US4400614A
Expired / Lapsed
US
⏱️ 0.0 years remaining
PTC Devices and their preparation
Assignee: Raychem Corp
•
Filing: 1981-11-18
•
Granted: 1983-08-23
•
Expires: 2001-11-18
Abstract
Abstract The flex life of devices comprising a relatively inflexible PTC conductive polymer element is improved by surrounding the PTC element with a layer of a relatively flexible polymeric composition which is melt-fused thereto. Particularly useful devices are self-limiting strip heaters in which the polymeric component of the PTC element comprises a mixture of two crystalline polymers having substantially different melting points, the higher melting polymer having a melting point of at least 160° C., preferably at least 200° C., for example a mixture of polyvinylidene fluoride and a copolymer of ethylene and tetrafluoroethylene. Such devices can be made by melt-extruding a layer of the relatively flexible polymeric composition around the PTC element, and heating to cause melt-fusion of the polymers at the interface of the layer and the PTC element.
Inventors
- 👤 Umesh K. Sopory
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:24
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; B; B29; B29C; B29C48/00; B29C48/03; B29C48/07; B29C48/08; B29C48/12; B29C48/15; B29C48/156; H05; H05B; H05B3/00; H05B3/10; H05B3/12; H05B3/14; H05B3/146; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49083
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
140 words
A flexible electrical device which comprises (a) an elongate flexible PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior and which comprises (i) a polymer component which comprises a mixture of a first crystalline polymer having a first melting point T 1 and a second melting point T 2 which is at least (T 1 +25)° C.; and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises a conductive filler; (b) two elongate metal electrodes which are electrically connected to the PTC element so that, when the electrodes are connected to a source of electrical power, current flows through said PTC element; and (c) surrounding said PTC element and melt-fused thereto, a layer of a second polymeric composition having substantially greater flexibility at 23° C. than said PTC composition.
Claim 2
Dependent Claim
140 words
A flexible electrical device which comprises (a) an elongate flexible PTC element composed of a PTC conductive polymer composition which exhibits PTC behavior and which comprises (i) a polymer component which comprises a mixture of a first crystalline polymer having a first melting point T 1 and a second melting point T 2 which is at least (T 1 +25)° C.; and (ii) a particulate filler component which has been dispersed in said polymer component and which comprises a conductive filler; (b) two elongate metal electrodes which are electrically connected to the PTC element so that, when the electrodes are connected to a source of electrical power, current flows through said PTC element; and (c) surrounding said PTC element and melt-fused thereto, a layer of a second polymeric composition having substantially greater flexibility at 23° C. than said PTC composition.
Claim 3
Dependent Claim
20 words
A device according to claim 1 wherein said electrodes are surrounded by and in physical contact with said PTC element.
Claim 4
Dependent Claim
16 words
A device according to claim 1 wherein T 2 is at least (T 1 +70)° C.
Claim 5
Dependent Claim
25 words
A device according to claim 1 wherein the second polymeric composition has a melting point of (T 1 -10)° C. to (T 1 +50)° C.
Claim 6
Dependent Claim
16 words
A device according to claim 1 wherein the second polymeric composition comprises said first crystalline polymer.
Claim 7
Dependent Claim
18 words
A device according to claim 5 wherein the second polymeric composition consists essentially of said first crystalline polymer.
Claim 8
Dependent Claim
20 words
A device according to claim 1 wherein said PTC composition has a resistivity of 10 2 to 10 5 ohm.cm.
Claim 9
Dependent Claim
14 words
A device according to claim 1 wherein T 2 is at least 160° C.
Claim 10
Dependent Claim
14 words
A device according to claim 8 wherein T 2 is at least 200° C.
Claim 11
Dependent Claim
14 words
A device according to claim 9 wherein T 1 is 100° to 175° C.
Claim 12
Dependent Claim
20 words
A device according to claim 1 wherein each of the crystalline polymers in the PTC composition is a fluorinated polymer.
Claim 13
Dependent Claim
23 words
A device according to claim 1 wherein the first crystalline polymer is polyvinylidene fluoride and the second crystalline polymer is an ethylene/tetrafluoroethylene copolymer.
Claim 14
Dependent Claim
28 words
A device according to claim 1 wherein said second polymeric composition has substantially greater flexibility than said PTC composition at all temperatures between 0° C. and 100° C.
Claim 15
Dependent Claim
32 words
A device according to claim 1 wherein said second polymeric composition has substantially greater flexibility than said PTC composition at all temperatures between 0° C. and the switching temperature of the composition.
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) | 1986-08-22 | 1987-02-21 | 1987-08-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-08-22 | 1991-02-21 | 1991-08-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-08-22 | 1995-02-21 | 1995-08-23 | $7700.00 | Window Closed / Lapsed |