阅读说明：本技术 干式真空泵 (Dry vacuum pump ) 是由 S·克罗谢 于 2019-02-14 设计创作，主要内容包括：本发明涉及一种干式真空泵(1),包括：-至少一个集油槽(2)；-至少一个泵送级(3a-3e)；-两个旋转轴(4),它们分别保持至少一个在至少一个泵送级(3a-3e)中延伸的转子(5),所述转子(5)构造为沿相反方向以同步方式旋转,以在真空泵(1)的进入口和排出口间运送待泵送的气体,所述轴(4)由被集油槽(2)中包含的润滑剂润滑的轴承支撑；-至少一个润滑剂密封装置(6),其在每个轴通道处插入集油槽(2)和泵送级(3e)之间,该密封装置(6)包括安装在轴(4)上以与该轴一起旋转的总体上盘形的导流板(14；24；26),其特征在于,该导流板(14)的盘部在周边具有环形端部(16),该环形端部朝泵送级(3e)延伸以构成保持凹部。(The invention relates to a dry vacuum pump (1) comprising: -at least one oil sump (2); -at least one pumping stage (3a-3 e); -two rotating shafts (4) each holding at least one rotor (5) extending in at least one pumping stage (3a-3e), said rotors (5) being configured to rotate in opposite directions in a synchronized manner to carry the gas to be pumped between an inlet and an outlet of the vacuum pump (1), said shafts (4) being supported by bearings lubricated by the lubricant contained in the oil sump (2); -at least one lubricant sealing device (6) interposed between the sump (2) and the pumping stage (3e) at each shaft passage, the sealing device (6) comprising a generally disc-shaped deflector (14; 24; 26) mounted on the shaft (4) for rotation therewith, characterized in that the disc of the deflector (14) has a ring-shaped end (16) at the periphery, which extends towards the pumping stage (3e) to constitute a retaining recess.)

1. Dry vacuum pump (1) comprising:

-at least one oil sump (2),

-at least one pumping stage (3a-3e),

-two rotating shafts (4) holding respectively at least one rotor (5) extending in said at least one pumping stage (3a-3e), these rotors (5) being configured to rotate in opposite directions in a synchronized manner so as to convey the gas to be pumped between an inlet (7) and an outlet (8) of said vacuum pump (1), these shafts (4) being supported by bearings lubricated by the lubricant contained in said oil sump (2),

-at least one lubricant sealing device (6) interposed between the sump (2) and the pumping stage (3e) at each shaft passage, the sealing device (6) comprising a generally disc-shaped deflector (14; 24; 26) mounted on the shaft (4) to rotate therewith,

characterized in that the disk of the deflector (14; 24; 26) has on its periphery a ring-shaped end (16) which extends towards the pumping stage (3e) so as to constitute a retaining recess.

2. Vacuum pump (1) according to claim 1, characterized in that said annular end portion (16) has a generally cylindrical shape, coaxial with the rotation axis (I-I) of said shaft (4).

3. Vacuum pump (1) according to any of the preceding claims, characterized in that the annular end portion (16) has a radial rim (25).

4. Vacuum pump (1) according to any of the preceding claims, characterized in that the sealing means (6) comprises an annular seal (11), the annular end (16) of the deflector (14; 24; 26) extending at least partially around the annular seal (11).

5. Vacuum pump (1) according to any of the preceding claims, characterized in that the sealing means (6) comprise a sleeve (18) mounted on the shaft (4), the deflector (14; 24; 26) being mounted on the sleeve (18).

6. Vacuum pump (1) according to the preceding claim, characterized in that said sleeve (18) has a two-stage cylindrical shape comprising a first cylindrical stage (18a) having an outer diameter suitable for being inserted in a central orifice (15) in said baffle (14) and a second cylindrical stage (18b) constituting an axial stop for said baffle (14; 24; 26).

7. Vacuum pump (1) according to any of the preceding claims, characterized in that the surface (27) of the deflector (26) bearing the annular end (16) has a generally frustoconical shape, coaxial to the centre of the deflector (26), and with its apex on the side of the oil sump (2).

8. Vacuum pump (1) according to any of the preceding claims, characterized in that the baffle (14; 24; 26) comprises a surface (17) opposite to the surface (23; 27) carrying the annular end (16), having a generally frustoconical shape, coaxial with the centre of the baffle (14; 24; 26) and having its vertex on the side of the pumping stage (3 e).

9. Vacuum pump (1) according to any of the preceding claims, characterized in that the stator (21) of the vacuum pump (1) and the edge of the surface (17) of the deflector (14; 24; 26) opposite the surface (23; 27) carrying the annular end (16) are separated by an axial distance (d) of less than 3mm_a) And a vertical distance (d) of less than 3mm_v)。

10. Vacuum pump (1) according to any of the preceding claims, characterized in that the sealing means (6) comprise an annular seal (11), such as a ring with a single or double lip (12a, 12b), or a segmented seal.

11. Dry vacuum pump (1) comprising:

-at least one oil sump (2),

-at least one pumping stage (3a-3e),

-two rotating shafts (4) holding respectively at least one rotor (5) extending in said at least one pumping stage (3a-3e), these rotors (5) being configured to rotate in opposite directions in a synchronized manner so as to convey the gas to be pumped between an inlet (7) and an outlet (8) of said vacuum pump (1), these shafts (4) being supported by bearings lubricated by the lubricant contained in said oil sump (2),

-at least one lubricant sealing device (6) interposed between the oil sump (2) and the pumping stage (3e) at each shaft passage, the sealing device (6) comprising a generally disc-shaped deflector (28) mounted on the shaft (4) to rotate therewith,

characterized in that the disk of the deflector (28) comprises at least one surface (17, 29) having a frustoconical shape and coaxial with the centre of the deflector (28).

12. Vacuum pump according to the preceding claim, characterized in that the surface (29) of the deflector (28) having a frustoconical shape, the vertex of which is located on the sump (2) side, is directed towards the pumping stage (3 e).

13. A vacuum pump according to claim 11 or 12, characterized in that the surface (17) of the deflector (28) having a frustoconical shape, the apex of which is located on the side of the pumping stage (3e), is opposite the oil sump (2).

Technical Field

The invention relates to a dry vacuum pump, such as a roots pump, a claw pump or a screw pump. More particularly, the present invention relates to lubricant sealing for vacuum pumps.

Background

A dry roughing vacuum pump comprises one or more pumping stages in series, wherein the gas to be pumped flows between an inlet and an outlet. Known roughing vacuum pumps are distinguished by rotary lobe pumps having two or more lobes, also known as roots pumps, claw pumps and screw pumps. Roots blower-type vacuum pumps are also known, which are used upstream of the roughing vacuum pump to improve pumping capacity at high flow rates. These vacuum pumps are called "dry" pumps because during operation the rotors rotate in the stators without any mechanical contact between the rotors or between the rotors and the stators, which makes it possible to dispense with the use of oil in the pumping stages.

The rotating shaft is supported by ball bearings lubricated by oil. During operation, rotation of the shaft in the bearings generates contaminants, such as oil droplets, which may move towards the pumping stages when subjected to pressure changes. However, it is important that for so-called "dry" applications, such as semiconductor substrate manufacturing processes, there is no oil smearing in the pumping stages. Therefore, the lubricated bearings must be isolated from the dry pumping stage by a seal arrangement, and the shaft can still rotate by this seal arrangement.

The sealing means used mainly consist of physical barriers, such as flanges on bearings, friction joints, ejector disks, gas drains, oil collectors, such as expansion and condensation chambers, or obstacles, such as labyrinths and bends. These solutions mainly attempt to prevent or limit the movement of the oil. However, during operation, the pressure exerted in the vacuum pump may fluctuate widely and create thrust between the lubricated bearings and the pumping stage, thereby enabling the entrainment of contaminant particles from the pumping stage into the sump and the entrainment of oil mist or vapour from the bearings into the pumping stage, particularly in applications where large amounts of gas are periodically vented.

It is particularly desirable to limit the movement of solid or liquid particles from the pumping stage or friction joint to the sump, as these particles are sometimes abrasive, which may lead to reduced lubrication performance, which may lead to premature wear of the ball bearings, for example.

Disclosure of Invention

It is therefore an object of the present invention to propose a dry vacuum pump which at least partially remedies the disadvantages of the prior art.

To this end, the invention relates to a dry vacuum pump comprising:

-at least one oil sump tank,

-at least one pumping stage, the pumping stages,

two rotating shafts, each holding at least one rotor extending in the at least one pumping stage, the rotors being configured to rotate in opposite directions in a synchronized manner so as to convey the gas to be pumped between an inlet and an outlet of the vacuum pump, the shafts being supported by bearings lubricated by lubricant contained in a sump,

at least one lubricant seal interposed between the sump and the pumping stage at each shaft passage, the seal comprising a generally disc-shaped baffle mounted on the shaft for rotation therewith,

characterized in that the disk of said baffle has on its periphery an annular end (tip) which extends towards the pumping stage, thus constituting a retaining recess.

The retaining recess of the deflector makes it possible to retain any particles or dust that may come from the pumping stage of the vacuum pump or from the friction joint and that will be radially expelled (ejected, dislodged) by the deflector. Thereby restricting the particles from moving toward the ball bearings or oil sumps.

Thereby, the life of the bearing can be increased, and the contamination of oil can be reduced, so that the oil consumption can be reduced. Thus, after 1000 hours of operation of a vacuum pump comprising such a baffle, it can be noted that the oil consumption is reduced by about 30%, and that the "clean" oil is almost completely free of contaminating particles.

A baffle made in this way is easy and inexpensive to manufacture. In addition, it is compatible with different types of "dynamic" or friction-type ring seals of the sealing device.

The vacuum pump may comprise a single sump. On a multistage vacuum pump, the oil sump can be arranged next to the so-called low-pressure pumping stage or next to the so-called high-pressure pumping stage. Alternatively, the bearings may be lubricated with grease.

The vacuum pump may also comprise two oil sumps. These oil sumps are each arranged at one end of the vacuum pump, that is to say, on a multistage vacuum pump, one of these oil sumps is close to the so-called high-pressure stage and the other is close to the so-called low-pressure stage. On single-stage vacuum pumps, such as roots blower-type vacuum pumps, these oil sumps are arranged on both sides of a single pumping stage.

The annular end portion may have any shape. It may be chamfered (beveled).

According to one embodiment, the annular end portion has a generally cylindrical (barrel) shape, which is coaxial with the axis of rotation of the shaft.

The annular end portion may also have a radial rim. The radial edge makes it possible to improve the particle or dust retaining capacity of the retaining recess.

The sealing means may comprise an annular seal, for example a friction type annular seal or a dynamic seal. The friction type annular seal includes, for example, a single lip ring or a double lip ring. The dynamic seal comprises, for example, a segmented seal.

According to one embodiment, the annular end of the baffle extends at least partially around the annular seal.

According to one embodiment, the sealing device comprises a sleeve mounted on the shaft, the deflector being mounted on the sleeve.

The sleeve has, for example, a two-stage cylindrical shape, comprising a first cylindrical stage having an outer diameter adapted to be inserted into the central orifice in the baffle, and a second cylindrical stage constituting an axial stop for the baffle.

The surface of the disc carrying the annular end portion may be perpendicular to the axis of rotation of the shaft. According to another embodiment, the surface of the baffle carrying the annular end has a generally frustoconical shape, is coaxial with the centre of the baffle, and has its apex on the side of the sump. This frustoconical shape makes it possible to guide back to the pumping stage any particles or dust from the pumping stage that are not trapped in the retaining recess.

The surface of the disc opposite the surface carrying the annular end portion may be perpendicular to the axis of rotation of the shaft. According to another embodiment, the surface opposite to the surface carrying the annular end has a frustoconical shape, is coaxial with the centre of the deflector and has its vertex on the pumping stage side. This frusto-conical shape of the rotating deflector allows any lubricant splash points that strike the deflector to be directed back to the sump.

In addition, an axial distance of less than 3mm and a vertical distance of less than 3mm may be provided to space the stator of the vacuum pump from the edge of the surface of the baffle opposite the surface carrying the annular end. Thereby forming a very narrow passage between the stator and the baffle. It allows relative expansion of the parts without contacting each other, while at the same time providing low conductivity for the lubricant, thereby restricting its movement out of the deflector.

The invention also relates to a dry vacuum pump comprising:

-at least one oil sump tank,

-at least one pumping stage, the pumping stages,

two rotating shafts, each holding at least one rotor extending in the at least one pumping stage, the rotors being configured to rotate in opposite directions in a synchronized manner so as to convey the gas to be pumped between an inlet and an outlet of the vacuum pump, the shafts being supported by bearings lubricated by lubricant contained in a sump,

at least one lubricant seal interposed between the sump and the pumping stage at each shaft passage, the seal comprising a generally disc-shaped baffle mounted on the shaft for rotation therewith,

characterized in that the disk portion of the baffle comprises at least one surface having a frustoconical shape and being coaxial with the center of the baffle.

One surface of the baffle having a frusto-conical shape with the apex on the sump side may be the surface opposite the pumping stage. This frusto-conical shape makes it possible to direct any particles or dust that may come from the pumping stage back to the pumping stage.

One surface of the deflector having a frustoconical shape with the apex on the pumping stage side may be the surface opposite the oil sump. The "concave" frusto-conical shape of the rotating deflector during operation allows any lubricant splash points that strike the deflector to be directed back to the sump.

Both surfaces of the baffle may have a frusto-conical shape.

Drawings

Other advantages and features will become apparent upon reading the description of the invention and the accompanying drawings, in which:

figure 1 shows a very schematic representation of one example of a dry vacuum pump.

Figure 2 shows a partial cross-sectional view of a portion of the vacuum pump of figure 1, particularly illustrating the sealing arrangement.

Fig. 3 shows an enlarged view of a detail of the sealing device in fig. 2.

Fig. 4 shows a perspective view of a baffle of the sealing device of fig. 2.

Fig. 5 shows a cross-sectional view of the baffle of fig. 4.

Fig. 6 shows an enlarged view of a detail of fig. 5.

Fig. 7 shows a perspective view of the sleeve of the sealing device of fig. 2.

Fig. 8 shows a cross-sectional view of the sleeve of fig. 7.

Fig. 9 shows a view similar to fig. 3 of a second embodiment of a baffle.

Fig. 10 shows a view similar to fig. 3 of a third embodiment of a baffle.

Fig. 11 shows a view similar to fig. 3 of a fourth embodiment of a baffle.

Fig. 12 shows a view similar to fig. 3 of a second embodiment of the ring seal.

In the drawings, like elements have like reference numerals. The drawings in the drawings are simplified for ease of understanding.

The following embodiments are examples. While the description refers to one or more embodiments, this does not necessarily mean that each reference refers to the same embodiment or that the feature only applies to a single embodiment. Simple features of different embodiments may also be combined or interchanged to provide further embodiments.

Detailed Description

Fig. 1 shows a dry vacuum pump 1.

The vacuum pump 1 comprises at least one oil sump 2, at least one pumping stage 3a-3e, two rotating shafts 4 and at least one lubricant seal 6 interposed between the oil sump 2 and the pumping stage 3 e.

The shaft 4 holds at least one rotor 5 extending in the at least one pumping stage 3a-3e, respectively.

In this illustrative example, the vacuum pump 1 comprises a plurality of, for example five, pumping stages 3a, 3b, 3c, 3d, 3e, which are mounted in series between an inlet 7 and an outlet 8 of the vacuum pump 1 and in which the gas to be pumped can flow. The pumping stage 3e adjacent to the sealing device 6 is here the last pumping stage 3e (referred to herein as the "high pressure" pumping stage, since it is configured to expel pumped gas at atmospheric pressure).

Each pumping stage 3a, 3b, 3c, 3d, 3e comprises a respective input and output. Successive pumping stages 3a-3e are connected in series with each other by respective inter-stage passages connecting the output of the previous pumping stage to the input of the next pumping stage.

The rotor 5 has, for example, lobes of the same profile, for example of the roots type (splayed or pea-shaped cross-section) or claw type, or is a screw rotor or is based on another similar positive displacement vacuum pump principle.

The rotors 5 having lobes of the same profile are angularly offset. These rotors 5 are driven so that they rotate in opposite directions in each stage in a synchronized manner, carrying the gas to be pumped between an inlet 7 and an outlet 8. During rotation, the gas sucked from the input is trapped in the space created by the rotor 5 and the stator, and then carried by the rotor 5 to the next stage.

The vacuum pump 1 is, for example, a rough vacuum pump, and the discharge pressure of the vacuum pump 1 is thus atmospheric pressure. According to another example, the vacuum pump 1 is a roots pump, known as a roots blower, which is used in series with the rough vacuum pump upstream thereof.

The shaft 4 is driven, for example, on the discharge side 8 by the motor M of the vacuum pump 1. These shafts are supported by bearings which are lubricated by the lubricant contained in the sump 2. A lubricant such as oil (lubricating oil) makes it possible to lubricate the ball bearings 9 and the gears of the bearings in particular (fig. 2).

At each shaft passage, a lubricant seal 6 is interposed between the sump 2 and the pumping stage 3 e. There is thus a sealing arrangement 6 on the drive shaft 4 and a sealing arrangement on the driven shaft 4.

As can be seen more clearly in fig. 2, the sealing means 6 may comprise at least one annular seal 11.

The annular seal 11 comprises, for example, a "dynamic" seal, i.e. a non-friction seal, e.g. a segmented seal, a labyrinth seal or a bend or a gas "wall", or a friction annular seal such as a lip seal, or a combination of these embodiments. The annular seal 11 produces very low conductivity around the rotating shaft 4 which makes it possible to greatly restrict the ingress of lubricant from the sump 2 into the dry pumping stages 3a-3e or vice versa, whilst allowing the shaft 4 to rotate.

In the example shown in fig. 1 to 11, the annular seal 11 is a friction seal.

The friction annular seal 11 comprises, for example, a ring with two lips 12a, 12b (fig. 3).

FIG. 12 shows another example in which the ring seal 11 is a dynamic seal comprising a segmented seal.

The segmented seal comprises one or more rings 13a rigidly mounted in the stator 21. These fixed rings 13a are separated by a small gap of about a few tenths of a from the complementary rings 13b mounted on the shaft 4 to rotate with them, providing a seal at the shaft passage.

The sealing device 6 also comprises a substantially disc-shaped baffle 14 (fig. 2, 3 and 4) which is mounted on the shaft 4 so as to rotate therewith. The disc has a central aperture 15 for mounting on the shaft 4. The centrifugal force created by the rapid rotation of the deflector 14 restricts the oil from moving towards the annular seal 11.

An oil recovery channel 10 may be formed in the stator 21 to return lubricant to the sump 2 (fig. 2). The inlet of the oil recovery channel 10 is for example in the lower part of the stator 21 and opposite the deflector plate 14. For example, a first oil recovery channel 10 is provided opposite the baffle plate 14 of the drive shaft 4 and a second oil recovery channel 10 is provided opposite the baffle plate 14 of the driven shaft 4.

The disk of the baffle 14 may also have on its periphery a ring-shaped end 16 which extends towards the pumping stage 3e, thus constituting a retaining recess. The retaining recess makes it possible to retain any particles or dust that may come from the pumping stages 3a-3e of the vacuum pump 1 or from the friction ring seal 11 and that will be radially expelled by the surface 23 of the deflector plate 14. Thereby preventing the particles from moving towards the bearing 9 or the sump 2.

The deflector 14 is made of steel, for example.

According to a first embodiment, the annular end 16 has a substantially cylindrical shape, coaxial with the rotation axis I-I of the shaft 4 (fig. 2, 5 and 6). Thus, the annular end 16 extends perpendicular to the disk portion of the baffle 14 and in a direction parallel to the axis of rotation I-I. The retaining recess is thus substantially cylindrical.

According to one embodiment, annular end 16 of baffle 14 extends at least partially around annular seal 11 interposed between baffle 14 and pumping stage 3e (fig. 2 and 3). In other words, the annular end 16 at least partially covers the annular seal 11.

In the example shown in fig. 2 and 3, the ring seal 11 partially emerges from the cavity of the stator 21 of the vacuum pump 1, into which cavity the back face of the ring is, for example, embedded. The ring of the annular seal 11 has, for example, an approximately parallelepiped cross section. Thus, a bend (a zigzag passage) can be formed between the stator 21 and the annular end portion 16 of the baffle plate 14 and between the retaining recess of the baffle plate 14 and the fixed portion of the annular seal 11.

In the example shown in fig. 12, the protruding shape of the ring seal 11 protruding into the retaining recess of the baffle 14 is constituted by the stator 21 at the fixing portion of the segmented seal (fig. 12).

The bend helps to retain particles from the pumping stages 3a-3e in the retaining recess of the deflector plate 14.

The sealing device 6 may also comprise a sleeve 18 mounted on the shaft 4 and on which the deflector 14 is mounted (fig. 3 and 7).

The seal between the sleeve 18 and the shaft 4 is provided by at least one, for example two, O-rings 19 mounted in series on the shaft 4 in an annular groove 20 formed in the shaft 4 (fig. 3). The sleeve 18 is held on the shaft 4 and the shaft 4 is held in its bearing, for example by means of a prestressed spring washer 22 inserted between the sleeve 18 and the stator 21.

The sleeve 18 has, for example, a two-stage cylindrical shape, comprising a first cylindrical stage 18a, the outer diameter of which 18a is adapted to be inserted in the central orifice 15 in the baffle 14, and a second cylindrical stage 18b, which 18b constitutes an axial stop for the baffle 14 (fig. 3 and 7). According to another embodiment, the sleeve 18 and the baffle 14 are made in one piece.

The lips 12a, 12b of the annular seal 11 are for example the second cylindrical stage 18b of the friction sleeve 18. One end of first lip 12a may be oriented toward sump 2 and one end of second lip 12b may be oriented toward pumping stage 3 e. Depending on the application, lips 12a, 12b may also be oriented in the same direction towards sump 2 or towards pumping stage 3 e.

In the example of fig. 12, the complementary ring 13b of the segmented seal is formed in the sleeve 18.

The sleeve 18 makes it possible in particular to mount the deflector 14 on the shaft 4.

The sleeve 18 is made of steel, for example, and the outer surface of the sleeve 18 may be treated, for example, by a heat treatment such as quenching and/or tempering followed by a skiving operation. This treatment makes it possible to obtain a surface condition and hardness compatible with the operating specifications of the friction annular seal 11.

According to one embodiment, the surface 17 of the deflector 14 opposite to the surface carrying the annular end 16 and facing the oil sump 2 has a frustoconical shape, which is coaxial with the centre of the deflector 14 and whose vertex is located on the side of the pumping stage 3e (fig. 2, 3, 4 and 5).

During operation, the "concave" frustoconical shape of the rotating deflector 14 directs the splash points of lubricant that strike the deflector 14 back to the sump 2.

Further, the axial distance d in a direction parallel to the rotation axis I-I may be made_aLess than 3mm and a perpendicular distance d in a direction perpendicular to the axis of rotation I-I_vLess than 3mm so that the stator 21 is spaced from the edge of the surface 17 of the baffle 14 opposite the surface carrying the annular end 16 (figure 3).

For example, two adjacent cylindrical cavities are formed in the stator 21. The diameter of the first cylindrical cavity is of the same order of magnitude as the diameter of the baffle 14, so that the perpendicular distance d_vLess than 0.5 mm. A second adjacent cylindrical cavity receives the baffle 14 and has a larger diameter. Axial distance d separating stator 21 from the edge of surface 17 of baffle 14_aFor example about 1 mm. Therefore, the passage formed between the stator 21 and the baffle 14 is very narrow. It allows relative expansion of the parts without contacting each other, while providing low conductivity for the lubricant, thereby restricting its movement out of baffle 14.

During operation, the deflector 14, which is mounted on the shaft 4 so as to rotate therewith, rotates at the same rotational speed as said shaft 4.

The centrifugal force created by the rapid rotation of the deflector 14 and the frusto-conical shape of the surface 17 of the deflector 14 opposite the oil sump 2 expel any lubricant that may come from the oil sump 2 and hit the deflector 14 towards the oil sump 2. Thereby limiting the advance of lubricant to the pumping stage 3e, which makes it possible to improve the lubricant tightness in the pumping stages 3a-3 e.

The annular end 16 of the deflector plate 14 retains any particles or dust that may come from the pumping stages 3a-3e in the retaining recess, thereby restricting the advance of the particles towards the oil sump 2. This reduces the oil contamination in the oil sump 2, which increases the service life of the ball bearing 9 and reduces oil consumption. Thus, after 1000 hours of operation of the vacuum pump 1 comprising such a baffle 14, it can be noted that the oil consumption is reduced by about 30%, and that the "clean" oil is almost completely free of contaminating particles.

Baffles 14 made in this manner are easy and inexpensive to manufacture. It is compatible with different types of "dynamic" or friction ring seals 11.

Fig. 9 shows a baffle 24 of a second embodiment.

In this second embodiment, the annular end portion 16 has a radial rim (flange) 25. The radial edge 25 extends substantially perpendicular to the axis of rotation I-I of the shaft 4. This makes it possible to improve the ability of particles and dust to be discharged radially by the deflector 24 to be retained in the retaining recess.

In the first two embodiments, the surface 23 of the disc carrying the annular end 16 is perpendicular to the axis of rotation I-I.

Fig. 10 shows a deflector 26 of a third embodiment, in which the surface 27 of the disc carrying the annular end 16 has a substantially frustoconical shape, coaxial with the centre of the deflector 26, and with its apex on the side of the sump 2.

The annular end 16 may be cylindrical and optionally provided with a radial rim 25 as in the above example, or may have other shapes, such as a chamfered shape as shown in fig. 10.

During operation, the centrifugal force generated by the rapid rotation of the deflector 26 and the frustoconical shape of the surface 27 of the deflector 26 opposite the pumping stage 3e make it possible to direct back to the pumping stage 3e any particles and dust that may come from the pumping stage 3e and that are not trapped in the retaining recess.

Fig. 11 shows a fourth embodiment of a baffle 28.

This embodiment differs from the previous embodiment in that the baffle 28 does not have an annular end 16.

In this example, the disk portion of the baffle 28 includes at least one surface 17, 29 coaxial with the center of the baffle 28 and having a frustoconical shape.

Only one surface may have a frustoconical shape, while the other surface may be perpendicular to the axis of rotation I-I of the shaft 4.

The surface 29 of the deflector 28 having a frustoconical shape, the apex of which is located on the oil sump 2 side, is for example the surface opposite the pumping stage 3 e.

The surface 17 of the deflector 28 having a frustoconical shape, the apex of which is located on the side of the pumping stage 3e, may be, for example, the surface opposite the oil sump 2.

Both surfaces of the baffle 28 may have a frustoconical shape (fig. 11).

The frusto-conical shape of the surface 17 opposite the sump 2 during operation makes it possible to direct back to the sump 2 any lubricant that may come from the sump 2 and hit the deflector 28. The frustoconical shape of the surface 29 opposite the pumping stage 3e makes it possible to direct back to the pumping stage 3e any particles or dust that may come from the pumping stage 3 e.