80 20091206 chard-safety

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80 20091206 chard-safety

  1. 1. SE ATS AND RE STR AINTS Reinventing the seat and belt restraints. Ta king this fact e use of safety sponsive seat etermin ing factor in th d eceleration-re ty Comfor t is a d e concept – a enhancing safe tion, this new and uniqu in g so massively Y into considera a crash, in do osition during e N e T H e R L A N D s I M AG E S C O U R T e s Y O F C H A R D s AFeT cupant p – optimises oc CHeL COeN eN, CHARD K & mI s A F e T Y, T H sKeR ANK Heem AU T H O R F R S afety systems for seats and seatbelts are seemingly in the twilight stages of their lifecycles, with any improvements becoming more costly to implement and less effective, while all the time increasing vehicle weight. What is abundantly clear is that for any significant advances to be made in the future, an entirely new approach will have to be adopted. The Deceleration Responsive Figure 1: Seat/Seatbelt, or DRS (codenamed DRs-Albatross Albatross) is the result of critical in most forward and unbiased analyses of 50 years crash position. of dynamic testing experience at The chest TNO test facilities in Delft, the remains behind Netherlands. This fundamentally the pelvis different approach takes into consideration that comfort is one of the most important safety aspects. The compulsory wearing of a seatbelt is not the same as an occupant wanting to put on a seatbelt for safety and comfort. In itself, this requires a lot more effort from safety engineers – and maybe even an entirely different philosophy… The new concept With the DRS-Albatross concept from Chard Safety in the Netherlands, the seatbelt anchorages are relocated from the sides of the occupant to central anchorages on the vehicle floor, in front of and behind the seat (Figure 10). Essentially, this is a seat integrated 058 VISION ZERO INTERNATIONAL JANUARY 2010
  2. 2. within a seatbelt, rather than the other of the concept and promised a fruitful desired level of deceleration (0.8g), the way around. Deceleration forces are development project. inertia release becomes active. The more efficiently transferred as a result occupant is then prevented from of the light yet incredibly strong Seat lock moving forward during braking, and seatbelt webbing, allowing for three Under normal driving conditions, the moves only slightly in crash position lightweight seat sections that are free sitting section and backrest are locked but remaining in control of the car as moving (rotating) in their joints. The to one another. Meanwhile, an ‘inertia the lower legs and eyes remain in the result of this unique design is an almost release’ for higher deceleration values same position. This effect will be ideal line of force and optimal use of alters the seat from a solid construction experienced as comfortable and is a the vehicle’s deceleration. to one with supporting seat sections major safety aspect as the occupant during a crash situation, if the does not move toward a later inflating The principle occupants are wearing their seatbelts. airbag. According to papers written by The seat sections move in a trapezium- As a consequence, what you have is a Waldemar Czernakowski in the early type action with the front leg and deceleration-responsive seat that also 1990s, [1] pre-impact braking occurs the backrest being the vertical has the potential to interact with in more than 60% of frontal crashes. components. The rigid and enforced information available from early With the avoidance of a collision, the position toward one another is assured warning sensor systems. seat returns to its normal position and as a result of the webbing of the seatbelt With the electromotor in the seat- supports the acceleration pressure. being threaded through the frames of adjustment system, some 500ms can be the seat sections. Under deceleration used for position changes with a non- Crash behaviour forces, the webbing route lengthens destructive pretension and positioning The crash behaviour of the seat and provides an excellent opportunity action, as opposed to the occupant can be predetermined exactly, and to program desired position changes losing control and the destructive is dependent on the characteristics of the occupant and seat during pretension at some 6-10ms. This of the webbing, film-spool and decelerations with a desired crash feature comes as a natural result of the elongation. Within the margin position sequence. Dynamic principle without extra components. of cushion pressure and body comparison tests (according to The prospect of using this feature deformation, the occupant cannot but ECE 16) showed the potential in braking is exciting (Figure 8). At any follow the seat sections, so is therefore “ESSEntially thiS iS a , SEat intEgRatEd within a SEatbElt RathER than , thE othER way aRound” Figure 3: sitting section is adjustable in height Figure 2: Rear impact forces are concentrated at the front anchorage, so no whiplash VISION ZERO INTERNATIONAL JANUARY 2010 059
  3. 3. SE ATS AND RE STR AINTS only subjected to predetermined forces. Figure 4a and 4b: The forces between the occupant Compulsory seatbelt usage brings Reaction forces – delivered at the Conventional and seat sections are balanced – in fact, about a responsibility for the safety webbing loop connection to the rear (top) crash the seat sections are under reverse force. industry. Clearly the goals of Vision anchorage – can only be translated behavior versus This element proved to be difficult to Zero can only be met if the crash safety in a larger route length and thus behavior in a understand, but is important when world makes efforts to improve the only in forward movement as DRs-Albatross considering unbelted rear passengers. comfort of specific safety features. opposed to higher forces. (above), i.e. The DRS-Albatross principle This new approach makes solving Clearly, the deceleration of eradicating also provides protection in rear-end problems simply easier and responds the occupant and the transfer of whiplash crashes. A resisting tongue prevents to any criticisms of the past. Seatbelts deceleration forces (with the help of the pelvis from moving up and the have done a great job over the years, the lower body ligaments, i.e. buttocks) run of the seatbelt inward at the but comfort matters and is essential to the sitting section also causes an shoulder will provide more control in the desire to get people to actually increase of the webbing route. As the over the occupant. The majority seek the protection of the seatbelt. sitting section is pulling directly on the of energy absorption will come This new concept actually opens rear anchorage and is independent from from deformation of the vehicle and up new possibilities. the forces in the webbing straps to the Figure 5: seat some will come directly from the occupant, it means that the forces on back stays with deformation of the sitting section and Specific characteristics those straps are significantly lower. occupant in backrest. The front-end anchorages, The general free space above the Note also that the vertical forces in crashes, in doing meanwhile, take almost all deceleration vehicle floor increases dramatically, the spinal cord are substantially so maximizing forces. This is a significant difference but car manufacturers should happily lower as a result of a more upright space for to anything existing in the field – it is accept the additional carpeting costs. crash behaviour. occupant behind impossible to overstretch the neck. At first sight, the connection to the rear anchorage may seem questionable in terms of access, but in actual fact it doesn’t really disturb entering and exiting the car. Support for the upper legs: Just in front and above the cross members in the sitting section, a webbing strap is placed for strength and preventing injury during a crash. Together with the strap section between the anchorages, it provides very strong support for the upholstery (Figure 6). Rebound protection: The outside support near the head provides extra comfort in sleeping positions as well as protection in crash rebound. The B-pillar poses a serious problem in off-centre crashes (EuroNCAP). Seatbelt anchorages: The format of the lower seatbelt anchorages have been changed (Figure 7), in that the webbing is threaded rather than stitched. Apart from the extra strength that this provides for the sitting section, 060 VISION ZERO INTERNATIONAL JANUARY 2010
  4. 4. SE ATS AND RE STR AINTS it allows the effective anchor point to move forwards. Indeed, this makes the “ClEaRly thE goalS of ViSion system much more comfortable for children and females. In fact, for ZERo Can only bE mEt if thE children of school-going age, this concept can meet the requirements in CRaSh SafEty woRld makES EffoRtS R44 without booster seats. The large adjustment of seat height towards the to impRoVE thE ComfoRt of headrest will be a desirable feature. Height adjuster: The shoulder strap SpECifiC SafEty fEatuRES” arrangement seems a great relief for all engineers trying to accommodate variations in posture for different-sized the angle of the backrest changes to occupants. This selected arrangement provide support in sleeping positions adjusts itself, even in moving sideways. and it prevents sliding ‘down and Figure 6 (left): Armrest and buckle reach ability: under’, in doing so relieving the tension Upper leg Although the armrest is reduced in size, required in the lower body to prevent support for it is nevertheless still effective where it it. From a reasonable sleeping position transfer of counts – for the elbow and in respect still protection will remain available. deceleration of sitting down and getting back out No head impact on seatback in front: forces of the seat. The sitting section is In fact it makes the use of three-point adapted so the belt buckle can be more seatbelts for seating positions with easily reached. In fact, there is a large a seat in front quite different. The Figure 7 (left): space for it in the sitting section. distance between seats can be much Adjustable height Retraction forces: The retraction forces smaller because there is enough leg for the sitting and shoulder strap position are major space anyway. In forward crashes the section reasons that people choose to ignore backrest in front has also gone forward compulsory seatbelt laws. However, severely and crashing the head onto in this design, the webbing runs the backrest in front is no longer centrally between the seatback cushion an issue. For coaches (Figure 5), and the seat frame, so simply leaning the principle provides much comfort back will cancel any retraction forces, and safety while savings in weight while any slight deceleration caused close to 1,000kg. ‹ by braking will restore the retraction force immediately. References Headrest position: The lower back Czernakowski, W, The effects [1] and sitting construction have become of pre-impact braking on dynamic one piece. Depending on the length test performance of child restraint Figure 8 (left): of the occupant, the sitting section systems (CRS) in frontal impacts slight changes can be adapted, which improves Czernakowski, W. & Otte, D, The of position the head space as opposed to effect of pre-impact braking on the during braking adjusting the headrest. performance of child restraint systems Sleeping: In the selected construction, in real-life accidents and under the angle of the sitting section versus varying test conditions eCe 16 pulse Albatross Deceleration curve occupant Deceleration difference occupant/vehicle Current difference bandwidth in deceleration differences Albatross indications: • Chest displacement 175mm • Pelvis displacement 140mm • Force on rear anchorage 33kN 30g • effective transfer of forces Figure 10: New to the vehicle 93% anchor position Difference in deceleration in arrangement pelvis and chest are marginal Figure 9: The makes the difference vehicle a in deceleration personal forces between energy absorber occupant and vehicle interior is reduced 30ms dramatically VISION ZERO INTERNATIONAL JANUARY 2010 061

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