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US 4,073,002 AGranted
Self-adjusting power supply for induction charging electrodes
AssigneePPG Industries, Inc.
InventorsJames E. Sickles, Richard M. Tepper
Life of this patent
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AssigneePPG Industries, Inc.
InventorsJames E. Sickles, Richard M. Tepper
Estimating the term…
A self adjusting power supply for induction charging electrodes used in electrostatic spray coating apparatus is disclosed. A first resistance of high ohmic value is connected in series between a source of high direct current voltage and the induction charging electrode, while a second resistance is connected between the source of voltage and a ground reference point. The first resistance acts as a voltage divider with the spacial impedance which exists between the charging electrodes and ground in the spray nozzle of the spray coating apparatus, and serves to regulate the charging voltage and to compensate for variations in the conductivity of the material being sprayed. If the value of the spacial impedance should decrease for any reason, the increased current flow therethrough produces an increase in the voltage drop across the first resistance, thereby reducing and thus regulating the potential at the charging electrodes and serving to prevent corona and arcing within the spray gun. The ohmic value of the first resistance, which is in the range of 1-50 gigohms, is sufficiently high to prevent any substantial current flow from the charging electrode, thereby reducing the shock hazard of the spray gun, and also to prevent any significant changes in the current flow due to changes in the conductivity of the spray material. The second resistance serves as a bleeder for the charges on the spray gun and the induction charging electrode when the gun is turned off.
In an electrostatic induction spray system including a spray nozzle, electrode means adjacent the nozzle and spaced therefrom to define an induction charging zone, and a power supply having a voltage source for supplying a DC voltage to said electrode to produce within said charging zone an electrostatic field which surrounds the discharge ports of said nozzle, the improvement comprising:
In an electrostatic induction spray system including a spray nozzle having liquid discharge ports, electrode means spaced around said nozzle to define a charging zone surrounding said spray discharge ports, and a power supply having a voltage source for applying a DC voltage between said electrodes and said liquid within said charging zone to provide an electrostatic field having a voltage gradient sufficient to induce on liquid spray particles ejected from said liquid discharge ports an electrostatic charge, the improvement in said power supply comprising:
Dependencies are inferred from the claim text.