Patent Publication Number: US-2023148199-A1

Title: Atomizer and associated operating method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of, and claims priority to, Patent Cooperation Treaty Application No. PCT/EP2020/081565, filed on May 13, 2022, which application claims priority to German Application No. DE 10 2019 130 612.4, filed on Nov. 13, 2019, which applications are hereby incorporated herein by reference in their entireties. 
     The disclosure relates to an atomizer (e.g. rotary atomizer) for applying a multi-component paint and an associated operating method. 
    
    
     BACKGROUND 
     In modern painting plants for painting motor vehicle body components, rotary atomizers are usually used as application devices, which in one design can also apply a multi-component paint, which is mixed together in the rotary atomizer from a master paint and a hardener. Such a painting system is known, for example, from DE 10 2015 010 158 A1. 
     A problem here is the collection of paint residues that occur, for example, during a color change. 
     One possibility for this is the use of so-called wet washout systems. In this case, the multicomponent reactive coating material introduced into the wet washout is filtered out of water with suitable chemicals (e.g. flocculation, floatulation), whereby the filter residue must then be disposed of as hazardous waste, which is extremely costly. 
     Another possibility is the use of so-called dry rinsing. In this case, the multi-component reactive paint material must not be discharged directly into the paint booth. Separate installations are currently required for this, such as solvent-flushed collection hoppers or collection containers with filter mats, which require a great deal of maintenance and cleaning. 
     With all currently available solutions, volatile organic compounds (VOCs), among other things, are introduced into the paint booth. These organic components may then have to be purified from the exhaust air in a further process step. 
     In the case of a color change with the associated flushing and pressurizing processes, the rotary atomizer is arranged, for example, above a rinsed collecting hopper or a collecting container, whereupon the paint residue of the multicomponent paint can then be rinsed out of the rotary atomizer into the collecting hopper or collecting container. However, this requires the rotary atomizer to move to the collecting hopper, which takes additional time and results in a high loss of cycle time, i.e. the time required for a paint change extends the required cycle time of the paint system. 
     Another disadvantage of this flushing of the multicomponent paint into a collecting hopper or a collecting container is that parallel cleaning of the outer surfaces of the atomizer is not possible during a paint change. As a result, these process steps have to be carried out one after the other, which in turn requires additional time. For example, the rotary atomizer can first be moved into a collecting hopper or collecting container to rinse out paint residues from the multicomponent paint. The rotary atomizer can then be moved into a cleaning device to clean the outer surfaces of the rotary atomizer. 
     Furthermore, DE 10 2009 020 064 A1 discloses a painting system for painting single-component paint, whereby an intrinsically medium-actuated return valve enables the recirculation of paint foam during a color change. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    a schematic representation of a rotary atomizer according to the disclosure on an arm of a painting robot, 
         FIG.  2 A  a cross-sectional view through a main needle valve according to the disclosure with an integrated return system, 
         FIG.  2 B  the main needle valve of  FIG.  2 A  with the opened return system, 
         FIG.  3 A and  3 B  a flow chart to illustrate the operating procedure according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is based on the task of creating a correspondingly improved atomizer and a corresponding operating method. 
     The disclosure comprises the general technical teaching of flushing paint residues of the multicomponent paint out of the rotary atomizer not in the direction of the application element (e.g., bell cup), but into a separate return. This offers the advantage that two process steps can take place at the same time during a color change, namely on the one hand the flushing of residues of the multicomponent paint from the atomizer and on the other hand the external cleaning of the atomizer. This makes it possible to shorten the cycle time of the painting system, i.e. the operating speed is increased. 
     The atomizer according to the disclosure has many similarities with the known atomizers as they are known from the prior art. 
     Thus, the atomizer according to the disclosure also has a master paint connection for supplying a master paint and a hardener connection for supplying a hardener. 
     In addition, the atomizer according to the disclosure also has a mixer for mixing the master paint with the hardener to form the multicomponent paint. Such a mixer is usually designed as a static mixer (e.g. grid mixer, spiral mixer). 
     In the atomizer, a hardener line runs from the hardener connection to the mixer. Furthermore, a master paint line runs in the atomizer from the master paint connection to the mixer. 
     Furthermore, the atomizer contains a main valve for controlling the paint delivery, the main valve being arranged downstream of the mixer and controlling the flow of the multicomponent paint to an application element (e.g. bell cup). 
     The atomizer according to the disclosure thus takes up hardener and basecoat on the input side, mixes these paint components in the mixer to form a multicomponent paint and then delivers the multicomponent paint via the application element (e.g. bell cup) to the component to be coated. 
     The atomizer according to the disclosure is now characterized by a first return connection for returning the multicomponent paint from the atomizer to a return system, which occurs, for example, during a color change, as will be described in detail. A first return line runs in the atomizer, which branches off in the atomizer between the mixer and the main valve and opens into the first return connection. During a color change, the main valve is usually closed so that no more multicomponent paint is dispensed via the application element. The residues of the multicomponent paint still present in the atomizer can then be fed via the first return line into the first return connection, which is usually connected to a return system. 
     It should be mentioned here that the atomizer can also have several main needle valves and several 2K return systems. 
     In general, it should be mentioned that the atomizer according to the disclosure is preferably a rotary atomizer which has a bell cup as an application element, as is in itself sufficiently known from the prior art. In principle, however, the disclosure can also be implemented with other atomizer types, such as air atomizers. 
     In a preferred embodiment of the disclosure, a downstream-located controllable first return valve and an upstream-located controllable second return valve, which can preferably be controlled independently of each other, are located in series in the first return line in the atomizer. This offers the possibility that flushing medium is trapped between the two return valves in the first return line to prevent a reaction between different mixed paint systems or to reduce it to a tolerable level. 
     In addition, the atomizer according to the disclosure preferably has a first flushing connection to supply thinner (flushing agent) and/or pulse air. In practice, pulsed air blasts and thinner are supplied alternately to achieve the best possible flushing effect. A first flushing line runs in the atomizer, starting from the first flushing connection and opening into the first return line downstream of the downstream first return valve. The return line provided in accordance with the disclosure can thus be flushed via this first flushing connection and the first flushing line originating therefrom. For this purpose, a first flushing valve is preferably arranged in the first flushing line in order to control the inflow of thinner or pulsed air from the first flush connection into the first return line. 
     Furthermore, the atomizer according to the disclosure preferably comprises at least one controllable hardener valve arranged in the hardener line to control the inflow of the hardener. Similarly, there is preferably at least one controllable master paint valve arranged in the master paint line and controlling the inflow of the master paint. 
     In addition, the atomizer according to the disclosure preferably has a second return connection for returning the master paint separately from the hardener before mixing with the hardener. A second return line runs in the atomizer, which branches off from the master paint line upstream of the master paint valve and opens into the second return connection. A controllable third return valve is preferably arranged in this second return line, which controls the recirculation of the master paint through the second return connection. Thus, during a recirculation of master paint, the master paint valve is usually closed while the third return valve is open, so that the master paint supplied on the inlet side is recirculated into the second return line. 
     Furthermore, the atomizer according to the disclosure preferably has a second flushing line which starts from a second flushing connection or from the first flushing connection and opens into the master paint line downstream of the master paint valve. Preferably, a second flushing valve is provided, which is arranged in the second flushing line and controls the inflow of flushing agent into the master paint line. In addition, a third flushing line is preferably provided, which starts from a third flushing connection or from the first flushing connection or the second flushing connection and opens into the hardener line downstream of the hardener valve. A third flushing valve is preferably arranged in this third flushing line, which controls the inflow of flushing agent into the hardener line. 
     Thus, in the atomizer according to the disclosure, the hardener line and the master paint line can preferably be flushed independently of one another, with the flushing agent supply being controlled in each case by a flushing valve. 
     In addition, the atomizer according to the disclosure can have a short-flushing line which leads downstream of the main valve to the application element and starts from the first flushing connection or from the second flushing connection or from a third flushing connection or from a further fourth flushing connection. In this short-flushing line there is preferably a controllable short-flushing valve which controls the flow of the flushing agent through the short-flushing line. 
     Furthermore, it should be mentioned that the atomizer according to the disclosure preferably includes a paint tube containing the mixer and the upstream second return valve. Here it should be mentioned that the paint tube preferably also contains the main valve, which can be designed as a main needle valve and has a displaceable valve needle. Here it is possible that the valve needle of the main needle valve is designed as a static mixer (e.g. lattice mixer, spiral mixer), i.e. the valve needle fulfills two functions here. On the one hand, the valve needle serves as a valve element for controlling the material flow. On the other hand, the valve needle also forms the static mixer. 
     In the preferred embodiment, the upstream second return valve is designed as a diaphragm needle valve. This means that the diaphragm needle valve has a valve seat and a displaceable valve needle which releases or blocks the valve seat depending on its position. In addition, such a diaphragm needle valve is characterized by a valve diaphragm which annularly surrounds the valve needle and serves to drive the valve needle and/or to seal it. Such diaphragm needle valves are known, for example, from WO 2009/019036 A1, so that the contents of this patent application can be fully attributed to the present description with regard to the design structure and operation of a diaphragm needle valve. 
     Here, the valve seat of the second return valve may be made of steel, while the valve needle of the second return valve may pass through a sealing disc made of plastic and may be made of titanium, for example. Furthermore, the mixer can open into a distributor on the outlet side, which passes on the mixed multicomponent paint and is at least partially made of metal. 
     It has already been explained above what is meant by a membrane needle valve in the context of the disclosure. In the preferred embodiment, the main valve, the first return valve, the second return valve, the hardener valve and/or the master paint valve are also designed as such membrane needle valves. 
     Furthermore, it should be mentioned that the disclosure does not only claim protection for the above generally described atomizer according to the disclosure. Rather, the disclosure also claims protection for a corresponding operating method for such an atomizer, in which master paint and hardener are supplied and mixed in the atomizer to form the multicomponent paint, and then finally applied, for example via a rotating bell cup. 
     The operating method according to the disclosure is characterized by the fact that the multicomponent paint is recirculated through the first return line, which branches off between the mixer and the main valve, during a color change. In contrast to the known rotary atomizer, the residues of the multicomponent paint are therefore not discharged via the application element. 
     Preferably, the main valve (e.g. main needle valve) of the atomizer (e.g. rotary atomizer) is closed during recirculation of the multicomponent paint. 
     In the case of a color change, the following steps are then preferably carried out in this sequence to press on the atomizer with new paint: 
     Closing of the main valve,
         opening the first return valve and the second return valve,   opening the master valve to fill the master line with the master paint,   opening the hardener valve to fill the hardener line with the hardener,   returning the old multicomponent paint and part of the remaining flushing agent and the new multicomponent paint through the first return line into the first return system, and   closing the master paint valve, the hardener valve, the first return valve and the second return valve in this order. The sequence of valve closure here ensures that the paint medium/solvent mixture in the first return line is sealed airtight. In addition, a reaction with atmospheric moisture can thus be prevented.       

     In the operating method according to the disclosure, the following steps are preferably carried out for flushing the atomizer during a color change:
         Opening of the second flushing valve and flushing of the master paint line,   opening the third flushing valve and flushing the hardener line,   opening the first return valve and the second return valve and flushing out the old multicomponent paint and the flushing agent through the first return line,   filling the master paint line and the hardener line and the first return line with the flushing agent, and   closing the first return valve and the second return valve when the first return line is filled with the flushing agent.       

     To flush the first return line during application of the multicomponent paint, the first flushing valve is then preferably closed and flushing agent is introduced into the first return line. Preferably, solvent and pulsed air are alternately fed in to achieve a good cleaning effect. At the end of the flushing process, solvent is then preferably supplied to partially fill the first return line with the flushing agent. 
     The design of the atomizer according to the disclosure allows the following steps to be carried out simultaneously or at least overlapping in time:
         External cleaning of the atomizer, in particular by spraying the atomizer with a solvent, and   color change in the atomizer, in particular with a flushing of the atomizer into the first return line and a pressurizing of the atomizer with the new master paint and the new hardener.       

     The disclosure offers several advantages that can be summarized as follows.
         During the color change, material is no longer discharged through the paint nozzle.   As a result, the atomizer external cleaning can be carried out in parallel with the paint change. This means that the paint change can be carried out in a normal cycle gap of 15 seconds without any loss of cycle time. This increases the capacity of the paint line.   Cost savings due to the elimination of the receiving hoppers or collecting containers. In this context, the time-consuming cleaning and maintenance of these installations is also eliminated.   Significant reduction in complexity due to the elimination of the following process steps or concepts:
           Positioning of the receiving hoppers or collecting containers in the paint booth   Motion travel (programming of teach programs)   Safety concept (software protection to switch off the high voltage)   
           As a result of the disclosure and the elimination of the rinsed receiving hoppers, significantly fewer VOCs are introduced into the booth and solvents are saved. This may mean omission or reduction of exhaust air purification, if necessary.
           When wet scrubbing is used, the use of chemicals can be significantly reduced.   The mixture of multi-component reactive paint material and solvent collected via the new recirculation system is collected in a central location and can be returned to the manufacturer for recycling. This contributes to cost reduction as well as environmental protection.   
               

       FIG.  1    shows a schematic representation of a rotary atomizer  1  according to the disclosure, which is mounted on a robot arm  2  of a conventional painting robot with serial robot kinematics. The robot arm  2  is the distal robot arm of the painting robot, which is also referred to as “arm  2 ” in accordance with the usual technical terminology. 
     The rotary atomizer  1  is used to apply a multicomponent paint via a rotating bell cup  3 , as is known from the prior art. 
     For the supply of a master paint, the rotary atomizer  1  has a master paint connection  4 , the master paint connection  4  of the rotary atomizer  1  being supplied with the desired master paint by a color changer  5  in the robot arm  2 . 
     A metering pump  6  is arranged between the color changer  5  and the master paint connection  4  of the rotary atomizer  1 , which delivers the master paint with the desired paint flow. The metering pump  6  can be bypassed by a bypass valve By 1  connected in parallel. 
     In addition, the rotary atomizer  1  has a hardener connection  7  for supplying hardener. The hardener is supplied by a valve unit  8  with a hardener valve H 1  and a thinner valve VH via a metering pump  9 . 
     In the rotary atomizer  1 , a master paint line  10  starts from the master paint connection  4 , which opens via a master paint valve SL 1  into a static mixer  11 , which in the preferred embodiment is designed as a spiral mixer, as shown in  FIGS.  2 A and  2 B . 
     Accordingly, a hardener line  12 , in which a hardener valve H 1  is arranged to control the inflow of hardener, emanates from the hardener connection  7 . The hardener line  12  also opens into the mixer  11 , so that the mixer  11  mixes the master paint with the hardener. 
     Downstream of the mixer  11 , a main needle valve HN 1  is arranged to control the flow of the multicomponent paint from the mixer  11  to the bell cup  3 . The structure and operation of the main needle valve HN 1  are shown in  FIGS.  2 A and  2 B , and will be described separately. 
     In addition, the rotary atomizer  1  has a return connection  13  for returning master paint to a recirculation system not shown. For this purpose, a return line  14  runs in the rotary atomizer  1 , which branches off from the master paint line  10  between the master paint connection  4  and the master paint valve SL 1  and opens into the return connection  13 . A return valve RF 1 /SL 1  is located in this return line  14 , which controls the flow into the recirculation. 
     Furthermore, the rotary atomizer has a flushing connection  15  for flushing the master paint line  10 . A flushing line  16  starts from the flushing connection  15  and opens into the master paint line  10  downstream of the master paint valve SL 1 . A flushing valve V/PL is located in the flushing line  16  for flushing the master paint line  10 . 
     A valve unit  17  with a thinner valve V and a pulsed air valve PL is located in the robot arm  2  of the painting robot, whereby the valve unit  17  can optionally supply thinner (flushing agent) or pulsed air to the flushing connection  15 . 
     Furthermore, the rotary atomizer  1  comprises a flushing connection  18  for flushing the hardener line  12 . A flushing line  19  starts from the flushing connection  18  and opens into the hardener line  12 , a flushing valve V/H 1  being arranged in the flushing line  19 . 
     Furthermore, the rotary atomizer  1  has short-flushing connections  20 ,  21  for short-flushing of the rotary atomizer  1 , as is known per se from the prior art and therefore need not be described in detail. It is only to be mentioned that the rotary atomizer  1  contains short-flushing valves KSL, KS for short-flushing. 
     The rotary atomizer  1  is now characterized by a return connection  22 , which enables recirculation of the multicomponent paint into a recirculation system not shown. For this purpose, a return line  23  branches off in the rotary atomizer  1  between the mixer  11  and the main needle valve HN 1  and opens into the return connection  22 . Two return valves RF 4 , RF 41  are located one after the other in the return line  23 , whereby the return valve RF 4  located upstream is also shown in  FIGS.  2 A,  2 B  and will still be described separately. 
     For flushing the return line  23 , the rotary atomizer  1  has a further flushing connection  24 , which can be supplied with thinner or pulse air by the valve unit  17 . In the rotary atomizer  1 , a flushing line  25  starts from the flushing connection  24 , which opens into the return line  23  via a flushing valve V 2 /PL 2  and enables flushing of the return line. 
     The valves in the robot arm  2  and in the rotary atomizer  1  are partly designed as conventional needle valves without a separating diaphragm, which can be recognized by the corresponding hatching, as indicated in the drawing legend. In part, however, the valves are designed as needle valves with a separating diaphragm, as known per se from WO 2009/019036 A1 GINA—see if there is a U.S. equivalent and if so add the words “which is incorporated herein by reference. 
     In the following,  FIGS.  2 A and  2 B  are described, which illustrate the design and operation of the main needle valve HN 1 , the mixer  11  and the return valve RF 4 .  FIG.  2 A  shows a closed state of both the main needle valve HN 1  and the return valve RF 4 . In the illustration according to  FIG.  2 B , the main needle valve HN 1  is also closed, while the return valve RF 4  is open. 
     The drawings here show an paint tube  26  accommodating the main needle valve HN 1 , the mixer  11  and the return valve RF 4 , whereby the paint tube  26  also leads to the bell cup  3 , as is known per se from the prior art. 
     A needle seat  27  is connected to the paint tube  26 , with a sealing disk  28  made of POM (polyoxymethylene) being arranged between the paint tube  26  and the needle seat  27 . 
     Finally, a distributor  29  is arranged behind the needle seat  27 , which is also made of POM and contains a paint line  30  that leads to the bell cup  3 . 
     The paint tube  26 , the sealing disk  28  and the needle seat  27  contain an axially continuous bore  31  which opens into the paint line  30 . 
     A valve needle  32  is displaceable in the bore  31  in the direction of the double arrow, the valve needle  32  having two functions. 
     Firstly, the valve needle  32  is designed as a spiral mixer and thus forms the mixer  11  for mixing the master paint and the hardener. 
     On the other hand, the valve needle  32  serves in a conventional manner as a valve element for controlling the paint flow into the paint line  30 . For this purpose, the valve needle  32  has a valve head  33  which either clears or closes a corresponding valve seat. 
     The return valve RF 4  is arranged in a further axial bore  34  and has a valve needle  35  which is displaceable in the bore  34  in the direction of the double arrow. The valve needle  35  of the return valve RF 4  also has a valve head  36  that either closes (as in  FIG.  2 A ) or clears (as in  FIG.  2 B ) a valve seat. 
     Further,  FIGS.  2 A and  2 B  show a line section of the return line  23  that is selectively unblocked or blocked by the return valve RF 4 . 
     In the following, the flowchart in  FIGS.  3 A and  3 B  will now be described, which explains the operating method according to the disclosure. 
     In a first step S 1 , an initial situation is first shown. 
     In this initial situation, the main channel is filled with flushing medium, while the return line  23  between the return valves RF 4 , RF 41  is filled with flushing medium. In this initial situation, the return valves RF 4 , RF 41 , RF 1 /SL 1  are closed. The main needle valve HN 1 , the master paint valve SL 1  and the hardener valve H 1  are also closed, as are the flushing valves V/PL, V/H 1  and V 2 /PL 2 . 
     Step S 2  now shows the pressurizing of the rotary atomizer  1  with a new paint. 
     The main channel is filled with the new paint. During this process, the return valves RF 4 , RF 41  are open, while the return valve RF 1 /SL 1  and the main needle valve HN 1  are closed. The master paint valve SL 1  and the hardener valve H 1 , on the other hand, are open, while the flushing valves V/PL, V/H 1  and V 2 /PL 2  are closed. 
     At the end of this pressure, the master paint valve SL 1  and the hardener valve H 1  are then closed first. Next, the return valve RF 41  is closed. The return valve RF 4  is then closed last. This sequence for closing the valves during press-on ensures that the paint medium/solvent mixture is sealed airtight in the atomizer recirculation. In addition, a reaction with atmospheric moisture can thus be prevented. 
     In a step S 3 , painting is then carried out with the new paint. During this step, the return valves RF 4 , RF 41 , RF 1 /SL 1  are closed, while the main needle valve HN 1 , the master paint valve SL 1  and the hardener valve H 1  are open. The flushing valves V/PL, V/H 1  and V 2 /PL 2  are also closed during painting. At the end of the painting process, the main needle valve HN 1 , the hardener valve H 1  and the master paint valve SL 1  are closed. 
     In a next step S 4 , flushing of the rotary atomizer  1  is then carried out after the end of the painting process. In this process, the return valves RF 4 , RF 41  are opened, while the return valve RF 1 /SL 1 , the main needle valve HN 1 , the master paint valve SL 1  and the hardener valve H 1  are closed, while the flushing valves V/PL and V/H 1  are opened. 
     In a next step S 5 , the filling with flushing agent then takes place, whereby the main channel and the flushing line  23  between the flushing valves RF 4  and RF 41  are filled with flushing agent. The valve position of the various valves is indicated here in step S 5 . 
     Finally, in a step S 6 , a flushing of the recirculation is carried out according to the disclosure, whereby the return line  23  can be flushed during the painting process described above. During this process, the main needle valve HN 1 , the master paint valve SL 1 , the hardener valve H 1  are open to allow painting. The flushing valves V/PL and V/H 1 , on the other hand, are closed, which also applies to the return valves RF 4 , RF 41 . The flushing valve V 2 /PL 2 , on the other hand, is open, and the flushing valve V 2 /PL 2  is closed again at the end of the flushing process. 
     The disclosure is not limited to the preferred embodiment described above. Rather, a large number of variants and modifications are possible which also make use of the inventive idea and therefore fall within the scope of protection. In particular, the disclosure also claims protection for the subject-matter and the features of the dependent claims independently of the claims referred to in each case and in particular also without the features of the main claim. The disclosure thus comprises various aspects of disclosure which enjoy protection independently of one another. 
     LIST OF REFERENCE SIGNS 
       1  Rotary atomizer 
       2  Robot arm (“Arm  2 ”) 
       3  Bell cup 
       4  Master paint connection 
       5  Color changer 
       6  Metering pump for master paint 
       7  Hardener connection 
       8  Valve unit with hardener valve H 1  and thinner valve VH for hardener 
       9  Metering pump for hardener 
       10  Master paint line 
       11  Mixer 
       12  Hardener line 
       13  Return connection for master paint 
       14  Return line for master paint 
       15  Flushing connection for flushing the master paint line 
       16  Flushing line for flushing the master paint line 
       17  Valve unit with pulsed air valve PL and thinner valve V for master paint 
       18  Flushing connection for flushing the hardener line 
       19  Flushing line for flushing the hardener line 
       20 ,  21  Short-flushing connections 
       22  Feedback connection 
       23  Return line 
       24  Flushing connection 
       25  Flushing line for flushing the return line 
       26  Paint tube 
       27  Needle seat 
       28  Sealing washer made of POM 
       29  Distributor made of POM 
       30  Paint line to bell cup 
       31  Bore for valve needle 
       32  Valve needle as helical mixer 
       33  Valve head of valve needle 
       34  Bore for return valve RF 4   
       35  Valve needle of return valve RF 4   
       36  Valve head of return valve RF 4   
     By 1  Bypass valve for metering pump 
     H 1  Hardener valve 
     SL 1  Master paint valve 
     RF 1 /SL 1  Return valve for master paint 
     V/PL Flushing valve for flushing the master paint line 
     V/H 1  Flushing valve for flushing the hardener line 
     HN 1  Main needle valve 
     RF 4 , RF 41  Return valves in the return line 
     V 2 /PL 2  Flushing valve for flushing the return line 
     KS, KSL Short-flushing valves