Patent ID: 6526799
Filing Date: 2003-03-04
Classification: B21D,H01M

Abstract:
A method of forming a cylindrical casing for an electrochemical cell comprising the steps of:(a) punching a sheet of metal through a cavity in a first die within a first punch step by the stroke of a first metal punch applied to a surface of said sheet thereby drawing said sheet into a cup shape having a cylindrical body surface, a closed end and an open end, wherein the wall thickness of said body surface and said closed end is the same as the thickness of said sheet of metal, and (b) transferring said cup to an intermediate punch step and punching said cup through a cavity in an intermediate die within said intermediate punch step producing a cup drawn to a longer length and smaller diameter than the cup produced in step (a); (c) transferring said cup to another punch step after step (b) and punching said cup through a cavity in another die within said other punch step by the stroke of another metal punch contacting the inside surface of said cup to produce a further drawn cup having a cylindrical body surface, a closed end and an open end; wherein said cup is drawn to a longer length and smaller diameter as it passes through said other die; wherein the wall thickness of said body surface of said further drawn cup is less than the wall thickness of the closed end thereof; and wherein a stepped peripheral edge of said further drawn cup is formed during said punching through said other die; said peripheral edge integrally extending from said body surface at the open end of said cup; and wherein the inside diameter of said peripheral edge is greater than the inside diameter of said body surface of said further drawn cup and said peripheral edge has a wall thickness greater than the wall thickness of said body surface.