A roots vacuum pump passive overload protection structure based on thermodynamic feedback

Abstract

This invention discloses a passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback, belonging to the field of Roots pump technology. It aims to address the shortcomings of traditional Roots pump overload protection structures that require an external power source and rely on springs for the reset mechanism, which carries the risk of fatigue failure. The invention includes a accumulator tube connected to the Roots vacuum pump. A pressure relief hole is provided in the cavity on the inlet side of the Roots vacuum pump, communicating with the outlet. A counterweight valve core is installed at the pressure relief hole, closing the hole. The accumulator tube contains a temperature-sensitive expansion fluid. A heat conductor is installed at the outlet of the Roots vacuum pump, extending into the accumulator tube. A piston is installed at the top of the accumulator tube, and the counterweight valve core is connected to a push rod. Moving the piston upward pushes the push rod upward, causing the counterweight valve core to move upward and open the pressure relief hole. This invention utilizes the thermal expansion of the temperature-sensitive expansion fluid for drive, eliminating the need for an external power source and relying on the gravity of the counterweight valve core for reset, thus avoiding the failure risk caused by spring fatigue.

Description

Technical Field

[0001] This invention relates to the field of Roots vacuum pump technology, and more specifically, to a passive overload protection structure for Roots vacuum pumps based on thermodynamic feedback. Background Technology

[0002] Roots vacuum pumps, as a type of dry positive displacement pump, are widely used in vacuum systems in chemical, pharmaceutical, and aerospace industries. Roots pumps are typically used in series with a backing pump (such as a liquid ring pump) to form a Roots liquid ring vacuum unit. In actual operation, Roots pumps have long faced a technical problem that has not been effectively resolved: the risk of overload seizure during startup and sudden changes in operating conditions. Specifically: During startup: When the Roots pump starts, the system pressure is atmospheric pressure, and the inlet-outlet pressure difference is as high as 80~100 kPa, far exceeding the maximum allowable pressure difference of the Roots pump (usually 30~50 kPa). This causes the rotor to expand rapidly due to compression heat, leading to metal-to-metal contact and seizure. During sudden changes in operating conditions: When the evacuated container suddenly receives air, the backing pump experiences momentary failure, or process parameters fluctuate, the inlet pressure of the Roots pump rises sharply, and the pressure difference instantly exceeds the limit, also leading to overload seizure.

[0003] Existing technologies offer the following solutions to the aforementioned problems: 1. Using electromagnetic switching valves, where the opening and closing of the solenoid valve is controlled by a pressure switch. This method is crude in adjustment, has a slow response, requires power, and has poor explosion-proof adaptability; 2. Using PLC-controlled electric regulating valves, where temperature and pressure signals are collected by sensors, and then the PLC controls the electric regulating valve. This method is complex, relies on multiple components, and has the risk of electrical failure; 3. Using mechanical safety valves, which open with a spring-loaded constant pressure. However, this method cannot provide proportional adjustment, has a slow recovery time, and has the risk of fatigue failure. The fundamental flaws of these existing technologies are that they either rely on external energy (electricity or gas), have a fixed and unadjustable opening temperature, or have a spring-dependent reset mechanism that is at risk of fatigue failure.

[0004] Chinese patent application number 2022222854983 discloses a bypass Roots pump that, regardless of the cause, opens a lower-pressure first check valve to provide bypass protection when the air pressure rises slightly to a warning value. However, the first check valve is a mechanical safety valve that opens under constant pressure via a spring, posing a risk of fatigue failure. Summary of the Invention

[0005] To overcome the above shortcomings, this invention provides a passive overload protection structure for Roots vacuum pumps based on thermodynamic feedback. It does not require external drive to relieve pressure, has a fast response speed, and avoids the risks of electrical failure and spring fatigue failure.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback, including a accumulator tube connected to the Roots vacuum pump, a pressure relief hole provided in the cavity on the inlet side of the Roots vacuum pump, the pressure relief hole communicating with the outlet of the Roots vacuum pump, a counterweight valve core installed at the pressure relief hole, the counterweight valve core closing the pressure relief hole, a temperature-sensitive expansion fluid filled in the accumulator tube, a heat conductor installed at the outlet of the Roots vacuum pump, the heat conductor extending into the accumulator tube; a piston installed at the top of the accumulator tube, the counterweight valve core connected to a push rod, the piston moving upward pushes the push rod upward, causing the counterweight valve core to move upward and open the pressure relief hole.

[0007] When a Roots vacuum pump is operating, gas enters through the inlet and exits through the outlet. If the pressure difference between the inlet and outlet exceeds the specified value (5000 Pa), it indicates that the gas being pumped cannot be promptly removed by the backing pump at the outlet, leading to an increase in outlet temperature. The heat at the outlet is transferred through a heat conductor to the temperature-sensitive expansion fluid in the accumulator tube. This expansion fluid expands, pushing the piston upwards. The piston's upward movement pushes the push rod upwards, causing the counterweight valve core to move upwards and open the pressure relief port. Under the pressure difference, the gas flows back through the pressure relief port to the inlet, achieving pressure relief. Once the pressure difference between the inlet and outlet of the Roots vacuum pump decreases, the outlet temperature drops, the temperature-sensitive expansion fluid contracts, and the piston and counterweight valve core return to their original positions, returning the Roots vacuum pump to normal operating status.

[0008] This invention utilizes the thermal expansion of a temperature-sensitive expansion fluid for driving, requiring no external power. It relies on the gravity of the counterweight valve core for reset, resulting in a fast response speed and avoiding the risks of electrical failure and spring fatigue failure.

[0009] Preferably, a plunger is installed on the heat conductor, and the plunger slides and adapts to the inner wall of the accumulator tube; one end of the plunger bears the hydraulic pressure of the temperature-sensitive expansion fluid, and the other end of the plunger bears the air pressure at the outlet of the Roots vacuum pump.

[0010] When the gas being pumped cannot be discharged from the outlet by the forepump in time, not only does its temperature rise, but its pressure also increases. At this time, while the heat conductor absorbs heat, the pressure of the gas acts on the plunger, pushing the plunger towards the temperature-sensitive expansion fluid, increasing the pushing effect of the temperature-sensitive expansion fluid on the piston, and making it easier to push the counterweight valve core.

[0011] Preferably, the Roots vacuum pump is provided with a mounting hole, and an outwardly extending connecting sleeve is provided at the outer end of the mounting hole. The heat conductor is installed at the mounting hole, the end of the accumulator tube is fastened to the connecting sleeve, and the plunger is limited at the end of the connecting sleeve.

[0012] When the Roots vacuum pump is working normally, the plunger end face is in contact with and limited by the end face of the connecting sleeve. The gas pressure at the outlet of the Roots vacuum pump is applied to the plunger end face through the mounting hole. The connecting sleeve facilitates the connection and fixation of the accumulator tube.

[0013] Preferably, the upper part of the accumulator is connected to a liquid filling pipe, and a valve is installed on the liquid filling pipe.

[0014] Temperature-sensitive expansion fluid is added to the accumulator tube through the filling tube. After the addition is completed, the valve is closed to form a closed cavity inside the accumulator tube.

[0015] Preferably, an extension tube connected to the lower part of the accumulator tube is provided, and an adjusting plug is installed inside the extension tube. The adjusting plug is connected to an adjusting knob, and rotating the adjusting knob pushes the adjusting plug to move.

[0016] Rotating the adjustment knob moves the adjustment plug, thereby adjusting the pressure inside the accumulator tube and consequently regulating the pressure difference between the inlet and outlet when the counterweight valve is opened, to meet different usage requirements. Moving the adjustment plug upwards increases the pressure inside the accumulator tube, decreasing the pressure difference between the inlet and outlet when the counterweight valve is opened. Moving the adjustment plug downwards decreases the pressure inside the accumulator tube, increasing the pressure difference between the inlet and outlet when the counterweight valve is opened.

[0017] Preferably, the power storage tube is a transparent tube with graduation lines on it.

[0018] The transparent accumulator tube facilitates observation of the liquid level. Accurate liquid level readings via the scale allow for precise control of the amount of temperature-sensitive expansion fluid added.

[0019] Preferably, a cavity is provided between the liquid surface of the temperature-sensitive expansion fluid and the piston.

[0020] A cavity is reserved above the surface of the temperature-sensitive expansion fluid. After the expansion fluid expands, the pressure inside the cavity increases, thereby pushing the piston to move. As the adjustment knob is turned to push the adjustment plug upward, the cavity provides space for the temperature-sensitive expansion fluid to fill, preventing the expansion fluid from directly pushing open the piston during this process.

[0021] Preferably, the lower end of the push rod is fastened to the piston.

[0022] The push rod is directly connected to the piston as an integral structure, and the push rod and piston move coaxially, ensuring smooth and reliable operation.

[0023] In another configuration, the piston is connected to the push rod, and the push plate is hinged to the Roots vacuum pump. The lower end of the push rod rests on the upper surface of the push plate, and the upper end of the push rod rests on the lower surface of the push plate. The distance from the push rod to the hinge point of the push plate is less than the distance from the push rod to the hinge point of the push plate.

[0024] The piston moves upward, pushing the push plate upward via the push rod. The push plate then pushes the push rod upward, thereby moving the counterweight valve core and opening the pressure relief port. The distance from the push rod to the hinge of the push plate is less than the distance from the push rod to the hinge of the push plate, thus forming a force-saving lever together with the push rod, push plate, and push rod, allowing a smaller piston thrust to move the counterweight valve core.

[0025] Preferably, a vent groove is provided on the outer wall of the counterweight valve core, a support protrusion is provided on the inner wall of the pressure relief hole, a sealing gasket is installed on the support protrusion, and the lower end of the counterweight valve core is supported on the sealing gasket.

[0026] The sealing gasket is placed between the support ring and the counterweight valve core, improving the sealing performance after the pressure relief hole is closed. The outer wall of the counterweight valve core is adapted to the inner wall of the pressure relief hole. After the counterweight valve core moves upward and disengages from the sealing gasket, the airflow flows upward from the vent groove.

[0027] Compared with the prior art, the beneficial effects of the present invention are: (1) The overload protection structure of the Roots vacuum pump of the present invention is driven by the thermal expansion of the temperature-sensitive expansion fluid, without the need for an external power source. It relies on the gravity reset of the counterweight valve core, has a fast response speed, and avoids the risk of electrical failure and spring fatigue failure; (2) While the heat conductor absorbs heat, the pressure of the air pressure acts on the plunger, pushing the plunger to move towards the temperature-sensitive expansion fluid, increasing the pushing effect of the temperature-sensitive expansion fluid on the piston, and making it easier to push the counterweight valve core; (3) When the counterweight valve core is opened, the pressure difference between the air inlet and the air outlet can be adjusted to meet different usage requirements; (4) The thrust of the piston moving upward is amplified by the push plate and then acts on the push rod, so that the counterweight valve core can be moved to open the pressure relief hole with a smaller piston thrust. Attached Figure Description

[0028] Figure 1 This is a structural diagram of the present invention.

[0029] Figure 2 This is a cross-sectional view of Embodiment 1 of the present invention.

[0030] Figure 3 This is a connection diagram of the heat conductor in Embodiment 1 of the present invention.

[0031] Figure 4 This is a cross-sectional view of Embodiment 2 of the present invention.

[0032] Figure 5 This is a connection diagram of the heat conductor in Embodiment 2 of the present invention.

[0033] Figure 6 This is a piston connection diagram of Embodiment 3 of the present invention.

[0034] In the diagram: 1. Roots vacuum pump, 2. Accumulator tube, 3. Scale line, 4. Inlet, 5. Pressure relief hole, 6. Outlet, 7. Baffle plate, 8. Counterweight valve core, 9. Vent groove, 10. Supporting convex ring, 11. Sealing gasket, 12. Temperature-sensitive expansion fluid, 13. Heat conductor, 14. Piston, 15. Push rod, 16. Connecting column, 17. Connecting hole, 18. Limiting convex ring, 19. Sinking groove, 20. Connecting... 21. Connecting ring, 22. Fastening sleeve, 23. Abutting ring, 24. Liquid filling pipe, 25. Valve, 26. Cavity, 27. Plunger, 28. Mounting hole, 29. Connecting sleeve, 30. Extension pipe, 31. Adjusting plug, 32. Adjusting knob, 33. Support, 34. Connector, 35. Mounting groove, 36. End cap, 37. Ball bearing, 38. Push rod, 39. Push plate, 40. Abutting ball, 51. Top ball. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example 1: A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback (see...) Figure 1 , Figure 2 , Figure 3 The system includes a accumulator tube 2 connected to the Roots vacuum pump 1. The accumulator tube 2 is a transparent tube with graduation lines 3 on it. A pressure relief hole 5 is provided in the cavity on the side of the inlet 4 of the Roots vacuum pump 1. The pressure relief hole 5 communicates with the outlet 6 of the Roots vacuum pump 1. The inlet 4 of the Roots vacuum pump 1 is located at the top of the Roots vacuum pump 1, and the outlet 6 of the Roots vacuum pump 1 is located at the bottom of the Roots vacuum pump 1. A baffle 7 is provided inside the Roots vacuum pump 1 near the inlet 4, and the pressure relief hole 5 is located on the baffle 7. A counterweight valve core 8 is installed at the pressure relief hole 5. The counterweight valve core 8 closes the pressure relief hole 5. The outer wall of the counterweight valve core 8 is adapted to the inner wall of the pressure relief hole 5. A venting groove 9 is provided on the outer wall of the counterweight valve core 8, with several venting grooves spaced circumferentially. A support convex ring 10 is provided on the inner wall of the pressure relief hole 5, located at the lower end of the pressure relief hole 5. A sealing gasket 11 is installed on the support convex ring 10, and the lower end of the counterweight valve core 8 is supported on the sealing gasket. The sealing gasket is placed between the support convex ring 10 and the counterweight valve core 8, improving the sealing performance after the pressure relief hole 5 is closed. The adaptation of the outer wall of the counterweight valve core 8 to the inner wall of the pressure relief hole 5 ensures the stability of the valve core installation. After the counterweight valve core 8 moves upward and disengages from the sealing gasket, airflow flows upward from the venting groove 9.

[0036] The accumulator tube 2 contains a temperature-sensitive expansion fluid 12, which is hydraulic oil, such as dimethyl silicone oil. Dimethyl silicone oil has a high coefficient of thermal expansion, resulting in a greater driving force on the piston 14 under the same temperature change. A heat conductor 13 is installed at the outlet 6 of the Roots vacuum pump 1. The heat conductor 13 is made of metal, such as gold, silver, copper, or aluminum; in this embodiment, copper is used. The heat conductor 13 extends into the accumulator tube 2, transferring heat from the outlet 6 of the Roots vacuum pump 1 to the temperature-sensitive expansion fluid 12 in the accumulator tube 2. A piston 14 is installed at the top of the accumulator tube 2. A counterweight valve core 8 is connected to a push rod 15. When the piston 14 moves upward, it pushes the push rod 15 upward, causing the counterweight valve core 8 to move upward and open the pressure relief port 5.

[0037] The accumulator tube 2 has an L-shaped structure, and its lower opening is securely connected to the Roots vacuum pump 1. The Roots vacuum pump 1 has a connecting post 16 with a connecting hole 17. A heat conductor 13 is connected to the connecting hole 17, with one end of the heat conductor 13 placed in the cavity at the outlet 6 of the Roots vacuum pump 1, and the other end placed in the accumulator tube 2. A limiting protrusion 18 is provided on the outer wall of the heat conductor 13, and a recessed groove 19 is provided at the end of the connecting post 16, with the limiting protrusion 18 placed in the recessed groove 19. A connecting protrusion 20 is provided at the lower opening of the accumulator tube 2, and the end face of the connecting protrusion 20 presses against the limiting protrusion 18 and the connecting post 16. The connecting post 16 is externally threaded to a fastening sleeve 21, and the fastening sleeve 21 has an abutting protrusion 22, which abuts against the end face of the connecting protrusion 20 to securely connect the accumulator tube 2. The upper part of the accumulator tube 2 is connected to an L-shaped liquid filling pipe 23, and a valve 24 is installed on the liquid filling pipe 23. The lower end of the liquid filling pipe 23 is positioned below the piston 14. A cavity 25 is provided between the liquid surface of the temperature-sensitive expansion fluid 12 and the piston 14.

[0038] The lower end of the push rod 15 is securely connected to the piston 14. The push rod 15 moves through the housing of the Roots vacuum pump 1. A PTFE skeleton oil seal is installed between the push rod 15 and the housing of the Roots vacuum pump 1, which allows for a complete seal at the connection between the push rod 15 and the housing of the Roots vacuum pump 1, while also allowing the push rod 15 to slide freely up and down. The outer surfaces of the counterweight valve core 8, the push rod 15, and the heat conductor 13 are all lined with a PTFE corrosion-resistant layer.

[0039] When the Roots vacuum pump 1 is working, air enters through inlet 4 and exits through outlet 6. When the pressure difference between inlet 4 and outlet 6 exceeds the specified pressure difference value (5000Pa), it indicates that the gas being pumped cannot be discharged from outlet 6 in time by the backing pump, which will cause the temperature of outlet 6 to rise. The heat at outlet 6 is transferred to the temperature-sensitive expansion fluid 12 in the accumulator tube 2 through the heat conductor 13. The temperature-sensitive expansion fluid 12 expands due to heat, thereby pushing piston 14 upward. The upward movement of piston 14 pushes push rod 15 upward, causing counterweight valve core 8 to move upward and open pressure relief hole 5. Under the action of pressure difference, the gas flows back to inlet 4 through pressure relief hole 5 to achieve pressure relief. After the pressure difference between inlet 4 and outlet 6 of the Roots vacuum pump 1 decreases, the temperature of outlet 6 of the Roots vacuum pump 1 decreases, the temperature-sensitive expansion fluid 12 contracts, piston 14 and counterweight valve core 8 return to their original positions, and the Roots vacuum pump 1 returns to normal working state.

[0040] The transparent accumulator tube 2 facilitates observation of the liquid level. Accurate liquid level readings are obtained via the scale 3, allowing for precise control of the amount of temperature-sensitive expansion fluid 12 added. Adjusting the amount of temperature-sensitive expansion fluid 12 allows for flexible setting of the opening temperature, thereby regulating the pressure difference between the inlet 4 and outlet 6 of the counterweight valve core 8 when it is open.

[0041] Compared to the scheme of using a single counterweight valve core 8 for depressurization at the outlet 6, this application has significant advantages. With only a single counterweight valve core 8, the opening pressure difference is fixed and cannot be adjusted. However, the processes for producing different products in the same unit require different pressure differences between the inlet 4 and outlet 6, and a single counterweight valve core 8 cannot achieve adjustment of the opening pressure difference. Furthermore, when the machine stops or operating conditions change, the large reset inertia of the single counterweight valve core 8 causes inertial impact on the reset plane, easily damaging the sealing surface and causing air leakage; moreover, the large inertial impact can easily cause equipment vibration and abnormal noise.

[0042] In this application, the thermal expansion of the temperature-sensitive expansion fluid 12 drives the movement of the counterweight valve core 8. By adjusting the amount of temperature-sensitive expansion fluid 12 added, the pressure difference between the inlet 4 and outlet 6 when the counterweight valve core 8 is open can be adjusted, which can meet the requirements of different production processes for the Roots vacuum pump 1. When the machine stops or the operating conditions change, the counterweight valve core 8 returns to its original position by the temperature-sensitive expansion fluid 12. The return is smooth and will not generate a large inertial impact, thus avoiding impact damage to the sealing surface and preventing equipment vibration and abnormal noise caused by inertial impact.

[0043] Example 2: A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback (see...) Figure 4 , Figure 5The system includes a accumulator tube 2 connected to the Roots vacuum pump 1. The accumulator tube 2 is a transparent tube with graduation lines 3 on it. A pressure relief hole 5 is provided in the cavity on the side of the inlet 4 of the Roots vacuum pump 1. The pressure relief hole 5 communicates with the outlet 6 of the Roots vacuum pump 1. The inlet 4 of the Roots vacuum pump 1 is located at the top of the Roots vacuum pump 1, and the outlet 6 of the Roots vacuum pump 1 is located at the bottom of the Roots vacuum pump 1. A baffle 7 is provided inside the Roots vacuum pump 1 near the inlet 4, and the pressure relief hole 5 is located on the baffle 7. A counterweight valve core 8 is installed at the pressure relief hole 5. The counterweight valve core 8 closes the pressure relief hole 5. The outer wall of the counterweight valve core 8 is adapted to the inner wall of the pressure relief hole 5. A venting groove 9 is provided on the outer wall of the counterweight valve core 8, with several venting grooves spaced circumferentially. A support convex ring 10 is provided on the inner wall of the pressure relief hole 5, located at the lower end of the pressure relief hole 5. A sealing gasket 11 is installed on the support convex ring 10, and the lower end of the counterweight valve core 8 is supported on the sealing gasket. The sealing gasket is placed between the support convex ring 10 and the counterweight valve core 8, improving the sealing performance after the pressure relief hole 5 is closed. The adaptation of the outer wall of the counterweight valve core 8 to the inner wall of the pressure relief hole 5 ensures the stability of the valve core installation. After the counterweight valve core 8 moves upward and disengages from the sealing gasket, airflow flows upward from the venting groove 9.

[0044] The accumulator tube 2 contains a temperature-sensitive expansion fluid 12, which is hydraulic oil, such as dimethyl silicone oil. Dimethyl silicone oil has a high coefficient of thermal expansion, resulting in a greater driving force on the piston 14 under the same temperature change. A heat conductor 13 is installed at the outlet 6 of the Roots vacuum pump 1. The heat conductor 13 is made of metal, such as gold, silver, copper, or aluminum; in this embodiment, copper is used. The heat conductor 13 extends into the accumulator tube 2, transferring heat from the outlet 6 of the Roots vacuum pump 1 to the temperature-sensitive expansion fluid 12 in the accumulator tube 2. A piston 14 is installed at the top of the accumulator tube 2. A counterweight valve core 8 is connected to a push rod 15. The piston 14 moves upward, pushing the push rod 15 upward, causing the counterweight valve core 8 to move upward and open the pressure relief hole 5. A cavity 25 is provided between the liquid surface of the temperature-sensitive expansion fluid 12 and the piston 14.

[0045] A plunger 26 is mounted on the heat conductor 13. The outer diameter of the plunger 26 is larger than that of the heat conductor 13. The plunger 26 slides and adapts to the inner wall of the accumulator tube 2. One end of the plunger 26 is subjected to the hydraulic pressure of the temperature-sensitive expansion fluid 12, and the other end is subjected to the air pressure at the outlet 6 of the Roots vacuum pump 1. The Roots vacuum pump 1 is provided with a mounting hole 27. A connecting sleeve 28 extending outward is provided at the outer end of the mounting hole 27. The heat conductor 13 is mounted at the mounting hole 27. The end of the accumulator tube 2 is fastened to the connecting sleeve 28, and the plunger 26 is limited at the end of the connecting sleeve 28.

[0046] The inner diameter of the connecting sleeve 28 is smaller than the outer diameter of the plunger 26. A connecting protrusion ring 20 is provided at the lower opening of the accumulator tube 2. The end face of the connecting protrusion ring 20 is pressed against the end face of the connecting sleeve 28. The connecting sleeve 28 is connected to the fastening sleeve 21 by an external thread. An abutting protrusion ring 22 is provided on the fastening sleeve 21. The abutting protrusion ring 22 abuts against the end face of the connecting protrusion ring 20 to achieve the connection and fastening of the accumulator tube 2.

[0047] When the pumped gas cannot be promptly discharged from the outlet 6 by the forepump, its temperature and pressure both increase. At this time, while the heat conductor 13 absorbs heat, the pressure exerted by the gas acts on the plunger 26, pushing it towards the temperature-sensitive expansion fluid 12. This increases the pushing effect of the expansion fluid 12 on the piston 14, making it easier to push the counterweight valve core 8. During normal operation of the Roots vacuum pump 1, the end face of the plunger 26 is fitted and limited against the end face of the connecting sleeve 28. The gas pressure at the outlet of the Roots vacuum pump 1 acts on the end face of the plunger 26 through the mounting hole 27. The connecting sleeve 28 facilitates the connection and fixation of the accumulator tube 2.

[0048] An extension tube 29, connected to the lower part of the accumulator tube 2, is provided. An adjusting plug 30 is installed inside the extension tube 29. The adjusting plug 30 is connected to an adjusting knob 31. Rotating the adjusting knob 31 moves the adjusting plug 30. A support 32 is fastened to the end of the extension tube 29. The adjusting knob 31 is threadedly connected to the support 32. A T-shaped connector 33 is provided at the upper end of the adjusting knob 31. An installation groove 34 is provided on the lower end face of the adjusting plug 30. The connector 33 is rotatably installed in the installation groove 34. An end cap 35 is connected to the open end of the installation groove 34. The end cap 35 axially limits the connector 33. Ball bearings 36 are installed between the upper end of the connector 33 and the bottom surface of the installation groove 34, and between the end cap 35 and the surface of the connector 33.

[0049] Rotating the adjusting knob 31 moves the adjusting plug 30, thereby adjusting the pressure inside the accumulator tube 2, and thus adjusting the pressure difference between the air inlet 4 and the air outlet 6 when the counterweight valve core 8 is opened, to meet different usage requirements. When the adjusting plug 30 moves upward, the cavity 25 between the temperature-sensitive expansion fluid 12 and the piston 14 decreases, the pressure inside the accumulator tube 2 increases, and the pressure difference between the air inlet 4 and the air outlet 6 decreases when the counterweight valve core 8 is opened. When the adjusting plug 30 moves downward, the cavity 25 between the temperature-sensitive expansion fluid 12 and the piston 14 increases, the pressure inside the accumulator tube 2 decreases, and the pressure difference between the air inlet 4 and the air outlet 6 increases when the counterweight valve core 8 is opened.

[0050] The lower end of the push rod 15 is securely connected to the piston 14. The push rod 15 moves through the housing of the Roots vacuum pump 1. A PTFE skeleton oil seal is installed between the push rod 15 and the housing of the Roots vacuum pump 1, which allows for a complete seal at the connection between the push rod 15 and the housing of the Roots vacuum pump 1, while also allowing the push rod 15 to slide freely up and down. The outer surfaces of the counterweight valve core 8, the push rod 15, and the heat conductor 13 are all lined with a PTFE corrosion-resistant layer.

[0051] When the Roots vacuum pump 1 is working, air enters through inlet 4 and exits through outlet 6. When the pressure difference between inlet 4 and outlet 6 exceeds the specified pressure difference value (5000Pa), it indicates that the gas being pumped cannot be discharged from outlet 6 in time by the backing pump, which will cause the temperature of outlet 6 to rise. The heat at outlet 6 is transferred to the temperature-sensitive expansion fluid 12 in the accumulator tube 2 through the heat conductor 13. The temperature-sensitive expansion fluid 12 expands due to heat, thereby pushing piston 14 upward. The upward movement of piston 14 pushes push rod 15 upward, causing counterweight valve core 8 to move upward and open pressure relief hole 5. Under the action of pressure difference, the gas flows back to inlet 4 through pressure relief hole 5 to achieve pressure relief. After the pressure difference between inlet 4 and outlet 6 of the Roots vacuum pump 1 decreases, the temperature of outlet 6 of the Roots vacuum pump 1 decreases, the temperature-sensitive expansion fluid 12 contracts, piston 14 and counterweight valve core 8 return to their original positions, and the Roots vacuum pump 1 returns to normal working state.

[0052] The transparent accumulator tube 2 facilitates observation of the liquid level. Accurate liquid level readings are obtained via the scale 3, allowing for precise control of the amount of temperature-sensitive expansion fluid 12 added. Adjusting the amount of temperature-sensitive expansion fluid 12 allows for flexible setting of the opening temperature, thereby regulating the pressure difference between the inlet 4 and outlet 6 of the counterweight valve core 8 when it is open.

[0053] The amount of temperature-sensitive expansion fluid 12 added is determined by adding it to the upper end of the accumulator tube 2. This fluid is added before the piston 14 is installed into the accumulator tube 2. When it is necessary to adjust the pressure difference between the inlet 4 and outlet 6 of the counterweight valve core 8 when it is open, the adjusting knob 31 is rotated to move the adjusting plug 30, thereby adjusting the pressure inside the accumulator tube 2 and thus adjusting the pressure difference between the inlet 4 and outlet 6 when the counterweight valve core 8 is open to meet different usage requirements. When the adjusting plug 30 moves upward, the pressure inside the accumulator tube 2 increases, and the pressure difference between the inlet 4 and outlet 6 decreases when the counterweight valve core 8 is open. When the adjusting plug 30 moves downward, the pressure inside the accumulator tube 2 decreases, and the pressure difference between the inlet 4 and outlet 6 increases when the counterweight valve core 8 is open.

[0054] Compared to the scheme of using a single counterweight valve core 8 for depressurization at the outlet 6, this application has significant advantages. With only a single counterweight valve core 8, the opening pressure difference is fixed and cannot be adjusted. However, the processes for producing different products in the same unit require different pressure differences between the inlet 4 and outlet 6, and a single counterweight valve core 8 cannot achieve adjustment of the opening pressure difference. Furthermore, when the machine stops or operating conditions change, the large reset inertia of the single counterweight valve core 8 causes inertial impact on the reset plane, easily damaging the sealing surface and causing air leakage; moreover, the large inertial impact can easily cause equipment vibration and abnormal noise.

[0055] In this application, the thermal expansion of the temperature-sensitive expansion fluid 12 drives the movement of the counterweight valve core 8. By adjusting the amount of temperature-sensitive expansion fluid 12 added, the pressure difference between the inlet 4 and outlet 6 of the counterweight valve core 8 when it is open can be adjusted, which can meet the requirements of different production processes for the Roots vacuum pump 1. When the machine stops or the operating conditions change, the counterweight valve core 8 returns to its original position by relying on the temperature-sensitive expansion fluid 12. The return is smooth and will not generate a large inertial impact, avoiding impact damage to the sealing surface and preventing equipment vibration and abnormal noise caused by inertial impact. Furthermore, in this application, while the heat conductor 13 absorbs heat, the pressure of the air pressure at the outlet 6 of the Roots vacuum pump 1 acts on the plunger 26, pushing the plunger 26 towards the temperature-sensitive expansion fluid 12, increasing the pushing effect of the temperature-sensitive expansion fluid 12 on the piston 14, and making it easier to push the counterweight valve core 8.

[0056] Example 3: A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback (see...) Figure 6 Its structure is similar to that of Embodiment 1 or Embodiment 2, with the main difference being that in this embodiment, piston 14 is connected to push rod 37, push plate 38 is hinged to Roots vacuum pump 1, the lower end of push rod 15 rests on the upper surface of push plate 38, and the upper end of push rod 37 rests on the lower surface of push plate 38. The distance from push rod 15 to the hinge point of push plate 38 is less than the distance from push rod 37 to the hinge point of push plate 38. An abutment ball 39 is provided on the lower surface of push rod 15, and a top ball 40 is provided on the upper end of push rod 37. The abutment ball 39 is supported on the upper surface of push plate 38, and the top ball 40 rests on the lower surface of push plate 38. Push rod 15 is located between push rod 37 and the outer wall of Roots vacuum pump 1.

[0057] When the pressure difference between the inlet 4 and the outlet 6 exceeds the specified pressure difference value (5000Pa), it indicates that the gas being pumped cannot be discharged from the pre-pump in time at the outlet 6, which will cause the temperature of the outlet 6 to rise. The heat at the outlet 6 is transferred to the temperature-sensitive expansion liquid 12 in the accumulator tube 2 through the heat conductor 13. The temperature-sensitive expansion liquid 12 expands when heated, thereby pushing the piston 14 to move upward. The piston 14 pushes the push plate 38 to rotate upward through the push rod 37. The push plate 38 pushes the push rod 15 to move upward, thereby pushing the counterweight valve core 8 to move and opening the pressure relief hole 5. Under the action of the pressure difference, the gas flows back to the inlet 4 through the pressure relief hole 5 to achieve pressure relief. Since the distance from the push rod 15 to the hinge of the push plate 38 is less than the distance from the push rod 37 to the hinge of the push plate 38, the push rod 37, the push plate 38, and the push rod 15 together form a force-saving lever, and a smaller piston 14 thrust can push the counterweight valve core 8 to move. When the counterweight valve core 8 moves upward, it opens the pressure relief hole 5, reducing the pressure difference between the inlet 4 and outlet 6 of the Roots vacuum pump 1. This lowers the temperature at the outlet 6 of the Roots vacuum pump 1, causing the temperature-sensitive expansion fluid 12 to contract. The piston 14 and counterweight valve core 8 then return to their original positions, and the Roots vacuum pump 1 returns to normal operation. Other structures are the same as in Example 1 or Example 2.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback, characterized in that, The system includes a accumulator tube connected to a Roots vacuum pump. A pressure relief hole is provided in the cavity on the inlet side of the Roots vacuum pump, which is connected to the outlet of the Roots vacuum pump. A counterweight valve core is installed at the pressure relief hole, which closes the pressure relief hole. The accumulator tube is filled with a temperature-sensitive expansion fluid. A heat conductor is installed at the outlet of the Roots vacuum pump, extending into the accumulator tube. A piston is installed at the top of the accumulator tube, and the counterweight valve core is connected to a push rod. When the piston moves upward, it pushes the push rod upward, causing the counterweight valve core to move upward and open the pressure relief hole.

2. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, A plunger is installed on the heat conductor, and the plunger slides and adapts to the inner wall of the accumulator tube; one end of the plunger bears the hydraulic pressure of the temperature-sensitive expansion fluid, and the other end of the plunger bears the air pressure at the outlet of the Roots vacuum pump.

3. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 2, characterized in that, The Roots vacuum pump is provided with a mounting hole, and an outwardly extending connecting sleeve is provided at the outer end of the mounting hole. The heat conductor is installed at the mounting hole, the end of the accumulator tube is fastened to the connecting sleeve, and the plunger is limited at the end of the connecting sleeve.

4. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, The upper part of the accumulator is connected to the liquid filling pipe, and a valve is installed on the liquid filling pipe.

5. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, An extension tube connected to the lower part of the accumulator tube is provided. An adjusting plug is installed inside the extension tube. The adjusting plug is connected to an adjusting knob. Rotating the adjusting knob pushes the adjusting plug to move.

6. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, The power storage tube is a transparent tube with graduation lines on it.

7. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, A cavity is provided between the liquid surface of the temperature-sensitive expansion fluid and the piston.

8. A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback according to any one of claims 1 to 7, characterized in that, The lower end of the push rod is fastened to the piston.

9. A passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback according to any one of claims 1 to 7, characterized in that, The piston is connected to the push rod, and the push plate is hinged to the Roots vacuum pump. The lower end of the push rod rests on the upper surface of the push plate, and the upper end of the push rod rests on the lower surface of the push plate. The distance from the push rod to the hinge point of the push plate is less than the distance from the push rod to the hinge point of the push plate.

10. The passive overload protection structure for a Roots vacuum pump based on thermodynamic feedback as described in claim 1, characterized in that, A vent groove is provided on the outer wall of the counterweight valve core, and a support protrusion is provided on the inner wall of the pressure relief hole. A sealing gasket is installed on the support protrusion, and the lower end of the counterweight valve core is supported on the sealing gasket.

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