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US3875477A
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Silicon carbide resistance igniter
Assignee: Saint Gobain Abrasives Inc
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Filing: 1974-04-23
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Granted: 1975-04-01
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Expires: 1994-04-23
Abstract
Abstract A monolithic ceramic resistance igniter of simple configuration is composed essentially of polycrystalline silicon carbide adapted for use in gas and liquid fuel burning systems. As a result of the combination of its sintered silicon carbide composition, its microstructure, controlled density and large cross-sectional area, the igniter possesses an unusually high degree of physical ruggedness. The igniter will attain a temperature of about 1,000*C in well under 20 seconds drawing a maximum of 6 amps at 132 volts, with a room temperature resistivity of 0.10 to 1.70 ohm centimeters and a resistivity at about 1000*C of from 0.06 to 0.26 ohm centimeter. The igniter also has a physical construction such that a high percentage of its hot surface area radiates directly to the environment.
Inventors
- 👤 John I Fredriksson
- 👤 Samuel H Coes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:35
CPC Classifications
F; F23; F23Q; F23Q7/00; F23Q7/22; C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B2235/00; C04B2235/02; C04B2235/30; C04B2235/32; C04B2235/3217; C04B2235/327; C04B2235/3272; C04B2235/38; C04B2235/3817; C04B2235/3826; C04B2235/46; C04B2235/50; C04B2235/54; C04B2235/5418; C04B2235/5436; C04B2235/60; C04B2235/602; C04B2235/6027; C04B2235/65; C04B2235/658; C04B2235/66; C04B2235/661; C04B2235/70; C04B2235/72; C04B2235/723; C04B2235/74; C04B2235/77; C04B2235/94
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
101 words
A CERAMIC RESISTANCE IGNITER, COMPRISED OF A PAIR OF TERMINAL CONNECTING ENDS AND A HOT-ZONE EXTENDING THEREFROM AND HAVING A COMPOSITION CONSISTING ESSENTIALLY OF FROM 95 TO 99.9% BY WEIGHT OF SILICON CARBIDE, 0.05 TO 0.50% BY WEIGHT OF ALUMINUM, 0 TO 4% BY WEIGHT OF SILICON OXIDE, 0 TO 0.25% BY WEIGHT OF IRON OR COMPOUNDS THEREOF, A MAXIMUM OF 100 PARTS PER MILLION OF BORON, AD UP TO 0.25% BY WEIGHT OF MISCELLANEOUS IMPURITIES, SAID COMPOSITION HAVING BEEN SINTERED AND THEN EXPOSED TO A NITROGEN ATMOSPHERE AT A TEMPERATURE OF FROM 1,500*C TO 2,000*C FOR 15 TO 180 MINUTES.
Claim 2
Dependent Claim
101 words
A CERAMIC RESISTANCE IGNITER, COMPRISED OF A PAIR OF TERMINAL CONNECTING ENDS AND A HOT-ZONE EXTENDING THEREFROM AND HAVING A COMPOSITION CONSISTING ESSENTIALLY OF FROM 95 TO 99.9% BY WEIGHT OF SILICON CARBIDE, 0.05 TO 0.50% BY WEIGHT OF ALUMINUM, 0 TO 4% BY WEIGHT OF SILICON OXIDE, 0 TO 0.25% BY WEIGHT OF IRON OR COMPOUNDS THEREOF, A MAXIMUM OF 100 PARTS PER MILLION OF BORON, AD UP TO 0.25% BY WEIGHT OF MISCELLANEOUS IMPURITIES, SAID COMPOSITION HAVING BEEN SINTERED AND THEN EXPOSED TO A NITROGEN ATMOSPHERE AT A TEMPERATURE OF FROM 1,500*C TO 2,000*C FOR 15 TO 180 MINUTES.
Claim 3
Dependent Claim
33 words
The ceramic resistance igniter of claim 1 having electrical characteristics such that said igniter draws a maximum of 6 amps at 132 volts and has an impact resistance of at least 125 g''s.
Claim 4
Dependent Claim
31 words
The ceramic resistance igniter of claim 2 having a response time at 80 volts of 60 seconds or less to attain 1,000*C and an operational life of at least 200,000 cycles.
Claim 5
Dependent Claim
117 words
A monolithic ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 0.25% by weight of iron or compounds thereof, 0 to 50 parts per million of boron, and up to 0.25% by weight of miscellaneous impurities; said silicon carbide containing from 0.05 to 0.50% by weight of aluminum in the crystal lattice thereof and nitrogen being introduced into said crystal lattice by subjecting said composition to an atmosphere of nitrogen at a temperature of from 1,500*C to 2,000*C for 15 to 180 minutes.
Claim 6
Dependent Claim
117 words
A monolithic ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 0.25% by weight of iron or compounds thereof, 0 to 50 parts per million of boron, and up to 0.25% by weight of miscellaneous impurities; said silicon carbide containing from 0.05 to 0.50% by weight of aluminum in the crystal lattice thereof and nitrogen being introduced into said crystal lattice by subjecting said composition to an atmosphere of nitrogen at a temperature of from 1,500*C to 2,000*C for 15 to 180 minutes.
Claim 7
Dependent Claim
29 words
The ceramic resistance igniter of claim 4 having a room temperature resistivity of 0.10 to 1.70 ohm centimeters and a resistivity at 1,000*C of 0.06 to 0.26 ohm centimeter.
Claim 8
Dependent Claim
154 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 97 to 99.9% by weight of polycrystalline silicon carbide, 0.1 to 0.3% by weight of aluminum contained in the crystal lattice of said silicon carbide, 0 to 100 parts per million of boron, and from 0 to 0.2% by weight of miscellaneous impurities, said composition having been doped with nitrogen by heating at 1,500*C to 2,000*C for 15 to 180 minutes; said ceramic igniter having a room temperature resistivity of 0.15 to 0.5 ohm centimeter, a resistivity at 1,800*F of at least 0.1 ohm centimeter, a response time of 10 to 60 seconds to attain 1,000*C, an operational life of at least 200,000 cycles, an impact resistance of at least 125 g''s, and the further property that said igniter draws a maximum of 6 amps at 132 volts.
Claim 9
Dependent Claim
154 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 97 to 99.9% by weight of polycrystalline silicon carbide, 0.1 to 0.3% by weight of aluminum contained in the crystal lattice of said silicon carbide, 0 to 100 parts per million of boron, and from 0 to 0.2% by weight of miscellaneous impurities, said composition having been doped with nitrogen by heating at 1,500*C to 2,000*C for 15 to 180 minutes; said ceramic igniter having a room temperature resistivity of 0.15 to 0.5 ohm centimeter, a resistivity at 1,800*F of at least 0.1 ohm centimeter, a response time of 10 to 60 seconds to attain 1,000*C, an operational life of at least 200,000 cycles, an impact resistance of at least 125 g''s, and the further property that said igniter draws a maximum of 6 amps at 132 volts.
Claim 10
Dependent Claim
126 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline alpha silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 100 parts per million of boron, 0.05 to 0.5% by weight of aluminum, said composition having first been preformed and fired at 2,250*C to 2,450*C in an inert atmosphere followed by firing in a nitrogen atmosphere at from 1, 500*C to 2,000*C for 15 to 180 minutes; said igniter having a density of 2.60 to 2.70 gms/cc, and having resistivity at room temperature of from 0.10 to 1.70 ohm centimeters and at 1,000*C of from 0.06 to 0.26 ohm centimeter.
Claim 11
Dependent Claim
126 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline alpha silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 100 parts per million of boron, 0.05 to 0.5% by weight of aluminum, said composition having first been preformed and fired at 2,250*C to 2,450*C in an inert atmosphere followed by firing in a nitrogen atmosphere at from 1, 500*C to 2,000*C for 15 to 180 minutes; said igniter having a density of 2.60 to 2.70 gms/cc, and having resistivity at room temperature of from 0.10 to 1.70 ohm centimeters and at 1,000*C of from 0.06 to 0.26 ohm centimeter.
Claim 12
Dependent Claim
112 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline alpha silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 100 parts per million of boron, 0.05 to 0.5% by weight of aluminum, said igniter having a density of 2.60 to 2.70 gms/cc, having resistivity at room temperature of from 0.10 to 1.70 ohm centimeters and at 1,000*C of from 0.06 to 0.26 ohm centimeter, and having at least 50% of the surface area of the hot zone of the igniter radiating directly to the environment.
Claim 13
Dependent Claim
112 words
A sintered ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting essentially of from 95 to 99.9% by weight of polycrystalline alpha silicon carbide, 0 to 4% by weight of silicon oxide, 0 to 100 parts per million of boron, 0.05 to 0.5% by weight of aluminum, said igniter having a density of 2.60 to 2.70 gms/cc, having resistivity at room temperature of from 0.10 to 1.70 ohm centimeters and at 1,000*C of from 0.06 to 0.26 ohm centimeter, and having at least 50% of the surface area of the hot zone of the igniter radiating directly to the environment.
Claim 14
Dependent Claim
95 words
A ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting of from 95 to 99.9% by weight of silicon carbide, 0.05 to 0.5% by weight of aluminum, 0.04 to 0.1% by weight of oxygen, 0 to 4% by weight of silicon oxide, 0 to 0.25% by weight of iron or compounds thereof, a maximum of 100 parts per million of boron, said composition having been exposed to a nitrogen atmosphere at a temperature of from 1,500*C to 2,000*C for 15 to 180 minutes.
Claim 15
Dependent Claim
95 words
A ceramic resistance igniter, comprised of a pair of terminal connecting ends and a hot-zone extending therefrom and having a composition consisting of from 95 to 99.9% by weight of silicon carbide, 0.05 to 0.5% by weight of aluminum, 0.04 to 0.1% by weight of oxygen, 0 to 4% by weight of silicon oxide, 0 to 0.25% by weight of iron or compounds thereof, a maximum of 100 parts per million of boron, said composition having been exposed to a nitrogen atmosphere at a temperature of from 1,500*C to 2,000*C for 15 to 180 minutes.
Claim 16
Dependent Claim
17 words
The ceramic resistance igniter of claim 9 wherein said ends having been treated with an aluminum alloy.
Claim 17
Dependent Claim
82 words
A monolithic ceramic resistance igniter having a flat elongated configuration essentially rectangular in cross-section, Including terminal connecting means at one end, a hot zone extending therefrom comprised of at least one leg having a hairpin shape, where the end of said leg opposite the terminal connecting ends has a greater cross-section than the cross-section of the individual elements making up said hairpin shaped leg, and having at least 50% of the surface area of said hot zone radiating directly to the environment.
Claim 18
Dependent Claim
82 words
A monolithic ceramic resistance igniter having a flat elongated configuration essentially rectangular in cross-section, Including terminal connecting means at one end, a hot zone extending therefrom comprised of at least one leg having a hairpin shape, where the end of said leg opposite the terminal connecting ends has a greater cross-section than the cross-section of the individual elements making up said hairpin shaped leg, and having at least 50% of the surface area of said hot zone radiating directly to the environment.
Claim 19
Dependent Claim
86 words
The monolithic ceramic resistance igniter of claim 11 comprised of polycrystalline silicon carbide and consisting of two interconnected hairpin shaped legs, the overall length of said igniter being from 2.125 to 2.625 inches, the ends of said legs opposite the terminal connecting ends having a cross-sectional area of from 0.013 to 0.049 square inch, the elements of said hairpin shaped legs having a cross-section of from 0.006 to 0.018 square inch, and the width of the slots separating said elements being from 0.012 to 0.080 inch.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |