Introduction

With the popularization of mechanization, comprehensive mechanization of coal mining has been achieved, resulting in a reduction in the particle size of the extracted coal and an increase in the amount of fine coal. At the same time, the increase in the water spraying volume for dust prevention underground has led to an increase in the moisture content of raw coal, causing the sieve holes of ordinary screening machines to become clogged when screening fine particles of damp coal. In recent years, the rapid development of economy and science and technology has placed higher demands on mineral screening technology, urgently requiring the development of screening equipment towards higher efficiency and larger size, as well as more advanced performance, more reliable operation, higher screening efficiency, greater processing capacity, and longer service life. Multi-angle zigzag sieve surface new banana screens of various types are needed.

Structure of the banana screen for mineral screening

The linear double-layer banana screen for mineral screening mainly consists of the screen body, screening exciter, exciter connection shaft, drive connection shaft, vibration drive motor, transmission device, exciter drive device, noise reduction and buffering device, and screening device.

Screen body

The screen body is composed of lifting beam installation piece, side installation piece, upper crossbeam, lower crossbeam, excitation beam, lifting beam and rear back installation plate. The lifting beam installation piece is inverted "V" shape, and the lifting beam is installed in the middle position between both sides of the lifting beam installation base. The side installation piece and the rear back installation plate are located at both ends of the lifting beam installation piece, and the lower ends of the two are installed with evenly distributed lower crossbeams through the lower crossbeam installation plate, and the middle part is installed with evenly distributed upper crossbeams through the upper crossbeam installation plate. The excitation beam is installed on the middle part of the lifting beam installation piece through the excitation flange.

Screening exciter

The screening exciter is divided into left and right two types, both are installed on the screen body, and they are connected by the exciter connection shaft. There is an excitation beam below. The drive connection shaft is connected to the exciter connection shaft at one end and the rotating shaft of the vibration drive motor at the other end. The rotating shaft disc of the vibration drive motor has a transmission device for connecting the rotating shaft disc with the exciter drive device. The noise reduction and buffering device is installed between adjacent upper crossbeams and adjacent lower crossbeams. The screening device is installed on the upper crossbeam installation plate and the lower crossbeam installation plate.

Composition and structure of the screening exciter

The screening exciter includes a box body, bearings, box body cover and respirator. The box body cover is connected to the box body through box body cover gasket, and a respirator is set at the upper end of the outer side of the box body. The box body has four bearings, two of which are set opposite to each other and the length of the bearings is 1/6 to 1/4 of the length of the box body. The two left bearings have short shafts, and the two right bearings have long shafts. The distance between the long shaft and the short shaft is 2/3 of the length of the bearing, the length of the short shaft is 3/2 of the length of the bearing, and the length of the long shaft is 5/2 of the length of the bearing. Short shafts are set on both sides of the middle position of the left rotating gear, and right rotating gears are set on both sides of the middle position of the right rotating gear. The first oil retaining disc is set on the upper side of the two above-mentioned bearings, and the second oil retaining disc is set on the lower side of the two below-mentioned bearings. On the upper side of the first and second oil retaining discs, there are bearing covers and labyrinth seal rings, and on the upper side of the short shaft and the long shaft, there is a frame oil seal. Two left rotating gears are connected on the upper side, and two right rotating gears are connected on the lower side. There is a gear isolation sleeve at the connection point between the left rotating gear and the short shaft, and at the connection point between the right rotating gear and the long shaft. There are weight blocks at both ends of the short shaft, and the weight blocks are connected to the short shaft or the long shaft through a swing block cover. The weight block includes a swing block and a weight shaft, and the weight shaft is connected to the long shaft or the short shaft through the swing block. A swing block isolation sleeve is set on the outer side of the long shaft, and an oil seal sleeve is set between the weight block on the short shaft and the bearing. A magnetic oil plug is set on the lower end of the outer side of the box body, and the magnetic oil plug is connected to the box body through an oil plug sealing gasket.

Excitation Beam

The excitation beam consists of the box, excitation flange, web plates, and double plates. The box includes a top plate, a bottom plate, and two side plates. It adopts a full penetration welding structure of a single plate. The top plate is connected to the bottom plate through the side plates. Four double plates are fixed on the top plate. Two double plates are evenly set at both ends of the top plate, with the distance between them being 1/12 to 1/10 of the length of the top plate. The double plates are used as the installation surface for the exciter. Five web plates are fixed on the outer side of the side plates. One web plate is set in the middle position of the side plate, and the other two web plates are set correspondingly on the side plate, with the distance between them being 3/2 to 2 times the distance between the two double plates. Excitation flanges are set on both ends of the top plate and bottom plate, and the upper end of the excitation flange is raised above the top plate by 1/5 to 1/4 of the total length of the excitation flange, and the lower end is raised above the bottom plate by 1/3 to 2/3 of the total length of the excitation flange. The excitation flange is set in the middle of the lifting beam mounting piece.

Exciter Drive Device

The exciter drive device includes the auxiliary shaft, SKF bearings, locking sleeve, labyrinth seal box, and open bearing seat. A SKF bearing is set on the outer side of the auxiliary shaft. A locking sleeve is set between the auxiliary shaft and the SKF bearing. The SKF bearing is set on the open bearing seat, which is set inside the labyrinth seal box. A transmission device is set on the outside of the SKF bearing.

Other Structural Parameters

The isolation sleeve of the swing block, the oil plug sealing pad, and the box cover gasket are all made of rubber. The distance between the left-hand gear and the right-hand gear is 5-8mm. The distance between the two upper bearings is 15-25mm, and the distance between the two lower bearings is 15-25mm.

Application and Characteristics of Banana Screen

Main Application

The banana screen is mainly used for coal classification, mud removal, dehydration, and medium removal, and is also applicable to the screening and classification of other minerals.

Core Design Principle

The exciter is optimized through the application of equal thickness screening principle and linear vibration theory. The vibration parameters such as amplitude, frequency, and excitation force are set reasonably according to the screening process requirements and scientific test results, precisely avoiding the natural frequencies of the screen body at all levels, reducing the negative impact of resonance forces on each part of the screen body, improving the performance of the screen machine, and extending the fatigue life of the screen machine.

Exciter Characteristics

The exciter adopts a high-efficiency reciprocating linear force box-type exciter manufactured by advanced technology. This type of exciter uses the latest specialized vibration bearings developed by SKF, and the gearbox body is precisely manufactured. It has a light structure, good sealing, fast heat dissipation, no oil leakage, is durable and reliable, has a high cost performance, and can operate at high frequency continuously. The swing block has multiple stuffing box filling methods, which can combine different eccentric torques or excitation forces to meet different vibration indices and usage requirements, suitable for various vibration equipment. It adopts splash lubrication, selects world-renowned high-grade lubricating oil to greatly improve the equipment's performance and lifespan. It uses magnetic oil plugs to timely adsorb iron filings in the gear lubricating oil, improves the quality of the lubricating oil, and is equipped with a special respirator. The exciter mating surfaces are all precisely processed by CNC machine tools before assembly, effectively ensuring the overall assembly quality of the screen machine.

Screen Body Assembly Process

Select high-quality bolts and adopt advanced clean and sealed assembly process to fasten the screen body according to the specified tightening torque.

Excitation Beam Characteristics

The excitation beam adopts a whole plate box-type design. All weld seams are fully melted through, undergo first-level UT flaw detection and magnetic particle flaw detection, and undergo heat treatment to eliminate welding stress. Its structural stiffness is large, strength is high, the force distribution is reasonable and balanced, the safety factor is large, the structure is compact, and the weight is light. The mating surfaces of the excitation beam are all precisely processed by CNC machine tools before assembly, effectively ensuring the overall assembly quality of the screen machine. Select high-quality bolts and adopt advanced clean sealing assembly technology to securely fasten the screen body according to the specified tightening torque. This ensures that under high-load and high-frequency vibration working conditions, cracking and wear can be avoided, and it has higher fatigue resistance, reliability and service life.

Advantages of the double-layer structure

By adopting a double-layer structure, it can further screen the minerals that have been separated to the lower layer, thereby improving the screening efficiency.

Conclusion

In conclusion, the double-layer banana screen used for mineral screening has effectively solved the problem of blockage in the screening of damp fine minerals through scientific structural design, advanced vibration technology, and high-quality manufacturing processes. It meets the modern requirements for efficient, large-scale, high reliability, and long lifespan in mineral screening. Its double-layer structure design further enhances the screening efficiency and is widely applicable to the classification, desliming, dehydration, and desintermediate operations of minerals such as coal, etc., possessing significant application value and broad market prospects.