Part 10 (1/2)

In order to increase the uniformity of the roving or strand of cotton, the ends from two of the slubbing rovings are conducted together through the rollers of the machine.

There are three pairs of these rollers, acting on the cotton in every way just as described for the drawing frame.

Although two rovings are put together behind the rollers, yet the ”draft” or drawing-out power of the rollers is such, that the roving that issues from the front of the rollers is about three times as thin as each individual roving put up behind the rollers. This drawing-out action of the rollers need not be further dilated upon at this stage.

The points which demand some little attention at our hands, are the methods and mechanism involved in twisting the attenuated roving, and winding it upon bobbins or spools in suitable form for the next process.

Image: FIG. 18.--Intermediate frame (bobbin and fly frame).

As regards twisting of the roving it must be distinctly understood that when the attenuated strand of cotton issues from the rollers of the first bobbin and fly frame, it has become so thin and weak that it can no longer withstand the requisite handling without being seriously damaged. Hence the introduction of ”Twist,” which is by far the most important strength-producing factor or principle entering into the composition of cotton roving and yarn.

Without twist there would be no cotton factories, no cotton goods; none of the splendid and gigantic buildings of one description or another which are found so plentifully intermingled with the dwellings and factories of large cotton manufacturing towns!

In a sense it is to this all-powerful factor of ”twist” that all these buildings owe their existence, since it would be practically impossible to make a thread from cotton fibres without the a.s.sistance of ”twist” to make the fibres adhere to each other. Hence there could be none of that wealth which has caused the erection of these buildings.

This is true in a double sense, since we have both the natural twist of the cotton fibres and the artificial twist introduced at the latter processes of cotton spinning, in order to make individual fibres and aggregations of fibres adhere to each other. What is termed the natural twist of the fibres may average in good cottons upwards of 180 twists per inch, while the twists per inch put into the finished threads of yarn from those fibres may vary, say, between 20 and 30 twists per inch.

In all the fly frames, therefore, this artificial twist is invariably and necessarily put into the roving. As the cotton leaves the front or delivery rollers, each strand descends to a bobbin of from 8 to 12 inches long, upon which it is wound by special mechanism. As in Arkwright's frame, this bobbin is placed loosely upon a vertical ”spindle,” and upon the latter is fitted a ”flyer,” whose duty it is to guide the cotton upon the bobbin.

The primary duty of the spindle is to insert the ”twist” which has been shown to be so necessary to give sufficient strength to the roving.

Let any reader of this story hold a piece of soft stuff in one hand while with the other hand he rotates or twists the roving and he will have an idea of the method and effect of twisting (see Fig. 19).

Without going into minute details we may say that the practical effect is that, while the roving is held firmly by the rollers, it is twisted by means of its connection at the other end to the rotating bobbin, spindle and flyer. The twist runs right from the spindle along the 6 to 12 inches of cotton that may extend from the spindle top to the ”nip” of the rollers, thus imparting the requisite strength to the roving as it issues from the rollers. The mechanism for revolving the spindles is by no means difficult to understand, simply consisting of a number of shafts and wheels revolved at a constant, definite and regulated speed per minute.

Not only is it necessary to provide special apparatus for twisting the cotton at the bobbin and fly frames, but also very complicated and highly ingenious mechanism for winding the attenuated cotton in suitable form upon the bobbins. Indeed it is with this very mechanism that some of the most difficult problems of cotton spinning machinery are a.s.sociated.

Although the cotton at this stage is strengthened by twist, yet it is extremely inadvisable and practically inadmissible to insert more than from 1 to about 4 twists per inch at any of these machines, so that at the best the rovings are still very weak.

If too much twist were inserted at any stage, the drawing rollers of the immediately succeeding machine could not carry on the attenuating process satisfactorily.

This winding problem was so difficult that it absolutely baffled the ingenuity of Arkwright and his contemporaries and immediate successors, and it was not until about 1825 that the difficulties were solved by the invention of the differential winding motion by Mr. Holdsworth, a well-known Manchester spinner, whose successors are still eminent master cotton spinners.

This winding motion is still more extensively used than any other, although it may be said that quite recently several new motions have been more or less adopted, whose design is to displace Holdsworth's motion by performing the same work in a rather more satisfactory manner.

In these pages no attempt whatever will be made to give a technical explanation of the mechanism of the winding motion. It may be said that it was a special application of the Sun and Planet motion originally utilised by Watt in his Steam Engine, for obtaining a rotary motion of his fly-wheel.

Sufficient be it to say that this ”Differential Motion,” acting in conjunction with what are termed ”Cone drums,” imparts a varying motion to the bobbins upon which the cotton is wound, in such a manner that the rate of winding is kept practically constant throughout the formation of the bobbins of roving, although the diameters of the latter are constantly increasing.

The spindles and bobbins always rotate in the same direction, but while the revolutions per minute of the spindles are constant, so as to keep the twist uniform, those of the bobbins are always varying, in order to compensate for their increasing diameters or thicknesses of the bobbins.

The delivery of cotton from the rollers is also constant and the mechanism required to operate them is exceedingly simple.

A vast number of details could easily be added respecting the operations performed by the bobbin and fly frames, but further treatment is deemed unnecessary in this story.

CHAPTER VII.

EARLY ATTEMPTS AT SPINNING, AND EARLY INVENTORS.

There can be no better ill.u.s.tration of the truth of the old saying, that ”Necessity is the mother of invention,” than to read the early history of the cotton manufacture, and the difficulties under which the pioneers of England's greatest industry laboured.