| 摘要 |
A tri-model thermal switch for use in a preheat-type discharge lamp. The thermal switch includes a glass bulb, first and second electrical leads sealed into and passing through the glass bulb, and a bimetallic element disposed within the bulb and having first and second end portions. The first end portion of the bimetallic element is affixed to the first electrical lead while the second end portion of the bimetallic element is formed to be in contact with the second electrical lead at a first elevated temperature higher than ambient temperature. The bimetallic element is spaced from the second electrical lead at ambient temperature and at a second elevated temperature higher than the first elevated temperature. During lamp operation, the thermal switch produces a double hot spot on the cathode by electrically shorting the cathode lead-in wires. As a result, the electrode temperature is lowered sufficiently to cause an improvement in the lumen maintenance and life of the lamp.
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