Patent Application
20250020502
The present invention generally relates to quality control techniques for fabricating sheet materials and, more particularly, to systems for measuring the actual gross weight of a roll immediately after its production in a sheet making facility. The weight data allows dynamic verification of the accuracy of on-line basis weight measurements so that adjustments to the operating conditions of the sheetmaking process can be made.
On-line measurements are used to detect properties of sheet materials during manufacture to enable prompt control of the sheetmaking processes and, thus, to assure sheet quality while reducing the quantity of substandard sheet material which is produced.
In the manufacture of paper on continuous papermaking machines, a web of paper is formed from an aqueous suspension of fibers (stock) on a traveling mesh papermaking fabric and water drains by gravity and suction through the fabric. The web is then transferred to the pressing section where more water is removed by pressure and vacuum. The web next enters the dryer section where steam heated dryers and hot air completes the drying process. The paper machine is, in essence, a water removal system. A typical forming section of a papermaking machine includes an endless traveling papermaking fabric or wire, which travels over a series of water removal elements such as table rolls, foils, vacuum foils, and suction boxes. The stock is carried on the top surface of the papermaking fabric and is de-watered as the stock travels over the successive de-watering elements to form a sheet of paper. Finally, the wet sheet is transferred to the press section of the papermaking machine where enough water is removed to form a sheet of paper.
It is well known to continuously measure certain properties of the paper material in order to monitor the quality of the finished product. These on-line measurements often include basis weight, moisture content, and sheet caliper, i.e., thickness. The measurements can be used for controlling process variables with the goal of maintaining output quality and minimizing the quantity of product that must be rejected due to disturbances in the manufacturing process. The on-line sheet property measurements are often accomplished by scanning sensors that periodically traverse the sheet material from edge to edge. It is conventional to measure the basis weight and/or caliper of sheet material after it leaves the main dryer section or at the take-up reel with scanning sensors. The basis weight of the sheet material produced is an important property however current production methods only provide online measurement estimates.
The present invention is based, in part, on the development of a wireless technique of measuring the gross weight of the sheet material that is wound on the finished reel spool which generates real time weight readings to a control system. The actual weight measurements allow for fast dynamic correlations and verifications to the online estimate weight measurements. The operator can then adjust operating parameters of the various actuators and sensors in the papermaking process in response to measurement discrepancies.
In one aspect, the invention is directed to a sheet production system that includes:
In another aspect, the invention is directed to a method of operating a sheetmaking system that produces a continuous sheet that travels in the MD which includes:
In a further aspect, the invention is directed to an apparatus for determining the gross weight of sheet material on a roll that includes:
In one embodiment, the apparatus includes a pair of lifting devices each equipped with a load cell which is connected to a Wi-Fi signal transmitter or a Bluetooth signal transmitter.
While the invention will be illustrated as being implemented in papermaking, it is understood that the invention is applicable in other continuous sheet making processes such as, for example, in the manufacturer of rubber sheets, plastic films, lithium-ion battery electrodes, fabrics and the like.
The papermaking machine 2 includes a headbox 8, which distributes an aqueous pulp suspension uniformly across the machine onto a continuous screen or wire 30 that is moving in the machine direction (MD). Headbox 8 includes slice openings through which the pulp suspension is distributed onto screen or wire 30 which comprise a suitable structure such as a mesh for receiving a pulp suspension and allowing water or other materials to drain or leave the pulp suspension. The formation of the paper sheet 12 is influenced by a plurality of linear actuators 3 extending in the cross direction across the sheet 12 of paper being formed. Actuators 3 control the sheet's weight in the cross direction (CD). Sensors located downstream from the actuators measure the properties of the sheet. The feedstock is fed from the head box through a gap or elongated orifice 5 onto a wire section 30. The orifice or gap is a relatively narrow opening that extends across the width of the machine. Weight profile control in such an arrangement is achieved by locally adjusting the position of the slice lip across the machine with motorized linear actuators 3 to vary the dimensions of the gap or orifice immediately adjacent the actuator. As used herein, the “wet end” forming portion of sheetmaking system 10 comprises headbox 8 and wire 30 and those sections before the wire 30, and the “dry end” comprises the sections that are downstream from wire 30.
Sheet 12 then enters a press section 32, which includes multiple press rolls where sheet 12 travels through the openings (referred to as “nips”) between pairs of counter-rotating rolls in press section 32. In this way, the rolls in press section 32 compress the pulp material forming sheet 12. This may help to remove more water from the pulp material and to equalize the characteristics of the sheet 12 on both of its sides. A tachometer 38 measures the MD line speed.
As sheet 12 travels over a series of heated rolls in dryer section 34, more water in sheet 12 is evaporated. A calendar 36 processes and finishes sheet 12, for example, by smoothing and imparting a final finish, thickness, gloss, or other characteristic to sheet 12. Other materials (such as starch or wax) can also be added to sheet 12 to obtain the desired finish. An array of induction heating actuators 24 applies heat along the CD to one or more of the rollers to control the roll diameters and thereby the size of the nips. Once processing by calendar 36 is complete, sheet 12 is collected onto reel 14. A Wi-Fi or Bluetooth receiver is positioned in the vicinity of reel 14.
Sheetmaking system 10 further includes an array of steam actuators 20 that controls the amount of hot steam that is projected along the CD. The hot steam increases the paper surface temperature and allows for easier cross direction removal of water from the paper sheet. Also, to reduce or prevent over drying of the paper sheet, paper material 14 is sprayed with water in the CD. Similarly, an array of rewet shower actuators 22 controls the amount of water that is applied along the CD.
In order to control the papermaking process, selected properties of sheet 12 are continuously measured and the papermaking machine 2 adjusted to ensure sheet quality. Typical physical characteristics of paper that are can be measured include, for example, thickness, basis weight, moisture content, chemical composition such as ash, surface roughness, gloss, caliper, color, and crepe pattern surface features. CD control may be achieved by measuring sheet properties using one or more scanners 26, 28 that are capable of scanning sheet 12 and measuring one or more characteristics of sheet 12. For example, scanner 28 could carry sensors for measuring the dry weight, moisture content, ash content, or any other or additional characteristics of sheet 12. Scanner 28 includes suitable structures for measuring or detecting one or more characteristics of sheet 12, such as a set or array of sensors. Scanner 28 is particularly suited for measuring the dry end dry weight and caliper of the paper product at the take-up reel 14. Suitable caliper scanning sensors, are described in U.S. Pat. No. 6,967,726 to King et al. and U.S. Pat. No. 4,678,915 to Dahlquist et al., which are incorporated herein by reference.
Measurements from scanners 26 and 28 are provided to control system 4 that adjusts various actuators or operations of papermaking machine 2 that affect machine direction and cross direction characteristics of sheet 12. A machine direction characteristic of sheet 12 generally refers to an average characteristic of sheet 12 that varies and is controlled in the machine direction. In this example, control system 4 is capable of controlling the dry weight of the paper sheet by adjusting the supply of pulp to the headbox 8. For example, control system 4 could provide information to a stock flow controller that regulates the flow of stock through valves and to headbox 8. Control system 4 includes any hardware, software, firmware, or combination thereof for controlling the operation of the sheetmaking machine 2 or other machine. Control system 4 includes computer with a processor and memory storing instructions and data used, generated, and collected by the processor.
Depending on the properties being monitored, the scanning sensors can be configured to operate in the transmissive mode or reflective mode. Basis weight scanning sensors are described, for example, in U.S. Pat. No. 10,935,368 to Tixier and U.S. 2015/0022220 to Tixier and Hughes, which are incorporated herein by reference. For instance, scanner head 54 can house a radiation source that directs a beam of radiation into a moving web or sheet 26 and scanner head 56 houses a radiation receiver that detects radiation that is transmitted through the material. As the dual scanner heads advances back and forth along the CD, the sensor measures one or more properties of the web or sheet 60. In the reflective mode, the upper scanner head 54 can house both a radiation source and detector to measure one or more characteristics of the web or sheet 26.
During paper production, the basis weight, caliper, sheet width and machine direction speed of the moving sheet of paper are continuously monitored. The accumulated data allows the weight of the paper that is wound onto a spool of a finished roll to be estimated.
The RFID tag can be either passive, active or battery assisted passive. Active tags have batteries and transmits signals intermittently. Battery assisted passive tags are activated when it is activated by an RFID reader. Passive tags do not have batteries and use the radio energy transmitted by the reader for its energy source. Passive tags include an integrate circuit that is coupled with a transponder antenna for receiving interrogation signals from a RFID reader antenna and for transmitting a transponder signal. In this example, the tags used are passive. Reading or scanning spool tag 80 reveals this spool's unique identification number which in turn allows retrieval of its tare weigh from the database. Alternatively, the tare weight can be stored into the tag 80 so that reading the tag will reveal the tare weight.
A lifting device 96 includes a cable 98 with a distal end 100, which is attachable to an overhead or bridge crane (not shown), and a proximal end which is secured to the top end of a strain gauge load cell 104 while a crane hook 106 is connected to its lower end. The load cell is operatively connected to a wireless transmitter 108.
The load cell 104 is capable of sensing the weight of the roll 82 and the transmitter sends wireless signals that includes information representative of the weight. In operation, a pair of lifting devices each with a weight sensor and associated wireless transmitter are employed to raise the roll 82. The two load cells in the pair of lifting devices are calibrated so that their combined readings indicate the weight of the roll. The transmitter devices can be configured to operate under any known wireless communication protocols such as, for example, Wi-Fi and Bluetooth. Weight signals from the pair of transmitter devices are received by wireless receiver 40 (
The RFID reader 110 in
The present invention can be applied to other sheet making processes that produce liquid containing materials that are wound into a roll such as in the production of lithium-ion electrodes.
The coater 206, such as a tape casting coater, includes actuators that control a slot die/doctor blade to regulate the amount of slurry that is extruded onto the sheet 230. A dryer 210 removes excess solvents and cures the slurry that is on a moving coated sheet 232 to form an electrode layer on the sheet. Imaging devices 258 and 278 capture surface images of the coated sheet 232 before and after the dryer 210.
A scanning beta gauge 212 measures the basis weight and/or thickness of the moving coated sheet 232 exiting the dryer 210 after the calender 254. Thereafter, rolling supports 234, 236 reverse the orientation of a moving sheet 238 so that the uncoated side is on top whereupon a coater 214 applies a layer of electrode slurry on the top uncoated surface of a moving sheet 238. The basis weight and/or thickness of a double-side coated sheet 240 are then measured with a scanning beta gauge 16 before entering a dryer 218. Imaging devices 270, 272, 274 and 276 are strategically located to capture top and bottom surface images.
Further downstream, a beta gauge that is housed together with an infrared temperature sensor in a scanning device 224 measures the basis weight and/or thickness and the temperature of the double-coated sheet 242 as the scanning device 224 moves back and forth across the double-coated sheet 242. In particular the basis weight of each electrode layer is measured. A rewinder takes up the double-side coated sheet 242 into roll 244 which includes a reel spool 246 that is supported on rails (not shown). Surface defects on the top and bottom coatings are monitored by imaging devices 226, 228. The roll 244 is typically transferred to a calendering station whereby the double-coated electrode layer from the roll is unwound and passes through a calender which finishes and smooths the electrode layer.
Reel spool 246 includes an RFID tag which can transmit an identification number and/or its tare weight. Before undergoing the calendering process, a pair of the lifting devices shown in
The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.
