2. Making Cotton Yarn

The Bale

Almost all cotton comes to the mill in standard compress bales of five hundred pounds gross. The cotton is condensed to about 22 pounds per cubic foot at the compress, wrapped in coarse jute bagging, and circled with iron hoops. For some time there has been a movement to improve the so-called square bale, or to replace it with a different form of packing. Sea Island cotton is frequently packed in a smaller round bale, and there is much to be said for this practice. What we are concerned with here, however, is that the mill receives the cotton in a compressed form which must be loosened before anything can be done with it.

The Bale-Breaker

Accordingly, the first thing that happens is that the hoops are cut, the bagging removed, and the cotton thrown by hand into the feed-apron of the bale-breaker. This machine does nothing more than to pick the compressed cotton apart and deliver it in tufts about the size of a handfull on a belt conveyor.

The Opener

The travelling belt or feeder delivers these bunches of cotton into machines called Openers, which simply repeat the operation of the bale-breaker on a more thorough scale, reducing the large tufts into many smaller ones. These small pieces are dropped into an air chute and drawn along parallel rods up to the picker room. During transit in the trunk much of the heavier dirt falls between the rods and is removed.

In the most recent installations larger bale-breakers are used which reduce the cotton to small tufts and deliver through an air pipe to a condenser in the picker-room. The condenser either empties into bins or else on to the automatic feed of the breaker-pickers.

Bale Breakers

Pickers Remove Coarse Dirt

As the tufts come out of the chute they fall into the first of three machines known as Pickers, whose function is to beat out the coarser impurities and deliver the cotton in rolls of batting called laps. In the first, or breaker-picker the tufts are thoroughly whirled and pounded over grid-bars by rollers armed with short flail-like projections, and then compressed into a continuous sheet or lap of a given weight per yard, which is wound on a large spool and delivered to the second, or intermediate picker. This machine practically repeats the operation only that it combines four laps from the first picker into one which it hands over to the last, or finisher picker. The latter again takes four intermediate laps and forms them into one sheet of fairly clean cotton, containing very little dirt or seed, but still fairly filled with small particles of leaf. In these preliminary operations the cotton has lost about five per cent. of its weight.

Picker Room

The Function of the Card

Before anything else can be done it is now necessary to remove the leaf particles, and to separate the individual fibres from their matted position. Both these functions are performed by the machine known as the Card, the principle of which is that of two surfaces armed with fine wire teeth revolving not quite tangent to each other. Originally carding was performed by hand, but the Wellman carding machine was one of the earliest textile inventions. This was considerably improved by the revolving flat card in 1857, the operation of which is somewhat as follows.

PRINCIPLE OF THE FLAT CARD

Its Operation

The lap from the finisher picker is fed over a plate on to a revolving cylinder bearing wire teeth, which combs it over a set of knives, thereby removing coarse dirt, and passes it on to a large cylinder armed with millions of fine wire teeth. The latter carries the cotton past a slowly revolving endless chain of flats which remove the neps and fine dirt. The clean, separated fibres are then picked off the cylinder by a smaller rapidly revolving roller called the doffer, which carries them in a filmy sheet to be in turn removed by the doffing comb. The latter, working so rapidly that the eye fails to see it, lifts the sheet of fibres clear so that it may be passed through a funnel and condensed into a single untwisted rope a little under an inch in diameter. This rope is called a sliver, and is automatically coiled into a can like an umbrella-stand.

Feed End of Card. Lap Entering

Delivery of Sliver

Counts of Yarn

Two Processes

We have now for the first time reduced the raw material to a continuous strand, comparatively free from impurities. Up to this point, no matter what kind of yarn is to be spun, the operations are practically identical, but from here on the processes vary according to the product desired. A hank of yarn is 840 yards (not to be confused with the worsted hank of 560 yards) and the number of hanks it takes to make a pound is the basis upon which yarn is classified. Thus a coarse yarn which weighs only twenty hanks to the pound, would be called 20s, while 80s would be a very fine yarn. Various fabrics require different grades of yarn, just as different finenesses of yarn must be spun from varying grades of cotton. The processes preparatory to spinning vary, not only with the counts to be spun, but with the use to which the yarn is to be put. Ordinary coarse and medium yarns for weaving usually follow one process, while fine counts for weaving, or knitting yarn, or coarse yarn made from long-staple cotton such as that used for tire-duck, go through a different preparation. The former are simply drawn and reduced, while the latter are in addition combed.

Drawing

First Process

Drawing

In the ordinary process, which is by far the most commonly used, the sliver from the card is put through successive similar operations, known as drawing, the object of which is to draw out the fibres and cause them to lie parallel to each other. Six card slivers are fed together between two pairs of rollers, the second of which is revolving faster than the first. The obvious result of this is the stretching of that portion of the slivers which is between the two sets of rollers. The operation is usually performed two or three times, in each case combining six strands into one. The sliver delivered by the third drawing machine will be of the same diameter as the original card sliver, but will contain more or less parallel fibres.

Roving Frame

Roving Operations

Slubber

There remains now only one series of operations before the yarn is ready to be spun. The sliver must be reduced in size and given a certain amount of twist; these objects are accomplished by the roving frames, of which there are either three or four. The first, or slubber, passes the drawn sliver through rollers without combining, and winds it up on bobbins set in spindles. The sliver is twisted by being fed onto the bobbin by an arm, or flyer, which revolves a little more slowly than the spindle, being drawn around after it. The result is a slightly twisted sliver, now called a roving, about the diameter of a clothes-line.

Four Stages of Roving

The intermediate, fine frame, and jack frame,—or, if there are only three roving boxes, the intermediate and fine frames,—combine two rovings into one of smaller size and more twist. The mechanism is much the same, except that in each successive frame the spindles are smaller and revolve faster, until finally the thread is small enough to spin.

Second Process

Lapper

Where it is desired to spin special kinds or very fine yarns twenty card slivers are usually combined in a machine similar to a drawing frame and known as a sliver-lapper. The twenty ends are drawn between rollers and delivered not as we should expect in one strand, but in a narrow band or lap, which is wound on spools. Four of these laps are again combined and drawn over a spiral surface in the ribbon lapper which delivers its product to the comb. The cotton is now in a band less than a foot wide, with fibres more or less parallel and practically clean. Since it is desired to spin a yarn which demands not only parallel but uniform fibres, the short fibres must be eliminated.

The Comb

There are a considerable number of combing machines in use at the present time, but their differences are mechanical rather than in the function they perform. The Heilmann principle is the most commonly used in this country. Eight rolls from the ribbon-lapper are placed in separate rests, or heads, end to end, and each lap is fed through rollers between teeth of a very fine and rapidly oscillating steel comb. Every back and forth motion, known as a nip, delivers about half an inch of filmy sheet from which the short fibres have been combed out. The eight combed sheets are then once more condensed into a single sliver and coiled into a cylindrical can.

Drawing

Doublings

Following the comb there are usually two drawing frames, each combining six slivers into one, and these are followed by the three or four roving frames as in the other process. In the ordinary process the last roving as it leaves the jack frame has been doubled 27,648 times; in the combed yarn there are 2,959,120 doublings before spinning begins.

Spinning proper is done either on the mule or the ring spindle. Very little cotton is spun on mules in this country, although mules are extensively used in Europe. We shall concern ourselves here only with the ring spindle, and that in bare outline. (See also Part Two, Page [83]).

The Ring Frame

The principle of the ring frame is very similar to that of the roving operations which immediately precede it. The thread is again drawn through two or three sets of rollers running at successively higher rates of speed, and then passes as shown on the accompanying sketch through a guide to a small metal loop, called the traveller, which runs around on a metal track or ring within which the spindle with its bobbin is revolving. Since the spindle pulls the traveller around after it, the yarn is twisted or spun as it is wound on the bobbin. Sometimes two spools of roving are spun into a single thread, but more frequently there is no combination. All the rings on one frame, usually about 256, are moved up and down together on their spindles, so that yarn will be wound evenly on the bobbin.

Ring Twister

THE RING FRAME PRINCIPLE

Yarn of Filling Bobbin, Warp Bobbin, and Spool

Warp and Filling Bobbins

Not only is a different bobbin used for spinning warp and filling yarns, but they are also wound differently on the bobbin. Warp yarn is wound evenly up and down the whole length of the bobbin, while the filling bobbins, which go straight from the spindle into the shuttle of the loom, are wound on in sections to facilitate rapid unwinding.

Twisting

We have now proceeded as far as the finished yarn. Sometimes, however, when a particularly strong thread is desired, or in case of fancy designs, it is desirable to twist two or more threads of yarn together, this being known as two-ply, three-ply, etc. Various effects are obtained by twisting different yarns together, and sometimes worsted and cotton strands are twisted together. The operation is done on a frame similar to the spinning frame.

The Barber Knotter

In these and subsequent operations the Barber Knotter, a little device worn on the hand of the operative, has enormously increased efficiency. By a single motion an entirely unskilled girl can knot and cut off evenly the ends of two threads.