Abstract:
The invention relates to a nacelle for a turbojet engine that includes 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 is attached the air intake structure in order to provide aerodynamic continuity, wherein the air intake structure includes at least one inner panel attached to the middle structure and defining, with the latter, a nacelle fixed structure and at least one outer longitudinal panel removably attached to the fixed structure and including an air intake lip in order to define a removable air intake structure, wherein the removable air intake structure is provided with a locking device including at least one electric lock capable of interaction with a complementary retention structure.

Description:
TECHNICAL FIELD 
     The present invention concerns a locking device for a translatable air intake structure equipping a turbojet engine nacelle. 
     BACKGROUND 
     An airplane is propelled by one or several propulsive assemblies comprising a turbojet engine housed in a tubular nacelle. Each propulsive assembly is attached to the airplane by a strut generally situated under a wing or at the fuselage. 
     A nacelle generally has a structure comprising an air inlet upstream from the engine, a middle section intended to surround a fan of the turbojet engine, and a downstream section designed to surround the combustion chamber of the turbojet engine and housing thrust reverse means. 
     The air inlet 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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
     Such a locking system therefore requires a large number of fixing means, the assembly and disassembly of which are long and tedious. 
     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 the adjustment of the gripping of the bolts is also long and tedious. 
     Because of these, 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 
     The disclosure 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 is attached the air intake structure 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 each capable of interaction with a complementary retaining means. 
     Thus, by equipping the nacelle with electric peripheral locking means, the locking and unlocking of the air intake structure are easily controllable and can be remotely actuated using one or several centralized controls, for example, an airplane control and/or a nacelle control. 
     The implementation of electric locking means also makes it possible to avoid the placement of manual outer locking and unlocking means (handles, cables) generating aerodynamic accidents while also avoiding the use of bolt systems, the placement and unlocking of which are long and tedious. Advantageously, the electric bolt comprises a hook capable of cooperating with a corresponding yoke. 
     Preferably, the removable air intake structure is equipped with a guide system of the rail/guideway type mounted on part of the fixed structure. Also preferably, the electric bolt(s) are each arranged essentially at the level of a guide rail. Thus, the locking means are preferably situated at the level of the stress zones and therefore allow better absorption of those stresses. 
     Advantageously, the electric bolts are associated with at least one means for detecting the locking and/or unlocking position. 
     Advantageously, the nacelle comprises a member for controlling the locking means. 
     According to one advantageous alternative embodiment, the control member is a handle, preferably retractable, capable of allowing the driving of the air intake structure in movement. 
     Advantageously, each electric locking means is capable of being locked and unlocked manually from the outside of the nacelle, for example via a hatch formed in the outer wall of the air intake structure. 
     Also advantageously, the electric locking means are capable of each receiving a mechanical inhibiting rivet designed to allow the blocking of the corresponding electric locking means. 
     Advantageously, the additional retaining means of each locking means can be adjusted in prestress. 
     According to a first alternative embodiment, the adjustment of the complementary retaining means is done using an adjusting screw capable of moving a lug having an inclined surface so as to allow adjustment of the complementary retaining means according to the direction of retention. 
     According to a second alternative embodiment, the adjustment of the complementary retaining means is done using a worm screw capable of cooperating with a threaded zone of said retaining means so as to allow translation of the retaining means along the retaining direction. 
     Advantageously, the complementary retaining means can be adjusted from outside the nacelle. 
     Preferably, the complementary retaining means are attached to the fixed structure while the electric bolts are attached to the removable structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The implementation of the invention will be better understood using the detailed description provided below with respect to the appended drawing, in which: 
         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 closed position. 
         FIG. 2  is a partial diagrammatic illustration of the air intake structure of  FIG. 1 , the air intake structure being in the opening position. 
         FIG. 3  is an enlarged partial diagrammatic illustration of a first embodiment of a locking means equipping the nacelle of  FIGS. 1 and 2 . 
         FIG. 4  is an enlarged partial diagrammatic illustration of a second embodiment of a locking means equipping the nacelle of  FIGS. 1 and 2 . 
         FIG. 5  is an enlarged partial diagrammatic illustration of a third embodiment of a locking means equipping the nacelle of  FIGS. 1 and 2 . 
         FIG. 6  is an enlarged partial diagrammatic illustration of a locking means equipping the nacelle of  FIGS. 1 and 2 , said locking means being mechanically inhibited. 
         FIG. 7  shows a first embodiment of the prestressing of a locking means equipping a nacelle according to the invention. 
         FIG. 8  shows a second embodiment of the prestressing of a locking means equipping a nacelle according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     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 attached systems such as a thrust reverser. 
     The nacelle is designed to be attached to a fixed structure of an airplane, such as a wing, via a pylon. 
     More precisely, the nacelle has a structure comprising a front section forming an air inlet  2 , a middle section (not visible) 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 illustrated). 
     The air inlet  2  is divided into two zones, i.e. on one hand, an inlet 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. 
     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 a case of the fan belonging to the middle section of the nacelle via fastening flanges  3 , integral with the downstream structure  2   b  and the case, respectively. 
     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.    
     The inner panel  21  is made from an acoustic shroud and is connected via flanges  3  to the case of the median section. 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. 
     It will be noted that alternatively, the outer panel  20  can also comprise all or part of an outer panel of the middle structure. 
     To do this, each flange  3  also supports a radial peripheral partition  5 . 
     This partition  5  can support center finders and secondary center finders extending perpendicularly to said partition  5  toward the upstream of the nacelle. 
     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. 
     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 . 
     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 . 
     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. 
     More particularly, the removable structure can be mounted, for example, on a rail  6 /guideway  7  sliding system comprising a plurality of rails  6 /guideways  7  distributed on the periphery of the air intake structure  2 . 
     According to the invention, the removable structure is maintained using locking means comprising at least one electric bolt  10  of the hook type each capable of cooperating with a complementary retaining means  11  of the yoke type. 
     In the case in point the complementary retaining means  11  are attached to the fixed structure while the electric locks  10  are attached to the removable structure. 
     The locking means can each be equipped with at least one stiffener supporting the bolt. In the case in point, the stiffeners are associated with guideways  7 , but this is not strictly necessary. 
       FIGS. 1 and 2  show the removable structure in the closed and open positions, respectively. 
     The locking and unlocking controls of the electric locking means are grouped together at the level of an outer control means of the nacelle and/or at the cockpit of the airplane. 
     The retaining means  11 , of the yoke type, are positioned on the fixed structure of the nacelle in a zone guaranteeing the best structural rigidity in order to avoid any deflection of that interface. 
     Advantageously, one may use electric bolts of known type in which at the end of the closing maneuver, a three-point system is exceeded by the system of rods driving the hook in order to guarantee optimal resistance under all of the loads seen by that equipment during flight cycle. 
     Each bolt advantageously has a screw  12  for driving the hook exceeding the bolt  10  toward the outside of the nacelle. 
     For each bolt a corresponding hatch  13  can be formed in the outer panel  20  allowing access to one end of the screw  12 . 
     By opening the hatch  13 , it is thus possible to connect, on the end of the screw  12 , a tool  9  capable of allowing manual driving of the latter. 
     The tool may advantageously be guided by a fitting  14  fixed on the inside of the outer panel  20  at the level of the hatch  13 . 
     If the rotor of the motor must be blocked to allow the movement of the driving screw  12  through the body of the motor, several solutions known by those skilled in the art can be applied such as the proposed example in which a second hole  22  is formed in the fitting  14  to allow the placement of an axle  24  for blocking the motor. 
     This embodiment is illustrated in  FIGS. 3 and 4 . 
     In normal conditions, a plug is placed inside the hatch  13  in the fitting  14  so as to restore the outer aerodynamic line. 
     The manual driving can also be done via a dedicated component of the MDU (Manual Drive Unit) type  30  connected to the drive motor of the electric bolt  10 . This embodiment is illustrated in  FIG. 5 . 
     One may also introduce, into the hatch  13 , a particular plug  15  having an appendage  15   a  capable of cooperating with the screw  12  so as to block it. Such a plug will then make it possible to mechanically inhibit the electric bolt. This configuration is illustrated in  FIG. 6 . The plug  15  may have an aerodynamic appendage visible from the outside of the nacelle in order to recall its presence. 
     At least one part of the locking means  10  are each associated with a means for signaling their locking or unlocking state and the information of which can be escalated to the cockpit or a control center, for example. 
     This signaling means can assume the form of a proximity detector situated on the yoke  11  opposite an end of the hook  10  so as to obtain an “all or nothing” type signal and ensure that the hook is sound and actually in place to perform its role. 
     The signaling means is preferably placed on a fixed element (yoke, for example) in order to reduce the disconnection interfaces, which would reduce the reliability of the system. 
     The locking means equipping a nacelle according to the invention also present prestress adjustment means. 
     Currently, the adjustment of the prestress in the mechanical locking systems is generally done by positioning a spring balance at the end of the handle, hook in contact on the yoke, then by pulling on the spring balance and verifying the traction value obtained. 
     When this value is not appropriate, it is then necessary to access the fixing system of the yoke and to adjust its axial position, then again perform the check until the desired value is obtained. 
     In the framework of an electric locking as used here, the prestress value can be checked in different ways, such as by the stress given to the motor during the locking, through a manual driving system using a dynamometric key, by a stress sensor installed on one of the mechanical parts in contact and stressed like the hook or the yoke, or by a torque limiter installed on one of the mechanical parts in contact and stressed like the hook or the yoke. 
     These various means are used to check and monitor the stress. 
     The present locking means are also equipped with adjustment means making it possible to adjust the pre-stress value when the removable structure is in the closed position. 
       FIG. 7  presents a first means for adjusting the prestress. 
     In the case in point, a fitting  40  is situated on the removable outer structure opposite the element to be adjusted (yoke  11  here) when said removable structure is in the closed position. An opening  41  is formed in the fitting so as to allow the passage of an adjustment tool such as a key. 
     Of course, for reasons of aerodynamic continuity, the opening will be made as small as possible. An aerodynamic plug may close the opening during exploitation. 
     The yoke  11  is mounted mobile in translation along the direction of locking, a lumen  42  is present capable of receiving a lug  43  having a first end of small thickness and a second end of greater thickness. 
     By moving the lug  43  using an adjusting screw  44  capable of being maneuvered owing to a tool introduced through the fitting  41 , it is possible to adjust the axial position of the yoke  11  and as a result, the stress in the hook  10  during locking. The precision of the adjustment will of course depend on the slope given to the lug  43 . 
     Of course, the access fitting  40  may be replaced by a hatch, for example, or any other means allowing access to the adjustment screw. 
       FIG. 8  presents a second means for adjusting the pre-stress. 
     In the case in point, an access hatch  50  is formed in the outer wall  20  of the removable structure opposite the element to be adjusted (yoke  11  here) when said removable structure is in the closed position. Access by fitting as previously described is of course possible. 
     The means for adjusting the pre-stress comprises a worm screw  51  cooperating with a threaded end  52  of the yoke, so as to thus allow an axial movement of the latter part when the worm screw  51  is made to rotate. 
     A locking device  53  of the worm screw is added so as to ensure resistance of the adjustment over time. 
     In order to reduce parasitic stresses and make the reading of the torque value more reliable on the dynamometric key, a specific stop for reducing friction can be inserted between the fixed support and the adjustment nut. 
     A torque limiter can also be added at the inlet of the worm screw, thereby ensuring control of the stress in the yoke without needing to use a dynamometric key. Moreover, this system can be motorized in order to ensure identical continuous stress by continuous stress check. 
     The locking can also be associated with a proximity detection of the removable upstream structure close to its closing position, said proximity detecting being able either to authorize the implementation of the locking. This makes it possible to guarantee a good distance for the gripping of the yoke by the hook. The proximity detection may potentially also be used to trigger an automatic locking as a function of that approach of the removable structure. 
     Although the invention has been described with one particular example of 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.