Device for spray-coating a workpiece with powder particles

Abstract

A booth forming a spraying chamber for workpieces to be coated with powder particles has a substantially fully open front side, giving access to an electrostatic spray gun, and a substantially fully open rear side adjoining a housing of a detachable powder-collecting unit which is open toward the chamber while being separated therefrom by an apertured screen. Tubular filter elements in the housing of the powder-collecting unit, having air-permeable peripheral surfaces, communicate with the suction end of a blower in an overlying clean-air unit, thereby giving rise to an air stream which passes generally horizontally through the chamber from its front side to its rear side and entrains particles discharged by the spray gun. Particles bypassing the workpiece to be coated may traverse the apertured screen and cling to the surfaces of the filter elements from which they may be intermittently dislodged by an air blast directed into these elements from the clean-air unit. The dislodged particles fall into a recovery compartment of the housing which lies below the level of the chamber bottom, this bottom sloping down toward the recovery compartment whereby particles dropping to the chamber floor can slide directly into that compartment underneath the apertured screen. A flexible conduit connects the recovery compartment with the spray gun for recirculation of the particles which, after passing through a strainer, are reconditioned by a fluidized bed in the recovery compartment. Cutouts in the sidewalls and a slot in the roof of the booth enable the introduction and withdrawal of workpieces suspended from above.