GB678502A - Improvements in temperature change responsive means for controlling electric circuits - Google Patents

Abstract

678,502. Sparking preventing in switches. SPEED DEVELOPMENT CO., Ltd., and RUFFLE, W. H. Sept. 26, 1947. [June 27, 1947] No. 17088/47. Class 38 (v). [Also in Groups XXXV and XXXVIII] In a temperature control or warning system a train relay is operated by a millivoltmetertype switch from a thermocouple; in series with the main relay coil and switch are the contacts of a continuously vibrating relay. The effect of the latter is to reduce the number of occasions on which the circuit to the main relay is made by the millivoltmeter-type switch, the contacts of which are conserved. As shown, the thermocouple 16 deflects the movable arm d between the contacts a, c of the meter-type switch 1. With the arm d at a, the relay coil 3 is energized, the contacts 5, 5a and 4, 4a are closed and a holding circuit for relay 2 is completed through 4, 4a which relieves the contacts a, b of the relay current. Upon the arm d reaching contact c, with a change in temperature, the relay coil 17 is energized, contacts 23, 23a close to relieve b, c of the relay currents and contacts 9, 9a open to de-energize coil 3, thereby opening 5, 5a, de-energizing 17 and disconnecting the controlling device H from the D.C. supply. The make and break contacts 32, 32a of the vibrating relay 7<SP>1</SP> are in series with switch 1 and will on occasions close after the millivoltmeter switch contacts so as to reduce the number of times on which the relay circuit 2 is made by the contacts a, b. In a further embodiment, not shown, an A.C., supply is employed.