CRANKCASE FOR AN AIRCRAFT TURBOMACHINE

Abstract

The invention relates to a casing for an aircraft turbomachine, comprising at least: an annular shell (102) which extends around an axis (A0) and which has an internal annular face (SE1); an annular acoustic insulation panel (106) which extends around the axis (A0) and which has an external face (SV2) intended to face the internal face (SE1) of the shell (102); and a fastening system (SFX) for the acoustic insulation panel (106) on the inner face (SE1) of the casing (102), the fastening system (SFX) comprising: at least one first magnetic block (120) fixed to the inner annular face (SE1) of the casing (102); at least one second magnetic block (140) fixed to the outer face (SV2) of the acoustic insulation panel, said at least one second block being arranged to cooperate by magnetic attraction with said at least one first block. Figure for the abbreviation: Figure 5

Description

Title of the invention: Casing for an aircraft turbomachine Technical field of the invention

[0001] The present invention relates to a housing for a turbomachine, in particular for an aircraft, and an aircraft turbomachine comprising such a housing, and a method for manufacturing this housing. Technological background

[0002] Generally, a turbomachine (not shown), particularly an aircraft turbomachine, comprises from upstream to downstream (i.e. in the direction of gas flow), a blower, one or more compressors, a combustion chamber, one or more turbines and a nozzle for ejecting the combustion gases exiting the turbine(s).

[0003] The blower, for example, includes a blade wheel which is surrounded by a casing, also called a retention casing because of its function of retaining the blades in the event of their breaking, or in the event of debris entering the blower.

[0004] With reference to [Fig. 1], a housing 100 for an aircraft turbomachine, and in particular a fan, comprises at least: - an annular envelope 102 which extends around an axis Ao and which includes an internal annular face SEi; - an annular acoustic insulation panel 106 extending around the axis Ao and comprising an external face SV2 intended to face the internal face SEi of the envelope 102; and - an SFX fixing system for the acoustic insulation panel 106 on the internal face SEi of the envelope 102.

[0005] The casing 102, which extends around the turbomachine's fan blades 300, can be, for example, but not limited to, made of metallic material or of composite material made from woven fibers embedded in a polymer resin. Preferably, the annular casing is made of composite material.

[0006] The housing may further include an abradable annular cartridge, positioned on the internal annular surface SEi of the casing 102, downstream of the acoustic insulation panel 106. This abradable cartridge may include an annular layer 104i of abradable material and a support 1042 supporting the annular layer 104i, the support 1042 being fixed to the casing 102.

[0007] The housing 100 may further include a second acoustic insulation panel 108 disposed downstream of the abradable cartridge.

[0008] With reference to [Fig.2], the acoustic insulation panel 106, positioned upstream of the abradable cartridge, extends around an axis Ai passing through the axis Ao of the casing 102. The acoustic insulation panel 106 serves to form an aerodynamic flow channel of the blower and to attenuate the noise of the blower.

[0009] The acoustic insulation panel 106 comprises a body 200 having the external surface SV2, intended to face the internal face SEi of the envelope 102, and an internal surface SVi opposite the external surface SV2.

[0010] Still with reference to [Fig.2], the external surface SV2 of the body 200 of the acoustic insulation panel 106 may include grooves 204 configured to receive means for fixing the acoustic insulation panel to the casing 102 of the housing 100.

[0011] The SFX fixing system of the acoustic insulation panel 106 to the envelope 102, as illustrated in [Fig.3], includes a first fixing tab 201 fixed by means of a screw or rivet 108 on the internal surface SEi of the envelope 102.

[0012] The SFX fixing system further includes a second fixing tab 202P, 202F fixed by means of a screw or rivet 109 on the external surface SV2 of the acoustic insulation panel 106.

[0013] The SFX fixing system further includes a screw 110 for fixing the second tab 202P, 202F to the first tab 201. The second fixing tab 202P, 202F includes at least one positioning tab 202P of the sound insulation panel on the internal surface SEi of the casing 102 of the housing 100, as illustrated, for example, in [Fig.4].

[0014] Still with reference to [Fig.3], the housing 102 further includes a sealing gasket 112 disposed between an annular edge Fi06 downstream of the acoustic insulation panel 106 and an annular edge F104 of the support 1042 supporting the annular layer 104i.

[0015] A SFX fixing system of the acoustic insulation panel 106 to the casing 102 of the housing 100, as described above, may have disadvantages due to fatigue stresses which tend to promote the appearance of cracks which can lead to the failure of the fixing means and to a degradation of the housing 102.

[0016] For example, for L-shaped legs such as those illustrated in [Fig. 4], significant radial stresses can be induced during fatigue loading. These radial stresses are due to the tight tolerances associated with assembling the legs 201, 202P, 202F using screws 108, 109, 110.

[0017] Furthermore, axial stresses related to the compression of the joint 112, disposed between the downstream annular edge Fi06 of the acoustic insulation panel 106 and an annular edge F104 of the support 1042 supporting the annular layer 104i, can lead to deformations, for example bending, of the fixing tabs and consequently degradation of the housing 100.

[0018] It may therefore be desirable to provide a casing 100 which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0019] A housing for an aircraft turbomachine is therefore proposed, comprising at least: - an annular envelope which extends around an axis and which has an internal annular face; - an annular acoustic insulation panel extending around the axis and comprising an external face designed to face the internal face of the envelope; and - a system for fixing the acoustic insulation panel to the inner face of the building envelope, characterized in that the fastening system comprises: - at least one first magnetic block fixed to the inner annular face of the envelope; - at least one second magnetic block fixed to the outer face of the acoustic insulation panel, said at least a second block being arranged to cooperate by magnetic attraction with said at least a first block.

[0020] Thus, thanks to the invention, it is possible to reduce the risk of failure of the acoustic insulation panel's attachment to the housing. Indeed, the magnetic attraction between the first block and the second block eliminates the need for a fastening system made entirely of screws. This reduces or eliminates radial and axial stresses.

[0021] Part of the magnets can attract each other radially to center the acoustic insulation panel, and another part of the magnets can exert an axial attractive force to compensate for the compressive force of the joint between the downstream annular edge of the acoustic insulation panel and an annular edge of the support bearing the annular layer. This prevents axial movement of the acoustic insulation panel.

[0022] The invention also makes it possible to improve the positioning of the acoustic insulation panel and to facilitate its replacement.

[0023] The invention thus has the advantage of improving the manufacture and maintenance of the housing and of saving overall cycle time.

[0024] The invention may further include one or more of the following optional features, in any technically feasible combination: - Each of the first and second blocks includes at least: • a magnet of opposite polarity to a magnet from the other of the first and second blocks; • a stud having a face configured to receive the magnet; - said at least second block and said at least first block are arranged to cooperate magnetic attraction in the radial direction, or in the axial direction, or in the axial and radial directions. - said at least second block and said at least first block are arranged to cooperate by magnetic attraction in the radial direction, and the fixing system further includes an axial stop disposed on one of the first and second blocks and intended to cooperate with the other of the blocks to define a predetermined axial position of the sound insulation panel relative to the envelope; - said at least one second block and said at least one first block are arranged to cooperate by magnetic attraction in the axial direction, and the fixing system further includes a radial stop disposed on one of the first and second blocks and intended to cooperate with the other of the blocks to define a predetermined radial position of the sound insulation panel relative to the envelope; - the fixing system also includes screws, in particular for fixing the stop to the block(s); - said at least a second block and said at least a first block are arranged to cooperate by magnetic attraction in the axial and radial direction, and the fastening system does not include any other means of fastening than these blocks; - the stop is a magnet placed on a portion of the first block; - the stop is a locking system located on an upstream face of the second block, said system comprising: • a plate that extends radially between the annular envelope and the acoustic insulation panel; • a first screw for fixing one end of the plate to the second block; • a second screw for fixing a second end to the said first block, the second end being opposite the first end and intended to come to rest against an upstream face of the first block; • a nut positioned on a downstream face of the first block, opposite said upstream face of the first block, and configured to immobilize the second screw; - the magnets of the first and second blocks are made of a samarium-cobalt or neodymium-iron-boron material; - the mounting blocks and screws are made of a non-magnetic or paramagnetic material; - the non-magnetic or paramagnetic material is titanium or aluminum; - the studs are made of a composite material; - the material is a pre-impregnated organic matrix composite or a 3D woven organic matrix composite.

[0025] The invention also relates to a turbomachine comprising a casing as described above.

[0026] The invention also relates to a method of manufacturing a housing as described above, the method comprising at least one assembly step including at least: - the creation of a first assembly consisting of the envelope and the first magnetic block which is fixed on the inner annular face of the envelope; - the creation of a second assembly consisting of the acoustic insulation panel and the second magnetic block, which is fixed to the outer face of the acoustic insulation panel; and - the positioning of the second set on the first set with the cooperation of the second and first blocks. Brief description of the figures

[0027] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig.1] is a schematic representation of a casing according to the prior art; - [Fig.2] is a schematic representation of an annular acoustic insulation panel according to the prior art; - [Fig.3] and a schematic representation of a system for fixing the acoustic panel of [Fig.2] onto the casing of [Fig.1]; - [Fig.4] is a schematic representation of the panel of [Fig.2] with the fixing tabs to the casing of the [Fig.1]; - [Fig.5] is a partial schematic representation of a housing according to the invention; - [Fig.6] is a schematic representation of the system for fixing an acoustic insulation panel to the casing of [Fig.5]; - [Fig.7] is a partial schematic representation of the variant of the crankcase of [Fig.5]; - [Fig.8] is a schematic representation of the system for fixing an acoustic insulation panel to the casing of [Fig.7]; - [Fig.9] is a schematic representation of the fixing of the acoustic insulation panel to the casing of the [Fig.7]; - [Fig. 10] is a partial schematic representation of another variant of the casing of [Fig. 5]; - [Fig.1 1] is a schematic representation of the system for fixing an acoustic insulation panel to the casing of the [Fig. 10]; - [Fig.12] is a schematic representation of a method for assembling a housing according to the invention. Detailed description of the invention

[0028] By convention, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis. This longitudinal axis corresponds substantially to an axis of rotation of a turbomachine. The terms "radial" or "vertical" refer to an orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner" and "outer," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an inner face facing the longitudinal axis and an outer surface opposite its inner surface. The terms "upstream" and "downstream" are defined with respect to the direction of airflow in the turbomachine.

[0029] Figures 1 to 4 have been described above and represent the technological background.

[0030] The invention can be implemented in a turbomachine as described above.

[0031] In the remainder of this description, the invention relates to a blower housing. However, the invention is not limited to this type of housing and can be applied to other housings of a turbomachine, including those incorporating a sound insulation panel.

[0032] With reference to [Fig.5], a turbomachine housing according to the invention will now be described.

[0033] The casing 100, for example of a blower, includes at least an annular envelope 102, an annular acoustic insulation panel 106 and a fixing system SFX of the acoustic insulation panel to the envelope 102.

[0034] The annular envelope 102 of the housing 100 extends around an axis Ao and has an internal annular face SEp. The envelope can be, for example, made of metallic material or of composite material made from woven fibers embedded in a polymeric resin.

[0035] The annular acoustic insulation panel 106 also extends around the axis Ao and has an external face SV2 intended to face the internal face SEi of the envelope 102.

[0036] The annular acoustic insulation panel 106 further includes an inner face SV1 carrying an acoustic insulation element (not shown).

[0037] The SFX fixing system, which is in block form, is arranged between the internal surface SEi of the envelope 102 and the external surface SV2 of the acoustic panel 106.

[0038] With reference to [Fig.6], the SFX fastening system will now be described in detail.

[0039] The fixing system includes at least a first block 120 fixed on the inner face SEi of the envelope 102 and a second block 140 fixed on the outer face SV2 of the acoustic insulation panel 106.

[0040] The first block 120 includes a stud 122 having an external face fixed to the internal face SEi of the casing 102 by means of at least one screw 128.

[0041] The first block 120 further comprises a first magnet 124i disposed on an inner face of a first portion of the stud 122, the inner face of the first portion being opposite to the outer face of the stud 122. The first magnet is fixed, via the screw 128, to the stud 122 of the first block 120.

[0042] The first block further comprises a second magnet 1242 disposed on an inner face of a second portion of the stud 122, the inner face of the second portion being oriented perpendicularly to the outer face of the stud 122 and to the inner face of the first portion. The second magnet 1242 can be fixed to the second portion by means of a screw or rivet 126.

[0043] Still with reference to [Fig.6], the second block 140 of the SFX fixing system also includes a stud 142 comprising an inner face fixed to the outer face SV2 of the acoustic insulation panel 106 by means of a screw or rivet 146.

[0044] The second block 140 further comprises a first magnet 144i fixed on a first face of the stud 142 opposite the inner face SEi of the casing 102, the first magnet 144i being fixed on the first face of the stud 142 via the screw 146.

[0045] The second block 140 further comprises a second magnet 1442 fixed on a second face of the stud 142 oriented perpendicularly to the first face of the stud 142 and opposite the second magnet 1242 of the first block 120. The second magnet 1442 of the second block 142 can be fixed on the second face by means of a screw or rivet 146.

[0046] Thus, the second block 140 is arranged so that, when the acoustic insulation panel 106 is moved from upstream to downstream, as indicated by the direction of the arrow SC, the second block 140, fixed to the acoustic insulation panel 106, cooperates by magnetic attraction with the first block 120 fixed to the inner face SEi of the envelope 102.

[0047] The magnets 124b 1242 of the first block 120 have a polarity opposite to that of the magnets 124b 1242 of the second 140 block so that when they come together, the two blocks 120, 140 attract each other until the second block 140 comes to rest on the first block 102 to form a single block.

[0048] Thus, the first magnet 124i of the first block 120 cooperates by magnetic attraction in a radial direction with the first magnet 144i of the second block 140. This cooperation between the first magnets 124b 144i of the first and second blocks 120, 140 makes it possible to define a predetermined radial position of the acoustic insulation panel 106 relative to the envelope 102.

[0049] Similarly, the second magnet 1242 of the first block 102 cooperates by magnetic attraction in the axial direction with the second magnet 1442 of the second block 140. This cooperation between the second magnets 1242, 1442 of the first and second blocks 120, 140 makes it possible to define a predetermined axial position of the acoustic insulation panel 106 relative to the envelope 102.

[0050] In the example of Figures 5 and 6, the second magnet 1242 of the first block 120 acts as a stop that replaces the sealing gasket 112 located between a downstream annular edge Fi06 of the acoustic insulation panel 106 and an annular edge F104 of the support 1042 supporting the annular layer 104i, as illustrated in [Fig. 3]. The second magnet 1242 of the first block 120 thus compensates for the compressive force of the gasket 112 and prevents axial movement of the acoustic insulation panel 106 relative to the casing 102.

[0051] Preferably, the magnets are made of a samarium-cobalt or neodymium-iron-boron material.

[0052] Preferably, the mounting studs, screws, and rivets are made of a non-magnetic or paramagnetic material. For example, the mounting studs, screws, and rivets are made of titanium or aluminum.

[0053] The pads can also be made of composite material. For example, the material is a pre-impregnated organic matrix composite or a 3D woven organic matrix composite (obtained by the RTM process, for Resin Transfer Molding).

[0054] With reference to figures [Fig.7] to 9, a first variant of the invention will now be described.

[0055] In this variant, the housing 100 also includes at least one annular envelope 102, an acoustic insulation panel 106 and a fixing system SFX of the acoustic insulation panel 106 on the internal surface SEi of the envelope 102 as illustrated in [Fig.7].

[0056] With reference to [Fig.8], the SFX fixing system also includes at least a first block 120 fixed to the inner face SEi of the envelope 102 and a second block 140 fixed to the outer face SV2 of the acoustic insulation panel 106.

[0057] In this configuration, the first block 120 includes a first magnet 124 fixed to the stud 122 by means of fixing screws or rivets.

[0058] The second block 140 includes a second magnet 1442 fixed to the stud 142 by means of fixing screws or rivets. The first 124 and second 144 magnets are arranged so as to cooperate only by magnetic attraction in a radial direction.

[0059] The SFX fixing system further includes an axial stop disposed on the second block 140 and intended to cooperate with the first block 120 to define a predetermined axial position of the acoustic insulation panel 106 relative to the envelope 102.

[0060] Still with reference to [Fig.8], the axial stop can be a locking system disposed partly on an upstream face of the second block 140.

[0061] The locking system includes a plate 150 which extends radially between the acoustic insulation panel 106 and the annular envelope 102.

[0062] The locking system further includes a first screw 152 for fixing one end of the plate 150 to the second block 140. A hole through the stud may be provided for fixing the first end of the plate.

[0063] The locking system may further include a second screw 132, as illustrated in [Fig. 9], for securing a second end of the plate to the first block 120. The second end of the plate 150, opposite the first end, is intended to abut against an upstream face of the first block 120. The second end includes an opening 154 for the insertion of the second screw 132. An opening 136 may also be provided through the stud 122 of the first block 102. for fixing the second end of the plate to the upstream face of the first block 120.

[0064] The locking system may further include a nut 134 disposed on a downstream face of the first block 120, opposite the upstream face of the first block, and configured to immobilize the second screw 132.

[0065] Thus, when the acoustic insulation panel 106 is attached to the inner face SE1 of the annular casing 102, the acoustic insulation panel 106 is moved from upstream to downstream, as indicated by arrow SC in [Fig. 8], until the magnets 124, 144 of the first and second blocks 120, 140 occupy a position in which they cooperate by magnetic attraction in a radial direction. This position corresponds to the position where the plate 150 of the locking system comes to rest against the upstream face of the first block 120.

[0066] The second screw is then inserted into the holes 154, 136 respectively of the second end of the plate 150 and of the stud 122 of the first block in order to prevent any axial movement of the acoustic insulation panel 106.

[0067] The plate 150, the screws 150, 132 and the nut 134 forming the locking system (or stop), can be made of titanium, aluminum or any other non-magnetic or paramagnetic material.

[0068] In the embodiment illustrated in Figures 5 and 6, the fastening system does not include any other fastening means than the first 120 and second 140 blocks. In contrast, in the alternative embodiment illustrated in Figures 7 to 9, the fastening system also includes screws 152, 132, in particular for fastening the stop to the block(s) 120, 140.

[0069] In another variant (not shown), the stop can be arranged on the first block 120. In this case, the stop can be arranged on the downstream face of the first block 120 so that the stop prevents any downstream movement of the acoustic insulation panel 106.

[0070] In another variant as illustrated in Figures 10 and 11, the second block 140 and the first block 120 are arranged so that, when the acoustic insulation panel 106 is moved from upstream to downstream, they cooperate by magnetic attraction in the axial direction as indicated in [Fig. 10] by the direction of the arrow SC. In this configuration, the fastening system may further include a radial stop 130 disposed on one of the first 120 and second 140 blocks and intended to cooperate with the other 140, 120 of the blocks to define a predetermined radial position of the acoustic insulation panel relative to the enclosure.

[0071] In the example illustrated in Figures 10 and 11, the stop 130 is positioned on the stud 122 of the first block 120. As illustrated in [Fig. 11], when the acoustic insulation panel 106 is moved from upstream to downstream, one end 146a of the screw or rivet 146 of the block 142 comes to rest on the stop 130 thus allowing to define the radial position of the insulation panel 106 in relation to the envelope 102.

[0072] The present invention also relates to a method 400 for manufacturing the housing described above. As illustrated in [Fig. 12], the method comprises at least one assembly step 500 of the housing 100.

[0073] Assembly step 500 comprises at least: - the realization 502 of a first assembly formed by the envelope 102 and the first magnetic block 120 which is fixed on the internal annular face SEi of the envelope 102, - the realization 504 of a second assembly formed by the acoustic insulation panel 106 and the second magnetic block 140 which is fixed to the external face SV2 of the acoustic insulation panel 106; and - the positioning 506 of the second set on the first set with the cooperation of the second 140 and first 120 blocks.

[0074] It is clear that a turbomachine casing such as the one described above reduces or prevents the formation of cracks that could damage the casing, thus improving the availability of the turbomachine engine (reducing turbomachine downtime related to the repair or replacement of damaged parts). Indeed, the invention prevents the occurrence of excessive stresses such as those observed in a fastening system comprising fasteners having, for example, an L-shape. Such stresses can lead to the formation of cracks or even the failure of these fasteners.

[0075] The invention also makes it possible to improve the positioning of the acoustic insulation panel and to facilitate its replacement.

[0076] The invention thus has the advantage of improving the manufacture and maintenance of the housing and of saving overall cycle time.

Claims

Demands

1. Housing (100) for an aircraft turbomachine, comprising at least: - an annular casing (102) extending around an axis (Ao) and having an inner annular face (SEi); - an annular acoustic insulation panel (106) extending around the axis (Ao) and having an outer face (SV2) intended to face the inner face (SEi) of the casing (102); and - a fastening system (SFX) for the acoustic insulation panel (106) on the inner face (SEi) of the casing (102), characterized in that the fastening system (SFX) comprises: - at least one first magnetic block (120) fixed to the inner annular face (SEi) of the casing (102); - at least one second magnetic block (140) fixed to the external face (SV2) of the acoustic insulation panel (106), said at least one second block (140) being arranged to cooperate by magnetic attraction with said at least one first block (120).

2. Carter (100) according to claim 1, each of the first (120) and second (140) blocks comprises at least: - a magnet (124, 144, 124b 1242, 144b 1442) of opposite polarity to a magnet (124, 144, 124b 1242, 144b 1442) of the other of the first (120) and second (140) blocks; - a stud (122, 142) having a face configured to receive the magnet (124, 144, 124b 1242, 144b 1442).

3. Carter (100) according to claim 1 or 2, wherein said at least second block (140) and said at least first block (120) are arranged to cooperate magnetic attraction in the radial direction, or in the axial direction, or in axial and radial directions.

4. A housing (100) according to claim 3, wherein said at least second block (140) and said at least first block (120) are arranged to cooperate by magnetic attraction in the radial direction, and the fastening system further comprises an axial stop disposed on one of the first (120) and second (140) blocks and intended to cooperate with the other of the blocks (140, 120) to define a predetermined axial position of the sound insulation panel (106) relative to the envelope (102).

5. Carter (100) according to claim 3, wherein said at least one second block (140) and said at least one first block (120) are arranged to cooperate by magnetic attraction in the axial direction, and the fastening system further comprises a radial stop disposed on one of the first (120) and second (140) blocks and intended to cooperate with the other (140, 120) of the blocks to define a predetermined radial position of the sound insulation panel relative to the envelope.

6. Housing (100) according to claim 4 or 5, wherein the fastening system (SFX) further comprises screws (152, 132), in particular for fastening the stop to the block(s) (120, 140).

7. Carter (100) according to claim 3, wherein said at least one second block (140) and said at least one first block (120) are arranged to cooperate by magnetic attraction in the axial and radial directions, and the fastening system (SFX) not comprising any other fastening means than these blocks (120, 140).

8. Carter (100) according to claim 4, wherein the stop is a magnet (1242) disposed on a portion of the first block (120).

9. A housing (100) according to claim 4, wherein the stop is a locking system disposed on an upstream face of the second block (140), said system comprising: - a plate (150) which extends radially between the annular casing (102) and the acoustic insulation panel (106), - a first screw (152) for fixing a first end of the plate (150) to the second block (140); - a second screw (132) for fixing a second end to said first block (120), the second end being opposite the first end and intended to abut against an upstream face of the first block (120); - a nut (134) disposed on a downstream face of the first block (120), opposite said upstream face of the first block (120), and configured to immobilize the second screw (134).

10. Carter (100) according to any one of claims 2 to 9, wherein the magnets (124, 144, 124b 1242, 144b 1442) of the first (120) and

11.

12.

13.

14. second (140) blocks are made of a samarium-cobalt or neodymium-iron-boron material. Carter according to any one of claims 2 to 10, wherein the studs (122, 142), the fixing screws (128, 152, 132, 126, 146) are made of a non-magnetic or paramagnetic material. Carter (100) according to any one of claims 2 to 11, wherein the studs (122, 142) are made of a composite material. Turbomachine comprising a casing (100) according to any one of claims 1 to 12. A method (400) for manufacturing a housing (100) according to any one of claims 1 to 12, characterized in that it comprises at least one assembly step (500) comprising at least: - the realization (502) of a first assembly formed by the envelope (102) and the first magnetic block (120) which is fixed on the inner annular face (SEi) of the envelope (102), - the fabrication (504) of a second assembly formed by the acoustic insulation panel (106) and the second magnetic block (140) which is fixed to the external face (SV2) of the acoustic insulation panel (106); and - the positioning (506) of the second set on the first set with the cooperation of the second (140) and first (120) blocks.

Images