US4481498A
Expired / Lapsed
US
⏱️ 0.0 years remaining
PTC Circuit protection device
Assignee: Littelfuse Inc
•
Filing: 1982-02-17
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Granted: 1984-11-06
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Expires: 2002-02-17
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 13:50
CPC Classifications
H; H01; H01C; H01C1/00; H01C1/02; H01C7/00; H01C7/02; H01C7/027
Claims Analysis
Total Claims: 42
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 insulating 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 insulating 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
172 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 which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; and (b) is substantially impervious to carbon dust; the ratio V 1 /A 1 being less than 0.0025 inch, where V 1 is the volume in cubic inches of the potential erosion zone of the PTC element and A 1 is the area in square inches of the surfaces within the enclosure which do not carry current during normal operation of the device, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 11
Dependent Claim
172 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 which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; and (b) is substantially impervious to carbon dust; the ratio V 1 /A 1 being less than 0.0025 inch, where V 1 is the volume in cubic inches of the potential erosion zone of the PTC element and A 1 is the area in square inches of the surfaces within the enclosure which do not carry current during normal operation of the device, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 12
Dependent Claim
14 words
A device according to claim 9 wherein said ratio is less than 0.002 inch.
Claim 13
Dependent Claim
14 words
A device according to claim 10 wherein said ratio is less than 0.001 inch.
Claim 14
Dependent Claim
32 words
A device according to claim 9 wherein the ratio of the exposed surface area of the potential erosion zone of the PTC element to the area A 1 is less than 0.08.
Claim 15
Dependent Claim
14 words
A device according to claim 12 wherein said area ratio is less than 0.04.
Claim 16
Dependent Claim
163 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 which (a) encloses and is spaced apart from the whole of the PTC element; and (b) is substantially impervious to carbon dust; the ratio V 2 /A 1 being less than 0.008 inch, where V 2 is the volume in cubic inches of the PTC element and A 1 is the area in square inches of the surfaces within the enclosure which do not carry current during normal operation of the device, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 17
Dependent Claim
163 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 which (a) encloses and is spaced apart from the whole of the PTC element; and (b) is substantially impervious to carbon dust; the ratio V 2 /A 1 being less than 0.008 inch, where V 2 is the volume in cubic inches of the PTC element and A 1 is the area in square inches of the surfaces within the enclosure which do not carry current during normal operation of the device, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 18
Dependent Claim
18 words
A device according to claim 14 wherein the ratio V 2 /A 1 is less than 0.003 inch.
Claim 19
Dependent Claim
34 words
A device according to claim 14 wherein the ratio V 2 /A 2 is less than 0.008 inch, where A 2 is the area in square inches of the internal surface of the enclosure.
Claim 20
Dependent Claim
26 words
A device according to claim 16 wherein A 2 is equal to A 1 and the ratio V 2 /A 2 is less than 0.007 inch.
Claim 21
Dependent Claim
97 words
A device according to claim 14 which further comprises two leads, one connected to each electrode; 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; wherein the interior surface of said enclosure, in an area which lies in the shortest geometrical path between the exit ports, is composed of an insulating material which passes the carbon burn-off test using a test voltage of 600 volts DC; and wherein said ratio V 2 /A 1 is from 0.0025 to 0.007 inch.
Claim 22
Dependent Claim
27 words
A device according to claim 14 wherein the ratio of the exposed surface area of the PTC element to the area A 1 is less than 0.2.
Claim 23
Dependent Claim
14 words
A device according to claim 19 wherein said area ratio is less than 0.16.
Claim 24
Dependent Claim
14 words
A device according to claim 20 wherein said area ratio is less than 0.10.
Claim 25
Dependent Claim
185 words
A circuit protection device which has a resistance of less than 1000 ohms and which comprises (1) a PTC element which a PTC element which (a) is composed of a PTC conductive polymer composition which has a resistivity at 23° C. of less than 100 ohm·cm and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; and (b) is in the form of a strip with substantially planar parallel ends, the length of the strip being greater than the largest cross-sectional dimension of the strip; and (2) two electrodes, each in the form of a cap having (i) a substantially planar end which contacts and has substantially the same cross-section as one end of the PTC element and (ii) a side wall which contacts the side of the PTC element; (3) an enclosure which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) is substantially impervious to carbon dust; whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 26
Dependent Claim
185 words
A circuit protection device which has a resistance of less than 1000 ohms and which comprises (1) a PTC element which a PTC element which (a) is composed of a PTC conductive polymer composition which has a resistivity at 23° C. of less than 100 ohm·cm and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; and (b) is in the form of a strip with substantially planar parallel ends, the length of the strip being greater than the largest cross-sectional dimension of the strip; and (2) two electrodes, each in the form of a cap having (i) a substantially planar end which contacts and has substantially the same cross-section as one end of the PTC element and (ii) a side wall which contacts the side of the PTC element; (3) an enclosure which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; (b) is substantially impervious to carbon dust; whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 27
Dependent Claim
17 words
A device according to claim 22 having a resistance at 23° C. of less than 100 ohms.
Claim 28
Dependent Claim
17 words
A device according to claim 23 having a resistance at 23° C. of less than 50 ohms.
Claim 29
Dependent Claim
14 words
A device according to claim 24 wherein the PTC element is cylindrical in shape.
Claim 30
Dependent Claim
16 words
A device according to claim 22 wherein said conductive polymer composition comprises a hydrated metal oxide.
Claim 31
Dependent Claim
38 words
A device according to claim 22 whose said enclosure has at least a part of the interior surface is composed of an insulating material which passes the carbon burn-off test at a test voltage of 600 volts DC.
Claim 32
Dependent Claim
73 words
A device according to claim 22 which further comprises an enclosure which encloses and is spaced apart from the whole of the PTC element; which is electrically insulated from the PTC element and the electrodes; and which is substantially impervious to carbon dust; the ratio of the volume of the PTC element in cubic inches to the area of the internal surface of the enclosure in square inches being less than 0.008 inch.
Claim 33
Dependent Claim
144 words
A circuit protection device which has a resistance of less than 1000 ohms and which comprises (1) a PTC element which (a) is composed of a PTC conductive polymer composition which has a resistivity at 23° C. of less than 100 ohm·cm and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; and (b) is in the form of a strip whose length is greater than the largest cross-sectional dimension of the strip; (2) two electrodes which are electrically connected to opposite ends of the PTC element; and (3) an enclosure which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; and (b) is substantially impervious to carbon dust, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 34
Dependent Claim
144 words
A circuit protection device which has a resistance of less than 1000 ohms and which comprises (1) a PTC element which (a) is composed of a PTC conductive polymer composition which has a resistivity at 23° C. of less than 100 ohm·cm and which comprises a polymeric component and, dispersed in the polymeric component, a particulate conductive filler comprising carbon black; and (b) is in the form of a strip whose length is greater than the largest cross-sectional dimension of the strip; (2) two electrodes which are electrically connected to opposite ends of the PTC element; and (3) an enclosure which (a) encloses and is spaced apart from at least the potential erosion zone of the PTC element; and (b) is substantially impervious to carbon dust, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 35
Dependent Claim
87 words
A device according to claim 29 which also comprises two electrical leads, one connected to each electrode, and wherein the enclosure (a) encloses and is spaced apart from the whole of the PTC element; (b) is electrically insualted from the PTC element, the electrodes and the leads; and (c) is in the shape of a tube with closed ends, the axis of the tube and the axis of the PTC element being substantially the same, and the closed ends comprising exit ports through which the leads pass.
Claim 36
Dependent Claim
37 words
A device according to claim 30 wherein the internal surfaces of the enclosure around the exit ports are composed of an insulating material which passes the carbon burn-off test at a test voltage of 600 volts DC.
Claim 37
Dependent Claim
180 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; (3) two electrical leads, one connected to each electrode, which are connectable to a source of electrical power to cause current to pass through the PTC element; and (4) an enclosure which (a) encloses, is spaced apart from and is insulated from the electrical leads, the electrodes and the whole of the PTC element; (b) is substantially impervious to carbon dust; and (c) comprises two exit ports through each of which passes one of the electrical leads; at least one of said electrical leads being electrically insulated over at least a substantial proportion of its length from the exit port through which it passes towards the electrode to which it is connected, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 38
Dependent Claim
180 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; (3) two electrical leads, one connected to each electrode, which are connectable to a source of electrical power to cause current to pass through the PTC element; and (4) an enclosure which (a) encloses, is spaced apart from and is insulated from the electrical leads, the electrodes and the whole of the PTC element; (b) is substantially impervious to carbon dust; and (c) comprises two exit ports through each of which passes one of the electrical leads; at least one of said electrical leads being electrically insulated over at least a substantial proportion of its length from the exit port through which it passes towards the electrode to which it is connected, whereby the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped are minimized.
Claim 39
Dependent Claim
39 words
A device according to claim 32 wherein at least one of the electrical leads is insulated over substantially the whole of its length between the exit port through which it passes and the electrode to which it is connected.
Claim 40
Dependent Claim
21 words
A device according to claim 33 wherein each of the electrical leads is insulated over substantially the whole of its length.
Claim 41
Dependent Claim
172 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 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 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 42
Dependent Claim
172 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 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 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.
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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) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |