loom(redirected from Hand loom)
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loom,frame or machine used for weavingweaving,
the art of forming a fabric by interlacing at right angles two or more sets of yarn or other material. It is one of the most ancient fundamental arts, as indicated by archaeological evidence.
..... Click the link for more information. ; there is evidence that the loom has been in use since 4400 B.C.
Modern looms are of two types, those with a shuttle (the part that carries the weft through the shed) and those without; the latter draw the weft from a stationary supply. There are basically three kinds of shuttleless looms. The dummy shuttle, the most widely used, contains no weft but moves through the shed depositing a trail of yarn. A second type, the newest of looms, makes use of jets of air or water to force the weft through the shed. A third kind, called the rapier type and widely used in carpet weaving, uses steel rods to move the weft into the shed.
The fundamental parts of all looms are the warp beam, a cylinder on which the warp threads are wound; heddles (rods or cords), each with an eye through which is drawn a warp thread; the harness, a rectangular frame set with a series of heddles operated to form a shed between the warp threads for the insertion of the weft threads; the reed, a comblike frame that pushes the filling yarn firmly against the finished cloth after each pick, or row; the breastbeam, over which the cloth is wound creating a tension with the warp beam; the cloth beam, on which the cloth is rolled as it is constructed; and the shuttle, if it is not a shuttleless loom.
Vertical looms, such as the Navajo and some tapestry looms, developed from the practice of hanging the warp beam from a tree and holding the yarns taut with stones, pegs, or a weighted pole. The horizontal form, at first two poles holding the warp extended on the ground, was widely used for the Western European handloom and for the foot loom, the forerunner of the modern power loom. In the foot loom the harnesses were operated by treadles, leaving the hands free to pass and catch the shuttle. John Kay invented (1733) the automatic fly shuttle, and in 1760 his son Robert devised a drop box by which trays automatically brought bobbins of colored threads in line as desired. These aids to weaving encouraged inventions to speed up spinningspinning,
the drawing out, twisting, and winding of fibers into a continuous thread or yarn. From antiquity until the Industrial Revolution, spinning was a household industry. The roughly carded fiber was at first held in one hand and drawn out and twisted by the other hand.
..... Click the link for more information. , which in turn made faster weaving essential.
Edmund Cartwright patented (1785) the first practical power loom, the basis of the modern loom with its multiplicity of automatic devices. By 1804, Joseph Marie JacquardJacquard, Joseph Marie
, 1752–1834, French inventor, whose loom is of the greatest importance in modern mechanical figure weaving. After several years of experimentation, he received a bronze medal for his model exhibited at the Industrial Exposition at Paris (1801).
..... Click the link for more information. had perfected an attachment applicable to the power loom whereby any design might be woven on it. In the modern Jacquard, one repeat of the design is laid out on squared paper, then punched on cards that are laced into a continuous chain rotated on an overhead device. The cards are brought in contact with needles, each controlling a wire that lifts a heddle when the needle passes through a hold in the card. In the Lefier robot, a design made on copper with insulating paint is transmitted by electricity to needles that lift the heddles.
a machine that produces different types of textiles from warp and weft yarns (threads); the principal machine used in weaving.
Looms may be classified in two categories, depending on the method used to form the fabric: looms in which the fabric is not formed continuously (both shuttle and shuttleless looms) and looms with continuous formation of the fabric in steps (multiple-shed looms). Depending on the design, looms may be flat or circular; the latter are used only for producing special fabrics, such as hose fabrics. Flat shuttle looms are the most widely used. Depending on the yarn used and the type and purpose of the fabric, looms may be designed for producing cotton, silk, wool, glass, metal, or other fabrics. They may be narrow, producing fabrics with widths up to 100 cm, or wide, and they may be designed for light, medium-weight, or heavy fabrics. Multishuttle looms are used for working wefts of different color or twist. Depending on the design of the shedding mechanism, looms may be classified as cam looms (for fabrics with simple weaves), dobby looms (for huckaback weaves), or Jacquard looms (for luxury fabrics; seeJACQUARD ATTACHMENT).
The operating principle of a loom is shown in Figure 1. The principal working parts are the heddle, the shuttle, which lays the weft, and the reed. The warp yarns wound on the warp beam run across a guide roller (whip roll) and assume a horizontal or inclined position. Then they pass through the openings of the lease rods (seeWARP STOP-MOTION) and through the eyes of the heddles, which move the warp threads in a vertical direction for forming the shed. The weft yarn is carried through the shed by means of a shuttle or other device, and the yarn is beaten up to the fell by a reed, which makes a horizontal reciprocating motion along with the batten. At the fell of the fabric, the warp threads are interlaced with the weft threads to form the fabric, which runs over the breast beam, sand roll, and guide and is wound on the cloth beam. The order in which the movements of the heddles are alternated produces fabrics with differing weaves. The number of teeth per unit of reed length and the number of threads passing through each space between the teeth determine the warp density; the movement, or advance, of the fabric per weft yarn determines the weft density.
On shuttle looms, the weft yarn is laid in the shed by a shuttle, which carries a package, or spool, of yarn and makes a horizontal reciprocating motion at a speed of 10–18 m per sec, depending on the width of the loom. The spool is changed automatically. The weight of the shuttle with the weft package ranges from 0.25 to 5 kg. The variable speed and high weight of the shuttle are the basic causes of the low productivity of shuttle looms.
The shortcomings of shuttle looms are eliminated in the shuttleless loom, which was introduced in the mid-20th century. In shuttleless looms, a large weft package, or bobbin, is located on the bed of the loom; the yarn is cut after each insertion of the weft mechanism. Depending on the method used to lay the weft yarn, shuttleless looms may be classified as dummy-shuttle (with small weft mechanisms), air-jet, water-jet, rapier, and air-jet-rapier looms.
In dummy-shuttle looms, which are now widely used, the dummy shuttle uses a spring clamp to grip the weft end as it comes off the bobbin. The dummy shuttle travels on a track as it lays the yarn in the shed at a speed of 23–25 m per sec. The dummy shuttle weighs approximately 40 gm. Such looms are approximately 2½ times more productive than shuttle looms. They make it possible to manufacture fabrics from all types of fibers and from fiber blends; up to four types of wefts may be used.
In air-jet and water-jet looms, the weft thread coming off the bobbin is laid by a jet of compressed air or water. The compressed air is delivered at pressures up to 3 × 105 newtons per m2(3 kilograms-force per cm2), and in water-jet looms the spray jet is discharged from the nozzle at a pressure of 15 × 105 newtons per m2 (15 kilograms-force per cm2). The speed at which the weft yarn is laid in these looms reaches 35 m/sec. Air-jet looms are used in the manufacture of cotton and silk fabrics. Water-jet looms are used for fabrics made from synthetic yarns; the yarns are not wetted by the water.
On a rapier loom, the weft yarn is introduced into the shed by grips fastened to the tips of rods (the rapiers) or flexible metal tapes, which make a horizontal reciprocating motion from both sides of the loom. Rapier looms are primarily used for manufacturing cloth and fabrics with warps and wefts of different type or color.
Other looms use a combination of the air-jet and rapier methods of laying the weft yarn in the shed. Two hollow rapiers are introduced into the shed from the right and left sides, forming an air channel. The weft yarn is blown into the right rapier by compressed air under a pressure of approximately 0.4 × 105 newtons per m2 (0.4 kilogram-force per cm2). At the same time, air is sucked into the left rapier; this provides great reliability of yarn movement through the rapier channels. After the weft is laid—at speeds of 18–20 m/sec—the rapiers withdraw from the shed, and the reed beats the yarn up to the fell of the fabric.
In multiple-shed looms, experimental models of which were shown in the USSR and Czechoslovakia in 1974, the interlacing of the yarns is carried out by shuttles at several places along the warp, since the distance between the shuttles is significantly less than the width of the fabric. The heddle consists of individual sections 2–4 cm wide. These sections move independently of one another by means of a cam mechanism, forming a “wave, ” or stepped, shed. A shuttle with the weft yarn moves in each wave of the shed. The shuttles are moved by rollers on a chain conveyor located under the warp yarns. Each weft yarn is beaten up in synchronization with the movement of the shuttle; this can be accomplished, for example, by disks mounted on a shaft. Between the disks there are spaces, through which pass the warp yarns. As the shaft turns, the weft yarn is caught by the disks and pressed to the fell of the fabric. The shuttles are loaded by means of reel heads; after the shuttle stops, the heads wind a coil of yarn on it with a length of one pick. The speed of the shuttle is 2 m/sec.
Further improvements in looms are primarily directed at increasing the speed at which the weft is laid and, consequently, the operating speed of the loom. The use of multiple-shed looms is expected to increase.
REFERENCESSidorov, Iu. P., and V. A. Kokorev. Pnevmaticheskie P-105 i gidravlicheskie G-1055 tkatskie stanki. Moscow, 1962.
Topilin, A. P., A. A. Kazurov, and V. A. Ianpol’skii.
Vysokoproizvoditel’nye avtomaticheskie tkatskie stanki tipa STB. Moscow, 1969.
Pnevmorapirnye tkatskie stanki. Moscow, 1974.
V. N. POLETAEV