High output discharge lamp with vapor pressure control means

Claim 1

A LOW-PRESSURE ELECTRIC DISCHARGE LAMP ADAPTED FOR OPERATION AT A PREDETERMINED POWER LOADING COMPRISING, AN ELONGATED VITREOUS ENVELOPE CONTAINING AN IONIZABLE GASEOUS MEDIUM AND A PREDETERMINED QUANTITY OF A VAPORIZABLE METAL IN EXCESS OF THAT REQUIRED FOR OPTIMUM EFFICIENCY AT SAID PREDETERMINED POWER LOADING, A PAIR OF SPACED ELECTRODES SEALED WITHIN SAID ENVELOPE, AND MEANS FOR REGULATING THE METAL VAPOR PRESSURE WITHIN SAID LAMP DURING THE OPERATION THEREOF COMPRISING A TUBULATION THAT IS INTEGRAL WITH AND EXTENDS FROM A SIDE WALL OF SAID ENVELOPE AND DEFINES A CHAMBER WHICH COMMUNICATES WITH THE INTERIOR OF SAID ENVELOPE AND PROVIDES A COOL REGION AT WHICH EXCESS METAL VAPOR CONDENSES, A SIDE WALL PORTION OF SAID ENVELOPE ADJACENT SAID TUBULATION EXTENDING INWARDLY FROM THE ENVELOPE PERIPHERY AND BEING DISPOSED BETWEEN THE DISCHARGE AND SAID TUBULATION AND THUS PROVIDING A SHIELD THAT REDUCES THE AMOUNT OF HEAT TRANSFERRED BY RADIATION INTO THE VAPOR-PRESSURE REGULATING CHAMBER.