US3920993A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Piggyback optical bench
Assignee: Rosemount Inc
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Filing: 1974-09-18
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Granted: 1975-11-18
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Expires: 1994-09-18
Abstract
Abstract An optical bench having a gas flow cell with an infrared source at one end and an infrared sensor at the other end is provided with an attachment or ''''piggyback'''' for determining the concentration of a second constituent or pollutant in a sample. The attachment comprises a sensor inserted into the gas cell adjacent to the end toward the infrared source so that a beam of radiant energy falls directly upon the inserted sensor. The invention is particularly well suited for determining the concentration of a pollutant which occurs in greater concentration or is more highly absorptive of radiant energy than that of the pollutant for which the optical bench was originally designed.
Inventors
- 👤 Carl N Cederstrand
- 👤 Jack J Keegan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:02
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/25; G01N21/31; G01N21/35; G01N21/3504
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
203 words
An optical bench for separate detection of two molecular constituents in a sample gas by determination of absorption of radiant energy passed through the sample, said bench comprising in combination: a chamber enclosing a longitudinally extending sample cell having first and second ends, a source of radiant energy mounted at the first end of the cell, first and second windows transparent to the radiant energy at the first and second ends of the cell and enclosing the cell at the ends to form an elongated gas-containing cell with first and second ends, a first sensor in the chamber at the first end of the cell, the first window being between the radiant energy source and the first sensor, a second sensor at the second end of the sample cell, the second window being mounted between the gas-containing cell and the second sensor, the chamber having sample inlet and outlet openings at the ends thereof, the sensors being selectively responsive to two different molecular sample gas constituents, whereby radiant energy passing through the first window affects the first sensor, radiant energy passing through both windows affects the second sensor to produce simultaneous indications by the sensors of two different constituents of the sample gas.
Claim 2
Dependent Claim
203 words
An optical bench for separate detection of two molecular constituents in a sample gas by determination of absorption of radiant energy passed through the sample, said bench comprising in combination: a chamber enclosing a longitudinally extending sample cell having first and second ends, a source of radiant energy mounted at the first end of the cell, first and second windows transparent to the radiant energy at the first and second ends of the cell and enclosing the cell at the ends to form an elongated gas-containing cell with first and second ends, a first sensor in the chamber at the first end of the cell, the first window being between the radiant energy source and the first sensor, a second sensor at the second end of the sample cell, the second window being mounted between the gas-containing cell and the second sensor, the chamber having sample inlet and outlet openings at the ends thereof, the sensors being selectively responsive to two different molecular sample gas constituents, whereby radiant energy passing through the first window affects the first sensor, radiant energy passing through both windows affects the second sensor to produce simultaneous indications by the sensors of two different constituents of the sample gas.
Claim 3
Dependent Claim
68 words
The optical bench defined in claim 1 wherein a reflector is mounted at the second end of the cell in suitable positional relationship to the second sensor for concentrating radiation from the radiant energy source upon the second sensor, whereby the first sensor receives radiation directly from the radiant energy source through the first window and the second sensor receives radiation from the radiant energy source by reflection.
Claim 4
Dependent Claim
27 words
The optical bench defined in claim 2 wherein the second sensor is provided with a shield for shielding it from direct radiation from the radiant energy source.
Claim 5
Dependent Claim
87 words
The optical bench defined in claim 3 wherein the radiation sensors comprise first and second holders forming first and second enclosures, each having an opening therein with a radiation selective filter in the opening and first and second radiation detectors within the first and second enclosures, each adjacent a filter, each filter having the property of selectively passing radiant energy related to the energy absorption characteristics of a gaseous constituent which is to be detected whereby the sensors are rendered selectively responsive to the two different constituents.
Claim 6
Dependent Claim
62 words
The optical bench defined in claim 4 wherein the source of radiant energy is a source of infrared radiation, the windows at the ends of the optical bench have the property of transmitting infrared radiation, the radiation detectors are thermistors and two appropriate amplifiers are coupled to said thermistors for giving simultaneous indications of the concentration of two different gaseous sample constituents.
Claim 7
Dependent Claim
58 words
The optical bench defined in claim 5 wherein the first sensor is mounted relatively close to the first window in comparison with the distance between infrared windows and the first infrared window is composed of a rigid material to eliminate the effects of window deflection upon the cell path length of infrared radiation received by the first sensor.
Claim 8
Dependent Claim
28 words
The optical bench defined in claim 6 wherein the first infrared window is composed of sapphire and the second infrared window is composed of an appropriate plastic material.
Claim 9
Dependent Claim
75 words
The optical bench defined in claim 7 wherein the first sensor is responsive to a gaseous constituent having the property of absorbing infrared energy to a substantitally greater extend that the constituent to which the second sensor is selectively responsive whereby effective operation will be obtained by having the first sensor relatively close to the first window with the second sensor affected by absorption occurring throughout the full length of the sample gas enclosing chamber.
Claim 10
Dependent Claim
28 words
The optical bench defined in claim 8 wherein the first sensor is responsive to carbon dioxide and the second sensor is responsive to carbon monoxide or unburned hydrocarbons.
Claim 11
Dependent Claim
119 words
The optical bench defined in claim 4 wherein the second enclosure for the second sensor is provided containing also a third radiation detector, whereby a dual unit is formed, and a rotatable mounting is provided for the dual unit for enabling either the second detector or the third detector to receive reflected radiation from the reflector, the second and third detectors being mounted back to back and the shield being mounted between the second window and the dual unit having rotatable mounting whereby one of the two detectors comprising the second and third detectors is exposed to reflected radiant energy and the other of the two detectors is shielded from direct radiation, the first detector receiving only direct radiation.
Claim 12
Dependent Claim
38 words
The optical bench defined in claim 10 wherein the first detector is responsive to absorption of carbon dioxide, the second detector is responsive to absorption of carbon monoxide and the third detector is responsive to absorption of hydrocarbons.
References Cited (Backward Citations)
US3820901A
Cited
US3860344A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |