Thrust reverser with sealing membrane and retention system

Abstract

The invention relates to a thrust reverser (1) for an aircraft propulsion unit, the thrust reverser (1) comprising a stationary structure (3), a movable structure (13) that is translatable with respect to the stationary structure (3) between a thrust position and a thrust reversal position, at least one sealing membrane (17) designed to deflect at least part of the secondary flow towards the outside, at least one retention system (21) designed to engage with the stationary structure (3) and the corresponding sealing membrane (17), the retention system (21) being configured to subject the corresponding sealing membrane (17) to a return force comprising a component opposite to the general direction of flow in the thrust reversal position.

Description

[0001] DESCRIPTION

[0002] TITLE: Thrust reverser with sealing membrane and restraint system

[0003] Field of invention

[0004] The present invention relates to a thrust reverser with a shutter membrane and a system for retaining the shutter membrane. The retaining system applies to the shutter membrane a force comprising a component opposite to a general direction of flow of an aircraft propulsion system.

[0005] Prior art

[0006] A thrust reverser of an aircraft propulsion unit comprises a fixed structure and a movable structure or assembly of at least one cowl intended, in a thrust reversal position, to move longitudinally to provide a radial opening in the nacelle.

[0007] A set of thrust reverser actuators, similar to that described in document FR 3 010 455, allows the transition from a thrust position, or operating position of the propulsion unit in flight, to the thrust reversal position, or position for redirecting a portion of the gases moving in the propulsion unit in the opposite direction through the radial opening.

[0008] The radial opening allows gases flowing in a secondary vein of the propulsion unit to escape outwardly. The thrust reverser further includes a deflector extending transversely in the secondary vein to guide the gases outwardly in the thrust reversal position.

[0009] The deflector may be a flap, connected to the fixed structure by a connecting rod and to the movable structure by a rotary connection, deploying as the movable structure moves from a thrust position to the thrust reversal position.

[0010] However, this technical solution requires the use of different parts representing a certain mass and the functional clearances between these parts are likely to disrupt the aerodynamics of the flow of gases in the propulsion unit.

[0011] An alternative is to use as a deflector a membrane that deploys like a sail when moving to the thrust reversal position. This sealing membrane is flexible and deploys by being fixed to the fixed structure on the one hand and to the mobile structure on the other hand as described in document FR 3 131 757.

[0012] The shutter membrane is in contact with certain parts of the moving structure and exerts axial forces in the general direction of flow on the moving structure. The use of the shutter membrane therefore requires an oversizing of the actuator assembly to allow the movement of the moving structure from the thrust reversal position to the thrust position if we compare the membrane system to the flap system.

[0013] There is therefore a need to improve the operation of the sealing membrane.

[0014] Statement of the invention

[0015] To this end, the present invention relates to a thrust reverser for an aircraft propulsion unit, the thrust reverser comprising: a fixed structure provided with a front frame and an internal delimiting wall of a secondary vein of the propulsion unit, the secondary vein being intended to be traversed by a secondary flow in a general direction of flow, a mobile structure provided with at least one cover, the mobile structure being movable in translation relative to the fixed structure along a longitudinal central axis of the thrust reverser between a thrust position and a thrust reversal position, at least one closure membrane designed to deflect at least a portion of the secondary flow outwards through a radial opening provided between the front frame and the mobile structure in the thrust reversal position, the at least one closure membrane extending into the secondary vein in the thrust reversal position,at least one retaining system designed to cooperate with the fixed structure and the corresponding sealing membrane, said retaining system being configured to subject the corresponding sealing membrane to a restoring force comprising a component opposite to the general direction of flow in the thrust reversal position.,

[0016] When moving from the thrust position to the reverse thrust position, the radial opening appears until it reaches its maximum size in the reverse thrust position. At the same time, the sealing membrane deploys and is subjected to the secondary flow which imposes a force on it including a component in the general direction of flow.

[0017] The sealing membrane, as it deploys in the secondary vein, is pressurized by the gas circulation. The orientation of the resultant of the forces evolves throughout the transit to become predominantly axial, i.e. in the general direction of flow, in the thrust reversal position. The vein is blocked axially by the sealing membrane with a flow that is deflected predominantly radially just upstream of the sealing membrane in the thrust reversal position.

[0018] The sealing membrane can then come into contact with the moving structure and in turn risks imposing a force on the moving structure in the general direction of flow.

[0019] The restraint system(s) make it possible to limit the movement of the corresponding sealing membrane in the general direction of flow and thus to avoid or limit the stress of the sealing membrane on the mobile structure.

[0020] A sealing membrane can have one or more retaining systems depending on the configurations.

[0021] In this text the terms upstream, downstream, front, rear are defined in relation to the general direction of flow.

[0022] According to one aspect of the invention, said retaining system is also configured to subject the corresponding closure membrane to the return force between an intermediate return start position and the thrust reversal position.

[0023] Thus, the restraint system is not active (no restoring force with a component opposite to the general direction of flow) in the pushing position. The restraint system is only activated from the intermediate position at the start of the restoring.

[0024] Preferably, the intermediate return start position corresponds to 50% or more, and preferably 70% or more, of a stroke between the thrust position and the thrust reversal position.

[0025] According to one aspect of the invention, the fixed structure comprises a rear frame, the at least one sealing membrane having a first end fixed to or cooperating with the rear frame, each cowl comprises an external delimiting wall configured to delimit the secondary vein with the internal delimiting wall in the thrust position and an external panel having an external aerodynamic surface of the thrust reverser, each cowl has a cavity open towards the front frame in the thrust position and arranged between the external delimiting wall and the external panel, the rear frame being located in the cavity in the thrust position so that the at least one sealing membrane is at least partly in the cavity in the thrust position.

[0026] It appears that during deployment and retraction of the sealing membrane between the thrust position and the reverse thrust position, the sealing membrane exits the cavity and then re-enters it.

[0027] This arrangement promotes the circulation of gas in the secondary vein in the pushing position.

[0028] According to one aspect of the invention, the at least one sealing membrane is configured to cooperate by contact with an upstream end of the external delimiting wall at least over a portion of a stroke of the thrust reverser between the thrust position and the thrust reversal position.

[0029] Due to the circulation of gas in the general direction of flow, the sealing membrane is forced towards the rear frame and comes into contact with the external boundary wall, in particular in an initial part of the stroke between the thrust position and the thrust reversal position.

[0030] The sealing membrane imposes, during this contact, a constraint with a component according to the general direction of flow on the mobile structure. The constraint corresponds to the cooperation between the sealing membrane and the upstream end of the external delimiting wall. The upstream end pushes the sealing membrane in the opposite direction to the general direction of flow. The sealing membrane is thus tensioned and rubs on the upstream end in the manner of a belt or a cable on a pulley, which pushes the mobile structure downstream.

[0031] This constraint is reduced or eliminated by the restraint system. For at least part of the thrust reverser stroke, the shutter membrane is in contact with the outer boundary wall but the force applied is less.

[0032] The restraint system may also, depending on the architecture, cause a separation over part of the travel between the thrust position and the thrust reversal position. During this separation, no stress is imposed by the sealing membrane on the moving structure.

[0033] The sealing membrane 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 sealing membrane may also be made using a composite material whose matrix is ​​particularly flexible, for example aliphatic polyurethane or silicone. In this case, the matrix provides a low flexural recovery capacity and the behavior of the structure obtained is indeed that of a membrane.

[0034] According to one aspect of the invention, the sealing membrane is configured to fold in a perfectly reversible manner. Preferably, this folding may correspond to an elastic extension or to sliding of fibers of the sealing membrane.

[0035] In particular, the folding of the sealing membrane has a very small radius of curvature compared to the surface of the sealing membrane.

[0036] According to one aspect of the invention, the sealing membrane has a very small thickness compared to the surface area of ​​the sealing membrane. For example, the thickness is of the order of 0.1 to 3 mm. For information purposes, it is observed that the sealing membrane behaves like a boat sail when it is put under pressure.

[0037] The external boundary wall is an acoustic panel or sliding panel of the transcowl.

[0038] According to one aspect of the invention, each retaining system comprises a connecting element configured to cooperate with a corresponding fixing point of the fixed structure on the one hand and configured to cooperate with the corresponding sealing membrane at an attachment point on the other hand, the attachment point being in the cavity in the pushing position.

[0039] Preferably, the attachment point is located on the front frame.

[0040] This arrangement allows the sealing membrane to be subjected to a restoring force in the opposite direction to the general direction of flow by a simple mechanism for attaching the sealing membrane to the front frame by means of a connecting element.

[0041] According to one aspect of the invention, the connecting element is configured to be included in a space delimited by the cavity and the front frame in the thrust position so as to be outside the secondary flow. This configuration of the connecting element in the thrust position avoids any disturbance of the circulation of the secondary flow and thus any unbalancing of the engine assembly.

[0042] According to one aspect of the invention, in the pushing position, the first end is located in the cavity so that the sealing membrane is at least partly in contact with the external delimiting wall inside the cavity, the attachment point being located at a determined distance from the first end, the determined distance defining an intermediate position of total detachment of the sealing membrane from the external delimiting wall which is located between the pushing position and the thrust reversal position, the sealing membrane no longer being in contact with the external delimiting wall from the intermediate detachment position.

[0043] In other words, between the intermediate separation position and the thrust reversal position, the sealing membrane is no longer in contact with the moving structure thanks to the action of the connecting element.

[0044] At the end of the opening of the mobile structure, the sealing membrane does not disturb the movement of the mobile structure, which requires less effort to move the mobile structure at the end of opening and at the start of closing.

[0045] When closing to the push position, the sealing membrane comes into contact with the external boundary wall in the intermediate detachment position. It should be noted that the forces of the sealing membrane on the external boundary wall are however limited by the action of the connecting element which retains the sealing membrane upstream.

[0046] This arrangement thus facilitates the movement of the mobile structure which is little disturbed by the presence of the sealing membrane.

[0047] The determined distance defines the stage of opening of the mobile structure from which the connecting element is stretched and applies a restoring force to the sealing membrane.

[0048] The greater the distance determined, the earlier the restoring force on the sealing membrane appears. One possibility is to define a force corresponding to an opening of approximately 80%. A more premature tensioning of the connecting element is of the order of 70% of the opening.

[0049] The tensioning by the connecting element does not necessarily correspond to the moment when the sealing membrane ceases to be in contact with the moving structure. The sealing membrane may be tensioned and still in contact with the moving structure and then completely detach from the moving structure as the opening progresses.

[0050] According to one aspect of the invention, the connecting element is dimensioned to extend rectilinearly between the attachment point and the fixing point in the pushing position.

[0051] This dimensioning of the connecting element allows it to be maintained inside the cavity in the pushing position.

[0052] According to a variant, the connecting element may have a length greater than a rectilinear distance between the attachment point and the fixing point in the thrust position. The connecting element is then relaxed in the thrust position and at the start of transit to the thrust reversal position.

[0053] The length of the connecting element thus also has an influence on the opening stage of the mobile structure from which the connecting element is tensioned.

[0054] According to one aspect of the invention, the restraint system further comprises an elastic restraint device configured to submit a restoring force to the connecting element towards the attachment point.

[0055] This arrangement makes it possible to reduce the force applied by the sealing membrane on the mobile structure by retaining the connecting element further upstream.

[0056] According to one possibility, the elastic retaining device is an elastic part connecting the front frame to the connecting element. The elastic part may be a cord made of an extensible material fixed on the fixed part, in particular on the front frame, and on the connecting element.

[0057] The elastic part is configured to expand as the mobile structure opens. This gradually and then completely detaches the sealing membrane from the mobile structure.

[0058] Alternatively, the elastic retaining device is a reel attached to or arranged in the front frame. The reel includes a return spring sized to allow the gradual detachment of the sealing membrane from the movable structure upon opening. As an alternative to the spring, a motor, for example an electric motor, can be used as a return force.

[0059] According to one aspect of the invention, the connecting element is a cable or a strap of fixed length. Alternatively, other devices could be used as long as they fulfill the function of connecting the front frame and the sealing membrane. According to one aspect of the invention, the restraint system also comprises a reinforcement element configured to connect the connecting element to the sealing membrane at a reinforcement location separate from the attachment point.

[0060] This arrangement ensures that the connecting element is correctly attached to the sealing membrane. Furthermore, the reinforcement location, separate from the attachment point, makes it possible to define the shape taken by the sealing membrane in the thrust reversal position more precisely than with only the attachment point.

[0061] According to one aspect of the invention, the reinforcing element is a cable or a strap made of the same material as the connecting element and connected to the latter.

[0062] According to one aspect of the invention, each sealing membrane comprises a second end opposite the first end and connected to the inner boundary wall by a corresponding connecting rod or other mechanical system, the connecting rod or other mechanical system being configured to move the second end between a low position near or in contact with the inner boundary wall in the reverse thrust position and a high position near or in contact with the outer boundary wall in the thrust position.

[0063] In the low position, the sealing membrane extends into the secondary vein at least partly transversely to the general direction of flow over almost all or the entire flow section, whereas in the high position the sealing membrane is almost or completely no longer present in the secondary vein and has retracted into the cavity.

[0064] According to one aspect of the invention, the other mechanical system may comprise an arrangement of cables and corresponding guides connecting the second end to the fixed structure, said arrangement being configured to be set in motion by the displacement of the mobile structure between the thrust position and the thrust reversal position.

[0065] According to one aspect of the invention, each connecting rod has a lower end configured to be mounted on the internal delimiting wall, preferably via a pivot or ball joint.

[0066] Each connecting rod is designed to move from the upper position in which said connecting rod projects radially into the secondary vein to the lower position in which said connecting rod is folded downstream.

[0067] In the upper position, each connecting rod may adopt a radial or substantially radial orientation relative to the longitudinal central axis of the thrust reverser, while in the lower position, each connecting rod may adopt an axial or substantially axial orientation.

[0068] Each connecting rod includes a return device configured to apply a force tending to tilt said connecting rod towards the low position. This ensures proper positioning of the sealing membrane when moving to the thrust reversal position.

[0069] The connecting rods are spaced circumferentially from each other within the secondary vein, and their number can vary, for example, from two to ten, depending on the angular extent of the sealing membrane.

[0070] According to one aspect of the invention, the mobile structure is configured to slide relative to the fixed structure by means of a rail-slide system of the thrust reverser, the rail-slide system being configured to guide the mobile structure from front to rear during the opening phase of the reverser to the thrust reverser position, and from rear to front during the closing phase to the thrust position, the thrust reverser comprising a set of actuators arranged in the fixed structure to move the mobile structure relative to the fixed structure.

[0071] According to one aspect of the invention, the actuator assembly is configured to be moved by at least one cylinder of the thrust reverser associated with a flexible shaft of the thrust reverser. A dedicated control assembly of the thrust reverser controls the at least one cylinder and the actuator assembly.

[0072] The use of the restraint system makes it possible not to oversize the at least one cylinder. Indeed, in the absence of a restraint system, the sealing membrane is in contact with the external delimiting wall which creates resistance to the movement of the mobile structure, particularly at the end of opening and when closing the mobile structure.

[0073] According to one aspect of the invention, the thrust reverser comprises at least one set of deflection grids or equivalent deflector device such as a set of deflector sails having an angular amplitude identical or similar to that of the corresponding cowl. The set of grids is fixed and extends between the front frame and the rear frame.

[0074] According to one aspect of the invention, the mobile structure comprises two covers. Preferably, each cover forms a complementary hemispherical half-shell so as to define a nacelle portion.

[0075] According to one possibility, a single sealing membrane is associated with each thrust reverser cowl. According to another possibility, several circumferentially adjacent sealing membranes are associated with each of the two cowls.

[0076] The different aspects defined above, which are not incompatible, can be combined.

[0077] Brief description of the figures

[0078] The invention will be better understood with the aid of the detailed description which is set out below with reference to the accompanying drawings.

[0079] [Fig. 1] is a schematic longitudinal sectional view of a thrust reverser with a shutter membrane.

[0080] [Fig. 2] is a schematic longitudinal sectional view of the thrust reverser in the thrust position with a shutter membrane retaining system.

[0081] [Fig. 3] is a schematic longitudinal sectional view of the thrust reverser between the thrust position and a thrust reversal position.

[0082] [Fig. 4] is a schematic longitudinal sectional view of the thrust reverser in the thrust reverser position.

[0083] [Fig. 5] is a schematic longitudinal sectional view of the thrust reverser with an elastic retaining device.

[0084] [Fig. 6] is a schematic longitudinal sectional view of the thrust reverser with a reel as an elastic retaining device.

[0085] [Fig. 7] is a schematic longitudinal sectional view of the thrust reverser with the restraint system including a reinforcement element.

[0086] [Fig. 8] is a perspective view of a thrust reverser forward frame, shutter membrane and restraint systems in the thrust reverser position.

[0087] [Fig. 9] is a perspective view of a thrust reverser actuator assembly and actuator assembly.

[0088] Description with reference to figures

[0089] In the following detailed description of the figures defined above, the same elements or elements fulfilling identical functions may retain the same references so as to simplify the understanding of the invention. As illustrated in Figure 1, a thrust reverser 1 for an aircraft propulsion unit comprises a fixed structure 3 provided with a front frame 5 and an internal delimiting wall 7 of a secondary vein 9 of the propulsion unit, the secondary vein 9 being intended to be crossed by a secondary flow in a general direction of flow 11.

[0090] The thrust reverser 1 comprises a mobile structure 13 provided with at least one cover 14, the mobile structure 13 being movable in translation relative to the fixed structure 3 along a longitudinal central axis 15 of the thrust reverser 1 between a thrust position illustrated in figures 2, 5 and 6 and a thrust reversal position illustrated in figures 4, 7 and 8.

[0091] Preferably, the mobile structure comprises two covers 14, each cover 14 forming a complementary hemispherical half-shell so as to define a nacelle portion.

[0092] According to one possibility, a single sealing membrane 17 is associated with each cover 14 of the thrust reverser 1.

[0093] According to another possibility, several circumferentially adjacent sealing membranes 17 are associated with each of the two covers 14.

[0094] Furthermore, the thrust reverser 1 comprises at least one shut-off membrane 17 designed to divert at least part of the secondary flow outwards through a radial opening 19 formed between the front frame 5 and the mobile structure 13 in the thrust reversal position, the at least one shut-off membrane 17 extending into the secondary flow path 9 in the thrust reversal position.

[0095] As illustrated in figures 2 to 9, the thrust reverser 1 further comprises at least one retaining system 21 designed to cooperate with the fixed structure 3 and the corresponding sealing membrane 17.

[0096] Said retaining system 21 is configured to subject the corresponding sealing membrane 17 to a restoring force comprising a component opposite to the general direction of flow 11 in the thrust reversal position and between the thrust reversal position and the thrust position.

[0097] When moving from the thrust position to the reverse thrust position, the radial opening 19 appears until it reaches its maximum size in the reverse thrust position.

[0098] At the same time, the sealing membrane 17 deploys and is subjected to the secondary flow which imposes a force on it in the general direction of flow 11. The sealing membrane 17 can then come into abutment against the mobile structure 13 as illustrated in figures 1 and 3.

[0099] A sealing membrane 17 may have several retaining systems 21 according to the configurations as illustrated in FIG. 8.

[0100] In this text the terms upstream, downstream, front, rear are defined in relation to the general direction of flow 11.

[0101] The restraint system 21 is also configured to subject the corresponding closure membrane 17 to the return force between an intermediate return start position and the thrust reversal position.

[0102] Thus, the retaining system 21 is not active in the pushing position, that is to say there is no restoring force with a component opposite to the general direction of flow 11.

[0103] The restraint system 21 is only activated from the intermediate return start position. Preferably, the intermediate return start position corresponds to 50% or more, and preferably 70% or more, of a stroke between the thrust position and the thrust reversal position.

[0104] The fixed structure 3 comprises a rear frame 23, the at least one sealing membrane 17 having a first end 25 fixed on or cooperating with the rear frame 23.

[0105] Each cowl 14 comprises an external delimiting wall T1 configured to delimit the secondary vein 9 with the internal delimiting wall 7 in the thrust position and an external panel 29 having an exterior aerodynamic surface of the thrust reverser 1.

[0106] Each cowl 14 has a cavity 31 open towards the front frame 5 in the thrust position and arranged between the external delimiting wall T1 and the external panel 29, the rear frame 23 being located in the cavity 31 in the thrust position so that the at least one sealing membrane 17 is at least partly in the cavity 31 in the thrust position and cooperates by contact with an upstream end 33 of the external delimiting wall T1 at least over part of a stroke of the thrust reverser 1 between the thrust position and the thrust reversal position.

[0107] It appears that during deployment and retraction of the sealing membrane 17 between the thrust position and the thrust reversal position, the sealing membrane 17 leaves the cavity 31 and then re-enters it.

[0108] Due to the circulation of gas in the general direction of flow 11, the sealing membrane 17 is forced in the direction of the rear frame 23 and comes into contact with the external delimiting wall T1, in particular in an initial part of the stroke between the thrust position and the thrust reversal position.

[0109] The sealing membrane 17 imposes, during this contact, a constraint with a component according to the general direction of flow 11 on the mobile structure 13. The constraint corresponds to the cooperation between the sealing membrane 17 and the upstream end 33 of the external delimiting wall 27. The upstream end 33 pushes the sealing membrane 17 in the opposite direction to the general direction of flow 11. The sealing membrane 17 is thus tensioned and rubs on the upstream end 33 in the manner of a belt or a cable on a pulley which pushes the mobile structure 13 downstream.

[0110] This constraint is reduced or eliminated by the restraint system 21. Over at least one of the thrust reverser strokes, the closure membrane 17 is in contact with the external boundary wall T1 but the force applied is less.

[0111] The restraint system 21 may also, depending on the architecture, cause a separation over part of the travel between the thrust position and the thrust reversal position. During this separation, no stress is imposed by the sealing membrane 17 on the mobile structure 13.

[0112] The sealing membrane 17 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 sealing membrane may also be made using a composite material whose matrix is ​​particularly flexible, for example aliphatic polyurethane or silicone. In this case, the matrix provides a low flexural recovery capacity and the behavior of the structure obtained is indeed that of a membrane.

[0113] The sealing membrane 17 is configured to fold in a perfectly reversible manner. Preferably, this folding may correspond to an elastic extension or to sliding of fibers of the sealing membrane 17.

[0114] In particular, the folding of the sealing membrane 17 has a very small radius of curvature relative to the surface of the sealing membrane 17.

[0115] The sealing membrane 17 has a very small thickness compared to the surface area of ​​the sealing membrane 17. For example, the thickness is of the order of 0.1 to 3 mm. For information purposes, it is observed that the sealing membrane 17 behaves like a boat sail when it is pressurized.

[0116] The external delimiting wall T1 is an acoustic panel or sliding panel of the transcowl. Each retaining system 21 comprises a connecting element 35 configured to cooperate with a corresponding fixing point 37 of the fixed structure 3, here in particular of the front frame 5, on the one hand and configured to cooperate with the corresponding sealing membrane 17 at an attachment point 39 on the other hand, the attachment point 39 being in the cavity 31 in the pushing position.

[0117] The sealing membrane 17 is thus subjected to a return force in the opposite direction to the general direction of flow 11 by a simple mechanism for fixing the sealing membrane 17 to the front frame 5 by means of a connecting element 35.

[0118] The connecting element 35 is configured to be included in a space delimited by the cavity 31 and the front frame 5 in the pushing position so as to be outside the secondary vein 9.

[0119] In the pushing position, the first end 25 is located in the cavity 31 so that the sealing membrane 17 is at least partly in contact with the external delimiting wall T1 inside the cavity 31, the attachment point 39 being located at a determined distance from the first end 25.

[0120] The determined distance defines an intermediate position of total detachment of the sealing membrane 17 from the external delimiting wall T1 which is located between the thrust position and the thrust reversal position, the sealing membrane 17 no longer being in contact with the external delimiting wall T1 from the intermediate detachment position.

[0121] In other words, between the intermediate separation position and the thrust reversal position, the sealing membrane 17 is no longer in contact with the mobile structure 13 thanks to the action of the connecting element 35 as shown in Figures 4 and 7.

[0122] At the end of opening of the mobile structure 13, the sealing membrane 17 does not disturb the movement of the mobile structure 13, which requires less effort to move the mobile structure 13 at the end of opening and at the start of closing.

[0123] When closing to the pushing position, the sealing membrane 17 comes into contact with the external delimiting wall T1 in the intermediate detachment position. It should be noted that the forces of the sealing membrane 17 on the external delimiting wall T1 are however limited by the action of the connecting element 35 which retains the sealing membrane 17 upstream.

[0124] The determined distance defines the stage of opening of the mobile structure 13 from which the connecting element 35 is tensioned and applies a restoring force to the sealing membrane 17. The greater the determined distance, the earlier the restoring force on the sealing membrane 17 appears. One possibility is to define a force corresponding to an opening of approximately 80%. A more premature tensioning of the connecting element is of the order of 70% of the opening.

[0125] The tensioning by the connecting element 35 does not necessarily correspond to the moment when the sealing membrane 17 ceases to be in contact with the mobile structure 13. The sealing membrane 17 can be tensioned and still in contact with the mobile structure 13 then detach completely from the mobile structure 13 with the advancement of the opening.

[0126] The connecting element 35 is dimensioned to extend rectilinearly between the attachment point 39 and the fixing point 37 in the pushing position as illustrated in Figure 2.

[0127] According to a variant shown in Figure 5, the connecting element 35 may have a length greater than a rectilinear distance between the attachment point 39 and the fixing point 37 in the thrust position. The connecting element 35 is then relaxed in the thrust position and at the start of transit to the thrust reversal position.

[0128] The length of the connecting element 35 thus also has an influence on the opening stage of the mobile structure 13 from which the connecting element 35 is stretched.

[0129] The retaining system 21 may optionally comprise an elastic retaining device 41 configured to submit a restoring force to the connecting element 35 towards the attachment point as illustrated in FIGS. 5 to 7.

[0130] According to one possibility, illustrated in Figure 5, the elastic retaining device 41 is an elastic piece connecting the front frame 5 to the connecting element 35. The elastic piece can be a cord of an extensible material fixed on the front frame 5 and the connecting element 35. This also works when the cord is fixed at another suitable location of the fixed part 3.

[0131] The elastic part is configured to expand as the mobile structure 13 opens. This gradually and then completely detaches the sealing membrane 17 from the mobile structure 13.

[0132] According to another possibility, illustrated in Figures 6 and 7, the elastic retaining device 41 is a reel attached to or arranged in the front frame 5. The reel comprises a return spring sized to allow the progressive detachment of the sealing membrane 17 from the movable structure 13 during opening. Alternatively to the spring, a motor, for example an electric motor, can be used as a return force.

[0133] The connecting element 35 is a cable or strap of fixed length. Alternatively, other devices could be used as long as they fulfill the function of connecting the front frame 5 and the sealing membrane 17.

[0134] The retaining system 21 may also include a reinforcing element 43 configured to connect the connecting element 35 to the sealing membrane 17 at a reinforcing location 45 separate from the attachment point 39 as illustrated in FIG. 7.

[0135] The reinforcement location 45, distinct from the attachment point 39, makes it possible to define the shape taken by the closure membrane 17 in the thrust reversal position more precisely than with only the attachment point 39.

[0136] The reinforcing element 39 is a cable or strap made of the same material as the connecting element 39 and connected to the latter.

[0137] As also visible in Figure 8, each sealing membrane 17 comprises a second end 47 opposite the first end 25 and connected to the internal delimiting wall 7 by a corresponding connecting rod 49 or another mechanical system, the connecting rod 49 or the other mechanical system being configured to move the second end 47 between a low position near or in contact with the internal delimiting wall 7 in the thrust reversal position and a high position near or in contact with the external delimiting wall T1 in the thrust position.

[0138] In the low position, the sealing membrane 17 extends in the secondary vein 9 at least partly transversely to the general direction of flow 1 over almost all or the entire flow section, whereas in the high position the sealing membrane 17 is almost or totally no longer present in the secondary vein 9 and has retracted into the cavity.

[0139] The other mechanical system may comprise an arrangement of cables and corresponding guides connecting the second end 47 to the fixed structure 3, said arrangement being configured to be set in motion by the displacement of the mobile structure 13 between the thrust position and the thrust reversal position.

[0140] Each connecting rod 49 has a lower end 51 configured to be mounted on the internal delimiting wall 7, preferably by means of a pivot or ball joint. Each connecting rod 49 is designed to move from the upper position in which said connecting rod 49 projects radially into the secondary vein 9 to the lower position in which said connecting rod 49 is folded downstream.

[0141] In the high position, each connecting rod 49 can adopt a radial or substantially radial orientation relative to the longitudinal central axis 15 of the thrust reverser 1, while in the low position, each connecting rod 49 can adopt an axial or substantially axial orientation.

[0142] Each connecting rod 49 includes a return device configured to apply a force tending to tilt said connecting rod 49 towards the low position. This ensures proper positioning of the sealing membrane 17 when moving to the thrust reversal position.

[0143] The connecting rods 49 are spaced circumferentially from each other within the secondary vein 9, and their number can vary for example from two to ten, depending on the angular extent of the sealing membrane 17 as can be seen in Figure 8.

[0144] The mobile structure 13 is configured to slide relative to the fixed structure 3 via a rail-slide system of the thrust reverser 1, the rail-slide system being configured to guide the mobile structure 13 from front to rear during the opening phase of the reverser to the thrust reversal position, and from rear to front during the closing phase to the thrust position.

[0145] As illustrated in Figure 9, the thrust reverser 1 comprises a set of actuators 53 arranged in the fixed structure 3 to move the movable structure 13 relative to the fixed structure 3.

[0146] The actuator assembly 53 is configured to be set in motion by a cylinder 55 of the thrust reverser 1 associated with a flexible shaft 57 of the thrust reverser 1. A dedicated control assembly 59 of the thrust reverser 1 controls the cylinder 55 and the actuator assembly 53

[0147] The thrust reverser 1 comprises at least one set of deflection grids having an angular amplitude identical or similar to that of the corresponding cowl. The set of grids is fixed and extends between the front frame and the rear frame.

[0148] It thus appears that the retaining system(s) 21 make it possible to limit the movement of the corresponding sealing membrane 17 in the general direction of flow 11 and thus to avoid or limit the stress of the sealing membrane 17 on the mobile structure 13. This arrangement thus facilitates the movement of the mobile structure 13 which is little disturbed by the presence of the sealing membrane 17.

[0149] Furthermore, the use of the retaining system 21 makes it possible not to oversize the jack 55. Indeed, in the absence of the retaining system 21, the closing membrane 17 is in contact with the external delimiting wall T1 which creates resistance to the movement of the mobile structure 13, in particular at the end of opening and during the closing of the mobile structure 13.

[0150] As goes without saying, the invention is not limited to the single embodiment described above as an example; on the contrary, it encompasses all variant embodiments.

Claims

CLAIMS 1. Thrust reverser (1) for an aircraft propulsion unit, the thrust reverser (1) comprising: a fixed structure (3) provided with a front frame (5) and an internal delimiting wall (27) of a secondary vein (9) of the propulsion unit, the secondary vein (9) being intended to be crossed by a secondary flow in a general flow direction (11), a mobile structure (13) provided with at least one cover (14), the mobile structure (13) being movable in translation relative to the fixed structure (3) along a longitudinal central axis (15) of the thrust reverser (1) between a thrust position and a thrust reversal position, at least one closing membrane (17) designed to deflect at least a portion of the secondary flow outwards through a radial opening (19) provided between the front frame (5) and the mobile structure (13) in the thrust reversal position,the at least one sealing membrane (17) extending into the secondary vein (9) in the thrust reversal position, at least one retaining system (21) designed to cooperate with the fixed structure (3) and the corresponding sealing membrane (17), said retaining system (21) being configured to subject the corresponding sealing membrane (17) to a restoring force comprising a component opposite to the general direction of flow (11) in the thrust reversal position, wherein the fixed structure (3) comprises a rear frame (23), the at least one sealing membrane (17) having a first end (25) fixed on or cooperating with the rear frame (23), wherein each cowl (14) comprises an external delimiting wall (27) configured to delimit the secondary vein (9) with the internal delimiting wall (7) in the thrust position and an external panel (29) having an external aerodynamic surface of the thrust reverser (1),in which each cover (14) has a cavity (31) open towards the front frame (5) in the pushing position and arranged between the external delimiting wall (27) and the external panel (29), the rear frame (23) being located in the cavity (31) in the pushing position so that the at least one sealing membrane (17) is at least partly in the cavity (31) in the pushing position, characterized in that each retaining system (21) comprises a connecting element (35) configured to cooperate with a fixing point (37), corresponding to the fixed structure (3) on the one hand and configured to cooperate with the corresponding sealing membrane (17) at an attachment point (39) on the other hand, the attachment point (39) being in the cavity (31) in the pushing position.

2. Thrust reverser (1) according to claim 1, wherein the connecting element (35) is configured to be included in a space delimited by the cavity (31) and the front frame (5) in the thrust position so as to be outside the secondary vein (9).

3. Thrust reverser (1) according to one of claims 1 or 2, wherein, in the thrust position, the first end (25) is located in the cavity (31) so that the closure membrane (17) is at least partly in contact with the external delimiting wall (27) inside the cavity (31), the attachment point (39) being located at a determined distance from the first end (25), the determined distance defining an intermediate position of total detachment of the closure membrane (17) from the external delimiting wall (27) which is located between the thrust position and the thrust reversal position, the closure membrane (17) no longer being in contact with the external delimiting wall (27) from the intermediate detachment position.

4. Thrust reverser (1) according to one of claims 1 to 3, wherein the connecting element (35) is dimensioned to extend rectilinearly between the attachment point (39) and the fixing point (37) in the thrust position.

5. Thrust reverser (1) according to one of claims 1 to 4, wherein the retaining system (21) further comprises an elastic retaining device (41) configured to subject a return force to the connecting element (35) towards the attachment point (37).

6. Thrust reverser (1) according to one of claims 1 to 5, wherein the retaining system (21) also comprises a reinforcing element (43) configured to connect the connecting element (35) to the sealing membrane (17) at a reinforcing location (43) separate from the attachment point (39).

7. Thrust reverser (1) according to one of claims 1 to 6, in which each sealing membrane (17) comprises a second end (47) opposite the first end (25) and connected to the inner boundary wall (7) by a corresponding connecting rod (49) or other mechanical system, the connecting rod (49) or other mechanical system being configured to move the second end (47) between a low position near or in contact with the inner boundary wall (7) in the thrust reversal position and a high position near or in contact with the outer boundary wall (27) in the thrust position.

8. Thrust reverser (1) according to one of claims 1 to 7, wherein the movable structure (13) is configured to slide relative to the fixed structure (3) by means of a rail-slide system of the thrust reverser (1), the rail-slide system being configured to guide the movable structure (13) from front to rear during the opening phase of the reverser to the thrust reversal position, and from rear to front during the closing phase to the thrust position, the thrust reverser (1) comprising a set of actuators (53) arranged in the fixed structure (3) to move the movable structure (13) relative to the fixed structure (3).

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