Fluid sprinkling – spraying – and diffusing – Electrostatic type – Pressurized spray material
Patent
1994-05-25
1995-05-02
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Electrostatic type
Pressurized spray material
239321, 239327, 239375, 222391, B05B 1102, B05B 516
Patent
active
054112117
DESCRIPTION:
BRIEF SUMMARY
The invention relates to electrostatic spray guns.
Many patents have been published on such guns, and further our previous patent application No. 9101812.7 (now PCT GB 92/00156 filed 25 Jan. 1992) relates to them. In our prior spray guns, however, the electrical forces have been applied to the fluid to be sprayed after its emergence from a container.
In current work, we have found the fluid may itself be part of the electrical path. Suitable fluids such as paints then appear to behave as if charged electrostatically, leading to generation of a cloud of separated charged droplets as soon as the paint issues from a nozzle. Then, with a suitably earthed target, the droplets are attracted and discharged electrically, to form a coating.
The invention thus provides an electrostatic spray gun comprising a housing for receiving a replaceable fluid container, a nozzle from which fluid is to be sprayed, means for expelling fluid from the container, and a high voltage generator for applying electrostatic potential to the fluid to form an electrically charged atomised spray at the nozzle, wherein the container is externally insulating and the electrical path from the generator passes through the fluid, entering it at a point remote from the nozzle.
The invention also provides an electrostatic spray gun comprising a housing for receiving a replaceable fluid container, a nozzle from which fluid is to be sprayed, means for expelling fluid from the container, preferably by mechanical pressure applied thereto, and a high voltage generator for applying electrostatic potential to the fluid to form an electrically charged atomised spray at the nozzle, wherein the electrical path from the generator to the nozzle passes through the fluid, entering the fluid prior to its emergence from the nozzle, conveniently via the wall of the container.
In a simple and convenient construction, in operation the container is drawn back towards the generator to commence spraying, the movement opening a valve for passage of fluid from the nozzle.
Use of such constructions allows very easy front loading of a container and its valve into a gun, or alternatively if required attachment of a complete disposable container
ozzle unit, dispensing with the need for complex conductive paths, without difficulty in securing proper electrical connections. Further where the container is externally insulating there is no risk of shock. Even if the gun is misused, with loading attempted with the generator on, the container cannot discharge the gun through the operator. A range of different units may be provided for a given gun. Specifically for example front loading of the container into the gun simultaneously makes connection to the electrical path from the generator or places the container in a position where a short further movement opening a valve for passage of fluid from the nozzle also makes such contact.
Electrical connection is conveniently made centrally of the rear of the container, passing through its wall for contact with the contents, but various constructions are suitable.
In one construction the container is at least in substantial part of flexible insulating material and the gun has means for compressing the container to feed fluid to the nozzle, the generator applying the potential to the fluid through a conductive connection in an insulating part of the container wall. It may then be convenient for the electrical connection to close an aperture in the container through which the container is filled. In such cases "flexible" implies that at least a substantial part of a fluid-containing portion of the container is flexible walled, not that the container is flexible walled throughout though such a construction is convenient.
Alternatively the container may be of rigid insulating material, fluid being expelled by a piston under pressure exerted on it by a forward part of the generator or otherwise. Electrical connection may then be through the piston, of conducting material or at least having an electrical connection through it to the fluid. Al
REFERENCES:
patent: 3554450 (1971-01-01), Muhula
patent: 3563258 (1971-02-01), Hechler, IV
patent: 4549243 (1985-10-01), Owen et al.
patent: 5221050 (1993-06-01), Jeffries et al.
patent: 5320291 (1994-06-01), Glooer et al.
Green Michael L.
Greene Robert H.
Jones Jonathan
Noakes Timothy J.
Outhwaite Alan C.
Kashnikow Andres
Weldon Kevin
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