WO2008070046A2

WO2008070046A2 - Powder coating system

Info

Publication number: WO2008070046A2
Application number: PCT/US2007/024786
Authority: WO
Inventors: Michael F. Riley; Jeffery E. Dailidas; Joseph G. Schroeder; Terrence M. Fulkerson; Terry J. Thompson; Jeffrey A. Perkins
Original assignee: Nordson Corporation
Priority date: 2006-12-05
Filing date: 2007-12-04
Publication date: 2008-06-12
Also published as: WO2008070046A3

Abstract

A coating material application system includes two or more guns with associated purge receptacles so that a gun may be purged and cleaned while the operator is using a different gun for a coating operation. Optionally, the cleaned and purged gun may be pre-charged with coating material so that it is ready to be used for a coating operation as soon as the operator is finished using the other gun. The purge receptacle may optionally include blow off devices for directing pressurized air at exterior surfaces of the gun. A purge operation may optionally include purging one or more supply devices such as for example, feed hoses, manifolds and pumps.

Description

METHOD AND APPARATUS FOR USING TANDEM GUNS WITH PURGE

Related Application

[0001] The present application claims the benefit of pending United States provisional patent application serial no. 60/868,621 filed on December 05, 2006 for METHOD AND APPARATUS FOR USING TANDEM GUNS WITH PURGE RECEPTACLES TO REDUCE COLOR CHANGE IN POWDER COATING SYSTEMS, the entire disclosure of which is fully incorporated herein by reference.

Background of the Disclosure

[0002] The present disclosure is directed to powder coating systems wherein powdered paint is electrostatically charged, sprayed onto a grounded workpiece by a spray gun and then melted in an oven to form a continuous coating on the workpiece. The powder coating is sprayed by one or more spray guns in a coating booth which contains oversprayed powder coating material. It is known to use more than one coating booth with different colors or types of coating material being used in the various booths. It is further known to provide the booths with wheels or other mechanisms by which the booths are transportable about the shop floor. For example, when a booth is to be changed over to another color, it can be wheeled away from the overhead conveyor and another booth moved into its place. While the first booth is offline it can be cleaned, without interrupting overall coating of parts coming down the conveyor.

[0003] Powder coating booths can be used to recover powder coating material for reuse or can be of the "spray-to-waste" type which do not recover oversprayed powder coating materials. In powder coating systems, the powder spray guns and the feed lines associated with the powder spray guns must be cleaned of any residual powder coating material from the color of powder coating material just sprayed, before a new color of powder can be introduced into the feed lines and spray guns to coat workpieces with the new color of powder. Otherwise, cross contamination of powder colors will occur and the workpieces being coated will have coating defects. In powder coating booths of the type which recover oversprayed powder, the booth must also be cleaned of any residual powder before the next color of powder is sprayed. In spray-to-waste booths on the other hand, the booth is not cleaned when changing from one color of powder to another. This process of cleaning application equipment, and possibly also the booth, between color changes is very time consuming.

Summary

[0004] In accordance with an inventive aspect of the present disclosure, a coating material application system is provided that uses two or more guns, or gun banks, with separate purge receptacles to reduce the amount of time required to clean residual powder out of the spray guns and feed lines to the spray guns. This concept thus reduces color change time in powder coating systems for both manual (i.e hand held) powder spray guns and automatic (i.e not hand held) powder spray guns. In an exemplary embodiment, a first gun or gun bank may be internally purged and externally cleaned while another gun or gun bank is being used for a coating operation. In another embodiment, a gun or gun bank may be pre-charged with coating material following a purge and clean operation so that it is ready for immediate use when an operator is finished using a different gun or gun bank. The inventions herein are applicable to any powder coating system wherein it is necessary to change from one color or type of powder to another color or type of powder. Thus, any manufacturer who uses a powder paints system to paint his products in multiple colors or types of powder coating material may use the inventions described herein. The inventions herein may be used with manual guns, automatic guns and systems that use both types of guns.

[0005] The disclosure also includes one or more inventive aspects for methods of powder coating embodied in the use of such apparatus, and in another embodiment a method of powder coating wherein a first spray gun or gun bank may be purged while a second spray gun or gun bank is being used for a coating operation. In one embodiment, a spray gun or gun bank to be purged is positioned with a purge receptacle which allows the spray gun or gun bank to be purged and cleaned without operator interaction, so that the operator may continue coating operations with a different spray gun or gun bank. In another embodiment, the method includes pre- charging a spray gun or gun bank with coating material after a purging operation so that coating operations may continue with no or little interruption. Brief Description of the Drawings

[0006] Fig. 1 is a block diagram schematic of a coating material application system that incorporates one or more of the inventive aspects of the present disclosure;

[0007] Fig. 2 is a block diagram schematic of an alternative embodiment of the system of Fig. 1; and

[0008] Fig. 3 is a simplified schematic of another embodiment of a coating material application system in accordance with one or more inventive aspects of the present disclosure.

Description of the Exemplary Embodiments

[0009] While the inventions and exemplary embodiments are described herein with specific details of a coating material application system, such descriptions are intended to be exemplary in nature and not limiting. For example, the inventions may be used with many different types of coating booths, material application devices (also referred to herein as spray guns), coating material supplies and feed centers, manifolds, pumps, purge receptacles, waste receptacles, control systems and so on. The inventions are also not limited to any particular configuration or arrangement of the various system components such as are shown in the figures herein. [0010] The inventions described herein are explained and illustrated in the context of a powder coating material application system that uses an application device, such as, for example, an electrostatic powder spray gun. However, the exemplary embodiments are not intended to be a limitation on the application or use of the various inventive aspects presented in this disclosure. For example, the inventions may be used with non-electrostatic material application devices and with tribo-charging guns that do not utilize an electrode, or combinations thereof. The inventions also are not limited to any particular type or use of coating material. The term 'powder' is used herein as being one form of 'coating material' that may be applied to work pieces, but the inventions herein are generally applicable to generally dry particulate coating materials whether or not such material would be understood as constituting powder. Additionally, the terms 'spray' and 'spray pattern' are intended to be understood in their broadest meaning to include not only those processes commonly referred to as 'spray' or 'spraying' but additionally any application technique involving the directing of a generally dry particulate coating material across a space towards a target. The spray pattern may be but need not be atomized. When used, atomization may be based on pressure, air, or both or other atomization techniques and combinations thereof. Still further, the terms 'spray' and 'spray patterns' are not to be limited to any particular time duration that the material is directed towards the target. In other words, very short bursts of material or narrow jets of material are still to be construed as falling within the understanding herein of the word 'spray' and 'spray pattern'. Many different configurations and designs may be used, far too many to identify or describe herein.

[0011] As used herein, a purge or purging operation refers to stopping flow of coating material from a material supply to a material application device, and applying pressurized purge air through part or all of the coating material flow path to remove as much of the coating material from the flow path as can be achieved for a given purging system design. As part of or in connection with a purging operation, there may also be a cleaning operation during which pressurized air is directed toward various exterior surfaces of a spray gun, for example, to clean coating material that may adhere to the gun exterior surfaces. Thus, a purging operation is considered herein optionally to include a cleaning operation, but need not require a cleaning operation for exterior surfaces, and further the cleaning operation may be performed during a purging operation or as a separate operation. As used herein, a coating operation refers to a set of events and/or various steps and operations that occur in order for a coating material to be applied to one or more objects. Thus the term coating operation is generally inclusive of one or more, and typically many, operations, functions, settings and conditions that determine the application of material to an object. For example, but not by way of limitation, a coating operation may include supply pump operation, spray booth and overspray recovery operations, conveyor system control, electrostatic control functions, material flow rates, atomization and flow air control, coating material characteristics and so on. For any particular coating operation then, there may be as few as one, but typically many parameters that are controlled or set, or in many cases are adjusted when coating operations are changed. These coating operation parameters may include but are not limited to, for example, voltage and current for electrostatic operations, coating material flow rates, air flow rates, purge timing and flow, as well as many other operations, functions, settings and conditions related to a coating operation. Therefore, the term coating operation parameter should be broadly construed as referring to any information, ^"control, function, input, output, operation, setting, condition or feature related to a coating operation that affects or influences a coating operation. The various parameters or subsets thereof, associated with a specific coating operation are generally referred to herein as recipes or coating operation recipes, and such recipes are typically, though need not be, predetermined and stored in memory for access by a main control system which controls the various system components to execute a coating operation in accordance with a selected recipe. Usually recipes are fixed as far as a line operator is concerned, but some systems may be designed to permit recipe changes and other variations by any personnel with proper authority to make such changes. Thus as used herein, recipe is not intended to be limited to a set of parameters that cannot be changed, but may include recipes in which one or more parameters, instructions, controls and functions may be changed. The term recipe thus also includes recipes that are predetermined or preset, as well as recipes that are put together on a more real time basis before a coating operation, or modified prior to a coating operation.

[0012] While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions— such as alternative materials, structures, configurations, methods, circuits, devices and components, software, hardware, control logic, alternatives as to form, fit and function, and so on—may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure; however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the scope of the inventions instead being set forth in the appended claims or the claims of related or continuing applications. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.

Introduction

[0013] With reference to Fig. 3, several inventive aspects of the present disclosure are illustrated for a coating material application system 10. In this embodiment, a coating material supply 12 may be used to source or supply coating material CM to a plurality of guns 14. The guns 14 may include a quantity N of manual guns, automatic guns or a combination thereof. The reference to 'gun' also is intended to include, as an alternative to individual guns, a gun bank in which a plurality of guns may be associated together, for example, a plurality of automatic guns mounted on a gun mover, reciprocator, oscillator and so on. It is contemplated that the system 10 will utilize at least two guns, and Figs. 2 and 3 below illustrate exemplary embodiments for manual guns and automatic guns. Therefore, in Fig. 3 the guns are identified as gun (1) through gun (N) wherein N is an integer greater than or equal to two.

[0014] The coating material supply 12 may be used to source a quantity Y of selectable types of coating material CM, such as different colors, different compositions such as metallic and so on. In Fig. 3 then, the coating materials are identified as CM(I) through CM(Y). The quantity Y of coating materials may be the same as N or may be different. In either case, the supply 12 operates to feed a coating material CM(Y) that is selectable for each gun (N). No inference is intended that CM(I) be used for gun (1) and so on, rather, any gun may have any selected coating material fed to it for a particular coating operation.

[0015] A control 16 is provided that may be but need not be conventional and well known in design. The control 16 may be a programmable type system, for example, that operates to control various functions within the system 10, for example, a coating booth 20, an overhead conveyor 18 that transports workpieces through a coating booth, the guns(N) and the supply 12. For example, in the exemplary embodiments of Figs. 1 and 2 herein, the supply 12 may include various pumps, hoppers, feed centers, manifolds, hoses and so on by which a particular coating material CM(Y) may be selected and fed to a particular gun(N). An exemplary control 16, gun 14 and supply 12 arrangement are shown and described in United States Patent Application Publication No. US 2005/0279860 Al the entire disclosure of which is fully incorporated herein by reference. Such a system however is exemplary and many other control systems and supply arrangements and guns may be used in alternative embodiments of the inventions described herein. [0016] As further shown in Fig. 3, a quantity X of one or more coating booths

20(X) may be used wherein X may be the same or different from N or Y. It is contemplated that in one embodiment, the booths 20(X) may be moveable so that while one booth is being used for a coating operation, another booth previously used may be positioned offline and cleaned. When it is desired to change the color or type of coating material being applied, the last used booth is rolled away to an offline position and the next booth rolled into position relative to the conveyor 18. However, in many cases only a single booth will be used, hi such cases, the present inventions allow for uninterrupted successive coating operations when the coating booth 20 does not need to be cleaned during a change in coating material (for example, in a spray to waste type system), and minimal interruption for the time needed to clean the coating booth in a recovery type system.

[0017] The system 10 may further include one or more purge receptacles 22.

In this embodiment, there may be a quantity N of purge receptacles so that each gun 14(N) has its own receptacle. This may be useful although not required for manual guns, whereas automatic guns, and especially gun banks, may share a purge receptacle (see, for example, Fig. 2 hereof). However, two or more manual guns 14 may share a purge receptacle.

[0018] The Fig. 3 drawing herein is not intended to imply that the purge receptacles are physically different or separate units, rather they may share a common housing or be completely separate from each other. Although not shown in Fig. 3 (but shown in Fig. 1 for example) each purge receptacle 22 may have an associated waste receptacle so that coating material that is blown off and/or purged from a gun 14 is received by the waste receptacle. Each purge receptacle 22 may be configured to provide a volume into which coating material that is purged by pressurized air from the coating material flow path (e.g. feed hoses, the gun, pumps, manifolds and so on) is received and either captured therein or passes on into a waste receptacle associated with the purge receptacle 22. The waste receptacle may be used to dump the purged coating material or to recycle it depending on the particular design of the coating system 10. Alternatively, a plurality of purge receptacles 22 may share one or more waste receptacles as will be further explained herein below. Still a further alternative is that the supply 12 may include one or more waste receptacles associated with the manifolds, and these waste receptacles may be the same as or different from the waste receptacles for the purge receptacles 22.

[0019] An exemplary but not required operation of the system 10 is as follows. Assume that gun(l) is a manual gun and that N=2 so that there is also a second gun(2). Further assume that there is a separate purge receptacle 22(1) and 22(2) for each of the guns, only a single coating booth 20 is being used, and further that there are Y=2 number of selectable colors of coating material CM(I) and CM(2). Finally, assume that an operator is currently performing a coating operation using gun(l) and that the operator is coating workpieces with color CM(I) and now wishes to change color to CM(2) for a new set of workpieces coming down the conveyor 18. [0020] The operator turns off the just used gun(l) and places it in its purge receptacle 22(1). The operator then may initiate a purging cycle or a sensor may be used that detects that the gun(l) is in the purge receptacle 22(1) so that a purging operation may start automatically. The purge receptacles 22 may optionally include blow off devices to direct pressurized air at the exterior surfaces of the gun(l) so that the gun may be cleaned externally and purged internally at about the same time with the coating material received in the purge receptacle 22(1). While this internal purging operation and optional external cleaning operation is going on, the operator is free to pick up the other gun(2) and start coating workpieces. In this way, coating operations may be continuous (for systems not needing coating booth clean out or alternatively having multiple coating booths).

[0021] The control 16 executes the purging operation for the gun(l), and after the gun(l) has been optionally cleaned and purged, the control 16 may execute a sequence by which a selected coating material CM is fed to the gun(l) so that the gun is pre-charged with coating material and ready for use when the operator picks the gun up. When the coating operation with gun(2) is completed, the operator positions the gun(2) in its purge receptacle 22(2) so that the gun(2) is purged, cleaned and pre- charged with coating material. In the meantime, the operator can grab the next gun(l) and continue coating workpieces with the newly selected coating material that has been pre-charged into that gun.

[0022] The coating operations may alternatively be performed in different coating booths as indicated in phantom in Fig. 3 by moving the various coating booths into offline positions for cleaning and online positions for coating operations. Thus, even in the case where the coating booth is to be cleaned, such can be done offline so that uninterrupted coating operations may take place because the guns 14 may be purged and cleaned while another gun is being used for a coating operation. In the exemplary embodiments, this methodology may be conveniently facilitated by use of the purge receptacles 22.

[0023] The above described operation of the system 10 may also be implemented with automatic guns and gun banks, as will be explained herein below with respect to Fig. 2. For automatic gun arrangements, the purge receptacle may include a volume under negative pressure. The purge receptacle for manual guns may also optionally and typically do include a volume under negative pressure (negative pressure meaning a pressure that is less than ambient atmospheric pressure). [0024] As additional alternative options, the purge receptacle may include an indicator that a purging operation is completed, as well as an indicator that the gun is pre-charged and ready for use. Such indicators may be, for example, lights or other indicators or signals recognizable by either an operator for manual systems or the control 16 for automatic systems. The purge receptacle 22 for the manual gun may include an optional sensor switch such as a proximity switch, for example, and related indicator to provide a signal or indication that the gun is positioned in the purge receptacle.

[0025] The purging operations as executed by the control 16 may include purging of the feed hoses, manifolds and pumps, as will be more apparent from the descriptions herein with respect to Figs. 1 and 2.

Manual Gun Powder Coating System

[0026] Fig. 1 shows the inventive aspects of the disclosure as applied to a system that uses manual guns. As shown in Fig. 1, hopper A is provided to supply a first color or type of powder or coating material, hopper B is provided to supply a second color or type of powder or coating material and hopper C is provided to supply a third color or type of powder coating material. Only three powder hoppers are shown for simplicity, but the invention may be practiced with numerous powder hoppers each supplying a different color or type of powder or coating material. [0027] It is assumed for the purpose of the present discussion that hopper A is supplying powder to gun A which is being used to paint the workpiece in the powder coating booth while gun B has just been used to spray workpieces with the hopper B powder coating material and is now at least partially disposed in holster B (described later).

[0028] Hopper A supplies powder coating material to manifold A which allows the material to be pulled from hopper A through manifold A. Pump A pumps the powder material to gun A. Preferably, pumps A and B may be dense phase pumps such as is shown in U.S. Published Application Serial Number 10/711,429, published as US 2005-0158187 Al on July 21, 2005 which is incorporated herein by reference in its entirety. Alternatively, the pump shown in US Patent 6,623,215, incorporated herein in its entirety, may be used, or other pump designs may be used as needed. Also, preferably, manifolds A and B are powder color changer manifolds of the type described in U.S. Published Application Serial Number 11/144,878, published as US 2005-0279860 Al on December 22, 2005 which is also incorporated herein by reference in its entirety. Alternatively the manifold shown is US Patent 6,935,366 also incorporated herein by reference in its entirety, or other manifold designs may be used.

[0029] Manifold A in this embodiment may include a series of powder flow passages, with flow through the passages controlled by pneumatically actuated pinch valves, hi the scenario described so far, the controller (corresponding to the control 16 in Fig. 3) is operating the pinch valves to block powder flow from hoppers B and C, while permitting powder flow from Hopper A. As noted, pump A pulls powder out of hopper A through manifold A and pushes its through gun A which sprays the powder on to the workpiece being coated.

[0030] Returning to gun B, it is assumed for the moment that the previous workpieces were just coated by gun B using powder coating material supplied by hopper B, and that as soon as coating of parts with the powder coating material from hopper B was finished, gun B was placed in the purge receptacle or holster B for cleaning. When gun B is placed in holster B, the presence of the gun is indicated to the controller by the gun sensor switch, hi response to the signal from the gun sensor switch, the controller may actuate an air jet ring to blow powder off of the outside of the spray gun into the holster waste receptacle. In addition, the controller actuates the purge function of pump B to blow any residual powder from pump B through the gun hose B and spray gun B into the holster waste receptacle B, and to blow any residual powder through the manifold hose B and manifold B into the manifold waste receptacle BM. After this purge function, manifold B, manifold hose B, pump B, gun hose B and gun B are cleaned and ready for the next color of powder. Note that as an alternative, the manifold waste receptacle BM and the holster waste receptacle B may be the same device, and to the extent that none of the purged coating material is to be recycled, all of the waste receptacles may be a single device.

[0031] Assuming that gun B will next be used to spray the color of powder from hopper C, the controller operates pump B and the pinch valves of the manifold B to pull powder out of hopper C through manifold B into pump B and out of pump B through gun hose B to gun B. The controller actuates pump B for a long enough period of time to fill up hopper hose C, manifold B, manifold hose B, gun hose B and the gun B powder flow passage with powder so that gun B is precharged with powder and is ready to immediately spray powder as soon as its trigger is pulled by the operator. The controller lights the indicator light on holster B to indicate to the operator when gun B is purged, cleaned, pre-charged and ready for use. [0032] If we next assume that the operator has painted the desired number of workpieces with the color of powder in the hopper A, the operator places gun A into purge receptacle or holster A and can immediately pick up gun B (assuming that the optional holster B indicator light, when used, is lit) and starts painting the next workpiece with the color of powder in hopper C. While the operator is painting with gun B, gun A, as well as gun hose A, pump A, manifold hose A and manifold A are cleaned of powder with purged powder being collected in the manifold A waste receptacle and the holster A waste receptacle in the same way as described above with respect to gun B. While the operator is painting with gun B, and assuming for discussion that gun A will next be used to spray the color of powder in hopper B, pump A and manifold A will be operated to fill hopper hose B, manifold A, manifold hose A, gun hose A and gun A with powder, so that gun A is waiting in the holster precharged with the next color of powder to be sprayed. Again, the controller lights the indicator light on holster A to indicated that to the operator when gun A is cleaned, precharged and ready for painting with the next color of powder to be used. [0033] Based on the above description, it can be appreciated that the system described can be used to reduce color change time. The inventions provide an apparatus and method to clean the gun and associated powder supply equipment off line, while the gun is not being used, and then precharges the gun and gun feed lines with the next color of powder to be sprayed. In spray-to-waste booths, this system provides the operator with the ability to virtually immediately change from coating workpieces with one color of powder to another color of powder, simply by switching spray guns, without the need for stopping or even slowing down the conveyor line. In booths of the type which recover oversprayed powder, this system requires only that time be spent to clean the booth during color changes since the gun is already cleaned and precharged with the next color of powder to be sprayed. With multiple booth embodiments, the change time again may be reduced to zero as the booth can be cleaned offline while the unused guns are being purged and cleaned and pre-charged. [0034] It will be appreciated by those in the art that the various manifolds need not be separate units but may all be combined into single manifold blocks or several manifolds may be combined into single manifold blocks. The waste receptacles that are associated with the purge receptacles may also be under negative pressure if needed. The holsters or purge receptacles as well as the blow-off or air jet rings may take on many different configurations. In a simplified embodiment, the holster may be realized in the form of a piece of PVC tube with appropriate supports for securely holding the gun in place during purge and clean, as well as in position to be detected by the sensor switch. The blow off device may be, for example, a ring or tube of plastic that receives pressurized air from a source (not shown) and having one or more openings that direct pressurized air streams or jets at the exterior surfaces of the gun when in the holster. Many other forms and structure may be used for the purge receptacles/holsters and the blow off devices.

[0035] Having described an exemplary embodiment of the inventions with manual powder coat guns, the inventions will next be described as applied in an exemplary embodiment to automatic powder coating guns. Automatic Powder Coating Gun System

[0036] Fig. 2 shows a powder coating system using automatic powder coating guns. So-called "automatic" powder coating guns are powder coating guns which are not handheld. Typically, automatic powder coating guns are carried on a gun mover or reciprocator (not shown) such as is shown in PCT Publication No. 03/080254 A2. Such a reciprocator supports a plurality of guns on a common frame which is moved up and down by the reciprocator as powder is sprayed from the guns onto the workpieces conveyed through the booth. The guns typically extend through a gun slot which is formed in the wall of the booth. When the coating operation with a particular color of powder is completed, the reciprocator is moved in the backward direction to retract the spray guns through the gun slot of the booth. Typically air blow off cleaning devices are mounted along the gun slots to blow compressed air onto the outside of the guns as the guns are retracted through the gun slot. In this way any powder which has collected on the outside of the guns is blown back into the booth and the exterior of the guns are cleaned off once they have been retracted from the booth. Such purge clean devices are shown in PCT Publication No. 03/080254 A2 fully incorporated herein by reference.

[0037] With reference to Fig. 2, assume that gun bank 1 is spraying powder from hopper 1 onto the parts being conveyed through the booth, hi that case, the controls would operate manifold Al and pump Al to supply the powder from hopper 1 through pump Al to gun Al and manifold A2 to supply of powder from hopper 1 through manifold A2 and pump A2 gun A2.

[0038] Assume also that gun bank 2 has just completed spraying powder from hopper 2 onto the parts moving through the spray booth and that gun Bl and gun B2 of gun bank 2, and the lines feeding them, must now be cleaned of any residual powder from hopper 2. As described above, when gun bank 2 is withdrawn from gun slot 2, the compressed air purge cleaning devices associated with gun slot 2 blow powder off of the exterior surfaces of the guns of gun bank 2 as they are withdrawn from the gun slot by the reciprocator. The reciprocator moves the guns not only backwards out of the gun slot but also sideways and forward into the fixed purge receptacle as shown by the dotted line path in Fig. 2. Once in the fixed purge receptacle, the controller actuates pumps Bl and B2 to blow any residual powder from pump Bl through gun hose Bl and gun Bl into the fixed purge receptacle and likewise from pump B2 through gun hose B2 and gun B2 into the fixed purge receptacle. A negative pressure may be maintained in the fixed purge receptacle so that the powder collected in the receptacle can be transported to a waste container or recycled for reuse. In addition, the controller actuates manifolds Bl and B2 and pumps Bl and B2 to blow any residual powder from manifold hose Bl and manifold Bl into the waste receptacle associated with manifold Bl, and likewise, blow any residual powder from manifold hose B2 and manifold B2 into the waste receptacle associated with manifold B2.

[0039] Once gun bank 2 and all associated lines to have been cleaned of residual powder coating material, and assuming that gun bank 2 will next be used to apply the powder coating material from hopper 3, the controller operates manifolds Bl and B2 and pumps Bl and B2 to pull powder out of Hopper 3 into manifold Bl and B2 and then from pumps Bl and B2 through gun hoses Bl and B2 to guns Bl and B2 to precharge the guns and gun feed lines with powder as described above with respect to the manual spray gun system. Once this has been done, the guns can be moved by the reciprocator back to a ready position just outside of gun slot 2. Thus, when the desired number of workpieces has been painted with the powder coating material from hopper 1, the guns of gun bank 1 can be turned off and retracted through the gun slot so that the booth can be cleaned of any residual powder from hopper 1. As soon as the booth is cleaned, gun bank 2 is ready to be inserted through gun slot 2 to start spraying powder from Hopper 3 onto the workpieces being conveyed through the spray booth. In the case of a spray-to-waste booth which is not cleaned between color changes, as soon as powder coating is stopped with the guns of gun bank 1, the guns of gun bank 2 can be used to immediately start spraying the next color powder, without the need for stopping or even slowing down the conveyor line. [0040] The purging of gun bank 1 will be described with respect to a moveable purge receptacle which could alternatively be used instead of the fixed purge receptacle described above. When the guns are withdrawn back through gun slot 1 by the reciprocator, with their exteriors surfaces cleaned by the compressed air cleaning devices, the guns are pulled back far enough so that the movable purge reciprocator can be moved to the position covering gun slot 1 which is shown by the dotted lines in Fig. 2. The foreword ends of guns of bank 1 would then be reciprocated into the movable purge receptacle so that any residual powder in the guns, and in the hoses and pumps feeding the guns, can be purged into the movable purge receptacle. Likewise, residual powder in the pumps and the hoses between the pumps and manifolds would be purged into the waste receptacles associated with manifolds Al and A2 as described above with respect to the purging of the feed lines associated with gun bank 2. Once the guns of gun bank 1 and associated lines have been cleaned, the guns and associated lines are then precharged with the next color of powder to be sprayed as described above with respect to gun bank 2. When that is complete, the guns of gun bank 1 are retracted out of the movable purge receptacle and the movable purge receptacle is moved back to its standby position so that it does not cover the gun slot. Gun bank 1 can then be moved foreword to a ready position just outside of gun slot 1 so that the guns of gun bank 1, having been cleaned and precharged with the next color of powder to be sprayed, can be used to coat workpieces as soon as they are needed.

[0041] hi the above described apparatus and method for automatic guns and gun banks, it will be appreciated that the guns may be positioned in several optional locations. For example, the guns may have a coating position in which they extend into the coating booth for coating workpieces. In order to change coating material (presuming cleaning is required), the guns may be withdrawn from the coating booth to a standby position, whereby the guns are blown off by the cleaning devices typically positioned near the gun slots of the coating booth as the guns are withdrawn from the coating booth. The guns may also be positioned at a purge position relative to either a fixed or movable purge receptacle for internal purging. Finally, the guns may be returned to the standby position in preparation for a next coating operation. The cleaned and purged guns may be pre-charged in the standby position or in the purge position or other suitable position as needed.

[0042] Thus, as was the case with the manual gun system, the inventions may be advantageously used with automatic powder spray gun as well to reduce the time required to switch from coating with one color of powder to another. [0043] Having described exemplary embodiments of the inventions for use with manual powder coating guns and with automatic powder coating guns, the following claims are made.

Claims

We claim:

1. A powder coating system comprised of: a first hopper containing a first color of powder coating material and a second hopper containing a second color of powder coating material; a first color change manifold connected to said first and second hoppers and a second color change manifold connected to said first and second hoppers; a first pump connected to said first manifold and a second pump connected to said second manifold; a first spray gun connected to said first pump and a second spray gun connected to said second pump; and a first purge receptacle for said first spray gun and a second purge receptacle for said second spray gun, said first purge receptacle being connected to a first waste receptacle and said second purge receptacle being connected to a second waste receptacle.

2. The system of claim 1 further comprising controls for selectively supplying powder from said first hopper through said first manifold and said first pump to said first spray gun.

3. The system of claim 1 further comprising a first waste receptacle associated with said first manifold and a second waste receptacle associated with said second manifold.

4. The system of claim 1 wherein said first spray gun is a manual spray gun and said first purge receptacle is a first holster for said first spray gun and wherein said second spray gun is a manual spray gun and said second purge receptacle is a second holster for said second spray gun.

5. The system of claim 4 further comprising to a first switch associated with said first holster which generates a signal indicating the presence of said first gun in the first holster.

6. The system of claim 4 further comprising a first indicator associated with said first holster which provides an indication that said first gun has been cleaned and precharged with powder coating material.

7. The system of claim 4 further comprising compressed air outlets which are usable to blow compressed air onto the exterior of said first gun when said first gun is in said first holster.

8. The system of claim 1 further comprising a first gun bank of two or more automatic spray guns and a second gun bank of two or more automatic spray guns.

9. The system of claim 8 further comprising a purge receptacle for said first gun bank.

10. The system of claim 9 wherein said purge receptacle is maintained at a negative pressure and is connected to a container for collecting powder purged into said purge receptacle from said first gun bank.

11. The system of claim 10 wherein said purge receptacle is fixed in position.

12. The system of claim 10 wherein said purge receptacle is movable.

13. A method of powder coating comprising the steps of: supplying powder from a first hopper containing a first color of powder coating material through a color change manifold to a first spray gun that sprays said first color of powder coating material onto a workpiece in a powder coating booth; discontinuing the supply of powder from said first hopper to said first spray gun; moving said first spray gun into a first purge receptacle and purging powder coating material of said first color from said first gun into said first purge receptacle; and removing a second spray gun from a second purge receptacle and spraying a second color of powder coating material from a second hopper through said second spray gun onto another workpiece.

14. The method of claim 13 wherein said first spray gun is a manual spray gun, further comprising the step of providing a signal to a control system when said first spray gun has been moved into said first purge receptacle.

15. The method of claim 13 further comprising the step of providing an indicator to the operator when said first spray gun has been cleaned of powder coating material and precharged with a new powder coating material.

16. The method of claim 13 further comprising the step of moving said first purge receptacle before moving said first spray gun into said first purge receptacle.

17. The method of claim 16 further comprising the step of moving said first purge receptacle after moving said first spray gun out of said first purge receptacle.

18. The method of claim 13 further wherein after said step of spraying said workpiece in said powder coating booth with said first color of powder coating material with said first spray gun is performed, the step of cleaning said first color of powder from said powder coating booth is performed and then said step of spraying said second color of powder coating material through said second spray gun onto another workpiece is performed.

19. A powder coating material application system, comprising: a selectable first supply of coating material, a selectable second supply of coating material, a first spray gun and a second spray gun, a first purge receptacle and a second purge receptacle, said first gun being at least partially disposed in said first purge receptacle for a first gun purging operation and said second gun being at least partially disposed in said second purge receptacle for a second gun purging operation.

20. The system of claim 19 wherein each said spray gun is operable during a coating operation during a time period when another spray gun is being purged.

21. The system of claim 19 comprising a control system for controlling which said supply is used during a coating operation.

22. The system of claim 19 wherein each said spray gun is operable to spray coating material from either said supply.

23. The system of claim 19 wherein each said supply comprises a source and a pump, and the system comprises at least one manifold to select which source is used by a spray gun during a coating operation.

24. The system of claim 19 comprising a coating booth in which said first and second gun are operable to coat workpieces.

25. The system of claim 19 wherein at least one of said spray guns is a manual gun.

26. The system of claim 19 wherein at least one of said spray guns is an automatic gun.

27. The system of claim 19 wherein at least one of said purge receptacles is moveable between a standby position and a purging operation position.

28. The system of claim 19 wherein a purge receptacle for a manual spray gun comprises a blow off device to remove coating material from exterior surfaces thereof, and a purge receptacle for an automatic spray gun operates with a negative pressure.

29. The system of claim 19 wherein a spray gun that has been purged is pre- charged with coating material from a different supply while another spray gun is being used during a coating operation.