This invention relates to an electrode for an arc lamp suitable, for example, as a carbon electrode for weather-and light-resistance testing.
The conventional electrode for arc lamps for weather-and light-resistance testing (hereinafter simply referred to as the "weathering test") is expensive and is rapidly consumed. When consumed below a predetermined length, the electrode must be discarded and replaced by a fresh one. In discarding the used electrode, it must be subjected to high temperatures in a combustion treatment which markedly damages the furnace in which such treatment is performed. Hence, it is by no means easy to dispose of the used electrode.
In the case of an ordinary ultraviolet weatherometer, for example, two lower electrodes each having a length of 100 mm are positioned to oppose an upper electrode having a length of 305 mm and are caused to alternately discharge and generate the arc. In the single discharge for 24 hours, the length of the upper electrode is reduced from 305 mm to about 190 mm while that of the lower electrodes is reduced from 100 mm each to 76 mm. At this time all the electrodes must of replaced by fresh electrodes, respectively. In this instance, the used upper electrode having the reduced length of 190 mm may be cut to 100 mm and used as one of the lower electrodes but the rest must be supplied afresh. This is of course very disadvantageous economically. Moreover, the used electrodes having the length of not greater than 100 mm can neither be further used nor burnt at a temperature below 2,000.degree. C. Hence, their disposal has, to date, been another serious problem.
Despite these problems, it has never been conventionally contemplated to use the used electrodes again by joining them together. This is quite understandable in view of the fact that when the electrodes are simply joined together, the spectral composition would naturally become unstable because the voltage used is so high that the discharge occurs at the joint portion.