GB1461436A - Apparatus for atomizing paint or a similar liquid - Google Patents

Abstract

1461436 Spray producers SKM 9 May 1974 [10 May 1973 (2)] 20432/74 Heading B2F Apparatus for atomizing paint or a similar liquid, comprises a spray gun having an atomizing head 3, Figure 2, incorporating a nozzle 13 for the hydrostatic atomization of paint, the nozzle having a slot-like outlet orifice 13a for discharging a flat, fan-shaped jet of paint, compressed air being fed around the paint jet from a concentric annular orifice 23 in the form of a hollow furstoconical air jet converging to a point adjacent the outlet orifice, and compressed air also being directed onto opposite sides of the paint jet from passages 28a, 28b disposed at right angles to the nozzle axis, these latter air jets being deflected by a frustoconical surface 21a of an air head 21 and by a frustoconical surface of the nozzle 13 and an annular member 14 surrounding the nozzle before they impinge on the paint jet. Paint is fed to the nozzle at a pressure of between 145 and 1450 psi, and compressed air at a pressure of between 7 and 29 psi, their flows being controlled by valves 9, 20a, respectively, the valves being simultaneously actuated upon operation of a trigger (11), Figure 1 (not shown). The annular orifice 23 is formed between frustoconical surfaces, of nozzle 13 and member 14, and between an inner frustoconical surface of air head 21, and may comprise locally widened portions, e.g. in the plane of the paint jet or at right angles thereto. In the embodiment of Figure 4 (not shown) the air passages 28a, 28b are forwardly inclined, and in the embodiment of Figure 5 (not shown) an additional pair of forwardly inclined air passages (32a), (32b) is provided, in each embodiment the frustoconical surface of air head 21 being omitted. In Figure 7 (not shown) both the nozzle 13 and the leading edge (14a) of annular member 14 project beyond the air head 21. In Figure 8 (not shown) the frustoconical surfaces of the nozzle 13 and annular member 14 have a more acute conical angle. In an electrostatic spray gun, Figure 9, the arrangement is similar to Figure 4, except that aligned primary E 1 and secondary E 2 electrodes are disposed in the air head 21 on opposite sides of the paint jet. E 1 is a needle electrode and is connected to the high voltage outlet of a voltage booster 36, disposed in a body 2 of the spray gun, by means of a key 27, which also prevents the nozzle from rotating in the air head, a socket 8, a ring 12 and the annular member 14, all of conducting material, the air head 21 being preferably of insulating material. The voltage booster 36 is connected to a medium voltage electrical source 34. E 2 , the secondary electrode, is insulated from the air head 21, and has a blunt end which collects electrical charge from the primary electrode E 1 , the discharge being in the form of a corona passing through the paint jet. A forwardly extending tip E 2a of secondary electrode E 2 leaks the charge away to ground. The nozzle 13 is electrically conducting and reaches the potential of primary electrode E 1 . Alternatively, the electrostatic spray gun may comprise a plurality of primary and/or secondary electrodes. In all embodiments the nozzle 13 may be of heattreated or carbide steel. The air passages 28a, 28b, (32a), (32b) may alternatively be located, e.g., in the plane of the paint jet. A further embodiment is similar to Figure 9 except that the electrodes E 1 , E 2 are omitted, the paint jet being charged via the conducting nozzle 13.