Two-for-One Twisting Machine

Overview

A two-for-one twisting machine combines two or more single yarns into a plied yarn, or adds twist to a single yarn, at twice the rate that the spindle turns. The name comes from the working principle: every revolution of the spindle puts two turns of twist into the yarn. A plain ring twister or an uptwister puts in one turn per spindle revolution, so for the same twist level and the same spindle speed the two-for-one machine produces twice as much. Twisting is the step that turns several singles yarns into a stronger, smoother, more even plied yarn for weaving, sewing thread, tyre cord, carpet yarn and industrial cord.

The machine is built as a long frame with two rows of spindles, one on each side, so an operator can tend both rows from the aisles. A typical machine carries 120 to 240 TFO Spindle Assembly positions. Each position twists one yarn and winds it onto its own take-up package, so the positions run independently and a break at one does not stop the rest.

The two-for-one principle

The trick of the machine is that the supply package does not turn. It sits inside a Stationary Supply Pot that is held stationary by a Magnet Pot Stabiliser, while the Hollow Spindle Shaft spins around and below it. The yarn is pulled up out of the stationary package and over the ceramic edge of the Pot Cover & Yarn Reserve. Because the package is fixed and the yarn is being drawn off over a fixed point, that first unwinding inserts one turn of twist for each turn of the spindle.

The yarn then runs down through the hollow bore of the spindle, out at the base, and is thrown outward by the Twist Disc into a spinning balloon. As the yarn sweeps around with the spindle and is gathered back to the spindle axis at the top, that second rotation inserts a second turn of twist for the same spindle revolution. One revolution, two twists. The Rotating Storage Disc holds a few turns of yarn between the two twisting points so the unwinding speed and the balloon speed stay matched and the tension does not surge.

Spindle and balloon

The spindle runs in a Spindle Bearing Pack pack inside the Spindle Bolster Housing, which is bolted to the machine rail. Spindle speed reaches about 14,000 rpm on fine yarns, so the bearing pack and the balance of the spindle decide how quietly and how long it runs. The spindle is driven by a Drive Whorl, a grooved pulley on its lower end.

As the yarn leaves the twist disc it swings out into a balloon whose diameter grows with spindle speed and with the weight of the yarn. If the balloon is left free it pulls hard on the yarn and the balloons of neighbouring spindles can touch. The Balloon Limiter Assembly assembly contains this. A Balloon Control Ring sets the outer limit of the balloon and holds tension steady, and a Balloon Separator Shield separates one position from the next. Balloon tension is one of the main settings on the machine because it decides how the yarn behaves at the take-up.

Yarn path and tension

After the balloon the yarn is gathered back to the spindle axis by the Spindle-Axis Top Guide above the pot, then runs through the Yarn Tension & Guide Unit unit. A Yarn Tensioner adds a set drag so the take-up package winds firm and to size. Polished Ceramic Thread Eyelet guides carry the yarn along the path with low friction so the high-speed yarn does not chafe. A Yarn Break Stop-Motion sensor stops the position if the yarn breaks, so no empty winding runs on and no faulty length reaches the package.

An Overfeed Delivery Unit unit feeds yarn to the take-up at a rate a few percent above or below the winding speed. This overfeed sets how hard the package builds and how much of the balloon tension carries through to the wind, which matters for how the package unwinds in the next process.

Take-up and overfeed

The twisted yarn is wound onto a cross-wound package at the Take-Up Winding Head head. A grooved Grooved Take-Up Drum drives the package by surface friction and, through its crossing groove, also traverses the yarn across the package face so it builds in even crossing layers. A Package Cradle holds the tube and keeps the growing package pressed against the drum at steady force. The Traverse Mechanism mechanism sets the crossing angle that lets the package unwind cleanly later.

Drive, threading and control

All spindles on one side of the machine are driven together by a single Tangential Belt Drive. A long Tangential Drive Belt runs the length of the side and presses against each whorl in turn, so every spindle turns at the same speed from one Main Drive Motor. A Spindle Inverter sets the belt speed, and so the spindle speed, and so the twists per metre. To change the twist level the operator changes this one setting.

Threading is done with the Suction & Threading System system. A Threading Suction Gun pulls the yarn end down through the hollow spindle bore and out at the base, where the operator catches it and leads it through the balloon guide and up to the take-up. The same suction clears broken ends and waste.

The Machine Control cabinet holds the twist recipe, drives the inverter, overfeed and take-up, watches the stop-motions and counts length and doffs per position. The whole machine sits on a welded Machine Frame & Guards that carries both spindle rows and the take-up rails above them.