Patent ID: 8683837
Filing Date: 2014-04-01
Classification: B21D,Y10T

Abstract:
1. A method of forming a metal container of defined shape and lateral dimensions, comprising (a) disposing a hollow metal preform having a wall, a closed end and an open end in a die cavity laterally enclosed by a die wall defining said shape and lateral dimensions, with a punch located at one end of the cavity and translatable into the cavity, the preform closed end being positioned in proximate facing relation to the punch and at least a portion of the preform being initially spaced inwardly from the die wall; (b) subjecting the preform to internal fluid pressure to expand the preform outwardly into substantially full contact with the die wall, thereby to impart said defined shape and lateral dimensions to the preform, said fluid pressure exerting force, on said closed end, directed toward said one end of the cavity; and (c) translating the punch into the cavity to engage and displace the closed end of the preform in a direction opposite to the direction of force exerted by fluid pressure thereon, deforming the closed end of the preform, wherein the preform, as disposed in the die cavity before it is subjected to the internal fluid pressure, has a wall thickness gradient such that the preform wall thickness decreases progressively from said closed end toward said open end and such that outward expansion of the preform begins at the open end and progresses sequentially from the open end to the closed end.