The drum of a belt conveyor
comes in two forms. One form for the electric drum, it is the motor and gear reduction device all designed in the drum, although compact structure, light volume, but not easy to install, disassembly, is not conducive to maintenance and repair, and the manufacturing process is complex, heat dissipation is difficult. Another form for the gear drum, it is the gear reduction device design in the drum, absorb the advantages of the electric drum compact structure, light volume, but it and the electric drum as the heat dissipation condition is poor, so can only be used in the low power belt conveyor. In this paper, we take the low power roller of 15kW as an example to illustrate the gear roller used for belt conveyor.
The main advantages of the gear driven drum are: reliable work, long service life, its instantaneous transmission ratio is constant, smooth work, high transmission efficiency. There are many kinds of gear drive drum, such as cylindrical gear drive, bevel gear drive, planetary gear drive, etc. As the transmission ratio of the reducer designed this time is only 12.828, and its working conditions are better, with the general ordinary gear transmission can meet the requirements. For economic consideration, we decided to use two - stage cylindrical gear drive drum.
1. Design of gear drum transmission scheme
(1) Original data
The service life of the gear drum is 10 years, 300 working days per year, 1 shift per day, 7h per shift. One year for minor repairs, three years for major repairs. The ambient temperature does not exceed 400 ° C. Its technological parameters are as follows:
Gear drum diameter (mm) : 500;
Conveyor belt width (mm) : 800;
Width of gear drum (mm) : 950;
Installation size (mm) : 1 300;
Conveyor belt running speed (m/s) : 210;
Motor power (kW) : 15;
Motor speed (r/min) : 980.
(2) Transmission scheme design
This design uses two level cylindrical gear transmission, motor output power transfer to the Ⅰ shaft, drive the Ⅰ shaft pinion 1 rotation, pinion 1 and big gear 2 meshing, at this time the power transfer to Ⅱ shaft, Ⅱ shaft drive pinion 3 and internal gear 4 meshing, so as to transfer the movement to the drum to achieve the purpose of deceleration. The whole gear drive is placed in a support frame, and a butterfly type support bar is designed to connect the inner gear 4 to the drum.
2. Determine the transmission parameters of the gear drum
Firstly, the transmission ratio of the two pairs of meshing gears should be allocated, and the following principles should be considered when allocating the transmission ratio:
① The transmission ratio of all levels of transmission should be within a reasonable range, not exceeding the maximum allowable value, in line with the transmission principle at all levels;
(2) Attention should be paid to make all levels of transmission size coordination, symmetrical and reasonable structure;
③ Try to make the outer dimension of the transmission device compact or small weight;
(4) Try to make all levels of gear oil immersion depth reasonable;
⑤ To consider the transmission parts will not interfere with the collision.
3, gear drum gear design
Pinion 1 and pinion 3 were treated with 40Cr, and the hardness was HB241 ~ HB286, with an average of HB260. Both big gear 2 and inner gear 4 were tempered with 45 steel, the hardness was HB229 ~ HB286, and the average was HB240. This design uses standard helical gear transmission, and no displacement. Gear design is considered from two aspects:
(1) The gear drum is calculated according to the contact fatigue strength of the tooth surface;
The gear drum is checked according to the bending fatigue strength of the tooth root.
Because there is no serious overload in the transmission, static strength is not checked. The modulus of the gear and the diameter of the dividing circle can be calculated, and the modulus can be rounded to determine the specific diameter of the dividing circle. When this is done, a suitable and safe gear is obtained. This design uses oil lubrication.
4. Design of gear drum shaft
The gear drum shaft is the main part in this design, so the shaft must be designed reasonably. In this design, the main design of two shafts, namely high speed shaft I and intermediate shaft II. After the preliminary design of shaft Ⅰ, we found that the shaft was not fixed firmly in the axial direction, so a sleeve and two round nuts were used to fix it to ensure the axial fixation.
After the preliminary design of the structure of the shaft, the strength of the shaft must be checked. First check the axle diameter, and then use the safety factor method to check the strength of the shaft. In the calculation of the strength of the shaft, according to the specific load and stress of the shaft, the corresponding calculation method is used, and the appropriate selection of the allowable stress. According to the structure diagram of the shaft, the calculation diagram of the shaft is made, and the bending moment diagram, torque diagram and equivalent bending moment diagram of the shaft are made according to the calculation diagram of the shaft, and then the dangerous section is determined as the middle section of the pinion. The strength of the shaft is checked according to the bending and torsion stress, usually only the section bearing the maximum calculated bending moment of the shaft is checked, and then the fatigue strength of the shaft is checked.
The above calculation shows that the design of the shaft is safe and reliable, and meets the requirements of use.
5. Selection of gear drum bearings
Because the bearing receives radial and axial loads, tapered roller bearings are selected. We choose the bearing model 7308, bearing rated dynamic load 48440N, rated static load 43540N, limit speed 5600r/min(oil lubrication), axial dynamic load coefficient 211, axial static load coefficient 112. After the initial determination of bearing type and model, we calculate and check from three aspects: (1) the calculation of life; (2) Calculation of static load; (3) Allowable speed check.
6. Structure design of other parts of gear drum
In this design, also designed a support frame and a butterfly support bar to fix the gear device in the drum.