Scraper device, use and method

Abstract

A scraper device and use thereof in a machine for producing or processing a fibrous-material web, comprising a doctor blade for contacting a moving surface, in particular a rotating roller, and also comprising a supporting blade, which is in contact with the doctor blade and is suitable for transferring force to the doctor blade, characterized in that one or more sensors are provided on or in the supporting blade for the purpose of determining a property of the supporting blade.

Description

[0001] Scraper device, use and method.

[0002] The invention relates to a doctor device according to the preamble of claim 1 and its use in a machine for producing or processing a fibrous web. Furthermore, it relates to a method for operating a machine with such a doctor device.

[0003] In machines that produce or process fibrous materials such as paper or pulp webs, the fibrous web is guided over a variety of different rollers and cylinders. These rollers incorporate doctor devices for a wide variety of purposes.

[0004] For example, cleaning or scraping blades are used to remove deposits of components of the fibrous web or coating medium from steam-heated drying cylinders or from the application rollers of coating units. Such scrapers are described, for example, in patent application DE 198 26 647.

[0005] In the production of tissue paper, so-called creping blades are used. They are used to crepe the tissue web from a large, heated Yankee cylinder and significantly influence product quality. Examples of such creping blades are described in documents DE 10 2009 025 066 and DE 10 2010 061 644.

[0006] Such scraper devices usually extend across the entire width of the machine. For optimal performance, these scrapers must be pressed down with a uniform force across the entire width of the machine. Furthermore, malfunctions such as vibrations or overheating of the scraper blade can occur during operation. Therefore, it is known in the art to equip the scraper devices with suitable sensors.

[0007] From DE 10 2019 117 901, for example, it is known to attach piezo sensors or strain gauges to the scraper blade in order to measure the contact force, while WO19084144 A1 describes the attachment of vibration sensors to the scraper blades.

[0008] The disadvantage of the described methods is that the scraper blades are wear parts that must be removed after a relatively short service life. Then, either the used sensors must be disposed of, which is neither economically nor ecologically advantageous. Or the sensors must be removed from the old scraper blade and reattached to the new one. This is a time-consuming process that incurs unnecessary costs and production delays for the operator.

[0009] To avoid this disadvantage, it is known to provide sensors in the scraper holder instead of directly on the scraper blade. For example, WO13059055 describes vibration sensors mounted on the solid support block of the scraper blade, while WO14176590 A1 provides strain or deflection sensors in a similar position.

[0010] The object of the invention is to overcome the disadvantages known from the prior art. It is also an object of the invention to propose an alternative scraper device that enables reliable monitoring of the scraper blade. Furthermore, the object of the invention is to enable simple retrofitting of existing systems.

[0011] The object is achieved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention can be found in the subclaims.

[0012] The object is achieved by a doctor device for use in a machine for producing or processing a fibrous web, comprising a doctor blade for contacting a moving surface, in particular a rotating roller, and a support blade which is in contact with the doctor blade and which is suitable for transmitting force to the doctor blade. According to the invention, one or more sensors are provided on or in the support blade to determine a property of the support blade.

[0013] Positioning the sensors on or in the support blade is advantageous for several reasons. Firstly, the support blade is integrated with the scraper holder and is not a wear part. It remains in the machine when the scraper blade is changed. This allows the sensors to remain in the machine as well.

[0014] Secondly, the inventor recognized that a measurement on the support blade accurately reflects the situation at the scraper blade. For example, the temperature or vibration of the scraper blade is transmitted very directly to the support blade. The transmission from the scraper blade to the support blade can be further improved by simple measures. For example, the contact area between the two strips can be enlarged, for example, through appropriate shaping, to further improve heat transfer.

[0015] The contact pressure can also be easily determined using the support blade.

[0016] Furthermore, it has been shown that vibration measurements on the support blade often provide better values / signals than measurements on doctor holders or doctor beams. This is especially true in the high-frequency range above 10 kHz, which allows conclusions to be drawn about the "softness" and "bulk / paper thickness." When positioning the vibration sensors or on the doctor holders / beams, there are too many other influencing factors, or the vibrations become blurred in the mass of the beam.

[0017] In addition, the support blade is easily accessible, allowing for any defective sensors to be easily replaced. Furthermore, simple cable routing is possible. This also allows for easy retrofitting of existing scraper devices with appropriate sensors.

[0018] A variety of sensor types can be used for scraper devices according to aspects of the invention. Preferably, at least some of the sensors are force sensors and / or temperature sensors and / or vibration or oscillation sensors. These can be implemented, for example, as strain gauges, piezo sensors, acceleration sensors, etc.

[0019] It is possible that all sensors are of the same sensor type (e.g. only strain gauges) or that different sensor types are provided.

[0020] It can be provided that a plurality of sensors are provided which are distributed over the entire length of the support blade so that measured values ​​can be determined across the entire width of the machine. The sensors of one sensor type can be evenly distributed over the length of the support blade. Alternatively, it can also be provided that the sensors of one sensor type are unevenly distributed. For example, it can be advantageous if the distances between adjacent sensors of the same sensor type are smaller in the area of ​​the edges of the support blade than in the middle of the support blade. For example, the large Yankee cylinders are filled with steam at a relatively high pressure, which causes the Yankee cylinder to "inflate". Since the jacket of the Yankee is firmly clamped at the end faces, the surface profile of the Yankee has strong gradients towards the end edges.To accurately capture the effects of these gradients, a high sensor density at the edges can be advantageous. However, such a high sensor density is not necessary in the center of the Yankee, so the sensors can be spaced further apart. Similar phenomena can also occur, for example, in temperature measurements.

[0021] Designs in which force sensors or vibration sensors are provided on or in the support blade together with temperature sensors have proven to be particularly preferred. In addition to the intended measurement of temperature and force, additional synergistic effects can be achieved. Sensors, in particular force sensors such as strain gauges or piezo sensors, are usually attached to the support blade with an adhesive. The inventor has recognized that a change in temperature changes the properties of this adhesive. This is particularly relevant for force sensors, but also for vibration sensors, since the transmission of force or vibration from the support blade to the sensor changes. This distorts the measured value.

[0022] However, if a temperature measurement is also available, this measurement error can be corrected. For this purpose, a model can be stored in the evaluation unit to determine the corresponding, corrected values ​​for the scraper blade from the sensor values ​​measured (e.g., for force or vibration) on the support blade. Such a model—e.g., in the form of a correlation table—can be created, for example, by determining the temperature dependence of the adhesive in the laboratory and storing it—e.g., in the form of a correlation table—in the evaluation unit.

[0023] Alternatively or additionally, the temperature influence on the force / vibration measurement can be determined using a reference measurement on an installed scraper device and stored in the evaluation unit. This is advantageous, for example, in the case of retrofits when some of the sensors were previously installed and no data on the type of adhesive is available.

[0024] Doctor devices according to aspects of the invention can be used, inter alia, as creping doctors, cleaning doctors or knock-off doctors in a machine for producing or processing a fibrous web.

[0025] Furthermore, a method for operating a machine for producing or processing a fibrous web is proposed, wherein the machine has a doctor device whose doctor blade is applied to a rotating roller. It is provided that the doctor device is designed according to one aspect of the invention, and the measured values ​​of the sensor(s) are recorded by an evaluation unit. The evaluation unit can be attached directly to the doctor device. However, it will usually be located some distance therefrom. The data transmission from the sensors can take place via cable. However, it can also be provided that the measured values ​​are transmitted completely or partially wirelessly from the doctor device to the evaluation unit. In this case, transmission means for wireless data transmission can be provided in or on the doctor device. Depending on the design of the sensors, these means can also be provided in the sensors.Such a solution is particularly advantageous for retrofitting, as no or very few cables need to be laid on the support blade.

[0026] If the measurement signals are sent to an evaluation unit, the absolute values ​​in [kN / m], [°C] and [m / s 2 ] and displays it in a line chart or waterfall chart.

[0027] In advantageous embodiments, it can be provided that a property profile, for example a temperature and / or force profile of the support blade across the width of the machine, is determined from the measured values ​​and, in particular, is also displayed on a display device.

[0028] In many cases, the measured values ​​from the support blade are completely sufficient. In applications where the condition of the scraper blade needs to be determined with greater accuracy, it can be advantageous to store a model in the evaluation unit to determine the corresponding values ​​for the scraper blade from the sensor values ​​measured for the support blade. Such a model—e.g., in the form of a correlation table—can be determined once for each type of scraper blade used through reference measurements.

[0029] In order to respond effectively to changes, it may be advantageous for the scraper device to have adjusting means, in particular profiling screws, to vary the contact pressure of the scraper blade against the roller surface across the width of the roller, and for the contact pressure to be adjusted depending on the measured sensor values. Such adjustment can be automated, for example, in the form of a closed-loop control system.

[0030] If, for example, no automated adjustment tools are available during a conversion, the adjustments can also be made manually during a standstill.

[0031] Application example: Crepe doctor on the Yankee cylinder of a tissue machine

[0032] A particularly advantageous application for doctor devices according to aspects of the present invention is creping doctors on the Yankee cylinder of a tissue machine. Since the support blade transfers the force and profile of the doctor holder to the creping doctor blade, the line load profile and the temperature profile of the creping doctor during the creping process in tissue production should be able to be measured, checked, and adjusted if necessary. An uneven line load leads to partially higher wear, which leads to shorter service life of the doctor blade and the cylinder coating. Furthermore, quality parameters attributable to the coating layer and its thickness can be influenced or controlled. A partially higher or lower line load results in different paper qualities.During the rotational movement of the cylinder (Yankee), the periodic deviation can be measured and displayed in order to improve the running characteristics of the Yankee.

[0033] The invention is further explained below with reference to figures. The invention is not limited to the embodiments shown here.

[0034] The figures show in detail:

[0035] Fig. 1 : Scraper device according to one aspect of the invention Fig. 2: Support blade for use in a scraper device

[0036] Figure 1 shows a doctor device 10 according to one aspect of the invention. The doctor blade 1, which is applied to a moving surface during use, for example, in a paper machine, is mounted in a holder 9. The doctor blade 1 is pressed against the moving surface by means of the support blade 2, which is also referred to as a “pressure blade”. The front end of the support blade 2 is in contact with the doctor blade 1, while the other end, in this embodiment, is supported on a compensating hose 6. To vary the contact force, adjusting means 5 in the form of adjusting screws 5 are provided. These adjusting means 5 are arranged at certain intervals across the width of the machine. The contact force can therefore be set differently at different positions on the doctor device. The adjusting screws 5 thus serve here as profiling screws 5 for the contact force.The entire scraper device 10 can be attached to a scraper bar 8.

[0037] In the embodiment shown in Figure 1, at least one sensor 3 is provided on the support blade 2 to determine a property of the support blade 2, from which the corresponding property of the scraper blade 1 can be inferred. In Figure 1, the sensor 3 is provided on the upper side of the support blade 2. Alternatively or additionally, sensors 3 can also be provided on the underside of the support blade 2 if the installation space permits. Such an arrangement offers the sensors 3 improved protection against contamination or damage, which can offset the disadvantage of more difficult accessibility in certain applications.

[0038] Sensor 3 can be, for example, a force sensor, a temperature sensor or a vibration sensor.

[0039] Figure 2 schematically shows a support blade 2 as can be used in a scraper device 10 according to aspects of the invention. While it is in principle possible for all sensors 3, 3a, 3b, 3b used to be of the same sensor type, Figure 2 shows a support blade 2 on or in which different sensor types are provided. Force sensors 3a, temperature sensors 3b, and vibration sensors 3c are attached. The force sensors 3a and the temperature sensors 3b are distributed over the entire length of the support blade 2 and make it possible to determine a force and temperature profile of the blade. The force sensors 3a and the temperature sensors 3b are evenly distributed over the length of the support blade 2. Adjacent sensors 3a, 3b are spaced 125 mm apart. Larger or smaller spacings can also be provided.The selected distances depend on factors such as the size of the sensors 3, 3a, 3b, 3c, the desired resolution of the property profile and the resulting costs.

[0040] An alternative to the uniform distribution of sensors 3, 3a, 3b, 3c may be to position the sensors 3, 3a, 3b, 3c closer to each other in certain regions, for example, at the edges of the support blade 2 (e.g., 100 mm or 75 mm), while in other areas, such as in the center of the blade 2, the spacing may be increased (e.g., to 250 mm or 500 mm). This can be particularly advantageous for doctor devices 10 for paper machines with large widths of 10 m or more.

[0041] In contrast to the force sensors 3a and the temperature sensors 3b, in the example of Figure 2, the vibration sensors 3c are not provided across the entire width of the support blade 2. Only two vibration sensors 3c are mounted, namely near the respective edges of the support blade 2—here at a distance of, for example, 780 mm.

[0042] This is sufficient, since generally, no vibration profile is to be created, but rather only to determine whether and / or how strongly the support blade 2 and thus also the scraper blade 1 vibrates. Such vibrations can, for example, result from the uneven rotation of a roller 4 or a cylinder 4 against which the scraper blade 1 rests.

[0043] The vibration sensors shown in Figure 2 can also be omitted. The force sensors 3a and the temperature sensors 3b are arranged here such that each force sensor 3a is assigned a temperature sensor 3b. Thus, the temperature-related measurement error of the force sensors 3a can be very easily corrected using the temperature measurement of the assigned temperature sensor 3b. Other arrangements are obviously also possible. For example, two or more force sensors 3a can be corrected using the temperature measurement value of a single temperature sensor 3b. Alternatively, the measurement value of a force sensor 3a can also be corrected using a suitable average value of several adjacent temperature sensors 3b. Here, the present invention allows for great flexibility in the application. List of Reference Symbols

[0044] scraper blade

[0045] Support blade

[0046] Sensor a Force sensor b Temperature sensor c Vibration sensor

[0047] Moving surface, roller surface

[0048] Adjusting means, profiling screw

[0049] Compensation hose

[0050] Attachment to the scraper beam Holder for scraper blade 0 Scraper device

Claims

Patent claims 1 . A doctor device for use in a machine for producing or processing a fibrous web, comprising a doctor blade for contacting a moving surface, in particular a rotating roller, and a support blade which is in contact with the doctor blade and which is suitable for transmitting force to the doctor blade, characterized in that one or more sensors are provided on or in the support blade to determine a property of the support blade.

2. Scraper device according to one of the preceding claims, characterized in that all sensors are of the same sensor type, or that different sensor types are provided.

3. Scraper device according to claim 1, characterized in that both temperature sensors and force and / or vibration sensors are provided as sensors.

4. Scraper device according to one of the preceding claims, characterized in that a plurality of sensors are provided which are arranged distributed over the entire length of the support blade 5. Scraper device according to claim 4, characterized in that the sensors of one sensor type are evenly distributed over the length of the support blade.

6. Scraper device according to claim 4, characterized in that the sensors of one sensor type are unevenly distributed, and preferably in the region of the edges of the support blade the distances between adjacent sensors of the same sensor type are smaller than in the center of the support blade.

7. Use of a doctor device according to one of the preceding claims as a creping doctor, cleaning doctor or knock-off doctor in a machine for producing or processing a fibrous web.

8. A method for operating a machine for producing or processing a fibrous web, the machine comprising a doctor device whose doctor blade is applied to a rotating roller, characterized in that the doctor device is designed according to one of the preceding claims, and the measured values ​​of the sensor(s) are recorded by an evaluation unit.

9. Method according to claim 8, characterized in that the measured values ​​are transmitted wirelessly from the scraper device to the evaluation unit.

10. Method according to one of claims 8 or 9, characterized in that a property profile, for example a temperature and / or force profile, of the support blade is determined from the measured values ​​over the width of the machine and is in particular also displayed on a display device.

11. Method according to one of claims 8 to 10, characterized in that a model is stored in the evaluation unit in order to determine the corresponding values ​​for the scraper blade from the determined sensor values ​​of the support blade.

12. Method according to claim 11, characterized in that the model is configured to adapt the measured values ​​of the force and / or vibration sensors using the measured temperature values.

13. Method according to one of claims 8 to 12, characterized in that the scraper device has adjusting means, in particular profiling screws, in order to adjust the contact force of the scraper blade to the roller surface across the width of the roller, and that the contact pressure is adjusted depending on the measured sensor values.

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