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US4046847A
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Process for improving the stability of sintered zinc oxide varistors
Assignee: General Electric Co
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Filing: 1975-12-22
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Granted: 1977-09-06
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Expires: 1995-12-22
Abstract
Abstract A process for making overvoltage surge protection varistors of the zinc oxide type includes the steps of: A. sintering a varistor body at an elevated temperature of at least about 1100° C; then B. cooling the body to a temperature below about 400° C; then C. reheating the body to a temperature below about 700° C; then D. recooling the body slowly to a temperature below about 400° C; and then E. repeating at least once the steps (c) and (d) For improving the current stability of the varistor under alternating voltage stresses while preserving the level of current leakage through the varistor.
Inventors
- 👤 James S. Kresge
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:22
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108; H01C7/112
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
89 words
A process for making a varistor body of the zinc oxide type, comprising the steps of: a. sintering the body at an elevated temperature of at least about 1100° C.; then b. cooling the body to a temperature below about 400° C.; then c. reheating the body to a temperature above 400° C. but below 700° C.; then d. recooling the body slowly to a temperature below about 400° C., and then e. repeating at least once the sequence of the reheating step (c) and then recooling step (d).
Claim 2
Dependent Claim
89 words
A process for making a varistor body of the zinc oxide type, comprising the steps of: a. sintering the body at an elevated temperature of at least about 1100° C.; then b. cooling the body to a temperature below about 400° C.; then c. reheating the body to a temperature above 400° C. but below 700° C.; then d. recooling the body slowly to a temperature below about 400° C., and then e. repeating at least once the sequence of the reheating step (c) and then recooling step (d).
Claim 3
Dependent Claim
19 words
The process of claim 1 and wherein said reheating is to between about 550° C. and about 630° C.
Claim 4
Dependent Claim
28 words
The process of claim 2 and wherein said reheating is by placing the varistor for about one hour inside a furnace which is held at said reheating temperature.
Claim 5
Dependent Claim
16 words
The process of claim 3 and wherein said reheatings are to substantially the same reheating temperatures.
Claim 6
Dependent Claim
25 words
The process of claim 4 and wherein said recoolings are at an average rate of about 100° C. per hour for about the first hour.
References Cited (Backward Citations)
US3867145A
Cited
US3959543A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-09-05 | 1981-03-07 | 1981-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-05 | 1985-03-07 | 1985-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-05 | 1989-03-07 | 1989-09-06 | $7700.00 | Window Closed / Lapsed |