An electrostatic pump in an electrostatic sprayer is disclosed which comprises an ion injection electrode means disposed in a liquid conduit for conveying liquid to a sprayhead, downstream of the ion injection electrode is an ion discharge electrode means comprising an earthed ring, a potential difference is provided between the electrodes to provide hydrostatic pressure for conveying liquid in a conduit to the sprayhead.

A method of substantially eliminating corona discharge at the high-value resistor of an electrostatic spray gun comprises the steps of inserting an insulating tube within a bore formed in the gun barrel, positioning a high-value resistor in the insulating tube, filling a portion of the insulating tube with a slug of dielectric material such as grease and then inserting a high voltage cable into the insulating tube so as to force the grease ahead of the cable. The grease encapsulates the resistor and flows into the space between the insulating tube and bore in the gun barrel to eliminate the presence of air around the resistor so as to prevent corona discharge.

A method and apparatus for replacing spent dielectric material at the high-valued resistor in an electrostatic spray gun, having an insulating tube disposed within a bore formed in the gun barrel which receives the resistor encapsulated with spent dielectric material, comprises the steps of inserting a syringe apparatus into the insulating tube, dispensing new dielectric material contained within the syringe into the insulating tube while withdrawing the syringe therefrom, and then inserting a high voltage cable into the insulating tube to force the new dielectric material ahead of the cable. The new dielectric material encapsulates the resistor and forces the spent dielectric material between the insulating tube and gun barrel bore away from the resistor.

An improved electrostatic spray gun, particularly of the hand-held type, is disclosed including an electrically insulative barrel and nozzle assembly, an electrically insulative air valve module mounted to the rear of the barrel assembly and externally thereof, and an electrically conductive metal handle assembly enclosing the rear end of the barrel and the air valve module. A charging electrode protrudes from the discharge orifice of the nozzle assembly. The flow of air through the barrel and nozzle assembly is controlled by a trigger which actuates the air valve. Actuation of the air valve in turn controls a needle and seat valve assembly close to the discharge orifice of the nozzle assembly to control the flow of coating material through the gun. A resistor is disposed inside the needle valve immediately upstream of the charging electrode. The elements of the electrostatic spray gun of this invention cooperate to provide a simple, lightweight, balanced gun having a high degree of reliability and repairability and clean and safe operation.

Apparatus is disclosed for resistively damping capacitively stored energy in electrostatic spray guns, wherein a fluid spray valve incorporates an electrode for carrying high electrostatic voltage, the electrode terminating in the spray valve and the spray valve having a conductor contacting the electrode and extending externally thereof. A resistive element at least partially encloses the spray valve and electrically contacts the conductor, permitting electrical conductivity while also permitting axial sliding movement of the spray valve inside of the resistive element.