Atomization of liquids

• US 4,476,515 A
• Filed: 10/21/1982
• Issued: 10/09/1984
• Est. Priority Date: 07/15/1976
• Status: Expired due to Term

• Current Assignee: Zeneca Incorporated (Astrazeneca PLC)
• Original Assignee: Imperial Chemical Industries PLC (IMPERIAL CHEMICAL INDUSTRIES)
• Inventors: Coffee, Ronald A.
• Primary Examiner(s): Moose, Jr., Harry E.
• Application Number:
  US06/435,743
• Time in Patent Office: 719 Days
• Field of Search: 361/226, 361/227, 361/228, 361/235, 118/626, 118/627, 118/628, 239/3, 239/690, 239/704, 239/706, 239/377, 239/376, 55/123, 43/132 A
• US Class Current: 361/226
• CPC Class Codes: B05B 5/04 characterised by having rotary outlet or deflecting elements , i.e. spraying being also effected by centrifugal forces
• CPC Class Codes: B05B 5/043 using induction-charging
• CPC Class Codes: B05B 5/0531 Power generators
• CPC Class Codes: B05B 5/0533 Electrodes specially adapted therefor; Arrangements of electrodes
• CPC Class Codes: B05B 5/0535 at least two electrodes having different potentials being held on the discharge apparatus, one of them being a charging electrode of the corona type located in the spray or close to it, and another being of the non-corona type located outside of the path for the material
• CPC Class Codes: B05B 5/1691 Apparatus to be carried on or by a person or with a container fixed to the discharge device
• CPC Class Codes: H01L 21/324 Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering H01L21/20 - H01L21/288 and H01L21/302 - H01L21/322 take precedence
• CPC Class Codes: Y10S 43/90 Liquid insecticide sprayer

Abstract

Electrostatic spraying for pesticides comprises an electrically conducting or semi-conducting surface; means for supplying liquid adjacent the surface; and a field intensifying member in close proximity to the surface. A process for the ultra-low volume application of concentrated pesticidal formulations by means of the apparatus is also described.

Claims

1. A process of spraying a liquid onto a target comprising supplying said liquid from a source thereof through a passage to a spray orifice which has a surface of a material having resistivity below 10¹² ohm.cm adjacent a field intensifying electrode, said surface being electrically charged and the electrode being at such a potential and so sited relative to said surface that an electrostatic field of such strength is created at said orifice that the liquid at said orifice is drawn out preponderantly by electrostatic forces substantially without corona discharge into ligaments which break up into electrically charged particles which are projected away from the electrode and into contact with the target.

2. In a process of spraying a liquid onto a target wherein a liquid is supplied from a source thereof through a passage to a spray orifice which has a surface of a material having a resistivity below 10¹² ohm.cm charged to such a potential that an electrostatic field is created at said orifice, the improvement comprising providing a field intensifying electrode adjacent said surface and so sited and at such a potential relative thereto that the electrostatic field generated by said charged surface between said surface and said electrode cause the liquid at said orifice to be drawn out preponderantly by electrostatic forces substantially without corona discharge into ligaments which break up into electrically charged particles which are projected away from the electrode and into contact with the target.

3. An electrostatic spraying apparatus suitable for spraying a liquid into contact with a target, comprising:

a spray-head having a spray orifice which has a surface of a material having a resistivity below 10¹² ohm.cm;

means for electrically charging said surface;

means for delivering said liquid through said spray orifice;

a field intensifying electrode mounted adjacent to said surface; and

means for connecting the field intensifying electrode to earth;

the electrode being so sited relative to said surface and said means for electrically charging said surface being capable of charging said surface to such a potential that, when said surface is charged to said potential, the electrostatic field thereat causes liquid at said orifice to be drawn out preponderantly by electrostatic forces without substantial corona discharge into ligaments which break up into electrically charged particles which are projected past the electrode and into contact with the target.

4. A portable, self-contained electrostatic spray gun comprising:

a reservoir for containing liquid to be sprayed;

a spray-head having a spray orifice which has a surface of a material having a resistivity of less than 10¹² ohm.cm adjacent which liquid may atomize;

means for delivering the liquid from the reservoir through said spray orifice;

a field intensifying electrode in close proximity to said surface;

a power source adapted to generate an electrostatic field between said surface and said electrode of such strength that said liquid is caused to atomize at said orifice without substantial corona discharge to form a cloud of electrically charged particles of said liquid which are projected past the electrode.

5. A process for spraying a liquid onto an earthed target comprising the steps of:

supplying a liquid from a source thereof through a passage under gentle hydrostatic pressure within a predetermined range of pressures to a spray orifice in a nozzle, the orifice having a surface of a material having a resistivity of less than 10¹² ohm.cm and is adjacent and spaced from an electrically conducting electrode;

applying an electrical potential to said surface;

providing an electrical pathway connecting said electrode to earth, the magnitude of the potential and the position of the electrode being such that the liquid at said surface is drawn out preponderately by electrostatic forces without corona discharge into ligaments which break up into electrically charged droplets of uniform size which are projected towards the target; and

moving said source, said nozzle and said electrode past said target.