CA1164645A - Rotary atomizing coater - Google Patents
Rotary atomizing coaterInfo
- Publication number
- CA1164645A CA1164645A CA000379370A CA379370A CA1164645A CA 1164645 A CA1164645 A CA 1164645A CA 000379370 A CA000379370 A CA 000379370A CA 379370 A CA379370 A CA 379370A CA 1164645 A CA1164645 A CA 1164645A
- Authority
- CA
- Canada
- Prior art keywords
- shaft
- air
- rotary atomizer
- flow
- speed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000011248 coating agent Substances 0.000 claims abstract description 26
- 238000000576 coating method Methods 0.000 claims abstract description 26
- 239000002245 particle Substances 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 11
- 230000003247 decreasing effect Effects 0.000 claims description 3
- 238000000889 atomisation Methods 0.000 abstract description 9
- 239000003973 paint Substances 0.000 description 40
- 239000007788 liquid Substances 0.000 description 4
- 101100409194 Rattus norvegicus Ppargc1b gene Proteins 0.000 description 1
- 102100034742 Rotatin Human genes 0.000 description 1
- 101710200213 Rotatin Proteins 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 108010085990 projectin Proteins 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
- B05B5/04—Discharge apparatus, e.g. electrostatic spray guns characterised by having rotary outlet or deflecting elements, i.e. spraying being also effected by centrifugal forces
- B05B5/0422—Discharge apparatus, e.g. electrostatic spray guns characterised by having rotary outlet or deflecting elements, i.e. spraying being also effected by centrifugal forces comprising means for controlling speed of rotation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
- B05B5/04—Discharge apparatus, e.g. electrostatic spray guns characterised by having rotary outlet or deflecting elements, i.e. spraying being also effected by centrifugal forces
- B05B5/0415—Driving means; Parts thereof, e.g. turbine, shaft, bearings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
- B05B5/04—Discharge apparatus, e.g. electrostatic spray guns characterised by having rotary outlet or deflecting elements, i.e. spraying being also effected by centrifugal forces
- B05B5/0426—Means for supplying shaping gas
Landscapes
- Nozzles (AREA)
- Electrostatic Spraying Apparatus (AREA)
Abstract
Abstract of the Disclosure An improved coating applicator of the type having a high speed rotary atomizer driven by an air turbine. A governor controls the speed of the air tur-bine to provide more uniform atomization throughout a wide range of loads on the atomizer.
Description
Rota~Atomlz~ Coater Backqround of the Irlventioll This inVentiOrl relates to coa tin-J apparatus and more particularly to an improved rotary a~omizing coater for depositing pairlt and similar materia] on a work piece.
One type of commercial coating apparatus for paint, and the like, comprises a rotar~ clisc or bell and an air motor Eor driving the disc or bell at a high speed. Paint deliverecl to the surface of the rapidly rotatin~J disc or bell is thrown off in small E~articles throu~h centrifucJal force. The surface of the bell is charcJed to a high voltage relative to the work piece so as to electro-statically charc3e the paint particles. The atomized charged paint particles are directed at and coat the work piece through a combination of the charge on the paint particles and, preferably, also a surrounding stream of air discharged from -the coater.
In one common commercial app:lication of coaters of this type, the coaters are mounted alon~ the path of a conveyor which carries the work pieces past the coaters.
The delivery of paint to the rotary atomizing coa-ter is turned on and off throu~h a suitable valve as work pieces enter and leave the coating area so as to minimize waste.
When the paint flow is shut off, the air motor driven bell ~5 tends to accelerate to a speed considerably higher than its normal operating speed due to the removal of the paint load. The hiyher rotational speed of the bell produces a finer particle size in the atomized paint. Con~
sequently, the particle size clecreases as the paint ~low is terminated and the initial paint particle size is smaller than normal when paint flow is first initiated~
Adjus-tments in the paint flow rate also chan~e the load on the atomizin~ bell and, consequentl~, affects the speed of the bell which in turn afEects the particle size.
Hiclher bell speeds resultin(J from a :lower t:han norlna.l, S
paint Elow rate rnay result ill.su~h a fine particle size that the pdint particl~s dry belore they reach the work piece. The fineness of tile atomization affects the color shadincJ, the surrace appearallc~, the transfer efficiency or perc~ntage of paint deposi-tedon the work sur~ace, the wrap-around and the edc~e coverage o~ the work piece. Optimizing the particle size can rnaximize the transfer effici.ency, give goocl ed~e covcrage with accept-able paint buildup on the edge of a panel, and control the wrap-around on -the back of a panel. The coverage will be adversely affected by chanc3~s in the speed of the atomizer bell as the palnt flow is triggered on and Of ~A
The air motor used for driving khe high speed atomiza-tion bell in a rotary atomizer coater is often an air driven turbine. It is known in the prior art that a govexnor may be built into an air turbine for limiting;the maximum speed of the turbine ou-tput ~haft. Such a governor is illustrated, ~or example, in United States patent 3,708,2~0. Mowever, this and other prior art does not use a governor in an air turbine which drives a rotary atomizer in order to maintain an o~timum paint particle size while the load on the atomization bell changes.
Su~nary of the Invention __. . . ..
According to the present invention, a yovernor is provided for a rotary atomizer driven by an air turbine so as to optirmize paint particle size through~varying loads. In one preferred embodiment, the air turbine generally comprises a hollow shaft on which a turbine wheel is mounted. Compressed air is supplied from a suitable source througll a rotating seal and the hollow shaft to the turbine wheel for drivinc3 the turbine.
valve located within the turbine shaft rnodulates the air ~low to the turbine wheel in rcsponse l:o the turbine speed to maintain a more unlForrn turbi.ne~ speed durinc3 changes ln loadinc3 on the rotary atornizer~ ~n atomi.zat:ion ~ . .... .
bell or disc is mounted on an ~nd ~f -the ~lrbine ~h.~ft Paint is suppliecl to a chamb~r wi-thin the bell ~nd such paint is discharged froTn thc bell through centrifugal force as the bell is ~apidly rotatecl. The bell is ~naintained at a hiqh electrical po-tential so as to electros-ta-tica~:ly charge the paint pàrticles dischar~ed from the bell. In addition, air is discharged in a pattern around the ~ell and towards the work surface so as to control the pattern of the discharged paint particles. Through the use of the governor for controlling the speed of the atomization bell, the uniformity of the paint par-ticles is greatly increased even though the flow rate of the paint is varied.
In a modified embodiment of the invention, the air modulating va]ve is located in the air supply hose. The speed of the turbine shaft is sensed electricall, mag-netically or optically and is ~upplied to a microprocessor which genera-tes .1 control signa] for modulating the valve to maint~jn a constant turbine speed.
Accordingly, it is an ohject of the invention to provide an improved rotary atomizing coater.
Ano-ther object of the inven-tion is -to provide a rotary atomizing coater driven by an air turbine in which the uni~ormity of the coating is maintained even though the flow rate of the coating material to the rotary atom--izer is increased or decreased.
Other objects and advarltages of the invention will become apparent from the following detailed description, with reference being made to the accornpanying drawing.
~rief Descri~tion of the Drawin~
J`he singl~ figure i~ a siclc elevational view in partial section of a rotary atomizing coater constructed in accordance with the present inventioll.
Detailed Descriptiol~
Turning now to the sing]e ~i3ure, a rotary atomizing coater 10 is shown construet:e(3 in accordance with the presen-t inven-~ion. The coater 10 ge~nerally co~nprises an air turbine 11 which drives an atomization bell 12 The air turbine 11 dri~es the bell 12 at hiyh ro~ational speeds, for example, in the rancle of 10,000 r.p.m. to ~0,000 r.p.m. or more. The air turbine 11 ineludes an internal governor for maintainincJ substanti~llly constant the spped at which the bell 12 is rotatecl r even though the load on the bell 12 may change due to changes in the lQ paint ~low rate or ehailges i~ the paint cdensity when, for example, the paint color is changed. The ~ubstantially eonstant speed is a function of the turbine air 5~1pply pres~ure.
Th~ air turbine 11 inclucles a main housing 5ection 13 which has a generally circular cros.s section and mounts a tuhular exten5ion 14. A shaft 15 is nlount~d within the housing section 13 and tubular extension 14 and is sup-ported by a plurality of bearings 16. The shaft 15 has an end 17 which mount~ t.he atomization bell 12 and has a hollow end 18 which is coupled throuyh a suitable rotary seal (not shown) to a compressed air hose :L9. The hollow shaft ~nd 18 de~ines an interior chamber 20 which cor~uni-cat~s throuc3h side openings 21 to the interior 22 of a turbine wheel 23. Compressed air normally f]ows from the air hose :L9 -throught the interior shaft chamber 20, the openinc3s 21 and the turbine wheel chamber 22 to radially directecl openings 24 on the turbine wheel 23 and thence the air is vented through rear openings 25 in the main housincJ section 13. The air flowing through the turbine ~heel 23 causes the turbine wheel 23 to rotate the shat 15 at a high rate of speed which is dependent~upon the load on the shaft 15, the air flow rate and the alr pressure.
The speed of the air turbine 11 is controlled by a goverrlor 2~ which i~ located within the shaft eham~er 20 for controllincJ a:ir flow from Ihe air hose ].9 to the turbine wheel cllamber 22. 'rhe (~overnor 28 inclucles a piston 29 whictl slides wlthin ~lle ctlamber 20 iiltO and out . . -- . _ . ~,, ~4~4S
of ~n~Jayement with a valve seat 30. The piston 2g ha~ a valve surface 31 which, when abul:tin~3 the valve seat 30, blocks air flow from the air hose :L9 to the turbi.ne wheel 23. A spring 32 urges the piston 29 against the valve seat 30 to block air flow in the turbine 23. At the same time, the compresse~ alr within the chamber Z0 acts upon a face 33 on the piston 29 to move the piston 29 against the spring 32, there~y opening the passageway from the chamber 20 to the turbine wheel interior chamber 22. A hole 34 extends through the piston 29 to allow a restrict(_d ~low o~ the compressed ai.r within -the chamber 20 throu~h the pi.ston 29 -to a chamber 35 located between the piStOIl 29 and an insert 36~ ~s wi].1 be shown below, the chamber 35 may be vented to the atmosphere or may be plugged, ~ependincJ upon -the action o~ the governor re-quired to mai.ntain a constant shaft speed. When the chamber 35 i.s vented to the atmosphere, the compressed air in the cham~er 20 applies a signifi.cantly higher force to the piston face 30 than appears at a face 37 on an opposite e~d of the piston 29. The difference in ~orce is sufficient to compress the spring 32, thereb~ openin~ the air flow passages from the chamber 20 into the turbi.ne wheel interior 22. On the other hand, i.f the chamber 35 is not vented -to the atmosphere, the compressed air will ~low through the piston hole 34 to pressurize the chambex ~5 a-t the same pressure as the chamber 20. Since the ~orces applied by the compressed air on the faces 33 and 37 o~ the piston 29 axe identical, the sprinc~ 32 acts to move the piston 29 into contact with the valve seat 30 to block the flow of air from the chamber 20 to the turbine wheel interior 22, thereby stop~)in-J the turbine. sy modulating the posltion of the pi.ston 29, the flow o~ air from the chamber 20 to the turbine wheel intexior 22 i.s modulate~] to control the speed at which the shaf-t 15 l.s 3~ rotated.
~6~ S
~ centrifugally actuatecl ~all valve 40 controls the air pressure within the chanlber 35. A valve seat: 41 i5 formed between a passage 42 in the insert 36 which com-municates ~Jlth the chamber 35 and a passaye 43 which is vented to atmospnere through an annular region between the shaft 15 and the tubular extension 14. A tubular plug 49 retains a ball 45 adjacellt the valve seat 41 while leavi.ng clearance for the l~all 45 to move into and out of contact with the seat ~31. The ball 45 is located so that at all times its center is positioned to the side of the a~is of the shaft 15 toward the seat 41. Conse-quently, as the shaft 15 is rotatec3 at an increasing speed, centrifu~al force urcJes the ball 45 a~ain~t the seat 41 with an increasing force.
1~ In operation, at slow speeds of the turbine wheel 23 the compressed air from the hose 19 is allowed to flow throuqh the piston hole 34, the chamber 35, the passage 42 and the passage 43 and thence is vented to the atrrlos-pnere~ Co3~sequently, the chamber 35 will have a pressure near or at atmospheric pressure ancl the pressure on the piston face 33 will move the piston 29 to allow an unrestricted air flow from the charnher 20 to the turbine wheel interior 22. As the speed of the shaftll~ increases, the ball 45 is folced more ti~htly against thé seat 41 and the pressure within the charnber 35 increases. The air pressure within the chamber 35 act.s against the piston ~ace 37 to offset the air pressure ac-ting on the piston face 33. ~t some increasing turbine speed, the increasing pressure within -the chamber 35 alony with the pressure of the spring 32 moves the piston 29 to progressively close the air flow passages frorn the chamber 20 to the turbine wheel int~rio3- 22. At this point, the r3peed of the sha~t 15 i~ co3ltrc)lled at n cons~ant level Thus, when load is removed fro~n atornization bbl]. 12 and the sha~t 15 tends to accelerclte, the piston 29 will mo~e to further c]ose thr air ~low passage and govern the speed S
of the shaf-t 15. The yovernor con-trolled speed is a function of the turbin~ air suppl~ pre~sure.
The end 17 o:E the shaft 15 e~tcnds through and projects from a ~ani~old 48. The atomizati.on~bell 12 is mounted on the projec-tin~J sha.Et end 17. ~ paint hose ~9 .is connected to deliver paint ~hrouyh a pas-sage 50 in the manifold 48 and thence through an ori-~ice 51 to an annular ~hamber 52 formed on the back of ~ the atomization bell ~ . As the hell 12 rotates at a high speed the paint within the cha~er 52 is thrown rad.ially outwardly and flows along a conical surEace 55. The paint continues to Elow outwardly along the surface 55 until it is thrown from an outer edge 56 on the bell 12 in the form of sma.l.]. particles The size of the discharged particles is de-termined by various factors including the rotatlonal speed of the bell 12, the flow rate of the paint and the properties of the paint.
~ir is supplied to the manifold 48 through a fit-ting (not shown) similar to 49. ~ passage similar to the passage 50 connects the air supply fit-ting to an annular chamber 59 located in a m~nifold face 60. A
plurality of openings 61 extend through the manifold face 60 and communicate with the chamber 59. The opening5 61 are uniforml~ spaced around the shaft and cause an ~ir flow which 5urrounds the bell 12 for directing the paint particles thrown off from khe bell 12 toward~ the work piece.
To prevent paint or solvent from entering the turbine 11 or the bearing 16 an annular slinger 62 is positioned on the shaft 15. The slin~er 62 ro-tates with the shaft 15 and prevents liquid from creeping along the shaf-t 15. The slinger includes a lip 63 which overlaps a fixed annular seal 65. The seal 64 is threaded i.n-to the tubular exten.C;ion 1~ and ... .... . ..
s -B-does not rotate with the sllaft 15. In cross~section,the seal 6~ has a cup shaped or hooked lip 65 located radiallyinward ~rom the slinger ].ip f~3. I;'low of any liquid coming into cont~ct wit]l t:hc 51i ncJer 63 will be thrown off onto the manifold 48 and ~7ill drain through a hole 57. Th~ liquid would have to follow a torturou5 path to continue along the sha:Et 15.
Teflon or polytetrafluroethylene annular seal 66 has a close running fit to the shaft 15. This serves to further restrict any possible Eluid flow alony the axial length of shaft 15. Thus, the slinger 62, the seal 64 and the seal 66 prevent the flow of liquid along the shaft 15 into the ai.r -turbine ll and the bearing 16.
In accordance with the present invention, the air turbine which drives the atomization bell for the rotary a-tomizing coater is yoverned to rnaintain a fai.rly constant speed for the atomi.æation bell throughout varying paint loads on the atomiæation bell. The governor 2a for regulating the turbine shaft speed has been described as being located within the turbine shaft 15. In a modified embodiment of the invention, an air flow con-trol valve may be located extern~l to the coater 10, for example, within the ~5 air supply hose 19, rather than within thc turbine shaft 15.. A conventional electrical, magnetic or optical sensor may be connected to gencrate a signal indicative of the speed of tile air turbine shaft.
This signal is applied to a microprocessor which in turn generates a signal for modulatirlg the air con-trol valve to regulate the tur~ine speed. Still another method of achieviny an approximately constant rotational speed for the air turbine f or uni f orm atomi~ation with varying paint flow is by measuring the paint flow rate. The pai.nt flow rate then is . . .
co~pared in a look up tahl~ with previou~1~ measured paint flo~ rate data versu.s alr flow rate data. The relationsh:ip be-tween the paint, flow rate, turbine air supply pressure and turbine speed are stored in a microprocessor. The microprocessor selects the pro-per turbine air supply pressure to produce the desired rotational speed and, accordingly, actuates an ~ir flow control valve.
Various modifications and changes may be made in the above described preferred ernbodimellts of the in-vention without departing from the splrit and the scope of the following claims. For example, onl~ an exemplary governor mounted withill the air turbine has been described. Other yovernor desiyns are recognized lS in the ,air turbine art,
One type of commercial coating apparatus for paint, and the like, comprises a rotar~ clisc or bell and an air motor Eor driving the disc or bell at a high speed. Paint deliverecl to the surface of the rapidly rotatin~J disc or bell is thrown off in small E~articles throu~h centrifucJal force. The surface of the bell is charcJed to a high voltage relative to the work piece so as to electro-statically charc3e the paint particles. The atomized charged paint particles are directed at and coat the work piece through a combination of the charge on the paint particles and, preferably, also a surrounding stream of air discharged from -the coater.
In one common commercial app:lication of coaters of this type, the coaters are mounted alon~ the path of a conveyor which carries the work pieces past the coaters.
The delivery of paint to the rotary atomizing coa-ter is turned on and off throu~h a suitable valve as work pieces enter and leave the coating area so as to minimize waste.
When the paint flow is shut off, the air motor driven bell ~5 tends to accelerate to a speed considerably higher than its normal operating speed due to the removal of the paint load. The hiyher rotational speed of the bell produces a finer particle size in the atomized paint. Con~
sequently, the particle size clecreases as the paint ~low is terminated and the initial paint particle size is smaller than normal when paint flow is first initiated~
Adjus-tments in the paint flow rate also chan~e the load on the atomizin~ bell and, consequentl~, affects the speed of the bell which in turn afEects the particle size.
Hiclher bell speeds resultin(J from a :lower t:han norlna.l, S
paint Elow rate rnay result ill.su~h a fine particle size that the pdint particl~s dry belore they reach the work piece. The fineness of tile atomization affects the color shadincJ, the surrace appearallc~, the transfer efficiency or perc~ntage of paint deposi-tedon the work sur~ace, the wrap-around and the edc~e coverage o~ the work piece. Optimizing the particle size can rnaximize the transfer effici.ency, give goocl ed~e covcrage with accept-able paint buildup on the edge of a panel, and control the wrap-around on -the back of a panel. The coverage will be adversely affected by chanc3~s in the speed of the atomizer bell as the palnt flow is triggered on and Of ~A
The air motor used for driving khe high speed atomiza-tion bell in a rotary atomizer coater is often an air driven turbine. It is known in the prior art that a govexnor may be built into an air turbine for limiting;the maximum speed of the turbine ou-tput ~haft. Such a governor is illustrated, ~or example, in United States patent 3,708,2~0. Mowever, this and other prior art does not use a governor in an air turbine which drives a rotary atomizer in order to maintain an o~timum paint particle size while the load on the atomization bell changes.
Su~nary of the Invention __. . . ..
According to the present invention, a yovernor is provided for a rotary atomizer driven by an air turbine so as to optirmize paint particle size through~varying loads. In one preferred embodiment, the air turbine generally comprises a hollow shaft on which a turbine wheel is mounted. Compressed air is supplied from a suitable source througll a rotating seal and the hollow shaft to the turbine wheel for drivinc3 the turbine.
valve located within the turbine shaft rnodulates the air ~low to the turbine wheel in rcsponse l:o the turbine speed to maintain a more unlForrn turbi.ne~ speed durinc3 changes ln loadinc3 on the rotary atornizer~ ~n atomi.zat:ion ~ . .... .
bell or disc is mounted on an ~nd ~f -the ~lrbine ~h.~ft Paint is suppliecl to a chamb~r wi-thin the bell ~nd such paint is discharged froTn thc bell through centrifugal force as the bell is ~apidly rotatecl. The bell is ~naintained at a hiqh electrical po-tential so as to electros-ta-tica~:ly charge the paint pàrticles dischar~ed from the bell. In addition, air is discharged in a pattern around the ~ell and towards the work surface so as to control the pattern of the discharged paint particles. Through the use of the governor for controlling the speed of the atomization bell, the uniformity of the paint par-ticles is greatly increased even though the flow rate of the paint is varied.
In a modified embodiment of the invention, the air modulating va]ve is located in the air supply hose. The speed of the turbine shaft is sensed electricall, mag-netically or optically and is ~upplied to a microprocessor which genera-tes .1 control signa] for modulating the valve to maint~jn a constant turbine speed.
Accordingly, it is an ohject of the invention to provide an improved rotary atomizing coater.
Ano-ther object of the inven-tion is -to provide a rotary atomizing coater driven by an air turbine in which the uni~ormity of the coating is maintained even though the flow rate of the coating material to the rotary atom--izer is increased or decreased.
Other objects and advarltages of the invention will become apparent from the following detailed description, with reference being made to the accornpanying drawing.
~rief Descri~tion of the Drawin~
J`he singl~ figure i~ a siclc elevational view in partial section of a rotary atomizing coater constructed in accordance with the present inventioll.
Detailed Descriptiol~
Turning now to the sing]e ~i3ure, a rotary atomizing coater 10 is shown construet:e(3 in accordance with the presen-t inven-~ion. The coater 10 ge~nerally co~nprises an air turbine 11 which drives an atomization bell 12 The air turbine 11 dri~es the bell 12 at hiyh ro~ational speeds, for example, in the rancle of 10,000 r.p.m. to ~0,000 r.p.m. or more. The air turbine 11 ineludes an internal governor for maintainincJ substanti~llly constant the spped at which the bell 12 is rotatecl r even though the load on the bell 12 may change due to changes in the lQ paint ~low rate or ehailges i~ the paint cdensity when, for example, the paint color is changed. The ~ubstantially eonstant speed is a function of the turbine air 5~1pply pres~ure.
Th~ air turbine 11 inclucles a main housing 5ection 13 which has a generally circular cros.s section and mounts a tuhular exten5ion 14. A shaft 15 is nlount~d within the housing section 13 and tubular extension 14 and is sup-ported by a plurality of bearings 16. The shaft 15 has an end 17 which mount~ t.he atomization bell 12 and has a hollow end 18 which is coupled throuyh a suitable rotary seal (not shown) to a compressed air hose :L9. The hollow shaft ~nd 18 de~ines an interior chamber 20 which cor~uni-cat~s throuc3h side openings 21 to the interior 22 of a turbine wheel 23. Compressed air normally f]ows from the air hose :L9 -throught the interior shaft chamber 20, the openinc3s 21 and the turbine wheel chamber 22 to radially directecl openings 24 on the turbine wheel 23 and thence the air is vented through rear openings 25 in the main housincJ section 13. The air flowing through the turbine ~heel 23 causes the turbine wheel 23 to rotate the shat 15 at a high rate of speed which is dependent~upon the load on the shaft 15, the air flow rate and the alr pressure.
The speed of the air turbine 11 is controlled by a goverrlor 2~ which i~ located within the shaft eham~er 20 for controllincJ a:ir flow from Ihe air hose ].9 to the turbine wheel cllamber 22. 'rhe (~overnor 28 inclucles a piston 29 whictl slides wlthin ~lle ctlamber 20 iiltO and out . . -- . _ . ~,, ~4~4S
of ~n~Jayement with a valve seat 30. The piston 2g ha~ a valve surface 31 which, when abul:tin~3 the valve seat 30, blocks air flow from the air hose :L9 to the turbi.ne wheel 23. A spring 32 urges the piston 29 against the valve seat 30 to block air flow in the turbine 23. At the same time, the compresse~ alr within the chamber Z0 acts upon a face 33 on the piston 29 to move the piston 29 against the spring 32, there~y opening the passageway from the chamber 20 to the turbine wheel interior chamber 22. A hole 34 extends through the piston 29 to allow a restrict(_d ~low o~ the compressed ai.r within -the chamber 20 throu~h the pi.ston 29 -to a chamber 35 located between the piStOIl 29 and an insert 36~ ~s wi].1 be shown below, the chamber 35 may be vented to the atmosphere or may be plugged, ~ependincJ upon -the action o~ the governor re-quired to mai.ntain a constant shaft speed. When the chamber 35 i.s vented to the atmosphere, the compressed air in the cham~er 20 applies a signifi.cantly higher force to the piston face 30 than appears at a face 37 on an opposite e~d of the piston 29. The difference in ~orce is sufficient to compress the spring 32, thereb~ openin~ the air flow passages from the chamber 20 into the turbi.ne wheel interior 22. On the other hand, i.f the chamber 35 is not vented -to the atmosphere, the compressed air will ~low through the piston hole 34 to pressurize the chambex ~5 a-t the same pressure as the chamber 20. Since the ~orces applied by the compressed air on the faces 33 and 37 o~ the piston 29 axe identical, the sprinc~ 32 acts to move the piston 29 into contact with the valve seat 30 to block the flow of air from the chamber 20 to the turbine wheel interior 22, thereby stop~)in-J the turbine. sy modulating the posltion of the pi.ston 29, the flow o~ air from the chamber 20 to the turbine wheel intexior 22 i.s modulate~] to control the speed at which the shaf-t 15 l.s 3~ rotated.
~6~ S
~ centrifugally actuatecl ~all valve 40 controls the air pressure within the chanlber 35. A valve seat: 41 i5 formed between a passage 42 in the insert 36 which com-municates ~Jlth the chamber 35 and a passaye 43 which is vented to atmospnere through an annular region between the shaft 15 and the tubular extension 14. A tubular plug 49 retains a ball 45 adjacellt the valve seat 41 while leavi.ng clearance for the l~all 45 to move into and out of contact with the seat ~31. The ball 45 is located so that at all times its center is positioned to the side of the a~is of the shaft 15 toward the seat 41. Conse-quently, as the shaft 15 is rotatec3 at an increasing speed, centrifu~al force urcJes the ball 45 a~ain~t the seat 41 with an increasing force.
1~ In operation, at slow speeds of the turbine wheel 23 the compressed air from the hose 19 is allowed to flow throuqh the piston hole 34, the chamber 35, the passage 42 and the passage 43 and thence is vented to the atrrlos-pnere~ Co3~sequently, the chamber 35 will have a pressure near or at atmospheric pressure ancl the pressure on the piston face 33 will move the piston 29 to allow an unrestricted air flow from the charnher 20 to the turbine wheel interior 22. As the speed of the shaftll~ increases, the ball 45 is folced more ti~htly against thé seat 41 and the pressure within the charnber 35 increases. The air pressure within the chamber 35 act.s against the piston ~ace 37 to offset the air pressure ac-ting on the piston face 33. ~t some increasing turbine speed, the increasing pressure within -the chamber 35 alony with the pressure of the spring 32 moves the piston 29 to progressively close the air flow passages frorn the chamber 20 to the turbine wheel int~rio3- 22. At this point, the r3peed of the sha~t 15 i~ co3ltrc)lled at n cons~ant level Thus, when load is removed fro~n atornization bbl]. 12 and the sha~t 15 tends to accelerclte, the piston 29 will mo~e to further c]ose thr air ~low passage and govern the speed S
of the shaf-t 15. The yovernor con-trolled speed is a function of the turbin~ air suppl~ pre~sure.
The end 17 o:E the shaft 15 e~tcnds through and projects from a ~ani~old 48. The atomizati.on~bell 12 is mounted on the projec-tin~J sha.Et end 17. ~ paint hose ~9 .is connected to deliver paint ~hrouyh a pas-sage 50 in the manifold 48 and thence through an ori-~ice 51 to an annular ~hamber 52 formed on the back of ~ the atomization bell ~ . As the hell 12 rotates at a high speed the paint within the cha~er 52 is thrown rad.ially outwardly and flows along a conical surEace 55. The paint continues to Elow outwardly along the surface 55 until it is thrown from an outer edge 56 on the bell 12 in the form of sma.l.]. particles The size of the discharged particles is de-termined by various factors including the rotatlonal speed of the bell 12, the flow rate of the paint and the properties of the paint.
~ir is supplied to the manifold 48 through a fit-ting (not shown) similar to 49. ~ passage similar to the passage 50 connects the air supply fit-ting to an annular chamber 59 located in a m~nifold face 60. A
plurality of openings 61 extend through the manifold face 60 and communicate with the chamber 59. The opening5 61 are uniforml~ spaced around the shaft and cause an ~ir flow which 5urrounds the bell 12 for directing the paint particles thrown off from khe bell 12 toward~ the work piece.
To prevent paint or solvent from entering the turbine 11 or the bearing 16 an annular slinger 62 is positioned on the shaft 15. The slin~er 62 ro-tates with the shaft 15 and prevents liquid from creeping along the shaf-t 15. The slinger includes a lip 63 which overlaps a fixed annular seal 65. The seal 64 is threaded i.n-to the tubular exten.C;ion 1~ and ... .... . ..
s -B-does not rotate with the sllaft 15. In cross~section,the seal 6~ has a cup shaped or hooked lip 65 located radiallyinward ~rom the slinger ].ip f~3. I;'low of any liquid coming into cont~ct wit]l t:hc 51i ncJer 63 will be thrown off onto the manifold 48 and ~7ill drain through a hole 57. Th~ liquid would have to follow a torturou5 path to continue along the sha:Et 15.
Teflon or polytetrafluroethylene annular seal 66 has a close running fit to the shaft 15. This serves to further restrict any possible Eluid flow alony the axial length of shaft 15. Thus, the slinger 62, the seal 64 and the seal 66 prevent the flow of liquid along the shaft 15 into the ai.r -turbine ll and the bearing 16.
In accordance with the present invention, the air turbine which drives the atomization bell for the rotary a-tomizing coater is yoverned to rnaintain a fai.rly constant speed for the atomi.æation bell throughout varying paint loads on the atomiæation bell. The governor 2a for regulating the turbine shaft speed has been described as being located within the turbine shaft 15. In a modified embodiment of the invention, an air flow con-trol valve may be located extern~l to the coater 10, for example, within the ~5 air supply hose 19, rather than within thc turbine shaft 15.. A conventional electrical, magnetic or optical sensor may be connected to gencrate a signal indicative of the speed of tile air turbine shaft.
This signal is applied to a microprocessor which in turn generates a signal for modulatirlg the air con-trol valve to regulate the tur~ine speed. Still another method of achieviny an approximately constant rotational speed for the air turbine f or uni f orm atomi~ation with varying paint flow is by measuring the paint flow rate. The pai.nt flow rate then is . . .
co~pared in a look up tahl~ with previou~1~ measured paint flo~ rate data versu.s alr flow rate data. The relationsh:ip be-tween the paint, flow rate, turbine air supply pressure and turbine speed are stored in a microprocessor. The microprocessor selects the pro-per turbine air supply pressure to produce the desired rotational speed and, accordingly, actuates an ~ir flow control valve.
Various modifications and changes may be made in the above described preferred ernbodimellts of the in-vention without departing from the splrit and the scope of the following claims. For example, onl~ an exemplary governor mounted withill the air turbine has been described. Other yovernor desiyns are recognized lS in the ,air turbine art,
Claims (8)
1. A coating applicator comprising: a rotary atomizer mounted on a shaft, an air-driven turbine connected to rotate said shaft, means for supplying a controlled flow of coating material to said rotary atomizer, and governor means for maintain-ing said air-driven turbine at a substantially constant speed as the flow of coating material to said rotary atomizer changes.
2. A coating applicator comprising: a rotary atomizer mounted on a shaft, an air-driven turbine connected to rotate said shaft, means for supplying a controlled flow of coating material to said rotary atomizer, such flow of coating material to said rotary atomizer changing in response to triggering of such coating applicator between off and on positions, and gover-nor means for maintaining said air-driven turbine and said rotary atomizer at a substantially constant speed during the same coat-ing operation as the flow of coating material to said rotary atomizer changes whereby the size of coating material particles thrown from the rotary atomizer remains relatively constant.
3. A coating applicator as defined in claim 1, wherein said governor means includes valve means for controlling the flow of air through said air-driven turbine, and means responsive to the speed of said shaft for positioning said valve means to limit the speed of said shaft.
4. A coating applicator as defined in claim 2, wherein said governor means includes valve means for controlling the flow of air through said air-driven turbine, and means responsive to the speed of said shaft for positioning said valve means to limit the speed of said shaft.
5. A coating applicator, as defined in claim 3, wherein said air-driven turbine is formed on said shaft and wherein said valve means is located within said shaft.
6. A coating applicator as defined in claim 4, wherein said air-driven turbine is formed on said shaft and wherein said valve means is located within said shaft.
7. A coating applicator, as defined in claim 5 or 6, wherein said means responsive to the speed of said shaft includes a second valve located within said shaft and having a movable element responsive to an increase in centrifugal force for closing said second valve.
8. A coating applicator comprising: a rotary atomizer mounted on a shaft, an air-driven turbine operatively connected to said shaft for rotating said shaft, means for supplying a pre-determined flow of coating material to said rotary atomizer, such flow of coating material increasing or decreasing upon triggering of said applicator between on an off positions wherein the load on said atomizer and said shaft is decreased or increased, and governor means for maintaining said rotary atomizer at a sub-stantially constant speed during the same coating operation dur-ing an increase or decrease of the load on said atomizer result-ing from an increase or decrease of the flow of coating material being supplied to said rotary atomizer whereby the size of the coating material particles being thrown from said rotary atomizer remains relatively constant, said governor means including ad-justable valve means for controlling air flow through said air-driven turbine in response to the speed of said rotary atomizer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US18326680A | 1980-09-02 | 1980-09-02 | |
| US183,266 | 1980-09-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164645A true CA1164645A (en) | 1984-04-03 |
Family
ID=22672120
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379370A Expired CA1164645A (en) | 1980-09-02 | 1981-06-09 | Rotary atomizing coater |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5745357A (en) |
| AU (1) | AU543407B2 (en) |
| BE (1) | BE889767A (en) |
| BR (1) | BR8105520A (en) |
| CA (1) | CA1164645A (en) |
| DE (1) | DE3133857A1 (en) |
| FR (1) | FR2489174A1 (en) |
| GB (1) | GB2082940B (en) |
| IT (1) | IT1171496B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2087264A (en) * | 1980-11-19 | 1982-05-26 | Graco Inc | A speed control apparatus for operating a centrifugal atomiser |
| US4491276A (en) * | 1982-07-06 | 1985-01-01 | Speeflo Manufacturing Corporation | Electrostatic spray apparatus |
| JPS6086469U (en) * | 1983-11-22 | 1985-06-14 | トリニテイ工業株式会社 | Electrostatic oil applicator |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3404823A (en) * | 1965-01-11 | 1968-10-08 | Metco Inc | Flame spray gun with improved drive mechanism |
| US3708240A (en) * | 1971-07-30 | 1973-01-02 | Hollymatic Corp | Speed governor |
| FR2360351A1 (en) * | 1976-08-04 | 1978-03-03 | Ransburg Sa | ATOMIZING CENTRIFUGAL HEAD FOR ELECTROSTATIC SPRAYING EQUIPMENT |
| DE3002206A1 (en) * | 1980-01-18 | 1981-07-23 | Ransburg Corp., Indianapolis, Ind. | Vehicle spray gun motor speed control device - utilises optical head assembly to detect rotational speed of patterned disc |
-
1981
- 1981-05-28 JP JP56080222A patent/JPS5745357A/en active Pending
- 1981-06-09 CA CA000379370A patent/CA1164645A/en not_active Expired
- 1981-07-28 BE BE0/205514A patent/BE889767A/en not_active IP Right Cessation
- 1981-08-27 DE DE19813133857 patent/DE3133857A1/en not_active Withdrawn
- 1981-08-28 GB GB8126306A patent/GB2082940B/en not_active Expired
- 1981-08-28 IT IT49196/81A patent/IT1171496B/en active
- 1981-08-28 BR BR8105520A patent/BR8105520A/en unknown
- 1981-08-31 AU AU74770/81A patent/AU543407B2/en not_active Ceased
- 1981-09-01 FR FR8116637A patent/FR2489174A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT1171496B (en) | 1987-06-10 |
| GB2082940A (en) | 1982-03-17 |
| AU7477081A (en) | 1982-03-11 |
| BE889767A (en) | 1981-11-16 |
| IT8149196A0 (en) | 1981-08-28 |
| BR8105520A (en) | 1982-05-18 |
| DE3133857A1 (en) | 1982-04-15 |
| GB2082940B (en) | 1984-06-13 |
| FR2489174A1 (en) | 1982-03-05 |
| JPS5745357A (en) | 1982-03-15 |
| AU543407B2 (en) | 1985-04-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |