A non-flush mechanical seal

Abstract

The present invention discloses a non-flush mechanical seal, comprising: a first shaft sleeve fixedly arranged on a rotating shaft; a gland fixedly arranged on a housing; a first sealing structure arranged between the first shaft sleeve and the gland and close to the atmosphere side; a second sealing structure arranged between the first shaft sleeve and the gland and close to the medium side, and a dynamic pressure groove for pumping outward to the outer diameter side is arranged on the sealing end face of the second sealing structure; a non-flush structure for realizing non-flush cooling of the second sealing structure. By arranging the dynamic pressure groove and the non-flush structure, the continuous flow of liquid at the sealing end face of the second sealing structure plays a role in cooling, avoiding the setting of a cooling system for flushing the second sealing structure, which is beneficial to the simplification of the structure; the sealing end face of the second sealing structure is in a full liquid film lubrication state, which is beneficial to improving the high temperature and high pressure resistance of the sealing device, reducing the friction and wear of the sealing end face, reducing the excessive frictional heat generated during the friction process, and improving the service life of the seal.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical seals, and particularly relates to a non-flushing mechanical seal. Background Art

[0002] With the increasing development of industries such as petroleum, chemical engineering, aerospace, and natural gas transportation, the requirements for mechanical seals are getting higher and higher. For mechanical seals for transporting high-temperature media without a flushing system, the requirements are even higher. During the operation of the seal, the sealing end faces of the moving and static rings rub and wear against each other, generating a large amount of frictional heat, resulting in a sharp rise in the temperature between the sealing end faces. Without an external flushing system, huge thermal stresses are generated on the sealing end faces, and in severe cases, phase changes such as vaporization and cavitation may occur on the sealing end faces, causing increased wear and severely shortening the service life of the seal. Therefore, it is necessary to set up a cooling system connected to the outside, with a liquid inlet hole provided so that the fluid impacts the sealing end face for flushing and cooling of the sealing end face, and a liquid outlet hole is provided so that the fluid circulates to play a role in cooling the sealing end face; when multiple sealing structures are serially arranged at the shaft end, a cooling system is provided for the sealing end face of each sealing structure, making the mechanical seal structure complex.

[0003] The above information disclosed in this background art is only used to increase the understanding of the background art of the present application. Therefore, it may include prior art that is not known to those of ordinary skill in the art. Summary of the Invention

[0004] The present invention aims at the above problems in the prior art and proposes a non-flushing mechanical seal.

[0005] To achieve the above invention purpose, the present invention adopts the following technical solutions to be realized:

[0006] A non-flushing mechanical seal, comprising:

[0007] A first shaft sleeve fixedly provided on a rotating shaft;

[0008] A gland fixedly provided on a housing;

[0009] A first sealing structure provided between the first shaft sleeve and the gland and close to the atmosphere side;

[0010] A second sealing structure provided between the first shaft sleeve and the gland and close to the medium side, and a hydrodynamic groove for pumping outward to the outer diameter side is provided on the sealing end face of the second sealing structure;

[0011] A non-flushing structure is used to achieve non-flushing cooling of the second sealing structure. The non-flushing structure has a first sealing cavity located on the outer diameter side of the sealing end face of the second sealing structure, a second sealing cavity located on the inner diameter side of the sealing end face of the second sealing structure, a flow-through cavity communicating with the second sealing cavity, and a liquid supply cavity for supplying liquid to the flow-through cavity. A movable first sealing ring is provided in the flow-through cavity and is used to achieve communication between the first sealing cavity and the flow-through cavity or between the liquid supply cavity and the flow-through cavity.

[0012] Further, the flow-through cavity communicates with the one of the first sealing cavity and the liquid supply cavity having a greater liquid pressure.

[0013] Further, the pressure difference between the liquids in the first sealing cavity and the liquid supply cavity pushes the first sealing ring to move in the flow-through cavity.

[0014] Further, a second shaft sleeve fixedly provided on the rotating shaft is further included. A pumping groove for pumping liquid into the first sealing cavity is provided on the outer end face of the second shaft sleeve. The second sealing structure is located between the first shaft sleeve and the first sealing structure.

[0015] Further, a first through hole communicating the second sealing cavity and the flow-through cavity is provided on the first shaft sleeve. The first through hole is used to supply the liquid in the flow-through cavity to the second sealing cavity.

[0016] Further, the first through hole has an axial section extending axially away from the second sealing cavity and a radial section extending radially.

[0017] Further, a second through hole communicating the second sealing cavity and the liquid supply cavity is provided on the first shaft sleeve. The diameter of the second through hole is greater than the diameter of the first through hole.

[0018] Further, the first through hole is connected to one end of the second sealing cavity close to the medium side. The sealing end face of the second sealing structure is located between the first through hole and the second through hole.

[0019] Further, a cooling structure system is further included, which is used to achieve flushing cooling of the first sealing structure. The cooling structure has a liquid inlet hole and a liquid outlet hole provided on the gland. The liquid inlet hole is located on the outer diameter side of the sealing end face of the first sealing structure. A third sealing cavity communicating with the liquid inlet hole is defined between the first sealing structure and the gland. The liquid outlet hole communicates with the second sealing cavity.

[0020] Further, a pumping ring for pumping the liquid in the third sealing cavity into the second sealing cavity is provided between the third sealing cavity and the second sealing cavity. The pumping ring is provided on the first shaft sleeve.

[0021] Furthermore, a limiting ring sleeving outside the pumping ring is provided on the gland, and there is a gap for communicating the third sealing cavity and the second sealing cavity between the pumping ring and the limiting ring.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows: By providing the hydrodynamic groove and the non-flushing structure, a second circulation flow path for cooling is formed flowing through the second sealing structure, so that the liquid continuously flows at the sealing end face of the second sealing structure, which is used to take away the heat at the sealing end face of the second sealing structure, playing a role in cooling, avoiding the setting of a cooling system for flushing the second sealing structure, and being beneficial to the simplification of the structure; and because the liquid continuously flows through the sealing end face of the second sealing structure, the cooling effect is better, and the sealing end face of the first sealing structure is in a full liquid film lubrication state, which is beneficial to improving the high temperature and high pressure resistance of the sealing device, reducing the friction and wear of the sealing end face, reducing the excessive frictional heat generated during the friction process, and improving the service life of the seal. The first sealing ring is provided to ensure that each chamber in the non-flushing structure can be self-regulated according to the liquid pressure therein, ensuring the continuous operation of the second circulation flow path and ensuring the cooling effect on the sealing end face of the second sealing structure.

[0023] After reading the specific embodiments of the present invention in conjunction with the drawings, other features and advantages of the present invention will become clearer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic structural diagram of an embodiment of a non-flushing mechanical seal proposed by the present invention;

[0026] Figure 2 For Figure 1 a schematic diagram of a partial structure in

[0027] Figure 3 For Figure 2 an enlarged structural diagram of the second sealing structure in

[0028] Figure 4 For Figure 2 an enlarged structural diagram of the first sealing structure in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the positional relationship shown in the accompanying drawings, with the direction close to the axis of the inner cylinder being "inner" and the opposite being "outer". The terms are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more, unless otherwise specifically and clearly defined.

[0031] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] See Figures 1-4 , which is an embodiment of a non-flushing mechanical seal proposed by the present invention. A non-flushing mechanical seal includes: a first shaft sleeve 10, a gland 20, a first sealing structure 30, a second sealing structure 40, and a non-flushing structure 50. The first shaft sleeve 10 is fixedly sleeved on the rotating shaft 100, and the gland 20 is fixedly arranged on the housing 200 of the mechanical equipment; the first sealing structure 30 and the second sealing structure 40 are axially connected in series between the first shaft sleeve 10 and the gland 20. The first sealing structure 30 is close to the atmosphere side, and the second sealing structure 40 is close to the medium side; a dynamic pressure groove for pumping outward to the outer diameter side is provided on the sealing end face of the second sealing structure 40; the non-flushing structure 50 is used to achieve non-flushing cooling of the second sealing structure. The non-flushing structure 50 has a first sealing cavity 51 located on the outer diameter side of the sealing end face of the second sealing structure 40, a second sealing cavity 52 located on the inner diameter side of the sealing end face of the second sealing structure 40, a flow supply cavity 53 communicating with the second sealing cavity 52, and a flow through cavity 55. A movable first sealing ring 56 is provided in the flow through cavity 55. By the movement of the first sealing ring 56, it is used to achieve the communication between the first sealing cavity 51 and the flow through cavity 55 or the communication between the flow supply cavity 53 and the flow through cavity 55.

[0033] The gland 20 has a first gland 21 and a second gland 22 assembled together, where the first gland 21 is used to fix the first stationary ring 31 of the first sealing structure 30, and the second gland 22 is used to fix the second stationary ring 41 of the second sealing structure 40. When the fluid supply chamber 53 communicates with the fluid passing chamber 55, the first sealing ring 56 is located on the medium side of the fluid passing chamber 55, that is, on the left side shown in the figure. At this time, the first sealing ring 56 seals between the first sealing chamber 51 and the fluid passing chamber 55. The fluid supply chamber 53 communicates with the fluid passing chamber 55, and the liquid in the fluid supply chamber 53 can reach the fluid passing chamber 55 and be supplied into the second sealing chamber 52; the dynamic pressure groove on the sealing end face of the second sealing structure 40 pumps the liquid from the inner diameter side to the outer diameter side, that is, from the second sealing chamber 52 to the first sealing chamber 51. The liquid flows through the sealing end face of the second sealing structure 40 to take away heat and cool the sealing end face of the second sealing structure 40; the continuous pumping of the dynamic pressure groove increases the liquid pressure in the first sealing chamber 51. When the liquid pressure in the first sealing chamber 51 is greater than the liquid pressure in the fluid supply chamber 53, the first sealing ring 56 in the fluid passing chamber 55 is pushed and moves towards the atmosphere side, so that the fluid supply chamber 53 is sealed from the fluid passing chamber 55, and the first sealing chamber 51 communicates with the fluid passing chamber 55; the liquid in the first sealing chamber 51 flows into the fluid passing chamber 55, then enters the second sealing chamber 52, and after flowing through the sealing end face of the second sealing structure 40, it flows into the first sealing chamber 51, forming a second circulation flow path for cooling that flows through the second sealing structure 40. When the liquid pressure in the fluid supply chamber 53 is greater than the liquid pressure in the first sealing chamber 51, the pressure difference between the liquid in the fluid supply chamber 53 and the liquid in the first sealing chamber 51 pushes the first sealing ring 56 in the fluid passing chamber 55 towards the medium side, so that the fluid supply chamber 53 communicates with the fluid passing chamber 55. By setting the first sealing ring 56, it is ensured that each chamber in the non-flushing structure can be self-regulated according to the liquid pressure therein, adjusting the communication between the first sealing chamber 51 and the fluid passing chamber 55 or the communication between the fluid supply chamber 53 and the fluid passing chamber 55, ensuring the continuous operation of the second circulation flow path, and ensuring the cooling effect on the sealing end face of the second sealing structure 40.

[0034] By setting the dynamic pressure groove and the non-flushing structure and forming a second circulation flow path for cooling that flows through the second sealing structure 40, the continuous flow of the liquid at the sealing end face of the second sealing structure 40 is achieved, which is used to take away the heat at the sealing end face of the second sealing structure 40 and play a role in cooling. Avoid setting a cooling structure for flushing the second sealing structure 40, which is beneficial to the simplification of the structure, and realizing the full liquid film lubrication state of the sealing end face of the second sealing structure 40, which is beneficial to improving the high temperature and high pressure resistance of the sealing device, reducing the friction and wear of the sealing end face, reducing the excessive frictional heat generated during the friction process, and improving the sealing service life; due to the continuous flow of the liquid through the sealing end face of the second sealing structure 40, the cooling effect is better.

[0035] The movement of the first sealing ring 56 is driven by the pressure difference between the liquid in the flow supply chamber 53 and the liquid in the first sealing chamber 51. There is no need to set up a structure for driving the movement of the first sealing ring 56, nor is it necessary to set up a monitoring system for the non-flushing structure, realizing self-regulation and facilitating the simplification of the structure. The flow-through chamber 55 is connected to the one with a larger liquid pressure among the first sealing chamber 51 and the flow supply chamber 53. That is, if the liquid pressure in the first sealing chamber 51 is greater than the liquid pressure in the flow supply chamber 53, the flow-through chamber 55 is connected to the flow-through chamber 55; if the liquid pressure in the first sealing chamber 51 is less than the liquid pressure in the flow supply chamber 53, the flow supply chamber 53 is connected to the flow-through chamber 55.

[0036] In order to maintain the pressure in the first sealing chamber 51, the non-flushing mechanical seal includes a second shaft sleeve 60 fixedly arranged on the rotating shaft 100. A pumping groove for pumping liquid into the first sealing chamber 51 is formed on the outer end face of the second shaft sleeve 60. The second sealing structure 40 is located between the first shaft sleeve 10 and the first sealing structure 30. During the rotation of the rotating shaft 100, the second shaft sleeve 60 is driven to rotate together. Through the pumping groove on the second shaft sleeve 60, the medium is pumped into the first sealing chamber 51. Under the combined action of the dynamic pressure groove on the sealing end face of the second sealing structure 40 and the pumping groove on the second shaft sleeve 60, after the pressure reaches dynamic balance, the liquid pressure in the first sealing chamber 51 is the highest, and the working medium will not leak out. And the first sealing chamber 51, the flow-through chamber 55, the second sealing chamber 52, and the sealing end face of the second sealing structure 40 form a second circulation path, which quickly takes away the heat generated at the sealing end face of the second sealing structure 40 under high-temperature conditions, reduces the frictional heat generated by the relative movement of the sealing end face of the second sealing structure 40, improves the mechanical seal performance, and prolongs the service life of the seal.

[0037] In this embodiment, both the flow-through chamber 55 and the flow supply chamber 53 are annular cavities coaxially arranged with the first shaft sleeve 10. An annular groove is formed on the inner diameter side of the first shaft sleeve 10. After the first shaft sleeve 10 is sleeved on the rotating shaft 100, the flow-through chamber 55 and the flow supply chamber 53 are formed between the first shaft sleeve 10 and the rotating shaft 100. The flow-through chamber 55 and the flow supply chamber 53 are connected through the gap between the first shaft sleeve 10 and the rotating shaft 100. The first sealing chamber 51 and the flow-through chamber 55 are also connected through the gap between the first shaft sleeve 10 and the rotating shaft 100. Such a setting is conducive to the simplification of the structure, is conducive to processing and manufacturing, is conducive to reducing the manufacturing cost, and is conducive to ensuring the structural strength of the first shaft sleeve 10.

[0038] To achieve the connection between the second sealing cavity 52 and the flow-through cavity 55, a first through-hole 57 is provided in the first shaft sleeve 10. One end of the first through-hole 57 is connected to the second sealing cavity 52, and the other end is connected to the flow-through cavity 55. The first through-hole 57 is used to supply the liquid in the flow-through cavity 55 into the second sealing cavity 52. Specifically, the first through-hole 57 is connected to one end of the second sealing cavity 52 close to the medium side. The first through-hole 57 has an axial section 571 extending axially away from the second sealing cavity 52 and a radial section 572 extending radially. The ratio of the length of the axial section 571 to the length of the radial section 572 is 5:2. By providing the axial section 571, the liquid flowing through the first through-hole 57 and entering the second sealing cavity 52 flows axially towards the atmosphere side, which is beneficial to the flow of the liquid towards the sealing end face of the second sealing structure 40 and beneficial to the flow of the liquid in the second sealing cavity 52. And by providing the axial section 571, it is beneficial for the flow-through cavity 55 to approach the first sealing cavity 51 axially and beneficial to shorten the distance of the gap between the flow-through cavity 55 and the first sealing cavity 51.

[0039] The distance between the left end face of the radial section 572 of the first through-hole 57 and the left end face of the flow-through cavity 55 is greater than the diameter of the first sealing ring 56, and the distance between the right end face of the radial section 572 of the first through-hole 57 and the right end face of the flow-through cavity 55 is greater than the diameter of the first sealing ring 56. When the first sealing ring 56 is located on the left or right side of the flow-through cavity 55, the first sealing ring 56 will not block the radial section 572 to ensure that the liquid flow from the flow-through cavity 55 into the radial section 572 will not be blocked by the first sealing ring 56.

[0040] To achieve the liquid supply in the supply cavity 53, a second through-hole 54 communicating the second sealing cavity 52 and the supply cavity 53 is provided in the first shaft sleeve 10, and the diameter of the second through-hole 54 is set to be greater than the diameter of the first through-hole 57. To ensure that the liquid reaching the second sealing cavity 52 preferably reaches the supply cavity 53 through the second through-hole 54, and preferably multiple second through-holes 54 are provided in the circumferential direction.

[0041] In other embodiments, the supply cavity 53 can be set to communicate with other chambers.

[0042] The outlet end of the first through-hole 57 is located at one end of the second sealing cavity 52 close to the medium side, and the sealing end face of the second sealing structure 40 is located between the first through-hole 57 and the second through-hole 54. The liquid supplied to the second sealing cavity 52 flows into the supply cavity 53 through the second through-hole 54. When the pressure of the liquid in the supply cavity 5 is greater than the pressure of the liquid in the first sealing cavity 51, the supply cavity 5 communicates with the flow-through cavity 55, and the liquid in the supply cavity 5 flows through the flow-through cavity 55 and then enters the second sealing cavity 52.

[0043] The non-flush mechanical seal further includes a cooling structure, which is used to achieve the flushing and cooling of the first seal structure. On the one hand, the cooling structure realizes the flushing and cooling of the first seal structure 30, and on the other hand, it inhibits the leakage of the sealed medium to the atmosphere. The cooling structure has a liquid inlet hole 211 and a liquid outlet hole 212 opened on the first gland 21. The liquid inlet hole 211 is located on the outer diameter side of the sealing end face of the first seal structure 30 to achieve the flushing of the sealing end face of the first seal structure 30. A third seal cavity 71 communicating with the liquid inlet hole 211 is defined between the first seal structure 30 and the gland 20, and the liquid outlet hole 212 communicates with the second seal cavity 52. The external isolating liquid enters the third seal cavity 71 through the liquid inlet hole 211, then enters the second seal cavity 52, and flows into the supply cavity 53 through the second through hole 54. When the pressure of the liquid in the supply cavity 53 is greater than the pressure of the liquid in the first seal cavity 51, the supply cavity 5 communicates with the overflow cavity 55. The liquid in the supply cavity 53 flows through the overflow cavity 55 and then enters the second seal cavity 52, and then flows out through the liquid outlet hole 212. The path of the liquid flowing through the liquid inlet hole 2, the third seal cavity 71, the second seal cavity 52, the supply cavity 53, the overflow cavity 55, the second seal cavity 52, and the liquid outlet hole 212 is the first circulation flow path, which realizes the cooling of the first seal structure 30 and is used to replenish the liquid for the second circulation flow path to adjust the liquid pressure in each cavity. During the rotation of the rotating shaft 100, the continuous pumping of the dynamic pressure groove on the sealing end face of the second seal structure 40 increases the liquid pressure in the first seal cavity 51. When the liquid pressure in the first seal cavity 51 is greater than the liquid pressure in the supply cavity 53, the first sealing ring 56 in the overflow cavity 55 is pushed and moves towards the atmosphere side, so that the seal between the supply cavity 53 and the overflow cavity 55 is formed, and the first seal cavity 51 and the overflow cavity 55 communicate. The dynamic pressure balance of each cavity is achieved, so that the liquid in the first seal cavity 51 flows into the overflow cavity 55, then enters the second seal cavity 52, and flows into the first seal cavity 51 after flowing through the sealing end face of the second seal structure 40, forming a second circulation flow path for cooling flowing through the second seal structure 40. At this time, the supply cavity 5 and the overflow cavity 55 in the first circulation flow path are not connected, that is, the liquid in the first circulation flow path flows through the liquid inlet hole 2, the third seal cavity 71, the second seal cavity 52, and the liquid outlet hole 212.

[0044] In order to enable the liquid to flow between the third sealing cavity 71 and the second sealing cavity 52, a pumping ring 81 is provided between the third sealing cavity 71 and the second sealing cavity 52 for pumping the liquid in the third sealing cavity 52 into the second sealing cavity 52. The pumping ring 81 is arranged on the first shaft sleeve 10. When the rotating shaft 100 rotates, the pumping ring 81 rotates together with the first shaft sleeve 10 to pump the liquid in the third sealing cavity 71 into the second sealing cavity 52; to ensure the circulation of the first circulation path, the liquid between the third sealing cavity 71 and the second sealing cavity 52 is made to flow through pumping, which is beneficial to ensuring the pressure of the liquid in the second sealing cavity 52. Specifically, a limiting ring 23 sleeving the outside of the pumping ring 81 is provided on the gland 20, and there is a gap for the third sealing cavity 71 and the second sealing cavity 52 to communicate between the pumping ring 81 and the limiting ring 23.

[0045] Describe the first sealing structure 30. The first sealing structure 30 has a first static ring 31, a first dynamic ring 32, a first pushing ring 33, and a first spring seat 34. The first static ring 31 is fixedly arranged on the first gland 21, the first spring seat 34 is fixedly arranged on the first shaft sleeve 60, a first spring is provided on the first spring seat 34, and a first pushing ring 33 is provided between the first spring and the first dynamic ring 32. The elastic force of the first spring acts on the first dynamic ring 32 through the first pushing ring 33, and the first dynamic ring 32 is axially movable and arranged on the first shaft sleeve 60. The pumping ring 81 is fixedly arranged on the outside of the first spring seat 34.

[0046] Describe the second sealing structure 40. The second sealing structure 40 has a second static ring 41, a second dynamic ring 42, a second pushing ring 43, and a second spring seat 44. The second static ring 41 is fixedly arranged on the second gland 22, the second spring seat 44 is fixedly arranged on the first shaft sleeve 60, a second spring is provided on the second spring seat 44, and a second pushing ring 43 is provided between the second spring and the second dynamic ring 42. The elastic force of the second spring acts on the second dynamic ring 42 through the second pushing ring 43, and the second dynamic ring 42 is axially movable and arranged on the first shaft sleeve 60.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, for those of ordinary skill in the art, it is still possible to modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions required to be protected by the present invention.

Claims

1. A non-flush mechanical seal, characterized in that, Comprising: A first bushing fixedly provided on a rotating shaft; A gland fixedly provided at an end of a housing of a mechanical device; A first sealing structure provided between the first bushing and the gland and near the atmosphere side; A second sealing structure provided between the first bushing and the gland and near the medium side, and a dynamic pressure groove for pumping outward to the outer diameter side is provided on a sealing end face of the second sealing structure; A non-flushing structure for realizing non-flushing cooling of the second sealing structure; the non-flushing structure has a first sealing cavity located on the outer diameter side of the sealing end face of the second sealing structure, a second sealing cavity located on the inner diameter side of the sealing end face of the second sealing structure, a flow-through cavity communicated with the second sealing cavity, and a liquid supply cavity for supplying liquid to the flow-through cavity. A first sealing ring that is movable and used to connect the first sealing cavity and the flow-through cavity or the liquid supply cavity and the flow-through cavity is provided in the flow-through cavity; The gland has a first gland and a second gland which are assembled and arranged.

2. The non-flush mechanical seal according to claim 1, wherein A pressure difference between liquids in the first sealing cavity and the liquid supply cavity pushes the first sealing ring to move in the flow-through cavity, and the flow-through cavity is communicated with the one with a larger liquid pressure in the first sealing cavity and the liquid supply cavity.

3. The non-flush mechanical seal according to claim 1, wherein It further includes a second bushing fixedly provided on the rotating shaft. A pumping groove for pumping liquid to the first sealing cavity is provided on an outer end face of the second bushing, and the second sealing structure is located between the first bushing and the first sealing structure.

4. The non-flush mechanical seal according to claim 1, wherein A first through hole communicating the second sealing cavity and the flow-through cavity is provided on the first bushing, and the first through hole is used to supply the liquid in the flow-through cavity to the second sealing cavity.

5. The non-flushing mechanical seal according to claim 4, characterized in that, The first through hole has an axial section extending axially away from the second sealing cavity and a radial section extending radially.

6. The non-flush mechanical seal according to claim 4, characterized in that, A second through hole communicating the second sealing cavity and the liquid supply cavity is provided on the first bushing, and the diameter of the second through hole is larger than that of the first through hole.

7. The non-flush mechanical seal according to claim 6, wherein The first through hole is connected to one end of the second sealing cavity near the medium side, and the sealing end face of the second sealing structure is located between the first through hole and the second through hole.

8. The non-flush mechanical seal according to any one of claims 1 to 7, characterized in that, It further includes a cooling structure system for realizing flushing and cooling of the first sealing structure. The cooling structure has a liquid inlet hole and a liquid outlet hole provided on the gland. The liquid inlet hole is located on the outer diameter side of the sealing end face of the first sealing structure; a third sealing cavity communicated with the liquid inlet hole is defined between the first sealing structure and the gland, and the liquid outlet hole is communicated with the second sealing cavity.

9. The non-flush mechanical seal according to claim 8, characterized in that, A pumping ring for pumping the liquid in the third sealing cavity into the second sealing cavity is provided between the third sealing cavity and the second sealing cavity, and the pumping ring is provided on the first bushing.

10. The non-flush mechanical seal according to claim 9, wherein A limiting ring sleeved outside the pumping ring is provided on the gland, and a gap for communicating the third sealing cavity and the second sealing cavity is provided between the pumping ring and the limiting ring.

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