Patent Publication Number: US-11020762-B2

Title: Coupling for the connecting of lines, powder coating facility including the coupling, and method for cleaning of the powder coating facility

Description:
This application claims priority under 35 USC § 119 to European patent application number 18167080, filed on Apr. 12, 2018, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates to a coupling for the connecting of lines, in particular of lines conducting coating powder or compressed air. The invention also relates to a powder coating facility including a coupling of this type and to a method for cleaning of the powder coating facility. 
     DESCRIPTION OF RELATED ART 
     During the electrostatic coating of workpieces with coating powder, or powder for short, the powder is sprayed onto the workpiece to be coated by means of one or more powder applicators. Subsequently, the workpiece coated with powder is heated to melt the powder. Once the workpiece has cooled down, the powder forms a hard, closed cover layer on the workpiece. During the coating process, the workpieces to be coated usually reside in a powder coating booth, which shall hereinafter be referred to as booth or coating booth for short. The powder applicators are supplied with coating powder by one or more powder conveyors that can be situated in a powder center. 
     If workpieces are to be coated with a different coating powder than the one used earlier, the coating process is interrupted and a so-called powder change takes place. During a powder change, i.e. when, for example, a different type of powder or powder of a different color is to be sprayed, more or less comprehensive cleaning measures are required in order to remove residues of the previously used powder from the powder-conducting components of the facility. Manual cleaning of these components can take considerable time to accomplish. During the cleaning process, the facility is not available for the coating of workpieces. This has a negative effect on the production costs. It is another disadvantage of manual cleaning that the staff runs the risk of inhaling powder particles during the cleaning process. Moreover, it must be made sure that the cleaning is done thoroughly. If, for example, the powder-conducting lines between powder conveyor and powder applicators are not cleaned sufficiently, there may be an undesirable carry-over of color after a color change. 
     A fluids switch for switching between two different fluids is known from the prior art, EP 2 361 691 A1. The fluids switch comprises a feed plate with two fluid feed lines and a purging air feed that is arranged between the two fluid feed lines. Moreover, the fluids switch comprises a discharge plate that touches the feed plate and has two fluid return lines and a discharge line that is arranged between the two fluid return lines. The feed plate can be shifted relative to the discharge plate such that the two fluid feed lines and the purging air feed can be connected to the discharge line. This solution is disadvantageous in that powder may become deposited between the feed plate and the discharge plate. This is the case, in particular, when the feed plate and the discharge plate are being shifted towards each other. The powder that is being deposited between the plates can be removed only with difficulty and additional effort during the cleaning of the fluids switch. It is another disadvantage that the connectors on the feed plate cannot really be positioned exactly opposite from the connectors on the discharge plate. The connectors being more or less offset with respect to each other generates ledges and dead spaces, in which powder may be deposited. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to devise a coupling for the connecting of lines, a powder coating facility including the coupling as well as a method for the cleaning of the powder coating facility, in which the degree of automation during the cleaning is increased even more. 
     The object is met by a coupling for the connecting of lines having the features described herein. 
     The coupling according to the invention for the connecting of lines comprises a first coupling disc with first line connectors and a second coupling disc with second line connectors. Moreover, a first drive is provided in order to be able to move the two coupling discs axially with respect to each other. Moreover, a second drive is provided in order to be able to rotate the two coupling discs with respect to each other. 
     The object is also met by a powder coating facility that includes the coupling described above and has the features described herein. 
     The powder coating facility according to the invention comprises the coupling described above and a powder conveyor that is connected to one of the first line connectors of the coupling by means of a powder line. Moreover, a powder applicator is provided that is connected to one of the second line connectors of the coupling by means of a further powder line. Moreover, a compressed air purging line that is connected to the coupling is provided. 
     The object is also met by a method for cleaning of the powder coating facility described above having the features described herein. 
     The method according to the invention for cleaning of the powder coating facility described above comprises the following steps. The coupling discs are arranged appropriately with respect to each other such that the compressed air purging line is connected to the powder line by means of the coupling. In a further step, the powder line is purged in the direction of the powder conveyor by means of compressed air. 
     Advantageous developments of the invention are evident from the features described herein. 
     In one embodiment of the coupling according to the invention, the two coupling discs are arranged coaxially. This allows the coupling to have a simple and inexpensive design. 
     In another embodiment of the coupling according to the invention, the first coupling disc comprises first axial channels, which each are connected to one of the first line connectors each. The second coupling disc comprises second axial channels, which each are connected to one of the second line connectors each. One seal each is arranged between the first channels and the second channels. 
     In an additional embodiment of the coupling according to the invention, the seals are designed to be sleeve-shaped. 
     In a development of the coupling according to the invention, an axle attached to the first coupling disc is provided. The axle forms the rotary axis for the second coupling disc. 
     Another development of the coupling according to the invention provides an axle bearing between the axle and the second coupling disc. The axle bearing comprises an air purge system. By this means, the degree of automation can be increased further and the coupling can be kept cleaner. 
     In an additional development of the coupling according to the invention, at least a part of the first line connectors are arranged on a first pitch circle. 
     Moreover, the invention can provide the coupling according to the invention such that at least another part of the first line connectors are arranged on a second pitch circle, whereby the radii of the two pitch circles differ. By this means, the surfaces available on the two coupling discs can be utilized optimally. 
     It is of advantage for the first drive of the coupling according to the invention to comprise a pneumatic cylinder. A drive of this type can be manufactured easily and inexpensively. Moreover, a drive of this type can also be used in areas with an elevated explosion hazard. 
     It is also of advantage for the second drive of the coupling according to the invention to comprise a pneumatic cylinder. A drive of this type can be manufactured easily and inexpensively. Moreover, a drive of this type can also be used in areas with an elevated explosion hazard. 
     In the coupling according to the invention, at least a part of the first and/or of the second line connectors can be designed as hose nozzles. 
     A development of the coupling according to the invention provides the one coupling disc to comprise a positioning pin and the other coupling disc to comprise sockets for accommodation of the positioning pin. The positioning pin and the sockets help in accurately positioning the (axially) adjacent channels of the two coupling discs with respect to each other such that no dead space arises at the transition between the adjacent channels and the seals and such that no powder can be deposited in this place. 
     Another development of the coupling according to the invention has at least one spacer arranged between the two coupling discs. 
     In a development of the powder coating facility, the compressed air purging line is connected to one of the second line connectors of the coupling. Moreover, a further compressed air purging line connected to one of the first line connectors of the coupling is provided. 
     In a development of the method for cleaning of the powder coating facility, the coupling discs are arranged appropriately with respect to each other such that the further compressed air purging line is connected to the powder applicator by means of the coupling and the further powder line. In a further step, the further powder line is purged in the direction of the powder applicator by means of compressed air. By this means, the degree of automation of the cleaning can be increased even more and the period of time required for cleaning can be reduced even more. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and several exemplary embodiments are illustrated in more detail in the following based on 19 figures. 
         FIG. 1  shows a first three-dimensional view of a first possible embodiment of the coupling according to the invention for the connecting of lines. 
         FIG. 2  shows a second three-dimensional view of the first embodiment of the coupling according to the invention. 
         FIG. 3 a    shows a side view of the first embodiment of the coupling according to the invention. 
         FIG. 3 b    shows a side view of the second embodiment of the coupling according to the invention. 
         FIG. 4  shows a longitudinal section of the first embodiment of the coupling according to the invention. 
         FIG. 5  shows a schematic block diagram of a possible embodiment of a powder coating facility with the coupling according to the invention. 
         FIG. 6  shows a first three-dimensional view of a first possible embodiment of the powder center according to the invention in powder conveying mode. 
         FIG. 7  shows a second three-dimensional view of the first embodiment of the powder center according to the invention. 
         FIG. 8  shows a top view of the powder center according to the invention. 
         FIG. 9  shows a first side view of the powder center according to the invention. 
         FIG. 10  shows a magnified sectioned view from the side of a part of the powder center according to the invention with the screen cleaning device. 
         FIG. 11  shows a magnified sectioned view from the side of another part of the powder center according to the invention with the container cleaning facility. 
         FIG. 12  shows a first three-dimensional view of the powder center according to the invention in cleaning mode. 
         FIG. 13  shows a second three-dimensional view of the powder center according to the invention in cleaning mode. 
         FIG. 14  shows a top view of the powder center according to the invention in cleaning mode. 
         FIG. 15  shows a three-dimensional view of a possible embodiment of a fresh powder station. 
         FIG. 16  shows a frontal view of the fresh powder station. 
         FIG. 17  shows a sectioned side view of the fresh powder station. 
         FIG. 18  shows a sectioned top view of the fresh powder station. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show two different three-dimensional views of a first possible embodiment of the coupling  130  according to the invention for the connecting of lines.  FIG. 3 a    shows a side view of the coupling  130  according to the invention and  FIG. 4  shows a longitudinal view along the line A-A. The coupling  130  according to the invention comprises a first coupling disc  135  and a second coupling disc  136 , which, preferably, are arranged such as to be concentric with respect to each other. Advantageously, the coupling disc  136  is designed to be round or even circular. The second coupling disc  136  is supported against the first coupling disc  135  such that it can be rotated. This is indicated by the double arrow  130 . 1 . A drive  134  is provided to be able to rotate the second coupling disc  136 . Moreover, the second coupling disc  136  can be moved in axial direction with respect to the first coupling disc  135  in translational manner. This is indicated by the double arrow  130 . 2  on the coupling disc  136 . A drive  133  is provided to be able to move the second coupling disc  136  in axial direction. 
     The drive  133  can comprise a pneumatic cylinder  133 . 1 . A piston  133 . 2  is situated on the inside of the pneumatic cylinder  133 . 1  and can be moved into a first position and into a second position by means of compressed air. For this purpose, the drive  133  comprises two compressed air connectors  133 . 3  and  133 . 4 . The two compressed air connectors  133 . 3  and  133 . 4  can each be connected to a compressed air source by means of a valve V 2  or V 3  (see  FIG. 4 ). When the valve V 3  is closed and the valve V 2  is open, the compressed air flows from the left into the cylinder  133 . 1  and presses the piston  133 . 2  towards the right.  FIG. 4  shows the piston  133 . 2  in the right end position. In contrast, when the valve V 2  is closed and the valve V 3  is open, the compressed air flows from the right into the cylinder  133 . 1  and presses the piston  133 . 2  towards the left. 
     The piston  133 . 2  is connected to an axle  138  in form-fitting manner by means of a stud  133 . 5 . For this purpose, the axle  138  can comprise a corresponding receptacle. The axle  138  is rigidly connected to the first coupling disc  135 , for example by being screwed to it. The second coupling disc  136  is supported on the axle  138  by means of a bearing  138 . 4  such that it can rotate. The cylinder  133 . 1  is rigidly connected to the second coupling disc  136  by means of connecting rods  133 . 6 . 
     When the piston  133 . 2  is being pushed to the left by compressed air, the two coupling discs  135  and  136  move away from each other. The stroke Δx, by means of which the coupling disc  136  moves away from the coupling disc  135 , depends on the stroke of the pneumatic cylinder  133 . 1 . 
     The first coupling disc  135  can be fitted, for example, with two sockets  135 . 4  and  135 . 5  and the second coupling disc  136  can be fitted with a positioning pin  136 . 2  that fits in the sockets  135 . 4 ,  135 . 5 . The positioning pin  136 . 2  can be screwed into the coupling disc  136 . When the coupling disc  136  moves away from the coupling disc  135 , the positioning pin  136 . 2  is pulled out of the corresponding socket  135 . 4  or  135 . 5 . When the piston  133 . 2  is being pushed to the right by compressed air, the two coupling discs  135  and  136  are pushed together and against each other again. In the course of this, the positioning pin  136 . 2  is plugged again into the corresponding socket  135 . 4  or  135 . 5  such that the two coupling discs  135  and  136  are accurately positioned with respect to each other. When the positioning pin  136 . 2  is being plugged into socket  135 . 4 , the coupling disc  136  is situated in the first rotary position. In contrast, when the positioning pin  136 . 2  is being plugged into socket  135 . 5 , the coupling disc  136  is situated in the second rotary position. 
     Like drive  133 , drive  134  can also comprise a pneumatic cylinder  134 . 1 . The drive  134  can be attached to a bracket  135 . 2 . The bracket  135 . 2  and the first coupling disc  135  can be implemented by components that can be separated from each other, and the coupling disc  135  can be mounted to the bracket  135 . 2 . However, the coupling disc  135  and the bracket  135 . 2  can be just one component. The coupling disc  135  can be partly round, as shown in  FIG. 1 . The coupling  130  can be fitted with leveling feet  139 . A piston with a piston rod  134 . 2  is situated on the inside of the pneumatic cylinder  134 . 1  and can be moved into a first position and into a second position by means of compressed air. For this purpose, the drive  134  comprises two compressed air connectors  134 . 3  and  134 . 4 . The two compressed air connectors  134 . 3  and  134 . 4  can each be connected to a compressed air source by means of a valve V 4  or V 5  (see  FIG. 1 ). When the valve V 4  is closed and the valve V 5  is open, the piston is pushed into the cylinder  134 . 1  and/or the piston rod  134 . 2  is pulled into the cylinder. In contrast, when the valve V 5  is closed and the valve V 4  is open, the compressed air pushes the piston with the piston rod  134 . 2  out of the cylinder  134 . 1 . The piston rod  134 . 2  is connected to the second coupling disc  136  by means of a hinge  134 . 5 . 
     When the piston with the piston rod  134 . 2  is being pushed out of the cylinder  134 . 1  by means of compressed air, the coupling disc  136  rotates accordingly. The angle of rotation a, by which the coupling disc  136  rotates, depends on the stroke of the cylinder  134 . 1 . When the piston with the piston rod  134 . 2  is being pulled into the cylinder  134 . 1  again by means of compressed air, the coupling disc  136  rotates by the angle of rotation a back into its original position. 
     The axle bearing, or bearing  138 . 4  for short, can, for example, take the shape of a socket, as is shown in  FIG. 4 . Preferably, it is fitted with an air purge system. The bearing  138 . 4  can be supplied with air for purging by means of the axle  138 . In this case, the axle  138  comprises a compressed air connector  138 . 1  adjacent to which there is an air channel  138 . 2  that extends axially and, on the end of the air channel  138 . 2 , an air channel  138 . 3  that extends radially. 
     Compressed air can flow into the two air channels  138 . 2  and  138 . 3  via a valve V 1  that is connected to the compressed air connector  138 . 1 . Once the air reaches the outer end of the radially extending air channel  138 . 3 , it flows along between the axle  138  and the bearing  138 . 4  and removes any powder that may have been deposited in this location. 
     Preferably, the two coupling discs  135  and  136  are arranged coaxially, on the same axis  138 . The axis  138  is the bearing axis of the coupling disc  135  and the rotation axis of the coupling disc  136 . 
     The first coupling disc  135  can comprise a series of line connectors  131 . The series of line connectors  131  shall also be referred to as first group of line connectors  131  hereinafter. If the line connectors  131  are to be connected to a compressed air line  83 , they can be designed as compressed air connectors  183 . 1  to  183 . n . If the line connectors  131  are to be connected to powder lines  81 . 1 ,  81 . 2  . . .  81 . n , they can be designed as hoses nozzles  131 . 1 ,  131 . 2 , . . .  131 . n , whereby n means any number of line connectors and/or lines. 
     The same applies analogously to the second coupling disc  136 . Accordingly, the second coupling disc  136  can comprise a series of line connectors  132 . The series of line connectors  132  shall also be referred to as second group of line connectors  132  hereinafter. If the line connectors  132  are to be connected to compressed air lines  84 , they can be designed as compressed air connectors  184 . 1  to  184 . n . If the line connectors  132  are to be connected to powder lines  82 . 1 ,  82 . 2 , . . .  82 . n , they can be designed as hose nozzles  132 . 1 ,  132 . 2 , . . .  132 . n.    
     The line connectors  131  of the first coupling disc  135  can be distributed over a first pitch circle T 1  with a radius of r 1  and over a second pitch circle T 2  with a radius of r 2  (see  FIG. 3 a   ). The same applies analogously to the line connectors  132  of the second coupling disc  136 . In the embodiment shown in  FIGS. 1, 2, 3   a , and  4 , a total of 52 line connectors  131  are present on the first coupling disc  135  and also a total of 52 line connectors  132  are present on the second coupling disc  136 . A total of 26 of the line connectors  132  are situated on the first pitch circle T 1 . A total of 26 further line connectors  132  are situated on the second pitch circle T 2 . Preferably, the line connectors  131  are arranged in the same way and manner as the line connectors  132 . The two pitch circles T 1  and T 2  are preferably arranged such as to be concentric. 
     When the piston rod  134 . 2  is in the position shown in  FIG. 3 a   , the line connector  184 . 1  is connected to the line connector  183 . 1 . Moreover, the line connector  184 . 2  is connected to the line connector  183 . 2 , the line connector  132 . 1  is connected to the line connector  131 . 1 , and the line connector  132 . 2  is connected to the line connector  131 . 2 . The same applies analogously to the remaining line connectors  184 . 3  . . .  184 . n ,  132 . 3  . . .  132 . n ,  183 . 3  . . .  183 . n , and  131 . 3  . . .  131 . n . Accordingly, by means of the coupling  130 , two of the line connectors each can be connected to each other via a channel that is situated in the coupling discs. 
     For this purpose, 26 channels  135 . 1  that extend axially are situated on the first pitch circle T 1  in the first coupling disc  135 . A total of 26 further channels  135 . 1  that extend axially are situated on the second pitch circle T 2 . Each of the channels  135 . 1  is assigned to one of the line connectors  131 . The second coupling disc  136  is identical in structure in this regard. Accordingly, there are 26 channels  136 . 1  that extend axially on the first pitch circle of the second coupling disc  136 . A total of 26 further channels  136 . 1  that extend axially are situated on the second pitch circle T 2 . Each of the channels  136 . 1  is assigned to one of the line connectors  132 . 
     When the coupling discs  135  and  136  are pressed against each other, the channels  135 . 1  of the first coupling disc  135  and the channels  136 . 1  of the second coupling disc  136  each are connected to each other in pairs. The transition from one channel  135 . 1  to the adjacent channel  136 . 1  is preferably fitted with a seal  137 . This applies to all transitions between two channels  135 . 1  and  136 . 1 . The seals  137  preferably take the shape of a sleeve. 
     Spacers  135 . 3  can be provided between the two coupling discs  135  and  136 . These can be attached, for example, to the coupling disc  135  (see  FIG. 1 ). For this purpose, the coupling disc  135  can comprise threaded holes into which the spacers  135 . 3  are screwed. When the two coupling discs  135  and  136  are pushed against each other (see, for example,  FIG. 4 ), the spacers  135 . 3  between the two coupling discs  135  and  136  make sure that the seals  137  are not being pushed together too firmly such that they would be damaged. 
     When powder is being conveyed via the powder line  81 . 1 , it gets into the powder line  82 . 1  via the connector  131 . 1 , the corresponding channel  135 . 1  of the coupling disc  135 , the corresponding channel  136 . 1  of the coupling disc  136 , and the connector  132 . 1 . When powder is being conveyed via the powder line  81 . 2 , it gets into the powder line  82 . 2  via the connector  131 . 2  and the corresponding channel  135 . 1  of the coupling disc  135 , the corresponding channel  136 . 1  of the coupling disc  136 , and the connector  132 . 2 . 
     The coupling  130  works as follows. In a first step, the drive  133  is used to place the second coupling disc  136  at a distance Δx from the first coupling disc  135  and, in the process, the positioning pin  136 . 2  is pulled, for example, out of the one socket  135 . 4 . In a second step, the coupling disc  136  is rotated by the angle of rotation a from a first rotary position into a second rotary position. For this purpose, the piston rod  134 . 2  is pushed out of the cylinder  134 . 1 . Subsequently, the drive  133  is used to move the second coupling disc  136  back to the first coupling disc  135  and to press it against said disc. In this context, the positioning pin  136 . 2  is now being plugged into the other socket  135 . 5 . The positioning pin  136 . 2  and the sockets  135 . 4  and  135 . 5  help in accurately positioning the adjacent channels  135 . 1  and  136 . 1  with respect to each other such that no dead space arises at the transition between the adjacent channels  135 . 1  and  136 . 1  and the seals  137  and such that no powder can be deposited in this place. 
     Once valve V 12  is being opened, compressed air flows via the line  84 , the connector  184 . 1 , the corresponding channel  136 . 1  of the coupling disc  136 , the corresponding channel  135 . 1  of the coupling disc  135 , and the connector  131 . 1  into the powder line  81 . 1 . Moreover, compressed air also flows via the line  84  through the connector  184 . 2 , the corresponding channel  136 . 1  of the coupling disc  136 , the corresponding channel  135 . 1  of the coupling disc  135 , and the connector  131 . 2  into the powder line  81 . 2 . The same applies analogously to the remaining connectors and lines. By this means, powder can be removed from the powder lines  81  by means of compressed air. 
     Powder can also be removed from the powder lines  82  by means of compressed air. For this purpose, the valve V 11  is being opened such that compressed air flows via the line  83 , the connector  183 . 1 , the corresponding channel  135 . 1  of the coupling disc  135 , the corresponding channel  136 . 1  of the coupling disc  136 , and the connector  132 . 1  into the powder line  82 . 1 , and such that the powder present there is transported out of the line  82 . 1  in the direction of the powder applicator  80 . The same applies analogously to the remaining connectors and lines. 
     Once the powder lines have been purged, the second coupling disc  136  is moved away from the first coupling disc  135 . Then the coupling disc  136  is rotated back into its original rotary position, is moved to the first coupling disc  135  again, and is pushed against said disc. Subsequently, the powder lines are available again for powder coating operation. 
     Further Embodiments 
     Basically, the connectors  131  and  132  of the first and second coupling discs  135  and  136  can be configured as desired. Accordingly, the lines  83  can be designed, for example, as further powder lines rather than compressed air lines. In this case, powder of a first color can be transported in the powder lines  81  and powder of a second color can be transported in the lines  83 . By rotating the coupling disc  136 , the pairings of the connectors  131  and  132  can be changed quickly such that a quick and simple color change between the first and the second color can take place. 
     The coupling disc  136  can just as well be rotated by a multiple of the angle of rotation a such that more than two rotary positions can be reached. The embodiment shown in  FIG. 3 b    is one example of this. By this means, for example additional colors can be added and a rapid and simple color change between the colors can take place in the manner described above. 
     The invention can just as well provide, for example, the coupling disc  136  to take on three different rotary positions: With, for example, the angle of rotation being 0° in the first position, the angle of rotation being a in the second position, and the angle of rotation being 2*a in the third position. By this means, in the first position, powder of a first color could be transported. In the second position, the powder-conducting lines can be cleaned with compressed air. In the third position, powder of a second color can be transported. 
     For the coupling disc  136  to be able to assume all three different rotary positions, a drive  134  with two pneumatic cylinders  134 . 1  and  134 . 10  is present in the embodiment shown in  FIG. 3 b   . The two pneumatic cylinders  134 . 1  and  134 . 10  are arranged one after the other. The piston rod  134 . 11  of the pneumatic cylinder  134 . 10  rests against the bracket  135 . 2 . The piston rod  134 . 2  of the pneumatic cylinder  134 . 1  is connected to the second coupling disc  136  by means of the hinge  134 . 5 . 
     By means of the pneumatic cylinder  134 . 10 , the pneumatic cylinder  134 . 1 , and thus the coupling disc  136 , can be transitioned into a first and a second position. By means of the pneumatic cylinder  134 . 10 , the coupling disc  136  can be transitioned into the third position. If the pistons  134 . 2  and  134 . 11  of the two pneumatic cylinders  134 . 1  and  134 . 10  are retracted, the coupling disc  136  is in its first rotary position. The coupling disc  136  can be transitioned into the second rotary position by driving out the piston rod  134 . 2  of the pneumatic cylinder  134 . 1  or the piston rod  134 . 11  of the pneumatic cylinder  134 . 10 . In order to transition the coupling disc  136  into the third rotary position, both the piston rod  134 . 2  of the pneumatic cylinder  134 . 1  and the piston rod  134 . 11  of the pneumatic cylinder  134 . 10  are driven out. 
     The number of the connectors  131  and  132  and the number of the pitch circles can also be changed and adapted to the pertinent needs. Accordingly, for example in the embodiment of the coupling  130  shown in  FIG. 3 b   , three pitch circles T 1 , T 2 , and T 3  with radii of r 1 , r 2 , and r 3  are present on the first and the second coupling discs  135  and  136 . The coupling  130  according to  FIG. 3 b    comprises 36 line connectors  135  and/or  136  per pitch circle. 
     The layout of the entire powder coating facility is illustrated in more detail in the following based on  FIGS. 5 to 18 . 
     The powder center  1 , also referred to as powder supplying device, powder center or integrated powder management system, comprises a powder reservoir container  3  that is used for storing the coating powder. Moreover, the powder center  1  comprises a powder conveying device  1 . 1  by means of which the powder is conveyed out of the powder reservoir container  3  and is transported to a powder applicator  80 . The powder conveying device  1 . 1  is integrated into the powder reservoir container  3  in the present case and shall be illustrated in more detail later on. The powder applicator  80  (see  FIG. 5 ) can be designed as a manual or automatic powder spraying device and comprises, on its outlet facing the workpiece  65 , a spray nozzle or a rotation atomizer. 
     The powder center  1  is designed as a module. By this means, the powder center  1  can be transported rapidly and easily as a compact unit. The individual components of the powder center  1  are attached to frame profiles  2  that can be made of aluminum or steel, for example. The frame profiles  2  form the outer boundary of the powder center  1 . In case of need, the powder center  1  can comprise a base  7 . 
     The powder reservoir container  3  of the powder center  1  can be arranged, for example, on a pedestal  6 . As shown, for example, in  FIG. 11 , the powder reservoir container  3  can be closed off by a powder container lid  23  during conveying mode. In the embodiment shown in  FIGS. 6 to 14 , the powder container lid  23  takes the shape of an inverted pot. By means of pneumatic locks  18 , the powder container lid  23  can be closed off tightly against the powder reservoir container  3 . For this purpose, the powder reservoir container  3  comprises seals and lock receptacles  3 . 1  that can be engaged by appropriately designed counterparts of the pneumatic lock  18 . The pneumatic lock  18  can be fitted, for example, with a cylinder, a piston, and a piston rod. When compressed air is being applied to the lower chamber of the cylinder, the piston and thus the piston rod are pushed upwards. The grab situated on the lower end of the piston rod engages the lock receptacle  3 . 1  and causes the powder container lid  23  to be pushed onto the powder reservoir container  3 . Three locks  18  of this type are present in one embodiment (for example shown in  FIGS. 8 and 9 ). The number of locks  18  as well as their design can be readily adapted to the respective needs. 
     A screen  24 , which can be designed as an ultrasound screen, is situated on the inside of the powder reservoir container  3 . The ultrasound transducer  24 . 1  of the screen  24  is preferably situated outside the powder reservoir container  3 . The screen  24  is accessible and can be taken out once the powder container lid  23  is taken off. For this to take place automatically, the ultrasound screen  24  is attached to a pivoting mechanism  16  by means of a support arm  22 . Using the pivoting mechanism  16 , the screen  24  can be pivoted out of the working position (see  FIG. 8 ) and can be moved into a cleaning position in a cleaning station  27  (see  FIG. 14 ). The cleaning station  27  shall also be referred to as screen cleaning station or screen-cleaning station hereinafter. 
     As shown in  FIG. 10 , a cleaning arm  20 , which is supported such that it can rotate, is situated on the inside of the cleaning station  27 . The cleaning arm  20  comprises a multitude of cleaning nozzles  20 . 1 , which are arranged on the top side of the cleaning arm  20 . The cleaning station  27  also comprises a lid  15  that can be opened and closed, for example, by means of a pneumatic cylinder  17 . The lid  15  is pivoted about a hinge  21  in this context. A curved double arrow indicates the pivoting motion. The lid  15  bears, on its underside, a cleaning arm  19 , which is also fitted with a multitude of cleaning nozzles  19 . 1 . 
     The cleaning nozzles  19 . 1  are preferably situated on the underside of the cleaning arm  19 . They are aligned appropriately such that they blow compressed air downwards onto the ultrasound screen  24 , which is situated below the cleaning arm  19 , during cleaning mode. The upper cleaning arm  19  is supported on the lid  15 , such that it can rotate, by a bearing  50 . The lower cleaning arm  20  is supported on the cleaning container  14 , such that it can rotate, by a bearing  51 . The two bearings  50  and  51  can just as well be designed in the form of air motors. The direction of rotation of the upper cleaning arm  19  and the direction of rotation of the lower cleaning arm  20  are each indicated by an arrow. The direction of rotation of the cleaning arm results from the offset arrangement of the cleaning nozzles and the recoil that arises when compressed air flows out through the nozzles. During cleaning mode, the ultrasound screen  24  is situated between the lower cleaning arm  20  and the upper cleaning arm  19 . 
     The cleaning arm  19  can be angled on both ends (as shown in  FIG. 10 ) such that it has a horizontal leg and two legs that are slanting upwards. The compressed air nozzles  19 . 1  can just as well be situated on the horizontal leg and on the legs slanting upwards. The cleaning arm  19  can be designed in the form of a tube for guiding the compressed air on the inside of the tube to the compressed air nozzles  19 . 1 . The same applies analogously to the lower cleaning arm  20 , even though the ends of the lower cleaning arm  20  are not angled in  FIG. 10 . 
     A lower container section  14 . 2  with an outlet  14 . 1  for accommodating the screen  24  is situated on the underside of the container  14 . The outlet  14 . 1  can be used to aspirate the powder-air mixture that is present in the cleaning station  27 . For this purpose, the outlet  14 . 1  is connected to an inlet opening  13 . 2  of a suction tube  13  by means of a hose that is not shown in the figures. The powder-air mixture can be suctioned via the suction tube  13  and a suction line  91  into an after-filter  100 . 
     The powder inlet of the working container  3 ,  23  is preferably situated in the upper part thereof. For example, it can be arranged in the powder container lid  23  of the working container  3 ,  23 . The working container  3 ,  23  can just as well comprise multiple powder inlets. The powder inlet  23 . 1  is connected to the powder outlet  4 . 2  of an intermediate container  4  by means of a powder valve M 21 , which can be designed, for example, in the form of a pneumatically controlled crusher. The intermediate container  4 , combined with the inlet valve M 20  and the outlet valve M 21 , serves as powder conveyor  4  and is usually arranged above the working container  3 ,  23 . By this means, gravity can be used to transport powder that is situated in the intermediate container  4  downwards into the working container  3 ,  23 . 
     A second powder conveyor  5  can be arranged above the working container  3 ,  23 . The powder outlet thereof also merges into the working container  3 ,  23 . The second powder conveyor  5  can be identical in structure to the first powder conveyor  4 . 
     The powder conveying device  1 . 1  that is integrated into the powder reservoir container  3  shall be illustrated in more detail in the following. The powder conveying device can be designed in the way described in European patent application EP 3 238 832 A1. The working container  3 ,  23  is designed and can be operated appropriately such that pressure can be applied to it. Powder can be conveyed out of the fresh powder station  30  and can be transported into the working container  3 ,  23  by means of the powder conveyor  4 . A corresponding powder inlet is present in the powder container lid  23  that covers the powder reservoir container  3  on the top. The working container  3 ,  23  comprises, in the area of the container base  25 , a fluidizing insert  25 . 1  for fluidizing the powder, and a series of powder outlets  3 . 2 . The invention can provide one powder outlet valve G 1 -G 36  to be connected to each of the powder outlets  3 . 2 . In turn, one powder line  81  each is connected to each of the powder outlet valves G 1 -G 36 . Moreover, each of the powder lines  81  ( 81 . 1  . . .  81 . n ) comprises an inlet for transport air on the inlet side, i.e. in the proximity of the corresponding powder outlet valve G 1 -G 36 . On the outlet side, each of the powder lines  81  is preferably connected to one of the powder applicators  80  each by means of the coupling  130  described above and the powder lines  82  ( 82 . 1  . . .  82 . n ). The amount of powder to be conveyed is controlled by repeatedly opening and closing the corresponding powder outlet valve G 1 -G 36  by means of a controller  70 . To avoid repetitions, reference shall be made to the aforementioned patent application EP 3 238 832 A1, the content of which shall herewith be made a part of the present application. 
     An embodiment of the working container  3 ,  23  provides a vibrator  220  that can be situated, for example, below the powder reservoir container  3  (see  FIG. 11 ). The shaking motions generated by the vibrator  220  can be used to fluidize the powder-air mixture in the powder reservoir container  3  even more homogeneously. Moreover, by this means, the powder-air mixture can flow even more optimally out of the powder outlet channel  203 . 
     The coupling  130  comprises the first group of connectors  131  on the one coupling disc  135  and the second group of connectors  132  on the second coupling disc  136 . The controller  70  can be used to adjust which connector of the first group  131  is connected to which connector of the second group  132 . Accordingly, each individual powder line  81  can be connected, on the outlet side, to one convector of the first group  131  each. Each individual powder line  82  can be connected to a connector of the second group  132  each, and can be connected, on the other side, to one of the powder applicators  80  each. 
     In one embodiment, 36 powder outlet valves G 1 -G 36  are used. However, more or fewer powder outlet valves can be used just as well. The number of powder outlet valves that is used depends on the number of powder applicators  80  that are used. 
     As an alternative to the integrated powder conveying device with the power outlet valve G 1  just described, the invention can just as well provide a powder injector that works according to the Venturi principle or a powder pump for dense phase conveying. 
     Instead of the powder conveyor  4 , a powder pump for dense phase conveying, a hose pump or a powder injector can just as well be provided. The same shall apply to the powder conveyor  5  analogously. 
     The powder reservoir container  3  and the powder container lid  23  thereof as well as the two powder conveyors  4  and  5  are attached to a vertical linear axle  12  and can be moved up and down by this device. The drive  12 . 1  of the linear axle  12  can be situated on the top of the linear axle  12 . The direction of motion thereof is indicated by the vertical double arrow in  FIG. 11 . 
     In addition, the powder center  1  comprises a container cleaning unit  28 , or cleaning unit for short, that comprises a cleaning container  10 , an upper cleaning arm  11 , and a lower cleaning arm  26 . The upper cleaning arm  11  and the lower cleaning arm  26  are supported in the cleaning container  10  such that they can rotate and each comprise a multitude of compressed air-operated cleaning nozzles  11 . 1  or  26 . 1 . The cleaning container  10  is attacked to a linear drive  9  and can be moved vertically upwards and downwards (in y direction) by the drive. The direction of motion thereof is indicated by the vertical double arrow in  FIG. 11 . The drive  9 . 1  of the linear drive  9  can be situated on the top of the linear drive  9 . The linear drive  9 , in turn, is attached to a horizontally-aligned linear drive  8  (also referred to as linear axle) and can be moved horizontally (in x direction) back and forth by same. The drive  8 . 1  of the linear axle  8  can be situated on the side of the linear axle  8 . It is possible, by means of the linear axle  8 , to position the container cleaning unit  28  laterally next to the working container  3 ,  23  (see  FIGS. 6 to 9 ) during conveying mode. During cleaning mode, the container lid  23  is driven upwards first; then the container cleaning unit  28  can be positioned appropriately by means of the two linear drives  8  and  9  such that the cleaning container  10  is first moved over the powder reservoir container  3  and is then lowered to the extent such that the cleaning arm  26  is situated at a defined distance from the base  25  of the powder reservoir container  3 . The cleaning arm  26  projecting on the bottom from the cleaning container  10  is then situated inside the powder reservoir container  3  and serves for cleaning the inner wall and the base  25  of the powder reservoir container  3 . 
     The linear drive  12  can then be used to lower the powder container lid  23  to the extent such that the cleaning arm  11  that projects on the top from the cleaning container  10  can be used to blow off, and thus clean, the inner surfaces of the powder container lid  23 . The cleaning arm  11  projects into the inside of the powder container lid  23  in this context. 
     One possible embodiment of the fresh powder station  30  is shown in various views in  FIGS. 15 to 18 . 
     The fresh powder station  30  can be designed, for example, as an independent module. The station comprises a first storage space  31  and a second storage space  32 , which each can accommodate a powder carton  110 ,  111  (see  FIG. 5 ). The two storage spaces  31  and  32  are preferably arranged such as to be slanted such that the powder migrates obliquely downwards into a corner in the powder carton supported by gravity. By this means, the powder carton can be readily emptied by means of a suction lance  33  without any residue or hardly any residue being left behind. As shown in  FIGS. 17 and 18 , the suction lance  33  can be moved horizontally by means of a linear drive  44  such that it can be used for both a powder carton that is arranged on the first storage space  31  as well as for a powder carton that is arranged on the second storage space  32 . Moreover, the fresh powder station  30  comprises an additional linear drive  38  to be able to move the suction lance  33  vertically as well. 
     A vibrator  54  and a scale  46  are situated below the storage space  31  for the powder carton  110 . The purpose of the vibrator  54  is to agitate the powder in the carton  110  such that it is distributed better and flows in the direction of the suction lance  33 . 
     The scale  46  can be used to determine the filling level in the carton  110 , and to initiate a change of powder cartons once the filling level drops below a certain level. Moreover, the measuring signal generated by the scale  46  can be used to recognize if there is still sufficient space in the carton  110  when powder is to be conveyed via the line  96  from the powder center  1  back to the powder station  30 . 
     Likewise, a vibrator  55  and a scale  47  are situated below the storage space  32 . Their purpose is analogous to that of the vibrator  54  and of the scale  46  in the case of storage space  31 . 
     To be able to clean the suction lance  33 , the fresh powder station  30  comprises, in addition, a cleaning station  52  that is equipped with a wiper ring and/or compressed air nozzles and/or a suction system. By this means, powder adhering to the outside of the suction lance  33  can be removed during the up and down motion. 
     In addition, air nozzles  57  can be provided on the cleaning station  53  for cleaning of the lower area of the suction lance  33 . If the suction lance  33  comprises a fluidizing crown for fluidizing the powder in the suction area, same can be cleaned with this as well. 
     Instead of two storage spaces  31  and  32  with two powder cartons  110  and  111 , just one storage space  32  and a powder container  150  with a fluidizing facility could be installed just as well. For example, two pumps  124  and  125  could be used to convey powder from a Big Bag  121  into the powder container  150  via a powder line  127  each. 
     Instead of or in addition to the Big Bag  121 , a Big Bag  120  with a pump  123  could be provided just as well. The powder can be pumped via a powder line  126  directly to the powder conveyor  4  by a pump  123 . 
     The Big Bag  120  or  121  is also referred to as Flexible Intermediate Bulk Container or FIBC, for short. It usually contains larger amounts of powder than the powder carton  110  and the powder carton  111 . Moreover, the Big Bag  120 / 120  usually stands farther away from the powder conveyor  4  than the powder carton  110  or  111 . Accordingly, the Big Bag  120 / 121  can stand at a distance of, for example, 30 m from the powder conveyor  4 , whereas the powder carton  110  or  111  stands, for example, at a distance of 5 m from the powder conveyor  4 . 
     The fresh powder station  30  can comprise multiple compressed air regulating valves  39  and  40  and adjusting knobs  41  and  42 . The compressed air regulating valve  39  can be designed for adjusting the fluid air of the fluid base of the powder container  150 . The purpose of the compressed air regulating valve  40  is to adjust the fluid air at the fluidizing crown of the suction lance  33 . The adjusting knob  41  can be used to control the position of the exhaust air damper. The adjusting knob  42  can be used to transmit a confirmation signal to the controller. 
     The fresh powder station  30  can comprise, in its base area, a suction system  37  with a suction opening  37 . 1  to be able to aspirate excess powder out of the inside of the fresh powder station  30 . The fresh powder station  30  can also comprise a flexible suction hose that can be used for manual cleaning in case of need. 
     The invention can provide the fresh powder station  30  to comprise a pivoting mechanism  45  for the powder conveyor  49 . The pivoting mechanism  45  comprises a drive, which can, for example, be designed as a pneumatic drive, and a pivoting arm  45 . 1 . The pivoting mechanism  45  can be used to transition the powder conveyor  49  (see  FIG. 15 ) out of the conveying position into a cleaning position. In the cleaning position, the powder conveyor  49  projects into the interior space of the fresh powder station  30 . In addition, air nozzles  56  can be provided for cleaning of the lower area of the powder conveyor  49  when it is being pivoted out of the conveying position into the cleaning position or out of the cleaning position into the conveying position. 
     The pneumatic drive can comprise two pneumatically driven cylinders. By this means, the powder conveyor  49  can be transitioned into a cleaning position, a first conveying position, and a second conveying position. To transition the powder conveyor  49  into the cleaning position (see  FIG. 15 ), the cylinder  1  and the cylinder  2  are being retracted. In the first conveying position, the powder conveyor  49  is situated above the storage space  31 . For this purpose, the cylinder  1  is being retracted and cylinder  2  is being driven out. In the second conveying position, the powder conveyor  49  is situated above the storage space  32 ; the cylinders  1  and  2  are driven out. In the first conveying position, powder can be conveyed back into the powder carton  110 , and, in the second conveying position, powder can be conveyed back into powder carton  111 . 
     The suction lance  33  can be transitioned into three different positions by the linear axle  38  and the linear drive  44 : In the cleaning position (see  FIG. 15 ), the suction lance  33  is situated in the cleaning station  53 . 
     In the first conveying position, the suction lance  33  is situated above the storage space  31  and, in the second conveying position, it is situated above the storage space  32 . 
     In case of need, the fresh powder station  30  can just as well be equipped with its own controller  43 . For example the suction lance  33 , the cleaning station  52  for the suction lance  33 , the linear axle  38 , the linear drive  44 , the pivoting mechanism  45 , and the blow nozzles  56  and  57  can be controlled by said controller  43 . 
     The powder conveyor  49  shown, for example, in  FIGS. 16 and 18  is advantageously being positioned directly above the powder carton  110  or  111  into which it is to convey powder. Since it utilizes gravity, the powder drops into the powder carton situated below the powder conveyor  49  once the outlet valve  49 . 2  of the powder conveyor  49  is opened. 
     The powder conveyor  49  used for returning the powder can just as well be designed differently. For example, it can be designed as a powder pump. Since a powder pump of this type does not utilize gravity, it can be arranged in different places. For example, it can be situated at the same height level as the powder carton  110 . 
     Two covers  35  and  36  that can be opened manually can be provided on the topside of the powder station  30 . By this means, the staff also has access from above to the inside of the fresh powder station  30 . 
     In case of need, the fresh powder station  30  can just as well be equipped with side walls  34  and a rear wall  48 . 
     One possible embodiment of a total facility for powder coating of workpieces  65  is shown in simplified manner as a block diagram in  FIG. 5 . The total facility can be controlled by means of a central controller  70 . The controller  70  can be connected via corresponding control lines (not shown in the Figures) to various components of the total facility and can be provided for controlling the powder coating cabin  60  including powder applicators  80 , the fresh powder station  30 , the powder center  1 , the powder recycling  90 , and/or the after-filter  100 . 
     Alternatively or in addition to the central controller  70 , the fresh powder station  30  can comprise a separate controller  43 , as has been mentioned above. The same applies analogously to all other components of the total facility for the coating of workpieces with powder. 
     Since all powder particles sprayed by the powder applicators  80  do not adhere to the workpieces  65  to be coated during the coating process, the excess powder, which is also referred to as overspray, needs to be removed from the cabin  60 . This is necessary, firstly, because the surrounding area outside of the cabin needs to be kept free of powder dust. Secondly, the explosion hazard increases when a certain powder concentration is exceeded by the powder dust cloud floating in the cabin. This needs to be prevented. 
     The overspray arising during the coating and the air present in the cabin  60  are suctioned out of the cabin  60  as a powder-air mixture and are fed to a device for powder recovery  90  via a residual powder pipeline  92 . The device for powder recovery  90  can be designed, for example, as a cyclone. The powder recovered therein can be fed to the powder center  1  again via a powder line  94  in case of need. In order to also remove, by filtering, the fraction of powder that was not removed, by filtering, in the cyclone  90 , the powder-air mixture can be fed from the cyclone via a suction line  93  to the after-filter  100 . 
     The powder-air mixture in the residual powder pipeline  92  is also referred to as residual powder air flow. For aspiration of the overspray out of the cabin  60 , the cabin  60  comprises, for example, a suction slit. It connects the inside of the cabin  60  to the residual powder pipeline  92 . The suction slit and the suction tube  61  are therefore used to aspirate excess powder from the inside of the cabin as a powder-air mixture and to feed it to a cyclone separator  90 , or cyclone for short, that can be designed as a mono-cyclone. The powder-air mixture flows tangentially into the cyclone  90  and flows spirally downward inside the cyclone. In the process, the powder particles are pushed outwards against the outer wall of the cyclone  90  by the centrifugal force that arises during the rotation of the powder-air flow. The powder particles are conveyed downwards in the direction of the powder outlet of the cyclone, and are collected there. The air from which the powder particles have been removed is aspirated via the vertical central tube that is situated in the cyclone  90 . Thus cleaned, the air flow is often fed to an after-filter  100  in order to remove, by filtering, even the last residual powder present in the air. The powder recycled in the cyclone  90  can be re-used for coating and can be fed to the powder center  1  via the powder line  94 . 
     Conveying Mode/Conveying Operation 
     In conveying mode, the ultrasound screen  24  is situated in the working container  3 ,  23 , between the powder reservoir container  3  and the powder container lid  23 . The locks  18  make sure that the working container is closed in airtight manner. The screen cleaning device  27  and the container cleaning unit  28  are situated in the parking position, as shown in  FIGS. 6 to 8 . 
     The parking position for the container cleaning unit  28  is situated next to the powder reservoir container  3 . The term «next to the powder reservoir container» shall also comprise above, below, in front of or behind the powder reservoir container. 
     The screen  24  is not obligatory for conveying mode. The conveying of powder can also take place without an ultrasound screen or without a screen  24  altogether. 
     Cleaning Mode/Cleaning Operation 
     For switching from conveying mode to cleaning mode, the conveying of powder out of the powder reservoir container  3  is stopped and the residual powder that is still present in the powder reservoir container  3  is aspirated via the outlet  25 . 1  and the line  96  by means of the powder conveyor  49 . For this purpose, the material valve M 11  is being opened, while the purging valve S 12  is closed during this time. The overpressure that is still prevailing in the working container  3 ,  23  is reduced to normal pressure and the locks  18  are opened. 
     Then, the powder container lid  23  is lifted by means of the linear drive  12  and the ultrasound screen  24  is pivoted out of the working position into the cleaning position by means of the pivoting mechanism  16 . 
     As shown in  FIGS. 12 to 14 , the linear drive  12  lifts the container lid  23  to the extent such that the cleaning container  10  can be driven in between the powder container lid  23  and the powder reservoir container  3  by the two linear axles  8  and  9 . Subsequently, the container cleaning unit  28  including the cleaning container  10  is lowered sufficiently until the lower cleaning arm  26  is situated on the inside of the powder reservoir container  3  and is situated at a defined distance from the base  25  of the powder reservoir container  3 . 
     The powder container lid  23  is then lowered to the extent such that the upper cleaning arm  11  is situated on the inside of the powder container lid  23  and is situated at a defined distance from the powder container lid  23 . 
     In the embodiment above, an air gap remains between the powder container lid  23  and the cleaning container  10 . Likewise, an air gap remains between the powder container  3  and the cleaning container  10 . The after-filter  100  aspirates air through the air gap. This prevents the powder-air mixture generated by the compressed air nozzles  11 . 1  and  26 . 1  during the cleaning process from escaping into the surroundings. 
     Instead, it is feasible just as well to lower the powder container lid  23  to the extent such that no gap remains between the powder container lid  23  and the cleaning container  10 . Likewise, the gap between the cleaning container  10  and the powder container  3  can be eliminated by lowering the cleaning container  10  to the extent such that it is placed on top of the powder container  3 . 
     In another embodiment, the locks  18  can close the unit made up of powder container lid  23 , cleaning container  10 , and powder reservoir container  3 , in airtight manner. 
     In a next step, compressed air is blown through the nozzles  11 . 1  and  26 . 1  in the direction of the inner walls of the powder container lid  23  and of the powder reservoir container  3 . The powder-air mixture thus generated is aspirated via the suction line  13  and can be fed to the cyclone  90  and/or to the after-filter  100 . 
     As soon as the screen  24  and/or the ultrasound screen is situated in the cleaning container  14 , the lid  15  is closed by means of the pneumatic cylinder  17 . An air gap can remain between the lid  15  and the cleaning container  14 . In another embodiment, the lid  15  can just as well be placed on the cleaning container  14  in airtight manner. 
     Now, compressed air is being blown through the nozzles  19 . 1  and  20 . 1  from above and below onto the screen  24 . The powder-air mixture thus generated is aspirated via the suction line  13  and can be fed to the cyclone  90  and/or to the after-filter  100 . 
     As soon as the screen  24  is clean, the blowing off of the screen is terminated. Once the powder container  3  and the container lid  23  are clean, the blowing off is terminated here as well. 
     If the locks  18  had previously been closed, they are now being opened again. The container lid  23  is being lifted and the container cleaning unit  28  is being moved back into the parking position (see  FIGS. 6-9 ). The lid  15  is being lifted as well. Once the cleaning mode is completed, the screen  23  is driven back into its working position. Subsequently, the conveying of powder can be started again. 
     Cleaning Mode with Intensive Cleaning 
     The following cleaning steps can be carried out in order to clean the powder center  1  and the other components of the facility contacting the coating powder even more thoroughly. The steps are preferably carried out automatically and are coordinated by the controller  70 . The cleaning unit  28  is used to clean the powder reservoir container  3  and the container lid  23 , as described above. In a further step, a switch to a different coating powder is carried out. The other coating powder in this context can be the powder that is the next to be used for coating the workpieces  65 . But this does not necessarily have to be the case. Instead, a switch to a special cleaning agent can be carried out just as well. The cleaning agent can be, for example, a granulate with a grain size between 2 mm and 7 mm. The grain size, the grain material, and the grain properties are preferably selected appropriately such that, firstly, the cleaning agent can be conveyed through all openings in the powder system and, secondly, has a good cleaning effect. The selection of the cleaning agent advantageously takes into consideration that no additional wear and tear in the powder system and no chemical incompatibility with the coating powder arises. 
     In an additional step, a switch to conveying mode is effected for a limited period of time such that the other coating powder and/or the cleaning agent flows through the individual components of the facility. During the brief conveying mode, for example 3 kg of powder that are ultimately lost can be conveyed. But it is also feasible to recover the material (the powder and/or the cleaning agent) in the cyclone  90 . As a result, the powder lines  91 ,  92 ,  93 , and  94  can also be purged with the new material. This is of advantage, in particular, if the new powder is conveyed to be recovered. 
     Subsequently, the powder reservoir container  3  and the container lid  23  are cleaned again by means of the cleaning unit  28 . 
     The preceding description of exemplary embodiments according to the present invention serves for illustrative purposes only. Various changes and modifications are feasible within the scope of the invention. Accordingly, for example, the various components of the coupling and of the powder center shown in  FIGS. 1 to 18  can be combined with each other in a way different from what is shown in the Figures. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Powder center 
           1 . 1  Powder conveyor 
           2  Frame profiles 
           3  Powder reservoir container 
           3 . 1  Lock receptacle 
           3 . 2  Outlet opening for powder 
           3 . 3  Compressed air connector for purging air 
           3 . 4  Powder outlet 
           4  Powder conveyor 
           4 . 2  Powder outlet 
           5  Powder conveyor 
           6  Pedestal 
           7  Base sheet 
           8  Linear drive 
           8 . 1  Drive motor 
           9  Linear drive 
           9 . 1  Drive motor 
           10  Cleaning container 
           10 . 1  Outlet 
           11  Cleaning arm for the lid 
           11 . 1  Cleaning nozzles 
           12  Linear drive 
           12 . 1  Drive motor 
           13  Suction line/suction tube 
           13 . 1  Inlet opening 
           13 . 2  Inlet opening 
           14  Screen cleaning container 
           14 . 1  Outlet 
           14 . 2  Lower container section 
           15  Lid of the screen cleaning device 
           16  Pivoting mechanism 
           17  Lifting cylinder 
           18  Lock 
           19  Cleaning arm 
           19 . 1  Screen cleaning nozzles 
           20  Cleaning arm 
           20 . 1  Screen cleaning nozzles 
           21  Hinge 
           22  Support arm for the powder screen 
           23  Container lid 
           23 . 1  Powder inlet 
           24  Ultrasound screen 
           24 . 1  Ultrasound transducer 
           25  Container base 
           25 . 1  Fluidizing insert 
           25 . 2  Outlet 
           26  Cleaning arm for the powder reservoir container 
           26 . 1  Cleaning nozzles 
           27  Screen cleaning device 
           28  Cleaning unit/container cleaning unit 
           30  Fresh powder station 
           31  First storage space 
           32  Second storage space 
           33  Suction lance 
           34  Side wall 
           35  Cover 
           36  Cover 
           37  Suction system 
           37 . 1  Suction opening 
           37 . 2  Suction opening 
           37 . 3  Suction opening 
           38  Linear axle for the suction lance 
           39  Compressed air regulating valve 
           40  Compressed air regulating valve 
           41  Adjusting knob 
           42  Adjusting knob 
           43  Controller 
           44  Linear drive 
           45  Pivoting mechanism for powder conveyor 
           45 . 1  Arm 
           46  Scale 
           47  Scale 
           48  Rear wall 
           49  Powder conveyor 
           49 . 1  Powder container 
           49 . 2  Inlet valve for powder 
           49 . 3  Outlet valve for powder 
           49 . 11  Inlet 
           49 . 12  Outlet 
           50  Bearing 
           51  Bearing 
           52  Cleaning station 
           53  Cleaning station 
           54  Vibrator 
           55  Vibrator 
           56  Compressed air nozzle 
           57  Compressed air nozzle 
           60  Powder coating cabin 
           65  Workpiece 
           70  Controller 
           71  Control line 
           80  Powder spray gun 
           81  Powder lines 
           81 . 1  First powder line 
           81 . 2  Second powder line 
           81 . 3  Third powder line 
           82  Powder lines 
           82 . 1  First powder line 
           82 . 2  Second powder line 
           82 . 3  Third powder line 
           83  Compressed air line 
           84  Compressed air line 
           90  Powder recovery 
           91  Suction line 
           92  Suction line 
           93  Suction line 
           94  Powder line 
           95  Suction line 
           96  Powder return line 
           97  Powder line 
           98  Powder line 
           100  After-filter 
           110  Powder carton 
           111  Powder carton 
           120  Big Bag 
           121  Big Bag 
           123  Powder pump 
           124  Powder pump 
           125  Powder pump 
           126  Powder line 
           127  Powder line 
           130  Coupling 
           130 . 1  Arrow 
           130 . 2  Arrow 
           131  First group of connectors 
           131 . 1  First connector of the first group 
           131 . 2  Second connector of the first group 
           131 . 3  Third connector of the first group 
           132  Second group of connectors 
           132 . 1  First connector of the second group 
           132 . 2  Second connector of the second group 
           132 . 3  Third connector of the second group 
           133  Drive 
           133 . 1  Pneumatic cylinder 
           133 . 2  Piston 
           133 . 3  Compressed air control connector 
           133 . 4  Compressed air control connector 
           133 . 5  Connecting stud 
           133 . 6  Rod 
           134  Drive 
           134 . 1  Pneumatic cylinder 
           134 . 2  Piston rod 
           134 . 3  Compressed air control connector 
           134 . 4  Compressed air control connector 
           134 . 5  Hinge 
           134 . 10  Pneumatic cylinder 
           134 . 11  Piston rod 
           135  Coupling disc 
           135 . 1  Channels 
           135 . 2  Bracket 
           135 . 3  Spacer 
           135 . 4  Socket 
           135 . 5  Socket 
           136  Coupling disc 
           136 . 1  Channels 
           136 . 2  Positioning pin 
           137  Seal 
           138  Axle 
           138 . 1  Compressed air connector 
           138 . 2  Air channel 
           138 . 3  Air channel 
           138 . 4  Bearing socket 
           139  Stand 
           141  Residual powder line 
           142  Residual powder line 
           150  Intermediate container for powder 
           160  Suction opening 
           162  Suction opening 
           183 . 1  Compressed air connector 
           183 . 2  Compressed air connector 
           184 . 1  Compressed air connector 
           184 . 2  Compressed air connector 
           220  Vibrator 
         M 11  Valve for powder material 
         M 20  Inlet valve for powder 
         M 21  Outlet valve for powder 
         M 22  Valve 
         r 1  Radius 
         r 2  Radius 
         r 3  Radius 
         S 11  Purging valve 
         S 12  Purging valve 
         S 13  Purging valve 
         T 1  First pitch circle 
         T 2  Second pitch circle 
         T 3  Third pitch circle 
         V 1  Valve 
         V 2  Control valve 
         V 3  Control valve 
         V 4  Control valve 
         V 5  Control valve 
         V 11  Valve 
         V 12  Valve 
         G 1 -G 36  Outlet valves 
         x x-axis 
         y-axis 
         Y 
         z z-axis 
         α Angle of rotation 
         Ax Stroke