Fluid sprinkling – spraying – and diffusing – Electrostatic type – Pressurized spray material
Patent
1995-02-23
1996-07-02
Weldon, Kevin P.
Fluid sprinkling, spraying, and diffusing
Electrostatic type
Pressurized spray material
239323, 239327, B05B 516, B05B 1104, B05B 5035
Patent
active
055313841
DESCRIPTION:
BRIEF SUMMARY
The invention relates to electrostatic spray guns.
Many patents have been published on such guns, and further our previous patent application GB 92/01490 relates to them; it was filed 12th Aug. 1992 and published as WO 93/03853 on 4th Mar. 1993. Among published patents is EPA 0 482 814, using a flexible sachet as a container for material to be sprayed.
In current work, we have tackled problems of satisfactory sealing of the fluid to be sprayed, within its container, as well as of ready, smooth advance of the piston under low pressure.
The invention provides an electrostatic spray gun comprising a housing with a replaceable fluid container, a forward part 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, characterised in that the container is rigid and fluid is expelled from it through a nozzle, for generation of the spray, by a piston within the container under pressure exerted on the piston through a forward part of the generator or otherwise, the piston having axially inner and outer parts with a fluid lubricant seal provided between them.
In the above the invention is characterised by the nature of the container, and the invention may thus alternatively be expressed as a container of fluid for electrostatic spraying, for replaceable reception in an electrostatic spray gun having a housing for the container, a forward part from which the 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, characterised in that the container is rigid and contains a piston disposed to receive when in place in the gun mechanical pressure exerted through a forward part of the generator or otherwise to expel the fluid through a nozzle for generation of the spray, the piston having axially inner and outer parts with a fluid lubricant seal between them.
In one embodiment the inner and outer parts of the piston are separate, assembled with the lubricant between them. Alternatively however the piston is essentially in one piece, a circumferential reservoir for the lubricant separating the axially inner and the axially outer parts. A convenient lubricant, for a gun for paint, is glycerol/starch, providing an expendable reservoir of lubricant both sealing in the paint and preventing it drying round the piston, seizing it, if a container is part used.
In such a construction the electrical path, generator to nozzle, conveniently passes through the fluid to be sprayed, entering the fluid prior to its emergence from the nozzle, via the wall of the container or more conveniently through the piston.
The container may thus be of insulating material, when electrical connection is through a piston of conducting material or at least having an electrical connection through it to the fluid.
Alternatively for example, still providing for the electrical path to be through the fluid to be sprayed, the container, while externally insulating, may be of metal, making the required electrical connection with the generator interiorly, at a position remote from the nozzle, and providing a direct electrical path to the fluid within the container interior. The material of the piston itself is then unimportant.
In a simple and convenient construction, in operation, the container and generator are drawn together 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 containe
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Cliffe Andrew I.
Greene Robert H.
Hunziger Karl B.
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