GB791305A - Improvements in or relating to electronic time delay relays - Google Patents

Abstract

791,305. Relay devices. ELESTA, Ltd. Jan. 5, 1956 [June 20, 1955], No. 446/56. Class 40 (3). In a time-delay relay device in which a relay 9 is operated to close contacts 11 in an external utilization circuit 12 by the firing of a cold cathode tube 5 the discharge of the latter is initiated by a trigger electrode 8, the firing voltage of which is derived from the voltage across a condenser 13 and the rate at which the latter charges when switch 4 is closed is determined by the leakage current produced by the ionizing effect of a radioactive source 17 on the gap between two electrodes 15, 16 connected in series with the charging circuit of the condenser. The source 17 consists, preferably, of a preparation containing plutonium, radium or actinium and the extent of the ionization and consequently the time required for the voltage across condenser 13 to reach the firing potential of the trigger electrode 8 may be varied by varying the distance between the source and the plates 15, 16 by rotation of arm 18 (carrying the source 17) about spindle 19 or, as described with reference to Fig. 2 (not shown), by employing a fixed radioactive source between which and the plates 15, 16, an adjustable screen is positioned. In this manner the delay between closing switch 4 and the operation of relay 9 may be varied from a few seconds to over twenty-four hours. When the relay operates the condenser is discharged through a low resistance 14 by means of a further set of contacts 10.