Seat-belt retractor

A seat-belt retractor is provided wherein no further belt retraction is necessary to unlock the belt spool following a tensioning of the belt webbing. Specifically, the seat-belt retractor has a belt spool that is rotatably mounted in a frame and a coupling pawl that is pivotally mounted on one face of the belt spool. The drive wheel is mounted in the frame co-axially with the belt spool. The drive wheel has an annular internal toothing extending around the coupling pawl. The coupling pawl has a free end shaped with a coupling tooth or a pair of coupling teeth and is movable, in a tension-released condition of belt webbing, from an engagement position where the coupling tooth or teeth is or are engaged in a tooth gap or two adjacent tooth gaps of the internal toothing, to a release position disengaged from the internal toothing. The electric motor has an output shaft connected to the drive wheel through a self-locking gear transmission that inhibits rotation of the drive wheel other than through rotation of the output shaft of the electric motor. By virtue of the self-locking feature of the gear transmission, the coupling pawl with the annular internal toothing of the drive wheel constitute, in fact, in addition to the selective coupling function, an automatic locking mechanism for the belt spool. To enable the coupling pawl to be returned to the release position without further retraction of belt webbing and after a belt tensioning operation, an appropriate geometry of the toothings involved is selected.