Energy absorbing seat belt retractor having a torsion bar

Abstract

A torsion bar (50) and seat belt retractor (20). The torsion bar (50) has a circular cross section where the torsion bar is formed as a cold headed extruded part and wherein the grain structure of the metal is aligned along the axis (axial direction) of the bar generally in the center of the bar and the grain structure smoothly diverges from the axial direction near an end formation (52a,b). The torsion bar is later annealed and twisted about 180 degrees. The seat belt retractor (20) includes: a frame (22) to rotationally support the torsion bar and spool (30). The torsion bar (30) is characterized by an elastic deformation zone and a sharp onset into a plastic deformation zone. The spool is operatively connected to rotate with the torsion bar. The retractor also includes a locking device, activated during a vehicle accident and operatively linked to the torsion bar for preventing one side of the torsion bar from rotating while permitting the other side and the spool to rotate once loaded by the occupant.

Dependencies are inferred from the claim text.