US 3687368 A
An electrogasdynamically powered electrostatic spray gun is provided which discharges a liquid stream toward an object to be coated therewith. A first seeded air stream is selectively discharged from the spray gun to effect atomization of the fluid stream into a circular pattern and a second seeded air stream is selectively discharged from the spray gun to modify the shape of the atomized stream. The first and second seeded air streams are fed to their respective discharging zones through separate conduits which are supplied from a single feed. The shaping stream of seeded air can be reduced and the portion of the seeded air stream which would normally flow therethrough is redirected to bypass same whereby an undesirably high back pressure at the outlet of the electrogasdynamic generator will be avoided.
Claims available in
Description (OCR text may contain errors)
United States Patent Geberth, Jr. Aug. 29, 1972  VALVE UNIT FOR AIR TYPE ELECTROSTATIC SPRAY GUN Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Reinhold W. Thieme 2 I [7 mentor s ii f N fl. Geberth Jr west Pater Attorney-Robert E. Isner and Peter J. Franco  ABSTRACT Assignee: Electrogasdynamics, Inc., Hanover,
An electrogasdynamically powered electrostatic spray Filed: April 19, 1971 gun is provided which discharges a liquid stream 21 A 135 159 toward object to be coated therewith. A first seeded air stream is selectively discharged from the spray gun to effect atomization of the fluid stream into  US. Cl. ..239/I5, 239/297, 239/300, a circular pattern and a Second Seeded air Stream is Int Cl selectively discharged from the spray gun to modify o e u of st d Second  new of Search "239/ 15 seeded air streams are fed to their respective discharg- 239/415 ing zones through separate conduits which are supplied from a single feed. The shaping stream of seeded  References C'ted air can be reduced and the portion of the seeded air UNITED STATES PATENTS stream which would normally flow therethrough is redirected to bypass same whereby an undesirably 2,827,330 3/ 1958 Baur ..239/415 high back pressure at the outlet f the l 2,829,006 4/1958 Johansson ..239/415 X trogasdynamic generator will be avoided 3 ,232,540 2/1966 Cassanmagnago ..239/4 1 6 3,339,841 9/1967 Beach, Jr ..239/l5 4 Claims, 6 Drawing figures -I76 I42 I35 I38 I I30 I00 i 112 146 I44 I74 "5 108 12 2 49 131132 32 I 93 88 28 1 I22 I40 I J V, I04 46 -9O 6O 64 62 74 75 82 I72 78 58 Patented Aug. 29, 1972 3 Sheets-Sheet 1 4 Q Q 0 4 4 0 0% o Q 0 2 .w a 0 o H...
mm ........-.M...m m f mm INVENTOR JOHN D; GEBERTH, JR. BY p ATTORNEY Patented Aug. 29, 1912 3 Sheets-Sheet 2 6m 9w mm mm om on mm vw mm E wk mm .3 mm WW 8 om mm v2 www 1 mm mm mm vm N9 09 u I an NE w M (I mm mm x mm mm v l 09 mm 2 on Q2 mm mm mm QQ Wm @T vm N GE ATTORNEY Patented Aug. 29, 1972 I I 3,687,368
3 Sheets-Sheet 3 I Cy fliwy/gq/ INVEN JOHN D. GEBER JR.
ATTORNEY VALVE UNIT FOR AIR TYPE ELECTROSTATIC SPRAY GUN This invention relates to electrogasdynamically powered electrostatic spraying apparatus employing a common air stream as an atornizing medium liquid coating material and for high voltage power generation.
Conventional electrogasdynamically powered electrostatic spray guns such as described in copending application Ser. No. 788,148, filed on Dec. 31, 1968 are adapted to deliver a single stream of seeded air emanating from a self contained electrogasdynamic power generator to a dividing conduit which separately feeds the atornizing air stream conduit and the fan or shaping air stream conduit. To vary the shape of the atomized spray the amount of the seeded air stream fed to the fan air stream apertures can be reduced with a concomitant increase in the amount of the seeded air stream fed to the atornizing air stream apertures. Since the total area of these atornizing apertures is constant the closing of the fan valve results in a large change in the pressure level at the atornizing apertures and hence at the exit of the electrogasdynamic high voltage generator. This increase in the back pressure at the generator can slow down the gas flow and result in a partial or total loss of generator power.
The present invention may be briefly described as an improved construction for self contained electrogasdynamically powered electrostatic spraying devices in which a wide variation in the flow of seeded air through the spray shaping orifices can be effected while maintaining the back pressure at the outlet of the electrogasdynamic power generator within such limits as to maintain efiicient operation thereof. In its broad aspects the subject invention includes a valve mechanism for automatically inversely varying the flow of seeded air emanating from the electrogasdynamic power generator through a spray shaping orifice and a vent to atmosphere to prevent the pressure at the outlet end of the generator from increasing to a magnitude that would materially decrease the electrical output of the generator while selectively varying the amount of seeded air emitted through the shaping orifice.
In its narrower aspects the subject invention introduces a first channel or conduit for directing a portion of the seeded air emanating from the outlet of the electrogasdynamic power generator to a locus of atomization for effecting emission of an atomized spray of the liquid coating material, a second channel or conduit for directing a second portion of the air emanating from the outlet of the generator to a shaping orifice positioned adjacent to the locus of atomization, a third conduit or channel connected to said second conduit for venting a portion of the air emanating from the generator to the atmosphere at a location remote from the locus of atomization and a valve member interposed at the junction of the second and third conduit means for varying the effective cross-sectional flow area of the third conduit means in inverse complemental relation with selected variations introduced into the effective cross-sectional flow area of the second conduit for controlling the amount of shaping air emitted from the shaping orifices so as to prevent the pressure at the outlet end of the electrogasdynamic generator from increasing to a magnitude that would materially decrease the electrical output thereof while effecting such variations in the emission of the spray shaping air.
Among the advantages of the present invention is the provision of a self contained electrogasdynamically powered electrostatic spraying device in which the back pressure at the outlet of the electrogasdynamic power generator will be maintained within allowable limits for efiicient operation independent of the shape of the emitted atomized spray.
Other objects and advantages of the present invention will become apparent from the following portions of this specification and from the accompanying drawings which illustrate, in accord with the mandate of the patent statutes a presently preferred embodiment incorporating the principles of the invention.
Referring to the drawings:
FIG. 1 is a schematic representation of the components of an electrostatic paint spray system.
FIG. 2 is vertical section through a self contained electrogasdynamically powered electrostatic air atornizing spray gun constructed in accordance with the teachings of the present invention.
FIG. 3 is a section taken at the lines 3-3 of FIG. 2.
FIG. 4 is a section view of an earlier used spray shaping valve assembly similar to that of FIG. 5.
FIG. 5 is a section taken at the line 55 of FIG. 3 with the fan valve in open position.
FIG. 6 is a view similar to that of FIG. 5 with the fan valve in closed position.
Referring to the drawings and particularly to FIG. 1, a hand-manipulable type of air atornizing electrostatic paint spraying system is provided. The system has a compressed air supply hose 10 connectable to a remote source of compressed air (not shown) suitably of a pressure of about 30 psig or greater and capable of supplying the requisite flow rates. The compressed air conjointly supplies pressure through a T-type fitting 12 and associated regulator and gauge assembly 14 to a paint supply pot l6 and supplies the necessary air alternately utilizable for atomization and electric power generation through line 18 to a vapor seed pot assembly 26. The line 18 may have an independent regulator and gauge assembly 20 to provide discrete and independent operational control over the pressure and flow rate of the air conveyed to the air atornizing paint spraying device 28 which may be a hand manipulable air atomized spray gun, as hereinafter described. The paint supply pot 16 is supported on an insulating stand 22 and fluid paint is conveyed therefrom to the insulated barrel portion of the spray gun 28 through an insulated paint supply hose 24 so as to insure when conducting paints are being utilized, against possible shorting of the voltage carrying spray gun components to ground through the above described components of the paint supply system.
Air and small quantities of seed material in the form of a vapor here suitably an inexpensive and conventionally employed paint solvent, is introduced into the vapor seed pot assembly 26. Upon exiting from the vapor seed pot assembly the seeded atornizing air passes through the single supply hose 30 to the air atornizing spray device 28 for utilization therein for the conjoint purposes of effecting atomization of the liquid coating material, shaping of the spray of atomized material and generating the electric power for eflecting electrostatic deposition of the atomized liquid. Excitation voltage for the self contained electrogasdynamic power generator is provided through lead 40 by power supply 38.
The workpiece or object 42 to be coated is suspended from a grounded support assembly 44 which may include a conveyor device or the like to sequentially present successive articles to be coated in predetermined spaced relation with the path of the emitted spray 46 from the spray device 28.
The hand manipulable spray gun has an insulating barrel portion 34 with a conducting pistol grip type handle portion 32 mounted at one end and an atomizing nozzle-charging electrode assembly, generally designated 36, disposed at the other end.
The constructional details of an electrostatic air atomizing type of spray gun that incorporates the principles of this invention and constitutes a presently preferred embodiment thereof are illustrated in FIG. 2. Included therewithin is a fluid paint delivery system 46 located in the lower portion of the barrel, a seeded atomizing air conveying system extending through the handle and barrel portions, an electrogasdynamic power generator 50 operably responsive to the flow of seeded atomizing air therethrough together with provision for introducing the necessary excitation voltages thereto through the handle member 32; and an atomizing nozzle and charging electrode assembly, generally designated 36, mounted at the terminal end of the barrel 34 wherein atomization of the fluid paint by the direct interaction with the seeded atomizing air and charging of the atomized spray particles is effected.
The seeded atomizing air and the electrogasdynamic power generator excitation voltages are conjointly supplied to the gun via a composite conduit and specialized entry fitting and connector assembly generally designated 56 that is removably insertable through an aperture in the base of the handle 32 into a bore 58 longitudinally disposed therein. Disposed within the upper reaches of the bore 58 is an elongated insulating sleeve 60 surrounding a spring biased electrical contact receptacle type assembly having a displaceable contact member 62 connected to one end of an internally disposed insulated excitation voltage lead 66 that leads to the electrogasdynamic voltage generator 50. Biasing of the contact member 62 is effected by the spring member 64 having its remote end fixedly positioned by the insulating plug 65. The connector assembly 56 has a selectively shaped elongated sleeve assembly 68 incorporating a plurality of atomizing air escape apertures 70 adjacent its midlength and upwardly terminating in a guide portion 72 sized and shaped to co-axially position the extending end portion 74 of the insulated electrogasdynamic power generator excitation lead 40. The end portion 74 of the lead 40 is encased in a rigid insulating sleeve 75 that is sized to be removably contained within the sleeve 60 and dependently terminating in an electrical contact element 76 that is adapted to be disposed in firm electrical contact with the spring biased contact member 62 when the connector assembly 56 is properly located within the boer 58. Suitable O-ring seals 78 and 80 are disposed in the walls of the sleeve member 68 on either side of the seeded atomizing air escape apertures 70 for disposition in sealing relation with the walls of the bore 58 to prevent leakage of the compressed seeded atomizing air therepast and to direct such seeded atomizing air therepast and to direct such seeded atomizing air through aperture 84 into bore 90. Insertion of the connector 56 into the bore 58 serves to automatically effeet proper interconnection of the gun to both the requisite supply of seeded atomizing air and to the requisite source of excitation voltage for the electrogasdynamic power generator. The desired proper positioning of the connector within the bore is maintained by the set screw 82.
The seeded atomizing air escape apertures are disposed in gaseous communication through the aperture 84 with an elongated bore that longitudinally traverses the handle portion 32 and is adapted to be closed at its dependent end by a threaded plug member 92. The upper end of the seeded atomizing air transmitting bore is designed to be in fluid communication with a transverse bore 94, adapted to contain a valve assembly responsive to manual actuation of a trigger member 96 to control the admission of seeded atomizing air into the electrogasdynamic power generator and its ultimate transmission to the locus of atomization. Suitably included in the valve assembly is a valve body member 98 having a base portion fixedly mounted in the open end of the bore 94 and an extension 106 shaped to provide an annular seat 104 and a plurality of apertures 110 disposed adjacent thereto in gaseous communication with the bore 112. Associated therewith is displaceable valve plug member 100 that is normally biased, as by the spring 102, into sealed relation with the valve seat. Displacement of the valve plug member 100 is effected by the push rod 108 that extends through the valve body member and associated plug and packing 88 and is longitudinally displaceable in response to rotative displacement of the trigger 96. Thus, rotative displacement of the trigger 96 in the clockwise direction as illustrated in FIG. 2 effects a rearward displacement of the push rod 108 against the action of the biasing spring 102 and valve plug 100 out of sealing engagement with the seat 104. Such lifting of the plug 100 off of the seat 104 permits a flow of seeded atomizing air from the bore 90 through the apertures and into the bore 112. The bore 112 is disposed in gaseous communication with the entry portion 114 of the electrogasdynamic power generator 50 and thus serves to effect the introduction of seeded atomizing air therein.
The liquid coating material is introduced into the gun from the paint supply-line 24 through a suitable fitting 122 disposed on the underside of the barrel portion 34. The fitting 122 is in fluid communication with a short bore 126 which in turn communicates with an elongated bore 128 running longitudinally of the barrel 34. Mounted at one end of the bore 128 is a fluid tip nozzle member 130 having a conically shaped end portion terminating in a short cylindrical section that defines a liquid paint emitting aperture. As best shown in FIG. 2 the fluid tip nozzle member is formed of electrically conducting material and includes an extending flange portion 131 disposed in abutting engagement with the front end 163 of the barrel member 34. Disposed in coaxial alignment with the liquid paint emitting aperture defined by the cylindrical section 120 and adapted to control the effective cross-sectional area thereof is a displaceable needle valve member 132. The needle valve member 132 is mounted at one end of an elongated fluid flow control shaft member 134 having a bellows type sealing assembly 136 disposed in encircling relation about the portion thereof disposed within the front or forward section of the bore 128 to limit the disposition of liquid paint under pressure to the front section of the bore 128. The fluid flow control shaft 134 extends rearwardly through a reduced intermediate section 144 of the bore 128, and into a rear enlarged section 146 thereof. The rear end of the fluid flow control shaft 134 is supported in an insulated coupling member 138 sized to be closely contained within the bore 146. The coupling member 138 is in turn connected to a shaft 135 included as a part of a spring biased and trigger displaceable actuating assembly. Such assembly includes a sleeve type adjusting stop screw 142 disposed about a biasing spring 148 for limiting the degree of displacement of shaft 135 and for controlling the amount of biasing force applied by such spring to the shaft 135 to maintain the fluid flow needle member 132 in sealing engagement with the fluid emitting aperture in the fluid tip nozzle member 130. In operation of the above described structure, displacement of the trigger 96 in a clockwise direction effects a rearward displacement of the shaft 135, coupling member 138 and fluid flow control shaft 134 against the opposition of the biasing spring 148. Such retraction of the shaft 134 removes the needle valve member 132 from sealing relation within the fluid emitting aperture to permit the emission of a stream of liquid paint therefrom.
The upper portion of the insulating barrel 34 contains a relatively large elongated bore 156 which is adapted to removably receive an electrogasdynamic power generator assembly, generally designated 50, in which the electric power necessary to charge the atomized paint spray particles and to create the electrostatic depositing field is derived from the direct con version of the kinetic energy of the moving stream of seeded atomizing air. The seeded atomizing air under pressure is introduced, in response to actuation of the trigger 96, through the bore 112 into an annularly shaped entry section 114 of the electrogasdynamic power generator which entry section is of relatively large cross-sectional area so as to produce a relatively low flow velocity and minimal pressure drop therewithin. Disposed within the entry section 114 is the extending portion of an insulated mounting sleeve assembly 190 which serves to coaxially position an elongated ionizer needle electrode 124 relative to a surrounding coverging transition section 192 and an annular attractor electrode 194. Such sleeve assembly 190 also serves to provide a receiving support for the end of the excitation supply voltage lead 66 which, in the illustrated embodiment, is connected to the said ionizer needle electrode 124. The ionizer electrode needle 124 extends axially downstream within the transition section 192 to the attractor electrode ring 194 which transition section operatively effects a marked decrease in the cross-sectional flow area for the moving seeded atomizing air stream. After passage through the attractor ring electrode 194, the atomizing air stream passes through an elongated channel 158 of relatively small, and preferably slightly increasing in the direction of flow, cross-sectional area suitably sized so that, within which and under the pressure conditions extant, the flow velocity of the seeded atomizing air will be markedly higher than that extant in the entry section 114 and which, for good performance, should preferably be in the vicinity of the sonic velocity. After exiting from the channel 158 the seeded atomizing air stream impinges against the adjacent axially disposed -collector needle electrode 198 mounted in a plug 196 and expands into the bore 156 and flows therewithin at reduced velocities toward the exit conduit 160 therefrom. The collector electrode 198 is directly connected, by a conducting metallic lead 200, to the fluid tip nozzle member which latter serves as the charging electrode.
As best shown in FIGS. 2 and 3 the outlet end of the generator is connected through exit conduit in gaseous communication with a discrete atomizing air transfer conduit 162 and a discrete fan air transfer conduit 164 running longitudinally of the barrel portion 34. The atomizing air transfer conduit 162 terminates at the forward end 163 of the barrel. The terminal end of the air transfer conduit 164 is plugged so as to direct shaping air into air transfer conduit 165. Air transfer conduit 165 terminates in the annular cavity 140 at the barrel end and shaping air exits therefrom via the conduit 174. The atomizing air and fan air conduits 162 and 164 and 165 respectively are selectively sized so as to permit delivery of the seeded atomizing air at the rates requisite to efiect desired atomization under the range of ambient pressures available within the gun.
In the early construction, as shown in FIG. 4, a screw type plug member 166 is associated with the exit conduit 160. The plug has member 166 is effectively longitudinally displaceable in response to rotative displacement thereof into selective overlying or closing relation with the end of the fan air transfer conduit 164 to thereby permit manual control of the amount of the seeded atomizing air stream diverted into the fan air transfer conduit 164. In such construction the atomizing air transfer conduit 162 and the fan air transfer conduit 164 terminated at spaced locations at the front end of the barrel portion 34 of the gun radially outward of the flange portion 131 of the fluid tip nozzle member 130. Disposed in overlying relation therewith and removably secured in desired position by a threaded retaining ring 172 is a selectively configured air cap member formed of insulating material. The air cap 170 is shaped to provide a first set of internal conduits, generally designated 174, disposed in fluid communication with the end of the fan air transfer conduit 164, 165 at the end 163 of the barrel portion of the gun and having the other ends thereof selectively terminating at one or more predesired locations downstream of the fluid tip nozzle member 1311 and with a positional location and angular disposition that serves to selectively direct the emission of jets of fan air to modify the shape of the spray of atomized material. In addition thereto the surface of the air cap 170 disposed in abutting facing relation with the end portion 163 of the barrel is contoured to provide for the transfer of atomizing air emanating from the transfer conduit 162 to one or more apertures 177 disposed in surrounding relation to the extending cylindrical section of the fluid tip nozzle 130 to effect, by direct inter-action, atomization of the liquid paint stream being emitted therefrom.
To control the shape of the fan spray the threadedly mounted fan valve 166 was rotated causing successive closing of the fan air transfer conduit 164 thus controlling the amount of seeded air leaving the gun through the fan orifices 174. While this early type of conventional screw type plug member illustrated in FIG. 4 provided a control over spray shape, its operation detrimentally caused unacceptable variations in the back pressure on the electrogasdynamic power generator. In particular, it was found that the closing of the fan valve 166 and blocking of flow through conduit 164 often resulted in a marked increase in the pressure level at the exit of the generating channel of such magnitude as to materially decrease the electrical output of the generator.
In accordance with the principles of this invention, high performance of the spray gun over a wide range of operating conditions can be obtained by the utilization of a fan valve construction whown in FIGS. 3, 5 and 6. Here the fan valve knob 201 is threadedly engaged with and fixed in position on a shaft 202 which is threadedly engaged with a valve retainer nut 204. The valve retainer nut 204 is threadedly engaged with a mounting boss 206 located on the side of the barrel member 34. The end portion 208 of the valve shaft 202 slidingly engages a continuous bore defined by the valve retainer nut bore 210 and the barrel member bore 212 and is sealed by an O-ring 214 which prevents air leakage from the fan valve. A blind axial bore 216 is established in this end'portion 208 of the valve shaft 202. One end of this bore 216 terminates at the end of the shaft and there communicates with the barrel member bore 212. The other end of the axial bore 216 communicates with a transverse diametral bore 218 which extends completely across the shaft 202. The valve retainer nut includes an annular recess 220 which communicates through one or more bores 222, 224 which extend parallel to the axis of the valve shaft with the atmosphere.
In the fan valve open position illustrated in FIG. 5 the atomizing air transfer conduit 162 and fan air transfer conduit 164,165 communicate with their respective discharge orifices and accordingly seeded atomizing air can be passed, without restriction therethrough atomizing and shaping the liquid stream. Valve sleeve 226 blocks the valve shaft transverse bore 218 preventing the venting of the seeded air stream to the atmosphere. In this valve open position the fan valve operates identically to the conventional fan valve illustrated in FIG. 4.
When the fan valve is in the closed position illustrated in FIG. 6, fan air transfer conduit 164 is blocked by the fan shaft 208 whereby no seeded air will be discharged from the spray gun to shape the atomized stream of liquid. In this position a venting conduit defined by axial bore 216, transverse bore 218, annular recess 220 and axially extending retainer nut bores 222, 224 is established through which a portion of the seeded air stream which is prevented from being discharged through the shaping orifices is vented to the atmosphere thus preventing the undesirable increase in back pressure. The location of the annular recess 206 is selectively chosen so that with the commencement of the restricting of the fan air transfer conduit 164 the venting conduit becomes partially open to vent a small portion of the seeded air stream and so that as the fan air transfer conduit is more and more restricted a larger and larger venting passageway will be established to handle the increasing amount of air being blocked by the fan valve and otherwise being redirected to the air atomizing transfer conduit 162.
The fan valve of the present invention prevents the generator back pressure from rising to such value as would detrimentally effect generator operation as the shape of the atomizing spray is changed. v
In operation of the described unit application of excitation voltage, suitably in the order of 5,000 volts, to the ionizer needle electrode 124 will initiate a corona discharge condition and cause a corona current to flow in the gap between the point of the ionizer needle elec trode 124 and the adjacent ring electrode 194. Concurrently therewith, the seeded atomizing air moving through the gun in the path described above will travel from the bore 112 and entry section 114 into the converging inlet or transition section 192 and the attractor electrode ring 194 and through the corona discharge area with progressively increasing velocity. Under corona discharge conditions as described above, the passage of the seeded atomizing air therepast at progressively increasing speeds will result in condensation of at least a portion of the seed vapor therein in the form of extremely small particles or droplets around the unipolar ions present in the corona discharge area. The ions in the region where the seed material condenses are thereby degraded in mobility, become fixed or nearly so in the stream of moving atomizing air and are swept out of the corona discharge area, past the attractor ring electrode 194 and down the elongated insulating channel 158 at high velocity, as for example at speeds in the vicinity of the sonic velocity. The ions in the moving gas stream will then be collected at the collector electrode 198 and will raise the potential thereof to extremely high values, with such potential being applied by the conductor 200 to the fluid tip nozzle member 130.
As will now be apparent, in operation of the described device, clockwise displacement of the trigger 96 will cojointly efi'ect emission of liquid paint through the aperture defined by the cylindrical nozzle portion of the fluid tip nozzle member and a flow of seeded atomizing air through the bore 90, the electrogasdynamic power generator 50, the atomizing air and fan air transfer conduits 162 and 164 respectively and through the various conduits of the air cap to effect atomization of the emitted liquid paint and to selectively shape the spray patterns of the atomized fluid. As noted above, the passage of the stream of seeded atomizing air through the electrogasdynamic power generator 50 results in the generation of high d.c. voltages at the collector electrode 198 and in the direct application thereof, through conductor 200, to the fluid tip nozzle member 130, which thereby performs the dual function of serving as the charging electrode for the electrostatic deposition system. Under such conditions the fluid tip nozzle member 130, which charged in the manner described, will also serve as one terminus of an electrostatic depositing field with the other terminus thereof being constituted by the grounded object to be coated.
While the invention has been described in conjunction with an air atomizing electrogasdynamically powered electrostatic liquid spray coating device, it may be utilized in other types of spray coating devices in which it may be desired to efiect variation in the distribution of the air emanating from the generator.
Having thus described my invention, I claim:
1. In an electrogasdynamically powered electrostatic spray device,
first conduit means for directing at least a portion of seeded air emanating from the outlet end of an electrogasdynamic power generator to a first location remote therefrom,
second conduit means for directing another portion of the seeded air emanating from the outlet end of said generator to a second location remote therefrom,
valve means for automatically inversely controlling the ratio of the flows of seeded air through said first and second conduit means while preventing the back pressure at the outlet end of said generator from increasing to a magnitude that would materially decrease the electrical output of said generator.
2. In an air atomizing electrogasdynamically powered electrostatic spray coating device operationally responsive to at least a portion of vapor seeded air emanating from the outlet end of a self-contained electrogasdynamic power generator,
first air emitting aperture means for effecting atomization of a stream of liquid coating material into an atomized spray,
second air emitting aperture means for controlling the shape of said atomized spray,
third aperture means disposed remote from the locus of atomization,
and valve means for automatically inversely varying the flow of seeded air emanating from said generator through said third and said second aperture means to prevent the pressure at the outlet end of said generator from increasing to a magnitude that would materially decrease the electrical output of said generator while varying the amount of seeded air emitted through said second aperture means. 3. In an air atomizing electrogasdynarnically powered electrostatic spray coating device wherein seeded air emanating from the outlet end of a self-contained electrogasdynamic power generator is employed for atomizing coating fluid into a spray thereof and for shaping said atomized spray,
first conduit means of fixed cross-sectional flow area for directing a portion of said seeded air from the outlet end of said generator to a locus of atomization,
second conduit means for directing a second portion of said seeded air from the outlet end of said generator to a shaping orifice positioned adjacent to said locus of atomization,
third conduit means connected to said second conduit means for venting a portion of the air emanating from said generator to the atmosphere at at location remote from said locus of atomization,
and selectively positionable valve means interposed at the junction of said second and third conduit means for varying the efiective cross-sectional flow area of said third conduit means in inverse complemental relation with selected variations introducable in the efiective cross-sectional flow areas of said second conduit for controlling the amount of shaping air emitted from said shaping orifice whereby the back pressure at the outlet end of said generator is prevented from increasing to a magnitude that would materially decrease the electrical output of said generator.
4. The device as set forth in claim 3 wherein said value means com rises means defining an elongated cylindrical bore having