Page 287 - Handbook of Properties of Textile and Technical Fibres

Tensile properties of cotton fibers: importance, research, and limitations 261

open-end spinning. The tensile behavior of cotton fibers is clearly tested during ring
spinning because there is a continuous need to stabilize yarn tension during spinning.
As it is well known, any opportunity to increase productivity in ring spinning must be
through an increase in traveler speed. Because the principle of ring spinning dictates a
continuous ringetraveler contact, high traveler speed will result in traveler burning out
due to the frictional heat initiated during traveler rotation. This point can simply be
illustrated by considering the two main forces acting on the area of travelerering
contact: the centrifugal force and the frictional force (see Fig. 7.16). The centrifugal
2
force can be expressed by the equation: CF ¼ 2m t V t d ring , where m t ¼ traveler
mass, V t ¼ traveler speed, and d ring ¼ ring diameter. The normal force acting on the
traveler during rotation may be approximated by the centrifugal force. By the
Amonton’s Law of friction, the following relationship between the frictional force,
F, and the normal force, N,is

F ¼ m ring=traveler N z m ring=traveler CF z m ring=traveler 2m t V t 2 d ring

where m ring/traveler ¼ the coefficient of friction between the ring and the traveler.
For a given ringetraveler system, the coefficient of friction, the traveler mass, and
the ring diameter are normally constant. Accordingly, an increase in the traveler speed
will result in an increase in the centrifugal force (or the normal force), and
consequently an increase in the frictional force. The reason that the traveler burns is
that the mechanical friction described above results in kinetic energy, which is

Front rollers
The spinning triangle
Nip of the front roll
b
Spinning tension
T y h
T y
T B
T w
α
Centrifugal
force
75 fibers/cross section
Traveler-ring Tension level/fiber: 0.07 cN 0.26 cN
friction force Tension peak/fiber: 0.70 cN 1.60 cN
4mm 4mm
The nip of n3
the front roller n1 n2 n1 n3
4 mm n2
T = Yarn tensile force (or spinning tension) 7 mm
y
T B = Balloon tensile force (balloon tension) The twisting
point
T = Winding-up tension
w
Figure 7.16 Spinning tension in ring spinning (The concept of dynamic tension on fibers).