The mule, by reason of the great size to which it has been developed, and the impressiveness of its large, rhythmic motion, is one of the most formidable of all cotton machines, as indeed it is one of the most complex. It received its name from the fact that, performing two principal functions—drawing and spinning—it was regarded as a hybrid, just as the mule is a hybrid cross between the horse and the donkey.
In the mule (see diagram on page [53]), which is a long and wide machine, carrying sometimes, in new models, as many as 1,300 spindles, the drawing and twisting are not continuous but consecutive. The rovings (B) are held on a creel (A) at the back of the machine, usually in three or 52 four tiers, or on long beams or spools. They pass from the creel, or spools, between three pairs of drawing rollers (C.) Coming out of the rollers, they are fed to the spindles on the carriage which backs away from the creel and recedes somewhat faster than the rovings are unwound. This receding is the essential motion of the mule, for thus the cotton receives its final drawing. The spindles, meanwhile, are revolving rapidly, spinning the yarn. The twist goes first to the thin places where the least resistance is offered. Then, as the carriage carrying the whirling spindles continues to back away, the thicker parts of the thread, being comparatively untwisted are pulled down to the average diameter and are twisted in turn. The carriage usually runs back about sixty-three inches. At the termination of its run, or stretch, the spindles increase their speed until the twisting is completed and the carriage starts on its return trip. This reverses the spindles, and the thread which has been wound upon them is unwound, the slack being taken up by one guide wire (D) while the other guides the thread to the winding point, and winds it up in the opposite direction on the cone-shaped cops on the spindles. The rollers do not feed out more roving as the carriage returns. Hence, there is no slack when the round trip is completed.
Slubbers, showing the U-shaped flyers
Except for the use of drawing rollers, there is little similarity between the mule and the ring frame. The latter has no movable carriage, none of the splendid sweep of motion that makes the mule so 53 fascinating to watch. The ring-frame is simple and business-like, and its speed is amazing. The bobbins holding the roving are placed directly over the spindles. Around each of the latter is a steel ring. There are at least 112 spindles on each machine, and all the machine rings for the spindles are fixed in a single frame. The upper edge of the ring is flanged, like a miniature railroad track, and snapped over the flange is a small but important C-shaped steel ring, called the traveler.
How Thread is Spun
on the Ring Spindle
When the machine is in operation (See diagram on page [56]) each roving (H) leaving its bobbin, runs through the usual drawing rollers (G) then through a guiding wire to the ring, where it is passed through its traveler (B) which is always at the winding point on the spindle. As the spindle and the rollers revolve, the roving is fed out at a considerably slower rate than the spindle takes it up, so that there is always a tension on the thread. The whirling spindle thus pulls on the traveler, drawing it round and round on its flanged track (A). It revolves just a little more slowly than the spindle and thus the yarn receives its twist. Meanwhile, the frame (C) on which the rings are fixed moves slowly up and down, so that the winding is properly regulated.
It is possible to operate the spindles at a remarkable speed. So perfect are the bearings which have been evolved that the average speed is ten thousand revolutions a minute, and on fine yarns it is sometimes 12,000 to 13,000 revolutions. The speed is limited by only two factors: the first is the ability of the operator to make splicings when threads break, and the second is the tendency of the traveler to fly off when the speed is too high. The number of travelers consumed is high at best, and in a mill which has long been in operation the floor in the front of the frame is likely to be paved with the little steel rings which have fallen and been ground into the planks by the heels of the worker.
