Method for assembling at least two parts by transparent welding, method for assembling a primary structure of an aircraft pylon by transparent welding, primary structure of an aircraft pylon thus obtained and aircraft comprising said primary structure

A method for assembling at least two parts includes using transparent welding using an energy input beam which travels a trajectory in a closed loop. The trajectory of the energy input beam and/or at least one parameter of the energy input beam is configured so that the weld bead has mechanical and/or geometrical characteristics that are substantially constant over all its length. A method for assembling a primary structure of an aircraft pylon which uses this assembly method to link the panels of the primary structure to one another, a primary structure of an aircraft pylon thus obtained, as well as an aircraft comprising at least one such primary structure is also described.

FIELD OF THE INVENTION

The present invention relates to a method for assembling at least two parts by transparent welding, to a method for assembling a primary structure of an aircraft pylon by transparent welding, to a primary structure of an aircraft pylon thus obtained and to an aircraft comprising said primary structure.

BACKGROUND OF THE INVENTION

According to a configuration that can be seen inFIG. 1, an aircraft10comprises several propulsions assemblies12which are positioned under the air foil14of the aircraft10. A propulsion assembly12comprises a nacelle16, an engine positioned inside the nacelle16and a pylon18which ensures the link between the engine and the air foil14. The pylon18comprises a primary structure20which ensures, among other things, the transmission of the forces between the engine and the air foil14.

According to a configuration that can be seen inFIGS. 2 to 4, the primary structure20comprises a top spar22, a bottom spar24, transverse frames26which link the top and bottom spars22,24and which are disposed in transverse planes, as well as two side panels28,30disposed on either side of the transverse frames26.

According to a first configuration, each side panel28,30comprises a body32, a top flange34which forms an angle with the body32as well as a bottom flange36which forms an angle with the body32, the body32, the top flange34and the bottom flange36being produced in a single piece.

According to a mode of assembly that can be seen inFIG. 4, each top or bottom flange34,36is linked to a top or bottom spar22,24by a plurality of through link elements38, such as, for example, screws or rivets.

According to a second configuration, each top or bottom flange34,36is replaced by an angle iron linking the top and bottom spars22,24and the side panels28,30pairwise. Each angle iron is linked to a top or bottom spar22,24and to a side panel28,30by a plurality of through link elements38, such as, for example, screws or rivets.

The mode of assembly by screwing or riveting requires the presence of top and bottom flanges34,36or of angle irons, which tends to increase the weight of the primary structure20.

BRIEF SUMMARY OF THE INVENTION

Aspects of the present invention may wholly or partly remedy the drawbacks of the prior art.

A subject of the invention is a method for assembling at least two parts by transparent welding using an energy input beam which travels a trajectory so as to generate a weld bead, disposed straddling the two parts and linking them.

According to an aspect of the invention, the trajectory follows a closed loop, the trajectory of the energy input beam and/or at least one parameter of the energy input beam being configured so that the weld bead has mechanical and/or geometrical characteristics that are substantially constant over all its length.

This solution makes it possible to avoid overdimensioning the parts linked by the weld bead and machining them after the welding step in order to eliminate the irregular ends of the weld bead, which correspond to the starting and stopping portions of the energy input beam, and to retain only the sections of the parts having a regular weld bead.

When this assembly technique is applied to a primary structure of an aircraft pylon, it makes it possible to reduce its weight, top and bottom flanges or angle irons no longer being necessary to link the panels of the primary structure to one another.

According to another feature, the trajectory comprises at least one overlap portion, travelled at least twice by the energy input beam, the overlap portion having a length greater than or equal to the sum of the lengths of the starting and stopping portions of the energy input beam.

According to another feature, the trajectory follows an oblong closed loop, the weld bead having two rectilinear sections that are approximately parallel with little spacing between them and two curved sections linking the rectilinear sections.

According to another feature, each curved section having a start and an end, the energy input beam has an intensity or a power which decreases from the start to the end of each curved section of the trajectory.

According to another feature, the energy input beam has, in each rectilinear section, an intensity or a power having a maximum value, the maximum values in the different rectilinear sections decreasing from one rectilinear section to the other along the trajectory of the energy input beam.

According to a first operating procedure, each rectilinear section having a start and an end, the energy input beam has an intensity or a power which increases from the start to the end of each rectilinear section except for the stopping portion of the energy input beam.

According to a second operating procedure, the energy input beam has an intensity or a power which is substantially constant over each of the rectilinear sections, except for the starting and stopping portions of the energy input beam.

Also a subject of the invention is a method for assembling a primary structure of an aircraft pylon comprising a top panel, a bottom panel, a right side panel and a left side panel, characterized in that at least one top or bottom panel is linked to at least one right or left side panel by using the assembly method according to one of the preceding features.

According to one configuration, each top and bottom panel is linked to each right and left side panel by using the assembly method according to one of the preceding features.

Also subjects of the invention are a primary structure of an aircraft pylon obtained from the assembly method according to the invention as well as an aircraft comprising at least one primary structure of an aircraft pylon thus obtained.

DETAILED DESCRIPTION

InFIGS. 5 and 6, a primary structure40of an aircraft pylon is represented which comprises:a top panel42, also called top spar, which has a right longitudinal edge42.1and a left longitudinal edge42.2,a bottom panel44, also called bottom spar, which has right longitudinal edge44.1and a left longitudinal edge44.2,a right side panel46which has a top longitudinal edge46.1linked to the right longitudinal edge42.1of the top panel42and a bottom longitudinal edge46.2linked to the right longitudinal edge44.1of the bottom panel44, anda left side panel48which has a top longitudinal edge48.1linked to the left longitudinal edge42.2of the top panel42and a bottom longitudinal edge48.2linked to the left longitudinal edge44.2of the bottom panel44.

For the rest of the description, a longitudinal direction is parallel to the direction of the engine axis when the pylon is mounted. The terms “front” or “Av” and “rear” or “Ar” refer to a direction of advance of the aircraft10following the thrust exerted by the propulsion assemblies12, this direction being represented by the arrow F inFIG. 1.

The term “right” and “left” refer to the right and left sides of an operator placed in front of the engine and looking in the longitudinal direction towards the rear of the engine. The terms “top” and “bottom” refer to the vertical direction when the pylon is mounted and the aircraft is on the ground.

The primary structure40can comprise other elements which are not described and represented, for the purpose of simplification.

According to one configuration, at least one of the panels42,44,46,48, such as the top panel42for example, is produced in two, front and rear parts42Av and42Ar which are each linked to the right and left side panels46,48.

Each top and bottom panel42,44has a face F42, F44oriented towards the right and left side panels46,48. Each right or left side panel46,48has, on each of its top and bottom longitudinal edges46.1,46.2,48.1,48.2, a rim configured to be pressed against one of the faces F42, F44of the top and bottom panels42,44.

The primary structure40comprises at least one transparent weld50linking at least one of the top and bottom panels42,44as well as at least one of the right and left side panels46,48. According to one configuration, the primary structure40comprises several transparent welds50linking each top or bottom panel42,44and each right or left side panel46,48.

Each right or left side panel46,48has, on each of its top and bottom longitudinal edges46.1,46.2,48.1,48.2, an overthickness52to accommodate the transparent weld50.

InFIGS. 7A and 7B, an assembly is represented comprising a first panel54which can be one of the top, bottom, right side or left side panels42,44,46,48, a second panel56which can be one of the top, bottom, right side or left side panels42,44,46,48and at least one weld50linking the first and second panels54and56.

The first panel54comprises a longitudinal edge54.1which can be one of the right, left, top or bottom longitudinal edges42.1,42.2,44.1,44.2,46.1,46.2,48.1,48.2of the top, bottom, right side or left side panels42,44,46,48of a primary structure40of an aircraft pylon. The first panel54has a first face F1, oriented towards the second panel56, and a second face F2opposite the first face F1.

The second panel56comprises a longitudinal edge56.1which can be one of the right, left, top or bottom longitudinal edges42.1,42.2,44.1,44.2,46.1,46.2,48.1,48.2of the top, bottom, right side or left side panels42,44,46,48of a primary structure40of an aircraft pylon, said longitudinal edge56.1having a rim58configured to bear against the first panel54. In addition, the first face F1of the first panel54comprises a contact surface60against which the rim58of the second panel56is pressed when the first and second panels54,56are assembled.

According to an aspect of the invention, the weld50is a transparent weld produced from the second face F2of the first panel54. A transparent weld is more particularly suitable for assembling two panels of a box-formed structure, like the primary structure of an aircraft pylon, the interior of which is difficult to access.

This weld50is produced using an energy input beam62, represented schematically in the form of an arrow inFIG. 8, configured to be displaced along a trajectory64so as to obtain a weld bead66disposed straddling the first and second panels54,56. As illustrated inFIGS. 7B and 8, the weld bead66passes through the first panel54and extends from the second face F2to the contact face60. The weld bead66extends from the rim58to a certain depth Prof in the second panel56.

According to one embodiment, the energy input beam62is an electron beam. Obviously, the invention is not limited to this embodiment. Thus, the energy input beam could be a laser beam or the like.

When the energy input beam62impacts the second face F2of the first panel54, it generates a local evaporation of the material and the formation of a cavity in which the weld bead66is formed.

The weld bead66can be obtained without metal filling or with a metal filling.

According to an aspect of the invention, the energy input beam62describes a trajectory64in the form of a closed loop, without ends, as illustrated inFIGS. 9A, 10A and 11A, so as to obtain a weld bead66in the form of a closed loop.

The provision of an endless weld bead66makes it possible to obtain a weld bead that is regular over all its length. Otherwise the start and the end of the weld bead are not regular so it is necessary to overdimension the first and second panels54,56so that, after the welding step, the first and second panels54,56are machined so as to eliminate the ends of the weld bead and to retain only the parts of the first and second panels54,56having a regular weld bead. Thus, the provision of a weld bead in the form of a closed loop makes it possible to avoid the machining step subsequent to the welding step, which tends to reduce the material quantities and the costs.

According to one configuration, each weld50comprises a weld bead66which has two rectilinear sections66.1,66.2, approximately parallel and with little spacing between them, and two curved sections66.3,66.4, in the form of a semicircle, linking the rectilinear sections66.1,66.2so as to obtain an oblong closed loop.

With little spacing between them it is understood to mean that the distance separating the two rectilinear sections66.1,66.2is of the same order of magnitude as the width of the weld bead66. Thus, the distance separating the two rectilinear sections66.1,66.2lies between 1 and 5 times the width of the weld bead66.

As an indication, the weld bead66has a width lying between 1 and 7 mm, preferably between 2 and 3 nm.

According to a feature of the invention, the trajectory64of the energy input beam62and/or at least one of the parameters of the energy input beam62out of the power, the intensity, the rate of advance, the focus, the vibration of the energy input beam, are configured so that the weld bead66has geometrical and/or mechanical characteristics that are substantially constant over all its length.

According to a first embodiment illustrated byFIGS. 9A, 9B, the trajectory64of the energy input beam62begins at a point of departure for P1and stops at a final point Pf, the final point Pf being offset relative to the point of departure P1so that the energy input beam62travels an overlap portion68of the weld bead66twice. The overlap portion68has a length L68such that the weld bead66has geometrical and/or mechanical characteristics that are substantially constant over all its length. If the energy input beam62generates a weld bead66with defects over a starting portion70which extends from the point of departure P1, over a length L70, and over a stopping portion72which extends to the final point Pf, over a length L72, the distance L68of the overlap portion68is greater than or equal to the sum of the lengths L70and L72of the starting and stopping portions70and72, as illustrated inFIG. 9A.

According to a configuration that can be seen inFIG. 9B, the overlap portion68is only positioned on one of the rectilinear sections66.1,66.2and does not extend over one of the curved sections66.3,66.4.

As illustrated inFIG. 9B, the energy input beam62has an intensity or a power:which increases from a zero value at the point of departure P1to a nominal value N at the end of the starting portion70represented by the point P2,which is constant and equal to the nominal value N from the point P2to the point Pf-1representing the start of the stopping portion72, andwhich decreases from the nominal value N to the zero value over the stopping portion72beginning at the point Pf-1and finishing at the point Pf.

According to another feature that can be seen inFIGS. 10B and 11B, the energy input beam62has an intensity or a power which decreases from the start to the end of each curved section66.3,66.4of the trajectory64.

According to a configuration that can be seen inFIGS. 10A and 11A, the starting portion70going from the point of departure P1to the point P2extends only over one of the rectilinear sections66.1,66.2of the weld bead66.

The starting70and stopping72portions do not overlap. According to an embodiment that can be seen inFIG. 10B, the stopping portion72extends over one of the curved sections66.3and over the adjacent rectilinear section66.2. According to another embodiment that can be seen inFIG. 11B, the stopping portion72extends over a rectilinear section66.2different from the rectilinear section66.1on which the starting portion70is positioned.

So as to obtain a gradual and slow increase in the intensity or the power of the energy input beam62, each of the starting and stopping portions70,72extends over almost all the length of the rectilinear sections66.1,66.2, as illustrated inFIG. 11B.

According to an embodiment that can be seen inFIG. 10B, the energy input beam62has an intensity or a power which is substantially constant over each of the rectilinear sections66.1,66.2, except for the starting and stopping portions70,72.

According to the embodiment that can be seen inFIG. 10B, the energy input beam62has an intensity or a power:which increases from a zero value at the point of departure P1to a first value N1at the end of the starting portion70represented by the point P2, the points P1and P2being situated on a first rectilinear section66.1,which is constant and equal to the first value N1from the point P2to a point P3corresponding approximately to the end of the first rectilinear section66.1and to the start of the first curved section66.3,which decreases from the first value N1to a second value N2from the point P3to a point P4corresponding approximately to the end of the first curved section66.3and to the start of the second rectilinear section66.2,which is constant and equal to the second value N2from the point P4to a point P5corresponding approximately to the end of the second rectilinear section66.2and to the start of the second curved section66.4,which decreases from the second value N2to a third value N3from the point P5to a point P6corresponding approximately to the end of the second curved section66.4and to the start of the first rectilinear section66.1,which is constant and equal to the third value N3from the point P6to a point P7situated on the first rectilinear section66.1, offset towards the centre of the first rectilinear section66.1relative to the point P3,which decreases from the third value N3to a zero value over the stopping portion72beginning at the point P7and finishing at the point Pf positioned approximately at the centre of the second rectilinear portion66.2.

According to an embodiment that can be seen inFIG. 11B, the energy input beam62has an intensity or a power which increases from the start to the end of each rectilinear section66.1,66.2, except for the stopping portion72.

According to the embodiment that can be seen inFIG. 11B, the energy input beam62has an intensity or a power:which increases, over almost all the length of the first rectilinear section66.1, from a zero value at the point of departure P1to a first value N1at the end of the starting portion70represented by the point P2, the point P2corresponding approximately to the end of the first rectilinear section66.1and to the start of the first curved section66.3,which decreases, over the first curved section66.3, from the first value N1to a second value N2, from the point P2to a point P3corresponding approximately to the end of the first curved section66.3and to the start of the second rectilinear section66.2,which increases, over the second rectilinear section66.2, from the value N2to a third value N3, lower than the first value N1, from the point P3to a point P4corresponding approximately to the end of the second rectilinear section66.2and to the start of the second curved section66.4,which decreases, over the second curved section66.4, from the third value N3to approximately the second value N2from the point P4to a point P5corresponding approximately to the point P1positioned at the end of the second curved section66.4and to the start of the first rectilinear section66.1,which increases, over the first rectilinear section66.1, from the value N2to a fourth value N4, lower than the third value N3, from the point P5to a point P6corresponding approximately to the point P2,which decreases from the fourth value N4to a zero value, from the point P6to the final point Pf corresponding approximately to the point P4passing through the point P7corresponding approximately to the point P3.

Whatever the embodiment, the trajectory64comprises at least one overlap portion68, travelled at least twice by the energy input beam62, the overlap portion68having a length greater than or equal to the sum of the lengths of the starting and stopping portions70,72of the energy input beam62.

Whatever the embodiment illustrated byFIGS. 10A, 10B, 11A and 11B, the energy input beam62has, in each rectilinear section66.1,66.3, an intensity or a power having a maximum value. These maximum values in the different rectilinear sections66.1,66.2(N1, N2, N3for the embodiment that can be seen inFIGS. 10A and 10B, and N1, N3, N4for the embodiment that can be seen inFIGS. 11A and 11B) decrease from one rectilinear section to the other along the trajectory64of the energy input beam62. Thus, the power or the intensity of the energy input beam62is adapted so as to take account of the heat input already provided to the panels54,56in the overlapping zones of the trajectory64.

Obviously, the welding assembly method according to the invention is not limited to the assembly of the panels of a primary structure of an aircraft pylon. It can be applied to the assembly of at least two parts, the weld being produced in a zone of overlay of the parts to be assembled.

When it is applied to the assembly of the panels of a primary structure40of an aircraft pylon, at least one weld50, a single weld50according to an embodiment that can be seen inFIG. 5, is produced in accordance with the invention to link each top or bottom panel42,44to each right or left side panel46,48. This mode of assembly makes it possible to reduce the weight of the primary structure by eliminating the flanges or the angle irons ensuring the joining of the panels to one another.