METHOD FOR OPERATING A WOOD PROCESSING MACHINE

Description

[0001] The invention relates to a method for operating a woodworking machine according to the preamble of claim 1. Such a method is known from document EP 3 113 919 B1.

[0002] In woodworking, edgebanding is applied to the narrow edges of flat workpieces. The edgebanding and workpiece are typically joined using an adhesive, such as a hot melt adhesive. To ensure the closest possible contact between the edgebanding and the workpiece, a pressure system is usually employed, which presses the edgebanding against the workpiece. Such a pressure system generally includes at least one pressure roller mounted on a bracket so that it can rotate around a pivot axis. This roller presses against the edgebanding on the outside, thus assisting the joining process. The pressure roller is typically positioned against the edgebanding material to ensure a uniform pressure force and a homogeneous joint.

[0003] This is usually solved by adjusting the pressure roller's position to a certain contact force. A generic pressure system is known from DE 10 2018 208062 A1, which is also intended to change the contact force. In particular, it describes how the force regulation is achieved by means of an eccentrically mounted pressure roller.

[0004] However, this does not always lead to the desired results. One reason for this is that tolerances inevitably exist between the individual components of a woodworking machine. These tolerances can, for example, cause the roller axis of the pressure roller to be at an angle to the joining plane, i.e., the plane between the workpiece and the edgebanding. This angle can have a random value, meaning that a preset pressure force can result in the edgebanding being pressed more firmly on one side and less firmly on the other. Such problems also arise depending on the joining material used, such as the workpiece, the adhesive, and the coating material.

[0005] The object of the present invention is therefore to provide a method for a woodworking machine with a pressure system, with which the problems described above can be solved.

[0006] This problem is solved by a method having the features of claim 1. Advantageous embodiments are found in the dependent claims.

[0007] The pressure system, which is part of a woodworking machine, serves to press a coating material, in particular an edge banding, onto the narrow side of a flat workpiece made of wood or wood substitute. It comprises at least one pressure roller rotatably mounted in a holder about a pivot axis and at least one measuring device. This measuring device is designed to record operating data concerning the position or operating state of the pressure roller relative to a predetermined reference line or surface. The pressure system further includes an evaluation unit which, depending on the operating data recorded by the measuring device, compares the position or location of the pressure roller relative to the predetermined reference line or surface, or the operating state of the pressure roller, with a predetermined target operating state.

[0008] The pressure system records operating data regarding the position, for example, the orientation or other operating state of the pressure roller relative to a predefined reference line or surface. This reference line or surface can, for example, coincide with the joining plane described above or be parallel to it. The plane of the workpiece's narrow side is an example of a reference plane or surface. Other operating states can include, for example, the inclination, rotation, and position of the pressure roller in the projection direction. This operating data can be used to adjust the pressure roller setting, enabling not only control of the pressure roller but also continuous readjustment of the setting. This means that deviations measured for one workpiece between actual and target operating data are corrected and then checked again for the next workpiece, and adjusted if necessary.It can be further adjusted until the pressure roller setting is within the desired range.

[0009] Furthermore, the collected data can be visualized in a display device to provide visual process support for the operator. Display devices can include, for example, screens, or "smart devices" such as smartphones, smartwatches, or tablets, as well as devices for displaying augmented reality.

[0010] According to the invention, the pressure system comprises a comparison unit that compares the recorded operating data with predetermined target data. This comparison unit is part of the evaluation unit. Furthermore, the pressure system also includes a control unit and is configured to adjust the distance of the pressure roller to the predetermined reference line or reference surface and / or the inclination of the pressure roller based on this comparison, such that the operating data essentially correspond to the predetermined target data.

[0011] As described above, the measuring device can detect a whole range of operating states. According to the invention, however, the measuring device is designed to detect the inclination angle of the pressure roller relative to the predefined reference line or reference surface. This measurement provides information about the inclination state of the pressure roller, which can then be evaluated, for example, by the machine control system or a corresponding evaluation unit.

[0012] In another preferred embodiment, the at least one measuring device is designed to detect the distance, in particular the distance of the mounting or the axis of rotation, of the pressure roller to the predetermined reference line or reference surface. The information about the distance can be used, for example, to adjust the distance to a specific target distance. It can also be provided that the evaluation device is designed to determine the angle of inclination of the pressure roller to the predetermined reference line or reference surface, depending on the distance detected by the measuring device.

[0013] The position of the measuring device, i.e., its arrangement within the pressure system, can vary depending on the application. For example, the measuring device may be mounted on the holder, the base of the pressure system, or on the pressure roller or its axis of rotation. It is also conceivable that the measuring device in a woodworking machine is an upstream sensor. This enables the workpiece to be measured upstream, in particular the inclination of the narrow side's surface relative to the current position of the pressure roller. The pressure roller can then be adjusted to the workpiece's contour so that its position is already at the target value before the workpiece reaches the pressure roller.

[0014] According to a further preferred embodiment, the measuring device can be designed to detect the (rotational) angle of the bearing of the pressure roller. Such a measurement also allows conclusions to be drawn about the inclination of the pressure roller to the reference line or reference surface.

[0015] The mounting of the pressure roller can, for example, be mounted on a substructure, in particular one that is linearly displaceable and / or pivotable. According to another embodiment, the mounting can be fixedly mounted on a linearly displaceable and / or pivotable substructure. A displaceable or pivotable substructure is particularly advantageous when the pressure system has more than one pressure roller and an adjustment of the pressure system, for example, based on operating data acquired by the measuring device, is intended to affect all existing pressure rollers equally. Of course, several pressure rollers can also be individually adjustable, i.e., adjustable in inclination or displaceable.

[0016] It is also conceivable that at least one pressure roller is pivotably mounted via a lever. Feed movements can be easily implemented using such a lever. It can be provided that at least one measuring device is designed to detect the (rotational) angle of the lever or the distance of the pressure roller from the measuring device. This information can also be evaluated by the evaluation unit and used for controlling the pressure system.

[0017] In addition to the position of the pressure roller, at least one measuring device can be designed to detect the rotational state of the pressure roller. This provides information about whether, for example, contamination from hardened hot melt adhesive or other blockages is present that impairs the proper operation of the pressure system by blocking the pressure roller. Such impairments can be detected very early in this way and evaluated by the monitoring unit. Based on the information obtained by the monitoring unit, the machine control system can then take countermeasures in a timely manner. These countermeasures can include adjusting the pressure roller setting or temporarily stopping the machine.

[0018] Depending on the data determined by the evaluation unit, the pressure system must be adjusted or regulated accordingly by the machine's control unit. Preferably, the pressure system therefore further comprises an adjusting device suitable for changing the position of the pressure roller relative to the predetermined reference line or reference surface. As described above, this adjustment can be achieved by simply moving the pressure roller, i.e., a purely control-based process, or, with continuous or at least regular measurement of the operating status, by means of a control system. This can be accomplished in various ways; for example, the adjusting device can be designed to adjust the position of the bracket and / or the base linearly and / or via at least one pivot point.

[0019] The method according to the invention uses a woodworking machine, in particular an edge banding machine, which has a pressure system as described above.

[0020] The woodworking machine has a machine bed, wherein the holder or holders of the pressure roller or the pressure roller itself is pivotally mounted relative to the machine bed and the pivot position of the holder or all holders or the pressure roller itself is adjustable by means of a pivot drive or actuator.

[0021] Depending on the error detected by the measuring device according to the invention, it may be advantageous to reject defective parts from the current processing operation. For this purpose, it is preferably provided that the woodworking machine has a marking device suitable for identifying defective workpieces. This marking indicates, for example, to the machine operator that the workpiece in question is defective and can be removed from the process. It is also conceivable, of course, that the markings are at least machine-readable. In such a case, the woodworking machine can, for example, include a reject device that rejects defective workpieces marked by the marking device.

[0022] The method according to the invention serves to operate the woodworking machine described above. The following steps are carried out in this method: a. The pressure roller is set to a predetermined or calculated target position, b. a first workpiece is i) machined and the current operating data of the pressure roller are recorded using at least one measuring device, or / and ii) before machining, the workpiece is measured via a first sensor and an edge band via a second sensor, whereby a target value for the setting of the pressure roller is calculated from the measured data, c. the recorded operating data are compared with the predetermined or calculated target data, d. if the current operating data deviates from the predetermined or calculated target values, correction values ​​are calculated and adopted as new target values, and the process is continued with these target values.

[0023] In a preferred variant, steps a to d are repeated. The latter serves in particular to continuously monitor the condition of the pressure system. In this way, it is also possible to continuously adjust the settings of the pressure roller relative to the workpiece during operation of the woodworking machine. Ultimately, this allows the settings to be adjusted to optimal values, which in turn improves both the processing process and the quality of the manufactured parts.

[0024] The invention is described below with reference to the Figures 1 to 16 explained in more detail. Figure 1 shows a schematic top view of a woodworking machine used in the method according to the invention. Figure 2 schematically shows a pressure roller inclined to a reference surface in a side view. Figures 3A and 3B show a first possible configuration for measuring the inclination ( Figure 3A ) and the location ( Figure 3B) a pressure roller in side view. Figure 4 shows a second possible configuration for measuring the inclination of a pressure roller in a side view. Figure 5 shows a third possible configuration for measuring the inclination of a pressure roller in a side view. Figure 6 shows a modified embodiment of the in Figure 5 The illustrated design shows how to measure the inclination of a pressure roller in a side view. Figure 7 shows a possible configuration for measuring the position of the pressure roller in a side view. Figure 8 shows a second possible configuration for measuring the position of a pressure roller in a side view. Figure 9 shows a third possible configuration for measuring the position of a pressure roller in a side view. Figure 10 shows a top view of a fourth possible configuration for measuring the position of a pressure roller. Figure 11shows a top view of a fifth possible configuration for measuring the position of a pressure roller. Figure 12A shows a configuration for measuring the rotational state of the pressure roller. Figure 12B illustrates the direction of rotation of the pressure roller. Figure 13 schematically shows various adjustment options for the pressure roller in a side view. Figure 14 shows a side view as an example of a possible embodiment for adjusting the inclination or position of the pressure roller. Figure 15 shows a side view of a second embodiment for adjusting the inclination or position of the pressure roller. Figure 16 shows a side view of an alternative mounting of the pressure roller.

[0025] In Figure 1Figure 1 shows a schematic top view of an exemplary woodworking machine in the form of an edgebanding machine. In this case, a workpiece 3, which is plate-shaped, is transported through the device in the X direction. Typically, the narrow side of the workpiece 3 is shaped using a milling unit 7 and then coated with adhesive at station 5. Behind this, an edgeband 2 is moved towards the workpiece and pressed against the narrow side of the workpiece 3 by means of a pressure system 60. Such a pressure system usually includes at least one pressure roller 62; in addition to this main pressure roller 62, at least one secondary pressure roller 62' is usually provided, which primarily serves to guide the edgeband, still under pressure, along with the workpiece 3 a short distance further in the feed direction X.

[0026] V denotes a reference line or reference surface, which will be explained in more detail below in connection with the invention. Positions 6 and 4 are sensors that, for example, measure the position of the narrow side of the workpiece 3 to be coated or the thickness of the edge banding 2. According to the invention, the information from these sensors 6 and 4 can be used to control or regulate the pressure system 60.

[0027] What other measurement options exist on the pressure system 60 itself will now be shown using the following: Figures 2 to 12B will be explained.

[0028] Figure 2Figure 1 schematically shows a pressure roller 62, which is part of a pressure system 60 according to the invention. The pressure roller 62 is rotatable about a rotational axis A. As can be seen in the drawing, the pressure roller 62 is angled with respect to its rotational axis relative to a reference line or reference surface V, such that the cylindrical surface of the pressure roller 62, or its rotational axis A, forms an angle α with the reference line or reference surface V. In the example shown, the reference line or reference surface V runs parallel to the vertical direction Z. Y denotes a direction perpendicular to Z, which also runs perpendicular to the aforementioned feed direction X. Depending on the machining of a workpiece, it may be desirable either to set a defined angle of inclination α or, for example, to correct an undesired skew. The present invention offers a number of different possibilities for this purpose.

[0029] First, the inclination angle α must be determined. For this purpose, a measuring device 68 can be provided, which – as in Figure 3A shown – the inclination of the axis of rotation A to the reference line or reference plane V is recorded. As shown in Figure 3B As shown, the pressure roller 62 can be mounted in a roller holder 63. To adjust the position or inclination of the pressure roller 62, either the roller can be adjusted in the roller holder 63 or the roller holder 63 itself can be adjusted relative to other components of the pressure system. In the example in Figure 3B The roller support 63 can be moved in the directions Y and Z via corresponding adjusting devices 66 and 67.

[0030] For tilt adjustment of the pressure roller 62, the pressure roller 62 can be pivotably mounted in the holder 63. In the example of the Figure 4A lower pivot bearing 65 and an upper pivot bearing 69, located at the opposite axial end of the pressure roller 62, serve this purpose. The upper pivot bearing 69 is mounted on a movable section 63a, which is part of the bracket 63. In the example shown, this movable upper bearing section is designed to be displaceable back and forth in the direction Y relative to the reference line or reference plane V. This is indicated by the arrow P1. In this configuration, displacing the section 63a in the direction of arrow P1 causes a change in the tilt angle α. If the displacement occurs in the direction of the reference line or reference plane V, the tilt angle α becomes smaller. Conversely, if the displacement occurs in the opposite direction, the tilt angle α becomes correspondingly larger. In the example shown, the tilt position can be adjusted by a measuring device 68, which is attached to the displaceable part 63a.When part 63a is moved, the distance S between the measuring device 68 and the remaining part of the bracket 63 also changes. Due to the geometry shown, this distance S is a measure of the inclination of the roller axis A, since it is connected to the bracket via the two pivot bearings 65 and 69. The evaluation of the measurement result from the measuring device 68 can therefore be used to set a desired inclination of the pressure roller 62. On the one hand, the measured current position, the measured rotational state, or the measured inclination of the pressure roller 62 can be used to compare these measured values ​​with target values ​​and to transmit corresponding information about the current state of the pressure roller 62 to the machine control. Naturally, a comparison of such values ​​can also be used to change the state of the pressure roller 62 to a predetermined target value.

[0031] As an alternative to the one in Figure 4 In the illustrated embodiment, the inclination of the pressure roller 62 can be adjusted as shown in Figure 5 The angle α of the pressure roller 62 can also be determined via an angle sensor 68 attached to the bracket 63, particularly to the upper part 63a. In this embodiment, the bracket 63 is articulated to the base 64 via a pivot bearing 61. The entire bracket 63 can therefore be articulated relative to the base 64. The pivot position is transmitted via the angle sensor 68 to the machine control or a corresponding evaluation unit and provides a measure of the angle α of the pressure roller 62 to the reference surface or reference line V.

[0032] Alternatively to the one in Figure 5In the illustrated embodiment, a corresponding measuring sensor 68 can also be arranged directly on the swivel bearing 61. Here, the rotational movement of the swivel bearing 61 can be directly detected, and the tilt angle α can thus be deduced. Naturally, such a measuring device must be calibrated to a zero line, for example, the reference line or reference plane V.

[0033] To detect the position of the pressure roller, i.e., in particular the distance L to the reference line or reference surface V, a distance sensor 68 can, for example, be arranged on a fixed part, such as the bearing axis or shaft 62a of the roller 62, as shown in Figure 7 The returned measured values ​​can then be converted into the distance L of the pressure roller 62 to the reference plane.

[0034] Such a distance sensor 68 can of course also be arranged on the bracket 63. This is shown in Figure 8As shown, when the bracket 63 is moved in the Y direction towards the reference line or reference surface V, the distance L decreases. Using a probe, the distance L can be continuously monitored during operation of the pressure system with this arrangement. The measured values ​​returned by the measuring sensor 68 can then be used to change the probe of the pressure roller 62 and, in particular, to adjust or regulate it to a target value. Of course, a corresponding measuring device 68 can also be arranged on the base 64 of the pressure system and detect a corresponding change in the distance L due to a relative change of the bracket 63 to the base 64. Such a situation is shown in Figure 9 depicted.

[0035] In a further embodiment of the invention, the adjustment of the pressure roller 62 can be effected via a rocker arm 70. By changing the angular position of the rocker arm 70, on which the pressure roller 62 is mounted, in the XY plane, indicated here by the arrow U, the distance L between the pressure roller 62 and the reference line or reference surface V is changed. The instantaneous angular position can, for example, be detected in the illustrated example by a rotary angle sensor 68, which is arranged on the axis of rotation 71 of the rocker arm 70 and determines its angle of rotation.

[0036] Alternatively, Figure 11It is possible to detect the rotation of the rocker arm 70 via a touch sensor 68, e.g., on the side of the pressure roller 62 facing away from the reference line or reference surface V. Here, the distance T of the pressure roller 62 to the touch sensor 68 is detected in order to then deduce or measure the distance L between the pressure roller 62 and the reference surface or reference plane V.

[0037] Another condition that can be detected alternatively or additionally with a measuring device 68 according to the invention is the rotational state of the pressure roller 62. For this purpose, the pressure roller 62 has a rotation sensor 68. Figure 12A , which performs the rotation (arrow R, Fig. 12BThe rotational speed of the pressure roller 62 is measured. This allows for the determination of the rotational speed, which can then be compared with a predefined target value. It is also possible to measure torque to determine whether the pressure roller 62 rotates freely or if any resistance hinders or prevents its proper rotation. If rotation is restricted, a message can be sent to the machine control system indicating that the pressure roller 62 is not functioning correctly and may require maintenance. Naturally, the rotational state of the pressure roller 62 can also be compared with a predefined target value to adjust the rotational speed of the pressure roller 68 if necessary.

[0038] Adjustment options that define the position of the pressure roller relative to the reference line or reference surface V are in Figure 13schematically represented. The inclination of the pressure roller 62 can be adjusted between a vertical orientation and an inclined orientation (indicated by the axis A' and the roller 62' in the dashed lines on the left side of the diagram) by means of corresponding adjusting devices 66 and 67, respectively. Figure 13 ) change. Similarly, the distance of the pressure roller 62 to the reference line or reference surface V can be adjusted in the Y direction (indicated by the axis A' or the roller 62' in the dashed lines on the right side of the diagram). Figure 13 It is quite possible that the pressure system according to the invention has only one of the two adjustment options shown.

[0039] In Figure 14For example, one option is shown in which the bracket 63 has an upper movable part 63a and a lower movable part 63a. An upper pivot bearing 69 and a lower pivot bearing 65, respectively, are located on these two movable parts 63a, by which the pressure roller 62 is mounted on the bracket 63. Synchronous movement of the two parts 63a results only in a change in the distance of the pressure roller 62 relative to the reference line or reference plane V. Asynchronous movement, i.e., different actuation of the two actuators 66, 67, causes the two parts 63a to be moved, but the pressure roller 62 also performs a pivoting movement about the upper pivot bearing 69 and the lower pivot bearing 65.In this way, the inclination of the pressure roller 62 can be achieved, if necessary together with a displacement towards or away from the reference line or reference surface V, since the pivot points are shifted accordingly.

[0040] In Figure 15 is a to Figure 14 An alternative embodiment is shown. Here, the holder 63 is mounted on the base 64. The holder 63 can then be moved by means of the adjusting devices 67 towards the reference line or reference surface V in the Y direction and, if necessary, also vertically thereto in the Z direction. To pivot the pressure roller 62, the adjusting device 66 is actuated, which moves the shaft of the pressure roller 62, mounted on the upper part 63a of the holder 63, in the Y direction. This pivots the pressure roller 62 about the axis 61. With this device, as with the one in Figure 14The device shown can realize both pure translational movements of the pressure roller 62 towards or away from the reference line or reference surface V, as well as an inclination adjustment of the pressure roller 62 alone or in combination with a translational movement.

[0041] It should be noted that a suitable holder is not strictly necessary for adjusting the tilt. It is also possible, as shown in... Figure 16 The illustration shows that the pressure roller 62 is mounted on one side with a cantilevered bearing. The rotary bearing 61 can, for example, be arranged on the base. Accordingly, a rotary drive must be provided that rotates the pressure roller 62 around the rotary bearing 61, for example in the direction of arrow P.

[0042] The pressure system according to the invention offers various options for positioning the measuring device on the one hand and the mounting of the pressure roller on the other. Tilt adjustments of the roller are possible, as are translational adjustments or combinations thereof. Furthermore, the rotational state of the pressure roller can be detected. With the present invention, it is possible to adjust the operating state of the pressure roller to a predetermined setpoint, for example, to a specific rotational speed, a specific angle of inclination to the reference line or reference plane, and / or a specific distance therefrom. Likewise, by continuously measuring the state of the roller and comparing the measured values ​​with target values, it is possible to adjust the pressure roller to an optimal value.

Claims

1. Method of operating a woodworking machine which comprises the following: a contact pressure system (60) for pressing a coating material, in particular an edgeband, onto the narrow side of a plate-type workpiece of wood or wood substitutes, having at least one contact pressure roller (62), which is mounted in a holder (63) so as to be rotatable about an axis of rotation (A), as well at least one measuring unit (68) which is configured to record operating data relating to the bearing or position or operating state of the contact pressure roller (62) relative to a predetermined reference line or reference surface (V), wherein the contact pressure system (60) further has an evaluating unit which compares in dependence on the operating data recorded by the measuring unit (68) the bearing or position of the contact pressure roller (62) relative to the predetermined reference line or reference surface (V) or the operating state of the contact pressure roller (62) with a predetermined target operating state, and wherein the measuring unit (68) is configured to detect the angle of inclination (α) of the contact pressure roller (62) relative to the predetermined reference line or reference surface (V); characterised in that the woodworking machine comprises: a machine bed wherein the holder (63) or the holders (63) of the contact pressure roller (62) or the contact pressure roller (62) itself is mounted for pivotal movement relative to the machine bed and the pivot position of the holder or of all of the holders or of the contact pressure roller (62) itself is adjustable by means of a pivot drive or actuator wherein for the method the following steps are carried out: a. the contact pressure roller (62) is set to a predetermined or calculated target position, b. a first workpiece (3) is i) machined and then the updated operating data of the contact pressure roller (62) are recorded by means of the at least one measuring device (68), and / or ii) prior to machining, the workpiece (3) is measured via a first sensor (6) and an edgeband (2) is measured via a second sensor (4), wherein a target value for setting the contact pressure roller (62) is calculated from the measured data, c. the recorded operating data are compared with the predetermined or calculated target values, d. in the event of a deviation of the updated operating data from the predetermined or calculated target values, correction values are calculated and adopted as new target values and the method is continued with these target values.

2. Method according to Claim 1 characterised in that the steps a to d are repeated.

3. Method according to Claim 1 characterised in that the woodworking machine (1) has an identification unit which is suitable for identifying faulty workpieces (3).

4. Method according to Claim 1 characterised in that the woodworking machine (1) has a sluice unit which ejects the faulty workpieces (3) marked out by the identification unit.

5. Method according to Claim 1 characterised in that the contact pressure system (1) further comprises a comparison unit which compares the recorded operating data with predetermined target data, and a control unit is provided and configured to undertake the change of the distance of the contact pressure roller (62) from the predetermined reference line or reference surface (V) and / or the incline of the contact pressure roller (62) in dependence on this comparison so that the operating data correspond substantially to the predetermined target data.

6. Method according to one of Claims 1, 5 characterised in that the at least one measuring unit (68) is configured to record the distance (L), in particular of the holder (63) or axis of rotation (A), of the contact pressure roller (62) from the predetermined reference line or reference surface (V).

7. Method according to Claim 6 characterised in that the evaluation device is configured to determine in dependence on the distance recorded by the measuring unit (68) the angle (α) of inclination of the contact pressure roller (62) to the predetermined reference line or reference surface (V).

8. Method according to one of Claims 1, 5-7 characterised in that the measuring unit (68) is attached to the holder (63), the base unit (64) of the contact pressure system (60) or to the contact pressure roller (62) or its axis of rotation.

9. Method according to one of claims 1, 5-8 characterised in that the measuring unit (68) is configured to record the angle (α) (of rotation) of the bearing of the contact pressure roller (62).

10. Method according to one of Claims 1, 5-9 characterised in that the holder (63) is mounted, in linearly displaceable and / or pivotal manner, on a base unit (64), or is mounted fixed on a linearly displaceable and / or pivotal base unit (64).

11. Method according to one of Claims 1, 5-10 characterised in that the contact pressure roller (68) is mounted for pivotal movement via a lever (70).

12. Method according to Claim 11 characterised in that the at least one measuring unit (68) is configured to record the angle (U) (of rotation) of the lever (10), or the distance (T) of the contact pressure roller (62) from the measuring unit (68).

13. Method according to one of Claims 1, 5-12 characterised in that the at least one measuring unit (68) is configured to record the rotational state (R) of the contact pressure roller (62).

14. Method according to one of claims 1, 5-13 characterised in that the contact pressure system further comprises a positioning system (66, 67) which is suitable for changing the bearing or position of the contact pressure roller (62) relative to the predetermined reference line or reference surface (V).

15. Method according to Claim 14, characterised in that the positioning system (66, 67) is designed to adjust the position of the holder (63) and / or of the base unit (64) linearly and / or through at least one rotational point (65, 69).