US4234786A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnesia insulated heating elements and method of making the same
Assignee: General Electric Co
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Filing: 1979-02-12
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Granted: 1980-11-18
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Expires: 1999-02-12
Abstract
Abstract Compacted, granular, fused magnesia used as thermally-conducting electrical insulation in tubular, electrical resistance elements is substantially improved in thermal conductivity through the addition of 0.1 to 10.0 percent of a glass comprising CaO, B 2 O 3 and optionally Al 2 O 3 and method of making said tubular, electrical resistance elements.
Inventors
- 👤 Marcus P. Borom
- 👤 John Schultz, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 14:10
CPC Classifications
H; H05; H05B; H05B3/00; H05B3/40; H05B3/42; H05B3/48; H05B3/10; H05B3/18; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49087; Y10T29/49089
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
92 words
In a tubular heating element including a metal sheath and a coaxial coil resistor enclosed in the sheath, the combination of a compacted electrically insulating mass filling the space in the sheath between the resistor and the sheath and comprising fused magnesia and from about 0.1% to about 10% of a glass of softening temperature below about 700° C. having resistivity greater than about 10 7 ohm-cm at 600° C. and being thermodynamically stable in oxygen partial pressure of 10 -15 atmosphere at temperature in the range of 750° to 1100° C.
Claim 2
Dependent Claim
92 words
In a tubular heating element including a metal sheath and a coaxial coil resistor enclosed in the sheath, the combination of a compacted electrically insulating mass filling the space in the sheath between the resistor and the sheath and comprising fused magnesia and from about 0.1% to about 10% of a glass of softening temperature below about 700° C. having resistivity greater than about 10 7 ohm-cm at 600° C. and being thermodynamically stable in oxygen partial pressure of 10 -15 atmosphere at temperature in the range of 750° to 1100° C.
Claim 3
Dependent Claim
45 words
The heating element of claim 1 wherein the glass is of composition from about 10 to about 50 mol percent CaO, from about 30 to about 90 mol percent B 2 O 3 and up to about 30 mol percent Al 2 O 3 .
Claim 4
Dependent Claim
22 words
The heating element of claim 2 wherein the glass is present in an amount from about 0.25 percent to about one percent.
Claim 5
Dependent Claim
103 words
In the method of making a tubular heating element including the step of positioning the coil resistor coaxially within a metal sheath, the combination of the step of filling the metal sheath and thereby embedding the coil resistor with an electrically insulating mixture of fused magnesia and from about 0.1% to about 10% of a glass of softening temperature below about 700° C. having resistivity greater than about 10 7 ohm-cm at 600° C. and being thermodynamically stable against metal oxide decomposition in the presence of oxygen partial pressure of 10 -15 atmosphere at temperature in the range of 750° to 1100° C.
Claim 6
Dependent Claim
103 words
In the method of making a tubular heating element including the step of positioning the coil resistor coaxially within a metal sheath, the combination of the step of filling the metal sheath and thereby embedding the coil resistor with an electrically insulating mixture of fused magnesia and from about 0.1% to about 10% of a glass of softening temperature below about 700° C. having resistivity greater than about 10 7 ohm-cm at 600° C. and being thermodynamically stable against metal oxide decomposition in the presence of oxygen partial pressure of 10 -15 atmosphere at temperature in the range of 750° to 1100° C.
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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) | 1983-11-18 | 1984-05-19 | 1984-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-11-18 | 1988-05-19 | 1988-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-11-18 | 1992-05-19 | 1992-11-18 | $7700.00 | Window Closed / Lapsed |