METHOD OF MOLDING CIRCULAR SHELL AND CIRCULAR SHELL MOLDED THEREBY

摘要

PURPOSE: To provide a method for easily forming a seamless outer shell for a toroidal shaped hybrid inflator for an air bag inflation system from a sheet blank at a low cost and a toroidal shaped shell formed by this method. CONSTITUTION: The method for forming the seamless toroidal shaped outer shell for the air bag inflator from the flat blank sheet is provided with a stage for cutting the sheet to a suitable length and width, a stage for setting the cut sheet to a progressive die and a deep drawing stage for forming a cup shaped blank 12 having the shapes corresponding to the lower half part of the toroidal shaped shell and the side wall 16 rising therefrom by deep drawing the sheet. The method includes a stage for trimming the excess material at the peripheral edge of the opening end of the cup shaped blank, a stage for simultaneously increasing the thickness of a region 28 near the peripheral edge while forming the upper half part of the toroidal shaped shell by drawing the upper part of the side wall 16 inward by pressing and a stage for forming a hole at the base surface of the blank.