Method to measure tension in a moving web and to control properties of the web

Abstract

A process for determining the tension in a moving web is provided. The process includes the step of providing a web that is moving at a determined speed. The speed has a determined basis weight. A wave is created in the moving web. The speed of the propagation of the wave is determined. Also, the tension on the moving web is determined through a mathematical relationship between the wave speed, the basis weight of the web, and the speed of the web. The instability index of the web is greater than or equal to 0.5.

1 - 8 . (Canceled)  
     
     
         9 . A process for producing a paper web having substantially uniform properties, comprising the steps of: 
 providing a moving paper web;    determining the tension on the paper web while the web is moving; and    adjusting a process condition of the web that affects modulus based on the determined tension to produce a web having more uniform properties, wherein the instability index of the web is greater than or equal to 0.5.    
     
     
         10 . The process for producing a paper web of  claim 9 , wherein the step of determining the tension on the paper web is accomplished in part by use of an air pulse onto the moving web.  
     
     
         11 . The process for producing a paper web of  claim 9 , wherein the step of determining the tension on the paper web comprising the steps of: 
 creating a wave in the moving paper web;    determining the speed of the propagation of the wave;    calculating the tension on the moving web through a mathematical relationship between the wave speed, the basis weight of the paper, and the speed of the web.    
     
     
         12 . The process for producing a paper web of  claim 9 , wherein the tension that is determined on the web is between about 10 Nt/m and about 35 Nt/m, and the speed of the moving web is about 25 m/s, and the basis weight of the web is about 15 gsm.  
     
     
         13 . The process for producing a paper web of  claim 9 , wherein the step of determining the tension on the moving web occurs when the instability index of the web is about 0.8 or higher.  
     
     
         14 . The process for producing a paper web of  claim 11 , wherein the step of creating the wave is accomplished by subjecting the web to an air pulse; and the step of determining the speed of propagation of the wave is accomplished by the use of two laser displacement transducers which each provide a signal and which also are configured for measuring the speed of the web.  
     
     
         15 . The process for producing a paper web of  claim 9 , wherein the process condition is selected from the group consisting of: 
 time to change doctor blades,    draw on a winder to maintain uniform tension in each section of the web,    tension in wound roll of the web,    flow adjustment to control cross directional dryer coating of the web,    control of cross directional moisture profile based on a given basis weight profile and a single point moisture,    control of cross directional basis weight based on a given moisture profile and an average basis weight from a softroll weight,    control of the web during turn-ups by optimizing sequence to maintain a desired tension,    control of the web during turn-ups by chemical addition to maintain a desired tension,    control of the web instability by adjusting stabilizing foils in response to the instability index calculated from the tension measurement,    control of the web instability by creping chemistry in response to the instability index calculated from the tension measurement,    control of the web handling by keeping the instability index in a desired range by adjusting creping chemistry at a certain web speed, and    control of the web handling by adjusting foil positions to maintain runability at a given web speed based on the instability index.    
     
     
         16 - 19 . (Canceled)  
     
     
         20 . A process for producing a paper web having substantially uniform properties, comprising the steps of: 
 providing a moving paper web;    determining the tension on the paper web while the web is moving, wherein the instability index of the web is greater than or equal to 0.5;    adjusting cross directional dryer coating of the web based on the determined tension of the web; and    adjusting creping chemistry based on the instability index.    
     
     
         21 . The process for producing a paper web of  claim 20 , wherein the step of continuing to determine the tension on the moving web occurs when the instability index of the web is about 0.8 or higher.  
     
     
         22 . A process for producing a paper web having at least two flows of different strengths, comprising: 
 providing a moving layered paper web;    providing at least one hardwood flow and at least one softwood flow to form at least one hardwood layer and at least one softwood layer of the paper web;    determining the tension on the paper web while the web is moving;    controlling the tension of the paper web by increasing the hardwood flow and decreasing the softwood flow in regions of high tension while maintaining a uniform basis weight, and by increasing the softwood flow and decreasing the hardwood flow in regions of low tension while maintaining a uniform basis weight, such that the tension is uniform.    
     
     
         23 . The process for producing a paper web of  claim 22 , wherein the instability index of the web is greater than or equal to 0.5.  
     
     
         24 . The process for producing a paper web of  claim 23 , wherein the instability index of the web is between about 0.8 and 1.0.