THE Jacquard machine was the invention of a Frenchman of that name, who exhibited the machine about the year 1800. It was introduced into this country about twenty years later. The chief advantage of the machine is that a large number of warp threads can be operated separately, and a larger figure be produced than with a shaft harness. The chief ideas in the machine are that each mail is connected separately to its hook, and the use of perforated cards to leave any hook over the griffe if it is required to be lifted, or to push it away from it if the hook is required to be left down in the shed.
The original Jacquard machine was a single-lift, and although many minor improvements have been made in it, the main features are practically the same to-day as in the earliest machines introduced into this country. At the present day the single-lift is comparatively little used in cotton manufacture owing to the increased speed at which double-lifts can be worked, but it is still preferred in silk manufacture for several reasons. One reason is that the character of the shed when beating up in a double-lift machine is essentially different to that produced by a hand-loom, where of course a single-lift is always used, and as hand-loom fabrics have a finer touch and appearance than power-loom fabrics, the object is to imitate the hand-loom production as nearly as possible. The cause of this difference in the character of the shed when beating up will be explained later in this chapter. Another reason is that silk-looms could never be run at any speed higher than that of which a single-lift machine is capable, and therefore the advantage of increased speed of the double-lift is of no use.
Double-lifts, owing to the counterpoise and the division of the work on to two knives, are undoubtedly steadier in working, and this is an argument decidedly in their favour. Single-lifts are still used in the manufacture of figured lenos, as no shaking motion has yet been successfully adapted to enable the crossing ends to cross with a double-lift machine.
A single-lift Jacquard for weaving a pattern which occupies 400 ends in a repeat consists of 400 hooks and 400 needles, with an extra row of eight hooks for selvedges, or other auxiliary use. The hooks are arranged in eight rows with 51 hooks in a row. A cross section of this Jacquard is shown at Fig. 106, where the uprights are the hooks and the horizontal wires the “needles.” A is the “needle board,” and this is a perforated board through which the needles pass. The bottom needle B is twisted or looped round the back hook D, and the connection of the other needles and hooks is shown. At the back of each needle a small spring made of fine brass or steel wire is placed. These springs are held in position in the “spring-box” S. There are, therefore, 408 springs required for the 408 needles. The hooks rest on the grate G, but in some makes of machine the grate is not used and the hooks rest upon a “bottom board.” In this case the hooks are very liable to turn round, and thus cause annoyance. To prevent this, flat hooks have been used, and the needle loop was shaped so as not to permit the hook to turn within it. The eight knives form the griffe. These knives are all fastened together, and are moved up and down from the crank-shaft of the loom. The illustration shows the knives at the bottom of their stroke, and at this point, or immediately after the griffe begins to move upwards, the card on the perforated cylinder E is pressed against the needles, and if there is a hole in the card, the needle directly opposite the hole will pass through it and into the perforation in the cylinder, and the knife will take up the hook to which this needle is connected. If the card is blank opposite any needle it will press back the hook, and as the knife lifts, the hook is left down. Thus it is possible to lift any of the 408 hooks in the machine for any pick. When the cylinder is taken away from the needles the hooks are forced back into their original position by the small springs in the spring-box S.
It will be noticed that the knives are leaning a little, and the reason for this will be apparent, as if they were not leaning they would catch the tops of the hooks in coming down, and would break or bend them. The sloping position enables the knives in coming down to press back the tops of the hooks and so get under them, ready for the next card to be pressed against the needles. The knives should come down low enough to be quite clear of the hooks, and therefore in this machine there is a considerable dwell when the shed is closed.
The harness for a straight-over pattern is mounted as shown at Fig. 107. In order to prevent confusion the connection of the cords to the machine is not shown, but the numbers on the line A represent the hooks in the machine to which the cords are to be attached. The “comber-board” or “cumber-board” B is a frame into which perforated slips are fitted. These slips are perforated to different degrees of fineness, the fineness being regulated by the number of ends per inch required in the cloth to be woven. The lingoes, L, are metal weights, and serve the purpose of keeping the mails down. MM are the mails, through which the warp threads are drawn in the order shown by the numbers, beginning at the back left-hand corner. The draft in straight-over patterns is always taken in this way in Jacquard weaving, although it is not compulsory. The harness is built with linen thread, and the method of tieing the lingoes to the hooks will be understood from the diagram.
When one lingoe has been connected to each of (say) 400 hooks, the first pattern is complete. Supposing there are 100 ends per inch, the pattern will occupy 4 inches, and therefore if cloth is required 28 inches wide in the harness, there must be seven lingoes attached to each hook, making seven patterns, or seven repeats of the pattern, in the width of cloth. Thus when one lingoe has been tied to each hook, beginning with the first and ending with the 400th, another is connected to each hook, beginning again with the first; and when this is done other patterns are formed in the same manner until the required number is complete.
It is important to have a clear understanding as to which is the hook which lifts the first end in the draft. This hook is the one connected with the bottom needle in the last row on the 25-side of the machine. As we stated previously, a 400s machine has 400 hooks arranged in 50 rows of 8, or 8 rows of 50 hooks, and in addition there is always a spare row of hooks, making 51 rows in all. As it is necessary to lace the cards in the middle as well as at the sides, a space has to be allowed for the lace holes, and therefore the machine is divided into two parts by a space between the 26th and 27th rows.
A plan of a card is given at Fig. 108. The length of the card between the two peg holes A and B is nearly 14½ inches, and the distance between the centre of the top needles and the bottom needles is 1⅞ inch exactly. This holds good for all English-made machines, but the American index is different.
It will be seen that there are 26 rows on the right of the machine and 25 rows on the left, and one is called the “26-side” and the other the “25-side.” The cards are always numbered at the “26-side,” and the cutting is commenced at this end. It may be as well to explain here the order in which the holes are cut from the design, as it will assist in following the point paper design to the loom. The cutting is usually done in a “piano” cutting machine, which will be explained more fully later on. By this machine one row of eight holes can be cut by operating eight punches and pressing down the right-foot treadle of the machine.
The number end of the card is gripped by the machine, and at the first stroke of the right foot, the lace holes EF and the peg hole A are cut, then one stroke of the treadle is made without cutting, and the pointer of the machine arrives at the 1st or spare row. If the selvedges are worked from this row, holes are cut accordingly. Then the pointer comes to the 2nd row, and in this row the cutting from the design is commenced.
At Fig. 109 the design is made on point paper, as it is required to appear in the cloth right side up, with the twill in the ground running in the same direction as shown on the design. When cutting, the design is usually turned round, as shown at Fig. 110, and the cutting commences from the top right-hand corner A. To show the matter clearly, the first row of holes cut are numbered, both in the design and the card, in consecutive order.
The first hole cut in the card is operated with the little finger of the right hand. Following this hole to the loom, we find it operates the last or 400th end in the draft, and that the hole cut last on the card (numbered 400) operates the first end in the draft. This is the hole which operates the bottom needle in the last row on the “25-side” of the Jacquard machine, which, as was previously stated, is the hook from which the draft begins.
Following out the operation of cutting the card. When the 26th row has been cut, the lace holes MN (Fig. 108) are cut, and then the cutting is again straight-forward to the 50th row. The piano machine is so constructed that with the same stroke of the treadle which cuts the 51st row the peg hole D is also cut, and then follows a stroke without cutting, after which the two lace holes T and Y are cut. This makes 56 strokes of the foot for each card.
It is usual, in order to economise space, for the Jacquards with straight, or “Norwich,” harnesses to be placed on the loom, so that on one loom the cards hang over the weaver’s head, and on the next the cards are at the back of the loom. In both cases the harnesses are built the same way, but in one case (cards over weaver’s head) the thread operated by the bottom needle on the “25-side” will be at the back of the comber-board, at the left hand; and in the other case (cards behind loom) the same thread will be at the front of the comber-board at the right-hand side.
As previously stated, the single-lift Jacquard for cotton weaving is not often employed except for special purposes, such as figured leno weaving. The advantage possessed by the double-lift Jacquard as regards speed is so very considerable that its adoption for ordinary forms of cotton weaving has become universal; and the advantage of speed is not the only advantage it possesses, as will be pointed out shortly.
A double-lift machine with one cylinder for a 400 end pattern consists of 800 hooks and 400 needles. Each needle is twisted or bent round two hooks, as shown at Fig. 111. The hooks are connected together in twos by neck cords, which are usually strong whipcord, as will be seen from the illustration. It will be seen that the bottom needle is bent round the back pair of hooks, the next needle round another pair, and so on. Each needle has a spring behind it, as in a single-lift machine.
There are two griffes, which work oppositely—that is, as one goes up the other comes down. The griffes (or knives) are worked by a double crank on the bottom shaft of the loom, so that each griffe moves from the bottom to top of its stroke in one pick, and from top to bottom in another pick.
The principle of the double-lift will be understood from Fig. 112. One knife, A, is at the top, and the other knife, B, is down. One hook of the pair is lifted, and therefore the ends in the mails connected to the neck cord at C will be lifted. Suppose now it is required to lift the same ends of warp for the next pick: a card is pressed against the needles, and if there is a hole in the card opposite the needle E, it will leave the needle and the hook N where they are, and as the knife B is lifted, the hook N will be taken up as the hook M is coming down. The hooks will cross at about the middle of their stroke, and the weight of the ends and lingoes on the cord C will at that moment pass from the hook M to the hook N. In the diagram the cord attached to the hook N is slack, but when this hook is lifted the cord will gradually tauten until it bears all the weight, when the cord from the hook M becomes slack. We thus have the ends for the second pick lifted whilst the ends which were up for the previous pick are coming down. This is where the advantage of the double lift lies. In a single lift the knife must lift the hooks up and then come down to the bottom before another card can operate the needles, whereas in a double lift the card for a second pick can be brought against the needles as soon as the ends which were up for the previous pick are ready to come down.
It is obvious that in the position shown in Fig. 112, when one knife is up and the other down and the needle pressed back by the card, that the hook M will also be pressed back, as shown by the dotted line. The bend of the hook over the knife, therefore, must be sufficient to prevent the hook being pushed off the knife, and it will be noticed that the hooks in this class of machine are bent more than the hooks in a single-lift machine. The hooks rest on the grate G, Fig. 111, and the shape of the hook at this point acts as a spring to straighten the lifted hooks after the pressure of the card has been taken off the needles. A machine of this kind can be run at a speed of about 160 or 170 picks a minute, as compared with the 130 or 140 picks of a single-lift.
A double-lift machine on another principle is illustrated at Fig. 113. This is a two-cylinder machine, and to weave a pattern repeating on 400 ends this machine requires 800 hooks and 800 needles. The cylinders work at opposite sides. The hooks are placed as shown in the diagram, the hooked parts facing each other in pairs, and by following carefully the manner in which the needles are twisted round the hooks it will be seen that there are really two single-lift machines placed together, alternate rows of hooks representing each machine. There are two griffes, as in the double-lift single-cylinder machine, and the griffes are worked in the same manner.
The cylinders work alternately, the cards being laced in two sets, all the odd numbers being together in one set and the even numbers forming another set. Immediately one knife is at the top and the other at the bottom, one cylinder is pressed against the needles, and it will be noticed that the hooks which each cylinder operates have the hooked parts in the direction of the cylinder. When the hooks operated by one cylinder are at the top the other cylinder is pressed against the needles, and thus the work done by one cylinder in Fig. 111 is divided between two in this machine. The advantage of this machine is in the lessened speed of the cylinders. The vibration caused by the cylinder working at a high speed in a single-cylinder machine is so great that the limit is reached at about 170 picks per minute, whereas a double-cylinder machine can be run up to 200 or sometimes even more picks per minute, though perhaps 180 is a more advantageous speed. The top set of needles project a little further through the needle board to compensate for the difference in leverage on the hooks.
Besides the advantage of speed, double-lifts have an advantage in the counterpoise obtained by one set of hooks going up as the other comes down. This causes a more even motion and steadier working. Another advantage possessed by double-lifts is that the beating up of the weft is effected in a crossed shed, thus enabling more weft to be put in than in a single-lift, where the beat-up is done with a closed shed. This beating up in a crossed shed also spreads the warp better, and prevents the reed marks from showing, for the same reason as was given when referring to the spreading of the warp in the tappet loom.
In silk weaving a single-lift machine has an advantage in imitating more closely hand-woven goods, as hand-loom weavers usually beat up in a closed shed. This causes the weft to be put in straighter—that is, less wavy, which is very desirable in silk fabrics.
The cause of this difference in the shed when beating up in the two kinds of looms will be understood by following the relative positions of the griffes and the loom crank throughout its revolution.
In a single lift the time allowed for opening and closing the shed must be used to the best advantage; that is, as much time as possible must be given for this purpose. On this account it is necessary to pick the moment the slay is sufficiently far back to allow the shuttle to enter the shed—that is, when the slay is half-way back, or the crank at the bottom centre. The griffe is worked by a crank on the top shaft of the loom, and there is no actual dwell of the griffe or of the ends when the shed is open; therefore the shed must be opened a little wider than would otherwise be necessary for allowing the shuttle to pass through.
The shed must be sufficiently open to allow the shuttle to enter when the loom crank is at the bottom centre. This regulates the timing of the other parts. Fig. 114 will make this quite plain. The shed must be nearly fully open when the crank is at the bottom centre to allow the shuttle to enter; and when the loom crank is at A the griffe must be nearly at the top. When the crank is at B the griffe will be at the extreme top, and when the crank is at the top centre, or C, the griffe will be as near the bottom as it was to the top when the loom crank was at A. As was previously pointed out, the griffe must go further down than the hooks to allow another card to operate the needles, and therefore it is when the loom crank has arrived at C that the knife is leaving the hooks resting on the grate, or bottom board. The griffe will be at the extreme bottom when the loom crank is at D, and when the griffe is up at the hooks again the crank is at the front centre, or E. Thus the shed has the fraction of a revolution between B and C to close in, and between E and B for opening. The shed remains closed for the quarter of a revolution, C to E.
In a double-lift the warp is much more leniently dealt with. As we have said, the shed must be open for the shuttle to enter when the loom crank is at the bottom centre. Therefore the griffes should be in their extreme position—one up and one down—when the crank is at the bottom centre.
The timing of the parts in a double-lift will be seen at Fig. 115. The cranks that work the griffes are on the bottom shaft, which of course makes a revolution every two picks. These cranks will be perpendicular when the shed is fully open; therefore when the loom cranks are at the bottom centre the cranks which drive the griffes must be in the position AB. If they are so set they will be in the position CD when the loom crank reaches the back centre, and in the position EF, or horizontal, when the loom crank arrives at the top centre, when the shed will be closed. We have thus a closed shed when the crank is at the top centre, as in a single-lift; but in this case when the shed is closed the griffes are moving quickly, whereas we have a quarter of a revolution dwell after the loom crank reaches the top centre in a single-lift. This causes, as we shall see, a difference in the shed when the slay beats-up, or is at the front centre. When the griffe cranks are in the position GH, the loom crank will be at the front centre, and thus the shed will be partly opened for the next pick when the reed comes in contact with the cloth.
Jacquards are made in various sizes. 100s, 200s, 300s, 400s, and 600s, are the most common. 100s are arranged in rows of four; 200s and 400s are in rows of eight; 300s and 600s in rows of twelve.
There are two distinct kind of harness mounting, the London and Norwich systems. In the former the Jacquard is placed with the narrow end towards the front of the loom, thus causing the cards to fall at the side. In the Norwich system, or “tie,” the machine is placed with the broad side facing the front of the loom, thus causing the cards to hang either over the weaver’s head or at the back of the loom. On this system, as there are eight rows in a machine, by taking the comber board eight rows deep the harness becomes what is called a straight neck. With the London system, the end of the machine facing the weaver, there must be a twist in each pattern in the harness. There is not much to choose between the two systems. Some prefer the London tie, as they say the twist in the harness causes the harness threads to support each other, and so last longer. The Norwich system is the more common, especially in the cotton trade.
Fig. 116 shows the method of tying up the harness on the Norwich system for a bordered fabric, such as handkerchiefs. In these goods it is usually preferred that both borders should point inwards, as in the sketches Figs. 116 and 117.
The hooks to which the harness threads are attached are numbered on the line A, and it will be seen that the draft begins in the left-hand corner at the back of the comber-board, the lingoes being numbered in the order of the draft. The cords are tied up just as for an ordinary straight-over harness for the first 400, or one full pattern of the machine, but then, instead of commencing with the first hook again, the 201st lingoe is tied to the 201st hook, and the second half of the pattern is repeated. This forms the middle of the handkerchief, and it must be repeated over a sufficient number of times to give the required width of cloth after allowing for the trimming and border. In Figs. 116 and 117 nothing but a border and middle are shown, but sometimes a trimming of another small weave is required outside the border, and this, which is usually on a small number of hooks, is repeated over in the same way as the middle. In Fig. 118 only two repeats of the middle are shown; but supposing that the harness had 100 ends per inch, and that the handkerchief was required to be twenty-four inches wide excluding the border, there would be twelve repeats of the middle required. When the middle has been repeated over a sufficient number of times, the other border must be tied up, and to obtain the reverse position of the figure the draft must be reversed. By tying the next lingoe to the 200th hook, and going backwards with the draft, it can easily be seen that the same figure will be woven at this side of the harness as at the opposite side; the only difference will be that the figure will point to the left, as will also the twill in the ground, if it is a twill. This system of tying up is compulsory in the Norwich system, as it is usual to keep the harness straight—that is, the harness threads from each of the eight rows in the Jacquard each form a separate row in the comber-board. We have thus eight rows in the machine and eight rows deep in the comber-board, and it would not do to have a thread taken from the front of the comber-board at one border and from the back of the comber-board at the other border to the same hook.
If the harness is a “London tie” it necessitates a half-turn in each pattern, as the machine is at right angles to the comber-board. Therefore the draft may be continuous, as shown at Fig. 117, where, after the middle has been repeated a sufficient number of times, finishing with a thread from the 400th hook at the front of the comber-board, the next one is taken from the 200th hook through the back of the comber-board, and the border will finish with a thread from the first hook going through a hole at the front of the board—just the reverse to the other side.
Bordered goods are often made with two borders at each side, and sometimes the borders are repeated a few times. The number of hooks taken for the border and middle respectively vary according to requirements. Sometimes, in a 400 machine, 300 will be taken for the border and 100 for the middle, and so on. The cross-border must of course be designed, and the cards cut. The number of cards in a set in these goods is often very large, as the middle must be repeated over the required number of times, and there will be as many cards used in the set as there are picks in the handkerchief.
In designing for the mounting given at Fig. 117, the design would be made on 400 ends: 200 for the border and 200 for the middle, and the cards would be cut just in the ordinary manner. The cross-border would also be designed in such a manner as to harmonize with the side borders. The portion to be designed is enclosed by the dotted lines.
Centre ties or point ties are another class of harness in regular use. This is really the two borders of a bordered harness joined together. Fig. 118 shows how the tying up is done for a pattern of this kind. The first 400 threads are connected as usual, the draft being from back to front. When the 400th has been reached, the draft is reversed until No. 1 is arrived at again. The same effect is obtained as in a point of V draft in a shaft harness. The pattern must be of such a character that one half is the exact reverse of the other. This kind of harness is used for weaving large damask figures, and it is obvious that the effect produced is really that of a figure on 800 ends, or twice the size of the machine. Designs of this character are of course rather stiff, but are suitable for damasks, and similar fabrics.