FR3105165A1 - Frame element for an aircraft fuselage provided with openings suitable for mounting by threading a stiffener. - Google Patents

Abstract

- Frame element for an aircraft fuselage provided with openings suitable for mounting by threading a stiffener. - The frame element (2) comprises a core (6) provided with at least one through opening (9), the opening (9) having a closed contour (10) and a size greater than the cross section of a stiffener intended to pass through said opening (9). The opening (9) allows both the passage of a stiffener, and possibly its guidance thanks to its closed contour (10). This allows easy assembly of a structural part of an aircraft fuselage. Figure for the abstract: Fig. 3

Description

Frame element for an aircraft fuselage provided with openings suitable for mounting by threading a stiffener.

The present invention relates to a frame element for an aircraft fuselage, as well as a structural fuselage part comprising at least one such frame element.

It is known that the fuselage of an aircraft, in particular of a transport aircraft, is designed in particular to resist loads induced by pressurization and by commercial loads (passengers and freight).

To do this, the fuselage of the aircraft generally comprises a structural part comprising frame elements extending circumferentially, and an aerodynamic skin to which these frame elements are fixed, as well as stiffeners extending longitudinally , which are arranged on an inner face of the skin.

Document EP2832634 discloses a frame element for such a structural part. This frame element comprises a web provided with a through opening intended for the passage of a fuselage stiffener. The opening is made in such a way as to emerge outside the frame element, via a mouthpiece. In addition, this frame element comprises a tongue which is made in one piece with the core and which is connected to the latter by a fold delimiting the opening. This tongue is intended for fixing the frame element to the stiffener.

When assembling the structural part, the frame elements are brought inside the structural part and placed on the stiffeners previously fixed to the skin. During this installation, the openings of the frame elements surround the stiffeners via their external mouth. These frame elements are not suitable for assembly requiring the frames to be fixed first and then the stiffeners.

The object of the present invention is to remedy this drawback. To do this, it relates to a frame element for an aircraft fuselage, said frame element comprising a web provided with at least one through opening.

According to the invention, said opening has a closed outline and a size greater than the cross section of a stiffener intended to pass through said opening.

Thus, the opening allows the passage of a stiffener by threading, and possibly its guidance, thanks to its closed contour, which is not the case of a mouth opening as mentioned above.

Each stiffener can thus be threaded through the holes of a plurality of frame elements arranged beforehand in an appropriate manner, as specified below.

Advantageously, the opening is enveloping. By "enveloping" is meant the fact that the shape of the opening is adapted to the shape of the cross section of the stiffener to allow its passage, while limiting the size of said opening.

In a particular embodiment, said opening has the general shape of an isosceles trapezoid with two parallel sides.

In this case, advantageously, the distance between the two parallel sides of the isosceles trapezium is greater than a height of the stiffener.

Furthermore, preferably, the length of a first of said parallel sides of the isosceles trapezoid is greater than the width of a first face of the stiffener and the length of the second of said parallel sides of the isosceles trapezoid is greater than the width of a second face of the stiffener.

In addition, advantageously, said opening is made in a so-called outer half of the core.

Further, advantageously, the web has an elongated shape and the frame member has a plurality of spaced apart apertures along the length of the web.

The present invention also relates to a structural part of an aircraft fuselage.

According to the invention, said structural part comprises at least one frame element as described above, as well as at least one stiffener and one stabilizer, said stiffener passing through the opening of the frame element and being fixed to this last through the stabilizer.

Advantageously, the stiffener is provided with a recess made on an outer face and configured to allow the stiffener to span a flange of the frame element when it passes through the opening.

Furthermore, in a particular embodiment, the stiffener has two side walls and it is provided with at least one retaining plate fixed to an internal face of each of said two walls.

In addition, in a particular embodiment, the stabilizer has, in cross section, the general shape of an L, of which a first branch is fixed to the web of the frame element and of which the second branch is fixed to one face. internal of the stiffener.

Furthermore, advantageously, the structural part further comprises at least one outer skin which is fixed to the frame element and to the stiffener.

Furthermore, in a particular embodiment, the structural part comprises a plurality of frames spaced from each other along a longitudinal direction of the structural part, a plurality of stiffeners arranged parallel to the longitudinal direction, each of which crosses the openings of a plurality of frames, and stabilizers securing the stiffeners to the frames at the openings.

The present invention further relates to an aircraft, in particular a transport airplane, which comprises at least one structural part of the fuselage, such as that described above.

The present invention also relates to a method of assembling a structural part of the fuselage.

According to the invention, said method comprises:
- a first sequence of steps consisting in assembling together the frame elements, the stiffeners and the skin; And
- a stabilization step consisting in fixing the stabilizers on the frame elements and the stiffeners.

Advantageously, the first sequence of steps includes a step for positioning stiffeners, consisting in mounting the stiffeners by threading them through the openings of a plurality of adjacent frame elements.

The appended figures will make it clear how the invention can be implemented. In these figures, identical references designate similar elements.

Figure 1 is a side view of an aircraft, to which the present invention can be applied.

FIG. 2 is a schematic view, in perspective, of a structural part of an aircraft fuselage.

Figure 3 is a partial view, in perspective, of a frame element provided with an opening.

FIG. 4 is a view, along a longitudinal axis of the aircraft, of the frame element of FIG. 3 provided with a sectional stiffener and with a stabilizer.

Figure 5 is a partial view, in perspective, of the representation of Figure 4 without the stabilizer.

Figure 6 is a schematic cross-sectional view of the frame member, stiffener and stabilizer of Figure 4.

FIG. 7 is a partial view, in perspective, similar to that of FIG. 5, showing in addition a stabilizer fixed according to a first method of fixing.

FIG. 8 is a partial view, in perspective, similar to that of FIG. 5, showing in addition a stabilizer fixed according to a second method of fixing.

Figure 9 is a partial view, in perspective, of a stiffener provided with a retaining plate.

Figure 10 is a schematic view, partial and in perspective, of a structural part of the fuselage during mounting by threading stiffeners.

Figures 11A-11D illustrate successive steps of a first embodiment of a method of assembling a structural part of an aircraft fuselage. More specifically:

FIG. 11A illustrates a first step,

Figure 11B illustrates a second step,

Figure 11C illustrates a third step, and

Figure 11D illustrates a fourth step.

Figures 12A-12D illustrate successive steps of a second embodiment of a method of assembling a structural part of an aircraft fuselage. More specifically:

FIG. 12A illustrates a first step,

Figure 12B illustrates a second step,

Figure 12C illustrates a third step, and

Figure 12D illustrates a fourth step.

In Figure 1, there is shown an aircraft AC, for example a transport aircraft, which comprises, in particular, a fuselage F.

This fuselage F is provided with a structural part 1, for example a fuselage section, as shown schematically, by way of illustration, in FIG. 2.

The structural part 1 has a longitudinal axis L, corresponding to the longitudinal axis of the aircraft AC. Along this longitudinal axis L are arranged a plurality of frame elements 2.

Each frame element 2 extends over the entire periphery 3 of the structural part 1 of the fuselage F, in a transverse plane P, that is to say in a plane which is orthogonal to the longitudinal direction L. The shape of each frame element 2 can be circular or have another shape. The shape of each frame element depends on the section of the AC aircraft.

Alternatively (not shown), the frame elements 2 can also extend over only part of the periphery of the structural part 1. In the example shown in Figure 2, the frame elements 2 have a circular shape. It is also conceivable to provide a frame element 2 having the shape of an arc of a circle or an arc shape having any curve, depending on the section of the aircraft AC.

Each frame element 2 can be made in one piece or be formed from several frame arcs assembled together, each frame arc forming in this case an angular sector of the frame element 2.

To facilitate the description, an arrow L1 has been shown in FIG. 2 which indicates a direction defining a so-called "forward" direction (directed along the longitudinal axis L), namely towards the front of the aircraft AC in the direction of flight (or movement) of the aircraft AC. The direction opposite to that of the arrow L1 defines a so-called “rear” direction.

Furthermore, the adjectives “internal”, “interior”, “external” and “exterior” are also defined with reference to the longitudinal axis L, and with respect to the direction of arrows R1 (figure 2) which are directed radially in s 'deviating from the longitudinal axis L. Double arrows R illustrate radial directions. The terms “external” and “exterior” are defined according to the direction of the arrows R1, that is to say deviating from the longitudinal axis L, and the terms “internal” and “interior” are defined according to the direction opposite to that of the arrows R1, i.e. approaching the longitudinal axis L.

There has also been shown in FIG. 2, by a double arrow C, a circumferential direction which is defined according to a curved shape evolving around the longitudinal axis L. In FIG. 2, the curved shape corresponds, by way of example, to an arc of a circle evolving around the longitudinal axis L.

The structural part 1 further comprises a plurality of stiffeners 4. These stiffeners 4 are arranged longitudinally, parallel to the longitudinal axis L, preferably crossing the frame elements 2, as specified below.

The structural part 1 further comprises a skin 5 (shown partially and schematically in Figure 2) which covers, towards the outside, the assembly formed by the frame elements 2 and the stiffeners 4.

In a preferred embodiment shown in Figure 2, the structural part 1 comprises a plurality of frame elements 2 spaced from each other along the longitudinal direction L and a plurality of stiffeners 4 arranged parallel to the longitudinal direction L , each of which passes through openings of a plurality of frames. In addition, stabilizers (not shown in Figure 2), specified below, fix the stiffeners 4 to the frame elements 2.

Each frame element 2 comprises, as shown in Figure 3, a core 6 which is arranged transversely, parallel to the plane P. The core 6 has a rounded elongated shape (for example in the arc of a circle), extending around the circumferential direction C. The core 6 is provided, at its outer end 6A, with a curved part forming a sole 7, and at its inner end 6B, with a curved part forming a wing 8. These parts are curved along different meanings. The sole 7 can be curved backwards and the wing 8 forwards (in the direction of the arrow L1 in FIG. 3), or vice versa. Thus, each frame element 2 can have a Z shape. However, each frame element 2 can also have a C shape in which the sole 7 and the wing 8 are curved in the same direction. Each frame element 2 can also have an I-shape or any other suitable shape.

In the example shown in Figure 3, sole 7 and wing 8 are arranged substantially orthogonally to web 6.

In addition, the core 6 includes at least one through opening 9. Preferably, the core 6 comprises a plurality of openings 9, as shown for example in Figure 10.

According to the invention, said opening 9 has a closed outline 10, that is to say without a mouth. In addition, the size of the opening 9 is greater than the cross section of a stiffener 4 intended to pass through said opening 9, as specified below and shown for example in Figure 6. By size is meant the dimensions of opening 9.

In addition, opening 9 is enveloping. By enveloping is meant the fact that the shape of the opening 9 is adapted to the shape of the cross section of the stiffener 4 (which can for example have the shape of an inverted Ω as represented in FIG. 5, of a Z or a C or another shape) to allow the passage of said stiffener 4, while limiting the size of the opening 9. In a preferred embodiment, the shape and size of the opening 9 are thus optimized to allow the passage of the stiffener 4 with a minimum size of the opening 9.

A closed contour 10 of the opening 9 can make it possible to obtain a frame element 2 which is less subject to deformations. Since the frame element 2 is thus less mechanically weakened by an opening 9 without a mouthpiece than it would have been with an opening with a mouthpiece, its structural strength, its deformation and its stability under mechanical loads are improved.

In the particular embodiment, represented in particular in FIGS. 3 and 4, the contour 10 of the opening 9 has the general shape of an isosceles trapezium.

This isosceles trapezium comprises two parallel sides 11A and 11B, namely an inner side 11A and an outer side 11B, and two sides 11C and 11D. In the example of Figures 3 and 4, the corners 12 of the trapezium are rounded, in particular to facilitate the production of the opening 9. The roundings also reduce the local over-stresses under loads. In addition, this shape enveloping the section of the stiffener makes it possible to gradually drain the circumferential loads towards the flange 7 and also contribute to the resistance to buckling of the core 6 of the frame element 2.

In this particular embodiment, the distance D (FIG. 4) between the two parallel sides 11A and 11B of the isosceles trapezium is greater than the height H of the stiffener 4 (FIG. 6). By height is meant the dimension of the stiffener 4 in a radial direction.

Moreover, preferably, the length e1 of the internal side 11A is greater than the width e3 of an internal face of the stiffener 4 and the length e2 of the external side 11B of the isosceles trapezoid is greater than the width e4 of an external face of the stiffener 4.

This isosceles trapezium shape is particularly well suited to a stiffener 4 having in cross section a general shape of an inverted Ω, as shown in FIG. 5.

In the example of figure 5, the stiffener 4 comprises an external wall 14, two side walls 15 and 16 and two internal flanges 17 and 18 forming the internal face of the stiffener 4.

Preferably, the opening 9 is made outwards and in particular in the outer half of the core 6, which allows the stiffener 4 to easily come into contact with the skin 5.

The stiffener 4 is provided with a recess 51 made on the outer wall 14. The recess 51 is configured to allow the stiffener 4 to span a flange 7 of the frame element 2 when it passes through the opening 9. This recess 51 facilitates the fixing of the stiffener 4 to the skin 5. The recess 51 in fact allows the stiffener 4 to reach the opening 9 to put it on and to be fixed on the skin 5.

In a variant (not shown), instead of making a recess, it is possible to provide a slight inward deformation of the stiffener (at its outer edge intended to be positioned in line with the sole of the frame element) . This deformation must generate sufficient play to allow the stiffener to span the flange.

Furthermore, the core 6 of elongated and rounded shape in the circumferential direction C (in a circle or an arc of a circle or following any curve as indicated above) is provided with a plurality of openings 9 spaced apart from each other. along the length of web 6, as shown in Figure 10.

As shown in Figure 10, stiffeners 4 are threaded through the openings 9 of the webs 6 in the direction indicated by an arrow G in the longitudinal direction L. Each of the openings 9 of a web 6 is opposite an opening 9 of a neighboring soul 6. FIG. 10 represents different positions P1 to P4 when threading stiffeners 4 through openings 9. In this figure 10, by way of illustration, a stiffener 4 (located in position P1) is ready to be threaded in the openings 9 in the direction of arrow G, a stiffener 4 (located in position P2) is threaded into an opening 9 in the direction of arrow G, a stiffener 4 (located in position P3) is threaded in two openings 9 in the direction of the arrow G, and a stiffener 4 (located in position P4) is threaded through all the openings 9.

In addition, a stabilizer 20 is fixed both to the web 6 of the frame element 2 and to the stiffener 4 to hold these two parts together.

In a particular embodiment represented in FIGS. 7 and 8, the stabilizer 20 has, in cross-section, the general shape of L, of which a first branch 201 is fixed to the web 6 of the frame element 2 and of which the second branch 202 is fixed on the internal face of the stiffener 4.

The stabilizer 20 can be made of a composite material or a metallic material.

The stabilizer 20 can be fixed to the core 6 and to the internal surface of the stiffener 4 by rivets 21 (FIG. 7).

The stabilizer 20 can also be fixed to the core 6 and to the internal surface of the stiffener 4 by gluing or by welding 22 (FIG. 8).

This stabilizer 20 makes it possible to stabilize both the stiffener 4 and the frame element 2.

Furthermore, in the particular embodiment of the stiffener 4 provided with walls 15 and 16 provided with lateral flanges 17 and 18, the stiffener 4 is provided with at least one retaining plate 41 which is fixed to an internal face of each side wings 17 and 18 of the two walls 15 and 16 as shown in Figure 9. It may comprise a plurality of such retaining plates 41 which are positioned longitudinally between the frame elements 4. This retaining plate 41 ensures the maintenance of the spacing between the two walls 15 and 16, which contributes to avoiding the deformation of the stiffeners 4.

The retaining plate 41 can be fixed to the internal face of each of the side wings 17 and 18 using rivets 23 or by gluing or welding.

The structural part 1 therefore comprises a skin 5 and structural elements attached to the skin 5 to give it its rigidity. These structural elements typically comprise longitudinal stiffeners 4, also called stringers, extending substantially in planes parallel to the longitudinal axis L of the fuselage F, and circumferential frame elements 2, which extend globally along a transverse plane P , that is to say orthogonal to the longitudinal axis L, all around this longitudinal axis L. The stabilizers 20 thus complete the assembly of the stiffeners 4 and the frame elements 2.

The structural part 1, as described above, can be assembled according to an assembly method, as specified below.

Preferably, said assembly method comprises:
- a first sequence of steps A1 to A3 or B1 to B3 consisting in assembling together the frame elements 2, the stiffeners 4 and the skin 5. This first sequence of steps comprises a step of positioning stiffeners 4 by passing them through openings 9 of a plurality of frame members 2, as shown in Figure 10; And
- A stabilization step E consisting in fixing the stabilizers 20 to the frame elements 2 and the stiffeners 4, as shown in FIGS. 11D and 12D.

Said assembly method (therefore comprising an assembly step consisting in threading the stiffeners 4 through the openings 9 of the frame elements 2) can be implemented in different ways. By way of illustration, two particular embodiments of said first sequence of steps of said method, comprising such an assembly step, are described below.

In a first embodiment represented in FIGS. 11A to 11D, the first sequence of steps implements a “part by part” type assembly method which comprises the following steps:
- a step A1 consisting in positioning the frame elements 2 (by spacing them) along an axis representing the longitudinal axis L of the fuselage (figure 2), and this by arranging them each time in an orthogonal transverse plane P at this longitudinal axis L, a single frame element 2 thus positioned being partially represented in FIG. 11A for reasons of simplification of the drawing;
- a step A2 consisting in positioning the skin 5 against the frame elements 2 (positioned in step A1) and in fixing the frame elements 2 on the skin 5 thus positioned, as represented in FIG. 11B for the part of the frame member 2 of Figure 11A;
- A step A3 consisting of threading the stiffeners 4 through the openings 9 of the frame elements 2, as shown in Figure 11C for the part of the frame element 2 of Figure 11B. The stiffeners 4 are threaded as explained above with reference to figure 10. The stiffeners 4 are then fixed on the skin 5.

In this first embodiment, the assembly method further comprises the stabilization step E consisting in fixing the stabilizers 20 to the frame elements 2 and the stiffeners 4, as represented in FIG. 11D for the part of the frame element 2 and stiffener 4 of Figure 11C.

In a second embodiment shown in Figures 12A to 12D, the first sequence of steps implements a "skeleton" type mounting method which includes the following steps:
- a step B1 consisting in positioning the frame elements 2 (by spacing them) along an axis representing the longitudinal axis L of the fuselage (figure 2), and this by arranging them each time in an orthogonal transverse plane P at this longitudinal axis L, a single frame element 2 thus positioned being partially represented in FIG. 12A for reasons of simplification of the drawing;
- A step B2 consisting in threading the stiffeners 4 through the openings 9 of the frame elements 2 (positioned in step B1), as shown in FIG. 12B for the part of the frame element 2 in FIG. 12A. The stiffeners 4 are threaded as explained above with reference to Figure 10;
- a step B3 consisting in positioning the skin 5 against the frame elements 2 and the stiffeners 4 and in fixing the frame elements 2 and the stiffeners 4 on the skin 5 thus positioned, as represented in FIG. 12C for the part of the frame member 2 and stiffener 4 of Figure 12B.

In this second embodiment, the assembly method further comprises the stabilization step E consisting in fixing the stabilizers 20 to the frame elements 2 and the stiffeners 4, as represented in FIG. 12D for the part of the frame element 2 and the stiffener 4 of FIG. 12C.

The structural part 1, as described above, has many advantages:
- Easier assembly of the structural part 1 by the reduced number of structural elements (stiffener 4, frame element 2, stabilizer 20) and by the simple configuration of each of the structural elements. Access to tools for assembly is also facilitated,
- assembly and fixing of structural elements carried out by robots,
- reduction in weight of the structural part by the reduced number of structural elements and improved structural efficiency due to their configuration,
- less elements are needed to link the structural elements by better integrated structural elements,
- possibility of forming fuselages with single or double curvature (if one has a trajectory compatible with threading into the openings of the frame elements).

Claims (16)

Frame element for an aircraft fuselage, said frame element (2) comprising a web (6) provided with at least one through opening (9),
characterized in that said opening (9) has a closed contour (10) and a size greater than the cross section of a stiffener (4) intended to pass through said opening (9). Frame element according to claim 1,
characterized in that said opening (9) is enveloping. Frame element according to one of Claims 1 and 2,
characterized in that said opening (9) has the general shape of an isosceles trapezium presenting two parallel sides (11a, 11B). Frame element according to claim 3,
characterized in that the distance (D) between the two parallel sides (11A, 11B) of the isosceles trapezium is greater than a height (H) of the stiffener (4). Frame element according to claim 4,
characterized in that the length (e1) of a first (11A) of said parallel sides (11A, 11B) of the isosceles trapezium is greater than the width (e3) of a first face of the stiffener (4) and the length (e2 ) of the second (11B) of said parallel sides (11A, 11B) of the isosceles trapezium is greater than the width (e4) of a second face of the stiffener (4). Frame element according to one of the preceding claims,
characterized in that said opening (9) is made in an outer half of the core (6). Frame element according to one of the preceding claims,
characterized in that the web (6) has an elongated shape, and in that the frame member (2) has a plurality of openings (9) spaced from each other along the length of the web (6). Aircraft fuselage structural part,
characterized in that it comprises at least one frame element (2) according to any one of Claims 1 to 7, as well as at least one stiffener (4) and one stabilizer (20), the said stiffener (4) passing through the opening (9) of the frame element (2) and being fixed to the latter via the stabilizer (20). Structural part according to claim 8,
characterized in that the stiffener (4) is provided with a recess (51) made on an outer wall (14) and configured to allow the stiffener (4) to span a flange (7) of the frame element ( 2) when it passes through the opening (9). Structural part according to one of claims 8 and 9,
characterized in that the stiffener (4) has two side walls (15, 16) and it is provided with at least one retaining plate (41) fixed to an internal face of each of the said two walls (15, 16). Structural part according to any one of claims 8 to 10,
characterized in that the stabilizer (20) has, in cross section, the general shape of an L, of which a first branch (201) is fixed to the web (6) of the frame element (2) and of which the second branch (202) is fixed on an internal face of the stiffener (4). Structural part according to any one of claims 8 to 11,
characterized in that it further comprises at least one outer skin (5) which is fixed to the frame element (2) and to the stiffener (4). Structural part according to any one of claims 8 to 12,
characterized in that it comprises a plurality of frame elements (2) spaced from each other along a longitudinal direction (L) of the structural part (1), a plurality of stiffeners (4) arranged parallel to the longitudinal direction (L), each of which passes through the openings (9) of a plurality of frame elements (2), and stabilizers (20) fixing the stiffeners (4) to the frame elements (2) at the openings (9). Aircraft,
characterized in that it comprises at least one structural part (1) of the fuselage according to any one of claims 8 to 13. A method of assembling a structural part of the fuselage according to claim 13,
characterized in that it comprises:
- a first sequence of steps (A1 to A3, B1 to B3) consisting in assembling together the frame elements (2), the stiffeners (4) and the skin (5); And
- a stabilization step (E) consisting in fixing the stabilizers (20) on the frame elements (2) and the stiffeners (4). Method according to claim 15,
characterized in that the first sequence of steps comprises a step of positioning stiffeners (4), consisting in mounting the stiffeners (4) by threading them through the openings (9) of a plurality of frame (2) adjacent.