Abstract:
The invention relates to a coating device, in particular for painting motor vehicle bodies, comprising a sprayer ( 1 ) for applying a coating material by means of an application element and an internal color-changer valve assembly ( 3 ), said assembly having several color inlets ( 4 - 7 ) for selecting coating materials of different colors. The internal color-changer valve assembly ( 3 ) is integrated into the sprayer ( 1 ) and is connected by its outlet to the application element ( 2 ), in order to feed the selected coating material to the application element ( 2 ). The invention also comprises an external color-changer valve assembly ( 14 ) with several color inlets for selecting coating materials of different colors, said external color-changer assembly ( 14 ) having a separate structure from the sprayer ( 1 ) and being connected by its outlet to the application element ( 2 ), in order to feed the selected coating material to the application element ( 2 ). The invention also relates to a corresponding operating method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of PCT/EP2007/003874, with a filing date of Nov. 22, 2007, which claims priority to DE 102006022570.8, filed May 15, 2006, which are hereby incorporated by reference in their entirety. 
     BACKGROUND 
     The invention relates to a coating device, in particular for painting motor vehicle bodies, and to a corresponding operating method in accordance with the preamble to the sub-claims. 
     In modern painting systems for the mass painting of motor vehicle bodies, painting is usually by means of atomisers (e.g. high-speed rotary atomisers) with only one paint inlet, which are therefore connected to a separate colour changer on the inlet side, so that one single atomiser can apply paint in different colours. The entire train of pipes between the colour changer and the atomiser must be flushed out when the colour is changed, to clear paint residue from the train of pipes. Firstly, this causes colour change losses in the range of 25-70 ml (depending upon the embodiment), which may even exceed 100 ml in exceptional cases, and, secondly, the time required for a colour change, in the range of 8-20 seconds is an irritation, although times of 13-15 seconds are usually achieved. The necessary colour change time depends on the flushability of the paints used, the flushing agent used, the pressure of the media, the structure of the paint-handling components and the position of the components in the application device. 
     Atomisers with an integrated colour changer (ICC) are also known, for example from EP 1 502 658 AI. The advantage of such known atomisers with an integrated colour changer is the low volume of the train of pipes between the integrated colour changer and the application element (e.g. a bell plate), which advantageously entails lower colour change losses and a short colour change time. However, the fact that the possible number of colours is limited, because the space available for installation in the atomiser is re-striated, is a disadvantage of known atomisers with an integrated colour changer. 
     Different painting systems, variously having an internal or external colour changer, are known from DE 697 22 155 T2, DE 696 22 407 T2, DE 103 42 643 A1, EP 1 502 658 A1, DE 101 57 966 A1, WO 2006/004601 A1, DE 103 35 358 A1, Dr. Richard Laible: “Umweltfreundliche Lackiersysteme für die industrielle Lackierung” [Environmentally-friendly painting systems for industrial painting], 1989, expert Verlag, Ehningen, p. 55; Joachim Domnick: “Oversprayarme Spritzlackiertechnik” [Low-overspray paint spraying systems], Metalloberfläche [Metal Surfaces] January 1997, pp. 43-45, DE 10 2004 038 017 A1, DE 10 2004 033 619 A1 and DE 36 41 416 A1. However, the external colour changer only has one paint outlet and is not configured as an A/B colour changer. If feeding low runners through the external colour changer, the problem therefore arises that a relatively long colour change time is required when changing from one low runner to another. 
     SUMMARY 
     The invention is therefore based upon the problem of creating a correspondingly improved coating device which is particularly suitable for painting motor vehicle bodies and attachments. 
     This problem is solved by a coating device and a corresponding operating method in accordance with the sub-claims. 
     The invention includes the general technical teaching that both an internal colour-changer valve assembly integrated into the atomiser and an external colour-changer valve assembly structurally separate from the atomiser and preferably configured as an A/B colour changer, must be provided in a coating device. 
     The colour-changer valve assembly, which is integrated in the atomiser, here is preferably used for colours applied frequently (high runners), as the colour-changing time and the colour-changing losses are extremely low when changing colour using the integrated colour-changer valve assembly. 
     In contrast, the separate external colour-changer valve assembly is preferably used for colours applied less frequently (low runners), as a colour change using the external colour-changer valve assembly is associated with greater colour-change losses, due to the longer train of pipes between the external colour-changer valve assembly and the application element, and demands a longer colour-change time. The average paint consumption/loss of the system is significantly reduced by the combination of high runners and low-runners. 
     In a preferred embodiment of the invention, the atomiser has at least one additional paint inlet, to which the external colour-changer valve assembly is connected, in addition to the paint inlets of the internal colour-changer valve assembly. 
     However, as an alternative, it is also possible for the external colour-changer valve assembly to feed a paint inlet of the internal colour-changer valve assembly, so that the external colour-changer valve assembly and the internal colour-changer valve assembly are in series. 
     In a preferred embodiment, the external colour-changer valve assembly is configured as an A/B colour changer with two separate, flushable paint outlets. Accordingly, the atomiser has at least two corresponding additional paint inlets to which both the paint outlets of the external colour-changer valve assembly are connected, in addition to the paint inlets of the internal colour-changer valve assembly. Colour-change losses and the colour change time are also minimised by the two separately-flushable paint outlets of the external colour-changer valve assembly in the case of the external colour-changer valve assembly, and brought up to the standard of the above-mentioned ICC. 
     At least one recirculation valve is provided here, permitting a flushing cycle in one channel (e.g. consisting of emptying under pressure, flushing, filling or pressure-feeding the next coating agent, compression in the recirculation pipe, i.e. sludge-thinner recirculation) during the painting process in the other channel. In an embodiment of the external colour-changer valve assembly configured as an A/B colour changer, two recirculation valves are preferably provided, facilitating recirculation for each paint outlet of the external colour-changer valve assembly and thus a flushing cycle. The recirculation valves may be located in the atomiser or outside it. Locating the recirculation valves in the atomiser facilitates flushing into the atomiser, whilst in case of a recirculation valve outside the atomiser, the flushing only takes place up to the recirculation valve being arranged there. 
     However, there is also an alternative possibility that the external colour-changer valve assembly has only one paint outlet, which is associated with lower investment costs, a smaller installation space and lower weight. In this version, high- and low-runners are preferably applied alternately, so that the internal colour-changer valve has enough time to flush the external colour-changer valve assembly and apply the next low runner to it under pressure during the application of a high runner. 
     The colour-changer valve assembly integrated into the atomiser is preferably fed with the coating materials of different colours by a first metering device, which is preferably structurally separate from the atomiser. 
     In a painting robot, the first metering device is preferably mounted on the so-called “arm  1 ” of the painting robot, which is its proximal arm. However, as an alternative, it is also possible for the first metering device for the colour-changer valve assembly integrated into the atomiser to be located on the so-called “arm  2 ” of the painting robot, which is its distal arm. Moreover, it is possible for the first metering device for the colour-changer valve assembly integrated into the atomiser to be mounted on a frame of the painting robot, where the frame can be moveable along a track (axis  7 ) and contains a pivot (axis  1 ), permitting rotation about the Z coordinate. It is also possible for the first metering device for the integrated colour-changer valve assembly to be mounted stationary in or outside a painting cabin, although this is more difficult in most cases. 
     Furthermore, the external colour-changer valve assembly is usually fed by a second metering device, which may be configured conventionally and therefore need not be described in more detail. 
     It is possible for the external colour-changer valve assembly and/or the second metering device allocated thereto to be mounted on the so-called “arm  1 ” or on the so-called “arm  2 ” of the painting robot. The above-mentioned components are therefore preferably mounted in the immediate vicinity of the atomiser and therefore preferably on “arm  2 ”. 
     In a preferred embodiment of the invention, the first metering device and/or the second metering device take the form of a geared pump, itself known from prior art, for example from DE 600 09 577 T2. 
     The geared pump preferably has a plurality of pumping chambers, each with an internal pair of gearwheels, arranged so that they will rotate, where the individual pumping chambers each supply one paint inlet of the atomiser with the respective coating agent. Furthermore, the geared pump preferably also has a common drive shaft to drive the individual geared pumps, which is not the case with the above-mentioned known geared pump. The inventive structure of the geared pump with a plurality of pumping chambers is worthy of independent protection, so that this application is for protection for this design of a geared pump even without the characteristics of the inventive coating device described above. 
     It is also advantageous for the inventive geared pump to have a common drive shaft to drive the individual gearwheels in the individual pumping chambers of the geared pump, facilitating drive by a single motor. 
     It is also advantageous for the geared pump to have a plurality of clutches, permitting selective engagement of the drive shaft with the individual pairs of gearwheels. The individual clutches can thus engage the respective pair of gearwheels with the drive shaft or disengage them from it. 
     In the inventive geared pump, the individual pumping chambers are preferably one behind the other in the axial direction of the drive shaft, facilitating compact design of the geared pump. The immediately adjacent pumping chambers can then have a common chamber wall, making a further reduction in the size of the geared pump possible. 
     Within the scope of the invention, there is also a possibility of the inventive atomiser having two sub-assemblies, separably connected with each other. The first sub-assembly of the atomiser preferably then contains the internal colour-changer valve assembly, whilst the second sub-assembly of the atomiser preferably contains the application element (e.g. a bell plate) and/or a main needle valve. This has the advantage that both sub-assemblies of the atomiser are connected to each other by only a few pipes, so that only minor contamination occurs if the two sub-assembles are separated. In contrast, should the dividing line between the two sub-assemblies run upstream of the internal colour-changer valve assembly, it would be crossed by numerous paint pipes, which would entail considerable contamination if the two sub-assemblies of the atomiser were separated. 
     From this description it is also evident that the internal colour-changer valve assembly need not necessarily be located in the same sub-assembly of the atomiser as the bell plate and the main needle valve. On the contrary, the internal colour-changer valve assembly may also be located in another sub-assembly of the atomiser within the scope of the invention, for example in a flange assembly, a manifold or an elbow. 
     It must also be mentioned that the concept of an “atomiser” should be interpreted in general terms, including, for example, rotary atomisers in the form of bell or disc atomisers, and ultrasonic atomisers, air atomisers, airless devices or Airmix devices. Correspondingly, within the scope of the invention, the application element may be a bell plate, a rotary disc or simply a nozzle. 
     It must also be mentioned that the inventive coating device can apply water-based paint or solvent-based paint, joint sealants e.g. PVC, or powder lacquer, so that the invention is not restricted in terms of the type of coating agent to be applied. 
     For example, the coating material may be filler, a base coat or clear varnish. 
     Other advantageous embodiments of the invention are characterised in the dependent claims or are evident from the following description of preferred embodiments on the basis of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic diagram of an inventive coating device with an atomiser with an integrated colour changer and an additional separate colour changer; 
         FIG. 2  is a modification of the coating device according to  FIG. 1 ; 
         FIG. 3  is a perspective view of an inventive painting robot with the coating device shown in  FIG. 1 ; 
         FIG. 4  is a modification of the embodiment according to  FIG. 2  with an external colour changer which has only one paint outlet; 
         FIG. 5  is a flow chart illustrating the operation of the embodiment in accordance with  FIG. 4 ; 
         FIG. 6A  is a geared pump of conventional design which may be used to supply high-runners or low-runners; 
         FIG. 6B  is a geared pump of novel design, with a plurality of pumping chambers, pairs of gearwheels located therein and a common drive shaft to drive said pairs of gearwheels; 
         FIG. 7  is a cutaway perspective view of the geared pump in accordance with  FIG. 6B ; 
         FIG. 8  is a perspective view of the geared pump in  FIG. 7 ; 
         FIG. 9  is a longitudinal section through the geared pump in accordance with  FIGS. 7 and 8 ; 
         FIG. 10  is a cross-section of the geared pump in accordance with  FIGS. 7 to 9  and 
         FIG. 11  is a cross-section through an inventive atomiser with an internal colour-changer valve assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of an inventive painting system which may be used for the mass painting of motor vehicle bodies and their attachments. 
     For this purpose the inventive coating device has an atomiser  1 , which is in the form of a high-speed rotary atomiser in this embodiment and which has a bell plate  2  as an application element. 
     The atomiser  1  has an integral colour changer valve assembly  3  with four paint valves F1, F2 F3, F4 to supply high runners. The paint valves F1-F4 of the integral colour-changer valve assembly  3  are each connected to a paint inlet  4 - 7 , wherein the paint inlets  4 - 7  are available on the connecting flange of the atomiser  1 . 
     A metering device  8  is connected to the paint inlets  4 - 7  of the integral colour-changer valve assembly  3 , which is structurally separate from the atomiser  1  and which has a volumetric metering pump  9 - 12  for each of the paint inlets  4 - 7  and a common drive motor  13 . 
     The high runners are fed to the metering device  8 , as the integral colour-changer valve assembly  3  only has low colour-change losses due to the short train of pipes between the integral colour-changer valve assembly  3  and the bell plate  2 , and requires a short colour change time. 
     The integral colour-changer valve assembly  3  is therefore connected to the bell plate  2  through a common main needle valve HN, which is only shown in diagrammatic form in the drawing. 
     A short flushing valve KS is also on a branch between the main needle valve HN and the bell plate  2 , ending in a flushing connection V on the connection flange of the atomiser  1 . The bell plate  2  can be flushed with a known flushing agent through the flushing connection V and the short flushing valve KS. 
     The common node at the outlet of the integral colour-changer valve assembly  3  and the inlet of the main needle valve HN is also connected to a pulsed air connection provided on the connecting flange of the atomiser  1  through a pulsed air valve PL. The train of pipes of the atomiser  1  can be cleaned with pulsed air through the pulsed air valve PL, which is itself also known. 
     A flushing agent valve VV also branches off from the common node of the colour-changer valve assembly  3  and the main needle valve HN, ending at the flushing connection V on the connection flange of the atomiser  1 , so that conventional solvent flushing is possible through the flushing agent valve VV. 
     In addition to the colour-changer valve assembly integrated into the atomiser  1 , the inventive coating system has a separate colour-changer valve assembly  14  which is structurally separate from the atomiser and which may take a conventional form, as described, for example, in EP 1 502 657 A2. At this point it need only be mentioned that the external colour-changer valve assembly  14  is configured as an A/B colour changer and has two paint outlets which are separately flushable, meaning that the colour changing time and colour changing losses can be reduced. 
     On the outlet side, the external colour-changer valve assembly  14  is connected to a metering device  15 , which has a volumetric metering pump  16 ,  17  for each of the two paint outlets of the external colour-changer valve assembly  14 , whereby the two metering pumps  16 ,  17  are each driven independently of each other by a drive motor  18 ,  19 . 
     In addition to the paint inlets  4 - 7  for the integral colour-changer valve assembly  3 , the atomiser  1  has two separate paint inlets  20 ,  21 , which are connected to the main needle valve HN through separately-actuatable paint valves FA, FB, to connect the atomiser  1  to the metering device  15 . 
     The external colour-changer valve assembly  14  is supplied with low runners, for which the longer colour change time and greater colour change losses play a less significant role. 
     A recirculation valve RA, RB is on a branch off the additional paint inlets  20 ,  21  for the external colour-changer valve assembly  14 , whereby the two recirculation valves RA, RB in this embodiment are structurally integrated into the atomiser  1 . In this way the paint inlets  20 ,  21  can be flushed as far as the atomiser  1 . 
     If high runners account for 65% of total capacity and colour change losses amount to 49 ml in the external colour-changer valve assembly and 5 ml in the internal colour-changer valve assembly  14 , the inventive coating device described above facilitates a reduction in average colour change losses from 49 ml to 20.4 ml, corresponding to a saving of 28.6 ml. 
       FIG. 2  shows a minor modification to the embodiment in  FIG. 1 , so reference is made to the above description to avoid repetition, whereby the same numbers are used for corresponding components. 
     A peculiarity of this embodiment is that both the recirculation valves RA, RB are located outside the atomiser  1 . 
       FIG. 3  is a perspective view of two painting robots  22 ,  23 , which may be moved linearly along a track  24 , which is known. Both the painting robots  22 ,  23  each have a moveable frame  25  and two robot arms  26 ,  27 , robot arm  26  being designated “arm  1 ” and robot arm  27  being designated “arm  2 ”. 
     A conventional robot wrist  28 , which guides the atomiser  1 , is fitted to the distal end of the robot arm  27 . 
     The metering device  8  (c.f.  FIG. 1 ) for the colour-changer valve assembly  3  integrated into the atomiser  1  is mounted in robot arm  26  (“arm  1 ”), whilst the external colour-changer valve assembly  14  is mounted in robot arm  27  (“arm  2 ”) 
     It must also be mentioned that the pulsed air valve PL and the flushing agent valve VV may also be located outside the atomiser  1 , for example on robot arm  27  (“arm  2 ”). The changeover then takes place outside the atomiser  1 . 
       FIG. 4  shows a modification to the embodiment in  FIG. 2 , so reference is made to the above description to avoid repetition, whereby the same numbers are used for corresponding components. 
     A peculiarity of this embodiment is that the external colour-changer valve assembly  14  is not configured as an A/B colour changer, but has only one paint outlet, which is associated with lower investment costs, a smaller installation space and lower weight. 
     In this version, high-runners and low-runners are applied alternately, as shown in the flow chart in  FIG. 5 , so that there is enough time during the application of a high runner through the internal colour-changer valve assembly  3  to flush the external colour-changer valve assembly  14  and apply the next low runner to it under pressure. The longer colour changing time required by the external colour-changer valve assembly  14  then has no irritating effect, but production scheduling becomes more involved, in order to ensure that the atomiser  1  can apply high-runners and low runners alternately. 
       FIG. 6A  shows an embodiment of a geared pump  29  which may, for example, be used instead of the metering device  8  in  FIG. 1  to supply the various paint inlets  4 - 7  of the atomiser  1  with the various high runners. 
     The geared pump  29  has a plurality of pumping chambers  30 - 33 , shown only in diagrammatic form here, each of which contains a pair of gearwheels, as is known, for example, from DE 600 09 577 T2. 
     The individual pairs of gearwheels in pumping chambers  30 - 33  are driven by a motor  35  through a drive shaft  34 . Clutches  36 - 39 , facilitating mechanical disconnection, are located between the individual pumping chambers  30 - 33  and between the pumping chamber  30  and the motor  35 . 
       FIG. 6B  shows a further, novel embodiment of a geared pump  29 , whereby this embodiment is partially identical to that described above and shown in  FIG. 6A , so reference is made to the above description of  FIG. 6A  to avoid repetition, the same numbers being used for corresponding components. 
     A peculiarity of this embodiment is that the common drive shaft  34  for the pairs of gearwheels located in the individual pumping chambers  30 - 33  extends through the entire length of the geared pump  29 . 
     The individual clutches  36 - 39  do not facilitate mechanical disconnection of the drive shaft  34  in an axial direction in this case. Instead, the individual clutches  36 - 39  make it possible for the pairs of gearwheels located in the pumping chambers  30 - 33  to be engaged with or disengaged from the drive shaft  34  selectively. 
     The structural design and method of operation of the geared pump  29  are described in more detail below, using  FIGS. 7 to 10 . 
     It is thus evident from these drawings that the individual pumping chambers  30 - 33  are each formed by a central plate  40 - 43  and adjacent end plates  44 - 51 , so that the individual pumping chambers  30 - 33  are behind one another in the axial direction of the drive shaft  34 . 
     For the sake of simplification, only five gearwheels  52 - 56  are shown in full in the cutaway three-quarter view in  FIG. 7 , although two gearwheels engaging with each other are located in each of the pumping chambers  30 - 33 . 
     In addition, the geared pump  29  has a draw key  57  for selective engagement of the pairs of gearwheels located in the pumping chambers  30 - 33  with the drive shaft  34 , facilitating engagement of the drive shaft  34  with the individual pairs of gearwheels by means of locking elements  58 - 60 . 
     The geared pump  29  also has a shaft seal  61  and a bearing  62  in this embodiment. 
     The compact size of this design of the geared pump  29  is advantageous, which is particularly important when the geared pump  29  is to be mounted in a robot arm. 
     Finally,  FIG. 11  is a schematic diagram of an inventive atomiser  63  with a bell plate  64  and a plurality of external electrodes  65  for electrostatic charging of the coating material to be applied. 
     Here, the atomiser  63  has a flange assembly  66 , a manifold  67 , an elbow  68  and a forepart  69 . 
     The manifold  67  contains an internal colour-changer valve assembly  70 , whilst a main needle vale  71  is located in the forepart  69 . This has the advantage that if the manifold  67  is separated from the elbow  68  and forepart  69 , only a few pipes will extend across the dividing line, entailing only minor contamination on separation. 
     The invention is not restricted to the embodiments described above. On the contrary, a variety of alternatives and modifications is possible, also using the inventive concept and therefore being within the scope of protection. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Atomiser 
           2  Bell plate 
           3  Integral colour-changer valve assembly 
           4 - 7  Paint inlets 
           8  Metering device 
           9 - 12  Metering pump 
           13  Drive motor 
           14  Colour-changer valve assembly 
           15  Metering device 
           16 ,  17  Metering pump 
           18 ,  19  Drive motor 
           20 ,  21  Paint inlets 
           22 ,  23  Painting robots 
           24  Track 
           25  Frame 
           26 ,  27  Robot arms 
           28  Robot wrist 
           29  Geared pump 
           30 - 33  Pumping chambers 
           34  Drive shaft 
           35  Motor 
           36 - 39  Clutches 
           40 - 43  Central plates 
           44 - 51  End plates 
           52 - 56  Gearwheels 
           57  Draw key 
           58 - 60  Locking element 
           61  Shaft seal 
           62  Bearing 
           63  Atomiser 
           64  Bell plate 
           65  External electrodes 
           66  Flange assembly 
           67  Manifold 
           68  Elbow 
           69  Forepart 
           70  Internal colour-changer valve assembly 
           71  Main needle valve F1-F4 Paint valves 
         FA, FB Paint valves 
         HN Main needle valve 
         KS Short flushing valve 
         PL Pulsed air valve 
         RA, RB Recirculation valves 
         V Flushing connection 
         VV Flushing agent valve