Top roller embossing theory Generation of friction and impact force
Whether it is a punch-knife top roller gin or a hob-type top roller gin, its working principle is roughly the same, that is, friction is used to exert traction on the cotton fibers through the top rollers, and in the other direction, the movable knife is used to impact the cotton, and the cotton is exert impact force. Under the combined action of friction and impact, the fibers and cotton seeds complete the ginning work respectively. Using mechanical action to generate the friction and impact required for embossing is the content of theoretical research on top roller embossing.
1. Generation of friction and impact force
Choose a top roller made of a certain material, and its surface is rough and elastic. The fibers on the sub-cotton have natural spiral curls, so the friction factor between the surface of the top roller and the cotton fibers is large. When the cotton fiber contacts the surface of the top roller with a certain pressure, the two hug each other and produce friction. When the friction force between the surface of the top roller and the fiber is large enough, the fiber can run with the surface of the top roller. The fibers on the cotton seeds are hugged and entangled with each other, so the cotton fibers can be continuously pulled by the top roller. When the cotton fiber pulled by the top roller reaches the fixed knife edge, it can pass through the fixed knife edge with the help of the elasticity of the top roller and the softness of the cotton fiber. Because the fixed knife is close to the surface of the top roller, the cotton cannot pass through and is blocked at the fixed knife edge. At this time, the fibers in the fixed knife edge are straightened, can no longer relax forward, and slide relative to the surface of the top roller. At this time, the knife is moved to the fixed knife edge and strikes the cotton seeds retained at the fixed knife edge. Under the combined action of the movable knife and the fixed knife, the fiber and cotton are separated. The fibers separated from the cotton seeds continue to move forward with the top roller. The fibers on each grain of cotton need to be pulled by the top roller many times and pinched by the movable knife and the fixed knife many times before they can be rolled out completely.
Because the separation of fiber and cotton is done on the top roller at the fixed knife edge, the part where the surface of the fixed knife and the top roller is in contact is called the ginning working point. The force of the fiber on the cotton is much smaller than the breaking strength of the cotton fiber itself. Therefore, when the knife impacts the ginning working point, the fiber will be pulled off at the weak base.
It can be seen that the reason why the cotton fiber is pulled by the top roller is because there is sufficient friction between the two. The cotton seeds are blocked at the fixed knife edge, and the cotton fibers in the fixed knife edges can only be straightened and can no longer relax with the top roller, because the friction between the two is less than the force of the fibers on the cotton seeds. The impact of the moving knife on the cotton seeds staying at the fixed knife edge can separate the fibers and cotton seeds because the friction and impact force work together to overcome the force of the fibers on the cotton seeds. In order to prevent the fiber from being pulled from the middle during the traction process of the top roller, the friction between the two must be less than the breaking strength of the fiber.
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