Abstract:
A nacelle for a turbojet engine of an aircraft is provided that includes a fan case, an internal structure positioned upstream from the fan case, and a thrust reverser positioned downstream from the fan case. The thrust reverser includes a cowl delimiting an external line (LE) and including two removable half cowls. A device for absorbing circumferential stresses are shaped so as to lock the half cowls in the closed position when it occupies a locking configuration on the one hand and for allowing the opening of the half cowls when it occupies an unlocking configuration on the other hand. The stress absorbing device is positioned under an upstream portion of a pylon and is exclusively attached to the half cowls in order to allow the opening of the two half cowls independently of the opening/closing of an external fan cowl.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/FR2011/051212 filed on May 27, 2011, which claims the benefit of FR 10/54323, filed on Jun. 3, 2010. The disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a nacelle for an aircraft turbojet engine. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Conventionally and as illustrated in  FIG. 1 , a nacelle  1  may be attached to a fixed structure SF of an aircraft or airplane, such as a wing, via a pylon or mast  2 . The nacelle  1  has a structure comprising an air intake section  3  upstream, a middle section for surrounding a fan (not visible) of the turbojet engine, and a downstream section  5  surrounding the turbojet engine and harboring a thrust reverser  50 . 
     The middle section  4  includes a case  41 , a so-called fan case, attached at its upstream end to the air intake structure  3  and at its downstream end to the downstream section  5  and thus to the thrust reverser  50 ; this fan case  41  being surrounded by an external fan cowl  40 . The fan case  41  is directly attached on the upstream portion  21  of the pylon  2 , while the downstream portion  22  of the pylon  2  is attached on the wing SF. The downstream section  5  further includes an internal structure (not visible) surrounding the turbojet engine and partly defining a ring shaped vein for letting through an airflow, this internal structure delimiting an internal line of this ring shaped vein. 
     For reasons of mass and of congestion with the external aerodynamic lines of the nacelle  1 , the pylon  2  has in its upstream portion  21  a relatively thin or not very thick structure, comparatively with its downstream portion  22 . 
     As illustrated in  FIG. 2 , in the majority of applications on airplanes and notably in applications of a turbojet engine under a wing, the thrust reverser  50  comprises a cowl defining with the internal structure the ring shaped vein, this cowl delimiting an external line LE (visible in  FIG. 3 ) of this ring shaped vein. Conventionally, the thrust reverser  50  in the closed position is maintained on the downstream end of the fan case  41  by a knife system inserted in a groove (not illustrated). 
     The cowl of the thrust reverser  50  includes two removable half cowls  51  respectively having upper edges  52  equipped with means  53  for jointing the half-cowls  51  on the pylon  2 . These jointing means  53  are shaped so as to allow pivoting of the half-cowls  51  between closed and open positions around respective longitudinal axes forming hinge lines LC. Conventionally, the joint of the half-cowls  51  on the pylon  2  is made by means of floating connecting rods  53  which define the hinge lines LC. 
     Both half cowls  51  also have free lower edges  54 , opposite to the upper edges  52 , which are generally provided with lower locking means (not illustrated such as for example a lock or hook system) designed so as to keep the half cowl  51  closed in the lower portion of the nacelle  1  (at 6 o&#39;clock). These lower locking means may for example be actuated by a lower locking handle positioned on one of the lower edges  54  and movable between a locking position and an unlocking position for the lower locking means. 
     The arrangement of the hinge lines LC allowing the opening of the half cowls  51  required for maintenance operations, should, in a wide upstream portion of the half-cowl  51 , not interfere with the hooking up of a thrust reverser  50  on the fan case  41 , with the risk of having a hyperstatic assembly and thereby generating parasitic and detrimental stresses between the thrust reverser  50  and the fan case  41 . 
     In order to rigidly bind the half cowls  51  to each other without interfering with the upstream hooking up of the half cowls  51  on the fan case  41 , the floating connecting rods  53  are installed through the pylon  2 , downstream from the upstream portion  21  (as is visible in  FIG. 3 ) wherein the pylon  2  is sufficiently thick for supporting a structural failure induced by the openings crossed by the connecting rods  53 . The floating connecting rods  53  are conventionally mounted with play through the pylon  2 , in order not to interfere during relative movements of the different structures of the nacelle  1 . 
     Now, in the case of a substantial displacement of the nacelle, there exists a risk of detaching the hooking up of the half cowls of the thrust reverser on the fan case, as this may be observed in a situation of fan blade breakage which generates very large displacements of the nacelle due to the unbalance generated by the off-balance of the shaft of the turbojet engine. 
     The state of the art may be illustrated by the teaching of document U.S. Pat. No. 4,679,750 A which discloses a nacelle including an upper safety system (upper latch assembly) which connects together the upper edges of the half cowls of the thrust reverser and which is shaped in order to lock these half cowls in the closed position when it occupies a locking configuration and for allowing opening of the half cowls when it occupies an unlocking configuration. 
     However, this upper safety system is also attached to the two external fan half cowls (fan cowl) via a connecting rod slidably mounted in the groove of a guide mounted on the external fan half cowls. Thus, this upper safety system gives the possibility of opening the half cowls of the thrust reverser only when the external fan half cowls are open. 
     SUMMARY 
     The present disclosure includes a nacelle equipped with a sufficiently strong mechanical link between both half cowls of the thrust reverser in order to be able to absorb the stresses which would tend to separate these half cowls from each other and to break the attachment of the half cowls on the fan case. 
     The nacelle is equipped with such a mechanical link between the half cowls which is positioned sufficiently close to the upstream end of the half cowls, as close as possible to the tie of the half cowls on the fan case, in order to not risk detaching the attachment of the thrust reverser on the fan case under very large displacements, notably during a fan blade failure. 
     The nacelle is also equipped with a mechanical link between the half cowls which is sufficiently close to the upstream end of the half cowls, which does not require piercing or crossing of the pylon at its upstream portion. Indeed, in this relatively thin upstream portion of the pylon, the structure of the pylon would risk not mechanically withstanding a structural continuity failure induced by an opening. 
     Additionally, the nacelle is equipped with a mechanical link between the half cowls which allows locking of the half cowls upon closing and allowing the half cowls to be opened, independently of the opening/closing situation of the external fan cowl. 
     For this purpose, the present disclosure includes a nacelle for a turbojet engine of an aircraft, including:
         a fan case intended to surround a fan upstream from the turbojet engine, said fan case being surrounded by an external fan cowl and being attached onto a pylon supporting the nacelle;   an internal structure positioned downstream from the fan case and intended to surround the turbojet engine; and   a thrust reverser positioned downstream from the fan case and comprising a cowl defining with the internal structure a ring shaped vein for letting through an airflow, said cowl delimiting an external line of said ring shaped vein and including two removable half-cowls respectively having upper edges equipped with means for jointing the half cowls on the pylon, said jointing means being shaped so as to allow pivoting of the half cowls between closed and open positions around respective longitudinal axes forming hinge lines; and   a device for absorbing circumferential stresses connecting together the upper edges of the half cowls, said stress absorbing device being shaped so as to lock the half cowls in the closed position when it occupies a locking configuration on the one hand and to allow the opening of the half cowls when it occupies an unlocking configuration on the other hand, the nacelle according to the present disclosure being remarkable in that the stress absorbing device is positioned under an upstream portion of the pylon, upstream from the means for jointing the half cowls on the pylon, and is inserted between the external line of the ring shaped vein and the two hinge lines, and in that the stress absorbing device is exclusively attached to the half cowls in order to allow the opening of the two half cowls independently of the opening/closing of the external fan cowl.       

     Thus, the stress absorbing device is positioned under the upstream portion of the pylon, shifted relatively to the hinge lines and above the external line of the ring shaped vein, so that it is located sufficiently close to the upstream end of the half cowls, as close as possible to the tie of the half cowls on the fan case, while forming a sufficiently strong mechanical link (in its locking configuration/position) in order to absorb the stresses which would tend to separate these half cowls from each other. This stress absorbing device transversely connects the upper edges of the half cowls, so that it is mounted in the upper (or high) portion of the nacelle at 12 o&#39;clock. 
     Further, the stress absorbing device is not attached to the external fan cowl and its operation is independent of the opening/closing situation of this external fan cowl. 
     According to one feature, the fan case has at its downstream end, upper means for attaching said fan case on the upstream portion of the pylon, and the stress absorbing device is positioned between said upper attachment means and the jointing means. 
     In a particular form, the stress absorbing device includes at least one actuator equipped with a rod slidably mounted in a hollow body between a retracted position in the body and a deployed position out of the body, said rod having a first end attached on the upper edge of one of the half cowls and a second opposite end extending into the body, said body having a first end provided with an orifice for letting through the rod and a second opposite end attached onto the upper end of the other half cowl, and the actuator further includes locking/unlocking means cooperating with the rod in order to not lock/unlock the rod in the retracted position. 
     In this form, the actuator may correspond to an actuator system with constant links, it being understood that such a system of an actuator with constant links designates a permanently attached actuator on both half cowls of the thrust reverser, so that it is not necessary to dismantle one of the attachments of the actuator in order to allow the opening of the half cowls of the thrust reverser, the maneuver for opening the half cowls being allowed by the internal system of the actuator during the release or exit of the actuator rod. 
     The installation of the actuator on the half cowls may be accomplished at the same time as the mounting of the means for jointing the half cowls on the pylon, in the upper portion for the nacelle (at 12 o&#39;clock). The control for unlocking the locking/unlocking means of the actuator is preferably accomplished remotely since the actuator once it is installed, is difficult to access just like the hinge lines defined by the jointing means. 
     According to a possibility of the present disclosure, the locking/unlocking means include:
         blocking means positioned in the body and cooperating with the rod, and notably with the second end of the rod, for blocking the latter in its retracted position, said blocking means being movably mounted in the body between a blocking position and unblocking position for the rod; and   driving means designed for driving the displacement the blocking means between the blocking and unblocking positions and vice versa.       

     According to other advantageous characteristics of this form with blocking means and driving means:
         the blocking means include at least one part forming a hook having a free end designed for cooperating with the second end of the rod, said part forming a hook being translationally movable in the body between the blocking position in which the free end of the part forming a hook cooperates with the second end of the rod and the unblocking position in which the free end of the part forming a hook is moved away from the second end of the rod and allows displacement of the rod;   the rod is at least partly threaded, the blocking means include a nut mounted on the threading of the rod inside the body and the driving means include a rotary motor designed for driving the rod into rotation;   the rotary motor is controlled by a system for opening the two half cowls of the thrust reverser so that the speed of rotation of the rod imposed by the rotary motor allows the nut to be driven into translation more rapidly than the opening of both half cowls by the opening system, thus the rotary motor of the actuator allows a disengagement advance of the internal nut so that the latter does not interfere during the opening sequence of the half cowls; or alternatively   the rotary motor is independent of a system for opening the system of both half cowls of the thrust reverser, and the rod has on its second end a part forming an abutment for the nut, and in this case the rotary motor of the actuator performs the complete maneuver for disengaging the nut before starting the sequence for opening the half cowls.       

     For this form with an actuator, the present disclosure also relates to the features hereafter:
         the actuator locks the half cowls in an optional direction, either in compression (direction for retracting the rod) or in extension (direction for moving out or releasing the rod) with respect to the axis of the actuator, according to the need of one skilled in the art, or alternatively the actuator locks the half cowl in both directions simultaneously (both in compression and in extension);   the actuator is with a lock and/or electric drive, or alternatively the actuator is with a lock and/or a mechanical drive;   the actuator is with a remote lock;   the actuator is coupled with a system for opening the half cowls, and more particularly coupled with the logic for opening the half cowls;   the actuator has locking means for the purpose of closing, these locking means with a closing purpose, being preferably shaped in order to assist with the maneuver for closing the half cowl;   the actuator is associated with a maneuvering system for opening the half cowls simultaneously, and in this case the motor of the actuator (for driving the rod) is maneuvered at the same time as the control for opening the half cowls of the thrust reverser; or alternatively   the actuator is associated with a maneuvering system for opening the half cowls in a sequential mode, and in this case the motor of the actuator (for driving the rod) is maneuvered before controlling the opening of the half cowls of the thrust reverser.       

     In another form, the stress absorbing device includes at least one lock system provided with: 
     a hook mounted on the upper edge of one of the half cowls; 
     a hooking-up member mounted on the upper edge of the other half cowl, said hook being movable between a locking position in which the hook restrainedly cooperates with the hooking-up member in the closed or substantially closed position of the half cowls, and an unlocking position in which the hook does not cooperate with the hooking-up member and allows opening of the half cowls; and 
     means for actuating said hook between the locking and unlocking positions. 
     In this form, the lock system corresponds to a system with a disconnectable link, allowing remote unhooking or disconnection of the link between both half cowls when the lock system is in the unlocking position. 
     According to a feature, the nacelle further includes lower locking means positioned on the free lower edges of the half cowls opposite to the upper edges and designed for keeping the half cowls closed, said lower locking means being actuated by a lower locking handle positioned on one of said lower edges and movable between a locking position and an unlocking position of the lower locking means, the means for actuating the lock system include an actuation handle connected to the hook and positioned on one of the lower edges of the half cowls, said actuation handle being movable between a position for locking the hook and a position for unlocking it, and the lower locking handle and the actuation handle are positioned relatively to each other so that the lower locking handle prevents maneuvering of the actuation handle and blocks it in its locking position as long as said lower locking handle is in its locking position. 
     In a particular form, the upper edges of the half cowls support abutments which will bear against each other in a junction plane of the half cowls when they are in the closed position and the hooking-up member of the lock system is fixedly mounted on the upper edge of the relevant half cowl and substantially extends in said junction plane. 
     Alternatively, the upper edges of the half cowl support abutments which will bear against each other in a junction plane of the half cowls when they are in the closed position, and the hooking-up member of the lock system is mounted on the upper edge of the relevant half cowl via a locking connecting rod having a first jointed portion on said upper edge and a second movable portion relatively to the first portion and supporting said hooking up member, so that said hooking-up member extends in a plane laterally shifted relatively to the junction plane. 
     This second portion of the locking connecting rod advantageously has guiding means mounted on the pylon. 
     For this form with a lock system, the present disclosure also relates to the features hereafter:
         the lock system is a system with a centered hook, i.e. the hook is located substantially in the junction plane between both half cowls;   the lock system is a system with an excentered hook, i.e. the hook is transversely shifted relatively to the junction plane between both half cowls, while being closer to one of the half cowls than to the other.       

     Advantageously, when a lock system with an actuator is used, the stress absorbing device is positioned as close as possible to the internal face of the pylon, and more particularly to the internal face of the upstream portion of the pylon, with a substantially balanced distribution of the hooking-up points of the stress absorbing device on the half cowls and of the joint points of the half cowls on the pylon. In this way, the kinematics of the maneuver for locking/unlocking the stress absorbing device shows that it will not be brought closer or by only very little to the internal face of the pylon regardless of the opening range of the half cowls. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       Other features and advantages of the present disclosure will become apparent upon reading the detailed description hereafter, of several non-limiting exemplary applications, made with reference to the appended drawings wherein: 
         FIG. 1 , having already been the subject of comments, is a schematic perspective view of a conventional nacelle supported by a pylon; 
         FIG. 2 , having already been the subject of comments, is a schematic cross-sectional view of a conventional nacelle supported by a pylon, in a sectional plane of the thrust reverser; 
         FIG. 3  is a schematic partial side view of the nacelle of  FIG. 2 , illustrating the downstream end of the fan case and the upper portion of the pylon; 
         FIG. 4  is a schematic cross-sectional view of a nacelle according to the present disclosure, in a sectional plane of the thrust reverser; 
         FIG. 5  is an enlarged view of the area v of  FIG. 4 ; 
         FIGS. 6   a  to  6   g  are schematic sectional views of a first stress absorbing device for a nacelle according to the present disclosure, in different positions or configurations; 
         FIGS. 7   a  and  7   b  are schematic sectional views of a second stress absorbing device for a nacelle according to the present disclosure, in two different positions or configurations; 
         FIGS. 8   a  to  8   f  are schematic sectional views of a third stress absorbing device for a nacelle according to the present disclosure, in different positions or configurations; 
         FIGS. 9   a  to  9   d  are schematic sectional views of a fourth stress absorbing device for a nacelle according to the present disclosure, in different positions or configurations; and 
         FIGS. 10   a  to  10   d  are schematic sectional views of a fifth stress absorbing device for a nacelle according to the present disclosure in different positions or configurations. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     A nacelle  1  according to the present disclosure is of the same type as the one described above with reference to  FIGS. 1 to 3 , except that it further includes a device for absorbing circumferential stresses, like one of the stress absorbing devices,  6 ,  7 ,  8 ,  9 ,  10  respectively illustrated in  FIGS. 6 to 9 . 
     Generally, the stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  connects together the upper edges  52  of the half cowls  51  of the thrust reverser  50 , and is therefore located in the upper portion of the nacelle  1 , otherwise at 12 o&#39;clock, as visible in  FIGS. 4 and 5 . 
     The stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  is located in an area Z (illustrated in  FIG. 3 ) below the upstream portion  21  of the pylon  2 , above or close to the external line LE of the ring shaped vein and shifted relatively to the hinge lines LC, so that this stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  is inserted between the external line LE of the ring shaped vein and the two hinge lines LC and is sufficiently close to the upstream end of the half cowls  51 , as close as possible to the tie of the half cowls  51  on the fan case  41  in order to be able to absorb the stresses which would tend to separate these half cowls  51  from each other. 
     Generally, the stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  is shaped in order to occupy:
         a locking configuration/position in which it locks the half cowls  51  in a closed position; and   an unlocking configuration/position in which it allows or authorizes the opening of the half cowls  51 .       

     As visible in  FIGS. 4 and 5 , the stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  is positioned as close as possible to the internal face of the pylon  2 , and more particularly to the internal face of the upstream portion  21  of the pylon  2 , with a substantially balanced distribution of the hooking up points PA 1 , PA 2  of the stress absorbing device  6 ,  7 ,  8 ,  9 ,  10  on the half cowls  51  (and more specifically on the other edges  52  of the half cowls  51 ) and the joint points  53  of the half cowls  51  on the pylon  2 . The hooking up points are referenced as PA 1  when the stress absorbing device is in the locking configuration/position and the half cowls  51  are in the closed position, and are referenced as PA 2  when the stress absorbing device is in an unlocking configuration/position and the half cowls  51  are in the open position. 
     This balance is expressed by the fact that the displacement angles AN 1  and AN 2  between the points PA 1  and PA 2  relatively to the vertical passing through the corresponding joint point  53  are substantially equal. 
     According to a first form illustrated in  FIGS. 6   a  to  6   g , the stress absorbing device  6  is made in the form of an actuator system with constant links and clutching. 
     This stress absorbing device  6  includes an actuator equipped with a rod  61  slidably mounted in a hollow body  62  between a retracted position in the body  62  and a deployed position out of the body  62 . 
     The rod  61  has a first jointed end  611  on the upper edge of one of the half cowls and a second opposite end  612  extending into the body  62 ; this first end  611  forming an anchoring point for the stress absorbing device  6  on one of the half cowls. The second end  612  of the rod  6  has a protrusion. Two respectively internal  613  and external  614  abutments are attached on the rod  61  so as to limit the displacement thereof, whether this be in the extension direction (displacement towards the deployed position) or in the retract direction (displacement towards the retracted position). 
     The body  62  has a first end  621  provided with an orifice for letting through the rod  61  and a second solid jointed opposite end  622  on the upper edge of the other half cowl; this second end  622  forming an anchoring point of the stress absorbing device  6  on the other half cowl. The body  62  has on its internal face a step or recess  620 , for example made as a reduction in the thickness from the second end  622  to the first end  621  of the body  62 ; this step or recess  620  has a ramp shape and is located at a predetermined distance from the second end  622  of the body  62 . 
     The stress absorbing device  6  further includes locking/unlocking means cooperating with the rod  61  in order to lock/unlock the rod  61  in the retracted position. These locking/unlocking means include:
         a part forming a hook  63  positioned in the bottom of the body  62 , opposite to its first end  621 , and designed for cooperating with the protrusion of the second end  612  of the rod  61  in order to block the latter in its retracted position, this part forming a hook  63  being movable in the body  62  between a position for blocking the rod  61  and a position for unblocking it; and   driving means  64 ,  65  designed for driving the displacement of the part forming a hook  63  between the blocking and unblocking positions and vice versa.       

     Of course other locking/unlocking means may be contemplated, such as for example a screw/nut system not shown. 
     The part forming a hook  63  includes at least two fingers having first free ends with the shape of a hook adapted so as to grasp and block the protrusion of the second end  612  of the rod  61 . 
     The driving means include a slider  64  on which are pivotally mounted the fingers of the part forming a hook  63  and a translational displacement system (not shown) for the slider  64 , such as a motor (preferably an electric motor) or a remotely actuated manual system, such as for example a cable device driven by rotation or by traction. The fingers of the part forming a hook  63  have second ends, opposite to the first end, jointed on the slider  64 . 
     The slider  64  may for example have an external threading and be mounted inside a nut  65  positioned in the bottom of the body  62 ; this nut  65  being driven into rotation, for example by a rotary motor, thereby leading to translational movement of the slider  64 . 
     The principle of this first form includes unlocking the blocking means, in this case the part forming a hook  63  of the rod  61 , in order to let the rod  61  be freely displaced during the maneuver for opening at least one of the two half cowls of the thrust reverser. During the maneuver for closing the half cowls, the locking/unlocking means of the stress absorbing device are put into action at the end of the closing of the half cowls in order to end this closing maneuver and to finally lock the half cowls in the closed position by locking the rod  61  in its retracted position. 
     The operation of this stress absorbing device  6  is described hereafter with reference to  FIGS. 6   a  to  6   g  which illustrate successive configurations of the stress absorbing device  6 . 
       FIG. 6   a  illustrates the stress absorbing device  6  in a locking configuration, when the half cowls are in the closed position, when the rod  61  is in a retracted position with the fingers of the part forming a hook  63  which hook up the protrusion of the second end  612  of the rod  61 , thereby blocking the rod  61  in the extend direction (towards the left in the figure); the external abutment  614  bearing against the first end  621  of the body  62 , thereby blocking the rod  61  in the retract direction (towards the right in the figure). 
       FIG. 6   b  illustrates the beginning of the maneuver for unlocking the stress absorbing device  6 , concomitantly at the beginning of the maneuver for opening one or both half cowls, where the slider  64  begins to move towards the first end  621  of the body  62 , as schematized by the arrow CS, leading to the displacement of the fingers of the part forming a hook  63  towards the step or recess  620  provided on the internal face of the body  62 ; the fingers of the part forming a hook  63  being detached from the protrusion of the second end  612  of the rod  61 . 
       FIG. 6   c  illustrates the unlocking of the stress absorbing device  6 , wherein the slider  64  is moved until the fingers of the part forming a hook  63  reach and engage into the step or recess  620  provided on the internal face of the body  62  and which are moved apart from each other according to an opening movement of the petal type, by means of an elastic member (not shown) shaped so as to separate and move away the fingers of the part forming a hook  63  from each other; the separation of the fingers of the part forming a hook  63  is such that, from now on, these fingers can no longer cooperate with the protrusion of the second end  612  of the rod  61  and thus can no longer block the rod  61 , so that the rod  61  is free to be displaced in the extend direction. 
       FIG. 6   d  illustrates the stress absorbing device  6  which is unlocked during the opening of the half cowls of the thrust reverser, wherein said stress absorbing device  6  allows this opening of the half cowls. The rod  61  is from now on free of any rectilinear movement, as schematized by the arrow TL, and the actuator acts like a simple piston without any maneuvering stress during the opening of the half cowls. 
       FIG. 6   e  illustrates the stress absorbing device  6  which is unlocked during the closing of the half cowls of the thrust reverser. Upon closing the half cowls, the rod  61  enters the body  62  as schematized by the arrow TR, until it reaches a transient position close to the locking position as illustrated in  FIGS. 6   a  and  6   b , wherein the external abutment  614  does not yet bear against the first end  621  of the body  62 . Indeed, certain parameters ensure that the rod  61  cannot be repositioned alone in abutment at the end of travel, such that the flexibility of the structure, the seal gaskets, the manufacturing and positioning tolerances of the constitutive elements of the stress absorbing device  6 . In this transient position, the protrusion of the second end  612  of the rod  61  is positioned inside the fingers of the part forming a hook  63 . 
       FIG. 6   f  illustrates the beginning of the maneuvering for locking the stress absorbing device  6 , wherein the rod  61  is in its transient position and wherein the slider  64  begins to move towards the second end  622  of the body  62 , as illustrated by the arrow CR, leading to the displacement of the fingers of the part forming a hook  63  in this same direction, which causes disengagement of the fingers of the part forming a hook  63  out of the step or recess  620  (the ramp shape facilitating this disengagement). Thus, the fingers of the part forming a hook  63  move closer to each other and again close on the protrusion of the second end  612  of the rod  61  in order to block this rod  61 ; the transient position of the rod  61  is such that a play between the first free hook-shaped ends of the fingers and the protrusion of the rod  61  is provided for allowing the fingers to retract on the rod  61  without any stress. Ensuring proper positioning of the protrusion of the rod  61  with respect to the fingers may be accomplished by any suitable detection means known to one skilled in the art, such as for example a proximity detector. 
       FIG. 6   g  illustrates the end of the maneuver for locking the stress absorbing device  6 , wherein the slider  64  ends its displacement towards the second end  622  of the body  62 , as schematized by the arrow CR, so that the fingers of the part forming a hook  63  will bear against the protrusion of the second end  612  of the rod  61  and these fingers drive the rod  61  as far as the locking position illustrated in  FIGS. 6   a  and  6   b . Thus, the stress absorbing device  6  continues the rectilinear closing movement of the rod  61  until it abuts at the end of travel. At the end of this movement, the driving means are automatically disconnected and locked in position. 
     According to a second form illustrated in  FIGS. 7   a  and  7   b , the stress absorbing device  7  is made in the form of an actuator system with constant links and with a screw/nut. 
     This stress absorbing device  7  includes an actuator equipped with a rod  71  at least partly threaded and slidably mounted in a hollow body  72  between a retracted position of the body  72  and a deployed position out of the body  72 . 
     The rod  71  has a first jointed end  711  on an upper edge of one of the half cowls and a second opposite end  712  extending into the body  72 ; this first end  711  forming an anchoring point of the stress absorbing device  7  on one of the half cowls. Two respectively internal  713  and external  714  abutments are attached on the rod  71  for limiting the displacement thereof, whether this is at the exit or at the entrance; the internal abutment  713  being attached onto the second end  712  of the rod  71 . 
     The stress absorbing device  7  further includes locking/unlocking means cooperating with the rod  71  for locking/unlocking the rod  71  in the retracted position. These locking/unlocking means include:
         a nut  73  mounted on the threading of the rod  71  inside the body  72 ; and   a rotary motor  74  designed for driving the rod  71  into rotation, wherein the rotary motor  74  is controlled, via links  75 , by a system (not shown) for opening both half cowls of the thrust reverser so that the speed of rotation of the rod  71  imposed by the rotary motor  74  allows the nut  73  to be driven into translation more rapidly than upon opening of both half cowls by the opening system.       

     The principle of this second form consists of unlocking the locking means, in this case the nut  73 , of the rod  71 , in order to let the rod  71  be freely displaced during the maneuver for opening at least one of the two half cowls of the thrust reverser. During the maneuver for closing the half cowls, the locking/unlocking means of the stress absorbing device  7  are put into action at the end of the closing of the half cowls in order to end this closing maneuver and to finally lock the half cowls in the closed position by locking the rod  71  in its retracted position. 
     In this second form, the locking/unlocking of the stress absorbing device  7  is accomplished in synchronization with the opening/closing of the half cowls achieved by the opening system. In this second form, the rod  71  freely slides through the body  72  with the association of the nut  73  stopped in translation between the first end  721  of the body  72  and the internal abutment  713  provided on the rod  71 . In an alternative not shown, the rod is directly screwed through the body, more specifically on the first end of the body. 
     The operation of this stress absorbing device  7  is described hereafter with reference to the  FIGS. 7   a  and  7   b  which illustrate two successive configurations of the stress absorbing device  7 . 
       FIG. 7   a  illustrates the stress absorbing device  7  in the locking configuration, when the half cowls are in the closed position, wherein the rod  71  is in a retracted position, with the nut  73  in abutment against the first end  721  of the body  72  thereby blocking the rod  71  in the extend direction (towards the left in the figure) and with the external abutment  714  bearing against the first end  721  of the body  72  thereby blocking the rod  71  in the retract direction (towards the right in the figure). 
       FIG. 7   b  illustrates the maneuver for unlocking the stress absorbing device  7 , concomitantly to the maneuver for opening one or both half cowls, wherein the system for opening the half cowls controls the rotary motor  74  for driving the rod  71  into rotation (as schematized by the arrow R) with a speed greater than that for the opening of the half cowls, causing displacement of the nut  73  towards the second end  712  of the rod  71 , as schematized by the arrow DE. The nut  73  is then detached from the first end  721  of the body  72 , consequently allowing exit of the rod  71 . The speed difference ensures that the nut  73  moves away more rapidly from the first end  721  of the body  72 , the rod  71  is displaced towards the exit, in other words towards the deployed position; the purpose being to avoid that the nut  73  interferes with this rod  71  exit and therefore with the opening of the half cowls. 
     The length of the rod  71  is defined so that the nut  73  will not come into contact with the internal abutment  713  provided on the second end  712  of the rod  71  before the end of the complete opening of the half cowls of the thrust reverser. Thus, the actuator may maneuver without any stress during the opening of the half cowls. 
     The maneuver for locking the stress absorbing device  7  is carried out concomitantly with the maneuver for closing the half cowls, on the same principle as described below with the rod  71  which enters the body  72 , the rotary motor  74  turns in the other direction and the nut  73  comes back into contact with the first end  721  of the body  72 . 
     According to a third form illustrated in  FIGS. 8   a  to  8   f , the stress absorbing device  8  is also made in the form of an actuator system with constant links and with a screw/nut. 
     This stress absorbing device  8  includes an actuator equipped with an at least partly threaded rod  81  and slidably mounted in a hollow body  82  between a retracted position of the body  82  and a deployed position out of the body  82 . 
     The rod  81  has a first jointed end  811  on the upper edge of one of the half cowls and a second opposite end  812  extending into the body  82 ; this first end  811  forming an anchoring point of the stress absorbing device  8  on one of the half cowls. Two respectively internal  813  and external  814  abutments are attached on the line  81  for limiting displacement thereof, whether this be at the exit or at the entrance; the internal abutment  813  being mounted on the second end  812  of the rod  81 . 
     The stress absorbing device  8  further includes locking/unlocking means cooperating with the rod  81  for locking/unlocking the rod  81  in the retracted position. These locking/unlocking means include:
         a nut  83  mounted on the threading of the rod  81  inside the body  82 ; and   a rotary motor  84  designed for driving the rod  81  into rotation.       

     Unlike the second form, this rotary motor  84  of the third form is independent of a system for opening both half cowls of the thrust reverser. The rotary motor  84  may be of the type with an electric or manual drive. 
     The principle of this third form includes unlocking the blocking means, in this case the nut  83  of the rod  81 , in order to let the rod  81  be freely displaced and allow the maneuver for opening at least one of the two half cowls of the thrust reverser. During the maneuver for closing the half cowls, the locking/unlocking means of the stress absorbing device  8  are put into action at the end of the closing of the half cowls in order to end this closing maneuver and to finally lock the half cowls in the closed position by locking the rod  81  in its retracted position, by bringing back the nut  83  into abutment against the first end  821  of the body  82 . 
     In this third form, the locking/unlocking of the stress absorbing device  8  is achieved sequentially as compared with the opening/closing of the half cowls achieved by the system for opening the half cowls. In this third form, the rod  81  freely slides through the body  82  with the association of the nut  83  stopped in translation between the first end  821  of the body  82  and the internal abutment  813  provided on the rod  81 . 
     The operation of this stress absorbing device  8  is described hereafter with reference to  FIGS. 8   a  to  8   f  which illustrate successive configurations of the stress absorbing device  8 . 
       FIG. 8   a  illustrates the stress absorbing device  8  in the locking configuration, when the half cowls are in a closed position, wherein the rod  81  is in a retracted position, with the nut  83  in abutment against the first end  821  of the body  82  thereby blocking the rod  81  in the extend direction (towards the left in the figure), and with the external abutment  814  bearing against the first end  821  of the body  82  thereby blocking the rod  81  in the retract direction (towards the right in the figure). 
     In order to initiate the maneuver for unlocking the stress absorbing device  8 , prior to the maneuver for opening one or both half cowls, the rotary motor  84  is actuated and drives the rod  81  into rotation (as schematized by the arrow R), driving the displacement of the nut  83  towards the second end  812  of the rod  81 , as schematized by the arrow DE. 
       FIG. 8   b  illustrates the ends of the maneuver for unlocking the stress absorbing device  8 , wherein the nut  83  has been displaced by an unlocking maneuver, until it bears against the internal abutment  813  provided on the second end  812  of the rod  81 . If the motor  84  has an electric drive, the latter is no longer powered at the end of this unlocking maneuver. 
       FIG. 8   c  illustrates the stress absorbing device  8  in the unlocked configuration allowing the opening of the half cowls of the thrust reverser. Once the stress absorbing device  8  is in the unlocking configuration, the maneuver for opening the half cowls is engaged, the rod  81  being free to be freely displaced and to exit from the body  82  along a rectilinear movement, as illustrated by the arrow TS. The actuator then acts as a simple piston without any maneuvering stress during the opening of the half cowls, the nut  83  remains bearing against the internal abutment  813 . 
       FIG. 8   d  illustrates the stress absorbing device  8  in the unlocked configuration allowing the closing of the half cowls of the thrust reverser. The maneuver for closing the half cowls is engaged, the rod is free to be freely displaced and to enter the body  82  along a rectilinear movement, as schematized by the arrow TE. The actuator still acts as a simple piston without any maneuvering stress during the closing of the half cowls, the nut  83  still remains bearing against the internal abutment  813 . The rod  81  enters the body  82  until it reaches a transient position close to the locking position illustrated in  FIGS. 8   a  and  8   b , wherein the external abutment  814  does not yet bear against the first end  821  of the body  82 . Indeed, certain parameters ensure that the rod  81  cannot be repositioned by itself in abutment at the end of travel, such as the flexibility of the structure, the seal gaskets, the manufacturing and positioning tolerances of the constitutive members of the stress absorbing device  8 . 
       FIG. 8   e  illustrates the beginning of the maneuver for locking the stress absorbing device  8 , wherein the rod  61  is in its transient position and wherein the rotary motor  84  drives the rod  81  into rotation, in the opposite direction with respect to the previous one, so that the nut  83  begins to move towards the first end  821  of the body  82 , as schematized by the arrow RE, leading this nut  83  to bearing against this first end  821  of the body  82 . 
       FIG. 8   f  illustrates the end of the maneuver for locking the stress absorbing device  8 , wherein the rotary motor  84  continues to rotate the rod  81  so that the nut  83  will tighten the external abutment  814  against the first end  821  of the body  82 . Thus, the rod  81  returns to its locked position with the nut  83  in abutment against the first end  821  of the body  82  thereby blocking the rod  81  in the extend direction, and with the external abutment  814  bearing against the first end  821  of the body  82  thereby blocking the rod  81  in the retract direction. At the end of this movement, the rotary motor is automatically disconnected and locked in position. 
     According to a fourth form illustrated in  FIGS. 9   a  to  9   d , the stress absorbing device  9  is made in the form of a centered system with a disconnectable link. 
     This stress absorbing device  9  includes a system with a lock approximately positioned in a middle plane of the nacelle, substantially corresponding to the junction plane of both half cowls  51  of the thrust reverser. This lock system includes:
         a hook  91  mounted on the upper edge  52  of one of the half cowls  51 ;   a hooking-up member  92  mounted on the upper edge  52  of the other half cowl  51 , the hook  91  being movable between a locking position in which the hook  91  cooperates with restraint with the hooking-up member  92  in the closed or substantially closed position of the half cowls  51 , and an unlocking position in which the hook  92  does not cooperate with the hooking-up member  92  and allows opening of the half cowls  51 ; and   means  93 ,  94  for actuating the hook  92  between the locking and unlocking positions.       

     The upper edges  52  of the half cowls  51  support abutments  55  which bear against each other in the junction plane of the half cowls  51  when they are in the closed position. The hooking up member  92  of the lock system is fixedly mounted on the upper edge  52  of the relevant half cowls  51  and substantially extends in this junction plane. 
     The actuation means may be shaped so as to electrically or manually (mechanically) actuate the lock system remotely. In the example illustrated in  FIGS. 9   a  to  9   d , the actuation is manual and is carried out by a return through a cable  94  on an actuation handle  93  positioned in the lower portion of the nacelle (at 6 o&#39;clock). In other words the means for actuating the lock system includes the actuation handle  93  connected to the hook  91  through a cable control system  94 , this actuation handle  93  being positioned on one of the lower edges (not visible) of the half cowls  51 . The actuation handle  93  is movable between a position for locking the hook  91  and a position for unlocking it. 
     In the example illustrated in  FIGS. 9   a  to  9   d , the nacelle further includes lower locking means (not visible and notably of the lock type) positioned on free lower edges of the half cowls  51  and designed so as to keep the half cowls  51  closed, so that these lower locking means are positioned in the lower portion of the nacelle (at 6 o&#39;clock). These lower locking means are actuated by a lower locking handle PIV positioned on one of these lower edges, in other words in the lower portion of the nacelle (at 6 o&#39;clock), and this lower locking handle PIV is movable between a locking position and an unlocking position of the lower locking means. 
     As explained hereafter, the lower locking handle PIV and the actuation handle  93  are positioned relatively to each other so that the lower locking handle PIV prevents maneuvering of the actuation handle  93  and blocks it in its locking position as long as this lower locking handle PIV is in its locking position. Also, closing again the half cowls  51  of the thrust reverser can only be accomplished when the locking is carried out (hook  91  in the locking position) with the actuation handle  93  closed in the locking position. 
     The operation of this stress absorbing device  9  is described hereafter with reference to  FIGS. 9   a  to  9   d  which illustrate successive configurations of the stress absorbing device  9  and of the half cowls  51 . 
       FIG. 9   a  illustrates the stress absorbing device  9  in the locking configuration with the half cowls  51  in the closed position, wherein the hook  91  restrainedly cooperates with the hooking-up member  92 , the actuation handle  93  is in the locking position, and the lower locking handle PIV is in the locking position so that it prevents maneuvering of the actuation handle  93 . The hook  91  is advantageously provided for locking three protruding points in order to guarantee the safety of the locking. 
       FIG. 9   b  illustrates the beginning of the maneuver for opening the half cowls  51 , with the stress absorbing device  9  still in the locking configuration and the half cowls  51  still in a closed position, wherein the hook  91  still restrainedly cooperates with the hooking up member  92 , the actuation handle  93  is still in the locking position and the lower locking handle PIV is now in the unlocking position. In spite of the unlocking of the lower locking means, the half cowls  51  cannot yet be opened since the stress absorbing device  9  in the unlocking position in a locking configuration. 
       FIG. 9   c  illustrates the continuation of the maneuver for opening the half cowls  51 , wherein the actuation handle  93  has switched into its unlocking position, following the switching beforehand of the lower locking handle PIV into its unlocking position. Accordingly, the hook  91  disengages from the hooking up member  92  and the stress absorbing device  9  passes into the unlocking configuration. 
       FIG. 9   d  illustrates the end of the maneuver for opening the half cowls  51 , wherein at least one of the half cowls  51  may open by pivoting around its jointing points  53 , as illustrated by the arrow P, since the stress absorbing device  9  is in the unlocking position, just like the lower locking means. 
     According to a fifth form illustrated in  FIGS. 10   a  to  10   d , the stress absorbing device  10  is made in the form of a decentered system with a disconnectable link. 
     This stress absorbing device  10  includes a shifted lock system relatively to a middle plane of the nacelle substantially corresponding to the junction plane of the two half cowls  51  of the thrust reverser. This lock system includes:
         a hook  101  mounted on the upper edge  52  of one of the half cowls  51 , in a side portion relatively to the junction plane of the half cowl  51 , advantageously in a reinforced area of the relevant half cowl  51 ;   a hooking up member  102  mounted on the upper edge  52  of the upper half cowl  51 , the hook  101  being movable between a locking position in which the hook  101  restrainedly cooperates with the hooking-up member  102  in the closed or substantially closed position of the half cowls  51 , and an unlocking position in which the hook  102  does not cooperate with the hooking-up member  102  and allows the opening of the half cowls  51 ; and   actuation means  107 ,  108  of the hook  101  between the locking and unlocking positions.       

     The upper edges  52  of the half cowls  51  support abutments  55  which will bear against each other in the junction plane of the half cowls  51  when they are in a closed position. The hooking            up member  102  of the lock system is mounted on the upper edge  52  of the relevant half cowl  51  via a locking connecting rod  103  having a first jointed portion  105  on this upper edge  52  and a second movable portion  104  relatively to the first portion  105  and supporting the hooking-up member  102 , so that this hooking-up member  102  extends in a plane laterally shifted with respect to the junction plane. The second portion  104  of the locking connecting rod  103  has guiding means  106  mounted on the pylon  2 . The locking connecting rod  103  is thus jointed around its hooking up point on the half cowl  51  (at its first portion  105 ), and it is guided in its kinematics by the guiding means  106  which may be borne by the pylon  2 . The hooking-up member  102 , mounted on the locking connecting rod  103  remains close to the structure of the pylon  2  through the guiding means  106  upon opening the half cowls  51  in order to avoid any interference with the surrounding structures. The arrangement of the guiding means  106  is provided for allowing the hook  101  to grasp or catch without any stress the hooking-up member  102  upon closing the half cowls  51  again.
     The actuation means may be shaped so as to electrically or manually (mechanically) actuate the lock system remotely. In the example illustrated in the  FIGS. 10   a  to  10   d , the actuation is manual and is carried out by a return via a cable  108  onto an actuation handle  107  positioned in the lower portion of the nacelle (at 6 o&#39;clock). In other words, the means for actuating the lock system include the actuation handle  107  connected to the hook  101  through a cable control system  108 , this actuation handle  108  being positioned on one of the lower edges (not visible) of the half cowls  51 . The actuation handle  107  is movable between a position for locking the hook  101  and a position unlocking it. 
     In the example illustrated in  FIGS. 10   a  to  10   d , just like the one of  FIGS. 9   a  and  9   d , the nacelle further includes lower locking means (not visible and notably of the lock type) positioned on the free lower edges of the half cowls  51  and designed so as to keep the half cowls  51  closed, so that these lower locking means are positioned in the lower portion of the nacelle (at 6 o&#39;clock). These lower locking means are actuated by a lower locking handle PIV positioned on one of these lower edges, in other words in the lower portion of the nacelle (at 6 o&#39;clock), and this lower locking handle PIV is movable between a locking position and an unlocking position of the lower locking means. 
     As explained hereafter, the lower locking handle PIV and the actuation handle  107  are positioned relatively to each other so that the lower locking handle PIV prevents the maneuvering of the actuation handle  107  and blocks it in its locking position as long as this lower locking handle PIV is in its locking position. 
     The operation of this stress absorbing device  10  is described hereafter with reference to  FIGS. 10   a  to  10   d  which illustrates successive configurations of the stress absorbing device  10  and of the half cowls  51 . 
       FIG. 10   a  illustrates the stress absorbing device  10  in the locking configuration with the half cowls  51  in the closed position, wherein the hook  101  restrainedly cooperates with the hooking-up member  102 , the actuation handle  107  is in the locking position and the lower locking handle PIV is in the locking position so that it prevents maneuvering of the actuation handle  107 . The locking connecting rod  103  is in the closed position. 
       FIG. 10   b  illustrates the beginning of the maneuvering for opening the half cowls  51 , with the stress absorbing device  10  still in the locking configuration and the half cowls  51  still in the closed position, wherein the hook  101  still restrainedly cooperates with the hooking-up member  102 , the actuation handle  107  is still in the locking position, the locking connecting rod  103  is still in the closed position and the lower locking handle PIV is now in the unlocking position. In spite of the unlocking of the lower locking means, the half cowls  51  cannot yet open since the stress absorbing device  10  in the unlocking position is in a locking configuration. 
       FIG. 10   c  illustrates the continuation of the maneuvering for opening the half cowls  51 , wherein the actuation handle  107  has switched into its unlocking position, following the switching beforehand of the lower locking handle PIV into its unlocking position. Accordingly, the hook  101  disengages from the hooking-up member  102  and the stress absorbing device  10  passes into an unlocking configuration with the locking connecting rod  103  still in the closed position. 
       FIG. 10   d  illustrates the end of the maneuvering for opening the half cowls  51 , wherein at least one of the half cowls  51  may open by pivoting around its jointing point  53 , as schematized by the arrow P, since the stress absorbing device  10  is in an unlocking configuration, just like the lower locking means, the locking connecting rod  103  passing into the open position with relative displacement of the first and second portions  105 ,  104  of the connecting rod  103  concomitantly with the pivoting of the first portion  105  of the connecting rod  103  with the guidance on the pylon  2 . 
     Of course, the exemplary application mentioned above does not have any limiting nature and other improvements and details may be brought to the nacelle according to the present disclosure without however departing from the scope of the invention wherein other forms of stress absorbing devices may be achieved.