GB906602A - Improvements in mercury button electric switches - Google Patents

Abstract

906,602. Mercury switches. GENERAL ELECTRIC CO. June 2, 1959 [June 2, 1958], No. 18798/59. Class 38 (5). A mercury button switch comprises a cylindrical metal shell 11 forming one terminal and welded to an annular metal ring 22 carrying an insulating window 21 and a second terminal 20, the whole enclosure being hermetically sealed. A tubular ceramic liner 25 with a partition 26 is fitted rigidly in the shell 11 and has an opening 27 to connect the mercury pools 29, 30, and a cavity 28 formed in one side of the liner and located so that in the " ON " position of the switch the lower cavity edge is in line with the top of the mercury and the centre of the opening 27 and liner 25, and in the " OFF " position the lower edge is below the mercury surface, Fig. 7 (not shown). This arrangement increases the kinetic energy of the pool 29 at the instant of circuit opening or closure, thus reducing arcing, and the use of a mixture of hydrogen and argon gas at 1.7 atmospheres is of further assistance in this respect. A silicone rubber washer 43 prevents leakage of mercury to the metal ring 22 and is screened from the arc by a ring 44 on the liner 25. A small spot of silver paint on one side of the partition 26, Fig. 5 (not shown), provides an anchor point for the adjacent mercury pool, and friction between the mercury and the surrounding enclosures is reduced by roughening the ceramic and metal parts. Specification 462,527 is referred to.