EP0837735A1 - Electrostatic nozzles for abrasive and conductive liquids - Google Patents
Electrostatic nozzles for abrasive and conductive liquidsInfo
- Publication number
- EP0837735A1 EP0837735A1 EP96926121A EP96926121A EP0837735A1 EP 0837735 A1 EP0837735 A1 EP 0837735A1 EP 96926121 A EP96926121 A EP 96926121A EP 96926121 A EP96926121 A EP 96926121A EP 0837735 A1 EP0837735 A1 EP 0837735A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- nozzle
- liquid
- channel
- electrode
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
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- 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
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- 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
-
- 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
- B05B5/043—Discharge apparatus, e.g. electrostatic spray guns using induction-charging
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- 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
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- 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
- B05B5/16—Arrangements for supplying liquids or other fluent material
- B05B5/1608—Arrangements for supplying liquids or other fluent material the liquid or other fluent material being electrically conductive
Definitions
- This invention relates to electrostatic spraying devices in general, and in particular to pneumatic-atomizing, hydraulic-atomizing and other types of induction-charging spraying systems.
- Induction-charging types of electrostatic nozzles are often selected for use in certain industrial and agricultural settings because they generally use lower input voltage and current than other types of electrostatic nozzles, such as those which are based upon corona, contact or electrohydrodynamic charging principles which utilize voltages on the order of 25 to 50 kV or greater for adequate charging.
- the second class of induction-based devices contains nozzles that have internal embedded electrodes that are placed very near a better defined atomization zone and, because ofthe proximity ofthe electrode to the atomization zone, are able to develop sufficient induction charging field gradients at electrode voltages of only 1 to 3 kV. Examples of this latter type are by Law and by Parmentar et al. The magnitude ofthe force by which charged droplets are electrically propelled toward the intended target is a function ofthe droplet charge level and the droplet size.
- the first effect ofthe stray currents on external surfaces is to increase the power requirement ofthe system which tends to reduce the output voltage ofthe nozzle's unregulated electrode power supply. This causes proportional reductions of both the electrode voltage and the spray charge level.
- the electrode's current drawn from the power supply increases dramatically. Under clean conditions, with water, a Law or Parmentar nozzle may draw only 20mA.
- the effective resistance from the induction electrode to ground is reduced and the resultant surface tracking causes the power supply output current to increase 200-fold or greater, depending on the output capability ofthe power supply.
- Patent Number 4,004,733 (which patent is inco ⁇ orated herein by this reference), it may be desirable to mount the power supply directly to the charging nozzle or to embed it within the nozzle.
- the advantages discussed by Law are that this avoids any high voltage leads that may be susceptible to mechanical damage or can present an electrical hazard.
- Law shows the power supply mounted directly to the nozzle portion containing the electrode.
- the problem with this embodiment is that the low voltage power supply input wires will become contaminated and the insulation will eventually degrade by electrical activity along the insulation surfaces.
- the potential difference between the conductor on the inside of the low voltage line and the contamination on the wire is usually near that ofthe electrode potential. Therefore dielectric breakdown ofthe insulation is likely, especially ifthe insulation is weakened from mechanical damage or electrical tracking damage.
- the device described by Parmentar et al. addresses the problem of electrical tracking on outer nozzle surfaces and attempts to limit the current by lengthening the surface insulation distance from the nozzle's outlet to the earthed mounting bracket with a series of grooves on the outer walls ofthe nozzle and a large radial flange surrounding the nozzle. But, since the grooves and flange are exposed directly to dust and to the charged spray cloud, they can quickly become sufficiently conductive to sustain substantial current from the electrode. In addition, the deep grooves can become filled with dried spray materials and are difficult to clean thoroughly and therefore can remain conductive after cleaning. A second effect of stray current on external nozzle surfaces is to reduce the intensity of spray charging because of electrical contact with the liquid supply through seams in the liquid input connection on the nozzle body.
- Some types of conventional induction charging nozzles use seals within the nozzle to insulate the liquid from the electrode positioned in the nozzle.
- the dielectric surfaces of these seals can become sufficiently conductive by contamination during disassembly to provide current paths to the liquid.
- the level of currents across the dielectric seals may not be sufficient to cause electrical arcing or surface etching.
- the electrical contact can be sufficient to elevate the voltage ofthe liquid stream toward that ofthe electrode resulting in a significant reduction ofthe induction spray charging electric field.
- a resistor in the gigohm range is placed between the power supply output and the nozzle's electrode to limit current to the electrode for the pu ⁇ ose of operator safety and for preventing gross electrical arcing on the interior ofthe nozzle.
- This resistor can also have the beneficial effect of limiting leakage currents originating at the electrode, but spray-charging levels are reduced because very small leakage currents over contaminated surfaces cause a substantial voltage drop over the high-value limiting resistor connected to the electrode.
- nozzle charging components must maintain a significantly higher value of leakage resistance to ground than the proper size current limiting resistors from the power source if such resistors are to be used effectively.
- the primary benefits of such a high leakage-impedance system are safety, longer nozzle life, improved operational reliability with poorly maintained nozzles, consistent spray charging over a wide range of liquid conductivities, the ability to use very small power supplies with relatively low voltages, and the ability to power many charging nozzles from a single power source.
- Sickles attempts to maintain a highly resistive pathway between the nozzle's electrode and ground by keeping nozzle surfaces clean using a secondary air stream designed to prevent charged spray from returning to the nozzle body.
- the charged spray cloud emitted from an induction nozzle's orifice creates an intense electric field terminating on the intended target as well as on the nozzle face and other sprayer components.
- the space-charge imposed field at the nozzle causes a strong attraction force between the nozzle surface and the charged droplets.
- Conventional induction nozzles such as by Law which utilize pneumatic atomization, have the benefit of a gas carrier to effectively propel most of the spray away from the nozzle face.
- droplets are mutually repelled and some droplets on the outer periphery escape entrainment by the gas jet.
- the intensity ofthe electric field at the peaks is sufficient to cause dielectric breakdown ofthe surrounding air.
- the resultant gaseous electric discharges send ionic charges of opposite polarity into the spray cloud, subsequently electrically neutralizing a substantial portion ofthe spray.
- the surface- accumulated liquid electrically drawn from the nozzle or dripping by gravity is wasteful and causes poor deposition from improperly atomized spray.
- the droplets dripping from a nozzle face are usually quite large and are charged opposite to the spray. In paint spraying applications, these large droplets mar an otherwise uniform surface coat. In the practice of pesticide spraying of plants, deposition of these large drops can cause severe plant tissue damage at sites where the overdose occurs.
- the shape ofthe conventional Parmentar nozzle reduces ionization points forming from surface films at the nozzle orifice area by recessing the outlet in a cup-shaped cavity with the outer rim facing the spray cloud.
- ionization and dripping occur at other surfaces ofthe nozzle as they become sufficiently wetted.
- Charged droplets returning to the nozzle are attracted to the cavity's rim edge since the electric field lines are concentrated there. This helps limit the amount of spray that coats the body rearward of the rim edge, but the collecting droplets accumulate and coalesce on the edge itself.
- the liquid is pulled toward the spray cloud into sha ⁇ peaks from which charge opposite ofthe spray cloud is emitted and tends to neutralize a significant portion ofthe charged spray cloud.
- Parmentar also inco ⁇ orates a large radial flange around the nozzle. This flange serves to lengthen the insulating surface and block returning charged spray from coating the upstream portion ofthe nozzle body.
- the front and edge surfaces toward the spray cloud eventually become coated and multiple ionization-prone drip points form.
- cup shaped cavity on the front ofthe nozzle prevents the nozzle from being used in an upward orientation since the cavity tends to fill with liquid which accumulates on the rim edge and drips into the cavity, eventually partially blocking the orifice and/or being ejected as large liquid slugs which dramatically degrade the spray deposition quality.
- the outlet of the nozzle can erode to double the initial diameter in a period of only a half-day while spraying certain abrasive materials such as diatomaceous earth or sodium aluminofluoride. Left unattended, the electrode will also begin to wear, beginning at the outlet end and continuing rearward. Air consumption, spray charge, and atomization quality can all be adversely affected by the abrasive wear.
- the present invention provides improved electrostatic spray charging nozzle systems for reliable spray charging with a wide variety of spray liquids, especially those containing relatively high mass concentrations of abrasive powders, metal elements, corrosive materials, and/or highly conductive materials. Such systems are also safer and more reliable in environments where nozzle surfaces are likely to become contaminated with spray and other material, nozzles are subject to operation by untrained operators and nozzle maintenance may be neglected.
- the systems also provide nozzles with low electrical power requirement to enable the operation of many electrostatic spray nozzles from a single miniature power supply or to allow operation of a single nozzle from a sub- miniature power supply which may be embedded, if desired, within the nozzle.
- Pneumatic-atomizing induction-charging nozzle systems advance the art, among other ways, by (a) maintaining stability ofthe internal electrostatic charging field between liquid jet and induction electrode through electrical insulation ofthe liquid stream from internal and external current leakage, and through establishment of an electrical barrier between the internal charging field and spray cloud fields originating external to the nozzle; (b) maintaining nozzle surface potentials to preclude leakage of charge on interior and exterior nozzle surfaces; (c) creating high electrical resistance between earthed sprayer parts, the high voltage power source, and the electrode ofthe spray nozzle; (d) utilizing abrasion resistant materials at the nozzle outlet; and (e) shaping the external surfaces ofthe nozzle to minimize nozzle coating and neutralization of spray by space-charge induced ionization.
- Nozzle assemblies include a body that terminates in a twin-fluid tip which is nested into a cover that contains a pneumatic atomization chamber and charging electrode.
- the induction electrode is properly positioned in the assembly in relation to the atomization zone so as to concentrate and maintain a suitably intense electric field at the surface ofthe liquid jet at the droplet-formation zone.
- the liquid jet is maintained at or near ground potential and connected to ground at an appropriate upstream location. Charge is induced to flow through the liquid and concentrate on the surface ofthe liquid jet entering the atomization zone in response to the electric field at the jet surface. Droplets are formed with pneumatic energy which also propels the charged spray away from the electrode area, through the nozzle jet outlet and toward the intended target.
- the nozzle assembly consists of a body that terminates in a twin-fluid tip which is removably connected to a cover.
- the cover features a conically or other aerodynamically shaped outer surface that terminates in a spray jet outlet. It contains an interior surface that forms an atomization channel and includes an induction electrode.
- the body and cover can be easily separated to provide access to all the areas that periodically need to be cleaned; including the air channels, liquid channel, liquid-orifice tip, atomization channel, charging electrode surface, and air plenum area.
- the liquid-orifice tip, electrode and other internal nozzle components are integral to the body or cover and do not need to be removed.
- the electrode's electrical contact with the power supply is interrupted when the cover is loosened or removed. This reduces the chance that an operator will inadvertently contact the power supply when inspecting or cleaning the electrode or other portions ofthe atomization zone. This feature also eliminates handling and straining any fragile wires while cleaning the atomization channel or other areas.
- nozzle according to the present invention eliminates stray currents across contaminant surface films which readily form on interior dielectric surfaces of induction charging nozzles, such as surfaces in the areas around the liquid-orifice tip and the atomization chamber.
- equipotential surfaces are intentionally maintained in the areas ofthe cover portion adjacent to and upstream ofthe electrode.
- the surfaces ofthe gas plenums, seals, and the atomization channel, which are internal portions ofthe cover assembly, are positioned between the electrode and a conductive or semiconductive annulus which is at a potential similar to the electrode.
- the internal conductive annulus also conveniently serves to make alignment- independent electrical contact from the power supply conduit in the body to the electrode in the cover.
- a further benefit ofthe interior charged annular surface is that it inherently imposes an electrical barrier between the internal induction charging electric field and any externally originating fields existing around the nozzle, such as that imposed by the spray cloud space charge, which is opposing and will suppress the nozzle's spray charging field.
- the liquid channel, liquid inlet connections, and liquid tip are contained within the low-voltage body portion.
- the liquid is grounded at some point upstream ofthe liquid orifice and the parallel resistance ofthe stream segment and its seamless conduit between the ground point and the electrode causes the potential ofthe liquid jet at the orifice to float between ground voltage during normal operation and the electrode voltage during a gross short circuit situation.
- the current is caused to move through the bridge of material causing the short, and through resistive liquid stream and its conduit.
- the liquid between the tip and its upstream ground point forms a resistor, which self-limits current and subsequently limits damage to nozzle components. Damage is further prevented as the nozzle liquid flow is stopped because current ceases when liquid contact discontinues as the liquid is evacuated from the channel at the liquid orifice tip.
- Chances of a short circuit at the liquid-orifice tip are further limited by the atomizing gas moving in the plenum surrounding the base ofthe tip and by the very high velocity gas which is forced into the atomization zone surrounding the liquid-orifice tip.
- the electrode voltage is preferably disconnected by way of a pressure switch controlling the power supply.
- a primary aspect ofthe present invention is the maintenance of a highly resistive path from the electrode to earth, thereby preventing significant charge flow from the electrode along the interior walls ofthe atomization channel rearward toward the twin-fluid tip and forward toward the exterior face ofthe nozzle and along contaminated exterior dielectric surfaces attached to ground points on the sprayer.
- the highly resistive path is created by protecting selected portions of nozzle surfaces from contamination.
- a method to maintain a high impedance path is to properly form cavities into selected nozzle surfaces, and/or on electrical standoffs which are used to connect the nozzle to grounded sprayer parts, and protect the interior of these cavities from contaminant entry.
- the aerodynamic shape ofthe nozzle aims to create a generally laminar flow on the nozzle surfaces in order to reduce proclivity of entrained particles to adhere to the nozzle surfaces, while certain carefully placed electrical field concentrators, such as rims or edges, create areas of field intensity which tend to repel or deflect such particles.
- the dielectric nozzle body on which the gas, liquid and electrical terminals are located and mounting connections are made, is electrically insulated from the cover portion by protected cavities formed into the body.
- the exterior body surface is thus maintained at near ground by the conductivity of the contaminated body surface and appreciable electrical current flow across the body surfaces from nozzle high voltage components is prevented by the resistivity ofthe protected cavity interior.
- a preferred embodiment also includes a protected surface on the cover portion ofthe nozzle assembly containing the internal electrode. This protected cavity further isolates the electrode from earth in the likely event of surface fouling, and thus causes the atomization channel and other external cover surfaces to elevate to a potential similar to the electrode and be held at that potential, thereby preventing charge flow from the electrode across all surfaces adjacent to the electrode.
- the potential imposed on the exterior surface ofthe cover is opposite in sign of that ofthe spray droplets, but this does not significantly increase the attraction of charged droplets towards the nozzle surface over that of a grounded nozzle surface, nor does charged spray impacting the cover cause significant power supply current.
- the magnitude ofthe space-charge electric field created by a negatively charged spray cloud has been measured to be over -3 kV/cm at a distance of 10 to 15 cm below the spray- jet centeriine at the nozzle outlet. Therefore, the space charge potential is near -35 kV relative to a grounded nozzle surface and -36 kV relative to a cover surface elevated to the +lkV electrode voltage.
- a charged cover at +lkV may preferentially attract negatively charged spray, but the force is only 3% greater compared to a ground surface of similar geometry and proximity to the spray cloud.
- a neutralization current is caused to flow from the induction electrode in order for the cover to maintain its potential, but the required current is very small.
- Nozzles according to the present invention greatly reduce charged spray rollback and particulate deposition on selected nozzle surfaces by proper shaping ofthe nozzle exterior.
- the nozzle shape creates ambient air flow fields, creates beneficial electric field patterns from the nearby potential ofthe charged spray cloud, and creates strategic curvilinear electric field shapes between fouled dielectric surfaces on which electrical potentials are intentionally maintained.
- Charged droplets returning to the face ofthe spray nozzle and causing induced- electrical-discharge neutralization ofthe spray cloud and electrical tracking is a problem encountered with all prior commercial versions ofthe Law device and other induction charging nozzles. That is because they have generally planer face surfaces pe ⁇ endicular to the axis ofthe droplet-laden gas jet.
- Liquid deposit may be especially heavy in situations where the nozzle is spraying upward, or is spraying horizontally, or in situations where oppositely charged nozzles are spraying toward each other, such as with vineyard sprayers.
- the surface finish is made smooth and is generally preferably conical or otherwise aerodynamically shaped, forwardly tapering so as to be as narrow as possible at the jet outlet.
- This conical forward taper terminating at the high velocity jet causes entrainment of a significant volume of ambient air.
- the entrained ambient air flows across the smooth nozzle exterior toward the main spray jet and creates an air "curtain" across the openings ofthe cavities, helping to prevent particulate entry.
- the air flow across nozzle surfaces helps prevent contaminant deposition and redirects particulates and stray spray droplets toward the intended target.
- the entrained gas volume adds to the outer layer ofthe main gas jet exiting the nozzle.
- the electric field lines originating from the electrical potential of the spray cloud are caused to concentrate at the forward end ofthe nozzle, nearest to the main gas/spray jet.
- the forwardly tapered shape ofthe cover reduces the deposition surface area immediately adjacent to the charged spray cloud and the increased curvature at the outlet causes the greatest portion ofthe electric field lines to terminate on the conductive-film surface just around the spray jet.
- Charged droplets returning to the nozzle are thus preferentially attracted toward this area of sha ⁇ curvature and, since the air flow field is also most concentrated in this region, nearly all droplets approaching this region are re-entrained into the main gas/spray jet prior to deposition and discharge on the nozzle face.
- liquid spray material may deposit on the upstream surfaces ofthe conical cover, although the influence ofthe spray cloud's field is made much weaker there by the distance from the main cloud and by the continuous smooth shape. In this case the liquid does not readily accumulate sufficiently to drip or initiate induced ionization, because the liquid is steadily drawn into the main jet by the sheath ambient air which is entrained towards the flow ofthe nozzle's main gas jet.
- the energy ofthe gas carrier is sufficient to propel nearly all the spray away from the nozzle, but a portion moves toward the nozzle surfaces along these field lines.
- These space-charge field lines terminate pe ⁇ endicularly on conductive contaminated nozzle surfaces.
- strong electric fields are also present between the high voltage cover and the low voltage body surfaces of the nozzle according the present invention. These two fields are complementary in flow direction. On planar surfaces the field lines are spaced evenly, but at surface discontinuities the electric field lines are much more concentrated.
- One aspect ofthe present invention is to place discontinuities or field concentrators on the nozzle surface to concentrate field intensity and cause electric field lines of a curvilinear shape which result from both the potential ofthe spray cloud and the potential intentionally maintained on nozzle surfaces. Charged spray droplets approaching the curved field lines experience strong centrifugal forces and are thrown outward away from the cavity openings, into the ambient air-flow field and re-entrained into the main spray cloud directed toward the intended target.
- the exterior surface ofthe cover is generally a forwardly converging cone shape and surrounds the atomization and charging zone.
- the cover surface is preferably a dielectric material and becomes sufficiently contaminated when exposed in a spraying environment to become somewhat conductive. Therefore, a beneficial electric field boundary is maintained which surrounds the internal charging induction field to effectively decouple it from the opposing space charge field created by the presence ofthe highly charged spray emitting from the nozzle outlet.
- the previously discussed protected cavity interior surfaces of the nozzle according to the present invention results in a high impedance between the nozzle's electrode power supply and ground and significantly reduces the current from the power supply compared to previous nozzles.
- This high impedance now allows the successful implementation of a protective resistive element in series with the nozzle, between the power supply and the induction charging electrode without suffering significant voltage drop at the electrode.
- this resistive element should be contained within the nozzle itself.
- a configuration where the power supply is mounted within the nozzle would simply have a resistor at the power supply output. In the event of multiple nozzles connected to a remote power supply, a resistor could be placed in the power supply in addition to the individual resistive elements within the nozzles.
- multiple output resistors could be placed within the power supply itself with direct connections to the nozzle. Resistive wire may also be employed to achieve this objective. If multiple nozzles are to be powered from a single source it is preferred to use an output resistor for each nozzle to prevent a shorted nozzle from affecting the others.
- One ofthe benefits of a resistive conduit between the power supply output and the high impedance nozzle's electrode is safety.
- the system can be designed so there is no noticeable shock when handling an energized nozzle.
- Other benefits observed due to a series resistor used in concert with a high impedance nozzle are the significant reduction in power supply current drawn due to induced electrical ionization ofthe liquid jet and consequential ion current from the induction electrode. Such ion currents have been noted in prior art nozzles once the electrode becomes wetted or has exposed edges or other discontinuities.
- the high impedance nature ofthe nozzle according to the present invention lends itself to successful positioning ofthe power supply on or within the nozzle.
- the reduced power supply current and voltage allow the use of very miniature DC-to-DC converters which can be conveniently fitted to the nozzle or enclosed within it, but the low voltage leads or battery providing input to the power transformer can be protected from damage due to electrical tracking originating at the electrode.
- the low voltage leads emanated from a surface ofthe nozzle which was susceptible to contamination and to voltage and current from the electrode. Ifthe power supply is to be mounted onto the nozzle or embedded in a portion of it, the preferred embodiment would have the low voltage input wires or connectors emanating from the low voltage section of a high impedance nozzle, such as that disclosed here.
- the power supply itself could be mounted to the high voltage section with the low voltage input conductors protected from contamination by positioning them within the low voltage nozzle portion.
- An additional primary feature ofthe nozzle according to the present invention is the use of a hard, abrasion resistant material which is inco ⁇ orated into the atomization channel to prevent premature electrical or mechanical etching of this channel.
- ceramic is chosen for its abrasion resistance and electrical insulation characteristics. Certain types of ceramics which are made electrically conductive can be used as an electrode material.
- the abrasion resistant electrode may form a portion ofthe walls ofthe atomization channel or make up the entire channel surface.
- the atomization-zone channel is a straight bore, diverging at the jet outlet, as opposed to a converging channel which has been used in previous designs and can cause build up of material in the channel or at the jet outlet.
- Figure 1 shows a perspective view of an assembled first embodiment ofthe induction spray charging nozzle according to the present invention.
- Figure 2 shows a perspective view of a disassembled first embodiment ofthe induction spray nozzle according to the present invention.
- Figure 3 shows a cross-sectional view ofthe first embodiment ofthe induction spray charging nozzle according to the present invention.
- Figure 4 shows a detailed perspective view ofthe twin-fluid tip section of an embodiment ofthe induction spray charging nozzle according to the present invention where air channels are used to direct air into the atomization zone.
- Figure 5 shows a cross-sectional elevational view of a second embodiment ofthe induction spray charging nozzle according to the present invention, which includes a hood.
- Figure 6 shows a perspective view of a third embodiment ofthe nozzle system according to the present invention.
- Figure 7 shows the entrained air flow field and the electric field imposed on a nozzle according to a preferred embodiment ofthe present invention.
- Figure 8 shows the entrained air flow field and electric field imposed on a nozzle according to the present invention having a hood installed over the cavities for mechanical protection ofthe surfaces as well as for creating an enhanced curvilinear electric field for the exclusion of charged particles.
- Figure 9 shows a fourth embodiment ofthe induction charging nozzle according to the present invention in which resistive elements are installed within the nozzle between the power supply outlet and the nozzle's electrode.
- Figure 10 shows a semi logarithmic graph ofthe electrode resistance to ground measured over a time span while spraying a common highly conductive agricultural mixture comparing a prior art nozzle to a nozzle according the present invention.
- Figure 11 is a graph showing the charging level achieved over time for a nozzle according to the invention compared with that of a prior art nozzle.
- Figure 12 is a semi logarithmic graph of the typical power supply current required over a day-long time span to operate a nozzle according to the invention compared with that for a prior art nozzle.
- Figure 13 is a schematic representation of a spray-charging nozzle system in which a resistor is inte ⁇ osed between the power supply and a nozzle having a contaminated resistive surface.
- Figure 1 shows a form of preferred embodiment of induction charging nozzles according to the present invention.
- the nozzle is broadly comprised of a body 1 and a cover 2.
- the liquid inlet 8, gas inlet 7 and electrical input 9 are located on the rear face ofthe body portion 1.
- Charged spray in a gas carrier 15 is emitted from the forward end ofthe nozzle through the outlet 33.
- the nozzle's conically shaped cover 2 tapers toward the outlet face 24.
- a hood 30 is shown positioned onto the body portion 1 ofthe nozzle.
- cover 2 can preferably be readily detached from the body 1 exposing the inner regions for servicing.
- the cover 2 preferably fastens onto the body 1 and is made easily separable using threads 3, or by screws, latches or other attachment means which allow disassembly for inspection, cleaning and reassembly without misalignment or damage by untrained persons and preferably without tools or with the use of common tools.
- the downstream end ofthe body is shaped into a twin-fluid tip 12 containing gas outlet 21 and plenum 13, and liquid orifice tip 16. Electrical contact with the power supply can be made through a contact terminal 23 which mates to the annular conductive surface 19 shown in Figure 3.
- the nozzle body 1 is preferably formed of a dielectric material, preferably having low-surface wettability, low surface and volume conductivity values, and low surface adhesion properties.
- the body 1 contains conduits for gas 4, liquid 5, and electrical power (not shown in this view, refer to Fig 9, numeral 6).
- the inputs of gas 7, liquid 8, and electrical power are preferably located on the rear face 10 of the body 1 at the farthest distance from the face 24 ofthe nozzle.
- the gas input 7 can be made to accommodate a filter screen 11 if desired.
- the fluid conduits 4 and 5, as well as the electrical conduit, are usually formed continuously through the nozzle body 1 without seams or separations in the body.
- the power supply may be encapsulated within or attach onto the nozzle body 1, thus eliminating a high voltage wire from the outside ofthe body portion 1.
- the body terminates in a twin-fluid tip 12, as shown in Figure 2 and a slightly modified version in Figure 4.
- the gas conduit 4 through the body 1 terminates at an outlet 21 into a plenum 13 which surrounds the base ofthe twin-fluid tip 12.
- the outer rim 22 ofthe plenum 13 may serve to seal against the base ofthe plenum 26 in the cover portion 2. Additional sealing may be provided by a flexible seal 17 against the rim 25 formed on the interior ofthe cover 2. These seals prevent gas leakage and also serve to limit the interior surface current paths.
- Pressurized gas from the plenum 13 can be channeled through multiple ports 14 surrounding the base 34 ofthe twin-fluid tip as shown in Figure 4, or, as in Figures 2 and 3, the base 34 ofthe twin-fluid tip 12 can be made more narrow and smooth to allow gas to completely flow around the circumference ofthe base 34. The latter is preferred for maximum electrical isolation ofthe fluid tip 12.
- slotted channels 14 are preferred to holes since the sidewall surfaces ofthe slots are exposed when the cover 2 is removed and they can be cleaned more easily than the insides of holes.
- These slots can be made in the axial direction ofthe spray stream 15 or the slots 14 can be formed at an angle (as shown in Figure 4) if a radial motion ofthe exiting gas is desired to create a wider spray angle.
- the liquid conduit 5 terminates in the outlet ofthe liquid-orifice tip 16.
- the orifice tip 16 be placed upstream from the electrode 18 as shown in Figure 3. But, it has been found that the location of this tip 16 can be varied to achieve desired atomization and charging qualities and to vary the liquid flowrate.
- a gas plenum 26 which surrounds the base 34 ofthe twin-fluid tip 12.
- the gas plenum 26 serves to equalize, accelerate, and direct the flow of pressurized gas into the atomization zone and can form part ofthe wall ofthe atomization channel 35.
- the shape ofthe plenum 26 is shown generally as a frustrum transitioning to a cylinder, which works well for a narrow directed spray, but other configurations may be used which can result in a modified spray pattern.
- the gas plenum 26 positioned around the base of the tip 12 helps to keep the area free of gross contamination while it is pressurized.
- a conductive induction electrode 18 is properly positioned so that its inner surface forms part ofthe wall ofthe atomization channel 35, preferably downstream from the liquid-orifice tip 16.
- Forward or downstream, preferably, ofthe electrode 35 is the atomization channel jet outlet 33 which serves to direct the spray jet and cover the forward edge ofthe electrode 35.
- the jet outlet 33 is preferably, but need not be, formed from abrasion resistant materials such as ceramic. It is not necessary that the outlet 33 be non-conductive, and hard conductive materials, such as stainless steel, may be selected, although insulating materials would be preferred for personnel safety.
- Prior art induction charging nozzles tend to wear or degrade in the jet outlet area when atomizing liquids containing abrasive powders or harsh chemicals.
- Nozzles according to the present invention inco ⁇ orate a jet outlet preferably formed of ceramic.
- alumina industrial ceramic is chosen for this pu ⁇ ose because of extremely high resistance to wear and degradation by acid solutions, alkaline solutions, salts, and solvents.
- Alumina ceramics exhibit a hardness level that exceeds nearly all other materials.
- these types of ceramic exhibit high dielectric strength, high surface resistivity, low surface wettability and low porosity.
- the ceramic shape can be molded using standard ceramic part forming techniques.
- Certain alumina ceramics of a type having glass bonded mica, such as the Corning product "MACOR" are particularly suitable for forming the jet outlet 33 by standard machining methods.
- Other materials suitable for this appliation include certain abrasion resistant plastics.
- the components which make up the walls ofthe atomized zone such as the electrode 18 and jet outlet 33, may be formed of one piece. This solution avoids the problem of embedding a metallic electrode and greatly simplifies manufacture and design ofthe nozzle.
- Principal concepts of this electrostatic spraying system include the maintenance of surface potentials on selected nozzle components and the maintenance of a highly resistive path from the electrode 18 to ground. Chief benefits include the prevention of surface current tracking, reduction of induced ionization at the nozzle face, a reduction in the size and output ofthe power supply, and increased safety. To eliminate surface charge flow, the exterior and interior nozzle surfaces contacting the electrode 18 through surface contamination are maintained at a voltage similar to the electrode 18.
- the body ofthe nozzle 1 is sufficiently insulated from the cover 2 so that in the event the rear base surfaces 10 become contaminated they will be at near ground potential with minimal current to fluid connections 7 and 8 and grounded sprayer parts to which the body 1 may be eventually connected.
- a method of achieving a high electrical resistance between the nozzle's electrode 18 and grounded portions is by physically protecting selected portions ofthe nozzle surfaces from contamination by spray or other materials which may deposit on the nozzle and cause the formation of stray current paths.
- the embodiments of Figures 2 and 3 show an example of a current-limiting cavity 28 which is formed on the body portion 1 and an additional current-limiting cavity 29 which is formed into the cover portion 2.
- These cavities 28 ,29 which may be annular or any other desired shape, create regions which are partially sheltered from spray or other contaminants and a highly resistive surface is preserved.
- Charged spray returning to the nozzle as driven on electric field lines lacks sufficient kinetic energy to readily penetrate into the cavity depth and most deposits on the cavity edge where the field lines are concentrated.
- the quantity is usually small and liquid does not accumulate to form a continuous path, liquid films being much more conductive than discrete small droplet deposits.
- the cavities 28, 29 can be cleaned periodically and are easily accessed when the body 1 and cover 2 portions are separated.
- gas jets 40 may be directed into the cavity 28, 29 to continuously or periodically purge the cavity interior.
- some ofthe gas could be directed through several small diameter holes 40 drilled radially or somewhat tangentially outward from the gas conduit 4 creating a pressure gradient and an active gas sweeping ofthe body cavity 28 to exclude particulate deposition on the interior.
- shields for mechanical shelter and to create beneficially shaped electric field lines to prevent charged droplet entry An example of such a shield is shown in the cross- sectional view of Figure 5 (although other structures or forms may be employed).
- This outer shield in the form of a hood 30 serves to further protect nozzle outer surfaces and the surfaces of nozzle body cavity 28 and the cavity ofthe cover 29.
- the hood 30 may be placed as shown for downward nozzle orientations, or inverted and fitted to the cover on the seat 31 for upward nozzle orientations.
- further protection can be added by the placement of a dielectric annular disk-shaped barrier 32 placed between the body and cover.
- This barrier 32 further covers the cavities 28, 29 and creates a maze of surfaces to deflect or otherwise limit entry and surface deposition of charged spray or other contaminants which may be traveling in air currents around the nozzle.
- the outer hood 30 and inner barrier 32 can be made as an integral part ofthe nozzle body or made separately, preferably formed from a dielectric material with low surface wettability, low volume and surface conductivity, and low surface adhesion characteristics, such as UHMW or PTFE.
- FIG. 6 Another shield configuration to preserve high resistance pathways from the nozzle's electrode 18 to ground is shown in Figure 6.
- a basically hood-shaped shield 36 is placed between a charging nozzle 38 and a grounded sprayer part 39.
- the dielectric standoff structure 37 is the gas and/or liquid lines entering the rear face 10 ofthe nozzle.
- the shield 36 mechanically protects the dielectric standoff support 37 from contamination. It also beneficially modifies the electric field to prevent charge droplet deposition on the shield interior.
- hoods, cavities or other shielding methods can be added to the nozzle body, cover, nozzle mountings, tubing or wires, placed one on top ofthe other so as to form a labyrinth, or otherwise added and/or configured if greater degrees of insulation are necessary.
- perforated outer shields offer protection from electro-deposition on inner surfaces while allowing accumulated liquid (or rain) to escape.
- the nozzle surfaces are configured to influence the shape and concentration of the space-charge electric field lines imposed on the various body 1 and cover 2 surfaces for the pu ⁇ ose of beneficially influencing the trajectory of charged spray droplets returning to the nozzle.
- a properly charged spray cloud emitted from an induction charging nozzle typically imposes a passive space-charge field of 2 to 4 kN/cm magnitude at planar nozzle surfaces.
- the space-charge field lines terminate uniformly spaced and pe ⁇ endicularly. As angular surface discontinuities are encountered, the field lines still terminate pe ⁇ endicularly, but are more concentrated at convex shapes, and less concentrated within the interior of concave shapes.
- nozzle surface films For the nozzle according to the present invention, potentials are maintained on nozzle surface films, and cavity edges and other nozzle surfaces are intentionally shaped so that an active curvilinear electric field is imposed to protect nozzle surfaces from charged spray deposition.
- Charged droplets moving along such curved field lines experience strong centrifugal forces which effectively repel them from the cavity opening area, and away from the nozzle, into an air flow field, thus protecting these zones from deposition.
- Charged droplets returning to the nozzle along space-charge electric field lines originating at the spray cloud are prevented from entering the cavities, because as they become entrained in the increasingly intense curvilinear field, they accelerate and centrifugal force causes the droplets to be cast away from the sha ⁇ ly curved path ofthe field lines and into the entraining air flow field 1 surrounding the spray nozzle.
- the air flow field 61 and this active electric field 60 work in concert, each moving stray charged droplets in the direction ofthe intended spray target. While negatively charged droplets resulting from a positive induction electrode are used for the pu ⁇ ose of the example, this resulting target-bound direction ofthe droplets moving in the curved field is the same regardless ofthe polarity ofthe induction electrode.
- the addition of a properly formed hood 30 over the cavity openings is used to create a very intense curvilinear field 62 across the entryway, between the hood rim 56 and an edge 57 formed on the nozzle cover 2.
- a typically 800 V positive potential on the surface film ofthe dielectric cover 2 positioned l ⁇ cm from a ground plane will create a linear electric field of 1.6 kV/cm.
- the field shape is curvilinear and can be made to approach the dielectric breakdown strength of air if so desired, although such a field strength is undesirable because the resultant ion current adds to the power supply demand.
- a field strength of much less is required to cause the centrifugal force repulsion of 30mm droplets charged at a level of -5 mC/kg.
- the liquid moves to the hood rim 56 and is pulled into the curved field 62 prior to formation of ionization-prone drip points. This liquid tends to attract to the cover 2, avoiding the cavities 28, 29 along curvilinear lines, and is pulled by venturi action into the jet and re- atomized.
- the cavity edges 54, 55 make use ofthe electric field actively maintained between nozzle and cavity edges, shaping the field to promote droplet repulsion from protected surface sites.
- the forward end ofthe nozzle 58 is shaped to attract droplets toward the face surface 24 at the outlet 33, utilizing the passive electric field 63 created by the nearby charged spray cloud.
- the high- velocity gas spray jet is used to repel and/or eject any charged or uncharged spray tending to collect onto nozzle surfaces.
- the localized high kinetic energy and velocity ofthe atomizing-gas jet as it and the accompanying charged droplets exit the jet outlet 33 produce a reduced pressure zone which pulls into the jet any spray tending to deposit and/or accumulate onto the small area faces ofthe abrasion resistant outlet 33, the face ofthe outlet 24, or other surfaces 50 ofthe cover 2.
- molecular impacts ofthe high velocity central gas jet exiting the nozzle at the forward jet outlet 33 impart a velocity and entrain a significant volume of surrounding ambient air.
- the present invention may include contouring ofthe external shape ofthe nozzle body and the accompanying cover pieces so that the beneficial effects of centrifugal force exerted on charged particles moving in curvilinear electric fields work in concert with aerodynamic flow fields to preclude excessive liquid accumulation, droplet discharge by deposition, and induced corona and liquid slugging problems observed with conventional charging nozzles.
- Figure 9 shows a cross-sectional elevational view taken through the axis ofthe electrical conduit 6 which terminates at the downstream end ofthe nozzle body 1 in a contact post 23.
- the electrical conduit 6 through the body 1 can contain a power supply wire, the power supply itself, or be formed of conductive or semiconductive material to connect to a power supply.
- an electrode power source 43 is to be inco ⁇ orated in the nozzle or attached to it, the preferred embodiment should include the low voltage input connections 64 on the low voltage body 1 section ofthe nozzle.
- the power supply 43 may be located on or within either the body 1 or the cover 2. Ifthe power supply 43 is mounted at the cover portion 2, the low voltage input leads should be within the low voltage nozzle body 1.
- the conduit 6 has a terminal end 23 which contacts with a conductive surface 19 which is electrically connected to the electrode in the cover portion 2.
- the conductive surface 19 can be a metal or conductive plastic annulus inserted in the cover cavity or it can be a conductive plastic which is poured or injected. It is preferable that the surface be continuous and surround the inside ofthe cover portion in order to set up an equipotential on the surface film on the internal surfaces 59 ofthe cover upstream of the electrode 18 to the conductive surface 19.
- This equipotential surface 59 prevents current paths from forming from the electrode 18 rearward to the any ofthe critical surfaces ofthe nozzle atomization zone and also prevents damage to the twin-fluid tip 12 region. In the event of a direct short circuit between the liquid-orifice tip 12 and the electrode 18 the current is directed towards the liquid stream itself, instead of along paths on the dielectric surfaces, and the liquid stream's resistive path and the resistive element on the electrode input limits gross arcing at the tip.
- An electrical passageway 20 is formed in the cover 2 between the conductive surface 19 and the electrode 18.
- a wire or other highly conductive material, or a fixed resistor 41, can be inserted in the passageway 20, or electrical contact can be through a conductive or semiconductive material which may be injected or poured, such as carbon- loaded plastics.
- a resistive element may be installed in the passageway 20 or in the electrical channel in the body 6. The latter is preferable for safety and to ensure equal potentials exist on interior surfaces ofthe cover components to prevent surface currents there.
- a lower-power unregulated supply can be used ifthe output loading characteristics are desirable, or a limiting resistor can be placed on a power supply circuit.
- a resistive element to each nozzle, whether these resistors are contained within the power supply or the nozzle. This prevents one shorted nozzle in the set from reducing the charging voltage at other nozzles operating from the same power source.
- the methods described in this invention to establish and maintain low surface leakage and a high resistance between the nozzle power supply output and earth allow the use of a proper current limiting resistor without sacrificing a significant voltage to the electrode.
- a resistor placed in the body or anywhere before the electrode 18 has the benefit of limiting current to a non-hazardous level in case contact with the electrode 18, or the contaminated nozzle surfaces is made.
- the graph shown in Figure 10 illustrates the results of a test where the electrical resistance values from the induction electrodes to ground of a conventional nozzle and a nozzle according to the present invention were monitored during a period of time while spraying water containing common agricultural chemicals.
- the spray mixture resistivities were near 28 ohm-cm for each ofthe solutions (in comparison with a typical 5,000-10,000 ohm cm value for tap water).
- the foliar fertilizer mixture also containing copper fungicide characteristically forms a thick coating on the nozzles and could not be tested with success in the conventional nozzle.
- the upper curve of Figure 10 shows the results ofthe test using a nozzle according to the present invention spraying a much heavier mixture ofthe very conductive foliar fertilizer with a substantial amount of copper fungicide added.
- the initially high system resistance to ground was maintained throughout the entire testing time span and a 1.2 megohm series resistor was successfully utilized. No electrical shock could be felt when touching the charging nozzle cover, even when it was substantially coated by the spray.
- each nozzle had a liquid flowrate of 120 ml/min so a spray cloud current level of 10 mA converts to a charge level of 5 mC/1. It has been determined previously that a desirable level of charging for a two-fold deposition benefit versus uncharged spray is in the range of 3 mC/1 or greater.
- the prior art nozzle charged water spray having an electrical resistivity value of 6500 ohm cm, to a level of 5.5 mC/1.
- the nozzle was irreversibly damaged: first the atomization channel became deformed (altering the atomization and intemal charging field geometry), and in under two hours the dielectric liquid-orifice tip was pitted to a severe degree and the nozzle would no longer charge the spray over 0.8 mC/1. Before the gross failure ofthe tip, usually the current requirement for the prior art nozzle was over 40-fold greater than the current required to operate the nozzle according to the present invention, while the charging level achieved with the present invention was over 3-fold higher than the conventional nozzle. Thus, the present invention provides a 120-fold greater spray current output per unit of nozzle current input the does the conventional nozzle.
Landscapes
- Electrostatic Spraying Apparatus (AREA)
- Catching Or Destruction (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
- Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)
Abstract
Description
Claims
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US506725 | 1983-06-22 | ||
US08/506,725 US5765761A (en) | 1995-07-26 | 1995-07-26 | Electrostatic-induction spray-charging nozzle system |
US08/620,088 US5704554A (en) | 1996-03-21 | 1996-03-21 | Electrostatic spray nozzles for abrasive and conductive liquids in harsh environments |
US620088 | 1996-03-21 | ||
PCT/US1996/012175 WO1997004876A1 (en) | 1995-07-26 | 1996-07-25 | Electrostatic nozzles for abrasive and conductive liquids |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0837735A1 true EP0837735A1 (en) | 1998-04-29 |
EP0837735A4 EP0837735A4 (en) | 2000-11-22 |
EP0837735B1 EP0837735B1 (en) | 2004-02-25 |
Family
ID=27055557
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96926121A Expired - Lifetime EP0837735B1 (en) | 1995-07-26 | 1996-07-25 | Electrostatic nozzles for abrasive and conductive liquids |
Country Status (10)
Country | Link |
---|---|
EP (1) | EP0837735B1 (en) |
JP (1) | JP3256547B2 (en) |
KR (1) | KR100437543B1 (en) |
AU (1) | AU711608B2 (en) |
CA (1) | CA2226502C (en) |
DE (1) | DE69631660T2 (en) |
DK (1) | DK0837735T3 (en) |
ES (1) | ES2216052T3 (en) |
IL (1) | IL122702A0 (en) |
WO (1) | WO1997004876A1 (en) |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3765538B2 (en) * | 2002-07-17 | 2006-04-12 | 株式会社内山産業 | Electrostatic spraying equipment |
KR100475879B1 (en) | 2002-11-11 | 2005-03-11 | 한국전자통신연구원 | An internet phone terminal for wire and wireless communication |
JP4668869B2 (en) * | 2006-08-24 | 2011-04-13 | 旭サナック株式会社 | Spray gun for electrostatic painting |
KR101143315B1 (en) * | 2009-06-12 | 2012-05-09 | 주식회사 아모그린텍 | Spray Nozzle for Electrospinning And Electrospinning Apparatus Therewith |
KR101060224B1 (en) * | 2009-06-12 | 2011-08-29 | 주식회사 아모그린텍 | Spray nozzle for electrospinning and electrospinning apparatus using the same |
PE20121059A1 (en) * | 2010-10-07 | 2012-08-09 | Alamos Vasquez Adolfo | HIGH FLOW RATE ELECTROSTATIC NEBULIZER, CAPABLE OF PRINTING A HIGH ELECTROSTATIC CHARGE ON THE NOZZLE TO THE DROP TO NEBULIZE, OF GREAT SIMPLE CONSTRUCTION |
DE102011050154A1 (en) | 2011-05-06 | 2012-11-08 | Sanovia Ag | Method for changing structure of minerals, particularly for micronizing in device with rotors, involves electrostatically charging mineral grains, where mineral is exposed to dynamic impact or friction process in housing between baffles |
DE102011054293A1 (en) | 2011-10-07 | 2013-04-11 | Sanoviva Ag | Method for producing an agent |
JP5973219B2 (en) * | 2012-04-26 | 2016-08-23 | 鹿島建設株式会社 | Charged water particle sprayer |
JP5918616B2 (en) * | 2012-04-26 | 2016-05-18 | 鹿島建設株式会社 | Dust removal system for sealed waste disposal sites |
WO2014164899A1 (en) * | 2013-03-11 | 2014-10-09 | Finishing Brands Holdings Inc. | System and method of producing a coating with an electrostatic spray |
PL3046676T3 (en) * | 2013-09-20 | 2019-02-28 | Spraying Systems Co. | Electrostatic spray nozzle assembly |
JP2016172248A (en) * | 2016-02-22 | 2016-09-29 | 鹿島建設株式会社 | Dust removal system for closed type waste disposal site |
CN105903587B (en) * | 2016-06-22 | 2018-02-27 | 江苏大学 | A kind of auxiliary formula swirling flow atomizing electrostatic gun of gas |
CN108115471A (en) * | 2017-12-25 | 2018-06-05 | 哈工大机器人(合肥)国际创新研究院 | A kind of Handheld plasma burnishing device |
CN108499763A (en) * | 2018-06-12 | 2018-09-07 | 静快省(苏州)智能科技有限公司 | Static nozzle |
EP4268971A1 (en) * | 2022-04-25 | 2023-11-01 | Wagner International Ag | Angle adapter for a powder spray device |
KR102577277B1 (en) * | 2022-09-15 | 2023-09-12 | (주)나노젯코리아 | Dispenser with function of detecting nozzle damage |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5044564A (en) * | 1989-11-21 | 1991-09-03 | Sickles James E | Electrostatic spray gun |
US5409162A (en) * | 1993-08-09 | 1995-04-25 | Sickles; James E. | Induction spray charging apparatus |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4009829A (en) * | 1975-02-11 | 1977-03-01 | Ppg Industries, Inc. | Electrostatic spray coating apparatus |
US4004733A (en) | 1975-07-09 | 1977-01-25 | Research Corporation | Electrostatic spray nozzle system |
US4106697A (en) * | 1976-08-30 | 1978-08-15 | Ppg Industries, Inc. | Spraying device with gas shroud and electrostatic charging means having a porous electrode |
-
1996
- 1996-07-25 EP EP96926121A patent/EP0837735B1/en not_active Expired - Lifetime
- 1996-07-25 ES ES96926121T patent/ES2216052T3/en not_active Expired - Lifetime
- 1996-07-25 JP JP50771097A patent/JP3256547B2/en not_active Expired - Fee Related
- 1996-07-25 DK DK96926121T patent/DK0837735T3/en active
- 1996-07-25 IL IL12270296A patent/IL122702A0/en unknown
- 1996-07-25 WO PCT/US1996/012175 patent/WO1997004876A1/en active IP Right Grant
- 1996-07-25 KR KR10-1998-0700607A patent/KR100437543B1/en not_active IP Right Cessation
- 1996-07-25 AU AU66371/96A patent/AU711608B2/en not_active Ceased
- 1996-07-25 CA CA002226502A patent/CA2226502C/en not_active Expired - Fee Related
- 1996-07-25 DE DE69631660T patent/DE69631660T2/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5044564A (en) * | 1989-11-21 | 1991-09-03 | Sickles James E | Electrostatic spray gun |
US5409162A (en) * | 1993-08-09 | 1995-04-25 | Sickles; James E. | Induction spray charging apparatus |
Non-Patent Citations (1)
Title |
---|
See also references of WO9704876A1 * |
Also Published As
Publication number | Publication date |
---|---|
ES2216052T3 (en) | 2004-10-16 |
DE69631660D1 (en) | 2004-04-01 |
CA2226502A1 (en) | 1997-02-13 |
EP0837735B1 (en) | 2004-02-25 |
IL122702A0 (en) | 1998-08-16 |
JPH11501253A (en) | 1999-02-02 |
DK0837735T3 (en) | 2004-06-21 |
CA2226502C (en) | 2009-09-01 |
KR19990035946A (en) | 1999-05-25 |
EP0837735A4 (en) | 2000-11-22 |
WO1997004876A1 (en) | 1997-02-13 |
AU6637196A (en) | 1997-02-26 |
DE69631660T2 (en) | 2004-12-23 |
KR100437543B1 (en) | 2004-08-25 |
AU711608B2 (en) | 1999-10-14 |
JP3256547B2 (en) | 2002-02-12 |
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