a  comprises stringers  5   a ′, the end  5   a   1 ′ of which does not extend beyond free edge  7  of first section  2   a , and stringers  5   a  the end  5   a   1  of which extends beyond free edge  7  of first section  2   a , in identical number. 
     In one embodiment, a stringer  5   a  the end  5   a   1  of which extends beyond free edge  7  and a stringer  5   a ′ the end  5   a   1 ′ of which does not extend beyond the free edge are arranged alternately along the circumference of skin  3   a  of first section  2   a.    
     In other embodiments, a set of stringers  5   a  the end  5   a   1  of which extends beyond free edge  7  are arranged consecutively along the circumference of skin  3   a  of first section  2   a . The same is true for a set of stringers  5   a ′ the end  5   a   1 ′ of which does not extend beyond free edge  7 . 
     In this way, sets formed by several stringers of the same type  5   a ,  5   a ′ are arranged alternately with each other along the circumference of skin  3   a  of first section  2   a.    
     For example, each set may contain a single stringer. Thus, a stringer  5   a  extending beyond free edge  7  and a stringer  5   a ′ not extending beyond free edge  7  are arranged alternately with one another. 
     Nevertheless, the number of stringers, in each set, may be greater than 1, for example 2 or more. 
     It is possible that in certain embodiments there is only one set comprising stringers  5   a  extending beyond free edge  7  and only one set comprising stringers  5   a ′ not extending beyond free edge  7 . 
     The number of stringers  5   a  extending beyond free edge  7  and stringers  5   a ′ not extending beyond the free edge may be different. For example, the number of stringers  5   a  extending beyond free edge  7  has a value of at least 10% of the number of stringers  5   a ′ not extending beyond free edge  7 . 
     In general, first section  2   a  and second adjacent section  2   b  are similar. Thus, second adjacent section  2   b  also comprises stiffener elements  5   b  extending along longitudinal axis X. 
     When the two sections  2   a ,  2   b  are assembled, stringers  5   b  of second section  2   b  are arranged with an angular offset around longitudinal axis X in relation to stringers  5   a  of first section  2   a  extending beyond free edge  7  of skin  3   a  of first section  2   a.    
     In another embodiment, all stringers  5   a ,  5   b  of the two fuselage sections  2   a ,  2   b  extend beyond free edges  7  of respective sections  2   a ,  2   b.    
     In this way, when the two sections  2   a ,  2   b  are assembled, stringers  5   a  of first section  2   a  are inserted between two stringers  5   b  of second fuselage section  2   b , and are arranged with an angular offset around longitudinal axis X with each other. 
     In this way, stresses are transmitted between the stringers of first and second fuselage sections  2   a ,  2   b , limiting the stresses to be passed between the skins of section  2   a  and  2   b.    
     By way of example in no way limitative, the angular offset around longitudinal axis X between a consecutive stringer  5   a  of first section  2   a  and a stringer  5   b  of second section  2   b  has a value belonging to a bracket of values between 5° and 20°, and more particularly between 5° and 10°. 
     The value of the offset between two consecutive stringers  5   a ,  5   b  belonging respectively to first section  2   a  and second section  2   b , expressed in circumference length belongs, for example, to a bracket of values between 130 mm and 200 mm. 
     In one embodiment, a circular section  6   a  of skin  3   a  of first fuselage section  2   a  situated at the end of section  2   a  (at junction means  4 ) has a skin thickness greater than the skin thickness of a second section  6   b  situated at the center of fuselage section  2   a.    
     In this way, the skin is reinforced locally, which makes the junction between the two fuselage sections  2   a ,  2   b  even more stable. 
     Another embodiment in accordance with the invention is going to be described with reference to  FIG. 4 . 
     This embodiment is similar to the embodiment described with reference to  FIG. 3 . 
     Thus, the elements in common will not be described here. 
     In this embodiment, fuselage element  1  comprises a ring (shown partially on  FIG. 4 ), for example, made in one piece with ferrule  8 . Ring  9   c  extends in a plane transverse to longitudinal axis X of the fuselage to the interior of the fuselage, that is to say from skin  3   a ,  3   b  to axis X of the fuselage. 
     This ring  9   c  is adapted for fastening body  9   a  of frame  9  and extends over certain parts of the circumference of the fuselage so as to implement a passage for projecting stiffener elements  5   a.    
     Consequently, the junction of sections  2   a ,  2   b  is all the more stable because the frame has no cut-outs for passing stringers  5   a  extending beyond free edge  7  of skin  3   a  of first section  2   a.    
     In another example, ring  9   c  could be an element independent of ferrule  8  and rest, for example, on skin  3   a ,  3   b  of a fuselage section  2   a ,  2   b.    
     Thus, by virtue of the invention, it is possible to assemble two adjacent fuselage sections by way of junction means that enable a good stability. 
     Moreover, assembly complexity is minimized and assembly automation is simpler to use. 
     Of course, many modifications may be made to the exemplary embodiment described above without departing from the context of the invention. 
     Thus, for example, as already indicated, the fuselage shapes may be different.