1. Field of the Invention
This invention relates generally to the field of consumer packaging, and more specifically to metal cans, such as the steel and aluminum cans that are commonly used for packaging soft drinks, other beverages, food and aerosol products.
2. Description of the Prior Art and Recent Technology
Metal cans for soft drinks, other beverages and other materials are of course in wide use in North America and throughout the world. The assignee of this invention, Crown Cork & Seal Company of Philadelphia, is the world's largest designer and manufacturer of such cans.
The art of making and packing metal cans is constantly evolving in response to improved technology, new materials, and improved manufacturing techniques. Other forces driving the evolution of technology in this area include raw material prices, the nature of new materials to be packaged and the marketing goals of the large companies that manufacture and distribute consumer products such as soft drinks.
Interest has existed for some time for a metal container that is shaped differently than the standard cylindrical can in such a distinctive way to become part of the product's trade dress, or to be otherwise indicative of the source or the nature of the product. To the inventors best knowledge, however, no one has yet developed a practical technique for manufacturing such an irregularly shaped can at the volume and speed that would be required to actually introduce such a product into the marketplace.
U.S. Pat. No. 3,224,239 to Hansson, which dates from the mid 1960's, discloses a system and process for using pneumatic pressure to reshape cans. This process utilized a piston to force compressed air into a can that is positioned within a mold. The compressed air caused the can wall to flow plastically until it assumed the shape of the mold.
Technology such as that disclosed in the Hansson patent has never, to the knowledge of the inventors, been employed with any success for the reshaping of drawn and wall ironed cans. One reason for this is that the stress that is developed in the wall of the can as it is being deformed can lead to defects that are potentially failureinducing, e.g., localized thinning, splitting or cracking. The risk of thinning can be reduced by increasing the wall thickness of the can, but this would make shaped cans so produced prohibitively expensive. The risk of splitting and cracking can be reduced by a process such as annealing, but at the expense of reduced toughness and abuse resistance of the final product.
A need exists for an improved apparatus and process for manufacturing a shaped metal can design, that is effective, efficient and inexpensive, especially when compared to technology that has been heretofore developed for such purposes, and that reduces the tendency of a shaped can to fail as a result of thinning, splitting or cracking.