The cloth guide roller is the most common universal device in open-width dyeing and finishing equipment. Its main function is to support and guide the fabric to run in a certain direction, and to adjust the tension of the fabric in the running direction.
The structure of the cloth guide roller is shown in Figure 2-1, which consists of three parts: the shaft head, the bulkhead and the roller body. The shaft head is the supporting part when the cloth guide roller is installed. The shaft head can be made into a stepped short shaft of different shapes according to the form of the supporting bearing and the movement of the cloth guide roller. The roller body is generally made of chromium-plated seamless steel pipes or stainless steel pipes. It can also be coated to form a roller surface of different materials, such as soft rubber rollers, hard rubber rollers, nylon rollers, etc. The shaft head and the roller body are connected by welding through the bulkhead.
According to the different movement states of the cloth guide roller, the cloth guide roller can be divided into fixed cloth guide roller and movable cloth guide roller, and the movable cloth guide roller can be divided into active cloth guide roller and passive cloth guide roller according to different power sources.
Under different motion states and power sources, the friction between the cloth guide roller and the open-width fabric is different, which accordingly affects the tension produced by the fabric differently, thus changing the processing state of the fabric and ultimately affecting the dyeing and finishing quality. . Therefore, it is necessary to analyze the friction between the cloth guide roller and the open-width fabric and understand its relationship with the changes in the tension of the open-width fabric (especially the warp tension).
Let’s analyze the changes in warp tension of the open-width fabric when it passes through the guide roller. For the convenience of discussion, the surface state of the cloth guide roller surface and the flexible deformation of the flat fabric will not be analyzed for the time being.
Therefore, after the open-width fabric passes through the passive guide roller, its warp tension will also follow. increase. The more passive guide rollers the open-width fabric passes through, the more the warp tension increases.
It is common for open-width fabrics to drag multiple cloth guide rollers in dyeing and finishing equipment. For example, in the flat washing tank of a flat washing machine, there are multiple passive cloth guide rollers arranged up and down. The fabric passes between the guide rollers to increase the number of washes and extend the wash time. In order to reduce the warp tension of the fabric, the cloth guide roller bearings must be kept well lubricated.
3. Stress analysis of open-width fabric when passing through the active cloth guide roller
As shown in Figure 2-4. Assume that the warp tension at the end of the fabric entering the guide roller is T0, and the warp tension at the end of the guide roller is T3. The space between the surface of the guide roller and the fabric The static friction force is f3, the external torque driving the cloth guide roller to rotate is M, and the radius of the cloth guide roller body is R. Obviously:
Therefore, after the open-width fabric passes through the active guide roller, its warp tension will be reduced. The more active guide rollers the open-width fabric passes through, the more the warp tension is reduced.
If the warp tension of the fabric is too small, it will relax and even wrinkle during operation. In order to overcome this problem, the active cloth guide roller is sometimes run at overspeed. In this way, a certain amount of slippage occurs between the fabric and the surface of the cloth guide roller.
Assuming that the sliding friction between the fabric and the surface of the cloth guide roller is f4, and the warp tension at the output end of the fabric during slippage is T′3, then:
In this way, due to the overspeed slip of the active cloth guide roller, the warp tension of the fabric increases. For example, the drop roller in the open-width cloth discharging device often uses an active cloth guide roller, and maintains a 1:1106 ratio with the speed of the traction roller to overspeed the fabric so that the fabric does not relax and wrinkle.
Since the surface of the cloth guide roller is in direct contact with the fabric, the roller surface is required to be straight and smooth without any burrs and defects. For the rotating shaft type cloth guide roller, it is also required that the roller surface and the journal have good concentricity, the installation must be straight, the rotation must be flexible, and the bearing must have good lubrication performance.
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