Webbing is the part of the seat belt in contact with the passenger that receives and softens the shock of an impact. It is made of polyester and woven from about 300 warp strands and one weft strand. The width of the webbing is about 48mm and has a tensile strength sufficient to support approximately three metric tons.
To encourage all passengers to fasten their seat belts, Takata pursues excellence in all aspects of webbing, including the fiber materials, coating materials, method of weaving, and elongation, with the aim of giving seat belt users a feeling of being held gently.
The retractor is a winding mechanism that allows the seat belt webbing to be withdrawn and brought back into its housing. It also serves to lock up in the event of a collision to help restrain the passenger. The retractor is usually installed either in the pillar section* of the car or in the seat. It has two sensors. One sensor locks the seat belt webbing when the car decelerates quickly or accelerates faster than a certain speed. The second sensor locks the extraction of webbing when it is pulled out at a faster rate than normal movement. Recently developed retractor models have motor drive functions and can control the winding of the webbing into the housing, thus adding to the "User-Friendly" aspect of our seat belt.
*The car´s pillar sections support the roof of the vehicle.
The tension reducer is a device that lessens the feeling of restraint and confinement when the seat belt is fastened. It helps reduce the force applied to the winding of the webbing around its spool.
In the event of a collision, the pretensioner is a device that instantly retracts some of the webbing to remove the slack between the passenger and the webbing. The reduction in space helps secure the passenger in the seat. This enhances the restraining features of the seat belt system. Pretensioners can be installed in various assemblies in the vehicle, including the retractor, the buckle, and even the lap anchor section (using lap pretensioners).
The pretensioner is usually activated by the force generated from the emission of gases. The force of the gas causes the webbing to rapidly retract, which tightens the seat belt around the passenger.
Load Limiter (Force Limiter)
When an impact occurs, the force limiter helps control the force exerted by the seat belt on the passenger. In recent years it has become common practice to protect passengers from the shock of accidents by having load limiter devices in seat belts and algorithms to determine the appropriate level of air bag deployment. For seat belts, the load limiter helps prevent the force exerted on the passenger by the webbing from becoming too strong. It effectively controls the degree of motion of the occupant to within a limited range while also relieving pressure on the passenger´s chest.
In recent years it has become common practice for pretensioners to be installed. They help to keep the force load levels transmitted to the occupant during a collision at a certain maximum level.
Motorized Seat Belt (MSB)
The Motorized Seat Belt (MSB) is a recently developed seat belt system now being installed in some automobiles. It is equipped with a motor in the retractor and alerts the driver to potential dangers through the movement of the webbing. When the car´s radar device, mounted in the front portion of the car, detects a potential hazard (which includes combining the distance from the car in front, the relative speed of the car, and other information), it warns the driver by lightly pulling two or three times on the webbing. When a collision is unavoidable, the MSB automatically retracts the webbing to eliminate any slack between the passenger and the seat belt. This enhances the restraining function of the seat belt and thereby, possibly reducing the seriousness of injuries.
In addition to this function, MSB also has the following three additional features:
- When sensors detect sudden braking, sudden movements in the steering wheel, or sideway movements, the webbing retracts automatically and helps control the posture of the passengers.
- When the passenger sits down, it is easier to extract the webbing. Also, as the seat belt is fastened, it automatically removes some of the slack in the webbing. The occupant may then have a reduced feeling of being restrained and be more comfortable.
- When the seat belt is unfastened, the motor assists rolling the webbing back into its housing.
When the seat belt is fastened or unfastened, the tongue, which is attached to the webbing, is inserted into or removed from the buckle. The buckle is designed to hold the tongue firmly and allows the seat belt to be fastened and unfastened with very little force. In an emergency situation, it is designed so another person can easily remove the tongue from the buckle and free the passenger.
Tongue Plate (Latch Plate)
The tongue is a connecting fitting, attached to the end of the webbing that fits into the buckle to secure the seat belt.