EP1301292B1 - Method for making a structural element having a generally tubular metal wall and structural element - Google Patents

Abstract

At least one plane blank ( 20 ) is cut out from a sheet of metal material, the blank comprising a main part having the developed shape of the wall of the structural element and at least one additional overlap and fixing tab ( 26, 27, 28 ), the cutout blank ( 20 ) is folded along a plurality of lines ( 23 ) so as to form the wall of the structural element comprising a plurality of annular segments that are not in axial alignment out of folded portions ( 22, 24, 24', 25 ) of the main part of the cutout blank ( 20 ), and welding is used to fix at least one additional overlap and fixing tab ( 26, 27, 28 ) on at least one of a folded portion ( 22, 24, 24', 25 ) and a second overlap tab. During welding, at least one overlap tab ( 26, 27, 28 ) and the folded wall portion ( 22, 24, 24', 25 ) or the second overlap tab are maintained bearing resiliently one against the other in a superposed disposition, welding is perfectly performed by means of a laser beam, in transparency, the structural element of the invention has numerous applications in a very wide variety of industries.

Description

The invention relates to a method for manufacturing a structural element. having a metal wall of generally tubular shape comprising at at least two sections that are not axially aligned and a structural element tubular metal wall which can be produced in forms and for very diverse applications. A structural element according to the preamble of claim 5 is known e.g. from document US-A-5,018,263.

In many industry sectors there is a need to have structural elements having a generally tubular shape comprising successive sections not axially aligned and a cross section more or less complex, in particular polygonal in shape.

Such structural elements may be curved or have successive straight sections in angular arrangements, for example making right angles between them, in the case of structural elements as square or rectangular frames.

In some applications, it is necessary to have frames with high rigidity and the smallest possible mass, these two conditions are generally difficult to reconcile, in the case of executives produced by assembling tubular profiles with polygonal section. In indeed, it is necessary, to carry out the assembly and fixing by welding sides of the frame at its corners, use tubes with walls of sufficient thickness. Generally it is difficult to achieve frames by assembling tubes, for example of square section, of which the wall thickness is less than 1 mm.

In certain applications, for example in the case of manufacturing of metal door frames one can look for in addition to a good rigidity and the smallest possible mass; aesthetic qualities of door frame, for example when this door is used in a building in which we are looking for a certain style of decoration. In that case, frames may be required with different sides sections of various shapes. It is therefore necessary to have tubes having sections of different shapes and possibly shapes completely unusual. In this case, the construction of the door frames is very expensive.

In some industries, for example the automotive industry, industry aeronautics or shipbuilding, we use structural elements, or frames, lightened, with tubular metal walls, of complex shape, which can be curved or even closed in on themselves to constitute an annular part. The construction of such elements structure whose tubular construction allows to obtain a gain of weight should be extremely rigid and extremely strong.

To achieve such complex structures, it is generally necessary to assemble a large number of parts previously formed, by a forming process and / or by cutting. The assembly of parts to achieve a complex shape structure with very good accuracy of shape and dimension is an operation expensive and the various assembly welds performed must be carefully checked.

In addition, in the case of metal material which is difficult to weld, such as aluminum and its alloys, the realization of complex structures is still more difficult and expensive and may require the use of assembly methods delicate implementation to avoid the presence of welds.

In the case of the production of structural elements from products flat such as metal sheets, we generally carry out the assembly of plates cut by welding along their edges, which requires generally the use of jigs and supports plates in their assembly position. The realization of such structures is therefore complex and requires the use of expensive tools. In addition, in some cases it is not even possible to use a template placed in a hollow part of the tubular structure, because the shape of the structure does not allow to remove the template after assembly and welding of the structure.

The object of the invention is therefore to propose a manufacturing process of a structural element having a metal wall of generally tubular shape comprising at least two axially non-aligned sections which is of a simple implementation and of a limited cost and which makes it possible to carry out structures of complex shape, rigid and light, made of metallic materials any.

• on découpe, dans une feuille en matériau métallique, au moins une plaque plane comportant une partie principale ayant la forme développée des tronçons de la paroi de l'élément de structure et, pour chacun des tronçons, au moins une partie complémentaire de recouvrement et de fixation, ainsi qu'au moins une partie complémentaire de fixation des tronçons entre eux;
• on plie la plaque découpée selon une pluralité de lignes, de façon à former la paroi de l'élément de structure à partir de portions pliées de la partie principale de la plaque découpée ; et
• on fixe par soudage l'au moins une partie complémentaire de recouvrement et de fixation de chacun des tronçons et l'au moins une partie complémentaire de fixation des tronçons entre eux sur l'une au moins d'une portion pliée du tronçon de la paroi de l'élément de structure et d'une seconde partie de recouvrement, l'au moins une partie complémentaire de recouvrement et de fixation de chaque tronçon et l'au moins une partie de fixation des tronçons entre eux et la portion pliée de la paroi ou la seconde partie de recouvrement étant maintenues en appui élastique l'une sur l'autre.

For this purpose :

• at least one flat plate comprising a main part having the developed shape of the sections of the wall of the structural element and, for each of the sections, at least one complementary covering part and fixing, as well as at least one complementary part for fixing the sections together;
• the cut plate is folded along a plurality of lines, so as to form the wall of the structural element from folded portions of the main part of the cut plate; and
• at least one complementary covering and fixing part of each of the sections is fixed by welding and the at least one complementary part for fixing the sections to each other on at least one folded portion of the section of the wall of the structural element and of a second covering part, the at least one complementary covering and fixing part of each section and the at least one fixing part of the sections between them and the folded portion of the wall or the second covering part being held in elastic support one on the other.

In order to clearly understand the invention, we will describe, by way of examples, several modes of implementing the method according to the invention and structural elements with completely new characteristics which can be obtained by this process.

Figure 1 is a plan view of a portion of a cut plate which can be used for the production of a post with a polygonal section of a structure according to the invention in the form of a frame.

Figure 2 is a schematic cross-sectional view of the upright polygonal section made by folding the plate shown on the Figure 1, in a phase prior to welding of a connection part and fixing.

Figure 3 is a perspective view of a curved surface door carried out by the method of the invention.

Figure 4 is a plan view of a cut sheet metal plate for the realization of the door frame shown in Figure 3.

Figure 5 is an enlarged view of part of the plate shown in figure 4.

Figures 6 and 7 are partial perspective views of the frame door produced by folding and welding the metal plate shown on Figure 4.

Figure 8 is a perspective view. of a structural element of annular shape which can be produced by the method of the invention.

Figure 9 is a plan view of part of a metal plate for the production of the structural element shown in FIG. 8.

Figure 10 is a perspective view of part of one of the faces of the plate shown in Figure 9.

Figures 11 and 12 are perspective views of part of the structural element shown in FIG. 8, during a phase of folding and an assembly phase of the manufacturing process.

In FIG. 1, part of a metal plate has been represented. generally designated by the reference 1, this part of the plate 1 being intended to constitute part of a section constituting the side of a polygonal frame which is a structural element according to the invention.

The metal plate 1 as a whole has extensions of the part shown in Figure 1, in the longitudinal direction 2 as well as other parts intended to constitute by folding on other sides of the frame possibly having cross sections of shape polygonal different from the shape of the section of the section represented on the figure 2.

FIGS. 1 and 2 have the simple aim of explaining the principle of the method of manufacture according to the invention, without describing the complete manufacture of a structural element.

The section of the metal plate 1 shown in Figure 1 shows the shape of a rectangular strip extending in the longitudinal direction 2 and having a sufficient width to make the section of a side of rectangular frame shown in Figure 2.

A first frame manufacturing operation consists of cutting the plate 1 in a sheet of metal material of nature and thickness desired.

Generally, as will be explained later, the process according to the invention makes it possible to produce structures of generally tubular shape whose wall thickness may be small and comprised, for example between 50 µm and 1 mm, such thin-walled structural elements cannot be manufactured by known methods such as angular assembly of tubes.

We realize on the part of the metal plate 1 intended to constitute the amount 3 of the frame whose section is shown in Figure 2 the layout fold lines which are all parallel to the longitudinal direction 2 and which delimit five portions of the metal plate designated by the marks 4, 5, 6, 7 and 8 and which have the shape of rectangular bands. The plate part 1 shown in Figure 1 on which have been traced fold lines separating the different portions of the plate constitutes the developed form of the section of the frame side 3 shown in the figure 2. The folding is carried out as shown in FIG. 2 so that the portions of plates 5 and 6 folded 90 ° upwards relative to the portion of plate 4 constitute two lateral sides of the frame side and the portions of plates 7 and 8 folded inwards from the side section 3 of the frame two flaps intended to be superimposed in positions 7 'and 8' to constitute the upper wall on the side 3 of the frame.

As shown in Figure 2, the inward folding of the portions 7 and 8 of the metal plate is made so that the flap 8 is located below the flap 7 and that the flaps 7 and 8 have an angle residual opening relative to their closed position 7 'and 8'.

The overlapping assembly and fixing of the portions 7 and 8 is produced by exerting a force 9 on the flap 7, in the vertical direction direction of the flap 8 and from the outside towards the inside of the section on the side of frame 3.

Under the effect of force 9, the flap 7 pivots around its folding axis and comes to press on the flap 8 which pivots itself around its axis of folding. The movement of the flaps 7 and 8 is determined so as to constitute the upper wall on side 3 of the frame by overlapping the flaps in the coplanar positions 7 'and 8'.

The flap 7 'is held in place by the pushing element exerting force 9 and element 8 in its position 8 'exerts, by elastic return, a pressing force against the underside of the flap 7 ', so that the flaps 7 and 8 in their position 7 'and 8' are perfectly flat and in contact elastic against each other.

The part of the upper flap 7 between the free edge of the flap 7 and the line 7a along which the free edge of the flap 8 is applied in the plated position constitutes a covering and fixing portion of the metal plate ensuring the closure of the tubular structure. For fix the flaps 7, 8 to each other, we can use an installation welding such as a laser welding head 10 with which several points or welding lines can be made in the direction longitudinal 2, through the superimposed parts of the flaps 7 and 8, that is to say through the covering part of the flap 7 and of the wall part of the flap 8 covered by the covering part. Such welding performed in the thickness of the superimposed parts of the flaps 7 and 8 using a beam laser is called transparent welding.

It is also possible to carry out welding between the flaps 7 and 8 along the free edge of the flap 7 superimposed on the flap 8 in their position assembly 7 ', 8' but such welding along the edge of the flap 7 requires more precise control of the direction and positioning of the beam welding than transparent welding along points or zones linearly placed in any overlapping parts flaps 7 and 8 in their assembly position.

As soon as the welding of the covering part on a part of wall of the structure has been made, the structure is stiffened because any sliding of the covering part on the wall has become impossible.

It therefore appears on the very simple example shown in Figures 1 and 2 that a structural section can be made such as a side of a frame having a polygonal section of any shape in a simple manner, by folding, elastic bearing of a covering part on a wall part and welding, for example using a laser, the covering part on the part of the wall covered.

Of course, it is possible to use a welding means other than a laser torch for making welding points or lines, this device must however be able to carry out welding from outside the structure, without contact with the walls of the structure.

In the case of welding of walls of a frame-like structure with a thickness of less than 1 mm, and for example of the order of 0.7 mm, it quality laser welding is possible, using a laser YAG, even in the case of an abundance of sheet thickness of a value up to 0.2 mm. We call it an abundance of stacked sheets, the excess thickness of the stack compared to the sum of the thicknesses of overlapping sheets. The expansion corresponds to the thickness average of the air layer between the overlapping sheets, presents made of an imperfect flatness of the sheets.

The process according to the invention can therefore be implemented in the case of industrial sheets whose flatness is such that there is a certain proliferation when stacking sheet metal parts.

We will now describe, by way of examples, two embodiments of a generally tubular structure by folding a metal plate cut from a sheet such as a sheet or strip, these two embodiments being only illustrative of the process of the invention which has been very generally described with reference to FIGS. 1 and 2.

Of course, the method according to the invention can be applied to the production of numerous structural elements of generally tubular shape with very diverse characteristics and uses.

A first device incorporating a structural element produced according to the invention has been shown in FIG. 3.

In Figure 3, there is shown a metal door designated generally by the reference 11 which includes a generally shaped frame rectangular 12 whose sides have a tubular structure and which has was carried out by the method according to the invention.

The frame has two horizontal sides, respectively, upper 12a and lower 12b and two vertical lateral sides, respectively, 12c and 12d.

The upper and lower sides 12a and 12b are produced under a tubular in shape and have a triangular cross-section and the lateral sides 12c and 12d, also produced in tubular form, have a rectangular cross section. The end edge upper and lower sides 12a and 12b connected together according to the tip part of the triangle of the cross section constitutes a surface curve on which can be fixed, at each of its upper ends and lower, a door facing 13 which thus has a curved shape. The facing 13 may be constituted by a simple sheet metal added and fixed by welding along the curved edges of the two sides 12a and 12b of the frame door.

As will be explained below with reference to FIGS. 4, 5, 6 and 7, the frame 12 of the door can be produced by the method according to the invention, by simple cutting and folding of a metal plate to form the walls of the frame and the covering parts of the walls allowing the assembly and fixing the folded parts of the frame and fixing the sides of the frame between them, to produce the closed structure shown in FIG. 3.

The facing sheet 13 is then added and fixed by welding on the edges of the frame and in particular on the upper and lower curved edges. A curved metal door is thus obtained, the frame of which has section sides of different shapes, which improves aesthetics of the door and give it an original appearance.

Such a door can be used to close cabinets or technical premises or to ensure the closure of premises in residential use.

A frame as shown in Figure 3, the manufacture of which will be described with reference to Figures 4 to 7 can be achieved not only so to constitute a door frame but also a usable frame, for example, in a screen printing machine. In this case, the frame which is made in a light and rigid manner can easily ensure the fixing and tensioning of a serigraphy canvas fixed along the edges of the frame.

We can also ensure the tension of the canvas on the frame by exerting a force between the upper 12a and lower 12b sides during assembly of the canvas and releasing the force on the end sides after fixing some cobweb.

In Figure 4, there is shown a metal plate designated generally by the reference 14 which has been cut from a metal sheet such as a sheet or strip, in the form of an elongated strip having cut-outs between each of the parts of the strip intended to form one side of the frame.

The walls of the end sides 12a and 12b of the frame are made at starting from the portions 15a and 15b of the plate 14 in the form of an elongated strip and the lateral sides with rectangular section 12c and 12d are made from portions 15c and 15d of the plate 14.

Also shown in FIG. 4, by dotted lines, the fold lines of the strip portions 15a, 15b, 15c and 15d to make by folding the corresponding side of the generally tubular section frame, respectively, triangular and rectangular.

Each of the plate portions 15a, 15b, 15c and 15d has a main part constituting a flat developed on the side of the frame and covering and fixing parts intended to ensure closure and fixing the sides of the frame as well as fixing the sides of the frame between them.

The sections 15a and 15b have three flat parts separated by parallel fold lines between them intended to constitute the three sides of the frame with triangular cross-section as well as two longitudinal edges intended to come in overlap to ensure assembly and fixing end sides of the frame. The two longitudinal edges of the parts 15a and 15b of the metal plate are limited by a curved line and the lower edges are slightly stamped so as to allow to nest the two edges brought together, the stamped parts ensuring more greater rigidity at the edge of the frame serving in particular to the fixing of a facing or a canvas.

The parts 15c and 15d of the metal plate include a part main consisting of four portions in the form of steering strips longitudinal separated by fold lines which are intended to constitute the four sides of the wall on the side of the rectangular section frame and two covering portions intended to overlap two portions folded constituting two constituent faces on the side of the form frame general parallelepiped.

The cuts between the successive parts of the metal plate 14 are made in such a way that after folding, the ends of the sides sides of the frame fit into the triangular section end sides and that each corner of the frame is broken. In addition, the cutting is made so as to provide tongues and flaps constituting parts for covering and fixing the frame walls and the sides of the frame between them.

In Figures 6 and 7, there is shown, respectively, the external part and the inner part of one end side of the frame and the end parts two lateral sides coming to be embedded inside the end sides after folding the plate 14 along the fold lines shown.

In the arrangement of the frame shown in FIG. 7 after folding, fixing the tubular walls on each side of the frame, through the covering parts which are set elastic support on plate portions constituting wall parts on the sides of the frame or on other covering parts.

As indicated above, the covering parts are constituted by the longitudinal outer edges of the parts 15a and 15b which are placed facing each other during folding and kept in elastic support, one on the other during the welding which is carried out, for example, by a laser beam, in transparency according to welding points or lines distributed according to the length of the edges placed in coincidence and in elastic support one on the other.

In FIG. 7, connection zones 16 have been shown, constituted by stamped depressions produced along each of the edges to connect end sides of the frame and engaged with each other when of the elastic support of the two edges to be assembled one on the other. The lines welding can be done in the depressions 16 in one direction parallel or in a direction perpendicular to the edges of the end side of the frame which is assembled.

When closing the lateral sides of the frame, the covering parts constituted by the two band-shaped portions cover two portions constituting faces of the walls of the lateral sides. By exerting a bearing force on these covering parts, we can achieve an elastic support of the covering parts on the folded portions constituting the faces of the lateral sides. We realize then the welding of the covering parts on the folded portions constituting the faces of the walls of the frame, for example in transparency, in using a laser beam or by electric welding. We can carry out the assembly and fixing the lateral sides of the frame with points or lines welded spaced along the length of the lateral sides.

The welding of the sides of the frame can be carried out in a simple and fast, by creating a limited number of distributed welding points or lines along the length of the sides of the frame in the junction zones. The elastic support of the covering parts one on the other or on a part of the wall makes it possible to achieve satisfactory contacting during welding that provides a strong junction.

As shown in particular in Figure 7, the fixing of the sides lateral to the end sides is provided by parts of covering constituted by flaps or tabs 17, in the parts joining the end or side sides of the frame. The flaps 17 constituting complementary parts for covering the walls of the end sides are resiliently pressed against side walls side while transparent laser welding of the flaps 17 on the walls. Similarly, the flaps 17 constituting parts side walls are overlapped and in elastic support on the walls of the end sides while carrying out transparent laser welding.

The joining by welding of the covering parts with additional covering parts or with frame walls makes it possible to obtain a perfectly rigid assembly, even in the case where a thin metal plate is used, for example a plate metal with a thickness of the order of 0.7 or even 0.5 mm.

In some cases, it is even possible to envisage the manufacture of frame by cutting and folding sheets having a thickness between 0.05 and 0.5 mm.

Such frames can have many applications in the case where both good rigidity and reduced mass are sought, for example in the case of a frame made from an expensive material.

In other cases, it is necessary to obtain a very high rigidity and a very high mechanical resistance of hollow structures of general shape tubular and may have an outline of complex shape.

In the case of such structures for which we are looking for a very high strength, relatively small metal plates can be used thick, for example metal plates with a thickness greater than 1 mm, to form the walls of the hollow structure and the covering parts ensuring assembly after folding of the structure.

In Figure 8, there is shown a part of annular structure and of general tubular shape which can be produced by the process of the invention from a single plate or strip of metal folded to form walls of the structure and of the covering and fixing parts.

Generally, the part 18 shown in Figure 8 has the shape of a ring which can be of large dimension and whose section hollow cross section has a substantially rectangular shape.

The part 18 consists of successive annular sections 19 having an angular amplitude adapted to the manufacturing process which will be described thereafter and which are connected by points or weld lines made on covering parts in elastic support on parts of wall of the structural element.

For example, it is possible to design an annular part 18 as shown in FIG. 8 comprising twelve sections 19 each having a angular amplitude of 30 °.

In FIG. 9, part of a metal plate has been represented. making it possible to manufacture the structural element shown on Figure 8, by folding and welding.

The metal plate, part of which is shown in Figure 9 is generally designated by the reference 20.

Each of the sections 19 of the metal structure is produced from of a section 21 of the metal plate 20.

Each section 21 has a portion 22 intended to constitute a part of the external cylindrical surface of the annular structural element 18, at a section 19.

We realize, in a longitudinal direction strip of the plate 20 cut from a metal sheet, a succession of stamped zones 22 in the form of a portion of cylindrical surface whose longitudinal section has the shape of an arc of a circle with an amplitude of 30 °.

The stamped portions 22 are separated from each other by lines or fold zones 23 of transverse direction spaced one of the other in the longitudinal direction of the strip-shaped plate 20.

Successive stamped areas can be achieved by a stamping machine comprising for example a wheel or a cylinder having successive stamping zones of cylindrical shape convex separated by transverse depressions.

On either side of each of the portions 22 of a section 21 of the strip 20, in the transverse direction, two portions of wall 24 and 24 'of trapezoidal shape intended to constitute two surfaces sides of the generally tubular wall of the annular part 18. The wall portions 24 and 24 'are separated from the stamped portion 22 by longitudinal direction fold lines.

One of the wall portions (24 ') is extended by a wall portion 25 having, as a length, the length of the small base of the walls 24 and 24 'and a width substantially equal to the width of the stamped zone 22. The wall portion 25 is intended to constitute an internal wall part prismatic of the annular part 18. Finally, the wall part 25 is extended laterally by an additional covering part 26 intended to ensure the closure of the tubular section 19, during folding and the assembly of section 21.

In addition, the wall portions 24 and 24 'comprise, according to one of their inclined lateral sides, a covering and fixing part constituted by a flap 27 or 27. '

Similarly, the wall portion 25 has on one of its lateral sides a covering part constituted by a flap 28.

The wall portions 24 ', 25 and 26 are separated from each other by fold lines of longitudinal direction.

In Figure 11, there are shown two successive sections 19 of the annular part 18 which have been shaped and assembled by folding wall portions 24, 24 'and 25 around the longitudinal fold lines and by folding down the covering part 26 against the outer face of the wall portion 24 folded substantially at 90 ° relative to the wall portion stamped 22. The assembly and the fixing of the section 19 of the annular part 18 can be produced by applying elastic support by pushing, in a transverse direction, the covering part 26 against the portion of wall 24. The covering part 26 and the wall portion 24 in elastic contact are perfectly pressed against each other, so that the section 19 of the annular part 18 can be assembled by transparent welding using a laser beam to perform weld points or lines in the thickness of the walls 26 and 24.

As shown in Figure 11, we then perform a following folding the fold line separating the two successive stamped zones 22, so as to engage the flaps 27 and 27 'of wall portions 24 and 24' to the interior of the longitudinal end portions of other wall portions. Stamped areas for receiving the flaps 27 and 27 ′ can be provided in the longitudinal end portions of the wall portions 24 and 24 'of the section 21 located adjacent to the section with flaps 27 and 27 '. The flaps 27 and 27 'are folded slightly towards the outside of so as to come into elastic support inside the stamped end zones walls 24 and 24 'of section 21 adjacent to the section comprising the flaps 27 and 27 ', during the engagement obtained by pivoting the two sections 21 relative to each other around the fold line separating the two zones 22.

Similarly, the flap 28 engages in a stamped area of the wall portion 25 of the section adjacent to the section comprising the flap 28. During of its engagement, the flap 28 is slightly folded inwardly of the annular part 18, so as to come into resilient abutment against the part end of the wall portion 25.

The flaps 27, 27 'and 28 are held in elastic support against the engaging parts of the walls of the neighboring section 19, during welding assembly.

The outside of the structure 18 of tubular shape produces the welds of the flaps 27, 27 ′ and 28 of the successive sections 19 of the device after folding along the fold line separating two stamped sections 22 successive.

Welding can be carried out transparently by a laser beam, the flaps being perfectly kept in contact with the end parts walls of a neighboring section 19, by elastic return. We can favor the contact between the end parts of the walls and the flaps by exerting pressing or pinching the walls, in the direction from the outside towards the inside of the tubular structure.

In FIG. 12, the different lines or points of laser welding 29, 30 making it possible to assemble two successive sections of tubular shape and to join together, by their common end, these two successive sections.

Preferably, it is determined by calculation, by performing a digital simulation of the loading in service of the structural element, areas of the structural element where the stress concentration is the weakest. We weld points or lines in these areas determined by calculation.

These weld points or lines are generally made in transparency by a laser but it may be possible to perform, in some cases, welds along the edges brought together against a part of connection and a portion of wall in elastic support against each other, this welding method being designated as lap welding.

It is possible to obtain very good dimensional accuracy of the structural element, this dimensional precision depending in particular the precision with which the cutting and folding of the metal plate as well as the immobilization position of the part or parts overlap and wall portions during welding. The precision positioning during welding can be obtained easily, the fact that it suffices to ensure the positioning of one of the two walls to be fixed by welding, the second wall being pressed by elastic return against the first wall.

The assembly can be carried out without template inside the structure tubular element, which allows for elements in which the cross section of the tubular structure is variable. Maintaining wall portions to be welded during welding can be performed by simple mechanical devices such as pliers or clamps.

The realization of structural elements of very complex shape is possible, especially using design software that allows optimize the layout of the metal part and its fold lines.

In the case of large structural elements, one can make the structural element from several metal plates, different parts obtained by folding and assembling the different plates of metal being then assembled by welding operations using overlapping parts and / or walls elastic against each other.

Extremely rigid structural parts can be produced from thin sheets, due to the stiffening effect obtained by the welding of a covering part on a wall element or another covering part of the structural element. Parts of the element of structure can be reinforced by superimposing an element of overlap to a wall portion, the overlap portion and the portion of the wall being immobilized by welding, for example in transparency.

It is thus possible to manufacture structural elements having thicknesses with a wall ranging from 0.05 to 1 mm, which is difficult to imagine in the manufacture of structural elements of generally tubular shape with polygonal section, from profiles.

As indicated above, it is also possible to carry out extremely rigid and resistant structures using metal plates thicker than 1 mm and up to thickness maximum conceivable with cutting and folding means which are available for the manufacture of the structural element.

The method of the invention makes it possible to manufacture structural elements in any metals and in particular structural elements difficult to weld metals such as aluminum and its alloys.

Possible applications of the process according to the invention and the elements of structure that can be obtained are extremely numerous.

Some possible applications of the process will be listed below. according to the invention and the structural elements produced by folding in different areas of the industry. This list is not, however, exhaustive.

The structural elements according to the invention are characterized by a generally tubular shape preferably of polygonal cross section comprising at least two tubular sections not axially aligned, the element structure possibly comprising curved parts which can be obtained by stamping parts of the metal plate before the operation folding, this stamping operation can be performed before or after cutting the metal plate.

The structural elements according to the invention of generally tubular shape and of polygonal cross section are characterized in that they comprise a plurality of sections, in angular arrangements one by relative to each other, separated by fold lines of the same metal plate and at least one additional covering and fixing part as well as an additional part for fixing successive sections between them superimposed and fixed by at least one welding line or point overlapping, at least one of a wall portion and a second covering part, the entire structural element being assembled and stiffened, only by at least one welding point or line at least one covering element in the superimposed position and in elastic support on at least one of the wall portion and the second covering and fixing part.

Structural elements according to the invention used in industry of the building can be for example frames constituting parts opening or sleeping frames and in particular doors or windows. These frames may have tubular sectional sides cross-section of various shapes, to obtain a decorative effect. These frames, in particular when they constitute doors, may include a facing of curved shape and, in general, have curved parts. A structural element according to the invention used in the building can also be a frame of double glazing for doors or windows. In this application, a structure made from a metal plate folded and assembled by welding has significant advantages by compared to the classic type frames formed by profiles of square shape bent at right angles to the angles of the double glazing frame. In such frames according to the prior art, the section of the profile is strongly modified by folding which also results in adaptation folds on the surface of the profile.

Structural elements according to the invention can be used for the construction of housings of electrical devices for example as cabinet door frames or electrical boxes.

In the field of printing machines, structural elements according to the invention can be used as screen printing frames.

The invention can also have many applications in the field of automobile, naval and aeronautical construction, structural elements according to the invention which can be used for the production hulls or chassis of vehicles and in particular of resistant structures in a squirrel cage which may include cover sheets.

Structural elements according to the invention can also be used in the production of cells and in particular of aircraft fuselages. In these applications, and in particular in the case of aeronautical applications, structural elements can be easily made from alloys light, difficult to weld such as aluminum or titanium alloys.

In general, structural elements according to the invention can be used to replace complex shaped structures from unusually shaped profiles.

The embodiments according to the invention make it possible to avoid the manufacture of such expensive profiles.

Generally speaking, in the field of metal construction, the structural elements according to the invention find applications as reinforcements or support structures which must have a very great rigidity and very great resistance and possibly a mass scaled down.

In particular, the structural elements according to the invention can be made up of curved profiles, possibly polygonal in section variable, or of structures in the form of a section frame or ring dig.

The structural elements according to the invention can also be used as heat exchangers, for example radiators or heating convectors.

In certain cases, the tubular structure produced according to the invention must be sealed. In this case, we will make lines of continuous welding between the covering parts and the portions of walls and possibly between certain portions of walls.

In general, the structural element according to the invention is such that it constitutes a practically continuous hollow body; when this hollow body is closed on itself, it can contain a flat closed line, located entirely inside the hollow body and passing inside each of its sections.

The invention is not strictly limited to the modes of implementation which have been described in two specific cases.

The metal plate (s) used to make the element structure according to the invention can be made of steel, in particular stainless steel, or any other ferrous alloy or even a non-ferrous alloy, for example aluminum alloy.

Welding can be carried out by a process different from the welding process. laser beam welding, although this process has advantages which were mentioned above.

The process according to the invention can be used to manufacture elements different from frames or annular parts with tubular structure.

The process according to the invention can be used for the manufacture of generally tubular parts with polygonal cross-section which are not closed on themselves like the frames or annular parts.

Claims (6)

1. Process for manufacturing a structural element having a metal wall with a generally tubular form comprising at least two non-axially aligned sections (19), characterized in that :

   at least one flat plate (14, 20) comprising a principal part having the developed shape of the sections of the wall of the structural element (11, 18) is cut from a sheet of metallic material and, for each of the sections (19), at least one complementary overlapping and fastening part, as well as at least one complementary part for fastening the sections together;

   the cut plate is folded along a plurality of lines so as to form the wall of the structural element (11, 18), from folded portions of the principal part of the cut plate (14,20), and

   there is attached by welding at least one complementary overlapping and fastening part of each of the sections and at least one complementary part for fastening the sections (19) together on at least one folded portion of the section of the wall of the structural element (11, 18) or a second overlapping part, at least one complementary covering and fastening part of each section (19) and at least one part for fastening the sections (19) together and the folded portion of the wall or the second overlapping part being held resting elastically on each other.
2. Process according to claim 1, characterised in that at least one zone (22) of the metallic plate (14, 20) is stamped out prior to folding the cut plate (14, 20).
3. Process according to either of claims 1 or 2, characterised in that welding is carried out with the aid of a laser beam preferably with transparency through the complementary overlapping and fastening part of each section (19) and the complementary part for fastening the sections (19) together, and at least one folded portion of a wall of structural element (11, 18) and a second overlapping part.
4. Process according to any one of claims 1 to 3, characterised in that the sheet of metallic material has a thickness of between 0.05 and 1 mm.
5. Structural element having a metallic wall with a generally tubular shape with a polygonal cross section comprising at least two non-axially aligned sections, the element comprising a plurality of wall portions (24, 24', 25, 26) in angular arrangements with respect to each other, separated by fold lines of the same metallic-plate (20), characterised in that it comprises at least one complementary overlapping and fastening part (17, 27, 27', 28) of each section (19) and at least one complementary part for fastening the sections (19) together superimposed and fastened by at least one overlapped weld line or point (29,30) to at least one wall portion (24, 24', 25, 26) and a second overlapping part of the element, all of the structural element (11, 18) being assembled and stiffened, solely by at least one weld point or line (29, 30) of at least one overlapping part of each section (19) and at least one part (17) for fastening the sections (19) together in a superimposed position elastically resting on at least the wall portion and the second overlapping and fastening part.
6. Structural element according to claim 5, characterised in that it constitutes all or part of one of the following elements : a door frame for a building, a door, a window, a double glazing frame, a frame or door for a cabinet or an electrical box, a silk screen print frame for a printing machine, a structural component for automotive, naval or aeronautic construction, a shell, a chassis for a motor vehicle, a cell, an aircraft fuselage, a strong structure in the form of a squirrel cage for a motor vehicle, a reinforcement and supporting structure for a metal construction, a complex curved profile with a polygonal section, an annular component with a hollow polygonal section, and a heat-exchanger element.

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