US4243622A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for manufacturing zinc oxide varistors having reduced voltage drift
Assignee: Hubbell Inc
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Filing: 1978-12-07
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Granted: 1981-01-06
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Expires: 1998-12-07
Abstract
Abstract Zinc oxide varistors are thermally treated, after sintering, at temperatures between 400° C. and 800° C. in air for a period of one to ten hours. The thermal treatment apparently removes residual strains resulting from the sintering process and substantially reduces voltage drift.
Inventors
- 👤 James S. Kresge
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 19:10
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108; H01C7/112; C; C04; C04B; C04B35/00; C04B35/01; C04B35/453; H01C17/00; H01C17/30
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
64 words
A method for treating a zinc oxide varistor after sintering to reduce voltage drift comprising steps of: heating the varistor for not more than one cycle in air at a temperature range from 580° to 750° C. for a period of from two to six hours; and cooling the varistor to room temperature at a rate of from 50° to 200° C. per hour.
Claim 2
Independent Claim
64 words
A method for treating a zinc oxide varistor after sintering to reduce voltage drift comprising steps of: heating the varistor for not more than one cycle in air at a temperature range from 580° to 750° C. for a period of from two to six hours; and cooling the varistor to room temperature at a rate of from 50° to 200° C. per hour.
Claim 3
Dependent Claim
21 words
The method of claim 1 wherein the heating is provided at a rate of from 50° to 200° C. per hour.
Claim 4
Dependent Claim
26 words
The method of claim 1 wherein the varistor contains at least one of the materials selected from the group consisting of boron oxide and barium oxide.
Claim 5
Dependent Claim
12 words
The method of claim 3 wherein the varistor further contains silicon dioxide.
Claim 6
Dependent Claim
20 words
The method of claim 4 wherein the boron oxide and barium oxide each comprise from 0.01 to 10.0 mole percent.
Claim 7
Dependent Claim
16 words
The method of claim 4 wherein the silicon dioxide comprises from 0.1 to 10.0 mole percent.
Claim 8
Dependent Claim
124 words
A process for manufacturing a zinc oxide varistor having stable-operating characteristics comprising the steps of: providing a mixture of zinc oxide, and at least one of the oxides selected from the group consisting of barium oxide, boron oxide, and silicon dioxide; sintering the mixture at a temperature of at least 1000° C. for a period of at least one hour to form a unitary varistor body; reducing the temperature of the varistor body to 400° C. heating of the varistor body for not more than one cycle in air to a temperature of from 580° to 750° C. for a period of two to six hours; and cooling the body to room temperature at a rate of from 50° to 200° C. per hour.
Claim 9
Dependent Claim
124 words
A process for manufacturing a zinc oxide varistor having stable-operating characteristics comprising the steps of: providing a mixture of zinc oxide, and at least one of the oxides selected from the group consisting of barium oxide, boron oxide, and silicon dioxide; sintering the mixture at a temperature of at least 1000° C. for a period of at least one hour to form a unitary varistor body; reducing the temperature of the varistor body to 400° C. heating of the varistor body for not more than one cycle in air to a temperature of from 580° to 750° C. for a period of two to six hours; and cooling the body to room temperature at a rate of from 50° to 200° C. per hour.
References Cited (Backward Citations)
US4165351A
Cited
US4046847A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-06 | 1984-07-07 | 1985-01-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-06 | 1988-07-07 | 1989-01-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-06 | 1992-07-07 | 1993-01-06 | $7700.00 | Window Closed / Lapsed |