A mechanical seal for a screw compressor

Abstract

The present invention provides a mechanical seal for a screw compressor, comprising a shaft sleeve, a gland, and a primary seal and a secondary seal mounted therebetween, with an isolation chamber formed between the primary seal and the secondary seal. A lip seal is provided on the inner cavity wall of the gland near the medium end, at a position corresponding to the mounting boss at one end of the shaft sleeve. The inner ring of the lip seal is sealed onto the outer wall of the mounting boss, so that a sealed chamber is formed between the outer side of the main seal and the inner cavity wall of the gland. The gland is provided with a liquid inlet and a liquid outlet, each of which is connected to the sealed chamber. A flow guide is provided on the inner cavity wall of the gland so that flushing liquid from the liquid inlet directly flushes the outer side of the friction pair of the main seal, and the liquid inlet and outlet are axially located on both sides of the flow guide. An exhaust port connected to the isolation chamber is provided on the side wall of the gland. The mechanical seal for a screw compressor disclosed by the present invention can effectively seal lubricating oil and stably seal refrigerant.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical seals, and in particular to a mechanical seal for a screw compressor. Background Art

[0002] A mechanical seal is a shaft sealing device for rotating machinery. Because the rotating shaft runs through the inside and outside of the equipment, a circumferential gap exists between the shaft and the equipment. The medium in the equipment can leak out through this gap. If the pressure inside the equipment is lower than atmospheric pressure, air will leak into the equipment. Therefore, a shaft seal device is necessary to prevent leakage. There are many types of shaft seals, but mechanical seals are the most common shaft sealing method used in these devices due to their advantages such as low leakage and long life.

[0003] Screw compressors combine the advantages of centrifugal and piston compressors while avoiding their shortcomings. This exceptional adaptability makes them widely applicable worldwide, from small chemical processes to large chemical plants. Therefore, process screw compressors are the preferred choice for many chemical and petrochemical operations and processes. Oil-injected twin-screw compressors, with their high reliability and low operating costs, are ideal compression equipment for process gases and other applications. Currently, there is a type of screw compressor whose medium is lubricating oil containing 20%-30% refrigerant, operating at speeds of 3000-5000 RPM and pressures up to 1.5 MPa. Existing mechanical seals for this type of compressor can seal the lubricating oil, but are less effective against the refrigerant. Furthermore, the seal chamber pressure of this type of compressor fluctuates significantly, placing certain demands on the mechanical seal's pressure regulation performance. Summary of the Invention

[0004] The problem to be solved by the present invention is to overcome at least one defect in the prior art and provide a mechanical seal for a screw compressor, which can effectively achieve lubricating oil sealing and stable refrigerant sealing.

[0005] In order to solve the above problems, the present invention provides a mechanical seal for a screw compressor, comprising a shaft sleeve and a gland sleeved on the outside of the shaft sleeve, a main seal is provided between the end of the shaft sleeve close to the medium and one end of the gland inner cavity, and a secondary seal is provided between the end of the shaft sleeve close to the atmosphere and the other end of the gland inner cavity, so that an isolation cavity is formed between the outside of the shaft sleeve and the gland inner cavity, a mounting boss is provided at the end of the shaft sleeve close to the medium, a first mounting groove is provided at one end of the gland inner cavity, one end of the main seal is fitted on the end of the mounting boss away from the medium, and the other end is fitted in the first mounting groove Inside; a lip seal is provided on the inner cavity wall of the gland at a position corresponding to the mounting boss, and the inner ring of the lip seal is sealingly sleeved on the outer wall of the mounting boss to form a sealed cavity between the outer side of the main seal and the inner cavity wall of the gland, and a liquid inlet hole and a liquid outlet hole respectively connected to the sealed cavity are provided on the gland, and a guide portion is provided on the inner cavity wall of the gland to enable the flushing liquid in the liquid inlet hole to directly flush the outer side of the friction pair of the main seal, and the liquid inlet hole and the liquid outlet hole are axially located on both sides of the guide portion; an exhaust port connected to the isolation cavity is provided on the side wall of the gland.

[0006] Compared with the prior art, the present invention has the following advantages:

[0007] The mechanical seal structure of the present invention adopts a double-end face series design structure, the main seal is a contact type, and the secondary seal is a non-contact type. Specifically, the main seal directly contacts the medium, and during its operation, the medium will enter the main seal grinding surface to form a wet liquid film, thereby achieving sealing performance; an isolation chamber is set between the secondary seal and the main seal, but no buffer is added to the isolation chamber, that is, the environment is always kept dry, so no liquid film will be generated between the secondary seal grinding surfaces. It is a dry gas seal. When the compressor shaft rotates at a high speed, an air film will form between the secondary seal grinding surfaces to be used for emergency sealing of the medium leaking from the main seal in the isolation chamber; more specifically, in the solution of the present invention, a lip seal structure is provided at the medium end, and a sealed chamber is formed between the lip seal and the outer side of the main seal. When the compressor is operating normally, the lip seal plays a sealing role, and cooperates with the liquid outlet to allow a stable pressure to be established in the main seal chamber, so that the refrigerant will not be released due to pressure reduction; when the pressure in the sealed chamber suddenly increases, the lip seal will open and release the pressure under the push of the high pressure, thereby preventing the mechanical seal from being damaged by the sudden high pressure. That is, there is a throttling and pressure regulating structure design near the medium end inside the gland, which effectively improves the dual sealing performance of the mechanical seal for lubricating oil and refrigerant; and a leakage collection is set on the outside of the gland, that is, the refrigerant leaked from the main seal can be discharged through the exhaust port and connected to the burner for combustion.

[0008] As an improvement, the guide portion is an annular guide sleeve, with the radial outer end of the guide sleeve connected to the inner cavity wall of the gland, the radial inner end of the guide sleeve extending toward the primary seal, and a channel between the inner sidewall of the guide sleeve and the outer sidewall of the primary seal. The radial outer end of the guide sleeve is provided with an exhaust hole extending axially therethrough. In this improved structure, the guide sleeve serves to guide the flushing liquid, aligning it with the primary sealing surface, thereby enhancing cooling and extending the service life of the seal. Furthermore, the exhaust hole effectively prevents gas accumulation in the sealing cavity from affecting its sealing performance.

[0009] In a further improvement, the inner cavity wall of the gland near the medium end is provided with two axially distributed positioning slots, each of which is fitted with a retaining spring. One end of the lip seal axially abuts against one end of the guide sleeve, while the other ends of the lip seal and guide sleeve are respectively axially secured against the two retaining springs. In this improved structure, the lip seal and guide sleeve are positioned and connected within the inner cavity of the gland via the two retaining springs, resulting in a simple structure and easy installation.

[0010] In a further improvement, a positioning hole is formed on the outer wall of the guide sleeve, and a positioning pin is provided through the side wall of the gland, with the inner end of the positioning pin being fitted into the positioning hole. In the above improved structure, the provision of the positioning pin and positioning hole achieves a circumferential anti-rotation limit effect for the guide sleeve, while also providing an axial anti-slip limit function.

[0011] Further improved, the main seal includes an active ring and a main static ring assembly, a dynamic ring groove is provided at the end of the mounting boss away from the medium, one end of the active ring is fitted in the dynamic ring groove, one end of the main static ring assembly is fitted in the first mounting groove, the other end of the main static ring assembly and the other end of the active ring are rotatably abutted relative to each other in the circumferential direction to form a main friction pair; and an elastic compensation element is fitted between the first mounting groove and the main static ring assembly.

[0012] Further improved, the main static ring assembly includes a main static ring, a main static ring seat and a first positioning ring, the main static ring seat includes a base plate and a positioning sleeve, and the positioning sleeve is axially formed at the radial inner end of the base plate, the base plate is fitted in the first mounting groove, a plurality of connecting bolts are movably passed through the base plate, the first positioning ring is located on the side of the base plate away from the first mounting groove, and the first positioning ring is provided with a plurality of threaded holes respectively connected to the connecting bolts; an anti-rotation lug is provided at the radial outer end of the first positioning ring, an anti-rotation groove which is fitted with the anti-rotation lug is provided on the radial outer side wall of the main static ring, the radial inner side seal of the main static ring is fitted in the positioning sleeve, and the end of the main static ring abuts against the first positioning ring; a first elastic compensation element is fitted between the first positioning ring and the base plate.

[0013] Further improved, the secondary seal includes a secondary dynamic ring and a secondary static ring, a drive ring is sleeved on the outside of the end of the sleeve near the atmosphere, and one end of the drive ring extends toward one end of the isolation chamber to form a mounting sleeve, and the secondary dynamic ring is sleeved on the outside of the mounting sleeve; the end of the pressure cover close to the atmosphere is connected to an end cover, and a static ring groove is provided on the side of the end cover close to the isolation chamber, one end of the secondary static ring is fitted in the static ring groove, and the other end of the secondary static ring is circumferentially rotatable with one end of the secondary dynamic ring to form a secondary friction pair; a second elastic compensation element is provided between the secondary static ring and the end cover.

[0014] As a further improvement, a limiting boss is provided on the outer wall of the mounting sleeve, and the end of the mounting sleeve away from the driving ring is threadedly engaged with the limiting sleeve, and the two ends of the auxiliary dynamic ring are respectively pressed against and limited between the limiting sleeve and the limiting step.

[0015] Further improvement, a second positioning ring is installed between the static ring groove and the end face of the secondary static ring, and the second elastic compensation element is arranged between the static ring groove and the second positioning ring; an anti-rotation pin is provided on the bottom surface of the static ring groove, and the outer walls of the second positioning ring and the secondary static ring are provided with anti-rotation grooves that cooperate with the anti-rotation pin.

[0016] Other improved features and advantages of the present invention will be described in the following detailed description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained through the structures particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a half-section structure of a mechanical seal for a screw compressor of the present invention;

[0018] Figure 2 for Figure 1 The X in the figure is enlarged;

[0019] Figure 3 for Figure 1 The structure diagram at position Y is enlarged;

[0020] Figure 4 Schematic diagram of the secondary sealing structure in the present invention;

[0021] Figure 5 It is a partial schematic diagram of the clamping block structure at one end of the shaft sleeve in the present invention.

[0022] Description of reference numerals:

[0023] 1. Bushing; 2. Gland; 3. Isolation Cavity; 4. Mounting Boss; 5. First Mounting Slot; 6. Lip Seal; 7. Sealing Cavity; 8. Liquid Inlet; 9. Liquid Outlet; 10. Guide Sleeve; 11. Exhaust Hole; 12. Positioning Slot; 13. Circlip; 14. Positioning Hole; 15. Positioning Pin; 16. Exhaust Port; 17. Active Ring; 18. Active Ring Groove; 19. Main and Static Rings; 20. Main and Static Ring Seat; 21. First Positioning Ring; 22. Bottom Plate; 23. Positioning Sleeve; 24. Connecting Bolt; 25. Anti-Rotation Lug; 26. Anti-Rotation Groove; 27. Auxiliary Active Ring Ring; 28. Auxiliary static ring; 29. Drive ring; 30. Mounting sleeve; 31. End cover; 32. Static ring groove; 33. Limiting boss; 34. Limiting sleeve; 35. Second positioning ring; 36. Anti-rotation pin; 37. First spring; 38. First spring hole; 39. Second mounting groove; 40. Second spring; 41. Second spring hole; 42. First connecting hole; 43. Set screw; 44. Positioning boss; 45. Positioning groove; 46. Second connecting hole; 47. Transmission screw; 48. Transmission groove; 49. Holding block; 50. Air inlet. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] In the description of the present invention, it should be noted that the terms "outer end", "inner end", "inner side wall", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and 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 understood as a limitation on the present invention. In addition, the terms "first" and "second" in the description are only for the convenience of distinction and understanding, and do not have specific or limited meanings. Among them, the tail end refers to the end away from the friction surface. For example, the tail end of the moving ring refers to the end on the moving ring away from the grinding surface.

[0026] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, it can mean a fixed connection, a detachable connection, or an integral connection; it can mean a direct connection, an indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0027] like Figure 1As shown, the present invention provides a mechanical seal for a screw compressor, comprising a sleeve 1 sleeved on the outside of the compressor shaft, with a sealing ring provided between the inner wall of one end of the sleeve 1 and the outer wall of the shaft; a gland 2 is sleeved on the outside of the sleeve 1, and the gland 2 is used to be connected and fixed to the installation cavity of the compressor.

[0028] In addition, a main seal is provided between the end of the sleeve 1 close to the medium and one end of the inner cavity of the gland 2, and a secondary seal is provided between the end of the sleeve 1 close to the atmosphere and the other end of the inner cavity of the gland 2, so that an isolation chamber 3 is formed between the outside of the sleeve 1 and the inner cavity of the gland 2; specifically, in this structure, the main seal is mainly used to achieve a primary seal at the medium end. Once the main seal leaks, part of the medium will enter the isolation chamber 3. At this time, the secondary seal can still be used as an emergency seal, so this double-face sealing structure can maintain a more stable sealing performance.

[0029] Specifically, such as Figure 2 As shown, in this embodiment, a mounting boss 4 is provided at the end of the sleeve 1 close to the medium, and a first mounting groove 5 is provided at one end of the inner cavity of the gland 2. One end of the main seal is fitted on the end of the mounting boss 4 away from the medium, and the other end is fitted in the first mounting groove 5; and a lip seal 6 is provided on the inner cavity wall of the gland 2 at a position corresponding to the mounting boss 4, wherein the inner ring of the lip seal 6 is sealed on the outer wall of the mounting boss 4, so that a sealed cavity 7 is formed between the outer side of the main seal and the inner cavity wall of the gland 2; on the other hand, a liquid inlet hole 8 and a liquid outlet hole 9 respectively connected to the sealed cavity 7 are opened on the gland 2, and a guide portion is provided on the inner cavity wall of the gland 2 so that the flushing liquid in the liquid inlet hole 8 can directly flush the outer side of the friction pair of the main seal, effectively improving the cooling efficiency of the friction surface, and in this structure, the liquid inlet hole 8 and the liquid outlet hole 9 are axially located on both sides of the guide portion. At the same time, under the action of the guide portion, the contact time between the coolant and the sealing surface can be better guaranteed, thereby improving the cooling and heat dissipation effect from another angle.

[0030] On the other hand, in the above structure, the lip seal 6 plays a sealing role when the compressor is working normally, and cooperates with the liquid outlet hole 9 to establish a stable pressure in the main sealing chamber 7, so that the refrigerant will not be released due to pressure reduction; when the pressure in the sealing chamber 7 suddenly increases, the lip seal 6 will open and release the pressure under the push of high pressure, thereby preventing the mechanical seal from being damaged due to sudden high pressure.

[0031] In this embodiment, the preferred guide portion is an annular guide sleeve 10, and the radial outer end of the guide sleeve 10 is connected to the inner cavity wall of the pressure cover 2, the radial inner end of the guide sleeve 10 extends toward the main seal, and a channel is left between the inner wall of the guide sleeve 10 and the outer wall of the main seal for the passage of coolant; on the other hand, an exhaust hole 11 is opened at the radial outer end of the guide sleeve 10 and extends axially therethrough to prevent the sealing performance of the sealing cavity 7 from being affected by gas accumulation.

[0032] More specifically, in this embodiment, a bevel is provided on the main static ring 19 (described in detail later) of the main sealing structure, and the side of the guide sleeve 10 close to the bevel is parallel to it to form an inclined flushing channel, and the central axis of the liquid inlet hole 8 is parallel to the bevel, so that the flushing liquid is flushed along an angle tangent to the bevel, thereby improving efficiency.

[0033] Two axially distributed positioning slots 12 are provided on the inner cavity wall of the pressure cover 2 near the medium end, and a retaining spring 13 is installed in each of the two positioning slots 12; one end of the lip seal 6 is axially abutted against one end of the guide sleeve 10, and the other ends of the lip seal 6 and the guide sleeve 10 are respectively axially pressed against the two retaining springs 13 for position limiting; and a positioning hole 14 is provided on the outer wall of the guide sleeve 10, and a positioning pin 15 is passed through the side wall of the pressure cover 2, and the inner end of the positioning pin 15 is installed in the positioning hole 14, realizing the circumferential anti-rotation limit of the guide sleeve 10, and also plays the role of axial anti-slip limit. More specifically, the rubber sealing strip in this structure is sealed and installed on the outer wall of the mounting boss 4 in the direction of the bending toward the medium end. In this structure, when the pressure in the sealing chamber 7 is too high, the rubber sealing strip can be pushed open along the bending direction to form an air release channel, and the main surface seal is damaged due to excessive pressure. In addition, in this structure, a wear-resistant coating is added to the outer wall of the mounting boss 4 at a position corresponding to the rubber sealing strip.

[0034] like Figure 1 As shown, in this embodiment, an exhaust port 16 connected to the isolation cavity 3 is provided on the side wall of the gland 2, so that the refrigerant leaking from the main seal can be discharged through the exhaust port 16 in a timed manner and connected to the burner for combustion.

[0035] The following is a detailed description of the structure of the main seal and auxiliary seal:

[0036] Among them, the main seal includes an active ring 17 and a main static ring assembly. A dynamic ring groove 18 is provided at the end of the mounting boss 4 away from the medium. One end of the active ring 17 is fitted in the dynamic ring groove 18, and the axial limitation of the active ring 17 is achieved by snapping into the corresponding positioning clamp on the outer wall of the sleeve 1 to prevent the active ring 17 from escaping from the dynamic ring groove 18. One end of the main static ring assembly is fitted in the first mounting groove 5, and the other end of the main static ring assembly and the other end of the active ring 17 are rotatably abutted in the circumferential direction to form a main friction pair; more specifically, the main static ring assembly includes a main static ring 19, a main static ring seat 20 and a first positioning ring 21. The main static ring seat 20 includes a base plate 22 and a positioning sleeve 23, and the positioning sleeve 23 is axially formed at the radial inner end of the base plate 22. The base plate 22 is fitted in the first mounting groove 5, and the base plate 22 is axially connected to the first mounting groove 5 by connecting screws; in addition, as Figure 3As shown, a plurality of connecting bolts 24 are movably penetrated on the base plate 22, the first positioning ring 21 is located on the side of the base plate 22 away from the first mounting groove 5, and a plurality of threaded holes are opened on the first positioning ring 21, which are respectively connected to the connecting bolts 24; an anti-rotation lug 25 is provided at the radial outer end of the first positioning ring 21, and an anti-rotation groove 26 matched with the anti-rotation lug 25 is provided on the radial outer side wall of the main static ring 19, thereby realizing circumferential anti-rotation of the main static ring 19.

[0037] In addition, such as Figure 2 As shown. The radial inner seal of the main static ring 19 is fitted in the positioning sleeve 23, and the end of the main static ring 19 is in contact with the first positioning ring 21; a first elastic compensation element is fitted between the first positioning ring 21 and the base plate 22, so that the main static ring 19 always has a tendency to move toward the active ring 17, that is, during the wear of the main sealing surface, under the elastic force of the first elastic compensation element, the main static ring 19 can always maintain a sealed fit with the active ring 17, thereby ensuring the stability of the sealing performance. In addition, a static ring compensation structure is adopted in this structure. Since the static ring component is stationary, the compensation structure can withstand a higher rotation speed. Preferably, the first elastic compensation element includes a plurality of first springs 37, and a plurality of first spring holes 38 uniformly distributed along the circumference are provided on the base plate 22. One end of each first spring 37 is fitted in the corresponding first spring hole 38, and the other end of each first spring 37 is in contact with the end face of the first positioning ring 21, as shown. Figure 2 shown.

[0038] like Figure 1 As shown, the flushing liquid admitted to the liquid inlet hole 8 in the above structure can not only cool and flush the main seal, but also flush the first spring 37, thereby preventing the first spring 37 from having unstable elastic compensation force due to accumulated impurities.

[0039] The provision of the first locating ring 21 in this embodiment facilitates the installation of the main static ring 19. Furthermore, the connecting bolts 24 provide guidance during the axial movement of the main static ring 19, ensuring smooth sliding. Furthermore, the first locating ring 21 is connected to the base plate 22 via the connecting bolts 24 to form a monolithic structure, facilitating assembly of the mechanical seal. Specifically, before the overall mechanical seal is assembled, the main static ring 19, first locating ring 21, and base plate 22 can be pre-assembled into the monolithic assembly structure, avoiding component loss during assembly, improving installation efficiency, reducing the probability of component omission, and ensuring the final sealing effect of the product.

[0040] In this embodiment, the active ring 17 and the main static ring 19 are both made of silicon carbide. Compared with the existing silicon carbide and graphite pairing structure, the refrigerant will expand and produce flash explosion when it is heated, and the graphite ring has low strength and is easily damaged, while silicon carbide does not have this problem.

[0041] In addition, such as Figure 4 As shown, the secondary seal includes a secondary dynamic ring 27 and a secondary static ring 28. A drive ring 29 is sleeved on the outside of the end of the sleeve 1 close to the atmosphere, and one end of the drive ring 29 extends toward one end of the isolation chamber 3 to form a mounting sleeve 30. The secondary dynamic ring 27 is sleeved on the outside of the mounting sleeve 30; specifically, an annular limiting boss 33 is provided on the outer wall of the mounting sleeve 30, and a limiting sleeve 34 is provided at the end of the mounting sleeve 30 away from the drive ring 29, and the limiting sleeve 34 is connected to the outside of the mounting sleeve 30 by threaded fitting, so that the two ends of the secondary dynamic ring 27 are respectively abutted and limited between the limiting sleeve 34 and the limiting step, thereby realizing the connection between the secondary dynamic ring 27 and the mounting sleeve 30, and a corresponding sealing ring is equipped between the inner wall of the secondary dynamic ring 27 and the outer wall of the mounting sleeve 30. In addition, a second mounting groove 39 is provided at the end of the gland 2 close to the atmosphere, and an end cover 31 is installed in the second mounting groove 39. The radial outer end of the cover plate is fixed to the end face of the gland 2 by screws, and an annular static ring groove 32 is provided at the radial inner end of the end cover 31 and on the side close to the isolation chamber 3. One end of the auxiliary static ring 28 is fitted in the static ring groove 32, and the other end of the auxiliary static ring 28 is rotatably abutted against one end of the auxiliary dynamic ring 27 along the circumferential direction to form a secondary friction pair; and a second elastic compensation element is provided between the auxiliary static ring 28 and the end cover 31, so that the auxiliary static ring 28 always has a tendency to move toward the side of the auxiliary dynamic ring 27, so as to better ensure the sealing performance of the sealing surface.

[0042] More specifically, in the above structure, a second positioning ring 35 is installed between the static ring groove 32 and the end face of the auxiliary static ring 28, and the second elastic compensation element is arranged between the static ring groove 32 and the second positioning ring 35; an anti-rotation pin 36 is provided on the bottom surface of the static ring groove 32, and the second positioning ring 35 and the outer wall of the auxiliary static ring 28 are provided with an anti-rotation groove 26 that cooperates with the anti-rotation pin 36; and a sealing ring groove is provided on the radial inner end of the second positioning ring 35 close to the side of the auxiliary static ring 28, and a sealing ring is sleeved on the outside of the vertical edge of the static ring groove 32, and the sealing ring is positioned between the sealing ring groove and the end face of the auxiliary static ring 28 along the axial direction of the mounting sleeve 30, so as to realize the sealed connection between the auxiliary static ring 28 and the end cover 31, and the sealing ring has a stable limit and will not move. Similarly, the second elastic compensation element in this structure includes multiple second springs 40. Multiple second spring holes 41 are opened at one end of the end cover 31. One end of the multiple second springs 40 is respectively abutted and fitted in each second spring hole 41, and the other end of the multiple second springs 40 is respectively abutted on the second positioning ring 35 to achieve axial elastic compensation of the auxiliary static ring 28. Figure 4 shown.

[0043] In the above structure, a plurality of first connecting holes 42 distributed along the circumferential direction are provided on the side wall of the drive ring 29, each of which is equipped with a set screw 43, and a positioning boss 44 is provided at the end of each set screw 43. Correspondingly, a plurality of positioning grooves 45 are provided on the outer wall of the sleeve 1 to match the positioning bosses 44. When the drive ring 29 is fitted onto the outer wall of the sleeve 1 and axially moved to the set position, the drive ring 29 and the sleeve 1 are pre-positioned by the plurality of set screws 43, so that they become an integral structure. In addition, the drive ring 29 is provided with a plurality of positioning grooves 45 on the outer wall of the sleeve 1 to match the positioning bosses 44. 9 is also provided with a plurality of second connection holes 46 that are offset from the first connection blocks, and a transmission screw 47 is installed in each second connection hole 46. Correspondingly, a transmission groove 48 is provided on the outer wall of the sleeve 1 corresponding to the position of each transmission screw 47. When the entire set of mechanical seals is installed on the outside of the rotating shaft to the set position, by tightening the plurality of second transmission screws 47, the ends of the transmission screws 47 drive the side wall of the sleeve 1 to slightly deform, thereby playing a clamping role. Compared with the traditional structure that is directly tightened on the rotating shaft, it can protect the outer wall of the rotating shaft. More specifically, in order to make the side wall of the sleeve 1 easy to deform and clamp, notches are opened at the ends of the sleeve 1 on both sides of the circumference of each transmission groove 48 to form a plurality of deformable clamping blocks 49, such as Figure 5 shown.

[0044] In this embodiment, the secondary seal utilizes a dry gas seal, meaning that there is no medium lubrication on the secondary seal's ground surface, and no isolation fluid is present within the isolation chamber 3. Under high-speed operation of the mechanical seal, a certain air film forms between the secondary dynamic ring 27 and the secondary static ring 28. If the primary seal leaks and medium enters the isolation chamber 3, this air film can contain the leaked medium. Furthermore, an air inlet 50 is provided on the sidewall of the gland 2. This allows gas at a certain pressure to be introduced into the isolation chamber 3, creating a high-pressure chamber within the isolation chamber 3. When the pressure within the isolation chamber 3 exceeds that of the sealing chamber 7, this inlet can prevent leakage of medium from the primary seal into the isolation chamber 3.

[0045] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A mechanical seal for a screw compressor, comprising a sleeve (1) and a gland (2) sleeved on the outside of the sleeve (1), wherein a primary seal is provided between one end of the sleeve (1) close to the medium and one end of the inner cavity of the gland (2), and a secondary seal is provided between one end of the sleeve (1) close to the atmosphere and the other end of the inner cavity of the gland (2), so that an isolation cavity (3) is formed between the outside of the sleeve (1) and the inner cavity of the gland (2), characterized in that: The end of the sleeve (1) close to the medium is provided with a mounting boss (4), and the end of the inner cavity of the gland (2) is provided with a first mounting groove (5). One end of the main seal is fitted on the end of the mounting boss (4) away from the medium, and the other end is fitted in the first mounting groove (5); a lip seal (6) is provided on the inner cavity wall of the gland (2) at a position corresponding to the mounting boss (4), and the inner ring of the lip seal (6) is sealed on the outer wall of the mounting boss (4), so that the outer side of the main seal is in contact with the gland ( 2) a sealed cavity (7) is formed between the inner cavity walls, a liquid inlet hole (8) and a liquid outlet hole (9) respectively connected to the sealed cavity (7) are provided on the gland (2), and a flow guide is provided on the inner cavity wall of the gland (2) so that the flushing liquid of the liquid inlet hole (8) can directly flush the outer side of the friction pair of the main seal, and the liquid inlet hole (8) and the liquid outlet hole (9) are axially located on both sides of the flow guide; an exhaust port (16) connected to the isolation cavity (3) is provided on the side wall of the gland (2); The guide portion is an annular guide sleeve (10), and the radial outer end of the guide sleeve (10) is connected to the inner cavity wall of the pressure cover (2), the radial inner end of the guide sleeve (10) extends toward the main seal, and a channel is left between the inner side wall of the guide sleeve (10) and the outer side wall of the main seal; the radial outer end of the guide sleeve (10) is provided with an exhaust hole (11) extending along its axial direction; the inner cavity wall of the pressure cover (2) near the medium end is provided with two positioning holes distributed along its axial direction. The two positioning slots are both equipped with retaining springs (13); one end of the lip seal (6) is axially abutted against one end of the guide sleeve (10), and the other ends of the lip seal (6) and the guide sleeve (10) are respectively axially pressed against the two retaining springs (13) for limiting position; a positioning hole (14) is provided on the outer wall of the guide sleeve (10), a positioning pin (15) is passed through the side wall of the pressure cover (2), and the inner end of the positioning pin (15) is equipped in the positioning hole (14).

2. The mechanical seal for a screw compressor according to claim 1, wherein: The main seal includes an active ring (17) and a main static ring (19) assembly. A dynamic ring groove (18) is provided at one end of the mounting boss (4) away from the medium. One end of the active ring (17) is fitted into the dynamic ring groove (18). One end of the main static ring (19) assembly is fitted into the first mounting groove (5). The other end of the main static ring (19) assembly is in circumferentially rotatable contact with the other end of the active ring (17) to form a main friction pair.

3. The mechanical seal for a screw compressor according to claim 2, wherein: The main stationary ring (19) assembly includes a main stationary ring (19), a main stationary ring seat (20) and a first positioning ring (21), the main stationary ring seat (20) includes a base plate (22) and a positioning sleeve (23), and the positioning sleeve (23) is axially formed on the radial inner end of the base plate (22), the base plate (22) is fitted in the first mounting groove (5), a plurality of connecting bolts (24) are movably provided on the base plate (22), the first positioning ring (21) is located on the side of the base plate (22) away from the first mounting groove (5), and the first positioning ring ( 21) is provided with a plurality of threaded holes respectively connected to the respective connecting bolts (24); the radial outer end of the first locating ring (21) is provided with an anti-rotation lug (25), the radial outer side wall of the main static ring (19) is provided with an anti-rotation groove (26) matched with the anti-rotation lug (25), the radial inner side seal of the main static ring (19) is fitted in the locating sleeve (23), and the end of the main static ring (19) is in contact with the first locating ring (21); a first elastic compensation element is fitted between the first locating ring (21) and the base plate (22).

4. The mechanical seal for a screw compressor according to claim 1, wherein: The secondary seal includes a secondary dynamic ring (27) and a secondary static ring (28); a drive ring (29) is sleeved on the outside of the end of the sleeve (1) close to the atmosphere, and one end of the drive ring (29) extends toward one end of the isolation chamber (3) to form a mounting sleeve (30); the secondary dynamic ring (27) is sleeved on the outside of the mounting sleeve (30); the end of the pressure cover (2) close to the atmosphere is connected to an end cover (31); a static ring groove (32) is provided on the side of the end cover (31) close to the isolation chamber (3); one end of the secondary static ring (28) is fitted in the static ring groove (32), and the other end of the secondary static ring (28) is rotatably abutted against one end of the secondary dynamic ring (27) along the circumferential direction to form a secondary friction pair; a second elastic compensation element is provided between the secondary static ring (28) and the end cover (31).

5. The mechanical seal for a screw compressor according to claim 4, characterized in that: A limiting boss (33) is provided on the outer wall of the mounting sleeve (30), and one end of the mounting sleeve (30) away from the driving ring (29) is threadedly engaged with a limiting sleeve (34), and both ends of the auxiliary driving ring (27) are respectively pressed against and limited between the limiting sleeve (34) and the limiting boss (33).

6. The mechanical seal for a screw compressor according to claim 5, characterized in that: A second positioning ring (35) is provided between the static ring groove (32) and the end surface of the auxiliary static ring (28), and the second elastic compensation element is arranged between the static ring groove (32) and the second positioning ring (35); an anti-rotation pin (36) is provided on the bottom surface of the static ring groove (32), and an anti-rotation groove (26) cooperating with the anti-rotation pin (36) is provided on the outer wall of the second positioning ring (35) and the auxiliary static ring (28).

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