Improvements in or relating to electromagnetic relays

1,021,771. Electromagnetic relays; electrically released switches. AUTOMATIC TELEPHONE & ELECTRIC CO Ltd. Jan. 8, 1963 [Jan. 23, 1962], No. 2408/62. Heading H2B. In a relay retained set by remanent magnetism a plurality of sealed magnetic contact units 5, 51 are mounted between the polepieces 3, 4 of a highly remanent core 2 carrying a winding 1 and a permanent magnet 6 is placed adjacent the units with its magnetic axis parallel to the core. One row of contact units is mounted above the core and another below it. A nickel-silver spring 7 is welded to one terminal of each unit and extends to the other terminal so that all the electrical connections can be made at one end. A ceramic permanent magnet, 6 or 21 (Fig. 2, not shown), is held between the springs 7 and glass envelopes of the units of each row. The terminals of the units are provided with insulating sleeves 11, 12 and the springs 7 are located in slots 10 in a spacer 9 which is interposed between the springs 7 and adjacent terminals. The units are secured to the polepieces by spring clips 13, 14. Covers 16, 161 of nylon or ebonite are screwed to the polepieces, the screws passing through holes 18 in spacer 9 and 19 in clip 3. Projections, such as 15, of the covers 16, 161 co-operate with recesses in the respective permanent magnets to locate them in position. Assuming that both permanent magnets 6, 21 are polarized in the same sense, Fig. 2 (not shown), and the core is polarized in the opposite sense by its remanent magnetism, all the contact sets will be open. When the polarity of the core is reversed by energizing the coil 1, the contacts close, and remain closed due to the remanent magnetism of the core. The polepieces may be made from an insulating ferrite.