METHOD AND DEVICE FOR THICKENING A PLASTICALLY DEFORMABLE HOLLOW BODY WALL OF A HOLLOW BODY, IN PARTICULAR IN PORTIONS, AND MANUFACTURING METHOD AND MACHINE FOR PRODUCING A HOLLOW BODY

Abstract

In a method for thickening a plastically deformable hollow body wall of a hollow body, with effective radial support of the unthickened hollow body wall on an outer supporting face of an outer mold and with effective radial support of the hollow body wall on an inner supporting face of an inner supporting body, the hollow body is acted on by a compressive force by two application members at application points by moving the application members towards one another in the axial direction with a compressing movement. The application points on the hollow body are distanced from one another in the axial direction. An expansion space of the outer mold is arranged between the application points. Due to the compressing movement of the application members, material of the hollow body wall between the application points is plasticised in the region of the expansion space of the outer mold, and plasticised material of the hollow body wall flows into the expansion space of the outer mold, thus thickening the hollow body wall.

Claims

1. A device for thickening a plastically deformable hollow body wall of a hollow body, the hollow body wall extending in an axial direction along a cavity axis of a cavity of the hollow body, which cavity is delimited by the hollow body wall, the device comprising: an outer mold having a receptacle configured to receive the hollow body wall, said receptacle comprising a receptacle wall associated with an outer side of the hollow body wall, said receptacle wall forming, by means of a first partial length that extends in the axial direction, an outer supporting face for the hollow body wall and delimiting, by means of a second partial length that extends in the axial direction, an expansion space of the outer mold, the second partial length of the receptacle wall being offset radially outwardly relative to the first partial length of the receptacle wall, thus forming a widened region of the receptacle to form an expansion space, an inner supporting body associated with an inner side of the hollow body wall, said inner supporting body forming, by means of a supporting body face that is associated with the inner side of the hollow body wall and extends in the axial direction, an inner supporting face for the hollow body wall, the inner supporting face of the inner supporting body being adapted to be arranged in the axial direction at a level of the outer supporting face and also at a level of the expansion space of the outer mold, two application members and a controllable motor drive for the application members, said application members being configured to apply on the hollow body a compressive force in the axial direction at application points on the hollow body when the hollow body wall is effectively radially supported on the outer supporting face of the outer mold and on the inner supporting face of the inner supporting body, wherein the application members are configured to be moved towards one another in the axial direction with a continuous compressing movement by means of the motor drive, the application points on the hollow body being distanced from one another in the axial direction and the expansion space of the outer mold being arranged between the application points and one of the application members protruding radially outwardly relative to the outer side of the hollow body wall and delimiting the expansion space of the outer mold in the axial direction, wherein when the application members apply the compressive force on the hollow body, material of the hollow body wall between the application points is plasticised in a region of the expansion space of the outer mold and flows into the expansion space of the outer mold, thus thickening the hollow body wall, wherein the application members and the outer mold are configured such that in addition to and simultaneously with the continuous compressing movement of the application members, an axial relative movement of the application members performing the continuous compressing movement and of the outer mold is performed in the axial direction with an extent of the expansion space of the outer mold in the axial direction increasing due to the axial relative movement, wherein the application members performing the continuous compressing movement are configured to axially move jointly and in the same direction during the axial relative movement, and wherein the axial relative movement of the application members performing the continuous compressing movement and of the outer mold is performed by an axial movement of the outer mold in the axial direction being performed at the same time as and, thus, temporally superimposed on the continuous compressing movement performed by the application members or by the application members, performing the continuous compressing movement, moving relative to the outer mold, which is stationary in the axial direction.

2. The device according to claim 1, wherein the outer mold is divided in the axial direction, thus forming a plurality of outer mold parts that are movable relative to one another in the radial direction so as to open the outer mold.

3. The device according to claim 1, wherein a controllable motor drive is provided by means of which the outer mold parts of the first axial outer mold part are movable relative to one another in the radial direction, so as to open the first axial outer mold part.

4. The device according to claim 1, wherein the outer mold is divided in a radial direction, thus forming a first axial outer mold part and a second axial outer mold part, a first partial length of the receptacle wall that forms an outer supporting face for the unthickened hollow body wall being provided on the first axial outer mold part and the expansion space of the outer mold being provided on the second axial outer mold part, and wherein the first axial outer mold part is divided in the axial direction, thus forming a plurality of outer mold parts, the outer mold parts of the first axial outer mold part being movable relative to one another in the radial direction, so as to open the first axial outer mold part.

5. The device according to claim 4, wherein a controllable motor drive is provided by means of which the outer mold parts of the first axial outer mold part are movable relative to one another in the radial direction, so as to open the first axial outer mold part.

6. A machine for producing a hollow body having a hollow body wall that delimits a cavity and extends in an axial direction along a cavity axis of the cavity, comprising the device according to claim 1.

7. The machine according to claim 6, wherein the machine is configured to produce as a hollow body a hollow shaft forming a steering shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention will be explained hereinafter in greater detail on the basis of exemplary schematic illustrations, in which:

[0030] FIGS. 1A to 4B show the sequence of a first variant of a method for thickening a wall of a hollow shaft in portions,

[0031] FIGS. 5A to 8B show the sequence of a second variant of a method for thickening the wall of a hollow shaft in portions, and

[0032] FIGS. 9A to 12B show the sequence of a third variant of a method for thickening a wall of a hollow shaft in portions.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] According to FIG. 1A, a machine that is indicated and is configured as a forming machine 1 comprises a first tool holder 2 and a second tool holder 3. A punch 4 is fixed in the first tool holder 2, and the second tool holder 3 holds a processing unit 5, which in turn is formed of a pressure piece 6 and a mandrel 7, which is formed in one piece with the pressure piece 6 and has a reduced cross section compared to the pressure piece 6. The mandrel 7 as well as the pressure piece 6 have a circular cross section. Due to the cross-sectional reduction of the mandrel 7 compared to the pressure piece 6, the pressure piece 6 forms a peripheral shoulder 8.

[0034] The punch 4 and the pressure piece 6 of the processing unit 5 form application members, the punch 4 being formed as a hollow member and comprising a punch cavity 9 as the member cavity. The punch cavity 9 as well as the mandrel 7 have a circular cross section. The size of the cross section of the punch cavity 9 exceeds the size of the cross section of the mandrel 7 to a minimal extent.

[0035] The punch 4 can be moved along a movement axis 11 by means of a motor drive unit 10. Correspondingly, a motor drive unit 12 is used to move the processing unit 5 along the movement axis 11. Both the motor drive unit 10 and the motor drive unit 12 in the illustrated example are hydraulic drives of conventional design. The motor drive units 10, 12 together form a motor drive 13 for the punch 4 and the processing unit 5 and thus for the pressure piece 6 and the mandrel 7. A programmable numerical control 14 of the motor drive 13 or the motor drive units 10, 12 is depicted suggestively in FIG. 1A.

[0036] Together with a reinforcement 15 provided as outer mold, the punch 4 and the processing unit 5 form a forming tool 16. The forming tool 16 is shown in all of FIGS. 1A to 8B, whereas the other parts of the forming machine 1 are depicted only in FIG. 1A, for the sake of simplicity.

[0037] The reinforcement 15 comprises a receptacle 17 with a receptacle wall 18. The receptacle wall 18 extends in parallel with the movement axis 11 of the punch 4 and the processing unit 5 and comprises a first partial length 19 and a second partial length 20, which adjoins the first partial length 19 along the movement axis 11 and is radially outwardly offset relative to the first partial length 19, thus widening the receptacle 17. The second partial length 20 of the receptacle wall 18 delimits an expansion space 21 of the reinforcement 15. The relevant drawing detail “A” of FIG. 1A is illustrated in an enlarged view in FIG. 1B.

[0038] The forming tool 16 is used as a device for thickening a plastically deformable hollow body wall of a hollow body in portions, in the example shown for thickening a wall 22, in portions, of a hollow shaft 23, the wall 22 consisting of plastically deformable steel. The wall 22 delimits a cavity of the hollow shaft 23, which cavity is circular in cross section. The movement axis 11 coincides with the cavity axis of the cavity and defines an axial direction by means of its course.

[0039] FIGS. 1A to 4B illustrate the sequence of a first method, which can be performed by means of the forming machine 1 or by means of the forming tool 16, for thickening the wall 22 of the hollow shaft 23 in portions. Methods modified in comparison to this method will be explained on the basis of FIGS. 5A to 8B and on the basis of FIGS. 9A to 12B. The different method stages are presented here in each case both with an overall view of the forming tool 16 and with an enlarged drawing detail “A”. The numbering of the overall views has the addition A; the numbering of the enlarged drawing detail is provided with the addition B.

[0040] In the case of the method variants according to FIGS. 1A to 4B and 5A to 8B, the hollow shaft 23 in the undeformed state is firstly slid from the side of the punch 4 in the axial direction (along the movement axis 11) into the receptacle 17 of the reinforcement 15 and in the process is slid onto the mandrel 7 of the processing unit 5 that is already arranged within the receptacle 17. The punch 4 is at this time set back in the axial direction relative to the reinforcement 15. The processing unit 5 assumes the position illustrated in FIGS. 1A and 5A in the axial direction relative to the reinforcement 15.

[0041] The wall 22 of the hollow shaft 23 in the illustrated example has a circular ring-shaped cross section. The outer diameter of the wall 22 corresponds to the diameter of the receptacle 17 at the reinforcement 15 and matches the diameter of the pressure piece 6 of the processing unit 5. The inner diameter of the wall 22 corresponds to the diameter of the mandrel 7 of the processing unit 5. The hollow shaft 23 that is slid into the receptacle 17 of the reinforcement 15 therefore rests on the mandrel 7 without play in the radial direction. On the outer side, the wall 22 of the hollow shaft 23 is arranged directly adjacently to the receptacle wall 18 of the receptacle 17. In the axial direction, the hollow shaft 23 rests, via a radial end face 24 of the wall 22, on the shoulder 8 of the pressure piece 6 extending around the movement axis 11.

[0042] On the basis of these conditions, the punch 4 is advanced by means of the motor drive 13 or the motor drive unit 10 in the axial direction towards the hollow shaft 23, until a radial end face 25 of the punch 4 comes into contact with a radial end face 26 of the wall 22 of the hollow shaft 23 and the hollow shaft 23 consequently is clamped in the axial direction between the pressure piece 6 or the shoulder 8 of the processing unit 5 on the one hand and the punch 4 on the other hand by a force of small magnitude. The end of the mandrel 7 that is remote from the pressure piece 6 enters the punch cavity 9 in the axial direction as the punch 4 is moved.

[0043] The advance movement of the punch 4 performed by the motor drive 13 or the motor drive unit 10 can be both path-controlled and force-controlled by the numerical control 14. In the case of path-dependent control, the punch 4 is moved, starting from its initial position, over a defined path length in the axial direction. In the case of force-dependent control, the rise in force in the drivetrain of the punch 4, which results when the radial end face 25 of the punch 4 strikes the radial end face 26 of the wall 22 of the hollow shaft 23, marks the end of the advance movement.

[0044] The described advance movement of the punch 4 is performed both in the method according to FIGS. 1A to 4B and in the method according to FIGS. 5A to 8B. The conditions resulting at the end of the advance movement of the punch 4 are illustrated in FIGS. 1A, 1B and in FIGS. 5A, 5B. The subsequent method steps differ from one another.

[0045] In the method according to FIGS. 1A to 4B, starting from the conditions according to FIGS. 1A and 1B, a compressing movement in the axial direction is performed by the punch 4 and the pressure piece 6 by the pressure piece 6 being moved in the axial direction towards the punch 4, which is stationary in the axial direction. Due to the compressing movement, material of the wall 22 of the hollow shaft 23 is plasticised between the application points at the wall 22, i.e. between the radial end faces 24, 26 of the wall 22, and plasticised material of the wall 22 flows into the expansion space 21 of the reinforcement 15 that is arranged between the application points or between the radial end faces 24, 26 of the wall 22. Any other material flow is prevented at the inner side of the wall 22 by the mandrel 7, which functions as an inner supporting body for the wall 22 of the hollow shaft 23 and which, with its axis-parallel lateral surface, forms a supporting body face or an inner supporting face for the wall 22 and by means of this face supports the wall 22 of the hollow shaft 23 in the radial direction. The first partial length 19 of the receptacle wall 18 acts accordingly on the outer side of the wall 22. The first partial length 19 of the receptacle wall 18 forms an outer supporting face for the wall 22 which outer supporting face extends in parallel with the wall 22 and accordingly supports the wall 22 of the hollow shaft 23 likewise in the radial direction.

[0046] The compressing movement, i.e. the movement performed in the axial direction by the pressure piece 6 relative to the stationary punch 4 of the forming tool 16, ends as soon as the expansion space 21 of the reinforcement 15 is filled with plasticised material of the wall 22, thus forming a thickening 27 of the wall 22, and therefore the method stage according to FIGS. 2A and 2B is reached.

[0047] Both path control and force control are also conceivable for the described compressing movement of the punch 4 and of the pressure piece 6. For path control, it is necessary to store a movement path length of the pressure piece 6, for example determined empirically, in the numerical control 14 of the motor drive 13. As soon as the pressure piece 6 has moved in the axial direction over the predefined path length, the motor drive unit 12 used for the movement of the pressure piece 6 is stopped.

[0048] In the case of a force control of the compressing movement, the motor drive unit 12 for the pressure piece 6 is switched off as soon as the rise in motor driving force, which is produced when the expansion space 21 of the reinforcement 15 is filled with plasticised material of the wall 22 and a further advance of the hollow shaft 23 in the axial direction is consequently blocked, is detected by means of a corresponding sensor system on the motor drive unit 12.

[0049] Proceeding from the method stage according to FIGS. 2A and 2B, the punch 4 is moved back, by means of the motor drive unit 10, relative to the radial end face 26 of the wall 22 of the hollow shaft 23 in the axial direction in a path-controlled manner by the path length over which the thickening 27 of the wall 22 is to be lengthened in the axial direction in the subsequent forming process.

[0050] Once the punch 4 has reached its target position in the axial direction, the motor drive unit 10 is stopped and a new compressing movement is performed in the above-described way by means of the motor drive unit 12. Here, the pressure piece 6 is again advanced in the axial direction in a path-controlled or force-controlled manner relative to the punch 4, which is stationary in this direction, by means of the motor drive unit 12 until the expansion space 21 of the reinforcement 15 that has been enlarged due to the prior retracting movement of the punch 4 is filled again completely with plasticised material of the wall 22 of the hollow shaft 23 and therefore the conditions according to FIGS. 3A and 3B have been provided.

[0051] The described process is repeated until the thickening 27 produced at the wall 22 of the hollow shaft 23 has the desired length in the axial direction. During the entire compressing movement, which is performed intermittently, the pressure piece 6 is guided via the mandrel 7 in the axial direction in the interior of the punch cavity 9. In the illustrated example, a thickening 27, which extends in a wave-like manner on the outer side in the axial direction, is built up on the wall 22 of the hollow shaft 23 in the expansion space 21 of the reinforcement 15. With each of the compression strokes of the compressing movement performed by the punch 4 and the pressure piece 6, one of the axial wave portions of the thickening 27 is produced. The wave shape can be smoothed as necessary by a subsequent secondary processing following on from the forming process.

[0052] Proceeding from the conditions at the end of the forming process illustrated in FIGS. 4A and 4B, the punch 4 is moved back rapidly in the axial direction relative to the reinforcement 15 into the initial position which it assumed prior to the start of the forming process. At the same time as the movement of the punch 4, or subsequently thereto, the processing unit 5 is advanced in the axial direction together with the hollow shaft 23 that rests on the mandrel 7 by actuating the motor drive unit 12, until the hollow shaft 23 is arranged at least partially outside the reinforcement 15 and is thus accessible for removal from the forming tool 16.

[0053] Also removing the formed hollow shaft 23 can be performed mechanically. For this purpose, clamping shells 28, 29 can be used, as illustrated highly schematically in FIG. 4A. The clamping shells 28, 29 can be moved in the radial direction of the formed hollow shaft 23 in the direction of double-headed arrows illustrated in FIG. 4a by means of a corresponding numerically controlled drive.

[0054] If the formed hollow shaft 23 is sufficiently pushed out of the reinforcement 15 in the axial direction by means of the motor drive unit 12, the clamping shells 28, 29 are moved towards one another in the radial direction of the hollow shaft 23 until they clamp the hollow shaft 23 behind the thickening 27. By actuating the motor drive unit 12 is the processing unit 5 now moved back in the axial direction and the mandrel 7 thus removed from the interior of the hollow shaft 23. Once the mandrel 7 has left the cavity of the hollow shaft 23, the formed hollow shaft 23 can be removed from the forming machine 1 by means of the clamping shells 28, 29. For this purpose, the clamping shells 28, 29 can be movable in the axial direction and/or pivotable. With a corresponding movement of the clamping shells 28, 29 in the opposite direction, an as yet undeformed hollow shaft can then be introduced into the forming machine 1 or the forming tool 16 in order to start a further forming process of the above-described type.

[0055] Within the method according to FIGS. 5A to 8B, a compressing movement is first performed, starting from the conditions according to FIGS. 5A and 5B, by the pressure piece 6 being moved in the axial direction relative to the punch 4, which is stationary in the axial direction, by means of the motor drive unit 12. If, as a result of the relative movement of the pressure piece 6 and of the punch 4, the expansion space 21 of the reinforcement 15 has become filled with plasticised material of the wall 22 of the hollow shaft 23, thus forming the thickening 27, the motor drive unit 12 is not now stopped and the punch 4 is not retracted relative to the radial end face 26 of the wall 22 of the hollow shaft 23.

[0056] Instead, as soon as the expansion space 21 of the reinforcement 15 has been filled for the first time with plasticised material of the wall 22 and the method stage according to FIGS. 6A and 6B has been reached accordingly, a movement of the punch 4 in the axial direction is initiated in addition to the movement of the pressure piece 6 already underway. The additional movement of the punch 4 is triggered either in a path-controlled manner as soon as the pressure piece 6 has moved over a defined path length in the axial direction starting from its initial position, or in a force-controlled manner as soon as the expansion space 21 of the reinforcement 15 has been filled with plasticised material of the wall 22 and consequently a rise of the forming force applied by means of the motor drive unit 12 has been detected.

[0057] The joint movement of the punch 4 and of the pressure piece 6 seamlessly follows the first movement phase, in which only the pressure piece 6 is moved in the axial direction.

[0058] In the phase of the compressing movement in which the punch 4 and the pressure piece 6 are moved together in the axial direction, the punch 4 and the pressure piece 6 move in the same direction, but the pressure piece 6 is moved at a higher speed than the punch 4. As a result of the speed difference, a compressive force is exerted by means of the punch 4 and the pressure piece 6 onto the wall 22 of the hollow shaft 23 in the axial direction, due to which compressive force some material of the wall 22 is plasticised. Since the punch 4 and the pressure piece 6 move together in the axial direction and since this movement is performed relative to the reinforcement 15, which is stationary in the axial direction, the expansion space 21 of the reinforcement 15, which expansion space is delimited by the punch 4, becomes larger during the compressing movement. The extent of the expansion space 21 increases in the axial direction. Plasticised material of the wall 22 flows continuously into the expansion space 21. In this way, the thickening 27 is created over the desired axial length at the relevant axial end of the wall 22 of the hollow shaft 23. Here, the wall 22 is supported in the radial direction on its inner side by the mandrel 7 and on its outer side by the first partial length 19 of the receptacle wall 18.

[0059] The relative movement of the punch 4 and of the pressure piece 6, which is performed as a continuous compressing movement, and the relative movement between the punch 4 and the pressure piece 6 on the one hand and the reinforcement 15, which is stationary in the axial direction, on the other hand, which relative movement is performed at the same time as the compressing movement, are controlled in such a way that the expansion space 21 of the reinforcement 15 that becomes longer in the axial direction during the course of the forming process is permanently completely filled with plasticised material of the wall 22. Consequently, the thickening 27 is produced over its entire axial length having an axis-parallel outer face that is flat in the axial direction and reproduces the wall of the expansion space 21 exactly.

[0060] In FIGS. 7A and 7B, the thickening 27 on the wall 22 of the hollow body 23 is lengthened in the axial direction compared to the conditions according to FIGS. 6A and 6B, but the final length of the thickening 27 has not yet been reached. With its final axial length, the thickening 27 at the relevant axial end of the wall 22 of the hollow shaft 23 is shown in FIGS. 8A and 8B.

[0061] Upon reaching the method stage according to FIGS. 8A and 8B, the speed of the punch 4 is increased by correspondingly controlling the motor drive unit 10 in such a way that the speed of the punch 4 exceeds the speed of the pressure piece 6. Consequently, the punch 4 lifts off with its radial end face 25 from the radial end face 26 of the wall 22 and moves rapidly into its initial position remote from the reinforcement 15 in the axial direction. At the same time, the formed hollow shaft 23 is pushed out of the reinforcement 15 by the processing unit 5, which continues its movement in the axial direction unchanged. The hollow shaft 23 that is arranged outside the reinforcement 15 can be grasped in the above-described way by means of the clamping shells 28, 29 (not illustrated in FIGS. 8A and 8B) and can be removed from the forming tool 16 or from the forming machine 1. A hollow shaft 23 that is to be processed can then be fed to the forming tool 16 by means of the clamping shells 28, 29.

[0062] In a deviation from the approach according to FIGS. 1A to 4B and according to FIGS. 5A to 8B, an axial movement performed by the reinforcement 15 in the axial direction relative to the punch 4 and the pressure piece 6 can be superimposed on the compressing movement performed by the punch 4 and the pressure piece 6. When the axial movement of the reinforcement 15 is appropriately controlled, the extent of the expansion space 21 at the reinforcement 15 increases in the axial direction, and the thickening 27 on the wall 22 of the hollow shaft 23 that builds up due to the compressing movement of the punch 4 and of the pressure piece 6 can lengthen in the axial direction.

[0063] The method illustrated in FIGS. 9A to 12B coincides in terms of its primary sequences with the method according to FIGS. 1A to 4B and according to FIGS. 5A to 8B. According to FIGS. 9A to 12B as well, a wall 22 of a hollow shaft 23 is plasticised by a compressing movement of a punch 4 and of a pressure piece 6 that is performed along a movement axis 11 in an axial direction, and plasticised material of the wall 22 builds up a thickening 27.

[0064] In a deviation from the method according to FIGS. 1A to 4B and 5A to 8B, a thickening 27 is produced at both axial ends of the wall 22 or the hollow body 23 within the method according to FIGS. 9A to 12B. For this purpose, a forming tool 30 is used according to FIGS. 9A to 12B, which forming tool, although it does not differ fundamentally from the forming tool 16 of FIGS. 1A to 8B, does differ therefrom in terms of design details.

[0065] Unlike the forming tool 16 according to FIGS. 1A to 8B, the forming tool 30 has a multi-part reinforcement 31 as outer mold. The reinforcement 31 is divided both in the radial direction and in the axial direction. Due to the division in the radial direction, the reinforcement 31 comprises a first axial outer mold part in the form of a first reinforcement unit 32 and a second axial outer mold part in the form of a second reinforcement unit 33. The first reinforcement unit 32 is in turn divided in the axial direction so as to form two lateral outer mold parts or reinforcement parts 34, 35. In FIG. 9A, the separating joint between the two lateral reinforcement parts 34, 35 of the first reinforcement unit 32 extends along the movement axis 11 perpendicularly to the drawing plane. Dividing the first reinforcement unit 32 into more than two outer mold parts or reinforcement parts, in particular into four or six lateral outer mold parts or reinforcement parts, is conceivable.

[0066] The second reinforcement unit 33 of the reinforcement 31 is formed in one piece.

[0067] Of the receptacle 17, provided on the reinforcement 31, for the wall 22 of the hollow shaft 23, only the part of the expansion space 21, the wall of which extends axis-parallel in the axial direction, is arranged on the second reinforcement unit 33. The first reinforcement unit 32 comprises the first partial length 19 of the receptacle wall 18 and a transition region between the first partial length 19 of the receptacle wall 18 and the part of the expansion space 21 that is provided on the second reinforcement unit 33. By means of a numerically controlled motor actuator of conventional design (not shown), the lateral reinforcement parts 34, 35 of the first reinforcement unit 32 can be moved or positioned relative to one another in the radial direction in order to open and close the reinforcement 31. In FIG. 9A, the relative movability of the lateral reinforcement parts 34, 35 is indicated by double-headed arrows.

[0068] In the stage illustrated in FIGS. 9A and 9B of the forming method that is performed by means of the forming tool 30, a thickening 27 has already been produced at an axial end of the hollow shaft 23. The relevant forming process corresponded to one of the methods explained above in relation to FIGS. 1A to 4B and 5A to 8B in terms of its sequence. The multi-part forming tool 30 was used here in the same way as the one-part forming tool 16 of FIGS. 1A to 8B.

[0069] Once the thickening 27 was completed, the punch 4 of the forming tool 30 was moved in the axial direction into a position away from the reinforcement 31. The hollow shaft 23 provided with the thickening 27 was then removed from the reinforcement 31. For this purpose, the mandrel 7 was firstly moved out of the interior of the hollow shaft 23 (downwardly in FIG. 9A) by a corresponding axial movement of the processing unit 5. The hollow shaft 23 was supported on the upper side of the first reinforcement unit 32 by the thickening 27 protruding in the radial direction relative to the first partial length 19 of the receptacle wall 18. The lateral reinforcement parts 34, 35 of the first reinforcement unit 32 were then moved away from one another in the radial direction to such an extent that it was possible to remove the thickening 27 in the axial direction out of the expansion space 21 at the second reinforcement unit 33, and that the hollow shaft 23 with the thickening 27 could pass through the first reinforcement unit 32 with a movement in the axial direction. The hollow shaft 23 was then rotated through 180 degrees outside the reinforcement 31 and was slid onto the mandrel 7 of the processing unit 5, with the thickening 27 formed at one end leading. Together with the hollow shaft 23 resting on the mandrel 7 and supported in the axial direction on the pressure piece 6, the processing unit 5 was then slid in the axial direction into the first reinforcement unit 32, which was still open. The first reinforcement unit 32 was then closed by a corresponding relative movement of the lateral reinforcement parts 34, 35 in the radial direction. Lastly, the hollow shaft 23 formed at one end was clamped in the axial direction with a force of small magnitude between the pressure piece 6 or the shoulder 8 of the processing unit 5 on the one hand and the punch 4 on the other hand by means of a movement of the punch 4 of the forming tool 30. This then resulted in the conditions according to FIGS. 9A and 9B.

[0070] Proceeding from these conditions, a thickening 27 of the wall 22 is produced at the second axial end of the hollow shaft 23 according to the method described above in relation to FIGS. 1A to 4B and illustrated in FIGS. 10A to 12B. Alternatively, the method according to FIGS. 5A to 8B could also be used in order to produce the second thickening 27 of the wall 22 of the hollow shaft 23.

[0071] Once the second thickening 27 has been produced, the hollow shaft 23 is removed out of the reinforcement 31 and then transported away from the forming tool 30 or the forming machine 1. The sequences with regard to the removal of the hollow shaft 23 with the wall 22 formed at both ends correspond to the sequences, described above in detail, with regard to the removal of the hollow shaft 23 that is formed only at one axial end.

[0072] Both the hollow shaft 23 formed at one end and the hollow shaft 23 formed at both axial ends can be subjected to secondary processing within a manufacturing method. In particular, it is conceivable that particular functional elements, such as a thread or gear teeth, are produced on the thickening(s) 27 of the wall 22 of the hollow shaft 23.