EP1126937B1 - Method and intermediate product for producing a hollow body and a hollow body produced by said method - Google Patents

Abstract

The invention relates to method for producing a hollow body (26) from sheet metal, especially from aluminum or aluminum alloys. According to the inventive method, a substantially flat sheet metal blank (4) is provided. At least one wall intermediate element (8) which is produced as one piece with the sheet metal blank (4) is folded and/or bent into several substantially superimposed layers. Marginal areas (16, 18) of the sheet metal blank (4) are placed closely side by side, preferably they are placed on top of one another in such a manner that they overlap to some degree, and they are connected to one another. The sheet metal blank (4) and the folded wall intermediate element (8) are subjected to a hydraulic or pneumatic internal high pressure so that the folded wall intermediate element (8) is freely unfolded to form the hollow body (26). The invention also relates to a hollow body (26) produced by said method and to an intermediate product (2) which can be used to produce such a hollow body (26) according to the inventive method.

Description

Technical field

The present invention relates to a method for Manufacture of a hollow body from sheet metal, in particular from Aluminum or aluminum alloys, as indicated in the preamble of claim 1.

The present invention further relates to a Intermediate product, as indicated in the preamble of claim 10, that for making one Hollow body used can be.

Such a process and such an intermediate product are over U.S. Patent No. 4,588,651.

State of the art

There are processes for making so-called pipe or Channel plates, i.e. pulled through with pipes or coils Sheet metal, known in which two superimposed flat Aluminum sheets are firmly connected to one another in places and those in between that are not connected Sheet areas in a form by introducing a Print medium to form channels between the sheets be arched apart. There are also processes for forming of single-layer sheets in one form by one-sided Applying the pressure of a liquid or gaseous Media and stretch drawing into the cavity of the mold known (EP-A-0 581 458 and AST Specialty Handbook, Aluminum and Aluminum Alloys, The Materials Information Society, 1993, page 245). These are known methods not always satisfactory, especially not when Workpieces when forming a relatively large change in shape should be subjected, for example in cases where a strong expansion of tubular bodies or Extruded profiles should be achieved. This in particular with aluminum and aluminum alloys that are not as good as Steel are deformable. But steel can also be larger Forming workpieces with the known methods not be carried out satisfactorily.

To enlarge the internal cross sections of a workpiece it is known from DE-A-42 32 161, a hollow body under Use of a welded together from the edge Boards manufactured by the combined body Application of the hydroforming process and To produce deep-drawing processes. Because of the required The combination of two processes is production of the hollow body comparatively complicated and expensive. On the other hand is the manufacturing facility required for this extremely complex and expensive. It is also in practice not possible, very large containers made of aluminum or one Aluminum alloy, e.g. Tanks for motor vehicles, Aircraft or ships, because of insufficient The ability of aluminum to deform.

A method for achieving improved reshaping of Workpieces made of aluminum or an aluminum alloy in DE-A-195 31 035, where several flat Sheet metal blanks made of aluminum or aluminum alloy their edges stacked and in places by soldering to be connected to the workpiece to be formed. in this connection are used to increase the volume of the workpiece later to produce hollow flat individual sheet metal blanks inserted into the workpiece. Then it will be like this trained workpiece to be formed inserted into a mold and by an in the mold to act on the workpiece initiated heated bl by hydroforming the hollow body expanded and deformed outwards. there lay the connected sheet metal blanks due to the applied internal pressure to the inner contour of the mold. the However, there is a degree of expansion of the hollow body volume Limits set, on the one hand, from the mechanical Resilience of the solder connections between the individual Sheet cuts result. The other occurs in the area sharp-edged cross-sectional transitions of the shape due to the extreme material deflection in these areas appropriate solidification of the already stretched material on. The increasing associated with the increase in strength Elongation of the material entails the risk of cracks occur. The smallest possible bending radius can therefore not fall below. Therefore, no tight molding can be realized in corner areas. It is with these Process possible a strong shaping of the workpiece the shape and to obtain a large-volume hollow body. The Size and shape of the to be manufactured However, the volume of the hollow body is also limited here. In particular, it is not possible with the known method smallest forming radii, almost to sharp edges, and also large hollow bodies from one piece and without over the manufacture circumferential flanges.

Presentation of the invention

Given these drawbacks and remaining problems the method known in the prior art is the Invention based on the object, a method and a Intermediate product for the production of a hollow body from sheet metal, especially of aluminum or aluminum alloys create the training with as little effort as possible of a large one that is available in an installed state available space (e.g. for tanks for Motor vehicles in the rear axle area) corresponding Allow hollow volume, while being smallest Forming radii and greatest forming depths can be achieved.

This problem is solved according to a first aspect of the invention by the method according to claim 1.

As a result, one becomes essentially flat Sheet metal cutting, in particular made of aluminum or one Aluminum alloy, provided as a workpiece. in the however, all are general as workpiece material metallic materials with sufficient Resilience suitable. This ranges from Light metals over unalloyed and alloyed case-hardened steels up to towards temperable and stainless steels. In this Method step of providing it is possible to shape to determine and size of the sheet metal blank and by suitable choice of the dimensions of the sheet metal blank already Influence on the desired final outer contour of the to produce hollow body. Editing the Sheet metal cutting is preferably done in a known manner and Mechanically by cutting or thermally Flame or laser cutting.

The sheet is cut to size in a suitable manner subsequent molding process in the area of one piece with the Sheet metal blank formed intermediate wall element folded and / or bent. The intermediate wall element forms here a section or part of the Sheet metal cut out, i.e. the intermediate wall element is in integrated into the sheet metal blank. This one-piece training facilitates the handling of the sheet metal blank as well as that Folding and / or bending significantly. Furthermore, the Productivity and accuracy of sheet metal cutting increased be, in particular in contrast to that in DE-A-195 31 035 method shown no individually shaped sections need to be soldered together. The through the invention Process to be produced in the hydroforming process Hollow bodies can thus be joined, e.g. soldered, welded or flanged constructions from individual sheet metal blanks replace and thus avoid problems with leaks or dynamic fractures in the joining zone and thereby guarantee improved strength properties.

Bending can be done in this step, for example be carried out by roll forming, with a large one Design freedom with regard to the shape of the Wall intermediate element results. Here is also a very sharp-edged bending of the sheet in the area of the intermediate wall element possible so that a fold in several, in essential superimposed layers is possible. Consequently can the individual sheet layers, for example, double, triple or folded in layers.

In the course of folding and / or bending the intermediate wall element can also regarding the Positioning of edge areas of the sheet metal blank relatively relationships are established that the subsequent connection of the edge areas easier. To the The edge areas of the sheet metal blank are connected put together, preferably with a certain Overlap, and for example by Soldering, welding, e.g. Squeeze seam welding or Laser beam welding, or flanging preferably along the longitudinal extension of the edges of the sheet metal blanks attached to each other. This results from this step a flat hollow body with a closed one Cross-sectional shape, which by connecting to the Edge areas essentially pressure-tight and so for one Forming process in the subsequent Hydroforming step is ready for use.

As part of the hydroforming step, a through the sheet metal cutting and the at least one folded intermediate wall element limited Cavity through a suitable connection, for example in the sheet metal blank or the intermediate wall element is tight inserted (e.g. by soldering) lines or pipe sockets hydraulic or pneumatic pressure medium introduced. The sheet metal is subsequently cut by the printing medium and the folded wall intermediate element with internal high pressure acted upon, whereby the multi-layer folded Wall intermediate element up to the full length Formation of the hollow body is unfolded. So it happens According to the invention, free formation of the hollow body shape by unfolding the intermediate wall element without the Workpiece is subject to significant material expansion. in the The difference to the known methods is the desired one So not shape from the geometry of the Tools involved in hydroforming processes, e.g. the die shape, fixed, but by the shape and size of the sheet metal blank provided at the beginning of the process and / or intermediate wall element.

The invention is therefore based on the idea of a primary one Volume increase of the hollow body by unfolding and unfolding to the extended length of the multilayer trained intermediate wall element to provide without however, there is a substantial expansion in the material cause. This has the great advantage that the full elasticity of the material for additional local Deepening by stretching or deep drawing in the course of one optionally subsequent hydroforming is still available stands. By the method according to the invention especially when using materials such as Aluminum, which have low deformability, Stress peaks in the material avoided, so that a Hollow body with small forming radii and large forming depths can be trained. So this is suitable Process according to the invention is particularly good for the production of Workpieces that are manufactured in lightweight construction and at who therefore use the specifically lighter material Aluminum is required, such as Tanks for Motor vehicles, airplanes, ships or the like.

The present invention is therefore based on the idea based on a method and an intermediate for Manufacture of a hollow body to create the training more complex geometries, higher dimensional accuracy and Strength properties with reduced workpiece mass in ensure a hollow body.

Advantageous embodiments of the invention Processes are described in the further claims.

To achieve the desired final contour of the to produce hollow body, it is preferred that the unfolded wall intermediate element and / or the Sheet cutting after the unfolding process by increased Internal pressure in the stretching or deep drawing process, for example by inserting the workpiece into a suitable die shape, are deformed at least in sections. Since the First cut the sheet metal with the intermediate wall element through the applied hydraulic or pneumatic Internal pressure only unfolded and not deep drawn or stretched is thus, by the inventive method Possibility created the hollow body in a second The shape of the shape is precisely matched to the desired shape by means of high pressure to deform. In contrast to the conventional ones Forming processes in which the shaping of the workpiece Barriers are set that are limited to the limited Deformability of the material can be attributed, can be stretched or deep drawn in one of them Unfold the hollow body separate this step Restrictions are lifted so that in this second Forming stage can also produce geometrically complex workpieces are. Thus, the desired larger volumes of Container through the folded sheet metal sections of the intermediate wall element achieved that unfold first and then optionally fully or partially stretch or be deep drawn.

It is used for the shaping of the hollow body to be produced preferred that at least one upper and one lower Sheet metal section of the sheet metal blank when folding and / or Bends to be overlaid. Here, the Sheet metal sections preferably parallel and essentially coplanar arranged one above the other, which creates an im essentially closed cross-sectional shape of a flat Hollow body results. This facilitates the following Overlap and join the edge areas of the sheet metal blank considerably.

For closing and sealing the workpiece before unfolding by applying the hypertension, it is advantageous to stacked sheet metal sections at least in sections on their end faces, e.g. by soldering or Welding, joining. Here the end faces or End faces of the sheet metal sections of the sheet metal blank preferably pressed together in such a way that the individual layers of the folded intermediate wall element towards each other come to lie. This allows the End faces of the layers of the intermediate wall element with each other and with the end faces of the adjacent Sheet metal sections connected, e.g. soldered or welded, become.

If through the multi-layer wall intermediate element an opening between the top and the bottom sheet section, it becomes a relief preferred to maintain a closed cavity Spacer, e.g. made of sheet metal, between the superimposed end faces of the sheet metal sections in the Area of the opening. This can be a distance or Free space created by the side folds of the multilayer arranged wall intermediate element between the Sheet metal sections are created, bridged in an advantageous manner and filled out so that a secure closure of the Cavity is guaranteed.

It is also for closing the cavity at the front advantageous if at least one lobe or tab-shaped Section at the edge of the upper or lower sheet metal section is trained. This lobe-shaped section can follow folding or bending the sheet metal blank into a desired one Shape on the front of the lower or upper Folded sheet metal section and with this, e.g. by soldering, get connected. This measure represents a tight one Closing the end faces of the workpiece securely.

For a simple geometric shape with a cuboid or rectangular contour, it is preferred to use the flat one Sheet cutting in the course of process step a) with a essentially rectangular outline or plan provide. Such a floor plan can be on the one hand in a simple manner and on the other hand ensures easy folding or bending of the sheet metal blank. But there are others here too Outline shapes possible for sheet metal cutting, e.g. round, oval, square or polygonal. Furthermore, on the Sheet cutting also approaches or via the e.g. rectangular outline outwardly projecting sections be trained, which is advantageously in the context of Process step b) are folded in to the later Unfold the desired unfolded sheet metal sections for one to provide large void volume. This training of flat sheet metal cut in various shapes and sizes ensures a diverse design for the hollow body to be produced.

For preforming or shaping to the final contour of the hollow body to be produced, it offers advantages folded sheet metal blank before or after Unfolding molding process in a closable form insert to facilitate the insertion of the folded sheet metal blank and the removal of the formed Hollow body is divided and the mold cavity preferably the desired outer contour of the hollow body to be produced equivalent. By flooding the workpiece with a liquid or gaseous pressure medium, the workpiece is from the inside pressurized and simultaneously with or after unfolding the multi-layer wall intermediate element reshaped to the inner contour of the form. The Shape provides additional stabilization of the workpiece during forming, so that this procedure is also difficult formable workpieces, e.g. made of aluminum or Aluminum alloys, easily a strong deformation can be subjected.

For loading the sheet metal blank with a hydraulic or pneumatic high pressure proves itself the use of an oil pressure medium that Has ambient temperature, or from heated oil as advantageous. In general, however, another can liquid or gaseous pressure medium, e.g. Water, Emulsion, compressed air or the like, for Hydroforming can be used. The use of However, oil offers the advantages of gases Incompressibility and a much larger one Heat capacity, so that the workpiece undergoes strong deformation can be subjected. In addition, when using of oil avoided the risk of an explosion, as was the case with Use of gas mixtures may be the case. The stake oil therefore offers considerable advantages over gases with regard to easier handling of the Print media. By heating the as a pressure medium used oil, preferably to a temperature of at least 150 ° C, there is also the advantage that during the hydroforming of the workpiece to be formed heat in one sufficient amount is supplied, wherein, especially in the Forming hollow bodies made of aluminum or Aluminum alloys, even with strong shaping large-volume hollow bodies have a high deformability preserved.

A manufactured by the inventive method Hollow body has at least one due to high internal pressure unfolded intermediate wall element. This hollow body has the already in connection with the invention Advantages described process like sharp-edged contours, small forming radii and large forming depths with a large one Hollow body volume and great strength from production a single sheet blank.

For the formation of a stable hollow body with good Strength properties are preferred that this one in has a substantially axially or rotationally symmetrical shape. For example, the manufacture is cuboid, however also oval, polygonal or polygonal hollow body possible. The formation of such axially symmetrical bodies results in an advantageous manner from the arrangement of an even number, for example two, intermediate wall elements in the workpiece to be formed.

For optimal adaptation of the hollow body volume to the in available in an installed state It offers space in certain applications Advantages if the hollow body is essentially partial shape expanded in one or more planes and directions having. Here, the hollow body can be, for example take on a conical shape. This shape can be simple Way by the arrangement of only one wall intermediate element realized in the workpiece to be formed become.

The object underlying the invention is further by an intermediate product for producing a hollow body solved according to the features of claim 10.

As can be seen from the foregoing, this shows Intermediate product according to the invention for producing a Hollow body made of sheet metal, in particular aluminum or Aluminum alloy, a sheet metal blank as well as at least one Wall intermediate element that is integral with the Sheet metal blank formed and in several, essentially superimposed layers are folded and / or bent. This results in an intermediate wall element sandwich-like structure. Furthermore, edge areas of the Sheet metal cutting with each other, e.g. by soldering, welding, Flanging or the like, connected so that a Intermediate with a closed cross-sectional contour in The shape of a flat hollow body is created. The intermediate wall element or several intermediate wall elements designed in this way, at least in sections to the full Length to be unfoldable. This can, as before described, by the folded wall intermediate elements the desired volume expansion essentially without Material expansion take place. Thus, the volume of the to produce hollow body effectively while maintaining the full elasticity of the material can be increased. Further ensures the one-piece design of the intermediate wall element a simplification in the sheet metal blank handling, since not several individual sheet metal blanks have to be put together with a lot of work. In addition, joining zones are avoided, which means that The strength of the workpiece is increased.

Advantageous embodiments of the invention Intermediate are in the further claims described.

To facilitate the manufacture of the intermediate it offers advantages if this is at least an upper and comprises a lower sheet metal section, which essentially are arranged one above the other. This simplifies it Connect and seal the edge areas of the Intermediate product, which leads to the effective creation of a High pressure for an internal high pressure forming process is required.

In certain applications, there are advantages if a folding of the intermediate wall element in one area extends between the upper and lower sheet metal section. With such a training it is possible, as already mentions the wall intermediate element by internal high pressure in Cross section of the intermediate product seen from the inside of the through the intermediate formed cavity to the outside to press and to unfold and expand without material stretching stretch. Here, the wall intermediate element folded for example to double, triple or multilayer be arranged between the two sheet metal sections.

Alternatively, it provides for a uniform expansion of the Intermediate product advantages if at least one folding of the Wall intermediate element on the other folds of the Wall intermediate element protruding outwards is, i.e. has a different length. in this connection are mainly used in the hydroforming process the upper and lower sheet metal sections with pressure acted on, so that the wall intermediate element in Cross-section viewed from the outside inwards and closed a wall section of the resulting hollow body is unfolded.

For sealing the intermediate product for later use Applying internal high pressure, it is advantageous that the Sheet metal sections on their faces at least in sections with each other and / or with the end faces of the Wall intermediate element are connected. This will make a flat hollow body closed to the outside.

Furthermore, it has bridged an opening between the superimposed end faces of the sheet metal sections, due to the intermediate wall element arranged between them can be present as beneficial shown to arrange a spacer that with the Face of the sheet metal sections to the face Closing is connected.

To facilitate the insertion of the intermediate in it offers a mold for hydroforming further advantages if this is as a substantially flat Hollow body is designed.

For introducing the print medium into the intermediate product it is preferred that this a blow nozzle or the like includes. The blow nozzle can be on any Place in the sheet metal blank or the intermediate wall element be inserted and makes filling easier of the cavity enclosed by the intermediate with the Print media.

Brief description of the drawings

Fig. 1

eine perspektivische Ansicht einer ersten Ausführungsform eines erfindungsgemäßen Zwischenprodukts;

Fig. 2

eine vergrößerte Querschnittsansicht des erfindungsgemäßen Zwischenproduktes entlang der Linie II-II nach Fig. 1;

Fig. 3

eine vergrößerte Querschnittsansicht des erfindungsgemäßen Zwischenproduktes entlang einer Stirnseite mit eingelegtem Abstandsstück;

Fig. 4

eine perspektivische Ansicht eines erfindungsgemäßen Hohlkörpers, der aus dem Zwischenprodukt nach Fig. 1 hergestellt ist;

Fig. 5

eine schematische Querschnittsansicht einer zweiten Ausführungsform des erfindungsgemäßen Zwischenproduktes;

Fig. 6

eine schematische Querschnittsansicht einer dritten Ausführungsform des erfindungsgemäßen Zwischenproduktes;

Fig. 7

eine schematische Querschnittsansicht einer vierten Ausführungsform des erfindungsgemäßen Zwischenproduktes; und

Fig. 8

eine perspektivische Ansicht eines erfindungsgemäßen Hohlkörpers, der aus dem Zwischenprodukt nach Fig. 7 hergestellt ist.

In the following, some embodiments of the invention illustrated by way of example in the drawings are explained in more detail. Show it:

Fig. 1

a perspective view of a first embodiment of an intermediate product according to the invention;

Fig. 2

an enlarged cross-sectional view of the intermediate product according to the invention along the line II-II of Fig. 1;

Fig. 3

an enlarged cross-sectional view of the intermediate product according to the invention along an end face with an inserted spacer;

Fig. 4

a perspective view of a hollow body according to the invention, which is made from the intermediate of FIG. 1;

Fig. 5

a schematic cross-sectional view of a second embodiment of the intermediate according to the invention;

Fig. 6

a schematic cross-sectional view of a third embodiment of the intermediate according to the invention;

Fig. 7

a schematic cross-sectional view of a fourth embodiment of the intermediate according to the invention; and

Fig. 8

a perspective view of a hollow body according to the invention, which is made from the intermediate of FIG. 7.

Detailed description of preferred embodiments of the invention

That shown in Fig. 1 in a perspective view Intermediate 2 for producing a hollow body is made formed a single thin-walled sheet metal blank 4. there consists of the sheet metal blank 4 in the present case Aluminum, so that the workpiece mass can be kept low can and a particularly light intermediate 2 is provided. At the right and left in Fig. 1 recognizing oblique sides of the intermediate 2 are each Folds 6 in the form of an intermediate wall element 8 arranged or folded. The intermediate wall elements 8 are in one piece from a workpiece with sheet metal blank 4 formed, the folds 6 of the wall intermediate elements 8 into one by intermediate 2 trained flat cavity 10 extend. This cavity 10 is therefore completely surrounded by the sheet metal blank 4 and limited. Furthermore, the sheet metal blank 4 has two Top of the intermediate 2 located top Sheet metal sections 12 and one arranged on the underside lower sheet metal section 14. The upper sheet metal sections 12 are essentially parallel and coplanar over the lower one Sheet metal section 14 is placed and thus delimit the cavity 10 of the intermediate product 2 in its width and Longitudinal extent.

As can also be seen in FIG. 1, Edge areas 16 of the sheet metal blank 4 at the top of the Intermediate 2 connected. Here are yourself overlapping inner and outer surfaces of the upper Sheet metal sections 12 stacked and soldered, so that Intermediate 2 only in the direction of its longitudinal extent has a solder connection. Furthermore, the in Fig. 1 are front and rear end of the intermediate 2 shown end faces 18 of the intermediate product 2 so compressed that the sections between each Layers of the folds 6 lie on one another, one Connection, in this case by soldering is. The soldering can be done using the Nokolok soldering method in a continuous furnace, in which Potassium fluoroaluminate is used as a flux. So is the flat cavity 10 enclosed by the intermediate product 2 completely sealed to the outside, so that the Intermediate 2 for a subsequent one Hydroforming process can be used. For this is to introduce a hydraulic or pneumatic pressure medium in the cavity 10 of the Intermediate 2 at the top of intermediate 2 a blow nozzle 20 arranged.

2 are in an enlarged perspective Cross-sectional view along the line II-II of FIG. 1 die Folds 6 of the intermediate wall elements 8 into individual layers shown. According to this first embodiment of the intermediate product 2 according to the invention are the wall intermediate elements 8 mirror-symmetrical to each other between the upper and lower sheet metal section 12, 14 of the Sheet metal blank 4 arranged and protrude into the cavity 10 of the Intermediate 2 into it. The intermediate wall elements 8 are bent into double layers in this case and in the bending radii of the sheet metal blank 4 folded in four layers, see above that a flat hollow body is formed. Furthermore, in the Fig. 2 clearly recognize that the intermediate product 2 from a single sheet metal blank 4 is formed, the Edge areas 16 of the sheet metal blank 4 at the top of the shaped intermediate 2 with a certain overlap with each other e.g. connected by soldering, welding or gluing are.

In the enlarged shown in Fig. 3 Cross-sectional view is a compressed and im In the present case, the soldered edge area of an end face 18 of the intermediate product 2 shown. By in several Lies between outer edge portions 22 of the Intermediate product 2 provided intermediate wall elements 8 there is an opening in the central region of the cut, which to maintain a closed cavity with a according to the height of the layers of the intermediate wall element 8 executed spacer 24 made of sheet metal is sealed. Here, the spacer 24 in the Opening inserted and fixed to the top and bottom Sheet metal section 12, 14 and the adjacent areas of the Wall intermediate element 8 at points 23, e.g. by soldering, connected. The spacer 24 is preferably made of one the sheet metal blank 4 corresponding material. It however, can also be used to connect the End faces 18 suitable material, such as e.g. an aluminum alloy, steel, galvanized sheet or high-strength sheets.

The built up in the way shown above Intermediate 2 is then when using the Hydroforming process for one in FIG. 4 cuboid hollow body 26 shown formed. In which Hollow body 26 can be, for example, the basic shape act for a motor vehicle tank. To the Internal high-pressure forming is carried out, for example, using that in FIG. 1 blow nozzle 20 shown a high pressure liquid, such as an oil in which through the sheet metal blank 4 with the wall intermediate elements 8 trained flat cavity of the Intermediate initiated. Here, the print medium high enough pressure to hold the top and the bottom lower sheet metal section 12, 14 to move outwards and thus to remove from each other as well as the intermediate wall elements 8 unfold, i.e. the curved and / or folded wall intermediate elements 8 in their outstretched state. An im arises essentially rectangular or cuboid Hollow body contour, since the wall intermediate elements 8 only unfolded, but not under material stretch be deformed. For the final shape of the Hollow body 26 can this in a shape, not shown be inserted, the mold cavity of a desired Corresponds to the outer contour of the hollow body. By loading the sheet metal blank 4 with an increased internal pressure can the unfolded intermediate wall elements 8 and the remaining wall parts, such as the upper and the lower Sheet metal section 12, 14 in a subsequent process in Stretching or deep drawing processes in a known manner desired contour can be further formed. As in FIG. 4 the training is also clearly recognizable a one-piece hollow body 26, i.e. one Sheet metal blank 4, possible, which is therefore only a very small one Number of connection points and none over the entire scope has circumferential flanges. As a result, the hollow body 26 very good strength properties in contrast to conventional in the hydroforming process manufactured hollow bodies.

5 is a second embodiment of the intermediate 2 according to the invention schematically in Cross section shown. This differs from that in Fig. 2 shown intermediate 2 essentially with regard to the design of the intermediate wall elements 8. In the present case there are two intermediate wall elements 8 axisymmetric with respect to an axis, not shown arranged and bent into three layers. in this connection come the individual layers in the outer edge portions 22nd of the intermediate product 2 to lie on one another and allow when unfolding one in contrast to that shown in Fig. 2 Embodiment of intermediate 2 an even larger Expansion of the container volume. Thus, the number the layers formed in the intermediate wall element 8 Influence on the size of the volume to be manufactured Hollow body 26 are taken. Furthermore, the edge areas 16 of the sheet metal blank 4 via a solder connection 23 Formation of a flat hollow body attached to each other.

6 in a schematic cross-sectional view illustrated third embodiment of the invention Intermediate is opposite to that shown in Fig. 5 second embodiment with regard to the formation of the Folds 6 of the intermediate wall elements 8 designed differently. The intermediate wall elements 8, as in FIG can be seen in each case a fold 6, which over the outer edge portions 22 of the upper and the two lower Protruding sheet metal sections 12, 14. Accordingly, the in Fig. 6 shown intermediate wall elements 8 layers and thus also folds 6 of different lengths. At the Unfolding the intermediate 2 unfold individual folds 6 of the wall intermediate elements 8, wherein the long fold 6 moves from the outside in and closes a wall part of the hollow body to be manufactured becomes. Thus determines the size and length of those in the intermediate wall element 8 trained layers or folds Size of the inner cross section of the hollow body to be produced.

The one shown schematically in cross section in FIG. 7 fourth embodiment of the invention The intermediate product is different from that in FIG. 2 illustrated first embodiment, the wall intermediate elements 8 each designed differently. Here is the wall intermediate element shown on the right in FIG. 7 8 provided in three layers, while that in the Drawing left between the top 12 and the bottom Intermediate wall element 8 located in sheet metal section 14 is only double-layered. Through this different shape of the intermediate wall elements 8 is the formation of a partially unfolded Hollow body shape possible, as shown in Fig. 8.

In Fig. 8 is from the intermediate product 2 of FIG. 7 through the high pressure forming process of unfolded hollow body 26 shown schematically, the one-sided conical shape having. Thus, by providing a certain Number of 8 formed in the intermediate wall elements Lay the desired shape and geometry of the hollow body 26 be determined. At any point of the in FIG. 8 shown hollow body is also a not shown Connection, for example a blow nozzle 20, as in Fig. 1st shown, or any tube, for feeding the hydraulic or pneumatic pressure medium provided. By increasing the internal high pressure in the hollow body 26 For example, the upper sheet metal sections 12 expanded and deformed outward as in FIG. 8 is indicated by dash-dotted lines, however any other location of the hollow body 26 further extended and to the desired final hollow body contour can be deformed. For an exact shape, the Hollow body 26 inserted into a mold and the sheet metal blanks 4 by increasing the internal pressure on the contour of the not mold cavity shown to be brought to the plant.

Claims (16)

1. Method for producing a hollow body (26) from sheet metal, in particular aluminium or aluminium alloys, by the following step:

   a) Preparing a flat sheet metal blank (4),
   characterised by the following steps:

   b) Folding and/or bending of at least one wall-intermediate element (8), which is constructed in one piece with the sheet metal blank (4), into a plurality of superimposed layers;

   c) Positioning side by side, preferably on top of each other with a certain overlap and joining of edge regions (16, 18) of the sheet metal blank (4);

   d) Subjecting the sheet metal blank (4) and the folded wall-intermediate element (8) to a hydraulic or pneumatic internal high pressure, so that the folded wall-intermediate element (8) is freely unfolded to form the hollow body (26).
2. Method according to claim 1, characterised in that after the process step d) the unfolded wall-intermediate element (8) and/or the sheet metal blank (4) are deformed to a desired contour at least in sections by increased internal high pressure by the stretch-forming or deep-drawing process.
3. Method according to claim 1 or claim 2 , characterised in that within the framework of the process step b) at least one top and at least one bottom sheet metal section (12, 14) of the sheet metal blank (4) are placed on top of each other.
4. Method according to claim 3, characterised in that prior to the process step d) the superimposed sheet metal layers (12, 14) are connected at their front sides (18) at least in sections.
5. Method according to claim 3 or claim 4, characterised in that at least one spacer piece (24) is arranged between the superimposed front sides (18) of the sheet metal sections (12, 14), the spacer piece filling in a free space created by the lateral folds.
6. Method according to at least one of the claims 2 to 5, characterised in that at least one flap-like section is formed at the top and bottom sheet metal section which after the process step b) is folded over onto the front side (18) of the bottom or top sheet metal section (12, 14) and is connected to this.
7. Method according to at least one of the preceding claims, characterised in that the flat sheet metal blank (4) is produced with an at least rectangular outline.
8. Method according to at least one of the preceding claims, characterised in that the folded sheet metal blank (4) before of after the process step d) is placed into a closable mould which is adapted to the shape of the hollow body to be produced.
9. Method according to at least one of the preceding claims, characterised in that oil at surrounding temperature or heated oil is used as the pressure medium.
10. Intermediate product for producing a hollow body (26) from sheet metal, in particular aluminium or aluminium alloys, which

    has a sheet metal blank (4),

    characterised by

    at least one wall-intermediate element (8) which is constructed in one piece with the sheet metal blank (4) and is folded and/or bent into a plurality of essentially superimposed layers, and

    edge regions (16, 18) which for forming the intermediate product (2) are connected to each other.
11. Intermediate product according to claim 10, characterised in that this comprises at least one top and at least one bottom sheet metal section (12, 14), which are arranged superimposed essentially parallel to each other.
12. Intermediate product according to claim 10 or claim 11, characterised in that a fold of the wall-intermediate element (8) extends in a region between the top and bottom sheet metal section (12, 14).
13. Intermediate product according to at least one of the claims 10 to 12, characterised in that the sheet metal sections (12, 14) are connected to each other at their front sides (18) at least in sections.
14. Intermediate product according to at least one of the claims 10 to 13, characterised in that at least one spacer piece (24) is arranged between the superimposed front sides (18).
15. Intermediate product according to at least one of the claims 10 to 14, characterised in that this is essentially a flat hollow body.
16. Intermediate product according to at least one of the claims 10 to 15, characterised in that this comprises a blow nozzle (20).

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