Door alert system and magnetic switch therefor
US3975723A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 14, 1975 |
| Grant date | Aug 17, 1976 |
| Priority date | — |
| Expiry date | May 14, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B21/18
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A circuit for energizing an annunciator or warning device is actuated whenever a door or the like is in any position other than in proximity to preselected locations such as the two ends of intended travel. Proximity detectors arranged in conformity with the limits of intended travel effect electrical switching so as to interrupt the annunciator circuit whenever the door is within acceptable distance of the limits. The proximity detectors can be provided by a dual magnetic arrangement with one magnet associated with travel and the other permanently affixed relative to a reed switch or the like. The fixed magnet maintains the reed switch closed except when its magnetic field is effectively cancelled by the movable magnet.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.