Patent Publication Number: US-2003232125-A1

Title: Apparatus and method for preselection of a coating program in powder coating

Description:
BACKGROUND OF THE INVENTION  
       [0001] The invention relates to an apparatus and a method for preselection of a coating program or formulation in powder coating by means of a coating gun, preferably a hand-held coating gun, comprising a control apparatus which may be arranged separate from the coating gun or integrated in the same.  
       [0002] In powder coating, especially if done manually, a worker using a known apparatus, is not in a position to adjust the coating parameters at least halfway properly in response to the geometry and material of the various workpieces to be coated, until after he has gathered an extensive amount of practical experience.  
       [0003] The parameters to be adjusted comprise in particular the electrode voltage, the electrode current or spray current, the electrode current/voltage characteristic, the conveying air amount, the atomizing air amount, the tribo air amount, the total air amount, and the amount of powder, as well as the coating time period.  
       [0004] Among them the electrostatic parameters, like electrode voltage and electrode current are especially difficult to select.  
       OBJECT OF THE INVENTION  
       [0005] It is, therefore, an object of the invention to provide an apparatus which will make it much easier for a user to select a program which is the respective most efficient one or a suitable formulation, for the most varied coating tasks.  
       [0006] The object is met, according to the invention, with an apparatus for preselection of a program or formulation in powder coating by means of a coating gun, comprising a control apparatus, characterized in that at least two selector keys are provided at the control apparatus and/or the coating gun for selecting two different coating techniques.  
       [0007] These coating techniques, preferably, are “corona coating” or “tribo coating”, both familiar to those skilled in the art so that they need not be described here in greater detail.  
       [0008] Advantageously, the selector keys permit further coating techniques to be selected alternatively, such as “metallic coating” or “individual coating”.  
       [0009] The selector keys may be designed so as to allow varying each coating technique selected as described above. Advantageous examples hereof are as follows. The selector keys  12 - 15  permit a selection to be made of a plurality of current/voltage characteristics  30 ,  32 ,  34 , especially of a characteristic  32  which is flatter by 20% to 40% or a characteristic  34  which is flatter by 60% to 80%, compared with a standard characteristic  30 . The selector keys  12 - 15  permit allowance to be made for different workpiece geometries. In addition, a selector key  14  may provide for consideration of an option of “re-coating”.  
       [0010] According to another modification of the invention, the magnitude of the essential parameters in powder coating may be adjusted variably by means of the selector keys in the sense of optimization, depending on the coating technique selected and the respective additional specification selected, as described in the above examples. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] The invention will be described further, by way of example, with reference to the accompanying drawings, in which:  
     [0012]FIG. 1 is a diagrammatic view of an installation for manual powder coating according to the invention.  
     [0013]FIG. 2 shows a first display level of a screen of a control apparatus belonging to the installation illustrated in FIG. 1 and also indicating associated selector keys.  
     [0014]FIG. 3 a  illustrates a first variant of a second display level of the screen.  
     [0015]FIG. 3 b  illustrates a second variant of a second display level of the screen.  
     [0016]FIG. 3 c  illustrates a third variant of a second display level of the screen.  
     [0017]FIG. 3 d  illustrates a fourth variant of a second display level of the screen.  
     [0018]FIG. 4 is a diagram illustrating variants of the spray current/electrode voltage characteristic which are selectable according to the invention. 
    
    
     DETAILED DESCRIPTION  
     [0019] As illustrated in the diagrammatic presentation of FIG. 1, two hand-held coating guns for alternative usage are provided, namely a tribo spray gun  1  and a corona spray gun  2 , both being of known design. Delivery hoses  3 ,  4  for a powder-air mixture connect these spray guns  1 ,  2  to a conventional injector  5  which communicates with the interior of a powder reservoir  6 .  
     [0020] The two spray guns  1 ,  2 , furthermore, are connected by electrical cables  7 ,  8  to a control apparatus  10  comprising a screen  1   1  and selector keys  12  to  18  for selection of a coating technique, including a program or formulation of the particular coating technique selected, and a display level.  
     [0021] Moreover, the control apparatus  10  is connected to the injector  5  by a dosing air conduit  21  and a conveying air conduit  22 .  
     [0022] Finally, the control apparatus  10  is connected to the tribo spray gun  1  by a tribo air conduit  23  and, alternatively, to the corona spray gun  2  by an atomizing air conduit  24 .  
     [0023] Reference numeral  25  designates a fluidizing air conduit which passes from the control apparatus  10  through a throttle  9  to the bottom of the powder reservoir  6  to fluidize the powder there.  
     [0024]FIG. 2 the screen  11  is illustrated in a situation where a first display level is to be seen the screen  11 .  
     [0025] The capital letters in the screen  11  are assigned to the selector keys  12  to  15  underneath them and have the following meaning:  
                                                      C   corona coating           T   tribo coating           M   metallic coating           I   individual coating.                      
 
     [0026] The selector keys  16 ,  17 , and  18  shown next to the screen  11  at the right hand side thereof in FIGS. 1, 2, and  3   d  have the following meaning:  
                                                      16   reset the display level           17   small powder cloud (little powder)           18   big powder cloud (much powder)                      
 
     [0027] The button marked  19  in FIG. 1 serves for switching on/off the control apparatus  10 .  
     [0028] When the control apparatus  10  is switched on and the first display level shown, actuation of the buttons  12  to  15  will result in one of the presentations according to FIGS. 3 a  to  3   d  to be shown in a second display level of the screen  11 . For example, when pressing selector key  12 , the presentation of FIG. 3 a  will appear, indicating that the “corona coating” technique was selected, with corona powder at a percentage quantity of powder of 65%.  
     [0029] With the second display level being shown on the screen, renewed pressing of any of the selector keys  12  to  15  permits the following coating parameters to be changed:  
     [0030] selector key  12 —small workpiece (little powder)  
     [0031] selector key  13 —big workpiece (much powder)  
     [0032] selector key  14 —re-coating  
     [0033] selector key  15 —deep workpiece.  
     [0034] Pressing of selector key  16  causes switchover of the display levels, i.e. from the second display level in FIGS. 3 a  to  3   d  back to the first display level according to FIG. 2.  
     [0035] Selective pressing of either one of keys  17 , 18  permits the choice of working with just a little powder (small powder cloud) or with a lot of powder (big powder cloud).  
     [0036] In addition to displaying the coating technique selected and the percentage content of powder in the powder-air mixture, the second display level of FIGS. 3 a  to  3   d  includes symbols which are associated with the selector keys and indicate the respective parameters chosen in the second display level. Their meaning is as follows:  
                                                      small rectangle   40 - small workpiece           big rectangle   42 - big workpiece           2x   44 - re-coating           rectangular profile   46 - deep workpiece           little powder   47 - small powder cloud           much powder   48 - big powder cloud.                      
 
     [0037] Having chosen and mechanically connected the desired spray gun  1  or  2  and having selected the desired coating technique C, T, M, I in the first display level by having pressed the respective selector key, the user will obtain automatic adjustment, in the second display level, of the program or formulation matching the selected coating technique, by again actuating the previously pressed selector key. Any further adjustment can be dispensed with.  
     [0038] On the whole, therefore, sixteen programs or formulations are available, allowing the user to set specific parameter data for the items listed below, simply by pressing the respective key:  
     [0039] electrode voltage  
     [0040] maximum spray current  
     [0041] electrode current/voltage characteristic  
     [0042] volume of conveying air for powder delivery  
     [0043] volume (amount) of atomizing air  
     [0044] total air volume (amount)  
     [0045] volume (amount) of tribo air in case of tribo charging.  
     [0046] Additionally, the user can vary the powder quantity by either pressing the respective selector key several times or holding the key pressed until the display indicates the desired increase which, of course, is also implemented at the gun.  
     [0047] The diagram of FIG. 4 illustrates three variants of the electrode current/electrode voltage characteristic, reference numeral  30  designating the maximum characteristic,  32  designating a characteristic which is flatter by between 20% and 40% and  34  designating a characteristic which is still flatter by between 60% and 80% than the maximum characteristic. The maximum characteristic is cut at an upper horizontal level of maximum current of 160 μA. This maximum current may be selected variably for each characteristic.  
     [0048] The features disclosed in the specification above, in the figures and claims may be significant to implementing the invention, both individually and in any ombination.