Leak detector

Details Leak detector Leak detector

1995-12-06

2001-09-04

Williams, Hezron (Department: 2856)

Measuring and testing

With fluid pressure

Leakage

Reexamination Certificate

active

06282946

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a leak detector. The invention relates more particularly to a detector using a secondary pump having a high compression ratio and making it possible to measure very large leaks by operating in “counter-current” mode, as well as large leaks, with good sensitivity and excellent pumping speed, and therefore a short response time.
OBJECT AND SUMMARY OF THE INVENTION
The invention provides a leak detector including at least one analysis unit connected to the inlet of a first secondary pump, a pre-evacuation set connected to an inlet coupling, the inlet of said pre-evacuation set further being connected to the outlet of said first secondary pump via a pipe provided with a first valve, wherein said pre-evacuation set comprises a second secondary pump and a mechanical primary pump connected together in series, and wherein a pipe provided with a second valve connects an intermediate point of said first secondary pump to the inlet of said second secondary pump.
In order to obtain a good pumping speed as well as a high compression ratio, in as small a volume as possible, hybrid pumps are preferably chosen as the secondary pumps, each pump comprising two portions: a first portion, at the inlet end, of the turbomolecular blade type so as to procure a very good pumping speed, and a second portion, at the outlet end, of the Holweck type so as to obtain a good compression ratio.
Such a hybrid pump is known per se, and it offers the advantage of being more compact, for the same compression ratio, than a single-type turbomolecular blade pump. The Holweck stages are disposed coaxially inside the bell-shaped rotor of the blade stage. Moreover, the Holweck stages are cheaper than the blade stages.
By using a secondary pump in the pre-evacuation set, it is possible to use a dry pump, such as a diaphragm pump, as the primary pump. Whereas on its own, such a dry pump cannot produce a sufficient vacuum, by associating it with a secondary pump, the necessary vacuum can be achieved, and the assembly comprising the two pumps is much lighter (lighter by half) than a vane primary pump. Furthermore, this enables a leak detector to be provided that is entirely dry, i.e. oil-free.


REFERENCES:
patent: 3690151 (1972-09-01), Briggs
patent: 4436998 (1984-03-01), Tallon
patent: 4472962 (1984-09-01), Mennenga
patent: 4773256 (1988-09-01), Saulgeot
patent: 5116196 (1992-05-01), Baret et al.
patent: 5297422 (1994-03-01), Baret
patent: 5317900 (1994-06-01), Bergquist
patent: 5341671 (1994-08-01), Baret et al.
patent: 0464292A1 (1992-01-01), None
patent: WO9405990 (1994-03-01), None

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