Dry vacuum pump

Abstract

Dry vacuum pump (1) comprising a cooling device (10) configured to cool the stator (2), the cooling device (10) comprising a fluid circuit (11) and at least one flow regulator (12) arranged in a regulating duct (15) of the fluid circuit (11), the flow regulator (12) comprising an orifice plate (17) traversed by an orifice (26), and a flexible membrane (20) having a central opening (14) smaller than said orifice (26), the flexible membrane (20) being positioned upstream of the orifice plate (17) in the direction of flow of the cooling fluid (f2). Abstract figure: figure 1

Description

Title of the invention: Dry vacuum pump Technical field of the invention

[0001] The present invention relates to a dry vacuum pump. Technical background

[0002] Dry type vacuum pumps comprise one or more pumping stages in series in which a gas to be pumped circulates between a suction and a discharge. Among the known vacuum pumps, a distinction is made between those with rotary lobes, also known as "Roots" with two or more lobes, or those with a claw, also known as "Claw" or even those with screws.

[0003] These vacuum pumps are called "dry" because in operation, the rotors turn inside the stator without any mechanical contact between them or with the stator, which makes it possible not to use oil in the pumping stage(s).

[0004] In operation, the compression of the gases causes significant heating of the vacuum pump. This rise in temperature makes it possible to avoid condensation or solidification into powder of polluting gaseous species inside the vacuum pump. However, in certain applications, the temperature of the stator must be controlled so as not to exceed a predefined maximum beyond which the pumped gaseous species could agglomerate in the pump and cause it to seize. It may also be necessary to cool the bearings or the motor of the vacuum pumps to avoid any malfunction.

[0005] In current vacuum pumps, cooling is generally achieved by circulating water in aluminum blocks in thermal contact with the stator. It is also possible to differentiate the temperature of specific locations in the pump by using several branches in which different water flow rates circulate. The cooling circuit thus generally comprises two to four branches distributing the water to different specific points in the vacuum pump, for example in the pump body at a first temperature and in the bearings at both ends of the vacuum pump at a second temperature.

[0006] The flow rates in each branch are generally set by means of nozzles whose conductance is chosen so as to obtain the desired cooling. However, this assumes a water supply pressure, upstream of all the branches of the circuit, which is constant. Indeed, the flow rate of water through a nozzle is proportional to the pressure prevailing upstream of the nozzle. However, this may not be the same at all times, for example due to the simultaneous use of the water network for different applications. This results in a certain uncertainty on the flow rates circulating actually in the vacuum pump cooling circuit.

[0007] Also, in this type of installation, the distribution of the flow rate in the different branches is generally only measured when the vacuum pump is first put into service. This distribution may, however, change over time and no longer correspond to the initial specifications after a certain period of use. In addition, the distribution of the flow rates may not be strictly the same from one vacuum pump to another depending on the geometric tolerances of the conductances and the water circuit.

[0008] From all this results that the vacuum pump may not be continuously correctly cooled.

[0009] It is possible to oversize the water supply flow rate, but this solution is not economical. Another solution may be to provide regulating valves and temperature sensors or flow meters to control the different water flow rates. However, this other solution is also expensive and is also bulky. Summary of the invention

[0010] One of the aims of the present invention is to propose a dry vacuum pump which at least partially resolves a drawback of the state of the art.

[0011] For this purpose, the invention relates to a dry vacuum pump comprising a stator, at least two rotors configured to rotate in the stator and a cooling device configured to cool the stator, the cooling device comprising a fluid circuit and at least one flow regulator arranged in a regulation conduit of the fluid circuit, characterized in that: - the regulating duct has at least a first duct and a second duct with a smaller section than the first duct, - the flow regulator comprises an orifice plate having an orifice therethrough, and a flexible membrane having a central opening smaller than said orifice, the orifice plate and the flexible membrane being positioned in the first conduit, the flexible membrane being positioned upstream of the orifice plate in the direction of flow of the cooling fluid, said flexible membrane being deflectable towards said orifice plate in response to a pressure differential across said flexible membrane between a position of maximum deflection, in which said flexible membrane abuts against said orifice plate, closing circumferential orifices of the flexible membrane, the flow of fluid being restricted by said central opening, and positions in which said flexible membrane is spaced from said orifice plate, thereby allowing the flow of fluid through said circumferential orifices,so as to maintain a constant flow rate of the fluid downstream of the orifice plate.

[0012] In operation, a decrease in differential pressure causes the openings to widen and an increase in differential pressure causes the dimensions of these same openings to reduce, which allows the flow rate to be stabilized automatically. The structure is simple and reliable because there are no wearing parts. It is compact and energy-saving because it is a mechanical solution, without a power supply. In addition, assembly is simple.

[0013] The dry vacuum pump may further comprise one or more of the features described below, taken alone or in combination.

[0014] The flexible membrane comprises, for example, at least one elastic blade in the shape of a star, such as a four-pointed star.

[0015] The flexible membrane may comprise two elastic blades mounted crosswise and fixed to each other in the circumferential zone of the central opening.

[0016] The orifice plate may have a recessed portion (set back from the flexible membrane), conical.

[0017] The fluid circuit comprises, for example, a common conduit connected to several bypass branches, each configured to cool a separate element of the stator, such as a bearing support, a motorization part or a pumping stage stator.

[0018] The common conduit is intended to be connected to a fluid supply.

[0019] The branch conduits may be at least partially internal or external to the stator elements. They are for example arranged inside the stator elements or in respective conductive blocks, for example metallic, such as aluminum, in thermal contact with a respective stator element.

[0020] The fluid is for example a liquid, such as liquid water, for example at room temperature.

[0021] At least one regulating conduit may be arranged in a common conduit connected to at least two branches of the bypass fluid circuit, each configured to cool a separate element of the stator.

[0022] At least one regulating conduit can be arranged in a branch of the fluid circuit configured to cool an element of the stator. A sufficient water flow rate can then be ensured permanently to cool the branch of the fluid circuit without influence of variations in fluid supply pressure. Furthermore, with this solution, minimal cooling can be ensured on one branch, which makes it possible to have more fluid available to promote cooling by the other branches of the fluid circuit.

[0023] The fluid circuit comprises, for example, several branches respectively configured to cool a separate element of the stator, the cooling device comprising a regulation conduit arranged in at least two of said branches. distribution of water flow rates in the branches cooling the stator elements can thus be ensured without influence from variations in fluid supply pressure.

[0024] At least two flow regulators arranged in the separate control conduits may be configured to deliver respective separate constant flow rates.

[0025] An element of the stator to be cooled may be a bearing support, a pumping stage stator or a motorization part of the vacuum pump.

[0026] The at least one regulation duct is for example arranged in a connection block of the cooling device, the at least one first duct being open to the outside of the connection block.

[0027] When the cooling device comprises several regulating conduits, it may be particularly advantageous to provide that the regulating conduits are arranged in a connection block of the cooling device, the first conduits being open to the outside of the connection block. This facilitates the assembly of the flow regulators in the first conduits and reduces the size of the fluid circuit.

[0028] The connector block includes for example: - at least one regulating conduit arranged in a common conduit of the fluid circuit into which the fluid is intended to enter, and - at least two regulating conduits arranged in respective branches of the fluid circuit in which the fluid is intended to exit, the common conduit being connected to said branches by pipes provided in said connection block.

[0029] This embodiment is particularly compact because it does not require fluid connections between the different regulation conduits.

[0030] An annular groove may be provided in the first conduit of a regulating conduit to receive a circlip of the cooling device to clamp the outer edges of the flow regulator.

[0031] A threaded portion may be provided in the first conduit of a regulating conduit and receives a threaded ring of the cooling device, for clamping the outer edges of the flow regulator. Brief description of the figures

[0032] Other advantages and characteristics will appear on reading the following description of a particular embodiment of the invention, but in no way limiting, as well as the appended drawings in which:

[0033] [Fig-1] [Fig.l] is a schematic representation of a vacuum pump according to a first example of realization.

[0034] [Fig.2] [Fig.2] shows a schematic front view of a flow regulator arranged in a regulating duct of a cooling device of the vacuum pump of [Fig.l].

[0035] [Fig.3] [Fig.3] shows a side and sectional view of the elements of [Fig.2].

[0036] [Fig.4] [Fig.4] is a graph showing the output flow rate for a regulator of flow rate (curve A) and for a prior art regulating valve (curve B) as a function of the fluid supply pressure.

[0037] [Fig.5] [Fig.5] shows a diagram similar to [Fig.3] for a first embodiment variant.

[0038] [Fig.6] [Fig.6] shows a diagram similar to [Fig.3] for a second embodiment variant.

[0039] [Fig.7] [Fig.7] is a schematic representation of a vacuum pump according to a second example of realization.

[0040] [Fig.8] [Fig.8] is a schematic representation of a vacuum pump according to a third exemplary embodiment.

[0041] [Fig.9] [Fig.9] is a schematic representation of a connector block of the cooling device.

[0042] In these figures, identical elements have the same reference numbers. Detailed description

[0043] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments.

[0044] The term "upstream" means an element which is placed before another with respect to the direction of circulation of the pumped gases F1 or with respect to the direction of flow of the cooling fluid, such as water f2. Conversely, the term "downstream" means an element placed after another with respect to the direction of circulation of the pumped gases F1 or with respect to the direction of flow of the cooling fluid f2.

[0045] The invention applies to any type of dry vacuum pump 1 comprising a stator 2 and at least two rotors configured to rotate in the stator 2. The invention applies to any type of dry vacuum pump, single-stage or multi-stage, that is to say comprising one or more stages, such as comprising one to ten pumping stages. This vacuum pump may be a multi-stage primary vacuum pump configured to discharge the pumped gases at atmospheric pressure or a dry vacuum pump with one to three pumping stages which, in use, is connected upstream of a primary vacuum pump and whose discharge pressure is that obtained by the primary vacuum pump.

[0046] [Fig.l] shows a first example of a dry vacuum pump 1.

[0047] The vacuum pump 1 comprises at least one pumping stage, such as for example several pumping stages T1-T5, mounted in series between a suction port 4 and a discharge port 5.

[0048] The vacuum pump 1 also comprises two shafts parallel to the axial direction, configured to rotate the rotors in respective compression chambers of the pumping stages T1-T5 around a respective axis of rotation. The shafts are configured to be rotated by at least one motor in a motorization part 3 of the vacuum pump 1 ([Fig.l]).

[0049] During rotation, the gas sucked from the inlet of the compression chamber is trapped in the volume generated by the rotors and the pumping stage stator, then is driven by the rotors towards the outlet and then towards the next stage. The arrows Fl in [Fig.l] show the direction of circulation of the gases to be pumped.

[0050] The successive pumping stages T1-T5 are connected in series one after the other by respective inter-stage channels connecting the output of the preceding pumping stage to the input of the following pumping stage.

[0051] The inlet of the first pumping stage T1 communicates with the suction port 4 of the vacuum pump 1. The outlet of the last pumping stage T5 communicates with the discharge port 5 via an outlet pipe.

[0052] The axial and / or radial dimensions and flow rates generated by the pumping stages T1-T5 are decreasing or equal with the order of arrangement of the pumping stages, the pumping stage T1 located on the side of the suction orifice 4 having the largest axial or radial dimension, generating the greatest pumping flow rate.

[0053] The vacuum pump 1 may further comprise a non-return valve 6 and a silencer 7 arranged in series upstream of the discharge orifice 5 in the outlet pipe. The silencer 7 may be mounted in series and upstream of the non-return valve 6 of the vacuum pump 1, at the outlet of the last compression chamber.

[0054] The vacuum pump 1 also comprises rotor synchronization gears and bearings lubricated by a lubricant, such as oil or grease, contained in at least one oil sump of the vacuum pump 1. The stator 2 comprises, for example, a bearing support 8 at each end of the vacuum pump 1. A lubricant-sealing device is interposed between the bearing supports 8 and the dry pumping part in which the gases circulate. The sealing device allows the shafts to rotate in the dry pumping part while limiting the transfer of lubricants. The at least one pumping stage stator, the at least one bearing support 8 and the motorization part 3 form different elements of the stator 2 of the vacuum pump 1.

[0055] These vacuum pumps are called “dry” because in operation, the rotors turn inside the stator 2 without any mechanical contact between them or with the stator 2, this which allows no oil to be used in the pumping stage(s) T1-T5.

[0056] The vacuum pump 1 also comprises a cooling device 10 configured to cool the stator 2. The cooling device 10 comprises a fluid circuit 11 and at least one flow regulator 12 arranged in a regulation conduit 15 of the fluid circuit 11 to regulate the fluid flow rate.

[0057] The fluid circuit 11 comprises, for example, a common conduit 18 connected to several branches 18a, 18b, 18c in bypass, each configured to cool a separate element of the stator 2, such as a bearing support 8, a motorization part 3 or a pumping stage stator.

[0058] The common conduit 18 is intended to be connected to a fluid supply.

[0059] The pipes of the branches 18a, 18b, 18c may be at least partially internal or external to the stator elements 2. They are for example arranged inside the stator elements 2 or in respective conductive blocks, for example metallic, such as aluminum, in thermal contact with a respective stator element 2.

[0060] The fluid is for example a liquid, such as liquid water, for example at room temperature.

[0061] According to a first exemplary embodiment shown in [Fig.l], the regulation conduit 15 is arranged in a common conduit 18 of the fluid circuit 11, said common conduit 18 being connected to at least two branches 18a, 18b, 18c of the fluid circuit 11 in bypass.

[0062] As can be seen in Figures 2 and 3, the regulating duct 15 has at least a first duct 15a and a second duct 15b of smaller section than the first duct 15a. The first and second ducts 15a, 15b are for example cylindrical.

[0063] The regulating conduit 15 is located upstream of the element to be cooled in the direction of flow of the fluid f2 in order to deliver the desired flow rate of fluid to cool said element.

[0064] The flow regulator 12 comprises an orifice plate 17 and a flexible membrane 20 ([Fig.3]). The orifice plate 17 and the flexible membrane 20 are for example metallic, such as stainless steel.

[0065] The orifice plate 17 is positioned inside the first conduit 15a, here being adjacent to the second conduit 15b. The orifice plate 17 is crossed by an orifice 26. The diameter of the orifice 26 corresponds for example substantially to the diameter of the second conduit 15b. The orifice plate 17 has for example a recessed portion (recessed relative to the flexible membrane 20), in which the orifice 26 is formed, for example conical, the conical recessed portion being here adjacent to the outlet conduit 15b.

[0066] The flexible membrane 20 is positioned inside the first conduit 15a, upstream of the orifice plate 17 in the direction of flow of the cooling fluid f2. The flexible membrane 20 has a central opening 14 of smaller dimension than the orifice 26 of the orifice plate 17 ([Fig.2]).

[0067] The flexible membrane 20 comprises at least one elastic blade 13a, 13b. Circumferential openings 16 are formed between the adjacent branches of the elastic blade 13a, 13b and the first conduit 15a.

[0068] According to an exemplary embodiment visible in [Fig.2], the elastic blade 13a, 13b has a star shape, such as a four-pointed star, the branches of the four-pointed star being spaced 90° apart from each other. The branches have, for example, triangular or trapezoidal shapes.

[0069] According to an exemplary embodiment, the flexible membrane 20 comprises several elastic blades 13a, 13b arranged one above the other, such as for example two elastic blades 13a, 13b mounted crosswise and fixed, for example riveted, to each other in the circumferential zone of the central opening 14. The two elastic blades 13a, 13b have for example a respective star shape. The two elastic blades 13a, 13b are for example offset by 45° from each other.

[0070] The cooling device 10 may comprise several flow regulators 12 arranged in the same regulation conduit 15 of the fluid circuit 11 to regulate the fluid flow rate, the regulation conduit 15 then comprising several first conduits 15a and second conduits 15b.

[0071] Furthermore, other embodiments of the flexible membrane 20 are possible, for example as described in document US4708166A.

[0072] In this first embodiment, the fluid enters the first conduit 15a and exits through the second conduit 15b. The orifice plate 17 is interposed between the flexible membrane 20 and the second conduit 15b.

[0073] According to an exemplary embodiment visible in [Fig. 3], the regulation conduit 15 is arranged in a connection block 19 of the cooling device 10, for example metallic, such as aluminum. The first conduit 15a, of larger diameter, is open to the outside of the connection block 19. A pipe, for example flexible, fluidically connects the first conduit 15a to the branches 18a, 18b, 18c of the fluid circuit 11 in order to deliver the fluid into the branches 18a, 18b, 18c to cool the stator elements 2.

[0074] An annular groove 21 may be provided in the first conduit 15a to receive a circlip 22 of the cooling device 10 in order to clamp the outer edges of the flow regulator 12, and more precisely the flexible membrane 20, thus locking the flexible membrane 20 and the orifice plate 17 in the first conduit 15.

[0075] Assembly is therefore made easier and requires neither fittings nor sealing glue, which reduces assembly time and costs.

[0076] The flexible membrane 20 is deflectable toward the orifice plate 17 in response to a pressure differential across the flexible membrane 20 between a position of maximum deflection, in which said flexible membrane 20 abuts against said orifice plate 17, closing the circumferential orifices 16 of the flexible membrane 20, the flow of fluid then being restricted by said central opening 14, and positions in which said flexible membrane 20 is spaced from said orifice plate 17, thereby allowing the flow of fluid through said circumferential orifices 16, so as to maintain a constant rate of flow of fluid downstream of the orifice plate 17.

[0077] Consequently, in operation, a decrease in differential pressure causes the openings 16 to widen and an increase in differential pressure causes the dimensions of these same openings 16 to reduce, which makes it possible to stabilize the flow rate automatically.

[0078] [Fig.4] shows an example of the output flow rate obtained for a flow regulator 12 (curve A) and for a prior art regulating valve (curve B) as a function of the fluid supply pressure.

[0079] In the system of the prior art, the flow rate of water through a nozzle is proportional to the pressure prevailing upstream of the nozzle (curve B). This results in the flow rate of water in the vacuum pump 1 not being controlled if the supply pressure varies.

[0080] On the other hand, for curve A of a flow regulator 12, it is noted that beyond a minimum fluid supply pressure, for example greater than 2 bar (2.105 Pa), the flow regulator 12 ensures an almost constant flow at the outlet.

[0081] The flow rate through the flow regulator 12 is determined by the pressure difference across the flow regulator as well as the dimensions of the circumferential orifices 16 and the central opening 14.

[0082] The structure is simple and reliable because there are no wearing parts. It is compact and energy-saving because it is a mechanical solution, without electrical power supply. In addition, assembly is simple.

[0083] [Fig.5] shows another example of the assembly of the flow regulator 12 in the regulation conduit 15.

[0084] In the illustrated example, the fluid is intended to enter the second conduit 15b and to exit through the first conduit 15a. The flexible membrane 20 is interposed between the orifice plate 17 and the second conduit 15b. The orifice plate 17 has a recessed portion (relative to the flexible membrane 20), conical.

[0085] A threaded portion 24 is provided in the first conduit 15a and receives a threaded ring 25 of the cooling device 10, to tighten the outer edges of the re flow regulator 12, here of the recessed part of the orifice plate 17 in which the orifice 26 is formed, thus blocking the flexible membrane 20 and the orifice plate 17 in the first conduit 15.

[0086] The assembly is simple and the fluid connection is easy to make.

[0087] This embodiment can also be implemented for the case where the fluid is intended to enter the first conduit 15a and to exit in the second conduit 15b ([Fig.6]).

[0088] In this case, the flow regulator 12 is mounted in the opposite direction in the first conduit 15a. The orifice plate 17 is interposed between the flexible membrane 20 and the second conduit 15b. The conically recessed portion of the orifice plate 17 is adjacent to the second conduit 15b.

[0089] The threaded portion 24 is provided in the first conduit 15a and receives a threaded ring 25 of the cooling device 10, to tighten the outer edges of the flow regulator 12, here of the flexible membrane 20, thus blocking the flexible membrane 20 and the orifice plate 17 in the first conduit 15.

[0090] [Fig.7] shows another exemplary embodiment for which the regulating conduit 15 is arranged in a branch 18c of the fluid circuit 11 configured to cool an element of the stator 2, such as a bearing support 8 or a pumping stage stator or the motorization part 3, here the motorization part 3. The other branches of the fluid circuit 11 may comprise a nozzle or a regulating valve 23 or not comprise a particular flow control element.

[0091] A sufficient water flow rate can then be ensured permanently to cool the motorization part 3 in the branch 18c of the fluid circuit 11, without influence from variations in fluid supply pressure.

[0092] The same result can be obtained by ensuring the temperature regulation of a bearing support 8 or a pumping stage stator.

[0093] Furthermore, with this solution it is possible to ensure minimal cooling on a branch 18c, which makes it possible to have more fluid available to promote cooling by the other branches 18a, 18b of the fluid circuit 11.

[0094] [Fig.8] shows another example of embodiment.

[0095] In this example, the cooling device 10 comprises a regulation conduit 15 arranged in at least two of the branches 18a, 18b, 18c, such as in each of the branches 18a, 18b, 18c of the fluid circuit 11.

[0096] The flow regulators 12 arranged in the regulating conduits 15 can be configured to deliver respective distinct constant flow rates.

[0097] The distribution of the water flow rates in the branches 18a, 18b, 18c cooling the stator elements 2 can thus be ensured without influence of variations in fluid supply pressure.

[0098] When the cooling device 10 comprises several regulation conduits 15, it may be particularly advantageous to provide that the regulation conduits 15 are arranged in a connection block 19 of the cooling device 10 ([Fig.9]), the first conduits 15a being open to the outside of the connection block 19. This facilitates the assembly of the flow regulators 12 in the first conduits 15 and reduces the size of the fluid circuit 11.

[0099] This is the case for example when the fluid circuit 11 comprises several branches 18a, 18b, 18c of which at least two are respectively provided with regulation conduits 15 for cooling an element of the respective stator 2 and / or when the cooling device 10 comprises a regulation conduit 15 arranged in the common conduit 18 and at least one regulation conduit 15 arranged in a branch 18a, 18b, 18c.

[0100] For example, the connection block 19 comprises at least one regulation conduit 15 arranged in the common conduit 18 into which the fluid is intended to enter and at least two regulation conduits 15 arranged in respective branches 18a, 18b, 18c into which the fluid is intended to exit ([Fig.9]).

[0101] The first conduit 15a of the regulating conduit 15 arranged in the common conduit 18 into which the fluid is intended to enter is open to the outside of the connection block 19. The at least two first conduits 15a of the regulating conduits 15 arranged in respective branches 18a, 18b, 18c into which the fluid is intended to exit are also open to the outside of the connection block 19.

[0102] Furthermore, the common conduit 18 is connected to the branches 18a, 18b, 18c by pipes also provided in said connection block 19. More precisely, these pipes connect the second conduit 15b of the regulation conduit 15 arranged in the common conduit 18 to the second conduits 15b of the regulation conduits 15 arranged in respective branches 18a, 18b, 18c.

[0103] Pipes, for example flexible, fluidically connect the first conduits 15a of the regulation conduits 15 to the pipes of the branches 18a, 18b, 18c in thermal contact with the respective stator elements 2 to be cooled.

[0104] The first conduit 15a of the regulating conduit 15 arranged in the common conduit 18 is intended to be connected to a source of fluid.

[0105] This embodiment using a connection block 19 is particularly compact because it does not require fluid connections between the different regulation conduits 15.

[0106] According to another example, the regulating conduits 15 arranged in respective branches 18a, 18b, 18c are directly produced, for example by machining, in the stator 2 of the vacuum pump 1, for example in the pumping stage stators.

[0107] The first conduits 15a of these regulation conduits 15, of larger diameter, are then open to the outside of the stator 2. The assembly of the flow regulators 12 can be directly produced in the stator 2. The second ducts 15b of these regulating ducts 15 are connected to pipes of the branches 18a, 18b, 18c in thermal contact with the respective stator elements 2 to be cooled, like internal channels of the stator 2.

[0108] Pipes, for example flexible, can fluidically connect the first conduits 15a of the regulating conduits 15 to a first conduit 15a of a regulating conduit 15 arranged in a common conduit 18.

Claims

1.

2.

3.

4. Claims Dry vacuum pump (1) comprising a stator (2), at least two rotors configured to rotate in the stator (2) and a cooling device (10) configured to cool the stator (2), the cooling device (10) comprising a fluid circuit (11) and at least one flow regulator (12) arranged in a regulation conduit (15) of the fluid circuit (11), characterized in that: - the regulating duct (15) has at least a first duct (15a) and a second duct (15b) of smaller section than the first duct (15a), - the flow regulator (12) comprises an orifice plate (17) traversed by an orifice (26), and a flexible membrane (20) having a central opening (14) smaller than said orifice (26), the orifice plate (17) and the flexible membrane (20) being positioned in the first conduit (15a), the flexible membrane (20) being positioned upstream of the orifice plate (17) in the direction of flow of the cooling fluid (f2), said flexible membrane (20) being able to be deflected towards said orifice plate (17) in response to a pressure differential on either side of said flexible membrane (20) between a position of maximum deflection, in which said flexible membrane (20) abuts against said orifice plate (17), closing circumferential orifices (16) of the flexible membrane (20), the flow of fluid being restricted by said central opening (14),and positions in which said flexible membrane (20) is spaced from said orifice plate (17), thereby allowing fluid flow through said circumferential orifices (16), so as to maintain a constant flow rate of the fluid downstream of the orifice plate (17), at least one regulating conduit (15) being arranged in a branch (18a, 18b, 18c) of the fluid circuit (11) configured to cool an element of the stator (2)., Vacuum pump (1) according to the preceding claim, characterized in that the flexible membrane (20) comprises at least one elastic blade (13a, 13b) in the shape of a star. Vacuum pump (1) according to the preceding claim, characterized in that the star has four branches. Vacuum pump (1) according to one of the preceding claims, characterized in that the flexible membrane (20) comprises two elastic blades (13a, 13b) mounted crosswise and fixed to each other in the circumferential area of the central opening (14).

5. Vacuum pump (1) according to one of the preceding claims, characterized in that the orifice plate (17) has a conical recessed portion.

6. Vacuum pump (1) according to one of the preceding claims, characterized in that at least one regulating duct (15) is arranged in a common duct (18) connected to at least two branches (18a, 18b, 18c) of the fluid circuit (11) in bypass, each configured to cool a separate element of the stator (2).

7. Vacuum pump (1) according to one of the preceding claims, characterized in that the fluid circuit (11) comprises several branches (18a, 18b, 18c) respectively configured to cool a separate element of the stator (2), the cooling device (10) comprising a regulating duct (15) arranged in at least two of said branches (18a, 18b, 18c).

8. Vacuum pump (1) according to the preceding claim, characterized in that at least two flow regulators (12) arranged in the separate regulating conduits (15) are configured to deliver respective separate constant flow rates.

9. Vacuum pump (1) according to one of claims 6 to 8, characterized in that an element of the stator (2) to be cooled is a bearing support (8), a pumping stage stator or a drive part (3) of the vacuum pump (1).

10. Vacuum pump (1) according to one of the preceding claims, characterized in that the at least one regulating duct (15) is arranged in a connection block (19) of the cooling device (10), the at least one first duct (15a) being open to the outside of the connection block (19).

11. Vacuum pump (1) according to the preceding claim, characterized in that the connection block (19) comprises: - at least one regulating conduit (15) arranged in a common conduit (18) of the fluid circuit (11) into which the fluid is intended to enter, and - at least two regulating conduits (15) arranged in respective branches (18a, 18b, 18c) of the fluid circuit (11) into which the fluid is intended to exit, the common conduit (18) being connected to said branches (18a, 18b, 18c) by pipes provided in said connection block (19).

12. Vacuum pump (1) according to one of the preceding claims, characterized in that an annular groove (21) is provided in the first duct (15a) of a regulating duct (15) for receiving a circlip (22) of the cooling device (10) in order to clamp the outer edges of the flow regulator (12).

13. Vacuum pump (1) according to one of the preceding claims, characterized in that a threaded portion (24) is provided in the first conduit (15a) of a regulating conduit (15) and receives a threaded ring (25) of the cooling device (10), for clamping the outer edges of the flow regulator (12).

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