One known type of spraying technology includes spray nozzles that atomize the sprayed material to achieve a more uniform distribution and coverage. One type of spray atomization includes use of electrostatic atomization nozzles, which are part of a family of electro-hydrodynamic (EHD) nozzles that use two electrodes positioned very close together generating a very strong electric field. In such devices, one electrode has a very high voltage of negative polarity, and the other electrode is the nozzle body, which is electrically grounded. A dielectric fluid such as oil may pass between the two electrodes and through the very strong electric field they create, causing current to be injected into the fluid and, thus, electrically charging the liquid. The charged liquid exits the nozzle through a small circular orifice producing a solid stream of charged oil. Outside the nozzle, the excess charge in the liquid electrically repulse each other within the oil inducing a spin in the oil jet that results in bending instability and eventually necking, which causes the fluid to break up into droplets and, thus, atomize. As can be appreciated, the omnidirectional repulsive forces of electrons within the charged fluid cause the spray plume to assume a full cone shape as it develops. The sprayed particles are then attracted to grounded, conductive surfaces that are to be coated by the fluid sprayed.
The invention provides a system and method for shaping a conical spray plume of charged droplets into, for example, a flat cone or fan shape. The very small orifice size required for this type of nozzle does not lend well to changing the orifice geometry to produce a flat spray, which is how sprays are typically shaped into a flat spray pattern. In one embodiment, the present disclosure utilizes an electrostatic spray nozzle, which produces a full cone plume. The full cone plume, which is made from charged fluid droplets, is subjected to a secondary electrical field, which can impose attractive or repulsive electrical forces onto the charged fluid droplets, thus affecting their trajectory and direction of travel as the plume develops. The intensity of the secondary electrical field may be constant or variable, and the shape of the secondary field electrodes is adjustable, such that steady or transient spray plume shaping can be achieved.
In one illustrated embodiment, a spray plume of charged droplets is subjected to an electric field. The electrical field squeezes the full cone spray into a flat fan. The electric field is generated by electrodes of negative polarity and produces a repulsive force on the negatively charged droplets forcing them to fan out.
A cross section view of a spray nozzle assembly 100 is shown in
In reference to
The spacer 110 is made from a non-electrically conductive material and acts as an electrical insulator between the high-voltage electrode 116 and the body 104. Any appropriate and desired electrical potential difference may be applied at the source 124 depending on the type of fluid being sprayed. For example, oil and other industrial fluids may be sprayed using an electrical potential between −20 and −30 kV, while heavier fluids such as paint or agricultural applications may operate at a higher electrical potential between −60 and −75 kV. The fluids may be conductive, semi-conductive, or non-conductive. In the illustrated embodiment, the voltage provided by the source 124 is selected to be between −5 to −10 kV, but other values can also be used.
The exposed end 120 of the electrode 116 protrudes from an end of the spacer 110 and is immersed in, or contact with, fluid present and passing through the internal cavity 108. As can be seen in
As shown in
In the illustrated embodiment, a set of secondary electrodes 206 is disposed around an area 208 that encompasses the spray stream 200 shortly after it emerges from the orifice opening 134. Although a set of secondary electrodes is shown, it should be appreciated that at least one secondary electrode can be used, in which case the area 208 would be an area surrounding a single secondary electrode in which an electric field created by the secondary electrode would be present. The area 208 may be selected to include the distance in which the spray stream 200 begins or has begun to break up into droplets that would otherwise have begun to form a conical spray plume. The secondary electrodes 206 (two shown) are disposed at diametrically opposite locations around the nozzle body 104 and are connected to a secondary voltage source 212 of electrical potential through a conductor 210. While the secondary voltage source 212 has a negative pole connected to the electrodes 206 and a positive pole connected to the earth ground 128, as shown in the figures, it should be appreciated that the polarity of one or both voltage sources may be reversed. Further, in the case of a single secondary electrode, the secondary voltage source 212 may be connected across the single secondary electrode, using its negative or positive pole, and an electrical ground. For example, the voltage source 124 may have a negative pole connected to the electrode 116, as shown in
When the secondary voltage source 212 is active, in the polarity shown in
These additional repulsive or attractive electrostatic forces provided by the secondary electrode(s) act to collapse or expand, as the case may be, the conical spray plume into a wide or flat fan spray plume 204. A flat fan spray plume 204 is shown in
For illustration, three alternative shapes for shaped electrode leads 214, as shown in
For example, in the embodiment of
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
The instant application claims priority to U.S. Provisional Patent Application No. 62/616,862, which was filed on Jan. 12, 2018, the contents of which are incorporated herein in their entirety by reference.
Number | Date | Country | |
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62616862 | Jan 2018 | US |