US 3507418 A
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April 1970 w. T. SAUNDERS 3,507,418
SCORELINB FQRNATION AND REPAIR Original Filed March 31, 1966 H63 PRIOR ART- :2 40 X 7 X 1\\ [so L Y W 446 45 49 WILLIAM T SAUNDERS ATTORNEYS United States Patent 3,507,418 SCORELINE FORMATION AND REPAIR William T. Saunders, Weirton, W. Va., assignor to National Steel Corporation, a corporation of Delaware Original application Mar. 31, 1966, Ser. No. 539,187. Divided and this application Oct. 1, 1968, Ser. No.
Int. Cl. B65d 17/24 US. Cl. 220-54 7 Claims ABSTRACT OF THE DISCLOSURE In repairing a scoreline on the interior surface of a container, a sealing material is used which carries a pulverant material providing anodic protection for the base metal.
This application is a division of application Ser. No. 539,187, filed Mar. 31, 1966 by William T. Saunders for Scoreline Formation and Repair.
This invention is concerned with easy-open sheet metal container stock and, in its more specific aspects, with formation and repair of scorelines on easy-open sheet metal container stock.
Reducing metal thickness of sheet metal container stock to form a scoreline is an essential but troublesome step in the manufacture of sheet metal containers referred to as easy-open, self-opening and hand operable containers. The gauge sheet metal used for such containers ranges from about .005 inch for steel to about .015 inch for aluminum. Residual metal at a steel container scoreline can have a thickness as low as .002 inch so that accuracy in scoring depth is essential in order to obtain high production yields of containers with sufficient strength to hold container contents yet frangible enough to be hand operable.
Scoring must also be carried out along a preselected line without damaging other portions of the container or opening structure, and without impeding other production steps.
Additionally, most sheet metal containers have protective coating, either a metallic plating, such as tin, or a non-metallic coating such as enamel, lacquer, and the like, or a combination of metallic and non-metallic coatings which must be repaired after scoring in order to protect container contents.
The teachings of the present invention permit scoring of sheet metal stock with much less force than that required in prior art practice, provide for more accurate scoreline placement, and provide for selective depth scoring with more accurate depth control. A novel scoreline repair is also provided which helps to solve container interior corrosion problems of the prior art by reducing solubility of container sheet metal in container contents.
Novel features and advantages of the invention will be more evident from a description of embodiments shown in the accompanying drawings. In these drawings:
FIGURE 1 is a top plan view of an easy-open container produced in accordance with the present invention,
FIGURE 2 is a cross-sectional view of FIGURE 1 along the line 22,
FIGURE 3 is a schematic view, partially in section, of apparatus illustrating prior art scoring practice,
FIGURE 4 is an exploded cross-sectional view of structure embodying the invention, and
FIGURE 5 is an exploded cross-sectional view of a portion of a sheet metal container embodying the invention.
Container closure 12 of FIGURES 1 and 2 includes edge seam material 14 and container endwall 16. Tab handle 18 is secured to endwall 16 by rivet 20. Scoreline 22 circumscribes handle 18 and is directed circumferentially about the container closure. Raised ridge 26 acts as a strengthening member for the thin gauge sheet metal of the endwall, adding rigidity to permit ripping out of the scored portion while preventing outward bending of the endwall. A more detailed description of typical easy-open containers suitable for practice of the present invention can be found in applicants corresponding application Container Structure and Manufacture, S.N. 495,796, filed Oct. 14, 1965, now Patent No. 3,437,228.
In manufacture of easy-open containers a score-last technique is preferred. That is, scoring is performed after formation of rivet 20, attachement of tab handle 18, and formation of ridge 26. Otherwise, the metal working involved in these steps may cause breakage at a scoreline. However, the invention is not limited to a score-last sequence and its advantages are realized when scoring is performed earlier in production.
One of the distinct advantages of localized backing as taught by the present invention is that it makes possible a score-last sequence in any situation where the tab handle does not cross the scoreline. With localized backing, backup surfaces can be raised sufiiciently to allow clearances for other parts of the container closure, such as ridge 26 or tab 18, while still providing the necessary backing to permit effective scoring using relatively low force and avoiding damage to the endwall sheet metal.
These advantages were not available in the prior art. Referring to FIGURE 3, which shows the relationship of the dies used in a scoring operation as practiced in the prior art, flat die 28 backs up sheet metal 30 during scoring. Cutting die 32, with knife edge 34, is brought into contact with the sheet metal blank 30. The knife edge 34 must displace metal in the sheet metal blank to form a scoreline. Metal displaced to form the scoreline cannot move upwardly because of backing die 28 and cannot move downwardly because of cutting die 32. In effect, displaced metal must be crushed sidewise often damaging the metal adjacent to the score. This crushing action requires force and is a large part of the total force required in the prior art scoring practice. This large part of the force required in the prior art practice is eliminated by the present invention because of localized backing.
An exploded view of localized backing structure as taught by the present invention is shown in FIGURE 4. Backing die 40 includes a narrow-width backup surface 42 formed in raised relationship to the remainder of the die. The narrow-width backup surface 42 contacts one surface of sheet metal blank 44 before contact by the remainder of backup die 40. On the opposite surface of sheet metal blank 44, die 46 with knife edge 48 contacts blank 44. As shown by arrows 49 in FIGURE 4, metal displaced by knife edge 48 in forming the scoreline is permited to move adjacent to backup surface 42, i.e. outwardly and upwardly without opposing force by the remainder of backing die 40. As a working example, backup surface 42 can be about .05 inch wide, and can be raised about .003 inch, or more, from the remainder of the die.
In a scoring operation using the present invention, the knife edge of the scoring die conforms to a preselected configuration scoreline as in the prior art, but need not be raised from the remainder of the scoring die surface as high as prior art knife-edges because of the raised position of the localized backup surface. The shallower depth knife edge permitted by the present invention has the advantage of greater strength and resultant longer life. Scoring dies and backing dies of the present invention can be used in prior art die operating machinery. Such machinery and its operation are well known in the art and need not be described for an understanding of the present invention.
The narrow-width backup surface provided by the present invention conforms to the pattern of the cutting die knife edge as determined by the preselected configuration of the scoreline. The height of the narrow-width backup surface above the remainder of the backup die can be determined by requirements of the particular scoring operation. Clearance can be allowed for structural parts of an easy-open container and selective depth scoring can also be accomplished by varying the height of the narrow-width backup surface.
Selective depth scoring includes variation of depth along a single scoreline, e.g. scoring may be deeper at the starting or ending portions of scoreline to help initial breakage of the metal in opening a container or to make final removal of metal from the container easier. It will be apparent that manufacture of dies and control of scoring depth can be carried out more readily and more accurately by control of the height of the narrow-width backup surface, rather than by control of the height of a knife edge.
In the scoring operation, the scoring die and backing die are brought together forceably using a standard die operating machine. The knife edge and narrow-width backup surface conform to the same pattern and mate on opposite surfaces of the sheet metal blank. That is, the narrow-width backup surface meets the sheet metal blank in opposed relationship to the knife edge, centrally of the localized backup surface, along the length of the desired scoreline. The narrow-Width backup surface permits metal to be dislocated by the knife edge adjacent to the narrow-width backup surface without opposing force from the remainder of the backing die as in the prior art.
The teachings of the invention are applicable to sheet metal container materials such as steel and aluminum and produce improved results when working with coated sheet metal. With coated sheet steel, for example tinplate, scoring is preferably performed on the interior surface of the container. A distinct advantage of localized backing is that the tinplate on the outer surface of the container is not broken and continues to provide normal corrosion protection and the desired finish appearance.
Interior coatings, including enamel protection, are broken during scoring. Included in the scoreline repair teachings of the present invention is a unique contribution which helps solve interior corrosion problems of long standing in the art.
With tinplated steel containers for example, corrosion occurs by iron going into solution in container contents. This occurs when iron is exposed after sacrifice of the tinplating or at the usual microscopic voids in the tinplating. Iron going into solution affects the taste of container contents and ultimately can lead to can failure. The same problem is experienced with enameled aluminum, especially with acid foods.
The present invention provides a solution which inhibits container metal going into solution while at the same time repairing the break in the protective coating on the interior surface of the container caused by scoring.
Scoring sealers taught by the present invention include hot melt cements, i.e. thermoplastic materials such as polyamides, polyesters, and polyethylene, and solvent type resins such as vinyls, epoxies, and phenolics, any of which can be applied in a fluid or semi-fluid condition to a scoreline by pattern printing or other suitable method. The invention teaches use of these settable sealing materials which can be applied in a fluid state and act as a carrier for material which provides anodic protection for container sheet metal. For example, when working with sheet steel a metal which is anodic with respect to iron is carried by the sealer. This anodic material, in pulverant form, is mixed with the fluid sealer and applied to the scoreline. The pulverant anodic materials is exposed to container contents at the outer surface of the sealer and goes into solution in preference to the iron or other sheet metal of the container to prevent corrosion of the interior surfaces of the sheet metal container. These anodic materials are commonly referred to as sacrificial in the art.
Pulverant aluminum is an example of a sacrificial material which is anodic to iron and protects sheet steel containers. Other suitable metals include magnesium, tin, zinc, and similar metals or alloys which are anodic to iron in a substantially oxygen-free environment. The cost of the anodic metal and its affect on the taste of container contents can determine the anodic metal used in the simultaneous scoring repair and corrosion protection taught by the present invention.
The cross-sectional view of FIGURE 5 shows a portion 49 of a sheet metal container including a scoreline 50. Sealer 52 covers the scoreline completely and includes a pulverant metal 54 which is exposed to container contents at the surface of the sealer.
Adaptation of the improved method of forming a scoreline and novel scoreline repair of the present invention to embodiments other than those specifically described will be possible in the light of the above disclosure, therefore, it is understood that the scope of present invention is to be determined from the appended claims.
What is claimed is:
1. In combination,
a sheet metal container having a non-metallic protective coating on an interior surface,
a scoreline of reduced metal thickness formed on an interior surface of the sheet metal container so as to break the non-metallic protective coating on the interior surface along at least a portion of the scoreline, and
sealing material overlaying the scoreline and repairing the non-metallic protective coating so as to prevent contact of container contents with sheet metal along the scoreline, the sealing material carrying an anodic material which provides anodic protection for the sheet metal container and which is disposed so as to contact container contents.
2. The combination of claim 1 in which the sealing material is thermoplastic.
3. The combination of claim 2 in which the sheet metal container comprises steel and the anodic material is a pulverant metal which is anodic to iron.
4. In combination,
a sheet steel container stock,
a scoreline of reduced metal thickness formed on an interior surface of the sheet steel container stock, and
a sealer overlaying the scoreline for preventing contact of container contents with the scoreline, the sealer including a pulverant metal which is anodic to iron dispersed in the sealer so as to contact container contents to inhibit interior corrosion of the sheet steel container.
5. For repairing a scoreline formed on an interior surface of sheet metal container stock and reducing interior corrosion in a container formed from the sheet metal container stock, the combination comprising a non-metallic setable sealing material which can be applied in fluid form to sheet metal container stock, and a pulverant metal which provides anodic protection for the sheet metal container stock, the pulverant metal being dispersed in the sealing material so as to provide surface contact with container contents.
metal is anodic to iron.
7. The combination of claim 6 in which the pulverant metal is aluminum.
References Cited UNITED STATES PATENTS JOSEPH R. LECLAIR, Primary Examiner G. T. HALL, Assistant Examiner