FR3128747A1 - Multi-stage vacuum pump - Google Patents

Abstract

The invention relates to a multi-stage vacuum pump (1) comprising a plurality of pumping stages (3a, 3b, 3c) respectively comprising an inlet (E) and an outlet (S), the pumping stages (3a, 3b, 3c) being connected in series between a suction (4) and a discharge (5) of the vacuum pump (1), a stator (2) comprising at least one stator element produced by the assembly of two complementary half-shells (2A, 2B) which join along an assembly surface (8), at least one evacuation channel (11) connected to the outlet (S) of a pumping stage ( 3a, 3b) and in fluid communication with the discharge (5), and at least one valve (13) associated with the discharge channel (11). According to the invention, the evacuation channel (11) is formed in one of the half-shells (2A, 2B) by opening out into at least one mouth in the assembly surface (8) and the valve (13) partner is arranged between the two half-shells (2A, 2B) while being at least partly movable so as to close or release the mouth of the evacuation channel (11), depending on a pressure difference on both sides other side of the valve (13). Figure for the abstract: Fig. 2

Description

Multi-stage vacuum pump

The present invention relates to a multi-stage vacuum pump. The invention applies in particular to a vacuum pump of the dry type.

Multi-stage vacuum pumps comprise several pumping stages in series in which a gas to be pumped circulates between a suction and a discharge. A distinction is made among the known vacuum pumps, those with rotary lobes also known under the name "Roots" with two or three lobes or those with double nozzle, also known under the name "Claw" or those with screws. Rotary lobe pumps comprise two rotors of identical profiles, rotating inside a stator in opposite directions. During rotation, the gas to be pumped is trapped in the free space between the rotors and the stator, and is driven by the rotors to the next stage or after the last stage at the discharge outlet. These vacuum pumps are called "dry" because in operation, the rotors turn inside a stator without any mechanical contact between the rotors and the stator, which means that no oil is used in the pumping stages. .

A constant objective is to facilitate the assembly of such vacuum pumps while reducing costs. For this purpose, the stators can be made in several parts. According to a known solution, the stator is formed by assembling at least two complementary half-shells. Such a half-shell architecture reduces assembly time and also reduces the risk of accumulation of misalignments.

Furthermore, to reduce their energy consumption, the last pumping stages, on the discharge side, can have a swept volume, that is to say a volume of pumped gas, smaller than that of the first pumping stages, on the pressure side. suction.

During certain applications, for example for the pumping of loading/unloading airlocks (or "load lock"), the enclosures of the airlocks are evacuated from atmospheric pressure, in order to be able to transfer a substrate into a process chamber. maintained at low pressure. To reduce the pressure in the enclosure from atmospheric pressure, the vacuum pump must absorb large initial gas flows, which are hardly admitted by the last pumping stages on the discharge side. All pumping stages are however necessary at low pressure, in order to be able to reach the desired limit vacuum pressures.

This same situation where the last stages can limit the overall pumping rate of the vacuum pump, can intervene for the pumping of the process chambers. Even if the process chamber is normally continuously under vacuum, the vacuum pump must be able to absorb a large pumping flow at the first evacuation.

It is therefore essential to shorten these pressure drop times so as not to slow down the manufacturing processes taking place in the process chamber, with high added value.

Some vacuum pumps therefore provide a load shedding device connecting the outlet of a pumping stage to be unloaded to the discharge. The load-shedding device makes it possible to evacuate the excess gas flow coming from the outlet of the pumping stage to be unloaded directly to the discharge of the vacuum pump.

To do this, a casing external to the vacuum pump is generally arranged below the stator comprising pumping stages. Such a box comprises, for each pumping stage to be shed, a channel connecting the outlet of this pumping stage to be shed to the discharge of the vacuum pump.

However, the assembly of the casing to the stator of the vacuum pump requires an additional operation, increases the cost of the vacuum pump and increases the size, in particular the height, of the vacuum pump. In addition, the channels for connecting the pumping stages to the discharge can be complicated to create and involve as many additional seals to manage.

An object of the present invention is to propose an improved vacuum pump making it possible to at least partially solve one of the aforementioned drawbacks of the state of the art.

To this end, the subject of the invention is a multi-stage vacuum pump comprising a plurality of pumping stages respectively comprising an inlet and an outlet, the pumping stages being connected in series between a suction and a discharge of the pump vacuum, a stator comprising at least one stator element produced by assembling two complementary half-shells which meet along an assembly surface, at least one evacuation channel connected to the outlet of a pumping stage and in fluid communication with the discharge, and at least one valve associated with the discharge channel.

According to the invention, the evacuation channel is formed in one of the half-shells by opening out into at least one opening in the assembly surface. The associated valve is arranged between the two half-shells while being at least partly mobile so as to close or release the mouth of the evacuation channel, depending on a pressure difference on either side of the valve.

The arrangement of the valve between the half-shells makes it possible to avoid the assembly of an additional box to the stator of the vacuum pump, for example to perform a load shedding and/or discharge function. This reduces the cost and size of the vacuum pump. In addition, the evacuation channel is made in a simple way within one of the half-shells. Finally, in the absence of an additional box, such a solution makes it possible to minimize the seals to be managed with the outside.

The vacuum pump may further comprise one or more of the following features described below, taken separately or in combination.

The evacuation channel or one of the evacuation channels may be a relief channel connected to the outlet of a pumping stage to be relieved and in fluid communication with the discharge.

According to one embodiment, the successive pumping stages are connected in series by a respective inter-stage channel connecting the output of a preceding pumping stage to the input of a following pumping stage.

A common channel can be connected at the output of the pumping stage to be shed. This common channel can be connected to at least two bypass portions, of which a first portion forms with the common channel an inter-stage channel connected to the input of the following pumping stage and a second portion forms with the common channel the relief channel.

The discharge channel or one of the discharge channels may be a discharge channel connected to the outlet of the last pumping stage and in fluid communication with the discharge.

The vacuum pump may comprise at least two valves respectively associated with a pumping stage. The valves can be sized differently depending on the associated pumping stage. The valves can be sized differently depending on the setting pressures.

The valve is mounted at least partially movable in a cavity formed in the half-shell opposite the half-shell comprising the evacuation channel, the valve being arranged opposite the mouth of the evacuation channel in the assembly surface.

The vacuum pump may include at least one outlet channel fluidly connecting the cavity to the discharge. This outlet channel can be formed in one of the half-shells.

According to an exemplary embodiment, the valve or at least one of the valves comprises a ball.

At least one annular seal can be arranged in the mouth of the evacuation channel associated with the valve.

The seal has for example a base received in a first groove of the mouth of the evacuation channel. The base may be of general toroidal shape. The first groove has for example a generally cylindrical shape.

The base can be surmounted by a portion delimiting a valve seat, for example for the ball, and received in a second groove of the mouth of the evacuation channel provided above the first groove. The portion delimiting the valve seat may be tapered. The second groove may have a generally frustoconical shape complementary to the frustoconical portion of the seal.

The vacuum pump may comprise at least one injection channel opening out via at least one injection orifice configured to inject a purge gas onto the valve and/or onto a bearing face of a valve seat.

The vacuum pump may include a delivery pipe arranged to connect the outlet of the last pumping stage to the delivery and fluidically connected to the evacuation channel. This discharge line has, for example, a housing for receiving a vacuum pump silencer interposed between the outlet of the last pumping stage and the discharge.

The discharge line can be attached to either half-shell.

Furthermore, the vacuum pump comprises, for example, two rotor shafts configured to rotate synchronously in opposite directions in the pumping stages to drive a gas to be pumped between the suction and the discharge.

The stator may include at least one end piece. The stator element is assembled axially with the end piece or with another stator element.

The invention also relates to a pump unit comprising at least one vacuum pump. This vacuum pump can for example be as defined previously.

The pumping unit may further comprise at least one additional pump upstream of the vacuum pump depending on the direction of gas circulation.

Advantageously, the pump unit may include at least one other valve arranged to move between the stators of the additional pump and of the vacuum pump. It is configured to block or release a mouth of a pipe connected to the vacuum pump discharge, depending on a pressure difference on either side of the valve.

The stator of the vacuum pump defines for example a seat for the valve.

The valve can be received in a cavity made in the stator of the additional pump.

Other advantages and characteristics of the invention will appear more clearly on reading the following description given by way of illustrative and non-limiting example, and the appended drawings, among which:

is a perspective view partially showing a stator of a multi-stage vacuum pump according to a first exemplary embodiment.

is a schematic representation of elements of a vacuum pump according to a second embodiment.

is a cross-sectional view of the stator of the showing a valve of a vacuum pump relief device in the closed position.

is a longitudinal sectional view of part of the stator of the showing two valves of the vacuum pump relief devices in the closed position.

is a schematic representation of elements of a vacuum pump according to a third embodiment.

is a schematic representation of elements of a vacuum pump according to a fourth embodiment.

is a schematic representation of elements of a vacuum pump according to a fifth embodiment.

is a schematic representation of elements of a vacuum pump according to a sixth embodiment.

is a schematic representation of elements of a vacuum pump according to a seventh embodiment.

is a schematic representation of elements of a vacuum pump according to an eighth embodiment.

is a schematic representation of a pump unit comprising the vacuum pump of the and an additional pump.

In these figures, identical or similar elements bear the same reference numbers. Figures have been simplified for clarity. Only the elements necessary for understanding the invention are represented.

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply to only one embodiment. Simple features of different embodiments can also be combined or interchanged to provide other embodiments.

There illustrates an embodiment of a multi-stage vacuum pump 1, that is to say comprising several stages (at least two). The vacuum pump 1 is in particular of the dry type.

This vacuum pump 1 can be a primary vacuum pump which can be started at atmospheric pressure. Such a primary vacuum pump is configured to suck, transfer and then discharge the pumped gases at atmospheric pressure.

The vacuum pump 1 comprises a stator 2 forming at least two pumping stages connected in series between a suction 4 and a discharge 5, and in which a gas to be pumped can circulate.

In the example shown in the , the vacuum pump 1 comprises for example five pumping stages. Of course, this number is not limiting. There shows another embodiment of a multi-stage vacuum pump 1, comprising for example three pumping stages 3a-3c.

The vacuum pump 1 further comprises two shafts of rotors 6 configured to rotate synchronously in opposite directions in the pumping stages 3a-3c so that the rotors 6 drive a gas to be pumped between the suction 4 and the discharge 5 .

The rotors 6 have, for example, rotary lobes with identical profiles, for example of the “Roots” type. Alternatively, they may be “Claw” type lobes or alternatively screw type or other similar principle of vacuum pump. The rotor shafts are driven in rotation by at least one motor (not shown) of the vacuum pump 1. The motor is located for example at one end of the vacuum pump 1.

Each pumping stage 3a, 3b, 3c is formed by a compression chamber receiving the rotors 6. The compression chambers comprise a respective inlet E and an outlet S. During rotation, the gas sucked in from inlet E is trapped in the volume generated by rotors 6 and stator 2, then is transferred by rotors 6 to the next stage and so on until discharge 5.

The vacuum pump 1 is said to be "dry" because in operation, the rotors 6 turn inside the stator 2 of the vacuum pump 1 in the opposite direction without any mechanical contact between them or with the stator 2, which makes it possible to do not use oil in pump stages 3a-3c.

The successive pumping stages 3a-3c are connected in series one after the other by respective inter-stage channels 7 connecting the output S of the pumping stage 3a-3b which precedes to the input E of the pumping stage 3b-3c which follows. The inlet E of the first pumping stage 3a, also called "suction stage", communicates with the suction 4 of the vacuum pump 1. The outlet S of the last pumping stage 3c, also called "discharge stage" communicates with the discharge 5. The pumping stage(s) connected in series between the suction stage 3a and the discharge stage 3c are also called intermediate stages.

In addition, the stator 2 comprises for example at least one stator element made by assembling a first and a second complementary half-shells 2A, 2B. A stator casing (not shown) may optionally surround the assembled half-shells 2A, 2B. The stator 2 may further comprise at least one end piece (not shown), for example two end pieces on either side of the two half-shells 2A, 2B. The end piece or pieces form, for example, supports for the bearings of the rotor shafts 6. The half-shells 2A, 2B and any end pieces are assembled together, for example by axial assembly. The axial direction is defined as the longitudinal direction of the vacuum pump 1 in which the axes of the rotor shafts 6 extend. hardenable and/or by screwing. One or more seals (not shown) may be provided to guarantee sealing between the various assembled elements of the vacuum pump 1.

The two half-shells 2A, 2B, when they are assembled, meet along an assembly surface 8, to form the compression chambers of the pumping stages 3a-3c. The compression chambers and the inter-stage channels 7 are partly formed in the first half-shell 2A and partly in the second half-shell 2B. The inter-stage channels 7 are for example provided on the sides of the compression chambers, in the half-shells 2A, 2B. They can extend on the same side of the compression chambers or on both sides of the compression chambers. There is for example an inter-stage channel 7 between two successive pumping stages 3a, 3b, 3c mounted in series or two inter-stage channels 7 mounted in parallel between these two pumping stages 3a, 3b, 3c on each side of the compression chamber.

The assembly surface 8 can be flat. It passes for example through a median plane of the dry primary vacuum pump 1 . This assembly surface 8 can be strictly flat or can have, for example, complementary shapes in relief or grooves or grooves, for example for seals between the half-shells 2A, 2B. In the assembled state of the half-shells 2A, 2B, the axes of the rotor shafts 6 are for example contained between the half-shells 2A, 2B at the level of the assembly surface 8.

In known manner, orifices are made in the transverse walls of the half-shells 2A, 2B separating the compression chambers, and possibly in the end pieces for the passage of the rotor shafts 6.

The stator 2 may comprise several stator elements and at least one end piece, for example two end pieces on either side of the stator elements (not shown). Each stator element is assembled axially (that is to say in a direction parallel to the axis of the rotor shafts 6) with another stator element or with an end piece of the stator 2, to form the compression chambers of the pumping stages 3a-3c receiving the rotors 6. At least one, or even each, of the stator elements can be produced by assembling two complementary half-shells which meet along an assembly surface .

The vacuum pump 1 further comprises at least one channel, also referred to as an evacuation channel, and a valve, associated with a pumping stage 3a, 3b, 3c to be connected to the discharge 5. Specific examples of such channels and valves associated are detailed below. In particular, it may be a discharge channel and valve and/or a relief channel and valve.

The evacuation channel is formed in one of the half-shells 2A or 2B by opening out into at least one mouth in the assembly surface 8. This mouth can be closed or released by the associated valve. Thus, the evacuation channel ends at the level of the assembly surface 8. In particular, the evacuation channel is connected by a first end to the output S of the associated pumping stage 3a-3c. Its second end is the mouth in the assembly surface 8 which can be closed or released by the associated valve.

The associated valve is in particular metallic. This associated valve is arranged between the two half-shells 2A, 2B. It is arranged opposite the mouth (or second end) of the associated evacuation channel in the assembly surface 8. The valve is at least partly movable so as to be able to release or close the mouth of the associated evacuation channel. Such a valve is configured to open according to pressure differentials on either side of the valve, more precisely when the pressure difference is greater than a predefined threshold. The valve can be movably mounted in a cavity formed in the other half-shell 2B, 2A. When the valve releases the mouthpiece (or second end), the evacuation channel then opens into the cavity.

In a non-limiting manner, the valve may comprise a ball, for example made of steel. The valve can be configured to move in translation, in rotation or even according to a combined movement.

By arranging the valve between the half-shells 2A, 2B, the assembly of an additional casing to the stator of the vacuum pump is avoided, which reduces the cost and size of the vacuum pump. In addition, the evacuation channel and sealing are simple to make.

According to one embodiment, the vacuum pump 1 comprises at least one channel 11 and a relief valve 13, associated with a pumping stage 3a, 3b, to be connected to the discharge 5.

Indeed, to reduce the energy consumption of the vacuum pump 1, the discharge stage 3c, or even also at least some of the last intermediate stages have a generated volume, that is to say a volume of pumped gas , smaller than that of the first stage(s). To absorb the strong flows of gas originating in particular from the beginning of a vacuuming of an enclosure at atmospheric pressure, the vacuum pump 1 can comprise at least one device 9 for relieving load from a pumping stage 3a, 3b.

The load shedding device 9 makes it possible to evacuate any excess gas flow coming from the outlet S of a pumping stage to be shed towards the discharge 5 of the vacuum pump 1. The choice of the pumping stage to be shed depends on the geometry of the vacuum pump 1 and more particularly on the volume generated in the pumping stages. Generally, the pumping stage with the highest compression ratio is relieved. As the generated volume decreases with the increase in pressure, the pumping stages to be relieved are most often the low pressure pumping stages such as the first or the second pumping stage. It is also possible to relieve several pumping stages, for example the first two pumping stages.

The or each load shedding device 9 comprises the load shedding channel 11 and the valve 13 for load shedding.

The relief channel 11 is connected to the output S of the pumping stage to be relieved 3a, 3b and is in fluid communication with the discharge 5 of the vacuum pump 1. It is in particular connected by a first end to the stage pumping to relieve 3a, 3b.

The relief channel 11 forms an evacuation channel arranged in one of the half-shells 2A or 2B. In the examples illustrated, the relief channel 11 is provided in the lower half-shell 2B with reference to the orientation of the vacuum pump 1 in the assembled state.

This relief channel 11 can be separate from the inter-stage channel 7 at the output of the pumping stage to be relieved 3a, 3b. According to an alternative not shown, a common channel connected at the output S of the pumping stage to be relieved 3a, 3b, can be connected to two bypass portions, a first portion of which forms an inter-stage channel 7 connected to the input E of the next pumping stage and a second portion forms the relief channel 11 opening onto the assembly surface 8.

Depending on the dimensions and/or pumping capacities of the vacuum pump 1, the latter may comprise only a single load shedding device 9 with a single mouth of the load shedding channel 11 and an associated load shedding valve 13. Alternatively, several offloading devices 9 connected in parallel can be provided to offload a larger flow of gas while maintaining a small footprint. For example, two relief channels and two associated valves can be provided to relieve a single pumping stage. In addition, several load shedding devices 9 can be provided to lighten several pumping stages.

When several relief devices 9 are provided to relieve several pumping stages, the various relief valves 13 can be sized differently depending on the associated pumping stage to be relieved and/or depending on the setting pressures.

The or each relief valve 13 is arranged so as to be able to release or close the mouth (or second end) of the associated relief channel 11.

More specifically, such a relief valve 13 is arranged at least partially in a cavity 15 provided in the other half-shell, that is to say in the half-shell opposite the relief channel 11, being screwed -à-vis the mouth (or second end) of the relief channel 11 associated. In the examples illustrated, the cavity 15 is formed in the upper half-shell 2A.

A single relief valve 13 can be arranged per cavity 15 or, on the contrary, several relief valves 13 can be arranged in a common cavity 15. In the latter case, the cavity 15 may have its own housing in which each relief valve 13 can move.

The relief valve 13 functions as a valve which opens to avoid undesirable overpressures in the vacuum pump 1. Thus, in normal operation of the vacuum pump 1, that is to say for the pumping of a flow of gas sized for the pumping capacity of the vacuum pump 1, the mouth (or second end) of the or each relief channel 11 is closed by the associated relief valve 13 . And in the event of overpressure in the associated pumping stage 3a, 3b, the relief valve 13 is configured to open.

In particular, when the pressure difference is below the calibration threshold of the relief valve 13, the latter is in a closed position, preventing the passage of gases to the discharge 5. This prevents the pumped gases from short-circuiting the next pumping stages. The pumped gas follows the path represented by the arrows F1 in solid lines. It is sucked up by all the pumping stages 3a-3c and comes out at the outlet S of the discharge stage 3c. Then, the gas circulates to delivery 5 of vacuum pump 1.

When the pressure difference is greater than the calibration threshold of the relief valve 13, the latter releases the passage of the gas to be pumped which can be evacuated from the relief pumping stage 3a, 3b towards the discharge 5. This makes it possible to short- circuit the last pumping stage(s) 3c of the vacuum pump 1 which could limit the overall generated flow rate. The relieved gas follows the path represented by the white arrows F2 whose contour is represented by broken lines.

Generally, in the closed position, the relief valve 13 is in contact with a bearing face of an associated valve seat. Such a valve seat has a passage or an opening in fluid communication with the relief channel 11. When the relief valve 13 is in the closed position, it closes the opening of the valve seat. On the contrary, when it opens, the relief valve 13 is for example away from the valve seat and frees the passage of gases.

According to the example of the relief valve 13 comprising a ball, the opening of such a valve 13 can be done according to a translational movement of the ball in the direction of a bottom 16 of the corresponding cavity 15. For example, a surplus of gas lifts the ball or balls from their respective valve seat.

In addition, the relief valve 13 is configured to close in a sealed manner. To this end, as can be seen in FIGS. 3 and 4, the load shedding device 9 may comprise at least one annular seal 17 arranged in the mouth (or second end) of the load shedding channel 11. Such a gasket seal 17 defines the valve seat.

When the relief valve 13, for example in the form of a ball, rests on the seat formed by the seal 17, and is partially housed in the cavity 15 facing the mouth (or second end) of the relief channel 11, it seals off the mouth of the relief channel 11 in a sealed manner.

The shape of the seal 17 is complementary in shape to the shape of the relief valve 13 and to the shape of the mouth (or second end) of the relief channel 11.

According to a particular embodiment, the seal 17 may be of generally frustoconical shape, which allows self-centering of the ball forming valve 13 of relief.

The seal 17 also serves to guide by damping the fall of the ball when it falls back on the valve seat, for example when the flow of gas decreases and can again be absorbed by the vacuum pump 1.

By way of example, the seal 17 has a base 17a surmounted by a portion 17b defining the valve seat. Such a seal 17 is preferably made in one piece, for example by molding. The seal 17 comprises at least one material chosen from an elastomeric material, a silicone material, which makes it possible to improve its mechanical strength and its resistance to high temperatures of the vacuum pump 1.

The base 17a is housed in a first groove 21 complementary to the mouth of the relief channel 11. This makes it possible to secure the seal 17 in the relief channel 11. The base 17a has for example a toric shape. The first groove 21 has, for example, a generally cylindrical shape, which makes it possible to leave a clearance around the toric base 17a of the seal 17 allowing its elastic fitting in the first groove 21.

According to one embodiment, the portion 17b delimiting the valve seat may have a frustoconical external shape. It is received in a second groove 23 complementary to the mouth of the relief channel 11 which is arranged above the first groove 21. In a complementary manner, the second groove 23 can be of frustoconical shape. Thus, the external frustoconical portion 17b of the seal 17 matches the complementary shape of the frustoconical portion of the mouth of the relief channel 11. The reinforcement provided by the frustoconical mouth of the channel 5 makes it possible to improve the mechanical strength of the seal sealing ring 17 and its fixing in the mouth.

As schematized on the , an elastic return member 25 can be arranged and configured to urge an associated relief valve 13 towards the closing position of the mouth of the relief channel 11 opposite. The elastic return member 25 comprises for example a spring, such as a helical spring, interposed between the load shedding valve 13 and the half-shell, here the half-shell 2A, of the stator 2 facing the relief channel 11. In particular, the spring may be integral with a bottom 16 of cavity 15. This spring also serves to guide the movement of the relief valve 13 .

Alternatively, it is also possible not to use such an elastic return. In this case, the relief valve 13 is urged into the closed position by the force of gravity.

Advantageously, an injection of a purge gas can be provided to clean the relief valve 13 or the valve seat. The purge gas is for example nitrogen. The injection of purge gas, which can be continuous or discontinuous and targeted over time, makes it possible to prevent the presence of deposits and to avoid contamination at the level of the relief valve 13, which could harm the operation of the valve 13 load shedding and generate a leak. This cleaning allows the sealing function in the closed position and the function of opening the relief valve 13 in the event of overpressure to be ensured longer between two maintenance periods.

To this end, the vacuum pump 1 may include at least one injection channel 27 shown in broken lines on the , emerging through at least one injection orifice (not visible in the figures). According to an exemplary embodiment, such an injection channel 27 can be made in one of the half-shells, this is the lower half-shell 2B in the example shown. The injection orifice can for example be obstructed by the relief valve 13 when it closes and closes the mouth of the relief channel 11, and released when the relief valve 13 opens and releases the mouth.

The purge gas can be injected on a bearing face of the valve seat. As a variant or in addition, the purge gas can be injected onto the relief valve 13, in particular the part resting on the valve seat in the position of closure of the mouth of the relief channel 11. The injection of the purge gas can be done for example when the relief valve 13 is open and releases the mouth (or second end) of the relief channel 11. Alternatively or in addition, the injection of the purge gas can be done when the relief valve 13 is closed, and closes off the mouth (or second end) of relief channel 11. In this case, the injection orifice opens out of the valve seat.

In the example of the , only one injection channel 27 is shown. This number is not limiting. Several injection channels 27 can be arranged to clean the same relief valve 13 and/or associated valve seat. Alternatively, several injection channels 27 can be provided for different relief valves 13 and/or valve seats.

Furthermore, the vacuum pump 1 further comprises at least one outlet channel 29 fluidly connecting the or each cavity 15 to the discharge 5. Such an outlet channel 29 can be provided in the half-shell (for example here 2B) comprising the relief channel 11, as shown in Figures 2 and 5. Alternatively, the outlet channel 29 can be provided in the half-shell (for example 2A) comprising the cavity 15, as shown in Figures 7 to 8b .

Thus, when the or one of the relief valves 13 opens, the gas at the outlet S of a pumping stage 3a, 3b relieved, passes under the relief valve 13 in the cavity 15 before entering in the outlet channel 29 then joins the discharge 5 of the vacuum pump 1 (arrows F2).

Finally, the vacuum pump 1 generally comprises a discharge valve 31 (also called a non-return valve) arranged at the outlet of the last pumping stage 3c ( ). As previously described, such a valve 31 is configured to open as a function of pressure differentials on either side of the valve 31. It can be urged into the closed position by an elastic return member such as a spring 33 or by the force of gravity. The discharge valve 31 prevents the return of the gases pumped into the vacuum pump 1.

In the examples of FIGS. 2, 5 and 6, the discharge valve 31 is mounted in a discharge line 35 arranged to connect the outlet S of the last pumping stage 3c to the discharge 5 of the vacuum pump 1. The discharge line 35 can be arranged under the pumping stages 3a-3c and be fixed to the lower half-shell 2B by any suitable fixing means. As a variant, the discharge pipe 35 can be arranged above the pumping stages 3a-3c by being fixed to the upper half-shell 2A as in the examples of FIGS. 8a, 8b. The discharge gases are generally hotter than those of the first stages (due to the compression rates and the rise in pressure in the so-called high pressure stages, that is to say the last pumping stage(s). In the case of a vacuum pump used for pumping process gases, such as used in processes for manufacturing semiconductor elements in particular, it may be desirable to control the temperature of the discharge gases. For this, the discharge pipe 35 can be insulated and/or heated in order to maintain the discharge gases at high temperature. The discharge pipe 35 fixed to one or the other of the half-shells 2A, 2B thus makes it possible to reach the temperatures required in the vacuum pump 1 by using the heat of the discharge gases to heat the stator 2.

In particular, the discharge pipe 35 can extend above or below the first pumping stage or stages. When the discharge pipe 35 is located above the pumping stages 3a-3c, it can be extended so as to be crossed by an inlet pipe connecting the suction 4 to the inlet of the first stage 3a as shown in the example of the . The heat of the discharge gases thus makes it possible to heat the pumping stages, in particular the so-called low pressure stages, that is to say the first pumping stage or stages, or even to heat the inlet pipe connected to the suction 4 .

Furthermore, the or each outlet channel 29 fluidly connected to at least one relief channel 11 opens into this discharge pipe 35.

In addition, the discharge pipe 35 may have a housing for receiving a silencer from the vacuum pump 1, interposed between the outlet S of the last pumping stage 3c and the discharge 5. The silencer is therefore fluidically connected to the outlets of the each output channel 29 as well as at the output S of the last pumping stage 3c. The discharge valve 31 is generally arranged upstream of the silencer in the direction of gas flow.

Alternatively, as shown in Figures 7 to 9, the discharge valve 31 is arranged between the two half-shells 2A, 2B in a manner similar to the relief valves 13, as previously described. According to this embodiment, the evacuation channel associated with the discharge valve 31 is a discharge channel 37 connected to the outlet S of the last pumping stage 3c. The discharge channel 37 is made in one of the half-shells, emerging in at least one mouth in the assembly surface 8. This discharge channel 37 can be arranged in the same half-shell, as the relief channels 11. In the examples illustrated, it is arranged in the lower half-shell 2B.

In addition, the discharge valve 31 is mounted at least partly movable in a cavity 39 fluidly connected to the discharge 5 of the vacuum pump 1. This cavity 39 is also referred to as a discharge cavity. Such a cavity 39 is made in the half-shell opposite the discharge channel 37, for example the upper half-shell 2A. This discharge cavity 39 may be provided in the same half-shell as the cavities 15 housing the relief valves 13.

As shown on the , the discharge cavity 39 can be formed in the same half-shell as the outlet channel 29 and open into this outlet channel 29. Thus, all the gas discharged or relieved can be evacuated from the half-shell through the outlet channel. outlet 29. In this case, a silencer can be interposed between the discharge 5 and the outlet of the outlet channel 29. Such a silencer can be simplified compared to the embodiments with several outlets connected to the silencer. The vacuum pump 1 is all the more compact.

It is also possible for the discharge cavity 39 and the outlet channel(s) 29 to open into a common discharge pipe 35 connected to the discharge 5. The discharge pipe 35 can be fixed on the first half-shell 2A ( or 8b) or under the second half-shell 2B ( ). In particular, when the discharge pipe 35 is fixed on the first half-shell 2A, this discharge pipe 35 can stop before the suction 4 ( ), or on the contrary the inlet pipe connecting the suction 4 to the inlet of the first stage 3a can pass through this discharge pipe 35 ( ). As previously described, these configurations make it possible to reach the required temperatures in the vacuum pump 1, or even to heat the inlet pipe connected to the suction 4 ( ).

Similar to the operation of the relief valves 13, the discharge valve 31 is arranged so as to block or release the mouth of the discharge channel 37 connected to the outlet of the last pumping stage 3c. When it is closed the discharge valve 31, such as a ball, can rest on a valve seat and when it opens it can move away from it. The valve seat can be defined by a seal 17 as described with reference to Figures 3 and 4. The discharge valve 31 can be urged towards the closed position closing the mouth of the channel 37 by the force of gravity. or through an elastic return member, such as a spring 25, as described with reference to .

Furthermore, in the examples of FIGS. 7 to 9, the half-shells 2A, 2B accommodate between them both a discharge valve 31 and relief valves 13. According to another embodiment, the discharge valve 31 can be arranged between the half-shells 2A, 2B without, moreover, providing for the interposition between the latter of the valves 13 for load shedding.

There shows an embodiment of a pump unit 100 comprising a vacuum pump 1 and at least one additional pump 200. The additional pump 200 is in this example arranged upstream of the vacuum pump 1, according to the direction of circulation of the gas. This additional pump 200 can complement the vacuum pump 1 according to one or other of the embodiments previously described with reference to Figures 1 to 9.

Such an additional pump 200 also called “booster” in English makes it possible to increase the pumping speed. It may in particular be a Roots depressor or compressor, also called a “Roots blower”, which may comprise one stage or be multistage. Each pump has a drive motor configured to drive the rotating rotors.

The pump unit 100 may also include one or more pipes 41, 43 between the additional pump called "booster" 200 and the vacuum pump 1.

In such a pumping unit 100, when a valve (not shown) is opened, the pumps 1, 200 undergo a pressure wave which can stress the mechanical parts. In order to punctually absorb large pumping flows at the inlet of the additional so-called “booster” pump 200, the pumping unit 100 comprises at least one valve 45, also called load shedding valve.

This valve 45 can be arranged between the additional so-called “booster” pump 200 and the vacuum pump 1. The relief valve 45 can be arranged between the stators of the additional so-called “booster” pump 200 and of the vacuum pump 1. More precisely, the load shedding valve 45 is arranged so as to short-circuit the stages 3a-3c of the vacuum pump 1. The load shedding valve 45 can be fluidically connected to the discharge 5 of the vacuum pump 1. For this, the valve 45 is arranged to move between the stators of the two pumps 1, 200, so as to close or release a mouth of a pipe 43, depending on a pressure difference on either side of the valve 45.

Relief valve 45 can be made similar to relief valve 13 or delivery valve 35 of vacuum pump 1.

A pipe 41 can be connected to the outlet of the additional so-called "booster" pump 200. This pipe 41 can comprise at least two bypass portions, a first portion of which is connected to the inlet of the first pumping stage 3a of the pump vacuum 1 and a second portion is connected to the relief valve 45. The other pipe 43 can be connected to the outlet of the relief valve 45 and to the discharge 5 of the vacuum pump 1.

In the example shown in the , the pipe 43 at the outlet of the relief valve 45 opens into the outlet channel 29 made in one of the half-shells 2A of the vacuum pump 1. According to a variant not shown, this pipe 43 can open into a pipe of discharge 35 of the vacuum pump 1 as previously described.

The relief valve 45 makes it possible to bypass the pumping stages 3a-3c of the vacuum pump 1 in the event of overpressure. When the pressure difference is lower than the calibration threshold of the relief valve 45, the pumped gas follows the path represented by the arrows F1 in solid lines and is sucked in by the first pumping stage 3a. On the contrary, when the pressure difference is greater than the calibration threshold of the relief valve 45, the gas at the outlet of the additional pump 200 follows the path represented by the white arrows F2' whose outline is represented in solid lines, so to "short-circuit the vacuum pump" and be evacuated to delivery 5 of vacuum pump 1.

In addition, one or more of the pipes 41, 43 between the additional pump or "booster" 200 and the vacuum pump 1 can be provided in the stator of one or both pumps 1, 200. In particular, the pipe 43 in output of relief valve 45 and connected to delivery 5 of vacuum pump 1 can pass through stator 2 of vacuum pump 1.

In particular, it is possible for the stator of one of the pumps, for example the stator 2 of the vacuum pump 1, to serve as a seat for the relief valve 45. In this case, the relief valve 45 can be arranged to move in a cavity formed in the stator of the additional pump called “booster” 200. The valve seat 45 is defined facing the cavity.

Thus, according to one or other of the embodiment variants previously described, one or more valves 13, 31 can be integrated directly into the functional pumping block, between the half-shells 2A, 2B, without it being necessary to provide an external casing to be attached to the vacuum pump 1. The assembly surface 8, that is to say the joint plane of the half-shells 2A, 2B, is used and shaped to receive such valves 13 , 31. For each valve 13, 31, an evacuation channel 11, 37 associated for the connection of at least one pumping stage 3a, 3b, 3c to the discharge of the vacuum pump 1, can be arranged simply in one of the half-shells, emerging on the assembly surface 8.

This can be implemented both to relieve a pumping stage, such as the first pumping stage 3a and/or an intermediate pumping stage 3b, and for the discharge at the outlet of the last pumping stage 3c. It is therefore no longer necessary to assemble an external box to carry out these load shedding / discharge functions. The vacuum pump 1 thus gains in compactness (in particular in height). In addition, there is less sealing to manage with the exterior of the vacuum pump 1, compared to the known solutions of the state of the art with an external casing added for load shedding and/or discharge.

Finally, all the gas discharged and/or relieved can be evacuated from a half-shell through a single channel connected to the discharge 5 of the vacuum pump 1 and into which the cavity or cavities 15, 39 housing a valve 13, 31 open. respective and fluidly connected to the output of a pumping stage 3a-3c. When the vacuum pump 1 comprises a silencer, the latter can then be made very simply.

Furthermore, a discharge pipe 35 can be integrated into the vacuum pump 1, by being fixed to one of the half-shells 2A, 2B, so that the discharge gases circulate in the parts of the pumping cell. This is advantageous for heating, with the help of these discharge gases, the parts of the pumping cell, in particular the first low-pressure stages, or even the inlet pipe connected to suction 4.

Claims (13)

Multi-stage vacuum pump (1) comprising:

• a plurality of pumping stages (3a, 3b, 3c) respectively comprising an inlet (E) and an outlet (S), the pumping stages (3a, 3b, 3c) being connected in series between a suction (4) and a discharge (5) from the vacuum pump (1),
• a stator (2) comprising at least one stator element produced by assembling two complementary half-shells (2A, 2B) which meet along an assembly surface (8),
• at least one evacuation channel (11, 37) connected to the outlet (S) of a pumping stage (3a, 3b, 3c) and in fluid communication with the discharge (5), and
• at least one valve (13, 31) associated with the evacuation channel (11, 37), characterized in that :
• the evacuation channel (11, 37) is formed in one of the half-shells (2A, 2B) by opening out into at least one opening in the assembly surface (8) and in that
• the associated valve (13, 31) is arranged between the two half-shells (2A, 2B) while being at least partially movable so as to close or release the mouth of the evacuation channel (11, 37), depending a pressure difference on either side of the valve (13, 31).

Vacuum pump (1) according to the preceding claim, in which at least one evacuation channel is a relief channel (11) connected to the outlet (S) of a pumping stage (3a, 3b) to be relieved and in fluid communication with the discharge (5). Vacuum pump (1) according to the preceding claim, in which:

• the successive pumping stages (3a, 3b, 3c) are connected in series by a respective interstage channel (7) connecting the output (S) of a previous pumping stage (3a, 3b) to the input (E ) of a following pumping stage (3b, 3c), and in which
• a common channel is connected at the output (S) of the pumping stage (3a, 3b) to be relieved, the common channel being connected to at least two bypass portions, a first portion of which forms with the common channel an inter-channel stage (7) connected to the input (E) of the following pumping stage (3b, 3c) and a second portion forms with the common channel the load shedding channel (11).

Vacuum pump (1) according to one of the preceding claims, in which at least one discharge channel is a discharge channel (37) connected to the outlet (S) of the last pumping stage (3c) and in fluid communication with the discharge (5). Vacuum pump (1) according to one of the preceding claims, comprising at least two valves (13, 31) respectively associated with a pumping stage (3a, 3b, 3c), and in which the valves (13, 31) are sized differently depending on the pumping stage (3a, 3b, 3c) associated. Vacuum pump (1) according to one of the preceding claims, in which the valve (13, 31) is mounted at least partly movable in a cavity (15, 39) made in the half-shell (2B) opposite the half-shell (2A) comprising the evacuation channel (11, 37), the valve (13, 31) being arranged opposite the mouth of the evacuation channel (11, 37) in the surface assembly (8). Vacuum pump (1) according to the preceding claim, comprising at least one outlet channel (29) fluidically connecting the cavity (15, 39) to the discharge (5), and provided in one of the half-shells (2A, 2B ). Vacuum pump (1) according to one of the preceding claims, in which:

• the valve (13, 31) comprises a ball, and
• at least one annular seal (17) is arranged in the mouth of the associated evacuation channel (11, 37), such as:
  • the seal (17) has a base (17a) of generally toric shape received in a first groove (21) of the mouth of the evacuation channel (11, 37) having a generally cylindrical shape, and such that
  • the base (17a) is surmounted by a tapered portion (17b) delimiting a valve seat for the ball, the tapered portion (17b) being received in a second groove (23) of the mouth of the evacuation channel ( 11, 37) formed above the first groove (21) and having a generally frustoconical shape complementary to the frustoconical portion (17b) of the seal (17).

Vacuum pump (1) according to one of the preceding claims, comprising at least one injection channel (27) opening out via at least one injection orifice configured to inject a purge gas onto the valve (13, 31) and / or on a bearing face of a valve seat. Vacuum pump (1) according to one of the preceding claims, comprising a delivery pipe (35) arranged to connect the outlet (S) of the last pumping stage (3c) to the delivery (5) and fluidly connected to the discharge (11, 37), the discharge pipe (35) having a housing for receiving a vacuum pump silencer (1) interposed between the outlet (S) of the last pumping stage (3c) and the discharge (5) . Vacuum pump (1) according to the preceding claim, in which the discharge pipe (35) is fixed to one or the other of the half-shells (2A, 2B). Vacuum pump (1) according to one of the preceding claims, comprising two rotor shafts (6) configured to rotate synchronously in opposite directions in the pumping stages (3a, 3b, 3c) to drive a gas to be pumped between suction (4) and discharge (5). Vacuum pump (1) according to one of the preceding claims, in which the stator (2) comprises at least one end piece, and in which the stator element is connected axially with the end piece or with a other stator element.