US3879984A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gas flow control
Assignee: Individual
•
Filing: 1973-03-15
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Granted: 1975-04-29
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Expires: 1993-03-15
Abstract
Abstract This is a flow control system for maintaining a constant flow rate of a gas to detector of gas chromatographic apparatus at various flow rates of the gas through the chromatographic column of the apparatus from which the gas flows to the detector, the gas being fed into the apparatus at a constant pressure. The subject system includes a flow regulator in the main gas flow to the column; the flow regulator consists of a pressure responsive valve resiliently biased to its open position, a gas flow impedance upstream from the valve, and a pressure conducting connection from the upstream side of the impedance, the whole being arranged for controlling the valve opening in proportion to changes in the pressure at the downstream side of the impedance so as to provide a constant pressure at the downstream side of the impedance. A by-pass flow path has one end coupled into the main flow path between the downstream side of the impedance and the valve, and its other end coupled into the input to the detector, so that the flow rate through the detector is maintained at a constant value. An adjustable impedance mechanism is provided in the by-pass flow path for adjusting the flow rate through the by-pass, and hence the flow rate through the column, without altering the resultant flow rate through the detector.
Inventors
- 👤 John Michael Welland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:15
CPC Classifications
G; G01; G01N; G01N30/00; G01N30/02; G01N30/26; G01N30/28; G01N30/32; G01N2030/022; G01N2030/025; G01N2030/324; Y; Y10; Y10T; Y10T137/00; Y10T137/2496; Y10T137/2559; Y10T137/2562; Y10T137/8593; Y10T137/87265; Y10T137/8733; Y10T137/87338; Y10T137/87539
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
297 words
In gas chromatographic apparatus in which gas at a substantially constant pressure is fed from a source via a main flow path to a chromatographic column and from the column to a detector, a system for maintaining the flow rate of gas to the detector steady for various selectable rates of flow through the column comprising: a flow regulator in the main flow path to the column consisting of a pressure responsive valve resiliently biased to an open position against a predetermined counter biasing pressure, and flow impedance means upstream from the valve, said valve being responsive to any pressure change caused by a flow change at its downstream side by adjusting the valve opening for maintaining a constant pressure at the downstream side of the impedance means in relation to the substantially constant pressure of gas from said source and thus steadying the flow through the column for any selected flow rate; a by-pass flow path having one end coupled into the main flow path between the downstream, low pressure, side of the impedance means and said valve and having its other end coupled into said main flow path at said detector input; and variable impedance means in the by-pass flow path for changing the gas flow through the by-pass flow path whereby a change in the by-pass flow produces a change in the pressure at the downstream side of the impedance which is immediately counteracted by said pressure responsive valve means causing the opening through the pressure responsive valve to vary an amount that changes the column flow inversely the amount of the by-pass flow change so that the pressure at the downstream side of the impedance is restored to its constant value and the flow to the detector is maintained at a steady rate.
Claim 2
Dependent Claim
297 words
In gas chromatographic apparatus in which gas at a substantially constant pressure is fed from a source via a main flow path to a chromatographic column and from the column to a detector, a system for maintaining the flow rate of gas to the detector steady for various selectable rates of flow through the column comprising: a flow regulator in the main flow path to the column consisting of a pressure responsive valve resiliently biased to an open position against a predetermined counter biasing pressure, and flow impedance means upstream from the valve, said valve being responsive to any pressure change caused by a flow change at its downstream side by adjusting the valve opening for maintaining a constant pressure at the downstream side of the impedance means in relation to the substantially constant pressure of gas from said source and thus steadying the flow through the column for any selected flow rate; a by-pass flow path having one end coupled into the main flow path between the downstream, low pressure, side of the impedance means and said valve and having its other end coupled into said main flow path at said detector input; and variable impedance means in the by-pass flow path for changing the gas flow through the by-pass flow path whereby a change in the by-pass flow produces a change in the pressure at the downstream side of the impedance which is immediately counteracted by said pressure responsive valve means causing the opening through the pressure responsive valve to vary an amount that changes the column flow inversely the amount of the by-pass flow change so that the pressure at the downstream side of the impedance is restored to its constant value and the flow to the detector is maintained at a steady rate.
Claim 3
Dependent Claim
59 words
The system of claim 1 in which said variable impedance means in the by-pass flow path comprises a plurality of flow restrictor devices connected in parallel, and each restrictor device having a valve connected at its upstream end, whereby any selected number of the restrictor devices are adapted to be switched into and out of the by-paSs flow path.
Claim 4
Dependent Claim
19 words
The system of claim 1 in which said variable impedance means in the by-pass flow path is a valve.
Claim 5
Dependent Claim
99 words
The system of claim 3 in which said by-pass path valve is an electrically operated valve and which includes: a servo motor connected to operate said by-pass path valve; a flowmeter in the main flow path to the column from said flow regulator producing an electrical output signal proportioned to the flow therethrough; means producing an electric reference potential; and comparator means connected for comparing the signals from the flowmeter with said reference potential and producing an output potential in relation to the comparison; said comparator means being connected to apply its output potential to actuate said servo motor.
Claim 6
Dependent Claim
160 words
The system of claim 1 in which said flow impedance means of the flow regulator in the main flow path is a flow restrictor device and which includes: a plurality of additional restrictor devices connected in parallel with said first mentioned restrictor device; a second pressure responsive valve in the by-pass flow path, similar to said valve of the flow regulator in the main flow path; and a pressure conducting connection between the upstream, high pressure, sides of said parallel connected restrictor devices and said second valve and being operable to close the opening of the second valve in proportion to increases in the pressure of gas at the upstream sides of the restrictor devices; each of said restrictor devices having a two-way valve connected at its downstream end, connected for directing the output flows from the respective restrictor devices alternatively to the valve in the main flow path and to said second valve gate in the by-pass flow path.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-28 | 1978-10-28 | 1979-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-28 | 1982-10-28 | 1983-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-28 | 1986-10-28 | 1987-04-29 | $7700.00 | Window Closed / Lapsed |