CA1250194A - Cleaning method upon color-change in an electrostatic multi-color coating apparatus - Google Patents
Cleaning method upon color-change in an electrostatic multi-color coating apparatusInfo
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- CA1250194A CA1250194A CA000500948A CA500948A CA1250194A CA 1250194 A CA1250194 A CA 1250194A CA 000500948 A CA000500948 A CA 000500948A CA 500948 A CA500948 A CA 500948A CA 1250194 A CA1250194 A CA 1250194A
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- paint
- color
- cleaning
- hose
- palnt
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Abstract
ABSTRACT OF THE DISCLOSURE
Cleaning method upon color-change in an electro-static multi-color coating apparatus adapted to supply paints of a multiplicity of colors, a cleaning air and a cleaning thinner selectively from a color-change device by way of a paint supply channel and a paint hose to an electrostatic multi-color coating machine, comprises suc-cessively steps of supplying a cleaning air and a cleaning thinner to the paint supply channel and cleaning the inside thereof by removing to discharge the paint remaining in the paint supply channel to a liquid discharge tank, sucking the paint remaining in the electrostatic coating machine and in the paint hose connected at one end thereof to the electrostatic coating machine from the other end of the paint hose and discharging the paint thus sucked to the liquid discharge tank, and then supplying a cleaning thinner and a cleaning air to the paint hose and the electrostatic coating machine to clean the inside thereof.
Cleaning method upon color-change in an electro-static multi-color coating apparatus adapted to supply paints of a multiplicity of colors, a cleaning air and a cleaning thinner selectively from a color-change device by way of a paint supply channel and a paint hose to an electrostatic multi-color coating machine, comprises suc-cessively steps of supplying a cleaning air and a cleaning thinner to the paint supply channel and cleaning the inside thereof by removing to discharge the paint remaining in the paint supply channel to a liquid discharge tank, sucking the paint remaining in the electrostatic coating machine and in the paint hose connected at one end thereof to the electrostatic coating machine from the other end of the paint hose and discharging the paint thus sucked to the liquid discharge tank, and then supplying a cleaning thinner and a cleaning air to the paint hose and the electrostatic coating machine to clean the inside thereof.
Description
Thls Inventlon concerns a cleanlng method Upon color-change In an electrostatlc multl-color coatlng apparatus In whlch palnts of a multlpliclty of colors are selectlvely supplled under color-change to an electrostatlc coatlng machlne havlng an atom-Izlng cup applled w;th a hlgh voltage and rotatlonally drlven ata hlgh speed.
It has been desired In the electrostatlc multl-color coatlng apparatus of thls type to reduce the cleanlng tIme requlred for color-change as short as poss~ble.
In vlew of the above, cleanlng alr and cleanlng thlnner are alternately supplled at high pressure to a palnt supply chan-nel connected between an electrostatlc coatlng machlne and a color-change device, so that the Inside of the color supply chan-nel and the atomlzlng cup of the electrostatlc coatlng machlne can be cleaned rapldly.
In thls method, however, slnce the cleanlng alr and the cleanlng thlnner are supplled at a great flow rate In a short tIme to the Inslde of the Palnt supply channel, palnt and palnt-contalnlng thinner are Instantaneously dlscharged In a great amount from the atomlzlng cup of the electrostatlc coatlng machlne, whlch overflow from a dlscharged llquld recoverlng shroud dlsposed around the perlphery of the atomlzlng cup of the electrostatlc coatlng machlne and are scattered around to contam-lnate perlpheral equlpments or the coatlng machlne maln body.
Accordlngly, thls inventlon provldes a cleanlng method upon color-change In an electrostatlc multl-color coatlng appara-tus for cleanlng a palnt supply channel and a palnt hose when supplylng a palnt selected from a color-change devlce to the electrostatlc coatlng machlne whlle preventlng the Palnt from scatterlng out of the atomlzlng cup of the coatlng machlne, by dlscharglng a palnt remalnlng in the palnt supply channel uslng a cleanlng alr and a cleanlng thlnner supplled from the color-.. \
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change devlce Into a liquld dlscharge tank and sucklng to remove the palnt remalning In the palnt hose connected at one end thereof to the coating machine from the other end thereof by means of an e)ector.
Accordlng to the present Inventlon there Is provlded a cleanlng method upon color-change In an electrostatlc mu I tl-color coatlng apparatus adapted to supply palnts of a multlpllclty of colors, a cleanlng alr and a cleanlng thlnner selectlvely from a color-change devlce by way of a palnt supply channel and a palnt hose to the atomlzlng cup of an electrostatlc multl-color coatlng machlne, whlch method comprlses successIve steps of: (a) changlng the connectlon of sald palnt supply channe I front that wlth sald palnt hose to that wlth a fIrst llquld dlscharge channel leadlng 1~ to a llquld dlscharge tank upon completlon of palnt coatlng, (b) supplylng a cleanlng alr and a cleanlng thlnner from sald color-change devlce to sald palnt supply channel, thereby dlscharglng the palnt remalnlng In sald palnt supply channel to sald llquld dlscharge tank and cleanlng the Inslde of sald palnt supply chan-nel, whlle (c) connectlng sald palnt hose to a second llquId dls-charge channel leadlng to sald tank, (d) sucklng the palnt remalnlng In sald electrostatlc coatlng machlne and In sald palnt hose and dlscharglng sald palnt by way of an eJector dlsposed In sald second llquld dlscharge channel to sald llquld dlscharge tank, and then (e) supplylng a cleanlng thlnner and a cleanlng alr to sald palnt hose and sald electrostatlc coatlng machlne thereby cleanlng the Insldes thereof.
Thus, the Inventlon provldes a cleanlng method upon color-change In an electrostatic multl-color coatlng apparatus adapted to supply palnts of a multlp!lclty of colors, a cleanlng alr and a cleanlng thlnner selectlvely from a color-change devlce by way of a palnt supply channel and a palnt hose to an electro-statlc multl-color coatlng machlne, whlch method comprlses suc-cesslvely steps of supplylng a cleanlng alr and a cleanlng thln-ner to the palnt supply channel and cleanlng the Inslde thereof by removlng to dlscharge the palnt remalnlng In the palnt supply channel to a llquld dlscharge tank, a second step of sucklng the palnt remainlng In the electrostatlc coatlng machlne and In the palnt hose connected at one end thereof to the coatlng machlne from the other end of the hose and dlscharglng the palnt thus sucked to the liquId dlscharge tank, and then a thlrd step of supplylng a cleanlng thlnner and a cleanlng alr to the palnt hose and the electrostatlc coatlng machlne to clean the Inslde thereof.
In accordance with thls Inventlon, the palnt remalnlng in the palnt supply channel connected to the color-change devlce Is dlscharged Into the llquld dlscharge tank by the cleanlng alr and the cleanlng thlnner supplled from the color-change devlce, whlle the palnt remalnlng In the electrostatlc coatlng machlne and In the palnt hose connected thereto are sucked by an eJector and dlscharged Into the llquld dlscharge tank and, thereafter, the cleanlng thlnner and the cleanlng alr are supplled to the palnt hose for cleanlng the Inslde thereof. Thus, slnce the palnt remalnlng In the palnt supply channel and the palnt hose Is not dlscharged as usual by belng blown out of the electrostatlc coatlng machlne, the trouble experlenced so far that the palnt dlscharged from the electrostatlc coatlng machlne Is scattered around to contamlnate the perlpheral equlpments and the coatlng machlne maln body.
The present Inventlon wlll now be descrlbed by way of a preferred embodlment wlth reference to the accompanylng drawlngs, whereln:-Flgure 1 Is a system chart showlng the schematlc con-stltutlon for one embodIment of an electrostatlc multl-color coatlng apparatus to whlch the method accordlng to thls Inventlon Is applled; and ~, ~ `
Flgure 2 Is a tlme chart Illustratlng one embodlment of the method accordlng to thls Inventlon.
~0 CONSTITUTION OF THE EMBODIMENT
In the drawings, there are shown an atomizing cup or bell 1 of an electrostatic coating machine which is applied with a high voltage and rotationally driven at a high speed, a first color-change device 2 supplied with paints of a multiplicity of colors from a plurality Or paint supply sources (not illustrated), cleaning air and cleaning thinner and a second color-change device 3 which is smaller in size than the first color-change device 2 and disposed near the atomizing cup (or, simply, cup) 1 of the electro-static coating machine, and supplied with paints of at least one color, cleaning airs at high and low pressures and cleaning thinners at high and low pressure.
A first paint supply channel ~ is extended over a relatively long distance from the first color-change device 2 toward the cup 1 of the electrostatic coating machine and connected to a first switching valve 7, which is disposed near the cut 1 and has 2-way exit channels 5 and 6 for supplying a paint of a desired color selected from the color-change device 2 to the cup 1.
The switching valve 7 is connected at one exit channel 5 thereof by way o~ a liquid discharging ON-OFF valve ~ to a liquid discharge channel 9, which is further connected to a .iquid discharge tank 10, while the other exit channel 6 is connected by way of a shorter paint hose 11 to the cup 1.
A second palnt supply channel 12 much shorter than the flrst palnt supply channel 4 Is dlsposed for supplylng a palnt selected by the second color-change devlce 3 to the cup 1 of the electrostatlc coatlng machlne, and the channel 12 Is connected to a second swltchlng valve 1~, whlch Is dlsposed near the cup 1 and had 2-way exlt channels 13 and 6.
The swltchlng valve 14 Is dlsposed between the flrst swltchlng valve 7 and the palnt hose 11, In whlch the exlt chan-nel 13 on one slde Is connected by way of a llquld dlscharglngON-OFF valve 1~ to a llquld dlscharge channel 16 and the exlt channel 6 on the other slde Is used In common wlth the exlt chan-nel 6 of the flrst swltchlng valve 7 and connected by way of the palnt hose 11 to the cup 1.
The llquld dlscharge channel 16 from the ON-OFF valve 15 Is connected to the llquld dlscharge tank 10 by way of an eJector 17. The eJector Is a devlce usually called a Jet pump or an eJector adapted to Jet fluld at high speed and hlgh pressure to cause a low pressure area to whlch low pressure fluld Is con-nected and sucked In and dlscharged hydrodynamlcally wlth the Jet. The eJector 17 has a port a for Introduclng a hlgh pressure alr stream for sucklng llquld palnt from the channel 16 by the sudden drop of pressure near the hlgh speed alr stream and a dls-~S charge port b for dlscharglng the resultlng alr-palnt mlxture to the llquld dlscharge tank 10.
The flrst color-change devlce 2 comprlses a plurallty of color-change valves CV1-CV13 connected to palnt supply sources of dlfferent colors (not Illustrated) respectlvely, a low pres-sure alr supply valve LE1, a hlgh pressure alr supply valve HE1 and a hlgh pressure thlnner supply valve HS1.
The second color-change devlce 3 comprIses a color 3S change valve CVw supplled wlth a palnt, for example, of whlte palnt and a color-change valve CVr supplled wlth a \
paint 7 for example 9 of red color both of which are used frequently, a low pressure air supply valve LE2 and a high pressure air supply valve HE2, as well as a low pressure thinner supply valve LS2 and a high pressure thinner supply valve HS2.
A shroud 18 is disposed retractably to the cup l.
OPERATION OF THE EMBODIMENT
The schematic constitution of the electrostatic coating apparatus for use in automobiles has been described in conjunction with Figure l. The method of this invention using such an illustrated apparatus will now be described specifically also referring to the time chart shown in Figure 2.
Assuming for instance, such a case where a white paint and a red paint most frequently used as the colors for a car body are supplied respectively to the color-change valves CVw and CVr of the second color-change device 3 disposed near the cup 1 of the electrostatic coating machine and an automobile of whi-te color (not illustrated) is conveyed into a painting region, a high voltage is at first applied to the cup l and, at the same time, it is rotationally driven at a high speed.
Then, the second switching valve 14 is opened while the first switching valve 7 is being closed, to thereby establish a flow path from the second color-change device 3 by way ~s~
of the second paint supply channel l2 and the paint hose 11 to the cup 1. Subsequently, the color-change valve CVw disposed to the second color change device 3 is opened to supply a white paint through the thus rormed ~low path.
Coating ls thus started, and the white paint is released rrom the cup 1 under electrostatiC atomization and coated electrostatically to -the surface of the car body being conveyed.
Then, the color-change va~ve CVw is closed just before the completion Or the coating and, at the same time, the low pressure air supply valve LE2 is opened to supply a cleaning air at low pressure about at the same level as that of the white paint having been supplied from the color-change valve CVw to the inside of the second paint supply channel 12.
In this way, the white paint is electrostatically atomi~ed from the cup 1 continuously till the completion Or the coating, so that non-painted areas are not le~t on the car body, as well as most o~ the paint which would otherwise remain in the flow path is discharged under electrostatic atomization and can be used effectively with no loss.
When the coating has thus been completed, the low pressure air supply valve LE2 is closed and, at the same time, the number Or rotation for the cup 1 is reduced and the shroud 18 retractably disposed near the cup 1 is ~"'h~
advanced so as to surround the cup 1. Then, after closing the second switching valve 14 and opening the liquid discharging ON-OFF valve 15, the high pressure air supply valve HE2 disposed to the second color-change device 3 is intermittently opened to discharge the white paint still remaining in the second paint supply channel 12 by way Or the liquid discharge channel 16 to the liquid discharge tank 10.
Then, the second switching valve 14 is opened in this state and the e~ector 17 is actuated to suck the paint remaining in the paint hose 11 and discharge the paint by way of the liquid discharge channel 16 to the inside of the liquid discharge tank 10. In this case, a small amount of the cleaning thinner may preferably be supplied from the low pressure thinner supply valve LS2 disposed to the second color-change device 3 to the paint hose 11 to dilute the residual paint in the paint hose before the actuation of the e~ector 17. This can much facilitate the sucking and discharging of the residual paint by the e~ector 17.
Then, after closing the second switching valve 14, the high pressure thinner supply valve HS2 and the high pressure air supply valve HE2 disposed to the second color-change device 3 are alternately opened and closed to clean the inside of the liquid discharge channel 16.
Subsequently, the liquid discharging ON-OFF valve 15 is closed, and the low pressure thinner supply valve LS2 and the low pressure air supply valve LE2 of the second color-change device 3 are successively opened to supply the low pressure cleaning thinner and the low pressure cleaning air by way of the second paint supply channel 12 and the paint hose 11 to the inside Or -the cup 1. Thus, the paint hose 11 and the cup 1 can be cleaned finely.
In this way, since only the cleaning thinner and the cleaning air under low pressure are discharged from the cup 1, there is no trouble as experienced so rar that the residual paint discharged from the cup 1 is scattered to the outside of the shroud 18 to contaminate the peripheral equipments and the electrostatic coating machine main body In a case where color Or the the coating paint is changed to that o~ a paint, for instance, supplied to the color change-valve CV1 of the first color-change device 2 (for example, blue paint) after the cleaning has thus been completed, the second switching valve 14 is closed and the first switching valve 7 is opened to est~blish a flow path communicating from the ~irst color-change device 2 by way Or the first paint supply channel 4 and the paint hose 11 to the cup 1. Meanwhile, the shroud 18 is retracted from the cup 1 and the number of rotation for the cup 1 is increased to a predetermined number Or rotation.
Then, the coating is started again by opening the color-change valve CV1 and supplying the blue paint supplied to the valve CV1 by way Or the flow path to l9~
the cup 1 thereby applying electrostatic coating on a succeeding car body now being conveyed.
Just before the completion of the coating~ the color-change valve CVl is closed and, simultaneously, the low pressure air supply valve LEl is opened to supply the low pressure cleaning air about at the same level as that of the paint supplied from the color-change valve CVl.
Thus, the paint in the first paint supply channel 4 is supplied to the cup 1 ~or electrostatic atomization continuously till the completion of the coating and, accordingly, most o~ the paint which would otherwise remain in the first paint supply channel 4 is electrosta-tically atomized ~rom the cup 1 and can be used effectively with no loss.
When the coating has thus been completed, the low pressure air supply valve LEl is closed and, at the same time, the number of rotation of the cup 1 is reduced and the shroud 18 is advanced so as to surround the cup 1.
Then, after closing the first switching valve 7 and opening the liquid discharging ON-OFF valve 8, the high pressure air supply valve HEl and the high pressure thinner supply valve HSl disposed to the first color-change device 2 are alternately opened to discharge the paint remaining in the first paint supply channel 4 by way of the liquid discharge channel 9 to the liquid discharge tank 10, by which the inside of the first paint supply ~5~
channel 4 is cleaned rapidly. In addition, af-ter closing the first switching valve 7 and opening the second switchlng valve 14 and the liquid discharging ON-OFF valve 15, the e~ector 17 is actuated to suck the paint remaining in the paint hose 11 and discharge it by way Or the liquid discharge channel 16 to the liquid discharge tank 10 as described above.
The liquid discharging ON-OFF valve 15 is then closed and the low pressure thinner supply valve LS2 and the low pressure air supply valve LE2 of the second color-change device 3 are successively opened to supply cleaning thinner and the cleaning air at low pressure by way of the second paint supply channel 12 and the paint hose 11 to the inside of the cup 1. Thus, the paint hose 11 and the cup 1 are cleaned finely.
Accordingly, since only the cleaning thinner and the cleaning air are discharged at low pressure from the cup 1 also in this case, there is no worry as has been experienced so far that the residual paint is discharged from the cup 1 and scattered to the outside of the shroud 18 to conta-minate the peripheral equipments and the electrostatic coating machine main body with the scattered paint.
As described above, a paint of particular color used most frequently is supplied from the second color-change device 3 disposed near the cup 1 of the electrostatic coating machine by way Or an extremely short second paint 9~
supply channel 12 and the hose 11 to the cup 1, whereby the amount of the paint used can be saved.
Further, since the paint in the relatively long rirst paint supply channel 4 connected between the ~irst color-change device 2 and the ~irst switching valve 7, as well as that in the second paint supply channel 12 connected between the second color-change device 3 and the second switching valve 14 are supplied by the cleaning air at low pressure to the cup 1 ~ust be~ore the completion o~ the coating, the residual amount o~ the paint in the first and the second paint supply channels 4 and 12 upon completion o~ the coating is extremely reduced, whereby the amount of the paint discharged as the discharge liquid can be decreased to ~acilitate the cleaning operation as well as reduce the loss of the paint.
Furthermore and particularly, since the paint remaining in the paint hose 11 and the cup 1 was previously discharged by the e~ector 17 to the liquid discharge tank 10 before the low pressure cleaning air and the low pressure cleaning thinner are supplied ~rom the second color-change device 3 to the paint hose 11 and the cup 1 for cleaning them, there is no worry as has been experienced so ~ar that the paint remaining in the paint hose is ~etted out ~rom the cup 1 and scattered around to the outside of the shroud 18 to contaminate the peripheral equipments and the electro-static coating machine main body.
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Although this invention has been described for the purpose o~ illustrated by way of its prererred embodiments shown in the appended drawings, it will be apparent to those skilled in the art not various modifications and alterations may be made without departing the spirit and scope of this invention.
_ 14
It has been desired In the electrostatlc multl-color coatlng apparatus of thls type to reduce the cleanlng tIme requlred for color-change as short as poss~ble.
In vlew of the above, cleanlng alr and cleanlng thlnner are alternately supplled at high pressure to a palnt supply chan-nel connected between an electrostatlc coatlng machlne and a color-change device, so that the Inside of the color supply chan-nel and the atomlzlng cup of the electrostatlc coatlng machlne can be cleaned rapldly.
In thls method, however, slnce the cleanlng alr and the cleanlng thlnner are supplled at a great flow rate In a short tIme to the Inslde of the Palnt supply channel, palnt and palnt-contalnlng thinner are Instantaneously dlscharged In a great amount from the atomlzlng cup of the electrostatlc coatlng machlne, whlch overflow from a dlscharged llquld recoverlng shroud dlsposed around the perlphery of the atomlzlng cup of the electrostatlc coatlng machlne and are scattered around to contam-lnate perlpheral equlpments or the coatlng machlne maln body.
Accordlngly, thls inventlon provldes a cleanlng method upon color-change In an electrostatlc multl-color coatlng appara-tus for cleanlng a palnt supply channel and a palnt hose when supplylng a palnt selected from a color-change devlce to the electrostatlc coatlng machlne whlle preventlng the Palnt from scatterlng out of the atomlzlng cup of the coatlng machlne, by dlscharglng a palnt remalnlng in the palnt supply channel uslng a cleanlng alr and a cleanlng thlnner supplled from the color-.. \
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change devlce Into a liquld dlscharge tank and sucklng to remove the palnt remalning In the palnt hose connected at one end thereof to the coating machine from the other end thereof by means of an e)ector.
Accordlng to the present Inventlon there Is provlded a cleanlng method upon color-change In an electrostatlc mu I tl-color coatlng apparatus adapted to supply palnts of a multlpllclty of colors, a cleanlng alr and a cleanlng thlnner selectlvely from a color-change devlce by way of a palnt supply channel and a palnt hose to the atomlzlng cup of an electrostatlc multl-color coatlng machlne, whlch method comprlses successIve steps of: (a) changlng the connectlon of sald palnt supply channe I front that wlth sald palnt hose to that wlth a fIrst llquld dlscharge channel leadlng 1~ to a llquld dlscharge tank upon completlon of palnt coatlng, (b) supplylng a cleanlng alr and a cleanlng thlnner from sald color-change devlce to sald palnt supply channel, thereby dlscharglng the palnt remalnlng In sald palnt supply channel to sald llquld dlscharge tank and cleanlng the Inslde of sald palnt supply chan-nel, whlle (c) connectlng sald palnt hose to a second llquId dls-charge channel leadlng to sald tank, (d) sucklng the palnt remalnlng In sald electrostatlc coatlng machlne and In sald palnt hose and dlscharglng sald palnt by way of an eJector dlsposed In sald second llquld dlscharge channel to sald llquld dlscharge tank, and then (e) supplylng a cleanlng thlnner and a cleanlng alr to sald palnt hose and sald electrostatlc coatlng machlne thereby cleanlng the Insldes thereof.
Thus, the Inventlon provldes a cleanlng method upon color-change In an electrostatic multl-color coatlng apparatus adapted to supply palnts of a multlp!lclty of colors, a cleanlng alr and a cleanlng thlnner selectlvely from a color-change devlce by way of a palnt supply channel and a palnt hose to an electro-statlc multl-color coatlng machlne, whlch method comprlses suc-cesslvely steps of supplylng a cleanlng alr and a cleanlng thln-ner to the palnt supply channel and cleanlng the Inslde thereof by removlng to dlscharge the palnt remalnlng In the palnt supply channel to a llquld dlscharge tank, a second step of sucklng the palnt remainlng In the electrostatlc coatlng machlne and In the palnt hose connected at one end thereof to the coatlng machlne from the other end of the hose and dlscharglng the palnt thus sucked to the liquId dlscharge tank, and then a thlrd step of supplylng a cleanlng thlnner and a cleanlng alr to the palnt hose and the electrostatlc coatlng machlne to clean the Inslde thereof.
In accordance with thls Inventlon, the palnt remalnlng in the palnt supply channel connected to the color-change devlce Is dlscharged Into the llquld dlscharge tank by the cleanlng alr and the cleanlng thlnner supplled from the color-change devlce, whlle the palnt remalnlng In the electrostatlc coatlng machlne and In the palnt hose connected thereto are sucked by an eJector and dlscharged Into the llquld dlscharge tank and, thereafter, the cleanlng thlnner and the cleanlng alr are supplled to the palnt hose for cleanlng the Inslde thereof. Thus, slnce the palnt remalnlng In the palnt supply channel and the palnt hose Is not dlscharged as usual by belng blown out of the electrostatlc coatlng machlne, the trouble experlenced so far that the palnt dlscharged from the electrostatlc coatlng machlne Is scattered around to contamlnate the perlpheral equlpments and the coatlng machlne maln body.
The present Inventlon wlll now be descrlbed by way of a preferred embodlment wlth reference to the accompanylng drawlngs, whereln:-Flgure 1 Is a system chart showlng the schematlc con-stltutlon for one embodIment of an electrostatlc multl-color coatlng apparatus to whlch the method accordlng to thls Inventlon Is applled; and ~, ~ `
Flgure 2 Is a tlme chart Illustratlng one embodlment of the method accordlng to thls Inventlon.
~0 CONSTITUTION OF THE EMBODIMENT
In the drawings, there are shown an atomizing cup or bell 1 of an electrostatic coating machine which is applied with a high voltage and rotationally driven at a high speed, a first color-change device 2 supplied with paints of a multiplicity of colors from a plurality Or paint supply sources (not illustrated), cleaning air and cleaning thinner and a second color-change device 3 which is smaller in size than the first color-change device 2 and disposed near the atomizing cup (or, simply, cup) 1 of the electro-static coating machine, and supplied with paints of at least one color, cleaning airs at high and low pressures and cleaning thinners at high and low pressure.
A first paint supply channel ~ is extended over a relatively long distance from the first color-change device 2 toward the cup 1 of the electrostatic coating machine and connected to a first switching valve 7, which is disposed near the cut 1 and has 2-way exit channels 5 and 6 for supplying a paint of a desired color selected from the color-change device 2 to the cup 1.
The switching valve 7 is connected at one exit channel 5 thereof by way o~ a liquid discharging ON-OFF valve ~ to a liquid discharge channel 9, which is further connected to a .iquid discharge tank 10, while the other exit channel 6 is connected by way of a shorter paint hose 11 to the cup 1.
A second palnt supply channel 12 much shorter than the flrst palnt supply channel 4 Is dlsposed for supplylng a palnt selected by the second color-change devlce 3 to the cup 1 of the electrostatlc coatlng machlne, and the channel 12 Is connected to a second swltchlng valve 1~, whlch Is dlsposed near the cup 1 and had 2-way exlt channels 13 and 6.
The swltchlng valve 14 Is dlsposed between the flrst swltchlng valve 7 and the palnt hose 11, In whlch the exlt chan-nel 13 on one slde Is connected by way of a llquld dlscharglngON-OFF valve 1~ to a llquld dlscharge channel 16 and the exlt channel 6 on the other slde Is used In common wlth the exlt chan-nel 6 of the flrst swltchlng valve 7 and connected by way of the palnt hose 11 to the cup 1.
The llquld dlscharge channel 16 from the ON-OFF valve 15 Is connected to the llquld dlscharge tank 10 by way of an eJector 17. The eJector Is a devlce usually called a Jet pump or an eJector adapted to Jet fluld at high speed and hlgh pressure to cause a low pressure area to whlch low pressure fluld Is con-nected and sucked In and dlscharged hydrodynamlcally wlth the Jet. The eJector 17 has a port a for Introduclng a hlgh pressure alr stream for sucklng llquld palnt from the channel 16 by the sudden drop of pressure near the hlgh speed alr stream and a dls-~S charge port b for dlscharglng the resultlng alr-palnt mlxture to the llquld dlscharge tank 10.
The flrst color-change devlce 2 comprlses a plurallty of color-change valves CV1-CV13 connected to palnt supply sources of dlfferent colors (not Illustrated) respectlvely, a low pres-sure alr supply valve LE1, a hlgh pressure alr supply valve HE1 and a hlgh pressure thlnner supply valve HS1.
The second color-change devlce 3 comprIses a color 3S change valve CVw supplled wlth a palnt, for example, of whlte palnt and a color-change valve CVr supplled wlth a \
paint 7 for example 9 of red color both of which are used frequently, a low pressure air supply valve LE2 and a high pressure air supply valve HE2, as well as a low pressure thinner supply valve LS2 and a high pressure thinner supply valve HS2.
A shroud 18 is disposed retractably to the cup l.
OPERATION OF THE EMBODIMENT
The schematic constitution of the electrostatic coating apparatus for use in automobiles has been described in conjunction with Figure l. The method of this invention using such an illustrated apparatus will now be described specifically also referring to the time chart shown in Figure 2.
Assuming for instance, such a case where a white paint and a red paint most frequently used as the colors for a car body are supplied respectively to the color-change valves CVw and CVr of the second color-change device 3 disposed near the cup 1 of the electrostatic coating machine and an automobile of whi-te color (not illustrated) is conveyed into a painting region, a high voltage is at first applied to the cup l and, at the same time, it is rotationally driven at a high speed.
Then, the second switching valve 14 is opened while the first switching valve 7 is being closed, to thereby establish a flow path from the second color-change device 3 by way ~s~
of the second paint supply channel l2 and the paint hose 11 to the cup 1. Subsequently, the color-change valve CVw disposed to the second color change device 3 is opened to supply a white paint through the thus rormed ~low path.
Coating ls thus started, and the white paint is released rrom the cup 1 under electrostatiC atomization and coated electrostatically to -the surface of the car body being conveyed.
Then, the color-change va~ve CVw is closed just before the completion Or the coating and, at the same time, the low pressure air supply valve LE2 is opened to supply a cleaning air at low pressure about at the same level as that of the white paint having been supplied from the color-change valve CVw to the inside of the second paint supply channel 12.
In this way, the white paint is electrostatically atomi~ed from the cup 1 continuously till the completion Or the coating, so that non-painted areas are not le~t on the car body, as well as most o~ the paint which would otherwise remain in the flow path is discharged under electrostatic atomization and can be used effectively with no loss.
When the coating has thus been completed, the low pressure air supply valve LE2 is closed and, at the same time, the number Or rotation for the cup 1 is reduced and the shroud 18 retractably disposed near the cup 1 is ~"'h~
advanced so as to surround the cup 1. Then, after closing the second switching valve 14 and opening the liquid discharging ON-OFF valve 15, the high pressure air supply valve HE2 disposed to the second color-change device 3 is intermittently opened to discharge the white paint still remaining in the second paint supply channel 12 by way Or the liquid discharge channel 16 to the liquid discharge tank 10.
Then, the second switching valve 14 is opened in this state and the e~ector 17 is actuated to suck the paint remaining in the paint hose 11 and discharge the paint by way of the liquid discharge channel 16 to the inside of the liquid discharge tank 10. In this case, a small amount of the cleaning thinner may preferably be supplied from the low pressure thinner supply valve LS2 disposed to the second color-change device 3 to the paint hose 11 to dilute the residual paint in the paint hose before the actuation of the e~ector 17. This can much facilitate the sucking and discharging of the residual paint by the e~ector 17.
Then, after closing the second switching valve 14, the high pressure thinner supply valve HS2 and the high pressure air supply valve HE2 disposed to the second color-change device 3 are alternately opened and closed to clean the inside of the liquid discharge channel 16.
Subsequently, the liquid discharging ON-OFF valve 15 is closed, and the low pressure thinner supply valve LS2 and the low pressure air supply valve LE2 of the second color-change device 3 are successively opened to supply the low pressure cleaning thinner and the low pressure cleaning air by way of the second paint supply channel 12 and the paint hose 11 to the inside Or -the cup 1. Thus, the paint hose 11 and the cup 1 can be cleaned finely.
In this way, since only the cleaning thinner and the cleaning air under low pressure are discharged from the cup 1, there is no trouble as experienced so rar that the residual paint discharged from the cup 1 is scattered to the outside of the shroud 18 to contaminate the peripheral equipments and the electrostatic coating machine main body In a case where color Or the the coating paint is changed to that o~ a paint, for instance, supplied to the color change-valve CV1 of the first color-change device 2 (for example, blue paint) after the cleaning has thus been completed, the second switching valve 14 is closed and the first switching valve 7 is opened to est~blish a flow path communicating from the ~irst color-change device 2 by way Or the first paint supply channel 4 and the paint hose 11 to the cup 1. Meanwhile, the shroud 18 is retracted from the cup 1 and the number of rotation for the cup 1 is increased to a predetermined number Or rotation.
Then, the coating is started again by opening the color-change valve CV1 and supplying the blue paint supplied to the valve CV1 by way Or the flow path to l9~
the cup 1 thereby applying electrostatic coating on a succeeding car body now being conveyed.
Just before the completion of the coating~ the color-change valve CVl is closed and, simultaneously, the low pressure air supply valve LEl is opened to supply the low pressure cleaning air about at the same level as that of the paint supplied from the color-change valve CVl.
Thus, the paint in the first paint supply channel 4 is supplied to the cup 1 ~or electrostatic atomization continuously till the completion of the coating and, accordingly, most o~ the paint which would otherwise remain in the first paint supply channel 4 is electrosta-tically atomized ~rom the cup 1 and can be used effectively with no loss.
When the coating has thus been completed, the low pressure air supply valve LEl is closed and, at the same time, the number of rotation of the cup 1 is reduced and the shroud 18 is advanced so as to surround the cup 1.
Then, after closing the first switching valve 7 and opening the liquid discharging ON-OFF valve 8, the high pressure air supply valve HEl and the high pressure thinner supply valve HSl disposed to the first color-change device 2 are alternately opened to discharge the paint remaining in the first paint supply channel 4 by way of the liquid discharge channel 9 to the liquid discharge tank 10, by which the inside of the first paint supply ~5~
channel 4 is cleaned rapidly. In addition, af-ter closing the first switching valve 7 and opening the second switchlng valve 14 and the liquid discharging ON-OFF valve 15, the e~ector 17 is actuated to suck the paint remaining in the paint hose 11 and discharge it by way Or the liquid discharge channel 16 to the liquid discharge tank 10 as described above.
The liquid discharging ON-OFF valve 15 is then closed and the low pressure thinner supply valve LS2 and the low pressure air supply valve LE2 of the second color-change device 3 are successively opened to supply cleaning thinner and the cleaning air at low pressure by way of the second paint supply channel 12 and the paint hose 11 to the inside of the cup 1. Thus, the paint hose 11 and the cup 1 are cleaned finely.
Accordingly, since only the cleaning thinner and the cleaning air are discharged at low pressure from the cup 1 also in this case, there is no worry as has been experienced so far that the residual paint is discharged from the cup 1 and scattered to the outside of the shroud 18 to conta-minate the peripheral equipments and the electrostatic coating machine main body with the scattered paint.
As described above, a paint of particular color used most frequently is supplied from the second color-change device 3 disposed near the cup 1 of the electrostatic coating machine by way Or an extremely short second paint 9~
supply channel 12 and the hose 11 to the cup 1, whereby the amount of the paint used can be saved.
Further, since the paint in the relatively long rirst paint supply channel 4 connected between the ~irst color-change device 2 and the ~irst switching valve 7, as well as that in the second paint supply channel 12 connected between the second color-change device 3 and the second switching valve 14 are supplied by the cleaning air at low pressure to the cup 1 ~ust be~ore the completion o~ the coating, the residual amount o~ the paint in the first and the second paint supply channels 4 and 12 upon completion o~ the coating is extremely reduced, whereby the amount of the paint discharged as the discharge liquid can be decreased to ~acilitate the cleaning operation as well as reduce the loss of the paint.
Furthermore and particularly, since the paint remaining in the paint hose 11 and the cup 1 was previously discharged by the e~ector 17 to the liquid discharge tank 10 before the low pressure cleaning air and the low pressure cleaning thinner are supplied ~rom the second color-change device 3 to the paint hose 11 and the cup 1 for cleaning them, there is no worry as has been experienced so ~ar that the paint remaining in the paint hose is ~etted out ~rom the cup 1 and scattered around to the outside of the shroud 18 to contaminate the peripheral equipments and the electro-static coating machine main body.
~Z5~
Although this invention has been described for the purpose o~ illustrated by way of its prererred embodiments shown in the appended drawings, it will be apparent to those skilled in the art not various modifications and alterations may be made without departing the spirit and scope of this invention.
_ 14
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A cleaning method upon color-change in an electro-static multi-color coating apparatus adapted to supply paints of a multipilcity of colors, a cleaning air and a cleaning thinner selectively from a color-change device by way of a paint supply channel and a paint hose to the atomizing cup of an electrostatic multi-color coating machine, which method comprises sucessive steps of: (a) changing the connection of said paint supply chan-nel from that with said paint hose to that with a first liquid discharge channel leading to a liquid discharge tank upon comple-tion of paint coating, (b) supplying a cleaning air and a clean-ing thinner from said color-change device to said paint supply channel, thereby discharging the paint remaining in said paint supply channel to said liquid discharge tank and cleaning the inside of said paint supply channel, while (c) connecting said paint hose to a second liquid discharge channel leading to said tank, (d) sucking the paint remaining in said electrostatic coat-ing machine and in said paint hose and discharging said paint by way of an ejector discharge in said second liquid discharge chan-nel to said liquid discharge tank, and then (e) supplying a cleaning thinner and a cleaning air to said paint hose and said electrostatic coating machine thereby cleaning the insides thereof.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000500948A CA1250194A (en) | 1986-02-03 | 1986-02-03 | Cleaning method upon color-change in an electrostatic multi-color coating apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000500948A CA1250194A (en) | 1986-02-03 | 1986-02-03 | Cleaning method upon color-change in an electrostatic multi-color coating apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1250194A true CA1250194A (en) | 1989-02-21 |
Family
ID=4132403
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000500948A Expired CA1250194A (en) | 1986-02-03 | 1986-02-03 | Cleaning method upon color-change in an electrostatic multi-color coating apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1250194A (en) |
-
1986
- 1986-02-03 CA CA000500948A patent/CA1250194A/en not_active Expired
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