Abstract: A seat belt retractor having a web tension controlling mechanism (36) includes a spool (32) for holding seat belt webbing (11), a frame (30) supporting the spool (32) for rotation in winding and unwinding directions, and a pinion (78) supported for rotation with the spool (32). A gear (104) is rotated by the pinion (78) and stresses a coil spring (102) upon rotation of the spool (32) in the unwinding direction. The gear (104) has a spiral array of gear teeth (156) which moves the gear axis (106) radially relative to the pinion axis (60) and which thus changes the effective pitch diameter (d) of the gear (104) upon rotation of the gear (104) by the pinion (78). The gear axis (106) is further directed to move pivotally about a pivot axis (132) when the gear axis (106) moves radially relative to the pinion axis (60).

Abstract: A seat belt retractor includes a spool with seat belt webbing wound thereon. A frame supports the spool for rotation in a belt withdrawal direction or a belt retraction direction. A pawl engages ratchet teeth formed on end portions of the spool to prevent rotation of the spool in the belt withdrawal direction when a predetermined amount of seat belt webbing is withdrawn from the spool. A cam which has a multi-loop cam groove is rotatably driven by a gear train in response to spool rotation. A lever with a cam follower portion in the cam groove is pivoted by the cam to move the pawl into engagement with the ratchet teeth.