Method and apparatus for forming a can shell

A method of forming a cup-shaped circular can shell from a flat metal sheet within a mechanical press, the shell including a center panel connected by an annular panel wall to an annular countersink having a generally U-shaped cross-sectional configuration and with the countersink connected to an annular crown by an inclined annular chuckwall, the method comprising the steps of

• blanking a disk from the sheet between an annular blank and draw die and an annular cut edge,
• gripping an annular portion of the disk between an annular die core ring and an opposing annular outer sleeve having an annular piston and surrounding a die center piston,
• positioning an annular inner pressure sleeve within the outer pressure sleeve and with the inner pressure sleeve having an annular piston within an annular air piston chamber surrounding the die center piston,
• forming an air reservoir chamber within the die center piston,
• connecting the air reservoir chamber to the annular air piston chamber for the inner pressure sleeve with a plurality of circumferentially spaced elongated air passages within the die center piston,
• drawing an inner portion of the disk within the outer pressure sleeve with the inner pressure sleeve and a die center punch within the inner pressure sleeve to form a cup,
• pressing a center portion of the cup with the die center punch against a panel punch within the die core ring and with the panel punch including a peripheral portion having a profile for forming the countersink and panel wall,
• clamping an inclined annular portion of the cup against the die core ring with the inner pressure sleeve to form the chuckwall, and
• reversing the direction of the panel punch and the die center punch while continuing to clamp the chuckwall between the inner pressure sleeve and the die core ring to form the countersink and the center panel with the peripheral portion of the panel punch.

Apparatus for forming a cup-shaped circular can shell from a flat metal sheet with a mechanical press, the shell including a center panel connected by an annular panel wall to an annular countersink having a generally U-shaped cross sectional configuration and with the countersink connected to an annular crown by an inclined annular chuckwall, said apparatus comprising

• an annular retainer supported by a die shoe of the press,
• a die center piston having an air reservoir chamber and supported within said retainer, said retainer cooperating with said die center piston to define an annular first air piston chamber therebetween,
• an annular blank and draw die mounted on said retainer and surrounding said die center piston with said die center piston supporting a die center punch,
• an annular outer pressure sleeve within said blank and draw die and having
• an annular piston within said first air piston chamber,
• said outer pressure sleeve and a portion of said die center piston defining an annular second air piston chamber therebetween,
• an annular inner pressure sleeve between said outer pressure sleeve and said die center punch and having an annular piston within said second air piston chamber, and
• a plurality of circumferentially spaced elongated air passages within said die center piston and connecting said air reservoir chamber to said second air piston chamber and cooperating with said air reservoir chamber to produce a controlled air spring force on said inner pressure sleeve.