EP1270475B1 - Monitoring of a fibrous web - Google Patents

Monitoring of a fibrous web Download PDF

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Publication number
EP1270475B1
EP1270475B1 EP02011402A EP02011402A EP1270475B1 EP 1270475 B1 EP1270475 B1 EP 1270475B1 EP 02011402 A EP02011402 A EP 02011402A EP 02011402 A EP02011402 A EP 02011402A EP 1270475 B1 EP1270475 B1 EP 1270475B1
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EP
European Patent Office
Prior art keywords
fibrous web
temperature
belt
region
measurement
Prior art date
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Expired - Fee Related
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EP02011402A
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German (de)
French (fr)
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EP1270475A2 (en
EP1270475A3 (en
Inventor
Wolfram Dick
Roland Mayer
Holger Prüssing
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Voith Patent GmbH
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Voith Paper Patent GmbH
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Publication of EP1270475A3 publication Critical patent/EP1270475A3/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H26/00—Warning or safety devices, e.g. automatic fault detectors, stop-motions, for web-advancing mechanisms
    • B65H26/02—Warning or safety devices, e.g. automatic fault detectors, stop-motions, for web-advancing mechanisms responsive to presence of irregularities in running webs
    • B65H26/025—Warning or safety devices, e.g. automatic fault detectors, stop-motions, for web-advancing mechanisms responsive to presence of irregularities in running webs responsive to web breakage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H20/00—Advancing webs
    • B65H20/06—Advancing webs by friction band
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00—Other details of machines for making continuous webs of paper
    • D21F7/04—Paper-break control devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
    • B65H2515/40—Temperature; Thermal conductivity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2801/00—Application field
    • B65H2801/84—Paper-making machines

Definitions

  • the invention relates to a method for detecting the presence of a paper, cardboard, tissue or another fibrous web or a strip of fibrous web in machines for producing and / or finishing the fibrous web, wherein the fibrous web is guided by at least one endlessly circulating belt.
  • the monitoring of the fibrous web takes place on the basis of optical sensors or camera analysis systems.
  • the bands are often colored, which should improve the visibility of the fibrous web.
  • the reliability of the optical detection is impaired by the contamination of the belts, the mostly warm, moist and polluted air in the area of the machine as well as the contamination of the sensors or cameras. In addition to the high price of the measuring units whose reliability is unsatisfactory.
  • the object of the invention is therefore to provide a method and a device for detecting the presence of the fibrous web or a strip thereof, which offers improved reliability using simple means.
  • this object is achieved in that the detection of the presence of the fibrous web or a strip thereof is carried out in an area of the machine in which the absence of the fibrous web or a strip thereof or the successful transfer of the fibrous web to a change in temperature of the belt and on the basis of the measurement of the temperature of the side of the fibrous web facing away from the belt during the support from the belt and / or the temperature of the, the fibrous web facing side of the belt after delivery of the fibrous web to a following unit and / or the temperature the, which is remote from the fibrous web side of the belt. This is done on the basis of the knowledge that in the absence or addition of the fibrous web or a strip thereof, the temperature of the belt changes relatively quickly.
  • At least one temperature sensor for measuring the temperature of the side of the fibrous web facing away from the belt during the support from the belt and / or the temperature of the side of the belt facing the fibrous web after delivery of the fibrous web to a following unit and / or the temperature assigned to the side facing away from the fibrous web side of the belt.
  • Temperature sensors are much cheaper and more reliable than optical sensors.
  • the use of the method and of the device is possible in particular where at least the temperature of the side of the fibrous web directed away from the strip deviates from the temperature of the strip. Above all, at least the temperature of the area of the strip touched by the fibrous web should deviate from the temperature of the fibrous web, but at least from the temperature of the side of the fibrous web directed away from the web.
  • This monitoring of the fibrous web on the temperature measurement can be realized within the machine on multiple bands. As a result, an outline of the fibrous web can be detected very early.
  • the use is also advantageous in the acquisition of the fibrous web through the belt in order to determine the spreading of the lead-in strip and thus the complete transfer of the fibrous web during start-up of the machine.
  • the temperature measurement at several points along the run of the tape and / or at several Make transverse to the direction of tape travel also allows monitoring of individual zones of the fibrous web, so that the transfer of the widening strip of the fibrous web during startup of the machine can be detected relatively accurately.
  • the temperature measurement should be made contactless. Temperature sensors in the form of IR sensors or IR thermography cameras are particularly suitable for this purpose. In this case, the temperature sensors may be assigned a cleaning element preferably in the form of an air nozzle and / or a cooling device. Both significantly increase the reliability of the measurement.
  • the temperature sensors should have a measuring surface with a diameter between 20 and 200 mm, preferably between 20 and 100 mm.
  • the distance between two temperature sensors should be between 100 and 1000 mm, preferably between 200 and 600 mm.
  • the sensors can also be arranged at several particularly interesting locations, for example in the edge regions of the fibrous web shortly before and / or after a floating dryer or drying hoods or the like. It may also be advantageous if at least one temperature sensor is designed traversable transversely to the fibrous web. Thus, the temperature can be detected over at least part of the width of the band or the fibrous web via this temperature sensor.
  • two temperature sensors can also be arranged very close to each other, wherein only temperature changes detected by both temperature sensors are evaluated.
  • the temperature measurement for fiber web registration in Area of the press section for dewatering the fibrous web, wherein the band is formed as press felt or transfer belt.
  • the fibrous web is heated prior to temperature measurement by at least one heating element, preferably in the form of a heated press roll, a steam blow box or the like.
  • the application of the method and the device can be carried out with advantage also in the region of a drying section for drying the fibrous web, wherein the tape is designed as a dryer fabric. This results in a high reliability of the method, if the fibrous web before the temperature measurement by at least one heating element, preferably in the form of an IR radiator, a heated drying cylinder, hot air nozzles or the like is heated.
  • the temperature of the strip prior to contact with the fibrous web is lower than that of the fibrous web.
  • the temperature of the strip it is possible for the temperature of the strip to be reduced at least in the area touched by the fibrous web in the absence of the fibrous web or at least a part thereof in the relevant section.
  • the temperature of the strip it is also possible for the temperature of the strip to increase rapidly, at least in the area touched by the fibrous web, in the absence of the fibrous web or at least a portion thereof in direct contact with the heating element. If the fibrous web is cooled, for example by means of blowers, the temperature conditions between the fibrous web and the belt change accordingly.
  • the result of the temperature measurement should be fed to a control unit which evaluates the temperature change. It is advantageous if, for determining a temperature comparison value, the temperature of the strip is also measured outside the area touched by the fibrous web.
  • Part of the fibrous web is the speed and / or the size of the temperature change.
  • an outline of the fibrous web leads to a jump in the temperature of the belt.
  • Corresponding temperature changes but also arise during insertion of the fibrous web.
  • the absence or addition of at least the part running in the area of the temperature measurement Fiber web can be closed.
  • This also applies to a temperature change within a time of max. 3s, preferably max. 1s of at least 2 ° C, preferably at least 5 ° C and in particular of at least 10 ° C.
  • control unit for detecting the location of a tear of the fibrous web can evaluate the rapidity of the temperature change, for example, suggesting a rapid change in the dryer section at a large distance to the location of the tear, since in the absence of the fibrous web, the drying group of the drying group of all drying cylinders thereof is heated. Also, the extent of the temperature change can be taken into account, since usually a large jump in temperature can be concluded even at a large distance to the place of demolition. However, it has to be considered that the speed of the temperature change also depends on the machine speed, the type of strip and the dry content of the fibrous web.
  • the controller upon detecting a tear in the fibrous web, the controller should provide a signal indicative of a routine, preferably the transition to tear-off operation and / or the discharge of the fibrous web and / or the shutdown of the machine or at least a part thereof triggers.
  • the heating power of the drying device can be controlled in the tearing operation. In this case, overheating but also excessive cooling should be avoided in order to optimize the starting process.
  • control unit Upon detection of the completed transfer of the entire fibrous web, the control unit should provide a signal which triggers a routine, in particular the transition to normal operation of the machine or at least a part thereof, for example, the raising of the heating power.
  • the press section is used for dewatering the fibrous web 1, wherein the fibrous web 1 here on both sides, each with a band 2.10 in the form of a water-absorbing press felt by a press nip formed by two 5.9 press nip.
  • the upper press roll 5 is heated here in order to intensify the dewatering.
  • the heat is transferred to the fibrous web 1 via the endlessly circulating upper belt 10.
  • this upper band is led away from the fibrous web 1 and the fibrous web 1 is supported only by the lower band 2.
  • the fibrous web 1 is transferred to a belt 3 of the subsequent drying group of the dryer section.
  • the band 3 is designed as an endlessly circulating, air-permeable dryer fabric, wherein the transfer of the fibrous web 1 is supported by a looped by the drying wire Saugleitwalze 11.
  • the fibrous web 1 donating belt 2 1 temperature sensors 8 are arranged before and after the transfer of the fibrous web. These temperature sensors 8 are mounted on the, touched by the fibrous web 1 side of the belt 2. Before the transfer of the fibrous web 1, the temperature sensor 8 can detect a tear of the fibrous web 1. Because of the warming of the fibrous web 1 from the upstream heating element in the form of the heated press roll 5, the temperature of the fibrous web 1 is higher than that of the area touched by the fibrous web 1 of the belt 2. In normal operation, the temperature sensor 8 detected before the transfer of the fibrous web 1, the relative high temperature of the fibrous web 1. However, if it comes before the press nip to a demolition, this temperature sensor 8 detects the lower temperature of the lower belt 2. This temperature difference can be determined by the coupled to the temperature sensor 8 control unit 7 as a lack of fibrous web 1, d. H. be considered as a demolition.
  • the arranged after the transfer of the fibrous web 1 temperature sensor 8 measures in normal operation, the relatively low temperature of the belt 2.
  • the temperature sensor 8 measures the relatively high temperature of the fibrous web 1. Only when the fibrous web 1 is completely transferred, the temperature sensor 8 detects the low temperature of the belt 2. This means that the temperature reduction can be concluded on the completed transfer of the fibrous web 1. If a plurality of temperature sensors 8 are arranged next to one another transversely to the strip running direction 4, the width change of the transferred strip of the fibrous web 1 can be detected.
  • the fibrous web 1 is guided by belts 3 in the form of drying wires over heated drying cylinders 6 and suctioned guide rollers, wherein the fibrous web 1 comes into direct contact with the drying cylinders 6.
  • the drying cylinders 6 can be arranged in one or two rows. At the end of the drying group, the belt 3 is led away from the last drying cylinder 6. The fibrous web 1 then runs on the drying cylinder 6 until it is taken over by a dry sieve of a following drying group.
  • a temperature sensor 8 in the wrapping region of the drying cylinder 6 can detect a tear of the fibrous web 1.
  • the temperature sensor 8 measures the temperature of the fibrous web 1 through the dryer fabric (if present at all).
  • the substantially higher temperature of the drying cylinder 6 is detected. The abrupt jump in temperature can be evaluated by the control unit 7 as a signal for a demolition.
  • the belt 3 is returned via a plurality of guide rollers 12 to the beginning of the dryer group.
  • the temperature of the belt 3 is substantially lower than that of the fibrous web 1, this also applies to the, of fibrous web 1 touched area of the belt 3.
  • the band 3 comes directly the drying cylinders 6 in contact, which leads to the heating of the band 3 over its entire width.
  • the temperature sensors 8 are designed as IR sensors, which allows a contactless temperature measurement.
  • the control unit 7 coupled to the temperature sensors 8 evaluates the speed and the extent of the temperature differences.
  • the temperature differences also depend on the type of drying device. In the case of heated drying cylinders 6, temperature changes of 2 to 15 ° C. and of hot air or infrared dryers of up to 35 ° C. can be taken as an indication of the absence of the fibrous web 1 in the event of a demolition or the addition of a part thereof during transfer. However, it is important that the temperature jumps occur quickly, ie within a time of 0.3 to 3 seconds. However, the time depends on the installation location and the distance to the demolition or addition of the fibrous web 1 from. The shorter the time, the closer the demolition is.
  • the machine Upon detection of a break by the control unit 7, for example, starting from this, the machine can be stopped and / or the fibrous web 1 can be selectively discharged into the machine cellar at an upstream location.
  • control unit 7 If the control unit 7 detects the successful transfer of the fibrous web 1 here between the press and dryer section, for example, trains can be closed or heating elements can be set to normal operation.
  • two temperature sensors 8 are always arranged very close to one another, with only temperature changes which are reported by both temperature sensors 8 being evaluated.
  • several of these pairs of temperature sensors 8 are arranged transversely to the strip running direction 4. Between these pairs there is a distance between 200 and 600 mm.
  • the measuring surface of the temperature sensors 8 has a diameter of about 40 to 80 mm.
  • Temperature sensors 8 are not only inexpensive, but also insensitive to the contamination of the belt 2,3. Air nozzles and cooling devices also minimize the influence of the ambient air on the temperature sensors 8.

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Description

Die Erfindung betrifft ein Verfahren zur Erkennung des Vorhandenseins einer Papier-, Karton-, Tissue- oder einer anderen Faserstoffbahn oder eines Streifens der Faserstoffbahn in Maschinen zur Herstellung und/oder Veredelung der Faserstoffbahn, wobei die Faserstoffbahn von zumindest einem endlos umlaufenden Band geführt wird.The invention relates to a method for detecting the presence of a paper, cardboard, tissue or another fibrous web or a strip of fibrous web in machines for producing and / or finishing the fibrous web, wherein the fibrous web is guided by at least one endlessly circulating belt.

Solch ein Verfahren ist aus der DE-A-4 126 601 bekannt.Such a method is known from DE-A-4 126 601.

Um die Schäden bei einem Abriss der Faserstoffbahn minimieren zu können, ist es wichtig, diesen möglichst frühzeitig zu erkennen. Dies erlaubt es nicht nur, mögliche Schäden an der Maschine durch einen Stau der Faserstoffbahn, sondern auch den Ausschuss zu verringern. Darüber hinaus ist es für die Steuerung der Maschine auch wichtig, die vollständige Überführung der Faserstoffbahn beim Anlauf der Maschine zu erfassen.In order to be able to minimize the damage caused by the pulp web being torn off, it is important to identify it as early as possible. This not only allows to reduce possible damage to the machine by jamming the fibrous web, but also the rejects. In addition, it is also important for the control of the machine to detect the complete transfer of the fibrous web during startup of the machine.

Im allgemeinen erfolgt die Überwachung der Faserstoffbahn auf der Basis optischer Sensoren oder Kameraanalysesysteme. Hierzu sind die Bänder oft farbig gestaltet, was die Erkennbarkeit der Faserstoffbahn verbessern soll. Die Zuverlässigkeit der optischen Erfassung wird allerdings beeinträchtigt durch die Verschmutzung der Bänder, die meist warme, feuchte und verschmutzte Luft im Bereich der Maschine sowie die Verschmutzung der Sensoren bzw. Kameras. Neben dem hohen Preis der Messeinheiten ist deren Zuverlässigkeit unbefriedigend.In general, the monitoring of the fibrous web takes place on the basis of optical sensors or camera analysis systems. For this purpose, the bands are often colored, which should improve the visibility of the fibrous web. However, the reliability of the optical detection is impaired by the contamination of the belts, the mostly warm, moist and polluted air in the area of the machine as well as the contamination of the sensors or cameras. In addition to the high price of the measuring units whose reliability is unsatisfactory.

Die Aufgabe der Erfindung ist es daher, ein Verfahren und eine Vorrichtung zur Erkennung des Vorhandenseins der Faserstoffbahn oder eines Streifens davon zu schaffen, das bzw. die unter Einsatz einfacher Mittel eine verbesserte Zuverlässigkeit bietet.The object of the invention is therefore to provide a method and a device for detecting the presence of the fibrous web or a strip thereof, which offers improved reliability using simple means.

Erfindungsgemäß wurde die Aufgabe dadurch gelöst, dass die Erkennung des Vorhandenseins der Faserstoffbahn oder eines Streifens davon in einem Bereich der Maschine erfolgt, in dem das Fehlen der Faserstoffbahn oder eines Streifens davon bzw. das erfolgreiche Überführen der Faserstoffbahn zu einer Veränderung der Temperatur des Bandes führt und auf der Basis der Messung der Temperatur der vom Band abgewandten Seite der Faserstoffbahn während der Stützung vom Band und/oder der Temperatur der, der Faserstoffbahn zugewandten Seite des Bandes nach der Abgabe der Faserstoffbahn an eine folgende Einheit und/oder der Temperatur der, von der Faserstoffbahn abgewandten Seite des Bandes erfolgt. Dies geschieht auf der Basis der Erkenntnis, dass sich beim Fehlen oder Hinzufügen der Faserstoffbahn oder eines Streifens davon die Temperatur des Bandes relativ schnell verändert. Dabei wird dem Band wenigstens ein Temperatursensor zur Messung der Temperatur der vom Band abgewandten Seite der Faserstoffbahn während der Stützung vom Band und/oder der Temperatur der, der Faserstoffbahn zugewandten Seite des Bandes nach der Abgabe der Faserstoffbahn an eine folgende Einheit und/oder der Temperatur der, von der Faserstoffbahn abgewandten Seite des Bandes zugeordnet. Temperatursensoren sind wesentlich billiger und zuverlässiger als optische Sensoren.According to the invention, this object is achieved in that the detection of the presence of the fibrous web or a strip thereof is carried out in an area of the machine in which the absence of the fibrous web or a strip thereof or the successful transfer of the fibrous web to a change in temperature of the belt and on the basis of the measurement of the temperature of the side of the fibrous web facing away from the belt during the support from the belt and / or the temperature of the, the fibrous web facing side of the belt after delivery of the fibrous web to a following unit and / or the temperature the, which is remote from the fibrous web side of the belt. This is done on the basis of the knowledge that in the absence or addition of the fibrous web or a strip thereof, the temperature of the belt changes relatively quickly. At least one temperature sensor for measuring the temperature of the side of the fibrous web facing away from the belt during the support from the belt and / or the temperature of the side of the belt facing the fibrous web after delivery of the fibrous web to a following unit and / or the temperature assigned to the side facing away from the fibrous web side of the belt. Temperature sensors are much cheaper and more reliable than optical sensors.

Der Einsatz des Verfahrens sowie der Vorrichtung ist insbesondere dort möglich, wo zumindest die Temperatur der vom Band weggerichteten Seite der Faserstoffbahn von der Temperatur des Bandes abweicht. Vor allem sollte zumindest die Temperatur des von der Faserstoffbahn berührten Bereiches des Bandes von der Temperatur der Faserstoffbahn, zumindest aber von der Temperatur der vom Band weggerichteten Seite der Faserstoffbahn abweichen.The use of the method and of the device is possible in particular where at least the temperature of the side of the fibrous web directed away from the strip deviates from the temperature of the strip. Above all, at least the temperature of the area of the strip touched by the fibrous web should deviate from the temperature of the fibrous web, but at least from the temperature of the side of the fibrous web directed away from the web.

Diese Überwachung der Faserstoffbahn über die Temperaturmessung kann innerhalb der Maschine auch an mehreren Bändern realisiert werden. Hierdurch kann ein Abriss der Faserstoffbahn sehr früh erkannt werden. Von Vorteil ist der Einsatz auch bei der Übernahme der Faserstoffbahn durch das Band, um das Breitfahren des Einführstreifens und somit die vollständige Überführung der Faserstoffbahn beim Anlauf der Maschine feststellen zu können.This monitoring of the fibrous web on the temperature measurement can be realized within the machine on multiple bands. As a result, an outline of the fibrous web can be detected very early. The use is also advantageous in the acquisition of the fibrous web through the belt in order to determine the spreading of the lead-in strip and thus the complete transfer of the fibrous web during start-up of the machine.

Um die Zuverlässigkeit der Messanordnung zu erhöhen, kann die Temperaturmessung an mehreren Stellen entlang des Laufs des Bandes und/oder an mehreren Stellen quer zur Bandlaufrichtung erfolgen. Die Anordnung mehrerer Temperaturmessstellen quer zur Bandlaufrichtung erlaubt außerdem die Überwachung einzelner Zonen der Faserstoffbahn, so dass die Überführung des breiter werdenden Streifens der Faserstoffbahn beim Anlauf der Maschine relativ genau erfasst werden kann.In order to increase the reliability of the measuring arrangement, the temperature measurement at several points along the run of the tape and / or at several Make transverse to the direction of tape travel. The arrangement of several temperature measuring points transverse to the strip running direction also allows monitoring of individual zones of the fibrous web, so that the transfer of the widening strip of the fibrous web during startup of the machine can be detected relatively accurately.

Um das Band bzw. die Faserstoffbahn nicht zu beeinträchtigen, sollte die Temperaturmessung kontaktlos erfolgen. Hierfür eignen sich insbesondere Temperatursensoren in Form von IR-Sensoren oder IR-Thermografiekameras. Dabei kann den Temperatursensoren ein Reinigungselement vorzugsweise in Form einer Luftdüsen und/oder eine Kühleinrichtung zugeordnet werden. Beides erhöht die Zuverlässigkeit der Messung erheblich. Die Temperatursensoren sollten eine Messfläche mit einem Durchmesser zwischen 20 und 200 mm, vorzugsweise zwischen 20 und 100 mm aufweisen.In order not to impair the band or the fibrous web, the temperature measurement should be made contactless. Temperature sensors in the form of IR sensors or IR thermography cameras are particularly suitable for this purpose. In this case, the temperature sensors may be assigned a cleaning element preferably in the form of an air nozzle and / or a cooling device. Both significantly increase the reliability of the measurement. The temperature sensors should have a measuring surface with a diameter between 20 and 200 mm, preferably between 20 and 100 mm.

Falls zur Temperaturüberwachung eines größeren Bereiches insbesondere quer zur Bandlaufrichtung mehrere Temperatursensoren vorhanden sind, so sollte der Abstand zwischen zwei Temperatursensoren zwischen 100 und 1000 mm, vorzugsweise zwischen 200 und 600 mm liegen. Die Sensoren können auch an mehreren besonders interessanten Orten, beispielsweise in den Randbereichen der Faserstoffbahn kurz vor und/oder nach einem Schwebetrockner oder Trockenhauben oder ähnlichem, angeordnet sein. Es kann außerdem von Vorteil sein, wenn zumindest ein Temperatursensor quer zur Faserstoffbahn traversierbar gestaltet ist. Damit kann über diesen Temperatursensor die Temperatur zumindest über einen Teil der Breite des Bandes bzw. der Faserstoffbahn erfaßt werden.If a plurality of temperature sensors are provided for monitoring the temperature of a larger area, in particular transversely to the direction of strip travel, then the distance between two temperature sensors should be between 100 and 1000 mm, preferably between 200 and 600 mm. The sensors can also be arranged at several particularly interesting locations, for example in the edge regions of the fibrous web shortly before and / or after a floating dryer or drying hoods or the like. It may also be advantageous if at least one temperature sensor is designed traversable transversely to the fibrous web. Thus, the temperature can be detected over at least part of the width of the band or the fibrous web via this temperature sensor.

Um die Zuverlässigkeit noch weiter zu verbessern können statt einem auch zwei Temperatursensoren sehr dicht beieinander angeordnet werden, wobei nur Temperaturveränderungen ausgewertet werden, die von beiden Temperatursensoren erfasst werden.In order to improve the reliability even further, instead of one, two temperature sensors can also be arranged very close to each other, wherein only temperature changes detected by both temperature sensors are evaluated.

Vorteilhaft ist der Einsatz der Temperaturmessung zur Faserstoffbahnerfassung im Bereich der Pressenpartie zur Entwässerung der Faserstoffbahn, wobei das Band als Pressfilz oder Transferband ausgebildet ist. Dies gilt insbesondere dort, wo die Faserstoffbahn vor der Temperaturmessung durch wenigstens ein Heizelement, vorzugsweise in Form einer beheizten Presswalze, eines Dampfblaskastens oder ähnlichem erwärmt wird.
Die Anwendung des Verfahrens und der Vorrichtung kann mit Vorteil auch im Bereich einer Trockenpartie zur Trocknung der Faserstoffbahn erfolgen, wobei das Band als Trockensieb ausgeführt ist. Dabei ergibt sich eine hohe Zuverlässigkeit des Verfahrens, wenn die Faserstoffbahn vor der Temperaturmessung durch zumindest ein Heizelement, vorzugsweise in Form eines IR-Strahlers, eines beheizten Trockenzylinders, Heißluftdüsen oder ähnliches aufgeheizt wird.It is advantageous to use the temperature measurement for fiber web registration in Area of the press section for dewatering the fibrous web, wherein the band is formed as press felt or transfer belt. This is especially true where the fibrous web is heated prior to temperature measurement by at least one heating element, preferably in the form of a heated press roll, a steam blow box or the like.
The application of the method and the device can be carried out with advantage also in the region of a drying section for drying the fibrous web, wherein the tape is designed as a dryer fabric. This results in a high reliability of the method, if the fibrous web before the temperature measurement by at least one heating element, preferably in the form of an IR radiator, a heated drying cylinder, hot air nozzles or the like is heated.

In der Pressen- und Trockenpartie ergibt sich im allgemeinen, insbesondere jedoch bei den beschriebenen Anordnungen, dass die Temperatur des Bandes vor dem Kontakt mit der Faserstoffbahn niedriger als die der Faserstoffbahn ist. Dabei ist es möglich, dass sich die Temperatur des Bandes zumindest im, von der Faserstoffbahn berührten Bereich beim Fehlen der Faserstoffbahn oder wenigstens eines Teiles davon im betreffenden Abschnitt verringert. In Abhängigkeit von der Art der Anordnung ist es jedoch auch möglich, dass sich die Temperatur des Bandes zumindest im, von der Faserstoffbahn berührten Bereich beim Fehlen der Faserstoffbahn oder wenigstens eines Teiles davon im betreffenden Abschnitt durch den direkten Kontakt mit dem Heizelement schnell erhöht. Sollte die Faserstoffbahn beispielsweise über Gebläse gekühlt werden, so ändern sich die Temperaturverhältnisse zwischen Faserstoffbahn und Band entsprechend.In the press and dryer section, in general, but in particular in the arrangements described, the temperature of the strip prior to contact with the fibrous web is lower than that of the fibrous web. In this case, it is possible for the temperature of the strip to be reduced at least in the area touched by the fibrous web in the absence of the fibrous web or at least a part thereof in the relevant section. Depending on the nature of the arrangement, however, it is also possible for the temperature of the strip to increase rapidly, at least in the area touched by the fibrous web, in the absence of the fibrous web or at least a portion thereof in direct contact with the heating element. If the fibrous web is cooled, for example by means of blowers, the temperature conditions between the fibrous web and the belt change accordingly.

Das Ergebnis der Temperaturmessung sollte einer Steuereinheit zugeführt werden, die die Temperaturveränderung auswertet. Dabei ist es von Vorteil, wenn zur Ermittlung eines Temperatur-Vergleichswertes auch die Temperatur des Bandes außerhalb des von der Faserstoffbahn berührten Bereiches gemessen wird.The result of the temperature measurement should be fed to a control unit which evaluates the temperature change. It is advantageous if, for determining a temperature comparison value, the temperature of the strip is also measured outside the area touched by the fibrous web.

Zur Erkennung des Fehlens des zumindest im Bereich der Temperaturmessung laufenden Teils der Faserstoffbahn dient die Schnelligkeit und/oder die Größe der Temperaturveränderung. So führt insbesondere ein Abriss der Faserstoffbahn zu einem Sprung der Temperatur des Bandes. Entsprechende Temperaturveränderungen ergeben sich aber auch beim Einführen der Faserstoffbahn.To detect the absence of at least in the field of temperature measurement ongoing Part of the fibrous web is the speed and / or the size of the temperature change. In particular, an outline of the fibrous web leads to a jump in the temperature of the belt. Corresponding temperature changes but also arise during insertion of the fibrous web.

Für die Steuereinheit gilt, dass bei einer Temperaturveränderung von mindestens 2 °C, vorzugsweise zumindest 5 °C innerhalb einer Zeit von höchstens 3s, vorzugsweise höchstens 1s und insbesondere höchstens 0,3s auf das Fehlen oder Hinzufügen zumindest des im Bereich der Temperaturmessung laufenden Teils der Faserstoffbahn geschlossen werden kann. Dies gilt auch bei einer Temperaturveränderung innerhalb einer Zeit von max. 3s, vorzugsweise max. 1s von zumindest 2 °C, vorzugsweise zumindest 5 °C und insbesondere von wenigstens 10 °C.For the control unit it holds true that, given a temperature change of at least 2 ° C., preferably at least 5 ° C., within a time of at most 3 s, preferably at most 1 s and in particular at most 0.3 s, the absence or addition of at least the part running in the area of the temperature measurement Fiber web can be closed. This also applies to a temperature change within a time of max. 3s, preferably max. 1s of at least 2 ° C, preferably at least 5 ° C and in particular of at least 10 ° C.

Außerdem kann die Steuereinheit zur Erkennung des Ortes eines Abrisses der Faserstoffbahn die Schnelligkeit der Temperaturveränderung auswerten, wobei beispielsweise eine schnelle Änderung in der Trockenpartie auf einen großen Abstand zum Ort des Abrisses schließen lässt, da beim Fehlen der Faserstoffbahn das Trokkensieb der Trockengruppe von allen Trockenzylindern derselben aufgeheizt wird. Auch der Umfang der Temperaturveränderung kann hierbei berücksichtigt werden, da meist ein großer Temperatursprung auch auf einen großen Abstand zum Ort des Abrisses schließen lässt. Zu berücksichtigen ist jedoch, dass die Schnelligkeit der Temperaturveränderung auch von der Maschinengeschwindigkeit, der Art des Bandes und dem Trockengehalt der Faserstoffbahn abhängt.In addition, the control unit for detecting the location of a tear of the fibrous web can evaluate the rapidity of the temperature change, for example, suggesting a rapid change in the dryer section at a large distance to the location of the tear, since in the absence of the fibrous web, the drying group of the drying group of all drying cylinders thereof is heated. Also, the extent of the temperature change can be taken into account, since usually a large jump in temperature can be concluded even at a large distance to the place of demolition. However, it has to be considered that the speed of the temperature change also depends on the machine speed, the type of strip and the dry content of the fibrous web.

Falls die Messung der Temperatur des Bandes nach der Abgabe der Faserstoffbahn erfolgt, so sollte dies möglichst schnell danach geschehen, um Fremdeinflüsse auf die Temperatur sowie die Reaktionszeit zu minimieren. Dieser Meßort bietet insbesondere Vorteile hinsichtlich der räumlichen Gestaltungsfreiheit.If the measurement of the temperature of the strip takes place after the delivery of the fibrous web, this should be done as soon as possible in order to minimize foreign influences on the temperature and the reaction time. This measuring location offers particular advantages in terms of spatial freedom of design.

In jedem Fall sollte die Steuereinheit bei Erkennen eines Abrisses der Faserstoffbahn ein Signal liefern, welches eine Routine, vorzugsweise den Übergang in den Abrißbetrieb und/oder die Abführung der Faserstoffbahn und/oder das Abstellen der Maschine oder zumindest eines Teiles davon auslöst.In any event, upon detecting a tear in the fibrous web, the controller should provide a signal indicative of a routine, preferably the transition to tear-off operation and / or the discharge of the fibrous web and / or the shutdown of the machine or at least a part thereof triggers.

Anhand der Bandtemperatur kann im Abrißbetrieb die Heizleistung der Trocknungseinrichtung gesteuert werden. Dabei soll eine Überhitzung aber auch eine zu starke Abkühlung vermieden werden, um so den Anfahrvorgang zu optimieren.On the basis of the belt temperature, the heating power of the drying device can be controlled in the tearing operation. In this case, overheating but also excessive cooling should be avoided in order to optimize the starting process.

Beim Erkennen der erfolgten Überführung der gesamten Faserstoffbahn sollte die Steuereinheit ein Signal liefern, welches eine Routine, insbesondere den Übergang in den Normalbetrieb der Maschine oder zumindest eines Teiles davon beispielsweise das Anheben der Heizleistung auslöst.Upon detection of the completed transfer of the entire fibrous web, the control unit should provide a signal which triggers a routine, in particular the transition to normal operation of the machine or at least a part thereof, for example, the raising of the heating power.

Nachfolgend soll die Erfindung an einem Ausführungsbeispiel näher erläutert werden. In der beigefügten Zeichnung zeigt die Figur den schematisch dargestellten Übergang zwischen Pressen- und Trockenpartie einer Papiermaschine mit möglichen Anordnungen von Temperatursensoren 8.The invention will be explained in more detail with reference to an exemplary embodiment. In the accompanying drawing, the figure shows the schematically illustrated transition between the press and dryer section of a paper machine with possible arrangements of temperature sensors 8.

Die Pressenpartie dient der Entwässerung der Faserstoffbahn 1, wobei die Faserstoffbahn 1 hier beidseitig mit je einem Band 2,10 in Form eines wasseraufnehmenden Pressfilzes durch einen von zwei Presswalzen 5,9 gebildeten Pressspalt läuft.The press section is used for dewatering the fibrous web 1, wherein the fibrous web 1 here on both sides, each with a band 2.10 in the form of a water-absorbing press felt by a press nip formed by two 5.9 press nip.

Beispielhaft ist hier zur Intensivierung der Entwässerung die obere Presswalze 5 beheizt. Die Wärme wird über das endlos umlaufende obere Band 10 an die Faserstoffbahn 1 übertragen.By way of example, the upper press roll 5 is heated here in order to intensify the dewatering. The heat is transferred to the fibrous web 1 via the endlessly circulating upper belt 10.

Nach dem Pressspalt wird dieses obere Band von der Faserstoffbahn 1 weggeführt und die Faserstoffbahn 1 nur vom unteren Band 2 gestützt. Vom Band 2 wird die Faserstoffbahn 1 an ein Band 3 der nachfolgenden Trockengruppe der Trockenpartie übergeben. Das Band 3 ist als endlos umlaufendes, luftdurchlässiges Trockensieb ausgeführt, wobei die Übergabe der Faserstoffbahn 1 von einer vom Trockensieb umschlungenen Saugleitwalze 11 unterstützt wird.After the press nip, this upper band is led away from the fibrous web 1 and the fibrous web 1 is supported only by the lower band 2. From the belt 2, the fibrous web 1 is transferred to a belt 3 of the subsequent drying group of the dryer section. The band 3 is designed as an endlessly circulating, air-permeable dryer fabric, wherein the transfer of the fibrous web 1 is supported by a looped by the drying wire Saugleitwalze 11.

Im Bereich des, die Faserstoffbahn 1 abgebenden Bandes 2 sind vor und nach der Übergabe der Faserstoffbahn 1 Temperatursensoren 8 angeordnet. Diese Temperatursensoren 8 sind auf der, von der Faserstoffbahn 1 berührten Seite des Bandes 2 angebracht. Vor der Übergabe der Faserstoffbahn 1 kann der Temperatursensor 8 einen Abriss der Faserstoffbahn 1 erkennen. Wegen der Aufwärmung der Faserstoffbahn 1 vom vorgelagerten Heizelement in Form der beheizten Presswalze 5 ist die Temperatur der Faserstoffbahn 1 höher als die, des von der Faserstoffbahn 1 berührten Bereiches des Bandes 2. Im Normalbetrieb erfasst der Temperatursensor 8 vor der Übergabe der Faserstoffbahn 1 die relativ hohe Temperatur der Faserstoffbahn 1. Kommt es jedoch vor dem Pressspalt zu einem Abriss, so erfasst dieser Temperatursensor 8 die niedrigere Temperatur des unteren Bandes 2. Dieser Temperaturunterschied kann von der mit dem Temperatursensor 8 gekoppelten Steuereinheit 7 als Fehlen der Faserstoffbahn 1, d. h. als Abriss gewertet werden.In the area of, the fibrous web 1 donating belt 2 1 temperature sensors 8 are arranged before and after the transfer of the fibrous web. These temperature sensors 8 are mounted on the, touched by the fibrous web 1 side of the belt 2. Before the transfer of the fibrous web 1, the temperature sensor 8 can detect a tear of the fibrous web 1. Because of the warming of the fibrous web 1 from the upstream heating element in the form of the heated press roll 5, the temperature of the fibrous web 1 is higher than that of the area touched by the fibrous web 1 of the belt 2. In normal operation, the temperature sensor 8 detected before the transfer of the fibrous web 1, the relative high temperature of the fibrous web 1. However, if it comes before the press nip to a demolition, this temperature sensor 8 detects the lower temperature of the lower belt 2. This temperature difference can be determined by the coupled to the temperature sensor 8 control unit 7 as a lack of fibrous web 1, d. H. be considered as a demolition.

Der nach der Übergabe der Faserstoffbahn 1 angeordnete Temperatursensor 8 misst im Normalbetrieb die relativ niedrige Temperatur des Bandes 2. Beim Anfahren der Maschine, das heißt hier dem Überführen der Faserstoffbahn 1 von der Pressen- zur Trockenpartie läuft jedoch anfangs die gesamte und später ein immer schmaler werdender Streifen der Faserstoffbahn 1 am unteren Band 2 in den Maschinenkeller. Dies bedeutet, dass der Temperatursensor 8 die relativ hohe Temperatur der Faserstoffbahn 1 misst. Erst wenn die Faserstoffbahn 1 vollständig überführt ist, erfasst der Temperatursensor 8 die niedrige Temperatur des Bandes 2. Dies bedeutet, dass die Temperaturverringerung auf die erfolgte Überführung der Faserstoffbahn 1 schließen lässt. Sollten quer zur Bandlaufrichtung 4 mehrere Temperatursensor 8 nebeneinander angeordnet sein, so kann die Breitenveränderung des überführten Streifens der Faserstoffbahn 1 erfasst werden.The arranged after the transfer of the fibrous web 1 temperature sensor 8 measures in normal operation, the relatively low temperature of the belt 2. When starting the machine, that is here the transfer of the fibrous web 1 from the press to the dryer section but initially runs the whole and later narrower and narrower expectant strip of fibrous web 1 on the lower belt 2 in the machine cellar. This means that the temperature sensor 8 measures the relatively high temperature of the fibrous web 1. Only when the fibrous web 1 is completely transferred, the temperature sensor 8 detects the low temperature of the belt 2. This means that the temperature reduction can be concluded on the completed transfer of the fibrous web 1. If a plurality of temperature sensors 8 are arranged next to one another transversely to the strip running direction 4, the width change of the transferred strip of the fibrous web 1 can be detected.

In der folgenden Trockenpartie wird die Faserstoffbahn 1 von Bändern 3 in Form von Trockensieben über beheizte Trockenzylinder 6 und besaugte Leitwalzen geführt, wobei die Faserstoffbahn 1 in direkten Kontakt mit den Trockenzylindern 6 kommt.In the following drying section, the fibrous web 1 is guided by belts 3 in the form of drying wires over heated drying cylinders 6 and suctioned guide rollers, wherein the fibrous web 1 comes into direct contact with the drying cylinders 6.

Die Trockenzylinder 6 können in einer oder zwei Reihen angeordnet sein. Am Ende der Trockengruppe wird das Band 3 vom letzten Trockenzylinder 6 weggeführt. Die Faserstoffbahn 1 läuft dann am Trockenzylinder 6 bis zur Übernahme durch ein Trokkensieb einer folgenden Trockengruppe.The drying cylinders 6 can be arranged in one or two rows. At the end of the drying group, the belt 3 is led away from the last drying cylinder 6. The fibrous web 1 then runs on the drying cylinder 6 until it is taken over by a dry sieve of a following drying group.

Für den Fall, dass das Trockensieb sehr grobmaschig ist, oder die Faserstoffbahn 1 ungestützt auf den Trockenzylindern 6 läuft, wie dies am Ende der Trockengruppe erfolgt, kann ein Temperatursensor 8 im Umschlingungsbereich des Trockenzylinders 6 einen Abriss der Faserstoffbahn 1 erkennen. Im Normalbetrieb misst der Temperatursensor 8 durch das Trockensieb (falls überhaupt vorhanden) die Temperatur der Faserstoffbahn 1. Bei einem Abriss wird jedoch die wesentlich höhere Temperatur des Trockenzylinders 6 erfasst. Der abrupte Temperatursprung kann von der Steuereinheit 7 als Signal für einen Abriss gewertet werden.In the event that the dryer fabric is very coarse-meshed, or the fibrous web 1 runs unsupported on the drying cylinders 6, as is done at the end of the drying group, a temperature sensor 8 in the wrapping region of the drying cylinder 6 can detect a tear of the fibrous web 1. In normal operation, the temperature sensor 8 measures the temperature of the fibrous web 1 through the dryer fabric (if present at all). In the case of a tear, however, the substantially higher temperature of the drying cylinder 6 is detected. The abrupt jump in temperature can be evaluated by the control unit 7 as a signal for a demolition.

Vom letzten Trockenzylinder 6 der Trockengruppe wird das Band 3 über mehrere Leitwalzen 12 zum Beginn der Trockengruppe zurückgeführt.From the last drying cylinder 6 of the dryer group, the belt 3 is returned via a plurality of guide rollers 12 to the beginning of the dryer group.

Nach der Wegführung dieses Bandes 3 von der Faserstoffbahn 1 sind hier zwei mögliche Temperatursensoren 8 dargestellt. Nach der Trennung von der Faserstoffbahn 1 sind Verfälschungen insbesondere durch Konditioniereinrichtungen noch gering, so dass die Messung sehr zuverlässig ist.After the removal of this band 3 of the fibrous web 1 two possible temperature sensors 8 are shown here. After separation from the fibrous web 1 distortions are still low, in particular by conditioning, so that the measurement is very reliable.

Wegen der Heizelemente in Form der Trockenzylinder 6 ist die Temperatur des Bandes 3 wesentlich geringer als die der Faserstoffbahn 1, dies gilt auch für den, von Faserstoffbahn 1 berührten Bereich des Bandes 3. Bei einem Abriss der Faserstoffbahn 1 kommt jedoch das Band 3 direkt mit den Trockenzylindern 6 in Kontakt, was zur Aufheizung des Bandes 3 über seine gesamte Breite führt.Because of the heating elements in the form of the drying cylinder 6, the temperature of the belt 3 is substantially lower than that of the fibrous web 1, this also applies to the, of fibrous web 1 touched area of the belt 3. In a demolition of the fibrous web 1, however, the band 3 comes directly the drying cylinders 6 in contact, which leads to the heating of the band 3 over its entire width.

Die Temperatursensoren 8 sind als IR-Sensoren ausgeführt, was eine kontaktlose Temperaturmessung ermöglicht.The temperature sensors 8 are designed as IR sensors, which allows a contactless temperature measurement.

Die mit den Temperatursensoren 8 gekoppelte Steuereinheit 7 wertet die Schnelligkeit und den Umfang der Temperaturunterschiede aus. Die Temperaturunterschiede hängen dabei auch von der Art der Trocknungseinrichtung ab. Bei beheizten Trokkenzylindem 6 können Temperaturveränderungen von 2 bis 15 °C und bei Heißluft- oder Infrarot-Trockner von bis zu 35 °C als Indiz für das Fehlen der Faserstoffbahn 1 bei einem Abriss oder das Hinzufügen eines Teiles davon beim Überführen gewertet werden. Wichtig ist jedoch, dass die Temperatursprünge schnell, das heißt innerhalb einer Zeit von 0,3 bis 3 Sekunden erfolgen. Die Zeit hängt jedoch von dem Einbauort und dem Abstand zum Abriss oder Hinzufügen der Faserstoffbahn 1 ab. Je kürzer die Zeit, um so näher ist auch der Abriss.The control unit 7 coupled to the temperature sensors 8 evaluates the speed and the extent of the temperature differences. The temperature differences also depend on the type of drying device. In the case of heated drying cylinders 6, temperature changes of 2 to 15 ° C. and of hot air or infrared dryers of up to 35 ° C. can be taken as an indication of the absence of the fibrous web 1 in the event of a demolition or the addition of a part thereof during transfer. However, it is important that the temperature jumps occur quickly, ie within a time of 0.3 to 3 seconds. However, the time depends on the installation location and the distance to the demolition or addition of the fibrous web 1 from. The shorter the time, the closer the demolition is.

Beim Erkennen eines Abrisses durch die Steuereinheit 7 kann beispielsweise davon ausgehend die Maschine gestoppt und/oder die Faserstoffbahn 1 an einem vorgelagerten Ort gezielt in den Maschinenkeller abgeführt werden.Upon detection of a break by the control unit 7, for example, starting from this, the machine can be stopped and / or the fibrous web 1 can be selectively discharged into the machine cellar at an upstream location.

Wenn die Steuereinheit 7 das erfolgreiche Überführen der Faserstoffbahn 1 hier zwischen Pressen- und Trockenpartie erkennt, können beispielsweise Züge geschlossen oder Heizelemente auf Normalbetrieb gestellt werden.If the control unit 7 detects the successful transfer of the fibrous web 1 here between the press and dryer section, for example, trains can be closed or heating elements can be set to normal operation.

Um ein möglichst genaues Ergebnis zu erhalten sind immer zwei Temperatursensoren 8 sehr eng beieinander angeordnet, wobei nur Temperaturveränderungen, die von beiden Temperatursensoren 8 gemeldet werden, zur Auswertung gelangen. Außerdem sind quer zur Bandlaufrichtung 4 mehrere dieser Paare von Temperatursensoren 8 angeordnet. Zwischen diesen Paaren besteht ein Abstand zwischen 200 und 600 mm. Die Messfläche der Temperatursensoren 8 hat einen Durchmesser von ca. 40 bis 80 mm.In order to obtain the most accurate possible result, two temperature sensors 8 are always arranged very close to one another, with only temperature changes which are reported by both temperature sensors 8 being evaluated. In addition, several of these pairs of temperature sensors 8 are arranged transversely to the strip running direction 4. Between these pairs there is a distance between 200 and 600 mm. The measuring surface of the temperature sensors 8 has a diameter of about 40 to 80 mm.

Temperatursensoren 8 sind nicht nur preiswert, sondern auch unempfindlich hinsichtlich der Verschmutzung des Bandes 2,3. Durch Luftdüsen und Kühleinrichtungen lässt sich außerdem der Einfluss der Umgebungsluft auf die Temperatursensoren 8 minimieren.Temperature sensors 8 are not only inexpensive, but also insensitive to the contamination of the belt 2,3. Air nozzles and cooling devices also minimize the influence of the ambient air on the temperature sensors 8.

Claims (31)

  1. Method for detecting the presence of a paper, board, tissue or another fibrous web (1) or strip of the fibrous web (1) in machines for producing and/or finishing the fibrous web (1), the fibrous web (1) being guided by at least one endlessly circulating belt (2, 3), characterized in that the detection of the presence of the fibrous web (1) or strip thereof is carried out in a region of the machine in which the lack or addition of the fibrous web (1) or a strip thereof leads to a change in the temperature of the belt (2, 3) and is carried out on the basis of the measurement of the temperature of the side of the fibrous web (1) facing away from the belt (2, 3) during the support by the belt (2, 3) and/or of the temperature of the side of the belt (2, 3) facing the fibrous web (1) after the fibrous web (1) has been passed on to a following unit and/or of the temperature of the side of the belt (2, 3) facing away from the fibrous web (1).
  2. Method according to Claim 1, characterized in that the temperature measurement is carried out on a plurality of belts (2, 3) within the machine.
  3. Method according to Claim 1 or 2, characterized in that the temperature measurement is carried out at a plurality of points along the run of the belt (2, 3).
  4. Method according to one of the preceding claims, characterized in that the temperature measurement is carried out at a plurality of points transversely with respect to the belt running direction (4).
  5. Method according to one of the preceding claims, characterized in that the temperature measurement is carried out without contact.
  6. Method according to one of the preceding claims, characterized in that the temperature measurement is carried out in the region of the press section for dewatering the fibrous web (1), the belt (2) being formed as a press felt or transfer belt.
  7. Method according to Claim 6, characterized in that, before the temperature measurement, the fibrous web (1) is warmed by at least one heating element, preferably in the form of a heated press roll (5), a steam blower box or the like.
  8. Method according to one of the preceding claims, characterized in that the temperature measurement is carried out in the region of a drying section for drying the fibrous web (1), the belt (3) being formed as a dryer fabric.
  9. Method according to Claim 8, characterized in that, before the temperature measurement, the fibrous web (1) is heated up by at least one heating element, preferably in the form of an infrared radiator, a heated drying cylinder (6), hot-air jets or the like.
  10. Method according to one of Claims 7 to 9, characterized in that the temperature of the belt (2, 3) in normal operation of the machine is lower than the temperature of the fibrous web (1).
  11. Method according to Claim 10, characterized in that, in the region touched by the fibrous web (1), the temperature of the belt (2, 3) decreases when the fibrous web (1) or at least part thereof is missing in the relevant section.
  12. Method according to Claim 10, characterized in that, in the region touched by the fibrous web (1), the temperature of the belt (2, 3) increases when the fibrous web (1) or at least part thereof is missing in the relevant section, as a result of direct contact with the heating element.
  13. Method according to one of the preceding claims, characterized in that the result of the temperature measurement is fed to a control unit (7) which evaluates the temperature measurement.
  14. Method according to Claim 13, characterized in that, in order to determine a comparative temperature value, the temperature of the belt (2, 3) is also measured outside the region touched by the fibrous web (1).
  15. Method according to one of the preceding claims, characterized in that, in order to detect the lack or addition of the part of the fibrous web (1) running at least in the region of the temperature measurement, the rate and/or or the magnitude of the temperature change is used.
  16. Method according to Claim 15, characterized in that, in the event of a temperature change of at least 2°C, preferably at least 5°C, within a time of at most 3 s, preferably at most 1 s and in particular at most 0.3 s, it is concluded that there is a lack or addition of at least the part of the fibrous web (1) running in the region of the temperature measurement.
  17. Method according to Claim 15 or 16, characterized in that, in the event of a temperature change within a time of at most 3 s, preferably at most 1 s, of at least 2°C, preferably at least 5°C and in particular of at least 10°C, it is concluded that there is a lack or addition of at least the part of the fibrous web (1) running in the region of the temperature measurement.
  18. Method according to one of Claims 15 to 17, characterized in that, in order to detect the location of a break in the fibrous web (1), the extent and/or the rate of the temperature change is evaluated.
  19. Method according to one of the preceding claims, characterized in that the measurement of the temperature of the belt (2, 3) is carried out as quickly as possible after the fibrous web (1) has been passed on.
  20. Method according to one of Claims 13 to 19, characterized in that, when a break in the fibrous web (1) is detected, the control unit (7) supplies a signal which triggers a routine, preferably changing to break operation, reducing the heating output and/or carrying the fibrous web (1) away and/or stopping the machine or at least part thereof.
  21. Method according to Claim 20, characterized in that, when a break is detected, the heating output is controlled as a function of the temperature of the belt (2, 3).
  22. Method according to one of Claims 13 to 21, characterized in that, when the transfer of the entire fibrous web (1) is detected, the control unit (7) supplies a signal which triggers a routine, preferably for changing to normal operation of the machine or at least part thereof.
  23. Apparatus for carrying out the method for detecting the presence of a paper, board, tissue or another fibrous web (1) or strip of the fibrous web (1) in machines for producing and/or finishing the fibrous web (1), the fibrous web (1) being guided by at least one endlessly circulating belt (2, 3), according to one of the preceding claims, characterized in that, in a region of the machine in which the lack or addition of the fibrous web (1) or a strip thereof leads to a change in the temperature of the belt, the belt is assigned at least one temperature sensor (8) for measuring the temperature of the side of the fibrous web (1) facing away from the belt (2, 3) during the support by the belt (2, 3) and/or the temperature of the side of the belt (2, 3) facing the fibrous web (1) after the fibrous web (1) has been passed on to a following unit and/or the temperature of the side of the belt (2, 3) facing away from the fibrous web (1).
  24. Apparatus according to Claim 23, characterized in that the temperature sensors (8) are formed as IR sensors or IR thermography cameras.
  25. Apparatus according to Claim 23 or 24, characterized in that the temperature sensor (8) is assigned a cleaning element, preferably in the form of an air jet.
  26. Apparatus according to one of Claims 23 to 25, characterized in that the temperature sensor (8) is assigned a cooling device.
  27. Apparatus according to one of Claims 23 to 26, characterized in that a plurality of temperature sensors (8) are arranged beside one another transversely with respect to the belt running direction (4).
  28. Apparatus according to Claim 27, characterized in that the distance between two temperature sensors (8) is between 100 and 1000 mm, preferably between 200 and 600 mm.
  29. Apparatus according to one of Claims 23 to 28, characterized in that the temperature sensors (8) have a measuring area with a diameter between 20 and 200 mm, preferably between 20 and 100 mm.
  30. Apparatus according to one of Claims 23 to 29, characterized in that in each case two temperature sensors (8) are arranged close beside each other.
  31. Apparatus according to one of Claims 23 to 30, characterized in that at least one temperature sensor (8) is configured such that it can be traversed transversely with respect to the fibrous web (1).
EP02011402A 2001-06-28 2002-05-24 Monitoring of a fibrous web Expired - Fee Related EP1270475B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10131281 2001-06-28
DE10131281A DE10131281A1 (en) 2001-06-28 2001-06-28 Web Inspection

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EP1270475A2 EP1270475A2 (en) 2003-01-02
EP1270475A3 EP1270475A3 (en) 2004-04-28
EP1270475B1 true EP1270475B1 (en) 2006-05-03

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EP02011402A Expired - Fee Related EP1270475B1 (en) 2001-06-28 2002-05-24 Monitoring of a fibrous web

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US (1) US6706149B2 (en)
EP (1) EP1270475B1 (en)
CA (1) CA2392067A1 (en)
DE (2) DE10131281A1 (en)

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DE102004046795A1 (en) 2004-09-27 2006-04-06 Voith Paper Patent Gmbh Device and method for monitoring the transfer of a material web and especially the broadening of the width of a transfer strip on a demolition of the transfer strip or the material web
DE102005054825A1 (en) * 2005-11-15 2007-05-24 Voith Patent Gmbh Method for determining paper strength
US7938935B2 (en) * 2007-10-11 2011-05-10 Honeywell Asca Inc. Infrared measurement of paper machine clothing condition

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CA2392067A1 (en) 2002-12-28
DE50206628D1 (en) 2006-06-08
US20030000671A1 (en) 2003-01-02
DE10131281A1 (en) 2003-01-09
EP1270475A2 (en) 2003-01-02
US6706149B2 (en) 2004-03-16
EP1270475A3 (en) 2004-04-28

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