GB517971A - Improvements in and relating to frequency controlled relays - Google Patents

Abstract

517,971. Electromagnetic relays. PRICE, D. R., WOOLNOUGH, G. L., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. July 12, 1938, Nos. 20701/38, 32451/38, 36828/38 and 14777/39. [Class 38 (v)] A resonance r e l a y operable by alternating current of a particula: frequency passing through a coil 13 comprises a tuned reed : clamped at its thickenec R.H. end, movable be. tween the poles 14 of a permanent magnet and adapted when it vibrate; to lift a relatively mas. sive member 7 which cannot follow its rapid vibrations, so that con. tact between the reed and the member 7 is broken during an appreciable part of the time the reed vibrates The member 7 may be s contact and may engage a contact 6 on the reed or the arrangement may be such that the member 7 is displaced by the reed into engagement with a fixed contact from which it is normally separated. A single coil 13 may control several reeds tuned to different frequencies. The current to the coil 13 may be supplied through a transformer device, Fig. 5 (not shown), adapted to damp down abnormal surges, the transformer having a third winding in series with a resistance with negative voltage characteristic. Varous systems in which the relays are used are described. In Fig. 9 two such relays 23, 25 control a hot wire relay 27. Opening of relay contacts 23 removes a short circuit from hot wire 27 and operates its relay. Later opening of contacts 25 breaks the hot wire circuit. In another modification (Figs. 10, 11, not shown), two relays of the invention control the heating coils of bimetallic strips forming actuating and trippng members of a switch. In other modifications, the relays of the invention move a bimetallic snap switch first one way and then the other, or control an induction relay. Specification 419,917 is refered to.