Voltage block for electrostatic spraying apparatus

Abstract

A voltage block device for use with electrostatic spraying apparatus for conductive coatings is disclosed. The device maintains an air gap which electrically isolates a grounded paint supply from a charged spray head to prevent the leakage of potential to the grounded paint supply. The device comprises a tube made of non-conductive material and having ends which are closed by upper and lower caps to define a closed space which is pressurized. A valve secured in the upper cap delivers paint into the closed space to raise the level of conductive coating material therein to the level of an external sensor. In a first mode of operation, valve interlock circuitry opens the valve when the spray head is not charged and the sensor detects a low level of coating material. The valve closes if the level of conductive coating material in the closed space reaches the external sensor or the spray head becomes charged, restoring an air gap which electrically isolates the grounded paint supply. In a second mode of operation, the valve interlock circuitry includes a timer and opens and closes the valve intermittently, when needed, so it dispenses discreet bodies of conductive coating material separated from each other, the upper cap and the conductive coating material in the cylinder by one or more air gaps having a combined length sufficient to electrically isolate the grounded paint supply. This valve cycle is repeatable and permits continuous charged operation of the spray head.