EP2138246B1 - Tube manufactured from a planar blank and method of manufacturing such a tube - Google Patents

Abstract

The tube (100) has fixation tabs (5, 6) realized in the form of excrescence projected from a folded rim (3) in one of two opposite edges (2) of the tube, where the tube is opened on its entire length and made of plastically deformable blank such as steel blank. The zone is folded towards a wall of the tube. The opposite edges are extended parallel to a longitudinal axis of the tube, where shapes of the edges are changed according to the resistance to be obtained. An independent claim is also included for a method for fabricating a tube.

Description

The invention relates to a tube according to the preamble of claim 1 (see eg BE-A-525 415 ), made from a plastically deformable material, such as metal, in the form of a blank or a strip.

Tubes of this type are already known, which have the characteristic characteristic that the longitudinal edges facing the tube are joined by a welding bead to give the tube rigidity and resistance against mechanical stresses. These tubes have the disadvantage that the welding operation after the formation of the tube is a relatively delicate additional operation and thus makes more expensive the manufacturing process of such tubes.

The invention aims to overcome this disadvantage.

To achieve this object, the invention is characterized in that the tube comprises at least one fastening lug or other member, which is made in the form of an outgrowth of the folded area of a tube edge.

According to a further feature of the invention, the two edges are folded.

According to yet another characteristic, the fold is made either inwardly or outwardly of the section of the tube.

According to another advantageous characteristic of the invention, the section of the tube is uniform over its entire length.

• la figure 1 est une vue en perspective d'un tube ouvert aux bords en regard repliés selon l'invention ;
• la figure 2 est une vue illustrant une section transversale du tube selon la figure 1, les bords étant repliés vers l'intérieur ;
• la figure 3 est une vue similaire à la figure 2 du tube selon l'invention, les bords étant repliés vers l'extérieur ;
• la figure 4 est une vue en perspective d'un tube selon l'invention pourvu de pattes de fixation ;
• la figure 5 est une vue de dessus illustrant schématiquement une presse automatique de formage par emboutissage des tubes selon l'invention ;
• la figure 6 est une vue schématique illustrant différentes étapes du processus de formage par emboutissage sous la presse automatique selon la figure 5 ;
• la figure 7 est une vue en perspective d'un tube pourvu de pattes de fixation, selon une variante de réalisation de l'invention ;
• la figure 8 est une vue de dessus, par extrait, d'une bande d'un matériau plastiquement déformable avec des découpes pour réaliser des tubes selon la figure 7 ;
• la figure 9 est une vue schématique illustrant différentes étapes du processus de formage par emboutissage d'un tube selon les figures 4 et 7 ;
• la figure 10 est une vue en perspective d'une traverse de planche de bord incorporant un tube selon l'invention ; et
• la figure 11 est un diagramme représentant la résistance mécanique d'un tube selon l'invention comparé à la résistance d'un tube classique.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows and which is made with reference to the attached schematic drawings given only in by way of example illustrating an embodiment of the invention and in which:

• the figure 1 is a perspective view of an open tube with the folded edges facing according to the invention;
• the figure 2 is a view illustrating a cross section of the tube according to the figure 1 the edges being folded inwards;
• the figure 3 is a view similar to the figure 2 tube according to the invention, the edges being folded outwards;
• the figure 4 is a perspective view of a tube according to the invention provided with fastening tabs;
• the figure 5 is a top view schematically illustrating an automatic press for forming by stamping tubes according to the invention;
• the figure 6 is a schematic view illustrating different stages of the stamping forming process under the automatic press according to the figure 5 ;
• the figure 7 is a perspective view of a tube provided with fixing lugs, according to an alternative embodiment of the invention;
• the figure 8 is a top view, by extract, of a strip of a plastically deformable material with cutouts for producing tubes according to the figure 7 ;
• the figure 9 is a schematic view illustrating different stages of the process of forming by stamping a tube according to the figures 4 and 7 ;
• the figure 10 is a perspective view of a dashboard crossmember incorporating a tube according to the invention; and
• the figure 11 is a diagram representing the mechanical strength of a tube according to the invention compared to the resistance of a conventional tube.

As we see on the figure 1 , A tube 1 according to the invention has the feature that _it is made from a blank made of plastically deformable material, in particular a blank sheet of steel, by stamping or profiling and that the edges 2 facing the tube, which extend substantially longitudinally, therefore at least approximately parallel to a longitudinal axis of the tube, are formed by folding a zone of matter towards the body of the tube, or inwards, as shown by Figures 1 and 2 outward, in accordance with the figure 3 , thus forming flanges 3. Thus, although the tube is open over its entire length, it still has good rigidity and resistance against any type of mechanical stress due to the flanges 3.

The shape of the edges with their edges 3 evolves according to the resistance to be achieved. The edges may have different shapes and the flanges 3 are not necessarily flat and glued against the main section of the tube.

As shown in figure 4 according to a first variant embodiment of a tube according to the invention, the flanges 3 of a tube 100 may be extended by protrusions in the form of fastening lugs 5 and 6, obtained by folding the section towards the outside. of the tube, at the free outer edge 7 of a flange 3.

As we also see clearly on the figure 4 , the rim of the tube 200 may be in the form of a continuous strip which extends over the entire length or only a part thereof. The rim could also be discontinuous along the length of the tube. The tube may still have several areas struck, punched or cut in various places. Both ends of the tube may be straight or have different shapes.

Thanks to the possibility of forming on a tube according to the invention different legs, if necessary with screws or nuts mounted on these tabs, for example the tab 6, the tubes according to the invention are particularly well suited for use in the domain of the automobile and can be used very advantageously for the production of dashboard crossmembers, door stiffeners, shock impactors, shock absorbers, beams, crossbars front and rear bumpers and the like. Both ends of the tube may be straight, as shown in the drawings, or have an evolutionary shape.

We will describe below, referring now to figures 5 and 6 the steps (a) to (f) of a method of manufacturing a tube according to the invention, by stamping based on the use of an automatic press. This process is only given as an example. The tubes according to the invention can also be made by profiling based on the use of rollers.

In general, a tube according to the invention is made by stamping from a blank, for example a steel sheet. As part of the process and the press according to figures 5 and 6 the pieces or blanks of sheet metal are cut from a strip of steel which is unwound from a not shown reel and brought to the automatic press whose figure 5 schematically shows the structure by a view from above. This press which carries the general reference 10 comprises a number of sectors of workstations each of which performs a specific function and each blank or piece of sheet metal passes through successively. During their passage through the press, the blanks cut from the original and successively converted into a tube, in particular a cylindrical tube, hang up to each other in order to be able to ensure a precisely controlled transport, step by step, of a tool sector to the other and within each sector from one workstation to another.

For this purpose, the strip of steel, for example 12 noted comprises along its longitudinal edges transport control points 13 regularly distributed, each between two blanks and then tubes being formed. It can be seen that even after cutting a blank, it remains connected to the previous blank and the next blank by a material bridge 14 at a control point 13.

As we see on the figure 5 , the press 10 comprises, in the direction of travel of the band 12 indicated by an arrow F, first of all a cutting sector 15 blanks in the band, which, in the example shown, comprises two cutting stations. In the first cutting station 16, the press makes two rectilinear cuts perpendicular to the X axis of the strip, each starting from the place which will subsequently constitute a front end of the tube, of a predetermined length in the direction of the axis, the part between these two cuts remaining intact. The next cutting station 18 cuts the remaining portions of the blank contour, except for the bridges 14, as indicated by the cutting lines of the front ends 19 parallel to the direction of travel of the web and the cutting line 20 of the area between the two cuts 17 made at the first station. The cutting sector 15 succeeds a vacuum station 22 in which the blank noted now 23, is completely cut, of course with the exception of the bridges 14 of attachment.

The press then comprises, in the example shown, a bending post sector 26, which comprises two bending stations 27, 28 and a crushing bending station 29.

At the first bending station is completed the first phase of the production of the flanges 3 to be folded along the front and rear ends 24 of a blank 23, that is to say perpendicular to the direction of advancement of the 12. The edges 3 are folded in this position at an angle slightly greater than 90 °. At the second bending station the flanges are bent to an angle of about 145 ° and at the third bending crimping station 29, the flanges 3 are entirely folded and pressed against the upper surface of the blank 23. The bending sector 25 follows the driving sector 32. In this sector, which comprises three rolling stations 33, 34, 35 the blank 23 with the folded edges 3 is transformed into a cylindrical tube as shown in the figure 1 .

Since the rolling axis extends perpendicular to the axis of the steel strip and the cutting line to form the longitudinal edges of the tube is also perpendicular to the axis of the strip, on the one hand , and that the rolling operation is done after the cutting operation of the blank from which the tube is made, the invention makes it possible to give the edges facing the tube any desired shape. Thus, the invention makes it possible to provide on the tube fastening lugs of other members, such as lugs 5 and 6, which are made in the stamping press. Thus, fastening lugs do not need to be attached to the tube, after its manufacture, during an additional operation, for example by welding.

The figure 7 represents a tube 200 according to a second variation of embodiment of the invention. The tube 200 is made, like the tube 100, from a blank made of a plastically deformable material, especially a sheet steel blank, by stamping or profiling and with fixing lugs 5, 6. The tube 200 differs from the tube 100 in that it comprises a flange 3A from which are formed fastening lugs 5, 6 and a flange 3B with notches or cuts corresponding to the material necessary to form the fastening lugs 5, 6. The figure 8 schematically represents how this variant embodiment affects the cutting blanks in a steel strip. Two successive blanks 201, 202 are cut with an edge 2A having protrusions giving the fixing lugs 5, 6 and with an edge 2B having cutouts 51, 61 corresponding to the material of the legs 5, 6. It is therefore clearly visible that the second embodiment allows to cut, to dimensions of the tube and legs equal, from a given steel roll, many more tubes 200 than 100 tubes.

The figure 9 represents steps (a) to (g) of the production of a tube 100 or 200 according to the invention. As schematically shows figure 9 it is sufficient to configure the fastening lugs 5, 6 appropriately with respect to the fold 3, before the bending operation to have the shape of the fastening lugs 5 or 6 according to the figure 4 or the figure 7 .

The invention also makes it possible to provide on the tube, a piece, tabs at the front ends by a suitable cut of the blank and the shaping of these tabs before the rolling operation of the blank to obtain the open tube according to the invention .

The figure 10 illustrates, by way of example, the application of the invention for producing a dashboard cross member of a vehicle. In this figure, it is found that the crossbar comprises two tubes according to the invention, namely a tube 1 without mounting tabs and a tube 200 with mounting tabs mounting in the vehicle environment.

The figure 11 shows for different tube configurations, the relationship between the stiffness of the tube under the effect of contact force, as a function of time. On the ordinate of this figure is reported the contact energy EC while the axis 6 is the axis of the flow of time t. The rigidity calculations that allowed the tubes to be made were made using RADIOSS naming software. The figure 11 shows four curves: in A the curve of a tube according to the invention whose rim is folded on the outside of the tube, in B the curve of a tube according to the invention with the fold inwards, in C the curve of a tube obtained from a blank but closed by a weld bead and at D the curve of an open tube without a flange.

It follows from the curves of the figure 11 that the tubes according to the invention, namely the curves A and B have a better rigidity than the tubes according to the state of the art represented by the curves C and D.

Of course, for the comparative study that resulted in figure 11 , Thickness, material and tube section diameter were identical and the same force is applied to the center of the tube via an impactor with a same speed. The embedding of the ends during the application are also identical.

Claims (11)

1. Tube produced starting from a plastically deformable material, such as metal, taking the form of a blank or a strip, the tube (1) being open over its entire length and at least one of the two edges (2) facing one another having at least one zone (3) which is folded back towards the wall of the tube, characterised in that the tube (1) has at least one fixing lug (5, 6) or other element produced in the form of a projection of the folded-back zone (3) of a tube edge.
2. Tube according to claim 1, characterised in that the edge (2) facing the edge (2) provided with the fixing lug (5, 6) has a recess of complementary shape, the fixing lug being formed as a result of cutting out the recess.
3. Tube according to claim 1 or 3, characterised in that both edges (2) are folded back.
4. Tube according to any one of claims 1 to 3, characterised in that the fold-back (3) is made either towards the interior or towards the exterior of the cross-section of the tube.
5. Tube according to any one of claims 1 to 4, characterised in that the cross-section of the tube is uniform throughout its length.
6. Tube according to one of claims 1 to 5, characterised in that it has fixing lugs at at least one end-face extremity.
7. Method of manufacturing a tube according to one of claims 1 to 6, characterised in that it is obtained starting from a blank having at least two edges which are parallel, by operations firstly of cutting out a blank and bending (at 26) for producing fold-backs (3), and then by rolling (at 32) to give the tube its cylindrical shape, the fixing lug or lugs being produced in the course of cutting out the blank, production of the fold-backs (3) including, at the edge being produced having one or more fixing lugs, a folding-back of the edge whilst maintaining the fixing-lug-forming projection or projections at least approximately perpendicular to the blank and also folding for forming the shape of the fixing lug or lugs after rolling of the blank.
8. Method according to claim 7, the fixing lug or lugs (5, 6) on one edge (2) of the tube being obtained by cutting out from the other edge (2) of the tube.
9. Method according to claim 8, characterised in that the blank is obtained by cutting out from a strip of material whilst keeping it joined to the strip by zones in the form of bridges (14), the method comprising operations of cutting out the blank, with the exception of the bridges, along cutting lines perpendicular to the axis of the strip, the connection points (14) being located at the longitudinal edges of the strip.
10. Method according to claim 9, characterised in that the strip includes, along its longitudinal edges, indexing points (13) for the movement of advancing the strip from one work station to another.
11. Method according to one of claims 7 to 10, characterised in that it includes, following the mentioned cutting-out operation, an operation of bending (at 26) of the cut-out edges of the blank for producing the fold-backs (3) followed by an operation of rolling (at 32) for producing the cylindrical shape of the tube.

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