Types Of Looms
The earliest looms were vertical shaft, with the heddles fixed in place in the shaft. The warp threads pass alternately through a heddle and through a space between the heddles, so that raising the shaft will raise half the threads (those passing through the heddles), and lowering the shaft will lower the same threads the threads passing through the spaces between the heddles remain in place.
A Dobby Loom is a type of floor loom that controls the warp threads using a device called a dobby. Dobby is short for “draw boy” which refers to the weaver’s helpers who used to control the warp thread by pulling on draw threads.
A dobby loom is an alternative to a treadle loom. Each of them is a floor loom in which every warp thread on the loom is attached to a single shaft using a device called a heddle. A shaft is sometimes known as a harness, but this terminology is becoming obsolete among active weavers. Each shaft controls a set of threads. Raising or lowering several shafts at the same time gives a huge variety of possible sheds through which the shuttle containing the weft thread can be thrown.
A manual dobby uses a chain of bars or lags each of which has pegs inserted to select the shafts to be moved. A computer assisted dobby loom uses a set of solenoids or other electronic devices to select the shafts. Activation of these solenoids is under the control of computer program. In either case the selected shafts are raised or lowered by either leg power on a dobby pedal or electric or other power sources.
On a treadle loom, each foot-operated treadle is connected by a linkage called a tie-up to one or more shafts. More than one treadle can operate a single shaft. The tie-up consists of cords or similar mechanical linkages tying the treadles to the lams that actual lift or lower the shaft.
On treadle operated looms, the number of sheds is limited by the number of treadles available. An eight shaft loom can create 254 different sheds. There are actually 256 possibilities which is 2 to the eight power, but having all threads up or all threads down isn’t very useful. However, most eight shaft floor looms have only ten to twelve treadles due to space limitations. This limits the weaver to ten to twelve distinct sheds. It is possible to use both feet to get more sheds., but that is rarely done in practice. It is even possible to change tie-ups in the middle of weaving a cloth but this is a tedious and error prone process so this too is rarely done.
With a dobby loom, all 254 possibilities are available at any time. This vastly increases the number of cloth designs available to the weaver. The advantage of a dobby loom becomes even more pronounced on looms with 12 shafts (4094 possible sheds), 16 shafts (65,534 possible sheds), or more. It reaches its peak on a Jacquard loom in which each thread is individually controlled.
Another advantage to a dobby loom is the ability to handle much longer sequences in the pattern. A weaver working on a treadled loom must remember the entire sequence of treadlings that make up the pattern, and must keep track of where they are in the sequence at all times. Getting lost or making a mistake can ruin the cloth being woven. On a manual dobby the sequence that makes up the pattern is represented by the chain of dobby bars. The length of the sequence is limited by the length of the dobby chain. This can easily be several hundred dobby bars, although an average dobby chain will have approximately fifty bars.
A computer controlled dobby loom (Computer-Dobby) takes this one step further by replacing the mechanical dobby chain with computer controlled shaft selection. In addition to being able to handle sequences that are virtually unlimited, the construction of the shaft sequences is done on the computer screen rather than by building a mechanical dobby chain. This allows the weaver to load and switch weave drafts in seconds without even getting up from the loom. In addition, the design process performed on the computer provides the weaver with a more intuitive way to design fabricas seeing it on the computer screen is easier than trying to visualize it by looking at the dobby chain.
Dobby looms expand a weavers capabilities and remove some of the tedious work involved in designing and producing fabric. Many newer cloth design techniques such as network drafting can only reach their full potential on a dobby loom.
The Jacquard Loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, that simplifies the process of manufacturing textiles with complex patterns such as brocade, damask, and matelasse. The loom is controlled by punchcards with punched holes, each row of which corresponds to one row of the design. Multiple rows of holes are punched on each card and the many cards that compose the design of the textile are strung together in order. It is based on earlier inventions by the Frenchmen Basile Bouchon (1725), Jean Falcon (1728) and Jacques Vaucanson (1740)
Principles of Operation
Each hole in the card corresponds to a “Bolus” hook, which can either be up or down. The hook raises or lowers the harness, which carries and guides the warp thread so that the weft will either lie above or below it. The sequence of raised and lowered threads is what creates the pattern. Each hook can be connected via the harness to a number of threads, allowing more than one repeat of a pattern. A loom with a 400 hook head might have four threads connected to each hook, resulting in a fabric that is 1600 warp ends wide with four repeats of the weave going across.
The term “Jacquard loom” is a misnomer. It is the “Jacquard head” that adapts to a great many dobby looms such as the “Dornier” brand that allow the weaving machine to then create the intricate patterns often seen in Jacquard weaving.
Jacquard looms, whilst relatively common in the textile industry, are not as ubiquitous as dobby looms which are usually faster and much cheaper to operate. However unlike jacquard looms they are not capable of producing so many different weaves from one warp. Modern jacquard looms are controlled by computers in place of the original punched cards, and can have thousands of hooks.
The threading of a Jacquard loom is so labor intensive that many looms are threaded only once. Subsequent warps are then tied in to the existing warp with the help of a knotting robot which ties each new thread on individually. Even for a small loom with only a few thousand warp ends the process of re-threading can take days.
Importance to Computing
The Jacquard loom was the first machine to use punch cards to control a sequence of operations. Although it did no computation based on them, it is considered an important step in the history of computing hardware. The ability to change the pattern of the loom’s weave by simply changing cards was an important conceptual precursor to the development of computer programming. Specifically, Charles Babbage planned to use cards to store programs in his Analytical engine.
Jacquard weaving makes possible in almost any loom the programmed raising of each warp thread independently of the others. This brings much greater versatility to the weaving process, and offers the highest level of warp yarn control. This mechanism is probably one of the most important weaving inventions as Jacquard shedding made possible the automatic production of unlimited varieties of pattern weaving.
In former times, the heddles with warp ends to be pulled up were manually selected by a second operator, apart from the weaver. This was known as a drawloom. It was slow and labour intensive, with practical limitations on the complexity of the pattern.
The Jacquard process and the necessary loom attachment are named after their inventor, Joseph Marie Jacquard (1752 – 1834). He recognized that although weaving was intricate, it was repetitive, and saw that a mechanism could be developed for the production of sophisticated patterns just as it had been done for the production of simple patterns. (Similar ideas were pursued by others before 1750, but Jacquard perfected and popularized the concept by about 1803.)
Jacquard’s invention had a deep influence on Charles Babbage. In that respect, he is viewed by some authors as a precursor of modern computing science
Mechanical Jacquard Looms
Originally the Jacquard machines were mechanical, and the fabric design was punched in pattern cards which were joined together to form a continuous chain. The Jacquards often were small and only independently controlled a relatively few warp ends. This required a number of repeats across the loom width. Larger capacity machines, or the use of multiple machines, allowed greater control, with fewer repeats, and hence larger designs to be woven across the loom width.
A factory must choose looms and shedding mechanisms to suit its commercial requirements. As a rule the more warp control required the greater the expense. So it would not be economical to purchase Jacquard machines if one could make do with a dobby mechanism. As well as the capital expense, the Jacquard machines are also more costly to maintain, as they are complex and require higher skilled personnel; also an expensive design system will be required to prepare the designs for the loom, and possibly also a card-cutting machine. Weaving will be more costly as Jacquard mechanisms are more liable to produce faults than dobby or cam shedding. The looms will not run as fast, and down time will increase as it takes time to change the continuous chain of cards when a design changes. Therefore with mechanical Jacquards it is best to weave larger batch sizes.
Looms Bonas Machine Company Ltd. launched the first electronic Jacquard at ITMA, Milan in 1983 . Although the machines were initially small, modern technology has allowed Jacquard machine capacity to increase significantly, and single end warp control can extend to more than 10,000 warp ends. This avoids the need for repeats and symmetrical designs and allows almost infinite versatility. The computer-controlled machines significantly reduce the down time associated with changing punched paper designs, thus allowing smaller batch sizes. However, electronic Jacquards are costly and may not be required in a factory weaving large batch sizes, and smaller designs. The larger machines allowing single end warp control are very expensive, and can only be justified where great versatility is required, or very specialized design requirements need to be met. For example, they are an ideal tool to increase the ability and stretch the versatility of the niche linen Jacquard weavers who remain active in Europe and the West, while most of the large batch commodity weaving has moved to low cost areas.
Linen products associated with Jacquard weaving are linen damask napery, Jacquard apparel fabrics and damask bed linen.
Jacquard weaving of course uses all sorts of fibers and blends of fibers, and it is used in the production of fabrics for many end uses. Research is under way to develop layered and shaped items as reinforcing components for structures made from composite materials.
The term “Jacquard” is not specific or limited to any particular loom, but rather refers to the added control mechanism that automates the patterning.
The Lancashire Loom was a semi automatic power loom invented by James Bullough and William Kenworthy in 1842. Although it is self-acting, it has to be stopped to recharge empty shuttles.It was the mainstay of the Lancashire cotton industry for a century.
The principal advantage of the Lancashire loom was that it was semi automatic, when a warp thread broke the weaver was notified. When the shuttle ran out of thread, the machine stopped. An operative thus could work 4 or more looms whereas previously they could only a single loom. Indeed the term A Four Loom Weaver was used to describe the operatives. Labour cost was quartered. In some mills an operative would operate 6 or even 8 looms. . Though this was governed by the thread being used. By 1900, the loom was challenged by the Northrop Loom which was fully automatic and could be worked in larger numbers. The Northrop was suitable for coarse thread but for fine cotton, the Lancashire loom was still prefered. By 1914, Northop looms made up 40% of looms in American mills but in the United Kingdom, labour costs were not as significant and they only supplied 2% of the British market.
Northrop had worked as a mechanic and foreman, he invented spooler guide while employed by Draper. He unsuccessfully tried to be a chicken farmer. And it was there he worked on his shuttle-charger for Mr Otis Draper,who saw a model of the device on March 5, 1889. Draper was also developing the Rhoades shuttle-charger. Northrop was given a loom to test his idea.
By May 20 he had concluded that his first idea was not practical, and had thought of another idea, On July 5, the completed loom was running, and as it seemed to have more advantages than the Rhoades loom. The Northrop device was given a mill trial in October 1889 at the Seaconnett Mills in Fall River. More looms were constructed. Meanwhile he invented a self-threading shuttle and shuttle spring jaws to hold a bobbin by means of rings on the butt. This paved the way to his filling-changing battery of 1891, the basic feature of the Northrop loom. Other members of the Draper organization had developed a workable warp stop motion which was also included. The first Northrop looms were marketed in 1894.
The principal advantage of the Northrop loom was that it was fully automatic; when a warp thread broke the loom stopped until it was fixed. When the shuttle ran out of thread, Northrop’s mechanism, ejected the depleted pirn, and loaded a new full one without stopping. An operative thus could work 16 or more looms whereas previously they could only operate 8. Thus the labour cost was halved. Mill owners had to decide whether the labour saving was worth the capital investment in a new loom. By 1900, Draper had sold over 60,000 Northrop looms, They were shipping 1500 a month, were employing 2500 men and enlarging their works to increase that output. In all 700,000 looms were sold.
By 1914, Northop looms made up 40% of American looms. However in the United Kingdom, labour costs were not as significant and they only supplied 2% of the British market. Northrops were especially suitable for coarse cottons, but it was said not particular suitable for fines, thus the financial advantage in their introduction into Lancashire was not as great as it had been in the States. Henry Philip Greg imported some of the first Northrops into Britain in 1902, for his Albert Mill in Reddish, and encouraged his brother Robert Alexander Greg to introduce Northrops into Quarry Bank Mill in 1909. The output increased from 2.31 lbs/manhour in 1900, to 2.94 lbs/manhour in 1914. Labour costs decreased from 0.9d per pound to 0.3d per lb.
Projectile Loom(Gripper Shuttle Loom)
The multi gripper projectile weaving machine,introduced by sulzer brothers in 1953,was the first system to begin shuttle weaving.The company and its successors have remained the sole suppliers of projectile weaving machinery.
Pick lengths of weft yarn are drawn from large cones by a weft accumulator.The free end is held in the jaws of a weft carrier gripper(projectile),88mm long weighing 40kg and the accumulated yarn is threaded to a sophisticated tensioning and braking system.The Projectile is lifted to the picking position and is propelled across the warp shed by a torsion bar system.At the other side of the loom,the projectile is recieved,the yarn is released and the projectile is ejected for eventual return to the picking side.The weft is cut at the picking side and is held at both sides by a selvedge grippers during beat up and shed change.During the next machine cycle,tucking needles draw the outer ends of weft yarn into fabric to form selvedges.Usually 10-12 projectiles are associated with a single-width loom.
picking rates are typically 380-420ppm for worsted yarns and 250-300 ppm for woolen yarns.
It offers the following advantages
Low power consuption
Reduced waste of filling material due to unique clean ,tucked-in selvedges
Quick warp and style change
Mechanical and operatonal reliability and ease of use
Low spare parts requirement and easy maintaince
Long machine life
Rapier Weaving is offered by many loom manufacturers and consequently is in widespread use in the worsted and woolen industry.
In this type of weaving a flexible or rigid solid element called rapier, is used to insert the filling yarn and carries it through thr shed .after reaching the destination, the rapier head returns empty to pick up the next filling yarn,which completes a cycle.a rapier performs a reciprocating motion.
Single Rapier Machines
A single,rigid rapier is used in these machines.the rigid rapier is a metal or composite bar usually with a circular cross section.the rapier enters the shed from one side and pases it across the weaving machine while retracting .therefore a single rapier carries the yarn in one way only and half of the rapier movement is wasted.also there is no yarn transfer since there is only one rapier.the single rapiers length is equal to the width of the weaving machine; this requires relatively high mass and rigidity of the rapier head.for these reasons,single rapier machines are not popular.however since there is no yarn transfer to rapier tp rapier,they are suitable for filling yarns that are difficult control.
Double Rapier Machines
Two rapiers are used in these machines.one rapier ,called the giver takes the filling yarn from the accumulator on one side of the weaving machine, brings it to the center of the machine and transfers it to the decond rapier which is called taker.the taker retracts and brings the filling yarn to the other side.similar to the single rapier machines,only half of the rapier movements is used for filling insertion.
Rapier machines are known for their reliability and performance.since 1972,the rapier weaving machine has evolved into successfull ,versatile and flexible weaving machine.
A very wide range of fabrics with 20 g/m2 to heavy fabrics with around 850 gm2 rapier machines are widely used for household textiles and industrial fabrics.Designed for universal use,the rapier weaving machine can weave not only the classic wool,cotton and manmade fibers,but also the most technicaly demanding filament yarns,finest silk and fancy yarns.
Air Jet Loom
Air jet loom, as one of the shuttleless looms, transports a yarn into warps using viscosity and kinetic energy of an air jet. Performance of this picking system depends on the ability of instantaneous inhalation/exhaust, configuration of nozzle, operation characteristics of a check valve, etc.
Air-jet weaving is an advanced weaving method with high efficiency and productivity
In air-jet looms, the weft is introduced into the shed opening by air flow.
The energy resulting from air pressure is converted into kinetic energy in the nozzle.
The air leaving from the nozzle transfers its pulse to stationary air and slows down.
To this end, in order to achieve a larger rib width, a confuser is developed, which maintains air velocity in the shooting line.
The confuser drop wires are profiles narrowing in the direction of shoot, and they are of nearly circular cross section open at the top.
These drop wires are fitted one behind the other as densely as possible. Therefore, they prevent in the shooting line the dispersion of air jet generated by the nozzle.
Water Jet Loom
A water jet is more coherant than an air jet.it does not break up easily, and the propulsive zone is elongated,making it much more effective.it is effective in terms of energy requirements ,it is quite and when the jet does break up, it goes into droplets which create very little turbulence to disturb the filling.
The droplets spread in such a way as to wet much of the warp; thus a sized warp containing a water soluble adhesive can be adversely affected.because of this ,water jet weaving is usually restricted to filament yarn,but there is some hope that it might become economically feasible to weave staple yarns on these looms.
Two main reasons for the efficiency of the water-jet loom are that there are no varying lateral forces to cause the filling to contract and the moving element is more massive because it is wet.thus there is less chance of fault due to contact with the warp.
The range of jet, and thus the width of the loom ,depends on the water pressure and the diameter odf the jet.water is virtually incompressible and a simple jerk pump can be used to give adequate pressure with difficulty.
A firmans hose has a tremendous range but the jet is several cm in diameter;large volumes of water and considerable pumping powers have to be used .in weaving , a much more modest jet is used; in fact , it is possible to reduce the diameter of the jet to some 0.1 cm, and the amount of water used per pick is commonly less than 2c.c. even with these small jets , it is possible to weave at upto 2 meters in width with small power consuptions.it is also possible to weave at upto 1000 picks/min on narrower looms .several forms of water-jet loom have now become established.
The circular weaving machine proposed by the invention is designed for the manufacture of tubular fabrics and has an annular frame with an upper ring plate and a lower ring plate Vertically moving laces are fitted to direct the warp ends and are mounted at constant intervals round at least one circular trackway . The two ring plates have bores in them for mounting and directing the laces . The lower ends of the laces have follower rollers which operate in conjunction with a cam plate.