Spraycoating device

#The present invention relates to a spraycoating device defined in the preamble of claim 1.

#A spraycoating device of this kind is disclosed in U.S. Pat. No. 4,993,645. Said patent shows a hand-held spraycoating device and a spraycoating device which is held in a support, both devices operating with coating powders. Moreover the European patent document 0,164,837 B1 discloses an electrostatic spraycoating device for liquid coating materials., They comprise high-voltage electrodes to electrostatically charge the coating material. In general the electrode is cannular or a kind of a filamentary wire situated in a compressed-air duct. The compressed air is used to prevent the coating material from adhering or sintering to the electrode. The electrode, its support and means required to constitute the compressed-air duct must be designed in such manner that they shall only minimally degrade the flow of coating material. At the same time, however, the electrostatic charging must be efficient.

#Several high-voltage electrodes also may be used instead of a single one.

#The dependent claims define further features of the invention.

#The invention is elucidated below by means of preferred illustrative embodiments and in relation to the attached drawings.

#FIG. 1 schematically shows an axial section of a spraycoating device of the present invention,

#The spraycoating device 2 shown in FIG. 1 includes a coating-material duct 4 within a housing 6. The coating-material duct 4 is fitted with an output aperture 8 in the front end of the device from where issues the pneumatically moved, powdery coating material that flows in the form of a powder cloud 9 onto the object to be coated.

#A thin tube (cannula) made of an electrically conducting material constitutes the high-voltage electrode 10 which is configured axially on the center line 12 of the flow of coating material. The tubular high-voltage electrode 10 runs axially through a baffle 13 which is configured downstream of the output aperture 8 and in the flow path of the coating material and which is affixed within the coating-material duct 4 by a bracket 14 to the housing 6. A compressed-air duct 16 runs through said bracket and communicates pneumatically on one hand with a compressed-air duct 18 in the housing 6 and on the other hand, at the rear end 20 of the tubular high-voltage electrode 10, with a connecting duct 22. As a result compressed air may flow through the connecting duct 22 of the high-voltage electrode 10 and then through its downstream compressed-air outlet 24 to prevent coating material from adhering or sintering to the downstream end 26 of the tubular high-voltage electrode 10. At the compressed-air outlet 24 and downstream from it, the flow of compressed air generates reduced pressure (venturi effect) to aspirate ambient air. This air flows over the outside of the high-voltage electrode 10 and keeps it free of coating material.

#The rear end 20 of the high-voltage electrode 10 is connected by an electric cable 28 to a high-voltage generator 30. The high-voltage generator 30 preferably is situated inside the housing 6. In another embodiment of the present invention, the high-voltage generator 30 may also be mounted outside the housing 6.