This reversal only occupies two or three seconds, and as the motion imparted to the spindles is very slow at this stage, the practical effect is, that a small portion of yarn is "_uncoiled_" from each spindle, sufficient to allow of two "guide wires" to a.s.sume proper and necessary positions for winding the attenuated threads upon the spindles.

These two wires are termed "faller wires," and while one is controlled by the cop-shaping mechanism and termed the "winding faller wire" the other simply keeps the threads in the requisite state of tension during "winding on" and is termed the "counter" or "tension faller wire." Both these wires can be seen in Fig. 28. During backing off, the "winding faller wire" has a descending motion, while the "counter faller" has an ascending motion, these being necessary for them to attain their proper positions for "winding on."

Image: FIG. 28.--Mule showing action of faller wires.

The movement of these faller wires into proper position, and the uncoiling of a small portion of yarn from each spindle, are both brought about by the "backing off" motion, which formed an important part of Roberts' Mule. It may be remarked, however, that certain of the predecessors of Roberts had made great efforts in this direction, thus making the way much easier for his applications, which were entirely successful. When "backing off" is completed, all the necessary parts are in position for winding the 64 inches of thread just given out upon each spindle.

This practically involves three primary and most important operations.

(1) The drawing-in of the carriage back to its original position. (2) The revolution of the spindles at a speed suitable for winding the threads upon the spindles as the carriage moves inwards. (3) The guiding of the threads upon the spindles in such a manner that a cop of yarn will eventually be formed upon each spindle, of such dimensions and shape as to be quite suitable for any subsequent processes or handling.

Taking these three important divisions in the order given, it may be said that the drawing-in of the carriage is effected through the medium of the "scroll" bands, which are attached to the carriage at one end, and to certain spiral scrolls or fusees at the other end. The scrolls being revolved, wind the cords or bands round them, so pulling in the carriage. There are usually two back scroll bands and one front band, the latter being a sort of check band upon the action of the other two.

What is termed the "rim band" revolves the spindles during the outward traverse of the carriage.

The drawing-in of the carriage in a sense causes the other two operations to be performed. With respect to the second of these, viz., revolving the spindles and thus winding the threads upon them, it may be said this action causes what is termed the "Winding Chain" to pull off a small drum of six inches diameter, thus rotating the latter and thereby the spindles. Here, however, comes in now the action of the very beautiful and effective piece of mechanism, "Roberts' quadrant" (see Fig. 26). The winding chain just mentioned is attached to one extremity to the arm of the quadrant, and the peculiar manner in which the quadrant moves in relation to the winding drum gives the variable motion to the spindles that is required.

When commencing a new set of cops it may take about eighty revolutions of the spindles to wind on the 64 inches of thread to each spindle, representing one stretch. The bare spindle may be about a quarter of an inch in diameter, but it may finally attain a diameter of an inch and a quarter (_i.e._, the cop upon the spindle). This cop will only require about twenty revolutions to wind on the 64 inches, which are only one-fourth of the revolutions necessary for the empty spindles. It is the action of the quadrant which gives this variation in speed to the spindles during winding-on.

But as has been pointed out previously, the quadrant imparts a "differential winding" motion to the spindles in two distinct and different ways, and the second motion is even more important than the first.

It is necessary for practical purposes that the cop of yarn should be built up of a conical shape in the upper part, as shown in the ill.u.s.tration. Now it must be obvious to the least technical of the readers of this story, that to wind a given portion of yarn upon the thin apex of a cone, will require a greater number of revolutions than would be necessary to wind the same length of yarn upon the base of the same cop. All the way between the apex and the base of the cone are also other varying diameters, and during each return movement of the mule carriage the thread is wound upon all the varying diameters of the cone in succession.

This implies the necessity for the revolutions of the spindles to a varying quant.i.ty all the time of the return or inward movement of the spindle carriage.

The quadrant gives this varying speed in a manner which is all but mathematically correct, any slight deviation from any such mathematical correctness being easily compensated for in other ways.

For the specific manner in which this quadrant works, the reader is referred to any of the recent text-books on cotton spinning.

The third primary and important operation, which takes place during each return movement of the carriage, is the guiding of the thread upon the spindles in a correct manner. This operation is closely a.s.sociated, however, with the action of the quadrant.

That portion of a "self-actor mule" which guides the faller wires is termed the "shaper" or "copping motion." It consists of an inclined iron rail upon the upper smooth surface of which slides the "copping bowl,"

this being a portion of the mechanism which connects the rail with the faller wires. The rail rests upon suitable inclines termed "copping plates," whose duty it is to regulate the movement of the rail so as to allow for the ever-increasing dimensions of the cop during the building process. When the carriage again reaches its initial position, suitable mechanism causes all the parts to return in the position required for spinning.

Such is the complete cycle of movements of the "mule," each succeeding cycle being simply a repet.i.tion of the preceding. It will probably take such a mule as the one described about six hours to make a "set of cops," _i.e._, one on each spindle, each cop being 1-1/4 inches in diameter and 7-1/2 inches long. Every fifteen seconds, while the mule is making a cycle of its movements, may be divided up approximately as follows: nine seconds for the drawing-out and twisting; two seconds for backing-off; four seconds for winding-on and resuming initial position.

A mult.i.tude of minor motions and details might be easily expanded into several chapters; in fact, more can be said about the mule than about any other spinning machine, but such detailed description would be out of place in this story.

All the motions just named are centred in what is termed the "Head Stock," this being placed midway in the length of the mule.

This head stock receives all the power to drive the various motions, from the shafting and gearing, and distributes it in a suitable manner to various parts of the machine.

It will have been observed by this time, that, as in the case of the bobbin and fly frames, the intricate and wonderful mechanism of the self-actor mule is not devoted to the formation of threads, but to the effective and economical placing of the threads of yarn, in the form of cops, after it has been spun.

Image: FIG. 29.--Mule head showing "copping rail."

The spinning processes take place during the outward traverse of the mule carriage, the mechanism involved in this motion being comparatively simple. The really complicated and difficult motions being "backing-off," revolving the spindles "during winding-on," and the guiding of the spun threads upon the spindles during the winding-on process. It was the addition of these three motions by the later inventors which gave the mule the t.i.tle of "Self-Acting."

CHAPTER X.

OTHER PROCESSES IN COTTON SPINNING.

=The Ring Spinning Machine.=--In a former chapter it was shown how within the s.p.a.ce of two decades the three rival spinning machines of Hargreaves, Arkwright and Crompton were introduced, also it was pointed out, that Crompton's machines contained the best points of both of his predecessors. The mule did not immediately become the sole spinning machine. From the outset there was a close contest between the continuous spinning machine of Arkwright and the intermittent spinning machine of Crompton. It was not long, however, before the mule a.s.serted its superiority over the water frame for fine muslin yarns, and for weft yarns. Eventually the water frame was relegated to the production of strong warp yarns, and later still it has come to be largely utilised as a doubling machine. As a matter of fact, it is contended by experts of the present day, that no machine ever made a rounder and more solid thread than the water frame, or flyer-throstle, as it has been called in its improved form.

Image: FIG. 30.--Ring spinning frame.

During the last thirty years, a revolution practically in cotton spinning has been gradually brought about, and even to-day active developments are to be seen. The continuous system of spinning, which for a time had to take a second place, now appears to be again forging ahead, and looks as though it would supersede its more ponderous rival.

Especially in countries outside England is this the case, for it is found that the method of ring spinning preponderates, and even in England the number of spindles devoted to continuous spinning is constantly increasing.

This change has chiefly been brought about by what may be termed a revolution in the winding and twisting mechanism of the continuous spinning machine itself.

Arkwright's flyer and spindle, after improvement by subsequent inventors, could not be revolved at anything like the speed of the spindle of the mule, and, in addition to this, the yarn had to be wound always upon the bobbin, very much after the style of the bobbin and fly frames previously described.

Experiments, however, were repeatedly made in the direction of dispensing with the flyer altogether, and some thirty years ago these unique spinning frames had attained very general adoption in the United States of America, where the comparative dearth of skilled mule spinners had furnished an impetus to improvement of the simple machine of Arkwright.

About this time, the attention of certain English makers being directed to the success of the new spinning frames in America, led to their introduction into England. But little time elapsed before they received a fair amount of adoption, but for many years they had a restricted use, viz., for doubling, that is, the twisting of two or more spun threads together, to form a stronger finished thread.

In this way, they were, strictly speaking, rivals of the throstle doubling frame more than the spinning mule.

By and by, however, the time came when the new frames began to be adopted as spinning machines, and to-day there are many English and foreign mills containing nothing else in spinning machines on the continuous system except these. In not a few mills in different countries, both types are found running.

A careful glance at the picture of this rival of the mule, will help in the following description of it:--

The flyer which is to be seen on the old Saxony wheel, and which was perpetuated in the celebrated machine of Arkwright, is entirely dispensed with, and all its functions efficiently performed by apparatus, simple in itself; it is yet capable of high speed and heavy production.

First of all, there is a vastly improved and cleverly constructed form of spindle, by which, in the latest and best makes, any speed can be attained which is likely to be required for spinning purposes.

Perhaps the apparatus which plays the most important part in performing the duties of the displaced flyer, is a tiny "traveller" revolving round a specially made steel ring about 2 inches in diameter.

The use of these two latter gives the distinctive names of "Ring-spinning" to the new system and "Ring Frame" to the machine itself.

In describing this system of spinning the creel of rovings to be operated upon, and the drawing rollers being practically identical with machines already described, little here is required to be said of them, but there is, however, a modification in the arrangement of the rollers which is referred to later on.

After leaving the rollers, a thread of yarn is conducted downwards and pa.s.sed through the "travellers," which may be seen in the ill.u.s.tration, and then attached to the bobbin. The "traveller" is a tiny ring made of finely tempered steel. It is sprung upon the edge of the ring shown in the frame, and which is specially shaped to receive the tiny ring or traveller referred to.

The bobbin in this case is practically fast to the spindle--unlike any other case in cotton-spinning machinery--and it is therefore carried round by the spindle at the same rate of speed.

As the spindle and bobbin revolve, they pull the traveller round by the yarn which pa.s.ses through it, being connected at one end to the bobbin and the rollers above forming another point of attachment. If the reader will look carefully at the ill.u.s.tration he will see how twist is put in the yarn. The joint action, then, of bobbin, traveller and fixed ring, is to put the necessary twist in the yarn which gives it its proper degree of strength. If no fresh roving from the rollers were issuing for the moment, the small portion of thread reaching from the rollers to the bobbins would simply be twisted without any "winding-on" taking place. As a matter of fact, the roving always is issuing from the rollers, and "winding-on" of the twisted roving is performed by the traveller lagging behind the bobbin in speed, to a degree equal to the delivery of roving by the rollers. It will be remembered that in the old flyer-throstle "winding-on" was performed by the bobbin lagging behind the spindle, a procedure which is impossible on the ring frame.

There is also an arrangement of the mechanism for guiding and shaping the yarn upon the bobbins in suitable form, the action being as nearly as possible an imitation of the mule.

For a number of years after the introduction of these frames, it was found that the threads often broke down owing to the twist not extending through the roving to the point where it issued from the rollers. This was eventually remedied by placing the drawing rollers in a different position, thus causing the thread running from the rollers to the traveller to approach more to the vertical; this const.i.tuting the modification which has just been referred to previously.

Another difficulty was experienced in the fact that during spinning the threads would sometimes fly outwards to such an extent that adjacent threads came in contact with each other, causing excessive breakage.

This was technically termed "ballooning," and has been very satisfactorily restricted by the invention of special apparatus.