This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/554,111, Filed Mar. 17, 2004, which is incorporated by reference in its entirety herein. 


   FIELD OF THE INVENTION 
   The present invention relates to beverage and food container manufacturing, and more specifically an apparatus and method for selectively removing surface coatings from a defined portion of a container, on end closure, while retaining the coating in other predetermined areas. 
   BACKGROUND OF THE INVENTION 
   During the manufacturing of metal containers used in the beverage and food industry, certain coatings are often applied to internal and external surfaces of the containers. These organic and inorganic chemical coatings are applied to prevent cans from staining during retorting and other processes, as well as to prevent corrosion and “scalping”, which is the alteration of the taste of a beverage or food stored in a container resulting from the beverage or food contacting the interior surface of the container. 
   One particular use of coatings involves the use of a “conversion coating”, which is typically a zirconium-phosphate coating that is applied to the exterior of a container to prevent staining of the container exterior during retort operations. As described herein, “retort” refers to any operation wherein a beverage or food container is heated beyond 200° F., and more typically between about 250-300° F., and which typically includes exposing the container to steam or hot water having a pH equal to or greater than 7.0, i.e. basic. 
   Although the conversion coating provides significant advantages when applied to an exterior lower portion, or dome of the container, it has the adverse effect of causing ink and decorative coating adhesion loss on the “neck” or upper portion of containers during manufacturing and retort operations. Hence, the container becomes unfit for its intended purpose and is subsequently discarded, which is both time consuming, expensive, and disruptive to a manufacturing operation. As appreciated by one skilled in the art, in modern can manufacturing facilities with the capability of producing over 20 million containers a day any loss in production is disruptive and expensive. 
   Thus, there is a significant need in the container industry for a method and apparatus for removing a conversion coating or other similar coating from a predetermined portion of a container, while retaining the coating on another portion of the container. Furthermore, as appreciated by one skilled in the art, the invention is not limited to the selective removal of coatings from containers, but rather may be used in any type of operation when a selective portion of a coating is desired to be applied or removed from a surface or portion of an apparatus. The following disclosure describes an improved apparatus and method for efficiently removing a predetermined amount of conversion coating deposited on a container during production. 
   SUMMARY OF THE INVENTION 
   It is thus one aspect of the present invention to provide an apparatus and method for selectively removing a coating from one portion or surface of a container, while retaining the coating on another portion or surface of the container. Thus, in one embodiment of the present invention, an “etchant” tank is provided with a plurality of fluid dispensing nozzles submerged below a solution/air interface of the etching solution. The nozzles generally discharge the solution through a washer mat or screen that supports the containers (typically inverted), and is controlled wherein the etchant tank solution only rises to a predetermined level on the container. Thus, the coating on a lower dome portion of the inverted container is preserved, while the coating on the neck or upper portion of the inverted container is removed, thereby addressing the adverse effect of decreased adhesion performance on the neck of the containers when the containers are later inked and/or retorted. More specifically, retorting operations are performed after a container has been conversion coated and after a portion of the conversion coating of the neck has been removed. The retort process exposes the container to temperatures above 200° F. from steam or hot water that has a pH equal to or greater that 7.0, which can cause ink and decorative coating adhesion loss. 
   To facilitate the mass treatment of thousands and even millions of containers per day, the washer mat is driven as a conveyor at a predetermined speed, and thus the speed and volume of treated containers may be selectively controlled. As further appreciated by one skilled in the art, the container may be inverted to remove coatings from a selected portion thereof, while retaining the coating on another predetermined portion. Thus, the apparatus and the method provided herein may be used on any object or apparatus that requires the selective removal of a coating material from only a predetermined portion. 
   It is a further aspect of the present invention to provide a conversion coating removal process that utilizes readily available equipment in a cost effective manner, is simplistic to operate, and is substantially maintenance free. Thus, in one aspect of the present invention, an apparatus is provided which is comprised substantially of an etchant tank, a pump mechanism with associated manifold, a plurality of nozzles, and a moving washer mat that supports a plurality of containers. 
   It is a further aspect of the present invention to provide an etchant and/or holding tank that maintains a substantially consistent fluid level wherein the height of solution being ejected from the nozzles above the tank solution surface is maintained. Accordingly, in one embodiment of the present invention a level control apparatus is provided in the etchant tank that automatically provides additional water or other solutions to the etchant tank on a continuous basis up to a overflow level of the etchant tank. Alternatively, in another embodiment of the present invention a smaller etchant tank is positioned within a larger holding tank, wherein the etchant tank includes the plurality of upwardly oriented spray nozzles that are in operable communication with a pumping apparatus. When the etchant tank overflows, the excess fluid is captured by the holding tank that includes a conduit that returns the overflow fluid to the pump for recirculation. In this embodiment, the fluid level in the etchant tank is maintained at a constant level. Since the nozzles are positioned in the etchant tank under the fluid level, the distance between the nozzles and the fluid level will necessarily be maintained. In addition, the etchant concentration, temperature, and other parameters may be maintained in the holding tank to ensure a proper solution is introduced to the containers. 
   In another aspect of the present invention, a method is provided for selectively removing a coating from a portion of a plurality of a container, and comprises the steps of: 
   providing an etchant tank that contains a solution known to remove a coating from the plurality of containers; 
   providing a plurality of nozzles in said etchant tank, said nozzles having a discharge port positioned below a surface of said solution; 
   providing a pump which circulates said solution at a predetermined pressure to said nozzles; 
   passing the plurality of containers over said nozzles at a predetermined speed and distance; and 
   discharging said solution through said discharge ports toward the plurality of containers, wherein only a portion of the plurality of containers is contacted by said solution to selectively remove the coating from a first portion of the plurality of containers while retaining the coating on a second portion of the plurality of containers. 
   The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of these embodiments. 
       FIG. 1  is a perspective view of one embodiment of the present invention; 
       FIG. 2  is a top plan view of the embodiment of the present invention shown in  FIG. 1  depicting an etchant tank, a plurality of risers, and a plurality of educator nozzles; 
       FIG. 3  is a front section view of the embodiment of the invention shown in  FIG. 1 ; 
       FIG. 4  is a left section view of the embodiment of the invention shown in  FIG. 1  depicting the interconnection of the educator nozzles to the riser; 
       FIG. 5  is a partial left section view of the embodiment of the invention shown in  FIG. 1  depicting the interconnection of educator nozzle pairs to the riser; 
       FIG. 6  is a partial left section view of the embodiment of the invention shown in  FIG. 1  depicting the interconnection of educator nozzle pairs to the riser, wherein a holding tank is employed to contain excess solution, thus maintaining fluid level in the etchant tank; 
       FIG. 7  is a left elevation view depicting the positioning of the containers on the washer mat and the orientation of flow from the educator nozzles; 
       FIG. 8  is a left perspective view of a plurality of containers positioned on the washer mat and the discharge of solutions from the educator nozzles; 
       FIG. 9  is a front elevation view depicting the removal of the conversion coating from a neck portion of the container and a finished beverage container; and 
       FIG. 10  are views of the educator nozzles used in one embodiment of the present invention. 
   


   For clarity, the following list of components associated with the present invention, and the numbering related thereto is provided herein: 
   
     
       
             
             
           
             
             
           
         
             
                 
             
             
               # 
               Component 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               2 
               Coating removal apparatus 
             
             
               4 
               Etchant tank 
             
             
               5 
               Holding tank 
             
             
               6 
               Etching solution 
             
             
               8 
               Riser 
             
             
               10 
               Riser support 
             
             
               12 
               Nozzle 
             
             
               14 
               Level control pipe 
             
             
               16 
               Liquid/air interface 
             
             
               18 
               Moving grid 
             
             
               20 
               Pump 
             
             
               22 
               Nozzle discharge port 
             
             
               24 
               Container 
             
             
               26 
               Container neck 
             
             
               28 
               Container dome portion 
             
             
               29 
               Sidewall 
             
             
               30 
               Riser couplings 
             
             
               32 
               Nozzle threads 
             
             
               34 
               Pump manifold 
             
             
               36 
               Header 
             
             
               38 
               Drain valve 
             
             
                 
             
           
        
       
     
   
   It should be understood that the drawings are not necessarily to scale. In certain instances, details which are not necessary for an understanding of the invention or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
   DETAILED DESCRIPTION 
   Referring now to  FIGS. 1-10  one embodiment of the present invention is shown herein. In general, the invention utilizes an etchant tank  4  with a plurality of nozzles  12  oriented to direct a flow of an etching solution  6  toward a predetermined portion of a plurality of containers  24 , and thus remove only a portion of a coating that has been applied thereto. As appreciated by one skilled in the art, numerous variations of the embodiments provided herein may be utilized to achieve the same results without changing the spirit or novelty of the invention. Further, the apparatus and method described herein is not limited to the treatment of containers. Rather, the apparatus and method may be utilized in any process or application where a portion of an apparatus requires selective coating or selective coating removal while the remaining portion of the apparatus is not altered. 
   Referring now to  FIGS. 1-6 , one embodiment of the present invention is shown herein. More specifically, the apparatus generally comprises an etchant tank  4  that is designed to retain the etching tank solution  6  within the confines of the enclosure. As appreciated by one skilled in the art, the etchant tank  4  may also be in the form of a catch basin located in a relatively large area. Within the etchant tank  4 , at least one but preferably a plurality of risers  8 , are provided that are interconnected to headers  36  that are interconnected to at least one solution supply line. A level control pipe  14  is also provided in one embodiment of the present invention to provide additional etching solution  6  to the etchant tank  4  when the etchant solution level is lowered below a predetermined position. 
   The coating removal apparatus  2  of the present invention additionally includes a moving washer mat  18  positioned above the etchant tank  4  and the etchant tank liquid/air interface  16  that is adapted to support a plurality of containers  24  that travel at a predetermined speed over the etchant tank  4 . In one embodiment, the washer mat  18  is comprised of a wire mesh material, a plastic grid, or other similar materials that allow the treatment solution to readily pass through the washer mat  18  and contact the plurality of containers. As additionally shown in  FIG. 1 , a plurality of nozzles  12  are interconnected to the risers  8  that provide an upwardly flow of etching solution  6  at a predetermined volume and velocity to create a controlled flow at a level above the washer mat  18 , thus operably contacting a predetermined and select portion of the plurality of containers  24 . Preferably the etching solution  6  is comprised of an aqueous based liquid having concentrations of nitric and hydrofluoric acids that are designed for efficient removal of the coating on the container, and which have a pH of between about 1.0 and 6.0. Alternatively, any type of liquid may be used to either selectively apply a coating to an apparatus or remove a coating from a selective portion of the apparatus. 
   The etchant tank  4  is an enclosure capable of retaining the etching solution  6 , and in one embodiment is rectangular in shape. As appreciated by one skilled in the art, the etchant tank  4  may have any conceivable shape such circular, oval, square, or other geometries. The etchant tank  4  is generally comprised of a metallic material, although plastics such as polyethylene may be used, as well as concrete, stainless steel, fiberglass, or any other type of substantially chemical and temperature impermeable material that is well known in the art. As further shown in  FIG. 3 , a pump manifold  34  is provided at a lower most portion of the etchant tank  4  that is interconnected to the risers  8  that provide the necessary etching solution for flow through the nozzles  12 . In one preferred embodiment of the present invention, a pump such as a Durco® Mark III with approximately 10-13 horsepower is used that is capable of providing a continuous flow rate of at least about 414 gpm. Preferably, this pump is run at a speed of about 1770-3550 Hz. As appreciated by one skilled in the art, depending on the size of the etchant tank and number of nozzles utilized, the size and output of the pump utilized may be changed. 
   Referring specifically now to  FIG. 3 , a front section view of one embodiment of the present invention is shown herein that clearly depicts the etchant tank  4 , the pump manifold  34 , and the other associated components. More specifically, the riser  8  and interconnected nozzles  12  are depicted, as well as the nozzle discharge port  22 , the moving mat  18 , and an amount of etching solution  6  that is propelled after being discharged from the nozzle discharge port  22  through the surface of the etching solution. 
   Referring now to  FIG. 6 , an alternate embodiment of the present invention is shown herein. More specifically, a system that employs a holding tank  5  to capture overflow etching solution  6  from the etchant tank  4  is provided. This embodiment of the present invention maintains solution level in the etchant tank  4  by continuously pumping etching solution  6  thereto. The overflow is captured by a holding tank  5  that is then redirected to the etchant tank  4  for reuse. In addition, the concentration temperature, purity, etc. of the overflow etching fluid may be monitored and/or altered in the holding tank  5  to ensure the containers  24  are treated pursuant to specifications. 
   Referring now to  FIG. 7 , a further depiction of the present invention is provided herein. More specifically, the risers  8  are shown positioned with a plurality of nozzles  12  extending on either side and oriented upwardly toward the moving mat  18 . The plurality of containers  24  are supported by the moving mat  18 , which in this example is constructed of rubber, stainless-steel mesh, plastics, or other materials commonly known in the art of about one-half inch thickness. The moving mat travels at a speed of between about 3 ft/min to 32 ft/min, and is driven in one embodiment by a 10-13 hp motor coupled to a 414 GPM pump, preferably a Durco® Mark III series device. 
   As further seen in  FIG. 7 , the positioning of the nozzles  12  with respect to the moving mat  18  and containers  24  is important to the effective operation of the apparatus. In this specific example, a distance of about 3½ inches is provided between the discharge port  22  of the nozzle  12  and the moving mat  18 , while the etching solution  6  is propelled upwardly in the direction of the containers  24 . The etchant tank solution  6  extends upwardly and approximately 2 inches over the container mat  18 , while allowing the container dome portion  28  to remain a sufficient distance from the nozzles  12  to prevent exposure to the etching tank solution  6 . As appreciated by one skilled in the art, the height of the solution  6  discharge may be adjusted as necessary by varying the operating speed of the pump and/or the size of the nozzle  12 , for example. Alternatively, it is possible to position the nozzles above the liquid/air interface without submerging the nozzles. 
   Referring now to  FIG. 8 , the positioning of the containers  24  with respect to the moving mat  18  and the nozzle discharge ports  22  is shown herein. More specifically, the height of the etchant tank solution  6  is depicted extending upwardly over a neck portion of a container neck  26  while not contacting with the container dome portion  28 . One of skill in the art will appreciate that the neck portion  26  of a container  24  is positioned proximate to an upper end of a sidewall  29 , the other end of the sidewall  29  being bounded by the dome portion  28 , for example. This process effectively removes the coating from at least the container neck  26 , while retaining the coating on the container dome portion  28  and on a portion of the sidewall  29 . A plurality of nozzles  12  are provided that include a nozzle discharge port  22  that is positioned below the moving mat  18  and the containers  24  that are supported by an upper surface of the moving mat  18 . The distance and positioning between the nozzle discharge port  22 , the moving mat  18 , and the associated containers  24  is dictated by any given application, and may vary depending on the size of the container  24 , the speed of travel of the moving mat  18 , the size of the pump  20  being utilized, and the type of nozzle discharge port  22 , which are all factors that dictate the height of spray of the etching solution  6 . 
   Referring now to  FIG. 9 , a front elevation view of an unfinished container is provided herein, as well as a finished container. More specifically, the unfinished container on the left side of  FIG. 9  depicts a container with a container dome portion  28  and a container neck  26  with a sidewall  29  positioned therebetween. The conversion coating has been removed from the container neck portion  26  and a portion of the sidewall. An example of a finished container is shown on the right side of  FIG. 9 , wherein the neck has been sized to be interconnected to an end closure and filled for distribution by a customer. 
   Referring now to  FIG. 10 , front elevation views of one type of nozzle  12  used in the present invention is provided herein, and which identifies a nozzle thread  32  on one end and the nozzle discharge port  22  on the opposing end. The nozzle  12  may utilize parasitic flow to increase mass flow therethrough. Preferably, the nozzle  12  is provided by Spring Systems Company of Wheaton, Ill. As appreciated by those skilled in the art, there are any number of types of nozzles and nozzles  12  and nozzle discharge ports  22  that may be employed without departing from the scope of the present invention, and the example provided herein is but one example of various types of possible nozzles  12 . 
   With reference to  FIGS. 1-10 , one embodiment of the present invention has a substantially rectangular etchant tank  4  that contains three risers  8  spaced about 5 to 7 inches (12.7 to 17.78 cm) from the bottom thereof. The etchant tank  4  of this embodiment has a length (l) of about 100 to 110 inches (254 to 279.4 cm), a width (w) of about 28 to 32 inches (71.12 to 81.28 cm), and a height (h 1 ) of about 7 to 11 inches (17.78 to 27.94 cm). In addition, the risers  8  of this embodiment of the invention are about 2 inch (5.08 cm) diameter (d) pipes spaced 8 to 10 inches (20.32 to 25.4 cm) apart, wherein one riser  8  is situated substantially in the center of the etchant tank  4 . The risers  4  of this embodiment of the invention are capable of supporting at least 92 nozzles  12 , preferably in 46 pairs. Alternatively, fewer nozzles  12  may be interconnected in single file along the tops of the risers  3 , wherein the exit of each nozzle  12  is preferably spaced about 3 inches (7.62 cm) from the outer diameter thereof. The moving grid  18  of one embodiment of the invention is about 0.5 inches (1.27 cm) thick and is situated (h 2 ) about 2 to 2.5 inches (5.08 to 6.35 cm) from the upper surface of the etchant tank  8 , which yields an etchant solution stream  6  that contacts about 2 inches (6.45 cm) of the inverted container  24 . 
   While an effort has been made to describe various alternatives to the preferred embodiment, other alternatives will readily come to mind to those skilled in the art. Therefore, it should be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. Present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not intended to be limited to the details given herein.
The present invention relates to an apparatus and method for removing a coating material from a predetermined first portion of a container, while retaining the coating on a second portion of the container, or alternatively applying a coating to a predetermined portion of a container or other apparatus.