Fluid handling – Processes – Involving pressure control
Patent
1975-10-03
1977-04-19
Cohan, Alan
Fluid handling
Processes
Involving pressure control
1374875, 250282, 250288, 250289, 250457, 251368, F16K 3102
Patent
active
040182410
ABSTRACT:
A method and inlet control system for controlling a gas flow sample to an evacuated chamber such as found in a mass spectrometer, is disclosed. The system utilizes a short inlet passage having an effective opening determined by a tapered diamond or steel tip needle adjacent to the inlet passage. The needle is positionally adjusted with respect to the inlet passage by being mounted on a piezoelectric crystal which is flexed by coupling thereto an electric potential derived by sensing the ions at the ionization chamber of a mass spectrometer, for example, and developing therefrom an electric signal indicative of the total pressure within the ionization chamber. The signal coupled to the piezoelectric crystal is preferably a pulse-width modulated signal with the needle maintaining the inlet passage closed except during the time that the piezoelectric crystal is flexed due to a received pulse. A vacuum pump, and a quadrupole filter, both of which are relatively small, are also disclosed, so that a mass spectrometer system, for example, is sufficiently compact so as to be useful, in conjunction with a respiratory valve, for the analysis of respiratory gases. The method for controlling a gas sample flow to a mass spectrometer, for example, comprises providing an inlet for a gas sample into the ionization chamber of the mass spectrometer, monitoring the pressure within the ionization chamber and developing an electrical signal indicative thereof, and utilizing the developed electrical signal to control the flow of gas sample through the inlet to maintain a substantially constant pressure within the ionization chamber.
REFERENCES:
patent: 3586027 (1971-06-01), Fitzgerald
patent: 3661528 (1972-05-01), Falk
patent: 3662605 (1972-05-01), Grotyohann
patent: 3834375 (1974-09-01), Sanctuary
Baer Norman W.
Hoivik Lars
Micco Alexander J.
Sodal Ingvar E.
Weil John V.
Cohan Alan
The Regents of the University of Colorado
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