Abstract: An acceleration sensor for a seat belt retractor of the type having an operating member, for example a pawl, engageable with a locking mechanism, for example a toothed wheel, the sensor comprising a pivoted driver situated below the pawl, and having a center of gravity located above its pivot so that it will tend to topple, a lifting surface on the driver positioned radially outwardly from the pivotal axis, and a yoke having its lower end engaging the lifting surface and constrained thereby, its upper end engaging the pawl and constrained thereby, arranged so that tilting of the driver about the pivotal axis lifts a portion of the lifting surface and in turn lifts the yoke, whereby the pawl is lifted to its wheel engaging position.