Ceramic envelope device, lamp with such a device, and method of manufacture of such devices
AssigneeOsram Sylvania Inc.
InventorsGeorge C. Wei, Stefan Juengst, Rodrique G. Thibodeau, John Selverian
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Abstract
This invention involves a new type of feedthrough-plug member for metal halide HID lamp using PCA envelopes. The construction of the lamp housing consists of a PCA envelope and specially designed axially graded alumina-metal cermet multi-layers to eliminate cracking in cermet or PCA due to thermal stresses arising from thermal expansion mismatch. The fills are metal halides such as Na--Sc--I, rare earth halides, Hg, Sn, and inert gases. The PCA vessel and directly sealed cermet-feedthrough assemblies allow the metal halide lamps to operate at high wall temperatures with better lumen output, color temperature, and CRI.
Claims24
A ceramic envelope device for a high pressure discharge lamp comprising:
- a translucent ceramic tube having a first end and a second end, the tube confining a discharge volume and defining a longitudinal axis
- a first at least essentially electrically non-conducting cermet end plug, said first plug closing said first end of the ceramic tube
- a second at least essentially electrically non-conducting cermet end plug, said second plug closing said second end of the ceramic tube
- at least said second plug having a multipart structure with at least three parts
- a first and second metal feedthrough passing through the first and second plug respectively, each feedthrough having a inner and outer end, respectively, said feedthroughs being made from one of the group of the metals tungsten, molybdenum and rhenium and alloys from at least two of these metals
- two electrodes located at the inner end of the first and second feedthrough respectively
- the coefficient of thermal expansion of at least one part of the multipart plug being between those of the arc tube and the feedthrough
- wherein said multipart plug comprises at least four axially aligned parts with different coefficients of thermal expansion, including a first and a last part, the first part being innermost with respect to the discharge volume and the last part being outermost with respect to the discharge volume
- the multipart plug is directly sintered both to the arc tube and the feedthrough in that manner that the first part of the multipart plug is directly sintered to the arc tube and the last part of the multipart plug is directly sintered to the related feedthrough.
Dependencies are inferred from the claim text.