Abstract:
The invention relates to an assembly for a turbojet engine which includes a pylon ( 1 ) and a nacelle supported by said pylon ( 1 ). Said nacelle ( 3 ) includes a grid thrust reverser ( 21 ) including an integral cowl mounted so as to slide on rails ( 15 ), which are arranged on both sides of said pylon ( 1 ), between a direct jet position and a thrust reversal position. Said assembly is characterised in that it includes means ( 23, 31 ) for blocking the sliding movement of the cowl on the rails ( 15 ), said means being inserted between the pylon ( 1 ) and the cowl.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an assembly for an aircraft turbojet engine. 
       BRIEF DESCRIPTION OF RELATED ART 
       [0002]    Known from the prior art, and in particular from document FR 2 916 426, is an assembly for a turbojet engine, comprising a pylon and a nacelle supported by said pylon, said nacelle comprising a grid thrust reverser comprising an integral cowl slidingly mounted on rails positioned on either side of said pylon between a direct jet position and a thrust reversal position. 
         [0003]    “Integral cowl” refers to a cowl with a quasi-annular shape, extending from one end of the pylon to the other without interruption. Such a cowl is often designated using the Anglo-Saxon term “O-duct,” in reference to the shroud shape of such a cowl, as opposed to a “D-duct,” which in fact comprises two half-cowls each extending over a half-circumference of the nacelle. 
         [0004]    In both cases, it is the withdrawal of the cowl by sliding along rails integral with the pylon that makes it possible to free the thrust reversal grids, and thus to implement the thrust reversal function. 
         [0005]    It is of course crucial for such a sliding movement not to be able to occur at an inopportune time: such an opening would in fact be fatal during a flight phase. 
         [0006]    For these reasons, safety bolts are provided at different locations of the thrust reverser to block unwanted opening of the cowl. 
         [0007]    In a “D-duct” reverser, three safety bolts are traditionally provided for each half-cowl: two bolts acting directly on two actuating cylinders of each half-cowl, and a third bolt inserted between the so-called “six o&#39;clock” beam (i.e. positioned in the lower portion of the nacelle and on which the two half-cowls are slidingly mounted) and the concerned half-cowl. 
         [0008]    Independent power sources are provided for these bolts, so as to increase the reliability of the safety device. 
         [0009]    The remote location of the third bolt relative to the other two offers increased security relative to a duct burst or a vane loss: in such a case, only one or two bolts may be destroyed, but not all of them. 
         [0010]    In an “O-duct” reverser, by definition there is no six o&#39;clock beam: the installation of a third bolt, as in a “D-duct” reverser, is therefore not possible. 
       BRIEF SUMMARY 
       [0011]    The present invention therefore aims to allow the installation of the third safety bolts in an “O-duct” reverser that provides the same degree of reliability and safety as that of a “D-duct” reverser. 
         [0012]    This aim of the invention is achieved with an assembly for a turbojet engine which includes a pylon and nacelle supported by said pylon, said nacelle including a grid thrust reverser including an integral cowl mounted so as to slide on rails, which are arranged on both sides of said pylon, between a direct jet position and a thrust reversal position, said propulsion assembly being remarkable in that it includes means for locking the sliding movement of the cowl on the rails, said means being inserted between the pylon and the cowl. 
         [0013]    The presence of these locking means in the interface area between the cowl and the pylon makes it possible to perform locking that is mechanically and geographically independent of that done in the actuating cylinders of the cowl, thereby offering the desired degrees of reliability and security. 
         [0014]    According to other optional features of this assembly according to the invention:
       said locking means comprise a bolt comprising a body and a strike articulated on said body on the one hand, and on the other hand a locking member capable of cooperating with said strike: such a bolt is in particular used as the third bolt in “D-duct” thrust reversers, and does not require any particular adaptation to be used in an “O-duct” reverser;   said bolt body is mounted inside said pylon, the strike passing through an opening formed in the pylon, and the locking member is secured to the cowl: this arrangement makes it possible to use the space available inside the pylon to install the bolt therein;   the bolt body is mounted inside the cowl, said strike passing through an opening formed in the cowl, and said locking member is secured with said pylon: this arrangement is symmetrical relative to the previous one;   the locking means are comprised in the thickness of the structure of said cowl;   electric power cables are provided for said bolt that have an excess length: this excess length allows the bolt to move with the cowl while remaining electrically connected;   electric power cables are provided for said bolt that can be disconnected from the stationary structure of the nacelle when said cowl goes from its direct jet position to its thrust reversal position: this arrangement makes it possible to do away with the aforementioned excess length, while allowing the bolt to be electrically connected in the position of the cowl where said bolt needs to be actuated, i.e. the closed position of said cowl;   said grids are slidingly mounted on other rails positioned on either side of the pylon, between a usage position and a maintenance position, said rails being radially and circumferentially offset relative to the sliding rails of said integral cowl: this sliding of the grid makes it possible to access the engine portions located under said grids; the offset of the sliding rail of said grids allows them to be moved without interfering with the bolts of the cowl;   circumferential play is provided between the locking member and the strike in the unlocked position: this play makes it possible to guarantee the possibility of sliding of the cowl once the strike is unlocked;   said bolt comprises a blocking pin of the locking system of said strike, which can be manually removed: this pin makes it possible to inhibit the thrust reversal function, which may be desirable for example when the thrust reverser is malfunctioning and one nevertheless wishes for the aircraft to be able to fly.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Other features and advantages of the present invention will appear upon reading the following description, and in reference to the appended drawings, in which: 
           [0025]      FIG. 1  is a perspective view of a propulsion assembly according to the invention, 
           [0026]      FIG. 2  is a perspective view of zone II of  FIG. 1 , the cowl of the thrust reverser having been removed, 
           [0027]      FIG. 3  is a side view of the zone of  FIG. 2 , 
           [0028]      FIG. 4  is a cross-sectional view of the members shown in  FIG. 3 , along line IV of that figure, 
           [0029]      FIGS. 5 and 6  are top views of the zone of  FIGS. 2 and 3 , the thrust reversal grids respectively being in the usage and maintenance positions, and the locking means respectively being in the locked and unlocked positions, 
           [0030]      FIG. 7  is a view similar to that of  FIG. 4  of another embodiment of the invention, 
           [0031]      FIG. 8  is a view similar to that of  FIG. 5  of said other embodiment, 
           [0032]      FIGS. 9 and 10  are views of an alternative of said other embodiment, the cowl of the thrust reverser being respectively in the direct jet and thrust reversal positions, and the locking means consequently respectively being in the locked and unlocked positions, and 
           [0033]      FIGS. 11 and 12 , similar to  FIGS. 4 and 7 , show manual blocking means of the bolt according to the invention, respectively for the two aforementioned embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    In reference to  FIGS. 1 , an assembly for an aircraft turbojet engine is shown, comprising a pylon  1  and, suspended from said pylon, a nacelle  3 . 
         [0035]    As is known in itself, said nacelle  3  typically comprises an upstream cowl  5  and a downstream cowl  7 , upstream and downstream being understood relative to the flow of air passing through the nacelle. 
         [0036]    In the particular case illustrated, the upstream cowl  5  also forms an air intake  9  of the nacelle. 
         [0037]    The downstream cowl  7  is slidingly mounted between the position shown in  FIG. 1 , called the “direct jet” position, corresponding to a situation where the aircraft is in flight, and a position slid in the downstream direction of the nacelle, making it possible to perform a thrust reversal function by discharging part of the air passing through the nacelle  9  upstream thereof. 
         [0038]    The thrust reverser shown in  FIG. 1  is of the “O-duct” type, i.e. the sliding cowl  7  forms a substantially annular integral piece extending without interruption from one side  11   a  of the pylon  1  to the opposite side  11   b  of said pylon. 
         [0039]    The appended  FIGS. 2 to 6  show a first embodiment of the invention. 
         [0040]    In  FIGS. 2 and 3 , which refer to zone II of  FIG. 1  once the sliding cowl  7  has been removed, the pylon  1  is shown and, on the side  11   a  of said pylon, a short rail  13  and a long rail  15 . 
         [0041]    These two figures also show the inner structure  17  surrounding the turbojet engine, defining the cold air tunnel  19 . 
         [0042]    The short rail  13  allows the thrust reversal grids  21  to slide between a usage position shown in  FIG. 2 , and a maintenance position in which said grids are slid to the back end of the short rail  13 , so as to allow access to the turbojet engine. 
         [0043]    The long rail  15  and its counterpart positioned on the other side of the pylon  1  allow the cowl  7  to slide between its “direct jet” position and its thrust reversal position in which it frees the thrust reversal grids  21 , allowing part of the air flow circulating in the tunnel  19  to be oriented toward the front of the nacelle. 
         [0044]    A bolt  23  is mounted inside the pylon  1 , a hatch  25  formed on the side  11   a  of the pylon  1  making it possible to access said bolt  23 . 
         [0045]    In reference to  FIGS. 4 to 6 , it is shown that the bolt  23  comprises a body  27  on which a strike  29  is pivotably mounted, under the action of an electric motor housed inside said body  27 . 
         [0046]    The body  27  fixed on the inner surface of the side  11   a  of the pylon  1  and the strike  29  pass through the wall forming said side  11   a  to cooperate with a locking member  31  secured to said sliding cowl  7 . 
         [0047]    In  FIG. 5 , the thrust reversal means  21  are shown in the in use position, and the sliding cowl (only the locking member  31  of which is visible) is shown in the “direct jet” position: in this position, said sliding cowl covers the thrust reversal grids  21 , and the strike  29  of the bolt  23  blocks the locking member  31  relative to a movement toward the back of the sliding cowl, i.e. to the left of the figure. 
         [0048]    In  FIGS. 4 and 6 , the thrust reversal grids  21  are shown in the maintenance position, i.e. they have slid toward the back (to the left of  FIG. 6 ) relative to the situation of  FIG. 5 . 
         [0049]    The sliding cowl  7  is in the thrust reversal position, i.e. withdrawn toward the back of the nacelle, this movement being allowed by the pivoting of the strike  29  of the bolt  23  toward the pylon  1 , making it possible to release the locking member  31  of the sliding cowl. 
         [0050]    As shown in  FIG. 4 , the short rail  13  of the thrust reversal grids  21  and the associated crosshead  33  of said grids are offset both radially (i.e. in the direction of arrow F 1 ) and circumferentially (i.e. in the direction of arrow F 2 ) relative to the long rail  15  and the associated crosshead  35  of the sliding cowl  7 . 
         [0051]    More specifically, play J (see  FIGS. 4 and 6 ) is provided between the crosshead  33  of the grids  21  and the strike  29  in the open position. 
         [0052]    The operating mode advantages of the propulsion assembly described above result from the preceding. 
         [0053]    In direct jet operation, the thrust reversal grids  21  and the sliding cowl  7  are therefore in the upstream position on their respective rails  13  and  15 , as shown in  FIG. 5 , and any inopportune sliding of the cowl  7  in the downstream direction of the nacelle is prevented by the cooperation of the strike  29  with the bolt  31 . 
         [0054]    When one wishes to actuate the thrust reverser, during landing of an aircraft, one first pivots the strike  29  toward the side  11  a of the pylon  1 , so as to bring it into the position shown in  FIGS. 4 and 6 : in this position, the locking member  31  is released, and the actuating cylinders of the cowl  7  (not shown) can make the latter part slide in the downstream direction of the nacelle, i.e. to the left in  FIG. 6 , so as to expose the thrust reversal grids  21 , and thereby discharge part of the cold air flow circulating in the tunnel  19  toward the front of the nacelle (see  FIG. 3 ). 
         [0055]    This thrust reversal position also makes it possible to perform the maintenance operations of the engine located inside the nacelle. 
         [0056]    To that end, it is also necessary to slide the thrust reversal grids  21  in the downstream direction of their rails  13 , so as to bring them into the position shown in  FIG. 6 . 
         [0057]    Owing to the play J that exists between the crosshead  33  of these grids and the strike  29  in the unlocked position, this sliding movement of the grids  21  can be done without blocking by the bolts  23 . 
         [0058]    It should also be noted that the radial stepping (i.e. in direction F 1  of  FIG. 4 ) of the crosshead  33  of the grids  21  and  35  of the cowl  7  makes it possible to obtain the necessary travels for the movements of each of these members. 
         [0059]    The circumferential stepping (arrow F 2  in  FIG. 4 ) makes it possible to move the crosshead  33  without blocking by the bolt  23 . 
         [0060]    Of course, with the aim of obtaining the maximum effective surface for the thrust reversal grids  21 , it is desirable to minimize the distance between the crossheads  33  and the side  11  a of the pylon  1 , and the locking member  31  and the associated fitting  37  connecting to the cowl  7  will in particular be sized so that said fitting is situated as close as possible to the side  11  a of the pylon  1 . 
         [0061]    The embodiment just described makes it possible to obtain a third bolt positioned in the sliding zone of the cowl  7  relative to the pylon  1 , remote from the bolts acting on the actuating cylinders of the cowl  7 , and which can be powered by a completely independent power source. 
         [0062]    In this way, excellent security and reliability are obtained relative to a risk of untimely opening of the sliding cowl. 
         [0063]      FIGS. 7 and 8 , which are respectively similar to  FIGS. 4 and 5 , show a second embodiment that differs from the preceding embodiment in that the bolt  23  is positioned inside the sliding cowl  7 , fixed on an inner wall  39  thereof. 
         [0064]    The locking member  31  and its associated fitting  37  are fixed on the side  11   a  of the pylon  1 . 
         [0065]    As before, play J is provided between the strike  29  in the open position and the locking member  31 . 
         [0066]    Inasmuch as, in that case, the bolt  23  moves with the sliding cowl  7 , it is necessary to provide that the electric power cables  41  of that bolt, connected to a stationary part of the nacelle, have an excess length, as shown in  FIG. 8 . 
         [0067]    According to one alternative shown in  FIGS. 9 and 10 , in which the assembly according to the invention is respectively shown when the sliding cowl is in the “direct jet” position and in the thrust reversal position, it can be provided for the electric cables  41  to be connected to a plug  43  that disconnects from a corresponding plug  45 , the latter part being mounted on the stationary part of the nacelle. 
         [0068]    In fact, the need to be able to actuate the bolts  23  only occurs when the sliding cowl  7  is in the direct jet position, such a need disappearing once the unlocking has been done and the cowl moves toward its thrust reversal position. 
         [0069]    For each of the embodiments described above, it is possible to consider means for prohibiting the movement of the strike of the bolt  23 , which can in particular comprise a blocking pin  43  whereof the head  45  is positioned so as to remain visible from the outside. 
         [0070]    In the first embodiment, as shown in  FIG. 11 , the pin  43  passes through the side  11   a  of the pylon  1 , for example locking a lever, belonging to the bolt, acting on the internal mechanics of the bolt, and its head  45  remains visible outside said side. 
         [0071]    In the second embodiment, as shown in  FIG. 12 , the pin  43  passes through the cowl  7  and for example directly locks the locking mechanics of the strike, and its head  45  remains visible outside said cowl. 
         [0072]    Of course, the present invention is in no way limited to the embodiments described and illustrated, which are provided only as examples.