Method and controller for detecting vibrations of a creping blade

Abstract

The present application relates to a method for detecting vibrations of a creping blade of a tissue paper machine, the tissue paper machine being provided with one or more vibration sensors arranged to detect vibrations of the creping blade, the method comprising the steps of: receiving a vibration signal from the vibration sensor, the vibration signal being indicative of vibrations of the creping blade; monitoring (302) the vibration signal in one or more resonance frequency ranges; identifying (304) one or more peak frequencies in the resonance frequency ranges; monitoring (306) the amplitude of the one or more peak frequencies; comparing (308) the amplitude of the one or more peak frequencies to one or more corresponding predetermined levels; and generating (310) a chatter alarm if one or more of the monitored amplitudes are higher than the corresponding predetermined levels.

Description

Technical Field

[0001] This application relates to the paper creping process and the occurrence of vibrations (especially flutter) in the creping doctor blade. Background Technology

[0002] In the production of tissue paper, a key component is the creping doctor blade, which comes into contact with the Yankee cylinder. The Yankee cylinder is used to dry the fiber web, and different types of chemicals are used as a coating on the Yankee cylinder to keep the web on its surface. The dried web is removed from the Yankee cylinder by the creping doctor blade. During the removal of the web, it is creped to produce soft tissue paper.

[0003] To produce a final product with desired properties, many interacting factors exist during creping, such as the Yankee cylinder, the coating, and the creping blade. During the creping process, the creping blade is subjected to vibration. This is due to the periodic changes in friction between the creping blade and the Yankee cylinder. This vibration causes the creping blade to bounce within the coating, resulting in an uneven surface. If the bouncing reaches a high level, there is a risk that the creping blade will cut through the coating and come into contact with the surface of the Yankee cylinder, causing damage to the cylinder in the form of chatter marks. This is more common when the creping blade is worn. A new creping blade will cut into the coating easily, but as the creping blade wears, its cutting ability decreases and any irregularities in the coating increase, leading to increased vibration.

[0004] Chatter marks on Yankee cylinders should be avoided because cylinders with chatter marks require regrinding, which is costly and causes production interruptions. Therefore, methods and systems have been developed to monitor the vibration of creased blades in order to detect vibration exacerbations that may lead to chatter marks. Vibration sensors are attached to the creased blade holder, and the signals from the sensors are analyzed. A common analysis method uses acceleration as a metric, and due to the complexity of the raw vibration signal, the root mean square (RMS) average is calculated. However, it is difficult to definitively identify chatter frequencies using RMS, and it is particularly difficult to set limits that require action such as replacing worn creased blades.

[0005] Therefore, there is room for improvement in preventing chatter marks and similar damage to Yankee cylinders. Summary of the Invention

[0006] The purpose of this application is to improve the monitoring and detection of the chatter frequency of a wrinkling doctor blade to avoid serious damage to the Yankee cylinder and other equipment that may be used during the wrinkling process. This purpose is achieved through the features of the independent claims of the patent. Preferred embodiments form the subject matter of the dependent claims of the patent.

[0007] According to a key aspect, a method is provided for detecting vibration of a creased doctor blade in a tissue paper machine, the tissue paper machine being provided with one or more vibration sensors arranged to detect vibration of the creased doctor blade.

[0008] The method includes the following steps: receiving a signal from a vibration sensor indicating vibration of a wrinkling scraper; monitoring vibration signals within one or more resonant frequency ranges; identifying one or more peak frequencies within the resonant frequency range; monitoring the amplitude of one or more peak frequencies; comparing the amplitude of one or more peak frequencies with one or more corresponding predetermined levels; and generating a flutter alarm if one or more of the monitored amplitudes are higher than the corresponding predetermined levels.

[0009] One advantage of the above method is that it focuses on a specific resonant frequency range of the vibration spectrum input from the vibration sensor, unlike conventional methods which use a broader vibration spectrum and perform RMS averaging of these signals. Using this method, chatter frequencies that may cause damage to Yankee cylinders can be detected more accurately and specifically, allowing for the setting of levels at which peak amplitudes should not exceed.

[0010] Preferably, the amplitude of one or more peak frequencies is monitored over time to track the behavior of the wrinkling scraper.

[0011] Regarding the frequency range used in the method, the first resonant frequency range is 10 kHz to 20 kHz. This first frequency range corresponds to the creased blade chatter frequency in a vibration direction that is substantially the same as the width of the creased blade and transverse to the longitudinal direction of the creased blade.

[0012] Further regarding the frequency range used in this method, the second resonant frequency range is from 1 kHz to 6 kHz. This second resonant frequency range corresponds to the creased blade chatter frequency in a vibration direction that is generally transverse to the width of the creased blade and transverse to the longitudinal direction of the creased blade.

[0013] According to another aspect of the method, vibration sensors can be arranged on both sides of the creased blade, and signals from the two sensors indicate the vibration of the creased blade and acquire one or more active resonance frequencies of the creased blade within the resonance frequency range.

[0014] This is advantageous when the creaser blade is long and chatter can occur at different locations along the blade. If a single sensor is used, it may be located far from the chatter location and therefore may not provide the expected vibration level to that sensor. This risk is mitigated by using vibration sensors on both sides. In this regard, multiple vibration sensors can be arranged along the extension direction of the creaser blade.

[0015] Regarding vibration sensors, they can be accelerometers, where the amplitude is the peak power. Furthermore, regarding the generation of alert signals, this can include the following steps: generating a warning signal if a predetermined level is exceeded, and generating an alarm signal if a higher predetermined level is exceeded.

[0016] By alerting operators of tissue paper creping machines to two or more levels of abnormal creping blade operation, more information and decision-making points can be provided regarding what actions to take if a certain level is exceeded.

[0017] According to other aspects of this application, a controller including program instructions is provided, which, when executed by the controller, cause the controller to perform the method according to this application. Furthermore, a computer-readable storage medium including program instructions, which, when executed by the controller, cause the controller to perform the method according to this application, can be provided.

[0018] These and other aspects and advantages of the invention will become apparent from the following detailed description and accompanying drawings. Attached Figure Description

[0019] In the following detailed description of the invention, reference will be made to the accompanying drawings, wherein:

[0020] Figure 1 This is a schematic diagram of a Yankee cylinder equipped with a creased scraper for the creased process.

[0021] Figure 2 and Figure 3 Different types of chattering in the scraper blade are shown, and

[0022] Figure 4 This is a flowchart of the method according to this application. Detailed Implementation

[0023] This application relates to tissue paper making machines, and more particularly to a creping doctor blade 10 used in conjunction with a Yankee cylinder 12 in the tissue paper manufacturing process for creping tissue paper webs, such as Figure 1 The diagram is schematically shown. To monitor the behavior of the wrinkling blade 10 during wrinkling, and to detect the presence of chatter in the wrinkling blade 10, the vibration sensor 14 is positioned in relation to the wrinkling blade. Preferably, as shown... Figure 1As seen, vibration sensors 14 are positioned at both ends of the creaser blade, i.e., on the drive side and the operating side, for example, or preferably on the creaser blade holder. Vibration sensors can be positioned on only one side, but in cases where the creaser blade is very long, the location of chattering may be far from the sensor, thus failing to provide the expected vibration level to the sensor. In this regard, several vibration sensors can be arranged along the length of the creaser blade. For example, vibration sensor 14 could be an acceleration sensor.

[0024] Vibration sensor 14 is operatively connected to controller 16 via a suitable communication channel 18. The controller is provided with I / O elements for receiving signals from the vibration sensor, data storage elements for storing data from the vibration sensor, and a processor element programmed to process data from vibration sensor 14.

[0025] The controller may include a computer, which may take the form of virtually any suitable type of hardware or hardware / firmware device implemented using processing circuitry, such as, but not limited to: a processor, central processing unit (CPU), controller, arithmetic logic unit (ALU), digital signal processor, application-specific integrated circuit (ASIC), digital signal processing circuitry (DSP), microcomputer, field-programmable gate array (FPGA), system-on-a-chip (SoC), programmable logic unit, microprocessor, application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner, or other processing logic capable of interpreting and executing instructions. As used herein, the term "computer" may refer to a processing circuitry structure comprising multiple processing circuits (such as any one, a portion, or all of the processing circuits described above).

[0026] The controller may also include a memory unit, to which a computer can be connected. This memory unit can provide the computer with stored program code and / or stored data, such as data that the computer might need to perform calculations. The computer may also be adapted to store portions or final results of calculations in the memory unit. The memory unit may include physical means for temporarily or permanently storing data or programs (i.e., sequences of instructions). According to some embodiments, the memory unit may include an integrated circuit comprising silicon-based transistors. In different embodiments, the memory unit may include, for example, a memory card, flash memory, USB storage, a hard disk, or other similar volatile or non-volatile memory units for storing data, such as ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc.

[0027] During operation, controller 16 acquires signals from vibration sensor 14. Software for detecting flutter is programmed to process a specific frequency range in the acceleration power spectrum where the active resonance frequency originates from the creased doctor blade. This range is identified as 10 kHz to 20 kHz for linear vibrations of the creased doctor blade, such as... Figure 2 As shown, the vibration direction is generally consistent with the width of the wrinkling scraper, that is, between the base and tip of the scraper; and the 1 kHz to 6 kHz vibration is for the bending vibration of the wrinkling scraper, as shown. Figure 3 As shown, the vibration direction is generally transverse to the width of the creased blade and transverse to the longitudinal direction of the creased blade. Regarding the above spectrum, it should be understood that these ranges may vary depending on operating parameters, the geometry of the creased blade, and other factors affecting the creased process, and therefore may need to be adjusted upward or downward along the spectrum.

[0028] When peak power occurs within these ranges, it indicates the resonant frequency of that particular creping blade. Continuous monitoring of data from sensor signals is crucial, particularly the highest peak of the resonant frequency detected within the range. This frequency may fluctuate slightly during operation, but not significantly. The controller continuously monitors peak power levels and amplitude over the entire lifespan of the creping blade. Limits can be preset on peak values ​​that should not be exceeded, as these could lead to chattering that could damage the Yankee cylinder. These limits can be set based on several operating parameters relevant to a typical tissue paper machine. Parameters related to the creping blade, such as the geometry of the creping blade holder, the blade angle and its stick-out, and the bevel angle, can be important. Furthermore, the final product can also have an impact, as some products require higher workloads to produce the desired paper properties, and the coating ratio and dosage used also play a role.

[0029] In this regard, the controller may be set with more than one limit against which the peak power level is compared. For example, there may be a lower limit, to which the controller can issue an abnormal warning signal if the peak exceeds this limit, but this may not require emergency measures such as shutting down the machine. Additionally, there may be an upper limit, to which the controller can issue a serious fault alarm signal if the peak exceeds this limit, which may require immediate shutdown of the machine to avoid damaging the Yankee cylinder.

[0030] As described above, the controller is configured with program code to execute method step 300 according to this application. This is in Figure 4 It is shown schematically in the diagram.

[0031] In step 302, the controller receives a vibration signal from a vibration sensor, wherein the vibration signal indicates the vibration of the wrinkling scraper.

[0032] In step 302, the controller monitors vibration signals within one or more resonant frequency ranges. Two different frequency ranges are provided to the controller based on the type of resonant frequency (linear vibration or bending vibration). For linear vibration, the provided frequency range is between 10 kHz and 20 kHz, while for bending vibration, the frequency range is between 1 kHz and 6 kHz. The controller is configured to analyze frequencies within these ranges. In step 304, the controller is programmed to identify one or more peak frequencies within the resonant frequency range. That is, targeting frequencies with higher amplitudes within the resonant frequency range. In most cases, there is a small frequency span providing these peak powers. In the next step, 306, the controller monitors the amplitudes of one or more peak frequencies, which are now considered important for detecting chatter of the wrinkling scraper. In step 308, the amplitudes of the monitored peak frequencies are compared to one or more corresponding predetermined levels, which can be set according to several factors affecting the wrinkling process. The above steps are continuously performed during operation. As an example, the signal from the vibration sensor can be sampled approximately every three minutes, which is important for the controller to monitor amplitude increases.

[0033] In step 310, the controller is programmed to generate a flutter alarm signal if one or more of the detected amplitudes exceed the corresponding predetermined levels. As a sub-step 312 of step 310, the controller can be programmed to generate a warning signal if one level is exceeded, and an alarm signal if a higher level is exceeded.

[0034] It should be understood that the embodiments shown in the above description and drawings should be considered as non-limiting examples of the present invention only, and can be modified in various ways within the scope of the patent claims.

Claims

1. A method for detecting vibration of a crease cutter (10) of a tissue paper machine, the tissue paper machine being provided with one or more vibration sensors (14) arranged to detect vibration of the crease cutter, the method comprising the steps of: - Receive vibration signals from the vibration sensor, the vibration signals indicating the vibration of the wrinkling scraper. - Monitor the vibration signal within one or more resonant frequency ranges. - Identify one or more peak frequencies within the resonant frequency range. - Monitor the amplitude of one or more peak frequencies mentioned in (306), - Compare the amplitude of the one or more peak frequencies with one or more corresponding predetermined levels (308), and - If one or more of the detected amplitudes are higher than the corresponding predetermined level, a flutter alarm is generated.

2. The method according to claim 1, wherein, Monitor the increase in amplitude of the one or more peak frequencies over time.

3. The method according to claim 1 or 2, wherein, The first resonant frequency ranges from 10 kHz to 20 kHz.

4. The method according to claim 3, wherein, The first frequency range corresponds to the wrinkling scraper chatter frequency in a vibration direction that is generally consistent with the width of the wrinkling scraper.

5. The method according to any one of claims 1 to 4, wherein, The second resonant frequency ranges from 1 kHz to 6 kHz.

6. The method according to claim 5, wherein, The second resonant frequency range corresponds to the wrinkling scraper chatter frequency in a vibration direction that is generally transverse to the width of the wrinkling scraper and transverse to the longitudinal direction of the wrinkling scraper.

7. The method according to any one of the preceding claims, wherein, Vibration sensors are arranged on both sides of the wrinkling blade, and signals from the two sensors indicate the vibration of the wrinkling blade, and one or more active resonant frequencies from the wrinkling blade within the resonant frequency range are acquired.

8. The method according to any one of claims 1 to 6, wherein, Multiple vibration sensors are arranged along the extension direction of the wrinkling scraper.

9. The method according to any one of the preceding claims, wherein, The vibration sensor is an acceleration sensor, and the amplitude is a peak power.

10. The method according to any one of the preceding claims further includes the following step: If a predetermined level is exceeded, a (312) warning signal is generated, and if a higher predetermined level is exceeded, an (312) alarm signal is generated.

11. The method according to any one of the preceding claims, wherein, The vibration signal includes one or more active resonant frequencies from the wrinkling scraper.

12. A controller (16) including program instructions, which, when executed by the controller, cause the controller to perform the method according to claims 1-11.

13. A computer-readable storage medium comprising program instructions that, when executed by a controller, cause the controller to perform the method according to claims 1-11.

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