GB418577A - Improvements in or relating to sensitive electro-magnetic relay arrangements - Google Patents

Abstract

418,577. Electromagnetic switches and light current relays. MOREAU, H., 14, Rue Theodore-de-Banville, Paris. Jan. 23, 1933, No. 2157. Convention date, Jan. 26, 1932. [Class 38 (v).] In a sensitive relay arrangement of the type in which the relay winding is connected to two points of a closed electric circuit comprising a variable resistance and in which a variation in voltage occurring in the closed circuit is due to variation of the voltage at the terminals of the resistance caused by alteration of the latter consequent upon temperature change, said variation of voltage causing operation of the relay when the value of the resistance increases rises above a predetermined amount is characterized by the operation of the relay closing a shunt circuit and consequently augmenting the voltage then existing across the relay. In the arrangement shown the coil 7 of a moving- coil relay is connected between normally equipotential points 5, 6 in the circuit of two transformers the secondaries of which supply a closed circuit including resistances 3, 4 through rectifiers 1, 2. When there is an increase in the value of the resistance 4 due to temperature change a voltage appears between the points 5, 6 and current commences to flow in the relay coil 7 causing operation of the relay when the value of the resistance 4 exceeds a predetermined amount. As soon as the contacts 7<a>, 7b are brought into engagement the circuit of a timelag relay 8 is completed in series with a resistance 9 in one of the transformer primaries. The completion of this circuit increases the degree of unbalance in the secondary circuit so increasing the current in the coil 7 and reinforcing the contact pressure between contacts 7<a>, 7b. The time-lag relay 8, when it has completed its contact closing operation, completes the circuit of the energizing coil 10 of a further relay which on attraction of its armature rocks two mercury tilting switches one of which breaks the circuit of the time-lag relay 8 and the other of which opens a controlled circuit. In a modification (Fig. 2, not shown) the movable coil is connected in the " galvanometer" connection of a Wheatstone bridge arrangement of resistances and on operation due to unbalance in the resistance ratios consequent upon temperature change, as the relay contact is made in either direction the contact pressure is automatically increased by arranging the connecting point of the coil to be automatically transferred by the contact arm to a tapping on the resistances such that an increased current flows in the moving coil. This tapping point may be made adjustable. The Specification as open to inspection under Sect. 91 describes also a bridge-operated relay similar to the modification shown in Fig. 2 in which the reinforcement of the sensitive relay contact was produced by an additional winding under the control of an electromagneticallyoperated switch brought into action by the sensitive relay and also an arrangement of photo-electric cells to replace the current sources in the closed circuit of Fig. 1. This subject-matter does not appear in the Specification as accepted.