GB891922A - Electromagnetic relays - Google Patents

Abstract

891,922. Electrically released switches. GENERAL RAILWAY SIGNAL CO. Nov. 18, 1960 [Dec. 9, 1959], No. 39702/60. Class 38 (5). A relay which is retained set, after electromagnetic actuation, by permanent magnetism and is released by a demagnetizing current, has the permanent magnet mounted on the end of the relay core and a flux return member which is secured to the other end of the core and extends to the first-mentioned end where it is bent inward towards the permanent magnet. As shown in Figs. 2 and 3, two such relays on a common plug-in base 11 have stacks of contact spring sets 41, 42, 43 operated by pushers 46 acted upon by respective armatures 23. The latter are pivoted at 25 and are biased by springs 33, 38. The electromagnets each comprise a coil 20, a rectangular core 16, a permanent magnet 21, a magnetic polepiece 22 and a U-shaped flux return member 17 having its ends 17A bent towards the polepiece 22 adjacent the armature 23. In an alternative arrangement, Fig. 7, the core 16 is circular in section and has an area 16A of reduced crosssection which may saturate to limit the demagnetizing flux. The armature may comprise a magnetic plate, of sufficient area to cover the pole faces of members 22, 17A, mounted on a non-magnetic pivoted support (Fig. 6, not shown). The armature may carry an adjustable screw 28 to set the residual gap or be plated with a non-magnetic material such as chromium.