GB559507A - Improvements in and relating to starting switches for electric discharge devices - Google Patents

Abstract

559,507. Thermal switches. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. '30, 1942, No. 17018. Convention date, Dec. 4, 1941. [Class 38 (v)] A thermal switch for starting electric discharge devices comprises two thermostats, one quickacting, the other relatively slow-acting, responsive to current flow through the lamps, and controlling contacts which break the starting circuit by differential snap action when current is applied for starting and make again subsequently by slow heating of the thermostat. In one example, Fig. 7, the quick-acting bimetal strip 20 is slotted at the free end, in which slot a member 30 moves with a toggle-like action, having a bearing at its inner end on an extension 34 of the slow-acting bimetal strip 21. A stop 36 carries one contact 17 and the toggle member 30 the other 18. Both strips bend under heating, in the same direction, downwards as here shown, the quick-acting strip 20 overtaking and snapping over the toggle 30 under the heating of the lamp and also on cooling. In the example, Fig. 5, the slow-acting strip 21a bears a contact 18a on the face towards the quick-acting strip 20a, and another 18b on its end. On first heating contact 17a on the strip 20a snaps off the end of strip 21a. On subsequent heating and cooling contact is remade with the end contact or the side contact 18a, depending on the position of strip 21a responsive to over-all temperature.