GB356803A - Improvements in alternating current relays - Google Patents

Abstract

356,803. Electromagnetic interrupters and light current relays. STANDARD TELEPHONES & CABLES, Ltd., SANDEMAN, E. K., SKILLMAN, T. S., and AUSTIN, B. B., Columbia House, Aldwych, London. June 12, 1930, No. 18030. [Class 38 (v).] An A.C. relay has a plurality of mechanically coupled tuned reeds which co-operate with one or more loosely-mounted contact devices so that the relay is adapted to be resonant at a plurality of frequencies so as to be operatively responsive to frequencies over a relatively wide range. As shown in Fig. 1, the balanced armature 13 is connected by a link 14 to a tuned reed 15 held between adjustable plates 17, 18. Above the reed 15 in a similar adjustable mounting 19 separated by an insulating sheet 20 is a second reed 16 differing in frequency from the reed 15 and extending between the free ends of the two reeds is a loosely-mounted contact device consisting of a weight 24 with hooked end-pieces 25, 28 which normally rest upon hooked projections 26, 29 secured to the ends of the reeds. Thus when the controlling electromagnet is energized by current of a frequency falling within the combined range of the two reeds the vibration of the loosely-mounted contact device causes an intermittent interruption of the controlled circuit. The Specification describes the electrical equivalent of such a relay as comprising two lined circuits of different frequencies, corresponding to the two tuned reeds with resistances corresponding to any damping effects which may be present in the reeds, the mass and damping effect of the weight 24 corresponding to an additional inductance and resistance in the first tuned circuit corresponding to the reed 15 which is supplied by an E.M.F. corresponding to the mechanical driving force of the armature. A modified form of relay shown in Fig. 5 has the two reeds 34, 35 connected at their free ends by a steel spring 36 and operating a loose-contact device 37, 38. In a further modification, Fig. 6, electrically equivalent to a bandpass filter four reeds 39 .. 42 each operating a loose-contact device 44, are employed, the reeds being driven from the armature through a linkage mechanism 43.