Vacuum pump

Abstract

A vacuum pump (1) comprising a stator (4) having at least one compression chamber (5), two rotors (6) configured to rotate in the compression chamber (5) about a respective axis of rotation (II), the axes of rotation (II) being vertical, and elements to be lubricated mounted on shafts (7) of the rotors (6), characterized in that the vacuum pump (1) further comprises an oil pump (9) comprising an oil sump (13) and at least one impeller (14) mounted on one of the shafts (7) of the rotors (6), the impeller (14) being immersed in a liquid lubricant received in a chamber of the oil sump (13), the rotation of the impeller (14) causing the circulation of a portion of the lubricant through a lubrication conduit (15) to the elements to be lubricated. (Shorthand figure: Figure 1)

Description

Title of the invention: Vacuum pump Technical field of the invention

[0001] The present invention relates to a dry vacuum pump such as of the "Roots" or "Claw" type or screw type, with vertical axes of rotation. Technical background

[0002] Dry vacuum pumps comprise one or more pumping stages in series through which a gas to be pumped circulates between a suction and a discharge port. Among the known vacuum pumps, we distinguish rotary lobe pumps, also known as "Roots" pumps, claw pumps, also known as "claw" pumps, and screw pumps. Roots blower type vacuum pumps are also known; they are used upstream of primary vacuum pumps to increase pumping capacity in high-flow situations. These vacuum pumps are called "dry" because, during operation, the rotors rotate inside the stator without any mechanical contact between themselves or with the stator, thus eliminating the need for oil in the pumping stages.

[0003] The rotors are supported by bearings lubricated with oil or grease and are synchronized by means of gears that are also lubricated. It is essential that no trace of oil or grease be found in the pumping section for so-called "dry" applications, such as semiconductor substrate manufacturing processes. A sealing device, through which the shafts are always able to rotate, isolates the area containing lubricants from the dry pumping section.

[0004] In the case of horizontally arranged vacuum pumps, an oil agitator disc is generally used to create a misted atmosphere of air and lubricants in the oil sump, facilitating the lubrication of the bearings. The oil agitator is fixed to one of the pump shafts, with one lower end of the agitator immersed in the liquid oil of the sump. The rotation of the shaft supporting the oil agitator creates an oil mist, projecting droplets of lubricant onto the walls of the sump, which then trickle down to the components to be lubricated.

[0005] In the case of a vertical architecture, it is no longer possible to use oil stirring discs efficiently. Therefore, a means is sought to force the oil to circulate in the channels and rise towards the bearings to be lubricated in a vertical vacuum pump. Summary of the invention

[0006] One object of the present invention is to provide a vacuum pump solving at least one of the disadvantages described above.

[0007] To this end, the invention relates to a vacuum pump comprising: - a stator having at least one compression chamber, - two rotors configured to rotate in the compression chamber around a respective axis of rotation, the axes of rotation being vertical, and - elements to be lubricated mounted on rotor shafts, characterized in that the vacuum pump further comprises an oil pump including an oil sump and at least one turbine mounted on one of the rotor shafts, the turbine bathed in a liquid lubricant received in a chamber of the oil sump, the rotation of the turbine causing the circulation of part of the lubricant in a lubrication conduit towards the elements to be lubricated.

[0008] During operation, the engine drives the rotating rotors in the compression chamber to pump gases into the dry pumping section. Simultaneously, the rotation of the shafts drives the rotation of the oil pump turbine. The turbine's rotation accelerates the liquid lubricant, which is then radially driven by centrifugal force or by mechanical elements of the rotating turbine (blades or gear teeth) into the lubrication channel. The oil pump can then force the lubricant to rise to the level of the components to be lubricated located above the oil sump. The oil pump is inexpensive because it uses the same rotational drive mechanisms as the vacuum pump rotors. Furthermore, the oil pump has no wear parts and is simple to implement.

[0009] The vacuum pump may also include one or more of the features described below, taken alone or in combination.

[0010] According to a first embodiment, the oil pump is a vane pump, the turbine having a disc and at least one vane protruding from an upper face of the disc.

[0011] The turbine comprises, for example, between two and six curved blades, extending over an arc of a circle between 10° and 120°, for example to the edge of the turbine disk.

[0012] According to a second embodiment, the oil pump is a centrifugal pump.

[0013] According to one embodiment, the turbine of the centrifugal pump comprises a smooth disc.

[0014] According to another embodiment, the centrifugal pump turbine has a disc extending through a cylindrical wall to form a cylindrical bowl, with at least two through holes being provided in the cylindrical wall of the bowl.

[0015] According to a third embodiment, the oil pump is a gear pump, comprising at least one turbine mounted on a rotor shaft, formed by a toothed wheel of a vacuum pump synchronizing gear.

[0016] The components to be lubricated include, for example, the gears of a synchronizing gear, mounted on a respective rotor shaft, and / or at least a first pair of bearings mounted on the end of the rotor shafts, and / or at least a second pair of bearings. The synchronizing gear and / or the bearing pairs are located along the rotor shafts, for example, above the oil pan.

[0017] The vacuum pump may include an oil return channel provided between the parts to be lubricated and the oil sump chamber. During operation, excess lubrication returns to the oil sump via the oil return channel.

[0018] The lubrication conduit may include an inlet conduit communicating with the chamber of the oil sump receiving the turbine, oriented tangentially or radially to the turbine.

[0019] The inlet conduit may include a flow restriction configured to accelerate the circulation of the lubricant by Venturi effect.

[0020] The inlet conduit can be straight and tangent to the turbine disk.

[0021] According to one embodiment, the inlet of the inlet duct is volute-shaped. The volute spirals around a turbine disk, the diameter of the volute channel increasing, for example, as it approaches a straight, tangential section of the inlet duct. The volute can extend in a complete circle around the disk, the periphery of the disk forming the inlet of the inlet duct. If the cross-section of the volute increases along the direction of lubricant flow, the volute channels the lubricant into the lubrication duct while limiting turbulence. If the cross-section of the volute decreases along the direction of lubricant flow, the volute accelerates the circulation of the lubricant in the lubrication duct by the Venturi effect.

[0022] It may also be provided that a central through orifice is provided in the turbine for fixing the turbine to the end of the rotor shaft.

[0023] Another object of the present invention is a vacuum pump comprising: - a stator having at least one compression chamber, - two rotors configured to rotate in the stator about a respective axis of rotation, the axes of rotation being vertical, - components to be lubricated, mounted on rotor shafts, - a motor configured to drive the rotor shafts in rotation, characterized in that the vacuum pump further comprises an external oil pump including its own means of rotational drive to drive the circulation of a part of the lubricant contained in an oil sump of the vacuum pump to the elements to be lubricated.

[0024] Because it has its own rotational drive means, the flow rate of The liquid lubricant circulated by the external oil pump is independent of the vacuum pump's rotational speed. This allows for precise adjustment of the desired lubrication flow rate without being dependent on the vacuum pump's frequency. In particular, a constant lubrication flow rate can be ensured even at reduced vacuum pump speeds.

[0025] The vacuum pump may further include one or more of the features described below, taken alone or in combination.

[0026] The external oil pump can be a positive displacement oil pump, such as a vane pump.

[0027] In this case, the desired lubrication flow rate can then be set without depending on the viscosity of the oil.

[0028] The external oil pump can also be a non-volumetric oil pump, such as a centrifugal pump.

[0029] In this case, the vacuum pump may include a temperature sensor configured to measure the temperature of the liquid lubricant and a control unit connected to the temperature sensor, configured to control the rotational speed of the drive means in rotation of the external oil pump to control the lubrication flow rate as a function of the measured temperature.

[0030] Another object of the present invention is a vacuum pump comprising two vacuum pump units, each comprising: - a stator comprising at least one compression chamber, - two rotors configured to rotate within a stator compression chamber around a respective axis of rotation, - Lubrication elements mounted on rotor shafts, and - a motor configured to drive the rotors in rotation.

[0031] The rotation axes of the vacuum pump units are vertical.

[0032] The vacuum pump further comprises an external oil pump including Properly designed rotary drive means to circulate a portion of the lubricant contained in an oil sump of each vacuum pump unit towards the components to be lubricated. More specifically, for example, the external oil pump forces the circulation of the lubricant through a lubrication line common to both vacuum pump units, towards the components to be lubricated in each unit. Brief description of the figures

[0033] Other advantages and features will become apparent from the following description of a particular, but by no means limiting, embodiment of the invention, as well as from the accompanying drawings in which:

[0034] [Fig.1] Fig.1 is a schematic representation of a vacuum pump.

[0035] [Fig.2] The [Fig.2] is a partial longitudinal cross-sectional view of the vacuum pump of the [Fig.1], according to a first embodiment.

[0036] [Fig.3] The [Fig.3] is a partial cross-sectional view of an oil pump of the vacuum pump of the [Fig.2].

[0037] [Fig.4] The [Fig.4] is a perspective view of the turbine of the oil pump of the [Fig.3].

[0038] [Fig.5] The [Fig.5] is a cross-sectional view of an oil pump according to a first embodiment.

[0039] [Fig.6] The [Fig.6] is a view similar to the [Fig.5] of an oil pump according to a second embodiment.

[0040] [Fig.7] Fig.7 shows a longitudinal cross-sectional view of an oil pump of a vacuum pump according to a second embodiment.

[0041] [Fig.8] The [Fig.8] shows a perspective view of a turbine of the oil pump of the [Fig.7].

[0042] [Fig.9] Fig.9 shows a partial cross-sectional view of an oil pump according to an alternative embodiment.

[0043] [Fig. 10] The [Fig. 10] shows a longitudinal cross-sectional view of a vacuum pump according to a third embodiment.

[0044] [Fig. 11] The [Fig. 11] shows a partial top view of an oil pump of the vacuum pump of the [Fig. 10].

[0045] [Fig. 12] The [Fig. 12] shows a perspective view of a turbine of the oil pump beyond [Fig. 11],

[0046] [Fig. 13] The [Fig. 13] shows a cross-sectional view of the oil pump of the [Fig.11].

[0047] [Fig. 14] The [Fig. 14] is a schematic representation of a vacuum pump according to an alternative embodiment.

[0048] [Fig. 15] The [Fig. 15] is a schematic representation of a vacuum pump according to another embodiment.

[0049] [Fig. 16] The [Fig. 16] is a schematic representation of a vacuum pump according to a fourth embodiment.

[0050] [Fig. 17] The [Fig. 17] shows a cross-sectional view of the vacuum pump of the [Fig.16].

[0051] [Fig. 18] The [Fig. 18] shows a cross-sectional view of an oil pump of the vacuum pump of the [Fig. 17].

[0052] [Fig. 19] The [Fig. 19] shows a vacuum pump according to another invention.

[0053] [Fig. 20] Fig. 20 shows an alternative embodiment of the vacuum pump of the [Fig.19]

[0054] The following embodiments are examples. Although the description refers to a or several embodiments; this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features from different embodiments can also be combined or interchanged to provide other embodiments.

[0055] 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 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 operation, is connected upstream of a primary vacuum pump and whose discharge pressure is that obtained by the primary vacuum pump.

[0056] In the description, the longitudinal or axial direction is parallel to the axes of rotation of the shafts. The transverse direction is the direction perpendicular to the axial direction of rotation. The vertical direction is the direction parallel to the direction of gravity. The horizontal direction lies in a plane perpendicular to the vertical. Detailed description

[0057] Figures 1 to 6 represent a first embodiment of the oil pump 9.

[0058] The vacuum pump 1 comprises a dry pumping part 2 and a mechanical drive part 3 ([Fig.1]).

[0059] The dry pumping section 2 comprises a stator 4 having at least one compression chamber 5 and two rotors 6 configured to rotate in the compression chamber 5 of the stator 4 about a respective axis of rotation II. The vacuum pump 1 is configured to be installed, i.e., for example, placed on the ground or on a frame, with the axes of rotation II vertical. The vertical arrangement of the vacuum pump 1 makes it possible to significantly reduce its footprint.

[0060] The rotors 6 have conjugate profiles that can be assembled onto the shafts 7, or they can be made as a single unit with the shafts 7 (so-called monobloc rotors). The rotors 6 are, for example, of the "Roots" type with at least two lobes, or of the "Claw" type, or of another similar positive displacement vacuum pump principle. These vacuum pumps are called "dry" because, during operation, the rotors 6 rotate inside the stator 4 without any mechanical contact between themselves or with the stator 4, thus eliminating the need for oil in the dry pumping section 2.

[0061] The vacuum pump 1 may comprise several pumping stages arranged in series. Each pumping stage includes a compression chamber 5 receiving two coupled rotors 6, the compression chambers 5 comprising an inlet and an outlet During rotation, the gas drawn in from the inlet is trapped in the volume created by the rotors 6 and the stator 4, and then driven by the rotors 6 to the next stage. The successive pumping stages are connected in series, one after the other, by respective interstage channels connecting the outlet of the preceding pumping stage to the inlet of the following pumping stage.

[0062] The vacuum pump 1 further includes a lubricant sealing device (not shown) interposed between the mechanical drive part 3 and the dry pumping part 2. The sealing device allows the rotation of the shafts 7 in the dry pumping part 2 while limiting the transfer of lubricants.

[0063] The mechanical drive part 3 includes a motor 8 configured to drive the rotors 6 in rotation.

[0064] The vacuum pump 1 also includes elements to be lubricated mounted on the shafts 7 of the rotors 6 and an oil pump 9 to force the circulation of a liquid lubricant towards these elements to be lubricated.

[0065] The elements to be lubricated include, for example, at least one first pair of bearings 10 mounted at the end of the shaft of the rotors 6 and / or at least one second pair of bearings 11. In the first embodiment, the motor 8 is interposed between the first pair of bearings 10 and the second pair of bearings 11.

[0066] Bearings 10, 11 include, for example, bearings.

[0067] The elements to be lubricated may also include a synchronizing gear comprising two toothed wheels 12 mounted on a respective shaft 7 of the rotors 6. The toothed wheels 12 are configured to synchronize the rotation of the shafts 7.

[0068] The oil pump 9 comprises an oil sump 13 and at least one turbine 14 mounted on one of the shafts 7 of the rotors 6, indifferently the driving shaft or the driven shaft, here the driven shaft. The oil sump 13 has a chamber configured to contain a reservoir of liquid lubricant, injected and drained, for example, via an orifice in the oil sump 13 provided in a closing plate of the chamber and which can be sealed by a plug 21 (see, for example, Figures 16 and 17).

[0069] The turbine 14 is bathed in the liquid lubricant received in the oil sump chamber 13. The rotation of the turbine 14 due to the rotation of the shaft 7 causes a portion of the lubricant to circulate in the lubrication channel 15 towards the elements to be lubricated, here the first pair of upper bearings 10 ([Fig. 1]).

[0070] An oil return channel 25 can be provided between the elements to be lubricated and the oil sump chamber 13. In operation, excess lubrication returns to the oil sump 13 through the oil return channel 25.

[0071] According to one embodiment, the oil sump chamber 13 communicates with the timing gear and the second pair of lower bearings 11.

[0072] In this first embodiment, the oil pump 9 is a paddle pump, the turbine 14 having a disc 16 and at least one blade 17 projecting from an upper face of the disc 16 (figures 2, 3 and 4). The disc 16 mounted on the vertical shaft 7 therefore extends in a horizontal plane.

[0073] The turbine 14 comprises, for example, between two and six blades 17, such as three blades 17. The blades 17 may be curved. They extend, for example, over an arc of a circle between 10° and 120°, such as 120° in the illustration of Figures 3 to 5. The rear edges of the blades 17 extend, for example, to the edge of the disk 16 of the turbine 14.

[0074] A central through hole 18 can be provided in the turbine 14 for fixing the turbine 14 to the end of the shaft of the rotors 6, for example by screwing onto an adapter 19 inserted into a hole in the end of the shaft ([Fig.2]).

[0075] The lubrication conduit 15 may include an inlet conduit 20 communicating with the chamber of the oil sump 13 receiving the turbine 14, oriented tangentially to the turbine 14. As seen in the example of [Fig. 3], the inlet conduit 20 is straight and tangent to the disk 16 of the turbine 14. According to another example not shown, the inlet conduit 20 is oriented radially to the turbine 14.

[0076] During operation, the motor 8 drives the rotors 6 in rotation within the compression chamber 5 for pumping gases into the dry pumping section 2. Simultaneously, the rotation of the shafts 7 drives the rotation of the turbine 14 of the oil pump 9. The rotation of the turbine 14 drives the rotation of the liquid lubricant in the oil sump chamber 13. The liquid lubricant is accelerated and driven radially to the edges of the disc 16 by the vanes 17 and then into the inlet conduit 20. The oil pump 9 can then drive a portion of the lubricant to circulate from the oil sump chamber 13 to the inlet conduit 20 and then into the lubrication conduit 15.The lubricant can then rise to the level of the elements to be lubricated located above the oil sump 13, in particular the second pair of bearings 11, the gears 12 of the timing gear and / or the first pair of bearings 10 located higher than the second pair of bearings 11. The excess lubrication returns to the oil sump 13 via the oil return channel 25. This circulation of the liquid lubricant is illustrated by arrows in [Fig. 1].

[0077] The oil pump 9 is inexpensive because it uses the same means of rotational drive as those of the rotors 6 of the vacuum pump 1. In addition, the oil pump 9 has no wear parts and is simple to implement.

[0078] Figure 5 illustrates a first embodiment of the oil pump 9.

[0079] In this example, the oil pump 9 is also a vane pump. It has the same impeller 14 as in the first embodiment. This example differs from the previous one in that the inlet of the inlet conduit 20 is volute-shaped 22.

[0080] The volute-shaped inlet 22 spirals around the disk 16 of the turbine 14, the diameter of the volute channel 22 increasing with the approach of the straight and tangential part of the inlet conduit 20.

[0081] The volute 22 extends for example over a complete circle around the disk 16, the periphery of the disk 16 forming the entrance of the inlet conduit 20.

[0082] The rear edges of the blades 17 located at the edge of the disk 16 of the turbine 14 are located downstream of the blades 17 in the direction of expansion of the volute 22 and rotation of the turbine 14 (see arrow on [Fig.5]).

[0083] The volute 22 allows the lubricant to be channeled towards the inlet conduit 20 while limiting flow turbulence.

[0084] Figure 6 illustrates a second embodiment of the oil pump 9.

[0085] In this example, the oil pump 9 is also a paddle pump. The turbine 14 includes, for example, curved blades 17. This example differs from the previous one in that the blades 17 are shorter and further from the center than in the first embodiment. They extend, for example, over an arc of a circle between 10° and 45°. The trailing edges of the blades 17 extend, for example, to the edge of the disk 16 of the turbine 14.

[0086] Shorter blades 17 are simpler to make and therefore less expensive but the lubricant flow can be less well controlled and is less important than for longer blades.

[0087] Figures 7 to 13 show a second embodiment of the oil pump 9.

[0088] In the second embodiment, the oil pump is a centrifugal pump.

[0089] In the example illustrated by Figures 7 to 9, the turbine 14 has a smooth disc 16. As in the previous examples, the disc 16 mounted on the shaft 7 extends in a horizontal plane.

[0090] A central through hole 18 can also be provided in the turbine 14 for fixing the turbine 14 to the end of the shaft of the rotors 6, for example by screwing onto an adapter 19 inserted into a hole in the end of the shaft.

[0091] The lubrication conduit 15 may include an inlet conduit 20 communicating with the oil sump chamber 13 receiving the turbine 14, oriented tangentially to the turbine 14 ([Fig. 9]). According to another example not shown, the inlet conduit 20 is oriented radially to the turbine 14.

[0092] According to a first embodiment illustrated by [Fig.7], the inlet conduit 20 is straight and tangent to the disk 16 of the turbine 14.

[0093] During operation, the motor 8 drives the rotors 6 in rotation within the compression chamber 5 to pump the gases into the dry pumping section 2. At the same time, the rotation of the shafts 7 drives the rotation of the turbine 14 of the oil pump 9. The rotation of the turbine 14 drives the rotation of the liquid lubricant in the oil sump chamber 13. The liquid lubricant is accelerated and driven radially to the edges of the disc 16 by centrifugal force and then into the inlet channel 20. The oil pump 9 can then circulate some of the lubricant from the oil sump chamber 13 to the inlet channel 20 and then to the lubrication channel 15. The lubricant rises to the level of the elements to be lubricated located above the oil sump 13, in particular the second pair of bearings 11, the sprockets 12 of the timing gears and / or the first pair of bearings 10 located above the second pair of bearings 11.

[0094] The smooth disc turbine 14 16 is simpler to make and therefore less expensive than a bladed turbine but the lubricant flow can be less well controlled and less important.

[0095] Fig. 9 illustrates an alternative embodiment of the centrifugal oil pump 9.

[0096] In this example, the oil pump 9 has the same smooth disc turbine 14 than in the previous embodiment illustrated by [Fig.7]. This example differs from it in that the inlet of the inlet duct 20 is in the shape of a volute 22.

[0097] As described previously, the volute 22 spirals around the disk 16 of the turbine 14, the diameter of the channel of the volute 22 increasing with the approach of the straight and tangential part of the inlet conduit 20.

[0098] The volute 22 extends for example over a complete circle around the disk 16, the periphery of the disk 16 forming the entrance of the inlet conduit 20.

[0099] Figures 10 to 13 show another example of an embodiment of the centrifugal oil pump 9.

[0100] In this embodiment, the turbine 14 has a disk 16 extending through a cylindrical wall 24 to form a cylindrical bowl, with at least two through holes 23 being provided in the cylindrical wall 24 of the bowl ([Fig. 10] and 12). The disk 16 of the bowl extends in a horizontal plane.

[0101] For example, there are between two and ten holes 23, here six, regularly distributed around the perimeter of the bowl (figures 12 and 13).

[0102] A central through hole 18 can also be provided in the turbine 14 for fixing the turbine 14 to the end of the shaft of the rotors 6, for example by screwing onto an adapter 19 inserted into a hole in the end of the shaft ([Fig. 10]).

[0103] The lubrication conduit 15 may include an inlet conduit 20 communicating with the oil sump chamber 13 receiving the turbine 14, oriented tangentially to the turbine 14. The inlet conduit 20 is, for example, straight and tangent to the disk 16 of the turbine 14 ([Fig. 11]). According to another example not shown, the inlet conduit 20 is oriented radially to the turbine 14.

[0104] In operation, the motor 8 drives the rotors 6 in rotation within the compression chamber 5 for pumping gases into the dry pumping section 2. In the At the same time, the rotation of the shafts 7 drives the rotation of the turbine 14 of the oil pump 9. The rotation of the turbine 14 drives the rotation of the liquid lubricant in the chamber of the oil sump 13. The liquid lubricant is accelerated and driven radially to the edges of the bowl by centrifugal force and then into the inlet conduit 20, via the holes 23. The oil pump 9 can then drive some of the lubricant from the chamber of the oil sump 13 to the inlet conduit 20 and then to the lubrication conduit 15. The lubricant rises to the level of the components to be lubricated located above the oil sump 13, in particular the second pair of bearings 11, the gears 12 of the timing gears and / or the first pair of bearings 10 located above the second pair of bearings 11.

[0105] Fig. 13 illustrates an alternative embodiment of the oil pump 9.

[0106] In this example, the oil pump 9 has the same cylindrical bowl turbine 14 as in the previous embodiment. This example differs from the previous one in that the inlet of the inlet conduit 20 is volute-shaped 22.

[0107] As described previously, the volute 22 spirals around the disk 16 of the turbine 14, the diameter of the channel of the volute 22 increasing with the approach of the straight and tangential part of the inlet conduit 20.

[0108] The volute 22 extends for example over a complete circle around the disk 16, the periphery of the disk 16 forming the entrance of the inlet conduit 20.

[0109] In all the embodiments described above, the arrangement of the oil sump 13, the motor 8 and the oil pump 9 can vary in the vacuum pump 1 without departing from the present invention, as can be seen for example in Figures 14 and 15.

[0110] Following the example of [Fig. 14], the oil pan 13 is arranged at the end of the shaft, the motor 8 being interposed between the oil pan 13 on one side, and the synchronizing gear and the second pair of bearings 11 on the other.

[0111] Furthermore, an oil filter 25 can be arranged in the lubrication channel 15 and / or in the oil return channel 25. This feature in particular can be applied to all embodiments and variants.

[0112] According to another variant, independent of the position of the oil sump 13, and visible in particular on [Fig. 14], the turbine 14 is mounted on the driving shaft 7.

[0113] Fig. 15 shows another embodiment of the vacuum pump 1 in which the motor 8 is arranged at the end of the shaft and the oil housing 13 is interposed between the motor 8 on one side and the timing gear and the second pair of bearings 11 on the other.

[0114] Figures 16 to 18 show a third embodiment of the oil pump 9.

[0115] In this embodiment, the oil pump 9 comprises a turbine 14 mounted on a shaft 7 of the rotors 6, the turbine 14 being formed by a toothed wheel 12 of the synchronizing gear. The toothed wheels 12 extend in a horizontal plane. rizontal.

[0116] In this example also, the lubrication conduit 15 includes an inlet conduit 20 communicating with the chamber of the oil sump 13 receiving the turbine 14. The inlet conduit 20 is oriented tangentially or radially to the turbine 14. It may include a flow restriction 27 configured to accelerate the circulation of the lubricant in the lubrication conduit 15 by Venturi effect ([Fig.18]).

[0117] The geared oil pump 9 uses the rotation of the timing gear 12 and the profile of the gears 12 to accelerate and drive the circulation of the liquid lubricant in the lubrication conduit 15.

[0118] The oil sump chamber 13 can also communicate directly with the second pair of lower bearings 11.

[0119] In the example shown in Figures 16 and 17, the motor 8 is interposed between the dry pumping part 2 on the one hand and the second bearing 11 and the synchronizing gear 12 on the other hand ([Fig. 16]).

[0120] During operation, the motor 8 drives the rotors 6 in rotation within the compression chamber 5 for pumping gases into the dry pumping section 2. At the same time, the rotation of the shafts 7 drives the rotation of the turbine 14 of the oil pump 9. The teeth of the gears 12, and therefore of the turbine 14, accelerate and carry a portion of the lubricant from the oil sump chamber 13 to the lubrication passage 15. The lubricant rises to the level of the elements to be lubricated located above the oil sump 13, in particular the second pair of bearings 11 and / or the first pair of bearings 10 located above the second pair of bearings 11.

[0121] In this embodiment, the synchronizing gear already present for the synchronization of the shafts 7 is used as a means of driving the rotation of the oil pump 9 for the forced circulation of the liquid lubricant.

[0122] Although in figures 16 to 18, only one gear 12 is used as turbine 14 of oil pump 9, it is quite conceivable to symmetrize the system by providing that the oil pump 9 comprises two turbines 14 mounted on a respective shaft 7 of the rotors 6, each formed by a gear 12 of the synchronizing gear.

[0123] Figures 19 and 20 show a vacuum pump 1 made according to another invention.

[0124] The vacuum pump 1 comprises a dry pumping part 2 and a mechanical drive part 3.

[0125] The dry pumping section 2 comprises a stator 4 having at least one compression chamber 5 and two rotors 6 configured to rotate in the compression chamber 5 of the stator 4 about a respective axis of rotation II. The vacuum pump 1 is configured to be installed, i.e., for example, placed on the ground or on a frame, with the axes of rotation II vertical. The vertical arrangement of the vacuum pump 1 allows for a significant reduction in the land footprint.

[0126] The rotors 6 have conjugate profiles that can be assembled onto the shafts 7, or they can be made as a single unit with the shafts 7 (so-called monobloc rotors). The rotors 6 are, for example, of the "Roots" type with at least two lobes, or of the "Claw" type, or of another similar positive displacement vacuum pump principle. These vacuum pumps are called "dry" because, in operation, the rotors 6 rotate inside the stator 4 without any mechanical contact between themselves or with the stator 4, which eliminates the need for oil in the dry pumping section 2.

[0127] The vacuum pump 1 may comprise several pumping stages arranged in series. Each pumping stage includes a compression chamber 5 receiving two coupled rotors 6, the compression chambers 5 having a respective inlet and outlet. During rotation, the gas drawn in from the inlet is trapped in the volume created by the rotors 6 and the stator 4, and is then driven by the rotors 6 to the next stage. The successive pumping stages are connected in series one after the other by respective interstage channels connecting the outlet of the preceding pumping stage to the inlet of the following pumping stage.

[0128] The vacuum pump 1 further includes a lubricant sealing device (not shown) interposed between the mechanical drive part 3 and the dry pumping part 2. The sealing device allows the rotation of the shafts 7 in the dry pumping part 2 while limiting the transfer of lubricants.

[0129] The vacuum pump 1 also includes elements to be lubricated mounted on the shafts 7 of the rotors 6 and an external oil pump 30 to force the circulation of a liquid lubricant towards these elements to be lubricated.

[0130] The elements to be lubricated include, for example, at least a first pair of bearings 10 mounted on the end of the shaft of the rotors 6 and / or at least a second pair of bearings 11, for example interposed between a motor 8 and the dry pumping part 2. Alternatively, the motor 8 can be interposed between the dry pumping part 2 and the second pair of bearings 11.

[0131] Bearings 10, 11 include, for example, bearings.

[0132] The elements to be lubricated may also include a synchronizing gear comprising two toothed wheels 12 mounted on a respective shaft 7 of the rotors 6. The toothed wheels 12 are configured to synchronize the rotation of the shafts 7.

[0133] The vacuum pump 1 also includes, for example, an oil sump 31 containing a reservoir of liquid lubricant, communicating, for example, with the timing gear, the second pair of bearings 11 and possibly also the motor 8.

[0134] A lubrication conduit 15 connects, for example, the liquid lubricant reservoir of the oil sump 31 to the external oil pump 30 and to the elements to be lubricated, here the first pair of bearings 10 located at the end of the shaft ([Fig. 19]).

[0135] An oil return channel 25 can be provided between the elements to be lubricated and the oil sump chamber 31. In operation, excess lubrication returns to the oil sump 31 through the oil return channel 25.

[0136] An oil filter 26 can be arranged in the lubrication channel 15 and / or in the oil return channel 25.

[0137] The external oil pump 30 includes its own rotational drive means. By its own means, it is understood that the rotational drive means of the external oil pump 30 are independent of the motor 8 that drives the rotors 6 of the dry pumping section 2 of the vacuum pump 1.

[0138] The external oil pump 30 can be a positive displacement oil pump, such as a vane pump. The rotational drive means are then configured to rotate an eccentric vane rotor of the external oil pump 30 in order to circulate a portion of the lubricant in the lubrication channel 15.

[0139] In operation, the external oil pump 30 drives the circulation of a portion of the liquid lubricant from the oil sump 31 to the elements to be lubricated, here the first pair of bearings 10. The circulation of the liquid lubricant is illustrated by arrows on [Fig. 19],

[0140] According to another embodiment, the external oil pump is a non-volumetric oil pump, such as a centrifugal pump. The rotational drive means are then configured to rotate a centrifugal disk of the external oil pump 30 in order to drive the circulation of the lubricant in the lubrication channel 15.

[0141] In this case, the vacuum pump 1 may further include a temperature sensor configured to measure the temperature of the liquid lubricant and a control unit connected to the temperature sensor, configured to control the rotational speed of the drive means in rotation of the external oil pump 30 to control the lubrication flow rate as a function of the measured temperature.

[0142] Because it has its own rotational drive means, the flow rate of liquid lubricant circulated by the external oil pump 30 is independent of the rotational speed of the vacuum pump 1. It is therefore possible to precisely adjust the desired lubrication flow rate without depending on the frequency of the vacuum pump 1. In particular, a constant lubrication flow rate can be ensured even when the speed of the vacuum pump 1 is reduced, for example, in standby mode (known as "idle"). This solution also simplifies the use of the oil filter 26 to guarantee an increased service life for the mechanical components.

[0143] Fig. 20 shows an alternative embodiment in which the external oil pump 30 is common to two vacuum pump units 1.

[0144] The vacuum pump 1 comprises two vacuum pump units 32 each comprising a stator 4 having at least one compression chamber 5, two rotors 6 configured to rotate in a compression chamber of the stator 4 around a respective axis of rotation II, elements to be lubricated mounted on shafts 7 of the rotors 6 and a motor 8 configured to drive the rotors 6 in rotation.

[0145] The rotation axes II of the vacuum pump units 32 are vertical.

[0146] The vacuum pump 1 further comprises an external oil pump 30 including its own rotational drive means for circulating a portion of the lubricant contained in an oil sump 31 of each vacuum pump unit 32 towards the elements to be lubricated. More specifically, for example, the external oil pump 30 forces the circulation of the lubricant in a lubrication channel 15 common to the two vacuum pump units 32, towards the elements to be lubricated of each unit 32, here the first pair of upper bearings 10.

Claims

Demands

1. A vacuum pump (1) comprising: - a stator (4) having at least one compression chamber (5), - two rotors (6) configured to rotate in the compression chamber (5) about a respective axis of rotation (II), the axes of rotation (II) being vertical, and - elements to be lubricated mounted on shafts (7) of the rotors (6), the vacuum pump (1) further comprising an oil pump (9) comprising an oil sump (13) and at least one impeller (14) mounted on one of the shafts (7) of the rotors (6), the impeller (14) being immersed in a liquid lubricant received in a chamber of the oil sump (13), the rotation of the impeller (14) causing the circulation of a portion of the lubricant in a lubrication conduit (15) towards the elements to be lubricated, characterized in that the oil pump (9) is a vane pump, the impeller (14) having a disc (16) and at least one vane (17) projecting from an upper face of the disk (16),the lubrication conduit (15) comprising an inlet conduit (20) communicating with the oil sump chamber (13) receiving the turbine (14), oriented tangentially or radially to the turbine (14).

2. Vacuum pump (1) according to claim 1, characterized in that the turbine (14) comprises between two and six curved blades (17), extending over an arc of a circle between 10° and 120°, up to the edge of the disk (16) of the turbine (14).

3. Vacuum pump (1) according to any one of the preceding claims, characterized in that the elements to be lubricated comprise toothed wheels (12) of a synchronizing gear, mounted on a respective shaft (7) of the rotors (6).

4. Vacuum pump (1) according to any one of the preceding claims, characterized in that the elements to be lubricated comprise at least a first pair of bearings (10) mounted at the end of the shafts of the rotors (6) and / or at least a second pair of bearings (11), located along the shafts (7) of the rotors (6), above the oil casing (13).

5. Vacuum pump (1) according to any one of the preceding claims, characterized in that the inlet conduit (20) has a flow restriction (27) configured to accelerate the circulation of the lubricant by Venturi effect.

6. Vacuum pump (1) according to any one of the preceding claims, ca- characterized in that an inlet (22) of the inlet conduit (20) is volute-shaped.

7. Vacuum pump (1) according to any one of the preceding claims, characterized in that it comprises an oil return channel (25) provided between the elements to be lubricated and the oil sump chamber (13).

8. Vacuum pump (1) according to any one of the preceding claims, characterized in that a central through orifice (18) is provided in the turbine (14) for fixing the turbine (14) to the end of the shaft of the rotors (6).

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