Xenon-metal halide lamp particularly suited for automotive applications having an improved electrode structure

An automotive headlamp comprising:

• (A) reflector having a predetermined focal length and focal point and provisions for mounting an inner envelope and means to connect the inner envelope to a suitable power source of an automobile,
• (B) a lens member mated to a front section of said reflector;
• and
• (C) said inner envelope being predeterminedly positioned within said reflector so as to be approximately disposed near said focal point of said reflector, said inner envelope containing a fill of xenon at a relatively high pressure along with mercury and metal halide ingredients, said inner envelope having a pair of opposite neck portions each with a coaxial central opening having a reduced section, said inner envelope having a pair of electrodes respectively positioned at said opposite neck portions and separated from each other by a predetermined distance, said electrodes comprising of a shank portion and a tip portion having a diameter which is substantially larger than that of the shank portion, said shank portion having a coil wrapped around its portion which is in contact with the inner surface of said reduced sections of said coaxial openings of said respective neck portion, said inner envelope being connected to said means mated to said sections so that said excitation source is capable of being applied across said electrodes, whereby upon such application;
• (1) a discharge is established which begins to heat the electrodes to a state of their thermionic emission while at the same time the xenon is excited to produce light, and (2) the mercury and metal halide are vaporized to produce light.