EP0371977A4

EP0371977A4 - Spray coating device with a rotary spray organ.

Info

Publication number: EP0371977A4
Application number: EP19880905505
Authority: EP
Inventors: Peter Hofmann; Michael Gras; Karl-Heinz Schalowski
Original assignee: Ransburg Corp
Current assignee: Ransburg Corp
Priority date: 1987-06-16
Filing date: 1988-05-25
Publication date: 1990-07-03
Also published as: DE3720200A1; WO1988010153A1; KR890701221A; JPH02503647A; EP0371977A1; ES2010758A6

Abstract

Spray coating device with a rotary spray organ for cleaning, a cleaning fluid (solution) is sprayed by the rotary spray organ (4). Created thereby within the sprayed cleaning fluid is an area of vacuum, injected into it through the sprayed cleaning fluid is air which entrains particles of the cleaning fluid and is drawn in the form of a gas/cleaning fluid mixture by the vacuum on the front (28) of the rotary spray organ (4), cleaning there also its center.

Description

SPRAY COATING DEVICE WITH A ROTARY SPRAY ORGAN

The invention concerns a spray coating device with a rotary organ for spraying coating liquid, with at least one channel that passes through the rotary spray organ and empties on its front, and which serves to feed cleaning fluid on the front, due to the rotation of which front the cleaning fluid flows across the front and is thrown off in the form of a cross-sectionally essentially ring-shaped fluid shell that produces on the front of a vacuum. Such a device is previously known from the U.S. patent 3,144,209. In this prior device, the rotary spray organ has essentially the shape of a flat disk. It is screwed onto a shaft and has a number of channels extending through it, arranged in several circles concentric with the shaft. Coating liquid, specifically enamel, can be fed to each circle of channels by way of a line. During the changeover from one type of coating liquid to another, and also at the beginning of longer operational interruptions, the spray coating device is cleaned in that cleaning fluid, instead of coating liquid, is passed through the lines and to the channels. Coating liquid thrown off the rotary spray organ during coating operations attracts air from the surroundings and creates thereby a vacuum on the front of the rotary spray organ. Particles of the thrown-off coating liquid are sucked back onto the front of the rotary spray organ by this vacuum. The coating liquid particles drawn back cling to the front of the rotary spray organ and must be rinsed off during the cleaning operations by the cleaning fluid. Therefore, cleaning fluid must during cleaning operations be passed through the radially innermost channels of the rotary spray organ to its front also when coating liquid was sprayed during a preceding coating operating only through channels which are situated radially farther outward. But coating liquid particles sticking to the front, radially within the innermost ring of channels, can in this way not be reached and rinsed away by the cleaning fluid. Therefore, the center of rotation of the front of the rotary spray organ that is situated within the innermost circle of channels must be cleaned separately in another way in an additional cleaning operation. This disadvantage is given also when the rotary spray organ is not disk-shaped but bell-shaped. Bell-shaped rotary spray organs are previously known from the U.S. patent 3,281,076 and the German patent 30 00 002. These too have the disadvantage that neither coating liquid nor cleaning fluid can in the axis of rotation proceed to the front of the rotary spray organ, so that the center of rotation of the front can be cleaned only by additional measures in an additional operation.

Other disclosures can be found in, for example, German Patent Specification 36 00 920; German Patent Specification 35 05 619; German Patent Specification 15 77 919; European Patent Specification 0 092 043; German Patent Specification 32 14 314; German Patent Specification 14 27 677; U.K. Patent Specification 2 163 675; German Patent Specification 6 59 062; European Patent Specification 0 032 391; French Patent Specification 2 543 853; German Patent Specification 31 05 186; German Patent Specification 34 31 758; and European Patent Specification 0 216 173.

The invention attempts to solve the problem of cleaning the center of rotation of the front of the rotary spray element in a simple way simultaneously and automatically when the other areas of the front are cleaned with cleaning fluid. The spray coating device is supposed to be small and to enable the cleaning of the entire front of the rotary spray organ in a time shorter than with prior devices.

This problem is inventionally solved in that radially outside the front, axially away from it and offset rearwardly beyond the rotary spray organ there is arranged a gas discharge setup which relative to the rotary spray organ is essentially ring-shaped and serves to discharge a cross-sectionally essentially ring-shaped gas flow and to inject this gas flow through the fluid shell of cleaning fluid into the area of the vacuum produced by the fluid shell on the front, so that part of the gas and of the cleaning fluid particles agitated by the gas will be sucked by the vacuum on the center of rotation of the front.

This makes it possible to perform a spray coating method where a) liquid coating material is during a spray coating operation sprayed by the rotary spray organ at the object to be coated and b) the front of the rotary spray organ is cleaned during spray coating pauses by a cleaning fluid which is passed from inside out across the front of the rotary spray organ and thrpwn-off due to the rotation of the rotary spray organ, with the thrown-off cleaning fluid forming a cross-sectionally essentially ring-shaped liquid shell that extends away from the rotary spray organ and whose flow creates a gas vacuum on the front of the rotary spray organ.

During the process step b) , gas is on the fluid shell side away from the area of the gas vacuum inventionally so injected into the fluid shell that it will agitate the cleaning fluid in the fluid shell and form a gas/cleaning fluid mixture which by the gas vacuum within the liquid shell is drawn on the center of rotation of the front of^' the rotary spray organ. The gas is preferably passed across the rotary spray organ and at the fluid shell formed by the cleaning fluid, in the form of a hollow gas shell surrounding the rotary spray organ, with the gas being fed at a pressure considerably higher than that of the cleaning fluid so that the gas penetrates the fluid shell of cleaning fluid and produces in it a venturi injector effect by which the cleaning fluid is agitated and fluid particles are entrained by the gas and carried into the area of vacuum up into the center on the front of the rotary spray organ. Cleaning fluid is thus inventionally sucked, in the cleaning of the front of the rotary spray organ, also into the center of the front, is radially thrown off the front, thereby cleaning the entire front including the center of rotation.

Further characteristics of the invention are contained in the subclaims. The invention will be described hereafter with reference to the drawing. The drawing shows in

Fig. 1, a broken-off longitudinal section of an inventional spray coating device with a vertically extending axis of rotation;

Fig. 2, a front elevation of the device relative to Figure 1, viewed in the direction of arrow II;

Fig. 3, another embodiment of an inventional spray coating device with a horizontal axis of rotation, and

Fig. 4, a front elevation of a device relative to Figure 3, viewed in the direction of arrow IV.

The spray devices illustrated in Figures 1 through 4 contain each a rotary spray organ 4 which is rotatably supported by a carrier 2, at least one line 6 for the alternative supply of coating liquid or rinsing fluid on a backside 8 of the rotary spray organ, at least two additional lines 12 and 14 for feeding rinsing fluid on the back 8, an annular air channel 16 from which, through orifices 20 arranged in ring fashion, a ring-shaped gas curtain flows forward through an outer shell surface 22 and keeps the outer shell surface 22 clean and envelopes coating fluid thrown off the front 28 on an outer edge 30 in the form of a fluid funnel, thereby limiting its radial expanse. Depending on the strength of flow of the gas curtain 24, the fluid shell 32 consisting of thrown-off and thus sprayed coating liquid has a smaller or larger diameter. The front 28 of the rotary spray organ 4 consists partly of a flat end face area 34 which is situated concentric with the center of rotation 36 and thus concentric with the axis of rotation 38 of the rotary spray organ and extends at least up to a ring-shaped outlet 40 radially outwardly. Coating liquid or cleaning fluid flows from the back 8 through the outlet 40 to the front 28. Another part of the front 28 is formed by the end face 42 of the head 44 of a screw 46 with which the rotary spray organ 4 is fastened on a shaft 48. The end face 42 is flat and lies in the same plane as the flat end face area 34. Cleaning fluid from the line 12 is "shot" through an annular channel 50, which concentric with the axis of rotation 38 is formed in the rotary spray organ 4, past the screw head 44 and to the front 28/ An area 54 curving forwardly in bell shape and on the end of which the edge 30 is.contained borders at a radial spacing 52 on the flat end surface area 34 on the front 28.

Insofar, all embodiments according to Figures 1 through 4 are of the same design. The embodiment according to Figures 1 and 2 is a so-called "roof machine" for coating the roof areas of objects, for instance of automobile bodies. The axis of rotation 38 is for the purpose arranged vertically and the front 28 directed down at the surface to be coated. In Figure 1, the side directed down is marked "X" while the side directed upward is marked "Y." Mounted on the carrier 2, coaxial with the axis of rotation 38, is a ring 60 which is axially and peripherally adjustable and has an annular channel 62 to which an air line 64 is connected. A number of bores 68 are formed in the ring 60 on a circle 66, distributed across the entire periphery, which bores are arranged concentric and parallel with the axis of rotation 38 and connect the annular channel 62 with the surrounding atmosphere. The bores 68 extend thus at an angle α of 90 relative to a plane 70 which is perpendicular to the axis of rotation 38. The bores 68 form thereby across 360 a ring-shaped gas discharge setup through which flows from the annular channel 62 a gas flow 72 having the shape of a hollow cylinder in which the rotary spray organ 4 is contained at a radial spacing. The front end 70 of the ring 60 is spaced from the edge 30 of the rotary spray organ 4 a distance 73 in the range of 30 to 50 mm. Air is discharged through the gas discharge setup, or the bores 68, not during the discharge of coating liquid but while cleaning fluid is passed through the lines 6, 12 and 14. This cleaning fluid, a solvent, is supplied at a pressure ranging from 1.5 to 3.5 bars and is thrown off on the front 28 from the edge 30 in the form of a fluid shell 32. The cleaning fluid flows at a high velocity across the front 28 because the rotary spray organ 4 rotates at a high speed, for instance of 25,000 rpm, entraining air from the area located before the front and creating in this area a vacuum. But this vacuum is not sufficient to draw cleaning fluid into the center 36 on the front 28. In order for the entire front 28, including the center of rotation 36, to receive an essential quantity of cleaning fluid and to be cleaned by it, air is injected from the bores 68 at a pressure of 5 to 6 bars, i.e., at a pressure higher than that of the cleaning fluid, across the rotary spray organ 4 and into the liquid shell formed of cleaning fluid, and through it up into the area 76 before the front 28 where the vacuum prevails. The air flow from the bores 68 and the gas shell of the cleaning fluid form thus together an inverted venturi injector where the gas flow 72 agitates the cleaning fluid of the fluid shell 32 and entrains particles thereof, thereby forming an air/cleaning fluid mixture. This mixture is attracted along arrows 80 by the vacuum in the area 76 before the front 28 and drawn onto the entire end face 34 and the end face 42 of the screw head 44, which form the front 28. The attracted mixture proceeds in this way up to the center of rotation 36 where it is caught by the end face 42 of the screw and driven radially outward, due to the rotation, thereby cleaning the entire front 28.

The embodiment illustrated in Figures 3 and 4 is a so-called "side machine" for coating side surfaces. The axis of rotation 38 is therefore horizontal in this embodiment. Another difference from the embodiment relative to Figures 1 and 2 is constituted in that a ring 90, which functionally corresponds to the ring 60, is arranged so as to be adjustable in the direction of rotation and in axial direction, in which ring there are bores 94 provided only in a lower section 92 across an angle c of 120°, which bores are concentric and parallel with the axis of rotation 38. A number of bores 96 are formed across. the remaining partial circle 93, across an angle α of 240°, the axes 98. of which bores inscribe with the front annular plane 70 an angle between 30 and 60°, preferably of 45°, so that the air discharged by them from the annular channel 62 flows downward at a slant. This ensures, in addition to the effects described already with reference to Figures 1 and 2, that cleaning fluid thrown off the rotary spray organ 4 cannot proceed onto a coated object surface when the spray coating device is not located completely below the object to be coated but is still at a level and a distance from the coating object such that, without the air flow directed downward through the bores 96, cleaning fluid thrown off the rotary spray organ would proceed on the object to be coated. Except for these differences, the embodiment illustrated in Figures 3 and 4 has the same. components and the same effects as the embodiment illustrated in Figures 1 and 2, for which reason reference is made to its description.

Claims

hat is claimed is:

1. Spray coating device with a rotary spray organ (4) for spraying coating liquid, with at least one channel (50) extending through the rotary spray organ and emptying on its front (28) while serving to feed cleaning fluid to the front, through the rotation of which front the cleaning fluid flows across the front and is thrown off in the form of a cross-sectionally essentially ring-shaped fluid shell which produces on the front (28) a vacuum, characterized in that radially outside the front (28) , axially away from it and rearwardly offset beyond the rotary spray organ (4) there is arranged a gas discharge setup (68; 94, 96) which relative to the rotary spray organ (4) is essentially ring-shaped and serves to discharge a cross-sectionally essentially ring-shaped gas flow (72; 72, 98) and to inject this gas flow through the liquid shell (32) of cleaning fluid and into the area of the vacuum produced by it on the front, so that part of the gas and cleaning fluid particles agitated by the gas will be sucked by the vacuum onto the center of rotation (36) of the front (28) .

2. Spray coating device according to claim 1, characterized in that the gas flow (72; 72, 98) has in the gas discharge setup (68; 94, 96) a pressure higher than the cleaning fluid of the fluid shell (32) in the channel (50) , and in that the gas flow and the liquid shell form a venturi arrangement by which, in conjunction with the rotation of the fluid shell due to -li¬

the rotation of the rotary spray organ (4), the cleaning fluid is agitated and a mixture is produced of agitated cleaning fluid and gas from the gas flow.

3. Spray coating device according to claim 1 or 2, characterized in that the front (28) of the rotary spray organ (4) features a flat end face area (34, 42) which extends across the center of rotation (37) and is concentric with it.

4. Spray coating device according to claim 3, characterized in that the end face (42) of the head (44) of a screw (46) with which the rotary spray organ (4) is fastened on the shaft (48) is flat and, as part of the flat end face area (42, 34); lies in the same plane as said end face area. 5. Spray coating device according to one of the claims 1 through 4, characterized in that the axis of rotation (38) of the rotary spray organ (4) is essentially vertical, and in that the gas discharge direction (72) of the gas discharge setup (78) extends essentially parallel with the axis of rotation (38) (Figures 1, 2) .

6. Spray coating device according to one of the claims 1 through 4, characterized in that the axis of rotation (38) of the rotary spray organ (4) is arranged essentially horizontally, that across an upper partial circle (93) of essentially 240° (d) the gas discharge direction (98) of the gas discharge setup

(part 96) is directed downward at an angle ( ) between 30° and 60° to the vertical plane (70), and in that across the remaining partial circle (92) of essentially 120° (c) the gas discharge direction (72) of the gas discharge setup (part 94) extends essentially parallel with the axis of rotation (38) (Figures 3, 4).

7. Spray coating device according to one of the claims 1 through 6, characterized in that the gas discharge setup (68; 94, 96) is formed in a ring (60; 90) that is arranged rotatably and axially adjustable to the axis of rotation (38) of the rotary spray organ (4) .

8. Spray coating device according to one of the claims 1 through 7, characterized in that the gas discharge setup is formed by a number of orifices (68; 94, 96) which radially outside the spray organ (4) are arranged annularly at a'n axial offset relative to the front (28) and offset rearwardly beyond the rotary spray organ.

9. Spray coating method where a) liquid coating material is during a spray coating operation sprayed by a rotary spray organ at an object to be coated, and b) the front of the rotary spray organ is during spray coating pauses cleaned by a cleaning fluid which from inside out is passed across the front of the rotary spray organ and thrown off the front due to the rotation of the rotary spray organ, the thrown-off cleaning fluid forming a cross-sectionally essentially ring-shaped fluid shell which extends away from the rotary spray organ and whose flow creates a gas vacuum on the front of the rotary spray organ, characterized in that during the cleaning operation according to process step b) , from the fluid shell side away from the area of the gas vacuum, gas is so injected into the fluid shell that it will agitate the cleaning fluid in the fluid shell and form a gas/cleaning fluid mixture which by the gas vacuum within the liquid shell is drawn on the center of rotation of the front of the rotary spray organ.

10. Spray coating method according to claim 9, characterized in that the gas is passed in the form of a hollow gas shell surrounding the rotary spray organ across the spray organ and at the fluid shell formed by the cleaning fluid, in that the gas is supplied at an essentially higher pressure than the cleaning fluid so that the gas penetrates the fluid shell of cleaning fluid, producing in it a venturi injector effect by which the cleaning fluid is agitated and liquid particles are entrained by the gas and carried into the area of the vacuum up onto the front of the rotary spray organ.

11. A method of cleaning a rotary atomizer between a first interval during which a material is dispensed by rotation of the rotary atomizer and a second interval during which a material is dispensed by rotation of the rotary atomizer, the rotary atomizer including a rotary atomizer edge from which atomization of material to be dispensed by the rotary atomizer takes place, the edge defining a plane, material dispensed from the edge being projected generally on a first side of the plane, the method comprising: providing a third interval between. the first and second intervals; continuing to rotate the rotary atomizer during the third interval; providing a nozzle or plurality of nozzles which extends or extend around the rotational axis of the rotary atomizer, the nozzle or plurality of nozzles opening to atmosphere on a second side of the plane opposite the first side; providing a supply of a gas or mixture of gases at superatmospheric pressure at least during the third interval to the nozzle or plurality of nozzles; and providing a medium to the rotary atomizer to be dispensed from the edge thereof during the third interval.

12. The method of claim 11 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the rotational axis of the rotary atomizer comprises the step of providing a nozzle or plurality of nozzles which extends or extend generally coaxially with the rotational axis of the rotary atomizer.

13. The method of claim 12 wherein the step of providing a nozzle or plurality of nozzles which extends or extend generally coaxially with the rotational axis of the rotary atomizer comprises the step of providing a plurality of nozzles, arrayed generally coaxially with the rotational axis of the rotary atomizer.

14. The method of claim 11 wherein the step of providing a nozzle or plurality of nozzles which extends or extend generally coaxially with the rotational axis of the rotary atomizer comprises the step of providing a plurality of nozzles, arrayed generally coaxially with the rotational axis of the rotary atomizer.

15. The method of claim 11 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the rotational axis of the rotary atomizer comprises the step of providing a plurality of nozzles, each of which defines a separate nozzle axis along which the gas or mixture of gases is discharged from the nozzle, the separate nozzle axes of a first group of nozzles extending generally parallel with the axis of rotation of the rotary atomizer and the separate nozzle axes of a second group of nozzles extending generally obliquely toward the axis of rotation of the rotary atomizer. 16. The method of claim 15 wherein the axis of rotation of the. rotary atomizer makes an angle of less than 45 to the horizontal, the axes of the nozzles of the first group lie predominantly below the axis of rotation of the rotary atomizer and the axes of the nozzles of the second group lie predominantly above the axis of rotation of the rotary atomizer.

17. The method of claim 11 wherein the step of providing a medium to the rotary atomizer to be dispensed from the edge thereof during the third interval comprises the step of providing a solvent for the material or materials dispensed during the first and second intervals.

18. A method of cleaning an atomizer between a first interval during which a material is dispensed by the atomizer and a second interval during which a material is dispensed by the atomizer, the atomizer including an atomizer axis along which material dispensed by the atomizer is projected, the atomizer axis defining a plane generally perpendicular thereto, the location from which material is to be atomized by the atomizer lying generally in the plane, and the material dispensed by the atomizer being projected generally along the axis in a first direction away from a first side of the plane, operation of the atomizer creating a pressure differential radially from the atomizer axis, the method comprising: providing a third interval between the first and second intervals; continuing to dispense material from the atomizer during the third interval; providing a nozzle or plurality of nozzles which extends or extend around the axis along which material dispensed by the atomizer is projected, the nozzle or plurality of nozzles opening to atmosphere on a side of the plane opposite the first side; providing a supply of a gas or mixture of gases at superatomospheric pressure at least during the third interval to the nozzle or plurality of nozzles; and providing a medium to the atomizer to be dispensed thereby during the third interval.

19. The method of claim 18 wherein the step of providing a medium to the atomizer to be dispensed thereby during the third interval comprises the step of providing a solvent for the material or materials dispensed during the first and second intervals. 20. The method of claim 18 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the axis along which material dispensed by the atomizer is projected comprises the step of providing a nozzle or plurality of nozzles which extends or extend generally coaxially with the axis along which material dispensed by the atomizer is projected.

21. The method of claim 18 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the axis along which material dispensed by the atomizer is projected comprises the step of providing a plurality of nozzles arrayed generally coaxially with' the axis- along which material dispensed by the atomizer is projected. 22. The method of claim 20 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the axis along which material dispensed by the atomizer is projected comprises the step of providing a plurality of nozzles arrayed generally coaxially with the axis along which material dispensed by the atomizer is projected.

23. The method of claim 18 wherein the step of providing a nozzle or plurality of nozzles which extends or extend around the axis along which material dispensed by the atomizer is projected comprises the step of providing a plurality of nozzles, each of which defines a separate nozzle axis along which the gas or mixture of gases is discharged from the nozzle, the separate nozzle axes of a first group of nozzles extending generally parallel with the axis along which material dispensed by the atomizer is projected, and the separate nozzle axes of a second group of nozzles extending generally obliquely toward the axis along which material dispensed by the atomizer is projected. 5 24. The method of claim 23 wherein the axis along which material dispensed -by the atomizer is projected makes an angle of less than 45 to the horizontal, the axes of the nozzles of the first group lie predominantly below the axis along which material 0 dispensed by the atomizer is projected, and the axes of the nozzles of the second group lie predominantly above the axis along which material dispensed by the atomizer is projected.

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