Beating-up mechanism
The function of the beating-up mechanism is to drive the weft yarn that has been introduced into the shed into the cloth fell to form the expected fabric. 1. Conditions that the beat-up mechanism should meet: (1) On the premise of ensuring that the weft yarn can fly smoothly through the shed, the reed holder movement should be small, which can reduce the friction on the warp yarn. (2) When the instantaneous speed of the reed is zero, the acceleration reaches a high level to increase the beating force; when the reed is near the rear dead center, the speed is low to facilitate weft insertion. (3) On the premise of meeting the beat-up force, the reed seat should be light in weight and rigid in order to increase the speed of the loom. Types of beat-up mechanisms: Usually there are three types of beat-up mechanisms: four-link beat-up, six-link beat-up and conjugate cam beat-up. Figure 2-17 is a schematic diagram of the three mechanisms. For the connecting rod type beat-up mechanism, its leisure performance depends on the length of each rod and its proportional relationship between each other, especially the ratio of the crankshaft radius and the length of the hand. The advantages of the four-link beat-up mechanism are simple structure, smooth operation during high-speed operation, and relatively low vibration. The disadvantage is that the relatively short resting time at the back center and strict weft flight time requirements are not conducive to the high-speed operation of wide-width looms. The four-link beat-up mechanism used on air-jet looms is mostly of short-hand type. It has a slightly longer relative rest time at the back center than the medium and long-hand four-link beat-up mechanisms, which is more conducive to weft insertion. The acceleration is relatively high, which is beneficial to beating up. The displacement curves of the four-link beat-up mechanism and its beat-up leisure and beat-up leisure are shown in Figure 2-18 to Figure 2-20 respectively.
The six-link beat-up mechanism is equivalent to the series connection of two sets of four-link mechanisms, which can extend the relative rest time of the reed at the rear center, allow the weft yarn to fly more fully, and increase the speed of the wide-width loom. The advantage of the conjugate cam beat-up mechanism is that the leisure pattern can be designed according to the needs of the weaving process, and the back center can have a longer absolute rest time, and the weft insertion time is more sufficient; during beat-up, higher acceleration can be obtained, and the beat-up force is greater big. The disadvantages are high finishing accuracy requirements, high manufacturing difficulty and high cost; large vibration and high energy consumption. Under the premise of the same reed width and same speed, the energy consumption is about 50% higher than that of the four-link mechanism. The above three types of beating-up mechanisms have their own strengths and weaknesses. There is no question of who is better or who is worse. The selection principle is to use a four-link beat-up mechanism when the reed width is below 250cm, use a six-link beat-up mechanism when the reed width is above 250cm, and use a conjugate cam beat-up mechanism when weaving extra heavy fabrics.
In Figure 2-19, when the reed seat is swung to the rear dead center, the reed groove and the auxiliary nozzle insert the weft in the middle of the shed. When the reed seat is swung to the front dead center, the reed groove pushes the weft yarn to the weaving fell. Because under the condition that the beating stroke and vehicle speed are equal, judging from the beating forces that the three beating mechanisms can provide, the conjugate cam is larger and the four-link type is smaller, that is, the conjugate cam beating mechanism is used It is suitable for weaving wide and heavy fabrics. At present, Japanese models mostly use four-link or six-link beat-up, while European models mostly use conjugate cam beat-up. 2. Drive of the beat-up mechanism (Figure 2-21) The main motor’s rotating crankshaft, connecting rod, and rocker rocker swing back and forth. The steel reed is fixed with the help of the reed seat and the batten installed on the rocking shaft, and the weft yarn entering the shed is driven into the fabric fell. Special-shaped steel reed is a fabric equipment, an important part of the weft insertion system, and an indispensable part of the beat-up mechanism. The specifications of the steel reed are usually expressed by the reed number. The so-called reed size, that is, the density of the reed teeth, is selected according to the warp density of the fabric. The metric system is expressed as the number of reed teeth per 10cm length; the imperial system is expressed as the number of reed teeth per 2 inches. Weaving fabrics with different warp densities requires the use of steel reeds with different reed sizes. The quality of the reed directly affects the quality of the fabric. The basic requirement for a steel reed is that the thickness of all the reed blades that make up a steel reed must be consistent, and the gaps between adjacent reed blades must also be consistent.
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