Method and apparatus for electrostatic painting

Abstract

A device and method for electrostatic powder coating include: obtaining continuously a working fluid constituted by air deprived of undesirable substances; supplying the working fluid, between 0.5 bar and 10 bar, in a container containing an amount of coating powder; extracting from the container; a first flow made up of working fluid and powder; atomizing the first flow with working fluid at a pressure of between 0.5 bar and 10 bar; supplying working fluid at a pressure of between 0.5 bar and 10 bar to create a second transport flow made up of working fluid and atomized powder; charging the second flow electrostatically under pressure; and sending the second electrostatically charged flow of working fluid and atomized powder onto a substrate, at a temperature of between −15° C. and +45° C., and a device and method for electrostatic painting including heating/cooling temperature adjustment of the painting mixture.

1 . A method for electrostatic spray painting of a support ( 50 ), comprising the steps of:
 supplying a carrier fluid to a spray gun ( 43 );   supplying a paint flow to said spray gun from a reservoir ( 48 );   atomizing said flow of paint with a pressurized jet of carrier fluid to form a painting mixture; and   sending a flow of working mixture onto the support ( 50 ), wherein,   i) said carrier fluid is made up of nitrogen in a range of 80-98%, oxygen in a range of 1-90%, argon in a range of 1-2%, and   ii) said carrier fluid is electrostatically pre-charged upstream of entry into said spray gun with positive and/or negative ions according to the desired final electrostatic charge,   wherein said flow of carrier fluid that is to be introduced into the spray gun ( 43 ) is thermally conditioned in an adjustable way to maintain a temperature of the painting mixture between −15° C. and +45° C.   
     
     
         2 . The method according to  claim 1 , wherein said flow of carrier fluid that is to be introduced into the spray gun ( 43 ) is thermally conditioned in the adjustable way to maintain the temperature of the painting mixture between between 5° C. and 20° C. 
     
     
         3 . The method according to  claim 1 , wherein said carrier fluid is a mixture of gases obtained from air modified in nitrogen/oxygen/argon produced with hollow-fiber membranes or a PSA system. 
     
     
         4 . The method according to  claim 1 , wherein an apparatus for electrostatic spray painting of the support ( 50 ) is provided, the apparatus comprising:
 a spray gun ( 43 ) provided with a reservoir ( 48 ) of a liquid paint, to spray onto a support ( 50 ) a painting mixture,   a source ( 40 ) of a carrier fluid under pressure for conveying along conduits ( 42 ) a flow of carrier fluid to said spray gun ( 43 ),   means ( 51 ) for electrostatically charging said flow of carrier fluid set between said source carrier fluid source ( 40 ) and said spray gun ( 43 ), wherein   said source ( 40 ) of carrier fluid is a source of modified air comprising nitrogen in a range of 80-99.9%, oxygen in a range of 1-90%, and argon in a range of 0.9-2%,   said electrostatically charging means ( 51 ) are arranged for electrostatically charging said flow of carrier fluid with positive and/or negative ions according to the desired final charge, whether positive, negative or neutral, or in the plasma state, and   heat-conditioning means ( 44 ) provided with both cooling and heating means, set upstream of said gun ( 43 ) in order to maintain said painting mixture at a temperature of between −15° C. and +45° C. and optimize its temperature according to the environmental conditions.   
     
     
         5 . The method according to  claim 4 , wherein said source ( 40 ) of said carrier fluid comprises hollow-fiber membrane devices for separating air modified in nitrogen/oxygen/argon starting from compressed. 
     
     
         6 . The method according to  claim 4 , wherein said source ( 40 ) of said carrier fluid comprises molecular-sieve devices for separating air modified in nitrogen/oxygen/argon starting from compressed air. 
     
     
         7 . The method according to  claim 4 , wherein the thermo conditioning device ( 44 ) is controlled by a control unit ( 45 ), temperature sensors ( 46 ,  47 ) being provided to sense the temperature of the carrier fluid and of the environment and to adjust in response the heating and or cooling of the carrier fluid to reach and to maintain a desired temperature of the painting mixture. 
     
     
         8 . An apparatus for electrostatic spray painting of a support ( 50 ), comprising:
 a spray gun ( 43 ) provided with a reservoir ( 48 ) of a liquid paint, to spray onto a support ( 50 ) a painting mixture;   a source ( 40 ) of a carrier fluid under pressure for conveying along conduits ( 42 ) a flow of carrier fluid to said spray gun ( 43 );   means ( 51 ) for electrostatically charging said flow of carrier fluid set between said source carrier fluid source ( 40 ) and said spray gun ( 43 ), wherein,   said source ( 40 ) of carrier fluid is a source of modified air comprising nitrogen in a range of 80-99.9%, oxygen in a range of 1-90%, and argon in a range of 0.9-2%,   said electrostatically charging means ( 51 ) are arranged for electrostatically charging said flow of carrier fluid with positive and/or negative ions according to the desired final charge, whether positive, negative or neutral, or in the plasma state; and   heat-conditioning means ( 44 ) provided with both cooling and heating means, set upstream of said gun ( 43 ) in order to maintain said painting mixture at a temperature of between −15° C. and +45° C. and optimize its temperature according to the environmental conditions.   
     
     
         9 . The apparatus according to  claim 8 , wherein said source ( 40 ) of said carrier fluid comprises hollow-fiber membrane devices for separating air modified in nitrogen/oxygen/argon starting from compressed. 
     
     
         10 . The apparatus according to  claim 8 , wherein said source ( 40 ) of said carrier fluid comprises molecular-sieve devices for separating air modified in nitrogen/oxygen/argon starting from compressed air. 
     
     
         11 . The apparatus according to  claim 8 , wherein the thermo conditioning device ( 44 ) is controlled by a control unit ( 45 ), temperature sensors ( 46 ,  47 ) being provided to sense the temperature of the carrier fluid and of the environment and to adjust in response the heating and or cooling of the carrier fluid to reach and to maintain a desired temperature of the painting mixture.