US3092799A - Apparatus for detecting combustible gases having an electrically conductive member enveloped in a refractory material - Google Patents
Apparatus for detecting combustible gases having an electrically conductive member enveloped in a refractory material Download PDFInfo
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- US3092799A US3092799A US790935A US79093559A US3092799A US 3092799 A US3092799 A US 3092799A US 790935 A US790935 A US 790935A US 79093559 A US79093559 A US 79093559A US 3092799 A US3092799 A US 3092799A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
- G01N27/16—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
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- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Description
June 4, 1963 AKER 3,092,799
A. R. B APPARATUS FOR DETECTING COMBUSTIBLE GASES HAVING AN ELECTRICALLY CONDUCTIVE MEMBER ENVELOPED IN A REFRACTORY MATERIAL Filed Feb. 3. 1959 Hum RICHHRD BAKER lnventar By MM,
A i turn eys United States Patent APPARATUS FOR DETECTING COMBUSTIBLE GASES HAVING AN ELECTRICALLY CONDUC- TIVE MEMBER ENVELOPED IN A REFRACTORY MATERIAL Alan Richard Baker, Sheflield, England, assignor, by direct and mesne assignments, to National Research Development Corporation, London, England Filed Feb. 3, 1959, Ser. No. 790,935 Claims priority, application Great Britain Feb. 18, 1958 7 Claims. (Cl. 338-34) This invention relates to electrically heatable filaments, and more particularly, although not exclusively, to the helical coil type resistance filaments used in connection with the detection of combustible gases in air, for which purpose it is usual to employ a pair of such filaments constituting detecting and compensating elements respectively, arranged in a Wheatstone bridge circuit.
Hitherto the filaments usedin this type of apparatus have been exposed directly to the gas sample being tested, the said sample, in the case of a combustible gas being oxidised by catalysis at the'metal surface of the detecting filament wire thereby raising the temperature of the latter and therefore its resistance, so that the normal balance of the electrical bridge circuit is upset, and the out-ofbalance current passed through an electric meter or any other suitable indicator.
In apparatus of the above type, the detecting filaments are often heated to a temperature of 900 C. or more, depending upon the particular metal of which the filaments are made. At these relatively high temperatures, the metal evaporates from the surface of the filament wire, in consequence of which, the resistance of the fila-, ment is continually increasing especially during the oxidation of combustible gases. This continuous increase in resistance, which is greater in the detecting filament than in the compensating filament, causes an increase in the zero reading of the bridge circuit which must therefore be reset at frequent intervals.
The object of the present invention is to provide a filament adapted to be electrically heated and more particularly intended for use in the detection of combustible gases in air, which filament is not only of more robust construction than those used hitherto, but which can be used at lower temperatures so that its resistance is not affected to the same extent by the oxidation, under catalytic action, of high concentrations of combustible gases.
In accordance with the invention, a filament to be electrically heated is embedded in a coating or pellet consisting of an oxide or other refractory materials so as to be enveloped on all sides by a layer of said oxide or other refractory materials.
Referring now to the accompanying drawing, a filament 57, which may be of a metal of the platinum group and in the form of a helically coiled wire, is embedded within or completely surrounded by an oxide or other refractory materials such as alumina or silica, so as to form a coating or pellet 58. The alumina or silica is applied to the filament by the evaporation and decomposition by heat, of a paste or solution of a compound such as a nitrate, hydroxide or alkali silicate. More particularly, the alumina pellet 58 may be formed by the application to the coiled filament 57 of successive layers or portions of a saturated solution of aluminium nitrate in Water, and after the application of each layer or portion, heating the layers or portions by passing an electric current through the filament.
When the filaments are to be used in apparatus for the detection of combustible gases in air, such as described, for example, in my co-pending United States application Serial No. 790,870, filed February 3, 1959, a catalyst such as palladium or a mixture of platinum and palladium may Patented June 4, 1963 be, added which by impregnation tends to form an outer coating 59 surrounding the oxide pellet 58 of the filament constituting the detecting element, which catalyst may be applied as a solution or dispersion of a compound or compounds of one or more metals of the platinum group. One example of catalyst solution which may be used, is obtained by mixing:
1.2 ml. of 8 percent (by weight) of palladous chloride (PdCl in 6 N hydrochloric acid,
0.8 ml. of 5 percent (by weight) of Chlorplatinic acid (H PtCl .6H O) in water 0.2 -ml. of 10 percent (by weight) of aluminium nitrate (Al(No) .6H O) in water.
The liquid is removed and the catalyst made active by heating in air, or if necessary, in another gas.
Alternatively the catalyst may be condensed on the pellet 58 by heating either the internal filament 57 embedded in the pellet, or an external filament in close proximity to the pellet, to a temperature above 1000 C. In so far as the compensating filament is concerned, for use at high temperatures, a suitable metallic oxide such aschromium oxide or some other catalyst poison may be added to the material forming the pellet so as to suppress the oxidation of combustible gases.
According to a modification adapted more particularly for use as a detecting element, and having its filament embedded within an oxide or other refractory materials such as alumina or silica coated externally with a catalyst in the manner already described, the pellet 58 is provided with an additional coating of alumina or other refractory materials applied on the top of the external coating of catalyst 59. After heating to approximately 1000 C. for a few minutes, preferably in a combustible gas, enough of the catalyst 59 diffuses through the additional coating to the external surface of the latter. The effect of this coating is to reduce the loss in catalytic activity which occurs when the detecting element is heated for several 'hours in air or in low concentrations of methane.
When the filaments are to be used in apparatus for the detection of one non-combustible gas in the presence of another or others, or high concentrations of a combustible gas in air such as described, for example, in my co-pending United States application No. 790,870, filed February 3, 1959, two similar filaments may be used. One filament is exposed to the sample of gas to be tested While the other is exposed to a standard or reference gas such as pure air. In this case, the material forming the pellet 58 may be modified by the addition of, for example, a metallic oxide to prevent any type of gaseous reaction so that the temperatures of the filaments 57 are affected only by the thermal conductivity and other physical properties of the gases in contact with the filaments.
Where the embedded filaments, according to the invention, are used in the detection of combustible gases, the latter are not oxidised on the filament wire and the filaments can be operated at a lower temperature than exposed filaments, as a result of which the rate of evaporation of metal from the wire filaments is negligible. The necessity, therefore, to make frequent zero adjustments to the electrical bridge circuit as required by the use of exposed filaments in gas detection apparatus as hitherto employed, no longer arises.
In addition, the operational life of these embedded filaments is considerably longer than is the case with eX- posed filaments.
I claim:
1. An electrically heatable element comprising a metal filament, a refractory material enveloping said metal filament and a coating of a catalytic material about said refractory material, in which the coating of catalytic material consists of palladium.
2. An electrically heatable element comprising a metal filament, a refractory material enveloping said metal filament and a coating of a catalytic material about said refractory material, in which the coating of catalytic material consists of a mixture of platinum and palladium.
3. A device for use in apparatus for detecting combustible gases in an atmosphere of the type surrounding said device, the device comprising an electrically conductive member having a given temperature coefficient of resistivity other than zero, an uncovered refractory material intimately enveloping said member on all sides to prevent said atmosphere from reaching any surface of said member, an oxidation controlling substance added to said refractory material and exposed, with said refractory material, to said atmosphere, the arrangement being such that any oxidation of the gases in said atmosphere at the surface of said refractory material exposed thereto generates heat afiecting the temperature and therefore the resistance of said electrically-conductive member while the member itself is protected from oxidation by said total refractory envelopment.
4. A device as set forth in claim 3 produced by applying at least one layer of refractory material on said electrically-conductive member, drying said refractory material to form an envelope about all of the surface of said electrically conductive member, applying at least one layer of said oxidation-controlling substance to the envelope, applying at least one additional layer of refractory material to the coated refractory material and heating the article to dry the refractory material and to diffuse the oxidation-controlling substance to the outer surface of the device.
5. A device as set forth in claim 3 in which the oxidation-controlling substance is a catalyst which induces the oxidation of combustible gases.
6. A device as set forth in claim 3 in which the oxidation-controlling substance is a catalyst poison which inhibits the oxidation of combustible gases.
7. A device as set forth in claim 3 in which the oxidation-controlling substance is dispersed through the outermost region of the refractory material.
References Cited in the file of this patent UNITED STATES PATENTS
Claims (1)
1. AN ELECTRICALLY HEATABLE ELEMENT COMPRISING A METAL FILAMENT, A REFRACTORY MATERIAL ENVELOPING SAID METAL FILAMENT AND COATING OF A CATALYTIC MATERIAL ABOUT SAID REFRACTORY MATERIAL, IN WHICH THE COATING OF CATALYTIC MATERIAL CONSISTS OF PALLADIUM.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US211802A US3200011A (en) | 1959-02-03 | 1962-07-23 | Electrically heatable filaments |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB3092799X | 1958-02-18 |
Publications (1)
Publication Number | Publication Date |
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US3092799A true US3092799A (en) | 1963-06-04 |
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US790935A Expired - Lifetime US3092799A (en) | 1958-02-18 | 1959-02-03 | Apparatus for detecting combustible gases having an electrically conductive member enveloped in a refractory material |
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Cited By (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3676820A (en) * | 1969-02-06 | 1972-07-11 | Naoyoshi Taguchi | Gas detecting element and method of manufacturing same |
US3959764A (en) * | 1974-10-09 | 1976-05-25 | Dictaphone Corporation | Gas analyzing element |
US4045177A (en) * | 1976-08-16 | 1977-08-30 | Cse Corporation | Apparatus for detecting combustible gases |
US4077775A (en) * | 1975-12-05 | 1978-03-07 | Comptoir Lyon-Alemand-Louyot | Element for detecting the presence of combustible gases in a gaseous atmosphere |
US4111658A (en) * | 1976-12-13 | 1978-09-05 | National Research Development Corporation | Catalytic gas detectors |
US4193964A (en) * | 1977-12-21 | 1980-03-18 | A-T-O Inc. | Microminiature palladium oxide gas detector and method of making same |
US4244918A (en) * | 1975-12-23 | 1981-01-13 | Nippon Soken, Inc. | Gas component detection apparatus |
US4246228A (en) * | 1977-08-25 | 1981-01-20 | English Electric Valve Company Limited | Combustible gas detectors |
US4259292A (en) * | 1977-01-31 | 1981-03-31 | Tokyo Shibaura Electric Co., Ltd. | Gas detecting element |
FR2473179A1 (en) * | 1980-01-02 | 1981-07-10 | Int Gas Detectors Ltd | GAS DETECTOR ELEMENTS AND METHODS OF MAKING SAME |
US4296399A (en) * | 1977-12-21 | 1981-10-20 | A-T-O Inc. | Microminiature palladium oxide gas detector and method of making same |
US4423407A (en) * | 1981-02-27 | 1983-12-27 | Dart Industries Inc. | Apparatus and method for measuring the concentration of gases |
US4447397A (en) * | 1982-08-05 | 1984-05-08 | Bacharach Instrument Company | Catalytic gas sensor |
US4502321A (en) * | 1981-02-27 | 1985-03-05 | Capital Controls | Apparatus and method for measuring the concentration of gases |
US4560585A (en) * | 1983-12-23 | 1985-12-24 | Rexnord Inc. | Poison resistant combustible gas sensor |
US4857275A (en) * | 1986-03-19 | 1989-08-15 | Ngk Spark Plug Co., Ltd. | Thick-film gas-sensitive element |
US5064693A (en) * | 1985-12-25 | 1991-11-12 | Ngk Spark Plug Co., Ltd. | Method of adjusting a gas sensor |
USRE33980E (en) * | 1986-03-19 | 1992-06-30 | Ngk Spark Plug Co., Ltd. | Thick-film gas-sensitive element |
US5549871A (en) * | 1993-01-21 | 1996-08-27 | Servomex Plc | Sensor for combustible gases |
US5599584A (en) * | 1994-12-16 | 1997-02-04 | Mine Safety Appliances Company | Microminiature combustible gas sensor and method of fabricating a microminiature combustible gas sensor |
US20030177815A1 (en) * | 2000-08-10 | 2003-09-25 | White Robert John | Pellet resistor sensor |
US20080156076A1 (en) * | 2006-12-29 | 2008-07-03 | Ravosh Samari | Low Power Combustible Gas Sensor |
US20090031784A1 (en) * | 2007-03-30 | 2009-02-05 | Fis Inc. | Hydrogen gas sensor |
US20120272720A1 (en) * | 2009-11-25 | 2012-11-01 | Manfred Wiesner | Heatable gas sensor and method for the production thereof |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB775522A (en) * | 1954-07-07 | 1900-01-01 | ||
GB422893A (en) * | 1933-08-12 | 1935-01-21 | British Thomson Houston Co Ltd | Improvements in and relating to electric resistance heaters |
US2234858A (en) * | 1938-12-16 | 1941-03-11 | Brown | Humidity control apparatus |
US2367561A (en) * | 1943-04-10 | 1945-01-16 | Michigan State Board Of Agricu | Electric hygrometer |
US2397568A (en) * | 1944-03-11 | 1946-04-02 | Ellsworth F Seaman | Shockproof electrical resistor |
US2703355A (en) * | 1950-10-23 | 1955-03-01 | Kanthal Corp | Electric heater |
-
1959
- 1959-02-03 US US790935A patent/US3092799A/en not_active Expired - Lifetime
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB422893A (en) * | 1933-08-12 | 1935-01-21 | British Thomson Houston Co Ltd | Improvements in and relating to electric resistance heaters |
US2234858A (en) * | 1938-12-16 | 1941-03-11 | Brown | Humidity control apparatus |
US2367561A (en) * | 1943-04-10 | 1945-01-16 | Michigan State Board Of Agricu | Electric hygrometer |
US2397568A (en) * | 1944-03-11 | 1946-04-02 | Ellsworth F Seaman | Shockproof electrical resistor |
US2703355A (en) * | 1950-10-23 | 1955-03-01 | Kanthal Corp | Electric heater |
GB775522A (en) * | 1954-07-07 | 1900-01-01 |
Cited By (29)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3676820A (en) * | 1969-02-06 | 1972-07-11 | Naoyoshi Taguchi | Gas detecting element and method of manufacturing same |
US3959764A (en) * | 1974-10-09 | 1976-05-25 | Dictaphone Corporation | Gas analyzing element |
US4068021A (en) * | 1974-10-09 | 1978-01-10 | Dictaphone Corporation | Method of making gas analyzing element |
US4077775A (en) * | 1975-12-05 | 1978-03-07 | Comptoir Lyon-Alemand-Louyot | Element for detecting the presence of combustible gases in a gaseous atmosphere |
US4322383A (en) * | 1975-12-23 | 1982-03-30 | Nippon Soken, Inc. | Gas component detection apparatus |
US4244918A (en) * | 1975-12-23 | 1981-01-13 | Nippon Soken, Inc. | Gas component detection apparatus |
US4045177A (en) * | 1976-08-16 | 1977-08-30 | Cse Corporation | Apparatus for detecting combustible gases |
US4111658A (en) * | 1976-12-13 | 1978-09-05 | National Research Development Corporation | Catalytic gas detectors |
US4259292A (en) * | 1977-01-31 | 1981-03-31 | Tokyo Shibaura Electric Co., Ltd. | Gas detecting element |
US4246228A (en) * | 1977-08-25 | 1981-01-20 | English Electric Valve Company Limited | Combustible gas detectors |
US4296399A (en) * | 1977-12-21 | 1981-10-20 | A-T-O Inc. | Microminiature palladium oxide gas detector and method of making same |
US4193964A (en) * | 1977-12-21 | 1980-03-18 | A-T-O Inc. | Microminiature palladium oxide gas detector and method of making same |
FR2473179A1 (en) * | 1980-01-02 | 1981-07-10 | Int Gas Detectors Ltd | GAS DETECTOR ELEMENTS AND METHODS OF MAKING SAME |
US4502321A (en) * | 1981-02-27 | 1985-03-05 | Capital Controls | Apparatus and method for measuring the concentration of gases |
US4423407A (en) * | 1981-02-27 | 1983-12-27 | Dart Industries Inc. | Apparatus and method for measuring the concentration of gases |
US4447397A (en) * | 1982-08-05 | 1984-05-08 | Bacharach Instrument Company | Catalytic gas sensor |
US4560585A (en) * | 1983-12-23 | 1985-12-24 | Rexnord Inc. | Poison resistant combustible gas sensor |
US5064693A (en) * | 1985-12-25 | 1991-11-12 | Ngk Spark Plug Co., Ltd. | Method of adjusting a gas sensor |
US4857275A (en) * | 1986-03-19 | 1989-08-15 | Ngk Spark Plug Co., Ltd. | Thick-film gas-sensitive element |
USRE33980E (en) * | 1986-03-19 | 1992-06-30 | Ngk Spark Plug Co., Ltd. | Thick-film gas-sensitive element |
US5549871A (en) * | 1993-01-21 | 1996-08-27 | Servomex Plc | Sensor for combustible gases |
US5599584A (en) * | 1994-12-16 | 1997-02-04 | Mine Safety Appliances Company | Microminiature combustible gas sensor and method of fabricating a microminiature combustible gas sensor |
US20030177815A1 (en) * | 2000-08-10 | 2003-09-25 | White Robert John | Pellet resistor sensor |
US20080156076A1 (en) * | 2006-12-29 | 2008-07-03 | Ravosh Samari | Low Power Combustible Gas Sensor |
US7833482B2 (en) | 2006-12-29 | 2010-11-16 | Honeywell International Inc. | Low power combustible gas sensor |
US20090031784A1 (en) * | 2007-03-30 | 2009-02-05 | Fis Inc. | Hydrogen gas sensor |
US7980116B2 (en) * | 2007-03-30 | 2011-07-19 | Fis Inc. | Hydrogen gas sensor |
US20120272720A1 (en) * | 2009-11-25 | 2012-11-01 | Manfred Wiesner | Heatable gas sensor and method for the production thereof |
US9052270B2 (en) * | 2009-11-25 | 2015-06-09 | Manfred Wiesner | Heatable gas sensor and method for the production thereof |
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