Measuring and testing – With fluid pressure – Leakage
Patent
1997-12-17
1999-11-02
Brock, Michael
Measuring and testing
With fluid pressure
Leakage
G01M 320
Patent
active
059748648
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a leak detector operated using helium as the test gas.
BACKGROUND OF THE INVENTION
There are known leak detectors of the kind equipped with a test gas detector (commonly a mass spectrometer), a high vacuum pump in which the test gas flows in the opposite direction, as well as a first relatively small back-up pump downstream with respect to the high vacuum pump. Moreover, a further back-up pump is provided having a relatively high pumping speed which serves the purpose of evacuating the test pieces or a test chamber in which leaks in the test pieces are detected. One reason for the use of two back-up pumps is, that on the one hand the test piece or test chamber shall be evacuated as quickly as possible. For this, the pumping speed of the separate back-up pump is made as high as possible. Production of the back-up vacuum required by the high vacuum pump would be possible with the aid of this second high vacuum pump; however, one would suffer a substantial loss in sensitivity. In order to avoid this, a second back-up pump having a relatively low pumping speed is connected downstream of the high vacuum pump.
It is the task of the present invention to reduce the complexity of generating the back-up vacuum in a leak detector of the kind affected here without having to suffer a loss in sensitivity.
SUMMARY OF THE INVENTION
This task is solved through the present invention by the characteristic features of the patent claims.
The proposed schemes are such that a separate back-up pump for the high-vacuum pump can be dispensed with. The valves can be switched in such a manner that on the one hand the test piece or the test chamber linked to the leak detector may be evacuated very quickly and that on the other hand precision leak detection will be possible.
It is particularly advantageous to use as the back-up pump a displacement pump operated according to the spiralling principle, such as known from DE-A-29 27 690, for example, the entire contents of which are hereby incorporated by reference. Pumps of this kind do not require a sealant (oil) in the pumping chamber so that--if the high vacuum pump is a friction pump--only oil-free vacuum pumps are present. The risk of contaminating the test piece or the test chamber with hydrocarbon molecules does not exist.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and details of the present invention shall be explained on the basis of the following design examples.
FIG. 1 is a leak detector according to the present invention with a single-stage high vacuum pump in the upper section and
FIG. 2 shows a leak detector with a multi-stage high vacuum pump.
DETAILED DESCRIPTION OF THE INVENTION
In the two design examples which follow the leak detector as such is designated as 1, its upper section as 2 (dash-dot line), the inlet or the connection for the test piece as 3, the test gas detector as 4, the high vacuum pump as 5, and the back-up pump located outside the upper section 2 as 6. The connection for the test piece 3 is linked via line sections 7 (with valve 8) and 9 (with valve 11) to the outlet of the high vacuum pump 5. Pressure gauge 12 is connected to line 7. Connected between valves 8 and 11 is a line 13 which leads to the inlet of the back-up pump 6 and which is equipped with a choke 14. Moreover, the connection 3 for the test piece and the inlet of the back-up pump 6 are connected via line 15 to the valve 16. A line incorporating valve 18 is designated as 17, which opens into line 13 and which--as detailed below--serves the purpose of admitting purge gas.
In the design example according to FIG. 1 the high vacuum pump 5 is a single-stage turbomolecular pump. During standby all valves--except valve 11--are closed. In this phase the high vacuum pump 5 produces the pressure necessary for operating the mass spectrometer 4. The back-up vacuum necessary to operate the high vacuum pump 5 is produced by back-up pump 6, the inlet of which is linked via the lines 9 (with valve 11 open) and 13 to the outlet of t
REFERENCES:
patent: 3690151 (1972-09-01), Briggs
patent: 3762212 (1973-10-01), Morley et al.
patent: 3824839 (1974-07-01), Briggs
patent: 4371323 (1983-02-01), Fischer et al.
patent: 4776207 (1988-10-01), Holme
patent: 4779449 (1988-10-01), Bley et al.
patent: 5537857 (1996-07-01), Bley
patent: 5585548 (1996-12-01), Grosse Bley et al.
patent: 5703281 (1997-12-01), Myneni
IPER PCT/EP96/01772 PCT Article 36 and Rule 70.
Technisches Messen TM 1982-1988 vol. 54, No. 3, 1987, Munchen DE, pp. 96-99 XP002010823.
Brock Michael
Leybold Vakuun GmbH
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