EP1510697A1 - Vacuum pump - Google Patents

Abstract

The pump has a motor (7) that is inserted inside a cavity (5c) of a molecular rotor (5a) of a molecular pumping stage (5). The motor permits a rotation speed higher than 20000 revolutions per minute, such that electrical power density is high. An upstream end (8b) of a crank shaft (8) is coupled to the rotor and a downstream zone (8b) of the shaft is connected to the primary rotor (9a).

Description

The present invention relates to vacuum pumps for generate and maintain a suitable vacuum in a vacuum enclosure or a line of empty.

Vacuum pumps of various types are known which are generally each adapted to particular flow conditions and pumped gas pressure.

Thus, we have designed primary pumps, which must repress to the atmospheric pressure, which have a plurality of compression stages, and whose last stages produce a strong compression under a volumetric flow relatively weak. An example of such a primary pump is a pump kinematic formed of a disc rotor with concentric ribs equipped with individual radial blades engaged in annular grooves corresponding communicating concentrics of the stator.

The primary pumps thus formed do not make it possible to achieve sufficiently advanced voids for many vacuum applications. Is the then associates in series with at least one secondary pump, for example a Molecular type or turbomolecular type pump, the repression of which is connected to the suction of the primary pump.

A molecular or turbomolecular pump must be able to immediate vicinity of the vacuum chamber that it must evacuate, in order to benefit from the maximum pumping speed in the vacuum chamber.

Now, usually, the size and weight of the pumping stage single-axis primary is incompatible with close integration of the empty, and therefore the primary pump must be removed from the vacuum chamber, and the pumping performance is thus degraded.

It has already been imagined to mechanically couple the primary pump and the secondary pump, to drive them by the same engine on the same motor shaft. Thus, it has already been described in US 5,848,873 A or in US Pat. US 6,135,709 A, a composite pump in which a stage of kinematic pumping with radial vanes engaged in annular grooves of the stator is mounted on a single rotor with a molecular pumping stage and possibly a turbomolecular pumping stage, the pumping stages being connected aerauliquement in series, the rotors being mounted one after the other others on the same motor shaft whose end is coupled to an engine drive. The kinematic pumping stage has the advantage of ensuring the primary pump function, repressing to atmospheric pressure, while having a high rotation speed compatible with the usual rotation speeds molecular or turbomolecular stages.

The engine of such a composite pump must be able to provide a sufficient power to drive the primary pump. The position of engine at the end of the motor shaft leads to a congestion that prevents the integration of the composite pump in the immediate vicinity of the vacuum chamber that the pump must evacuate.

The solutions proposed in documents US 5,848,873 and 6,135,709 A are therefore not sufficient for vacuum applications in which one wants to integrate the pumping system directly close to the vacuum chamber.

The problem proposed by the present invention is to design a new composite pump structure which is compact enough to be integrated in close proximity to the vacuum chamber or process chamber, and which is capable of pumping from atmospheric pressure (1000 mbar). to the high vacuum usually required in some industries (10 ^-8 mbar).

The idea underlying the invention is to reduce both the size of the engine itself which drives the pump, and to place the engine inside the pump to further reduce the overall footprint of the motor-pump assembly.

According to another aspect of the invention, a pump structure is provided with a primary stage which has improved and adjustable pumping properties, in order to achieve a satisfactory pumping using a smaller pump volume.

• le rotor moléculaire comporte une cavité axiale borgne ouverte vers l'aval du corps de pompe,
• le moteur est logé au moins partiellement dans ladite cavité axiale borgne du rotor moléculaire,
• l'arbre-moteur est couplé par son extrémité amont au rotor moléculaire,
• l'arbre-moteur est couplé par sa portion aval au rotor primaire.

To achieve these and other aims, a vacuum pump according to the invention comprises, in a same pump body, at least one molecular pumping stage connected in series with at least one primary pumping stage at a compatible speed, the molecular pumping stage having a molecular rotor cooperating with a molecular stator provided in the pump body, the primary pumping stage having a primary rotor cooperating with a primary stator provided in the pump body, the molecular and primary rotors being driven in rotation by the same motor shaft coupled to a motor; according to the invention:

• the molecular rotor has a blind axial cavity open downstream of the pump body,
• the motor is housed at least partially in said blind axial cavity of the molecular rotor,
• the motor shaft is coupled by its upstream end to the molecular rotor,
• the motor shaft is coupled by its downstream portion to the primary rotor.

The speed-compatible primary pumping stage is a structure of mechanical pumping with viscous drive stator and rotor that allows back to atmospheric pressure and that works properly at speeds normal rotation of the molecular or turbomolecular stages, that is to say speeds of the order of 20,000 revolutions / minute.

In a practical embodiment, the motor shaft is rotated by a upstream bearing and a downstream bearing, the upstream bearing being located between the engine and the zone coupling with the molecular rotor, the downstream bearing being located between the engine and the coupling area to the primary rotor.

• le rotor primaire est un rotor cinématique multiétagé à entraínement visqueux comprenant un disque dont une face transversale comporte une série de nervures annulaires concentriques ayant chacune des lames individuelles radiales,
• le stator primaire est un stator cinématique comprenant une face transversale correspondante ayant une série de gorges annulaires concentriques dans lesquelles s'engagent les lames individuelles radiales du rotor cinématique,
• les gorges annulaires concentriques du stator cinématique ont une section transversale plus grande que les lames individuelles radiales correspondantes du rotor cinématique, à l'exception d'une courte zone de gorge à section réduite dans laquelle les lames individuelles radiales s'engagent à faible jeu,
• les gorges annulaires concentriques successives sont reliées l'une à l'autre par un canal de communication prévu à l'extrémité aval de la zone de gorge à section réduite.

According to a first embodiment, a composite vacuum pump according to the invention is such that:

• the primary rotor is a multi-stage kinematic rotor with viscous drive comprising a disk, a transverse face of which comprises a series of concentric annular ribs each having individual radial blades,
• the primary stator is a kinematic stator comprising a corresponding transverse face having a series of concentric annular grooves in which the individual radial blades of the kinematic rotor engage,
• the concentric annular grooves of the kinematic stator have a greater cross-section than the corresponding individual radial blades of the kinematic rotor, with the exception of a short region of reduced section groove in which the individual radial blades engage with low clearance,
• the successive concentric annular grooves are connected to each other by a communication channel provided at the downstream end of the reduced section groove area.

The areas of reduced section grooves have the role of achieving a leakage barrier between two distinct annular grooves, which are different pressures.

According to a second embodiment, a vacuum pump according to the invention is such that the primary rotor is a multi-stage kinematic rotor with drive viscous material comprising one or more disks having a transverse face oblique centrifugal ribs which cooperate with a transverse face corresponding of a multi-stage kinematic stator.

An improvement consists in providing that the primary pumping stage is further such that the primary rotor has an upstream transverse face to oblique centrifugal ribs which cooperate with a transverse face corresponding pump body to constitute a pumping stage additional kinematics. Thus, without increasing the size of the pump, a pumping stage is added which makes it possible to improve the performances of pumping.

• les nervures centrifuges obliques de rotor coopèrent avec la face transversale correspondante du corps de pompe pour constituer un joint dynamique aval qui produit une aspiration protégeant le palier aval,
• un dernier étage moléculaire est inversé pour réaliser un joint dynamique amont qui produit une aspiration protégeant le palier amont,
• une purge de gaz neutre est adaptée pour amener un courant de gaz neutre dans le logement contenant le moteur, et pour produire ainsi un courant de gaz neutre à travers les paliers.

Alternatively, according to another variant, the primary pumping stage is further such that:

• the oblique centrifugal rotor ribs cooperate with the corresponding transverse face of the pump body to form a downstream dynamic seal which produces a suction protecting the downstream bearing,
• a last molecular stage is inverted to produce an upstream dynamic seal which produces a suction protecting the upstream bearing,
• a purge of neutral gas is adapted to bring a stream of neutral gas into the housing containing the engine, and thereby produce a neutral gas stream through the bearings.

Preferably, in the embodiments above, the vacuum pump composite according to the invention comprises a plurality of pumping stages Molecules consisting of rotor elements in the form of concentric cylinders connected to the motor shaft according to their upstream ends, and of stator elements in form of concentric cylinders with helical ribs connected to the pump body according to their downstream and engaged ends between the concentric rotor cylinders successive.

Also, to increase the pumping performance, one can provide that the pump according to the invention further comprises at least one stage of turbomolecular pumping connected aeraulically upstream of the stage or stages of molecular pumping, the turbomolecular pumping stage comprising a rotor turbomolecular having at least one stage of radial vanes and a stator turbomolecular having at least one annular groove in which are engaged the radial fins of the turbomolecular rotor.

Preferably, a plurality of turbomolecular stages are provided consisting of a rotor having a plurality of radial fin stages distributed along of the motor shaft, and a plurality of corresponding annular grooves distributed on the stator.

In the embodiments defined above, the inner position of the motor preferably leads to providing means for increasing the overall efficiency of the motor, in order to reduce the losses and thus the heating of the motor in operation. The goal is to provide the mechanical energy needed to the drive of the pump, with a smaller motor. For this we can in particular provide recessed cooling means in the stator of the motor, for example pipes in which a fluid of cooling.

• le moteur est adapté pour une vitesse de rotation élevée supérieure à 20 000 tours par minute en régime nominal,
• les gorges annulaires concentriques et les lames individuelles radiales correspondantes de l'étage primaire de type cinématique ont une taille plus réduite au voisinage du refoulement de l'étage de pompage cinématique.

Preferably, it is furthermore provided that:

• the engine is suitable for a high speed of rotation greater than 20 000 rpm in nominal speed,
• the concentric annular grooves and the corresponding individual radial blades of the kinematic-type primary stage have a smaller size in the vicinity of the discharge of the kinematic pump stage.

According to the invention, it is advantageous to provide a primary stator of multi-stage kinematic type mounted movable in the axial direction relative to to the pump body, and biased by displacement means allowing modify its relative axial position with respect to the primary rotor, so that the pumping performance is adjustable. It should be noted that this provision may be used in a kinematic stage pump regardless of the presence or the absence of the other characteristics defined above, and that it constitutes thus an independent invention.

Moreover, the motor shaft can advantageously be guided in rotation by magnetic bearings that allow an increase in the service life and a reduction of vibrations.

• la figure 1 est une vue schématique en coupe longitudinale d'une structure de pompe à vide composite selon un premier mode de réalisation de la présente invention ;
• la figure 2 illustre la face transversale principale aval du rotor cinématique de la pompe de la figure 1 ;
• la figure 3 illustre soit la face transversale amont du rotor cinématique de la pompe de la figure 1 selon un mode de réalisation avantageux, soit la face transversale principale aval d'un rotor cinématique selon un second mode de réalisation ;
• la figure 4 illustre la face transversale amont active du stator cinématique de la pompe de la figure 1 ;
• la figure 5 est une vue en coupe longitudinale de la pompe de la figure 1, avec le stator cinématique déplacé ; et
• la figure 6 est une vue en coupe longitudinale d'une pompe à vide composite selon un autre mode de réalisation de la présente invention.

Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, with reference to the accompanying drawings, in which:

• Figure 1 is a schematic longitudinal sectional view of a composite vacuum pump structure according to a first embodiment of the present invention;
• FIG. 2 illustrates the main downstream transverse face of the kinematic rotor of the pump of FIG. 1;
• FIG. 3 illustrates either the upstream transverse face of the kinematic rotor of the pump of FIG. 1 according to an advantageous embodiment, or the main downstream transverse face of a kinematic rotor according to a second embodiment;
• FIG. 4 illustrates the active upstream transverse face of the kinematic stator of the pump of FIG. 1;
• Figure 5 is a longitudinal sectional view of the pump of Figure 1, with the kinematic stator displaced; and
• Figure 6 is a longitudinal sectional view of a composite vacuum pump according to another embodiment of the present invention.

In the embodiment illustrated in FIG. 1, a vacuum pump composite according to the invention comprises, in the same pump body 100 having a suction port 1 and a delivery port 2, at least one pumping stage Aeraulically connected molecular 5, via a transfer line 6, in series with at least one primary pumping stage 9 of multi-stage kinematic type viscous training.

In the illustrated embodiment, the pump further comprises at least one turbomolecular pumping stage 4, connected aeraulically upstream of or molecular pumping stages 5.

The molecular pumping stage 5 comprises a molecular rotor 5a which cooperates with a molecular stator 5b provided in the pump body 100.

The primary pumping stage 9 comprises a primary rotor 9a of the type kinematic cooperating with a primary stator 9b kinematic type provided in the pump body 100.

The molecular rotor 5a and the primary rotor 9a are driven in rotation by the same motor shaft 8 coupled to an electric motor 7.

The engine 7 comprises a motor rotor 7a, fixed on the central section of the motor shaft 8, and rotating in a motor stator 7b itself fixed in a housing 100b of the pump body 100.

The motor shaft 8 is rotated by an upstream bearing 15 and a bearing downstream 16, on either side of the motor rotor 7a. In the illustrated embodiment on the 1, the bearings 15 and 16 are mechanical bearings with ball bearings. In alternatively, it can advantageously be provided that the bearings 15 and / or 16 are magnetic bearings, in a manner known per se.

The molecular rotor 5a has a blind axial cavity 5c, open downstream of the pump body 100 that is to say open towards the discharge port 2, and closed upstream, that is to say in the direction of the suction port 1, by a transverse wall 5d.

According to the invention, the motor 7 is housed at least partially in said blind axial cavity 5c of the molecular rotor 5a. Preferably, as shown in FIG. 1, the motor 7 is housed entirely in the blind axial cavity 5c of the molecular rotor 5a. For this, the motor shaft 8 is coupled by its end upstream 8a to the molecular rotor 5a, and the motor shaft 8 is coupled by its downstream portion 8b to the primary rotor 9a.

In the example shown, the upstream end 8a of the drive shaft 8 crosses an axial hole provided in the transverse wall 5d of the molecular rotor 5a, and it is secured by a nut 8c. Similarly, the downstream portion 8b of the motor shaft 8 through a hole in the primary rotor 9a, and is fixed to it by a nut 13.

The upstream bearing 15 comprises, in the illustrated embodiment, a elastic washer 15a for precharging the ball bearing constituting said bearing upstream 15.

The upstream bearing 15 is located between the engine 7 and the upstream end 8a of the motor shaft 8 or coupling zone to the molecular rotor 5a.

The downstream bearing 16 is located between the engine 7 and the downstream portion 8b of the motor shaft 8 or coupling zone to the primary rotor 9a.

In the embodiment of FIG. 1, the primary rotor 9a is a kinematic rotor comprising a disk having a transverse face, for example the downstream transverse face in the illustrated embodiment, comprises a series concentric annular ribs each having individual blades radials. In this respect, reference can be made to Figure 2, which illustrates in perspective an embodiment of such a transverse face 9c of a kinematic rotor 9a disc-shaped: we distinguish the concentric annular ribs successive 9d, 9e, 9f, 9g and 9h, which extend from the periphery to the center of the disk. Each concentric annular rib 9d-9h has blades individual radial such as the blade 10, protruding axially from the ridge of the corresponding concentric annular rib 9d and oriented each substantially in a radial direction relative to the disk forming the rotor kinematic 9a.

The kinematic stator 9b has a transverse wall integral with the pump body 100 and which comprises a corresponding transverse face, the upstream transverse face in the illustrated embodiment, which comprises a series of concentric annular grooves. In this respect, reference may be made to FIG. 4, which illustrates in perspective an embodiment of such a stator kinematic 9b, with concentric annular grooves 9j, 9k, 9l, 9m and 9n, which correspond respectively to the respective concentric annular ribs 9d-9h of the kinematic rotor 9a. Individual radial blades such as the blade 10 of the kinematic rotor 9a engage in the concentric annular grooves 9j-9n, and for this the concentric annular grooves 9j-9n of the kinematic stator 9b have a larger cross-section than the individual radial blades 10 corresponding to the kinematic rotor 9a, except for a short throat area reduced section in which the individual radial blades 10 engage to It is thus possible to distinguish, for example, for the groove 9k of FIG. throat area with reduced section 9o in which the groove 9k is not flared towards its bottom, unlike the other portions of the same 9k throat.

The successive concentric annular grooves 9j-9n are connected one to the other via a communication channel provided at the downstream end of the corresponding throat. For example, the channel 9p which connects the concentric annular grooves 9j and 9k.

In the embodiment of Figure 1, there is further shown a additional pumping stage 11, at the interface between the primary rotor 9a and the upstream portion of the pump body 100. In this case, the second transverse face or upstream transverse face of the kinematic rotor disk 9a may be such that represented in perspective in FIG. 3 to form a rotor 11a, comprising oblique centrifugal ribs 11c, 11d, 11e and 11f, to cooperate with a corresponding transverse face 11 b (Figure 1) of the pump body 100 which constitutes a stator.

Referring again to Figure 1, we see that, in the mode of illustrated embodiment, there is provided a plurality of molecular pumping stages 5, consisting of rotor elements in the form of concentric cylinders connected to the motor shaft 8 according to their upstream ends, that is to say according to the transverse wall 5d, and stator elements in the form of concentric cylinders with helical ribs connected to the pump body 100 along their downstream ends and engaged between the successive concentric rotor cylinders. In the figure, there are three stator cylinders and two rotor cylinders nested within each other.

Also, in the figure, we distinguish the pumping stage turbomolecular 4 having a turbomolecular rotor 4a having at least one radial fin stage, two stages of radial fins in the figure, and a stator Turbomolecular 4b having annular rings, two crowns in the figure 1, which engage between the radial vanes of the turbomolecular rotor 4a. The crowns can be patches, stacked axially with appropriate spacers, in a manner known per se. Alternatively, so also known per se, the stator may consist of the assembly peripheral of several shells reported radially around the rotor.

In order to reduce the volume of the whole, we try to realize a motor 7 of small size, allowing its insertion inside the cavity 5c of the molecular rotor 5a. For this, it is necessary in particular to improve the cooling of the motor 7, and it can be provided for this purpose cooling means 17 recessed in the motor stator 7b, for example conduction of a cooling fluid.

Alternatively or in addition, the motor 7 must be adapted for allow a high rotational speed, greater than 20 000 rpm rated speed. The electrical power density is, in this way, more high, which reduces the size of the engine.

Alternatively or in addition, concentric ring grooves 9j-9n and corresponding individual radial blades 10 have a larger size reduced in the vicinity of the discharge of the kinematic stage. In practice, on Figures 2 and 4, the transverse dimension of the grooves and the blades is becoming smaller when going from the peripheral ring groove 9j to the throat 9n central annular, and it is the same concentric ribs 9d-9h and radial individual blades 10. In this way, the blades are reduced in the high pressure zone, that is to say in the vicinity of the axis of rotation, which reduces viscous friction and reduces the power that must develop the engine.

As an alternative or in addition, means are provided for reducing leaks between the kinematic pumping stages, providing for a very low clearance between the individual radial blades 10 and the sections of section grooves reduced 9o. This can be achieved by providing high precision machining of corresponding parts, but also by providing means for adjusting the the axial position of the kinematic stator 9b with respect to the kinematic rotor 9a, as will be described below.

In the embodiment illustrated in FIGS. 1 and 5, the stator kinematic 9b can be moved axially between a close position shown in FIG. 1 and a maximum distance position illustrated in FIG. For this, the kinematic rotor 9a can slide axially in the pump body 100, with the interposition of an annular seal 100a, in being guided by guide means 21 and biased by means of displacement such as a jack not shown.

In the maximum approach position illustrated in FIG. individual radial 10 penetrate deep into the throats corresponding 9j-9n, which reduces to the smallest possible size the clearance between the individual radial blades 10 and the sections of section grooves reduced 9o, as shown in Figure 1 in the right part of the kinematic rotor 9a. In the maximum recoil position as shown in FIG. 5, the clearance between the individual radial blades 10 and the kinematic stator 9b, increasing internal leakage and thus reducing pumping performance.

It is thus possible to modify at will the pumping performance of the kinematic pump, regardless of its speed, and quickly and effective by positioning at will the kinematic stator 9b in any position between its positions of maximum approximation and maximum retreat. At the same time, Axial position adjustment means make it possible to reduce leaks as much as possible when in the closest approach position of FIG. enabling the constitution of a kinematic pump with improved performance.

It will be understood that the use of the position adjustment means of the kinematic stator 9b with respect to the kinematic rotor 9a is independent of the presence or absence of other pump structure parts of the figure 1, and in particular the presence of molecular stages and / or stages turbo. This means thus constitutes an independent invention which can be used alone, for certain kinematic pump applications.

We now consider the embodiment as illustrated on the figure 6. In this case, the composite pump takes up the essential means of the embodiment of FIG. 1, with the molecular pumping stages 5, possibly the turbomolecular pumping stages 4, with the stage of kinematic pumping 9, and with the motor 7 engaged in the posterior cavity 5c and mounted on the central portion of the motor shaft 8 whose upstream end 8a is coupled to the molecular rotor 5a and whose downstream zone 8b is coupled to the rotor kinematic 9a.

In this second embodiment, the means for protect the bearings 15 and 16 against the harmful action of corrosive gases, powders and dust that the pump is often required to extract vacuum chambers. For this is provided a purge 19 by which one can introduce a neutral gas of purge in the housing 100b containing the engine 7, and means are provided for aspirate the neutral gas through the areas occupied by the bearings 15 and 16.

Thus, there is provided a suction duct 20 which goes directly from the discharge of the molecular pumping stage 5 to the pumping stage kinematic 9, at the periphery of the disk forming the kinematic rotor 9a, and reverse the direction of the helical grooves in the last pumping stage 5th molecular so that it forms an upstream dynamic seal that aspires the gas from the upstream bearing 15 to push back to the pumping stage 9. Simultaneously, it can be expected that the second transverse face upstream 11a of the kinematic rotor disk 9a, as illustrated in FIG. 3, comprises oblique centrifugal ribs 11c-11f for cooperating with a face corresponding 11 b of the pump body 100 and constitute a dynamic joint downstream which draws the gases from the downstream bearing 16 to the primary pumping stage 9.

The motor 7 is powered by electrical conductors connected to a power supply connector 18.

According to the invention, it is possible to replace the face-facing primary rotor downstream transverse with individual radial blades engaged in grooves concentric rings of a kinematic stator, by any other structure of multi-stage kinematic primary pump with viscous drive that works satisfactorily at the speed of rotation of the molecular pumps or turbo.

An example of another possible structure of such a primary stage is shown in Figure 3. It is considered that the face 11a constitutes the main face of the rotor 9a, and that the oblique centrifugal ribs 11c-11f, cooperating with a corresponding transverse face of the stator or body of pump, constitute a kinematic stage with viscous drive. We can then design a stack of several similar disks including a transverse face has the oblique centrifugal ribs which cooperate with one side cross section of a multi-stage kinematic stator.

This embodiment is also compatible with the presence of a additional kinematic pumping stage consisting of the transverse face upstream of the rotor with other oblique centrifugal ribs.

The embodiment is also compatible with a provision special dynamic seals and neutral gas purges in the bearing area.

In all cases, a plurality of pumping stages can be provided molecular and / or turbomolecular.

The present invention is not limited to the embodiments which have have been explicitly described, but it includes the various variants and generalizations that are within the reach of those skilled in the art.

Claims (13)

- Vacuum pump comprising, in a same pump body (100), at least one molecular pumping stage (5) connected in series with at least one primary pumping stage (9) at a compatible speed, the pumping stage molecular system (5) having a molecular rotor (5a) cooperating with a molecular stator (5b) provided in the pump body (100), the primary pump stage (9) having a primary rotor (9a) cooperating with a primary stator (9b) provided in the pump body (100), the molecular rotors (5a) and primary rotors (9a) being rotated by a same motor shaft (8) coupled to a motor (7), characterized in that : the molecular rotor (5a) has a blind axial cavity (5c) open downstream of the pump body (100), the motor (7) is housed at least partially in said blind axial cavity (5c) of the molecular rotor (5a), the motor shaft (8) is coupled by its upstream end (8a) to the molecular rotor (5a), the motor shaft (8) is coupled by its downstream portion (8b) to the primary rotor (9a). - Vacuum pump according to claim 1, characterized in that the motor shaft (8) is rotatably supported by an upstream bearing (15) and a downstream bearing (16), the upstream bearing (15) being located between the motor (7) and the coupling zone (8a) to the molecular rotor (5a), the downstream bearing (16) being located between the motor (7) and the coupling zone (8b) to the primary rotor (9a). Vacuum pump according to one of claims 1 or 2, characterized in that : the primary rotor (9a) is a viscous multi-stage kinematic rotor comprising a disk having a transverse face (9c) comprising a series of concentric annular ribs (9d-9h) each having individual radial blades (10), the primary stator (9b) is a kinematic stator comprising a corresponding transverse face having a series of concentric annular grooves (9j-9n) in which the individual radial blades (10) of the kinematic rotor (9a) engage, the concentric annular grooves (9j-9n) of the kinematic stator (9b) have a larger cross-section than the corresponding individual radial blades (10) of the kinematic rotor (9a), except for a short sectioned groove area reduced (9o) in which the individual radial blades (10) engage with low clearance, the successive concentric annular grooves (9j-9n) being connected to each other by a communication channel (9p) provided at the downstream end of the reduced section groove area (9o). - Vacuum pump according to one of claims 1 or 2, characterized in that the primary rotor (9a) is a multi-stage kinematic rotor with viscous drive comprising one or more disks having a transverse face comprises oblique centrifugal ribs which cooperate with a corresponding transverse face of a multi-stage kinematic stator. - Vacuum pump according to one of claims 3 or 4, characterized in that the primary pumping stage (9) is further such that the primary rotor (9a) has a transverse face (11a) upstream with centrifugal ribs obliques (11c-11f) which cooperate with a corresponding transverse face (11b) of the pump body (100) to form an additional kinematic pumping stage (11). Vacuum pump according to Claim 5, characterized in that the primary pumping stage (9) is furthermore such that: the oblique centrifugal ribs (11c-11f) of the rotor cooperate with the corresponding transverse face (11b) of the pump body (100) to form a downstream dynamic seal which produces a suction protecting the downstream bearing (16), a last molecular stage (5d) is inverted to produce an upstream dynamic seal which produces a suction protecting the upstream bearing (15), a purge of neutral gas (19) is adapted to bring a stream of neutral gas into the housing (100b) containing the motor (7), and thereby to produce a stream of neutral gas through the bearings (15, 16). Vacuum pump according to any one of claims 1 to 6, characterized in that it comprises a plurality of molecular pumping stages (5) consisting of rotor elements in the form of concentric cylinders connected to the shaft. motor (8) according to their upstream ends, and stator elements in the form of concentric cylinders with helical ribs connected to the pump body (100) along their downstream ends and engaged between the successive concentric rotor cylinders. - Vacuum pump according to any one of claims 1 to 7, characterized in that it further comprises at least one turbomolecular pumping stage (4) connected aerauliquement upstream of the molecular pumping stage or stages (5), turbomolecular pumping stage (4) comprising a turbomolecular rotor (4a) having at least one stage of radial vanes and a turbomolecular stator (4b) having at least one annular groove in which are engaged the radial vanes of the turbomolecular rotor (4a) . Vacuum pump according to claim 8, characterized in that it comprises a plurality of turbomolecular stages consisting of a rotor having a plurality of radial fin stages distributed along the motor shaft (8), and a plurality of corresponding annular grooves distributed over the stator (4b). - Vacuum pump according to any one of claims 1 to 9, characterized in that the motor (7) comprises cooling means (17) embedded in the motor stator (7b). Vacuum pump according to one of Claims 1 to 10, characterized in that : the motor (7) is adapted for a high speed of rotation greater than 20 000 rpm in nominal speed, the concentric annular grooves (9j-9n) and the corresponding individual radial blades (10) have a smaller size in the vicinity of the discharge of the kinematic pump stage (9). - Vacuum pump according to any one of claims 1 to 11, characterized in that the primary stator (9b) is mounted displaceable in the axial direction relative to the pump body (100) and is biased by displacement means allowing to change its relative axial position with respect to the primary rotor (9a), so that the pumping performance is adjustable. - Vacuum pump according to any one of claims 1 to 12, characterized in that the motor shaft (8) is guided in rotation by magnetic bearings (15, 16).

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