US3878423A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical surge arrestor having fail-safe properties
Assignee: Comtelco UK Ltd
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Filing: 1973-12-11
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Granted: 1975-04-15
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Expires: 1993-12-11
Abstract
Abstract An electrical surge arrestor having fail-safe properties and providing breakdown at a predetermined region within a sealed structure. The arrestor comprises a pair of axially symmetric electrically and thermally conductive electrodes having integral terminal portions and discharge portions. The discharge portions are disposed coaxially in spaced confronting or nesting relationship within a coaxial ceramic insulative housing to provide a discharge gap at a selected area to form a sealed enclosure. The discharge gap is configured so that the discharge portions of the electrodes will fuse in response to the presence of a predetermined overload condition. The operating lifetime of the surge arrestor may be lengthened by shading an annular inner surface portion of the insulating housing from the discharge gap in order to minimize the deposite thereon of conductive material discharged from the electrodes during breakdown. The electrodes and insulating housing are formed of materials having substantially similar thermal expansion coefficients for providing a metal to ceramic seal resistant to thermal shock.
Inventors
- 👤 John Hill
- 👤 Henryk Turczanski
- 👤 Frederick Henry Wallis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 01:28
CPC Classifications
H; H01; H01T; H01T1/00; H01T1/14; H01T4/00; H01T4/10; H01T4/12
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
233 words
An electrical surge arrestor comprising: first and second axially symmetric electrical discharge electrodes, each formed of a unitary solid block of the same material consistency throughout, each block having an electrical discharge surface formed in one end face thereof, a peripheral flange extending transversely of the central axis of the block, a location portion contiguous with one side of said flange and extending therefrom along said axis and a terminal portion contiguous with the opposite side of said flange and extending therefrom along said axis; and an insulative sleeve of uniform internal cross-section at least over a major portion of its length and into each end of which said electrodes are respectively received; said peripheral flange of each electrode being seated against and hermetically sealed to a respective end face of said sleeve to form a sealed chamber and said location portion of each electrode being fitted in a respective end of said sleeve to align the electrodes along a common axis centrally within said sealed chamber; said electrodes being dimensioned to provide an annular gap between the electrodes and the confronting inner surface of said sleeve and to define a discharge gap between confronting discharge surfaces of said electrodes; the discharge surfaces of said electrodes being shaped to provide relative male and female confronting surfaces; said electrodes and said sleeve being constructed of materials having substantially the same coefficient of thermal expansion.
Claim 2
Dependent Claim
233 words
An electrical surge arrestor comprising: first and second axially symmetric electrical discharge electrodes, each formed of a unitary solid block of the same material consistency throughout, each block having an electrical discharge surface formed in one end face thereof, a peripheral flange extending transversely of the central axis of the block, a location portion contiguous with one side of said flange and extending therefrom along said axis and a terminal portion contiguous with the opposite side of said flange and extending therefrom along said axis; and an insulative sleeve of uniform internal cross-section at least over a major portion of its length and into each end of which said electrodes are respectively received; said peripheral flange of each electrode being seated against and hermetically sealed to a respective end face of said sleeve to form a sealed chamber and said location portion of each electrode being fitted in a respective end of said sleeve to align the electrodes along a common axis centrally within said sealed chamber; said electrodes being dimensioned to provide an annular gap between the electrodes and the confronting inner surface of said sleeve and to define a discharge gap between confronting discharge surfaces of said electrodes; the discharge surfaces of said electrodes being shaped to provide relative male and female confronting surfaces; said electrodes and said sleeve being constructed of materials having substantially the same coefficient of thermal expansion.
Claim 3
Dependent Claim
45 words
A surge arrestor as in claim 1 wherein said insulative housing is formed of ceramic material containing a major proportion of alumina and the material of which said first and second electrodes are formed is a nickel-iron alloy containing between 40 and 52 percent nickel.
Claim 4
Dependent Claim
30 words
A surge arrestor according to claim 1 provided with an atmosphere of ionized gas within the sealed chamber to thereby provide a selected breakdown potential threshold across said discharge gap.
Claim 5
Dependent Claim
25 words
A surge arrestor as in claim 1 wherein said insulative sleeve is provided with at least one annular surface facing away from said discharge gap.
Claim 6
Dependent Claim
46 words
A surge arrestor as in claim 1 wherein the shapes of said discharge surfaces are such that the discharge gap is of greatest magnitude at the radially outermost edge of said surfaces and decreases smoothly in magnitude towards the central and mutual axis of said electrodes.
Claim 7
Dependent Claim
54 words
A surge arrestor as in claim 5 wherein the discharge surface of said first electrode is substantially convex in configuration and the discharge surface of said second electrode is substantially planar, both discharge surfaces being symmetrical about the central axis and the radially outermost edges of said discharge surfaces lying in mutually parallel planes.
Claim 8
Dependent Claim
55 words
A surge arrestor as in claim 5 wherein the discharge surface of said first electrode is of substantially convex configuration and the discharge surface of said second electrode is of substantially concave configuration, both discharge surfaces being symmetrical about the central axis, the radially outermost edges of said discharge surfaces lying in mutually parallel planes.
Claim 9
Dependent Claim
28 words
A surge arrestor as in claim 7 wherein both discharge surfaces of said first and second electrodes are of substantially conical configuration, one being nested within the other.
Claim 10
Dependent Claim
18 words
A surge arrestor as in claim 7 wherein the discharge gap is disposed substantially within said second electrode.
Claim 11
Dependent Claim
36 words
A surge arrestor as in claim 5 wherein the radially outermost edges of the discharge surfaces of said first and second electrodes lie in planes parallel with the central axis and disposed on either side thereof.
Claim 12
Dependent Claim
34 words
A surge arrestor as in claim 10 wherein at least one of said discharge surfaces is shaped so as to provide a gap of least and constant magnitude across and along the central axis.
Claim 13
Dependent Claim
55 words
A surge arrestor as in claim 1 wherein the discharge surfaces of said first and second electrodes are shaped to provide a gap therebetween which narrows at least along one transverse axial line toward the aligned central axis of said electrodes, such that discharge is encouraged to predominate in the region of said narrowed gap.
Claim 14
Dependent Claim
65 words
A surge arrestor as in claim 1 wherein the discharge surfaces of said first and second electrodes are symmetrical about the central axis thereof and have radially outermost edges lying in mutually parallel planes, said discharge surfaces being shaped to provide a gap therebetween which tapers toward said central axis such that discharge is encouraged to predominate at the central axis region of said gap.
Claim 15
Dependent Claim
51 words
A surge arrestor as in claim 1 wherein said location portion of each of said first and second electrodes has a cylindrical location surface conforming to the confronting surface of the respective end of said sleeve, said location surface of each electrode being fitted in a respective end of said sleeve.
Claim 16
Dependent Claim
59 words
A surge arrestor as in claim 8 wherein the electrode having said conical discharge surface with respect to which the other conical discharge surface is nested includes a coaxial annular groove contiguous with the outermost edge of said conical discharge surface and said peripheral flange and confronting said chamber and a portion of the inner wall of said sleeve.
Claim 17
Dependent Claim
44 words
A surge arrestor as in claim 1 wherein said sleeve includes at least one annular groove provided in the inner wall thereof and having an annular lip operative to shield said groove from deposition of sputtered metal present during a discharge across said gap.
Claim 18
Dependent Claim
50 words
A surge arrestor as in claim 1 wherein said sleeve includes an annular groove provided in at least one end of said sleeve and having a circumferential surface of greater dimension than that of the inner dimension of said sleeve and an annular surface facing away from said discharge gap.
Claim 19
Dependent Claim
49 words
A surge arrestor as in claim 1 wherein said sleeve includes an annular groove provided in each end of said sleeve and each having a circumferential surface of greater dimension than that of the inner dimension of said sleeve and an annular surface facing away from said discharge gap.
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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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |