Tension and Weight.—The texture of a fabric on any given knitting machine can be varied according to a number of factors and of these quite an important one is the length of loop drawn by the needle. An examination of Fig. 11 will show that the needle beds on the flat knitting machine are stationary and that the needles during stitch formation draw the yarn over the top ends of the beds and obviously the length of the loop will depend on the distance which the needle is drawn below the edge of the needle bed, this distance being determined by the adjustment of the knitting cams A and B shown in Fig. 12.
Cam B is shown in a dotted position raised so as to draw a shorter loop and the length of the loop can be varied according to the height of either knitting cams A or B within certain limits. If the loop is drawn too long, that is, if the knitting cam is set too deep, the yarn may not stand the strain and breakage will result; on the other hand, if the loop is too short the fabric will appear stodgy in character.
Patterns Produced.—This type of knitting machine has an extensive range of patterns and textures which can be obtained and amongst the first variations possible are those which result from an alteration of the needle arrangement. The normal setting is to have one needle in the front stage for one in the back stage, and these being arranged alternately give the ordinary 1-and-1 rib stitch. This is shown in Fig. 13, where the upper row of small circles represents the needles in the back bed or stage whilst the lower row gives those in the front stage. The next, Fig. 14, shows the needles in exactly the same sett except that the needles have been arranged to give the 2-and-2 rib pattern, this being shown in diagrammatic enlargement in Fig. 16 at the side. The third sett of needles given in Fig. 15 represents the arrangement for a 3-and-1 rib pattern where every third needle only is allowed to remain in the front stage whilst the back stage retains its full complement. From these examples it will be clear that by altering needles in this way to any scheme a large variety of rib effects may be produced, nor need the arrangement be uniform throughout the width, for the borders may be in one pattern and the ground or interior in another. Novel effects in imitation of lace work may also be produced by leaving a needle out of one or other of the beds which makes an opening in the fabric which can be manipulated to give an effect of a lace-like character.
Figs. 17, 18, 19 and 20
Manipulation of Knitting Cams.—Figs. 17 to 20 have been prepared to illustrate the manner in which the cams are altered to give certain well-known stitches in the flat knitting machine, and the construction is the same as Diagram 12, with corresponding letters for the various parts. On the left of the plate are arranged the cams as in the front bed whilst the right-hand arrangement gives the set of the cams in the back. In Fig. 17 the two beds are shown arranged for plain rib work where both back and front needles are in action at the same time. Fig. 18 shows the cam setting in front and back beds for making the well-known half-cardigan or royal rib which has played such an important part as the stitch for cardigan jackets supplied to the troops during the war period. It will be seen that on the front bed cam A is raised into what is termed a tucking position, that is, the needles are pushed up by D to receive the thread but are not drawn down far enough to have their loops discharged over the needle ends. At the same time the cams in the back bed are set for plain work and the needles there knit as usual at every course. The real stitch, however, does not appear until the direction of knitting is reversed, because the needles on the front bed are again pushed up to receive a second thread and on this occasion are drawn down the full distance by B to knock off the stitches. This means that on the front bed stitches are formed in double threads after every two courses whilst the back discharges its loops at every course, which enables a much greater weight of yarn to be inserted into the texture, making it more rigid and stable. The cams in Fig. 19 are arranged in front and back beds to produce the polka or full cardigan stitch, where double courses are worked on both front and back. This may be clear if we consider the cam arrangements as illustrated moving first to the right when the stitches on the front bed are "tucked" whilst those on the back bed knit to the position of cam A. In reversing the knitting to proceed to left, two yarns are drawn through in the front needles whilst no discharge takes place on the back. In this way the knitting occurs on the cardigan rib plan on both front and back needle beds and the resulting fabric is much heavier in weight than half-cardigan and when taken from the machine shows a strong tendency to expand in width owing to the yarn seeking to take up a more expanded position. The full cardigan stitch tends to be loose in character, the weight of material is greatly increased over plain 1-and-1 rib, but there is a lack of structural firmness and cohesion. In Fig. 20 the part C of the cam comes into the picture as being necessary to give circular work on the flat knitting machine. This can be drawn up out of action in both front and back beds by a small finger lever, and an examination of this arrangement will show that in going to the right the needles of the front bed will knit as usual, but in reversing, as shown on the right of Fig. 20, the needles pass completely under part D owing to the absence of part C and knitting is not performed; the cam portion D is raised by a spring to allow the needles to pass over the dotted position. It will thus be seen that to make circular work we arrange the cams on the front bed so that they will knit in going to right but miss in going to left, whilst in the opposite bed the reverse holds good. Thus a course of loops is made on the front with the back not knitting, alternated by a course made on the back with the front not knitting. The fabric's being worked from one yarn causes the loops to be joined at the edges and so a continuous length of circular webbing is produced.
CHAPTER IV
Types of Knitting Yarns
The qualities necessary for knitted goods have already been outlined as applied to the fabric, but if ideal results are to be secured, the yarns require to possess certain specific features of their own, for the most efficient textures can only be got by combining the qualities of yarn and fabric. The range of yarns covers a wide variety of material and systems of manufacture and the type selected depends entirely on the use to which it has to be applied; price is its primary consideration, and whether required for outer, intermediate or under garments is also important. Speaking generally, the knitting yarn should be open in texture, full in handle, and the material should be soft and comfortable to the touch. Except for some classes of outer wear the thread should have a plentiful proportion of surface-projecting fibres which are of value in covering raw loop formation.
Woollen Spun Yarns.—Yarns spun in the woollen system are still used to a considerable extent in the knitting trade, such having large scope in the more moderate priced qualities. The yarn is produced by the ordinary methods of woollen yarn spinning, the wool being teased, scribbled, carded, condensed and spun into threads on the woollen mule. The combined effect of these operations is to give a yarn which has its constituent fibres crossing and re-crossing at every angle so as to give a melange of fibres, confused at first sight only because these are arranged in a yarn regular in diameter and compact in structure. Carding and spinning are done in the grease so that goods made from them require a more liberal scouring and fulling. The best known type in the coarse variety of woollen-spun yarns is, perhaps, the wheeling, which is illustrated by means of photo-micrograph, Fig. 21, and given in the form of two-ply, but large numbers are used in three or more ply for goods of the coarsest gauge. The name Wheeling is probably derived from the early days of hand spinning on the wheel when the wool grown on the farm was dealt with by the farmer's daughter by means of the distaff and spindle. In this type of yarn the wool fibres were spun as they hung on the distaff, and the chief care of the spinster was to draw them out so as to present as even a strand as possible to the torsion of the whorl. The single yarns were therefore rather irregular, but these deficiencies were to a large extent overcome subsequently by folding two or three plies according to the weight desired. In the days of hand spinning it was deemed most easy to specialize in one uniform thickness of ground thread and obtain the thicker counts by twisting these threads two or more ply. The wheeling yarns as made to-day partake very much of the same character; they are spun from the coarser grades of wool where long and short fibres are used promiscuously, all of which features may be noted by an examination of photo-micrograph 21 which gives the thread original magnified forty-fold. Fig. 22 gives a similar enlargement under the microscope of a yarn of the same class as used for utility wear at a moderate price, this yarn is three-fold and is spun on the woollen system with fibres showing in every variety of angle. The three-ply yarn shows very dense and gives a garment in a coarse gauge with considerable weight and of most serviceable character; it is found very adaptable for thick woollen socks for artisan wear.
