Abstract:
The invention relates to a nacelle for a turbojet engine that comprises an air intake structure ( 2 ) capable of directing an air flow towards a fan of the turbojet engine, and an intermediate structure for surrounding said fan and to which the air intake structure is attached in order to ensure aerodynamic continuity, wherein the air intake structure includes, on the one hand, at least one inner panel ( 21 ) attached to the intermediate structure and defining with the latter a fixed nacelle structure and, on the other hand, at least one longitudinal outer panel ( 20 ) removably attached to the fixed structure and including an air intake lip ( 2   a ) in order to form a removable air intake structure, characterised in that the air intake structure is provided with peripheral locking means including at least one locking means ( 10 ) attached to the inner panel or to the air intake lip and each capable of interacting with an additional retaining means ( 11 ) respectively attached to the air intake lip or to the inner panel.

Description:
TECHNICAL FIELD 
       [0001]    The present invention concerns a locking device for a translatable air intake structure equipping a turbojet engine nacelle. 
       BACKGROUND 
       [0002]    An airplane is propelled by one or several propeller assemblies comprising a turbojet engine housed in a tubular nacelle. Each propeller assembly is attached to the airplane by a mast situated generally under a wing or at the fuselage. 
         [0003]    A nacelle generally has a structure comprising an air intake upstream from the engine, a middle section designed to surround a fan of the turbojet engine, and a downstream section intended to surround the combustion chamber of the turbojet engine and housing thrust reverser means. 
         [0004]    The air intake comprises, on one hand, an intake lip adapted to allow optimal collection toward the turbojet engine of the air necessary to supply the fan and the internal compressors of the turbojet engine, and on the other hand, a downstream structure on which the lip is attached and designed to suitably channel the air toward the blades of the fan, said downstream structure comprising an outer shroud and an inner acoustic panel. The assembly is attached upstream from a case of the fan belonging to the middle section of the nacelle. 
         [0005]    The middle structure surrounds the fan and generally breaks down into an inner wall forming said fan case and an outer wall assuming the form of removable cowls mounted pivotably around a longitudinal axle forming a hinge in the upper portion (at 12:00) of the nacelle in order to allow access to the inside of the nacelle. 
         [0006]    The assembly of these various elements (mobile cowls, case, air intake lip, outer shroud, acoustic panel) creates many aerodynamic breaks due to the presence of offsets and gaps between these elements inherent to their fastening together. Moreover, the mobile cowls are mounted on hinges, also generating aerodynamic disturbances. 
         [0007]    One solution to improve the aerodynamic continuity of the outer surface of a nacelle was the object of French patent applications no. 06/08599 and no. 07/01256, not yet published. 
         [0008]    This solution consists of integrating the air intake lip into the outer shroud, including all or part of the cowl there surrounding the fan case so as to form a single-piece structure. The whole of the wall thus formed is mounted mobile in translation. 
         [0009]    The French patent application, not yet published, registered under number 07/03699 describes a manual locking system of said air intake structure and an associated manual system for helping the translation. 
         [0010]    In a turbojet engine nacelle having such a translatable structure, the inner edge of the air intake lip comes, when said translatable structure is in closed position, into contact with a zone upstream from an inner wall of the air intake structure, inner wall generally realized in the form of an acoustic panel. 
         [0011]    The translatable structure is guided and maintained on a fixed structure, comprising the inner wall of the air intake structure, by a plurality of rails. 
         [0012]    The interface is made sealed by a joint system and is reinforced by a system of centering pins arranged on the periphery of the air intake lip/acoustic shroud junction and making it possible to improve its resistance to radial movements. 
         [0013]    The maintenance of the mobile structure along longitudinal directions is done primarily by bolting the mobile structure on a fixed structure in a zone close to an installation interface of the acoustic shroud on the fan case. 
         [0014]    Such a locking system therefore requires a large number of fixing means, the assembly and disassembly of which are long and tedious. 
         [0015]    Moreover, the interface between the air intake lip and the inner acoustic panel is of particular importance, because said interface must penalize the internal aerodynamic continuity of the nacelle as little as possible and avoid any deformation of the interface as much as possible during load stresses undergone by the air intake or the inner acoustic panel. 
         [0016]    Also known is a manual locking system comprising a system for gripping the mobile structure by the handle at the end of maneuver of the structure. This technique makes it possible to avoid a long and tedious assembly/disassembly with a system of maintenance by bolting. However, such a system is not suited to motorized driving of the mobile structure since the manual drive system and the locking are coupled. One will also note that adjusting the prestressing of the bolts is also long and tedious. 
         [0017]    Because of this, there is a need for a locking system of such a mobile structure making it possible to resolve all or part of these problems. 
       BRIEF SUMMARY 
       [0018]    To do this, the present invention concerns a nacelle for a turbojet engine comprising an air intake structure capable of directing an air flow towards a fan of the turbojet engine and a middle structure for surrounding said fan and to which the air intake structure is attached in order to provide aerodynamic continuity, the air intake structure comprising, on one hand, at least one inner panel attached to the middle structure and defining, with the latter, a nacelle fixed structure and, on the other hand, at least one longitudinal outer panel removably attached to the fixed structure and including an air intake lip in order to define a removable air intake structure, characterized in that the removable air intake structure is provided with peripheral locking means including at least one electric lock attached to the inner panel or to the air intake lip and each capable of interaction with a complementary retaining means attached to the air intake lip or to the inner panel, respectively. 
         [0019]    Thus, by equipping the junction between the air intake structure and the inner panel with discrete locking means, easy to actuate remotely, it is possible to thus easily ensure optimal resistance of a junction capable of resisting deformation stresses. 
         [0020]    According to a first embodiment of the invention, the locking means comprises a hook. Advantageously, the hook is a hook with three-point projection system. 
         [0021]    According to a second embodiment, the hook is a rotating hook. 
         [0022]    Preferably, the complementary retaining means is a yoke. Also preferably, the complementary retaining means assumes the form of a return presented by one end of the air intake lip or of the inner panel. 
         [0023]    Advantageously, the inner panel or the air intake lip comprises at least one centering pin capable of cooperating with a corresponding bore of the air intake lip or of the inner panel, respectively. 
         [0024]    According to a first alternative, the centering pin is mounted rotatingly mobile and has a first end in the form of a cam capable of passing alternatingly between an unlocking position in which the cam-type end can be removed from the complementary retaining means and a locking position in which the cam-type end abuts against the complementary retaining means and cannot be removed from it. 
         [0025]    According to a second alternative, the centering pin is mounted rotatingly mobile and has an outer thread capable of cooperating with an inner tapping of the corresponding bore. Advantageously, the tapped bore comprises a ball bearing system. 
         [0026]    Advantageously, the centering pin has a transverse bore capable of forming a complementary retaining means. 
         [0027]    According to another alternative, the locking means is an electric locking means capable of being remotely controlled. 
         [0028]    According to still another embodiment, the locking means is a manual locking means capable of being remotely controlled by a manual drive means of the cable type or cardan mechanical return type. 
         [0029]    Advantageously, the control means of the locking means are centralized. 
         [0030]    Also advantageously, the control member is a handle, preferably retractable, capable of allowing the driving of the air intake structure in motion. 
         [0031]    Preferably, the electric bolt(s) is/are associated with at least one means for detecting the locking and/or unlocking position. 
         [0032]    Advantageously, the prestressing of the locking means is adjustable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    The implementation of the invention will be better understood with the detailed description below in light of the appended drawing, in which: 
           [0034]      FIG. 1  is a partial diagrammatic illustration of an air intake structure of a nacelle according to the invention, the air intake structure being in the closing position. 
           [0035]      FIG. 2  is a partial diagrammatic illustration of the air intake structure of  FIG. 1 , the air intake structure being in the opening position. 
           [0036]      FIG. 3  is an enlarged diagrammatic illustration of a three-point bolt in the locking position. 
           [0037]      FIG. 4  is an enlarged diagrammatic illustration of the bolt of  FIG. 3  in the opening position. 
           [0038]      FIG. 5  is a diagrammatic illustration of a locking method by rotating hook, said hook being in the opening position. 
           [0039]      FIG. 6  is an illustration of the rotating hook of  FIG. 5  in the locking position. 
           [0040]      FIG. 7  is an illustration of a locking mode by rotating pin having an end forming a cam, said pin being in the unlocking position. 
           [0041]      FIG. 8  is an illustration of the pin of  FIG. 7  in the locking position. 
           [0042]      FIGS. 9 and 10  show a locking mode via threaded rotating pin. 
           [0043]      FIGS. 10 to 14  show two locking modes by hooking of a centering pin, by a beveled hook, respectively, and a hook having a cavity corresponding to the pin. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    A nacelle according to the invention as partially illustrated in  FIGS. 1 and 2  constitutes a tubular housing for a turbojet engine (not shown) for which it serves to direct the air flows it generates by defining inner and outer aerodynamic lines necessary to obtain optimal performance. It also houses different components necessary to the operation of the turbojet engine as well as related systems such as a thrust reverser. 
         [0045]    The nacelle is intended to be attached to a fixed structure of an airplane, such as a wing, via a pylon. 
         [0046]    More precisely, the nacelle has a structure comprising a front section forming an air intake  2 , a middle section  3  (partially visible) comprising a case  3   a  surrounding a fan (not visible) of the turbojet engine, and a rear section (not visible) surrounding the turbojet engine and able to house a thrust reverser system (not shown). 
         [0047]    The air intake  2  is divided into two zones, i.e. on one hand, an intake lip  2   a  adapted to allow optimal collection toward the turbojet engine of the air necessary to supply the fan and inner compressors of the turbojet engine, and on the other hand, a downstream structure  2   b  comprising an outer panel  20  and an inner panel  21 , generally acoustic. 
         [0048]    According to the nacelle of the prior art, to which the present invention is applicable, the lip  2   a  is integrated into the outer panel  20  so as to form a single disassemblable piece, the inner panel  21  being attached upstream from the case  3   a  of the fan belonging to the middle section  3  of the nacelle via fastening flanges  4 , integral with an inner panel  21  and the case  3   a , respectively. 
         [0049]    The air intake structure  2  can be modular and comprise a plurality of outer panels  20  each defining a corresponding air intake lip portion  2   a.    
         [0050]    The inner panel  21  is made from an acoustic shroud and is connected via flanges  4  to the case  3   a  of the middle section  3 . This inner panel  21  therefore constitutes a fixed part of the air intake structure  2  on which the outer panel  20 , integrating the air intake lip  2   a , is designed to be removably attached and fixed. 
         [0051]    It will be noted that alternatively, the outer panel  20  can also comprise all or part of an outer panel of the middle structure. 
         [0052]    To do this, each flange  4  can support a radial peripheral partition  5 . 
         [0053]    This partition  5  can support center finders and secondary center finders extending perpendicularly to said partition  5  toward the upstream of the nacelle. 
         [0054]    It will also be noted that the air intake structure  2  can extend axially via its outer panel  20  beyond a valve guide plate of an inner plate  21  to the fixed structure of the nacelle  1  to be close to an outer structure of a thrust reverser structure belonging to the downstream section of the nacelle and possibly to cover the cowls. A system of bolts can then be provided to maintain the air intake structure on the partition  5  integral with the structure of the case or a structure upstream from the downstream structure. 
         [0055]    It will also be noted that the radial peripheral partition  5  can be supported directly by the very structure of the fan case in order to provide a maximum inner envelope for the air intake  2 . 
         [0056]    The outer panel  20  integrating the air intake lip  2   a  therefore forms, according to the prior art, a removable portion designed to be attached on the fixed portion and more particularly on the peripheral partition  5 . 
         [0057]    Inner reinforcements of the existing inner and outer panels are not shown and depend on the stiffness desired by the person skilled in the art. 
         [0058]    More particularly, the removable structure can be mounted, for example, on a rail/guideway sliding system comprising a plurality of rails/guideways distributed on the periphery of the air intake structure  2  and/or the case  3   a.    
         [0059]    According to the invention, the removable structure is maintained at the junction between the air intake lip using discrete locking means comprising at least one hook  10 , in this case mounted on the inner panel  21 , capable of cooperating with a complementary retaining means  11  of the yoke type, itself attached to the air intake lip  2   a.    
         [0060]      FIGS. 1 and 2  show the removable structure in the closed and open positions, respectively. 
         [0061]      FIGS. 3 and 4  are an enlarged view of the locking hook  10  cooperating with the yoke  11 . It will be noted that the interface between the air intake lip  2   a  and the inner panel  21  is completed by centering pins  12 , arranged essentially at each hook  10  and supported by a peripheral return  15  of the inner panel  21 , each cooperating with a corresponding bore  13  arranged in a return  14  of the air intake lip. 
         [0062]    The described example uses a hook  10  with three-point locking system. Such a locking system is known in particular from document FR 2 857 400. 
         [0063]    The lower shape of the hook  10  serves as a release ramp of the yoke  11  during the unlocking maneuver. In particular, the proper release of the hook  10  relative to the yoke  11  is ensured through the shape given to the hook  10  in contact with a fixed axis of rotation of a rod of the three-point system. 
         [0064]    The projection of the three-point system makes it possible to ensure the security of the locking and be assured of the latter in all flight cases and in case of break of the drive system of the locking rods. 
         [0065]    The hook  10  and the three-point locking system are actuated by an electric motor  30 . 
         [0066]    The locking and unlocking controls for the electric locking means are grouped together at an external control means of the nacelle and/or at the cockpit of the airplane. 
         [0067]    The retaining means  11 , of the yokes type, are positioned on the air intake lip  2   a  of the nacelle in a zone guaranteeing the best structural rigidity in order to avoid any deflection of that interface. 
         [0068]      FIGS. 5 and 6  present a second embodiment of the locking comprising a rotating hook  40  driven by an electric motor  41  capable of engaging with the return  15  of the inner panel  21 , which then serves as complementary retaining means. 
         [0069]    The centering pins can also be used directly in the locking means. 
         [0070]    Thus,  FIGS. 7 and 8  show a third embodiment in which the centering pin  50  is passed through by a blocking cam  52  capable of being driven in rotation by an electric motor  51  supported by the return  14  of the air intake structure  2   a.    
         [0071]    The pin  50  is capable of cooperating with a bore  54  formed in the return  15  of the inner panel  21 . 
         [0072]    The return  21  also supports retaining means  55  of the cam  52  designed such that said cam  52  has an unblocking position in which it can be removed from the retaining means  55  through the bore  54  and a blocking position in which it abuts against the retaining means  55 , which then prevent its removal. 
         [0073]    Of course, the cam  52  can be an integral part of the pin  50 , which is then itself driven in rotation. Advantageously, the pin shall, however, be kept fixed in rotation. 
         [0074]      FIGS. 9 and 10  present a screw locking system. 
         [0075]    To do this, the return  15  of the inner panel  21  supports a threaded centering pin  60  capable of being driven in rotation by an electric motor  61 . The centering pin  60  is capable of cooperating with a tapped bore  62  supported by the return  14  of the air intake lip  2   a . The rotation can be improved by the presence of ball bearings  63 . 
         [0076]      FIGS. 11 to 14  illustrate a locking mode by wedging. 
         [0077]      FIGS. 11 and 12  show a locking mode by wedging with beveled cam. In this case the inner panel  21  supports a hook  70  capable of being actuated essentially perpendicularly to the inner panel  21  by an electric motor  71 . When the hook  70  is actuated in the direction of the inner panel  21 , it is intended to penetrate a bore  72  arranged in a centering pin  73  when the latter has been inserted through a corresponding bore  74  of the air intake structure  2   a.    
         [0078]    The beveled form of the hook  70  allows adjustment of the prestressing of the locking system depending on the penetration depth of the hook  70 . 
         [0079]      FIGS. 13 and 14  illustrate a locking system by wedging and rectilinear retraction of the pin or cam. 
         [0080]    In this case the inner panel  21  supports a straight hook  80  capable of being actuated essentially perpendicularly to the inner panel  21  by an electric motor  81 . When the hook  80  is actuated towards the inner panel  21 , it is intended to penetrate the bore  72  formed in the centering pin  73  when the latter has been inserted through a corresponding bore  74  of the air intake structure  2   a.    
         [0081]    A cavity  82  can be formed near one end of the hook  80 . Once the hook  80  is brought into the locking position, the centering pin  73  can be actuated in the downstream direction so as to be placed in the cavity  82  of the hook  80  and block the latter. 
         [0082]    For the unlocking phase, the pin  73  will then be maneuvered first so as to release the cavity  82  and allow the distancing of the hook  80 . 
         [0083]    In such a case, the prestressing stress is done by the pin  73  during the closing of the system. 
         [0084]    All of the locking systems described in this application may include means for signaling the locking and/or unlocking position, the information from which may be escalated to the cockpit, for example. For greater reliability of that signaling function, the signaling means could be positioned relative to an active locking element guaranteeing an “all or nothing” signal. The signaling means is preferably placed on the inner panel  21  constituting a fixed portion of the nacelle in order to reduce the disconnection interfaces, which is one of the factors reducing the reliability of the system. 
         [0085]    The prestressing of the described locking systems can also be adjusted. 
         [0086]    In the case of the hook  10  shown in  FIGS. 1 to 4 , the adjustment of the prestressing may be done by fastening of the locking means on an adjustable platen (for example by screw) allowing a slight translation along the inner panel  21 . The adjustment of the yoke  11  may be done in the same way. 
         [0087]    Concerning the bolt with rotating hook  40  illustrated in  FIGS. 5 and 6 , the adjustment of the prestressing may be done by adjusting the position of the bolt by wedging of the housing of the motor  41  or by action on an axis of the hook  40 . 
         [0088]    Advantageously, the electric and/or manual control means of the locking means may be centralized, said control being able to be, for example, situated inside the middle structure and accessible after opening of an outer panel of that structure, or apparent to the structure and directly accessible from the outside of the nacelle. 
         [0089]    In the case of a direct accessibility, the control can, for example, assume the form of an appendix not aerodynamically protected, or be protected by a hatch or a switchbox allowing outer aerodynamic smoothing. 
         [0090]    It will be noted that the presented examples show an electric motor with bolt, but it is obviously possible to provide a reduced number of electric motors, or even a single electric motor, the propelling force of which is sent to the different bolts by a mechanical driving system. 
         [0091]    Also advantageously, one will provide a centralized mechanical unlocking system of the electric bolts in case of breakdown of one or several electric motors. Indeed, normally, each bolt should be accessed individually by a dedicated access hatch. These hatches would then generate significant aerodynamic disturbances in addition to being heavy, costly and disrupting the structural integrity of the outer structure. 
         [0092]    Each electric motor can then advantageously be equipped with a manual drive unit (MDU) capable of being actuated by a mechanical drive system with centralized manual control. 
         [0093]    Lastly, one may also provide a mechanical inhibition system of the locking means, preferably visible from the outside. Such a mechanical inhibition may assume the form of a locking lug having an appendage introduced into the manual drive member and capable of blocking the latter. 
         [0094]    Although the invention has been described with a particular embodiment, it is of course in no way limited thereto and includes all technical equivalents of the means described as well as their combinations if they fall within the scope of the invention. One will also note that most of the locking modes presented can be used for other nacelle interfaces, in particular the upstream interface between the removable air intake structure and the fan case.