Apparatus and method for improving contact between a web and a roll

Abstract

This invention discloses a conductor roll that is surrounded by a crown that extends along a substantial portion of the length of the conductor roll. The crown is designed to compensate for the deflection of the conductor roll when the conductor roll is placed under a load.

1 . An apparatus for reducing or eliminating the occurrence of arc pits in a metallic sheet during an electrocoating process comprising: 
 a conductor roll;    a crown surrounds said conductor roll and extends along a substantial length of said conductor roll, said crown being designed to compensate for the deflection of said conductor when said conductor roll is placed under a load; and    a hold down roll is positioned adjacent to said conductor roll thereby applying pressure to said metallic sheet that passes between the opposing surfaces of said conductor roll and said hold down roll.    
   
   
       2 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 1  wherein said crown has a substantially straight top when said metallic sheet is wrapped around said conductor roll, said top of said crown being in direct contact with said metallic sheet.  
   
   
       3 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 1  wherein said crown is fabricated from a layer that is deposited over a surface of said conductor roll.  
   
   
       4 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 3  wherein said layer is chromium, inconel, or an alloy based on iron, nickel, or chromium.  
   
   
       5 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 3  wherein said layer is deposited over said surface of said conductor roll using electroplating, thermal spraying, or cold spraying.  
   
   
       6 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 5  wherein thermal spraying comprises plasma spraying, high velocity powder combustion, high velocity wire combustion, and wire arc.  
   
   
       7 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 1  wherein a surface of said crown has a maximum Ra surface roughness of about 0.127 μm (5 μin).  
   
   
       8 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 1  wherein said crown is able to conduct an electrical current up to about 70,000 amperes.  
   
   
       9 . An apparatus for reducing or eliminating the occurrence of arc pits during an electrocoating process according to  claim 1  wherein said crown is a jacket that surrounds and is affixed to said conductor roll.  
   
   
       10 . A conductor roll comprising a crown that surrounds said conductor roll, said crown extending along a substantial length of said conductor roll, said crown being designed to compensate for the deflection of said conductor roll when said conductor roll is placed under a load.  
   
   
       11 . A conductor roll according to  claim 10  wherein said crown is fabricated from a layer that is deposited over a surface of said conductor roll.  
   
   
       12 . A conductor roll according to  claim 11  wherein said layer is chromium, inconel, or an alloy based on iron, nickel, or chromium.  
   
   
       13 . A conductor roll according to  claim 10  wherein said crown is a jacket that surrounds and is affixed to said conductor roll.  
   
   
       14 . A conductor roll according to  claim 10  wherein said crown has a substantially straight top when a metallic sheet is wrapped around said crown, said top of said crown being in direct contact with said metallic sheet.  
   
   
       15 . A conductor roll according to  claim 10  wherein said layer is deposited over said surface of said conductor roll using electroplating, thermal spraying, and cold spraying.  
   
   
       16 . A conductor roll according to  claim 15  wherein thermal spraying comprises plasma spraying, high velocity powder combustion, high velocity wire combustion, and wire arc.  
   
   
       17 . A conductor roll according to  claim 10  wherein a surface of said crown has a maximum Ra surface roughness of about 0.127 μm (5 μin).  
   
   
       18 . A conductor roll according to  claim 10  wherein said crown is able to conduct an electrical current up to about 70,000 amperes.  
   
   
       19 . A method for reducing or eliminating the occurrence of arc pits in a metallic sheet during an electrocoating process comprising: 
 providing a metallic sheet;    feeding said metallic sheet between the opposing surfaces of a crowned conductor roll and a hold down roll;    wrapping said metallic sheet around said crowned conductor roll wherein said crowned conductor roll is deformed by the mechanical forces resulting from the sheet tension; and    applying an electrical current through said crowned conductor roll to electrochemically deposit a coating onto a surface of said metallic sheet.    
   
   
       20 . A method for reducing or eliminating the occurrence of arc pits in a metallic sheet during an electrocoating process according to  claim 19  further comprising: 
 providing a first roll or coil of said metallic sheet;    unwinding said metallic sheet prior to feeding said metallic sheet between the opposing surfaces of said crowned conductor roll and said hold down roll; and    winding said metallic sheet into a second roll or coil after depositing said coating onto said surface of said metallic sheet.    
   
   
       21 . A method for reducing or eliminating the occurrence of arc pits in a metallic sheet during an electrocoating process according to  claim 19  further comprising curing said coating onto said surface of said metallic sheet after depositing said coating onto said metallic sheet.  
   
   
       22 . A method for reducing or eliminating the occurrence of arc pits in a metallic sheet during an electrocoating process according to  claim 19  wherein providing a first roll or coil of aluminum, aluminum alloy, steel, or steel alloy sheet.  
   
   
       23 . A metallic sheet manufactured by the process comprising: 
 providing a metallic sheet;    feeding said sheet between the opposing surfaces of a crowned conductor roll and a hold down roll;    wrapping said metallic sheet around said crowned conductor roll wherein said crowned conductor roll is deformed by the mechanical forces resulting from the sheet tension; and    applying an electrical current through said crowned conductor roll to electrochemically deposit a coating onto a surface of said metallic sheet.    
   
   
       24 . A method for making a conductor roll for use in an electrocoating line process comprising: 
 providing a conductor roll;    measuring or modeling the amount of deflection of said conductor roll when a metallic sheet is wrapped around said conductor roll; and    fabricating a crown that surrounds and extends along a substantial length of said conductor roll, said crown being designed to compensate for the deflection of said conductor roll when said conductor roll is placed under a load.    
   
   
       25 . A method of making a conductor roll according to  claim 24  wherein fabricating a crown to compensate for said deflection of said metallic cylinder by depositing a layer onto a surface of said conductor roll thereby surrounding said conductor roll with said layer.  
   
   
       26 . A method of making a conductor roll according to  claim 25  wherein depositing said layer onto said surface of said conductor roll using electroplating, thermal spraying, or cold spraying.  
   
   
       27 . A method of making a conductor roll according to  claim 26  wherein depositing a layer of chromium, inconel, or an alloy based on iron, nickel or chromium; and 
 shaping said layer to compensate for said deflection of said conductor roll.    
   
   
       28 . A method of making a conductor roll according to  claim 24  wherein fabricating said crown so that a surface of said crown has a maximum Ra surface roughness of about 0.127 μm (5 μin).  
   
   
       29 . A method of making a conductor roll according to  claim 24  wherein fabricating a crowned jacket through which said conductor roll is inserted and affixed.