Control means for controlling the position of an electrode in a carbon arc lamp

In a carbon arc lamp having a transparent enclosure with a lower electrode therein and a cover plate over the enclosure through which an electrode control rod held in a holder slidably extends for holding an upper electrode in the enclosure, and an electric circuit for supplying arc discharge current across said electrodes, an improved control means for automatically adjusting the vertical position of said electrode control rod for automatically starting the arc if it has been extinguished and for compensating for consumption of the upper electrode during normal use, said control means comprising:

• a pulley on said lamp above the level of said control rod, a line over said pulley and hanging downwardly therefrom, a magnetic core on one end of said line, a solenoid coil connected in the electric circuit and within which said core is movable for pulling the core downwardly into the solenoid coil as discharge current increases, a rod clutch on the other end of said line and above said cover plate in which said control rod is normally gripped and for releasing said control rod for vertical downward movement through said rod clutch when the rod clutch descends sufficiently to contact the cover plate.