Patent Abstract:
In a turbojet thrust reverser comprising, in an annular section of an outer cowling of the turbojet, a number of movable doors which, in an inactive position during operation in a forward thrust configuration, close off passages separating rigid spars of a fixed structure, there is provided, between two adjacent doors, a locking system which allows substantially simultaneous opening of the two doors. The locking system comprises, for each door, at least one hook mounted on the fixed structure so that it can be pivoted by an olive secured to the door between a door locking position and an unlocked position during opening or closing movement of the door. The two hooks of the locking system are rotationally interlinked by a mechanical linkage device, for example link rods, so as to prevent the unlocking of one door if the other door is closed.

Full Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The invention relates to a thrust reverser device for a bypass turbojet. 
     More particularly the invention relates to a turbojet thrust reverser comprising, in an annular section of an outer cowling surrounding a gas ejection duct, a fixed structure comprising longitudinal spars delimiting passages between them, and a plurality of movable doors which, in an inactive position during operation of the turbojet in forward thrust, close off said passages and constitute part of the outer cowling and which, in a reverse thrust configuration, at least partially close off the ejection duct and deflect a gaseous jet toward the passages. 
     The doors are moved by control means consisting, for example, of rams supported by a rigid front frame situated upstream of the passages. The doors are generally mounted, in an intermediate region of their side walls, by pivots to the spars. In the reverse thrust configuration, the doors pivot in such a way that a part of the doors situated downstream of the pivots more or less completely closes off the bypass or cold stream and in such a way that an upstream part of the doors uncovers the passages in the outer cowling so as to allow the bypass stream to be routed radially with respect to the axis of the turbojet. 
     The upstream part of the doors projects out from the outer cowling for reasons of sizing of the passage which has to be capable of allowing this stream to pass through without compromising engine operation. The angle of pivoting of the doors is adjusted so as to allow the stream to pass and in such a way as to destroy the thrust of this stream, or even to begin to generate backthrust by creating a component of the stream deflected in the upstream direction. 
     The role of the thrust reverser in reverse thrust mode is to create reverse thrust which slows down the aircraft particularly when it is running along a runway after landing. 
     It is therefore essential that the doors be kept in the inactive or closed position during flight. This is why systems are provided for locking the doors in the closed position. 
     2. Summary of the Prior Art 
     In the event of an engine disk shattering, the reverser may sustain serious damage. In the (albeit unlikely) event of this happening, the reverser must not, in spite of this, deploy to the reverse thrust configuration. To achieve this objective, it is possible to use lateral locks usually fitted into the fixed structure of the reverser and situated at a longitudinal position remote from another door-locking system so that the debris of a disk cannot simultaneously hit both reverser door locking systems. 
     Reverser safety with regard to inadvertent deployment may be enhanced generally, and not just for the eventuality of the shattering of an engine disk, by adding a third lock which may lessen the effect of failure of the other locking systems if necessary. This addition enhances the reliability of the locking systems. Now, in the current state of the art, this lock is equipped with a control system more or less independent of that of the other locking systems. This lock generates an increase in mass and, to a certain extent, a reduction in the reliability of the control system. 
     The philosophy behind improving the resistance to shattered engines consists in securing as many moving parts of the reverser as possible. It is therefore highly advantageous to synchronize the opening of two doors of a door-type thrust reverser, because the probability of damaging the members that retain each of two doors in the event of a breakage is far lower than the possibility of breaking the locking system for just one door. 
     One possible solution consists in synchronizing the moving parts of the reverser, to give a mechanical line of defense independent of the reverser control system. However, the devices for synchronizing the doors are generally heavy. These are often ram synchronizing screws, whose reliability as locking members is sometimes debatable. 
     Finally, it is extremely tricky to synchronize the doors via their pivots, because of the significant torques generated by the pressure forces to which they are subjected. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a thrust reverser as defined in the introduction and in which the doors are held in the closed position if an engine shatters or if there is complete failure of the locking system of one door. 
     Another object of the invention is to provide a thrust reverser which comprises a passive locking system, the operation of which is based on synchronizing the opening of two doors of the thrust reverser, without any external control member. 
     Accordingly the invention provides a thrust reverser for a turbojet having an outer cowling surrounding a gas ejection duct, said thrust reverser comprising a fixed structure including longitudinal spars delimiting passages between said spars in an annular section of said cowling, and a plurality of doors mounted to move between an inactive position occupied during forward thrust operation of said turbojet wherein said doors close off said passages and constitute part of said outer cowling, and a reverse thrust position wherein said doors at least partially close off said ejection duct and deflect the gaseous jet toward said passages, wherein there is provided, between two adjacent doors of said thrust reverser, a locking system allowing substantially simultaneous opening of said two doors, said locking system comprising, for each of said two doors, at least one hook mounted on said fixed structure so that it can pivot between a door locking position and an unlocked position, at least one olive secured to each of said two doors for engaging and pivoting said hooks during opening or closing movement of said doors, and a mechanical linkage device rotationally interconnecting the hooks of said two doors so as to prevent the unlocking of one door if the other door is closed. 
     The following advantageous provisions are also adopted: 
     each hook comprises an olive housing delimited by a lower internal profile and an upper internal profile, said internal profile being configured in such a way that said lower internal profile is constantly in the path of the corresponding olive and said upper internal profile can move out of said path, and in such a way that said olive exerts a locking torque when it presses against said lower internal profile and exerts an unlocking torque when it presses against said upper internal profile; 
     each hook is urged toward said unlocked position by resilient means; 
     said unlocked position of said hook is defined by a stop; and 
     said olive is mounted on a retractable support so as to allow non-simultaneous closure of said two doors, this support being urged toward an active position of said olive by resilient means. 
     According to a first embodiment of the invention, said hooks are mounted so that they can pivot about pivot pins substantially parallel to the axis of rotation of the turbojet. 
     The mechanical linkage device may consist of two intermeshed toothed sectors, formed respectively in peripheral walls of said hooks and centered on said pivot pins. 
     The mechanical linkage device may comprise a link rod articulated at each end to a respective one of said hooks by means of a ball-type joint. 
     As a preference, the mechanical linkage device comprises at least two link rods, each link rod being articulated in the manner of a ball joint to a respective hook by one of its ends and being connected slidingly to the other hook by the other end so that said link rods work mainly in tension. 
     According to a second embodiment of the invention, each hook is mounted so that it can pivot about the axis of a transmission shaft substantially parallel to the pivot pin of the corresponding door. The mechanical linkage device transmits torque between said two transmission shafts, and is, for example, of the cardan type. 
     According to an alternative form of this second embodiment, each hook is mounted so that it can pivot about a transmission shaft parallel to the pivot pin of the corresponding door, which shaft is rotationally linked to a transmission shaft of a control latch associated with the other door, said control latch being capable of being driven in rotation between a locked position and an unlocked position by a second olive with which the other door is equipped. Each hook comprises an upper internal profile preventing said hook from rotating when said olive is pressing against said profile as a consequence of premature opening of said door. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a turbojet engine comprising a thrust reverser with doors in a closed position; 
     FIG. 2 depicts a perspective part view of one embodiment of a locking system of the invention in a passive locked position, in which system locking is synchronized by link rods; 
     FIG. 3 depicts, on a larger scale, a detail of the locking system of FIG. 2; 
     FIG. 4 depicts a view, in section on a plane perpendicular to the engine axis, of the locking system of FIGS. 2 and 3, in an active locked position, following non-simultaneous opening or an attempt at the deployment of just one door; 
     FIG. 5 partially depicts a section on a plane through V—V of FIG. 4; 
     FIG. 6 depicts a partial detail, in perspective, showing the fitting into a spar of a mounting plate with a locking hook equipped with a return system; 
     FIG. 7 corresponds FIG. 2, but shows the locking system in an unlocked position, the two doors opening practically simultaneously; 
     FIG. 8 depicts, on a larger scale, a detail of the locking system of FIG. 7; 
     FIG. 9 depicts a view, in section on a plane perpendicular to the engine axis, of the locking system of FIGS. 7 and 8; 
     FIGS. 10 a ,  10   b  and  10   c  depict, in a view identical to FIG. 4, in three positions, a retractable olive support which allows non-simultaneous closure of the two doors; 
     FIG. 11 depicts, in a view analogous to that of FIG. 3, a locking system according a second embodiment of the invention, in a locked position, in which locking is synchronized by transmitting torque and in which a locking hook is naturally self-opening; 
     FIG. 12 depicts, in a direction parallel to the axis of rotation of the hook, a part view of the second embodiment of FIG. 11; 
     FIG. 13 corresponds to FIG. 11, but shows the locking system in an unlocked position; 
     FIG. 14 corresponds to FIG. 12, but shows the locking system in the unlocked position; 
     FIGS. 15 a ,  15   b  and  15   c  depict, in a sectional view normal to a side wall of the door, in three positions, a retractable olive support which allows non-simultaneous closure of the two doors; 
     FIG. 16 depicts, in a view analogous to that of FIG. 11, an alternative form of the second embodiment of the invention, in a locked position, in which locking is synchronized by transmitting torque and in which a locking hook is naturally self-closing; 
     FIG. 17 depicts, in a view analogous to that of FIG. 13, the alternative form of the second embodiment of FIG. 16, in an unlocked position; 
     FIGS. 18 a - 18   d  simultaneously depict, schematically, in a direction parallel to the axes of rotation of the locking hooks, the locking systems of two linked doors, in a passive locked position (see FIGS. 18 a  and  18   c ) and in an active locked position (see FIGS. 18 b  and  18   d ) following non-simultaneous opening or an attempt at the deployment of just one door; and 
     FIGS. 19 a - 19   c  depict, in a direction parallel to the axis of rotation of a hook, three steps in placing the locking members in the locked position during simultaneous closure of the doors. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A system for the synchronized locking of the doors of a thrust reverser is installed on a fixed structure  1  and  1   b  is of the reverser, in an integration region  5  commonly known as a spar, situated between two doors which are identified differently for clarity, as door  2  and door  3 . With the same objective of clarity, the upper part of the spar  5  situated above the locking system  4  is omitted from the perspective views. The locking synchronization system is made up of at least two hooks connected to one another by a mechanical linkage member, which slaves the opening of one of the hooks to the opening of the door of the other hook. 
     According to a first embodiment depicted in FIGS. 2 to  10 , the locking synchronization system  4  is made up of at least two hooks  6  and  7  which can move in rotation about their respective pins  12  secured to mounting plates  13  fixed to side walls of the spar  5 , their rotation being in a plane identical to or close to a plane perpendicular to the longitudinal axis of the engine. 
     The hooks  6  and  7  are joined together by at least two link rods  8  and  9  which slave the opening of one of the hooks to the opening of the door of the other hook, these link rods being situated in two different planes which may or may not be mutually parallel. The link rod  8  is connected to the hook  6  at an axis  15  and to the hook  7  at an axis  16 , the link rod  9  being connected to the hook  7  at an axis  17  and to the hook  6  at an axis  18 . It will be noted that the connection of the link rod  9  to the hook  7  is achieved at the axis  17  by a link of the pivot or ball-joint type, and that its connection to the opposite hook  6 , shown in detail in FIG. 5, is achieved by means of an intermediate pin  20 , mounted so that it can pivot about the axis  18  and secured to the hook  6 , the link between the pin  20  and the link rod  9  being of the sliding pivot or slide type, allowing relative movement between these two elements in a direction  21 , parallel to the link rod  9 , which can occur during the dynamics of opening or of closing the hooks. This particular device also allows the link rod to be worked mainly in tension and to avoid any risk of buckling. The links described in respect of the link rod  9  are identical on the link rod  8 . Moreover, it is possible to design a system equipped with just one link rod, ball-jointed at both ends, able to work both in compression and in tension. 
     It is also possible to design a system devoid of link rods, in which system each hook  6  and  7  has a toothed sector in a region of its profile opposite to the profile that provides locking. These two toothed sectors mesh with one another, thus driving and synchronizing said hooks. 
     As shown in FIG. 4, the doors  2  and  3  each have, on their lateral walls contiguous with the spar  5 , a fitting  11  equipped with an olive  10 . In the event of an attempted inadvertent deployment of just one door, in this instance the door  2 , this olive  10  comes into contact with an upper internal profile  6   a  of the hook  6 , the action  28  creating a moment that tends to cause said hook  6  to pivot about the pin  12  towards the inside of the spar  5 , thus placing the link rod  9  in tension between its attachment points  17  and  18 . Since the door  3  is locked, the action  29  of the olive  10  associated with it on a lower internal profile  7   b  of the hook  7  keeps the latter in the closed position. The result of this is that the hook  6  is also immobilized in terms of rotation about its pin  12 , thereby keeping the door  2  in a position close to its closed position, which is satisfactory from a safety point of view. 
     FIGS. 7,  8  and  9  show that in the event of practically simultaneous opening of the two doors  2 ,  3 , during reverse thrust operation, the two hooks  6  and  7  each pivot about their pin  12  and place themselves in a position that allows the two doors  2 ,  3  to open fully. This adoption of position may be initiated by one or other of the two olives  10  or by both simultaneously. One or more return systems, such as a torsion spring  14  for example, coaxial with the pin  12  depicted in FIG. 6 facilitates the opening of hooks  6  and  7 , and keeps the latter in a standby position such that their respective lower internal profiles  6   b  and  7   b  guarantee, under the action of the olives  10  during re-closure of the doors, that the locking system  4  will automatically go into a passive locked position. Each hook  6 ,  7  is equipped with a fixed or adjustable stop  23  limiting its rotation toward the inside of the spar  5  to the standby position. Significant desynchronization of the re-closure of the doors  2 ,  3  may lead to it being impossible for the lagging door to lock again, its olive  10  coming into abutment with an external profile  6   c  of the hook associated with it. 
     FIGS. 10 a ,  10   b  and  10   c  represent a retractable olive support  25  allowing non-simultaneous closure of the two doors. In FIG. 10 a , with the door  3  in the closed position, the olive  10  of the door  2  comes into contact with the external profile  6   c  of the hook  6 , the latter being already in the passive locked position, and kept in this position by the link rod  9 . The support  25 , articulated about a longitudinal pin  24  secured to the fitting  11 , pivots towards the inside of the door  2  under a force  26 , resulting from the contact between the olive  10  and the external profile  6   c , until the door  2  is allowed to close as shown in FIG. 10 b . It may be sensible to combine the rotation of the support  25  with a position sensor which will make it possible to detect excessive desynchronization of closure and thus identify certain failures in the door activation system (such as a leaky ram). This could, for example, be combined with a stop  25   a  on the support  25 . 
     In the event of an attempt at deploying just one door (FIG. 10 c ), the position of the resultant of a retaining force  28  with respect to the pin  24  is such that the support  25  tends to pivot towards the outside of the door, thus making the locking self-closing. The same is true of the resultant of the contact  29  of the olive  10  with the lower internal profile  7   b  but, as excessive rotation of the support  25  could be detrimental to the entire locking system, the associating of its external profile with an appropriate internal profile  11   a  of the fitting  11  limits this rotation. It should be noted that a return system, not depicted, such as a torsion spring for example, coaxial with the pin  24 , keeps the support  25  in a position that makes it possible both to avoid any risk of interference with the spar  5  and also to retain the olive  10  with the internal profiles of the hooks  6 ,  7 . The stop  25   a  may also be replaced by a double-acting spring which places the olive  10  in a position suited to its engagement during normal locking thereof by contact with the profile  6   b , while at the same time allowing it to engage correctly in the hook  6 , during desynchronized locking of the doors by contact with the profile  6   c , so as to cause the force  29  to pass correctly from the olive  18  to the lock when immobilizing the corresponding door. 
     It will also be noted that other principles of retraction known to those skilled in the art may be envisioned, such as, for example, a support  25  for an olive  10  retracting by rotation about a vertical axis parallel to the side walls of the door or, alternatively, by replacing the support  25  and the olive  10  with a hook pivoting about an axis normal to the side walls of the doors. 
     According to a second embodiment depicted in FIGS. 11 to  15 , the locking synchronization system  4  is made up of at least two hooks  6  and  7  equipped with respective transmission shafts  30  and  31 . Each assembly  6 ,  30  and  7 ,  31  is mounted so that it is free to rotate about its respective axis  32  in bearings formed by the mounting plates  33  used for incorporating the whole of the locking system  4  into the side walls of the spar  5 , rotation of said assemblies being in a plane substantially parallel to a side wall of their respective doors. It should be noted that each assembly comprising a hook  6 ,  7  plus shaft  30 ,  31  may comprise a one-piece unit. 
     A mechanical linking member  34 , generally situated inside the spar  5 , transmits torque between the shafts  30  and  31 . The link  34  may be of the cardan type as depicted in FIGS. 11 and 13, but it is possible to envision a transmission of the bevel gear type, or any other mechanical transmission that is satisfactory in terms of synchronization and of transmission of torque, known to those skilled in the art. 
     FIG. 12 depicts the hook  6  and the olive  10  which are associated with the door  2  in a passive locked position, the hook  7  and the olive  10  associated with the door  3  (none shown) occupying an identical position. In an attempt at the deployment of just one door, for example the door  2 , its olive  10  comes into contact with the upper internal profile  6   a  of said hook  6 , creating a torque tending to open the lock by rotating the hook  6  and shaft  30  assembly about the axis  32 . This torque is transmitted in full via the link  34  to the shaft  31  and to the hook  7 . The door  3 , being kept closed and locked by its primary and/or secondary locking members, prevents this by creating, through contact of its olive  10  with the lower internal profile  7   b  of the hook  7  associated with it, a torque that opposes the previous one, thus preventing the hook  6  from rotating and therefore preventing the door  2  from deploying. 
     During substantially simultaneous opening of the two doors  2 ,  3  during the thrust-reversal phase, the two hooks  6  and  7  each pivot about their axes  32  and place themselves in a position that allows the two doors  2 ,  3  to open fully, as shown in FIG.  14 . This adoption of position may be initiated by one or other of the two olives  10  or by both simultaneously. One or more return systems, not depicted, facilitate the opening of the hooks  6  and  7 , and keep the latter in a standby position such that their respective lower internal profiles  6   b  and  7   b , under the action of the olives  10  during the re-closure of the doors, automatically places the locking system in the passive locked position. At least one of the two mounting plates  33  has a fixed or adjustable stop  23  limiting the opening of the hooks  6 ,  7  to the standby position (FIG.  14 ). FIGS.  15 ( a ), ( b ) and ( c ) depict a retractable olive support  25  analogous to the one described previously in FIGS.  10 ( a ), ( b ) and ( c ), the pin  24  in this case being perpendicular to the side walls of the door, the rotation of the lever  25  about this pin being towards the front or rear of the door  2 ,  3 . 
     It should be noted that the direction of rotation for the opening of the hooks  6  and  7  may, with equal preference, be toward the front or toward the rear of the doors  2 ,  3 . 
     It will also be noted that it is possible to install the whole of the synchronized locking system  4  in the fixed structure of the reverser situated upstream of the doors  2  and  3 , it being possible in this case for the fittings  11  to be installed with equal preference either on the side walls or front walls of the doors, the hooks  6  and  7  then opening from the upstream to the downstream direction. 
     FIGS. 16,  17 ,  18   a - 18   d , and  19   a - 19   c  depict an alternative form of the embodiment described previously, in which the retaining hooks  6  and  7  have an upper internal profile  6   a  and  7   a  preventing these hooks from rotating in the event of contact  28  with the olive  10  and making said hooks  6  and  7  self-closing. 
     To allow the doors  2  and  3  to be opened in normal reverse-thrust operation, it is essential that the hooks  6  and  7  be able to be placed in a position that allows the passage of the olive  10  situated facing them. As this position cannot be achieved by contact with the olive  10  on the upper internal profiles  6   a  and  7   a , each of the two hooks  6  and  7  equipped with its respective transmission shaft  30  and  31  is associated via a mechanical linkage  34  with a control latch  36 ,  37 , also provided with a transmission shaft  38 ,  39 . 
     As FIGS. 16 and 17 show, the hook  6  equipped with its shaft  30  is connected to the latch  36  equipped with its shaft  38 , while the hook  7  equipped with its shaft  31  is connected to the latch  37  equipped with its shaft  39 , the opening of the latches  36  and  37  being controlled by their respective olive  40  located on the doors  2 ,  3  near the locking olives  10 . 
     FIGS. 18 a - 18   d  schematically depict the slaving of the opening of a hook  7  to the opening of the door  2  associated with the other hook  6 . FIGS. 18 a  and  18   c  depict the doors  2  and  3 , respectively, in the closed position, each olive  40  being in contact with the internal profile  36   a  or  37   a  of the control latch  36 , 37  associated with it. As FIGS. 18 b  and  18   b  show, in the event at an attempted inadvertent deployment of just one door, in this instance the door  2 , the olives  40  and  10  associated with this door  2  move through the same angle A until the olive  10  comes into contact  28  with the upper internal profile  6   a  of the hook  6 , thus aborting the attempted deployment. 
     While the angular travel A of the olive  10  gives rise to no significant movement of the hook  6 , the same angular travel of the olive  40  causes the latch  36  to rotate through an angle B, which is wholly transmitted by the link  34  to the hook  7  mounted opposite on the door  3 , the latter door being in the same closed position in FIG.  18 ( a ) FIGS. 18 a  and  18   c . An appropriate design of the lower internal profile  7   b  and  6   b  of the hooks  6  and  7  allows this angle of travel B, so as to guarantee that the forces retaining the door  2  are taken up only by the hook  6 , or the forces retaining the door  3  are taken up only by the hook  7 . As a result, in this embodiment, as the forces induced in the hooks  6  and  7  are transmitted directly to the fixed structure of the reverser, the torques transmitted through the links  34  are not very high, which means that it is possible to use components of small cross section, something which is always advantageous from the mass point of view. 
     Each latch  36  and  37  is connected to at least one return system which may, as depicted in FIGS. 18 a - 18   d  and  19   a - 19   c , consist of a tension spring  41 , one of the ends of which is secured to the mounting plate  33  at a point  42 , its opposite end being secured to a latch at a point  43 . The points  42  and  43  are sited with respect to the axis of rotation  35  of the latches  36 ,  37  in such a way that during the dynamics of opening or closing said latches  36  and  37 , the return moment generated by each spring  41  is reversed. Return systems effecting identical operation may also be installed on the hooks  6  and  7 . 
     FIGS. 19 a - 19   c  break down the dynamics of the re-closure of the hook  6  and of the latch  37 , corresponding to practically simultaneous re-closure of the doors  2  and  3 , into three phases. Phase 1 (see FIG. 19 a ) corresponds to the position of the two olives  10  coming into contact with the hooks  6  and  7 , the latter, together with the latches  36  and  37 , being held open under the action of the springs  41 . Phase 2 (see FIG. 19 b ) corresponds to the position where the olive  10  and the lower internal profiles  6   b  and  7   b  of the hooks  6  and  7  break contact. The rotation of the hooks  6  and  7  between phase 1 and phase 2 is such that it positions the springs  41  in a position that provides a torque for reclosing said hooks  6 ,  7  and latches  36 ,  37 , to the point that they are brought into and kept in the passive locked position depicted in phase 3. It should be noted that, in the event of significant desynchronization of the doors  2  and  3 , the olives  10  and  40  may be installed on retractable supports, of a design identical or similar to those described in FIG.  15 . 
     These locking systems  4  may be applied to a cascade reverser equipped with sliding covers. The lock then synchronizes the simultaneous translational movement of the two covers, using exactly the same principle as the one set out here for the doors  2 ,  3 .

Technology Classification (CPC): 8