Drum and method for coating workpieces with a non-metallic coating

Abstract

The invention relates to a drum which has a wall, wherein at least the inside of the wall is provided with a surface of insulating material, an opening, defined by wall segments of the wall, radially spaced from one another with respect to a central rotational axis of the drum, and a drive mechanism for rotating the drum in a first or in a second direction, wherein at least one first electrode is arranged on the inside of the wall, and wherein at least one counter electrode is arranged on or between a central axis of the drum and the wall, and a method for coating workpieces.

1 . A drum, comprising
 a wall ( 4 ), wherein at least the inside of the wall is provided with a surface of insulating material,   an opening ( 8 ), defined by wall segments ( 4   a ,  4   b ) of the wall ( 4 ), radially spaced from one another with respect to a central rotational axis ( 6 ) of the drum ( 2 ), and   a drive mechanism ( 18 ) for rotating the drum ( 2 ) in a first or in a second direction, wherein   at least one first electrode ( 10 ) is arranged on the inside of the wall, and wherein   at least one counter electrode ( 14 ) is arranged on or between a central axis of the drum ( 2 ) and the wall ( 4 ).   
   
   
       2 . The drum according to  claim 1 , wherein the first electrode ( 10 ) is a cathode or an anode. 
   
   
       3 . The drum according to  claim 1 , wherein at least two first electrodes ( 10 ) are arranged on the inside of the wall ( 4 ) of the drum ( 2 ). 
   
   
       4 . The drum according to  claim 1 , wherein the at least one first electrode ( 10 ) is fixed on or into the inside of wall ( 4 ) using screws, snap locking, adhesion or casting. 
   
   
       5 . The drum according to  claim 1 , wherein the counter electrode ( 14 ) is formed as an arcuate segment. 
   
   
       6 . The drum according to  claim 1 , wherein the at least one counter electrode ( 14 ) is arranged halfway between the central axis and the wall ( 4 ) of the drum ( 2 ). 
   
   
       7 . The drum according to  claim 1 , wherein at least the inner surface of the drum wall ( 4 ) is of plastic material. 
   
   
       8 . The drum according to  claim 1 , wherein the wall ( 4 ) is either manufactured in one piece or is composed of a plurality of segments ( 4   a ,  4   b ). 
   
   
       9 . The drum according to  claim 1 , wherein the segments ( 4   a ,  4   b ) of the wall ( 4 ), arranged radially spaced from one another, overlap by at least 15°of 360°. 
   
   
       10 . The drum according to  claim 1 , wherein, in an operating state, the drum ( 2 ) comprises above the level of the coating agent a wall ( 4 ) being perforated at least in parts. 
   
   
       11 . The drum according to  claim 1 , wherein the drum ( 2 ) is arranged in a housing ( 16 ). 
   
   
       12 . A method for coating workpieces of conductive material with a non-metallic coating, in particular a corrosion-protective coating, in a drum ( 2 ), comprising
 a wall ( 4 ), wherein at least the inside of the wall ( 4 ) is provided with a surface of insulating material,   an opening ( 8 ), formed by wall segments ( 4   a ,  4   b ) of the wall ( 4 ), radially spaced from one another,   a drive mechanism ( 18 ) for rotating the drum ( 2 ) in a first or in a second direction,   at least one first electrode ( 10 ), arranged on the inside of the wall ( 4 ), and   at least one counter electrode ( 14 ), arranged on or between a central axis of the drum ( 2 ) and its the wall ( 4 ),   
     comprising the steps of:
 loading the drum with liquid coating agent and workpieces in a predefined proportion, 
 venting the workpieces, 
 halting the drum ( 2 ), 
 applying, maintaining and switching off electrical voltage, and subsequently 
 emptying the drum ( 2 ). 
 
   
   
       13 . The method according to  claim 12 , wherein the workpieces to be coated are made of metal. 
   
   
       14 . The method according to  claim 12 , wherein venting the workpieces in the coating agent is achieved by rotating the drum ( 2 ). 
   
   
       15 . The method according to  claim 12 , wherein the drum ( 2 ) rotates at least intermittently during the application of voltage to avoid uncoated places in the coating to be applied to the workpieces. 
   
   
       16 . The method according to  claim 12 , wherein the coated workpieces are separated and, if necessary, freed of excess coating agent after discharge from the drum ( 2 ). 
   
   
       17 . The method according to  claim 12 , wherein the applied coating is cured after discharge from the drum ( 2 ). 
   
   
       18 . The method according to  claim 12 , wherein the coating process is carried out under application of a voltage in the range of 20 V to 500 V. 
   
   
       19 . The method according to  claim 12 , wherein the coating process is carried out using current in the range of 1 A to 500 A. 
   
   
       20 . The method according to  claim 12 , wherein the coating process is carried out at temperatures of 15° C. to 60° C. 
   
   
       21 . The method according to  claim 12 , wherein the coating process is carried out over a time period of 1 second to 10 minutes. 
   
   
       22 . The drum according to  claim 3 , wherein at least five electrodes ( 10 ) are arranged on the inside of the wall ( 4 ) of the drum ( 2 ). 
   
   
       23 . The drum according to  claim 3 , wherein at least seven electrodes ( 10 ) are arranged on the inside of the wall ( 4 ) of the drum ( 2 ). 
   
   
       24 . The drum according to  claim 7 , wherein the plastic material is selected from the group consisting of polyethylene, ceramic, a material covered with an insulating material and combinations thereof. 
   
   
       25 . The drum according to  claim 9 , wherein the segments ( 4   a ,  4   b ) of the wall ( 4 ) overlap by at least 30° of 360°. 
   
   
       26 . The method according to  claim 12 , wherein the coating process is carried out under application of a voltage in the range of 100 V to 350 V. 
   
   
       27 . The method according to  claim 12 , wherein the coating process is carried out under application of a voltage in the range of 150 V to 250 V. 
   
   
       28 . The method according to  claim 12 , wherein the coating process is carried out using current in the range of 1 A to 400 A. 
   
   
       29 . The method according to  claim 12 , wherein the coating process is carried out using current in the range of 1 A to 350 A. 
   
   
       30 . The method according to  claim 12 , wherein the coating process is carried out using current in the range of 1 A to 200 A. 
   
   
       31 . The method according to  claim 12 , wherein the coating process is carried out at temperatures of 20° C. to 40° C. 
   
   
       32 . The method according to  claim 12 , wherein the coating process is carried out at temperatures of 25° C. to 30° C. 
   
   
       33 . The method according to  claim 12 , wherein the coating process is carried out over a time period of 10 seconds to 120 seconds. 
   
   
       34 . The method according to  claim 12 , wherein the coating process is carried out over a time period of 30 seconds to 90 seconds.