A stacked multi-stage threaded pumping seal structure

Abstract

The present invention discloses a stacked multi-stage threaded pumping sealing structure, wherein a sealing structure is installed between a cavity and a rotating shaft, wherein the sealing structure comprises a sealing shell composed of a high-pressure side shell and a low-pressure side shell, wherein an outer ring cavity and a plurality of threaded ring cavities are arranged in the sealing shell; a rotor is installed in the center of the sealing shell, an outer ring is arranged in the circumference of the rotor, and a plurality of threaded rings are arranged on both sides of the outer ring, and the rotor, the outer ring and the plurality of threaded rings rotate in corresponding threaded ring cavities; the invention can seal both liquid and gas, and although the invention is a non-contact seal, it has a better throttling effect and a smaller leakage, and even in the parking state with the weakest sealing ability, its sealing ability is still better than that of a conventional labyrinth seal, and this is due to the radial expandability of the stacked multi-stage structure itself, and the more stages there are, the stronger the blocking effect on the fluid.

Description

Technical Field

[0001] The invention belongs to the technical field of sealing, and in particular relates to a stacked multi-stage threaded pumping sealing structure. Background Art

[0002] As a key component in mechanical equipment, seals are mainly in the scope of mechanical engineering and sealing technology. Seals mainly study how to effectively prevent the leakage of liquids or gases in mechanical equipment to ensure the normal operation and safety of the equipment. Seals can be divided into two categories: dynamic seals and static seals. Here we mainly explain dynamic seals. Dynamic sealing technology is mainly used between various coupling parts in continuous motion (such as rotation and reciprocation) to achieve effective sealing and prevent fluid leakage. This technology has a wide range of applications in industrial production, especially in the fields of hydraulic systems, pneumatic systems, mechanical transmission systems, etc., playing an irreplaceable role.

[0003] In addition, dynamic sealing technology is mainly divided into contact type and non-contact type. Among them, contact dynamic seals include: mechanical seals, packing seals, leather cup seals, etc. This form of sealing relies on the contact pressure between the seal and the contact surface to seal. The advantages are simple structure and low cost, but the disadvantages are: wear, high power consumption, and not suitable for high speed occasions. Non-contact dynamic seals include: labyrinth seals, centrifugal seals, spiral seals, labyrinth spiral seals, etc. The advantages of this type of seal are: small or even zero wear, low power consumption, reduced or even no friction resistance, and low heat generation; the disadvantages are: 1. Limited by the influence of the straight-through air permeability effect, the throttling efficiency of most non-contact seals is generally not high. 2. For example, labyrinth seals and centrifugal seals have the problem of large leakage. 3. Magnetic fluid seals are prone to heat and demagnetization at high speeds, and the sealing performance under high-speed conditions is insufficient. Spiral seals need to increase the length of the spiral to resist high-pressure media, and the increase in spiral length will cause the axial size of the device to be too large, and the sealing ability for high-pressure conditions is weak. 4. Traditional spiral seals, labyrinth spiral seals, spiral groove liquid film seals, etc. fail when rotating in the reverse direction and have a single requirement for the direction of rotation. Summary of the invention

[0004] In view of the problems and shortcomings of non-contact seals in the background technology, a stacked multi-stage threaded pumping seal structure is proposed. The present invention is applied in high-speed occasions, has very low wear and low power consumption.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A stacked multi-stage threaded pumping sealing structure, characterized in that: the sealing structure includes a sealing shell composed of a high-pressure side shell and a low-pressure side shell, and an outer ring cavity and a plurality of threaded ring cavities are provided in the sealing shell; a rotor is installed in the center of the sealing shell, an outer ring is provided in the circumference of the rotor, and a plurality of threaded rings are provided on both sides of the outer ring, and the rotor, the outer ring and the plurality of threaded rings rotate in the corresponding threaded ring cavities.

[0007] Furthermore, a sealing ring is installed between the high-pressure side housing and the low-pressure side housing, and the housing is connected by screws.

[0008] Furthermore, the sealing structure is fixed to the rotating shaft circumferentially by keys and axially by set screws; the sealing shell and the cavity are fixed by screws.

[0009] Furthermore, the threaded rings on the two side surfaces of the outer ring are arranged horizontally in parallel or staggered in parallel.

[0010] Furthermore, the external threads of the plurality of threaded rings are left-handed or right-handed, and the internal threads of the plurality of threaded rings are left-handed or right-handed.

[0011] Furthermore, based on the turning of internal and external threads, the arrangement methods include inward liquid rushing type, two-side to middle liquid rushing type, multi-stage liquid rushing type, vacuum type, pressure difference liquid rushing type, and reverse pressure difference liquid rushing type.

[0012] Furthermore, the thread profile is a combination of one or more of rectangle, triangle and trapezoid.

[0013] Furthermore, the radial clearance between the threaded ring and the threaded ring cavity is 0.3 mm, and the axial clearance between the outer ring and the outer ring cavity is greater than 1 mm.

[0014] Furthermore, the thread lead angle is 14-17°, the ratio of the groove width to the tooth width + the groove width is 0.4-0.6, and the groove depth is 0.2-0.3 mm.

[0015] The following beneficial effects can be obtained through the above technical solution:

[0016] The invention can seal both liquid and gas. Although it is a non-contact seal, it has a good throttling effect and a small leakage. Even in the parking state with the weakest sealing ability, its sealing ability is still better than that of the conventional labyrinth seal. This is due to the radial expandability of the stacked multi-stage structure itself. The more stages, the stronger the blocking effect on the fluid. It still has sealing ability under high pressure conditions. The pressure of the fluid that can be sealed by the spiral seal is basically proportional to the length of the thread. The longer the thread length, the greater the fluid pressure that can be sealed, the greater the thread linear speed, and the stronger the sealing ability. The structure described in the present invention greatly increases the thread length without changing the axial size, and increases the linear speed generated by the rotation. It can rotate in both directions, and the number, total length and rotation direction of the spirals on both sides of the rotor are different. Under different spindle rotation directions, spirals of different rotation directions will work adaptively to achieve sealing. The structure as a whole is a rotating body, which is convenient and economical to process. All parts in the device are rotating bodies, and the materials should be metal materials, which can be processed by general machine tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a three-dimensional diagram of the sealing structure with the shell cut open.

[0018] Figure 2 It is a three-dimensional diagram of the cutaway shell and threaded ring of the sealing structure.

[0019] Figure 3 It is a schematic diagram of the application of the embodiment.

[0020] Figure 4 It is a cross-sectional view of an embodiment.

[0021] Figure 5 It is a cross-sectional view of a stacked multi-stage threaded pumping seal structure.

[0022] Figure 6 It is a schematic diagram of a threaded ring.

[0023] Figure 7 It is a schematic diagram of thread rings at different layers.

[0024] Figure 8 It is a steering diagram.

[0025] Fig. 9 It is a schematic diagram of the inward liquid-driving combination.

[0026] Fig.10 It is a schematic diagram of the combination of two sides rushing liquid to the middle.

[0027] Fig.11 It is a schematic diagram of a multi-stage liquid-rushing combination.

[0028] Fig.12 It is a schematic diagram of a vacuum combination.

[0029] Fig.13 It is a schematic diagram of the pressure difference liquid-driving method.

[0030] Fig.14 It is a schematic diagram of the reverse pressure difference liquid-driving method.

[0031] Fig.15 It is a schematic diagram of a rectangular tooth shape.

[0032] Fig.16 It is a schematic diagram of a triangular tooth shape.

[0033] Fig.17 It is a schematic diagram of trapezoidal tooth type.

[0034] Fig.18 It is a schematic diagram of the combined tooth type.

[0035] Fig.19 It is a schematic diagram of a staggered arrangement.

[0036] Fig. 20 It is a schematic diagram of radial clearance.

[0037] Fig.21 It is a schematic diagram of axial clearance.

[0038] Fig. 22 It is a schematic diagram of the thread structure. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings:

[0040] The present invention designs a stacked multi-stage threaded pumping sealing structure, including a cavity and a rotating shaft, a sealing structure is installed between the cavity and the rotating shaft, the sealing structure includes a sealing shell composed of a high-pressure side shell and a low-pressure side shell, an outer ring cavity and a plurality of threaded ring cavities are arranged in the sealing shell; a rotor is installed in the center of the sealing shell, an outer ring is arranged in the circumference of the rotor, and a plurality of threaded rings are arranged on both sides of the outer ring, and the rotor, the outer ring and the plurality of threaded rings rotate in the corresponding threaded ring cavity. A sealing ring is installed between the high-pressure side shell and the low-pressure side shell, and they are connected by screws at the same time, the rotating shaft and the sealing structure are fixed circumferentially by a key, and axially by a set screw; the sealing shell and the cavity are fixed by screws. The structure is easy to process, easy to adjust, has a fixed sealing gap, has zero wear during stable operation, has low power consumption, is suitable for high-viscosity liquids and gases, high-speed occasions, can work in different rotation directions, and can achieve high-pressure sealing.

[0041] The sealing structure is Figure 1 , Figure 2 , Figure 5 as well as Figure 6As shown: rotor 1, high-pressure side housing 2, screw 7, auxiliary sealing ring 6, low-pressure side housing 3, and threaded ring 4. Among them, the high-pressure side housing 2, low-pressure side housing 3, and auxiliary sealing ring 6 are connected by screw 7 to form a sealed housing. An outer ring cavity and several threaded ring cavities 8 are provided inside the sealed housing. The threaded ring 4 is welded to the outer ring 5 of the rotor 1. Since the inner hole of the rotor 1 is fixedly connected to the rotating shaft, and the outer ring 5 on the rotor 1 is fixedly connected to the threaded ring 4, the rotor 1 and the threaded ring rotate with the rotating shaft, while the high-pressure side housing and the low-pressure side housing are fixedly connected to the cavity, and the high-pressure side housing and the low-pressure side housing remain stationary. When the rotor rotates, the outer ring and the threaded ring rotate in the outer ring cavity and several threaded ring cavities, and the sealed housing formed by the high-pressure side housing and the low-pressure side housing remains stationary.

[0042] Embodiment: The overall structure consists of Figure 3 , Figure 4 In: rotating shaft 9, key 10, sealing structure, cavity 11, first screw 12, set screw 13, gland 14, second screw 15, and sealing ring. Among them, the rotating shaft 9 and the stacked multi-stage threaded pumping sealing structure are circumferentially fixed by key 10 and axially fixed by set screw 13. Among them, the rotating shaft 9, sealing ring, and gland 14 are fixed by second screw 15. Among them, the stacked multi-stage threaded pumping sealing structure, sealing ring, and cavity are fixed by first screw 12.

[0043] Based on the above embodiment: The number of threaded rings can be changed, such as Figure 7 , specifically determined according to the pressure of the fluid to be sealed. The higher the pressure of the fluid to be sealed, the more the number of rings, and the larger the occupied radial dimension, while the axial dimension remains unchanged.

[0044] Based on the above embodiment: Regarding the helix direction of the thread Figure 8 As shown, there are various different arrangements. In the following various ways, three layers of threaded rings are respectively arranged on both sides of the outer ring. The three layers of threaded rings are horizontally parallel, specifically forming a "king" character structure. The three layers of threaded rings from bottom to top are the first layer, the second layer, and the third layer. The number of layers adopted in this embodiment is only for illustrating the arrangement method. In actual application, increasing or decreasing the number of rings will cause the number of layers to change. The following combination forms are different technical solutions defined by the present invention, and other combination forms are not excluded.

[0045] The first type: inward liquid driving type

[0046] The inward liquid driving type combination utilizes the pumping action of the helix to push the medium along the leakage direction of the sealing gap back to achieve sealing, and can be used for sealing liquids. Fig. 9As shown, this method limits the rotation direction of each thread ring. The external threads of the thread rings on both sides of the first layer, the second layer and the third layer adopt a right-hand structure, and the internal threads of the thread rings on both sides of the second layer and the third layer adopt a left-hand structure. The following specifically shows each part: the thread ring on the left side of the first layer adopts a right-hand external thread, the thread ring on the left side of the second layer adopts a left-hand internal thread and a right-hand external thread, the thread ring on the left side of the third layer adopts a left-hand internal thread and a right-hand external thread, the thread ring on the right side of the third layer adopts a right-hand external thread and a left-hand internal thread, the thread ring on the right side of the second layer adopts a right-hand external thread and a left-hand internal thread, and the thread ring on the right side of the first layer adopts a right-hand external thread.

[0047] The second type: the liquid is driven from both sides to the middle

[0048] This method can be used to seal gas or liquid that is immiscible with the sealing liquid. When in use, the sealing liquid must be injected into the structure in advance. When working, the structure will squeeze the sealing liquid to the middle of the highest layer gap (circle), forming a local high pressure. The pressure of the liquid seal is slightly greater than or equal to the pressure of the sealed medium, and sealing can be achieved. Fig.10 As shown, this method is to use opposite rotation directions for the external thread and internal thread of each layer of threaded ring. Specifically, the first, second and third layers have left-handed external threads on the left side and right-handed external threads on the right side, the second and third layers have right-handed internal threads on the left side and left-handed internal threads on the right side, and local high pressure is formed in the radial gap in the middle of the third layer.

[0049] The specific threads shown in the accompanying drawings are: the threaded ring on the left side of the first layer adopts a left-handed external thread, the threaded ring on the left side of the second layer adopts a right-handed internal thread and a left-handed external thread, the threaded ring on the left side of the third layer adopts a right-handed internal thread and a left-handed external thread, the threaded ring on the right side of the third layer adopts a right-handed external thread and a left-handed internal thread, the threaded ring on the right side of the second layer adopts a right-handed external thread and a left-handed internal thread, and the threaded ring on the right side of the first layer adopts a right-handed external thread.

[0050] The third type: multi-stage liquid-rushing type

[0051] This method can be used to seal gas or liquid that is immiscible with the sealing liquid. When in use, the sealing liquid needs to be injected into the structure in advance. When working, the structure will cause the sealing liquid to form multiple high-pressure areas (circled in the figure), forming a multi-level liquid seal. Specifically, each layer of sealing liquid forms high pressure in the axial gap. Fig.11 As shown, the internal and external threads of the first, second and third layers of the threaded rings on the left are all left-handed, while the internal and external threads of the first, second and third layers of the threaded rings on the right are all right-handed.

[0052] The specific threads are: the thread ring on the left side of the first layer adopts a left-hand external thread, the thread ring on the left side of the second layer adopts a left-hand internal thread and a left-hand external thread, the thread ring on the left side of the third layer adopts a left-hand internal thread and a left-hand external thread, the thread ring on the right side of the third layer adopts a right-hand external thread and a right-hand internal thread, the thread ring on the right side of the second layer adopts a right-hand external thread and a right-hand internal thread, and the thread ring on the right side of the first layer adopts a right-hand external thread.

[0053] The fourth type: vacuum type

[0054] In this way, the liquid expelling directions of the left and right threads are opposite, and the gas is discharged to both sides during high-speed rotation to achieve sealing. Fig.12 As shown, the external threads of the first, second and third layer thread rings have opposite rotation directions, specifically, the external thread on the left side is right-handed, the internal thread on the left side is left-handed, the external thread on the right side is left-handed, and the internal thread on the right side is right-handed.

[0055] The specific threads are: the thread ring on the left side of the first layer adopts a right-hand external thread, the thread ring on the left side of the second layer adopts a left-hand internal thread and a right-hand external thread, the thread ring on the left side of the third layer adopts a left-hand internal thread and a right-hand external thread, the thread ring on the right side of the third layer adopts a left-hand external thread and a right-hand internal thread, the thread ring on the right side of the second layer adopts a left-hand external thread and a right-hand internal thread, and the thread ring on the right side of the first layer adopts a left-hand external thread.

[0056] The fifth type: pressure difference liquid driving type

[0057] This type of multi-stage threaded pumping seal structure can have sealing capabilities in both bidirectional rotation. It is necessary to reduce several sections of threads on the high-pressure side so that the total length of the threads on the right side is greater than the total length of the threads on the left side. Fig.13 As shown, the fluid is driven back by the left thread (the number of left thread rings needs to be determined according to the fluid pressure so that the fluid is driven back without contacting the right thread), achieving a sealing effect.

[0058] In the reversal, Fig.14 As shown, the fluid will be pressurized by the right thread, but because the right thread is longer than the left thread, the fluid can still be driven back by the right thread to achieve a sealing effect. The specific threads are: the thread ring on the left side of the first layer has no threads, the thread ring on the left side of the second layer adopts a left-handed external thread, and the internal thread adopts a smooth structure, the thread ring on the left side of the third layer adopts a right-handed internal thread and a left-handed external thread, the thread ring on the right side of the third layer adopts a right-handed external thread and a left-handed internal thread, the thread ring on the right side of the second layer adopts a right-handed external thread and a left-handed internal thread, and the thread ring on the right side of the first layer adopts a right-handed external thread.

[0059] Based on the above embodiments and various forms of stacked multi-stage thread pumping seal structures, the thread profile can be changed, such as rectangular ( Fig.15 shown), triangle ( Fig.16 As shown), trapezoidal ( Fig.17 Different tooth types are suitable for fluids with different viscosities, or a combination of multiple tooth types, such as Fig.18 shown.

[0060] Considering the manufacturing process, the invention can be made into a staggered type by changing the arrangement of the rings. Fig.19 shown.

[0061] The basic sealing principle of the threaded pumping seal of the present invention is that the thread, as a propulsion structure, exchanges energy with the medium, generates the so-called "pumping action", and generates a pumping pressure head, which is balanced with the pressure of the sealed medium, thereby preventing leakage. The present invention radially arranges dynamic and static rings of different sizes, so that the length of the thread is greatly increased without changing the axial dimension. When the pressure of the fluid to be sealed is large, it is only necessary to increase the number of dynamic and static rings. The more the number, the longer the thread length, the larger the radial dimension, the greater the linear speed under rotation, and the stronger the sealing ability, so as to achieve sealing of high-pressure fluids. Regarding thread parameters: the thread lead, pitch, and number of threads described in the present invention are all variable, and changes in the lead and pitch will affect the pumping performance (sealing performance) of the device. In actual design, a larger lead and a larger number of thread heads are usually selected.

[0062] Regarding radial clearance, the position of radial clearance is as follows Fig. 20 At the circle shown, the smaller the radial clearance of the seal, the more favorable the sealing effect is, the greater the fluid pressure it can resist, but the more difficult it is to process and assemble. If the radial clearance is large, the liquid medium may not adhere to the surface of the threaded ring. Assuming that the liquid medium only adheres to the stationary wall and is separated from the threaded ring, the threaded pumping seal will not play the role of pushing the medium away, that is, the seal fails. However, if the radial clearance is too small, it will increase the chance of the threaded ring colliding with the stationary wall. Therefore, the radial clearance is generally designed to be 0.3mm, and it can also be adjusted up and down according to actual working conditions, processing conditions, etc. In order to avoid friction and wear of the sealing metal parts, a lubricating coating can be added to the surface of the hole wall.

[0063] About axial clearance: The position of axial clearance is as follows: Fig.21 The axial clearance value at the circle shown should take into account the rotation speed, medium viscosity, working environment, axial movement of the equipment itself, etc., and at high speed rotation, a low pressure area will be formed at the axial clearance, and unreasonable clearance design will aggravate leakage. Therefore, the axial clearance value needs to be designed according to the specific working conditions, but it can generally be designed to be more than 1mm.

[0064] Regarding the axial length of the ring and the number of rings: the longer the axial length of the ring and the greater the number of rings, the better the sealing performance, but the larger the axial space occupied by the device. The specific length and number of the rings need to be determined according to the working conditions and installation space.

[0065] About the radial thickness of the ring: The radial thickness of the ring refers to the difference between the outer diameter and the inner diameter of the ring. The smaller the radial thickness, the smaller the radial size occupied when the number of rings is the same. However, too small radial thickness will lead to unstable connection between the ring and the rotor. Therefore, the radial thickness design should ensure the reliability of the connection. Generally, the radial thickness is 6-10mm.

[0066] Regarding the influence of rotation speed on sealing ability (sealing liquid pressure): the sealing structure described in the present invention has a strong dependence on rotation speed, and its sealing ability is basically linearly related to the rotation speed, that is, the higher the rotation speed, the stronger the sealing ability. At zero rotation speed, the structure can be regarded as a new type of labyrinth blocking composite seal, at which time the structure still has sealing ability for gas, and the throttling ability is higher than that of conventional labyrinth seals and blocking seals. The principle of ordinary labyrinth seals is to change the volume of the fluid through the scaling of the flow channel, thereby generating energy loss and reducing leakage. This new type of labyrinth blocking composite seal continues the above principle, and the fluid will impact the wall of the high-pressure side shell 12, the low-pressure side shell 15, and the rotor 11, further reducing the fluid energy and thus reducing leakage. There are some prior arts for this technical solution of impacting the wall, such as the sealing structure with application number: 202221696502.9 and application number: 202122442952.7. These two structures use the method of axially setting a multi-stage blocking wall to increase the number of impacts between the fluid and the wall, thereby reducing leakage. However, these prior arts do not fully consider the assembly problem of the structure, and the structure will interfere during the assembly process.

[0067] Regarding the lead, pitch and number of threads: The lead, pitch and number of threads described in the present invention are general geometric parameters that describe threads. In fact, the above geometric parameters are affected by the tooth width, groove width, thread diameter and thread lead angle. The thread lead angle has a more complex effect on the sealing liquid pressure. Taking the rectangular structure as an example, the recommended thread lead angle is 14-17°. Too small or too large a thread lead angle will weaken the sealing ability. Regarding the above tooth width and groove width: The ratio of groove width to tooth width + groove width has a certain effect on the sealing ability. The recommended ratio is 0.4-0.6. Too small or too large will weaken the sealing ability. In general, the tooth width can be equal to the groove width. Regarding the thread diameter: At the same speed, the larger the thread diameter, the greater the linear speed, and the stronger the sealing ability. Regarding the effect of groove depth on sealing ability: The effect of groove depth on sealing ability is theoretically a more complex nonlinear relationship. A larger groove depth will enhance the pumping ability of the structure, but it will also increase the ratio of fluid leakage along the thread groove. Therefore, the groove depth is not the deeper the better. Here, the recommended groove depth is 0.2-0.3mm.

[0068] Based on the above technical solution, the present invention can seal both liquid and gas. Although the invention is a non-contact seal, it has a good throttling effect and a small leakage. Even in the parking state with the weakest sealing ability, its sealing ability is still better than that of a conventional spiral seal. This is due to the radial expandability of the stacked multi-stage structure itself. The more stages, the stronger the blocking effect on the fluid. It still has sealing ability under high-pressure conditions. The pressure of the fluid that can be sealed by the spiral seal is basically proportional to the length of the thread. The longer the thread length, the greater the fluid pressure that can be sealed, the greater the thread linear speed, and the stronger the sealing ability. The structure described in the present invention greatly increases the thread length without changing the axial size, and increases the linear speed generated by the rotation.

[0069] The number, total length and rotation direction of the spirals on both sides of the rotor are different. Under different main shaft rotation directions, the spirals with different rotation directions will work adaptively to achieve sealing. The overall structure is a rotating body, which is convenient and economical to process; all parts in the device are rotating bodies, and the materials should be metal materials, which can be processed by general machine tools. The seal described in the present invention is a non-contact seal, which has the common advantages of non-contact seals: the sealing structure will not produce wear during normal operation; the power consumption is small; and it is suitable for high-speed occasions.

[0070] The above are all preferred embodiments of the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, various equivalent modifications to the present invention belong to the protection scope of the claims attached to this application.

Claims

1. A stacked multi-stage threaded pumping seal structure, characterized in that: The sealing structure comprises a sealing shell composed of a high-pressure side shell and a low-pressure side shell, wherein an outer ring cavity and a plurality of threaded ring cavities are arranged in the sealing shell; a rotor is installed in the center of the sealing shell, an outer ring is arranged in the circumference of the rotor, and a plurality of threaded rings are arranged on both sides of the outer ring, and the rotor, the outer ring and the plurality of threaded rings rotate in the corresponding threaded ring cavities; a sealing ring is installed between the high-pressure side shell and the low-pressure side shell, and the two shells are connected by screws; The sealing structure and the rotating shaft are fixed circumferentially by keys and axially by set screws; the sealing housing and the cavity are fixed by screws; The threaded rings on the two sides of the outer ring are arranged horizontally and in parallel or staggered and in parallel, and a plurality of threaded rings are arranged in a concentric circle manner to form a stacked multi-level structure; The external threads of the plurality of threaded rings are left-handed or right-handed, and the internal threads of the plurality of threaded rings are left-handed or right-handed; The radial clearance between the threaded ring and the threaded ring cavity is 0.3 mm, and the axial clearance between the outer ring and the outer ring cavity is greater than 1 mm; The thread lead angle is 14-17°, the ratio of groove width to tooth width + groove width is 0.4-0.6, and the groove depth is 0.2-0.3mm.

2. A stacked multi-stage threaded pumping seal structure according to claim 1, characterized in that: The thread profile is a combination of one or more of rectangle, triangle and trapezoid.

3. The stacked multi-stage threaded pumping seal structure according to claim 1, characterized in that: Based on the rotation of internal and external threads, the arrangement is an inward-driving liquid type. The structure of the inward-driving liquid type is that the external threads of the thread rings on both sides of the first, second and third layers adopt a right-hand structure, and the internal threads of the thread rings on both sides of the second and third layers adopt a left-hand structure.

4. The stacked multi-stage threaded pumping seal structure according to claim 1 is characterized in that: Based on the rotation of internal and external threads, the arrangement method is a two-sided middle liquid-rushing type. The structure of the two-sided middle liquid-rushing type is that the external thread and the internal thread of each layer of the thread ring adopt opposite rotation directions. Specifically, the left side of the first, second and third layers adopts left-handed external threads, and the right side adopts right-handed external threads. The left side of the second and third layers adopts right-handed internal threads, and the right side adopts left-handed internal threads. Local high pressure is formed in the radial gap in the middle of the third layer.

5. The stacked multi-stage threaded pumping seal structure according to claim 1 is characterized in that: Based on the rotation of internal and external threads, the arrangement is a multi-stage liquid-driving type. The structure of the multi-stage liquid-driving type is that the internal and external threads of the first, second and third layers of the thread rings on the left are all left-handed, while the internal and external threads of the first, second and third layers of the thread rings on the right are all right-handed.

6. The stacked multi-stage threaded pumping seal structure according to claim 1, characterized in that: Based on the rotation of internal and external threads, the arrangement is vacuum type. The vacuum type structure is that the external threads of the first, second and third thread rings have opposite rotation directions. Specifically, the external thread on the left is right-handed, the internal thread on the left is left-handed, the external thread on the right is left-handed, and the internal thread on the right is right-handed.

7. The stacked multi-stage threaded pumping seal structure according to claim 1, characterized in that: Based on the turning of internal and external threads, the arrangement method is pressure differential liquid-driving type. The structure of the pressure differential liquid-driving type is that the thread ring on the left side of the first layer has no threads, the thread ring on the left side of the second layer adopts left-handed external threads, and the internal threads adopt a smooth structure, the thread ring on the left side of the third layer adopts right-handed internal threads and left-handed external threads, the thread ring on the right side of the third layer adopts right-handed external threads and left-handed internal threads, the thread ring on the right side of the second layer adopts right-handed external threads and left-handed internal threads, and the thread ring on the right side of the first layer adopts right-handed external threads.

8. The stacked multi-stage threaded pumping seal structure according to claim 1, characterized in that: Based on the steering of internal and external threads, the arrangement method is a reverse pressure differential liquid-driving type. The structure of the reverse pressure differential liquid-driving type is that the threaded ring on the left side of the first layer has no threads, the threaded ring on the left side of the second layer adopts a left-handed external thread, and the internal thread adopts a smooth structure, the threaded ring on the left side of the third layer adopts a right-handed internal thread and a left-handed external thread, the threaded ring on the right side of the third layer adopts a right-handed external thread and a left-handed internal thread, the threaded ring on the right side of the second layer adopts a right-handed external thread and a left-handed internal thread, and the threaded ring on the right side of the first layer adopts a right-handed external thread.

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