EP2087304A1

EP2087304A1 - Casing for holding a fluid for a heat exchanger, method for producing a casing of this type and heat exchanger

Info

Publication number: EP2087304A1
Application number: EP07846868A
Authority: EP
Inventors: Joachim Kopp; Wolfgang Kramer; Karl-Heinz Staffa; Florian Moldovan; Haymo BRÖDER; Jörg BERGSCHNEIDER; Klaus Hassdenteufel
Original assignee: Behr GmbH and Co KG
Current assignee: Mahle Behr GmbH and Co KG
Priority date: 2006-12-04
Filing date: 2007-11-29
Publication date: 2009-08-12
Anticipated expiration: 2027-11-29
Also published as: CN101573578A; EP2087304B1; WO2008067940A1; DE102006057031A1; US20100051251A1

Abstract

The invention relates to a casing for holding a coolant for a heat exchanger (1) for motor vehicles, said casing having two side walls (22, 24 and 22a, 24a), two front walls (26, 28 and 26a, 28a), a cover (18 and 18a) and a base (20 and 20a) lying opposite the cover (18 and 18a), said base being provided with one or more openings (60) for receiving tubes, in particular connecting tubes such as flat tubes. According to the invention, the casing consists of a single formed, in particular folded, shaped part, said formed shaped part, in particular a sheet metal blank, forming the two side walls (22, 24 and 22a, 24a), the two front walls (26, 28 and 26a, 28a), the cover (18 and 18a) and the base (20 and 20a).

Description

Box for holding a fluid for a heat exchanger and method for producing such a box, heat exchanger

The invention relates to a box for holding a fluid for a heat exchanger, a method for producing such a box and a heat exchanger,

From EP 1 139 054 B1 a box for receiving a fluid for a heat exchanger is known.

This known box has a bottom with receiving slots for connecting tubes or flat tubes and a lid arranged opposite this base. This cover is formed integrally with the two end walls.

The invention has for its object to provide a cost-effective and easy to manufacture fluid box for a heat exchanger.

This object is achieved by a box for receiving a fluid for a heat exchanger, by a method for producing such a box for receiving a fluid and by a heat exchanger having the features of the respective independent claim. Advantageous embodiments and further developments are the subject of the dependent claims. The subject matters of the dependent claims relate both to the box according to the invention for receiving a fluid for a heat exchanger, to the inventive method for producing such a box and to the heat exchanger according to the invention.

According to the invention, in particular, a box for receiving a fluid is proposed, wherein the fluid is preferably a coolant, for which reason the box, without this being intended to represent a restriction, is also referred to below as a coolant box.

The coolant box, which is preferably intended for a heat exchanger, in particular for a heat exchanger of a motor vehicle, has two side walls, two end walls, a lid and a bottom.

It is specifically contemplated that the addressed walls, i. the end walls, the side walls, the bottom and the lid, an interior of the coolant box limit.

According to the invention, the coolant box consists of only one formed, in particular folded, molded part, the formed part, in particular a stamped sheet, forming the two side walls, the two end walls, the cover and the bottom.

Particularly preferably, the formed, in particular folded, molded part is soldered, in particular solder-plated. It can also be provided more preferably that in the coolant box the end walls are spaced apart and are preferably arranged parallel to one another, in particular transversely to a longitudinal direction of the box or coolant box. The same applies to the side walls, which are then arranged in particular in the longitudinal direction of the coolant box. Also, the lid and the bottom are in particular spaced from each other.

In particular, the molded part is a stamped sheet, which is foldable over or along predeterminable folding or folding or folding lines to the coolant box, wherein the two side walls, the two end walls, the lid and the bottom are formed.

The folding or folding or folding lines are preferably arranged in transition regions between in each case two of the above-mentioned walls.

If appropriate, the molded part can be processed before or after folding by other shaping methods, such as a drawing method, in particular a deep-drawing method, and / or hydroforming and / or compression molding.

Furthermore, at least one of the side walls (22, 24 or 22a, 24a) preferably has a bulge, in particular for receiving a neck, in particular a nozzle with a large diameter.

Here it can be further preferred that the lid has a corresponding bulge, which is substantially adapted to the course of the side walls, in particular to the bulge for receiving the nozzle in the side walls. The floor is preferably curved.

One or more receiving openings for pipes can be provided in the floor, in particular for connecting pipes. The tubes can be designed, for example, as flat tubes and be part of a tube-ribbed block. It can also be provided that a separate opening in the bottom is provided for each separate tube. But it can also be provided a large opening for receiving all the tubes of the tube-fin block.

Preferably, it can also be provided that one of the above-mentioned, the interior of the coolant box defining walls has a, in particular laterally arranged and / or bendable, tab and / or up position.

The at least one tab and / or installation can be angled such that it is arranged substantially parallel to a connection wall and / or connected thereto, in particular by a solder connection.

Also, in the molded part, one, in particular a plurality, substantially triangular, recess may be formed in a transition region between each two walls. This can be provided in particular to simplify a processing of the one-piece molding, in particular a bending or folding or flaps.

It can further be provided that a depression is provided in the lid, into which extends a partition which divides the interior of the coolant box into sub-chambers. In a preferred embodiment, the lid is U-shaped in cross-section so as to form two spaced-apart flanges connected by an intermediate connecting portion, a lid base. This U-shape can be formed for example from vertical or approximately vertical sections. Rounded designs are also preferred.

The lid may be arranged in the coolant box, so that the flanges surround the side walls of the coolant box from the outside or from the inside.

In a particularly preferred embodiment extend from the flanges of the U-shape, which are also referred to as legs, tabs, which are particularly preferably arcuately shaped. These tabs preferably surround the side walls of the coolant box. It can preferably be provided that the cover is arranged in the coolant box, that the flanges protrude in the direction away from the bottom of the coolant tank direction of the connecting portion and connect at the ends located in this direction the tabs, which are then bent outward, so that they embrace the side walls of the coolant box from the outside. It is provided in particular that - seen in the longitudinal direction of the coolant box - a plurality of spaced such tabs are provided on the lid.

In the inventive method for producing a box for receiving a fluid, such as a coolant, for a heat exchanger, in particular for the production of the coolant box according to the invention, an interior of the box through walls, in particular by two Side walls, two end walls, a lid and the lid opposite the bottom, limited.

In the manufacture of the coolant box, a one-piece part, in particular a stamped sheet, is produced in a first step by a separation method, in particular by punching, wherein the one-piece part includes the walls bounding the interior of the box.

The one-piece part is reshaped in a second step to a substantially closed box, in particular bent or folded over or along predetermined bending or folding lines.

Subsequently, in a third step, the formed, one-piece part for forming the coolant box, in particular by solder plating, connected.

Of particular advantage is when folded over an end wall or both end walls.

Particularly preferably, it can also be provided that in the one-piece part, in particular in a region of the one-piece part which forms the bottom of the box, one or more openings for receiving pipes, in particular connecting pipes, such as flat tubes, is introduced or introduced.

The one or more openings for receiving tubes may or may be introduced before the second step, in particular after the first or simultaneously with the first step. Furthermore, it is of particular advantage if one or more tubes, in particular connecting tubes, such as flat tubes, in particular before the second step, are inserted into the one or more openings.

It can also be provided that the one-piece part is processed by further shaping processes, in particular drawn, in particular thermoformed, and / or hydroformed and / or molded.

The heat exchanger, in particular a radiator for a motor vehicle, has a tube-fin block and a box or coolant box according to the invention, wherein tubes of the tube-and-fin block open into the bottom of the box in the latter.

Embodiments of the invention will be explained below with reference to the figures. It shows:

1a shows an exemplary heat exchanger according to the invention, which is designed as a cooler, with an exemplary box according to the invention for receiving a fluid, which is here a coolant box th;

Fig. 1 b, the heat exchanger of Figure 1 in a view from above.

Fig. 1c is a side view of the heat exchanger of FIG. 1;

Fig. 2a is a unit of a coolant box of the heat exchanger of Figure 1, which has two side walls, two end walls and a bottom in plan view of one of the two side walls. FIG. 2b shows the unit according to FIG. 2a in plan view of the floor; FIG. Fig. 2c, the unit of FIG. 2a in plan view of the other of the two

Side walls; Fig. 2d is a partial sectional view taken along the line AA of Fig. 2b; 3a shows an exemplary design of a lid of a box according to the invention in side view, this design of the lid is given in particular in the design according to Figure 1 a to 3i.

FIG. 3b shows the cover according to FIG. 3a in plan view; FIG.

FIG. 3c shows the lid according to FIG. 3a in a three-dimensional oblique view from below; FIG.

Fig. 3d is a section along the line C-C of Fig. 3a; Fig. 3e is a section along the line D-D of Figure 3b in partial view.

Fig. 3f is a section along the line E-E of Fig. 3b;

Fig. 3g is a section along the line F-F of Fig. 3a;

Fig. 3h is a section along the line G-G of Fig. 3a; 3i is an oblique view of a tabbed portion of the lid of FIG 3a from above.

4 is a perspective view of a partially completed or fully folded integral unit 16 or 16a of the box according to the invention according to FIGS. 1a to 3i;

Fig. 5 is a plan view of a stamped from a sheet base plate, which forms the illustrated in Fig. 4, partially finished or fully folded one-piece unit 16 or 16a of the box according to the invention according to FIGS. 1a to 3i.

1 a to 5 show an exemplary embodiment of a heat transfer 1 according to the invention with a box according to the invention, produced by folding a one-piece part, for receiving a fluid. This box for holding a fluid is in particular a cooling middle box, so that in the following for simplification of the coolant box is spoken.

The heat exchanger 1 has a first coolant box 10 and a second coolant box 12 spaced therefrom, as well as a tube-and-finned block 14, which is arranged between these coolant box 10, 12.

The tube-fin block 14 has a plurality of parallel aligned connecting tubes, which are designed in this example as flat tubes, on. Between these connecting tubes are - formed transversely to their longitudinal direction - tube spaces in which ribs are arranged in a known manner, in such a way that the tube-fin block is transverse to the plane formed by the tube assembly of air flowed through.

The connecting tubes of the tube-fin block 14 each open at a first end into the first coolant box 10 and at its second end into the second coolant box 12.

The coolant boxes 10, 12 are each formed from a one-piece, folded (sheet metal) part 16 or 16a and consequently each have only one substantially closed (box-shaped) unit 16 or 16a.

The unit 16 or 16a has a lid 18 or 18a and on the lid 18 and 18a opposite side to a bottom 20 and 20a. Further, the unit 16, 16a, a first side wall 22 and 22a, one of these first side wall 22, 22a opposite second side wall 24, 24a, a the interior of the coolant box 10 and 12 in a first orientation of his (indicated by the double arrow 30) Longitudinal limiting first end wall 26 and 26 a and a this Interior of the first 10 and second coolant box in the opposite orientation (this longitudinal direction 30) limiting second end wall 28 and 28a.

The lid 18 or 18a, the side walls 22, 24 and 22a, 24a and the bottom 20 and 20a define the interior of the coolant box 10 and 12 respectively.

4 and 5 show how the lid 18 and 18a, the bottom 20 and 20a, the side walls 22, 24 and 22a, 24a and the end walls 26, 28 and 26a, 28a in the one-piece part 16 and 16a are connected and folded to the folded unit 16, 16a and the coolant box 10 and 12, respectively.

It should be noted that other basic configurations with other connections of cover 18 or 18a, bottom 20 or 20a, side walls 22, 24 and 22a, 24a and end walls 26, 28 and 26a, 28a in the one-piece part 16 and 16a - can be realized with the result, other folds or with other Faltreihenfolgen.

In the exemplary embodiment according to FIGS. 1 a to 5, which may also be different, the heat exchanger 1, which is also referred to as a cooler, can be functionally divided into two (part) coolers or (part) heat exchangers. For this purpose, seen in the longitudinal direction 30 at the same height in the two coolant boxes 10, 12, in each case transverse to this longitudinal direction 30, a partition wall 32 and 34 is provided. It is also possible to provide further partition walls arranged in the coolant boxes 10, 12 at different heights in the longitudinal direction 30 (which are not shown in the figures), which cause a serpentine deflection of the coolant. It may be provided, for example, that the upper part of the cooler in Fig.1a part of a high-temperature cooling circuit and the lower part of cooler 38 is part of a low-temperature circuit.

In the first coolant box 10 and in the second coolant box 12 respectively opens a main nozzle 40 and 42, via one of these main nozzle 40, 42 coolant can flow into the upper part of cooler 36 and wherein the other of these nozzles 40, 42, the coolant from the Upper part cooler 36 can flow out again.

In a corresponding manner, the lower part of the cooler 38 has a opening into the first coolant box 10 spigot 44 and an opening into the second coolant box 12 spigot 46, also here by one of these stub 44, 46 coolant can flow into the lower part of the cooler 38 and through the other of these nozzles 46, 44 can flow out of this lower part cooler 38.

In the region of the first coolant box 10, a drain screw 48 is further provided for discharging coolant. Further, in the region of the first coolant box 10, here in the region of the upper end, a nozzle 50 for the filling with coolant and / or the vent is provided.

Fig. 1 b shows a plan view of the design of FIG. 1a from above.

Fig. 1c shows a side view of the design of FIG. 1a from the left.

2a to 2d show different views of the first coolant box 10 and the closed by folding unit 16 of this first coolant box 10. However, in Figs. 2a to 2d, the lid 18 of Coolant box 10 is not shown, which is illustrated by 19 designated cutting edges in the transition between the lid 18 and the end wall 26 and and the end wall 28.

Figs. 2a and 2c show a plan view of the side walls 22 and 24 from the outside. Fig. 2b shows a plan view of the bottom 20 from the outside.

In Fig. 2a and 2c can be easily seen that the bottom 20 is formed wave-shaped. In cross section, the bottom 20 is curved.

FIG. 2 b clearly shows that slot-shaped openings are provided in the bottom for receiving the flat tubes of the tube / fin block 14.

Figs. 2a and 2c - as well as the Fig. 1a - are also well taken that the tube-rib block 14 remote from the end of the side walls 22, 24 is substantially substantially straight, and in the area in which the main nozzle is arranged, having a bulge.

This bulging is provided in particular, since the main nozzle 40 is dimensioned here correspondingly large.

It can be seen from FIGS. 2 a and 2 c that the dividing wall 32 does not extend as far as the end of the side walls 22, 24 facing away from the tube / fin block. Nevertheless, this partition 32 divides the interior 62 of the coolant box 10 into two sub-chambers 64, 66.

This is made possible because the lid, which is not shown in FIGS. 2 a to 2 d, projects as far as into the unit 16 after folding, so that it abuts against this dividing wall 32 substantially. Fig. 2d shows a sectional view taken along the line AA of Fig. 2b in partial view.

In Fig. 2d can be clearly seen that the wavy formed in the longitudinal direction 30 and curved between the side walls 22, 24 trained floor forms by its wave profile insertion bevels for the flat tubes of the tube-rib block 14. The slots 60 are arranged substantially in the region of the lower points of the wave profile - seen from the outside. The wave structure also achieves a certain stiffening effect in the area of the soil.

In Fig. 2d it can be seen that the transition region 68 between the bottom 20 and the end wall 26 and 28 is integrally formed, as well as the illustrated by the cutting edge 19, but not shown transition area 68 between the end wall 26 and the lid 18th

FIGS. 2c and 2d can also be easily seen that the end walls 26, 28 in their side walls 22, 24 facing end portions each have lateral tabs or lists 72.

These tabs 72 are in the longitudinal direction 30 and in the direction of the side walls 22, 24 of the end wall 26, 28 and are soldered, for example by means of Lotplattieren on the side walls 22 and 24 outside or inside.

Alternatively, it can also be provided that such tabs 72 are respectively provided on the side walls 22 and 24 at the appropriate location and these tabs are bent so that they extend in the direction of the end wall plane and on the corresponding end wall 26, 28 - in particular by means of solder plating - are soldered. 3a to 3i show an exemplary cover 18 of the coolant box 10, which is cut along the cut edges 19 from the one-piece part 16 and between the end walls 26 and 28, respectively.

3 a shows a top view of the cover 18, FIG. 3 c shows a three-dimensional view of the cover 18 from below, FIG. 3 d shows a sectional view along the line CC from FIG. 3 a, 3 e 3f is a sectional view taken along line EE of FIG. 3b, FIG. 3g is a sectional view taken along line FF of FIG. 3a, and FIG. 3h is a sectional view taken along line GG Fig. 3a.

FIG. 3i shows an oblique top view of the cover according to FIG. 3a in the region of tabs arranged at the end of the legs.

As seen in the longitudinal direction 30, the lid 18 has a substantially U-shaped cross-section, which can be clearly seen in FIGS. 3c, 3d, 3f, 3g, 3h and 3i.

This U-shape is formed approximately at right angles and is formed by two spaced-apart legs 82, 84, which may also be referred to as flanges, and a connecting section 86 connecting these two legs.

This cover 18 is inserted into the unit 16 on the side facing away from the bottom 20 of the unit 16 in the folding (see Fig.4), that the connecting portion 86 faces this floor and the legs 82, 84 in the bottom-facing direction of the Protrude connecting portion 16. Of the legs 82, 84 of the U-shaped profile extend a plurality of tabs 88th

These tabs 88 are designed arcuate in the embodiment. The tabs 88 extend from the ends of the legs 82, 84 facing away from the connection region 86, in particular bent outward. But these tabs 88 may also have a bent course instead of a curved course.

In the tabs 88 end portions of the side walls 22, 24 are received. In the region of these tabs, the side walls 22, 24 are soldered to the lid 18, in particular by solder plating. The lid 18 is in particular soldered so that a tight connection is formed, wherein in particular the method of Lotplattierens can be used.

The tabs 88 are arranged spaced apart as seen in the longitudinal direction 30, so that in this longitudinal direction 30, tab-free regions are formed on the legs 82, 84 between adjacent tabs 88.

Due to the size of the opening 40, the lid has a bulge, which is adapted to the shape of the side walls 22, 24 substantially.

The lid also has a recess 94. This depression extends transversely or perpendicularly to the longitudinal direction 30 approximately through the entire lid 18.

The recess 94, which here has a substantially rectangular cross-section, but may alternatively be provided with run-on slopes, or arched, serves to receive the partition wall 32. The recess 94 in particular also facilitates the soldering process, in that the dividing wall 32 can be introduced there and subsequently soldered. The soldering can be done in particular by means of solder plating.

FIGS. 4 and 5 are diagrams illustrating the folding of the one-piece part into the closed unit 16 or 16a of the coolant box 10 and 12 according to the invention as shown in FIGS. 1a to 3i.

FIG. 4 shows a perspective view of a partially finished or fully folded integral unit 16 or 16a. There are in particular the opposite, already folded, i. along the bending lines 22-1 and 24-1 upwardly curved, side walls 22 and 24 shown, and the bottom 20, which is curved here.

At the perspective further away lying longitudinal bottom end 20-1 integrally joins the partially already along the bending line 26-1 upwardly bent end wall 26 at. This is further integrally connected to the lid 18, wherein this is folded along the bending line 18-1 relative to the end wall 26. The further integrally connected to the lid 18 end wall 28 is bent relative to this along the bending line 18-2.

As FIG. 4 shows, the bulge 18-3 is formed in the cover 18, which is adapted substantially to the profile of the side walls 22, 24.

This one-piece unit 16, 16a is like Fig. 5 shows formed from a sheet, which was first punched (base plate, 16b) and was deep drawn where necessary. The base plate 16b, which already contains the preformed side parts 22, 24, the bottom 20, the end walls 26, 28 and the cover 18, is then folded to the closed unit 16 or 16a along the bending lines 22-1, 24-1, 26-1, 18-1 and 18-2. The folded base plate 16b is subsequently soldered.

By way of example, the folding of the end wall 26 will be briefly described here. In order to bring the end wall 26 in position, it is bent in the context of the manufacturing process to the bending or bending edge 26-1 upwards so that they with their side flaps 112, 114 at the front end of the already bent up side walls 22, 24 abuts or strike.

These tabs 112, 114 are then also bent, in such a way that they are arranged substantially parallel to the side walls 22, 24 and thus form areas for a solder connection with the side walls.

As can be clearly seen in FIG. 5, triangular recesses are provided in the regions 116, 118, which permit simplified bending.

Such tabs 112, 114 are also provided on the end wall 28.

In the base plate 16b, one or more openings 60 for receiving tubes, in particular connecting tubes, such as flat tubes, are introduced before the folding in the region which forms the bottom of the box 20. The openings 60 for receiving the tubes can also be introduced when punching the base plate 16 at the above-mentioned point. Before the folding of the base plate, it can also be processed by further shaping processes, in particular drawn, in particular thermoformed, and / or hydroformed and / or molded.

Preferably, the box 10, 12 made of metal, in particular aluminum.

It should also be noted that instead of a stamped and subsequently bent base plate 16b, the use of box profiles for the production of the coolant boxes 10 and 12 is possible.

Claims

Patent claims

1. box for receiving a fluid, such as coolant, for a heat exchanger (1), in particular for motor vehicles, with two side walls (22, 24 or 22 a, 24 a), two end walls (26, 28 or 26 a, 28 a), a Cover (18 or 18a) and a cover (18 or 18a) arranged opposite bottom (20 or 20a), in which one or more openings (60) for receiving pipes, in particular connecting pipes, such as flat tubes, are provided characterized in that the box consists of only one formed, in particular folded, molded part, wherein the formed part, in particular a stamped sheet, the two side walls (22, 24 and 22a, 24a), the two end walls (26, 28 or 26a, 28a), the lid (18 or 18a) and the bottom (20 or 20a) is formed.

2. Box according to one of the preceding claims, characterized in that at least one of the side walls (22, 24 or 22a, 24a) has a bulge, in particular for receiving a nozzle.

3. Box according to one of the preceding claims, characterized in that the lid (18 or 18 a) has a bulge which substantially to the course of the side walls (22, 24 or 22 a, 24 a), in particular to a bulge in the Side walls (22, 24 or 22a, 24a), is adjusted.

4. Box according to one of the preceding claims, characterized in that in the bottom (20 or 20a) one or more openings (60) for receiving pipes, in particular connecting pipes, such as flat tubes, are introduced.

5. Box according to one of the preceding claims, characterized in that the molded part has bending / folding or folding lines, in particular in transition areas between each two walls, over which the walls are foldable.

6. Box according to one of the preceding claims, characterized in that the deformed, in particular folded, molded part soldered, in particular solder-plated, is.

7. Box according to one of the preceding claims, characterized in that at least one of the end walls (26, 28 or 26a, 28a) has at least one, in particular laterally arranged and / or bendable, tab and / or installation.

8. Box according to one of the preceding claims, characterized in that the at least one tab and / or installation is angled such that they are arranged substantially parallel to one of the side walls (22, 24 or 22 a, 24 a), and / or connected to one of the side walls (22, 24 or 22a, 24a), in particular connected by a solder joint.

9. Box according to one of the preceding claims, characterized in that in the molded part at least one, in particular two, in particular substantially triangular, recess in a transition region between two walls, in particular between the bottom (20 or 20a) and one of the end walls (26, 28 or 26a, 28a) is formed.

10. A heat exchanger, in particular radiator for a motor vehicle, with a tube-fin block (14) and a box (10 or 12) according to one of the preceding claims, wherein the tubes of the tube-fin block (14) in the region of Bottom (20 or 20a) of the box (10 or 12) in these open.

11. A method for producing a box for receiving a fluid, such as coolant, for a heat exchanger (1), in particular for producing a box according to one of claims 1 to 9, characterized in that - in a first step, an integral part, in particular a Sheet metal, by a separation method, in particular by punching, is produced, wherein the one-piece part of an interior of the box bounding walls, in particular two side walls (22, 24 or 22a, 24a), two end walls (26, 28 and 26a, 28a ), a lid (18 or 18a) and a bottom (20 or 20a) arranged opposite the lid (18, 18a),

in a second step, the integral part is formed into a substantially closed box, in particular bent or folded along predetermined bending or folding lines, and in a third step, the deformed one-piece part is solder-plated, wherein the box is formed.

12. The method according to the preceding method claim, characterized in that in the forming over an end wall or folded over both end walls (26, 28 or 26 a, 28 a).

13. The method according to the preceding method claim, characterized in that the one-piece part before or after folding by other shaping processes, such as a drawing process, in particular In particular, a deep-drawing process, and / or a hydroforming and / or a compression molding, is processed.

14. The method according to the preceding method claim, characterized in that in the one-piece part, in particular in a region of the one-piece part, which forms the bottom of the box (20 or 20a), one or more openings (60) for receiving pipes , Especially connecting tubes, such as flat tubes, are introduced.

15. The method according to at least one of the preceding method claims, characterized in that the one or more openings (60) for receiving tubes before the second step, in particular after the first or simultaneously with the first step, are introduced.

16. The method according to at least one of the preceding method claims, characterized in that in the one or more openings (60) one or more tubes, in particular connecting tubes, such as flat tubes, are inserted.

17. The method according to at least one of the preceding method claims, characterized in that the one or more tubes are inserted before the second step.