GB1188682A - Improvements in and relating to Spray Coating Apparatus - Google Patents

Abstract

1,188,682. Spray-producers. RANSBURG ELECTRO-COATING CORP. 27 April, 1967 [28 April, 1966 (3)], No. 19535/67. Heading B2F. An electrostatic spray gun suitable for discharging a liquid coating material comprises a narrow annular opening 30 for the emission of the spray particles. said opening being defined by the adjacent ends of a pair of coaxial electroconductive tubes 26, 27 which are connected to the opposite terminals of a voltage source, means for supplying a stream of air through the tube 26, and a cap 32 arranged so that the liquid supplied under pressure through the tube 27 is discharged through an annular gap as a thin film into the air stream. The film meets the air stream approximately at right-angles and the said gap is substantially coincident with the adjacent edge of the said opening. Both tubes 26, 27 may be earthed, an electrode 29, charged from a line 17 via a resistor 34, being mounted on the tube 26 by a ring 28 of insulating material. The spreading of the discharged spray may be prevented by air induced through openings 35 in a housing 23 by the flow of the spray particles. An earthed barrier 22 prevents the electrode 29 being reached through the openings 35. The particle deposition may be aided and dispersion prevented by an external electrode (37), Fig. 3 (not shown) which is insulated from the gun. The electrode (37) has hollow walls containing metal shavings or metal wool (41) and is charged by an air stream ionized by an electrode (45). Air may be induced through holes (46), (47) in the electrode. Alternatively the external electrode may comprise sharply pointed members (50) which are charged by the spray particles and are adjustably mounted, figs. 4 and 5 (not shown). In a further embodiment, fig. 6 (not shown) the external electrode is charged by a body of radioactive material (55), which body is adjustably mounted. A trigger controls the supply of air, liquid and voltage.