Scissor mechanism
Function and classification of scissor mechanism: Generally, the scissor mechanism of air jet loom can be divided into two parts: yarn supply side scissor mechanism and transmission side scissor mechanism. The function of the yarn supply side scissors is to cut the weft yarn in time after each weft insertion to facilitate the next weft insertion. The function of the drive side scissors is to cut off excess weft yarn from the edge of the fabric to make the edge of the fabric neat and beautiful. Scissors can be divided into two categories: mechanical and electric according to the driving mode. 1. Mechanical scissor mechanism (1) Scissor mechanism on the yarn supply side (left side): This mechanism is installed on the sliding seat on the breast beam. After each weft insertion, cut the weft yarn connected to the fabric and the main nozzle for the next weft insertion. The mechanism is shown in Figure 2-30(a).
The driving method of the yarn supply side scissors: The scissor cam on the main shaft rotates, pushing the scissor rocker arm to pull the scissor connecting rod, and driving the scissors to move. After each beat-up, the weft is cut according to the set timing. The yarn supply side scissors must cut the weft yarn every time, otherwise the next weft insertion cannot be carried out. The yarn supply side scissors are set between the main nozzle and the fabric edge. The yarn cutting time is at 30°. At this time, the weft yarn has been interlaced with the warp yarn, and the high-pressure airflow from the main nozzle has stopped spraying. After the weft yarn is cut, it stays in the main nozzle under the action of the constant jet jet, waiting for the next weft insertion. (2) Transmission side scissor mechanism (right side): installed on the front side of the side stay in front of the cloth fell. When the end of the weft yarn intersects with the selvage yarn, it moves toward the cloth fell and reaches the scissors. The scissors cut the weft yarn, and the selvedge yarn is separated from the cloth and returned to the waste selvedge yarn barrel by the selvedge take-up mechanism. The purpose of cutting off the excess weft yarn that is larger than the width of the cloth from the edge of the cloth is to make the edge of the cloth neat and beautiful. The structure is shown in Figure 2-30(b). The driving method of the transmission side scissor mechanism: There are two methods according to different power sources. One is powered by an eccentric cam and a return compression spring installed on the right open shaft, and drives the scissor blades through two sets of four-bar linkages in series, and the loom cuts once every two revolutions. The other is to use the leisure of the rocking shaft as the power source. The swing of the rocking shaft causes the scissor arms to move. Through the scissor connecting rod and the scissor arm B, the scissor shaft is driven so that the scissor arm C on the scissor shaft drives the scissor connecting rod (2). Drive the scissors blade movement. This device cuts once per revolution of the loom. The latter mechanism is relatively simple, has a large number of movements, and has a relatively short lifespan of the scissors. 2. Electric scissors The working principle of the electric scissors mechanism: a crank linkage mechanism is used as the execution component. A separate motor drives the crank to move in a circle. The connecting rod makes the rocker swing back and forth. The scissors blade fixed at one end of the rocker will move. Continuously open and close to complete the shearing action. The speed of the transmission side motor should be less than or equal to the speed of the loom to ensure that the loom beats two more wefts each time the scissors cut. If the scissors move too fast, the life of the scissors will be short. If the scissors are cut too slowly, the sharpness and shearing force of the scissors will be required. The yarn supply side scissors must ensure that the mechanism driven by the motor and the crankshaft of the loom are running in synchronization, and can complete the shearing action within the specified time.
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