Improvements in or relating to electric timing devices

摘要

590,530. Valve relay circuits. BUDD MANUFACTURING CO., E. G. March 13, 1945; No. 6326. Convention date, Jan. 4, 1944. [Class 40 (v)] In an automatically repeating timing device a single relay is operated to connect one or other of two load circuits to A.C. mains, timing means determining the period when current flows through the relay. Upon closing the switches 57, 58 in succession, the thyratron 31 fires, causing retay 20 to operate and load circuit 15 to be completed. During the negative half - cycle when thyratron 31 is extinguished, the relay remains operated due to its shaded pole construction and capacitor 62 is partially charged over diode 36 and resistor 50. The capacitor 62 continues to charge during each negative half cycle until the outer grid becomes sufficiently negative for the thyratron 31 not to refire in a positive half-cycle. The relay 20 releases, completing the load circuit 18 and a discharge circuit for capacitor 62 over resistors 75, the control grid being connected to prevent thyratron 31 refiring immediately. The capacitor 65 is discharged until the thyratron 31 refires when the cycle recommences. The banks of resistors 50, 75 are included in the charge and discharge paths of capacitor 62 to permit the selection of suitable periods of operation.