GB407861A - Improvements in or relating to mercury or like electric switches or relays - Google Patents

Abstract

407,861. Mercury and thermal switches and interrupters. TERRELL, H., 17, Lauriston Road, Wimbledon Common, and POOLE, R. R., 6, Devonshire Place, both in London. July 17, 1933, No. 20179. [Class 38 (v).] In a mercury or other conducting liquid switch or interrupter which has the free surface of the mercury &c. in contact with a gas, vapour or liquid in a closed vessel so that when current is passed through a heating coil therein the variation in volume of the gas &c. causes a separation of two or more masses of mercury &c. in corresponding cups or depressions formed in the vessel, the portion of the wall of the containing vessel connecting the cups or depressions wherein the masses of mercury &c. are respectively located extends for a finite distance in a substantially horizontal direction. As shown in Fig. 1 the mercury or other conducting liquid is contained within a U-tube 7 the ends of which communicate with a pair of closed bulbs 3, 4. Normally the mercury completes a circuit between sealed conductors 7, 8 but when the gas in the bulb 3 is heated by passage of current through the resistance coil 9 the mass of mercury separates as shown so that the circuit between the mercury 6 left in the recess 5 in contact with lead 8 and the main mass in the U-tube in contact with the lead 7 is broken. The heating coil 9 may alternatively surround the outside of the bulb 3 or may extend within a depression formed in its upper end. In an alternative form the mass of mercury after breaking contact with that in the recess 6 adjacent the bulb 3 may make a second circuit by engaging mercury in a corresponding recess similarly arranged adjacent to the bulb 4 (Fig. 4, not shown). In a further modification two separate U-tubes separately controlling two separate circuits may be employed. In the further modified form Fig. 6 the mercury connection may be completed to an annular channel formed in the base 18 of the bulb 3, the leads 7, 8 in the mercury circuit passing through the glass pinch 10 supporting the heating resistence 9. If arranged as an interrupter both bulbs may contain heating resistances which are so connected as to be alternately operable.