Patent GB-515216-A (GB)
Title: Improvements in and relating to electric protective arrangements more particularly for luminious electric discharge tube systems
IPC: H02H3/12
Filed: 1938-05-24
Abstract: 515,216. Protective cut-out arrangements; electromagnetic switches. CLAUDE-GENERAL NEON LIGHTS, Ltd., and HIGGINS, C. May 24, 1938, No. 15486. [Class 38 (v)] Relay means for protection of a circuit comprise a first relay means responsive to current in said circuit and adapted to open it in the event of a current-decrease therein due to a fault, a second relay means responsive to voltage across the circuit, and interlock means between the first and second relay such that in the event of a fault causing release of the first relay, further operation of the first relay can only be effected after a manual resetting at least of the interlock means. In Fig. 1, the winding 11 and mercury switch 4 are in series with the primary of a transformer supplying a luminous discharge tube (not shown), whereas the winding 12 is across the supply, a manually-operated switch (not shown) being also provided for de-energizing both windings. The mercury switch 4 is supported on the armature 5 of the winding 11, which armature also carries an interlock arm 7 co-operating with a cam 8 on the armature 9 of the winding 12. In the de-energized condition of 12, the cam presents a surface 14 which is engaged by the arm 7 so that opening of the switch 4 by spring 6 is prevented. When, however, 12 is energized by closure of the manual switch, a dwell 13 comes opposite the arm 7 so that, if the winding 11 carries a reduced current due to a fault, for example, an earth fault to one electrode conductor of the tube, 5 retracts and the arm 7 is latched in the dwell 13 and the switch 4 is opened. In order to reclose it, the manual switch is opened and the parts 7, 8 reset manually so that arm 7 re-engages the surface 14. When the manual switch is reclosed, both windings are energized and armature 9 again attracted to bring the dwell 13 opposite the arm 7. When the manual switch is opened, both windings are de-energized but the arm 7 engages the. cam surface 4 and 4 remains closed. In Fig 2, spring-controlled movable contacts 5, 9 are independently movable on a spindle 18 connected to one side of the supply circuit, and co-operate with fixed contacts 14, 15 to provide alternate circuits for the series winding 11. In the de-energized condition of the shunt winding 12, a spring 10 moves an interlock arm 8 whereby an indent 19 thereon engages contact 9 to cause contacts 15, 9 to close. When the manual switch 3 is closed, the circuit to the primary of transformer 2 is made over contacts 15, 9, whereby 11 is energized to attract its armature-contact 5 and move an interlock bar 7 from a slot 13 in arm 8. Since the winding 12 is also energized, the arm 8 moves to a position in which it opens 15, 9. On fault, armature 5 is released and the circuit opened, the bar 7 engaging the top of a lip in the dwell 13 of bar 8 to prevent it from releasing contacts 15, 9 which are reset manually, after 3 is opened, by moving bar 7 manually to free the bar 8. In a further modification, Fig. 3 (not shown), the mercury switch is carried on a balanced armature, the ends of which are operated upon by the windings 11, 12 in such a manner that when both are energized, 11 holds the armature and switch closed. When 11 is deenergized, 12 moves the armature and opens the mercury switch, the armature being latched by means which must be released before the armature can be moved back manually against the winding 11.