Cotton Weaving and Designing / 6th Edition

by John T. Taylor

DAMASK OR TWILLING JACQUARDS.

These Jacquards are now extensively used for weaving linen, damasks, and similar fabrics, and are used where pressure harnesses were formerly used. The pressure harness puts a great strain on the warp, and requires a longer distance between the cloth and the warp beam than is usually allowed for in power looms; therefore much ingenuity has been expended on these Jacquards with the view of obtaining a large design without using several ordinary Jacquards above each loom, with the accompanying great expense in cards and other attachments.

The principle of damask attachments and twilling Jacquards is entirely different to the principle of the pressure harness, and for fine silk fabrics which require a very large extent of pattern and woven on the hand loom, the pressure harness on the principle shown at [Fig. 126] is not likely to be replaced.

FIG. 132.

FIG. 133.

In the pressure harness a number of warp threads are placed in each mail, the number of threads varying from five to sixteen; but in the twilling Jacquard only one end is drawn in each mail, and a separate hook is required for every end. The advantage comes in making each needle serve for several hooks and in making one card serve for several picks. One of the first inventors of this kind of Jacquard was Mr. Barcroft, of Newry, Ireland, and it has been improved since by him and others. The principle is illustrated at Figs. [132] and [133]. There may be any number of hooks to each needle. In the illustration there are three. The machine is necessarily a single-lift, the griffe goes up and down every pick. Only two needles are shown, operating six hooks. When the top needle is pressed back it will press back the hooks 1, 2, and 3, and when the bottom needle is pressed back it will press back the hooks 4, 5, and 6. These hooks are bent at the bottom as in the diagram, and a bar or rod A is passed through each row of hooks the full length of the machine. These bars A are lifted by the twilling hooks, shown in the diagram in dotted line. These hooks are placed at the sides of the machine: two hooks for each long row of the ordinary hooks, or one for each end of every bar, A. The blades of the griffe are movable about the centres EE, and at each end of the blades and immediately behind each twilling hook (dotted) there is a projecting piece, P, also shown in a dotted line in the diagram.

Now, when the griffe is at the bottom, the blades are operated by a pegged barrel, and by turning the blades one at a time out of the way of the hooks as the blade M is turned, it is obvious that a whole row of hooks can be left down which would otherwise be lifted.

Turning the blade has also another effect. On the front of the blade at each end, as previously pointed out, is a projecting piece, P, and when the blade is turned, this projection pushes the twilling hook in front of it (dotted) on to the next blade of the griffe, and the twilling hook is lifted. The bottom of the twilling hook is fastened to the end of a bar, A, and the bar is lifted, thus lifting a whole row of hooks which would otherwise be left down. In this manner it is obvious that by operating the blades of the griffe in regular order, the figure can be woven warp twill and the ground weft twill, or vice versâ. At [Fig. 133] the position of the six hooks is shown after the griffe is lifted. It will be seen that the blank opposite the top needle pressed the first, second, and third hooks back, and they would all three have been left down but for the bar A being lifted. The hole opposite the bottom needle leaves the fourth, fifth, and sixth hooks over the griffe, and they would all have been lifted but for the blade M being turned, which also caused the bar A to be lifted. It will be obvious that the twill must repeat on the number of bars A, or on the number of rows of hooks, in the machine, exactly as in a split harness the ground weave must repeat on the number of shafts or rods used under the comber board. In these machines, as in the pressure harness, the same card is pressed against the needles two, three, or more times in succession, so as to give a great extent of pattern with a small number of cards. The number of times a card is pressed against the needles depends on the number of hooks there are to each needle, and on the relative amount of warp and weft in the fabric. If there are three hooks to a needle and the same number of picks as ends per inch, the card should be used three times in succession, but sometimes there are more picks per inch than ends, in which case each card should be used oftener; and sometimes, as in silk damasks, there are 400 or more warp threads per inch and 100 picks, and supposing there were eight threads in a mail, it would make a step of eight ends in the warp; therefore, to make the steps in the weft balance it would be necessary to bring the same card against the needles only twice in succession.

[Fig. 134] is another arrangement for weaving damask. It is called a damask attachment, and was patented by Tschorner and Wein. Its construction differs from ordinary twilling Jacquards, but the principle is much the same.

Each needle is twisted round several hooks, and the knives are operated separately by cams at the side of the machine. The illustration shows one of the knives left down, leaving down a row of hooks which would in the ordinary course have been lifted, and one of the bottom lifters is taking up a row of hooks which would in the ordinary course have been left down.

FIG. 134.

The foregoing are the chief kinds of Jacquards and harnesses (except lenos) attached thereto, but there are many combinations of shaft and Jacquard or mail harness which need not be mentioned in a book of this size. We may mention a system, sometimes called half harness, in which only half the ends are drawn through the Jacquard harness, and the other half through shafts in front or behind. A double-sized figure may thus be formed.

CHAPTER VII
LENO WEAVING

FIG. 135.

THE word “leno” has latterly become a general term given to all classes of cross weaving. Originally it had a different meaning to gauze, but the word is now often applied to gauze as well as other fabrics woven with doups. A pure gauze fabric is one in which the crossing thread is brought up on one side of a standard end, and up the other side of the standard end on the next pick. [Fig. 135] shows how the threads are interlaced in gauze weaving. It will be seen that the weave repeats every two picks. The crossing end, and the end round which it crosses, must be placed in one dent, and if an end is made to cross round a number of ends they must all be in the same dent or split in the reed, as it is very obvious that an end cannot be made to cross into another dent with the ordinary doup heald.

FIG. 136.

FIG. 137.

The end is made to cross from one side to the other by means of a doup heald. These healds consist of an ordinary heald with an extra half, generally called a “loose half” or slip. The method of knitting the doup heald will be understood from [Fig. 136]. It is obvious that when the doup is lifted at A, the end contained in the doup will be lifted up on the right-hand side of the end E. In order to bring the same end up on the left-hand side of E, the ends are drawn through the healds, as shown at [Fig. 137]. There are two ordinary staves, and the ends are drawn through them as for plain cloth with two staves. Then the end which is drawn through the first stave is crossed under the end which is drawn through the second stave, and is then drawn through the doup in the manner shown at [Fig. 136]. When the doup is lifted it will lift the crossing end A up on the right-hand side of the standard end B; but in order to do this easily the end must be slackened. This is done by taking all the crossing ends A from the warp beam over a slackening rod or vibrator, R; the other ends of the warp B are taken over the back rest in the ordinary manner. The slackener is usually in the form of a lever, one end of which can be lifted by the dobby or whatever shedding motion is used, and when the dobby lifts one end of the lever the rod is moved downward, thus slackening the warp which is drawn over the rod. Whenever the doup is lifted the crossing warp must be slackened, or it would cause the standard end B to be lifted, as it is crossed under it. In this manner when the doup is lifted the doup end is brought up on the right of the end B. In order to bring the same end up on the left of B, it is necessary to lift the first stave and the loose half of the doup. The first stave naturally takes the end up on the left-hand side of B, but it is necessary to lift the loose half in order to let the end go up on that side. It is usual to show the doup by a double line in the draft, the front line always representing the loose half. The pegging plan or lifting plan for the healds is for leno fabrics not usually shown on point paper, although it may be, just as easily as any other way. The usual way is to rule horizontal lines representing the staves and perpendicular lines representing the picks, and to put a / on the shafts to be lifted for each pick. It is easy to do this by continuing the lines which represent the shaft in the draft, and to make the pegging plan on the same lines by the side of the draft, as in [Fig. 137]. The two perpendicular lines one and two represent the picks, and the marks on the first pick are on the loose half, the doup, and the slackener; therefore all these will have to be lifted. (It is usual to peg the dobby to lift the loose half along with the doup to take the strain off the healds.) On the second pick the marks are on the loose half and the first stave, therefore these must be lifted for the second pick.

With the same draft as in [Fig. 137], a considerable variety of patterns can be made of a style known as crossover lenos. This style consists in weaving a number of picks plain, and then making a cross with the end. At [Fig. 138] the design draft and pegging plan are given for a “five and one” crossover leno. From the design it will be seen that the doup is required to be lifted for the first pick, and the first stave and loose half for the second pick, the second stave for the third pick, and so on. This lifting is shown in the pegging plan at the right of the draft, where on the first pick marks are put on the doup and loose half the slackener, and on the second pick on the loose half and first stave, and so on. There are in this pattern six picks to the round. The appearance of the cloth will be a bar of five picks plain, and then a crank or open space, in the middle of which is a single pick; the crack is caused by the crossing of the ends.

FIG. 138.

In gauzes and fabrics of this description, a thin open fabric in which the ends will not fray or slide is the object. The nature of the weave enables a firmer fabric to be obtained with a smaller number of ends and picks per inch than in ordinary weaving where the threads are not crossed.

FIG. 139.

FIG. 140.

Another and quite distinct effect is produced with doups. This is commonly called “lace” or net, and is often combined with gauze or other “open” leno effect in stripes known as “lace and leno stripes.” This lace effect is produced by making a thick end form a zigzag on the plain ground. The interlacing of the threads in a simple lace or net stripe is shown at [Fig. 139]. A thick end, A, is brought up first on one side and then on the other side of two plain or nearly plain ends, B and C. There are ten picks to the round, and by the side of this dent there is another thick end twisting in the opposite direction, first up one side, and then up the other of two more plain or nearly plain ends. Each thick end comes up for two picks at one side and then crosses under and comes up on the other side after an interval of three picks, and vice versâ. The marks represent the ends lifted. By the side of the lace there are two plain ends shown, which represent the unlimited number of ends used for the ground of the fabric. In weaving this pattern the draft and pegging given at [Fig. 140] would be used. By carefully following the design with the draft and pegging plan the principle will be easily mastered. The arrangement of the shafts is rather important. The doup is placed in front, the ground staves next, and the leno or net staves next. It is immaterial whether the crossing ends be taken through the first stave of the three used for the leno, or the back one—some prefer one way, some another—but it is necessary to get the leno staves as far back as possible to give the thread a better chance of crossing. Four staves are taken for the plain, as in ordinary weaving, to prevent overcrowding. The lifting marks on the pegging plan will be easily followed if the one in [Fig. 138] was understood. Where the fifth stave is lifted the loose half is lifted also, and both thick threads come up on the inside. Where the doup is lifted the slackener is lifted also, and the ends are brought up on the outside as on the sixth and seventh picks. More will be said on the arrangement of shafts in the chapter dealing with designs for leno. The explanations on the structure of the fabrics at this point are only for the purpose of enabling the requirements of the looms for weaving them to be understood. Some manufacturers prefer to work with the doups at the top of the loom, especially in weaving net lenos. In this case the crossing end is crossed over the others and slipped downwards.

It used to be considered that gauze and lenos could not be woven on double-lift machines. In other places than Lancashire this idea prevails to-day to a great extent, but of course this is a great mistake. The simpler kinds of lenos, such as pure gauze and crossovers, are sometimes woven on tappets, which are, of course, double-lift. The tappets are of the ordinary kind, drawn on the same principle as described earlier in this book; but the tappet which operates the standard ends is made to lift the staves halfway when the doup end is crossing. Tappets of this kind have been used for some time past, and it is not surprising that the same principle should be applied to double-lift dobbies. Instead of drawing the tappets to lift the standard ends half way or a little way to enable the ends to cross easier, the easing motion usually employed for dobbies is often used, and the tappets are of the ordinary kind.

In a double-lift dobby the healds begin to lift for one pick when the healds which are up for the previous pick begin to come down. In the case of [Fig. 137], when the doup is lifted for the first pick and begins to come down, the same end is being taken up the other side of B by the stave No. 1 being lifted. If the end B were not moved it would very soon be broken by the crossing end being made to act in this saw-like manner upon it. It is necessary, therefore, to lift the end B about halfway up at the moment the crossing end begins to come down and to pass to the other side of B. If the end A has not to cross for the next pick, it would not be necessary to lift the end B at all. In a single-lift machine the doup will get to the bottom before the first stave begins to rise, and therefore there would be no difficulty in the end crossing. In a double-lift dobby the staves containing the ends round which the doup thread crosses are lifted partly up every pick by a lever worked from the crank arm of the loom. This easing motion or “shaker” is shown at [Fig. 141]. AB is the crank-arm, and the upright CD is connected to the crank-arm at C, and to a lever ED at D. EG is another lever on the rod E, and the healds which are to be lifted half way are connected to this lever at G, as well as to the jacks in the dobby. As the crank revolves the oscillation of the crank arm imparts a similar movement to the lever ED, and to the staves which are connected to EG. This motion commences just at the proper time. Of course, when the crank-arm is lifting the healds, the cords connecting these healds to the dobby will be slack, as indicated at [Fig. 141]. By thus lifting the standard healds, the crossing is greatly facilitated.

FIG. 141.

This easing motion is not required where there is no crossing of the end immediately, as, for instance, in [Fig. 139], the doup end after being brought up on one side is never required up on the other side on the pick immediately succeeding, therefore the end has time to get down before being lifted on the other side and an easing motion is not required.

FIG. 142.

The method of slackening the warp when the doup lifts is shown at [Fig. 142]. This diagram shows a two-doup arrangement. For gauze and similar weaves it is not necessary to have a separate beam for the crossing warp, as one end pulls the other and the take-up is about the same; but for net lenos or laces after the manner of the fabric in [Fig. 139] it is necessary to have the crossing ends on a separate beam, as a great deal more in length of this warp is required than for the plain. Sometimes several beams are used, the only limit being the number which can be placed in a given space.

At [Fig. 142] the crossing warp from the bottom beam is taken over the slackening rod A, and over the carrier E. The crossing warp from the top beam is taken under the slackening rod B. A moves about a centre D, and B moves about a centre C.

The slackener B is connected to a jack in the dobby by the cord L, and the slackener A is connected to another jack by the cord M. When either L or M is lifted, the warp over its rod will be slackened.