DEVICES AND METHOD FOR SHAPING A TUBULAR HOLLOW ELEMENT

Abstract

A device for forming a tubular hollow body has a forming die, a mandrel and a forming drive with a die drive. Die profile projections arranged on the outer side of a hollow body wall and mandrel profile intermediate spaces arranged on the inner side of the hollow body wall as well as die profile intermediate spaces arranged on outer side of the hollow body wall and mandrel profile projections arranged on the inner side of the hollow body wall lie opposite to each other on the hollow body wall in the radial direction. A method for forming a tubular hollow body involves moving the forming die along the hollow body axis, and by exceeding of the flow limit of the material of the hollow body wall, material of the hollow body wall flows into the mandrel profile intermediate spaces, forming an inner profile of the hollow body wall.

Claims

1: A device for forming a tubular hollow body (1) having a hollow body wall (2) made of a plastically deformable material and a hollow body axis (3) extending in a longitudinal direction of the hollow body (1), comprising: a forming die (9, 9a) designed to be arranged on an outer side of the hollow body (1) and provided with a die opening (11, 11a) designed for receiving the hollow body (1), a mandrel (10, 10a) designed to be arranged in an interior of the hollow body (1) and provided on a circumference thereof with a shape-imparting mandrel profile (15, 15a) having mandrel profile projections (16, 16a) and mandrel profile intermediate spaces (17, 17a) formed between the mandrel profile projections (16, 16a), with the mandrel profile projections (16, 16a) and the mandrel profile intermediate spaces (17, 17a) extending along the hollow body axis (3) on the mandrel (10, 10a) arranged in the interior of the hollow body (1), and the mandrel profile intermediate spaces (17, 17a) opening towards an axially parallel inner side of the hollow body wall (2), and a forming drive (20, 20a) with a die drive (19, 19a), by means of which the forming die (9, 9a) can be moved with an axial die movement along the hollow body axis (3) relative to the hollow body (1) and thereby along the mandrel (10, 10a) arranged in the interior of the hollow body (1), wherein material of the hollow body wall (2) flows into the mandrel profile intermediate spaces (17, 17a) of the mandrel (10, 10a) due to the axial die movement of the forming die and an associated exceeding of a flow limit of the material of the hollow body wall (2), forming an inner profile (18, 18a) of the hollow body wall (2), wherein the forming die (9, 9a) is provided at the die opening (11, 11a) with a shape-imparting die profile (12, 12a) having die profile projections (13, 13a) and die profile intermediate spaces (14, 14a) formed between the die profile projections (13, 13a), wherein, when the forming die (9, 9a) is moved with the axial die movement, the die profile projections (13, 13a) and the die profile intermediate spaces (14, 14a) extend along the hollow body axis (3) and the die profile intermediate spaces (14, 14a) open towards the axially parallel outer side of the hollow body wall (2) and die profile projections (13, 13a) arranged on the axially parallel outer side of the hollow body wall (2) and mandrel profile intermediate spaces (17, 17a) arranged on the axially parallel inner side of the hollow body wall (2) as well as die profile intermediate spaces (14, 14a) arranged on the axially parallel outer side of the hollow body wall (2) and mandrel profile projections (16, 16a) arranged on the axially parallel inner side of the hollow body wall (2) in each case lie opposite to each other on the hollow body wall (2) in a radial direction of the hollow body axis (3), with the die profile projections (13, 13a) impinging material of the hollow body wall (2) in a direction of the mandrel profile intermediate spaces (17, 17a) opposite the die profile projections (13, 13a), forming the inner profile (18, 18a) of the hollow body wall (2).

2: The device according to claim 1, wherein a mandrel-side toothed profile having mandrel teeth as the mandrel profile projections (16, 16a) and having mandrel tooth intermediate spaces as the mandrel profile intermediate spaces (17, 17a) is provided as the shape-imparting mandrel profile (15, 15a), and wherein a die-side toothed profile having die teeth as the die profile projections (13, 13a) and having die tooth intermediate spaces as die profile intermediate spaces (14, 14a) is provided as the shape-imparting die profile (12, 12a), and wherein die teeth arranged on the axially parallel outer side of the hollow body wall (2) and mandrel tooth intermediate spaces arranged on the axially parallel inner side of the hollow body wall (2) as well as die tooth intermediate spaces arranged on the axially parallel outer side of the hollow body wall (2) and mandrel teeth arranged on the axially parallel inner side of the hollow body wall (2) lie opposite to each other on the hollow body wall (2) in the radial direction of the hollow body axis (3) and the die teeth impinge material of the hollow body wall (2) in the direction of the mandrel tooth intermediate spaces opposite the die teeth, forming the inner profile (18, 18a) of the hollow body wall (2).

3: The device according to claim 1, wherein the die opening (11) has an opening cross-section that is smaller than a hollow body cross-section (4), extending perpendicularly to the hollow body axis (3), in an initial state, and wherein the cross-section (4) of the hollow body (1) is reduced due to the axial die movement and an associated exceeding of the flow limit of the material of the hollow body wall (2).

4: The device according to claim 1, wherein an axial abutment (23) is provided for the hollow body (1), on which abutment the hollow body (1) is supported in the direction of the axial die movement and which abutment is stationary along the hollow body axis (3) during the axial die movement carried out by the forming die (9) relative to the hollow body (1).

5: The device according to claim 1, wherein the forming drive (20, 20a) has a mandrel drive (21, 21a) and a drive controller (22, 22a) in addition to the die drive (19, 19a), the mandrel drive (21, 21a) is configured to move the mandrel (10, 10a) arranged in the interior of the hollow body (1 along the hollow body axis (3) through the die opening (11, 11a) with an axial mandrel movement counter to the axial die movement, the hollow body wall (2) can be subjected to tensile stress by means of the mandrel (10, 10a) in a direction of the axial mandrel movement due to the axial mandrel movement and can thereby be drawn through the die opening (11, 11a) relative to the forming die (9, 9a) in the direction of the axial mandrel movement, and the drive controller (22, 22a) of the forming drive (20, 20a) is configured to control the mandrel drive (21, 21a) and the die drive (19, 19a) in such a way that the axial mandrel movement and the axial die movement are superposed on one another.

6: The device according to claim 5, wherein the drive controller (22, 22a) is configured to control the die drive (19, 19a) and the mandrel drive (21, 21a) in such a way that a ratio of speeds of the axial mandrel movement and of the axial die movement is dependent on a ratio of the cross-section of the hollow body (1) in an initial state and the cross-section of the hollow body (1) after a forming process.

7: The device according to claim 5, wherein the ratio of the amounts of the axial mandrel movement and of the axial die movement is reciprocal to the ratio of the speeds of the axial mandrel movement and of the axial die movement.

8: The device according to claim 5, wherein the forming die (9, 9a) is movable by means of the die drive (19, 19a) with a positioning movement from a position away from the hollow body (1) to be formed to a position in which the forming die (9, 9a) is arranged on the outer side of the hollow body (1) and the drive controller (22, 22a) is configured to control the die drive (19, 19a) and the mandrel drive (21, 21a) in such a way that the mandrel drive (21, 21a) initiates the axial mandrel movement before the forming die (9, 9a) is arranged on the outer side of the hollow body (1) due to the positioning movement of the forming die (9, 9a).

9: An arrangement for forming a tubular hollow body (1) having a hollow body wall (2) made of a plastically deformable material and a hollow body axis (3) extending in the longitudinal direction of the hollow body (1), comprising: a first forming device (7) and a second forming device (8), the second forming device (8) being arranged downstream of the first forming device (7) in a forming process, wherein the first forming device (7) is designed to produce a preform (32) of a finished formed hollow body from the hollow body (1) in an initial state, wherein the preform (32) is designed as a tubular hollow body having a preform wall (38) made of a plastically deformable material and having a preform axis (37) coinciding with the hollow body axis (3), and wherein the second forming device (8) being designed to produce a subsequent form of the preform (32), to produce the finished formed hollow body, which has a subsequent form wall, wherein the first forming device (7) comprises: a first forming die (26) designed to be arranged on an outer side of the hollow body (1) and provided with a first die opening (28) designed for receiving the hollow body (1), a first mandrel (27) designed to be arranged in an interior of the hollow body (1) and provided on a circumference with a first shape-imparting mandrel profile (29) having first mandrel profile projections (30) and first mandrel profile intermediate spaces (31) formed between the first mandrel profile projections (30), with the first mandrel profile projections (30) and the first mandrel profile intermediate spaces (31) extending along the hollow body axis (3) on the first mandrel (27) arranged in the interior of the hollow body (1), and the first mandrel profile intermediate spaces (31) opening towards an axially parallel inner side of the hollow body wall (2), and a first forming drive (34) with a first die drive (33), by means of which the first forming die (26) is movable with an axial die movement along the hollow body axis (3) relative to the hollow body (1) and thereby along the first mandrel (27) arranged in the interior of the hollow body (1), wherein material of the hollow body wall (2) flows into the first mandrel profile intermediate spaces (31) of the first mandrel (27) due to an axial die movement of the first forming die (26) and an associated exceeding of a flow limit of the material of the hollow body wall (2), forming an inner profile (39) of the preform wall (38), and wherein the second forming device, comprises: a second forming die (40) designed to be arranged on an outer side of the preform (32) and having a second die opening (42) designed for receiving the preform (32), a second mandrel (41) designed to be arranged in an interior of the preform (32) and provided on a circumference with a second shape-imparting mandrel profile (46) having second mandrel profile projections (47) and second mandrel profile intermediate spaces (48) formed between the second mandrel profile projections (47), with the second mandrel profile projections (47) and the second mandrel profile intermediate spaces (48) extending along a preform axis (37) on the second mandrel (41) arranged in the interior of the preform (32), and the second mandrel profile intermediate spaces (48) opening towards an axially parallel inner side of the preform wall (38) and receiving an inner profile (39) of the preform wall (38), and a second forming drive (50) with a second die drive (49), by means of which the second forming die (40) is movable with an axial die movement along the preform axis (37) relative to the preform (32) and thereby along the second mandrel (41) arranged in the interior of the preform (32), wherein material of the preform (32) flows into the second mandrel profile intermediate spaces (48) of the second mandrel (41) due to the axial die movement of the second forming die (40) and an associated exceeding of a flow limit of the material of the preform wall (38), forming an inner profile (53) of the subsequent form wall, wherein the second forming die (40) is provided at the second die opening (42) with a shape-imparting die profile (43) having die profile projections (44) and die profile intermediate spaces (45) formed between the die profile projections (44), and wherein, when the second forming die (40) is moved with the axial die movement, the die profile projections (44) and the die profile intermediate spaces (45) of the second forming die (40) extend along the preform axis (37) and the die profile intermediate spaces (45) open towards an axially parallel outer side of the preform wall (38) and wherein die profile projections (44) arranged on the axially parallel outer side of the preform wall (38) and second mandrel profile intermediate spaces (48) arranged on the axially parallel inner side of the preform wall (38) as well as die profile intermediate spaces (45) arranged on the axially parallel outer side of the preform wall (38) and second mandrel profile projections (47) arranged on the axially parallel inner side of the preform wall (38) in each case lie opposite to each other on the preform wall (38) in a radial direction of the preform axis (37), with the die profile projections (44) impinging material of the preform wall (38) in a direction of the second mandrel profile intermediate spaces (48) opposite the die profile projections (44), forming the inner profile (53) of the subsequent form wall.

10: The arrangement according to claim 9, wherein the first shape-imparting mandrel profile (29) of the first mandrel (27) and the second shape-imparting mandrel profile (46) of the second mandrel (41) correspond to one another in their geometry.

11: The arrangement according to claim 10, wherein the first mandrel (27) is provided as the second mandrel (41).

12: The arrangement according to claim 9, wherein the first die opening (28) of the first forming die (26) has a smooth opening wall.

13: The arrangement according to claim 9, wherein the first forming die (26) is provided at the first die opening (28) with a first shape-imparting die profile having first die profile projections and first die profile intermediate spaces formed between the first die profile projections, wherein, when the first forming die (26) is moved with the axial die movement, wherein the first die profile projections and the first die profile intermediate spaces extend along the hollow body axis (3) and the first die profile intermediate spaces open towards the axially parallel outer side of the hollow body wall (2) wherein first die profile projections arranged on the axially parallel outer side of the hollow body wall (2) and first mandrel profile intermediate spaces arranged on the axially parallel inner side of the hollow body wall (2) as well as first die profile intermediate spaces arranged on the axially parallel outer side of the hollow body wall (2) and first mandrel profile projections arranged on the axially parallel inner side of the hollow body wall (2) in each case lie opposite to each other on the hollow body wall (2) in the radial direction of the hollow body axis (3), with the first die profile projections impinging material of the hollow body wall (2) in the direction of the first mandrel profile intermediate spaces opposite the first die profile projections, forming the inner profile (39) of the preform wall (38), and wherein the second forming die (40) has, as a shape-imparting die profile, a second shape-imparting die profile having second die profile projections and second die profile intermediate spaces formed between the second die profile projections.

14: The arrangement according to claim 9, wherein the first die opening (28) of the first forming die (26) has an opening cross-section that is smaller than a hollow body cross-section (4) of the hollow body (1) in the initial state, the hollow body cross-section (4) extending perpendicularly to the hollow body axis (3), with the cross-section (4) of the hollow body (1) being reduced due to the axial die movement of the first forming die (26) and an associated exceeding of the flow limit of the material of the hollow body wall (2) and/or wherein the second die opening (42) of the second forming die (40) has an opening cross-section that is smaller than a preform cross-section of the preform (32) extending perpendicularly to the preform axis (37), with the cross-section of the preform (32) being reduced due to the axial die movement of the second forming die (40) and an associated exceeding of the flow limit of the material of the preform wall (38).

15: A method for forming a tubular hollow body (1) having a hollow body wall (2) made of a plastically deformable material and a hollow body axis (3) extending in the longitudinal direction of the hollow body (1), a forming die (9, 9a) being arranged on the outer side of the hollow body (1) and provided with a die opening (11, 11a) designed for receiving the hollow body (1), a mandrel (10, 10a) being arranged in the interior of the hollow body (1) and provided on a circumference with a shape-imparting mandrel profile (15, 15a) having mandrel profile projections (16, 16a) and mandrel profile intermediate spaces (17, 17a) formed between the mandrel profile projections (16, 16a), with the mandrel profile projections (16, 16a) and the mandrel profile intermediate spaces (17, 17a) extending along the hollow body axis (3) on the mandrel (10, 10a) arranged in an interior of the hollow body (1), and the mandrel profile intermediate spaces (17, 17a) opening towards the axially parallel inner side of the hollow body wall (2), comprising the steps of: moving the forming die (9, 9a) by means of a die drive (19, 19a) of a forming drive (20, 20a) with an axial die movement along the hollow body axis (3) relative to the hollow body (1) and thereby along the mandrel (10, 10a) arranged in the interior of the hollow body (1), wherein material of the hollow body wall (2) flows into the mandrel profile intermediate spaces (17, 17a) of the mandrel (10, 10a) due to the axial die movement and an associated exceeding of the flow limit of the material of the hollow body wall (2), forming an inner profile (18, 18a) of the hollow body wall (2), wherein the forming die (9, 9a) is moved by means of the die drive (19, 19a) with the axial die movement relative to the hollow body (1), which forming die is provided at the die opening (11, 11a) with a shape-imparting die profile (12, 12a) having die profile projections (13, 13a) and die profile intermediate spaces (14, 14a) formed between the die profile projections (13, 13a), wherein, when the forming die (9, 9a) is moved with the axial die movement, the die profile projections (13, 13a) and the die profile intermediate spaces (14, 14a) extend along the hollow body axis (3) and the die profile intermediate spaces (14, 14a) open towards the axially parallel outer side of the hollow body wall (2) and die profile projections (13, 13a) arranged on an axially parallel outer side of the hollow body wall (2) and mandrel profile intermediate spaces (17, 17a) arranged on an axially parallel inner side of the hollow body wall (2) as well as die profile intermediate spaces (14, 14a) arranged on the axially parallel outer side of the hollow body wall (2) and mandrel profile projections (16, 16a) arranged on the axially parallel inner side of the hollow body wall (2) in each case lie opposite to each other on the hollow body wall (2) in a radial direction of the hollow body axis (3), with the die profile projections (13, 13a) impinging material of the hollow body wall (2) in a direction of the mandrel profile intermediate spaces (17, 17a) opposite the die profile projections (13, 13a), forming the inner profile (18, 18a) of the hollow body wall (2).

16: A method for forming a tubular hollow body (1) having a hollow body wall (2) made of a plastically deformable material and a hollow body axis (3) extending in the longitudinal direction of the hollow body (1), the method comprising a first method stage and a second method stage with the second method stage following the first method stage in the method, a preform (32) of a finished formed hollow body being produced in the first method stage from the hollow body (1) in an initial state, the preform (32) being designed as a tubular hollow body (1) having a preform wall (38) made of a plastically deformable material and having a preform axis (37) coinciding with the hollow body axis (3), and in the second method stage, a subsequent form of the preform (32), in particular the finished formed hollow body, is produced, which has a subsequent form wall, wherein in the first method stage a first forming die (26) of a first forming device (7) is arranged on an outer side of the hollow body (1) in such a way that the first forming die (26) receives the hollow body (1) at a first die opening (28), a first mandrel (27) of the first forming device (7) is arranged in an interior of the hollow body (1) and provided on a circumference with a first shape-imparting mandrel profile (29) having first mandrel profile projections (30) and first mandrel profile intermediate spaces (31) formed between the first mandrel profile projections (30), with the first mandrel profile projections (30) and the first mandrel profile intermediate spaces (31) extending along the hollow body axis (3) on the first mandrel (27) arranged in the interior of the hollow body (1), and the first mandrel profile intermediate spaces (31) opening towards an axially parallel inner side of the hollow body wall (2), and the first forming die (26) is moved by means of a first die drive (33) of a first forming drive (34) of the first forming device (7) with an axial die movement along the hollow body axis (3) relative to the hollow body (1) and thereby along the first mandrel (27) arranged in the interior of the hollow body (1), wherein material of the hollow body wall (2) flows into the first mandrel profile intermediate spaces (31) of the first mandrel (27) due to the axial die movement of the first forming die (26) and an associated exceeding of the flow limit of the material of the hollow body wall (2), forming an inner profile (39) of the preform wall (38), and in the second method stage a second forming die (40) of a second forming device (8) is arranged on an outer side of the preform (32) in such a way that the second forming die (40) receives the preform (32) at a second die opening (42), a second mandrel (41) of the second forming device (8) is arranged in an interior of the preform (32) and provided on a circumference with a second shape-imparting mandrel profile (46) having second mandrel profile projections (47) and second mandrel profile intermediate spaces (48) formed between the second mandrel profile projections (47), with the second mandrel profile projections (47) and the second mandrel profile intermediate spaces (48) extending along the preform axis (37) on the second mandrel (41) arranged in the interior of the preform (32), and the second mandrel profile intermediate spaces (48) opening towards an axially parallel inner side of the preform wall (38) and receiving the inner profile of the preform wall (38), and the second forming die (40) is moved by means of a second die drive (49) of a second forming drive (50) of the second forming device (8) with an axial die movement along the preform axis (37) relative to the preform (32) and thereby along the second mandrel (41) arranged in the interior of the preform (32), wherein material of the preform (32) flows into the second mandrel profile intermediate spaces (48) of the second mandrel (41) due to the axial die movement of the second forming die (40) and an associated exceeding of the flow limit of the material of the preform wall (38), forming an inner profile (53) of a subsequent form wall, wherein the second forming die (40) is moved by means of the second die drive (49) with the axial die movement relative to the preform (32), which second forming die is provided at the second die opening (42) with a shape-imparting die profile (43) having die profile projections (44) and die profile intermediate spaces (45) formed between the die profile projections (44), wherein, when the second forming die (40) is moved with the axial die movement, wherein the die profile projections (44) and the die profile intermediate spaces (45) of the second forming die (40) extend along the preform axis (37) and the die profile intermediate spaces (45) open towards an axially parallel outer side of the preform wall (38) and wherein die profile projections (44) arranged on the axially parallel outer side of the preform wall (38) and second mandrel profile intermediate spaces (48) arranged on the axially parallel inner side of the preform wall (38) as well as die profile intermediate spaces (45) arranged on the axially parallel outer side of the preform wall (38) and second mandrel profile projections (47) arranged on the axially parallel inner side of the preform wall (38) in each case lie opposite to each other on the preform wall (38) in a radial direction of the preform axis (37), with the die profile projections (44) impinging material of the preform wall (38) in a direction of the second mandrel profile intermediate spaces (48) opposite the die profile projections (44), forming the inner profile (53) of the subsequent form wall.

Description

[0052] In the following, the invention is explained in more detail on the basis of schematic illustrations given by way of example. Shown are:

[0053] FIG. 1 a tube to be formed in an initial state,

[0054] FIG. 2 a single-stage device for forming the tube shown in FIG. 1 in a single-stage forming method with a cross-sectional reduction and with a profiling of the tube wall,

[0055] FIG. 3a a first forming device of a two-stage forming arrangement for producing a preform of a finished formed tube in the context of a two-stage forming method,

[0056] FIG. 3b a second forming device of the two-stage forming arrangement for producing the finished formed tube from the preform shown in FIG. 3a in the context of the two-stage forming method, and

[0057] FIG. 4 a single-stage device for forming the tube shown in FIG. 1 in a single-stage forming method with a profiling of the tube wall, but without a cross-sectional reduction of the tube wall.

[0058] According to FIG. 1, a tube 1 made of a plastically deformable metallic material is provided as the hollow body to be formed. The tube 1 has a tube wall 2 as the hollow body wall and a tube axis 3 extending in the longitudinal direction of the tube 2 as the hollow body axis. The tube 1 is cylindrical with a circular tube cross-section 4 as a hollow body cross-section, which can be seen in the end-face view of the tube 1 in FIG. 1, and with an annular wall cross-section.

[0059] A steering shaft for a motor vehicle is to be manufactured from the tube 1.

[0060] For this purpose, single-stage devices 5, 5a shown in FIG. 2 and FIG. 4 are used or, alternatively, a multi-stage arrangement 6 shown in FIGS. 3a and 3b, which is two-stage in the example shown, is used. The two-stage arrangement 6 comprises a first forming device 7 and a second forming device 8.

[0061] The devices 5, 5a and the forming devices 7, 8 with the respective formed workpieces are shown in FIG. 2 and in FIGS. 3a, 3b and 4, in each case in a highly schematized side view and also in a view of the end face that is on the right in the side view.

[0062] The device 5 shown in FIG. 2 is mounted on an axial forming machine of conventional design, for example on an axial forming machine such as is offered by FELSS Systems GmbH, 75203 Knigsbach-Stein, Germany, under the product name Aximus.

[0063] A forming die 9 of the device 5 designed to be arranged on the outer side of the tube 1 is installed in a tool holder of the axial forming machine that can move along the tube axis 3. A mandrel holder of the axial forming machine, also movable along the tube axis 3, is used to fix a mandrel 10 of the device 5. The tool holder for the forming die 9 and the mandrel holder for the mandrel 10 are not shown in FIG. 2 for the sake of simplicity.

[0064] The forming die 9 has a die opening 11 (calibration section) designed for receiving the tube 1. At the die opening 11, the forming die 9 is provided with a shape-imparting die profile in the form of a shape-imparting die toothing 12. The die toothing 12 has die teeth 13 as die profile projections and die tooth intermediate spaces 14 formed between the die teeth 13 as die profile intermediate spaces. The root circle diameter of the die opening 11 is smaller than the diameter of the tube cross-section 4 in the initial state with the tube 1 still undeformed.

[0065] The mandrel 10 is designed to be arranged in the interior of the tube 1 and is provided on its circumference with a shape-imparting mandrel profile designed as a shape-imparting mandrel toothing 15. The shape-imparting mandrel toothing 15 is formed by mandrel profile projections in the form of mandrel teeth 16 and by mandrel tooth intermediate spaces 17 arranged between the mandrel teeth 16 as mandrel profile intermediate spaces.

[0066] The die teeth 13 and the die tooth intermediate spaces 14 extend along the tube axis 3 on the forming die 9, which is seated on the outer side of the tube 1. The die tooth intermediate spaces 14 open towards the axially parallel outer side of the tube wall 2.

[0067] On the mandrel 10 in the interior of the tube 1, the mandrel teeth 16 and the mandrel tooth intermediate spaces 17 also extend along the tube axis 3. The mandrel tooth intermediate spaces 17 open towards the axially parallel inner side of the tube wall 2.

[0068] The forming die 9 and the mandrel 10 are positioned relative to one another around the tube axis 3 in such a way that the die teeth 13 arranged on the axially parallel outer side of the tube wall 2 and the mandrel tooth intermediate spaces 17 arranged on the axially parallel inner side of the tube wall 2 as well as the die tooth intermediate spaces 14 arranged on the axially parallel outer side of the tube wall 2 and the mandrel teeth 16 arranged on the axially parallel inner side of the tube wall 2 in each case lie opposite to each other on the tube wall 2 in the radial direction of the tube axis 3.

[0069] By means of the device 5, the tube cross-section 4, specifically the wall thickness of the tube wall 2, is reduced, and at the same time the tube wall 2 is provided on the inner side thereof with an inner profile in the form of an internal toothing 18.

[0070] A die drive 19 of a forming drive 20 of the device 5 is used to produce an axial die movement of the forming die 9 required for this purpose. In addition to the die drive 19, the forming drive 20 comprises a mandrel drive 21 and a drive controller 22.

[0071] At the start of the forming process, the die drive 19 moves the tool holder of the axial forming machine together with the forming die 9 along the tube axis 3 until the forming die 9 reaches from a position away from the tube 1 the right-hand end of the tube 1 in FIG. 1 and this tube end is directly adjacent to the tube-side mouth of the die opening 11. At this point in time, the tube 1 is still in its undeformed initial state.

[0072] In addition, the mandrel drive 21 moves the mandrel holder of the axial forming machine with the mandrel 10 along the tube axis 3 from a position to the left of the tube 1 in FIG. 1 to the right until the mandrel 10 fixed to the mandrel holder assumes the position shown in FIG. 2 in the interior of the tube 1.

[0073] The tube 1 to be formed is mounted on the axial forming machine with its left-hand end in FIGS. 1 and 2 on an axial abutment 23 that is stationary along the tube axis 3.

[0074] In order to form the tube 1, the forming die 9 is now moved by means of the die drive 19 from its initial position at the right-hand end of the tube 1 with an axial die movement relative to the tube 1, which is supported on the stationary axial abutment 23 and is therefore also stationary, in the direction of the stationary axial abutment 23. During the axial die movement, the forming die 9 moves along the tube axis 3 relative to the tube 1 and also along the mandrel 10 arranged in the interior of the tube 1. The direction of movement of the forming die 9 during the axial die movement is illustrated by an arrow 24 in FIG. 2.

[0075] Due to the oversize of the undeformed tube cross-section 4 compared to the opening cross-section of the die opening 11, the axial die movement of the forming die 9 causes the flow limit of the material of the tube wall 2 to be exceeded on the side of the forming die 9 located in the direction of arrow 24. The tube cross-section 4 is reduced due to the axial die movement and material from the tube wall 2 flows into the mandrel tooth intermediate spaces 17 of the mandrel 10, forming the internal toothing 18 of the tube wall 2 and simultaneously elongating the tube wall 2.

[0076] The die teeth 13 of the die toothing 12, due to their arrangement opposite the mandrel tooth intermediate spaces 17 of the mandrel 10, ensure that the mandrel tooth intermediate spaces 17 are completely filled with the flowing material of the tube wall 2, and that the internal toothing 18 of the tube wall 2 is therefore produced precisely with its target geometry specified by the mandrel toothing 15.

[0077] FIG. 2 illustrates a point in time in the forming process at which the processing of the tube 1 has not yet been completed and the forming die 9 therefore still has a residual path to cover in the direction of the axial abutment 23.

[0078] In the case of the tube 1, if there is a risk of the tube 1 being compressed during the forming process, for example due to the tube length, the above kinematics of the forming process are modified.

[0079] In deviation from the sequences described above, in order to avoid a compression of the tube 1, an axial mandrel movement of the mandrel 10 directed in the opposite direction to the axial die movement and carried out in the direction of an arrow 25 in FIG. 2 is superposed on the axial die movement of the forming die 9 by means of the drive controller 22.

[0080] The speeds of the axial die movement and of the axial mandrel movement can be different in this case. For example, by means of the drive controller 22, the speed of the axial die movement of the forming die 9 in the direction of arrow 24 can be set to 60 mm/s and the speed of the axial mandrel movement of the mandrel 10 in the direction of arrow 25 can be set to 15 mm/s.

[0081] When the free end of the tube 1 enters the die opening 11 at the start of the forming process, the tube wall 2 is pressed against the mandrel 10 in the relevant region. A force fit is thereby produced between the tube wall 2 and the mandrel 10.

[0082] At the same time, the axial movement of the forming die 9 causes the tube wall 2 to be subjected to pressure on its side located in the direction of arrow 24, and the flow limit of the material of the tube wall 2 is thereby exceeded. The axial abutment 23, which supports the tube 1 acted upon by the forming die 9, is stationary along the tube axis 3 even when an axial die movement and an axial mandrel movement are superposed while the tube 1 is being acted upon by the forming die 9.

[0083] As a result of the force fit between the tube wall 2 and the mandrel 10, the tube wall 2, which is acted upon on the outer side by the forming die 9, is subjected to tensile stress in the direction of arrow 25 by means of the mandrel 10. The mandrel 10 driven by means of the mandrel drive 21 therefore actively pulls the tube wall 2 in the direction of arrow 25 through the die opening 11, and the thickness of the tube wall 2 is reduced while simultaneously elongating the tube 1 and simultaneously producing the internal toothing 18 on the tube wall 2.

[0084] Due to a corresponding coordination of the axial die movement in the direction of arrow 24 and the axial mandrel movement in the direction of arrow 25, i.e., by corresponding control of the die drive 19 and the mandrel drive 21 by means of the drive controller 22, the forming of the tube wall 2 takes place without the tube 1 being compressed on the side of the forming die 9 located in the direction of arrow 24. As a result, in order to prevent compression of the tube 1, in the case of the device 5 there is also no need for additional reinforcement on the outer side of the tube 1.

[0085] Corresponding control of the die drive 19 and the mandrel drive 21 ensures that the die drive 19 and the mandrel drive 21 can be stopped simultaneously when the desired forming length is reached on the tube 1.

[0086] Due to the fact that an axial die movement and an axial mandrel movement directed in the opposite direction thereto are carried out at the same time, a high forming speed can be achieved. Regardless of the high forming speed, a high-quality processing result is obtained on the tube 1.

[0087] While the devices 5, 5a shown in FIG. 2 and FIG. 4 are used to produce the internal toothing on the tube wall 2 in a single-stage forming process, the arrangement 6 shown in FIGS. 3a and 3b with the first forming device 7 and the second forming device 8 is used to carry out a two-stage forming method.

[0088] The first forming device 7 of the arrangement 6 (FIG. 3a) comprises a first forming die 26 for arrangement on the outer side of the tube 1 and a first mandrel 27 for arrangement in the interior of the tube 1.

[0089] The first forming die 26 of the first forming device 7 is provided with a first die opening 28 for receiving the tube 1. In the example shown, the first die opening 28 is smooth-walled. The diameter of the first die opening 28 corresponds to the root circle diameter of the toothed die opening 11 on the forming die 9 shown in FIG. 2 and is therefore also smaller than the diameter of the tube cross-section 4 of the tube 1 in the undeformed initial state.

[0090] On its circumference, the first mandrel 27 of the first forming device 7 has a first shape-imparting mandrel toothing 29 as the first shape-imparting mandrel profile with first mandrel profile projections in the form of first mandrel teeth 30 and first mandrel tooth intermediate spaces 31 formed between the first mandrel teeth 30 as the first mandrel profile intermediate spaces. On the first mandrel 27 arranged in the interior of the tube 1, the first mandrel teeth 30 and the first mandrel tooth intermediate spaces 31 extend along the tube axis 3. The first mandrel tooth intermediate spaces 31 open towards the axially parallel inner side of the tube wall 2. The toothing geometry of the toothed first mandrel 27 of the first forming device 7 forms the target geometry of the toothed inner side of the tube wall 2 on the finished formed tube.

[0091] In a first method stage of the two-stage forming process, a preform 32 of the finished formed tube is produced from the undeformed tube 1 in the initial state.

[0092] The sequences of the first method stage of the two-stage forming process in principle correspond to the sequences of the single-stage forming method in FIG. 2 described in detail above.

[0093] A first die drive 33 of a first forming drive 34 of the first forming device 7 produces an axial die movement of the first forming die 26, which is seated on the tube 1, relative to the tube 1 along the tube axis 3 and along the first mandrel 27 arranged in the interior of the tube 1.

[0094] If there is a risk of compression, an axial mandrel movement of the first mandrel 27 carried out by means of a first mandrel drive 35 of the forming drive 34 and directed in the opposite direction to the axial die movement of the first forming die 26 is superposed on the axial die movement of the first forming die 26. The active axial die movement of the first forming die 26 and the active axial mandrel movement of the first mandrel 27 are optionally controlled in a coordinated manner by a first drive controller 36 of the first forming drive 34.

[0095] The product of the first method stage of the two-stage forming process is the preform 32 of the finished formed tube with a preform axis 37 coinciding with the tube axis 3 and a preform wall 38. The wall thickness of the preform wall 38 is reduced compared to the wall thickness of the tube wall 2. In addition, the preform wall 38 is provided with an inner profile in the form of an internal toothing 39.

[0096] Since the geometry of the internal toothing 39 on the preform wall 38 still has too large a tolerance compared to the target geometry of the finished formed tube, the first method stage shown in FIG. 3a is followed by the second method stage of the two-stage forming process carried out by means of the second forming device 8.

[0097] According to FIG. 3b, the second forming device 8 comprises a second forming die 40 for arrangement on the outer side of the preform 32 and a second mandrel 41 for arrangement in the interior of the preform 32.

[0098] A second die opening 42 of the second forming die 40 is designed for receiving the preform 32 and has a shape-imparting die toothing 43 as a shape-imparting die profile on the opening wall. The shape-imparting die toothing 43 is formed by die profile projections in the form of die teeth 44 and die tooth intermediate spaces 45 formed between the die teeth 44 as die profile intermediate spaces.

[0099] With the second forming die 40 arranged on the outer side of the preform 32, the die teeth 44 and the die tooth intermediate spaces 45 extend along the preform axis 37. The die tooth intermediate spaces 45 open towards the axially parallel outer side of the preform wall 38. The root circle diameter of the die toothing 43 at the second die opening 42 of the second forming die 40 corresponds to the diameter of the smooth-walled first die opening 28 at the first forming die 26 of the first forming device 7.

[0100] The second mandrel 41 of the second forming device 8 has the same design as the first mandrel 27 of the first forming device 7.

[0101] On its circumference, the second mandrel 41 has a second shape-imparting mandrel toothing 46 as a second shape-imparting tooth profile with second mandrel profile projections in the form of second mandrel teeth 47 and with second mandrel profile intermediate spaces in the form of second mandrel tooth intermediate spaces 48. Also the second shape-imparting mandrel toothing 46 reproduces the internal toothing to be created on the finished formed tube with its target geometry.

[0102] On the second mandrel 41 arranged in the interior of the preform 32, the second mandrel teeth 47 and the second mandrel tooth intermediate spaces 48 extend along the preform axis 37. The second mandrel tooth intermediate spaces 48 open towards the axially parallel inner side of the preform wall 38.

[0103] The second forming die 40 and the second mandrel 41 are arranged relative to one another around the preform axis 37 in such a way that the die teeth 44 arranged on the axially parallel outer side of the preform wall 38 and the second mandrel tooth intermediate spaces 48 arranged on the axially parallel inner side of the preform wall 38 as well as the die tooth intermediate spaces 45 arranged on the axially parallel outer side of the preform wall 38 and the second mandrel teeth 47 arranged on the axially parallel inner side of the preform wall 38 in each case lie opposite to each other on the preform wall 38 in the radial direction of the preform axis 37. At the start of the second method stage of the forming process, the mandrel tooth intermediate spaces 48 receive the inner profile 39 of the preform 32 produced in the first method stage.

[0104] The sequences of the second method stage of the two-stage forming process also correspond in principle to the sequences of the single-stage forming process carried out by means of the device 5 and shown in FIG. 2.

[0105] A second die drive 49 of a second forming drive 50 moves the second forming die 40, which is seated on the preform 32, with an axial die movement relative to the preform 32 along the preform axis 37 and along the second mandrel 41 arranged in the interior of the preform 32.

[0106] If there is a risk of compression, an axial mandrel movement of the second mandrel 41 directed in the opposite direction and produced by a second mandrel drive 51 is superposed on the axial die movement of the second forming die 40. In doing so, the second die drive 49 and the second mandrel drive 51 are controlled in a coordinated manner by a second drive controller 52 of the second forming drive 50.

[0107] During the second method stage, the die teeth 44 of the die toothing 43 on the second forming die 40, due to their arrangement opposite the second mandrel tooth intermediate spaces 48 of the second mandrel 41, ensure that the second mandrel tooth intermediate spaces 48 are completely filled with the flowing material of the preform wall 38 and that, on the finished formed tube, an internal toothing 53 is therefore produced as an inner profile, the geometry of which corresponds precisely to its target geometry specified by the second mandrel toothing 46.

[0108] Just like the device 5 shown in FIG. 2 and the forming devices 7, 8 shown in FIGS. 3a, 3b, the device 5a shown in FIG. 4 is also mounted on an axial forming machine of conventional design.

[0109] A forming die 9a of the device 5a has a die opening 11a (calibration section) designed for receiving the tube 1. At the die opening 11a, the forming die 9a is provided with a shape-imparting die profile in the form of a shape-imparting die toothing 12a. The die toothing 12a has die teeth 13a as die profile projections and die tooth intermediate spaces 14a formed between the die teeth 13a as die profile intermediate spaces.

[0110] In deviation from the forming die 9 shown in FIG. 2, the root circle diameter of the die toothing 12a on the forming die 9a is greater than the outer diameter of the tube 1 in the initial state with the tube 1 still undeformed. The tip circle diameter of the die toothing 12a is slightly smaller than the inner diameter of the tube 1 in the initial state.

[0111] A mandrel 10a is designed to be arranged in the interior of the tube 1 and is provided on its circumference with a shape-imparting mandrel profile designed as a shape-imparting mandrel toothing 15a. The shape-imparting mandrel toothing 15a is formed by mandrel profile projections in the form of mandrel teeth 16a and by mandrel tooth intermediate spaces 17a arranged 16a as mandrel profile intermediate spaces between the mandrel teeth.

[0112] The die teeth 13a and the die tooth intermediate spaces 14a extend along the tube axis 3 on the forming die 9a, which is seated on the outer side of the tube 1. The die tooth intermediate spaces 14a open towards the axially parallel outer side of the tube wall 2.

[0113] On the mandrel 10a in the interior of the tube 1, the mandrel teeth 16a and the mandrel tooth intermediate spaces 17a also extend along the tube axis 3. The mandrel tooth intermediate spaces 17a open towards the axially parallel inner side of the tube wall 2.

[0114] The forming die 9a and the mandrel 10a are positioned relative to one another around the tube axis 3 in such a way that the die teeth 13a arranged on the axially parallel outer side of the tube wall 2 and the mandrel tooth intermediate spaces 17a arranged on the axially parallel inner side of the tube wall 2 as well as the die tooth intermediate spaces 14a arranged on the axially parallel outer side of the tube wall 2 and the mandrel teeth 16a arranged on the axially parallel inner side of the tube wall 2 in each case lie opposite to each other on the tube wall 2 in the radial direction of the tube axis 3.

[0115] Due to the dimensioning of the tip and root circle diameters on the die toothing 12a, the device 5a produces an inner profile in the form of an internal toothing 18a on the inner side of the tube wall 2, without reducing the wall thickness of the tube wall 2.

[0116] The sequences in forming the tube 1 by means of the device 5a also correspond to the sequences on the device 5 shown in FIG. 2.

[0117] A die drive 19a of a forming drive 20a of the device 5a is used to produce an axial die movement of the forming die 9a. In addition to the die drive 19a, the forming drive 20a comprises a mandrel drive 21a and a drive controller 22a.

[0118] In order to form the tube 1, the forming die 9a is moved by means of the die drive 19a from its initial position at the right-hand end of the tube 1 with an axial die movement relative to the tube 1, which is supported on the stationary axial abutment 23 and is therefore also stationary, in the direction of the stationary axial abutment 23. During the axial die movement, the forming die 9a moves in the direction of arrow 24 along the tube axis 3 relative to the tube 1 and also along the mandrel 10a arranged in the interior of the tube 1.

[0119] Due to the oversize of the undeformed tube wall 2 compared to the tip circle diameter of the die toothing 12a, material of the tube wall 2 flows into the mandrel tooth intermediate spaces 17a of the mandrel 10a, forming the internal toothing 18a of the tube wall 2.

[0120] Also the die teeth 13a of the die toothing 12a ensure, due to their arrangement opposite the mandrel tooth intermediate spaces 17a of the mandrel 10a, that the mandrel tooth intermediate spaces 17a are completely filled with the flowing material of the tube wall 2 and the internal toothing 18a of the tube wall 2 is therefore produced precisely with its target geometry specified by the mandrel toothing 15a.