Rubber blanket pre-shrinking machine
During the dyeing and finishing process, the unstable phenomenon of weft shrinkage and warp elongation occurs because the fabric is stretched by warp tension. During subsequent cleaning and use, a certain degree of shrinkage will occur when exposed to moisture and heat, affecting product quality and causing losses and trouble to consumers. Therefore, the fabric should be pre-shrunk before leaving the factory to obtain a stable shape. Using a preshrinking machine for preshrinking finishing can reduce the warp shrinkage of the fabric.
Commonly used pre-shrinking machines include rubber blanket pre-shrinking machines, felt blanket pre-shrinking machines and damping pre-shrinking machines. They are suitable for pre-shrinking and finishing of cotton and cotton-type fabrics, and can reduce the shrinkage to less than 1%.
1. Rubber blanket pre-shrinking machine
11 Rubber blanket pre-shrinking mechanism
The shrinkage of the fabric is caused by the pressure between the rubber blanket, the fabric feeding pressure roller and the heated pressure roller, as well as the elastic shrinkage of the rubber blanket. formed by the effects produced. When the rubber blanket is bent under force, it can be seen that its outer arc elongates and the inner arc shrinks; if the rubber blanket is bent in the opposite direction under force, the originally elongated side shrinks, and the originally contracted side shrinks. Stretch, as shown in Figure 9-1.
If a moist cotton fabric is placed close to the surface of the rubber blanket, the fabric will deform along with the rubber blanket, and will elongate and compress as the rubber blanket stretches and compresses, thus increasing the weft density of the fabric. Increase and meridional shrinkage to achieve a certain pre-shrinking effect.
As shown in Figure 9-2, during mechanical pre-shrinking and finishing, the rubber blanket runs with the guide roller, and the extension and compression are constantly changing. When feeding the fabric, place the fabric close to the extension part a of the rubber blanket. When the rubber blanket surrounds the cloth feeding roller, the outer surface is elongated and the inner surface is shortened, that is, a>b>c. After running to the heated pressure roller, section a changes from elongation to shortening, and section b remains unchanged (b is the rubber blanket (middle part), segment c elongates, and a′<b′a′. Due to the pressure between the cloth feeding roller and the heated pressure-bearing roller, the rubber blanket is severely compressed and becomes thinner and elongated. When running to point S, this squeezing effect disappears, and the rubber blanket will pop back outward, resulting in Due to the backward squeezing force F, this reaction force makes the rubber blanket press tightly against the pressure roller, which means that the fabric is tightly attached to the rubber blanket and cannot slide. In this way, the shape of the fabric will be completely deformed according to the rubber blanket and enter the compression area. The rubber blanket will compress and the fabric will shrink with its compression, thereby achieving the purpose of pre-shrinking. When the rubber blanket leaves the pressure roller, the fabric must leave the rubber blanket immediately. Therefore, the rubber blanket is in a stretched state on the guide roller at the back. If the fabric does not leave the rubber blanket in time, it will be stretched again and the pre-shrinking effect will be removed. The moisture and heating on the fabric increase the plasticity of the fiber and improve the pre-shrinking effect of the fabric.
It can be seen from the fabric pre-shrinking mechanism that the pre-shrinking effect of the fabric depends on the thickness of the rubber blanket, the pressure between the cloth feeding roller and the pressure roller, the moisture content of the fabric and the temperature of the pressure roller. Therefore, the thicker the rubber blanket, the greater the pressure, the more uniform the moisture content, and the higher the temperature, the better the preshrinking effect of the fabric.
21 Types and structures of rubber blanket pre-shrinking machines
The currently used rubber blanket pre-shrinking machines mainly include simple three-roller rubber blanket pre-shrinking machines, cloth clip chain pre-shrinking and finishing combined machines and general three-roller rubber Blanket pre-shrinking machine, etc.
(1) Simple three-roller rubber blanket pre-shrinking machine: As shown in Figure 9-3, it consists of a cloth inlet and outlet device, a moisture supply device and a three-roller rubber blanket pre-shrinking device. Its core mechanism is a three-roller rubber blanket pre-shrinking device, as shown in Figure 9-4. It consists of a rubber blanket, a heated pressure roller, a pressurized guide roller and a rubber blanket adjustment device. The pressure roller is heated with steam to provide Use water pipe spray to moisten.
The fabric operation process is: Dry cloth feeding on the cloth feeding rack → Moistening by water pipe spray → Three-roller rubber blanket pre-shrinking → Cloth dropping rack dropping cloth. This machine has a simple structure, low cost and easy operation, but the pre-shrinking effect Unstable.
(2) Cloth clip chain pre-shrinking and finishing combined machine: As shown in Figure 9-5, the whole machine consists of a cloth inlet and outlet device, a steaming and moistening device, a short cloth clip tenter device, and a three-roller rubber It consists of blanket pre-shrinking machine and blanket drying part. The cloth inlet and outlet device consists of a tensioner, an edge suction device, a feeding roller and a cloth speed measuring instrument. Use sprays and steam boxes for moistening to improve the penetration and moisture absorption effect. The short clip tenter device allows the fabric to enter the three-roller blanket shrinking machine flat and without wrinkles, and can adjust the feeding speed and warp and weft tension of the fabric according to process needs. The preshrinking device is the core component of the preshrinking machine and consists of cloth feeding, heated pressure rollers, rubber blankets, pressure rollers, rubber blanket guide rollers and tension regulators, rubber blanket cooling and other devices. The function of the blanket dryer is to dry and shape the fabric preshrunk by the three-roller rubber blanket to ensure the shrinkage stability of the fabric and improve the feel and finish of the fabric.
The fabric operation process is: Dry feeding of cloth on the cloth feeding rack → Spray and steam moisture feeding in the humidification box → Single drying cylinder pre-drying → Short cloth tenter → Three-roller rubber blanket pre-shrinking → Woolen blanket The finishing machine flat irons and dries → cooling device → removes static electricity → drops cloth on the drop rack.
(3) General three-roller rubber blanket pre-shrinking machine: The structure is shown in Figure 9-6. Compared with the cloth iron chain pre-shrinking machine, it only lacks a short cloth clip chain tenter device.The humidification part is humidified by a humidification box. The humidification box is equipped with a steam spray pipe and a spray pipe. The fabric can be sprayed and moistened on both sides, and the spray and steam heating can be performed at the same time to increase the penetration moisture supply rate of the fabric.
The fabric operation process is: dry fabric feeding on the cloth feeding rack → double-sided spray moistening in the moisture supply box → pre-drying with a single drying cylinder → pre-shrinking of the three-roller rubber blanket → ironing and drying of the felt → falling The cloth falls from the cloth stand.
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