Patent ID: 8141406

Claim:
Apparatus for forming a cup-shaped circular can shell from a flat metal sheet with tooling mounted on 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 inner wall portion of an annular crown by an inclined annular chuckwall, said apparatus comprising an annular retainer supported by a die shoe connected to the press, a die center piston defining an air reservoir chamber and supported for movement with said retainer and with said retainer defining an annular first air piston chamber, a passage for supplying controllable air pressure to said reservoir chamber, 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, said retainer supporting an annular outer pressure sleeve within said blank and draw die with said outer pressure sleeve having an annular piston within said first air piston chamber, said outer pressure sleeve and said die center piston defining an annular second air piston chamber therebetween, an annular inner pressure sleeve within said outer pressure sleeve around said die center piston and having an annular piston within said second air piston chamber, and a plurality of circumferentially spaced air passages within said die center piston and extending from said air reservoir chamber to said second air piston chamber causing the controllable air pressure in said air reservoir chamber and said air passages to produce a controllable air spring force on said inner pressure sleeve.