EP1284162B1 - Process and apparatus for cleaning a paint supply device in a painting installation - Google Patents

Abstract

The equipment may have two containers (2,9) for lacquer paints of different colors. They have supply and return lines (5,6) and (10,11) connected to a paint supply changeover system (8). The output line (1) passes to the spray nozzle (4) via a control system (17). The purging system (23) has supplies of nitrogen (28) and purging fluid (29) connected to pressure regulators (34,38) and pressure sensors (35,39) and further control valves (36-40). Fluid flows through a purge line (24) to the nozzle.

Description

The invention relates to a method according to the preamble of claim 1 and a Device according to the preamble of claim 8.

A method and apparatus of this kind are known from US-A-5863352. she discloses a method and apparatus having a paint feed path through which each one of several color reservoir coating color a coating robot can be fed. When changing from one color to another color, the ink feed path becomes cleaned of paint residues of the first color by the following steps: rinsing and Blowing out the first color by gas, z. Nitrogen or air; Rinsing with thinner; Rinsing and blowing out residues of the diluent again with gas, z. B. nitrogen or Air; rinse again with thinner; rinsing again and purging with gas; Feed the new paint for the next spray coating operation. A device for a similar process also shows the US-A-5330101.

Methods and devices of this kind are particularly associated with Lackiereinrichtungen applied in the form of robotic painting machines, the z. B. in the Automotive industry for painting body parts can be used varied. by virtue of customer behavior, today's production requirements (eg just in time) and ever greater variety of colors, especially in the car sector must such Painting equipment often on different-colored paints or on paints with changing Properties are converted, with z. B. up to 80 paint changes per day certainly are common. Modern painting facilities are therefore not only with powerful Color changing and dosing systems, which can choose from up to 30 different Allow paints, but also equipped with rinsing and cleaning units, by means of which ensures that after a paint change no unwanted residues of each previously used paints reach the respective workpiece surface.

See well-known methods and devices of the genera mentioned between two work phases carried out with different paints, one each Cleaning phase before. This consists essentially in the fact that a delivery line, the Paint from a selected reservoir of a paint or varnish change unit to an applicator (e.g., nebulizer unit or the like), with one of them flowing through, usually liquid detergent is processed. This is the Cleaner with the aid of compressed air either in the same direction in which the paint flows (DE 20 43 789 C3), or in the opposite direction to the paint stream (DE 91 10 650 U1) pressed by the delivery line. In both cases, the detergent must be removed from the support line before the start of the next phase of work. The cleaning effect can be enhanced by a ball or other generally referred to as "pig" body in the delivery line is moved back and forth (EP 0 888 825 A2).

One in such methods and apparatus for cleaning the delivery lines occurring problem is that many of the liquid paints used today and especially their hardeners are extremely sensitive to oxygen. Even the smallest Lackreste react in the air to form solid lumps or chunks, although are small, on a smooth, painted surface but visible and the relevant Make the workpiece almost unusable. To ensure that such Lumps whose formation due to the compressed air used in the cleaning step is unavoidable, safely removed from the delivery line before the new paint in On the one hand, the order unit arrives, the use of comparatively large quantities required for cleaning agents. On the other hand, during the entire break between two working phases carried out with different paints air-free or oxygen-free Cleaning agents should be left in the delivery line during this time also to avoid the formation of the smallest harmful air bubbles and thus lumps of paint. This has the consequence that at the beginning of a new working phase or at the beginning of a new Painting step not only the detergent itself, but also one certain minimum amount of the inflowing paint through the applicator device expelled and must be transferred to a container before the actual Painting work can be started, thereby ensuring that no Residual amounts of most solvent-containing detergent on the get the painting workpiece surface.

The amount of paint and thus lost in each cleaning phase in this way Detergents are considerable and represent a significant cost factor. Above In addition, the paint and the cleaning agent must be disposed of as hazardous waste, which the costs are further increased and the environment burdened. All this applies regardless of whether the Cleaning process with the help of a so-called pig is supported or not.

Against this background, the invention is based on the technical problem that Process and the device of the type indicated initially in such a way that during the cleaning steps lower amounts of paint and cleaning agents to be disposed of arise and the risk of lump formation from paint residues largely is avoided.

To solve this problem, the characterizing features of claims 1 and 8.

The invention has the significant advantage that because of the application of a Inert gases instead of compressed air there is no longer a risk that liquid paint residues be converted into solid clumps during the purification phases. Thereby can the cleaning phases overall designed simpler and with smaller amounts Cleaning agents are performed. Finally, by the invention a Significant reduction in the amount of paint and cleaning agents to be disposed of thereby contributing to the reduction of environmental impact.

Further advantageous features of the invention will become apparent from the dependent claims.

The invention will be explained in more detail with reference to an embodiment which is shown in the accompanying drawing in the form of a schematic flow diagram.

The enclosed drawing first shows a conventional paint or lacquer change and metering device of e.g. for painting body parts suitable painting. A delivery line 1 for paint is used at a first end 1a for connection to a paint reservoir 2 and is at a second end 1b with a coating device 3 fluidly connected. The applicator 3 includes an applicator 4, the e.g. from a spray gun, an atomizer or any other known per se An element for spraying, spraying or otherwise applying lacquer in a jet 5 may exist. All other, for the invention unimportant parts of the applicator 3 have been omitted for the sake of simplicity.

The reservoir 2 is preferably by means of a loop, which has a flow 6 and a return 7, to a known color or lacquer change unit. 8 connected. With this is preferably at least one except the reservoir 2 another reservoir 9 connected, for which purpose another, also a Flow 10 and a return 11 having ring line is provided. In both Ring lines is each a controllable valve 12 and 14 connected, the corresponding Flow 6, 10 either with the associated return 7, 11 or at one connection point 15, 16 with the first end 1a of the delivery line 1 connects. Is the lead 6, 10 connected to the associated return line 7, 11 circulates in the relevant reservoir 2, 9, liquid paint having a preselected pressure (e.g., about 4 bar) in the relevant ring line. Connects the valve 12, 14, however, the flow 6, 10th with the associated connection point 15 or 16, then paint from the relevant Reservoir 2, 9 pressed into the feed line 1 and in this direction of the Applicator 3 transports.

The reservoirs 2 and 9 are e.g. as a pressure vessel or as a membrane or Piston pumps provided container formed from which, as it is in painting the type described is common, the paint pumped into the ring line 6, 7 and 10, 11 becomes. Subsequently, the storage containers 2, 9 are therefore generally referred to as "paint supplies" designated.

For accurate metering of the paint, e.g. a dosing unit 17. This contains in Embodiment a paint pressure regulator 18 and a e.g. as motor driven Gear pump trained metering pump 19, both in series into the delivery line 1 are switched. The pressure in front of the metering pump 19 can by means of a pressure sensor 20, while measuring the pressure with which the paint the Applicator 3 is supplied, another, in the flow direction behind the metering pump 19 arranged pressure sensor 21 is used. Depending on which of the two valves 12, 14 to the delivery line 1 is opened, thus paint from the reservoir 2, 9 is the Applicator 3 supplied. In addition, a parallel to the metering pump 19 extending Beipaßleitung 22 may be connected in the delivery line 1 to use certain Lacks a variety of paint instead of the slow-running metering pump 19 by to let the bypass line 22 run.

Devices of the type described are generally known to the skilled person and need will not be explained in detail. To avoid repetition, therefore, the initially mentioned publications (DE 91 10 650 U1, DE 20 43 789 C3, EP 0 888 825 A2) by reference to them to the subject of the disclosure of the present invention made.

According to the invention, the device described has one with an inert gas, preferably Nitrogen-operating flushing unit 23 for cleaning the feed line 1 on. The Rinsing unit 23 is by means of a line 24 either directly or via a not shown Valve of the applicator 3 is connected to the second end 1 b of the conveying line 1, that in a position of this valve through the feed line 1 supplied paint in the form of the beam 5 flows out of the applicator 3, while in another Position of the valve, the line 24 fluidly connected to the feed line 1 is. Normally, however, the applicator 4 has a free to the lines 1, 24th connected passage to which a spray nozzle or the same is connected. This is, if not painted, sealed with a needle, which is for a painting process is pulled out of the nozzle to release the beam 5.

The rinsing unit 23 has an inert gas source 28 and a cleaning fluid source 29. The inert gas source 28 consists for example of a conventional nitrogen cylinder, from which when opening a valve gaseous nitrogen is forced into a conduit 30 which is connected via a terminal 31 to the conduit 24. In contrast, the cleaning fluid source 29, for example, from a reservoir from which a cleaning fluid can be pressed under pressure into a conduit 32 which is connected via a terminal 33 to the conduit 24. In this case, in line 30 in the flow direction of the inert gas (arrow v ) one behind the other, a pressure regulator 34, a pressure sensor 35, for example, designed as a two-way valve, controllable valve 36 and a check valve 37 connected to the reverse flow of unwanted media in the arrow v opposite direction prevented. The components 34 to 37 not only form a means for connecting the inert gas source 28 to the delivery line 1, but at the same time also a means for filling the delivery line 1 with inert gas, as explained in more detail below. Accordingly, a pressure regulator 38, a pressure sensor 39, a check valve 40 and a controllable valve 41 are connected in line 32 in the flow direction of the cleaning liquid (arrow w ) in succession, by means of which the cleaning liquid can be introduced at the terminal 33 in the line 24. The check valve 40 also prevents unwanted backflow. The components 30 to 41, as explained below, also form a means for forming a foam mixture.

The cleaning fluid source 29, like the reservoir 2, 9 a pressure vessel or contain a container with a pump system. The desired pressure can then be adjusted with the pressure regulator 38 and monitored with the pressure sensor 39.

The first end 1a of the delivery line 1 opens according to the accompanying drawing via a controllable discharge valve 42 into a collecting container 43. The arrangement is preferably made so that the connection points 15 and 16, viewed from the discharge valve 42, in the flow direction (arrow x ) behind this lie and the shortest possible line sections 44, 45 are connected to the valves 12, 14. In the flow direction immediately behind the last connection point 15 is also a od in the manner of a proximity switch. Like. Formed, for example, inductive or capacitive sensor 46 is arranged, whose function is explained below.

The operation of the described painting and the invention Rinsing unit 23 is essentially as follows.

During a normal working phase, the valves 12, 14, 36, 41 and 42 are first closed. By opening one of the valves 12, 14 it is then selected which Paint is to be delivered by the applicator 3 during the working phase. The Valve 22 is open or closed depending on the paint used. In the assumption that that Valve 12 is opened, thus flows liquid paint from the reservoir 2 in through set the pressure regulator 18 and the metering pump 19 and by means of the pressure sensors 20, 21 monitored dosage to the applicator 3, so that this by automatic or manually opening and closing its outlet nozzle in the usual manner can be. This mode of operation remains unchanged as long as the paint from the reservoir 2 is processed.

If it is intended to proceed to a processing of the paint from the storage container 9, a cleaning phase for the delivery line 1 is initially provided. For this purpose, the valve 36 of the purging unit 23 is opened when the applicator 3 is closed, whereby the inert gas from the inert gas source 28 via the lines 30 and 24 and the applicator 3 or directly into the second end 1b of the delivery line 1 passes. The pressure of the inert gas readable at the sensor 35 is determined by the setting of the pressure regulator 34. The pressure of the inert gas (eg 10 bar) is chosen so that the standing in the delivery line 1 paint opposite to the usual conveying direction (arrow x ) is pushed back in the direction of the reservoir 2 and its ring line. Because of the short line piece 44, the return transport of the paint can be almost complete.

The sensor 46 monitors this process and outputs a signal as soon as it is received by the Interface between paint and inert gas is passed. This signal can not be over shown, preferably automatic control device can be used to Close valve 12 and the drain valve 42 to open. This has the consequence that the very small amount of paint still standing in front of the inert gas column now through the end 1a of the Delivery line 1 is pressed into the collecting container 43. It is therefore only one here small amount of paint to be disposed of.

By the response of the sensor 46 can simultaneously the valve 41 of the flushing unit 23rd be opened. As a result, liquid cleaning or solvent flows out of the Reservoir 29 in the line 32, which then in a by means of the pressure regulator 38th set and controlled by the sensor 39 amount via the junction 33rd enters the line 24. By suitable adjustment of the pressures and delivery speeds It is preferably ensured that the cleaning liquid and the Inert gas form a cleaning or rinsing agent in the form of a foam mixture, the like previously the pure inert gas is pressed in the reverse direction through the delivery line 1, until finally the front of the foam mixture column passes into the collecting container 43.

During this process, the element 4 of the applicator 3 can also be used for a short time opened and thereby be freed from paint. At the appropriate pressure of the inert gas the flushing unit 23 operates in the manner of a high-pressure cleaner and thus extremely effective and fast. In addition, the foam mixture, depending on the paint used be set differently, so that it is always possible to achieve optimal flushing.

Shortly after the sensor 46, the interface between the inert gas and the foam mixture recognized and has issued a corresponding signal, the valve 41 for the Cleaning fluid closed. Optionally, the cleaning phase can also have a preset expiry time from the beginning of the detergent supply or from the time the detergent is activated Sensors 46 are terminated. As a result, now again alone inert gas through the Feed line 1 driven and thereby the cleaning agent still in it is completely pushed into the collecting container 43. The termination of this process is again displayed with the sensor 46 or by a preselected expiration time established.

A short time later, the entire delivery line 1 is filled exclusively with inert gas, whereupon the valve 42 is closed and this state is maintained until the next one Work phase begins and, for example the valve 14 instead of the valve 12 is opened and the valve 36 is closed. This will ensure that the inert gas over time between the end of the actual cleaning process and the beginning of the next one Working phase with such a high pressure in the delivery line 1 is that the penetration from air or oxygen through uncontrollable leaks with certainty is avoided.

According to a preferred embodiment, after the filling of the delivery line. 1 with inert gas to a pressure selected by the pressure regulator 34 of e.g. 1 bar too the valve 36 is closed, whereby the delivery line 1 is closed on all sides. in the Following this, the prevailing in the delivery line 1 pressure is continuously using the Pressure sensors 20, 21 controlled. Is a component leaking or does any medium flow from the outside uncontrolled in the delivery line 1, then this is with the help of Pressure sensors 20, 21 detected and for generating an alarm signal, a shutdown signal used for the entire facility or the same. The valve 22 is here preferably opened.

After the beginning of the next working phase at the latest, the closure of the Valve 36 and the opening of the valve 14, if necessary, the element 4 of Applicator 3 are opened again. This forces the newly added paint first, the inert gas column standing in the delivery line 1 out of this. The the Influx of the lacquer signaling sensor 46 can be used to a to determine from the length of the delivery line 1 resulting lead time before with the actual painting work is started when the spraying of the inert gas on the workpiece to be painted should be avoided. However, because it is inert gas In general, if the element 4 acts immediately after the Release of the paint through the valve 14 directed to the relevant workpiece surface and thus first some inert gas on the workpiece surface to be painted arrives.

During normal operation of the painting device described, the delivery line 1 in the same way as described above in connection with the inert gas with Help the located in the delivery line 1 paint pressure checked for any errors become. For this purpose, e.g. after a preset time (e.g., 10 seconds) from the completion the last paint removal on applicator 3, the relevant valve 12, 14th closed, located at this time in the delivery line 1 paint pressure as Specified target pressure and this means of the pressure sensors 20, 21 monitored. at unwanted increase or decrease of this pressure is with the help of automatic Control device in turn generates an alarm or shutdown signal or the like. Again, the valve 22 is preferably open. Should be repainted afterwards, the relevant valve 12, 14 is opened again and the valve 22 is closed again.

The inert gas in the inert gas source 28 is in particular when it is in the Inert gas is nitrogen, preferably at a certain minimum temperature held, e.g. is equal to or greater than 10 ° C or 20 ° C. This will ensure that the paints used are not limited to temperatures below e.g. 5 ° C cooled where some paints can be destroyed.

In painting, where more than one applicator 3 to the conveyor line. 1 is connected, it may be appropriate, the paint pressure in the ring lines 6, 7th or 10, 11 to choose larger (for example, 15 to 20 bar). In this case, the valves 12, 14 preferably further valves or the like upstream, during the cleaning phases reduce the pressure in the ring lines 6, 7 or 10, 11 to a value or downset sufficiently smaller than the pressure of the inert gas (e.g., 10 bar) is to achieve the desired recovery of the paint during the cleaning phases guarantee. After the paint in the relevant ring line 6, 7 or 10, 11 has been pushed back, in this again the required delivery pressure is produced.

The invention brings numerous advantages. First, by the application an inert gas which does not react with the types of lacquer used and the final one Filling the delivery line 1 with the inert gas ensured that in the delivery line. 1 remaining paint residues do not od in disturbing lumps. Like. Are transformed. this applies for the entire duration of a cleaning phase between two working phases. This can also be avoided that at the beginning of a working phase for safety's sake once a certain, exiting the applicator 3 paint amount in one Container must be initiated to apply the detergent to the Safely avoid workpiece surface, i. when applying the invention, the newly emerging paint can be processed immediately and without waste. It is also advantageous that during the cleaning process a formed from the cleaning liquid and the inert gas Cleaning foam can be used, reducing the required amounts of cleaning fluid be significantly reduced. Both measures contribute significantly Cost reduction, since to a corresponding extent the cost of disposal of Special waste can be lowered. Since at no time there is a risk that from paint residues lump od. Like. Form, the intensity of the performed Cleaning work can be reduced. Apart from that, after a work phase can still in the delivery line 1 standing paint almost completely recovered.

Furthermore, it is advantageous that not only the delivery line with the described method 1 itself, but also all its fittings, valves, etc. (e.g., 16, 18, 19, 20, 21, 22) be cleaned easily, which is especially in plants working with pigs Not readily possible because the pigs od usually no fittings. Like. can go through. Finally, all the operations described can be done easily be controlled automatically, which is why the invention with particular advantage in Robotor-Lackierautomaten can be applied.

The invention is not limited to the described embodiment that can be modified in many ways. This applies in particular to the number of different types of paint provided in the individual case, which can be selected with the aid of the color change unit 8. Instead of paints of different colors, it is also possible to select varnishes or varnishes with other different properties, for example conventional varnishes in addition to varnishes for so-called metallic coatings. It is clear that instead of paints and other liquids, especially colors can be transported through the conveyor line 1 and the term "paint" in the context of the present invention, all such, suitable for coatings liquids. Furthermore, the various steps during the cleaning phases may be performed in a different order and / or in a different direction and / or with different timings. It would be possible, for example, again to remove the cleaning agent after the recovery of the remaining in the feed line 1 paint column in the conveying direction of the paint (arrow x ), in which, for example, a second, at the first end 1a of the feed line 1 arranged inert gas source is provided. Furthermore, it is preferable not to use a nitrogen cylinder as the source of inert gas 28, but rather a commercially available nitrogen generator which generates, for example from nitrogen, nitrogen at a pressure of up to 15 bar. Furthermore, the delivery line 1 may contain other functional components, such as a micro-filter, which passes only particles to a size that is little larger than the pigment size of the paints used. Furthermore, the valves 12, 14 of the color changing unit 8 can be combined together with the discharge valve 42 into a compact block, thereby further shortening the line sections 44, 45 or omitted entirely. Furthermore, it is clear that the invention is intended to include not only the described apparatus for cleaning a paint delivery line 1, but also a complete, equipped with such a device painting. Finally, it should be understood that the various features may be applied in combinations other than those illustrated and described.

Claims (19)

1. Method on a painting installation for cleaning a paint conveying line (1), which leads from at least one storage tank (2, 9) for fluid paint to at least one application device (3) for the paint, wherein during operating stages the paint is conveyed from the storage tank (2, 9) to the application device (3) and during the intermediate cleaning stages a cleansing agent and inert gas are forced through the conveying line (1), characterised in that the conveying line (1) is filled with the inert gas at the end of the cleaning stage and held until the start of the following operating stage in each case filled with the inert gas at such a great pressure that the penetration of air or oxygen is safely avoided.
2. Method according to claim 1, characterised in that during the cleaning stages the paint in the conveying line (1) is firstly forced back into the storage tank (2, 9) by means of the inert gas, then a cleansing agent is conducted through the conveying line (1) and then the cleansing agent is removed from the conveying line (1) again by the inert gas.
3. Method according to claim 2, characterised in that the cleansing agent is forced into the conveying line (1) in the direction of the storage tank (2, 9) and removed from the conveying line (1) in the same direction.
4. Method according to one of claims 1 to 3, characterised in that the inert gas in the conveying line (1) is driven out of the conveying line (1) through the application device (3) at the start of an operating stage by means of the paint supplied from the storage tank (2, 9).
5. Method according to one of claims 1 to 4, characterised in that the application device (3) is briefly opened when the cleansing agent is conducted through the conveying line (1).
6. Method according to one of claims 1 to 5, characterised in that nitrogen is used as inert gas.
7. Method according to one of claims 1 to 6, characterised in that a foam mixture formed from a cleansing fluid and the inert gas is used as cleansing agent.
8. Apparatus on a painting installation for cleaning a paint conveying line (1), which connects at least one storage tank (2, 9) to at least one application device (3) for the paint, to transport the paint from the storage tank (2, 9) to the application device (3) during operating stages, wherein a rinsing unit (23) is provided for conveying a cleansing agent from a cleansing agent source (29) and an inert gas under pressure from an inert gas source (28) through the conveying line (1) during cleaning stages between the operating stages, characterised in that means are provided for filling the conveying line (1) with the inert gas at the end of a cleaning stage and for leaving the inert gas in the conveying line (1) until the start of the following operating stage, wherein the inert gas is in the conveying line (1) at such a high pressure that the penetration of air or oxygen is safely avoided.
9. Apparatus according to claim 8, characterised in that the rinsing unit (3) is connected to the second end (1b) of the conveying line (1).
10. Apparatus according to claim 9, characterised in that the means (36, 42) contain a first controllable valve (36) for connecting the inert gas source (28) to the conveying line (1).
11. Apparatus according to claim 9 or 10, characterised in that the rinsing unit (23) has a cleansing agent source (29) and the first end (1a) of the conveying line (1) runs out into a collecting tank (43) via a second controllable valve (42).
12. Apparatus according to one of claims 8 to 11, characterised in that the rinsing unit (23) has means (30 to 41) for forming a foam mixture from the cleansing agent and the inert gas.
13. Apparatus according to one of claims 9 to 12, characterised in that the storage tank (2) is connected to the conveying line (1) by means of a third controllable valve (12).
14. Apparatus according to one of claims 8 to 13, characterised in that the conveying line (1) is connected at the first end (1a) by means of at least one fourth controllable valve (14) to at least one further storage tank (9) and the third valve (12) and the fourth valve (14) are components of a paint interchanging unit (8) intended for optional supply of paints of different properties, in particular colours.
15. Apparatus according to one of claims 8 to 14, characterised in that a metering unit (17) is connected into the conveying line (1) for the paint conveyed by it.
16. Apparatus according to claim 15, characterised in that the metering unit (17) contains a metering pump (19) and a bypass line connected parallel to this and having a fifth controllable valve (22).
17. Apparatus according to one of claims 8 to 16, characterised in that it has a control device for the controllable valves (12, 14, 22, 36, 42) in such a way that after an operating stage paint in the conveying line (1) is firstly forced back into the storage tank (2, 9) in question by opening the first controllable valve (36), then the third or fourth valve (12, 14) is closed and the second valve (42) opened, after this cleansing agent is forced through the conveying line (1) by additional opening of a sixth controllable valve (41) and then after closing the sixth valve (41) the cleansing agent is removed from the conveying line (1), which is then filled exclusively with the inert gas by closing the second valve (42).
18. Apparatus according to claim 17, characterised in that the control device is installed in such a way that the first controllable valve (36) is closed at the latest on opening of the application device (3) intended for renewed conveying of paint.
19. Apparatus according to claim 8, characterised in that a control device and valves (12, 14, 36, 41, 42) controlled by it in such a way that after an operating stage paint in the conveying line (1) is firstly forced back into the storage tank (2, 9) in question, after that cleansing agent is forced through the conveying line (1) and then the cleansing agent is removed from the conveying line (1) and this is then filled exclusively with the inert gas and after that the inert gas is held in the conveying line (1) until the start of a following operating stage at such a high pressure that the penetration of air or oxygen is safely avoided.

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