A double-track motion vibrating screen and an application method

Abstract

The present invention relates to a double-trajectory motion vibrating screen with adjustable exciting force and a trajectory adjustment method, belonging to the technical field of drilling mud treatment equipment. The double-trajectory motion vibrating screen includes a machine base, an exciter A, an exciter B, a screen box and a support spring; the screen box is installed on the machine base through a plurality of support springs; an assembly plate is installed obliquely in the middle of the screen box; the exciter A is installed on the assembly plate; the exciter B is installed on the assembly plate below the exciter A; the exciter A includes an exciting motor and a variable eccentric block; variable eccentric blocks are fixedly installed on the two output shafts of the exciting motor respectively. The double-trajectory motion vibrating screen has a compact structure and ingenious design, achieving the solution of the problems of single motion trajectory and easy blockage existing in the existing vibrating screen through mode switching, and is particularly suitable for the need of screening mud during the oil drilling process.

Description

Technical Field

[0001] The present invention relates to a double - track motion vibrating screen and an application method thereof, belonging to the technical field of drilling mud treatment equipment. Background Art

[0002] During the process of oil drilling, a drilling vibrating screen is required to screen the mud so that the mud can be recycled. Existing vibrating screens mostly use an exciter with a single exciting force as the power to drive the vibrating screen to operate, and there is a problem that they can only operate in a single mode. The operating modes of existing vibrating screens are generally divided into a linear motion mode, a circular motion mode, and an elliptical motion mode. The vibrating screen with a linear motion mode has the advantages of high screening efficiency and the disadvantage of being easily blocked; the vibrating screens with a circular motion mode and an elliptical motion mode have the advantages of anti - blocking and the defect of easy damage to the screen mesh. Therefore, it is necessary to develop a vibrating screen with multi - track motion to solve the problem of the single operating mode existing in existing vibrating screens. Summary of the Invention

[0003] The purpose of the present invention is to provide a double - track motion vibrating screen with a compact structure and ingenious design to solve the problem of the single operating mode existing in existing vibrating screens.

[0004] The technical solution of the present invention is as follows:

[0005] A double - track motion vibrating screen includes a machine base, exciter A, exciter B, a screen box, and support springs; the screen box is installed on the machine base through a plurality of support springs; an assembly plate is installed on the screen box in an inclined shape; exciter A is installed on the assembly plate; exciter B is installed on the assembly plate below exciter A; it is characterized in that: exciter A includes an excitation motor and a variable eccentric block; variable eccentric blocks are respectively and fixedly installed on two output shafts of the excitation motor; the variable eccentric block includes a driving block, a driven slider, a return spring, and a connecting pin shaft; the driving block is eccentrically and fixedly installed on the output shaft of the excitation motor; a guide hole is arranged in the middle of the driving block; the driven slider is slidably installed at the lower end of the driving block; the connecting pin shaft is inserted at the bottom of the driven slider; the upper end of the connecting pin shaft passes through the driven slider and the driving block and extends into the interior of the guide hole; a sliding baffle is fixedly installed at the upper end of the connecting pin shaft; a return spring is sleeved on the connecting pin shaft below the sliding baffle; under the action of the elastic force of the return spring, the driven slider always has a tendency to press against the driving block; exciter B includes an excitation motor and a fixed eccentric block; fixed eccentric blocks are respectively and fixedly installed on two output shafts of the excitation motor.

[0006] The driving block has a "square block" structure; an assembly hole is arranged on the driving block above the guide hole; a telescopic joint is arranged above the assembly hole; the output shaft of the excitation motor is fixedly connected to the assembly hole through a flat key; a compression bolt is fixedly installed on the telescopic joint above the assembly hole.

[0007] On the inner wall of the guiding hole, guiding sliding grooves are symmetrically arranged; at the lower end of the guiding sliding grooves, mounting sliding grooves are provided; the guiding sliding grooves and the mounting sliding grooves communicate with each other; at both ends of the sliding baffle, guiding sliding pins are provided; the guiding sliding pins are slidably connected with the guiding sliding grooves.

[0008] The driven slider has a "semicircular" structure; a guiding sliding opening is arranged in the middle of the driven slider; the driven slider is slidably connected with the lower end of the driving block through the guiding sliding opening; a stepped through hole is arranged on the driven slider below the guiding sliding opening; the connecting pin shaft is slidably connected with the stepped through hole.

[0009] The connecting pin shaft has a "stepped shaft" type structure.

[0010] The fixed eccentric block has an integral structure; the fixed eccentric block has a semicircular structure; a connecting convex block is arranged in the middle of the upper end of the fixed eccentric block; the fixed eccentric block is fixedly connected with the output shaft of the excitation motor through the connecting convex block; an adapting hole is arranged in the middle of the fixed eccentric block; an adapting pin is installed in the adapting hole; an adapting plate is fixedly installed at the upper end of the adapting pin; the adapting plate is fixedly connected with the adapting hole; an adapting spring is installed on the adapting pin below the adapting plate.

[0011] The advantages of the present invention are as follows:

[0012] The double-track motion vibrating screen has a compact structure and ingenious design. The exciting force generated by the variable eccentric block during operation can change with the change of the rotational speed of the excitation motor. In this way, during operation, the vibrating screen can achieve a linear track motion mode and an elliptical track motion mode by changing the exciting force, thereby solving the problem of easy blockage existing in the existing vibrating screen through mode switching, and is especially suitable for the need of screening mud during the oil drilling process. Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of the present invention;

[0014] Figure 2 It is a schematic structural diagram of the exciter A and the exciter B of the present invention;

[0015] Figure 3 It is a schematic structural diagram of the variable eccentric block of the present invention;

[0016] Figure 4 It is Figure 3 The schematic structural diagram in the A-A direction in

[0017] Figure 5 It is a schematic structural diagram of the driving block of the present invention;

[0018] Figure 6 It is a schematic structural diagram of the driven slider of the present invention;

[0019] Figure 7 Structural schematic diagram of the fixed eccentric block of the present invention;

[0020] Figure 8 Schematic diagram of the centroid position of the resultant force under the translational elliptical motion trajectory of the present invention

[0021] Figure 9 Force analysis diagram of the vibrating screen under the translational elliptical motion trajectory;

[0022] Figure 10 Force analysis diagram of the vibrating screen under the variable linear motion trajectory;

[0023] Figure 11 Schematic diagram of the vibrating screen realizing the variable linear motion trajectory;

[0024] Figure 12 Schematic diagram of the rotating coordinate system;

[0025] Figure 13 Schematic diagram of the vibrating screen realizing the elliptical motion trajectory;

[0026] Figure 14 Function image of the straight line where the resultant force of the eccentric block exciting force is located under the variable linear motion trajectory of the vibrating screen;

[0027] Figure 15 Schematic diagram of the change of the magnitude of the resultant force of the eccentric block exciting force with time under the variable linear motion trajectory of the vibrating screen;

[0028] Figure 16 Schematic diagram of the translational elliptical motion trajectory of the vibrating screen under the exciting force of the eccentric block;

[0029] Figure 17 Schematic diagram of the change of the magnitude of the resultant force of the eccentric block exciting force with time under the translational elliptical motion trajectory of the vibrating screen;

[0030] Figure 18 Schematic diagram of the acceleration vector acting on the particles stuck in the sieve holes under the variable linear motion trajectory and the translational elliptical motion trajectory; (a) in the figure represents variable linear vibration; (b) represents translational elliptical vibration.

[0031] In the figure: 1. Machine base; 2. Exciter A; 3. Exciter B; 4. Sieve box 4; 5. Support spring; 6. Assembly plate; 7. Output shaft; 8. Fixed eccentric block; 9. Exciting motor; 10. Variable eccentric block; 11. Driving block; 12. Guide hole; 13. Driven slider; 14. Connecting pin shaft; 15. Sliding baffle; 16. Return spring; 17. Expansion joint; 18. Flat key; 19. Compression bolt; 20. Guide slide opening; 21. Guide chute; 22. Installation chute; 23. Guide slide pin; 24. Step through hole; 25. Connecting convex block; 26. Adaptation hole; 27. Adaptation pin; 28. Adaptation plate; 29. Adaptation spring. Detailed implementation mode

[0032] This double-track motion vibrating screen includes a machine base 1, an excitation vibrator A 2, an excitation vibrator B 3, a screen box 4, and support springs 5 (see the attached drawings of the specification Figure 1 ).

[0033] The screen box 4 is installed on the machine base 1 through a plurality of support springs 5 (see the attached drawings of the specification Figure 1 ). An assembly plate 6 is installed on the middle part of the screen box 4 in an inclined shape; the excitation vibrator A 2 is installed on the assembly plate 6; the excitation vibrator B 3 is installed on the assembly plate 6 below the excitation vibrator A 2 (see the attached drawings of the specification Figure 1 ).

[0034] The excitation vibrator A 2 includes an excitation motor 9 and a variable eccentric block 10 (see the attached drawings of the specification Figure 2 ); variable eccentric blocks 10 are fixedly installed on the two output shafts 7 of the excitation motor 9 respectively; when the excitation motor 9 works, it can drive the variable eccentric blocks 10 to rotate synchronously.

[0035] The variable eccentric block 10 includes a driving block 11, a driven slider 13, a return spring 16, and a connecting pin shaft 14; the driving block 11 is fixedly installed on the output shaft 7 of the excitation motor 9 in an eccentric shape (see the attached drawings of the specification Figure 3 ).

[0036] The driving block 11 has a "square block" structure (see the attached drawings of the specification Figure 5 ); a guide hole 12 is arranged in the middle of the driving block 11; an assembly hole is arranged on the driving block 11 above the guide hole 12; a telescopic joint 17 is arranged above the assembly hole; the output shaft 7 of the excitation motor 9 is fixedly connected to the assembly hole through a flat key 18; a compression bolt 19 is fixedly installed on the telescopic joint 17 above the assembly hole (see the attached drawings of the specification Figure 4 and 5 ). Under the action of the compression bolt 19, it can fixedly install the driving block 11 on the output shaft 7 of the excitation motor 9. In this way, when the excitation motor 9 works, it can drive the driving block 11 to rotate synchronously through the output shaft 7.

[0037] The lower end of the driving block 11 is slidably installed with a driven slider 13 (see the attached drawings of the specification Figure 4 ); the driven slider 13 has a "semicircular" structure; a guide sliding opening 20 is arranged in the middle of the driven slider 13; the driven slider 13 is slidably connected to the lower end of the driving block 11 through the guide sliding opening 20 (see the attached drawings of the specification Figure 6 ); a stepped through hole 24 is arranged on the driven slider 13 below the guide sliding opening 20; the connecting pin shaft 14 has a "stepped shaft" type structure and is slidably connected to the stepped through hole 24 (see the attached drawings of the specification Figure 4 and 6 ).

[0038] The upper end of the connecting pin shaft 14 passes through the driven slider 13 and the driving block 11 and then extends into the inside of the guiding hole 12; a sliding baffle 15 is fixedly installed at the upper end of the connecting pin shaft 14 (see the attached Figure 6 of the specification).

[0039] Guiding sliding grooves 21 are symmetrically arranged on the inner side wall of the guiding hole 12; an installation sliding groove 22 is arranged at the lower end of the guiding sliding groove 21; the guiding sliding groove 21 is communicated with the installation sliding groove 22; guiding sliding pins 23 are arranged at both ends of the sliding baffle 15; the guiding sliding pins 23 are slidably connected with the guiding sliding grooves 21. The purpose of arranging the driven slider 13 and the driving block 11 in this way is: when the excitation motor 9 works to drive the variable eccentric block 10 to rotate synchronously, when the rotation speed of the excitation motor 9 is relatively low, the driven slider 13 and the driving block 11 remain relatively fixed. When the excitation motor 9 moves at a high rotation speed, the driven slider 13 will overcome the elastic force of the return spring 16 under the action of centrifugal force, so that the driven slider 13 slides a certain distance relative to the driving block 11 and finally remains relatively fixed with the driving block 11.

[0040] The exciter B3 includes an excitation motor 9 and a fixed eccentric block 8; fixed eccentric blocks 8 are fixedly installed on the two output shafts 7 of the excitation motor 9 respectively.

[0041] The fixed eccentric block 8 is of an integral structure; the fixed eccentric block 8 is of a semi-circular structure; a connecting convex block 25 is arranged in the middle of the upper end of the fixed eccentric block 8; the fixed eccentric block 8 is fixedly connected with the output shaft 7 of the excitation motor 9 through the connecting convex block 25; an adapting hole 26 is arranged in the middle of the fixed eccentric block 8; an adapting pin 27 is installed in the adapting hole 26; an adapting plate 28 is fixedly installed at the upper end of the adapting pin 27; the adapting plate 28 is fixedly connected with the adapting hole 26; an adapting spring 29 is installed on the adapting pin 27 below the adapting plate 28 (see the attached Figure 7 of the specification). The purpose of arranging the fixed eccentric block 8 in this way is: to make the structure of the fixed eccentric block 8 consistent with the initial state of the variable eccentric block 10, so that the exciting forces generated by the variable eccentric block 10 and the fixed eccentric block 8 are the same when rotating at a low speed.

[0042] This double-track motion vibrating screen can realize two motion modes of tracks, one is a variable straight-line motion track mode and the other is a translational elliptical motion track mode.

[0043] The application method of this double-track motion vibrating screen is as follows:

[0044] 1. Determine the initial parameters of this vibrating screen;

[0045] Let the center point of the output shaft 7 of the variable eccentric block 10 be O1 ; The center point of the output shaft 7 of the fixed eccentric block 8 is O 2 ; Let the center of mass of the vibrating screen box 4 be C; The position of the center of mass C can be calculated by the solidworks software;

[0046] Let the total masses of the variable eccentric block 10 and the fixed eccentric block 8 be M 0 、M 1 ; The mass of the driving block 11 is m 0 , and the eccentricity is r 0 ; r 0 The value of can be calculated by the solidworks software; The mass of the driven slider 13 is m 1 , the eccentricity under the variable linear motion trajectory is r 1 , and the eccentricity under the translational elliptical motion trajectory is r 1 ′, r 1 can be calculated by the solidworks software;

[0047] Let the mass of the equivalent part of the fixed eccentric block 8 corresponding to the driven slider 13 be m 2 , and the eccentricity is r 2 ; Let the mass of the equivalent part of the fixed eccentric block 8 corresponding to the driving block 11 be m 3 , and the eccentricity is r 3 ; The eccentricity r 2 and the eccentricity r 3 can be calculated by the solidworks software;

[0048] Among them, M 0 = M 1 , m 0 = m 3 , m 1 = m 2 , r 0 = r 3 , r 1 = r 2 ≠ r 1 ′; The initial phase angles of the fixed eccentric block 8 and the variable eccentric block 10 are the same as α; The center distance between the two axes of the exciters A2 and B3 is 2l (see the attached drawings of the specification Figure 2 and Figure 8 ), and the included angle between the vertical bisector of the axis connection and the horizontal direction is the inclination angle β (see the attached drawings of the specification Figure 13 ); The screen mesh is installed horizontally; The elastic coefficient of the return spring 16 is k 1 , the compression amount of the given initial pre-tightening force of the return spring 16 is x; Set the rotational angular velocity of the fixed eccentric block 8 and the variable eccentric block 10 under the variable linear motion trajectory to be ω, and the rotational angular velocity under the translational elliptical motion trajectory to be ω′, and the critical angular velocity of the two motion trajectories to be ω″, all of which are controlled by the excitation motor 9; The mass of the vibrating screen box 4 is M2 , the combined stiffness k of the support spring 5 in the vertical direction, and the natural frequency ω of the vibrating screen n ;

[0049] 2. Determine the initial conditions of the vibrating screen;

[0050] (1) Determine the installation positions of the exciters A2 and B3;

[0051] Since the straight line where the resultant exciting force is located in the straight-line motion trajectory mode of the vibrating screen does not pass through the centroid C of the moving part of the vibrating screen 1 , and the force center L of the resultant exciting force coincides with the centroid C of the moving part of the vibrating screen in the translational elliptical motion trajectory mode 1 , the position of the force center L can be determined first. Given that the vector end trajectory of the resultant force in the elliptical motion trajectory is an ellipse, the major axis direction of the ellipse is the direction where the two exciting forces are the same, and the minor axis direction is the direction where the two exciting forces are opposite. Then the intersection point of the resultant forces in these two directions is the center of the ellipse, which is also the force center L; during on-site operation, the initial phase angles of the two eccentric blocks 8 are both α, and the rotational angular velocities ω′ are equal. Then the direction where the two exciting forces are the same is perpendicular to the connection line of the axes of the exciters A2 and B3, and the direction where the two exciting forces are opposite is on the connection line of the axes of the exciters A2 and B3; F 2 ′ and F 2 ″ are the resultant exciting forces in the direction where the two exciting forces are the same and the direction where the two exciting forces are opposite respectively. In the direction where the exciting forces F a and F b generated by the variable eccentric block 10 and the fixed eccentric block 8 are the same, there is the following force relationship formula (see the attached Figure 8 of the specification):

[0052] F 2 ′ = F a + F b # (1)

[0053] F 2 ′d = 2lF b # (2)

[0054] Among them, the expressions of the exciting forces F a and F b generated by the variable eccentric block 10 and the fixed eccentric block 8 are respectively:

[0055] F a = m 0 r 0 ω′ 2 + m 1 r 1 ′ω′ 2 # (3)

[0056] F b = m2 r 2 ω′ 2 +m 3 r 3 ′ω′ 2 # (4)

[0057] Rearranging equations (2), (3), and (4) gives:

[0058]

[0059] That is, the line where the resultant exciting force F 2 ′ is located and the center point O of the output shaft 7 of the variable eccentric block 10 1 The distance between them is d (see the attached drawings of the specification Figure 8 ). The intersection point of the two resultant force lines is the center of force L, and the center of force L is located on the axis connection O 1 O 2 of the exciters A2 and B3, and the distance between it and the O 1 of the variable eccentric block 10 is d; among them, the distance d changes with the magnitudes of the exciting forces F a and F b ;

[0060] Coinciding the center of force L with the centroid C of the moving part of the vibrating screen 1 is the key to the vibrating screen achieving a translational elliptical trajectory. The vibrating screen is regarded as a system composed of the screen box 4 and two groups of eccentric masses. First, by adjusting the installation positions of the exciters A2 and B3, the center of force L is made to coincide with the centroid C of the screen box 4, and the origin of the xoy coordinate system is placed at the centroid C, and the x-axis coincides with the axis connection of the exciters A2 and B3 (see the attached drawings of the specification Figure 9 ), then the coordinates of the center of force L are (x L , y L ); According to the eccentric block structures of the exciters A2 and B3, the mass relationship formula is:

[0061] M 0 =m 0 +m 1 # (6)

[0062] M 1 =m 2 +m 3 # (7)

[0063] M 0 =M 1 # (8)

[0064] Then write the expression for the position of the overall centroid C 1 (x C , y C ) of the moving part of the vibrating screen changing with time t:

[0065]

[0066] As can be seen from the above equations (9) and (10), due to the influence of the rotating eccentric mass, the centroid C 1 (x C , y C ) is not fixed, but changes periodically near a certain position. This certain position is the average value of the instantaneous positions of the centroid calculated based on the cancellation of the positive and negative values of the sine and cosine functions during the periodic change It is called the average centroid, and the expression is:

[0067]

[0068] Simplified from equations (6), (7), (11), and (12) to get:

[0069]

[0070] When M 0 +M 1 << M 2 , Since the eccentric block mass of the vibrator is much smaller than the mass of the sieve box 4, within a certain allowable range, the centroid C of the sieve box 4 can be used to approximately represent the centroid C of the moving part of the vibrating screen 1 , which simplifies the design work; at this time, making the force center coincide with the centroid of the moving part of the vibrating screen can achieve a translational elliptical motion. Under the linear motion trajectory, the straight line where the resultant force of the exciting force is located coincides with the perpendicular bisector of the axis connection of the vibrator A2 and the vibrator B3, and forms an offset Δx with the centroid (see the attached instruction Figure 10 ), then there is:

[0071] Δx = l - d# (15)

[0072] Thus, a variable linear trajectory motion can be achieved, and its offset Δx changes with the magnitudes of the exciting forces F a and F b .

[0073] (2) Determine the operating parameters of the motion trajectory mode;

[0074] The variable linear motion trajectory mode refers to the motion mode in on-site operation where the initial phase angles of the two eccentric blocks are both α (see the attached instruction Figure 10 ), and the two exciting motors 9 rotate in the same direction at the same speed within a certain limited angular velocity ω″ range. The translational elliptical motion trajectory mode refers to the motion mode where the initial phase angles of the two eccentric blocks are both α and the angular velocity is greater than ω″, and they rotate in the same direction at the same speed; this angular velocity ω″ is the critical value at which the centrifugal force of the driven slider 13 is balanced with the pre-tightening force F 3 of the spring 5, and the expression is:

[0075] m 1 ω″ 2 r 1 = k 1 x# (16)

[0076] After arrangement, we get:

[0077]

[0078] In this way, the critical angular velocity ω″ is obtained. When the moving angular velocities of the exciters A2 and B3 are less than ω″, it is a variable linear motion mode; when the moving angular velocities of the exciters A2 and B3 are greater than ω″, it is a translational elliptical motion trajectory mode;

[0079] When the critical angular velocity ω″ is less than the rated speed of the excitation motor 9, directly enter step 3;

[0080] When the critical angular velocity ω″ is greater than the rated speed of the excitation motor 9, reduce the compression amount x of the spring 5 to reduce the pre-tightening force of the spring 5 so that the critical angular velocity ω″ is less than the rated speed of the excitation motor 9, and then enter step 3.

[0081] 3. Operating steps of this vibrating screen;

[0082] 3.1) The startup process of this vibrating screen is as follows;

[0083] Synchronously start the excitation motors 9 of the exciters A2 and B3; when the two excitation motors 9 are just started, control the rotational angular velocity below the critical angular velocity ω″. At this time, the excitation force generated by the variable eccentric block 10 is not sufficient to overcome the pre-tightening force of the return spring 16 and the structure does not change. It is the same as the structure of the fixed eccentric block 8, and the two excitation forces generated are equal. By reasonably adjusting the installation positions of the exciters A2 and B3 in advance, make the straight line where the resultant force of this excitation force is located not pass through the centroid C of the moving part of the vibrating screen 1 , and at this time, this vibrating screen vibrates in a variable linear trajectory;

[0084] 3.2) The screening process of this vibrating screen is as follows;

[0085] When this vibrating screen vibrates in a variable linear trajectory, it has the advantage of high screening efficiency. At this time, input the slurry into the screen box 4, and the screen box 4 screens the slurry by vibrating in a variable linear trajectory. During the screening process when the screen box 4 vibrates in a variable linear trajectory, when the screen box 4 is severely blocked and affects the screening efficiency; adjust the excitation motors 9 of the exciters A2 and B3 so that the rotational angular velocities of the exciters A2 and B3 move at a speed greater than the critical value ω″. At this time, the screen box 4 vibrates in a translational elliptical trajectory;

[0086] When the rotational angular velocity of the excitation motors 9 of the exciters A2 and B3 is controlled above the critical angular velocity ω″, the exciting force generated by the variable eccentric block 10 overcomes the pre-tightening force of the spring and the structure changes. The eccentricity gradually increases, that is, the resistance moment also gradually increases, avoiding the problem of a large starting resistance moment. Eventually, the eccentricities generated by the exciters A2 and B3 are different, that is, the two exciting forces obtained are not equal, and the center of force L of the resultant force of the two exciting forces coincides with the centroid C of the moving part of the vibrating screen. 1 At this time, the vibrating screen vibrates in a translational elliptical trajectory.

[0087] When the screen box 4 vibrates in a variable straight-line trajectory, although it has the advantage of high screening efficiency, the acceleration vector during its operation only acts in one direction. For solid-phase particles stuck in the sieve holes, there is a throwing dead zone (i.e., the direction where the acceleration vector is zero), and it is very difficult to throw them out of the sieve holes, which is not conducive to the solid control of the drilling fluid and is prone to clogging problems. The "major axis" of the ellipse of the translational elliptical vibrating screen is the component that strengthens the removal of drill cuttings, and the "minor axis" is the component that promotes the drilling fluid to pass through the sieve, which can significantly reduce the phenomena of "sieve blockage" and "sieve paste", thus solving the clogging problem of the screen box 4.

[0088] After the clogging problem of the screen box 4 is solved, the rotational angular velocity of the excitation motors 9 of the exciters A2 and B3 is controlled below the critical angular velocity ω″ to make the vibrating screen vibrate in a variable straight-line trajectory; by repeating such actions in a cycle, the purpose of efficiently screening the drilling fluid with the vibrating screen vibrating in a variable straight-line trajectory and solving the clogging problem with a translational elliptical trajectory can be achieved.

[0089] 3.3) The shutdown process of the vibrating screen is as follows.

[0090] Adjust the excitation motors 9 of the exciters A2 and B3 to gradually reduce their speeds to 0; during this process, as the speed of the excitation motor 9 decreases, the centrifugal force generated by the driven slider 13 on the variable eccentric block 10 is not sufficient to overcome the elastic force of the spring, and the driven slider 13 slowly slides towards the direction of the rotation center, the eccentricity decreases, the moment of inertia decreases, and thus the speed decreases rapidly, making it easy for the vibrating screen to stop.

[0091] To verify the correctness of this application, the applicant carried out the following calculation verification;

[0092] Calculation process of variable straight-line motion trajectory

[0093] When the angular velocity is less than ω″, the centrifugal force generated by the driven slider 13 in the variable eccentric block 10 is not sufficient to overcome the pre-tightening force of the spring, and the structure remains unchanged. In this mode, when the driving block 11 drives the driven slider 13 to rotate, under the action of the centrifugal force, the driven slider 13 cannot overcome the elastic force of the return spring 16 through the sliding baffle 8, that is, it cannot slide along the guiding chute 21 and the structure does not change, and it is the same as the eccentric block structure of another vibrator. Thus, the two exciting forces generated are equal. As Figure 10 shown, the expressions of the exciting forces are respectively:

[0094] F′ = (m 0 r 0 + m 1 r 1 )ω 2 # (18)

[0095] F″ = (m 2 r 2 + m 3 r 3 )ω 2 # (19)

[0096] The equations of the action lines of the two eccentric block forces F′ and F″ are respectively:

[0097] y 1 = -tan(α + ωt)(x 1 - l)# (20)

[0098] y 2 = tan(α + ωt)(x 2 - l)# (21) Since the equations of the action lines of the two eccentric block forces F′ and F″ are in the same coordinate system, and in the actual installation, the installation inclinations of the vibrator A2 and the vibrator B3 are β, according to the knowledge of the rotation of the function image around the coordinate origin in the rectangular coordinate system, then (20) and (21) can be sorted out to obtain the equation of the action line of the resultant force F 1 as:

[0099] y = -l tan(α + ωt)# (22)

[0100]

[0101] The schematic diagram is as Figure 11 shown. According to equations (18) and (19), the expression of the magnitude of the resultant force F 1 changing with time is:

[0102] F 1 = 2(m 0 r 0 + m 1 r 1 )ω 2sin(α + ωt) # (24)

[0103] Then the resultant exciting force generated by exciters A2 and B3 is as follows:

[0104] F 3 = 4(m 0 r 0 + m 1 r 1 )ω 2 sin(α + ωt) # (25) By reasonably adjusting the installation positions of exciters A2 and B3 in advance, the straight line where the resultant exciting force is located does not pass through the centroid C of the moving part of the vibrating screen 1 .

[0105] Thus, it can be obtained that when the rotational angular velocity of the excitation motor 9 is lower than ω″, since the variable eccentric block 10 does not change its structure, the resultant force generated by exciters A2 and B3 does not pass through the centroid C of the moving part of the vibrating screen 1 , and it can be concluded that the vibrating screen has a variable straight-line motion trajectory; the calculation process of the translational elliptical motion trajectory

[0106] When the angular velocity is greater than ω″, the vibrating screen is in the translational elliptical motion trajectory mode. Specifically, during on-site operation, when the initial phase angles are the same as α and the two excitation motors 9 rotate in opposite directions at the same speed, the centrifugal force generated by the driven slider 13 in the variable eccentric block 10 increases, overcoming the pre-tightening force of the spring to further compress the spring, thereby changing the structure. In this mode, when the driving block 11 drives the driven slider 13 to rotate, under the action of the centrifugal force, the driven slider 13 slides along the guiding chute 21 by overcoming the elastic force of the return spring 16 through the sliding baffle 8, resulting in a structural change. At this time, the newly generated compression amount of the spring is Δy, and the total compression amount of the spring is (x + Δy). The following relational expression can be obtained:

[0107] m 1 ω′ 2 r 1 ′ = k 1 (x + Δy) # (26)

[0108] Meanwhile, the eccentric distances r 1 ′ and r 2 generated by the equivalent parts of the driven slider 13 and the fixed eccentric block 8 are not equal, and the following relational expression exists:

[0109] r 1 ′ = r 2 + Δy # (27)

[0110] Since r 1 = r 2 , the following can be obtained:

[0111] r1 ′ = r 1 + × y# (28)

[0112] By arranging equations (26) and (28), the expression for Δy is obtained as follows:

[0113]

[0114] Substituting into equation (28) gives the expression for r 1 ′ as follows:

[0115]

[0116] Thus, it is obtained that the eccentric block structures of vibrator A2 and vibrator B3 are different, that is, the two exciting forces obtained are not equal, realizing the translational elliptical trajectory motion of the vibrating screen. The schematic diagram is as Figure 9 shown. Let E, D, A, B, β 1 , β 2 , X, Y, P, Q, S, T, X′ and Y′ be reference symbols, and let

[0117] E = m 0 r 0 + m 1 r 1 ′# (31)

[0118] D = m 2 r 2 + m 3 r 3 # (32)

[0119] According to equations (3), (4), (31), and (32), the exciting forces F a , F b generated by the variable eccentric block 10 and the fixed eccentric block 8 are respectively expressed as:

[0120] F a = Eω′ 2 # (33)

[0121] F b = Dω′ 2 # (34)

[0122] Performing a dynamic analysis on the double-vibrator translational elliptical vibrating screen, the expression of the motion differential equation is:

[0123]

[0124] where M ------ the sum of the mass of the screen box 4 and the mass of the drilling fluid participating in vibration;

[0125] c x , c y------Damping coefficients in the x- and y-directions;

[0126] k x ,k y ------Stiffness coefficients in the x- and y-directions;

[0127] x, y, ------Displacements, velocities, and accelerations in the x- and y-directions, respectively.

[0128] Let

[0129] (Eω′ 2 -Dω′ 2 )cos(α + ω′t) = A cos(β 1 + ω′t)# (37)

[0130] (Eω′ 2 -Dω′ 2 )cos(α + ω′t) = B cos(β 2 + ω′t)# (38)

[0131] Then we have

[0132]

[0133]

[0134] After rearrangement, we get:

[0135] β 1 = β 2 = α# (43) The steady-state solution of the differential equation of motion can be expressed as:

[0136]

[0137] It can be solved to obtain:

[0138]

[0139] where ω nx -------Natural frequency in the x-direction,

[0140] ω ny -------Natural frequency in the y-direction,

[0141] ξ x , ξ y -------Viscous damping factors in the x- and y-directions, respectively,

[0142] For simplicity in calculation, let again:

[0143]

[0144] wherein

[0145]

[0146] By eliminating the parameter t, the equation of the motion trajectory is obtained as follows:

[0147] (S 2 + T 2 )X 2 - 2XY(SQ + PT)+(P 2 + Q 2 )Y 2 = (PS - QT) 2 # (52)

[0148] As shown in Figure 9 and Figure 12 , the coordinate system xOy is rotated by an angle Λ to the coordinate system x'Oy' to eliminate the XY product term and standardize the equation. The relationship between the X and Y quantities in the coordinate system xOy and the X' and Y' quantities in the coordinate system x'Oy' is obtained as follows:

[0149] X = X'cosδ - Y'sinδ# (53)

[0150] Y = X'sinδ - Y'cosδ# (54) After rearrangement, the ellipse equation is obtained as follows:

[0151]

[0152] wherein

[0153] the angle between the major axis direction and the x-axis is δ and the semi-axis lengths on the x' axis and y' axis are respectively:

[0154]

[0155] and

[0156]

[0157] If k x , k y , c x , c y and M are known, the ellipse trajectory diagram can be obtained by computer. In actual design, k x = k y = k, c x = c y = 0 can be set, then ω nx = ωny = ω n , ξ x = ξ y = 0, The coefficients in the equation are respectively:

[0158] The rotation angle δ of the coordinate axes should satisfy:

[0159]

[0160] Substitute A, B, β 1 and β 2 into Equation (58), and the rotation angle can be obtained:

[0161] δ = 0# (59)

[0162] Then as Figure 12 shown, the coordinate system x′Oy′ coincides with the coordinate system xOy, and the semi-major axis length A on the x′ axis can be calculated x as:

[0163]

[0164] The semi-major axis length A on the y′ axis y is:

[0165]

[0166] Substitute Equations (31) and (32) and simplify to get:

[0167]

[0168] Then the equation of the motion trajectory of the translating ellipse is:

[0169]

[0170] Since the installation inclinations of the exciters A2 and B3 are β during actual installation, taking the center of mass C as the origin of the coordinate system, the direction parallel to the screen as the x′ axis, and the direction perpendicular to the screen as the y′ axis, a rectangular coordinate system x′cy′ is established. As Figure 13 shown, according to the knowledge of the rotation of the ellipse around the origin of the coordinate system in the rectangular coordinate system, Equation (64) can be simplified to obtain the final equation of the motion trajectory of the translating ellipse as:

[0171]

[0172] Among them, the displacement in the y′ direction is the displacement S1 in the direction perpendicular to the screen surface, and the displacement in the x′ direction is the displacement S2 in the direction along the screen surface.

[0173] As Figure 9As shown, according to equations (3) and (4), the resultant force F generated by the two exciting forces 2 has an expression for its variation with time as follows:

[0174] F 2 =[F a 2 +F b 2 -2F a F b cos(2α + 2ω′t)] 1 / 2 # (66)

[0175] Then the resultant exciting force generated by exciter A2 and exciter B3 is:

[0176] F 4 = 2[F a 2 +F b 2 -2F a F b cos(2α + 2ω′t)] 1 / 2 # (67)

[0177] In this way, when the rotational angular velocity of the exciting motor 9 is greater than ω″, due to the structural change of the variable eccentric block 10, when the center of force L that generates the resultant force of exciter A2 and exciter B3 coincides with the center of mass C of the moving part of the vibrating screen 1 it can be obtained that the vibrating screen has a translational elliptical motion trajectory; to verify the correctness of this application, the applicant has carried out specific practical applications, and the examples of practical applications are as follows.

[0178] 1. Determine the initial parameters of the vibrating screen;

[0179] Suppose the total mass M of the fixed eccentric block 8 and the variable eccentric block 10 is 25 kg each, the mass m 0 of the driving block 11 is 5 kg, and the eccentricity r 0 is 0.1 m; the mass m 1 of the driven slider 13 is 20 kg, and the eccentricity r 1 under the variable linear motion trajectory is 0.12 m; the mass m 2 of the equivalent part of the fixed eccentric block 8 to the driven slider 13 is 20 kg, and the eccentricity is r 2 is 0.12 m; the mass m 3 of the equivalent part of the fixed eccentric block 8 to the driving block 11 is 5 kg, and the eccentricity r 3 is 0.1 m; the initial phase angle α of the fixed eccentric block 8 and the variable eccentric block 10 is The installation center distance 2l between exciter A2 and exciter B3 is 0.3 m, and the inclination angle β is The elastic coefficient of the return spring 16 is k 1 is 5700 N / m, the compression amount x of the initial pre-tightening force of the return spring 16 is 0.02 m, the rotational angular velocity ω of the fixed eccentric block 8 and the variable eccentric block 10 under the variable linear motion trajectory is 2.1π rad / s, the rotational angular velocity ω′ under the translational elliptical motion trajectory is 3.8π rad / s, the combined stiffness k of the support spring 5 in the vertical direction is 40000 N / m, and the natural frequency ω n of this vibrating screen is 12.9 s -1 .

[0180] 2. Determine the initial conditions

[0181] (1) Determine the installation positions of the vibrator A2 and the vibrator B3;

[0182] As Figure 8 shown, the force center L on the axis connection O 1 O 2 of the vibrator A2 and the vibrator B3, and the distance d expression between the variable eccentric block 10 at O 1 is shown in Equation (5). Substituting the data, we get:

[0183]

[0184] In actual situations, the mass of the eccentric block of the vibrator is much smaller than the mass of the screen box 4, so the centroid C of the screen box 4 can be used to approximately represent the centroid C of the moving part of the vibrating screen 1 , which simplifies the design work. Coincide the force center L with the centroid C of the screen box 4, place the origin of the xoy coordinate system at the centroid C, and the x-axis coincides with the axis connection of the vibrator A2 and the vibrator B3. As Figure 9 shown, at this time, it is considered that the force center L coincides with the centroid C 1 of the moving part of the vibrating screen, and translational elliptical motion can be achieved. Under the linear motion trajectory, the straight line where the resultant exciting force is located coincides with the perpendicular bisector of the axis connection of the vibrator A2 and the vibrator B3, and forms an offset Δx with the centroid. As shown in Equation (15), substituting the data to obtain the offset as

[0185] Δx = l - d = 0.032 m# (69)

[0186] Thus, variable linear trajectory motion can be achieved.

[0187] (2) Determine the operating parameters of the motion trajectory mode;

[0188] The variable linear motion trajectory mode means that during on-site operation, when the initial phase angles are the same the two exciting motors 9 rotate in the same direction at the same speed within a certain limited angular velocity ω″ range, as Figure 10as shown; the angular velocity ω″ is the critical value at which the centrifugal force of the driven slider 13 is balanced with the pre-tightening force F of the spring 3 Substituting the data into expression (17), we get:

[0189]

[0190] In this way, the critical angular velocity ω″ is obtained as 6.892 rad / s. When the angular velocity is less than 6.892 rad / s, it is in the variable linear motion mode, and when it is greater than 6.892 rad / s, it is in the translational elliptical motion trajectory mode.

[0191] 3. Operating steps of the vibrating screen;

[0192] 3.1) The startup process of the vibrating screen is as follows;

[0193] When the two excitation motors 9 are just started, the rotational angular velocity is controlled below the critical angular velocity of 6.892 rad / s. At this time, the excitation force generated by the variable eccentric block 10 is not sufficient to overcome the pre-tightening force of the return spring 16, and the structure remains unchanged. It is the same as the structure of the fixed eccentric block 8, and the two excitation forces generated are equal. By reasonably adjusting the installation positions of the exciter A2 and the exciter B3 in advance, the straight line where the resultant force of the excitation force is located does not pass through the centroid C of the moving part of the vibrating screen 1 , and at this time, the vibrating screen vibrates in a variable linear trajectory;

[0194] 3.2) The screening process of the vibrating screen is as follows;

[0195] When the vibrating screen vibrates in a variable linear trajectory, it has the advantage of high screening efficiency. At this time, the mud is input into the screen box 4, and the screen box 4 screens the mud by vibrating in a variable linear trajectory. During the screening process when the screen box 4 vibrates in a variable linear trajectory, when the screen box 4 is severely blocked and affects the screening efficiency; adjust the excitation motors 9 of the exciter A2 and the exciter B3 so that the rotational angular velocities of the exciter A2 and the exciter B3 move at a speed greater than the critical value of 6.892 rad / s. At this time, the screen box 4 vibrates in a translational elliptical trajectory to solve the blockage problem. After the problem is solved, the rotational angular velocities of the excitation motors 9 of the exciter A2 and the exciter B3 are controlled below the critical angular velocity of 6.892 rad / s, so that the vibrating screen vibrates in a variable linear trajectory; repeating such actions can achieve the purpose of efficiently screening the drilling fluid with the vibrating screen vibrating in a variable linear trajectory and solving the blockage with a translational elliptical trajectory vibration.

[0196] The rotational angular velocity of the excitation motors 9 of the exciters A2 and B3 is controlled above the critical angular velocity of 6.892 rad / s. At this time, the excitation force generated by the variable eccentric block 10 overcomes the pre-tightening force of the spring, and the structure changes. The eccentricity gradually increases, that is, the resistance moment also gradually increases, avoiding the problem of a large starting resistance moment. Eventually, the eccentricities generated by the exciters A2 and B3 are different, that is, the two excitation forces obtained are not equal, and the center of force L of the resultant force of the two excitation forces coincides with the center of mass C of the moving part of the vibrating screen. 1 At this time, the vibrating screen vibrates in a translational elliptical trajectory.

[0197] 3.3) The shutdown process of the vibrating screen is as follows.

[0198] Adjust the excitation motors 9 of the exciters A2 and B3 to gradually reduce their speeds to 0; during this process, as the speed of the excitation motor 9 decreases, the centrifugal force generated by the driven slider 13 on the variable eccentric block 10 is not sufficient to overcome the elastic force of the spring, and the driven slider 13 slowly slides towards the direction of the rotation center, the eccentricity decreases, the moment of inertia decreases, and thus the speed decreases rapidly, making it easy for the vibrating screen to stop.

[0199] 4. Double-trajectory calculation

[0200] (1) Calculation process of the variable linear motion trajectory

[0201] When the angular velocity is less than 6.892 rad / s, the vibrating screen vibrates in a variable linear trajectory, and the resultant force F of the excitation forces generated by the eccentric blocks of the exciters A2 and B3 1 The equation of the action line is shown in Equations (22) and (23). Substituting the data and organizing, we get

[0202]

[0203] Then the function image of the straight line where the resultant force of the eccentric block excitation force is located under the variable linear motion trajectory of the vibrating screen can be obtained as Figure 14 shown.

[0204] The resultant force F of the excitation forces generated by the exciters A2 and B3 3 The expression is shown in Equation (25). Substituting the data and organizing, we get

[0205]

[0206] Then the schematic diagram of the change of the magnitude of the resultant force of the eccentric block excitation force with time under the variable linear motion trajectory of the vibrating screen can be obtained as Figure 15 shown.

[0207] (2) Calculation process of the translational elliptical motion trajectory

[0208] When the angular velocity is greater than 6.892 rad / s, the vibrating screen is in the translational elliptical motion trajectory mode. In this mode, the angular velocity ω′ is 3.8π rad / s. Substituting the data into Equation (30) gives the value of r 1 ′ as:

[0209]

[0210] Through the derivation in the previous text, it can be obtained that Figure 13 The calculation expressions for the semi-major axis length on the x′ axis and the semi-major axis length on the y′ axis shown are as shown in Equations (62) and (63) respectively. Substituting the data and organizing gives:

[0211]

[0212] Substituting the calculation results of Equations (75) and (76) and the known parameters into the motion trajectory equation (65) of the translational ellipse and organizing gives

[0213] 485.775x 2 +188.362y 2 -515.135xy = 1# (77)

[0214] The schematic diagram of the translational elliptical motion trajectory of the vibrating screen under the exciting force of the eccentric block can be obtained as shown in Figure 16 shown.

[0215] According to the exciting forces F a 、F b generated by the variable eccentric block 10 and the fixed eccentric block 8, the expressions (3), (4), and the resultant exciting force F 4 of the exciting force generated by the exciters A2 and B3, substituting the data and organizing gives:

[0216]

[0217] The schematic diagram of the change of the resultant exciting force of the eccentric block of the vibrating screen under the translational elliptical motion trajectory with time can be obtained as shown in Figure 17 shown.

[0218] This double-trajectory motion vibrating screen has a compact structure and ingenious design. The exciting force generated by the variable eccentric block 10 during operation can change with the change of the rotational speed of the exciting motor 9. When working in this way, the vibrating screen can achieve the variable straight-line trajectory motion mode and the translational elliptical trajectory motion mode by changing the exciting force, thereby solving the problems of single motion trajectory and easy blockage existing in the existing vibrating screen through mode switching, and is especially suitable for the need of screening mud during oil drilling.

Claims

1. A double-track motion vibrating screen, comprising a machine base (1), an exciter A (2), an exciter B (3), a screen box (4) and support springs (5); the screen box (4) is mounted on the machine base (1) through a plurality of support springs (5); an assembly plate (6) is mounted on the middle part of the screen box (4) in an inclined shape; an exciter A (2) is mounted on the assembly plate (6); an exciter B (3) is mounted on the assembly plate (6) below the exciter A (2); Characterized in that: The exciter A (2) includes an excitation motor (9) and a variable eccentric block (10); variable eccentric blocks (10) are fixedly mounted on the two output shafts (7) of the excitation motor (9) respectively; the variable eccentric block (10) includes a driving block (11), a driven slider (13), a return spring (16) and a connecting pin shaft (14); the driving block (11) is fixedly mounted on the output shaft (7) of the excitation motor (9) in an eccentric shape; a guide hole (12) is arranged in the middle of the driving block (11); the lower end of the driving block (11) is slidably mounted with the driven slider (13); the connecting pin shaft (14) is inserted at the bottom of the driven slider (13); the upper end of the connecting pin shaft (14) passes through the driven slider (13) and the driving block (11) and then extends into the interior of the guide hole (12); a sliding baffle (15) is fixedly mounted at the upper end of the connecting pin shaft (14); a return spring (16) is sleeved on the connecting pin shaft (14) below the sliding baffle (15); under the action of the elastic force of the return spring (16), the driven slider (13) always has a tendency to press against the driving block (11); the exciter B (3) includes an excitation motor (9) and a fixed eccentric block (8); fixed eccentric blocks (8) are fixedly mounted on the two output shafts (7) of the excitation motor (9) respectively; The fixed eccentric block (8) is of an integral structure; the fixed eccentric block (8) is of a semi-circular structure; a connecting convex block (25) is arranged in the middle of the upper end of the fixed eccentric block (8); the fixed eccentric block (8) is fixedly connected with the output shaft (7) of the excitation motor (9) through the connecting convex block (25); an adaption hole (26) is arranged in the middle of the fixed eccentric block (8); an adaption pin (27) is installed in the adaption hole (26); an adaption plate (28) is fixedly mounted at the upper end of the adaption pin (27); the adaption plate (28) is fixedly connected with the adaption hole (26); an adaption spring (29) is mounted on the adaption pin (27) below the adaption plate (28); The exciting force generated by the variable eccentric block (10) during operation changes with the change of the rotational speed of the excitation motor (9), and the linear trajectory motion mode and the elliptical trajectory motion mode are switched by changing the exciting force.

2. A double-track motion vibrating screen according to claim 1, Characterized in that: The driving block (11) is of a "square block" structure; an assembly hole is arranged on the driving block (11) above the guide hole (12); a telescopic joint (17) is arranged above the assembly hole; the output shaft (7) of the excitation motor (9) is fixedly connected with the assembly hole through a flat key (18); a pressing bolt (19) is fixedly mounted on the telescopic joint (17) above the assembly hole.

3. A double-track motion vibrating screen according to claim 2, characterized in that: guide chutes (21) are symmetrically arranged on the inner side walls of the guide holes (12); an installation chute (22) is arranged at the lower end of the guide chute (21); the guide chute (21) communicates with the installation chute (22); guide sliding pins (23) are arranged at both ends of the sliding baffle (15); the guide sliding pins (23) are slidably connected with the guide chute (21).

4. A double-track motion vibrating screen according to claim 2, characterized in that: the driven slider (13) has a "semicircular" structure; a guide sliding opening (20) is arranged in the middle of the driven slider (13); the driven slider (13) is slidably connected with the lower end of the driving block (11) through the guide sliding opening (20); a stepped through hole (24) is arranged on the driven slider (13) below the guide sliding opening (20); the connecting pin shaft (14) is slidably connected with the stepped through hole (24).

5. A double-track motion vibrating screen according to claim 4, characterized in that: the connecting pin shaft (14) has a "stepped shaft" type structure.

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