{"id":1072,"date":"2018-11-23T17:15:07","date_gmt":"2018-11-24T00:15:07","guid":{"rendered":"http:\/\/2passdd.com\/Arizona-Defensive-Driving-School\/?p=1072"},"modified":"2018-11-23T17:15:07","modified_gmt":"2018-11-24T00:15:07","slug":"the-pyrotechnics-in-your-seat-belt","status":"publish","type":"post","link":"https:\/\/2passdd.com\/Arizona-Defensive-Driving-School\/2018\/11\/23\/the-pyrotechnics-in-your-seat-belt\/","title":{"rendered":"The Pyrotechnics in your Seat Belt"},"content":{"rendered":"

The most popular seat belt pretensioners designs today use pyrotechnics<\/b> to pull in the belt webbing. The diagram below shows a representative model.<\/h1>\n
\"seatbelt_pretensioner\"
When the gas is ignited, the pressure pushes the piston up to rotate the retractor.<\/figcaption><\/figure>\n

The central element in this pretensioner is a chamber of combustible gas. Inside the chamber, there is a smaller chamber with explosive igniter<\/b> material. This smaller chamber is outfitted with two electrodes, which are wired to the central processor.<\/p>\n

When the processor detects a collision, it immediately applies an electrical current across the electrodes. The spark from the electrodes ignites the igniter material, which combusts to ignite the gas in the chamber. The burning gas generates a great deal of outward pressure. The pressure pushes on a piston<\/b> resting in the chamber, driving it upward at high speed.<\/p>\n

A rack gear<\/a> is fastened to one side of the piston. When the piston shoots up, the rack gear engages a gear connected to the retractor spool mechanism. The speeding rack rotates the spool forcefully, winding up any slack belt webbing.<\/p>\n

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