There are two forms of cotton transportation in cotton processing plants. In the past, negative pressure transportation and three-tube cotton distribution were more commonly used. Nowadays, spiral (auger) cotton distribution is mostly used.
Spiral cotton distribution uses a spiral to rotate in a spiral groove to transport cotton to the cotton distribution box of the gin at the bottom of the spiral. The structure of the spiral cotton distribution device is shown in Figure 11-4. The spiral cotton distribution device consists of a cotton distribution spiral, an overflow cotton bin and an overflow cotton conveying device.
The cotton distribution screw is a horizontal fixed screw conveyor, which consists of three parts: the screw machine body, the feed port and the discharge port, and the driving device.
The screw machine body is composed of head bearing, tail bearing, intermediate bearing, spiral, trough, cover plate and other parts. In order to facilitate the smooth falling of the cotton into the cotton distribution box of the gin at the discharge port, the spiral blade adopts a special solid surface, which is a trapezoidal structure with thick roots and thin ends.
The trough adopts a special inclined wall trough, and the spiral is installed on one side of the asymmetric inclined wall trough. The minimum gap between the spiral blade and the trough is 15mm. The intermediate bearing is fixed on the side wall of the trough and hangs diagonally.
Figure 11-5 shows the cotton-equipped auger produced by the American Rams Company.
The overflow cotton conveying device is a suction-type pneumatic conveying device, which consists of a suction nozzle, a sub-cotton pipe, an overflow cotton separator, an overflow cotton suction fan, an air pipe, a dust collector and other components. Its main function is to store excess cotton after ginning and blending, or to store cotton in the process pipeline when the gin fails.
The three-tube cotton distribution device is mainly composed of sub-cotton pipes, three-tube cotton distribution boxes, return air ducts, cotton distribution fans, dust collectors, choke valves, throttle valves and throttle valve reversing mechanisms, as shown in Figure 11 -6 shown.
The three-pipe cotton distribution box is the main equipment of the three-pipe cotton distribution device. It consists of a feeding pipe, two suction pipes, a box and other parts, as shown in Figure 11-7. The three-tube cotton distribution box can be made of thin steel plates. There is a canvas valve in the box. Its function is to automatically close when the ventilator suctions air and maintain the negative pressure in the box to facilitate the suction and storage of cotton. There are also two screens in the box, which are used to separate the cotton from the air. The fine impurities mixed into the cotton will enter the dust collector through the mesh and the fan.
The cross-sectional area of the upper part of the cotton distribution box is slightly smaller than the cross-sectional area of the lower part (about 15% smaller). This structure is conducive to the falling of cotton.
The size of the lower part of the cotton distribution box depends on the size of the cotton inlet of the gin. The height of the box depends on the required storage capacity of cotton, and the storage capacity of cotton is based on the principle of ensuring continuous production of the gin. Usually, the height of the cotton box is designed based on the output of the gin and the number of gins on the production line. Generally, the cotton storage height of the cotton distribution box is required to be 1000~2000mm, and the total height of the cotton distribution box is 2500~3500mm.
In the two parallel feeding arms after the bifurcation of the sub-cotton conveying tee pipe, there is an air blocking valve. Its function is to prevent the other group from adding air when one group is feeding.
Because the three-pipe cotton distribution works in two groups, the sub-cotton pipes, damper valves, return air ducts, and throttle valves must be divided into two groups. The cotton distribution box must also be divided into two groups with the sub-cotton pipes and sub-cotton valves. Return air duct connection.
Two choke valves are respectively installed in the two branches of the cotton pipe tee (the pipe section where the choke valve is installed is a square cross-section) to control the air flow and the transport direction of cotton. The damper valve is generally a square valve made of steel. One side of the valve is fixed on the small shaft, and the other three sides are free edges. To ensure tight closing, rubber can be added around the valve.
The filter uses a woven mesh with a mesh size of 8 to 10 mesh and a rectangular shape. It is fixedly installed at the entrance of the upper return duct in the cotton distribution box. The height of the filter determines the ventilation area of the filter.
The canvas cover is placed in the lower part of the cotton distribution box. The upper end of the cylindrical canvas cover is fixed on the box wall with screws on both sides. The screws are arranged in a “Y” or “V” shape to prevent the canvas cover from rolling up. When the cotton distribution box is in working condition (i.e. negative pressure state), the canvas cover automatically closes, which not only prevents outside air from entering the box, but also can accept the cotton sucked in by the cotton tube. The height of the canvas cover requires that it can neither be sucked over by the airflow (caused by being too short) nor be tightly closed (caused by being too long) when working with cotton boxes. It is usually around 1m.
The air valve consists of a gland and a spring. The opening and closing of the air valve is completed by utilizing the counterbalance between the negative pressure suction force of the air flow and the deformation force of the spring. When the cotton distribution box is in the working state, the air flow negative pressure suction overcomes the deformation force of the spring, causing the air valve to close, preventing outside air from entering the box; when the cotton distribution box is in the non-working state, the air flow negative pressure suction disappears and the spring resumes its deformation. , so that the air valve opens and outside air can enter the box.
There are many types of throttle valve reversing mechanisms, and the two most commonly used ones are electric push rod type and timing disk type. The structure of the electric push rod throttle valve reversing mechanism is shown in Figure 11-8. It realizes the throttle valve reversal through the expansion and contraction of the electric push rod. The opening and closing time of the throttle valve is controlled by a time relay. The opening and closing time of the throttle valve of the timing disk reversing mechanism is determined by the shape and rotation speed of the cam timing disk. The biggest disadvantage of this mechanism is that the structure is complex and the opening and closing time of the throttle valve cannot be adjusted arbitrarily, so it has been eliminated.
The working process of three-tube cotton distribution is as follows: When the first group of solar terms When the valve is opened by the reversing mechanism, the throttle valve of the second group is reversed and closed. Negative pressure is formed in the cotton distribution box of the first group, the damper valve is opened, and the cotton enters the cotton distribution box through the cotton tube and damper valve. The dusty air is sent to the dust collector through the return duct, throttle valve, and fan. Purification treatment; the negative pressure in the second group of cotton distribution boxes disappears, the damper valve is closed, and the cotton in the cotton distribution box is supplied to the gin for processing. After the predetermined opening time, the throttle valves of the first group are closed again by the reversing mechanism, and the throttle valves of the second group are reversed and opened. At this time, the negative pressure in the cotton distribution box of the first group disappears, the damper valve is closed, and the cotton in the cotton distribution box is supplied to the gin for processing; a negative pressure is formed in the cotton distribution box of the second group, the damper valve is opened, and the cotton is supplied to the gin. The warp cotton pipe and damper valve enter the cotton distribution box, and the dusty air passes through the return duct, throttle valve, and fan and is sent to the dust collector for purification. The opening and closing cycle of the throttle valve is also called the cotton distribution cycle. In order to ensure the continuous production of the gin, when each group of throttle valves is opened for cotton distribution, the amount of cotton stored in the cotton distribution box after being sucked from the cotton pipe should be sufficient for one cotton distribution cycle of the gin.
Due to the development of the cotton fiber processing industry and the continuous upgrading of the three-tube cotton distribution device, the three-tube cotton distribution system has been recognized within the industry, especially when processing long-staple cotton flower distribution systems, the three-tube cotton distribution device It has many advantages:
(1) The control is simple and reliable. When the amount of cotton suction exceeds the limit, it can stop sucking flowers freely, and there is no problem of cotton overflow;
(2) It is easy to install, and it has no impact on the previous process of cotton. There are no special requirements for the installation of the cleaning machine;
(3) The three-tube cotton distribution device has a simple structure, low failure rate and easy maintenance. Especially when processing long-staple cotton, the long-staple cotton seed cotton runs in the air transport pipeline, which reduces mechanical movement and can reduce lint defects during the processing;
(4) The seed cotton processed during the processing is transported in the three-pipe distribution When the cotton moves in the cotton device, the cotton is isolated from the air in the workshop, forming a negative pressure, which reduces the pollution of dust in the air of the workshop, keeps the workshop clean and hygienic, and reduces the harm of dust to workers.
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