Fluid sprinkling – spraying – and diffusing – With viscosity or temperature responsive control means
Patent
1994-03-14
1995-08-15
Grant, William
Fluid sprinkling, spraying, and diffusing
With viscosity or temperature responsive control means
239133, 239135, 239288, B05B 124, B05B 720
Patent
active
054412013
DESCRIPTION:
BRIEF SUMMARY
The present application is a U.S. National Phase Application from International Application No. PCT/GB92/00757 with an International Filing Date of Apr. 24, 1992 and a priority date from Great Britain Application No. 9108865.8, filed Apr. 25, 1991.
FIELD OF THE INVENTION
The present invention relates to liquid spray devices, and more particularly to devices where liquid is discharged in the form of a thin sheet which subsequently breaks down to form droplets.
SUMMARY OF THE INVENTION
This invention relates to liquid spray devices, particularly but not exclusively to devices of the kind wherein liquid is discharged in the form of a thin sheet which subsequently breaks down to form droplets. The sheet can be flat or fan shaped or may have the shape of a hollow cone. The liquid spray devices of this invention find particular application in agricultural or horticultural spraying apparatus and in coating apparatus such as is used for paint application. Regulation of the droplet size is important, particularly to minimize wastage of expensive agrochemicals or other materials. Small drops which can be lost as mist or large drops which can fall to the ground are uneconomical and may create toxicity problems. Elimination of spray drive is especially important.
GB1561642 discloses a liquid spray device wherein hot gas from a methane burner is led to the vicinity of the orifice of a conical sprayer nozzle. The present invention relates to an improvement on the prior disclosure which enables the invention to be put into practice effectively. Several improvements are also realized.
According to the present invention, a liquid spray device includes a nozzle adapted to form a conical sheet of liquid which disintegrates downstream of the nozzle to form a spray, a source of heated gas and a shroud adapted to protect said gas in the vicinity of the nozzle from drafts the source being located so that the gas stream is directed onto the spray at a region wherein the sheet disintegrates to form droplets.
In preferred embodiments of the invention, the gas stream impinges directly on said region of the liquid so that heated gas is drawn through the conical liquid curtain so that the gas contacts the interior surface of it at the point of initiation of the break-up into droplets or immediately upstream of that point.
Transmission of heated gas to the interior of the cone through a tube is not practical due to the efficient cooling of the exterior of the tube by the constant flow of liquid over it. Application of the gas downstream of the break-up region is ineffective and application upstream, for example at the nozzle orifice is wasteful and can damage the nozzle.
Reduction in atmospheric pressure within the apex of the cone due to the Bernouilli effect is believed to draw combustion gas through the curtain without need for additional apparatus. Contact of warm ionized gas is believed to initiate rupture of the liquid sheet.
The heated gas stream is preferably provided by combustion of gaseous fuel, although liquid fuel burners may be employed. While electrically heated gas streams are not excluded, use of combustion gas is more efficient and practically convenient.
Use of the present invention affords many advantages. The droplet size distribution is enhanced by reduction in the number of undersized droplets. The apical angle of a conical spray is increased, enhancing the coverage achieved by the spray and allowing reduction in hydrostatic pressure.
A particular advantage arises because the heated gas stream is located at a precise position in spaced relation downstream of the nozzle. This reduces the heating of the nozzle in use allowing use of conventional plastic nozzles rather than expensive metal constructions.
In preferred embodiments of the invention, the shroud encloses the nozzle and has inlets through which air can be drawn by the spray, and an outlet for the spray and entrained air. The shroud is preferably arranged to enclose a toroidal body of gas to maintain the heated gas stream in contact with the break-up
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Grant William
The University of Leeds
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