GB669978A - Improvements in or relating to electrostatic coating method and apparatus - Google Patents

Abstract

<PICT:0669978/III/1> In apparatus for coating articles by electrostatic deposition the articles 10, Fig. 1, are conveyed through a booth 1 between ionising electrodes 5, 6; 8, 9 and are sprayed with coating material by two guns or banks of guns 21, 28 arranged at opposite sides of the path of the articles and at opposite ends of the booth so as to direct their sprays in opposite directions the arrangement being such that the regions at which the opposed streams cross the path are spaced far enough apart to prevent or reduce interference between the streams. At the coating zone 5, 6, the articles are heavily coated on the edges 22 facing the guns 21 and more lightly coated on the sides and rear faces and at the further coating zone 8, 9 the edges 27 are heavily coated and the other parts are lightly coated. The second coating is applied before the first coat has dried so that the two deposits are blended and a layer of very uniform thickness results on all surfaces of the articles. Electrodes 5, 8; 6, 9 may be united into a single pair of electrodes, or either 5, 6 or 8, 9 may be united at the bottom to provide a trough-shaped electrode. Each electrode 5, 6; 8, 9 consists of corona discharge wires 7, 7 carried on frames. Two columns of air are drawn in from the inlet and outlet of the booth and expelled via chambers 31 leading into a single duct, Fig. 2 (not shown), to further reduce interference between the two streams and so to aid the deposition. The articles may be automobile window frames and are arranged obliguely at an angle of about 45 degrees to the direction of travel but in parallel overlapping relation to one another. They are carried on spring hooks. The guns 21, 28 may be parallel to the articles or at a slight angle to them (up to 15 degrees). In a modification, Fig. 5 (not shown), the paths through the two coating zones are at right angles and a single exhaust chamber is provided to cause two columns of air to pass through the apparatus from the inlet and outlet of the booth respectively.