| 摘要 |
A spray gun for applying powder to coat a work piece uses triboelectric and optionally a corona discharge electrode to charge powder particles electrostatically. The gun communicates with a source of pressurized air through a handle with an air valve controlling flow of the air. Powder in a container in fluid communication with the air flow is fluidized and entrained when the valve is opened. A nozzle with an internal surface defining a passageway to an open end communicates with the powder container. The internal surface of the nozzle frictionally imparts a net electrical charge of a first polarity to part of the powder by frictional contact during spraying. A plurality of discrete tubes are disposed in the central passageway and impart a net electrical charge of a second polarity to another part of the powder due to frictional contact as that part flows around and through the tubes. The powder then exits the nozzle, passes the corona discharge electrode which produces a corona that charges the powder with an electrical potential in the range from about 8 kV to about 20 kV.
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