Читать книгу Jacquard Weaving and Designing - T. F. Bell - Страница 4

Table of Contents

Though the term ‘jacquard weaving’ is properly applied to work done by the jacquard machine, it will here be taken to apply to all harness weaving, or work that extends beyond the range of shafts, or leaves of heddles.

The question arises, When is the limit to the number of shafts that ought to be used reached? It apparently used to be when no more could be got into the loom, as up to ninety-six shafts were used; and this seems to be quite enough for any weaver to get the yarn through, or for any loom to hold, but it must be remembered that at present the appliances are much more suited to the work than they formerly were; and now, except in woollen or worsted goods, where it is desirable to use shafts on account of their firmness in comparison with that of a harness, from twelve to sixteen shafts are as many as it is generally thought desirable to have in a power loom. I have seen thirty-five shafts, all in one tier or set, working diaper very conveniently in a hand loom, and more than double that number of leaves working worsted in a power loom; but whether the latter was desirable, or not, I must leave to the judgment of the manufacturer who possessed it.

Many ingenious inventions have been made for the purpose of simplifying the working of a large number of shafts, but as a description of them would be out of place here, we may pass on to the draw loom, which appears to be the first form of harness of which we have an accurate description. How the cloths of Babylon were woven, in which

Men’s figured counterfeits so like have been

That if the party’s self had been in place,

Yet Art would vie with Nature for the grace—

is not known, though in Gilroy’s report of Arphaxad’s description of his loom to Deioces, king of the Medes, it is stated to have been accomplished by means of carved blocks of wood acting on needles, which wrought the harness or heddles and thus formed the pattern; but as Gilroy has admitted that the introduction to his work on weaving is a pure invention of his own, for the purpose of making it appear that the Ancients were acquainted with motions similar to those on our modern looms, or as a ‘take-off on those who angle hourly to surprise, and bait their hooks with prejudice and lies,’ we need not dwell further on the subject. In any case, figured cloths must have attained considerable excellence in very early ages. The curtains of the Tabernacle were embroidered with figures, and the veil of the Temple was, according to Josephus, embroidered with all sorts of flowers, and interwoven with various ornamental figures, the door curtain being embroidered with blue and purple and scarlet. The ephod of the High Priest was similarly embroidered.

Fig. 1

The Egyptians worked coloured patterns in the loom so rich that they vied with the Babylonian cloths, which were embroidered with the needle. The method of working is unknown, but cloths taken from the tombs in Egypt, which may be seen in South Kensington Museum and in the Gobelins tapestry manufactory, Paris, appear to be made on a principle similar to that of the Gobelins tapestry; the warp is of flax and the weft of coloured wool: and the looms depicted on the catacombs in Egypt are very similar in appearance to tapestry looms.

Embroidering was practised in Egypt prior to the Exodus of the Israelites; and gold and silver threads or wires were used both for embroidering and weaving, being known nearly 4,000 years.

The Babylonish garment taken by Achan, whose sin brought much woe upon the Israelites, is said, by Josephus, to have been a Royal garment woven entirely of gold; but it might only have been embroidered with gold, and was probably wrought in the plain of Shinar, as it was not till long after that Babylon was celebrated for its manufactures.

Pliny says that weaving cloth with gold thread was invented by Attalus, an Asiatic king, and that the Babylonians were most noted for their skill in weaving coloured cloths. This was in Homer’s time, about 900 B.C., when weaving and embroidering appear to have attained great excellence, and to have been very gorgeous. At that time the labour of the loom was considered an accomplishment, which ladies and even princesses tried to excel in.

As before stated, the draw loom is the first form of machine for figured weaving of which we have any record. It is not known where it was invented, but it probably passed from China to Western Asia with the silk manufacture. The ancient Egyptians, Greeks, and Romans do not appear to have known it. The Chinese have still in use a draw loom in which the drawboy stands on the top and draws up the parcels of twines which have been previously arranged for him. After being established in Damascus (hence the name damask), the draw loom passed on to Europe, where the Chinese method of working was used till 1604, when M. Simblot, in France, connected to the neck a separate series of cords, called the ‘Simple’ (perhaps a corruption of his name), so that the drawboy could work when standing at the side of the loom. It is said to have been introduced into England in 1567. The next improvement was to dispense with the drawboy’s services, and for this purpose a patent was taken out in 1687, by Joseph Mason, for ‘a draw boy engine by which a weaver may performe the whole worke of weaving such stuffe as the greatest weaving trade in Norwich doth now depend upon without the help of a draught boy.’ In 1779 William Cheape patented a plan to dispense with the drawboy by having the ‘simple’ above his head, and drawing it down with knots which were held in notches, as described in Fig. 2.

Before beginning to describe the draw loom it may be better first to describe what it is required to do.

Its principal use appears to have been for the weaving of damask, which is one of the simplest forms of figured weaving. Reduce a damask texture to its elementary form, and it consists of twilling, or, more correctly, turned or reversed twilling. If we take a common dice pattern woven with shafts, it will easily be seen that one dice is formed by a warp twill, and the next one by a weft twill, or that the dices are formed by warp and weft twills alternately.

Fig. 2

Now, what forms the pattern? The yarn may be all of one colour, the threads may be so closely set together as to make them individually invisible, or to appear as a plain surface, and yet the dices come out distinctly in two shades of colour. The play of light on the longitudinal and latitudinal threads produces this effect. The dices formed by the latitudinal or horizontal threads will always appear darker than the yarn in the cloth when the latter is placed between the observer and the light, whether these threads be warp or weft, as there is a certain amount of shade on each of them, and of shadow cast by them, whereas the longitudinal or vertical threads are illuminated, without any shade or shadow, and appear lighter than the yarn did before being woven; and this is the reason why a good side light is the best for showing up the pattern on damask, it developing the above to the utmost. In a good material the difference of shade between the ground and figure is very considerable, but in some thin, coarse goods it is hardly visible, requiring them to be held in a favourable light to show the distinction: the pattern will appear light on a darker ground, or the reverse of this, according as the surface threads forming it run across the light or in the direction of it.

This is the reason of the pattern appearing on the cloth; then it is the business of the designer to regulate what form it is to partake of, by preparing a suitable design; and according to instructions furnished to him by the design, it is the duty of the drawboy to raise the warp by regulating the cording of his harness, and drawing it so as to reverse the twill from a weft one to a warp one wherever the figure is to be formed on the cloth, and to do so in such order as to produce the pattern required.

The draw-loom mounting consists of two parts—the drawboy mounting, or the harness with its tail and simples, to be wrought by the drawboy; and the shaft mounting, which is required to form the texture of the cloth, or to interlace the warp and weft through both ground and figures; the harness only interlaces them at the edges of the pattern, or causes either warp or weft to be above, to form the figure en bloc, but without interlacing them together.

It is therefore a ‘compound mounting,’ and is known as a ‘presser’ or ‘pressure’ harness. For simplicity’s sake let us suppose the principle of the drawboy to be applied to shafts or healds, and take a simple figure, as Fig. 1.

For it there are 5 parts, or it could be wrought with 5 leaves of heddles with a straight draught. Fig. 2 shows the mounting; A A is the back mounting, which in this case is a shaft mounting, but would be a harness for a more extensive pattern. B, B are the pressure heddles or front mounting. These are 5 in number, as the ground or texture is taken as a 5-end satin or twill, C is the pulley box with the tail cords, D, D, passing over the pulleys, and tied to the wall or to the loom framing as at E. The knobs F hang over the weaver’s head, and are attached by cords H, passing through a hole board G, to the tail cords, D, D. There are heads on the cords H, and the holes in the hole board are made thus ; so that when the weaver pulls down a knob the bead can pass through the round hole, and the shaft or shafts of the back mounting attached to it will be raised, and can be kept in this position by drawing the cord into the notch or narrow part of the hole, which the bead will not pass through. Any number of shafts can be raised that are required to form the pattern, either by pulling down the knob for each shaft, or by having the knots corded to the shafts, so that each one will raise the proper number of shafts. Thus, in the figure, each knob is only tied to one of the tail cords; therefore a knob must be pulled down for each leaf of heddles to be raised, but each knob might be attached to any number of the tail cords according to the number of leaves of heddles it is required to raise, so that pulling down each knob in succession will complete the pattern. It might require too many knobs to do this, and then the former method would have to be adopted. When the weaver begins to work he draws the first figure shed with the back mounting by pulling down one or more of the knobs as is required; he then works over the ground treadles, b, b, till a change of pattern is required. Next he releases the drawn shed by pulling the cord out of the notch in the hole board; draws another shed, and works over the ground treadles as before. This gives the principle of how the draw loom works, but the principle of forming the texture with the back and front mountings combined will be fully explained under ‘Pressure Harness.’

Fig. 3 gives the draw-loom harness; A, A is the carriage, or the rails that support the harness, which rests on the capes or side rails of the loom. Supported by the carriage is the pulley box P, which is a frame fitted with small pulleys, and must be sloped at such an angle as will allow the tail cords to sink when opening the sheds without obstructing the pulleys underneath them. The neck twines extend from the figures 1 to 8 to the knots above the hole board D D. The cords which connect the neck twines to the mails E, E are called sleepers, and those which connect the mails with the leads F, F are called hangers. The hole board is made of hardwood perforated with holes, which run from front to back in diagonal rows from right to left; it should be a little finer than the set of the reed, to allow for empty holes that are sometimes caused by the tie of the harness ending with broken rows of hooks in some or all of the repeats. In Scotland, for this reason, when the reed is set on 37 in., the cumber board, or hole board, is set on 36 in.

Fig. 3

B, B are the tail cords, attached to the neck of the harness at one end, and at the other end all of them are fastened to the tail stick M, by means of which they are secured to the roof of the house. There must be a tail cord for each part of the harness; here only eight are shown for the front row of the harness, and if there were eights rows of harness in the hole board, 64 tail cords would be required, and the complete harness would be made up of several repetitions of the 64 neck twines; four of these repetitions are here given for the first row of the hole board. Of course there might be 400 to 600 tail cords in a full mounting.

From each tail cord descends a vertical cord to the ground, as shown at G, G. These are the simple cords, which, taken collectively, are termed the ‘Simple.’ It is on these cords that the pattern is read, or, rather, tied up. The simple cords are gathered together, according to the pattern, by passing twines round them and forming the twines into lashes or leashes, as shown at I, I. Heads of stronger cord, to which the lashes are attached, are shown at N, N. The leashes or lashes are made of cotton yarn No. 48, from six to eighteen plies of which are moderately twisted together so that the twine will not curl; the heavy twine is used for coarse work, where only a small number of lashes is necessary. The length of the lashes is from 8 to 12 in., according to the breadth of the simple. The heads are about 4–½ in. long, of good cord, as foot twine, which is used finer or coarser according as more or less heads are required. The heads are made with a noose on them that will run up or down on the gut cord L, which is a strong cord, generally extending from the ground to the roof of the house. K, K are the bridles connected with the lashes, and used to draw them down in succession as they are wanted by the drawboy. When there are a great number of lashes, two gut cords are used, as shown at No. 1 (Fig. 3), and the lashes are looped alternately on each and bridled accordingly. In coloured work, where three or four draws are required for each weft line of the pattern—that is, one draw for each colour—it is usual to have two gut cords with cross bridles from the one to the other which will slide up and down on them. On these, cross bridles the heads of the lashes are fastened, about 1 in. apart, so that the drawboy can take them in succession and draw the shed for each colour.

The method of preparing and mounting the draw-loom harness is much the same as that now in use for jacquard harnesses, and, as it is entirely out of use, it is unnecessary to describe it.

In order to make the neck twines draw evenly, rollers are placed between each set of cords at the points 1, 2, 3, &c.; these rollers keep the cords straight and make them all rise the same height at the mails, which they would not do unless they all sloped to the hole board at the same angle.