Method and apparatus for electrostatic spray coating
First Claim
1. A method for electrostatically spray-coating an article in a coating zone with a liquid coating material, the method comprising the steps of:
- supplying air to an atomizing device having a spray head;
supplying the liquid coating material to the atomizing device;
utilizing the air entering the atomizing device to atomize the liquid coating material with the air at the spray head, the air having a flow rate in excess of 5 CFM at the spray head and a delivery pressure of less than 15 psi over atmospheric pressure at the spray head; and
creating an electrical charge differential between the atomized liquid coating material and the article in the coating zone for causing the atomized liquid coating material to be directed to the article.
2 Assignments
0 Petitions
Reexamination
Accused Products
Abstract
Method and apparatus are provided for electrostatically spray coating an article in a coating zone with a liquid coating material, such as paint, wherein air is supplied to the spray head of an air spray gun at an atomizing air flow rate in excess of 5 CFM and at a delivery pressure of less than 15 psi to atomize the liquid coating material. At this combination of relatively low pressure and relatively high volume of air the transfer efficiency is substantially higher than for conventional air spray guns. A turbine unit filters and heats the air so that the air has a temperature in excess of 70° F. at the spray head. An elongated conductive rod is reciprocably supported within a nozzle of the spray head to create an electrical charge differential between the atomized liquid coating material and the article in the coating zone when charged by a high voltage source. Preferably, the rod is positioned within a liquid discharge orifice of the nozzle to alternatively open and close the nozzle. Also, preferably, the air flow rate at the spray head is in the range of 5-35 CFM, and the air delivery pressure at the spray head is in the range of three to nine psi over atmospheric pressure.
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Citations
21 Claims
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1. A method for electrostatically spray-coating an article in a coating zone with a liquid coating material, the method comprising the steps of:
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supplying air to an atomizing device having a spray head; supplying the liquid coating material to the atomizing device; utilizing the air entering the atomizing device to atomize the liquid coating material with the air at the spray head, the air having a flow rate in excess of 5 CFM at the spray head and a delivery pressure of less than 15 psi over atmospheric pressure at the spray head; and creating an electrical charge differential between the atomized liquid coating material and the article in the coating zone for causing the atomized liquid coating material to be directed to the article. - View Dependent Claims (2, 3, 4, 5, 17, 18, 19, 20, 21)
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6. A method for electrostatically spray-coating an article in a coating zone with a liquid coating material, the method utilizing a turbine which includes a series of vanes supported on a central spindle, the method comprising the steps of:
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rotating the central spindle of the turbine to cause air supplied to the interior of the turbine to flow from an air outlet of the turbine; supplying air from the air outlet to an atomizing device having a spray head; supplying the liquid coating material to the atomizing device; utilizing the air entering the atomizing device to atomize the liquid coating material with the air at the spray head, the air having a flow rate in excess of 5 CFM at the spray head and a delivery pressure of less than 15 psi over atmospheric pressure at the spray head; and creating an electrical charge differential between the atomized liquid coating material and the article in the coating zone for causing the atomized liquid coating material to be directed to the article.
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7. Apparatus for electrostatically spray-coating an article in a coating zone, the apparatus comprising:
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an atomizing device having an input liquid coating passage, a separate input air passage and a spray head, said coating passage providing a connection to a source of liquid coating material; a source of air for connection to the air passage, the air having a flow rate in excess of 5 CFM at the spray head and a delivery pressure of less than 15 psi over atmospheric pressure at the spray head, the atomizing device utilizing the air entering the atomizing device to atomize the liquid coating material at the spray head; and means, including a high voltage source, for creating an electrical charge differential between the atomized liquid coating material and the article in the coating zone. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for electrostatically spray-coating an article in a coating zone, the apparatus comprising:
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an atomizing device having an input coating passage, a separate input air passage and a spray head, said coating passage providing a connection to a source of liquid coating material; a source of air for connection to the air passage, the source of air including a turbine having a series of vanes supported on a central spindle for causing air supplied to the interior of the turbine to have a flow rate in excess of 5 CFM at the spray head and a delivery pressure of less than 15 psi over atmospheric pressure at the spray head, the atomizing device utilizing the air entering the atomizing device to atomize the coating material at the spray head; and means, including a high voltage source, for creating an electrical charge differential between the atomized liquid coating material and the article in the coating zone.
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Specification