In order to solve the drawbacks of traditional mineral sizers using safety pin as overload protection, such as easy to break pin, difficult to replace, long maintenance time and high cost, the traditional safety pin overload protection mode is reformed by using the principle of dental insert safety clutch. The results show that the clutch can reset automatically after the overload fault is eliminated, the operation is reliable, the maintenance is simple and fast, the cost is low, the service life is long, and the direct and indirect economic benefits are significant.
Double-tooth roller crusher has the advantages of large crushing ratio (5~8), large processing capacity, simple structure, easy maintenance, etc., widely used in coal, metallurgy, mining, chemical industry, building materials and other industries, mainly used in coal preparation plant for raw coal crushing. The equipment in the working process will have large pieces of debris and other materials into the crusher, easy to cause the crushing tooth roller blockage, may burn the motor and damage the crusher, for this reason, the equipment are equipped with reliable and effective overload protection measures. Generally, safety pin or limited distance hydraulic coupling is used as overload protection of double-tooth roller crusher, most of which use safety pin overload protection. However, the effect of the overload protection of the safety pin is not ideal, because the raw coal often contains iron, large debris, etc., causing the frequent occurrence of broken pins. Replacing the safety pin is laborious and time-consuming, and the maintenance cost is high, which affects the normal production. In order to solve the many drawbacks of safety pin overload protection in mineral sizers, the principle of dental safety overload clutch is used to improve the safety pin overload protection during use, which can reduce the failure rate, reduce the maintenance time and cost, and extend the service life of safety overload device. 1.1mineral sizers The mineral sizers used in coal preparation plants are mainly composed of an electric motor (double motors), a drive system (consisting of main and passive belt wheels and drive belts), a crushing roller (including a drive shaft, a bearing seat, a tooth plate, etc.), a frame, a shield, an electrical control system, etc. The working principle is as follows: The two motors transmit the power to two large passive belt wheels through their small active belt wheels respectively, and the two passive belt wheels drive the two crushing tooth rollers for continuous relative rolling. After the broken material enters the crushing area from the human material port, the material smaller than the product particle size falls from the gap between the crushing teeth, and the large material is caught by the crushing teeth. Under the action of the relative rotation of the two crushing teeth rollers, as the containing volume continues to shrink, the tooth tip splits the material, and the broken material is discharged from the discharge port.
1.2 Composition and working Principle mineral sizers safety pin overload protection device mineral sizers safety pin overload protection device consists of a CAM disc on the drive spindle, bevel key, passive tape wheel, coupling sleeve and safety pin. After each part is in place, The exposed end face of the coupling sleeve is 7mm away from the end face of the coupling press plate. The limit switch is installed on the crusher support. The distance between the roller of the limit switch and the passive tape wheel is 1mm. The working principle is: When the raw coal is mixed with iron or large debris, the tooth roller is stuck, the safety pin on the main shaft is cut, and the belt wheel continues to drive the CAM to rotate due to inertia. Under the action of the bevel key, the bevel key on the main shaft is completely separated from the belt wheel. At this time, the belt wheel moves towards the end of the shaft, and the belt wheel touches the limit switch roller to make the control loop operate and the main loop is powered off. The motor stopped because of a power failure.
Although the feeding front end of the coal preparation mill crusher is generally equipped with iron removal and hand selection of bulk gangue and debris, there are still iron objects such as skimming plates, chains, connecting rings or large debris entering the crusher with the coal, which often causes the crusher to be blocked and overloaded leading to the occurrence of breaker accidents. The maintenance personnel have the following problems in the process of replacing the safety pin: (1) Before replacing the broken pin, the maintenance personnel must first clean the iron, debris, and coal stuck between the tooth rollers, before they can remove the broken pin and replace the new safety pin. (2) Because the cutting edge of the broken pin grinds the inner hole of the coupling sleeve (the rotating inertia of the passive tape wheel can not be stopped immediately), causing the bite between the shaft and the hole, it is very difficult to replace the safety pin each time, and it is more difficult each time, and finally can only use fire welding to cut the coupling sleeve and replace the coupling sleeve. (3) Resulting in long maintenance time and high maintenance costs, the average time for each treatment of broken pins takes 1.5h, and the average maintenance needs to invest 3 people. (4) Due to the constant overload load value of the safety pin, the breaking pin accident will also occur when the large gangue with greater hardness is encountered.
2 Modification of mineral sizers safety pin overload Protection Device 2.1 Structural Features of the dental clutch The mineral sizers safety pin overload protection device in use was modified using the working principle of the dental clutch. The structure is shown in Figure 3. The overload protection device is composed of a guide key on the transmission spindle, a passive belt wheel, a coupling shaft, a compression spring and two half clutches, etc. After each part is assembled in turn, the limit switch is installed on the crusher support, and the distance between the roller of the limit switch and the half clutch 1 is 3~5mm. Select the appropriate compression spring and stiffness according to the hardness of materials such as broken gangue, and adjust the compression round nut to a certain degree of tightness to ensure that the clutch will not be loosened when breaking normal materials. The shape of the clutch is trapezoidal, which can transmit a large torque, and the inclination Angle is generally 50°~70°. If the inclination Angle is too small, the clutch is difficult, the inclination Angle is too large, and the compression force required by the spring is too large.
2.2 The overload protection device adopts the working principle after the safety clutch transformation
When the crusher tooth roll is stuck by a large iron and debris, the half clutch 1 on the belt wheel continues to rotate to disengage the half clutch 2, while pushing the half clutch 2 compression spring to the shaft head end, the half clutch 2 end face triggers the limit switch roller, so that the control loop action, the main circuit power off, the motor is shut down due to power failure. At the same time, the half clutch 2 compresses the spring through the spring base. After the fault is removed, the tooth roller rotates and the spring compression base moves in the direction of the tooth roller, so that the half clutch 1 and the half clutch 2 engage normally, so as to quickly resume normal operation.
3 Transformation effect and economic benefit analysis 3.1 Structural characteristics of overload protection device after transformation mineral sizers who use safety pin as overload protection can adopt this technology for transformation. The transformation process is as follows: It is only necessary to replace the coupling shaft sleeve on one side of the passive belt wheel of the original crusher with a safety overload clutch, machining 1 or 2 guide keyways on the spindle of the tooth roller, adding 1 compression spring and spring pressure plate. The renovation project is small, the input cost is low, the total cost of the workpiece and the spring is only about 4000 yuan. The biggest advantage of the improved structure is that the spring with different stiffness can be replaced and the compression force of the spring can be adjusted to meet the normal crushing of materials with different hardness, and the blockage fault can be automatically reset after elimination. It can be designed or manufactured according to this structure form, and the structure is more compact, and the use and maintenance are more simple and convenient.
After the transformation is completed and put into production, when the iron or large debris enters the crusher and causes a card accident, under normal circumstances, as long as the iron is not stuck in the tooth roller, the post operator can reset the overload safety clutch by itself after cleaning the debris, and does not need maintenance personnel to deal with it on site. If there is a large piece of iron stuck in the tooth roller, only two maintenance personnel need to go to the scene to cut the iron with fire welding, less than 10min can make the overload safety clutch reset, you can start up and run, greatly shortening the maintenance time, with obvious economic effects.
(1) Direct economic benefits. mineral sizers Safety pin overload protection device after the technical transformation, the safety load pin in the original design is replaced by a safety clutch, and the transmission components are modified to extend the service life and reduce the operating cost. Each year can reduce the use of safety load pin 90, each pin cost calculated by 60 yuan, a year can save 5400 yuan: can save 6 pieces of coupling sleeve per year, according to 600 yuan per piece, a total of 3600 yuan: the annual cost can be saved 9000 yuan. (2) Indirect economic benefits. After the renovation of the mineral sizers safety pin overload protection device, not only the maintenance time is reduced, but also the maintenance is simple and convenient, thus greatly reducing the time affecting production, creating conditions for ensuring the normal production of the coal preparation plant, with incalculable indirect economic benefits.
After improving the overload protection device of mineral sizers safety pin with safety clutch, the crusher operates reliably and the failure rate is reduced, which greatly reduces the time affecting the normal production of coal preparation plant, reduces the labor intensity and maintenance cost of maintenance personnel, saves manpower and material resources, and achieves good economic benefits.