Arrangement for improving the beginning of the drying section

Abstract

An arrangement for improving the beginning of the drying section joined to a closed web transfer between the press section and the drying section in a paper machine. In order to achieve less fouling of the drying cylinder, that is, less formation of fluff, to achieve easier doctorability and better doctoring tolerance of the drying cylinder surface in the drying section, the surface of at least the first drying cylinder in the drying section has a coating which includes a thin preferably hard layer of ceramic material and/or metal ceramic and/or metal, to which the web will adhere weakly, and/or another softer material, to which the web will adhere weakly, is absorbed into the drying cylinder surface, whereby separation of the web from the surface of the drying cylinder is improved.

We claim:  
     
         1 . A papermaking machine of the type having: 
 a pressing section;    a dryer section having a first drying cylinder of a first bank of drying cylinders, the first drying cylinder having a drying surface;    a paper web passing through the pressing section, and supported by a means for supporting the web, between the press section and the first bank of drying cylinders of the drying section, so that a closed web transfer is formed between the pressing section and the first drying cylinder,    the improvement which comprises: 
 a coating on the drying surface of at least the first drying cylinder of the first bank of drying cylinders, the coating including a thin hard layer to which the web attaches weakly, said coating being composed of material selected from the group consisting of: ceramic, metal, and metal ceramic.  
   
     
     
         2 . The apparatus of  claim 1  wherein the dryer section has at least a second drying cylinder, and at least the first drying cylinder and the second drying cylinder of the drying section are coated with said coating.  
     
     
         3 . The apparatus of  claim 1  wherein a material selected from the group consisting of: fluorated plastic and fluorated epoxy, is absorbed into the surface of the drying surface of at least the first drying cylinder.  
     
     
         4 . The apparatus of  claim 3  wherein the fluorated plastic is polytetrafluoroethylene.  
     
     
         5 . The apparatus of  claim 1  wherein the coating of the drying cylinder includes the thin hard layer and a softer layer of fluorated plastic absorbed into the thin hard layer.  
     
     
         6 . The apparatus of  claim 1  wherein the ceramic material forming the hard layer of the coating is oxide ceramic, selected from the group of oxides consisting of: Zr, Al, Si, Ti, Y and Cr.  
     
     
         7 . The apparatus of  claim 1  wherein the ceramic material forming the hard layer of the coating is a metal carbide, selected from the group of carbides consisting of: Cr, W, Ti and Ni carbide ceramic.  
     
     
         8 . The apparatus of  claim 1  wherein the metal ceramic forming the hard layer of the coating is a mixture of an oxide ceramic, and a carbide ceramic, and a metal.  
     
     
         9 . The apparatus of  claim 1  wherein the metal forming the hard layer of the coating is selected from the group consisting of: Cr, Ni and Mo.  
     
     
         10 . The apparatus of  claim 1  wherein the thickness of the thin hard layer is in a range of 0.03-6 mm.  
     
     
         11 . The apparatus of  claim 1  wherein the thickness of the thin hard layer is in a range of 0.05-2 mm.  
     
     
         12 . The apparatus of  claim 1  wherein the thin hard layer is sprayed thermally on to the surface of the first drying cylinder, and an adhesive layer, which is a non-porous metal layer, is used in between the hard layer of the coating and the cylinder surface of the drying cylinder.  
     
     
         13 . A papermaking machine of the type having: 
 a pressing section;    a dryer section having a first drying cylinder, of a first bank of drying cylinders, the first drying cylinder having a drying surface;    a paper web passing through the pressing section, and supported by a means for supporting the web, between the press section and the first bank of drying cylinders of the drying section, so that a closed web transfer is formed between the pressing section, and the first drying cylinder,    wherein the improvement comprises: 
 a coating on the drying surface of at least the first drying cylinder of the first bank of drying cylinders, the coating including a thin hard layer to which the web attaches weakly, said coating being composed of at least two materials selected from the group consisting of: oxide ceramics of Zr, Al, Si, Ti, Y and Cr, carbide ceramics of Cr, W, Ti and Ni, metal ceramics of Zr, Al, Si, Ti, Y and Cr metals, Ni, Cr and Mo, and PTFE, and fluorated epoxy.  
   
     
     
         14 . A papermaking machine of the type having: 
 a pressing section;    a dryer section having a first drying cylinder of a first bank of drying cylinders, the first drying cylinder having a drying surface;    a paper web passing through the pressing section, and supported by a means for supporting the web, between the press section and the first bank of drying cylinders of the drying section, so that a closed web transfer is formed between the pressing section and the first drying cylinder,    wherein the improvement comprises: 
 a material selected from the group consisting of: a fluorated plastic, polytetrafluoroethylene and fluorated epoxy, said material being absorbed into the drying cylinder drying surface.