The invention relates to improvements in electrostatic spray guns, especially for spraying pulverized or pulverulent coating materials. More particularly, the invention relates to improvements in electrostatic spray guns of the type wherein the barrel comprises inner and outer tubes defining an annular clearance for the flow of a liquid, gaseous or flowable solid material toward a deflector at the front end of the inner tube and wherein an electrode is connected with a high-voltage conductor which is installed in the inner tube of the barrel.
German Offenlegungsschrift No. 34 12 694 of Kirchner et al. discloses an electrostatic spray gun wherein the annular clearance between the inner and outer tubes of the barrel serves for admission of a mixture of air and pulverulent material. The front end of the inner tube of the barrel extends forwardly beyond the front end of the outer tube and is provided with a circumferential groove for a stream of swirling control air. Ionization is effected by means of a third air stream which is admitted through an axial channel in the inner tube and is diverted radially outwardly through a conical gap at the front end of the inner tube to enter the mixture of air and pulverulent material issuing from the front end of the annular clearance between the inner and outer tubes. A disc-shaped electrode constitutes a portion of the boundary for the conical gap. The ionization of flowable materials in such types of spray guns is not entirely satisfactory.
Applicants are further aware of the disclosure of U.S. Pat. No. 4,548,363 to McDonough which deals with a muzzle for electrostatic spray guns and with the manner of connecting a conductive rod in a tube of the muzzle with a power terminal.