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All About Seat Belts

The Wonder of Seat Belts

Do you know how seat belts work? We fasten our seat belts without having to think about it. However, every component of a seat belt plays an important role of helping to protect the vehicle’s passengers. Therefore, when riding in a car, always fasten you seat belts. Now we would like to tell you some of the fascinating things about seat belts.

How Do Seat Belts Work?

When the brakes are applied sharply or when the car is impacting something, the vehicle may be stopped, but due to inertia, the passengers motion will keep moving forward. Seat belts can help restrain that motion. Inside, the retractor has a silver-colored bead that is slightly larger than a ball bearing. The movement of the ball due to the vehicle deceleration that is occurring (either brake application or vehicle impact), results in an actuator moving up to lock the spool rotation, locking of the seat belts.

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Mechanism for locking the seat belt

  1. The silver-colored bead (ball sensor) moves forward
  2. The ball sensor pushes the braking claw (actuator) upward
  3. To lock the belt, the actuator engages with the lock gear, thus keeping any additional webbing from further extraction.

What Is a Pretensioner?

To help increase passenger protection, the Pretensioner reduces the slack between the seat belt and the passenger’s body during a collision. When a collision occurs, the pretensioner is activated and the power generated by the micro gas generator instantly recoils some webbing back into its housing. This enhances the effectiveness of the seatbelt by bringing the passenger as close to the seat as possible.

The sequence for this is as follows: The signal from the sensors is transmitted to the ECU (electronic control unit) which determines if a collision has occurred. If this is the case, a signal is sent to the pretensioners in the seat-belt system initiating the webbing retraction. The Pretensioner in the belt almost instantaneously winds webbing back into its housing, removing all slack.

Pretensioners may be installed in various places. In some vehicles, the Pretensioner is in the retractor. In other vehicles, the Pretensioner is part of the buckle assembly. Additionally, some vehicle may have both.

How Strong Are Seat Belts?

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The belt portion of the seat belt system is commonly called “webbing.” Approximately 300 polyester fibers are woven finely into a single belt. With this number of fibers, the strength of the belt has been measured to hold a weight of about three tons.

What Are Takata´s Newest Belts?

To help prevent collisions before they happen, Takata’s newest seat belts can alert the driver to impending danger.
A radar device installed in the front portion of the car measures both relative speeds and the distance between vehicles plus other related information. When there is a danger of collision, the car’s sensing systems gives the belt a light tug inward, two or three times to warn the driver of imminent danger. This early warning enhances the driver’s ability to apply the brakes and take evasive action before the collision takes place, thus increasing the probability the accident itself can be avoided.
When a collision is unavoidable, the system pulls the belt in to restrain the passengers securely.

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