Patent ID: 7374157

Claim:
A manufacturing method of a spring assembly, for assembling an annular plate and a compression coil spring, the method comprising: forming a protrusion having a tapered portion that is folded inwardly on the annular plate; and inserting a punch, including a first portion having a larger diameter than an inner diameter of a tip end of the tapered portion, from the tip end side of said protrusion toward a plate portion of said annular plate and into the protrusion to expand at least part of the tapered portion, wherein: the expansion of the at least part of the tapered portion involves expanding a base portion of the protrusion adjacent the tapered portion and has a larger inner diameter than that of the tip end of the tapered portion, along a surface of an end turn of the compression coil spring, wherein the protrusion extends from the plate portion toward the tip portion, wherein said diameter of said first portion of said punch is smaller than an inner diameter of said protrusion adjacent to said plate portion.