UNIT IIISAFETY EQUIPMENTSSeat belt, Regulations, Automatic seat belt tightener system, Collapsible steering column, Tiltable steering wheel, Air bags,Electronic system for activating air bags, Bumper design for safety.

Seat Belt RegulationsSeat belt legislation requires the fitting of seat belts to motor vehicles and the wearing of seat belts by motor vehicle occupants.In Australia, the use of seat belts by all vehicle passengers is compulsory. The states of Victoria and South Australia introduced a requirement for belt anchorages in 1964, although not for the belts themselves.[In 1970, the use of seat belts by vehicle occupants was made compulsory in the state of Victoria, followed by the rest of Australia and some other countries during the 1970s and 1980s. All provinces in Canada have primary enforcement seat belt laws. Ontario was the first province to pass a law which required vehicle occupants to wear seat belts in 1976.In the United Kingdom, seat belts must be worn at all times if they are fitted to a vehicle. Passengers may be exempt from wearing a seat belt for different reasons. Since September 18, 2006, children travelling in the UK must also use an appropriate child seat in addition to the standard seat belt, unless they are 12 years or over and/or have reached at least 135 centimetres (53in) in height.

continuedIn the UK, a requirement for anchorage points was introduced in 1965, followed by the requirement in 1968 to fit three-point belts in the front outboard positions on all new cars and all existing cars back to 1965. In India, all cars manufactured after March 25, 1994 are equipped with front seat belts. The rule was extended for rear seats in 2002. The usage of seat belts is to be implemented by the respective states with most states making seat belt usage for front seat passengers mandatory in 2002. Older vehicles that did not have seat belts originally were exempted.

Effects Studies by road safety authorities conclude that seat belt legislation has reduced the number of casualties in road accidents.Experiments using both crash test dummies and human cadavers also indicated that wearing seat belts should lead to reduced risk of death and injury in car crashes.

Seat Belt Regulations in IndiaVehicle, in which seat-belts have been provided, it shall be ensured that the driver, and the person seated in the front seat or the persons occupying front facing rear seats, as the case may be, wear the seat belts while the vehicle is in motion.Rule 125 (1) requires the manufacturer of every motor vehicle other than motor cycles and three wheelers of engine capacity not exceeding 500 cc, shall equip every such vehicle with a seat belt for the driver and for the person occupying the front seat. Rule 125 (1A) requires the manufacturer of every motor vehicle that is used for carriage of passengers and their luggage and comprising no more than 8 seats in addition to the driver's seat, shall equip it with a seat belt for a person occupying the front facing rear seat.ConclusionNot only is it important to wear a seat belt but also it must be worn correctly to help reduce chances of injury or death. The shoulder belt should be worn as closely fitted to the body as possible, over the shoulder, never under the arm (as this may crush ribs and injure internal organs.)

Crashing Concepts The basic idea of a seatbelt is to keep you from flying through the windshield or hurdling toward the dashboard when your car comes to an abrupt stop.If a car is speeding along at 50 miles per hour, anything that is in the car, including the driver and passengers, has its own inertia, which is separate from the car's inertia. The car accelerates riders to its speed. But if the car were to crash into a telephone pole, it would be obvious that your inertia and the car's were absolutely independent. As the pole slowed the car down, the dashboard, windshield or the road would slow you down by exerting a tremendous amount of force.A seatbelt applies the stopping force to more durable parts of the body over a longer period of time.A seatbelt's job is to spread the stopping force across sturdier parts of your body in order to minimize damage.

SEAT BELTA seatbelt's job is to spread the stopping force across sturdier parts of your body in order to minimize damage.A typical seatbelt consists of a lap belt, and a shoulder belt.Correctly worn belt will apply most of the stopping force to the rib cage and the pelvis, which are relatively sturdy parts of the body. Seatbelt webbing is made of more flexible material which stretches a little bit so that no abrupt stop.Safe seatbelts will only let you shift forward slightly.Have the ability to extend and retract

Three point seat belt

Five Point Seat Belt

Retractor MechanismThe central element in the retractor is a spool, which is attached to one end of the webbing. Inside the retractor, a spring applies a rotation force, or torque, to the spool. This works to rotate the spool so it winds up any loose webbing.

Locking Mechanismlocking mechanism stops the spool from rotating when the car is involved in a collision. Types of locking systems systems triggered by the car's movementsystems triggered by the belt's movement

systems triggered by the car's movement The first sort of system locks the spool when the car rapidly decelerates The central operating element in this mechanism is a weighted pendulum. When the car comes to a sudden stop, the inertia causes the pendulum to swing forward. The pawl on the other end of the pendulum catches hold of a toothed ratchet gear attached to the spool. With the pawl gripping one of its teeth, the gear can't rotate counter-clockwise, and neither can the connected spool. When the webbing loosens again after the crash, the gear rotates clockwise and the pawl

systems triggered by the belt's movement This system locks the spool when something jerks the belt webbing.Centrifugal clutch acts as the central operating element.When something yanks the webbing, spinning the spool more quickly, centrifugal force drives the weighted end of the lever outward.The extended lever pushes a cam piece which is connected to a pivoting pawl by a sliding pin. As the cam shifts to the left, the pin moves along a groove in the pawl. This pulls the pawl into the spinning ratchet gear attached to the spool. The pawl locks into the gear's teeth, preventing counter-clockwise rotation.

Pre tensionerPretensioner tightens up any slack in the belt webbing in the event of a crash. It normally work together with conventional locking mechanisms.The central element is a chamber of combustible gas. Inside the chamber, there is a smaller chamber with explosive igniter material. When the processor detects a collision, it immediately applies an electrical current to ignite gas in the chamber.The pressure generated pushes a piston, driving it upward at high speed.

A rack gear is fastened to one side of the piston. When the piston shoots up, the rack gear engages a gear connected to the retractor spool mechanism. The speeding rack rotates the spool forcefully, winding up any slack belt webbing.

Deceleration to standstill and forward displacement of an occupant at an impact speed of 50 km/h.1 Impact, 2 Firing of belt tightener/airbag, 3 Belt tightened, 4 Airbag inflated. ----without/ ____with restraint systems.

Shoulder-belt Tightener 1 Ignition cable2 Firing element3 Propellant charge 4 Piston5 Cylinder6 Metal cable 7 Belt reel 8 Belt strap

straight column WITHOUT a collapsible intermediate shaftWith a telescopic intermediate shaft the column slides togethersteering system with angular collapsibilityCOLLAPSIBLE STEERING COLUMN

COLLAPSIBLE STEERING COLUMNMesh Type JacketBall Type Jacket

Collapsible Steering ColumnWorking of a Ball Type Collapsible Steering Column

Before Collapse(b)After collapse

Collapsible Steering Column with Corrugated Deformable Section

Telescopic Safety Steering Column

Tilt Wheel Steering Column

Internal Steering shaft for tilt column

Tilt and Telescopic Steering Column

Steering Column with Anti-theft lock

FRONT AIR BAGS

Air bag is like a nylon balloon that quickly inflates to stop the forward movement of the occupants upper body during a collisions.Air bags are designed to be used with seat belts, not replace them.If there is a coll ision, an air bag takes less than 1 second to protect the and / or passengers.Front airbags protect the driver and the front passenger against head and chest injuries in a vehicle impact with a solid obstacle at speeds of up to 60 km/h another vehicle at relative speeds of up to 100 km/h. Airbags have different filling capacities and pressure build-up sequences adapted to the specific vehicle conditions.The systems and parts used to deploy an air bag vary with the year and manufacturer of the vehicle as well as the location of the air bag.

Operating conceptPyrotechnical gas inflators inflate the airbags in pyrotechnical, highly dynamic fashion.Airbag must be fully inflated before the occupant comes into contact with it. Airbag responds to upper-body contact with partial deflation.This significantly reduces or even prevents head and chest injuries.The maximum permissible forward displacement is approx. 12.5 cm, corresponding to a period of approx. 10 ms + 30 ms = 40 ms after the initial impact (at 50 km/h with a solid obstacle).It needs 10 ms for electronic firing to take place and 30ms for the airbag to inflate, totally 40 ms and a further 80...100 ms to deflate through the deflation holes. The entire process thus takes little more than a tenth of a second, i.e. the batting of an eyelid.

Some vehicles have front and rear seat cushion air bags that inflate the front of the seat cushion to restrain the occupants lower hip.This helps dampen the impact energy that acts on the occupants upper body, including the head and chest.Pickups and other two-seat vehicles dont have a passenger side SIR or have a switch that prevents it from deploying.Indicator light in the instrumental panel shows the current status of passenger-side SIR

Various Stages of Air Bag Inflation

Dont be a Crash Test Dummy

Air Bag in Action

OPERATION The driver is in the normal seating position prior to impact.

About 15 ms after the impact the vehicle is strongly decelerated and the threshold for triggering the air is reached . The igniter ignites the fuel tablets in the inflater.

After about 30ms the airbag unfolds and the driver will have moved forwards as the vehicles crumple zones collapse. The seat belt will have locked or been tensioned depending on the system.

At 40 ms after impact the airbag will be fully inflated and the drivers momentum will be absorbed by the airbag.

About 120 ms after impact the drier will be moved back into the seat and the airbag will have almost deflated through the side vents, allowing driver visibility

Location of Common Airbag System ComponentsAir Bag Crash Sensors consist of a sensing mass that rolls forward on impact and closes the contacts to activate the deployment circuit

Components of a Typical Air Bag Module

Igniter AssemblyIt holds the chemical that generates the gas as well as the mechanism that provides the electrical impulse to start the chemical reaction

Inflater in the Steering WheelBase and ConnectorInflaterAirbagCover

Piezoelectric Crystal Accelerometer

Airbag Circuit Block Diagram

SIDE AIRBAG

Side impacts make up approx. 20 % of all accidents. Vehicles are therefore being fitted with side airbags in addition to seat-belt tighteners and front airbags.Side airbags, to protect the head and upper body inflate across the length of the roof lining (e.g. inflatable tubular systems, window bags, inflatable curtains) and from the door or the seat backrest (thorax bags), are designed to cushion the occupants gently and thus protect them against injury in the event of a side impact.

OPERATING CONCEPT

Due to the lack of a crumple zone, and the minimum distance between the occupants and the vehicle's side structural components, it is particularly difficult for side airbags to inflate in time. In the case of severe impacts, therefore, the time needed for impact detection and activation of the side airbags must be approx. 3...5 ms and the time needed to inflate must not exceed 10 ms.Bosch offers the following option for satisfying the above requirements: an instrument-cluster ECU which processes the input signals of peripheral (mounted at suitable points on the body), side-sensing acceleration sensors, and which can trigger side airbags as well as the belt tighteners and the front airbags.

Side Air Bag

Side Air Bag

Airbag and inflation system stored in the steering wheel

Airbag and inflation system stored in the steering wheel

The inflation system uses a solid propellant and an igniter.Air Bag Inflation Device

Pedestrian Impact Test Procedure

Pedestrian leg-form injury criteria

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