Better Ways To Handle the Bale

Charles L. Sens.

By the time a bale of cotton hits the concrete floor of the opening room in a textile mill, it has run a ruthless gauntlet. Saws at the gin have separated the lint from the seed and removed some sand and plant trash. Covered with burlap or cotton bagging and girded with steel bands, the bale has undergone repeated compression, none of which is a gentle operation. At each exchange of ownership in its trade route, the bale is knifed to give up a sample. Its wrapping no longer looks the same. With the many cut places, or burlap patches, and tags, it resembles anything but a unit possessing potential beauty. Yet the down-soft contents must find their way into fine and sheer articles of wearing apparel, as well as into rugged materials for heavy industrial uses.

In this day and time, manufacturing usually is closely associated with assembly lines. But cotton processing consists of many interrelated steps, each of which is performed by human hands, often without the help of automatic machinery.

To get a better idea of this course, go with me into a typical cotton textile mill. A far different sight now meets the eye that observes a hundred or more bales of snow-white cotton, wrappings removed.

Cotton at this stage is a mass of tangled fibers of varied lengths. It contains motes, sand, particles of leaf and stalk of the cotton plant, and some seed fragments.

Its route to the spinning frame or weaving loom is long and involved. The mass of matted lumps of fibers, sometimes as compact as a board, is progressively reduced, first to small tufts and then to separate fibers. Although all the cotton in a bale may be white, it needs blending, for cotton in a single bale usually differs in character, grade, and staple length. Blending cotton is comparable to mixing paint, where a better consistency is obtained by thoroughly compounding a hundred gallons in one container than by duplicating the process in a hundred 1-gallon vessels.

To fluff the tightly matted fibers, to blend or mix the cotton for a more even consistency throughout, and to clean the cotton, a series of vigorous operations is employed. Batteries of hoppers with spiked lifting aprons and regulated air currents convey the crude cotton to revolving beaters. Under these are adjustable grid bars or perforated screens. The foreign matter is thrown through these openings into waste-collecting areas beneath each beater.

The cotton does not have to be cleaned to the same extent for all end products. But highly efficient cleaning and preparation methods are required for fine goods that are to receive special finishes, and to insure the unbroken swift passage of thread through the eye of a needle in knitting or sewing. The same cleaning is essential for cotton materials that must hold up under severe mechanical uses, such as hose or outdoor conveyor belts.

Loose and partly cleaned, the cotton is drawn by air to what is called picking, a textile term, not to be confused with harvesting. Picking is an intermediate step in cleaning. Cleaning, however, is not its only purpose. Of equal importance is that by this operation the loose mass of cotton is delivered in a predetermined form, and becomes a continuous roll of certain length and weight. The product is called a lap. For example, it may be upwards of 50 yards long and 40 inches wide, weighing generally 12 1/2 to 14 ounces to the yard. In the picking process, blades or pins on the surface of a horizontal and fast-revolving beater remove small quantities of cotton at each blow by picking, or plucking, upon a fringe of cotton as it is delivered from between two fluted steel feed rolls.

Picking machines are much alike in principle, but vary in detail. Most of them have two or three sections. Each section generally has a control unit that regulates the transfer of cotton to feed rolls. A fast revolving beater moves forward small quantities of cotton in rapid succession. Again we find adjustable grid-bar openings beneath each beater. Through these vents is thrown more trash, in the form of motes and broken leaf particles. Aiding the beater is a stream of air, the volume of which in 1 minute is approximately equal to that filling a room 15 feet long, 12 feet wide, and 8 feet high. To avoid a turbulence like that which results when a big bag of feathers is dumped in a windstorm, the air is separated from the cotton by two revolving and converging cage-like cylinders. The cylinders not only perform this trick, but also begin to condense the fluffy, downy material. Finally, the cotton moves through a set of heavy steel rolls, which press and form the lap, or roll, of cotton, which now can be handled by hand, on a truck or by some automatic system.

The reader who asks, "What is so wonderful about this invention?" might note that one-process picking is not an invention. It is a development the result of 15 years of experiment and research. To move cotton by an air stream through a duct or on a trough conveyor is no more difficult than carrying your hat in your hand.

But to clean cotton thoroughly without damage to the fibers is a job yet to be completed. To place minute quantities of cotton at the rate of from 300 to 500 pounds every hour, with homogeneous distribution, upon moving surfaces of specified areas, and to do so economically, is a problem now engaging the talents of many engineers and scientists. This stream of cotton-laden air is moving at velocities of more than 3,000 feet a minute. Because cotton fibers are so volatile in an air current and so subtle as to lodge on the surface of glass, they defy control.

Before 1915, most processors had to use two and sometimes three picking operations. The cotton was poorly blended, insufficiently cleaned, and unevenly supplied to the first picking machine. The laps were removed by hand from the delivery end of each machine and placed on the feed end of the next one. Development of a one-process system, or a continuous picking operation, has done away in many instances with as much as one-half of the manual labor. Two of the several reasons why a virtually automatic procedure became possible are: First, compartments were supplied within the machines for a regulated storage of cotton; second, automatic devices to control the flow of cotton were developed. The result was a decided improvement in the uniformity of feed to the last, or finisher, section.

The economies and better preparation resulting from improved precleaning and the benefits of better regulation for uniformity of feed and delivery do not end at the picker. They carry forward and are reflected in all subsequent processes.

ONE EXAMPLE is at the carding machine, where the 40-inch-wide lap is reduced to a soft, ropelike strand of cotton, called a sliver. This unit is measured in, say, 50 to 60 grains a yard. The card formerly was expected to do more than its share of cleaning to the detriment of quality. But constant improvement in the early stages of cotton preparation, with respect to the removal of heavier trash particles and to the better separation of the cotton fibers, enables the card to improve upon its cleaning task in its specialized sense. Further investigation doubtless will disclose that the card is better able to perform such other functions as fiber blending, and that a superior sliver, whose fibers are more. favorably arranged, can be produced. Obviously, this would influence the adaptation for the next significant step, which is drawing, based on the principle of roll drafting, by which the fibers are drawn parallel to one another.

Still other benefits have been obtained. Bearing directly on lower costs, the improvements have shortened operations by doing away with one entire step of drawing and roving. The process of roving has changed slowly. And as we proceed from a bulky strand of cotton to a roving (smaller in diameter and many more yards to the ounce or pound) just enough twist must be inserted to give the unit sufficient strength for normal handling, such as winding.

Roving and spinning are essentially drafting processes in which the bulk or diameter of the loosely twisted strand of cotton is successively reduced, or drafted, by sliding the individual fibers along one another to produce yarn. It is accomplished by maintaining the proper ratio of progressively increasing surface speeds of each following pair of rolls or aprons (small endless bands) binding the fibers.

Since the invention of drafting, textile men have constantly been trying to reduce costs by increasing the draft in every process. The early system of drafting used three pairs of rolls, defining two drafting zones. The first zone, between the back and middle pairs of rolls, served as the break-draft zone to "unlock" the fibers; the second, between the middle and front pairs, served to thin down the bulk of fibers to the extent of the draft performed. For example, the first zone operated, say, at 1.5 and the second or extended zone at 8, the product being the total draft of 12. This system had its limitations. Having only two zones, the second draft zone for greater elongation was incapable of uniformly stretching out the bulk of mixed length of fibers. The shorter fibers reacted in waves between the nips of pairs of rolls; unevenness resulted because of thick and thin portions of the slightly twisted small strands of cotton. Even with more uniform length of fibers, the spreading tendency of the ribbons of fibers could not be kept within the bounds of the main body of the loose cotton strand. The result was yarn of inferior quality.

There are several types of high-draft systems. They perform the same function and can be considered as a whole.

While the 3-roll system of drafting gave a maximum total draft of 12, the improved, or high-draft, system is capable of 30 with as high as 50 appearing evident. The mechanical stretching of these smaller strands of cotton, consisting of long and short fibers, is now attained by an appropriate combination of aprons or narrow bands and rolls. These devices have their surface speeds in proper ratios with one another. This drafting assembly allows the fibers to be held gently and to yield under proper tensions. The fibers are then drawn forward by the pressure of the aprons and rolls. The spacing or setting between the nip of the front rolls and the delivery nip of the aprons is within the staple length of practically all fibers. In the usual commercial, so-called 1-inch cotton, the fibers vary greatly. Although the predominant number of fibers are close to 1 inch in length, there may be appreciable quantities of fibers varying in length from 1 1/8 inch to 1/4 inch. Besides length, such properties as fineness, strength, spirability, wall thickness, elasticity, and moisture content may complicate any drafting system in the attainment of uniformity in yarns.

Although the principle of high, or long, drafting names synonymous with many trade names in use today introduced obvious improvements, applications were not widely realized until 1918, 50 years after its invention. The new draft system permitted the elimination of one roving process; but, like many advances, the improved system demanded concessions on the part of mill operators. Because of the greater number of exposed parts, more frequent cleaning was necessary and the machinery was more expensive. These objectionable features are fast being corrected.