APPARATUS AND METHOD FOR ELECTROSTATICALLY POWDERSPRAYING, PARTICULARLY OF ENAMEL

摘要

Powder spray operation for electrostatically spraying inorganic powders such as enamel suspensions up till now was only possible by increasing the electrical resistance by coating the particles with an organic coating, but because of the considerable hardness of the enamel powder particles an unacceptable wear in the recovery installations, especially in the exhaust system, transport system and cyclone was developed when spraying this powder in an apparatus which was known per se for the organic powder spraying operation whereby the not deposited powder was returned to a recuperation installation. It has been tried to adapt this method for inorganic powders, but the organic coating of the particles was damaged and the powder was polluted by abraded metal particles, so that strong undesired changes of color of the enamel surface were caused after being passed through the furnace in spite of extensive cleaning operations. All this problems have been solved by embodying the powder recirculation completely within a powder spray module having filtering devices and a reservoir which are preferably simply exchangeable which reduces the number of necessary modules.