Metal deforming – With 'coating' of work
Patent
1982-08-30
1984-06-26
Gilden, Leon
Metal deforming
With 'coating' of work
72347, B21D 2200
Patent
active
044558503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
Two-piece cans for beer and other pressurized beverages generally have a reentrant convex shape for their bottom. This permits the use of thinner metal while resisting distortion of the can by the pressure of the beverage.
Coatings are generally used on the inside of beverage cans to prevent corrosion and to protect the flavor of the beverage. Coatings are also used on the outside of beverage cans to facilitate decoration and identification of the can and its contents. However, if the can is made of adequately corrosion resistant material such as aluminum or tin-plated steel of an appropriate quality, it is generally not necessary to apply any coatings to the outside of the bottom of the can.
Although it probably is unlikely, some think it conceivable that a concave can bottom of uncoated shiney metal, especially bright aluminum, could act as a reflector to concentrate the sun's rays and possibly start a fire in dry grass or underbrush if a used can is discarded by the roadside or in the woods.
Exterior coatings are generally applied to two-piece cans after the can body has been formed. If they were applied before forming, they could be abraided or damaged by the can forming process. And it is difficult to spray a matte coating on the bottom of a formed can without overspraying onto the sides.
SUMMARY OF THE INVENTION
The present invention provides a process for making a cylindrical can body with one end closed from a sheet of metal by a deformation process, said closed end having a reentrant convex shape, wherein first only the area of said sheet which will become the outside surface of said closed end is coated with a flexible coating composition which gives a matte finish, minimizing specular reflectance of light from said area, then the can body is formed from said sheet by a deformation process.
Generally two-piece cans are formed by a drawing and ironing process wherein a ram pushes the center of a flat sheet of metal into a female mold, often involving more than one ram and mold or more than one step. The initial forming steps are known as drawing. The final step or steps in which the precise can shape is formed is known as ironing. The ironing ram and mold typically will be shaped to form a reentrant convex shape at the bottom of the can.
Such a can is called a two-piece can to distinguish it from a three-piece can. A two-piece can includes a cup-shaped can body and one lid or end piece. A three-piece can includes a cylinder open at both ends and two lids.
Preferably, the coating composition is applied to flat sheet metal before any of the deformation is done to form the can body.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a plan view of part of an uncoiled sheet of metal indicating the location of can blanks which are to be coated according to the invention and cut from the sheet.
FIG. 2 is a perspective view of a partially formed cup shape drawn from a blank of FIG. 1.
FIG. 3 is a perspective view of a formed can body drawn and ironed from a blank of FIG. 1.
FIG. 4 is a cross-sectional view along the section line 4--4 in FIG. 3.
DETAILED DESCRIPTION
Suitable coating compositions are known in the art which are quite flexible and which dry to give matte finishes. By minimizing specular reflectance, any potential for discarded cans to accidentally cause fires in dry grass can be minimized. Matte finishes can be obtained by pigmentation, rough surfaces, or combinations thereof, such as by using the compositions disclosed herein.
The flexibility of the coating composition permits applying it to flat sheet and subsequently forming the can body. This avoids the difficulties of applying a paint to the reentrant bottom of a preformed can body. If the reentrant bottom of a preformed can is painted by spraying, it can be desirable to mask the sides of the can to prevent overspray. It is easier to confine the spray to a desired area of a flat sheet.
The reentrant convex bottom of the can body can have a variety of shapes. Generally the shapes will include some portions of smooth curves,
REFERENCES:
patent: 2116345 (1938-05-01), Floraday
patent: 3927217 (1976-08-01), Misonoo
E. I. Du Pont de Nemours and Company
Gilden Leon
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