GB648656A - Improvements in electromagnetic relays - Google Patents

Abstract

648,656. Electromagnetic relays. WESTERN ELECTRIC CO., Inc. Oct. 1, 1948, No. 25606. Convention date, Oct. 1, 1947. [Class 38(v)] The components of a polarized relay including the operating coil 17, the polarizing magnet 25 and the sealed tube 1 containing armature and contacts are assembled in an outer vessel 18 of magnetic material, the vessel is then filled with a plastic filling such as wax which is inserted when in a fluid state and then caused to harden thereby securely holding the components in place. The vessel 18 provides magnetic shielding. In the form shown the armature 10 is mounted on a spring 11 and carries a contact 15, Fig. 4, made out of a bent wire so as to form a wick up which mercury is pulled by capillary action from a pool 14 this action being aided by pieces 12, 13 of mercury wettable material 12, 13. The spring 11 tends to hold the armature against back contacts 4, 5 but when the coil 17 is energized the armature is attracted to the front contacts 8, 9 which are wires of magnetic material magnetized by the permanent magnet 25 which is soldered to the wire 9 and separated from the wire 8 by insulation 16, Fig. 2. The strength of the magnet 25 may be such that when the coil 17 is de-energized the armature returns to its original position. Alternatively it may be such that the armature is retained and only later released by sending a current through thecoil in the opposite direction. In a modification, Fig. 10 (not shown), the armature' moves between two fixed contacts each polarized by a separate permanent magnet. The permanent magnet 25 may be magnetized after assembly by imposing on it a strong magnetic field which saturates the steel cover 18 and penetrates to the magnet 25, Figs. 6, 7 (not shown). It may then be subjected to a gradually diminishing A.C. till it is demagnetized to the amountrequired, Figs. 8, 9 (not shown).