There are many classifications of looms. According to the weft insertion method of weaving, they can be divided into shuttle looms and shuttleless looms.
The weft insertion of shuttle loom is a loom that uses traditional wooden shuttle or plastic shuttle for weft insertion. Due to the large size and heavy weight of the shuttle, the shuttle is repeatedly projected back and forth, causing the machine to vibrate loudly, produce high noise, high energy consumption, slow speed, and low efficiency.
The weft insertion methods of shuttleless looms are also diverse, including rapier, air jet, water jet, projectile and multi-shed (multi-phase) methods.
Air-jet loom
Air-jet loom The shuttleless loom is a new type of loom that uses the high-speed airflow generated by the release of compressed air to pull the weft yarn through the cloth fell to complete the weft insertion. It is currently the fastest growing model among shuttleless looms.
1. Historical development
In 1949
Czechoslovakia first made an air-jet loom. Due to the lack of control measures for the diffusion of airflow, the width of the woven fabric was only 45cm.
1956
Developed combined duct pieces to limit airflow diffusion , resulting in a breakthrough in jet technology.
In 1963
The Netherlands developed auxiliary nozzle weft insertion technology. The width and loom speed are greatly increased.
1970s
New form of restricting airflow diffusion— —The advent of special-shaped buttons has brought new progress in the range and quality of fabrics woven by air-jet looms.
In recent years
The new development trend of air-jet looms is Energy saving, intelligence, networking, expanded variety adaptability, high speed and low vibration, etc.
2. Principle of weft insertion
Jet weft insertion uses air as the weft insertion medium, and uses the jetted compressed airflow to generate frictional traction on the weft yarn to bring the weft yarn through the shed. The purpose of weft insertion is achieved through the jet generated by the air jet.
Characteristics of jet weft insertion
The characteristics of jet weft insertion are: High speed, large tension, small shed, relatively high requirements for raw yarn and semi-finished products.
Jet weft insertion is a passive weft insertion method. When the weft yarn jumps over the shed, the tension is small and there is no control. Therefore, it is not suitable for yarns with large linear density or fancy yarns. The weft yarn lacks sufficient traction. At the same time, the warp opening state has a great influence on the quality of weft insertion, and it is easy to produce fabric defects such as weft shrinkage and weft foldback.
3. Main structure and characteristics
The air-jet loom mainly consists of frame, transmission and braking system, shedding mechanism, weft insertion mechanism, beating-up mechanism, let-off mechanism, winding mechanism, selvedge mechanism, scissors mechanism, edge yarn catching device, centralized oil supply and Automatic control system and other components.
The main structural and technical characteristics of the air-jet loom:
1. The weft insertion method uses the release of compressed air under the action of the main and auxiliary nozzles and special-shaped reeds. The high-speed airflow generated pulls the weft yarn through the fabric fell to complete the weft insertion.
2. Opening methods include crank opening, cam opening, dobby opening and jacquard opening, which can be selected according to the fabric weave. The general conventional configuration is a cam opening.
3. Beating-up methods include four-link beat-up, six-link beat-up and conjugate cam beat-up.
4. The let-off mechanism mainly uses electronic semi-active and semi-passive continuous let-off and mechanical semi-active and semi-passive continuous let-off.
5. The coiling mechanism has mechanical continuous coiling and electric coiling. Domestic air-jet looms are generally equipped with mechanical continuous take-up.
6. Cloth rolling: Generally, the cloth is rolled inside the machine, and it is optional to roll the cloth outside the machine.
7. Rack Japanese models use box-type wall panel racks, while European models mostly use panel-type wall panel racks. Both types of frames exist in domestic air-jet looms.
8. Transmission and braking reluctance motor direct transmission and braking, stepless speed regulation; super-start motor transmission, electromagnetic brake braking; ordinary motor and flywheel and clutch Transmission, electromagnetic brake braking.
9. Lubrication: The main transmission part adopts oil bath lubrication, and other parts adopt oil cup lubrication or centralized oil supply.
10. Yarn supply: There is a floor-standing yarn supply rack outside the machine, which can be equipped with 2 bobbins, 4 bobbins, 6 bobbins and 8 bobbins.
11. Length measurement and weft storage: The electric drum stores the weft, and the drum diameter and yarn stop pin are fixed to the length.
12. The hemming mechanism includes planetary hemming, leno hemming, electronic hemming, fold-in hemming and hot-melt hemming. Choose according to fabric requirements.
13. There are two types of selvedge: raw edge and smooth edge. Depends on the institution chosen.
14. Ring temple support. Choose the number of loops and needle size according to the fabric.
15. Weft cutting There are mechanical scissors and electronic scissors.
16. Weft finder Photoelectric weft finder. Divided into reflective and transmissive types.
17. Weft stopping device The weft detector detects the flying status of the weft yarn, and the weft detection control unit determines whether the flight is normal or not and issues a command to stop or continue running.
18. Stopping device: There are electrical contact rod stopping device, far infrared detection stopping device and combing stopping device. At present, the warp-stop type is mostly used, and 4, 6 or 8 rows can be used according to the warp density.
19. Display keyboard display (parameter setting, loom statusMonitoring, self-diagnosis of faults); multi-color indicator lights indicate warp stop, weft stop, waiting and other information.
20. Attachment devices auxiliary main spray, drafting spray, weft braking device, etc.
21. The control system adopts micro The computer serves as the control core and controls weft insertion, weft selection, weft storage, warp let-off and loom movements respectively, and sets the weaving process parameters (warp tension, color, solenoid valve opening and closing time, etc.) on the keyboard. Each control unit controls the corresponding actions. There is an operation button board on the left, right or in the middle of the front of the loom to facilitate the operator’s operation.
4. Scope of application and fabric varieties
Early air-jet looms had a very small scope of application. It mainly produces white gray cloth, and the cloth width is small, the speed is slow, the fabric has great limitations, and the fabric quality is not high. However, starting from the early 1980s, with the development of special-shaped reed and relay weft insertion technology of air-jet looms, as well as the application of electronic computers, sensors and frequency conversion speed regulation technology, the speed of air-jet looms and the automatic monitoring of looms have been greatly improved. level, especially the rapid development of air-jet looms in the past 10 years, which has enabled air-jet looms to have many advantages such as high quality, high speed, high output, and high automatic control level, and the range of varieties has been greatly improved.
The machine width of air-jet looms has increased from 190cm and 280cm to more than 340cm, 360cm and 400cm; the main nozzle has been increased from single nozzle to double nozzle and four nozzle; by computer software The controlled multi-color weft insertion system can select weft from 4 to 12 colors; the weft yarn raw material can be chemical fiber filament, chemical fiber short fiber, pure cotton yarn, wool yarn, glass fiber yarn, various fancy yarns, etc.; products Varieties can be produced from high-density, thin, and high-end fabrics to coarse-count, high-density, thick fabrics. Dornier air-jet looms have been used to produce industrial fabrics such as filter fabrics, emery cloth twill fabrics, steamed fabrics, and glass fiber wall coverings. The new air-jet looms of Belgium’s Picano and Japan’s Tsudakoma are also equipped with electronic jacquard, dobby and other shedding systems to adapt to the production of multiple types of fabrics.
5. Comparison with other shuttleless looms
Rapier loom
Rapier loom has adaptability to varieties Unique advantages, but the weft insertion rate is lower than that of air-jet looms, only 1400m/min, which is about 50% of that of air-jet looms; the yarn recovery rate is higher than other shuttleless looms. At present, rapier looms are mainly used for the production of small batches and various weft yarn fabrics such as decorative items.
Projectile loom
Projectile loom is used in weaving It has advantages in wide fabrics and high-end decorative fabrics, but the weft entry is lower than that of air-jet looms, which is 1200m/min; the energy consumption for projectile acceleration only accounts for 15%, and the energy consumption is unreasonable; on the material properties of the shuttle picking torsion shaft, Mechanical weaving requires high precision; it is expensive and requires a large one-time investment.
Water-jet loom
Water-jet loom in production It has limitations in quality and is only suitable for weaving hydrophobic yarns such as synthetic fibers and glass fibers. Relevant components on the loom should be made of stainless steel.
Polyphase looms
Polyphase looms can be extremely weaving at the weft insertion rate. But it can only produce simple ordinary fabrics, and the power consumption per square meter of fabric is higher than other shuttleless looms. </p
