Water pump sealing structure

Abstract

A water pump sealing structure belongs to the technical field of water pumps and aims to solve the problem that only one mechanical seal can be mounted on a lower end cover of an existing water pump. Comprising an end cover, a mounting cylinder is arranged on the end cover, a first bearing body and a first outer mechanical seal are coaxially connected to form a sealed bearing, the side, away from a motor cavity, of an outer ring of a second bearing body is connected with a double-end-face mechanical seal to form a combined seal, and at least one set of sealed bearings and a set of bearingless sealing pieces are arranged in the mounting cylinder. An oil chamber is formed between the sealing bearing and the adjacent bearing-free sealing piece, or at least two sets of sealing bearings are arranged in the installation cylinder, and an oil chamber is formed between the two adjacent sets of sealing bearings, or at least one set of combined seal is arranged in the installation cylinder, and an oil chamber is formed between the two ends of the double-end-face mechanical seal. Multiple sets of outer mechanical seals or combined seals can be installed only through one end cover, water leakage points are reduced, the structure is compact, the sealing effect is good, and the application occasion is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pumps, and in particular relates to a water pump sealing structure. Background Art

[0002] Submersible pumps are important equipment for deep well water extraction. When in use, the entire unit submerges in water to extract groundwater to the surface. They are widely used in many scenarios such as domestic water use, mine rescue, industrial cooling, farmland irrigation, seawater lifting, ship loading, fountain landscaping, etc.

[0003] Existing submersible pumps typically have a bearing seat between the motor and pump head. An end cap is connected to one side of the bearing seat, forming an insulating oil chamber between the end cap and the bearing seat. The bearing seat houses a bearing that supports the motor's rotating shaft, and the end cap is equipped with a mechanical seal. The bearing and mechanical seal are separate. For example, Chinese utility model patent publication number CN201155483Y discloses an integrated submersible pump with this structure. This submersible pump has a complex pump casing and high manufacturing costs. Furthermore, there is only a lower end cap between the motor and impeller, which can only accommodate a single mechanical seal, and this cannot guarantee absolute leakage prevention. Summary of the Invention

[0004] The purpose of the present invention is to provide a water pump sealing structure to solve the problems of the existing water pump casing being complex in structure, high in manufacturing cost, and only being able to install a single mechanical seal on the lower end cover, which cannot guarantee absolute non-leakage. The technical solutions adopted by the present invention are as follows:

[0005] A water pump sealing structure includes an end cover with a mounting cylinder provided on the end cover, defining a single-end mechanical seal in which a static ring and a dynamic ring are arranged from near to far relative to a motor chamber as an external mechanical seal, a first bearing body is coaxially connected to the first external mechanical seal to form a sealed bearing, and the outer ring of the second bearing body is connected to the double-end mechanical seal on the side away from the motor chamber to form a combined seal, at least one group of sealed bearings and one group of bearingless seals are arranged in the mounting cylinder, the bearingless seal is one of an external mechanical seal, an oil seal or a sealing ring, an oil chamber is formed between the sealed bearing and the adjacent bearingless seal, or at least two groups of sealed bearings are arranged in the mounting cylinder, an oil chamber is formed between the two adjacent groups of sealed bearings, or at least one group of combined seals is arranged in the mounting cylinder, and an oil chamber is formed between the two ends of the double-end mechanical seal.

[0006] Furthermore, the first external mechanical seal includes a first dynamic ring and a first static ring. The first static ring is integrally formed with the outer ring of the first bearing body or is separately connected. The first dynamic ring and the first static ring are rotated and sealed together.

[0007] Furthermore, the first stationary ring and the outer ring of the first bearing body are sealed against each other by a sealing gasket.

[0008] Furthermore, the outer periphery of the first static ring and the inner periphery of the mounting cylinder are sealed against each other via a sealing gasket.

[0009] Furthermore, an annular seat is provided on the outer ring of the first bearing body, and the sealing static ring is provided in the annular seat. The first static ring and the annular seat are sealed against each other via a sealing gasket.

[0010] Furthermore, a single-end mechanical seal in which a static ring and a dynamic ring are arranged from far to near relative to the motor chamber is defined as an internal mechanical seal. An internal mechanical seal is provided on the other side of the sealed bearing, and the static ring of the internal mechanical seal is integrally formed with or separately connected to the outer ring of the first bearing body.

[0011] Furthermore, a fixed gasket is provided between the first stationary ring and the outer ring of the first bearing body. The first stationary ring and the fixed gasket are sealed against each other through a sealing gasket, and the fixed gasket is against the outer ring of the first bearing body.

[0012] Furthermore, the double-end mechanical seal includes two second stationary rings and two second dynamic rings. The second stationary ring at one end is integrally formed with the outer ring of the second bearing body or is sealed in a split manner. The second stationary ring at the other end is sealed and connected to the inner circumference of the mounting tube. The two second stationary rings and the two second dynamic rings rotate and seal in a one-to-one manner, and an oil chamber is formed between the two second stationary rings.

[0013] Furthermore, an oil filling hole is opened on the side wall of the oil chamber, and the oil filling wire opens or blocks the oil filling hole.

[0014] Furthermore, a first sealing groove is provided on the outer periphery of the outer ring of the first bearing body, and a first O-ring is provided in the first sealing groove; a second sealing groove is provided on the outer periphery of the outer ring of the second bearing body, and a second O-ring is provided in the second sealing groove; a third sealing groove is provided on the inner wall of the mounting tube, and a third O-ring is provided in the third sealing groove; the mounting tube and the first bearing body are sealedly connected via the first O-ring and the third sealing ring, or the mounting tube and the second bearing body are sealedly connected via the second O-ring and the third sealing ring.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention fixes the first external mechanical seal on the first bearing body, combines the bearing and the external mechanical seal into one, which is "self-sealing" and changes the installation structure and sealing form of the existing seals and bearings. In order to achieve a better sealing effect, multiple sets of seals can be arranged at intervals in the installation cylinder, and only one end cover is required to install multiple sets of external mechanical seals or combined seals, which solves the problem that only one end cover of the existing water pump can be installed with one external mechanical seal. The number of external mechanical seals is not limited by the number of end covers, and solves the problem of having to set both a bearing seat and an end cover to install the bearing and the seal respectively, and the problem that only one set of external mechanical seal can be installed on one end cover. It can provide support for the rotating shaft of the motor and realize the rotation sealing of the rotating shaft. The present invention can eliminate the bearing seat of the water pump body and the specially arranged oil chamber, and set the bearing and multiple external mechanical seals on one end cover, shortening the length of the water pump body, reducing the leakage points, saving the bearing seat or end cover, and having a compact structure, good sealing effect, and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the present invention in which a sealed bearing is provided at the upper end and an oil seal is provided at the lower end;

[0018] Figure 2 This is a schematic diagram of the structure of the combined seal provided in the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the present invention in which a third external mechanical seal is provided at the upper end and an external mechanical seal is provided at the lower end;

[0020] Figure 4 This is a schematic diagram of the structure of the present invention in which two sets of sealed bearings are provided;

[0021] Figure 5 is a structural diagram of embodiment 3 of the present invention;

[0022] Figure 6 is a structural diagram of embodiment 6 of the present invention;

[0023] Figure 7 is a structural diagram of a fourth embodiment of the present invention;

[0024] Figure 8 is a structural diagram of embodiment 2 of the present invention;

[0025] Figure 9 is a structural diagram of a fifth embodiment of the present invention;

[0026] Figure 10 is a structural diagram of embodiment 7 of the present invention;

[0027] Figure 11 It is a structural schematic diagram of the present invention applied to a submersible pump.

[0028] In the figure, 1. End cover, 2. Mounting cylinder, 3. Rotating shaft, 4. Oil filler thread, 5. Sealed bearing, 6. Bearingless seal, 7. Oil chamber, 8. Combined seal, 9. First bearing body, 10. Sealing gasket, 11. First rotating ring, 12. Rotating ring seat, 13. Spring, 14. Spring seat, 15. First stationary ring, 16. Sealing ring, 17. Retaining gasket, 18. Annular seat, 19. Second bearing body, 20. Second stationary ring, 21. Second rotating ring, 22. Impeller, 23. Pump body, 24. Stator, 25. Rotor. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0030] The connections mentioned in the present invention are divided into fixed connections and detachable connections. The fixed connection refers to a non-detachable connection, including but not limited to conventional fixed connection methods such as hem connection, rivet connection, adhesive connection, and welding connection. The detachable connection refers to but not limited to conventional detachable connection methods such as bolt connection, snap connection, pin connection, and hinge connection. When the specific connection method is not clearly specified, it is assumed that at least one connection method can be found among the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example, a welded connection is selected for a fixed connection, and a bolted connection is selected for a detachable connection.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are provided to explain the present invention, but the present invention is not limited to the following embodiments.

[0032] Example 1: Figure 1-Figure 4 As shown, it includes an end cover 1, on which a mounting cylinder 2 is provided. A single-end mechanical seal in which a static ring and a dynamic ring are arranged from near to far relative to the motor chamber is defined as an external mechanical seal. The first bearing body 9 is coaxially connected to the first external mechanical seal to form a sealed bearing 5. The outer ring of the second bearing body 19 is connected to the double-end mechanical seal on the side away from the motor chamber to form a combined seal 8. At least one group of sealed bearings 5 ​​and one group of bearingless seals 6 are arranged in the mounting cylinder 2. The bearingless seal 6 is one of an external mechanical seal, an oil seal or a sealing ring. An oil chamber 7 is formed between the sealed bearing 5 and the adjacent bearingless seal 6, or at least two groups of sealed bearings 5 ​​are arranged in the mounting cylinder 2, and an oil chamber 7 is formed between the two adjacent groups of sealed bearings 5, or at least one group of combined seals 8 is arranged in the mounting cylinder 2, and an oil chamber 7 is formed between the two ends of the double-end mechanical seal.

[0033] Figure 1-Figure 4Four different forms of the sealing structure are shown respectively, specifically, Figure 1 The upper end of the middle mounting tube 2 is provided with a sealing bearing 5, and the lower end is provided with a skeleton oil seal. Figure 2 A combined seal 8 is provided in the middle mounting cylinder 2. Figure 3 The upper end of the middle mounting cylinder 2 is provided with a third external mechanical seal and the lower end is provided with a sealing bearing 5. Figure 4 Two sets of sealed bearings 5 ​​are arranged in the middle mounting tube 2. In fact, under the condition that the size allows, multiple seals can be set in the mounting tube 2, as long as the multiple seals include two external mechanical seals or a combined seal 8, a good sealing effect can be achieved.

[0034] For the sake of distinction, the single-end mechanical seal in which the static ring and the dynamic ring are arranged from far to near relative to the motor chamber is called an internal mechanical seal. Due to the action of centrifugal force, the liquid on one side of the static ring will seep out from the gap between the static ring and the dynamic ring and flow to the side of the dynamic ring. That is, if an external mechanical seal is installed on the end cover between the motor and the impeller, the insulating oil on one side of the motor will leak to the impeller side. If an internal mechanical seal is installed on the end cover between the motor and the impeller, the pumping medium on the impeller side will leak into the motor chamber, causing damage to the motor.

[0035] In the prior art, an end cover and a bearing seat are generally provided between the motor and the impeller of the water pump. The bearing is provided on the bearing seat, and only one external mechanical seal or one internal mechanical seal can be provided on the end cover. The sealing effect of one external mechanical seal cannot absolutely guarantee the sealing performance, and an oil chamber needs to be specially provided between the end cover and the bearing seat.

[0036] The present invention can be used between the pump head and the motor of a submersible pump or a land pump, such as Figure 11 The submersible pump shown in the figure comprises a pump body 23, a rotating shaft 3 is provided in the pump body 23, a rotor 25 is sleeved on the rotating shaft 3, a stator 24 is provided on the inner wall of the pump body 23, the rotor 25 and the stator 24 are rotated in an inner and outer sleeve, and the water inlet seat is replaced with a water inlet pipe. Figure 11 The submersible pump can be transformed into a ground pump, the end cover 1 is connected to the pump body 23, the stator 24 and the rotor 25 are sealed in the closed motor chamber, the lower end of the rotating shaft 3 passes through a group of sealed bearings 5 ​​and a group of bearingless seals 6, and is connected to the impeller 17, or the lower end of the rotating shaft 3 passes through two groups of sealed bearings 5, or the lower end of the rotating shaft 3 passes through a group of combined seals 8, or the lower end of the rotating shaft 3 passes through multiple seals, wherein the multiple seals have at least two external mechanical seals or one combined seal to achieve a good sealing effect.

[0037] The rotating shaft 3 and the mounting cylinder 2 are rotatably connected through the first bearing body 9 or the second bearing body 19 to achieve support for the rotating shaft 3. The rotating shaft 3 and the mounting cylinder 2 are rotatably sealed through a group of sealed bearings 5 ​​and a group of bearingless seals 6, or the rotating shaft 3 and the mounting cylinder 2 are rotatably sealed through two groups of sealed bearings 5, or the rotating shaft 3 and the mounting cylinder 2 are rotatably sealed through a group of combined seals 8, or the rotating shaft 3 and the mounting cylinder 2 are rotatably sealed through a combination of the multiple seals.

[0038] The first bearing body 9 or the second bearing body 19 can achieve axial limitation with respect to the mounting tube 2 through a hole elastic retaining ring or an annular step structure provided on the inner wall of the mounting tube 2, or can achieve axial limitation with respect to the rotating shaft 3 through a shaft elastic retaining ring or a cylindrical pin.

[0039] The present invention fixes the first external mechanical seal on the first bearing body 9, combines the bearing and the external mechanical seal into one, which is "self-sealing" and changes the installation structure and sealing form of the existing seals and bearings. In order to achieve a better sealing effect, multiple groups of seals can be arranged at intervals in the installation cylinder 2, and only one end cover is required to install multiple sets of external mechanical seals or combined seals, which solves the problem that only one end cover of the existing water pump can be installed with one external mechanical seal. The number of external mechanical seals is not limited by the number of end covers, and solves the problem of having to set both a bearing seat and an end cover to install the bearing and the seal respectively, and the problem that only one set of external mechanical seal can be installed on one end cover. It can provide support for the rotating shaft 3 of the motor and realize the rotation sealing of the rotating shaft 3. The present invention can eliminate the bearing seat of the water pump body and the specially arranged oil chamber, and set bearings and multiple external mechanical seals on one end cover, shortening the length of the water pump body, reducing leakage points, saving bearing seats or end covers, and having a compact structure, good sealing effect, and a wide range of applications.

[0040] Example 2: This embodiment is described in conjunction with Example 1. Figure 1 、 Figure 4 、 Figure 8 As shown, the first external mechanical seal includes a first dynamic ring 11 and a first static ring 15 . The first static ring 15 is integrally formed with the outer ring of the first bearing body 9 . The first dynamic ring 11 and the first static ring 15 cooperate in a rotational sealing manner.

[0041] The first external mechanical seal also includes a dynamic ring seat 12, a spring 13 and a spring seat 14. The first static ring 15 is connected to the outer ring of the first bearing body 9. The first dynamic ring 11 is arranged at one end of the dynamic ring seat 12. The first dynamic ring 11 and the first static ring 15 are rotated and sealed. The first dynamic ring 11 and the dynamic ring seat 12 are connected by a sealing ring 16. The other end of the dynamic ring seat 12 is against the spring seat 14 through the spring 13.

[0042] Figure 1 and Figure 4The first bearing body 9 used in the middle sealed bearing 5 is the structure described in detail in this embodiment.

[0043] The spring seat 14 is sleeved on the rotating shaft 3, and the axial limitation of the spring seat 14 and the rotating shaft 3 can be achieved by a cylindrical pin or a shaft elastic circlip.

[0044] The first bearing body 9 can be made of materials such as steel, titanium alloy or ceramic, and the first static ring 15 can be directly made into one piece with the outer ring of the first bearing body 9. In this way, the sealing and fixing problems between the first bearing body 9 and the first static ring 15 can be solved at the same time. The first dynamic ring 11 is sleeved on the rotating shaft 3 so that it rotates together with the rotating shaft 3, and the first dynamic ring 11 and the rotating shaft 3 are sealed by the sealing ring 16. Then, the first dynamic ring 11 and the first static ring 15 are rotated and sealed, so that one end of the oil chamber 7 can be sealed by the sealing bearing 5.

[0045] Example 3: This embodiment is described in conjunction with Example 2. Figure 3 、 Figure 5 As shown, the difference between this embodiment and the second embodiment is that the first stationary ring 15 and the outer ring of the first bearing body 9 are sealed against each other by the sealing gasket 10 .

[0046] Figure 3 The first bearing body 9 used for the sealed bearing 5 at the lower end is the structure described in detail in this embodiment. The first static ring 15 includes a static grinding ring and a sealing gasket 10. The sealing gasket 10 is covered on one end and the outer periphery of the static grinding ring. The sealing gasket 10 is a rubber component. When the first static ring 15 is in contact with the first bearing body 9, it is sealed by the sealing gasket 10. The outer periphery of the static grinding ring is sealed with the inner wall of the mounting tube 2 through the sealing gasket 10.

[0047] Example 4: This embodiment is described in conjunction with Example 3. Figure 7 As shown, an annular seat 18 is provided on the outer ring of the first bearing body 1 , the sealing static ring 7 is provided in the annular seat 18 , and the first static ring 15 and the annular seat 18 are sealed against each other via a sealing gasket 10 .

[0048] Figure 7 The first bearing body 9 used in the upper sealed bearing 5 is the structure detailed in this embodiment. An annular seat 18 is provided on the outer ring of the first bearing body 9 to reliably fix the first external mechanical seal. The static grinding ring and annular seat 18 are sealed together by a sealing gasket 10.

[0049] Example 5: Figure 9 As shown, this embodiment is described in combination with Example 1 and Example 2. The difference between this embodiment and Example 2 is that a single-end mechanical seal in which a static ring and a dynamic ring are arranged from far to near relative to the motor chamber is defined as an inner mechanical seal, and an inner mechanical seal is provided on the other side of the sealed bearing 5. The static ring of the inner mechanical seal is integrally formed with or separately connected to the outer ring of the first bearing body 9.

[0050] The internal mechanical seal can prevent the insulating oil in the motor chamber from leaking out.

[0051] Example 6: Figure 4 、 Figure 6 As shown, this embodiment is explained in combination with embodiment three. The difference between this embodiment and embodiment three is that a fixed pad 17 is provided between the first stationary ring 15 and the outer ring of the first bearing body 9. The first stationary ring 15 and the fixed pad 17 are sealed against each other through the sealing pad 10, and the fixed pad 17 is against the outer ring of the first bearing body 9.

[0052] The fixing gasket 17 is used to raise the first outer mechanical seal and provide an installation position for the first outer mechanical seal.

[0053] Example 7: Figure 2 、 Figure 10 As shown, this embodiment provides a specific structure of the combined seal 8. The double-end mechanical seal includes two second stationary rings 20 and two second dynamic rings 21. The second stationary ring 20 at one end is integrally formed with the outer ring of the second bearing body 19 or is sealed in a split manner. The second stationary ring 20 at the other end is sealed and connected to the inner periphery of the mounting tube 2. The two second stationary rings 20 and the two second dynamic rings 21 are rotated and sealed in a one-to-one manner, and an oil chamber 7 is formed between the two second stationary rings 20.

[0054] Example 8: Figure 1-Figure 4 As shown, an oil filling hole is opened on the side wall of the oil chamber 20, and the oil filling wire 19 opens or blocks the oil filling hole. By opening an oil filling hole on the side wall of the oil chamber 20 and blocking the oil filling hole through the oil filling wire 19, the oil chamber 20 can be filled with oil.

[0055] Example 9: Figure 1 、 Figure 5 As shown, in order to prevent water from entering between the mounting cylinder 2 and the first bearing body 9 or the second bearing body 19, a first sealing groove is provided on the outer periphery of the outer ring of the first bearing body 9, and a first O-ring is provided in the first sealing groove. A second sealing groove is provided on the outer periphery of the outer ring of the second bearing body 19, and a second O-ring is provided in the second sealing groove. A third sealing groove is provided on the inner wall of the mounting cylinder 2, and a third O-ring is provided in the third sealing groove. The mounting cylinder 2 and the first bearing body 9 are sealedly connected by the first O-ring and the third sealing ring, or the mounting cylinder 2 and the second bearing body 19 are sealedly connected by the second O-ring and the third sealing ring.

[0056] The above embodiments are merely illustrative of the present invention and do not limit its scope of protection. Those skilled in the art may make partial changes thereto, which are within the scope of protection of the present invention as long as they do not exceed the spirit of the present invention.

Claims

1. A water pump sealing structure, characterized in that: The invention comprises an end cover (1), a mounting cylinder (2) is provided on the end cover (1), a single-end mechanical seal in which a static ring and a dynamic ring are arranged from near to far relative to a motor chamber is defined as an external mechanical seal, a first bearing body (9) is coaxially connected to the first external mechanical seal to form a sealed bearing (5), an outer ring of a second bearing body (19) is connected to a double-end mechanical seal on a side away from the motor chamber to form a combined seal (8), at least one set of sealed bearings (5) and one set of bearingless seals (6) are arranged in the mounting cylinder (2), the bearingless seals (6) are one of an external mechanical seal, an oil seal or a sealing ring, an oil chamber (7) is formed between the sealed bearing (5) and the adjacent bearingless seals (6), or at least two sets of sealed bearings (5) are arranged in the mounting cylinder (2), an oil chamber (7) is formed between the two adjacent sets of sealed bearings (5), or at least one set of combined seals (8) is arranged in the mounting cylinder (2), and an oil chamber (7) is formed between the two ends of the double-end mechanical seal.

2. A water pump sealing structure according to claim 1, characterized in that: The first external mechanical seal comprises a first dynamic ring (11) and a first static ring (15); the first static ring (15) is integrally formed with the outer ring of the first bearing body (9) or is separately connected; the first dynamic ring (11) and the first static ring (15) are engaged in a rotational sealing manner.

3. A water pump sealing structure according to claim 2, characterized in that: The first stationary ring (15) and the outer ring of the first bearing body (9) are sealed against each other through a sealing gasket (10).

4. A water pump sealing structure according to claim 3, characterized in that: The outer periphery of the first stationary ring (15) and the inner periphery of the mounting cylinder (2) are sealed against each other via a sealing gasket (10).

5. A water pump sealing structure according to claim 4, characterized in that: An annular seat (18) is provided on the outer ring of the first bearing body (9), a sealing static ring (7) is provided in the annular seat (18), and the first static ring (15) and the annular seat (18) are sealed against each other via a sealing gasket (10).

6. A water pump sealing structure according to claim 5, characterized in that: Definition: A single-end mechanical seal in which a static ring and a dynamic ring are arranged from far to near relative to the motor chamber is called an internal mechanical seal. An internal mechanical seal is provided on the other side of the sealed bearing (5). The static ring of the internal mechanical seal is integrally formed with or separately connected to the outer ring of the first bearing body (9).

7. A water pump sealing structure according to claim 3, characterized in that: A fixed gasket (17) is provided between the first stationary ring (15) and the outer ring of the first bearing body (9). The first stationary ring (15) and the fixed gasket (17) are sealed against each other through a sealing gasket (10), and the fixed gasket (17) is against the outer ring of the first bearing body (9).

8. The water pump sealing structure according to claim 1, characterized in that: The double-end mechanical seal comprises two second stationary rings (20) and two second dynamic rings (21), wherein the second stationary ring (20) at one end is integrally formed with the outer ring of the second bearing body (19) or is sealed separately, and the second stationary ring (20) at the other end is sealedly connected to the inner circumference of the mounting cylinder (2), the two second stationary rings (20) and the two second dynamic rings (21) are rotated and sealed in a one-to-one correspondence, and an oil chamber (7) is formed between the two second stationary rings (20).

9. A water pump sealing structure according to any one of claims 1 to 8, characterized in that: An oil filling hole is provided on the side wall of the oil chamber (7), and an oil filling wire (19) opens or blocks the oil filling hole.

10. A water pump sealing structure according to any one of claims 1 to 8, characterized in that: A first sealing groove is provided on the outer circumference of the outer ring of the first bearing body (9), and a first O-ring is provided in the first sealing groove. A second sealing groove is provided on the outer circumference of the outer ring of the second bearing body (19), and a second O-ring is provided in the second sealing groove. A third sealing groove is provided on the inner wall of the mounting cylinder (2), and a third O-ring is provided in the third sealing groove. The mounting cylinder (2) and the first bearing body (9) are sealed and connected via the first O-ring and the third sealing ring, or the mounting cylinder (2) and the second bearing body (19) are sealed and connected via the second O-ring and the third sealing ring.

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