Electric lamp and discharge devices – With gas or vapor – Having particular electrode structure
Reexamination Certificate
1998-11-19
2001-10-02
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having particular electrode structure
C313S484000, C313S632000, C313S492000, C313S110000, C313S113000, C313S030000, C313S035000, C315S169100, C315S246000
Reexamination Certificate
active
06297591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to arc lamps and specifically to devices and methods used to cool the anode electrode of arc lamps.
2. Description of the Prior Art
Short arc lamps provide intense point sources of light that allow light collection in reflectors for applications in medical endoscopes, instrumentation and projection. Also, short arc lamps are used in industrial endoscopes, for example in the inspection of jet engine interiors.
A typical short arc lamp comprises an anode and a cathode positioned along the longitudinal axis of a cylindrical, sealed concave chamber that contains a gas pressurized to several atmospheres. U.S. Pat. 4,633,128, issued Dec. 30, 1986, to Roy D. Roberts, the present inventor, and Robert L. Miner, describes such a short arc lamp in which a copper sleeve member is attached to the reflecting wall to conduct heat from the reflecting wall through to the exterior wall and eventually to circulating ambient air.
The lamp illustrated in
FIG. 2
of Roberts, et al., can be operated at one kilowatt. At higher power levels, the heat generated by an electric arc between cathode
42
and anode
44
encounters thermal resistance to the ambient which may result in overheating and potential failure. Specifically, applying too much power to the lamp creates thermal gradients in the ceramic material that may cause cracks in the body and possibly an explosion of a weakened lamp.
Conventional short arc lamps have solid anodes that tend to get very hot at the center of the face supporting the arc. A portion of the electrode metal usually vaporizes and then deposits on the reflector. These deposits blacken the reflector and cause increased heat absorption. As a result, lamp life is seriously curtailed by such deposits.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide an arc lamp with electrodes that operate at cooler temperatures and therefore improve lamp life.
Briefly, an arc lamp embodiment of the present invention comprises a hollowed-anode electrode with an arc-face having a central hole in it connected to an internal chimney. An opposing cathode electrode is set facing the hollowed anode electrode and provides for a short electric arc all around the central hole in the arc-face of the hollowed anode electrode. The anode and cathode electrodes are disposed in an inert gas, such as xenon. The internal gas is subject to an “arc wind” that can transport metal deposits downstream of the short electric arc. Critically, such arc wind is made to flow from the short electric arc down the chimney. Such operation provides for an improvement in arc lamp life because the reflector blackens far less rapidly.
An advantage of the present invention is that a lamp is provided with a much longer life than conventional designs.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the drawing figure.
REFERENCES:
patent: 3723782 (1973-03-01), Thomsen
patent: 3723783 (1973-03-01), Beese et al.
patent: 4633128 (1986-12-01), Roberts et al.
patent: 4785216 (1988-11-01), Roberts et al.
patent: 5399931 (1995-03-01), Roberts
patent: 5633556 (1997-05-01), Fujina et al.
Haynes Mack
ILC Technology, Inc.
Law Offices of Thomas E. Schatzel A Prof. Corp.
Patel Nimeshkumar D.
Schatzel Thomas E.
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