Patent Grant
7074274
The invention relates generally to powder coating spray systems, and more particularly, to methods and systems for facilitating the change of powder paints and coatings in such spray systems, including improved methods and apparatuses for the recovery and re-use of over-sprayed powder coatings in a spray booth, for feeding powder coatings to be sprayed, and for purging powder coatings from system components.
Powder coating spray systems are used to apply powder paints and coatings to a variety of products including, for example, appliances automotive components, furniture and storage shelving, electrical transformers, and recreational equipment. These systems often apply the coating materials to such products electrostatically by using one or more electrostatic spray devices in a spray booth enclosure setting. A powder feed system is used to supply the coating material to the spray devices and a powder recovery system is typically employed to capture over-sprayed powder material for re-use. The recovered powder coatings may be transferred to a collection bin for later re-use or disposal.
Known powder recovery systems, especially those employed in larger production-type powder coating spray booths using a plurality of spray application devices, often use cyclone separators and/or filter elements for collection of over-sprayed powder coating material. Such a powder coating spray system using cyclone separators is disclosed in International Application Number PCT/GB98/02569, owned in common by the assignee of the present invention, the entire disclosure of which is fully incorporated herein by reference.
Cyclone separators used in powder recovery systems have either been very large single or dual side by side cyclones, multicyclones, or pairs of such cyclones having tangential or axial feed inlets.
In cyclones of the vertical feed type, the air entrained over-spray powder is fed vertically downwards from a common inlet manifold into the separators and a circumferential velocity is imparted to the air-entrained powder coating material by veins. In addition to the inlets, which are typically located in the booth walls near the ceiling, and are useful for capturing air-entrained powder coating material, intakes are sometimes provided near the floor of the powder spray booth. In such cases, a vertical channel connects the intake to the inlet to the cyclone which is near the ceiling of the booth. Such intakes are useful for recovering powder coating material from the area near the floor of the booth.
Sweeper devices may be employed to move over-sprayed powder coating material which has collected on the floor to a recovery intake. The sweeper device may take the form of a scraper bar which may be magnetically coupled to a drive positioned externally of the powder booth, such as is disclosed in International Application Number PCT/GB98/02569. The advantage of this is that the drive mechanism is outside the booth and therefore not covered by powder, and therefore it does not need to be cleaned when changing powder color.
To maximize the amount of powder which settles on the floor of the booth and can, therefore, be collected at the floor level cyclone intakes by the sweeper device, the booth walls and ceiling, or the booth canopy, are preferably made from non-conductive material. For example, the booth canopy may be made from a plastic material. Alternative materials include stainless steel.
In vertical cyclones, the over-spray powder is separated from the air by the combined effect of centrifugal and gravitational forces and falls to the bottom of the separators to be collected and removed. The cleaned air is then typically directed vertically upwards through ducts, one per cyclone separator, which pass through the center of the cyclone and into an exhaust manifold. The air then passes through a further powder, or dust, recovery unit containing one or more filter elements to remove any fine powder particles still entrained in the air, before being exhausted to atmosphere.
The captured powder coating material may be collected below the cyclones in a collection bin or hopper, for disposal or re-use. In addition, a sieve member may be employed between the cyclone exhaust at the cyclone's open throat end and the collection bin. Known sieve members are typically of similar size to the circular exhaust end of the cyclone. Known transfer means to deliver the captured powder from the collection bin, or hopper, located below the cyclone to a more distant collection hopper whereby the collected powder can be dumped into a feed hopper, is through a series of at least two pinch valves. Alternatively, an improved transfer means, found in International Application Number PCT/GB98/02569, comprises a venturi pump in combination with a mini cyclone. The known improved combination requires far less sophisticated controls than the dual pinch valve setup. Both methods still require cleaning of all surfaces contacted by the powder coating between powder coating color changes.
Known powder feed systems include a powder pump, a powder hose connecting the pump to a spray application device, and a pick-up, or suction, tube. Of course, there may be a plurality of such components. The suction tube may be inserted directly into a feed hopper or a virgin powder box. It is known to place the box, or hopper, on a vibratory table to provide continuous movement of powder and help break up any agglomerates. When a plurality of pumps, suction tubes and powder spray devices are employed, output can vary between pumps and can randomly surge, affecting powder coating application quality.
In such systems, changing the powder type (e.g., powder paint color) generally requires the cleaning of all system components that have come in contact with the previously applied powder. This cleaning process is intended to avoid the contamination of the new powder by the previously used powder. However, the longer it takes for the cleaning process to complete, the longer the spray system is off-line. The cleaning process completion time is dependent on a number of factors including, for example, the number of spray system components, their internal and external geometries that may have come in contact with the previously applied powder coating, and the type of powder. Hence, if the spray system includes a larger number of components having complicated or irregular geometries, the longer it takes to clean the system and the longer the spray system is “off-line” or not working. Long off-line times are very undesirable because they cause a decrease in overall spray system productivity. Hence, apparatuses and methods that minimize the time required for changing powder colors in powder coating systems are highly desirable.
According to the present invention, systems, apparatuses, and methods for efficiently supplying and using powder coating materials, in order to simplify systems and minimize powder contacting areas and over-sprayed powder in the system, are provided. These systems, apparatuses and methods are provided to facilitate color change operations for successive coating operations. For example, a novel powder coating spray system is provided. In a powder coating spray booth system of the type including one or more powder spray devices, a powder feed system including a feed hopper, and a powder recovery system to capture over-sprayed powder, a powder transfer conduit is provided which is connected at a first end to a reclaim powder collector of the powder recovery system, and at a second end, lower in elevation than the first end, to a powder feed hopper of the powder feed system. Such a set-up in its simplest form provides for direct gravity transfer of reclaimed powder back to the feed system for re-use by the spray application devices. Such a system minimizes the sophisticated controls necessary for the multiple pinch valve or venturi pump/mini-cyclone system described above. In addition to simplifying controls and minimizing internal component powder contacting surfaces, direct feed of the reclaimed powder to a feed hopper of the feed system is disclosed by the present invention.
Additionally, the inventive recovery system may include one or more cyclone separators fluidly connected to the booth via one or more inlets (preferably one per cyclone) connected via a channel to one or more intakes for recovering deposited coating material on the floor of the booth. The cyclones may have to be connected with one or more additional, optional intakes for airborne powder coating material located in a booth wall near the tope of the booth. These cyclones may exhaust captured powder coating material to a reclaim powder collector, or hopper. Interposed between the reclaim powder collector and the cyclone exhaust end, or open throat end, may be a sieving mechanism. The sieving mechanism may have an exciter device to excite the sieving member and facilitate the sieving function. To facilitate the gravity transfer of the captured powder of such a system back to the feed system, the reclaim powder collector may have an underlying fluidizing bed including a plenum, a fluidizing plate and a source of pressurized gas, such as air. In addition, at the interface of the reclaim powder collector and the powder transfer conduit, a selectively operable valve member, operable to allow captured powder to enter the powder transfer conduit in a first open position and to seal the reclaim powder collector in a second closed position, is provided. Furthermore, a sealing mechanism is provided to seal the cyclone exhaust at the open exhaust, or throat end of the cyclone separator, to isolate the cyclone from the reclaim powder hopper during a powder transfer operation. By fluidizing the powder with a source of pressurized gas and a fluidizing plate, the transfer rate and efficiency of reclaimed, or captured, powder to the feed hopper is significantly increased. Not only gravity, but the fluidization of the powder and pressure serve to facilitate the powder transfer in this inventive embodiment.
During cyclone operation, a vortex break device, such as an annular plate or valve member positioned across and perpendicular to the cyclone exhaust, or throat end, is provided in the present invention. The valved plate-like member can also be rotated to facilitate cleaning. In either case, such a device is smaller in diameter than an open conical cyclone's circular exhaust, or throat end, thereby creating an annular gap that allows the captured powder to be delivered along the interior cyclone wall through the gap to the reclaim powder collector. With a vortex break device, already captured powder is prevented from being re-entrained in the cyclone exhaust back through the center of the cyclone. With such a vortex break device, the sealing mechanism used to isolate the cyclone from the reclaim powder hopper, may take the form of an annular valve member or an inflatable annular seal device which selectively closes the annular gap.
In addition, bulk powder unloading into the process stream upstream of the sieve is provided by the inclusion of a powder inlet port for virgin powder unloading into the process stream up line of the sieving mechanism, but below the vortex break device. The sieving mechanism serves to screen out impurities and foreign materials, as well as to break up any agglomerates in the powder coating material. The virgin powder can then be transferred to the feed hopper via the powder transfer conduit already described, using gravity alone, or in combination with the fluidization plate and pressure.
To transfer either or both captured and virgin powder to a feed hopper of the feed system in one embodiment of the present invention, the cyclone would be isolated with respect to the reclaim powder collector and sieving mechanism. Isolation would occur by sealing, such as by inflation of an annular seal member around the circumference of a butterfly type valve, or by a pinch-type or iris valve, to seal the cyclone with the vortex break device. A valve member would then be opened at a lower elevation of the reclaim powder collector at the interface with the powder transfer conduit. The powder coating material in the reclaim powder collector would be fluidized, whereby the fluidized powder coating material is transferred to the feed hopper via the powder transfer conduit under the influences of gravity and pressure.
In some configurations with one or more cyclones near each end of a spray booth, it may be desirable to have one or more of the cyclones, or sets of cyclones, to be mounted in a tilted configuration with respect to the vertical. This may be desirable to raise the cyclone exhaust end, and subsequent reclaim powder collector height, to facilitate gravity transfer of reclaimed powder over longer horizontal distances, back to feed hoppers positioned near opposite side walls of a spray booth, for example.
The present invention provides for an improved powder feed system and interface of the feed system with the spray booth. A lance assembly is provided including one or more each of powder suction tubes and powder pumps. The powder pumps may be novel venturi-type pumps, as discussed in more detail below. Typically a powder supply conduit is provided to connect each pump with a spray application device in the spray booth. The lance assembly of the present invention is operable to move from a first lower position to a second higher position, such as by a controller, an actuator and one or more guide rods wherein the lance assembly may slide vertically from the lower to the higher position along the guide rod, or rods. The lower position corresponds to a position wherein the one or more powder coating suction tubes each have an open powder intake end proximate a lower elevation within a powder supply. Powder feed is accomplished in this lower position, simplifying the controls of known systems, wherein the powder suction tubes must be repositioned within the powder supply during a powder spray coating operation.
The powder supply for the present invention may be any bin, or box of powder, and may be placed on a vibratory table, as described above. More preferably, the powder coating material supply to the feed system will take the form of a rollable fluidizing bed powder hopper directly connecting with the powder transfer conduit of the recovery system, as described above. The fluidizing hopper includes a source of pressurized fluidizing gas, such as air, a fluidizing plate and a hopper body. The fluidizing plate may be made of a sintered material, such as polyethylene, or other plastic. The fluidizing powder hopper of the present invention can have a containment lid to seal the hopper about the installed lance assembly. In such a configuration, there may be a vent connecting the hopper to the interior of the spray booth for venting the excess pressure.
Inventive apparatuses and methods for cleaning the powder feed system of the present invention are also disclosed. The lance assembly can be raised to its higher position, the rollable fluidizing hopper can be disconnected from the booth, powder transfer conduit, source of fluidizing gas, and rolled out the way. A purge manifold can be moved into position and the lance assembly can be lowered to its lower position, wherein each open powder coating suction tube end of the lance assembly will engage with a purge port, or nozzle of the purge manifold. The purge system can be activated with the spray devices connected to the system, and the internal surfaces of the feed system from the lance through to the gun can be readily purged and cleaned of any powder adhering to the internal surfaces of the powder flow path. Such a purge manifold connected to a purge gas, would preferably be swingable from a first stowed position to a second purge position wherein the lances could meet with it in the lower position of the lance.
Furthermore, the feed system of the present invention can be located proximate a side wall section of the booth. The area surrounding the feed system can be made ventable directly to the cyclone exhaust. A plenum area spaced from the booth side wall and a perforated screen section, or other porous side wall section communicating with the plenum area, to diffuse the air entering the plenum area when the cyclones are running and exhausting air, is provided. Connectivity with the cyclone exhaust ducting and out through the last stage dust filters of the booth powder recovery system is made via a powder feed center damper which is a dampered inlet from the plenum area to the cyclone exhaust ducting. In such a configuration, to clean the powder feed section, the powder feed center damper can be opened allowing air external to the spray booth to communicate through the perforated screen and into the plenum area and then into the cyclone exhaust ducting. With the cyclones running, the feed system external surfaces can be blown down with an air lance proximate the perforated screen and plenum area. Any loosened powder will flow through the screen, into the plenum and out the cyclone exhaust ducting to be filtered before the transport air is exhausted to atmosphere. During a coating operation, the damper will normally be closed thereby preventing external air from communicating with the interior of the plenum area and reducing cyclone efficiency.
An apparatus for supplying powder coating materials having a pump assembly block in fluid communication with and physically attached to an air line attachment plate, a suction tube plate, and a hose manifold plate is provided. A plurality of attachment members removably attach the air line attachment plate, suction tube plate, and hose manifold plate to the pump assembly block. The attachment members can be conventional fasteners such as, for example, screws or similar devices, and/or resilient o-rings.
The pump assembly block includes, for example, two or more pump chambers machined into the block. The two or more pump chambers are each capable of receiving a removable venturi throat member. Each pump chamber has a powder inlet port, a diffuser air inlet port, and an ejector air inlet port. The air line attachment plate has a diffuser air passage and an ejector air passage for each diffuser air inlet port and ejector air inlet port of the pump assembly block. A plurality of attachment members secure the air line plate to the pump assembly block in an assembled position and release the air line plate from the pump assembly block into a disassembled position. The diffuser air passages and ejector air passages of the air line plate communicate with the diffuser air inlet and ejector air inlet ports of pump assembly block when the pump assembly block and the air line plate are in the assembled position. An air line connects each of the diffuser air passages and ejector air passages of the air line plate to a regulated compressed air source.
According to another aspect of the present invention, a method of applying a first powder color and a second powder color from a powder feed center is provided. The method includes, for example, the steps of: applying the first powder color through a first pump assembly and a first hose manifold plate in fluid connection with one or more spray devices, ceasing the application of the first powder color, replacing the at least one of the first pump assembly and the first hose manifold plate with a second pump assembly and a second hose manifold plate in fluid communication with the one or more spray devices; and applying the second powder color through the second pump assembly and the second hose manifold plate. In this manner, the time required to implement a powder change and the amount of color cross-contamination is greatly reduced.
To facilitate collection of powder coating material that has fallen to the spray booth floor, an improved floor sweeper system is also disclosed in the present invention. Included in the preferred rectangular floor of the booth are one or more collection troughs, each of which is located in the floor between the cyclone powder intakes and the one or more spray devices. The sweeper substantially spans the width of the booth from the first side wall to the second opposed side wall. The sweeper is controlled to run back and forth across the booth floor via magnetically being coupled to one or more drive tracks positioned under the booth floor, or proximate the booth side walls near the floor. Such a configuration makes cleaning easier, as a sweeper used for one color of powder coating material can be exchanged for a cleaned sweeper in preparation for a color change operation. Preferably, there will be two collection troughs, each having a bottom that is slanted in elevation from a first end proximate the first side wall to a second lower end proximate the second side wall. The bottoms of the troughs may further include a fluidized bed connected to a source of pressurized gas, whereby the collection troughs each form a fluidized slide for collected powder. Powder collected by the floor troughs can be deposited in either removable collection bins or be sent directly to feed hoppers of the feed system. Alternatively, the powder can be first sent to a collection bin and then transferred to the feed hoppers by transfer means, such as a series of pinch valves, as previously described above for known powder transfer from cyclone collectors to hoppers or bins.
Additionally, an inventive spray booth explosion door is provided. The explosion door has a first section hingedly attached to a wall and in communication with the cyclone inlet. It is operable to vent the inlet of the cyclone in the event of a first over-pressure condition within the booth, such as caused by a deflagration. The explosion door has a second, larger section hingedly attached to the booth wall and operable to vent the cyclone in the event of a second, larger over-pressure condition within the cyclone. The hinges retain or capture the door sections in the event of a deflagration and allow the door sections to be opened to facilitate cleaning of the booth during a color change.
It is, therefore, one objective of the present invention to provide a system and method that reduces the time required when changing from a first powder color to a second powder color in a powder coating system.
It is a further objective of the present invention to provide a method of reducing the cross-contamination that occurs when changing from a first powder color to a second powder color in an electrostatic spray system.
In the accompanying drawings, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to illustrate the various features of this invention.
Referring now to
The powder coating spray booth system can include one or more conical-bodied cyclone separators 30 to facilitate recovery of over-sprayed powder coating material within the booth. The cyclone separators 30 may be mounted on a rollable fixture to facilitate cleaning and maintenance. Shown in
In a preferred embodiment illustrated, the cyclone inlets 34 are located near confluence of the ceiling 14 and the end walls 16. See
In an alternative embodiment (not shown, but similar to that described in International Application Number PCT/GB98/02569), there may be optional intakes for capturing air-entrained powder coating material over-spray within the booth 10 located near the ceiling 14 in the end walls 16. The floor intakes 36s, on the other hand, are for recovering powder coating material over-spray within the booth 10 located near the ceiling 14 in the end walls 16. The floor intakes 36, on the other hand, are for recovering powder coating material over-spray that has already fallen to the floor 18 of the booth 10 are thus located proximate the floor 18, either in the floor 18, in the end walls 16, proximate the floor 18, or in and interface region of the end walls 16 and floor 18, as described above. Both types of intakes would be connected to the cyclone inlets 34 such as by the same channels 35, or by separate such channels.
In the illustrated embodiment, the cyclone separators 30 share common exhaust ducting 40. One or more dust filters, or final stage filtration devices, 42, are in fluid communication with the ducting 40. Suction means 44, such as may be provided by one or more high flow exhaust fans draw powder entrained air from within the booth 10 through the cyclones 30, the ducting 40 and the filters 42, before the cleaned air is exhausted to atmosphere.
In addition, the powder coating spray booth 10 will have one or more spray application devices 15 positioned with respect to one or both booth side walls 12, a powder feed system, shown generally at 50, and a powder recovery section below the cyclones, shown generally at 60.
A powder transfer conduit 48 (see
In the illustrated embodiments, there is a common reclaim powder collector 62 for each cyclone pair 32. The reclaim powder collectors 62 collect powder coating material captured by the cyclones 30. The coating material is separated in the cyclones 30 via the effects of centrifugal force, friction and gravity, and falls out the open smaller diameter end of the cyclones' cones. We refer to this smaller diameter end of the conical-bodied cyclones 30 as the cyclone open end, or throat end, 31. The reclaim powder collectors 62 are located below the cyclones 30. In the illustrated embodiment, each pair 32 of cyclones 30 share a common reclaim powder collector 62.
Interposed between the reclaim powder collectors 62 and the cyclones' exhaust, or open throat ends 31 is a sieving device 63. In the illustrated embodiment, the sieving device 63 takes the form of a very fine mesh screen, made of stainless steel or other suitable material, with an exciter device 69 to excite the screen and facilitate the sieving function. The exciter device 69 may generate a vibratory input, an ultrasonic input or a combination of both to the sieving device 63.
Referring now to
Furthermore, a sealing mechanism is provided to seal the cyclone exhaust at the open exhaust, or throat end 31 of each cyclone separators 30, to isolate the cyclone 30 from its corresponding reclaim powder hopper 62 during a powder transfer operation. The scaling mechanism can be a simple valve member, operable to effectively seal each cyclone throat 31, but more preferably takes the form of a vortex break device in combination with a sealing member, as further described below. By isolating the cyclone exhaust end 31 from the reclaim powder collector 62, and by fluidizing the powder in hopper 62 with a source of pressurized gas and a fluidizing plate 66, the transfer rate of reclaimed powder from the reclaim hopper 62 to the feed hopper 52 is significantly increased. Not only gravity, but the fluidization of the powder and the fact that the fluidizing air pressurizes the reclaim hopper 62 once it is sealed from the cyclones 30 facilitates the powder transfer in this inventive embodiment, since the powder is not only being fed by gravity through tube 48 but is also being pushed through the tube 48 by the pressurization of hopper 62.
During cyclone operation, a vortex break device 70, such as an annular plate or valve member normally positioned across and perpendicular to the cyclone exhaust, or throat end, 31 is provided in the present invention. See
An interface plate 74 (
A further benefit of the inventive design is that bulk powder, or virgin powder, can be unloaded upstream of the sieving device 63 without significant loss due to the negative pressure effects of the cyclone. The sieving device 63, which is preferably circular as illustrated and may take the form of a simple vibratory deck screen with a vibratory-type exciter device 69, is much larger than the diameter of the cyclone throat 31. In view of the substantial isolation of cyclone 30 by the vortex break device 70, bulk transfer of virgin powder onto the top of the sieving device 63 can be done.
A method is thereby disclosed wherein to transfer either or both reclaimed and virgin powder to a feed hopper 52 of the feed system 50 in an embodiment of the present invention, the powder would be sieved and stored in the reclaim powder collector 62. The cyclones 30 would be isolated with respect to the reclaim powder collector 62 and sieving mechanism 63. Isolation would occur by sealing, such as by inflation of the annular seal member 72, or by a pinch-type or iris valve, to seal the cyclone 30 at the throat 31 with the vortex break device 70. Alternatively, in embodiments not using a vortex break device, a sealing mechanism (not shown) to seal the entire throat 31 to isolate the cyclone 30 from the reclaim powder collector 62, may be employed. A valve member, such as illustrated and described as reference 49 would then be opened at a lower elevation of the reclaim powder collector 62 at the interface with the powder transfer conduit 48. The powder coating material in the reclaim powder collector 62 could then be fluidized by a pressurized gas, such as air entering plenum 65 and diffusing through fluidizing plate 66, whereby the fluidized powder coating material is transferred to the feed hopper 52 via the powder transfer conduit 48 under the influences of both gravity and pressure. Of course gravity feed alone may work fine, without fluidization of the powder, especially where a steep angle between the reclaim powder collector 62 and the feed hopper 52 can be maintained for the powder transfer conduit 48.
Valve member 49 remains in the closed position shown in
Note that a hole is shown in the wall of the hopper 62 in
Although not shown, in some configurations with one or more cyclones near each end of a spray booth, it may be desirable to have one or both of the cyclones, or pairs or sets of cyclones, to be mounted in a tilted configuration with respect to the vertical. This may be desirable to raise the cyclone exhaust end, and subsequent reclaim powder hopper height, to facilitate gravity transfer of reclaimed powder over longer horizontal distances back to two or more feed hoppers positioned near opposite side walls of a spray booth, for example.
A novel powder feed system 50 is also disclosed by the present invention. See
Referring now to
Since the roll-in fluidizing bed feed hopper 52 is used, the suction tubes can be placed fully into the feed hopper 52, near the fluidizing plate (not shown). As such, the lance assembly 80 is simply movable from a first lower position (not shown), proximate the fluidizing plate within the feed hopper 52, to a second higher position (
In addition to the simplified controls, by adding a containment lid 58 to the fluidizing powder feed hopper 52, and venting the hopper directly to the spray booth 10 via a duct 57, the fluidized gravity feed and bulk unloading via the powder transfer conduit 48 can take place. The containment lid 58 can take the form either of a multiple piece assembly wherein the lid is secured about the installed lance assembly 80, or of a preferred one-piece configuration wherein the lowered lance assembly 80 effectively seals with the containment lid 58 upon seating in the first lower position of the lance assembly 80. The vent duct 57 can be made integral to the containment lid 58, and quickly connectable to communicate with the interior of the booth 10.
Furthermore, a movable purge manifold 90, connectable to a source of pressurized purge gas (not shown), is disclosed in the present invention. The purge manifold 90 has a first stowed position, substantially vertical to minimize its footprint, and a second purge position, substantially horizontal. A preferred form is to have the purge manifold 90 swingable from its stowed to its purge positions. The manifold 90 has one or more purge nozzles, or ports, 92 each of which is designed to engage with a corresponding open end of suction tubes 82 when lance assembly 80 is lowered into its first position for a purge operation and hopper 52 is rolled away. The first position of the lance assembly 80 corresponds to both the feed position in the powder feed hopper 52 and the purge position to engage with the manifold 90.
Alternatively, and more preferably for shorter coating operations, a simple vibratory table and powder feed box, or hopper can be installed in the present system (not shown).
To facilitate cleaning of the external lance assembly 80 and other powder feed system 50 surfaces during a color change operation, such as by blowing off with an air wand, by brushing, etc., a porous wall section 94, preferably a perforated screen member, communicating with a plenum area 96 and the cyclone ducting 40 through a damper 98 is disclosed proximate the position of feed center 50. In addition, side walls 97 (
To summarize the method of quick color change now available using the disclosed apparatuses, an operator first raises the lance assembly 80 up and out of a first powder source, such as powder feed hopper 52, from a first lance position to a second lance position. The operator then removes the first powder source from a powder source feed location, such as by disconnecting the fluidizing air and vent duct 57 and rolling fluidized feed hopper 52 away. Next, the purge manifold 90 is moved from a first stowed position to a second, purge position, such as by swinging it from the vertical to the horizontal. The lance assembly 80 is then lowered back down such that each of the one or more powder suction tubes 82 have an open powder suction end engaged with a purge nozzle 92 of the purge manifold 90. This is followed by activating a purge pump to purge the lance assembly 80 with a purge gas. Of course, with the application devices 15 on, they are effectively purged along with their corresponding powder feed conduits, as well. The operator then raises the lance assembly 80 to the second lance position and swings the purge manifold 90 back to the stowed position (such as vertical). A second feed hopper 52 with a new color is rolled into place and connected to the fluidizing air source and the vent duct 57. Lastly, the lance assembly 80 is lowered back into the feed hopper 52, effectively sealing it with the containment lid 58.
The pumps 84 described above, can be of the venturi type, as further detailed below.
Referring to
To operate the system, air from source 104 passes through air line attachment plate 114 into pump assembly block 112. The pumps in block 112 draw powder up tubes 126 from powder source 106, through plate 116, into pump assembly block 112, and pump the powder through hose manifold plate 118 and hoses 128 to spray guns 108.
Referring now to
The pump assembly block 112 further includes a bottom surface 206 that has a plurality of suction ports such as suction port 212. See
Referring now to
The air line attachment plate 114 further includes a plurality of attachment members 310. Each attachment member 310 is preferably formed as a flanged portion extending from top and bottom surfaces 304 and 314, respectively, and includes a tapped or threaded hole for accepting a fastener. Alternatively, a mechanical latch may be used instead of a threaded fastener. The attachment members 310 are positioned so as to align with attachment members 216 of the pump assembly block 112 when plate 114 is attached to block 112. To further facilitate proper attachment or connection of the air line attachment plate 114 to the pump assembly block 112, guide pins 312 are formed that protrude from bottom surface 314 of the air line attachment plate 114. The guide pins 312 are physically coordinated with corresponding guide holes 218 on the top surface 204 of the pump assembly block 112. See
Referring now to
Illustrated in
The body 502 of suction tube plate 116 also includes a mounting feature 516 for mounting or fastening the suction tube plate 116 to a reciprocator 150 (see
Referring now to
The body 602 also includes a plurality of bore holes or cavities (e.g., 606) that extend from the front surface 602 through to rear surface 603. As shown in
Consistent with the present embodiment of the powder feed center, nine bore holes are shown in the hose manifold plate of
Referring now to
Illustrated in
Inlets 707 and 709 are preferably cylindrical in shape and form inlet cavities or bores 721 and 723. A chamber 720 fluidly communicates inlet cavities 721 and 723 with the nozzle portion 704. As will later be discussed in more detail, ejector air enters through inlet cavities 721 and 723 at an angle of approximately 90 degrees relative the chamber 720 and is then directed through chamber 720 and exits through nozzle portion 704. Chamber 720 includes a threaded portion 722 which is used for inserting a threaded plug-type device for sealing the portion of the chamber 720 distal the nozzle portion 704. However, it should be noted that threaded portion 722 may be connected to an additional, or alternative, ejector air source or air line. In such a configuration, inlet cavities 721 and 723 may or may not be eliminated.
The shoulder portion 714 performs a number of functions. In particular, shoulder portion 714 restricts the insertion depth of the ejector air nozzle 700 into the pump assembly block pump chamber 211 (see
Referring now to
Body 802 further includes a shoulder portion 803 configured to control the insertion depth of the venturi throat device 800 in the pump assembly block 112. By controlling the insertion depth, shoulder portion 803 controls the spacing between the ejector air nozzle portion 704 and the venturi throat member 800. Additionally, shoulder portion 803 is similarly configured with locking portions such as portion 805 that are used for interlocking the venturi throat device 800 with the pump assembly block 112 to prevent the venturi throat device from blowing out of the pump assembly block (see
Body 802 further includes one or more diffuser air inlet ports 810 and 812 that provide diffuser air into an internal chamber 822. With reference to
So configured (as shown in
With further reference to
To complete the pump assembly block, venturi throat holders 800 are first inserted into openings in hose attachment plate 600A. Locking members 803 are engaged with flange 902 to lock the members 800. An o-ring 808 is used to frictionally secure the venturi members 800 to the plate 118 and to provide an airtight seal therebetween. The venturi members 820 are inserted into the ends of the venturi throat holders 800 and are frictionally retained by o-rings 920 and 922 which form an air-tight seal therebetween. This assembly, comprised of the throat holders 800, venturi throats 820 and hose manifold plate 600A is now installed as a unit onto the pump block 400. As the assembly 600A, 800, 820 is installed, each of the venturi members 800 is inserted into one of the pump cavities of the block 400 opposite to an ejector nozzle 700 already installed into the opposite end of the pump cavity as described above. O-rings 816 frictionally secure the venturi holders 800 to the wall of the pump cavities and provide an air tight seal therebetween. Alignment pins can be provided on the hose plate 600A to be received in corresponding holes in the pump block 400 to ensure proper alignment between plate 600A and block 400.
Air line attachment plate 114 is attached to this completed pump assembly block by means of releasable attachment devices. These attachment devices can be in the form of tabs 310 which are secured to corresponding tabs 216 of pump block 400 by bolts or other releasable attachment means. To ensure that all the air passages 306 and 308 of plate 114 align with the corresponding air passages of block 400, guide pins 312 in the plate 114 are received in holes (not shown) of the block 400.
Suction tube attachment plate 116A is now assembled to block 112. First, however, suction tubes 126 are threaded into the openings 510A in the suction tube plate 116. Then plate 116 is assembled to the block 112 by attachment devices (not shown). The assembly is preferably accomplished via an o-ring fit wherein o-rings reside in recessed surface portions 222 and 224 of block 112. In the case of alternative pump assembly block 400, conventional flanges and fasteners (not shown) preferably attach suction tube plate 116A to pump assembly block 400 with o-rings provided for the function of sealing the mechanical interfaces. (See
Referring now to
More specifically, with reference to
When a change in powder color is required, one of two general procedures for effecting the change are provided by the present invention. According to a first embodiment, electrostatic spraying with the first powder color is discontinued after the last product has been painted. A manual blow-down of the exterior of the powder feed center components is preferably performed with the fan 193 running to draw powder blown off of the components out of housing 185. While not necessary, it is preferable that the hose manifold plate 118 be detached from pump block assembly 112 for a manual blow-down of the exterior of the hose manifold plate 118, hoses 128, and spray devices 108. The hose manifold plate 118 is re-attached to the pump assembly block 112 and, after the powder source 106 is removed, the entire feed center 102 is connected to a purge air system 1010 through suction tubes 126. To accomplish this, the reciprocator 150 indexes down to seal the bottoms of suction tubes 126 onto purge nozzles 1012. Purge air is cycled into suction tubes 126 through air nozzles 1012 which comprise part of an air manifold 1010 supplied by a pressurized air conduit 1014 connected to air supply 104. The purge air passes through suction tube plate 116, pump assembly block 112, hose manifold plate 118, hoses 128, and spray devices 108. The ejector and diffuser air lines 124 are preferably connected to air line attachment plate 114 through a plurality of check-valves 316 to prevent introduction of purge air into the diffuser and ejector air control system 104 during this purge step. Moreover ejector and diffuser air can also be supplied during the purge cycle to further increase the purge effects on the powder feed center 102. The purpose of the purge cycle is to “purge” as much of the remaining powder as possible out of the system. Once the purge cycle is completed, reciprocator 150 moves tubes 126 to the “up” position and any powder on the outside of tubes 126; plate 116 or any of the other feed system components is manually blown off with an air wand while the fan 193 is operating to withdraw any dislodged powder out of housing 185. A new box or source 106 of a second color is now placed in the feed center 102 on gridwork 1020, and reciprocator 150 lowers the tubes 126 into the new box 106. The powder feed center 102 is now ready to resume coating but with powder of a second color. In this manner, the purge cycle is relied upon as the primary vehicle for reducing powder color cross-contamination, and the feed center is not disassembled for cleaning.
A second color change procedure is provided by the present invention that further reduces the effects of color cross-contamination when changing between a first powder color and a second powder color. The initial steps are the same as those described for the first procedure. However, after purge cycle completion, reciprocator 150 moves the tubes 126 to the up position out of engagement with nozzles 1012, and air line attachment plate 114 and hose manifold plate 118 are detached from the pump assembly block 112. Additionally, pump block 112 is detached from suction tube plate 116 which remains attached to reciprocator 150. A second pump assembly block 112 is substituted for the present pump assembly block wherein the second pump assembly block 112 can be a new, previously cleaned, or color dedicated pump assembly block. Additionally, a second hose manifold block 118 can be substituted for the present hose manifold block. In similar fashion, the second hose manifold block 118 can be a new, previously cleaned, or color dedicated hose manifold block. It is preferable that the pump assembly block 112 and hose manifold plate 118 be shifted-out or substituted in pairs. The air line attachment plate 114 and suction tube plate 116 are not changed. Therefore, the new or cleaned pump assembly block 112 is re-attached to the suction tube plate 116. The new or cleaned hose manifold plate 118 is attached to the pump block 112 and the air line attachment plate 114 is attached to the pump block 112. Any residual powder on the exterior of these components is blown-off with an air wand with the fan 193 operating to draw any over-sprayed powder from the housing 185 through the duct 190 to the filtering apparatus 187. One advantage of this second color change procedure is that there is no time-consuming step of disconnecting and reconnecting individual air lines since all air lines remain connected to the air line attachment plate 114. The new box of a second color is now placed in feed center 102 on gridwork 1020 and reciprocator 150 lowers the tubes 126 into the new box 106. Regulated air supply 104 can now be operated to provide compressed air to the clean pump assembly to pump powder from the new box of powder through the pump assembly to the spray guns for spraying onto products.
By allowing for the change or substitution of the pump assembly block 112 and hose manifold block 118, the present invention provides a range of options for reducing or eliminating color cross-contamination during powder color changes. For example, if a new pump assembly block 112 and a new hose manifold plate 118 are substituted for the present pump assembly block 112 and hose manifold plate 118, the amount of color cross-contamination is greatly reduced or even eliminated given the new and uncontaminated components. If a previously cleaned pump assembly block 112 and hose manifold plate 118, which preferably have been cleaned off line while the system is in operation, are substituted for the present pump assembly block and hose manifold plate, the amount of color cross-contamination is also largely reduced, depending on the quality of the previously administered cleaning.
There are situations were some degree of color cross-contamination is tolerable. More specifically, light shades of various powder colors can effectively mask contamination caused by other light shades of powder colors. Similarly, dark shades of powder colors can also effectively mask contamination caused by other dark shades of powder colors. Therefore, a first color dedicated pump assembly block can be used for a range of light shades of powder color and a second color dedicated pump assembly block can be used for a range of dark shades of powder color. With such a configuration, the first pump assembly block would be substituted when a powder color change from a light shade of powder color to a dark shade of powder color is required. On the other hand, a powder color change from a light shade of a first particular powder color to a light shade of second particular powder color would not necessarily require a change in the pump assembly block 112 and hose manifold plate 118. In this manner, the present invention provides various degrees of control over the time required to effect color changes throughout the course of production depending on the color differences between the current color of powder and the next color of powder to be used and the amount of color cross-contamination which can be tolerated.
With reference to
Even with such systems, hundreds of pounds of coating material may have to be cleaned from a spray booth after a coating operation in preparation for a color change operation. Positioning of the cyclones 30 at the ends of the booth 10 creates a low air velocity area near the center of the booth 10. Consequently, more powder coating material falls to the floor. This inventive embodiment places troughs 6 in the floor 18 between the application devices 15 and the cyclone intakes 36. The collection troughs can be from about 4 to 6 inches wide and have a slanted bottom 7 as shown in
Referring now to
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in some detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, more or less than nine pump chambers may be included in the pump assembly block 112, more than one ejector air line may be provided to each pump chamber ejector inlet port, and more than one diffuser air line may be provided to each pump chamber diffuser inlet port. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
This application claims priority to U.S. Provisional Application No. 60/154,624, filed Sep. 17, 1999, the entire disclosure of which is hereby incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US00/25383 | 9/15/2000 | WO | 00 | 2/28/2003 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO01/19529 | 3/22/2001 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 60154624 | Sep 1999 | US |
