Method and apparatus for forming ends

Claim 1

A method of forming a container end having a minimum buckle resistance of 90 psi and a minimum rock resistance of 60 psi from a sheet metal material having a maximum thickness of 0.0120 inches comprising the steps of aligning upper and lower die elements for relative movement along a path with said lower die element having an annular recess defined by inner and outer die members movable relative to each other along said path, said inner die member having an inner annular flat wall parallel to said path with an arcuate surface on the upper end of said inner wall having an outer radius less than 0.030 inches, said outer die member having an outer annular flat wall defining an angle of less than 5 degrees with respect to said path, said upper die element having an annular punch having a lower arcuate surface having a radius of approximately 0.030 inches and having a length along said path of more than twice said radius, moving said inner and outer die members relative to each other along said path so that an upper edge of said outer annular flat wall is above an upper free edge of said arcuate surface on the upper end of said inner wall of said recess, inserting said sheet metal material between said die elements, and moving said die elements towards each other to force said punch into said recess and produce a countersink between a substantially flat central portion and a peripheral curl with the countersink having a depth of at least 0.075 inches and an outer flat wall portion in engagement with said outer flat wall of said lower die element, said outer flat wall having a length to locate an upper free edge of said outer flat wall portion above the peripheral lower edge of said central portion and produce an arcuate portion having a radius of less than 0.030 inches between said inner flat wall and said central portion.

Claim 2

A method of forming a container end having a minimum buckle resistance of 90 psi and a minimum rock resistance of 60 psi from a sheet metal material having a maximum thickness of 0.0120 inches comprising the steps of aligning upper and lower die elements for relative movement along a path with said lower die element having an annular recess defined by inner and outer die members movable relative to each other along said path, said inner die member having an inner annular flat wall parallel to said path with an arcuate surface on the upper end of said inner wall having an outer radius less than 0.030 inches, said outer die member having an outer annular flat wall defining an angle of less than 5 degrees with respect to said path, said upper die element having an annular punch having a lower arcuate surface having a radius of approximately 0.030 inches and having a length along said path of more than twice said radius, moving said inner and outer die members relative to each other along said path so that an upper edge of said outer annular flat wall is above an upper free edge of said arcuate surface on the upper end of said inner wall of said recess, inserting said sheet metal material between said die elements, and moving said die elements towards each other to force said punch into said recess and produce a countersink between a substantially flat central portion and a peripheral curl with the countersink having a depth of at least 0.075 inches and an outer flat wall portion in engagement with said outer flat wall of said lower die element, said outer flat wall having a length to locate an upper free edge of said outer flat wall portion above the peripheral lower edge of said central portion and produce an arcuate portion having a radius of less than 0.030 inches between said inner flat wall and said central portion.

Claim 8

A method of forming an end panel for a container from sheet metal stock having a thickness of about 0.0120 inches with the end panel having a minimum buckle resistance of 90 psi and a minimum rock resistance of 60 psi comprising the steps of deforming a flat generally circular metal disc with a punch having an annular projection cooperating with a die having an annular recess for receiving said projection to produce a generally U-shaped trough between a substantially flat central portion and a peripheral curl with said trough having a flat inner wall and a flat outer wall extending substantially parallel to each other and substantially perpendicular to said flat central portion, said outer wall defining an angle of less than 5 degrees with respect to a plane perpendicular to said cental portion and said inner wall being joined with said flat central portion by an arcuate portion having a radius of less than 0.030 inches, the annular spacing between said inner annular flat wall and an adjacent surface of said punch being less than one and one-half times the thickness of said metal stock so that the inner flat wall defines a minimum angle with respect to said reference plane, said flat outer wall having a length sufficient such that the outer periphery of said central portion is located below the upper edge of said outer flat wall.

Claim 9

A method of forming an end panel for a container from sheet metal stock having a thickness of about 0.0120 inches with the end panel having a minimum buckle resistance of 90 psi and a minimum rock resistance of 60 psi comprising the steps of deforming a flat generally circular metal disc with a punch having an annular projection cooperating with a die having an annular recess for receiving said projection to produce a generally U-shaped trough between a substantially flat central portion and a peripheral curl with said trough having a flat inner wall and a flat outer wall extending substantially parallel to each other and substantially perpendicular to said flat central portion, said outer wall defining an angle of less than 5 degrees with respect to a plane perpendicular to said cental portion and said inner wall being joined with said flat central portion by an arcuate portion having a radius of less than 0.030 inches, the annular spacing between said inner annular flat wall and an adjacent surface of said punch being less than one and one-half times the thickness of said metal stock so that the inner flat wall defines a minimum angle with respect to said reference plane, said flat outer wall having a length sufficient such that the outer periphery of said central portion is located below the upper edge of said outer flat wall.