Seat belt retractor with two tensioning devices

Abstract

A self-blocking belt retractor has an emergency tautening device, which is provided for the belt shaft and which can be tripped, in particular, during an accident, and has a second tautening device, which is also connected to the belt shaft and which is designed as a reversibly operating pre-tautening device. The invention is characterized in that the emergency tautening device ( 15 ) is designed to work at a higher rotating speed than the rotating speed produced by the pre-tautening device ( 11 ), and the coupling ( 13, 17, 20 ) between the pre-tautening device ( 11 ) and the belt shaft ( 14 ) is designed in such a manner that after the emergency tautening device ( 15 ) is tripped, the belt shaft ( 14 ) thereby set in a faster rotating motion brings the coupling ( 13, 17, 20 ) back into its releasing position whereby releasing the coupling connection between the belt shaft ( 14 ) and the pre-tautening device ( 11 ).

1 . Self-locking belt roller with an emergency tensioning device for the belt shaft which can particularly be triggered in case of an accident and with a second tensioning device designed in the form of a reversibly- operating preliminary tensioning device which is also connected to the belt shaft, whereby a device is provided for ending the tensioning process effected by the pretensioning device when the emergency tensioning device is triggered, characterised in that the emergency tensioning device ( 15 ) is designed with a greater rotational speed than the rotational speed created by the preliminary tensioning device ( 11 ), and the coupling ( 13 ,  17 ,  20 ) is formed between preliminary tensioning device ( 11 ) and belt shaft ( 14 ) in such a way, that following triggering of emergency tensioning device ( 15 ), the belt shaft ( 14 ) which is thereby caused to rotate more rapidly leads coupling ( 13 ,  17 ,  20 ) back to its release position and therefore cancels the coupling connection between belt shaft ( 14 ) and preliminary tensioning device ( 11 ).  
   
   
       2 . Belt roller according to  claim 1 , characterised in that the coupling between belt shaft ( 14 ) and preliminary tensioning device ( 11 ) consists of a coupling bell ( 17 ) connected in fixed fashion with belt shaft ( 14 ) and supplied with inner teeth, and of toothed disc ( 20 ) located on the take-off wheel ( 13 ) of preliminary tensioning device ( 11 ) which is capable of being triggered so as to engage in the inner teeth ( 22 ) of coupling bell ( 17 ), whereby toothing ( 23 ,  24 ,  25 ,  26 ) of coupling bell ( 17 ) and toothed disc ( 20 ) are harmonised with each other in such a way that if the coupling bell ( 17 ) is at a standstill or is rotating more slowly that coupling bell ( 17 ) turning take-off wheel ( 13 ), blocking occurs in the winding direction and if the coupling bell ( 17 ) rotates at a higher speed than the take-off wheel ( 13 ), tooth flanks ( 26 ) of inner toothing ( 22 ) of coupling bell ( 17 ) push the toothed disc ( 20 ) out of engagement with the allocated tooth flanks ( 25 ).  
   
   
       3 . Belt roller according to  claim 2 , characterised in that the toothed disc ( 20 ) is arranged in a slidable manner in a recess ( 19 ) formed in the take-off wheel ( 13 ) between a release position inside the contour of take-off wheel ( 13 ) and a blocking position projecting over the circumference of the take-off wheel ( 13 ) and which is held in the release position by a friction element ( 18 ).  
   
   
       4 . Belt roller according to any of  claims 1  to  3 , characterised in that the pretensioning device exhibits an electric motor ( 11 ) working in reverse as a drive.  
   
   
       5 . Belt roller according to any of  claims 1  to  4 , characterised in that the emergency tensioning device ( 15 ) is provided with a pyrotechnic drive.