Seat Belt

1. Safety Belt (Seat Belt for Motor Vehicle)
Introduction -:
Definition
Seat belt also known as safety belt is an energy absorbing device designed to secure the bodyof
occupant of a vehicle against sudden load imposed on his body during a crash down or sudden
stop.
Function of seat belt
According to newton’s first law during motion of vehicle driver & passengers are travelling at
same speed as vehicle. If the vehicle is suddenly stops or crashes, the occupant continue at the
same speed of vehicle was going before it stopped. Seat belt applies an opposing force to the
driver & passengers to prevent them ejecting from vehicle or any harmful movement.
Safety Belt keeping occupants positioned correctly for the maximum effectiveness of airbag and
by prevent occupants being ejected from vehicle during sudden stop or crash.
Lead Manufacturer of Seat belt
 Takata, Japan
 GWR, United States
 Sabelt, Italy

2. Manufacturingprocess of seat belt -:
Webbing
Seat belt webbing is a narrow woven fabric which is made from multifilament yarns made of
polyester or polyamide (Nylon) filament yarns. Polyester is mainly used in warp way due to its
lower extensibility, higher stiffness & high tenacity. In the mechanical performance of seat belt
weft yarn have less influence. Multifilament yarn that used in seat belt webbing cab be twisted or
untwisted. Untwisted yarn belts are thinner & smoother. Untwisted filaments packed themselves
closer together hence beneficial effect on the tensile strength and tear strength of seat belt
webbing. In addition coating was often necessary to improve abrasion resistance of webbing.
Earlier in 1980s twisted yarn is preferred but since the 1990s untwisted coarser grades of yarn
have become more popular. Japanese weavers are preferred to manufacture their webbing from
1100dtex war and 559dtex weft threads.
Conventionally, most of belt like narrow webbings are woven on
shuttle looms, around 1959. These looms were capable of delivering 200 wefts insertions per
minute. Later these looms were replaced by needle loom which is capable to run at higher speed
up to 1000 picks per minute. In the needle loom, weft is inserted from one side of the warp sheet
and here a selvedge is formed. The other side of webbing is held by an auxiliary needle which
manipulates a binder and a lock thread. Once these threads are combined with the weft yarn, a
run proof selvedge is created. It is important to ensure that the selvedge is soft and comfortable
to wear.
Filament yarn for webbing
 Polyester
 Polyamide (Mainly Nylon)
Warping -: A fully auto high speed warping machine is
Use to prepare a beam of suitable size for required webbing.

3. Weaving of Seat belt webbing
Seat belt webbing has been made on Needle looms due to its higher speed. (More than 1000 picks
per minute)
High speed needle loom for narrow Fabric.
A narrow fabric needle loom weaving system employing a hook secured to the mounting plate of
the loom on the side into which needle enters the shed and around which weft thread is wound to
form a straight edge without contraction of the warp threads during beat-up on the side of the
woven material opposite the knitted selvage edge produced by a latching needle pick. An
improved weft thread feed is provided with a simple, relatively inexpensive mechanical drive
disk that can be easily adjusted to vary the amount of weft thread fed during each pick. A weft
thread supportspring structure provides tensioning supportfor the weft thread and reduces wear
on the leaf spring members. An improved header frame assembly prevents undesired twisting of
the header elements and makes it easier for a technician to change the machine over from one
weaving pattern to the next. Eccentrically mounted drive disks are provided for the respective
sets of oppositely reciprocated header frames. A lever arm adjustable drive is provided for the
take-up roll which simplifies the problem of adjusting the number of picks provided for a given
length of woven material during loom operation. A drive for the latching needle of the loom also
is provided which provides a horizontal reciprocating motion to the latching needle in a simple
manner. A spring biased braking arrangement for braking rotation of the warp beam supplying
warp thread from the supply spool also is made available.

4. Weave Used In Seat Belt Webbing
 Herringbone Twill
 Satin weave
Twill belt Design
Satin Belt Design Draft & Peg Plan
Twill Weave Seat belt

5. Essential Mechanical Properties of Seat Belt
 Higher Tenacity
 Lower Extensibility
 High Abrasion resistance
 Higher Breaking Strength
References-:
 Properties of automotive seat belt fabrics by Anita A Desai
 Wikipedia
 http://www.takata.com/en/contact/seatbelt.html
 Narrow fabric needle loom weaving system, Patent US4577665A
 Automotive textile Progress by S.K. Muukhopadhyay and J F Partridge