Method for calibrating the position of blades of slitter-winder in fibrous- web machine and device applying the method

The present invention relates to a method for calibrating the position of blades of a slitter-winder in a fibrous-web machine, which blades are arranged to move in blade carriages set into connection with guides or equivalents in relation to a frame of the slitter-winder, the position of which blade carriage is specified and, in which method, the position of the blades of the slitter-winder is measured in the cross-direction of the machine.

Furthermore, the present invention relates to a device for calibrating the position of blades of a slitter-winder in a fibrous-web machine, in which slitter-winder the blades are arranged to move in blade carriages set into connection with guides or equivalents in relation to a frame of the slitter-winder, the position of which blade carriage is specified, and which device includes calibration means by which the position of the blades of the slitter-winder is measurable in the cross-direction of the machine.

In the slitter-winders of paper and board machines, a web is longitudinally cut into several partial webs and a pair of blades consisting of a top blade and a bottom blade is used in the slitting. The width of the partial webs slit by the blades and thus the position of the slitting blades can vary to a great extent during different blade settings depending oh the set widths of the reels being produced. The slitting blades have to be positioned in the correct slitting position equivalent to the desired reel widths in the lateral direction of the web. In order to produce partial-web reels of a desired width, the slitting blades of the slitter-winder are spaced apart as desired in the lateral direction of the paper or board web, i.e., a change of the blade setting is performed.

Such methods and devices for specifying the position of the blades are known previously, one of which is known of FI patent specification 115615. There, the blades are arranged in carriages fastened in guides the position of which is specified. In the method, the position of an edge of the bottom blade is calibrated with a separate calibration tool first by bringing the moving calibration tool at the point of the slitting edge of the bottom blade, after which the position of the calibration tool is measured. Based on these two measurements (carriage position and calibration tool position), the position of the blade is specified.

As to prior art related to the invention, reference is made to FI patent specification 68185 which discloses a method and a system for position change. This specification describes the use of the method in a system used in the slitting of a paper web, which system employs to observe the position of the slitting device a measuring device which is in a position arrangement in which there are actuators for controlling and performing the motion of the measuring device in the cross-direction of the web and, in which system, there is at least one limiter i.e. limiting the operation of the measuring device along the distance between the extreme positions such that one extreme position is the datum position for the specification. An observing device in both directions of motion observes at least one element of the slitting device. The system includes drive devices for the actuators and moving devices for performing a corrective motion of a movable device or element. With this known arrangement, the position of the slitting blades has been specified during a stoppage of the machine, aiming at minimising the duration of the stoppage.

It is known of prior art to measure the position of blades used in slitting by means of a carriage-type arrangement, in which a sensor is placed in a moving carriage via which sensor, by optic or magnetic measurement, the position of the blades has been established. These

measurement methods are used in connection with the changing of blade settings.

In a prior-art application based on magnetic measurement, each blade carriage is provided with a fixed permanent magnet and the distance of the permanent magnet to the slitting blade is constant, and the position of the permanent magnet connected to the blade carriage is measured by means of a magnetic measuring device, whereby the position of the blade is established. In connection with the changing of blade settings, information is also required, in addition to the position data of the sharpening blades, on the position of the new, replacing blades and after the detachment and grinding of the blades, since after these measures the distance of the slitting blade edge to the magnet of the blade carriage changes, whereby no exact information on the blade position is available based on the results of the above-described measurement methods. Also, the slitting edge of the blade wears, which leads to inaccuracy when using the above measurement methods. In the above-described situations when using prior-art applications, so-called tuning runs have been required in order to specify the position of the slitting edge of the blade.

An object of the invention is to provide a method and a device by means of which the calibration event is simplified, particularly in connection with detaching/replacing the blade and the blade motor (maintenance measures).

For achieving the above object, the method according to the present invention is characterised by that, in the method, there is at least one stationary fixed point of the frame in relation to which the edge of at least one blade is positioned, and that the position of the positioned blade edge is specified in relation to the position of the blade carriage, and that each fixed point is in the lateral direction of the frame such that each blade being positioned extends to at least one fixed point.

Furthermore for achieving the above object, the device applying the method according to the present invention is characterised by that the calibration means includes at least one stationary fixed point arranged in the frame in relation to which the edge of at least one, blade is positionable, and that the position of the positioned blade edge is specifiable in relation to the position of the blade carriage, and that each fixed point is arranged in the lateral direction of the frame such that each blade extends to at least one fixed point.

With such a method and device, a quick and reliable calibration is obtained for calibrating the blade position. As the position of the blade edge is positively known when it has been led to the fixed point, additional check runs are avoided and the calibration is fast and simple.

Next, the invention will be described with reference to the enclosed drawing in which:

Fig. 1 schematically shows a front view of a device for calibrating the position of a bottom blade of a slitter-winder,

Fig. 2 partially schematically shows a top view of the device shown in Fig. 1, and

Fig. 3 shows a top view of another embodiment of the device.

Figure 1 hence schematically shows a front view of a slitter-winder which is designated with reference number 1. The slitter-winder includes a frame Ia, in which is arranged a space or slot Ib through which a material web 2, such as a paper web, is led.

Into connection with the space or slot Ib are arranged pairs of blades 3, 4 used in slitter-winders, of which Fig. 1 shows one pair as an example. The bottom blade 3 is joined to a below blade carriage 5

which is arranged movable in a bottom guide 7 cross-directional in relation to the travel direction of the web 2. The below blade carriage 5 is provided with a sensor by which the position of the blade carriage can be specified. Such a sensor is in this embodiment a position magnet 9a connected to the blade carriage into connection with which is arranged a magnetostrictive position sensor 9. The sensor can also be some other sensor suitable for measuring a distance, such as an inductive or pulse sensor. Also laser measurement can be applied.

The top blade 4 is joined to an above blade carriage 6 which is also arranged movable in a top guide 8 cross-directional in relation to the travel direction of the web 2. The above blade carriage 6 is provided with a position magnet 10a into connection with which is arranged a magnetostrictive position sensor 10. The principles of such an arrangement are known from FI patent specification 115615.

According to the invention, there are stationary (in relation to the frame) fixed points 11 for calibrating the position of the bottom blade. Advantageously, there are fixed points 11 arranged in the frame 1 in the lateral direction of the frame with even and/or required distances in the area of at least the whole width of the web 2, still such that each bottom blade 3 extends to at least one fixed point 11 for performing the calibration. The fixed point 11 can be a groove, recess, flange, protrusion or equivalent machined in the frame Ia, the position of which is exactly specified and/or is exactly specifiable also afterwards after machining, e.g. in connection with the calibration of the bottom blade 3. The specification can also be performed e.g. with a tacheometer.

Figure 2 schematically shows a top view of the arrangement shown in Fig. 1 for the part of one bottom blade 3. In the fixed point 11 is arranged a measurement surface 11a in relation to which an edge 3a of the bottom blade 3 can be positioned. For this measurement surface

11a, into connection with the fixed point 11 can be connected a separate calibration tool 12. In the calibration tool 12 is composed a contact surface 12a. The calibration tool 12 being connected to the fixed point 11, the contact surface 12a is positioned/locked in relation to the fixed point 11 accurately at a standard distance from the measurement surface 11a of the fixed point 11. Thus, the edge 3a of the bottom blade 3 can be led against the contact surface 12a, whereby the edge 3a is also accurately positioned in relation to the measurement surface 11a.

When the position of the bottom blade is this way specified and the position of the below blade carriage 5 (position of position magnet 9a of position sensor 9) is specified in a way described above, a distance L of the edge 3a to the position magnet 9a (blade carriage 5) can be specified. In other words, the calibration of the position of the blade 3 is performed. The specification can be performed e.g. programmatically in a control unit (not shown in the figures) or equivalent of the slitter- winder 1 or the fibrous-web machine connected to it, in which the calibration data can also be set. It is also possible to calibrate the sensor 9 internally.

Figure 3 shows another advantageous embodiment of the invention. There, the calibration tool 12 shown in Fig. 2 is substituted by a sensor the position of which in the frame is known or is measurable/ calibratable. With the sensor, the position of the edge 3a of the blade 3 is measured and the distance between the edge 3a and the observed position (blade carriage) is specified, based on which the blade 3 is positioned. The sensor lib observes the position of the edge 3a of the blade 3 when the blade 3 is run past the sensor lib. Because the position of the blade carriage is continuously known, a position comparison between the edge 3a and the carriage 5 can be performed. The edge can also be positioned at the point of the sensor manually, which is a so-called static way of positioning.

According to an advantageous embodiment, the distance between the fixed point 11 and the edge 3a of the blade 3 is measured with an external separate measuring device. After this, the distance between the edge 3a and the observed position (blade carriage) is specified, based on which the blade 3 is positioned.

A variation of the embodiment according to Fig. 3 is that the sensor lib is a distance sensor or equivalent which measures the position of the blade 3 (advantageously the edge) at the moment of calibration. In other words, for specifying the position of the blade, the blade 3 can be at a distance from the fixed point 11 (sensor lib) and it is not necessary to run the blade 3 past it.

Changes in temperature affect the end result of calibration. Hence, it is also advantageous to observe this fact in connection with calibration by specifying the temperature and its change, based on which a temperature compensation is performed based on modelling and/or measurement. Fig. 1 shows temperature sensors 13a and 13b with which temperature is measured, advantageously at certain intervals. Alternatively, the measurement can be performed with one or more sensors (at one or more points). Based on the measuring results, a correction coefficient can be specified based on which the compensation is implemented.

According to an embodiment, the sensors lib are arranged at two fixed points such that a change between these two fixed points 11 is measured. The measurement can be performed e.g. with the sensors lib the operating principle of which corresponds the one of the magnetostrictive sensor 9, 9a of the blade carriages 5. Then, in the fixed points 11 are connected position magnets the position of which is identified with the sensor. It is also possible to use other sensors suitable for measuring distance. In addition, into connection with the sensors lib are arranged temperature sensors (not shown in the

figures) corresponding the ones shown in Fig. 1, which sensors measure the temperature of the fixed points. Based on the measured values, a correction coefficient can be specified.

The device advantageously includes a sensor or sensors with which possible measuring errors can be calibrated. These sensors intended for checking are advantageously more accurate than the sensor/sensors lib.

The present invention does not solely limit to the described embodiment, but it can be varied in many ways within the scope defined by the enclosed claims.