TECHNICAL FIELD

The present invention is directed to an electrohydrodynamic device having a dielectric shield, wherein the shield may comprise a first section and one or more second sections extending out from the first section.

BACKGROUND ART

U.S. Patent Application Publication No. US 2004/0195403A1 discloses a spray nozzle 154 and an upstream discharge electrode 150. A relatively high electric field is formed at pointed ends of the discharge electrode 150 causing air molecules surrounding the discharge electrode pointed ends to be electrically ionized to form a cloud of positively charged ions. At least a portion of the positively charged ions move outwardly from the discharge electrode pointed ends, around a dielectric shroud 152 and form a virtual positive electrode cloud in front of the spray nozzle 154. The positive cloud of ions and the oppositely charged spray nozzle create a strong electrical field in the vicinity of spray nozzle tips, thereby causing liquid exiting the spray nozzle tips to be broken up into electrically charged fine aerosol droplets. The positive ions also function to neutralize the aerosol.

The dielectric shroud 152 provided between the spray nozzle 154 and the upstream discharge electrode 150 reduces wetting of the discharge electrode 150. It is believed that the shroud 152 also functions to prevent positive ions generated by the discharge electrode 150 from traveling along a direct path to tips of the spray nozzle. If the positive ions are permitted to move directly to the spray nozzle tips, the positive ions may reduce the strength of or prevent the generation of an electric field at the nozzle tips such that liquid exiting the nozzle tips is not aerosolized.

DISCLOSURE OF INVENTION

In accordance with a first aspect of the present invention, an

electrohydrodynamic (EHD) device comprising: spray structure comprising one or more spray nozzles defining one or more EHD comminution sites; liquid supply structure coupled to the spray structure to supply liquid to the one or more spray nozzles; one or more electrically conductive discharge electrodes spaced from the one or more spray nozzles; a dielectric shield positioned between the one or more spray nozzles and the one or more discharge electrodes; and a power supply. The shield may comprise a first section and one or more second sections extending out from the first section toward the one or more discharge electrodes. The power supply may be coupled to the one or more discharge electrodes such that the one or more discharge electrodes generate ions which move along a path extending over the dielectric shield toward the one or more spray nozzles.

The power supply may be further coupled to the one or more spray nozzles or the liquid supply structure. The power supply may cause the one or more spray nozzles or liquid in the liquid supply structure to be at a first electrical potential and the one or more discharge electrodes to be at a second electrical potential. The ions generated by the one or more discharge electrodes may generate with the one or more spray nozzles or the liquid in the liquid supply structure an electric field in the vicinity of the one or more spray nozzles causing liquid exiting each spray nozzle to be comminuted into a spray of charged droplets. The ions may further interact with and neutralize the droplets generated at the spray nozzles.

The second potential may be greater than the first potential.

The second potential may comprise a high voltage and the first potential may comprise a ground potential.

The one or more second sections may extend out from the first section at an angle of from about 45 degrees to about 135 degrees.

The one or more second sections may extend out from the first section at an angle of about 90 degrees.

At least one pair of the second sections may be spaced apart from one another by between about 0.25 times to about 3 times the spacing between a pair of the discharge electrodes. More specifically, the pair of second sections may be spaced apart from one another by amount generally equal to the spacing between two discharge electrodes. It is further contemplated that each of the second sections may be aligned with a location midway between two adjacent discharge electrodes.

The dielectric shield first section comprises a planar section or a curvilinear section.

The first section may comprise a generally planar first section and the one or more second sections may comprise a plurality of second sections extending out from the first section at an angle of about 90 degrees toward the one or more discharge electrodes.

The liquid supply structure may comprise a plurality of tubes or similarly shaped elements to allow for capillary action, wherein the tubes may be formed from a high surface energy material. The tubes may have end sections defining a plurality of the spray nozzles. The plurality of the spray nozzles define a plurality of the EHD comminution sites.

In accordance with a second aspect of the present invention, an

electrohydrodynamic (EHD) device is provided comprising: spray structure comprising one or more spray nozzles defining one or more EHD comminution sites; liquid supply structure coupled to the spray structure to supply liquid to the one or more spray nozzles; one or more electrically conductive discharge electrodes spaced from the one or more spray nozzles; a dielectric shield positioned between the one or more spray nozzles and the one or more discharge electrodes; and a power supply. The shield may comprise a first section and one or more second sections extending out from the first section. The power supply may be coupled to the one or more discharge electrodes such that the one or more discharge electrodes generate ions which move along a path extending over the dielectric shield toward the one or more spray nozzles.

The first section may comprise a generally planar first section and the one or more second sections may comprise a plurality of second sections extending out from the first section toward the one or more discharge electrodes.

The first section may comprise a generally planar first section and the one or more second sections may comprise a plurality of second sections extending out from the first section toward the one or more spray nozzles.

Use of second sections extending out from the dielectric shield first section is believed to allow the spacing between the spray nozzles and the discharge electrodes to be reduced, so as to allow the EHD device to be more compact.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a perspective view of an electrohydrodynamic (EHD) device constructed in accordance with a first embodiment of the present invention;

Fig. 2 is a side view of the device illustrated in Fig. 1 ; Fig. 3 is a power supply forming part of the EHD device illustrated in Fig. 1 ;

Fig. 4 is a perspective view of an EHD device constructed in accordance with a second embodiment of the present invention;

Fig. 5 is a perspective view of an EHD device constructed in accordance with a third embodiment of the present invention;

Fig. 6 is a cross sectional view of the device of Fig. 5; and

Figs. 7 and 8 illustrate other embodiments of a dielectric shield second section. MODES FOR CARRYING OUT THE INVENTION

In accordance with a first embodiment of the present invention, an

electrohydrodynamic (EHD) device 10 is provided comprising spray structure 20 comprising a plurality of generally aligned spray nozzles 22 extending from a liquid container or well 24 defining a liquid supply structure 26. The spray nozzles 22 are preferably formed from a high surface energy material. The spray nozzles 22 have ends or tips 22A defining a plurality of EHD comminution sites. As will be discussed further below, during operation of the device 10, liquid flows via capillary action from the well 24, through the nozzles 22 to the nozzle tips 22A. The liquid may comprise an insecticide, a fragrance, an odor eliminator, or the like.

It is further contemplated that a liquid container, such as a bottle (not shown), filled with liquid and having a liquid conduit, a wick or the like extending from the liquid container to the nozzles 22 may be provided for delivering liquid to the nozzles 22. It is further contemplated that a pump (not shown) may be provided for supplying liquid to a manifold, which, in turn, is coupled to the spray nozzles 22.

In the illustrated embodiment, a plurality of electrically conductive discharge electrodes 30 extend from and are integral with a base electrode 32, see Fig. 1 . The base electrode 32 and, hence, the discharge electrodes 30, are coupled to a power supply 40, see Fig. 3. In the illustrated embodiment, the discharge electrodes 30 are spaced in an X-direction away from the nozzles 22, see Fig. 1 .

A dielectric shield 50 is positioned between the spray nozzles 22 and the discharge electrodes 30, see Figs. 1 and 2. In the illustrated embodiment, the shield 50 comprises a generally planar first section 52 and a plurality of generally planar second sections 54. The second sections 54 extend out from the first section 52 at an angle Θ of about 90 degrees toward the discharge electrodes 30, see Fig. 1 . It is contemplated that the second sections 54 may extend from the first section 52 at any angle between about 45 degrees to about 135 degrees. The dielectric shield may be formed from a dielectric polymeric material such as polypropylene, acetal copolymer, polycarbonate, polyimide, or polytetrafluoroethylene.

Each pair of adjacent second sections 54 may be spaced apart from one another by a distance D equal to about 0.25 times to about 3 times the spacing S between a pair of the discharge electrodes 30, see Fig. 1 . In one embodiment, the distance D is generally equal to the spacing S. It is further contemplated that each of the second sections 54 may be aligned with a location midway between a pair of adjacent discharge electrodes 30.

In the illustrated embodiment, the power supply 40 is also coupled to the nozzles 22, which nozzles 22 may be formed from a high surface energy, electrically conductive material. In another embodiment, the power supply 40 comprises an electrode positioned within the liquid well 24 so as to apply a charge directly to the liquid instead of the nozzles 22. In this other embodiment, the liquid is at least semi- conductive. Further with regard to the other embodiment, the nozzle tips 22A may not be electrically conductive.

The power supply 40 comprises a high voltage generator 42 powered by a battery 44 having one terminal (a positive terminal in the illustrated embodiment) coupled to the high voltage generator 42 via a switching circuit (SW) 46, see Fig. 3. The other terminal of the battery 44 is coupled to a second input terminal of the high voltage generator 42 and the coupling conductor extending between the battery 44 and the high voltage generator 42 may be floating or connected to ground as shown in Fig. 3. The high voltage generator 42 acts to multiply the voltage supplied by the battery 44 to provide a voltage sufficient to generate an electric field required to achieve comminution of the liquid carried by the nozzles 22. In the illustrated embodiment, the nozzles 22 are connected to the low voltage terminal (a common or reference potential terminal in the illustrated embodiment) of the high voltage generator 42, while the discharge electrodes 30 are connected via a resistance R to the high voltage terminal (a positive potential terminal in the illustrated embodiment) of the high voltage generator 42. As noted above, in the other embodiment, an electrode extending into the well 24 is coupled to the low voltage terminal instead of the nozzles 22. The switching circuitry 46 may consist of a simple mechanical switch such as a push or rocker button manually updated by a user or may consist of an electrically activated switch such as a relay or an electronic switch.

If the nozzles 22 are formed from a high surface energy material, liquid formulation travels from the well 24, through the nozzles 22 to the nozzle tips 24 via capillary action.

When the switching circuitry 46 is operated to activate the high voltage generator 42, a relatively high electric field is formed at the discharge electrodes 30 causing air molecules surrounding the discharge electrodes 30 to be electrically ionized to form a cloud of positively charged ions. It is believed that at least a portion of the positively charged ions move outwardly from the discharge electrodes 30 and initially travel along a first segment of a generally linear first path. The first path extends from the discharge electrodes 30, through the dielectric shield first section 52 to the spray nozzles 22. The first path is defined by electric field lines of force. However, when those ions, moving along the generally linear first path, encounter the dielectric shield 50, they are diverted along a second path different from the first path.

If the dielectric shield 50 is not provided to divert the positively charged ions from the first path, those ions travel along the first path directly to the spray nozzles 22. Upon reaching the spray nozzles 22, the ions may vary or change the charge on the spray nozzles 22 to prevent an electric field of sufficient strength from being generated near each nozzle tip 24 such that comminution of liquid into aerosol droplets is prevented.

If the dielectric shield comprises only a first section, i.e., without any second sections coupled to the first section, it is believed that the positively charged ions generated by the discharge electrodes 30 will move toward the dielectric shield first section. An initial portion of the ions will effectively coat the dielectric shield first section. Subsequent positively charged ions will also move toward the dielectric shield first section, but are believed to be significantly repelled by the attached ions in a direction away from the shield first section. It is believed that the repelled ions still move toward the nozzle tips 22, but, due to being significantly repelled by the attached ions, are believed to be distorted from the first path so as to follow a lengthy, circuitous third path toward the spray sites. In the present invention, it is believed that an initial portion of the positively charged ions move along the first path until they encounter outer edges 54A of the dielectric shield second sections 54. It is further believed that those ions attach to the outer edges 54A of the dielectric shield second sections 54, yet are not discharged by electrons in the outer edges 54A of the dielectric shield second sections 54. It is also believed that subsequent positively charged ions generated by the discharge electrodes 30 encounter the positively charged ions attached to the outer edges 54A of the second sections 54 and are repelled away from the outer edges 54A by those attached ions. The amount to which the subsequent positively charged ions are repelled is believed to be much less than in the scenario where the dielectric shield comprises only a first section, i.e., without second or other sections extending from the first section. It is still further believed that the repelled ions move along the second path so as to travel over an upper surface 50A of the shield, see Fig. 2, and then move to locations just above the nozzle tips 22A where they form a virtual positive electrode cloud above the nozzle tips 22A. It is believed that the second path is shorter and less circuitous than the third path, discussed above, such that the spacing between the nozzles 22 and the discharge electrodes 30 in an X direction, see Fig. 1 , can be reduced in the EHD device 10 illustrated in Fig. 1 as compared to a distance between the nozzles and electrodes in an EHD device where a shield is provided having only a first section. Hence, it is believed that the EHD device 10 of the present invention can be made more compact. Also, it is believed that because the second path is shorter than the third path, fewer positive ions are lost when the ions travel along the second path, such that a greater number of the generated ions reach the nozzle tips 22A allowing a lower operating voltage to be used.

The virtual positive electrode cloud and the grounded nozzle tips 22A create a strong electrical field in the vicinity of the nozzle tips 22A, which, as noted above, define EHD comminution sites. A negative surface charge is induced via the electric field in the liquid at each nozzle tip 22A. This causes the liquid surface tension to break down such that an electrically charged dispersion of droplets, in this embodiment, negatively charged droplets, substantially all of the same size (a "monodispersion"), is formed. Hence, the liquid is broken up, or comminuted, into a spray of fine aerosol droplets. The cloud of positively charged ions may also function to interact with and neutralize the negatively charged droplets generated at the EHD comminution sites. This results in droplets that are electrically neutral and able to be dispersed in the air without substantial influence of electric fields.

It is also contemplated that the discharge electrodes 30 may be coupled to the low voltage terminal comprising ground of a high voltage generator and the nozzles 22A may be coupled to a high voltage terminal comprising a negative polarity of the high voltage generator such that positive ions are generated by the discharge electrodes 30. It is further contemplated that the discharge electrodes 30 may be coupled to a high voltage terminal comprising a negative polarity of the high voltage generator and the nozzles 22 may be coupled to the low voltage terminal comprising ground, such that negative ions are generated by the discharge electrodes 30. It is still further contemplated that that the nozzles 22 may be coupled to a high voltage terminal comprising a positive polarity of the high voltage generator and the discharge electrodes 30 may be coupled to the low voltage terminal comprising ground, such that negative ions are generated by the discharge electrodes 30. It is believed that the negative ions will travel along generally the same second path as the positive ions when the dielectric shield 50, comprising first and second sections 52 and 54, is positioned between the nozzles 22 and the discharge electrodes 30.

In a second embodiment, where elements common to the embodiment of

Figs. 1 -3 and the embodiment of Fig. 4 are referenced by the same reference numerals, a dielectric shield 150 is positioned between the spray nozzles 22 and the discharge electrodes 30. The dielectric shield 150 comprises a generally planar first section 52, a plurality of generally planar second sections 54 and a plurality of generally planar third sections 56. The second sections 54 extend out from the first section 52 at a first angle θι of about 90 degrees toward the discharge electrodes 30, while the third sections 56 extend out from the first section 52 at a second angle θ ₂ of about 90 degrees toward the spray nozzles 22A. It is contemplated that the second and third sections 54 and 56 may extend from the first section 52 at any angle between about 45 degrees to about 135 degrees. It is further believed that the second and third sections 54 and 56 cause positive ions generated by the discharge electrodes 30 to move along a fourth path to locations just above the nozzle tips 22A, where they form a virtual positive electrode cloud above the nozzle tips 22A. The fourth path is believed to be very similar to the second path discussed above, except that a first set of positive ions become coupled to upper surfaces 56A of the third sections 56 causing subsequent positive ions to be distorted away from the third section upper surfaces 56A in Z and X directions, see Fig. 4, before moving to the locations just above the nozzle tips 22A.

In a third embodiment of the present invention, illustrated in Figs. 5 and 6, an EHD spray device 200 is provided having a main housing 210 comprising a base portion 212 and an upper portion 214. A refill bottle 220 comprising a container 222 filled with liquid, a cap 226 and a bottle wick 226A extending from the container 222 and through a sleeve section 226B of the cap 226 are housed within the main housing 210. A nozzle plate/wick assembly 230 is coupled to the upper portion 214 via ribs 214A. The assembly 230 comprises a permanent wick 232 housed in a cylinder section 234 and a nozzle plate 236 coupled to an end of cylinder section 234. A plurality of capillary tubes 238 extend through the nozzle plate 236 into the permanent wick 232. The tubes 238 are preferable formed from high surface energy material. The capillary tubes 238 have tips 238A that define EHD comminution sites. The tubes 238 are also referred to herein as spray nozzles.

When a refill bottle 220 is positioned within the main housing 210, an end 226A' of the bottle wick 226A abuts against an end 232A of the permanent wick 232 so as to define a liquid pathway from the container 222 to the capillary tubes 238. The bottle wick 226A and the permanent wick 232 may be formed from an open cell foam, packed fibers, a combination of open cell foam and packed fibers or any other material. A coating provided within the sleeve section 226B and the cylinder section 234 that allows for capillary action may be provided instead of the wick.

A plurality of electrically conductive discharge electrodes 240 extend from and are integral with a base electrode 242, see Fig. 6. The base electrode 242 is generally cylindrical in shape and coupled to the conical upper portion 214 via the ribs 214A. The base electrode 242 and, hence, the discharge electrodes 240, are coupled to a power supply.

A dielectric shield 250 is positioned between the capillary tubes 238 and the discharge electrodes 240, see Figs. 5 and 6. In the illustrated embodiment, the shield 250 comprises a generally cylindrical first section 252, and a plurality of generally planar second sections 254. The second sections 254 extend radially out from the first section 252, see Fig. 6. The dielectric shield 250 may be formed from a polymeric material such as polypropylene, acetal copolymer, polycarbonate, polyimide, or polytetrafluoroethylene.

Also housed in the main housing 210 is a power supply (not shown) similar to power supply 40 shown in Fig. 3. The capillary tubes 238 may be connected to the low voltage terminal of the high voltage generator, while the discharge electrodes 240 may be connected via a resistance R to the high voltage terminal of the high voltage generator.

During operation of the spray device 200, liquid formulation flows from the container 222, through the bottle wick 226A and permanent wick 232, into the capillary tubes 238, where the liquid flows to the capillary tube tips 238A via capillary action. When the power supply is operated to activate the high voltage generator, the grounded or low voltage at the tubes 238 and the high voltage at the discharge electrodes 240 results in positively charged ions being generated by the discharge electrodes 240. It is believed that an initial portion of the positively charged ions move along an initial path until they encounter outer edges 254A of the dielectric shield second sections 254. It is further believed that those ions attach to the outer edges 254A of the dielectric shield second sections 254, yet are not discharged by electrons in the outer edges 254A of the dielectric shield second sections 254. It is also believed that subsequent positively charged ions generated by the discharge electrodes 240 encounter the positively charged ions attached to the outer edges 254A of the second sections 254 and are repelled away from the outer edges 254A by those attached ions. It is still further believed that the repelled ions move in an outward direction so as to travel over an upper surface 250A of the shield, see Fig. 6, and then move to locations just above the capillary tubes 238 where they form a virtual positive electrode cloud above the capillary tubes 238. The virtual positive electrode cloud and the grounded or negatively charged capillary tubes 238 create a strong electrical field in the vicinity of the capillary tubes 238, which, as noted above, define EHD comminution sites. Hence, a negative surface charge is induced via the electric field in the liquid at each capillary tube 238. This causes the liquid surface tension to break down such that an electrically charged dispersion of droplets is formed. The cloud of positively charged ions may also function to interact with and neutralize the negatively charged droplets generated at the EHD comminution sites. It is contemplated that the dielectric shield second sections 54 in the embodiment illustrated in Figs. 1 and 2 and the second sections 54 and/or the third sections 56 in the embodiment illustrated in Fig. 4 may have a non-rectangular shape, see, for example, second sections 350A and 350B in Figs. 7 and 8, which include at least one curvilinear section.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.