Thursday, May 27, 2021

Structure and working principle of water-jet loom weft insertion system

 Water-jet loom weft insertion system:


The weft insertion is carried out into the shed from one selvedge to another selvedge with the help of a high pressure water stream. The water is fed to the fine jet nozzle through a high pressure water pump. A fine stream of water emerges from the jet. It carries the weft yarn with it. The water jet loom is mainly suitable for those fabrics which are woven with hydrophobic material in character. The mono and multi filament yarns are mostly used on water jet looms because these yarns have very low moisture content. Water jet loom consumes low energy. The productivity of the loom is very high. The noise level of water jet loom is too low. It requires very low maintenance in comparison to any other looms. This loom is suitable for light and medium weight fabrics. 

Weft yarn passage of water jet loom weft insertion system:

The structure of water jet loom is much similar to air jet loom. The weft yarn passage of water jet loom is given below: 

The weft yarn package is mounted on the weft creel. First of all, the weft yarn gets passed through the weft accumulator. 

Next, the weft yarn passes through the weft guide.

Now this weft yarn passes between the two plates of the weft brake. 

The weft yarn further passes through another weft guide. 

Finally, the weft yarn passes through the water-jet nozzle and rests there. You can see clearly in the below picture.

Function of various parts of water jet loom:

The weft package is mounted on the package holder of the weft creel. One thread guide is mounted in the creel for each package holder. The number of weft package holders depends upon the number of weft colours getting used in the fabric to be woven. There are balloon separators also used to prevent the striking of two adjacent weft yarns. The weft yarn passes through the weft accumulator in next. There are three objectives of weft accumulator in the water-jet loom. The weft accumulator ensures the regular weft yarn supply during weft insertion at constant yarn tension. The weft accumulator neutralises the tension variation effect when the weft yarn package reaches the exhaustion situation. Secondly, it controls the required pick length according to the reed space used in the loom. First of all, the perimeter of the accumulator is calculated precisely then number of weft coils required per pick is calculated. The number of weft coils should always be a whole number. If number of coils per picks is not a whole number, the diameter of the accumulator drum is adjusted and the number of coils per pick is calculated. The drum diameter adjustment continues till the achievement of number of coils per picks as a whole number. Third objective of the weft accumulator is to stop the machine immediately when the weft yarn package gets exhausted. The unnecessary pick finding time gets saved by this bobbin brake stop motion. The weft yarn now passes through the ceramic thread guide. This thread guide keeps the weft yarn in its proper place and prevents to entangled of two adjacent weft yarns to each others. Now, the weft yarn passes through the weft brake. This weft brake imparts the required tension to the weft yarn when needed. Next, the weft yarn further passes through another weft guide. Finally, the weft yarn passes through the water-jet nozzle and rests there. The water jet nozzle is mounted on the sley in picking side very close and adjacent to the reed. This water jet nozzle is connected to the high pressure water supply through the pipe line. The high pressure water pump is used to feed the water in the nozzle at very high pressure. The water pump consists of cylinder and piston. This water pump is connected to the water tank through pipe line. The vertical arm of L- shape lever is connected to the piston and an antifriction bowl is mounted at the end of the horizontal arm of L-shape lever. This anti friction bowl touches the eccentric cam. When the cam rotates, the piston attached with vertical arm of L- shape lever makes a reciprocating motion. Water is sucked from water tank by pump and is fed it to the water jet nozzle. The nozzle opening and closing gets controlled by magnetic valves. The opening and closing timings are entered into control computer. The opening and closing of the electromagnetic valve, weft brake, and water supply of nozzle are controlled by control computer.  



weft insertion cycle of water jet loom: 

A new weft insertion cycle of water jet loom begins after beating motion. As the reed beats the last inserted pick, the weft cutter( mechanical cutter or thermal cutter) cuts the weft yarn very close to the selvedge. Now reed begins to move toward the back dead centre position. After angular movement of few degrees of reed shaft, the sley enters into dwell period. Now, the pin of electromagnetic valve mounted on the accumulator lifts up and the accumulator gets ready for weft unwinding. The weft brake also releases the weft yarn tension at the same time. A high pressure water supply of the nozzle gets begun now. When the valve of water jet nozzle opens, a fine water stream emerges from the nozzle. Since the tail of weft yarn rests inside the water jet nozzle so that a emerging fine water stream carries the weft yarn with it into the shed from one selvedge to another selvedge. The electromagnetic valve of accumulator gets closed and the pin drops on he accumulator drum after insertion of complete pick length. The weft brake is also closed at the same time. The catch selvedge ends hold the weft yarn properly. Now reed begins to move toward the front dead centre position and beats the yarn finally. The weft cutter cuts the weft yarn and the selvedge cutter trims the weft yarn at right hand side. This cycle gets repeated continuously.


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