Abstract:
The present invention relates to a multiple-acting linear actuator ( 100 ) intended to drive at least two elements capable of moving relative to a fixed element comprising a plurality of rod-forming concentric tubular bodies ( 103, 102, 104 ) engaged successively one inside the next via external and/or internal screw threads ( 105, 106, 107, 108 ), characterized in that one of the bodies is connected to rotational-drive means ( 109 ), the other bodies then together forming an internal and/or external transmission train, and in that said bodies are associated with selective lock-up means whereas the outermost bodies of the internal and/or external transmission trains are permanently prevented from rotating.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a telescopic linear actuator for moving a first element and a second element relative to one another and with respect to a fixed element, these three elements in particular belonging to a thrust reverser of a turbojet engine nacelle as described for example in the as yet unpublished French patent application filed under the No. 06.09265 and in the likewise as yet unpublished French application filed under the No. 06.05512, both filed in the name of the Applicant Company and incoproated herein by reference. 
       BACKGROUND 
       [0002]    An airplane is propelled by a number of turbojet engines each housed in a nacelle that also houses a collection of auxiliary actuating devices associated with its operation and for forming various functions when the turbojet engine is operating or not operating. These auxiliary actuating devices comprise, for example, a mechanical system for actuating thrust reversers. 
         [0003]    A nacelle generally has a tubular structure comprising an air intake upstream of the turbojet engine, a central section intended to surround a fan of the turbojet engine, a downstream section housing thrust-reversal means and intended to surround the combustion chamber of the turbojet engine, and generally ends in a jet pipe, the outlet of which is situated downstream of the turbojet engine. 
         [0004]    Modern nacelles are intended to house a bypass turbojet engine able, using the blades of the rotating fan, to generate a flow of hot air (also known as the primary flow) coming from the combustion chamber of the turbojet engine, and a flow of cold air (the bypass or secondary flow), which flows around the outside of the turbojet engine through an annular passage also known as a flow path, formed between a cowling of the turbojet engine and an internal wall of the nacelle. The two air flows are ejected from the turbojet engine via the rear of the nacelle. 
         [0005]    The purpose of the thrust reverser is, when an airplane is coming into land, to improve the ability of the airplane to brake by redirecting forward at least some of the thrust generated by the turbojet engine. During this phase, the reverser obstructs the flow path for the cold flow and directs the latter toward the front of the nacelle, thereby generating a reverse thrust which adds to the braking of the wheels of the airplane. 
         [0006]    The means used to perform this redirection of the cold flow vary according to the type of reverser. However, in all cases, the structure of a reverser comprises moving cowls that can be moved between, on the one hand, a deployed position in which they open up within the nacelle a passage intended for the diverted flow and, on the other hand, a retracted position in which they close off this passage. These cowls may perform a deflecting function or may simply activate other deflection means. 
         [0007]    In the case of a cascade-type thrust reverser, the airflow is redirected by cascades of deflection vanes, the cowl having a simple function of sliding aimed at uncovering or covering these cascades of vanes, the translational movement of the moving cowl being along a longitudinal axis substantially parallel to the axis of the nacelle. Complementary blocking doors, also known as shutters, activated by the sliding of the cowling, generally allow the flow path to be closed off downstream of the cascade of vanes so as to optimize the redirection of the cold flow. 
         [0008]    These shutters are generally pivot-mounted, via an upstream end, on the sliding cowl so that they pivot between a retracted position in which they, together with the moving cowl, ensure the aerodynamic continuity of the internal wall of the nacelle, and a deployed position in which, in a thrust-reversal situation, they are least partially close off the annular duct so as to divert a flow of gas toward the cascades of deflection vanes uncovered by the sliding of the moving cowl. The pivoting of the shutters is guided by link rods attached, on the one hand, to the shutter and, on the other hand, to a fixed point of the internal structure delimiting the angular duct. 
         [0009]    French application 06.09265 aims to address the disadvantages whereby these link rods pass across the flow path. 
       BRIEF SUMMARY 
       [0010]    The present patent application seeks to provide a suitable double-acting actuator of simple design and which meets the requirement of maneuvering a configuration of shutters without a link rod as described in application FR 06.09265. 
         [0011]    More specifically, the actuating of the moving cowl and the pivoting of the shutters needs to be performed simultaneously, but at different speeds. 
         [0012]    The obvious solution is therefore to provide one dedicated actuator per moving part. However, a solution such as this is cumbersome and entails complex electronic or mechanical synchronizing of the actuating means. 
         [0013]    The present invention therefore proposes a double-acting actuator, that is to say an actuator able to actuate each of the two moving parts with its own dynamics while at the same time requiring just one actuator drive member. 
         [0014]    To do this, the invention includes a multiple-acting linear actuator intended to drive at least two moving elements relative to a fixed element, comprising a plurality of concentric tubular bodies forming rods and engaged in succession inside one another via external and/or internal screw threads, characterized in that one of the bodies is connected to rotational drive means, the other bodies then together forming an internal and/or external drive train, and in that said bodies are associated with selective lock-up means while the end most bodies of the internal and/or external drive trains are permanently prevented from turning. 
         [0015]    Thus, by providing a single rotationally driven body able to transmit said rotational movement to one or more concentric bodies through mutually interacting screw threads, the various moving bodies are automatically synchronized through the screw threads. The relative sizing of the screw threads allows the speeds of relative translational movement of the bodies with respect to one another to be adapted from the starting point of an identical rotational drive speed. 
         [0016]    Advantageously, the actuator comprises a base intended to be attached to the fixed element, and serving as a housing supporting the concentric bodies. 
         [0017]    For preference, the actuator comprises an external body, a central body and an internal body, all three of them forming rods, the actuator being characterized in that the central body has an external first screw thread able to collaborate with a corresponding screw thread of the external body, and an internal second screw thread designed to collaborate with a corresponding screw thread of the internal body, one of the bodies being prevented from translational movement and able to be connected to suitable rotational drive means while the other two bodies, each intended to be connected to one of the moving elements that are to be driven, are free to effect translational movement but prevented from turning, with the exception of the scenario in which one of these bodies is the central body which is then associated with disengageable rotational lock-up means. 
         [0018]    According to a first alternative form of embodiment, the external screw thread of the central body has a pitch that is longer (coarser) than the pitch of the internal screw thread. The speed of translational movement of the external body will therefore be higher than the speed of translational movement of the internal body. 
         [0019]    According to a second alternative form of embodiment, the external screw thread of the central body has a pitch that is shorter (finer) than the pitch of the internal screw thread. The speed of translational movement of the external body will therefore be lower than the speed of translational movement of the internal body. 
         [0020]    According to a third embodiment, the external and internal screw threads have identical pitches. The speeds of translational movement will then be identical. 
         [0021]    According to a first embodiment of the invention, the body connected to the rotational drive means is the central body. 
         [0022]    In such a case, the actuator according to the invention is perfectly suited to actuating a blocking shutter concurrently with a thrust reverser panel, as described previously. 
         [0023]    For preference, the central body is intended to be connected to a moving thrust-reverser cowl while the external body is intended to be connected to means of driving the pivoting of a shutter. 
         [0024]    Quite obviously, a configuration such as this can also be used for simultaneously actuating two moving parts relative to one another and with respect to a fixed part in instances where these two moving parts have different travels and different speeds of opening and of closing. 
         [0025]    According to a second embodiment, the body connected to the rotational drive means is the external body. 
         [0026]    This embodiment makes it possible to adapt the structure of the actuator previously described and adapt it to address the problems associated with actuating a variable nozzle, as described in document FR 06.05512, for example. 
         [0027]    The problem with actuating a variable nozzle stems from the fact that this nozzle has to be maneuverable during various phases of flight when the thrust reverser is in the closed position. 
         [0028]    Since the variable nozzle is mounted on the moving thrust-reverser cowl, it needs to be able to be driven at the same time as the latter, although the “variable nozzle” function that allows the outlet cross section of the nacelle to be adapted can be deactivated and is not used when the thrust reverser is activated. 
         [0029]    Thus, by driving the actuator according to the invention through the agency of the external body, it is possible to achieve this synchronization in an easy way. 
         [0030]    More specifically, when the moving cowl needs to be maneuvered, the central body is prevented from turning. It does not therefore transmit the rotational movement to the internal body, which will therefore be driven by the same movement as the central body. 
         [0031]    When the moving cowl is in the closed position, the internal body connected to the variable nozzle can be actuated independently by disabling the rotational lock-up of the central body using the selective lock-up means. 
         [0032]    In so doing, the central body then allows the rotational movement with which the external body is driven to be transmitted to the internal body which, prevented from turning, is given a corresponding translational movement. 
         [0033]    For preference, the central body is intended to be connected to a moving thrust-reverser cowl while the internal body is intended to be connected to a moving nozzle with which said thrust reversal system is equipped. 
         [0034]    Quite obviously, this same actuator can be used in other applications that address the same technical problem. 
         [0035]    For preference, the disengageable rotational lock-up means take the form of a system of claws fixed to the central body and able to collaborate with corresponding teeth exhibited by the internal body. 
         [0036]    Advantageously, the system of claws has elastic return means forcing said claws into their position of engagement with the teeth of the internal body. Thus, by default and in the absence of any specific command, only the nozzle part may be actuated. 
         [0037]    For preference, the internal body can be translationally driven by engagement of the disengageable lock-up means with which the central body is equipped only when the variable nozzle is in a set position relative to the moving cowl. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The implementation of the invention will be better understood with the aid of the detailed description set out hereinbelow with reference to the attached drawing. 
           [0039]      FIG. 1  is a schematic part view in longitudinal section of a thrust reverser according to application FR 06.09265, equipped with a moving cowl and with a deflection shutter. 
           [0040]      FIG. 2  is a view in longitudinal section of a first alternative form of a first embodiment of an actuator according to the invention, in the retracted position. 
           [0041]      FIG. 3  is a view in longitudinal section of the actuator of  FIG. 3 , in the deployed position. 
           [0042]      FIG. 4  is a view in longitudinal section of a second alternative form of a first embodiment of an actuator according to the invention, in the retracted position. 
           [0043]      FIG. 5  is a view in longitudinal section of the actuator of  FIG. 4 , in the deployed position. 
           [0044]      FIG. 6  is a schematic sectional view of a moving thrust-reverser cowl in the closed position, equipped with a variable nozzle, in the cruising position, and actuated using an actuator according to a second embodiment of the invention. 
           [0045]      FIG. 7  is a view of the system of  FIG. 6  for driving the variable nozzle. 
           [0046]      FIG. 8  is a view of the system of  FIG. 6  showing the variable nozzle in a slightly retracted (short nozzle) position. 
           [0047]      FIG. 9  is a view of the system of  FIG. 6  showing a nozzle returned to the cruising position and preparing for the maneuvering of the moving cowl. 
           [0048]      FIG. 10  shows a view of the system of  FIG. 6  with opening of the moving cowl, the position of the variable nozzle being kept fixed with respect to this said cowl. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]      FIGS. 1 to 5  show a first embodiment of an actuator according to the invention intended for actuating a moving cowl of a reverser equipped with a shut-off shutter. 
         [0050]      FIG. 1  is a schematic part view in longitudinal section on a plane passing through cascades of deflection vanes, of a cascade-type thrust reverser equipped with a shut-off shutter as described in application FR 06.09265 in the thrust-reversal situation. 
         [0051]    In the known way, the thrust reverser  1  depicted in  FIG. 1  is associated with a bypass turbojet engine (not depicted) and comprises an external nacelle which, together with a concentric internal structure  11 , defines an annular flow duct  10  for a secondary flow path. 
         [0052]    A longitudinally sliding cowl  2  includes two semi-cylindrical parts mounted on the nacelle in such a way as to be able to slide along slideways (not depicted). 
         [0053]    An opening fitted with cascades of fixed deflection vanes  4  is formed in the external nacelle of the thrust reverser  1 . This opening, when the gases are providing direct thrust, is closed by the sliding cowl  2  and is uncovered, in a thrust-reversal situation, by a longitudinal translational movement in the downstream direction (with reference to the direction in which gases flow) of the sliding cowl  2 . 
         [0054]    A plurality of reversal shutters  20 , distributed about the circumference of the cowl  2  are each pivot mounted, by a upstream end, about an axis of articulation (not visible) on the sliding cowl  2  so that they pivot between a retracted position and a deployed position in which, in the thrust-reversal situation, they shut off the annular duct  10  so as to deflect a stream of gas toward the opening fitted with the cascades of vanes  4 . There is a seal (not depicted) at the periphery of each shutter  20  to isolate the flow flowing through the annular duct  10  from the flow external to the nacelle. 
         [0055]    When the turbojet engine is operating in direct thrust mode, the sliding cowl  2  forms all or part of a downstream part of the nacelle, the shutters  20  then being retracted inside the sliding cowl  2  which closes off the opening fitted with the cascades of vanes  4 . 
         [0056]    The shutters  20  therefore ensure the external aerodynamic continuity of the annular duct  10 . 
         [0057]    In order to reverse the thrust from the turbojet engine, the sliding cowl  2  is moved into a downstream position and the shutters  20  pivot into the shut-off position so as to deflect the secondary or bypass flow toward the cascades of vanes  4  and form a reversed flow guided by the cascades of vanes  4 . 
         [0058]    As shown in  FIG. 1 , a slider  24  for driving a shutter (or driving two shutters  20  positioned on either side of the slider  24 ) is mounted such that it can move into lateral slideways  33  that guide translational movement and are formed in a structure of the sliding cowl  2 . 
         [0059]    The driving slider  24  is connected to a downstream end of the shutter  20  by a driving link  30  articulated to the shutter about an axis  31  and to the slider  24  about a transverse axis  26 , such that a translational movement of the slider  24  in its guiding slideways  33  is accompanied by a pivoting of the link  30  and therefore of the shutter  20 . 
         [0060]    Here, the driving slider forms an intermediate moving portion  24  of a “telescopic” actuating cylinder  22  positioned along the longitudinal axis of the reverser. 
         [0061]    This pneumatic, electrical or hydraulic actuating cylinder  22  comprises a tubular base  23  linked, fixed or ball-jointed to the external nacelle upstream of the reverser  1 . The base  23  houses the driving slider  24  and an end rod  25 , both mounted, independently of one another, with the possibility of axial sliding in the base  23  of the actuating cylinder  22 . 
         [0062]    A downstream end of the end rod  25  is connected to the sliding cowl  2  by a transverse drive axis  27 . 
         [0063]    The actuating cylinder  22  is operated in such a way as to drive the slider  24  in a translational movement in its guiding slideways  33  when the sliding cowl  2  is in an end phase of its translational travel in the downstream direction. 
         [0064]    It will thus be understood that, according to this earlier embodiment, the moving cowl  2  and the shutter  20  are both able to move in the same phase and are therefore set in motion simultaneously although at different speeds. This therefore requires an additional mechanism for synchronizing the two rods  24 ,  25  of the telescopic actuating cylinder  22 . 
         [0065]    According to the present invention, there is therefore provided a self-synchronizing actuator. Such an actuator is depicted in  FIGS. 2 to 5 . 
         [0066]    An actuator  100  according to the invention comprises a cylindrical sleeve  101  inside which there are housed three concentric bodies forming rods, namely an external body  102 , a central body  103  and an internal body  104 . 
         [0067]    Each of the three bodies  102 ,  103 ,  104  is mechanically engaged with the adjacent body via screw threads. 
         [0068]    More specifically, the external body  102  has an inside screw thread  105  engaged with a corresponding external screw thread  106  borne by the central body  103 , the latter also having an internal screw thread  107  engaged with a corresponding external screw thread  108  borne by the internal body  104 . 
         [0069]    What is more, the central body  103  is prevented from translational movement and mounted such that it can turn on drive means  109  housed in a base  110  of the actuator. 
         [0070]    The external body  102  and the internal body  104  for their part are prevented from turning but left free to move translationally. Rotational lock-up may be achieved simply by the attaching of the external body  102  and of the internal body  103  to the moving parts that they are respectively intended to drive, namely the moving cowl  2  and the shutter  20 . For this, the internal body  104  ends in a securing eye  111  while the external body  102  has lateral drive pins  112 . 
         [0071]    The way in which an actuator such as this works is as follows. When the actuating means  109  are turning the central body  103 , it imparts this movement to the external  102  and internal  104  bodies through the respective screw threads  105 ,  106  and  107 ,  108 . Since the external  102  and internal  104  bodies are prevented from turning, the drive movement of the central body  103  is converted into a translational movement. The external body  102  and the internal body  104  are thus given a translational movement the direction of which is dependent on the direction in which the drive means are turning and the hand of the screw threads  105 ,  106  and  107 ,  108 . Furthermore, the linear translational speed of the external  102  and internal  104  bodies is dependent on the pitch of each screw thread  105 ,  106  and  107 ,  108  although the rotational speed is identical. 
         [0072]    From a single rotational drive of the central body  103 , it therefore becomes possible to drive the translational movement of each of the bodies  102 ,  104  connected to a corresponding moving part, this drive being performed synchronously at relative speeds that can readily be adapted via the pitch of the screw threads  105 ,  106  and  107 ,  108 . 
         [0073]    According to a first alternative form of embodiment depicted in  FIGS. 2 and 3 , the pitch of the external screw threads  105 ,  106  is shorter (finer) than the pitch of the internal screw threads  107 ,  108 . It then follows that the external body will effect its translational movement at a speed lower than that of the internal body. 
         [0074]    Conversely, according to a second alternative form of embodiment depicted in  FIGS. 4 and 5 , the pitch of the external screw threads  105 ,  106  is longer (coarser) than the pitch of the internal screw threads  107 ,  108 . It then follows that the external body will effect its translational movement at a speed that is higher than that of the internal body. 
         [0075]    Quite obviously, these parameters are adjusted by the person skilled in the art to suit the start and end point of each moving part. 
         [0076]    As mentioned previously, the fundamental structure of the actuator described can be adapted to allow the driving of a variable nozzle. An embodiment such as this is depicted in  FIGS. 6 to 10 . 
         [0077]    These figures schematically show a moving thrust-reverser cowl  200  equipped with a nozzle end section  201  mounted such that it can move relative to the moving cowl in such a way as to form what is known as a variable nozzle. 
         [0078]    Each moving part of this thrust-reversal system can be translationally driven using a single actuator  203  according to a second embodiment of the invention. 
         [0079]    Like the actuator  100 , the actuator  203  comprises an external body  204 , a central body  205  and an internal body  206 , all of these being concentric. 
         [0080]    The external body  204  is mechanically engaged with the central body  205  and for this purpose has an internal screw thread  207  engaged with a corresponding external screw thread  208  of the central body  205 . 
         [0081]    Further, the central body  205  has an internal screw thread  209  engaged with a corresponding external screw thread  210  of the internal body  206 . 
         [0082]    The external body  204  is mounted fixed in terms of rotation movement but able to move in terms of translational movement and is connected to rotational drive means  211  housed in a casing  212  that forms a base of the actuator. 
         [0083]    The internal body  206  for its part is capable of translational movement but prevented from turning. 
         [0084]    Thus, the rotationally driven external body  204  transmits its movement to the central body  205  via the screw threads  208  and  209 . 
         [0085]    It then follows that if the central body  205  is prevented from turning, the movement of the external body  204  will be converted into a translational movement of the central body  205 . The internal body  206  therefore receives no movement and remains stationary with respect to the central body  205 . It therefore moves translationally simultaneously and at the same speed. 
         [0086]    If the central body  205  is left free to turn, the movement of the external body  204  is then no longer converted into a translational movement but the rotational movement is imparted to the internal body  206  which, prevented from turning, is given an independent translational movement. 
         [0087]    In order to provide the option as to whether to drive the internal body  206  by itself or together with the central body  205 , the latter is equipped with selective translational lock-up means in the form of a claw coupling  213  mounted inside the central body  205  and having cutouts able to collaborate with corresponding teeth  214  borne by one end of the internal body  206 . 
         [0088]    These lock-up means are associated with control means  215  designed selectively to apply to the claws of the claw coupling  213  enough pressure that they can be pushed back away from the teeth  214 . 
         [0089]    With the internal body  206  prevented from turning, engagement of the claws  213  with the teeth  214  of this body allows the central body  205  to be prevented from turning. 
         [0090]    Thus, when there is the wish to activate the thrust reverser, that is to say to actuate the moving cowl via the central body  205 , the control means  215 ; of the electromagnetic type, are left retracted so that the claws  213  are engaged with the teeth  214 . It then becomes possible simultaneously to drive the moving cowl  200  and the variable nozzle section  201  connected to the internal body  206 . 
         [0091]    Conversely, when there is a wish to activate only the variable nozzle  201 , the control means  213  are actuated to move the claws  213  of the coupling away from the teeth  214 , thus making the central body  205  free to turn. 
         [0092]    Actuation of the nozzle  201  is depicted in  FIGS. 7 to 9 . 
         [0093]    Actuation of the moving cowl is depicted in  FIG. 10  after the unlocking of the complementary means  218  of locking the moving cowl  200 . 
         [0094]    It will be noted that, in this particular instance, the moving cowl  200  can be driven only if the central body  205  is prevented from turning, that is to say if the claws  213  of the coupling are engaged with the teeth  214 , which corresponds to a set position of the nozzle  201  relative to the moving cowl  200 . If the nozzle  201  is in a retracted position or in a deployed position, it will be necessary first of all to return it to a normal position to allow the teeth  214  to engage with the claws  213  and lock up the central body  205  in terms of rotational movement. 
         [0095]    Moreover, because the central body  205  is intended to be rotationally driven, it will be connected to the moving cowl  200  by ball means  220  such as a ring mounted on ball bearings for example. 
         [0096]    Although the invention has been described using a specific embodiment, it is quite obvious that it is not in any way restricted thereto and that it encompasses all technical equivalents of the means described and combinations thereof where these fall within the scope of the invention.