Optimized heat roll apparatus

Abstract

One embodiment of the heated roll apparatus uses an optimized roll whose surface layer is composed of a material responsive to being heated, particularly by external magnetic induction, and the depth of which, as well as the construction of the rest of the roll, uses one or more other materials whose properties are optimized with respect to maximizing the roll's rate of temperature change, minimizing energy usage, and performing the intended application. A thin outer ferrous layer over top of a thicker ceramic, insulating layer may be used. The roll may also include an outer layer that is responsive to heating, particularly by magnetic induction, and one or more inner layers of different material(s) chosen to increase the roll's rate of temperature change and reduce energy usage, but which are further selected to promote rapid lateral heat conduction to reduce lateral temperature variations. This roll could include a thin outer ferrous layer over top of a thicker aluminum core. The roll may instead be constructed of a single contiguous material (such as a carbon-fiber composite) that is particularly responsive to heating by magnetic induction, and which has a higher strength-to-weight ratio than ferrous alloys (i.e. cast iron or steel), thereby allowing it to be lower in weight and more thermally responsive than conventional heated rolls. The roll may also have a surface layer or contiguous depth composed of a material responsive to being heated, particularly by magnetic induction, but which in addition has a minimal outside diameter (regardless of its internal construction) in order to minimize its mass, so that it can be heated more quickly to a higher temperature, by a given heat input rate generated by any means, than would be possible with a larger, conventional heated roll.

1 . A cylindrical roll for use in a heated roll apparatus, said roll comprising: 
 a surface layer constructed of a material responsive to being heated by external magnetic induction, said surface layer covering the lateral surface of the roll;    an inner layer supporting said surface layer, said inner layer being constructed of an insulating material having a thermal mass that is one half or less than the thermal mass of steel;    a heater for externally heating said surface layer.    
   
   
       2 . The cylindrical roll of  claim 1  wherein said insulating material is a ceramic material.  
   
   
       3 . The cylindrical roll of  claim 1  wherein said surface layer is constructed of a ferrous material.  
   
   
       4 . The cylindrical roll of  claim 1  wherein said inner layer has a greater thickness than said surface layer.  
   
   
       5 . The cylindrical roll of  claim 1  further comprising an forced-convection air plenum positioned adjacent said roll to provide inexpensive, external, non-contact cooling of said surface layer.  
   
   
       6 . The cylindrical roll of  claim 1  wherein said surface layer comprises a plurality of annular sections and said heater comprises a plurality of heaters.  
   
   
       7 . The cylindrical roll of  claim 1  wherein said heater is an induction heater.  
   
   
       8 . A cylindrical roll for use in a heated roll apparatus, said roll comprising: 
 a surface layer constructed of a material responsive to being heated by external magnetic induction, said surface layer covering the lateral surface of the cylindrical roll;    an insulating layer supporting said surface layer;    an inner layer supporting said insulating layer;    a heater for externally heating said surface layer.    
   
   
       9 . The cylindrical roll of  claim 8  wherein said surface layer comprises a plurality of annular sections and said heater comprises a plurality of heaters.  
   
   
       10 . The cylindrical roll of  claim 8  wherein said heater is an induction heater.  
   
   
       11 . A cylindrical roll for use in a heated roll apparatus, said roll comprising: 
 a surface layer constructed of a material responsive to being heated by external magnetic induction, said surface layer covering the lateral surface of the cylindrical roll;    an aluminum core supporting said surface layer;    a heater for externally heating said surface layer.    
   
   
       12 . The cylindrical roll of  claim 11  wherein said surface layer comprises a plurality of annular sections and said heater comprises a plurality of heaters.  
   
   
       13 . The cylindrical roll of claim  111  wherein said heater is an induction heater.  
   
   
       14 . A cylindrical roll for use in a heated roll apparatus, said roll comprising: 
 a single cylindrical contiguous body of a material that is responsive to induction heating and has a thermal mass that is one half or less than the thermal mass of steel;    a heater for externally heating said surface layer.    
   
   
       15 . The cylindrical roll of  claim 14  further comprising fluid-carrying chambers within said single cylindrical contiguous body.  
   
   
       16 . The cylindrical roll of  claim 8  wherein said contiguous body is made from carbon fiber composite.  
   
   
       17 . A cylindrical roll for use in a heated roll apparatus, said roll comprising: 
 a single contiguous cylindrical body constructed from a material responsive to heating by magnetic induction, said single cylindrical contiguous body having a diameter of less than twelve inches;    a magnetic induction heater for externally heating said surface layer.