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Belt pretensioners

Belt pretensioners


The belt tensioner is a device which takes up the slack in the front-seat belt straps in the event of a collision, thus reducing the forward movement of the seat occupant.

The belt pretensioner consists of a tensioned spring in an aluminium tube. This spring is connected to the belt reel shaft by means of a steel cable. In a collision, a mechanical sensor activates the spring so that it expands in the tube. The movement of the spring causes the belt reel shaft to rotate and so reel in the belt. As a result, the slack which the belt normally has is taken up and this appreciably improves the safety afforded by the belt in a collision.

If the system is activated, a noticeable noise will be heard as the belt is reeled in and out. In addition, the marking on the belt reel cable will rise up in the aluminium tube.

The belt pretensioner is provided with a safety catch to prevent its activation during fitting, removal and transit.

Apart from its sound-absorbing properties, sound- absorbing material located under and behind the belt reel protects it from splashes of anti-rust oil.