This invention relates to a winding device for a vehicle safety belt having a housing, a sleeve rotatable in the housing and spring-biased to wind up the safety belt, a ratchet wheel with ratchet teeth arranged at one end of the sleeve, counter teeth disposed on the housing, a catch wheel with catch teeth arranged between the ratchet wheel and housing and being displaceable into a locking position of simultaneous engagement with the ratchet teeth and counter teeth, and tension limiting means connecting the ratchet wheel for rotation with the sleeve supporting the safety belt and consisting of a torsion bar extending coaxially through the sleeve and connected at one end thereof with the sleeve and at the other end with the ratchet wheel.
During rapid deceleration of the vehicle, such as on impact with another object, the body of the passenger seated in the vehicle is thrown against the restraining safety belt, thereby subjecting the body to dangerously high forces. In safety belt winding devices, it is known that these forces may be dissipated through use of a torsion bar placed between the sleeve carrying the safety belt and the ratchet wheel which on impact becomes locked in engagement with the safety belt winding device housing, as shown in German Offenlegungsschrift No. 2,064,710, for example. When pre-determined, acceptable belt forces are exceeded, the torsion bar placed between the sleeve and ratchet wheel is twisted thereby absorbing energy.
However, it has been found that when the torsion bar is twisted, it undergoes an increase in axial length. The lengthening of the torsion bar may result in disengagement of the ratchet wheel from its locking position due to the lengthening torsion bar's lifting the ratchet wheel away from the locking catch wheel interposed on the sleeve between the ratchet wheel and the safety belt housing. Such disengagement seriously impairs the operability and effectiveness of the safety belt winding device as a whole.