Patent Publication Number: US-2013240072-A1

Title: Control Device for Paint Spraying Systems and Application Systems

Description:
The invention relates to a control device for paint spraying systems and application systems which are used, in particular, for the quick-change application of paint in batch productions, with a piping system carrying fluids, such as paint, lacquer, coating particles, and solvents of different cleanliness classes, with individual separating elements, such as pigs, enabling a fluid separation inside the piping system. 
     Users of industrial paint spraying systems, such as those used, for example, in the assembly sequence in the automobile industry, are often confronted with the task of providing individual products (motor vehicles) or individual items of a batch production with a custom paint finish. In such cases, it is in the interest of an efficient and economical production to be able to quickly change the color, and this color change has to be performed with the spraying robots or hand spray guns that are in service without disrupting the flow of the assembly sequence. In order to satisfy this requirement, the production process is configured in such a way that the separation of the individual fluids is carried out inside the system&#39;s piping system that feeds the spraying robots and/or spray guns by conveying, on an alternating basis, charges of the different fluids, such as paint or cleaning solvents, through the piping system in succession and separated from each other. The amount of control engineering required for this purpose significantly increases the complexity and cost of existing systems. 
     With respect to the foregoing, the object of the present invention is to provide a control device that enables a quick change of the fluids to be applied to other components, such as the components of a vehicle body, at a low cost and with minimal technical complexity of the control system. 
     The invention achieves this object by means of a control device having the features specified in claim  1  in its entirety. 
     Accordingly, the control device according to the invention is characterized in that individual control blocks of the control device are composed of a plurality of actuatable switching valves, which enable, on the one hand, the input and/or output of pigs and/or, on the other hand, for this purpose, the simultaneous conveying of fluids in the piping system. The use of control blocks in which a plurality of switching valves, which perform a variety of control functions, are combined to form a control unit, reduces, compared to an operation of individual valve devices serving as control elements, both the complexity of the control system and also the design efforts, so that the result is a reduction in both the system costs and also the operating costs. 
     In especially advantageous exemplary embodiments, the piping system has an input control block at the beginning of a piggable pipeline that runs to at least one spraying station. This input control block has two switching valves, of which the first switching valve can be actuated as the controlling component of a pig launcher for the pigs and the second switching valve can be actuated to release and block the fluid inputs leading to the pipeline. The result of this arrangement is that all of the functions that are necessary for supplying the spraying station for the spraying operation and for changing the color can be executed by a single control block, in that one switching valve controls the fluid inputs for the fluids. In this case, one input can be provided for the paint, and at least one additional input can be provided for the cleaning solvents of different cleanliness classes, and the other switching valve for a necessary separation of the successive fluid flows controls the launching of the respective pigs. 
     The arrangement can be configured with a distinct advantage in such a way that the first switching valve of the input control block is arranged, based on the operational fluid flow, downstream of the second switching valve in the block and can be actuated for switching positions, in which either an input port for inserting a pig is released and a connection to the second switching valve is blocked, or this connection is released for the movement of the launched pig and/or the conveying of the respective fluid through the pipeline. 
     Preferably, the second switching valve, which is arranged upstream of the first switching valve in the input control block, can be actuated for switching positions, in which, on the one hand, a paint port is connected to the pipeline by means of a connection with the first switching valve; or, on the other hand, this connection is blocked; or, thirdly, the paint port is blocked, and the at least one fluid port for solvents of different cleanliness classes is connected to the pipeline by means of the connection with the first switching valve. Therefore, owing to the interaction of the first and second switching valves, all of the functions that are required to supply the spraying station and for changing the color are combined in one control block, including the launching of the necessary pigs. 
     The pipeline continues to run in an advantageous way from the respective spraying station to an end control block, which comprises two switching valves, of which one switching valve can be actuated for blocking and inputting an end of the pipeline that is connected to the block; and the second switching valve, which is situated downstream, is a controlling component of a pig receiver for pigs. The result of this arrangement is that once again the additional functions, which are necessary for retrieving the pertinent pigs, are also combined in one uniform control block. 
     The arrangement can be configured with a distinct advantage in such a way that a compressed air connection is provided at the fluid connection between the first and the second switching valve of the end control block. The result is that when the end of the pipeline is blocked, a pig, which has arrived at the end control block and is to be retrieved, can, through the admission of compressed air, be pushed out by way of the opened second switching valve. 
     In order to detect the position of the pig that is to be retrieved, a sensor, which signals the presence of a pertinent pig, can be provided at the fluid connection between the first and the second switching valve of the end control block. This approach can be implemented with a distinct advantage in such a way that the pigs have a permanent magnetic insert, so that a magnetic inductive sensor or a reed switch provides a notification signal. 
     In order to retrieve the pertinent pig, the arrangement can be configured in such a way that an output port for the pigs can be released or blocked with the second switching valve of the end control block. 
     Particularly advantageous exemplary embodiments provide a connecting line, which runs from the end control block to a distributor control block and which extends from a port at the end control block; and this port may be found at a fluid connection between the first and the second switching valve. 
     The distributor control block can comprise in an advantageous way five switching valves, which can be actuated for alternating connections from the connecting line to a first and/or a second paint reservoir or to a reservoir for slightly contaminated solvent or to a collector for highly contaminated solvent. The distributor control block can be used to recover the excess paint as well as the excess solvent, which was used in the course of the pig passage for precision cleaning, from the fluid flow, which arrives at said distributor control block from the pipeline, leaving the spraying station, by way of the end control block, for further use and to separate out the highly contaminated solvent that was used for preliminary cleaning. 
     The arrangement can be configured with a distinct advantage in such a way that the switching valves of at least one control block and preferably all of the control blocks are formed by ball valves comprising ball elements, which can be rotated by means of a respective controllable drive, which can be actuated as a function of the signal of an associated rotary position sensor and/or as a function of the signal of the pig sensor at the end control block and/or as a function of the signals from sensors that are distributed in the piping system and that detect the passing of pigs. 
    
    
     
       The invention is explained in detail below by means of one exemplary embodiment shown in the drawings. Referring to the drawings: 
         FIG. 1  is a highly simplified drawing in schematic form of the piping system of a paint spraying system, which is provided with an exemplary embodiment of the control device according to the invention; 
         FIG. 2  is a perspective oblique view of an input control block of the exemplary embodiment of the control device according to the invention; 
         FIGS. 3 and 4  are longitudinal sectional views of the control block from  FIG. 3  with the section planes rotated by 90 degrees with respect to each other; 
         FIG. 5  is a perspective oblique view of an end control block of the exemplary embodiment; 
         FIG. 6  is a side view of the control block from  FIG. 5 ; 
         FIG. 7  is a longitudinal sectional view of the end control block according to the section line VII-VII from  FIG. 6 ; 
         FIG. 8  is a longitudinal sectional view of the end control block with the section plane rotated by 90 degrees with respect to  FIG. 7 ; 
         FIG. 9  is a perspective oblique view of a distributor control block of the exemplary embodiment; 
         FIG. 10  is a highly simplified drawing in schematic form of the fluid circuit of the distributor control block from  FIG. 9 ; and 
         FIG. 11  is a highly exploded longitudinal view of a pig for use in the control device according to the invention. 
     
    
    
     The invention is explained below by means of one exemplary embodiment, in which the control device is provided for the operation of a paint spraying system, as shown in schematic form in  FIG. 1 , whereby a spraying station  3  can be supplied by means of a piping system  1 . In the exemplary drawing from  FIG. 1 , this spraying station is depicted by a spraying robot  5  and two hand spray guns  7 . In order to be able to change the color for the spraying station  3 , which is necessary for a clean separation of the fluids fed to the spraying station  3 , the system makes use of the known pigging technology. For this purpose, the piping system  1  has a piggable pipeline  9  with an inflow section  11  upstream of the spraying station  3  and an outflow section  11  downstream of the spraying station  3 . Pigs  15 , of which only one is shown in an enlarged form in  FIG. 11 , are provided for the passage through the sections  11  and  13  of the pipeline  9 . The pigs  15  can be launched into the pipeline from a magazine  17  by means of an input control block  19 , which is located at the beginning of the inflow section  11  of the pipeline  9 , and can be retrieved from the pipeline  9  by means of an end control block  21 , which is located at the end of the outflow section  13 . 
     The input control block  19 , which is shown in detail in  FIGS. 2 to 4 , comprises two switching valves in the form of a ball valve  23  and  25  respectively as the fluid control elements.  FIGS. 2 and 4  show that a rotary drive  27  in the form of a pneumatic drive is provided for the switching or rotary movement of the ball element of the ball valves  23 ,  25 , with each drive  27  being assigned a rotary position sensor  29 , which delivers an electric signal that signals the switching position of the associated ball valve  23 ,  25 . In the drawing from  FIGS. 3 and 4 , the switching valve  23  is in a switching position in which it closes an input port  31 , by way of which the pigs  15  can be inserted from the magazine  17 , as well as a decompression port  33 , by way of which the pressure can be reduced when a pig  15  is inserted. At the same time, a connection  35 , which is formed in the control block  19 , is connected to the section  11  of the pipeline  9  by means of the ball valve  23 . In the illustrated state, the second ball valve  25  closes a fluid port  37 , while a connection is established between the paint ports  39  and  41 , so that a neutral paint circulation can take place in connection with a paint reservoir  43  (see  FIG. 1 ). When the first ball valve  23  is rotated 90 degrees, starting from the switching position shown in  FIGS. 3 and 4 , a pig  15  can be launched from the magazine  17  by way of the input port  31 . By continuing to rotate the first ball valve  23  by another 90 degrees into the position shown in  FIGS. 3 and 4 , the launched pig  15  can be moved through the pipeline  9  in that the second ball valve  25  is rotated out of the illustrated position in such a way that either the paint port  39  or the fluid port  37  is in fluid communication with the connection  35 , so that the pertinent pig  15  is moved through the pipeline  9  due to the paint supplied from the paint port  39  or due to the fluid supplied from the fluid port  37 . 
       FIGS. 5 to 8  show in more detail the end control block  21  at the end of the section  13  of the pipeline  9 . The end control block  21  comprises, like the input control block  19 , two switching valves in the form of a ball valve  45  and  47  respectively. Again, as in the case of the input control block  19 , each ball valve  45 ,  47  has a pneumatic drive  27 , which is assigned a rotary position sensor  29  for generating an electric position signal. A pig sensor  51  may be found at the inner fluid connection  49  between the first ball valve  45  and the second ball valve  47 . When using pigs  15 , which have a permanent magnetic core or a core  53  provided with magnetic particles (see FIG.  11 ), a magnetic inductive sensor or a reed contact can be provided as the pig sensor  51 . The second ball valve  47  of the end control block  21  is a component of a pig receiver for pigs  15  that can leave by way of a pig receiver output  55  in the switching position shown in  FIGS. 7 and 8 . When the pig sensor  51  signals the presence of a pig  15  to be retrieved, the retrieval process can be carried out in such a way that the fluid admitted from the pipeline section  13  moves the pig  15  out of the end control block  21  by way of the output  55  when the ball valves  45  and  47  are opened. At the same time, the fluid displaced by this pig  15  is also expelled along with said pig. The issuing fluid together with this pig  15  passes into a collecting tank  57  (see  FIG. 1 ). In the operating phases in which the pigs are not retrieved, the second ball valve  47  is closed; that is, the pig output  55  is blocked. When the first ball valve  45  is opened, the fluid that is outputted from the spraying station  3  over the section  13  of the pipeline  9  flows over the connection  49  in the end control block  21  to a connecting port  59  and, from there, over a connecting line  61  to a distributor control block  63 . This distributor control block comprises five switching valves that in the present example are formed, as in the case of the two other control blocks  19  and  21 , by ball valves, likewise with a pneumatic drive  27  and an electric rotary position sensor  29 . Since, however, these switching valves do not have to be piggable, it is also possible to provide other types of valves that can be electrically actuated as a function of the control signals of the pig sensor  51  as well as other sensors (not depicted) that are distributed in the piping system  1  and that signal the passage of pigs. 
     In normal paint spraying operation, excess paint flows from the spraying station  3  over the connecting line  61  to the distributor control block  63  when the ball valve  45  is opened and the ball valve  47  of the end control block  21  is closed. In order to recover such excess paint, the distributor control block  63  establishes, starting from a paint output  65 , the connection to the paint reservoir  43  (see  FIG. 1 ). In order to change the color, the second ball valve  25  of the input control block  19  is moved into the switching position shown in  FIGS. 3 and 4 ; the first ball valve  23  is rotated in order to launch a pig  15  and then moved again into the switching position shown in  FIGS. 3 and 4 . Then the paint ports  39 ,  41  are blocked by changing over the second ball valve  25 , and the connection from the fluid port  37  to the connection  35  is established. 
     Then the launched pig  15  is moved by feeding in a preliminary cleaning solvent by way of the fluid port  37 . In this case, a slightly contaminated solvent, used previously as the preliminary cleaning agent, is supplied from a preliminary cleaning solution reservoir  67  by way of a switching valve  69 . The result is that the pig  15  is moved and forces the paint, located in the pipeline  9 , through the end control block  21 , of which the first ball valve  45  is opened and the second ball valve  47  is closed, as well as through the connecting line  61  to the distributor control block  63 , of which the switching valves are switched in such a way that the paint is recovered and is returned from the paint output  65  to the paint reservoir  43 . As soon as the pig sensor  51  at the end control block  21  determines the presence of the pig  15 , the second ball valve  47  is opened, while the second ball valve  25  at the input control block  19  is switched over, in order to close the fluid input  37 . Thereupon, the first ball valve  23  is actuated again in such a way that a second pig  15  is launched. 
     Upon completion, the second ball valve  25  is switched over again in such a way that by way of the fluid input  37  an unused, clean solvent can be supplied by way of the fluid input  37  for precision cleaning, with the clean solvent moving this pig  15 , which displaces the highly contaminated solvent, which is loaded with residual paint and which may be found upstream of the pig, through the end control block  21  and the connecting line  61  to the distributor control block  63 . At the same time, as soon as the second pig  15  begins to move, the second ball valve  47  at the end control block  21  is opened; and this ball valve releases the pig output  55 . As a result, the highly contaminated solvent, which is moved by the second pig  15 , forces the first pig  15 , which may be found in the end control block  21 , into the collecting tank  57  together with a portion of the highly contaminated solvent. 
     After this pig  15  has exited, the second ball valve  47  at the end control block  21  is closed again, so that the rest of the highly contaminated solvent is moved by the second pig through the connecting line  61  to the distributor control block  63 , until the second pig  15  arrives in the end control block  21 , a state that is signaled by the pig sensor  51 . If this is the case, then the first ball valve  45  of the end control block  21  is closed, the second ball valve  47  is opened in order to release the pig output  55 , and compressed air is admitted by way of a compressed air connection  74  (see  FIG. 8 ), which is protected by a check valve (not shown), which can be opened by means of pressure from the outside, in order to push the pig  15  out into the collecting tank  57 . Then the second ball valve  47  is closed again. At this point, the solvent, which effects precision cleaning and may be found in the pipeline  9 , in this operating phase is pushed out of the pipeline  9  by means of a third pig  15  and flows by way of the end control block  21  to the distributor control block  63 . This displacement of the third pig takes place in that the fluid port  37  is closed by means of the second ball valve  25  at the input control block  19 ; and the connection between the paint port  39  to the beginning section  11  of the pipeline  9  is released. 
     In order to change the color, the paint ports  39 ,  41  of the input control block  19  are connected to a corresponding paint reservoir for the changed color (in  FIG. 1  only one paint reservoir  43  is shown in schematic form for the sake of simplicity). At this point, the third launched pig  15  is moved by means of the new color that is supplied by way of the paint ports  39 ,  41 , so that said third pig moves the solvent, which is just slightly contaminated, to the distributor control block  63  by way of the end control block  21 , until the third pig  15  arrives at the end control block  21 . This means that the pipeline  9  is filled with the new color up to the end section  13 . By closing the first ball valve  45  and opening the second ball valve  47  of the end control block  21 , the third pig  15  in turn is discharged into the collecting tank  57  due to the admission of compressed air. 
     In the course of the subsequent spraying process of the spraying station  3 , the excess paint, which is delivered by way of the line section  13 , flows in turn through the connecting line  61  to the distributor control block  63 . Therefore, in the working cycle of spraying operation/color change, clean paint, clean solvent, slightly contaminated solvent, as well as a solvent which is highly contaminated by residual paint during the preliminary cleaning, flow on an alternating basis to the distributor control block  63 . These fluids are divided in the distributor control block  63 , as indicated symbolically in  FIG. 1 , and can be recognized by the solid lines, dashed and dotted lines, thick dashed lines, and/or fine dashed lines. From a port  75 , the highly contaminated solvent passes through a line  77  to a collector  73  for disposal; and this collector also receives highly contaminated solvent from the collecting tank  57  for the pigs  15 . From a port  79 , slightly contaminated solvent, which has previously carried out the precision cleaning of the pipeline  9 , passes through the line  81  to the preliminary cleaning solution reservoir  67 , while the paint, for recovery purposes, flows to the paint reservoir  43  by way of the paint output  65  and a line  83 .  FIG. 10  shows that the distributor control block  63  comprises five switching valves  85 ,  87 ,  89 ,  90 , and  91 . While ball valves are provided for this purpose, it is also possible to consider other types of valve designs, unlike those used in the case of the additional shutoff valves  93  and  95 , which are provided in the line sections  11  and  13  and, therefore, have to be piggable, for which reason ball valves are used herein. In particular, an additional paint or fluid circuit (not shown) of an additional paint spraying system is connected to the output of the switching valve  85 . 
       FIG. 11  shows that the pigs  15  are provided for the direction of travel indicated with the arrow  96  and have plate-shaped annular bodies  100  at both ends of a central part  97  between the end parts  98 , with these annular bodies being made of an elastomeric material, for example, a synthetic rubber. These annular bodies have inclined sealing lips  99  on the plate edge opposite the direction of travel that is indicated by the arrows  96 . In the undeformed state, these sealing lips define an outside diameter that is somewhat larger than the inside diameter of the pipeline  9  and have a larger diameter relative to the central part  97 , so that the result is a shape that resembles a diabolo. In the case of pipelines that have sharper bends, the axial length of the central part  97  is chosen correspondingly small, so that the pig  15  moves easily through the bends of the line.