GB1367072A - Method and apparatus for electrostatic coating - Google Patents

Abstract

1367072 Coating by electrostatic spraying RANSBURG-PEABODY Ltd 20 July 1971 [20 April 1970] 18686/70 Heading D1L In apparatus for electrostatically depositing a material in spray form upon the surface of an article, e.g. a continuous sheet or web 10, Fig. 1, which comprises spray producers 14, 15 having outlets 16, 17 and main electrostatic charging electrodes 18, 19, supplementary electrostatic electrodes 26, 27 are provided to control the spray entering the deposition zone 23. By correlating the voltage applied to the electrodes 26, 27 with the motion of the earthed web 10, a more uniform deposition can be obtained, excess spray material being deposited on electrodes 28, 29 between which and opposing electrode 26, 27 an electrostatic field is established. Each electrode 26, 27 comprises an elongate plate 39 of high resistivity material along approximately the centre of which an inserted strip 40 of lower resistivity material is provided. Voltage reaches the strip 40 through a cable 45, contact spring 48, high value resistor 49, and a spring 50 all of which are enclosed in a sleeve 46 within an insulating sleeve 43 which is retained by adhesive 44 in a boss 41 glued at 42 to the back of the plate 39. In a modification, Fig. 4, (not shown), insulating surfaces (52), (53) are joined by a conductor (54) and are provided adjacent each side of the web outlet 25 so that charged particles may be deposited on the surfaces (52), (53) to repel further particles into the web 10. Air is withdrawn from the zone 23 through a conduit 24.