Chapter XII: Winding: Rolls and Cops

The actual spinning and twisting operations being thus completed, the yarns are ready to be combined either for more elaborate types of twist, or for the processes of cloth manufacture. In its simplest definition, a fabric consists of two series of threads interlaced in such way as to form a more or less solid and compact structure. The two series of threads which are interlaced receive the technical terms of warp and weft--in poetical language, warp and woof. The threads which form the length of the cloth constitute the warp, while the transverse threads are the weft.

The warp threads have ultimately to be wound or "beamed" on to a large roller, termed a weaver's beam, while the weft yarn has to be prepared in suitable shape for the shuttle. These two distinct conditions necessitate two general types of winding:

(_a_) Spool winding or bobbin winding for the warp yarns.

(_b_) Cop winding or pirn winding for the weft yarns.

For the jute trade, the bulk of the warp yarn is wound from the spinning bobbin on to large rolls or spools which contain from 7 to 8 lb. of yarn; the weft is wound from the spinning bobbin into cops which weigh approximately 4 to 8 ounces.

Originally all jute yarns for warp were wound on to flanged bobbins very similar to, but larger than, those which are at present used for the linen trade. The advent of the roll-winding machine marked a great advance in the method of winding warp yarns as compared with the bobbin winding method; indeed, in the jute trade, the latter are used only for winding from hank those yarns which have been bleached, dyed or similarly treated. Fig. 22 illustrates one of the modern bobbin winding machines for jute made by Messrs. Charles Parker, Sons & Co., Dundee. The finished product is illustrated by two full bobbins on the stand and close to a single empty bobbin. There are also two full bobbins in the winding position, and several hanks of yarn on the swifts. Each bobbin is driven by means of two discs, and since the drive is by surface contact between the discs and the bobbin, an almost constant speed is imparted to the yarn throughout the process. An automatic stop motion is provided for each bobbin; this apparatus lifts the bobbin clear of the discs when the bobbin is filled as exemplified in the illustration.

The distance between the flanges of the bobbin is, obviously, a fixed one in any one machine, and the diameter over the yarn is limited. On the other hand, rolls may be made of varying widths and any suitable diameter. And while a bobbin holds about 2 lb. of yarn, a common size of roll weighs, as already stated, from 7 to 8 lb. Such a roll measures, about 9 in. long and 8 in. diameter; hence for 8 lb. yarn, the roll capacity is 14,400 yards.

Rolls very much larger than the above are made on special machines adopted to wind about six rolls as shown in Fig. 23. It is built specially for winding heavy or thick yarns into rolls of 15 in. diameter and 14 in. length, and this particular machine is used mostly by rope makers and carpet manufacturers. One roll only is shown in the illustration, and it is winding the material from a 10 in. x 5 in. rove bobbin. The rove is drawn forward by surface or frictional contact between the roll itself and a rapidly rotating drum. The yarn guide is moved rapidly from side to side by means of the grooved cam on the left, the upright lever fulcrumed near the floor, and the horizontal rod which passes in front of the rolls and upon which are fixed the actual yarn guides. This rapid traverse, combined with the rotation of the rolls, enables the yarn to be securely built upon a paper or wooden tube; no flanges are required, and hence the initial cost as well as the upkeep of the foundations for rolls is much below that for bobbins.

Precisely the same principles are adopted for winding the ordinary 9 in. x 8 in. or 8 in. x 7 in. rolls for the warping and dressing departments. These rolls are made direct from the yarn on spinning bobbins, but the machines are usually double-sided, each side having two tiers; a common number of spools for one machine is 80.

The double tier on each side is practicable because of the small space required for the spinning bobbins. When, however, rolls are wound from hank, as is illustrated in Fig. 24, and as practised in several foreign countries even for grey yarn, one row only at each side is possible. Both types are made by each machine maker, the one illustrated in Fig. 24 being the product of Messrs. Charles Parker, Sons & Co., Dundee.

In all cases, the yarns are built upon tubes as mentioned, the wooden ones weighing only a few ounces and being practically indestructible, besides being very convenient for transit; indeed it looks highly probable that the use of these articles will still further reduce the amount of yarn exported in bundle form.

The machine illustrated in Fig. 24, as well as those by other makers, is very compact, easily adjustable to wind different sizes of rolls, can be run at a high speed, and possesses automatic stop motions, one for each roll.

A full roll and a partially-filled roll are clearly seen. A recent improvement in the shape of a new yarn drag device, and an automatic stop when the yarn breaks or the yarn on the bobbin is exhausted, has just been introduced on to the Combe-Barbour frame.

Weft Winding. A few firms wind jute weft yarn from the spinning bobbins on to pirns (wooden centres). The great majority of manufacturers, however, use cops for the loom shuttles. The cops are almost invariably wound direct from the spinning bobbins, the exception being coloured yarn which is wound from hank. There are different types of machines used for cop winding, but in every case the yarn is wound upon a bare spindle, and the yarn guide has a rapid traverse in order to obtain the well-known cross-wind so necessary for making a stable cop. The disposition of the cops in the winding operation is vertical, but while in some machines the tapered nose of the cop is in the high position and the spinning bobbin from which the yarn is being drawn is in the low position, in other machines these conditions are opposite. Thus, in the cop winding frame made by Messrs. Douglas Fraser & Sons, Ltd., Arbroath, and illustrated in Fig. 25, the spinning bobbins are below the cops, the tapered noses of the latter are upwards in their cones or shapers, and the yarn guides are near the top of the machine. This view shows about three-fourths of the full width of a 96-spindle machine, 48 spindles on each side, two practically full-length cops and one partially built. The illustration in Fig. 26 is the above-mentioned opposite type, and the one most generally adopted, with the spinning bobbins as shown near the top of the frame, the yarn guides in the low position, and the point or tapered nose of the cop pointing downwards. Six spindles only appear in this view, which represents the machine made by Messrs. Urquhart, Lindsay & Co., Ltd., Dundee, but it will be understood that all machines are made as long as desired within practicable and economic limits.

The spindles of cop machines are gear driven as shown clearly in Fig. 26; the large skew bevel wheels are keyed to the main shaft, while the small skew bevel wheels are loose on their respective spindles. The upper face of each small skew bevel wheel forms one part of a clutch; the other part of the clutch is slidably mounted on the spindle. When the two parts of the clutch are separated, as they are when the yarn breaks or runs slack, when it is exhausted, or when the cop reaches a predetermined length, the spindle stops; but when the two parts of the clutch are in contact, the small skew bevel wheel drives the clutch, the latter rotates the spindle, and the spindle in turn draws forward the yarn from the bobbin, and in conjunction with the rapidly moving yarn guide and the inner surface of the cone imparts in rapid succession new layers on the nose of the cop, and thus the formed layers of the latter increase the length proportionately to the amount of yarn drawn on, and the partially completed cop moves slowly away from its cup or cone until the desired length is obtained when the spindle is automatically stopped and the winding for that particular spindle ceases. Cops may be made of any length and any suitable diameter; a common size for jute shuttle is 10 in. long, and 1-5/8 in. diameter, and the angle formed by the two sides of the cone is approximately 30 degrees.