Balanced Polar Mercury Contact Relay

In a previous paper a mercury contact relay is described in which the contact elements are maintained wet with mercury through a capillary path to mercury reservoir below the contacts. The present paper describes a new design making use of this same mercury contact principle, but with a symmetrical polar structure which gives improvement in sensitivity and speed capabilities over the previous neutral structure. 1 VERTICAL RELAY Fig. 1 shows one design of the relay, adapted for general use in a vertical position. It provides a single pole double throw magnetic switch in a sealed glass tube, enclosed along with an operating coil and polarizing magnets in a steel can with a medium octal plug base similar to the previous type relay (275 type). Fig. 2 shows the glass enclosed magnetic switch element. The armature is a tapered reed welded to a tubular stem which is sealed in the glass at the lower end. Mercury, and gas under pressure are introduced through this tube, which is then welded closed. The magnetic working gaps are formed between the armature and fixed pole-pieces which are sealed in J. T. L. Brown and C. E. Pollard, Mercury Contact Relays, Elec. Eng., 66, Nov., 1947. 1