FI114041B - Pressure measurement method in manufacture of paper board paper, involves measuring force exerted on nip positioned between shoe roll and counter roll, using piezo and pyroluminescent sensors - Google Patents

Abstract

The force exerted on a nip positioned between shoe roll (1) a counter element (2) are measured at various points by the piezo and pyroluminescent sensors (3). The pressure distribution of the nip is determined by using the detection result obtained from the sensors. An independent claim is included for pressure measurement system.

Description

114041

Measurement method and apparatus for making paper or paperboard

The invention relates to a measuring method and apparatus for the manufacture of paper or board, which measures various forces and stresses on a paper or board web or structures carrying a paper or board web at a sensor whose measurement data is received and used to control and / or control paper or board production.

The measuring method is intended to be used in a plurality of applications on a paper or board machine or in a paper or board finishing apparatus to measure force, stress or thermal change.

One application is measuring the pressure distribution of the nip and utilizing the measurement data in the calender. The measuring method is also intended to be used for controlling wire tension. The measurement method is also intended for use in monitoring the thermal and load changes in the structures of a paper or board machine or of equipment generally carrying a paper or board web. One example of measuring the nip force of a calender nip by sensors placed in the calender roll 20 is U.S. Patent 5,383,371.

It is an object of the present invention to provide a new method by which measurement data [can be transmitted outside the measurable points optically in a paper or board machine or in a paper or board finishing apparatus.

The method presents a new way of using PPL sensors to measure, e.g., nip *>: pressure distribution information and wire tension information. The method is: characterized in that the sensor is a piezo-and pyroluminescent sensor, and · · · at least initially, the measurement data is received optically from the sensor either by imaging the sensor directly with a detector to measure ·· 30 luminance or by a light guide such as optical fiber light intensity.

According to the invention, the piezoluminescent (* ···: cent / pyroluminescent) sensor is applied to the papermaking process.

:. **: 35 Piezo and pyroluminescent transducer means a thin film structure which, under external mechanical or thermal stress, emits radiation proportional to that of the unit. point stress.

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US Patent No. 5,446,334 describes the operation of the sensor in detail. In essence, the sensor consists of two combined well structures, one of which is a so-called. the piezo-pyroelectric film (PPE) and the other is a luminescent (emitting LED) film. The PPE film observes the thermomechanical stress changes it exerts as voltage differences between the different surfaces of the film, which in turn control the LED film so that the local stress differences are reflected in varying degrees of light intensity. The composite well structure is called a piezo-pyroluminescent (piezo-py-10 roluminescent) sensor, or PPL sensor. Thus, the PPL sensor converts the thermomechanical stress distribution into a visible image, where the (local) intensity of the luminescence represents the local amplitude of the corresponding thermomechanical stress. The method requires that the films and any layers that cover them are transparent or that the radiation emitted by the films can be recorded and transmitted, for example with optical fibers.

In measuring the pressure distribution of the calender nip, e.g. for calender control purposes, the optical pressure distribution information emitted by the PPL sensors is recorded using camera technology, or the information 20 is transmitted from the sensors placed in the polymer layer of the roll by optical fibers. For example, it is possible to transmit, by means of optical fibers, information in optical form to a transmitter part rotating with a roll, where it is converted into an electronic form and transmitted by radio technology to a fixed receiver part outside the roll:: 25 connected to a data processing device Such a so-called. the telemetry principle for transmitting measurement data from the roll to the outside of the roll is known e.g. U.S. Patent 5,383,371.

·: ·: Sensors can also be used on other moving parts in paper or ”·: 30 board machines or paper or board finishing equipment.

By placing a thin PPL elastic film sensor directly inside the wire fabric, for example, the wire tension can be measured and its tension / movement controlled / adjusted.

, ·: 35 The measurement method can also be applied to static nip pressure distribution measurements instead of the current nip paper. By placing an elastic,: flexible PPL sensor film inside a transparent (elastic) gauge socket * · · »* * 3 114041 (structure), this sock can be pulled on the polymer roll when the roll is replaced and the nip pressure distribution can be measured with the roll (+ PPL sensor).

5 Typical targets for monitoring the thermal and load changes of the paper web transporting equipment are the transverse support structures of the machine. For example, the temperature curvature of the scraper bar or coating station cutter bar can be detected by a PPL sensor located on the cutter bar. Sensor data can also be used for feedback control 10 by controlling the cooling water circuits of the blade bar (camera + PPL) based on measurement. Similarly, changes in the stress state of large (machine) structural surfaces can be observed, and differences in these stress states can be observed from different measuring points. The method is also suitable for monitoring vibration and structural stress changes. Monitoring and monitoring of shaft, bearing and 15 piping vibrations are clear applications.

The air flows at the nozzle ends of the web fluidized bed dryer can be measured with PPL sensors. The optical information provided by the sensor in contact with the bypassing drying air stream indicates the pressure of the drying air stream 20. The measurement data can be transmitted from the sensors forward by optical fibers.

Because the PPL sensor also registers changes due to thermal stresses, it can also be used as temperature change indicators *: 25 eg in machine structures.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 illustrates the working principle of a PPL sensor and Figure 2 illustrates an embodiment of the invention in connection with a calender.

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Figure 1 schematically illustrates the operating principle of a PPL sensor, known from, e.g., U.S. Patent 5,446,334. The sensor is capable of converting the thermomechanical stress of a given region into that visible: luminescence. The sensor is film-like and has a piezo-pyroelectric • * · 4 114041 membrane portion (PPE) having a continuous film of conductive material, a film of piezo-pyroelectric material attached thereto, and another film of conductive material on one side of said film. , which forms a film inside the sensor. A film or layer of piezo-pyroelectric material is capable of producing a potential difference depending on the thermomechanical stress applied to it between its opposite surfaces. On one side of the film of conductive material inside the sensor is an electroluminescent film or a layer of material LED, on the other side 10 of which, in direct contact with it, is a film of conductive material. The electroluminescent membrane portion is capable of emitting visible light, the intensity of which is dependent on the potential difference produced by the piezo-pyroelectric membrane portion. The layers adhered to the electroluminescent material layer should be transparent to the extent that the light emitted by the material can be detected. For example, the outer conductive film associated with the material layer LED may be of sufficiently transparent material.

Similarly, the different thermomechanical stresses of the various regions 20 in the 2-dimensional plane of the film-like sensor material 3 are similarly displayed at varying luminous intensities by dividing the film inside the sensor into separate conductive regions between electrically insulating regions. The conductive regions of the membrane thus insulated from one another have different potentials at respective points, depending on the thermo-mechanical stress applied, and act: 1 thus on the electroluminescent material in different ways, producing correspondingly varying light intensities. As discussed below, sensors 3 located at different locations may be separate sensor films, each providing a luminous intensity 30 corresponding to their position, or a sensor film extending over a wider area and having different regions of different luminance intensities.

; / Figure 2 shows an embodiment where the method is used in connection with a roll of a paper or board machine or a paper or board finishing machine 35 for measuring the forces exerted on the roll. A particular application is to measure the pressure distribution in the nip between the roll and the counter element. Fig. 2 shows a calender having at least one roll 1 with a soft roll coating 1a and a counter-element 2 forming a nip with the roll, which may also be a roll.

In the case shown in Fig. 2, this counter element is a hard surface metal roll, so-called. die cast roll. The distribution of pressure in the nip N between the roller 1 and the counter element 2 in the transverse direction of the machine, i.e. in the axial direction of the roll, the pressure profile, is shown in the lower part of Figure 2.

The calender roll 1 shown in Figure 2 is a so-called. a lightweight roll having a core 1c of lightweight material (foam, honeycomb structure or lightweight composite material), surrounded by a tubular casing 1b and a soft surface coating layer 1a, for example, a polymer coating. The PPL sensors 3 are disposed, e.g. at regular intervals, in circumferential strips over the width of the roller 1 so that nip pressure can be measured according to the above principle in a given zone. The PPL sensors 15 3 may also be disposed in other ways, such as spirally or pointwise, but provided that, in all embodiments, comprehensive nip pressure information is obtained over the entire roll width by a given spacing in the roll width direction. The sensors 3 are disposed between the core 1c and the pipe 1b around it, as shown in Figure 2. It is also possible to place the sensors 20 between the pipe 1b and the outermost coating layer 1a or within the coating layer 1a. In all placement alternatives, the PPL sensor 3 must be able to detect a force proportional to the nip pressure at a corresponding point in the axial direction of the roll.

In order to measure the luminous intensity of the output quantity provided by the sensors 3, a detector device 4, in this case a camera, •, '', which depicts the surface of the roll 1 over its entire width, is disposed. To measure intensities with an external detector device, the light emitted by sensors 3! * i should get off the roll. In this case, the material of the shell 1b and the polymeric coating 1a must be light-transmitting to such an extent that differences in intensity can be detected by the detector device. If the sensors are located immediately below or within the coating layer 1a, the coating layer or its surface layer, respectively, must be of sufficient light-transmitting material.

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The detector device 4 may be, for example, a camera with optics and light. : sensitive sensor for measuring and distinguishing the intensities emitted by the different sensors 6 114041. For this purpose, the detector device may have a sensor comprising a plurality of pixels, whereby the different pixels of this sensor may convert the intensity of light, for example, into an electrical signal directly proportional thereto for subsequent processing of the measurement data, e.g. The detector device need not necessarily form an image of the subject. Furthermore, it is possible that the detector device is a scanning device which moves in the axial direction of the roll and at a time only describes a particular axial zone and a sensor or sensors 3 thereon. The camera information can be transmitted directly to the light intensity 10 outside the rotating roll 1.

Instead of direct imaging, it is possible, for example, to transmit light along optical fibers from the proximity of the sensors 3 to the detector device, whereby the intensity of the light can be measured from different sensors. The detector device may convert the light intensity into a proportional electrical quantity and be part of a roller-rotating transmitter unit that transmits measurement data wirelessly to a fixed receiver portion outside the roller that communicates with the data processing device for processing the measurement data. Such a detector device 4 'is depicted in Figure 2 by a dashed line, and also by a dotted line depicting a receiver part 5 outside the roll.

With the sensor arrangement of Figure 2, it is also possible to measure the pressure distribution of at least one nip of a multi-nip calender and, based on the information 25, perform a feedback control of at least one variable of the calendering process.

If the sensors 3 are placed in a beam ·: ·· or similar in the transverse direction of the web, the data transmitted by the sensors can be retrieved optically by camera technology, or the data transmitted by the sensors can also be transmitted along the optical fibers and the intensity of light transmitted.

The tension profile of the wire can be determined by arranging the wire as: 35 35 several sensors located at various points across the machine 3. Local tension variations within the wire are transmitted through the wire. · *; a sensor 3 at the corresponding position, which transmits a luminous intensity equal to tension • 11 · 414. Based on the tension profile information provided by the sensors 3, the tension of the wire can be adjusted. The optical measurement data provided by the sensors can be received, for example, directly by shooting.

Claims (8)

1. Measurement process in the manufacture of paper or paperboard, in which various forces and stresses directed to paper or paperboard web or structures of the apparatus carrying paper or paperboard web are fed with a sensor, whose measurement information is received and used for monitoring and / or control of manufacture of paper or cardboard, characterized in that the sensor (3) is a piezo and pyroluminescent sensor, and the measurement information is initially initially optically received from the sensor (3), either by imaging the sensor directly with a detector device used to measure the brightness, or through a light conductor, such as an optical fiber, to the detector device used to measure the brightness. 15 Method according to claim 1, characterized in that the wire tension is measured from the wire with a piezo and pyroluminescent sensor (3) located in the wire. Method according to any of the preceding claims, characterized in that there are several piezo and pyroluminescent sensors (3) in the transverse direction of the paper or paperboard web, and they are used. . to determine the distribution of power or voltage in the transverse direction f · • / by receiving measurement information from different sensors. '> I I V 25 4. A method according to claim 3, characterized in that a sensor (3) placed in a rotating roller is used to measure the pressure distribution in the nip in which the roller (1) forms with a counter element. 5. A method according to claim 4, characterized in that the sensors (3) are used to measure the pressure distribution in the nip formed by ·. calender roll. » Method according to claim 5, characterized in that the sensors (3) are used to measure pressure distribution in at least one nip of one! 35 flemyp calendars. > 1 »t» · 114041 Method according to any of the preceding claims, characterized in that on the basis of measurement information, a back-linked government is carried out. 5 8. A measuring device comprising one or more sensors (3) located in a device carrying a paper or cardboard path and a means for receiving measurement signals transmitted by the sensor or sensors, characterized in that said one or more sensors (3) is a piezo and pyroluminescent transducer, and said means is a detector device which measures the brightness, which detector device is arranged to receive measurement signals coming from the transducer or transducers (3) optically either by imaging the transducer directly, or through a light conductor, such as a optical fiber. 15 »*» '* * * I