Yarn Tensioners are devices by the help of which tension is given to the yarn. This is an important device because it enables us to provide necessary tension to the yarn as it moves through the different parts of the mschine.
Types of tensioning device
There are basically three types of method by which tension is applied to yarn. They are as follows
- Capstan method
- Additive method
- Combined method
Capstan Method
This is the simplest form of yarn tensioning device where the yarn is passed around posts where the tension on the yarn is provided from the friction between the posts and yarns.
This follows the classic law of
Output tension = Input tension x eµθ
Additive method
In this method the yarn is passed through the middle of two surfaces in contact. The force is applied from above to give suitable tension to the yarn.
Combined method
The combined system is a combination of capstan and additive method. This device is a complicated system which on allows the addition of tension. We cannot decrease the tension with this device. It is seldom used.
Important effects of tensioning device
If the tension is too high then
- The yarn can be damaged
- The rate of yarn breakage will be high
- The elongation property of yarn will change
If the tension is too low then
- It can lead to unstable or loose package formation which will cause problems during unwinding
Variation in yarn in different parts of a wound package will cause undesirable effects
For man made filament yarn improper tension will cause
- Change in molecular structure
- Variation in colour shades
For staple or spun yarn too high tension will cause
- Yarn breakage at thin places
Factors influencing the selection of Tensioners
- The device must be reliable to control uniform tension
- The device must be easily thread able
- It must not introduce or magnify tension variation
- It must not introduce variation in twist
- It must not be affected by wear
- It must be easily adjustable
- It must not be affected by oil and dirt
- It must not encourage dirt collection
- It must be easily cleanable
- The operating surface must be smooth
- It must be cheap
