Patent Application
20140096925
The present disclosure relates to Tissue and Towel paper making machines and, more specifically, to a process of coating a Yankee dryer and the Creping process.
A Yankee dryer is a pressure vessel used in the production of tissue paper. Yankee dryers are primarily used to remove excess moisture from pulp that is about to be converted into paper. The Yankee cylinder can be equipped with a creping blade (in combination with a doctor blade) where the cylinder is sprayed with adhesives to make the paper stick. Creping is done by scraping the dry paper off the cylinder surface with the Doctor Blade and thereby creping the paper at the Creping Blade. The resulting crinkle is controlled by the strength of the adhesive, geometry of the Doctor blade/Creping Blade combination, speed difference between the Yankee and final section of the paper machine and paper pulp characteristics.
Currently, the actual lubrication of the doctor blade over 23 zones (number of spray nozzles×6 inches) is accomplished based on the principle of delivering the release coating at a constant pressure to a common manifold. Based on this principle, achieving common flow rate for all nozzles is assuming a common pressure on the manifold equals a common flow rate at the spray nozzles resulting in a gross assumption. Thus, the principle implies the friction loss for all 23 nozzles will always be the same and that all of the nozzles and piping delivery mechanisms were created under exact manufacturing practices and will never show any effect due to wear. If this were the case, everything might work well for a day or two but in reality, 23 or more nozzles on a single manifold will not perform well for very long. Minor differences in manufactured parts as well as the current state of buildup in the piping will cause variances in friction losses thereby changing the individual flow rates dynamically. Also, wet spots on the product being processed at the Yankee dryer will have a tendency to absorb different rates of release coating thus changing the residual coating level. This change cannot be compensated for on a single manifold control unless an operator opens or closes a spray valve manually. Detecting the problem and correcting the problem, from a human standpoint is only accomplished if the problem has become catastrophic. There is a need to address the coating release residual level which can change due to wet streaks in the web or the improper flow control at each nozzle.
A coating system and method thereof to take control and correct the application of the release coating chemistry to insure: the release coating chemistry is at the proper mix ratio as programmed by a recipe set point which may be adjustable by the operator, the release coating is being applied in the proper thickness across the Yankee dryer surface at all times, increase and decrease the proportional valves at each nozzle in order to compensate for, and maintain, a constant flow rate independent from variations in supply pressure, increase and decrease the flow rate in order to compensate for variations in production speed (ft/min), detect and report graphically areas that are not coated properly if the system cannot correct a specific problem, provide a graphical view of the concurrent production as to speed, flow rates, release coating thickness, and Yankee temperature profile over the entire surface, extend the life of the creping and doctor blades, decrease maintenance on the spray nozzles, and translate the production data obtained into clear visual results and warn operators in an audio, and visual (graphical) manner of process problems.
The present disclosure provides for Yankee Dryer Release Coating Application. An aspect of the disclosure to realize the disability of the single manifold type of control with its indiscriminate application of release coating is based on an averaging response by a single control point mechanism. However, through the implementation of individual control over each spray nozzle, one can tailor each nozzle output precisely and independently over the entire Yankee dryer surface. For example, each nozzle may be independently controlled to servo its flow rate to a master flow rate set point. Variations due to friction losses, pressure differentials, and spray nozzle wear, etc. can be compensated precisely. Thus, this would be accomplished in having each nozzle controlled by its own microcontroller, proportional flow rate control valve, precision flow rate meter, and spray nozzle. Each spray flow rate would be independently controlled to the master set point within <=1% (+/−0.05%). There will however be a need to implement corrections to individual nozzle flow rates based on residual coating thickness, detected after the release, in order to prohibit wear on the creping and doctor blades. The maximum allowable deviation from the master set point flow rate will be a programmable limit at a maximum value of about 10%. Thus verifying the release coating thickness on the Yankee dryer may be critical in order to implement the automatic corrections in the individual flow rates in order to correct for wear of the creping blade.
A further aspect of the present disclosure relates to measuring the difference and detecting the Yankee dryer release coating thickness and coating quality using an industrialized Ultraviolet Visible Near-Infrared (UV-VIS-NIR) spectrometer. The present disclosure provides an industrialized UV-VIS-NIR spectrometer which can optically analyze the release coating thickness as well as the accuracy of the solution applied. The UV-VIS-NIR spectrometer may be driven back and forth (left to right) across about 3-4 inches from the Yankee dryer surface, yielding the actual coating thickness for each 0.02 inch of linear movement across the surface. A different scanning spectrometer will yield an accurate temperature profile, 50 points per inch, for the entire surface. This data may then be displayed in a graphical manner on a display monitor so that an operator can, at a glance, correlate the temperature and coating thickness imaging to process problems. Wherein error/fault regions will have their positions marked for example in red. If a problem is beyond the capability of being solved by the computer control system or its programmable limits as set, alarms may sound and markers may be placed on the screeen to show the location of the error as well as a text message to describe the type of error involved. This alarm, as well as all alarms, are date and time stamped for permanent recording on the system hard drive. Thus the system of the present disclosure saves all running data, maintanence records, and all alarms annunciated with date and time stamp continuosly. These records are permanent and can be reviewed with our data viewing software. Maintanence reports may be viewed daily and since the machine keeps track of its own maintanence issues, maintanence issues are scrolled in the maintanence issue window as they are needed to be performed. Therefore, the machine may tell the user if it requires maintanence.
Regarding the water used as a reference in measuring the difference and detecting the Yankee dryer release coating thickness and coating quality, a water softening system with dual tanks may be used that recharging can be accomplished without interruption. Untreated water may affect the manifolds, spay nozzles, valves, etc. of the coating system, thus the need to remove the CaCO3, MnO, Fe2O3 that may cause side effects, or otherwise, chemistries you are not trying to effect on the process such as precipitations, gumming or unexpected catalyzed polymerizations. The coating system may use less than 200 gallons per day. A water softening system produces water that has a sodium (Na) based chemistry. Although softened water is not as good as distilled water, it may be practical. It will remove the calcium (Ca), Iron (Fe), manganese (Mn), and vanadium (V), and other metal ions prevalent in untreated water. The use of treated water will provide long term predictability in applying the release coating of the present disclosure.
The main system control used in the present disclosure may consist of a NEMA 12 enclosure which will house the 8 core Windows 7 based computer with the specific control software, 22 inch wide screen monitor, excess electronic circuitry, a Freon based 4000 BTU air conditioner to cool the system, internet radio communications for factory personnel 24 hour a day 7 days a week, power supplies and an interface mechanism to communicate to the in-plant programmable logic controller (PLC) such as Ethernet. The main system may have numerous extra input/output (I/O) and analog I/O available for future expansions.
The main system control may be made available as a remote unit, remote operator's station, which takes up a fraction of the space and works in parallel with the main station. Essentially consisting of but not limited to a monitor, key board and mouse with all of the main control buttons.
The release coating application assembly of the present disclosure may consist of a manifold assembly which may be installed in parallel to an existing system. If such system fails, the existing system will continue to run until the manifold assembly system is back up and running, thus resulting in no down time. The manifold assembly may consist of but not limited to the following: a main manifold wherein all wetted parts are stainless steel, a manifold conduit prewired in water proof conduit, twenty-three proportional flow rate valve ASCO 202 Series pulse width modulated drive, twenty-three Cole Parmer EW-32718-06 flow sensor flow rate amplifier and twenty-three quick disconnect spray nozzle by spraying systems.
A release coating inspection system of the present disclosure may consist of a temperature and humidity controlled NEMA 12 enclosure which will travel back and forth on a lubricated linear ball and guide assembly. The linear ball and guide bars may be made of stainless steel for the shafting with powder coated support beams. The linear ball screws may be continuously lubricated in order to dissolve any build up of sprayed chemicals. The assembly can handle dirty environments and ambient temperatures up to 250° F. The radiant intensity controlled UV and variable power controlled incandescent light sources for the spectrometer as well as two infra-red temperature cameras for complete temperature profiling of the Yankee Dryer surface. A solid state refrigeration and heating system to keep the enclosed sensors at a constant 70° F. all year round. A replaceable desiccation stem to keep moisture out of the spectrometer and cameras. A 200 nm through 1000 nm spectrometer which will cover from ultra violet through the entire visual range and into the near infrared wherein the resolution of the spectrometer is 0.3 nm. A stepper motor drive and electronics for positioning the inspection station to within about 0.001 inch. Quadrature encoder to track the position of the Yankee dryer to within about 0.001 inch thus requires the positions of defects/errors in the process to be tracked. Clean filtered and electronically monitored air purging pump to keep the lenses clean. Plant air is dirty and costly, thus controlling the quality of the purging air is enhanced by the present system as well as the use of electronics to monitor the system for proper flow and filter condition. A master pulsed type flow meter and pressure gauge for the incoming process water. A water purification system which consists of 5 micron filters and carbon filters. In general, PLC's are handling what they can do. However PLC's cannot analyze millions of data items per second, nor can they evaluate workable solutions for problems involving trillions of calculations. Thus, a personal computer (PC) on the other hand was made for this purpose. Software written for the PC may also provide solutions in a graphical and text manner that provide clear cut instructions to the operator. The advantage is the ability to go through a multitude of complex problems, involving millions of equations, in the time it takes a PLC to loop once through its program. The types of problems with production processes, which have not been handled thus far with PLC solutions are difficult, thus with the present disclosure those problems can be solved using PC based systems which is specialized in complex production problems.
Advantages of the present disclosure include a coating system and method thereof to take control and correct the application of the release coating chemistry to insure: the release coating chemistry is at the proper mix ratio as programmed by a recipe set point which may be adjustable by the operator, the release coating is being applied in the proper thickness across the Yankee dryer surface at all times, increase and decrease the proportional valves at each nozzle in order to compensate for, and maintain, a constant flow rate independent from variations in supply pressure, increase and decrease the flow rate in order to compensate for variations in production speed (ft/min), detect and report graphically areas that are not coated properly if the system cannot correct a specific problem, provide a graphical view of the concurrent production as to speed, flow rates, release coating thickness, and Yankee temperature profile over the entire surface, extend the life of the creping and doctor blades, decrease maintenance on the spray nozzles, and translate the production data obtained into clear visual results and warn operators in an audio, and visual (graphical) manner of process problems.
As known in the art, applying more release coating in an area to solve a coating thickness problem may solve the thickness problem but may cause other problems. If the coating is too thin, it could be caused by a wet spot on the web. Thus, the present disclosure addresses correcting the coating thickness problems known in the art resulting in improved release coating thickness and ratio. However, wet spots in the web will absorb more coating than normal making the coating thinner. This may also cause a slightly cooler area since the evaporating water and absorbed coating will remove a proportional amount of heat. Temperature losses may be greater in those areas showing a corresponding decrease in temperature left as a ghost image on the Yankee dryer. Thus increasing the release coating flow rate in that area may have a good effect. However, at some increased flow rate of release coating, one may expect the existing quality problem, due to a wet spot, to worsen. Limits may be implemented to control how much the system can change the flow rates at each nozzle. Therefore, the Yankee dryer temperature profile obtained from the scanning camera may allow the PC to confirm, along with the spectrometer data, that this is a problem caused by a wet spot generated at the head box. The system of the present disclosure may graphically show the operator where the wet spot is located on the web allowing the system to address the specific problem.
In order to determine the thickness of the release coating of the present disclosure a first determination of the exact thickness of the release coating solution on the Yankee dryer surface must be made by first obtaining the exact solution spectrum and derive from it the concentration of individual components in that solution. In other words, the solution make up of MAP, coating, and release oil in terms of percent concentration of each in the final solution prior to spraying the mixture onto the Yankee dryer surface. It is important to have a predetermined curve of the desired solution spectrum, determined from a recipe. This recipe spectrum can be created from known spectrums for each individual component at varying concentrations in purified water.
Once the spectrums have been obtained for each pure component at different concentrations which are in the useful concentration range, the pixel data (0.3 nm) may be used from the spectrometer of those varying concentration spectrums, which were taken at a known radiant energy of short wave UV, apply the equation of y=mx+b for two known concentration points, plot any pixel response at any concentration for the given component thereby creating a new spectrum for that component at any concentration. Wherein y=the pixel response at (x) concentration at a constant radiant power at short wave UV (peak @ 365 nm); m=slope=(y2−y1)/(x2−x1); b=(offset)=y2−(x2*m).
Next, obtain the same reference curves at different temperatures of the solution for each component wherein this is also used to correct the individual reference spectrums, mentioned above, for the pixel response of each component under varying temperatures. Temperature may affect changes in the absorption spectra because the component molecules will be at different energy states at different temperatures. This will be calculated per pixel (0.3 nm) and applied to the spectra above so that new spectra can be calculated for the above reference spectra at the calibrated concentrations with a known radiant power UV. Again applying the equation of: y=mx+b for each pixel wherein, y=the pixel response at x temperature for each component at the known concentration for each component that we used in the equation above; m=slope=(y2−y1)/(x2−x1); b=(offset)=y2−(x2*m). This will now allow recalculation any reference spectra of any pure component solution for any concentration (over the range of solutions concentrations tested) and correct it for the proper response over any temperature variations expected in the real application of this device.
Next, correction for variations in the Radiant Power applied to the solution, again at the known concentrations used above is done. As the light source ages, the intensity of the source may vary. A spectrometer will also monitor the spectral energy of the UV source to correct the output power over the life of the source. However variations in radiant power per pixel will occur. Evaluating the known concentrations of the pure components at the already known concentrations, and by varying radiant power levels one can again apply the equation: y=mx+b to the calibration spectra above per pixel (0.3 nm). Now, varying the radiant UV power intensity with a high and low level changes can be obtained in pixel response due to changes in radiant power over the range of variance expected from the UV source. Wherein y=mx+b for each pixel; y=the pixel response at x radiant power level for each component and at the known concentration for each component that we used in the equation above; m=slope=(y2−y1)/(x2−x1); b=(offset)=y2−(x2*m).
Finally, one can determine and plot a new spectrum from stored data and by sequentially applying the equations above. Based on real time sensor inputs for temperature and radiant power levels, one can create new spectra that will modify the stored reference spectra, which will reflect the actual variances in those spectra caused by the real time sensor data for temperature and radiant power levels of the light source and at any concentration of this component in water.
This may be accomplished for each individual component needed in a recipe of components. For example, the corrected spectra for MAP, release, and coating would be calculated and stored in memory. These reference spectra would be continuously recalculated to reflect changes in temperature and radiant power.
As shown in
Determining the spectra of the release coating mixtures/solutions for a recipe consists when a recipe is needed for production, a mixture of the three components is blended in order to accomplish proper lubrication of the creping blade as well as provide the proper release of the tissue product from the Yankee Dryer. Different mixes of the raw components above are blended to accomplish the same tasks but need different mix ratios for different types of tissue being processed. A means of calculating a dynamic master recipe spectrum, as a reference spectrum in memory, is required in order to evaluate the actual blended recipe in real time. This recipe spectrum would characterize the ideal mixture of components but also be dynamic in nature so as to be modified continuously by recalculating and thereby compensating for temperature changes and a varying radiant power.
Establishing the mechanism to recalculate the single component curves for temperature, radiant power, and individual component concentration may be done using the method above. By taking the recipe at known component concentrations for each as described per the recipe, the resulting curve to be calculated as a master recipe can be put together based on each pixel response at a given wave length and also on the percentage of each component in the recipe solution. For example, if the MAP component is to be added at a final concentration of 4%, the release component at 5.5%, and the coating component at 10%, then for a given pixel response for each, corrected for temperature and radiant power, and at the stated concentration, one can easily calculate the new expected pixel response for each pixel of the master recipe spectra dynamically, for the level of the components in that recipe at their concentration levels and corrected for temperature and radiant power.
Variations in real time component concentrations may occur due to mechanical issues encountered in normal production practices. A spectrometer would be used in the raw feed supply of the made up recipe in order to measure the accuracy of the scanned real time spectrum of that raw feed recipe. By analysis of the real incoming spectral data and comparing it to the stored master recipe spectra, one can mathematically determine the true concentrations of the mixture. With this, one can affect a proportional change in the mix ratio in order to correct these errors in the final solution of the components recipe being made in real time. The pump speeds and flow rates for each component can be adjusted in order to effect the changes needed in order to bring the actual production mix back into the recipe specifications. The actual analysis is based in the integration of the pixel response over the spectral range in order to receive a percentage error, while a derivative value of the pixel data, for a given wave length range, will yield particular component concentration errors. Again, discrete derivatives will be peculiar to one mix component more so than other components for a given wave length and the integration of the pixel data will yield the overall percentage error of the mixed ratios. In order to acquire the depth of the residual recipe left on the Yankee dryer, an exact composition of the real time solution must be known prior to application of the mixture onto the Yankee dryer surface. Knowledge of exactly what the mixture is composed of and how much of each individual component is in the applied solution is needed. Then one can evaluate how much of each component the process used after the creping blade has released the tissue. As some of the aspects of the present disclosure is to increase the life of the creping blade as well as increasing the quality of the tissue product, the ability to analyze the residual left over coating is an important aspect of the present disclosure.
Determining residual release coating thickness on the Yankee dryer after the creping blade release consists of the ability to determine individual component concentrations through the mathematical evaluation of the spectra above, these methods can now be used to determine not only the residual composition after the creping blade, but also determine the thickness of the coating as well.
While emitting a quantum amount of UV energy with a peak at 365 nm, controlled by measuring and adjusting the radiant power through control circuitry, the stored reference spectra as described earlier, and the same methods as described above are determined by correcting for temperature, radiant power and concentration of each, the calculated thickness of the residual release coating can be used. This will be determined by integrating the absorption response per pixel across the spectra. Since the recipe of components used, during the manufacturing process all absorb UV energy, the amount of UV energy absorbed by the residual, left over, release coating may be readily detectable and may vary in proportion to this residual thickness. This residual thickness and the residual component concentrations may then be correlated to the linear movement across the Yankee dryer surface by a linear ball screw device in order to develop a complete profile of the Yankee dryer surface in real time. Minute changes in the integrated absorption response, being proportional to the thickness of the residual coating but also yielding detectable component concentrations, should allow one to vary the original recipe in order to effect quality enhancements in the manufacturing of the tissue product in real time. By passing the spectrometer back and forth along the Yankee dryer surface one will be able to develop a surface profile as well as pin point problems in manufacturing such as correcting deficient areas of release coating by adjusting the recipe, changing flow rates, and warning the operator of problems elsewhere in the process that could affect quality or downtime. An example of the latter would be a wet spot cause by a vacuum problem on the felt or a dry spot caused by insufficient fiber content in the stock being fed at a location in the head box.
Determining Residual Release Coating Thickness on the Yankee Drier after the Creping Blade Release
Since we have established the ability to determine individual component concentrations through the mathematical evaluation of the spectra above, these methods can now be used to determine not only the residual composition after the creping blade, but also determine the thickness of the coating as well.
Since we are emitting a quantum amount of UV energy with a peak at 365 nm, controlled by measuring and adjusting the radiant power through control circuitry, we can use stored reference spectra just as described earlier. Using the same methods as described to determine, by correcting for temperature, radiant power and concentration of each, the calculated thickness of the residual Release & Coating. This will be determined by integrating the absorption response per pixel across the spectrum. Since the recipe of components used, during the manufacturing process all absorb UV energy, the amount of UV energy absorbed by the residual (left over) release & coating will be readily detectable and will vary in proportion to this residual thickness.
This “thickness” at this point is not dimensional. It relates only to the density of the coating in terms of the amount of each component present. We need to know the moisture content in order to give us a volume leading to a better idea of thickness and its topography information to give us depth information.
Measure the Moisture Content of the Residual Yankee Drier Coating
A liquid moisture-detecting camera will be used in determining the actual moisture content of the residual coating. Since the moisture content determines the hardness of the coating, a coating with little residual moisture content will be harder and denser than a coating with a greater concentration of water embedded. If the moisture content of the coating is too little or too great, degradation of the coating will occur in the form of cracking and its ability to give release of the tissue at the creping blade and improper adhesion at the Roll-Nip point.
In determining the actual moisture content of the Release Coating, we will take advantage of the absorption of liquid water in the 1900 nm to 1950 nm range. The moisture content of the coating will be non-linear but proportional to the formula; a*v1+v2+b*v3 where a+b=1. In the formula, v1 is symmetrical stretch of the H—O—H water molecule bonding distance of the hydrogen atoms from the Oxygen atom at its center. The v2 is a measure of a changing bond angle from the normal 104.4 degrees at 20 C. Finally, v3 is the asymmetrical stretch where the Hydrogen atoms are in stretch mode but one Hydrogen atom is stretching toward the Oxygen atom and the other away from it. There are many absorption bands for liquid water; however, we have chosen this band, even though it is of low energy, because it is more peculiar to water. The detected signals will reflect less interference from compounding absorption with other molecules in this spectral region. The intensity of the IR source for this camera will be varied to correct for the emissivity of the real time coating conditions and the ageing of the filament over time.
The calculations for the derivation of the actual coating thickness at this point, and with the methods described above, are rather intense. Mathematically determining coating thickness strictly from methods described thus far would at best implement a theoretical component, which could still lead us towards making incorrect process changes. From the implementation of the above methods, we will yield a good averaged determination of the Coating thickness across the Yankee surface. Coupled with the Moisture Camera readings, a very accurate Coating density can be obtained. A very accurate Coating temper can also be implied which tells us much about the quality of the coating and its ability to effect adherence of the tissue at the Roll-Nip point and its ability to release the tissue properly at the creping blade. It also will give us a good determination of the average derived topography of the over entire Yankee Drier Surface. However, knowing the exact topography of the Coated Yankee Drier surface is desirable in order to determine blade wear points and pin pointing defective release points at the Creping Blade as well as, defective adhesion points at the roll-nip.
Measure the True Topography of the Residual Yankee Drier Coating
In order to evaluate the coating properties reliably, knowing the exact topography of the coating, one must have an acute understanding of how the coating surface affects the functionality of the coating. For example; even if the coating properties, as revealed through the analysis of the methods described thus far, indicate a perfect moisture content, proper temper, adequate curing, etc., the height or thickness at a particular location on the Yankee Drier may be insufficient due to gouging by the Creping Blade mechanism. The instantaneous pressure along the length of the blade may be too high or too low. This can lead to a condition where the Creping Blade may modulate; self resonate, or create the condition commonly called “Chattering” across the Coated surface of the Yankee Drier. Imperfections in the tissue web being processed can lead to the same types of defects. Therefore, obtaining the exact shape of the Yankee Surface Coating is required.
The surface of the underlining Yankee machined surface is also important, not only from the aspect of maintenance, but due to the obvious fact that any imperfection in the machined Yankee metal surface will also replicate itself in the applied coating as well.
The device created to measure this will employ a line generating diode laser at 635 nm, a Plano-convex lens at 12.5 mm focal length in order to diverge (+/−45 degrees) the emitted rays back to straight and parallel in the original axis of emission. It will also employ a series of three optical slits measuring 10 microns×1 mm spaced 0.250 inches apart in order pass these focused parallel coherent beams of light onto the coated surface. The angle of emission when applied to a perfectly flat surface will effect reflection at an acute angle exactly equal to the angle of emission but away from the angle of emission. In other words, if the angle of emission hits a perfectly flat reflecting surface at an obtuse angle of 120 degrees the acute angle of reflection will be 90 degrees minus 30 degrees (90+30=120), which equals 60 degrees acute. When this ray reflects, it should land at a predictable location at some known distance from the reflected surface. We will be using a 3000 pixel line-scan camera to detect this reflection. As the surface becomes less flat, this perfect angle will disperse from the corresponding predicted pixel location. It will be received as distributed (a dispersion) amongst the adjacent pixels relative to the amount of imperfections on the reflecting coated surfaces. A modulated surface topography will show up on the CCD pixels of the Line-Scan Camera as modulated. Performing standard Fast Fourier Transform (fft) calculations on the individual scan data as measures will yield the type of deformations and their dimensions in order to reproduce accurate amplitudes and frequencies of surface defects encountered. These are a description of the microscopic hills and valleys on the surface, the dimensions of them, and the frequency of each type. The magnitude and frequency of these topography features can then be compared to settable limits in order to effect changes in process control. This Topography method, coupled with the previous methods, will be used to implement a feedback mechanism for the Tissue Process Control as well as the Yankee Coating Process control.
An interesting side effect of the Yankee coating Chemistry is that it is translucent. Although some lensing effect will occur, a secondary reflection will occur on the Yankee Drier machined metal surface. If it is perfectly flat, and ignoring the lensing affect (double passing through the Yankee Coating) as negligible, the reflected rays received on the CCD array should occur exactly shifted from the Coating Surface reflections equal to the dimension of the exact coating thickness. In other words, if the true thickness of the coating is 0.010″ thick, then this secondary Yankee Surface reflection should be exactly received by the pixel location 0.010 inches upward of the original reflection caused by the initial Coating refection. Of course, as the surface of each (Coating Surface and Yankee Surface) become worn, or out of tolerances, the dispersion of the beams will be evaluated with fft calculations, as described previously, in order to affect process control and or maintenance of both surfaces.
Correcting for the Alignment of the Detector Bank Array to the Yankee Drier
In order to be able to resolve the desired integrity of the signals coming in from the detector bank array for the Yankee Drier mechanism, we will have to be able to re-evaluate, continuously, the registration of the Detector Bank Array of sensors, per this discussion, to the Machined Yankee Drier Surface. This surface wears with use. Taking the Detector Bank and Rail system out for Yankee Drier maintenance will inject an associated misalignment when reinstalling the Detector Bank Array back into its scanning position. Therefore, it is necessary to create a means of evaluating the true alignment of the Detector Bank Array to the Yankee surface.
Array to the Yankee surface by Chromatic (color) Aberration. Color Aberration occurs due to that fact that different wavelengths of light, traveling through a lens, exhibit a different index of refraction at these differing wavelengths. Since this is true, different wavelengths will experience different focal points based on:
In using this principle, it is possible to create a distance finder by implementing the scheme described in the next diagram. This technique is well known and documented. However, we are mentioning it here as part of the mechanism for alignment detection, which is part of this invention. From the components chosen, and using a spectrometer to analyze the returning light, we should be able to resolve distances down to 0.001″ from the Yankee Drier Surface to the Detector Bank Array. The true distances being derived will allow us to implement corrections for misalignment in the instrument data in order to maintain dynamic real time calibrations.
The theoretical resolution for the components chosen should be 0.383/((1000 nm-200 nm)/(0.3 nm/pixel)) divisions or 0.00014 inches however, a resolution of 0.0014 inches is expected.
Basically, the closer the Yankee Drier Surface is to the Detector Bank Array, the more short wave will be in focus and will be reflected back where as if further away, more red light will be in focus at that distance and be reflected back toward the Spectrometer input.
A Further Description of the Creping Station
In
A measurement of the folding process (as the tissue hits the Creping Blade) is normally expressed in folds per inch. As the proper number of folds per inch (FPI) increases beyond a the desired target FPI , the Tissue will become weak losing its strength properties diminishing inter-fiber bonding to a level that is unacceptable. Conversely, if the FPI decreases the pliability of the product will diminish causing the product to be not as soft as would be desired. Maintaining the desired equilibrium is beyond the scope here but being able to measure the FPT is a required aspect of this invention. Since the Tissue Paper is traveling at a speed of around 27 inches per second, or at about 70 miles an hour, when it encounters the Creping Blade edge, the energy departed onto the Creping Blade edge is substantial. This is evident at how quickly the edges wear even though the edges are made of hardened metal alloy tips. When conditions are just right for this process, it is said that the tissue will explode at the Creping Blade. Under this principle, the Creping process is certainly going to carry this vibrational energy from the tip of the blade to its absorbing point, which is the holder. During this process, the plane (width) of the blade is going to oscillate as the wave moves through it. These waves will be at a frequency which equals this explosion frequency or a harmonic there of. In other words, it will become a Speaker humming a tune equivalent to the folds per inch of the Creping process. Installing a Piezoelectric microphone device near, or in close contact, along the oscillating plane of the blade will enable us to measure this frequency. Implementing a dual twin T notch type of filtering on the raw analog signals (removes unwanted frequencies, which will simplify the equations) and further applying Fast Fourier Transforms on the measures of data received will enable the derivation of the FPI (Folds/Inch) of the Tissue process.
It may be feasible to measure the Folds per inch of the Tissue by using a CCD device and lighting in a high contrast mode. It could be feasible to, mathematically, pull the FPI sine wave generated out of the signals using fft calculations.
As both Blades increase in wear, a noticeable temperature change should occur due to the corresponding change in friction. Placing temperature detectors along the length of the Blade Planes should indicate the amount of wear as these temperature differential moves across the blade planes. In addition, if the Doctor Blade cuts through the Yankee Coating, the temperature rise will be quickly dramatic, indicating the need for the immediate attention of the operator. This will be an audio alarm and an appropriate texting message to the operator.
The force of the blade assembly across the entire length of the Yankee Drier needs to be monitored. If the force exerted on the Blades is not correct, or if a hot spot develops during production, damage to the coating and or Yankee Drier Surfaces will occur. The force exerted on the blades and the blade assembly will cause a deflection on the blade plane (width). Changes on this pressure during the process will occur as the blades wear but also could arise for other reasons as well. For instance, if a wet spot is encounter in the tissue web. This condition will soften the coating slightly thereby decreasing the blade force slightly. Many conditions can change this force in production. However, for the purposes of this invention, it is sufficient to say that changes will occur and that those changes will need to be monitored.
The Hall Effect Method (see
The Capacitive Load Cell shown in
Load Cells (see
The Capacitive Plate method (see
The LED intensity method (see
As is now apparent, are several ways this can be monitored. A Hall effect sensor, to measure changes in magnetic field, could be used. Creating a magnetic field above and below the Blades assembly will initiate measurable disturbances in that field as blade deflection occurs. This assumes an Iron component to the metallurgy of the blades.
Load cells could be installed which, as deflection occurs, will cause a proportional force to be applied on the load cell device. Placing load cells every inch along the Blade planes should give accurate description of the blade pressures at any point.
Capacitive change type of detection can be used which works on the principle of changing the distance of the gap between two or more plates will change the value of the microfarad value. If the Creping Blade acts as one plate while another plate mounted above the blade acts as a charged reference, as the blade deflects due to a changing pressure, the capacitor value of these plates will change proportionally. This change can be measured and amplified.
Finally, a changing light intensity can be employed, which will measure the changing distance between the Creping blade and the emitter-receiver pair. This changing distance is proportional to the force on the blade assembly.
Roll Up Inspection Station
This station (see
A Final Solution
The final solution (see
In evaluating the residual Coating thickness and the residual component concentrations of that coating, then correlating this data to the linear movement across the Yankee Drier surface by a linear ball screw device, we will be able to develop a complete profile of the Yankee Drier Coated surface in real time. Minute changes in the integrated absorption response, Topography, temperature, and moisture content, will be proportional to the quality of the residual coating and to the quality of the tissue being made. We should be able to vary the original recipe component concentrations in order to effect quality enhancements in the manufacturing of the tissue product in real time, while dynamically maintaining the desired quality of the coating as well. By passing the Detector Bank Array back and forth along the Yankee Drier surface, we will be able to develop a surface profile. This Profile will pin point problems in manufacturing such as correcting deficient areas of Coating by adjusting the recipe, changing flow rates, and warning the operator of problems elsewhere in the process that could affect quality or downtime. An example of the latter would be a wet spot cause by a vacuum problem on the felt or a dry spot caused by insufficient fiber content in the stock being fed at a location in the head box as well as a multitude of other process problems. In any case, Correcting the issues mentioned will lead to better overall Quality, decreased down time, and increase all of our profits, and just as a subtlety... initiate a propensity toward longer Blade life . . . a successful proposition for us all.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting. As used in the specification and appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth as used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless otherwise indicated, the numerical properties set forth in the specification and claims are approximations that may vary depending on the desired properties sought to be obtained in embodiments of the present invention. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. One of ordinary skill in the art will understand that any numerical values inherently contain certain errors attributable to the measurement techniques used to ascertain the values.
Having described the disclosure in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these preferred aspects of the disclosure.
This application claims the benefit of U.S. Provisional Application Serial No. 61/711,462 filed Oct. 9, 2012.
| Number | Date | Country | |
|---|---|---|---|
| 61711462 | Oct 2012 | US |
