Measuring and testing – With fluid pressure – Leakage
Patent
1997-05-12
1999-03-09
Brock, Michael
Measuring and testing
With fluid pressure
Leakage
G01M 320
Patent
active
058803572
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a leak detection device with a high-vacuum pump implemented as a friction vacuum pump and two further vacuum pumps working against atmospheric pressure. The invention, furthermore, relates to a process for operating such leak detection device.
A leak detector of this type is disclosed in EU-A-283543. It operates according to the principle of counterflow (with helium as the test gas) and permits the detection of the impermeability of a test sample, respectively its permeability, and specifically gross impermeability to extremely small leaks (leakage rates up to 10.sup.-10 mbars l/s). In the helium leak detection with a device of the prior known type, the danger exists of hydrocarbon contamination occurring in the region of the test sample and/or the test chamber. These are caused by molecules which originate in the suction chambers of the oil-sealed vacuum pumps operating against atmospheric pressure and which diffuse back into the high-vacuum region against the delivery direction of the vacuum pump.
SUMMARY OF THE INVENTION
The invention addresses the problem of avoiding hydrocarbon contaminations in the region of the test sample and/or of the test chamber.
This problem is solved according to the invention thereby that both further vacuum pumps are dry-sealing vacuum pumps. Dry-sealing vacuum pumps are those which operate without sealing oil in its suction chamber. Among the pumps of this type are diaphragm vacuum pumps or vacuum pumps (spiral pumps) operating according to the principle of the spiral such as are known for example from DE-A-28 31 179.
Preferably a flushing gas line terminates in the inlet region of one or both dry-sealing vacuum pumps, via which, during or between the measuring times, flushing gas (for example air) can be supplied. Thereby, in spite of using dry-sealing vacuum pumps, the response time of the leak detector can be kept short and its detection sensitivity high. Without a flushing gas inlet, the replacement of oil-sealing vacuum pumps working against atmospheric pressure would cause an extension of the response time and an impairment of the detection sensitivity of the leak detector. Dry-sealing forevacuum pumps of the cited type have the characteristic that their suction capability in the proximity of their relatively high terminal pressure have a suction capability which approximates zero. Therefore the response time is extended. In addition, this characteristic leads to the fact that a helium background stemming from the leakages impairs the detection sensitivity.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic of a leak detection device according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a leak detection device 100 includes an inlet 1 connected through lines 2 (with choke 3 and valve 4) and 5 (with valve 6) guided in parallel as well as a line 7 with the entrance side connection 8 of a high-vacuum pump stage 9.
The high-vacuum pump stage 9 is a stage of a friction vacuum pump, preferably a two-stage turbomolecular pump 11, whose second stage is denoted by 12. At the entrance side connection 13 of the second stage 12 is connected a test gas detector, preferably a mass spectrometer 14. The two exit sides 15 and 16 of the high-vacuum pump stages 9 and 12 are connected in common via the line 17 with the entrance side connection 18 of a friction pump 19, preferably a turbomolecular pump. At the pressure side a diaphragm pump 21 is connected via the connection line 20 to the turbomolecular pump 19. Diaphragm pump 21 operates against atmospheric pressure. In line 20 terminates a flushing gas feed line 22 with a choke 23. To the line 17 is additionally connected the pressure measuring site 25.
The t
REFERENCES:
patent: 4779449 (1988-10-01), Bley et al.
patent: 4893497 (1990-01-01), Danielson
patent: 5107697 (1992-04-01), Tallon et al.
patent: 5297422 (1994-03-01), Baret
patent: 5341671 (1994-08-01), Baret et al.
Theory and Practice of Vacuum Technology, Friedr. Vieweg & Sohn, pp. 449-457, 1989.
Trockenlaufende Vakuumpumpen, Robert Lamprecht, pp. 255-259, 1993.
Brock Michael
Leybold Aktiengesellschaft
LandOfFree
Leak detector with vacuum pumps and operating process for same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Leak detector with vacuum pumps and operating process for same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Leak detector with vacuum pumps and operating process for same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1323012