Abstract:
The invention relates to a nacelle ( 1 ) that comprises a first cowling ( 7 ) and a second cowling ( 9 ) capable of covering in particular the area ( 15 ) located around the casing of the fan ( 19 ) of a turbojet engine ( 3 ). The nacelle further includes an intermediate cowling ( 23 ) attached to said first cowling ( 7 ) so as to sandwich a mast ( 5 ) holding said turbojet engine ( 3 ). The second cowling ( 9 ) is mounted onto the intermediate cowling ( 23 ) via removable fastening means.

Description:
[0001]    TECHNICAL FIELD 
         [0002]    The present invention concerns a nacelle with a simplified cowling arrangement. 
       BACKGROUND 
       [0003]    In  FIGS. 1 to 4 , we have illustrated a nacelle  1  of the prior art, surrounding a turbojet engine  3  fixed on a mast  5 . 
         [0004]    Such a nacelle typically comprises a fixed upper cowling  7  and a lower cowling  9  mounted pivotably on said upper cowling owing to hinges  11 , with bolts  13  being provided to lock/unlock the lower cowling for maintenance operations of the members found in the peripheral zone  15  situated between the air inlet  17 , the casing of the fan  19  and the thrust reverser  21 . 
         [0005]    Such a nacelle therefore requires the implementation of hinges and bolts, as well as rods making it possible to maintain the lower cowling  9  in the open position. 
         [0006]    These articulation, locking and maintenance members have the drawback of putting a strain on the weight and cost of the assembly. 
       BRIEF SUMMARY 
       [0007]    The present invention therefore aims in particular to provide a nacelle of the abovementioned type which has a lower weight and lower cost. 
         [0008]    This aim of the invention is achieved with a nacelle comprising a first cowling and a second cowling capable of covering in particular the zone situated around the casing of the fan of a turbojet engine, remarkable in that it also comprises an intermediate cowling fixed to said first cowling so as to sandwich a support mast of said turbojet engine, and in that said second cowling is attached on said intermediate cowling by removable fastening means. 
         [0009]    Owing to these features, the first cowling and the intermediate cowling constitute fixing supports for the second cowling, and when one wishes to access said zone, one need only disassemble the second panel and remove it completely. 
         [0010]    No articulation, bolt or maintenance rod is necessary: in this way one saves weight, gains simplicity and lowers the cost. 
         [0011]    According to other optional features of the nacelle according to the invention:
       said nacelle also comprises axial fixing pins of said first cowling and/or of said second cowling and/or of said intermediate cowling on a downstream part of said nacelle, such as a thrust reverser,   said nacelle also comprises removable fixing means of said first cowling and/or of said second cowling and/or of said intermediate cowling on an upstream part of said nacelle, such as an air inlet;   said nacelle comprises locking means of said first cowling and/or of said second cowling and/or of said intermediate cowling on an upstream part of said nacelle, such as an air inlet;   said removable fixing means comprises screws cooperating with nut casings;   the means for fixing said intermediate cowling to said first cowling comprises fittings mounted on said cowlings and rods extending between said fittings;   joints are fixed on the edges of said intermediate cowling and said first cowling that are designed to cooperate with said mast;   said first cowling is an upper cowling and said second cowling is a lower cowling;   said cowlings comprise reinforcing means.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Other features and advantages of the present invention will appear in light of the following description, and upon examination of the appended figures, in which: 
           [0021]      FIGS. 1 to 4  designate a nacelle of the prior art; more particularly,  FIGS. 1 and 2  are perspective views of such a nacelle in the normal operating position and in maintenance position, respectively,  FIG. 3  is an axial cross-sectional view of said nacelle along the plane P of  FIG. 1  observed along the direction III, and  FIG. 4  is a transverse cross-sectional view of said nacelle along line IV-IV of  FIG. 3 ,
         FIG. 5  is an exploded perspective view of a nacelle according to the invention,     FIGS. 6 to 8  are perspective views of an upper cowling, an intermediate cowling and a lower cowling of the nacelle of  FIG. 5 ,     FIGS. 9 and 10  are views similar to those of  FIGS. 3 and 4  of the nacelle according to the invention, in the normal operating position,     FIGS. 11 to 14  are views similar to that of  FIG. 9 , indicating the opening kinematics of the lower cowling of the nacelle according to the invention,     FIG. 15  is a view similar to that of  FIG. 10 , corresponding to the opening state of the cowling  9  of  FIG. 14 , and     FIG. 16  is a view similar to that of  FIG. 9  of another embodiment of a nacelle according to the invention.         
           [0028]    In all of these figures, identical or similar numerical references designate identical or similar members or sets of members. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    In reference now to  FIGS. 5 to 8 , one can see that the nacelle according to the invention comprises a cowling including three distinct parts: an upper cowling  7 , a lower cowling  9  and an intermediate cowling  23 . 
         [0030]    The upper  7  and lower  9  cowlings essentially have the shape of half cylinders and include, on their internal faces, reinforcements in the form of ribs  25 ,  27 . The intermediate cowling  23  is essentially in the form of a plate, also provided on its inner face with reinforcements  29 . 
         [0031]    These three cowlings include, on their downstream edge (relative to the direction of circulation of the air in the turbojet engine  3 ), axial pins  31 ,  33 ,  35 , the function of which will be explained below. 
         [0032]    The upper cowling  7  and the intermediate cowling  23  also include fittings  37 ,  39 , connected together in pairs by rods  41 . 
         [0033]    One can also see in  FIG. 8  that the lower cowling  9  includes, on its two longitudinal edges, a plurality of perforations  43 ,  45  designed to allow the attachment of said lower cowling on the corresponding edges of the upper cowling  7  and the intermediate cowling  23 , respectively. 
         [0034]    In reference to  FIG. 9 , one can see that the axial pins  33  of the lower cowling  9  cooperate with the receptacles  47  fixed on the thrust reverser  21 . 
         [0035]    The upstream edge of the lower cowling  9  is fixed on angle irons  49  mounted on the air inlet  17 , owing to fastening members such as screws  51  cooperating with nut casings  53 . 
         [0036]    One can also see in  FIG. 10  that such screws  51  and casings  53  are also used to fasten the lateral edges of the lower cowling  9  to the corresponding edges of the upper cowling  7  and the intermediate cowling  23 . 
         [0037]      FIG. 10  also shows the manner in which the rods  41  extend between the fittings  37  of the upper cowling  7  and the fittings  39  of the intermediate cowling  23 . 
         [0038]    It will also be noted, as shown in this figure, that joints  55 ,  57  are fastened on the lateral edges of the upper cowling  7  and the intermediate cowling  23  cooperating with the mast  5 ; the reverse is possible, i.e. the joints can be fastened on the mast  5  and rest on the upper cowling  7  and the intermediate cowling  23 . 
         [0039]    When one wishes to access the peripheral zone  15  surrounding the casing of the fan  19 , in particular for maintenance operations of the members found in that zone (electrical, pneumatic, hydraulic, electronic, etc.), one proceeds as indicated in  FIGS. 11 to 15 . 
         [0040]    One begins by removing the line of screws  51  situated on the upstream edge of the lower cowling  9 , as indicated by arrow F 1  of  FIG. 11 . 
         [0041]    One then removes the screws connecting the two lateral edges of the lower cowling  9  to the respective edges of the upper cowling  7  and of the intermediate cowling  23  (of course, this order of removing the attachments is purely indicative). 
         [0042]    One then separates the upstream edge of the lower cowling  9  from the angle irons  49  fastened downstream from the air inlet  17 , as indicated by arrow F 2  of  FIG. 12 . 
         [0043]    One then slides the lower cowling  9  toward the front of the nacelle, as indicated by arrow F 3  of  FIG. 13 , making it possible to release the axial pins  33  from their respective receptacles  47 . 
         [0044]    Lastly, one can radially separate the lower cowling  9  from the nacelle, as indicated by arrow F 4  of  FIGS. 14 and 15 . 
         [0045]    Once the lower cowling  9  is removed in this way, one can access the peripheral zone  15 . 
         [0046]    If one wishes to access the upper part of this peripheral zone  15 , after having removed the lower cowling  9 , one can access the fittings  39  of the intermediate cowling  23 , and thus detach the rods  41  from said fittings. 
         [0047]    One can then remove both the intermediate cowling  23  and the upper cowling  7 , thereby completely freeing the peripheral zone of the fan casing  19 . 
         [0048]    As can be understood from the preceding, the nacelle according to the invention includes a cowling that can be placed and removed extremely simply, owing to removable fastening means. 
         [0049]    No articulation, locking and opening maintenance rod system is necessary, which makes it possible to save in terms of weight, simplicity and cost. 
         [0050]    It will also be noted that the assembly/disassembly of the lower cowling  9  is done easily due to the fact that this cowling does not act on the compression of the joints  55  and  57 . 
         [0051]      FIG. 16  indicates one possible alternative of the invention, in which a locking means  58  is provided only on the upstream edge of the lower cowling  9 , such locking means typically being able to comprise actuating handles  59  acting on mobile pins  61  cooperating with the receptacles  63  integral with the air intake  17 . 
         [0052]    In this alternative, one does, however, keep the axial pins  33  and the removable fastening means of the screw/nut type for the lateral edges of the cowlings. 
         [0053]    Of course, the present invention is in no way limited to the embodiments described and illustrated, provided as simple examples. 
         [0054]    For instance, one may consider placing one or several quick access doors on the lower cowling  9 , these doors for example being mounted pivotably on the cowling  9  using hinges.