Discharge lamp with cathode shields

Claim 1

A LOW PRESSURE ELECTRIC DISCHARGE LAMP COMPRISING A VITREOUS ENVELOPE DEFINING AN ELONGATED DISCHARGE CHANNEL HAVING A PAIR OF FILAMENTARY ACTIVATED CATHODES SUPPORTED ON INLEAD WIRES SEALED INTO OPPOSITE ENDS AND MOUNTED TRANSVERSELY TO THE LONGITUDINAL AXIS OF SAID DISCHARGE CHANNEL, SAID ENVELOPE CONTAINING AN IONIZABLE MEDIUM COMPRISING MERCURY VAPOR AND AN INERT STARTING GAS, SAID CATHODES BEING PROPORTIONED IN RESISTANCE AND THERMAL MASS TO ACHIEVE AN ELECTRON EMISSION SPOT TEMPERATURE IN THE RANGE OF 1050 TO 1200* C. WITH 100% EMISSION OF DISCHARGE CURRENT ON THE CATHODE HALF-CYCLE AND 0 TO 25% COLLECTION OF THE ANODE HALF-CYCLE, AND CONDUCTIVE SHIELDS FASTENED TO SAID INLEADS ENCOMPASSING THE CATHODE GLOW REGION OF SAID CATHODE AND COLLECTING SUBSTANTIALLY THE BALANCE OF DISCHARGE CURRENT, SAID SHIELDS BEING ARRANGED WITH SURFACES EXTENDING SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL AXIS OF THE CHANNEL THEREAT AT A DISTANCE GREATER THAN 3 MM. FROM THE CENTER OF THE FILAMENTS AND WITH THE LEADING EDGE OF THE SHIELDS APPROXIMATELY EVEN WITH A PLANE THROUGH THE FILAMENT TRANSVERSE TO SAID LONGITUDINAL AXIS.