GB1209653A - Apparatus for electrostatic spray coating - Google Patents

Abstract

1,209,653. Coating apparatus; spray producers. AIR-O-STATIC Inc. 2 July, 1968, No. 31511/68. Headings B2F and B2L. Electrostatic spraying apparatus comprises a rotary head for centrifugally atomising and radially projecting coating material supplied thereto, electrode means located rearwardly of the atomiser head, and a high voltage source having one terminal connected to the electrode means and the opposite terminal connected to the atomiser head and to an article located forwardly of the atomiser head. The article and atomiser head are thereby maintained at the same potential and an electrostatic field is established between the electrode means and article, said field surrounding and being spaced radially from the atomiser head for receiving therein the atomised coating material. An insulating body 30 and a metallic tubular member 34 support an air motor rotating a metallic dished atomiser head 12. Member 34 is rigid with a metallic base 18 having an earthed connection G2. Compressed air is supplied to the motor via a pipe 20 and is discharged, together with compressed air supplied by a pipe 22 to the space between the motor and member 34, over the rear surface of head 12. Coating liquid, supplied via a pipe 24 and passages within member 34, is directed radially on to the front surface of head 12 near the axis thereof, and is discharged radially from the rim of lead 12 in finely atomised condition. The air passing over the rear surface of head 12 forms a shroud for the atomised liquid. Body 30 carries a circumferential row of charging electrodes 16, each of which is an insulating rod containing a metallic core terminating in a forwardly-directed point 100 located rearwardly of head 12. Said cores are connected via a cable 26 to the negative terminal of a high voltage generator 28, the positive terminal of which has an earth connection G1. The arrangement is thereby such that a primary field E and a secondary field F are respectively established between electrodes 16 and an article 14 having an earth connection G4 and between electrodes 16 and head 12. The droplets discharged from head 12 are initially positively charged and, after being carried through field F by their initial momentum, are negatively charged in field E by the ions emitted by the electrodes 16 and are thereby conveyed for deposition upon article 14. In a modification the electrodes have tubular metal cores which are connected to generator 28 and also convey compressed air to form a shroud for the atomised liquid particles.