THRUST REVERSER COMPRISING AT LEAST ONE DEPLOYABLE MEMBRANE, HAVING DEPLOYMENT MEANS WITH LOW WEIGHT

Abstract

The invention relates to a thrust reverser for an aircraft propulsion unit, comprising a membrane (58) for closing the secondary flow path, a second end of which is connected to the internal wall of the secondary flow path by a cable (62) cooperating with an actuating device (70) for this cable, the device (70) comprising an elastic means (80) cooperating with the second cable end (62b) of the deployment member (62), and the reverser being configured so that during an initial phase of a movement of the mobile structure towards its retracted thrust reversal position, the elastic means (80) releases previously stored energy by stressing the second cable end (62b), and so that during a subsequent phase of this movement of the mobile structure, the elastic means (80) stores energy by being stressed by this second end (62b). Figure for abstract: Fig. 7

Description

Title of the invention: THRUST REVERSER COMPRISING AT LEAST ONE DEPLOYABLE MEMBRANE, HAVING MEANS OF DEPLOYMENT WITH LOW WEIGHT Technical field

[0001] The invention relates to the field of nacelles and thrust reversers for aircraft propulsion systems, and, more particularly, to thrust reversers equipped with deployable membranes. State of the prior art

[0002] Thrust reversers are devices for diverting the airflow passing through the propulsion unit forward, so as to shorten landing distances and limit the stress on the brakes on the landing gear.

[0003] The grid reversers currently used in the aeronautical sector comprise deflection grids integrated into a fixed or mobile structure of the reverser. The mobile structure of the reverser comprises one or more mobile reverser cowls, and it is mounted so as to be movable in translation relative to the fixed structure between a forward direct thrust position and a rearward thrust reversal position.

[0004] In the rearward thrust reversal position, to divert at least part of the secondary flow towards the grilles, the reverser is usually equipped with shutters, which, when deployed, at least partially close the secondary vein. In a known manner, this forces the air of the secondary flow radially outwards, towards the grilles, which then generate the counter-thrust air flow towards the front.

[0005] The flaps are generally pivotally mounted on the radially inner wall of the movable reverser cowls, this wall delimiting the secondary flow radially outwards. Thus, recesses are provided in this radially inner wall of the reverser cowls in order to receive the shutter flaps in the retracted position, as adopted in direct jet. However, in direct jet, the presence of the recesses and the flaps is a source of aerodynamic disturbances on the secondary flow. In addition, this presence locally limits the installation of an acoustic panel on the radially inner wall of the reverser cowls.

[0006] To provide a technical solution to these problems, it has been proposed to replace the shutters with one or more deployable membranes for closing the secondary vein. Such a design is known, for example, from document FR 3 076 864 AL

[0007] There remains, however, a need to optimize the design of the means allowing the deployment of the sealing membranes, in the secondary vein. Indeed, it is essentially envisaged to deploy the membrane connecting rods, which represent a non-negligible mass, impacting the overall mass of the inverter. This mass is all the more impacted since the connecting rods are generally coupled to actuating devices allowing their rotation, such as spring systems, which are heavy and complex.

[0008] More specifically, a radially outer end of each connecting rod is provided to be connected to one end of the membrane, and a radially inner end of the connecting rod is articulated on the radially inner delimiting wall of the secondary vein. When the mobile structure moves towards its retracted thrust reversal position, the membrane gradually deploys in the vein by plunging radially towards the inside thereof, driven by the connecting rod(s) which tilt downstream and also radially inwards.

[0009] In the direct jet position, the end of the membrane connected to the connecting rods is generally sandwiched between a deflection edge of the fixed structure, and an upstream end of the radially internal wall of the movable cover.

[0010] During an initial phase of movement of the mobile structure from its forward direct thrust position to its retracted thrust reversal position, there is a need to limit the risks of the membrane being pressed against an internal surface of the radially internal wall of the mobile cowl. Indeed, such a pressing of the membrane impairs its proper deployment radially inwards, and is therefore not desirable. This is the reason why a device for actuating the connecting rod is provided, designed to apply a tensile force to the membrane from the start of the reverser opening phase. The force applied by the actuating device is transmitted to the connecting rod, which then transmits it to the membrane, with the effect of detaching it. The risks of this membrane being undesiredly pressed against the mobile cowl are thus reduced, or even harmed.

[0011] However, it may also be important for the elastic means integrated into the actuating device to continue to develop a force forcing the connecting rod into the folded position, when the reverser is in its thrust reversal configuration. This reinforces the stability of the membrane, when it fulfills the function of diverting the secondary flow.

[0012] To do this, an elastic means is provided with a high stroke, allowing a release of energy during the entire movement of the mobile structure, from its forward direct thrust position to its retracted thrust reversal position. Such an extended stroke of the elastic means, however, leads to significant bulk, as well as a negative impact on the overall mass of the reverser. Statement of the invention

[0013] To at least partially address the aforementioned drawbacks, the invention firstly relates to a thrust reverser for an aircraft propulsion unit, the reverser comprising a fixed structure equipped with a radially internal delimiting wall of a secondary vein of the propulsion unit intended to be crossed by a secondary flow, the reverser also comprising a mobile structure comprising at least one reverser cowl having a housing open upstream and delimited between a radially external wall and a radially internal wall of the reverser cowl, the mobile structure being movable in translation relative to the fixed structure along a longitudinal central axis of the reverser,between an advanced direct thrust position and a retracted thrust reversal position in which the retracted radially internal wall of the reverser cowl reveals upstream an opening for passage of the secondary flow stream towards a flow deflection member, the reverser also comprising a membrane for closing the secondary flow stream, a first end of which is connected to the fixed structure of the reverser, as well as a membrane deployment member, a first end of which is attached to a second end of the closing membrane, and a second end of which is attached to the radially internal delimiting wall, cooperating with a device for actuating this membrane deployment member.

[0014] According to the invention, the actuating device comprises an elastic means cooperating with the second end of the deployment member, and the reverser is configured so that during an initial phase of a movement of the mobile structure from its forward direct thrust position to its retracted thrust reversal position, the elastic means releases previously stored energy by stressing the second end of the deployment member, and so that during a subsequent phase of this movement of the mobile structure, the elastic means stores energy by being stressed by the second end of the deployment member.

[0015] With this design, the invention no longer requires the presence of membrane deployment rods, these being able to be replaced by lighter deployment members, such as cables or straps, or any other flexible and elongated force transmission element. This results in a significant reduction in the overall mass of the reverser. The invention is therefore the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of these aircraft (decarbonization).

[0016] Above all, the invention breaks with the principle of providing an elastic means which relaxes throughout the opening stroke of the mobile structure of the reverser. Indeed, the reverser is here advantageously designed so that during the initial phase of the opening of the mobile structure, the elastic means releases energy, as is known from the prior art to pull on the membrane which begins to deploy. But then, during the opening stroke, the elastic means stores energy by being stressed by the deployment member, itself stressed by the membrane which is subjected to the pressure of the air of the secondary flow. This inversion in the load of the elastic means, during the same movement of the mobile structure of the reverser towards its rearward thrust reversal position, allows a limited stroke of this elastic means. This advantageously results in a reduced size, as well as a reduction in the overall mass of the reverser, with a further reduction in the environmental impact of aircraft.

[0017] The invention preferably provides at least one of the following optional technical features, taken alone or in combination.

[0018] Preferably, the first membrane end is connected to a rear support frame of the flow deflection member, even if any other location can be envisaged within the fixed structure of the inverter, without departing from the scope of the invention.

[0019] Preferably, when the mobile structure occupies its forward direct thrust position, the second end of the deployment member is downstream relative to the first end of this deployment member. Preferably, the situation is reversed when the mobile structure occupies its rearward thrust reversal position.

[0020] Preferably, the membrane deployment member has at least one portion with an aerodynamic profile-shaped section. This reduces drag on the secondary flow, in the direct thrust configuration.

[0021] Preferably, the elastic means of the actuating device comprises a coil spring, preferably a compression spring.

[0022] Preferably, the elastic means of the actuating device comprises a leaf spring, preferably generally U-shaped, or of any shape deemed suitable, for example generally S-shaped or Z-shaped.

[0023] Preferably, the actuating device comprises one or more guide members, such as pulleys, through which the second end of the deployment member passes before cooperating with the elastic means. These guide members make it possible in particular to give the desired incidence to the deployment member in the secondary vein.

[0024] Preferably, the second end of the deployment member is fixed to the elastic means, or it is in sliding support on the latter.

[0025] Preferably, the radially internal delimiting wall is formed by an internal skin on which is fixed, externally, an acoustic skin, and the means elastic is located at least partly in a radial space between the inner skin and the acoustic skin.

[0026] Finally, the invention relates to a nacelle for an aircraft propulsion unit, comprising at least one fan cowl and a thrust reverser as described above.

[0027] Other advantages and characteristics of the invention will appear in the detailed non-limiting description below. Brief description of the drawings

[0028] The following detailed description refers to the accompanying drawings in which:

[0029] [Fig.l] is a schematic half-view in longitudinal section of a propulsion assembly, comprising a thrust reverser shown in direct thrust configuration;

[0030] [Fig.2] is a schematic half-view in longitudinal section of the inverter equipping the propulsion assembly shown in [Fig.l], according to a preferred embodiment of the invention and with the reverser shown in direct thrust configuration;

[0031] [Fig.3] is a schematic half-view of the inverter shown in [Fig.2], represented in reverse thrust configuration;

[0032] [Fig.3A] is a schematic half-view of the inverter similar to that of [Fig.3], according to an alternative;

[0033] [Fig.4] is a perspective view of the inverter shown in Figures 2 and 3, re presented in direct push configuration;

[0034] [Fig.5] is a perspective view of the inverter shown in [Fig.4], shown in reverse thrust configuration;

[0035] [Fig.6] is a perspective view of a cable actuating device fitted the reverser shown in the preceding figures, according to a preferred embodiment of the invention, and with the reverser being in the direct thrust configuration;

[0036] [Fig.7] is a perspective view of a portion of the actuating device shown in the previous figure;

[0037] [Fig.7A] is a cross-sectional view of a preferred embodiment for the membrane deployment cable;

[0038] [Fig.8] is a graph showing the evolution of the compression of a spring equipping the actuating device shown in Figures 6 and 7, during movement of the mobile structure of the reverser towards its rearward thrust reversal position;

[0039] [Fig.9] is a sectional view of the cable actuating device, according to another preferred embodiment of the invention;

[0040] [Fig. 10] is a perspective view of the cable actuating device shown in the preceding figure;

[0041] [Fig. 11] is a perspective view of the cable actuating device shown in the preceding figure, from another viewing angle;

[0042] [Fig. 12] is a sectional view of the cable actuating device, according to another preferred embodiment of the invention, and with the reverser in the direct thrust configuration;

[0043] [Fig.13] is a view similar to that of [Fig.12], showing the different orientations of the cable during opening of the inverter;

[0044] [Fig. 14] is a perspective view of the cable actuating device, according to another preferred embodiment of the invention, and with the reverser in the thrust reverser configuration;

[0045] [Fig. 15] is a perspective view of a portion of the cable actuating device shown in the preceding figure, from another viewing angle;

[0046] [Fig. 16] is a sectional view of the actuating device shown in the preceding figure, according to an alternative and with the reverser in direct thrust configuration;

[0047] [Fig. 17]

[0048] [Fig. 18]

[0049] [Fig. 19]

[0050] [Fig.20] are alternative embodiments to that shown in [Fig. 16];

[0051] [Fig.21]

[0052] [Fig.22]

[0053] [Fig.23] are sectional views showing the evolution of the actuating device of [Fig.20], during the opening of the inverter;

[0054] [Fig.24] is a sectional view of the cable actuating device, according to another preferred embodiment of the invention, and with the reverser in direct thrust configuration;

[0055] [Fig.25] is a sectional view of the actuating device of the preceding figure, with the reverser in thrust reverser configuration;

[0056] [Fig.26]

[0057] [Fig.27]

[0058] [Fig.28] are alternative embodiments to that shown in [Fig. 16]. Detailed description of embodiments

[0059] [Fig.l] shows an aircraft propulsion unit 1, having a longitudinal central axis A1.

[0060] Subsequently, the terms “upstream” and “downstream” are defined relative to a general direction SI of flow of the gases through the propulsion unit 1, along the axis A1 when the latter generates thrust. These terms “upstream” and “downstream” could respectively be substituted by the terms “front” and “rear”, with the same meaning.

[0061] The propulsion unit 1 comprises a turbomachine 2, a nacelle 3 as well as a mast (not shown), intended to connect the propulsion unit 1 to a wing (not shown) of the aircraft.

[0062] The turbomachine 2 is in this example a double-flow, double-spool turbojet 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 turbojet engine 2 is provided with a fan casing 11 connected to the gas generator by structural arms 12.

[0063] The nacelle 3 comprises a front section forming an air inlet 13, a middle section which comprises two fan cowls 14 surrounding the fan casing 11, and a rear section 15.

[0064] In operation, an air flow 20 enters the propulsion unit 1 through the air inlet 13, passes through the fan 5 and then divides into a primary flow 20A and a secondary flow 20B. The primary flow 20A flows in a primary gas circulation vein 21A passing through the gas generator. The secondary flow 20B flows in a secondary vein 21B surrounding the gas generator. The secondary vein 21B is delimited radially inwards by a fixed internal fairing which envelops the gas generator. In this example, the fixed internal fairing comprises a first section 17 belonging to the middle section 14, and a second section 18 extending rearwardly from the first section 17, so as to form a 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.This same section will subsequently be called wall 18 of radially internal delimitation of secondary vein 21B.

[0065] Radially outwardly, the secondary vein 21B is delimited by the fan casing 11, and, in the configuration of [Fig.l], by one or more movable reverser cowls 33 forming a part of the rear section 15 of the nacelle 3, and which will be described later. More precisely, between the fan casing 11 and the reverser cowls 33, there is provided an outer shroud 40 of an intermediate casing 42, the latter comprising the aforementioned structural arms 12, the radially outer end of which is fixed to this shroud 40. The latter therefore also participates in delimiting the secondary vein 21B radially outwardly, by being located in the downstream axial extension of the fan casing 11.

[0066] The nacelle 3 therefore comprises a thrust reverser 30 centered on the axis A1 and comprising on the one hand a fixed structure 31 secured to the fan casing 11, and on the other hand a structure 29 movable relative to the fixed structure 31. The fixed structure 31 comprises for example a front frame 46 which fixedly connects it to the fan casing 11, preferably via a knife flange assembly located downstream of the outer shroud 11. This front frame 46 contains a profiled aerodynamic part called a deflection edge 46B, which guides the flow in an inverted jet.

[0067] Here, the fixed structure 31 also comprises a plurality of deflection grids 32 arranged adjacent to each other around the axis A1, in a circumferential direction of the reverser 30 and the propulsion assembly 1. These grids 32 thus form flow deflection members to generate the counter-thrust. In this regard, it is noted that this flow reversal function can alternatively or simultaneously be carried out using a flexible structure, of the membrane / textile type.

[0068] Furthermore, the mobile structure 29 comprises the covers mobile reverser 33 mentioned above, for example two cowls 33 each extending over an angular amplitude of approximately 180°. This configuration with two cowls 33 is particularly well suited in the case of a nacelle design in which the cowls / walls 18 are also mounted articulated, the reverser 30 then having a so-called “D-shaped” architecture, known by the Anglo-Saxon name “D-Duct”. In this architecture, the cowls 18, 33 are connected so as to open / close simultaneously during maintenance operations on the engine. However, other architectures are possible, such as for example a so-called “C-shaped” architecture, known by the Anglo-Saxon name “C-Duct”, or a so-called “O-shaped” architecture, known by the Anglo-Saxon name “O-Duct”.

[0069] Each movable reverser cowl 33 comprises a radially external wall 50, forming an external aerodynamic surface of the reverser and the nacelle, this surface being matched by the external air. Each cowl 33 also comprises a radially internal wall 52 participating in the delimitation of the secondary vein 21B radially outwards. This wall 52 is located in the downstream continuity of the external shell 40 of the intermediate casing. The two walls 50, 52 define a cavity 54 preferably open axially towards the front, at the upstream end of the reverser cowl 33.

[0070] [Fig. 1] shows the reverser 30 in a direct forward thrust configuration, called “direct jet”, corresponding to a standard flight configuration. In this configuration, the cowls 33 of the mobile structure 29 are in a closed position, called the advanced thrust or “direct jet” position, in which these reverser cowls 33 bear on the fixed structure 31, in particular on the deflection edge 46B forming an integral part of the latter. Indeed, in the direct thrust configuration, the upstream end 52a of the radially internal wall 52 of each cowl 33 bears axially against the deflection edge 46B.

[0071] Maintaining the movable hood 33 in the forward direct thrust position is ensured by means for locking this cover on the fixed structure 31 of the inverter. These controlled locking means (not shown) are conventional, so they will not be described further. As an indicative example, active locks can be implemented capable of unlocking under load to counter the compressive force of a joint between the mobile structure and the deflection edge. This type of lock can in fact overcompress the joint, so that unlocking can then be controlled.

[0072] The mobile structure 29 is thus movable in translation relative to the fixed structure 31 along the axis A1 of the reverser, between the forward direct thrust position shown in [Fig.l], and a retracted thrust reversal position which will be described later. In the forward direct thrust position of the mobile structure 29, the deflection grids 32 are arranged in the cavity 54 of the reverser cowls 33, being isolated from the secondary vein 21B by the radially internal wall 52 of these sliding reverser cowls 29. This wall 52, forming the external wall of the secondary vein, is also called an acoustic internal panel.

[0073] This direct thrust configuration is also shown in Figures 2 and 4, while the rearward thrust reversal position of the mobile structure 29 is shown in Figures 3, 3A and 5.

[0074] In [Fig. 3], it is shown that the internal acoustic panel 52 set back from the reverser cowls reveals upstream a passage opening 56 of the secondary stream 21B towards the deflection grilles 32. The opening 56 is therefore also delimited upstream by the deflection edge 46B, which flares radially outwards going towards the rear, to channel an air flow intended to pass through the grilles 32 when the mobile system is in this retracted thrust reversal position. In other words, the deflection edge 46B gradually moves away from the axis A1 going from the front to the rear, to guide / deflect the air towards the grilles 32 in the thrust reversal configuration. Downstream, the passage opening 56 is delimited in particular by the upstream end 52a of the radially internal wall 52.

[0075] In order to divert at least a portion of the secondary flow 20B toward the passage opening 56 defined axially between the deviation edge 46B and the upstream end 52a of the radially inner wall 52 of each cover 33, the inverter 30 comprises one or more sealing membranes 58. Subsequently, an embodiment will be described in which a single membrane 58 is associated with each inverter cover 33 while having an identical or similar angular amplitude, but it remains conceivable to provide several circumferentially adjacent membranes associated with each cover 33. Similarly, only the cooperation between a membrane 58 and its associated cover 33 will be described below, it being understood that this cooperation is identical or similar for all the covers of the inverter 33. It is however noted that in addition to the possibility of providing several membranes 58, one or more rigid, more conventional, shutters could be provided in association with this / these membranes, for example alternating in the circumferential direction.

[0076] The membrane 58 may be made of a material known to those skilled in the art for this type of application. For example, it may be a non-impregnated fabric, for example aramid fibers. The membrane 58 may also be made using a composite material whose matrix is ​​particularly flexible, for example aliphatic polyurethane, which allows use under different temperature conditions, in particular lower temperatures in the case of an aliphatic polyurethane membrane than in the case of a silicone membrane. The matrix gives a low bending recovery capacity and the behavior of the structure obtained is indeed that of a membrane. One of the major properties of this membrane 58 is that it can bend in a perfectly reversible manner (elastic or by fiber sliding) with a very small radius of curvature relative to its surface, and to have a very small thickness, for example of the order of 0.1 to 3 mm.For information, it is observed that this membrane 58 behaves like a boat sail or a parachute / a flying wing when it is put under pressure.

[0077] It is recalled that in a conventional grid inverter, the mobile structure slides relative to the fixed structure by means of a rail / slide system which guides the mobile structure from front to rear during the opening phase of the inverter, and from rear to front during the closing phase. A rearward force applied to the mobile structure of the inverter therefore causes it to move backward, relative to the fixed structure. This force is usually generated by conventional actuators such as jacks or ball screws.

[0078] Still with reference to figures 1 to 5 representing a preferred embodiment of the invention, the membrane 58 has two opposite ends, namely a first end 58a connecting to one or more deployment members 62, as well as a second end 58b connected to a rear frame 60 supporting the grids 32. This support is annular, or in the form of an annular section connecting in fact the rear end of several adjacent grids.

[0079] In this preferred embodiment, the deployment elements 62, arranged at least partly in the secondary vein 21B, take the form of cables or straps, or any other force transmission element of a flexible nature and of elongate shape. As mentioned previously, the cables 62 are circumferentially spaced from each other within the secondary vein 21B, and their number can for example vary from two to ten in association with the same membrane.

[0080] Each cable 62 comprises a first end 62a connected to the second membrane end 58b. Its second end 62b, opposite the first, is attached to the radially internal delimiting wall 18, cooperating with a device 70 for actuating this cable. This actuating device 70, of passive design, is specific to the invention, and it will be described later.

[0081] As can be seen in Figures 1, 2 and 4, when the mobile structure 29 occupies its forward direct thrust position, at least a portion of the closure membrane 58 is arranged radially between the deflection grids 32 and the radially inner wall 52 of the inverter cover 33, in the cavity 54. Preferably, the portion of the membrane 58 which is located in this cavity 54 of the inverter cover 33, radially covers the entire length of the grids 32. As a result, when the mobile structure 29 adopts its forward direct thrust position, the first end 58a of the membrane 58 is pinched between the upstream end of the wall 18, and the deflection edge 46B, close to the cable connection point which is located in the vein. In order to avoid possible damage to the membrane 58 due to this pinching, the deflection edge 46B may locally have a notch of a shape adapted to receive the upstream end 52a of the wall 52.Thus, the membrane 58 is also pressed into this notch of the deflection edge 46B, by the support of the upstream end of the wall 52.

[0082] It is also noted that in this forward direct thrust position, the second cable end 62b is located downstream relative to the first end 62a of this deployment member 62. The taut cable 62 in fact has a substantially radial orientation in the vein 21B, with a slight inclination relative to this radial direction, for example up to a value of 10 to 20°. On the other hand, in the retracted thrust reversal position, the second cable end 62b is located upstream relative to the first cable end 62a. Indeed, the cable 62, still taut and straight, is here folded back into the secondary vein, with an axial or substantially axial orientation, a slight inclination towards the upstream of approximately 10 to 20° relative to the axial direction being able to be adopted, as has been shown in [Fig.3].

[0083] Still with reference to this [Fig. 3], when the mobile structure 29 occupies its rearward thrust reversal position, the closing membrane 58 is partly in contact with the upstream end 52a of the radially internal wall 52 of the reverser cowl, thus corresponding to the acoustic panel. More precisely, during the rearward movement of the mobile structure 29, the membrane 58 slides on this upstream end 52a of the radially internal wall 52. The membrane 58 is therefore in axial contact downstream against the upstream end 52a. It should be noted that depending on the extent of the axial travel of the reverser, the membrane 58 may no longer be in contact with the internal acoustic panel 52 in the fully deployed position of the reverser, where the cowl 33 is in its most rearward position. Such a configuration is shown in [Fig.3A], in which it is clearly shown that the membrane 58 is located upstream and at a distance from the upstream end 52a of the wall 52 of the reverser cover. The option with contact corresponds to a minimized stroke of the reverser, while the option without contact generally corresponds to a smoother membrane shape in reverse jet, therefore more efficient from an aerodynamic point of view.

[0084] Thus, the part of the membrane 58 which is located radially outwards relative to its bearing zone on the wall 52 closes off a part of the upstream axial opening of the cavity 54, while the other part located radially inwards closes off at least a part of the secondary vein 21B, thereby diverting at least a part of the secondary flow 20B towards the passage opening 56 in the direction of the grids 32.

[0085] Another possibility, not shown, consists of carrying out the radially external attachment of the membrane 58 on the radially external wall 50 of the sliding cover 33.

[0086] As mentioned previously, the cable actuation device 70 allows the second cable end 62b to be connected to the radially internal delimiting wall 18 of the vein (also called IFS, from the English “Inner Fixed Structure”).

[0087] A preferred embodiment of the actuating device 70 is shown in Figures 6 and 7. It comprises a fixing fitting 72, fixedly attached to the wall 18 using screws, or using other fixing elements, such as rivets. In this regard, it is noted that the radially internal delimiting wall 18 is here formed by a double skin, namely an internal skin 18a on which is fixed, radially outwards, an acoustic skin 18b. The internal skin 18a, also called the rear skin, fulfills a more structural function for the wall 18.

[0088] The two skins 18a, 18b are radially spaced from one another, and they define between them a space 74 in which at least part of a spring module 76 is located. The latter, which is an integral part of the actuating device 70, comprises a housing 78 secured to the fixing fitting 72, and possibly made in one piece with this fitting. The module 76 also comprises an elastic means 80 housed in the housing 78, also called elastic return means. This is preferably a spring, and even more preferably a coil spring, operating in compression. This spring 80 is therefore located at least partly in the inter-skin space 74, housed in its housing. This design of the actuating device 70, called buried or semi-buried, makes it possible to limit aerodynamic disturbances on the secondary flow.

[0089] A first end of the spring 80 is fixed or resting on a wall of the housing 78, while a second end of the spring is resting or fixed on a slider 82, slidably housed in the housing. It is on this slider 82 that the second end of cable 62b is attached, which makes it fixed to the second end of the compression spring 80.

[0090] The fixing fitting 72 is here fixed to the acoustic skin 18b, externally on the latter, even if other arrangements are possible, without departing from the scope of the invention. The fitting 72 carries a yoke 84 on which is mounted a cable guide member 86, such as a pulley. The second end of the cable 62b therefore passes through this pulley 86 before cooperating with the second end of the spring 80, via the slider 82.

[0091] It is noted that the cable 62 is not necessarily of circular section. As visible in [Fig.7A], it may have a section in the form of an aerodynamic profile, for example with a reinforced core of circular section. In order to facilitate its passage through the pulley 86, the latter may have a general shape of revolution with a concave generator. This allows it to wind naturally around this hollowed pulley, with its incoming and outgoing portions which are offset from each other so as not to be located in the same plane. Alternatively, it may be provided that only one portion of the cable has an aerodynamic section to limit disturbances on the secondary flow, in a direct thrust configuration. In such a case, the other portion of cable, which winds onto the pulley 86, may remain of circular section, as has been shown in FIGS. 6 and 7.

[0092] With reference to [Fig.8], one of the specific features of the present invention is described, in connection with the behavior of the spring 80 during the opening of the reverser.

[0093] In the direct thrust configuration, when the percentage of opening of the mobile structure of the reverser is zero, the percentage of compression of the spring is 100%, or close to 100%. Indeed, the turns of the spring can all be in contact with each other, or clearances can remain, to allow axial movement of the mobile structure arranged in this configuration.

[0094] Thanks to the highly compressed spring 80, it exerts forces on the membrane 58, via the cable 62, which make it possible to keep this membrane in tension when it is stored in the hood cavity 54. This contributes to its stability, and facilitates its deployment during a subsequent operation of opening the inverter.

[0095] Indeed, it is ensured that during the initial phase of movement of the mobile structure 29 from its forward direct thrust position, towards its retracted thrust reversal position, the spring 80 releases previously stored energy, and this by decompressing, as shown schematically in the two diagrams on the left under the abscissa axis of the graph of [Fig.8].

[0096] By pulling in this way on the cable 62 at the start of the reverser opening, it is advantageously prevented that the membrane 58, which begins to deploy in the vein 21B, comes to press against the radially internal surface of the wall 52 of the cover 33, moving towards the rear.

[0097] During this decompression of the spring 80, its second end and the slider 82 effectively drive the second end of the cable 62b, up to a maximum decompression percentage permitted by the housing 78. This maximum percentage of decompression of the spring, for which the latter provides minimal force on the membrane 58 via the cable 62, is for example reached after approximately 20% of the total opening stroke of the mobile structure. The compression percentage of the spring 80 can then drop for example to around 10 to 40%.

[0098] Then, during a subsequent phase of this movement of the mobile structure, which can go until the end of this opening or end before, for example at approximately 60% of the total stroke as shown in the graph of [Fig. 8], the spring 80 then stores energy, by recompressing. This recompression is due to the fact that at this stage of the opening of the inverter, it is the cable 62 which stresses the spring 80, the cable itself being stressed by the membrane 58 in deployment, which undergoes the pressure of the air of the secondary flow in the vein. This recompression phase has been illustrated in the third diagram from the left, under the abscissa axis of the graph of [Fig. 8].

[0099] The inversion in the load of the spring 80, during the same movement of the mobile structure 29 towards its retracted thrust reversal position, advantageously allows a limited stroke of this spring, and therefore a housing 78 of lower mass, and of more restricted dimensions.

[0100] The subsequent phase of recompression of the spring 80 may be such that it leads to the maximum compression of the latter, in which all the turns are in contact with each other. Once this recompression is completed, the end of the opening stroke can be carried out while keeping the spring 80 with a maximum compression percentage, as illustrated in the diagram on the right, under the abscissa axis of the graph of [Fig.8]. This makes it possible to generate a significant counter-force on the deployed membrane 58, via the cable 62, and therefore contributes to the stability of this membrane in the thrust reversal configuration.

[0101] Other preferred embodiments may be envisaged, such as that shown in FIGS. 9 to 11, which provides that the fixing fitting 72 is fixed to the internal skin 18a of the wall 18.

[0102] The preferred embodiment of Figures 12 and 13 is such that the actuating device 70 comprises two pulleys 86 cooperating successively with the second cable end 62b, before the latter is fixed on the spring 80, via the slider 82. This makes it possible to improve the guidance of the cable 62, and to offer greater freedom in the orientation of this cable through the secondary vein, in the direct thrust configuration. The pulley(s) 86 also make it possible, by their positioning, to obtain a design ensuring the unloading and loading phases of the spring 80, during the same opening stroke of the reverser.

[0103] Referring now to Figures 14 and 15, a preferred embodiment of the invention is shown with leaf springs 80, which replace the coil spring of the previous embodiments. This involves two leaf springs 80 arranged in parallel, even if only one of them could be sufficient. Each spring 80 is for example laid down so as to have a general U shape open towards the upstream, and whose radially inner branch is connected to the fixing fitting 72, intended to be fixed to the acoustic skin 18b of the wall 18. It is the free end of the radially outer branch of the U which ensures the connection with the second cable end 62b.

[0104] In the alternative of [Fig. 16], the cable actuating device 70 differs in that a single pulley 86 is provided to guide the second cable end 62b, and no longer two pulleys as in the embodiment of FIGS. 14 and 15. In addition, this single pulley is provided to be fixed on the internal skin 18a.

[0105] Figures 17 to 20 correspond to other alternatives, in which no pulley is provided, even if these could be retained, without departing from the scope of the invention. In [Fig. 17], the lying leaf spring 80 remains generally U-shaped, with its radially outer branch fixed to the acoustic skin 18b of the wall 18. In [Fig. 18], the leaf spring 80 is generally Z-shaped, with its radially inner branch fixed to the inner skin 18a of the wall 18. In [Fig. 19], the alternative is similar, since the leaf spring 80 is generally S-shaped.

[0106] In [Fig.20], the lying leaf spring 80 is generally U-shaped, with its radially inner branch fixed on the inner skin 18a of the wall 18. The following figures 21 to 23 show the evolution of the spring 80 during the opening of the reverser, with first of all a decompression phase up to the state of [Fig.21], state which can be maintained during a transient phase. Then, figures 22 and 23 represent a recompression phase of the spring 80, up to a state of total compression of the spring which can be maintained until the complete opening of the reverser, as has been detailed for a previous preferred embodiment.

[0107] Figures 24 and 25 show another preferred embodiment of the invention, in which the second cable end 62b is not fixed to the leaf spring 80, but arranged to slide on the latter, while being fixed to the fitting 72. The spring 80 is also fixed to this fitting 72. In this mode, it is actually the support between the two elements 62b, 80 which generates the stress on the cable 62, and the recompression of the spring 80.

[0108] [Fig.26] shows an embodiment in which the leaf spring 80 is fixed to its two opposite ends on the internal skin 18a, and the second end of cable 62b is attached to the central part of this spring 80, in the general shape of an inverted V. [Fig.27] shows a similar embodiment, in which the spring 80 adopts a generally flat or curved shape, with its two fixing ends curved.

[0109] Finally, [Fig.28] shows an embodiment similar to that of [Fig.27], with the spring 80 made in two parts, symmetrical or not, and connected together at the fixing point with the second cable end 62b.

[0110] Various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims. For example, the thrust reverser 30 may alternatively have a “C” or “O” architecture. Furthermore, the membranes specific to the invention may coexist with conventional grids within the reverser. Furthermore, all the features disclosed above, in the various preferred embodiments and their alternatives, are combinable with each other. Moreover, it is noted that in all the figures which have been described above, the elements which bear the same numerical references correspond to identical or similar elements.

[0111] Finally, it is noted that the elastic means described above can take many forms, such as a torsion, compression, or spiral spring. For example, legs of a torsion spring can bear on the deployment member 62 and on the wall 18, to ensure the rotation of this member. For the spiral spring, it can be in tension in the direct jet configuration, with a winding of the cable around the axis of the spring during the recoil movement of the mobile reverser cover, in order to actuate the deployment member 62.

Claims

1.

2.

3. Claims Thrust reverser (30) for an aircraft propulsion unit, the reverser comprising a fixed structure (31) equipped with a radially internal delimiting wall (18) of a secondary vein (21B) of the propulsion unit intended to be traversed by a secondary flow (20B), the reverser also comprising a movable structure (29) comprising at least one reverser cowl (33) having a housing (54) open upstream and delimited between a radially external wall (50) and a radially internal wall (52) of the reverser cowl (33), the movable structure being movable in translation relative to the fixed structure along a longitudinal central axis (A1) of the reverser, between an advanced direct thrust position and a retracted thrust reversal position in which the retracted radially internal wall (52) of the reverser cowl reveals upstream a passage opening (56) of the secondary vein (21B) towards a member of flow diversion (32),the reverser also comprising a membrane (58) for closing the secondary vein (21B) of which a first end (58a) is connected to the fixed structure of the reverser, as well as a membrane deployment member (62) of which a first end (62a) is attached to a second end (58b) of the closing membrane (58), and of which a second end (62b) is attached to the radially internal delimiting wall (18), cooperating with a device (70) for actuating this membrane deployment member, characterized in that the actuating device (70) comprises an elastic means (80) cooperating with the second end (62b) of the deployment member (62), and the reverser being configured so that during an initial phase of a movement of the mobile structure from its forward direct thrust position to its retracted thrust reversal position,the elastic means (80) releases previously stored energy by stressing the second end (62b) of the deployment member, and so that during a subsequent phase of this movement of the mobile structure, the elastic means (80) stores energy by being stressed by the second end (62b) of the deployment member., Inverter according to claim 1, characterized in that the membrane deployment member (62) is a cable or a strap. Inverter according to claim 1 or 2, characterized in that the first membrane end (58a) is connected to a rear frame (60) supporting the flow deflecting member (32).

4. Inverter according to any one of the preceding claims, characterized in that when the mobile structure (29) occupies its advanced direct thrust position, the second end (62b) of the deployment member (62) is located downstream relative to the first end (62a) of this deployment member.

5. Inverter according to any one of the preceding claims, characterized in that the elastic means (80) of the actuating device (70) comprises a coil spring, preferably a compression spring.

6. Inverter according to any one of claims 1 to 4, characterized in that the elastic means (80) of the actuating device (70) comprises a leaf spring, preferably generally U-shaped.

7. Inverter according to any one of the preceding claims, characterized in that the actuating device (70) comprises one or more guide members (86) through which the second end (62b) of the deployment member (62) passes, before cooperating with the elastic means (80).

8. Inverter according to any one of the preceding claims, characterized in that the second end (62b) of the deployment member (62) is fixed to the elastic means, or it is in sliding support on the latter.

9. Inverter according to any one of the preceding claims, characterized in that the radially internal delimiting wall (18) is formed by an internal skin (18a) on which is fixed, externally, an acoustic skin (18b), and in that the elastic means (80) is located at least partly in a radial space (74) between the internal skin (18a) and the acoustic skin (18b).

10. Nacelle (3) for an aircraft propulsion unit, comprising at least one fan cowl (14), as well as a thrust reverser (30) according to any one of the preceding claims.

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