VACUUM-GENERATING PUMPING SYSTEM AND PUMPING METHOD USING THIS PUMPING SYSTEM

Abstract

The present invention relates to a pumping system to generate a vacuum (SP), comprising a main vacuum pump which is a dry screw pump (3) having a gas suction inlet (2) connected to a vacuum chamber (1) and a gas discharge outlet (4) leading into a gas evacuation conduit (5) in the direction of a gas exhaust outlet (8) outside the pumping system. The pumping system comprises a non-return valve (6) positioned between the gas discharge outlet (4) and the gas exhaust outlet (8), and an auxiliary vacuum pump (7) connected in parallel to the non-return valve. In a pumping method by means of this pumping system (SP), the main vacuum pump (3) is started up in order to pump the gases contained in the vacuum chamber (1) and to discharge these gases through its gas discharge outlet (4), simultaneously to which the auxiliary vacuum pump (7) is started up. Moreover the auxiliary vacuum pump (7) continues to pump all the while that the main vacuum pump (3) pumps the gases contained in the vacuum chamber (1) and/or all the while that the main vacuum pump (3) maintains a defined pressure in the vacuum chamber (1).

Claims

1. Pumping system for generating a vacuum, comprising a main vacuum pump which is a dry screw pump having a gas suction inlet connected to a vacuum chamber and a gas discharge outlet leading into a gas evacuation conduit in the direction of a gas exhaust outlet outside the pumping system, the pumping system being characterized in that it comprises a non-return valve positioned between the gas discharge outlet and the gas exhaust outlet, and an auxiliary vacuum pump connected in parallel to the non-return valve.

2. Pumping system according to claim 1, characterized in that the auxiliary vacuum pump is selected from among a dry screw pump, a claw pump, a multi-stage Roots pump, a diaphragm pump, a dry rotary vane pump and a lubricated rotary vane pump.

3. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump is a dry screw pump.

4. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump is a claw pump.

5. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump is a multi-stage Roots pump.

6. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump is a diaphragm pump.

7. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump a dry rotary vane pump.

8. Pumping system according to claim 2, characterized in that the auxiliary vacuum pump is a lubricated rotary vane pump.

9. Pumping system according to claim 1, characterized in that the auxiliary vacuum pump is designed to be able to pump all the while that the main vacuum pump pumps the gases contained in the vacuum chamber and/or all the while that the main vacuum pump maintains a defined pressure in the vacuum chamber.

10. Pumping system according to claim 1, characterized in that the auxiliary vacuum pump comprises a discharge end which is connected downstream from the non-return valve, to the gas evacuation conduit.

11. Pumping system according to claim 1, characterized in that nominal flow rate of the auxiliary vacuum pump is selected as a function of the volume which the gas evacuation conduit delimits between the main vacuum pump (3) and the non-return valve.

12. Pumping system according to claim 1, characterized in that the nominal flow rate of the auxiliary vacuum pump is from 1/500 to 1/20 of the nominal flow rate of the main vacuum pump.

13. Pumping system according to claim 1, characterized in that the auxiliary vacuum pump is single-staged or multi-staged.

14. Pumping system according to claim 1, characterized in that the non-return valve is configured to close when the pressure at the suction end of the main vacuum pump is less than 500 mbar absolute.

15. Pumping system according to claim 1, characterized in that the auxiliary vacuum pump is made of materials having high chemical resistance to substances and gases commonly used in the semi-conductor industry.

16. Pumping method by means of a pumping system according to claim 1, characterized in that the main vacuum pump is started up in order to pump the gases contained in the vacuum chamber and to discharge these gases through its gas discharge outlet; simultaneously the auxiliary vacuum pump is started up; and the auxiliary vacuum pump continues to pump all the while that the main vacuum pump pumps the gases contained in the vacuum chamber and/or all the while that the main vacuum pump maintains a defined pressure in the vacuum chamber.

17. Pumping method according to claim 16, characterized in that the auxiliary vacuum pump pumps <at> a flow rate on the order of 1/500 to 1/20 of the nominal flow rate of the main vacuum pump.

18. Pumping method according to claim 16, characterized in that the non-return valve closes when the pressure at the suction end of the main vacuum pump is less than 500 mbar absolute.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] The features and the advantages of the present invention will appear with more details within the context of the description which follows with example embodiments, given by way of illustration and in a non-limiting way, with reference to the attached drawings:

[0032] FIG. 1 represents in a diagrammatic way a pumping system suitable for implementation of a pumping method according to a first embodiment of the present invention; and

[0033] FIG. 2 represents in a diagrammatic way a pumping system suitable for implementation of a pumping method according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0034] FIG. 1 represents a pumping system SP for generating a vacuum, which is suitable for implementing a pumping method according to a first embodiment of the present invention.

[0035] This pumping system SP comprises a chamber 1, which is connected to the suction end 2 of a main vacuum pump constituted by a dry screw pump 3. The gas discharge outlet of the main dry screw vacuum pump 3 is connected to an evacuation conduit 5. A non-return discharge valve 6 is placed in the evacuation 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 a volume 4, contained between the gas discharge outlet of the main vacuum pump 3 and itself.

[0036] The pumping system SP also comprises the auxiliary vacuum pump 7, connected in parallel to the non-return valve 6. The suction end of the auxiliary vacuum pump is connected to the space 4 of the evacuation conduit 5 and its discharge end is connected to the conduit 8.

[0037] Already with the actuation of the main dry screw vacuum pump 3, the auxiliary vacuum pump 7 is itself actuated. The main dry screw vacuum pump 3 suctions the gases in the chamber 1 through the conduit 2 connected at its inlet and compresses them in order to discharge them subsequently at its exit in the evacuation conduit 5 through the non-return valve 6. When the closure pressure for the non-return valve 6 is reached, it closes. Starting from this moment the pumping of the auxiliary vacuum pump 7 makes the pressure in the space 4 drop progressively to the value of its pressure limit. In parallel, the power consumed by the main dry screw vacuum pump 3 decreases progressively. This takes place in a short time period, for example for a certain cycle in 5 to 10 seconds.

[0038] With a clever adjustment of the flow rate of the auxiliary vacuum pump 7 and of the closure pressure of the non-return valve 6 as a function of the flow rate of the main dry screw vacuum pump 3 and the volume of the chamber 1, it is moreover possible to reduce the time before the closure of the non-return valve 6 with respect to the duration of the evacuation cycle and thus reduce the quantity of energy consumed during this time of operation of the auxiliary pump 7 without effect on the pumping. On the other hand, the advantage of simplicity gives an excellent reliability to the system.

[0039] According to a first possibility, the auxiliary vacuum pump 7 is itself a dry screw pump. Thus, the main pump and the auxiliary pump can be of the same type, which simplifies the operation and the handling. Also, this combination of pumps permits the pumping system SP to be used for all the applications where only a dry screw pump can be used.

[0040] According to the other possibilities, the auxiliary vacuum pump 7 is a claw pump, a multi-stage Roots pump, a diaphragm pump, a dry rotary vane pump or a lubricated rotary vane pump. All these combinations of pumps have the advantages connected with the specific properties of each type of individual pumps.

[0041] FIG. 2 represents a pumping system SPP suitable for implementation of a pumping method according to a second embodiment of the present invention.

[0042] With respect to the system shown in FIG. 1, the system shown in FIG. 2 represents the controlled pumping system SPP, further comprising suitable sensors 11, 12, 13 which check either the current of the motor (sensor 11) of the main dry screw vacuum pump 3, or the pressure (sensor 13) of the gases in the space of the exit conduit of the main dry screw vacuum pump, limited by the non-return valve 6, or the temperature (sensor 12) of the gases in the space of the exit conduit at the exit of the main dry screw vacuum pump, limited by the non-return valve 6, or a combination of these parameters. In effect, when the main dry screw vacuum pump 3 begins to pump the gases of the vacuum chamber 1, the parameters such as the current of its motor, the temperature and the pressure of the gases in the space of the exit conduit 4 begin to change and reach threshold values detected by the sensors. After a time lag, this causes the startup of the auxiliary vacuum pump 7. When these parameters return to the initial ranges (outside the set values), with a time lag the auxiliary vacuum pump is stopped.

[0043] In the second embodiment of the invention of FIG. 2, the auxiliary vacuum pump can be of type dry screw, claw, multi-stage Roots, diaphragm, dry rotary vane or lubricated rotary vane, as in the first embodiment of the invention of FIG. 1.

[0044] Although diverse embodiments have been described, it is well understood that it is not conceivable to identify in an exhaustive way all the possible embodiments. Of course replacing a described means with an equivalent means can be envisaged 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.