Page:EB1911 - Volume 28.djvu/837

Rh coating of wool into the slowly retreating teeth of the doffer H, which carries it forward until angle stripper C′ strips the doffer, to be in its turn stripped by swift D′ and so on. The speeds of the cylinders are in the first place obviously dependent upon the principle of carding adopted, the greater speed always stripping (save in the case of the fancy). As to whether the speed shall be obtained by actual revolutions or by a larger diameter of cylinder depends upon the nature of the wool to be carded (long or short), the part which each cylinder has to play in the card, and upon the question of wear of clothing and power consumed. As a rule the strippers are all driven from a smaller circumference of the swift to obtain conveniently the necessary reduction in speed, and the slowly revolving workers are chain driven from the doffer, which indirectly receives its motion from the swift. The principles involved in the relative inclinations of teeth are very apparent, but the principles involved in the relative densities of teeth on the respective cylinders are again much involved and little understood.

A complete scribbler or first card engine consists of a breast, or small swift, and two swifts with the accompanying workers, strippers, fancies, doffers, &c. The wool is stripped from this card as a thin film by means of the doffing comb. This is usually weighed onto the next machine—whether intermediate or condenser—a given weight giving a definite count of condensed sliver. Should an intermediate be employed, there must be an automatic feed, taking the wool, as stripped from the last doffer of the intermediate, and feeding it perfectly evenly on to the feed sheet of the condenser. The condenser is usually a one-swifted card, the only difference in principle being that, whereas the sliver comes out of the scribbler or intermediate in one broad film, it is broken up into a number of small continuous slivers or films, each one of which will ultimately be drafted or drawn out and twisted into a more or less perfect thread. These slivers—which are delicate and pith-like in substance—are wound on to light bobbins, and these bobbins are placed on the mule for the final roving and spinning operations. There are many forms of condensing mechanisms such as the single-doffer, the double-doffer and the tape-condensers, but their construction is too complex to be described here. Whatever the type may be, the result is that noted above, but it should be noted that the tape enables a much finer sliver to be taken from the card than is possible with either the single- or double-doffer condenser.

9.—Sectional View of the Woollen Mule.

The principles involved in mule spinning are comparatively simple, but the necessary machinery is very complex; indeed it is questionable

if a more ingenious machine than the mule exists. The pith-like slivers received from the card-loom must be attenuated until the correct count of yarn is obtained; they must be twisted while this attenuation or drafting is in process, otherwise they would at once break; and after being attenuated to the required fineness the requisite number of turns must be inserted. Great stress must be laid on the effects of what is termed the “drafting-twist” noted above; it is probably this simultaneous drafting and twisting which develops the most pronounced characteristics of the woollen yarn and cloth, and differentiates it entirely from the worsted yarn and cloth. The mule (see fig. 9) consists of the delivery cylinders A, upon which the sliver bobbins B from the condenser are placed, which deliver the slivers as required to the front delivery rollers C (these rollers controlling perfectly the delivery of sliver for each stretch of the carriage), and the carriage EE carrying the spindles which may be run close up to the front delivery rollers and about two yards away from them to effect the “spin,” which is of an intermittent character. The spindles D are turned by bands passing round a tin drum K in the carriage, but this motion, and every other motion in the mule, is controlled perfectly from the headstock. In brief, the operation of spinning is as follows: as the carriage begins to recede from the delivery rollers these rollers deliver condensed sliver at about the same rate as the carriage moves out, the spindles putting in a little twist. When the carriage has perhaps completed half its traverse (say 36”) away from the front rollers these suddenly stop delivering the condensed sliver, the carriage goes more and more slowly outwards until it completes its traverse, drafting the sliver out to perhaps double the length. This drafting could not be effected but for the “drafting-twist,” which, running into the thin parts of the yarn during drafting.

strengthens them and thus from beginning to end equalizes the thread. Upon the completion of drafting the spindles are thrown on to “double speed” to complete the twisting of the 72” of yarn just spun as rapidly as possible, the carriage being allowed to run inwards for a few inches, to allow for the take-up due to twisting. The mule now stops dead, backs-off the turns of yarn from the bottom of the spindle to the top, the faller H wire falls into position to guide the thread on to the spindle to form the required cop G, and the counter-faller I wire rises to maintain a nice tension on the yarn. The carriage now runs in, the spindles being revolved to wind up the yarn, and, in conjunction with the guiding on of the faller wire, builds up a firm cop or spool, as the case may be.

Woollen mules are made with several hundred spindles and of varying pitch to suit particular requirements. Thus if the mules are to follow a set of say three carders with a tape condenser, and are required to spin fine counts, the pitch of the spindles may be much finer than ordinary, but a greater number will be required to work up the sliver delivered by the set of machines. There are many other details which require careful consideration; the inclination of the spindles, for example, must be suited to the material to be spun. And when all the mechanical arrangements are perfect there is still the necessity of correct judgment as to the qualities of the blend in hand, for in this case perhaps more than in any other the machine must be adjusted to the material and not the material to the machine.

10.—Plan and Section of a Preparing Box (Sheeter). A is the back-shaft receiving its motion from the driving shaft upon which are the pulleys. This back-shaft A drives the back-rollers B at a slow speed by the reducing train of wheels C; also the front rollers D at a much quicker speed through the train of wheels E, and the fallers F at an intermediary speed by means of the levels and screws G. G. The wool is “made up” on the feed sheet and on emerging from the front rollers is built up layer by layer into the lap H, which is finally broken across and feeds up at the next machine.

The yarn as delivered by the mule is “single” and will serve as warp or weft for the great bulk of woollen cloths, warp being as a rule twisted harder than weft. Sometimes for strength, sometimes for colour, however, it will be necessary to twist two or more of these single strands together. This is best effected on a twisting frame of the ring type, which consists of delivery rollers, to deliver a specified length of yarn in relationship to the turns of the spindles, and the spindles, which serve to put in twist and to wind the yarn upon the bobbin or tube, which they carry by reason of the retarding action of the traveller. Fancy twists such as knops, loops, slubs, &c., may also be produced if the frame is fitted up with two pairs of delivery rollers and two or three special but simple appliances.

The essential feature of a worsted yarn is straightness of fibre. Prior to the introduction of automatic machinery there was little difficulty in attaining this characteristic, as long wool was invariably employed and the sliver was made up by hand and then twisted. With the introduction of Arkwright's “water frame” or “throstle” the necessity for prepared slivers became apparent, and with the later introduction of cap and mule spinning the necessity for perfectly prepared slivers has been so accentuated that the preparatory machinery has quite