Jacquard Weaving and Designing

by T. F. Bell

Fig. 22

[Fig. 20] is a view of the interior of a single-acting jacquard machine with the framework removed; only one row of hooks and needles are given, to avoid confusion. The blades or knives of the griffe, with a support running across their centres, are shown at B. A is the face-plate or needle board, sometimes made of iron, but better to be of hard wood. C is the spring-box, the detail of which is given in [Fig. 24]. E, E¹ are the hooks, and F, F¹ the needles. D is the grating through which the hooks pass, and are supported by it. It will be seen that the hooks and needles are arranged in rows of eight: a 400 machine would have 50 or 51 of these rows in it; 500 machines are usually arranged in rows of 10, and 600 machines in rows of 12. The hooks should be set perfectly upright or vertical, and should be close up against the knives, but not pressing against them. There should be a provision made for shifting both the grating and the knives, so as to admit of both them and the hooks being properly set in relation to each other; but if set correctly by the maker, which they should be, no alteration is necessary. A ([Fig. 21]) is a side view of four hooks and needles, with the ends of the knives of the griffe shown at a, a, a, a. When the machine is working the needles are acted upon by perforated cards cut from the pattern. Suppose we take plain cloth—that is, a pattern in which each half of the warp, or every alternate thread, is raised and sunk alternately; then, if the first card acts on all the odd numbers of the needles, and the second card on all the even numbers, this repeated would make plain cloth. Whenever a hook of the jacquard is to be raised a hole is cut in the card for the needle connected with that hook, and a card with all the even numbers of holes cut in it will cause the griffe to raise all the even-numbered hooks. Refer to b ([Fig. 21]), where the second and fourth holes are cut in the card. If the card is pressed against the needles, as at c, the first and third needles will be pressed back, and will push the first and third hooks back from their position—shown by the dotted lines—to the position in which they are shown in B ([Fig. 21]); but the second and fourth hooks are not moved, as their needles pass through the holes in the card. If the griffe is now raised, the blades or knives will pass the first and third hooks, but will lift the second and fourth; and if the odd numbers of holes are cut on the next card, the first and third hooks will be lifted when it is pressed against the needles, as shown at C ([Fig. 21]), thus making the cross-shed; and this explains the principle of working any pattern by the jacquard without taking into consideration the intricacies of mounting, &c. In C ([Fig. 21]), it will be seen that if the knives d, d were upright instead of slanting, they would come down on the heads of the hooks that are under them, but, being slanted, their lower edges pass the heads of the hooks, and press them away as the griffe descends. Sometimes, even with slanting knives, if there is much vibration in the hooks, or if the loom ‘bangs off,’ some of the hooks are liable to get under the knives and be ‘crowned,’ or bent down. To avoid this deep blades are often used, principally in double-acting machines, so that the lower edges of the blades will not pass the bottom hook, as shown at D ([Fig. 21]). This prevents any danger of crowning, but it darkens the machine a little—that is, makes it more difficult to see down into it if any of the wires require to be examined; it also requires the heads of the hooks to be somewhat higher above the heads of the needles than is necessary with the narrow blades. Another principle has been tried—viz. that of making the heads of the hooks as shown in [Fig. 22], and using narrow blades. This effects its object well, but there is too much friction of the knives against the hooks, and the latter are liable to wear out too quickly. A good machine with firmly set hooks should work very well without these protections if it is steadily placed above the loom, and it is better not to be resting on the loom framing, if convenient to have it so. It will be seen from the foregoing explanation that the proper time, or, rather, the necessary time, for the cylinder to press against the needles is just after the griffe begins to rise. When the griffe is down the top edges of the knives should be 3/16in. or 1/4in. lower than the turned points of the hooks, and before this edge rises up to the hooks those that are not to be lifted should be full back, or the cylinder should be close in, having the front of the head of the hooks 3/16in. or 1/4in. behind the blades. The cylinder should have a short dwell in this position; and if it has a longer dwell it may assist to reduce the friction of the heads of the hooks against the knives; but if it has too great a dwell it may have to travel out and in too quickly to make up for the lost time, which will probably not be compensated for by the advantage of the increase in the dwell. Now, when the cylinder is driven with an independent motion, as in Figs. 17 and 18, it is easy to set the eccentric so that it can be brought in at any required time; but when a self-acting motion is used, it is plain that if the cylinder must press against the needles when the blades of the griffe are passing the heads of the hooks in rising, it must also press against them in the same position when the griffe is falling, unless some special escapement motion could be devised to avoid it, and this is where the dwell is required, and where the evil effect of the motion takes place; and it is worse in a double-lift machine with one cylinder, as the heads of the hooks in it are larger, or have a longer turn on them. A little consideration will suffice to show that when the brander or griffe is falling, say, with one-half of the hooks hanging on its knives, and the cylinder is brought in against the needles before the hooks are quite down, as it must be, it will either cause the hooks to be shot off the knives, or will put a considerable strain on them, as well as upon the needles and cards. It is for this reason that these motions are objectionable, particularly in power-loom work, where the speed is high and the hooks are strong. In hand-loom work it is not so objectionable, as there is more spring in the wires, and the heads of the hooks need not be too large, and, besides, the speed is less and the wear and tear not so great; but, even with this, if a hand-loom machine that has been in use for some time be examined, it will be seen that the points of the hooks are considerably worn, and that the edges of the knives are hollowed out like a coarse saw by the friction of the hooks on them. This latter will partly arise from the lifting of the hooks.

Fig. 23

In the old Jacquard, given in Figs. 15 and 16, the hooks are shown resting on a perforated board, and it was mentioned that in order to prevent them from turning round a frame lay in the turned-up portion of the hooks. The grating in [Fig. 20], through which the turned-up bottoms of the hooks pass, readily accomplishes this object. Sometimes flattened hooks are used, as in C ([Fig. 23]), with the needles twisted once or twice round the hooks; this makes a firm arrangement, but if anything goes wrong with a hook it is not easy to get it clear of the needle. When the needles were made with a full twist or loop on them, as at B, the same was the case; they are now usually made as at A, and if arranged in the machine as in [Fig. 20], there is no danger of the hooks sliding out of the recess in the needle, and if a hook gets bent or broken, it can be taken out and replaced by a new one without disturbing the needles.

[Fig. 16] shows how the needles press against the springs in the spring-box, which is much the same as that at present in use. Fig. 24 is the present arrangement. No. 1 gives a plan of the end of a needle, B. C C is the horizontal wire which supports it as shown in section at C C in No. 2. D (No. 1) is a section of the vertical wire shown at D D (No. 2), which passes through the loops or eyes on the ends of the needles, and keeps the springs from shooting them too far forward. A (No. 2) is a wire which passes down at the outside of the box over the ends of a row of springs, so that by drawing out this wire any of the springs can be drawn out without taking off the spring-box, as the springs pass through the box. The springs should be strong enough to keep the hooks and needles steady, but if unnecessarily strong they give the card and cylinder unnecessary work.