DE102008017922B4 - Laser welding connection of plastic pipes with other plastic parts - Google Patents

Abstract

Laser welding method for producing a connection (1) of a plastic tube (2) with another plastic part (3), in which one end (4) of the plastic tube (2) is overlapped with a tubular end (5) of the other plastic part (3), wherein the plastic pipe end (4) and the plastic part end (5) in the region of the compound (1) an inner dimension (6) and an outer dimension (7), and wherein the largest outer dimension (7) of the in the region of the compound (1) inside End (4, 5) is greater than the smallest inner dimension (6) of the outer end in this area (5, 4), whereby between the two ends (4, 5) forms a contact pressure, the mutual thermal contact during laser welding improved, and wherein the mated ends (4) of the plastic tube (2) and the other plastic part (3) consist predominantly of polyamides, characterized in that - the mated ends (4) of the plastic tube (2) and the and the plastic part (3) are held in place without the use of a mandrel during which a laser beam used for welding is guided around the fixed pipe connection, and that - the laser beam is directed around the fixed pipe connection by means of optical components, and in that - the plastic pipe end (4 ) and the plastic part end (5) have a rotationally symmetrical cross section, wherein the smallest inner dimension (6) is an inner diameter and the largest outer dimension (7) is an outer diameter, and in that - the plastic pipe end (4) via the plastic part end (5) is inserted, and in that - the inner plastic part end (5) has at least one outer surface (8) substantially impermeable to laser light, and the plastic tube end (4) is substantially transparent at least in the region of the intended connection (1) for laser light, the plastic tube end (4) being laser light is irradiated until the irradiated Au heat and melt the outer surface (8) of the plastic part end (5) and the inner surface (9) of the plastic pipe end (4) pressed on it, so that a fusion bond (10) between the plastic pipe (2) and the other plastic part (3) at the irradiated point is formed, and that the plastic tube (2) is constructed multi-layered and an inner layer (11) which is not transparent to laser light, the plastic pipe end (4) in a first region (15) of the provided compound (1) all for Laser light are not transparent layers removed, so that only the laser light largely transparent layer of the plastic tube (2) on the plastic part end (5) rests and during laser welding with ...

Description

The invention relates to a laser welding method for establishing a connection of a plastic tube with another plastic part, in which one end of the plastic tube is mated with a tubular end of the other plastic part overlapping, wherein the plastic tube end and the plastic part end in the region of the connection have an internal dimension or an external dimension , and wherein the largest outer dimension of the inner end in the region of the connection is greater than the smallest inner dimension of the outer end in this area, whereby a contact pressure is formed between the two ends, which improves the mutual thermal contact during laser welding.

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 proportion of ethanol 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 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 pipe even comes loose from the connector. A similar observation as with fuel lines had to be made also with oil cooling lines, because even there the traditional connections (pine cone profiles) often fail because of the increased temperatures and pressures.

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

The joining 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 the 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.

Laser plastic welding is well-known and the freedom in coloring the components to be welded has hitherto been limited, and the absorption of the laser radiation in most cases is determined by the embedded additives such as pigments and not by the polymer matrix. Since these absorbers usually also have a pronounced intrinsic color in the visible range (in the case of carbon black, 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 shows strong absorption at the common laser wavelengths in the near infrared (NIR) range, no absorption in visible light (ie no intrinsic color, but optionally does 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, dyestuffs are known which, conversely, allow the laser beam to pass through, but cause a color impression in the visible region, that is to say color. laser-transparent color developments. Such laser-transparent dyes are used in the laser transmission welding in the top joint partner, if a self-color of the plastic part is desired for the end use.

The German patent application DE 103 04 071 A1 discloses forming a composite of at least two tubes which are radially telescoped and laser spot welded. However, such compounds do not allow a safe passage of liquids or fluids in the connected pipes, because no tight connections are achieved by the spot welding.

The German patent application DE 10 2005 010 193 A1 discloses a low cost method and apparatus for joining plastic tubing employing a non-coherent light source (ie, not a laser).

In the DE 10 2005 052 825 A1 describes a method for producing a laser welding connection between a pipe connector and a pipe end, both made of polyamide, wherein the outer diameter of the pipe end has a slight oversize relative to the inner diameter of the connector and is inserted into the connector. The connector is well-transparent to the laser beam when the glass fibers of the fiber-reinforced connector according to the teachings of DE 10 2005 052 825 A1 are aligned parallel in the welding area. In this method, the laser beam remains in place and the connector with the inserted tube is rotated about a rotation holder about the longitudinal axis. There are no electrically conductive versions mentioned.

In the document WO 2007/046536 A1 (equivalent to EP 1 939 254 A1 ) flat glass fibers are used in laser welding to reduce the distortion. The 2A This document does not show any optical components for deflecting the laser beam, but the possibility that the material partners to be connected are stationary and instead the laser source itself can be guided along the welding path to be formed. As absorption additive for the laser beam, a very small amount of carbon black is used in the plastic, which results in the specified concentration no electrical conductivity.

In the document JP 2005-193614 A For example, as described in the preceding document, guiding the laser nozzle about the tubular article to create a welded joint between two polyamide tube ends is described in the examples. Also in this document are disclosed no electrically conductive embodiments, since 0.5 wt .-% carbon black only just as specified sufficient for a laser absorption, and also the second tube contains no soot.

From the German patent application DE 2 261 388 A 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 during welding at a speed of 1500 rpm. 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, an interference 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 object of the invention is to propose an alternative method in which the advantages of the laser welding method can be utilized and the disadvantages of the connections known from the prior art can be avoided.

This object is achieved with the laser welding method according to the invention according to the features of the independent claim 1. This laser welding method is used to create a compound of a plastic tube with another plastic part, in which one end of the plastic tube is mated with a tubular end of the other plastic part overlapping, wherein the plastic tube end and the plastic part end in the region of the compound have an internal dimension or an external dimension, and wherein the largest outer dimension of the inside in the region of the end of the connection end is greater than the smallest inner dimension of the outer end in this area, whereby forms a contact pressure between the two ends, which improves the mutual thermal contact during laser welding. The laser welding method according to the invention is characterized in that the mated ends of the plastic tube and the other plastic part consist predominantly of polyamides and are held without the use of a mandrel, during which a laser beam used for welding is guided around the fixed tube connection, that the plastic tube end and the plastic part end have a rotationally symmetrical cross-section, wherein the smallest inner dimension is an inner diameter and the largest outer dimension is an outer diameter that the plastic pipe end over the plastic part end is plugged that the inner plastic part end has at least one set for laser light largely impermeable outer surface and the plastic tube end is at least in the region of the intended compound for laser light largely transparent, the plastic tube end is irradiated with laser light until the irradiated outer surface of the plastic part end and the thereon Pressed inner surface of the plastic pipe end to heat and melt, so that at the irradiated point a fusion bond between the plastic tube and the other plastic part is formed, that the plastic tube is constructed multi-layered and includes an inner layer which is not transparent to laser light, wherein the plastic pipe end in a the first area of the connection provided all layers not transparent to laser light are removed, so that only the largely transparent to laser light layer of the plastic pipe on Kun the material dividing rests and forms a fusion bond with the laser welding with that, and wherein the inner layer is an ESD layer, which is connected in a second region of the intended connection electrically conductively connected to the other plastic part.

In this laser welding method, it is particularly preferred for the plastic part end to have an inner surface or an outer surface which comprises at least one relief structure that reduces the inner dimension or increases the outer dimension, as a result of which an increased contact pressure is formed when the two ends are plugged together, which further increases mutual thermal contact during laser welding improved.

Further preferred and inventive features emerge 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, thus improving the weld or the weld points.

The present invention will now be elucidated with reference to selected exemplary embodiments which are not intended to limit the scope of the invention. Showing:

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 inside dimension 6 or an external dimension 7 on. The largest external dimension 7 in the area of the connection 1 inside end 5 is larger than the smallest internal dimension 6 of the outer end in this area 4 , Preferably exceeds the largest external dimensions 7 this hose connection piece the smallest inside dimension 6 the plastic pipe end 4 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 external dimension 7 forms between the two ends 4 . 5 a contact pressure that improves 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 welded joints 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 to laser light. The plastic pipe 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 heats and melts, so that at the irradiated point at least one here substantially along the circumference of the two 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 joint (cf. 1 and 3 ) formed only a single circumferential and thus sealing weld. In contrast thereto, the laser welding connection according to the invention according to the second embodiment (cf. 2 ) a double circumferential weld on. Optionally, one of these two welds could be formed as a chain of a plurality of spaced welding spots (not shown).

If no completely circumferential weld is produced, and the welds serve only for mechanical anchoring, it is preferable to use a rubber seal, eg in the form of an O-ring, in addition to the punctiform welds. 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 welds, 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 with carbon black dyed 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 unirradiated 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 11 is 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 adjusted by means known per se additives such as Leitruß, carbon fibrils, graphite fibrils (carbon nanotubes), steel fibers, etc.

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 welded joint 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 in that the plastic part end 5 an outer surface 8th which has at least one outer dimension 7 Enlarged 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 surpasses the largest external dimension 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 generally by 15% to 70%. By this excess of the largest external dimension 7 forms between the two ends 4 . 5 a contact pressure that further improves 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 dimension 7 this hose connection piece the smallest inside 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 outer 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 corresponding oversize or undersize.

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 laser welding connection according to the invention 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 laser welding connection according to the invention 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 laser welding connection according to the invention 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 together, a fusion of the three weld seams can occur with one another, 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 for laser light are removed, so that only those for laser light are largely removed transparent outer layer and possibly the intermediate layer of the plastic pipe 2 at the plastic part end 5 rests and during laser welding with that a fusion 10 received. This inner layer 11 is 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 be converted into heat already 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 external dimension 7 in the area of the connection 1 inside end 5 is larger than the smallest internal dimension 6 of the outer end in this area 4 of the corrugated pipe 19 , Preferably also surpasses the largest external dimensions 7 this hose connection piece the smallest inside dimension 6 the plastic pipe end 4 at least the percentages already given above. By this excess of the largest external dimension 7 forms between the two ends 4 . 5 a contact pressure that improves 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 joints 10 (But at least one of them) preferably designed as circumferential welds. If the corrugated pipe 19 however, only serve as a protective tube such as for electrical cables, 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 pipe following welds 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 welded joints 10 ,

In contrast to the previously shown figures show the 10 to 12 an axial section through a hose connection piece, wherein 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 that 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 laser welding connection according to the invention was here on the formation of a (this time inner) holding hook 17 not waived.

As regards the oversize or undersize of the overlapping diameters of the two parts to be joined, the same preferred percentage values apply to the variant with the inserted tube as in the embodiments with the plugged-on tube.

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 outer diameter. However, it is expressly noted that a tube does not need to have a circular cross section in each case. So are oval, elliptical, triangular, square, hexagonal, octagonal, arbitrary polygonal and curved, deviating from the circular shape Tube cross-sections 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, the same parts are provided with the same reference numerals, even if not all parts are described in detail in each case. Any combinations of the illustrated or described embodiments that are obvious to one skilled in the art are within the scope of the present invention.

Special formulations 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) Rußeinfärbung 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.

As plastic or polymers, preference is given to predominantly using polyamides for the present invention, i. Homopolyamides, copolyamides, and their blends and mixtures, as known in the art. These polyamides can be dyed with laser-transparent dyes, so that the plastic pipes produced with them do not differ visually or only slightly from the known plastic pipes. Other additives, such as stabilizers (e.g., heat, hydrolysis, and UV stabilizers), reinforcing agents (e.g., glass fibers), and fillers are known to those skilled in the art and may be blended with the polymer composition as desired. The polyamides can be used in multi-layer composites together with layers of other polymers, e.g. 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, laser welding was performed on all three ribs (cf. 7 ). Cases C and D are embodiments of 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.

After plugging together each a connector and a plastic pipe section and the laser transmission welding in cases C and D, the thus obtained tubular test pieces were filled with an E50 mix fuel, sealed on both sides with a stopper and 500 hours at a temperature of 100 ° C and stored static under the thereby developing in the test pieces vapor pressure. This fuel mixture was composed of E50 (50% ethanol), 5% water, 1% methanol and 44% unleaded regular grade petrol (all in vol%). With this fuel mixture, which swells strongly due to the high proportion of ethanol, the quality of the compound was tested under extreme conditions.

After fuel storage, the test pieces were tested for connector pull-out force (force needed to pull plastic tubing off hose fitting) in accordance with SAE J 2260 standard. In this case, the minimum tolerable pull-out force according to SAE standards J 2044 and J 2045 must be greater than 300 N. The tightness was tested by blowing air into the test piece kept under water and by optically detecting leaking air bubbles. The pressure used to inject the air was 2 bar (gauge pressure). 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, the withdrawal forces necessary for releasing a conventional connection have dropped sharply. The laser welding connections, 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 with fuels having a high ethanol content.

In addition, the plastic pipes fastened with laser welding joints are immovable, i. non-rotating on the connectors or hose connectors. In fact, in the attempted pulling off of the welded lines from the hose connecting pieces, the breakage of the plastic pipe or even of the connecting piece was observed. To achieve the security against twisting would be sufficient to attach the conventional connector with some laser welding points. Of course, but to release a connector, which is attached with a weld, higher withdrawal forces are expended, so that this connection is preferable.

Because the swelling of the test pieces by the ethanol is particularly pronounced, this test, as stated above, represents an extreme burden on the tested joints. The results can also be applied to pipes for other swelling fluids, such as e.g. Biodiesel, oils, glycols, or be transferred to non-swelling fluids to achieve a higher load capacity. Of course, the laser welding connections according to the invention can also be used in conventional applications and then have the advantage of a greater safety margin and improved tightness.

As plastic for the plastic pipe 2 and the plastic part 3 are predominantly used polyamides, which are understood by the generic term "polyamides" homopolyamides, copolyamides, and their blends and mixtures. Preferably, the group comprising aliphatic, cycloaliphatic and partially aromatic (the latter eg in the form of polyphthalamides) polyamides, such as these (as well as their depending on the selected type of polyamide used monomers) per se are known in the art. For the assembled ends 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 around 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 particularly advantageous 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 completing 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 adapted, two- or three-dimensional curved complex geometry.

LIST OF REFERENCE NUMBERS

1

connection

2

Plastic pipe

3

Plastic part

4

End of plastic pipe, plastic pipe end

5

End of the other plastic part, plastic end piece

6

Internal dimensions

7

External dimensions

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

Claims (11)

Laser welding process to create 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 ) and an external dimension ( 7 ), and wherein the largest external dimension ( 7 ) in the area of the connection ( 1 ) inside end ( 4 . 5 ) is larger than the smallest inner 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, and wherein the mating ends ( 4 ) of the plastic pipe ( 2 ) and the other plastic part ( 3 ) consist predominantly of polyamides, characterized in that - the mating ends ( 4 ) of the plastic pipe ( 2 ) and the other plastic part ( 3 ) are held without using a mandrel during which a laser beam used for welding is directed around the fixed pipe joint, and that - the laser beam is directed around the fixed pipe joint by means of optical components, and that - the plastic pipe end ( 4 ) and the plastic part end ( 5 ) have a rotationally symmetrical cross section, wherein the smallest inner dimension ( 6 ) an inner diameter and the largest external dimension ( 7 ) is an outer diameter, and that - the plastic pipe end ( 4 ) over the plastic part end ( 5 ) is plugged, and that - the inner plastic part end ( 5 ) at least one outer surface which is substantially impermeable to laser light (US Pat. 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, and that the plastic pipe ( 2 ) is multilayered and an inner layer ( 11 ), which is not transparent to laser light, wherein 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 ) rests and during laser welding with that a fusion compound ( 10 ), and wherein the inner layer ( 11 ) is an ESD layer which 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, characterized in that the plastic part end ( 5 ) an outer surface ( 8th ), which at least one of the external dimensions ( 7 ) enlarged 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 or 2, 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 2, 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 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 5 or 6, characterized in that the largest external dimension ( 7 ) the smallest internal dimension ( 6 ) exceeds by 15% to 70%, preferably by approximately 41%. Laser welding method according to claim 3, 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 enamel joints and / or non-circumferential welds. Laser welding method according to one of the preceding claims, 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 aliphatic, cycloaliphatic and partially aromatic polyamides. Laser welding method according to claim 9, 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.

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