A pump housing and vacuum pump

Abstract

The application discloses a pump shell and a vacuum pump, characterized in that the pump shell is an integral structure, a cavity is arranged in the pump shell, two partition plates are detachably arranged in the cavity, the two partition plates divide the cavity into a first-stage rotor cavity, a second-stage rotor cavity and a third-stage rotor cavity which are arranged in sequence from front to back, the size of the first-stage rotor cavity is larger than that of the second-stage rotor cavity, and the size of the second-stage rotor cavity is larger than that of the third-stage rotor cavity; the first-stage rotor cavity, the second-stage rotor cavity and the third-stage rotor cavity are respectively used for accommodating a first-stage rotor, a second-stage rotor and part of a third-stage rotor; the pump shell is provided with a first-stage gas channel which is connected with the first-stage rotor cavity and the second-stage rotor cavity and a second-stage gas channel which is connected with the second-stage rotor cavity and the third-stage rotor cavity. The application improves the assembly precision of the vacuum pump and reduces the maintenance rate.

Description

Technical Field

[0001] This invention relates to a vacuum pump, and more particularly to a pump housing and a vacuum pump. Background Technology

[0002] Vacuum pumps are classified in many ways, with different pumps used in different industries. For example, Roots vacuum pumps and screw vacuum pumps can be used individually or in combination. For hybrid vacuum pumps used in combination, such as the patent application "202421278655.0" entitled "A Two-Shaft Hybrid Pump," a three-stage vacuum pumping system is constructed using a two-stage Roots rotor and a single-stage screw rotor. In this structure, the pump casing is a three-section design: two independent casings for the two-stage Roots pump and one independent casing for the screw pump. During assembly, sealing is required at the joints of each casing section, and a long screw is needed to pass through all three casing sections for assembly. This structure has the following drawbacks: 1. Every joint of the pump casing needs to be sealed. The more seals there are, the greater the risk of leakage. 2. The three-section pump casing needs to be assembled together and also needs to be assembled with the three-stage rotor, which results in particularly high requirements for machining accuracy and assembly accuracy. 3. When assembling the screw rotor and the pump casing, it is inconvenient to adjust the gap between them. Summary of the Invention

[0003] The purpose of this invention is to provide a pump housing and a vacuum pump. By using this structure, the risk of leakage is effectively reduced, the assembly accuracy is improved, and the assembly difficulty is also reduced.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a pump casing, wherein the pump casing is an integral structure, and the pump casing has a chamber extending through both ends in the axial direction. Two partition plates are detachably installed in the chamber and are spaced apart along the axial direction of the chamber. The two partition plates divide the chamber into a primary rotor chamber, a secondary rotor chamber, and a tertiary rotor chamber arranged from front to back. The size of the primary rotor chamber is larger than the size of the secondary rotor chamber, and the size of the secondary rotor chamber is larger than the size of the tertiary rotor chamber. The primary rotor cavity is used to accommodate the primary rotor, the secondary rotor cavity is used to accommodate the secondary rotor, and the tertiary rotor cavity is used to accommodate part of the tertiary rotor. The pump casing is provided with a primary air passage connecting the primary rotor chamber and the secondary rotor chamber, and a secondary air passage connecting the secondary rotor chamber and the tertiary rotor chamber.

[0005] In the above technical solution, each of the partitions is provided with at least two shaft holes in the middle, and the shaft holes connect the first-stage rotor cavity and the second-stage rotor cavity or connect the second-stage rotor cavity and the third-stage rotor cavity.

[0006] In the above technical solution, an annular groove is provided on the inner surface of the shaft hole, and a shaft sealing plate is detachably installed in the annular groove, with the inner surface of the shaft sealing plate exposed inside the shaft hole.

[0007] In the above technical solution, the top of the pump casing is provided with a main air inlet that communicates with the top of the first-stage rotor cavity; The primary air passage is located inside the pump casing outside the chamber. The inlet of the primary air passage is connected to the bottom of the primary rotor chamber, and the outlet of the primary air passage is connected to the top of the secondary rotor chamber.

[0008] The above technical solution also includes a bypass channel, which is located inside and / or outside the pump housing. The inlet of the bypass channel is connected to the primary air passage, and the outlet of the bypass channel is connected to a pressure relief device or connected to the outside. A one-way valve is also provided on the bypass channel, which is located between the inlet and outlet of the bypass channel.

[0009] In the above technical solution, the three-stage rotor cavity is a three-stage screw rotor cavity, and a cavity is provided between the three-stage rotor cavity and the rear partition. The secondary air passage is located inside the pump casing, the inlet of the secondary air passage is connected to the bottom of the secondary rotor cavity, and the outlet of the secondary air passage is connected to the cavity.

[0010] In the above technical solution, the connection between the partition and the corresponding position of the chamber is sealed.

[0011] In the above technical solution, the bottom of the rear partition is provided with a notch, which connects the secondary rotor cavity and the tertiary rotor cavity.

[0012] In the above technical solution, a jacketed water chamber is also provided inside the pump casing outside the three-stage rotor cavity; And / or, the outer wall of the pump casing is provided with an inlet and an outlet that communicate with the jacketed water chamber.

[0013] In the above technical solution, the outer wall of the pump casing is provided with an inspection port that communicates with the primary air passage, and a sealing cover is detachably installed on the inspection port.

[0014] In the above technical solution, the length of the three-stage rotor cavity is 4 / 5 to 2 / 3 of the length of the three-stage rotor.

[0015] The present invention also provides a vacuum pump, including the pump housing described above.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1. In this invention, the pump casing adopts an integral structure that can accommodate three-stage rotors. The three-stage rotors are separated by partitions, and the size of the three rotor cavities decreases step by step. This facilitates the assembly of the vacuum pump. Compared with the previous segmented pump casing structure, it can reduce the number of sealing connections, reduce the risk of leakage, improve the processing accuracy of the pump casing, and ensure assembly accuracy. The step-by-step changing size also facilitates the assembly of the vacuum pump. 2. In this invention, the length of the third-stage rotor cavity is shorter than the length of the third-stage rotor. During assembly, the end of the third-stage rotor will extend out of the pump casing, which facilitates the adjustment of the gap between the third-stage rotor and the third-stage rotor cavity, thereby improving the convenience of assembly and reducing the assembly difficulty. 3. In this invention, a shaft sealing plate is provided on the shaft hole, which can reduce friction and noise between the shaft and the partition during shaft runout, extend service life, reduce maintenance rate, and ensure vacuuming effect; 4. In this invention, a cavity is provided between the partition and the third-stage rotor cavity, so that the compressed gas delivered from the second-stage rotor cavity can be pre-distributed evenly in the cavity, making it easy to be sucked away by the third-stage rotor, reducing noise during the vacuuming process, reducing the impact of airflow on the third-stage rotor, extending service life, and reducing maintenance rate. 5. The present invention also includes a bypass channel with a pressure relief device connected to the primary air passage, which can effectively prevent pressure buildup in the primary rotor cavity, reduce the temperature of the pump casing and the primary Roots rotor, and extend the service life. 6. The present invention also includes a jacketed water cavity, which facilitates cooling of the pump casing at the highest temperature point of the third-stage rotor cavity, thereby reducing the maintenance rate and extending the service life. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the pump casing structure in Embodiment 1 of the present invention; Figure 2 yes Figure 1 A cross-sectional view of the cavity of the first-stage Roots rotor. Figure 3 This is a schematic cross-sectional view of the pump casing in Embodiment 1 of the present invention; Figure 4 yes Figure 3 A three-dimensional image; Figure 5 This is a cross-sectional view of the pump casing in Embodiment 1 of the present invention (the partition is not shown). Figure 6 yes Figure 5 A schematic diagram of the three-dimensional structure; Figure 7 yes Figure 1 A cross-sectional view of the cavity of the second-stage Roots rotor.

[0018] The components are: 1. Pump casing; 2. Baffle plate; 3. First-stage Roots rotor cavity; 4. Second-stage Roots rotor cavity; 5. Third-stage screw rotor cavity; 6. First-stage air passage; 7. Second-stage air passage; 8. Shaft hole; 9. Annular groove; 10. Shaft seal; 11. Main air inlet; 12. Bypass passage; 13. One-way valve; 14. Cavity; 15. Notch; 16. Jacket water cavity; 17. Inspection port. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: Example 1: See Figure 1-7 As shown, a pump casing 1 is an integral structure. The pump casing 1 has a chamber that extends through both ends axially. Two partition plates 2 are detachably installed in the chamber and are spaced apart along the axial direction of the chamber. The two partition plates 2 divide the chamber into a first-stage Roots rotor chamber 3, a second-stage Roots rotor chamber 4, and a third-stage screw rotor chamber 5, which are spaced apart from front to back. The size of the first-stage Roots rotor chamber 3 is larger than the size of the second-stage Roots rotor chamber 4, and the size of the second-stage Roots rotor chamber 4 is larger than the size of the third-stage screw rotor chamber 5. The first-stage Roots rotor cavity 3 is used to accommodate the first-stage Roots rotor, the second-stage Roots rotor cavity 4 is used to accommodate the second-stage Roots rotor, and the third-stage screw rotor cavity 5 is used to accommodate part of the third-stage screw rotor; The pump casing 1 is provided with a primary air passage 6 connecting the primary Roots rotor cavity 3 and the secondary Roots rotor cavity 4, and a secondary air passage 7 connecting the secondary Roots rotor cavity 4 and the tertiary screw rotor cavity 5.

[0020] The present invention also provides a vacuum pump, including the pump casing described above. The mixing vacuum pump further includes two sets of rotor components. Each rotor component includes a shaft and a first-stage Roots rotor, a second-stage Roots rotor, and a third-stage screw rotor arranged sequentially from front to back on the shaft. The size of the first-stage Roots rotor is larger than that of the second-stage Roots rotor, and the size of the second-stage Roots rotor is larger than that of the third-stage screw rotor. The first-stage, second-stage, and third-stage Roots rotors can be integrally formed with the shaft, or they can be detachably mounted on the shaft. Preferably, the first-stage and second-stage Roots rotors are integrally formed with the shaft, while the third-stage screw rotor is detachably mounted on the shaft. (The assembly clearance between the Roots rotor and the Roots rotor cavity can be larger, and the assembly precision can be lower, while the assembly clearance between the screw rotor and the screw rotor cavity is smaller, and the assembly precision is higher. Therefore, a detachable structure is preferred to facilitate adjustment of the clearance between the screw rotor and the screw rotor cavity during assembly.) A baffle is placed between the first-stage and second-stage Roots rotors, and another baffle is placed between the second-stage and third-stage screw rotors, making the entire vacuum pump a three-stage vacuum pump. During evacuation, gas enters the first-stage Roots rotor chamber, is compressed by the two meshing first-stage Roots rotors, and is then sent to the second-stage Roots rotor chamber through the first-stage gas passage. After being compressed by the two meshing second-stage Roots rotors, it is sent to the third-stage screw rotor chamber through the second-stage gas passage, and is then compressed by the two meshing third-stage screw rotors before being discharged, achieving a high vacuum level.

[0021] In this invention, the primary and secondary rotor cavities are identical; either both can be Roots rotor cavities or both can be screw rotor cavities, thus the primary rotor is a Roots rotor. The tertiary rotor cavity can be either a Roots rotor cavity or a screw rotor cavity.

[0022] In this embodiment, end caps are provided at both ends of the pump casing. The front end cap seals the front end of the chamber and can also be used to install bearings supporting the front end of the rotating shaft and accommodate gears. The rear end cap seals the rear end of the chamber and can also be used to install bearings supporting the rear end of the rotating shaft and accommodate gears. Additionally, the rear end cap has a chamber for accommodating part of the three-stage screw rotor, so that part of the three-stage screw rotor is located within the three-stage screw rotor chamber, and part is located within the rear end cap, completely accommodating the three-stage screw rotor for easy vacuuming. In this embodiment, the pump casing adopts a one-piece structure, which allows for higher machining and assembly precision compared to a split structure, and also reduces the number of sealing connections, lowering the risk of leakage. Furthermore, the internal chambers adopt a progressively smaller structure from front to back, which does not affect the assembly of the pump casing and rotor components, facilitating the assembly of the rotor components with the pump casing. During the assembly of the rotor components, the corresponding partitions can be pre-positioned between the first-stage and second-stage Roots rotors, and between the second-stage and third-stage Roots rotors, and then inserted into the chamber from front to back to assemble the rotor components and the pump casing. Subsequently, the partitions are connected to the pump casing. (Since the front end of the chamber is larger than the rear end, when assembling the rotor components with the pump casing, inserting them from front to back allows for smooth and convenient insertion into the pump casing without scratching the inner wall of the chamber.) The partition can adopt a symmetrical two-half structure (similar to the partition structure in application number "202322077615.1", patent title "A Two-Stage Roots Vacuum Pump", or similar to the partition structure in application number "202421278655.0", patent title "A Two-Shaft Mixing Pump"). Multiple screw holes can be provided on the outer surface of the partition, and through holes or screw holes can be provided on the pump housing. Bolts are used to connect the pump housing and the partition through the screw holes to fix the partition, or other structures or methods can be used to fix the partition to the pump housing. Of course, a drive mechanism, such as a motor, will be installed on one end cover to drive one set of rotor components to rotate. A gear will be provided on the shaft at the ends of both sets of rotor components. The two gears mesh, driving one set of rotor components to rotate through the drive mechanism. Through the meshing of the two gears, both sets of rotor components will rotate synchronously, achieving the vacuuming action.

[0023] In this invention, a portion of the three-stage screw rotor is located within the three-stage screw rotor cavity, while another portion protrudes outside the pump casing. In this embodiment, the length of the three-stage screw rotor cavity is 4 / 5 to 2 / 3 of the length of the three-stage screw rotor. Preferably, the length of the rear end of the three-stage screw rotor protruding from the three-stage screw rotor cavity is 20% to 30% of the length of the three-stage screw rotor. Because the assembly precision between the screw rotor and the screw rotor cavity is relatively high (the assembly precision requirements for the screw rotor and screw rotor cavity are relatively high, especially for dry screw rotors), if the assembly precision is not high enough, due to thermal expansion and contraction caused by high and low temperatures during operation, friction between the two screw rotors and friction between the screw rotor and the inner wall of the screw rotor cavity can easily occur, leading to high maintenance rates, jamming, and problems affecting vacuum pumping. Alternatively, the exhaust port at the end of the vacuum pump is where the temperature is highest; high temperatures can cause expansion, exceeding the reserved gap and causing pump jamming. Therefore, the reserved gap between the rotor at the exhaust port and the pump casing is larger. In the prior art, the rotor and the corresponding rotor... Since all the sub-cavities are present, adjusting the space during installation is quite troublesome, and the gap is difficult to control. This is not limited to screw rotors or Roots rotors; in this embodiment, the three-stage rotor uses a screw rotor. In conventional assembly methods, such as in application number "202421278655.0" and patent title "A Two-Shaft Mixing Pump," the screw rotor is fully inserted into the screw rotor cavity before the gap is adjusted. This assembly method makes gap adjustment quite difficult (the meshing gap between the two screw rotors, the axial gap, and the outer circle gap between the screw rotor and the inner wall of the screw rotor cavity, etc.), and it is inconvenient to observe the gap during or after the adjustment process. Therefore, in this embodiment, a portion of the three-stage screw rotor extends beyond the three-stage screw rotor cavity. This allows for easy inspection of the meshing clearance and axial clearance between the two three-stage screw rotors during assembly, as well as the clearance between the three-stage screw rotor and its cavity from the rear end. This facilitates clearance adjustment, improves assembly convenience, and reduces assembly difficulty. Furthermore, during subsequent maintenance, simply opening the rear end cap allows for quick inspection of the clearance between the three-stage screw rotor and its cavity, facilitating inspection and maintenance.

[0024] See Figure 2-4 As shown in Figures 7 and 8, each of the partition plates 2 has at least two shaft holes 8 in the middle, and the shaft holes 8 connect the first-stage Roots rotor cavity 3 and the second-stage Roots rotor cavity 4 or connect the second-stage Roots rotor cavity 4 and the third-stage screw rotor cavity 5.

[0025] In this embodiment, the partition plate has two shaft holes in its middle, corresponding to the rotating shafts of the two sets of rotor components. The shaft holes allow space for the rotating shafts. The partition plate adopts a symmetrical two-half structure (the partition plate includes two symmetrically arranged half partition plates). Each half partition plate has two semicircular holes on its end face. The semicircular holes of the two half partition plates are arranged opposite each other, and the two opposite semicircular holes form a shaft hole. During assembly, each half partition plate is respectively locked above and below the rotating shafts of the two sets of rotor components. The upper half of each rotating shaft is located in the semicircular hole of the upper half partition plate, and the lower half of each rotating shaft is located in the semicircular hole of the lower half partition plate. The partition plate is set between adjacent rotors (between the first-stage Roots rotor and the second-stage Roots rotor, and between the second-stage Roots rotor and the third-stage screw rotor). There is a micro-gap between the side wall of the partition plate and the end of the corresponding rotor. In this way, when the rotor components rotate, the corresponding rotor will not contact or rub against the partition plate, preventing rotor wear and ensuring smooth rotation. At the same time, the micro-gap is small and does not affect vacuuming. The presence of the shaft hole allows space for the shaft to pass through the first-stage, second-stage, and third-stage Roots rotor chambers without affecting its normal rotation. It also facilitates assembly. The partition divides the chambers into three independent rotor chambers, enabling the vacuum pump to function as a three-stage vacuum pump. Preferably, the diameter of the shaft hole is slightly larger than the outer diameter of the shaft, and the outer surface of the shaft does not contact the shaft hole. This ensures that the shaft and partition are not worn during operation, guarantees smooth rotation of the rotor components, reduces energy consumption, and lowers maintenance rates.

[0026] See Figure 2-4 As shown in Figure 7, an annular groove 9 is provided on the inner surface of the shaft hole 8, and a shaft sealing plate 10 is detachably installed in the annular groove 9. The shaft sealing plate 10 has an annular structure, and the inner surface of the shaft sealing plate 10 is exposed in the shaft hole 8.

[0027] In this embodiment, preferably, the shaft seal is made of PTFE, a flexible and smooth material. Because a gap exists between the inner surface of the shaft hole and the outer surface of the shaft to avoid friction, during vacuuming, some airflow from the second-stage Roots rotor cavity will flow back into the first-stage Roots rotor cavity through this gap, and some airflow from the third-stage screw rotor cavity will flow back into the second-stage Roots rotor cavity through this gap, resulting in noise or affecting the vacuum level. Furthermore, because the shaft in the rotor assembly experiences some shaft runout during rotation, it may collide with the shaft hole during this runout, i.e., the shaft collides with the partition, resulting in rigid metal-to-metal friction (both the shaft and the partition are made of metal), generating noise and causing wear on the shaft. Therefore, a shaft seal is also provided. The inner surface of the shaft seal contacts the outer surface of the shaft, or the inner diameter of the shaft seal is slightly larger than the outer diameter of the shaft (and the inner diameter of the shaft seal is smaller than the inner diameter of the shaft hole). The inner surface of the shaft seal is set close to the outer surface of the shaft (the shaft, shaft hole, and shaft seal are coaxially arranged). This can significantly reduce gas backflow. When the shaft vibrates, it will come into contact with the shaft seal and be blocked by the shaft seal. It will not come into contact with the inner wall of the shaft hole, or only momentarily. The elastic restoring force of the shaft seal also has the thrust to push the shaft back to its original position, thereby preventing rigid friction between the shaft and the shaft hole from generating noise, and will not damage the shaft, or will minimize the damage to the shaft, reduce wear on the shaft (as far as possible, only wear on the shaft seal, which is relatively inexpensive and easy to replace), extend its service life, and reduce the maintenance rate.

[0028] Preferably, multiple holes can be provided on the side wall of the partition at the outer edge of the shaft hole. The shaft seal can be detachably installed in the annular groove by bolts or other fasteners passing through the holes. The worn shaft seal can be replaced in a timely or periodic manner, which is more cost-effective than replacing the shaft.

[0029] See Figure 1 , 5 As shown in Figure 7, the top of the pump housing 1 is provided with a main air inlet 11 that communicates with the top of the first-stage Roots rotor cavity 3; The primary air passage 6 is located inside the pump casing 1 outside the chamber. The inlet of the primary air passage 6 is connected to the bottom of the primary Roots rotor chamber 3, and the outlet of the primary air passage 6 is connected to the top of the secondary Roots rotor chamber 4.

[0030] The main air inlet is used to connect to the equipment, components, pipelines, or other places requiring vacuuming. During operation, the two sets of rotor components rotate simultaneously in opposite directions, both facing inwards. This draws the gas from the main air inlet into the first-stage Roots rotor chamber above the two sets of first-stage Roots rotors. The gas is then compressed downwards and sent into the first-stage Roots rotor chamber below the two sets of first-stage Roots rotors, and further into the inlet of the first-stage air passage at the bottom of the first-stage Roots rotor chamber. The gas then passes through the first-stage air passage within the pump casing surrounding the chamber and is delivered to the outlet of the first-stage air passage, and finally into the second-stage Roots rotor chamber above the two sets of second-stage Roots rotors. Finally, the rotation of the two sets of second-stage Roots rotors sends the gas into the second-stage Roots rotor chamber below the two sets of second-stage Roots rotors.

[0031] See Figure 5 , 6 As shown, a bypass channel 12 is also provided. The bypass channel 12 is located inside and / or outside the pump housing 1. The inlet of the bypass channel 12 is connected to the primary air passage 6, and the outlet of the bypass channel 12 is connected to a pressure relief device. A one-way valve 13 (one-way pressure relief valve) is also provided on the bypass channel 12. The one-way valve 13 is located between the inlet and outlet of the bypass channel 12.

[0032] In this embodiment, a portion of the bypass channel is located outside the pump casing, and a portion is located inside the pump casing. The portion located outside the pump casing is a bypass pipe, and the portion located inside the pump casing is a bypass groove. The bypass pipe and the bypass groove are connected. Alternatively, only one bypass groove can be provided, located inside the pump casing; or only one bypass pipe can be provided, located outside the pump casing. One end of the bypass channel is an inlet, connected to the primary air passage, preferably connected to the inlet of the primary air passage. The other end of the bypass channel is an outlet, directly connected to the pressure relief device. The one-way valve adopts a pressure relief ball structure and operates by its own weight. The structure of this one-way valve can adopt existing technology, such as the one-way valve structure in application number "202422334498.7", patent title "A Pump Body of a Hybrid Vacuum Pump". During the vacuuming process, when the exhaust pressure in the first-stage Roots rotor chamber exceeds the pressure in the second-stage Roots rotor chamber and also exceeds the weight of the pressure relief ball, the pressure relief ball will be lifted. At this point, the gas discharged from the first-stage Roots rotor chamber will not be sent into the second-stage Roots rotor chamber through the first-stage air passage but will be discharged through the bypass passage. When the pressure in the first-stage Roots rotor chamber exceeds atmospheric pressure, the pressure relief device will activate (the pressure relief device can be a pressure relief valve or other pressure relief mechanism), directly discharging the gas from the first-stage Roots rotor chamber into the vacuum pump, thus preventing internal pressure buildup in the vacuum pump.

[0033] Of course, in another preferred embodiment, the outlet of the bypass channel may not be connected to the pressure relief device and may be directly connected to the outside.

[0034] See Figure 3-6 As shown, a cavity 14 is provided between the third-stage screw rotor cavity 5 and the rear partition 2. The secondary air passage 7 is located inside the pump housing 1. The inlet of the secondary air passage 7 is connected to the bottom of the secondary Roots rotor cavity 4, and the outlet of the secondary air passage 7 is connected to the cavity 14.

[0035] In existing technologies, such as application number "202421278655.0" and patent title "A Two-Shaft Mixing Pump," gas from the Roots rotor cavity is fed into the screw rotor cavity. The gas directly impacts the outer surface of the screw rotor, with the impact direction perpendicular to the axis of the shaft. The shaft is subjected to radial force from the gas for extended periods, easily leading to shaft deformation (even slight deformation). This deformation can cause friction between the two screw rotors or between the screw rotor and its cavity, resulting in jamming and wear, leading to high maintenance rates and short service life. Furthermore, because the screw rotor has a helical structure, the helical gaps within the helical structure form the gas flow path. With radial air intake, gas can only enter the screw rotor cavity through a portion of the helical grooves, resulting in higher exhaust pressure during vacuuming, higher temperature within the screw rotor cavity, and greater radial pressure on the shaft at that point. This further contributes to the short service life and high maintenance rate of the three-stage screw rotor.

[0036] Therefore, in this embodiment, a cavity is provided, and the third-stage screw rotor is not located in the cavity. That is, there is a cavity between the third-stage screw rotor and the rear partition plate. In this way, the gas delivered from the second-stage Roots rotor cavity, after being transported through the second-stage gas passage (when the two sets of second-stage Roots rotors rotate, the gas in the second-stage Roots rotor cavity above the second-stage Roots rotor is sent to the second-stage Roots rotor cavity below the second-stage Roots rotor, and then sent into the second-stage gas passage), will be sent into this cavity. The gas can be evenly distributed in this cavity and can easily enter from the end face of the third-stage screw rotor along the helical groove of the third-stage screw rotor. The gas can fully contact the front end face of the helical groove of the third-stage screw rotor, reduce the pressure of the gas in the second-stage Roots rotor cavity entering the helical groove of the third-stage screw rotor, reduce the impact force on the third-stage screw rotor, and also reduce the overall temperature of the third-stage screw rotor cavity, extend its service life, and reduce the maintenance rate. Furthermore, preferably, the outlet of the secondary air passage is positioned directly opposite the gap between the two rotating shafts. This prevents radial impact on the rotating shafts when gas enters the cavity, effectively preventing shaft deformation, extending service life, and reducing maintenance rate. Simultaneously, the presence of the cavity ensures uniform gas distribution within the tertiary screw rotor cavity, thus dispersing the impact force on the tertiary screw rotor, extending its service life, and reducing maintenance rate. (Of course, if the tertiary rotor is a Roots rotor, the cavity is not required; the outlet of the secondary air passage is connected to the top of the tertiary rotor cavity. In this embodiment and accompanying drawings, the primary and secondary rotors are Roots rotors, and the tertiary rotor is a screw rotor.)

[0037] The two partition plates 2 are sealed at their corresponding positions with the chamber 14. This effectively separates the first-stage, second-stage, and third-stage Roots rotor chambers, ensuring the compressibility of the gas in the Roots rotor chamber and the second-stage Roots rotor chamber, thus guaranteeing a vacuum effect. This sealing method can be achieved by placing a sealing ring between the outer surface of the partition plate and the inner wall of the chamber, or by placing a sealing ring at the end face of the outer edge of the partition plate where it contacts the chamber, or by using other connection methods that can achieve a seal.

[0038] Furthermore, the bottom of the rear partition 2 is provided with a notch 15, which connects the secondary Roots rotor cavity 4 with the cavity 14 and the tertiary screw rotor cavity 5.

[0039] In this embodiment, the inlet of the secondary air passage is connected to the bottom of the secondary Roots rotor cavity, and the outlet of the secondary air passage is connected to the bottom of the cavity (of course, the outlet of the secondary air passage can also be connected to the top or middle of the cavity, or there can be multiple outlets of the secondary air passage, as long as they can connect to the cavity). The connection between the outlet of the secondary air passage and the bottom of the cavity facilitates processing (an air passage can be directly processed at the bottom of the chamber, and this air passage is set at the position of the partition at the rear end of the installation, so that this air passage constitutes a secondary air passage, which is convenient for processing). The addition of the notch increases the amount of air fed into the cavity from the secondary Roots rotor cavity (since the cavity is connected to the tertiary screw rotor cavity, the amount of air fed into the tertiary screw rotor cavity is increased). This results in a larger gas flow rate and a lower flow velocity from the secondary Roots rotor cavity into the tertiary screw rotor cavity, thereby reducing the temperature at that location. Furthermore, due to the lower gas flow velocity, the impact force of the gas on the tertiary screw rotor is further reduced, extending the service life and reducing the maintenance rate. Preferably, the notch is connected to the secondary air passage.

[0040] See Figure 1-7 As shown, a jacketed water chamber 16 is also provided inside the pump casing 1 outside the three-stage screw rotor cavity 5; The outer wall of the pump casing 1 is provided with an inlet and an outlet that communicate with the jacketed water chamber 16. Because the compression ratio of a screw vacuum pump is much greater than that of a Roots vacuum pump, the temperature rises rapidly and is relatively high during vacuuming at the three-stage screw rotor and its cavity. The inlet and outlet are connected to the supply and return lines, respectively, facilitating the provision of cooling medium to cool the pump casing at the three-stage screw rotor cavity, extending service life and reducing maintenance.

[0041] See Figure 1 , 2 As shown, the outer wall of the pump casing 1 is provided with an inspection port 17 that communicates with the primary air passage 6. At the same time, the outer wall of the pump casing 1 is also provided with an inspection port that communicates with the jacket water chamber 16. A sealing cover plate (not shown in the figure) is detachably installed on the inspection port 17.

[0042] The presence of the inspection port allows for quick inspection or cleaning when the primary air passage or jacketed water chamber becomes blocked or otherwise obstructed, or when internal cleaning is required. This eliminates the need to disassemble the rotor components inside the pump casing, or to reassemble or adjust them, thus improving the convenience of cleaning and maintenance.

[0043] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. For instance, the two components can be mechanically connected by contact or abutting; they can also be directly hooked or connected by an intermediate medium; or they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A pump casing, characterized in that: The pump casing is an integral structure, and the pump casing has a chamber that extends through both ends axially. Two partitions are detachably installed in the chamber and are spaced apart along the axis of the chamber. The two partitions divide the chamber into a primary rotor chamber, a secondary rotor chamber, and a tertiary rotor chamber arranged from front to back. The size of the primary rotor chamber is larger than the size of the secondary rotor chamber, and the size of the secondary rotor chamber is larger than the size of the tertiary rotor chamber. The primary rotor cavity is used to accommodate the primary rotor, the secondary rotor cavity is used to accommodate the secondary rotor, and the tertiary rotor cavity is used to accommodate part of the tertiary rotor. The pump casing is provided with a primary air passage connecting the primary rotor chamber and the secondary rotor chamber, and a secondary air passage connecting the secondary rotor chamber and the tertiary rotor chamber.

2. The pump casing according to claim 1, characterized in that: Each of the partitions has at least two shaft holes in its middle, the shaft holes connecting the first-stage rotor cavity and the second-stage rotor cavity or connecting the second-stage rotor cavity and the third-stage rotor cavity.

3. The pump casing according to claim 2, characterized in that: An annular groove is provided on the inner surface of the shaft hole, and a shaft sealing plate is detachably installed in the annular groove, with the inner surface of the shaft sealing plate exposed inside the shaft hole.

4. The pump casing according to claim 1, characterized in that: The top of the pump casing is provided with a main air inlet that communicates with the top of the first-stage rotor chamber; The primary air passage is located inside the pump casing outside the chamber. The inlet of the primary air passage is connected to the bottom of the primary rotor chamber, and the outlet of the primary air passage is connected to the top of the secondary rotor chamber.

5. The pump casing according to claim 1, characterized in that: A bypass channel is also provided, which is located inside and / or outside the pump housing. The inlet of the bypass channel is connected to the primary air passage, and the outlet of the bypass channel is connected to a pressure relief device or connected to the outside. A one-way valve is also provided on the bypass channel, which is located between the inlet and outlet of the bypass channel.

6. The pump casing according to claim 1, characterized in that: The third-stage rotor chamber is a three-stage screw rotor chamber. A cavity is also provided between the third-stage rotor chamber and the rear partition. The second-stage air passage is located inside the pump casing. The inlet of the second-stage air passage is connected to the bottom of the second-stage rotor chamber, and the outlet of the second-stage air passage is connected to the cavity.

7. The pump casing according to claim 1, characterized in that: The partition is sealed at the corresponding position of the chamber.

8. The pump casing according to claim 7, characterized in that: The bottom of the rear partition is provided with a notch, which connects the secondary rotor cavity and the tertiary rotor cavity.

9. The pump casing according to claim 1, characterized in that: The pump casing outside the third-stage rotor cavity is also provided with a jacketed water cavity; And / or, the outer wall of the pump casing is provided with an inlet and an outlet that communicate with the jacketed water chamber.

10. The pump casing according to claim 1, characterized in that: The outer wall of the pump casing is provided with an inspection port that communicates with the primary air passage, and a sealing cover is detachably installed on the inspection port.

11. The pump casing according to claim 1, characterized in that: The length of the three-stage rotor cavity is 4 / 5 to 2 / 3 of the length of the three-stage rotor.

12. A vacuum pump, characterized in that: Includes the pump housing as described in any one of claims 1-11.

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