Patent Publication Number: US-8524065-B2

Title: Systems and methods for electrocoating a part

Description:
SUMMARY 
     Embodiments of the present invention relate generally to systems and methods for electrocoating a part. More particularly, the embodiments relate to systems that are configured to electrically charge a fluid with an external anode positioned outside of an electrocoating tank. Thereby, the fluid is electrically charged by the anode before the fluid is delivered to the tank for electrocoating a part. The electric charging of the fluid by the external anode promotes equal charge distribution throughout the fluid before it is delivered to the tank. Equal charge distribution throughout an electrically charged fluid promotes uniform coating thickness of the fluid deposited on a part during an electrocoating process. In addition, the positioning of an anode outside, rather than inside, of the tank creates additional space inside of the tank for the electrically charged fluid and parts for electrocoating. 
     In accordance with one embodiment, an electrocoating system comprises a tank, a pump in fluid communication with the tank, and an external anode positioned outside of the tank. The pump is configured to deliver a fluid to the tank for electrocoating a part, while the external anode is configured to provide an electric charge to the fluid delivered by the pump. 
     In accordance with another embodiment, an electrocoating system further comprises one or more internal nozzles positioned inside of the tank and a return path extending from the tank to the pump. The one or more internal nozzles are configured to direct at least a portion of the electrically charged fluid from the pump into the tank to electrocoat a part, while the return path is configured to recycle the fluid from the tank to the pump. In addition, an external anode positioned outside of the tank comprises a substantially membrane-free metal pipe. 
     In accordance with yet another embodiment, a method of electrocoating a product comprises: providing an electrocoating system comprising a tank, a pump in fluid communication with the tank, an external anode positioned outside of the tank, and one or more internal nozzles positioned inside of the tank; positioning a part for electrocoating in the tank; delivering a fluid to the tank with the pump; electrically charging the fluid with the external anode; coating a part with the electrically charged fluid delivered by the one or more internal nozzles; and recycling the electrically charged fluid from the tank to the pump. 
     These and additional objects and advantages provided by the embodiments of the present invention will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of specific embodiments can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  is an illustration of an electrocoating system with an external anode positioned outside of a tank according to one embodiment of the present invention; 
         FIG. 2 . is an illustration of an electrocoating system with an external anode positioned outside of a tank and internal nozzles positioned inside of the tank according to another embodiment of the present invention; and 
         FIG. 3  is an illustration of an electrocoating system with an external anode and a nozzle, both positioned outside of a tank, according to another embodiment of the present invention. 
     
    
    
     The embodiments set forth in the drawings are illustrative in nature and are not intended to be limiting of the invention defined by the claims. Moreover, individual aspects of the drawings and the invention will be more fully apparent and understood in view of the detailed description. 
     DETAILED DESCRIPTION 
     Referring initially to the embodiment shown in  FIG. 1 , an electrocoating system  10  generally comprises a tank  12 , a pump  14 , and an external anode  16 . The tank  12  is configured to retain, at least temporarily, a fluid  20 , or fluids, that is capable of carrying an electric charge. For example, the fluid  20  may be a ceramic, dye, pigment, or polymer, such as paint. Further, the tank  12  is configured to contain, at least partially, a part  22  for electrocoating. The tank  12  may be a closable and/or sealable structure to entirely contain a part  22  or may be open-ended to permit a portion of a part  22  to project there-from. In addition, a part  22  positioned in the tank  12  generally is stationary in the tank  12  during electrocoating, but it is contemplated that the part  22  may be conveyed through the tank  12  during electrocoating by a conveyor belt or other assembly. The part  22  for electrocoating may be a grounded electrical conductor and generally is substantially configured of a metallic substance. In one exemplary embodiment, the part  22  is a cathode. As such, an electrically charged fluid  20  is attracted to, and deposits on, the part  22 . Equal, or substantially equal, charge distribution throughout the electrically charged fluid enhances the electrocoating process by generally providing a substantially uniform coating thickness of the fluid  20  deposited on the part  22 . 
     As shown in  FIG. 1 , the pump  14  is in fluid communication with the tank  12 . The pump  14  is configured to deliver a fluid  20  to the tank  12  for electrocoating a part  22 . As such, the pump  14  is configured to deliver a fluid  20  to the tank  12  at a flow rate and pressure appropriate for electrocoating a part  22  as described herein. For example, but not by way of limitation, the pump delivers the fluid  20  to the tank  12  at a pressure from about 1 psi to about 50 psi, more particularly, from about 15 psi to about 40 psi, and at a flow rate from about 0.1 liters per second to about 3.0 liters per second. In one exemplary embodiment, the pump  14  is a centrifugal pump. It is contemplated, however, that any pump configured to perform the purposes stated herein may be utilized with embodiments of the electrocoating system  10 . 
     The external anode  16  is positioned outside of the tank  12 , generally between the pump  14  and the tank  12 . The external anode  16  is configured to provide an electric charge to the fluid  20  delivered by the pump  14 . As such, the external anode  16  provides the electric charge to the fluid  20  prior to its delivery into the tank  12  for electrocoating. The pump  14  generally delivers the fluid  20  past the external anode  16  to the tank  12  at a flow rate appropriate for the external anode  16  to sufficiently electrically charge the fluid  20 . This flow rate of the fluid  20  delivered past the external anode  16  may vary depending upon a volume of the fluid  20  delivered by the pump  14 . For example, it is contemplated that as a volume of the fluid  20  increases, a slower flow rate of the fluid  20  may be provided to increase a contact time between the fluid  20  and the external anode  16  and enable the external anode  16  to sufficiently electrically charge the fluid  20 . The external anode  16  may be configured in any variety of shapes, such as, but not limited to, tubular, flat plate, C-shape, or annular, such as a pipe. 
     As shown in  FIG. 1 , the external anode  16  generally is contained within an insulating part  17 . The insulating part  17  prevents a user of the electrocoating system  10  from being exposed to the electric charge of the external anode  16 . In one exemplary embodiment, the insulating part  17  is a polyvinyl chloride (PVC) pipe in which the external anode  16  is contained. It is contemplated, however, that any insulating part configured to perform the purposes stated herein may be utilized with embodiments of the electrocoating system  10 . 
     Further, it is common practice in the electrocoating industry that membranes may be used to cover anodes so as to remove acid from the fluid during the electrocoating of a part  22 . Typically, about 80% of a surface area of an anode is covered by a membrane to control pH through acid removal. Membrane covered anodes generally are referred to in the industry as anolyte cells. An anode that is substantially membrane-free is one that may not be entirely free of a membrane, but that is membrane-free to an extent that any existing membrane does not interfere, to any significant degree, with the electric charging of the fluid by the anode. In one embodiment, the external anode  16  is membrane-free, or substantially membrane-free. In another embodiment, the external anode  16  is substantially covered by a membrane. In another embodiment, the electrocoating system  10  also comprises one or more internal anodes  18  positioned inside of the tank  12  to provide an additional electric charge to the electrically charged fluid  20  delivered to the tank  12 . The internal anodes  18  also may be membrane-free, or substantially membrane-free, or substantially covered by a membrane. 
     In one embodiment, the external anode  16  comprises a membrane-free 316 type stainless steel pipe. Such anodes  16 , by virtue of the fluid  20  passing through an enclosed channel of the metal pipe anode  16 , are configured to provide substantially unlimited anode surface area in providing the electric charge to the fluid  20  as it passes through the anode  16 . More particularly, the entirely exposed wall of the channel of the metal pipe external anode  16  may be unlimited in anode surface area in comparison to an internal anode positioned inside of a tank  12  where an anode surface area of the internal anode is limited by that portion of the anode positioned alongside of an interior wall of the tank  12 . The unlimited anode surface area aids in the external anode  16  providing the electric charge substantially uniform to the fluid  20  so as to promote substantially equal electric charge distribution throughout the fluid  20 . Substantially equal electric charge distribution throughout the fluid  20  optimizes the electrocoating of the part  22  by providing a substantially uniform attraction of molecules of the fluid  20  to the part  22 . Further, it is contemplated that as a volume of the fluid  20  delivered to the external anode  16  by the pump  14  increases, a greater surface area of the external anode  16  may be provided to sufficiently electrically charge the fluid  20  delivered by the pump  14 . Thus, it is contemplated that a minimum surface area of the external anode  16  per unit volume of fluid  20  flow may be provided to sufficiently charge the fluid  20  prior to its delivery to the tank  12  for electrocoating a part  22 . 
     In one embodiment, shown in  FIG. 1 , with the external anode  16  being positioned outside of the tank  12 , the system  10  comprises no anodes positioned inside of the tank  12 . In another embodiment, however, shown in  FIG. 2 , the system  10  further comprises one or more internal anodes  18  positioned inside of the tank  12 . As mentioned above, these internal anodes  18  may be configured to provide an additional electric charge to the electrically charged fluid  20  delivered to the tank  12  to ensure that the fluid  20  is sufficiently electrically charged for completion of the electrocoating process. Generally, the internal anodes  18  positioned inside of the tank  12  are substantially covered by a membrane. It is contemplated, however, that the internal anodes  18  inside of the tank  12  may be membrane-free or substantially membrane-free. 
     The electrocoating system  10  generally further comprises a direct current (DC) rectifier  26 . The rectifier  26  generally is electrically coupled to the external anode  16  positioned outside of the tank  12 , and, if present in the system  10 , to the internal anodes  18  positioned inside of the tank  12 , so as to provide an electric current to the anodes  16 ,  18  sufficient for the anodes  16 ,  18  to provide an electric charge to the fluid  20  at least adequate for electrocoating purposes. For example, but not by way of limitation, the electric current provided to the anodes  16 ,  18  may be, but is not limited to, from about 25 DC volts to about 600 DC volts or higher. The voltage provided to the anodes  16 ,  18  may vary according to a volume of the fluid  20  delivered by the pump  14 . For example, a higher voltage may be provided to the anodes  16 ,  18  to sufficiently charge an increased volume and/or increased flow rate of the fluid  20  delivered by the pump  14 . The electrocoating system  10  may also comprise any additional or other electrical circuitry desired or needed for embodiments of the electrocoating system  10  to perform the purposes stated herein. 
     In one embodiment, shown in  FIG. 1 , the electrocoating system  10  may further comprise one or more nozzles  24  positioned inside of the tank  12  through which the pump  14  delivers the electrically charged fluid  20  to the tank  12 . More particularly, the nozzles  24  are configured to direct at least a portion of the electrically charged fluid  20  from the pump  14  into the tank  12  for electrocoating a part  22 . Further, as shown in  FIG. 2 , one or more of the internal nozzles  24  positioned inside of the tank  12  may be configured to direct at least a portion of the electrically charged fluid  20  from the pump to one or more selected areas of a part  22  positioned for electrocoating. The use of such nozzles  24  to direct an electrically charged fluid  20  to selected areas of a part  22  may substantially minimize variation in charge distribution in the electrically charged fluid  20  present throughout the tank  12  and, thereby, substantially optimize the electrocoating of both those selected areas of the part  22  and the part  22  in its entirety. 
     In another embodiment, shown in  FIG. 3 , the electrocoating system  10  may further comprise one or more external nozzles  24  positioned outside of the tank  12  through which the pump  14  delivers the electrically charged fluid  20  for electrocoating a part  22 . More particularly, the external nozzles  24  are configured to direct at least a portion of the electrically charged fluid  20  from the pump  14  to one or more selected areas of a part  22  positioned for electrocoating outside of the tank  12 . 
     It is contemplated that, in another embodiment, the electrocoating system  10  may comprise one of any various combinations of embodiments of electrocoating systems  10 , including, but not limited to, those embodiments described herein and shown in  FIGS. 1-3 . More particularly, an electrocoating system  10  may comprise one or more nozzles  24  positioned inside of the tank  12  configured to direct at least a portion of the electrically charged fluid  12  from the pump  14  into the tank  12  for electrocoating a part  22 ; one or more nozzles  24  positioned inside of the tank  12  and configured to direct at least a portion of the electrically charged fluid  20  from the pump  14  to one or more selected areas of a part  22  positioned for electrocoating; one or more nozzles  24  positionable outside of the tank  12  and configured to direct at least a portion of the electrically charged fluid  20  from the pump  14  to one or more selected areas of a part  22  positioned for electrocoating outside of the tank  12 ; or any combinations thereof. 
     As illustrated in  FIGS. 1-3 , the electrocoating system  10  generally also comprises a return path  28  that extends from the tank  12  to the pump  14 . This return path  28  is configured to recycle the fluid  20  from the tank  12  to the pump  14 . The return path  28  may comprise any combination of pipes, hoses, values, and any other fluid conveying devices configured to perform the purposes stated herein may be utilized with embodiments of the electrocoating system  10 . 
     Further, it is contemplated that embodiments of the electrocoating system  10  may alternatively comprise and utilize a cathode, inside and/or outside of the tank  12 , to provide an electric charge to the fluid  20  for electrocoating an anode part. 
     It is noted that recitations herein of a component of the present invention being “configured” in a particular way or to embody a particular property, or function in a particular manner, are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is “configured” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component. 
     It is noted that terms like “generally” and “typically,” when utilized herein, are not utilized to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to identify particular aspects of an embodiment of the present invention or to emphasize alternative or additional features that may or may not be utilized in a particular embodiment of the present invention. 
     For the purposes of describing and defining the present invention it is noted that the terms “substantially” and “approximately” are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms “substantially” and “approximately” are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.