GB519150A - Electric relays or switches with time lag devices - Google Patents

Abstract

519,150. Mercury switches. MESTITZ, E. (Drahonovsky, P.). Oct. 14, 1938, No. 29865. [Class 38 (v)] In a short-time switching arrangement suitable for staircase lighting &c. depression of a push button 23 completes the circuit to a heating coil 9 in a gas-chamber 1, the consequent expansion of gas causing the movement of mercury in an M-shaped tube connecting the chamber 1 to a chamber 2 so that contacts 12, 13 in the load circuit are bridged at 5. In the form shown in Fig. 1 the heating circuit includes the coil 20 of an electromagnetic relay which by attracting a core 18 short-circuits the push button 23 and maintains the heating circuit closed after the push button is released. After a certain time the mercury descends so as to break at 4 the circuit to the heater 9 and coil 20. The gas in 1 now cools, the mercury moves back but the heating circuit is not again completed since the maintaining circuit is now broken. Eventually the mercury reaches its original level and the circuit to the load 22 is broken at 5. In a modification, Fig. 2, the electromagnetic relay 20 is replaced by a thermal relav mounted in the vessel 2. Depression of a button 23 completes the circuit to the heater 9. The consequent movement of mercury forces the gas in the vessel 2 through a hole 29 and forces mercury in a vessel 28 to move up a narrow funnel 25 to bridge contacts 26, 27 in a maintaining circuit, Further pressure causes bubbles of gas to pass by the bubble of mercury held in the funnel 25. When mercury in the bulb 1 has sunk so as to break the heater circuit at 4 the gas in 1 contracts, and the mercury at 25 falls so as to break the maintaining circuit. Subsequent reunion of the mercury at 4 cannot now remake the heater circuit, so that cooling continues till the load circuit is broken at 5. The amount of mercury in the vessels 1 and 2 may be adjusted by pouring some of it into a side tube 11.