Roots screw vacuum unit

Abstract

This invention relates to the field of vacuum unit technology, and more particularly to a Roots screw vacuum unit. It includes a base frame, on which a screw pump, a motor, and a transmission box are mounted. A Roots pump housing is fixedly connected to the base frame and communicates with the screw pump. The transmission box has two output shafts, each fixedly connected to a rotating shaft. An impeller is fixedly connected to the rotating shaft, and symmetrically distributed scrapers are slidably connected to the impellers. A first elastic element is fixedly connected between each scraper and an adjacent impeller. Symmetrically distributed weights are slidably connected to both sides of each impeller. This invention uses scrapers to remove impurities adhering to the inner wall of the Roots pump housing, reducing the amount of impurities adhering to the inner wall, ensuring the stability of the gap between the impeller and the inner wall of the Roots pump housing, thereby reducing the probability of impeller wear, extending the disassembly and maintenance cycle of the device, and ensuring its normal operation.

Description

Technical Field

[0001] This invention relates to the field of vacuum unit technology, and more particularly to a Roots screw vacuum unit. Background Technology

[0002] A Roots screw vacuum unit is a vacuum generating device consisting of a Roots pump and a screw pump. The existing Roots pump consists of a pump housing and two impellers. The rotation of the impellers draws gas from the inlet to the outlet of the Roots pump housing. In actual use, the air drawn by the Roots pump often contains impurities (e.g., in the chemical and pharmaceutical industries, the air often contains dust and particulate matter). Once these impurities enter the Roots pump housing, some will adhere to the inner wall. However, a gap is required between the Roots pump housing and the impellers to prevent impeller wear. The gradual accumulation of these impurities will cause wear on the impeller. Once the impeller wears, it will affect the vacuuming effect of the Roots pump, requiring disassembly and repair, thus affecting its normal operation. Summary of the Invention

[0003] In order to overcome the shortcomings pointed out in the background art above, the present invention provides a Roots screw vacuum unit.

[0004] The technical solution is as follows: A Roots screw vacuum unit includes a base frame, on which a screw pump, a motor, and a transmission box are mounted. The output shaft of the motor is fixedly connected to the input shaft of the transmission box. A Roots pump housing is fixedly connected to the base frame and communicates with the screw pump. The transmission box has two output shafts, each fixedly connected to a rotating shaft. The rotating shaft is rotatably connected to the Roots pump housing. An impeller is fixedly connected to the rotating shaft. Symmetrically distributed scrapers are slidably connected to the impeller. The Roots pump housing is used to compress all the scrapers. A first elastic element is fixedly connected between the scrapers and adjacent impellers. Symmetrically distributed weights are slidably connected to both sides of the impeller. A second elastic element is fixedly connected between the weights and adjacent impellers. The symmetrically distributed weights are located on both sides of adjacent scrapers. The symmetrically distributed weights and adjacent scrapers are fixedly connected by connecting ropes that pass through adjacent impellers.

[0005] As a further preferred embodiment, the scraper is provided with symmetrically distributed inclined surfaces, and the Roots pump housing is used to extrude the inclined surfaces.

[0006] As a further preferred embodiment, the impeller is fixedly connected to symmetrically distributed curved plates, and the curved plates are fixedly connected to cleaning plates. Both the curved plates and the cleaning plates are made of elastic materials. The cleaning plates on the impeller are used to clean the other impeller. The curved plates are fixedly connected to symmetrically distributed first extrusion strips that are slidably connected to adjacent impellers. The weight is fixedly connected to a second extrusion strip that is slidably connected to an adjacent impeller. The second extrusion strip is used to extrude the adjacent first extrusion strip.

[0007] As a further preferred embodiment, the elastic coefficient of the first elastic element is greater than that of the second elastic element, and the elastic coefficient of the bending plate is greater than that of the first elastic element.

[0008] As a further preferred embodiment, both sides of the Roots pump housing are fixedly connected to a fixed shell, and both sides of the impeller are slidably connected to an end cover. The end cover is rotatably connected to the fixed shell, and both the fixed shell and the end cover are rotatably connected to the adjacent rotating shaft in a sealed manner. An elastic sealing gasket is fixedly connected between the end cover and the adjacent impeller, and the elastic sealing gasket is sealed and fitted to the adjacent cleaning plate.

[0009] As a further preferred embodiment, a third elastic element is fixedly connected between the end cap and the adjacent impeller.

[0010] As a further preferred embodiment, the Roots pump housing is connected to symmetrically distributed shells, a piston is slidably connected within the shells, and a fourth elastic element is fixedly connected between the piston and the adjacent shell.

[0011] As a further preferred embodiment, the rotating shaft is rotatably connected to a missing gear, and the base frame is slidably connected to symmetrically distributed racks. The missing gear is used to drive adjacent racks, and the racks are fixedly connected to a connecting rod passing through adjacent housings. The connecting rod is fixedly connected to adjacent pistons.

[0012] As a further preferred embodiment, the sliding trajectory of the rack is parallel to the central axis of the adjacent housing.

[0013] As a further preferred embodiment, a sliding plate is slidably connected inside the impeller, the middle part of the sliding plate slides within the adjacent rotating shaft, and the sliding plate is fixedly connected with symmetrically distributed limiting blocks, which are used to compress the movement of the adjacent weights. The rotating shaft is threadedly connected with a threaded rod, and the threaded rod is rotatably connected to the adjacent sliding plate.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention uses a scraper to remove impurities adhering to the inner wall of the Roots pump housing, thereby reducing the amount of impurities adhering to the inner wall of the Roots pump housing, ensuring the stability of the gap between the impeller and the inner wall of the Roots pump housing, thus reducing the probability of impeller wear, extending the disassembly and maintenance cycle of the device, and ensuring its normal operation. Furthermore, the cleaning plate on one impeller wipes the surface of the other impeller, reducing the amount of impurities adhering to the other impeller, thus ensuring the stability of the gap between the two impellers. When the impeller speed increases to the normal operating state, the scraper no longer contacts the inner wall of the Roots pump housing, and the impeller no longer contacts the cleaning plate, thus cleaning the device without interfering with its normal operation. The system operates continuously, reducing the probability of impeller wear and extending the disassembly and maintenance cycle of the device. Wear on the end cover replaces wear on both ends of the impeller. Furthermore, during the wear process of the end cover, the third elastic element continuously pops out, ensuring the end cover always presses tightly against the adjacent fixed shell. This reduces the probability of changes in the gap between the impeller and the Roots pump housing due to wear from impurities at both ends of the impeller, thus ensuring the air volume during impeller rotation and consequently the vacuuming efficiency of the device. During impeller rotation, the piston automatically draws gas from the inlet on the Roots pump housing and automatically outputs the gas to the exhaust port, thereby increasing the air volume during impeller rotation and improving the vacuuming efficiency of the device. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a three-dimensional structural cross-sectional view of the housing of the Roots pump of the present invention; Figure 3 This is a three-dimensional structural cross-sectional view of the rotating shaft of the present invention; Figure 4 This is a three-dimensional structural diagram of the impeller of the present invention; Figure 5 This is a three-dimensional structural diagram of the missing gear in this invention; Figure 6 This is a three-dimensional structural cross-sectional view of the impeller of the present invention; Figure 7 This is a three-dimensional structural diagram of the bending plate and cleaning plate of the present invention; Figure 8 This is a three-dimensional structural diagram of the threaded rod of the present invention.

[0016] The components are as follows: 1. Base frame; 101. Screw pump; 2. Motor; 3. Transmission box; 4. Roots pump housing; 5. Rotating shaft; 6. Impeller; 7. Scraper; 8. First elastic element; 9. Weight; 10. Second elastic element; 11. Inclined surface; 12. Bending plate; 13. Cleaning plate; 14. First extrusion bar; 15. Second extrusion bar; 16. Fixed shell; 17. End cap; 18. Third elastic element; 19. Housing; 20. Piston; 21. Fourth elastic element; 22. Gear; 23. Rack; 24. Connecting rod; 25. Sliding plate; 26. Limiting block; 27. Threaded rod. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0018] A Roots screw vacuum unit, such as Figures 1-7As shown, the system includes a base frame 1, on which a control terminal (not shown) is mounted. The base frame 1 houses a screw pump 101, a motor 2, and a transmission box 3. The motor 2 is electrically connected to the control terminal, and its output shaft is fixedly connected to the input shaft of the transmission box 3. A Roots pump housing 4 is fixedly connected to the base frame 1. The upper and lower parts of the Roots pump housing 4 have air inlets and exhaust ports, respectively. The exhaust port of the Roots pump housing 4 is connected to the screw pump 101. The transmission box 3 has two output shafts with opposite rotation directions. A rotating shaft 5 is fixedly connected to each output shaft, and the rotating shaft 5 is rotatably connected to the Roots pump housing 4. Impellers 6 are fixedly connected to the rotating shaft 5. There is a distance between them, and the impeller 6 does not contact the inner wall of the Roots pump housing 4. The impeller 6 is slidably connected to two symmetrically distributed scrapers 7. The Roots pump housing 4 is used to squeeze all the scrapers 7. The scrapers 7 are provided with symmetrically distributed inclined surfaces 11. When the scraper 7 rotates to contact the inner wall of the Roots pump housing 4, the Roots pump housing 4 squeezes the inclined surfaces 11, causing the scraper 7 to move to fit against the inner wall of the Roots pump housing 4. A first elastic element 8 is fixed between the scraper 7 and the adjacent impeller 6. The first elastic element 8 is a tension spring. Initially, when the impeller 6 is not rotating and the scraper 7 is in contact with the inner wall of the Roots pump housing 4, the first elastic element 8 is in a stretched and stored state. Both sides inside the impeller 6 are... A symmetrically distributed weight block 9 is slidably connected. A second elastic element 10, which is a compression spring, is fixed between the weight block 9 and the adjacent impeller 6. The symmetrically distributed weight blocks 9 are located on both sides of the adjacent scraper 7, and are fixed to the adjacent scraper 7 by a connecting rope that passes through the adjacent impeller 6. When the impeller 6 starts to rotate, it drives all the scraper 7 on it to rotate. The scraper 7 scrapes away impurities adhering to the inner wall of the Roots pump housing 4 (particulate impurities that enter and adhere to the inner wall of the Roots pump housing 4 during the vacuuming process) to reduce the amount of impurities adhering to the inner wall of the Roots pump housing 4, ensuring the smooth operation of the impeller 6 and the Roots pump housing 6. The stability of the gap width between the inner wall of the Roots pump housing 4 reduces the probability of impeller 6 wear, thereby extending the disassembly and maintenance cycle of this device and ensuring its normal use. As the impeller 6 speed increases, the centrifugal force on the weight 9 increases, and the weight 9 moves away from the rotation axis of the impeller 6. The second elastic element 10 is compressed, and the weight 9 drives the scraper 7 to move through the connecting rope. The first elastic element 8 continues to be stretched, and the scraper 7 no longer contacts the inner wall of the Roots pump housing 4. That is, when the impeller 6 speed increases to the normal operating state, the scraper 7 no longer contacts the inner wall of the Roots pump housing 4, reducing the probability of scraper 7 being worn and ensuring the normal use of this device.

[0019] like Figures 4-7As shown, the impeller 6 is fixedly connected to symmetrically distributed curved plates 12, and the curved plates 12 are fixedly connected to cleaning plates 13. Both the curved plates 12 and the cleaning plates 13 are made of elastic material. Initially, the middle parts of the curved plates 12 and the middle parts of the cleaning plates 13 deform away from the rotation axis of the impeller 6. The curved plates 12 and the cleaning plates 13 are in a state of stored force. After the scraper 7 starts to rotate and rotates to fit with the adjacent cleaning plate 13, since the elastic coefficient of the first elastic element 8 is greater than that of the second elastic element 10, and the elastic coefficient of the curved plate 12 is greater than that of the first elastic element 8, the curved plates 12 and the cleaning plates 13 will press the scraper 7 back into the impeller 6. The cleaning plates 13 on the impeller 6 wipe the surface of the other impeller 6, reducing the amount of impurities adhering to the impeller 6, so as to ensure the stability of the gap width between the two impellers 6, thereby reducing the probability of impeller 6 wear, and thus extending the disassembly and maintenance cycle of this device. The cleaning plate 13 is used to clean another impeller 6. The curved plate 12 is fixed with symmetrically distributed first extrusion strips 14 that are slidably connected to the adjacent impeller 6. The weight 9 is fixed with second extrusion strips 15 that are slidably connected to the adjacent impeller 6. The opposing sides of the first extrusion strips 14 and the adjacent second extrusion strips 15 are provided with inclined surfaces. When the impeller 6 speed increases to the normal operating state, the weight 9 moves away from the rotation axis of the impeller 6. The weight 9 drives the second extrusion strips 15 to move. The second extrusion strips 15 extrude pressure on the inclined surfaces of the adjacent first extrusion strips 14 through their inclined surfaces, so that the first extrusion strips 14 move towards the rotation axis of the impeller 6. The middle parts of the curved plate 12 and the cleaning plate 13 continue to deform towards the rotation axis of the impeller 6, so that the impeller 6 does not contact the cleaning plate 13 during normal use, thus cleaning the impeller 6 surface impurities without interfering with the normal operation of the impeller 6.

[0020] The specific workflow is as follows: When the operator needs to use this device for vacuuming, the operator turns on the motor 2 through the control terminal. The output shaft of the motor 2 drives two rotating shafts 5 through the transmission box 3. The rotating shafts 5 drive the impellers 6 to rotate. Through the rotation of the two impellers 6, the gas at the air inlet of the Roots pump housing 4 is guided to the exhaust port. Then the gas enters the screw pump 101 and is discharged after being processed by the screw pump 101.

[0021] When the impeller 6 starts to rotate, the scraper 7 contacts the inner wall of the Roots pump housing 4. As the rotation speed of the impeller 6 increases, the impeller 6 drives all the scrapers 7 on it to rotate. The scrapers 7 scrape off the impurities attached to the inner wall of the Roots pump housing 4 to reduce the amount of impurities attached to the inner wall of the Roots pump housing 4, ensuring the stability of the gap width between the impeller 6 and the inner wall of the Roots pump housing 4, thereby reducing the probability of impeller 6 wear, and thus extending the disassembly and maintenance cycle of this device, ensuring the normal use of this device.

[0022] After the scraper 7 starts to rotate and comes into contact with the adjacent cleaning plate 13, since the elastic coefficient of the first elastic element 8 is greater than that of the second elastic element 10, and the elastic coefficient of the bending plate 12 is greater than that of the first elastic element 8, the bending plate 12 and the cleaning plate 13 will press the scraper 7 back into the impeller 6. The cleaning plate 13 on the impeller 6 will wipe the surface of the other impeller 6, reducing the amount of impurities adhering to the impeller 6, so as to ensure the stability of the gap width between the two impellers 6, thereby reducing the probability of impeller 6 wear and extending the disassembly and maintenance cycle of this device.

[0023] As the impeller 6 rotates faster, the centrifugal force on the weight 9 increases, causing the weight 9 to move away from the axis of rotation of the impeller 6. The second elastic element 10 is compressed, and the weight 9 drives the scraper 7 to move through the connecting rope. The first elastic element 8 continues to be stretched, and the scraper 7 no longer contacts the inner wall of the Roots pump housing 4. That is, when the impeller 6 rotates faster to the normal operating state, the scraper 7 no longer contacts the inner wall of the Roots pump housing 4, reducing the probability of wear on the scraper 7 and ensuring the normal use of the device.

[0024] When the impeller 6 speed increases to the normal operating state, the weight 9 moves away from the rotation axis of the impeller 6. The weight 9 drives the second extrusion strip 15 to move. The second extrusion strip 15 extrudes the adjacent first extrusion strip 14, causing the first extrusion strip 14 to move towards the rotation axis of the impeller 6. The middle parts of the bending plate 12 and the cleaning plate 13 deform towards the rotation axis of the impeller 6, so that the impeller 6 does not come into contact with the cleaning plate 13 during normal use. This cleans the impeller 6 surface impurities without interfering with the normal operation of the impeller 6.

[0025] When the operator no longer needs to use this device for vacuuming, the operator shuts off impeller 6 via the control terminal. The impeller 6 gradually slows down. The above steps are repeated. Scraper 7 cleans the inner wall of the Roots pump housing 4, and cleaning plate 13 on impeller 6 cleans the other impeller 6, thereby reducing the wear of impeller 6 when the device is used again and ensuring the normal use of the device next time. Example 2

[0026] Based on Example 1, such as Figure 3 and Figure 4As shown, fixed housings 16 are fixedly connected to both the left and right sides of the Roots pump housing 4. End covers 17 are slidably connected to both sides of the impeller 6. The end covers 17 are rotatably connected to the fixed housings 16. Both the fixed housings 16 and the end covers 17 are rotatably connected to the adjacent rotating shafts 5 in a sealed manner. An elastic sealing gasket is fixedly connected between the end cover 17 and the adjacent impeller 6. This elastic sealing gasket is sealed and fitted to the adjacent cleaning plate 13. A third elastic element 18 is fixedly connected between the end cover 17 and the adjacent impeller 6. The third elastic element 18 is a compression spring and is initially in a compressed state. During the rotation of the impeller 6, the impeller 6 drives the impeller 6 to rotate. The end caps 17 on both sides rotate, and the relative rotation of the end caps 17 and the fixed shell 16 causes the wear of the end caps 17 to replace the wear at both ends of the impeller 6. Furthermore, during the wear process of the end caps 17, the third elastic element 18 continuously pops out, and the elastic sealing gasket between the end caps 17 and the adjacent impeller 6 deforms, so that the end caps 17 always presses tightly against the adjacent fixed shell 16. This reduces the probability that the gap between the impeller 6 and the Roots pump housing 4 will change due to the wear of the impeller 6 at both ends by impurities, so as to ensure the air volume during the rotation of the impeller 6, and thus ensure the vacuuming efficiency of this device. Example 3

[0027] Based on Example 2, such as Figures 1-5 As shown, the Roots pump housing 4 is connected to symmetrically distributed shells 19. A piston 20 is slidably connected within the shell 19. A fourth elastic element 21, a compression spring, is fixed between the piston 20 and the adjacent shell 19. A gear 22 is rotatably connected to the rotating shaft 5. The gear 22 has two sets of teeth, and the teeth on the two gears 22 are asymmetrically distributed. A symmetrically distributed rack 23 is slidably connected to the base frame 1. The gear 22 is used to drive the adjacent rack 23, such as... Figure 4 As shown, during the process of impeller 6 rotating from a horizontal position to a vertical position, the missing gear 22 rotates to mesh with the adjacent rack 23 and gradually drives the adjacent rack 23 to move. When impeller 6 rotates to a vertical position, the missing gear 22 loses mesh with the adjacent rack 23. The rack 23 is fixedly connected to a connecting rod 24 that passes through the adjacent housing 19. The connecting rod 24 is fixedly connected to the adjacent piston 20. The sliding trajectory of the rack 23 is parallel to the central axis of the adjacent housing 19. Taking one impeller 6 as an example, during the movement of the rack 23, impeller 6 rotates from a horizontal position to a vertical position. The rack 23 moves through the connecting rod... Piston 24 drives piston 20 to move, and the fourth elastic element 21 is compressed, so that the gas in the inlet of the Roots pump housing 4 enters the corresponding housing 19 through the inside of the Roots pump housing 4. When the impeller 6 rotates to the vertical position, the missing gear 22 loses meshing with the adjacent rack 23. With the rotation of the impeller 6, the fourth elastic element 21 rebounds, and piston 20 drives rack 23 to reset through connecting rod 24. Piston 20 squeezes the gas in housing 19 back into the Roots pump housing 4, so that the gas enters the exhaust port of the Roots pump housing 4, thereby increasing the pumping volume during the rotation of impeller 6 and improving the vacuuming efficiency of this device. Example 4

[0028] Based on Example 3, such as Figure 8 As shown, a sliding plate 25 is slidably connected inside the impeller 6. The middle part of the sliding plate 25 slides within the adjacent rotating shaft 5. Two symmetrically distributed limiting blocks 26 are fixed to the sliding plate 25. Both limiting blocks 26 are located on one side within the adjacent impeller 6, for example... Figure 8 As shown, both limiting blocks 26 are located in the upper part of the impeller 6. The dynamic balance of the impeller 6 can be adjusted by setting a counterweight structure inside the impeller 6. The limiting blocks 26 are provided with inclined surfaces, which are used to compress adjacent weight blocks 9 to move. The rotating shaft 5 is threadedly connected to a threaded rod 27, which is rotatably connected to an adjacent sliding plate 25. When the impeller 6 experiences uneven weight distribution due to wear, the position of the sliding plate 25 is adjusted by rotating the threaded rod 27. The sliding plate 25 drives all the limiting blocks 26 on it to move, thereby changing the position of the limiting blocks 26 in limiting the adjacent weight blocks 9. Figure 8 Taking the impeller 6 as an example, if the upper part of the impeller 6 is worn more than the lower part, the position of the weight block 9 is moved away from the rotation axis of the impeller 6. If the lower part of the impeller 6 is worn more than the upper part, the position of the weight block 9 is moved closer to the rotation axis of the impeller 6. This changes the centrifugal force on the two weight blocks 9 in the upper part of the impeller 6, so as to balance the weight distribution on the impeller 6 during rotation, extend the service life of the impeller 6, and ensure the normal operation of the device.

[0029] Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A Roots screw vacuum unit, comprising a base frame (1), wherein a screw pump (101), a motor (2), and a transmission box (3) are mounted on the base frame (1), the output shaft of the motor (2) is fixedly connected to the input shaft of the transmission box (3), a Roots pump housing (4) is fixedly connected to the base frame (1), the Roots pump housing (4) is connected to the screw pump (101), the transmission box (3) is provided with two output shafts, each output shaft is fixedly connected to a rotating shaft (5), the rotating shaft (5) is rotatably connected to the Roots pump housing (4), and an impeller (6) is fixedly connected to the rotating shaft (5), characterized in that, The impeller (6) is slidably connected to symmetrically distributed scrapers (7). The Roots pump housing (4) is used to squeeze all the scrapers (7). A first elastic element (8) is fixed between the scraper (7) and the adjacent impeller (6). Symmetrically distributed weights (9) are slidably connected to both sides inside the impeller (6). A second elastic element (10) is fixed between the weights (9) and the adjacent impeller (6). The symmetrically distributed weights (9) are located on both sides of the adjacent scraper (7). The symmetrically distributed weights (9) are fixed to the adjacent scraper (7) by a connecting rope, which passes through the adjacent impeller (6).

2. The Roots screw vacuum unit according to claim 1, characterized in that, The scraper (7) is provided with symmetrically distributed inclined surfaces (11), and the Roots pump housing (4) is used to squeeze the inclined surfaces (11).

3. A Roots screw vacuum unit according to claim 1, characterized in that, The impeller (6) is fixed with symmetrically distributed curved plates (12), and the curved plates (12) are fixed with cleaning plates (13). Both the curved plates (12) and the cleaning plates (13) are made of elastic material. The cleaning plates (13) on the impeller (6) are used to clean the other impeller (6). The curved plates (12) are fixed with symmetrically distributed first extrusion strips (14) that are slidably connected to the adjacent impellers (6). The weight (9) is fixed with a second extrusion strip (15) that is slidably connected to the adjacent impellers (6). The second extrusion strip (15) is used to extrude the adjacent first extrusion strip (14).

4. A Roots screw vacuum unit according to claim 3, characterized in that, The elastic coefficient of the first elastic element (8) is greater than that of the second elastic element (10), and the elastic coefficient of the bending plate (12) is greater than that of the first elastic element (8).

5. A Roots screw vacuum unit according to claim 1, characterized in that, Both sides of the Roots pump housing (4) are fixedly connected to a fixed shell (16), and both sides of the impeller (6) are slidably connected to an end cover (17). The end cover (17) is rotatably connected to the fixed shell (16). The fixed shell (16) and the end cover (17) are both rotatably connected to the adjacent rotating shaft (5). An elastic sealing gasket is fixed between the end cover (17) and the adjacent impeller (6). The elastic sealing gasket is sealed and fitted to the adjacent cleaning plate (13).

6. A Roots screw vacuum unit according to claim 5, characterized in that, A third elastic element (18) is fixedly connected between the end cap (17) and the adjacent impeller (6).

7. A Roots screw vacuum unit according to claim 1, characterized in that, The Roots pump housing (4) is connected to symmetrically distributed housings (19), and a piston (20) is slidably connected inside the housing (19). A fourth elastic element (21) is fixed between the piston (20) and the adjacent housing (19).

8. A Roots screw vacuum unit according to claim 7, characterized in that, The rotating shaft (5) is rotatably connected to a missing gear (22), and the base frame (1) is slidably connected to symmetrically distributed racks (23). The missing gear (22) is used to drive the adjacent racks (23). The racks (23) are fixedly connected to a connecting rod (24) that passes through the adjacent housing (19). The connecting rod (24) is fixedly connected to the adjacent piston (20).

9. A Roots screw vacuum unit according to claim 8, characterized in that, The sliding trajectory of the rack (23) is parallel to the central axis of the adjacent housing (19).

10. A Roots screw vacuum unit according to claim 1, characterized in that, A sliding plate (25) is slidably connected inside the impeller (6). The middle part of the sliding plate (25) slides within the adjacent rotating shaft (5). The sliding plate (25) is fixed with symmetrically distributed limiting blocks (26). The limiting blocks (26) are used to squeeze the adjacent weight (9) to move. The rotating shaft (5) is threadedly connected with a threaded rod (27). The threaded rod (27) is rotatably connected to the adjacent sliding plate (25).

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