Industrial Technicology
INDUSTRIAL TECHNICOLOGY All weaving schemes are reducible to a few elementary principles, but no attempted classification has been quite successful, for fabrics are constantly met with that possess characteristics supposed to be peculiar to one class, but lack others which are deemed equally typical. Nevertheless, since some classification is essential, the following will be adopted, namely: Group i, to include all fabrics made from one warp and one weft, provided both sets of threads remain parallel in the finished article and are intersected to give the requisite feel and appearance. Group 2, to include (a) fabrics constructed from two warps and one weft, or two wefts and one warp, as in those that are backed, reversible and figured with extra material; (b) two or more distinct fabrics built simultaneously from two or more warps and wefts, as in two, three and other ply cloths; (c) fabrics built by so intersecting two or more warps and wefts that only one texture results, as in loom-made tapestries and figured repps. Group 3, to include fabrics in which a portion of the weft or warp rises vertically from the groundwork of a finished piece, as in velveteens, velvets, plushes and piled carpets. Groups 4, to embrace all fabrics in which one portion of the warp is twisted partially, or wholly, round another portion, as in gauzes and lappet cloths. Although some fabrics do not appear to fall into any of the above divisions, and in others the essential features of two or more groups are combined, yet the grouping enumerated above is sufficiently inclusive for most purposes.
The fabrics included in Group I are affected by the nature and closeness of the yarns employed in their construction, by colour, or by the scheme of intersecting the threads. The most important section of this group is Plain Cloth, in which the warp and weft threads are approximately equal in thickness and closeness, and pass over and under each other alternately, as in fig. i, which shows a design, plan and two sections of plain cloth. Such a fabric would, therefore, appear to admit of but slight ornamentation, yet this is by no means the case, for if thick and thin threads of warp and weft alternate, the resultant fabric may be made to assume a corrugated appearance on the face, while beneath it remains flat, as in popiins, repps and cords. A plan and a longitudinal section of a repp cloth is shown at fig. 2. Colour may also be employed to ornament plain fabrics, and its simplest application produces stripes and checks. But colour may convert these fabrics into the most artistic and costly productions of the loom, as is the case with tapestries, which FIG. I. Plain Cloth.
Repp Cloth.
are at once the oldest and most widely diffused of ornamented textiles. Tapestries only differ from simple plain cloth in having each horizontal line of weft made up of numerous short lengths of parti-coloured thread. Many fine specimens of this art have been recovered from ancient Egyptian and Peruvian tombs, and many are still produced in the Gobelins and other celebrated manufactories of Europe.
Twills are next in importance to plain cloth on account of their wide range of application and great variety of effects; in elaborately figured goods their use is as extensive as where they provide the only ornament. Twills invariably form diagonal ribs in fabrics, and these are due to the intervals at which the warp and weft are intersected ; thus two or more warp threads are passed over or under one or more than one weft thread in regular succession. Twills are said to be equal when similar quantities of warp and weft are upon the face of a fabric, unequal when one set of threads greatly preponderates over the other set, as in figs. 3, 4, which require four warp and weft threads to complete the scheme of intersections. If the ribs form angles of 45 degrees, the warp and weft threads per inch are about equal in number, but for an unequal twill the material most in evidence should be closest and finest. The angle formed may be greater or less than 45 degrees, as in figs. 5, 6; if greater, the warp preponderates, if less, the weft preponderates. Twills are simple and fancy; both terms refer to the schemes of intersecting. In the former the same number of warp threads are placed successively above or below each weft thread, and the ribs are of uniform width, as in figs. 3, 4. In the latter more warp threads may be above one p, G . 3- Four-thread J Twill. FIG. 4. Four-thread J Twill.
ck than another, the ribs may vary in width and small ornament ay be introduced between the ribs, as in figs. 5, 6 and 7, where the ark squares represent warp upon the surface. Twills may _ be oken up into zigzags, lozenges, squares and other geometrical aesigns; all of which may be produced by reversings in the diagonal lines, or by reversing the weave of an unequal twill. Fig. 8 is a -gzag, namely, a twill reversed in one direction. Fig. 9 is a diamond, FIG. 5 Upright Twill.
FIG. 6. Reclining Twill.
or a twill reversed in two directions, and fig. 10 is a diaper, or an unequal twill which gives a warp face in one place and a weft face ' i another. Satins and satteens form another important section of 3roup i. In a satin the bulk of the warp, and in a satteen the bulk f the weft, is on the face of a fabric. If perfect in construction both sent a smooth, patternless appearance, which is due in part to scheme of intersections, in part to using fine material for the FIG. 7. Fancy Twill.
FIG. 8. Zigzag.
surface threads and placing it close enough together to render 'the points of intersection invisible; the threads of the other set being coarser and lewer in number. Satins differ from twills in having each warp thread lifted, or depressed, separately, but not successively. From five to upwards of thirty threads of warp and weft are required to complete the various schemes of intersecting. If the intervals between the intersections are equal the weave is said to be perfect, IJ!!IJZZIZI1ZZIIIJ-X FIG. 9. Diamond.
FIG. 10. Diaper.
as in fig. 1 1 , but if the intervals are irregular it is said to be imperfect, as in fig. 12. In Damasks a satin is combined with a satteen weave, and since any desired size and shape of either weave may be produced, great facilities are offered for the development of all kinds of ornamentation. But in combination neither the satin nor the satteen can be perfect in construction, for one requires a preponderance of warp, the other a preponderance of weft; as a sequence every point of intersection is distinctly visible on both surfaces. Brocades are fabrics in which both sets of threads may be floated irregularly upon the surface to produce ornamental effects, and they may be taken as typical of all one warp and one weft fabrics that are figured by irregularly floated materials, whether the threads, are uniformly or irregularly distributed, and whether one weave or several weaves be employed.
Group 2 includes all backed and reversible fabrics, as well as those ornamented with extra material and compounded. Cloths intended for men's wear are often backed, the object of which is to give weight and bulk to a thin texture without interfering with the FIG. II. Five-thread Satteen.
FIG. 12. Six-thread Satteen.
face effects. Either warp or weft may be used as backing; if the former there are two series of warp to one series of weft threads, while in the latter there are two series of weft to one series of warp threads. The face material is superposed upon that of the back, but the ratio of face threads may be one or two to one of back. In order to avoid disturbing the face weave, only those threads are used to bind the backing that are hidden on the face, as in fig. 13, which gives the design and a transverse section of a backed fabric; A is face weft; B back weft, and the circles are warp threads; of the latter C, D, are beneath both B and A. This diagram will serve equally as a longitudinal section of a warp-backed fabric, if A represents a thread of face warp, B a thread of back warp and the circles are weft threads. Weft backing is capable of giving a more spongy feel to a fabric than warp, because softer materials may be used, but in these fabrics the length output of loom is reduced by reason of the wefts being superposed. Warp-backed fabrics, whether uniformly coloured or striped, do not materially reduce the output of a loom, for every weft thread adds to the cloth length. Reversible fabrics may have either two series of differently coloured wefts or warps to one of the other series, in which event they may be similarly figured on both sides by causing the threads of the double series to change places, as in the design and transverse section, fig. 14; or, by allowing one series to remain constantly above the other, as in backed cloths, both sides may be similar or dissimilar in colour and pattern. Fabrics figured with extra material may have two ,- ,, T ,. , series of warp or weft threads to one FIG - 1 3~ Weft-backed series of the other set, and they may yield Fabric.
reversible or one-sided cloths. A ground texture may have extra material placed above or below it, as in fig. 15, where a design and transverse section of the cloth are given; the waved lines and circles represent a cross-section of plain cloth and A is a thread of extra material; or ordinary and extra material may be used conjointly for figuring. Compound cloths must have at least two textures, and be as distinct in character as if woven in separate looms; they have many advantages over backed cloths, thus: the same design and colouring may be produced on both sides ; where bulk and weight are required a fine surface texture may be formed over a ground of inferior material, and soft weft be passed between the upper and lower textures. The fabric is more perfect and admits of either simple or elaborate patterns being wrought upon the surface, with simple ones beneath, as in piques and matelasscs. One texture may be constantly above the other and connected at the selvages only, as in hose pipes and pillow slips; or at intervals a thread may pass from one texture into the other, in which event both are united, as in many styles of bed-covers and vestings. If differently coloured, FIG. 14. Weft Reversible Fabric.
FIG. 15. Figuring with Extra Weft.
the textures may change places at pleasure, as in Kidderminster carpets; or, from three to twelve textures may be woven simultaneously, and united, as in belting cloth. There may be from one to three threads of face warp to one of back, and the wefting may or may not correspond with the warping. Fig. 16 shows the face and FIG. 16. Compound Fabric.
FIG. 17. Tapestry with Two Warps and Two Wefts.
back weaves, the design, and a transverse section of a compound cloth with two threads of face warp and weft to one of back, and both are stitched together. The circles in the upper and lower lines represent face and back warps respectively, and A, B, C are weft threads placed in the upper and lower textures. Loom-made tapestries and figured repps form another section of Group 2. As compared with true tapestries, the loom-made articles have more limited colour schemes, and their figured effects may be obtained from warp as well as weft, whether interlaced to form a plain face, or left floating more or less loosely. Every weft thread, in passing from selvage to selvage, is taken to the surface where required, the other portions being bound at the back. Some specimens are reversible, others are onesided, but, however numerous the warps and wefts, only one texture is produced. When an extra warp of fine material is used to bind the wefts firmly together a plain or twill weave shows on both sides. If a single warp is employed, two or more wefts form the figure, and the warp seldom floats upon the surface. Where warps do assist to form figure it rarely happens that more than three can be used without overcrowding the reed. Fig. 1 7 gives the design, and a transverse section of a reversible tapestry in four colours, two of which are warps and two wefts. If either warp or weft is on the surface, corresponding threads are beneath. The bent lines represent weft and the circles warp. Figured repps differ from plain ones in having threads of one, or more than one, thick warp floated over thick and thin weft alike; or, in having several differently coloured warps from which a fixed number of threads are lifted over each thick weft thread; the face of the texture is then uniform, and the figure is due to colour.
Group 3. Piled Fabrics. In all methods of weaving hitherto dealt with the warp and weft threads have been laid in longitudinal and transverse parallel lines. In piled fabrics, however, portions of the weft or warp assume a vertical position. If the former there are two series of weft threads, one being intersected with the warp to form a firm ground texture, the other being bound into the ground at regular intervals, as in the design and transverse section of a velveteen, fig. 18; the circles and waved lines form plain cloth, and the loose thread A is a pile pick. After leaving the loom all threads A are cut by pushing a knife lengthwise between the plain cloth and the pile. As each pick is severed both pieces rise vertically and the fibres open out as at B. Since the pile threads are from two to six times as numerous as those of the ground, and rise FIG. 18. Velveteen. from an immense number of places, a uniform brush-like surface is formed. Raised figures are produced by carrying the threads A beneath the ground cloth, where no figure is required, so that the knife shall only cut those portions of the pile weft that remain on the surface. The effect upon the face varies with the distribution of the binding points, and the length of pile is determined by the distance separating one point from another.
Chenille. When chenille is used in the construction of figured weft-pile fabrics? it is necessary to employ two weaving operations, namely, one to furnish the chenille, the other to place it in the final fabric. Chenille is made from groups of warp threads that are separated from each other by considerable intervals; then, multicoloured wefts are passed from side to side in accordance with a predetermined scheme. This fabric is next cut midway between the groups of warp into longitudinal strips, and, if reversible fabrics such as table-covers and curtains are required, each strip is twisted axially until the protruding ends of weft radiate from the core of warp, and form a cylinder of pile. In the second weaving this chenille is folded backward and forward in a second warp to lay the colours in their appointed places and pile projects on both sides of the fabric. If chenille is intended for carpets, the ends of pile weft are bent in one direction, and then woven into the upper surface of a strong ground texture.
Warp-piled Fabrics have at least two series of warp threads to one of weft, and are more varied in structure than weft-piled fabrics, because they may be either plain or figured, and have their surfaces cut, looped or both.
Velvets and Plushes are woven single and double. In the former case both ground and pile warps are intersected with the weft, but at intervals of two or three picks the pile threads are lifted over a wire, which is subsequently withdrawn; if the wire is furnished with a knife at its outer extremity, in withdrawing it the pile threads are cut, but if the wire is pointed a line of loops remains, as in terry velvet. Fig. 19 is the design, and two longitudinal sections of a Utrecht velvet. The circles at A are weft threads, and the bent line is a pile thread, part of which is shown cut, another part being looped over a wire. At B the circles are repeated to show how tl ground warp intersects the weft.
Double Plushes consist of two distinct ground textures which a kept far enough apart to ensure the requisite length of pile. As weaving proceeds the pile threads are interlaced with each series of weft threads, and passed from one to the other. The uniting pile material is next severed midway between the upper and lower textures, and two equal fabrics result. Fig. 20 gives three longi- FIG. 19. Utrecht Velvet.
FIG. 20. Double Plush.
tudinal sections of a double pile fabric. The circles A, B are weft threads in the upper and lower fabrics respectively; the lines that interlace with these wefts are pile warp threads which pass vertically from one fabric to the other. At C, D the circles are repeated to show how the ground warps intersect the wefts, and at E the arrows indicate the cutting point.
Figured Warp-pile Fabrics are made with regular and irregular cut and looped surfaces. If regular, the effect is due to colour, and this again may be accomplished in various ways, such as (a) by knotting tufts of coloured threads upon a warp, as in Eastern carpets; (b) by printing a fabric after it leaves the loom ; (c) by printing each pile thread before placing it in a loom, so that a pattern shall be formed simultaneously with a pile surface, as in tapestry carpets; (d) by providing several sets of pile threads, no two of which are similar in colour; then, if five sets are available, one-fifth of all the pile warp must be lifted over each wire, but any one of five colours may be selected at any place, as in Brussels and Wilton carpets. Fig. 21 is the design, and a longitudinal section of a Brussels carpet. The circles represent two tiers of weft, and the lines of pile threads, when not lifted over a wire to form loops, are laid between the wefts; the ground warp interlaces with the weft to bind the whole together. When the surface of a piled fabric is irregular, also when cut and looped pile are used in combination, design is no longer dependent upon colour, for in the FIG. 21. Brussels Carpet, former case pile threads are only lifted over wires where required, at other places a flat texture is formed. In the latter case the entire surface of a fabric is covered with pile, but if the figure is cut and the ground looped the pattern will be distinct.
Group 4. Crossed Weaving. This group includes all fabrics in which the warp threads intertwist amongst themselves to give intermediate effects between ordinary weaving and lace, gauzes. Also those in which some warp threads are laid transversely in a piece to imitate embroidery, as in lappets.
Plain Gauze embodies the principles that underlie the construction of all crossed woven textiles. In these fabrics the twisting of two warp threads together leaves large interstices between both warp and weft. But although light and open in texture, gauze fabrics are the firmest that can be made from a given quantity and quality of material. One warp thread from each pair is made to cross the other at every pick, to the right and to the left alternately, therefore the same threads are above every pick, but since in crossing from side to FIG. 22. Plain Gauze.
side they pass below the remaining threads, all are bound securely together, as in fig. 22, where A is a longitudinal section and B a plan of gauze.
Lena is a muslin composed of an odd number of picks of a plain weave followed by one pick of gauze. In texture it is heavier than gauze, and the cracks are farther apart transversely.
Fancy Gauze may be made in many ways, such as (a) by using crossing threads that differ in colour or count from the remaining threads, provided they are subjected to slight tensile strain; (b) by causing some to twist to the right, others to the left simultaneously; (c) by combining gauze with another weave, as plain, twill, satin, brocade or pile; (a) by varying the number of threads that cross, and by causing those threads to entwine several ordinary threads; (e) by passing two or more weft threads into each crossing, and operating any assortment of crossing threads at pleasure.
Lappet weaving consists in diapering the surface of a plain or gauze fabric with simple figures. This is done by drawing certain warp threads into a transverse position and then lifting them over a thread of weft to fix them in the texture; after which they are moved in the opposite direction and lifted over the following pick. The material between one binding point and another must float loosely, and this limits the usefulness of lappet figuring. In fig- 2 3i the thick lines show a lappet spot upon a plain texture. Notwithstanding diverse structure, intricate mechanisms are t ir,K not essential to the production of IG. 23. Lappet Fabnc. ekher s{mple or com lex tex t ures ; the most elaborate and beautiful specimens of the weaver's art have been manufactured upon simple machinery.
Weaving Machinery.
The longitudinal threads of a fabric are called warp, caine, twist and organzine, and the transverse threads are weft, shoot, woof, filling and tram. A loom for intersecting these several threads must provide for: (i) Shedding; namely, raising and lowering the warp threads in a predetermined sequence so as to form two lines between which the weft may be passed. (2) Picking, or placing lines of weft between the divided warp. (3) Beating-up, or striking each weft thread into its appointed position in the fabric. (4) Letting-off , or holding the warp tense and delivering it as weaving proceeds. (5) Taking-up, or drawing away the cloth as manufactured. (6) Temples, for stretching the fabric widthwise in order to prevent the edge threads of a warp from injuring the reed, and from breaking. Power looms require the above-named contrivances to act automatically, and in addition: (7) A weft -fork, to stop a loom when the weft becomes exhausted or breaks. (8) Mechanism for stopping a loom when the shuttle fails to reach its appointed box. (9) For weaving cross stripes, multiple shuttle boxes are needed to bring different colours, or counts of weft, into use at the pioper time. (10) In some looms a device for automatically ejecting a spent cop, pirn or shuttle, and inserting a full one, is requisite, (n) If a weaver has to attend to a greater number of looms than usual, a device for stopping a loom when a warp thread fails is essential.
The Hand-Loom. During the iyth and the first half of the 18th centuries it was observed that wherever any branch of the textile industry had been carried to a high state of excellence the looms FIG. 24. Diagram of Hand-Loom.
used to manufacture a given fabric were similar in essentials, although in structural details they differed greatly. Prior to the invention of the fly shuttle by John Kay, in 1733, no far-reaching invention had for generations been applied to the hand-loom, and subsequently the Jacquard machine and multiple shuttle boxes represent the chief changes. A hand-loom as used in Europe at the present time (see fig. 24) has the warp coiled evenly upon a beam whose gudgeons are laid in open steps formed in the loom framing. Two ropes are coiled round this beam, and weighted to prevent the warp from being given off too freely. From the beam the threads pass alternately over and under two lease rods, then separately through the eyes of the shedding harness, in pairs between the dents of a reed, and finally they are attached to a cloth roller. For small patterns heald<? are used to form sheds, but for large ones a Jacquard machine i- required. Healds may be made of twine, of wire or of twine loops into which metal eyes, called mails, are threaded. But they usually consist of a number of strings which are secured above and below upon wooden laths called shafts, and each string is knotted near the middle to form a small eye. From two to twenty-four pairs of shafts may be employed, but the healds they carry must collectively equal the number of threads in the warp. These healds will be equally or unequally distributed upon the shafts according to the nature of the pattern to be woven, and the threads will be drawn through the eyes in a predetermined order. The upper shafts are suspended from pulleys or levers, and the lower ones are attached directly or indirectly to treadles placed near the floor. The weaver depresses these treadles with his feet in a sequence suited to the pattern, and the scheme of drawing the warp through the healds. When a treadle is pressed down, at least one pair of shafts will be lifted above the others, and the warp threads will ascend or descend with the healds to form a shed for a shuttle, containing weft, to be passed through (see SHUTTLE). The reed (fig. 25) is the instrument FIG. 25. Weaver's Reed.
by which weft is beaten into position in the cloth ; it also determines the closeness of the warp threads, and guides a moving shuttle from side to side. It is made by placing strips of flattened wire between two half round ribs of wood, and binding the whole together by passing tarred twine between the wires and round the ribs. Such a reed is placed in the lower portion of a batten, which is suspended from the upper framework of the loom. In front ol the reed, and immediately below the warp, the projecting batten forms a race for the shuttle to travel upon from side to side. Before Kay's invention a shuttle was thrown between the divided warp and caught at the opposite selvage, but Kay continued the projecting batten on both sides of the warp space, and constructed boxes at each end. Over each box he mounted a spindle, and upon it a driver, or picker. Bands connected both pickers to a stick which the weaver held in his right hand, while with the left hand he controlled the batten. Thus: a treadle is pressed down by one foot to form a shed; the batten is pushed back till a sufficient portion of the shed is brought in front of the reed, and the depressed threads lie upon the shuttle race; a clear way is thus provided for the shuttle. A quick movement of the stick tightens the cord attached to a picker and projects the shuttle from one box to the other. The batten is now drawn forward, and the reed beats up the weft left by the shuttle. As the next treadle is depressed to form another division of the warp for the return movement of the shuttle, the last length of weft is enwrapped between intersecting warp threads, and the remaining movements follow in regular succession (see fig. 26).
In cases where the weft forms parti-coloured stripes across a fabric, also where different counts of welt are used, shuttles, equal in number FIG. 26. Section of Plain Web in Process of Weaving on the Loom.
a, The warp beam. d, The reed in position for pick- b, The lease rods by which the ing, and also for beating-up.
warp is divided and crossed, e, Woven cloth. c,c, Two pairs of shafts containing /, The cloth beam, healds.
to the colours, counts or materials, must be provided. By Robert Kay's invention of multiple shuttle boxes, in 1760, much of the time lost through changing shuttles by hand was prevented. His drop boxes consist of trays formed in tiers and fitted into the ordinary' shuttle boxes. Each tray is capable of holding a shuttle, and by operating a lever and plug with the forefinger and thumb of the left hand, the trays may be raised and lowered at pleasure to bring that shuttle containing the colour next needed into line with the picker.
The Draw Loom. Large figured effects were formerly produced in draw looms, where the warp threads were so controlled by separate strings that any assortment could be lifted when required. Thus: to the lower end of each string a dead weight, called a lingoe, was attached, and a few inches above the lingoe a mail was fixed for the FIG. 27. Diagram of Jacquard Machine and Harness.
control of a warp thread. The strings passed through a drilled board which held the mails and warp threads facing the proper reed dents. Still higher up, groups of strings were connected to neck cords; each group consisted of all strings required to rise and fall together constantly. If, for example, in the breadth of a fabric there were twelve repeats of a design, twelve strings would be tied to the same neck cord, but taken to their respective places in the comber board. The foregoing parts of a draw loom harness are clearly shown in fig. 27 : A are lingoes, and the dots represent mails. __^___ B is the comber board; between B and C are mounting strings and neck cords, two strings being attached to each cord; and C is the bottom board. Each neck cord, after being led through a perforated bottom board C, and over a grooved pulley, was threaded through a ring on the top of a vertical cord called the simple, and passed horizontally to, and tied upon a bar rigidly fixed near the ceiling of the weaving room. The simple cords were similarly attached to a bar placed near the floor. From one hundred to several thousands of neck and simple cords could be used in one harness. The design to be reproduced in cloth was read into the parallel lines of the simple by looping a piece of string round each cord that governed warp threads to be lifted for a given shed; after which all the loops were bunched together. By pulling at a bunch of loops the simple cords were deflected and they caused all warp threads controlled by them to be lifted above the level of those undisturbed. Similar bunches of loops were formed for every shed required for one repeat of a design, and they were pulled in succession by the draw-boy, while the weaver attended to the batten and picking.
The Jacquard machine is the most important invention ever applied to the hand-loom, but it is not the work of one man; it represents the efforts of several inventors whose labours extended over three-quarters of a century. This apparatus has taken the places of the simple, the loops, the pulleys and the draw-boy of the older shedding motion, but other parts of the harness remain unchanged. _In 1725 Basile Bouchon substituted for the bunches of looped string an endless band of perforated paper by which the simples for any shed could be selected. In 1728 M. Falcon constructed the machine since known as the Jacquard and operated it through the medium of perforated cards, but it was attached to the simple cords and required a draw-boy to manipulate it. In 1745 Jacques de Vaucanson united in one machine Bouchon's band of paper and the mechanism of Falcon. He placed this machine where the pulley box previously stood, and invented mechanism for operating it from one centre.
It is said that about the year 1801 J. M. Jacquard was called upon to_correct the defects of a certain loom belonging to the state, in doing which he asserted that he could produce the desired effects by simpler means, and this he undoubtedly accomplished. In or about 1804 he discarded the simple and all but a few inches of the vertical neck cords; he placed Falcon's apparatus immediately over the centre of the loom and severally attached the upper portions of the neck cords to the hooks; all of which Vaucanson had previously done. He then perforated each face of a quadrangular frame used by Falcon to guide the cards to the draw-boy, and since known as the cylinder and invented means whereby the cylinder could be made to slide horizontally to and fro, and at each outward journey make one-quarter of a revolution. Cards were so held upon this cylinder by pegs that 'at each rotatory movement one was brought into action and another moved away. By means of two treadles placed beneath the warp one weaver could operate the entire loom. The cylinder was controlled with one foot, the selecting parts with the other, and both hands were free to attend to picking and beatingup.
In a Jacquard machine the warp threads are raised by rows of upright wires called hooks. See D, fig. 27. These are bent at both extremities and are normally supported upon a bottom board C, which is perforated to permit the neck cords from the harness beneath to be attached to the hooks. Each of a series of horizontal needles E one of which is shown enlarged and detached at the foot of the drawing is provided with a loop and a coiled eye; the former to permit of a to-and-fro movement, the latter to receive a hook._ The straight ends of the needles protrude about one-quarter of an inch through a perforated needle board G, but the looped ends rest upon bars placed in tiers. A wire passed through all the loorjg of the needles which form one vertical line limits the extent of their lateral movement, and small helical springs, a, enclosed in a box F, impinge upon the loops of the needles with sufficient force to press them and their hooks forward. A frame H, called a griffe, is made to rise and fall vertically by a treadle which the weaver actuates with one foot. This frame contains a blade for each line of hooks, and when the blades are in their lowest position the hooks are free and vertical with their heads immediately over the blades, hence, an upward movement given to the griffe would lift all the hooks and thereby all the warp threads. Only certain hooks, however, must be lifted with the griffe, and the selection is made by a quadrangular block of wood, I, called a cylinder, and cards which are placed upon it. Thus, each face of the cylinder has a perforation opposite each needle, so that if the cylinder be pressed close to the needle board the needle points will enter the holes in the cylinder and remain undisturbed. But if a card, which is not perforated in every possible place, is interposed between the cylinder and the needles, the unpunctured parts of the card close up some of the holes in the cylinder, and prevent corresponding needles from entering them. Each needle so arrested is thrust back by the advancing card ; its spiral spring a is contracted and its hook D is tilted as shown in the figure. If at this instant the griffe H ascends, its blades will eng the heads of all vertical hooks and lift them, but those dislocated being tilted will remain unlifted So soon as the pressing force < a card is removed from the needles the elasticity of the spring restores both needles and hooks to their normal positions. Cards ar perforated by special machinery from a painted design, after whic they are laced into a chain and passed over conical pegs upon tl cylinder; the number required to weave any pattern equals th number of weft threads in that pattern. The cylinder is generally drawn out and turned by each upward movement of the griffe and restored to the needles by each downward movement, so tha each face in succession is presented to the needles, and each rotator movement brings forward a fresh card. As the griffe rises wit vertical hooks a shed is formed, and a thread of weft is passed acros the warp. The griffe then descends and the operation is repeate but with a new combination of lifted threads for each card. Jacquard may contain from 100 to 1200 hooks and needles, ar two or more machines may be mounted upon the same loom.
Since Jacquard 's time attempts have been made to dispense wit hooks, needles, springs, cards, the cylinder and several other parts machines have also been specially designed for effecting economic in the manufacture of certain fabrics; but although some of thes devices are used in different sections of the industry, the single lif Jacquard remains unchanged, except in its details, which have be modified to give greater certainty of action to the moving par The most far-reaching changes are directly due to efforts made adapt the Jacquard to fast running power looms. Alfred Barlov John and William Crossley, and others, devised means whereby t hooks could control the same warp thread, and they provided th machine with two griffes, each capable of actuating alternate row of hooks. One griffe was caused to ascend as the other descended therefore, if one of the two hooks that operate a warp thread i lifted for the first shed, the other hook can begin to rise for a second shed immediately the first begins to fall. About half the time originally needed for shedding is thus saved , and as a result Jacquards can now be run at 210 to 220 picks per minute.
Preparing Warp and Weft for Weaving. The power loom is only one of a series of machines which revolutionized weaving. Although early inventors of the power loom did much to perfect its various movements, the commercial results were disappointing, chiefly because means had not been devised for preparing warp and weft in a suitable manner for such a machine. William Radcliffe, of Stockport, perceived these shortcomings, and concluded that, by division of labour, weaving could be brought into line with, the then recently invented, spinning machinery. He, therefore, set himself the task of solving the problems involved, and by inventing the beam warper, the dressing sizing machine, the shuttle tongue, and the pin cop, he enabled the power loom to become a factor in the textile industry. The term preparation embraces winding, warping, sizing, Yorkshire dressing, drawing-in, twisting and occasionally other operations.
Weft Winding. Weft yarns invariably receive simpler treatment than warp yarns ; in many cases none at all. Cops and ring spools pass direct to the loom unless their dimensions are unsuited to the shuttles, in which case they, together with wefts bleached or dyed in hanks or used in a saturated condition, require winding upon pirns, or into cops of suitable sizes. Pirn winders differ greatly in construction, but the majority are furnished with conical shapers, consisting either of slip cups, or of cone rollers mounted upon studs. A pirn, whose head is coned to fit inside a shaper, is slipped over a spindle, and both are passed, either vertically or horizontally, through a shaper; the basal end of the spindle being flattened to enter a rectangular hole in a wharve which is driven from a central tin drum. A thread is attached to a rotating pirn, and a vibrating guider leads it to and fro inside the shaper. Both spindle and pirn recede from the shaper until the pirn is full, when they become stationary. Hanks are carried by ryces, and cops and ring spools by skewers. Cop winders are chiefly used for coarse yarns, which they coil upon bare spindles. By this means a greater length of weft can be placed in a shuttle than when pirns are used.
Warp winding consists in transferring yarn from cops, ring spools or hanks, either to warpers, bobbins or cheeses (see COTTON-SPINNING MACHINERY). Machines for this purpose are of two kinds, which arc known respectively as spindle and drum. In the former each bobbin is placed upon a vertical spindle and rotated by frictional contact; a yarn guider meanwhile rises and falls far enough to lay the threads in even coils between the bobbin flanges. In the latter each bobbin, or tube, is laid upon a rotating drum and a thread guide moves laterally to and fro; slowly for a bobbin, but quickly for a tube.
Warping. The number of longitudinal threads in a web vary according to their closeness and its breadth. It is the function of a warper to provide a sufficient number of parallel threads for a web, all of equal length, and to retain their parallelism. Warpers are of thnv types, viz. mill, beam and sectional.
Mill warping is the oldest type now in extensive use. A mill warper has a creel in which from 50 to upwards of 300 bobbins or cheeses, are supported horizontally upon pegs, and the mill has a vertical axis which carries three wheels, upon whose rims vertical staves are fixed about I ft. apart to form a reel, from 5 to upwards of 20 yds. in circumference. The threads from the creel are threaded in succession through leasing needles, then passed in groups of four to twenty threads between runners, and, finally, fastened by a peg to the mill staves. The needles are mounted alternately in two frames which may be moved up inclined planes; one to elevate odd threads, the other even ones, and both separations thus formed are retained upon separate pegs; this is the lease which enables a weaver to readily fix the position of a broken thread. As the mill rotates the threads form a tape about I in. wide, and the leasing apparatus slides down a post to coil the threads spirally upon the red. When the full length of warp has been made the mill is stopped, a half beer lease is picked by hand from the divisions formed by the runners, and also retained upon pegs. The mill next reverses its direction of rotation, and as the leasing apparatus ascends the threads are folded back upon themselves. Hence, if a reel is 20 yds. in circumference, and 200 threads are in use to make a warp 600 yds. long, and containing 2000 threads, the reel will make 30 revolutions (600-5-20 = 30) also 10 reversals, for at each reversal 200 additional threads will be added (2000-7-200 = 10). When a warp is complete, strings are passed through the leases, and it is coiled into a ball, loosely linked into a chain, or dropped into a sheet. If a mill has its axis horizontal the leasing apparatus must slide horizontally.
Winding on Frame. After a ball warp has been bleached, dyed or sized, the half beers are laid amongst the teeth of a coarse comb to open out the threads to the necessary breadth, in which condition they are coiled upon a loom beam.
Beam warping is the system most extensively used in the cotton trade. The creels for these machines have an average capacity of about 600 bobbins, and are often V-shaped in plan. In each leg of the V the bobbins are arranged in tiers of 1 6 to 20, and row behind row. The threads are drawn separately between the dents of an adjustable reed, then under and over a series of rollers; from here they are dropped amongst the teeth of an adjustable comb and led down to a warpers beam, which rests upon the surface of a drum. As the drum rotates the threads are drawn from the bobbins and wrapped in even coils upon the beam. On most of these machines mechanism is attached for arresting motion on the fracture of a thread, and also for accurately measuring and recording the lengths of warp made. When full, a warpers beam holds threads of much greater length than are needed for any warp, but they are insufficient in number. Thus: If 500 threads are in use, and warps of the above-named particulars are required, four similar beams must be filled (2000 -5-500 = 4) and the threads from all are subsequently united. The chief parts of a beam warper may be used as a substitute for a mill warper, provided that mechanism be employed to contract the threads to the form of a loose rope and coil them into a cylindrical ball, which will be subsequently treated as a mill warp. Or, one of these warpers may be furnished with parts which, when the threads are roped, links them loosely into a chain.
Sectional warping is chiefly employed for coloured threads and its outstanding features consist in contracting the threads to form a ribbon of from 3 in. to 12 in. wide. This ribbon is coiled upon a block placed between flanges, and when completed is set aside until a sufficient number of similar sections have been made; after which they are slipped upon a shaft and by endlong pressure converted into a compact mass. All the threads are then collected and transferred in the form of a sheet to a loom beam; each section contributing its own width to that of the warp. Sectional warps are also made upon horizontal mills by superposing the coils of a ribbon of yarn upon a portion of the staves. When the first section is formed a second is wound against it, and the operation continued until all the sections have been made; after which the yarn is run upon a loom beam.
Yorkshire dressing is used to make striped warps from balled warps which have been dyed in different colours. The operation is as follows: The requisite number of threads of any colour is split from a uniformly dyed ball and set aside until warps of the remaining colours have been similarly treated. The split sections from the several balls collectively contain as many threads as are needed for a warp, but those threads have still to be placed in their proper sequence. This is done by drawing them in groups of two or four between the dents of a reed to a predetermined colour scheme, then all are attached to a loom beam which is supported in a frame. The beam is rotated by stepped cones and gearing, and winds the threads upon itself. But in order to hold the threads taut they are passed between weighted rollers and deflected by bars arranged ladderwise; in passing from one part of the machine to another they are gradually opened out to the width of the beam.
Sizing. In cases where single yarns are made from short fibrous materials, smooth surfaces are obtained by laying the outstanding ends of fibres upon the thread, and fastening the fibres together to impart sufficient strength to resist the strains of weaving. This is accomplished either by coating a thread or by saturating it with an adhesive paste. In hand-loom days the paste was applied by brushes to successive stretches of warp while in a loom. But with the advent of mechanical weaving it was found necessary to size a warp before placing it in a loom. Two systems were evolved, the one invented by William Radcliffe sizes, dries and beams a warp in one operation, the yarn is made to pass in the form of a sheet between a pair of rollers, the lower one being partly immersed in warm size. In rotating this roller carries upon its surface a film of size which it deposits upon the threads, while, by pressure, the upper roller distributes the size evenly. Brushes acting automatically smooth down the loose fibres and complete the distribution of size. As the yarn advances it is separated by reeds and lease rods, so that in passing over steam chests and fans the moisture contained in the threads may be quickly evaporated. This machine is a duplex one, for the warpers beams are divided into two setsand placed at opposite ends of the machine. Both halves receive similar treatment as they move to the centre, where the loom beam is placed.
The Ball Warp Sizer. While efforts were being made to perfect Radcliffe's dressing machine a system of sizing ball warps was being gradually evolved and this system is still largely employed. The machine consists of a long trough, inside which a series of rollers are fitted, either in one horizontal plane or alternately in two horizontal planes; but over the front end of the trough a pair of squeezing: rollers are mounted. The trough contains size, which is maintained at a boiling temperature and in sufficient quantity to submerge the rollers. Two warps, in the form of loose tapes, may be simultaneously led over, under and between the rollers. As the warps advance the threads become saturated with size, and the squeezing rollers press out all but a predetermined percentage, the latter being regulated by varying the pressure of the upper roller upon the lower one. If more size be required than can be put into the threads during one passage through the machine, they may be similarly treated a second time. This process does not lay all the loose fibres, but the threads remain elastic. After sizing, the warps are passed backward and forward, and over and under, a set of steam-heated cylinders by which the moisture contained in the threads is evaporated ; they are next either rcballed, or wound upon a loom beam.
Slasher Sizing. For sizing cotton yarns Radcliffe's dressing machine has to a large extent been displaced by the slasher, but in some branches of the textile industry it is still retained under various modifications. In a slasher the threads from a number of warping beams are first combined into one sheet, then plunged into a trough filled with size which is kept at a boiling temperature by perforated steam pipes; and next squeezed between two pairs of rollers mounted in the trough. The under surfaces of the sizing rollers are in the size, but the upper squeezing rollers are covered with flannel, and rest by gravitation upon the lower ones. On leaving the size trough the sheet of yarn almost encircles two steam-heated cylinders whose diameters are respectively about 6 ft. and 4 ft. ; these quickly expel moisture from the yarn, but so much heat is generated that fans have to be employed to throw cool airfamongst the threads. The yarn is next measured, passed above and below rods which separate threads that have been fastened together by size, smeared with piece marks, and coiled upon a loom beam by means of a slipping friction gear. The last-named is employed so that the surface speed of winding shall not be affected by the increasing diameter of the loom beam. By means of mechanism which greatly reduces the velocities of the moving parts, much necessary labour may be performed without actually stopping the machine; this relieves the yarn of strain, and gives better sizing, yet slashed warps are less elastic than dressed, or balled sized ones, and they lack the smoothness of dressed warps.
Hank sizing is chiefly, but not exclusively, employed for bleached and coloured yarns. Machines for doing this work consist of a tank which contains size, flanged revolving rollers and two hooks. One hook is made to rotate a definite number of times in one direction, then an equal number the reverse way; the other has a weight suspended from jts outer end and can be made to slide in and out. Size in the tank is kept at the required temperature by steam pipes, and " doles " of hanks are suspended from the rollers with about one-third their length immersed in size. As the hanks rotate all parts of the yarn enter the size, and when sufficiently treated they are removed from the rollers to the hooks where they are twisted to wring out excess, and force in required size. If sufficient size has not been added by one treatment, when untwisted, the wrung-out hanks are passed to a similar machine containing paste of greater density than the first there to be again treated ; if necessary this may be followed by a third passage. On the completion of sizing the hanks are removed either to a drying stove or a drying machine. If to the former, they are suspended from fixed, horizontal poles in a specially heated and ventilated chamber. If to the latter, loose poles containing hanks are dropped into recesses in endless chains, and slowly carried through a large, heated and ventilated box, being partially rotated the while. On reaching the front of the box they are removed, brushed and made up into bundles. After which the yarn is wound, warped and transferred to a loom beam.
Drawing-in, or entering, is the operation of passing warp threads through the eyes of a shedding harness, in a sequence determined by the nature of the pattern to be produced, and the order of lifting the several parts. It is effected by passing a hook through each harness eye in succession, and each time a thread is placed in the hook by an attendant, it is drawn into an eye by the withdrawal of the hook.
Twisting or looming consists in twisting, between the finger and thumb, the ends of a new warp separately upon those of an old one, the remains of which are still in the eyes of the shedding harness. The twisted portions adhere sufficiently to permit of all being drawn through the eyes simultaneously.
The Power Loom. Little is known of the attempts made before the beginning of the 17th century to control all parts of a loom from one centre, but it is certain the practical outcome was inconsiderable. In the year 1661 , a loom was set up in Danzig, for which a claim was made that it could weave four or six webs at a time without human aid, and be worked night and day; this was probably a ribbon loom. In order to prevent such a machine from injuring the poor people, the authorities in Poland suppressed it, and privately strangled or drowned the inventor. M. de Gennes, a French naval officer, in 1678 invented a machine whose chief features consisted in controlling the healds by cams, the batten by cams and springs and the shuttle by a carrier. From 1678 to 1745 little of importance appears to have been done for the mechanical weaving of broadcloth. But in the last-named year M. Vaucanson constructed a very ingenious, selfacting loom, on which the forerunner of the Jacquard machine was mounted; he also adopted de Gennes's shuttle carrier. All early attempts to employ mechanical motive power for weaving failed, largely because inventors did not realize that success could only be reached through revolution. Mechanical preparing and spinning machinery had first to be invented, steam was needed for motive power, and the industry required reorganization, which included the abolition of home labour and the introduction of the factory system.
During the last quarter of the 18th century it was generally believed that, on the expiry of Arkwright's patents, so many spinning mills would be erected as to render it impossible to consume at home the yarns thus produced, and to export them would destroy the weaving industry. Many manufacturers also maintained it to be impossible to devise machinery which would bring the production of cloth up to that of yarn. It was as a protest against the last-named assertions that Dr Edmund Cartwright, a clergyman of the church of England, turned his attention to mechanical weaving. More fortunate than his predecessors, he attacked the problem after much initial work had been done, especially that relating to mechanical spinning and the factory system, for without these no power loom could succeed. In 1785 Dr Cartwright patented his first power loom, but it proved to be valueless. In the following year, however, he patented another loom which has served as the model for later inventors to work upon. He was conscious that for a mechanically driven loom to become a commercial success, either one person would have to attend several machines, or each machine must have a greater productive capacity than one manually controlled. The thought and ingenuity bestowed by Dr Cartwright upon the realization of his ideal were remarkable. He added parts which no loom, whether worked manually or mechanically, had previously been provided with, namely, a positive let-off motion, warp and weft stop motions, and sizing the warp while the loom was in action. With this machine he commenced, at Doncaster, to manufacture fabrics, and by so doing discovered many of its shortcomings, and these he attempted to remedy: by introducing a crank and eccentrical wheels to actuate the batten differentially; by improving the picking mechanism; by a device for stopping the loom when a shuttle failed to enter a shuttle box; by preventing a shuttle from rebounding when in a box; and by stretching the cloth with temples that acted automatically. In 1792 Dr Cartwright obtained his last patent for weaving machinery ; this provided the loom with multiple shuttle boxes for weaving checks and cross stripes. But all his efforts were unavailing; it became apparent that no mechanism, however perfect, could succeed so long as warps continued to be sized while a loom was stationary. His plans for sizing them while a loom was in operation, and also before being placed in a loom, both failed. Still, provided continuity of action could be attained, the position of the power loom was assuied, and means for the attainment of this end were supplied in 1803, by William Radcliffe, and his assistant Thomas Johnson, by their inventions of the beam warper, and the dressing sizing machine.
For upwards of thirty years the power loom was worked under numerous difficulties; the mechanism was imperfect, as were also organization, and the preparatory processes. Textile workers were unused to automatic machinery, and many who had been accustomed to labour in their own homes refused employment in mills, owing to dislike of the factory system and the long hours of toil which it entailed, that spinners and manufacturers were compelled to procure assistants from workhouses; this rendered mill life more distasteful than it otherwise would have been to hand spinners and weavers. Their resentment led them to destroy machinery, to burn down mills, to ill-use mill workers and to blame the power loom for the distress occasioned by war and political disturbances. Yet improvements in every branch of the textile industry followed each other in quick successions, and the loom slowly assumed its present shape. By using iron instead of wood in its construction, and centring the batten, or slay, below instead of above the warp line, the power loom became more compact than the hand-loom.
Motion is communicated to all the working parts from a main shaft A (fig. 28), upon which two cranks are bent to cause the slay B to oscillate; by toothed wheels this shaft, drives a second shaft, C, at half its own speed. For plain weaving four tappets are fixed upon the second shaft, two, D, for moving the shuttle to and fro, and two others, E, for moving the healds, L, up and down through the medium of treadles M, M. For other schemes of weaving shedding tappets are more numerous, and are either loosely mounted upon the second shaft, or fixed upon a separate one. In either event FIG. 28. Vertical Section of a Power Loom.
they are driven by additional gearing, for the revolutions of the tappets to those of the crank shaft must be as one is to the number of picks in the repeat of the pattern to be woven. Also, when two or more shuttles are driven successively from the same side of a loom, if the picking tappets rotate with the second shaft, those tappets must be free to slide axially in order to keep one out of action so long as the other is required to act. The warp beam F is often put under the control of chains instead of ropes, as used in hand looms, and the chains are attached to adjustably weighted levers, G, whereby the effectiveness of the weights may be varied at pleasure. In the manufacture of heavy fabrics, however, it may be necessary to deliver the warp by positive gearing, which is either connected, or otherwise, to the taking-up motion. The cloth is drawn forward regularly as it is manufactured by passing it over the rough surface of a roller, I, and imparting to the roller an intermittent motion each time a pick of weft is beaten home. This motion is derived from the oscillating slay, and is communicated through a train of wheels. The loom is stopped when the weft fails by a fork-and-grid stop motion, which depends for its action on the lightly balanced prongs of a fork, N. These prongs come in contact with the weft, between the selvage of the web and the shuttle box each time the shuttle is shot to the side at which the apparatus is fixed. If the prongs meet no thread they are not depressed, and being unmoved a connexion is formed with a vibrating lever, T; the latter draws the fork forward, and with it a second lever O, by which the loom is stopped. On the other hand, if the prongs are tilted, the loom continues in action. If more than one shuttle is used it may be necessary to feel for each, instead of alternate threads of weft. In such cases a fork is placed beneath the centre of the cloth and lifted above a moving shuttle; if in falling it meets with weft it is arrested, and the loom continues in motion, but if the weft is absent the prongs fall far enough beneath the shuttle race for a stop to act upon a lever and bring the loom to a si. i nd. To prevent a complete wreck of the warp it is essential to I the loom when a shuttle fails to reach its appointed box. For this purpose there are two devices, which are known respectively >t and loose reed stop motions. The first was invented in 1796 by Robert Miller, and its action depends upon the shuttle, as it is a box, raising two blades, K, which if left down would strike against stops, and so disengage the driving gear. The second was invented in 1834 by VV. H. Hornby and William Kenworthy; it is an appliance for liberating the lower part of a reed when a shuttle remains in the warp, thus relieving it, for the time being, of its function of beating up the weft. On the release of a reed from the motion of the slay, a dagger stops the loom. Temples must keep a fabric distended to the breadth of the warp in the reed, and be selfadjusting. This is usually accomplished by small rollers whose surfaces are covered with fine, closely set points. The rollers are pl.n-fd near the selvages of a web which is prevented from contracting xv it It h wise by being drawn tightly over the points.
Looms are varied in details to suit different kinds of work, but as a rule fabrics figured with small patterns are provided with healds for shedding as at L, while those with large patterns are provided with the Jacquard and its harness. Healds may be operated either by tappets or dobbies, but the range of usefulness in tappets is generally reached with twelve shafts of healds and with patterns having sixteen picks to a repeat; where they are unsuitable for licakl shedding a dobby is used. A dobby may resemble, in construction and action, a small Jacquard; if so the selection of healds that rise and fall for any pick is made by cards. In other types of dobbies the selection is frequently made by lags, into which pegs are inserted to pattern in the same manner that cards are perforated. By acting upon levers the pegs bring corresponding hooks into contact with oscillating griffe bars, and these lift the required heald shafts. Such machines are made single and double acting, and some have rollers in place of pegs to form a pattern. When multiple shuttles are required for power looms one of two types is selected, namely, drop or rotating boxes; the former are applicable to either light or heavy looms, but the latter are chiefly confined to light looms. As previously stated, Robert Kay invented drop boxes in 1760, but they were not successfully applied to the power loom until 1845, when Squire Diggle patented a simple device for operating them automatically. Since his time many other methods have been introduced, the most successful of these being operated indirectly from the shedding motion. Revolving boxes v/ere patented in 1843 by Luke Smith. They consist in mounting a series of shuttles in chambers formed in the periphery of a cylinder, and in moving the cylinder far enough, in each direction, to bring the required shuttle in line with the picker.
Automatic Weft Supply. Many devices have been added to power looms with a view to reduce stoppages, amongst which those for the automatic supply of weft are probably the most important. These efforts originated with Charles Parker, who, in 1840, obtained the first patent, but no marked success was achieved until 1894, when J. ri. Northrop patented a cop changer. By his plan a cylindrical hopper, placed over one shuttle box, is charged with cops or pirns. At the instant fresh weft becomes necessary the lowest cop in the hopper is pressed into a shuttle from above, the spent one is pressed out from beneath, and the new weft is led into the shuttle eye, while the loom is moving at its normal speed. The mechanism is controlled by the weft fork, or by a feeler which acts when only a predetermined quantity of weft remains inside a shuttle. Many inventions are designed to eject an empty shuttle and introduce a full one; others change a cop, but differ in construction and action from the Northrop, yet, at the time of writing, they have not been so successful as the last-named. By relieving a weaver of the labour of withdrawing, filling, threading and inserting shuttles it w.i- si-en that a large increase might be made in the number of looms allotted to one weaver, provided suitable mechanism could be devised for stopping a loom on the failure of a warp thread.
Warp Stopping Motions date from 1786, when Dr Cartwright siis|K'iulcd an independent detector from each warp thread until a fracture occurred, at which time a detector fell into the path of a vibrator and the loom was arrested. The demand for warp stop motions was, however, small until automatic weft supply mechanisms were adopted. The majority of those devices now in use are constructed upon Dr Cartwright's lines, but some are so attached to wire healds that, at one position in every shed, an unbroken thread supports both hcald and detector until a thread fails, when a detector is engaged by a vibrator, and the driving mechanism is dislocated. In other warp stop motions pairs of threads are crossed between the lease rods, and a wire passed between them is held forward by the crossed threads until one breaks; the wire then springs back, makes contact with a metal bar, and electro-mechanical connexions stop the loom.
Smallware Looms. _A loom, which was for a long period operated manually, but to which mechanical power could be applied, was brought into use more than a century before Dr Cartwright's invention. It was known as the Dutch engine loom, and was designed to weave from eight to upwards of forty tapes or ribbons simultaneously. This machine may be regarded as a series of looms mounted in one frame, each having a complete set of parts, and as the first practical effort to connect and control all the motions of weaving from one centre. The place and date of its invention are uncertain ; but it is known that in some districts its use was entirely prohibited, in others it was strictly limited, and that it was worked in Holland about 1620. In England the first patent was obtained by John Kay and John Snell, in 1745, for additions which enabled it to be worked by hand, by water, or other force, and in 1760 John Snell appears to have added the draw harness for weaving flowered ribbons. In 1765 a factory in Manchester was filled with ribbon looms which were either invented by M. Vaucanson, or Kay and Snell, but one weaver could only attend to one machine. When worked by hand it was known as the bar loom, because the weaver oscillated by hand a horizontal bar that set in motion all parts of the machine. The shuttles and reeds are actuated from the batten, the former originally by pegs, but later by a rack and pinion arrangement, which in action shoot the shuttles simultaneously across a web, to the right and left alternately, each into the place vacated by its next neighbour. One small warp beam is required for each web, but tappets, dobbies, or Jacquards are available for dividing the threads. Where differently coloured wefts are needed in one web the shuttles are mounted in tiers and all raised or lowered at once to bring the proper colour in line with the shed.
In Swivel Weaving similar shuttles are added to the battens of broad looms in order to diaper small figure effects, in different colours or materials, over the surface of broad webs.
Pile Weaving. Looms for weaving piled fabrics differ in certain important respects from those employed for ordinary weaving; they are also made to differ from each other to suit the type of fabric to be manufactured, as, for example, double and single, plain and figured, textures.
In Double Pile Looms the special features are those that control the pile threads, and those that sever the vertical lines of pile. Two ground warps are requisite, and unless they are kept a uniform distance apart the piled effects will be irregular. For plain goods the pile threads are wound upon two or more beams, and, as they move from web to web, cloth-covered rollers deliver them in fixed lengths. Meanwhile, a shuttle passes twice in succession through each ground warp, and the pile threads in moving above or beneath the wefts are bound securely. Both fabrics are furnished with taking-up rollers which draw the pieces apart and so stretch the uniting pile in front of a knife, which severs it, thus forming two pieces at once. A knife may consist of a short blade that merely moves to and fro across the webs, or of a disk mounted upon a spindle, which, in moving from side to side, revolves; in either case it is automatically sharpened. But if a knife is longer than the breadth of a fabric it receives only a slight lateral movement, and must be periodically removed for sharpening. In plain and printed goods healds control all the warps ; but in figured goods, other than those made from printed warps, a Jacquard is needed to lift, and a creel to hold, the pile threads.
Single Pile Looms. The chief feature which renders most single pile looms dissimilar from others is the mechanism by which wires are woven upon, and withdrawn automatically from, a ground texture. Wires are of two kinds, namely, without and with knives; the former, being flattened and somewhat pointed, are woven above the weft of a ground texture, but beneath the pile, hence, by withdrawing them, looped pile is formed. A wire terminating in a knife with a sloping blade, on being withdrawn, cuts the pile and produces a brush-like surface. The mechanism for operating the wires is placed at one end of a loom and consists of an arm which moves in and out; at each inward movement a wire is inserted, and at each outward movement one is withdrawn. In weaving tapestry carpets, and certain other fabrics, a wire and a shuttle move simultaneously, but a shuttle passes through the ground warp, while a wire passes beneath the pile. After several wires have been woven upon the ground texture the one first inserted is withdrawn by the vibrating arm, and at the next inward movement the same wire enters the warp near the reed, where it is beaten up with the weft, and, from this point, the operation is continuous. Tapestry carpets require three warps, one for the ground texture, a second, o_r stuffing warp, to give bulk and elasticity to the tread, and a third to form the pile. The last named is printed upon a large drum, thread by thread to the colour scheme of the design, then, when the colours have been fixed, and the threads^ccurately placed, they are wound upon a beam, and all the warps are operated by healds. For figured velvets, and Brussels and Wilton carpets, the pile warp beam is replaced by a creel, in order that each thread of pile may be wound upon a bobbin and separately tensioned. This is essential, because, in the weaving of a design, it is probable that no two threads of pile will be required in equal lengths. Creels are made in sections called frames, each of which usually carries as many bobbins as there are loops of pile across a web, and the number of sections equal the number of colours. In weaving these fabrics healds are used to govern the ground warp, but a Jacquard is needed for the pile. It must form two sheds, the lower one to receive a shuttle, the upper one to make a selection of threads beneath which the wire is to pass.
Terry Looms. Looms for weaving piled textures, of the Turkish towel type, have the reed placed under the control of parts that prevent it from advancing its full distance for two picks out of every series that separate one line of loops from another. At such times the weft is not beaten home, but a broad crack is formed. So soon as the reed again moves through its normal space three picks of weft are simultaneously driven home, thus closing the gap, and causing part of the pile to loop upward, the remainder downward. The system is available for plain and figured effects.
Gauze Textures are woven in looms having a modified shedding harness, which, at predetermined intervals, draws certain warp threads crosswise beneath others, and lifts them while crossed. Also, a tensioning device to slacken the crossed threads and thus prevent breakages due to excessive strain. At other times the shedding is normal.
Lappet Looms have a series of needles fixed upright in laths, and placed in a groove cut in the slay, in front of the reed. Each needle carries a thread which does not pass through the reed, hence, by giving the laths an endlong movement of varying extent, and lifting the needles for each pick, their threads are laid crosswise in the web to pattern. _ (T. W. F.)
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
