Long life nozzle flap for aircraft turbojets

1. Nozzle flap for aircraft turbojet, characterised in that it is composed of a hollow tapered body ( 10 ) flattened in the transverse direction along straight geometric generating lines ( 11 ), the body ( 10 ) forming a thin wall ( 12 ) with an approximately constant thickness E, this wall ( 12 ) being divided transversely into four adjacent parts namely:

a plane “hot” trapezoidal wall ( 13 );

a flat “cold” trapezoidal wall ( 14 ) parallel to the hot wall ( 13 ) and two symmetric side walls ( 15 ) connecting the cold wall ( 13 ) and the hot wall ( 14 ) laterally;

the wall ( 12 ) comprising a continuous inner surface ( 17 ) with a radius of curvature equal to at least 2×E, the wall ( 12 ) being made of a refractory composite material composed of continuous reinforcing fibres ( 18 ) made crosswise from a refractory material, the reinforcing fibres ( 18 ) being embedded in a matrix made of another refractory material.

2. Flap according to claim 1 , characterised in that it comprises an articulation element ( 30 ) called the “upstream” element at one end fixed to an insert ( 31 ) called the “upstream” insert penetrating into the cavity ( 16 ) in the flap 1 , the insert ( 31 ) being held in place by screws ( 35 ) in contact with the cold wall ( 14 ), the cold wall ( 14 ) being locally sandwiched between the screw heads ( 35 ) and the upstream side insert ( 31 ), the screws ( 35 ) passing through the cold wall ( 14 ) and screwing into the upstream insert ( 31 ).

3. Flap according to claim 1 , characterised in that it includes an articulation element ( 40 ) called the “downstream” element fixed to a “downstream” insert ( 41 ) and a connecting rod clevis ( 42 ) forced into contact with the cold wall ( 14 ) on the outside of the flap ( 1 ), the connecting rod clevis ( 42 ) being located on the median part of the flap ( 1 ), the downstream insert ( 41 ) being extended on the inside of the flap ( 1 ) as far as underneath the median part of the flap ( 1 ) as far as underneath the connecting rod clevis ( 42 ), the downstream insert ( 41 ) being fixed in contact with the cold wall ( 14 ) by at least three screws ( 43 ), the head of which is on the external surface of the flap ( 1 ), the screws ( 43 ) passing through the cold wall ( 14 ) and screwing into the downstream insert ( 41 ), one of the three screws ( 43 ) also passing through the connecting rod clevis ( 42 ) and holding it in place in contact with the cold wall ( 14 ).

4. Flap according to claim 1 , characterised in that the side walls ( 15 ) include flat portions connected to trapezoidal and flat walls ( 13 , 14 ) through rounded portions with a radius of curvature equal to at least 2×E on the inner surface ( 17 ).

5. Flap according to claim 1 , characterised in that it includes ribs joining trapezoidal and plane walls ( 13 , 14 ) essentially parallel to the side walls and connected to trapezoidal and plane walls through rounded portions with a radius of curvature equal to at least 2×E on an inner surface ( 17 ).

6. Flap according to claim 5 , characterised in that the thickness of the trapezoidal and plane walls increases from the side walls towards a central strip.

7. Method for manufacturing a nozzle flap, including a step for creating a texture with continuous edges of refractory fibres arranged crosswise, a step for tensioning the texture around rigid and porous sections, opposite each other and curved inwards with convex parts facing towards divergent directions and with radii of curvature equal to at least 2×E, where E is the thickness of the texture, and a step for depositing a refractory matrix by vapour phase deposition on the texture and through the sections.

8. Method for manufacturing a nozzle flap including a step to create a plurality of textures ( 53 , 54 , 62 , 63 , 64 ) with continuous edges of refractory fibres arranged crosswise, a step to tension the textures around pairs of rigid and porous sections ( 55 , 56 , 70 , 71 ), opposite each other and curved inwards with convex parts facing towards divergent directions for each pair, the sections having radii of curvature equal to at least 2×E, where E is the thickness of one of the textures that is tensioned on the sections, and a step for the deposition of a refractory matrix by vapour phase deposition on the textures and through the sections, the textures having superposed portions and the matrix being continuous through the said superposed portions.

9. Manufacturing method according to claim 8 , characterised in that the pairs of sections are arranged symmetrically to a common plane, and the superposed sections of textures are flat and located between pairs of sections.

10. Manufacturing method according to claim 8 , characterised in that it includes a step for binding textures to each other and to the superposed portions before the vapour phase deposition.

11. Manufacturing method according to claim 7 , characterised in that the texture is made continuous by folding a sheet of crosswise fibres, joining the two opposite edges of the sheet and fixing the said two edges together by a connection fitting ( 60 ).

12. Manufacturing method according to claim 8 , characterised in that the textures are made continuous by folding a sheet of crosswise fibres, joining the two opposite edges of the sheet and fixing the said two edges together by a connection fitting ( 60 ).