Abstract:
The present invention relates to a supporting structure ( 200 ) for a nacelle of a jet engine, in particular provided with a thrust reverser device, including at least one base body ( 201 ) made of a composite material, characterised in that the base body has a transverse section which is essentially open and provided with at least one reinforcement means.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a supporting structure for a thrust reverser, in particular having cascades. 
       BRIEF DISCUSSION OF RELATED ART 
       [0002]    Traditionally, a cascade thrust reverser includes two half-cowls each slidingly mounted on a supporting half-beam called 12 o&#39;clock beam pivotably mounted on a nacelle support mast. 
         [0003]    A lower support beam called 6 o&#39;clock beam may also exist, including two half-beams generally each equipped with connecting means between one another and locking means for locking the two half-structures. Each 6 o&#39;clock half-beam is traditionally connected to the corresponding 12 o&#39;clock half-beam by means of an inner structure surrounding the turbojet engine. 
         [0004]    The support structures or beams are also generally equipped with guide rails allowing a sliding movement of each half-cowl on its associated half-beam alternating between a thrust reverser position called direct jet position, and a thrust reverser position called reverse jet. 
         [0005]    The rotational movement of each half-beam on the nacelle support mast makes it possible to pivot each half-cowl relative to said mast for maintenance operations. 
         [0006]    As illustrated in the appended  FIGS. 1 and 2 , each half-beam  1  is made from a ribbed metal alloy  3 , and typically comprises, on the outer surface thereof, primary  5  and secondary  7  rails capable of allowing the movement of the associated half-cowl (not shown), and a plurality of hinge yokes  9   a,    9   b,    9   c,    9   d  capable of allowing the half-beam  1  to be hinged on the associated nacelle mast. 
         [0007]    A receptacle  11 , mounted on the upstream portion (relative to the direction of airflow in the nacelle) of the half-beam  1 , makes it possible to fasten the front frame intended to support the thrust reverser cascades (frame and cascades not shown). 
         [0008]    As shown in  FIG. 3 , the half-beam  1  is attached by riveting  13  on the upper portion  15  of an inner fixed half-structure panel  17 , generally made from a composite material, and defining, with the associated thrust reverser cowl, a tunnel for the circulation of a secondary flow of the turbojet engine. 
         [0009]    The assembly formed by the half-beam  1 , its rails  5 ,  7  and its hinge yokes  9   a  to  9   d,  is often designated as “12 o&#39;clock structure,” given its position at the top of the circle defined by a nacelle section, and in comparison with the dial of a clock. 
         [0010]    The 6 o&#39;clock beams have substantially the same structure, with the exception that they do not include hinge yokes, but locking yokes and/or corresponding locking means. 
         [0011]    In order to lighten the half-beams and reduce the production costs thereof, it has been considered to use known composite materials to allow a significant decrease in the mass while meeting the mechanical and structural strength requirements. 
         [0012]    Document WO 2007/147193 discloses such a supporting and guiding structure capable of supporting a thrust reverser half-cowl, said beam including the base structure made up of a hollow profile having an essentially closed transverse section and made from a composite material. 
         [0013]    The presence of an essentially closed structure makes it possible to ensure the mechanical strength of the beam. 
         [0014]    However, there is a need to lighten aeronautical structures. 
       BRIEF SUMMARY 
       [0015]    The present invention aims to propose an even lighter supporting structure, and to that end, comprises of a supporting structure for a turbojet engine nacelle, 
         [0016]    in particular equipped with a thrust reverser device, including at least one base body made from a composite material, characterized in that the base body has an essentially open transverse section equipped with at least one reinforcement means. 
         [0017]    In fact, it has surprisingly been observed that the necessary rigidity could be obtained not only by providing an essentially closed section, but an open section also making it possible, in particular associated with a corresponding reinforcement means, to meet this requirement even while using composite materials. 
         [0018]    The total mass of the structure is therefore greatly decreased. 
         [0019]    Such a beam structure also allows a significant reduction in production costs, since an open section makes it possible to use a simple mold not requiring the placement of an inner core, or its extraction after molding. Furthermore, an open structure allows better accessibility for the installation of components on the finished piece, and in particular the hinge pins, or for quality or strength checks of the produced parts during use, or during repair operations. 
         [0020]    It will also be noted that an open section allows great freedom in the shape of the beam. In fact, in the case of a gradual reduction in section, for example, such a reduction in section in particular allowing the beam to be better adapted to the inner aerodynamic lines and allowing better integration of the fairing piece inside the circulation tunnel for the secondary flow, a closed section will require the use of soluble mold cores. 
         [0021]    Preferably, the base body is made using a resin infusion molding method, and more particularly by resin transfer molding (RTM). 
         [0022]    Advantageously, the structure includes at least one guide means, in particular of the rail type, made from carbon, metal, or a metal alloy, in particular, for slidingly mounting a movable cowl of the thrust reverser device. Such a rail is adapted to the case of a cascade thrust reverser. The rails could be attached, in particular by gluing, riveting, and other fastening methods, on the structure or integrated into the composite material used to make the assembly in a single piece. 
         [0023]    Advantageously, said support structure is connected to part of a panel of an inner fixed fairing structure of a turbojet engine. 
         [0024]    According to a first alternative, the panel of the inner fixed structure is attached, in particular by gluing, riveting, or any other fastening method, on the support structure. Advantageously, the panel of the inner fixed structure is attached so as to close the open section of the base body. The closed section thus re-created increases the strength of the assembly. 
         [0025]    According to a second alternative, the panel of the inner fixed structure is integrated into the supporting structure. The inner structure may in particular be integrated into the draping of the structure or by making the inner structure from a composite material and in a single piece with the supporting structure. 
         [0026]    The integration of the inner fixed structure (generally designated as IFS) makes it possible to avoid riveting the supporting structure to the inner structure panel, which procures mass gains on the one hand, and simplification of the assembly on the other. 
         [0027]    Preferably, the supporting structure includes at least one yoke or fitting for fastening, preferably so as to be disassemblable and/or pivotable, to a load-bearing structure of the pylon type or another supporting structure according to the invention. The yokes and fittings could indifferently be made from a metal alloy, carbon, composite material, etc. and attached (in particular by gluing, riveting, bolting, or any other fastening method) or integrated into the supporting structure (integrated to the draping of the structure or also made from a composite material with the structure, for example). 
         [0028]    According to a first embodiment of the invention, the structure is a 12 o&#39;clock beam. 
         [0029]    According to a second embodiment of the invention, the structure is a 6 o&#39;clock beam. 
         [0030]    Advantageously, the base body has at least one reinforcement. 
         [0031]    Also advantageously, the base body includes a plurality of reinforcements distributed along said structure. 
         [0032]    Preferably, at least part of the reinforcements are square shaped. 
         [0033]    Advantageously, the reinforcements are made from a composite material. This makes it possible to integrate them into the molding of the part. 
         [0034]    Advantageously, the reinforcements are an integral part of the supporting structure. 
         [0035]    Advantageously, the supporting structure integrates at least one connecting portion for connecting to a front frame. 
         [0036]    According to a first alternative, the supporting structure has at least one portion stiffened by stamping, in particular a floor wall of the structure. 
         [0037]    Alternatively or complementarily, the supporting structure has at least one portion stiffened by corrugation, in particular a floor wall of the structure. 
         [0038]    Also alternatively or complementarily, the supporting structure has at least one portion stiffened by wall lamination, in particular a floor wall of the structure, for example in the shape of a U. 
         [0039]    Advantageously, the supporting structure integrates a fairing wall capable of ensuring inner aerodynamism at a secondary flow circulation tunnel. 
         [0040]    This application also relates to an aircraft nacelle, characterized in that it comprises at least one supporting structure according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    The present invention will be better understood in light of the following detailed description, in reference to the appended drawing, in which: 
           [0042]      FIGS. 1 and 2  are perspective views of a metal 12 o&#39;clock structure of the state of the art, mentioned in the preamble of this description; 
           [0043]      FIGS. 3 and 4  are views of a first general embodiment of a supporting structure respectively in standard section and in a hinge yoke zone; 
           [0044]      FIG. 5  is a view similar to  FIG. 3  of one alternative embodiment of the invention; 
           [0045]      FIG. 6  is a partial view of a first preferred embodiment of a supporting structure according to the invention; 
           [0046]      FIG. 7  is a partial view of a second preferred embodiment of a supporting structure according to the invention; 
           [0047]      FIGS. 8 and 9  are partial and cross-sectional views, respectively, of a third preferred embodiment of the invention; 
           [0048]      FIG. 10  is a partial view of a fourth preferred embodiment the invention. 
       
    
    
       [0049]    In all of these figures, identical or similar references designate identical or similar members or sets of members. 
         [0050]      FIGS. 3 to 5  show a half-beam  100  in transverse cross-section in standard section and at a hinge yoke  9   c,  respectively. 
       DETAILED DESCRIPTION 
       [0051]    The beam  100  has a box  45  with an open section and made from a composite material, the box in this case being formed by draping several layers of composite fibers. 
         [0052]    The open box  45  has two free ends  45   a,    45   b  at each of which a guide rail  5 ,  7  is arranged. As previously mentioned, the rails  5 ,  7  can be made from a metal alloy or a composite material and can be fastened on the box or integrated therewith, in particular by insertion into the draping as shown in  FIG. 5 . 
         [0053]    As described for  FIGS. 1 and 2 , the half-beam  100  includes hinge yokes  9   a,    9   b,    9   c,    9   d  arranged at predefined intervals along a longitudinal axis of said half-beam  100 . 
         [0054]      FIG. 4  is a cross-sectional view at one of said yokes  9   c.  As for the guide rails  5  and  7 , the yokes  9   a,    9   b,    9   c,    9   d  can traditionally be made from a metal alloy, a composite material, or forged carbon, for example, and attached on the half-beam  100  or integrated therewith. 
         [0055]    The half-beam  100  may be obtained by molding, in particular using a resin infusion method or by resin transfer (RTM) in a mold comprising at least one core and at least one die. These techniques are known by those skilled in the art and are not the subject-matter of the present application. 
         [0056]    In general, and as shown on the beam  110  of  FIG. 5 , slugs  51   a,    51   b  defining the rails  5  and  7  are placed on the core, and the layers of composite material making up the box  45  are draped on said slugs  51   a,    51   b,  and on the core. 
         [0057]    The die is then closed on the core, and resin is injected into the interface between said die and said core, thereby making it possible to assemble the various elements making up the half-beam  100  using a resin transfer method known as RTM, i.e. “resin transfer molding.” 
         [0058]    Alternatively, the box  45  can be made from at least two draping subassemblies clamping the rail slugs  51   a,    51   b  (result  FIG. 5 ). 
         [0059]    This particular arrangement, which can also be obtained using an RTM method, allows a close connection of the rails  5 ,  7  with the open box  45 , and therefore excellent strength of the assembly. 
         [0060]    It will also be noted that the rails  5 ,  7  may be associated with a support plate then fastened on the half-beam. All of the alternatives for integrating and fastening rails  5 ,  7  known by those skilled in the art may be used in the context of the present invention. 
         [0061]      FIGS. 6 to 10  shows several preferred embodiments of the base body of a half-beam according to the invention including a base body equipped with at least one reinforcement means and in particular setting out several solutions to increase the strength of a composite beam with an open section according to the invention. 
         [0062]      FIG. 6  shows a beam  200  made from a composite material having, according to the invention, a base body  201  with an open section, and more particularly an L-shaped section. 
         [0063]    The beam  200  has a plurality of square-shaped reinforcements  202  discretely distributed along said beam  202 . The reinforcements can be made from a metal alloy or composite material, for example, and can be attached or integrated into the base body  201 . 
         [0064]    In the case at hand, the reinforcements  202  are made by integration into the draping of the beam of  200  by stamping plies. Each reinforcement  202  has a core  203  which can, in particular, be made from a composite material, foam, or other material. 
         [0065]      FIG. 7  shows a beam  300  having a base body  301  with a substantially L-shaped open section. The base body has a foot forming a floor wall  302  of the base body, and while being configured so as to have a corrugated surface imparting increased rigidity to the assembly. 
         [0066]      FIG. 8  shows a beam  400  having a base body  401  with a substantially L-shaped open section. The base body has a foot assuming the form of a double wall  402 ,  402 ′. According to the invention, the double floor wall  402 ,  402 ′ is open, in the case at hand, laterally. 
         [0067]    According to one advantageous aspect of the invention, and as shown in  FIG. 9 , a wall of an upper panel  15  of an inner fixed structure  17  closes the open double wall  402 ,  402 ′. As previously mentioned, the wall  15  of the fixed structure  17  may be attached using means known by those skilled in the art, in particular by adhesion or riveting. 
         [0068]      FIG. 10  shows a beam  500  having a base body  501  with a substantially L-shaped open section. The base body has a foot  502  in the thickness of which cells  503  are formed, thereby creating an open section. The cells  503  may be covered by a fairing attached on the beam, in particular, as in the illustrated case, where the cells open into a lower surface, through a fairing aiming to ensure aerodynamism of an air circulation tunnel. 
         [0069]    As previously mentioned, the half-beams are connected to a panel  15  of a fixed structure  17 . In the event that panel does not close the section of the base body, it may be integrated into the half-beam, and potentially made from a composite material itself. 
         [0070]    The integration may in particular be done by surrounding the composite plies of the half-beam on either side of the panel  15 , and in particular of the inner structure thereof. 
         [0071]    Although the invention has been described with one particular embodiment, it is of course in no way limited thereto and encompasses all technical equivalents of the described means as well as combinations thereof if they are within the scope of the invention. Such equivalents and combinable means may for example be found in application FR 08/00264.