EP1710440A2 - Vacuum pumping with energy limitation - Google Patents

Abstract

The device has a motor (1) driving a ROOTS type mechanical dry pump (2) with four-stages (5-8) comprising suction sides (5c-8c) and outlets (5d-8d). Inter-staged pipelines (9-11) connect the outlets (5d-7d) to the sides (6c-8c), respectively. Bypass lines (12, 13) are arranged between the side (5c) and the pipeline (9) and between the pipelines (9, 10), respectively. Bypass lines (14, 15) are arranged between the pipelines (10, 11) and between the pipeline (11) and the outlet (8d), respectively. Valves (16-19) are inserted in the pipeline (9, 11) and in the bypass lines (13, 15). An independent claim is also included for a method for vacuum pumping by a multi-staged mechanical dry pump.

Description

The present invention relates to vacuum pumping devices capable of establishing and maintaining an appropriate vacuum in an enclosure.

The establishment of a vacuum in a chamber is commonly used in particular in industrial processes for manufacturing semiconductors, some manufacturing steps to be performed under vacuum.

In such processes, substrates are fed into a load lock chamber connected to a vacuum pumping device which lowers the internal pressure of the charging chamber to a satisfactory value and then transfers the semiconductor substrates into a process chamber in which there is a vacuum suitable for manufacture.

It will be understood that each loading or unloading of substrates necessitates lowering then alternately raising the gaseous pressure in the loading chamber, which implies the frequent intervention of the vacuum pumping device.

It is also understood that the establishment of the vacuum in the loading chamber is not instantaneous, and that this constitutes a limit to the overall speed of the manufacturing process.

This limit is even more sensitive when the substrates have a large dimension. This is the case, in particular, for the manufacture of flat screen television or display, the loading chamber necessarily having the appropriate volume to contain one or more flat screens.

For example, at present, the loading chambers used for the production of flat screens have large volumes, generally of the order of 500 to 1000 liters, and sometimes exceeding 5000 liters, which must therefore be pumped as quickly as possible. .

The solution currently used for rapidly pumping such large volume loading chambers is to use large pumps equipped with large engines. As a result, pumps and motors are cumbersome and expensive components that consume a large amount of energy.

The problem proposed by the invention is to rapidly pump a large volume chamber, to quickly reach the appropriate vacuum inside the chamber, reducing the size of the pumping device to empty and limiting the energy consumption used to reach the satisfactory vacuum.

The invention results from the observation that a given vacuum pumping device generally has a flow rate characteristic as a function of pressure which has a maximum within a given pressure range, and the maximum flow pressure range depends on the architecture of the vacuum pumping device.

The invention takes advantage of this observation to design a variable geometry vacuum pumping device, in which the geometry is varied one or more times in order to optimize the flow rate of the pumping device at each stage of the pumping, that is to say say in the different successive pressure ranges in the pumped enclosure.

The invention thus achieves the desired purpose by using a multi-stage dry mechanical pump and a principle of intelligent connection of the stages in series / parallel mode, possibly combined with a control of the speed of the pump.

Thus, a succession of several configurations of the pumping stages is used, which configurations follow one another as the suction pressure decreases, and the configuration which ensures the maximum pumping rate of the pumping device is chosen at each instant. pumping.

In practice, one goes from one configuration to the next, either by a time delay adjusted according to the volume to be pumped, or by the electrical consumption information of the pump motor, or by the pressure information given by a pressure gauge. measuring the pressure in the pumped enclosure.

In this way, a relatively small pump is able to pump faster, which avoids the use of larger pumps driven by larger engines and consuming more energy.

The savings in volume of the pumping device and energy consumed can reach about 40%.

To achieve these and other aims, the invention proposes a vacuum pumping device, for the descent pressure of an enclosure, comprising a motor driving a multi-stage dry mechanical vacuum pump, each stage having a suction and a discharge, and comprising pipes for connecting the stages to each other, in the gas suction circuit of the enclosure. The device includes fluidic connection means which connect the stages to pass from a first configuration in which the stages are connected at least two by two in parallel in a first pumping step to a last configuration in which the stages are connected in series in a last stage pump, passing through at least one intermediate configuration, optimizing the pumping rate in the current pressure range, wherein at least one stage is connected in parallel with at least one other stage and at least one stage is connected in series at least one other floor.

In practice, the fluidic connection means may advantageously comprise valves controlled by electronic control means and inserted into the pipes.

According to one embodiment of the invention, the electronic control means actuate the valves to move from one configuration to the next in response to an evolution of the gas pressure in the chamber. Indeed, the gas pressure in the enclosure is a reliable indicator of the pumping capacity of the vacuum pumping device in the current configuration, and the flow curves of the different configurations can be compared to choose, at any moment , the configuration that has the best pumping capacity.

Alternatively, the electronic control means can actuate the valves to move from one configuration to the next in response to a change in the power consumed by the pump motor. Indeed, the power consumed by the engine is also a possible parameter that gives an indication of the optimal state or not of the current configuration of the stages, because the power consumed by the pumping device increases beyond a value limit after the maximum of the flow curve has been reached.

According to another possibility, the electronic control means can actuate the valves to go from one configuration to the next after a predefined duration which is a function of the volume of the pumped enclosure. Indeed, for the same volume of enclosure to be pumped, it can be determined, by learning, which are the times when it is necessary to switch from one configuration to the next to remain permanently in the configuration optimizing the flow rate of the pumping device. empty.

Preferably, the valves and the interstage channels are integrated in the body of the vacuum pump.

In the first pumping step, when the pressure in the chamber is still high, a first configuration is chosen in which stages are in parallel. In the last pumping step, when the pressure is low in the chamber, a final configuration is chosen in which the stages are in series in order to increase the compression ratio and thus to achieve an even lower pressure in the enclosure . In addition, in the last pumping step, the electronic control means can advantageously increase the speed of the motor, and therefore the speed of the pump, beyond its nominal speed, being observed that the nominal speed can be increased without exceeding the power limit because the low pressure stage, which limits the power, is in a zone of low compression during this step.

When the desired state of pressure is reached in the enclosure, the electronic control means can put the pumping device empty in an economical operating mode, or by reducing the rotational speed of the engine to ensure a holding pumping. pressure, or by connecting an additional pumping stage of small flow to the discharge, to maintain the pressure.

• a) selon la première configuration, en première étape de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un premier couple d'étages, les troisième et quatrième étages sont connectés en parallèle l'un avec l'autre, formant un second couple d'étages, les deux couples d'étages et étant connectés en série dans le chemin d'écoulement des gaz,
• b) selon une seconde configuration, en étape intermédiaire de pompage, les premier et second étages restent connectés en parallèle l'un avec l'autre, les troisième et quatrième étages sont connectés en série l'un avec l'autre, le premier couple d'étages des premier et second étages étant connecté en série avec le second couple d'étages des troisième et quatrième étages,
• c) selon une troisième configuration, en dernière étape de pompage, les quatre étages sont connectés en série les uns avec les autres.

According to a first embodiment of the invention, the device comprises four stages connected according to the following successive configurations during pumping:

• a) according to the first configuration, in the first pumping step, the first and second stages are connected in parallel with each other, forming a first pair of stages, the third and fourth stages are connected in parallel with each other; with the other, forming a second pair of stages, the two pairs of stages and being connected in series in the gas flow path,
• b) according to a second configuration, in an intermediate pumping step, the first and second stages remain connected in parallel with each other, the third and fourth stages are connected in series with each other, the first pair stages of the first and second stages being connected in series with the second pair of stages of the third and fourth stages,
• c) according to a third configuration, in the last pumping step, the four stages are connected in series with each other.

• a) selon la première configuration, en première étape de pompage, les premier, second et troisième étages sont connectés en parallèle, formant un groupe d'étages, les quatrième et cinquième étages sont connectés en parallèle l'un avec l'autre, formant un couple d'étages, le groupe d'étage et le couples d'étages étant connectés en série l'un avec l'autre dans le chemin d'écoulement des gaz,
• b) selon une seconde configuration, en première étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un premier couple d'étages, les troisième et quatrième étages sont connectés en parallèle l'un avec l'autre, formant un second couple d'étages, les premier et second couples d'étages étant connectés en série l'un avec l'autre et avec le cinquième étage,
• c) selon une troisième configuration, en deuxième étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un couple d'étages, les troisième, quatrième et cinquième étages étant connectés en série et avec le couple d'étages,
• d) selon une quatrième configuration, en dernière étape de pompage, les cinq étages sont connectés en série les uns avec les autres.

According to a second embodiment of the invention, the device comprises five stages connected according to the following successive configurations during pumping:

• a) according to the first configuration, in the first pumping step, the first, second and third stages are connected in parallel, forming a group of stages, the fourth and fifth stages are connected in parallel with each other, forming a pair of stages, the stage group and the pair of stages being connected in series with each other in the gas flow path,
• b) according to a second configuration, in the first intermediate pumping step, the first and second stages are connected in parallel with each other, forming a first pair of stages, the third and fourth stages are connected in parallel with one another; with each other, forming a second pair of stages, the first and second pairs of stages being connected in series with each other and with the fifth stage,
• c) according to a third configuration, in the second intermediate pumping step, the first and second stages are connected in parallel with each other, forming a pair of stages, the third, fourth and fifth stages being connected in series and with the couple of floors,
• d) according to a fourth configuration, in the last pumping step, the five stages are connected in series with each other.

• a) selon la première configuration, en première étape de pompage, les premier, second et troisième étages sont connectés en parallèle, formant un premier groupe d'étages, les quatrième, cinquième et sixième étages sont connectés en parallèle, formant un second groupe d'étages, les premier et second groupes d'étages étant connectés en série l'un avec l'autre dans le chemin d'écoulement des gaz,
• b) selon une seconde configuration, en première étape intermédiaire de pompage, les premier, second et troisième étages sont connectés en parallèle, formant un groupe d'étages, les troisième et quatrième étages sont connectés en parallèle l'un avec l'autre, formant un couple d'étages, le groupe d'étages et le couple d'étages étant connectés en série l'un avec l'autre et avec le sixième étage,
• c) selon une troisième configuration, en deuxième étape intermédiaire de pompage, les premier, second et troisième étages sont connectés en parallèle, formant un groupe d'étages, les quatrième, cinquième et sixième étages étant connectés en série et avec le couple d'étages,
• d) selon une quatrième configuration, en troisième étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un couple d'étages, les troisième, quatrième, cinquième et sixième étages étant connectés en série et avec le couple d'étages,
• e) selon une cinquième configuration, en dernière étape de pompage, les six étages sont connectés en série les uns avec les autres.

According to a third embodiment of the invention the device comprises six stages connected in the following successive configurations during pumping:

• a) according to the first configuration, in the first pumping step, the first, second and third stages are connected in parallel, forming a first group of stages, the fourth, fifth and sixth stages are connected in parallel, forming a second group of stages; stages, the first and second groups of stages being connected in series with each other in the gas flow path,
• b) according to a second configuration, in the first intermediate pumping step, the first, second and third stages are connected in parallel, forming a group of stages, the third and fourth stages are connected in parallel with each other, forming a pair of stages, the group of stages and the pair of stages being connected in series with each other and with the sixth stage,
• c) according to a third configuration, in the second intermediate pumping step, the first, second and third stages are connected in parallel, forming a group of stages, the fourth, fifth and sixth stages being connected in series and with the torque of floors
• d) according to a fourth configuration, in the third intermediate pumping step, the first and second stages are connected in parallel with each other, forming a pair of stages, the third, fourth, fifth and sixth stages being connected in series and with the couple of floors,
• e) according to a fifth configuration, in the last pumping step, the six stages are connected in series with each other.

• a) selon la première configuration, en première étape de pompage, les premier, second et troisième étages sont connectés en parallèle, formant un premier groupe d'étages, les quatrième, cinquième et sixième étages sont connectés en parallèle, formant un second groupe d'étages, les premier et second groupes d'étages étant connectés en série dans le chemin d'écoulement des gaz,
• b) selon une seconde configuration, en première étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un premier couple d'étages, les troisième et quatrième étages sont connectés en parallèle l'un avec l'autre, formant un second couple d'étages, les cinquième et sixième étages sont connectés en parallèle l'un avec l'autre, formant un troisième couple d'étages, les premier, second et troisième couples d'étages étant connectés en série,
• c) selon une troisième configuration, en deuxième étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un premier couple d'étages, les troisième et quatrième étages sont connectés en parallèle l'un avec l'autre, formant un second couple d'étages, les cinquième et sixième étages sont connectés en série l'un avec l'autre et avec les premier et second couples d'étages,
• d) selon une quatrième configuration, en troisième étape intermédiaire de pompage, les premier et second étages sont connectés en parallèle l'un avec l'autre, formant un couple d'étages, les troisième, quatrième, le cinquième et le sixième étages étant connectés en série et avec le couple d'étages,
• e) selon une cinquième configuration, en dernière étape de pompage, les six étages sont connectés en série les uns avec les autres.

According to a fourth embodiment of the invention, the device comprises six stages connected according to the following successive configurations during pumping:

• a) according to the first configuration, in the first pumping step, the first, second and third stages are connected in parallel, forming a first group of stages, the fourth, fifth and sixth stages are connected in parallel, forming a second group of stages; stages, the first and second groups of stages being connected in series in the gas flow path,
• b) according to a second configuration, in the first intermediate pumping step, the first and second stages are connected in parallel with each other, forming a first pair of stages, the third and fourth stages are connected in parallel with one another; with one another, forming a second pair of stages, the fifth and sixth stages are connected in parallel with each other, forming a third pair of stages, the first, second and third pairs of stages being connected in series,
• c) according to a third configuration, in the second intermediate pumping step, the first and second stages are connected in parallel with each other, forming a first pair of stages, the third and fourth stages are connected in parallel with one another; with each other, forming a second pair of stages, the fifth and sixth stages are connected in series with each other and with the first and second pairs of stages,
• d) according to a fourth configuration, in the third intermediate pumping step, the first and second stages are connected in parallel with each other, forming a pair of stages, the third, fourth, fifth and sixth stages being connected in series and with the pair of stages,
• e) according to a fifth configuration, in the last pumping step, the six stages are connected in series with each other.

According to another aspect, the invention proposes a multi-stage dry mechanical pump vacuum pumping method for lowering the pressure of an enclosure, in which the stages of the pump are connected in several successive configurations to pass from one first configuration in which the stages are connected at least two by two in parallel in a first pumping step to a last configuration in which the stages are connected in series in a last pumping step, passing through at least one intermediate configuration, selected each to optimize the pumping rate in the current pressure range. In the intermediate configuration, at least one suction stage is connected in parallel with at least one other suction stage and at least one discharge stage is connected in series with at least one other stage.

In such a method, it can be provided that, in the first pumping step, the stages are connected at least two by two in parallel, in the last pumping stage the stages are connected in series, with or without an intermediate pumping step in which the suction stages remain in parallel while the discharge stages are in series.

In addition, in the last pumping step, the speed of the pump can temporarily be increased beyond its nominal speed.

• la figure 1 illustre schématiquement une structure connue de dispositif de pompage à vide, dans lequel la pompe multi-étagée est de type ROOTS, avec quatre étages de pompage en série,
• la figure 2 est une vue schématique d'un dispositif de pompage à vide selon un mode de réalisation de la présente invention, comportant à nouveau quatre étages de type ROOTS, les étages étant connectés selon une première configuration,
• la figure 3 est une vue en perspective partiellement ouverte du dispositif de pompage de la figure 2,
• la figure 4 est un schéma de principe illustrant le mode de connexion des étages de la pompe dans la première configuration de la figure 2,
• la figure 5 illustre schématiquement le dispositif de pompage du mode de réalisation de la figure 2, dans une seconde configuration,
• la figure 6 est le schéma de principe illustrant le mode de connexion des étages de la pompe dans la seconde configuration de la figure 5,
• la figure 7 est un schéma de principe illustrant la connexion des étages de la pompe dans une troisième configuration,
• la figure 8 représente la courbe de débit du dispositif de pompage des figures 2 à 7, en fonction de la pression dans l'enceinte pompée, et
• la figure 9 illustre la courbe de consommation électrique du dispositif de pompage des figures 2 à 7 au cours de la descente en pression d'une enceinte,
• les figures 10A à 10D illustrent schématiquement un dispositif de pompage à vide selon un mode de réalisation de la présente invention, comportant cinq étages de type ROOTS, dans quatre configurations successives au fur et à mesure de la baisse de pression dans la chambre,
• les figures 11A à 11 DE illustrent schématiquement un dispositif de pompage à vide selon un mode de réalisation de la présente invention, comportant six étages de type ROOTS, dans cinq configurations successives au fur et à mesure de la baisse de pression dans la chambre,
• les figures 12B et 12C représente un mode de réalisation alternatif respectivement des figures 11B et 11C.

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

• FIG. 1 schematically illustrates a known structure of a vacuum pumping device, in which the multi-stage pump is of the ROOTS type, with four pumping stages in series,
• FIG. 2 is a schematic view of a vacuum pumping device according to an embodiment of the present invention, again comprising four stages of ROOTS type, the stages being connected in a first configuration,
• FIG. 3 is a partially open perspective view of the pumping device of FIG. 2,
• FIG. 4 is a block diagram illustrating the connection mode of the stages of the pump in the first configuration of FIG. 2,
• FIG. 5 diagrammatically illustrates the pumping device of the embodiment of FIG. 2, in a second configuration;
• FIG. 6 is the block diagram illustrating the connection mode of the stages of the pump in the second configuration of FIG. 5,
• FIG. 7 is a block diagram illustrating the connection of the stages of the pump in a third configuration,
• FIG. 8 represents the flow rate curve of the pumping device of FIGS. 2 to 7, as a function of the pressure in the chamber pumped, and
• FIG. 9 illustrates the electric consumption curve of the pumping device of FIGS. 2 to 7 during the pressure drop of an enclosure,
• FIGS. 10A to 10D schematically illustrate a vacuum pumping device according to one embodiment of the present invention, comprising five ROOTS-type stages, in four successive configurations as the pressure drop in the chamber,
• FIGS. 11A to 11 DE schematically illustrate a vacuum pumping device according to one embodiment of the present invention, comprising six ROOTS-type stages, in five successive configurations as the pressure drop in the chamber,
• Figs. 12B and 12C show an alternative embodiment respectively of Figs. 11B and 11C.

Consider firstly the known pumping device structure illustrated in FIG.

Such a device comprises a motor 1 which drives a pump 2 of the multi-stage ROOTS type which draws the gases from an enclosure 100 by a suction 3 and which delivers them to the discharge 4.

The pump 2 comprises, in the illustrated embodiment, four successive stages respectively 5, 6, 7 and 8, each having a stator stage, respectively 5a, 6a, 7a and 8a, and a double rotor stage respectively 5b, 6b, 7b and 8b.

Each stage comprises a suction, respectively 5c, 6c, 7c and 8c, and a discharge, respectively 5d, 6d, 7d and 8d.

In this known device, the successive stages are connected in series one after the other by respective interstage lines 9, 10 and 11. Each interstage line 9-11 1 connects, in this known pump, the discharge from the floor preceding the aspiration from the floor that follows. For example, the interstage pipe 9 connects the discharge 5d to the suction 6c. This connection is not changed during the pumping process.

FIG. 2, which illustrates a vacuum pumping device structure according to one embodiment of the invention, is now considered.

This embodiment takes the general structure of a traditional multi-stage ROOTS pump as illustrated in Figure 1, providing adaptations for changing the connection of the stages with each other. Thus, in Figure 2, we find the main elements of the pump of Figure 1, and these elements are identified by the same reference numerals.

Thus we find the four stages 5-8, with their respective aspirations 5c-8c, with their respective upsets 5d-8d, and with the inter-stage pipes 9-11.

The interstage pipe 9 connects the discharge 5d to the suction 6c; the interstage duct 10 connects the discharge 6d to the suction 7c; the interstage pipe 11 connects the discharge 7d to the suction 8c.

According to the invention, provision is furthermore made for a first bypass pipe 12 between the suction 5c and the interstage pipe 9, a second bypass pipe 13 between the interstage pipe 9 and the interstage pipe 10, a third bypass pipe 14 between the interstage pipe 10 and the interstage pipe 11, and a fourth bypass pipe 15 between the interstage pipe 11 and the discharge 8d, as illustrated in FIG.

Finally, in FIG. 2, four valves are provided, 16, 17, 18 and 19, respectively. The valve 16 is arranged to selectively bring the suction 6c into communication with either the bypass pipe 12 or with the interstage pipe 9 and the repression 5d. The valve 17 is arranged to selectively close off the bypass pipe 13. The valve 18 is arranged to selectively put in communication the suction 8c is with the bypass line 14, or with the interstage pipe 11 and the discharge 7d. Finally, the valve 19 is arranged to selectively close off the bypass line 15.

In the embodiment illustrated in FIG. 2, the valves 16 and 17 are mechanically coupled to one another by a longitudinal actuating rod engaged in the interstage pipe 9 and requested by a Actuator 20. Similarly, the valves 18 and 19 are mechanically coupled to one another on a longitudinal rod urged by an actuator 21.

In the first configuration of the pumping device, during a first pumping step E1, the actuators 20 and 21 are lowered, the valves 16-19 are lowered as shown in Figure 2. The first 5 and second 6 stages are connected in parallel with each other, forming a first pair of stages, and the third 7 and fourth 8 stages are in parallel with each other, forming a second pair of stages. The two pairs of stages are in series in the gas flow path between the suction 3 and the discharge 4.

The actuators 20 and 21 are controlled by an electronic control 22, to which they are connected by lines 20a and 21a. The electronic control 22 comprises, for example, a processor associated with memories containing a program for appropriately feeding the actuators 20 and 21 and ensuring the appropriate positioning of the valves 16-19 according to the various operating steps of the device as they will be described. below.

The motor 1 is also controlled in speed by the electronic control 22, to which it is connected by a line 1a and an external variable speed drive or integrated into the motor 1 or to the electronic control 22.

Figure 3 shows the elements of Figure 2, shown in space. We thus find the motor 1, the pump 2 with its suction 3 and its discharge 4. We distinguish the two actuators 20 and 21, the valves 16 and 18, and the ROOTS type rotors 5b, 6b and 7b of the respective stages 5, 6 and 7. The discharge stage 8 is not visible.

In FIG. 4, the configuration of the stages of FIG. 2 is illustrated, and between the suction 3 and the discharge 4 the two stages 5 and 6 connected in parallel are found, their respective aspirations 5c and 6c being connected. one to the other by the bypass line 12, their respective upsets 5d and 6d being connected to each other by the bypass line 13. The stages 7 and 8 are also connected in parallel, their respective aspirations 7c and 8c being connected to each other by the bypass line 14, their respective forcings 7d and 8d being connected to each other by the bypass line 15. The two couples 5-6 and 7- 8 are connected to one another in series through the interstage pipe 10 in the path of gas path between the suction 3 and the discharge 4.

This first configuration illustrated in FIGS. 2 and 4, with two pairs of parallel stages, constitutes the first configuration that is given to the device in the first step of pumping an enclosure.

In FIGS. 5 and 6, the system is given a second configuration, in an intermediate pumping step E2. The first 5 and second 6 stages or suction stages remain connected in parallel with each other, while the third 7 and fourth 8 stages or discharge stages are connected in series with each other. The first pair of stages formed by the first 5 and second 6 stages is connected in series with the third 7 and the fourth 8 stages. For this, the actuator 20 remains lowered while the actuator 21 is raised.

Finally, in the third or last configuration illustrated in FIG. 7, which is chosen in the last pumping step E3, the four stages 5, 6, 7 and 8 are all connected in series with each other in the path of FIG. flow of gases. For this, the two actuators 20 and 21 are lowered.

The interest of the invention will now be explained by performing a simulation by calculation.

It is assumed that an enclosure 100 having a volume V of 1000 liters, that one wants to empty in a time t of 45 seconds; in practice, it is desired to pass the internal pressure of the chamber from a pressure p1 of 1 atmosphere to a pressure p2 of 0.1 mBar for example.

For comparison, it is assumed first of all that a traditional pump is used. The average flow rate S of the conventional pump should be about 700 m ³ / h, applying the formula S = V / t In (p1 / p2).

The electrical power necessary to drive a pump of 700 m ³ / h which compresses the flow S of 0.1 mBar at 1 atmosphere is given by the formula: Pw = (p1-p2) .S (Pw in watt, p1 and p2 in Pascal, and S in m ³ / sec). In the example, Pw = 19.5 kW.

Given the gradual increase in power at the start of pumping, the average electrical power to empty the volume will be around 13 kW (see Figure 9).

It will now be shown, by calculation below, that the invention makes it possible to obtain a flow rate close to 700 m ³ / h in three successive stages with a pump initially provided for an optimum flow rate of 400 m ³ / h.

Stage 5 is considered to have a flow S1 of 400 m ³ / h, stage 6 has a flow S 2 of 300 m ³ / h, stage 7 has a flow S ³ of 300 m ³ / h and the floor 8 a a flow S4 of 200 m ³ / h. We will show that the average power consumed remains less than 10 kW.

During a first pumping step in the chamber 100, the gas pressure is passed from the chamber of 1 atmosphere to a pressure p1. The vacuum pumping device being in the configuration illustrated in Figures 2 and 4.

Expected flow rate of the pump: S = K (S1 + S2) $$\mathrm{K}=\mathrm{K}0/\left(\mathrm{K}0-1+\left(\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="imgf0001.png"\; state="\{\{state\}\}">S</figure-callout>}1+\mathrm{S}\mathrm{two}\right)/\left(\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}3+\mathrm{S}4\right)\right)=0,93\mathrm{}\mathrm{with}\mathrm{}\mathrm{K}0=5\mathrm{}\mathrm{at}\mathrm{}\mathrm{P\; atm}.$$

$$\mathrm{P}\mathrm{w}=700.\left({\mathrm{p}}^{\prime }-\mathrm{p}2\left(\mathrm{a}\mathrm{s}\mathrm{p}\mathrm{i}\right)\right)+500\left(\mathrm{p}\left(\mathrm{ref}\right)-{\mathrm{p}}^{\prime }\right)$$

avec p' : pression intermédiaire = p1(aspi).(S1+S2)/(S3+S4) de par la conservation du flux.KO is the zero flow compression ratio of the pump. $$\mathrm{S}=650{\mathrm{<figure-callout\; id="3"\; label="m"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">m</figure-callout>}}^3/\mathrm{h}\mathrm{.}$$

$$\mathrm{P}\mathrm{w}=700.\left({\mathrm{p}}^{\text{'}}-\mathrm{p}\mathrm{two}\left(\mathrm{at}\mathrm{s}\mathrm{p}\mathrm{i}\right)\right)+500\left(\mathrm{p}\left(\mathrm{ref}\right)-{\mathrm{p}}^{\text{'}}\right)$$

with p ': intermediate pressure = p1 (aspi). (S1 + S2) / (S3 + S4) by the conservation of the flow.

The power consumed is higher on the high pressure stage. The power increases on each stage with the decrease of the pressure p1 (aspi).

We determine p1 (aspi) so as not to exceed Pw = 10 kW.

If one calculates the consumed power for p1 = 300 mBar by distributing the work on the 2 stages then p '= 420 mBar and,
Pw = 700 m ³ / hx 120 mbar + 500 m ³ / hx 580 mbar = 10.3 kW.

With this new configuration of the pump stages and in this pressure range, the power is reduced again and the pumping speed is close to 700 m ³ / h.

Consider Figure 8 which illustrates the flow rate of the device as a function of the pressure in the pumped enclosure. During step E1, the flow rate of the vacuum pumping device according to the invention, in the first configuration, follows a curve A which has a maximum.

When the pressure p1 is reached, the system is switched to the following configuration.

In FIG. 9, the energy consumption is illustrated to mechanically drive the pump in rotation, as a function of the pressure in the enclosure. During the step E1, the power consumption increases regularly according to the curve B, and then drops sharply to the pressure p1 when switching the device in the second configuration.

In the second configuration, illustrated in FIGS. 5 and 6, the pressure of the enclosure is passed from a pressure p1 to a pressure p2.

At p1, the parallel discharge stage 7-8 is split in series so as to reduce the power consumed on the high pressure stage.

K' = 0,78 avec K0 = 5 dons S = 550 m³/h.Expected flow rate of the pump: $$\mathrm{S}={\mathrm{K}}^{\text{'}}\mathrm{}(\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="imgf0001.png"\; state="\{\{state\}\}">S</figure-callout>}1+\mathrm{S}\mathrm{two})$$

K '= 0.78 with K0 = 5 donations S = 550 m ³ / h.

$$\mathrm{P}\mathrm{watt}=700\times \left(100-50\right)+300\times \left(550-100\right)+200\times \left(1000-550\right)$$

soit Pw = 7.2 kWatt.Power consumption for p2 = 50 mBar assuming the following pressure distribution between the three stages: $$50-\to 100-\to 550-\to 1000$$

$$\mathrm{P}\mathrm{watt}=700\times \left(100-50\right)+300\times \left(550-100\right)+200\times \left(1000-550\right)$$

or Pw = 7.2 kWatt.

In FIG. 8, it can be seen that during step E2 between the pressures p1 and p2, the flow characteristic S of the device according to the invention follows a curve C exhibiting a maximum. In FIG. 9, it can be seen that, during this same step E2, the power characteristic of the device follows a curve D.

The configuration of the device is then changed to make the pressure in the chamber go from a pressure p2 to a pressure p3. The configuration is then that shown in Figure 7, with all stages 5-8 in series.

At the pressure p2, this configuration of the stages in series makes it possible to increase the rate of compression.

To maintain a high flow rate of 700m ³ / h, the nominal pumping speed must be increased by increasing the speed of rotation.

We increase the speed of a coeff. Kn.

Expected flow S = 400 x Kn.

We choose Kn = 7/4 and we obtain S = 700 m ³ / h.

Power consumption for p3 = 1 mBar with a hypothesis on the compression ratio of the stages according to the pressure of use:

$$\mathrm{P}\mathrm{w}=10.9\mathrm{\hspace{0.17em}}\mathrm{kW}.$$

The stage 5 works from 1 to 10 mBar (K0 = 10) / the stage 6 works from 10 to 50 mBar (K0 = 5) / the stage 7 works from 50 to 250 mBar / the stage 8 works from 250 at 1000 mBar (K0 = 4). $$\mathrm{P}\mathrm{w}=\mathrm{K}\mathrm{not}\left(400\times 9+300\times 40+300\times 200+200\times 750\right)$$

$$\mathrm{P}\mathrm{w}=10.9\mathrm{}\mathrm{kW}.$$

In FIG. 8, the influence of the speed increase of the pump is seen: with a constant speed, the flow characteristic follows the curve E, that is to say that the flow rate drops with respect to that which was obtained in steps E1 and E2. However, by increasing the speed, the Flow characteristic follows the curve F, which maintains a flow rate close to the maximum flow rate during a consequent pressure range.

It can be seen from the diagram of FIG. 8 that the following of the curves A, C and F characterizes a pumping with an average flow rate close to 700 m ³ / h (the curve G of a reference pump of 700 m ³ / h). , while the largest stage of the pump is only 400m ³ / h.

In FIG. 9, it can be seen that the power required to drive the pump is limited to about 10 kW, following the successive curves B, D and H, whereas a traditional multi-stage pump of 700 m ³ / h required power of 19.5 kW as shown in curve I.

The invention thus allows a gain on the maximum electric power of 40 to 45%, and a gain on the average energy consumed from 20% to 25%.

It is also considered that the invention allows a gain on the nominal size of the pump of about 40%.

The example described relates to a pumping device with dry mechanical pump type ROOTS four stages. Naturally, the invention applies in the same way to pumping devices based on a dry mechanical pump having a different number of stages, the number of stages being greater than or equal to four.

Figure 10 is an example of successive configurations of the pumping device according to the invention as the pressure drop, when the device comprises five stages.

FIG. 10A shows, between the suction 100 and the discharge 101, the three stages 102, 103 and 104 connected in parallel, their respective aspirations 102c, 103c and 104c being connected to one another by the pipe Bypass 105, their respective upsets 102d, 103d and 104d being connected to each other by the bypass line 106. The two stages 107 and 108 are also connected in parallel, their respective aspirations 107c and 108c being connected to each other. to each other through the bypass line 109, their respective upsets 107d and 108d being connected to each other by the bypass line 110. The two groups 102-103-104 and 107-108 are connected to each other. one to the other in series through the interstage line 111 in the path of gas path between the suction 100 and the discharge 101.

This first configuration, illustrated in FIG. 10A, constitutes the configuration that is given to the device in the first pump step E1 of an enclosure.

In FIG. 10B, the system is given a second configuration in an intermediate pump step E2. The first 102 and second 103 stages are connected in parallel with each other, as are the third 104 and fourth 107 stages. The first pair of stages formed by the first 102 and second 103 stages is connected in series with the second pair of stages formed by the third 104 and fourth 107 stages and with the fifth stage 108.

A third configuration, in an intermediate pumping step E3, is illustrated in FIG. 10C. The first 102 and second 103 stages are connected in parallel with each other. The third 104, fourth 107 and fifth 108 stages are connected in series with the first pair of stages formed by the first 102 and second 103 stages.

Finally, in the fourth or last configuration illustrated in FIG. 10D, which is chosen in the last pumping step E4, the five stages 102, 103, 104, 107 and 108 are all connected in series with each other in the gas flow path.

FIG. 11 is an example of successive configurations of the pumping device according to the invention as and when the pressure drop, when this device comprises six stages.

FIG. 11A shows, between the suction 200 and the discharge 201, the three stages 202, 203 and 204 connected in parallel, their respective aspirations 202c, 203c and 204c being connected to one another by the pipe 205, their respective backs 202d, 203d and 204d being connected to each other by the bypass line 206. The three stages 207,208 and 209 are also connected in parallel, their respective aspirations 207c, 208c and 209c being connected to each other through the bypass line 210, their respective upsets 207d, 208d and 209d being connected to each other by the bypass line 211. The two groups 202-203-204 and 207-208 are connected to one another in series through the interstage line 212 in the gas path between the suction 200 and the discharge 201.

This first configuration, illustrated in FIG. 11A, constitutes the configuration that is given to the device in the first pump step E1 of an enclosure.

In FIG. 11B, the system is given a second configuration in an intermediate pumping step E2. The first three stages 202, 203 and 204 are connected in parallel. The fourth 207 and fifth 208 stages are also connected in parallel with each other. The group 202-203-204, the pair 207-208 and the sixth stage 209 are connected in series.

A third configuration, in an intermediate pump step E3, is illustrated in FIG. 11C. The first three stages 202, 203 and 204 are connected in parallel. The fourth 207, fifth 208 and sixth 209 stages are connected in series with the group 202-203 204.

A fourth configuration, in an intermediate pumping step E4, is illustrated in FIG. 11D. The first 202 and second 203 stages are connected in parallel with each other. The third 204, fourth 207, fifth 208 and sixth 209 stages are connected in series with the first pair of stages formed by the first 202 and second 203 stages.

Finally, in the fifth or last configuration illustrated in FIG. 11E, which is chosen in the last pumping step E5, the six stages 202, 203, 204, 207, 208 and 209 are all connected in series with each other in the gas flow path.

FIG. 12 is an example of alternative configurations of the pumping device according to the invention comprising six stages. The first configuration is illustrated in FIG. 11A, and constitutes the configuration that is given to the device in the first pump step E1 of an enclosure.

In FIG. 12B, the system is given a second configuration in an intermediate pump step E2. There are, between the suction 300 and the discharge 301, the two first stages 302 and 303 connected in parallel, their respective aspirations 302c and 303c being connected to each other by the bypass line 304, their respective upsets 302d and 303d being connected to each other by the bypass line 305. The next two stages 306 and 307 are also connected in parallel, their respective aspirations 306c and 307c being connected to each other by the pipeline of branch 308, their respective upsets 307d and 308d being connected to each other by the Bypass line 309. Finally the two last stages 310 and 311 are also connected in parallel, their respective aspirations 310c and 311c being connected to each other by the bypass line 312, their respective forcings 310d and 311 d being connected to one another by the bypass line 313. The three couples 302-303, 306-307 and 310-311 are connected to each other in series through the interstage channels 314 and 315 respectively, in the gas path between the suction 300 and the discharge 301.

A third configuration, in an intermediate pumping step E3, is illustrated in FIG. 12C. The first two stages 302 and 303 are connected in parallel. The third 306 and fourth 307 stages are also connected in parallel. The last two stages 310 and 311 are connected in series with the couples 302-303 and 307-308.

The fourth and fifth configurations are similar to those shown in Figures 11D and 11E.

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

Claims (15)

Vacuum pumping device, for the pressure reduction of an enclosure (100), comprising a motor (1) driving a multi-stage dry mechanical vacuum pump (2), each stage (5-8) having a suction (5c) 8c) and a discharge (5d-8d), and comprising ducts (9-11) for connecting the stages (5-8) to each other, in the gas suction circuit of the enclosure, characterized in that it comprises means of fluid connection (12-19) connecting the stages (5-8) to move from a first configuration in which the stages are connected at least two by two in parallel in a first pump stage ( E1) to a last configuration in which the stages are connected in series in a last pumping step (E3), passing through at least one intermediate configuration (E2), optimizing the pumping rate in the current pressure range, in which at least one stage (5) is connected in parallel with at least one another stage (6) and at least one stage (7) is connected in series with at least one other stage (8). Device according to claim 1, wherein the fluidic connection means (12-19) comprise valves (16-19) controlled by electronic control means (22) and inserted into the pipes (9, 11, 13, 15). . Device according to claim 2, wherein the electronic control means (22) actuates the valves (16-19) to move from one configuration to the next in response to a change in the gas pressure in the chamber (100). Device according to claim 2, wherein the electronic control means (22) actuates the valves (16-19) to move from one configuration to the next in response to a change in the power consumed by the engine (1) of the pump. Apparatus according to claim 2, wherein the electronic control means (22) actuates the valves (16-19) to switch from one configuration to the next after a predefined time. Device according to one of claims 1 to 5, wherein the valves (16-19) and the inter-stage pipes (9-11) are integrated in the body of the vacuum pump (2). Device according to one of claims 2 to 6, wherein, in the last pumping step (E3), the electronic control means (22) increase the speed of the motor (1). Device according to one of claims 2 to 7, wherein, when the desired pressure state is reached in the enclosure (100), the electronic control means (22) reduce the rotational speed of the motor (1) to ensure pressure keeping pumping. Device according to one of claims 2 to 7, wherein, when the desired pressure state is reached in the enclosure (100), the electronic control means (22) connect to the discharge (4) an additional pump stage a small flow which maintains the pressure. Device according to one of claims 1 to 9, comprising four stages (5-8) connected in the following successive configurations during pumping: a) according to the first configuration, in first pumping step (E1), the first (5) and second (6) stages are connected in parallel with each other, forming a first pair of stages, the third ( 7) and fourth (8) stages are connected in parallel with each other, forming a second pair of stages, the two pairs of stages (5, 6) and (7, 8) being connected in series in the gas flow path, b) according to a second configuration, in an intermediate pumping step (E2), the first (5) and second (6) stages remain connected in parallel with each other, the third (7) and fourth (8) stages are connected in series with each other, the first pair of stages (5-6) of the first and second stages being connected in series with the second pair of stages (7-8) of the third and fourth stages, c) according to a third configuration, in the last pumping step (E3), the four stages (5-8) are connected in series with each other. Device according to one of claims 1 to 9, comprising five stages (102, 103, 104, 107, 108) connected in the following successive configurations during pumping: a) according to the first configuration, in the first pumping step (E1), the first (102), second (103) and third (104) stages are connected in parallel, forming a group of stages (102-104), the fourth (107) and fifth (108) stages are connected in parallel with each other, forming a pair of stages (107-108), the stage group (102-104) and the pair of stages (107-108) being connected in series with each other in the gas flow path, b) according to a second configuration, in the first intermediate pumping step (E2), the first (102) and second (103) stages are connected in parallel with each other, forming a first pair of stages (102- 103), the third (104) and fourth (107) stages are connected in parallel with each other, forming a second pair of stages (104-107), the first (102-103) and second (104-107) -107) pairs of stages being connected in series with each other and with the fifth (108) stage, c) according to a third configuration, in the second intermediate pumping step (E3), the first (102) and second (103) stages are connected in parallel with each other, forming a pair of stages (102-103 ), the third (104), fourth (107) and fifth (108) stages being connected in series and with the pair of stages (102-103), d) according to a fourth configuration, in the last pumping step (E4), the five stages (102, 103, 104, 107, 108) are connected in series with each other. Device according to one of claims 1 to 9, comprising six stages (202, 203, 204, 207, 208, 209) connected in the following successive configurations during pumping: a) according to the first configuration, in first pumping step (E1), the first (202), second (203) and third (204) stages are connected in parallel, forming a first group of stages (202-204), the fourth (207), fifth (208) and sixth (209) stages are connected in parallel, forming a second group of stages (207-209), the first (202-204) and second (207-209) groups of stages being connected in series with each other in the gas flow path, b) according to a second configuration, in the first intermediate pumping step (E2), the first (202), second (203) and third (204) stages are connected in parallel, forming a group of stages (202-204), the third (207) and fourth (208) stages are connected in parallel with each other, forming a pair of stages (207-208), the group of stages (202-204) and the pair of stages; stages (207-208) being connected in series with each other and with the sixth (209) floor, c) according to a third configuration, in the second intermediate pumping step (E3), the first (202), second (203) and third (204) stages are connected in parallel, forming a group of stages (202-204), the fourth (207) fifth (208 and sixth (209) stages being connected in series and with the pair of stages (102-103), d) according to a fourth configuration, in the third intermediate pumping step (E4), the first (202) and second (203) stages are connected in parallel with each other, forming a pair of stages (202-203 ), the third (204), fourth (207), fifth (208) and sixth (209) stages being connected in series and with the pair of stages (202-203), e) according to a fifth configuration, in the last pumping step (E5), the six stages (202, 203, 204, 207, 208, 209) are connected in series with each other. Device according to one of claims 1 to 9, comprising six stages (302, 303, 306, 307, 310, 311) connected in the following successive configurations during pumping: a) according to the first configuration, in the first pumping step (E1), the first (302), second (303) and third (306) stages are connected in parallel, forming a first group of stages (302-306), the fourth (307), fifth (310) and sixth (311) stages are connected in parallel, forming a second group of stages (307-311), the first (302-306) and second (307-311) groups of stages being connected in series in the gas flow path, b) according to a second configuration, in the first intermediate pumping step (E2), the first (302) and second (303) stages are connected in parallel with each other, forming a first pair of stages (302); 303), the third (306) and fourth (307) stages are connected in parallel with each other, forming a second pair of stages (306-307), the fifth (310) and sixth (311) stages are connected in parallel with each other, forming a third pair of stages (310-311), the first (302-303), second (306-307) and third (310-311) pairs of stages being connected in series, c) according to a third configuration, in the second intermediate pumping step (E3), the first (302) and second (303) stages are connected in parallel with each other, forming a first pair of stages (302); 303), the third (306) and fourth (307) stages are connected in parallel with each other, forming a second pair of stages (306-307), the fifth (310) and sixth (311) stages are connected in series with each other and with the first (302-303) and second (306-307) pairs of stages, d) according to a fourth configuration, in the third intermediate pumping step (E4), the first (302) and second (303) stages are connected in parallel with each other, forming a pair of stages (302). -303), the third (306), fourth (307), fifth (310) and sixth (311) stages being connected in series and with the pair of stages (302-303), e) according to a fifth configuration, in the last pumping step (E5), the six stages (302, 303, 306, 307, 310, 311) are connected in series with each other. Method for vacuum pumping by multi-stage dry mechanical pump (2) for lowering the pressure of an enclosure, characterized in that the stages (5-8) of the pump (2) are connected in several successive configurations to go from a first configuration in which the stages are connected at least two by two in parallel in a first pumping step (E1) to a last configuration in which the stages are connected in series in a last pumping step (E3) passing through at least one intermediate configuration (E2), each selected to optimize the pumping rate in the current pressure range, wherein at least one suction stage (5) is connected in parallel with at least one other suction stage (6) and at least one discharge stage (7) is connected in series with at least one other stage (8). The method of claim 14, wherein, in the last pumping step, the speed of the pump is temporarily increased beyond its rated speed.

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