A method for pre-tightening a screw pump screw sleeve

Abstract

The application discloses a screw pump screw sleeve pre-tightening method and belongs to the technical field of screw pump machining, and comprises the following steps: S1, clamping nuts are installed at the pre-tightening positions of screw sleeves; S2, a transmission shaft and the screw sleeves are placed in a pre-tightening device, and the pre-tightening device is assembled; S3, a hydraulic pump is started, and the hydraulic stretcher makes the transmission shaft produce elastic deformation; S4, according to the functional relationship between the pre-tightening torque and the output pressure of the hydraulic pump, the clamping nuts are locked when the pre-tightening torque reaches the technical requirement; and S5, the hydraulic pump pressure is unloaded, and the pre-tightening device is disassembled. The application can accurately control the pre-tightening torque of the screw sleeve, does not bring about destructive torsional load, and avoids damage to the clamping nuts and the transmission shaft.

Description

Technical Field

[0001] This invention belongs to the field of screw pump processing technology, and particularly relates to a method for pre-tightening the screw sleeve of a screw pump. Background Technology

[0002] A twin-screw pump is a rotary pump that transports or pressurizes liquids by relying on the change and movement of the meshing space formed by the pump body and the screws. When the driving screw rotates, it simultaneously drives the driven screw meshing with it to rotate. The meshing space volume of the screws at the suction end gradually increases, and the pressure decreases. Under the action of pressure difference, the liquid enters the meshing space volume. When the volume increases to form a sealed cavity, the liquid moves continuously axially in each sealed cavity until it reaches the discharge end. At this time, the meshing space volume of the screws at the discharge end gradually decreases, and the liquid is discharged.

[0003] In the traditional screw pump sleeve pre-tightening process, the sleeve is usually pre-tightened by striking with a wrench or torque wrench. This pre-tightening method has the following drawbacks: 1. It is impossible to accurately control the pre-tightening torque of the sleeve; 2. It will generate a destructive torsional load, which can easily damage the clamping nut and drive shaft, causing damage to the clamping nut and making it impossible to disassemble, and at the same time causing potential hazards such as deformation of the drive shaft. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a screw pump helical sleeve pre-tightening method that can precisely control the helical sleeve pre-tightening torque, generating only axial tensile loads and avoiding destructive torsional loads, thus preventing damage to the clamping nut and drive shaft, thereby achieving high-quality assembly.

[0005] This invention is implemented as follows: a method for pre-tightening the screw sleeve of a screw pump, comprising the following steps:

[0006] S1. Install the clamping nut in the pre-tightened position of the screw sleeve;

[0007] S2. Place the drive shaft and screw sleeve into the pre-tightening device to complete the assembly of the pre-tightening device;

[0008] The pre-tightening device includes a support sleeve, in which the drive shaft and the spiral sleeve are placed. One end of the support sleeve is fitted with a pressure plate that abuts against the drive shaft. A clamping nut for limiting the position of the pressure plate is located on the drive shaft outside the pressure plate. The other end of the support sleeve, opposite the pressure plate, is fitted with a tensioning head threaded onto the drive shaft. A hydraulic tensioner is mounted on the tensioning head, with its piston end face abutting against the tensioning head. The cylinder end face of the hydraulic tensioner abuts against the support sleeve via a support ring. The hydraulic tensioner is connected to an external hydraulic pump via a quick-connect coupling.

[0009] The pressure plate is abutted against the support sleeve through the annular groove, and the clamping nut is tightened to ensure that the position of the pressure plate is relatively fixed; the hydraulic tensioner is set on the tensioning head, and the tensioning head is threaded onto the drive shaft. The cylinder end face of the hydraulic tensioner abuts against the support sleeve through the support ring to complete the assembly of the pre-tightening device.

[0010] S3. Start the hydraulic pump, and the hydraulic tensioner causes the drive shaft to undergo elongated elastic deformation.

[0011] S4. Based on the functional relationship between the preload torque and the hydraulic pump output pressure, tighten the clamping nut when the required preload torque is reached.

[0012] S5. Unload the hydraulic pump pressure and disassemble the pre-tightening device.

[0013] Furthermore, an annular groove for engaging the support sleeve is provided on the end face of the pressure plate that abuts against the support sleeve.

[0014] Furthermore, the functional relationship between the preload torque and the hydraulic pump output pressure in step S4 is as follows:

[0015] Calculate the preload P0:

[0016] P0 = σ0·As (1)

[0017] As = Π·ds·ds / 4 (2)

[0018] ds = (d2 + d1 - H / 6) / 2 (3)

[0019] σ0 = (0.5~0.7)σs (4)

[0020] Where: σ0 is the allowable stress of the material, and σs is the yield strength of the material, in units of... H is the nominal working height of the thread tooth, in mm; d1 is the minor diameter of the thread, in mm; d2 is the minor diameter of the thread, in mm; ds is the calculated diameter of the critical section of the thread, in mm; As is the nominal stress cross-sectional area, in mm. ;

[0021] Calculate the preload torque Mt = K· ·d / 1000 Nm (5)

[0022] Where K is the tightening factor; d is the nominal diameter of the thread, in mm;

[0023] K-value lookup table:

[0024]

[0025] The relationship between high-pressure oil pressure and tensile force in a hydraulic tensioner:

[0026] P1=F1 / A1(6)

[0027] P2=P1(7)

[0028] Where: P1 is the high-pressure oil pressure in the hydraulic tensioner, in MPa; F1 is the thread tensioning force of the tensioning head, in kN; A1 is the hydraulic area in the hydraulic tensioner, in kN. P2 is the hydraulic pump output pressure, in MPa.

[0029] Relationship between hydraulic pump output pressure and preload torque:

[0030] When the tension force F1 of the threaded head reaches the preload P0, and the drive shaft is within the elastic deformation range, it can be seen from the above equations (1) to (7):

[0031] Mt=K·P2·A1·d / 1000(8)

[0032] P2≤(0.5~0.7)σs·(d2+d1-H / 6)2·Π / 16(9)

[0033] From equation (8), it can be seen that the preload torque Mt is directly proportional to the tightening coefficient K, the hydraulic pump output pressure P2, the hydraulic area A1 in the hydraulic tensioner, and the nominal thread diameter d. When the hydraulic tensioner is determined, the hydraulic area A1 in the hydraulic tensioner and the nominal thread diameter d are constants, that is, equation (8) is changed to:

[0034] Mt=C·K·P2(10)

[0035] Where: C is a constant;

[0036] As can be seen from equation (10), when the tightening coefficient K is determined and the transmission shaft is within the elastic deformation range, the preload torque Mt and the hydraulic pump output pressure P2 are linearly related.

[0037] Furthermore, an adjustment slot for adjusting the clamping nut is provided on the support sleeve relative to the clamping nut.

[0038] Furthermore, the stretching head includes a force-receiving part and a mounting part. The stretching head has a horizontally through threaded hole. The diameter of the force-receiving part is larger than the diameter of the mounting part. The hydraulic tensioner is mounted on the mounting part, and the piston end face of the hydraulic tensioner abuts against the force-receiving surface of the force-receiving part.

[0039] The advantages and technical effects of this invention are as follows: By employing the above-mentioned technical solution, and utilizing the hydraulic power source provided by a hydraulic pump, the tensile force is determined based on the tensile strength, yield coefficient, and elongation of the material. The tensile force generated by the hydraulic pump elongates the drive shaft within its elastic deformation range, causing a slight deformation in the drive shaft diameter, thereby locking the clamping nut and screw sleeve. Using pure tensile force to elongate the drive shaft causes no frictional damage to the connecting contact surfaces and allows for precise control of the screw sleeve preload torque. Only axial tensile loads are generated, avoiding destructive torsional loads, thus preventing damage to the clamping nut and drive shaft, resulting in high-quality assembly. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure provided in an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the stretching head structure provided in an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the pressure plate structure provided in an embodiment of the present invention.

[0043] In the diagram: 1. Drive shaft; 2. Screw sleeve; 3. Clamping nut; 4. Tensioning head; 5. Hydraulic tensioner; 6. Quick-change connector; 7. Support ring; 8. Support sleeve; 8-1. Adjustment slot; 9. Pressure plate; 9-1. Annular groove; 10. Pressure nut. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] like Figures 1 to 3 As shown, this application provides a method for pre-tightening the screw sleeve of a screw pump, comprising the following steps:

[0046] S1. Install the clamping nut 3 in the pre-tightened position of the screw sleeve 2.

[0047] The spiral sleeve 2 is placed on the drive shaft 1, and the clamping nuts 3 are respectively placed on the drive shaft 1 at both ends of the spiral sleeve 2.

[0048] S2. Place the drive shaft 1 and the spiral sleeve 2 into the pre-tightening device to complete the assembly of the pre-tightening device.

[0049] The pre-tightening device includes a support sleeve 8, within which the drive shaft 1 and the spiral sleeve 2 are placed. One end of the support sleeve 8 is fitted with a pressure plate 9 that is sleeved on the drive shaft 1. The pressure plate 9 abuts against the support sleeve 8, and an annular groove 9-1 for engaging the support sleeve 8 is provided on the end face of the pressure plate 9. This ensures a more stable connection between the support sleeve 8 and the pressure plate 9, guaranteeing the reliability of the connection during the stretching process and preventing damage to the equipment and components caused by the support sleeve 8 detaching from the pressure plate 9 during stretching. A clamping nut 10 for limiting the position of the pressure plate 9 is provided on the drive shaft 1 on the outer side of the pressure plate 9; a tensioning head 4 threadedly connected to the drive shaft 1 is provided on the other end of the support sleeve 8 relative to the pressure plate 9; a hydraulic tensioner 5 is provided on the tensioning head 4; the piston end face of the hydraulic tensioner 5 abuts against the tensioning head 4. Specifically, the tensioning head 4 includes a force-bearing part 4-1 and a mounting part 4-2; a horizontally penetrating threaded hole 4-3 is provided inside the tensioning head 4; the tensioning head 4 is threadedly connected to the drive shaft 1 through the threaded hole 4-3; the diameter of the force-bearing part 4-1 is larger than the diameter of the mounting part 4-2, forming a stepped shaft structure; the hydraulic tensioner 5 is mounted on the mounting part 4-2; the piston end face of the hydraulic tensioner 5 abuts against the force-bearing surface of the force-bearing part 4-1, i.e., the plane where the stepped shaft shoulder is located. The cylinder end face of the hydraulic tensioner 5 abuts against the support sleeve 8 through a support ring 7; the hydraulic tensioner 5 is connected to an external hydraulic pump through a quick-connect coupling 6.

[0050] Place the drive shaft 1 and the spiral sleeve 2 inside the support sleeve 8, and abut the pressure plate 9 against the support sleeve 8 through the annular groove 9-1. Tighten the clamping nut 10 to ensure that the position of the pressure plate 9 is relatively fixed. Set the hydraulic tensioner 5 on the tensioning head 4 and thread the tensioning head 4 onto the drive shaft 1. The cylinder end face of the hydraulic tensioner 5 abuts against the support sleeve 8 through the support ring 7 to complete the assembly of the pre-tightening device.

[0051] S3. Start the hydraulic pump, and the hydraulic tensioner 5 causes the drive shaft 1 to undergo an elongated elastic deformation.

[0052] High-pressure oil output by the hydraulic pump is delivered to the hydraulic tensioner 5 through the quick-connect coupling 6. Under pressure, the piston of the hydraulic tensioner 5 moves away from the spiral sleeve 2 and pushes the tensioning head 4, thereby lengthening the drive shaft 1. Under the action of the reaction force, the cylinder end face of the hydraulic tensioner 5 pushes the support ring 7, support sleeve 8 and pressure plate 9 to abut tightly and fix them relatively.

[0053] S4. Based on the functional relationship between the preload torque and the hydraulic pump output pressure, tighten the clamping nut when the required preload torque is reached.

[0054] The support sleeve 8 relative to the clamping nut 3 is provided with an adjustment slot 8-1 for adjusting the clamping nut 3. The adjustment slot 8-1 allows the operating tool to be easily inserted into the support sleeve 8 to adjust the clamping nut 3.

[0055] The functional relationship between the preload torque and the hydraulic pump output pressure is as follows:

[0056] Calculate the preload P0:

[0057] P0 = σ0·As (1)

[0058] As = Π·ds·ds / 4 (2)

[0059] ds = (d2 + d1 - H / 6) / 2 (3)

[0060] σ0 = (0.5~0.7)σs (4)

[0061] Where: σ0 is the allowable stress of the material, and σs is the yield strength of the material, in units of... H is the nominal working height of the thread tooth, in mm; d1 is the minor diameter of the thread, in mm; d2 is the minor diameter of the thread, in mm; ds is the calculated diameter of the critical section of the thread, in mm; As is the nominal stress cross-sectional area, in mm. ;

[0062] Calculate the preload torque Mt = K· ·d / 1000 Nm (5)

[0063] Where K is the tightening factor; d is the nominal diameter of the thread, in mm;

[0064] K-value lookup table:

[0065]

[0066] The relationship between high-pressure oil pressure and tensile force in a hydraulic tensioner:

[0067] P1=F1 / A1(6)

[0068] P2=P1(7)

[0069] Where: P1 is the high-pressure oil pressure in the hydraulic tensioner, in MPa; F1 is the thread tensioning force of the tensioning head, in kN; A1 is the hydraulic area in the hydraulic tensioner, in kN. P2 is the hydraulic pump output pressure, in MPa.

[0070] Relationship between hydraulic pump output pressure and preload torque:

[0071] When the tension force F1 of the threaded head reaches the preload P0, and the drive shaft is within the elastic deformation range, it can be seen from the above equations (1) to (7):

[0072] Mt=K·P2·A1·d / 1000(8)

[0073] P2≤(0.5~0.7)σs·(d2+d1-H / 6)2·Π / 16(9)

[0074] From equation (8), it can be seen that the preload torque Mt is directly proportional to the tightening coefficient K, the hydraulic pump output pressure P2, the hydraulic area A1 in the hydraulic tensioner, and the nominal thread diameter d. When the hydraulic tensioner is determined, the hydraulic area A1 in the hydraulic tensioner and the nominal thread diameter d are constants, that is, equation (8) is changed to:

[0075] Mt=C·K·P2(10)

[0076] Where: C is a constant;

[0077] As can be seen from equation (10), when the tightening coefficient K is determined and the transmission shaft is within the elastic deformation range, the preload torque Mt and the hydraulic pump output pressure P2 are linearly related.

[0078] S5. Unload the hydraulic pump pressure and disassemble the pre-tightening device.

[0079] Remove the tension head 4 and hydraulic tensioner 5 from the drive shaft 1, remove the support ring 7 and support sleeve 8 that are in series, loosen the clamping nut 10 and remove the clamping nut 10 from the drive shaft 1, and remove the pressure plate 9.

[0080] By employing the above technical solution, the hydraulic pump provides the hydraulic power source, and the tensile force is determined based on the material's tensile strength, yield coefficient, and elongation. The tension generated by the hydraulic pump stretches the applied drive shaft 1 within its elastic deformation range, causing a slight deformation in the diameter of the drive shaft 1, thereby locking the clamping nut 3 onto the screw sleeve 2. Using pure tensile force to stretch the drive shaft 1 causes no frictional damage to the connecting contact surfaces and allows for precise control of the screw sleeve 2's preload torque. It only generates axial tensile loads, avoiding destructive torsional loads, thus preventing damage to the clamping nut 3 and the drive shaft 1, resulting in high-quality assembly.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for pre-tightening the screw sleeve of a screw pump, characterized in that, Includes the following steps: S1. Install the clamping nut (3) in the pre-tightened position of the screw sleeve (2); S2. Place the drive shaft (1) and the screw sleeve (2) into the pre-tightening device to complete the assembly of the pre-tightening device; The pre-tightening device includes a support sleeve (8) which holds the drive shaft (1) and the spiral sleeve (2) inside the support sleeve (8). One end of the support sleeve (8) is provided with a pressure plate (9) sleeved on the drive shaft (1). The pressure plate (9) abuts against the support sleeve (8). A clamping nut (10) for limiting the position of the pressure plate (9) is provided on the drive shaft (1) outside the pressure plate (9). The other end of the support sleeve (8) relative to the pressure plate (9) is provided with a tension head (4) threaded to the drive shaft (1). A hydraulic tensioner (5) is provided on the tension head (4). The piston end face of the hydraulic tensioner (5) abuts against the tension head (4). The cylinder end face of the hydraulic tensioner (5) abuts against the support sleeve (8) through a support ring (7). The hydraulic tensioner (5) is connected to an external hydraulic pump through a quick-change connector (6). The pressure plate (9) is abutted against the support sleeve (8) through the annular groove (9-1), and the clamping nut (10) is tightened to ensure that the position of the pressure plate (9) is relatively fixed; the hydraulic tensioner (5) is set on the tension head (4), and the tension head (4) is threaded onto the drive shaft (1). The cylinder end face of the hydraulic tensioner (5) abuts against the support sleeve (8) through the support ring (7) to complete the assembly of the pre-tightening device; S3. Start the hydraulic pump, and the hydraulic tensioner (5) causes the drive shaft (1) to undergo an elongated elastic deformation. S4. Based on the functional relationship between the preload torque and the hydraulic pump output pressure, when the required preload torque is reached, tighten the clamping nut (3); the functional relationship between the preload torque and the hydraulic pump output pressure in step S4 is as follows: Calculate the preload P0: P0 = σ0·As (1) As = Π·ds·ds / 4 (2) ds = (d2 + d1 - H / 6) / 2 (3) σ0 = (0.5~0.7)σs (4) Where: σ0 is the allowable stress of the material, and σs is the yield strength of the material, in units of... H is the nominal working height of the thread tooth, in mm; d1 is the minor diameter of the thread, in mm; d2 is the minor diameter of the thread, in mm; ds is the calculated diameter of the critical section of the thread, in mm; As is the nominal stress cross-sectional area, in mm. ; Calculate the preload torque Mt = K·P0·d / 1000 Nm (5) Where K is the tightening factor; d is the nominal diameter of the thread, in mm; K-value lookup table: The relationship between high-pressure oil pressure and tensile force in hydraulic tensioner (5): P1=F1 / A1(6) P2=P1(7) Where: P1 is the high-pressure oil pressure in the hydraulic tensioner (5), in MPa; F1 is the thread tensioning force of the tensioning head (4), in KN; A1 is the hydraulic area in the hydraulic tensioner (5), in kN. P2 is the hydraulic pump output pressure, in MPa. Relationship between hydraulic pump output pressure and preload torque: When the thread tension F1 of the tension head (4) reaches the preload P0, and the transmission shaft is within the elastic deformation range, it can be seen from the above equations (1) to (7): Mt=K·P2·A1·d / 1000(8) P2≤(0.5~0.7)σs·(d2+d1-H / 6)2·Π / 16(9) From equation (8), it can be seen that the preload torque Mt is directly proportional to the tightening coefficient K, the hydraulic pump output pressure P2, the hydraulic area A1 in the hydraulic tensioner (5), and the nominal thread diameter d. When the hydraulic tensioner (5) is determined, the hydraulic area A1 and the nominal thread diameter d in the hydraulic tensioner (5) are constants, that is, equation (8) is changed to: Mt=C·K·P2(10) Where: C is a constant; As can be seen from equation (10), when the tightening coefficient K is determined and the transmission shaft (1) is within the elastic deformation range, the preload torque Mt and the hydraulic pump output pressure P2 are linearly related. S5. Unload the hydraulic pump pressure and disassemble the pre-tightening device.

2. The screw pump helical sleeve pre-tightening method according to claim 1, characterized in that, An annular groove (9-1) for engaging the support sleeve (8) is provided on the end face of the pressure plate (9) that abuts against the support sleeve (8).

3. The screw pump helical sleeve pre-tightening method according to claim 1, characterized in that, An adjustment slot (8-1) for adjusting the clamping nut (3) is provided on the support sleeve (8) relative to the clamping nut (3).

4. The screw pump helical sleeve pre-tightening method according to claim 1, characterized in that, The stretching head (4) includes a force-bearing part (4-1) and a mounting part (4-2). A horizontally penetrating threaded hole (4-3) is provided inside the stretching head (4). The diameter of the force-bearing part (4-1) is larger than the diameter of the mounting part (4-2). The hydraulic tensioner (5) is mounted on the mounting part (4-2). The piston end face of the hydraulic tensioner (5) abuts against the force-bearing surface of the force-bearing part (4-1).

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