Powder hopper with quiet zone, a combination of a powder hopper and a powder spray gun and a method of operating a powder hopper

Abstract

A powder hopper is provided with a low turbulence zone for supplying powder to a spray gun. The low turbulence zone is defined by a baffle inside the hopper with the low turbulence zone being within a volume of the baffle, and an annular zone between the baffle and the hopper is used to bulk feed powder into the hopper. The low turbulence zone may alternatively be in the annular zone with powder added to the volume of the baffle. One preferred application for this hopper is in connection with the use of fine powder coating materials to coat the interior of small diameter cans.

We claim: 
     
         1 . A method for applying powder coating material to an internal surface of a container, comprising the steps of:
 fluidizing powder coating material in a powder coating material hopper, sucking fluidized powder coating material from a quiet zone region in the powder coating material hopper,   conveying the fluidized powder from the hopper to a spray gun and out a nozzle of the spray gun, to coat an interior surface of the container.   
     
     
         2 . The method of  claim 1  wherein a coating operation is performed electrostatically. 
     
     
         3 . The method of  claim 1  comprising adding powder coating material to an annular region in the hopper that is around the quiet zone region. 
     
     
         4 . The method of  claim 1  wherein a coating operation is performed using a nozzle adapted for being partially inserted into an open or closed end container, said nozzle having a plurality of discrete flow passages disposed about a longitudinal axis of said nozzle wherein powder flows through said flow passages to coat the container interior during a coating operation. 
     
     
         5 . The method of  claim 1  wherein the hopper has a bottom surface and wherein the quiet zone region is contained within an interior annular wall, the interior annular wall being contained within the hopper and having a bottom edge which is located above the bottom surface of the hopper. 
     
     
         6 . The method of  claim 5 , wherein the hopper has an outer wall and an annular region that is located between the outer wall and the interior annular wall, comprising the step of adding powder coating material to the annular region.