EP4028183B1 - Stretch rolling device and stretch rolling method - Google Patents

Description

technical field

The invention relates to a stretch-rolling device and a stretch-rolling method for pressure-forming workpieces by rolling. For this purpose, the stretch-rolling device has a pair of work rolls with two rolls, which implement a plurality of stages in the axial direction, which are set up for the gradual deformation of the workpieces, in that the workpieces pass through the stages successively.

Background of the Invention

The stretch rolling process is one of the longitudinal rolling processes in which the rolling stock is transported through the roll gap perpendicularly to the rolling axes and is thereby deformed. This is characterized by the fact that a blank to be rolled, for example a round or square material, is fed to the rolls by a manipulator and in individual stages, which are arranged in the axial direction of the rolls and are also referred to as "passes", "calibres" or "sectors " are designated, is transformed. The steps of the rollers therefore usually have different rolling profiles and the blank to be rolled passes through one after the other, as a result of which the profile cross-section of the blank is changed step by step.

Stretch rolling is particularly suitable for the production of intermediate forms, such as semi-finished products or preforms, and in rarer cases also of finished parts. In the case of the production of intermediate shapes, downstream processing steps such as drop forging can be simplified by stretch rolling. For example, the Reduce the use of materials and the process forces in drop forging and increase the surface quality of the components. In concrete terms, stretch rolling is used, for example, to produce intermediate forms for components such as crankshafts, axles and link components.

The DE 10 2014 101 150 A1 describes a stretch rolling device which has a pair of rolls with two reversible rolls and two gripping devices for handling the workpieces to be rolled. The two gripping devices are arranged on opposite sides of the pair of rollers. Furthermore, the rollers have at least two rolling tools, ie steps, in the axial direction, the steps being set up for the gradual deformation of the workpiece.

The output of the workpieces is in accordance with the DE 10 2014 101 150 A1 The technique described is limited in that the handling of the workpieces by the two gripping devices only takes up part of the pair of rollers, ie not all stages are used at the same time.

An increase in output is with a stretching device according to DE 10 2016 112 946 A1 , which forms the basis for the preamble of claim 1, achieved. For this purpose, a plurality of gripping devices are installed on the opposite sides of the pair of rollers, with two opposite gripping devices forming a pair of gripping devices being assigned to one step and gripping the corresponding workpiece. In addition, the stretch-rolling device has a transfer device in order to convey the workpieces in the working cycle of the device from one pair of gripping devices to one pair of gripping devices.

The output increase according to the DE 10 2016 112 946 A1 is paid for by a considerable design effort, because two gripping devices are used per step to grip the workpiece at both ends for the parallel assignment of the steps. The parallel rolling of several workpieces is also involves a technical problem resulting from the fact that the workpieces have different lengths due to the deformation at different stages along the axial direction of the rolls. For this purpose, length compensation between the individual gripping devices must be ensured in order to ensure a reliable and high-quality rolling process.

More stretching devices are in the DE 1 269 087 A , WO 2018/171828 A1 , DE 10 2014 101 151 A1 and EP 2 316 589 A1 described.

Presentation of the invention

One object of the invention is to specify an improved stretch-rolling device and an improved stretch-rolling method, in particular to realize a high output of workpieces with reduced structural complexity.

The object is achieved with a stretch rolling device with the features of claim 1 and a stretch rolling method with the features of claim 10. Advantageous developments follow from the dependent claims, the following description of the invention and the description of preferred embodiments.

The stretch-rolling device according to the invention is used for pressure forming of workpieces, preferably metallic workpieces, by rolling.

The stretch-rolling device has a pair of work rolls with two rolls which can each be rotated about their roll axes and form a roll gap between them. The rollers are set up in such a way that they realize several stages in the axial direction, which are intended to deform the workpieces step by step, the workpieces passing through the stages successively. When transforming the workpieces rotate in the opposite direction to the work rolls. The work rolls can be reversible in rotation. However, this is not absolutely necessary. Normally, the rolled profiles differ at the different stages in order to carry out a gradual deformation of the workpieces. Preferably, each workpiece goes through all stages, from the lowest stage to the highest stage. However, in special cases it may also be possible that not all stages act on the workpieces, ie stages are omitted or skipped. The designations "successively", "stepwise" etc. thus do not necessarily limit the processing to a complete run through of all available stages.

The stretch-rolling device also has one, preferably precisely one, manipulator with a plurality of gripping devices. Preferably, the number of gripping devices is equal to the number of steps. The gripping devices, preferably all or substantially all of the manipulator, are arranged on a working side of the pair of work rolls and are adapted to grip the workpieces and guide them through the nip at an associated stage in an advance/retract direction. The working side is defined by the position of the pair of working rolls and the gripping devices. The side opposite the working side (relative to the pair of working rolls) can be designed as a tool changing side, via which maintenance work, such as a roll change, can be carried out.

The stretch rolling apparatus further comprises a shelf arranged to temporarily support workpieces and transfer them in cooperation with the manipulator to another gripping device, preferably the adjacent gripping device of the next higher stage. In other words, the workpieces are transferred from one gripping device to another gripping device, preferably a gripping device of a higher level, for example the next higher level. This transfer of the workpieces normally takes place once per work cycle of the stretching device. The workpiece that has completely gone through the processing, preferably the workpiece of the highest level, is ejected. Furthermore, a new workpiece, which is also referred to herein as a blank, is fed to the lowest processing stage. Thus, when handing over the workpieces normally only the first workpiece (the blank) to the last but one workpiece are gripped and picked up by a gripping device. It should be noted that the term "finished work" refers only to the stretch rolling process, ie does not necessarily indicate a finished product or finished part. Rather, the finished workpiece, having passed through all the intended stages of the stretch rolling apparatus, is preferably an intermediate form, such as a stock or preform.

The tray is not a manipulator because the tray does not have gripping devices configured to grip the workpieces and feed them through the nip in an advance/retract direction. In particular, the tray does not have any gripping devices that enter or pass or can pass through the nip. The deposit can be set up passively in that the workpieces are placed on it for transfer or the deposit supports the workpieces without actively gripping or clamping them. Alternatively, the tray can have retaining means that are set up to temporarily retain or stabilize the workpieces, for example to grip or clamp them.

The stretch-rolling device constructed in this way allows several workpieces to be processed at the same time by a parallel occupation of all or at least several stages, for example every second stage. The output of the workpieces, and thus the productivity, can be increased thanks to the parallel allocation. This is achieved without installing two or more manipulators on opposite sides of the pair of work rolls. The manipulator on the working side may only be expanded to include additional gripping devices, such as tongs, as a result of which the improved functionality is achieved without a significant increase in the structural and procedural complexity of the stretching rolling device. The transfer of the workpieces to gripping devices in the course of the process in subsequent stages is realized in connection with a deposit. In this way, a high output is achieved with a comparatively small number of assemblies, which also improves the reliability and maintainability of the stretching rolling device.

One or more gripping devices are preferably set up to be rotatable about their own axis in order to enable the corresponding workpieces to be rotated between the individual stages. This means a rotation of the workpieces about their longitudinal axis by a certain angle, for example 90°. The rotation can take place before or after the forming at the respective stage.

According to the invention, the gripping means are arranged to grip the workpieces at one end and feed them through the nip at an associated stage, while the workpieces are not gripped at the other end. It is not necessary for the "second" end of the workpiece to be gripped by an additional gripping device of a manipulator, which not only reduces the structural complexity but also the process control.

The tray can preferably be moved in the axial direction and/or in the advance/retraction direction. In particular, the movability of the storage area can be used to implement or at least support the transfer of the workpieces by transporting them transversely through the storage area. Alternatively or additionally, the tray can be set up to be movable in the up/down direction, for example in order to descend during rolling and not to impede the rolling process.

The shelf is preferably arranged on the working side. Thus, the side opposite the working side, which is advantageously designed as a tool changing side, is not obstructed by the shelf or has limited access. This improves the maintainability of the roll-forging device.

Preferably, the number of gripping devices is equal to the number of stages, the assignment of gripping device to stage being a one-to-one assignment. In this way, the pair of work rolls can be optimally used along the axial direction, with the nature and control of the individual gripping devices being able to be designed in the best possible way for the associated stage.

The gripping devices can preferably be moved by the manipulator in the axial direction and/or feed/retraction direction, with the manipulator itself being particularly preferably moveable relative to the pair of work rolls in the axial direction and/or feed/retraction direction for this purpose. In particular, the movability of the gripping devices or the manipulator can be used to carry out the transverse transport, i.e. transport of the workpieces for transfer in the axial direction, either in connection with a stationary deposit or in combination with a deposit that can also be moved.

At the end of the rolling process, the workpieces of the different stages usually have different lengths. In order to compensate for this different elongation, at least one gripping device can preferably be adjusted relative to the manipulator in the advance/retraction direction. This can be realized by means of a length compensation section, which can adjust the gripping means, such as the clamps, of the corresponding gripping device for length compensation in the advance/retraction direction. Preferably, at least N-1 (N denotes the number of stages) gripping devices have such a length compensation section. The increase in length and/or the rate of increase in length may vary from stage to stage. Thus, the gripping devices are preferably individually movable. For this purpose, the individual mobility or movability in the advance/retraction direction can be implemented passively, for example spring-loaded, or actively, for example pneumatically, by an electric motor, etc.

Preferably, the deposit has holding means that are set up to temporarily hold the workpieces for transfer to the respectively adjacent gripping device of the next higher level, preferably to clamp them while the gripping devices grip. In this way, the reliability of the handover can be improved. In this case, the retaining means are preferably essentially stationary, i.e. for example apart from a clamping movement, relative to the tray.

The object is also achieved by a stretching method for pressure forming of workpieces by means of a stretching device according to the above description solved. The method includes: gripping a plurality of workpieces by a respective gripping device of the manipulator; passing the workpieces through the nip formed by the pair of work rolls at an associated stage in the advancing/retreating direction; rotating the rollers, preferably in opposite directions, and applying pressure to the workpieces through the rollers, thereby deforming the workpieces according to their stage; Transporting the workpieces to a transfer position and supporting the workpieces by the tray, preferably depositing the workpieces onto the tray; releasing the workpieces from the gripping devices; and gripping of workpieces by another gripping device, preferably the adjacent gripping device of the next higher level. The gripping devices of the manipulator grip the workpieces at one end and feed them through the nip at the appropriate step, while the workpieces are not gripped at the other end.

The features, technical effects, advantages and exemplary embodiments that have been described in relation to the stretch-rolling device apply analogously to the stretch-rolling method.

One or more workpieces are thus preferably rotated between the individual steps about their longitudinal axes, for example by 90°. The rotation can take place before or after the forming at the respective stage.

In order to transfer the workpieces to another gripping device, the deposit preferably moves in the axial direction and/or in the advance/retraction direction and/or up/down in order to implement or at least support the transfer. Alternatively or additionally, the gripping devices move through the manipulator in order to transfer the workpieces to another gripping device in the axial direction and/or in the advance/retraction direction. For this purpose, it is particularly preferred that essentially only the manipulator itself moves relative to the pair of work rolls in the axial direction and/or in the feed/retraction direction.

In order to compensate for a different elongation of the workpieces at the various stages, at least one gripping device is preferably used according to the length of the associated workpiece relative to the manipulator in the feed/retraction direction. The gripping devices are preferably moved individually during rolling, since the increase in length and/or the rate of increase in length can differ from stage to stage. This can be done passively, for example with a spring, or actively, for example pneumatically, with an electric motor, etc.

The number of workpieces to be rolled is preferably smaller than the number of stages available, for example approximately half as large. A reduced occupancy of the stages may be favorable or necessary to comply with machine limits with regard to force or energy consumption.

Further advantages and features of the present invention are evident from the following description of preferred embodiments. The features described there can be implemented on their own or in combination with one or more of the features set out above, insofar as the features do not contradict one another. The following description of the preferred embodiments is made with reference to the accompanying drawings.

Brief description of the figures

• The Figures 1a to 1c are schematic top views of a stretching device in different process stages according to an embodiment.
• The Figures 2a to 2c are schematic plan views of a stretching device in different process stages according to a further embodiment.
• The Figures 3a to 3c are schematic plan views of a stretching device in different process stages according to a further embodiment.
• The Figures 4a to 4c are schematic plan views of a stretching device in different process stages according to a further embodiment.

Detailed description of preferred embodiments

Preferred embodiments are described below with reference to the figures. The same, similar or equivalent elements are provided in the figures with identical reference numerals, and a repeating Description of these elements is partially omitted to avoid redundancies.

The Figures 1a to 1c are schematic plan views of a stretching device 1 in different process stages according to an embodiment. The stretch rolling device 1 is set up for press-forming workpieces W by rolling.

First, the components of the stretch-rolling device 1 and then a stretch-rolling method that can be carried out with it will be explained.

The stretch rolling device 1 has a pair of work rolls with an upper and a lower roll 10 . The top roller is omitted from the figures to make the manipulation and transport of the workpieces W easier to see. The rollers 10 are oppositely rotatable. Their direction of rotation can be reversible, but this is not absolutely necessary. In the axial direction, the rollers 10 comprise a plurality of stages S1 to S4, which are also referred to as passes, calibers or segments. Preferably, the rolling profile of the work rolls differs at the different stages S1 to S4. The steps S1 to S4 are used for the gradual reshaping of the workpieces W, such a workpiece W successively passing through the steps S1 to S4 for this purpose. Four stages S1 to S4 are shown as examples in the figures.

Between the stages S1 to S4, the workpieces W are preferably rotated through an angle, for example 90°, as indicated by arrows in FIG Figure 1b is indicated. The rotation can take place before or after the forming at the respective step S1 to S4.

The stretch-rolling device 1 also has a manipulator 20 with a plurality of gripping devices 21 . The gripping devices 21 are assigned according to the stages S1 to S4, not necessarily a one-to-one assignment is required. For example, a gripping device 21 can be set up to operate several stages. However, the number of grippers 21 is preferably equal to the number of stages S1 to S4 as shown in the figures, in which case the association is one-to-one. The side on which the manipulator 20 with the gripping devices 21 is located relative to the pair of work rolls is referred to herein as the work side AS. The gripping devices 21 have adjustable clamping jaws, for example, in order to be able to grip the workpieces W securely and release them for transfer.

The manipulator 20 is according to the embodiment of Figures 1a to 1c in the axial direction of the rollers 10 (referred to as "axial direction" or "transverse direction") and in the horizontal radial direction thereof (referred to as "radial direction" or "feed/retreat direction") thereof, as indicated by arrows in the figures . However, alternatively or additionally, one or more of the degrees of freedom can also be realized individually by the gripping devices 21 . Individual mobility of the gripping devices 21 or part of the gripping devices 21 (preferably at least three out of four) in the advance/retraction direction, also represented by arrows in the figures, is particularly preferably provided in order to provide a length compensation function for compensating for a change in the length of the workpiece W caused by the to realize different levels S1 to S4. For this purpose, the individual movability in the advance/retraction direction can be implemented passively, for example with a spring, or actively, for example pneumatically, with an electric motor, etc. In addition, the gripping devices 21 can be configured to be rotatable about their own axis in order to enable the workpieces W to be rotated between the individual stages S1 to S4.

The stretch rolling device 1 also has a shelf 30, according to the embodiment of FIG Figures 1a to 1c is arranged on the side opposite the working side AS. The tray 30 can be set up to be stationary or movable along one or more degrees of freedom. The Tray 30 can be provided passively so that the workpieces W are in a feed position ( Figure 1b , described in detail below) are placed on it or the tray 30 supports the workpieces W without actively gripping or clamping them. Alternatively, the tray 30 can have retaining means 31 which are set up to temporarily retain the workpieces W, for example to grip or clamp them.

Since the tray 30 and/or the manipulator 20 or its gripping devices 21 can be moved in the axial direction, a separate transfer device for transferring the workpieces W to adjacent gripping devices 21 can be omitted.

In the Figures 1a to 1c shows the stretching device 1 in positions of different process stages.

The stretching device 1 according to the Figure 1a is in a retracted position in which all the workpieces W being processed, held by the respective gripping devices 21, are completely withdrawn from the nip formed by the pair of work rolls.

Then the manipulator 20 moves the workpieces W to the fully advanced position shown in FIG Figure 1b . The gripping devices 21 enter the nip and, if necessary, pass through it with their front ends. Preferably, no rolling, ie no plastic deformation of the workpieces W by the rollers 10, takes place during this transfer. Instead, the purpose of the transfer is to align the workpieces W, positioning them on the tray 30 and optionally rotating one or more of the workpieces W about their own axes, preferably 90°. The transfer to the fully advanced position has an axial component, ie the workpieces are transversely in each shifted to the higher stage S2 to S4 (upward in the figures), as a result of which there is no workpiece W on the first stage S1 at the end of the transfer.

During or after the transfer to the fully advanced position, a new workpiece/blank Wn is fed to the first stage S1 by a feeder (not shown in the figures) by positioning it on the corresponding position of the tray 30. The supply of a new workpiece Wn is in the Figure 1b represented by an arrow. The feeding device can be implemented by a robot, for example, which takes the workpiece Wn from a storage container, furnace or the like (also not shown in the figures) and places it on the shelf 30 at the stage S1. The feed device can be part of the stretching device or a separate component.

After the transfer into the completely advanced position, the finished workpiece Wf, which has completely passed through the rolling process, is also gripped by a delivery device (not shown in the figures) and discharged or removed from the process. This step is in the Figure 1c is shown, with the delivery of the finished workpiece Wf being indicated by an arrow. The delivery device can be implemented, for example, by a robot that grips the workpiece Wf and transfers it to a subsequent device, for example a transport device or a storage container. The dispensing device can be part of the stretching device or a separate component. The removal of the finished workpiece Wf by the discharger and the supply of a new workpiece Wn by the feeder may occur simultaneously, substantially simultaneously, or sequentially.

With the workpieces W held in the fully advanced position by the tray 30, the grippers 21 can release their associated workpieces W and the manipulator 20 drives the grippers 21 substantially in the axial direction toward the first stage S1 (downward in the figures), where the first gripper 21 grips the newly fed work Wn and the other grippers 21 grip the adjacent work W of the preceding stage S2 to S4, respectively. The transfer of the workpieces W is based on a comparison of the Figures 1b and 1c out.

After the finished workpiece Wf has been delivered and all workpieces W, including the new workpiece/blank Wn, have been gripped by the gripping devices 21—this process stage can be regarded as the beginning of a work cycle—the workpieces W are rolled. For this purpose, the workpieces W are gripped by the rolled profiles of the corresponding steps S1 to S4 of the rollers 10, transported by rotating the rollers 10 (in the opposite direction of rotation to the transfer into the advanced position) and plastically deformed. The direction of rolling (to the left in the figures) is denoted herein by the reference character WR. Then the stretching device comes back into the position of Figure 1a . Various operating modes are possible for carrying out a work cycle. For example, the rollers 10 can be driven continuously at a constant or variable speed. Alternatively, the rollers 10 may be operated in a start/stop mode, such as by means of a direct drive and/or using a clutch and/or brake.

The Figures 2a to 2c are schematic plan views of a stretching device 1 in different process stages according to a further embodiment. Since the structure and the process flows largely with those of the embodiment of Figures 1a to 1c match, essentially only the differences are set out below. This applies equally to the embodiment of Figures 3a to 3c as well as embodiment of Figures 4a to 4c .

The stretch rolling device according to Figures 2a to 2c differs from the previous embodiment essentially in that the shelf 30 is arranged on the working side AS. The tray 30 can also be provided passively, so that the workpieces W are placed on it or the tray 30 supports the workpieces W without actively gripping or clamping them. Alternatively, the tray 30 can have retaining means 31 which are set up to temporarily retain the workpieces W, for example to grip or clamp them. According to this embodiment, the supply and discharge of the workpieces W is realized on the working side AS, as can be seen from FIGS Figures 2b and 2c emerges. In order to support the transfer of the workpieces W to adjacent gripping devices 21, the tray 30 can be set up so that it can be moved in the axial direction. Movability in the feed/retraction direction and/or up/down direction (=direction perpendicular to the axial direction and feed/retraction direction) can also be implemented, for example to support or not to hinder the transfer of the workpieces W through the nip.

In addition to the technical effects common to all of the embodiments set forth herein and described further below, an advantage of the present embodiment is that Figures 2a to 2c in that the side opposite the working side AS, which is advantageously designed as a tool changing side, is not obstructed by the shelf 30 or has limited access. Thus, the stretch rolling device can be maintained more easily and quickly.

The two embodiments of Figures 1a to 1c and 2a to 2c implement the transfer of the workpieces W to the next higher level S2 to S4 essentially in that the manipulator 20 and/or its gripping devices 21 are moved in the axial direction. The following two embodiments of the Figures 3a to 3c and 4a to 4c realize the conversion of the workpieces W essentially by moving the tray 30 in the axial direction.

For this purpose, the tray 30 is designed to be movable at least in the axial direction. It can be provided passively, so that the workpieces W are placed on it or the tray 30 supports the workpieces W without actively gripping or clamping them. Alternatively, the tray 30 can have retaining means 31 which are set up to temporarily retain the workpieces W, for example to grip or clamp them.

The tray 30 can be installed on the working side AS as shown in FIGS Figures 3a to 3c shown. Alternatively, the tray can be arranged on the side opposite the working side AS, as can be seen from FIGS Figures 4a and 4b emerges.

It should be pointed out that the tray 30 can alternatively or additionally be set up so that it can be moved in the advance/retraction direction between the two sides, ie the working side AS and the side opposite the working side AS. Furthermore, several shelves 30 can be provided, as exemplified by FIG Figure 4c emerges, for example if this improves or simplifies the handling of the workpieces W, or in order to be able to implement different process sequences with one and the same stretching rolling device 1 without considerable conversion measures.

At the end of the rolling process, the workpieces W of stages S1 to S4 usually have slightly different lengths. In order to compensate for this different elongation, at least some, preferably at least N-1 (here N designates the number of stages), gripping devices 21 have a length-compensating section 22 . The length-compensating sections 22 can be implemented, for example, by a spring system that can deflect to different extents to compensate for the length of the gripping devices 21 .

In the embodiments set forth herein, the workpieces W on the "return", ie during the transfer from the advanced position to the home position of the Figures 1a , 2a , 3a and 4a rolled. However, alternatively or additionally, a plastic deformation of the workpieces by the rollers 10 can also take place during the forward transfer, ie during the transfer into the advanced position.

The stretch-rolling concept presented here allows simultaneous occupation of all or at least several stages S1 to S4, for example every second stage. A reduced assignment of stages S1 to S4 may be necessary to comply with machine limits with regard to force or energy consumption. Nevertheless, the stretch-rolling device 1 enables the output of the workpieces W to be optimized due to the parallel configuration. This is achieved without the need for two manipulators on opposite sides of the pair of work rolls. The manipulator on the working side AS is only expanded by further gripping devices 21, such as tongs, as a result of which the improved functionality is achieved without a significant increase in the structural and procedural complexity. The transverse transport, ie transport of the workpieces W in the axial direction, is implemented, for example, either by an additional transverse transport axis in the manipulator 20 in conjunction with a stationary tray 30 or by combining a stationary manipulator 20 in the axial direction with a tray 30 movable in the axial direction. In this case, it is not necessary for the “second” end of the workpieces W to be gripped by another manipulator. In this way, a high output is achieved with a comparatively small number of assemblies, which also improves the reliability and maintainability of the stretching rolling device.

Reference List

1

stretching device

10

roller

20

manipulator

21

gripping device

22

length compensation section

30

filing

31

restraining means

S1 - S4

Step

W

workpiece

Wn

New workpiece/blank

wf

Finished Workpiece

AS

working page

WR

rolling direction

Claims (15)

1. Stretch-rolling device (1) for pressure-reshaping of workpieces (W) by rolling, which comprises:

   a work roll pair with two rolls (10) which are respectively rotatable about the roll axes thereof and form a rolling gap therebetween, wherein the rolls (10) in axial direction realise a plurality of stages (S1 to S4) which are arranged for reshaping of the workpieces (W) in steps in that the workpieces (W) successively run through the stages (S1 to S4);

   a manipulator (20) with a plurality of gripper devices (21) which are disposed on a work side (AS) of the work roll pair and are arranged to grip the workpieces (W) and at an associated stage (S1 to S4) to lead them through the rolling gap in a feed/return direction; and

   a repository (30) arranged to temporarily support workpieces (W) and in co-operation with the manipulator (20) to transfer them to another gripper device (21), preferably the adjacent gripper device (21) of the next-higher stage (S2 to S4);

   characterised in that

   the gripper devices (21) are arranged to grip the workpieces (W) at one end and to guide them to an associated stage (S1 to S4) via the rolling gap, wherein the workpieces (W) are not gripped at the other end.
2. Stretch-rolling device (1) according to claim 1, characterised in that one or more gripper devices (21) are arranged to be rotatable so as to realise rotation of the gripped workpiece (W) about the longitudinal axis thereof, preferably through an angle of 90°, between the corresponding stages (S1 to S4).
3. Stretch-rolling device (1) according to one of the preceding claims, characterised in that the repository (30) is movable in the axial direction and/or feed/return direction and/or upward/downward direction, wherein the manipulator (20) is preferably stationary.
4. Stretch-rolling device (1) according to any one of the preceding claims, characterised in that the repository (30) is arranged on the work side (AS) or the side opposite the work side (AS) in rolling direction.
5. Stretch-rolling device (1) according to any one of the preceding claims, characterised in that the number of gripper devices (21) is equal to the number of stages (S1 to S4), wherein the association of gripper device (21) with stage (S1 to S4) is a one-to-one association.
6. Stretch-rolling device (1) according to any one of the preceding claims, characterised in that the gripper devices (21) are movable by the manipulator (20) in the axial direction and/or feed/return direction, the manipulator (20) preferably being movable relative to the work roll pair in the axial direction and/or feed/return direction, and wherein the repository (30) is preferably stationary.
7. Stretch-rolling device (1) according to any one of the preceding claims, characterised in that at least one gripper device (21) is individually movable relative to the manipulator in the feed/return direction so as to provide compensation for different elongation of the workpieces (W) at the different stages (S1 to S4).
8. Stretch-rolling device (1) according to claim 7, characterised in that the individual movability of the corresponding gripper devices (21) is realised passively, preferably by spring-loading, or actively, preferably pneumatically or electromagnetically.
9. Stretch-rolling device (1) according to any one of the preceding claims, characterised in that the repository (30) comprises fixing means (31) arranged to temporarily fix, preferably clamp, the workpieces (W) for transfer to the respectively adjacent gripper device (21) of the next-higher stage (S2 to S4).
10. Stretch-rolling method for pressure-reshaping of workpieces (W) by means a stretch-rolling device (1) according to any one of the preceding claims, comprising:

    gripping a plurality of workpieces (W) each by a respective gripper device (21) of the manipulator (20);

    guiding the workpieces (W) through the rolling gap, which is formed by the work roll pair, to an associated stage (S1 to S4) in the feed/return direction;

    rotating the rolls (10) and exerting pressure on the workpieces (W) by the rolls (10), whereby the workpieces are reshaped in correspondence with their stage (S1 to S4);

    transporting the workpieces (W) to a transfer position and supporting the workpieces (W) by the repository (30);

    releasing the workpieces (W) by the gripper devices (21); and

    gripping workpieces (W) by another gripper device (21), preferably the adjacent gripper device (21) of the next-higher stage (S2 to S4); wherein

    the gripper devices (21) grip the workpieces (W) at one end and guide them through the rolling gap in accordance with the associated stage (S1 to S4), wherein the workpieces (W) are not gripped at the other end.
11. Stretch-rolling device (1) according to claim 10, characterised in that one or more workpieces (W) are rotated about the longitudinal axes thereof, preferably through an angle of 90°, between the corresponding stages (S1 to S4).
12. Stretch-rolling device (1) according to claim 10 or 11, characterised in that for transfer of the workpieces (W) to another gripper device (21) the repository (30) is moved in the axial direction and/or feed/return direction and/or upward/downward direction.
13. Stretch-rolling device (1) according to any one of claims 10 to 12, characterised in that for transfer of the workpieces (W) to another gripper device (21) the gripper devices (21) are moved by the manipulator (20) in the axial direction and/or feed/return direction, wherein the manipulator (20) preferably moves relative to the work roll pair in the axial direction and/or feed/return direction.
14. Stretch-rolling device (1) according to any one of claims 10 to 13, characterised in that at least one gripper device (21) is individually moved relative to the manipulator in the feed/return direction according to the elongation of the associated workpiece (W).
15. Stretch-rolling device (1) according to claim 14, characterised in that the individual movement of the corresponding gripper devices (21) is carried out passively, preferably by spring-loading, or actively, preferably pneumatically or electromagnetically.

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