Patent Application
20190314836
This application claims priority under 35 USC § 119 to European patent application number 18167085, filed on Apr. 12, 2018, the entire disclosure of which is incorporated herein by reference.
The invention relates to a conveying device for the conveying of coating powder. The invention also relates to a powder center with a conveying device of this type and to a method for the cleaning of the powder center.
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 are situated 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 conveyor or the powder center is not cleaned sufficiently there may be an undesirable carry-over of color after a color change.
A powder conveying device for the conveying of coating powder to a powder applicator is known from European patent application EP 3 238 832 A1. The powder conveying device comprises a powder conveyor that is connected to a working container arranged below it and serves for the conveying of coating powder from a powder reservoir container into the working container. During a powder change, powder that is still present in the working container is removed from the working container. For this purpose, a powder line projecting into the working container and a valve are provided. Once the valve is opened, it can be used to remove the residual powder from the working container. A returning container that may be present to take up the residual powder removed from the working container needs to be placed directly below the working container, which is disadvantageous. As a result, the working container needs to be placed very far up which may lead to space problems under confined spatial circumstances. When the residual powder flows out of the working container and/or the valve for residual powder, a powder dust is generated that soils the surroundings, which then need to be regularly cleaned by hand. Moreover, the powder dust thus generated may inadvertently be inhaled by the operating staff.
It is an object of the invention to devise a conveying device for the conveying of coating powder, a powder center with the conveying device as well as a method for the cleaning of the powder center, in which the degree of automation during the cleaning is increased even more.
Advantageously, the conveying device according to the invention for the conveying of coating powder allows the immission of powder dust to be reduced even more. By this means, the risk of the operating staff inhaling powder dust during the cleaning is minimized.
It is another advantage of the conveying device according to the invention for the conveying of coating powder that the powder reservoir container and/or the working container, which is part of the conveying device, no longer needs to be lifted up and moved to a different place by the operating staff.
Moreover, with the conveying device according to the invention for the conveying of coating powder, the quality of the cleaning can be maintained at a particularly high level and the cleaning can be made to take place in a process-safe manner.
Moreover, the automated cleaning provided for the conveying device according to the invention can be performed more rapidly than the cleaning of the conveying device by the operating staff.
It is another advantage of the invention that the conveying device and the powder return container, which is to take up the residual powder removed from the working container, do not necessarily have to stand right next to each other. The distance between the conveying device and the powder return container can well be up to 20 or 30 m.
The object is met by a conveying device for the conveying of coating powder having the features described herein.
The conveying device according to the invention for the conveying of coating powder comprises a powder reservoir container that comprises, on the bottom, a powder outlet channel. The powder outlet channel is connected to a first powder conveyor for conveying powder out of the powder reservoir container back to a powder storage container. Moreover, a second powder conveyor is provided for conveying powder out of the powder reservoir container to a powder applicator.
The object is also met by a powder center comprising the conveying device and having the features described herein.
The powder center according to the invention with the conveying device described above comprises a cleaning unit for the cleaning of the powder reservoir container and of the container lid. The cleaning unit can be moved from a parking position next to the powder reservoir container into a cleaning position inside the powder reservoir container by means of a manipulator. Moreover, a controller is provided by means of which the cleaning unit and the manipulator can be controlled.
The object is also met by a method for the cleaning of the powder center described above, whereby the method comprises the features described herein.
The method for the cleaning of the powder center comprises the following steps. The residual powder situated in the powder reservoir container is conveyed out of the powder reservoir container by means of the first powder conveyor. Subsequently, the cleaning unit is used to clean the powder reservoir container and the container lid.
Advantageous developments of the invention are evident from the features described herein.
An embodiment of the conveying device according to the invention provides a third powder conveyor for conveying powder out of the powder storage container into the powder reservoir container. This allows the degree of automation to be increased even more.
Another embodiment of the conveying device according to the invention provides a valve for purging air that is connected to the powder outlet channel via a purging air inlet and is provided for blowing purging air into the powder outlet channel and/or to the first powder conveyor. This is advantageous in that an even more highly automated cleaning can take place.
Another embodiment of the conveying device according to the invention provides a fluidizing element in the powder outlet channel. By this means, the transport of the residual coating powder out of the working container can be improved even more.
The fluidizing element can be designed to be ring-shaped in the conveying device according to the invention. A fluidizing element of this type can be manufactured easily and inexpensively. It is another advantage that this fluidizing element can be incorporated appropriately such that no dead space is generated and such that, consequently, no powder can be deposited there. Moreover, a fluidizing element of this type is easy to clean. And the air for fluidization can easily be distributed homogeneously over the circumference of the powder channel with a fluidizing element of this type.
Moreover, the invention can provide the fluidizing element of the conveying device according to the invention to be made from a micro-porous material. By this means, air can pass through the fluidizing element, but the coating powder can not.
In a development of the conveying device according to the invention, the powder reservoir container has a circular cross-section. This is advantageous in that the powder reservoir container has fewer corners and edges, in which powder may become deposited. As a result, the powder reservoir container is easier to clean.
In another development of the conveying device according to the invention, the powder reservoir container comprises a base that slants downwards towards the middle of the powder reservoir container. Gravity can be used in supporting manner for collecting and transporting away the residual powder.
In an additional development of the conveying device according to the invention, the orifice of the powder outlet channel is situated in the middle of the downward slanting base. This allows the transportation of the residual powder to be improved even more.
Advantageously, the powder outlet channel of the conveying device according to the invention extends such as to be funnel-shaped. This also allows the transportation of the residual powder to be improved even more.
It is feasible just as well in the conveying device according to the invention, that the first powder conveyor comprises a powder container with a powder inlet and a powder outlet, as well as a powder inlet valve and a powder outlet valve. The powder inlet is connected to the powder inlet valve and the powder outlet is connected to the powder outlet valve. A negative pressure can be applied to the powder container.
In an embodiment of the conveying device according to the invention, the third powder conveyor is identical in structure to the first powder conveyor.
In another embodiment of the conveying device according to the invention, a container lid, which can be taken off, at least in part, is provided on the powder reservoir container.
The invention and several exemplary embodiments are illustrated in more detail in the following based on 16 figures.
In the embodiment shown in
The powder reservoir container 3 can have a circular cross-section. A screen 24 can be arranged on the inside of the powder reservoir container 3, as shown in
A fluidizing base 25.1 may be situated in the lower area of the powder reservoir container 3. The powder reservoir container 3 is closed off in downward direction by a base 25. In a preferred embodiment, the fluidizing base 25.1 is arranged directly above the base 25 and slants downwards towards the middle of the powder reservoir container 3 and/or towards a powder outlet 25.2.
The powder outlet 25.2 serves as outlet for residual powder and forms the inlet orifice of a powder outlet channel 203. It is preferably designed to be funnel-shaped and comprises a fluidizing element 201. A fluidizing element 201 can be designed to be ring-shaped and can be made from a micro-porous material. The fluidizing element 201 can be, for example, tube-shaped. The inlet orifice 25.2 of the powder outlet channel 203 is preferably situated in the middle of the downward slanting fluidizing base 25.1.
An embodiment of the conveying device provides a vibrator 220 that can be situated, for example, below the powder reservoir container 3 (see
The powder outlet channel 203 comprises, on the bottom, a purging air inlet 212 by means of which it is connected to a valve for purging air S12. The purging air valve S12, in turn, is connected to a compressed air source by means of the connector 3.3.
The purging air valve S12 can be used for purging in two different ways. Firstly, it can blow purging air into the powder outlet channel 203 via the purging air inlet 212 for cleaning purposes. For this purpose, the material valve M11 is being opened, the inlet valve 49.2 and, if applicable, the outlet valve 49.3 of the powder conveyor 49 are being closed. The suction system of the cleaning device 28 is being switched on. Once the purging air valve S12 is being opened, the compressed air flows from bottom to top through the powder channel 203 and cleans said channel. Secondly, the purging air valve S12 can also be used in order to blow purging air via the line 96 and the powder conveyor 49 in the direction of the aspiration opening 162. The material valve M11 is being closed for this purpose. The inlet valve 49.2 and the outlet valve 49.3 of the powder conveyor 49 are being opened. The suction system at the aspiration opening 162 is being switched on.
On the outlet side, the powder channel 203 is connected to the connector 3.4 via a valve M11. The connector 3.4 can have a line 96 connected to it by means of which the residual powder that is still present in the powder reservoir container 3 can be transported back to a powder reservoir container 110 by means of a powder conveyor 49. The powder reservoir container 110 can be part of a fresh powder station 3 (see
The powder conveyor 49 comprises, on the input side, a powder inlet valve 310 with a powder inlet 310.1. When the powder inlet valve 310 is open, powder can be suctioned or pumped into a container 301 that is adjacent to the powder inlet valve 310. The container 301 shall also be referred to as intermediate container hereinafter. It comprises a container housing, or housing for short, with a top part of the housing 302, a middle part of the housing 303, and a bottom part of the housing 304.
The powder inlet valve 310 can be designed as a crusher. To open the powder inlet valve 310, the control connector 313.1 of the valve 313 is switched such as to be depressurized. The valve 313 is preferably designed as a quick exhaust valve. In case of need, this allows the pressure in the powder inlet valve 311 to be reduced more rapidly and its valve opening time to be shortened.
The powder conveyor 49 comprises, on the output side, a powder outlet valve 320 with a powder inlet 320.1 and a powder outlet 320.2. The powder outlet valve 320 can be designed as a crusher. To open the powder outlet valve 320, the control connector 323.1 of the valve 323 is switched such as to be depressurized. Like valve 313, valve 323 can also be designed as a quick exhaust valve. In case of need, this allows the pressure in the powder outlet valve 320 to be reduced more rapidly.
As shown in
When the tube 305 is being pushed in the direction of the ledge 302.2 by its upper end, the side wall 302.3 forms a guidance that tapers in upward direction and thus acts as a centering aid for the tube 305. Another ledge is situated adjacent to and below the side wall 302.3, and another side wall 302.5 is situated adjacent to said ledge.
The lower end of the top part of the housing 302 is designed as a round socket 302.7. The middle part of the housing 303 is plugged onto said socket 302.7 that bears a seal. The middle part of the housing 303 can be screwed to the top part of the housing 302 by means of multiple screws 309. The lower end of the middle part of the housing 303 is plugged into a ring-shaped receptacle of the bottom part of the housing 304.
Like the top part of the housing 302, the bottom part of the housing 304 also comprises a funnel-shaped inner side 304.1. The funnel-shaped contour helps channeling the powder that is present in the intermediate container 301 to the outlet 320.1 without the powder adhering to the inner wall 304.1 of the bottom part of the housing 304. In the upper area, a ledge 304.2 is situated adjacent to the funnel-shaped inner side 304.1. The ledge 304.2 shall be referred to as lower ledge hereinafter and is a ringshaped surface that extends such as to be slightly slanted with respect to the horizontal line.
When the tube 305 is being pushed in the direction of the lower ledge 304.2 by its lower end, the side wall 304.3 forms a guidance that tapers in downward direction and thus acts as a centering aid for the tube 305. Another ledge is situated adjacent to and above the side wall 304.3, and another side wall 304.5 is situated adjacent to said ledge.
Like the side wall 302.5, the side wall 304.5 is situated at a distance from the outer side 305.9 of the tube 305 such that a clearance 306 is generated between the side walls 302.5, 304.5, and the outer side of the tube 305. At the clearance 306, the air can pass through the semipermeable tube 305, but the powder can not.
The upper end of the bottom part of the housing 304 is preferably designed as a round socket 304.7 and forms a receptacle for the lower section of the middle part of the housing 303. The lower section of the middle part of the housing 303 is plugged into the receptacle and can be screwed and/or glued to same. This produces, in simple manner, a secure and tight connection between the middle part of the housing 303 and the bottom part of the housing 304.
If the powder conveyor 49 is to be used in an area with an elevated explosion hazard, a grounding can be provided on the powder conveyor. The grounding cable 314 can be electrically connected, for example, to the middle part of the housing 303 of the powder conveyor 49.
The powder conveyor 4, which serves for supplying the working container 3, 23, can be identical in structure to the powder conveyor 49. The operating mode of the powder conveyor 4 shall be illustrated in more detail in the following. It is presumed that there is no powder present in the intermediate container 301 initially. In a first step, the valves 310 and 320 are being closed such that neither can powder get into the intermediate container 301 nor can powder be transported out of the intermediate container 301. Then, the vacuum valve 327 is being opened in order to generate a negative pressure in the intermediate container 301. In this context, the air is aspirated out of the intermediate container 301 through the air-permeable pores of the tube 305. As soon as the powder inlet valve 310 is being opened, powder is suctioned into the intermediate container 301 and/or the powder chamber 307. There is no need to wait for a definite negative pressure to be established in the intermediate container 301. The powder inlet valve 310 can be opened at any time, i.e. shortly before the vacuum valve 327 is being opened, simultaneous with the vacuum valve 327 being opened or after the vacuum valve 327 was opened. Once a sufficient powder quantity has accumulated in the powder chamber 307 of the intermediate container 301, the vacuum valve 327 and the powder inlet valve 310 are being closed again. A suction process of this type can take, for example, 6 seconds to be completed. Subsequently, the outlet valve 320 is being opened such that the powder can flow out of the intermediate container 301. This can take place utilizing the effect of gravity. In order to support the transport of powder out of the intermediate container 301, compressed air can be blown through the connector 308 and the opening 308.1 into the intermediate container 301. The valve 328 is being opened for this purpose. Initially, the compressed air moves through the connector 308 and the opening 308.1 into the space 306. Subsequently, it flows through the semipermeable tube 305 into the powder chamber 307. The compressed air aids the cleaning of the inner wall of the tube 305 during each conveying cycle.
As shown in
As shown in
The powder conveyor 4 can comprise a flange 324. The purpose of the flange 324 and screws 325 is to be able to connect the powder conveyor 4 to a further component.
The powder conveyor 4 described above can be used in various places in a powder coating facility.
The layout of the entire powder coating facility is illustrated in more detail in the following based on
The powder center 1, also referred to as powder supplying device, powder center or integrated powder management system, comprises the powder reservoir container 3 that is used for storing the coating powder. Moreover, the powder center 1 comprises a powder conveying device 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 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
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
The 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
As shown in
The cleaning arm 19 can be angled on both ends (as shown in
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 the intermediate container 301 by means of the powder valve M21, which can be designed, for example, in the form of a pneumatically controlled crusher. The intermediate container 301, combined with the inlet valve M20 and the outlet valve M21, 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 301 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 (see
The powder conveying device 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 G1-G36 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 G1-G36. Moreover, each of the powder lines 81 comprises an inlet for transport air on the inlet side, i.e. in the proximity of the corresponding powder outlet valve G1-G36. On the outlet side, each of the powder lines 81 is preferably connected to one of the powder applicators 80 each by means of a coupling 130. The amount of powder to be conveyed is controlled by repeatedly opening and closing the corresponding powder outlet valve G1-G36 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.
For this purpose, the coupling 130 comprises a first group of connectors 131 and a second group of connectors 132. 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 connector of the first group 131 each. Each individual powder line 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 G1-G36 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 powder outlet valve G1 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 are attached to a vertical linear axle 12, which is also referred to as linear lifting device, 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
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 attached to a linear lifting device 9 and can be moved vertically upwards and downwards (in y direction) by the device. The direction of motion thereof is indicated by the vertical double arrow in
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 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
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
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 out of the conveying position (see
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
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
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
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
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.
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
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.
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 M11 is being opened, while the purging valve S12 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 lifting device 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
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 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.
The cleaning of the powder conveyor 4 can take place as follows. A purging valve S13 (see
As a matter of principle, the cleaning of the powder conveyor can proceed analogously by the way and manner described above.
The two powder conveyors 4 and 5 can be connected to each other by a material valve M22 (see
The powder conveyor 49 can also be cleaned by the way and manner described above. Instead of the purging valve S13, the purging valve S12 is used during the cleaning of the powder conveyor 49. The powder removed during the cleaning can be aspirated via the suction opening 162 and line 37.
For the reasons stated above, it is advantageous to blow a large amount of compressed air (e.g. 5 bar) not only through the purging valve S13, but also through the purging valve S12.
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
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 feaBible within the scope of the invention. Accordingly, for example, the various components of the conveying device and the powder center shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 18167085 | Apr 2018 | EP | regional |
