Propulsion assembly for an aircraft, comprising an intermediate cowl of the stationary, removable type, mounted on a hinge system

Abstract

The invention relates to a propulsion assembly for an aircraft, comprising a nacelle (24) which comprises a fan compartment (48), a front cowling (34) forming an air inlet, and an intermediate section (36) including at least one intermediate cowling (66, 70) of the stationary and removable type that delimits the fan compartment (48) on the outside and is attached to another structure of the propulsion assembly via removable attachment through-members (86, 90, 94). The intermediate cowling is connected to another element of the propulsion assembly by means of a hinge system (96, 100) which, by removing the removable attachment through-members, is configured to enable movement of the intermediate cowling between a closed position, in which it extends as a continuation of the front cowling (34), and an open position, in which the intermediate cowling is offset upstream or downstream so as to open the fan compartment (48).

Description

[0001] Propulsion unit for aircraft comprising a removable fixed-type intermediate cowl mounted on an articulation system

[0002] Description

[0003] Technical field

[0004] The present invention relates to the field of propulsion units for aircraft, and more particularly concerns a propulsion unit whose nacelle is of the type whose intermediate section comprises one or more removable fixed cowls, that is to say cowls rigidly fixed to the rest of the nacelle by means of through-fixing members which it is necessary to dismantle to allow access to the interior of the propulsion unit.

[0005] State of the prior art

[0006] A propulsion unit nacelle for an aircraft generally has a tubular structure comprising, from upstream to downstream, a front section comprising an air inlet, an intermediate section intended to surround a turbojet fan, and a rear section comprising thrust reversal means and intended to surround the gas generator of the turbojet.

[0007] The air inlet, generally annular in shape, is intended to separate, during operation, the air flow entering the turbojet and the air flow bypassing the propulsion unit.

[0008] Generally speaking, the nacelle must have mechanical rigidity performance in order to limit its deformations due to stresses during operation.

[0009] In some nacelles, the intermediate section cowls, commonly referred to as fan cowls, are hingedly mounted on a fixed structure of the nacelle or the propulsion unit mast and are thus capable of pivoting laterally from a closed position to an open position, in a so-called "butterfly" movement, to allow access to the interior of the propulsion unit, for example for maintenance operations. These nacelles generally have a significant mass, a large footprint, a significant cost, and their opening involves high loads.

[0010] In other nacelles, particularly when it is desired to avoid the aforementioned drawbacks, the cowls of the intermediate section are rigidly fixed to the rest of the nacelle by means of removable through-fastening members, such as bolts, which must be removed to allow access to the interior of the propulsion unit. The cowls can in this case be described as "fixed" and "removable". This solution is particularly suitable for a front section designed without a rear bulkhead, that is to say without a wall transversely connecting an internal shell of the front section to an external shell thereof behind and at a distance from the air intake.

[0011] Document FR3004700 discloses an example of a nacelle with removable fixed hoods.

[0012] The present disclosure is intended to improve nacelles comprising such covers.

[0013] Statement of the invention

[0014] For this purpose, it offers a propulsion system for aircraft, comprising:

[0015] - a turbojet engine comprising a fan and a fan casing surrounding the fan; and

[0016] - a nacelle surrounding the turbojet engine and comprising a fan compartment delimited internally by the fan casing; in which the nacelle comprises, from upstream to downstream along an axis of the propulsion unit:

[0017] - a front cowling forming an air intake; and

[0018] - an intermediate section comprising at least one intermediate cowling of fixed and removable type, externally delimiting the fan compartment, and fixed to at least one other structure of the propulsion unit by removable through-fastening members. According to the invention, said at least one intermediate cowling is connected to another element of the propulsion unit by means of an articulation system which, by means of dismantling of said removable through-fastening members, is configured to allow movement of the intermediate cowling between a closed position, in which the intermediate cowling extends in continuity with the front cowling, and an open position, in which the intermediate cowling is offset upstream or downstream relative to its location in the closed position so as to open the fan compartment.

[0019] The articulation system makes it possible to support the intermediate cowling in the open position, and thus avoids maintenance operators having to handle this cowling by carrying it to place it on a suitable support, which, in addition to requiring the provision of such a support, can prove tiring or even dangerous for the operators.

[0020] In preferred embodiments, the articulation system comprises at least two articulation devices each having a first end articulated on said at least one intermediate cowling, and a second, opposite end, articulated on said other element of the propulsion assembly, so as to allow movement of the intermediate cowling between the closed position and the open position, preferably in translation, in particular in curvilinear translation.

[0021] In preferred embodiments, each of the articulation devices includes at least one passive sliding link member configured to allow a variation in spacing between the first end and the second end of the articulation device.

[0022] In preferred embodiments, said passive sliding-link member is a passive actuator.

[0023] In preferred embodiments, each of the articulation devices further comprises means for securing the first end of the articulation device along an elliptical trajectory. In preferred embodiments, said means for securing the first end of the articulation device along the elliptical trajectory comprise:

[0024] - a first pulley mounted on said at least one intermediate cowling;

[0025] - two second pulleys mounted on said other element of the propulsion assembly so as to substantially define two foci of the elliptical trajectory; and

[0026] - a closed cable engaged around the first pulley and the second pulleys so as to constrain the first pulley to follow the elliptical trajectory.

[0027] In preferred embodiments, said at least one intermediate cowling has an internal surface provided with first relief patterns configured to cooperate by interlocking with second patterns of complementary shape formed on an external surface of said at least one other structure of the propulsion assembly, in the closed position.

[0028] In preferred embodiments, said at least one other structure of the propulsion assembly comprises at least one of the front cowling, a rear bulkhead rigidly carried by the fan casing, and another cowling of the intermediate section.

[0029] In preferred embodiments, said at least one intermediate cowling comprises a lower cowling extending at least in a lower angular portion of the propulsion assembly, for which said removable through-fastening members comprise at least first removable through-fastening members by which said lower cowling is fixed to said other structure of the propulsion assembly, for which said other element of the propulsion assembly is the turbojet, and for which the open position is a position in which said lower cowling is spaced apart transversely, by means of circumferential bending deformation of said lower cowling, and axially offset, relative to its location in the closed position.

[0030] In preferred embodiments, the propulsion assembly further comprises a mast connected to the turbojet engine, said at least one intermediate cowling comprises an upper cowling comprising a mast cowl and an apron extending circumferentially on either side of the mast cowl, and the mast cowl extends in front of the mast in continuity with the latter in the closed position and is spaced from the mast in the open position.

[0031] In preferred embodiments, the upper cowling has a rear bearing face arranged to exert pressure against a support structure of the mast when the air inlet experiences a vertical thrust from bottom to top.

[0032] In preferred embodiments, the upper cowling comprises an internal stiffening structure having a closed hollow section, and an internal support structure embedded in the internal stiffening structure and having said rear support face, and said support structure of the mast has a front support face arranged axially opposite and in contact with the rear support face of the internal stiffening structure, when the upper cowling is in the closed position.

[0033] Brief description of the drawings

[0034] The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0035] [Fig. 1] is a partial schematic axial sectional view of an aircraft propulsion assembly, illustrating a nacelle and a turbojet thereof;

[0036] [Fig. 2] is a partial schematic side view of the propulsion assembly, illustrating a forward portion of a mast, and elements of the nacelle and turbojet engine of the propulsion assembly;

[0037] [Fig. 3A] is a partial schematic side view of the propulsion assembly, illustrating a forward portion of the mast and forward and intermediate sections of the nacelle, and showing in particular an upper cowling and a lower cowling in their closed positions;

[0038] [Fig. 3B] is a partial schematic view of the propulsion unit in section along plane BB of Figure 3A, showing in particular the upper cowling and the lower cowling in their closed positions; [Fig. 4A] is a view similar to Figure 3A, showing the upper cowling and the lower cowling in their open positions;

[0039] [Fig. 4B] is a view similar to Fig. 3B showing in particular the lower cowling in its open position;

[0040] [Fig. 5] is a view similar to Figure 3A of a propulsion assembly according to an alternative embodiment; [Fig. 6] is a view similar to Figure 4A, illustrating the propulsion assembly of Figure 5;

[0041] [Fig. 7] is a view similar to Figure 3A of a propulsion assembly according to another variant;

[0042] [Fig. 8] is a view similar to Fig. 4A, illustrating the propulsion assembly of Fig. 7;

[0043] [Fig. 9] is a partial schematic axial sectional view of the propulsion assembly of any one of Figures 3A, 5 and 7, showing an overlap region of an end portion of the lower cowling and an end portion of an adjacent cowling or cowling, according to plane IX-IX of Figure 11;

[0044] [Fig. 10] is a view similar to Fig. 9, along plane XX of Fig. 11;

[0045] [Fig. 11] is a partial schematic view of said end portion of the lower cowling, seen radially from the inside;

[0046] [Fig. 12] is a view similar to Fig. 9, illustrating an overlap region of an end portion of the lower cowling and a structure of the turbojet engine;

[0047] [Fig. 13] is a partial schematic cross-sectional view of the propulsion assembly of any one of Figures 3A, 5 and 7, showing a hinge arrangement connecting the lower cowling to a fan casing of the turbojet engine and comprising fixed length connecting rods;

[0048] [Fig. 14] is a view similar to Fig. 13, illustrating a variant;

[0049] [Fig. 15] is a partial schematic axial sectional view of the propulsion assembly of any one of Figures 3A, 5 and 7, showing the lower cowling in the closed position;

[0050] [Fig. 16] is a view similar to Fig. 15, showing the lower cowling during movement to its open position;

[0051] [Fig. 17] is a view similar to Fig. 15, showing the lower cowling in the open position; [Fig. 18] is a schematic axial sectional view of a passive cylinder forming part of an articulation device according to an alternative embodiment, shown in the deployed configuration;

[0052] [Fig. 19] is a view similar to Fig. 18, showing the passive actuator in the retracted configuration;

[0053] [Fig. 20] is a view similar to Figure 13, illustrating a variant in which the fixed-length connecting rods of the articulation device are replaced by passive cylinders such as that of Figures 18 and 19, and in which the articulation device further comprises means for securing its hood-side end along an elliptical trajectory;

[0054] [Fig. 21] is a view similar to Fig. 15, illustrating a variant in which the articulation device is of the type illustrated in Fig. 20;

[0055] [Fig. 22] is a view similar to Fig. 16, illustrating the variant in which the articulation device is of the type illustrated in Fig. 20;

[0056] [Fig. 23] is a view similar to Fig. 17, illustrating the variant in which the articulation device is of the type illustrated in Fig. 20;

[0057] [Fig. 24] is a view similar to Fig. 21, illustrating a variant in which the articulation device further comprises a drive means;

[0058] [Fig. 25] is a view similar to Fig. 20, illustrating a variant in which the articulation device comprises a lateral reinforcement means;

[0059] [Fig. 26] is a view similar to Fig. 20, illustrating another variant in which the articulation device comprises a lateral reinforcement means;

[0060] [Fig. 27A] is a view similar to 3B, illustrating another variant in which the lower cowling comprises an elastically deformable central strip;

[0061] [Fig. 27B] is a view similar to 4B, illustrating the variant of Fig. 27A;

[0062] [Fig. 28] is a partial schematic side view and axial section of the propulsion assembly of any one of Figures 3B, 5 and 7, showing in particular an internal support structure of the upper cowling, by which the latter is axially supported on a support structure of the mast;

[0063] [Fig. 29] is a partial schematic cross-sectional view of the propulsion assembly of any one of Figures 3B, 5 and 7, according to plane AA of Figure 28, showing in particular the support structure of the mast and a forward engine attachment. In all of these figures, identical references may designate identical or similar elements.

[0064] Detailed disclosure of preferred embodiments

[0065] Figure 1 illustrates a propulsion unit 8 for an aircraft, comprising a turbojet engine 10 for example of the double-flow and double-spool type, the latter generally comprising a fan 12 intended for the suction of an air flow Fl dividing downstream of the fan into a primary flow F2 circulating in a primary flow channel, hereinafter called primary vein PV, within a core of the turbojet engine, and a secondary flow F3 bypassing this core in a secondary flow channel, hereinafter called secondary vein SV.

[0066] The core of the turbojet engine generally comprises a low pressure compressor 14, a high pressure compressor 16, a combustion chamber 18, a high pressure turbine 20 and a low pressure turbine 22.

[0067] The respective rotors of the high pressure compressor and the high pressure turbine are connected by a shaft called the "high pressure shaft", while the respective rotors of the low pressure compressor and the low pressure turbine are connected by a shaft called the "low pressure shaft", in a well-known manner.

[0068] The turbojet engine is shrouded by a nacelle 24 surrounding the secondary vein SV. Furthermore, the rotors of the turbojet engine are rotatably mounted around an axis of the turbojet engine, which coincides with the axis of the nacelle 24 within the propulsion assembly 8. These two axes are indifferently designated by the reference 28 throughout this description.

[0069] Throughout this description, the axial direction X is the direction of the axis 28, the vertical direction Z is a direction orthogonal to the axial direction X and oriented along the vertical when the propulsion unit 8 equips an aircraft parked on the ground, and the transverse direction Y is orthogonal to the two preceding directions. Furthermore, the radial direction R and the circumferential direction C or azimuthal direction are defined with reference to the axis 28, while the “upstream” and “front” directions on the one hand, and “downstream” and “rear” directions on the other hand, are defined according to the direction of the axis 28, with reference to the general direction of flow of the gases in the turbojet, from upstream or front to downstream or rear.

[0070] The turbojet engine comprises an inter-compressor casing 30 arranged axially between the low-pressure compressor 14 and the high-pressure compressor 16. In the non-limiting context of a twin-spool turbojet engine, such an inter-compressor casing 30 is sometimes referred to as an intermediate casing.

[0071] Furthermore, the inter-compressor casing 30 carries a fan casing 32 arranged upstream of it, around the fan 12.

[0072] In addition, the nacelle 24 comprises, from front to rear, a front section consisting of a front cowling 34 forming a lip-shaped air inlet at its upstream end, an intermediate section 36, and a rear section 38.

[0073] With reference to Figure 2, the front cowling 34 mainly comprises an external wall 40 with a generally C-shaped section, with a convexity oriented upstream, intended to separate, in operation, the air flow entering the turbojet 10 and the air flow bypassing the propulsion unit 8. The external wall 40 thus has two opposite end portions respectively defining an internal shroud 42 (visible by transparency in broken line in Figure 2) and an external shroud 44, connected to each other by an intermediate portion 46 of annular shape with a convex section. The external wall 40 thus delimits a front portion of an internal volume of the nacelle 24, hereinafter called the fan compartment 48. The internal shroud 42 has for example a rear end portion forming an acoustic panel 42A (also visible by transparency in broken line in Figure 2).The inner 42 and outer 44 shrouds and the intermediate portion 46 of the outer wall 40 are preferably formed in one piece so that the front cowling 34 is of the type commonly referred to as an “extended front lip”, but these elements may, as a variant, be assembled to each other by means of removable fixing members such as bolts.

[0074] The inner shroud 42 defines, at its rear end, an inner rear end 50 of the front cowling 34, while the outer shroud 44 defines, at its rear end, an outer rear end 52 of the front cowling 34. The inner rear end 50 forms an annular flange, sometimes called flange A1, by which the front cowling 34 is rigidly fixed in a removable manner to an upstream annular flange 54 of the fan casing 32, for example by means of one or more annular rows of removable through-fastening members such as bolts.

[0075] The fan casing 32 further comprises a downstream annular partition 56, hereinafter referred to as the rear partition, arranged downstream relative to the upstream annular flange 54. This rear partition 56 projects radially outward so as to form a fixing support for the intermediate section 36, as will become more clearly apparent in the following. The rear partition 56 thus axially divides the fan compartment 48 into two parts, namely the aforementioned front portion thereof and a rear portion.In the present disclosure, the front portion 32A of the fan casing is the part of the latter arranged upstream of the rear partition 56 and which participates in internally delimiting the front portion of the fan compartment 48, and the rear portion 32B of the fan casing is the part of the latter arranged downstream of the rear partition 56 and which participates in internally delimiting the rear portion of the fan compartment 48.

[0076] Figure 2 shows in particular a front engine attachment 60 connected to the rear portion 32B of the fan casing and by which the turbojet 10 is connected to a mast 62 of the propulsion unit 8, of which only a front part is visible in Figure 2 and the following figures. The front engine attachment 60 extends into the rear portion of the fan compartment 48.

[0077] Figure 2 further allows a view of a thrust reverser grid 64 in an advanced position adapted to operation of the propulsion unit in direct thrust mode. In such an advanced position, the grid 64, which is integral with the rear section 38 of the nacelle, extends around the rear portion 32B of the fan casing 32. The teachings of the present disclosure are in fact advantageously applicable to propulsion units in which the rear section of the nacelle comprises a thrust reverser of the sliding grid type, that is to say the grid of which is movable between an advanced position for operation in direct thrust mode, and a retracted position for operation in thrust reversal mode.

[0078] With reference to Figures 3A, 3B and 4A, 4B, the intermediate section 36 of the nacelle comprises a lower cowling 66 extending around the front portion 32A of the fan casing, that is to say radially opposite the latter, and thus delimiting a part of the front portion of the fan compartment 48. This lower cowling 66 is preferably formed of a single cowl, but may, as a variant, be formed of several cowls juxtaposed circumferentially, with or without overlapping of their adjacent circumferential ends.

[0079] The intermediate section 36 further comprises an upper cowling 70 comprising a central portion forming a mast cowl 72, and lateral portions extending circumferentially on either side of the mast cowl 72 and forming an apron 74. The upper cowling 70 delimits another part of the front portion of the fan compartment 48 as well as a part of the rear portion of the fan compartment 48.

[0080] The lower cowling 66 and the upper cowling 70 each constitute an intermediate cowling, according to the terminology of the present invention.

[0081] The intermediate section 36 finally comprises a rear cowling 76 arranged behind the lower cowling 66. This rear cowling 76 is preferably formed of a single cowling, but may, as a variant, be formed of several cowlings juxtaposed circumferentially. The rear cowling 76 delimits another part of the rear portion of the fan compartment 48.

[0082] More specifically, the lower cowling 66 extends around a certain lower angular portion of the front portion 32A of the fan casing 32 around the axis 28, and has two circumferential ends 78 which reveal, between them, an upper angular portion of the front portion 32A of the fan casing 32 (FIGS. 3A and 3B). This upper angular portion of the front portion 32A is covered by the upper cowling 70. The lower angular portion of the front portion 32A extends for example over more than 180 degrees around the axis 28, for example over 300 degrees. Similarly, the rear cowling 76 extends around a certain lower angular portion of the rear portion 32B of the fan casing 32 around the axis 28, and has two circumferential ends 80 which reveal, between them, an upper angular portion of the rear portion 32B of the fan casing 32.This upper angular portion of the rear portion 32B is also covered by the upper cowling 70. The lower angular portion of the rear portion 32B extends for example over more than 180 degrees around the axis 28, for example over 300 degrees.

[0083] The lower cowling 66, the rear cowling 76, and the upper cowling 70 are of the fixed and removable type, that is to say that they are fixed to other structures of the propulsion unit, in this case elements of the nacelle and the turbojet, by means of removable through-fastening members.

[0084] In particular, the lower cowling 66 has a front end 82 fixed to the external rear end 52 of the front cowling 34, and a rear end 84 fixed to the turbojet, in this case on the rear partition 56.

[0085] The fixing of the front 82 and rear 84 ends of the lower cowling 66 respectively to the front cowling 34 and to the rear partition 56 is carried out by means of first removable through fixing members 86.

[0086] In addition, the circumferential ends 78 of the lower cowling 66 are respectively attached to circumferential ends 88 of the upper cowling 70. In the illustrated example, the circumferential ends 88 of the upper cowling 70 cover the circumferential ends 78 of the lower cowling 66. Alternatively, the circumferential ends 78 of the lower cowling 66 may cover the circumferential ends 88 of the upper cowling 70.

[0087] Similarly, the circumferential ends 80 of the rear cowling 76 are respectively fixed to the circumferential ends 88 of the upper cowling 70. The circumferential ends 88 of the upper cowling 70 cover the circumferential ends 80 of the rear cowling 76.

[0088] The attachment of the circumferential ends 88 of the upper cowling 70 to the circumferential ends 78 and 80 of the lower cowling 66 and the rear cowling 76 is carried out by means of second removable through-fastening members 90.

[0089] The upper cowling 70 further has a front end 92 fixed to the external rear end 52 of the front cowling 34 by means of third removable through-fastening members 94.

[0090] According to a first aspect of the present disclosure, the lower cowling 66 is connected to the turbojet by means of a first articulation system 96.

[0091] The first articulation system 96 is configured to allow movement of the lower cowling 66 between a closed position and an open position, when the first removable through-fastening members 86 connecting the lower cowling 66 to the front cowling 34 and to the rear partition 56 are removed, and where appropriate, when the second removable through-fastening members 90 connecting the upper cowling 70 to the lower cowling 66 are also removed.

[0092] The closed position of the lower cowling 66 corresponds to the closed configuration illustrated in FIGS. 3A and 3B, in which the lower cowling 66 extends in continuity in particular with the front cowling 34, but also, in the example illustrated, with the upper cowling 70 and with the rear cowling 76.

[0093] The open position of the lower cowling 66, illustrated in FIGS. 4A and 4B, is a position in which the lower cowling 66 is moved radially outwardly by elastic deformation following a kinematic determined by the first articulation system 96, and is axially offset relative to its location in the closed position, so as to open the front portion of the fan compartment 48 and thus provide in particular access to the internal rear end 50 of the front cowling 34, for example to allow removal of the latter. In the open position, the lower cowling 66 partially or completely covers the rear cowling 76, in the case of a rearward axial movement. Alternatively, the lower cowling 66 may partially or completely cover the front cowling 34, in the case of a forward axial movement.The first articulation system 96 makes it possible to support the lower cowling 66 in the open position, and thus to avoid maintenance operators having to handle the lower cowling 66 while carrying it to place it on a suitable support, which, in addition to requiring the provision of such a support, can prove tiring or even dangerous for the operators.The first articulation system 96 makes it possible in particular to induce the elastic deformation of the lower cowling 66 resulting in a separation of the circumferential ends 78 thereof towards the outside of the nacelle and allowing a displacement of the entire lower cowling 66 downwards, for example under the effect of its own weight, which makes it possible to move the latter backwards around the rear cowling 76 or forwards around the front cowling 34 for example under the effect of a request from an operator, as will appear more clearly in the following in view of the detailed description of the first articulation system 96.

[0094] According to a second aspect of the present disclosure, the upper cowling 70 is connected to at least one of the turbojet 10 and the mast 62, by means of a second articulation system 100, which offers an advantage similar to that mentioned above with regard to the lower cowling 66.

[0095] The second articulation system 100 is configured to allow movement of the upper cowling 70 between a closed position and an open position, when the second removable through-fastening members 90 connecting the upper cowling 70 to the lower cowling 66 are removed, and if necessary, when the third removable through-fastening members 94 connecting the upper cowling 70 to the external rear end 52 of the front cowling 34 are also removed.

[0096] The closed position of the upper cowling 70 corresponds to the closed configuration illustrated in FIGS. 3A and 3B, in which the mast cowling 72 extends in front of the mast 62 in continuity with the latter, and the apron 74 extends in aerodynamic continuity with the lower cowling 66 and with the front cowling 34.

[0097] The open position of the upper cowling 70, illustrated in FIG. 4A, is a position in which the upper cowling 70 is offset forward or rearward relative to its location in the closed position so as to open the fan compartment 48, in particular the rear portion thereof, so as to provide in particular access to the front engine attachment 60.

[0098] Furthermore, in the case where, as in the illustrated examples, the circumferential ends 88 of the upper cowling 70 cover the circumferential ends 78 of the lower cowling 66 in the closed configuration, the open position of the upper cowling 70 is such that the circumferential ends 88 of the upper cowling 70 are distant from the circumferential ends 78 of the lower cowling 66 so as to allow the movement of the lower cowling 66 between the closed position and the open position thereof.

[0099] In the example of Figures 3A and 4A, the second articulation system 100 is configured to form a pivot connection between the upper cowling 70 and the mast 62, and thus allow rotation of the upper cowling towards the rear around a transverse axis 104, to move from the closed position to the open position of the upper cowling 70. For this purpose, the second articulation system 100 comprises for example two pivots 106 arranged on each side of the mast 62 (only one of these pivots is visible in Figures 3A and 4A).

[0100] Figures 5 and 6 illustrate a variant in which the second articulation system 100 is configured to connect the upper cowling 70 to the fan casing 32 or to the front cowling 34 in a manner allowing rotation of the upper cowling forwards about a movable transverse axis 108 to move from the closed position to the open position of the upper cowling 70. For this purpose, the second articulation system 100 comprises for example a link 109 having a first end 109A articulated to a front region of the upper cowling 70 and defining the movable transverse axis 108, and having a second end 109B articulated to the fan casing 32 or to the front cowling 34.

[0101] Figures 7 and 8 illustrate another variant, in which the second articulation system 100 has a deformable parallelogram configuration.

[0102] For this purpose, the second articulation system 100 comprises at least one front link 110 having a first end 112 articulated to a front region of the upper cowling 70, and having a second end 114 articulated to the fan casing 32 or to the front cowling 34, and in which the second articulation system 100 further comprises at least one rear link 116 having a first end 118 articulated to a rear region of the upper cowling 70, and having a second end 120 articulated to the fan casing 32, for example to the rear partition 56, or to another part of the turbojet engine.

[0103] The articulation system 100 may of course comprise two such front connecting rods 110 arranged symmetrically with respect to each other, on either side of a median vertical plane of the propulsion assembly, and / or two such rear connecting rods 116 also arranged symmetrically with respect to each other, on either side of the median vertical plane.

[0104] The connecting rods 110, 116 are configured to guide the upper cowling 70 in a circular translational movement, between the closed position and the open position thereof.

[0105] Alternatively, the links 110 and 116 may be of different lengths so that the movement of the upper cowling 70 is a combination of curvilinear translation and rotation.

[0106] According to a third aspect of the present disclosure, with reference to Figures 9 to 12, at least one of the lower cowling 66 and the upper cowling 70 has an internal surface 122 provided with first raised patterns 124 configured to cooperate by interlocking with second patterns 126 of complementary shape formed on an external surface 128 of at least one adjacent cowling and / or of a structure of the turbojet, in the closed configuration.

[0107] Figures 9 and 10 show for example the front end 82 of the lower cowling 66, which is for example made of a composite material of the fiber-reinforced plastic type, which overlaps (i.e. at least partially covers) the external rear end 52 of the front cowling 34, which is for example made of metal.

[0108] The inner surface 122 of the lower cowling 66, also visible in FIG. 11, is provided with first raised patterns 124, comprising for example two circumferential ribs 124A spaced apart from each other axially and connected to each other by axial ribs 124B spaced apart from each other. The ribs 124A, 124B thus define hollows 130 delimited by the latter both in the axial direction X and in the circumferential direction C.

[0109] The external surface 128 of the front cowling 34 has second patterns 126 of a shape complementary to the first patterns 124, comprising for example two circumferential grooves 126A spaced from each other axially and connected to each other by axial grooves 126B spaced from each other (only one of which is visible in FIG. 10). The grooves 126A, 126B thus define bumps 132 delimited by the latter both in the axial direction X and in the circumferential direction C.

[0110] Thus, the ribs 124A, 124B of the lower cowling 66 and the grooves 126A, 126B of the front cowling 34 define reciprocal abutment surfaces both in the axial direction X and in the circumferential direction C.

[0111] The ribs 124A, 124B of the lower cowling 66 fit into the grooves 126A, 126B of the front cowling 34 while the bosses 132 of the front cowling 34 fit into the hollows 130 of the lower cowling 66. The patterns 124 and 126 thus establish a reciprocal fit between the lower cowling 66 and the front cowling 34, which involves supports both in the axial direction X and in the circumferential direction C.

[0112] The ribs 124A, 124B and grooves 126A, 126B are advantageously of a section having V-shaped sides 134, 135, separated for example by a flat bottom 136.

[0113] An interposing plastic layer 138 is for example provided on one of the surfaces 122 and 128 to improve the contact between the latter, reduce any gaps between them, and allow, if necessary, smoothing or attenuating the aerodynamic steps, that is to say the differences in levels between the external surface 139 of the cowling considered 66 or 70 and the external surface 128 of the aforementioned element. The interposing plastic is advantageously a strong plastic having a low coefficient of friction with the materials with which the layer 138 must be in contact, for example a material marketed under the names ERTACETAL™ or TEFLON™. The interposing plastic layer 138 thus helps to ensure the proper functioning of the opening kinematics of the cowling considered.

[0114] With reference to Figure 11, passage orifices 140 for the first removable through-fastening members 86 are advantageously provided within the hollows 130 of the lower cowling 66. Similarly, with reference to Figure 9, passage orifices 142 for the first removable through-fastening members 86 are advantageously provided within the bosses 132 of the front cowling 34, in alignment with the passage orifices 140.

[0115] Furthermore, the inclination of the sides 134, 135 is adapted so as not to hinder the opening kinematics of the cowling in question, as will appear more clearly in the following, and is adapted to the flow of shear force to be passed between the elements. It is advantageous for said inclination to be significant so that the structure absorbs the shear as much as possible and transmits only a small vertical component to the corresponding fixing members 86.

[0116] When an overlap is provided between the circumferential ends 78 of the lower cowling 66 and the circumferential ends 88 of the upper cowling 70, as in the illustrated examples, a cooperation by interlocking of relief patterns as described above is advantageously provided between these circumferential ends 78, 88.

[0117] Such cooperation by interlocking relief patterns is also advantageously provided at the interface between the upper cowling 70 and the front cowling 34.

[0118] Figure 12 shows the rear end 84 of the lower cowling 66 which covers the rear bulkhead 56. Here again, the inner surface 122 of the lower cowling 66 is provided with raised patterns 124, while the outer surface 128 of the rear bulkhead 56 is provided with complementary shaped patterns 126, in a manner similar to that described above.

[0119] The axial and tangential supports induced by the interlocking of the relief patterns 124, 126 allow the absorption of part of the axial and tangential forces passing between adjacent cowls or between a cowl and the structure of the turbojet engine, and thus make it possible to reduce the stress undergone by the removable through-fastening members concerned. The number and / or the clamping force of these fastening members can thus be reduced, which in particular allows the use of quick-tightening fastening members. In addition, such supports make it possible to block the parts concerned relative to each other and thus reduce the friction between these parts.

[0120] Figures 13-26 illustrate in more detail the implementation of the first aspect of the present disclosure, relating to the first articulation system 96, which will be described with constant reference to Figures 3A-4B.

[0121] The first articulation system 96 is formed of one or more articulation devices 144, preferably a central articulation device 144A and two lateral articulation devices 144B symmetrical to each other with respect to the median vertical plane of the propulsion assembly (FIGS. 4A and 4B).

[0122] The lateral articulation devices 144B are advantageously offset in the axial direction X relative to the central articulation device 144A. Such an arrangement makes it possible to take up the moment which tends to rotate the lower cowling 66 around a substantially vertical axis under the action of the opening force of an operator acting on only one side of the cowling. Alternatively, the three articulation devices 144 can be anchored to the turbojet in the same transverse plane, in which case the aforementioned moment is advantageously taken up by means of an additional articulation device axially offset relative to said transverse plane.

[0123] With reference to Figure 13, such an articulation device 144 has a first end 146 in ball joint connection with a corresponding base 148 rigidly carried by the lower cowling 66, and a second end 152, opposite, in ball joint connection with the turbojet, in this case with the fan casing 32.

[0124] In the example of Figure 13, the articulation device 144 comprises two connecting rods 156 which, in the closed position, are for example arranged symmetrically with respect to a median axial plane XR of the device. The connecting rods 156 have respective first ends 158 in the form of rings, connected by ball joints to a first articulation axis 150 extending orthogonally to the axis 28 and carried by a clevis 160 of the base 148 on either side thereof, and which, together, define the first end 146 of the articulation device 144. In addition, the connecting rods 156 have respective second ends 162 in the form of rings, connected by ball joints to respective second articulation axes 154 extending orthogonally to the axis 28 and carried by respective clevises 164 of corresponding bases 166 rigidly secured to the fan casing 32.The aforementioned rings typically form cages for receiving ball joints 167 mounted on the corresponding axis 150, 154. The first articulation axis 150, common to the two connecting rods 156, extends substantially in the circumferential direction C.

[0125] In the case corresponding to Figure 13, the connecting rods 156 being of fixed length, the arrangement of the lateral articulation devices 144B is such that for the latter, the connection points of the second ends 162 to the second articulation axes 154 are offset from each other in the axial direction X so as to allow the separation of the circumferential ends 78 of the lower cowling 66 by circumferential elastic deformation. For the same purpose, the first ends 158 are connected to the first articulation axis 150 with a certain capacity for movement in the direction of this axis. For this purpose, the corresponding ball joints are for example mounted on the first articulation axis 150 with a clearance in the direction of this axis.

[0126] Figure 14 illustrates a variant in which such an articulation device 144 comprises a single connecting rod 170 centered relative to the median axial plane XR of the device. The connecting rod 170 preferably has a reinforced structure with, for example, a first end 172 in the form of a double ring defining an air gap in which the yoke 160 of the base 148 is housed, and a second end formed of two legs 174 having respective ends each provided with a corresponding ring articulated respectively to two yokes 164 carried by a common base 166. In such a case, the second articulation axis 154, common to the two legs 174, extends substantially in the circumferential direction C.

[0127] With reference to figures 15 to 17, the movement of the lower cowling 66 from the closed position (figure 15) to the open position (figure 17) substantially involves, for each articulation device 144, a translation of the corresponding base 148 along a circular trajectory T1. As illustrated in figure 15, the movement of the lower cowling 66 is permitted by the fact that the initial direction DI of the movement makes, with the axial direction X, an angle 01 greater than an angle 02 defined between the downstream flanks 135 of the circumferential ribs 124A and circumferential grooves 126A on the one hand, and the axial direction X on the other hand.

[0128] As shown in Figures 16 and 17, the movement of the lower cowling 66 towards the open position involves a separation of the cowling transversely to the axis 28, and a shift of the cowling in the axial direction X, for example towards the rear. As explained above, the separation of the lower cowling transversely to the axis 28 takes place by means of a bending deformation of the cowling in the circumferential direction, that is to say with a bending moment substantially parallel to the axis 28, which may in certain cases be supplemented by a slight torsional deformation of the cowling.

[0129] In preferred variants, the (or each) articulation device 144 comprises at least one passive sliding connection member configured to allow a variation in spacing between the first end 146 and the second end 152 of the articulation device. Such a variation in spacing between the ends generally makes it possible to reduce the spacing of the cowling concerned in the transverse direction, imposed by the kinematics of the device, and therefore to reduce the stresses applied to the cowling to allow the latter to move.

[0130] Instead of the connecting rod 170 or the connecting rods 156, such an articulation device 144 therefore comprises one or more passive members with sliding connection. Such a member comprises two parts in sliding connection with respect to each other, and which are therefore movable with respect to each other according to a relative rectilinear translational movement, one of the parts defining the first end 146 of the articulation device 144 while the other part defines the second end 152 of the device.

[0131] Preferably, the (or each) passive sliding-link member is a passive cylinder 178, as illustrated in FIGS. 18 and 19. Such a cylinder comprises a rod 180 provided with a ring 182 which defines, for example, the first end 146 of the articulation device 144, and a body 184 provided with a ring 186 defining, for example, the second end 152 of the device. The rod 180 comprises a piston 188 housed in the body 184 and urged towards the ring 182 of the rod 180 by an elastic means, such as a spring 190 housed in the body 184, or, as a variant, a pressurized gas trapped in a chamber delimited by the piston 188 within the body 184. The rings 182 and 186 form, here too, receiving cages for ball joints 181, 187 intended to be mounted on the articulation axes 150, 154.

[0132] The elastic means makes it possible in particular to reduce the efforts required by operators during the opening and closing operations of the lower cowling 66.

[0133] Figures 20 to 23 illustrate an articulation device 144 similar to that of Figure 13, but whose connecting rods are replaced by passive cylinders 178.

[0134] The articulation device 144 of Figures 20-23 further comprises means for securing the first end 146 of the device along an elliptical trajectory T2. Such means comprise a first pulley 192 mounted on the base 148 carried by the lower cowling 66, with the ability to rotate in the direction of the first articulation axis 150; two second pulleys 194 mounted on the turbojet engine, in this case on bases 195 provided for this purpose on the fan casing 32, with the ability to rotate along axes 196 parallel to the first articulation axis 150 and substantially defining two foci of the elliptical trajectory; and a closed cable 198, engaged around the first pulley 192 and the second pulleys 194.

[0135] The cable 198 constrains the sum of the distances between the first articulation axis 150 and each of the axes 196 defined by the second pulleys 194 to be constant regardless of the position of the lower cowling 66.

[0136] In addition, the or each passive cylinder 178 of the device is configured to permanently urge the first pulley 192 against the cable 198 so as to maintain the latter in a state of tension.

[0137] As a result, the trajectory of the first articulation axis 150 is an ellipse (the centers of the second pulleys 194 being substantially the foci of this ellipse). It is therefore the same with regard to the base 148, and therefore the entire lower cowling 66 with which said base 148 is integral. Such an elliptical trajectory T2 makes it possible to increase the amplitude of axial displacement of the lower cowling 66 for a given level of radial displacement (and therefore of bending deformation), by comparison with the circular trajectory T1 inherent in the use of connecting rods of fixed lengths as in the embodiments described above with reference to Figures 13-17.

[0138] Alternatively, the second pulleys 194 can be replaced by fixed attachment points for the cable 198 on the bases 195, or by eyelets secured to the bases 195 in which the cable 198 is retained.

[0139] Furthermore, the passive cylinders 178 may, as a variant, be dimensioned so as to be in maximum extension, and therefore have a constant length, at the start and end of the trajectory, the cable 198 then not being taut. In a middle part of the trajectory, the passive cylinders 178 are compressed by the cable so that said middle part has the elliptical character described above. Such a variant has the advantage of increasing the angle 0i at the start of the trajectory in order, if necessary, to more easily disengage the patterns 124 and 126.

[0140] With reference to Figure 24, an articulation device 144 similar to that of Figures 20-23 further comprises a drive member 200, for example a motor having an output shaft 202 in contact with the cable 198 so that a rotation of the output shaft 202 causes a movement of the cable 198 around the set of three pulleys 192, 194, and therefore a movement of the base 148 along the elliptical trajectory T2.

[0141] Figure 25 shows one of the lateral articulation devices 144B in a configuration similar to that of Figures 20-23 or Figure 24, but further comprising a reinforcing rod 204 connecting a part of the body 184 of one of the passive cylinders 178 remote from the ring 186 thereof to a base 206 provided for this purpose on the fan casing 32 (and partially hidden in Figure 25 by one of the bases 195) to participate in the absorption of forces induced by gravity. The base 206 can alternatively be merged with the base 195. The connections between the ends of the reinforcing rod 204 and respectively the body 184 of the cylinder in question and the base 206 are ball joints. In the illustrated example, the reinforcing rod 204 is arranged on the upper side of the device so as to work in compression. Alternatively, such a reinforcing rod may be arranged on the lower side of the device so as to work in tension.The reinforcing rod 204 makes it possible to constrain the trajectory of the passive cylinder 178 in question and thus ensure that the latter laterally takes up part of the weight of the lower cowling 66.

[0142] Figure 26 shows one of the lateral articulation devices 144B in another configuration also similar to that of Figures 20-23 or Figure 24, but in which one of the passive cylinders, referenced 178', is connected to the corresponding base 166' by a pivot connection instead of a ball joint connection. The corresponding second articulation axis 154' extends in this case substantially in the circumferential direction C. The passive cylinder 178' comprises one or more rings 186 defining the second end 152 of the device 144B, pivotally mounted on the corresponding second articulation axis 154.

[0143] Generally speaking, taking into account the information presented above, the dimensioning of the articulation devices 144 allowing opening and closing maneuvers of the lower cowling 66 without applying harmful stress to the latter falls within the skills of the person skilled in the art.

[0144] In this regard, the base 148 of each of the lateral articulation devices 144B may, as a variant, be mounted movably on the internal surface of the lower cowling 66 along a trajectory comprising at least one circumferential component, instead of being rigidly fixed on this cowling as in the examples described above. Such an arrangement is intended to allow the base 148 to move towards the corresponding circumferential end 78 of the lower cowling during the overall flexural deformation of the latter at the start of an opening maneuver.

[0145] Figures 27A and 27B illustrate a variant in which the lower cowling 66 comprises two rigid lateral portions 66A connected to each other by an elastically deformable middle strip 66B, making it possible to facilitate the overall flexural deformation of the lower cowling 66 at the start of an opening maneuver. For this purpose, the middle strip 66B is for example made of an elastomeric material. In general, it should therefore be understood that the lower cowling 66 preferably follows a generally curvilinear translational movement between its closed and open positions.

[0146] Furthermore, Figures 28 and 29 illustrate in more detail the structure of the upper cowling and show axial support means by which the upper cowling 70 is able to transmit forces to the mast 62.

[0147] The axial and tangential supports induced by the interlocking of relief patterns 124, 126 as described above, at the interface between the upper cowling 70 and the front cowling 34, allow good transmission of forces from the front cowling 34 to the upper cowling 70. In particular, the forces resulting from a high incidence of the air intake, for example encountered during takeoff, can pass through the upper cowling in a significantly more efficient manner than in propulsion units of known type.

[0148] To take full advantage of this improved force transmission, the upper cowling 70 comprises an internal stiffening structure 210 having a closed hollow section (figure 28). Such a structure is for example formed by an extension 212 of the apron 74 under the mast cowling 72, by a substantially radial bottom wall 214 connecting a rear end of the extension 212 to the mast cowling 72, and by the mast cowling itself, in the manner of a box.

[0149] The upper cowling 70 further comprises an internal support structure 216 embedded in the internal stiffening structure 210 and having a rear support face 218.

[0150] The mast 62 comprises a support structure 220 (figures 28 and 29) having a front support face 222 arranged axially opposite and in contact with the rear support face 218 of the internal stiffening structure 210 (figure 28), when the upper cowling is in the closed position.

[0151] Preferably, the bearing faces 218 and 222 extend transversely to the axis 28 of the propulsion unit, so as to transmit only axial forces. Due to the connection by the second removable through-fastening members 90 between the lower cowling 66 and the upper cowling 70, the bearing structures 216 and 220 thus allow in particular an efficient transmission of the forces resulting from the bending moment undergone by the upper cowling 70 and the lower cowling 66 during a pitch-up of the aircraft equipped with such a propulsion unit, which makes it possible to limit the deformation of these cowlings.

Claims

DEMANDS 1. Aircraft propulsion unit (8), comprising: - a turbojet engine (10) comprising a fan (12) and a fan casing (32) surrounding the fan; and - a nacelle (24) surrounding the turbojet (10) and comprising a fan compartment (48) internally delimited by the fan casing (32); in which the nacelle (24) comprises, from upstream to downstream along an axis (28) of the propulsion assembly: - a front cowling (34) forming an air intake; and - an intermediate section (36) comprising at least one intermediate cowling (66, 70) of a fixed and removable type, externally delimiting the blower compartment (48), and fixed to at least one other structure of the propulsion assembly by means of removable through-fastening members (86, 90, 94); characterized in that said at least one intermediate cowling is connected to another element of the propulsion assembly by means of an articulation system (96, 100) which, by means of dismantling said removable through-fastening members, is configured to allow movement of the intermediate cowling between a closed position, in which the intermediate cowling extends in continuity with the front cowling (34), and an open position, in which the intermediate cowling is offset upstream or downstream relative to its location in the closed position so as to open the blower compartment (48).

2. Propulsion assembly according to claim 1, wherein the articulation system (96, 100) comprises at least two articulation devices (144, 110, 116) each having a first end (146, 112, 118) articulated on said at least one intermediate cover, and a second, opposite end (152, 114, 120) articulated on said other element of the propulsion assembly, so as to allow movement of the intermediate cover between the closed position and the open position.

3. Propulsive assembly according to claim 2, in which each of the articulation devices (144) includes at least one passive sliding-link member configured to allow a variation in spacing between the first end (146) and the second end (152) of the articulation device.

4. Propulsive assembly according to claim 3, wherein said passive sliding joint member is a passive cylinder (178).

5. Propulsive assembly according to claim 3 or 4, wherein each of the articulation devices (144) further comprises means for securing the first end (146) of the articulation device along an elliptical trajectory (T2).

6. Propulsive assembly according to claim 5, wherein said means for securing the first end (146) of the articulation device (144) along the elliptical trajectory (T2) comprise: - a first pulley (192) mounted on said at least one intermediate cover (66); - two second pulleys (194) mounted on said other element of the propulsion assembly so as to define substantially two foci of the elliptical trajectory (T2); and - a closed cable (198) engaged around the first pulley (192) and the second pulleys (194) so ​​as to constrain the first pulley (192) to follow the elliptical trajectory (T2).

7. Propulsion assembly according to any one of claims 1 to 6, wherein said at least one intermediate cowling has an internal surface (122) provided with first raised motifs (124) configured to cooperate by interlocking with second motifs (126) of complementary shape formed on a external surface (128) of said at least one other structure of the propulsion assembly, in the closed position.

8. Propulsion assembly according to any one of claims 1 to 7, wherein said at least one other structure of the propulsion assembly comprises at least one of the front cowling (34), a rear bulkhead (56) rigidly supported by the blower housing (32), and another cowling (70, 66, 76) of the intermediate section.

9. Propulsion assembly according to claim 8, wherein said at least one intermediate cowling comprises a lower cowling (66) extending at least into a lower angular portion of the propulsion assembly, wherein said removable through-fastening members comprise at least first removable through-fastening members (86) by which said lower cowling is fixed to said other structure of the propulsion assembly, wherein said other element of the propulsion assembly is the turbojet (10), and wherein the open position is a position in which said lower cowling (66) is moved transversely, by means of a circumferential bending deformation of said lower cowling, and axially offset, relative to its location in the closed position.

10. Propulsion assembly according to any one of claims 1 to 9, further comprising a mast (62) connected to the turbojet, in which said at least one intermediate cowling comprises an upper cowling (70) comprising a mast cowling (72) and an apron (74) extending circumferentially on either side of the mast cowling (72), in which the mast cowling (72) extends in front of the mast (62) in continuity with the latter in the closed position and is away from the mast (62) in the open position.

11. Propulsion assembly according to claim 10, wherein the upper cowling (70) has a rear support face (218) arranged to exert pressure against a support structure (220) of the mast (62) when the air inlet is subjected to an upward vertical thrust.

12. Propulsion assembly according to claim 11, wherein the upper cowling (70) comprises an internal stiffening structure (210) having a closed hollow section, and an internal support structure (216) embedded in the internal stiffening structure (210) and having said rear support face (218), and said support structure (220) of the mast (62) has a front support face (222) arranged axially opposite and in contact with the rear support face (218) of the internal stiffening structure (210), when the upper cowling (70) is in the closed position.

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