Patent ID: 7849573

Claim:
An apparatus for riveting two or more sheets together, comprising: a punch for driving a self-piercing rivet toward and into the sheets; a die having a rounded tip portion, a circular platform portion and a lip portion, wherein the tip portion tapers radially inwardly in the direction of the punch, the platform portion forms a relatively flat surface facing the punch for limiting downward deformation of the sheets and the lip portion extends radially outward from the longitudinal axis of the die; a plurality of blades are assembled around the tip portion and the lip portion, wherein the blades are retained, in part, by the lip portion; a relief cavity is defined by the die and the plurality of blades, the cavity provides space for local deformation of the sheets; and a blade collar engages the blades for resiliently biasing the blades inwardly towards the tip portion, wherein the punch drives the rivet into the sheets deforming a mating portion of the sheets between the punch and the die into the cavity which causes the blades to move radially outward from the tip portion, and thereby expanding the cavity to reduce reaction force applied by the blades to the mating portion that is deformed into the cavity.