Patent GB-440831-A (GB)
Title: Improvements in or relating to electric relays
IPC: H01H50/62
Filed: 1934-09-10
Abstract: 440,831. Electromagnetic switches. ENGLISH ELECTRIC CO., Ltd., 28, Kingsway, London, and CONNON, E. W., 27, Weeping Cross, Stafford. Sept. 10, 1934, No. 25977. [Class 38 (v)] In a sensitive electromagnetic relay in which an auxiliary or holding electromagnet and armature is provided for the purpose of increasing the contact pressure and this auxiliary armature is driven by the main armature to close.the main contacts and also control the auxiliary or holding electromagnet acting on said auxiliary armature to apply reinforcing pressure to the main contacts, a mechanical connection is provided between the armatures which permits the main armature to move back towards the " off " position after it has made its operating stroke, while the auxiliary armature is still held by its auxiliary magnet, in combination with auxiliary contacts acting in response to such relative movement of the two armatures to de-energize the holding magnet and so allow the main contacts to open. As shown in Fig. 2 applied to a relay of the type described in Specification 315,447, [Class 38 (v)], the pivoted main armature 20 carries on a depending piece of insulating material 1 pins 3, 3a which on rotation of the armature engage contact rods 6, 6a projecting downwardly from a freely-pivoted insulating member 2 to which is attached an arch-shaped support 11 bearing the armatures 5, 5a of the auxiliary or holding magnets 7, 7a. Thus when a deflection of the main armature 20 occurs consequent on variation of current in the main energizing coil 15 the main armature after lost-motion engages and drives the auxiliary armature. As the lost motion is taken up contacts 3a or 3 engage contact bars 6a or 6 and on further combined movement of the armatures the main contacts 4, 13 or 4a, 13a are engaged, and complete simultaneously a controlled circuit D or D<1> (Fig. 3, Provisional Specification), and a holding magnet circuit 7 or 7a. The main contacts engaged are thus pressed firmly together by the additional attraction of the auxiliary' armature to its electromagnet, the main armature being however free to return toward its central position on variation of the current in the main energizing coil 15. In doing so the opposite pin 3 or 3a engages with the contact bar 6 or 6a and the holding coil which has been energized is now short-circuited. The auxiliary armature is consequently released and falls away from the magnet so that the parts resume their original positions in readiness for a subsequent operation. The armature 2 is provided with a dashpot 17 and counterweight 16. The device may be alternatively adapted to make contact only in one direction of movement and the auxiliary coil may be rendered ineffective on the return movement of the main armature in any suitable manner. A protective resistance is included in the auxiliary coil circuit to prevent short-circuiting of the mains T when either of the auxiliary electromagnets is short circuited, or alternatively, in modified circuit arrangements also described, a separate resistance in each auxiliary coil circuit may be provided.