GB1522612A - Apparatus and method for electrostatic spraying of particulate material - Google Patents

Abstract

1522612 Electrostatic spraying apparatus IMPERIAL CHEMICAL INDUSTRIES Ltd 11 Aug 1975 [16 May 1974[ 21764/74 Heading B2F Electrostatic spraying apparatus suitable for spraying crops or coating surfaces with powder, comprises a casing 2, a conduit (7), Fig. 2 (not shown) for introducing particles from a container (8) into the casing, an insulating barrel 1 extending from the casing to an outlet port 1a, a fan 4 mounted within the casing for causing a flow of particles entrained in gas through the barrel, said particles becoming electrically charged as a result of frictional contact with the fan blades and with the walls of the barrel, a toroidal aluminium capacitor 11 surrounding the outlet end of the barrel, and needle electrode 12 extending into the barrel for collecting charge from the particles and transferring this charge to the capacitor so that it repels the charged particles emerging from the outlet port. An inverted cone may be mounted in the outlet of the barrel to reduce air motion at the target surface. In Fig. 3 (not shown) the barrel (1b) is made of metal and the capacitor (11b) is attached around the outlet end of the barrel by means of insulating spacers (50). In Figs. 4 and 5 (not shown) the powder is fed to the casing from a vibrating hopper (22), and an earthed electrically conductive wire (31) disposed within the barrel removes charge from the inner surfaces of the barrel. The apparatus depicted in Fig. 5 (not shown) may alternatively be used for spraying liquid droplets and includes a corona discharge electrode (40) which projects into the barrel and is surrounded by, but electrically insulated from, an earthed aluminium insert (42).