PUMPING METHOD IN A SYSTEM OF VACUUM PUMPS AND SYSTEM OF VACUUM PUMPS

Abstract

The present invention relates to a pumping method in a pumping system (SP) comprising: a primary dry screw-type vacuum pump (3) with a gas entry orifice (2) connected to a vacuum chamber (1) and a gas exit orifice (4) leading into a conduit (5) before coming out into the gas outlet (8) of the pumping system (SP), a non-return valve (6) positioned in the conduit (5) between the gas exit orifice (4) and the gas outlet (8), and an ejector (7) connected in parallel to the non-return valve (6). According to this method, the primary dry screw-type vacuum pump (3) is put into operation in order to pump the gases contained in the vacuum chamber (1) through the gas exit orifice (4); in a simultaneous way, the ejector (7) is fed with working fluid, and the ejector (7) continues to be fed with working fluid all the time that the primary dry screw-type vacuum pump (3) pumps the gases contained in the vacuum chamber (1) and/or all the time that the primary dry screw-type vacuum pump (3) maintains a defined pressure in the vacuum chamber (1). The present invention also relates to a pumping system (SP) able to be used for implementing this method.

Claims

1. Pumping method in a system of vacuum pumps comprising: a primary dry screw-type vacuum pump with a gas entry orifice connected to a vacuum chamber and a gas exit orifice leading into a conduit before coming out into the gas outlet of the system of vacuum pumps, a non-return valve positioned in the conduit between the gas exit orifice and the gas outlet, and an ejector connected in parallel to the non-return valve, the method being characterised in that the primary dry screw-type vacuum pump is put in operation in order to pump the gases contained in the vacuum chamber through the gas exit orifice; in a simultaneous way, the ejector is fed with working fluid; and the ejector continues to be fed with working fluid all the time that the primary dry screw-type vacuum pump pumps the gases contained in the vacuum chamber and/or all the time that the primary dry screw-type vacuum pump maintains a defined pressure in the vacuum chamber.

2. Pumping method according to claim 1, characterised in that the ejector outlet rejoins the conduit after the non-return valve.

3. Pumping method according to claim 1, characterised in that the ejector is dimensioned in order to have a minimal consumption of working fluid.

4. Pumping method according to claim 1, characterised in that the nominal flow rate of the ejector is selected as a function of the enclosed space of the exit conduit of the primary dry screw-type vacuum pump which is limited by the non-return valve.

5. Pumping method according to claim 4, characterised in that the flow rate of the ejector is from 1/500 to 1/20 of the nominal flow rate of the primary dry screw-type vacuum pump.

6. Pumping method according to claim 1, characterised in that the working fluid of the ejector is compressed air and/or nitrogen.

7. Pumping method according to claim 1, characterised in that the ejector is single-staged or multi-staged.

8. Pumping method according to claim 1, characterised in that the non-return valve closes when the pressure at the suction end of the primary dry screw-type vacuum pump is between 500 mbar absolute and the final vacuum.

9. Pumping method according to claim 1, characterised in that the ejector is made of a material having increased chemical resistance to substances and gases commonly used in the semi-conductor industry.

10. Pumping method according to claim 1, characterised in that the ejector is integrated in a cartridge which incorporates the non-return valve.

11. Pumping method according to claim 10, characterised in that the cartridge is accommodated in an exhaust muffler fixed to the gas exit orifice of the primary dry screw-type vacuum pump.

12. Pumping method according to claim 1, characterised in that the flow rate of gas at the pressure necessary for the functioning of the ejector is provided by a compressor.

13. Pumping method according to claim 12, characterised in that the compressor is driven by at least one of the shafts of the primary dry screw-type pump.

14. Pumping method according to claim 12, characterised in that the compressor is driven in an autonomous manner, independently of the primary dry screw-type pump.

15. Pumping method according to claim 12, characterised in that the compressor evacuates the atmospheric air or gases in the gas exit conduit after the non-return valve.

16. System of vacuum pumps comprising: a primary dry screw-type vacuum pump with a gas entry orifice connected to a vacuum chamber and a gas exit orifice leading into a conduit before coming out into the gas outlet of the system of vacuum pumps, a non-return valve positioned in the conduit between the gas exit orifice and the gas outlet, and an ejector connected in parallel to the non-return valve, the system of vacuum pumps being characterised in that the ejector is designed to be able to be fed with working fluid all the time that the primary dry screw-type vacuum pump pumps the gases contained in the vacuum chamber and/or all the time that the primary dry screw-type vacuum pump maintains a defined pressure in the vacuum chamber.

17. System of vacuum pumps according to claim 16, characterised in that the ejector outlet rejoins the conduit after the non-return valve.

18. System of vacuum pumps according to claim 16, characterised in that the ejector is dimensioned in order to have a minimal consumption of working fluid.

19. System of vacuum pumps according to claim 16, characterised in that the nominal flow rate of the ejector is selected as a function of the enclosed space of the exit conduit of the primary dry screw-type vacuum pump which is limited by the non-return valve.

20. System of vacuum pumps according to claim 19, characterised in that the flow rate of the ejector is from 1/500 to 1/20 of the nominal flow rate of the primary dry screw-type vacuum pump.

21. System of vacuum pumps according to claim 16, characterised in that the working fluid of the ejector is compressed air and/or nitrogen.

22. System of vacuum pumps according to claim 16, characterised in that the ejector is single-staged or multi-staged.

23. System of vacuum pumps according to claim 16, characterised in that the non-return valve closes when the pressure at the suction end of the primary dry screw-type vacuum pump is between 500 mbar absolute and the final vacuum.

24. System of vacuum pumps according to claim 16, characterised in that the ejector is made of a material having increased chemical resistance to substances and gases commonly used in the semi-conductor industry.

25. System of vacuum pumps according to claim 16, characterised in that the ejector is integrated in a cartridge which incorporates the non-return valve.

26. System of vacuum pumps according to claim 25, characterised in that the cartridge is accommodated in an exhaust muffler fixed to the gas exit orifice of the primary dry screw-type vacuum pump.

27. System of vacuum pumps according to claim 16, characterised in that the system comprises a compressor which provides the flow rate of gas at the pressure necessary for functioning of the ejector.

28. System of vacuum pumps according to claim 27, characterised in that the compressor is driven by at least one of the shafts of the primary dry screw-type pump.

29. System of vacuum pumps according to claim 27, characterised in that the compressor is driven in an autonomous manner, independently of the primary dry screw-type pump.

30. System of vacuum pumps according to claim 27, characterised in that the compressor evacuates the atmospheric air or gases in the gas exit conduit after the non-return valve.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0025] The particularities and the advantages of the present invention will become evident with more details within the context of the description which follows with embodiment examples given by way of illustration and in a non-limiting way with reference to the attached drawings which represent:

[0026] FIG. 1 represents diagrammatically a system of vacuum pumps adapted to achieve a pumping method according to a first embodiment of the present invention; and

[0027] FIG. 2 represents diagrammatically a system of vacuum pumps adapted to achieve a pumping method according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0028] FIG. 1 represents a system of vacuum pumps SP adapted to implement a pumping method according to a first embodiment of the present invention.

[0029] This system of vacuum pumps SP comprises a chamber 1, which is connected to a suction orifice or intake 2 of a primary dry screw-type vacuum pump 3. The gas exit orifice of the primary dry screw-type vacuum pump 3 is connected to the conduit 5. A non-return release valve 6 is placed in the conduit 5, which, after this non-return valve, continues into the gas exit conduit 8. The non-return valve 6, when it is closed, permits the formation of an enclosed space 4, contained between the gas exit orifice of the primary vacuum pump 3 and the valve itself. The system of vacuum pumps SP also comprises an ejector 7, connected in parallel to the non-return valve 6. The intake of the ejector is connected to the enclosed space 4 of the conduit 5 and its release orifice is connected to the conduit 8. The feed pipe 9 provides the working fluid for the ejector 7.

[0030] With the setting in operation of the primary dry screw-type vacuum pump 3, the working fluid for the ejector 7 is injected by the feed pipe 9. The primary dry screw-type vacuum pump 3 suctions the gases in the chamber 1 through the connected conduit 2 at its inlet and compresses them in order to release them afterwards at its exit in the conduit 5 through the non-return valve 6. When the pressure for closure of the non-return valve 6 is reached, the valve closes. Starting from this moment the pumping of the ejector 7 progressively reduces the pressure in the enclosed space 4 to the value of its pressure limit. In parallel the power consumed by the primary dry screw-type vacuum pump 3 drops progressively. This takes place in a short period of time, for example for a certain cycle in 5 to 10 seconds.

[0031] With a suitable adjustment of the flow rate of the ejector 7 and of the closure pressure of the non-return valve 6 as a function of the flow rate of the primary dry screw-type vacuum pump 3 and the enclosed space of the chamber 1, it is moreover possible to reduce the time before the closure of the non-return valve 6 in relation to the duration of the cycle of evacuation and thus reduce the losses in working fluid during this time of operation of the ejector 7 without effect on the pumping. Furthermore, these losses, which are minute, are taken into account in the evaluation of the total amount of energy consumption. In contrast, the advantage of the simplicity results in an excellent reliability for the system as well as a 10% to 20% lower price compared with similar pumps equipped with programmable automatic devices and/or with variable speed drive units, control valves, sensors, etc.

[0032] FIG. 2 represents a system of vacuum pumps SP adapted for implementing a pumping method according to a second embodiment of the present invention.

[0033] With respect to the system represented in FIG. 1, the system represented in FIG. 2 further comprises a compressor 10 which provides the gas flow rate at the pressure necessary for the functioning of the ejector 7. In effect, this compressor 10 can suction the atmospheric air or gases in the gas exit conduit 8 after the non-return valve 6. Its presence makes the system of vacuum pumps independent of a compressed gas source, which can be suitable for certain industrial environments. The compressor 10 can be driven by at least one shaft of the primary dry screw-type pump 3 or by its own electric motor, thus in a way completely independent of the pump 3. In all cases its consumption of energy to enable it to provide the gas flow rate at the pressure necessary in order to make the ejector 7 operate is by far much smaller (for example on the order of 3% to 5%) in relation to the savings achieved in energy consumption of the main pump 3.

[0034] Of course the present invention is subject to numerous variations as regards its implementation. Although diverse embodiments have been described, it is well understood that it is not conceivable to identify all the possible embodiments in an exhaustive way. It can of course be envisaged to replace one means described with an equivalent means without departing from the scope of the present invention. All these modifications form part of the common knowledge of one skilled in the art in the field of vacuum technology.