Apparatus for applying powdered coating materials includes a channel portion wherein the powder coating material is passed around a conduit which delivers an air jet to the powder material, and where the powder material is ionized, and then forced through an outlet channel. The latter is made of nonconductive material, and includes a non-conductive insert disposed in the channel, with the dielectric constant of the insert being different from the dielectric constant of the material of the remainder of the channel. The ionized powder is directed by gas pressure through the channel toward a grounded object to be coated. The ionization electrode within the apparatus is hollow and an air jet is passed therethrough to aid in the dispersion of the powdered coated material.
An apparatus and method for applying powdered coating materials includes a central channel for directing the powdered coating material passed a conduit that mixes an air jet with the powdered material. The powder is then ionized and forced outwardly towards the workpiece. A conductive cathode attractor ring for creating a corona space charge which ionizes the particles is provided and includes a radially inner porous portion. Contamination of the attractor ring due to adherence thereon of powder particles is inhibited by diverting a secondary pressurized air flow through said porous portion thereby dislodging powder particles adhering to the ring. The porous inner portion is formed of a sintered mass of individual particles which provides an increased surface area for the attractor ring that, in turn, increases the corona space charge. A slidable deflector member is provided at the end of the central channel to alter the spray pattern of the apparatus.
A powder charging apparatus, in which a plasma electrode pair is disposed within an insulative tubular passage for transporting powder as carried by gas, a device for intermittently applying a D.C. voltage between that pair of plasma electrode is provided to form a space where mainly desired polarity ions drawn from the plasma electrode pair exist and another space where mainly opposite polarity ions exist, well dispersed powder is fed to the former space where mainly the desired polarity ions exist, and thereby stable and strong charging performances can be assured for a long term without adhesion and accumulation of the powder to and on either one of the pair of plasma electrodes; and an electrostatic powder painting apparatus containing this powder charging apparatus therein and having excellent penetrating performance and painting efficiency.
On the downstream side of a large-diameter cylindrical flow path is disposed a small-diameter cylindrical flow path having a smaller inner diameter than the inner diameter of the large-diameter cylindrical flow path contiguously to the large-diameter cylindrical flow path, an annular electrode is disposed at the upstream end of the small-diameter cylindrical flow path, a needle electrode is provided at the center of the annular electrode applying a D.C. high voltage between the electrodes, and upon charging powder contained in a mixed-phase flow through said cylindrical flow paths, a substantial slip velocity is given to the mixed-phase flow adjacent to the surface of the annular electrode.
An electrostatic spray apparatus wherein a charging chamber is formed as an enlargement in the conduit feed to the spray nozzle. The charging electrode is disposed axially of the conduit with a pointed end located at the exit end of the enlargement and facing upstream of a particle stream flow and opposed to a counterelectrode end located at the inlet side of said enlargement. The counterelectrode may be an obtuse end of an elongated element or may be formed as a grid extending across the conduit or as an annular element formed about a wall of the conduit. Optionally shown are a plurality of enlarged charging chambers, as annular element forming a constricted flow path and a charging electrode second end extending beyond the spray nozzle. Means introduce an air flow into the particle stream at both the nozzle and at the charging chamber.
A device for painting by electrostatic powder spraying wherein a passage for triboelectrifying powder particles is formed in an electrically conductive housing and is surrounded by an electric insulator layer of a synthetic macromolecular material, such as nylon or fluorocarbon resin, containing powder of an electrically conductive material, such as copper, aluminum or carbon. As the electrostatic powder moves through the passage, it frictionally engages the insulator layer and causes an electric charge on the surface of the electric insulator, due to the triboelectrification movement in the electric insulator, and a current flows to the powder. Therefore, powder particles can be continuously triboelectrified without suppling any voltage or with supplying a very low voltage for forming an electric field.
