Electric lamp and discharge devices – With temperature modifier – Having heat conducting path
Reexamination Certificate
1999-04-28
2001-01-30
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With temperature modifier
Having heat conducting path
C313S570000, C313S643000, C313S634000, C313S113000
Reexamination Certificate
active
06181053
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 Roberts. et al., can be operated at one kilowatt. At higher power levels, the heat generated by an electric arc between the cathode and anode electrodes encounters thermal resistance to the surrounding areas which may result in overheating and potential failure. When too much power is applied to such lamps, thermal gradients within the ceramic lamp body may cause cracks and possibly a dangerous explosion of the lamp.
Conventional short arc lamps have solid anodes that tend to get very hot at the center of the face supporting the arc. If a portion of the electrode metal gets too hot, it vaporizes, and black deposits will form on the reflector. Such deposits reduce the reflector's ability to tend off heat absorption, and a catastrophic thermal runaway can develop.
At power levels of three thousand watts, heat management becomes the most limiting factor. A fine balance must always be struck between long lamp life and useful lamp output and efficiency.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide a three-thousand watt xenon arc lamp.
It is another object of the present invention to provide a xenon arc lamp with improved lamp life.
Briefly, an embodiment of the present invention is an improved arc lamp with a ceramic body, an anode supported by a base, and a cathode suspended by a strut system opposite to the anode, and having an inside volume filled with xenon gas. The improvements include a groove in the ceramic body such that an angled area is presented to a head area of the anode that reduces heat coupling by radiation. A neck in the anode provides for a thermal choking such that a head portion of the anode will elevate in temperature during operation. A cavity is relieved in the base and all around the anode to provide a fixed means for managing the temperature of a head portion of the anode during operation. A xenon gas-fill volume of about seventeen cubic inches is used to improve lamp life for lamps operated at about three-thousand watts. A stem portion of the cathode has a reduced diameter for attachment to the strut system and this provides reduced optical blockage. A base for the anode has a longer length than its diameter for improved heat transfer to an anode heatsink. A braze-ring recess is machined in an inner diameter of the base to help prevent a contamination of the surface of the anode facing the cathode with any braze material during manufacturing. A chamfer is cut in each of three legs in the strut system to reduce the tendency for electricity to arc-over to a reflector that surrounds the anode. A cathode heatsink surrounds a window sleeve supporting a lens and has an angled inside face for reducing lamp-thermal gradients. This improves heat flow compared to more conventional straight-sided inside faces. A waist-area heatsink is clamped-on the ceramic body in the gap on an outside surface between an anode heatsink and a cathode heatsink with enough clearance provided so that inter-heatsink electrical arcing does not occur.
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: 4633128 (1986-12-01), Roberts et al.
patent: 5399931 (1995-03-01), Robets
patent: 5721465 (1998-02-01), Roberts
patent: 5789863 (1998-08-01), Takahashi et al.
patent: 5903088 (1999-05-01), Sugitani et al.
EG&G ILC Technology, Inc.
Law Offices of Thomas E. Schatzel
Patel Ashok
Schatzel Thomas E.
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