Apparatus for and method of metering coating material in an electrostatic spraying system

A system for supplying electrically conductive coating materials to high voltage electrostatic coating apparatus, comprising a color changer having inlets for connection with respective ones of a plurality of supplies of the coating materials and an outlet for the materials;

• a pair of reservoirs;
• coupling means for selectively connecting said color changer outlet to one or the other of said reservoirs;
• means for operating said color changer and said coupling means to flow coating materials from selected ones of the supplies from said color changer outlet into and through said coupling means alternately to and into one and then the other of said reservoirs;
• first metering means for metering the volume flows of coating materials flowed into one and then into the other of said reservoirs;
• means for cleaning coating material from at least a portion of said coupling means between said color changer outlet and whichever reservoir coating material has just been flowed into, to electrically isolate such reservoir and coating material therein from said color changer and the supplies of coating material;
• means for alternately flowing coating material from one and then from the other of said reservoirs to the coating apparatus for electrostatic charging and emission of the coating material by the coating apparatus, such that coating material in the reservoir that has just been filled and electrically isolated from the color changer and coating material supplies is flowed to the coating apparatus while the other reservoir is being filled with coating material and then electrically isolated from said color changer and coating material supplies;
• second metering means for metering the volume flows of coating materials flowed from one and then from the other of said reservoirs to the coating apparatus;
• means responsive to said first and second metering means for interrupting the flow of coating material from a reservoir to the coating apparatus upon said second metering means metering a preselected volume flow of coating material from such reservoir to the coating apparatus;
• and means, responsive upon interruption of the flow of coating material from one reservoir to the coating apparatus and prior to flowing coating material from the other reservoir to the coating apparatus, for cleaning coating material from at least a portion of said means for alternately flowing, between the coating apparatus and the reservoir from which coating material has just been flowed, to electrically isolate such reservoir from the coating apparatus.

A method of supplying electrically conductive coating material to high voltage electrostatic coating apparatus from a coating material supply, while maintaining electrical isolation between the high voltage at the coating apparatus and the coating material supply, said method comprising the steps of coupling the coating material supply to a reservoir through a supply path;

• connecting the reservoir to the coating apparatus through a delivery path;
• flowing coating material from the coating material supply into and through the supply path to and into the reservoir;
• measuring the volume of coating material flowed through the supply path into the reservoir;
• after flowing coating material into the reservoir, cleaning coating material from at least a portion of the supply path to electrically isolate the reservoir and coating material therein from the coating material supply;
• after completion of said cleaning step, delivering coating material in the reservoir through the delivery path to the coating apparatus for being electrostatically charged and emitted by the coating apparatus;
• metering the volume of coating material delivered from the reservoir to the coating apparatus;
• and, in response to said measuring and said metering steps, interrupting delivery of coating material from the reservoir to the coating apparatus upon metering a selected volume of coating material delivered from the reservoir to the coating apparatus.

A method of supplying selected electrically conductive coating materials to high voltage electrostatic coating apparatus with a color changer having inlets for connection with respective ones of a plurality of supplies of the coating materials and an outlet for the materials, while maintaining electrical isolation between the high voltage at the coating apparatus and the color changer and supplies of coating materials, said method comprising the steps of coupling the color changer outlet to first and second reservoirs through respective first and second supply paths;

• connecting the first and second reservoirs to the coating apparatus through respective first and second delivery paths;
• flowing coating materials from selected ones of the coating material supplies from the color changer outlet alternately to and into the first and second reservoirs through the respective first and second supply paths;
• measuring the volume flows of coating materials flowed into the first and second reservoirs;
• after flowing coating material into a reservoir, electrically isolating such reservoir and coating material in it from the color changer and coating material supplies by cleaning coating material from at least a portion of its respective supply path;
• while flowing coating material into one reservoir and then electrically isolating such reservoir and coating material in it from the color changer and coating material supplies, delivering coating material from the other reservoir through its respective delivery path to the coating apparatus for being electrostatically charged and emitted by the coating apparatus;
• metering the volume of coating liquid delivered from a reservoir to the coating apparatus;
• in response to said measuring and metering steps, interrupting delivery of coating material from a reservoir to the coating apparatus upon metering a predetermined volume flow of coating material from such reservoir;
• upon interruption of delivery of coating material from a reservoir to the coating apparatus, electrically isolating such reservoir from the coating apparatus by cleaning coating material from at least a portion of its respective delivery path;
• upon electrical isolation of a reservoir from the coating apparatus, delivering coating material from the other reservoir through its respective delivery path to the coating apparatus for being electrostatically charged and emitted by the coating apparatus;
• upon completion of electrical isolation of a reservoir from the coating apparatus, cleaning such reservoir before flowing the next selected color of coating material into it.