CN103878118A - Novel elliptical equal-thickness vibrating screen - Google Patents

Abstract

The invention discloses a novel elliptical vibrating equal-thickness screen, which adopts hanging installation, and it includes a screen box, a two-axis inertial vibrator, an elastic element, a transmission mechanism, a hanging device and a bracket, and a perforated screen plate with an aperture of 6mm. The feeding end of the screen box is suspended on the supporting device by two springs, and the discharging end is connected to the supporting device by two movable rigid connecting rods at both ends. The exciter is installed near the screen box at the feed end, and a feed chute is installed above the feed end of the screen box, and a thin iron sheet is used as a feed baffle, and a discharge chute is installed at the tail of the discharge end of the screen box. The sieve surface of the feeding section of the present invention makes an elliptical motion, and the discharge section makes a linear motion, and along the length direction of the sieve surface, the amplitude perpendicular to the sieve surface decreases gradually, and the moving speed of the material on the sieve surface decreases from the feeding end to the discharging end. The surface has different ejection strength, which promotes the stratification and screening of materials, and the processing capacity and screening efficiency of the vibrating screen are significantly improved.

Description

A new type of elliptical vibrating equal thickness screen

Technical field:

The invention relates to a vibrating sieve for dry screening of fine-grained materials, in particular to a novel elliptical vibrating equal-thickness sieve. the

Background technique:

At present, in the coal industry, with the improvement of coal mining mechanization, the content of fine particles in raw coal is increasing, coupled with the high content of steam coal pulverized coal, and the adoption of measures such as hydraulic coal mining, water spraying and dust prevention, raw coal The moisture content is high. In this case, when ordinary vibrating screens are used to sieve raw coal, fine-grained materials are easy to agglomerate on the screen surface, and then block the screen holes, resulting in serious deterioration of the screening process and low screening and classification efficiency. , The screening of fine-grained materials, especially the dry screening of wet fine-grained viscous materials is a difficult point in the research of screening technology at home and abroad today, and it is a problem that needs to be solved urgently in screening operations. the

At present, the elliptical vibrating equal-thickness screens at home and abroad are mainly to change the inclination angle of each section of the screen surface, but the thickness of the feeding end is still greater than the thickness of the discharging end on each section of the screen surface, which can only be called equal thickness on the whole and partial thickness on the part. The above is still non-equal thickness, and the same screen surface needs to achieve two or more types of projectile intensities, so that the same screen machine may need two or more sets of driving devices, and the vibrating screen often uses two sets of different frequencies and different amplitudes. The excitation device adopts elliptical excitation at the feeding end, and linear excitation at the discharging end, so that the vibration track along the length of the screen surface does not change gradually from the feeding end to the discharging end. When dealing with wet materials with a particle size of 6mm, the screen The separation efficiency is not ideal, and the plugging is serious, which cannot fundamentally solve the problem of plugging and sticking of wet fine-grained materials. the

Invention content:

The invention provides a novel elliptical equal-thickness vibrating screen with simple structure, low cost, and convenient installation and debugging. The purpose is to promote the stratification and screening of fine-grained materials, and improve the processing capacity and screening efficiency of the vibrating screen. the

The implementation of the technical solution of the present invention is that the novel elliptical vibrating equal-thickness screen adopts hanging installation, including a screen box, a dual-axis inertial vibrator, an elastic element, a transmission mechanism, a hanging device and a bracket, and the aperture is a 6mm punched screen plate. , the feeding end of the screen box is hung on the support device by two springs, the discharge end is connected to the support device by two rigid connecting rods, the two ends of the connecting rod are movable, and the inclination angle of the screen surface of the screen box is 10°, the vibrator adopts a synchronous gear transmission dual-axis inertial vibrator, which is installed near the screen box at the feeding end, and the motor drives the vibrator to vibrate through a belt. Due to the forced vibration mechanism connected by gears, the two exciters The vibrating mechanism maintains a stable phase difference angle and performs synchronous reverse rotation. A feeding chute is installed above the feeding end of the screen box with an angle of 35°-40°. A thin iron sheet is used as the feeding baffle, and the side of the vertical baffle is close to the feeding end. The tail of the screen box discharging end is installed The discharge chute is equipped with two horizontal springs with small rigidity to prevent the driving device from swaying strongly due to resonance when starting or stopping, ensuring the stability of the belt drive. the

Through the implementation of the present invention, the elliptical vibration track of the vibrating screen along the length of the screen surface changes gradually from the feed end to the discharge end, and the equal thickness screening is realized by utilizing the different projection strengths of the different elliptical vibration tracks along the length of the screen surface , when the processing capacity is 5t/(h·m ² ), it is used to sieve a coal sample with a particle size of -13mm, an ash content of 43.25%, and an external moisture content of 2.10%, and the efficiency can reach 96.8%.

Description of drawings:

Fig. 1 The mechanical model of the new elliptical vibrating screen with equal thickness;

Fig. 2 The trajectory of the sieve surface in the feed section and discharge section of the new type elliptical vibrating equal-thickness sieve;

Figure 3 The trajectory of the center of mass of the new type elliptical vibrating equal thickness screen with different vibration frequencies;

Fig. 4 The motion trajectory of the center of mass of the same eccentric mass of the new type elliptical vibrating equal thickness screen;

Figure 5 The trajectory of the center of mass of the new type elliptical vibrating equal thickness screen with different initial phase difference angles;

Fig. 6 The trajectory of the screen surface under different spring stiffnesses of the new type elliptical vibrating equal thickness screen;

与抛离角θ_d的关系曲线；  Figure 7 throwing start angle

The relationship curve with throwing angle θ _d ;

The relationship curve of Fig. 8 throwing index D and throwing off coefficient i _D ;

Figure 9 is the distribution diagram of the sieve capacity of the new elliptical equal-thickness sieve along the length of the sieve surface. the

Detailed ways:

Specific implementation mode 1 Simulation of motion trajectory of new elliptical vibrating equal-thickness sieve surface

The dynamic factors of the new elliptical vibrating equal-thickness screen are the spring stiffness K, the mass m ₁ and m ₂ of the eccentric block, the mass M of the box, the radius of gyration r of the eccentric block and the excitation frequency ω determine the magnitude of the amplitude. Its mechanical model is shown in Figure 1. According to the design, the angular frequency of the new elliptical equal-thickness sieve is 94.2rad/s, the frequency ratio λ=6, the initial phase angle of m ₁ is 90°, and m ₂ lags behind Δα , where the initial phase difference angle Δα=60° is taken, and Matlab software can be used to simulate the motion track of the centroid of the new elliptical vibrating equal-thickness screen and the screen surface under different spring stiffnesses.

Due to the difference in spring stiffness K in the vertical direction between the feeding end and the discharging end of the new type elliptical vibrating equal-thickness sieve, the hanging spring stiffness of the feeding end is K ₁ , and the discharging end assumes that the tension rod stiffness is K ₂ =∞, now take The spring stiffnesses of the material end and the discharge end are K ₁ and K ₂ respectively, and according to the above simulation analysis, selecting appropriate working parameters can simulate the motion track of the screen surface near the feed end and discharge end.

According to the simulation in Figure 2, it can be seen that the motion trajectory near the feeding section of the screen surface is an elliptical motion; the motion trajectory of the screen surface in the discharging section is a straight line, and its vibration direction is consistent with the short axis direction of the elliptical motion trajectory of the screen surface in the feeding section. The amplitude is the length of the minor axis of the ellipse trajectory in the feeding section. Therefore, the amplitude of the feeding section can be larger than that of the discharging section, and the vibration direction angles of the feeding section and the discharging section are different. the

Under the condition that other working parameters remain unchanged, changing the working frequency can obtain the motion trajectory of the center of mass at different vibration frequencies, as shown in Fig. 3 . the

It can be seen from the simulation in Figure 3 that when the vibration frequency changes, the amplitude value changes. When the vibration frequency ω decreases from 94.2rad/s to 15.70rad/s, the amplitude of the long axis of the ellipse increases sharply. At this time, the resonance phenomenon of the screen machine is serious. This situation occurs because the working frequency of the screen machine is just equal to that of the screen machine. machine natural frequency, resonance occurs. the

It can also be seen from this that the change of the working frequency has a significant impact on the amplitude, so a reasonable working frequency should be selected during design to keep it away from the natural frequency of the screen machine, so as to ensure the stable operation of the screen machine and prolong the life of the screen machine. the

In the case of keeping the radius of gyration and other working parameters unchanged, adjust the mass of the two eccentric blocks so that the sum and difference ratios are 5:1, 4:1, and 2.5:1 respectively. In order to facilitate comparison and observation, adjust the eccentric block and The sum of the two is kept constant when the difference ratio is used, so that the trajectory of the center of mass with different eccentric masses and difference ratios can be obtained through simulation, as shown in Figure 4. the

It can be seen from the simulation in Figure 4 that, under the condition that the radius of gyration of the eccentric block is constant, when (m ₁ +m ₂ )/(m ₁ -m ₂ ) decreases, the ratio of the major and minor axes of the elliptical trajectory also decreases. Small. Therefore it can be concluded that:

1) When the radius of gyration of the eccentric mass remains unchanged, the change of the mass of the eccentric mass has a significant effect on the amplitude;

2) When the radius of gyration of the eccentric blocks is constant, the sum-to-difference ratio of the masses of the two eccentric blocks determines the ratio of the major and minor axes of the ellipse trajectory, and the ratio of the major and minor axes of the ellipse decreases as the mass and the difference ratio decrease. the

In essence, when the radius of gyration is constant, the change of the mass of the eccentric block causes the change of the magnitude of the exciting force, which can be deduced from p= ^mrω2 , so the ratio of the long and short axes of the ellipse track is essentially determined by the eccentric block It depends on the magnitude of the exciting force generated.

Under the condition that the initial phase angle of m ₁ and other working parameters remain unchanged, changing the initial phase difference angle of the two eccentric blocks can obtain the mass center movement trajectory under different initial phase difference angles, as shown in Figure 5.

From the simulation in Figure 5, it can be seen that when the initial phase difference angle Δα increases or decreases, the shape of the elliptical trajectory (the size of the ellipticity) does not change, while the vibration direction angle (the angle between the long axis of the ellipse and the x direction) However, the size changes, and when the initial phase difference angle Δα decreases, the vibration direction angle increases, and when the initial phase difference angle Δα increases, the vibration direction angle decreases. the

It can be explained from this:

1) The initial phase difference angle does not affect the amplitude in the x and y directions, which is consistent with the analysis of vibration characteristics, that is, the amplitude has nothing to do with the initial conditions;

2) To change the vibration direction angle of the new type elliptical vibrating equal thickness screen, it can be realized by adjusting the initial phase difference angle of the two eccentric blocks. the

Since the transition area between the feeding end and the discharging end of the new type elliptical vibrating equal thickness screen is between the spring stiffnesses K ₁ and K ₂ =∞, therefore, depending on the spring stiffness, it is much less than and much greater than (M In the range of +m ₁ +m ₂ )ω ² , a number of K values with different spring stiffnesses can be chosen arbitrarily, so that the motion trajectory of the screen surface with different stiffnesses can be simulated.

It can be seen from attached drawing 6 (left) that when the spring stiffness K≤(M+m ₁ +m ₂ )ω ² , even if K changes within a certain range, the shape of the elliptical motion trajectory of the screen surface remains basically unchanged, and the amplitude Stablize. As K increases, the shape of the ellipse trajectory also changes.

When K crosses the natural frequency and is equal to the operating frequency and increases to K>(M+m ₁ +m ₂ )ω ² , with the increase of K, the size of the major axis AB of the elliptical trajectory decreases continuously, while the size of the minor axis CD remains constant When the length of the long axis decreases to close to the length of the short axis CD, the screen surface appears a circular motion trajectory; when K increases further, the amplitude in the AB direction will further decrease, while the CD amplitude remains unchanged. When it reaches infinity, the AB The amplitude of the direction is zero, while the length of the original minor axis CD remains unchanged, so the screen surface only reciprocates linearly around the pull rod with the amplitude of the CD direction. The motion trajectory and the amplitude change process in the AB direction of the figure reflect to a certain extent the variation trend of the motion trajectory of the screen surface in the transition area of the new elliptical vibrating equal-thickness screen, indicating that the amplitude in this area is continuously decreasing along the length of the screen surface.

Specific implementation mode 2 Selection of process parameters of new type elliptical vibrating equal-thickness sieve

The new-type elliptical vibrating equal-thickness sieve is mainly used for screening fine-grained materials, and for the purpose of improving screening efficiency and processing capacity, the screen surface inclination of the new-type elliptical vibrating equal-thickness sieve is now selected α = 10°, and the vibration direction angle β ₁ =45°, the working frequency is n=900r/min, that is, ω=2πn/60≈94.2rad/s, the amplitude of the feeding section is 3mm, and the minor axis of the ellipse is 2mm. According to the dynamics and simulation analysis of the design, the amplitude of the screen surface from the feeding section to the discharging section decreases gradually, and the trajectory transitions from an elliptical trajectory to a linear trajectory. The double amplitude of the intermediate transition zone is taken as 3-1.5mm, and the amplitude of the discharging section is selected 1mm.

有解为29.7°，故物料能作抛掷运动，又1.75＜D_入＝2.02＜3.3,故筛面入料段物料处于中速抛掷运动状态。由D_入＝2.02或

根据利用Matlab软件作出的

与θ_d、D与i_D的关系曲线，如附图7、8，可以查得：抛离角θ_d＝255°，抛离系数i_D＝0.8，从而通过计算可得入料段筛面物料的理论平均速度为0.13m/s。  According to the calculation of the selected relevant parameters, the throwing index D in the feeding section can be calculated _as 2.02, because the throwing index D _in the feeding section > 1, so the nominal throwing start angle

The solution is 29.7°, so the material can be thrown, and 1.75< _D = 2.02<3.3, so the material in the feeding section of the screen surface is in a medium-speed throwing state. From D _into = 2.02 or

According to the use of Matlab software to make

The relationship curve with θ _d , D and i _D , as shown in Figures 7 and 8, can be checked: throwing off angle θ _d = 255°, throwing off coefficient i _D = 0.8, so that the screen surface of the feeding section can be obtained by calculation The theoretical average velocity of the material is 0.13m/s.

Because the discharge end of the new type elliptical vibrating equal-thickness screen makes an approximate linear motion, the screen surface of this section makes a sliding motion. The reverse sliding of the material can just slow down the conveying efficiency of the material on the screen surface and reduce the movement speed of the material. Therefore, in order to slow down the material conveying speed in the discharge section, the material can appear in a reverse sliding state. Therefore, the reverse sliding index D _q0 > 1 is selected, D _q0 = 2 ~ 3, and the forward sliding index D _k0 ≤ 1 is selected. Since the sieve plate is made of stainless steel, the static friction angle between the material and the sieve surface is selected as μ ₀ =40°, so the vibration direction angle of the discharge section of the sieve surface is calculated as β ₂ =-31°.

即239°～301°，由于排料段抛掷指数D_排≈0.48＜1，则

无解，故该段筛面上物料颗粒不能出现抛掷运动，仅能作滑行运动，且作反向滑行运动，设物料对筛面的动摩擦系数f＝tanμ＝0.7，则动摩擦角μ＝35°，因而通过计算可得反向滑动角θ_q＝111°，反向滑动系数为i_q＝0.3，物料在筛面排料段反向滑动的理论平均速度为0.01m/s。  Since the horizontal amplitude of the screen surface discharge section is very small, the double amplitude 2A=2mm is now selected, that is, A=1mm, and the calculation can be obtained. The reverse sliding index D _q0 is 1.2. Since the reverse sliding index D _q0 > 1, the reverse The starting angle of sliding to φ _q0 = 239°, so at this time the material will slide in reverse on the screen surface of the discharge section, and the interval of possible reverse sliding is

That is, 239°～301°, because the throwing index D _{of the discharge section} ≈0.48<1, then

There is no solution, so the material particles on the screen surface of this section cannot be thrown, but can only slide and reverse slide. If the dynamic friction coefficient f=tanμ=0.7 of the material on the screen surface, then the dynamic friction angle μ=35° , so by calculation, the reverse sliding angle θ _q = 111°, the reverse sliding coefficient is i _q = 0.3, and the theoretical average speed of the material reverse sliding in the discharge section of the screen surface is 0.01m/s.

有解，则物料能出现抛掷运动，又1＜D_中≈1.38＜1.75，故物料处于轻微抛掷运动状态。随着y方向振幅的进一步减小，至y方向振幅刚好等于x方向振幅即A=1mm时，D_中≈0.92＜1名义抛始角

无解，则物料不能出现抛掷运动。  In the middle transition zone of the screen surface, the amplitude perpendicular to the screen surface direction decreases from the feeding section to the discharge section, and the amplitude in the y direction is equal to the amplitude in the x direction, and the screen surface approximates a circular motion. Therefore, the particles of the screen surface material in the middle section should transition from the projectile motion of the feeding section to the sliding motion. The amplitude A=1.5～0.75mm in the transition area of the middle section can be calculated. When the vertical amplitude of the screen surface decreases _to A=1.5mm, the throwing index D is ≈1.38>1, and the nominal throwing start angle is

If there is a solution, the material can appear in throwing motion, and 1<D _≈ 1.38<1.75, so the material is in a state of slight throwing motion. With the further reduction of the amplitude in the y direction, until the amplitude in the y direction is just equal to the amplitude in the x direction, that is, when A=1mm, the nominal throwing start angle _in D is ≈0.92<1

If there is no solution, the material cannot be thrown.

，正向滑动角θ_k＝186.2°，正向滑动系数为i_k＝0.52，过渡区域的理论平均速度0.04m/s。  When the amplitude A=1mm in the middle section perpendicular to the screen surface, the material on the screen surface can no longer be thrown, so the middle section amplitude A=1mm and 0.75mm are selected, and the selected parameters ω=94.2rad/s, α=10° and the static friction angle μ ₀ =40°, the forward sliding index D _k0 of the middle section is calculated to be 1.8 and 1.4 respectively. The positive sliding index D _k0 =1.8 obtained from A=1mm can calculate the forward sliding start angle to be 33.8°, and now the dynamic friction angle μ=35° can be calculated to obtain the forward sliding stop angle

, the forward sliding angle θ _k =186.2°, the forward sliding coefficient is i _k =0.52, and the theoretical average velocity in the transition area is 0.04m/s.

Specific implementation mode 3 Development of a new type of elliptical vibrating equal-thickness sieve machine and optimization of the best working parameters

In order to test the technological performance of the new elliptical equal-thickness sieve prototype developed by the company and determine the optimal working parameters of the sieve machine, for this reason, according to the "GB/T15716-2005 Coal Screening Equipment Process Performance Evaluation Method" and the technical economics of the sieving process Index, select the screening efficiency as the investigation index, and test it by reasonably arranging the screening test. The test factor level table is shown in Table 1, where in the test, σ ₂ =21.0mm, and the test index is the screening efficiency η, the larger the value, the better.

α—原给料中小于筛孔尺寸粒级的含量，%；β—原给料中小于筛孔尺寸粒级的含量，%；θ—筛上产品中小于筛孔尺寸粒级的含量，%。  in

α—the content of the particle size smaller than the sieve size in the raw material, %; β—the content of the particle size smaller than the sieve size in the raw material, %; θ—the content of the particle size smaller than the sieve size in the product on the sieve, % .

Table 1 Test factor level table

The purpose of this test is to find out the best collocation of factors such as excitation frequency, thickness of eccentric block, processing capacity on screening efficiency and factor level, and whether there is interaction between factors, so we choose orthogonal test design Methods Minitab software was used for experimental design, and data processing and analysis and test result prediction of optimal scheme were carried out to test the significance of the influence of factors and interaction on test indicators, and to determine the optimal test conditions with a small number of tests. the

In the test, a coal sample with a particle size of -13mm, an ash content of 43.25%, and an external moisture content of 2.10% was selected. On a new type elliptical vibrating equal-thickness sieve test prototype, a 6mm perforated sieve plate was used for dry screening to determine the quality of the sieve machine. optimal working parameters. the

According to the orthogonal table and test factors and levels selected by the orthogonal test design, the orthogonal table design is carried out by Minitab, so as to obtain the test plan in Table 2. the

Table 2 Orthogonal test scheme

According to the test scheme designed by Minitab software, the sieving experiment was carried out on the test prototype according to the following steps:

(1) Pre-screen the coal sample with a vibrating screen in the laboratory to obtain a coal sample with a particle size of -13mm;

(2) Classify the obtained coal samples with a grain size of -13mm with a standard sieve with a pore size of 6mm (the hole type is the same as the screen surface of the prototype), and obtain fine coal with a grain size of -6mm and coarse coal with a grain size of 6-13mm ;

(3) According to the requirements of the input amount of the test plan, weigh the coarse and fine coal samples of the required quality according to a certain proportion, and mix them evenly to prepare for the test feeding;

(4) According to the sequence of the test plan, adjust the level of the parameters of the new elliptical vibrating equal-thickness sieve prototype;

(5) Turn on the test prototype, and after the sieve machine works stably, use a stopwatch to time and feed the material evenly;

(6) Weigh the quality of each section of the oversize and undersize, and sieve it with a standard sieve, then weigh the quality of the undersize and oversize fine particles (-6mm particle size), and record the data;

(7) Clean the sieve surface, and carry out the next test according to the above steps according to the sequence of the test plan. the

Carry out the screening test according to the above test steps and record the data to obtain the test results, see Table 3

Table 3 test results

The test results show that the thickness of the eccentric block of the driving shaft σ ₁ =35.0mm (thickness of the eccentric block of the driven shaft σ ₂ =21.0mm) when the eccentric blocks have the same radius of rotation for the new type elliptical vibrating equal thickness screen, and the excitation frequency f=13Hz , the processing capacity Q=24.0kg/2min, that is, the ratio of the major axis to the minor axis of the elliptical motion track of the screen machine is 4:1, the vibration frequency of the screen machine is 780r/min, and the processing capacity is 5t/(h·m ² ), The sieving machine has the highest screening efficiency, and when used to screen coal with an external moisture of 2.10%, the efficiency can reach 96.8%

Using Minitab software to analyze the results of the orthogonal test, the best combination of factor levels is A ₂ B ₁ C ₂ , using Minitab software to predict, and the optimal test level combination A ₂ B ₁ C ₂ to obtain the predicted mean value of screening efficiency It is as high as 98.6%, which shows that the prediction effect of the optimal level combination A ₂ B ₁ C ₂ is extremely obvious, and the obtained screening efficiency is high.

Specific implementation mode 4 Verification test of new type elliptical vibrating equal thickness sieve and equal thickness screening

In the sieving test, by measuring the content of the material under the sieve surface in the feeding section, the middle section and the discharging section, it is determined whether the thickness of the material layer on the sieve surface of each section remains basically unchanged, thereby verifying the equal thickness screening principle of the sieve machine . the

It is divided into three sections on average along the length of the screen surface, that is, the 0-200mm screen surface is the first section (feeding section), the 200-400mm screen surface is the second section (the middle section), and the 400-600mm screen surface is the III section (rowing section). material section), install a material receiving chute under each section of the screen surface with a thin iron sheet. the

Adjust the parameters of the prototype according to the determined optimal working parameters of the new-type elliptical vibrating equal-thickness sieve prototype machine, turn on the prototype machine, and perform a screening test on the coal samples with an external moisture content of 2.10% according to the steps after the work is stable, and use the receiving trough to pick up each coal sample separately. The materials under the section sieve were weighed and recorded, and two repeated tests were carried out under the same conditions, and the obtained test results were recorded in Table 4. the

Table 4 Equal thickness screening verification test

Table 4 (continued)

According to the content of undersieve in the feeding section, middle section and discharging section obtained from the test, that is, the amount of sieve through is the ordinate, and the length of the sieve surface from the feeding end to the discharging end of the prototype machine is the abscissa, and the average value is used to draw the scattered Point diagram, the distribution diagram of the amount of screen penetration along the length direction of the screen surface can be obtained, as shown in Figure 9. the

In the new elliptical equal-thickness sieve prototype, the sieving test of the coal sample with an external moisture content of 2.10% is obtained from the distribution diagram of the sieve penetration along the length of the sieve surface. The amount of screen penetration in the discharge section is close to that of the equal thickness screen, and the thickness of the material layer on the screen surface of each section basically tends to be balanced. Therefore, the new elliptical vibrating equal thickness screen can realize equal thickness screening. the

Claims (8)

1. A new type of elliptical vibrating equal-thickness screen, which is installed by hanging, includes a screen box, a dual-axis inertial vibrator, elastic elements, a transmission mechanism, a hanging device and a bracket, and the aperture is a 6mm punched screen plate. The feeding end of the box is hung on the supporting device by two springs, and the discharging end is connected to the supporting device by two rigid connecting rods. The two ends of the connecting rod are movable. The above vibration exciter adopts a synchronous gear transmission dual-axis inertial vibration exciter, which is installed near the screen box at the feeding end. The motor drives the vibration exciter through a belt to generate vibration. Due to the forced vibration mechanism connected by gears, the two excitation mechanisms maintain one Stable phase difference angle, from synchronous reverse rotation. A feeding chute is installed above the feeding end of the screen box with an angle of 35°-40°. A thin iron sheet is used as the feeding baffle, and the side of the vertical baffle is close to the feeding end. The tail of the screen box discharging end is installed The discharge chute is equipped with two horizontal springs with small rigidity to prevent the driving device from swaying strongly due to resonance when starting or stopping, ensuring the stability of the belt drive. 2. A novel elliptical vibrating equal thickness screen according to claim 1, characterized in that the elliptical vibration trajectory of the vibrating screen along the length of the screen surface changes gradually from the feed end to the discharge end, utilizing Different elliptical vibration trajectories have different projectile intensities to achieve equal-thickness screening. 3. A novel elliptical vibrating equal thickness screen according to claim 2, characterized in that the sieve surface near the feeding section of the novel elliptical vibrating equal thickness sieve machine performs an elliptical motion, and the ratio of the major axis and the minor axis of the elliptical track determines the The shape of the elliptical motion trajectory, the motion trajectory of the screen surface in the middle transition area gradually transitions from elliptical motion to circular motion, the vertical amplitude of the screen surface near the discharge end tends to zero, and the screen surface of the screen machine moves approximately linearly with a small amplitude, and enters The vibration amplitude in the vertical direction of the material section is greater than that in the vertical direction of the discharge section. 4. A new type of elliptical vibrating equal thickness screen according to claim 2, characterized in that the movement states of the screen surface materials in each section of the new type elliptical vibrating equal thickness screen are different. The material particles on the screen surface in the feeding section are thrown at a medium speed on the screen surface; the material particles on the screen surface in the transition area of the intermediate section are slightly thrown on the screen surface, and gradually become a positive sliding motion as the throwing index decreases. ;Because the dynamic friction angle of the new elliptical vibrating equal-thickness screen is greater than the inclination angle of the screen surface, after a period of time, the positive sliding angle of the discharge section will be equal to the positive sliding stop angle, and the positive sliding will stop, and the amplitude of the discharge section perpendicular to the screen surface will be extremely high. Small, at this time the screen surface slides in reverse. 5. A new type of elliptical vibrating equal thickness screen according to claim 2, characterized in that the inclination angle of the screen surface is α=10°, the initial phase angle of the eccentric block m ₁ is 90°, and the initial phase angle between the eccentric block m ₂ and m ₁ The phase difference angle is 60°, the working frequency is n=900r/min, that is, ω=2πn/60≈94.2rad/s, the amplitude of the feeding section at the feeding end is 3mm, the vibration direction angle β ₁ =45°, and the feeding section is thrown The index D _is 2.02, and the starting angle of throwing

is 29.7°, throw-off angle θ _d =255°, throw-off coefficient _id =0.8, and the average velocity of the material on the screen surface in the feeding section is 0.13m/s. 6. A novel elliptical vibrating equal thickness screen according to claim 2, characterized in that the discharge section amplitude is 1 mm, the discharge end vibration direction angle β ₂ =-31 °, the reverse sliding index D _q0 is 1.2, reverse slip angle

, reverse slip angle

The reverse sliding angle θ _q =111°, the reverse sliding coefficient is i _q =0.3, and the average speed of the reverse sliding of the material in the discharge section of the screen surface is 0.01m/s. 7. A new type of elliptical vibrating equal-thickness screen according to claim 2, characterized in that the amplitude of the transition area of the screen surface is A=1.5-0.75mm, when the amplitude in the vertical direction of the screen surface decreases to A=1.5mm, the throwing index D _Middle = 1.38 > 1, nominal throwing start angle

If there is a solution, the material can appear throwing motion, and 1<D=1.38<1.75, so it is in a state of slight throwing motion. When the amplitude A=1mm, the forward sliding index D _ko =1.8, and the forward sliding start angle

, positive slip angle

, the forward sliding angle θ _k =186.2°, the forward sliding coefficient is i _k =0.52, and the average velocity in the transition area is 0.04m/s. 8. A new type of elliptical vibrating equal thickness screen according to claim 5-7, characterized in that when the eccentric blocks have the same radius of rotation, the thickness of the eccentric block of the driving shaft σ ₁ =35.0mm, (thickness of the eccentric block of the driven shaft σ ₂ =21.0mm,) excitation frequency f=13Hz, processing capacity Q=24.0kg/2min, that is, the ratio of the long axis to the short axis of the elliptical motion track of the screen machine is 4:1, the vibration frequency of the screen machine is 780r/min, and the processing capacity When it is 5t/(h·m ² ), the screening efficiency of the sieve machine is the highest, and when it is used to screen coal with an external moisture content of 2.10%, the efficiency can reach 96.8%.

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