Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
  • B05B5/03—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
  • B05B5/053—Arrangements for supplying power, e.g. charging power
  • B05B5/0533—Electrodes specially adapted therefor; Arrangements of electrodes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/02—Spray pistols; Apparatus for discharge
  • B05B7/04—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge
  • B05B7/0416—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid
  • B05B7/0441—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid with one inner conduit of liquid surrounded by an external conduit of gas upstream the mixing chamber
  • B05B7/045—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid with one inner conduit of liquid surrounded by an external conduit of gas upstream the mixing chamber the gas and liquid flows being parallel just upstream the mixing chamber

Definitions

• the object of invention is a method and a head for carrying out an agrotechnical spraying with chemical substances, especially with agrochemicals, that are used in the field of plant protection during cultivation.
• Induction electrode is supplied with direct voltage of selected positive or negative polarization and value from a few hundred V to 5 kV, generated in electronic direct current converter supplied for example form 12 V installation, all components of the high current system being built in directly into the nozzle.
• Other construction of spraying nozzle according to this patent description consists of connected together: cylindrical body and housing. In the body made of electrically conducting materials, for example metal, there is an axial channel guiding the atomized liquid, supplied under pressure from the back part of the body from the liquid tank.
• the body also comprise a coaxial, tapered towards the front of the body channel guiding a gas, for example the air, supplied under pressure from the back part of the body from the gas source, the channel can consist of many separate channels converging at the outlet from the body from the side of its connection with the housing.
• Dielectric housing mechanically connected with the body also comprise an internal channel, guided axially with respect to the liquid channel. From the body side, this channel is of constant diameter, while at the front outlet orifice, its diameter is reduced.
• the body houses outlets of channels guiding the liquid and gas corresponding to inlets of the channel in the housing where the liquid and gas are guided together. Jets of gas and liquid act together in the area of the housing channel of constant diameter, called the area of generating aerosol drops.
• Annular induction electrode made of electrically conducting material, for example brass, is built into the housing and directly encloses the area of drops generation so that its back surface is located from the front side of the channels guiding the gas, and liquid and its front surface is located from the side of the outlet orifice of the housing at accurately set distance.
• Toroidally arranged lines of electric field forces, generated by induction electrode concentrate in the area of drops generation, and because the gap between the electrode and centre of the drops generation area is very small, gradient of electrical field in this area is very high even for relatively low voltage polarizing the electrode. This leads to effective polarization of liquid drops even at relatively low voltages polarizing the induction electrode.
• the induction electrode is connected to high voltage source by means of high voltage conductor built into the head housing.
• Such nozzle provides generation of solid particles in airborne or not airborne liquefied drops of aerosols of typical size of particles at least 50 micrometers and larger from liquids, solutions and suspensions. Maximum value of charge transferred to aerosol particles in this solution is about 15% of limit value, resulting from Rayleigh's limitation (according to A. G. Bailey, chiefElectrostatic spraying of liquids", 1st ed., Taunton Research Studies Press, London, 1988) with aerosol particles diameter of 50 ⁇ and 26 % and 40 % for particle diameters of 75 m and 100 ⁇ respectively.
• the object of the invention is to remove or to limit the current inconveniences by developing a new technical solution.
• the method consists in that the pneumatic atomization is performed using convergent - divergent nozzle, to which gas, preferably air, is supplied, under pressure within the range from 1 to 4 bar, where within the convergent part of the nozzle it gains speed and reaches at the narrowest point the critical speed equal to the speed of sound and in the divergent part in the widest point it reaches speed a few times faster than the speed of sound, so that gas accelerated to ultrasonic speed disintegrates the technological liquid flowing from the capillary tube into drops of size from a few to a dozen micrometers, of which the particles charge in the electrical field with direct current of voltage from a few hundred to 3 kilovolts, the annular electrode being supplied with voltage no more than 70 percent of voltage at which electrical discharge begins to occur in the space between the annual electrode and capillary tube with technological liquid.
• gas preferably air
• the matter of the head according to invention consists in that it contains gas channel, gas nozzle, capillary tube, channel supplying the technological fluid, outlet chamber with annular electrode connected via a conductor with high voltage feeder, outlet chamber housing with port hole that is characterized in that the gas channel represents a bent hose with one end equipped with seat for supplying pressurized gaseous agent and the other end connected to the convergent - divergent nozzle.
• the convergent - divergent nozzle is divided to four segment arranged along one axis, the first segment being in a shape of convergent truncated cone with element of a cone of acute angle within the range from 55 degrees to 65 degrees, the second element of the nozzle being in a shape of short cylindrical cylinder at the spot, where the convergent - divergent nozzle diameter is the smallest, the third segment of the nozzle being in a shape of divergent truncated cone with element of a cone of acute angle within the range from 35 degrees to 25 degrees, the fourth segment being in a shape of cylindrical cylinder at the spot, where the convergent - divergent nozzle diameter is the biggest.
• the convergent - divergent nozzle is introduced into the outlet chamber and the channel supplying the technological liquid is in a shape of bent hose with one end equipped with seat for supplying the technological liquid under pressure of 1 to 5 bar and the other end is connected to capillary tube positioned concentrically coaxially inside the convergent - divergent nozzle, the end of the capillary tube being introduced into the outlet chamber interior.
• the convergent - divergent nozzle is made of dielectric material.
• the capillary tube is made of conducting material and is connected with earthed pole of high voltage feeder.
• the annular electrode is connected with the not earthed pole of high voltage feeder.
• the outlet chamber housing is made of dielectric material.
• Maximum value of charge transferred to aerosol particles generated using the method according to the invention is about 5 % of limit value, resulting from Rayleigh's limitation for particles of diameter 10 pm (according to A. G. Bailey, carefulElectrostatic spraying of liquids", 1st ed., Taunton Research Studies Press, London, 1988).
• the solution according to the invention allows reducing losses amounting 1000 PLN / ha related to insufficient protection of crops against pests, such as European corn borer preying in a lower parts of high plants, which within a region of intensive cultivation causes loss of yield reaching 30%.
• particle with charge Q In order for the electrical forces to act, particle with charge Q must be in the electrical field of intensity E. In case of charged particles, present near the conducting and earthed objects, the basic source of field is so called “mirrored charge”. If a particle with charge (+)Q is present at a distance (+)x from the conducting surface of earthed object, it is subjected to a force like from charge (-)Q present at a distance (-)x from the object surface. Charge (+)Q "sees” behind the conducting object surface "mirrored charge” of value (-)Q. Occurrence of charge (-)Q leads to appearance of force attracting the particle with charge (+)Q to the surface of earthed object - Coulomb's law. Each charged particle is attracted by a conducting and earthed object.
• This phenomenon is used in the processes of electrostatic coating of surfaces such as spraying, painting. Force from the mirrored charge depends on the second power of Q particle charge. For the electrical forces action to appear that attract the technological fluid particle, aerosol drop must provided with Q charge. To do that, particles are subjected to electrification.
• Electrification of particles consists in introducing surplus charge Q on them.
• the method of induction that use the phenomenon of electric induction is used for the electrification of particles from solid and liquefied conducting materials:
• induction method In case of nozzles with pneumatic spraying, it is preferred to apply induction method. Said method allows to limit the space where strong electric field is present. This property allows in turn to:
• the principle of aerosol particles electrification using the electric induction method consists in that the cone of jet of conducting liquid is subjected to strong electrical field E, generated in the area limited by two electrodes, between which high direct voltage is applied.
• One electrode, located at the earth potential is represented by a capillary tube together with the jet cone of electrically conducting fluid, the other is annular electrode connected to high voltage feeder output.
• Maximum value of charge carried by drop depends on the drop size i.e. surface subjected to action of electrical field E and intensity of field E in the place of drops generating and breaking apart.
• the need to obtain high value of parameter (Q/m) requires introduction of relatively large charge Q on to the particle, this fact in turn necessitates the application of field E of possibly high intensity.
• Maximum value of field E is limited by the electrical strength of air and on the head of given geometry can be specified by voltage U p , at which electrical discharges shall appear in the zone: annular electrode - capillary tube. Spark and corona discharge can be observed. Discharges are accompanied by sudden increase of induction electrode supply current that is fed by high voltage feeder. Characteristics given in the fig. 2 allows to determine voltage U p above which electric discharges appear what in turn leads to limitation of maximum value of parameter (Q/m) given in the fig. 3.
• Value of voltage U p is determined experimentally based on examinations of dependencies of supply current / from voltage U for the annular electrode using the method given in the fig. 2.
• the head comprises the metal body 1 that include such elements as gas channel 2, convergent - divergent nozzle 3, capillary tube 4, channel 5 supplying the technological liquid, outlet chamber 6 with annular electrode 7 connected by means of conductor 8 with high voltage feeder, housing 9 of the outlet chamber 6 with port hole.
• Gas channel 2 is made of bent hose with one end is equipped with seat 10 to supply the gaseous agent and the other end is connected to convergent - divergent nozzle 3, the convergent - divergent nozzle 3 consisting of four segments located along one axis, the first segment 1 1 of the nozzle 3 being in a shape of convergent truncated cone with element of a cone of acute angle within the range from 55 degrees to 65 degrees, the second element 12 of the nozzle 3 being in a shape of short cylindrical cylinder at the spot where the nozzle diameter is the smallest, the third segment 13 of the nozzle 3 being in a shape of divergent truncated cone with element of a cone of acute angle within the range from 35 degrees to 25 degrees, the fourth segment 14 of the nozzle 3 being in a shape of cylindrical cylinder at the spot where the convergent - divergent nozzle 3 diameter is the biggest, at the same time the end of the convergent - divergent nozzle 3 is introduced into the outlet chamber 6 and the channel 5
• Sprayed liquid is supplied via capillary tube 4 in to the zone of decompressed gas in the outlet chamber 6 supplied through the convergent - divergent nozzle 3 made of dielectric material.
• Drops of aerosol generated at the end of capillary tube 4 are being electrified in strong electrical field generated between the capillary tube 4 made of conducting material and the annular electrode 7 made of stainless steel supplied from direct high current source of low power by means of the conductor 8 connected to it via bolt 16.
• Body 1 from side of the outlet chamber 6 is covered from outside by means of the housing 9 made of dielectric material. The housing 9 also protects the annular electrode against direct contact with operating personnel and drops of back jet of charged aerosol particles (returning from the head).
• channel 5 supplying the technological liquid and channel 2 supplying for example air are of varying cross sections, with necking and bends of hoses that provide turbulent flow and vortexes in the supplied agents.
• Individual feeders are used to supply induction electrodes of the heads, each head is equipped with own feeder.
• high voltage feeders are located in the closest vicinity of the spraying heads located on the sprayer construction surface.

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• Electrostatic Spraying Apparatus (AREA)
• Catching Or Destruction (AREA)
• Special Spraying Apparatus (AREA)

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Publications (1)

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• 2011
  • 2011-08-25 PL PL396084A patent/PL224862B1/pl unknown
  • 2011-09-30 EP EP11778721.8A patent/EP2747892A1/de not_active Withdrawn
  • 2011-09-30 WO PCT/PL2011/000099 patent/WO2013028084A1/en active Application Filing

Non-Patent Citations (1)

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