Fluid sprinkling – spraying – and diffusing – Electrostatic type – With fluid entrainment
Patent
1990-03-13
1991-08-27
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Electrostatic type
With fluid entrainment
239171, 244136, B05B 516
Patent
active
050427237
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to electrostatic spraying apparatus.
BACKGROUND OF THE INVENTION
One of the advantages of electrostatic spraying is that the charged spray tends to wrap around the target. This can be of particular use in, say, agricultural spraying because the spray will cover both sides of the leaves of a plant, not merely the outer or upper surfaces as would be achieved with conventional spraying. Another feature is that the attraction of the spray to the target may reduce the amount lost by drift. More or most of the spray reaches its intended target. This reduces the total amount of spray which has to be used which reduces the cost of effective treatment and is thought to be generally better for the environment.
Electrostatic spraying apparatus is known in which a spray head has a spraying edge, an electrically conducting or semiconducting surface and means for delivering liquid to be sprayed to the edge via the surface; an electrode spaced from the edge; and high voltage supply means for generating a high voltage between the surface and the electrode so that, in use, when covered by the liquid to be sprayed, the electric field strength at the edge is intensified sufficiently, that the liquid at the edge is drawn out preponderantly by electrostatic forces into ligaments which break up into electrically charged droplets.
An apparatus falling within this broad type is disclosed in British patent specification No. 1569707.
An advantage of this apparatus is that the ligaments break up into droplets having a very narrow spectrum of diameters. This is preferred because if a droplet of a particular size is required to carry a lethal dose of an insecticide, say, smaller droplets are wasted as ineffective while larger droplets require a larger amount of insecticide to provide the same number of sites.
In order to treat large areas spraying can be effected from aircraft. Although aerial electrostatic spraying has been proposed, e.g. European patent application No. EP-A1-186353, a problem which has not been addressed is that caused by the airstream past the aircraft. In fixed wing aircraft used for spraying, there is an airstream past the vehicle due to its movement and possibly accentuated by the slipstream from a propeller, of the order of 70 mph. The problem cause by the airstream, is that turbulence around the electrostatic spray head interferes with the formation of the ligaments and thus spoils the spectrum of droplet diameters or even prevents spraying.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided apparatus for spraying liquid electrostatically into an airstream comprising: a spray head having a spraying edge, an electrically conducting or semiconducting surface and means for delivering liquid to be sprayed to the edge via the surface; an electrode spaced from the edge; and high voltage supply means for generating a high voltage between the surface and the electrode, the sprayhead comprising an aerofoil the trailing edge of which constitutes the spraying edge, the sprayhead and the electrode being mounted for part of the airstream to pass between them, the shape and position of the sprayed and the electrode producing a sufficiently low turbulence wake in the region of the spraying edge, and the electric field at the edge being intensified sufficiently when covered by liquid to be sprayed, that: the liquid at the edge is drawn out preponderantly by electrostatic forces into ligaments which break up into elactrically charged droplets.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which:
FIGS. 1 and 2 show the general disposition on a light aircraft of apparatus embodying the invention;
FIG. 3 shows a cross section through spraying apparatus embodying the invention;
FIGS. 3a and 3b show details of FIG. 3;
FIG. 4 shows an end view of an alternative embodiment;
FIG. 5 shows the fluid delivery arrangement of the embodiment of FIG. 3; a
REFERENCES:
patent: 3297281 (1967-01-01), Felici
patent: 3618857 (1971-11-01), Rautenbach
patent: 3887129 (1975-06-01), Brown
patent: 4328940 (1982-05-01), Malcolm
patent: 4412654 (1983-11-01), Yates et al.
patent: 4509694 (1985-04-01), Inculet et al.
patent: 4542855 (1985-09-01), Stacey
patent: 4703891 (1987-11-01), Jackson et al.
Green Michael L.
Grocott Arend L.
Noakes Timothy J.
Wilson Edward H.
Grant William
Imperial Chemical Industries plc
Kashnikow Andres
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