Part 9 (1/2)

It is at this stage that the bulk of the heavier impurities still found in the cotton are removed, as these fall through certain grids below the taker-in immediately they are loosened from the retaining fibres by the powerful teeth of the taker-in.

The great bulk of the cotton fibres, however, are retained by the teeth of the taker-in and carried round the under side to a point where they are exposed to the action of the central and most important part of every Carding Engine, viz., the main ”cylinder.” The licker-in contains about twenty-eight teeth per square inch, but the ”cylinder” is the first of the parts that the cotton arrives at, previously referred to as being covered with a vast number of closely set steel wire teeth.

Just to convey an idea of this point to the uninitiated reader, it may be said that it is quite common to have on the ”cylinder” as many as 600 steel wire teeth in one square inch. For a cylinder 40 inches wide and 50 inches diameter, this works out to the vast number of over 3,800,000 steel wire teeth on one cylinder, each tooth being about 1/4 inch long, and secured in a cloth or rubber foundation before the latter is wound round the cylinder.

The steel teeth of the cylinder strip the fibres from the taker-in and carry them in an upward direction, the surface speed of the cylinder being over 2000 feet per minute.

Placed over the cylinder, and extending for nearly one-half of its circ.u.mference, are what are technically known as the ”flats.”

These are narrow iron bars, each about 1-3/8 inches wide; each being covered with steel wire teeth in the same manner as the cylinder; and each extending right across the width of the cylinder, and resting on a suitable bearing termed the ”bend.”

They are formed into an endless chain containing about 108 ”flats,” but only about 44 of which are in actual work at one time; this endless chain of flats being given a slow movement of about 3 inches per minute.

Here it may be said that the various working parts are set as close as possible to each other without being in actual contact, the usual distance being about 1/143rd of an inch determined by a specially constructed gauge, in the hands of a skilled workman.

The steel teeth of the flats, being set very close to those of the cylinder, catch hold of and retain a portion of the short warty fibres and fine impurities that may be on the points of the cylinder teeth, the amount of this reaching about 3 per cent. of the cotton pa.s.sed through the machine. In addition to this the teeth of the flats work against those of the cylinder so as to exercise a combing action on the cotton fibres.

Having pa.s.sed the ”flats,” the cotton is deposited by the cylinder on what is termed the doffer. This is a cylindrical body, exactly similar to the main ”cylinder” excepting that it is only about half the diameter, say 24 inches. Its steel wire teeth are set in the opposite way to those of the cylinder, and its surface speed is only about 75 feet per minute. These two circ.u.mstances acting together enable it to take the cotton fibres from the main cylinder.

The operations of carding may now be said to be practically performed, as the remaining operations have for their object the stripping, collecting, and guiding of the cotton into a form suitable for the next succeeding processes. The fleece of cotton is stripped from the doffer by the ”Doffer Comb,” which is a thin bar of steel, having a serrated under edge, and making about 1600 beats or strokes per minute. From this point cotton is collected into the form of a loose rope or ”sliver,” and pa.s.sed first through a trumpet-shaped mouth, and then through a pair of calender rollers about six inches wide and four inches in diameter.

Image: FIG. 16.--Lap, web, and sliver of cotton.

Finally, the sliver of cotton is carried upward, as shown in the ill.u.s.tration (Fig. 15), and pa.s.sed through special apparatus and deposited into the can, also shown. This latter is about 10 inches in diameter and 36 inches in length, and the whole arrangement for depositing the cotton suitably into the can is denominated the ”Coiler.”

In the next ill.u.s.tration (Fig. 16) are shown three forms in which the cotton is found before and after working by the Carding Engine. That to the left is the lap as it enters, the middle figure is part of the web as it comes from the doffer, and that to the right is part of a coil of cotton from the can.

Such is a brief description of the most important of the preparatory processes of cotton spinning. There are innumerable details involving technical knowledge which fall outside the province of this story.

=Drawing Frames.=--It is a very common thing for a new beginner in the study of cotton spinning to ask--what is the use of the drawing frame?

As a matter of fact, the unpractised eye cannot see any difference between the sliver or soft rope of cotton as it reaches, the drawing frame and as it leaves the frame.

The experienced eye of the practical man can, however, detect a wonderful difference.

It has been shown that the immediately preceding operation of carding--amongst other things--reduces the heavy lap into a comparatively thin light sliver; thus advancing with one great stride a long way toward the production of the long fine thread of yarn ready for the market.

No such difference can be perceived in the sliver at the drawing frame.

This machine is practically devoted to improving the thread finally made in two distinct and important ways.

1. The fibres of cotton in the sliver, as they leave the Carding Engine, are in a very crossed and entangled condition, not at all suited to the production of a strong yarn by the usual processes of cotton spinning.

The first duty of the drawing frame may be said, therefore, to be the laying of the fibres in parallel order to one another, by the action of the drawing rollers.

2. The sliver of cotton, as it leaves the card, is by no means sufficiently uniform in weight per yard for the production of a uniform and strong finished thread. It will easily be conceived by the readers of this story of the cotton plant that the strength of any thread is only that of its weakest portions.

Take a rope intended to hold a heavy weight suspended at its lower end, and a.s.sume it to be made of the best material and stoutest substance, but to contain one very weak place in it; this rope would practically be useless, because the strength of the rope would only be that of the weakest part.

The drawing machine in cotton spinning aims at removing the weak places in cotton thread, thus making the real strength of the thread vastly greater than it would otherwise be.