Fluid sprinkling – spraying – and diffusing – Electrostatic type
Patent
1989-11-16
1991-04-30
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Electrostatic type
239706, 118629, B05B 547
Patent
active
050110853
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus in a powder sprayer which includes an annular, friction charging channel defined by an inner longitudinal body with a surface of electrically insulating material and a tubular body surrounding the inner longitudinal body, with an inner surface of electrically insulating material, the channel being surrounded by an outer electric conductor.
BACKGROUND ART
Swedish Patent Application 8500530-4 discloses a powder sprayer in which use is made of an elongate, annular charging channel which is inwardly defined by an elongate rod of insulating material and which is outwardly defined by a tubular body of insulating material.
In certain cases, a sprayer of this configuration may function satisfactorily, but it suffers, not least, from the drawback that the powder cloud emitted from the nozzle at the discharge end of the gun shows a tendency to `kick back` onto the external surfaces of the gun so that a considerable amount of powder is deposited there. Furthermore, the charging level will be uneven, and, in certain powder qualities, so low that satisfactory powder coating cannot be achieved.
Swedish Printed Application 446 825 discloses another type of powder sprayer which includes a plurality of irregularly bent charging channels of insulating material through which a powder-air mixture is positively forced for charging the powder. Each one of these irregularly bent charging channels has on its outside an electrically conductive layer.
The construction according to this Printed Application also suffers from considerable drawbacks, partly in that the charging result will not be satisfactory, and partly in that the powder spraygun is constructed in such a manner that it is as good as impossible to clean in conjunction with change of powder quality.
Further problems which are inherent in prior art powder sprayguns reside in the fact that such high tensions have locally been formed in the gun that spark formation or discharges more or less of the light-arc nature have occurred in or at the gun. If such discharges have taken place in contact with the powder in the gun, in certain cases the powder has melted or sintered to form a large aggregate which has caused operational disruptions or a poor end result.
OBJECTS OF THE INVENTION
The present invention has for its object to realise a powder spraygun of the type disclosed by way of introduction, the powder spraygun being designed in such a manner as to provide extremely good and uniform charging results irrespective of the quality of the discharged powder. The present invention further has for its object to realise a powder spraygun of the type disclosed by way of introduction which is constructed in such a manner that it is extremely easy to manufacture and keep clean, and that it wholly obviates the risk that the discharged powder cloud will `kick back` and adhere exteriorly on the spraygun. Finally, the present invention also has for its object to realise an apparatus which is designed in such a manner that the risk of discharges and light-arcs in or at the powder spraygun is wholly eliminated.
SOLUTION
The objects forming the basis of the present invention will be attained if the apparatus intimated by way of introduction is characterised in that there is disposed, inside the annular channel, an inner electric conductor which is electrically connected to the outer conductor.
According to one preferred embodiment of the present invention, the outer conductor is suitably of a length which is sufficient to cover substantially the entire length of the spraygun. Furthermore, the inner conductor is, according to this preferred embodiment, disposed centrally interiorly in the inner body throughout substantially the entire length thereof.
As a result of these constructional features, a high grade and uniform charging of the powder passing through the powder spraygun will be achieved and, furthermore, the risk that the powder cloud `kicks back` on the powder spraygun is effectively obviated. These construc
REFERENCES:
patent: 3735925 (1973-05-01), Benedek et al.
patent: 4706890 (1987-11-01), Talacko
patent: 4747546 (1988-05-01), Talacko
AC Greiff Ytbehandling AB
Kashnikow Andres
Merritt Karen B.
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