Method for manufacturing a monolithic aircraft door by die-cutting and machining

Abstract

A method for manufacturing an aircraft door with an integral structure. The method includes the following steps: producing a forged blank (7); die-cutting the forging blank (7) between a substantially smooth lower die (8) and an upper die (9) defining a plurality of cells and producing a die-cut part having a honeycomb structure having an open face and a closed face closed by a wall; an inner wall of the honeycomb structure is machined to define at least one recess defined by a web connecting the closed face and the open face and a base protruding substantially perpendicular to the web on the open face of the die cut component.

Claims

1. A method for manufacturing an aircraft door having a monolithic structure comprising an outer skin (1) and an internal frame (2) in one piece, the internal frame (2) having at least one portion having: a core (5) attached transversely to the outer skin (1); and a flange (6) opposite the outer skin (1); the method comprising the following steps: producing a forged blank (7) with a constant thickness from a metal alloy that can be stamped; stamping the forged blank (7) between a smooth lower die (8) and an upper die (9) defining cells, a clearance being retained between the lower die (8) and the upper die (9), and obtaining a stamped part (26) with a cellular structure having an open face (27) and a closed face (28) closed by a wall with a thickness corresponding to the clearance; machining the internal walls of the cellular structure of the stamped part (26) to define at least one reinforcement delimited: by a core (5) connecting the closed face (28) and the open face (27); and by a flange (6) projecting substantially perpendicularly to the core (5), on the open face (27) of the stamped part (26).

2. The method as claimed in claim 1, wherein the upper die (9) has punches (29) surrounded by recesses (10) defining said cells.

3. The method as claimed in claim 1, wherein the lower die (8) and the upper die (9) are arched along a curvature defining a curvature for the aircraft door.

4. The method as claimed in claim 3, wherein the cellular structure of the stamped part (26) is produced by intersecting ribs (11, 12).

5. The method as claimed in claim 3, wherein the forged blank (7) is planar and arched by the stamping operation.

6. The method as claimed in claim 3, wherein the forged blank (7) is pre-arched along the same curvature as the arching of the dies (8, 9).

7. The method as claimed in claim 4, wherein some of the ribs (11) are perpendicular to the direction of curvature (25).

8. The method as claimed in claim 7, wherein from among said ribs (11) that are perpendicular to the direction of curvature (25), those located closer to the center of the stamped part (26), in the direction of curvature (25), have side walls forming an angle less than the angle formed by the side walls of those located further away from the center.

9. The method as claimed in claim 7, wherein the ribs (11) are located at a closer distance to the center of the stamped part (26), in the direction of curvature (25), have a smaller thickness than those located further away from the center, the thickness of the ribs (11) increasing with their distance to the center of the stamped part (26).

10. The method as claimed in claim 1, wherein the machining step includes a machining operation using a side-and-face milling cutter (23) machining the bottom of the flange (6) and a corresponding portion of the core (5) at the same time.

11. The method as claimed in claim 1, wherein the machining step includes a machining operation, using a conical milling cutter (30), machining a portion of the core (5) located under a flange (6), the axis of the milling cutter being oblique with respect to the plane of the core (5).

12. The method as claimed in claim 1, wherein during the stamping operation, blocks (13) of material are formed on the cellular structure of the stamped part (26), and includes an additional machining step of machining the blocks (13) to form locking stops (3) for the aircraft door.

Description

BRIEF DESCRIPTION THE FIGURES

(1) Other features and advantages of the invention will become apparent from the following nonlimiting description, with reference to the appended drawings in which:

(2) FIG. 1 shows the internal face of an aircraft door obtained by a method according to the invention;

(3) FIG. 2 shows the external face of the aircraft door of FIG. 1;

(4) FIG. 3 illustrates the stamping operation of the manufacturing method according to the invention;

(5) FIG. 4 is a view in section of the stamped part obtained by the stamping operation of FIG. 3;

(6) FIG. 5 is a perspective view of the stamped part of FIG. 4;

(7) FIG. 6 shows the stamped part of FIG. 3 with its machining profile;

(8) FIG. 7 is a view in section through a horizontal plane of the door of FIG. 1;

(9) FIG. 8 is an enlarged view of a section through a vertical plane of the door of FIG. 1;

(10) FIG. 9 illustrates a machining operation of the method according to the invention;

(11) FIG. 10 illustrates another machining operation of the method according to the invention;

(12) FIG. 11 shows a variant of the door of FIG. 1.

DETAILED DESCRIPTION

(13) FIGS. 1 and 2 show perspective views of an aircraft door obtained by the method according to the invention. In the present example, this aircraft door is a passenger boarding door for a commercial airliner and its dimensions are about two meters of height for one meter of width. FIG. 1 illustrates the internal face of this door, that is to say the face facing the inside of the cabin of the aircraft. FIG. 2 illustrates the external face of the door. The door illustrated is a complete mechanical structure, with no need of other structural elements, and is ready to receive various added items of equipment and mechanisms necessary for its function.

(14) The door of FIGS. 1 and 2 is a monolithic door, made in one piece, with no need of any assembly of structural elements. As a variant (see FIG. 11 and the end of the description), this monolithic structure may optionally be hybrid and accommodate additional added structural elements.

(15) The door comprises an outer skin which will be sealed with respect to the fuselage by supplementary seals and windows. In this instance, this outer skin has a thickness ranging from a few millimeters to approximately one centimeter.

(16) The mechanical strength of the outer skin 1 is provided by a frame 2 made of horizontal beams 16 and vertical beams 18 that intersect at a right angle in the present example without any added connecting parts.

(17) The door moreover comprises locking stops 3 intended to interact with a mechanism located on the door framework to lock the door in the closed position. The door also comprises other items of equipment such as supports 4 for rotationally mounting a transverse shaft intended for the mechanisms that will be borne by the door.

(18) The beams 16, 18 that constitute the frame 2 each have a core 5 formed by a planar wall of predetermined thickness (of about one millimeter to half a centimeter) that projects from the outer skin 1. In the present example, the core 5 projects substantially perpendicularly to the skin 1. The beams 16, 18 also have a flange 6 extending perpendicularly to the core 5, on the opposite side to the skin 1. The flanges 6 preferably extend substantially perpendicularly to the skin 1.

(19) The frame 2 thus has an external face connected to the outer skin 1 and an internal face connected to the flanges 6.

(20) Furthermore, in this example the door has a curvature along a horizontal axis in order to be adapted to the cylindrical shape of the fuselage of the aircraft. As a variant, the door may also have a double curvature, with one curvature along a vertical axis in addition to the curvature along a horizontal axis, in order to be adapted to a tapered fuselage.

(21) At the joins between the beams 16, 18, the cores 5 of the beams are joined together by continuity of material, the same applying for the flanges 6 which form lattices. A particularly rigid door exhibiting significant static and dynamic integrity is thus obtained.

(22) FIGS. 3 to 10 illustrate the method for manufacturing the door of FIGS. 1 and 2.

(23) A first step consists in producing a substantially flattened blank forged by any known forging means, for example by cold rolling, open-die forging, or hot rolling. This operation is performed on a stampable alloy suitable for aeronautics, such as a 7050, 7010 or 2050 aluminum alloy. The forged blank may be for example a rectangular parallelepiped corresponding to the dimensions of the door. This blank is substantially planar, that is to say that its thickness is substantially constant, possibly with slight variations in thickness to meet the local needs in terms of material on the surface of the door.

(24) In a following step, illustrated in FIG. 3, the forged blank 7 is stamped between a lower die 8 and an upper die 9 in a stamping direction 17. FIG. 3 is a basic schematic view, in a section corresponding to a section through a vertical plane of the door, with schematically depicted forms and proportions.

(25) In this example, the forged blank 7 may be formed by a shape extending in a plane (the blank 7 is a right-angled parallel in this case). As a variant, the blank 7, while still having a substantially constant thickness, may be pre-arched to impart the corresponding curvature to the final curvature of the door.

(26) The lower die 8 has a work surface which is smooth and which corresponds to the external surface of the outer skin 1. The upper die 9 is intended to form a cellular structure in the blank 7. To that end, the upper die 9 defines the negative of the cells by virtue of the punches 29, the form of which corresponds to the empty spaces between the beams 16, 18 of the frame 2 on the finished door after the machining operations. Between the punches 29, the upper die 9 has recesses 10 intended to form ribs corresponding to the beams 16, 18 of the frame 2.

(27) FIG. 3 schematically shows that the width of the recesses 10 tends to increase from the middle to the edges of the door in the direction 25 (which corresponds to the vertical direction of the door).

(28) FIG. 4 illustrates the result of the stamping operation corresponding to the door of FIGS. 1 and 2. In practice, the result of FIG. 4 will be able to be obtained with one or more stamping operations, since the forms required may necessitate multiple stamping operations with a gradual increase in the fineness of the passes.

(29) The stamping is carried out by moving the dies close to the press leaving a clearance between the dies, this clearance corresponding to the desired thickness for the wall corresponding to the outer skin 1. With reference to FIG. 4, the stamped part 26 obtained is a cellular structure having an open face (the face corresponding to the internal face of the door) and a closed face (the face corresponding to the external face of the door), which is closed by a wall which has a thickness corresponding to the clearance and which corresponds to the outer skin 1.

(30) In FIG. 4, the stamped part 26 has eight ribs 11 of material, corresponding to eight horizontal beams 16 of the door.

(31) The stamped part is also shown in perspective in FIG. 5. The stamped part 26 has the final arching corresponding to the curvature of the door and comprises the ribs 11 corresponding to the horizontal beams 16 and ribs 12 corresponding to the vertical beams 18.

(32) The stamped part of FIG. 5 moreover has blocks 13 of material located at the positions of stops 3 of the door, and blocks 14 of material located at the positions of supports 4, and possibly other additional blocks of material for any other items of equipment provided on the door.

(33) All of the ribs 11, 12 and blocks 13, 14 of material have a taper angle relative to the stamping operation, for example 7? on either side of the stamping direction. For the vertical ribs 12, which extend in a plane parallel to the stamping direction 17, the curvature of the door does not interfere with the stamping and the taper angle will simply be applied on either side of the rib 12.

(34) With respect to the horizontal ribs 11, the stamping interferes with the curvature of the door. FIG. 6 illustrates the stamped part 26 with a superimposed illustration of the profile 15 of the finished door. This profile 15 thus has the outer skin 1 and the eight horizontal beams 16 of the door. This figure takes account of the material to be removed on each rib 11 to form the beams 16.

(35) In FIG. 6, each form of a rib 11 (and therefore the form of each recess 10 of the upper die 9) is provided on the basis of the orientation of the desired beams 16. Each form of a rib 11 corresponds to a form of a recess 10 of the upper die 9.

(36) In relation to the stamping direction 17, the beams closest to the median horizontal axis of the door are virtually parallel to the stamping direction 17, such that the corresponding rib 11 substantially symmetrically surrounds the future beam 16 and the rib 11 is therefore substantially symmetrical.

(37) With increasing distance away toward the top and bottom ends of the door, the ribs 11 are thicker since the inclination of the future beam 16 causes asymmetry:

(38) on one flank, the rib 11 is closest to the future beam 16, substantially parallel to the core 5;

(39) on the other flank, the rib 11 is further away from the future beam 16, with an angle close to twice the taper angle, measured from the future beam 16.

(40) Thus, the ribs 11 located closest to the center (in the direction of curvature 25) have, with respect to the ribs 11 located further away from the center, that is to say closer to the top and bottom ends of the door:

(41) a smaller thickness;

(42) side walls that form a smaller angle between one another.

(43) The stamped part 26 is then machined so that the beams 16, 18 are produced by removing material on the ribs 11 and 12.

(44) FIG. 7 is a view in section of the door of FIGS. 1 and 2 in a median horizontal plane. This FIG. 7 illustrates the various machining zones necessary to form the beams 16, 18. These machining zones are:

(45) zones 19 corresponding to the flank of the core 5 of the beam;

(46) zones 20 corresponding to underneath the flanges 6;

(47) zones 21 corresponding to the join between the cores 5 of the beams 16, 18;

(48) zones 22 corresponding to the join between the frame 2 and the outer skin 1.

(49) These zones are the same for all of the beams 16, 18 of the door.

(50) FIG. 8 is an enlarged view showing the machining zones, this time in vertical section through a portion of the door. In a particularly advantageous embodiment, the machining zone 20 extends over the bottom of the flange 6 and over a portion of the flanks of the core 5. The operation of machining this zone is carried out in accordance with FIG. 9 with a side-and-face milling cutter 23 with a diameter which is adapted to the width of the corresponding flange 6. The side-and-face milling cutter 23 thus machines the bottom of the flange 6 and an upper portion of the core 5 in one pass, with favorable accessibility even though this operation is carried out in a nook.

(51) This machining operation thus makes it possible, in a single pass, to define a reinforcement delimited on one side by the core 5 and on the other side by the flange 6.

(52) Another machining operation targeting the zone 19 is then concerned with finishing the machining of the flank of the core 5. This machining operation is carried out in accordance with FIG. 10 by a conical milling cutter 30, which likewise promotes accessibility in this context. The conical milling cutter 30 machines the portion of the core 5 located below a flange 6, the axis of the milling cutter being oblique with respect to the plane of the core 5.

(53) The machining operations of FIGS. 9 and 10 make it possible, in two simple types of machining operations, to produce the forms of the frame 2 that are the most inaccessible and the most essential for the formation of the door.

(54) The other contours of the flange 6, the stops 3, and supports 4, can furthermore be machined conventionally by milling cutters, drill bits, and any other conventional tool.

(55) The machining zone 22 can preferably be produced by a spherical milling cutter passing over the join between the core 5 and the outer skin 1.

(56) The zone 21 is preferably machined by a hemispherical milling cutter that operates vertically and has a spindle length which is adapted to the problem of accessibility.

(57) Moreover, the surfaces forming the internal and external faces of the outer skin 1 may be obtained directly by the stamping, or also machined, depending on the surface finish and the desired dimensional tolerances.

(58) FIG. 11 shows a variant of the door of FIGS. 1 and 2. In this variant, most of the frame 2 is made by virtue of the method according to the invention. However, additional beams 24 are fitted on the frame by known fixing means. Such a door thus combines portions obtained according to the invention and portions fitted conventionally.

(59) The door is thus obtained solely using operations making it possible to benefit from the favorable mechanical properties afforded by the forging from the raw material through to the finished product. This is because the stamped part 26 is intended to undergo these machining operations which do not interfere with the orientation of the fibers of the material. The stamping operation can moreover be adjusted by influencing parameters such as the stamping temperature, the thickness and the forms of the blank 7, or any other forging technique parameter, to vary the mechanical properties of the whole of the door, such as the yield strength or the tensile strength.

(60) Variant embodiments of the method for manufacturing the aircraft door can be implemented without departing from the scope of the invention. As a variant with respect to FIGS. 9 and 10, the flange 6 may be centered on the core 5 rather than being cantilevered.