Patent US4296002A successfully refreshed from Google Patents.
US4296002A
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Metal oxide varistor manufacture
Assignee: Cooper Industries LLC
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Filing: 1979-06-25
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Granted: 1981-10-20
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Expires: 1999-06-25
Abstract
Abstract The method of manufacturing metal oxide varistors wherein pressed blocks of selected mixtures of metal oxide powders and additives are joined to form a single varistor unit by vertically stacking and firing the blocks at a high temperature. Sintering of these stacked blocks during the firing cycle results in a strong mechanical and electrical bond between the adjacent blocks in the stack.
Inventors
- 👤 Theodore O. Sokoly
- 👤 John Niedzialkowski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:59
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
117 words
A method of making a metal oxide varistor, which comprises the steps of: forming a powdered mixture comprised of at least one electrically conductive metal oxide powder, and a small percentage of at least one preselected powdered additive, said additive being selected from the group consisting of different metal oxides and metal florides; forming of said powdered mixture, by pressing, a plurality of blocks, each having complementary top and bottom surfaces, forming a stack of said plurality of blocks; (and) sintering said stack of blocks, whereby said complementary abutting top and bottom surfaces of adjacent blocks are bonded together to form a varistor; and applying metallic contacts only to the top and bottom surfaces of said varistor.
Claim 2
Independent Claim
117 words
A method of making a metal oxide varistor, which comprises the steps of: forming a powdered mixture comprised of at least one electrically conductive metal oxide powder, and a small percentage of at least one preselected powdered additive, said additive being selected from the group consisting of different metal oxides and metal florides; forming of said powdered mixture, by pressing, a plurality of blocks, each having complementary top and bottom surfaces, forming a stack of said plurality of blocks; (and) sintering said stack of blocks, whereby said complementary abutting top and bottom surfaces of adjacent blocks are bonded together to form a varistor; and applying metallic contacts only to the top and bottom surfaces of said varistor.
Claim 3
Dependent Claim
26 words
The method of claim 1 wherein adjacent blocks are joined together during sintering by the electrically conductive metal oxide in adjacent blocks combining during grain growth.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein adjacent blocks are joined together by intergranular glassy material extending between adjacent blocks.
Claim 5
Dependent Claim
32 words
The method of claim 1 wherein the blocks are vertically stacked while being sintered, whereby the weight of the blocks provides pressure between complementary abutting top and bottom surfaces of adjacent blocks.
Claim 6
Dependent Claim
17 words
The method of claim 1 wherein a clamping force is applied to said stack while being sintered.
Claim 7
Dependent Claim
19 words
The method of claim 1 wherein said complementary top and bottom surfaces of said blocks are flat and parallel.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-10-19 | 1985-04-20 | 1985-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-19 | 1989-04-20 | 1989-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-19 | 1993-04-20 | 1993-10-20 | $7700.00 | Window Closed / Lapsed |