GB912655A - - Google Patents

Abstract

912,655. Electrostatic paint-spraying. RANSBURG, H. J., RANSBURG, G., RANSBURG, H. P., and RANSBURG, E. M., [trading as RANSBURG CO., HARPER J.]. Dec. 15, 1958 [Dec. 16, 1957], No. 40351/58. Class 95 An electrostatic paint-spraying device comprises a body, an orifice-type mechanical atomizer having an orifice at the forward end of the' body, a charging electrode closely adjacent the orifice and presenting a point at its most forward part and connected to a high voltage source for producing a deposition field between the electrode and an article to be painted, and a zone of high ionization adjacent the forward part of the electrode, those parts of the body which are forward of the forward part of the electrode, or sufficiently close thereto to be able to influence the ionization or the deposition effect of the field, being of insulating material. As shown, a spray-gun 10 is mounted on a highly insulating shaft 12, and consists of a body 14, a liquid cap 15 and an air cap 16 with a metal rod 17 projecting axially through the body and caps. The forward end of the rod 17 is formed by a fine wire 17c which protrudes through a passage 15a in the liquid cap; the rod 17 also carries a conical valve 17b, controlling the supply of liquid, which enters the gun through a passageway 20, and a cylindrical valve 17a controlling the supply of compressed air through a passageway 21. The rear end of the rod 17 is attached to a piston 31 which can be moved against the pressure of a spring 30 by compressed air admitted to the space 32 through the passage 22, this allowing liquid and compressed air to be supplied to the caps 15 and 16 respectively. The air cap 16 provides an annular hole 16a surrounding the liquid passageway 15a and may be provided with further holes. In addition, two spray-pattern shaping air horns 27 and 28, which may be of a highly insulating material such as nylon, or, if suitably rounded and located behind the end 17c of the electrode, of metal, are provided, having air holes directed towards the axis of the spray. The entire gun is maintained at a high negative potential of the order of 100 kilovolts, by a source 34, a high resistance 36 being inserted in the supply line to diminish the danger of sparking, and the article being coated is moved past the gun on an earthed conveyer. A manually-operated gun, in which the gun body is of highly insulating material, and the supply of liquid and of compressed air is controlled by valves operated by a trigger, is also described. Atomization may be effected by hydrostatic pressure instead of compressed air. Specifications 865,765 and 912,656 are referred to.