Thermal cut-off device with an activating spring that is held in a prestressed condition by a thermally fusible pellet
US4259656A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 11, 1979 |
| Grant date | Mar 31, 1981 |
| Priority date | — |
| Expiry date | May 11, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01H37/765
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A thermal cut-off device is disclosed in which a first axial lead extends through an insulating member at one end of the device and a second axial lead contacts and extends through a conductive cylindrical housing at the other end of the device. A domed electrical contact cup is used in one embodiment to make electrical connection between the insulated lead and the outer metallic housing, and this electrical connection is maintained by a coiled helical spring. One end of the coiled spring is larger in diameter than the other end. The large diameter end is in engagement with the end of the conductive housing through which the second axial lead projects, while the smaller end of the conductive spring is in engagement with the insulated first axial lead, either directly or through the domed contact cup. The spring is held in a prestressed condition by a solid thermally fusible or meltable pellet which surrounds the spring, and which holds it in its stressed condition until the predetermined melting, or fusible, temperature of the pellet is reached at which time the stress is relieved in the spring and it contracts away from the insulated first axial lead, so as to break electrical con…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.