ULTRASONIC ATOMIZER FOR APPLYING A COATING TO A SUBSTRATE WITH ELECTROSTATIC CHARGE TO PREVENT DROPLET COALESCENCE DURING ATOMIZATION

Abstract

An atomizer for applying a coating to a substrate includes a nozzle and at least one electrode. The nozzle defines a plurality of apertures. The nozzle includes a nozzle plate, a nozzle body, and an actuator. The nozzle plate defines the apertures. The nozzle body and an inner side of the nozzle plate define a reservoir in fluid communication with the first apertures. The actuator is configured to vibrate the nozzle plate to eject droplets of a liquid from the reservoir through the first apertures. The at least one electrode is configured to directly or indirectly electrostatically charge the droplets with a charge that repels the droplets from each other to reduce coalescence of the droplets before the droplets reach the substrate.

Claims

1. An atomizer for applying a coating to a substrate, the atomizer comprising: a nozzle defining a plurality of first apertures and at least one second aperture, the at least one second aperture being configured to direct a flow gas to exit the nozzle, the nozzle including: a nozzle plate defining the plurality of first apertures; a nozzle body, the nozzle body and an inner side of the nozzle plate defining a reservoir in fluid communication with the plurality of first apertures; and an actuator configured to vibrate the nozzle plate to eject droplets of a liquid from the reservoir through the plurality of first apertures; and at least one electrode configured to electrostatically charge the flow of gas, wherein the at least one second aperture is configured to direct the flow of gas toward the droplets as the droplets are ejected from the plurality of first apertures to electrostatically charge the ejected droplets.

2. The atomizer according to claim 1, wherein the nozzle plate defines the at least one second aperture.

3. The atomizer according to claim 2, wherein the at least one electrode is coupled to the nozzle plate and configured to electrostatically charge a portion of the nozzle plate that defines the at least one second aperture.

4. The atomizer according to claim 3, wherein the at least one electrode is configured to electrostatically charge a portion of the nozzle plate that defines the plurality of first apertures to directly charge the droplets ejected from the plurality of first apertures.

5. The atomizer according to claim 1, wherein the at least one second aperture includes a plurality of second apertures.

6. The atomizer according to claim 5, wherein the plurality of second apertures are configured to shape a spray pattern of the droplets as the droplets are ejected from the plurality of first apertures.

7. The atomizer according to claim 6, wherein the nozzle plate is disposed about an axis and the plurality of second apertures are disposed radially about the plurality of first apertures relative to the axis.

8. The atomizer according to claim 1, wherein the at least one electrode is positioned upstream of the at least one second aperture such that the at least one electrode charges the flow of gas before the flow of gas exits the nozzle.

9. The atomizer according to claim 1, wherein the at least one electrode is positioned to charge the flow of gas as the flow of gas exits the nozzle through the at least one second aperture or immediately after the flow of gas exits the nozzle through the at least one second aperture.

10. The atomizer according to claim 1, wherein the nozzle body defines at least one conduit in fluid communication with the at least one second aperture and configured to provide the flow of gas to the at least one second aperture.

11. The atomizer according to claim 1, wherein the at least one electrode is configured to electrostatically charge the droplets to have a voltage potential less than or equal to 10 kV.

12. An atomizer for applying a coating to a substrate, the atomizer comprising: a nozzle including: a nozzle plate defining a plurality of first apertures; a nozzle body, the nozzle body and an inner side of the nozzle plate defining a reservoir in fluid communication with the plurality of first apertures and configured to hold a liquid; and an actuator configured to vibrate the nozzle plate to eject droplets of the liquid from the reservoir through the plurality of first apertures; and at least one electrode coupled to at least one of the nozzle plate and the nozzle body such that the at least one electrode is configured to electrostatically charge the at least one of the nozzle plate and the nozzle body to electrostatically charge the droplets ejected from the plurality of first apertures.

13. The atomizer according to claim 12, wherein the at least one electrode is configured to electrostatically charge the liquid in the reservoir.

14. The atomizer according to claim 12, wherein the nozzle defines at least one second aperture configured to direct a flow of gas toward the droplets as the droplets are ejected from the plurality of first apertures.

15. The atomizer according to claim 14, wherein the at least one electrode is configured to charge the flow of gas as it exits the at least one second aperture such that the charged flow of gas charges the droplets.

16. The atomizer according to claim 15, wherein the nozzle plate defines the at least one second aperture.

17. The atomizer according to claim 12, wherein the at least one electrode is coupled to the nozzle plate to charge the nozzle plate such that the nozzle plate is configured to directly charge the droplets as the droplets are ejected from the plurality of first apertures.

18. The atomizer according to claim 12, wherein the at least one electrode is configured to electrostatically charge the droplets to have a voltage potential less than or equal to 10 kV.

19. An atomizer for applying a coating to a substrate, the atomizer comprising: a nozzle defining a plurality of first apertures and at least one second aperture, the at least one second aperture being configured to direct a flow of gas to exit the nozzle, the nozzle including: a nozzle plate defining the plurality of first apertures; a nozzle body, the nozzle body and an inner side of the nozzle plate defining a reservoir in fluid communication with the plurality of first apertures; and an actuator configured to vibrate the nozzle plate to eject droplets of a liquid from the reservoir through the plurality of first apertures; and at least one electrode configured to electrostatically charge the flow of gas before the flow of gas exits the nozzle, wherein the at least one second aperture is configured to direct the flow of gas toward the droplets as the droplets are ejected from the plurality of first apertures to electrostatically charge the ejected droplets.

20. The atomizer according to claim 19, wherein the at least one electrode is configured to electrostatically charge the droplets to have a voltage potential less than or equal to 10 kV.

Description

DRAWINGS

[0015] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0016] FIG. 1 is a side view of a paint spray system according to the teachings of the present disclosure;

[0017] FIG. 2 is a front view of an array of micro-applicators of the paint spray system of FIG. 1;

[0018] FIG. 3 is a cross-sectional view of one of the micro-applicators of FIG. 2, taken along line 3-3 shown in FIG. 2;

[0019] FIG. 4 is a cross-sectional view similar to FIG. 3, illustrating a micro-applicator of a second construction according to the teachings of the present disclosure;

[0020] FIG. 5 is a cross-sectional view similar to FIG. 3, illustrating a micro-applicator of a third construction according to the teachings of the present disclosure;

[0021] FIG. 6 is a cross-sectional view similar to FIG. 3, illustrating a micro-applicator of a fourth construction according to the teachings of the present disclosure;

[0022] FIG. 7 is a cross-sectional view similar to FIG. 3, illustrating a micro-applicator of a fifth construction according to the teachings of the present disclosure;

[0023] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

[0024] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0025] The present disclosure provides a variety of devices, methods, and systems for controlling the application of paint to automotive vehicles in a high production environment. It should be understood that the reference to automotive vehicles is merely exemplary and that other objects that are painted, such as industrial equipment and appliances, among others, may also be painted in accordance with the teachings of the present disclosure. Further, the use of “paint” or “painting” should not be construed as limiting the present disclosure, and thus other materials such as coatings, primers, sealants, cleaning solvents, among others, are to be understood as falling within the scope of the present disclosure.

[0026] Generally, the teachings of the present disclosure are based on a droplet spray generation device in which a perforate membrane is driven by a piezoelectric transducer. This device and variations thereof are described in U.S. Pat. Nos. 6,394,363, 7,550,897, 7,977,849, 8,317,299, 8,191,982, 9,156,049, 7,976,135, 9,452,442, and U.S. Published Application Nos. 2014/0110500, 2016/0228902, and 2016/0158789, which are incorporated herein by reference in their entirety. Referring now to FIG. 1, a paint spray system 2 for painting a workpiece or part P (also referred to herein as a substrate) using a robotic arm 4 is schematically depicted. The robotic arm 4 is coupled to at least one material applicator 10 and a rack 5. A material source 8 (e.g., a paint source) is included and includes at least one material M (materials M.sub.1, M.sub.2, M.sub.3, . . . M.sub.n shown in FIG. 1; referred to herein simply as “material M” and “material(s)”). In some aspects of the present disclosure the material M includes paint materials, priming materials, corrosion resistance materials, adhesive materials, sealant materials, and the like. The arm 4 moves according to xyz coordinates with respect to the rack 5 such that the material applicator 10 moves across a surface S of the part P. Also, a power source 6 is configured to supply power to the arm 4 and the rack 5. The arm 4, rack 5, and the power source 6 are configured to supply material M from the material source 8 to the material applicator 10 such that a coating is produced on the surface S of the part P. While FIG. 1 schematically depicts a paint system 2 with one robotic arm 4, it should be understood that the paint spray system 2 can include more than one robotic arm 4 while being included in the teachings of the present disclosure. It should also be understood that the robotic arm 4 and the rack 5 are optional such that the material applicator 10 may be mounted to another device such as a movable gantry for example while remaining within the teachings of the present disclosure. It should also be understood that the material applicator 10 may alternatively be mounted to a stationary support structure and the part P can be moved relative to the material applicator 10, such as by a conveyor or robotic arm for example, while remaining within the teachings of the present disclosure.

[0027] Referring now to FIGS. 2 and 3, the material applicator 10 according to the teachings of the present disclosure is schematically shown. In one form of the present disclosure, the material applicator 10 includes an array plate 100 with an applicator array 102 including a plurality of micro-applicators 110. In some aspects of the present disclosure, the array plate 100 with the applicator array 102 is positioned within a housing 140. In other forms of the present disclosure, not specifically shown, the material applicator 10 can include only one micro-applicator 110.

[0028] Each of the micro-applicators 110 includes a micro-applicator plate 114 (also referred to herein as the nozzle plate 114) that defines a plurality of apertures 112 extending through the nozzle plate 114, through which the material M is ejected such that atomized droplets 3 are formed and propagate generally normal to the nozzle plate 114 as schematically depicted in FIG. 3. In the example provided, the nozzle plate 114 is a generally circular shaped disc disposed concentrically about the axis 1, though other shapes can be used. Also, each of the micro-applicators 110 includes a transducer 120, a frame or nozzle body 130, a material inlet 138, and an electrode 142. Each of the micro-applicators 110 may also include one or more gas apertures 146 coupled to one or more gas conduits 148.

[0029] In the example provided, the gas apertures 146 and gas conduits 148 are defined by the nozzle body 130, though other configurations can be used, such as being separate from the nozzle body for example. While only two gas apertures 146 are illustrated in diametrically opposed positions that are radially outward of the nozzle plate 114, it should be understood that other configurations can be used. For example, a plurality of gas apertures 146 can be disposed in any suitable configuration. One such configuration may be an array circumferentially disposed about the nozzle plate 114. In an alternative configuration, a single gas aperture may be used while remaining within the scope of the present disclosure. In one example, a single, annular gas aperture may be disposed concentrically about the nozzle plate 114.

[0030] The gas apertures 146 are configured to direct gas (represented by arrows 150) exiting therefrom toward the droplets 3. As used herein, the term “gas” includes any suitable gas such as air, nitrogen, or other suitable gases. In the example provided, each gas aperture 146 is angled radially inward toward the exiting droplets 3. Each gas aperture 146 includes a corresponding electrode 142 configured to electrostatically charge the gas 150 provided by the gas aperture 146. In one form, each electrode is configured to charge the gas 150 with a charge of less than 10,000 volts. In another form, the electrode can be configured to charge the gas 150 with a charge of more than 10,000 volts.

[0031] In the example shown, the electrode 142 charges the gas 150 so that the gas 150 has a positive charge, though a negative charge may be used instead of a positive charge as long as all of the gas 150 exiting the gas apertures 146 are charged with the same sign (i.e., positive or negative) of charge. In the example provided, the electrode 142 is positioned in the gas conduit 148 upstream of the gas aperture 146.

[0032] In an alternative configuration, not specifically shown, the electrode 142 can be located at (i.e., in or immediately outside of) the gas aperture 146 such that the electrode charges the gas 150 as it exits the gas aperture 146.

[0033] The electrode 142 can be in direct contact with the gas to directly charge the gas or can charge the component (e.g., the nozzle body 130) defining the gas aperture 146 or gas conduit 148 such that the electrode 142 indirectly charges the gas 150 via the component. The charged gas 150 then impacts or otherwise comes close enough to the droplets 3 to charge the droplets 3 (charged droplets are indicated in the drawings by reference number 3′).

[0034] In one form, the gas pressure and gas apertures 146 are configured such that the gas 150 is also shaping gas that can direct or shape the pattern of droplets. In another form, the gas pressure and gas apertures 146 can be configured such that the gas 150 charges the droplets 3 but does not directly shape their pattern in any meaningful way. In another form, not specifically shown, separate shaping gas conduits can provide non-charged gas at positions and pressures configured to shape the pattern of the charged droplets 3′ separately from the gas conduits 148 that charge the droplets 3. In configurations where the charged gas does not also act as shaping gas, the pressure of the charged gas can be less than the pressure of typical shaping gas.

[0035] The transducer 120 is in mechanical communication with the nozzle plate 114 such that activation of the transducer 120 ultrasonically vibrates the nozzle plate 114 as schematically depicted by the horizontal (z-direction) double-headed arrows in FIG. 3. The nozzle body 130 includes a back wall 134 and at least one sidewall 132 that cooperate with the nozzle plate 114 to define a reservoir 136 for containing the material M. The apertures 112 are sized such that surface tension of the material M prevents the material from exiting the apertures 112 absent actuation by the transducer 120. The inlet 138 is in fluid communication with the reservoir 136 and the material source 8 (FIG. 1) such that the material M flows from the material source 8, through inlet 138 and into reservoir 136.

[0036] The transducer 120 is a piezoelectric transducer such that electrical power actuates the transducer 120 to vibrate. The transducer 120 is connected to a controller 122 (FIG. 2) for electrical communication therewith. The controller 122 is configured to control actuation of the transducer 120 by controlling electrical power thereto. In the example shown in FIG. 3, the transducer 120 is an annular shape and disposed between the nozzle plate 114 and the nozzle body 130, though other configurations can be used. In one alternative configuration, not specifically shown, the nozzle plate 114 is connected to the nozzle body 130 and the transducer 120 is affixed to the nozzle plate 114. In such a configuration, the transducer 120 may or may not be annular in shape. In another alternative configuration, not specifically shown, the transducer 120 is mounted to the nozzle body 130 separate from the nozzle plate 114 such that the transducer 120 indirectly vibrates the nozzle plate 114 by producing vibrations in either the nozzle body 130 or by producing vibration waves in the material M that is within the reservoir 136. In such a configuration, the transducer 120 may or may not be annular in shape.

[0037] The controller 122 is also connected to the electrode 142 for electrical communication therewith and configured to control operation of the electrode 142.

[0038] In operation, the controller 122 actuates the transducer 120 to cause the material M to exit the apertures 112 as droplets 3. The droplets 3 exit the apertures 112 generally perpendicular to the nozzle plate 114.

[0039] The controller 122 also activates a source of pressurized gas 152 (FIG. 2) to provide gas 150 to the gas conduits 148 such that the gas 150 exits the gas apertures 146.

[0040] The controller 122 also activates the electrodes 142 to electrostatically charge the gas 150. The electrostatically charged gas 150 exits the gas apertures 146 and electrostatically charges the droplets 3 (indicated by 3′ after being charged). The charge of the droplets 3′ is sufficient to repel individual droplets 3′ from other individual droplets 3′.

[0041] The gas apertures 146 may be angled to direct the charged gas 150 in a direction that has a radially inward component (i.e., toward the droplets 3) and an axial component (i.e., toward the surface S). The gas apertures 146 are constructed such that the charged gas 150 charges the droplets 3 before the droplets 3′ can coalesce. In one non-limiting configuration, the gas apertures 146 are angled to engage the droplets 3 within 20 millimeters of the nozzle plate 114.

[0042] In one form, the charge of the droplets 3′ is sufficient to repel the individual droplets 3′ from each other but insufficient to meaningfully attract the droplets 3′ to the surface S. In an alternative configuration, the charge is sufficient to repel the individual droplets 3′ from each other and may also be sufficient to attract the droplets 3′ to the surface S.

[0043] Referring to FIG. 4, a micro-applicator 410 of a second construction is illustrated. The micro-applicator 410 is similar to the micro-applicator 110 described above except as otherwise shown and described herein. Accordingly, similar reference numbers refer to similar features and only differences are described in detail herein.

[0044] In the micro-applicator 410, the nozzle plate 114 defines the gas apertures 146 and the gas conduits 148 extend through the nozzle body 130. In one form, the electrodes 142 are disposed within the gas conduits 148 to directly charge the gas 150. In an alternative form, the electrodes 142 can charge the walls of the gas conduits 148 so that the gas conduits 148 charge the gas. In yet another form, not specifically shown, the electrodes 142 can be disposed downstream of the gas apertures 146 such that the electrodes 142 charge the gas 150 immediately after the gas 150 exits the gas apertures 146. In still another form, not specifically shown, the electrodes 142 can be disposed on the nozzle plate 114 near the gas apertures 146 such that the electrodes 142 charge the gas 150 as it exits the gas apertures 146.

[0045] In the example provided, the gas apertures 146 are radially outward of the apertures 112, though other configurations can be used. In one alternative example, not specifically shown, the gas apertures can be disposed between the apertures 112. In the example shown, the micro-applicator 410 does not include gas apertures radially outward of the nozzle plate 114, though other configurations can be used. In one alternative construction, not specifically shown, additional gas conduits and gas apertures can be disposed radially outward of the nozzle plate 114, similar to those shown in FIG. 3 and described above, in addition to the gas apertures 146 defined by the nozzle plate 114. In one such example, the gas 150 from the gas apertures 146 defined by the nozzle plate 114 can charge the droplets 3 and the gas from the gas apertures that are disposed radially outward of the nozzle plate 114 can be shaping gas that can be either charged or not charged.

[0046] Referring to FIG. 5, a micro-applicator 510 of a third construction is illustrated. The micro-applicator 510 is similar to the micro-applicator 110 described above except as otherwise shown and described herein. Accordingly, similar reference numbers refer to similar features and only differences are described in detail herein.

[0047] In the micro-applicator 510, the electrode 142 does not charge the gas 150 that exits from the gas apertures 146. In the example shown, the electrode 142 is coupled to the nozzle body 130 and extends into the reservoir 136 to electrostatically charge the material M in the reservoir 136. In alternative configuration, not specifically shown, the electrode 142 can be configured to charge the nozzle body 130 and the nozzle body is an electrically conductive material such that the charged nozzle body 130 charges the material M in the reservoir 136. In yet another alternative configuration, not specifically shown, the electrode 142 is mounted to the nozzle body 130 or another component of the micro-applicator 510 that is in electrical communication with the nozzle plate 114 such that the nozzle plate 114 is charged indirectly by the electrode 142 and the material M becomes charged by the nozzle plate 114. In such a configuration, the material M in the reservoir 136 can be charged by the nozzle plate 114 or the material M can be charged by the nozzle plate 114 as it is ejected from the apertures 112 in the form of droplets 3′.

[0048] In the example shown, the gas apertures 146 provide uncharged shaping gas. In an alternative construction, not specifically shown, the gas exiting the gas apertures 146 can also be charged by an additional electrode. In yet another alternative configuration, not specifically shown, the micro-applicator 510 can be without the gas apertures 146, such as without shaping gas, for example.

[0049] Referring to FIG. 6, a micro-applicator 610 of a fourth construction is illustrated. The micro-applicator 610 is similar to the micro-applicator 110 described above except as otherwise shown and described herein. Accordingly, similar reference numbers refer to similar features and only differences are described in detail herein.

[0050] In the micro-applicator 610, the electrode 142 does not charge the gas 150 that exits from the gas apertures 146. In the example shown, the electrode 142 is coupled to the nozzle plate 114 to charge a portion of the nozzle plate 114. The portion of the nozzle plate 114 may include the entire nozzle plate 114 or may be less than the entire nozzle plate 114 such as just a portion proximate to the apertures 112. The material M in the reservoir 136 can become charged or the material M can become charged as it is ejected from the apertures 112 as droplets 3′.

[0051] In the example shown, the gas apertures 146 provide uncharged shaping gas. In an alternative construction, not specifically shown the gas exiting the gas apertures 146 can also be charged. In yet another alternative configuration, not specifically shown, the micro-applicator 610 can be without the gas apertures 146, such as without shaping gas, for example.

[0052] Referring to FIG. 7, a micro-applicator 710 of a fourth construction is illustrated. The micro-applicator 710 is similar to the micro-applicator 110 described above except as otherwise shown and described herein. Accordingly, similar reference numbers refer to similar features and only differences are described in detail herein.

[0053] In the micro-applicator 710, the electrodes 142 do not charge gas that exits from the gas apertures. Instead, the electrodes 142 is configured to charge ambient gas proximate to the nozzle plate 114 such that the charged ambient gas charges the droplets 3 after they exit the apertures 112. In the example provided, the electrodes 142 are mounted to the nozzle body 130 though other configurations can be used.

[0054] The micro-applicators of the present disclosure electrostatically charge the fine droplets created by an ultrasonic atomizer with sufficient charge such that the droplets repel each other to inhibit coalescence of the droplets before the droplets reach the surface S of the workpiece P. In some forms, the charge is small enough (e.g., less than 10,000 volts) such that the attraction of the charged droplets to the surface S of the workpiece P is negligible. Accordingly, the present disclosure provides for a paint applicator that can provide an improved surface finish.

[0055] Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

[0056] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0057] In this application, the term “controller” and/or “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components (e.g., op amp circuit integrator as part of the heat flux data module) that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0058] The term memory is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0059] The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general-purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

[0060] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.