Liquid line with a plastic corrugated hose

Abstract

Liquid line (1), in particular for a cleaning device in a vehicle, comprising at least one corrugated hose (2) and at least one connector (3) for connecting the liquid line (1) to another component, wherein the corrugated hose (2) has alternating outer bulges (8) and inner bulges (9) in cross-section; wherein the corrugated hose (2) and the connector (3) are made of plastic and are connected to each other by at least one welded joint (4); wherein the welded joint (4) is produced by means of a laser welding process; wherein the welded joint (4) is leak-tight at least up to a defined operating pressure in the liquid line (1); wherein a stop (5) is formed in the connector (3) which defines an axial end position of the corrugated hose (2) in the connector (3);• wherein the connecting piece (3) is made of a laser-transparent plastic and has a pipe section (6) which radially surrounds an end section (7) of the corrugated hose (2) comprising at least one outer bulge (8), characterized in that the end section (7) is prepared separately by flattening a radially outer tip of the at least one outer bulge (8) to a defined calibration diameter (Dk), which is selected to be smaller than an uncalibrated outer diameter (Da) of the corrugated hose (2) (Dk < Da) such that the end section (7) is received in the pipe section (6) with an interference fit, and wherein the welded joint (4) is formed in a region of a contact surface between the at least one calibrated outer bulge (8) of the end section (7) of the corrugated hose (2) and an inner wall of the pipe section (6).

Description

The invention relates to a liquid line with a corrugated hose made of plastic. Fluid lines with a corrugated plastic hose are well-known and widely used. For example, such fluid lines are used to convey washer fluid in vehicle cleaning systems. During manufacturing, the corrugated hose is cut to the required length and fitted with appropriate connectors at each end to quickly connect the fluid line to other components and assemblies such as nozzles, pumps, tanks, etc. Such a connection must be hydraulically leak-proof to withstand the operating pressure within the fluid line permanently, which is usually up to 5 bar. The cross-section of a corrugated hose wall consists of an alternating sequence of outward and inward bulges. This design makes the hose flexible and pressure-resistant, and also provides high resistance to kinking. However, for the same reason, a reliable seal when connected to other components presents a challenge. For example, German patent DE 103 22 972 A1 discloses an established solution for producing a tensile-resistant and pressure-tight connection. According to this method, the corrugated hose is sealed in the connector with an O-ring and secured with a separate retaining ring. However, the large number of components used, the associated increased effort for logistics, assembly, quality control, as well as long production cycle times and material costs, are considered areas for improvement. From CN 110 594 516 A, a cable consisting of a corrugated plastic hose and plastic push-fit connectors is known, in which the corrugated hose is connected to the push-fit connector via a welded joint produced by a laser welding process. The push-fit connector is made of a laser-transparent plastic and has a tubular section for this purpose. The corrugated hose is inserted into the tubular section and welded to it radially from the outside using a laser beam. The proposed solution, however, requires special measures in the tooling to position the corrugated hose and connector correctly relative to each other and to hold them in place during welding, resulting in comparatively high manufacturing costs and a long cycle time. Process reliability and consistency of results appear to be in need of improvement, particularly for small-diameter hoses. German patent DE 103 22 090 A1 proposes welding a corrugated hose at its end or cut edge to the bottom of a groove using an axially aligned laser beam. The groove is formed by a circumferential rim projecting radially from a connecting piece and featuring an axially extended edge. Such a method requires high precision in cutting the corrugated hose to length and a defined axial contact pressure during the welding process. Therefore, it is prone to malfunctions and, from a production engineering perspective, in need of optimization. The maximum achievable tensile strength also requires improvement. Further state of the art is DE 103 36 494 A1 . Against this background, the invention aims to propose an improved fluid flow system which, in particular, enables effective manufacturability with high process and quality reliability. This problem is solved by a fluid line with the combination of features according to claim 1. The combination of features according to the independent method claim defines a connection method for a generic fluid line. Further developments and embodiments of the invention are described in the dependent claims and the following description and figures. Individual details and advantages of the invention are explained in more detail below using an exemplary embodiment. Figure 1 shows an exemplary partial view of a liquid line. Figure 2 shows an embodiment of the liquid line in axial section through the connector. Figure 3 shows a connector in top view and axial section. Figure 4 shows an enlarged view of the stop profile. Fig. 1. Fig. 1 shows by way of example a section of a liquid line 1 according to the invention using the example of a cleaning agent line for a cleaning device of a motor vehicle. A hydraulically tight connection piece 3 is attached to one side of a corrugated hose 2, which serves for a quick connection of the liquid line 1 to a unit, assembly, or another component. The connector 3 is directly laser-welded to the corrugated hose 2, as explained in more detail in Fig. 2 below. For this to work, the connector 3 must be made of a laser-transparent plastic. It is entirely possible to make both components from the same laser-transparent base material, with a suitable coloring agent (such as carbon black) being added to the base material for the corrugated hose 2 to reduce or eliminate its transparency. Fig. 2 Fig. 2 shows one end of the liquid line 1 according to Fig. 1 in axial section. In the illustrated embodiment, the connecting piece 3 is designed with a nozzle 16 and is essentially rotationally symmetrical about a central axis A. However, other embodiments, for example with a receiving cavity instead of a nozzle, angled instead of straight, etc., remain permissible within the scope of the invention. The connector 3 has a pipe section 6 on the corrugated hose side, into which the corrugated hose 2 engages with a separately prepared end section 7. Pipe section 6 has a defined inner diameter Di. The corrugated hose 2 has a cross-section consisting of an alternating sequence of overlapping outer bulges 8 and inner bulges 9 and has an outer diameter Da > Di. The end section 7 of the corrugated hose 2 is therefore calibrated to a defined calibration diameter Dk < Da. For a reliable pressure-tight connection, the end section 7 should preferably comprise at least 3 corrugations of the corrugated hose 2. The calibration diameter Dk is selected such that the end section 7 is received in the pipe section 6 with an interference fit. Such calibration can be carried out particularly effectively and quickly using a suitable device. In this process, the radially outer tips of the outer bulges 8 are plastically deformed and flattened at a defined temperature. In addition to reducing the diameter, this advantageously increases the contact area between the corrugated hose 2 and the pipe section 6. This allows the subsequent weld joints 4, 4', 4'' to be executed more reliably and with a wider profile. The calibration, together with the press fit used, also ensures that the corrugated hose 2 rests securely against the inner surface of the pipe section 6 across its entire circumference in the areas of the future weld joints 4, 4', 4'', without any air gap. This reduces the precision requirements for aligning and focusing the laser beam 17, thereby allowing for a simpler and more cost-effective welding tool design. In order to position the corrugated hose 2 in relation to the connector 3 in a defined axial position with high precision and reproducibility without additional measuring and alignment effort for the welding process, a stop 5 is formed in the connector. The corrugated hose 2 simply needs to be inserted into pipe section 6 until it rests against the stop 5, thus automatically reaching its desired axial end position. This significantly reduces assembly errors and inspection effort. During manufacturing, the corrugated hose 2 can be used as a continuous length, fitted with the connector 3 at one end, and only then measured and cut at the other end. The resulting length tolerances can therefore be halved compared to a method where the corrugated hose is first cut to a defined length and only then fitted with connectors at both ends. To further improve the precision of positioning the corrugated hose 2, the stop is designed with a cross-sectional profile that is essentially complementary to the corresponding end of the corrugated hose 2 along its entire length. This ensures that the axial contact surface between the corrugated hose 2 and the connector 3 extends across the entire radial length of the corrugated hose wall. The negative effects of angular tolerances and other cutting errors during the lengthening of the corrugated hose 2 on the precision of its axial positioning in the connector 3 are thus significantly reduced or even completely eliminated. For further details on the stop 5, please refer in particular to Fig. 4. To eliminate any potential influence of cutting errors during the lengthening of the corrugated hose 2 on the nearest weld joint 4'* and to further simplify the insertion of the end section 7 into the pipe section 6, the corrugated hose 2 should preferably end, be cut, or be shortened within the course of an inner curve (9). Particularly preferably, the cut or the end of the corrugated hose should pass through the radially inner low point of the inner curve 9, as shown in Fig. 2. To further simplify the assembly of the corrugated hose 2 in the connector 3, to stabilize the position of the end section 7, and to prevent possible kinking or misalignment of the corrugated hose in the connector, the connector is equipped with a guide element 10. In the preferred embodiment shown, the guide element is designed as a tubular projection which is aligned coaxially with the pipe section 6 and engages axially on one side in the corrugated hose 2 or end section 7. This creates a receiving space 11 in the radial direction between the guide element 10 and the pipe section 6, in which the end section 7 of the corrugated hose 2 can be securely and protected. After the end section 7 is inserted into the pipe section 6 up to the stop 5, weld connections 4, 4', 4'' are created simultaneously or sequentially in the area of ​​the contact surfaces between the calibrated outer bulges 8 of the end section 7 and the inner wall of the pipe section 6 using radial or rotational optical laser technology. Fig. 3 Fig. 2 serves in particular to illustrate the design of a preferred embodiment of the connector 3. It is especially noteworthy that the pipe section 6 is provided with an internal chamfer 14 at its end facing the corrugated hose, and the guide element 10 has a tapered section 15 on one side. These design elements act as a kind of insertion ramp during the assembly or insertion of the corrugated hose 2 into the connector 3, further facilitating this process. Equivalent solutions, such as various types of bends or radii, are also permissible within the scope of this invention. Furthermore, the connector 3 has a circumferential flange 12. The flange 12 has two radially opposite flattened flanks 13. These flanks improve handling when gripping, manipulating, and connecting the connector 3 during the installation of the liquid line 1 at its point of use, and can also be effectively used for product marking. Fig. 4 Fig. 4 shows a preferred embodiment of the stop 5 in an enlarged section. The figure makes it particularly clear that the cross-section of the stop 5 follows the course of the outer and inner curvatures 8, 9 from radially outside to radially inside, so that the corrugated hose 2 can be supported axially over its entire surface and not just at the cut edge against the stop 5. Reference symbol list 1 Liquid line 2 Corrugated hose 3 Connector 4 Welded joint 5 Stop 6 Pipe section 7 End section 8 Outer bulge 9 Inner bulge 10 Guide element 11 Receiving chamber 12 Flange 13 Flank 14 Inner chamfer 15 Tapered section 16 Nozzle 17 Laser beam Da Outer diameter Di Inner diameter Dk Calibration diameter A Center axis

Claims

Liquid line (1), in particular for a cleaning device in a vehicle, comprising at least one corrugated hose (2) and at least one connector (3) for connecting the liquid line (1) to another component, wherein the corrugated hose (2) has alternating outer bulges (8) and inner bulges (9) in cross-section; wherein the corrugated hose (2) and the connector (3) are made of plastic and are connected to each other by at least one welded joint (4); wherein the welded joint (4) is produced by means of a laser welding process; wherein the welded joint (4) is leak-tight at least up to a defined operating pressure in the liquid line (1); wherein a stop (5) is formed in the connector (3) which defines an axial end position of the corrugated hose (2) in the connector (3);• wherein the connecting piece (3) is made of a laser-transparent plastic and has a pipe section (6) which radially surrounds an end section (7) of the corrugated hose (2) comprising at least one outer bulge (8), characterized in that the end section (7) is prepared separately by flattening a radially outer tip of the at least one outer bulge (8) to a defined calibration diameter (Dk), which is selected to be smaller than an uncalibrated outer diameter (Da) of the corrugated hose (2) (Dk < Da) such that the end section (7) is received in the pipe section (6) with an interference fit, and wherein the welded joint (4) is formed in a region of a contact surface between the at least one calibrated outer bulge (8) of the end section (7) of the corrugated hose (2) and an inner wall of the pipe section (6). Liquid conduit (1) according to claim 1, characterized in that the flattening is produced thermally by plastic deformation. Liquid line (1) according to at least one of the preceding claims, characterized in that the end section (7) comprises at least three corrugations of the corrugated hose (2) such that at least three outer bulges (8) are flattened to the calibration diameter (Dk). Liquid conduit (1) according to at least one of the preceding claims, characterized in that the stop (5) has a profile which in its entire radial extension is essentially completely complementary to the corresponding end of the corrugated hose (2). Liquid conduit (1) according to at least one of the preceding claims, characterized in that the corrugated hose (2) terminates at the stop end within the course of an inner bulge (9), in particular at the radially inner low point of the inner bulge (9). Liquid line (1) according to at least one of the preceding claims, characterized in that the connecting piece (3) has a guide element (10) which engages axially at its end in the corrugated hose (2). Liquid line (1) according to claim 6, characterized in that the guide element (10) is designed to be tapered at least at the end on the corrugated hose side or inclined or curved radially inwards. Method for producing a liquid line (1) by means of a welded connection (4) between a corrugated hose (2) and a connector (3) for connecting the liquid line (1) to another component, wherein the (2) and connector (3) are made of plastic, wherein the connector (3) is made of a laser-transparent plastic and has a pipe section (6) which is configured to radially encompass an end section (7) of the corrugated hose (2), wherein the end section (7) comprises at least one outer bulge (8), characterized in that, prior to inserting the end section (7) into the pipe section (6), a radially outer tip of the at least one outer bulge (8) in the end section (7) is flattened to a defined calibration diameter (Dk), which is smaller than an uncalibrated outer diameter (Da) of the corrugated hose (2) (Dk < Da).- the calibrated end section (7) is subsequently inserted into the pipe section (6) up to a stop (5) and - at least one welded joint (4) is made in the area of ​​a contact surface between the at least one flattened calibrated outer bulge (8) of the end section (7) and the inner wall of the pipe section (6) by a laser welding process, Method according to claim 8, characterized in that the flattening of the at least one outer bulge (8) is carried out thermally in a suitable device by plastic deformation at a defined temperature.

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