An electrostatic device for spraying electrically conductive liquid coating product comprises a storage tank for the product in which the product is at a high voltage. The tank is defined in a substantially cylindrical cavity formed in an insulative material body and inside in which is a piston forming in the cavity a mobile wall separating a coating product chamber from an actuation chamber filled with an electrically insulative actuation fluid. The body is fixed to a conductive material socket which is grounded and to which is connected an actuation fluid supply circuit extending between the socket and the actuation chamber and discharging into the actuation chamber near a back wall of the cavity which is not in contact with the coating product. A section of the supply circuit runs substantially parallel to the cavity in the direction away from the socket starting from the back wall.

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.

A fluid supply cylinder with improved flusbability, useable for supplying paints to a dispenser in electrostatic coating systems. The fluid supply cylinder having generally a piston reciprocatingly disposed in a chamber of a body member, the piston having a head with a face opposite an end wall of the chamber, a plurality of chamber fluid ports disposed in the end wall of the chamber, and a plurality of fluid conduits between a corresponding one of the plurality of chamber fluid ports and a common outer fluid port, whereby the reciprocating piston draws fluid into the cylinder chamber and supplies fluid from the cylinder chamber through the plurality of chamber fluid ports in the end wall thereof.

A paint dosage device is particularly adapted to be mounted in close proximity to a spray gun (P) in a program controlled spray painting installation for dosed paint supply to the spray gun. The device includes at least two dosage cylinders (SA,SB), each having a regulating piston (PA,PB) connected to a piston departure position and displacement velocity regulator (RA,MA:RB,MB) for setting the paint filling amount of the associated cylinder by controlled adjustment of the departure position of the regulating piston in the cylinder, and for setting the dosage rate of the cylinder when supplying paint to the spray gun, by program controlling the displacement velocity of the regulating piston in the cylinder. A valve assembly (V1,V2,V3,V4) is arranged for connecting the cylinders (SA,SB) alternately to the spray gun (P) and putting the cylinder disconnected from the gun in connection with means for cleansing and paint filling apparatus. This paint dosage device is particularly suitable for application in the case the spray gun is provided with high tension electrode (E) for electrostatically charged atomizing of supplied electrically conductive paint. Each regulating piston (PA,PB) of the cylinders is then connected with the a piston departure position and displacement velocity regulator by means of an electrically insulating motion-transferring connection (IA,IB) and each valve (V1,V2,V3,V4) of the valve assembly is made electrically insulating.

An apparatus for electrostatically coating a workpiece has an insulating separator valve mechanism for electrically separating a paint supply passage for supplying an electrically conductive paint to a coating gun, into a paint supply passage to which a high voltage will be applied and a paint supply passage to which no high voltage will be applied. The insulating separator valve mechanism has a first valve body connectable to said paint supply passage through a first on/off valve, and a second valve body connectable to said paint supply passage through a second on/off valve. While the first and second valve bodies are connected to each other and the first and second on/off valves are closed, a paint trap is cleaned by a cleaning medium, which is discharged into a second dump passage. A process of cleaning the paint trap for a paint color change is efficiently and reliably carried out to reliably remove paint residuals from the paint trap.