A seat belt retractor with a pretensioner, comprises a preferably gas propelled drive means 6 to linearly move a rack 25 in a first direction, and rotate a meshing pinion gear 21 and connected rotary drive member 12 in a first direction of rotation. A normally inactive clutch mechanism 30 transmits motion between the rotary drive member 12 and a belt take-up spindle 4 when the drive member rotates, in the first direction of rotation. As shown the clutch mechanism 30 is driven through step-up epcyclic gearing 35. <IMAGE>
