Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With bimetallic element
Patent
1976-06-04
1977-08-02
Hickey, Robert J.
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With bimetallic element
335 31, 335145, 337344, H01H 3754, H01H 3766
Patent
active
040399931
ABSTRACT:
The disclosure relates to an over-temperature limit switch for automatically making or breaking an electrical circuit at a predetermined temperature. The actuating force for the switch is provided by a temperature dependent bimetallic spring and the latching function of the switch is provided by a pair of magnets. One of the magnets, a permanent magnet, is secured to the bimetallic spring and the other magnet, a non-permanent or "soft" magnet, is disposed in the base of the switch opposite the permanent magnet. The non-permanent magnet has a transition temperature associated therewith indicating the temperature above which the permeability of the magnet diminishes to such an extent that it can no longer carry sufficient magnetic lines of flux from the permanent magnet to hold it against the force of the bimetallic spring. The bimetallic spring is adapted to exert a bias force tending to open the switch at a temperature below the transition temperature of the non-permanent magnet. In this manner, the switch "snaps" open when the transition temperature of the magnet is reached. When the temperature of the switch cools below the transition temperature of the switch, the permeability of the non-permanent magnet is restored and the switch "snaps" shut as the bimetallic spring returns the permanent magnet to within close proximity of the non-permanent magnet. Alternative embodiments are also disclosed for varying the operating temperatures of the switch.
REFERENCES:
patent: 3011037 (1961-11-01), Welsh
patent: 3728658 (1973-04-01), Kasahara
Hickey Robert J.
Mechanical Products
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