Abstract: The invention provides a gun for spraying a powder onto a work piece to form a coating and includes a pistol-grip housing having an air valve coupled to a source of pressurized air. The housing also supports a source of variable electrical potential. A powder container is disposed in fluid communication with the air valve so that powder within the container may be fluidized by air from the source of pressurized air when the valve is opened. A nozzle is positioned within the housing and includes a central passageway having an open end and disposed in fluid communication with the powder container. The central passageway frictionally imparts a net electrical charge of a first polarity to a first portion of the powder when the first portion of the powder contacts the surface during the spraying.

Abstract: The invention provides a gun for spraying a powder onto a work piece to form a coating and includes a pistol-grip housing having an air valve coupled to a source of pressurized air. The housing also supports a source of variable electrical potential. A powder container is disposed in fluid communication with the air valve so that powder within the container may be fluidized by air from the source of pressurized air when the valve is opened. A nozzle is positioned within the housing and includes a central passageway having an open end and disposed in fluid communication with the powder container. The central passageway frictionally imparts a net electrical charge of a first polarity to a first portion of the powder when the first portion of the powder contacts the surface during the spraying.

Abstract: 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.

Abstract: 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.