FIELD OF THE INVENTION :
The invention relates to the field of textile technology in general and to
measurement and testing of textile fiber in laboratory in particular.
BACKGROUND OF THE INVENTION:
Most of the textile testing laboratories in India and abroad measure fiber friction
as per ASTM-D 2612-991 method which refers to the measurement of cohesive
force of the sliver comprising of a bundle of fibers, which is an indirect method of
measuring inter-fiber frictional force. This test procedure is based on the
measure of the maximum resisting force when a length of sliver is pulled in an
axial direction. Specified lengths of sliver are placed in the clamps of a tensile
testing machine and the maximum force developed during separation of the
fibers between the clamps is recorded. The cohesive tenacity is calculated in
terms of the force per unit linear density of the tested specimen. The cohesive
tenacity is considered a measure of the cohesion of the fibers, and is expressed
as gm force/denier.
Woolmark, U.K. 2 has an in-house test method STD-21 for single fiber friction
measurement. It utilizes Constant Rate of Extension (CRE) with a very sensitive
load cell. Individual fibers are wrapped around either a glass or metal rod and
the frictional properties of the fiber moving against it are measured in grams.
The measurements are usually carried out against and with the direction of the
scales in fiber to give two values.
Northern India Textile Research Association (NITRA)3 jointly with Indian
Institute of Technology (IIT), New Delhi has designed and developed a Friction
Tester for measuring the frictional properties of staple fibers as well as fabrics.

But it refers to relative movement between two layers of fibers or fabrics with a
known load with standard foot area placed over the two layers of fibers or
fabrics, and displacing one layer against the other. Thus, it is a measure of
friction between two tufts of fibers rather than between single fibers.
A research paper published by the Swedish Institute for Textile Research,
Gothenburg, Sweden 4 describes a principle to measure "friction between single
fibers" which involves a twist between the two fibers and the force necessary to
slide the fibers in the twist gives a measure of the friction which was derived as
follows:

The prior art however does not have a single device to measure important
characterizes like single fibers friction, breaking strength and elongation at break.
The industry has long felt the need of such facility in a testing laboratory, which
provides accurate and more reliable results much faster than is possible at
present.

The device in accordance with the present invention overcomes these drawbacks
of the prior art.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a single device which can measure and
test single fiber friction, breaking strength and elongation at break of textile
fiber.
Another object of the invention is to provide a device that can produce accurate
and more reliable result much faster than at present.
A further object of the invention is to provide a device that can be used in a
common textile testing laboratory.
Yet another objective of the invention is to provide a simple device which can be
operated by a person with only average technical skill.
DESCIPTION OF THE INVENTION:
The device and procedure for operating the device in accordance with the
present invention will now be described in details with the help of the following
drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig. 1 shows the single fiber friction-cum-strength tester in accordance with the
invention in fiber friction test.
Fig. 2 shows the tester in fiber strength test.
Fig. 3 shows the main components of the tester in accordance with the
invention.

Working Principle:
(A) As a Friction Tester, best seen in Fig. 1:
It measures friction between two single fibers which are given a predetermined
twist as shown. Each fiber (1) under test is held vertically in a specially designed
clamp (2) at the upper end and attached to hook (3), one of which is fixed to a
movable transducer (6) which senses and displays the force exerted on that
fiber, while the other clamp (2) is not provided with a transducer. The twisted
part remains over the roller (4). One fiber slides against the other in the twist.
The lower end of each fiber is attached to an initial weight, Pi (5). The weights
are equal in both the fibers.
(B) As a Breaking Strength Tester, best seen in Fig. 2 :
The fiber (1) under test is held between the two clamps (2), the lower end being
held in the stationary hook (3) and the upper end being held in the movable
hook (3) fixed to the movable transducer (6), as shown.
Sample Preparation:
The fiber sample/s (1) under test is/are fixed on clamp/s (2) and weights (5) as
shown in Fig. 3. Each clamp (2) as well as weight (5) is marked at the fiber
holding portion with black color on one side and white color at its back. The
black side is meant for better visibility of the fiber end. For friction measurement,
weight (5) is attached at one end of fiber (1) and clamp (2) at the other end.
A small quantity of a quick-setting synthetic adhesive is applied on the clamp (2)
and using forceps fiber end is positioned onto it such that about 2-3 mm fiber
rests on it. It is covered with black craft paper tag to firmly secure it. About 5-10
minutes is allowed for setting so that the fiber end is firmly held & it doesn't slip
off subsequently during test. For friction test two fiber samples (1) are prepared

each with clamp (2) at one end and weight (5) at the other end. For strength
test one fiber (1) is prepared with clamps (2) at both the ends.
Test Procedure:
(A) Friction test
The two fiber sample/s are attached on the upper hook (3). The fibers (1) are
given a predetermined twist manually by way of number of turns (n) as
schematically shown in Figure 1, without introducing any tension in the fibers
(1). The twisted portion of the fiber pair should remain over the roller (4). The
number of turns (n) in the twist and twist length (1) are measured. One fiber (1)
is then pulled up against the other fiber (1) along the twist by about 15 to 20
mm by moving the transducer (6). This movement is gradual and uniform which
is achieved by using a worm and worm wheel device (7). The amount of force
thus applied on the fiber sample (1) is much lower than the breaking load and is
governed by "static friction". Once this is overcome, the force then required is
lower than the former force, governed by "dynamic friction". The maximum force
(P2) required to slide the fiber (1) is sensed by the transducer (6) and stored in
the electronic circuit and displayed. This load (P2) is greater than load (Pi). By
incorporating P1 and P2 values in the formula as explained earlier along with
other values of fiber diameter, twist length and number of turns in the twist, the
coefficient of friction between the two fibers is calculated.
(B) Strength Test
For strength testing, clamp (2) is used at both the ends. The tension/force is
imparted to the fiber (1) by gradually moving the transducer (6) carrying upper
end of fiber sample attached to it and is increased by stretching the fiber (1) till
it breaks. The value of force exerted is sensed by the transducer (6) and stored
and displayed by the electronic circuit. The ratio of breaking load to fiber's cross

sectional area gives the value of breaking strength. The instrument also has a
facility to measure the vertical travel of the movable clamp (2), which along with
original sample length can give percentage elongation at break.
Novel features of the invention:
1. Measurement of Single Fiber Friction, Breaking Strength and Elongation at
Break
2. Digital Technology for Computerization and Data Integration in Testing
Laboratory
3. Fast, Accurate and Reliable Results
4. Economically Designed for Better User Interface and Easy Maintainability
5. Suitable for Worsted Fibers, Man-made Fibers/Filaments and Human Hair
References:
1. Standard Test Method for Fiber Cohesion in Sliver and Top (Static Tests)
ASTM-99
2. Woolmark Textile Testing Services, www.wool.com
3. Design and Development of a Friction Tester for Measuring the Frictional
Characteristics of Staple Fibers and Fabrics, A. Das, Vikas Sharma and S.
M. Istiaque; Resume of Papers, 43rd joint Technological Conference, at
NITRA, Ghaziabad, India, March 2002
4. Measurement of Friction Between Single Fibers; Part II- Frictional
Properties of Wool Fibers Measured by the Fiber-Twist Method, Joel
Lindberg and Nils Gralen, Swedish Institute for Textile Research,
Gothenburg, Sweden, Textile Research Journal Vol. 18, No. May
(1948):287-301)

WE CLAIM:
1. A single fiber friction-cum-strength tester for textile fiber comprising of
sample fibers (1) attached to clamps(2) which are attached to hooks (3)
at one end for friction test and at both ends for strength testing, weights
(5) being attached to the other ends of fiber (1) for friction test,
transducer (6) with worm and worm wheel (7) and roller(4), characterized
in that both friction test and strength test can be performed on fiber with
the same tester.
2. A single fiber friction-cum-strength tester as claimed in claim 1, wherein
worm and worm-wheel (7) is deployed to move transducer (6) up and
down to vary the force applied on fiber (1).
3. A single fiber friction-cum-strength tester as claimed in claim 2, wherein
the transducer (6) electronically measures and records the force applied
on the fiber (1).
4. A single fiber friction-cum-strength tester as claimed in claiml, wherein
the weights (5) attached to fibers (1) for friction test are equal in
magnitude.

A single fiber friction-cum-strength tester for textile fiber comprising of sample
fibers (1) attached to clamps(2) which are attached to hooks (3) at one end for
friction test and at both ends for strength testing, weights (5) being attached to
the other ends of fiber (1) for friction test, transducer (6) with worm and worm
wheel (7) and roller(4), characterized in that both friction test and strength test
can be performed on fiber with the same tester.