Abstract:
This invention generally relates to a mixing apparatus and a method useful in the repair of coating adhered on a can end used in the food and beverage packaging industry. The mixing apparatus has a plurality of holding tanks in fluid communication with a first fluid delivery system and a mixer. A pressure tank is provided which is in fluid communication with the mixer. A spray device is provided which is in fluid communication with a second fluid delivery system and the pressure tank. A plurality of liquids or fluids are flowed through the first fluid delivery system, the plurality of liquids or fluids are mixed in the mixer to yield a mixed solution which is flowed to the pressure tank and the mixed solution is flowed through the second fluid delivery system and dispensed on the can end. A method for the repair of coating adhered on a can end is provided as well.

Description:
FIELD OF THE INVENTION 
   This invention generally relates to a mixing apparatus and a method useful in the manufacture of can ends used in the food and beverage packaging industries. More specifically, the invention provides a mixing apparatus and a method for use in the corrosion preventative repair of tooling induced damage to can end coatings, which may occur to coated steel can ends during the conversion of a steel shell into a full open or easy open food or beverage can end. 
   BACKGROUND OF THE INVENTION 
   Many can bodies for food, beverages or other products are provided with easy open can ends that are characterized by having a pull tab attached to the can end which is used to fracture a tear panel on the can end defined by a score line on the can end. The pull tab may be lifted to depress the tear panel in order to provide an opening in the can end for dispensing the contents of the container. 
   Likewise, many food products are sold in can bodies provided with full open easy open can ends that are characterized by having a pull tab attached to the can end which is used to fracture a score line that circumscribes the circumference of the end panel to define an opening panel. The pull tab may be lifted to fracture the score line. After the score line is fractured, the pull tab may be pulled upward from the container which severs the remainder of the score line in order to remove the entire opening panel for dispensing the contents of the container. 
   In the manufacture of an easy open can end, a shell is conveyed to a conversion press. In the industry, a pre-converted can end is commonly referred to as a shell. In the typical operation of a conversion press, a shell is introduced between an upper tool member and a lower tool member, which are in the open, spaced apart position. A press ram advances the upper tool member toward the lower tool member in order to perform any of a variety of tooling operations such as rivet forming, paneling, scoring, embossing, and final staking. After performing a tooling operation, the press ram retracts until the upper tool member and lower tool member are once again in the open, spaced apart position. The partially converted shell is transported to the next successive tooling operation until an easy open can end is completely formed and discharged from the press. As one shell leaves a given tooling operation, another shell is introduced to the vacated operation, thus continuously repeating the entire easy open can end manufacturing process. Examples of easy open can ends can be found in U.S. Pat. Nos. 4,465,204 and 4,530,631. Conversion presses can operate at speeds that manufacture in excess of 500 can ends per minute per lane, with certain presses having four lanes of tooling manufacturing in excess of 2000 converted can ends per minute. 
   It has been the practice in the industry to continue to strive to reduce the starting gauge of the metal sheet stock used to form the can end. The current practice is to use metal with a starting gauge of approximately 0.008 inch (0.20 mm). As such, tooling stations in a conversion press must be rigorously maintained within prescribed operating tolerances due to the thin sheet stock used in the press. In the production of a converted can end in a conversion press, the scoring station is of particular concern. The scoring station employs a tooling member that has a knife edge which defines the tear panel or opening panel on the public side of the can end. 
   Steel sheet stock used in the manufacture of can ends has a coating which protects the metal by inhibiting oxidation, corrosion or rust from forming on the surface of the metal. During the conversion process, damage to the protective coating typically occurs while forming the score that defines the tear panel or opening panel of the can end. As noted above, in the conversion of a shell into a can end with openable features thereon, a score line is formed. This score line defines the tear panel or opening panel described above. The score line is the most likely location where damage is caused to the pre-conversion, protective coating. Any oxidation, corrosion or rust on the surface of the can end represents an unattractive product appearance to the consumer and is unacceptable to canmakers in general. 
   In the industry, as a precautionary measure to prevent oxidation, corrosion or rust from appearing on the can end, many canmakers apply a mixed solution to the scored area of the can end by spraying the can end. The accepted spraying apparatus and method in the industry for score repair on full open easy open ends utilizes a single holding tank that holds a plurality of components (e.g., solvent and epoxy) that are flowed through a fluid delivery system and a spray apparatus for applying the mixed solution to the can end. 
   These score repair machines use many different variations of two or more component epoxy mixtures for the application of mixed solution to the score lines of the can end. The fluid delivery systems require routine maintenance because the two or more component mixed solution has a finite tank life when mixed and need to be cleaned or purged from the machine when the mixed solution expires. The existing fluid delivery systems pump mixed solution and the mixed solution wets many of the pumping components and auxiliary components including, by way of example and not limitation, filters, valves, pumps, pressure transducers and check valves, etc. The mixed solution has a negative effect on the overall efficiency of many components of the machine because so many components are wetted with the mixed solution and require cleaning when the mixed solution expires. 
   Conversely, the mixing apparatus and method of the present invention will mix the components of the mixed solution on demand. The apparatus also contains a pressure tank that eliminates the exposure of the mixed solution to the pumping components and auxiliary components used in the fluid delivery system which simplifies cleaning and maintenance of the fluid delivery system. The apparatus of the present invention does not have any high pressure pumps or repair fluid pressure regulators that contact the mixed solution and can be designed for low pressure spray devices or high pressure spray devices. The apparatus also provides the end-user with greater flexibility by being able to use different mixing ratios of the base components (e.g., 4:1—solvent:epoxy, or any other combination.) The apparatus also allows the holding tanks to be continuously replenished with liquids or fluids while the mixing apparatus is operating because the liquids or fluids are drawn from storage tanks at atmosphere. 
   There continues to be a need in the art for a mixing apparatus and method of the present invention that mixes components of a mixed solution on demand. Also, there continues to be a need in the art for a mixing apparatus and method of the present invention that uses a pressure tank that eliminates the exposure of the mixed solution to the pumping components and auxiliary components used in the system in order to simplify cleaning and maintenance of the fluid delivery system. Additionally, there continues to be a need in the art for a mixing apparatus and method of the present invention that can accommodate different mixing ratios of the components of the mixed solution. Also, there continues to be a need in the art for a mixing apparatus and method of the present invention that allows holding tanks to be continuously replenished with liquids or fluids while the mixing apparatus is operating. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a mixing apparatus and method that mixes repair fluid components on demand. It is an additional object of the present invention to provide a mixing apparatus and method that uses a pressure tank that eliminates the exposure of the mixed repair fluid solution to the pumping components and auxiliary components used in the fluid delivery system in order to simplify cleaning and maintenance of the fluid delivery system. It is an additional object of the present invention to provide a mixing apparatus and method that can accommodate different mixing ratios of the repair fluid components. It is an additional object of the present invention to provide a mixing apparatus and method that allows holding tanks to be continuously replenished with liquids or fluids while the mixing apparatus is operating. 
   Certain objects of the present invention are obtained by providing a mixing apparatus for the repair of coating adhered on a can end. The mixing apparatus has a plurality of holding tanks in fluid communication with a first fluid delivery system and a mixer. A pressure tank is provided which is in fluid communication with the mixer. A spray device is provided which is in fluid communication with a second fluid delivery system and the pressure tank. A plurality of liquids or fluids are flowed through the first fluid delivery system, the plurality of liquids or fluids are mixed in the mixer to yield a mixed solution which is flowed to the pressure tank and the mixed solution is flowed through the second fluid delivery system and dispensed on the can end. 
   Other objects of the present invention are obtained by providing a mixing apparatus for the repair of coating adhered on a can end. The mixing apparatus has a plurality of holding tanks in fluid communication with a first fluid delivery system and a mixer. The first fluid delivery system has a plurality of valves coupled to the holding tanks, wherein the valves selectively flow liquids or fluids held in the holding tanks into the first fluid delivery system. The first fluid delivery system also has a plurality of pumps, wherein the pumps pump the liquids or fluids to flow the liquids or fluids into the mixer. A pressure tank is in fluid communication with the mixer and a relieving type pressure regulator is coupled to the pressure tank. A spray device is in fluid communication with a second fluid delivery system and the pressure tank, wherein the plurality of liquids or fluids are mixed in the mixer to yield a mixed solution which is flowed into the pressure tank. Pressure in the pressure tank flows the mixed solution through the second fluid delivery system and dispenses the mixed solution on the can end. 
   Other objects of the present invention are obtained by providing a method for the repair of coating adhered on a can end. The method comprises: flowing a plurality of liquids or fluids from a plurality of holding tanks into a first fluid delivery system in fluid communication with the holding tanks and a mixer; flowing the plurality of liquids or fluids into the mixer; mixing the plurality of liquids or fluids to yield a mixed solution; flowing the mixed solution into a pressure tank; flowing the mixed solution from the pressure tank into a second fluid delivery system in fluid communication with the pressure tank and a spray device; and dispensing the mixed solution on the can end. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top plan view of a full open easy opening end; and 
       FIG. 2  is a schematic drawing of a mixing apparatus and a method for the repair of can ends. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   For purposes of the description hereinafter, the terms “upper”, “lower”, “vertical”, “horizontal”, “top”, “bottom”, “aft”, “behind”, “forward”, “rear”, “beneath”, “below” and derivatives thereof shall relate to the invention, as it is oriented in the drawing FIGS. However, it is to be understood that the invention may assume various alternative configurations except where expressly specified to the contrary. It is also to be understood that the specific elements illustrated in the drawings and described in the following specification are simply exemplary embodiments of the invention. Therefore, specific dimensions, orientations and other physical characteristics related to the embodiments disclosed herein are not to be considered limiting. 
   As employed herein, the term “number” refers to one or more than one (i.e., a plurality). As employed herein, the term “fastener” refers to any suitable fastening, connecting or tightening mechanism expressly including, but not limited to, integral rivets. As employed herein, the statement that two or more parts are “coupled”, “attached” or “connected” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. 
   Turning to  FIG. 1 , a full open easy open can end  10  is displayed. The can end  10  has a score line  12  which defines an opening panel  14 . A pull tab  15  may be lifted to fracture the score line  12 . After the score line  12  is fractured, the pull tab  15  may be pulled upward from the container which severs the remainder of the score line  12  in order to remove the entire opening panel  14  for dispensing the contents of the container. 
   Turning to  FIG. 2 , a schematic drawing of a mixing apparatus  18  and a method for the repair of can ends is shown. The mixing apparatus  18  has a plurality of holding tanks  20  for holding various liquids or components of such liquids including, by way of example and not limitation, liquid components of a repair fluid, lacquer, epoxy or paint that when mixed together yield a mixed solution. Alternatively, one of the holding tanks  20  could hold a liquid or solvent  22  for cleaning or flushing a first fluid delivery system  24  which is in fluid communication with the holding tanks  20  and a mixer  40 . The liquids dispensed from the holding tanks  20  could be, by way of example and not limitation, any aqueous or organic liquid or fluid known in the art which is suitable for: (i) mixing with one or more components to yield a mixed solution; or (ii) dissolving or releasing liquids or fluids disposed within the first fluid delivery system  24 . The holding tanks  20  may be continuously replenished with liquids or fluids while the mixing apparatus  18  is operating because the liquids or fluids are drawn from storage tanks at atmosphere. 
   The holding tanks  20  and the first fluid delivery system  24  may have filters or strainers  26  that remove contaminants from the liquids or fluids flowed into the holding tanks  20  or the first fluid delivery system  24 . The first fluid delivery system  24  of the present invention may contain additional elements, by way of example and not limitation, a plurality of first valves  28 , a plurality of second valves  30 , a plurality of conduits, hoses or passageways  32 , a plurality of pumps  34 , a plurality of pressure transducers  36 , a plurality of pressure relief valves  38  or a plurality of second check valves  50 . The plurality of first valves  28  are coupled to the holding tanks  20  for selectively flowing the contents of one or more of the holding tanks  20  through the first fluid delivery system  24  by a programmable logic control device or other control device. The plurality of second valves  30  are coupled to the first valves  28  for selectively flowing the contents of one or more of the holding tanks  20  through the first fluid delivery system  24  by a programmable logic control device or other control device. The first fluid delivery system  24  may contain a plurality of conduits, hoses or passageways  32  for flowing the liquids or fluids held in the holding tanks  20  which are in fluid communication with the conduits, hoses or passageways  32 . The conduits, hoses or passageways  32  are in fluid communication with the mixer  40 . The first fluid delivery system  24  may also contain a plurality of pumps  34  coupled to the plurality of pressure transducers  36 . The pumps  34  are metering pumps with an eccentric drive element for selectively applying pressure and pumping the liquids or fluids that were held in the holding tanks  20  to flow such liquids or fluids into the mixer  40  and on into a small pressure tank  42 . The pressure transducers  36  coupled to the pumps  34  are used to selectively monitor the pressure in the first fluid delivery system  24  to ensure flow within the first fluid delivery system  24  between a selected value lower than the operating pressure of the mixing apparatus  18  and the limiting upper end of pressure allowed for pumps  34  by a programmable logic control device or other control device. The first fluid delivery system  24  may also contain a plurality of pressure relief valves  38  which check the first fluid delivery system  24  for blockage or obstruction downstream from the pumps  34  by a programmable logic control device or other control device. These pressure relief valves  38  are designed to mechanically relieve pressure at a value that is less than the maximum operating pressure of the pumps  34  selected. The pressure relief valves  38  protect the pumps  34  from pressure surges due to blockages or obstruction downstream while the pressure transducers  36  are shutting off motor motion to the pumps  34 . 
   The liquids or fluids held in the holding tanks  20  flow under pressure supplied by pumps  34  through the first fluid delivery system  24  into the mixer  40  which mixes the liquids or fluids to yield a small amount of a mixed solution prior to flowing the mixed solution from the pressure supplied by pumps  34  into the small pressure tank  42  which is in fluid communication with mixer  40 . The pressure tank  42  has a size of about 1 gallon (3.79 liters) whereas existing fluid delivery systems that pump mixed solution through the pumping components and the auxiliary components have a pressure tank size of about 15 gallons (56.78 liters). As can be seen, the size of the pressure tank  42  of the present invention is a substantial reduction over the size of the pressure tank in existing fluid delivery systems that pump mixed solutions. It has been found that the 1 gallon (3.79 liters) size also meets the maximum flow demands observed in operation of the mixing apparatus  18 . Generally speaking, about 1 gallon (3.79 liters) per hour is about the maximum mixed solution output that has been observed, which allows for a smaller volume of mixed solution to be stored in pressure tank  42 . Such an approach also avoids running pumps  34  continuously to pump the liquids or fluids from holding tanks  20  into the pressure tank  42  leading to an energy savings in the operation of the present invention. A supply of gas optionally flows into an amplifier  44  which increases the pressure of the gas. A pressure regulator  46  may be coupled to the optional amplifier  44  and coupled to the pressure tank  42  for selectively relieving the pressure of the gas in the pressure tank  42 . The amplifier  44  is typically provided in those systems that use a high pressure droplet or atomization spray method on a spray device  58 . The amplifier  44  is typically not provided in those systems that use a low pressure solid stream or non-atomization spray method on the spray device  58 . 
   The small pressure tank  42  eliminates the exposure of the mixed solution to the pumping components and the auxiliary components located within the first fluid delivery system  24  such as first valves  28 , second valves  30 , conduits, hoses or passageways  32 , pumps  34 , pressure transducers  36 , pressure relief valves  38  and second check valves  50  and allows small amounts of liquids or fluids held in holding tanks  20  to be selectively mixed at the discretion of the end-user. As previously mentioned, prior art mixing systems require routine cleaning and maintenance because the mixed solution has a finite life span and requires more frequent cleaning of the pumping components and the auxiliary components such as first valves  28 , second valves  30 , conduits, hoses or passageways  32 , pumps  34 , pressure transducers  36 , pressure relief valves  38  and second check valves  50  that may come in contact with the mixed solution. The present invention which does not have mixed solution contacting such elements reduces the amount of cleaning and maintenance that is needed for the first fluid delivery system  24 . As such, the first fluid delivery system  24  may be easily cleaned with any aqueous or organic liquid or fluid known in the art which is suitable for dissolving or releasing liquids or fluids disposed within the first fluid delivery system  24 . 
   The mixer  40  is coupled to a first check valve  48  which separates the contents of the pressure tank  42  and the mixer  40 . The mixer  40  is also coupled to a plurality of second check valves  50  which separate the mixer  40  from the first fluid delivery system  24 . With the present invention, after the liquids or fluids have been mixed, the mixed solution is flowed from pressure tank  42  through a second fluid delivery system  52  which may contain additional elements, including, by way of example and not limitation, conduits, hoses, passageways, one or more filters  54  or one or more flow sensors  56 . Spray devices  58  are coupled to pressure tank  42 , filters  54 , flow sensors  56  and are in fluid communication with the second fluid delivery system  52  and the pressure tank  42 . The small size of the pressure tank  42  and the small amount of mixed solution stored therein allows the second fluid delivery system  52  to be easily cleaned with any aqueous or organic liquid or fluid known in the art which is suitable for dissolving or releasing mixed solution disposed within the second fluid delivery system  52 . 
   The pressure generated by the pumps  34  provide enough pressure to the liquids or fluids in the first fluid delivery system  24  to overcome the pressure in the pressure tank  42  where a small amount of the mixed solution is stored. The relieving type pressure regulator  46  coupled to the pressure tank  42  selectively controls the pressure that flows the mixed solution from the pressure tank  42  through the second fluid delivery system  52 . The pressure regulator  46  is a relieving type to allow for relieving pressure due to the changing volume of mixed solution in the pressure tank  42  as well as to relieve the higher pressure generated by pumps  34  to flow the liquids or fluids held in the holding tanks  20  into the pressure tank  42 . The filters  54  remove contaminants from the mixed solution flowed from the pressure tank  42  through the second fluid delivery system  52 . The mixed solution then flows through fluid flow sensors  56  which monitor the flow rate of the mixed solution. The fluid flow sensors  56  allow the end-user to selectively monitor the flow rate of the mixed solution from the spray devices  58 . By monitoring the flow rate of the mixed solution from the spray devices  58 , the end-user can identify changes in the amount or weight of mixed solution that is dispensed onto each can end  10  (e.g., blockages, line failures, etc.). The mixed solution then flows to the rotating or translating spray devices  58  attached to a spray machine which are rotating or translating in a circular or elliptical pattern and dispensing mixed solution on the can ends  10 . 
   While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended hereto and any and all equivalents thereto.