GB900260A - Improvements in or relating to instrument type moving coil electric relays - Google Patents

Abstract

900,260. Light current relays. SANGAMO WESTON Ltd. May 25, 1960 [June 4, 1959], No. 18515/60. Class 38 (5). [Also in Group XXXVI] A moving coil relay having an additional winding on the coil assembly arranged to be energized when the contacts close so as to increase the contact pressure is provided with two sets of contacts, one set being magnetic. As shown, the coil 10 which may be in series with a photo-electric cell or thermocouple 13 carries a pointer arm 14 comprising two rigid parts 14a, 14b and a helical spring 14c. A magnetic contact 17 mounted on the part 14b co-operates with a magnetized contact 18 and a second moving contact 21 of flexible material, such as platinum-iridium alloy, co-operates with a fixed contact 22. As the coil 10 moves the pointer clockwise a position is reached in which the contact 17 is attracted to snap against the contact 18 and complete the circuit including the load 28, source 26 and the additional winding on the coil assembly, thus urging contacts 17, 21 against contacts 18, 22 and stressing the respective springs. Contacts 21, 22 preferably close after contacts 17, 18, but they may close at the same time or just before the magnetic contacts. Since there will be wiping action between contacts 21, 22 the contact 21 may be given a sharp edge and contact 22 may be made of a harder material such as a rhodium alloy. When the switch 27 is opened so that the additional winding is deenergized the potential energy of the flexed elements 14c and 21 imparts a counter-clockwise movement to the moving coil assembly with sufficient force to separate contacts 17, 18. In an alternative arrangement (Fig. 6, not shown), the arm 14 includes no flexible portion and the magnetized contact 18 is resiliently mounted.