Measurement method and apparatus in the manufacture of paper or paperboard

Abstract

In a paper or paperboard machine measurements are conducted with at least one measurement means attached to an element in the paper or paperboard machine. The measurement means has two surfaces made of electrically conductive material and has insulating material between them. The change in the capacitance between the surfaces made of conductive material is measured.

1 . A measurement method in a paper or paperboard machine or finishing apparatus for paper or paperboard, comprising the step of taking measurements by means of at least one measurement means attached to at least one element in the paper or paperboard machine or finishing device for paper or paperboard, wherein the measurement means comprises two surfaces made of conductive material and having insulating material between them, and that the capacitance and/or the change in the capacitance between the conductive material surfaces is measured, wherein the measurement means is positioned between separate layers of a coating of the at least one element.  
     
     
         2 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a measurement means in which at least one conductive material surface and/or insulating material is positioned in a roll and/or roll coating in the paper or paperboard machine.  
     
     
         3 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a measurement means in which at least one conductive material surface and/or insulating material is positioned in one of the following: a belt, a wire, a coating blade or rod, a doctor blade or a guide rod.  
     
     
         4 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a measurement means in which at least one conductive material surface and/or insulating material is positioned in the roll shell or in the roll coating.  
     
     
         5 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a measurement means that is provided with a substantially strip-like shape.  
     
     
         6 . The method according to  claim 5 , wherein the capacitance and/or the change in the capacitance is measured by means of a strip-like measurement means that is positioned in the element in such a manner that in the longitudinal direction of the measurement means different sections of the same enter the measurement point, such as a nip, alternately as a result of the movement of the element.  
     
     
         7 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with at least one measurement means which is composed of substantially separate fragments and has two layers made of conductive material and having insulating material between them.  
     
     
         8 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a perforated measurement means.  
     
     
         9 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured with a measurement means that is positioned at least partly as a spiral around the roll.  
     
     
         10 . The method according to  claim 1 , wherein the total linear load and/or nip pressure profile between two elements pressed together in the paper or paperboard machine or finishing device for paper or paperboard is measured on the basis of the capacitance and/or the change in the capacitance.  
     
     
         11 . The method according to  claim 10 , wherein the total linear load and/or nip pressure profile of at least one roll nip is determined on the basis of the capacitance and/or the change in the capacitance.  
     
     
         12 . The method according to  claim 1 , wherein at least one of the following is determined on the basis of the capacitance and/or the change in the capacitance: moisture content, temperature or tension of the web.  
     
     
         13 . The method according to claims  1 , wherein the capacitance and/or the change in the capacitance is measured with at least two measurement means coupled together by means of a half-bridge coupling, and the bridge is measured by means of alternating voltage.  
     
     
         14 . The method according to  claim 1 , wherein the capacitance and/or the change in the capacitance is measured when the roll is rotating.  
     
     
         15 . A measurement apparatus in a paper or paperboard machine or finishing apparatus for paper or paperboard, in which apparatus at least one measurement means is attached to at least one element in the paper or paperboard machine or finishing device for paper or paperboard, wherein the measurement means comprises two surfaces made of conductive material and having insulating material between them, and that the measurement means is arranged to measure the capacitance and/or the change in the capacitance between the conductive material surfaces, wherein the measurement means is positioned between separate layers of a coating of the at least one element.  
     
     
         16 . The apparatus according to  claim 15 , wherein in the measurement means at least one conductive material surface and/or insulating material is positioned in a roll and/or roll coating in the paper or paperboard machine.  
     
     
         17 . The apparatus according to  claim 15 , wherein in the measurement means at least one conductive material surface and/or insulating material is positioned in one of the following: a belt, a wire, a coating blade or rod, a doctor blade or a guide rod.  
     
     
         18 . The apparatus according to  claim 16 , wherein roll has multiple layers of coating thereon, and the measurement means is positioned between the coating layers of the roll coating, and intermediate layer formed of an adhesive substance, overlies the measurement means.  
     
     
         19 . The apparatus according to  claim 15 , wherein the measurement means has a substantially strip-like shape.  
     
     
         20 . The apparatus according to  claim 19 , wherein the strip-like measurement means is positioned in the element in such a manner that in the longitudinal direction of the measurement means, different sections thereof enter the measurement point, such as a nip, alternately as a result of the movement of the element.  
     
     
         21 . The apparatus according to  claim 15 , wherein at least one measurement means is substantially a separate fragment composed of two layers made of conductive material and having insulating material between them.  
     
     
         22 . The apparatus according to  claim 15 , wherein the measurement means is perforated.  
     
     
         23 . The apparatus according to  claim 15 , wherein at least one measurement means is positioned at least partly as a spiral around the roll.  
     
     
         24 . The apparatus according to  claim 15 , wherein the apparatus comprises means for determining the total linear load and/or nip pressure profile between two elements pressed together in a paper or paperboard, machine or finishing device for paper or paperboard on the basis of the measured capacitance and/or the change in the capacitance.  
     
     
         25 . The apparatus according to  claim 24 , wherein the apparatus comprises means for determining the total linear load and/or nip pressure profile of at least one roll nip on the basis of the measured capacitance and/or the change in the capacitance.  
     
     
         26 . The apparatus according to  claim 15 , wherein the apparatus comprises means for determining on the basis of the measured capacitance and/or the change in the capacitance one of the following: moisture content or tension of the web.  
     
     
         27 . The apparatus according to  claim 15 , wherein the apparatus comprises means for coupling at least two measurement means together by means of a half-bridge coupling, as well as means for measuring the bridge by means of alternating voltage.  
     
     
         28 . A measurement method in a paper or paperboard machine or finishing apparatus for paper or paperboard, comprising the step of taking measurements by means of at least one measurement means attached to at least one element in the paper or paperboard machine or finishing device for paper or paperboard, wherein the measurement means comprises two surfaces made of conductive material and having insulating material between them, and that the capacitance and/or the change in the capacitance between the conductive material surfaces is measured, wherein the capacitance and/or the change in the capacitance is measured with a measurement means in which the paper or paperboard web forms at least part of the insulating material.  
     
     
         29 . A measurement apparatus in a paper or paperboard machine or finishing apparatus for paper or paperboard, in which apparatus at least one measurement means is attached to at least one element in the paper or paperboard machine or finishing device for paper or paperboard, wherein the measurement means comprises two surfaces made of conductive material and having insulating material between them, and that the measurement means is arranged to measure the capacitance and/or the change in the capacitance between the conductive material surfaces, wherein in the measurement means the paper or paperboard web forms at least part of the insulating material.