Two-stage single-head screw and double-screw vacuum pump composed of two-stage single-head screw

Abstract

The invention discloses a double-stage single-head screw and a double-screw vacuum pump composed of the same, and relates to the technical field of vacuum pumps. The double-stage single-head screw comprises a first-stage screw body, a short shaft and a second-stage screw body, the first-stage screw body and the second-stage screw body are fixedly connected with the two ends of the short shaft respectively, the first-stage screw body and the second-stage screw body are single-head equal-pitch screw bodies, and the spiral faces of the first-stage screw body and the second-stage screw body are the same in rotation direction. And the screw pitches of the primary screw rod and the secondary screw rod are not equal. The invention further discloses a double-screw vacuum pump, the main screw and the auxiliary screw of the double-stage single-head screw structure are adopted in the double-screw vacuum pump, and the main screw and the auxiliary screw are connected with a synchronous gear pair and driven by a motor to operate synchronously. The pump has the advantages of a variable-pitch screw vacuum pump and an equal-pitch screw vacuum pump, rapid and precise forming machining of a single-head equal-pitch screw is facilitated, and the manufacturing cost of the screw of the pump is greatly reduced. And front and rear end face molded lines and front and rear screw pitches of the first-stage screw and the second-stage screw can be designed according to the overall dynamic balance requirement, the internal compression ratio is high, the exhaust temperature is low, and noise is low.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum pumps, and particularly to a double-stage single-screw and a twin-screw vacuum pump composed thereof. Background Art

[0002] Twin-screw vacuum pumps have the advantages of no friction between rotors, cleanliness, and being suitable for pumping condensable gases or fluids containing fine particles, etc. They are widely used in petrochemical industry, electronic coating, vacuum melting, aerospace, biological extraction, distillation separation, etc., and there is a trend to replace existing vacuum pumps such as oil-sealed rotary vane pumps, slide valve pumps, and liquid ring pumps.

[0003] Most of the existing screw vacuum pumps on the market adopt single-head equal-pitch and variable-pitch screws with a continuous pitch length of more than 3 pitches.

[0004] The exhaust temperature of equal-pitch screw vacuum pumps is high, and the thermal deformation of the pump body and the screw is serious. Especially when applied in the fields of biology, medicine, and chemical industry, it is easy to cause coking of unsaturated organic substances, and the screw rotor is very easy to get stuck, with a short maintenance period, which is very annoying.

[0005] The exhaust temperature of variable-pitch screw vacuum pumps is relatively low, but they require expensive four-axis or five-axis linkage CNC machine tools, and the variable-pitch part is complex to process, and the finish machining time is too long, so the cost is high and the price is expensive. At the same time, the compression ratio of the existing variable-pitch vacuum pumps is also relatively small, and the pumping speed range under high vacuum conditions is also relatively narrow.

[0006] CN118030526A discloses a multi-stage variable-pitch screw vacuum pump with adjustable compression ratio. Taking two stages as an example, in the first-stage pump cavity, there are two parallel first-stage screws with equal pitches, and in the second-stage pump cavity, there are two parallel second-stage screws with equal pitches. The pitch of the first-stage screw is greater than that of the second-stage screw. Synchronous gears are installed on the shafts at one end of each first-stage screw and each second-stage screw, and a variable-speed gear is installed on the shaft at the other end of one of the first-stage screws. The variable-speed gear is located outside the bearing at this end. Correspondingly, a variable-speed gear is also installed on the shaft at the other end of a second-stage screw directly below this first-stage screw. The multi-stage variable-pitch screw vacuum pump with adjustable compression ratio uses layered variable pitch but equal pitch for each layer to achieve adjustable compression ratio, but its vacuum pump structure is complex and the manufacturing cost is high. Summary of the Invention

[0007] The purpose of the present invention is to provide a double-stage single-screw with discontinuous helical surfaces, the same helix direction, and the same or different front and rear end profiles, and a twin-screw vacuum pump composed thereof, so that the existing twin-screw vacuum pump has the advantages of both variable-pitch and equal-pitch screw vacuum pumps, while avoiding their disadvantages, and solving the problems of precision and rapid forming machining of single-screw and rapid dynamic balance treatment, so as to solve the problems raised in the above background art.

[0008] The technical solution adopted by the present invention to solve its technical problems is as follows: A double-stage single-headed screw includes a first-stage screw, a short shaft, and a second-stage screw. The first-stage screw and the second-stage screw are respectively fixedly connected to both ends of the short shaft. The first-stage screw and the second-stage screw are single-headed screws with equal pitches, and the spiral surfaces of the two have the same helix direction; the pitches of the first-stage screw and the second-stage screw are not equal.

[0009] The double-stage single-headed screw of the present invention is a single-headed screw with discontinuous spiral surfaces, the same helix direction, the end profiles of the front and rear screws can be the same or different, and the concave profiles of the end teeth of the front and rear screws are rotated 180° relative to each other. It combines the advantages of variable-pitch screws and equal-pitch screws, while avoiding their disadvantages, greatly improving the pumping speed per unit volume and the vacuum degree of the vacuum pump using this double-stage single-headed screw, and reducing the exhaust temperature of the pump.

[0010] Preferably, the pitch ratio of the second-stage screw to the first-stage screw is 1.5 to 3.5.

[0011] In a certain exemplary embodiment, the effective thread length of the first-stage screw is 2 to 4 pitches, and the effective thread length of the second-stage screw is 1 to 2 pitches.

[0012] The end profiles of the first-stage screw and the second-stage screw are the same or different. The concave profiles of the end teeth of the first-stage screw and the second-stage screw connected to both ends of the short shaft are rotated 180° relative to each other.

[0013] The double-stage single-headed screw is an integrally formed structure. Alternatively, the central shaft and the spiral body of the double-stage single-headed screw are of a split structure. The central shaft and the spiral body are processed in a modular and standardized manner, and then assembled. This double-stage single-headed screw is convenient for rapid and precise forming processing, greatly reducing its manufacturing cost and the manufacturing cost of the vacuum pump using this screw.

[0014] To further solve its technical problems, the present invention further adopts the following technical solution: A double-screw vacuum pump includes a motor, a motor frame, a gearbox, a synchronous gear pair, a front end seat, a main screw and a sub-screw, a partition board, and a pump cylinder body and a pump rear seat; the motor is installed on the motor frame, the output shaft of the motor is connected to the main screw through a coupling, the motor frame is fixed on the gearbox, the gearbox is installed on the front end seat, the synchronous gear pair is installed on the main screw and the sub-screw and is arranged inside the gearbox, the main screw and the sub-screw are meshed with each other and arranged inside the pump cylinder body, and their two ends are respectively connected to a front rolling bearing in the shaft hole of the front end seat and a rear rolling bearing in the shaft hole of the pump rear seat. Both the main screw and the sub-screw are the above-mentioned double-stage single-headed screws.

[0015] In a certain exemplary embodiment, a partition plate with an air flow channel is provided on the short shafts of the main screw and the auxiliary screw. The partition plate is fixed within the pump cylinder body, and the partition plate divides the pump cylinder body into two cavities. The exhaust end in front of the pump near the partition plate is the first-stage pump cavity, and the intake end behind the pump near the partition plate is called the second-stage pump cavity. The first-stage screws of the main screw and the auxiliary screw are installed in the first-stage pump cavity, and the second-stage screws are located in the second-stage pump cavity, making it a two-stage composite pump.

[0016] For the twin-screw vacuum pump of the present invention, the main screw and the auxiliary screw adopt two-stage single-start screws, combining the advantages of variable pitch screws and equal pitch screw vacuum pumps, greatly improving the pumping speed per unit volume and the vacuum degree of the pump, reducing the exhaust temperature of the pump and the manufacturing cost of the pump; and a partition plate with an air flow channel is provided between the outer part of the middle short shafts of the main screw and the auxiliary screw and the inside of the pump cylinder body to ensure the continuity of the suction, compression, and exhaust of the pump and the high vacuum of the pump.

[0017] In a certain exemplary embodiment, a seal is provided between the bearing and the end face of the pump cylinder body.

[0018] The central shafts of the main screw and the auxiliary screw and the spiral bodies are manufactured in a split modular and standardized manner, or can also be integrally manufactured.

[0019] In a certain exemplary embodiment, if the central shafts of the main screw and the auxiliary screw and the spiral bodies are of an integral one-piece forming structure, the partition plate should be of a split combined structure. The partition plate is composed of an upper partition plate and a lower partition plate, and is fixed within the pump cylinder body by dowel pins. The upper partition plate and the lower partition plate are each provided with 2 arc-shaped grooves for the central shafts of the main screw and the auxiliary screw to pass through respectively, and the two arc-shaped grooves are combined to form a shaft through-hole. An air flow channel is provided between the arc-shaped grooves of the upper partition plate and the lower partition plate. An exhaust hole communicating with the air flow channel is provided on the side of the upper partition plate facing the first-stage pump cavity, and an intake hole communicating with the air flow channel is provided on the side of the lower partition plate facing the second-stage pump cavity. The upper partition plate and the lower partition plate are provided with dowel pin fixing holes for connecting with the pump cylinder body at both ends.

[0020] In a certain exemplary embodiment, if the central shafts of the main screw and the auxiliary screw and the spiral bodies are of a split type, the partition plate should be of an integral type, integrally cast, or integrally cast with the pump cylinder body. The partition plate is of an integral structure, and the overall shape is an 8-shaped plate body. The partition plate is respectively provided with shaft through-holes for the central shafts of the main screw and the auxiliary screw to pass through in the middle. An air flow channel is provided between the 2 shaft through-holes. An exhaust hole communicating with the air flow channel is provided on the side of the partition plate facing the first-stage pump cavity, and an intake hole communicating with the air flow channel is provided on the side of the partition plate facing the second-stage pump cavity. The partition plate is provided with dowel pin fixing holes for connecting with the pump cylinder body at both ends.

[0021] Compared with the prior art, the beneficial effects of the present invention are: The double-stage single-head screw of the present invention combines the advantages of variable pitch and equal pitch screws, while avoiding their disadvantages, facilitating the rapid and precise forming process of single-head equal pitch screws, and greatly reducing the manufacturing cost of the pump screws.

[0022] The front and rear end profiles of the first-stage screw and the second-stage screw of the double-stage single-head screw can be designed arbitrarily, and the pitches of the first-stage screw and the second-stage screw can be designed according to the overall dynamic balance requirements of the double-stage single-head screw.

[0023] In addition, the accuracy of the screw profile and the meshing accuracy are improved, thereby reducing the gas leakage between the gaps, having a high internal compression ratio, and thus reducing the exhaust temperature and noise.

[0024] The twin-screw vacuum pump of the present invention uses two main screws and auxiliary screws with the same structure and meshing fit. By using the unequal pitches at the front and rear ends of the single-head screw, a high internal compression ratio is achieved, thereby reducing the exhaust temperature and the noise of the pump and improving the energy efficiency of the pump.

[0025] And an air flow channel partition is arranged on the short shaft connecting the first-stage screw and the second-stage screw, reducing the gas leakage between the gaps, improving the ultimate vacuum degree of the vacuum pump, and enabling the pump to obtain an extremely high vacuum degree within a relatively wide rotational speed range. Brief Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the twin-screw vacuum pump of the present invention; Figure 2 It is a schematic A-A sectional structural diagram of the twin-screw vacuum pump of the present invention; Figure 3 It is a three-dimensional structural diagram of the double-stage single-head threaded rod used in the twin-screw vacuum pump in Embodiment 1 of the present invention; Figure 4 It is a front view of the double-stage single-head threaded rod used in the twin-screw vacuum pump in Embodiment 1 of the present invention.

[0027] Figure 5 It is a B-B sectional view of the double-stage single-head threaded rod used in the twin-screw vacuum pump in Embodiment 1 of the present invention.

[0028] Figure 6 It is a three-dimensional structural diagram of the partition in the twin-screw vacuum pump in Embodiment 1 of the present invention.

[0029] Figure 7 It is an exploded structural diagram of the partition in the twin-screw vacuum pump in Embodiment 1 of the present invention.

[0030] Figure 8 It is a longitudinal sectional structural diagram of the partition in the twin-screw vacuum pump in Embodiment 1 of the present invention.

[0031] Figure 9Schematic three-dimensional structure diagram of the double-stage single-headed screw rod used in the double-screw vacuum pump in Embodiment 2 of the present invention; Figure 10 Front view of the double-stage single-headed screw rod used in the double-screw vacuum pump in Embodiment 2 of the present invention.

[0032] Figure 11 C-C sectional view of the double-stage single-headed screw rod used in the double-screw vacuum pump in Embodiment 2 of the present invention.

[0033] Figure 12 Schematic three-dimensional structure diagram of the middle partition plate in the double-screw vacuum pump in Embodiment 2 of the present invention.

[0034] Figure 13 Longitudinal sectional structure diagram of the middle partition plate in the double-screw vacuum pump in Embodiment 2 of the present invention.

[0035] Figure 14 Schematic three-dimensional structure diagram of the double-stage single-headed screw rod used in the double-screw vacuum pump in Embodiment 3 of the present invention.

[0036] Figure 15 Schematic three-dimensional structure diagram of the double-stage single-headed screw rod used in the double-screw vacuum pump in Embodiment 4 of the present invention.

[0037] In the figure: 1, motor; 2, motor frame; 3, gearbox; 4, synchronous gear pair; 5, front end seat; 6, main screw rod; 7, auxiliary screw rod; 8, partition plate; 81, upper partition plate; 82, lower partition plate; 83, shaft through hole; 831, arc-shaped groove; 84, pin fixing hole; 85, exhaust hole; 86, intake hole; 87, air flow channel; 9, pump cylinder body; 10, pump rear seat; 11, coupling; 12, front rolling bearing; 13, rear rolling bearing; 14, seal; 15, double-stage single-headed screw; 151, first-stage screw; 152, short shaft; 153, second-stage screw; 154, spiral body; 155, central shaft. Detailed implementation manners

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1 Please refer to Figure 1 and 2, A two-screw vacuum pump according to this embodiment includes a motor 1, a motor bracket 2, a gearbox 3, a synchronous gear pair 4, a front seat 5, a main screw 6, a sub-screw 7, a partition 8, a pump cylinder block 9 and a pump rear seat 10; the motor 1 is installed on the motor bracket 2, the output shaft of the motor 1 is connected to the main screw 6 through a coupling 11, the motor bracket 2 is fixed on the gearbox 3, the gearbox 3 is installed on the front seat 5, the synchronous gear pair 4 is installed on the main screw 6 and the sub-screw 7 and is arranged inside the gearbox 3, the main screw 6 and the sub-screw 7 are meshed with each other and arranged inside the pump cylinder block 9, and their two ends are respectively connected to the front rolling bearing 12 in the shaft hole of the front seat 5 and the rear rolling bearing 13 in the shaft hole of the pump rear seat 10. The main screw 6 and the sub-screw 7 are both the above-mentioned double-stage single-start screw 15.

[0040] A seal 14 is arranged between the bearing and the end face of the pump cylinder block 9.

[0041] A partition 8 with an air flow passage 87 is arranged on the short shaft 152 of the main screw 6 and the sub-screw 7. The partition 8 is fixed inside the pump cylinder block 9. The partition 8 divides the pump cylinder block 9 into two cavities. The exhaust end in front of the pump near the partition 8 is the first-stage pump cavity, and the intake end behind the pump near the partition 8 is called the second-stage pump cavity, making it a two-stage composite pump.

[0042] See Figures 3 - 5 , In this embodiment, both the main screw 6 and the sub-screw 7 adopt the double-stage single-start screw 15. The double-stage single-start screw 15 includes a first-stage screw 151, a short shaft 152 and a second-stage screw 153. The first-stage screw 151 and the second-stage screw 153 are respectively fixedly connected to both ends of the short shaft 152. The first-stage screw 151 and the second-stage screw 153 are single-start equal-pitch screws, and the spiral surfaces of both have the same helix direction; the pitches of the first-stage screw 151 and the second-stage screw 153 are not equal.

[0043] The ratio of the pitch of the second-stage screw 153 to the pitch of the first-stage screw 151 is 3.0. For example, the pitch of the first-stage screw 151 is 60 mm, and the pitch of the second-stage screw 153 is 180 mm.

[0044] The effective thread length of the first-stage screw 151 is 3 pitches, and the effective thread length of the second-stage screw 153 is 1 pitch.

[0045] The end face profiles of the first-stage screw 151 and the second-stage screw 153 are the same. The concave surface profiles of the end teeth of the first-stage screw 151 and the second-stage screw 153 connected to both ends of the short shaft 152 are rotated 180° relative to each other.

[0046] The double-stage single-start screw 15 is an integrally formed structure.

[0047] The central axes 155 of the main screw 6 and the auxiliary screw 7 in this embodiment are integral with the spiral bodies 154. The partition plate 8 has a split and combined structure and is fixed in the pump cylinder block 9 by dowel pins. Dark pin holes are provided at both ends of the central axes 155 of the main screw 6 and the auxiliary screw 7, and a thread for connecting with the output shaft of the motor 1 is provided on the central axis 155 of the main screw 6.

[0048] It should be noted that the central axes 155 of the main screw 6 and the auxiliary screw 7 in this embodiment can also be manufactured in a split, modular and standardized manner.

[0049] See Figures 6 - 8 , the partition plate 8 is composed of an upper partition plate 81 and a lower partition plate 82, and is fixed in the pump cylinder block 9 by dowel pins. Two arc-shaped grooves 831 for the central axes 155 of the main screw 6 and the auxiliary screw 7 to penetrate respectively are provided on both the upper partition plate 81 and the lower partition plate 82, and the two arc-shaped grooves 831 are combined to form a shaft through hole 83. An air flow channel 87 is provided between the arc-shaped grooves 831 of the upper partition plate 81 and the lower partition plate 82. An exhaust hole 85 communicating with the air flow channel 87 is provided on the side of the upper partition plate 81 facing the primary pump chamber. The exhaust holes 85 are symmetrically distributed on both sides of the air flow channel 87. An air inlet hole 86 communicating with the air flow channel 87 is provided on the side of the lower partition plate 82 facing the secondary pump chamber. Pin fixing holes 84 for connecting with the pump cylinder block 9 are provided at both ends of the upper partition plate 81 and the lower partition plate 82.

[0050] A double-screw vacuum pump in this embodiment has a geometric pumping speed of 180 L / s, and can reach a vacuum degree of 50 - 5 Pa at a rotational speed of 1000 - 2500 r / min; when the rotational speed is higher than 2500 r / min, the vacuum degree can be stably maintained at 5 Pa or below. During long-term operation, the temperature difference between the exhaust port temperature of the pump and the ambient temperature is small. Even in summer, the temperature difference between the exhaust port temperature of the pump and the ambient temperature is less than or equal to 35 °C.

[0051] Embodiment 2 Please refer to Figures 9 - 11 , a double-screw vacuum pump in this embodiment has the following differences compared with Embodiment 1: The central axes 155 of the main screw 6 and the auxiliary screw 7 are split from the spiral bodies 154, and the partition plate 8 should be integral or integrally cast with the pump cylinder block 9.

[0052] The double-stage single-head screw 15 includes a primary screw 151, a short shaft 152 and a secondary screw 153. The primary screw 151 and the secondary screw 153 are respectively fixedly connected to both ends of the short shaft 152. The primary screw 151 and the secondary screw 153 are single-head equal-pitch screws, and the spiral surfaces of the two have the same helix direction; the pitches of the primary screw 151 and the secondary screw 153 are not equal.

[0053] The pitch ratio of the secondary screw 153 to the primary screw 151 is 2.0. For example, if the pitch of the primary screw 151 is 90 mm, the pitch of the secondary screw 153 is 180 mm.

[0054] The effective thread length of the primary screw 151 is 2 pitches, and the effective thread length of the secondary screw 153 is 1 pitch.

[0055] The end face profiles of the primary screw 151 and the secondary screw 153 are different. The concave profiles of the end teeth on the primary screw 151 and the secondary screw 153 connected to both ends of the short shaft 152 are rotated 180° relative to each other.

[0056] In this embodiment, the central shafts 155 of the main screw 6 and the auxiliary screw 7 and the helical bodies 154 are integral, and the partition plate 8 has a split combined structure and is fixed in the pump cylinder block 9 by dowel pins. The structure of the partition plate 8 is the same as that in Embodiment 1.

[0057] It should be noted that the central shafts 155 of the main screw 6 and the auxiliary screw 7 and the helical bodies 154 in this embodiment can also be of a split type, that is, the central shafts 155 of the main screw 6 and the auxiliary screw 7 are first sleeved into the partition plate 8, and then the helical bodies 154 and the central shafts 155 are fixedly connected by welding or other means. In this case, the partition plate 8 can be integral or integrally cast with the pump cylinder block 9.

[0058] Please refer to Figure 12 and Figure 13 , the partition plate 8 has an integral structure and is an 8-shaped plate body as a whole. The middle part of the partition plate 8 is respectively provided with shaft through holes 83 for the central shafts 155 of the main screw 6 and the auxiliary screw 7 to pass through. An air flow channel 87 is provided between the two shaft through holes 83. The side of the partition plate 8 facing the primary pump chamber is provided with an exhaust hole 85 communicating with the air flow channel 87, and the side facing the secondary pump chamber is provided with an air inlet hole 86 communicating with the air flow channel 87. The two ends of the partition plate 8 are provided with dowel pin fixing holes 84 for connecting with the pump cylinder block 9. In addition, positioning holes for connecting with the pump cylinder block 9 can also be provided in the middle part of the partition plate 8.

[0059] Embodiment 3 Please refer to Figure 14 , a double-stage single-head screw 15 in this embodiment has the following differences compared with Embodiment 1: The pitch ratio of the secondary screw 153 to the primary screw 151 is 1.5. For example, if the pitch of the primary screw 151 is 60 mm, the pitch of the secondary screw 153 is 90 mm.

[0060] The effective thread length of the primary screw 151 is 3 pitches, and the effective thread length of the secondary screw 153 is 2 pitches.

[0061] The end profiles of the first-stage screw 151 and the second-stage screw 153 are the same. The concave profiles of the end tooth surfaces of the first-stage screw 151 and the second-stage screw 153 connected to both ends of the short shaft 152 are rotated 180° relative to each other.

[0062] Embodiment 4 Please refer to Figure 15 , a two-stage single-head screw 15 in this embodiment has the following differences compared with Embodiment 2: The pitch ratio of the second-stage screw 153 to the first-stage screw 151 is 2.0. For example, the pitch of the first-stage screw 151 is 45 mm, and the pitch of the second-stage screw 153 is 90 mm.

[0063] The effective thread length of the first-stage screw 151 is 4 pitches, and the effective thread length of the second-stage screw 153 is 2 pitches.

[0064] The end profiles of the first-stage screw 151 and the second-stage screw 153 are different. The concave profiles of the end tooth surfaces of the first-stage screw 151 and the second-stage screw 153 connected to both ends of the short shaft 152 are rotated 180° relative to each other.

[0065] It should be noted that: due to different gear ratios, different speed ratios can be achieved, so that the rotational speeds of the screws in the first-stage and second-stage pump cavities can be adjusted according to the working conditions. After the rotational speed is adjusted, the compression ratio between layers can also change accordingly. Correspondingly, for a two-stage single-head screw 15 of the present invention, the pitch ratio of the second-stage screw 153 to the first-stage screw 151 can also be 2.5 or 3.5. The effective thread length of the first-stage screw 151 is adjusted according to the screw length required by different twin-screw vacuum pumps. For example, the effective thread length of the first-stage screw 151 is 4 pitches, and the effective thread length of the second-stage screw 153 is 1 pitch; or the effective thread length of the first-stage screw 151 is 3 pitches, and the effective thread length of the second-stage screw 153 is 2 pitches. Those skilled in the art can understand and implement the above technical features according to the text, so they will not be described in detail in the drawings.

[0066] For a two-stage single-head screw 15 of the present invention, the first-stage screw 151 near the exhaust end of the vacuum pump and the second-stage screw 153 near the intake end of the vacuum pump are both of equal pitch structure, and the pitch of the second-stage screw 153 is 1.5 to 3.5 times that of the first-stage screw 151, so that the pumping rate at the exhaust end of the vacuum pump is several times that at the intake end, thereby achieving staged compression. A twin-screw vacuum pump composed of a main screw 6 and a sub-screw 7 with the same structure forms an overall vacuum pump structure with a staged variable pitch. The synchronous gear pair 4 enables the main screw 6 and the sub-screw 7 to rotate synchronously. During the wear process between the main screw 6 and the sub-screw 7, the symmetric force distribution of the two screws cancels the radial load, reducing vibration and noise.

[0067] In summary, due to the adoption of the above technical means, the present invention is not only convenient for processing and installation, but also greatly improves the air extraction and exhaust capabilities of the twin-screw vacuum pump. It has high working efficiency and flexible adjustment methods, and can effectively cope with complex and changeable working conditions.

[0068] The above only describes the characteristics of some examples of the present invention, and does not limit the protection scope of the present invention. Any modification or deformation that may utilize the technical content disclosed by the present invention still belongs to the protection scope of the present invention.

Claims

1. A two-stage single-headed screw (15), characterized in that: It includes a primary screw (151), a short shaft (152) and a secondary screw (153). The primary screw (151) and the secondary screw (153) are respectively fixedly connected to both ends of the short shaft (152). The primary screw (151) and the secondary screw (153) are single - head equal - pitch screws, and the spiral surfaces of both have the same helix direction; the pitches of the primary screw (151) and the secondary screw (153) are not equal.

2. The double-stage single-head screw (15) according to claim 1, characterized in that: The ratio of the pitch of the secondary screw (153) to the pitch of the primary screw (151) is 1.5 to 3.

5.

3. The double-stage single-headed screw (15) according to claim 1, characterized in that: The effective thread length of the primary screw (151) is 2 to 4 pitches, and the effective thread length of the secondary screw (153) is 1 to 2 pitches.

4. The double-stage single-headed screw (15) according to claim 1, characterized in that: The end profiles of the primary screw (151) and the secondary screw (153) are the same or different, and the concave profiles of the end tooth surfaces of the primary screw (151) and the secondary screw (153) connected to both ends of the short shaft (152) are rotated 180° relative to each other.

5. The double-stage single-headed screw (15) according to any one of claims 1-4, characterized in that: The double - stage single - head screw (15) is an integrally formed structure.

6. The double-stage single-headed screw (15) according to any one of claims 1-4, characterized in that: The central shaft (155) and the spiral body (154) of the double - stage single - head screw (15) are of a split - type structure.

7. A twin-screw vacuum pump, characterized in that: The twin - screw vacuum pump includes a main screw (6) and an auxiliary screw (7). Both the main screw (6) and the auxiliary screw (7) adopt the structure of the double - stage single - head screw (15) as described in claims 1 to 6. The main screw (6) and the auxiliary screw (7) are connected to the synchronous gear pair (4) and are driven to rotate synchronously by the motor (1).

8. The twin-screw vacuum pump according to claim 7, wherein: The twin - screw vacuum pump includes a motor (1), a motor frame (2), a gearbox (3), a synchronous gear pair (4), a front end seat (5), a main screw (6) and an auxiliary screw (7), a partition plate (8), a pump cylinder body (9) and a pump rear seat (10); the motor (1) is installed on the motor frame (2), the output shaft of the motor (1) is connected to the main screw (6) through a coupling (11), the motor frame (2) is fixed on the gearbox (3), the gearbox (3) is installed on the front end seat (5), the synchronous gear pair (4) is installed on the main screw (6) and the auxiliary screw (7) and is arranged inside the gearbox (3), the main screw (6) and the auxiliary screw (7) are arranged inside the pump cylinder body (9), and their two ends are respectively connected to a front rolling bearing (12) in the shaft hole of the front end seat (5) and a rear rolling bearing (13) in the shaft hole of the pump rear seat (10). A partition plate (8) with an air flow passage (87) is provided on the short shaft (152) of the main screw (6) and the auxiliary screw (7). The partition plate (8) is fixed inside the pump cylinder body (9). The partition plate (8) divides the pump cylinder body (9) into two cavities. The exhaust end in front of the pump near the partition plate (8) is the primary pump cavity, and the intake end behind the pump near the partition plate (8) is called the secondary pump cavity. The primary screws (151) of the main screw (6) and the auxiliary screw (7) are installed in the primary pump cavity, and the secondary screws (153) are located in the secondary pump cavity. Sealing elements (14) are provided between the bearings and the end face of the pump cylinder body (9).

9. The twin-screw vacuum pump according to claim 8, characterized in that: When the central axes (155) of the main screw (6) and the auxiliary screw (7) and the spiral body (154) are of an integral one-piece forming structure, the partition plate (8) is of a split combined structure. The partition plate (8) is composed of an upper partition plate (81) and a lower partition plate (82), and is fixed in the pump cylinder block (9) by a dowel pin. Both the upper partition plate (81) and the lower partition plate (82) are provided with 2 arc-shaped grooves (831) respectively for the central axes (155) of the main screw (6) and the auxiliary screw (7) to penetrate through, and the two arc-shaped grooves (831) are combined to form a shaft through hole (83). An air flow channel (87) is provided between the arc-shaped grooves (831) of the upper partition plate (81) and the lower partition plate (82). An exhaust hole (85) communicating with the air flow channel (87) is provided on the side of the upper partition plate (81) facing the first-stage pump chamber, and an air inlet hole (86) communicating with the air flow channel (87) is provided on the side of the lower partition plate (82) facing the second-stage pump chamber. Dowel pin fixing holes (84) for connecting with the pump cylinder block (9) are provided at both ends of the upper partition plate (81) and the lower partition plate (82).

10. The twin-screw vacuum pump according to claim 8, characterized in that: If the central axes (155) of the main screw (6) and the auxiliary screw (7) and the spiral body (154) are of a split type, the partition plate (8) is of an integral type and is integrally cast. The partition plate (8) is a plate body integrally in the shape of an 8. Shaft through holes (83) for the central axes (155) of the main screw (6) and the auxiliary screw (7) to penetrate through are respectively provided in the middle of the partition plate. An air flow channel (87) is provided between the 2 shaft through holes (83). An exhaust hole (85) communicating with the air flow channel (87) is provided on the side of the partition plate facing the first-stage pump chamber, and an air inlet hole (86) communicating with the air flow channel (87) is provided on the side of the partition plate facing the second-stage pump chamber. Dowel pin fixing holes (84) for connecting with the pump cylinder block (9) are provided at both ends of the partition plate.

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