Low-temperature combined pump based on molecular pump

Abstract

The invention relates to the field of vacuum acquisition, in particular to a low-temperature combined pump based on a molecular pump, which comprises a vacuum chamber, a cooling tower, a molecular pump set, a first connecting pipe and a second connecting pipe, the vacuum chamber is provided with a containing cavity, the outer wall of the vacuum chamber is provided with an extraction opening, the extraction opening is communicated with the containing cavity, the cooling tower is provided with a cooling cavity, and the molecular pump set is arranged in the cooling cavity. The cooling tower is provided with a feeding port and a discharging port, the feeding port and the discharging port are both communicated with the cooling cavity, the molecular pump set is provided with an air inlet, the extraction opening is communicated with the feeding port through a first connecting pipe, and the discharging port is communicated with the air inlet through a second connecting pipe. The molecular pump set is started to extract air from the vacuum chamber, the air is extracted after passing through the cooling tower, impurities such as water vapor in the air are left in the cooling chamber, the working quality of the molecular pump is improved, and the vacuum chamber can be conveniently pumped to a certain vacuum degree.

Description

Technical Field

[0001] The present application relates to the field of vacuum acquisition, and in particular to a low-temperature combined pump based on a molecular pump. Background Art

[0002] A molecular pump is a vacuum pump that uses a high-speed rotating rotor to transfer momentum to gas molecules, allowing them to obtain a directional velocity, thereby being compressed, driven to the exhaust port, and then extracted by the previous stage. It is widely used in fields that require high vacuum or ultra-high vacuum environments, such as semiconductor manufacturing, optical manufacturing, materials science, food processing, medical equipment manufacturing, and research laboratories.

[0003] An accelerator is a device that increases the speed (kinetic energy) of charged particles (such as electrons, protons, alpha particles, etc.). In a particle accelerator, ultra-high vacuum ensures that particles are not disturbed by gas molecules during acceleration and collision. In order to control the normal acceleration of particles in the accelerator tube, the chamber in the accelerator tube needs to maintain a certain vacuum degree. When the equipment is not used for a long time, outside air may enter the chamber, affecting the acceleration effect. Therefore, before the equipment is used, the air in the chamber needs to be exhausted. However, conventional molecular pump sets cannot meet the vacuum requirements required by some accelerators. Summary of the invention

[0004] In order to improve the vacuum degree of the chamber, the present application provides a low-temperature combined pump based on a molecular pump.

[0005] The present application provides a low temperature combined pump based on a molecular pump, which adopts the following technical solution: A low-temperature combined pump based on a molecular pump comprises a vacuum chamber, a cooling tower, a molecular pump group, a first connecting pipe and a second connecting pipe, wherein the vacuum chamber is provided with a containing chamber, an outer wall of the vacuum chamber is provided with an air extraction port, the air extraction port is connected to the containing chamber, the cooling tower is provided with a cooling chamber, the cooling tower is provided with a feed port and a discharge port, the feed port and the discharge port are both connected to the cooling chamber, the molecular pump group is provided with an air inlet, the air extraction port is connected to the feed port through the first connecting pipe, and the discharge port is connected to the air inlet through the second connecting pipe.

[0006] By adopting the above technical solution, the molecular pump group starts to evacuate the vacuum chamber, the gas is pumped out after passing through the cooling tower, and impurities such as water vapor in the gas remain in the cooling chamber, thereby improving the working quality of the molecular pump and facilitating the evacuation of the vacuum chamber to a certain vacuum degree.

[0007] Preferably, it also includes a Dewar flask, the Dewar flask is provided with a heat preservation chamber, one end of the Dewar flask is provided with a mounting port, the mounting port is connected to the heat preservation chamber, the cooling tower is connected to the inner wall of the mounting port, the heat preservation chamber is used for placing a coolant, and the coolant is set to liquid nitrogen.

[0008] By adopting the above technical solution, the coolant is placed in the Dewar flask, which can well insulate the coolant, making it easier for the coolant to cool the cooling tower. The cost of liquid nitrogen is low, and there is no need to purchase expensive cryogenic pumps, and there is no need for expensive cryogenic pump operation and maintenance costs. Under the conditions of limited funds and time, the vacuum quality can be improved.

[0009] Preferably, the cooling tower includes a cooling cylinder, a feed pipe and a discharge pipe, the opening of the installation port faces upward, the cooling cylinder is connected to the inner wall of the installation port, the cooling cylinder is provided with a cooling cavity, the upper end of the cooling cylinder is provided with a feed port and a discharge port, the feed pipe is coaxially fixedly connected to the inner wall of the feed port, the discharge pipe is coaxially fixedly connected to the inner wall of the discharge port, the distance from the feed pipe to the bottom wall of the cooling cavity is smaller than the distance from the discharge pipe to the bottom wall of the cooling cavity, the first connecting pipe is coaxially fixedly connected to the feed pipe, and the second connecting pipe is coaxially fixedly connected to the discharge pipe.

[0010] By adopting the above technical solution, the gas enters the cooling chamber from the feed pipe and is then discharged from the discharge port, which is convenient for cooling the gas before discharging it, and is convenient for handling impurities in the gas, thereby improving the working quality of the molecular pump group and the vacuum degree of the vacuum chamber.

[0011] Preferably, it further comprises a heat-conducting block, one end of which is fixedly connected to the outer wall of the feed pipe, and the other end of which is fixedly connected to the inner wall of the cooling chamber.

[0012] By adopting the above technical solution, it is convenient for the gas passing through the feed pipe to exchange heat with the coolant in the heat preservation chamber, thereby improving the cooling efficiency.

[0013] Preferably, the cooling cylinder comprises a cylinder body and a cover plate, the cylinder body is detachably connected to the inner wall of the installation port, a disassembly port is provided at the lower end of the cylinder body, the cover plate is detachably connected to the lower end of the cylinder body, and the cover plate is used to cover the disassembly port.

[0014] By adopting the above technical solution, the cooling cylinder and the Dewar flask are detachably connected, which is convenient for cleaning the Dewar flask, and the cylinder body and the cover plate are detachably connected, which is convenient for cleaning impurities in the cooling cavity and facilitating repeated use of the device.

[0015] Preferably, it also includes a sealing component, which includes a sealing airbag, a spring and an extrusion block. The outer wall of the cylinder is coaxially provided with a sealing ring groove, the sealing airbag is embedded in the sealing ring groove, the inner wall of the mounting port is provided with a mounting groove, one end of the spring is fixedly connected to the bottom of the mounting groove, and the other end of the spring is fixedly connected to the extrusion block, the extrusion block is used to be embedded in the sealing ring groove and extrude the sealing airbag, the end of the extrusion block facing away from the spring is set to a spherical surface, the top wall of the insulation chamber is provided with a connecting groove, the connecting groove is connected to the mounting groove, and the coolant is set to liquid nitrogen.

[0016] By adopting the above technical scheme, the cylinder slides into the insulation cavity from the installation port, the extrusion block is embedded in the sealing ring groove to squeeze the sealing airbag, the sealing airbag makes the cylinder and the Dewar flask sealed, the liquid nitrogen is gasified so that the air pressure in the Dewar flask is greater than the atmospheric pressure, the extrusion block further slides into the sealing ring groove to press the sealing airbag, thereby enhancing the sealing performance, the aspherical surface of the extrusion block penetrates deeply into the sealing ring groove so that the cylinder cannot be removed from the Dewar flask, thereby completing the relative fixation of the cylinder and the Dewar flask, after the pressure in the Dewar flask is released, the extrusion block moves, and the spherical surface makes it easy for the cylinder to be removed from the installation port, thereby facilitating the cleaning of the Dewar flask and the cooling tower.

[0017] Preferably, the sealing assembly further comprises a sealing ring, the outer wall of the extrusion block is provided with a sealing groove, the sealing ring is embedded in the sealing groove, and the outer wall of the sealing ring abuts against the groove wall of the installation groove.

[0018] By adopting the above technical solution, the sealing ring enhances the sealing performance between the extrusion block and the wall of the installation groove, reduces nitrogen overflow, and reduces resource waste.

[0019] Preferably, a circulation component is further included, and the circulation component includes a liquid storage tank, a liquid nitrogen pump, a third connecting pipe, a fourth connecting pipe, a condenser, a first valve and a pressure relief valve. The Dewar flask is provided with a liquid inlet and a pressure relief port, and the liquid inlet and the pressure relief port are both connected to the insulation chamber, the outlet of the liquid storage tank is connected to the inlet of the liquid nitrogen pump, and the outlet of the liquid nitrogen pump is connected to the liquid inlet through the third connecting pipe, the pressure relief port is connected to the inlet of the condenser through the fourth connecting pipe, and the outlet of the condenser is connected to the inlet of the liquid storage tank, the first valve is connected to the inner wall of the third connecting pipe, and the first valve is used to control the on and off of the third connecting pipe, and the pressure relief valve is connected to the inner wall of the fourth connecting pipe.

[0020] By adopting the above technical solution, the pressure relief valve adjusts the air pressure in the insulation chamber to prevent safety accidents caused by excessive air pressure. The circulation component facilitates the control of the recycling of liquid nitrogen and reduces the waste of liquid nitrogen resources.

[0021] Preferably, it also includes a mechanical pump, a fifth connecting pipe, a second valve and a third valve. The outer wall of the vacuum chamber is provided with an exhaust port, the exhaust port is connected to the accommodating chamber, one end of the fifth connecting pipe is coaxially fixedly connected to the inner wall of the exhaust port, the other end of the fifth connecting pipe is coaxially fixedly connected to the inner wall of the inlet of the mechanical pump, the second valve is connected to the inner wall of the fifth connecting pipe, the second valve is used to control the on-off of the fifth connecting pipe, the third valve is connected to the inner wall of the first connecting pipe, and the third valve is used to control the on-off of the first connecting pipe.

[0022] By adopting the above technical solution, the mechanical pump first extracts most of the gas in the vacuum chamber. After the vacuum degree in the vacuum chamber reaches about 10Pa, the second valve is closed, the third valve is opened, and the molecular pump is started to achieve a better vacuum degree and reduce the deposition of impurities in the cooling tower.

[0023] In summary, the present application includes at least one of the following beneficial technical effects: 1. The molecular pump group starts to pump air into the vacuum chamber. The gas is pumped out after passing through the cooling tower. The water vapor and other impurities in the gas remain in the cooling chamber, which improves the working quality of the molecular pump and facilitates pumping the vacuum chamber to a certain vacuum degree. 2. The cylinder slides into the insulation cavity from the installation port, and the extrusion block is embedded in the sealing ring groove to squeeze the sealing airbag. The sealing airbag makes the cylinder and the Dewar flask sealed. The liquid nitrogen gasification makes the air pressure in the Dewar flask greater than the atmospheric pressure. The extrusion block further slides into the sealing ring groove to press the sealing airbag to enhance the sealing performance. The aspherical surface of the extrusion block penetrates into the sealing ring groove so that the cylinder cannot be removed from the Dewar flask, completing the relative fixation of the cylinder and the Dewar flask. After the pressure in the Dewar flask is released, the extrusion block moves, and the spherical surface makes it easy for the cylinder to be removed from the installation port, which is convenient for cleaning the Dewar flask and the cooling tower. 3. The mechanical pump first extracts most of the gas in the vacuum chamber. After the vacuum degree in the vacuum chamber reaches about 10Pa, close the second valve, open the third valve, and start the molecular pump to achieve a better vacuum degree and reduce the deposition of impurities in the cooling tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of a cryogenic combined pump based on a molecular pump.

[0025] Figure 2 is a cross-sectional view of the Dewar flask, cooling tower, and seal assembly.

[0026] Figure 3 It is a cross-sectional view of a cryogenic combined pump based on a molecular pump.

[0027] Figure 4 yes Figure 2 Enlarged view of point A in the middle.

[0028] Description of reference numerals: 1. vacuum chamber; 11. containing chamber; 12. air extraction port; 13. exhaust port; 2. air extraction assembly; 21. mechanical pump; 22. fifth connecting pipe; 23. second valve; 3. dewar flask; 31. mounting port; 311. mounting groove; 32. heat preservation chamber; 321. connecting groove; 33. liquid inlet; 34. pressure relief port; 4. circulation assembly; 41. liquid inlet pipe; 42. pressure relief pipe; 43. liquid storage tank; 44. liquid nitrogen pump; 45. third connecting pipe; 46. fourth connecting pipe; 47. condenser; 48. first valve; 49. pressure relief valve; 5. cooling tower; 51. cooling cylinder; 511. cylinder; 5 111. Cooling chamber; 5112. Disassembly and assembly port; 5113. Feed port; 5114. Discharge port; 5115. Thermal insulation layer; 5116. Sealing ring groove; 512. Cover plate; 5121. Connecting ring; 5122. Baffle; 513. Sealing pad; 514. Rotating handle; 52. Feed pipe; 53. Discharge pipe; 54. Heat transfer block; 6. Connecting assembly; 61. First connecting pipe; 62. Third valve; 63. Second connecting pipe; 7. Molecular pump group; 71. Air inlet; 8. Sealing assembly; 81. Sealing airbag; 82. Spring; 83. Extrusion block; 831. Spherical surface; 832. Sealing groove; 84. Sealing ring. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1-4 This application is described in further detail.

[0030] The present application embodiment discloses a low temperature combined pump based on a molecular pump. Figure 1 and Figure 2 A low-temperature combined pump based on a molecular pump includes a vacuum chamber 1, a vacuum component 2, a Dewar flask 3, a circulation component 4, a cooling tower 5, a connecting component 6, a molecular pump group 7 and a sealing component 8.

[0031] Reference Figure 3 The vacuum chamber 1 is provided with a containing chamber 11 , and an air suction port 12 and an air exhaust port 13 are provided on the outer wall of the vacuum chamber 1 , and both the air suction port 12 and the air exhaust port 13 are connected to the containing chamber 11 .

[0032] The vacuum assembly 2 includes a mechanical pump 21, a fifth connecting pipe 22 and a second valve 23. One end of the second connecting pipe 63 is coaxially fixedly connected to the inner wall of the exhaust port 13. The other end of the fifth connecting pipe 22 is fixedly connected to the inner wall of the inlet of the mechanical pump 21. The second valve 23 is connected to the inner wall of the fifth connecting pipe 22. The second valve 23 is used to control the on-off of the fifth connecting pipe 22. The second valve 23 is set as a ball valve. The mechanical pump 21 is started to evacuate the accommodating chamber 11 to increase the vacuum degree of the vacuum chamber 1.

[0033] Reference Figure 2The upper end of the Dewar flask 3 is coaxially provided with an installation port 31, and the Dewar flask 3 is provided with a heat preservation chamber 32. The installation port 31 is connected to the heat preservation chamber 32, and the diameter of the installation port 31 is smaller than the diameter of the heat preservation chamber 32. The heat preservation chamber 32 is used to place a coolant, and the coolant is set to liquid nitrogen.

[0034] Reference Figure 1 and Figure 2 The coolant can be directly poured into the Dewar flask 3, and the circulation of liquid nitrogen can also be controlled by the circulation component 4. The circulation component 4 includes a liquid inlet pipe 41, a pressure relief pipe 42, a liquid storage tank 43, a liquid nitrogen pump 44, a third connecting pipe 45, a fourth connecting pipe 46, a condenser 47, a first valve 48 and a pressure relief valve 49. The upper end of the Dewar flask 3 is provided with a liquid inlet 33 and a pressure relief port 34, the liquid inlet 33 and the pressure relief port 34 are arranged on the outer periphery of the mounting port 31, the liquid inlet 33 and the pressure relief port 34 are both connected to the heat preservation cavity 32, the liquid inlet pipe 41 is coaxially fixedly connected to the inner wall of the liquid inlet 33, the lower end of the liquid inlet pipe 41 is close to the bottom wall of the heat preservation cavity 32, the pressure relief pipe 42 is coaxially fixedly connected to the inner wall of the pressure relief port 34, the height of the lower end of the pressure relief pipe 42 is higher than the height of the liquid nitrogen liquid level, and the liquid inlet pipe 41 and the pressure relief pipe 42 are both set as insulation pipes.

[0035] The outlet of the liquid storage tank 43 is connected to the inlet of the liquid nitrogen pump 44, one end of the third connecting pipe 45 is coaxially fixedly connected to the inner wall of the outlet of the liquid nitrogen pump 44, the other end of the third connecting pipe 45 is coaxially fixedly connected to the liquid inlet pipe 41, one end of the fourth connecting pipe 46 is coaxially fixedly connected to the inner wall of the pressure relief port 34, the other end of the fourth connecting pipe 46 is coaxially fixedly connected to the inner wall of the inlet of the condenser 47, the outlet of the condenser 47 is connected to the inlet of the liquid storage tank 43, the first valve 48 is connected to the inner wall of the third connecting pipe 45, the first valve 48 is used to control the on-off of the third connecting pipe 45, the pressure relief valve 49 is connected to the inner wall of the fourth connecting pipe 46, the pressure relief valve 49 is used to control the on-off of the fourth connecting pipe 46.

[0036] Reference Figure 2The cooling tower 5 includes a cooling cylinder 51, a feed pipe 52, a discharge pipe 53 and a heat conducting block 54. The cooling cylinder 51 includes a cylinder body 511, a cover plate 512, a sealing gasket 513 and a rotating handle 514. The cylinder body 511 is detachably connected to the inner wall of the installation port 31. The cylinder body 511 is provided with a cooling cavity 5111. The lower end of the cylinder body 511 is coaxially provided with a disassembly port 5112. The disassembly port 5112 is connected to the cooling cavity 5111. The cover plate 512 includes a connecting ring 5121. The baffle 5122 is fixedly connected to one side of the baffle 5122, the sealing gasket 513 is sleeved on the outer circumference of the connecting ring 5121, the outer wall of the connecting ring 5121 is threadedly connected to the inner wall of the disassembly opening 5112, one side of the sealing gasket 513 abuts against the lower end of the cylinder 511, and the other side of the sealing gasket 513 abuts against the baffle 5122, the baffle 5122 covers the disassembly opening 5112, and the outer wall of the baffle 5122 is coplanar with the outer wall of the cylinder 511. The rotating handle 514 is fixedly connected to one end of the baffle 5122 away from the cylinder 511.

[0037] A feed port 5113 and a discharge port 5114 are provided at the upper end of the cylinder 511, and the feed port 5113 and the discharge port 5114 are both connected to the cooling chamber 5111, the feed pipe 52 is coaxially fixedly connected to the inner wall of the feed port 5113, and the discharge pipe 53 is coaxially fixedly connected to the inner wall of the discharge port 5114, and the distance from the feed pipe 52 to the bottom wall of the cooling chamber 5111 is smaller than the distance from the discharge pipe 53 to the bottom wall of the cooling chamber 5111, the feed pipe 52 and the discharge pipe 53 are both provided as insulation pipes, and the outer wall of the cylinder 511 is fixedly connected with an insulation layer 5115, and the insulation layer 5115 is provided outside the Dewar flask 3.

[0038] Reference Figure 2 One end of the heat conductive block 54 is fixedly connected to the outer wall of the feed pipe 53, and the other end of the heat conductive block 54 is fixedly connected to the inner wall of the cooling chamber 5111. A plurality of heat conductive blocks 54 are provided, and the plurality of heat conductive blocks 54 are evenly spaced along the axial direction of the feed pipe 53.

[0039] Reference Figure 3 The connecting assembly 6 includes a first connecting pipe 61, a third valve 62 and a second connecting pipe 63. One end of the first connecting pipe 61 is coaxially fixedly connected to the feed pipe 52, the other end of the first connecting pipe 61 is coaxially fixedly connected to the inner wall of the air extraction port 12, the third valve 62 is connected to the inner wall of the first connecting pipe 61, and the third valve 62 is used to control the on and off of the first connecting pipe 61. The molecular pump group 7 is provided with an air inlet 71, one end of the second connecting pipe 63 is coaxially fixedly connected to the discharge pipe 53, and the other end of the second connecting pipe 63 is coaxially fixedly connected to the inner wall of the air inlet 71. The molecular pump group 7 is a combination of a molecular pump and a mechanical pump, and the molecular pump group 7 pumps air to further improve the vacuum degree of the vacuum chamber 1.

[0040] Reference Figure 4The sealing assembly 8 includes a sealing airbag 81, a spring 82, an extrusion block 83 and a sealing ring 84. The outer wall of the cylinder 511 is coaxially provided with a sealing ring groove 5116, and the sealing airbag 81 is embedded in the sealing ring groove 5116. The inner wall of the mounting port 31 is provided with a mounting groove 311. There are four mounting grooves 311. The four mounting grooves 311 are evenly spaced around the axis of the mounting port 31. One end of the spring 82 is fixedly connected to the groove bottom of the mounting groove 311, and the other end of the spring 82 is fixedly connected to the extrusion block 83. The extrusion block 83 is used to be embedded in the sealing ring groove 5116 and squeeze the sealing airbag 81. The end of the extrusion block 83 away from the spring 82 is set as a spherical surface 831. The top wall of the heat preservation chamber 32 is provided with a connecting groove 321. There are four connecting grooves 321. The connecting grooves 321 are arranged one by one corresponding to the mounting grooves 311, and the connecting grooves 321 are connected to the mounting grooves 311. The outer wall of the extrusion block 83 is provided with a sealing groove 832 , which is provided on the side of the spherical surface 831 close to the spring 82 . The sealing ring 84 is embedded in the sealing groove 832 , and the outer wall of the sealing ring 84 abuts against the groove wall of the installation groove 311 .

[0041] The implementation principle of a low-temperature combined pump based on a molecular pump in an embodiment of the present application is as follows: when it is necessary to evacuate the vacuum chamber 1, first try to use the vacuum component 2 to evacuate the accommodating chamber 11 to a certain vacuum degree, then close the second valve 23, open the third valve 62, start the molecular pump group 7, and the gas in the accommodating chamber 11 passes through the first connecting pipe 61, the feed pipe 52, the discharge pipe 53, the second connecting pipe 63 and the molecular pump group 7 in sequence. When the gas passes through the cooling chamber 5111, the impurities in the gas are processed by the low temperature, the circulation component 4 allows the liquid nitrogen to be recycled, and the sealing component 8 enhances the sealing of the cooling cylinder 51 and the Dewar flask 3. At the same time, it makes it difficult for the cooling cylinder 51 to fall out of the Dewar flask 3. After use, the liquid nitrogen is discharged, the cooling cylinder 51 is disassembled, and the Dewar flask 3 and the cooling cylinder 51 are cleaned for the next use.

[0042] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low temperature combined pump based on a molecular pump, characterized in that: The invention comprises a vacuum chamber (1), a cooling tower (5), a molecular pump group (7), a first connecting pipe (61) and a second connecting pipe (63), wherein the vacuum chamber (1) is provided with a containing chamber (11), an outer wall of the vacuum chamber (1) is provided with an air extraction port (12), the air extraction port (12) being connected to the containing chamber (11), the cooling tower (5) is provided with a cooling chamber (5111), the cooling tower (5) is provided with a feed port (5113) and a discharge port (5114), the feed port (5113) and the discharge port (5114) being both connected to the cooling chamber (5111), the molecular pump group (7) is provided with an air inlet (71), the air extraction port (12) is connected to the feed port (5113) through the first connecting pipe (61), and the discharge port (5114) is connected to the air inlet (71) through the second connecting pipe (63).

2. A low temperature combined pump based on a molecular pump according to claim 1, characterized in that: The invention also comprises a Dewar flask (3), wherein the Dewar flask (3) is provided with a heat preservation chamber (32), one end of the Dewar flask (3) is provided with a mounting port (31), the mounting port (31) is connected to the heat preservation chamber (32), the cooling tower (5) is connected to the inner wall of the mounting port (31), the heat preservation chamber (32) is used for placing a coolant, and the coolant is set to liquid nitrogen.

3. A low temperature combined pump based on a molecular pump according to claim 2, characterized in that: The cooling tower (5) comprises a cooling cylinder (51), a feed pipe (52) and a discharge pipe (53); the opening of the mounting opening (31) faces upward; the cooling cylinder (51) is connected to the inner wall of the mounting opening (31); the cooling cylinder (51) is provided with a cooling cavity (5111); the upper end of the cooling cylinder (51) is provided with a feed port (5113) and a discharge port (5114); the feed pipe (52) is coaxially fixedly connected to the inner wall of the feed port (5113); the discharge pipe (53) is coaxially fixedly connected to the inner wall of the discharge port (5114); the distance from the feed pipe (52) to the bottom wall of the cooling cavity (5111) is smaller than the distance from the discharge pipe (53) to the bottom wall of the cooling cavity (5111); the first connecting pipe (61) is coaxially fixedly connected to the feed pipe (52); and the second connecting pipe (63) is coaxially fixedly connected to the discharge pipe (53).

4. A low temperature combined pump based on a molecular pump according to claim 3, characterized in that: It also includes a heat-conducting block (54), one end of which is fixedly connected to the outer wall of the feed pipe (53), and the other end of which is fixedly connected to the inner wall of the cooling cavity (5111).

5. A low temperature combined pump based on a molecular pump according to claim 3, characterized in that: The cooling cylinder (51) comprises a cylinder body (511) and a cover plate (512); the cylinder body (511) is detachably connected to the inner wall of the installation opening (31); a disassembly opening (5112) is provided at the lower end of the cylinder body (511); the cover plate (512) is detachably connected to the lower end of the cylinder body (511); and the cover plate (512) is used to cover the disassembly opening (5112).

6. A low temperature combined pump based on a molecular pump according to claim 5, characterized in that: The invention also comprises a sealing assembly (8), wherein the sealing assembly (8) comprises a sealing airbag (81), a spring (82) and an extrusion block (83); the outer wall of the cylinder (511) is coaxially provided with a sealing ring groove (5116); the sealing airbag (81) is embedded in the sealing ring groove (5116); the inner wall of the mounting opening (31) is provided with a mounting groove (311); one end of the spring (82) is fixedly connected to the bottom of the mounting groove (311); the other end of the spring (82) is fixedly connected to the extrusion block (83); the extrusion block (83) is used to be embedded in the sealing ring groove (5116) and to extrude the sealing airbag (81); one end of the extrusion block (83) facing away from the spring (82) is set as a spherical surface (831); the top wall of the heat preservation cavity (32) is provided with a connecting groove (321); the connecting groove (321) is connected to the mounting groove (311).

7. A low temperature combined pump based on a molecular pump according to claim 6, characterized in that: The sealing assembly (8) further comprises a sealing ring (84); the outer wall of the extrusion block (83) is provided with a sealing groove (832); the sealing ring (84) is embedded in the sealing groove (832); and the outer wall of the sealing ring (84) abuts against the groove wall of the installation groove (311).

8. The low temperature combined pump based on a molecular pump according to claim 6, characterized in that: The invention also comprises a circulation assembly (4), wherein the circulation assembly (4) comprises a liquid storage tank (43), a liquid nitrogen pump (44), a third connecting pipe (45), a fourth connecting pipe (46), a condenser (47), a first valve (48) and a pressure relief valve (49); the Dewar flask (3) is provided with a liquid inlet (33) and a pressure relief port (34); the liquid inlet (33) and the pressure relief port (34) are both connected to the heat preservation chamber (32); the outlet of the liquid storage tank (43) is connected to the inlet of the liquid nitrogen pump (44); The outlet of the liquid nitrogen pump (44) is connected to the liquid inlet (33) through the third connecting pipe (45), the pressure relief port (34) is connected to the inlet of the condenser (47) through the fourth connecting pipe (46), the outlet of the condenser (47) is connected to the inlet of the liquid storage tank (43), the first valve (48) is connected to the inner wall of the third connecting pipe (45), the first valve (48) is used to control the on and off of the third connecting pipe (45), and the pressure relief valve (49) is connected to the inner wall of the fourth connecting pipe (46).

9. The low temperature combined pump based on a molecular pump according to claim 1, characterized in that: The vacuum chamber (1) further comprises a mechanical pump (21), a fifth connecting pipe (22), a second valve (23) and a third valve (62); an outer wall of the vacuum chamber (1) is provided with an exhaust port (13); the exhaust port (13) is connected to the accommodating chamber (11); one end of the fifth connecting pipe (22) is coaxially fixedly connected to the inner wall of the exhaust port (13); the other end of the fifth connecting pipe (22) is coaxially fixedly connected to the inner wall of the inlet of the mechanical pump (21); the second valve (23) is connected to the inner wall of the fifth connecting pipe (22); the second valve (23) is used to control the on-off of the fifth connecting pipe (22); the third valve (62) is connected to the inner wall of the first connecting pipe (61); the third valve (62) is used to control the on-off of the first connecting pipe (61).

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