HEADRESTS. HOW DO THEY WORK?
It is common knowledge that headrests are designed to protect passengers when striking the neck from behind. This useful invention was massively used in vehicles as early as 1970. However, manufacturers have not yet been agreed on their best design. What kind of headrests are there, what is the difference and how to set them up properly?
During the rear-end collision it is likely to receive a so-called whiplash injury. The headrests are designed to protect both drivers and passengers from the head and neck injuries. The introduction of such seemingly simple preventive measure was not as easy. Of course, no one organized mass boycotts when looking at auto companies advertising headrests, as it was with the air bags and even seat belts. Still, with the headrests it was at least convenient, and at best – safer. But car manufacturers didn’t introduce this useful “function” overnight. So, driving early Alfa Romeo Montreal or Ford Taunus was not at all as safe as modern Hyundai Tucson or Toyota Camry.
The first thing the professionals noticed was the size of the headrests and the ability to adjust them. The first headrests which due to the small size, acted as “neck breakers”. Therefore, manufacturers started making them larger, and also provided for adjustment of the height, and later – the slope. The increase in the size of the headrests contributed not only to the safety of the front passengers but also to the enjoyment of the back seat ones, as now it is possible to install monitors into them.
The first tests with mannequins in the clashes were carried out only in the 1980s. The pioneer was the Mercedes-Benz. This was the major impetus for the further study and development of headrests.
According to the seat mounting structure it is possible to distinguish individual and integrated headrests. The integrated ones are most commonly used in motorsport and sporting modifications of cars.
Integrated headrests paralyze the freedom of movement a bit, but are considered safer. It is worth mentioning that the latter statement is true only in the case if the upper part of the seat is on the same level with the vertex.
Up until the mid-1990s, headrests were passive and their effectiveness depended only on the correct setting. But already in 1997, Saab introduced the first car equipped with active headrests. The mechanism was simple and reliable – the lever system was adjusted in the front seat which under the weight of the head moved forward. Mechanical systems of headrests are often referred to as reactive.
Mechanical drive of the active headrests first appeared on the Saab 9-3 and 9-5. The system was called Saab Active Head Restraint.
In the 2000s, thanks to the development of electronics engineers taught headrests operate not only during, but also before the accident. As soon as the control unit is paired with rear sensors detects a dangerous situation, electric headrests are pushing towards the head. Such systems exist, for example, in BMW, Lexus, Mercedes-Benz and crossover model like Nissan Rogue. It is noteworthy that the effectiveness of active headrests in comparison with the passive ones has not yet proven. Moreover, Volvo, which was one of the pioneers in their latest models renounced active headrests, preferring the careful selection of materials and the correct fitting of the profile and shape of the chairs.