METHOD AND SELF-CENTERING FIXING DEVICE FOR FIXING A WELDING DEVICE TO A PIPE SECTION

Abstract

Fixing device (1) for fixing a pipe welding device to a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) to be welded, wherein the fixing device (1) comprises: a rotating device (22) for rotating, in particular in a circular arc shape, a welding head of the pipe welding device about an axis of rotation; a gripping device comprising a first gripping arm (2) with a first clamping jaw (6) attached thereto with exactly one first concave clamping surface and a second gripping arm (3) with a second clamping jaw (7) attached thereto with exactly one second concave clamping surface, where: the first clamping jaw (6) is rotatably mounted on the first gripping arm about an axis (4) running parallel to the axis of the pipe section (32, 33) over a predetermined angular range, such that it can be selectively brought into different orientations (8, 10, 12) relative to the first gripping arm (2) by means of a rotational movement about the axis (4) running parallel to the axis of the pipe section (32, 33) and can be fixed in these orientations (8, 10, 12), each of which corresponds to an associated pipe diameter; wherein for each such diameter of the pipe section (32, 33) a respective first bore is provided on the first clamping jaw (6) and the first clamping jaw (6) can be fixed by means of an inserted fixing pin (9) through the respective first bore into a second bore of the first gripping arm (2); wherein the second clamping jaw (7) is attached to the second gripping arm in such a way that it is freely rotatable relative to the latter over a predetermined angular range about an axis of rotation (5) running parallel to the axis of rotation of the pipe section (32, 33); and The gripping device is configured to fix the pipe welding device to the pipe section (32, 33) by means of a clamping action exerted by the clamping jaws via their concave clamping surfaces on the pipe section (32, 33) from an open position to a closed position dependent on the currently selected and fixed orientation (8, 10, 12) of the first clamping jaw, with a reduced distance between the concave clamping surfaces compared to the open position, in which a symmetry axis of a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) clamped between the concave clamping surfaces of the clamping jaws (6, 7) running parallel to the axis of rotation of the rotating device (22) is spaced from the axis of rotation by a maximum specified amount of a maximum of 2% of the diameter of the pipe section (32, 33).

Description

[0001] A self-centering fixing device for fixing a welding device to a circular cylindrical pipe section, a clamping jaw for such a fixing device and a method for fixing such a fixing device to a pipe section are described.

[0002] Orbital welding is a mechanized welding process in which the welding head is guided mechanically in a circular path (an orbit) around a stationary workpiece during welding. This process is primarily used in pipeline construction, where consistently high weld quality and, in some cases, specific hygiene requirements must be met under controlled conditions.

[0003] Orbital-guided welding machines for pipe sections often feature a pipe section holder that also ensures centering. This holder is usually connected to a device that guides the welding needle in a circular motion around the outside of the pipe section. A moving sensor can be used to maintain a consistent distance between the welding needle and the outer wall of the pipe section. In a simple design, pipe centering chains are used to hold the pipe sections.

[0004] To ensure the correct distance between the outer wall of the pipe section and the welding needle (in inert gas welding, this distance is the arc length), the axis of the pipe section must run as precisely as possible through the axis around which the welding head traces its orbital path. It has been shown that the use of special fixtures, so-called clamping devices, can be more accurate than using a centering chain. A clamping device is usually adapted to a specific diameter range, e.g., 10 mm to 50 mm, 20 mm to 115 mm, 40 mm to 170 mm, or 160 mm to 320 mm. Clamping devices often consist of a pair of gripping arms that grasp the pipe section on two sides opposite each other with respect to its circular cross-section. At the ends of each of the two gripping arms, there are usually clamping jaws for securing the pipe section.Special measures are required to ensure that the axis of the pipe section coincides with the axis of the circular arc orbital path of the welding head.

[0005] Ideally, the clamping jaws would be in contact with the pipe section across their entire width to ensure the most secure clamping possible. The width of the clamping jaw is measured along the circumference of the pipe section. This would mean that the inner radius of curvature of the clamping jaw would essentially have to correspond to the radius of curvature of the outer surface of the pipe section. This would require a separate pair of clamping jaws for each individual pipe diameter. Therefore, clamping jaws are often designed so that each jaw is in contact with the pipe section at only two points around the circumference, or along two lines running axially along the cylindrical pipe section. These points or lines are located in different positions on the clamping jaw for each diameter. Such clamping jaws can only cover a portion of the aforementioned diameter ranges, e.g.,The clamping device accommodates pipe diameters from 40 mm to 170 mm and has a diameter range of 40 mm to 80 mm. Therefore, the clamping jaws are equipped with several pairs of inserts for each sub-range of the pipe section's outer diameter. This ensures that the entire diameter range achievable with the clamping device can be covered. Each clamping device requires multiple pairs of inserts for the clamping jaws because a single pair of inserts can only cover a portion of the total diameter range permissible for that clamping device.

[0006] Document US 7,226,047 B1 concerns a tool for holding two pipe sections in the correct alignment for a welder. The aim is to hold the two pipe sections in a fixed, coaxial alignment while a worker welds them together.

[0007] Document GB 1 416 853 A concerns an orbital welding device. It is designed to allow for quick and easy clamping and detachment from the workpiece.

[0008] Document CN 1 10 682 050 A concerns a clamping device for pipelines, in particular a clamp for clamping pipelines. It is intended to improve pipe positioning and pipe locking.

[0009] To solve the problems mentioned above, the task is to provide an improved fixing device and improved clamping jaws.

[0010] A first aspect concerns a fixing device for fixing a pipe welding device to a dimensionally stable, in particular circular cylindrical, pipe section to be welded, wherein the fixing device comprises: a rotating device for rotating a welding head of the pipe welding device, in particular in a circular arc, about an axis of rotation, a gripping device, comprising a first gripping arm with a first clamping jaw attached thereto having exactly one first concave clamping surface and a second gripping arm with a second clamping jaw attached thereto having exactly one second concave clamping surface, wherein the first clamping jaw is attached to the first gripping arm in such a way that it can be selectively fixed in different orientations relative to the first gripping arm, each corresponding to an associated pipe diameter, and the second clamping jaw is attached to the second gripping arm in such a way thatthat it is freely rotatable relative to this over a predetermined angular range about an axis of rotation running parallel to the axis of rotation of the pipe section, and the gripping device is configured to fix the pipe welding device to the pipe section by means of a clamping action exerted on the pipe section by the clamping jaws via their concave clamping surfaces, from an open position to a closed position dependent on the currently selected and fixed orientation of the first clamping jaw with a reduced distance between the concave clamping surfaces compared to the open position, in which an axis of symmetry of a dimensionally stable, in particular circular cylindrical, pipe section clamped between the concave clamping surfaces of the clamping jaws, running parallel to the axis of rotation of the rotating device, is spaced from the axis of rotation by a maximum of a specified amount of a maximum of 2% of the diameter of the pipe section.

[0011] In this arrangement, the pipe section is fixed to the clamping device by means of the gripping device, i.e., the two gripping arms and the clamping jaws attached to them. However, instead of two clamping jaws with inserts that can only be used for a limited range of the pipe section's outer diameter, the solution described above allows circular cylindrical pipe sections to be fixed to the clamping device without the need to change clamping jaw inserts depending on the outer diameter of the circular cylindrical pipe section. As long as the pipe section's diameter is within the permissible range for the clamping device, it can be processed using only the first and second clamping jaws.When transitioning to a different outer diameter, it is only necessary to select a different orientation for the first clamping jaw, adapted to the now existing outer diameter, and to fix it in this orientation. This arrangement has the advantage of reducing the number of parts. Only the first and second clamping jaws are required for each fixing device, instead of the larger number of clamping jaw inserts required in the prior art, which, in a fixing device, can only cover a limited portion of the diameter of the circular cylindrical pipe section instead of the entire range that can be processed with a single fixing device. A "rotation axis" within the meaning of the invention is understood to be, in particular, a straight line that describes a rotation or turn, especially of a body, about this axis.The axis of rotation can be a real axis or a purely imaginary straight line. An "axis of symmetry" is defined here as a straight line connecting the centers of the circular cylindrical pipe section. It, too, can be a real axis or a purely imaginary straight line. The maximum spacing of 2% of the pipe diameter refers to tolerance class D0 of ISO 1127. This percentage may be lower for higher tolerance classes.

[0012] According to the invention, the fixing device is designed such that the first clamping jaw is rotatably mounted on the first gripping arm about an axis running parallel to the axis of the pipe section over a predetermined angular range; and that the first clamping jaw can be brought into various selectable orientations relative to the first gripping arm by means of a rotational movement about the axis running parallel to the axis of the pipe section, each of which corresponds to an associated pipe diameter, and can be fixed in these orientations.

[0013] This arrangement has the particular advantage of allowing for easy transitions between different radii. The first clamping jaw is easily fixed to the first gripper arm by inserting a locking pin into a hole. The position of the chosen hole on the clamping jaw corresponds to the outer diameter of the circular cylindrical pipe section. Only a single hole for the pin can be provided on the gripper arm. Alternatively, it is also possible to provide only a single hole on the clamping jaw and several holes on the first gripper arm. This allows for adjustments to the outer diameter of the circular cylindrical pipe section simply by rotating the clamping jaw and repositioning the pin.

[0014] In another advantageous embodiment of the fixing device, the second clamping jaw is identical to the first clamping jaw.

[0015] The identical design of both clamping jaws allows for a further reduction in the variety of parts.

[0016] A second aspect concerns a clamping jaw for fixing a pipe welding device to a dimensionally stable circular cylindrical pipe section to be welded on a fixing device, for attachment to a gripping arm, wherein the clamping jaw can be fixed relative to the gripping arm in various selectable orientations, each corresponding to a diameter of a pipe section.

[0017] Using such a clamping jaw reduces the number of different parts. With a clamping jaw designed in this way, any pipe section with an outer diameter suitable for the respective clamping device can be secured to the clamping device without having to change inserts for the clamping jaws depending on the outer diameter of the circular cylindrical pipe section used. Multiple inserts for each clamping device are no longer required.

[0018] In an advantageous embodiment, the clamping jaw can be rotatably mounted on the gripping arm about an axis running parallel to an axis of the pipe section over a predetermined angular range; and can be brought into various selectable orientations relative to the gripping arm by means of a rotational movement about the axis running parallel to the axis of the pipe section, each corresponding to the diameter of the pipe section, and can be fixed in these orientations.

[0019] With such a clamping jaw, it is particularly easy to switch between different diameters of the circular cylindrical pipe section. A clamping jaw designed in this way also allows the use of only one type of clamping jaw on all gripping arms mounted in a fixing device, even if the fixing action is only applied to one of the clamping jaws used in the fixing device.

[0020] According to the invention, a first bore is provided for each outer diameter of the circular cylindrical pipe section on the first clamping jaw, and the first clamping jaw can be fixed into a second bore of the first gripping arm by means of an inserted fixing pin through the respective first bore.

[0021] This particularly simple design for fixing the clamping jaw allows for very quick adaptation to a different outer diameter of the circular cylindrical pipe section.

[0022] In a further advantageous embodiment, the radius of curvature of a concave clamping surface of the clamping jaw facing the pipe section is less than half a minimum diameter of the pipe section, so that the clamping jaw rests against the pipe section with the ends of the concave clamping surface facing the outer surface of the pipe section.

[0023] If the radius of curvature of the concave clamping surface of the clamping jaw, which comes into contact with the outside of the circular cylindrical pipe section, is smaller than half the minimum permissible outside diameter of the circular cylindrical pipe section for the present fixing device, only the ends (viewed in the circumferential direction) of the clamping jaw can come into contact with the pipe section. This is a further measure with regard to the objective of covering the entire range of the outside diameter of the circular cylindrical pipe section available for the respective fixing device using a single clamping jaw.

[0024] In a further advantageous embodiment, at least one contact body is provided on the clamping jaw, which is attached to the clamping jaw in an area where the circular cylindrical pipe section rests against the clamping jaw.

[0025] This measure provides easily manufactured and replaceable wear parts. This prevents the entire clamping jaw from having to be replaced in case of damage or wear.

[0026] In a further advantageous embodiment, the support body attached to the clamping jaw is made of a material that has a lower hardness than the material from which the circular cylindrical pipe section is made.

[0027] For example, if brass is used as the material for the clamping body when working with steel pipes, damage to the pipe section by the clamping jaws is prevented. Furthermore, this allows for quick and easy adjustment of the clamping jaw if the material of the pipe sections to be welded changes.

[0028] Another aspect deals with a method for fixing a pipe welding device to a dimensionally stable circular cylindrical pipe section to be welded in a fixing device according to the invention, comprising the steps: (i) Fixing the first clamping jaw attached to the first gripping arm relative to the first gripping arm in an orientation dependent on the outside diameter of the pipe section, (ii) Gripping the section of pipe to be welded, in particular a circular cylindrical section, with the gripping device;By fixing the pipe welding device to the pipe section, the gripping device is moved from an open position to a closed position, dependent on the currently selected and fixed orientation of the first clamping jaw, by means of a clamping action exerted on the pipe section by the clamping jaws via their concave clamping surfaces, with a reduced distance between the concave clamping surfaces compared to the open position, so that in the closed position an axis of symmetry of a dimensionally stable, in particular circular cylindrical, pipe section clamped between the concave clamping surfaces of the clamping jaws, running parallel to the axis of rotation of the rotating device, is spaced from the axis of rotation by a maximum of a defined amount of a maximum of 2% of the diameter of the pipe section, by rotating the second clamping jaw about an axis running parallel to the axis of the circular cylindrical pipe section.

[0029] These steps ensure that the axis of the circular cylindrical pipe section coincides as closely as possible with the axis of rotation of the rotating device. By defining a maximum distance between these two axes, the clearance between the outer wall of the pipe and the welding head is maintained without the radially movable welding head hitting a stop. This guarantees consistent weld quality.

[0030] This method makes it possible to use the aforementioned fixing device with its associated clamping jaws. In just a few steps, the outer diameter of the circular cylindrical pipe sections to be fixed and welded in the fixing device can be changed. It is not necessary to replace any parts of the fixing device when changing the outer diameter of the circular cylindrical pipe sections.

[0031] In summary, this document describes a clamping system for a fixing device in an orbital welding system, which allows clamping of the entire permissible outer diameter range of circular cylindrical tubes for a specific type of fixing device without additional components. This system utilizes a clamping jaw, also known as a pendulum jaw, which can compensate for the out-of-roundness of the components to be welded. All components within the working range—that is, the range from a minimum to a maximum outer diameter of the components to be processed with the fixing device—can be held centrally by the clamping system, regardless of their respective outer diameter. The clamping system mechanism consists of at least two clamping arms. A clamping jaw is attached to each of these clamping arms, also referred to as gripping arms.On a first gripper arm, the clamping jaw is preset to the outer diameter of the component to be machined with the fixing device. On a second gripper arm, the clamping jaw adjusts freely to different diameters. Fig. Figure 1 shows an oblique view of a fixing device with gripping arms and clamping jaws; Fig. 2 shows an oblique view of the same fixing device from a different viewing direction; Fig. Figure 3 shows the fixing device with a pipe section of minimal diameter fixed therein; Fig. 4 shows the fixing device with a pipe section of maximum diameter fixed therein; Fig. Figure 5 shows the fixing device with the pipe section fixed in it. Fig. 3 from the side; Fig. Figure 6 shows the fixing device with the pipe section fixed in it. Fig. 4 from the side; Fig. Figure 7 shows the fixing device with the pipe section fixed in it. Fig. 3 from the opposite direction; Fig. Figure 8 shows the fixing device with the pipe section fixed in it. Fig. 4 from the opposite direction; Fig. Figure 9 shows the fixing device in a setting for a pipe diameter between the extreme values; Fig. Figure 10 shows the fixing device with contact bodies for the clamping jaws; Fig. Figure 11 shows a gripper arm with clamping jaw and support bodies; Fig. 12 shows the gripper arm of the Fig. 11 in two further views.

[0032] In Fig. Figure 1 shows a fixing device 1 with a gripping device consisting of gripping arms 2, 3 and clamping jaws 6, 7 attached to them. The gripping arms 2, 3 can be moved towards or away from each other by means of a clamping lever 18 on the gripping device. When the gripping arms have been moved as far away from each other as possible, i.e., at maximum distance between the gripping arms 2, 3, a circular cylindrical pipe section can be inserted between the gripping arms and fixed by means of the clamping jaws 6, 7 attached to the gripping arms 2, 3 by moving the gripping arms towards each other. The clamping surfaces of the clamping jaws 6 and 7 are concavely shaped to accommodate a circular cylindrical, and therefore convex, pipe. A welding needle (not shown) can be mounted in a holder 21, which can be moved circularly by means of the rotating device 22. During the circular movement, radial movement of the holder 21 is enabled by means of a spacer device 23.This allows deviations of the pipe circumference from a perfect circle to be compensated for to a certain extent. The same fixing device is also used in... Fig. Figure 2 is shown, with the same reference numerals for the same elements being used throughout the description and in all figures. In addition to the elements shown in Fig. The elements shown in 1 are in Fig. Figure 2 shows a pivot axis 4 on the first clamping jaw 6 and a pivot axis 5 on the second clamping jaw 7. It further shows how a fixing pin 9 is attached to a hole in the clamping jaw 6. Of course, it is also possible to fix the first clamping jaw 6 to the gripping arm 2 in another way, for example by clamping it in a specific orientation or by using a fixing screw.

[0033] The Fig. 3, Fig. 5 and Fig. Figure 7 shows the fixing device 1 in which a circular cylindrical pipe section 32 of minimum diameter is clamped. Fig. 4, Fig. 6 and Fig. Figure 8 shows the fixing device 1 in which a circular cylindrical pipe section 33 of maximum diameter is clamped. Here, the Fig. 3 and Fig. 4 the fixing device 1 with a viewing direction in the axial direction of the clamped circular cylindrical pipe section and the Fig. 7 and Fig. 8 the fixing device 1 with a viewing direction in the opposite direction to the viewing direction of the Fig. 3 and Fig. 4, also in the axial direction of the clamped circular cylindrical pipe section. The Fig. 5 and Fig. Figure 6 shows the fixing device 1 from the side, i.e., viewed perpendicular to the axis of the clamped circular cylindrical tube section. In the Fig. 3, Fig. 5 and Fig. 7 is the circular cylindrical pipe section of minimum diameter marked with reference numeral 32 and in the Fig. 4, Fig. 6 and Fig. 8 the circular cylindrical pipe section of maximum diameter with reference numeral 33. The Fig. 3 and Fig. Figure 7 further contains a crosshair 31. This indicates the axis of the circular cylindrical pipe section. Ideally, the axis of this circular cylindrical pipe section coincides with the axis of the orbital path of the rotating device 22.

[0034] To reduce the variety of parts, the first clamping jaw 6 and the second clamping jaw 7 can be identical, as can the first gripper arm 2 and the second gripper arm 3. If a locking pin is used in the first gripper arm 2 to fix the orientation of the first clamping jaw 6, and a rotation about the axis 4 is used to change the orientation of the first clamping jaw 6, it is recommended to also provide a hole for the locking pin in the first gripper arm 2. This hole for the locking pin is advantageously located between the axis of rotation 4 for the first clamping jaw and the end of the first gripper arm 2 where the first gripper arm 2 is connected to the rest of the clamping device 1.The second clamping jaw 7, which is identical to the first clamping jaw 6, is advantageously attached to the gripper arm 3 such that the holes for the locking pin 9 are located on the side of the second clamping jaw 7 and the axis of rotation 5 that is furthest from the end of the second gripper arm 3 where it is connected to the rest of the fixing device 1. This allows the second clamping jaw 7 to remain freely movable and prevents it from being accidentally fixed to the second gripper arm 3, thus reducing the potential for errors.

[0035] The pipe sections 32 and 33 shown in these figures can, for example, be sections of a straight pipe or pipe bends. The clamping device is used to join two pipe sections. Before using the clamping device, the pipe sections to be joined are welded together at two or three points. These temporarily joined pipe sections are then clamped together with the clamping device. The final weld can then be produced automatically using the orbital welding machine. The rotating device guides the welding head along a circular arc around the pipe section.

[0036] In Fig. Figure 7, with reference numeral 8, shows that the fixing pin fixes the first clamping jaw 6 in an orientation corresponding to the minimum diameter of the circular cylindrical pipe section 32. Fig. Figure 8, with reference numeral 10, shows that the fixing pin secures the clamping jaw 6 in an orientation corresponding to the maximum diameter of the circular cylindrical pipe section 33. This varying positioning of the first clamping jaw 6 depending on the outer diameter of the circular cylindrical pipe section is a step in the process by which the axis of the circular cylindrical pipe section is centered on the axis of rotation of the circular path along which the rotating device 22 guides the welding needle mounted in the holder 21 around the circular cylindrical pipe section.

[0037] In comparison between the Fig. 3 and Fig. 4 further clarifies that in Fig. 3 the second clamping jaw 7 is inclined about the axis of rotation 5 at a different angle relative to the second gripping arm 3 than in Fig. 4. This is also true in the Fig. 7 and Fig. 8 recognizable. If the second clamping jaw 7 assumes a certain rotational position when fixing a pipe section depending on the outer diameter of the circular cylindrical pipe section, this is a further step in the process by which the centering of the axis of the circular cylindrical pipe section on the rotation axis of that circular path on which the rotating device 22 guides the welding needle attached in the holder 21 around the circular cylindrical pipe section is carried out.

[0038] In Fig. Figure 9 shows the fixing device 1 when, prior to receiving a circular cylindrical pipe section, it is set to the second largest outer diameter of the circular cylindrical pipe section that is possible with the fixing device. This is represented by the fixing pin in the orientation indicated by reference numeral 12.

[0039] In Fig. Figure 10 shows an embodiment in which the clamping jaws 6 and 7 are equipped with contact bodies 13. In this example, these are attached to the clamping jaw with two screws 14 each. This embodiment has the advantage that the contact bodies 13 can be made of a softer material than the material of the pipe section to be welded. For example, brass is recommended for steel pipe sections.

[0040] The Fig. 11 and Fig. Figure 12 shows a single gripper arm 16 with the attached clamping jaw from different perspectives. The gripper arm 3 itself is connected to the clamping jaw 7 at the pivot axis 5. The support bodies 13 are attached to the clamping jaw 7.

[0041] In known clamping devices, inserts for the clamping jaws are used for a portion of the area that can be machined with the clamping device, corresponding to the outer diameter of the circular cylindrical pipe section. For each outer diameter of the pipe section, the respective pipe section rests against the inserts at different points. If such an insert is damaged, deviations from the desired centering can occur for one or more outer diameters of the circular cylindrical pipe section.

[0042] If, however, clamping jaws are used as described in this document, these jaws always rest against the cylindrical pipe section at both ends (viewed in the circumferential direction), regardless of its outer diameter. This requires that the radius of curvature of the concave clamping surface of the jaw facing the cylindrical pipe section be smaller than the smallest permissible outer diameter of the cylindrical pipe section for the respective clamping device. This ensures the correct centering of the cylindrical pipe section.

[0043] This design of the clamping jaws, which always bear against the circular cylindrical pipe section with their concave clamping surfaces at their outer ends, enables the use of interchangeable support bodies 13. If these support bodies become damaged, it is not necessary to replace the entire clamping jaw, but only a component that is easy to manufacture. Such a component could, for example, be a cylindrical brass pin with at least one bore, screwed to the clamping jaw. Alternatively to the screws 14, other fastening methods can be used, such as rivets.

[0044] The use of such a fixing device with a gripping device that has gripping arms arranged essentially symmetrically to a plane passing through the axis of the pipe section makes it possible to hold the pipe section, regardless of its diameter, in such a way that it is centered relative to this plane. Fig. 3 and Fig. 7, whose viewing direction runs along the axis of symmetry of the pipe section, this plane is represented as the perpendicular line of a crosshair 31. A second plane perpendicular to this plane, which passes through the pipe axis, is shown in Fig. 3 and Fig.7, whose viewing direction runs along the axis of symmetry of the pipe section, is represented as a horizontal line of a crosshair 31. The design of the first and second clamping jaws 6 and 7 makes it possible to center the pipe sections to be welded relative to these two planes, whereby a change in the orientation of the clamping jaw 6 on the first gripping arm 2 is sufficient as the sole measure to adapt the fixing device 1 to the outer diameter of the pipe section to be processed. A change of inserts for the clamping jaws is not necessary. Thus, in addition to the variety of parts, the susceptibility to errors is also reduced.

[0045] When producing a circumferential weld to join two pipe sections, the following procedure is recommended according to this description: First, the outer diameter of the pipe sections to be joined is determined. The first clamping jaw 6 on the first gripping arm 2 of the fixing device 1 is fixed in the orientation corresponding to this outer diameter. The two pipe sections to be joined are welded together as precisely as possible at two or three points to determine their relative positions. Since the two pipe sections are now firmly joined, the remainder of this description refers to a single pipe section.

[0046] Then, the two gripping arms 2 and 3 of the fixing device 1 are opened by actuating the clamping lever 18 until the connected pipe sections can be inserted into the fixing device. The pipe section is positioned in the fixing device so that the welding needle, in its holder 21, reaches the location of the intended circumferential weld seam. The gripping arms 2 and 3 are moved towards each other by actuating the clamping lever 18 so that the clamping jaw 6 comes into contact with the outer wall of the pipe section. Simultaneously, the clamping jaw 7 on gripping arm 3 also moves towards the pipe. During this movement, the clamping jaw 7 rotates about the axis 5. This positions the pipe section relative to the center of the circular motion of the rotating device 22 such that the axis of the circular cylindrical pipe section and the axis of rotation of the rotating device 22 coincide.

[0047] The rotating device 22 then describes a circular movement along an arc around the cylindrical pipe section. During this rotation, it is checked whether the distance between the welding needle located in the holder 21 and the outer wall of the cylindrical pipe section corresponds to the target value for the intended welding process. Using the distance sensor 23, the distance of the welding needle to the outer wall of the cylindrical pipe section can be changed within certain very narrow limits during the rotation. This change serves to compensate for irregularities on the outer wall of the cylindrical pipe section. Furthermore, very slight deviations from the ideal centering of the pipe section relative to the rotating device 22 can be compensated for.If, during this preliminary cycle, it is determined that the distance probe 23 is running against preset limits, the orientation of the first clamping jaw 6 and the centering of the circular cylindrical pipe section must be checked. It may also be necessary to correct any irregularities on the outer surface of the circular cylindrical pipe section (e.g., by grinding or similar means). Should corrections be required, the preliminary cycle is repeated until the weld can finally be produced. REFERENCE MARK LIST 1 fixing device 2 first gripper arm 3 second gripper arm 4. Rotary axis, first clamping jaw 5. Rotary axis, second clamping jaw 6 first (fixable) clamping jaw 7 second (freely rotatable) clamping jaw 8. Fixing the first clamping jaw (minimum diameter) 9 Fixing pin 10. Fixing the first clamping jaw (maximum diameter) 12. Fixing the first clamping jaw (second largest diameter) 13 plant components 14 Fasteners for the installation body 16 Gripper arm with clamping jaw 18 clamping levers, gripping arms 19 Curvature radius of the clamping jaw 21 Holder welding needle 22 Rotating device welding needle 23 Spacer device 31 Crosshairs 32 circular cylindrical pipe section (minimum diameter) 33 circular cylindrical pipe section (maximum diameter)

Claims

[1] Fixing device (1) for fixing a pipe welding device to a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) to be welded, wherein the fixing device (1) comprises: a rotating device (22) for rotating, in particular in a circular arc shape, a welding head of the pipe welding device about an axis of rotation; a gripping device comprising a first gripping arm (2) with a first clamping jaw (6) attached thereto with exactly one first concave clamping surface and a second gripping arm (3) with a second clamping jaw (7) attached thereto with exactly one second concave clamping surface, where: the first clamping jaw (6) is rotatably mounted on the first gripping arm about an axis (4) running parallel to the axis of the pipe section (32, 33) over a predetermined angular range, such that it can be selectively brought into different orientations (8, 10, 12) relative to the first gripping arm (2) by means of a rotational movement about the axis (4) running parallel to the axis of the pipe section (32, 33) and can be fixed in these orientations (8, 10, 12), each of which corresponds to an associated pipe diameter; wherein for each such diameter of the pipe section (32, 33) a respective first bore is provided on the first clamping jaw (6) and the first clamping jaw (6) can be fixed by means of an inserted fixing pin (9) through the respective first bore into a second bore of the first gripping arm (2); wherein the second clamping jaw (7) is attached to the second gripping arm in such a way that it is freely rotatable relative to the latter over a predetermined angular range about an axis of rotation (5) running parallel to the axis of rotation of the pipe section (32, 33); and The gripping device is configured to fix the pipe welding device to the pipe section (32, 33) by means of a clamping action exerted by the clamping jaws via their concave clamping surfaces on the pipe section (32, 33) from an open position to a closed position dependent on the currently selected and fixed orientation (8, 10, 12) of the first clamping jaw, with a reduced distance between the concave clamping surfaces compared to the open position, in which a symmetry axis of a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) clamped between the concave clamping surfaces of the clamping jaws (6, 7) running parallel to the axis of rotation of the rotating device (22) is spaced from the axis of rotation by a maximum specified amount of a maximum of 2% of the diameter of the pipe section (32, 33). [2] Fixing device (1) according to claim 1, wherein the second clamping jaw (7) is identical to the first clamping jaw (6). [3] Method for fixing a pipe welding device to a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) to be welded in a fixing device (1) according to claim 1, comprising the steps: Fixing the first clamping jaw (6) attached to the first gripping arm (2) relative to the first gripping arm (2) in an orientation (8, 10, 12) corresponding to the outer diameter of the pipe section (32); Gripping the pipe section (32, 33), in particular circular cylindrical, to be welded, with the gripping device; by moving the gripping device from an open position to a closed position, dependent on the currently selected and fixed orientation of the first clamping jaw, with a reduced distance between the concave clamping surfaces compared to the open position, in order to fix the pipe welding device to the pipe section (32, 33), by means of a clamping action exerted on the pipe section (32, 33) by the clamping jaws via their concave clamping surfaces, such that in the closed position an axis of symmetry of a dimensionally stable, in particular circular cylindrical, pipe section (32, 33) clamped between the concave clamping surfaces of the clamping jaws, running parallel to the axis of rotation of the rotating device (22), is spaced from the axis of rotation by a maximum of a defined amount of a maximum of 2% of the diameter of the pipe section (32, 33), in order to fix the pipe welding device to the pipe section (32, 33).by rotating the second clamping jaw (7) about an axis parallel to the axis of the circular cylindrical pipe section (32, 33).

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