Swedish aeronautical engineer, Nils Bohlin patented the “V” scheme with three attachment points in 1958, still used today on road cars. Volvo made it available to all manufacturers, making a fundamental contribution to reducing physical damage due to accidents
Don’t hate that screeching noise that stuns you as soon as your car moves; don’t wake him up, because the gesture necessary to silence him – fastening your seat belt – can save your life. Throughout the world and over the years, many lives have been saved, thanks also, but perhaps above all, to a gentleman who few know, but who is always worth remembering: Nils Bohlin, the creator of the three-point harness. A simple but fundamental passive safety tool (the one that intervenes at the time of an accident), today perfectly integrated with other advanced devices such as airbags.
a life for safety
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Nils Bohlin was an aeronautical engineer born in 1920 in Härnösand, Sweden, employed in the early 1940s by Saab (Svenska Aeroplan Aktiebolaget) which, at the time, was known for its airplanes and not for cars, the production of which would only begin with the 92 of 1949. In 1955 Bohlin became responsible for the development of ejection seats and other safety devices for airplane pilots, but his interest was more aimed at protecting their bodies in cases of high decelerations; this attitude led him to accept, in 1958, a job offer from the company Volvo as a security specialist. Already in the second half of the 1950s, the Swedish company had begun to develop solutions to avoid or reduce the consequences of car accidents, such as the collapsible steering column, the padding of the dashboards and the seat belts for the front seats with two attachment points (therefore, no longer just abdominal): the latter, with a diagonal development, had been introduced by Volvo already in 1957 and had proven effective, but could be improved; the buckle, in fact, was located right at the height of the passenger’s ribcage, with the risk that, at the moment of an impact, it would damage the internal organs of the body, instead of protecting them. Gunnar Engellau, President of Volvo at the time, he was a person particularly sensitive to the issue of vehicle safety, having lost a relative in a road accident, and this led him to ask engineer Bohlin to work on improving the effectiveness of seat belts.
the solution
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“I realized” – Bohlin said – “how both the upper and lower parts of the body had to be held securely in place using a band placed diagonally across the chest and a at the pelvis; the seat belt also needed a fixed anchor point for the buckle placed as low as possible, on the side of the occupant’s thigh, so as to be able to correctly restrain the body in the event of a collision. It was just a matter of finding a simple, effective solution, not too expensive and which could be attached with just one hand”. A solution that arrived in 1958, with the patent application for a new three-point attachment belt, capable of satisfying the fundamental requirements of the Swedish engineer: to provide a horizontal band to protect the hips and hips and a diagonal for the torso, both arranged in the most correct way from the point of view of the physiology of the human body, i.e. transversely with respect to the hips and ribcage, with a of lateral anchorage placed at the bottom, next to the seat, the geometric shape of the belt resembled a “V” facing the floor of the car; once pulled by hand and fastened, the solution, which proved to be much more effective (up to 75%) than the previous three-point anchorage belts with a “Y” shape, was made available by Volvo to all car manufacturers. Bohlin – who did not perceive any benefit from this – prevented them from adopting it.
rapid spread
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However, it was always Volvo that adopted the belt scheme devised by the Swedish engineer first, installing them in the 1959 on P120 (also known as Amazon) e PV 544 intended for Scandinavian markets; a few years later, in 1963, it was the turn of all the cars like the P130 intended for the United States and other markets. As for the rear passengers, although the company had provided attachment points for them as early as 1958, it was not until 1967 that buyers accepted their usefulness, which is still too little understood today – decades later and despite the obligation to use them introduced in Italy with the Highway Code of 1992. As for Bohlin, his career at Volvo continued in the field of safety, under the sign of the need to protect cars against side impacts, one of the weakest points of the body structure even today; his studies in the 70s led to the creation of SipsThe Side impact protection systema system that Volvo was among the first manufacturers in the world to adopt. Bohlin, who retired in 1985 but remained active as a consultant, passed away at the age of 82, after having been awarded countless awards and having been admitted, in 1989, to the Hall of Fame international for American safety and health and, subsequently, for those of the automotive sector. Death overtook him September 26, 2002on the very day he was admitted to the Hall of Fame American inventors.
integrated systems
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Since their introduction, three-point seat belts have changed little overall in their forms and methods of use. One of the most significant improvements was the adoption of the automatic winder, which they initially did not have: this forced the user to adapt them to their own size, without obtaining freedom of movement once the operation was completed. The new system includes the presence of a reel on which the belt is wound, a return spring that provides rewinding, an inertial sensor and locking teeth; the belt can thus be easily widened and rewound and is held in a position close to the body. In the event of a strong deceleration, due to braking or impact, and an overturning, the inertial sensor immediately blocks the coil; a load limiter avoids excessive pressure on the chest, allowing the belt to slide in a controlled manner. Precious was the introduction of the adjustment of the belt attachment point on the upright, which allowed the diagonal strap of the belt to be positioned correctly on the shoulder and chest (even in the absence of seat height adjustment). Del 1981 it is, instead, the introduction by the Mercedes on his flagship S class of the pyrotechnic pretensioner, later adopted on a large scale by other manufacturers: a small pyrotechnic charge is activated within about ten milliseconds, rewinding the belt until 15cm in the very early stages of an accident and ensuring that the body adheres to the seat, without being thrown forward by the sudden deceleration. Starting from the 1980s, the combination of the three-point seat belt with inertia reel with airbags (initially only the driver’s, then more and more, up to the fifteen often present on cars today) has made all our cars much safer.
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