Patent Application
20170327337
In the manufacturing and conversion of web materials, particularly fibrous web materials, and more specifically tissue web materials, the properties of the web are monitored by means of on-line measurements. The measurements are conducted in the cross-machine direction (CD) of the web in order to produce a CD profile of the measured property. Typically the measurements are performed by means of measuring apparatuses in which the moving web is measured by means of a measuring sensor moving back and forth in the CD. The properties to be measured may include, for example, moisture, caliper, basis weight, ash content, color, opacity, brightness, gloss, or smoothness of the web.
The results obtained from the measuring sensors are used not only for monitoring the properties of the web, but also for controlling the manufacturing and converting processes. For example, the measurement results may be transmitted to a control unit where they are utilized to determine control signals for profiling apparatuses belonging to either the manufacturing or converting process. Based upon the control signal the manufacturing or converting process may be adjusted to alter the CD properties of the web.
To-date however, it has not been possible to quickly and accurately measure the CD caliper of a web in real time so as to use the measurement to accurately and effectively control the manufacturing and converting processes. For example, methods that rely upon moving a sensor across the web in the CD are not sufficiently fast to enable accurate and reliable control. Similarly, sensors that sense only a small portion of the web do not provide sufficient data regarding the CD web profile upon which to base process control. Thus, there remains a need in the art for a method of quickly and accurately measuring web caliper across at least a portion of the cross-machine direction of the web and controlling one or more manufacturing or converting operations based upon the measured web caliper.
Moreover, there remains a need in the art for a method of coordinating caliper control by calendering and finished roll winding that provides for well wound finished product rolls and is capable of preserving desired physical properties of the web substrate throughout the entirety of the winding process.
The present inventors have now discovered a means of accurately and quickly measuring web caliper in real time during the converting process, which measurement may be used to control one or more manufacturing or converting unit operations. For example, in one embodiment the present invention provides a method of using a winding apparatus to wind tissue web onto a core to form a rolled tissue product, comprising the steps of providing a first winding algorithm; winding the tissue web about the core in accordance with the first winding algorithm; measuring the caliper of the web across at least a portion of the cross-machine direction of the web, such as across at least a 2.0 cm portion of the web and more preferably at least a 3.0 cm portion of the web; comparing the measured caliper to a target caliper value; providing a second winding algorithm based upon the comparison of the measured caliper to the target caliper; and adjusting at least one winding parameter in accordance with the second winding algorithm.
In other embodiments the present invention provides a web winding and measuring system, comprising a calender system; a rotatably-mounted spool onto which a web of material is wound to form a roll; a draw roll over which a web of material is conveyed prior to being wound to form a roll; a light-emitting device configured to illuminate the web as it is conveyed over the draw roll, providing a line on the upper surface of the web in a cross-machine direction; a light-receiving device configured to detect the line; a means for generating measurement data from the detected line; a computing device communicatively coupled to the light-receiving device and configured to receive the measurement data and calculate web caliper; a comparison means for comparing the calculated web caliper to a target web caliper value and determining whether the target web caliper has been achieved, upon determining that the at least one target characteristic has not been achieved, determine an adjustment to at least one parameter to achieve the target characteristic; and adjust the at least one parameter based on the determined adjustment.
In still other embodiments the present invention provides a web winding and measuring system, comprising a web tensioning system; a rotatably-mounted spool onto which a web of material is wound to form a roll; a draw roll over which a web of material is conveyed prior to being wound to form a roll; a light-emitting device configured to illuminate the web as it is conveyed over the draw roll, providing a line on the upper surface of the web in a cross-machine direction; a light-receiving device configured to detect the line; a means for generating measurement data from the detected line; a computing device communicatively coupled to the light-receiving device and configured to receive the measurement data and calculate web caliper; a comparison means for comparing the calculated web caliper to a target web caliper value and determining whether the target web caliper has been achieved, upon determining that the at least one target characteristic has not been achieved, determine an adjustment to at least one parameter to achieve the target characteristic; and adjust the at least one parameter based on the determined adjustment.
These and other embodiments of the present invention will now be described further in the following detailed description taken in connection with the accompanying drawings.
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the disclosure.
The present invention solves the problem of accurately measuring the thickness of a moving web, and in certain embodiments a non-planar web being conveyed over a conveying surface, and making adjustments to the web converting machinery based upon the measured web caliper. Generally the web caliper is measured without contacting the web and in real time while the web is being conveyed at high rates of speed. At the same time the method provides for caliper measurement across at least a portion of the web in the cross-machine direction, which further improves the accuracy of the caliper measurement and is a significant improvement over single point measurements. Additionally, by measuring across at least a portion of the cross-machine direction and by taking a continuous measurement, a three dimensional image of the web surface may be generated. The three-dimensional image not only provides for a highly accurate caliper measurement, but provides the additional benefit of enabling the detection of flaws in the web.
Further, the accurate and continuous measurement of web caliper may be used to improve the manufacture and processing of the web. For example, winding of the web may be improved by enabling compressive strain to be accurately determined and continuously monitored during winding. Compressive strain is determined from the difference between the actual thickness of the layers of material on the roll and the theoretical thickness of layers of material wound with no compressive strain. The actual thickness of the layers of material on the roll is obtained by accurately measuring the length of material in each layer on the roll and hence the diameter of each layer. The thickness of a band comprising a number of layers can be calculated from the difference of the diameters of its inner and outer layers. By continuously measuring the thickness of the material before it is wound onto the roll, variations in the thickness of the material can be taken into account in determining the compressive strain, increasing the accuracy of the measurement. This results in improved roll structure control and fewer rejected rolls.
Accurate web caliper measurement may also enable more accurate web tension control. For example, the measured caliper may be used to calculate sheet density, which may be in-turn used to adjust the metered winding algorithm. Adjustments to the winding algorithm may control the rotational speed of the mandrel in order to maintain the web of material under constant tension.
Measurement of web caliper may also be used to control the tension of the web as it is fed to the log winding device. For example, the web may be trained around a driven draw roll and then passed through a dancer assembly. From there, it may be trained under a guide roll and drawn into the log winding device. In response to tension changes in the web, the dancer assembly moves from its reference position to lengthen or shorten the web path as necessary to maintain uniform tension in the web. The dancer motion may be controlled by applying a drive torque or a holdback torque to the draw roll depending on detected web caliper. That, in turn, decreases or increases the tension in the web entering the dancer assembly as needed to return the dancer assembly to its reference position.
Additionally, the accurate and continuous measurement of web caliper may be used to adjust web caliper prior to winding the web into a rolled product, such as by adjusting calendering of the web. Thus, in certain embodiments, to properly control the structure of the finished roll product the caliper of the web may be measured prior to winding, and more preferably immediately prior to winding, to generate a first caliper measurement value. The first caliper measurement value may be compared to a desired caliper measurement value to yield a determined caliper differential, which may be in-turn be used to adjust the calendering system load profile.
Turning now to
When using a calendering device, the calendering device may be a gap calendering device or a contact calendering device. Further, the rollers 14 and 16 may be steel rollers, rubber-coated rollers, or mixtures thereof. In addition to a calendering device, any suitable caliper control device may be used in accordance with the present invention. For example, in an alternative embodiment, an embossing device may be used in order to control the caliper of the web. In still other embodiments the caliper may be controlled by adjusting tension in the web as the web is unwound from the parent roll. Tension control devices are well known in the art and may include, for example, a dancer roll.
With further reference to
In their operational positions the first 14 and second 16 opposed calender rollers are held by two hydraulic actuators 15, 17, which act on the mounting faces of the rollers. With the aid of stops against which the piston of the lower hydraulic actuator works the bottom roller 14 is held in a predetermined position. The position of the second roller 16 is adjusted by lowering or raising with the aid of the upper hydraulic actuator 17.
The weight of the rollers 14 and 16, because of their vertically shiftable mounting, produces a minimal pressure on the roller nip 18. This pressure can be increased with the aid of a loading device, which in one embodiment acts on the top roller with a downward force and, in an exemplary embodiment, consists of a hydraulic actuator 17 capable of inserting small increases of downward force on the two mounting faces of the top roller 14. While this is an exemplary embodiment of a calendering operation the specific structure of the calendering stack is not critical to the functioning of the invention.
Once the web 40 leaves the calender nip 18 it is passed over a series of draw rolls 30, 32, 34, 36 and finally to a log winding device (one embodiment illustrated further in
The system further comprises a first computing device 102 communicatively coupled to a hydraulic pressure control unit 26, which is in-turn communicatively coupled to a hydraulic actuator 21. The hydraulic actuator 21 comprises a moveable arm 23 which is in communication with a calender roll 16 to move the roll from a first to a second position. Additionally the system 100 comprises a caliper meter 50 communicatively coupled to the interface board 124. The interface board 124 may be communicatively coupled to a router or switch 126, which is in communication with the first computing device 102 and the PLC 26. In some implementations, a second computing device is communicatively coupled to the PLC.
In the illustrated embodiment, the first computing device 102 generates instructions for configuring the PLC 26 to control the actuator 21. More specifically, the first computing device 102 generates instructions based on predetermined parameters for controlling winding of a web 40 into a roll 90. The parameters incorporate assumptions regarding, for example, the density and compressibility of the finished roll 90, a target number of sheets in the finished roll 90, and a target diameter of the finished roll 90. The first computing device 102 configures the PLC 26 to operate in accordance with the parameters. More specifically, the PLC 26 transmits instructions to the actuator 21 to operate the calender system 12 according to caliper loading algorithm 24 based on the parameters. The caliper loading algorithm 24 dictates the relative position of the first 14 and second 16 calender rolls, which in-turn affects the calender nip pressure, based on the parameters.
The caliper meter 50 repeatedly emits light 52 towards the upper surface 42 of the web 40 and samples the light to generate measurement data. The caliper meter 50 transmits the measurement data to the interface board 124. The interface board 124 may further be configured to receive additional information regarding the web, the roll and the winding device, such as the relative position of the winding device mandrel, the web tension and speed of the winding device. The interface board 124 transmits the measurement data to the first computing device 102.
The first computing device 102 receives the measurement data from the interface board 124 and calculates the web caliper (Mc). As the web 40 is continuously wound into rolls 90 the caliper meter 50 repeatedly generates measurement data and transmits the measurement data to the first computing device 102 through the interface board 124. Accordingly, the first computing device 102 continuously collects measurement data and repeatedly calculates the caliper of the web as the roll 90 grows. In some embodiments, the first computing device 102 generates, in memory, a three dimensional profile of the web of material based on the collected measurement data. In other suitable implementations, the first computing device 102 determines at least one target characteristic of the roll 90 to be achieved by the web winding and measuring system 100 and analyzes the measurement data to determine whether the at least one target characteristic has been achieved. The at least one target characteristic may include, for example, a target number of sheets of the roll 90, a target diameter for the roll 90, and/or a target ratio of a number of sheets of the roll 90 to a diameter of the roll 90.
In some embodiments the first computing device 102, upon determining that the at least one target characteristic has not been achieved, determines an adjustment to at least one parameter to achieve the target characteristic. The first computing device 102 then transmits the at least one adjusted parameter to the first computing device to the PLC 26 to cause the PLC 26 to be configured based on the at least one adjusted parameter. In some implementations the first computing device 102 determines, for example, an adjustment to the calender nip pressure by the actuator 21.
Additionally, in some embodiments, and as described in more detail herein, the first computing device 102 generates a mathematical model of how the starting parameters and operating parameters affect the resulting characteristics of a roll. The first computing device 102 generates the mathematical model by applying one or more statistical techniques, such as linear or polynomial regression, and/or principal component analysis to the collected data to determine how parameters affect the resulting characteristics of a roll and which parameters have the most influence in affecting the resulting characteristics of the roll.
Accordingly, upon entering a set of parameters into the first computing device, an operator of the web winding and measuring system may execute a simulation of forming a roll, based on the parameters, prior to actually forming the roll on the web winding and measuring system. In other instances, an operator may enter a set of target characteristics and starting parameters into the first computing device and the first computing device provides the operator with a set of operating parameters required to achieve the target characteristics, based on the mathematical model. To control the caliper of the web, the first computing device may be configured with a comparison means that compare the measured caliper values to the target caliper values. On the basis of the comparison, the comparison means forms an error profile that may be used to determine a corrected error profile. The corrected error profile may be transmitted to the PLC for controlling the calender nip load. For example, using the corrected error profile a new control signal may be transmitted to one or more actuators to adjust the calender nip pressure.
One method for determining corrected error profiles and new control commands is illustrated in block charts in
As was stated above, the control unit comprises means for controlling the manufacturing or finishing process of a web. In addition to the above-mentioned means the control unit may also comprise other means. The steps of the above-described control method can be performed by a program, for example a microprocessor. The means may be composed of one or more microprocessors and the application software contained therein. The means may also comprise means for transmission of information and signals between the means. In this example, there are several means carrying out the steps, but the different steps of the method can also be performed in a single means. The means for determining the corrected error profile can be arranged as an independent part of the control unit, or they can be integrated as a part of the control means. The means for determining the corrected error profile can also be arranged as a separate program unit outside the control unit. Thus, the control unit and the means for determining the corrected error profile have been provided with means for transmitting information between them.
The measurement results measured by the measuring devices can be transmitted to the control unit via conductors or wirelessly. If the measurements are transmitted to the control unit wirelessly, the measuring means are provided with a transmitter for transmitting measurement results, and the control unit is provided with a receiver for receiving measurement results. The control commands produced by the control unit can also be conveyed to the control unit either via conductors or wirelessly. If the control commands are transmitted to the actuators wirelessly, the control unit is provided with a transmitter for transmitting control commands and the actuator is provided with a receiver for receiving control commands.
Turning now to
In the illustrated embodiment the caliper measurement device 50 comprises a radiation source 51 which generates a line 45 generally oriented in the cross-machine direction (CD), which is generally perpendicular to the machine direction (MD). The caliper measurement device 50 further comprises a detector 46 configured to detect radiation reflected from the surfaces of the upper surface 42 of the web 40 or the surface 38 of the draw roll 36. The radiation source 51 and detector 46 are generally illustrated as being contained within a single apparatus, i.e., caliper measurement device 50, however, in certain embodiments the devices may be housed separately.
The radiation source may be any structure for generating an illumination line, such as a laser or narrow-band light emitting diode (LED) and optics for focus and fine line generation. The radiation source could generate radiation with substantially identical visible or other wavelengths, although different wavelengths can be used. For instance, near-infrared (NIR) wavelengths could be used. The radiation source may produce radiation continuously or in a pulsed fashion, meaning the illumination line 45 could be generated intermittently or continuously. In the illustrated embodiment the radiation source projects a reference laser plane towards the upper web 42 and forms a line 45 in the cross-machine direction on the surface 42 of the web 40. While the line is illustrated as being projected normal to the nominal web surface other angles maybe used so long as the line illuminates a portion of both the web surface and the conveyor surface. In certain embodiments the line measures at least about 1.0 cm, still more preferably at least about 2.0 cm and still more preferably at least about 3.0 cm, such as from about 3.0 to about 10.0 cm.
The detector 46 detects the illuminated line 45. The detector 46 may be any suitable structure for capturing information about lines projected onto a sheet. In one embodiment the detector 46 comprises a lens 47 and a detector array 48. In addition to providing a focused image, the lens 47 may include filters to exclude unwanted wavelengths of light from acquired images. The detector array 48 may be photo-detector arrays of either linear or matrix types, or Position sensing photodiodes (PSDs) which provide image position data as a voltage. Where photo-detector arrays are used, processing to determine zone image position can use thresholded centroids and multiple centroids or first moment calculations. Suitable detector arrays include, for example, a charge-coupled device (CCD), a complementary metal oxide semiconductor (CMOS) device, or a charge injection device (CID).
In the illustrated embodiment a single light source 51 projects a line of light 45 such that light is reflected from the upper surface 42 of the web 40 in nominal alignment along a reflection axis. The reflected light is assessed for displacement from a nominal position (for example height of the surface from which the light is reflected, i.e. vertical displacement). A measurement plane is defined to include the reflection axis and the possible displaced locations of the reflections. The reflected light passes through the lens 47 and is detected by the detector array 48.
The analysis of the images captured by the detector could be performed by any suitable device or system. In some embodiments, the detector is included within a “smart” camera, where some or all operations in the analysis of an image and the calculation of a triangulated distance to a point are done by the camera itself. In other embodiments, the detector provides images or other information to an external device or system that processes the images and calculates the triangulated distances. For example, as illustrated in
In one embodiment the distance between the surface 38 of the draw roll 36 and the caliper measuring device 50 is first determined by illuminating the surface 38 with a line of light 45 prior to the web 40 being conveyed over the surface 38 of the draw roll 36. The caliper measuring device 50 is located a distance H above the surface 38 and a horizontal distance x from radiation source 51. Detector 48 detects the line 45. A computerized Image processing unit 102 computes the height (H1) from the caliper measuring device 50 to the surface 38 by applying the formula:
where θ is the angle at which detector 48 views line 45. A second measurement (H2) is taken once the web 40 is being conveyed along the surface 38 of the draw roll 36. With the addition of the web 40 to the draw roll surface 38 the height increases causing θ to increase. Further as the height of the web relative to the surface of the draw roll increases and decreases the value of θ increases and decreases.
The actual position of line 45 and the vertical distance of line 45 above the surface 38 of the draw roll 36 can be determined by triangulation. It is a straightforward image processing task to determine the angle φ and the height (H2) from the images captured by the camera. Once H2 is determined, caliper (C) of the web 40 is calculated by simply subtracting H1 from H2. Although the camera cannot see the bottom surface of the web (surface opposite the upper surface 42), it is assumed that the lower surface lies substantially in-plane with the known plane of the conveyor surface 16.
In other embodiments the height of the draw roll surface (H1) and the height of the web (H2) are measured concurrently by illuminating the upper surface of the web and the draw roll surface concurrently as the web is conveyed across the surface. In this embodiment the upper web 40 surface 42 and the draw roll surface 38 are illuminated using a radiation source 51 to form a line 45 disposed substantially in the cross-machine direction of the web 40 normal to the machine direction and the direction of travel of the web. Thus, the line 45 extends beyond the edge 44 of the web 40 and onto the surface 38 of the draw roll 36. To determine the location of the edge 44 a matrix array is used to sense the line 45. A contour of the web surface 42 is produced by the light section principle, and the location of the edge 44 can be determined by the location of rapid contour fall of the image. For example, by sequentially scanning lines of the array of the first location at which the line location is for example, 100 pixels less than the previous, can be chosen as the edge 44 of the web 40. The caliper C of the web 40 may then be calculated by simply subtracting H1 from H2.
In addition to the encoder 220 a caliper measurement device 50 is communicatively coupled to the interface board 124. The caliper measurement device 50 preferably continuously measures at least a portion of the web caliper in the cross-machine direction as the web is being conveyed over the surface 38 of the draw roll 36 before it is wound into a roll on the mandrel 138. Preferably the CD portion of the web measured by the caliper measurement device is at least about 1.0 cm, still more preferably at least about 2.0 cm and still more preferably at least about 3.0 cm, such as from about 3.0 to about 10.0 cm. The interface board 124 is communicatively coupled to a first computing device 102.
The first computing device 102 may also be communicatively coupled to a second PLC 26 for controlling a calender unit. Based upon measurement data received from the caliper measurement device 50 the first computing device 102 may generate signals to control the calender device as described above. In this manner measurement data from the caliper measurement device 50 may be transmitted to the first computing device 102 and used to adjust the web caliper by making adjustments to the calender system load profile. The adjusted web caliper may then be measured and fed forward to adjust the metered winding algorithm used to control the winding apparatus and/or one or more components of the winding apparatus.
In the illustrated embodiment, the first computing device 102 generates instructions for configuring the PLC 204 to control the servo drive 206. More specifically, the first computing device 102 generates instructions based on predetermined parameters for controlling winding of a web of material into a roll. The parameters incorporate assumptions regarding, for example, the density and compressibility of the finished roll, a target number of sheets in the finished roll, and a target diameter of the finished roll. The first computing device 102 configures the PLC 204 to operate in accordance with the parameters. More specifically, the PLC 204 transmits instructions to the servo drive 206, to operate the servo motor 208 according to an electronic cam profile based on the parameters. The electronic cam profile dictates positions and velocities for the servo motor 208, based on the parameters. The servo drive 206 transmits power and instructions to the servo motor 208 in accordance with the electronic cam profile and receives feedback regarding the position and/or velocity of the servo motor 208 from the encoder 210.
The servo motor 208 rotates the motor pulley which is coupled to the spool pulley by the drive belt. As the spool pulley rotates the spool the encoder 220 generates position and velocity data about the spool and transmits the data to the interface board 124. A tension sensor 221 measures tension exerted by the spool on a web of material being wound by the spool and transmits tension data to the interface board 124. The caliper measuring device 50 repeatedly emits light 52 towards the web (not illustrated) traveling over the draw roll 36 and samples the light to generate caliper data, as described in more detail above. The caliper measuring device 50 transmits the measurement data to the interface board 124.
The first computing device 102 receives the measurement data from the interface board 124 and calculates the caliper of the web. As the web continuously passes over the draw roll 36 and is wound into a web on a core supported by the mandrel 138, the caliper measuring device 50 repeatedly generates measurement data and transmits the measurement data to the first computing device 102 through the interface board 124. Accordingly, the first computing device 102 continuously collects measurement data and repeatedly calculates the caliper of the web as the roll grows.
Thus the controller may be configured to receive the calculated caliper of the web immediately prior to its being wound into a roll and, based on this information, to then control the metered winding algorithm should the caliper of the web be outside preset limits. Specifically, the controller can be configured to make adjustments in the amount of tension that is placed upon the web of material during winding. Through the system, the diameter of the rolls of material produced and/or the firmness of the rolls of material produced may be controlled within preset limits such that every roll produced has substantially uniform and desirable characteristics.
When introducing elements of the present disclosure or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Many modifications and variations of the present disclosure can be made without departing from the spirit and scope thereof. Therefore, the exemplary embodiments described above should not be used to limit the scope of the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US14/72755 | 12/30/2014 | WO | 00 |
