In a coupling (18) for a belt tensioner (10) in a vehicle comprising an input element (26), an output element (34), a coupling element (28) which is movably supported between an initial position and an activated position and in the activated position couples the input element (26) to the output element (34), and a control element (36) which upon movement of the input element (26) relative to the control element (36) moves the coupling element (28) between the initial position and the activated position, the control element (36) is coupled to an inertia mass (36).

A pretensioner and safety belt assembly may include includes a base member fixed to a vehicle, a torsion shaft having a first side and a second side rotatably supported on the base member, a torsion tube having a first end portion fixed on an external surface of the torsion shaft and a second end portion rotatably supported on the external surface of the torsion shaft wherein a belt configured to restrain an occupant is wound around an external surface of the torsion tube, a traction wire wound around an end portion of the torsion shaft on an opposite side to where the torsion tube is fixed to the torsion shaft in an opposite direction to a direction in which the belt is wound, and a pulling device configured to pull the traction wire to rotate the torsion shaft.

In a belt retractor (10) for a seat belt comprising a belt reel (12) onto which webbing (14) can be wound while being spring-loaded and comprising a tensioning device (16) which is adapted to act on the belt reel (12) in a winding direction (A), a control (18) is provided which is adapted to activate the tensioning device (16) when the seat belt is unloaded and not fastened.

A pretensioner and safety belt assembly may include includes a base member fixed to a vehicle, a torsion shaft having a first side and a second side rotatably supported on the base member, a torsion tube having a first end portion fixed on an external surface of the torsion shaft and a second end portion rotatably supported on the external surface of the torsion shaft wherein a belt configured to restrain an occupant is wound around an external surface of the torsion tube, a traction wire wound around an end portion of the torsion shaft on an opposite side to where the torsion tube is fixed to the torsion shaft in an opposite direction to a direction in which the belt is wound, and a pulling device configured to pull the traction wire to rotate the torsion shaft.

In a coupling (18) for a belt tensioner (10) in a vehicle comprising an input element (26), an output element (34), a coupling element (28) which is movably supported between an initial position and an activated position and in the activated position couples the input element (26) to the output element (34), and a control element (36) which upon movement of the input element (26) relative to the control element (36) moves the coupling element (28) between the initial position and the activated position, the control element (36) is coupled to an inertia mass (36).