ES299121A1 - Electrostatic coating apparatus - Google Patents

Abstract

Electrostatic coating apparatus comprises means for creating a floating cloud of finely divided coating substance at a coating station, means for presenting articles to be coated at said station, charging electrode means connected to a high electric potential relative to said articles and positioned to be closely approached by substantially all the particles in said cloud to charge the particles to a corresponding potential whereby particles from the cloud will be guided over lines of electric force towards said articles, and auxiliary ionizing electrode means connected to a potential substantially the same as the potential of the articles and positioned in spaced relation with said charging electrode and with the articles for controlling the spatial extent of the cloud by discharging the electrical charge of the particles entering into the ionizing zone of the auxiliary electrode means. The apparatus shown includes an insulated tank 1 having a perforated false bottom 2 which supports coating material 3. The space under false bottom 2 is connected by pipe 4 to a source of fluidizing gas under pressure and a vibrator unit 5 may be provided to assist in the fluidization of coating material 3. Means for electrically charging the particles in the fluidized cloud of coating material consists of an array of point electrodes or ionizers 6 connected to one terminal of high voltage source 7. In operation with source 7 in action and compressed air delivered through pipe 4 the coating material 3 is converted into a turbulent floating cloud and the electrodes 6 impart to substantially all the particles in the cloud a high electric potential. When articles to be coated (not shown) and at earth potential are support above the tank 1 said coating particles flow along the lines of force established and are deposited on the surface of the article to be coated. To control the spatial extent of the fluidized cloud of coating material control. electrodes 8 are fitted and in operation these electrodes act to discharge any cloud particles approaching them and thus prevent any undesirable spilling from the tank. The electrodes 8 may be in the form of point electrodes as shown or they can be in the form of wires running round the periphery of the tank. In a further embodiment the fluidized cloud is produced by an electrostatic spray-gun.