GB1057431A - Improvements in and relating to electro-static spray painting - Google Patents

Abstract

1,057,431. Electrostatic spraying process and apparatus. RANSBURG ELECTRO-COATING CORPORATION. Feb. 1, 1963 [Nov. 1, 1961], No. 39084/61. Headings B2F and B2K. A method of electrostatically spray coating an article comprises supplying liquid coating material under high hydrostatic pressure to a small orifice, projecting the coating material from said orifice into the surrounding atmosphere as a thin expanding liquid film to effect atomisation from the edge of said film into fine spray particles, establishing by a single electrode means positioned closely adjacent but spaced from said liquid film an electrostatic field extending between the electrode means and the article to charge the atomized spray particles and to promote the movement to and deposition on said article, while still in liquid state, of spray particles. Apparatus comprises a barrel 101 of insulating material attached to a metal body 103 which is earthed. High voltage is applied via line 104, connection 105, resistor 106 (typically of about 160 megohms) and contact 106a to a fine wire electrode 107 having a terminal portion 108. The electrode is preferably .01 or .02 inch in diameter, and pointed. The distance from the electrode to the nearest earthed part of the gun (i.e. the metal body) is about six inches, which with an applied potential of 50,000 volts gives a fixed minimum potential gradient of over 8000 volts per inch so as effectively to charge the particles. Paint is supplied via passages 111, 112 and valve 114 to a nozzle 110 in a member 126 of tungsten carbide or diamond. The nozzle may be elongated with a major diameter of .015 inch and a minor diameter of .005 inch so as to produce a fan-shaped spray.