Patent ID: 7663318

Claim:
A high intensity discharge lamp, comprising: an envelope having a wall defining an enclosed volume; a fill chemistry and a fill gas positioned in the enclosed volume; a first main electrode having an exterior end and an interior end, the first main electrode extended through the wall in a sealed fashion with the interior end positioned in the enclosed volume; a second main electrode having an exterior end and an interior end, the second main electrode extended through the wall in a sealed fashion with the interior end positioned in the enclosed volume; the interior end of the first main electrode being offset from the interior end of the second main electrode; the first main electrode and the second main electrode defining between them in normal lamp operation a region of plasma discharge; at least a first starting electrode having an exterior end and an interior end, the first starting electrode extended through the wall in a sealed fashion with the interior end positioned in the enclosed volume; a second starting electrode having an exterior end and an interior end, and extended through the wall in a sealed fashion with the interior end positioned in the enclosed volume; the interior end of the first starting electrode being offset from the interior end of a second starting electrode; and aligned such that a line from the interior end of the first starting electrode to the interior end of the second starting electrode crosses through or adjacent to the region of plasma discharge formed between the interior end of the first main electrode and the interior end of the second main electrode during normal lamp operation; the first starting electrode including a thermo-mechanical element intermediate the wall and the interior end of the first starting electrode such that when the thermo-mechanical element is in a cool state the interior end of the first starting electrode is in a first position, and when the thermo-mechanical element is in a heated state the interior end of the first starting electrode is in a second position; such that in a cold state the impedance from the exterior end of the first starting electrode in the first position through the interior end of first starting electrode, to the interior end of the second starting electrode is less than the impedance from the exterior end of the first main electrode through the interior end of first main electrode to the interior end of the second main electrode, and such that in a hot state the impedance from the exterior end of the first starting electrode in the second position, through the interior end of first starting electrode to the interior end of the second starting electrode is greater than the impedance from the exterior end of the first main electrode through the interior end of first main electrode to the interior end of the second main electrode.