Patent US2749129A successfully refreshed from Google Patents.
Patent EP0063440A2 successfully refreshed from Google Patents.
EP0063440A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Radiation cross-linking of PTC conductive polymers
Assignee: Raychem Corp
•
Filing: 1982-04-02
•
Granted: —
•
Expires: 2002-04-02
Abstract
Abstract The higher the voltage applied to an electrical device comprising a PTC conductive polymer, the more likely it is that intermittent application of the voltage will cause the device to fail. According to the invention, the likelihood of such failure is substantially reduced by irradiating the PTC conductive polymer (1) so that it is very highly cross-linked, for example to a dosage of at least 50 Mrads, preferably at least 80 Mrads, especially at least 120 Mrads. In this way, for example, it is possible to make a circuit protection device which will continue to provide effective protection even after repeated exposure to a voltage of 200 volts.
Inventors
- 👤 Stephen M. Jacobs
- 👤 Mary Sandra Mctavish
- 👤 James Michael Taylor
- 👤 Frank Anthony Doljack
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 06:25
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; H01B; H01B1/00; H01B1/20; H01B1/24; H05; H05B; H05B3/00; H05B3/10; H05B3/12
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
113 words
A process for the preparation of an electrical device comprising (a) a cross-linked PTC conductive polymer element and (b) two electrodes which can be connected to a power source to cause current to flow through the PTC element, which process comprises cross-linking the PTC element by radiation, characterised in that the PTC element is irradiated to a dosage of at least 50 Mrads, subject to the proviso that if each of the electrodes has a substantially planar configuration, then either (a) the element is irradiated to a dosage of at least 120 Mrads, or (b) the electrodes are metal foil electrodes which are secured to the PTC element after it has been cross-linked.
Claim 2
Dependent Claim
113 words
A process for the preparation of an electrical device comprising (a) a cross-linked PTC conductive polymer element and (b) two electrodes which can be connected to a power source to cause current to flow through the PTC element, which process comprises cross-linking the PTC element by radiation, characterised in that the PTC element is irradiated to a dosage of at least 50 Mrads, subject to the proviso that if each of the electrodes has a substantially planar configuration, then either (a) the element is irradiated to a dosage of at least 120 Mrads, or (b) the electrodes are metal foil electrodes which are secured to the PTC element after it has been cross-linked.
Claim 3
Dependent Claim
35 words
A process according to claim 1, characterised in that each of the electrodes has a columnar shape and the device is irradiated to a dosage of at least 60 Mrads, preferably at least 80 Mrads.
Claim 4
Dependent Claim
105 words
A process according to claim 1 characterised in that (A) the PTC element 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; (B) each of the electrodes is 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; and (C) the device is irradiated to a dosage of at least 60 Mrads, preferably at least 80 Mrads.
Claim 5
Dependent Claim
58 words
A process according to claim 1 characterised in that (A) the PTC element is laminar; (B) the electrodes are displaced from each other so that current flow between them is along one of the large dimensions of the element; and (C) the device is irradiated to a dosage of at least 60 Mrads, preferably at least 80 Mrads.
Claim 6
Dependent Claim
60 words
A process according to claim 1 characterised by the steps of (1) irradiating a laminar PTC conductive polymer element in the absence of electrodes; (2) contacting the cross-linked PTC element from step (1) with metal foil electrodes under conditions of heat and pressure, and (3) cooling the PTC element and the metal foil electrodes while continuing to press them together.
Claim 7
Dependent Claim
25 words
A process according to claim 5 characterised by irradiating the PTC element to a dose of at least 60 Mrads, preferably at least 80 Mrads.
Claim 8
Dependent Claim
30 words
A process according to any one of the preceding claims characterised in that the device is irradiated to a dosage of at least 120 Mrads, preferably at least 160 Mrads.
Claim 9
Dependent Claim
103 words
An electrical device which comprises (a) a radiation cross-linked PTC conductive polymer element and (b) two electrodes which can be connected to a power source to cause current to flow through the PTC element, characterised in that, when the device is subjected to SEM scanning (as hereinbefore defined), the maximum difference in voltage between two points separated by 10 microns is less than 4.2 volts, preferably less than 3 volts, particularly less than 2 volts, especially less than 1 volt, subject to the proviso that if each of the electrodes has a substantially planar configuration, the maximum difference is less than 3 volts.
Claim 10
Dependent Claim
103 words
An electrical device which comprises (a) a radiation cross-linked PTC conductive polymer element and (b) two electrodes which can be connected to a power source to cause current to flow through the PTC element, characterised in that, when the device is subjected to SEM scanning (as hereinbefore defined), the maximum difference in voltage between two points separated by 10 microns is less than 4.2 volts, preferably less than 3 volts, particularly less than 2 volts, especially less than 1 volt, subject to the proviso that if each of the electrodes has a substantially planar configuration, the maximum difference is less than 3 volts.
Claim 11
Dependent Claim
25 words
A device according to claim 8 characterised in that each of the electrodes has columnar shape and the maximum difference is less than 4.0 volts.
Claim 12
Dependent Claim
96 words
A device according to claim 8 characterised in that (A) the PTC element 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: (B) each of the electrodes is 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; and (C) the maximum difference is less than 4.0 volts.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.