US2826451A - Spray device for electrostatic deposition of a fluid - Google Patents

Description

March 11, 1958 J. SEDLACSIK SPRAY DEVICE FOR ELECTROSTATIC DEPOSITION OF A FLUID Filed Nov. 1, 1954 IN V EN TOR.

United States Patent- 9 "SPRAY DEVICE FOR "ELECTROSTATIC DEPOSITION OF A FLUID .John-Sedlacsik, -.Garfield, N. J. Application November 1, 1954, Serial No. 465,938

3 Claims. (Cl..;299-1) :This. invention :relates. to. the. nebulizing oft liquidswand, more particularly,.it relates to newanduseful improvements in anapparatus @forapplying-a liquid coating toan article or articles :by electrostatically charginganddepositingthe comminuted coating materialupon the Marticle withinan electrostatiefield created'betweenthe article zto.be coated and the issuing source of the coating material. '.That is to say, "the invention relates to means for imdeposition of the 'atoniized particles from achargedgun .wrn'echanisrn upon anaopp os'itely charged article.

eSam'e is accomplished by -a rneans which provides greater stability to the projected spray or jetandimparts sarsharpcnedge definition: to its issuing pattern.

.ThGLjDVEDL'l'Ol'li envisions a paint spray :gun mechanism wherein the forward atomiz'ing and spray elements :are isolated from :the :rezar support and l'control e1ernents and -thesstructureris such as d0ipfillllltfihfiidesllfid elimination of the possibility. of a a transmittal aof tan electrical charge tin the forward-:areaof the mechanism rearWar'dly to the irearwardarearthereof.

The rear portion of the mechanism?iseatjgoundipotem :tialafort-the convenience and safetyiof :thevoperator while,

at ithe sameitime, the :fo 1 lard portion thereofzis adapted toreceiveea high-electrical potential.

In applying coating materials to articles tbyimeanswof iknowntspraydevices, .therso called spray guns of: the-prior art, the artioftemploying compressed .air-as a :means for atomizing -.or reducing the material into a fluid "of -fine coinminuted particles and also as a carrying medium in ,sprayingthesame upon .the surface of the'articlesbeing covered I'has been known. But such :guns :have been flirn'ited to a comparatively .smalLfield of dispersion. "Also, jthey'havetcaused the coating material to'be discharged-in non-uniform sized particles, as well astin variable patterns, whereby an uneven dispersion of the coating particles over thejsurfacebeing coated results.

Incertaimprior art devices, the projected spray oryjetis 'moreorlesstunstable. Thatis, the axis of the sprayer jet "shifts :erratica'lly from :one position to another. fBxpressed otherwisethe cross-sectionalishape o't'ihespray orj et pattern'hasbeen observed .to vary during operation. such instability results in an obviously objectionable irregular scattering of .the .coating material upon theisur- Qfacezoftthearticle being coated.

In certain other prior art apparatus, a variablepattern of .spLa-yhas been created-and reproduced upon the surface being "coated, dhe :heavier coating particles being tcausedto impinge rover-one, particular area and the more finely divided particles being caused to 1 impinge 'overa di-iferent area. By 'reason of such variance, it "oftenshas been found advisable to arrange a plurality 'ofsprayguns in more or less 'ofqa bankpwithparticular regardtothe rvariable pattern-of: each: specific; gun, which; guns when t properlywarranged complementeach other, all tothe-lend that :the ,pattern produced -therewith -is smoothed =or evened out. p

-.='1 he-.inherent telectricab effect: in prior -art guns of this general typereausest-the particles to repel eaeh otherrrnore cor :less whereby alateral spreading thereofresults. This spreading phenomenon is especially tnoticeable at che outer portionsofathe spray or jet area where-anuneven,

lirregular andLindistinctv edge definition toth-e patternof fthe coatingamaterialabeing deposi-ted upon the article-'15 Hnormally'observed. u p

.' By.surroun'din g in close proximity the atonnzing,. proflj ecting and'depositing lestrostatic ifield with an envelope of air, whichiis substantially coextensive longitudinally with theformer, the -.projec'ti1 1g. spray jet is stabilized,- and is made more definite in shape and more constant in direction. The scattered spreading effect upon the particles, particularly at'the'outer portions of 'the jt, is materially reduced. This results in adepo'sited"patternwhich is more uniformly dense throughoutand which has a de- "sired sharp'edgedefinition.

"One of'the objects of this inventionlis'tofiprovidea stabilizing area adjacent the electrostaticsprayfatomizing,

projecting and deposi'ting fi eld, which. "areais effective tostabilize the jetproducedby. the latter, both-inrespect 'todirection and in "respect to"'shape,*and"to give-a resulting deposited --'pa'ttern having a *relatively sharpe'r "edge :"definition=through'out its entire periphery arid/or over one or more per-tions'thereof.

*The atonrizing elem'ent of my appara'tus consists "esdefined distributing or atomizing point or tip from which tthe co a'tin'g materiabds metered -at a f-predetejrmine'duate in the form of atomized particles.

"Acsource of electrostatichighapotential, having one terminal grounded and its opposite terminal connected to .the atomizing :head 1 creates :a strong electrostaticfiield between the head and the article to be coated, which article? is also .igrounded.

tTheeforce of this afield transforms tthea coating material into aaspray' ofifinegcharged particles and creates :an at traction which pulls the spray to :the grounded aarticle,

thus accounting. for complete J electrostaticideposition.

.I s have a determined, :through considerable investigative eifort, that= optimum iresults :are obtained--where theamass wot the .atomizing poinbortip yismaintained asvsinallwas possible where t as thetmass of the -article being coatediis relatively larger. Such facilitateslleakage of the atomized materialifrom thehigh ,potential; point or tip to the/artibeingofrubber, glass, ceramic, .qfilatio, or siniilar nonconducting material. fByrneans'the'reof, the high voltage nozzleor headendjofthe gun appara'tusis separated from the grounded =support or control end in such imannerith'at the support and control mechanisms, aswellas'thebperator, are;safeguarde'd"against dangerous backfiring from the nozzle onhea'dend.

It should beladditionallyimentioned here tliat' in appaalong a horizontal or vertical axis, or both, past the articles. In either event, the articles to be coated are usually supported in spaced relation to the discharge electrode, between which and the articles, a potential difference of sufficient magnitude is maintained so as to create an electrostatic field with an atomizing corona discharge in the region adjacent the discharge end of the discharge electrode.

Broadly speaking, the coating material is normally supplied to the discharge end and its region of corona discharge at a rate at which it can be electrically atomized by the corona discharge most efiiciently and effectively, after which the charge particles are projected in spray I form toward and deposited upon the oppositely charged article. Depending upon the viscosity and other characteristics of the material, the control of the supply is such as to permit the discharge of precisely the correct quantity and size of the particles so as to effect the greatest efficiency in coating a surface.

All of the above cited objects, I accomplish by means of such structure as will fully appear by a perusal of the description which follows and by various specific features which will be hereinafter set forth.

With the foregoing and various other and ancillary objects of my invention as will become more readily apparent as the description proceeds, my invention consists in certain features of novelty, in mode of operation, and in the combination and arrangements of parts as will be hereinafter more particularly pointed out in the claims hereunto annexed and more fully described and referred to in conjunction with the accompanying drawings wherein:

Fig. l is a side elevational view of the device of the invention parts being shown in section;

Fig. 2 is an enlarged sectional view on the line 22 of Fig. 1; and

Fig. 3 is an enlarged sectional view on the line 3-3 of Fig. 1.

In the accompanying drawing, I have illustrated a complete example 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 application of the principles of the invention.

' It will however'be understood that changes and alterations are contemplated and may be made in these exemplifying drawings and mechanical structures, within the scope of the claims, without departing from the basic principles of the invention.

In the following description and claims, various details will be identified 'by specific names for convenience. These names however are intended to be as generic in their application as the art will permit.

Referring now to the drawing more in detail, in which similar characters of reference indicate corresponding parts in the several figures, and referring more particularly to the preferred form of my invention selected for illustrative purposes. I have shown an arrangement of apparatus which is suitable for coating articles (not shown) which are preferably moved along a path of article-movement through a coating zone which the device of the invention, fixed in location, projects.

Disposed at one side of the path of article-movement is a horizontally positioned atomizing head generally designated by the numeral 10, by means of which head the liquid coatingmaterial is electrostatically atomized.

Said atomizing head may be fixedly or adjustably mounted up n a suitable support, or it may be hand ingly is not shown.

4 manipulated by means of a handle, all as may be desired.

An elongated liquid spray material tube 20 made from glass, rubber, plastic, or similar material is provided with a longitudinal bore 21 extending therethrough. A coating material is adapted to be passed therethrough as will presently be observed.

Another elongated gas tube 22 extends parallel to the tube 20 and is spaced a distance away therefrom. Tube 22 is also provided with a longitudinal bore 23 extend ing therethrough. A gaseous material, such as air, is adapted to be passed therethrough, all as will hereinafter appear.

At the opposite extremities of the tubes 20 and 22, connecting means are provided.

At the nozzle end of the head, a nose piece 26 is provided and the tubes 29 and 22 may be threadedly or otherwise engaged therewith.

' disposed members shortly to be described.

The spray gun contemplated for use in this invention consists of a conventional main body portion which is disposed rearwardly of the apparatus of this invention. Same does not form a part of this invention and accord- It also includes a spray head similar to the type disclosed in U. S. Letters Patent #2,070,696, dated February 16, 1937.

The nose piece 26 is of such configuration as to be adapted to receive, in threaded engagement therewith the spray head of the above patent or of any other of the well known commercial types of atomizing spray gunsusing air for the atomizing medium.

The spray head comprises an inner fluid nozzle 40 formed with a forwardly disposed tip 42 having a central orifice 43 therethrough through which the coating material is emitted.

The inner fluid nozzle 40 is threadedly receivable in a sleeve 44 which is receivable in an appropriate opening in the forward face of the member 26.

An annular outer nozzle 46 surrounds the member 44 in spaced relation therewith so as to provide an annular opening 48 through which the air may be emitted.

The rear end portion of the member 44 is enlarged as shown at 50 and is connected in any suitable manner with the member 26.

The enlarged portion 50 of the member 44 is formed with a suitable annular seat 52 against which the forward end of nose 26 is held by a union nut 54 or other suitable means.

Forwardly of the member 40, an elongated connecting member 60 is provided having a central orifice 62 extending therethrough throughout the longitudinal length thereof.

The member 60 has an outwardly extending annular skirt portion 64 which is adapted to be engaged at its outer peripheral edge by the union nut 54 so as to hold the member 60 in extended coaxial relation to member 40 with the tip 42 extending into the opening 62 affording direct communication therebetween.

A sleeve 70 which may be made of metal or of insulating material such as rubber or the like as desired has a central opening extending longitudinally through the forward area thereof which is of reduced diameter, as shown. The forward opening leads into an enlarged opening within the sleeve member 70 at the rearward area thereof.

The rearmost portion of the inside wall of the member 70 is threadedly engaged with the member 60, as shown.

A needle having an orifice 81 extending throughout the length thereof is extendable through the forward opening in the sleeve 70 so as to have a free outer 5 end 83 extending therebeyond. If desired, the free outer end-=83 may+not heextendedbeypn'd the outer end,of the bore.

Thej-inner end 84 of the needle "80 is;receivable'in"the opening 62 of the member '60 and affordsdirecncominunicationtherebetween. The inner-end fifihas a'sho111- -der 86-which-abutstheouter endof the openingt'62.

The needle SO-may be secured to the member-"60 by means of a coupling 88, as shown.

The nose piece 26 an'dthe other elements at the forward end of. thegun. arewpreferablytmade from electrical conducting .material, the nose piece ;being connected to the ungroundedterminal of a high ,voltag'e :source ;by ..means.-of;, a;high voltage instrumentali ty 27. Thepor.t irltial source is electrically connecteddo the structure by a? .COnductonassociated with. the. connection 27 for: raising .the discharge edge to a suflicienthigh.electrical potenl i l for ,electrostatically atomizing .liquid material suppliedgthereto as will presently be observed. The ,potential at;the discharge edge approXimates l,Q0,000 volts. 1D.C.

{The coating material passes th iQllghthe tube ,20 and appropriate conducting means'in the nose piece 26 to the member 40 and out through theopening 43 thereof into the opening 62 of the member 60 and theneejnto and v through the opening -81-of the needle-80.

"The atomizing -air -is adaptedto' be supplied "through the member 22 to the nose piece 26, then through the opening 48 and past the member 46, and thence through the openings 66 and into and through the opening in the sleeve 7 around the needle 80.

It will be appreciated that the needle 80 extends coaxially throughout the opening in the sleeve 70 and passes out therebeyond as a pointed metal rod electrode.

As the stream of liquid passes outwardly through the needle and as the stream of air passes outwardly around the surface of the needle, the same are subjected to the atomizing effect of the corona discharge from the rod electrode whereby the finely divided particles comprising the spray have each imparted thereto electrical charges of like polarity.

As previously stated, under certain conditions, the projected jet wavers erratically and continuously. This results in a scattered dispersion of the particles comprising the jet and thereby causes the deposited pattern upon the article to have irregularly disposed lakes. In addition, the mutual electrical repulsion of the particles due to their being charged to the same sign causes them to spread and scatter laterally, particularly at the outer portions of the jet. This makes a less sharply defined edge at the boundary of the deposited pattern.

To overcome these objectionable characteristics, I provide a gaseous field surrounding in close proximity the electrostatic atomizing field and coextensive in length with the latter. That is, it extends along the rod member with which it is substantially coaxial and terminates at the surface of the article to be coated.

In this manner, an air chamber is provided adjacent the outer periphery of the point of the needle 80 whereby a gaseous medium of any desired intensity may be introduced around the stream being dispersed through the needle so as to surround or envelop same.

Understandably, valve means (not shown) may be provided whereby the flow of liquid and air may be better controlled.

By means of this concentration of air around the liquid, the center of the area being sprayed receives as much of the sprayed material as the outer edges thereof, the air blast having the capability of directing the sprayed material inwardly toward said central area.

The insulated sleeve member 70 surrounds the needle 80 so as to insure against the discharge of coating material except along the free uncovered outermost portion of the needle.

The needle tip presents toward the articles to be coated a reduced or relatively sharp tip or discharge point from 1 6 which the coating material may be withdrawnin theforni "Of'ZPQI'tlCIeS. l j

The inner-extremitiesOfthetubesZO and zz'aret hreadedly engaged with atail-piece'-90*by"=means of-couplings 92-and-94 respectively.

lhe ta-il' pieceis connected to--sources of supply'of the coating material:- and *air (not shown )"by"means of con- .mect-ionsdf any of theconventional designs.

In the drawing,a-connection-"96 m shownwhich may be connecte'dto -a source= f air (not showny and a con- --nection'i9Sis shownMhich may be connected-to'a'source .of coating material?: (not slrown) The liquid and: gaseous materials are supplied through their .1 respective conduits to the muzzle assembly as I previouslysdescribed.

Without'rfurthemanalysis, rthe foregoing will tfully reveal .the :gist of'rmylinventionx whereby'other's can, by applying :current .isnowledge, \rreadily .zadapt it for uv'arious zappliciations :without {omitting :features which, :from athe .-stand.p.oint1.ofw-prior amrfairly constitute-essential charac- :teristics of '.'l1h6 generienr .qspecific :aspects cof r this inven- .tion. ;-,Such adaptationsathereforetshonld and are intend- ;ed to be comprehended within :themean-ing and range of: equivalence ofthe. claimslbelowz -,What it is desired to claim and; securei'bylLetters. Patent eef the-UnitedStates is:

.-1. .In combination, an areo=e1ectrostatic L atomizing :device attached to a spray gun for use in discharging an electrically charged air-supported stream of fluent coating material at high velocity, a dual motive agent-coating material atomizing nozzle comprising a combined coaxially disposed rearward connector and forward needle of electrically conductive material and having a fluent coating material bore extending longitudinally therethrough, having the forward portion of uniform diameter and terminating at the forward end in an outer forwardly facing discharge orifice of the same diameter as that of the forward portion of said bore, said connector being engaged with the forward-extremity of the spray gun of electrically conductive material having means for connection to a high voltage source, an outer elongated sleeve of insulating material disposed forwardly of said spray gun and in axial alignment therewith and engaged with the rear connector, said sleeve having a motive agent longitudinal bore, the forward portion of which is of uniform diameter terminating at its outer end in a forwardly facing discharge orifice of the same diameter as that of said forward portion of said last-named bore, concentric with, rearwardly of, and disposed around the discharge orifice of the fluent coating material bore, all adapted and arranged whereby a motive agent discharged from the motive agent orifice impinges the electrically discharged particles of the fluent coating material discharged from the fluent coating material orifice in a plurality of points lengthwise thereof.

2. In combination, an aero-electrostatic atomizing device attached to a spray gun for use in discharging an electrically charged air-supported stream of fluent coating material at high velocity, a dual motive agent coating material atomizing nozzle member comprising a combined axially disposed rearward connector and forward needle having a fluent coating material longitudinal bore connecting at its forward end with discharge orifice means, said connector being of electrically conductive material and being connected with the forward extremity of the spray gun, said gun being of electrically conductive material and having thereon a high voltage instrumentality, an outer longitudinal sleeve member disposed forwardly of said spray gun in axial alignment therewith and connected with the rear end of the connector, said sleeve having a longitudinal motive agent bore communicating at its forward end with discharge orifice means disposed around and adjacent the coating material orifice means, one of said members being of electrically conductive material, whereby a motive agent discharged from the 3. In an aero-electrostatic atomizing device attached to a spray gun member of electrically conductive material for use in discharging an electrically-charged air-supported stream of fluent coating material at high issuing velocity, a dual motive agent-coating material atomizing nozzle comprising a combined coaxially disposed rearward connector and forward needle member of elec trically conductive material, one of said members having a high voltage instrumentality thereon, the rearward extremity of the connector of said combined connectorneedle member being engaged with the forward extremity of the spray gun, said combined connector-needle member being provided with a fluent coating material bore longitudinally and interiorly thereof and terminating in an outer forwardly facing discharge orifice at the forward extremity thereof, an outer elongated sleeve of electrically insulating material disposed forwardly of the spray gun and in axial alignment therewith, the rearward extremity of said sleeve being engaged with the rearward extremity of said combined connector-needle member, said sleeve being provided with a motive agent bore longitudinally and interiorly thereof and terminating in an outer forwardly-facing discharge orifice at the forward ego-e1 extremity thereof concentric with and disposed around the discharge orifice of the fluent coating material bore, all adapted and arranged whereby a motive agent discharged from the motive agent bore impinges the electrically charged particles of the fluent coating material discharged from the fluent coating material bore in a multiplicity of points lengthwise thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,757,573 Heinrich May 6, 1930 1,779,849 Lusk Oct. 28, 1930 1,992,426 Herbsman Feb. 26, 1935 2,302,185 Campbell Nov. 17, 1942 2,302,289 Bramston-Cook Nov. 17, 1942 2,334,648 Ransburg et al. Nov. 16, 1943 2,577,437 Stringer Dec. 4, 1951 2,625,590 Peeps Jan. 13, 1953 2,658,009 Ransburg Nov. 3, 1953 2,710,773 Sedlacsik June 14, 1955 FOREIGN PATENTS 1,017,822 France Dec. 19, 1952 1,017,823

France Dec. 19, 1952

Images