Abstract: Induction charging apparatus for HVLP spray guns and air-assisted airless spray guns includes an air cap having a central orifice for receiving a spray gun nozzle. The cap includes one or more charging electrodes adjacent the orifice and carrying a voltage sufficiently large to induce on the spray droplets charges of a polarity opposite to that on the electrodes. A rotatable electrical connector enables the cap to rotate 360.degree. while maintaining electrical connections between the electrodes and a power supply. The spray gun nozzle is an airless nozzle receiving liquid at a pressure of about 1,000 psi and having a spray tip from which liquid is sprayed along a flow path coaxial with the electrodes. Air at less than about 10 psi is directed along the flow path to assist in the atomization of the liquid from the airless nozzle.

Abstract: Induction charging apparatus for HVLP spray guns includes an air cap having a central fluid exit orifice for receiving the spray gun nozzle. The cap includes one or more charging electrodes surrounding the orifice and carrying a voltage sufficiently large to induce on the spray droplets charges of a polarity opposite to that on the electrodes. The cap includes a rotatable electrical connector to enable the cap to rotate 360.degree., while maintaining electrical connections between the electrodes and a power supply.

Abstract: An adapter for converting spray guns to electrostatic or induction charging includes a housing mountable on a spray gun. A high voltage power source is contained in the housing and is connected to an electrode assembly mounted on the front of the housing. The electrode assembly includes four electrodes which extend in front of the spray gun nozzle and air cap and are spaced symmetrically around the spray axis. The nozzle is electrically grounded, while the electrodes carry a voltage in the range of 3-15 kV, to produce in the spray path from the nozzle an electrostatic field which produces electrical charges on the sprayed particles. When conductive liquids are sprayed, the particles are charged by induction at relatively low electrostatic field gradients, while nonconductive liquids require high electrostatic field gradients which produce corona effects. These corona effects are enhanced by the provision of a corona needle mounted on the nozzle at the spray axis.

Abstract: Disclosed is a spray gun having a gas nozzle and a fluid nozzle, each of said nozzles being in cooperative spatial relationship with the other to cause a fluid stream issuing from the fluid nozzle to be atomized and sprayed as fluid particles by gas issuing from the gas nozzle. In a preferred embodiment the fluid nozzle orifice has therein an axially disposed rod to increase surface area from which said fluid particles can be formed, said rod being electrically grounded at least during fluid issue from the nozzle. The spray gun additionally has an induction charging electrode disposed adjacent the gas and fluid nozzles, said electrode defining a charging zone wherein an electrostatic charge is imparted to atomized electrically-chargeable fluid particles.

Abstract: An electrostatic spray coating apparatus is disclosed which comprises a spray nozzle containing both air and liquid discharge ports, an inductive charging device or charging electrode located exteriorly of the discharge ports and attached to the spray nozzle, and electrical connections for applying an electric potential to the inductive charging device. The inductive charging device or charging electrode creates a charging zone, and is preferably positioned so that ambient air is mixed with air and fluid exiting from the discharge ports within the charging zone.

Abstract: A spray head for use with conventional air-atomizing spray equipment is disclosed which has spray-forming means that includes a secondary atomization annulus which provides improved atomization of liquid materials and which is especially suitable for spray devices having electrostatic induction charging means. The secondry annulus minimizes deposition on the spray head of particles electrically charged with a polarity opposite that of components of the spray head and provides re-atomization of sprayable material which collects on the walls of the nozzle.

Abstract: A method of applying a coating composition, which preferably has a high solids content, to a workpiece. The method is one wherein a coating composition is atomized into liquid particles, an electrical charge is imparted with an induction charging electrode means on the particles substantially simultaneously with their formation, and the charged particles are directed to an electrically-receptive workpiece, and includes the improvement comprising heating the coating composition to adjust its conductivity and to enhance the induction charging of the particles formed from the heated coating composition. In a preferred embodiment, the charged particles are cooled before they reach the workpiece.

Abstract: Disclosed is a spray gun having a gas nozzle and a fluid nozzle, each of the nozzles being in cooperative spatial relationship with the other to cause a fluid stream issuing from the fluid nozzle to be atomized and sprayed as fluid particles by gas issuing from the gas nozzle. In a preferred embodiment the fluid nozzle orifice has therein an axially disposed rod to increase surface area from which the fluid particles can be found, the rod being a corona discharge electrode of a first polarity. The spray gun additionally has an induction charging electrode of a second polarity opposite the first polarity and disposed adjacent the gas and fluid nozzles, the induction charging electrode defining a charging zone wherein an electrostatic charge is imparted to atomized electrically-chargeable fluid particles. Relatedly disclosed is a method of applying a liquid coating composition having an electrical conductivity of less than about 0.06 .mu.

Abstract: A cable terminal connector includes means for securing a terminus of a grounding or shielding conductor of a coaxial or non-coaxial type cable within a body of dielectric material. The junction of the grounding or shielding conductor with the dielectric material is characterized by means for distributing and lessening the intensities of mechanical or electrical stresses that may occur at the junction during use of the terminal connector in transmitting high DC voltage, low current power for electrostatic applications.

Abstract: Electrostatic spraying apparatus comprising a housing having an opening, liquid atomization means and induction charging electrode means mounted in said housing to deliver an electrically charged spray of liquid particles outwardly through the opening, inlet means to said housing for delivering to the housing a flow of gas for subsequent envelopment of the electrically charged spray of liquid particles upon exit from the housing, and repelling electrode means of a polarity the same as the electrically charged spray and defining an electrical repulsion zone for repelling said spray immediately prior to and after the exiting of said spray from the opening. Relatedly disclosed are an electrostatic induction charging gas shroud adapter and a repelling electrode adapter, each to be employed with appropriate atomization means to deliver an electrically charged spray of liquid particles as described above.

Abstract: An induction-charging adapter head may be quickly and easily mounted on, or demounted from, a conventional spray device equipped with a plate-like adapter of the type disclosed. The plate-like adapter also provides for safe connection or disconnection of a high voltage source to the induction-charging adapter head electrode by providing means for maintaining an electrical path to ground between the adapter head and plate-like adapter during the making or breaking of the high voltage connection.

Abstract: A light-weight, portable power pack for supplying a high voltage output to an electrostatic spray gun from a low voltage input is disclosed. The power pack is mounted on and forms a part of the spray gun and is detachable therefrom for replacement purposes. The power pack comprises a voltage multiplier circuit for converting a low voltage DC to a high voltage DC for induction charging of material discharged from the spray gun, the circuit being encapsulated in an epoxy resin material to provide a suitable mounting case therefor. The case is molded into a suitable shape and is attached, in one embodiment, to the bottom portion of the barrel of the gun by means of screws, bolts or the like, the power pack being provided with external contacts which serve to engage corresponding contacts on the spray gun to provide electical contact through the gun to the power source, which may be a battery pack carried by the operator, and to the inductive charging device for the spray gun.

Abstract: A spraying device having a liquid dispersing nozzle mountable in association with a chamber for directing a stream of gas can be used to provide a spray stream enveloped within a shroud of temperature and humidity conditioned air or gas for controlled evaporation of solvent from spray particles or for preventing reaction of particle components with the ambient atmosphere, and/or to prevent particle deposition and build-up on electrodes positioned so as to produce electrostatically charged particles.

Abstract: 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.

Abstract: An improved electrostatic spray charging device for spray guns is disclosed. The device comprises an adapter formed from a dielectric material in the shape of a generally cylindrical tube adapted at one end to be secured to the end of a conventional spray gun and constructed at the second end to provide an inductive charging field for materials discharged by the spray gun. The second end of the adapter is formed, in the preferred embodiment, into two diametrically opposed lobes, each of which carries on its interior surface at least one charging plate to which a d.c. voltage on the order of 10-20 KV is applied. The exterior surface of each lobe carries an electrically grounded electrode which preferably is annular in shape to provide an electric field configuration that prevents accumulation of charged spray particles on the exterior surfaces of the adapter.