Читать книгу Jacquard Weaving and Designing - T. F. Bell - Страница 5

Table of Contents

Fig. 4

The pattern, painted on design paper, same as for pressure-harness damask, is fixed upon a lashing frame, as shown in Fig. 4, and the lower ends of the simples are passed over it and fastened to the crossbar B. The simple cords are held in position over the design by the comb C, C, which must be of such a fineness as to make each simple cord stand directly opposite that space of the pattern to which it corresponds, one simple cord being placed between each pair of teeth of the comb. It will thus be seen that there must be a simple cord for each vertical line on the pattern, or rather for each vertical space between the black lines. In the same way, there must be a head of lashes for each horizontal space, or line, as it is usually called, and which would answer to a card for the jacquard or dobby. The straight-edge E E is made so that it will slide up and down in the frame, to mark the line on the design paper that is to be next read by the lasher. Now refer to the line of the pattern above the straight-edge, and it will be seen that the first square or check to the left is blank, and it is accordingly passed over by the lasher; the second and third checks are painted, and as the simple cords corresponding to them have to be drawn to form the pattern, the lasher twists one end of his lash over the pin G, and takes a turn of it round the second and third simples, again passing it round the pin G. The fourth check, being blank, is passed over, and a turn or tack of the lash twine is taken round the fifth, sixth, and seventh simples, as the checks on the design paper opposite these are painted. The reading and lashing proceeds in this way till the line is finished, as shown in the figure; then the two ends of the lash twine are tied together round the pin G, which is then taken out, and the loop made round it by the lash twine is twisted round and formed into a snitch for the purpose of fastening it to the head. The lash is now pushed down behind the board H, to make room for another; the straight-edge is then shifted to the next line, and the lashing proceeded with as before. If too many painted squares of the design paper come together, all the simple cords corresponding to them must not be looped or lashed together, but can be taken in two or more loops or tacks, never taking more than six or seven simple cords into one tack of the lash twine.

It will be observed that the board H is rounded at the back; this is for the purpose of having all the simples at an equal distance from the pin G when they are tacked up by the lash twine, and consequently a more regular shed will be produced when they are drawn in the process of weaving.

The method of fastening the head to the lash is to loop the cord for the head, which should be double, round the gut cord, then knot the two ends of it together, and take this knot through the snitch formed on the end of the lash, and when the snitch is drawn tight the knot prevents the head from slipping out.

In weaving with the draw loom two persons are required—the weaver, who works over the ground treadles, throws the shuttle, beats up the weft, &c.; and the drawboy, who takes the lashes in succession as he draws them down by the bridle, and by pulling out the simples raises the harness and holds it in this position till the weaver has worked as many shots as are required to be given to each draught.

When some thousands of twines were required for the harness, and with a simple of three or four hundred cords, the weight and friction made it very severe work for the drawboy. To assist him a fork, as shown at V, No. 2, Fig. 3, was used. It was made to run to and fro on a carriage, so that when the simples were drawn forward by the lashes, one spike of the fork could be run in behind those drawn forward, while the other spike was in front of them. When the fork was depressed, till the handle T came to the position shown by the dotted lines, it drew down the simple cords, and they could easily be held in that position till a change of draught was required.

Fig. 5

When the mounting of the draw loom was very extensive, it was necessary to employ from two to ten pulley-boxes and as many drawboys, so that it is not surprising that many endeavours were made to work without the aid of a drawboy. One of these machines, known as the ‘Parrot’ or ‘Pecker,’ is shown in Fig. 5. It is wrought by the treadles T, which are attached to the marches M, and these are connected by the pulley P, on the rocking shaft R, by a cord which passes over and is fastened to it. When one of the treadles is pressed down the pulley rocks and turns the shaft to one side, and when the other treadle is pressed down the shaft will rock to the other side. The parrot or pecker K is movable on the rocking shaft—that is, it can slide along it—but it must rock from one side to the other with the shaft. The cords C, C are passed through holes in the boards B, B, for the purpose of keeping them in position, and they have knots or beads on them at m, m, and weights, W, W, at their ends to keep them in tension. Fastened to the cords C, C is another set of cords, S, connected with the tail cords of the draw-loom harness, and so corded or arranged as to draw those tail cords required to be sunk to raise the harness to form the pattern. As the shaft R is rocked from side to side by depressing the treadles in succession, it carries with it the pecker K, and the groove or notch at the point of the pecker, shown clearly in Nos. 2 and 6, coming into contact with the knots or beads on the cords, draws them down alternately, first at one side of the machine and then at the other, until the pecker, as it slides along the rocking shaft, has passed over all the cords; it is then released and drawn back to its original position by means of the weight D, attached to it by the cord e. At the end of the rocking shaft is a ratchet wheel, N. The cord e passes from the pecker through the segmental hole in the pulley P, as shown in No. 4, and is fastened to a boss, O, on the inner side of the ratchet wheel. This wheel receives its motion from a catch, as shown at E, No. 5, which is simply a pin fixed in a slotted piece of wood. The pin y forms the catch, and the slot acts as a guide, which passes over the edge of the ratchet wheel, and keeps the catch in position. The catch is attached to the marches and works vertically. It is raised by the treadles, and when released is drawn down by the weight attached to it, the wire y catching one of the teeth of the ratchet and moving it round. There are two pins, z and t, in the ratchet, as shown in No. 3, and it is according to their distance apart that the length of traverse of the pecker is determined. The bar q, shown in No. 3 attached to the pulley V, which is loose on the axle, is raised by the stud t, as the ratchet wheel is advanced tooth by tooth, till it comes into contact with the catch S, and raises it; this allows the ratchet wheel to be reversed by the weight D on the end of the cord e till the stud z comes round and draws away the bar, which allows the catch to fall into position again and stops the pecker where the pattern is to begin. Thus, the distance between the studs z and t must be arranged to suit the number of cords the pecker has to pass, or to give the number of threads in the pattern. The teeth of the ratchet wheel and traverse of the catch must be of such a pitch that as each tooth is moved round the pulley will be turned the exact distance required to move the pecker from one cord to the next one. No. 2, Fig. 5, is an elevation of a ‘parrot’ arranged for a single row of cords, as these machines were first made. There was only one treadle, as shown in section at M, No. 2, and the pecker only rocked to one side. Either this or the double machine could be used for a shaft mounting where a large number of treads are necessary. The cords C pass over pulleys, and are fastened to long coupers or levers with their fulcrum at the side of the loom, and to these the shafts are hung from jacks or otherwise. These machines were made to work very exactly. In the double machine the pecker would travel over three or four hundred cords in consecutive order.

To avoid confusion the beads are not shown on the front cords in No. 1.