Three-screw pump with L-shaped shaft shoulder sleeve

Abstract

The three-screw pump comprises a mechanical seal, a sealing support, a front cover, a pump body, a lining, a driving screw, driven screws, the L-shaped shaft shoulder sleeve and a bearing, the lining is fixed in the pump body, and the driving screw and the two driven screws are assembled in a cavity of the lining in a meshed mode; the front cover is fixed to the front end of the pump body, the sealing support is fixed to the outer side of the front cover, the mechanical seal sleeves the end, extending out of the front cover, of the driving screw, a static ring of the mechanical seal is connected with the sealing support, and a movable ring is connected with the driving screw. The bearing is arranged at the end, away from the driven screw, of the driving screw, the inner ring of the bearing is in interference fit with the driving screw, the outer ring of the bearing is fixedly connected with the cover plate, and the shaft shoulder section of the driving screw is sleeved with the L-shaped shaft shoulder sleeve which is located between the driving screw and the front cover. And the mounting mode and the fit clearance of the L-shaped shaft shoulder sleeve are selected according to different pressure grades, so that the economic loss and the repair progress influence after shaft sticking are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fluid machinery, and particularly relates to a three-screw pump, especially a three-screw pump suitable for conveying lubricating oil under low pressure, medium pressure and high pressure conditions, BACKGROUND In the three-screw pump, a small gap is left between the driving screw and the front cover, and lubricating oil can enter the bearing and mechanical seal through the gap for lubrication, but such a small gap also brings the risk of shaft seizure. In the conventional three-screw pump, the driving screw is usually made of alloy steel, and the front cover is usually made of nodular cast iron or cast copper material. Although the risk of shaft seizure can be reduced by the difference in hardness, shaft seizure may still occur due to improper fit clearance, assembly deviation, and overloading of working conditions during actual production and use. After shaft seizure occurs, the driving screw shaft shoulder size and the front cover inner circle size can be restored by trimming, but if the shape tolerance is exceeded, the driving screw or the front cover can only be scrapped, causing economic losses and delaying progress.

[0002] In the prior art, the improvement of the three-screw pump is mostly focused on axial force balance, sealing leakage prevention, and structural compactness optimization, but the risk of shaft seizure caused by the gap between the driving screw and the front cover and the repair difficulty after shaft seizure are generally ignored: For example, the "new three-screw pump with independent limiting sealing lubrication of driven screw" disclosed in Chinese Patent Application CN120273895A solves the problems of uneven axial force and insufficient lubrication by designing an independent pressure bearing for the driven screw, but the small gap between the driving screw and the front cover is still retained as in the traditional design - the gap is used for the flow of lubricating oil to lubricate the bearing and the seal, but it is easy to cause direct contact between the driving screw and the front cover due to improper fit clearance, assembly deviation, or overloading of working conditions, resulting in shaft seizure failure. After shaft seizure, the driving screw shaft shoulder or the front cover inner circle needs to be trimmed, and if the tolerance is exceeded, the two types of high-value components need to be scrapped, causing significant economic losses.

[0003] The "three-screw pump" disclosed in Chinese Patent CN204532810U optimizes the structural stability and leakage prevention performance through a safety valve and a single-ring rolling bearing, but it does not design a protective structure for the gap risk between the driving screw and the front cover, and still faces the dilemma of "scraping core components - high cost - progress delay" after shaft seizure.

[0004] In summary, the existing three-screw pump generally has the technical defects of "uncontrollable shaft seizure risk, high repair cost after shaft seizure, and significant progress delay", and an improved scheme is needed to reduce the risk of shaft seizure from the source and simplify the repair process. SUMMARY

[0005] To overcome the shortcomings of existing three-screw pumps, such as the high risk of shaft seizure due to the gap between the drive screw and the front cover, and the need to scrap high-value components such as the drive screw and front cover after seizure, resulting in economic losses and schedule delays, this invention provides a three-screw pump with an L-shaped shoulder sleeve. The purpose is to reduce the impact on economy and schedule when seizure occurs. It adopts an L-shaped shoulder sleeve structure and the form and fitting clearance of the L-shaped shoulder sleeve under different pressure level operating conditions.

[0006] To achieve the above objectives, the technical solution of the present invention is: a three-screw pump with an L-shaped shoulder sleeve, comprising a mechanical seal, a sealing bracket, a front cover, a pump body, a bushing, a bottom cover, a driving screw, a driven screw, an L-shaped shoulder sleeve, a bearing, a cover plate, and a safety valve; the bushing is fixed inside the pump body, and the driving screw and two driven screws are meshed and assembled in the cavity of the bushing; the front cover is fixed to the front end of the pump body, the sealing bracket is fixed to the outside of the front cover, the mechanical seal is sleeved on the end of the driving screw extending out of the front cover, and the stationary ring of the mechanical seal is connected to the sealing bracket, and the rotating ring is connected to the driving screw; the bearing is located at the end of the driving screw away from the driven screw, the inner ring of the bearing is interference-fitted with the driving screw, and the outer ring is fixedly connected to the cover plate; the L-shaped shoulder sleeve is sleeved on the shoulder section of the driving screw and located between the driving screw and the front cover. This three-screw pump is used to transport lubricating oil, and the L-shaped shoulder sleeve is selected according to different pressure levels. The installation method and fitting clearance of the shaft shoulder sleeve are designed to reduce economic losses and the impact on repair progress after shaft seizure.

[0007] Furthermore, when the three-screw pump is used in low-pressure conditions, a positive L-shaped shoulder sleeve or a negative L-shaped shoulder sleeve is adopted, and the L-shaped shoulder sleeve and the front cover are clearance fit to ensure that the lubricating oil lubricates the bearing and mechanical seal through the clearance.

[0008] Furthermore, when the three-screw pump is used in medium-pressure conditions, a positive L-shaped shoulder sleeve or a negative L-shaped shoulder sleeve is adopted, and the L-shaped shoulder sleeve and the front cover are transition fit to improve the sealing performance under medium-pressure conditions and prevent media leakage.

[0009] Furthermore, when the three-screw pump is used in high-pressure conditions, only a positive L-shaped shoulder sleeve is used, and the L-shaped shoulder sleeve and the front cover are in transition fit to improve the resistance to high-pressure deformation.

[0010] Furthermore, the L-shaped shoulder sleeve includes an integrally formed L-shaped radial sleeve and an L-shaped axial retaining ring; the inner hole of the L-shaped radial sleeve is fitted onto the shoulder section of the drive screw and is clearance-fitted with the drive screw; the end of the L-shaped radial sleeve away from the L-shaped axial retaining ring abuts against the outer ring of the bearing, restricting the axial movement of the bearing.

[0011] Furthermore, the inverted L-shaped shoulder sleeve includes an integrally formed inverted L-shaped radial sleeve and an inverted L-shaped axial retaining ring; the inner hole of the inverted L-shaped radial sleeve is fitted onto the shoulder section of the drive screw and is clearance-fitted with the drive screw; the inverted L-shaped axial retaining ring is located on the side of the inverted L-shaped radial sleeve near the bearing and abuts against the outer ring end face of the bearing.

[0012] Furthermore, the axial length of the L-shaped shoulder sleeve is greater than the length of the active screw shoulder, reserving a lubricating oil flow channel to avoid the risk of shaft seizure caused by excessive axial tightness.

[0013] Furthermore, the L-shaped shoulder sleeve is made of wear-resistant alloy, and the hardness of the L-shaped shoulder sleeve is between that of the drive screw and the front cover. When the shaft is engaged, the L-shaped shoulder sleeve is worn first, thus protecting the drive screw and the front cover.

[0014] Furthermore, the cover plate is fitted onto the outside of the pump body; the safety valve is connected to the high-pressure chamber of the pump body. Furthermore, the bushing is made of bronze and is fixedly connected to the pump body by bolts; the pump body is made of cast steel and the front cover is made of ductile iron to ensure the overall structural strength of the pump body.

[0015] This invention, through its innovative design of the L-shaped shoulder sleeve and its pressure rating adaptation scheme, offers the following significant advantages over existing technologies: 1. Reduce the risk of bearing seizure from the source: The L-shaped shoulder sleeve isolates the active screw from the front cover, avoiding direct contact between the two. At the same time, the pressure-grade matching clearance design takes into account both lubrication and structural stability, reducing bearing seizure failures caused by improper clearance. 2. Significantly reduces repair costs and schedule impact: After a shaft seizure, only the L-shaped shaft shoulder sleeve needs to be repaired or a new shaft shoulder sleeve needs to be replaced. There is no need to scrap the drive screw or front cover, which greatly shortens the repair cycle. 3. Adaptable to multiple pressure conditions and has a wide range of applications: low-pressure clearance fit ensures lubrication, medium and high-pressure transition fit improves sealing, and positive or negative L-shaped shoulder sleeves adapt to different installation spaces, covering lubricating oil delivery scenarios from low pressure to high pressure; 4. Protect high-value components: The L-shaped shoulder sleeve has a lower hardness than the drive screw. When the shaft seizes, the shoulder sleeve is worn first, avoiding damage to the drive screw (core power component) and further reducing maintenance costs; 5. High compatibility and easy industrialization: The overall structure retains the compactness of the existing three-screw pump, and the L-shaped shaft shoulder sleeve installation does not require modification of the pump body. It can be directly used for new pump production or upgrade of existing pumps.

[0016] In summary, the L-shaped shoulder sleeve of this invention is mainly used for transporting lubricating oil. When shaft seizure occurs, it can be repaired by adjusting the inner hole of the L-shaped shoulder sleeve and the outer circle of the drive screw. If the dimensions of the drive screw after repair exceed the tolerance, the L-shaped shoulder sleeve is scrapped and a new L-shaped shoulder sleeve that meets the clearance requirements is reprocessed. Because the L-shaped shoulder sleeve is small in size, light in weight, simple in structure, and easy to process and install, it can effectively reduce the impact on economy and schedule compared to scrapping the front cover and screw. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the three-screw pump with L-shaped shoulder sleeve of the present invention ((a) is a main sectional view, (b) is a side sectional view). Figure 2 This is a schematic diagram of a positive L-shaped shaft shoulder sleeve.

[0018] Figure 3 This is a schematic diagram of an inverted L-shaped shaft shoulder sleeve.

[0019] Explanation of reference numerals in the attached drawings: 1-Mechanical seal, 2-Sealing bracket, 3-Front cover, 4-Pump body, 5-Bushing, 6-Bottom cover, 7-Driving screw, 8-Driven screw, 9-L-shaped shoulder sleeve, 10-Bearing, 11-Cover plate, 12-Safety valve. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] like Figure 1 As shown in (a) and (b), the L-shaped shoulder sleeve of the present invention provides a three-screw pump, which includes a mechanical seal 1, a sealing bracket 2, a front cover 3, a pump body 4, a bushing 5, a bottom cover 6, a driving screw 7, a driven screw 8, an L-shaped shoulder sleeve 9, a bearing 10, a cover plate 11, and a safety valve 12.

[0022] The system comprises: a bushing 5 fixed inside the pump body 4; a drive screw 7 meshing with two driven screws 8 within the chamber of the bushing 5 to achieve sealed delivery of lubricating oil; a front cover 3 fixed to the front end of the pump body 4; a sealing bracket 2 fixed to the outside of the front cover 3; a mechanical seal 1 fitted onto the end of the drive screw 7 extending beyond the front cover 3, with the stationary ring of the mechanical seal 1 connected to the sealing bracket 2 and the rotating ring connected to the drive screw 7 to achieve shaft end sealing; a bearing 10 located at the end of the drive screw 7 furthest from the driven screws 8, with the inner ring of the bearing 10 interference-fitted with the drive screw 7 and the outer ring fixedly connected to the cover plate 11, which covers the outside of the pump body 4 to ensure stable rotation of the drive screw 7; a safety valve 12 connected to the high-pressure chamber of the pump body 4 to control the pump pressure from exceeding a safety threshold; and an L-shaped shoulder sleeve 9 fitted onto the shoulder section of the drive screw 7 and located on the drive screw 7. Between the front cover 3 and the active screw 7, there is a space to isolate the active screw 7 from the front cover 3, preventing direct contact.

[0023] Selecting different L-shaped shoulder sleeve installation methods and fitting clearances for different pressure levels can effectively reduce the impact on economy and schedule when shaft seizure occurs.

[0024] Low-pressure operation: Use L-shaped shoulder sleeve ( Figure 2 ) or reverse L-shaped shoulder sleeve ( Figure 3 The L-shaped shoulder sleeve 9 and the front cover 3 are clearance fit, which ensures that the lubricating oil can pass through the clearance to lubricate the bearing 10 and the mechanical seal 1, while avoiding the installation difficulties caused by the interference fit. Medium pressure operation: Uses L-shaped shoulder bushing ( Figure 2 ) or reverse L-shaped shoulder sleeve ( Figure 3 The L-shaped shoulder sleeve 9 and the front cover 3 are in transition fit to improve sealing performance and prevent leakage of medium-pressure media; High-pressure operating conditions: Only L-shaped shoulder sleeves are used ( Figure 2 The L-shaped shoulder sleeve 9 and the front cover 3 are in a transition fit, which takes into account both sealing and structural stability.

[0025] The specific structure of the L-shaped shoulder sleeve is as follows: L-shaped shoulder sleeve: includes an integrally formed radial sleeve body and an axial retaining ring; the inner hole of the radial sleeve body is fitted into the shoulder section of the drive screw 7 (with clearance fit with the drive screw 7), and the end of the radial sleeve body away from the axial retaining ring 92 abuts against the outer ring of the bearing 10, restricting the axial movement of the bearing 10.

[0026] Inverted L-shaped shoulder sleeve: includes an integrally formed radial sleeve body and an axial retaining ring; the inner hole of the radial sleeve body is fitted into the shoulder section of the drive screw 7 (with clearance fit with the drive screw 7), and the axial retaining ring is located on the side of the radial sleeve body near the bearing 10 and abuts against the outer ring end face of the bearing 10, adapting to the installation scenario where the bearing 10 is close to the front cover 3, simplifying the structure.

[0027] Material selection: The L-shaped shaft shoulder sleeve is made of wear-resistant alloy, and its hardness is between that of the drive screw 7 and the front cover 3, ensuring that the L-shaped shaft shoulder sleeve is worn first when the shaft is seized, thus protecting the high-value drive screw 7 and front cover 3.

Claims

1. A three-screw pump with an L-shaped shoulder sleeve, comprising a mechanical seal, a sealing bracket, a front cover, a pump body, a bushing, a bottom cover, a driving screw, a driven screw, an L-shaped shoulder sleeve, a bearing, a cover plate, and a safety valve; the bushing is fixed inside the pump body, and the driving screw and two driven screws are meshed and assembled in the cavity of the bushing; the front cover is fixed to the front end of the pump body, the sealing bracket is fixed to the outside of the front cover, the mechanical seal is sleeved on the end of the driving screw extending out of the front cover, and the stationary ring of the mechanical seal is connected to the sealing bracket, and the rotating ring is connected to the driving screw; the bearing is located at the end of the driving screw away from the driven screw, the inner ring of the bearing is interference-fitted with the driving screw, and the outer ring is fixedly connected to the cover plate, characterized in that... The L-shaped shoulder sleeve is fitted onto the shoulder section of the drive screw and is located between the drive screw and the front cover. This three-screw pump is used to transport lubricating oil. The installation method and fitting clearance of the L-shaped shoulder sleeve are selected according to different pressure levels to reduce economic losses and the impact on repair progress after the shaft seizes.

2. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, When the three-screw pump is used in low-pressure conditions, a positive L-shaped shoulder sleeve or a negative L-shaped shoulder sleeve is used, and the L-shaped shoulder sleeve and the front cover are clearance fit to ensure that the lubricating oil lubricates the bearing and mechanical seal through the clearance.

3. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, When a three-screw pump is used in medium-pressure conditions, a positive L-shaped shaft shoulder sleeve or a negative L-shaped shaft shoulder sleeve is used, and the L-shaped shaft shoulder sleeve and the front cover are transition fit to improve the sealing performance under medium-pressure conditions and prevent media leakage.

4. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, When the three-screw pump is used in high-pressure conditions, only a positive L-shaped shaft shoulder sleeve is used, and the L-shaped shaft shoulder sleeve and the front cover are transition fit to improve the resistance to high-pressure deformation.

5. The three-screw pump with an L-shaped shoulder sleeve according to claim 2, 3, or 4, characterized in that, The L-shaped shoulder sleeve includes an integrally formed L-shaped radial sleeve and an L-shaped axial retaining ring; the inner hole of the L-shaped radial sleeve is fitted onto the shoulder section of the drive screw and is clearance-fitted with the drive screw; the end of the L-shaped radial sleeve away from the L-shaped axial retaining ring abuts against the outer ring of the bearing, restricting the axial movement of the bearing.

6. The three-screw pump with an L-shaped shoulder sleeve according to claim 2 or 3, characterized in that, The inverted L-shaped shoulder sleeve includes an integrally formed inverted L-shaped radial sleeve and an inverted L-shaped axial retaining ring; the inner hole of the inverted L-shaped radial sleeve is fitted onto the shoulder section of the drive screw and is clearance-fitted with the drive screw; the inverted L-shaped axial retaining ring is located on the side of the inverted L-shaped radial sleeve near the bearing and abuts against the outer ring end face of the bearing.

7. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, The axial length of the L-shaped shoulder sleeve is greater than the length of the active screw shoulder, which provides a channel for lubricating oil flow and avoids the risk of shaft seizure caused by excessive axial tightness.

8. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, The L-shaped shoulder sleeve is made of wear-resistant alloy, and its hardness is between that of the drive screw and the front cover. When the shaft is engaged, the L-shaped shoulder sleeve is worn first, thus protecting the drive screw and the front cover.

9. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, The cover plate is fitted onto the outside of the pump body; the safety valve is connected to the high-pressure chamber of the pump body.

10. The three-screw pump with an L-shaped shoulder sleeve according to claim 1, characterized in that, The bushing is made of bronze and is fixedly connected to the pump body by bolts; the pump body is made of cast steel and the front cover is made of ductile iron to ensure the overall structural strength of the pump body.

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