Seat Belts

Many motorists may believe the most important safety system installed on an automobile is the supplemental inflatable restraints, commonly called, airbags. Although this system ranks high on the list of preventing injuries, it’s completely useless unless the passenger is fastened securely by the seat belt.

It is critical for drivers and passengers to be in the right position for the airbags to provide effective protection. This article covers the different types of seat belts found on both newer and older vehicles. Discover exactly what a pretensioner is and why they’re so important during an accident. Review some of the largest recalls related to seat belt problems on popular model cars and trucks.

Different Kinds of Seat Belts

All restraint systems fall into two basic categories of active or passive. An active system means the driver or passengers must complete an action to gain the benefit. An example is when a driver pulls a shoulder belt across his body and clicks it into the buckle. A passive system is one that works automatically. A properly operating airbag system is a prime example of a passive restraint.

Another example of a passive system would be the automatic style installed on Ford vehicles in the mid to late 80s. These automatically applied the restraint by running the buckle side across a motorized track at the top of the doors. For the most part this system was abandoned due to noisy and annoying operation.

How Seat belt Retractors Work

An automatic seat belt retractor conveniently stores the shoulder and lap belts when the buckle is released by the occupant. These can be spring-loaded or motorized, but will automatically coil the fabric belt around a cylinder. The operation of the retractor, allows for comfort when driving normally, but provides a lockup function that prevents the forward movement of the occupant during an accident.

This can be accomplished in several ways, but on older vehicles, a common method was using an inertia lock that sensed a sudden slowdown in vehicle speed to stop the fabric belt from uncoiling, thereby physically holding the driver in place.

Seatbelt Retractor Problems

Seat belt retractors can be mounted just about anywhere, but are often found mounted to the floor. With this vulnerable location come problems associated with dirt, spilled drinks, debris and foreign objects finding their way down inside. When this occurs, it results in a few common problems. Failure to retract is often attributed to this situation. Also a fabric belt that becomes folded can impede its ability to smoothly retract and can be a struggle to pull out when latching in passengers.

Pretensioning Seat belt Retractor Operation

Since the primary function of the seat belt is to hold the driver in place during a crash event, Vehicle manufacturers identified that removing any slack was beneficial. This led to the invention of the pretensioning seatbelt retractor, which automatically removes the slack and snugly pulls the driver into the proper position for an accident.

The two common types of pretensioner are the electric variety that depends on a motor to quickly tighten the belt. Another popular method is a pyrotechnic version that uses a small explosion in the retractor assembly to physically pull the belt tight. The activation of these automatic systems are triggered by the same crash sensors used to deploy the airbag.

Causes of Seatbelt Failure

Today, seatbelt failure due to malfunction is not common. However, there are some very real problems with seatbelt design, and seatbelt problems that could put you or your passengers at risk. Take a moment to learn a bit about causes of seatbelt failure. Being able to spot a seatbelt problem could save your life. Here are the most common causes of failure:

Not wearing the seatbelt properly: Most of the seatbelt design you see today is the three-point design, which has a conjoined sash and lap belt. However, some people, especially children, like to pull the sash part behind their backs or not wear the seatbelt at all. This is extremely dangerous. You should also wear the seatbelt properly, according to federal law and state laws, with the sash going from the center of your shoulder and across your chest to your waist. If the seatbelt is too big to be worn that way, your child should be in a child safety seat with a harness or use an adjustable holder for the strap. Lap belt designs alone are very ineffective.

Unlatching: There have been some cases of seatbelts coming unlatched (called inertial unlatching), which is a type of seatbelt failure that usually happens during a high-impact motor vehicle accident. One of the main ways inertial unlatching can occur is through false latching initially. With false latching, the seatbelt looks and sounds like it has clicked into place, but the release is actually only partially engaged or not engaged at all. You can avoid inertial unlatching seatbelt failure problems by tugging on your seatbelt a few times after you’ve secured it to make sure that the latch plate really is in place correctly. Of course, seatbelt latch failure can also occur even if it latches correctly the first time.
Seatbelt latch failure is a very serious problem. Not only can it cause accidents when you’re surprised by a seatbelt suddenly unlatching, but it can also cause you to become ejected from car. A high percentage of victims ejected from car due not survive.

Torn Webbing: Seatbelts are made with webbing, a material that is designed to withstand incredible forces. If this webbing tears, it is a result of a seatbelt defect and could cause seatbelt failure during a car crash. Under normal conditions, the webbing should stay intact in any survivable collision. It is important to check the belts carefully, looking for damage, which can happen over time. Again, you could be ejected from car if the webbing is torn.

Retractor Failure: Seatbelt designs all have retractors, which are meant to “lock” the webbing and hold you in place if there is an accident. However, if this device fails, it could result in extra slack. Even a few inches of extra slack could mean the difference between life and death during a car crash.


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