In former chapters it has been pointed out that the knitted stitch is apparently a simple structure, but on closer examination a number of elements are discovered which together form a complex whole. In the knitting operation the chief essential is accuracy of loop formation and regularity of stitch right along the entire width of loops in the course. If at any point the thread is drawn slightly tighter than the normal, this tightening is at once apparent in the formation of the loops and a grave defect occurs which on account of its minuteness is impossible to remedy in after operations. In the knitting operation correct tension of thread is indispensable to good quality fabric, and this again depends on an absolutely uniform feed of yarn to the needles of the machine. In this yarn supply one of the first essentials is a proper package for the yarn and one which will insure that the thread unwinds with absolutely even tension throughout. It is a very serious matter indeed to the hosiery manufacturer if even slight obstacles occur on the bobbin for these at once injure the fabric quality. Another frequent cause of defects occurs by what is termed the ballooning of the thread as it comes from the bobbin, that is, the swing which the thread makes in unwinding itself when it encounters the resistance of the air, a matter which depends on the bulk of the thread and the amount and nature of its surface fibre. It also varies according as the bobbin is full or nearly empty with intermediate stages of differential variation. So important is this matter of uniform yarn feed recognized to be for first-class fabric, that the Americans in particular have given the utmost attention to yarn supply devices, by which the yarn is measured into the needles by an arrangement which deadens all the minor variations of tension before the yarn approaches the sinkers and needles, and the amount fed into the needles is measured absolutely level for each stitch. There is also a The Winding Operation.—Sufficient has been stated to indicate that the winding of yarn usually regarded as subsidiary in other branches of textiles is a first essential in the knitting business. An evenly-wound package is of great importance, and in regard to the size of bobbin conditions are quite different to those prevailing in the weaving trade. In weaving the weight of the package is restricted to the capacity of the shuttle, this being limited in size so that the weight may be kept at the minimum required for throwing across the lay of the loom. In knitting the position is more favourable, for the bobbin or yarn package is usually stationary and the thread is drawn from it to be fed into the needles of the frame. For this it is naturally an advantage to have the package as large as possible so as to reduce to the lowest minimum the time required for changing from an empty bobbin to a full one. To insure uniformity of yarn delivery to the needles and sinkers it is essential to have a perfectly built bobbin, and for the older types of winding frames, the usual shape was a bobbin with a high centre where the yarn got frequently caught in the grooves or on the bottom end. This primitive system of yarn winding was not unsuitable for the coarser types of knitting yarns in the stout gauges, and for this work the older form of winder is found in many of our factories even to-day. This machine has the advantage of being simply constructed and easily manipulated by an unskilled worker, and it is also rapid in action. Figs. 48 and 49 Bobbin Building.—The outstanding advantage of this machine is the efficient manner in which the bobbin is built, and in this process several factors have to be considered. The thread guide G has a regular up-and-down motion for the traverse, this upward and downward sweep being brought about by the heart-shaped cam C which, by its revolving action, causes the whole stage P to rise and fall, thus giving a similar motion to the thread guide. Partaking in this traverse is the spiral S with the wheel W, which has a ribbed surface to preserve contact with the yarn level. The wheel W has a finger V attached, which in turn works into the spiral of rod S, and whenever the yarn rises to a certain level on the bobbin, it comes into frictional contact with the ribbed wheel which receives a turn sufficient to cause the wheel and guide to rise higher on the spiral and with it the thread guide also assumes a more elevated position. In this way the The Differential.—The final element in successful bobbin building is the differential and the means of securing this are ingenious in the highest degree. The driving wheel DW with its rough leather rim works on the disc FW and causes it to rotate, but the speed of rotation must vary according as the upper or the lower part of the bobbin is being filled. When the yarn is passing on to the bare part of the bobbin as it does at the upper sweep of the traverse, one revolution coils a very much smaller length of thread than it does at its lowest position when the bobbin is full. The rate of winding varies differentially according to the intermediate positions of the thread, in the upward sweep of the traverse the speed of the bobbin accelerates as the bare part is approached, whilst on the downward sweep the speed of the bobbin decreases, reaching its slowest when the full part of the bobbin is attained. This differential is produced by a side-to-side movement of the driving wheel DW over the rim of the disc FW, from the outer rim and slowly towards the inner rim and vice versÂ. When the wheel is driving at its extreme position on the outer rim the bobbin is running at its slowest, because the driving wheel has a longer distance to traverse in order to effect one bobbin revolution. When the driving wheel is acting at its furthest position inwards the bobbin is at its highest speed, and this takes place with graduated differences in the intermediate stages of the process. Yarn Clearing.—On most winding machines for the hosiery trade are placed in front of each spindle for winding a pair Damping.—Damping is one of the subsidiary operations of hosiery manufacture which, apparently of little account, may yet have serious consequences if neglected or improperly performed. Manufacturers are divided as to the merits of damping or lubricating as it is often called, and in many progressive factories it is seldom if ever performed. The object of damping is to soften those classes of woollen, silk and cotton yarns which are deficient in pliability and do not allow themselves to be formed into symmetrical loops. In the case of woollen yarns some varieties are hard and unyielding, and when knitted in loops they display small irregularities of stitch which are known popularly under the term of pinholes. These occur irregularly all over the texture and seriously impair its quality and lubrication or damping is found to have a beneficial effect by giving greater elasticity and bending power to the thread. The lubricating or damping agent varies according to the type of yarn, woollen yarns are damped with an emulsion of oil and soap, lard is often used for silk materials, whilst cottons are passed through cakes of paraffin wax. For woollen yarns the lubricating is performed Evils of Damping.—The beneficial effects of damping dry and hard woollen yarn is at once evident in the improved nature of the fabric, but there are serious drawbacks to the indiscriminate adoption of the process. Woollen yarn has considerable hygroscopic capacity and it laps up this moisture very greedily, altering its physical properties considerably in so doing. One effect of damping is to considerably augment the elasticity and stretch of the yarn and this induces variation in the dimensions of garments, introducing an unstable element which is very difficult to gauge accurately. The sizes of garments tend to vary considerably, and difficulty is experienced in seaming or joining them together to have each side terminate equally. There are also differences in the weight of the garments owing to the capacity which the woollen fibre has of absorbing moisture far in excess of what is recognized as essential, and the effect is to vitiate size measurements. This gives rise to pants longer in one leg than another, and one side of a seam going to a greater length than the neighbouring one to which it has to be attached. The lubricating materials supplied as substitutes have not always proved suitable, for in many instances they fail to emulsify, and if the oil is left to go on to the yarn by itself it causes stickiness if the brand proves to be inferior or contains |