DE102023101205A1 - Pipe bending machine - Google Patents

Abstract

A pipe bending machine (20) for bending a steel pipe is disclosed. A bending head (24) of the pipe bending machine (20) has a fitting (26), a bending element (28), on a pivoting unit (30), and a pressure unit (32). The fitting (26) defines a minimum inside bending radius for the steel pipe (22). The bending element (28) is mounted on the pivoting unit (30) in such a way that the bending element (28) bends the steel pipe (22) by pivoting the pivoting unit (30) and a path described by pivoting the bending element describes an outer bending radius of the steel pipe. The pressure unit (32) is designed to exert an angle-dependent pressure force (36) on the end face of the steel pipe (22) during the bending process.

Description

The invention relates to the pipe bending of steel pipes, in particular steel pipes that are tempered and tempered for high strength. High-strength tempered steels, for example, have a hardness of at least 1200 MPa, preferably more than 1300 MPa, more preferably more than 1500 MPa, even more preferably more than 1700 MPa.

Tubular stabilizers made of formed steel tubing are known in the prior art in a variety of embodiments. Tubular stabilizers are also referred to, for example, as torsion bars, stabilization torsion bars or torsion spring bars. Tubular stabilizers are used in particular in motor vehicles, with stabilizers being used, for example, in spring/damping systems to cushion uneven road surfaces, to stabilize against rolling when a motor vehicle is cornering and when a motor vehicle is traveling over changing road surfaces.

Such stabilizers are usually arranged in the area of the front and rear axles and usually extend over the entire width of the vehicle. The steel pipe can be shaped into stabilizers using a pipe bending machine. Before or after this shaping, the steel pipe can undergo various preparation steps that influence the spring and strength properties and improve other specific performance properties of the material. For production speed and production costs, it is advantageous to temper the steel pipes as straight lengths before shaping. In this way, tubular stabilizers can be produced with high strength using comparatively little material and thus low weight and material costs.

Compared to the solid rod stabilizers that are also available, tubular stabilizers have a lower weight with the same spring properties, for example the torsional moment of resistance. The stiffness and bending ability of tubular stabilizers depends on the diameter and wall thickness. The aim here is currently to increase the diameter-to-wall thickness ratio in order to achieve greater weight savings. However, the larger the diameter-to-wall thickness ratio, the lower the bending ability of the steel pipe. This negative effect is further increased by the tempering of the steel pipe before bending.

If the bending ability of the steel pipe is too low, the steel pipe may break when bent. Even if the steel pipe does not break directly during bending, the reduced bending ability results in higher internal stress due to the shaping (bending) and operation of the stabilizer. The bending radius can therefore become a predetermined breaking point. The properties of tubular stabilizers are therefore limited to a narrow range of geometric dimensions and the resulting spring properties, or the formability of the steel pipe or steel wire is limited in some forming processes known in the prior art. In particular, the parameters strength and toughness are related to the forming capacity and service life of a pipe stabilizer.

The object of the present invention is therefore to create an improved concept for pipe bending machines.

The task is solved by the subject matter of the independent patent claims. Further advantageous embodiments are the subject of the dependent claims.

Exemplary embodiments show a pipe bending machine for bending a steel pipe. The pipe bending machine comprises at least one (first) bending head, optionally also a second, in particular similar (for example mirror-inverted) bending head. The part of the pipe bending machine in which the steel pipe is bent is called the bending head. The bending head, optionally also both bending heads, have a fitting, a bending element, a swivel unit and a pressure unit. The fitting defines a minimum inside bending radius for the steel pipe. Advantageously, the steel pipe lies completely against the fitting, so that the fitting defines the actual internal bending radius.

The bending element is mounted on the pivoting unit in such a way that the bending element bends the steel pipe by pivoting the pivoting unit. A path described, ie traveled, by pivoting the bending element then describes an external bending radius of the steel pipe. Ie, the bending element is guided along the outside of the steel pipe. This makes the use of a bending mandrel, for example, obsolete. The path is the sequence of points at which the bending element comes into contact with the steel pipe. If the fitting describes the actual inside bending radius, the outside bending radius advantageously corresponds to the radius of the fitting. Ie, advantageously, each point that is occupied by the bending element through the pivoting and at which the bending element is in contact with the steel pipe has a distance from the fitting that corresponds to the (outer) diameter of the steel pipe. The distance is preferably measured perpendicular to the steel pipe. A bending roller can be used as a bending element. This can unroll on the steel pipe. Alternatively, it is also possible to make the bending element rigid. It is then advantageously provided with a surface that slides well on the steel pipe. It should also be noted that the bending element adjusts the bending radius of the steel pipe by bending the steel pipe on one side, starting from the fitting.

The pressure unit is designed to exert an angle-dependent pressure force on an end face of the steel pipe during the bending process. This means that the pressure unit applies the force perpendicularly to a cut surface of the steel pipe. The end face that is bent in the bending head is preferably used. This is typically the shorter end of the steel pipe. So that the pressure unit can continuously exert the pressure force on the end face of the steel pipe during the bending process, the pressure unit is also mounted on the swivel unit or travels along a path parallel to the bending head in another way. For example, the swivel unit and bending head can move on a circular path with the same center. The printing unit and bending head can be structurally connected to one another in order to execute the paths parallel to one another. Furthermore, it is advantageous if the compressive force is exerted axially evenly on the end face of the steel pipe.

In principle, any pressure curve can be used as the angle-dependent pressure force. For example, the printing unit can keep the pressure force constant up to a certain angle and then reduce the pressure, in particular to zero. It is possible for the pressure unit to exert a (gradual) increase or decrease in pressure on the end face of the steel pipe. Here too, the pressure force can be reduced if a predetermined angle is exceeded, in particular to zero. The step length can be constant so that there is a linear increase in pressure. However, the step length can also change so that a curved course of the pressure force is set using the pressure unit. By means of the curved course, a wave-shaped compressive force can also be achieved, for example.

The present application is based on a combination of ideas in order to be able to bend thin-walled steel pipes, e.g. for the lightweight construction of vehicles, after tempering, without the steel pipes breaking or developing predetermined breaking points. Bending after tempering is advantageous because it shortens the production times per workpiece (e.g. a stabilizer) made from the steel pipe compared to tempering after bending. The pressure unit supplies additional material to the bending point during bending, so that a reduction in the wall thickness due to stretching, especially in the outer area of the curvature, is counteracted. This means that the maximum elongation at the critical point is reduced. If a material-specific maximum expansion occurs in an area, a crack or break occurs, i.e. the maximum deformation capacity of the material in this area is exhausted. Furthermore, the printing unit also supplies additional material to the interior area. This leads to a reduction in stress in this area and thus prevents predetermined breaking points.

Furthermore, the pressure unit arranged on the front side has the advantage that a manipulator for inserting the steel pipe into the pipe bending machine only needs to be used for this purpose. Otherwise, one could imagine that, at least with a single-head pipe bending machine, the manipulator could take over the tracking of the steel pipe from the fixed side during the bending process. However, this would extend manufacturing times.

In addition, it has surprisingly been found that it is advantageous to adjust the pressure force of the printing unit depending on the angle. This means in particular that it can be disadvantageous to exert the same force on the end face of the steel pipe during the entire bending process.

In exemplary embodiments, the pipe bending machine is designed as a two-head pipe bending machine and therefore has two bending heads. The second bending head advantageously has the same features as the first bending head. A two-head bending machine significantly reduces production times compared to a single-head bending machine. Using the two-head bending machine, it is possible to bend the steel pipe at both ends at the same time. For a symmetrical workpiece, the bending heads of a two-head bending machine are advantageously also symmetrical. If the workpiece is asymmetrical, the two bending heads have at least the same basic features, such as the shaped piece, the bending element, the swivel unit and the pressure unit. With a two-head bending machine, it is no longer possible to move the steel pipe using the inserted manipulator if both pipe ends of the steel pipe are to be bent at the same time.

Further exemplary embodiments show that the pivoting unit is designed to apply a torque of at least 9 kilonewton meters, in particular at least 11 kilonewton meters, preferably at least 13 kilonewton meters or at least 15 kilonewton meters, in order to bend the steel pipe. The greater the torque, the swivel unit The harder or more solidly tempered steel pipes the pipe bending machine can bend.

In further exemplary embodiments, the bending head has a hold-down device which is designed to clamp the steel pipe, in particular in connection with the shaped piece, during the bending process. The hold-down device can exert counterpressure on the steel pipe during the bending process, in particular on the straight part of the steel pipe that cannot be bent. The steel pipe cannot therefore move outside the bending radius during the bending process. For example, the hold-down device can press the steel pipe onto the fitting during the bending process, so that the steel pipe is clamped between the hold-down device and the fitting. This is advantageous for obtaining a defined bending radius.

In exemplary embodiments, the pressure unit is designed to exert its pressure force on the end face of the steel pipe to a maximum of 5% of a maximum pressure force averaged over 10° from a bending angle of 60°. This means that the average compressive force can be determined over a 10° bending radius for every 10° angle up to 60°. This procedure can be described as a moving average. The maximum 10° bending radius, in which the greatest compressive force is exerted on average, serves as a reference. Alternatively, instead of looking at 10° angles, an angle of 5° can also be used. From a bending radius of 60° at the latest, the maximum compressive force is a maximum of 5% of the reference value and is therefore significantly reduced. Surprisingly, it has been shown that it is no longer an advantage and can actually be detrimental to strength if a large force is still exerted on the end face of the steel pipe with a bending radius of more than 60°. In exemplary embodiments, the limitation of the compressive force applies from a bending radius of 50°, preferably from a bending radius of 45°.

Alternatively, up to a bending angle of 30°, in particular up to 35° or up to 40°, the pressure unit can limit its pressure force to a maximum of 5% of a maximum pressure force averaged over 10° from this bending angle on the end face of the steel pipe. In contrast to the previous exemplary embodiment, pressure is initially not exerted on the end face of the steel pipe by the pressure unit, or at least not significantly. The compressive force is only increased above the specified bending angle. Alternatively, instead of considering 10° angles, an angle of 5° can also be used for the moving average.

Further exemplary embodiments show the pressure unit, which is designed to exert the pressure force on the steel pipe in such a way that an average wall thickness of the steel pipe along its inner bending radius is greater than an average wall thickness of the steel pipe before bending. This means in particular that no countermeasures are taken to counteract the material compression on the inside of the bent steel tube.

In further exemplary embodiments, the pivoting unit is designed to pivot through an angle of greater than 90° in order to bend the steel pipe with a corresponding angle of greater than 90°.

zu biegen.According to further exemplary embodiments, it is disclosed that the pipe bending machine is designed to be a steel pipe with a wall thickness ratio of the steel pipe diameter D to the wall thickness s of $\frac{D}{s}\ge 10$

to bend.

bevorzugt von $\frac{D}{r}\ge \mathrm{0,7}$

zu biegen.Embodiments also show that the pipe bending machine is designed to be a steel pipe, in particular a high-strength tempered steel pipe, with a ratio of the steel pipe diameter D to the bending radius r of $\frac{D}{r}\ge \mathrm{0.4,}$

preferred by $\frac{D}{r}\ge 0.7$

to bend.

• 1: eine schematische Draufsicht auf eine Rohrbiegemaschine, wobei 1a die Rohrbiegemaschine mit einem Biegekopf und 1b die Rohrbiegemaschine mit zwei Biegeköpfen darstellt;
• 2: eine schematische Draufsicht auf die Rohrbiegemaschine gemäß Ausführungsbeispielen, wobei 2a die Rohrbiegemaschine in ihrem Ausgangszustand mit geradem Stahlrohr und 2b die Rohrbiegemaschine mit zu einem Zeitpunkt des Biegevorgangs mit einem um ca. 70° gebogenen Stahlrohr darstellt;
• 3: die Rohrbiegemaschine gemäß 2a in einer schematischen perspektivischen Darstellung.

Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. Show it:

• 1 : a schematic top view of a pipe bending machine, where 1a the pipe bending machine with a bending head and 1b represents the pipe bending machine with two bending heads;
• 2 : a schematic top view of the pipe bending machine according to exemplary embodiments, where 2a the pipe bending machine in its initial state with straight steel pipe and 2 B represents the pipe bending machine with a steel pipe bent by approximately 70° at a time during the bending process;
• 3 : the pipe bending machine according to 2a in a schematic perspective view.

Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it should be noted that identical, functionally identical or equivalent elements, objects and/or structures are provided with the same reference numerals in the different figures, so that the in Description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

1 shows a pipe bending machine 20 for bending a steel pipe 22. The pipe bending machine includes a bending head 24. The bending head 24 has a fitting 26, a bending element 28, a pivot unit 30 and a pressure unit 32. The fitting 26 defines at least a minimum inside bending radius of the bent steel pipe. The bending element 28 is mounted on the pivot unit 30. By pivoting the pivot unit 30, the bending element 28 follows a trajectory that describes the outer bending radius of the steel pipe 22. The direction of rotation of the pivot unit 30 is shown by arrow 34. The printing unit 32 is shown here as a piston 32a, which extends from a housing 32b. The pressure unit 32 exerts an angle-dependent pressure force 36 (represented by the corresponding arrow) on the end face of the steel pipe 22 during the bending process. Arrow 38 represents the movement of the pressure unit 32 so that it can continuously exert the pressure force on the steel pipe 22 on the head side during the bending process.

Furthermore, in 1 a hold-down device 40 is shown. This can clamp the steel pipe 22 during the bending process. Alternatively, in the case of a pipe bending machine with two bending heads, the pipe can optionally be movably fixed under the hold-down device, so that the pipe can slip minimally, at least axially. In this case, the steel tube 22 is still held in position because of the (preferably symmetrical) pressure forces of the pressure cylinders.

1a now shows the pipe bending machine 20 with a bending head 24. The reference numbers used also refer to this bending head. 1b . shows an alternative pipe bending machine 20 with two bending heads 24, 24 '. The numbers of the reference numbers are chosen to identify the features of the second bending head 24 'like the reference numbers of the first bending head 24, but an apostrophe "'" has been added.

2 shows a schematic detailed representation of the bending head 24 in an exemplary embodiment, also in a top view. 2a shows the bending head with inserted steel tube 22 without bend and 2 B the bending head 24 with a bent steel tube 22. It can be clearly seen that the piston 32a of the pressure unit 32 in 2 B is further extended than in 2a . A compressive force has therefore been exerted on the end face of the steel pipe. The printing unit 32 is mounted on a mounting plate 42. The printing unit 32 is mechanically connected to the pivoting unit 30 by means of the mounting plate 42. The alignment of the printing unit 32 to the end face of the steel pipe 22 thus remains the same during pivoting.

In 2 the hold-down device 40 is shown in connection with a (pneumatic, hydraulic or electric) cylinder 40a. The cylinder 40a can apply the necessary force to hold the hold-down device 40 in position against the bending force. For example, to insert and remove the steel pipe 22, the hold-down device 40 can be moved to the side by retracting the cylinder 40a and release the clamped steel pipe.

Furthermore, the bending unit 28 is assigned a (pneumatic, hydraulic or electric) cylinder 28a. The cylinder 28a can apply the necessary force to hold the bending unit 28 in position against the bending force. For example, to insert and remove the steel pipe 22, the bending unit can be moved to the side by retracting the cylinder 28a and simplify the insertion or removal of the steel pipe.

In addition to the bending unit 28, a guide unit 28b is also shown. The guide unit 28b can advantageously also be mechanically connected to the cylinder 28a. The guide unit 28b makes it easier to bend the steel pipe. Bending is made easier because the guide unit 28b has a larger lever arm compared to the bending unit 28. In 2 the guide unit 28b is shown as a shaped piece. For example, it is also possible to train this as a leadership role.

3 shows a schematic perspective view of the bending head 24 2 . The steel pipe 22 is shown in its starting position (without bending) and with 4 exemplary snapshots during the bending. The fitting is not shown in order not to obscure the steel pipe and the structure of the bending head behind it. In addition to the previous illustrations, an optional guide rail 44 for the printing unit is also shown. The guide rail 44 can stabilize the printing unit 32 during the bending process.

Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or a component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously, aspects that were described in connection with or as a process step also represent a description of a corresponding block or detail or feature of a corresponding device.

The embodiments described above are merely illustrative of the principles of the present invention. It will be understood that modifications and variations of the arrangements and details described herein will occur to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented from the description and explanation of the exemplary embodiments herein.

List of reference symbols:

20

Pipe bending machine

22

Steel pipe

24

bending head

26

fitting

28

bending element

30

Swivel unit

32

Pressure unit

34

Bend movement arrow

36

Compressive force

38

Movement arrow of the pressure unit during bending

40

Hold-down device

42

Mounting plate

44

Guide rail

Claims (10)

Pipe bending machine (20) for bending a steel pipe, a bending head (24) of the pipe bending machine (20) having the following features: - a fitting (26) which defines a minimum inside bending radius for the steel pipe (22); - a bending element (28) which is mounted on a pivoting unit (30) in such a way that the bending element (28) bends the steel pipe (22) by pivoting the pivoting unit (30) and a path described by pivoting the bending element forms an external bending radius of the steel pipe describes; - A pressure unit (32) which is designed to exert an angle-dependent pressure force (36) on an end face of the steel pipe (22) during the bending process. Pipe bending machine (20) according to Claim 1 , wherein the pivoting unit (30) is designed to apply a torque of at least 9 kilonewton meters, in particular at least 11 kilonewton meters, preferably at least 13 kilonewton meters or at least 15 kilonewton meters, in order to bend the steel pipe Pipe bending machine (20) according to one of the preceding claims, wherein the bending head (24) has a hold-down device (40) which is designed to clamp the steel pipe, in particular in connection with the fitting (26), during the bending process. Pipe bending machine (20) according to one of the preceding claims, wherein the pressure unit (32) is designed, from a bending angle of 60°, in particular from 50° or from 45°, its pressure force (36) to a maximum of 5% of a maximum up to this bending angle , a pressure force averaged over 10°, to be exerted on the face of the steel pipe (22). Pipe bending machine (20) according to one of the preceding claims, wherein the pressure unit (32) is designed up to a bending angle of 30°, in particular up to 35° or up to 40°, its pressure force (36) to a maximum of 5% of a maximum from this bending angle , compressive force averaged over 10°, to be limited to the end face of the steel pipe (22). Pipe bending machine (20) according to one of the preceding claims, wherein the steel pipe is a high-strength tempered steel pipe. Pipe bending machine (20) according to one of the preceding claims, wherein the pivoting unit (30) is designed to pivot through an angle >90° in order to bend the steel pipe (22) at an angle >90°. Pipe bending machine (20) according to one of the preceding claims, wherein the pipe bending machine (20) is designed to be a steel pipe (22) with a wall thickness ratio of the steel pipe diameter D to the wall thickness s of $\frac{D}{s}\ge 10$

to bend. Pipe bending machine (20) according to one of the preceding claims, wherein the pipe bending machine (20) is designed to produce a steel pipe (22) with a ratio of the steel pipe diameter D to the bending radius r of $\frac{D}{r}\ge 0.4$

to bend. Pipe bending machine (20) according to one of the preceding claims, wherein the pipe bending machine (20) is a two-head pipe bending machine (20) and has two bending heads, the second bending head (24) having the same features as the first bending head.

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