Belt conveyor is the main modern bulk material handling equipment, widely used in electric power, metallurgy, chemical, coal, mining, port, building materials, and other fields. The roller is one of the main parts of the belt conveyor. The function of the roller is to support the conveyor belt, reduce the running resistance, and make the conveyor belt sag does not exceed a certain limit, to ensure the smooth operation of the belt. The total mass of the idler accounts for about 30%~40% of the total mass of the belt conveyor, and its value accounts for about 20% of the whole machine. The operation reliability of the idler directly affects the normal operation of the belt conveyor. To ensure the stable operation of idlers, improve the service life of belt conveyors and reduce operating costs, different scholars have carried out detailed studies on conveyor roller idlers’ manufacturing, bearing sealing, and spacing arrangement. The problem of idlers should be considered not only from the layout of idlers but also from the structure of idlers. Especially in the actual use of long-distance, large volume, high belt speed plane turning belt conveyor, DTII (A) type belt conveyor roller group can not meet the requirements of normal use, although some rollers can be used normally, because of special process requirements, the service life of roller is greatly reduced. This paper studies the structural forms of the idlers in the turning section and the convex arc section of the long-distance plane turning belt conveyor and designs a new type of idlers structure, which provides a new idea for the design of the belt conveyor.
1 Structure of idlers in-plane turning section
The main difference between the plane turning belt conveyor and the ordinary belt conveyor is that the plane turning belt conveyor can change the direction of conveying, and produce a centripetal force under the action of the conveyor belt tension in the curve section so that the conveyor belt tends to slip towards the inside of the curve. The design of the turning structure of the plane turning belt conveyor should produce a guiding force to the outside of the turning to offset the centripetal force so that the belt conveyor can turn naturally.
Basic measures for belt conveyor to realize plane turning:
(1) The idlers in the turning section have an installation support Angle, that is, the connection between the mixing group and the middle frame is connected by long-hole bolts, and the idlers are installed inclinedly along the running direction of the conveyor belt ;
(2) Increase the groove Angle of the rolling group in the turning section;
(3) Set the inner curve elevation Angle, that is, raise the inner side of the roller support by an Angle, to raise the inner curve of the conveyor belt.
Due to the particularity of plane turning belt conveyors, there are many difficulties in the installation and debugging of the plane turning roller groups produced by different production companies. It is necessary to repeatedly start and stop the conveyor belt to adjust its deviation, and sometimes it is even necessary to remove the support and mixing frame to adjust, check and weld again. The whole debugging process is very costly manpower and material resources, greatly prolonging the construction period. To solve this problem, a new type of flat turning upper roller group is designed.
In addition to the above basic measures in the turning section of the plane turning belt conveyor, sometimes it is necessary to increase the blocking gear on both sides of the support group to realize the turning of the conveyor belt. Realize flat belt conveyor and conveyor belt tension of turning, turning radius, turning Angle groove Angle, roller group and mixed spacing related, but due to the site conditions, environment temperature, production, manufacture, and installation error and makes practical and theoretical calculation and design of large deviation, as a result, with adjustable rolling group structure forms in the installation and debugging stage is particularly important.
Positioning sleeve bearing by bolt connection in the middle of the side frame and the lower end of the shaft bracket circle tube inserted into the positioning of Jane bearing, shaft bracket, and the positioning sleeve bearing clearance fit for Jane and can revolve around positioning set of Jane in 0 ~ 360 °, side pillar bottom welding two belt round hole of ear plate, shaft bracket and the ear plate through the fixed end positioning pin shaft coupling, so that the rod holder frame can be round The fixed end locating pin rotates in the plumb surface. The outer side of the other side prop of the roller support is welded? The movable end support is made up of a bottom plate with a long round hole and a section of channel steel welded, the channel steel is provided with a row of round holes on both sides, the movable end support and the roller are connected by the movable end positioning pin, the movable end support is connected with the other side of the middle frame by bolts.
The roller set on the turning section of the plane can move around the center of the positioning sleeve in the horizontal plane because of the long round hole in the movable end support bottom plate. By adjusting the positioning hole between the movable end support and the roller , the roller can rotate in the vertical plane around the positioning pin of the fixed end. The upper roller set can not only adjust the installation support Angle along the running direction of the belt conveyor but also adjust the elevation Angle in the running direction of the vertical belt conveyor. Using the upper roller set in the plane turning section makes the site installation and debugging more flexible and convenient, saves time and effort, and effectively shortens the construction period.
2 Convex arc roller set structure
In the convex arc section of the belt conveyor, the gravity of the conveyor belt and material and the tension of the conveyor belt press the conveyor belt onto the idler. When the conveyor belt passes through the convex arc segment, the stress of the conveyor belt is different from that of the straight segment in the transverse distribution. The stress on the edge of the conveyor belt is larger, and the radial pressure on the roller on the convex arc segment is larger than that on the straight segment. When turning, a large enough turning radius is needed to make the conveyor belt tension within the allowable limit. If the tension in the middle of the convex arc conveyor belt is low, the phenomenon of the central part of the conveyor belt. To prevent adverse factors such as conveyor belt belt buckling and material spreading, the convex arc section should be arranged in a place where the conveyor belt tension is lower as far as possible during the design, and the curvature radius of the design line should be large enough to keep the conveyor belt stress and the bearing capacity of the idler within the permitted range. The following factors should be considered in convex arc design:
(1) Conveyor belt side tensile stress does not exceed the allowable value;
(2) The tensile stress of the center part of the conveyor belt is greater than the minimum allowable value;
(3) The design and arrangement of the roller should ensure that the roller has enough bearing capacity.
The stress characteristics of the convex arc section of the belt conveyor determine that the supporting roller of the convex arc section is easier to be damaged than that of other positions. The service life of the supporting roller of the arc convex section is shortened because the spacing between the supporting rollers is too large. It is necessary to replace the supporting roller constantly. If roller spacing is too small, the number of rollers increases, the cost increases, and the resistance of the conveyor belt increases. For the long belt conveyor, the belt conveyor does not reduce the spacing of the supporting rod to 1/2 of the straight line according to the design manual, nor can it meet the stress requirements of the roller. Therefore, it is particularly important to design a new type of convex arc idler group structure by analyzing the stress of the convex arc idler in detail and combining idler spacing and idler diameter under the condition that the convex arc radius of the arc idler feeding machine cannot be changed. Aiming at the characteristics of belt conveyor convex arc conveyor belt edge stress is significantly higher than the middle stress. The structural characteristics of the roller set of the new arc convex section are as follows:① The support of the spoke bracket is raised upward compared with the roller set of the straight section, which makes the roller set move downward in the middle bracket. This arrangement makes the center of gravity of the roller group move downward and increases the turning radius of the convex arc segment, which can not only effectively improve the load on the roller due to the conveyor belt tension, but also improve the deformation resistance of the material and the bending resistance of the conveyor belt, to improve the stress state of the roller and improve the service life of the roller. The side pillar with adjustable groove Angle is adopted, and the side pillar of the roller frame is provided with? Round holes a re arranged, each row of holes corresponds to the position of 3 slot angles which can be adjusted, and round holes in different positions are also opened on the side plate of the roller support. The purpose of adjusting the groove Angle of the roller is achieved by connecting the side plate of the roller support and the side pillar of the roller by bolts. During the field debugging, the tension at the edge of the conveyor belt can be effectively improved by adjusting the angle of the spoke groove without affecting the conveying of materials, and the pressure change on the roller due to the change of conveyor belt tension can be improved, thus improving the stress distribution on the roller body, which plays an extremely important role in improving the service life of spoke.
(1) The new type of support and mixing group structure in the plane turning section can rotate the sleeve positioning in the plane by 0~360° through the fixed end positioning sleeve support. The movable end support and the roller are connected by the movable end positioning pin to realize the rotation of the support and mixing group in the vertical plane around the fixed end positioning pin. The connection between roller support and the middle frame adopts a long round hole, which can make the roller group move in the horizontal plane . The upper roller set of the plane turning section makes the site installation and debugging more flexible and convenient, save time and effort, and effectively shortens the construction period;
(2) The new convex arc roller set structure is raised by the roller support, so that the overall arrangement of the roller set in the middle frame moves down, which can effectively improve the force on the roller due to the conveyor belt tension and gravity , and improve the service life of the roller. The edge pillar with adjustable groove Angle can effectively reduce the tension at the edge of the conveyor belt, improve the stress distribution on the roller body, and play an extremely important role in improving the service life of the roller.
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