Shaft seal structure of anti-corrosion screw vacuum pump

Abstract

The invention provides a shaft seal structure of an anti-corrosion screw vacuum pump, and belongs to the technical field of screw vacuum pumps. The shaft seal structure solves the technical problem that a shaft seal structure of an existing screw vacuum pump cannot give consideration to the sealing effect and normal and stable operation of a rotating shaft. The anti-corrosion screw vacuum pump comprises a machine shell, a side cover, two rotating shafts and two screw rotors, the machine shell is in a splayed barrel shape and connected with the side cover, an exhaust port is formed in the outer side of the side cover, the shaft seal structure comprises a positioning partition plate, the two sides of the positioning partition plate are divided into a pressurization cavity and a pressure relief cavity, the pressurization cavity is communicated with the exhaust port, and the peripheries of the rotating shafts are fixedly sleeved with isolation sleeves. The isolation sleeve penetrates through the positioning partition plate, one end of the isolation sleeve extends out of the positioning partition plate, a spiral groove covers the periphery of the isolation sleeve, the two ends of the spiral groove communicate with the two sides of the positioning partition plate, and a flow guide pressure relief hole which is formed downwards and communicates with the exhaust port is formed in the bottom face of an inner cavity of the pressure relief cavity and located under the end, extending out of the positioning partition plate, of the isolation sleeve. The screw vacuum pump integrates the sealing and corrosion-resistant performance and the stable operation of the rotating shaft.

Description

Technical Field

[0001] The present invention belongs to the technical field of screw vacuum pumps and relates to a shaft seal structure for an anti-corrosion screw vacuum pump. Background Art

[0002] A screw vacuum pump is a gas extraction device that uses a pair of screws to rotate synchronously and at high speed in opposite directions in a pump casing to generate suction and exhaust effects. It is an upgraded product of oil-sealed vacuum pumps and can pump gas in situations containing a large amount of water vapor and a small amount of dust. It is widely used in domestic enterprises in the pharmaceutical, chemical, semiconductor and other fields with high requirements for clean vacuum.

[0003] The patent with the application number: CN200920013059.9 discloses a labyrinth composite mechanical seal device, including at least a pair of dynamic and static rings perpendicular to the axis. And the dynamic ring or the static ring acts as a compensation ring under the action of an axial elastic element to keep the dynamic and static rings in a fitting sliding and rotating fit. The dynamic ring is connected to the shaft or the shaft sleeve, and the static ring is connected to the gland on the body. A labyrinth seal sleeve is provided between the shaft hole of the body and the shaft. The labyrinth seal sleeve is fixedly installed on the shaft. Thread grooves are provided on the front half of the outer ring surface of the labyrinth seal sleeve. The outer ring surface of the labyrinth seal sleeve is in a sliding and rotating fit with the shaft hole of the body. The thread grooves on the labyrinth seal sleeve and the shaft hole of the body form a spiral pump to transport the medium particles entering the thread grooves of the labyrinth seal sleeve back to the front end of the labyrinth seal sleeve, so that the particles in the medium cannot pass through.

[0004] The above device has a good sealing effect in a negative pressure state far from the gland end, such as various centrifugal pumps like water ring pumps. However, when used for the shaft seal of the rotating shaft of a screw vacuum pump, there are some deficiencies: During the operation of the screw vacuum pump, a pulsed exhaust pressure is generated, resulting in positive and negative pressure changes. When it is in a positive pressure state, some liquid media or dust will overcome the thrust of the thread grooves under the action of the pressure difference and penetrate into the sealing surface of the mechanical seal, causing it to fail. At the same time, the outlet temperature of the screw vacuum pump during operation plus the rotational friction temperature of the shaft is relatively high, resulting in the heating and drying of dust particles and liquid media in the thread grooves and continuous accumulation, affecting the normal rotation of the rotating shaft. For this reason, those of ordinary skill in the art usually easily consider: 1. Try to increase the cross-sectional size of the thread grooves as much as possible and increase the periodic purge and cleaning of the compressed gas to enable the particles or liquid media entering the thread grooves to be discharged smoothly; 2. Set a wind baffle at the port of the thread grooves to reduce the influence of positive and negative pressure changes on the sealing effect of the thread grooves. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the present invention provides a shaft seal structure for an anti-corrosion screw vacuum pump. The technical problem to be solved by the present invention is that the shaft seal structure of the existing vacuum pump is difficult to balance the sealing effect and the normal and stable operation of the rotating shaft.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A shaft sealing structure of an anti-corrosion screw vacuum pump, the vacuum pump comprises a casing, a side cover, two rotating shafts and two screw rotors, the casing is in an eight-shaped cylinder shape, the casing is connected to the side cover, the outer side of the side cover has an exhaust port, the shaft sealing structure comprises a positioning baffle located in the casing, the two sides of the positioning baffle are separated to form a pressurized chamber located in the casing and a pressure relief chamber located on the inner side of the side cover, the pressurized chamber is connected to the exhaust port through the through hole on the positioning baffle, the screw rotor is located in the casing and is integrally fixedly connected to the end of the rotating shaft that passes through the positioning baffle, and is characterized in that the shaft sealing structure also comprises a A cylindrical isolation sleeve, wherein the isolation sleeve is fixedly sleeved on the outer periphery of the rotating shaft, the isolation sleeve passes through the positioning baffle, and one end of the isolation sleeve facing away from the screw rotor extends out of the positioning baffle, the outer diameter of the isolation sleeve is adapted to the inner diameter of the positioning baffle, the outer periphery of the isolation sleeve is covered with a spiral groove whose spiral direction is opposite to the spiral direction of the screw rotor, the two ends of the spiral groove are connected to the two sides of the positioning baffle, the bottom surface of the inner cavity of the pressure relief chamber has a diversion pressure relief hole arranged downward and connected to the exhaust port, and the diversion pressure relief hole is located directly below the end of the isolation sleeve extending out of the positioning baffle.

[0008] By setting a rotating shaft including an isolation sleeve radially opposite to the positioning partition, a screw groove covering the isolation sleeve and opposite to the spiral direction of the screw rotor is set on the outer periphery of the isolation sleeve, and the two ends of the screw groove are respectively located on both sides of the positioning partition to connect the pressurization chamber and the pressure relief chamber, and at the same time, a diversion pressure relief hole connected downward to the exhaust port is set on the bottom surface of the inner wall of the sealing groove just below the end of the isolation sleeve extending out of the positioning partition. In this way, when the exhaust port of the screw vacuum pump is under normal pressure, the pumping of the screw rotor and the pushing of the isolation sleeve are offset, so that it is difficult for particles and liquid media entering the screw groove to reach the other side of the positioning partition through the long path of the screw groove. At the same time, the isolation sleeve can make the exhaust port enter the screw groove through high-speed rotation. The medium entering the screw groove is continuously sent back to the pressurizing chamber and discharged through the exhaust port, avoiding the intrusion of the medium and affecting the subsequent mechanical seal; in the initial operation of the screw vacuum pump, when the pulse air pressure is generated, the pressure in the pressurizing chamber is greater than the pressure relief chamber. Since the two ends of the screw groove are connected, the high-pressure gas entering the screw groove can smoothly push the internal medium to the screw groove opening at the other end of the isolation sleeve for discharge, avoiding the medium from being retained in the screw groove for a long time and causing adhesion, and the medium discharged from the other end of the isolation sleeve can fall downward into the guide pressure relief hole under the action of gravity and finally be discharged to the outside with the air in the exhaust port, avoiding affecting the components in the pressure relief chamber, and taking into account the sealing and corrosion resistance performance and the stable operation of the shaft.

[0009] In the shaft seal structure of the above anti-corrosion screw vacuum pump, a gap is left between the end of the isolation sleeve extending out of the positioning partition plate and the inner wall of the pressure relief chamber along the radial direction. This is beneficial to ensure that the medium discharged from one end of the screw groove located in the pressure relief chamber during the rotation of the isolation sleeve can be discharged smoothly without being blocked. The discharged medium enters the gap space and can fall into the diversion pressure relief hole by its own gravity, avoiding the inner wall of the pressure relief chamber blocking the port where the direction of the screw groove changes and affecting the normal discharge of the medium.

[0010] In the shaft seal structure of the above anti-corrosion screw vacuum pump, a ring-shaped disc-like labyrinth rotor is fixedly sleeved on the outer periphery of the rotating shaft, and a ring-shaped disc-like labyrinth stator is fixedly arranged on the inner wall of the pressure relief chamber. One side surface of the labyrinth rotor facing away from the isolation sleeve has a circumferentially arranged ring-shaped convex ring, and the convex ring has a radially penetrating notch. The side surface of the labyrinth stator has a circumferentially arranged ring-shaped labyrinth groove, and the convex ring is located in the labyrinth groove and a gap is left between the convex ring and the inner wall of the labyrinth groove. In this way, the convex ring on the side surface of the labyrinth rotor and the labyrinth groove on the side surface of the labyrinth stator cooperate to form a labyrinth channel, further forming a labyrinth seal after the screw groove of the isolation sleeve, reducing the probability of some medium directly invading along the rotating shaft through the screw groove. At the same time, even if a small amount of medium enters between the labyrinth rotor and the labyrinth stator, due to the action of the centrifugal force of the rotation of the labyrinth rotor, a continuously radially outward acting force will be generated on the invading medium. With the cooperation of gravity, when this part of the medium moves along the inner edge of the convex ring to the notch, it can be thrown out downward, effectively preventing the invasion of the medium and improving the sealing effect.

[0011] In the shaft seal structure of the above anti-corrosion screw vacuum pump, there are multiple convex rings which are arranged at intervals along the radial direction of the labyrinth rotor, the number of the labyrinth grooves is the same as the number of the convex rings, and the notches on the multiple convex rings are all located at the same position along the circumference of the labyrinth rotor. In this way, the cooperation of the multiple convex rings and the multiple labyrinth grooves can increase the length of the labyrinth path and improve the sealing performance. The circumferential positions of the notches of the multiple convex rings are the same, which is beneficial to enabling the media invading the inner edges of different convex rings to be thrown out at one time when thrown downward, avoiding repeated falling into different convex rings and unable to be thoroughly cleaned.

[0012] In the shaft seal structure of the above anti-corrosion screw vacuum pump, a gap is left between the outer edge surface of the convex ring located on the outermost layer of the labyrinth rotor and the inner wall of the corresponding labyrinth groove. This is beneficial to avoiding the inner wall of the outermost labyrinth groove directly blocking the notch of the outer convex ring, so that the medium can be smoothly thrown out from the labyrinth rotor without repeatedly entering between the labyrinth rotor and the labyrinth stator.

[0013] In the shaft seal structure of the above-mentioned anti-corrosion screw vacuum pump, the inner wall of the labyrinth groove opposite to the outer edge surface of the convex ring on the outermost layer of the labyrinth rotor is in the shape of a conical surface with the large end facing outwards. This facilitates the medium thrown out from the fracture to directly collide with the inner wall of the labyrinth groove, and then fly away in the direction of the open end of the labyrinth groove under the action of the conical surface, avoiding the re-invasion of the medium; at the same time, the conical surface can also prevent the medium falling from above from easily accumulating on the inner wall of the labyrinth groove, reducing the probability of the medium invading between the labyrinth rotor and the labyrinth stator, and improving the sealing effect.

[0014] In the shaft seal structure of the above-mentioned anti-corrosion screw vacuum pump, the outer diameter of the isolation sleeve is smaller than the outer diameter of the labyrinth rotor, and the other end of the labyrinth rotor is limited and abutted against the isolation sleeve. In this way, the side of the labyrinth rotor can also block the medium discharged from the screw groove nearby, making the structure more compact, and at the same time avoiding the medium from easily invading the other side of the labyrinth rotor.

[0015] In the shaft seal structure of the above-mentioned anti-corrosion screw vacuum pump, the top surface of the inner wall of the exhaust port has a guiding surface inclined downward, and the diversion pressure relief hole is located at the upper edge of the guiding surface. When the air is discharged from the pressurizing cavity through the exhaust port, it can be blocked and guided by the guiding surface, so that the air turns and discharges downward. At this time, the air flow at the upper edge of the guiding surface has not started to turn, so as to avoid the air discharged below the diversion pressure relief hole from generating eddy currents and affecting the normal discharge of the falling medium.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] This anti-corrosion screw vacuum pump can effectively improve the sealing performance of the screw vacuum pump. When it is used in the medical and chemical industries to evacuate corrosive media, it can better prevent the corrosive media from invading the gear assembly of the screw vacuum pump along the rotating shaft, thus having better anti-corrosion performance; at the same time, in the initial stage of the screw vacuum pump starting to work, when the internal exhaust generates pulsed air pressure, the pressure in the pressurizing cavity is greater than that in the pressure relief cavity, and the high-pressure gas can smoothly push the internal medium into the screw groove at the other end of the isolation sleeve through the screw groove and discharge it from the opening of the screw groove, avoiding the medium from staying in the screw groove for a long time and causing adhesion, which affects the movement of the rotating shaft. The medium discharged from the other end of the screw groove can fall downward under the action of gravity into the diversion pressure relief hole and finally be discharged with the air in the exhaust port, avoiding affecting the internal components of the pressure relief cavity, and taking into account both the sealing performance and the working stability. Brief Description of the Drawings

[0018] Figure 1 is a partial cross-sectional structural schematic diagram of this embodiment.

[0019] Figure 2 is Figure 1 the enlarged view of part A in

[0020] Figure 3 is Figure 2 the enlarged view of part B in

[0021] Figure 4 It is a front view structural schematic diagram of the labyrinth rotor in this embodiment.

[0022] Figure 5 It is a three-dimensional structural schematic diagram of the spacer sleeve in this embodiment.

[0023] In the figure, 1 is the casing; 11 is the pressurizing chamber; 2 is the rotating shaft; 3 is the screw rotor; 4 is the positioning partition; 41 is the through hole; 5 is the labyrinth rotor; 51 is the convex ring; 511 is the fracture; 6 is the labyrinth stator; 61 is the labyrinth groove; 7 is the drive motor; 8 is the spacer sleeve; 81 is the screw groove; 9 is the side cover; 91 is the exhaust port; 911 is the guiding surface; 92 is the pressure relief chamber; 93 is the diversion and pressure relief hole; 10 is the gear assembly. Specific Embodiments

[0024] The following are specific embodiments of the present invention and, in conjunction with the accompanying drawings, further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0025] As Figures 1-5As shown in the figure, the anti-corrosion screw vacuum pump includes a casing 1, a side cover 9, two rotating shafts 2, a driving motor 7, a gear assembly 10 and two screw rotors 3. The gear assembly 10 is an existing transmission assembly for reducing speed and increasing torque of the power output by the driving motor 7. The structure of the screw rotor 3 can refer to the prior art. The casing 1 is in the shape of an eight-shaped cylinder. The side cover 9 is fixedly connected to the casing 1. The rotating shafts 2 are horizontally arranged inside the casing 1. The ends of the two rotating shafts 2 are driven by the gear assembly 9 to rotate at the same speed in opposite directions. The other ends of the two rotating shafts 2 are respectively fixedly connected to the two screw rotors 3. The bottom side of the side cover 9 has an exhaust port 91. The shaft seal structure includes a positioning partition 4 located inside the casing 1. A pressurizing chamber 11 located inside the casing 1 and a pressure relief chamber 92 located inside the side cover 9 are formed on both sides of the positioning partition 4. The pressurizing chamber 11 is communicated with the exhaust port 91 through a through hole 41 on the positioning partition 4. The screw rotor 3 is located in the pressurizing chamber 11. The rotating shaft 2 penetrates through the positioning partition 4. The shaft seal structure further includes an isolation sleeve 8 opposite to the positioning partition 4 in the radial direction. The isolation sleeve 8 is sleeved on the outer periphery of the rotating shaft 2 and penetrates through the positioning partition 4. The outer diameter of the isolation sleeve 8 is adapted to the inner diameter of the positioning partition 4. One end of the isolation sleeve 8 facing away from the screw rotor 3 extends out of the positioning partition 4. The outer periphery of the isolation sleeve 8 is covered with a spiral groove 81 whose spiral direction is opposite to that of the screw rotor 3, so that both ends of the spiral groove 81 communicate with both sides of the positioning partition 4. The inner wall bottom surface of the pressure relief chamber 92 has a downwardly arranged diversion and pressure relief hole 93 communicated with the exhaust port 91. The diversion and pressure relief hole 93 is directly below the other end of the isolation sleeve 8. Specifically, the inner wall top surface of the exhaust port 91 has a downwardly inclined guiding surface 911. The diversion and pressure relief hole 93 is located at the upper edge of the guiding surface 911. A gap is left between the end of the isolation sleeve 8 and the inner wall of the pressure relief chamber 92 in the radial direction. A labyrinth rotor 5 in the shape of an annular disc is fixedly sleeved on the outer periphery of the rotating shaft 2. An annular disc-shaped labyrinth stator 6 is fixedly arranged on the inner wall of the pressure relief chamber 92. One side surface of the labyrinth rotor 5 facing away from the isolation sleeve 8 has a circumferentially arranged annular convex ring 51. The convex ring 51 has two radially through breaks 511. The side surface of the labyrinth stator 6 has a circumferentially arranged annular labyrinth groove 61. The convex ring 51 is located in the labyrinth groove 61 and a gap is left between the convex ring 51 and the inner wall of the labyrinth groove 61. There are two convex rings 51 and they are arranged at intervals in the radial direction of the labyrinth rotor 5. The number of the labyrinth grooves 61 is the same as that of the convex rings 51. The breaks 511 on the two convex rings 51 are all located at the same position along the circumference of the labyrinth rotor 5. A gap is left between the outer edge surface of the outermost convex ring 51 of the labyrinth rotor 5 and the inner wall of the corresponding labyrinth groove 61. The inner wall of the labyrinth groove 61 opposite to the outer edge surface of the outermost convex ring 51 of the labyrinth rotor 5 is in the shape of a conical surface with the large end facing outwards. The outer diameter of the isolation sleeve 8 is smaller than the outer diameter of the labyrinth rotor 5 and larger than the inner diameter of the labyrinth rotor 5. Both ends of the isolation sleeve 8 are fixedly clamped between the screw rotor 3 and the labyrinth rotor 5.

[0026] During operation, the driving motor 7 delivers torque to the rotating shaft 2 via the gear assembly 10 to drive the screw rotor 3 to rotate within the pressurizing chamber 11, thereby evacuating air and discharging it from the exhaust port 91. Some particles and liquid media in the air invade from the spiral groove 81 on the outer periphery of the isolation sleeve 8. When the exhaust port 91 of the screw vacuum pump is under atmospheric pressure, the pumping of the screw rotor 3 cancels out the pushing of the isolation sleeve 8, causing the invading media to be sent back towards the pressurizing chamber 11 under the action of the rotating spiral groove 81 and then discharged through the exhaust port 91. At the initial stage of the operation of the screw vacuum pump, the media can be discharged from the other end of the spiral groove 81 due to the impact of pulsed pressurized air and most of it falls into the diversion pressure relief hole 93 and is discharged with the air from the exhaust port 91. A small part of the media is blocked by the labyrinth rotor 5 or flung away under the centrifugal action of the labyrinth rotor 5, making it difficult for the corrosive media to invade the gear assembly 10 along the rotating shaft 2 towards the driving motor 7 side and cause corrosion.

[0027] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar means for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A shaft seal structure of an anti-corrosion screw vacuum pump. The vacuum pump includes a casing (1), a side cover (9), two rotating shafts (2), and two screw rotors (3). The casing (1) is in the shape of an eight-shaped cylinder. The casing (1) is connected to the side cover (9). An exhaust port (91) is provided on the outer side of the side cover (9). The shaft seal structure includes a positioning partition plate (4) located inside the casing (1). A pressurized chamber (11) located inside the casing (1) and a pressure relief chamber (92) located inside the side cover (9) are separated on both sides of the positioning partition plate (4). The pressurized chamber (11) is communicated with the exhaust port (91) through a through hole (41) on the positioning partition plate (4). The screw rotor (3) is located inside the casing (1) and is integrally and fixedly connected to the end of the rotating shaft (2) passing through the positioning partition plate (4). It is characterized in that, The shaft seal structure also includes a cylindrical isolation sleeve (8), which is fixedly sleeved on the outer periphery of the rotating shaft (2), and the isolation sleeve (8) passes through the positioning baffle (4), and one end of the isolation sleeve (8) facing away from the screw rotor (3) extends out of the positioning baffle (4), the outer diameter of the isolation sleeve (8) is compatible with the inner diameter of the positioning baffle (4), the outer periphery of the isolation sleeve (8) is covered with a spiral groove (81) whose spiral direction is opposite to the spiral direction of the screw rotor (3), and the two ends of the spiral groove (81) are connected to the two sides of the positioning baffle (4), and the inner cavity bottom surface of the pressure relief chamber (92) has a guide pressure relief hole (93) arranged downward and connected to the exhaust port (91), and the guide pressure relief hole (93) is located directly below the end of the isolation sleeve (8) extending out of the positioning baffle (4).

2. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 1, characterized in that A gap is left between the end of the isolation sleeve (8) extending out of the positioning partition plate (4) and the inner wall of the pressure relief chamber (92) in the radial direction.

3. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 1 or 2, characterized in that, The outer peripheral fixed sleeve of the rotating shaft (2) is provided with a labyrinth rotor (5) in the shape of an annular disk, the inner wall of the pressure relief chamber (92) is fixedly provided with a labyrinth stator (6) in the shape of an annular disk, the side surface of the labyrinth rotor (5) facing away from the isolation sleeve (8) is provided with a convex ring (51) arranged in an annular shape around the circumference, the convex ring (51) has a radially penetrating fracture (511), the side surface of the labyrinth stator (6) is provided with a labyrinth groove (61) arranged in an annular shape around the circumference, the convex ring (51) is located in the labyrinth groove (61) and a gap is left between the convex ring (51) and the inner wall of the labyrinth groove (61).

4. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 3, characterized in that, There are a plurality of convex rings (51) which are arranged at intervals along the radial direction of the labyrinth rotor (5); the number of the labyrinth grooves (61) is consistent with the number of the convex rings (51); and the cutouts (511) on the plurality of convex rings (51) are all located at the same position along the circumference of the labyrinth rotor (5).

5. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 3, characterized in that, A gap is left between the outer edge surface of the convex ring (51) located at the outermost layer of the labyrinth rotor (5) and the inner wall of the labyrinth groove (61) where it is located.

6. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 5, characterized in that, The inner wall of the labyrinth groove (61) opposite to the outer edge surface of the convex ring (51) at the outermost layer of the labyrinth rotor (5) is in the shape of a cone with the larger end facing outward.

7. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 3, characterized in that, The outer diameter of the isolation sleeve (8) is smaller than the outer diameter of the labyrinth rotor (5), and the end faces of the labyrinth rotor (5) and the isolation sleeve (8) are in position-limiting abutment with each other.

8. The shaft seal structure of the anti-corrosion screw vacuum pump according to claim 1 or 2, characterized in that, The inner wall top surface of the exhaust port (91) has a guide surface (911) arranged to be inclined downward, and the diversion and pressure relief hole (93) is located at the upper edge of the guide surface (911).

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