US4550301A
Expired / Lapsed
US
⏱️ 0.0 years remaining
PTC Circuit protection device
Assignee: Littelfuse Inc
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Filing: 1984-07-23
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Granted: 1985-10-29
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Expires: 2004-07-23
Abstract
Abstract Circuit protection devices comprise a PTC conductive polymer element and means for minimizing the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped. An enclosure encloses, but is spaced apart from, the PTC element. In one embodiment at least part of the interior surface of the enclosure is composed of polytetrafluoroethylene, a ceramic or another material which discourages the formation of permanent low resistance paths through carbonaceous material lying on its surface. In another embodiment the enclosure has a large internal surface area compared to the volume of the PTC element. In further embodiments, electrical leads are connected to and pass through the enclosure, and at least one of the leads is insulated along its length and/or the leads pass through opposite ends of the enclosure.
Inventors
- 👤 Mary S. McTavish
- 👤 Robert W. Stodieck
- 👤 Frank A. Doljack
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 00:11
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; H01C1/00; H01C1/02
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
147 words
A circuit protection device which comprises (1) a PTC element composed of a conductive polymer composition which exhibits PTC behavior and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; (2) two electrodes which are electrically connected to the PTC element and which are connectable to a source of electrical power to cause current to pass through the PTC element; and (3) an enclosure (a) which encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) which is substantially impervious to carbon dust; and (c) at least a part of whose interior surface is composed of an unsulating material which passes the carbon burn-off test at a test voltage of 440 volts DC, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 2
Dependent Claim
147 words
A circuit protection device which comprises (1) a PTC element composed of a conductive polymer composition which exhibits PTC behavior and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; (2) two electrodes which are electrically connected to the PTC element and which are connectable to a source of electrical power to cause current to pass through the PTC element; and (3) an enclosure (a) which encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) which is substantially impervious to carbon dust; and (c) at least a part of whose interior surface is composed of an unsulating material which passes the carbon burn-off test at a test voltage of 440 volts DC, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 3
Dependent Claim
23 words
A device according to claim 1 wherein said insulating material passes the carbon burn-off test at a test voltage of 600 volts DC.
Claim 4
Dependent Claim
21 words
A device according to claim 1 wherein the enclosure encloses and is spaced apart from the whole of the PTC element.
Claim 5
Dependent Claim
40 words
A device according to claim 1 which further comprises at least one electrical lead which (a) is connected to one of the electrodes, (b) passes through an exit port in the enclosure, and (c) is electrically insulated from the enclosure.
Claim 6
Dependent Claim
44 words
A device according to claim 1 which further comprises two electrical leads, one connected to each electrode, and wherein the enclosure (a) is electrically insulated from the PTC element, the electrodes and the leads and (b) comprises exit ports through which the leads pass.
Claim 7
Dependent Claim
26 words
A device according to claim 5 wherein the interior surface of the enclosure around each of the exit ports is composed of a said insulating material.
Claim 8
Dependent Claim
16 words
A device according to claim 1 wherein said insulating material is selected from polytetrafluoroethylene and ceramics.
Claim 9
Dependent Claim
30 words
A device according to claim 1 wherein said enclosure is pervious to any gases which are generated within it when the PTC element is converted to a high resistance state.
Claim 10
Dependent Claim
99 words
An electrical circuit which comprises (a) a power source having a voltage V which is at least 440 volts DC; (b) an electrical load; and (c) a circuit protection device which comprises (1) a PTC element composed of a conductive polmyer composition which exhibits PTC behavior and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; (2) two electrodes which are electrically connected to the PTC element and which are connectable to a source of electrical power to cause current to pass through the PTC element; and (3) an enclosure
Claim 11
Dependent Claim
99 words
An electrical circuit which comprises (a) a power source having a voltage V which is at least 440 volts DC; (b) an electrical load; and (c) a circuit protection device which comprises (1) a PTC element composed of a conductive polmyer composition which exhibits PTC behavior and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; (2) two electrodes which are electrically connected to the PTC element and which are connectable to a source of electrical power to cause current to pass through the PTC element; and (3) an enclosure
Claim 12
Dependent Claim
74 words
3 (a) which encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) which is substantially impervious to carbon dust; and (c) at least a part of whose interior surface is composed of an insulating material which passes the carbon burn-off test at a test voltage of V volts, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it it tripped are minimized.
Claim 13
Dependent Claim
74 words
3 (a) which encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) which is substantially impervious to carbon dust; and (c) at least a part of whose interior surface is composed of an insulating material which passes the carbon burn-off test at a test voltage of V volts, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it it tripped are minimized.
Claim 14
Dependent Claim
21 words
A circuit according to claim 9, wherein the enclosure encloses and is spaced apart from the whole of the PTC element.
Claim 15
Dependent Claim
40 words
A circuit according to claim 9, which further comprises at least one electrical lead which (a) is connected to one of the electrodes, (b) passes through an exit port in the enclosure, and (c) is electrically insulated from the enclosure.
Claim 16
Dependent Claim
44 words
A circuit according to claim 9 which further comprises two electrical leads, one connected to each electrode, and wherein the enclosure (a) is electrically insulated from the PTC element, the electrodes and the leads and (b) comprises exit ports through which the leads pass.
Claim 17
Dependent Claim
25 words
A circuit according to claim 12 wherein the interior surface of the enclosure around each of the exit ports is composed of said insulating material.
Claim 18
Dependent Claim
16 words
A device according to claim 9 wherein said insulating material is selected from polytetrafluoroethylene and ceramics.
Claim 19
Dependent Claim
30 words
A circuit according to claim 9 wherein said enclosure is pervious to any gases which are generated within it when the PTC element is converted to a high resistance state.
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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) | 1988-10-28 | 1989-04-29 | 1989-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-28 | 1993-04-29 | 1993-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-28 | 1997-04-29 | 1997-10-29 | $7700.00 | Window Closed / Lapsed |