Patent ID: 6662427
Filing Date: 2003-12-16
Classification: B21K,B23P,Y10T

Abstract:
A method for forming a cavity structure provided with a thin bottom plate comprising the steps of:plastically deforming a part of a metal plate so as to form a cavity having a profile of a predetermined shape on a first surface side of the metal plate, said cavity having a bottom surface formed in a rugged shape provided with subsections different from each other in depth; simultaneously forming a protrusion on a second surface side of the metal plate, which is a rear side of said first surface side, by shifting an amount of metal corresponding to said cavity into said protrusion, said protrusion having a rugged shaped top surface with a substantially similar configuration to said bottom surface of said cavity; forming a coupling section for keeping said protrusion integral with the metal plate at the circumference of the protrusion by making an outline of said protrusion smaller than an outline of said cavity; and removing said protrusion from the metal plate so as to make said second surface side of the metal plate flat and to form said thin bottom plate of said cavity while retaining said coupling section.