Yarn Clearing.—On most winding machines for the hosiery trade are placed in front of each spindle for winding a pair of upright plates which comprise the yarn clearers YC, which are regulated in their distance from each other by means of a small screw. The thread clearer is shown in front section in Fig. 49 where the plates are marked YC, their distance apart being regulated to a nicety by the small screw marked X operated by the two fingers. These thread clearers are fixed there so that by passing the yarn through between them on its way to the bobbin B, thick places, burrs, slubs, etc., may be removed from the yarns and extra large knots caught between them. In other words, the function of the thread clearer may be stated as a qualifying of the thread for its passage through the thread-carriers into the needles and sinkers of the knitting frame, and by removing these obstructions in winding, subsequent trouble in knitting is avoided and loss of time averted. In many hosiery factories, however, it is noted that these clearers are by no means in general use, and certainly if the yarn is in anything like clean condition, it should be permitted to pass on to the bobbin in an unruffled condition.
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 on the winding machine by passing the yarn through a lubricating trough marked N, Fig. 48, the trough being half filled with liquor marked L and in which the roller R is made to revolve. The ideal emulsion for the damping agent is olive oil and soft soap heated and mixed together to form an emulsion, but the high cost of these commodities have placed them out of the reach of practical work and now various substitutes are employed. The roller R is made to revolve in the damping solution by means of a band connected with the side drive of the machine, and this brings a fresh supply of liquor into persistent contact with the thread. The yarn should be worked on the frame as soon as possible after winding, for when the bobbin has stood for twelve hours or so the liquor begins to lose its effect due to evaporation, and if left standing overnight the effect of the damping may to a considerable extent be lost on a yarn.
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 resinous substitutes. In the coarser varieties of hosiery yarn which are spun in the grease, lubrication is not so essential, as the yarn is quite pliable, but in the varieties known as dry-spun where little or no oil is inserted in the sliver during preparation, damping greatly improves the loop-forming propensities. It would seem that a certain amount of fat is essential to the fullest possession of the wool fibre of all its important properties; in wool scouring the natural fat or yolk of the material is extracted, and if this be not replaced at a subsequent stage of spinning or knitting, the resilient properties are seriously diminished. In dry spinning we have greater cleanliness of yarn, but what is gained in cleanness is lost in resilience and pliability, and to restore these physical properties the natural oil or fat present in the cells of the fibre is artificially replaced by a soap-oil emulsion. In the case of silk it is often found that the crispness of fibre and the frictional resistance cause the fibres to resist the curves of looping and a form of electricity is generated during the contact of the silk material with the needles of the frame. In such cases when the quality of stitch is seriously impaired the yarns are passed through cakes of lard on their way to the winding bobbin which has the effect of greatly improving the knitting qualities of the yarn, the loops being at once transformed from half-made and rugged structures into perfectly-arched specimens.
CHAPTER XI
Circular Knitting
Knitting machines are divided into two classes according as they produce fabric in flat portions or in circular shape. In the methods of stitch formation already described the courses of loops are constructed in a flat piece, whilst the circular machine makes its fabric in circular form. This system of fabric production has many advantages over the plain width fabric and is indispensable for various branches of the hosiery trade. In seamless articles such as hose and half-hose it is an advantage to have them worked circular as this fits the shape of the body part where they have to be worn. Also large quantities of fabric are expeditiously worked on the circular frame with big diameter head, these lengths being often suitable for making into articles such as nightdresses where the circle of fabric may be used for the body part. The great bulk of fabrics made on large diameter circulars are intended for the cut-up trade, and they are so made because of the great advantages possessed by such frames in point of speed. In flat rotary frames where the work is made by an alternating motion of the thread-carrier from side to side a principle of motion is utilized which has a certain jerkiness as characteristic. With the circular principle of motion there is an entire absence of jars and jerks in working, the movement being steady and accurate, whilst the addition of eight or more feeds to a machine makes an enormous production possible. One of the most easily understood forms of this type of motion is incorporated in the well-known Griswold type of circular knitting machine used still in considerable numbers in one or other of its modifications for the footwear trade. An illustration of this class of knitting machine is shown in section in Fig. 50, which is so arranged as to give a side view of the cylinder which makes the plain work and the dial as used for rib work. The machine is constructed in a circle which for men's half-hose is about 4¼ in. in diameter for a normal size, and the upright cylinder marked C is fitted with grooves cut according to the set of the article as it is fine or coarse. An average set of machine is 84 needles in the 4¼ in. diameter, but there are as few as 64 in the cylinder for the coarse varieties, and up to 144 for fine gauges of footwear. A section of the dial or ribber, as it is often called, is shown crosswise at D with the cams at CB1. The cylinder needles are indicated by CN whilst the dial or ribber needles are marked DN. The thread-carrier is shown on the right by TC, whilst the thread is recognized by the letter T.
Movement of the Parts.—The upright cylinder receives its rotatory movement by means of a handle at the side which operates the bevel gearing to drive the thread-carrier and the set of cams. The action of the cams is to give the needles their up-and-down motion in loop formation, they move round to work on the needle butts in succession, pushing them up so that the hooks receive the thread from the carrier, and drawing them down again so as to discharge and knock over the loops. The thread-carrier and the cams are made to revolve together by the turning of the machine handle, or in the case of power machines this motion proceeds from the drive of the frame. The machine may be worked without the dial, using the cylinder needles only for knitting, in which case plain stitch fabric is produced as would be required for a plain hose article. When ribbed work is needed the dial or ribber needles are set in connection with the upright cylinder needles and are made to rotate with the cylinder so that the dial needles share the thread with the cylinder needles. The process of feeding the thread to both sets of needles is clearly illustrated at the right-hand corner of Fig. 50, where the thread T is seen to be proceeding through the eye of the thread-carrier TC, when part of the thread is taken by the cross needle issuing from the dial and part taken by the upright needles working in the cylinder. The dial needles discharge their stitches towards the right, whilst the cylinder needles throw their stitches over to the left, and this alternation in direction of the stitch discharge is responsible for the ribbed effect in the fabric. The ribber needles radiate from the centre of the dial outwards, whilst the cylinder needles all stand parallel to each other in an upright circle. The fabric F proceeds down the centre of the machine, as shown, and is maintained at the correct tension by suspension of weights in the hand machine, whilst for the power frame we have an automatic motion for winding up the fabric as it is produced.
Figs. 50, 51 and 52
Stitch Formation.—The principle of stitch formation may be understood from an examination of Fig. 51, which gives a view of the type of cams found inside the cam box of the hand machine. Except where it is required to knit the needle rests on what may be termed the normal ledge, and it is only moved from this position when the cams reach it to make it knit. The normal ledge is indicated by L and L1, and whilst the needle is resting on this part of the platform no motion can result. To form the stitch the first stage is to have the needle knocked above the general level of the needle hooks to catch its share of the thread as it is being fed into the needles, and this push-up is given by the small triangular-shaped cam marked PC which raises the needles just sufficiently above the normal height to receive their share of the thread from the carrier. This done, the needle is at once operated upon by the knitting cam KC, which is of the shape shown so as to draw down the needle for the discharge of the loop. The butts of the needles N are depressed by the knitting cam KC, and when they have reached their lowest extremity N they have discharged their loops completely. The part M of the cam causes the needles to rise once more into their normal inoperative position, where they remain until the cams swing round to them again to resume the knitting operation. On the right of Fig. 51 will be noted a push-up cam in a dotted position PC1, and it should be explained that this is for the case of reciprocal knitting such as is required in making the heel or the toe of an article of hose. In this we operate only one-half of the needles in the cylinder, and in so doing cause the cams to move from side to side in an oscillatory fashion. When the cams are rotating in one direction push-up cam PC1 operates the needles, and when the direction of knitting is reversed PC gives the needles their upward thrust to receive the yarn. From Fig. 51 it will be clear that the depth of stitch drawn by the needle depends on the adjustment of the knitting cam KC, and the lower this is set the longer will be the loop drawn through. If the loop is required shorter so as to accommodate a larger number of courses per inch, the knitting cam is raised in its adjustment so that a shorter stitch is the result. The dial needles have a corresponding arrangement by which the needles are drawn farther in to make a longer loop and for a shorter loop are not pulled inwards to the same degree.
Making of a Ribbed Sock.—Fig. 52 gives a view of an ordinary type of sock where the various sections are marked as they are produced on the machine. A start is made with the rib top marked R which in this case is 1 and 1 rib, that is, one upright needle in the cylinder for every needle in the dial or ribber, and when all these are in operation at the same time 1 and 1 rib work is formed on the power stocking-knitter. Before beginning the rib top proper it is usual to make what is termed a welt which consists in working a number of courses in the upright needles only and letting the ribbed stitches draw round so as to give a finished appearance to the edge. On reaching the end of the rib top it is necessary to change the needle arrangement for making 3 and 1 rib, and in the case of the power-rib stocking-knitter every second needle in the upper ribber cylinder which is in the same plane as the lower one is made to slide into the lower cylinder, that is, we have three needles in the lower cylinder for every needle in the upper one. The 3 and 1 rib continues for the leg portion, as shown by Fig. 52, when arrangements require to be made for the heel-which has to be in the plain stitch and continued for the sole of the foot and round the toe. To effect the plain stitch for the heel, the front half of the dial needles are made to slide into the lower cylinder and fashioning for the heel is soon commenced. This is brought about by reducing the needles in work at each side one at a time until only about twelve needles are left in operation, when the process is reversed and the needles again brought into knitting position at each successive course until the full complement is available. This action gives a nicely-rounded pocket for the accommodation of the heel, and at the same time it is usual to introduce some form of reinforcing thread known as splicing, which has the effect of considerably increasing the period of wear of such articles. The plain stitch introduced for the heel is continued for the sole, where the top of the foot A is worked in rib stitch and the under portion B plain, as indicated in the diagram. When the foot has been worked in this manner to its full length, the reciprocating motion is repeated for the making of the toe exactly as for the heel, and several extra courses are inserted so that one article may be kept separate from another, and the next sock is worked exactly as the last. On the modern automatic rib sock machine about seven dozen pairs of men's socks can be produced by a single machine in a working day of eight hours, and as one girl can mind a set of half a dozen machines, it will be seen that the cost of production is infinitesimal when compared with hand-driven machines or with the hand stocking-knitter. One heavier item in the upkeep is the outlay required for a skilled mechanic, who is most essential if the machines are to be maintained in thorough working order, and this expense is proportionately the greater if the manufacturer has only a few machines in this department. It is essential to instal a series of machines of adequate scope of gauge and fineness to warrant the employment of a skilled mechanic who can repair and keep them in constant working order.