Apparatus for applying a coating agent

Abstract

The invention relates to an apparatus (100) for electrostatically applying a liquid, atomised coating agent (1) to a substrate (110), in particular a metal strip or sheet metal strip to be wound as a coil, which substrate can be moved in a feed direction F, said apparatus comprising: a delivery device (2) or pump for the coating agent (1) that is provided in a tank or otherwise; a control unit (3) for the application process; a carrier (5) for holding an outlet device (2) in the form of a nozzle bar (50), wherein the outlet device (2) is arranged at least above, preferably above and below, the substrate (110) at a distance therefrom and is provided with at least one chamber (51, 52) and a plurality of outlets, slots or nozzle openings (54) directed towards the substrate (110), wherein the nozzle bar (50) has at least two chambers (51, 52) which are hydraulically separated from one another and each have separate feed lines (41, 42) for selectively different or the same types of coating agent (1) in the chambers (51, 52), and dedicated and integrated switching valves (60) for opening / closing the chambers (51, 52) and connections to the nozzle openings (54) or a group of nozzle openings (54) are provided in the nozzle bar (50) for each of the chambers (51, 52).

Description

[0001] Device for applying a coating agent

[0002] The invention relates to a device with at least one nozzle bar for the electrostatic application of a coating agent or various types of coating agents to a substrate movable past the nozzle bar at a constant or variable speed, in particular for applying a coating agent in the form of a corrosion inhibitor, such as oil, to a sheet metal, metal strip, or sheet metal strip conveyed past the nozzle bar. Various systems and methods have been proposed in the prior art as devices for such strip coating processes. The present invention relates to electrostatic coating processes in which atomized coating agents can be sprayed via a so-called nozzle bar with a plurality of individual nozzle openings or slot-like, elongated openings.

[0003] During the production of sheet metal strip, it is known to coat the metal sheet with a defined thickness of a corrosion inhibitor before it is wound into a so-called coil or before a further production step and processing into products from the sheet metal strip, in order to reliably protect the surface against corrosion until further processing. Other types of coating agents are also used in such metal strip processing plants, which can be continuously applied as a thin layer to the surface of the sheet metal strip using such devices. For this purpose, in such known devices in the prior art, so-called nozzle bars are arranged above and / or below the substrate or material to be coated.Metal strips are arranged, with which pre-programmed quantities of a corrosion inhibitor can be applied as a coating evenly and without interruption on the top side and, if necessary, simultaneously on the underside of the sheet metal strip.

[0004] Such devices, as previously known in the prior art, are described, for example, in IT 1223608 B and DE 83 19 162 U1. The nozzle beams of these known devices have one or two internal chambers which are completely or partially filled with oil as a coating agent, and connected holes arranged in the longitudinal direction of the nozzle beams or, alternatively, continuous slots as outlet devices, from which, due to the high-voltage field applied for electrostatic application, finely atomized corrosion inhibitor emerges, which wets the surface of sheets or metal strips moving past the nozzle beam in the conveying direction with a coating film.

[0005] In the device of IT 1223608 B, a first chamber for an oil or corrosion inhibitor is provided in the nozzle beam, with a heat transfer fluid flowing through a second, parallel chamber to provide a heating device for the nozzle beam for heating the coating agent used in the coating process. When changing the type of coating agent used, the device requires a time-consuming stoppage of the production process, since the oil-filled chamber must first be completely flushed or cleaned before being filled with a different, new coating agent.

[0006] In the case of the prior art according to DE 83 19 162 U1, it is described that, in order to set a desired application quantity, different slot widths of the outlet device can be manually adjusted by adjusting a distance between several plates of the nozzle bar. The two oil chambers formed between the inner and outer plates are filled with one and the same corrosion inhibitor, and only the width of the slots is varied here for different application quantities of the corrosion inhibitor. In these known devices, the chambers for the coating agent in nozzle bars are each completely or partially filled with a considerable amount of coating agent. If a change to a different type of coating agent, e.g. a different type of oil, occurs, these residual quantities must first be completely expelled, which leads to losses and defective parts in the coating process.Buyers of such coated metal strips or coils often specify different corrosion inhibitors as coating agents for corrosion protection and subsequent applications. During operation of the coating plant, it is therefore often necessary to switch from one coating agent to another, a second coating agent.

[0007] A disadvantage of the devices known from the prior art, in particular IT 1223608 B and DE 83 19 162 U1, with the described designs of the nozzle bars is that when changing from one type of coating agent to another, chambers in the nozzle bar that are completely or partially filled with a coating agent or oil must first be emptied by pressing out the old coating agent in order to be filled with new coating agent. This process causes quite long downtimes on the production lines because the next coating process can only begin once the change of coating agent in the nozzle bar has been fully completed. Alternatively, a certain amount of oil mixing on the substrate to be coated must be accepted over a certain period of time.The duration of oil mixing on the substrate varies depending on the oil layer and line speed and is usually a significant quality defect for this part of the sheet metal strip or substrate.

[0008] In addition, in the relatively large and long coating agent chamber of such devices in the nozzle bar, in the known devices, mixing occurs between the previous and the next coating agent each time the coating agent is changed, which requires a complex rinsing process or cleaning, during which a considerable amount of mixed oil is generated that has to be disposed of as waste.

[0009] In the daily production operation of such coating systems, these known devices with conventional nozzle bars therefore cause high costs due to downtime when changing the coating agent. Each coating agent change generates a significant amount of unusable mixed oil as waste, which must be properly disposed of. Therefore, flexibility regarding changing or adjusting spray quantities of oil is not provided. In the case of the slot width manually variable by adjusting the spacing of plates in DE 83 19 162 U1, the system must also be stopped to adjust larger or smaller quantities of applied corrosion protection agent.

[0010] Against this background, the object of the present invention is to improve a device of the type mentioned above in such a way that greater flexibility is provided in adapting to different quantities and types of coating agents. In particular, a change between two different types of coating agents can be carried out very quickly without system downtime and with a minimal amount of unwanted mixed oil as waste. The present invention should also make it possible to change between more than two coating agents without downtime for the entire system.

[0011] This object is achieved by a device having the features of claim 1. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0012] According to the invention, a device for electrostatically applying a liquid, atomized coating agent to a substrate movable in a feed direction F, in particular a metal strip or sheet metal strip to be wound as a coil, with a conveyor device or pump for the coating agent provided in a tank or otherwise, in particular from the outside, with a control unit for the application process, with a support for holding a discharge device in the form of a nozzle bar, wherein the outlet device is arranged at least above, preferably above and below the substrate at a distance therefrom, and is provided with at least one chamber and a plurality of outlets, slots or nozzle openings in the direction of the substrate, wherein the device is characterized in thatthat the nozzle bar has at least two hydraulically separated chambers with separate supply lines for optionally different or identical types of coating agents in the chambers, and that the nozzle bar has its own integrated switching valves for opening / closing the chambers and connections to the nozzle openings or a group of nozzle openings. Thus, an efficient and flexible device for electrostatic application of coating agents is provided, in which the nozzle bar is provided with at least two, preferably more than two chambers for coating agents, so that separate or different coating agents can be filled into the chambers as needed and sprayed out with the device via the switching valves.while a quick change from a first coating agent to another coating agent is desired. With the device according to the invention, the same coating agent can be present in both chambers or in several chambers of the nozzle bar in order to achieve a thicker coating on the substrate by means of two feed pumps and from the nozzle openings or outlet devices of the respective chambers. For this purpose, the invention has integrated switching valves which are designed to switch the connection from the at least two chambers to the nozzle openings. The switching valves can be provided for each individual nozzle opening as well as for specific sections or areas of several combined nozzle openings. With the integrated,Switching valves installed directly in the nozzle bar not only allow the at least two different chambers to be opened and closed separately for the application of different coating agents, but also allow different coating patterns to be flexibly adjusted.

[0013] Unlike the devices of this type provided in the prior art, the application of coating agents, for example, serving as corrosion inhibitors, can thus be continued without interruption during ongoing operation of a coating system or sheet metal processing system, even if a change to a different coating agent, for example, from type A to type B, is necessary. For this purpose, one of the chambers is simply closed, while the other chamber is opened for the continued application of corrosion inhibitors using switching valves via a control unit.With at least two hydraulically separated chambers integrated into the nozzle bar, it is possible to vary the coating agents to be sprayed in the nozzle bar via the outlet device, specifically in terms of their application rate in specific areas, their overall application rate, or their type and composition between different types of coating agents. The technical advantages of the new device for applying coating agents are therefore considerable compared to such devices previously known in the prior art. Hollow spaces integrated directly into one and the same nozzle bar can be provided as at least two separate chambers for coating agents.It is also possible to produce a composite form of a one-piece nozzle bar based on a split housing, in which at least two separate chambers for coating agents are provided. In both cases, the outlet devices in the form of a plurality of nozzle openings arranged in a row or alternatively in the form of elongated slots are connected to the two chambers via corresponding internal lines, channels, or the like, and can be switched on or off via the integrated switching valves.

[0014] In this way, the complete actuation of the hydraulic application of coating agent can take place within the nozzle bar, which can be controlled via a preferably externally arranged control unit. The number of nozzle openings is not limited, and with each of the coating chambers / switching valves, both a complete row of nozzle openings of the device and just a section of a specific number or group of nozzle openings can be opened or closed. This advantageously allows different coating patterns to be created on the surface of the substrate using the invention, which do not require complex adaptation and modification of the nozzle bar. According to the invention, at least two chambers and correspondingly associated at least two switching valves can be provided. Alternatively, more than two chambers and correspondingly more switching valves can be provided.

[0015] It is also possible to control the various nozzle openings in the nozzle bar of the device using a separate switching valve, each of which is integrated into the nozzle bar, so that individual nozzle openings can also be selectively opened or closed via the control unit. Signal lines are preferably connected to control the nozzle bars and in particular the switching valves for opening and closing the chambers and the nozzle openings. The control unit can also control the feed pump for supplying the pressurized coating agent to the nozzle bar. According to the invention, a separate supply line is provided for each of the provided chambers, i.e., at least two chambers, so that the different types of coating agents can be used during operation.

[0016] To switch between a first coating agent and an alternative, second coating agent within a chamber, the second, also present chamber can continue to be operated for coating. The first chamber only needs to be completely rinsed, which does not affect the continued operation of the second chamber. This means that the invention allows for switching between different types of coating agents without interrupting ongoing operation. Alternatively, the same coating agent can be filled into both chambers and applied via separate feed lines with corresponding feed pumps for fine atomization using an electrostatic application process. The feed pumps can also be operated at different speeds if the control unit controls them accordingly. Or one of the feed pumps can be stopped so that only one oil is applied from one of the chambers.This makes it easy to achieve variable spray quantities by changing the respective coating quantities at a given conveying speed of the substrate to be coated.

[0017] According to an advantageous embodiment of the invention, a central branch line is provided between the at least two chambers of the nozzle bar and the nozzle openings in the nozzle bar. The central branch line is connected via internal channels or lines in the nozzle bar, each selectively to the first chamber, the second chamber, or a further chamber via the switching valves, in order to instantly dispense the coating agent present in the desired chamber onto the substrate or sheet metal strip and apply it as a thin coating. The branch line is integrated into the nozzle bar and is accordingly relatively short. As a result, when switching between the first chamber, the second chamber, or a further chamber in order to coat the substrate with a different coating agent, only the small residual amount in the branch line needs to be discharged.This eliminates the need to interrupt ongoing operations in the coating system or the sheet metal strip production line. This eliminates downtime, and the device according to the invention is also low-maintenance due to the compact nozzle bar.

[0018] According to an advantageous embodiment of the invention, the control unit is configured to individually control the control valves. The control unit, which is preferably arranged externally of the nozzle bar and outside the electrostatic high-voltage field, is thus specifically adapted to control the individual control valves in order to be able to separately control individual chambers, groups of nozzle openings, or even individual nozzle openings themselves in each of the nozzle bars of the device. This allows the device according to the invention to be flexibly configured for a wide variety of applications, for example, to variably provide or change different coating patterns or coating thicknesses as required. For this purpose, only the corresponding actuation of the switching valves must be carried out by means of the central control unit. No modifications to the nozzle openings, the switching valves, or the nozzle bar itself are required.

[0019] According to a further advantageous embodiment of the invention, pneumatically controllable directional control valves are integrated into the nozzle bar as switching valves, each for at least the two chambers or for each of the nozzle openings. These valves can be controlled externally from the nozzle bar by means of the control unit via electrically insulated pneumatic hoses. The switching valves are thus protected from interference by the application of the high electrical voltage required for electrostatic coating according to the device according to the invention. Furthermore, the switching valves are thus implemented as low-maintenance and reliably functioning directional control valves, so that no malfunctions occur over an extended period of time and no maintenance work is required.The control valves are controlled via the control unit, with which individual switching valves can be controlled separately or a group of switching valves can be operated jointly, for example to open or close an entire chamber of the nozzle bar. According to an advantageous embodiment of the invention, the nozzle bar of the device has a heating unit for heating the coating agent, in particular in the form of chambers and / or channels for a heat transfer fluid, which is provided with or through which heated heat transfer fluid flows. The heating unit can, for example, be provided in the form of additional chambers also integrated in the nozzle bar, parallel to the chambers for the coating agent, i.e. in the longitudinal direction of the nozzle bar.The chambers for the heat transfer fluid can be filled from the outside with a heated heat transfer fluid via appropriate channels or lines and feed pumps. This ensures sufficient heating to achieve the required viscosity of the coating agent, which is necessary for the electrostatic coating process and the fine atomization of the oil or other corrosion protection agent. The heating unit can also be provided and attached to the nozzle bar as a separate component from the outside. Alternatively, the heating unit can also be provided in the form of another heating element that is not flowing with a liquid heat transfer fluid.

[0020] According to a further advantageous embodiment of the invention, at least one flushing valve is provided for each of the chambers, i.e., for at least two chambers, with which flushing valve the respective chambers can be carried out when changing the coating agent from one type A to another type B of coating agent, even during ongoing operation of the coating process. For example, flushing valves for this purpose are attached at one end in the longitudinal direction of a nozzle bar of the device, with corresponding lines for flushing and cleaning the interior of the chambers. The interiors of the coating agent chambers are each connected to the flushing valves in such a way that automatic flushing can be carried out for the purpose of cleaning the chambers when changing the type of coating agent, for example, oil types in the case of corrosion inhibitors, or for cleaning the device as a whole.This allows for cleaning, rinsing, and effective switching to a different coating agent even during ongoing operation. The device according to the invention is thus more flexibly adapted to different types of coating agents and does not require the costly, long downtimes of the system, as is the case with the prior art, when adapting to the specific requirements of the substrates to be coated.

[0021] According to a further advantageous embodiment of the invention, a plurality of N nozzle openings and two associated switching valves for each of the nozzle openings are provided for each of the chambers of the nozzle bar. With this provision, each nozzle opening has the option of being supplied with coating agent either from the first of the two chambers or the second of the two chambers. The double number of switching valves in the nozzle bar for each of the nozzle openings thus offers the option of supplying the coating agent to the nozzle openings for spraying onto the substrate either from the first chamber or from the second chamber, or optionally also from additional chambers with a correspondingly larger number of switching valves.

[0022] According to a further advantageous embodiment of the invention, the switching valves in the nozzle bar and the openings are each provided in segments as defined groups for switching on and off. This measure allows individual areas to be switched on or off. The variability in generating spray patterns for the coating agent is thus further increased.

[0023] According to a further advantageous embodiment of the invention, the nozzle bar(s) are mounted so that their distance from the substrate is adjustable. Height adjustment perpendicular to the surface of the substrate to be sprayed allows for larger or smaller lateral spray areas to be created. Height adjustment also has the advantage of allowing for different viscosities of the coating agents to be accommodated accordingly, for example, when a certain form of oil requires closer positioning to the surface of the substrate than another, easier-to-spray coating agent.

[0024] According to a further advantageous embodiment of the invention, the flushing valves of the nozzle bar, which are provided separately at least in the number of chambers on the nozzle bar, are implemented as pneumatically controllable directional control valves or switching valves that can be controlled via electrically insulated hoses or lines. This prevents interference from the high-voltage electric field, and the device is not susceptible to influences due to the atomization method for the coating agent to be applied.

[0025] Further advantages, features, and aspects of the present invention will be described in more detail below with reference to the accompanying drawings, in which several embodiments of the invention are shown. In the drawings:

[0026] Fig. 1 is a schematic cross-sectional view of an embodiment of a device according to the invention with nozzle bars above and below the sheet metal strip;

[0027] Fig. 2 is a detailed cross-sectional view of an embodiment of a device according to the invention with chambers and switching valves integrated into the nozzle bar; and

[0028] Fig. 3 is a schematic plan view of an embodiment of a device according to the invention with flushing valves for the two separate chambers.

[0029] According to the embodiments shown in the drawings, the device 100 for electrostatically applying a liquid, atomized coating agent 1 to a movable substrate 110, such as a sheet metal strip, comprises an outlet device 2 in the form of a nozzle bar 50 or a plurality of nozzle bars 50 arranged next to one another or opposite one another from the substrate 110. The nozzle bars 50 are provided with supply lines 41, 42 (cf. Fig. 3) for a coating agent 1, wherein in the illustrated embodiments a coating agent 1 of a first type A and a different coating agent of a type B are provided in the two separate hydraulic chambers 51, 52 by a respective pump or conveying device (not shown).The nozzle beams 50 thus have at least two separate chambers 51, 52 inside, which can be controlled by integrated switching valves 60, each for opening or closing nozzle openings 54 for applying coating agent 1 to the substrate 110, via a control with signals from the control unit 3. The outlet devices 2 in the form of the nozzle beams 50 are arranged above and below in the embodiment of Fig. 1 via a support 5 or a suspension. The support 5 can, for example, be provided in the form of a plastic beam or another electrically non-conductive component at the front ends of the nozzle beam 50. This allows the electrostatic field between the nozzle beam 50 and the substrate 110 to build up undisturbed and remain constant.

[0030] In the first embodiment of Fig. 1, a nozzle bar 50 is provided both above the substrate 110 or sheet metal strip and below the substrate 110 as an outlet device 2 for the coating agent 1, in order to achieve a double-sided coating of the sheet metal strip as substrate 110, for example, with oil as a corrosion inhibitor. A precise coating thickness and a continuous coating shape are important to prevent defects or uncoated areas.For this purpose, the device 100 according to the invention has at least one nozzle bar 50 according to the invention, which is specially designed for an outlet of different coating agents 1 of type A, B or C by means of the at least two separate chambers 51, 52 in the nozzle bar 50 and the provided separate switching valves 60, which in this example are realized as pneumatic switching valves, which can each be controlled via pneumatic lines 61 by the control unit 3 to open or close a connection between the chambers 51, 52 and an outlet in the form of nozzle openings 54 or a slot-shaped outlet of the nozzle bar 50. Other types of switching valves 60 can also be used for the invention.

[0031] In Fig. 1 to Fig. 3, embodiments of a device 100 according to the invention for applying two coating agents 1 via feed lines 41 and 42 to a substrate 110, for example a metal strip or a metal sheet, are shown in schematic representations to illustrate the basic structure and the components of the device 100 according to the invention.

[0032] According to an embodiment shown in Fig. 1 in a schematic cross-sectional view, the device 100 according to the invention comprises at least one nozzle bar 50 mounted on a support 5 or other non-conductive component, at least two switching valves 60 integrated therein, at least two separate chambers 51 and 52 for the provision of coating agent(s) 1, and a central branch line 53 leading to a nozzle opening 54 of the outlet device 2 at a conically tapered end of the nozzle bar 50. The device 100 preferably serves for the alternate application of at least two coating agents 1 of different types A, B, or C, which are permanently present in two chambers 51 and 52 of a nozzle bar 50 via a pump (not shown) and supply lines 41, 42 (cf. Fig. 3), onto a substrate 110.The central branch line 53, which leads to nozzle openings 54 of the nozzle bar 50, can be alternately connected to the chambers 51 or 52, which can be filled with two different coating agents 1, by opening and closing the integrated switching valves 60.

[0033] Alternatively, the same coating agent 1 of type A can be present in both chambers 51, 52. From the nozzle opening 54 of the outlet device 2, the selected coating agent 1 is finely atomized due to a high-voltage field 70 applied by high-voltage cables 72 and transported through the nozzle openings 54 to the surface of the substrate 110. By switching the branch line 53 by means of the switching valves 60 via the control unit 3 to from one of the chambers 51 and

[0034] 52 to the respective other chamber 51, 52, a quick switchover from a first type A of coating agent 1 to another coating agent of a type B can be achieved without the chambers 51 and 52 having to be completely rinsed. In the alternating operation of two coating agents 1, long downtimes of the device 100 and thus of a sheet metal processing plant as a whole, with corresponding costs, are avoided and the amount of mixed oil produced, which in the short and thin branch line

[0035] 53 is produced in much smaller quantities than with a complete flushing of the large and long chambers 51 or 52, as was required in the prior art.

[0036] According to an embodiment shown schematically in cross section in Fig. 2, the device 100 according to the invention comprises at least one nozzle bar 50 and at least two switching valves 60 integrated therein, at least two chambers 51, 52 for the supply of coating agents 1 and a central branch line 53 which leads to a nozzle opening 54 of the outlet device 2. The device 100 is preferably used for the alternate application of two coating agents 1, which are permanently supplied to two chambers 51 and 52 of a nozzle bar 50 by pumps and supply lines 41, 42, onto a substrate 110. The central branch line 53, which leads to a nozzle opening 54 of the nozzle bar 50, can be alternately connected to the chambers 51 or 52, which can be filled with two different coating agents 1 of type A or B, via a central control unit 3 by opening and closing the integrated switching valves 60.The selected coating agent 1 is finely atomized from the nozzle openings 54 due to the applied high-voltage field 70 and transported to the surface of the substrate 110. By switching the branch line 53 from one of the chambers 51 and 52 to the other chamber 51, 52 using the switching valves 60, a rapid switch from one coating agent 1 to another coating agent 1 can be achieved without the chambers 51 and 52 having to be completely flushed.

[0037] The switching valves 60 are pneumatically actuated by signals from the control unit 3 via electrically insulating hoses 61 so that the high-voltage field 70 applied via the high-voltage cable 72 does not interfere with the actuation of the switching valves 60 and the actuation of the switching valves 60 can be automated via externally arranged, cost-effective, commercially available solenoid valves and control devices without having to use expensive high-voltage-suitable components in the area of ​​the nozzle bar 50.

[0038] In this embodiment of Fig. 2, a heated heat transfer fluid circulates in the two additional chambers 55 on both sides of the nozzle bar 50. By symmetrically heating the nozzle bar 50 on both sides, the entire nozzle bar 50 is set to a uniform operating temperature. As a result, the coating agents 1 in the chambers 51 and 52 are gently and reliably heated over the entire length of the bar to the defined viscosity that is advantageous for optimal atomization at the nozzle openings 54. In the illustrated embodiments, the chambers 51, 52, 55 are closed off laterally on the nozzle bar 50 by covers 6 with seals. Like the channels for the oil, they can be incorporated into a two-part aluminum housing for the nozzle bar 50. According to one embodiment shown in Fig.3 in a schematic plan view, the device 100 according to the invention comprises at least one nozzle bar 50 with chambers 51, 52 and at least two switching valves 60 integrated therein. The switching valves 60 are arranged on the nozzle bar 50 in pairs in N segments as switching valves 60 with the numbers 1 to 40, transversely to the feed direction F of the substrate 110 to be coated. In the illustrated embodiment, in the first segment, switching valve number 1 and switching valve number 21 are connected to a nozzle opening 54 via a common branch line 53. In this example, switching valve number 1 is open, and switching valve number 21 is closed. Type A coating agent 1 flows from chamber 51 into branch line 53 via the open switching valve number 1, and from there via nozzle opening 54 and the high-voltage electric field 70 onto the substrate 110.

[0039] To switch to the type B coating agent 1 located in the other chamber 52 of the nozzle bar 50, the switching valve no. 1 is closed and then the switching valve no. 21 is opened. After a few seconds, the new type B coating agent has forced the residues of type A coating agent out of the short, thin branch line 53, and only type B coating agent 1 now flows from the nozzle opening 54.

[0040] At the end of the nozzle bar 50 in this embodiment of Fig. 3 there are two flushing valves 71 with which the chambers 51 or 52 can be quickly flushed when changing from a coating agent 1 of type A or B to a third coating agent 1 of type C, so that the change from coating agent 1 of type B to a third coating agent 1 of type C can also be carried out quickly. Preferably, while the substrate 110 is still being coated with coating agent of type A from chamber 51, the flushing valve 71 at the end of chamber 52 is opened and the coating agent 1 of type B still remaining in chamber 52 is flushed out with the new coating agent 1 of type C. To change to the new coating agent 1 of type C, which is then already in chamber 52 of the nozzle bar 50, the switching valve no. 1 is closed and then the switching valve no. 21 is opened.After a few seconds, the new coating agent 1 of type C has pushed the residues of coating agent type A out of the short, thin branch line 53 and the new coating agent 1 of type C now flows out of the nozzle opening 54.

[0041] The users of the coated sheet metal strip do not want the mixed oil produced in the branch line 53 during the changeover on the substrate 110. Therefore, the changeover between two coating agents 1 of type A and B located in the nozzle bar 50 is preferably carried out when a coil length of the substrate 110 to be coated ends and a new coil with a weld seam is fed to the end of the first coil. By means of the present invention, during the time in which the end of the last coated coil and the beginning of the new, not yet coated coil, connected with an unusable weld seam, are in the coating chamber of the device 100, the mixed oil can be forced out of the short, thin branch line 53 and discharged from the nozzle opening(s) 54 without causing any downtime of the entire system.This also works due to the device 100 according to the invention and in particular the flushing valves 71 when changing from coating agent 1 of type B to coating agent 1 of type C, because the chamber 52 not currently being used for coating can be pre-equipped with the new coating agent 1 of type C by flushing during ongoing coating operation, without stopping the system that is currently applying coating agent 1 of type A from chamber 51 to the substrate 110.

[0042] List of reference symbols

[0043] 1 coating agent

[0044] 2 outlet device

[0045] 3 Control unit

[0046] 4 Heating unit

[0047] 5 carriers

[0048] 6 lids

[0049] 41 , 42 supply lines

[0050] 50 nozzle bars

[0051] 51 , 52 Chamber

[0052] 53 spur line

[0053] 54 Nozzle opening or outlet slot of the outlet device 2

[0054] 55 Chamber for heat transfer fluid heating unit 4

[0055] 60 switching valve

[0056] 61 electrically insulated pneumatic hoses switching valves

[0057] 70 high-voltage field

[0058] 71 Flush valve

[0059] 72 high-voltage cables

[0060] 100 device

[0061] 110 Substrate or sheet metal strip

[0062] F Feed direction of substrate or sheet metal strip

Claims

Claims 1. Device (100) for the electrostatic application of a liquid, atomized coating agent (1) onto a substrate (110) movable in a feed direction F, in particular a metal strip or sheet metal strip to be wound up as a coil, with a conveyor device (2) or pump for the coating agent (1) provided in a tank or otherwise, with a control unit (3) for the application process, with a carrier (5) for holding an outlet device (2) in the form of a nozzle bar (50), wherein the outlet device (2) is arranged at least above, preferably above and below the substrate (110) at a distance therefrom, and is provided with at least one chamber (51, 52) and a plurality of outlets, slots or nozzle openings (54) in the direction of the substrate (110), characterized in that the nozzle bar (50) has at least two hydraulically separated chambers (51, 52) each with separate Supply lines (41 ,42) for optionally different or identical types of coating agent (1) in the chambers (51, 52), and that in the nozzle bar (50) for each of the chambers (51, 52) separate and integrated switching valves (60) are provided for opening / closing the chambers (51, 52) and connections to the nozzle openings (54) or a group of nozzle openings (54).

2. Device (100) according to claim 1, characterized in that a central branch line (53) is provided between the chambers (51, 52) and the nozzle openings (54) in the nozzle bar (50).

3. Device (100) according to claim 1 or 2, characterized in that the control unit (3) is designed to individually control the control valves (60).

4. Device (100) according to one of the preceding claims, characterized in that pneumatically controllable directional control valves are used as switching valves (60) are provided, which can be controlled externally from the nozzle bar (50) by means of the control unit (3) via electrically insulated pneumatic hoses (61).

5. Device (100) according to one of the preceding claims, characterized in that the nozzle bar (50) has a heating unit (4) for heating the coating agent (1), in particular in the form of chambers (55) and / or channels for a heat transfer fluid.

6. Device (100) according to one of the preceding claims, characterized in that a flushing valve (71) is provided for each of the chambers (51, 52), with which a flushing valve (71) can be carried out when the coating agent (1) is changed from one type A to another type B, even during ongoing operation of the coating process.

7. Device (100) according to one of the preceding claims, characterized in that for each of the chambers (51, 52) a plurality of N nozzle openings (54) and two associated switching valves (60) for each of the nozzle openings (54) are provided.

8. Device (100) according to one of the preceding claims, characterized in that the switching valves (60) and nozzle openings (54) are provided in segments as defined groups for switching on and off.

9. Device (100) according to one of the preceding claims, characterized in that the nozzle bar(s) (50) are mounted so as to be adjustable at a distance from the substrate (110).

10. Device (100) according to one of claims 6 to 9, characterized in that the flushing valves (70) are pneumatically controllable directional control valves or switching valves (71) which can be controlled via electrically insulated hoses or lines.

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