Abstract:
This invention generally relates to a spray apparatus and a method useful in the repair of coating adhered to can ends used in the food and beverage packaging industries. The spray apparatus has one or more elongated shafts rotatably coupled to a frame. One or more bearing members are rotatably coupled to the shafts. One or more plates are rotatably coupled to the bearing members. One or more spray guns are coupled to the plates. The spray guns of the spray apparatus are structured to apply fluid to the can end with a solid stream emitted from the spray guns in a circular pattern. 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 spray 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 spray 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 fluid, repair fluid, lacquer or paint 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 high pressure spray atomization which forms small droplets or particles of fluid, repair fluid, lacquer or paint from the fluid, repair fluid, lacquer or paint. Atomization can be achieved by high pressure impingement (between 100 psi (0.690 MPa) to 600 psi (4.137 MPa)) on an orifice of a spray head or using a secondary low pressure air source (around 100 psi (0.690 MPa)) to break the fluid into small controlled droplets or particles. The problem with the atomization method is that it generates overspray which is detrimental to the efficiencies of the machine due to the extensive cleaning required on the surrounding transfer mechanism or belt of the machine. Overspray is defined herein as the additional fluid, repair fluid, lacquer or paint that does not transfer directly to the can end and sprays beyond the scored surface of the can end onto the transfer mechanism, belt or machine. The two part epoxy coating mixtures commonly used as a fluid is difficult to manage on a continuously operating machine when overspray occurs because the fluid, repair fluid, lacquer or paint builds up on the surrounding transfer mechanism of the machine, and requires routine cleaning and maintenance to keep the machine running efficiently. 
   The present invention implements a low pressure solid stream spray head and method, which significantly reduces spray beyond the scored surface of the can end and allows for greater machine efficiencies due to reduced downtime associated with routine cleaning and maintenance. The solid stream nozzle provides prolonged stream integrity, which results in delayed breakup and drop formation after leaving the nozzle orifice. The fluid is essentially extruded in a continuous stream as opposed to a pattern of droplets or particles. 
   In certain humid environments where oxidation and corrosion are of greater concern than in less humid environments, many canmakers apply more fluid, repair fluid, lacquer or paint to the can end to prevent rust from appearing on the can end. The present low pressure non-atomization or solid stream spray head and method allows for a low and high film weight (up to 20 mg or more) to be applied on the can end without the heavy overspray associated with prior art high pressure atomized or droplet spray head repair systems. The industry accepted high pressure atomization or droplet spray head applies a lower film weight (around 10 mg) on a can end by providing a very thin layer of fluid, repair fluid, lacquer or paint coating at high pressure. Even at this reduced film weight, the industry accepted atomization spray head presents overspray problems. Also, the prior art atomized spray head does not apply enough film weight to the can ends in certain environments and contaminates the transfer mechanism, belt or machine because of overspray. 
   There continues to be a need in the art for a spray apparatus and method for the repair of can ends that can apply low and high film weights to the can ends than was previously known in the art. Additionally, there continues to be a need in the art for a spray apparatus and method that does not generate a high volume of overspray or substantially avoids overspray. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a spray apparatus and method for the repair of can ends that can apply low and high film weights to a can end. It is another object of the present invention to provide a spray apparatus and method for the repair of can ends that does not generate a high volume of overspray or substantially avoids overspray. 
   Certain objects of the present invention are obtained by providing a spray apparatus for the repair of coating adhered on a can end. The spray apparatus has one or more elongated shafts rotatably coupled to a frame. One or more bearing members are rotatably coupled to the shafts. One or more plates are rotatably coupled to the bearing members. One or more spray guns are coupled to the plates. The spray guns of the spray apparatus are structured to apply fluid to the can end with a solid stream emitted from the spray guns in a circular pattern. 
   Other objects of the present invention are obtained by providing a spray apparatus for the repair of coating adhered on a plurality of can ends. The spray apparatus has a frame and an elongated first shaft rotatably coupled to the frame. An elongated second shaft is rotatably coupled to the frame. A third shaft is coupled to the first shaft which passes through an aperture in a first bearing member and a first plate. A fourth shaft is coupled to the second shaft which passes through an aperture in a second bearing member and the first plate. A fifth shaft is coupled to the third shaft which passes through an aperture of a third bearing member and a second plate. A sixth shaft is coupled to the fourth shaft which passes through an aperture in a fourth bearing member and the second plate. A first bracket is coupled to the first plate and a second bracket is coupled to the second plate. A first spray gun is coupled to the first bracket and a second spray gun is coupled to the second bracket. The spray guns of the spray apparatus are structured to apply fluid to the can ends with a solid stream emitted from the spray guns in a circular pattern. 
   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: supplying fluid to a low pressure tank; filtering the fluid through a fluid filter; flowing the fluid through a fluid flow sensor; and dispensing the fluid from a nozzle in a solid stream and in a circular pattern toward the can end. The low pressure tank, the fluid filter, the fluid flow sensor and the nozzle are in fluid communication with one another and define a fluid delivery system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a top plan view of a full open easy opening end; 
       FIG. 2  is a schematic drawing of a low pressure solid stream or non-atomization spray head and a high pressure droplet or atomization spray head fan patterns; 
       FIG. 3  is an isometric view of a spray head assembly; 
       FIG. 4  is a side cross-sectional view of a spray head assembly; 
       FIG. 5  is a side cross-sectional view of a bearing support mechanism; 
       FIG. 6  is a detailed side cross-sectional view of a bearing support mechanism taken generally in the area of circle  6  in  FIG. 5 ; 
       FIG. 7  is an isometric view of a spray gun; 
       FIG. 8  is a side view of a spray machine; 
       FIG. 9  is a side view of a spray machine; and 
       FIG. 10  is a schematic drawing of a low pressure solid stream or non-atomization spray method. 
   

   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 , fan patterns emitted from a low pressure solid stream or non-atomization spray head  16  and a high pressure droplet or atomization spray head  18  are displayed. As can be seen, the fan pattern  20  of the spray head  16  is circular and concentrated whereas the fan pattern  22  of the spray head  18  is elliptical and disperse. The spray head  16  uses a solid stream nozzle  24  at a relatively low pressure of less than 100 psi (0.690 Mpa) from a compressed gas source or the like. The length that the fluid leaves the nozzle  24  allows for a continuous circular vector of fluid without turbulence or fluid breakup as it leaves the nozzle  24 . Conversely, spray head  18  disperses an elliptical pattern of fluid in droplet form as it leaves nozzle  26 . The emission of the fluid from spray head  16  in a solid stream and in a circular pattern allows the fluid to be sprayed on the score line  12  of the can end  10  in higher volumes and minimizes overspray onto a transfer mechanism or belt that negatively effects the machine efficiency equipped with spray head  18  due to the elliptical fan pattern  22 . 
   The spraying method of spray head  16  is performed with low pressure on a translating or rotating spray head assembly  28  shown in  FIG. 3 . The spray path of the spray head assembly  28  is in a controlled manner if a solid stream spraying technique is employed. The spray head assembly  28  is dynamically balanced with a rigid bearing support mechanism  30  shown in  FIGS. 4-5 . The rigid bearing support mechanism  30  allows for accurate dispensing of the fluid to the can end  10  located in the transfer mechanism or belt located below the spray head assembly  28 , a spray gun  82  and the nozzle  24 . The solid stream method requires an accurate rotating assembly to control the spray location of the fluid. The bearing support mechanism  30  assists in controlling the rotating path of the spray head assembly  28 . 
   As can be seen in  FIGS. 4-5 , the bearing support mechanism  30  is rotatably coupled to a motor  32  by an elongated first shaft  34  coupled to a coupling member  36  and a frame  40 . With reference to  FIG. 4 , an elongated second shaft  38  is rotatably coupled to the frame  40 . Each of the shafts  34 ,  38  are rotatably coupled to the frame  40  with one of a plurality of connectors  42 . Each of the shafts  34 ,  38  passes through either a first or a second tubular spacer  44 , a portion of a plurality of bearing members  46  coupled to the frame  40  and an aperture of either a first or a second sprocket  48 . Bearing members  46  could be ball bearings, ball thrust bearings, flange bearings, needle bearings, preloaded bearings, roller bearings, roller thrust bearings, split sleeves, tapered roller bearings and other types of bearing members that are known in the art. The connectors  42  assist in keeping the upper bearing members  46  in place. Connectors  49  assist in keeping the lower bearing members  46  in place. Rotary motion applied by the motor  32  to shaft  34  is translated to shaft  38  by a belt  50  rotatably coupled to the sprockets  48 . Sprockets  48  are spaced from shafts  34 ,  38  by spacing members  52  which have apertures through which one of the shafts  34 ,  38  pass. Mounting plates  54  are coupled to one or the other of the shafts  34 ,  38 . 
   One end of each eccentric third and fourth shafts  56  are coupled to one or the other of mounting plates  54  and one or the other of the shafts  34 ,  38 . Each of shafts  56  passes through an aperture of either a first or a second bearing member  58 . Bearing members  58  could be ball bearings, ball thrust bearings, flange bearings, needle bearings, preloaded bearings, roller bearings, roller thrust bearings, split sleeves, tapered roller bearings and other types of bearing members that are known in the art. Bearing members  58  pass through apertures of first plate  60  and are encased within rings  62  which may be, by way of example and not limitation, sealing rings. Plate  60  is rotatably coupled to bearing members  58 . The other end of each eccentric third and fourth shafts  56  are coupled to one or the other plate  64 . Each of the bearing members  58  are spaced apart from the plates  54 ,  64  by a certain number of spacing members  66 . Each plate  64  is also coupled to one or the other of fifth and sixth eccentric shafts  68  which are coupled to one or the other of third and fourth shafts  56 . Each of shafts  68  pass through an aperture of either a third or a fourth bearing member  70 . Bearing members  70  could be ball bearings, ball thrust bearings, flange bearings, needle bearings, preloaded bearings, roller bearings, roller thrust bearings, split sleeves, tapered roller bearings and other types of bearing members that are known in the art. Bearing members  70  pass through apertures of second plate  72  and are encased within rings  74  which may be, by way of example and not limitation, sealing rings. Plate  72  is rotatably coupled to bearing members  70 . Each of the bearing members  70  are spaced apart from the plate  72  by a certain number of spacing members  76 . A cap  78  is coupled to each of the shafts  68  to assist in keeping the bearing members  70  in place. 
   With reference to  FIG. 3 , plate  60  has a mounting bracket  80  for securing a spray gun  82  of the type shown in  FIG. 7 . Spray gun  82  has a low pressure solid stream or non-atomization spray head  16  and nozzle  24 . Of course, one could attach a high pressure droplet or atomization spray head  18  to the mounting bracket  80  as well. The spray gun  82  has a plurality of apertures  84  for coupling the spray gun  82  to the mounting bracket  80 .  FIG. 8  shows the spray gun  82  coupled to bracket  80 . Various hoses that supply fluid to the spray gun  82  have been omitted from  FIG. 8  for the purpose of simplifying  FIG. 8 . Likewise, plate  72  has a mounting bracket  86  for securing a spray gun  82  of the type shown in  FIG. 7 . Of course, one could attach a high pressure droplet or atomization spray head  18  to the mounting bracket  86  as well.  FIG. 8  shows the spray gun  82  coupled to bracket  86 .  FIG. 9  shows the spray guns  82  connected to a spray machine  88 . As in  FIG. 8 , various hoses that supply fluid to the spray gun  82  have been omitted from  FIG. 9  for the purpose of simplifying  FIG. 9 . A transfer mechanism or belt  90  is shown in  FIG. 9  below the spray guns  82  and nozzle  24  which conveys can ends  10  below the spray guns  82  for application of fluid, repair fluid, lacquer or paint to the can ends  10 . The can ends  10  are typically transferred to the transfer mechanism  90  by a downstacker or the like. 
   With reference to  FIG. 7 , apertures  84  are located on mounting brackets  92 . The spray gun  82  is equipped with a manifold  94  for delivery of the fluid to spray head  16 . Hoses (not shown) are coupled to connectors  96  for delivery of the fluid to the manifold  94 . The hoses (not shown) are additionally secured to the spray gun  82  by connector assembly  98 . As an example, connector assembly  98  is shown as a plurality of brackets coupled together. 
   With reference to  FIG. 10 , the fluid delivery system of the present invention is a low pressure tank system. Fluid is supplied to a low pressure tank  100 . Next, the tank  100  is pressurized using conventional compressed gas sources or the like which are typically less than 100 psi (0.690 MPa). The tank  100  does not require additional complicated amplification systems and equipment for flowing the fluid through the fluid delivery system. The fluid is then filtered through a fluid filter  102 . The fluid then flows through a fluid flow sensor  104  which monitors and/or controls the flow rate of the fluid. The fluid flow sensor  104  allows the end-user to selectively control the flow rate of the fluid from the spray gun  82 . By controlling the flow rate of the fluid from the spray gun  82 , the end-user can control the amount or weight of fluid that is dispensed onto each can end  10 . The fluid then flows to the rotating spray gun  82  attached to the spray machine  88  which is rotating in a circular pattern. The tank  100 , the fluid filter  102 , the fluid flow sensor  104  and the spray gun  82  are in fluid communication with one another and define a fluid delivery system. The fluid is dispensed from the nozzle  24  in a circular pattern in a solid stream from the nozzle  24  toward the can end  10 . The circular pattern is concentrated and emitted with low pressure using conventional compressed gas sources which are typically less than 100 psi (0.690 MPa) without further amplification whereas the prior art spray head  18  emits the fluid in an elliptical and disperse pattern at a higher pressure which is typically greater than 100 psi (0.690 MPa). The circular and concentrated pattern of the present invention significantly reduces the problem associated with the overspray produced by spray head  18 . The fluid is dispensed from the spray head  16  in a controlled manner due to the rigid bearing support system  30  of the present invention. The length that the fluid leaves nozzle  24  allows for a continuous circular vector of fluid without turbulence or fluid breakup as it leaves the nozzle  24 . Dispensing the fluid from spray head  16  allows the fluid to be sprayed on the score line  12  of the can end  10  in low and high volumes and minimizes overspray that negatively effects the machine efficiency equipped with spray head  18 . 
   The spray machine  88  has been omitted from  FIG. 10  for the purpose of simplifying the FIG. The low pressure of this system minimizes the number of components that are wetted by the fluid which oftentimes consists of mixed epoxy coatings. Avoiding overspray is important to machine efficiency because it reduces the downtime of cleaning and maintaining the transfer mechanism, belts or other components of the machine. 
   The industry has not utilized this type of spraying method because it has not been provided as an option by the can machinery original equipment manufacturers (“OEMs”) since the OEMs did not have appropriate spray head control technology of the rigid bearing support system  30  used in the present invention that implements the low pressure solid stream or non-atomization spray method. The apparatus and method of the present invention allows for the spray head to translate or rotate in a precise circular motion that places the spray pattern within approximately a +/−0.050 inch (1.27 mm) radial band around the centerline of the score line  12 . This precise motion allows the circular band to fully cover the score line  12  even though the band width is substantially smaller than the commonly used atomized fan pattern as is shown in  FIG. 2 . 
   Solid stream or non-atomization spraying is typically applied by dispensing the fluid through a nozzle  24  at a low pressure using conventional compressed gas sources which are typically less than 100 psi (0.690 MPa) whereas high pressure methods used in the droplet or atomization process generally use high pressure circulating fluid circuits at a pressure of between 100 psi (0.690 MPa) to 600 psi (4.137 MPa) or using a secondary low pressure air source of around 100 psi (0.690 MPa) with specialized pumps for the two part epoxy mixtures predominantly used as fluid in score repair. The low pressure solid stream spraying method uses less complicated fluid delivery systems. For example, the present invention uses the pressure pot system of  FIG. 10  that minimizes the number of components wetted by the two part epoxy coatings. 
   The low pressure requirement for the solid stream spray head  16  greatly simplifies the fluid delivery method of the present invention. This is particularly important to machine efficiency because the two part epoxy coating mixtures used are difficult to manage because they usually have a finite pot life and the apparatus requires routine maintenance. The low pressure method of the present invention limits the number of wetted components in the apparatus. See  FIG. 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.