WO2015034774A1

WO2015034774A1 - Powder collector with multiple fluidizing beds

Info

Publication number: WO2015034774A1
Application number: PCT/US2014/053413
Authority: WO
Inventors: Jeffrey R. Shutic
Original assignee: Nordson Corporation
Priority date: 2013-09-03
Filing date: 2014-08-29
Publication date: 2015-03-12

Abstract

A powder coating system (10) includes a spray booth (12) and a powder collector (14). The powder collector (14) includes a first fluidizing bed (52) and a second fluidizing bed (52). The first fluidizing bed and the second fluidizing bed (52) are arranged side by side, with a divider (54) that separates the first fluidizing bed (52) and the second fluidizing bed (52). In an embodiment, the divider (54) comprises an overflow passage (62), for example a weir, through which powder can overflow and equalize between the side by side fluidizing beds (52).

Description

POWDER COLLECTOR WITH MULTIPLE FLUIDIZING BEDS

Related Application

[0001] This application claims the benefit of pending United States Provisional Patent Application No. 61/872,916 filed on September 3, 2014, entitled POWDER COLLECTOR WITH MULTIPLE FLUIDIZING BEDS, the entire disclosure of which is fully incorporated herein by reference.

Technical Field of the Disclosure

[0002] The disclosure relates generally to material application systems that are used for spraying powder coating material onto a workpiece or object. More particularly, the disclosed inventions relate to a powder collector.

Background of the Disclosure

[0003] Powder coating systems commonly include a powder coating spray booth and an associated powder overspray recovery system. One or more powder coating spray guns are used to apply powder coating material to a workpiece within the powder coating spray booth during a coating operation. The powder coating material may be applied using electrostatic or non-electrostatic technologies. Not all of the sprayed coating material adheres to the workpiece, and this powder or material overspray that does not adhere either falls to the coating spray booth floor or remains airborne. The powder overspray recovery system is used to remove the powder overspray from the coating spray booth, especially during a coating operation, but also during color change operation and other cleaning operations.

[0004] A known powder overspray recovery process includes the use of one or more filter cartridges housed in a powder collector. Large fans are used to draw powder overspray entrained air from the powder coating spray booth into the powder collector where the filter cartridges separate the powder overspray from the air. The powder adheres to the filter cartridge or falls to the powder collector floor while the separated exhaust air is pulled into an after filter system. The powder collector floor may include a fluidizing bed that maintains the powder in a fluid-like state so that a suction mechanism such as a suction pump can remove the powder overspray from the powder collector. The recovered powder may be reclaimed for use by returning the powder to a supply hopper for the spray guns, or may be otherwise reclaimed for later use or dumped to waste.

[0005] Some coating operations can generate large amounts of powder overspray. The large volume of powder overspray can reduce the efficacy of the fluidizing bed and the suction pump, even to the extent that the powder overspray is blown back or overflows back into the powder coating spray booth.

Summary of the Disclosure

[0006] In an embodiment presented in this disclosure, a powder collector includes a first fluidizing bed and a second fluidizing bed. The first fluidizing bed and the second fluidizing bed being arranged side by side, with a divider that separates the first fluidizing bed and the second fluidizing bed. In another embodiment, the divider comprises an overflow passage through which fluidized powder can overflow between the side by side fluidizing beds.

[0007] In another embodiment presented herein, a powder collector includes a plurality of more than two fluidizing beds. The fluidizing beds being arranged side by side, with a divider that separates each adjacent pair of fluidizing beds. In another embodiment, each divider comprises an overflow passage through which fluidized powder can overflow between each adjacent pair of side by side fluidizing beds.

[0008] In another embodiment, each divider that is used to separate adjacent fluidizing beds has an overflow passage in the form of a weir.

[0009] In another embodiment, a powder collector includes a first fluidizing bed and a second fluidizing bed. The first fluidizing bed and the second fluidizing bed being arranged side by side, with a divider that separates the first fluidizing bed and the second fluidizing bed. The powder collector further includes one or more filter cartridges.

[0010] In another embodiment, a powder collector includes a first fluidizing bed and a second fluidizing bed. The first fluidizing bed and the second fluidizing bed being arranged side by side, with a divider that separates the first fluidizing bed and the second fluidizing bed. The powder collector is paired with a powder coating spray booth such that powder overspray that is generated in the powder coating spray booth is drawn into the powder collector. In another embodiment, the powder coating spray booth comprises an optional moving floor, such as a continuous web or belt, that transfers powder from the powder coating spray booth into the powder collector. In another embodiment, the powder collector comprises one or more filter cartridges.

[0011] In another embodiment, a powder coating system includes a powder coating spray booth, one or more powder coating spray guns, and a powder collector having a first fluidizing bed and a second fluidizing bed. The first fluidizing bed and the second fluidizing bed being arranged side by side, with a divider that separates the first fluidizing bed and the second fluidizing bed. In a further embodiment, the one or more powder coating spray guns receive powder coating material from a powder coating material supply and spray the powder coating material powder to coat a workpiece that is in or transported through the powder coating spray booth. The powder collector is paired with the powder coating spray booth such that powder overspray that is generated in the powder coating spray booth is drawn into the powder collector.

[0012] In another embodiment, the powder coating system includes a spray booth having a moving floor or continuous web that transfers powder overspray from the powder coating spray booth into the powder collector.

[0013] These and other embodiments, concepts and advantages of the present inventions will be appreciated and understood by those skilled in the art from the following detailed description of the exemplary embodiments in view of the accompanying drawings.

Brief Description of the Drawings

[0014] Fig. 1 is a front perspective of a powder coating system having an embodiment of a powder coating spray booth and powder collector.

[0015] Fig. 2 is a rearward perspective of the system of Fig. 1.

[0016] Fig. 3 is the powder collector embodiment of Figs. 1 and 2 in longitudinal center cross-section.

[0017] Fig. 4 is a view of the powder collector of Fig. 1 in plan view from the open side of the powder collector, with a slight forward tilt.

[0018] Fig. 5 is a perspective of an embodiment of a divider that may be used in the embodiments of Figs. 1-4.

Detailed Description of Exemplary Embodiments

[0019] Although the inventions are described in terms of exemplary embodiments of a powder collector and a powder coating spray booth, such descriptions are intended to be exemplary and not viewed in a limiting sense. The inventions may be used with many different powder coating spray booth designs and configurations, as well as used with different spraying technologies, including but not limited to electrostatic, non-electrostatic, tribo-charging, corona and so forth. The powder collector may also have many different designs and configurations other than those presented herein. For example, a powder collector having two or more fluidizing beds as taught herein may optionally be used with or without filter cartridges. The exemplary embodiments illustrate a powder coating spray booth that may be used, for example, for coating large diameter pipe. For example, pipe can be as large as twelve inches to fifty- four inches or more in diameter and in lengths of a few feet to five to six feet or more. These are just examples, and the pipe may be smaller or larger in diameter and length. Also, the inventions herein may be used with other powder coating systems and spray booths that are designed for other types of workpieces, including workpieces that are suspended from an overhead conveyor and presented to one or more powder coating spray guns within the powder coating spray booth.

[0020] A first concept presented herein contemplates a powder collector that in an embodiment has a first fluidizing bed and a second fluidizing bed arranged side by side, and a divider that separates the side by side fluidizing beds. The divider comprises an overflow passage through which powder can overflow between the side by side fluidizing beds. This can be used, for example, to provide self-equilibrating or self-balancing fluidizing beds or zones. Additional embodiments of this concept are presented herein.

[0021] A second concept presented herein contemplates a fluidizing bed arrangement for a powder collector that in one embodiment has a plurality of side by side arranged fluidizing beds with a divider between each adjacent pair of fluidizing beds. At least one of the dividers comprises an overflow passage through which powder can overflow between said side by side fluidizing beds. The overflow passage, for example, may be a weir-style passage provided in an upper portion of the divider structure. Additional embodiments of this concept are presented herein.

[0022] A third concept presented herein contemplates a powder coating system that in one embodiment includes a powder coating spray booth and a powder collector. The powder collector in an embodiment has a first fluidizing bed and a second fluidizing bed arranged side by side, and a divider that separates the side by side fluidizing beds. The divider comprises an overflow passage through which powder can overflow between the side by side fluidizing beds. Additional embodiments of this concept are presented herein.

[0023] In various alternative embodiments herein, optional features include but are not limited to a powder collector having more than two side by side fluidizing beds as well as additional dividers. A powder collector may optionally include one or more filter cartridges. A powder coating spray booth may optionally include a floor comprising a moving web or belt that transfers powder overspray from the powder coating spray booth into the powder collector. A divider may optionally include a geometry or shape that promotes shedding of powder from the surfaces of the divider down onto the fluidizing bed or at least into the fluidizing zone or region above the fluidizing bed. A powder collector may optionally include a suction device for removing powder from the fluidizing zones that are associated with the fluidizing beds. An optional suction device may include a suction tube positioned to draw powder from a fluidizing zone above a fluidizing bed, and a pump to apply suction to the suction tube.

[0024] Turning now to Figs. 1 and 2, an embodiment of a powder coating system 10 includes a powder coating spray booth 12 and a powder collector 14. The powder collector 14 may be, for example, a filter cartridge style powder collector that, for example, mates up with a blower and after-filter assembly 16 that is optionally located above the powder collector 14. The powder collector 14 when used in a filter cartridge embodiment may include one or more filter cartridges 18 (partially shown in Fig. 1) that are supported, for example, from a top wall of the powder collector.

[0025] The powder coating system 10 may further include one or more powder coating spray guns G that each receives powder coating material from an associated powder pump P (for example, a Venturi pump or a dense phase pump.) The powder coating spray guns G are represented in a general schematic fashion in Fig. 1 , in phantom for clarity. The powder pumps P may draw powder coating material from a powder coating material supply S. The design and operation of the spray guns G, the pumps P and the powder coating material supply S may be selected from many designs known to those skilled in the art and, therefore, need not be further explained herein in order to understand and practice the present inventions. The spray guns G may be aimed into the front or first side opening (32) of the powder coating spray booth 12. For some pipe coating operations, the spray guns G may be supported on a frame (shown schematically), and in practice may comprise a large bank or array of many spray guns which is represented by dashed lines in Fig. 1. The spray guns G may be but need not be electrostatic spray guns. The spray guns G are omitted in the remaining figures for clarity.

[0026] The powder coating spray booth 12 may include a base 20 supported on the shop floor or other foundation, and a canopy 22 such as may be made from any suitable material, for example, sheet metal. A frame 24 including two vertical support legs 26 may be used optionally to support the canopy 22. The frame 24 also may support optionally the blower and after- filter assembly 16. The canopy 22 may include a workpiece entry opening 28 and a workpiece exit opening 30. In the case of workpieces such as pipe, the workpieces may be rotated about a longitudinal axis and may be moved through the powder coating spray booth axially and horizontally where the workpieces are presented to the one or more, and often many, powder coating spray guns G. The spray guns G may be positioned so as to extend partially into the powder coating spray booth through a first open side 32 of the canopy 22 which may also be referred to as a front open side. This spray booth 12 configuration is also known as a side draft spray booth. A second open side 34 of the canopy 22 that is opposite the first open side 32, and may also be referred to as a back open side, faces the powder collector 14.

[0027] The powder coating spray booth 12 may include an optional moving web or belt 36. The web 36 may be supported inside the base 20 below the spray guns and the workpieces. Overspray powder that does not adhere to the workpieces will tend to fall onto the web 36. The web 36 moves as a continuous conveyor belt so that powder overspray that falls onto the web 36 is dumped into the powder collector 14. A roller brush or similar mechanism (not shown) that is driven by a suitable motor 36a may be used to help remove the powder overspray from the web 36 at the point of entry into the powder collector 14. As an example, about thirty percent of the overspray powder may fall onto the web 36. The remainder powder coating material either adheres to the workpiece or remains airborne and is drawn into the powder collector 14.

[0028] The powder collector 14 is preferably although not necessarily a separate mobile module that can be rolled or otherwise moved into position for a coating operation and away from the powder coating spray booth 12 for a color change or other cleaning operations. In the module style embodiment illustrated, the powder collector 14 may be realized in the form of a walled enclosure 38 made of sheet metal or other suitable material but that has an open side 40 (Fig. 1) that faces the second or back open side 34 of the canopy 22. The enclosure 38 may be provided with casters 42 or other suitable means for moving the powder collector into and out of position relative to the powder coating spray booth 12.

[0029] The position shown in Figs. 1 and 2 is for a powder coating operation. In this position, the powder collector 14 is placed under the blower and after-filter assembly 16, and the open side 40 is juxtaposed with the second open side 34 of the canopy 22. In this configuration, the blower and after-filter assembly 16 pulls a large volume of air flow through the powder coating spray booth 12 and into the powder collector 14 via the filter cartridges 18. The powder entrained air is filtered by operation of the filter cartridges 18 that separate the powder overspray from the air. The separated powder falls to the lower region of the powder collector 14 or adheres to the filter cartridges 18. Reverse pneumatic pulses of air may be periodically applied optionally to the filter cartridges 18, as is known, to knock the separated powder off of the filter cartridges 18 and into the lower region of the powder collector 14. The filter cartridges 18 may be pulsed at a desired rate based on the volume of powder being received in the powder collector 14. For example, the cartridges 18 may be pulsed about every seven seconds or so, but other pulse rates may be used as needed. [0030] In order to provide a close interface between the powder collector 14 and the powder coating spray booth 12, optional pull straps and latches 44 may be used to draw the powder collector 14 up close to the powder coating spray booth 12, as well as to maintain position of the powder collector 14 during operation. The pull straps 44 may be anchored to the upright frame legs 26, for example.

[0031] Optional handles 46 may be attached to the enclosure 38 to facilitate one or more operators being able to move the modular-type powder collector 14 manually into position or to a desired location.

[0032] With reference to Fig. 3, an embodiment of the powder collector 14 includes the enclosure 38 with the open side 40. One or more filter cartridges 18 are suspended from a cover or top wall 48. The blower and after- filter assembly 16 (not shown in Fig. 3) mates with the cover 48 and the filter cartridges 18 so that exhaust air is pulled through the filter cartridges 18 and the entrained powder is separated and collects on the exterior surfaces of the filter cartridges 18 or falls to the lower region 50 of the powder collector 14.

[0033] With reference to Fig. 3 and also to Fig. 4, the lower region 50 of the powder collector 14 provides a space or volume also referred to herein as a fluidizing zone 50 for the separated powder overspray (labeled 53 in Fig. 4) to be fluidized and removed from the powder collector 14. A plurality of fluidizing beds 52 are provided as part of or supported by a floor of the enclosure 38, and are arranged side by side with a divider 54 between each adjacent pair of side by side fluidizing beds 52. Each divider 54 separates adjacent fluidizing beds 52 and thereby delimits a separate fluidizing zone 50 for each fluidizing bed 52. The use of separated multiple fluidizing beds 52 provides more consistent and controlled fluidization of the powder compared to using a single large fluidizing bed. This is in part due to the fluidization being improved with a higher aspect ratio of the height (i.e. depth) of the powder being fluidized within a fluidizing zone 50 to the width of the associated fluidizing bed 52. As is known, fluidized powder is powder that has air added so that the powder takes on a fluid-like character, somewhat like a liquefied solution. The fluidized powder therefore can "flow" much like a liquid flows.

[0034] In the exemplary configuration, the fluidizing beds 52 may be shallow, meaning that the height of the fluidized powder 53 is smaller than might be achieved with a deeper fluidizing bed. Deeper fluidizing beds commonly require a trench be made in the shop floor below the collector. But, the use of multiple fluidizing beds with higher aspect ratios provides for shallower fluidizing beds without the need for a trench. Shallower fluidizing beds might be needed, for example, when a large amount of overspray powder is generated during a coating operation but when there are space or height restrictions for the coating system, and particularly where there is a desire not to use a trench. Trenches are not always desirable in that they limit the location of the powder coating system within a facility.

[0035] It is preferred although not required that the individual fluidizing beds 52 each have tapered sides 56 in plan view (Fig. 4), with the widest end 58 of each fluidizing bed 52 being closest to the open end 40 and thus to the powder coating spray booth 12. The tapered fluidizing beds 52 (viewed in plan in Fig. 4) result from each divider 54 optionally being tapered in a complementary manner in plan view. The included taper angle Θ may be, for example, sixty degrees, but other angles may be used as needed. Each tapered divider 54 design allows for a narrower end portion 60 to be located near the open end 40 of the powder collector enclosure 38. Each divider 54 may taper to a forward point 64. Each divider 54 may further be provided with an overflow passage 62 that preferably but not necessarily is located in a narrower end portion 60 of the divider 54 towards the open end 40 of the powder collector 14. This location allows for a preferred but not required reduced span for the overflow passage 62. As an example, each overflow passage 62 may be realized in the form of a weir. It is preferred to keep the width of each weir narrow to reduce or prevent a denser non-fluidized volume of powder from getting trapped in the weir or overflow passage 62. The optional tapered design allows the weir to be narrow and therefore more easily promote overflow of powder between adjacent fluidization zones 50. However, many different geometries may be used for the dividers 54, including tapered and non-tapered, that also provide a narrower width overflow passage 62. In some circumstances, the overflow passage 62 may not need to be narrow.

[0036] A suction arrangement may be provided for each fluidizing bed 52. In an embodiment, a suction tube 66 extends into the fluidizing zone 50 for each fluidizing bed 52, preferably just above the fluidizing bed surface. Each suction tube 66 may be connected at an opposite end to a respective pump 68 (Fig. 2). An open end 66a of each suction tube 66 may be positioned so as to maximize the ability to pull fluidized powder from the powder collector 14.

[0037] The overflow passages 62 allow fluidized powder to equalize between adjacent fluidizing beds 52 and fluidizing zones 50 to reduce the opportunity for powder to backflow into the powder coating spray booth 12. Without the overflow passages 62, fluidized powder may build up unevenly in the individual fluidizing zones 50, especially if there is a pump failure of one of the suction tubes 66. Should a pump fail, the fluidized powder that no longer is pulled out of the respective suction tube 66 can overflow from its fluidizing zone 50, through the overflow passage 62, and into the adjacent fluidizing zone 50. The overflow passage 62 thus allows for equalization of fluidized powder in adjacent fluidizing zones, so that the fluidized powder can be removed by the suction arrangement rather than possibly back flowing or overflowing back into the spray booth 12. This concept of an overflow passage and equalization also allows for a single level sensor 70 (Fig. 3) to be used to detect the level of fluidized powder in the powder collector 14, rather than needing a separate level sensor for each fluidizing bed 52.

[0038] Although in Figs. 3 and 4 the use of four fluidizing beds 52 and three dividers 54 is shown, such is not required, and more or fewer fluidizing beds may be used as needed. The use tapered fluidizing beds 52 and tapered dividers 54 is also not required in all applications.

[0039] From Fig. 3 it will be noted that each divider 54 when viewed in elevation may also taper or slope downward from a rearward end 54a near the filter cartridges 18 to a forward end 54b nearest the open side 40 of the powder collector 14. This downward slope assists in letting gravity shed powder from the dividers 54 onto the wider portion of the fluidizing beds 52. The slope angle a may be sixty degrees, for example, but other angles may be used as needed. The downward taper also reduces air blockage or obstruction at the open end 40 into the powder collector 14.

[0040] Fig. 5 illustrates that preferably but not necessarily each divider 54 has sides 72, 74 that merge to a peak 76 to further assist in shedding powder. It is also preferred but not required that each divider 54 slope to a zero elevation angle at the narrow end of the divider (Fig. 5) near or at the open side 40 of the powder collector (meaning that the forward point 64 of each divider is preferably flush or near flush with the web 36,) as well as taper to a zero angle (see Fig. 4) or apex in plan view.

[0041] Fluidizing air 78 may be provided to a plenum 80 below each fluidizing bed 52 (Fig. 3) through a suitable fitting 82.

[0042] Fig. 3 also illustrates an alternative embodiment for the suction tube 66. The suction tube 66' may be angled so as to provide more convenient access, for example for connection to the associated pumps.

[0043] The inventions have been described with reference to the exemplary embodiments. Modifications and alterations will occur to others upon a reading and understanding of this specification and drawings. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

Exemplary claims:

1. A powder collector for a powder coating booth, comprising: an enclosure comprising an open side through which powder overspray from a powder coating booth can enter said enclosure, a first fluidizing bed and a second fluidizing bed, said first fluidizing bed and said second fluidizing bed being arranged side by side, a divider that separates said first fluidizing bed from said second fluidizing bed, said divider comprising an overflow passage through which powder can overflow between said side by side fluidizing beds.

2. The powder collector of claim 1 comprising more than two fluidizing beds arranged side by side with a divider between adjacent pairs of fluidizing beds.

3. The powder collector of claim 1 wherein said overflow passage comprises a weir opening across each said divider.

4. The powder collector of claim 1 comprising a respective suction device for each fluidizing bed to extract powder that is fluidized by each fluidizing bed.

5. The powder collector of claim 1 comprising a level sensor to detect powder level above at least one of said fluidizing beds.

6. The powder collector of claim 1 wherein each said fluidizing bed is tapered with a larger end being closer to said open side than a narrower end of said tapered fluidizing bed.

7. The powder collector of claim 6 wherein each said fluidizing bed is tapered in plan view.

8. The powder collector of claim 1 wherein each divider is tapered in plan view with a narrower end being closer to said open side than a wider end of said tapered divider.

9. The powder collector of claim 8 wherein each said tapered divider is tapered in elevation view with a higher elevation end being further from said open end than a shorter elevation end of said tapered divider.

10. The powder collector of claim 9 wherein each said tapered divider tapers to a zero elevation and a zero angle in plan view.

11. The powder collector of claim 8 wherein each said overflow passage is positioned at a narrower portion of the respective tapered divider.

12. The powder collector of claim 1 comprising a plurality of filter cartridges within said enclosure and supported from an upper wall of said enclosure.

13. The powder collector of claim 12 in combination with a spray booth and an exhaust air system that pulls powder entrained air from said powder coating booth into said enclosure where said filter cartridges separate exhaust air from powder.

14. The powder collector of claim 13 wherein said powder coating booth comprises a moveable web onto which powder overspray falls, said moveable web transferring powder into said powder collector through said open side.

15. A powder coating system comprising: a powder coating booth having a product inlet opening through which a workpiece to be powder coated is transported and a product outlet opening through which the workpiece is transported after it has been powder coated, spray guns for spraying powder coating onto the workpiece as the workpiece is transported through the powder coating booth, and a powder collector, said powder collector including an enclosure having an open side through which powder overspray from a powder coating booth can enter said enclosure, a first fluidizing bed and a second fluidizing bed within said enclosure, said first fluidizing bed and said second fluidizing bed being arranged side by side, a divider that separates said first fluidizing bed and said second fluidizing bed, said divider comprising an overflow passage through which powder can overflow between said side by side fluidizing beds.

16. The powder coating system of claim 15 comprising more than two fluidizing beds arranged side by side with a divider between adjacent pairs of fluidizing beds.

17. The powder coating system of claim 15 wherein said overflow passage comprises a weir opening across each said divider.

18. The powder coating system of claim 15 comprising a respective suction device for each fluidizing bed to extract powder that is fluidized by each fluidizing bed.

19. The powder coating system of claim 15 comprising a level sensor to detect powder level above at least one of said fluidizing beds.

20. The powder coating system of claim 15 wherein each said fluidizing bed is tapered with a larger end being closer to said open side than a narrower end of said tapered fluidizing bed.

21. The powder coating system of claim 20 wherein each said fluidizing bed is tapered in plan view.

22. The powder coating system of claim 1 wherein each divider is tapered in plan view with a narrower end being closer to said open side than a wider end of said tapered divider.

23. The powder coating system of claim 21 wherein each said tapered divider is tapered in elevation view with a higher elevation end being further from said open end than a shorter elevation end of said tapered divider

24. The powder coating system of claim 23 wherein each said tapered divider tapers to a zero elevation and a zero angle in plan view.