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Spray application of coating compositions utilizing induction and corona charging means

  • US 4,266,721 A
  • Filed: 09/17/1979
  • Issued: 05/12/1981
  • Est. Priority Date: 09/17/1979
  • Status: Expired due to Term
First Claim
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1. A method of applying a sprayable liquid coating composition to a workpiece, said composition having an electrical conductivity between about 0.005 and about 0.06 μ

  • mho/cm, said method comprising spraying said composition by employing a spray gun having;

    (a) a gas nozzle and a fluid nozzle, each of said nozzles being in cooperative spatial relationship with each other to cause a fluid stream of said composition issuing from said fluid nozzle to be atomized and sprayed as fluid particles by gas issuing from said gas nozzle,(b) electrically grounded means for increasing surface area from which fluid particles can be formed, said means being disposed within said fluid stream and having at least one sharp edge, and(c) induction charging electrode means disposed adjacent said gas and fluid nozzles and having a rear edge located rearward of a plane which is perpendicular to the axis of liquid flow and which passes through the discharge point of said fluid nozzle;

    said method further comprising supplying sufficient voltage to said induction charging electrode means to produce a corona discharge at said sharp edge of said surface area increasing means, said method producing corona charging and induction charging of sprayed fluid particles.

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