Dry-type vacuum pump and intake / exhaust unit

Abstract

To propose a vacuum pump that can reduce the risk of oil leaking into an intake and exhaust chamber and can reduce the impact on the intake and exhaust performance of the vacuum pump. [Solution] The present invention relates to a vacuum pump (1;100) having at least one injection device (12) for injecting purge gas into an oil sump (6) adapted to inject purge gas into the oil sump and at least one intake and exhaust device (13) for inhaling and evacuating gas from the oil sump adapted to inhale and evacuate gas in the oil sump (6), so that purge gas is injected into the oil sump (6) and simultaneously inhaled and evacuated from the oil sump (6).

Description

Technical Field

[0001] The present invention relates to a dry vacuum pump type vacuum pump and an intake and exhaust unit. More specifically, it relates to a seal between the intake and exhaust chamber of the vacuum pump and an oil sample.

Background Art

[0002] A positive displacement vacuum pump includes one or more intake and exhaust stages in series through which gas to be intake and exhausted flows between an intake port and an exhaust port. A low vacuum pump having rotating lobes ( is also known as a "Roots" pump having two or more lobes ) and is distinguished from a "Claw" pump or a screw pump. A Roots compressor or a "Roots blower" type vacuum pump used upstream of the low vacuum pump is also known to increase the intake and exhaust capacity in a high flow situation. Such a vacuum pump is called a "dry" pump. This is because during operation, the rotors rotate within the stator without mechanically contacting each other or the stator, which means that it is possible not to use oil in the intake and exhaust stages.

[0003] The rotation of the rotors is synchronized using gears. The rotors are generally rotationally induced by ball bearings arranged on both sides of the intake and exhaust chamber. These gears and bearings are lubricated with oil or grease contained in an oil sample isolated from the intake and exhaust chamber by sealing means that allow the shaft to rotate. The sealing means mainly includes physical barriers to the lubricant, such as rubbing lip seals, ejector disks, gas purges, or obstacles such as labyrinths and baffles.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, during operation, the pressure inside the vacuum pump fluctuates significantly, especially in applications where large volumes of gas are periodically placed under vacuum, such as in the intake and exhaust of solar panels. Although the atmosphere inside the oil sump remains at atmospheric pressure rather than a vacuum, this atmosphere is also affected to some extent by the pressure fluctuations that occur in the intake and exhaust sections. This is because the sealing means, which are relatively effective for the lubricant, are not completely sealed to the gas because they must allow the shaft to rotate. Consequently, a pressure difference develops between the oil sump and the intake and exhaust chamber, which can cause the intake and exhaust gases to leak into the oil sump. These gases, which can sometimes be corrosive or contain contaminants such as silica-based abrasive particles and hard particles, then flow into the oil sump. This gas or solid contamination can cause premature degradation of the lubricant's properties or lead to poor lubrication of rolling bearings. This can cause ball bearings to wear out prematurely and even fail over time, potentially shortening the lifespan of the vacuum pump. This phenomenon is accelerated in periodic intake and exhaust applications where repeated emptying and refilling of the oil sump promotes gas movement, thereby accelerating lubricant contamination.

[0005] Therefore, the object of the present invention is to propose a dry vacuum pump type vacuum pump that at least partially overcomes the drawbacks of the prior art. [Means for solving the problem]

[0006] To achieve this objective, one objective of the present invention is to provide a dry vacuum pump type vacuum pump, - At least one oil sump, - At least one intake / exhaust stage, - Two rotating shafts whose rotation is induced within bearings lubricated by a lubricant contained in the oil sump, and which drive the rotation of the rotor in the intake and exhaust stages between the inlet and outlet of the vacuum pump, - Each shaft passage includes at least one lubricant seal device interposed between the oil sump and the intake / exhaust stage, The vacuum pump further comprises at least one injection device for injecting purge gas into an oil sump, which is configured to inject purge gas into the oil sump, and at least one intake / exhaust device for intake / exhaust gas from the oil sump, which is configured to intake / exhaust gas from the oil sump, characterized in that it injects purge gas into the oil sump and simultaneously intake / exhausts gas from the oil sump.

[0007] Injecting purge gas dilutes the intake and exhaust gases present in the oil sump. This reduces the partial pressure of reactive gas species and increases the pressure within the oil sump, thereby reducing pressure differences that could cause leakage into the oil sump. Intake and exhaust of gas from the oil sump avoids excessive overpressure in the intake and exhaust chamber, which could lead to excessive leakage into the chamber, and circulates the gases contained within the oil sump. By preventing gas from accumulating in the oil sump, the possibility of the gas reacting with the lubricant and degrading it is reduced. Since a complete fluid sealing means cannot be provided, the present invention proposes diluting and removing the intake and exhaust gases before they can contaminate the lubricant. The combination of dilution and intake / exhaust of the oil sump reduces the risk of lubricant contamination in the oil sump.

[0008] A vacuum pump may also be equipped with one or more of the following features, either individually or in combination.

[0009] An injection device for injecting purge gas into an oil sump comprises, for example, an injection line that opens into the gas space of the oil sump. If the lubricant contained in the oil sump is liquid, the injection line opens above the liquid level of the liquid lubricant.

[0010] The purge gas injected is, for example, nitrogen.

[0011] An injection device for supplying purge gas to an oil sump may include a throttle and a check valve mounted in series with the injection line. The check valve prevents gas from the oil sump from flowing into the injection line when the pressure difference between the oil sump and the injection line exceeds the check valve's rated pressure threshold. The throttle (also called a calibrated orifice or nozzle) allows for fixing the maximum amount of purge gas that can be injected. Thus, the throttle and check valve enable mechanical control of the injection gas flow and are simple and inexpensive to implement.

[0012] The maximum injection volume of purge gas is, for example, 2 slm (approximately 3.6 Pam). 3 ( / s)

[0013] An intake and exhaust device for drawing in and exhausting gas from an oil sump may include intake and exhaust lines that communicate with the gas space of the oil sump. If the lubricant contained in the oil sump is liquid, the inlet of the intake and exhaust line is located above the liquid level of the liquid lubricant.

[0014] An intake / exhaust device for drawing in and exhausting gas from an oil sump comprises a check valve and a throttle installed in series with the intake / exhaust line. The check valve prevents gas drawn in and exhausted by a low-vacuum pump from entering the intake / exhaust line when the pressure difference between the intake / exhaust stage and the intake / exhaust line exceeds the check valve's rated pressure threshold. The throttle (also called a calibrated orifice or nozzle) allows for the determination of the maximum intake / exhaust volume. Thus, the throttle and check valve mechanically control the flow of the drawn-in and exhausted gases and are simple and inexpensive to implement.

[0015] An intake and exhaust device for drawing in and exhausting gases from an oil sump may include a deflector located within the oil sump at the inlet of the intake and exhaust line to restrict the entry of lubricant into the intake and exhaust line.

[0016] To prevent lubricant from flowing into the injection line, the same type of deflector can be placed inside the oil sump at the outlet of the injection line.

[0017] An intake and exhaust device for drawing gas from an oil sump may include an oil separator located in the intake and exhaust line, for example, upstream of a check valve or throttle. The oil separator can separate oil from the gas, thus preventing oil from being pumped out of the oil sump. The oil separator may include a filter, for example, a sintered stainless steel filter.

[0018] The maximum intake and exhaust volume is, for example, 10 slm (approximately 18 Pam). 3 ( / s)

[0019] The vacuum pump may have two oil sumps, with one oil sump located on each side of at least one intake / exhaust stage. For each oil sump, the vacuum pump may have an injection device for injecting purge gas into the oil sump and an intake / exhaust device for drawing gas from the oil sump, with no fluid communication between the intake / exhaust devices for drawing gas from the oil sump.

[0020] The intake and exhaust lines can communicate the gas space of the oil sump with the intake and exhaust stages of a multistage vacuum pump, for example, at the inlets and / or outlets of intake and exhaust stages except for the last intake and exhaust stage, or in the interstage passages of a multistage vacuum pump connecting the outlet of one intake and exhaust stage to the inlet of the next intake and exhaust stage. In this way, the intake and exhaust device for drawing gas from the oil sump does not require any additional intake and exhaust devices. Therefore, it is easy to implement, inexpensive, autonomous, and compact.

[0021] An injection device for injecting purge gas into an oil sample and an intake / exhaust device for sucking and exhausting gas from the oil sample are configured to control the pressure in the oil sample, for example, to a pressure lower than atmospheric pressure, for example, lower than 50,000 Pa (500 mbar), for example, a pressure between 5,000 Pa (50 mbar) and 40,000 Pa (400 mbar).

[0022] Another object of the present invention is an intake / exhaust unit including a rough vacuum pump having a plurality of intake / exhaust stages, the intake / exhaust unit including the above-described roots vacuum pump arranged in series and upstream of the rough vacuum pump, and an intake / exhaust device for sucking and exhausting gas from the oil sample includes an intake / exhaust line that communicates the gas space of the oil sample of the vacuum pump with, for example, at the inlet of an intake / exhaust stage and / or at the outlet of an intake / exhaust stage excluding the last intake / exhaust stage, for example, in an inter-stage passage of the rough vacuum pump connecting the outlet of one intake / exhaust stage and the inlet of the next intake / exhaust stage, with one of the intake / exhaust stages of the rough vacuum pump. Next, some of the intake / exhaust stages having different intake / exhaust volumes of the rough vacuum pump are selected. By the selected intake / exhaust stage, in particular, in order to suppress the influence on the performance of the vacuum pump and the risk of oil leakage into the intake / exhaust chamber, the intake / exhaust device for sucking and exhausting gas can be optimized according to the required overpressure level in the oil sample with respect to the intake / exhaust chamber. Therefore, the intake / exhaust device for sucking and exhausting gas from the oil sample is "adjustable" according to the selected intake / exhaust stage.

[0023] The intake / exhaust line communicates, for example, the gas space of the oil sample with the outlet of the second intake / exhaust stage of the rough vacuum pump.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic diagram showing an embodiment of the intake / exhaust unit. [Figure 2] It is an enlarged detailed view of the vacuum pump of the intake / exhaust unit shown in FIG. 1. [Figure 3]This graph shows a curve of pressure (unit: mbar) against time (unit: hr) in an application where a fixed amount of gas is periodically drawn in and out, and includes: - pressure on the intake side or upstream side of the vacuum pump (curve A), - inlet pressure of the oil sump of a conventional first vacuum pump that changes according to curve A (curve B), - inlet pressure of the oil sump of a conventional second vacuum pump that changes according to curve A (curve C), and - inlet pressure of the oil sump of the vacuum pump according to the present invention that changes according to curve A (curve D). [Modes for carrying out the invention]

[0025] Further advantages and features will become apparent upon reading the specification of the present invention and examining the accompanying drawings.

[0026] In these diagrams, identical elements are given the same symbols. The diagrams have been simplified for easier understanding.

[0027] The following embodiments are examples. While this specification refers to one or more embodiments, this does not necessarily mean that each reference refers to the same embodiment or that features apply to only one embodiment. Other embodiments may also be provided by combining or substituting simple features from various embodiments.

[0028] "Upstream" refers to components located before other components in the direction of gas circulation. In contrast, "downstream" refers to components arranged sequentially in the direction of gas circulation.

[0029] The present invention applies to any type of dry vacuum pump, i.e., a vacuum pump having one or at least two intake / exhaust stages, for example, 1 to 10 intake / exhaust stages. This vacuum pump may be a low vacuum pump 100 having multiple intake / exhaust stages and configured to exhaust the intake / exhaust gas at atmospheric pressure, or a dry vacuum pump 1 called a Roots pump or Roots compressor. The dry vacuum pump 1 has 1 to 3 intake / exhaust stages and is connected in series upstream of the low vacuum pump during use, and its exhaust pressure is obtained by the low vacuum pump.

[0030] Figure 1 shows an example of an intake and exhaust unit 101 comprising a Roots vacuum pump 1 and a low vacuum pump 100. The inlet 2 of the Roots vacuum pump 1 is connected to a closed chamber that is inhaled and exhausted via a shut-off valve. The outlet 3 of the Roots vacuum pump 1 is connected to the inlet 4 of the low vacuum pump 100, whose outlet 5 is at or above atmospheric pressure.

[0031] The Roots vacuum pump 1 or low vacuum pump 100 comprises at least one oil sump 6, an intake / exhaust chamber having at least one intake / exhaust stage T1-T5, two rotating shafts 7 (only one is shown for each of the two vacuum pumps in the intake / exhaust unit 101 in Figure 1), and at least one sealing device 8 for sealing the lubricant interposed between the oil sump 6 and the intake / exhaust stage in each passage through which the rotating shafts 7 pass.

[0032] In an exemplary embodiment, the Roots vacuum pump 1 comprises a single intake and exhaust stage T1.

[0033] The low vacuum pump 100 comprises several intake and exhaust stages T1 to T5, for example five stages, installed in series between the inlet 4 and the outlet 5. In this example, intake and exhaust stages T1 and T5, adjacent to the sealing device 8, are the first and last intake and exhaust stages.

[0034] Each intake / exhaust stage T1 to T5 has its own inlet and outlet. When vacuum pumps 1, 100 have several intake / exhaust stages, successive intake / exhaust stages are connected in series by interstage passages that connect the outlet of the previous intake / exhaust stage to the inlet of the next stage. The intake / exhaust volumes of intake / exhaust stages T1 to T5 decrease or remain constant depending on the position between the inlet and outlet of the vacuum pump, with the flow rate generated by the first intake / exhaust stage T1 at the minimum pressure corresponding to the maximum intake / exhaust volume.

[0035] The rotating shaft 7 drives the rotation of the rotor 9 in intake and exhaust stages T1 to T5, carrying the gas to be drawn in and exhausted from the inlet to the outlet of the vacuum pumps 1 and 100. The rotor 9 of the low vacuum pump 100 is rotationally driven by at least one motor M1 of the low vacuum pump 100. The rotor 9 of the Roots vacuum pump 1 is rotationally driven by at least one motor M2 of the Roots vacuum pump 1.

[0036] While the rotor 9 is rotating, the gas drawn in from the inlet is confined in the space formed by the rotor 9 and the stator and is carried by the rotor 9 toward the next stage. The rotor 9 of the low vacuum pump 100 has lobes of the same contour, such as, for example, a "Roots" type (cross section in the shape of the number 8 or a kidney bean) or a "claw" type, or it is screw type, or follows the principle of other similar positive displacement vacuum pumps.

[0037] The rotating shaft 7 supporting the rotor 9 is driven to rotate by bearings lubricated by a lubricant contained in the oil sump 6. The lubricant, such as oil or grease, is particularly effective in lubricating the ball bearings 10 and the gears 11 that synchronize the shaft.

[0038] The vacuum pumps 1, 100 include, for example, two oil sumps 6, one on each side of at least one intake / exhaust stage, and a sealing device 8 for sealing the lubricant interposed between the oil sumps 6 and the intake / exhaust stage in each passage through which the shaft passes on both sides of the intake / exhaust stage.

[0039] The sealing device 8 may comprise at least one annular seal, such as a “dynamic” seal, i.e., a non-friction seal such as a segment seal, a labyrinth seal, or a “curtain” of baffles or gas, or a friction annular seal such as a lip seal, or a combination of such embodiments. This annular seal forms a very low conductance around the rotating shaft 7, thereby significantly restricting the passage of lubricating fluid from the oil sump 6 to the dry intake and exhaust stages and vice versa, while simultaneously allowing rotation of the shaft 7. The sealing device 8 may also comprise a deflector disc in the shape of a whole disc mounted on the rotating shaft 7 so as to rotate integrally with the rotating shaft 7. The centrifugal force generated by the high-speed rotation of the deflector disc prevents oil from entering the annular seal. An oil recovery passage may be located at the bottom of the stator, opposite the deflector disc of each rotating shaft, to return the discharged lubricant towards the oil sump 6.

[0040] The vacuum pump 1,100 further comprises at least one injection device 12 for injecting purge gas into the oil sump 6, and at least one intake / exhaust device 13 for injecting gas into the oil sump 6 and simultaneously injecting gas into and exhausting gas from the oil sump 6.

[0041] Injecting purge gas dilutes the intake and exhaust gases present in the oil sump 6. This reduces the partial pressure of reactive gas species, and on the other hand, increases the pressure within the oil sump 6, reducing the pressure difference that could cause leakage into the oil sump 6. Intake and exhaust of gas from the oil sump 6 prevents excessive overpressure of the intake and exhaust chamber, which could lead to excessive leakage into the chamber, and circulates the gas contained within the oil sump 6. By preventing gas from accumulating in the oil sump 6, the possibility of the gas reacting with the lubricant and degrading it is reduced. Since it is difficult to provide a complete fluid sealing means, the present invention proposes diluting and removing the intake and exhaust gases before they can contaminate the lubricant. The combination of dilution and intake / exhaust of the oil sump 6 makes it possible to reduce the risk of lubricant contamination in the oil sump 6.

[0042] The injection device 12 for injecting purge gas into the oil sump 6 includes, for example, an injection line 14 that opens into the gas space 20 of the oil sump 6. If the lubricant contained in the oil sump 6 is liquid, the injection line 14 opens above the liquid level of the liquid lubricant (dotted line in Figure 1). The inlet of the injection line 14 is connected to the purge gas source, for example, via a flow meter (or "mass flow controller"). The purge gas to be injected is, for example, nitrogen.

[0043] The injection device 12 for injecting purge gas into the oil sump 6 may include a throttle 15 and a check valve 16 mounted in series with the injection line 14.

[0044] The check valve 16 prevents gas from the oil sump 6 from flowing into the injection line 14 when the pressure difference between the oil sump 6 and the injection line 14 exceeds the rated pressure threshold of the check valve 16. The throttle 15 allows setting the maximum injection amount of purge gas. Thus, the throttle 15 and the check valve 16 enable mechanical control of the injection gas flow, and the implementation is simple and inexpensive.

[0045] The maximum injection volume of purge gas is, for example, 2 slm (approximately 3.6 Pam). 3 ( / s)

[0046] The intake and exhaust device 13 for drawing in and exhausting gas from the oil sump includes, for example, an intake and exhaust line 17 that communicates with the gas space 20 of the oil sump 6. If the lubricant contained in the oil sump 6 is liquid, the inlet of the intake and exhaust line is located above the liquid level of the liquid lubricant.

[0047] The intake and exhaust line 17 connects the gas space 20 of the oil sump 6 to the intake and exhaust stages of a multistage vacuum pump, for example, at the inlets and / or outlets of the intake and exhaust stages except for the last intake and exhaust stage, and for example, in the interstage passages of the multistage vacuum pump connecting the outlet of one intake and exhaust stage to the inlet of the next intake and exhaust stage. In this way, the intake and exhaust device 13 for drawing in and exhausting gas from the oil sump does not require any additional intake and exhaust devices. Therefore, it is easy to implement, inexpensive, autonomous, and compact.

[0048] In the case of the Roots vacuum pump 1, the intake and exhaust line 17 connects, for example, the gas space 20 of the oil sump 6 of the Roots vacuum pump 1 to one of the intake and exhaust stages T1 to T4 of the low vacuum pump 100, which is located downstream of and in series with the Roots vacuum pump 1, excluding the last intake and exhaust stage T5 (Figure 1). Next, one of several intake and exhaust stages of the low vacuum pump 100 with different intake and exhaust volumes is selected. Depending on the selected intake and exhaust stage, the intake and exhaust device 13 for drawing in and exhausting gas can be optimized according to the desired overpressure level in the oil sump 6. With regard to the adjacent intake and exhaust stage T1, particular consideration is given to its impact on the performance of the vacuum pump and minimizing the risk of oil leakage into the intake and exhaust chamber. Thus, the intake and exhaust device 13 for drawing in and exhausting gas from the oil sump is "adjustable" according to the selected intake and exhaust stage. The intake and exhaust line 17 connects, for example, the gas space 20 of the oil sump 6 to the outlet of the second intake and exhaust stage T2 of the low vacuum pump 100.

[0049] The injection device 12 for injecting purge gas into the oil sump and the intake / exhaust device 13 for drawing in and exhausting gas from the oil sump are configured, for example, to control the pressure in the oil sump 6 to a pressure lower than atmospheric pressure, for example, lower than 50,000 Pa (500 mbar), for example, between 5,000 Pa (50 mbar) and 40,000 Pa (400 mbar).

[0050] The intake and exhaust device 13 for drawing in and exhausting gas from the oil sump may include a check valve 16 and a throttle 15 mounted in series with the intake and exhaust line 17.

[0051] The check valve 16 prevents the gas drawn in and out by the low vacuum pump 100 from entering the intake and exhaust line 17 when the pressure difference between the intake / exhaust stage T2 and the intake / exhaust line 17 exceeds the rated pressure threshold of the check valve 16. The throttle 15 (also known as a calibrated orifice or nozzle) can be used to determine the maximum intake / exhaust volume. Thus, the throttle 15 and the check valve 16 mechanically control the flow of the intake / exhaust gas and are simple and inexpensive to implement.

[0052] The maximum intake and exhaust volume is, for example, 10 slm (approximately 18 Pam). 3 ( / s)

[0053] The intake and exhaust device 13 for drawing in and exhausting gas from the oil sump may also include an oil separator 18 located upstream of the intake and exhaust line 17, for example, a check valve 16 or a throttle 15. The oil separator 18 can separate the oil from the gas so that oil is not pumped out of the oil sump 6, and therefore the oil sump 6 does not become empty of oil. The oil separator 18 may include a filter, for example, a sintered stainless steel filter.

[0054] Another advantage of the intake / exhaust device 13 for drawing in and exhausting gas from the oil sump provided in this manner is that the check valve 16 automatically closes as a result of overpressure in the intake / exhaust stage T2. This is brought about by the intake / exhaust cycle in the sealed chamber drawn in and exhausted by the intake / exhaust unit 1, and is therefore generally periodic, which allows the gas to blow through the filter and discharge the oil, enabling the filter to self-clean. In this way, the filter is automatically regenerated periodically.

[0055] The intake and exhaust device 13 for drawing in and exhausting gas from the oil sump may further include a deflector 19 positioned within the gas space 20 of the oil sump 6 at the inlet of the intake and exhaust line 17 to suppress the inflow of lubricant into the intake and exhaust line 17.

[0056] An exemplary embodiment can be seen in the cross-sectional view of the stator of the oil sump in Figure 2. This figure shows that an oil separator 18, formed of a sintered stainless steel filter, is positioned in the intake and exhaust line 17. A deflector 19 is positioned in front of the inlet of this same line 17. Here, the deflector 19 comprises a substantially L-shaped plate. The first vertical L-shaped portion of the deflector 19 is positioned facing the inlet of the intake and exhaust line 17 at a certain distance from the inlet of the intake and exhaust line 17 so as to form a screen that prevents lubricant from entering the intake and exhaust line 17 from the front. However, it is possible for gas to flow into the intake and exhaust line 17 by passing between this screen and the wall of the stator of the oil sump 6. The second L-shaped portion of the deflector 19 protrudes from the wall of the stator so as to form a porch-like shelter for the inlet of the line 17.

[0057] To prevent lubricant from flowing into the injection line 14, the same type of deflector can be placed inside the oil sump 6 at the outlet of the injection line 14.

[0058] The advantages of the present invention can be better understood by referring to the graph in Figure 3, which shows the pressure curves in the oil sumps of different vacuum pumps for applications in which large amounts of gas are periodically drawn in and out at atmospheric pressure, in the field of intake and exhaust applications required for solar power generation panels.

[0059] Curve A shows one example of pressure changes on the intake or upstream side of the Roots vacuum pump 1 of the intake and exhaust unit. Large periodic fluctuations in pressure can be observed between atmospheric pressure of 1,000 mbar (100,000 Pa) and 5 mbar (500 Pa).

[0060] Curve B shows the pressure change in the oil sump of the first Roots vacuum pump in a conventional intake / exhaust unit. With no purge gas injection or gas intake / exhaust from the oil sump, the pressure at or upstream of the intake port changes according to curve A. It can be seen that each time the shut-off valve upstream of the intake / exhaust unit opens, the intake / exhaust gas suddenly flows into the vacuum pump, causing a pressure increase in the oil sump. The pressure rapidly rises to 100 mbar (10,000 Pa), then decreases over several tens of minutes to approximately 5 mbar (500 Pa), with this cycle repeating every 40 minutes. The periodic pressure increase in the oil sump is caused by the intake / exhaust gas flowing from the intake / exhaust chamber through the sealing device into the oil sump. This increases the risk of contamination of the oil sump lubricant.

[0061] Curve C shows the pressure in the oil sump of the second vacuum pump in a conventional intake / exhaust unit, where the pressure at or upstream of the intake port changes according to curve A. The purge gas is injected into the oil sump under overpressure relative to atmospheric pressure, without being simultaneously intake or exhausted. This overpressure is approximately 2 bar (200,000 Pa). In this case, the vacuum pump is less affected by the "intake / exhaust" of the oil sump. Furthermore, since the gas leak is directed from the oil sump to the intake / exhaust chamber, the risk of lubricant contamination by intake / exhaust gases or particles generated from the intake / exhaust chamber can be reduced. However, this overpressure causes a significant leak of purge gas from the oil sump towards the intake / exhaust chamber. This poses a risk of lubricant contamination of the intake / exhaust chamber, affecting bearing lubrication and contaminating the chamber.

[0062] Curve D shows the change in pressure within the oil sump 6 of the Roots vacuum pump 1 according to the present invention, where the pressure at or upstream of the intake port changes according to curve A. An injection device 12 for injecting purge gas into the oil sump and an intake / exhaust device 13 for drawing gas from the oil sump lower the pressure within the oil sump 6 below atmospheric pressure, in this example, 5,000 Pa (50 mbar) and 40,000 Pa. ( 400mbar ) It can be controlled between these two values. It can be seen that the pressure fluctuations in the oil sump 6 are significantly attenuated. They are approximately 100 mbar. ( 10,000 Pa ) The pressure changes nearby, placing the oil sump 6 under a slight overpressure relative to the intake and exhaust chambers. This reduces the risk of oil leakage into the intake and exhaust chambers and minimizes the impact on intake and exhaust performance.

[0063] Although Figure 1 shows an injection device 12 for injecting purge gas into one of the two oil sumps 6 and an intake / exhaust device 13 for drawing in and exhausting gas from the oil sump, the present invention can be applied to each of the two oil sumps 6 of the Roots vacuum pump 1. Furthermore, by ensuring that there is no fluid communication between the two intake / exhaust devices 13 for drawing in and exhausting gas from the oil sumps 6 of the Roots vacuum pump 1, the risk of mutual contamination can be avoided.

[0064] Similarly, the present invention can be applied to one or both of the oil sumps 6 of the low vacuum pump 100, regardless of whether the low vacuum pump 100 is connected downstream of the Roots vacuum pump 1. It is also possible to avoid fluid communication between the two intake / exhaust devices for drawing gas from the oil sump of the low vacuum pump 100, or between the intake / exhaust devices for drawing gas from the oil sumps of the Roots vacuum pump 1 and the low vacuum pump 100. [Explanation of Symbols]

[0065] 1. Dry vacuum pump (Roots vacuum pump) 2. Inlet (Roots vacuum pump) 3. Outlet (Roots vacuum pump) 4. Inlet (low vacuum pump) 5. Outlet (low vacuum pump) 6. Oil sump 7-rotation shaft 8. Sealing devices 9 rotors 10 ball bearings 11 gears 12 Injection devices 13 Intake and Exhaust Devices 14 Injection lines 15 aperture 16. Check valve 17 Intake and exhaust lines 18 Oil Separator 19 Deflector 20 Gas space 100 Low Vacuum Pump 101 Intake and Exhaust Unit T1-T5 Intake and Exhaust Stages M1 Motor (Low Vacuum Pump) M2 motor (Roots vacuum pump)

Claims

1. A dry vacuum pump (1), - At least one oil sump (6) and - At least one intake / exhaust stage (T1), - Two rotating shafts (7) whose rotation is induced within bearings lubricated by the lubricant contained in the oil sump (6), and which drive the rotation of the rotor (9) in the intake / exhaust stage (T1) between the inlet (2) and outlet (3) of the vacuum pump (1), - Each shaft passage is equipped with at least one lubricant seal device (8) interposed between the oil sump (6) and the intake / exhaust stage (T1), The vacuum pump (1) further comprises at least one injection device (12) for injecting purge gas into the oil sump (6), and at least one intake / exhaust device (13) for intake / exhaust gas from the oil sump (6), and is configured to intake / exhaust gas from the oil sump (6), thereby injecting purge gas into the oil sump (6) and simultaneously intake / exhaust gas from the oil sump (6). The vacuum pump (1) is arranged in series with the low vacuum pump (100) and upstream of the low vacuum pump (100), and the intake / exhaust device (13) for drawing in and exhausting gas from the oil sump (6) is characterized by having an intake / exhaust line (17) that connects the gas space (20) of the oil sump (6) of the vacuum pump (1) to one of the intake / exhaust stages (T1 to T4) of the low vacuum pump (100) at the outlet of the intake / exhaust stages (T1 to T4) of the low vacuum pump (100), excluding the last intake / exhaust stage (T5) of the vacuum pump (1).

2. The vacuum pump (1) according to Claim 1, characterized in that the injection device (12) comprises an injection line (14) that opens into the gas space (20) of the oil sump (6), and a throttle (15) and a check valve (16) attached in series to the injection line (14).

3. The vacuum pump (1) according to claim 1 or 2, characterized in that the intake and exhaust device (13) comprises a check valve (16) and a throttle (15) installed in series with the intake and exhaust line (17).

4. The vacuum pump (1) according to any one of claims 1 to 3, characterized in that the intake and exhaust device (13) comprises a deflector (19) located in the oil sump (6) at the inlet of the intake and exhaust line (17) to suppress the inflow of lubricant into the intake and exhaust line (17).

5. The vacuum pump (1) according to claim 3 or 4, characterized in that the intake and exhaust device (13) comprises an oil separator (18) disposed within the intake and exhaust line (17).

6. The vacuum pump (1) comprises two oil sumps (6), the oil sumps (6) being arranged on each side of the intake / exhaust stage (T1), and the vacuum pump (1) comprises, for each oil sump (6), an injection device (12) for injecting the purge gas into the oil sump (6) and an intake / exhaust device (13) for drawing in and exhausting the gas from the oil sump (6), and is characterized in that there is no fluid communication between the oil sump (6) and the intake / exhaust device (13), as described in any one of claims 1 to 5.

7. The vacuum pump (1) according to any one of claims 1 to 6, characterized in that the injection device (12) and the intake / exhaust device (13) are configured to control the pressure in the oil sump (6) to a pressure lower than atmospheric pressure.

8. An intake and exhaust unit (101) comprising a low vacuum pump (100) having a plurality of intake and exhaust stages (T1 to T5), wherein the intake and exhaust device (13) for intake and exhausting the gas from the oil sump (6) comprises an intake and exhaust line (17) that connects the gas space (20) of the oil sump (6) of the vacuum pump (1) to one of the intake and exhaust stages (T1 to T4) of the low vacuum pump (100) at the outlet of the intake and exhaust stages (T1 to T4) of the low vacuum pump (100), excluding the last intake and exhaust stage (T5).

9. The intake and exhaust line (17) is characterized in that it connects the gas space (20) of the oil sump (6) to the outlet of the second intake and exhaust stage (T2) of the low vacuum pump (100) to the intake and exhaust unit (101) according to claim 8.

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