US2858798A - Electrostatic coating apparatus utilizing both direct current and alternating current to supply current to successive discs - Google Patents

Description

Nov. 4, 1958 J. J. SEDLACSIK I 2,853,798

ELECTROSTATIC COATINGAPPAP-ATUS UTILIZING BOTH DIRECT CURRENT AND ALTERNATING CURRENT T0 SUPPLY CURRENT TO SUCCESSIVE DISCS 2 Sheets-Sheet 1 Filed Feb. .6. 1957 INVENTOR. v

2,858,798 UTILIZING BOTH RENT TO 2 Sheets-Sheet 2 J. J.'SEDLACSIK ELECTROSTATIC COATING APPARATUS Nov. 4, 1958 DIRECT CURRENT AND ALTERNATING CUR SUPPLY CURRENT TO SUCCESSIVE DISCS Filed Feb; 6, 1957 United States PatentiO 1"? NATING. CURRENT T0,;v TO

ING BOTH DIRECT CURRENT :ALTE'R- SUCCESSIVE DISCS JOhn' J. sedlac sikgGarfielm'N J. {Application February ,6, 1957 Serial No.- 638,568 10' Claims. c1.- 11 s :=62-1' "Thisinve'ntion relates to new'and;u'seful improvements inthe electrostatic deposition "or a fluent material such .as a coating liquidupon an article to.be coated.

More particularly,ifrelates to an improvedgmethodof and structure for dispersing a coating "liquid into a5 fine spray at, a' relatively. low kineticenergy" discharge in a highly ionized state and 'charged to' a high potential of a polarity opposed to, that of the-articletobecoated; byv such -means," an electrostatic" field-betweenthe"discharge:elec- -trode; 01""SPI'EIY6I" head," and' *the' article" to be" coated, is formed.

In electrostatic spraying, it is essentialth'at thegcoating liquid be a dielectric substance (i. e., non-coirductiye-= to fiuid must be so treated that each moleculeis subjected to 'an' eq-ual'char-ge' of high='intensity.

The desider-atum is "that the coatingfluid is so atomized that, "when leaving '1 the discharge electrodeyaiid because of the'mutu'al repulsion -fof 'the" molecules, jtheqliqiiid bursts' into a barely visible'mist. Inflthi's mannergtthe liquid "loses inertia iof its own" and is'free'to' be' attracte tothe oppositely charged article'tobe coated.

. around to the rear of they article being coated.

"However, it is ditficult to maintair'rideal operating conditions. If it was possibleQtodischarge alburst'of ionized liquid in sufficient quantity to ,coverthe .whfole surface of .an article in a fraction of a second, withoutany external force other than electrostatic.attraction,.ther[ theyvvhole time delay permits leakagevto neutralize theelectnostatic' charge on the. deposited surface and. attracts..more;of the surface could be uniformly covered, irrespective, shape. In actual practice, however,fthe sourc ionized liquid supply is at a remote p'oint fromfthe' article to be coated, and the rate. of .the supplyjs'limitd sothat it takes'timev to cover a,giv en area with a coatipg. This coating material tothe'farea, nearest to'thef dischargefelec- -trode.

. external force, either by an air spray gun oriby centrifugal "To reduce .this eifect, it is a"general practice. to use an I force to expel 'or' project :the coatinggmatrial towatd the article to..be coated atan:optimiimwateisufiicient td ioniZflblllZ not at an excess rate sufficientto'cause sputtering. One object hereof 'iSjtO: approach 'the idealjbynreating the coatingmaterial preparatory tdits"being-ionizedand "discharged in such'a manner that-it is=preconditioned-for a thorough molecular 'electrostaticcharge' at a' felatively 1 high rate of expulsion without-resortingto-"any mechanical force to "direct the' ionized liquid -toward the'- artiele or target. 1

I Patented Nov. 4, 1958 "ice 2 "Another object hereof isto reducethe time required tocover the givensurface of an article, thereby reducing Fth'estatic leakage efiect and thus obtaining a more uniform 1 coating. 7 5 In'the accompanying drawing, I have illustrated a comp'leteexample of a physical embodiment of the invention .in which the parts" are combined and arranged in accordance ;with one mode which I- have devised for the. practical iapplication of*the principles of the invention. It will be 10 "understood 'however that changes and alterations are .contemplated and may be made-in these exemplifying drawingsandmechanical structures, within the scope of (the-claims,--without=departingfrom the principles of the "invention.

In the drawings: FigS.'*:.1iaI1d-'1 A arelongitudinalsectional views of the device o'f' the invention, Fig. 1A being acontinuation of Fig/' 1;

Fig. 2--is a'sectional .view on the line '2 -2 of Fig. l; Eig."'3='is--a sectional view on'the line 3-1-3. of Fig. v1A. Fig. =4 is-an enlarge'deleva-tional view, partly-in section, showing certain" features of the invention.

In the following description and claims, various details w ill' be identifiedby specific :names :for convenience.

Thesenames however .areintendedto, :be ,as ;generic in their application aszthe artwillxpermit.

- Refenring mow-totthe. drawing more in detail in vvhich similarscharacters .of reference ,indicate ;correspondi ng -partslin' the tseverahfigures ,and-referring rnore particularly ttiy thetpreferred form of myinvention selected for illusotrative npurposes, 'I have .,.-s.h,ow,n :a power transmission tih-wsingwr casing .10 withwwhirh isassosi ted a co 'zplate :12. :The. plate :12 may be ifixed to the housing 10 as by bolts 14 or the like. I

lugttll, integral ,with the; -housing nk may, he suit- :xably formedtzasflosreceive therein a setzscrew llfior the like so as to .perrnit the holding of; the housing 10 and nits;attached components vrelative to a; supporting stand in feanyoofsither conyentional manners. p a Armotor housing 16 is; associated.with the, housing 10 by any conventional means and, enclosesa motor 18 vwhich =1nay. be; fixed to. the housinglfl as by bolts,;20 or the like. An electrical connection 19 leads to the mot;or 18 through ..a= suitablezopeningin the housing. 16, from; a. source of eleceMotorsh-aft 22 driven; by ,the-motor-ls extends through .,--an-;enlarged.opening -23 in the wall of the. housingltl so at there. ;is .sufficient clearance therearound for purposes -;presently.-,to be observed.

-; Bulley24 is fixed to theouterfreevend .of rno. tor shaft 22 and imparts rotation through -a-;belt;26 to a pulley-lfi awhich is journalledona hollow stud or hub 30 fixed to 1 i one wall oftthe.housing;l0,. as. shown.

A flange 32 may be provided to secure thepulley zfi and the ,bearing associated therewith (not shown) to the stud 30. l I

.Ihe hub ofmflange 32 is provided withahub extension 34;having, a ;bore extending axially therethrough which is aligned 'coa'xially with a borelextendingaxially through ,th e, hub 30, as shown.

,lAfxfluent coating'material conduit-40 extends through .lthehaligned. bores in hubs 30 and 34 with a clearance sufii- ;cient; 'tq al'low'air to pass thereziround, as will hereinafter be made apparent.

v The rearward end of the conduit 40 extends outwardly -beyond itlie housing 10 1 and terminates in. an appropriate =-fittin'g '4'2 engageablexwith a boss 44' extending upwardly from the housingi 16- and to which conduit-is connected, i throughithdboss-M to-a similar conduit- 46,-leading from a source'iof coatinggmaterial supply (not shown), a fitting 48 connecting the conduit;46-to;the;bo ss, 44. A fitting.-S0:may befiXedtQthe hQuSi g 0 any suitable means and is provided with a transversel 9 ing V bore 52 into and through which conduit 4 xtends. The bore 52 is of sufficient diameter as to p fovlde an annular space around the conduit dispos. ed therewithin. H

At one side of member 50, bore 52 is of reduce meter, as shown, and has a sealing gland 54 ass m tted therewith and held relative thereto by a coupli g 56.

which insures against any rearward escape of air fln'IQHgh ary air led thereinto may surround the motor18 so as to aid in the cooling thereof and additionally in the pressuriz'ing thereof so as to make same explosion proof.

A hollow transmission shaft is concentrically dis.- posed around the conduit 40 and is spaced therefrom so as to provide an annular air space therebetween. Its. rearward extremity is suitably secured to the hub 34 in any convenient manner as by keying, splining, brazing, welding or the like.

The shaft 70 is made of insulating material and the spline thereof, being of metal is screwed into the hubs- 34 in the direction of rotation by the motor.

The housing cover 12 is provided with a suitable annular hub extension which is adapted to receive the rearward extremity of a hollow tube 82 and is further 4 i threadedly engageable with, and is disposed forwardly of, the sleeve member 112.

The inwardly extending flange 117 of member 116 clamps the outer race of the bearing 102 into the seat in the forward end of the sleeve 112.

The forward end of spindle is provided with an outwardly tapered bore 118 which communicates with the longitudinal bore or opening extending through the member 100. 10*.

The extreme forward end face of the spindle 100 is provided with a plurality of annularly disposed notches .120 leading from the bore 118 outwardly through the outer peripheral surface of the spindle.

An' annular ring 122 is threadedly engaged with the outer peripheral surface of spindle 100 and is provided I with a plurality of radially disposed openings 123 which provided with an annular hub extension 84, concentrically.

disposed within the hub extension 80 and adapted to receive the rearward extremity of a drive shaft sheath 86 which is concentrically disposed around the transmission shaft 70.

The conventional clamp means 88 and clamp screw 89 may be provided on the hub extension 80 so as to insure the tight fit of members 80 and 82. 4

Members 40, 70, 82 and 86 are made of a suitable insulating material so as to separate the high potential elements, shortly to be described, from ground and to prevent objectionable arc-over.

The spray head of the device of the invention will now be described. 1

A rotating spindle or member 100 is journalled by ball bearings 102 and 104 which are separated by a spacer 106 and are held relative to the spindle 100 by means of a fitting 108 which may be fixed to the rearward extremity of the spindle 100'as bythreaded engagement therewith and which extends upwardly. The rear end of member 108 is connected to the forward end 71 of the member 70 by means of interfitting splines.

Said member 71 may be a separate member secured 5 to the member 70 as shown in Fig. 4 and provided with a plurality of splines 73.

Any other equivalent positive driving connection may be employed.

The outer races of the bearings 102 and 104 maybe fixed to the interior wall of an annular sleeve member 112 shortly to be described.

An annular quill 110 having a transverse opening therethrough is disposed rearwardly of the spindle 100';

The forward extremity of the drive shaftsh eath s fi may be suitably seated within an opening in the quill 110..

The outer periphery of the quill 110 is threadedly engaged with an inner wall of an annular sleeve member 112, as shown, which member 112 is suitably formed'so as to receive the forward extremity of the tube 82.

The conventional clamp means 114 including clamp screw 115 may be associated with member 112 to insure clamping of members 112 and 82.

' A secondary sleeve member 116 is provided-which is may be aligned with the notches 120 so as to permit egress of the coating material and motive agent from within the bore 118 of the spindle 100, all as will herein- :after appear.

Thefannular disc 140, subsequently to be described, is

fixed to the annular ring 122 and rotates therewith.

The forward end portion of the conduit 40 extends through the longitudinal bore of the spindle 100 and into the bore 118 thereof.

' A brush-like member 124 is fixed to the forwardmost end of the member 40 and is of such configuration and dimension as to provide a ring comprising a plurality of bristle members 126 which embrace the wall of the an- :nular bore 118.

Adjacent the forward extremity of the conduit 40, one orrnore openings 128 through the wall of the conduit are provided through which the fluent coating material passes from the conduit outwardly into the bore 118. It will be appreciated that said material is projected toward the :ing in the spindle 100 at its point of communication with the bore 118 thereof. It will be appreciated that such design of shoulder 130 provides a sharp annular edge for purposes subsequently to be referred to.

' The annular disc 140.is disposed forwardly of spindle 100 and, as aforesaid, is held relative thereto by means of ring 122. That'is, the ring 122 is fixed to the disc and is threadedly engaged with the spindle 100.

The outer periphery of disc 140 is provided with a sharp edge 141 to produce a corona discharge when a high potential is applied, all to the end that efiective ioni- .zation of the discharged coating material is obtained as will be more clearly disclosed hereinafter.

The forward end of sleeve 116 is threaded to receive I adapter 142.to which a stationary annular dielectric disc 144 may be fixed and which is thereby held in spaced relation from the rotating disc 140 so as to provide a space 146 therebetween.

A secondary annular metallic ring 148 may be fixed to the rearward face of disc 144 as by cementing or the like and may be provided with a terminal 150 for electrical connection as will appear.

Disc 148 is smaller in diameter than the disc 144 and is provided with an enlarged central opening therethrough of such diameter as to insure'against arc-over therefrom to the sleeve 116 and/or, the adapter 142, with both of which members it is concentric, when high potential is applied between the disc 148 and the spray head with its associated elements including the rotating disc 140.

In this way,- it is to be appreciated that the combina tion of the components including the stationary metal disc 148,-the stationary dielectric disc 144 and the rotating metal disc 140 form an effective electrostatic capacito the minimum. As an example, I prefer to use a t ,sl1e.et-.-of melamine, impregnated:glassxfihet cloth iwhich combines high physical :strength -with a ,--high .rliclectric -quality of: nearly. that: oflmica.

rithe' notches 1 120;.iand :thenaligned: openings, 1123 :intoxthe Secondary-air'passagewayssintthe structure will now be described., .Suchpassagewaysinclude1160 in the cover 12, r162:,in,:the.sleeve.:1;12, .-:164--in. the-sleeve 116, and v .166. between-the adapter.=142.-and.the-.ring122.

.The; apparatus of the invention havipgtbeerr-described, its operation will now be defined.

- ..Rotation is..imparted.:to...disc 1,40. lay-the .motor 18 wardly from. r the conduits-40.1mm the shore 118v ofjthe I.

rotating. spindle 110 .-and.;thence outwardly past the bristles 126 to and through.theaaligned-openings 120 and 123. of themembers 100 .and1122respectively tothe I space 146-between the rotating 'disc.-1'40-;and .the sta- .-.tionary dielectric: disc 144,-,and thencewoutwardly to .the'

. outer annular" edge :thereof.

The primary; air is forced-tat atpredetermined ,andcon- @trolled rate from the sourcepf supplyythereofithrough the -conduit-62 tothenpassageways 58;;and 52 ofjthe '1 .member 50- and -thence {forwardly s-t-hrough the opening .inthe hubs mid -34 and around :the conduit rvidisposed :therewithin. Thereafter it moves forwardly within the rotating, transmission. shaft- :and. around ,the .con-

duit 40; disposed. therewithinqto the longitudinal opening .nin'; the spindle 100. and.,-.around thaeonduit;240::disposed therewithin. and thence, into:the;vbore..I18zFof. the; spindle 100..-where -:it mixes e'withthe. fluentscoatingqmaterial tend-passes.therefromtthrough :the openingsx1'23.

The secondary air ispgforced at a predetermined" and controlled zrate fromthersource of-supply thereofthrough :the conduit 66 to the housing 16.where it surrounds the motor :18; as aforementionedxand thence passes outwardly throughq-opening l 23 .-;intoi5 the housingr 10- passing for- -wa'rdly.therefrom through passageways 160 in the cover 12 into the interior of the tube '82-from which it passes V throughpassageways 162in'the'sleeve 112 and passage- =ways 164 in the sleeve 116- to the interior of said sleeve 116. i It then passesoutwardly through'the passage 166 "into' the space 146 where it merges with the fluent coating '.material.and primary motive agent and is discharged outwardlyfrom the space 146 toward the article A to be coated. .Inasmuch as fluent'poating' material is forced through conduit .40 into the bore 118 and the primary motive agent isforced through the shaft 70, into the bore 118, allas aforesaid,1aspray of the. coating. material'against the bristles 126 ofv the brush-like member 124 is obtained. It may be mentioned here that the sharp annular edge of the shoulder 130 creates a turbulence of the primary motivev agent as it leaves said edge, which turbulence effectively aids in the breakup .of.the coating material was it enters the bore 118-:from'theconduit 40 through "theradially-disposed openings 128 therein,-the coating -material being led in asputtering manner into the nip between the brush-like member 124 and the wall of the bore 118.

' The brush-like member 124 being'stationary (itbeing fixed to the end ofthe conduit 40) and the spindle 100 .having a rotary movement, the rotation 'ofthe, spindle effectively wipes the coating materialinto a uniform layer uponvthe-wall ofthe. bore 118. Partly by the action of -.-the.,.brush.-like member 124 and partly by-the centrifugal action of .thetrotatingspindle,.the coating'material is then Lforcedforwardly to the front/of the spindle. and. through space 146.

. Thevsecondaryvairs is i;alsd.;forced. intozthe :space 146 1' between the dielectricrdiscsill44 and therotatingl'disc140.

.A' terminal 152 ,is securedtto member 112 and maybe in the form of a screw-,.-;as!shown. -.A transformer; T;-;has

. a -seco'ndary 154 connected by, leads156 and. 158" to the terminals 150.: and 152, respectively. Theprimary 1 1.61: of the transformer; T; is :connected by-leadsis163.-and 10' 1.65 to an .A. ,Ctline represented by-167.

A D. C. power.supplyyisjrepresented by 168. Its :nega- .tive side ,is connectedhby: 170 tothe secondary. 154:0f

the transformer T,--, and. its positive side .is connected by 172: togground. Each-of the articles .A to-be. coated will .be. connected to ground.

Alternating current yoltage in-the, order. of 10,000 to 25,000 volts is applied between the stationarytdisc 148 andthetrotating disc 140.1and. a negative D. C potential in. the order 75,000..t6.200,000 voltsis appliedbetween the. disc, and ,the...a'rticle.to .be coated. Thepositive ....terminal, of, the. DJC. supply .isgrounded :and the article to be. coated. is also; grounded .soas to form azhighly (charged.,electrostziticfield.between the rotating disc. 140

. and lthearticle Alto .be. coated.

As;the paint works, itself outonto' the.rear; surface.. of the, "disc 140,1,it is -propelled, ;.,partly by centrifugal. force and .partly by the secondary air flow toward the periphery ..of the disc. (During thisimovement, it .passesfthru the -alternating electrostatic field. between discs. 140 -and.'1.48,

forming an additionalfdielectric layer withfldielectricfdisc "As. iswell known; the atomic structure 'of a dielectric :substance. is suchthat its electrons are tightly bound. {.De-

" pending upon" the "electric potentialapplied; the electronic orbit 'of-theatoms are distorted due to the =stress,,teiiding -todisrupt the-structure by a' mutual repulsion of the electrons. If the charge'is carried far enough, disintegration takes place and the insulating quality 'of3thedielectric =materialbre'aks down. A'similar action takesv place with a' fluid dielectric. Here,- however, the molecules have mobility and 'the highly charged electronic orbit of the molecules tend to repulse each other in the direction following the path of least resistance so that a molecular --motiontakes place. Accordingly, whenthe fluid coating material reaches the zone of alternatingelectrostatic field between the discs 140 and 148, its atoms aresubjectedto alternating positive and negative charges. "Due tothe'diselectric'hysteresis, a-rapid mutualrepulsion-ahd attraction takes place with attendant molecular friction and consequent heating, so that the viscosity of the coating fluid is considerably reduced and formed into a suspendedfog within the zone of the alternating electrostatic'field. *By

the combined action of the rotating disc 140 and the seconclary air flow through the space 146, the fog is driven out into the: zone of negatively charged direct current 1:elcctrostaticlfield. When' itxreachestheedgeof thedisc 140 into the zone of the corona discharge of maximum energy transfer, the finely divided and highly charged particles are repulsed from the energy source and fromea'ch other expanding into a barely visible mist and attracted to-.the oppositely charged object to be coated.

.t The methodyof preconditioning the coating fiuid'by :subjecting itto alternating electrostatic stresses makes the target. .Its prime-function, with the aid of'the secondary air flow is to carry the fluid to the edge of-the disc. T For this reason, maximum effectiveness is obtained .if' both the rate of rotation of the disc 140 and the air xpressure are, adjustable.

Depending. upon the object to be covered, the atomizer head may be placed axial or tangentially toward the objects moved by a conveyor.

While I have illustrated and described the invention as embodied in certain specific arrangements, I do not intend to be limited to the details shown since various modifications and structural changes may be made with out departing in any way from the spirit of the invention. Without further analysis, the foregoing is intended to so fully reveal the gist of my invention that others can,

by applying current knowledge, readily adapt it for various applications without omitting features which, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims below.

I claim:

1. An electrostatic atomizing apparatus of the class described, comprising discharge electrode means, a rotating metallic disc adapted to be spaced from an article to be coated and which article is of an opposite polarity to that of said means for constituting a collector electrode, a stationary dielectric disc spaced rearwardly of said, rotating disc, a stationary metallic disc adjacent and rearward of said dielectric disc and dimensioned to prevent arc-over when high potential is applied between saidrotating and stationary metallic discs to form a capacitor, a hollow spindle fixed to said rotating metallic .disc and having a conical bore, passages from the bore of said spindle to the rearward face of said rotating metallic disc for the passage of a fluent coating material into the space between said rotating metallic disc and said dielectric disc, a stationary fluent coating material conduit projecting into the bore of .said spindle and having radially disposed openings in the wall of said conduit near the small end of the bore of said spindle, a hollow transmission shaft concentric with and disposed around said conduit including means for permitting the passage of air therethrough and around said conduit, a motor, means to impart rotation to said rotating metallic disc, means for forcing a supply of secondary air into the space between said rotating metallic disc and said dielectric disc, a high potential D. C. supply connected across said rotating metallic disc for forming an intense uninterrupted electrostatic field between said rotating metallic disc and the article, a high potential A. C. supply connected across said rotating and stationary metallic described, comprising discharge electrode means, a first metallic disc having a sharp peripheral edge adapted to be spaced from an article to be coated and which article is of an opposite polarity to that of said means for constituting a collector electrode a dielectric disc spaced rearward of said first metallic disc, at second metallic disc disposed rearwardly of said dielectric disc and insulated by the latter from said first metallic disc to form a ca pacitor when high potential is applied to said first and second metallic discs, means to supply coating fluid into the space between said first metallic disc and said dielectric disc, means to propel coating fluid toward said edge of said first metallic dis for atomization therefrom, a high potential direct current supply connected across said first metallic disc and the article to be coated to form an intense uninterrupted electrostatic field between said first metallic disc and said article, and a high potential alternating current supply connected across said first and second metallic discs for molecular agitation of the coating fluid passing between said first metallic disc and said dielectric disc for maximizing charging and atomization of the coating fluid emerging at the edge of said first metallic disc, whereby the thus highly charged and atomized coating fluid is repulsed from its source and readily attracted to the article to be coated in an accelerated manner.

3. An electrostatic atomizing apparatus of the class described, comprising discharge electrode means, a rotating metallic disc adapted to be spaced from an article to be coated and which article is of an opposite polarity to that of said means for constituting a collector electrode, a stationary dielectric disc spaced rearwardly of said rotating disc, a stationary ring-like metallic disc adjacent and rearward of said dielectric disc, said stationary metallic disc being dimensioned to prevent arc-over when high potential is applied'between said rotating and stationary metallic discs to form a capacitor at one end and provided with a hollow spindle fixed to said rotating metallic disc and having a conical bore, passages from the bore of said spindle to the rearward face of said rotating metallic disc for the passage of a fluent coating material into the space between said rotating metallic disc and said dielectric disc, a stationary fluent coating material conduit projecting into the bore of said spindle and having radially disposed openings that extends through the Wall of said conduit adjacent the small end of the bore of said spindle, a hollow transmission shaft disposed about said conduit and including means for permitting the passage of air therethrough and around said conduit, means for imparting rotation to said rotating metallic disc, means for forcing a supply of secondary air into the space between said rotating metallic disc and said dielectric disc, a high potential D. C. supply connected to said rotating metallic disc and adapted to be connected to the article for forming an electrostatic field between said rotating metallic disc and the article, a high potential A. C. supply connected across said rotating and stationary metallic discs for forming therebetween an electrostatic field of alternating polarity for effecting molecular agitation of the fluent coating material passing through the space between said rotating metallic disc and said dielectric disc.

4. In an atomizing spray device having means for electrically charging particles of coating material discharged thereby for improving the deposition of the material upon the electro-conductive surface being coated, the improvement comprising, a rotating metallic disc, a stationary dielectric disc spaced rearwardly of said rotating disc, a stationary metallic disc adjacent and rearward of said stationary dielectric disc and dimensioned to prevent arc-over when high potential is applied between said rotating and stationary metallic discs to form a capacitor, a hollow spindle fixed to said rotating metallic disc and having a conical bore therethrough, passages from the bore of said spindle to the rearward face of said rotating metallic disc for the passage of a fluent coating material into the space between said rotating metallic disc and said dielectric disc, a stationary fluent coating material conduit projecting into the bore of said spindle and having radially disposed openings in the wall of said conduit near the small end of the bore of said spindle, a hollow transmission shaft concentric with and disposed around said conduit including means for permitting the passage of air therethrough and around said conduit, a motor, means for imparting rotation to said rotating metallic disc, means for forcing a supply of secondary air into the space between said rotating metallic disc and said dielectric disc, a high potential D. C. supply connected across said rotating metallic disc and the electro-conductive surface forming an electrostatic field therebetween, a high potential A. C. supply connected across said rotating and stationary metallic discs forming an electrostatic field of alternating polarity disc and said dielectric disc for charging and atomizing the fluent coating material emerging at the edge of said rotating metallic disc.

5. An electrostatic atomizing apparatus of the class described, comprising discharge electrode means, a rotating metallic disc having a sharp marginal edge and adapted to be spaced from an article to be coated and which article is of an opposite polarity to that of said means for constituting a collector electrode, a stationary dielectric disc closely spaced rearwardly of said rotating metallic disc, a stationary metallic disc disposed rearwardly of .said dielectric disc and dimensioned to form a capacitor and prevent arc-over when a high potential is applied between said rotating metallic disc and said stationary dielectric disc, a spindle having a passage therethrough terminating in a conical bore in its outer end adjacent said rotating disc and provided with passage means leading from the conical bore of said spindle to the rearward face of said rotating metallic disc for allowing the coating fluid to pass into the space between said rotating metallic disc and said stationary dielectric disc, a stationary coating fluid supply conduit projecting into the conical bore of said hollow spindle and equipped within said bore with a brush-like member having wiping engagement with the wall defining said bore, said conduit being provided with an opening effecting communication between said bore and the interior of said conduit for supplying said bore with coating fluid from said conduit, said conduit being circumspaced within said spindle to provide an air passage within the spindle to permit a supply of air to be blown through said spindle to eflect spraying of the fluid emerging from said conduit against said brush, a motor, means to transmit and impart rotation to said rotating metallic disc from said motor, conduit means independent of said fluid conduit for blowing air through the space between said rotating metallic disc and said stationary dielectric disc, a highpotential D. C. supply connected to said rotating metallic disc and adapted to be connected to the article to be coated to form an electrostatic field between said rotating metallic disc and the article, a high potential A. C. supply connected across said rotating metallic disc and said stationary metallic disc for forming an electrostatic field of alternating polarity for eifecting molecular agitation of the coating liquid passing through the space between said rotating metallic disc and said stationary dielectric disc for maximizing charging and atomization of the coating fluid emerging at the edge of said rotating metallic disc, whereby, the highly charged and atomized coating fluid being repulsed from its source is readily attracted by the article to be coated in a shorter period of time.

6. In an atomizing spray device having means for electrically charging particles of coating material discharged thereby for improving the disposition of the material upon the electro-conductive surface of an article to be coated, the improvement comprising, a first metallic disc having a sharp peripheral edge at the extreme outer end, a dielectric disc disposed rearwardly of and spaced from said metallic disc, a second metallic disc disposed rearwardly of said dielectric disc and insulated there- 10 from to form a capacitor when high potential is applied to said first and second metallic discs, means for supplying coating material into the space between said first metallic disc and said dielectric disc, means for propelling coating material toward said edge of said first metallic disc, a high potential direct current supply connected across said first metallic disc and with the article to be coated adapted to coact with said first metallic disc to form an intense uninterrupted electrostatic field between said first metallic disc and the article to be coated, and a high potential alternating current supply connected across said first and second metallic discs for effecting molecular agitation of the coating material passing between said first metallic disc and said dielectric disc for maximizing the charging and atomizing of the coating material emerging from said space at said edge, whereby, the thus highly charged and atomized coating material is repulsed from its source and readily attracted to the article to be coated in an accelerated manner.

7. The structure as set forth and defined in claim 5, including a motor housing having a chamber housing said motor and communicating with said conduit and said conduit means for supplying said conduit and said conduit means with air introduced into said chamber whereby air introduced into said chamber serves to prevent explosion of said motor due to arcing thereof.

8. In apparatus for coating articles by atomization of fluid material including an atomizer including a circular centrifugal disc, means for propelling said fluid material to an atomizing zone of said atomizer, means for impressing unidirectional high potential voltage across said atomizer and said articles to be coated for elec- :trostatic atomization and coating of said articles by said fluid material, and means to provide molecular agitation of said fluid material substantially immediately prior to atomization thereof, last said means comprising conductor means spatially positioned from said atomizer and terminating within the confines thereof a distance sufficient to avoid arc-over and forming a capacitor therewith to provide a passageway therebetween for said fluid material, and an alternating power source connected to said conductor means and said atomizer to provide said molecular agitation of said fluid material.

9. In apparatus for coating articles as set forth in claim 8, wherein said conductor means is circular and of a diameter smaller than the diameter of said atomizer.

10. Apparatus for electrostatically coating articles comprising a rotatably mounted disc type atomizer, means for rotating said atomizer to propel said coating material to an atomizing zone adjacent the edge of said atomizer, means for charging the particles of said coating material for atomization and electrostatic deposition thereof onto said articles, conductor means spatially positioned adjacent said atomizer and terminating within the confines thereof a distance sufiicient to avoid arcover providing a passageway for said coating material between said conductor means and said atomizer, means for supplying coating material to said passageway, and a source of alternating current connected across said atomizer and said conductor means to provide molecular agitation of said coating material prior to atomization.

No references cited.

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