Method of and apparatus for manufacturing top plate for metallic drum container

An apparatus for manufacturing a top plate for a metallic drum container, the to plate having an opening defined therein and a tubular flange projecting upwardly and extending axially from the opening, the tubular flange having a predetermined height and a predetermined inside diameter, said apparatus comprising:

• punching means for defining a circular hole in a top plate stock of thin sheet steel, said circular hole having a diameter smaller than said inside diameter of the opening and having a peripheral edge immediately adjacent the opening;
• first forming means comprising a first rounded section disposed on an upper portion of a die and projecting radially outwarldy for pressing a peripheral edge of said circular hole to raise and radially outwardly expand the peripheral edge of said circular hole into a substantially frustoconical first flange blank, said first flange blank having a circular hole whose diameter is smaller than said inside diameter of the opening and a height smaller than said predetermined height of the tubular flange;
• second forming means comprising a second rounded section disposed on a lower portion of said die and projecting radially outwardly for raising and radially outwardly expanding a peripheral edge of a proximal portion of said first flange blank into a substantially frustoconical second flange blank contiguous to said first flange blank, said second flange blank having a lower portion beneath said peripheral edge of the proximal portion, said lower portion having a diameter which is substantially equal to said inside diameter of the tubular flange, said first and second flange blanks jointly serving as a substantially frustoconical third flange blank;
• a third rounded section disposed between said first and second rounded sections and projecting radially inwardly;
• and
• third forming means for drawing said third flange blank into a tubular flange which has said predetermined inside diameter and said predetermined height;
• wherein said first, second and third rounded sections are fixedly disposed contiguously on said die such that said third rounded section merges with said first and second rounded sections so that said peripheral edge springs inwardly toward said third rounded section as said peripheral edge moves from said first rounded section to said second rounded section.

A method of manufacturing a top plate for a metallic drum container, the top plate having an opening defined therein and a tubular flange projecting upwardly and extending axially from the opening, the tubular flange having a predetermined height and a predetermined inside diameter, said method comprising:

• positioning a plate stock of thin sheet steel over a die member, said die member comprising a substantially cylindrical lower portion, and an upper head portion having a flat top surface and first and second substantially frustoconical forming surfaces, said first forming surface comprising a rounded convex surface disposed beneath said flat top surface and projecting radially outwardly therefrom, and said second forming surface comprising a rounded convex surface disposed beneath said first forming surface and projecting radially outwardly therefrom, and further comprising a concave rounded surface disposed between said first and second forming surfaces, wherein said first and second forming surfaces and said concave surface are fixedly disposed contiguously on said die such that said concave rounded surface means with said first and second forming surfaces;
• punching a circular hole in said plate stock of sheet steel, said circular hole having a diameter smaller than a diameter of said top flat surface and having a peripheral edge immediately adjacent the opening;
• pressing said sheet steel downwardly over said upper head portion of said die member, thereby forcing said upper head portion of said die member through said circular hole, whereby said circular hole and said peripheral edge of said sheet steel around said circular hole are progressively raised and expanded radially outwardly by said first and second forming surfaces with said peripheral edge springing inwardly toward said concave surface as said peripheral edge moves from said first forming surface to said second forming surface;
• and
• pressing said sheet steel further downwardly over said cylindrical lower portion of said die member thereby drawing said peripheral area into a tubular flange having said predetermined inside diameter and said predetermined height.