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SEAT BELTS

Seat belts are your FIRST line of defense against injury in a crash.


About Seatbelts - History - Pretensioners - Post Collision Repair

About Seatbelts

Seatbelts work by limiting movement of the body, when your vehicle has a sudden change of speed or direction. They keep you positioned in your seat, so you don't bounce around or get thrown from your vehicle. This positioning is also what is used to increase the effectiveness of the Airbag.

Modern seatbelts use a three point anchorage system to accomplish this.

This is not a new development.

In 1958 a VOLVO engineer developed this system.
Prior to the three point system, severe head, neck and chest injuries were common in collisions. The addition of the shoulder harness has had a dramatic impact on reducing these injuries.

The front lap belts are anchored on the door side of the floor of the vehicle and to the floor in the center of the car next to the seat back. Modern belts have the shoulder belt attached to the end of the buckle which runs up the side of the vehicle to an anchor point behind the front seat and contain a pretensioner. When you buckle up you pull the belt across your body and insert the belt into the receiver in the middle of the car. Wearing your Seatbelts keeps you in the best position to benefit from the Airbag when a collision occurs.

American Seat Belt History

  • 1947 The first time seat belts were offered in a American car was the Tucker.
  • The state of the art then were Lap belts.
  • 1956 Ford introduces seat belts in American cars
  • 1964 Seatbelts became a "standard" feature in American cars
  • 1966 Rear Seatbelts became Standard
  • 1967 Front Seatbelts became Mandatory
  • 1968 Shoulder Belts became Mandatory
  • 1969 Headrests became Mandatory
  • 1973 GM installs air bags in fleet of Chevrolet Impalas
  • 1974 General Motors offers the first air bags in its 1974-1976 Buicks, Oldsmobiles and Cadillacs
  • 1986 Ford offers the airbag as an option on the Tempo
  • 1991 Driver Airbags are made Mandatory

Pretensioners

Pretensioners are incorporated into the belt assemblies to remove slack from the seat belt during a collision. Within milliseconds of a crash, the pretensioner is activated and increases the tension of the seat belt system around the occupant. This is what keeps you from bouncing around and keeps you in the proper position to benefit from the airbag if the crash is severe enough to trigger them. It contains an inertial reel with a pendulum device that senses sudden deceleration and automatically locks the belt in a crash. Currently there are three types of pretensioners in use today.

  • Mechanical
    These use an inertial reel with a pendulum device that senses sudden deceleration to lock the belt.
  • Electrical
    These are activated with a sensor that may or may not be tied into the Airbag circuits depending on the manufacturer.
  • Pyrotechnic
    These are activated with a sensor and contain an explosive charge to lock the belt in place. These are the most high-tech and the most expensive.

Post Collision Repair


In almost ALL cases, the seat belts will require replacement. This is because they are stretched out during the crash, or in the case of the electric and pyrotechnic pretensioners, certain components are One Time Only Use Components.


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