Patent Publication Number: US-2023136624-A1

Title: System and method for electrostatic coating

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Application Nos. 63/272,725 filed Oct. 28, 2021 and 63/334,326 filed Apr. 25, 2022, the content of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a system for applying an electrostatic coating to a medium, and in particular to one or more apparatuses for spraying a stream of particles onto multiple surfaces of a medium, wherein the apparatus is equipped with a dual-chamber enclosure or with a plurality of variable openings for successive layer coating onto a medium. 
     BACKGROUND OF THE INVENTION 
     During the industrial coating process, a wide variety of media are covered with different surface materials. For example, paper may be covered with starch solutions for improved heat resistance characteristics, and metal sheeting may be coated with paint or latex for aesthetic value or corrosion protection of oxidizing surfaces. The coating of materials on media is widely used in the industry, and improved, cost-effective apparatuses, methods, and devices are continuously sought. The coating of liquids may utilize volatile solvents and require drying processes that create gas wastes requiring treatment. Apparatuses and methods for applying coating material in powder form to a medium do not suffer from the above shortcomings. Powders must adhere temporarily to the medium and be uniformly spread to prevent bumps or cause problems during post-treatment operations. Once applied to a medium, powders may require post-treatment operations such as baking to fix the powder permanently on the surface. 
     One of the known ways to adhere a powder to a surface without adding unnecessary agents or adhesives is by using the electrostatic adhering capacity of a charged stream of particles made from a powder suspended in a gas and placed in contact with a medium that has a different electrical energy or is grounded. The Law of Coulomb provides that electrostatic force felt by two bodies charged with the same polarity charge is a repulsive force, and the force felt by two bodies charged with opposite polarity is an attractive force. Once the powder particles in a stream are charged, either by removing or adding surface electrons, the particles are then drawn by the electromagnetic force to a grounded medium in proportion to Coulomb&#39;s Law. Another advantage of electrostatic charging of a stream of particles is the creation of repulsion forces between neighboring particles in the stream placed at equivalent energy to aid in the spatial distribution of the particles within the stream of particles. Additionally, charged particles are drawn by a stronger electrostatic force on a surface where other particles have not yet attached. 
     Electrostatic charges can be placed on a medium by contact electrification, triboelectric electrification, or physical rubbing of surfaces such as the friction of a balloon on a piece of clothing or the displacement of shoes over a carpet. Another way to create an electrical charge on an item is to circulate the item in a strong electrical field in excess of the breakdown strength of air, a field of such intensity that ionized particles are formed. These ions are collected on the surface of the item in the corona discharge zone around a conductor by moving the powder through the corona region. These particles exit the corona superficially charged with an ionic charge and are then vulnerable, due to their low mass, to electrostatic forces created by their charge. Particles of both conductive material and insulating material are vulnerable to corona charging. Nonconductive particles, since they are less likely to redirect the position of superficial ionic charges, are more likely to maintain their newly gained electrostatic charge. 
     Existing approaches to applying coatings include spraying a fine powder made of a material such as epoxy, polyester, polyurethane, or nylon that is electrostatically applied to a medium or substrate comprising a metal or other material that is grounded. After being applied, the powder is heated to cure and harden, generally in an oven. 
     Additionally known is the use of a high-level energy conductor located at the source of a stream of particles to ionize the powder or the use of a highly charged and dangerous conductive net structure placed in proximity to a medium. What is also known is the use of a chamber wherein the medium and the conductor are placed in contact with particles in the closed environment, or the use of an enclosure where ionized particles are collected after being placed in proximity to a conductor in a small enclosure before the ionized particle flow is directed onto a medium outside the enclosure. Drawbacks of these known technologies include the creation of corona discharges between the conductor surrounding low-level charge elements located in close proximity to the source of powder particles, the need to place the conductor in the path of the stream of particles, the creation of enclosed devices where high-level voltage must be managed, and distribution systems where the particles are not suspended in the air sufficiently enough to offer an optimal collection of the ions in the air. Although many of these devices are able to perform their intended functions in a workmanlike manner, none of them adequately addresses the combination of these drawbacks. 
     Further, existing systems and methods generally are either unable to apply a coating to multiple surfaces of a medium or require multiple passes to accomplish a desired coating. What is needed is an improved apparatus able to adequately fluidize the particles from a powder source and place them in a particle stream, an apparatus where conductors are protected and offset from the particle stream, an apparatus able to uniformly deposit the particles onto a medium, an apparatus able to avoid overspray and recover particles not deposited on the medium, and an apparatus able to (alone or jointly) coat multiple surfaces of a medium. Further control systems able to monitor and adjust the stream of particles in real time is desirable to ensure a specified coating is adequately applied. The present invention solves these and many other problems associated with currently available apparatuses for electrostatic coating. 
     SUMMARY 
     The present invention generally relates to a system for applying an electrostatic coating to a medium, and in particular to a system comprising one or more electrostatic coating apparatuses for spraying a stream of particles onto a medium. In embodiments, the one or more apparatuses include a multivolume chamber coupled to a volute for mixing and spreading the stream of particles before they are distributed by one or more electrostatic emitters. In embodiments, discrete width control mechanisms are used to restrict the size of the particle spray and a rotational control mechanism permits the electrostatic emitters to rotate to finely tune the electrostatic field applied to the particle stream. In embodiments, a powder reclamation system operates to reclaim overspray and other particles that do not adhere to the medium, allowing particles to be collected, filtered, and recycled for subsequent reuse. The particle stream is deposited onto a medium moving past the electrostatic emitters. In embodiments, a shroud surrounds the medium and the emitters to ensure the particle stream is contained (making it available for easy reclamation and preventing particles from escaping the system). 
     The present disclosure relates to an in-line industrial device able to apply paint, starch, thermoplastics or any other powder material onto a medium by successively controlling a plurality of parameters, including the above-mentioned novel features, such as (but not limited to), in various embodiments, the size of an inside aperture within the enclosure, the rotation or angle of the electrostatic emitters, the speed of the medium moving between the electrostatic emitters, the powder velocity/flow rate, the pressure in the powder lines, the change in the flow of input gas, the change in the voltage or the location of the conductor, the measured film thickness applied to the medium previously, the weight of powder delivered, the powder blower speed, the oven temperature, the vacuum flow rate, the excess air flow rate, temperature in various components of the apparatus, ambient temperature, measured pressure at various locations in the apparatus, and the weight of reclaimed powder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present disclosure are believed to be novel and are set forth with particularity in the appended claims. The disclosure may be best understood by reference to the following description taken in conjunction with the accompanying drawings. The figures that employ like reference numerals identify like elements. 
         FIG.  1   a    is a front perspective view of an electrostatic coating system with the enclosure panels removed; 
         FIG.  1 B  is a front view of the electrostatic coating system of  FIG.  1   a    with the enclosure panels in place on a first apparatus and partially removed from a second apparatus; 
         FIGS.  2   a  and  2   b    are perspective views of the electrostatic coating apparatuses (without enclosure panels) removed from the other components of the electrostatic coating system of  FIG.  1     a;    
         FIG.  3    is an exploded view of the enclosure panels of one of the electrostatic coating apparatus of  FIG.  1     a;    
         FIG.  4    is a top view of the electrostatic coating apparatuses of the system of  FIG.  1   ; 
         FIG.  5   a    is a perspective view of the system of  FIG.  1   a    with the apparatuses retracted and the shroud partially retracted; 
         FIG.  5   b    is a perspective view of the system of  FIG.  1   a    with the apparatuses retracted and the shroud in place; 
         FIG.  5   c    is a perspective view of the system of  FIG.  1   a    with the apparatuses in place and the shroud retracted; 
         FIG.  6   a    is a front cross-sectional view of a mini manifold; 
         FIG.  6   b    is a partial cutaway perspective view of the mini manifold of  FIG.  6     a;    
         FIG.  6   c    is a side cross-sectional view of the mini manifold of  FIG.  6     a;    
         FIG.  7    is a perspective view of a multivolume chamber of an electrostatic coating apparatus of  FIG.  2     a;    
         FIG.  8    is a side view of the multivolume chamber of  FIG.  7   ; 
         FIG.  9    is a front view of the multivolume chamber of  FIG.  7   ; 
         FIG.  10   a    is a perspective view of an electrostatic emitter bar generating a simulated ionization field; 
         FIG.  10   b    is a perspective view of the electrostatic emitter bar generating a simulated ionization field of  FIG.  10   a    in an enclosure; 
         FIG.  11   a    is a process flow diagram of a method of using an overspray collection system; 
         FIG.  11   b    is a process flow diagram of a second method of using an overspray collection system; 
         FIG.  12    is a diagram of a powder management system; 
         FIG.  13    is a perspective view of the powder management system of  FIG.  12    and the electrostatic coating system of  FIG.  1     a;    
         FIG.  14    is a front view of the Bag Hoist Tower and Hopper and Scale Tower shown in  FIG.  13   ; 
         FIG.  15    is a perspective view of an alternate arrangement of the powder management system of  FIG.  12    and the electrostatic coating system of  FIG.  1     a;    
         FIG.  16   a    is the first portion of a process flow diagram of a control system; 
         FIG.  16   b    is the second portion of a process flow diagram of a control system; 
         FIG.  17   a    is a process flow diagram of an apparatus of  FIG.  1     a;    
         FIG.  17   b    is a process flow diagram of a plant containing the system of  FIG.  1     a;    
         FIG.  18   a    is the first portion of a process flow diagram of a second embodiment of a control system; 
         FIG.  18   b    is the second portion of a process flow diagram of a second embodiment of a control system; 
         FIG.  18   c    is the third portion of a process flow diagram of a second embodiment of a control system; 
         FIG.  19    is a side view of the electrostatic coating system and all of its components; 
         FIG.  20    is a perspective view of the overspray collection system within the electrostatic coating system of  FIGS.  1   a    and  1   b.    
         FIG.  21    is an expanded view of reclaim ducts within the overspray collection system of  FIG.  20   . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, a possible industrial embodiment of the disclosure centered around an improved electrostatic coating apparatus. This embodiment is described with detail sufficient to enable one of ordinary skill in the art to practice the disclosure. It is understood that each subfeature or element described in this embodiment of the disclosure, although unique, is not necessarily exclusive and can be combined differently and in a plurality of other possible embodiments because they show novel features. It is understood that the location and arrangement of individual elements, such as geometrical parameters within each disclosed embodiment, may be modified without departing from the spirit and scope of the disclosure. In addition, this disclosed embodiment can be modified based on a plurality of industrial and commercial necessities, such as, in a nonlimiting example, a large-scale coating process where several units are required at different locations along a production line or in a confined area when the atmospheric control of the stream of particles is to be recycled. The disclosed apparatus can be modified according to known design parameters to implement this disclosure within these specific types of operation. Other variations will also be recognized by one of ordinary skill in the art. The following detailed description is, therefore, not to be taken in a limiting sense. 
     Electrostatic Coating System 
     The present disclosure relates to an electrostatic coating system  100  and its component parts as shown in  FIGS.  1   a   - 21 . The electrostatic coating system  100  includes a first electrostatic apparatus  102   a  (or top-coating apparatus) for coating a top surface of a medium  1502  (omitted from  FIGS.  1   a  and  1   b    for clarity) that is offset vertically from a second electrostatic apparatus  102   b  (or bottom-coating apparatus) for coating a bottom surface of a medium  1502 . This offset prevents interference between the electrostatic fields generated by each apparatus. As will be clear to one of ordinary skill in the art, other arrangements could also be employed. In an embodiment (not shown), the top-coating apparatus  102   a  and the bottom-coating apparatus  102   b  are aligned (which may be preferable for use cases in which greater space savings are desired or electrostatic interference is not problematic). 
     In the embodiment shown, the medium  1502  is contemplated as being a material having a top side and a bottom side. In an embodiment, the medium  1502  is a metal sheet. Other configurations of materials (which may necessitate additional apparatuses) are also contemplated. In the embodiment shown, the medium  1502  is passed vertically between the top-coating apparatus  102   a  and the bottom-coating apparatus  102   b . Uncoated material is first sprayed by the bottom-coating apparatus  102   b  before being sprayed by the top-coating apparatus  102   a . The coated material is then passed through the oven  106  for curing. 
     The oven  106  heats the coated material to a temperature range of about 400 to 550 degrees to treat the coating and improve chemical resistance, improve resistance to harsh environmental conditions, and maintain color stability. 
     While  FIGS.  1   a  and  1   b    contemplate a vertically oriented medium  1502  (shown in  FIG.  15   ) grounded to earth passing between the pair of electrostatic coating apparatuses  102   a ,  102   b , the electrostatic coating system  100  may be placed in any orientation resulting in a medium  1502  also oriented in any orientation. One of ordinary skill in the art understands that the medium  1502  may be a linear, rigid strip of material or a rolled medium  1502  which is unfolded before passing through the electrostatic coating system  100  before again being rolled, folded, or stored. It is also understood that any type of medium  1502 , made of any type of conductive or nonconductive material and presenting a variety of surface geometry and topology, can be coated. While in a preferred embodiment (shown) the medium  1502  is grounded using conventional grounding techniques, the electrostatic coating system  100  functions on attractive forces created between the powder particles and the medium  1502  by creating a difference in ionic potential, so what is contemplated is the use of a medium  1502  at any ionic potential sufficiently different from the average ionic potential of the particles emitted by the electrostatic coating system  100  to induce electrostatic attraction forces. 
     In the embodiment shown, the top-coating apparatus  102   a  is substantially identical in structure to the bottom-coating apparatus  102   b . The enclosures  104   a ,  104   b  are depicted in  FIGS.  1   a  and  1   b    as an open frame. In other examples, the enclosures  104   a ,  104   b  has a solid exterior. In an embodiment, enclosures  104   a ,  104   b  are NEMA-4 enclosures that house pneumatic controls and powder supplies for the apparatus. 
     The components of each apparatus  102   a ,  102   b  are made of a thick wall of strength sufficient to contain internal pressures created during the process of suspending the powder particles within a gas, also known as fluidization of the particles.  FIGS.  1   a  and  1   b    show one possible industrial and commercial embodiment of the invention. These figures show a stainless steel casing with surface strengtheners described in detail hereinafter. The fluidization process includes the use of a pump (not shown) that supplies pressurized air to each apparatus  102  through a plurality of mini manifolds  200 , each having a respective air inlet  108 . Each apparatus  102  also comprises a plurality of mini manifolds  200  each having a powder inlet  110  connected to a plurality of powder supply lines. Each apparatus  102  discharges a controlled volume of particles in a powder form to be coated on the medium  1502 . 
     As shown in  FIGS.  2   a  and  2   b   , in an embodiment of the electronic coating system  100 , enclosures  104   a ,  104   b  comprise a solid outer surface (such as metal sheeting) which conceals the apparatus  102  within from view and protects it from physical impacts. The solid enclosures  104   a ,  104   b  are each comprised of panels  107   a - 107   f  and further serves to insulate the apparatus  102  from ambient temperature changes. In other embodiments, such as also shown in  FIG.  1 B , an enclosure  104   b  may be partially open to permit access to the apparatus  102   b  within while still providing some degree of physical protection. Other configurations of enclosures  104   a ,  104   b  are also contemplated. In an embodiment, the exterior surface (i.e., panels  107   a - 107   f ) of the enclosures  104   a ,  104   b  is formed from sheets of 80/20 extruded aluminum that is joined to an interior frame  105  by t-nut connectors. Each apparatus  102   a ,  102   b  is supported within the enclosures  104   a ,  104   b  by neoprene rubber isolators to reduce vibrations. In other embodiments, alternative materials or other techniques for vibration damping may be used, as will be understood by one of ordinary skill in the art. In embodiments such as that shown in  FIGS.  1   a  and  1   b   , handrails  118  may surround the electrostatic coating system  100  to protect users of the system  100  and the equipment. In an embodiment, the panels  107   a - f  of the enclosures  104   a ,  104   b  are removable to allow a user to partially or fully open the enclosures  104   a ,  104   b  and access the interior of the apparatuses  102   a ,  102   b.    
       FIGS.  2   a  and  2   b    depict an electrostatic coating system  100  with the solid panels  107   a - 107   f  and the enclosures  104   a ,  104   b , respectively, removed to better illustrate the components of the apparatuses  102   a ,  102   b . As shown, each apparatus  102   a ,  102   b  comprises a plurality of air inlets  108  and powder inlets  110  proximate the top of the apparatus  102 . As shown, the apparatuses  102  are each secured to their respective frame  105  by a plurality of mounting brackets  112 . These mounting brackets  112  may be made of metal and include neoprene rubber isolators, as discussed above, thereby reducing the vibration passed between each apparatus  102   a ,  102   b  and its respective frame  105 . 
       FIG.  3    depicts an exploded view of an enclosure  104   a ,  104   b  including a bottom panel  107   a , front panel  107   b , pair of side panels  107   c , back panel  107   d , top panel  107   e , and header panel  107   f    
     Retraction of Apparatuses 
     As shown, each apparatus  102   a ,  102   b  and its respective enclosure  104   a ,  104   b  may be supported by wheels  114  and configured to slide along rails  116  so as to permit access to the apparatuses  102   a ,  102   b  by moving it away from the oven  106 . This permits each apparatus  102   a ,  102   b  and the oven  106  to be more easily inspected or maintained. As shown in  FIG.  5   a   , each apparatus  104   a ,  104   b  may be slid along rails  116  away from the oven  106 . Removably connected to the bottom of the oven  106  is a strip shroud which protects the medium  1502  and spray area from airborne dust or other contamination. Further, the strip shroud  120  may be slid away from the oven  106  to permit easier access to the oven  106  or the medium  1502  for inspection and cleaning.  FIG.  5   b    depicts the electrostatic coating system  100  with the apparatuses  102   a ,  102   b  slid away from the oven  106  while the strip shroud  120  is left in place, while  FIG.  5   c    depicts the electrostatic coating system  100  with just the strip shroud  120  retracted away from the oven  106  and apparatuses  102   a ,  102   b . In an embodiment, the strip shroud  120  is a permanent structure and can flexibly index with the apparatus to prohibit fugitive powder during operation. In this alternative embodiment, the retraction of the strip shroud  120  is controlled by a pneumatic piston system, the pneumatic piston system comprising a silicone boot which provides a means for retracting the strip shroud  120  from the oven  106  and allowing a user access to the oven  106  and interior of the strip shroud. 
     Mini Manifolds 
       FIGS.  6   a  through  6   c    depict various views of a mini manifold  200 . Each mini manifold  200  comprises an inlet  202  that may be used as either an air inlet  108  or a powder inlet  110 , depending on the configuration of the mini manifold  200 . At least one inlet flange  204  forms a ring around the exterior surface  218  of the mini manifold  200  proximate the inlet  202 . Particles (e.g., air or powder) pass into the mini manifold  200  from a hose (not shown) through the inlet  202  and an initial chamber  206  before being focused by a nozzle  208 . Thereafter, particles pass through a straight segment  210  before expanding through the outlet  212  that is connected to the mixing chamber  306  (not shown). Each mini manifold  200  includes an outlet flange  214  with one or more holes  216  through which fasteners may secure the mini manifold  200  to the mixing chamber  306  or air extension  320 . 
     The dimensions and shape of the mini manifold  200  is designed optimally to get an even and widespread flow of air and powder into the mixing chamber  306 . To maintain the integrity of the inlets, the mini manifold  200  ensures that the flow is consistent across the length and width of the inlets. In an embodiment, the mini manifolds  200  include a threaded portion aiding in providing an even and widespread flow of air and powder into the mixing chamber  306 . 
     The mini manifold(s)  200  may be arranged as depicted in  FIG.  2   a   , with the air inlets  108  placed in a vertical orientation and the powder inlets  110  placed in a horizontal orientation. Other arrangements of mini manifold(s)  200  are also contemplated. 
     Chamber 
       FIGS.  7  through  10     b  depict a chamber  300 . The chamber  300  comprises a mixing chamber  306  which receives air through a plurality of air inlets  108  in a first plurality of mini manifolds  200  and powder through a plurality of powder inlets  110  in a second plurality of mini manifolds  200 . An air opening  302  located in the top of the mixing chamber  306  receives air from an air extension  320  while powder openings  304  in the back of the mixing chamber  306  receive powder from one or more mini manifolds  200 . This arrangement is preferred in some embodiments as it has experimentally been demonstrated to produce an even distribution of powder and air throughout the mixing chamber  306  and volute  308 . As will be clear to one of ordinary skill in the art, other arrangements of openings are also contemplated. In an embodiment, air hoses are directly connected to the mixing chamber  306  by way of one or more mini manifolds  200  without the use of an air extension  320 . 
     In the embodiment depicted in  FIGS.  7  through  10     b , the air extension  320  connects to the top of the mixing chamber  306 . The air extension  320  provides additional separation between the air inlets  108  and the mixing chamber  306 , allowing the air to mix and flow uniformly into the mixing chamber  306  through the plurality of mini manifolds  200 . Specifically, the air extension  320  controls the flow volume of conditioned air to the mixing chamber  306  to vary the thickness of the mixture of powder particles and air particles (the “mixture”). Increased air flow leads to a thinner mixture. Alternatively, decreased air flow increases the thickness of the mixture. As a result, modulation of the air flow in the air extension  320  impacts the finish and thickness of the coating applied to the surface of the medium  1502 . 
     Air and powder are intermixed and fluidized in the mixing chamber  306  before exiting through openings (not shown) at the lower end  312  of the mixing chamber  306 . The fluidized air/powder mixture then flows through the volute  308  to the electrostatic/vacuum chamber  309  and then through the outlet  310 . The electrostatic/vacuum chamber  309  creates a zone of ionization which electrostatically charges the mixture. When the electrostatically charged mixture is discharged and applied to the medium  1502 , the powder flows to the surface of the medium  1502  to ground the charge. Therefore, electrostatic charge helps the mixture “stick” to the surface of the medium  1502  and provides an even application of the mixture to the medium  1502 . The ionized powder (having a negative charge) is attracted to the steel surface and electrostatically adheres to the surface of the medium  1502 . 
     The exterior surface  316  of the mixing chamber  306  and volute  308  contain a plurality of ridges  318  that provide structural integrity to the chamber  300 , while the interior surface is smooth and uninterrupted to ensure the fluidize powder/air mixture flows uninterrupted through the chamber  300 . Excess powder (i.e., overspray) is evacuated from the electrostatic/vacuum chamber  309  through the main reclaim duct  504 . In an embodiment, the electrostatic/vacuum chamber  309  comprises at least one reclaim port  502  and a diverter to control the flow of overspray. 
     Each outlet  310  is flanked by a pair of electrostatic emitter bar  314  each containing a plurality of electrostatic emitters (not shown) that generate the electromagnetic field to propel/discharge the fluidized powder onto the medium  1502 . It is understood by one of ordinary skill in the art that emitters must be placed in a position able to maintain the electrical charge in the emitter bar  314 , insulate the emitter bar  314  from surrounding elements, protect the emitter bar  314  from accidental corona discharges created by a high voltage placed on the emitters, and protect operators of the apparatus  102  from shocks. A pair of width control mechanisms  322  adjust the width of the outlet  310  by moving horizontally along a pair of rails  324  to block a portion of the outlet  310 . Each electrostatic emitter bar  314  is connected to a pair of rotational control mechanisms  326  that permit the emitter bar  314  to rotate. 
       FIG.  10   a    depicts a single electrostatic emitter bar  314  with a simulated ionization field  330 , while  FIG.  10   b    depicts the simulated ionization field  330  generated by a pair of electrostatic emitter bars  314  working in conjunction with one another. By rotating the emitter bars  314  individually, the orientation of the generated ionization field  330  may be adjusted, while varying the power supplied to each emitter bar  314  (or to individual emitters within each bar) permits the magnitude and dimensions of the ionization field  330  may be similarly controlled. 
     The ionization field  330  is adjustable to optimize the thickness of the mixture based on the volume of the mixture being applied to the medium  1502 . By increasing or decreasing the level of ionization, the mixture will either “fully charge” or diminish in ionization. The level of ionization optimizes the charge of the mixture. In order to coat the medium  1502  in a single pass, the mixture needs to have sufficient charge. The electrostatic field  330  is optimized to result in a desired finish (or “film thickness”) of coating on the medium  1502 . The adjustment of film thickness is controlled by the speed of the medium  1502  as it passes through the spray area, the volume of powder applied to the medium  1502  surface, and the ionization filed 330. These elements are balanced in order to achieve a precise coating on the medium  1502  surface. 
     In the embodiment shown, one or more edge conditioners  328  surround the outlet  310 . The edge conditioners  328  output deionized air used to condition the edges of the expelled particle spray. By surrounding the desired spray area with deionized air, the particle spray is further restricted and overspray is prevented. 
     Overspray Collection 
       FIGS.  11   a  and  11   b    depict methods  400  for collecting and recycling oversprayed powder. The elements of the overspray collection system (the “reclaim system” or “collection unit”)  500  are further illustrated in  FIGS.  20  and  21   . In an embodiment, the reclaim system  500  functions to collect overspray from a plurality of apparatuses  102   a ,  102   b  coating multiple surfaces of a medium  1502 . As will be clear to one of ordinary skill in the art, alternative arrangements are also contemplated hereby, including but not limited to having a separate reclaim system  500  for each apparatus  102 . 
     The method  400  begins at step  402  when powder over sprays, or is not electrostatically seated on the medium  1502 . At step  404 , a vacuum motor in the collection unit  500  creates a low pressure area, ingesting the oversprayed powder. In an embodiment, the spray area around one or more apparatuses  102  is substantially covered by a shroud  120  to prevent overspray from escaping the area. The vacuum motor is sized such that it collects all overspray within the shroud  120 . The air/powder mixture collected by the vacuum motor is then passed through a cyclone separator at step  406  wherein the air is separated from the powder. At step  408 , the powder is filtered into a collection container in a solid form while the air is filtered and vented outside the shroud  120  at step  410 . Optionally, the powder may then be settled and fed into a transport container for recycling or reintroduction into the virgin powder supply at step  412 . Such recycling and reuse may occur either at a separate location or locally. In embodiments, the powder is transferred via tubing or other structure rather than using a discrete transport container. 
     In the embodiment of  FIG.  11   b   , the one or more apparatuses  102  comprise at least six reclaim ports  502  through which overspray is evacuated. The method  1100  begins as step  1102  when powder over sprays, or is not electrostatically seated on the medium  1502 . Attached to each respective reclaim port  502  is a reclaim duct  504 . Each reclaim duct  504  connects to one or more bag houses  1108 . 
     In step  1104 , the overspray powder is drawn into the reclaim ducts  504  by a VFD Blower Motor  1110 . The overspray collection system  500  comprises blowback dampers  1106  to prevent the overspray from traveling backwards towards the apparatuses  102  in the event that the bag house(s)  1108  are destroyed. The bag house(s)  1108  comprise non-conductive filter bags which are pulsed with air and any free powder falls into the collectors  1114 . The bag house(s)  1108  include a knife gate which is capable of blocking overspray to allow for a collector  1114  to be changed. The VFD blower motor  1110  creates the negative pressure which draws the overspray  1102  to and through the bag house(s)  1108  and its filters. The overspray powder is vented into the atmosphere  1112 . 
     In this embodiment, the electrostatic coating system  100  has two-color application capability, enabling the apparatuses  102  to apply single or two color paint and the overspray collection system allows for the colors to be collected independently from the apparatuses  102 . The apparatuses  102   a ,  102   b  are applied oppositely and facing one another. One apparatus applies the mixture to the top side of the medium  1502  and the opposite apparatus applies the mixture to the bottom side of the medium  1502 . These apparatuses  102   a ,  102   b  allow application of the mixture on each side of the medium  1502  simultaneously. 
     In an embodiment, the electrostatic coating system  100  is configured to implement a cleaning mode wherein all air and residual powder are completely evacuated from within the shroud. Such mode may be used, for example, prior to retracting the shroud to inspect the oven  106  and/or apparatuses  102 . Further, during regular operation, the electrostatic coating system  100  may be configured to evacuate only the motive gas and excess powder material from the shroud (e.g., so as to collect overspray as it occurs). 
     Powder Management System 
       FIGS.  12  and  15    depict a powder management system  1200  connected to an electrostatic coating system  100 . Specifically,  FIGS.  13  and  14    depict components of the powder management system  1200 . 
     As shown in  FIGS.  12  and  13   , the powder management system  1200  comprises a compressor  1202  that provides compressed air to a wet air receiver  1204 . The compressed air then is fed to a dryer/conditioner  1206  (e.g., a desiccant air dryer) before being passed to a dry air receiver and/or air controls panel  1208  where it is stored until needed. 
     In the embodiments shown, the foregoing components are common to all apparatuses  102  in the facility. As shown, each separate apparatus  102  is then fed by a distinct supply comprising an air line  1210  from the dry air receiver/air controls panel  1208  to a bag hoist tower  1212 , which is itself coupled in turn to a hopper and scale tower  1214 , a powder line  1216 , and a splitter  1218  (such as, in embodiments, a resistive splitter). In addition, each apparatus  102  is fitted with a separate accessory air manifold  1220  that receives dry air from the dry air receiver/air controls panel  1208  via an air supply line  1213  and provides air to the mixing chamber  306 , electrostatic/vacuum chamber  309 , and edge conditioner  328  of the apparatus  102  along with air to a separate air cleaning wand  1222  (which may be used, for example, for cleaning the electrostatic coating system  100 ). 
     The powder management system  1200  provides a desired amount of powder paint to the apparatuses  102   a ,  102   b . The hopper stores a volume of powder and delivers the powder to the scale tower  1214  prior to feeding the powder into the apparatuses  102   a ,  102   b . The splitter  1218  evenly distributes the powder to the mixing chamber  306  for consistency and to enable even distribution of the mixture to a medium  1502 . Specifically, the splitter  1218 , splits the incoming mixture to distribute an even volume of powder throughout the apparatuses  102   a ,  102   b  such that a uniform film is applied across the width of the medium  1502 . Other arrangements are also contemplated. These components are discussed in turn below. 
     Bag Hoist Tower and Hopper and Scale Tower 
       FIG.  14    depicts embodiments of a bag hoist tower  1212  and a hopper and scale tower  1214 . The elements of each tower  1212 ,  1214  are supported by a truss system  1410 . Air is received at the bag hoist tower  1212  via supply line  1210 . At the bag hoist tower  1212 , the air is mixed with powder initially contained in bulk bag  1404  suspended from a hoist with a power trolley  1402 . The air/powder mixture is pumped by an educator  1409  through a hose  1412  to the hopper and scale tower  1214 . The hoist tower  1212  further comprises one or more seal plate confinement boxes  1406  and a confinement box extension  1408 . 
     The air/powder mixture is received at a surge hopper  1414  in the hopper and scale tower  1214 . A probe  1416  is provided to monitor the contents of the surge hopper  1414 . The mixture passes through a first rotary airlock  1418 , a dust collection mechanism  1420 , a loss in weight feeder  1422 , and a second rotary airlock  1426  before being sent to an apparatus  102   a ,  102   b  by a second educator  1428  via powder supply line  1216 . In parallel with the main dust path, the hopper and scale tower  1214  further comprises a vent hopper  1424  which assists with dust collection and removal. The first and second rotary airlocks  1418 ,  1426  control fill of powder (ensuring that a continuous flow of the desired flow rate is provided to the apparatus  102   a ,  102   b ). 
     The two-tower approach enables a continuous powder flow, even when replacing powder bags in the bag hoist tower  1212 . Further, by separating components into multiple towers, facility space may be used more efficiently and components may be more easily accessed (rather than requiring a single, taller tower). Other arrangements in which the towers are combined are also contemplated. 
     It is understood that while one possible air mixing configuration is shown any configuration where gas can be used, funneled, and directed to fluidize the powder into suspended particles is contemplated. 
     Controller 
       FIG.  16    provides a process flow diagram of an embodiment of a controller system  1600  for the powder management system  1200  and electrostatic coating system  100 . 
     The controller system  1600  may comprise as executable instructions stored on non-transitive memory for execution by one or more processors contained in one or more computers. Alternatively, the control system  1600  may comprise programmable logic gates or specialized hardware devices. As will be clear to one of ordinary skill in the art, the controller could also be implemented using other architectures and individual components may be software and/or hardware based. 
     As shown, the control system  1600  comprises one or more data hubs  1640  that receive control inputs  1620  and, based on those control inputs  1620 , generate outputs  1650  leading to feedback  1656  that is processed along with further control inputs  1620  to refine decisions and optimize performance of the electrostatic coating system. 
     In the embodiment shown, the control inputs  1620  comprise a plurality of monitor-only inputs (exclusive monitor inputs)  1602  which act as variables that are not directly adjusted by the controller in the embodiment shown. As will be clear to one of ordinary skill in the art, many of the monitor-only inputs  1602  may be controlled to an extent in alternative embodiments (such as, for example, by adding additional temperature regulation devices). The monitor-only inputs  1602  comprise the measured temperature  1604  in the powder line  1216  (which may be measured using a temperature probe), the temperature  1606  in each apparatus  102   a ,  102   b , the measured ambient temperature  1608  proximate the electrostatic coating system  100  and powder management system  1200 , the measured pressure  1610  in the volute  308 , the measured pressure  1612  in the mixing chamber  306 , the measured pressure  1614  in one or more of the mini manifolds  200 , the measured temperature  1616  of the medium  1502 , and the measured weight  1618  of reclaimed powder. 
     In addition, the control inputs  1620  comprise a plurality of variables that are directly adjusted and optimized by the controller, including the measured film thickness  1622  applied to the medium  1502 , the measured weight  1624  of powder delivered to each apparatus  102 , the speed  1626  of each powder blower delivering powder, the electrostatic voltage  1628  at each electrostatic emitter bar  314  (or, in an embodiment, each individual electrostatic emitter), the rotational angle  1630  of each electrostatic emitter bar  314 , the line speed  1632  of the medium  1502  passing through the system  100 , the measured temperature  1634  of the oven  106 , the measured vacuum flow rate  1636 , and the measured excess air flow rate  1638 . The control system  1600  functions to monitor and modify operating conditions based on film thickness  1622  and uniformity as well as other predetermined variables and parameters. 
     The control system  1600  monitors inputs  1602  and adjusts outputs to optimize the accuracy and distribution of coating to the medium  1502 . For example, adjustments to the rotation or angle  1630  of the electrostatic emitter bar(s)  314  impact the distribution of coating along the medium. This is similarly the case for other control outputs directed by the controller. 
     In the embodiment shown, various of the control inputs  1620  are processed by individual data hubs  1640 . As shown, all of control the inputs  1620  are processed by a data acquisition system (DAQ)  1642  which displays results on one or more monitors  1652  (which may be physical displays and/or graphical user interfaces available on discrete devices) and generates a log file  1654  for later analysis. 
     The controller  1644  similarly receives all of the control inputs  1620  for use in adjusting various outputs  1650 . In the embodiment shown, the controller  1644  adjusts parameters of the powder management system  1200  including the weight of powder delivered  1658  (which directly affects the measured weight  1624  of powder delivered), the temperature  1660  in the powder line  1216  which may be controlled by a heating and/or cooling system and directly affects the measured temperature  1604 , and the powder blower speed  1626 . The controller  1644  similarly adjusts the electrostatic voltage  1628  at each electrostatic emitter bar  314  (or, in an embodiment, each individual electrostatic emitter) and the rotational angle  1630  of each electrostatic emitter bar  314  in the electrostatic enclosure  309 . The controller  1644  is configured to change the vacuum flow rate  1636  of the vacuum system (not shown), the temperature  1634  of the oven  106  (which may be independently controlled in various zones  1672 ), and the excess air flow rate  1674  of the air blower/compressor  1202 . These varied inputs are then received as feedback  1656  used to make further adjustments 
     As shown in  FIGS.  17   a  and  17   b   , the apparatuses  102   a ,  102   b  may comprise a local controller  1646  that is responsible for receiving instructions from the controller  1644  and adjusting local variables and make local measurements. As shown, the plant interface  1648  controls the line speed  1632  functions. 
     The invention as disclosed herein is not limited to the particular details of the described electrostatic coating apparatus, and other modifications and applications may be contemplated. Further changes may be made in the above-described method and device without departing from the true spirit and scope of the invention herein involved. It is intended, therefore, that the subject matter in the above disclosure should be interpreted as illustrative, not in a limiting sense. 
       FIGS.  18   a - 18   c    provide a process flow diagram of a second embodiment of a controller system  1800 . 
     As shown, the control system  1800  comprises one or more interfaces  1884 - 1894  that control  1804  or monitor  1802  key data  1806 - 1882 , which are in turn controlled  1804  and monitored  1802  by the S7-1500 SIEMENS PLC  1896 . 
     As shown, the plant interface  1884  monitors the temperature of strip after chill roll bulk system  1806 , entry and exit accumulator  1814 , and alert/faults functions  1816 . The plant interface  1884  controls and monitors the line speed  1808 , oven temperature  1810 , and quench unit  1812  functions. 
     As shown, the air delivery system  1886  monitors the humidity/temperature  1818 , filter delta pressures  1820 , wet tank pressures  1822 , and alerts/faults  1824  functions. 
     As shown, the S7-1500 SIEMENS PLC  1896  directly monitors the CFM  1826  and weight of reclaim powder or fill probe  1876  functions. 
     As shown, the NOL-TECH powder management system interface  1888  monitors the powder convey line CFM  1830 , the powder convey line flow control valves  1832 , powder air line flow control valves  1834 , and alerts/faults  1838 . The NOL-TECH powder management system interface  1888  controls and monitors the Powderjet Air CFM  1828  and weight of powder delivered  1836 . 
     As shown, the Powderjet System interface  1890  monitors the nozzle pressure sensor  1844 , temperature within the Powderjet  1846 , mixing chamber pressure sensors  1852 , motor position limit switches  1854 , jet position limit switches  1856 , mezzanine  1  cabinet humidity/temperature  1858 , powder convey line splitter valves  1860 , powder air line splitter valves  1862 , powder air/powder line flow meters  1864 , reclaim pressure sensor  1866 , and alerts/faults  1868 . As shown, the Powderjet System interface  1890  controls and monitors solenoid valves for accessory air  1840 , electrostatic voltage and current  1842 , and servo motor control (width)  1848 , servo motor control (angle)  1850  functions. 
     As shown, the Film Thickness Indicator interface  1892  monitors the film thickness  1870 , film thickness statistics  1872 , and alerts/faults  1874  functions. 
     As shown, the Powder Reclaim System  1894  monitors the vacuum flow rate  1878 , pressure over filters  1880 , and alerts/faults  1882  functions.