Device and method for producing formed hollow profiles

Abstract

A device for producing formed hollow profiles (3) has at least one supporting device (1) with at least one recess (2) into which a hollow profile (3) can be inserted. The recess (2) is designed to match or be larger than a cross-section (4) of the insertable hollow profile (3), wherein the supporting device (1) is mounted so as to be rotatable about a rotation axis. In addition, at least one clamping device is provided which is designed to fix the hollow profile (3), wherein a tensile force along an axis (5) perpendicular to the cross-sectional area of ​​the recess (2) for the hollow profile (3) and a torsional moment about the rotation axis can be applied to the hollow profile (3) by the clamping device.

Description

[0001] The present invention relates to a device and a method for producing formed hollow profiles.

[0002] Steam turbines and other power machines typically use solid blades. For various reasons, these blades are being replaced with lightweight blades. These can be made as hollow shapes or from composite materials with a protective metal shell. The production of hollow blades from sheet metal is challenging due to the complex blade geometry. One solution is to produce a suitable preform, which is then finally formed. The shape of the blade geometry can be described as a twisted, thin-walled hollow profile with a cross-section that varies along the longitudinal axis. The variation affects both the circumference and the cross-sectional shape itself, which can alternate between convex and non-convex. In order to produce the shell as a single piece, a corresponding hollow profile (not circular) is required.This is twisted before it can be finally calibrated, for example, by applying active media from the inside out against an external tool shape. During twisting, different areas of the profile elongate unevenly. This, among other things, initiates wrinkles that are generally irreversible. This occurs in both open (multi-part components) and closed hollow profiles.

[0003] Until now, blades have generally been manufactured from solid material, which avoids the problem of wrinkling. Another approach is to design the blade as a two-part component consisting of two opposing half-shells. Here, too, attempts are made to preform the sheet metal half-shells by twisting them together before the actual geometry is realized. As expected, wrinkling occurs in this process, but it can at least be mitigated by superimposing tensile stresses during twisting.

[0004] For example, DE 3 904 903 A1 discloses a device in which a rigid support part is divided into several support wedge parts, the wedge surfaces of which form an acute angle with a longitudinal axis of the hollow profile and which are provided with a clamping device for clamping the support wedge parts against each other and against the inner surfaces of the hollow profile. In this way, the support wedge parts can be permanently pressed against at least two diametrically opposed surfaces inside the hollow profile, which correspond to the outer surfaces of this hollow profile subjected to the clamping pressure.

[0005] The present invention is therefore based on the object of proposing a device and a method for producing formed hollow profiles, wherein the hollow profiles that can be produced do not form any wrinkles.

[0006] This object is achieved according to the invention by a device for producing formed hollow profiles according to claim 1 and a method for producing formed hollow profiles according to claim 6. Advantageous embodiments and further developments are described in the dependent claims.

[0007] A device for producing formed hollow profiles comprises at least one support device with at least one recess into which a hollow profile can be inserted. The recess is configured to match or be larger than the cross-section of the insertable hollow profile, and the support device is mounted for rotation about a rotation axis. Furthermore, at least one clamping device is provided, which is configured to fix the hollow profile in place. A tensile force along an axis perpendicular to the cross-sectional area of ​​the recess for the hollow profile and a torsional moment about the rotation axis can be applied to the hollow profile by the clamping device.

[0008] First of all, "conforming" means that the recess is designed such that the hollow profile can be guided or inserted into the recess. This means that the outer circumference of the cross-section or the shape of the hollow profile approximately corresponds to the inner circumference of the recess or the shape of the recess. This makes it possible to induce deformations without uneven elongation of certain areas of the hollow profile. This, in combination with the applicable tensile force and the torsional moment, makes it possible to produce wrinkle-free formed hollow profiles. Here, the "axis of rotation" is understood to be a straight or spiral central axis. Furthermore, the axis of rotation can coincide with the axis perpendicular to the cross-sectional area of ​​the recess for the hollow profile or at least extend in the direction perpendicular to the cross-sectional area of ​​the recess.In this process, the support device stabilizes at least part of the cross-section of the hollow profile, thus preventing buckling and wrinkling of the hollow profile. The support device can be configured over almost the entire length of the hollow profile along the axis perpendicular to the cross-sectional area of ​​the recess. This means that the hollow profile can be formed almost entirely within the support device. Alternatively, only part of the hollow profile can be formed within the support device. Furthermore, closed or open hollow profiles can be inserted or guided. This design also makes it possible to produce formed hollow profiles in a single process step without any post-processing.

[0009] Furthermore, "larger" refers to a recess with a larger circumference than a hollow profile, so that during the twisting process or after the twisting process, the circumference of the hollow profile is at least locally increased by the application of increasing internal pressure. This allows the calibration process that would otherwise follow, which would be carried out in a separate fixture, to be fully or partially anticipated and integrated into the existing fixture and process.

[0010] In addition, at least two support devices can be formed, wherein the support devices are aligned along the axis perpendicular to the cross-sectional area of ​​the recess for the hollow profile. This makes it possible to easily guide or insert straight hollow profiles, i.e. hollow profiles without curvature or twisting about the axis perpendicular to the cross-sectional area of ​​the recess for the hollow profile. Here, too, the support devices can guide the hollow profile in the recess over almost its entire length. In other words, apart from the sections of the hollow profile that are required for clamping in the clamping device, the rest of the hollow profile can be guided completely within the recesses, or the rest of the hollow profile is completely surrounded by at least one support device.In addition, the support devices can be designed in direct contact with each other, while still allowing separate rotation of the individual support devices.

[0011] Furthermore, the support device can have an initial state and a final state, wherein the initial state can be converted into the final state by rotating the hollow profile by a rotation angle. The initial state can be determined by the recess in the initial state at least partially, i.e., in sections, replicating the course of the straight, untwisted hollow profile. Accordingly, the final state can be determined by the recess in the final state partially, i.e., in sections, replicating the course of the formed, twisted hollow profile. This can make it possible to determine the intended final geometry of the hollow profile through the structural design of the recess and the specification of the rotation angle.

[0012] In addition, the support device can be constructed in multiple parts, particularly in two parts, so that the recess is formed by at least a first part and at least a second part. This allows the hollow profile to be easily inserted into the support device by separating the first part from the second part, or removed after forming. This facilitates handling of the device.

[0013] Furthermore, the support device can have at least one stop for limiting the angle of rotation. This makes it possible to limit the rotation and thus effectively prevent over-rotation, i.e., rotation beyond the intended angle of rotation. The stops can be formed by at least one circular recess.

[0014] In a method for producing formed hollow profiles, a hollow profile is inserted into at least one recess in at least one support device, wherein the recess corresponds to or is larger than a cross-section of the hollow profile. The hollow profile is then secured by a clamping device, and a tensile force along an axis perpendicular to the cross-sectional area of ​​the hollow profile and a torsional moment about a rotation axis are exerted on the hollow profile by the clamping device, causing the hollow profile to rotate about the rotation axis.

[0015] First, the axis perpendicular to the cross-sectional area of ​​the hollow profile coincides with the axis perpendicular to the cross-sectional area of ​​the recess for the hollow profile. These process steps make it possible to produce formed hollow profiles in such a way that additional post-processing or further process steps are not necessary to complete the formed hollow profile. Furthermore, wrinkle-free forming is achieved. This is ensured, among other things, by the fact that both a tensile force and a torsional moment act on the hollow profile during the forming process. During the actual forming process, the support device, which rotates passively with the hollow profile, supports the hollow profile and thus prevents wrinkles.

[0016] After twisting the hollow profile around the twist axis, the hollow profile can have a straight center curve or a non-straight center curve, for example, a spiral center curve. The formation of a spiral center curve occurs primarily when the hollow profile is twisted and an insufficient tensile force is applied in the longitudinal direction of the hollow profile. This causes the hollow profiles to additionally twist into a large spiral. This effect can be enhanced by placing recesses in the support discs slightly off-center.

[0017] In addition, the hollow profile can be subjected to vibration and / or heat treatment during the forming process. This makes it possible to prevent wrinkling during the forming process even more effectively.

[0018] The hollow profile can also be supported in its interior during forming, particularly by a formless material or by applying internal pressure. This alternative design variant can actively improve the quality of the formed hollow profiles by reducing wrinkling. This can be achieved by generating counterpressure acting from the interior to the outside or by limiting the possible deformation range. Wrinkling is generally understood to mean that the surface of the hollow profiles exhibits an unintentional corrugated structure.

[0019] In addition, the hollow profile can have a thickness of less than or equal to 0.02 times the width of the hollow profile and a length of greater than or equal to 10 times the width of the hollow profile. This allows thin-walled hollow profiles in particular to be formed without wrinkles.

[0020] Finally, the cross-section of the hollow profile can vary in a direction perpendicular to the cross-sectional area of ​​the hollow profile. This means that the cross-section changes along the length of the hollow profile. Complex hollow profiles can thus be formed in a wide variety of variations. This means that the recess(es) must also reflect this change in the cross-section of the hollow profile along the length of the hollow profile.

[0021] The described method can be carried out with the device according to the invention, ie the device is suitable for carrying out the described method.

[0022] Embodiments of the invention are illustrated in the drawings and are described below with reference to Fig. 1 to 6. Recurring features are provided with identical reference numerals.

[0023] They show: Fig. 1 a straight hollow profile inserted into three first parts of three support devices each in a perspective view; Fig. 2 three support devices each made of two parts with inserted straight hollow profile in perspective view; Fig. 3 three support devices each formed from two parts with twisted hollow profile in perspective view; Fig. 4 a twisted hollow profile inserted into three first parts of three support devices each in a perspective view; Fig. 5 a two-part untwisted support device in a housing in front view; and Fig. 6 a twisted support device formed from two parts in a housing in the front view.

[0024] In Fig. 1 shows a non-circular hollow profile 3, wherein the hollow profile has a cross-section 4. Furthermore, an open hollow profile is shown in this exemplary embodiment. Alternatively, the hollow profile can also be closed. Furthermore, the hollow profile 3 is inserted into three first parts 1a, each of three support devices 1, which are aligned along a first alignment line 7. The first alignment line 7 corresponds to an axis 5 perpendicular to a cross-sectional area of ​​the cross-section 4 of the hollow profile 3 (in this exemplary embodiment corresponds to a straight axis of rotation as the central axis corresponding to the longitudinal axis of the hollow profile 3) and is determined by laterally formed stops of the respective support devices 1. Furthermore, the hollow structure 3 has a non-circular cross-section 4, wherein the cross-section 4 is uniform over the length of the hollow profile 3, i.e. along the alignment line 7.Alternatively, the cross-section 4 can also vary over the length of the hollow profile 3, so that complex formed hollow profiles 3 can be produced. Alternatively, the rotation axis can also be a spiral-shaped central axis, which corresponds to a thread with a very large thread pitch.

[0025] The Fig. The state shown in Figure 1 represents the first method step in this exemplary embodiment, namely that the hollow profile 3 is inserted into the support device 1, which is formed in two parts here. Alternatively, it is also possible for the support device 1 to be formed in one piece, so that the insertion of the hollow profile 3 can be understood as an insertion of the hollow profile 3 into the recess 2. In this exemplary embodiment, the two-part support device 1, as shown in Fig. 2, is designed such that the first parts 1a and second parts 1b can be connected to one another to form a recess 2. In this exemplary embodiment, clear positioning as well as a simple and secure connection are ensured by the use of so-called puzzle tabs. However, any easily separable connection between two components can be used, allowing repeated non-destructive assembly and separation of the first parts 1a and the second parts 1b.

[0026] The hollow profile 3 is guided in the recesses 2. The recesses 2 are always locally adapted to the cross-section 4 of the hollow profile 3. This means that if the cross-section 4 of the hollow structure 3 changes over its length, the geometry of the recess 2 of the relevant support device 1, which is arranged locally at this cross-section 4, also changes. Thus, the support device 1 always forms a cavity through the recess 2 which at least partially, i.e. in sections, reproduces the course of the hollow profile 3 in the longitudinal direction, here along the first alignment line 7, so that the hollow profile 3 can be guided in the recesses 2. This cavity is enlarged by a series of support devices 1 with the respective recesses 2, so that the course of the hollow profile 3 can be reproduced more precisely, i.e. the section of the hollow profile 3 which is surrounded by the support devices 1 is enlarged.Alternatively, this can also be achieved by a single support device 1 which has a larger extension along the length of the hollow profile 3, ie has an increased thickness.

[0027] For better illustration, Fig. 2, the support devices 1 are shown spaced apart along the first alignment line 7. However, a preferred embodiment is one in which the support devices 1 are designed in direct contact with one another, i.e., they are designed directly one behind the other. In both variants, the support devices 1, which are to be understood here as support disks, can be coated and / or lubricated in order to reduce frictional resistance. Basically, the support devices 1 are mounted so as to be rotatable about an axis 5 perpendicular to the cross-sectional area of ​​the recess 2. This means that the support devices 1 can be rotated about the axis 5. In addition, the support devices 1 cannot be displaced relative to one another, i.e., the device only permits translational movement along the axis 5 and rotational movement about the axis 5 of the support devices 1. In addition, Fig. 2 two stops 6 are formed, which limit a rotation angle of the respective support device 1.

[0028] Not shown in this embodiment is that the hollow profile 3 is fixed, i.e. held, by a clamping device. The hollow profile can be fastened on one side or both sides by a clamping device. In addition, the clamping device is designed such that a tensile force along the axis 5 perpendicular to the cross-sectional area of ​​the recess 2 and a torsional moment about the axis 5 perpendicular to the cross-sectional area of ​​the recess 2 is exerted on the hollow profile 3. A rotation of the hollow profile 3 thus causes a passive rotation of the support devices 1, so that the hollow structure 3 presses against the support devices 1 or against the inner surface of the recesses 2 during the rotation. The clamping device itself can be designed, for example, as a wedge clamping device for clamping and applying a tensile force. A wedge force can be applied via a spindle.Alternatively, the wedge force can also be applied pneumatically or hydraulically. For hollow profiles 3, the clamping jaws can be adapted to the existing contour, if necessary, and a mandrel or filler piece can be inserted into the hollow profile 3. Hollow profile 3 can also be compressed flat and then clamped.

[0029] The Fig. Figure 2 thus shows parts of a device according to the invention with an inserted hollow profile 3, which is in its initial state. This means that the inserted hollow profile 3 is still untwisted, i.e., straight, with the support devices 1 aligned along a first alignment line 7. In contrast, Fig. 3 shows the same parts of the device, whereby the two rear support devices 1 have now been rotated relative to the frontmost support device 1 in such a way that a second alignment line 9 is formed. The second alignment line 9 is formed along the upper stops 6. This means that in this exemplary embodiment, the hollow profile 3 is rotated in such a way that the support devices 1 passively rotate from the initial state to the final state. This means that the hollow profile 3 is rotated by a specific angle of rotation α so that the support devices 1 change from the alignment with the first alignment line 7 (initial state) to the alignment with the second alignment line 9 (final state). Thus, a rotation of the hollow profile 3 by a defined angle of rotation α can result in different angles of rotation with respect to the individual support devices 1.In other words, the angle of rotation α of the hollow profile may differ from the angles of rotation of the individual support devices 1. Furthermore, the angles of rotation of the individual support devices 1 may also differ from each other.

[0030] Fig. 4 now shows the twisted hollow profile 3 from Fig. 3, wherein the second parts 1b of the support device 1 are dismantled again in order to remove the hollow profile 3 from the support devices 1 in a simple manner.

[0031] The twisting of the hollow profile is again in Fig. 5 or in Fig. 6. Here, the support device 1 is now rotatably mounted in a housing 8, wherein Fig.6, the support device 1 shown in the front view is rotated by a certain angle of rotation. In this embodiment, the angle of rotation of the support device corresponds to the angle of rotation α of the hollow profile. The angle of rotation is limited by the stops 6, which only allow a predefined maximum angle of rotation. Thus, the final state can be determined in advance by design. This increases the reproducibility of the manufactured hollow profiles 3 and also reduces the error rate.

[0032] In the exemplary embodiments shown, the method was always carried out with a preformed hollow profile 3. Alternatively, the method may also include the preformed hollow profile 3 being first produced by preforming.

[0033] Thus, the technical solution to the problem described above consists in first forming the cross-section 4 of the hollow profile 3, for example, from a suitable sheet metal. This hollow profile 3 is then twisted and can finally be calibrated by applying pressure from the inside against an external tool mold. This process can be applied to both open and closed hollow profiles 3 to avoid unwanted wrinkles.

[0034] The invention thus relates to a method and a device for producing formed hollow profiles, which prevents or reduces the formation of wrinkles during twisting. For this purpose, the hollow profile 3, which is pre-formed with regard to the circumferential profile and the cross-section 4, is held by a device which is layered perpendicular to the twisting axis, for example by a large number of support devices 1 arranged one behind the other. The support devices 1 can be designed as cylindrical discs and each have a recess 2 with the desired cross-section 4 of the hollow profile 3. In addition, an angular recess or defined stops 6 can be provided on the circular circumference of the support device 1, which, within an outer device (housing 8), enable rotation relative to the upstream and downstream support device 1. The hollow profile 3 inserted in this way can be clamped on both sides by two clamping devices, for example.One clamping device is fixed, and the other is rotatably and slidably mounted. Between the clamping devices, the hollow profile 3 is subjected to tension and twisting. During twisting, the hollow profile 3 is locally elongated. The hollow profile 3 can be additionally stabilized by formless fillers (e.g., powder or sand, i.e., materials whose shape is not fixed but whose volume is constant) or by internal pressure to prevent inward buckling and folding.

[0035] Thus, the process can be designed as follows, for example: • Provision of a) a sheet metal blank or b) a suitable hollow profile 3 in a straight state (untwisted) • Additional steps in case of a) ◯ Forming and joining the sheet metal blank to a closed straight hollow profile 3 (untwisted) ◯ local adaptation of the circumferences of the initial hollow profile to the circumferences of the final geometry, for example by a first internal high-pressure forming • Inserting the hollow profile 3 into the device (ie into the housing 8) with aligned support discs • Clamping the hollow profile 3 at the beginning and end of the hollow profile 3 to apply a tensile force along the longitudinal direction of the hollow profile 3 as well as moments for torsion of the hollow profile 3 • Twisting of the hollow profile 3, if necessary with additional axial preload and if necessary with internal support, to the desired angle of rotation. The support discs in the device (housing 8) rotate passively with the provided stop 6. • Release of the clamping of the twisted hollow profile 3 • Removal of the twisted hollow profile 3

[0036] The support discs can lie against each other in the fully equipped device (in the housing 8) and can thus fill the device.

[0037] The shape of the discs is selected so that they are rotatably mounted in the device and can rotate against each other, but cannot shift. Furthermore, the support discs can be designed in two parts, so that the second parts 1b of the support discs have a circular recess that serves as stops 6 for rotation. In the initial state, the support discs are oriented along the first alignment line 7. This represents the just untwisted hollow profile 3. Furthermore, the support disc halves (first parts 1a and second parts 1b) have elements (puzzle tabs) that enable clear positioning and a secure connection of the halves, but are also easy to separate. After twisting the hollow profile 3, the support discs are no longer aligned along the first alignment line 7.The support discs are rotated along the fixture (housing 8) so that the notches of the upper disc halves (second parts 1b) abut against the stop 6 in the housing 8 and form the second alignment line 9. The forming of the hollow profile 3 can be carried out cryogenically, at room temperature, or in a heated state. The axial tensile stress can be applied passively, by supporting the clamping elements on the laminated core, or actively by external forces. With external forces, the tensile force applied by the fixture (the tensile stresses arise in the component) can be varied, controlled, or even regulated throughout the twisting process.

[0038] The housing 8 contains a largely cylindrical opening in which the support discs are rotatably mounted. The rotation itself is limited by a circular segment, which forms the stops 6. The disc-shaped twisting device (the entirety of the support devices 1) stabilizes the individual cross-sections and prevents buckling and wrinkling of the hollow profile 3, especially in the case of closed hollow profiles 3.

[0039] Compared to a two-part variant (forming two half shells separately and then joining them to form a closed shell), a very complex and time-consuming (and costly) joining process is avoided. A thin-walled shell could, in principle, be cast or built up layer by layer using various additive manufacturing processes. Disadvantages of this approach are generally insufficient dimensional accuracy and excessive surface roughness, which can, however, be optimized through appropriately complex rework.

[0040] The hollow profiles 3 produced in this way, particularly hollow sheet metal profiles with a non-cylindrical cross-section, can be used as such for various purposes or as preforms (favorable material pre-distribution) for further processing steps, e.g., calibration using hydroforming. The components produced in this way are suitable for use as flow profiles such as propellers (propulsion technology for hybrid-electric aircraft) and turbine blades (hybrid blades made of composite and metal shell for steam turbines in the geothermal sector). They serve both to convert flow energy into rotational motion and vice versa. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 3 904 903 A1

[0004]

Claims

[1] Device for producing formed hollow profiles (3), comprising: at least one support device (1) with at least one recess (2) in which a hollow profile (3) can be inserted, wherein the recess (2) is designed to match a cross-section (4) of the insertable hollow profile (3) or to be larger than the cross-section (4) of the insertable hollow profile (3), wherein the support device (1) is rotatably mounted about a rotation axis and at least one clamping device which is designed to fix the hollow profile (3), wherein a tensile force along an axis (5) perpendicular to the cross-sectional area of ​​the recess (2) for the hollow profile (3) and a torsional moment about the rotation axis can be applied to the hollow profile (3) by the clamping device. [2] Device for producing formed hollow profiles (3) according to claim 1, characterized bythat at least two support devices (1) are formed, wherein the support devices (1) are aligned along the axis (5) perpendicular to the cross-sectional area of ​​the recess (2) for the hollow profile (3). [3] Device for producing formed hollow profiles according to claim 2, characterized by that the support device (1) has an initial state and a final state, wherein the initial state can be converted into the final state by rotating the hollow profile (3) by a rotation angle (α). [4] Device for producing formed hollow profiles (3) according to one of the preceding claims, characterized by that the support device (1) is designed in several parts, in particular in two parts, so that the recess (2) is formed by at least a first part (1a) and at least a second part (1b). [5] Device for producing formed hollow profiles (3) according to one of the preceding claims, characterized bythat the support device (1) has at least one stop (6) for limiting the angle of rotation (α). [6] Method for producing formed hollow profiles (3), in which a hollow profile (3) is introduced into at least one recess (2) in at least one support device (1), wherein the recess (2) corresponds to or is larger than a cross-section (4) of the hollow profile (3) and then the hollow profile (3) is fixed by a clamping device and then a tensile force along an axis (5) perpendicular to the cross-sectional area of ​​the cross-section (4) of the hollow profile (3) and a torsional moment about a rotation axis are exerted on the hollow profile (3) by the clamping device, so that the hollow profile (3) is rotated around the rotation axis. [7] Method for producing formed hollow profiles (3) according to claim 6, characterized bythat during the forming the hollow profile (3) is vibrated and / or heat treated. [8] Method for producing formed hollow profiles (3) according to one of claims 6 or 7, characterized by that the hollow profile (3) is supported in its interior during the forming process, in particular by a formless material or by the application of internal pressure. [9] Method for producing formed hollow profiles (3) according to one of the preceding claims, characterized by that the hollow profile (3) has a thickness less than or equal to 0.02 times the width of the hollow profile (3) and a length greater than or equal to 10 times the width of the hollow profile (3). [10] Method for producing formed hollow profiles (3) according to one of the preceding claims, characterized by that the cross-section (4) of the hollow profile (3) varies in the direction perpendicular to the cross-sectional area of ​​the cross-section (4) of the hollow profile (3).

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