Dual level retractor for oblique or offset impacts

摘要

An energy absorbing seat belt retractor (10) for controlling protraction of seat belt webbing (24) during a collision is provided. The seat belt retractor (10) includes a frame (12), a spool (20) rotatably supported on the frame (12) having webbing (24) wound thereabout, a bifurcated spool shaft (22) having a first portion (52) and a second independently rotatable portion (54), a locking mechanism (90, 91) associated with each portion of the spool shaft (22), and a load limiting mechanism (41, 43) interconnecting each shaft portion to the spool (20). The locking mechanisms (90, 91) are independently and simultaneously actuable by vehicle sensors (86, 87) to selectively engage and prevent rotation of either one or both of the first and second shaft portions (52, 54) to initiate operation of either one or both of the load limiting mechanisms (41, 43) to effectively control the threshold input force level required to permit controlled protraction of the seat belt webbing (24).