EP1640497A2 - Device and method for monitoring web breaks during transfer of a material web, in particular during widening of a leader of the web - Google Patents

Abstract

In a machine (10) for producing and/or treating a sheet (12) of material, in which the sheet is fed using a guiding device from a production or supply section along a path adapted to a treatment device (14), where a transfer strip of material is formed and transported through the machine by forming a precursor transfer strip and increasing the width to the full width of the sheet (designated 'broad travel'), a device (18) for seizing a tear in the sheet during transfer of the sheet (especially during increasing the width of the transfer strip) is provided to correspond with a tear in the transfer strip or the sheet. Independent claims are included for: (A) a variant of the machine (10), in which the sheet is fed using a guiding device from a production or supply section along a path adapted to a treatment device (14), having a reduced pressure device (18) including a suction chest for seizing a tear in the sheet and including at least one pressure sensor for evaluating the operating pressure in the suction chest; (B) a method for monitoring the transfer of sheet by 'broad travel' as described above, in which monitoring of a tear is carried out during transfer of the sheet (especially during increasing the width of the transfer strip); and (C) apparatus for carrying out the monitoring process, preferably consisting of a machine (10) as described above.

Description

The invention relates to a machine for producing or / and treating a material web, in particular made of paper or cardboard, in which the material web can be guided by means of at least one material web guiding device of a material web forming section or material web input section along a material web guide path to pass at least one material web treatment device, with a device for Forming a transfer strip of the material web and transfer of the transfer strip through the machine, wherein the material web is thereby along the web path can be transferred, that formed by the means for forming and transfer of the transfer strip a leading transfer strip of the web and passed through the machine and the width of the transfer strip on the full web width is increased (so-called "widening"), and with means for detecting a tear the material web.

The invention further relates to a method for monitoring the transfer of a web of paper or cardboard along a material web guide path of a machine for producing or / and treatment of the web, wherein the transfer of the web takes place in that a leading transfer strip of the web passed through the machine and the Width of the transfer strip is increased to the full web width (so-called "broad driving").

The so-called web threading in a machine for producing or / and treating a material web, especially a material web of paper or cardboard, is usually carried out by means of at least one transfer strip, which is separated from the web and then passed through subsequent guiding and / or treatment facilities. This type of web presentation is standard in both paper or board making machines with at least one headbox each, a wet end (in particular wire section and / or press section), a dryer section, possibly one or more processing sections (such as coating section) and offline. Treatment of an otherwise produced material web provided paper or board processing machines, such as so-called coating machines. For the formation or separation of the transfer strip various devices are known. Thus, so-called stripping devices, water jet cutting devices, laser cutting devices, etc. are used. In connection with papermaking machines, a so-called "rubber jack" is usually used, which cuts a strip into the paper web (or cardboard or tissue web) on a wire of the wire section, which then cuts through the further sections of the machine, in particular at least one press section and at least one dryer section and optionally at least one treatment section is performed. In the case of transfer devices which are downstream of the dryer section, a so-called top cutter is used in place of the rubber collar. Once the transfer strip runs stably through the machine, then with the Gautschknecht on the screen on "full width", ie approximately from a strip position adjacent the guide side to the drive side or vice versa from a strip position adjacent the guide side driven to the drive side, then automatically the full web width passes through the machine. In the field of engineering one speaks in this connection of the so-called "broad driving". This type of web presentation or a similar type of web presentation (for example, the transfer strip could also be formed in a middle region of the web) has also been proven in relation to all conventional web handling devices, both as an on-line web handling device and as an off-line web handling device . like press sections, pre-drying sections, after-dryer sections, coating machines, calendering machines (eg calenders), reels, etc.

Existing web break detectors, however, only monitor the "normal operation" on web break, namely, if the web is already listed. Various types of web tear detection are known, for example based on detection of the web speed (cf., for example, DE 101 57 914 A1), the detection of a temperature change (cf., for example, DE 101 31 281 A1), the optical detection of surface characteristics (cf. For example, DE 201 03 070 U1 and DE 42 16 653 C2) as well as the detection of pressures or pressure changes in connection with a vacuum web guiding device, in particular suction roll (cf., for example, EP 0 660 898 B1 and DE 100 31 163 A1). Traditionally, the demolition monitoring during spreading is not effective or disabled. If it comes to a demolition during spreading, it must be recognized by the operator and then all measures must be initiated manually to avoid damage to the machine and to re-list the material to be able to transfer. This is true despite the fact that modern paper machines generally pursue the goal of increasing production efficiency. Automated web tear detection may have been countered by the idea that the introduction of the transfer strip into the machine and widening are transient, non-stationary operations or conditions that should be better controlled by humans for greater reliability.

It has surprisingly been found that also in connection with the transfer of the transfer strip and especially in connection with the spreading an automatic, machine-based monitoring of the occurrence of a web break can be done with high reliability.

Accordingly, according to a first aspect of the invention, it is proposed for the machine mentioned at the outset that the device for detecting a tear in the material web is provided and designed for transferring the material web, in particular during the enlargement of the width of the transfer strip, to a tear of the transfer strip or the material web to address. With regard to the method mentioned at the outset, it is proposed according to the invention that, during the enlargement of the width of the transfer strip, an inspection of the transfer strip or of the material web be monitored.

On the basis of the invention, failures during web threading, especially during spreading, can be automated and thus quickly recognized, and a restart of the web threading and spreading can be initiated quickly and automatically. The transfer times that occur when the machine is operating can be reduced, resulting in a greater degree of productivity. Automated monitoring and, where appropriate, the initiation of suitable reaction measures is also advantageous insofar as damage to machine components as a result of a web break can be avoided, in particular by initiating a web break in the event of a web break. Furthermore, as already mentioned, above all, it is also thought that the detection of a web break automatically initiates all the necessary reaction measures in order to be able to transfer the web again. Thus, for example, by actuating corresponding actuators, vacuum breaker shutters can be closed, the blanket cutter or, in general, a transferred strip forming device driven to strip position, fan speeds lowered, to name but a few examples. The railway transfer can be faster and more successful. The initiation of appropriate measures (rail cutting and preparing the new railway overpass) by hand by the operator can be omitted.

Was the widening successful, so no demolition occurred during the transfer of the transfer strip and during widening, so it can be useful automatically switched to a "normal operation" in which then the conventional demolition monitoring can be done according to the above-mentioned solutions of the prior art ,

It is primarily contemplated that the means for detecting a tear of the web is adapted to respond based on at least one of the width of the transfer strip directly or indirectly representing detection amount to a demolition of the transfer strip or the web. Based on the method according to the invention can accordingly be provided that is monitored on the basis of at least one of the width of the transfer strip directly or indirectly repesentierenden detection size on a demolition of the transfer strip or the material web.

The further development proposal is based on the consideration that the width of the transfer strip at a given position along the material web guide path is a measure of the progress of spreading. In the case of a successful web performance, the width of the transfer strip at a reference position of the transfer strip width at the location of formation of the transfer strip must correspond to a previous time dependent on the web travel speed. If one sees by appropriate control of the Gautschknechts or generally the means for forming the transfer strip, that during spreading of the transfer strip is continuously wider, so must also apply elsewhere along the material web guide path, as long as the web performance is done properly and in particular no web break occurs.

In principle, all come from the state of the art known web break detection and monitoring techniques in connection with the demolition detection or monitoring according to the invention. For example, the means for detecting a tear may include an optical detection arrangement for detecting a web break or for providing the detection amount. Based on the method according to the invention, it is proposed that the monitoring be based on an optical detection, in particular an optical detection of the width of the transfer strip. Further, the means for detecting a tear may include a temperature detecting arrangement to detect a web break or to provide the detection amount. Based on the method according to the invention, it is proposed that the monitoring takes place on the basis of a detection of temperature values.

In contrast, it is particularly preferred that the device for detecting a tear has a pressure detection arrangement or pressure change detection arrangement in order to detect a web break or to provide pressure values as the detection variable. With regard to the method according to the invention, it is particularly preferred that the monitoring takes place on the basis of a detection of pressure values or pressure change values or a pressure change.

Advantageously, for several sections or sections of the machine, for example a plurality of dryer groups or other treatment devices, at least one separate pressure detection arrangement or pressure change detection arrangement can be provided to detect a web break in each section immediately and thus very quickly reacting or for the web break detection To provide pressure values as a detection quantity.

In the context of these training proposals, it is primarily thought that the pressure-sensing arrangement or pressure-change detection arrangement is designed and arranged to detect at least one momentary operating pressure at least one acting on the material web or the transfer strip vacuum device. It is, for example, thought of a so-called suction roll, which serves for material web guide and possibly web deflection. Alternatively or additionally, the pressure detection arrangement or pressure change detection arrangement can be designed and arranged to detect at least one instantaneous operating pressure of at least one overpressure device acting on the material web or the transfer strip. In this context, for example, a so-called Airturn is used, which serves for non-contact web guidance and possibly web deflection.

Based on the method according to the invention, it is proposed that at least one instantaneous operating pressure of at least one vacuum device or overpressure device acting on the material web or the transfer strip is detected.

Background of this training proposals is that when spreading the vacuum device or overpressure device is increasingly covered by the broader transfer strip or the widening web, which in a vacuum device as a result of a decreasing air flow increases the negative pressure, thus reducing the prevailing operating pressure, and in one Overpressure device as a result of increasing throttling of the air outlet increases the pressure, so let the operating pressure rise. The prevailing in the negative pressure or overpressure operating pressure reflects so far the width of the web or the transfer strip on the device again.

In general, it will be useful if the vacuum device or overpressure device in question is provided anyway, as part of the material web guiding device on the leadership of Material web or the transfer strip at least cooperate.

The vacuum device may comprise at least one suction roll and / or at least one suction box or / and at least one vacuum conveyor belt. The overpressure device may comprise at least one blower roll and / or at least one blow box or / and at least one airlock.

It is proposed to be particularly preferred that at least one pressure sensor of the pressure detection arrangement is arranged to / a suction box or blow box. In the case of a suction roll, the pressure sensor is preferably arranged in a suction box associated with the suction roll. This offers over a known solution in which the pressure sensor is provided in a line connecting the suction box with a vacuum source line, the great advantage that strong, acyclically occurring pressure fluctuations are avoided, the cause is not fully understood. The problem of pressure measurement in a suction line could be that the pressure measurement is influenced by the flow velocity of the air. Such influences are avoided when the pressure in the suction box is measured. More reliable monitoring of material web transfer and, more generally, more reliable demolition monitoring is achieved.

If the suction box comprises a transfer suction zone assigned to the transfer strip and an operating suction zone associated with the transfer line suction zone of the full material web width, which is connected or connectable to a vacuum source via the transfer suction zone, the pressure sensor is preferably arranged in the operating suction zone. Between the Überführsaugzone and the Betriebssaugzone at least one can be provided by a valve flap or the like closable connection opening or connecting line, for purely inserting the narrow threading of the Transfer strip is closed in order to suck this with sufficient negative pressure can. For spreading, this connection opening or connection line is then opened in order to be able to monitor the proper broadening of the transfer strip or the material web via the operating pressure.

The machine may advantageously have an evaluation unit which is designed to compare detected pressure values or dependent thereon successive values with each other and / or at least one predetermined reference value and then, if at least one demolition condition is met, output a tear-off signal. Based on the tear-off signal, the addressed reaction measures can then be initiated and the demolition signaled to the operating personnel. Based on the method according to the invention, it is proposed that detected pressure values or dependent values dependent thereon be compared with one another and / or with at least one predetermined reference value in order to determine the fulfillment or non-fulfillment of at least one demolition condition.

It is primarily thought that the evaluation unit is designed to compare the size of successively recorded pressure values or corresponding consequential values with each other for checking a demolition condition, wherein the demolition condition is met when the values deviate from a predetermined desired course , With regard to the method according to the invention, it is accordingly proposed that, according to a demolition condition, successively recorded pressure values or corresponding corresponding values be compared with each other and that the demolition condition be determined to be satisfied if the values deviate from a predetermined desired course.

According to an expedient design, the demolition condition is satisfied when, in the case of a vacuum device, a pressure value assigned at a later time is greater than or equal to an earlier time assigned pressure value or in the case of a pressure device, a pressure value assigned to a later time is less than or equal to a pressure value associated with an earlier time. Based on the method according to the invention, it is proposed that the demolition condition be determined to be satisfied if, in the case of a vacuum device, a pressure value assigned to a later time is greater than or equal to a pressure value associated with an earlier time, or in the case of an overpressure device assigned to a later time Pressure value is less than or equal to a previously assigned to a pressure value.

This design of the evaluation unit or of the method is then expedient and reliable if the pressure values or subsequent values compared with one another are assigned to points in time which have a certain minimum time interval relative to the path speed and the speed of broadening of the transfer strip or the material web, so that in the event of a successful, proper course, it is always ensured that the operating pressure decreases (in the case of a vacuum device) or increases (in the case of a pressure device), which applies accordingly in the case of a processing of subsequent values derived from the pressure values. If, on the other hand, an evaluation of pressure values or subsequent values which are closer together in terms of time is provided, this could lead to the detection of a break, due to possibly occurring smaller pressure fluctuations, although such has actually not occurred. In order to avoid such error detection, one can also include in the comparison a tolerance range expressed, for example, by a threshold value. In this regard, it is concretely proposed that the demolition condition is satisfied if, in the case of a vacuum device, a pressure value associated with a later point in time adjusts a pressure value associated with an earlier point in time by a predetermined threshold value exceeds or in the case of an overpressure device, a pressure value assigned to a later time falls below a predetermined threshold value by a pressure value associated with an earlier time. Based on the method according to the invention, it is accordingly proposed that the demolition condition be determined to be satisfied if, in the case of a vacuum device, a pressure value associated with a later time exceeds a previously assigned pressure value by a predetermined threshold or, in the case of an overpressure device, a later time associated pressure value falls below a predetermined threshold value below an associated pressure value.

According to a particularly expedient development, the evaluation unit is designed to compare detected pressure values or dependent values of these values with a predefined reference value in order to check a widening finished condition which is satisfied when the pressure value reaches a threshold value corresponding to the reference value. With regard to the method according to the invention, it is proposed that detected pressure values or dependent values dependent thereon be compared with a predetermined reference value in order to determine the fulfillment or non-fulfillment of a widening ready condition which is then determined to be satisfied if the Pressure value reaches a threshold value corresponding to the reference value.

On the basis of the fulfillment of the widening finished condition, the device for detecting a tear of the material web can then be switched to a normal operation monitoring mode, in which monitoring for the occurrence of a web break can then take place in a conventional manner.

It is specially thought that in the case of a machine with several each separately during the increase in the width of the transfer strip on a demolition monitored sections (especially several drying groups and material web treatment facilities) each separately for the respective section is already switched to the normal mode monitoring mode, if for this section, the fulfillment of the wide-phase ready condition is determined. Conventional demolition detection systems are only activated when the material web has been completely driven over the entire machine.

It has already been mentioned that the machine can be expediently designed to automatically initiate at least one reaction measure in order to detect a break in the material web, in order to prevent damage to the machine as a consequence of the break and / or to prepare a new transfer of the material web. As a reaction measure, one or more of the following measures may be provided: initiation of a Bahnabschlag, moving machine components into a waiting or safety state, control of the overpressure or vacuum device for re-transferring the web, driving the means for forming and transfer of the transfer strip for the re-transfer of the material web.

The invention further provides, according to the first aspect, a device for carrying out the method according to the invention, for example for providing a machine according to the invention, for example by equipping or retrofitting a machine as mentioned above.

According to another (second) aspect, the invention further provides a machine for producing and / or treating a web of material, in particular paper or cardboard, in which the web of material, mediated by at least one web guiding device, is provided by a material web forming section or web web input section along a web guide path is feasible to pass at least one material web treatment device, comprising means for detecting a tear of the material web based on a detected operating pressure of a suction device having a suction box.

According to the invention, it is provided that at least one pressure sensor for detecting the operating pressure is arranged in the suction box. It has been found that a pressure sensor arranged at this point can respond particularly reliably to pressure changes as a result of a web break. The same applies to a web tear detection in connection with the spreading of the material web according to the first aspect of the invention. Furthermore, on the basis of the pressure detected here, a diagnosis of components of the vacuum device or of an associated vacuum source (for example a valve arrangement) can be carried out particularly reliably. Erroneous detection of a tear and misdiagnosis concerning such components are thus avoided. If the suction box has a transfer suction zone assigned to the transfer strip and an operating suction zone associated with or connected to the transfer line suction zone at a vacuum source, it is preferred that the pressure sensor is arranged in the operating suction zone.

With regard to the machine or the device according to the first aspect of the invention, the following should be pointed out. The evaluation unit can be constructed on the basis of an electronic computer unit, in particular a microprocessor arrangement, on which an evaluation program runs, which has the comparison of the values and the checking of the different conditions providing software functionalities. Concerning the values to be compared, it should be noted that it is not necessarily necessary to process original pressure readings, but that can also be processed from these derived values or data, the "following values" mentioned above, for checking for the demolition conditions and the widening finished condition. It is also possible to compare electrical signals with one another as the mentioned printing or following values, for example measuring sensor output signals or converter output signals, for example output signals of a PI converter without conversion into pressure values, possibly also to analog, no digital-to-analog conversion Providing way.

In the context of the invention, in addition to the here directly addressed criteria or parameters for the current state during widening or the occurrence of a break, other criteria or parameters may be used, in particular also the criteria and characteristics mentioned in the publications mentioned above. Reference is made in particular to the publications DE 101 31 281 A1, DE 201 03 070 U1, DE 42 16 653 C2 and EP 0 660 898 B1.

According to the invention, it is possible or intended to monitor both the normal operation of the machine and at least the widening during the transfer of the web (web presentation). Further training is also thought to automatically monitor the transfer of the transfer strip or its Einfädelabschnitts in terms of demolition, for example, based on the aforementioned known detection techniques.

Fig. 1

zeigt eine schematische Darstellung eines Teilabschnitts einer Papiermaschine gemäß einem Ausführungsbeispiel der Erfindung;

Fig. 2

zeigt eine Draufsicht einer Unterdruckvorrichtung mit einer erfindungsgemäßen Druckerfassungsanordnung;

Fig. 3

zeigt eine Stirnseitenansicht auf die Unterdruckvorrichtung von Fig. 2 und

Fig. 4

zeigt den zeitlichen Verlauf des Drucks innerhalb der Unterdruckvorrichtung während des Breitfahrens eines Überführstreifens einer Materialbahn.

The invention will be explained in more detail below with reference to embodiments shown in the figures.

Fig. 1

shows a schematic representation of a section of a paper machine according to an embodiment of the invention;

Fig. 2

shows a plan view of a vacuum device with a pressure sensing device according to the invention;

Fig. 3

shows an end view of the vacuum device of Fig. 2 and

Fig. 4

shows the time course of the pressure within the vacuum device during the spreading of a transfer strip of a material web.

In Fig. 1 is a side view schematically shows a section of a dryer section of a generally designated 10 papermaking machine or paper processing machine. In a manner known per se, a drying section within a paper machine fulfills the function of extracting moisture from a manufactured or processed material web, i. h. to dry this. In the example shown in FIG. 1, this is done by contact drying, whereby a material web 12 to be supplied from the left in the drawing is dried by direct contact with a plurality of drying cylinders 14 on the one hand and an endless drying felt 16 circulating the drying cylinders 14 on the other hand. In Fig. 1, two dry felts 16 are shown in their complete circulation path, each of the dryer felts 16 each circulating a group of drying cylinders 14. More specifically, each dryer felt 16 in the region of the drying cylinder 14 is wavy up and down, wherein the dryer felt 16 is deflected at the wave crest of a drying cylinder 14 and is deflected in the trough by a suction roll of a respective vacuum device 18. After leaving the last drying cylinder 14 of the corresponding group, the dryer felt 16 is returned via several guide rollers 20 back to the first drying cylinder 14 of the group.

To provide the demolition monitoring according to the invention is for each Group of drying cylinders 14 at least one vacuum device 18 equipped with a device for detecting a web break, which will be described later in more detail.

For drying the web 12, it is introduced into the system of drying rollers 14 and vacuum devices 18 so as to be guided on the drying cylinders 14 between the dryer felt 16 and the surface of the drying roller 14 while circulating the vacuum devices on the outside of the dryer felt 16.

When starting the machine 10 after feeding a new material web or after a demolition of the web, it is necessary to reintroduce a leading transfer strip of the web into the roller system of the drying line and thereby alternately transfer between a drying roller 14 and a vacuum device 18. In order to redirect against the outside of a vacuum device 18 deflected transfer strip against gravity and feed the following drying roller 14, the vacuum devices 18 are connected at least during the transfer operating state of the machine to a vacuum source, so that the vacuum device 18 forces the transfer strip by suction on the predetermined web path ,

The transfer strip is generally automatically cut out of the web of material directly prior to threading the web using a suitable means, such as a so-called gutter. Such a device may, for. B. a transverse to the direction of the web slidable cutting device, such as a water jet or laser cutting device, a circular blade or the like or a so-called Streifenabschlagvorrichtung include. During cutting or the formation of the transfer strip, the material web moves in the direction of travel. It will be described below by the Using a Gautschknechts assumed in a papermaking machine. The crumb is initially in a strip position and intersects a narrow foremost portion of constant width as a threading portion or ribbon which is fed through the machine by suitable means of guidance. After a certain feed distance of the web, the Gautschknecht moves uniformly in the direction of the opposite edge of the web and thus cuts the transfer strip with preferably uniformly increasing width until it reaches the full width of the web and the cutting of the transfer strip is completed. The web continues to move and threads into the paper machine.

An intended for use in a paper machine according to the present embodiment, serving as a vacuum deflecting vacuum device 18 with means for detecting a web break is explained in more detail below with reference to FIGS. 2 and 3. It comprises a suction roll 22, on which the material web 12 is deflected, and a suction box 24. The suction box 24 is connected via a connecting line 26 to a vacuum source, not shown, in order to generate a negative pressure in the suction box 24 can. The suction box 24 is adjacent to the suction roll 22 and has these facing openings 28. Through these openings 28 and through holes 30 in the shell of the suction roll 22, a vacuum built up in the suction box 24 can continue into the interior of the suction roll 22, so that a negative pressure can also be built up in the suction roll 22.

If a negative pressure is generated and maintained in the suction box 24 and in the suction roll 22, this negative pressure is propagated through the boreholes 30 of the suction roll 22, which are just opposite the suction box 24, and through further openings 32 in the suction box 24 on the outside and through the negative pressure device 18 revolving porous dry felt 16 and sucks a to be deflected at the vacuum device 18 web portion, in particular a transfer strip to be transferred in order to keep this on the material web guide path and feed the following drying cylinder 14.

In Fig. 2, a valve 34 and a partition wall 36 is further indicated. The partition wall 36 divides the interior of the suction box 24 into a Überführsaugzone 38 and a Betriebssaugzone 40, wherein the Überführsaugzone 38 and the Betriebssaugzone 40 are connected to each other by the valve 34 or separable from each other. The width of the transfer suction zone 38 measured in the material web transverse direction corresponds approximately to the width of the leading threading section of the transfer strip of the material web. When transferring the transfer strip of a material web to be newly threaded, the valve 34 is closed so that air is sucked out of the transfer line suction zone 38 of the suction box 23 and out of the suction roller 22 via the connecting line 26. In this way, the areas of the suction box 24, which are not covered by material web during the transfer of the transfer strip, not sucked in order to use the suction power of the vacuum source to build a negative pressure in the Überführsaugzone 38 can.

The front threading section of the transfer strip is followed by another section in which the width of the transfer strip continuously increases until the transfer strip finally reaches the full width of the actual material web and at this point merges integrally into the actual material web or is connected thereto. The operating state of the paper machine, in which the continuously widening transfer strip is transported, is referred to as "spreading" of the material web. During the spreading of the web, the valve 34 is open and in both the Überführsaugzone 38 and in the Betriebssaugzone 40 and in the suction roll 22 builds up a roughly uniform negative pressure. The sucked air counteracts this build-up of negative pressure, which is sucked through those boreholes 30 or those openings 32 which are not yet covered by the transfer strip. The self-adjusting pressure in the suction box 24 thus depends on the number of not covered by the transfer strip openings 30 and 32 at a constant suction power of the vacuum source. This number decreases continuously as the width of the transfer strip increases, so that the airflow entering the suction box 24 from the outside and counteracting the evacuation of the suction box 24 also decreases. As the width of the transfer strip increases, the pressure within the suction box 24 thus drops until it reaches a minimum value after the material web has been fully extended. The decreasing with the width of the transfer strip operating pressure p in the suction box 24 is schematically illustrated in the diagram of FIG.

The material web tear-off detection device of the present invention utilizes the previously described flow of pressure within the suction box 24 during spreading of the web transfer strip to monitor proper widening and, in particular, to detect the occurrence of breakage of the transfer strip. For this purpose, in the suction box 24, more precisely in the operating suction zone 40 of the suction box 24, a pressure sensor 42 is arranged, which detects the pressure in the suction box 24. Preferably, the pressure sensor 42, as shown in Fig. 2, arranged in the suction box 24 close behind the partition wall 36. The arrangement of the pressure sensor 42 in the suction box 24 is advantageous because in the suction box 24, the flow cross section is relatively large and thus pressure fluctuations are relatively low.

The pressure sensor 42 is connected to a PI converter (pressure-current converter, not shown), which is the size of the measured pressure representing a current signal to an electronic control unit (not shown). The electronic control unit can also be supplied with a position signal which indicates the movement position of the rubber bushing transversely to the running direction of the material web. From the speed of the material web as well as the distance from the rubber jack to the monitoring negative pressure device, a current target web width of the transfer strip at the monitoring vacuum device can then be determined in the electronic control unit or in an upstream computing unit in order to be available to the control unit.

The control unit is configured to decide, in a manner to be described later, based on the instantaneous current value communicated to it by the PI converter, as well as possibly also the instantaneous desired web width, whether a tear in the material web, in particular their flyer, present or not. The electronic control unit is further arranged and implemented in the paper machine so that it can initiate certain actions in response to web break in the event of web break detection. In particular, it is contemplated that the electronic control unit is connected to a knock-off device which abuts the material web in a demolition upstream of the break point in order to avoid damage to the machine by winding operations and to prepare the web for a new threading. As further measures may be provided to drive the Gautschknecht for cutting the transfer strip on strip position to transfer various equipment units of the manufacturing or processing lines in a waiting position, zurückzufahren or vacuum vacuum conveyors or close (close vacuum folding doors) or to indicate the occurrence of the web break operating personnel. Other measures to be taken when a web break occurs are obvious to one skilled in the art.

The electronic control unit according to the embodiment of the invention is further adapted to detect the successful completion of the widening and to output a corresponding widening ready signal. In response to this widening ready signal, the paper machine can be automatically switched to a normal operating mode in which, for example, a normal operation monitoring mode for detecting a tear of the web is turned on, in which the tear of the web is detected, for example, in a conventional manner can. Further measures which are to be performed when switching the paper machine from the transfer and wide travel mode to the normal operating mode are familiar to the person skilled in the art.

With reference to Fig. 4, the operation of the electronic control unit of the embodiment for detecting a web break as well as for detecting a complete successful spreading of the web is explained below. The graph shows the course of the measured by the pressure sensor 42 pressure p in the period starting shortly before the start of the spreading t ₁ (just before the opening of the valve 34) to a point shortly after the complete spreading of the web. During the transfer of the threading section of the transfer strip, ie for times t <t ₁ , the valve 34 is closed and the pressure p within the operating suction zone assumes relatively high values in the vicinity of the normal pressure. As soon as the width of the transfer strip begins to increase, the valve 34 is opened, as a result of which the operating suction zone 40 is now also connected to the connecting line 26 and air is sucked out of the operating suction zone 40. Therefore, the measured pressure p decreases shortly after the time t ₁ of the opening of the valve 34 quickly and reaches shortly thereafter at a time t ₂ a pressure p _2, which corresponds to the presence of a transfer strip of minimum width. During the further Transports of the transfer strip grows its width gradually, so that more and more of the openings 30 and 32 are covered by material web and the pressure p consequently decreases steadily. The pressure p reaches its minimum value p ₃ at the time t ₃ , when the width of the transfer strip becomes maximum and reaches the width of the actual material web. After complete widening of the material web, ie for times t> t ₃ , the pressure p remains essentially constant, since the number of holes covered by the material web 30 or 32 then no longer changes.

The pressure curve shown in FIG. 4 corresponds to a desired pressure profile during the proper widening of the material web. The electronic control unit recognizes the occurrence of a web break during widening because at least one pressure value measured at a specific time deviates significantly from the pressure profile shown in FIG. 4. The accuracy and reliability of the demolition detection depends on the knowledge of operating parameters as well as on temporal fluctuations of the operating parameters. These operating parameters include, in particular, the position of the valve 34 (throttle valve angle) and the power of the vacuum source connected to the suction box.

It is expedient for the detection of a web break, in particular, to use the following three variants for a method for the detection of tears.

In a first embodiment variant, the desired print run shown in FIG. 4 is stored in a memory of the electronic control unit and / or can be calculated by the control device on the basis of the current desired web width and on the basis of operating parameters of the paper machine, in particular the suction power of the vacuum source , In principle, the knowledge of a single point of the pressure curve would be sufficient to detect a web break However, the desired pressure curve of the electronic control unit will advantageously be available for a multiplicity of times in order to be able to provide the most continuous possible web break monitoring. The desired pressure values of the desired pressure profile that are available to the electronic control unit are then compared with the actual pressure values measured by the pressure sensor 42, and the demolition of the material web is detected precisely when the actual pressure at a given instant in time reaches the corresponding setpoint pressure. Pressure significantly, ie by a predetermined threshold (tolerance range) exceeds. Namely, in a web break, the openings 30 and 32 of the suction roll 22 and the suction box 24 are exposed in a short time, so that through this air in the suction roll 22 and the suction box 24 can penetrate and causes a sudden increase in pressure. In any case, there is a lack of increasing coverage of other openings 30, 32, so that the pressure at least does not fall further.

The size of the threshold may be set depending on the size of possible pressure fluctuations in the suction box 24 so that a random pressure increase z. B. due to short-term fluctuations in the suction power of the vacuum source or due to a local short-term lifting of the web, does not lead to the detection of a web break.

In the method according to the first embodiment variant, furthermore, the successful complete widening can be detected by the fact that for measured times t> t ₃ the measured pressure is equal to a pressure p ₃ up to a threshold value, ie a widening ready signal can be output if the difference between the measured actual pressure and the target pressure p ₃ falls below the threshold value.

The pressure p ₃ corresponds to a minimum pressure at full weitgefahrener web, which also sets during the normal operating mode. Advantageously, the pressure p _{3 should be} close to a minimum pressure p _min , which corresponds to the best possible evacuation of the suction box 24 and the suction roll 22 by the vacuum source. In most cases, the pressure is p _3, however, be greater than the minimum achievable pressure p _min since the web of material 30 and 32 cover the openings hardly fully dense mostly certain (especially when using a narrower web of material) and in the vacuum device leakages occur.

In a second embodiment, the electronic control device compares the measured pressure values do not directly target pressure values of the nominal pressure gradient, but compares two different times t ₄ and t ₅ received pressure values p ₄ and p ₅ with each other. In the case of a proper widening of the transfer strip, the pressure value p ₅ recorded at the later time t ₅ must then be smaller than the pressure value p ₄ recorded at the time t ₄ in accordance with the curve shown in FIG. ₄ . If this is not the case, then the control device closes on a demolition of the transfer strip. This embodiment variant has the advantage that it manages without specification or calculation of desired pressure values and recognizes a web break using the simple demolition condition that a pressure value recorded at a later point in time is not smaller than a pressure value recorded at an earlier point in time.

Furthermore, a third embodiment variant for detecting a breakaway of the transfer strip during the widening is conceivable, in which the demolition is carried out on the basis of the comparison of two pressure values p ₆ , p ₇ recorded at a short time interval (at t ₆ , t ₇ ). Although in this case, the use of a demolition condition according to the second embodiment is in principle applicable, it could, however, in temporally closely spaced pressure measurements due to random Pressure fluctuations within the suction box 24 come to a false triggering a tear signal. Namely, as shown in Fig. 4, the target pressure values p ₆ and p _{7 are} also relatively close to each other, and their difference may be in the order of magnitude of random pressure fluctuations. According to the third embodiment, therefore, a Bahnabrisssignal is only generated when the measured at time t ₇ pressure p ₇ exceeds the previously measured time t ₆ pressure p ₆ at least by a predetermined threshold s, so if p ₇ (t ₇ )> p ₆ (t ₆ ) + s. Using such a demolition condition a reliable demolition detection is also possible in the evaluation of tightly consecutive pressure measurements.

The aforementioned three variants for detecting a material web break in the region of the profile strip can be combined as desired with one another in order to provide the most optimal possible tamping detection. It is considered to be particularly preferred if the electronic control unit continuously receives pressure values of the pressure sensor 42 (or the current values of the PI converter representing the pressure values) and the electronic control unit continuously sends the currently received pressure values to a deviation from that shown in FIG Target pressure profile monitored. Further, a combination of the first and the third embodiment may be configured such that the threshold value s used for the demolition condition according to the third embodiment is adjusted in response to the measured pressure to provide a variable threshold s (p) corresponding to the changing slope the pressure curve or a variable Fluctuationsamplitude of the pressure in response to the pressure takes into account.

A combination of the above-described three variants can also be used expediently in the assessment of a successfully completed latitude test for generating the latitude-finished signal.

Thus, a widening-ready condition can be used which indicates the successful widening when the tearing conditions according to the embodiment variants 1 and 2 have not been triggered and the pressure p reaches a target pressure value p ₃ (third embodiment variant).

The paper machine described in more detail above is to be understood as a preferred embodiment of the invention. In the context of the invention, not only a continuous pressure drop (vacuum rise) in the suction box can be used as a monitoring variable for a correct spreading of the transfer strip, but it is also possible, with a plurality of transversely arranged to the web optical sensors or temperature sensors or the like, the continuous broadening of Overpass strip to monitor. In principle, the same electronic control device described above in detail can then be used for various measuring methods as long as it is supplied with a signal representing the instantaneous actual width of the transfer strip. In this context, it should again be emphasized that the pressure variables (p ₁ to p ₇ , see Fig. 4) used in the description of the embodiment were merely designated as pressure variables for better illustration. However, in most cases, instead of the direct pressure values, the electronic control unit will process equivalent signal values (current signal values, voltage signal values, etc.) which are related to the pressure p measured by the pressure sensor 42. In the event that a directly proportional relationship is provided for the relationship between these signal values and the actual pressure p, all statements made in this description and in the claims about pressure values (tearing conditions, etc.) can be equivalently applied to the corresponding signal values. In the case of using other relationships between the signal values processed in the electronic control unit and the pressure values, it will be readily apparent to those skilled in the art from the above-described To formulate conditions for demolition or processing for the electronic control unit.

It should also be pointed out once again that the method according to the invention can also be applied to other sections of the paper machine, for example to the press section, the pre-and / or post-dryer section, to a coater, a calender, a reel etc.

Claims (31)

Machine (10) for producing or / and treating a material web (12), in particular made of paper or cardboard, in which the material web (12) can be guided by at least one material web guiding device (18) from a material web production section or material web input section along a material web guide path to at least one Material web treatment device (14) to pass
with a device for forming a transfer strip of the material web (12) and transfer of the transfer strip through the machine (10), wherein the material web (12) is thereby along the Materialbahnführungsweg be transferred, that by means of the means for forming and transfer of the transfer strip a leading transfer strip of Material web (12) formed and guided by the machine (10) and the width of the transfer strip is increased to the full web width (so-called "broad travel"), and
with a device (18) for detecting a tear of the material web (12),
characterized in that the device (18) for detecting a tear of the material web (12) is provided and designed for, during the transfer of the material web (12), in particular during the enlargement of the width of the transfer strip, on a demolition of the transfer strip or the material web (12) to address. A machine (10) according to claim 1, characterized in that the means (18) for detecting a tear of the material web (12) is arranged based on at least one directly or indirectly representing the width of the transfer strip (p) Detection size to respond to a demolition of the transfer strip or the material web (12). A machine according to claim 1 or 2, characterized in that the means for detecting a tear has an optical detection arrangement or / and a temperature detection arrangement to detect a web break or to provide the detection amount. A machine (10) according to any one of claims 1 to 3, characterized in that the means (18) for detecting a tear has a pressure detecting arrangement (34) or pressure change detection arrangement for detecting a web break or pressure values (p) to provide as a detection quantity. Machine (10) according to claim 4, characterized in that the pressure-detecting arrangement (34) or pressure change detection arrangement is designed and arranged for at least one momentary operating pressure (p) of at least one vacuum device acting on the material web (12) or the transfer strip (18) or overpressure device to detect. Machine (10) according to claim 5, characterized in that the vacuum device (18) or overpressure device at least as part of the material web guiding device on the guide of the material web (12) or of the transfer strip cooperates. Machine (10) according to claim 5 or 6, characterized in that the vacuum device (18) comprises at least one suction roll (22) and / or at least one suction box (24) and / or at least one vacuum conveyor belt. Machine according to one of claims 5 to 7, characterized in that the overpressure device comprises at least one blower roll and / or at least one blow box or / and at least one Airturn. Machine (10) according to claim 7 or 8, characterized in that at least one pressure sensor (34) of the pressure detection arrangement in the / a suction box (24) or blow box is arranged. Machine (10) according to claim 9, characterized in that the suction box (24) comprises a Überführsaugzone associated with the transfer strip and an associated with the Überführsaugzone (38) of the full web width associated Betriebssaugzone (40), wherein the Betriebssaugzone (40) via the Überführsaugzone (38) is connected to a vacuum source or connectable and the pressure sensor (34) is arranged in the Betriebssaugzone (40). Machine (10) according to any one of claims 5 to 10, characterized in that an evaluation unit is designed for detected pressure values (p) or dependent on these subsequent values with each other and / or at least one predetermined reference value (p _min , p ₂ . ... p ₇ ) and, if at least one demolition condition is satisfied, output a tear-off signal. Machine (10) according to claim 11, characterized in that the evaluation unit is designed to test a demolition condition, the size of successively recorded pressure values (p) or to compare the corresponding following values with each other, the demolition condition is satisfied when the values deviate from a given desired course. Machine (10) according to claim 12, characterized in that the demolition condition is met when in the case of a vacuum device (18) a later time (t ₅ ) associated pressure value (p ₅ ) greater than or equal to an earlier time (t ₄₎ associated pressure value (p ₄₎ or in the case of a pressure reduction device, an associated later pressure value is less than or equal to an earlier associated pressure value. Machine (10) according to claim 12, characterized in that the demolition condition is met when, in the case of a vacuum device (18) a later time (t ₇ ) associated pressure value (p ₇ ) an earlier time (t ₆ ) associated pressure value (P ₆ ) exceeds by a predetermined threshold value (s) or in the case of an overpressure device, a pressure value associated with a later time falls below a predetermined threshold value associated with an earlier time value. Machine (10) according to any one of claims 5 to 14, characterized in that the evaluation unit is designed to compare detected pressure values (p) or dependent on these subsequent values with a predetermined reference value (p ₃ ) to a spreading ready-condition to be checked, which is satisfied when the pressure value (p) reaches a threshold value corresponding to the reference value (p ₃ ). Machine (10) according to claim 15, characterized in that means for detecting a tear of the material web (12) on the fulfillment of the wide-drive finish condition in a normal operation monitoring mode is switchable. Machine (10) according to one of Claims 1 to 16, characterized in that it is designed to automatically initiate at least one reaction to the detection of a tear in the material web (12) in order to damage the machine (10) as a result of the tear avoid or / and prepare a new transfer of the material web (12). Machine (10) according to claim 17, characterized in that as a reaction measure one or more of the following measures are provided: triggering a Bahnabschlages, moving machine components into a waiting or safety state, controlling the pressure or vacuum device for re-transferring the web (12), control of the means for forming and transferring the transfer strip for the re-transfer of the material web (12). Machine (10) for producing or / and treating a material web (12), in particular made of paper or cardboard, in which the material web (12) can be guided by at least one material web guiding device (18) from a material web production section or material web input section along a material web guide path to at least one Material web treatment device (14) to pass
with a device (18) for detecting a break in the material web on the basis of a detected operating pressure (p) of a vacuum device (18) having a suction box (24),
characterized,
in that at least one pressure sensor (34) for detecting the operating pressure (p) is arranged in the suction box (24). Machine according to Claim 19, characterized in that the suction box (24) has an associated with the transfer strip Transfer operating zone (40) associated with the Überführsaugzone (38) of the full web width, wherein the Betriebssaugzone (40) via the Überführsaugzone (38) connected to a vacuum source or connectable and the pressure sensor (34) in the Betriebssaugzone (40 ) is arranged. A method for monitoring of transferring a material web (12) of paper or board along a Materialbahnführungsweg a machine (10) for producing and / or treating the material web (12), wherein the transfer of the material web (12) thereby takes place that a leading forming transfer strip of Material web (12) guided by the machine (10) and the width of the transfer strip to the full web width is increased (so-called "wide driving"),
characterized in that during the transfer of the material web (12), in particular during the enlargement of the width of the transfer strip, is monitored for a demolition of the transfer strip or the material web (12). A method according to claim 21, characterized in that on the basis of at least one of the width of the transfer strip directly or indirectly repesentierenden detection size (p) is monitored for a demolition of the transfer strip or the material web (12). A method according to claim 21 or 22, characterized in that the monitoring is based on an optical detection, in particular an optical detection of the width of the transfer strip, and / or a detection of temperature values. Method according to one of claims 21 to 23, characterized in that the monitoring based on a detection pressure values (p) or pressure change values or a pressure change takes place. A method according to claim 24, characterized in that at least one momentary operating pressure (p) of at least one on the material web (12) or the transfer strip acting vacuum device or overpressure device is detected. Method according to claim 24 or 25, characterized in that detected pressure values (p) or dependent values dependent thereon are compared with one another and / or with at least one predetermined reference value (p _min , p ₂ ... p ₇ ) in order to fulfill or non-fulfillment of at least one demolition condition. A method according to claim 26, characterized in that according to a demolition condition chronologically successively recorded pressure values (p) or these corresponding following values are compared with each other and that the demolition condition is determined to be satisfied if the values (p) deviate from a predetermined desired course. Method according to claim 25 and claim 27, characterized in that the tear-off condition is determined to be fulfilled if in the case of a vacuum device (18) at a later time (t ₅₎ associated pressure value (p ₅₎ is greater than or equal to an earlier (t ₅ ) associated pressure value (t ₄ ) is or in the case of an overpressure device, a pressure value associated with a later time is less than or equal to a pressure value assigned to an earlier time. A method according to claim 25 and claim 27, characterized in that the demolition condition then determined to be satisfied If, in the case of a vacuum device (18), a pressure value (p ₇ ) assigned to a later point in time (p ₇ ) exceeds a given value (p ₆ ) by a predetermined threshold value (s) or in the case of an earlier value (t ₆ ) an overpressure device, a pressure value associated with a later time falls below a predetermined threshold value by a pressure value associated with an earlier time. Method according to one of Claims 24 to 29, characterized in that detected pressure values (p) or dependent values dependent thereon are compared with a predetermined reference value in order to determine the fulfillment or non-fulfillment of a widening ready condition, which is then referred to as is determined when the pressure value (p) reaches a threshold value corresponding to the reference value. Device for carrying out the method according to one of Claims 21 to 30, in particular for a machine (10) according to one of Claims 1 to 18.

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