CAN BOTTOM HAVING IMPROVED STRENGTH AND APPARATUS FOR MAKING SAME

摘要

A can bottom (6) having an approximately frustoconical portion (8) extending downardly and inwardly from the can side wall (4), an annular nose portion (16) extending downwardly from the approximately frustoconical portion, and a central portion (24) extending upwardly and inwardly from the nose. The nose (16) is formed by inner and outer circunferentially extending frustoconical walls (12, 13) that are joined by a downwardly convex arcuate portion (18). The inner surface (29) of the arcuate portion of the nose has a radius (R3) of curvature adjacent the nose inner wall (12) of at least 0.060 inch (1.52 mm). The central portion of the can bottom has a substantially flat disc-shaped central section (26), having a diameter (D3) of at least about 0.14 inch (3.6 mm), and an approximately dome-shaped and downwardly concave (25) having a radius (R6) of curvature no greater than 1.475 inches (37.47 mm). In a preferred embodiment of the invention, the inner surface of the arcuate portion of the nose (16) is formed by a sector of a circle and has a radius of curvature which is no greater than about 0.070 inch (1.8 mm). An apparatus for making the can bottom comprises a nose punch (52) whose distal end (60) has a radius of curvature (R3') that is equal to the radius of curvature of the can bottom nose (16) and a die (50) whose radius of curvature (R6') equals that of the dome.