SEAT BELT WITH PRE-TENSIONER
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The seat belt pre-tensioner is built into the driver's and passenger's front seat belt retractor.
Upon front impact the pre-tensioner ignites the gas alternator and emits gas with the SRS-ECU signal when the front impact sensor, attached to the front of the body, detects an impact that exceeds the thresh-hold. The gas pressure moves the ball in the pipe and the balls come in contact with the protrusion of the ring gear, push the ring gear and then it is interlocked with the pinion. The ring gear rotation forces the pinion to turn the spool toward the belt wind direction to wind the webbing.