Abstract:
A thrust reverser of a bypass turbojet engine nacelle is disclosed, which includes movable cowls that move backwards with respect to a fixed front structure to uncover thrust reverser cascades and a variable secondary nozzle connected to the movable cowls by guide means allowing an axial sliding of the system which controls the movement of this variable secondary nozzle, wherein it includes cylinders bearing on the front structure for controlling reversal means of the displacement direction connected to the movable cowls, which move the variable secondary nozzle backwards when these cylinders output a forward stroke, as well as blocking devices which connect the secondary nozzle to the movable cowls when this nozzle is deployed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/FR2015/050567, filed on Mar. 9, 2015, which claims the benefit of FR 14/52823 filed on Mar. 31, 2014. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure concerns a thrust reverser for an aircraft nacelle accommodating a turbojet engine as well as an aircraft nacelle equipped with such a thrust reverser. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    The driving assemblies for the aircrafts generally include a nacelle forming a generally circular outer envelope, comprising inside a turbojet engine disposed along the longitudinal axis of said nacelle. The turbojet engine accommodates the fresh air coming from the upstream or front side, and rejects from the downstream or rear side the hot gases coming from the combustion of the fuel, which give a certain thrust. 
         [0005]    The bypass turbojet engines exhibit around this turbojet engine of the fan blades generating a significant secondary cold air flow along an annular flow path passing between the motor and the nacelle, which adds a high thrust. 
         [0006]    Some nacelles include a thrust reverser system which closes at least partially the annular cold air flow path, and rejects the secondary flow forward in order to generate a braking thrust of the aircraft. 
         [0007]    A known type of thrust reverser, shown in particular by the document FR-A1-2758161, includes rear movable cowls called “trans-cowls” axially sliding rearwards under the effect of cylinders by deploying flaps in the annular flow path in order to close the most part of this flow path. The flaps radially return the cold air flow outwardly by passing through the cascades uncovered by the movable cowls during their sliding, comprising blades which direct this flow forward. 
         [0008]    Furthermore some nacelles include a rear secondary nozzle called a “Variable Fan Nozzle” (VFN), providing a variable secondary flow due to a translation movement of the control system of this nozzle which is connected to the movable cowls of the thrust reverser by guide means allowing an axial movement. 
         [0009]    A known system for actuating the thrust reverser as well as the variable secondary nozzle, includes cylinders bearing on the fixed front structure in order to, firstly slide the secondary nozzle rearwards, then when it abuts on its guide means connected to the movable cowls of the thrust reverser, secondly to drive these movable cowls which are open rearwards. 
         [0010]    A problem with this actuating system is that the cylinders must include a significant stroke, representing the sum of the stroke of the secondary nozzle and the movable cowls. These cylinders are then difficult to design because of their length, to resist in particular to the bending, the buckling and the fatigue behavior. 
         [0011]    Furthermore, the significant length of the cylinders makes their integration complicated into the front portion of the nacelle dedicated to the equipment, while avoiding the areas including risks of projections in the case of the bursting of the turbine. 
       SUMMARY 
       [0012]    The present disclosure includes a thrust reverser of a bypass turbojet engine nacelle, comprising movable cowls which move backwards with respect to a fixed front structure to uncover thrust reverser cascades, as well as a variable secondary nozzle connected the movable cowls by guide means (or a guide device) allowing an axial sliding, characterized in that it includes cylinders bearing on the front structure for controlling reversal means of the displacement direction connected to the movable cowls, which move the variable secondary nozzle backwards when these cylinders output a forward stroke, as well as blocking devices which connect the secondary nozzle to the movable cowls when this nozzle is deployed. 
         [0013]    One advantage of this thrust reverser combined with a variable secondary nozzle is that the cylinders may, firstly, by a forward stroke, implement the reversal means of the axial displacement in order to move the control system of the variable secondary nozzle backwards to the deployed position, and secondly by connecting this nozzle to the movable cowls when it is in the deployed position, by a backward stroke in order to move the movable cowls backwards. 
         [0014]    Cylinders having a total stroke only equal to that of the movable cowls are then used, the displacement of the secondary nozzle being integrated into this same stroke by the forward movement of the cylinder. The cylinders are shorter, the design of these cylinders as well as their setting up in the nacelle are facilitated. 
         [0015]    The thrust reverser according to the present disclosure may further include one or more of the following features, which can be combined therebetween. 
         [0016]    Advantageously, the reversal means/device of the displacement direction comprise connecting rods (links) fastened by pivots to the movable cowls, which constitute simple means performing this reversal. 
         [0017]    In particular, each connecting rod (link) may be fastened in a central portion by a pivot to the movable cowls, one end being connected by a hinge to the cylinder, the other end being also connected by a hinge to the secondary nozzle. 
         [0018]    According to one form, the thrust reverser includes latches which block the ends of the connecting rods (links). 
         [0019]    The thrust reverser may include double connecting rods (links) disposed symmetrically with respect to the axis of the cylinder, each having a pivot connected to the cowls. In this manner, the efforts applied to the reversal means/device are balanced and this also allows increasing the number of controls for the actuation of the variable secondary nozzle and thus, for example, the number of flaps of said nozzle. 
         [0020]    According to another form, the blocking means/device has two positions which can alternately block the cowls on the fixed front structure, or block the secondary nozzle on these cowls. With one control means/device of this blocking device, a blocking of the two positions is thus alternately carried out. 
         [0021]    In this case, the blocking devices may include a latch connected to the cowls, which sways to alternately engage a hooking means located on one side on the front structure (fixed relative position), or another hooking means/device located on the other side on the reversal means/device of the displacement direction. 
         [0022]    Advantageously, the blocking devices include elastic means providing two stable blocking and unblocking positions. Thus these two positions are simply secured. 
         [0023]    In this case the blocking devices may include levers connected by pivots to the cowls, including blocking means fitting on the members connected to the cylinders, a spring being compressed between these levers in order to provide the two stable blocking and unblocking positions. 
         [0024]    The present disclosure also relates to a turbojet engine nacelle including a thrust reverser comprising any one of the preceding features. 
         [0025]    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 
         [0026]    In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
           [0027]      FIGS. 1 a , 1 b  and 1 c    are axial sectional diagrams of a thrust reverser according to the prior art, successively shown in the closed position with the retracted then deployed secondary nozzle, and in the open position; 
           [0028]      FIGS. 2 a , 2 b  and 2 c    are axial sectional diagrams of a thrust reverser according to the present disclosure, successively shown in the closed position, then a deployed secondary nozzle, and then in the open position; 
           [0029]      FIGS. 3 a  and 3 b    show in axial section a first example of latch, successively in the blocked and unblocked position; 
           [0030]      FIG. 4  shows this latch in an axial section orthogonal along the sectional plane IV-IV; 
           [0031]      FIG. 5  shows a second example of a latch; and 
           [0032]      FIGS. 6 a , 6 b  and 6 c    are diagrams of a third example of a latch, successively shown in the closed position, then with the deployed secondary nozzle, and then in the open position. 
       
    
    
       [0033]    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 
       [0034]    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. 
         [0035]      FIG. 1  a shows the rear portion of a turbojet engine nacelle, the rear axial direction being indicated by the arrow “AR,” comprising a fixed front frame  2  and movable cowls  4  adjusted rearwards of this structure. 
         [0036]    Each cowl  4  is connected to the front structure  2  by longitudinal guide means, which allow a sliding of these cowls rearwards to open the passage of the secondary flow radially outwards, through not-shown thrust reverser cascades. 
         [0037]    A secondary nozzle  6  disposed rearwards of the nacelle, is connected to the cowls  4  by axial guide rails allowing a retracted forward position shown in  FIG. 1 a   , and a deployed position rearwards shown in  FIG. 1 b    which improves the efficiencies for the high speeds of rotation of the turbojet engine. 
         [0038]    Cylinders  8  longitudinally disposed along the cowls  4 , include the front end of their body fastened to the front structure  2 , and a rod extending rearwards which is fastened to the secondary nozzle  6 . 
         [0039]    Each cylinder  8  performs, after having opened a latch  10  connecting the secondary nozzle  6  to the cowls  4 , a first stroke C 1  which deploys this nozzle, then when the nozzle is in the end of stroke position of its guide rails, a second stroke C 2  which move the cowls  4 , shown in  FIG. 1 c    backwards. The cylinders  8  then include a total stroke C equal to the sum of two particular strokes C 1  and C 2 . 
         [0040]    Each cylinder  8  include, in its retracted position, a relatively large total length L necessary to perform the total stroke C imposed by the addition of two particular strokes, which raises design problems of these cylinders. Furthermore the fastening of the rod of the cylinder  8  on the secondary nozzle  6  is located in an area  12  capable of accommodating projections in the case of the bursting of the turbine, which raises safety problems. 
         [0041]      FIG. 2 a    shows a connecting rod (link)  2  fastened by a pivot  22  from its central portion to a cowl  4 , the lower end  24  being connected by a hinge to the rod of the cylinder  8 , and its upper end  26  being also connected by a hinge to an upper arm  28  of the secondary nozzle  6 , while crossing a complementary connecting rod (link)  34 . 
         [0042]    The thrust reverser includes a first latch  32  which blocks the upper end  26  of the connecting rod (link)  20  on the cowl  4  when the secondary nozzle  6  is retracted, the upper end being in its forward position. 
         [0043]    After having opened the first latch  32 , the cylinder  8  performing a retraction of its rod forwards along a stroke C 3 , as shown in  FIG. 2 b   , performs a swaying of the connecting rod (link)  20  about its pivot  22  which drive the secondary nozzle  6  rearwards. 
         [0044]    It is possible, by expecting the lengths of the different connecting rods (links)  20  starting from its pivot  22 , to perform a multiplication of the movement output by the cylinder  8 . In particular as shown in these figures, the upper portion of the connecting rod (link)  20  being longer than its lower portion, the movement is multiplied. 
         [0045]    The thrust reverser includes a second latch  30  which blocks the lower end  24  of the connecting rod (link)  20  on the cowl  4 , when the secondary nozzle  6  is deployed, this connecting rod (link) having its maximum inclination. It is then possible, as shown in  FIG. 2 c   , to control an output of the rod  8  along a stroke C 2 , which, the connecting rod (link)  20  being blocked, drives the assembly formed by the cowl  4  and the secondary nozzle  6 , to open this cowl. 
         [0046]    Thus, a cylinder  8  having a total length L′ which is shorter, having only to perform the stroke C 2  for opening the cowls  4  is obtained. This cylinder  8  is easier to be housed in the nacelle, and includes less stresses for its design. Also it will be noted that the cylinder  8  does not fit into the area which may accommodate projections  12 . 
         [0047]      FIGS. 3 a , 3 b    and  4  show the rod of the cylinder  8  including at its end a transverse hole accommodating an axis  40  engaged in the holes of the lower end of the connecting rod (link)  20 . 
         [0048]    The structure supporting the cowls includes symmetrically with respect to the cylinder  8 , two parallel pivots  42  disposed perpendicular to the axis of this cylinder, each of which accommodates a blocking lever  44  comprising two arms forming an elbow. 
         [0049]    The end of a first arm of each lever  44  includes a blocking ring  46  fitting on one end of the axis  40 , the end of the second arm bearing on a helical compression spring  48 , which is symmetrically tightened with the second arm of the other blocking lever. 
         [0050]    A control lever  50  oscillating about a pivot  54  fastened to the structure supporting the cowls, includes its upper end actuated by a double-effect control system, and its lower end having a fork  52  accommodating the spring  48  in order to laterally guide and displace it. 
         [0051]    By performing a switching between two positions of the control lever  50 , firstly, the spring  48  is compressed, which then expands to provide two stable positions of blocking or unblocking of the latch, comprising respectively the engagement of blocking rings  46  on the axis  40  as shown in  FIG. 3 a   , or the release of these rings as shown in  FIG. 3   b.    
         [0052]      FIG. 5  shows a doubling of the reversal connecting rods (links) of the axial displacement, comprising two connecting rods (links)  20  disposed symmetrically with respect to the axis of the cylinder  8 , each having a pivot  22  connected by a first small lever  62  to the structure supporting the cowls  4 . The lower end  24  of the connecting rods (links)  20  is fastened to the rod of the cylinder  8 , the upper end  22  being connected by a second small lever  64  to the secondary nozzle  6 . 
         [0053]    In this manner, an axial displacement of the rod of the cylinder  8  causes a simultaneous swaying of the two connecting rods (links)  20 , the force being equally distributed between these two connecting rods (links) which decreases the maximum stresses. 
         [0054]      FIGS. 6 a , 6 b  and 6 c    show another type of latch  70 , comprising two hooks disposed symmetrically with respect to a pivot  72  fastened to the structure supporting the cowls  4 . 
         [0055]    The latch  70  may sway under the action of a double-acting control, in order to alternately engage its front hook in a blocking slug  74  disposed on the front structure  2 , or its rear hook on another blocking slug disposed at the lower end of the connecting rod (link)  20 . 
         [0056]    Thus, there are obtained a blocking of the cowls  4  on the front fixed structure  2  which locks the closing of the thrust reverser, in a first position where the front hook is engaged, and a blocking of the lever  20  in its inclined position after the deployment of the secondary nozzle  6 , which allows securing the cowls with this nozzle to move the assembly backwards, in the second position where the rear hook is engaged.