DE102008017922A1 - Laser welding method for establishing connection of plastic pipe with plastic part in fuel pipes of motor vehicle, involves forming contact pressure between end of plastic pipe and end of plastic part - Google Patents

Abstract

The method involves sticking together an end (4) of a plastic pipe (2) with an end (5) of a plastic part (3) in an overlapping manner, where the ends respectively exhibit an inner dimension (6) and/or outer dimension (7) in the area of connection of the plastic pipe with the plastic part. The stuck ends predominantly consist of polyamide. Largest outer dimension of the ends lying inside the area of connection is larger than lowest inner dimension of the ends lying outside the area of connection. A contact pressure is formed between the ends.

Description

The The invention relates to a laser welding method for creating a Connection of a plastic pipe with another plastic part, wherein one end of the plastic tube with a tubular End of the other plastic part overlapped together is, with the plastic pipe end and the plastic part end in Area of the compound have an internal dimension or an external dimension, and being the largest outside of the area of the connection inside is greater than the smallest internal dimension of the in this area outermost end, resulting in between the two ends forms a contact pressure, the mutual Thermal contact during laser welding improved.

Connections between plastic pipes and other plastic parts are known for example in the automotive industry. There are in particular fuel pipes whose connections or their couplings must be connected to the plastic pipes used to conduct the fuel sealingly and safely. Due to the increasing ethanol content in the fuel, there is often a significant swelling in the fuel lines, which are softer so that traditional joints with Schlaucholiven, such as this z. B. off DE 38 43 995 C2 are known, or with Tannzapfenprofilen no longer withstand the increased pressure and tightness requirements. In the worst case, it comes to releasing a connection between the pipe and connector (eg., In the form of a quick coupling piece), so that they can be rotated against each other, or that the tube even dissolves from the connector. A similar observation as with fuel lines had to ge ge also be made of oil cooling lines, as there, the traditional compounds (pine cone profiles) often fail because of the increased temperatures and pressures.

Increasingly, such compounds are being produced by means of rotary friction welding (cf. EP 0 635 670 B1 ) or by gluing (cf. DE 103 36 494 A1 ) produced. However, it is known that in rotary friction welding due to the process resulting abrasion particles accumulate in the interior of the line and can contaminate it. Also by gluing may occur disturbing particles or even constrictions in the pipeline.

The connection of a plastic pipe with another plastic part by means of a laser welding process is out EP 1 403 030 A1 known. The outer layer of the plastic tube and the other plastic part, for example by means of addition of carbon black, calcium silicate or iron oxide for laser light impermeable, ie absorbing set. One end of the plastic tube is overlapped with a tubular end of the other plastic part. In addition, an intermediate piece made of a laser-transmissive (ie, laser-transparent) plastic is positioned so as to cover both a part of the plastic tube and a part of the tubular end of the other plastic part and to make good thermal contact with these two covered parts. Each covered part is heated by means of laser irradiation and thus connected to the melting in this area spacer with at least one circumferential weld. The other plastic part may be a pipe, a quick connector, a branch, a valve or a cover for the pipe.

Generally known is the laser plastic welding from the Article "Laser Plastic Welding in All Colors" by Böhm, Seiffert and Renner, published in 2004 in number 23 of the Swiss magazine "Technischen Rundschau" (Swiss Professional Media AG, Wabern, Switzerland) has been published. There is mentioned in particular that the freedom in the color of the components to be welded was previously limited, and that the absorption of the laser radiation is determined in most cases by the embedded additives such as pigments or dyes and not by the polymer matrix. Since these absorbers generally also have a pronounced intrinsic color in the visible range (in the case of Russ, for example, a deep black), a compromise between the technical design and the color wishes had previously been concluded. The ideal absorbing laser additive for use in transparent plastics exhibits strong absorption at the common laser wavelengths in the near infrared (NIR) range, no absorption in visible light (ie no intrinsic color, but may not disturb a visible color to the eye) and no optical scattering. It does not affect the mechanical properties of the polymer matrix, is not toxic and can be processed even at high injection molding temperatures. This is the reason why additives are of great interest in laser welding. On the other hand, dyes are known (cf the mentioned article from the "Technical Review"), which conversely indeed allow the laser beam to pass, but produce a color impression in the visible range, ie laser-transparent color developments. Such lasertransparenten dyes are used in the laser transmission welding in the overhead joint partner, if a natural color of the plastic part is desired for the end use.

The German patent application DE 103 04 071 discloses making a composite of we at least two tubes which are telescoped radially into one another and laser spot welded. However, such compounds do not allow for a safe passage of liquids or fluids in the connected tubes, because no dense connections are achieved by the spot welding.

The German patent application DE 10 2005 010 193 discloses a low cost method and apparatus for joining plastic tubing employing a non-coherent light source (ie, not a laser).

From the German patent application DE 2 261 388 is a generic method for welding a tail of plastic (polyethylene head, pigmented, low density) on a plastic body (polyethylene tube, transparent, high density) known. The end piece is supported by an inner mandrel and rotated at a speed of 1500 rpm during welding. So that the parts to be welded together touch as intimately as possible at the interface, so that as little material as possible needs to be melted to fuse the two parts, a press fit between the parts to be welded is preferably produced. Alternatively, a rib may be formed on the shell for producing a pressure contact between the head and the tube body. In any case, the tube body and head are mounted on a rotating mandrel and arranged so that the area to be welded is near the focal point of a lens that is irradiated by a laser beam. The surface of this mandrel is suitably polished so that maximum reflection of the laser beam is achieved. This method can serve well for welding straight pipes or tube bodies to a head or plastic part, but it has the disadvantage that the mandrel must be removed after welding, which can cause problems or even be impossible, especially in non-straight pipes ,

The The object of the invention is an alternative method to propose, in which the advantages of the laser welding process used and the disadvantages of the compounds known from the prior art can be avoided.

These The object is achieved with the laser welding method according to the invention according to the features of the independent claim 1 fulfilled. This laser welding process is for creating a connection of a plastic pipe with another plastic part, wherein one end of the plastic tube with a tubular End of the other plastic part overlapped together is, with the plastic pipe end and the plastic part end in Area of the compound have an internal dimension or an external dimension, and being the largest outside of the area of the connection inside is greater than the smallest internal dimension of the end lying in this area, resulting in between the two ends forms a contact pressure, the mutual Thermal contact during laser welding improved. The Laser welding method according to the invention is characterized in that that the mated ends of the plastic tube and the other Plastic part consist mainly of polyamides and without use of a thorn while holding one for welding used laser beam around the fixed pipe connection around is steered.

Especially is preferred in this laser welding process that the plastic part end an inner surface or an outer surface which has at least one inner diminishing the or Exterior dimensions of increasing relief structure, which when you put the two ends together an enlarged Contact pressure forms, the mutual thermal contact further improved during laser welding.

Further preferred and inventive features arise from the dependent claims.

• – Durch die Verwendung einer lasertransparenten Leitung und eines absorbierenden Konnektors (Standardprodukt schwarz) können die Dichtigkeit und die Konnektor Auszugskräfte deutlich verbessert werden. Ebenso ist eine extreme Verbesserung nach Kraftstofflagerung feststellbar.
• – Im Gegensatz zu dem aus dem Stand der Technik bekannten Laserschweissen (vgl. EP 1 403 030 A1 ) ist keine zusätzliche Hülse, d. h. kein zusätzliches Zwischenstück notwendig.
• – Durch den Einsatz von Reliefstrukturen am Konnektor wird der Wärmekontakt zwischen den beiden zu verschweissenden Komponenten intensiviert und damit die Schweissnaht bzw. die Schweisspunkte verbessert.

Advantages of the method according to the invention include:

• - By using a laser-transparent cable and an absorbent connector (standard product black), the tightness and the connector pull-out forces can be significantly improved. Likewise, an extreme improvement after fuel storage is noticeable.
• - In contrast to the known from the prior art laser welding (see. EP 1 403 030 A1 ) is no additional sleeve, ie no additional spacer necessary.
• - The use of relief structures on the connector intensifies the thermal contact between the two components to be welded and thus improves the weld seam or welding points.

The The present invention will now be described with reference to selected, exemplary embodiments, the scope of the invention should not be explained. there shows:

1 an axial section through a hose connection piece with attached plastic pipe, according to a first embodiment;

2 an axial section through a hose connection piece with attached plastic pipe, according to a second embodiment;

3 an axial partial section through a hose connection piece with attached plastic pipe, according to a third embodiment;

4 an axial section through a hose connection piece with attached plastic pipe, according to a fourth embodiment;

5 an axial partial section through a hose connection piece with attached plastic pipe, according to a fifth embodiment;

6 an axial section through a hose connection piece with attached plastic pipe, according to a sixth embodiment;

7 an axial partial section through a hose connection piece with attached plastic pipe, according to a seventh embodiment;

8th an axial partial section through a hose connection piece with attached plastic pipe, according to an eighth embodiment;

9 an axial section through a hose connection piece with attached plastic pipe, according to a ninth embodiment;

10 an axial partial section through a hose connection piece with inserted plastic pipe, according to a tenth embodiment;

11 an axial partial section through a hose connection piece with inserted plastic pipe, according to an eleventh embodiment;

12 an axial partial section through a hose connection piece with inserted plastic pipe, according to a twelfth embodiment.

1 shows a connection made with the laser welding method according to the invention 1 a plastic pipe 2 with another plastic part 3 , The plastic pipe 2 may be a mono tube or a multilayer tube. This is an end 4 of the plastic pipe 2 with a tubular end 5 the other plastic part 3 overlapped together. The plastic pipe end 4 and the plastic part end 5 show in the area of the connection 1 an internal dimension 6 or an external dimension 7 on. The largest outside dimension 7 in the area of the connection 1 inside end 5 is greater than the smallest internal dimension 6 of the end lying in this area 4 , Preferably exceeds the largest external dimensions 7 This hose connection piece the smallest internal dimension 6 the plastic pipe end 4 by at least 0.05 mm (eg in a typical automotive plastic fuel pipe with 6 mm inner diameter and 8 mm outer diameter), or more generally at least 1%. By this excess of the largest outside measure 7 forms between the two ends 4 . 5 a contact pressure that improves the mutual thermal contact during laser welding. Even more preferred is an excess of at least 5%, more preferably one of at least 10%.

In the in the 1 and 3 The laser welding connections shown became the plastic pipe end 4 over the plastic part end 5 plugged. The inside plastic part end 5 has at least one outer surface substantially impermeable to laser light 8th on and the plastic pipe end 4 is at least in the area of the intended connection 1 largely transparent for laser light. The plastic tube end 4 is irradiated with laser light (jagged arrow) until the irradiated outer surface 8th of the plastic part end 5 and the inner surface pressed thereon 9 the plastic pipe end 4 heated and melted, so that at the irradiated point at least one here substantially along the circumference of the the assembled ends 4 . 5 circumferential fusion 10 between the plastic pipe 2 and the other plastic part 3 is formed. In fact, in the first and third embodiments, the laser welding compound of the present invention (see FIG. 1 and 3 ) formed only a single circumferential and thus sealing weld. In contrast, the inventive laser welding compound according to the second embodiment (see. 2 ) a double circumferential weld. Optionally, one of these two welds could be formed as a chain of multiple, spaced welding points (not shown).

If no completely circumferential weld seam is produced at all, and the welding points serve only for mechanical anchoring, it is preferable to use a rubber seal in addition to the punctiform melting joints, eg. In the form of an O-ring. For such a seal would be in the overlap region of the plastic pipe end 4 and the plastic part end 5 make a job geometrically suitable.

At the location of or in addition to punctiform welded joints, a plurality of short, non-circumferential welds can generally also be formed. Especially preferred are three short welds, which are preferably uniform on the circumference of the plastic pipe end 4 or Kunststoffteilendes 5 are distributed and essentially the extent of one of these ends 4 . 5 consequences.

The 2 shows a compound produced by the laser welding method according to the invention 1 in which the plastic pipe end 4 over the plastic part end 5 was plugged. The plastic pipe end shown here 4 includes at least in the area of the intended connection 1 a largely impermeable for laser light, inner layer 11 (eg colored black with carbon black or antistatic). The thickness of this layer 11 is preferably adapted to the laser light used (ie, still so thin) that when irradiated together with the non-irradiated outer surface 8th of the plastic part end 5 heated and melted, so that at the irradiated point at least one fusion bond 10 between the plastic pipe 2 and the other plastic part 3 is formed. The inner layer is preferred 11 an ESD layer (ESD = electrostatically discharged), which covers the entire connection 1 electrically conductive with the other plastic part 3 , which is also electrically conductive here, is connected. The electrical conductivity of the ESD layer is determined by means of known additives such. B. Leitruss, carbon fibrils, Graphitfibrillen (carbon nanotubes), steel fibers, etc. set.

The third embodiment (cf. 3 ) differs from the first two in particular by the formation of a holding hook 17 in the form of a circumferential rib. This retaining hook 17 is suitable for securely holding the plastic pipe end 4 opposite to the preferably at the plastic part end 5 trained stop 18 until the welding connection 10 is made. In addition, with the retaining hook 17 the withdrawal force of the finished compound increases. Optionally, the formation of a stop 18 be omitted (not shown).

The 4 shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. This fourth embodiment of the laser welding connection according to the invention differs from the preceding ones in that the plastic part end 5 an outer surface 8th which has at least one outer dimension 7 magnifying relief structure 14 includes (shown here in the form of a circumferential bulge), resulting in the mating of the two ends 4 . 5 forms an increased contact pressure, which further improves the mutual thermal contact during laser welding.

Especially thanks to the relief structure 14 exceeds the largest external dimensions 7 the smallest internal dimension 6 the plastic pipe end 4 advantageously about 1 mm to about 4 mm (in a typical automotive plastic fuel line with 6 mm inner diameter and 8 mm outer diameter), or in general says about 15% to 70%. By this excess of the largest outside measure 7 forms between the two ends 4 . 5 a contact pressure, which further improves the mutual thermal contact during laser welding. Preferably, at least one circumferential fusion bond 10 on the relief structure 14 the other plastic part 3 arranged.

In preferred test pieces (see the test for the tightness of the compound shown below 1 and the connector pull-out forces) exceeds the largest external dimensions 7 This hose connection piece the smallest internal dimension 6 the plastic pipe end 4 around 2.5 mm or about 41%. The exemplary effective inner diameter of the plastic pipe end 4 and the exemplary effective outer diameter of the plastic part end 5 is 6 mm each. Through the relief structure 14 on the outside surface 8th of the plastic part end 5 increases the largest outside diameter 7 in this example to 8.5 mm or about 41%. Plastic pipes and plastic parts with different dimensions (larger or smaller diameters) achieve the same effects with appropriate over- or under-masses.

The 5 shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. In contrast to the fourth embodiment of the inventive laser welding connection was here on the formation of a holding hook 17 waived and there were two circumferential welds 10 produced in the form of sealing welds.

The 6 shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. In contrast to the fourth embodiment of the inventive laser welding connection was here on the formation of a holding hook 17 not waived and the relief structure 14 separated into two parts. Indeed were related to the two relief structures 14 and the widened retaining hook 17 three circumferential welds 10 produced in the form of sealing welds.

The 7 shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. In contrast to the sixth embodiment of the inventive laser welding connection was here on the formation of a holding hook 17 omitted, the relief structure 14 separated into three parts and in connection with the three relief structures 14 three circumferential welds 10 produced in the form of sealing welds. If these three weld seams are close enough to one another, a fusion of the three weld seams can occur together, so that a particularly wide weld seam is produced in this way.

The 8th shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. However, here in the eighth embodiment is the plastic pipe 2 multi-layered and includes an inner layer 11 which is not transparent to laser light. At the plastic pipe end 4 be in a first area 15 the intended connection 1 According to the invention, all layers which are not transparent to laser light are removed, so that only the outer layer which is largely transparent for laser light and possibly the intermediate layer of the plastic tube 2 at the plastic part end 5 rests and during laser welding with that a fusion 10 received. This inner layer is preferred 11 an ESD layer, which is in a second area 16 the intended connection 1 electrically with the other plastic part 3 is in intimate contact. The formation of a holding hook 17 in the second area 16 at the plastic part end 5 additionally improves the electrical contact of the ESD layer with the electrically conductive hose connector. An embodiment according to 8th offers itself when the laser-absorbing inner layer is so thick or contains such a high concentration of laser-absorbing additives that the greater part of the laser energy would already be converted into heat in this inner layer instead of at the contact point to the other plastic part 3 ,

The 9 shows how the preceding an axial partial section through a hose connection piece with attached plastic pipe. However, here in the ninth embodiment, the plastic pipe is a corrugated pipe 19 educated.

The largest outside dimension 7 in the area of the connection 1 inside end 5 is greater than the smallest internal dimension 6 of the end lying in this area 4 of the corrugated pipe 19 , Preferably also exceeds the largest external dimensions 7 This hose connection piece the smallest internal dimension 6 the plastic pipe end 4 at least the percentages already given above. By this excess of the largest outside measure 7 forms between the two ends 4 . 5 a contact pressure that improves the mutual thermal contact during laser welding. If the corrugated pipe 19 for conducting fluids (ie liquids, vapors or gases, eg fresh air), are the two welded connections 10 (But at least one of them) preferably designed as circumferential welds. If the corrugated pipe 19 however, only as a protective tube such. B. should serve for electrical lines, is a sealing connection between the plastic pipe end 4 and the plastic part end 5 unnecessary; in this case, a secure fixation of the corrugated pipe is sufficient 19 (Which is preferably carried out in the troughs) by means of a series of at least substantially the circumference of the corrugated tube following welding points and / or short, mutually non-contiguous welds. Again, attaching a relief improves 14 on the outside surface 8th of the plastic part end 5 the thermal contact with the corrugated pipe 19 while creating the welds 10 ,

In contrast to the previously shown figures show the 10 to 12 an axial partial section through a hose connection piece, in which the plastic pipe end 4 in the plastic part end 5 put into it. In the tenth embodiment of the compound produced by the laser welding method according to the invention 1 in which the plastic pipe end 4 in the plastic part end 5 is inserted, has the inner plastic pipe end 4 at least one outer surface which is largely impermeable to laser light 12 on. In contrast, the plastic part end 5 at least in the area of the intended connection 1 largely transparent to laser light. When creating the fusion 10 becomes the plastic part end 5 irradiated with laser light (jagged arrow) until the irradiated outer surface 12 the plastic pipe end 4 and the inner surface pressed thereon 13 of the plastic part end 5 heat and melt so that at the irradiated point a fuse 10 between the plastic pipe 2 and the other plastic part 3 is formed.

In an eleventh, alternative embodiment (cf. 11 ) includes the plastic part end 5 at the end additionally an inner retaining hook (circumferential rib) 17 ,

In one in the 12 illustrated twelfth embodiment (which in principle corresponds to a reversal of the fourth embodiment), has the plastic part end 5 an inner surface 13 on, which at least one the Innenmaß 6 decreasing relief structure 14 includes, whereby when mating the two ends 4 . 5 forms an increased contact pressure, which further improves the mutual thermal contact during laser welding. As in the fourth embodiment of the inventive laser welding connection was here on the formation of a (this time inner) holding hook 17 not waived.

What the over- or undersize of the overlapping Diameter of the two parts to be connected also applies in the variant with the inserted pipe the same preferred Percentages as in the embodiments with the plugged Pipe.

In all figures are plastic pipe end 4 and plastic dividers 5 shown, which have a rotationally symmetrical cross section. This is the smallest internal dimension 6 an inner diameter and the largest external dimension 7 an outside diameter. However, it is expressly noted that a tube does not need to have a circular cross section in each case. Thus, oval, elliptical, triangular, quadrangular, hexagonal, octagonal, arbitrary polygonal and curved, deviating from the circular tube cross-sections are conceivable and also known from the prior art. In addition, in special cases, the plastic part 3 also next to or at an angle to the axis of the plastic pipe 2 be attached. As an example of non-circular lines of a special hollow profile, in which the connectors are sometimes not mounted in the line of the axes, is on the EP 1 705 050 A1 directed.

In the figures are the same parts with the same reference numerals provided, even if not in any case, all parts in detail are described. Any combinations that are obvious to a person skilled in the art The illustrated or described embodiments include to the scope of the present invention.

Special recipes for laser transmissive, thermoplastic molding compositions are known from the European patent EP 1 240 243 B1 known. Here, instead of a single laser-transparent dye, at least two laser-transparent dyes are used in the polymer matrix, preferably in the complementary colors, which, according to color theory, gives a gray or dark color impression to the eye. Thus, a (laser-absorbing) black dyeing can be replaced by a combination of two laser-transparent dyes, if the finished article still a dark or direction black going color impression is desired. Such molding compositions can be used inter alia in the laser welding process shown here.

When Plastic or polymers are used for the present invention preferably used predominantly polyamides, d. H. Homopolyamides, Copolyamides, and their blends and mixtures, as known to those skilled in the art are. These polyamides can be laser-transparent with dyes be colored so that the plastic pipes produced with it visually of the known plastic pipes not or only slightly differ. Other additives, such as stabilizers (eg heat, Hydrolysis and UV stabilizers), reinforcing agents (e.g. As glass fibers) and fillers are known in the art and may be mixed with the polymer composition as required become. The polyamides can be combined in multilayer composites be used with layers of other polymers, for. B. with Barrier layers in fuel lines.

Experiment examples:

The tightness of the connection 1 and the connector extraction forces were tested by the behavior of a standard fir tree profile with three ribs or relief structures 14 (Cases A, B and C; 7 ) with the behavior of a hose connecting piece with a specially preferred relief structure (Case D, cf. 5 ) was compared under the influence of a strongly swelling medium. These four cases can be distinguished as follows based on the relief structure and the mounting conditions. Table 1: case Relief structure connector Mounting conditions pipe A Fir tree profile (Standard 1) plugged B Fir tree profile (standard 2) plugged C Fir tree profile (Standard 1) attached and laser welded D Specially preferred relief structure attached and laser welded

In case C, the laser welding was carried out on all three ribs (cf. 7 ). Cases C and D are embodiments according to the invention. For the test pieces, a single-layer, laser-transparent piece of a polyamide PA 12 plastic tube and another laser-absorbing black plastic member (connector) made of polyamide PA 12 with 30% glass fiber reinforcement and carbon black filling were selected.

To the mating of a connector and a plastic pipe piece and laser transmission welding in cases C and D became the tubular test pieces thus obtained filled with an E50 mix fuel, both sides with each closed with a stopper and during 500 hours at a temperature of 100 ° C and below that in Static storage of the test pieces developing vapor pressure. This fuel mixture was composed of E50 (50% ethanol), 5% water, 1% methanol and 44% unleaded regular gasoline (all information in% by volume). With this due to the high ethanol content strongly swelling On the polyamide acting fuel mixture could the quality checked the connection under extreme conditions become.

To In fuel storage, the test pieces became the connector pull-out force (required force to remove the plastic pipe from the Remove hose connection piece) in accordance with the SAE standard J 2260 tested. The minimum tolerable pull-out force must be according to SAE standards J 2044 and J 2045 than 300 N. The tightness was achieved by blowing air into it held under water test piece and by optical detection checked by leaking air bubbles. The pressure used for blowing in the air was 2 bar (overpressure).

All test pieces were also compared with corresponding test pieces (original) which had not been stored in fuel. In addition, the strength of the connector connection was checked by hand. The following results were achieved. Table 2: case original After storage in the fuel Force [N] tightness strength Force [N] tightness strength A 738 close firmly 220 close loose, mobile B 750 close firmly 270 close loose, mobile C 780 close firmly 509 close firmly D 714 close firmly 614 close firmly

As a result of these tests, it can be stated that all original compounds without long-term exposure to fuel meet the requirements. However, especially after long-term exposure of the test pieces to fuels with a high ethanol content, those used to dissolve a conventional ver binding necessary deduction forces fell sharply. The laser welding joints, however, always provide a secure connection, and the triggering forces required for release are well above the required limit even after long-term exposure of the test pieces to fuels in a range. On the other hand, in order to loosen conventional connections (cases A and B), lower withdrawal forces are sufficient than the 300 N specified as the tolerance limit, so that these conventional connector connections must be regarded as unsafe for use in fuels with a high ethanol content.

moreover sit the plastic pipes fastened with laser welding connections immovable, d. H. non-rotating on the connectors or hose connectors. In fact, when trying to peel off the most welded Lines from the hose connection piece the breakage of the plastic pipe or even the connecting piece observed. To achieve the security against twisting would in itself an attachment of the conventional connector suffice with some laser welding points. Of course but have to release a connector that fastened with a weld, higher pull-off forces be spent so that this connection is preferable.

Because the swelling of the test pieces by the ethanol especially pronounced, this test poses as already said above an extreme burden on the tested connections The results can also be displayed on leads for other swelling fluids, such as. B. Biodiesel, oils, glycols, or in non-swelling fluids to achieve a higher Resilience transferred. The inventive Laser welding connections can of course can also be used in conventional applications and then have the advantage of a larger safety reserve and the improved tightness.

As plastic for the plastic pipe 2 and the plastic part 3 polyamides are predominantly used, the term "polyamides" being understood to mean homopolyamides, copolyamides and their blends and mixtures, preference being given to the group comprising aliphatic, cycloaliphatic and partially aromatic (the latter, for example, in the form of polyphthalamides) polyamides, how these (as well as their monomers, depending on the type of polyamide used) are known per se to any person skilled in the art 4 of the plastic pipe 2 and the other plastic part 3 Especially preferred are polyamides selected from a group consisting of the aliphatic polyamides PA 6, PA 610, PA 612, PA 11 and PA 12, as well as polyphthalamides.

Plastic pipes made with such polyamides 2 and plastic parts 3 are particularly suitable for the production of fuel lines for motor vehicles, such as cars, motorcycles, ships and aircraft. The laser welding method according to the invention is particularly suitable for joining plastic pipes 2 and plastic parts 3 of fuel lines for motor vehicles, because these plastic pipes 2 and plastic parts 3 very often have a complex geometry (in particular, the tubes are often not rectilinear) and during the laser welding can not be moved or rotated. It is therefore of great advantage if according to the invention the laser beam and not the parts to be welded are moved.

One possibility is to move the laser source itself around the pipe joint. Preferably, for moving or deflecting the laser beam used for welding to the fixed, from the mating ends 4 of the plastic pipe 2 and the other plastic part 3 existing pipe connection, but optical components (lenses, prisms and / or mirrors), in particular a cone mirror used. Thus, only the laser beam is moved relative to the pipe joint to be welded and not the laser source itself.

It is of particular advantage that the laser welding method according to the invention for creating a connection 1 a plastic pipe 2 with another plastic part 3 is performed without using a mandrel. Thus eliminating the removal of the mandrel after finishing the welding. In particular, when connecting plastic pipes 2 and plastic parts 3 Of fuel lines for motor vehicles, it would even be impossible in most cases to remove the mandrel without destroying the pipe. This is because such fuel lines for motor vehicles, depending on the intended space or installation conditions in the engine compartment and the fuel tank, often have a, for example, by thermoforming generated for installation in the vehicles, two- or three-dimensional curved, complex geometry.

1

connection

2

Plastic pipe

3

Plastic part

4

The End the plastic pipe, plastic pipe end

5

The End the other plastic part, plastic part end

6

iNTERNAL DIMENSIONS

7

external dimension

8th

Outer surface of 5

9

Inside surface of 4

10

fusible link

11

inner layer

12

Outer surface of 4

13

Inside surface of 5

14

relief structure

15

first area of 1

16

second area of 1

17

retaining hook

18

attack

19

corrugated pipe

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3843995 C2 [0002]
• - EP 0635670 B1 [0003]
• - DE 10336494 A1 [0003]
• - EP 1403030 A1 [0004, 0013]
• - DE 10304071 A [0006]
• - DE 102005010193 A [0007]
• - DE 2261388 A [0008]
• EP 1705050 A1 [0046]
• - EP 1240243 B1 [0048]

Cited non-patent literature

• - Article "Laser Plastic Welding in All Colors" by Böhm, Seiffert and Renner, published in 2004 in number 23 of the Swiss magazine "Technischen Rundschau" (Swiss Professional Media AG, Wabern, Switzerland) [0005]

Claims (20)

Laser welding process for creating a connection ( 1 ) of a plastic pipe ( 2 ) with another plastic part ( 3 ), where one end ( 4 ) of the plastic pipe ( 2 ) with a tubular end ( 5 ) of the other plastic part ( 3 ) is overlapped, wherein the plastic pipe end ( 4 ) and the plastic part end ( 5 ) in the area of the compound ( 1 ) an inside dimension ( 6 ) or an external dimension ( 7 ), and wherein the largest external dimension ( 7 ) in the area of the connection ( 1 ) inside end ( 4 . 5 ) is greater than the smallest internal dimension ( 6 ) of the end lying in this area ( 5 . 4 ), whereby between the two ends ( 4 . 5 ) forms a contact pressure, which improves the mutual thermal contact during laser welding, characterized in that the mating ends ( 4 ) of the plastic pipe ( 2 ) and the other plastic part ( 3 ) are made predominantly of polyamides and are retained without the use of a mandrel while a laser beam used for welding is directed around the fixed pipe joint. Laser welding method according to claim 1, characterized that the laser beam by means of optical components around the fixed Pipe connection is directed around. Laser welding method according to claim 1 or 2, characterized in that the plastic pipe end ( 4 ) and the plastic part end ( 5 ) have a rotationally symmetrical cross section, wherein the smallest internal dimension ( 6 ) an inner diameter and the largest external dimension ( 7 ) is an outer diameter. Laser welding method according to claim 1, 2 or 3, characterized in that the plastic pipe end ( 4 ) over the plastic part end ( 5 ) is plugged. Laser welding method according to claim 4, characterized in that the inner plastic part end ( 5 ) at least one laser light is largely impermeable outer surface ( 8th ) and the plastic pipe end ( 4 ) at least in the area of the proposed connection ( 1 ) is substantially transparent to laser light, the plastic tube end ( 4 ) is irradiated with laser light until the irradiated outer surface ( 8th ) of the plastic part end ( 5 ) and the inner surface ( 9 ) of the plastic pipe end ( 4 ) and melted, so that at the irradiated point a fusion compound ( 10 ) between the plastic pipe ( 2 ) and the other plastic part ( 3 ) is formed. Laser welding method according to claim 4, characterized in that the plastic pipe end ( 4 ) at least in the area of the proposed connection ( 1 ) an inner layer which is largely impermeable to laser light (US Pat. 11 ), the thickness of which is adapted to the laser light used in such a way that it is irradiated together with the unirradiated outer surface ( 8th ) of the plastic part end ( 5 ) is heated and melted, so that at the irradiated point a fusion compound ( 10 ) between the plastic pipe ( 2 ) and the other plastic part ( 3 ) is formed. Laser welding method according to one of claims 5 or 6, wherein the plastic pipe ( 2 ) is multilayered and an inner layer ( 11 ), which is not transparent to laser light, characterized in that at the plastic pipe end ( 4 ) in a first area ( 15 ) of the intended connection ( 1 ) all non-transparent to laser light layers are removed, so that only the laser light for the most part transparent layer of the plastic tube ( 2 ) at the plastic part end ( 5 ) and during laser welding with that a fusion compound ( 10 ) received. Laser welding method according to claim 6 or 7, characterized in that the inner layer ( 11 ) is an ESD layer which over the entire compound ( 1 ) or in a second area ( 16 ) of the intended connection ( 1 ) electrically conductive with the other plastic part ( 3 ) is connected. Laser welding method according to claim 1, 2 or 3, characterized in that the plastic pipe end ( 4 ) in the plastic part end ( 5 ) is plugged. Laser welding method according to claim 9, characterized in that the inner plastic pipe end ( 4 ) at least one laser light is largely impermeable outer surface ( 12 ) and the plastic part end ( 5 ) at least in the area of the proposed connection ( 1 ) is substantially transparent to laser light, the plastic part end ( 5 ) is irradiated with laser light until the irradiated outer surface ( 12 ) of the plastic pipe end ( 4 ) and the inner surface ( 13 ) of the plastic part end ( 5 ) and melted, so that at the irradiated point a fusion compound ( 10 ) between the plastic pipe ( 2 ) and the other plastic part ( 3 ) is formed. Laser welding method according to one of the preceding claims, characterized in that the plastic part end ( 5 ) an inner surface ( 13 ) or an outer surface ( 8th ), which has at least one inner dimension ( 6 ) reducing or the external dimension ( 7 ) enlarging relief structure ( 14 ), whereby when mating the two ends ( 4 . 5 ) forms an increased contact pressure, which further improves the mutual thermal contact during laser welding. Laser welding method according to one of the preceding claims, characterized in that a plurality of punctiform melting connections ( 10 ) and / or non-circumferential welds substantially along the circumference of the two mating ends ( 4 . 5 ) getting produced. Laser welding method according to one of claims 1 to 11, characterized in that at least one substantially along the circumference of the two assembled ends ( 4 . 5 ) circumferential fusion compound ( 10 ) between the plastic pipe ( 2 ) and the other plastic part ( 3 ) will be produced. Laser welding method according to claim 11, characterized in that a plurality of punctiform melting connections ( 10 ) and / or non-circumferential welds or at least one circumferential fusion bond ( 10 ) on the relief structure ( 14 ) of the other plastic part ( 3 ) is arranged. Laser welding method according to one of the preceding claims, characterized in that the largest outer dimension ( 7 ) the smallest internal dimension ( 6 ) exceeds by at least 1%, preferably by 5%, more preferably by 10%. Laser welding method according to claim 14 or 15, characterized in that the largest outer dimension ( 7 ) the smallest internal dimension ( 6 ) exceeds by 15% to 70%, preferably by approximately 41%. Laser welding method according to claim 12, characterized in that in the overlapping region of the plastic pipe end ( 4 ) and the plastic part end ( 5 ) a rubber seal, preferably in the form of an O-ring, is used in addition to the punctiform welds and / or non-circumferential welds. Laser welding method according to one of the preceding claims, characterized in that the polyamides for the mating ends ( 4 ) of the plastic pipe ( 2 ) and the other plastic part ( 3 ) are selected from a group consisting of aliphatic, cycloaliphatic and partially aromatic polyamides. Laser welding method according to claim 18, characterized in that the polyamides for the mated ends ( 4 ) of the plastic pipe ( 2 ) and the other plastic part ( 3 ) are selected from a group consisting of the aliphatic polyamides PA 6, PA 610, PA 612, PA 11 and PA 12 and polyphthalamides. Use of the laser welding method according to one of the preceding claims for connecting plastic pipes ( 2 ) and plastic parts ( 3 ) of fuel lines for motor vehicles.