Patent GB-1449998-A (GB)
Title: Electrogas dynamic production line coating system
IPC: B05B5/10
Filed: 1974-05-30
Abstract: 1449998 Spray coating apparatus; sprayproducers ENERGY INNOVATIONS Inc 30 May 1974 [1 June 1973] 23961/74 Headings B2F and B2L A production line coating system comprises means for conveying articles 11 through a particle charging section 13 of a chamber 10 in which a cloud of electro gas dynamically charged particles are produced, and a precipitation section 16 in which particles are deposited on the articles, the cloud being moved through the chamber with the article by air, or other gas, flow. As shown in Fig. 1 air enters the section 13 from the EGD (electro gas dynamic) guns 18, 20, 22, 24 and an air source 12a and leaves through openings 28, 30 with baffles 32, 34, further air from a source 34a preventing loose particles leaving on the articles or this conveyor. The lining 26 of the section 16 is a conductor and charged, as by a lead 26a from the section 13, to prevent deposition of particles on its walls. The walls are preferably dielectric and adjustable in position to be as close as the articles allow. The articles may be charged at the opposite polarity to the cloud in a pre-charge section having EGD or corona discharge means. A plurality of EGD guns may be provided in the chamber for coating with alternative colours and separate clouds of coloured charged particles may be moved by the gas flow alongside respective articles as in Fig, 17 in which a high air flow (60 ft/min) enters the left hand end of the chamber 210 and is withdrawn by fans 218 and 218a at both ends adjusted to give a flow equal to the conveyor speed (20 ft/min). To provide a neutral charge on the articles they may pass through a first precipitation section as described with particles charged at a positive or negative potential and then through a second section in which the particles are charged at the opposite potential and move in the opposite direction to the conveyor, the apparatus having a single central exhaust section (Fig. 12, not shown). The EGD gun in Fig. 6 comprises an earthed venturi section with high pressure air and powder inlets 60 and 58; an ionization section with a dilution air inlet 70, an attractor ring 66 which sustains a corona discharge from an earthed needle point 64 or a cat whisker rod 161 of stainless steel mounted in a stainless steel tube 165 (Fig. 16 not shown), the molecular ions so produced charging the particles positively or negatively, as suits the articles being coated; and a barrel section with a deflection cone 76 which may be interchangeable. The ring 66 is charged by a solid state inverter on the gun at 6000V or from a remote supply via a cable. The flow of dilution air may be sufficient to eliminate the need for the air inlet 60. The powder is drawn through the hollow piston-rod 58' of a piston 58 mounted just above powder in a cylindrical container 78. A helical groove 84 in the piston causes the air flow to entrain particles from the coating material 80. A plurality of cylinders with open tops may be placed in a shipping container (88) (Figs. 8 to 10, not shown) which may be rotated or have a rotary rake (92) suspended therein to maintain an even level.