ES343577A1 - Method and apparatus for Electrostatically Coating the Surfaces of Articles with Pulverulent Materials - Google Patents

Abstract

The surface of an article is coated with pulverulent material by dispersing the material in an air current and electrically changing and spraying the material on to the surface, drawing off the particles not adhering to the article by suction, separating the particles from the air current coming from the suction line, liminating the electric charge of the entire recovered material and screening the material before it is sprayed again. In Fig. 1 the material is conveyed through suction line 18 leading from blower 12. into the collecting container 3 composed of cylindrical vessel 4 and funnel-like supply container 5. The material is supplied from the supply container 5 to the gate wheel 19 by gravity, the nozzle 7 adopted to pass blasts of compressed air into outlet channel 6 of the container preventing the material from being packed in the outlet channel 6. The gate wheel 19 conveys the material in measured quantities into a sifter 21 where the material is disintegrated and screened. The material then emerges from the outlet 22 passes into the storage container 24 of a pneumatic conveying device. The material is dispersed therein within an air current and conducted through the connecting line 25 to the spray gun 26 in which the particles are electrically charged before being ejected. Various parts of the spray material which do not settle on and adhere to the article to be coated are drawn off by the suction of the blower 12 through the opening 15 of a suction channel 16 located on the bottom of the spray chamber 17 and are blown into vessel 4. The blower 12 forms, together with the vessel 4, a cyclone separator. The particles are blown from the outlet tube 11 of the blower and precipitate from the air current. Those parts of the drawnoff material which are not separated from the air current are separated in filters 8 and 9 through which the exhaust air of the cyclone separator is conducted and fall into the collecting container 3 when the air supply is interrupted. The particles of the material which are separated from the exhaust air come in contact with the wall of the vessel 4 and partly also the wall of the supplying container 5 and thereby lose their electric charge. In further embodimends: (Figs. 4 to 6 not shown) the material is suspended in air in the collecting container, the bottom of which is provided on the inside with a porous layer spaced from the outer wallthereby forming a chamber which communicates with a compressed-air supply line, the inner side of the porous layer being provided with an electrically conductive coating which participates in completely removing the electric charge from the recovered particles when the air supply is interrupted (Fig. 7, not shown,), two separating units are connected by separate connecting lines to the inside of the spray chamber.