US20080121362A1 - Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and a dryer fabric for performing the method - Google Patents

Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and a dryer fabric for performing the method Download PDF

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Publication number
US20080121362A1
US20080121362A1 US11/938,929 US93892907A US2008121362A1 US 20080121362 A1 US20080121362 A1 US 20080121362A1 US 93892907 A US93892907 A US 93892907A US 2008121362 A1 US2008121362 A1 US 2008121362A1
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United States
Prior art keywords
dryer fabric
color pattern
fibrous web
characteristic color
web
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Abandoned
Application number
US11/938,929
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English (en)
Inventor
Armin Bauer
Robert Kling
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Voith Patent GmbH
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Voith Patent GmbH
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Publication date
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Assigned to VOITH PATENT GMBH reassignment VOITH PATENT GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAUER, ARMIN, DR., KLING, ROBERT
Publication of US20080121362A1 publication Critical patent/US20080121362A1/en
Abandoned legal-status Critical Current

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    • 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

Definitions

  • This invention relates to a method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web, whereby the fibrous web is passed through the drying section by way of at least one dryer fabric, whereby the tear is detected by at least one web tear detection device and whereby a cut-off apparatus for the fibrous web is activated by the web tear detection device.
  • the invention relates to a dryer fabric for a drying section of a machine for producing a fibrous web, in particular for performing the inventive method.
  • web tears can be detected very reliably, for example by light barriers.
  • light barriers are unsuitable in situations in which the fibrous web rests on a skin acting as a web carrier, for example on a forming mesh, a press felt or a dryer fabric.
  • optical systems such as laser or fiberoptic sensors, with a detector and a light or radiation source of the web tear detection device mounted on the same side of as the fibrous web.
  • FIG. 1 shows the signal flow, plotted in a color intensity/time diagram (F-t diagram), of an optical web tear detection device upon occurrence of a web tear.
  • F-t diagram color intensity/time diagram
  • a signal is sent to a cut-off apparatus.
  • the trigger threshold value S for the signal to the cut-off apparatus can lie at, for example 50% of the color intensity F.
  • a drawback of the color detection system is that it becomes more and more unreliable as the color difference between the fibrous web and the dryer fabric decreases. This is the case, for example, on machines for producing paperboard or packing paper, where brownish paper or paperboard webs lie on red or amber dryer fabrics. Here it is no longer possible to differentiate clearly between the fibrous web and the dryer fabric. This results in either web tear detection without a tear or in a tear without web tear detection.
  • the former leads to an unnecessary stoppage of production and hence to financial loss for the plant operator, the latter runs the risk of causing damage to the machine.
  • dryer fabrics can become severely soiled the longer they are used, as the result of which the actual color of the dryer fabric is covered by dirt deposits. In such cases also it has been discovered that a color detection system no longer works reliably.
  • Another known method is the “detection of changes to light scatter (pseudo-structure detection)”, whereby light is scattered differently on the structured dryer fabric than on the fibrous web. This difference is used to detect web tears.
  • pseudo-structure detection systems likewise do not work reliably. This is owed presumably to soiling in the dryer fabric or to the transparency of the still partly wet fibrous web.
  • the present invention includes a method that uses a dryer fabric with at least one characteristic color pattern which is reliably detected by the web tear detection device in the event of a fibrous web tear.
  • the object of the invention is completely accomplished in this manner.
  • the reliability of the fibrous web tear detection is notably improved, in particular with regard to the conventional methods.
  • Yet another advantage of the present inventive method is that the at least one color pattern to be detected is far larger than the structures of the dryer fabric and therefore less vulnerable to soiling in the dryer fabric.
  • color is used in the context of this disclosure to mean light with a certain wavelength and/or light from a certain wave length range such as the R channel on an RGB sensor. This covers UV and IR radiation.
  • the characteristic color pattern of the dryer fabric is formed by several color stripes which are differently colored and aligned, preferably transverse, to the running direction of the fabric.
  • the colored stripes of the dryer fabric can have a plurality of different colors. This multicoloredness contributes likewise to a distinct improvement in the reliability of the tear detection.
  • the characteristic color pattern of the dryer fabric is formed by several differently colored threads. During production of the dryer fabric it is possible therefore to influence its later use selectively and at a relatively low cost.
  • the characteristic color pattern of a woven dryer fabric is produced by differently colored weft threads.
  • white polytetrafluorethylene can be used for the weft threads and red polyester for the warp threads.
  • the basic color of the dryer fabric can be red, for example, and every 30 cm there can be a white colored stripe, with a black colored stripe arranged alongside every fourth white colored stripe.
  • one thread thickness of the weft thread is used as the minimum width for the characteristic color pattern.
  • the characteristic color pattern of a spiral mesh is produced by differently colored spirals. Due to the method used to produce spiral meshes, the meshes include differently colored spirals that can be produced without any great additional effort and hence without extra costs as compared to single-colored meshes. In this case preferably one spiral thickness of the spiral is used as the minimum width for the characteristic color pattern.
  • the maximum width of the characteristic color pattern can result from the maximum permissible web length which does not cause any damage on the machine for producing the fibrous web before the cut-off apparatus is activated by the web tear detection device.
  • a typical value would be, for example, a 10 meter web length, meaning the color pattern should be repeated on the dryer fabric no later than every 10 meters. Colored stripes which are much wider than 10 meters would thus make no sense.
  • the colored stripes of the characteristic color pattern can vary of course in their width.
  • a dryer fabric can be made of 90 cm wide red colored stripes and 10 cm wide white colored stripes.
  • the characteristic color pattern can also be produced by subsequent coloring of the dryer fabric, preferably by way of thermography. This has the advantage of being able to use identical dryer fabrics, produced if necessary in large quantities at low unit costs, for various applications on account of different colorings.
  • the detection of the fibrous web tear takes place, according to the present invention, by using various measurement methods: for example taking a spot measurement with a laser beam, a light beam or the like, a line measurement with a line camera or the like, and/or an area measurement with a CCD camera or the like. All measurement methods are characterized by high reliability and good usability even in difficult environments.
  • one embodiment of the present invention makes use of the difference between a non-periodic, in particular stochastic signal, of the fibrous web and a periodic signal of the characteristic color pattern in order to detect the fibrous web tear.
  • a non-periodic, in particular stochastic signal of the fibrous web
  • a periodic signal of the characteristic color pattern in order to detect the fibrous web tear.
  • the detected fibrous web tear is evaluated, preferably by way of a Fourier or power spectrum of the signal, whereby at least one trigger threshold value is set at a frequency characteristic for the dryer fabric.
  • the characteristic trigger frequency results from the width of the colored stripe and the speed of the fibrous web.
  • the characteristic frequency is advantageous for the characteristic frequency to be adjustable by selecting the widths of the colored stripes.
  • This object of the invention is accomplished with a dryer fabric of the type initially referred to in that said fabric has at least one characteristic color pattern which is reliably detected by a tear detector in the event of a fibrous web tear.
  • FIG. 1 is shows an exemplary signal flow of an optical web tear detection device upon occurrence of a web tear
  • FIG. 2 shows a schematic representation of a subsection of a machine for producing a fibrous web according to an embodiment of the present invention
  • FIG. 3 shows an exemplary signal flow of an inventive solution according to the present invention
  • FIG. 4 shows the detection of a fibrous web tear by a Fourier spectrum
  • FIG. 5 shows details of a plan view of a dryer fabric formed from threads, the fabric having an embodiment of a characteristic color pattern
  • FIG. 6 shows details of a plan view of a dryer fabric formed from spiral threads, the fabric having another embodiment of a characteristic color pattern of the present invention.
  • FIG. 2 is a side view of a detail of a drying section 2 of a machine, generally designated by 1 , for producing a fibrous web 3 .
  • drying section 2 performs in a known manner the function of removing moisture from a produced and/or processed fibrous web 3 , meaning the function of drying it.
  • the drying is done in the example shown in FIG. 2 by way of contact drying, whereby fibrous web 3 , being fed from the left in the drawing, is dried by direct contact with a plurality of drying cylinders 4 on the one hand and an endless dryer fabric 5 circulating around drying cylinders 4 on the other hand.
  • each dryer fabric 5 in their complete path of rotation, whereby each of dryer fabrics 5 circulates respectively around one group of drying cylinders 4 .
  • each dryer fabric 5 undulates in the region of drying cylinders 4 , whereby at the wave peak dryer fabric 5 is deflected by a drying cylinder 4 and at the wave valley by a suction roller of a respective vacuum device 6 .
  • dryer fabric 5 is returned by way of several guide rollers 7 to the first drying cylinder 4 of the group.
  • each group of drying cylinders 4 To perform the inventive method for detecting a tear in fibrous web 3 in drying section 2 of machine 1 for producing fibrous web 3 , provision is made for each group of drying cylinders 4 to have at least one web tear detection device 8 (symbolically represented), which is described later. Furthermore, provision is made for each group of drying cylinders 4 to have at least one cut-off apparatus 9 (only schematically represented) for fibrous web 3 , which is activated by web tear detection device 8 .
  • each group of drying cylinders 4 use is made of a dryer fabric 5 woven from threads and having at least one characteristic color pattern 10 , which is reliably detected by web tear detection device 8 in the event of fibrous web 3 tearing.
  • a spot measurement with a laser beam, a light beam or the like a line measurement with a line camera or the like, and/or an area measurement with a CCD camera or the like.
  • these preferred measurement methods are known to those skilled in the art, they will not be described in more detail at this point.
  • To detect a tear in fibrous web 3 use is made accordingly of the difference between a non-periodic, in particular, stochastic signal of fibrous web 3 and a periodic signal of a characteristic color pattern 10 .
  • the change of color of characteristic color pattern 10 or the periodic signal generated by the color change of characteristic color pattern 10 must be detected.
  • the detected tear in fibrous web 3 is evaluated by way of a Fourier or power spectrum of the signal, whereby at least one trigger threshold value S is set at a frequency f characteristic for dryer fabric 5 (see for example FIG. 4 ).
  • the characteristic trigger frequency results from the width of characteristic color pattern 10 and the speed v (arrow) of fibrous web 3 .
  • FIG. 3 there is shown an exemplary signal flow of an inventive solution in a color intensity/time diagram (F-t diagram).
  • a signal is sent to a cut-off apparatus 9 of the respective group of drying cylinders 4 .
  • the trigger threshold value S for the signal to cut-off apparatus 9 can thus lie, for example, at 50% of color intensity F.
  • FIG. 4 there is shown the detection of a tear in a fibrous web by way of a Fourier spectrum, once in the situation existing before the tear (representation on the left) and once in the situation existing after the tear (representation on the right).
  • the respective intensity/frequency diagram (I-f diagram) presents the characteristic frequency f of the respective color pattern.
  • the characteristic frequency f does not overshoot the trigger threshold value S at any time.
  • the characteristic frequency f overshoots the trigger threshold value S at least once, whereby a signal to the cut-off apparatus 9 , shown schematically in FIG. 2 , of the respective group of drying cylinders 4 is generated.
  • FIG. 5 there is shown details of a plan view of a dryer fabric 5 formed from threads 11 , fabric 5 having a first embodiment of a characteristic color pattern 10 .
  • FIG. 6 shows details of a plan view of a dryer fabric 5 formed from spiral threads 12 , the fabric having a second embodiment of a characteristic color pattern 10 .
  • Each dryer fabric 5 has at least one characteristic color pattern 10 which is reliably detected by a tear detector of web tear detection device 8 in the event of a tear in the fibrous web 3 .
  • the characteristic color pattern 10 of each dryer fabric 5 shown in FIG. 5 is made of several colored stripes 13 , which are differently colored, arranged preferably transverse to the fabric's running direction L (arrow) and made of several differently colored threads 14 . Shown, by way of example, is only one colored strip 13 , which is made of seven differently colored threads 14 . In this case it is possible of course for different threads 14 to have the same color.
  • the characteristic color pattern 10 on woven dryer fabric 5 in FIG. 5 includes seven preferably differently colored weft threads 14 .
  • Weft threads 14 are made from white polytetrafluorethylene and the warp threads from red polyester.
  • characteristic color pattern 10 on a woven dryer fabric 5 has a minimum width Bmin in the range of one thread thickness DF of weft thread 14 .
  • characteristic color pattern 10 on dryer fabric 5 constructed as a spiral mesh in FIG. 6 includes differently colored spirals 16 .
  • the characteristic color pattern 10 has a minimum width Bmin in the range of one spiral thickness DS of spiral 16 .
  • characteristic color pattern 10 has a maximum width Bmax resulting from the maximum permissible web length which does not cause any damage on machine 1 for producing fibrous web 3 before cut-off apparatus 9 is activated by web tear detection device 8 .
  • colored stripes 13 can vary in their width.
  • dryer fabric 5 can be made of 90 cm wide red colored stripes and 10 cm wide white colored stripes 13 .
  • the characteristic color pattern 10 can also include a subsequent coloration of dryer fabric 5 , preferably by way of thermography, which is known to those skilled in the art, and it can also exist on dryer fabric 5 in certain regions only.
  • colored stripes 13 can have a certain length, meaning they must not necessarily extend over the entire transverse width of dryer fabric 5 .
  • the present invention also develops a dryer fabric of the type initially referred to such that a more reliably detection of web tears as compared to the prior art is made possible, in particular in single-row drying sections of a machine for producing a fibrous web.

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US11/938,929 2006-11-27 2007-11-13 Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and a dryer fabric for performing the method Abandoned US20080121362A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102006055823.5 2006-11-27
DE102006055823A DE102006055823A1 (de) 2006-11-27 2006-11-27 Verfahren zur Erfassung eines Abrisses einer Faserstoffbahn in einer Trockenpartie einer Maschine zur Herstellung der Faserstoffbahn und Trockensieb zur Durchführung des Verfahrens

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US (1) US20080121362A1 (fr)
EP (1) EP1925725A1 (fr)
DE (1) DE102006055823A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090237664A1 (en) * 2008-03-18 2009-09-24 Armin Bauer Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and apparatus for performing said method
CN109416327A (zh) * 2016-05-06 2019-03-01 博西迈科思公司 用于监控制造过程的机器视觉方法和系统

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3552252A (en) * 1968-12-30 1971-01-05 Black Clawson Co Veneer defect detector and clipper control
US4071899A (en) * 1976-07-09 1978-01-31 Hughes Aircraft Company System and method for the measurement of repetitive patterns
US4837715A (en) * 1987-01-27 1989-06-06 Kimberly-Clark Corporation Method and apparatus for detecting the placement of components on absorbent articles
US5150175A (en) * 1991-03-13 1992-09-22 American Research Corporation Of Virginia Optical imaging system for fabric seam detection
US5590577A (en) * 1992-05-20 1997-01-07 J.M. Voith Gmbh Device for cutting a paper web in a press end of a paper machine
US6526369B1 (en) * 1998-07-14 2003-02-25 Voith Sulzer Papiertechnik Patent Gmbh Apparatus and process for a cross-direction profile of a material web

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9101972U1 (de) * 1991-02-20 1991-05-08 Thomas Josef Heimbach GmbH & Co, 5160 Düren Papiermaschinenbespannung
DE19825368A1 (de) * 1998-06-06 1999-12-09 Heimbach Gmbh Thomas Josef Verfahren zum Einfärben von Teilbereichen einer technischen Textilbahn

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3552252A (en) * 1968-12-30 1971-01-05 Black Clawson Co Veneer defect detector and clipper control
US4071899A (en) * 1976-07-09 1978-01-31 Hughes Aircraft Company System and method for the measurement of repetitive patterns
US4837715A (en) * 1987-01-27 1989-06-06 Kimberly-Clark Corporation Method and apparatus for detecting the placement of components on absorbent articles
US5150175A (en) * 1991-03-13 1992-09-22 American Research Corporation Of Virginia Optical imaging system for fabric seam detection
US5590577A (en) * 1992-05-20 1997-01-07 J.M. Voith Gmbh Device for cutting a paper web in a press end of a paper machine
US6526369B1 (en) * 1998-07-14 2003-02-25 Voith Sulzer Papiertechnik Patent Gmbh Apparatus and process for a cross-direction profile of a material web

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090237664A1 (en) * 2008-03-18 2009-09-24 Armin Bauer Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and apparatus for performing said method
US7986410B2 (en) * 2008-03-18 2011-07-26 Voith Patent Gmbh Method for detecting a fibrous web tear in a drying section of a machine for producing the fibrous web and apparatus for performing said method
CN109416327A (zh) * 2016-05-06 2019-03-01 博西迈科思公司 用于监控制造过程的机器视觉方法和系统
US20190129396A1 (en) * 2016-05-06 2019-05-02 Procemex Oy Machine vision method and system for monitoring manufacturing processes
US10884401B2 (en) * 2016-05-06 2021-01-05 Procemex Oy Machine vision method and system for monitoring manufacturing processes

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DE102006055823A1 (de) 2008-05-29
EP1925725A1 (fr) 2008-05-28

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Owner name: VOITH PATENT GMBH, GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BAUER, ARMIN, DR.;KLING, ROBERT;REEL/FRAME:020340/0156

Effective date: 20071213

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION