The first big advance in knitting with the bearded needle on an automatic machine was made possible by the invention of William Cotton of Loughborough, which in its present-day form is one of the most efficient means of knitting. It is the system universally adopted for the full-fashioned trade where the garments are worked correct to size and shape, twelve full-sized garments being possible on one machine. The chief functional parts of this machine operated during loop formation are given in detail in Fig. 35 where, for purposes of comparison, the corresponding parts have been lettered similar to the parts in the hand-frame sketch. Briefly stated these are: N = needle, B = needle beard, NL = needle lead, NB = needle bar, S = sinker, P = presser, SB = sinker bar, J = jack, SC = slurcock, T = thread, TC = thread-carrier, DP = discharging piece, CB = catch bar, NP = narrowing points.

It will be noted that this machine presents a great difference in arrangement as compared with the hand-frame, the needles being vertical, whilst in the hand-frame they are horizontal. Hand-frame needles are stationary in every respect whilst the needle bar of the power frame has a finely graduated series of movements in vertical and horizontal directions compounded to give a series of delicate sweeps in stitch-forming. The sinker is horizontal and not attached to the jack, the presser is rigid, whilst the fashioning points marked NP are placed above the machine and can be brought down over the needle beards for loop transference.

Knitting Operations.—The general principles of loop formation on this machine have already been described in reference to Figs. 30 to 33. The central feature of the frame is the main shaft on which is located the cams for giving the needle bars, catch bars, etc., their various motions. In stitch-making the thread-carrier and slurcock move across the frame from left to right and back again alternately, the carrier proceeding a little distance in front of the slurcock. The slurcock has the effect of pressing against the ends of the jacks to push forward the sinkers which in turn press into the yarn just laid over the needles to form a series of loops over the needle stems. The jack sinkers are arranged alternately in the machine so that the dividing sinkers are pushed forward in a body and the loops equally divided over the needle stems. At this stage the needle bar cam operates and the needles descend in a body so as to allow of the sinker loops passing under their beards, the needles then immediately move to the left to push their beards against the presser P placed in front of the sinker bar SB. Beneath the sinkers on the right are placed the knocking-over bits or the discharging pieces DP, and on the comb formed by these blades the fabric F rests with the loops of the last course down on the needle stems. When the needles have been pressed and the stitches landed on to the needle beards, a further downward movement of the needle bar is made to allow the stitches to be discharged at the needle extremities, with the arms of the new stitches resting on the edges of the knocking-over bits. When this is done the needles rise again to their former position as was described in detail in connection with Figs. 30 to 33. An important feature of this mechanism is the catch bar marked CB which has the work of controlling the action of the sinkers and dividers during loop formation. The catch bar, as is noted by the shape, fits into the groove at the sinker ends and when it assumes this position it is able to work the sinkers as desired for loop formation.

CHAPTER VIII
Setting of Knitted Fabrics

By the setting of a fabric is meant the closeness in which the loops are knitted in the fabric, and this question also bears reference to the weight of the fabric and its density. The first item which affects the setting is the gauge of the frame, that is, the closeness with which the needles are set in the machine and a firm producing a full range of knitted goods requires to instal a range of machines from fine to coarse. In machines of the Cotton's Patent type the gauge is given by the number of leads which occupy 3 in., there being as a rule two needles cast in the lead. Twice the gauge number gives the needles on 3 in., and to obtain the needles per inch we divide by 3. In other words, the needles per inch are equivalent to two-thirds of the gauge number of the machine. From 8 to 12 gauge is considered coarse, from 14 to 20 gauge is medium, whilst the fine numbers range from 20 to 40 gauge. At the one end of the scale we have gauges on which the coarsest kinds of military articles are worked, whilst at the other are numbers suitable for the finest silk-knitted hosiery. Thus the work produced from a 16-gauge frame is termed 16-gauge fabric, that from the 30-gauge is termed 30-gauge texture. Between these extremes, however, there is a certain variation of texture possible on each frame according as the yarn is heavy, medium or light, and within certain limits fabrics of different weights may be forthcoming from one and the same machine.

Texture Variation on Individual Frames.—Fig. 36 gives a series of diagrams which, if examined, will throw light on the interesting question of variation of set on any one gauge of machine. The diagram represents the conditions on a frame of the Cotton's Patent type where the needles are shown in shaded circles marked N and given in end section, whilst the sinkers are noted to pass between these and are marked S. The rope-like structure which envelops these indicates the thread and is marked by T, the whole diagram representing the action of sinking the loops on any spring needle machine where the sinkers are pushing the thread between the needles to provide the material for loops. In all the diagrams marked A to E the dimensions of the stitch-forming parts such as the sinkers and needles are constant in size and the variation occurs entirely in the thickness of the yarn. In diagram A it will be noted that each needle space, that is, from one needle to the next, is divided thus: needle, space for yarn; sinker, space for yarn. Between each needle, therefore, we have needle, yarn, sinker, yarn in sequence, and this order persists throughout the frame. It will thus be seen that we have various factors of variation, the first being in the relative spacing of sinkers and needles, this proportion being determined by the machine builders. Strange to say all machines of the same type do not have the spacing arranged in the same proportion, different makers adopting a somewhat varying practice in this regard. From the point of view of the machine constructor he has to decide on relative measurements which give the greatest strength to the parts, the sinkers have to be of the size which will make them sufficiently stable in working and make wear and tear the lowest possible.

Fig. 36

Yarn Variation.—The real foundation of this problem lies in the way in which the yarn can be increased in size for any given frame gauge, and the counts can be varied within certain limits to give widely-differing results. If the spaces marked 1 and 2 of Diagram A in Fig. 36 be noted, it will be seen that the whole matter depends on the way in which these are filled by the yarn. If the spaces are but sparsely occupied, then the setting of the loops will of necessity be slack, and the texture will suffer owing to the yarn not being bulky enough to fill up the interspaces. The interspaces are in the first instance created by the presence of the parts, and for a normally good texture the yarn closes up to a considerable extent after the fabric has left the needles. If the space exceeds a certain ratio, the resulting texture is loose and open in appearance and of little value for ordinary clothing purposes. True, such texture may be useful in what are termed gauze varieties, where the thickness of the yarn is diminished out of all proportion to the gauge, and the fabric has an appearance which is so loose that the loops cannot be supported in their usual symmetrical form. Diagram B of Fig. 36 shows a further stage in the yarn thickness where the relationship between the yarn size and the gauge is approaching normal and under certain circumstances would give quite satisfactory results in summer or light-weight goods. The succeeding three diagrams C, D and E show a graduated thickening of the yarn where the thickness is increased from normal condition to that in which the yarn is too thick for the gauge. Diagrams C, D, and E mark the transition from light-weight to normal and from normal to heavy-weight textures. In Diagram E the yarn is already occupying all the available space, and to extend the thickness further in relation to the gauge would give rise to unsatisfactory results in the texture. Even in Diagram D the yarn is approaching the stage where it is uncomfortable to work, for if a certain amount of free space be not allowed, the loops are stiff and crowded together in too little space. The weight of the fabric is undoubtedly increased, but owing to the congested state of the loops little or no interaction is possible amongst them and the cloth becomes stodgy in character. It may happen that the thickness of yarn is increased to make stouter fabrics and more durable, but when the thickness of yarn has exceeded a certain proportion of space, we have increased weight with a great reduction in elasticity. The net result is to lower the wearing value of the texture, for what is gained in dead weight is lost in elasticity. In the wearing properties of the knitted fabric elasticity is a most important item, and unless there is a modicum of this property the fabric is seriously reduced in durability. In addition to this, grave injury is done to the working parts of the machine by making "full" fabrics, because the extra strain imposed on sinkers and needles augments the depreciation of the mechanism.