Abstract:
An actuator for an aircraft turbine engine nacelle with a one-piece annular rear part, includes an engine assembly having a nut which is capable of rotating but not of translational movement, and a shaft for turning this nut. The actuator also includes a screw assembly having a screw capable of translational movement without rotating, in mesh with the nut, and a ball joint at one end of this screw intended to be fixed to the annular rear part.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/FR2012/052597, filed on Nov. 12, 2012, which claims the benefit of FR 11/03589, filed on Nov. 24, 2011. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to an actuator for an aircraft turbine engine nacelle with notably one-piece annular rear part. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    As is visible on  FIG. 1 , in certain nacelles for dual-flow turbine engines, the rear part A, defining, with the fairing C of the turbine engine (often designated by “IFS”—or inner fixed structure”) the cold flow stream V, is exhibited in the form of a one-piece ferrule: in this case, it is usually called an “O-duct” type nacelle. 
         [0005]    In this type of nacelle, the rear part of the nacelle A is slidingly mounted on an uppermost beam S by means of rails R, between the operating position visible on  FIG. 1 , and a maintenance position visible on FIG.  2 , in which the rear part of the nacelle is moved to the rear of the nacelle, thus allowing access to the turbine engine T for maintenance work. 
         [0006]    More particularly, once the rear part A has slid towards its downstream position visible on  FIG. 2 , the IFS C may be opened from the outside of the nacelle, by making the two halves which constitute it swivel around axes substantially parallel with the nacelle. 
         [0007]    The sliding movement of the rear part of the nacelle towards its maintenance position may be achieved manually or by means of electrical or hydraulic actuators. 
         [0008]    An example of such an actuator of the prior art is represented on  FIG. 3 . 
         [0009]    As is visible on this figure, such an actuator comprises a worm drive  1  on which is screwed a nut  3 , itself secured to an actuating tube  5  of which the free end ends by an eyelet or ball joint  7 . 
         [0010]    Preferably, balls  8  are interposed between the threads of the screw  1  and those of the nut  3 , in such a manner as to reduce friction, such that this type of actuator is commonly called “ball screw”. 
         [0011]    The screw  1  comprises, at the end opposite that of the ball joint  7 , a pinion  9  with oblique toothing cooperating with a master pinion  11  itself directly or indirectly driven by an electrical engine. 
         [0012]    Under the action of this electrical engine, the screw  1  may be swiveled in one direction or the other, and thus translate the nut  3  in one direction or the other, and hence elongate or retract the tube  5 . 
         [0013]    These movements of the tube  5  allow, by means of the ball joint  7 , to act on the rear part of the nacelle A. 
         [0014]    As it may be understood, when such an actuator is in complete extension position, its cantilever is very important, namely substantially equal to twice the length of the screw  1 . 
         [0015]    Apart from the fact that such a cantilever may generate significant friction, or even, blocking particularly the nut  3  with respect to the screw  1 , it requires an important dimensioning of the different pieces (screw  1 , nut  3 , tube  5 ) in order to provide sufficient resistance to buckling forces; such a dimensioning leads to excess weight. 
       SUMMARY 
       [0016]    The present disclosure provides an actuator for aircraft turbine engine nacelle with a notably annular one-piece rear part, the actuator comprising:
       an engine assembly comprising a nut which is capable of rotating but not of transitional movement and means for turning this nut, and   a screw assembly comprising a screw capable of transitional movement without rotating, in mesh with said nut and a ball joint at one end of this screw intended to be fixed to said rear part.       
 
         [0019]    Thanks to these features, the screw, which hence crosses the nut, may be translated by putting the nut in rotation: this screw may hence switch from a position in which the fixing ball joint is practically in contact with the nut, to a position in which it is distant from this nut by a length that is substantially equal to the length of the screw. 
         [0020]    Hence, it can be understood from the fact that it provides, when in retracted position, a point of attachment from the rear part of the nacelle closest to the engine assembly, the actuator according to the present disclosure allows substantially reducing by half, with respect to the aforementioned prior art, the cantilever when it is in complete extension position. 
         [0021]    In this way, the dimensioning of this actuator may be reduced with a weight gain. 
         [0022]    According to other features of the actuator according to the present disclosure:
       said engine assembly comprises a support and a casing able to be fixed on this support and enclose said nut;   said actuator comprises a protective tube fixed on said support, able to contain said screw when the actuator is in retracted position: this tube allows to protect the screw from particles liable to jam the actuator and limit the vibration movements of the screw.       
 
         [0025]    The present disclosure also relates to an aircraft turbine engine nacelle with a rear annular one-piece part, comprising a plurality of actuators in accordance with what precedes, disposed between a stationary part of this nacelle and said rear part of the nacelle. 
         [0026]    According to other features, this nacelle comprises an uppermost beam and said rear part of the nacelle is slidingly mounted on rails disposed on either side of the beam, an actuator in accordance with what precedes being mounted on each side of this beam, in the vicinity of said rails: in such a nacelle, due to the characteristic of the rear part, two actuators may be sufficient; the fact of providing that they are at the vicinity of the rails makes it possible to reduce the tipping movements imparted by these actuators on the rear part of the nacelle during its opening, and hence the jamming risks; 
         [0027]    The present disclosure also relates to a propulsion assembly, comprising a nacelle in accordance with what precedes, and a turbine engine placed inside this nacelle. 
         [0028]    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 
         [0029]    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: 
           [0030]      FIG. 1  is a view of a nacelle of “O-Duct” type of the prior art, such as described in preamble of the present description, in normal operating configuration; 
           [0031]      FIG. 2  is a view of this nacelle in maintenance configuration; 
           [0032]      FIG. 3  is an axial cross-sectional view of an actuator of the prior art, mentioned in the preamble of the present description; 
           [0033]      FIGS. 4 and 5  are perspective views of a propulsion assembly comprising a nacelle according to the present disclosure, comprising a rear part represented respectively in normal and maintenance operating positions; 
           [0034]      FIG. 6  is a perspective view of the actuating system of the rear part of the nacelle of  FIGS. 4 and 5 ; and 
           [0035]      FIG. 7  is a side view of one of the actuators of the actuating system of  FIG. 6 . 
       
    
    
       [0036]    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 
       [0037]    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. 
         [0038]    It has furthermore been represented on this set of figures a frame of reference X, Y, Z, of which axes X and Z are respectively parallel with the axis A of the nacelle and to the vertical, and axis Y is perpendicular to the two other axes. 
         [0039]    It is worth noting that in the present patent application, the terms “upstream” and “downstream” must be understood with respect to the circulation of the air flow inside the propulsion assembly formed by the nacelle and the turbine engine, that is to say from the left to the right of  FIGS. 4 and 5 . 
         [0040]    It is now referred to  FIGS. 4 and 5 , on which can be seen an aircraft propulsion assembly, comprising on the one hand a turbine engine  15  and on the other hand a nacelle  17  enveloping this turbine engine. 
         [0041]    On  FIGS. 4 and 5 , solely the rear part A of the nacelle is represented, but obviously, it is to be understood that the nacelle is designed to act as a fairing around the entire turbine engine  15 . 
         [0042]    The turbine engine  15  comprises in particular, an upstream part  21  forming a fan casing, and a downstream part  23  forming the actual engine, in which are achieved the compression, combustion and gas ejection making the aircraft propulsion possible. 
         [0043]    The rear part of the nacelle  25  may incorporate a thrust reversal function, for example of grid type. The rear part of the nacelle  25  is slidingly mounted between a normal operating position represented on  FIG. 4 , and a maintenance position represented on  FIG. 5 , allowing to perform maintenance work on the ground: in this position, an operator may in particular, access the engine  23 . 
         [0044]    The rear part of the nacelle  25  is a one-piece, that is to say, which is formed of one single piece, and is slidingly mounted by means of rails on an uppermost beam  27 . 
         [0045]    As indicated in the preamble of the present description, it is frequently talked of “O-Duct” type thrust reversers, as opposed to “D-Duct” type grid thrust reversers, in which there are two rear half-parts each slidingly mounted on an upper beam and a lower beam. 
         [0046]    The uppermost beam  27  allows in particular, the fixing of the propulsion assembly to a suspension pylon, disposed under the wing of an aircraft. 
         [0047]    As can be seen on  FIGS. 4 and 5 , two actuators  29   a  and  29   b  are disposed on either side of the uppermost beam  27 , each interposed between the fan casing  21  and the rear part of the nacelle  25 . 
         [0048]    It is worth noting that the fact of positioning the two actuators  29   a  and  29   b  in the vicinity of the uppermost beam  27  allows limiting the tipping movements imposed by the actuators to the rear part of the nacelle  25 , and thus reducing jamming risks of this rear part while sliding. 
         [0049]    By referring to  FIG. 6 , it can be seen the two actuators according to the present disclosure  29   a  and  29   b  are moved by a flexible rotating shaft  31 , itself actuated by an electrical or hydraulic engine: this type of flexible shaft is often designated by “flexshaft”, by technicians in the field. 
         [0050]    Now, by referring, in particular, to  FIG. 7 , it can be seen that each actuator  29  comprises a support  33  on which a casing  35  is fixed. 
         [0051]    Inside this casing  35  is a nut (not represented), liable to turn around the axis of the actuator  29 , as a result of the rotation of the flexible shaft  31 . 
         [0052]    Hence, this nut is rotatably mounted inside the casing  35 , but is immovable in translation, as opposed to the actuator of the prior art. 
         [0053]    The actuator  29  further comprises a worm drive  37  ( 37   a,    37   b  on  FIG. 5 ) engaged with the nut which is inside the casing  35 , comprising at its free end a ball joint  43  intended to be fixed on the rear part of the nacelle  25 . 
         [0054]    Opposite the ball joint  43 , the actuator according to the present disclosure comprises a protective tube  45  fixed on the support  33 , able to accommodate the entire length of the worm drive  39 . 
         [0055]    The operating mode and advantages of the actuator according to the present disclosure directly result from the preceding description. 
         [0056]    When the nacelle is closed ( FIG. 4 ), the worm drive  39  is retracted, that is to say that it occupies the whole internal volume of the protective tube  45 : in this position, the ball joint  43  is nearest to the support  33  as represented on  FIG. 7 . 
         [0057]    Thanks to this proximity, the actuator according to the present disclosure may be practically fixed on the upstream edge of the rear part of the nacelle  25 , thus interfering as least as can be with the structure thereof: thus the interference of the actuator is limited, particularly with the regions of this rear part of the nacelle which are encumbered by other members. 
         [0058]    The protective tube  45  allows to protect the worm drive  39  of the actuator, as well as limit its the vibrations when it is in the retracted position represented on  FIG. 5 . 
         [0059]    When it is required to make the rear part of the nacelle  25  slide towards its maintenance position represented on  FIG. 5 , the nut which is inside the casing  35  is turned, by means of the flexible shaft  31 : this rotation provides an extension of the worm shaft  39 , that is to say a displacement of this screw to the right of  FIG. 5 . 
         [0060]    The ball joint  43  thus, drives the rear part of the nacelle  25  towards its downstream position, given that in the maximum extension position represented in  FIG. 5 , the distance separating the support  33  from the point of attachment of the worm drive  39  to the rear part of the nacelle  25 , is at the most equal to the length of this screw, and not to twice the length of this screw, as opposed to the actuator of the prior art. 
         [0061]    In this manner, the cantilever of the actuator may be substantially diminished when it is in complete extension position, and as a result reduce the dimensioning of the different pieces constituting this actuator, allowing in fine, a weight gain. 
         [0062]    Obviously, when it is sought to bring the rear part of the nacelle  25  from its downstream position represented on  FIG. 5  to its closed position ( FIG. 4 ), the nut which is inside the casing  35  is turned in the opposite direction, allowing the retraction of the worm drive  39  inside the protective tube  45 . 
         [0063]    Obviously, the present disclosure is in no way limited to the described and represented forms, provided by way of mere examples.