Thrust reverser comprising an improved translational actuation system for the reverser's moving structure

Abstract

The invention relates to a thrust reverser (30) for an aircraft propulsion system, the reverser comprising a movable structure (29) that can be moved in translation relative to a fixed structure (18) between an advanced position of direct thrust and a rearward position of thrust reversal, the reverser comprising an actuation system (70) for moving the movable structure, consisting of one or more actuators (70a, 70b1, 70b2) each comprising an actuation member (72) that is movable in translation and centered on an actuation axis (74), the two movable reverser hoods being arranged symmetrically with respect to each other along a first median plane (P1) of the reverser. According to the invention, among the actuator(s) of the actuation system (70), an eccentric actuator (70a) is provided, the actuation axis of which (74) is circumferentially offset with respect to the first median plane (P1). Figure for the abstract: Fig. 6

Description

Title of the invention: Thrust reverser comprising an improved translational actuation system for the moving structure of THE REVERSER technical field

[0001] The invention relates to the field of nacelles and thrust reversers for aircraft propulsion systems, and, more particularly, to the translational actuation system of the moving structure of the reversers. Prior art

[0002] Thrust reversers are devices that allow the airflow through the propulsion assembly to be diverted forward, in order to shorten landing distances and limit the stress on the brakes on the landers.

[0003] The grid-type reversers currently used in the aeronautical sector include deflection grids integrated into a fixed or movable structure of the reverser. The movable structure of the reverser comprises one or more movable reverser hoods, and it is mounted to be movable in translation relative to the fixed structure between an advanced position for direct thrust and a rearward position for thrust reversal.

[0004] In the thrust reverser retracted position, to deflect at least part of the secondary flow towards the grilles, the reverser is usually equipped with shutters which, when deployed, at least partially block the secondary flow. In a known manner, this forces the air of the secondary flow radially outwards, towards the grilles, which then generate the forward counter-thrust airflow. The shutters are generally pivotally mounted on the radially inner wall of the reverser's movable cowlings, this wall delimiting the secondary flow radially outwards.

[0005] To ensure the translational movement of the moving part, the inverter includes an actuation system usually consisting of several actuators, distributed circumferentially.

[0006] With a view to limiting the mass and cost of the inverter, and thus reducing harmful emissions (CO, CO2, NOx, etc.) in order to contribute to reducing the environmental impact of aircraft, it may be considered to reduce the number of actuators within the actuation system, while guaranteeing the desired functionalities, both in normal operating mode and in the event of a malfunction. operation of one or more actuators. In particular, these actuators ensure the absorption of aerodynamic forces exerted on the movable reversing hoods, especially during thrust reversal phase.

[0007] Usually, to ensure even distribution of forces by the actuators, they are arranged symmetrically with respect to a median plane of the reversing gear, generally a vertical and longitudinal median plane when the propulsion system is intended to be suspended under an aircraft wing. Reducing the number of actuators may lead to one of them being arranged on this same median plane, as is known, for example, from document FR 2 980 173 A1. However, in a reversing gear with movable cowlings known as a "C" or "D" configuration, the actuator centered on the median plane is located in an interface zone where two movable cowlings lock into place in the closed operating position. This creates potential difficulties in positioning this actuator, since the interface zone where the movable cowlings lock into place, in the 6 o'clock position, is typically already heavily congested by the presence of equipment and utilities.

[0008] Moreover, whether the movable hood architecture is in "C", "D" or "O", the implantation of an actuator in this 6 o'clock position can locally lead to an increase in the radial dimension towards the bottom of the nacelle, potentially incompatible with the need to maintain sufficient ground clearance for the engine assembly. Description of the invention

[0009] To address the problems outlined above, the invention relates to a propulsion system for an aircraft, comprising a turbomachine, a nacelle including at least one fan cowl, a turbomachine mounting mast, and a thrust reverser including a fixed structure equipped with a radially internal boundary wall for a secondary flow of the propulsion system intended to be traversed by a secondary flow, the reverser also including a movable structure including one or two movable reverser cowls each equipped with a radially internal reverser cowl wall delimiting the secondary flow radially outwards, the reverser also including at least one deflection grid, the movable structure being translationally movable relative to the fixed structure along a longitudinal central axis of the reverser, between an advanced direct thrust position and a rearward thrust reversal position,the reverser comprising an actuation system for moving the mobile structure between its forward position of direct thrust and its rearward position of thrust reversal, the actuation system consisting of one or more actuators each comprising a movable actuation member in translation and centered on an actuation axis, , the reversing gear having a first median plane of the reversing gear passing through the central longitudinal axis and through the mounting mast, as well as a second median plane of the reversing gear passing through the central longitudinal axis and perpendicular to the first median plane.

[0010] According to the invention, among the said actuator(s) of the actuation system, there is provided an eccentric actuator arranged on a first side of the second median plane opposite a second side of the second median plane where the attachment mast is located, and whose axis of actuation is circumferentially offset with respect to the first median plane, and, in the case of several actuators constituting the actuation system, the eccentric actuator is preferably but not necessarily asymmetrical with respect to each of the other actuators with respect to the first median plane.

[0011] The invention is thus akin to a technological breakthrough, making it possible to consider a reduction in the number of actuators of the mobile structure, without providing for an actuator at the level of the area located opposite the attachment mast corresponding to an area cluttered with a locking interface between the two mobile reversing hoods in the reversing configuration in "C" and in "D", nor of actuators arranged symmetrically to the eccentric actuator, in relation to the first median plane of the reversing.

[0012] Also, regardless of the reversing gear configuration chosen and the resulting number of movable cowlings, the eccentric location of the actuator opposite the mast eliminates the problem of increasing the radial dimension of the nacelle towards the ground. Advantageously, the placement of this eccentric actuator does not negatively impact the ground clearance of the propulsion system.

[0013] Thanks to the reduction in the number of actuators, there are cost advantages, particularly with regard to the cost of components and assembly costs.

[0014] This also results in a reduction of the mass of the inverter, via the removal of certain actuators and two of their associated fixing means.

[0015] Due to the removal of these means of fixing the actuators, there is also an advantageous increase in the surface area of ​​the movable covers that can be equipped with an acoustic coating.

[0016] Furthermore, thanks to the reduction in the number of actuators, better aerodynamic performance results from the decrease in the number of access hatches to these actuators.

[0017] Finally, in the case of two movable covers arranged symmetrically with respect to the first median plane, since the eccentric actuator is not located in the cluttered area of ​​the locking interface of these two movable covers, its installation is greatly facilitated. Obviously, any other actuators constituting the actuation system can be arranged relatively freely. in order to guarantee the desired functionalities, both in normal operating mode and in the event of a malfunction of one or more of these actionors.

[0018] The invention preferably provides for at least one of the following optional technical features, taken individually or in combination.

[0019] Preferably, the actuation system consists of an odd number of actuators, preferably three or five, the actuators being distributed circumferentially among themselves in a regular or irregular manner. This means that the angles between two directly consecutive actuators can be equal or different.

[0020] Preferably, the actuation system consists of three actuators, among which:

[0021] - the eccentric actuator;

[0022] - two other actuators arranged on either side of the first median plane, of preferably in a symmetrical manner with respect to this first median plane.

[0023] Preferably, in the case of two movable hoods arranged symmetrically with respect to the first median plane, the eccentric actuator is located near the locking means of the reversing movable hoods.

[0024] Preferably, one of said two movable reversing gear covers comprises a beam to which are attached:

[0025] - means for guiding the movable reversing cover in translation;

[0026] - a fixing fitting for the movable actuation member of the eccentric actuator;

[0027] - part of the locking means for the two movable covers.

[0028] This beam thus advantageously integrates several functions, for a gain in compactness and mass.

[0029] Preferably, a fixed part of the eccentric actuator is fixed to a front deflection grid support frame, or to a fixed longitudinal beam of the inverter, extending rearward from the front grid support frame.

[0030] Preferably, the reverser includes, associated with at least one of said one or two movable reverser hoods, at least one deflection limiting device for said hood in the thrust reversal rearward position, in the event of malfunction of one or more actuators.

[0031] Preferably, the inverter has a C, D or O hood architecture.

[0032] The invention applies equally to a reversing grid belonging to the fixed structure of the inverter, or to its moving structure.

[0033] Other advantages and features of the invention will appear in the detailed, non-limiting description below. Brief description of the drawings

[0034] The detailed description that follows refers to the accompanying drawings in which:

[0035] [Fig-1] is a schematic half-view in longitudinal section of an assembly propulsive, including a thrust reverser shown in direct thrust configuration;

[0036] [Fig.2] is a more detailed half-view of the reversing gear equipping the propulsion assembly shown in [Fig.1], with the reverser presented in the form of a preferred embodiment of the invention, and represented in thrust reversal configuration;

[0037] [Fig.3] is a schematic cross-sectional view of the inverter shown on the previous figures, the left part showing the hoods in the folded-down operating position, and the right part showing the hoods in the open maintenance position;

[0038] [Fig.4] is a schematic cross-sectional view similar to the previous one, more detailed, and showing the hoods both in the folded-down operating position, and in the open maintenance position, this figure being taken along line IV-IV of [Fig.5];

[0039] [Fig. 5] is a bottom view showing the inverter hoods shown in the figures Previously, the hoods were presented in the folded-down operating position;

[0040] [Fig.6] is a schematic cross-sectional view of the inverter, also taken along line IV-IV of [Fig.5], and on which the positioning of the inverter actuators has been schematically represented;

[0041] [Fig.6A] is a schematic cross-sectional view of the inverter similar to that of the previous one, showing an alternative embodiment;

[0042] [Fig.7] is a bottom view of the inverter, similar to [Fig.5], and on which of more detailed elements of the invention have been shown;

[0043] [Fig.8] is a bottom view of one of the two inverter covers shown on the previous figure;

[0044] [Fig.9] is a cross-sectional view taken along line IX-IX of [Fig.7];

[0045] [Fig. 10] is a schematic view showing an alternative for fixing an actuator on the fixed structure of the inverter;

[0046] [Fig. 11] is a schematic view showing another alternative for fixing an actuator on the fixed structure of the inverter;

[0047] [Fig. 12] is a schematic view showing a solution for limiting the deflection of the reversing gear's movable hood, with this hood shown in the forward direct thrust position;

[0048] [Fig. 13] is a schematic view similar to the previous one, with the movable hood shown in the thrust reversal rearward position;

[0049] [Fig. 14] is a schematic view showing another solution for limiting the deflection of the movable cover of the inverter, with this cover shown in the advanced position of direct thrust;

[0050] [Fig. 15] is a schematic view similar to the previous one, with the movable hood shown in the thrust reversal rearward position;

[0051] [Fig. 16] is a schematic view showing yet another solution for limiting the deflection of the reversing gear's movable cover, the movable cover not being shown in this figure; and

[0052] [Fig. 17] is a schematic cross-sectional view of the inverter similar to that of [Fig.3], according to an alternative embodiment in which the inverter has an "O" configuration. Detailed description of implementation methods

[0053] Figure [Fig. 1] shows a propulsion assembly 1 of an aircraft, having a longitudinal central axis Al.

[0054] Hereafter, the terms "upstream" and "downstream" are defined relative to a general SI direction of gas flow through the propulsion assembly 1, along the axis Al when it generates a direct thrust. These terms "upstream" and "downstream" could respectively be substituted by the terms "front" and "rear", with the same meaning.

[0055] The propulsion unit 1 comprises a turbomachine 2, a nacelle 3, and a mast (not shown) for connecting the propulsion unit 1 to a wing (not shown) of the aircraft. In this case, the propulsion unit is intended to be suspended below the aircraft wing by the mast, which is therefore located above the turbomachine in the vertical direction. However, other configurations are possible, such as mounting this propulsion unit laterally on the rear of the fuselage.

[0056] In this example, the turbomachine 2 is a twin-spool, turbofan engine comprising, from front to rear, a fan 5, a low-pressure compressor 6, a high-pressure compressor 7, a combustion chamber 8, a high-pressure turbine 9, and a low-pressure turbine 10. The compressors 6 and 7, the combustion chamber 8, and the turbines 9 and 10 form a gas generator. The turbofan engine 2 has a fan casing 11 connected to the gas generator by structural arms 12.

[0057] The nacelle 3 comprises a front section forming an air inlet 13, a middle section which includes two blower hoods 14 enveloping the blower housing 11, and a rear section 15.

[0058] During operation, an airflow 20 enters the propulsion assembly 1 through the air inlet 13, passes through the blower 5, and then splits into a primary flow 20A and a secondary flow 20B. The primary flow 20A flows into a primary gas circulation channel 21A passing through the gas generator. The secondary flow 20B flows into a secondary channel 21B surrounding the gas generator. The channel Secondary 21B is radially delimited inwards by a fixed internal fairing that encloses the gas generator. In this example, the fixed internal fairing comprises a first section 17 belonging to the midsection 14, and a second section 18 extending rearwards from the first section 17, so as to form part of the rear section 15. This second section 18 is an integral part of a fixed structure of a thrust reverser, which will be described below, also centered on the axis A1. This same section will subsequently be referred to as the radially internal boundary wall 18 of the secondary 21B.

[0059] Radially outwards, the secondary stream 21B is delimited by the fan housing 11. In the configuration of [Fig. 1], two movable reversing hoods 33 form part of the rear section 15 of the nacelle 3. More precisely, between the fan housing 11 and the two reversing hoods 33, there is an outer ring 40 of an intermediate housing 42, the latter comprising the aforementioned structural arms 12, the radially external end of which is fixed to this ring 40. This ring therefore also contributes to delimiting the secondary stream 21B radially outwards, by being located in the downstream axial extension of the fan housing 11.

[0060] The nacelle 3 therefore includes a thrust reverser 30 (represented only schematically and partially on [Fig. 1]), centered on the axis Al and comprising on the one hand a fixed structure 31 integral with the fan casing 11, and on the other hand a structure 29 movable relative to the fixed structure 31. The fixed structure 31 includes for example a front frame 46 which connects it fixedly to the fan casing 11, preferably via a knife flange assembly located downstream of the outer ferrule 11. This front frame 46 contains a profiled aerodynamic part called a deflection edge 46B, which guides the flow in reverse jet.

[0061] In this preferred embodiment, the fixed structure 31 also comprises a plurality of deflection grids 32 arranged adjacent to one another around the axis Al, in a circumferential direction of the reverser 30 and the propulsion assembly 1. Furthermore, the mobile structure 29 comprises the two aforementioned movable reverser cowlings 33, corresponding to two cowlings 33 of generally semi-cylindrical shape, each extending over an angular amplitude of approximately 180°. This configuration with two cowlings 33 is particularly well suited in the case of a nacelle design in which the cowlings / walls 18 are also mounted articulated, the reverser 30 then having a so-called "D-duct" architecture. In this architecture, hoods 18, 33 are connected in such a way as to open / close simultaneously during maintenance operations on the engine.Nevertheless, other architectures are possible, such as for example a so-called "C-shaped" architecture, known by the Anglo-Saxon name "C-Duct", in which the hoods 18 of the internal structure can be articulated in-. depending on the two movable hoods 33.

[0062] Each movable reversing gear cover 33 comprises a radially external wall 50 forming an external aerodynamic nacelle surface, and a radially internal wall 52 contributing to the outward delimitation of the secondary duct 21B. This wall 52 lies in the downstream continuity of the deflection edge 46B in the direct thrust configuration. The two walls 50 and 52 define a housing 54 open axially at the upstream end of the reversing gear cover 33, and in which at least a portion of the grids 32 are located in the direct thrust configuration.

[0063] Figure 1 shows the reversing gear 30 in a forward thrust configuration, known as "direct jet," corresponding to a standard flight configuration. In this configuration, the cowlings 33 of the movable structure 29 are in a closed position, known as the forward thrust or "direct jet" position, in which these reversing gear cowlings 33 bear against the fixed structure 31, in particular against the deflection edge 46B, which is an integral part of the latter. Indeed, in the direct thrust configuration, the upstream end 52A of the radially internal wall 52 of each cowling 33 bears axially against the deflection edge 46B.

[0064] The movable structure 29 is thus translationally movable relative to the fixed structure 31 along the axis A1 of the reverser, between the forward direct thrust position shown in [Fig. 1], and a rearward thrust reversal position which will be described later. In the forward direct thrust position of the movable structure 29, the deflection grids 32 are arranged in the housing 54 of the reverser covers 33, being isolated from the secondary stream 21B by the radially internal wall 52 of these sliding covers 33. This wall 52, forming the external wall of the secondary stream, is also called the internal acoustic panel.

[0065] The thrust reversal rearward position of the moving structure 29 is shown in [Fig. 2]. This figure shows that the rearward internal acoustic panel 52 of the reversing hoods exposes upstream an opening 56 for the secondary flow 21B towards the deflection grilles 32. The opening 56 is also delimited upstream by the deflection edge 46B, which flares radially outwards towards the rear, to delimit an airflow intended to pass through the grilles 32 when the moving system is in this thrust reversal rearward position. In other words, the deflection edge 46B gradually moves away from the axis A1 from front to rear, to guide / deflect the air towards the grilles 32 in the thrust reversal configuration.

[0066] In order to divert at least part of the secondary flow 20B towards the passage opening 56 defined axially between the deflection edge 46B and the upstream end 52A of the radially internal wall 52 of each hood 33, the inverter 30 conventionally comprises gates 58 which deploy in the channel 21B. These gates 58, by closing the vein, force at least part of the secondary flow 20B to orient itself towards the opening 56, and to pass through the fixed grids 32 to obtain the desired counter-thrust function.

[0067] As previously stated, the inverter has a D-shaped hood configuration, namely that each hood 33 forms an external hood associated with an internal hood formed by the wall 18. Each assembly can then be considered as a single hood 60 hinged at the upper end on the mounting mast 59, so as to be able to pivot from a folded operating position to an open maintenance position, these positions being shown in Figures 3 to 5.

[0068] The two hoods 60 are arranged symmetrically with respect to a first median plane PI of the reversing gear, this first fictitious plane being here a vertical and longitudinal plane, passing through the axis Al and traversing the mast 59 at its midpoint. Each hood 60 therefore comprises the movable outer reversing gear hood 33 and the fixed inner hood 18, each having a semi-cylindrical shape. At their ends, the hoods 33 and 18 are connected by an upper bifurcation 62a, as well as by a lower bifurcation 62b. The two hoods 60 are arranged on either side of the first median plane PI, and the two upper bifurcations 62a are also arranged at a distance on either side of this plane PI, for the passage of a fixed upper longitudinal beam 64a.The two upper bifurcations 62a are positioned clockwise near 12 o'clock relative to the AL axis. Similarly, the two lower bifurcations 62b are also arranged at a distance on either side of the PI plane, to allow passage for a lower fixed longitudinal beam 64b. The two lower bifurcations 62b are positioned clockwise near 6 o'clock, again relative to the AL axis. At the rear end of the cowlings 60, behind the lower fixed beam 64b, the two lower bifurcations 62b are closer together, and the space between them is used for the installation of equipment and the passage of utilities 66, as can be seen at the bottom of [Fig. 4]. Preferably, the passage of utilities is carried out along the entire length of the bifurcations.At these rear extremities, the two movable hoods 33 are provided, near the lower bifurcations 62b, with conventional locking means 68, also schematically shown in [Fig. 4]. These locking means 68 are traversed by the first median plane PI, and they allow the two hoods 60 to be held together in the folded-down operating position. Furthermore, by being located near the lower bifurcations 62b, the hood locking means are situated on one side of a second median plane P2 of the inverter, this second plane P2 being perpendicular to the first median plane PI and also passing through the axis AL. In other words, the locking means 68 are located on the lower side of the fictitious second median plane P2, which is oriented longitudinally and transversely.

[0069] Although forming part of the same hinged cowling 60, the two outer and inner cowlings 33, 18 that compose it are designed to be able to be moved axially relative to each other, in order to bring the reverser from the direct thrust configuration to the thrust reversal configuration, and vice versa. To achieve this, the reverser is equipped with a translational actuation system 70, allowing the entire movable structure 29 of the reverser to be moved relative to the fixed structure 31.

[0070] With reference now to [Fig.6], the actuation system 70 is shown, which is therefore the only system within the inverter dedicated to the axial translational movement of the mobile structure 29. The system 70 is here made up of three actuators 70a, 70b1, 70b2, each equipped with an actuation member 72 movable in translation and centered on an actuation axis 74, of longitudinal orientation.

[0071] One of the particularities of the invention lies in the fact that the actuators 70a, 70b 1, 70b2 no longer form a set of actuators symmetrical with respect to the first median plane PI, in particular because one of them forms an eccentric actuator 70a, arranged on the first side of the second median plane P2, corresponding to the side opposite to that where the mast is located. Indeed, the actuation axis 74 of the eccentric actuator 70a is circumferentially offset with respect to the first median plane PI, and it remains asymmetrical with respect to each of the other two actuators 70b1, 70b2 with respect to the first median plane PL. In other words, neither of these other two actuators 70b1, 70b2 of the actuation system 70 is arranged symmetrically to the eccentric actuator 70a with respect to the first median plane PL.

[0072] In the case of three actuators retained for this embodiment, the eccentric actuator 70a is still located near the locking means 68, preferably in an angular position between 155 and 175°. Preferably, the eccentric actuator 70a is arranged circumferentially offset with respect to the lower bifurcation 62b of the cover 60 to which this actuator 70a is associated, even if this offset in the circumferential direction 76, in the direction going in the opposite direction to the other cover 60, can remain small, or even very small.

[0073] Thanks to this particular positioning of the eccentric actuator 70a, in total rupture with the configurations known in the state of the art, its implantation is facilitated because it takes place at a distance from the cluttered area where the locking means 68 are located, as well as the servitudes and equipment 66 in the space between the two lower bifurcations 62b.

[0074] The two other actuators 70b1, 70b2 constituting the actuation system 70 are arranged on the same second side of the second median plane P2, namely on the upper side where the mast 59 is located, and also on either side of the first plane PL. Together, the three actuators 70a, 70b1, 70b2 can be distributed among themselves in a regular manner along the circumferential direction 76, as can be seen on the [Fig. 6], although other arrangements remain possible, without departing from the scope of the invention. In the case of a regular distribution, the two other actuators 70bl, 70b2 are therefore asymmetrical with respect to the first median plane PI.

[0075] In this regard, it is noted that the distribution of the actuators is essentially dictated by the resumption of aerodynamic forces on the cowlings 60, particularly in thrust reversal configuration.

[0076] Another preferred configuration is shown in [Fig. 6A]. It consists of arranging the two actuators 70bl, 70b2 symmetrically with respect to each other, relative to the first median plane PI. This configuration reduces the risk of the covers jamming during their translation, since the distance between each of these two actuators and their associated guide system is identical or substantially identical.

[0077] In the embodiment described, the number of actuators 70a, 70b1, 70b2 constituting the actuation system 70 is fixed at three, but it could be different, for example five, while preferably remaining an odd number with an optimized distribution so as to limit the number, for cost and mass gains.

[0078] It is noted that the actuators 70a, 70bl, 70b2, preferably oriented parallel to the axis Al, are of conventional design, for example in the form of electric cylinders, hydraulic cylinders, or even ball or roller screws.

[0079] With reference now to figures 7 to 9, the hood 60 cooperating with the eccentric actuator 70a is shown. This articulated hood 60 has its movable hood 33 equipped with a beam 78 of general axial orientation, and located on a lower edge of this movable hood 33. The beam 78 has the particularity of offering several functions, which will be described below.

[0080] First, the main axially oriented portion of the beam 78 permanently supports means 80 for guiding the translation of the movable cover 33. These guide means 80, for example in the form of a rail, cooperate with a supplementary rail 82 fixed to a lateral side of the fixed beam 64b, to allow satisfactory translational guidance of the movable structure 29. It is noted that preferably, the eccentric actuator 70a is therefore also arranged circumferentially offset in the opposite direction to the other cover 60, relative to the guide means 80 and the rail 82.

[0081] In addition to the securing of the guide means 80 on the beam 78 of the movable hood 33, a fixing fitting 84 of the movable actuation member 72 of the eccentric actuator 70a is also secured to the main axial orientation part of the beam 78, preferably towards the rear.

[0082] Finally, at the level of a rear end of the beam 78, curved until adopting a circumferential orientation and delimiting the housing space of the fixed beam 64b axially towards the rear, a part 68a of the locking means 68 is secured to this rear end of the beam 78.

[0083] On the other hood 60, similar means are attached to its beam 78, with the exception of the fixing fitting 84 of the movable actuating member 72.

[0084] In figures 7 and 8, it is planned to fix the fixed part 86 of the eccentric actuator 70a on the front frame 46 of support for the grids 32. More specifically, this fixed part 86 of the actuator 70a has a front end fixed on the front frame 46 of support for the grids, and it projects axially towards the rear.

[0085] Alternatives are shown in Figures 10 and 11. In [Fig. 10], the fixed part 86 of the eccentric actuator 70a remains fixed on the front support frame 46 of the grids 32. The junction 63 in dashed line between the beam 64b at the clockwise position at 6 o'clock, and the front support frame 46 of the grids 32, is angularly located between the eccentric cylinder 70a, and the beam 64b.

[0086] In [Fig. 11], the fixed part 86 of the eccentric actuator 70a is fixed near the front support frame 46 of the grids 32, on the fixed beam 64b, at a circumferential protrusion thereof. The junction area 63 between the beam 64b and the front support frame 46 of the grids 32 is then angularly / circumferentially offset from the cylinder 70a, in the direction opposite to the other cover 60.

[0087] The grids 32 can be offset slightly circumferentially from the fixed beam 64b, in order to provide the necessary space for housing the fixed part of the actuator 86.

[0088] The following figures show various technical solutions to limit the risks of deflection of one or both of the movable cowlings 33, in the event of malfunction of one or more actuators 70a, 70b1, 70b2. Indeed, since these actuators are responsible for maintaining the movable cowlings 33, and even all the cowlings 60, in position, particularly in thrust reversal configuration, specific means can be implemented to avoid such deflections which may occur under the effect of aerodynamic forces acting on the cowlings.

[0089] In Figures 12 and 13, a first solution consists of placing an axial stop 90a on a front end of the movable hood 33, as well as a complementary axial stop 90b on the fixed beam 64b. The two stops 90a, 90b are intended to come into contact only in the rearward thrust reversal position of the movable hood 33. In addition, several pairs of stops of this type are preferably distributed circumferentially around the axis Al, in a regular or irregular manner.

[0090] In figures 14 and 15, the additional axial stop 90b is located on a rear frame 46c supporting the grids 32.

[0091] Finally, in [Fig. 16], the additional axial stop 90b is always located on the rear frame 46c supports the grids 32, but it is connected to an axial longitudinal member 92 located between the grids 32. This longitudinal member 92 transmits the forces experienced by the stop 90b directly into the front support frame 46, to provide better force transfer.

[0092] Various modifications can be made by a person skilled in the art to the invention just described, solely by way of non-limiting examples, the scope of which is defined by the appended claims. For example, the thrust reverser 30 can alternatively have a "C" configuration, still with two movable cowlings 33, or an "O" configuration with a single movable cowling 33 extending over an angular range close to 360°, and being interrupted only at the 12 o'clock position by the fixed upper longitudinal beam 64a, as schematically illustrated in [Fig. 17]. As another example, the propulsion assembly could be arranged laterally in the rear part of the fuselage.

[0093] Furthermore, all the features disclosed above, in the various embodiments and their alternatives, are combinable. Moreover, it is noted that in all the figures described above, elements bearing the same numerical references correspond to identical or similar elements.

Claims

1. Demands Propulsion assembly (1) for aircraft, comprising a turbomachine (2), a nacelle (3) having at least one fan cowl (14), a turbomachine mounting mast, and a thrust reverser (30) comprising a fixed structure (31) equipped with a radially internal boundary wall (18) of a secondary flow (21B) of the propulsion assembly intended to be traversed by a secondary flow (20B), the reverser also comprising a movable structure (29) comprising one or two movable reverser cowls (33) each equipped with a radially internal reverser cowl wall (52) delimiting the secondary flow (21B) radially outwards, the reverser also comprising at least one deflection grid (32), the movable structure being translationally displaceable relative to the fixed structure along a longitudinal central axis (Al) of the reverser, between an advanced direct thrust position and a rearward thrust reversal position,the reverser comprising an actuation system (70) for moving the mobile structure between its forward direct thrust position and its rearward thrust reversal position, the actuation system consisting of one or more actuators (70a, 70b1, 70b2) each comprising an actuation member (72) movable in translation and centered on an actuation axis (74), the reverser having a first median plane (PI) of the reverser passing through the central longitudinal axis (Al1) and through the attachment mast, as well as a second median plane (P2) of the reverser passing through the central longitudinal axis (Al1) and perpendicular to the first median plane (PI), characterized in that among the said actuator(s) of the actuation system (70), there is provided an eccentric actuator (70a) arranged on a first side of the second median plane (P2) opposite a second side of the second median plane (P2) where the attachment mast is located,and whose actuation axis (74) is circumferentially offset with respect to the first median plane (PI), in that in the case of several actuators constituting the actuation system (70), the eccentric actuator (70a) is asymmetrical with respect to each of the other actuators (70b1, 70b2) with respect to the first median plane (PI), and in that the actuation system (70) consists of an odd number of actuators (70a, 70bl, 70b2), preferably three or five, the actuators being distributed circumferentially among themselves in a regular or irregular manner.

2. Propulsive assembly according to claim 1, characterized in that the actuation system (70) consists of three actuators (70a, 70b1, 70b2), among which: - the eccentric actuator (70a); - two other actuators (70bl, 70b2) arranged on either side of the first median plane (PI), preferably symmetrically with respect to this first median plane.

3. Propulsion assembly according to any one of the preceding claims, characterized in that one of said two movable reversing hoods (33) comprises a beam (78) on which are fixed: - means (80) for guiding in translation of the movable reversing hood (33); - a fitting (84) for fixing the movable actuating member (72) of the eccentric actuator (70a); - a part (68a) of locking means (68) of the two movable hoods (33).

4. Propulsion assembly according to any one of the preceding claims, characterized in that a fixed part (86) of the eccentric actuator (70a) is fixed on a front frame (46) of deflection grid support (32), or on a fixed longitudinal beam (64b) of the inverter, extending rearward from the front frame (46) of grid support.

5. Propulsion assembly according to any one of the preceding claims, characterized in that it comprises, associated with at least one of said one or two movable reversing hoods (33), at least one deflection limitation element (90a, 90b) of said movable hood in the rearward thrust reversal position, in the event of malfunction of one or more actuators (70a, 70b1, 70b2).

6. Propulsion assembly according to any one of the preceding claims, characterized in that the reverser has a C, D or O hood architecture.

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