Method for producing hybrid pipes, and hybrid pipes

Abstract

The invention relates to a method for producing hybrid pipes having flange connections or screw-in connections arranged at the ends of said hybrid pipes, wherein a flange connection or screw-in connection is welded to a pipe section on at least one side. A fibre composite material is then wound around the pipe section and around part of the flange connection or screw-in connection which is welded on at least one side. The invention further relates to hybrid pipes produced according to the aforementioned method.

Description

[0001] Process for the production of hybrid pipes and hybrid pipes

[0002] The invention relates to a method for producing hybrid pipes and hybrid pipes produced by this method.

[0003] For the purposes of the present invention, hybrid pipes are thin-walled pipes wrapped with a fiber composite material. To use such a hybrid pipe for applications under internal pressure, it must be provided with a thickened section at the ends. This allows for flange or screw-in connections to be implemented at the respective ends of the hybrid pipes.

[0004] Thick-walled pipes are typically used to manufacture such hybrid pipes. These are machined to a smaller diameter from the outside, except for their end sections, and then the reduced-diameter section is wrapped with fiber composite material. The extensive material removal leads to very high material and manufacturing costs.

[0005] Furthermore, the significant material removal leads to deformation of the pipes and thus to undesirable out-of-roundness. This, in turn, compromises the function of the mating surfaces for seals, necessitating additional machining steps to rework the sealing surfaces.

[0006] Hybrid tubes are known, for example, from DE 31 21 506 C2. This tube comprises a pressure cylinder with a metallic inner tube, a metallic outer tube, and a core made of epoxy-bonded carbide material arranged between the outer and inner tubes. Such a three-layer hybrid tube is also known from DE 10 2004 008 523 B4. There, the hybrid cylinders are used as pressure cylinders for actuators, particularly hydraulic, pneumatic, or hydropneumatic actuators, or shock absorbers.

[0007] The object of the invention is to improve the method for producing hybrid pipes described above in such a way that hybrid pipes can be produced with less manufacturing effort, while additional processing steps for post-processing are avoided.

[0008] According to the invention, this object is achieved by a method having the features of claim 1.

[0009] Accordingly, in a method for producing hybrid pipes with flanged or screwed connections arranged at their ends, the following process sequence is proposed according to the invention:

[0010] - Providing a metallic pipe section with a defined outer diameter,

[0011] - Providing at least one flange or screw-in connection which has on one side a first outer diameter which corresponds to or is similar to the outer diameter of the pipe section and on the other side a second outer diameter which is larger than the outer diameter of the pipe section, - Welding a flange or screw-in connection onto at least one

[0012] side of the pipe section,

[0013] - Wrapping the pipe section and part of the flange or screw-in connection welded on at least one side with a fibre composite material.

[0014] The process according to the invention allows for significantly thinner pipe walls to be used for production. This results in a significant cost advantage compared to the currently used process. Furthermore, the problem of deformation during machining is minimized, as the pipes only require minimal internal machining.

[0015] Advantageous embodiments of the process result from the subclaims following the main claim.

[0016] It is advantageous if the flange or screw-in connection provided has a constant outer diameter in the area adjoining the pipe section over a certain length, which corresponds to that of the pipe section or is of a similar size. This results in an extension of the pipe section with a constant outer diameter on one side after welding the pipe section to the flange or screw-in connection. At the end of the flange or screw-in connection, an area is provided over a certain length with a comparatively larger outer diameter than the pipe section. This larger diameter is necessary so that the flange or screw-in connection can be provided here. Between the two aforementioned areas with different diameters, the outer diameter increases in a transition area from the outer diameter of the pipe section to the final diameter of the flange or screw-in connection.In the area of ​​the reduced diameter, i.e., in the area of ​​the pipe section and the immediately adjacent area of ​​the flange or screw-in connection, an outer pipe made of fiber composite material is created by wrapping it with the fiber composite material. This outer pipe has an outer diameter that advantageously corresponds to the diameter at the end of the flange or screw-in connection, resulting in an essentially constant outer diameter over the entire length of the hybrid pipe. Depending on the application, however, it is also possible for the outer diameter of the outer pipe to differ from the outer diameter of the ends of the flange or screw-in connection.

[0017] High-modulus fibers are advantageously used in fiber composites. For example, carbon fiber reinforced plastic (CFRP) is a suitable material. It is a composite material consisting of a plastic matrix, such as a thermoset or thermoplastic, and embedded carbon fibers.

[0018] According to a further advantageous method, the fiber composite material is wrapped around the pipe section and a part of the flange or screw-in connection welded on at least one side in such a way that the fibers of the fiber composite material run essentially in the circumferential direction.

[0019] Due to the circumferential orientation of the fibers, the resulting circumferential forces are absorbed here. The metallic pipe section or the adjacent areas of the flange and screw-in connections, which are also wrapped with the fiber composite material, serve to absorb the axial forces.

[0020] The invention also relates to hybrid pipes produced by the aforementioned method.

[0021] Accordingly, the hybrid pipes consist of a metallic pipe section with a defined outer diameter and a flange or screw-in connection welded on at least one side. The flange or screw-in connection has a first outer diameter on one side that corresponds to or is similar to the outer diameter of the pipe section and a second outer diameter on the other side that is larger than the outer diameter of the pipe section. Furthermore, an outer pipe made of a fiber composite material is provided, which covers the metallic pipe section and at least part of the at least one flange or screw-in connection.The outer pipe, made of fiber composite material, thus covers not only the pipe section, but also the adjacent area of ​​the flange or screw-in connection and, in particular, the weld seam connecting the metal pipe section and the flange or screw-in connection welded on at least one side. The outer pipe, made of fiber composite material, absorbs the radial forces resulting from internal pressure loading both in the free area of ​​the pipe and in the area of ​​the weld seam. The axial force transmission is implemented by the metal pipe section and the adjacent welded flange or screw-in connections, which are also made of metal. The flange itself serves to adapt screwed-in or flanged closure elements.

[0022] Because the fiber composite material also absorbs forces resulting from internal pressure in the area of ​​the weld seams, the metallic pipe cross-section can be made smaller than was the case with conventional hybrid pipes from the state of the art.

[0023] Further advantageous embodiments of the hybrid tube emerge from the further subclaims.

[0024] Accordingly, the metallic pipe section and at least one flange or screw-in connection are made of steel.

[0025] The outer tube is preferably made of a high-modulus fiber-reinforced plastic composite such as carbon fiber reinforced plastic (CFRP).

[0026] At least one flange or screw-in connection has, from one side, on which it has the outer diameter of the pipe section or a similar diameter, an initially essentially constant diameter over a certain length. On the opposite side, it also has a diameter over a certain length that is larger than the outer diameter of the pipe section. In the transition region, the diameter preferably increases continuously from the outer diameter of the pipe section to the diameter at the opposite end of the flange or screw-in connection.

[0027] It is also advantageous if the outer tube has essentially the same diameter as the free end of the flange or screw-in connection. However, this outer diameter may also differ within the scope of the invention.

[0028] Finally, the fibers in the outer tube made of the fiber composite material advantageously run essentially in the circumferential direction.

[0029] Further features, details and advantages of the invention are explained with reference to an embodiment shown in the drawing.

[0030] The single figure shows a schematic longitudinal section through a hybrid pipe according to an embodiment of the present invention.

[0031] The hybrid pipe consists of a metallic pipe section 12, which is advantageously a steel pipe in this case. Flange or screw-in connections 14, each of which is advantageously also made of steel, are connected to the pipe section 12 via weld seams 18. In the exemplary embodiment shown here, flange or screw-in connections 14 are provided on both sides. Within the scope of the invention, an embodiment can of course also have a corresponding flange or screw-in connection 14 on only one side.

[0032] The flanged or screw-in connection 14 has a first outer diameter on one side that corresponds to or is similar to the outer diameter of the pipe section 12. The welded connection 18 is provided on this side. On the opposite side, the flanged or screw-in connection 14 has an outer diameter that is larger than the outer diameter of the pipe section 12. This enlarged diameter is necessary because the adaptation of screwed-in or flanged closure elements is to be provided here. As can be seen from the figure, in the flanged or screw-in connection 14, the area adjoining the pipe section 12 runs with a constant outer diameter over a certain length. At its end, the flanged or screw-in connection 14 also has a constant outer diameter over a certain length, which is larger than the diameter of the pipe section 12.Between the two aforementioned areas of different diameters, a transition area of ​​the outer diameter is provided, from the outer diameter of the pipe section 12 to the final diameter of the flange or screw-in connection 14. This transition area features a continuous increase in diameter over a relatively short distance. However, the transition area can also be designed differently.

[0033] An outer tube 16 made of fiber-reinforced plastic is arranged on the outside of the pipe section 12 and the adjacent area of ​​the flange and screw-in connection 14. This outer tube 16 is formed by appropriately wrapping the reduced-diameter areas, with a corresponding winding of fiber-reinforced plastic being applied in the transition area between the different diameter ranges of the flange or screw-in connection 14. As shown in the figure, the outer tube 16 has an outer diameter that essentially corresponds to the end area of ​​the flange or screw-in connection 14.

[0034] Within the scope of the invention, the final diameter of the flange or screw-in connection can of course also be larger than the diameter of the outer pipe 16.

[0035] A key feature of the invention is that the fibers forming the outer tube run in the circumferential direction. According to the invention, the outer tube formed from the fibers serves to absorb the resulting circumferential forces. The inner tube section 12 can be designed as a relatively thin-walled steel tube, since only the axial forces need to be absorbed here. The corresponding winding made of fiber-reinforced plastic absorbs the circumferential forces, i.e., the radial forces resulting from internal pressure loading, not only in the free area of ​​the tube, but also in the area of ​​the weld seams. Hybrid tubes according to the present invention can be used in a wide variety of applications. For example, they can be used as pressure cylinders for actuators, in particular hydraulic, pneumatic, or hydropneumatic actuators, or shock absorbers.

Claims

Patent claims 1. A method for producing hybrid pipes (10) with flanged or screwed connections (14) arranged at their ends, characterized by the following steps: - Providing a metallic pipe section (12) with a defined outer diameter, - Providing at least one flange or screw-in connection (14) which has on one side a first outer diameter which corresponds to the outer diameter of the pipe section (12) and on the other side a second outer diameter which is larger than the outer diameter of the pipe section (12), - welding a flange or screw-in connection (14) on at least one side of the pipe section (12) and - Wrapping the pipe section (12) and a part of the flange or screw-in connection (14) welded on at least one side with a fiber composite material.

2. Method according to claim 1, characterized in that the provided flange or screw-in connection (14) in the area adjoining the pipe section (12) has a constant outer diameter over a certain length, which corresponds to or is similar to that of the pipe section (12), so that after welding of the pipe section (12) to the flange or screw-in connection (14) an extension of the pipe section (12) with a constant outer diameter results, that at the end of the flange or screw-in connection (14) an area has a comparatively larger outer diameter than the pipe section (12) over a certain length and that between the two aforementioned areas of different diameters the outer diameter increases from the outer diameter of the pipe section (12) to the final diameter of the flange or screw-in connection (14).

3. Method according to claim 1 or 2, characterized in that high-modulus fibers, for example carbon fibers, are used as the fiber composite material.

4. Method according to one of the preceding claims, characterized in that the fiber composite material is wrapped around the pipe section (12) and a part of the flange or screw-in connection (14) welded on at least one side in such a way that the fibers of the fiber composite material run substantially in the circumferential direction.

5. Hybrid pipe produced by a method according to one of the preceding claims, with a metallic pipe section (12) with a defined outer diameter and with a flange or screw connection (14) welded on at least one side, which has a first outer diameter on one side which corresponds to or is similar to the outer diameter of the pipe section (12) and on the other side a second outer diameter which is larger than the outer diameter of the pipe section (12), and with a an outer tube (16) consisting of a fiber composite material, which covers the metallic tube section (12) and at least part of the at least one flange or screw-in connection (14).

6. Hybrid pipe according to claim 5, characterized in that the metallic pipe section (12) and the at least one flange or screw-in connection (14) are made of steel.

7. Hybrid pipe according to claim 5 or 6, characterized in that the outer pipe (16) consists of a high-modulus fiber-plastic composite, for example carbon fiber-reinforced plastic (CFRP).

8. Hybrid pipe according to one of the preceding claims, characterized in that the at least one flange or screw-in connection (14) has, from one side thereof, on which it has the outer diameter of the pipe section (12) or a similarly large outer diameter, an initially substantially constant diameter over a certain length, that it has, on its opposite side, also over a certain length, a diameter which is larger than the outer diameter of the pipe section (12), and finally has a transition region in which the diameter increases from the outer diameter of the pipe section (12) to the diameter at the opposite end of the flange or screw-in connection (14).

9. Hybrid pipe according to one of the preceding claims, characterized in that the outer pipe (16) has substantially the same diameter as the free end region of the flange or screw-in connection (14).

10. Hybrid pipe according to one of the preceding claims, characterized in that the fibers in the outer pipe (16) made of the fiber composite material run essentially in the circumferential direction.

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