Electroplating of gravure cylinders

Abstract

The present invention relates to an apparatus and method for electroplating gravure cylinders that are used for gravure printing. The apparatus and method preferably utilize rectifiers that are able to pulse direct current several hundred times per second in order to repeatedly and intermittently establish an electric field between a supply of plating material and the gravure cylinder.

What is claimed is:  
     
         1 . An apparatus for electroplating a cylinder used in gravure printing, the apparatus comprising: 
 a container;    an ionic fluid bath stored within said container such that the gravure cylinder is at least partially submerged within the ionic fluid bath;    a supply of plating material within the ionic fluid bath; and    an electrical power source operatively connected with the gravure cylinder and the supply of plating material, wherein said power source cycles current at different levels through the ionic fluid to establish different electric fields between the supply of plating material and the gravure cylinder.    
     
     
         2 . The apparatus of  claim 1  wherein said supply of plating material is stored on a reservoir that is submerged within the ionic fluid.  
     
     
         3 . The apparatus of  claim 1  wherein said electrical power source is a pulsing direct current rectifier.  
     
     
         4 . The apparatus of  claim 1  wherein said electrical power source cycles current at two levels.  
     
     
         5 . The apparatus of  claim 4  wherein one of said current levels is substantially near zero current.  
     
     
         6 . The apparatus of  claim 1  wherein said electrical power source cycles current at different levels at least several hundred times per second.  
     
     
         7 . The apparatus of  claim 1  further comprising a filter, wherein said ionic fluid bath is circulated through said filter to remove contaminants in said ionic fluid bath.  
     
     
         8 . The apparatus of  claim 1  wherein said container and said ionic fluid bath are sized such that the gravure cylinder is wholly submerged within said ionic fluid bath.  
     
     
         9 . A method of electroplating a gravure cylinder comprising: 
 partially submerging the gravure cylinder with an ionic fluid bath;    submerging a supply of plating material within the ionic fluid bath; and    pulsing different levels of current between the supply of plating material and the gravure cylinder.    
     
     
         10 . The method as claimed in  claim 9  wherein the gravure cylinder is submerged wholly within the ionic fluid bath.  
     
     
         11 . The method as claimed in  claim 9  wherein the ionic fluid bath is kept at temperature between 28 and 32 degrees Centigrade.  
     
     
         12 . The method as claimed in  claim 9  wherein the current is cycled between two different levels.  
     
     
         13 . The method as claimed in  claim 12  wherein one of the current levels is substantially near zero.  
     
     
         14 . The method as claimed in  claim 12  wherein one of the current levels is zero.  
     
     
         15 . The method of  claim 9  wherein the current flows in one direction.  
     
     
         16 . The method of  claim 9  wherein the current alternately flows in opposite directions.  
     
     
         17 . The method of  claim 9  wherein the current primarily flows in one direction and is periodically reversed in an opposite direction.  
     
     
         18 . The method of  claim 17  wherein the current is pulsed at different levels when the current is periodically reversed in the opposite direction.  
     
     
         19 . The method of  claim 9  wherein the current is cyclically pulsed in a forward direction for 16 milliseconds and then turned substantially off for 8 milliseconds.  
     
     
         20 . The method of  claim 19  wherein the current is reversed every 1500 cycles.  
     
     
         21 . The method of  claim 20  wherein the current is reversed for 1 second.  
     
     
         22 . The method of  claim 9  wherein the current is cyclically pulsed in a forward direction for 50 milliseconds and then turned substantially off for 10 milliseconds.  
     
     
         23 . The method of  claim 22  wherein the current is reversed every 1500 cycles.  
     
     
         24 . The method of  claim 23  wherein the current is reversed for 1 second.  
     
     
         25 . The method as claimed in  claim 9  further comprising rotating the cylinder within the ionic fluid bath.  
     
     
         26 . The method as claimed in  claim 25  wherein the cylinder is rotated at 70 revolutions per minute.  
     
     
         27 . A method of electroplating a gravure cylinder comprising: 
 partially submerging the gravure cylinder within an ionic fluid bath;    submerging a supply of plating material within the ionic fluid bath;    rotating the cylinder within the ionic fluid bath; and    cycling current between the supply of plating material and the gravure cylinder where the current is cycled in one direction between substantially zero current and some higher level of current.    
     
     
         28 . The method as claimed in  claim 27  wherein the current is periodically reversed in an opposite direction.  
     
     
         29 . The method as claimed in  claim 28  wherein the current is reversed every 1500 cycles.  
     
     
         30 . The method of  claim 27  wherein the current is cycled several hundred times per second.