Working principles of ring doubler and two-for-one twister

1. Ring Doubler

The object of doubling is to double the individual threads. Doubling avoids unevenness and the strength of the doubled yarn is correspondingly better than the single thread. So doubled yarns are preferred.Doubling reduces unevenness of single yarns and the strength of the doubled yarn is correspondingly better than the single yarns.

1. Objectives of Doubling
  • To increase the strength of the yarn
  • To increase smoothness, evenness, luster, uniformity, and compactness of yarn.
  • To obtain the better deposition of a twist.
  • To combine two or more single threads into one.
  • To insert sufficient amount of twist for holding the yarns.
  • To increase strength, smoothness and luster.
  • To reduce hairiness.
  • To make sewing thread.
  • To wind a suitable bobbin.
2. Doubling Applications
  • Jeans sewing thread
  • Type Cord
  • Cable yarn
  • Cutting yarn
3. Types of Doubling
1. Ring Doubling
2. Two for One Twister
3. Up Twister
4. Three for One Twister

2. Two for One Twister

The unwound from the feed package goes to the snail wire through the tensor, inside the spindle and outside the rotary disc. The yarn receives its first twist between the capsule and the bending part and the second turn between the bending part and the snail wire thus obtaining two twists with one rotation of the spindle.

Spindle: One spindle rotation gives the yarn two twisting, therefore the productivity in the T.F.O. twister equals twice as much as that in the ring twister. The rotary disc is made free from vibrations and surely balanced, because its circumference speed reaches as high as 375 kmph in case of machines for cotton yarns. Each guide is made of Alumina porcelain in order to maintain anti abrasion characteristics of the rotary disc specially processed for giving a good slide to the yarn.

The Cheese Cover: The cheese cover is furnished in order to prevent the interference of unwinding yarn with ballooning yarn. It stands still by virtue of magnetic force while the spindle is rotating. Even a scar or scratch may damage the yarn to cause ends down, because the yarn touches the upper edge of the cheese cover at starting.cradle- Even a little slip of the take up bobbin may cause uneven twisting. Ball bearings are mounted at both sides of the cradle in order to ensure the smooth and light bobbin rotating. A contact pressure of about 1.5 kg is given to the package at the beginning of winding to enable the package driven smoothly. The pressure is designed to be decreased in proportion to the increase in the package diameter.

Feed Roller: The circumference speed of the feed roller is rated 157 to 181% over the yarn speed thus converting the high ballooning tension to the lower take up tension. Take up tension can be arbitrarily adjusted by virtue of the effective usage of slip between the feed roller and the yarn, resulted from changing the yarn contact angle wound around the feed roller.

Anti-Patterning Device: This device is built in the gearbox. It prevents ribbon winding changing the yarn path by varying the cam speed slightly with a certain interval.Tailing device- Used to take off the no twist yarn at the start of winding. Rotating disc- The unwound yarn from the feed package is clung around the circumference of the storage disc automatically through inside of the spindle and via yarn guide of the storage disc, then it reaches to the snail wire, twisted diagonally by the air resistance. The degree of winding around the storage disc is conventionally called “storage angle” or the “winding off angle”. The storage angle is the one that the yarn from the yarn guide makes in contact with the storage disc. If the angle is more than 90o, the variance in unwinding will be thrown by its own centrifugal force collapsing balloon shape, and breaking the yarn. The yarn breakage in this case is called “breakage caused by extended winding angle”. Therefore, twisting condition of the machine can be judged by the storage angle around the storage disc. The storage disc is adjustable by the tensor.

Twist Direction-Normally, folded yarns have the doubling twist in the opposite direction to the spinning twist, ie direction of twist in ring yarn is ‘Z’ and direction of doubled yarn twist is ‘S’. However, for special applications, there are yarns with twist on twist, with the folding twist in the same direction as the spinning twist, say ‘Z’ on ‘Z’. In this study, except 3 cases, all the folded yarns produced are with ‘S’ on ‘Z’ twist direction.

Spindle drive

1)Tangential Belt Drive-Using one single long belt to drive all the spindles through a centralized tensioning arrangement.

2)Four Spindle Tape Drive-Of the 1440 TFO twisters covered in the study, nearly two-thirds are working with 4 spindle tape drive while the remaining are with tangential belt drive. Indigenous manufacturers largely use 4 spindle tape drive system while almost the entire imported machines are with tangential belt drive system.

Protection Pot-The basic requirement of TFO twisters is to house a cylindrical stationary feed package and provide support at the time of unwinding of yarn from the package during working. For this purpose, yarns require a protection pot around the package. The main objectives of providing protection pot are to:

  • protect the feed package from damage
  • facilitate start-up of the balloon
  • separate the balloon and the feed yarn to avoid abrasion and
  •   protect the feed yarn from dust and fly