CN108941251B

CN108941251B - Straightening machine and method for operating the same

Info

Publication number: CN108941251B
Application number: CN201810486757.4A
Authority: CN
Inventors: F·穆勒莱勒
Original assignee: Kohler Maschinenbau GmbH
Current assignee: Kohler Maschinenbau GmbH
Priority date: 2017-05-18
Filing date: 2018-05-17
Publication date: 2022-01-07
Anticipated expiration: 2038-05-17
Also published as: EP3403737B1; US20180333758A1; EP3403737A2; EP3403737A3; DE102017110891B3; CN108941251A; PL3403737T3

Abstract

The invention relates to a straightening machine and a method for operating the same for straightening a metal strip or a flat metal part, having a plurality of upper straightening rollers which are supported in an upper roller frame by a first bearing point and a second bearing point, respectively, and a plurality of lower straightening rollers which are supported in a lower roller frame by a first bearing point and a second bearing point, respectively. The upper and lower straightening rolls are arranged such that they form a straightening gap between the inlet and the outlet of the straightener to be able to act on the metal strip or piece to be straightened from above and below and to guide the metal strip or piece through the straightener. Furthermore, a coupling element is provided on one end side of the straightening roller for connection to a drive shaft of a drive and the straightening roller can be removed from the respective roller frame. At least one part of the straightening rollers is provided on both end sides with coupling elements in order to be able to turn the straightening rollers over on the roller frame.

Description

Straightening machine and method for operating the same

Technical Field

The present invention relates to a straightener for straightening a metal strip or a flat metal piece according to the preamble of solution 1 and a method for operating the straightener according to the preamble of solution 12.

Background

Such a straightener comprises a plurality of upper straightening rolls which are supported in an upper roll stand and a plurality of lower straightening rolls which are supported on a lower roll stand. The upper and lower straightening rolls are arranged such that they form a straightening gap between the inlet and the outlet of the straightener to be able to act on the metal strip or piece to be straightened from above and below and at the same time guide it through the straightener. The straightening roller is provided on one end side with a coupling element for connection to a drive shaft of a drive, generally a cardan shaft. And finally, the straightening roller can be taken down from the corresponding roller frame, so that the straightening roller can be replaced when the abrasion limit is reached.

The straightener described above is capable of relieving stresses and irregularities in the metal strip or piece. The upper straightening rollers and the lower straightening rollers are arranged offset to one another along the straightening gap, so that the material to be straightened is guided through the straightening gap in the form of a serpentine and in the process the material to be straightened is bent alternately upwards and downwards on the straightening rollers. The medium-bending form can be such that the material is bent beyond its tensile limit at least on the first straightening roll, so that undesired bending and stresses in the material are eliminated as completely as possible. Usually the material is plastically deformed strongly on the first straightening roll. The bending of the material is weak on the remaining rolls and the material is no longer plastically deformed, i.e. only elastically deformed, on the last straightening roll.

In the metal processing industry, metal strips are generally used, which are supplied in the form of a disc and the disc-shaped structure is unwound for production. By winding the strip material into a coil, but also possibly as a result of possible previous heat treatments or the like, irregularities or stresses can occur in the strip material, which are disadvantageous for further processing. Therefore, after the metal strip having a plate-like structure has been unwound, the metal strip is usually guided through a straightening gap of a straightening machine and leaves the straightening gap flat and stress-free.

This is not the only use, however, since the straightening machine of the above-described construction is also used for straightening flat metal pieces, from which undesired bends and stresses should be removed in order to be able to continue working the metal piece. In particular in such a component straightening machine, great advantages are achieved by the invention.

ｃA straightener constructed as described above is disclosed for example in EP- ｃA-2712687. The disclosed straightener is also particularly suitable for straightening flat metal pieces and solves the following problems. That is, when the upper and lower roll frames are connected by the positioning bolts, the straightening gap of the leveler becomes wider during the straightening. According to this prior art proposal, the positioning bolt is provided with an adjusting device for changing the effective length of the positioning bolt, so that changes in the effective length of the positioning bolt, which usually grows under load, can be compensated for in real time during operation.

Other straightening machines as described above are disclosed, for example, by EP-A-2002907, which relates in particular to the drive train for the straightening machine, and by EP-A-1491270.

The straightening rollers of a straightening machine of this type usually have a coupling element on one end side for connection to the universal shaft of the drive. The coupling element is usually configured as a coupling journal with an outer contour. On the opposite end sides of the straightening rollers, bearing journals are provided which serve as axial bearings in the respective roller frame. In order to remove the straightening roller from the roller frame, the cardan shaft is pulled off the straightening roller on the drive side, the associated bearing is detached and the straightening roller is pulled off the opposite bearing.

The straightening rolls of the straightener constructed as described above are subjected to strong force and thus rapid wear occurs to some extent. When the straightening rolls wear to such an extent that visible defects remain on the surface of the metal strip or piece to be straightened, the straightening rolls must be replaced. Since the straightening rolls need to have high stability, strength and dimensional stability, the cost required for replacement of the straightening rolls is correspondingly high.

Disclosure of Invention

The object of the invention is therefore to provide a straightening machine of the type mentioned above and a method for operating the same, with which the service life of the straightening rolls can be increased, in particular when the straightening machine is used for straightening flat metal pieces.

This object is achieved by a straightener having the features of claim 1 and by a method having the features of claim 12. Preferred embodiments of the straightener according to the invention are given in claims 2 to 11; advantageous developments of the method according to the invention are given in claims 13 to 15.

According to the invention, it is recognized that the straightening rolls of a straightening machine for straightening flat metal pieces are rapidly worn on the side of the straightening machine opposite the drive. This is related to the fact that: the operator operates the straightener and feeds it into the inlet of the straightener, usually by placing the metal piece to be straightened on a roller table or other transport device in front of the inlet of the straightener, for which purpose the operator has to stay on the side of the straightener opposite to the drive. Of course, if the metal piece to be straightened is narrower than the width of the entry opening, the metal piece is usually not centered but rather is located close to the operator, i.e. the metal piece to be straightened enters the straightening gap from the side of the straightening machine facing away from the drive. This results in the straightening rolls wearing out more quickly on the operating side of the straightener than on the drive side.

Furthermore, it is recognized according to the invention that the service life of the straightening roll can be increased in a very simple manner when the straightening roll is subjected to such asymmetrical loads, with the straightening roll wear occurring mainly on one side. That is, the straightening rolls are reversed inside the leveler, that is, the straightening rolls are removed from the respective roll frames after the completion of the straightening process a plurality of times, and are reloaded into the roll frames after reversing the straightening rolls so that both end sides of the straightening rolls are interchanged.

In order to achieve this operation, according to the invention, the straightening roll to be turned is not provided with coupling elements only on one end side as described in the prior art, but on both end sides.

As is customary in the prior art, the coupling element can be designed as a drive journal with a profiled cross section in order to transmit torque axially via a drive shaft or cardan shaft that can be inserted; alternatively, it can be provided that the coupling element is designed as a drive sleeve with a profiled cross section, into which a correspondingly profiled journal of the drive shaft can be inserted. The same applies to both alternatives in that the above-described connection and disconnection of the straightening roller to the drive shaft of the drive can be achieved by a movement in the axial direction.

The design of the straightening roll that can be reversed according to the invention makes it possible to achieve a significant improvement in the service life of the straightening roll, wherein the improvement is more pronounced the higher the frequency of the metal parts that normally enter the straightening gap with a straightening operation that deviates to the side of the straightening machine. This is because by alternating the turning of the straightening rolls, the regions of the straightening rolls which are subjected to a higher load and cause a higher wear are shifted from the regions which are subjected to a lower load and cause a lower wear. In the ideal case, a substantially uniform loading of the straightening roller is thereby achieved.

In order to further increase the service life of the tiltable straightening rollers, it is preferred within the scope of the invention if the straightening rollers not only alternately tilt the straightening rollers and reassemble them to the roller stand in the form of interchanging the two end sides of the straightening rollers, but also if the straightening rollers alternately change the order of the individual straightening rollers in the straightening gap. Since it has been realized that the closer the straightening rolls are to the inlet of the straightener, the greater the load they are subjected to during straightening and the correspondingly greater the wear. If the straightening rolls are changed regularly in sequence between the inlet and the outlet of the straightener, the effect is achieved that the straightening roll which is subjected to a greater load is exchanged for the straightening roll which is subjected to a lesser load, so that as a result all the straightening rolls are loaded substantially uniformly and wear out uniformly.

As is known from the prior art, in the case of the straightening machine according to the invention it is also preferred that at least two pairs of support rolls are assigned to the side of each straightening roll facing away from the straightening gap, said support rolls being used to support the straightening rolls in order to prevent the straightening rolls from bending during the straightening process.

In this case, of course, large loads of the straightening rollers occur in the contact region between the support rollers and the straightening rollers, which loads lead primarily to large wear on the end-side edges of the support rollers. It is therefore preferred within the scope of the invention for the support rolls to be arranged for each straightening roll such that they are positioned asymmetrically with respect to a central section of an imaginary connecting line between the two bearing points of the straightening roll. This allows the contact area between the support roll and the straightening roll to be located at another point of the straightening roll after the straightening roll has been turned over, so that premature wear in this contact area, in particular in the area of the end-side edges of the support rolls, is avoided. This also further increases the service life of the straightening roll.

In order to adapt the cycle of the reversing straightening roll according to the invention as optimally as possible to the particular loading of the straightener and its straightening rolls, it is preferred within the scope of the method according to the invention that the forces acting between the upper and lower roll stands during straightening and the time curve of said forces are detected and summed. This can be done purely quantitatively in that the value of the force of the upper roll stand away from the lower roll stand is above a certain threshold value and at the same time the time period for which said force is above the threshold value exceeds a predetermined minimum time period, a counter is activated, which represents the completion of a straightening cycle. However, it is of course also possible to qualitatively detect the force and/or its time curve and calculate the load exerted on the straightener during the detected straightening by integrating it accordingly. The load is accordingly a measure for the load and indirectly for the expected wear due to the respective straightening cycle, for example, because the material has different lengths and the remaining dimensions are the same and are made of the same material, for example, when the force is applied for a shorter period of time than during the straightening with a longer period of time, the load has a smaller value or, corresponding to the detected asymmetry of the force, the load has a higher value.

Preferably, additionally, a single value of the forces acting simultaneously at different positions between the two roll stands inside the straightener is measured and, in the presence of an asymmetric distribution of the forces, the asymmetric distribution of the forces is preferably also detected. This can also be regarded as purely quantitative, in that a count is made when a threshold value for the respective asymmetry of the force is exceeded, and a threshold value for the time period when the asymmetry exceeds the threshold value is exceeded. However, when the possible asymmetrical distribution of the force and its time curve are detected qualitatively and integrated if necessary, a better approximation of the actual process caused by wear can be achieved.

The invention determines an expected value of the wear of the straightening roll on the basis of a quantitatively and/or qualitatively detected force acting between the upper roll stand and the lower roll stand during the straightening process, on the basis of a time curve of the force and, if necessary, also on the basis of an asymmetrical distribution of the force, and, when the expected value reaches a predetermined expected threshold value, removes the straightening roll from the roll stand, turns over the straightening roll so that the two end sides of the straightening roll are interchanged and reassembled to the roll stand. In this case, a compromise must be found between the desired, as uniform as possible, wear of the straightening rollers and the frequency of the turning process which can lead to machine standstill.

In order to be able to operate the straightening machine according to the invention in the manner described above, it is preferred that sensors are provided for detecting the forces acting between the upper roll stand and the lower roll stand during the straightening process. The detection of the force can also be carried out quantitatively and/or qualitatively. Preferably, the sensor is arranged on the straightening machine for detecting the asymmetrical distribution of the forces, in addition to the forces acting between the upper roll stand and the lower roll stand during the straightening process, also quantitatively and/or qualitatively.

In straightening machines having positioning bolts for connecting the upper roll stand and the lower roll stand, which are known per se, the elongation of the positioning bolts is compensated for during the straightening process by changing their effective length, in such straightening machines the positioning bolts are usually provided with sensors, in particular displacement sensors, which detect the elongation of the respective positioning bolt. It is therefore advantageous within the scope of the invention if the sensor for detecting the forces acting between the roll stands and, if appropriate, the asymmetrical distribution of the forces can also be a sensor for detecting the elongation of the respective positioning bolt, for example, if the sensor is designed as a displacement sensor.

Preferably, the sensor is provided with a load spectrum recorder, wherein said sensor according to the invention is used for quantitatively and/or qualitatively detecting the force between the upper roll stand and the lower roll stand, the time curve of said force and/or the asymmetry thereof during the straightening process. The load spectrum recorder is used for storing the detected force and/or accumulating a straightening cycle determined quantitatively or qualitatively by the detected force.

Alternatively or additionally, the load spectrum recorder may be configured such that the load spectrum recorder stores the forces detected during straightening and the time profiles of the forces and, in the detection of an asymmetrical distribution of the forces, also stores the asymmetrical distribution of the forces and/or, from this, the loads calculated respectively and, in the detection of an asymmetrical distribution of the loads, calculates the asymmetrical distribution of the loads and stores the calculated values as load cycles. Such a load cycle is a measure of the load of the straightening roller which causes wear, wherein, if necessary, an asymmetrical distribution is included in the load cycle with a weighting, so that the summation of the load cycles in the load spectrum recorder makes it possible to estimate the wear caused by the load.

Thereby obtaining a plurality of precision levels; counting the number of loads above the load threshold, which leads to a certain number of straightening cycles resulting from the straightening process, makes it possible to make a rough estimate of the straightening roll wear caused by the straightening process, said straightening cycles being accumulated in the load spectrum recorder, a qualitative load detection being carried out for calculating the load cycles accumulated in the load spectrum recorder by analytically evaluating the forces acting at different positions and a qualitative detection of the time profile of said forces, thereby more accurately reflecting the actual situation occurring when the straightening roll is worn.

In any case, it is preferable that the straightening machine according to the invention is provided with a wear computer, and the wear computer is configured such that the wear computer calculates a wear value from the straightening cycles or load cycles accumulated in the load spectrum recorder and outputs a signal when the wear value reaches a preset wear threshold value. Alternatively, in order to approach the actual state, the wear calculation means are configured such that the wear computer calculates an expected value of the straightening roll wear from the force stored in the load spectrum recorder and detected by the sensor and the time profile of the force, and from the spatial distribution of the force when the spatial distribution of the force is detected, and emits a signal when the expected value reaches a preset expected threshold value. In the latter case the intermediate step of accumulating the straightening cycle or the load cycle can be dispensed with.

Drawings

An embodiment of a straightening machine designed according to the invention will be described and explained in detail with reference to the drawings. Wherein:

FIG. 1 shows a schematic top view from above of a straightener of the type described above;

FIG. 2 shows a schematic front view of a straightener designed according to the invention;

fig. 3 shows a detail of the end side of a straightening roll according to the prior art;

FIG. 4 shows a bearing point of a straightening roll according to the prior art;

FIG. 5 shows a supporting portion of a straightening roll in the straightening machine according to the present invention;

figure 6 shows a schematic view of a straightening roll with cooperating support rolls.

Detailed Description

Figure 1 shows a top view of a straightener of the kind in question. The actual straightener 1, in which the straightening rolls are mounted (not shown here), is provided on the drive side, shown on the left, with a drive, which is composed of a drive motor 2 and a gear unit 3, as well as a plurality of cardan shafts 4, which connect the respective gear unit connection ends to the coupling elements 5 of the straightening rolls.

The inlet 6 and the outlet 7 of the straightener are provided with an inlet roller table 8 and an outlet roller table 9 for feeding flat metal pieces 10 from the inlet 6 or for taking them out from the outlet 7 after straightening.

In the actual straightener 1 only the frame 11 and the upper roll holder 12 and the adjusting device 13 for the positioning bolt (not shown here) are visible. The illustration of figure 1, which shows the problem in the part straightener, has led to the idea of the invention and finally to the realization of the invention:

the task of the operator shown in figure 1 is to feed the metal piece 10 to be straightened from the inlet 6 and to remove it from the outlet 7 after the straightening process has been completed. For this purpose, as shown in figure 1, the operator will naturally place the metal piece 10 onto the entry table 8 so that it is in the vicinity of the operating side, i.e. the left side of the straightener 1 in figure 1. When, as in the embodiment shown, the straightener 1 has a wide inlet 6, there will normally be metal pieces 10 in operation which have a width which is not equal to the width of the inlet 6. As shown in fig. 1, the metal piece is now placed on the entry table 8 offset towards the operating side. Accordingly, when straightening the metal piece 10, the straightening rolls of the straightening machine 1 are loaded only in the region oriented toward the operating side, while in this straightening process the straightening rolls are not loaded at all in the region oriented toward the drive side shown on the right in fig. 1.

FIG. 2 is a schematic side view of the leveler 1 of FIG. 1 from the operation side. An upper roll stand 12 and a lower roll stand 14 are supported on the machine frame 11, and the two roll stands 12, 14 are connected to each other by four positioning bolts 20.

In this case, nine upper straightening rollers 15 are supported on the upper roller frame 12, and ten lower straightening rollers 16 are supported on the lower roller frame 14. The upper straightening rollers 15 and the lower straightening rollers 16 are each arranged in a row, so that a straightening gap 17 is formed between the upper straightening rollers 15 and the lower straightening rollers 16, which gap extends from the inlet 6 to the outlet 7 and through the straightener 1. If the metal piece is now fed into the inlet 6, it is conveyed through the straightener 1 in the straightening gap 17 between the upper straightening roll 15 and the lower straightening roll 16, and at this time it is bent alternately in a serpentine shape up and down around the upper straightening roll 15 and the lower straightening roll 16. For this purpose, the straightening

rollers

15, 16 are arranged offset in the straightening gap 17.

A positioning bolt 20 connecting the upper roller housing 12 and the lower roller housing 14 is fixedly anchored in the lower roller housing by means of an anchor 18, while said positioning bolt is adjustably arranged in the upper roller housing 12. In fig. 1, the adjusting device 13 can be seen; one side of the adjusting device is connected and fixed with the upper roll frame 12, while the other side is provided with a support for a positioning bolt 20. The height of the abutment with respect to the upper roll stand can be changed by means of the adjusting device 13, so that the elongation of the positioning bolt 20 can be compensated upwards by displacement of the abutment during the straightening process, in which the straightening gap 17 widens as a result of the metal piece, in such a way that the supporting structure of the positioning bolt 20 in the upper roll stand 12 is also "elongated" in a corresponding manner. In this connection, the adjusting device 13 is not used to change the actual length of the positioning bolt 20, but only its effective length, which is proportional to the straightening gap 17, and thus the straightening gap 17 can be kept constant.

As the metal piece 10 passes through the straightening gap 17, a force transmission flow of the reaction force extends from the upper roll stand 12 via the positioning bolt 20 into the lower roll stand 14. At this time, the positioning bolt 20 is extended, and the extension becomes more remarkable as the structure of the positioning bolt 20 becomes simpler. Due to the elongation of the positioning bolt 20, the straightening gap 17 widens, which can be compensated for by the adjusting device 13.

In order to compensate this in real time and to keep the straightening gap 17 constant, sensors 19 are attached to all four positioning bolts 20, which sensors are in this case embodied as displacement sensors. Based on the elongation values of the positioning bolts 20 reported by said sensors 19 to the machine controller, the adjusting device 13 can correspondingly increase the height of the seats of the positioning bolts 20 on the upper roll stand 12 so that the effective length of the positioning bolts 20 does not change despite the elongation of the positioning bolts, whereby the straightening gap 17 remains unchanged. That is, the straightening gap does not widen. This design of the straightener is known per se from EP-A-2712687.

According to the invention, the sensors 19, which have been used as displacement sensors for the adjusting device 13, can also be used to detect the forces acting between the upper roll stand 12 and the lower roll stand 14 during the straightening process, which can be detected at all four corners of the roll stands 12, 14, i.e. at each positioning bolt 20, at a mutual distance.

It is thus possible to derive the force present in the straightening gap 17 and the time profile of said force, at least over the time period of the action of said force, and if necessary also the asymmetrical distribution of said force, from the values provided by the sensor 19.

Depending on the desired accuracy, the values provided by the sensors 19 can be used to derive the wear of the straightening

rollers

15, 16 in different ways.

For example, the completed straightening cycles can be counted, wherein a straightening cycle is counted when the duration of the time period of the determined force effect in the straightening gap 17 is exceeded, or, in the present embodiment, when the duration of the time period determined when the sensor 19 for detecting the elongation of the positioning bolt 20 detects that a certain displacement continues. Or a number of asymmetric straightening cycles, which are defined accordingly, in such a way that when an asymmetry determined by the value of the sensor is detected which exceeds a certain threshold value and is detected over a predetermined period of time, the asymmetric straightening cycles are counted.

If the accumulated number of straightening cycles and/or the accumulated number of asymmetrical straightening cycles reaches a predetermined threshold value, the straightener 1 is controlled to output a signal indicating that the straightening rolls 15, 16 should be reversed and/or the sequence of the straightening rolls along the straightening gap 17 should be changed in order to achieve a uniform wear of all the straightening rolls 15, 16.

However, it is also possible to determine the degree of asymmetrical wear of the straightening

rollers

15, 16 by measuring the values at different points and at different times of the forces acting in the straightening gap and to use this degree as a trigger/trigger condition for reversing and/or exchanging signals of the straightening

rollers

15, 16.

In order to be able to invert the straightening

rollers

15, 16, according to the invention, coupling elements 5 are provided on both end sides of the straightening rollers. Fig. 3 shows the two end sides of a straightening roll 15 according to the prior art, as can be seen from fig. 3: according to the prior art, the straightening roller 15 has a coupling element 5 only on one end side thereof, the coupling element 5 being designed here as a drive journal for the axial transmission of torque and having a profiled cross section. According to the prior art, the other end side of the straightening roller 15 has a bearing journal 21.

As shown in fig. 4, the bearing journals 21 of the straightening rolls 15 are supported on the associated roll stand 12 by conventional axial bearings 22, according to the prior art.

In order to achieve the reversibility of the straightening

rollers

15, 16 according to the invention, the connecting elements 5 are provided on both end sides of the straightening rollers, for which purpose the bearing arrangement of the straightening

rollers

15, 16 on the roller frames 12, 14 has to be modified, as shown in fig. 5, in that an axial bearing 22, which is provided in the prior art on one outer side of the roller frame 12, is displaced on the inner side of the

roller carrier

12 or 14, as shown in fig. 5.

Fig. 6 finally shows a schematic representation of a row of lower straightening rollers 16 and of two associated

support rollers

23a and 23 b. The straightening rollers 16 are supported in the roller stand 14 by the

support rollers

23a, 23b to take up the straightening pressure, so that on the one hand, it is not necessary to take up all the straightening pressure by the first bearing point 24 and the second bearing point 25, and on the other hand, bending of the straightening rollers 16 is avoided.

According to a preferred embodiment of the invention, in this exemplary embodiment, the two pairs of supporting

rollers

23a, 23b are positioned asymmetrically with respect to the central section of an imaginary connecting line of the two

bearing points

24, 25 of the straightening roller 16, but offset to the left by a distance. Thus, by turning over the straightening roll 16, the support points of the support rolls 23a, 23b are now located in different regions of the straightening roll 16 or slightly offset from the original regions, so that here a wear equalization by contact of the support rolls 23 and the straightening roll 16 is achieved.

In other words, in this embodiment, a straightening machine 1 known per se from the prior art is used and is modified according to the invention in that coupling elements 5 are provided on both end sides of the straightening rolls 15, 16, respectively. The sensor 19, which is already present in the prior art, can be used to carry out the method according to the invention. In the simplest case, the following can be recognized by the different extensions of the four positioning bolts 20, which are reported by the sensor 19: the metal piece 10 is fed in from the inlet 6 of the straightener 1 offset so that the straightening rolls 15, 16 are loaded asymmetrically. This straightening cycle, which is identified as asymmetrical, is accumulated in the load spectrum recorder. Once the sum has reached a predetermined threshold value, the straightening

rollers

15, 16 are reversed or a signal is output which initiates this reversal.

However, since the sensor 19 is able to provide values which are proportional to the forces present in the straightening gap 17 at different positions and at different times, it is also possible to calculate from said values more precise load values for the loads which lead to wear of the straightening

rollers

15, 16 and to weight them with asymmetry and to sum them up as a load cycle for storage and accumulation, if necessary. From the load values or optionally the sum of the load cycles, a wear value can be calculated and, when a predetermined wear threshold is reached, a signal for turning over and/or exchanging the straightening

rollers

15, 16 is output.

Claims

1. A straightening machine for straightening metal strips or flat metal pieces (10)

The straightener has a plurality of upper straightening rollers (15) and a plurality of lower straightening rollers (16), the upper straightening rollers (15) are supported in an upper roller frame (12), the lower straightening rollers (16) are supported in a lower roller frame (14),

the upper straightening roll (15) and the lower straightening roll (16) are arranged in such a way that the upper straightening roll (15) and the lower straightening roll (16) form a straightening gap (17) between the inlet (6) and the outlet (7) of the straightening machine (1) in order to be able to act on the metal strip or metal piece (10) to be straightened from above and below the metal strip or metal piece (10), respectively, and to guide the metal strip or metal piece (10) through the straightening machine (1),

the straightening rollers (15, 16) are each provided on one end face with a coupling element (5) for connection to a drive shaft of a drive (2, 3, 4),

and the straightening rollers (15, 16) can be removed from the respective roller frame (12, 14),

it is characterized in that the preparation method is characterized in that,

at least one part of the straightening rollers (15, 16) is provided on both end sides with a coupling element (5) respectively;

wherein at least two pairs of support rollers (23) are arranged on the side of each straightening roller (15, 16) facing away from the straightening gap (17), wherein the at least two pairs of support rollers (23) are positioned asymmetrically with respect to a central section of an imaginary connecting line between a first bearing point (24) and a second bearing point (25) of the straightening roller (15, 16).

2. Straightening machine according to claim 1, wherein the coupling elements (5) of the straightening rolls (15, 16) are configured as drive journals or drive sleeves having a profiled cross section for the axial transmission of torque.

3. Straightening machine according to claim 1, wherein the straightening machine is provided with a plurality of sensors (19), which sensors (19) are used to detect the forces acting between the upper roll stand (12) and the lower roll stand (14) during the straightening process.

4. Straightener according to claim 3, wherein the sensor (19) is arranged on the straightener (1) for detecting an asymmetrical distribution of the forces acting between the upper roll stand (12) and the lower roll stand (14) in addition to the forces acting during straightening.

5. Straightener according to claim 3, wherein the upper and lower roll housings (12, 14) are connected to each other by a plurality of positioning bolts (20), at least a part of the positioning bolts (20) being provided with a sensor (19) for detecting the elongation of the respective positioning bolt (20).

6. Straightening machine according to claim 5, wherein the sensor (19) is configured as a displacement sensor.

7. Straightening machine according to any one of claims 3 to 6, wherein a load spectrum recorder is arranged on the sensor (19) for storing the detected forces and/or for storing and accumulating the straightening cycles determined by the detected forces.

8. Straightening machine according to claim 7, wherein the load spectrum recorder is configured such that it stores the forces detected during the straightening and the time profiles of the forces and, when an asymmetrical distribution of the forces is detected, it also stores the asymmetrical distribution of the forces, and/or that it calculates the loads from the forces detected during the straightening and the time profiles of the forces, respectively, and, when an asymmetrical distribution of the loads is detected, it also calculates the asymmetrical distribution of the loads and stores, as load cycles, accumulates the individual load cycles.

9. Straightener according to claim 7, wherein the straightener (1) is provided with a wear computer, the wear calculation means being configured such that the wear computer calculates a wear value from the straightening cycles or load cycles accumulated in the load spectrum recorder and outputs a signal when the wear value reaches a preset wear threshold.

10. Straightening machine according to claim 7, wherein the straightening machine (1) is provided with a wear computer, the wear computer being configured such that it calculates an expected value of the wear of the straightening rolls (15, 16) from the force stored by the load spectrum recorder and detected by the sensor (19) and the time profile of the force and from the spatial distribution of the force when the spatial distribution of the force is detected, and signals when the expected value reaches a preset expected threshold value.

11. Method for operating a straightening machine (1) according to any one of claims 1 to 10, wherein, after a plurality of straightening processes have been carried out, the straightening rolls (15, 16) are periodically removed from the respective roll stand (12, 14), the straightening rolls (15, 16) are reversed so that the two end sides of the straightening rolls (15, 16) are interchanged and then are reassembled onto the roll stand (12, 14).

12. Method according to claim 11, wherein the straightening process to be performed is counted as a straightening cycle by detecting the forces acting between the upper and lower roll frames (12, 14) and/or the asymmetry of the forces acting during the straightening process, the straightening rolls (15, 16) are removed from the respective roll frames (12, 14) after the number of completed straightening processes has reached a preset threshold value of the straightening cycle, the straightening rolls (15, 16) are reversed so that the sides of the straightening rolls (15, 16) are interchanged, and then re-assembled to the roll frames (12, 14).

13. A method according to claim 11, wherein an expected value for the wear of the straightening rolls (15, 16) is determined from the detection and accumulation of the forces acting between the upper and lower roll holders (12, 14) during straightening, from the time curve of the forces and from the asymmetrical distribution of the forces when the latter is detected, and when the expected value reaches a preset expected threshold value, the straightening rolls (15, 16) are removed from the respective roll holder (12, 14), the straightening rolls (15, 16) are reversed so that the sides of the straightening rolls (15, 16) are interchanged and then reassembled to the roll holders (12, 14).

14. Method according to claim 12 or 13, wherein the order of the individual straightening rolls (15, 16) in the straightening gap (17) is also changed during the reassembly to the roll stand (12, 14) after the straightening rolls (15, 16) have been reversed so that the two end sides of the straightening rolls (15, 16) are interchanged.