Abstract:
The invention relates to a twelve-hour structure for a thrust reverser, that comprises a half beam ( 1 ) capable of holding a reverser half cowling and including a plurality of hinge yokes ( 9   c ) for rotatingly mounting said half beam ( 1 ) on a nacelle-holding mast. The half beam ( 1 ) is at least partially made of a composite material.

Description:
TECHNICAL FIELD 
       [0001]    The present invention concerns a twelve-hour structure for thrust reverser, in particular with grids. 
       BACKGROUND 
       [0002]    Traditionally, a thrust reverser with grids comprises two half-cowlings mounted each sliding on a half-beam mounted pivoting on a nacelle-holding mast. 
         [0003]    The sliding movement of each half-cowling on its associated half-beam makes it possible to make the thrust reverser go from a direct jet configuration to a reverse jet configuration, and vice versa. 
         [0004]    The rotational movement of each half-beam on the nacelle-holding mast makes it possible to make each half-cowling pivot relative to said mast for maintenance operations. 
         [0005]    As illustrated in the appended  FIGS. 1 and 2 , each half-beam  1  is formed in a ribbed metal alloy  3 , and typically comprises, on its outer face, primary  5  and secondary  7  rails capable of allowing the movement of the associated half-cowling (not shown), and a plurality of hinge yokes  9   a,    9   b,    9   c,    9   d  capable of allowing the articulation of the half-beam  1  on the associated nacelle mast. 
         [0006]    A receptacle  11 , mounted on the upstream part (relative to the direction of air flow in the nacelle) of the half-beam  1 , allows the fixing of a front frame designed to support the grids of the thrust reverser (frame and grids not shown). 
         [0007]    As visible in  FIG. 3 , the half-beam  1  is attached by riveting  13  on the upper part  15  of an internal fixed half-structure panel  17 , generally made of a composite material, and defining, with the associated thrust reverser cowling, the cold air jet  18 . 
         [0008]    The assembly formed by the half-beam  1 , its rails  5 ,  7  and its hinge yokes  9   a  to  9   d  is often referred to as “twelve-hour structure”, given its position at the top of the circle defined by a nacelle section, and by analogy with the dial of a watch. 
       BRIEF SUMMARY 
       [0009]    The present invention aims in particular to provide a twelve-hour structure lightened relative to those of the prior art. 
         [0010]    This aim of the invention is achieved with a twelve-hour structure for thrust reverser, comprising a half-beam capable of supporting a reverser half-cowling and including a plurality of hinges for the rotational mounting of said half-beam on a nacelle-holding mast, remarkable in that said half-beam is formed at least in part in composite material. 
         [0011]    The use of composite material to manufacture this half-beam makes it possible to considerably lighten its weight. 
         [0012]    According to other optional features of the present invention:
       said half-beam also comprises at least one rail for slidingly mounting said half-cowling: such a rail is adapted to the case of a thrust reverser with grids;   said half-beam is integrated into the upper part of an internal fixed half-structure panel: in this first embodiment, it is no longer necessary to rivet the half-beam on the internal fixed half-structure panel (this internal structure frequently being designated by “IFS”, i.e. Internal Fixed Structure), which makes it possible to save assembly/disassembly time;   said half-beam comprises a foam core enveloped in the skin of said panel: this variation, in which the foam can be ROHACELL 110 WF, for example, makes it possible to obtain the desired rigidity for the half-beam while having a low weight;   said half-beam comprises a case in composite material enveloped in the skin of said panel: this variation, in which the case can for example be in HEXPLY 914, makes it possible to save weight relative to the foam filling of the preceding variation;   said hinge yokes are formed in a metal alloy;   said half-beam comprises a core including one part in foam and a tube in composite material, this core being enveloped in the skin of said panel: this variation makes it possible to save weight relative to the first of the abovementioned variations, while using a standard composite tube, i.e. not specially formed for this particular use;   said tube is formed in forged carbon: this material offers an excellent resistance/weight compromise;   said rails and said hinge yokes sandwich said skin: this arrangement allows good resistance both of the rails and the hinge yokes;   said half-beam is attached on the upper part of an internal fixed half-structure panel: this second embodiment can be adapted to a traditional internal fixed half-structure without requiring any modification of the latter;   said half-beam comprises a closed case in composite material whereof one of the faces is formed by a plate supporting said at least one rail: such a half-beam can be manufactured by simple assembly of a small number of pieces;   said half-beam comprises an open case in composite material integrating said at least one rail: this variation can be obtained by molding, for example of the “RTM” (Resin Transfer Molding) type, such molding making it possible to obtain a single-unit piece;   said at least one rail is connected to said open case on a single face thereof: this variation can be obtained by drape molding of a single half-mold, the rails being placed in the other half-mold;   said at least one rail is held between two layers of said open case: this variation, making it possible to obtain rails connected more closely to the rest of the case, requires the drape molding of two half-molds;   said hinge yokes are formed in forged carbon: these yokes, which offer excellent resistance with a low weight, can be placed in the molds for the open case variations.       
 
         [0027]    The present invention also relates to a nacelle for aircraft engine, remarkable in that it comprises a twelve-hour structure according to the preceding. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Other features and advantages of the present invention will appear in light of the following description, and upon examining the appended figures, in which: 
           [0029]      FIGS. 1 and 2  are perspective views of a twelve-hour structure of the prior art, mentioned in the preamble of the present description; 
           [0030]      FIG. 3  is a transverse view of said twelve-hour structure, taken at one of the hinge yokes of said structure; 
           [0031]      FIGS. 4 and 5  are transverse cross-sectional views of a first embodiment of a twelve-hour structure according to the invention, in running section and in the zone where one of the hinge yokes is found, respectively; 
           [0032]      FIGS. 6 and 7  are views similar to  FIGS. 4 and 5  of a variation of the first embodiment according to the invention; 
           [0033]      FIG. 8  diagrammatically indicates all of the components making it possible to realize a twelve-hour structure according to  FIGS. 6 and 7 ; 
           [0034]      FIGS. 9 and 10  are views similar to  FIGS. 4 and 5  of another variation of the first embodiment according to the invention; 
           [0035]      FIG. 11  is an axial cross-sectional view of the tube forming the twelve-hour structure of  FIGS. 9 and 10 , in the zone of one of the hinge yokes of said structure; 
           [0036]      FIGS. 12 and 13  are views similar to  FIGS. 4 and 5  of a second embodiment according to the invention; 
           [0037]      FIG. 14  is a view similar to  FIG. 8  of said second embodiment; 
           [0038]      FIGS. 15 and 16  are views similar to  FIGS. 4 and 5  of a variation of this second embodiment; 
           [0039]      FIG. 17  diagrammatically indicates the manner in which the variation of  FIGS. 15 and 16  can be obtained by molding; 
           [0040]      FIG. 18  is a view similar to  FIG. 4  of a third variation of the second embodiment according to the invention; and 
           [0041]      FIG. 19  is a view similar to  FIG. 17  of the molding operation of the structure of  FIG. 18 . 
       
    
    
       [0042]    In all of these figures, identical or similar references designate identical or similar members or sets of members. 
       DETAILED DESCRIPTION 
       [0043]    In reference now to  FIGS. 4 and 5 , one can see that, according to a first embodiment of the twelve-hour structure of the invention, the half-beam  1  is integrated into the upper part  15  of an internal fixed half-structure panel  17 . 
         [0044]    More specifically, in the variation illustrated in  FIGS. 4 and 5 , the half-beam  1  comprises a foam core  18  enveloped in the skin  19  situated on either side of the honeycomb structure  21  of the panel  15 . 
         [0045]    The foam  18 , which can for example be a ROHACELL 110 WF foam, the skin  19  and the honeycomb structure  21  are made in a single co-curing operation. 
         [0046]    A plate  23  integrating the primary  5  and secondary  7  rails, formed for example in a metal alloy, is fixed by riveting  25  on the skin  19 . 
         [0047]    Preferably, between this plate  23  and this skin  19  is a profile  27  defining an aerodynamic shape suitable for the flow of cold air along the panel  15 . 
         [0048]    As visible in  FIG. 5 , in the zones of the hinges  9   a  to  9   d,  the skin  19  is interrupted and the foam  18  comprises housings  29  in which the hinge yokes are arranged ( 9   c  in  FIG. 5 ). 
         [0049]    These hinge yokes are bolted on the plate  23 , thus sandwiching on one hand the aerodynamic profile  27 , and on the other hand the skin  19 . 
         [0050]    In the alternative illustrated in  FIGS. 6 and 7 , the foam core  18  is replaced by a monolithic case  31 , formed in composite material. 
         [0051]    This case is preferably pre-cured, the skin  19  then being overmolded on this case. 
         [0052]      FIG. 8  shows that the alternative illustrated in  FIGS. 6 and 7  is formed by the assembly of a plurality of simple elements: skin parts  19   a,    19   b,    19   c , honeycomb structure  21  and monolithic case  31 . 
         [0053]    The assembly of all of these simple elements is done by complete co-curing. 
         [0054]    The fixing of the plate  23  and the yokes  9   a  to  9   d  is similar to that of the preceding alternative. 
         [0055]    It is understood that, due to the hollow nature of the monolithic case  31 , this alternative allows a significant weight savings relative to the preceding alternative. 
         [0056]    In the variation illustrated in  FIGS. 9 to 11 , the skin  19  surrounds a tube  33  in composite material, connecting the hinge yokes  9   a  to  9   d  to each other. 
         [0057]    This tube and these yokes can be realized for example in forged carbon, making it possible to obtain an excellent resistance/weight compromise. 
         [0058]    In the zone between the honeycomb structure  21  and the tube  33  is a foam core  18  similar to that of the alternative of  FIGS. 4 and 5 . 
         [0059]    The plate  23  supporting rails  5  and  7  is connected to the panel  15  via the profile  27 . 
         [0060]    In the zones where the hinge yokes  9   a  to  9   d  are found, this plate  23  is also bolted on these yokes, as is visible in  FIG. 10 . 
         [0061]    This alternative is interesting because it allows the use of forged carbon tubes  33  of standard dimension around which one tapes the skin  19 : one is thus freed from the need to design a custom piece, which makes it possible to reduce the manufacturing cost. 
         [0062]    We will now look at  FIGS. 12 to 14 , in which we have shown a second embodiment of the twelve-hour structure according to the invention. 
         [0063]    In the embodiment illustrated in these three figures, this twelve-hour structure comprises a closed case  35  made in composite material, one of the faces of this case being defined by the plate  23  supporting the primary  5  and secondary  7  rails. 
         [0064]    This plate can be formed in a metal alloy, or in “extruded” composite. 
         [0065]    Contrary to the preceding embodiment, the case  35  is attached by bolting  37  on the upper part  15  of the internal fixed half-structure panel  17 . 
         [0066]    As visible in  FIGS. 12 and 13 , the profile  27  of aerodynamic form connecting the case  35  to the panel  15  can be held by the rivets  39  connecting the plate  23  to the rest of the case  35 . 
         [0067]      FIG. 13  shows that the hinge yokes  9   a  to  9   d,  which can for example be formed in forged carbon, are placed inside the case  35 , and fixed to the panel  15  by rivets  37 . 
         [0068]      FIG. 14  shows that this alternative can be formed by the assembly of simple elements: plate  23 , case half-shell  41 , hinge yokes  9   a  to  9   d  and fastening bolts  37 . 
         [0069]    This  FIG. 14  also shows that the plate  23  can advantageously comprise a return  43  designed to be held by the bolts  37 , thereby avoiding having to use rivets  39 . 
         [0070]    Contrary to the previous embodiment, it is understood that this embodiment can be attached on a standard internal fixed half-structure  17 , thus not requiring any modification of the upper panel  15  of said structure. 
         [0071]    In the alternative of this second embodiment illustrated in  FIGS. 15 to 17 , the half-beam  1  of the twelve-hour structure according to the invention comprises an open case  45  formed by the drape molding of several layers of a composite material. 
         [0072]    At the free ends  45   a,    45   b  of said open case  45  are the rails  5  and  7 , also preferably formed by drape molding of several successive layers of composite material. 
         [0073]    Inside the open case  45  are the hinge yokes  9   a  to  9   d,  as illustrated in  FIG. 16 . 
         [0074]    As visible in  FIG. 17 , the twelve-hour structure illustrated in  FIGS. 15 and 16  can be realized by molding in a mold  47  comprising a core  49   a  and a matrix  49   b.    
         [0075]    The preforms  51   a,    51   b  defining the rails  5  and  7  are placed on the core  49   a  and the composite material layers forming the case will be draped on these preforms  51   a,    51   b,  and on the core  49   a.    
         [0076]    One then closes the matrix  49   b  on the core  49   a,  and injects resin into the interface between said matrix and said core, thus making it possible to assemble the various elements forming the half-beam  1  (this molding method is traditionally known as “RTM”, or “Resin Transfer Molding”). 
         [0077]    In the alternative illustrated in  FIGS. 18 and 19 , one sees that one can advantageously form the open case  45  from two drape molding sub-assemblies  53   a,    53   b,  clamping the rail preforms  51   a,    51   b.    
         [0078]    This particular arrangement, which can also be obtained using a RTM-type method, allows a close connection of the rails  5 ,  7  with the open case  45 , and therefore excellent resistance of the assembly. 
         [0079]    As one can understand in light of the preceding, the two embodiments of the invention and their associated alternatives make it possible to obtain a twelve-hour structure half-beam whereof at least one part is realized in composite material, thereby allowing an important weight savings relative to the twelve-hour structures of the prior art. 
         [0080]    Of course, the present invention is in no way limited to the embodiments described and illustrated, provided as simple examples.