CA1327882C - Air bearing rotary atomizer - Google Patents

Abstract

ABSTRACT OF THE INVENTION
A rotary atomizer (20) includes a manifold assembly (22) adapted to be attached to a mechanism for moving the atomizer and an air bearing turbine motor housing assembly (21) releasably secured to the manifold assembly. Sources of pressured fluid for actuating the atomizer and coating fluid are connected to the manifold (29) which has fittings (32, 33, 34, 35, 36) for releasably sealing to apertures (42) in the rear cover (43) of the housing assembly. The opposite end of the housing includes a shaping air cap (24) and a shaping air ring (25) which cooperate to define an annulus for discharging a thin ring of shaping air over the peripheral edge of an atomizer bell (26) to direct fluid particles toward a target. Exhaust air from the turbine motor (46) is vented to the inside of the housing and directed to a chamber (79) behind the atomizer bell to aid in directing the fluid particles. A magnetic speed pickup (103, 104) generates a signal which is coupled through a circuit (105, 106) that electrically isolates the high voltage which is applied to the atomizer to electrostatically charge the coating particles.

Description

1~278~2 M TLE
~1R ~EARING ~OTAR~ ~TOMIZER
~ he lnve~tio~ selstes generally to rotary ~tomizer6 for depos~tlng coati~gs on workpleces &~d, ln p~rtlcular, to ~ rotary ats~i~er ~th l~proved flow of th~ coatlDg ~2terlal through the ato~l~er s~d onto the ~orkpiece.
BACKGROUND 0~ ~HE INVE~TION
One type sf prlor art dev~ce utillzed to ~pply coatings to ~orkpiece6 i6 a ro~ary ato~lzer. Such ~ de~lce 16 p~rticularly u~eful in coaeing l~rge aurface6 ln hlgh ~olu~e 6uch a~ the paintl~g of ~uto~obile bodles ~nd the llke. A di~k or a bell ~5 dsiYen ~ rot~tion by an air-po~ered turbine ~otor. Psint i5 delivered to the l~ner ~urface of the dl6k or bell and i~ thrown of~ ~n ~mall pasticle6 ehro~gh centrlfugal force.
Typically, the surface of the bell i6 charged to 8 hlgh ~ol~ge normally between 30KV and l25~V to electro6tatically charge the paint particle6.
One for~ of rotary atomizer 16 disclo6ed i~ ~.S. Patent No. 4,555,058. This devle2 ha6 a bell whlch i6 rotat~d a~ high speeds, ~or~ally bet~een 10~000 and 40,000 rp~. The rotary be~l hs~ a plurality of pslnt opening6 formed therei~ eonnected ~o a Bource of pai~t. Alr u~der 20 pre68Ure iB fo~ced through another pluralley of ope~in~ 6 front plate to ~' direct ahap~g air over the outs~de of the bell to thereby ~hape the 6tream o~ pa1nt partiole6 e~l~ing from the bell and direct the~ toward the ob~ect ` to be painted.
~ U.S. Patent No. 4,423,840 di6closes an ultra ~igh-6peed rotary '~ 25 ~to~izer bell d~6ig~ed to ell~inate ~08~ or bubbles 1~ the appllet coat~ng.
he bell i~ rotated at high ~peed, ce~trifugal ~orce c~uBe6 the paint to flDw throu~h distrlbut~on aperture~ to a generally eonical i~terior flow 6urface on ~he dl~charge ~ite o~ the bell. Ce~trifugal force alfio causes he palnt to ~lo~ along the c4nlcal lnterior ~urf~ce ln a continuous fil~ to ;~ 3~ a charp dl~char~e edge bet~een the eonical ~urface ~d the ~ront end of ehe ^~ bell. The front e~d of the bell ha6 a predeterained wall thickne6s and form6 a charp di~ch~rge edge at the ihterior ~urface s~d i~ rounded at ehe exterior 0ur~ace. By rounding ehe discharee end on the exterlor ~urface, '~ 3~
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' ,' ~ ' ' , ' ' " ~ ' : , " - 1327~82 the entrapped air or other cau~e of bubbles ln the applied coating is eli~lnated, even ~hough the roatary atomizer bell iB operated a~ extreme ~peed6 which ~ay be o~ the o~der of 40,000 rpm, or more.
SUMMARY OF THE INVENTIO~
S The present invention ~oncerus a rotary atomizer l~cluding a mRnifold relea6ably connected to a~ outes cD~ln~ or ~Ihroud housing an sir bearing turbine as6embly. The msnifold includes ~nlets or sources of bearing alr, brake air, ~hapi~g air, turbine air, nnd coa~ing fluid, as well ~6 an aperture for a magnetic 6peed pickup coil co~nec~lon. A larger diameter ent of the outer ca6ing or ~hroud i~ closed by a rear cover plate havlng ~ plurality of aperatures for~ed therei~ for cealingly accepting correspondin~ fittings protrudlng from a faci~g 6urface of the manifolt and connectet to the air inlet6.
The coatlng fluld i6 dlrectet through a centrally located fluld feed tube that extends through the air turbine motor and terminates ln a nozzle located in a pa$~t chamber formed by the forward end of the air turbi~e motor, an atomizer bell, and an annular shaping ~ir cap. The feed tube has a rear flange which unt~ into an spert~re in the rear coYer plate for precise ali~ment ~ith the ~urbine drlven ~otor 6haft.
The smaller diameter end of the ~hroud rece~ves ehe shaping ~- alr cap a~d an ~nnular ~haping air ring ~hich are thre~dably engaged~; Nestlug t~per~ for~ed on i~ner surface6 of the cap aud rlng define a shaplng air annulus wh$ch d$rects shapi~g air over the outer edge of the atomizer bell in sn l~wartly directed path a6 a uniform eh$n ring of air.
A flexible cap retalner iB mounted on the front cover o~ the air turbine motor to 6eparate the 6haping air passage from the e~haust air ps66age. The cap reta$ner al~o provide6 an ela~ic containment to retain the ~h~ping air cap should lt become di6engaged from ehe zhaping air ; manlfold to which it 1~ threadably en8aged.
E~haust ~ir e~it6 the rear of the turbine and ls ported into the ~ - shrout ~here it ~lows for~ard ~long the outside of the turbine to provlde 1 cooling a~d then lt i~ directed into the p~int chamber bet~een the shaping air cap and the rear of the ato~lzer bell ~rom which it e~lts through the annulus for~ed bet~een the outer edge of the bell and the front edge of the cap. This air prevent~ the coating fluid from ~rapping back around the .
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outside of khe shroud and entering the chamber. This use of the exhaust air reduces the amount of shaping air required and also reduces the cleaning re~uired. Furthermore the volume of the exhaust air inherently increases as the speed of the air turbine increases to offset the radial momentum of the coating fluid particles.
A pickup coil is located adjacent the path of magnets mounted on the rear of the turbine wheel in the motor and is connected to a loop of high voltage wire. The wire extends awav from the atomizer and through a toroidal coil to isolate the magnetically generated speed signal from the high voltage used with the atomizer.
The invention may be summarized as a rotary a~omizer for coating with a coating fluid comprising, in combination, a housing, a rotary fluid atomizing device rotatably supported at one end of said housingl said device having a front surface facing away from said housing and a rear surface facing toward said housing and an annular edge from which such coating fluid is discharged by centrifugal force for atomization, said housing including an annular portion at said one end surrounding at least a portion of said atomizing device, said annular portion and said rear surface of said device forming a chamber therebetween which opens behind said annular edge, an air driven turbine located in said housing and connected for rotating said atomizer device, said turbine generating pressurized exhaust air during operation, said chamber having an annular opening formed between said annular edge ~27882 - 3a - 27905-12D

of said atomizing device and said housing and vented to atmos-phere, means for delivering said turbine exhaust air to said chamber for maintaining said chamber above atmospheric pressure during operation of said rotary atomizer to prevent atomized coat-ing fluid from entering said chamber, said annular opening directing turbine exhaust air at atomized fluid discharged from said annular edge, wherein said housing incIudes an air cap surrounding at least a portion of said rear surface of said atomizing device, said air cap including an annular opening sur-rounding said annular chamber opening located for directing pattern shaping air at atomized fluid discharged :Erom said annular edge of said device, and means for delivering pressurized air to said annular air cap opening.
BRIEF DESCRIPTION OP THE 1: RAWINGS
The aforementioned advantages of the invention will become manifest to one skilled in the art from reading the follow-ing detailed description of what is now considered to represent its best embodiment when considered in the light of the accompany-ing drawings, in which:
Figure 1 is an exploded perspective view of a rotary atomizer according to the present invention;
Figure 2 is a side elevational view in partial cross-section of the rotary atomizer shown in Figure l;
Figure 3 is a rear elevational view of the rotary atomizer shown in Figure l;
Figure 4 is an enlarged, fragmentary, cross~sectional side elevational view of the front end of the rotary atomizer " ~ :

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of Figure l;
Figure 5 is a schematic diagram of the speed sensor circuit of the rotary atomizer of Figure 1, and Figure 6 is a schematic diagram of a valve system for the rotary atomizer of Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A rotary atomizer 20 according to the present invention includes a housing assembly 21 which can be releasably secured to a manifold assembly 22. The housing assembly 21 in-cludes an outer casing or shroud 23 having a larger diameter end for attachment to the ma~ifold assembly 22 and tapering to an opposite smaller diameter front end. Abutting the opening in the smaller diameter end of the shroud 23 is an annular shaping air cap 24. Attached to the cap 24 is an annular shaping air ring 25 which forms an opening in which is centered an atomizer bell 26.

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13~7~2 The ~ousing a~sembly ~1 can be relea6ab}y attached to the mani~old ~ssembly 22 by a pl~rallty of latche6 havlng a ~irst ~ortion ~7 attached to Qn outer 6ursce Df the 6hroud 23 and ~ ~econd portlo;l 28 ~ttached to an outer 6ur~ace of the manifold assembly 22. As ~hown, three g~nerally equally ~pacet latchiDg ~ech~ni6m~ are utilized, but any conven~ent number and 6pacing of conventional latching ~echani~s are suitable. Ihe manifold ss6embly 22 lncludes a generally cylindrical ~anifold body 29 ~o ~hich the eecond latch portion6 2B a~e affi~ed to the outer curved surface thereof.
Al~o attached to ~he curved 6urfaee o~ ~he ~anifolt bDdy 29 i6 a radially 1~ extending 6tud a6sembly 30 for attach~ænt ~o a de~ice for posltloning the rotary atomizer 20 at a ~ork 6tation 6uch 8~ an indu~trial robot or reclprocating mechanism (not 6hown~.
The msnlfold bodg 29 has a central ~perture 31 formed theretn for the delivery of coating flu~d to the hou6~ng as~embly 21 as wlll be 1~ di~cu66ed below. Al~o, a plurallty of itting6 e~tend from the 6urface of the manifold body 29 which faces the larger diameter end of the ~hroud 23.
These fittings i~clude a ~haplng air fit~ing 32, an exhaust air fleting 33, a bearlng alr fl~ting 34, a turbine sir fltting 35 and a brake air fi~tlng 36. Al~o fQrmed ln the m~n~fold ~ody 29 i6 ~ ~peed monltor access ~ port 37 utilizet to carry 6ignals representing ~he speed of the a~r turbine motor~ For e~ample, the alr turb~ne ~otor can be fitted ~ith a ~a~netic pickup for ~enerating pul~es repre~enting the revolution6 of ~he turbine.
Signal-carrylng ~ire6 from the pickup can be e~tended through the acce6s port 37 to ~ high voltsge lsolation device and t~en to 6ultable monitorlng and di6play equlp~ent (~ot shown).
The rotary aeomizer 20 of Fig. 1 iB chown ln a fr gmentary, cro~s-6ectlonal 6ide elevational vie~ in Fig. 2. The housing assembly 21 ~nd the ma~$fold a6~e~bly 22 ~re 6hown c~nnected by the fir~t lstch por~ion6 27 and the ~econd latch pcrtion~ 28~ The ~anl~old body 29 has an outer planar ace 38 and a generally parallel ~ner planar face 39 bet~een which extend a plurality of spertures formln~ p~sages for the various fluid~ ~hich are ~upplied to the h~using ~s~embly 21. An apertuse 40 ls reprefientative of ~ive ~uch pssssges~ one for each of the 6haping air, exhau~t air, bearing ais, turblne air, and brake air. The end of the pas~age~ay 40 stJacent the ~ace 38 1~ threaded to receive a co~nection to a : , , ;~:

13278~2 source of ~haping air (not ~hown). Typlcally~ ~ conventional ~ourc~ of pressured air i8 conneo~ed to a line having B threaded fitting on the end thereof ~o threadably engage the pa~sageway 40. The end Df thc pas6ageway 40 adjacent ~he lnner planar face 39 is also threaded and threadably rereive~ ~ne end of the fittlng 32.
The pr~ruding end of the fitting 32 retaln6 an "0" rlng 41 ln a ~uitable groove ~nd extend~ ~to an aperture 42 formed in a mountin~ rlng 43 ~hich extend6 around the lnner periphery of ~he lsrger d$ameter end of the 6hroud 23. A planar face 44 of rhe ~ount~g ri~g 43 ~b~ts the face 39 of the m2nifold body 29. The ~pe~ing of the aperture 42 to the face 44 ls tBpered BO as to guide the flttlng 32 ~nd the ~0 ring 41 lnto the aperture 42 ~herenpon the ~0 rlng 6eals ag~lnst the walls of the aperture 42. Thua, the manlfold body 29, the fitting 3Z, the ~0" rlng 41 and the ~ountlng ring 43 cooperate to 6eal the 6haping air path from its 60urce through the manifold as~e~bly 22 and lnto the hou6ing assembly 21. A
6ealed path for each of the brake air, exhaust air, turbine air, and bearing air lc for~ed ln a similar manner to the rear cover of the housing. When the latch portionc 27 and 28 are released, the hou6ing a6se~bly 21 can be essily separa~ed from the manlfold a6~embly 22 whtch can remaln sttached to the robot or reciproc~tor.
The ~ou~ting rirg 43 engage~ ~ flange 45 formed on one end of an alr be~ring turblne 3~tor 46. The ~ounting ring 43 i8 attached to the ~otor 46 with one or oore threaded fastener~ 47 e~tending through a radial ~perture formed ln the mounting ring 43 and lnto thseaded engage~ent ~ith a ~5 threadet aperture for~ed ln the flange 45. ~ plurallty of aperture6 (n~t ~own) are for~ed ln 8 rear c~p 48 of the ~otor ~lthln the center area of ~e ring 43 and receive the pro~ruding endc of the flttlng6 33, 34, 35 and 36. Thu6, the end cover 48 ~nd ~he rlng 43 cooperaee ~s a rezr cover plate for the shrout 23. The opposite end of ~he ~urbine ~otor 46 extends through 8n ~nnular ~haping sir ~anlfold 49. The 6haping air manifold 49 i6 at~ached to the ~otor 46 with one or ~Dre threated fastener~ S0 estendlng through a radial ~perture ~or~ed in the ~anifold 49 ~d into threaded engagement wlth a thre~ded aperture in the outer susface of ~he ~otor 46.

', ' ' - :" ' ' ~327882 The radial}y ~xtending ~pertu~e for the f~stener 50 iB formed ln a larger diameter portion 51 of the manifold 49. T~e larger di~meter portion 51 is connected to a 6maller dlameter portion 52 ~hlch iB loca~ed closer to the forward end of the mo~or 46. The 6maller dla~eter portion 52 5 has external threads f or~ed thereon for engaging internal thread~ formed on an inner 6urface of ~he ~nnular ~h~ping ~lr cap 24. The c~p 24 includes 5 ~ma}ler diameter rear portion 53, ~hich threadably engages the portion 52 of the ~anifold 49, and ~ smaller diameter front por~ion 54 connected on opposlte sides of ~ larger dlameter central portlon 55. ~ rearwardly facing outer edge of the central portion 55 has ~ clrcumferential notch 56 formed therein for engaging and retsining 8 leadlng edge of the 6hroud 23. The 6ma11er diameter frone portion 54 hs6 external threads formed thereon for engsging lnternal threads formed on an lnner wall of the ~nnular ~haping air ring Z5.
The turbine ~otor 46 include6 a front cover plate 57 which cooperates with the ~otor houslng to form a r~dially extending groove 580 The groove 58 retains an lnner edge of sn ~nnular ~haping air ~sp retainer 59. An cuter edge of the cap retainer 59 engages an inner 6urfsce of the ~haping air cap 24. Extending from the cover plste 57 i6 a forward end of a threaded driv~ 6haft 60 upon whlch is ~ounted the atomlzer bell 26.
A ~ource of pres~ured air (~ot ~hown) ls connected to the pi6ton chamber of a conventional fluid valve 61 which in turn i6 connectçd to a valvè fluld ~6se~bly 62. The valve fluid as6embly 62 lncludes one or more 2S radlally extending threaded spertureR 63 for connection to a source of coating fluit (~t shown). The valve fluid sssembly 62 ex~end~ lnto ~nd is threadably e~gaged in the central sperature 31 form~d tn the ~nifold body ~9. The valve piston ~ssembly 61 includes A 6tem 61~ which extends through the valve fluid assembly 62 3nd terminates in ~ ealing element 61b which cooperate~ wi~h 8 sealing ~urface formed in the aperture 31. ~hus, ~hen air pressure exceedi~g a predeter~lned value 16 applied to the v~lve 61, the valve will open to atmi~ the coa~lng fluid from ~he valve fluld a6se~bly 62 thereby forc$ng coatin~ fluid through the central aperture 31 in the manifold 2ssembly 22. The ~nd of the central aperture 31 ad~acent the f~ce 39 receive6 one end of ~ rigld fluld feed tube or line 64.

13278~2 The fluid line 64 retain6 sin ~0" rlng 65 ~ an e~tern,~l ~0" rlng groove to seal again6t the lnner 6~rface of the central ~iperture 31. The fluid line 64 extend6 through the flange 45, the ce~ter of the fluid ~otor 46 and the dri~e ~haft 60 ~nd terminates at the forward ~nd of the ~rl~e ~haft.
Aetached to and extending from the interior o~ the fluid llne 64 i5 ~ fluid nozzle 66. ~he atomizer bell 26 has ~i central sperture fo~med thereln which 16 closed by a clrcular 6plash plate 67. ~6 will be di6cu66ed below, the Kiplash plate 67 has an ln~ardly facing conic~l center ~hich e~tend6 lnto the open end of the fluid no2z}e 66 which end is l~ter~ially tapered to m~tch the ~sper on the 6plash plate 67.
The aperture 42 ~ the ~unt~ng rlng 43 i6 connected to one end of a barbed fltting 68. The barbed end of the ~itting 68 16 in6erted into one end of a len~th of 1exible tublng 69. A 6iecond barbed fitting 70 hss lts bsrbed end lnserted lnto the opposite end of ~he plece of tubing 69.
The barbed f~ttlng 70 i~ connected to an aperture 71 formed in the larger ~ameter portion 51 of the 6hapin~ air manlfold 49. The aperture 71 extends longitudinally through ~he 6haping alr ~nifold 49 and i~ open to a cavity 72 def~ned by the ~haping air ~anifold 49, thP ~ihaping siir cap 24, the shaping air csip retainer 59 and the housing of the turbine ~otor 46. A
longltudi~ally ~xtending pa66~geway 73 i6 ~or~ed through the 6ma11er dls~eter ~ront portlon 54 and the larger d~meter central portion 55 of the ~haplng alr cap 24 to connect the cavlty 72 with a cavity 74 formed between the exterior 6iurf~ce of the smaller dia~eter front portlon 54 of the 6haplng alr cap 24 a~d the interlor ~urface ~f the ~haping air ring 25 .
~ the shaping a~r ring 25 i6 threaded onto the shaping air cap 24, the outer ~urf~ice of the ~haplng air rlng 25 forward of the cavity 74 will engage or abut the inner 6urface of the forward end of the 6haplng ais C8p 24 to prevent the 6haplng air from e~itln~ from the cavity 74. ~ioweve~ ~ plurallty of grooves or Eilo~s 75 ~6howmi in Fig. 4) sre formed ln the outer w rf~ce of the forward e~d of the front portlon 54 and are generally equslly 6paeed about the periphery. The6e 610ts 75 permlt ~he ~haping air to exlt the ~avity 74 ~etween the cap 24 and the r~ng ~5 and flow lDito an annulsr ~pace 75a between the 6p~eed sipart forward endEi of the c~ip 24 and the ring 25- The shsplng alr exlt~ the annular ~pace 75a st the forward etge6 thereof ~d~acent ~n oueer edge 76 ~f the atomiPer bell 26.

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~327882 The slots 75 are formed at an angle to the longltudinal axls o~
the houslng assembly 21 to provide an inwardly directed stream of shaplng alr about the circumferential edge 76. The slots 75 and the annular space 75a dellver the shaping alr as a thln ring to offset the momentum of the atomlzed coating fluid partlcles which escape ln a radial direction from the edge of the bell 26. The inwardly dlrected shaping air provldes a æmall pattern and greater efficiency to the shaping air for controlling the radial pattern of the atomized fluid.
The exhaust air from the turbine motor 46 ls normally expelled from an aperture (not shown) in the planar end 48, lnto the flttlng 33 and through the manifold bo~y 29 to an exhaust air line (not shown). However, the exhaust alr can be expelled from one or more apertures 45a ln the flange 45 lnto a cavlty 77 formed between the motor 46 and the shroud 23. A passageway 78 extends through the larger diameter central portion S5 of the shaping air cap 24 to connect the cavity 77 with a cavlty or chamber 79 formed between the inner surface o~ the shaplng alr cap 24 and the outer surface of the atomizer bell 26. As the exhaust air passes through the cavity 77, it cools the turbine motor 46 and reduces the heat generated by the internally mounted air bearings. The exhaust ~ir exits the cavlty 79 between the forward end of the shaping alr cap 24 and the outer edge 76 of the atomizer bell 26 to aid the shapiny alr exlting the annular space 75a. This air prevents coatlng fluid from wrapping back around the outside of the shroud 23 as well as enterlng the chamber 79. Also, since the exhaust air exits ln a forward direction, lt reduces the amount of shaplng alr required to drive the coating fluid toward the target.

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8a 27905-12D
Also, more shaping air ls normally re~uired to offset the increas-ed momentum of the coatlng partlcles as the atomlzer speed in-creases. Slnce the volume of exhaust air lncreases as the speed of the turblne motor 46 increases, the exhaust alr helps to meet the need for more shaping air.
In Fig. 3, the surface 38 of the manifold body 29 and the stud assembly 30 are shown in more detail. The stud assembly 30 lncludes a generally cylindrlcal post 80 extendlng in a radlal dlrection from a semi-circular mounting bracket 81 secured to the outer clrcumferential surface of the manifold body 29 by a pair Oe fasteners 82. As stated above, the stud assembly 30 ls adapted to be attached to an arm of a robot or ., . ~ , . .

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reciproc~tor- A180 6hown ~n ~lg. 3 a~e the threaded pas~ageway 83 for conuection to an exhaust line, ~ ~hreaded pa~sageway 84 for connectlon ~o a ~ource of bearing air, a threaded pa~sage~ay 85 for connectlon to a source of turbine alr, nd a threaded passage~ay B6 for connection to ~ ~ource of brAke air. The exhaust ~perture 83 can be bloc~ed or provided ~ith a restrlctor ~alve to tirec~ the e~.haus~ a~r lnto ~he cavity 77~
. Fig. 4 i6 a 61de elevational v~e~ of the forward ends Df the eap 24, the ring 25, ~he bell 26, and the ~plash pl~te 67 and a portlon of the cavity or chamber 79 of Flg. 2 ln par~lal cro~s-~ectlon. The body of the splash plate 67 i~ di6k-ghaped with a V-~haped groove 90 for~ed iD the clrcu~ferential etge thereof. The groove 90 engages ~ radially extending flange 90a formed tn the opening ln the atom¢zer bell 26. Ihus, the splash plate 67 16 a 6nap f~t in 6uch opening. A re~rwardly ~acing surface 91 of the spla6h plate 67 has a conlcal extenslon 92 ce~erally locsted thereon. A
1~ pair of dia~etrically opposed pas~agewsy 93 ~re formed through the conicalextenslon 92 to connect with an spereure 94 formed in a forwardly facing ~urface 95 of the 6plash plate 67.
During rotation of the ato~izer bell 26 and the splash plate 67, coating fluld will exlt the fluid noz~le 66 and spread over the 6urf~ce of the con$cal exten~lon 92. Uader ce~trlfugal force, the coatlng fluid will flo~ ou~ onto the rearwardly fAclng ~rface 91 of ~he 6plash plate 67 and o~to ~ rearwardly ~cing 6urface 96 of the atomizer bell 26. The fl~id will then flow through pa6sageway 97 which represents one of a plursllty of such pa~sage~ay6 equally epaced ln a clrcular pst ern and connectlng the 2S ~urface 96 to the for~ardly facing ~urface of the outer edge 76 of the atomizer bell~ A ~All portion of ~he coatlng fluid will also flsw through the passages 93 ~nt lnto the aperture 94. Th~6 fluid will flo~ from the aperture 94 over the forwardly faoing surface 95 of the 6plash plate 67 and onto the forwardly faci~g 6~rf~ce of the atom~er bell 26 toward the ~ ~0 passageway 97. Therefore, ~ ~hin f~l~ of ~et coating fluid will be ; ~a~ntalned on ~he central portion~ of the ~to~izer bell 26 and ~plashplate 67 a~ an a~d to cleanin those part6 wlth ~olvent 8~ ~ell a~ ~he lnternal and external surf~ce6 of ~he bell 26 which are ~et when ~he coating job has been completet.

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As 6how~ ln Flgo 2, one or ~ore generally ~adially extending aperture~ 98 are formed ln the outer 6urface of 'he s~ap~ng alr r~ng 25.
The aperture 98 are adaptet to be engaged by a ~uit~ble tool for threadin~
the ring 25 lnto ~nt oue of engagement wlth the cap 24. Simllar aperture~
can be for~ed ln the ou~er surf~ce of the cap 24 for threadlng into a~d out ~f engagement ~th the ~anifold 49.
Flg. 5 i6 a schematic diagram of the 6peed l~onitoring circuit for the rotary atomizer of F$g. 1. The motor 46 ~nclude6 a turbine wheel 101 attschet to the drive ~haft 60. ~ pair o~ permanent Dagnet~ 102 sre ~ounted at dls~etricAlly opp~et loca~lon~ ~n the turblne wheel~ ~lthough one Yagnet i8 sufficlent to generate a speed 6ignal, two or ~re ~agnets are typlcally utlli~ed to ma~ntsln the bslancQ of the turbine wheel 101. A
pickup coil 103 ~ncluding ~ ~agnetlc core 104 i6 located sd~acent the path of the magnet 102. The end~ of the plckup coil 103 are connectet to opposite end6 of a single loop of dielectrically ln6ulated hlgh voltage ~ire 105 i~ a ~eries loop. The pickup coil 103 and the ~agnetiG core 104 are positioDed inside the motor 46. The high voltage w~re 105 e~tends through an sperture (not 8hown) ~ormed ln the end cover 4~ and through the ~perture 37 fcrmed ~ the ~anlfold body 29. Typic~lly, the high ~oltage ~ire 105 extends appro~l~ately t~o or ~ore feet from the rotary atomdzer 20 ~nd pa6ses through ehe center of a ~oroldal coil 106. The ent6 of the lsolation coll 106 ~re connec~ed to a conventional 6peed ~onltorlng devlce 107.
E~ch time one o~ the ~agnets 102 pa~ses ~he plckup coil 103, an el~ctr~cal pul8e 16 generated in the coil 103 s~d 1B conducted through the high voltage wire 105. The PU1Be 18 ~nductlvely coupled to the toroidal coil 106 and i6 ~ensed by the ~peed ~onitorlng device 107n The high volta~e ire 105 and the toroidal isolatlon coll 106 provide high vol~sge i601atlon of the fipeed monitorlng circuit from the hi~h voltage power ~upply (not 30 6hown) ~hich 16 connec~ed to the rotary atomizer ln a conventional manner ~o ~lectrostatically charge the psrtlcle6 of coatlng fluid.
The fluld valve 61 snd valve fluit a66embly 62 ~how~ in Fig. 2 can be utilized eo eo~trol the flow of ~ultlple color~ of paint s~d cleaning ~olvent to the rotary ~tomlzer 20. There iB ~hown in Fig. 6 a echematic 3~ diagr~m of a ~alve control circuit i~ ~hleh ~ ~ulttple color psint ; - :;; ~ . .:

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1~7882 ~ource 111 6upplie6 palnt tv B rotary a~omiz r 20. I~le palnt Bource 111 i6 conventio~al nnd typicslly i~cludes ~ plurallty of paint re6ervoirs, one for each color *o be 6prayed, conneceed through valves to ~ m~nlfold. The outlet ~ro~ the pal~t ~ource 111 is ln fluld communicatio~ ~lth ~ valve 112 repre~enting t~e combi~atlon of the fluid ~alve 61 and the valve flu~d ~s~e~bly 62 described ~bove. ~he val~e 112 ln turn 1~ ln fluid communication wlth ~ne inlet o~ an ad~ptes 113 ~hlch hss an outlet ln fluid communication ~ith the rotary ato~izer 20. Ihe outlet of the adapter 113 i6 threaded to engage the central aperture 31 formed in ~he ~an~fold body 29.
~nother valve 114 i6 connectet bet~een ~ du~p reservoir 115 snd the llne between the paint source 111 and the valYe 112. The valve 114 can be the combin~tion of the fluld valve 61 a~d the valve fluid asse~bly 6~. A ~imilar valve 116 ifi connected bet~een ehe adapter 113 and a Bource of 601vent 117.
~hen the rDtary atomizer 20 i6 being utilized to paint an ob~ect such ~ sn automobile, the 6eleeted color of paint i6 forced under pressure irom the palnt 6~uree 111 through the Yal~e 112 ~hlch i8 actuated to the open positlon under air pre6sure. The palnt flow~ through the adapter 113 to the rotary atomizer 20. Typically, the next automobile ~ody to be 6prayed i6 to receive a different color o~ pal~t. The paiat 60urce 111 ~16c~nnect6 the color being u~ilized and ln~ect6 n bead of fiol~ent through the line to~ard the valve 112. However, the valve 112 16 clo6ed and the du~p valve 114 i6 op~ned to the du~p re6ervvir 115. Thus, the e~d of the color ~hich ha6 ~6t been 6prayed flow6 to the du~p re erYolr and ~he bead of solvent clean6 the llne6. The bead of sQlvent 16 follo~ed by the new color to be ~p~ayed a~d the timing i~ ~uch th~t the dump valve 114 1~ not clo6et and the flr6t valve 112 i~ Dot opened untll the bead of ~olvent has pa6sed ~nd the fiecond color i8 nvailable to be directed to the rotary ato~i~er.
At the 6a~e time the color i~ being ~han~ed, the valve 116 i6 o~ened and a high pre6sure, ~hort duration b~r~t of ~ol~eut from the 601vent re~ervoir 117 $8 ~orced through the adapter 11~ a~d the rDtary a~omizer 20 to clean the palnt flow path ant the ato~lz~r bell. The valve 116 1~ then clo~ed before the valve 112 i8 reopenet for the ne~ color.
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In accordance ~ith the provislons of the patent statutes, the presen~ ~nvention has been de6cribed in whae i6 con6idered to repre6ent lts preferred embodiment. ~owever, lt ~hould be noted that the l~vention can be practiced otherwlse than as 6peciflcally illu6trated and described without teparting fro~ lt6 spirit or ccope.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A rotary atomizer for coating with a coating fluid comprising, in combination, a housing, a rotary fluid atomizing device rotatably supported at one end of said housing, said device having a front surface facing away from said housing and a rear surface facing toward said housing and an annular edge from which such coating fluid is discharged by centrifugal force for atomiza-tion, said housing including an annular portion at said one end surrounding at least a portion of said atomizing device, said annular portion and said rear surface of said device forming a chamber therebetween which opens behind said annular edge, an air driven turbine located in said housing and connected for rotating said atomizer device, said turbine generating pressurized exhaust air during operation, said chamber having an annular opening formed between said annular edge of said atomizing device and said housing and vented to atmosphere, means for delivering said turbine exhaust air to said chamber for maintaining said chamber above atmospheric pressure during operation of said rotary atom-izer to prevent atomized coating fluid from entering said chamber, said annular opening directing turbine exhaust air at atomized fluid discharged from said annular edge, wherein said housing includes an air cap surrounding at least a portion of said rear surface of said atomizing device, said air cap including an annular opening surrounding said annular chamber opening located for directing pattern shaping air at atomized fluid discharged from said annular edge of said device, and means for delivering pressurized air to said annular air cap opening.

2. A rotary atomizer for spraying a coating fluid as set forth in claim 1, and including outlet means for venting turbine exhaust air from said chamber in a direction to prevent accumulation of atomized fluid on said housing.

3. A rotary atomizer for spraying a coating fluid com-prising, in combination, a housing, a rotary fluid atomizing device rotatably supported at one end of said housing, said device having a front surface facing away from said housing and a rear surface facing toward said housing and an annular edge from which such coating fluid is discharged by centrifugal force for atomization, said housing including an annular portion at said one end surrounding at least a portion of said atomizing device, said housing including an air cap surrounding at least a portion of said rear surface of said atomizing device, said air cap including an annular opening located for directing pattern shaping air at atomized fluid discharged from said annular edge of said device, means for delivering pressurized pattern shaping air to said annular air cap opening, said annular housing portion and said rear surface of said device forming a chamber therebetween which opens behind said annular edge, an air driven turbine located in said housing and connected for rotating said atomizer device, said turbine generating pressurized exhaust air during operation, means for delivering said turbine exhaust air to said chamber for maintaining said chamber above atmospheric pressure during operation of said rotary atomizer to prevent atomized paint from entering said chamber, said housing further including a shroud surrounding said turbine, and wherein said turbine includes an exhaust outlet open to an interior of said shroud, and wherein said means for delivering said turbine exhaust air to said chamber includes passageway means for connecting said shroud interior to said chamber.

4. A rotary atomizer for spraying a coating fluid as set forth in claim 3, wherein said passageway means is formed in said air cap.

5. A rotary atomizer for spraying a coating fluid as set forth in claim 4, wherein said exhaust outlet is located at one end of said turbine and said passageway means is located adjacent an opposite end of said turbine such that exhaust air flows through said shroud from said exhaust outlet to said passageway means over an exterior surface of said turbine and said housing to cool said turbine.

6. A rotary atomizer for spraying a coating fluid as set forth in claim 3, and including outlet means for venting turbine exhaust air from said chamber in a direction to prevent accumulation of atomized fluid on said shroud.