METHOD OF FORMING A CASING FOR AN ELECTROCHEMICAL CELL

摘要

A casing (10) for cylindrical electrochemical cells, for example, alkaline cells or lithium cells. The casing (10) is characterized by having a non-uniform wall thickness. The casing comprises a cylindrical body (20) surface, an open end and an integrally formed closed bottom (30). A portion of the casing body (20) forms the peripheral edge of the casing at the open end (17) thereof. The casing body surface has a wall thickness which is less than the wall thickness of the casing bottom. The casin (10) has a peripheral edge which has a wall thickness which is greater than the wall thickness of the body surface. The peripheral edge wall thickness is desirably about the same or greater than the wall thickness of the casing bottom. The casing is formed by subjecting a sheet of metal to a series of discrete punching steps. A partially formed cup is punched through a die cavity in each step thereby progressively drawing the cup to a progressively reduced diameter and increased length. This is accomplished desirably without changing any portion of the cup's wall thickness. The cup is subjected to a finishing step wherein the wall thickness of the body surface is reduced without altering the wall thickness of the bottom. The wall thickness of the peripheral edge remains the same or is increased in the finishing step.