JP2024506811A - Dry vacuum pump type vacuum pump and suction/exhaust unit - Google Patents

Abstract

[Problem] To propose a vacuum pump that can suppress the risk of oil leakage into an intake/exhaust chamber and suppress the influence on the intake/exhaust performance of the vacuum pump. The invention includes at least one injection device (12) for injecting purge gas into the oil sump and adapted to inject the purge gas into the oil sump (6). A vacuum pump (1; 100) comprising at least one intake/exhaust device (13) for intake/exhaust gas from an oil sump adapted for intake/exhaust, the vacuum pump (1; 100) comprising at least one intake/exhaust device (13) for injecting purge gas into said oil sump (6). At the same time, the oil is taken in and exhausted from the oil sump (6). [Selection diagram] Figure 1

Description

The present invention relates to a dry vacuum pump type vacuum pump and a suction/exhaust unit. More specifically, it relates to a seal between a vacuum pump intake and exhaust chamber and an oil sump.

Positive displacement vacuum pumps include one or more stages in series between an inlet and an outlet through which the gas to be pumped and pumped flows. A distinction is made between low vacuum pumps with rotating lobes (also known as "roots" pumps with two or more lobes) and "claw" or screw pumps. Roots compressor or "Roots blower" type vacuum pumps are also known that are used upstream of low vacuum pumps to increase pumping capacity in high flow situations. Such vacuum pumps are called "dry" pumps. This is because during operation, the rotors rotate within the stator without mechanical contact with each other or with the stator, which means that it is possible to use no oil in the intake and exhaust stages. .

The rotation of the rotors is synchronized using gears. The rotor is guided in rotation by ball bearings, typically located on both sides of the intake and exhaust chambers. These gears and bearings are lubricated with oil or grease contained in an oil sump that is isolated from the intake and exhaust chambers by sealing means through which the shaft can rotate. Sealing means primarily comprise physical barriers to the lubricant, such as rub-grip seals, ejector discs, gas purges, or obstacles such as labyrinths and baffles.

However, during operation, the pressure within the vacuum pump fluctuates widely, especially in applications where large amounts of gas are periodically placed under vacuum, such as in the field of photovoltaic panel intake and exhaust applications. Although the atmosphere within the oil sump remains at atmospheric pressure rather than vacuum, this atmosphere is also subject to some pressure fluctuations that occur in the intake and exhaust sections. This is because the sealing means, which are relatively effective against lubricants, are not completely sealed against gases because of the need to allow rotation of the shaft. Therefore, a pressure difference may develop between the oil sump and the intake and exhaust chambers, which may cause, in particular, the intake and exhaust gases to leak towards the oil sump. These gases, which are sometimes corrosive or can be accompanied by contaminant particles such as silica-based abrasive particles and hard particles, then flow into the oil sump. This gas or solid contamination can cause premature deterioration of the lubricant properties or can cause poor lubrication of rolling bearings. This can cause premature wear and even breakage of the ball bearings over time, potentially shortening the lifespan of the vacuum pump. This phenomenon is accelerated in cyclic pumping applications where repeated emptying and filling of the oil sump promotes gas movement, thereby promoting lubricant contamination.

It is therefore an object of the present invention to propose a vacuum pump of the dry vacuum pump type, which at least partially overcomes the drawbacks of the prior art.

In order to achieve this objective, one object of the present invention is to provide a dry vacuum pump type vacuum pump,
- at least one oil sump;
- at least one intake and exhaust stage;
- two rotating shafts whose rotation is induced in bearings lubricated by the lubricant contained in the oil sump and which are adapted to drive the rotation of the rotor in the intake and exhaust stages between the inlet and outlet of the vacuum pump; and,
- at least one lubricant sealing device interposed between the oil sump and the intake and exhaust stages in each shaft passage;
The vacuum pump includes at least one injection device adapted to inject purge gas into the oil sump, and an oil sump adapted to inject gas in the oil sump. The apparatus further includes at least one intake/exhaust device for intake/exhaust gas from the oil sump, and is configured to simultaneously inject purge gas into the oil sump and exhaust gas from the oil sump.

By injecting the purge gas, it is possible on the one hand to dilute the gas present in the oil sump to be pumped out. This reduces the partial pressure of the reactive gas species and, on the other hand, increases the pressure in the oil sump, making it possible to reduce pressure differences that could cause leakage into the oil sump. The intake and exhaust of gas from the oil sump makes it possible, on the one hand, to avoid excessive overpressure on the intake and exhaust chambers, which could lead to excessive leakage into the intake and exhaust chambers, and on the other hand, in the oil sump The gas contained in the can be circulated. By preventing gas from accumulating in the oil sump, the likelihood that the gas will react with and degrade the lubricant is reduced. Since it is not possible to provide a perfect fluid-tight seal, the invention proposes to dilute and simultaneously remove the gases being pumped in and out before they contaminate the lubricant. The combination of oil sump dilution and intake and exhaust makes it possible to reduce the risk of contamination of the oil sump lubricant.

The vacuum pump may further include one or more of the features described below, alone or in combination.

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

The injected purge gas is, for example, nitrogen.

The injection device for injecting purge gas into the oil sump may include a restriction and a check valve mounted in series with the injection line. The check valve makes it possible to prevent gas in the oil sump from flowing into the injection line when the pressure difference between the oil sump and the injection line exceeds the rated pressure threshold of the check valve. A restriction (also called a calibrated orifice or nozzle) allows the maximum injection volume of purge gas to be fixed. The throttle and check valve therefore allow mechanical control of the flow of the injected gas and are simple and inexpensive to implement.

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

The intake/exhaust device for intake/exhaust gas from the oil sump can include an intake/exhaust line communicating with the gas space of the oil sump. When the lubricant contained within the oil sump is a liquid, the inlet of the intake and exhaust line is located above the level of the liquid lubricant.

An intake/exhaust device for intake/exhaust gas from an oil sump includes a check valve and a throttle mounted in series with an intake/exhaust line. The check valve prevents the gas pumped by the low vacuum pump from entering the intake and exhaust line when the pressure difference between the intake and exhaust stage and the intake and exhaust line exceeds the rated pressure threshold of the check valve. enable. A restriction (also called a calibrated orifice or nozzle) allows the maximum intake and exhaust volume to be determined. Throttles and check valves thus mechanically control the flow of inhaled and exhausted gases and are simple and inexpensive to implement.

The intake and exhaust device for extracting gas from the oil sump may include a deflector located within the oil sump at the entrance of the intake and exhaust line to limit the ingress of lubricant into the intake and exhaust line.

A deflector of the same type can be placed in the oil sump at the outlet of the injection line to reduce the flow of lubricant into the injection line.

The intake and exhaust device for intake and exhaust gas from the oil sump can comprise an oil separator arranged in the intake and exhaust line, for example upstream of a check valve or a throttle. The oil separator can separate oil from the gas, thus preventing oil from being pumped from the oil sump. The oil separator includes a filter, such as a sintered stainless steel filter.

The maximum intake and exhaust amount is, for example, 10 slm (about 18 Pam ³ /s).

The vacuum pump may include two oil sumps, one oil sump located on each side of the at least one intake and exhaust stage. The vacuum pump may include, for each oil sump, an injection device for injecting purge gas into the oil sump, and an intake/exhaust device for sucking gas from the oil sump. No fluid communication is provided between the intake and exhaust devices for exhaust.

The intake and exhaust lines connect the gas space of the oil sump, e.g. The interstage passage of the multistage vacuum pump that connects the inlet of the stage can communicate with the suction and exhaust stages of the multistage vacuum pump. In this way, the intake and exhaust devices for extracting gas from the oil sump do not require additional intake and exhaust devices. Therefore, it is easy to implement, cheap, autonomous and compact.

The injection device for injecting purge gas into the oil sump and the intake and exhaust device for extracting gas from the oil sump may, for example, reduce the pressure in the oil sump to a pressure below atmospheric pressure, for example below 50,000 Pa (500 mbar). The pressure is controlled to be, for example, between 5,000 Pa (50 mbar) and 40,000 Pa (400 mbar).

Another object of the present invention is a suction/exhaust unit including a low vacuum pump including a plurality of suction/exhaust stages, the suction/exhaust unit comprising the above-mentioned Roots vacuum pump arranged in series with and upstream of the low vacuum pump. and the intake/exhaust device for intake/exhaust gas from the oil sump is configured to cover the gas space of the oil sump of the vacuum pump, for example at the inlet of the intake/exhaust stage and/or at the intake/exhaust stage except the last intake/exhaust stage. At the outlet of the low vacuum pump, for example, an interstage passage of the low vacuum pump connecting the outlet of one stage and the inlet of the next stage is provided with a suction line that communicates with one of the suction and exhaust stages of the low vacuum pump. Then choose among several suction and exhaust stages with different suction and displacement volumes of the low vacuum pump. Depending on the selected intake and exhaust stages, in particular the required overpressure level in the oil sump relative to the intake and exhaust chambers, in order to reduce the impact on the performance of the vacuum pump and the risk of oil leakage into the intake and exhaust chambers. Intake and exhaust devices for inhaling and exhausting gas can be optimized. Thus, the intake and exhaust devices for extracting gas from the oil sump are "tunable" depending on the selected intake and exhaust stages.

The suction and exhaust lines, for example, communicate the gas space of the oil sump with the outlet of the second suction and exhaust stage of the low vacuum pump.

FIG. 2 is a schematic diagram showing an example of an intake/exhaust unit. FIG. 2 is an enlarged detailed view of the vacuum pump of the suction/exhaust unit shown in FIG. 1; It is a graph showing a curve of pressure (unit: mbar) against time (unit: hr) in an application where a fixed amount of gas is periodically pumped and pumped, - the pressure on the suction side or upstream side of the vacuum pump (curve A); - the inlet pressure of the oil sump of the first vacuum pump of the prior art varying in accordance with curve A (curve B); - the inlet pressure of the oil sump of the second vacuum pump of the prior art varying in accordance with curve A (curve C); ), and - the inlet pressure of the oil sump of the vacuum pump according to the invention (curve D) varying according to curve A.

Further advantages and features will become apparent from reading the specification of the invention and studying the accompanying drawings.

In these figures, the same elements are given the same reference numerals. The diagram has been simplified for ease of understanding.

The following embodiment is an example. References herein to one or more embodiments do not necessarily imply that each reference is referring to the same embodiment or that the features apply to only one single embodiment. isn't it. Simple features of the various embodiments may also be combined or interchanged to provide other embodiments.

"Upstream" means a component located in front of other components with respect to the circulation direction of the gas being taken in and exhausted. In contrast, "downstream" refers to components arranged one after the other with respect to the direction of circulation of the gas being pumped and pumped.

The invention applies to any type of dry vacuum pump, ie a vacuum pump with one or at least two suction and exhaust stages, for example from 1 to 10 suction and exhaust stages. This vacuum pump may be a low vacuum pump 100 that is equipped with a plurality of suction/exhaust stages and exhausts sucked and exhausted gas at atmospheric pressure, or a dry vacuum pump 1 called a Roots pump or Roots compressor. can. The dry vacuum pump 1 has 1 to 3 suction and exhaust stages, and during use is connected in series upstream of the low vacuum pump, the exhaust pressure of which is obtained by the low vacuum pump.

FIG. 1 shows an example of an intake/exhaust unit 101 including a Roots vacuum pump 1 and a low vacuum pump 100. The inlet 2 of the Roots vacuum pump 1 is adapted to be connected to a closed chamber which is pumped and evacuated 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, where the outlet 5 is at atmospheric pressure or higher.

The Roots vacuum pump 1 or the low vacuum pump 100 has at least one oil sump 6, an intake/exhaust chamber comprising at least one intake/exhaust stage T1 to T5, and two rotary shafts 7 (two shafts of the intake/exhaust unit 101 in FIG. 1). (only one shown for each of the three vacuum pumps) and at least one seal for sealing the lubricant interposed between the oil sump 6 and the intake and exhaust stages of each passage through which the rotating shaft 7 passes. A device 8 is provided.

In the exemplary embodiment, the Roots vacuum pump 1 comprises a single suction and exhaust stage T1.

The low vacuum pump 100 comprises several suction and exhaust stages T1 to T5, for example five stages, mounted in series between the inlet 4 and the outlet 5. The intake and exhaust stages T1, T5 next to the sealing device 8 are in this example the first and last intake and exhaust stages.

Each intake and exhaust stage T1-T5 has a respective inlet and outlet. If the vacuum pump 1, 100 comprises several suction and exhaust stages, successive suction and exhaust stages are connected in series one after the other by respective interstage passages connecting the outlet of the previous suction and exhaust stage to the inlet of the next stage. be done. The suction/exhaust volumes of the suction/exhaust stages T1-T5 decrease or become equal depending on the position between the inlet and the outlet of the vacuum pump, such that the flow rate produced by the first suction/exhaust stage T1 with the lowest pressure is the highest suction/exhaust volume. corresponds to the quantity.

The rotating shaft 7 drives the rotation of the rotor 9 in the suction/exhaust stages T1 to T5, and transports the gas to be sucked and exhausted from the inlet to the outlet of the vacuum pump 1, 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.

During rotation of the rotor 9, gas sucked 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, for example of the "roots" type (figure 8 or kidney bean-shaped cross section) or the "claw" type, or is of the screw type. or other similar positive displacement vacuum pump principles.

Rotation of a rotating shaft 7 supporting a rotor 9 is guided by a bearing lubricated by a lubricant contained in an oil sump 6. A lubricant such as oil or grease makes it possible in particular to lubricate the ball bearing 10 and the gear 11 which serves to synchronize the shaft.

The vacuum pump 1, 100 includes, for example, two oil sump 6s arranged one on each side of at least one suction/exhaust stage, and a suction pump in each passage through which a shaft passes on both sides of the oil sump 6 and the suction/exhaust stage. A sealing device 8 is provided for sealing the lubricant interposed between the exhaust stage and the exhaust stage.

The sealing device 8 can be, for example, a "dynamic" seal, i.e. a segment seal, a labyrinth seal or a non-frictional seal such as a baffle or a "curtain" of gas, or a friction annular seal such as a lip seal, or a combination of such embodiments. At least one annular seal may be provided. This annular seal forms a very low conductance around the rotating shaft 7, thereby significantly reducing the passage of lubricating fluid from the oil sump 6 to the dry intake and exhaust stages and vice versa, while at the same time the shaft 7 rotation. The sealing device 8 may also comprise a deflector disc in the general shape of a disc mounted on the rotary shaft 7 for rotation therewith. The centrifugal force generated by the high speed rotation of the deflector disc prevents oil from entering the annular seal. An oil recovery passage can be formed in the lower part of the stator, which is arranged opposite to the deflector disk of each rotating shaft, and which returns the discharged lubricant towards the oil sump 6.

The vacuum pump 1 , 100 includes at least one injection device 12 for injecting purge gas into the oil sump, adapted to inject purge gas into the oil sump 6 , and at least one injection device 12 for injecting purge gas into the oil sump 6 and at the same time injecting purge gas into the oil sump 6 . It further comprises at least one intake/exhaust device 13 for intake/exhaust gas from the oil sump, such as for intake/exhaust gas from the oil sump.

By injecting the purge gas, it is possible, on the one hand, to dilute the gas present in the oil sump 6 to be sucked and exhausted. This reduces the partial pressure of the reactive gas species and, on the other hand, increases the pressure in the oil sump 6 and reduces the pressure difference that causes leakage into the oil sump 6. The intake and exhaust of gas from the oil sump 6 makes it possible, on the one hand, to avoid excessive overpressure on the intake and exhaust chambers, which could lead to excessive leakage into the intake and exhaust chambers, and on the other hand, the oil sump The gas contained within 6 can be circulated. By preventing gas from accumulating in the oil sump 6, the likelihood that the gas will react with and degrade the lubricant is reduced. Since it is difficult to provide a perfect fluid-tight seal, the present invention proposes to dilute and simultaneously remove the gases being pumped and pumped out before they contaminate the lubricant. The combination of dilution and intake/exhaust of the oil sump 6 makes it possible to reduce the risk of contamination of the lubricant in the oil sump 6.

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

The injection device 12 for injecting purge gas into the oil sump 6 may comprise a restriction 15 and a check valve 16 mounted in series on the injection line 14 .

The check valve 16 prevents gas in the oil sump 6 from entering 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. enable. The maximum injection amount of purge gas can be set by the throttle 15. Therefore, the throttle 15 and check valve 16 allow mechanical control of the flow of the injection gas and are simple and inexpensive to implement.

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

The intake/exhaust device 13 for intake/exhaust gas from the oil sump includes, for example, an intake/exhaust line 17 communicating with the gas space 20 of the oil sump 6 . When the lubricant contained in the oil sump 6 is a liquid, the inlet of the intake and exhaust line is located above the level of the liquid lubricant.

The intake and exhaust line 17 connects the gas space 20 of the oil sump 6, for example at the inlet of the intake and exhaust stage and/or at the outlet of the intake and exhaust stage except for the last stage, for example at the outlet of one intake and exhaust stage and the next. The interstage passage of the multistage vacuum pump connects the inlet of the suction and exhaust stage of the multistage vacuum pump to the suction and exhaust stage of the multistage vacuum pump. In this way, the intake/exhaust device 13 for intake/exhaust gas from the oil sump does not require an additional intake/exhaust device. Therefore, it is easy to implement, cheap, autonomous and compact.

In the case of the Roots vacuum pump 1, the suction and exhaust line 17 connects, for example, the gas space 20 of the oil sump 6 of the Roots vacuum pump 1 to the last of the low vacuum pumps 100 located in series with the Roots vacuum pump 1 and downstream thereof. It communicates with one outlet of the intake and exhaust stages T1 to T4, excluding the intake and exhaust stage T5 (FIG. 1). Next, a selection is made from among several suction and exhaust stages of the low vacuum pump 100 having different suction and displacement volumes. The selected intake and exhaust stage allows the intake and exhaust device 13 for intake and exhaust gas to be optimized depending on the desired level of overpressure in the oil sump 6. With regard to the adjacent intake/exhaust stage T1, consideration is given in particular to the influence on the performance of the vacuum pump and to suppressing the risk of oil leakage into the intake/exhaust chamber. The intake/exhaust device 13 for intake/exhaust gas from the oil sump is therefore "adjustable" depending on the selected intake/exhaust stage. The intake/exhaust line 17 communicates, for example, the gas space 20 of the oil sump 6 with the outlet of the second intake/exhaust stage T2 of the low vacuum pump 100.

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

The intake/exhaust device 13 for intake/exhaust gas from the oil sump may include a check valve 16 and a throttle 15 attached in series to the intake/exhaust line 17 .

The check valve 16 allows the gas sucked and exhausted by the low vacuum pump 100 to pass through the suction and exhaust line 17 when the pressure difference between the suction and exhaust stage T2 and the suction and exhaust line 17 exceeds the rated pressure threshold of the check valve 16. It is possible to prevent it from entering. A restriction 15 (also known as a calibrated orifice or nozzle) allows the maximum intake and exhaust volume to be determined. Therefore, the throttle 15 and the check valve 16 mechanically control the flow of the intake and exhaust gas, and are easy and inexpensive to implement.

The maximum intake and exhaust amount is, for example, 10 slm (about 18 Pam ³ /s).

The intake/exhaust device 13 for intake/exhaust gas from the oil sump can also include an oil separator 18 arranged upstream of the intake/exhaust line 17 , for example a check valve 16 or a throttle 15 . The oil separator 18 is able to separate the oil from the gas so that no oil is pumped up from the oil sump 6 and therefore the oil sump 6 is not emptied of oil. Oil separator 18 includes a filter, such as a sintered stainless steel filter.

Another advantage of the intake/exhaust device 13 for intake/exhaust gas from an oil sump provided in this way is that the check valve 16 closes automatically as a result of an overpressure in the intake/exhaust stage T2. This is generally periodic as it is brought about by a cycle of intake and exhaust in a closed chamber evacuated by the intake and exhaust unit 1, which allows the gas to blow through the filter and drain the oil, allowing the filter to self-clean. It becomes possible. In this way, the filter is automatically regenerated periodically.

An intake/exhaust device 13 for intake/exhaust gas from the oil sump is arranged in the gas space 20 of the oil sump 6 at the entrance of the intake/exhaust line 17 in order to suppress the inflow of lubricant into the intake/exhaust line 17. A deflector 19 can further be provided.

One exemplary embodiment can be seen in the cross-sectional view of the oil sump stator in FIG. This figure shows that an oil separator 18 formed of a sintered stainless steel filter is placed in the intake and exhaust line 17. A deflector 19 is placed in front of the inlet of this same line 17. The deflector 19 here comprises a substantially L-shaped plate. The L-shaped vertical first portion of the deflector 19 is arranged at a distance from the inlet of the intake and exhaust line 17 to form a screen that prevents lubricant from entering the intake and exhaust line 17 head-on. It is arranged facing the entrance of line 17. 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 L-shaped second part of the deflector 19 projects from the stator wall so as to form a shelter for the entrance of the line 17 like a pouch.

A deflector of the same type can be placed in the oil sump 6 at the outlet of the injection line 14 to suppress the inflow of lubricant into the injection line 14 .

An advantage of the invention is in the field of intake and exhaust applications required for photovoltaic panels. Figure 3 shows pressure curves in the oil sump of different vacuum pumps for applications that periodically intake and exhaust large amounts of gas at atmospheric pressure. can be better understood by referring to the graph.

Curve A shows an example of a pressure change on the suction side or upstream side of the Roots vacuum pump 1 of the suction/exhaust unit. Large periodic fluctuations in pressure can be seen between atmospheric pressures of 1,000 mbar (100,000 Pa) and 5 mbar (500 Pa).

Curve B shows the change in pressure in the oil sump of the first Roots vacuum pump of the prior art intake and exhaust unit. No purge gas is injected, no gas is taken in or taken out from the oil sump, and the pressure at or upstream of the inlet varies according to curve A. It can be seen that every time the upstream isolation valve of the suction and exhaust unit opens, the suctioned and exhausted gas suddenly flows into the vacuum pump, increasing the pressure in the oil sump. The pressure increases rapidly to 100 mbar (10,000 Pa) and then decreases over several tens of minutes to about 5 mbar (500 Pa), and this cycle is repeated every 40 minutes. The periodic pressure increase in the oil sump is caused by the flow of intake and exhaust gases from the intake and exhaust chambers through the sealing device and into the oil sump. This increases the risk of contamination of the oil sump lubricant.

Curve C shows the pressure in the oil sump of the second vacuum pump of the prior art intake and exhaust unit, with the pressure at or upstream of the intake varying in accordance with curve A. The purge gas is injected into the oil sump under overpressure relative to atmospheric pressure, without being simultaneously pumped in and out. This overpressure is on the order of 2 bar (200,000 Pa). In this case, the vacuum pump becomes less susceptible to the "intake and exhaust" of the oil sump. Additionally, gas leakage is directed from the oil sump to the intake and exhaust chambers, thereby reducing the risk of contamination of the lubricant by exhaust gases or particles originating from the intake and exhaust chambers. However, this overpressure causes significant leakage of purge gas from the oil sump toward the intake and exhaust chambers. This risks lubricant getting into the intake and exhaust chambers, affecting the lubrication of the bearings and contaminating the intake and exhaust chambers.

Curve D shows the variation of the pressure in the oil sump 6 of the Roots vacuum pump 1 according to the invention, as the pressure at or upstream of the inlet varies according to curve A. An injection device 12 for injecting purge gas into the oil sump and an intake/exhaust device 13 for intake/exhaust gas from the oil sump keep the pressure in the oil sump 6 below atmospheric pressure, in this example 5,000 Pa (50 mbar). ) and 40,000 Pa (400 mbar). It can be seen that the pressure fluctuations within the oil sump 6 are significantly attenuated. They vary around approximately 100 mbar (10,000 Pa), placing the oil sump 6 at a slight overpressure with respect to the intake and exhaust chambers. Thereby, the risk of oil leaking into the intake and exhaust chambers can be suppressed, and the influence on intake and exhaust performance can be suppressed.

FIG. 1 shows, for only one of the two oil sumps 6, an injection device 12 for injecting purge gas into the oil sump, and an intake/exhaust device 13 for intake/exhaust gas from the oil sump. However, 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 and exhaust devices 13 for intake and exhaust gas from the oil sump 6 of the Roots vacuum pump 1, the risk of mutual contamination can be avoided.

Similarly, the invention can be applied with respect to one or both of the oil sump 6 of the low vacuum pump 100, regardless of whether the low vacuum pump 100 is connected downstream of the Roots vacuum pump 1. Between two intake/exhaust devices for intake/exhaust gas from the oil sump of the low vacuum pump 100, or between intake/exhaust devices for intake/exhaust gas from the oil sump of the Roots vacuum pump 1 and the low vacuum pump 100. , it is also possible to have no fluid communication.

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 Rotating shaft 8 Seal device 9 Rotor 10 Ball bearing 11 Gear 12 Injection device 13 Suction/exhaust device 14 Injection line 15 Restriction 16 Check valve 17 Suction/exhaust line 18 Oil separator 19 Deflector 20 Gas space 100 Low vacuum pump 101 Suction Exhaust unit T1-T5 Suction/exhaust stage M1 Motor (low vacuum pump)
M2 motor (Roots vacuum pump)

Claims (10)

The dry vacuum pump type vacuum pump (1, 100) is
- at least one oil sump (6);
- at least one intake and exhaust stage (T1, T1 to T5);
- rotation is induced in a bearing lubricated by a lubricant contained in said oil sump (6) and between the inlet (2, 4) and outlet (3, 5) of said vacuum pump (1, 100); two rotating shafts (7) adapted to drive rotation of a rotor (9) in the intake and exhaust stages (T1, T1 to T5);
- at least one lubricant sealing device (8) interposed between said oil sump (6) and said intake and exhaust stages (T1, T1-T5) in each shaft passage;
Said vacuum pump (1, 100) comprises at least one injection device (12) for injecting purge gas into said oil sump, adapted to inject purge gas into said oil sump (6); (6) at least one intake/exhaust device (13) adapted to intake/exhaust gas from the oil sump (6), the device (13) configured to intake/exhaust gas from the oil sump (6); A vacuum pump (1, 100) characterized in that the vacuum pump (1, 100) is configured to inject oil into the oil sump (6) and at the same time take in and exhaust air from the oil sump (6). The injection device (12) for injecting purge gas into the oil sump is mounted in series with the injection line (14) opening into the gas space (20) of the oil sump (6). The vacuum pump (1, 100) according to claim 1, characterized in that it comprises a restrictor (15) and a check valve (16). The intake/exhaust device (13) for intake/exhaust the gas from the oil sump includes an intake/exhaust line (17) communicating with the gas space (20) of the oil sump (6), and an intake/exhaust line (17) that communicates with the gas space (20) of the oil sump (6). ) A vacuum pump (1, 100) according to claim 1 or 2, characterized in that it comprises a check valve (16) and a throttle (15) attached in series to the vacuum pump (1, 100). The intake/exhaust device (13) for intake/exhaust the gas from the oil sump includes an intake/exhaust line (17) communicating with the gas space (20) of the oil sump (6), and an intake/exhaust line (17) that communicates with the gas space (20) of the oil sump (6). ) a deflector (19) arranged in the oil sump (6) at the inlet of the intake and exhaust line (17) to suppress the inflow of lubricant into the oil sump (6). 3. The vacuum pump (1, 100) according to any one of 3. 5. The intake/exhaust device (13) for intake/exhaust the gas from the oil sump comprises an oil separator (18) arranged in the intake/exhaust line (17). Vacuum pump (1) as described. The vacuum pump (1, 100) comprises two oil sump (6), one oil sump (6) arranged on each side of at least one suction/exhaust stage (T1, T1-T5), The pump (1, 100) includes, for each oil sump (6), an injection device (12) for injecting purge gas into the oil sump, and an intake/exhaust device for intake/exhaust the gas from the oil sump. (13), wherein no fluid communication is provided between the intake/exhaust device (13) for intake/exhaust the gas from the oil sump. Vacuum pump as described (1, 100). The intake/exhaust device (13) for intake/exhaust the gas from the oil sump includes an intake/exhaust line (17) that communicates the gas space (20) of the oil sump (6) with an intake/exhaust stage of a multistage vacuum pump. Vacuum pump (1) according to any one of claims 1 to 6, characterized in that it comprises: The injection device (12) for injecting purge gas into the oil sump and the intake/exhaust device (13) for intake/exhaust the gas from the oil sump reduce the pressure in the oil sump (6) to atmospheric pressure. Vacuum pump (1) according to any of the preceding claims, characterized in that it is adapted to control a lower pressure, for example a pressure lower than 50,000 Pa. A suction/exhaust unit (101) comprising a low vacuum pump (100) having a plurality of suction/exhaust stages (T1 to T5), the suction/exhaust unit (101) being connected in series with the low vacuum pump (100) and The intake/exhaust device for intake/exhaust the gas from the oil sump, comprising the vacuum pump (1) according to any one of claims 1 to 8, disposed upstream of the low vacuum pump (100). (13) is an intake/exhaust line (17) that communicates the gas space (20) of the oil sump (6) of the vacuum pump (1) with one of the intake/exhaust stages (T1 to T5) of the low vacuum pump (100). An intake/exhaust unit (101). 9. The intake/exhaust line (17) communicates the gas space of the oil sump (6) with the outlet of the second intake/exhaust stage (T2) of the low vacuum pump (100). The intake and exhaust unit (101) described.

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