BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an arc discharge lamp;
FIG. 2 is a sectional view of an arc discharge vessel employing an embodiment of the invention;
FIG. 3 is a similar view of an alternate embodiment of the invention;
FIG. 4 is a similar view of yet another embodiment of the invention;
FIG. 5 is a similar view of still another embodiment of the invention;
FIG. 6 is a cross-sectional view of one embodiment of a centering structure;
FIG. 7 is an elevational view of an alternate centering structure;
FIG. 8 is an elevational view of still another centering structure;
FIG. 9 is an illustration of one method for inserting a centering structure;
FIG. 10 is a partial cross-sectional view of another method of inserting a centering structure;
FIG. 11 is an elevational view of another centering structure;
FIG. 12 is an elevational view of another embodiment of a centering structure;
FIG. 13 is an elevational view of still another embodiment of a centering structure; and
FIG. 14 is a sectional view of another mounting method.
DETAILED DESCRIPTION OF THE INVENTION
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
Referring now to the drawings with greater particularity, there is shown in FIG. 1 a metal halide arc discharge lamp 10 including a lamp envelope 12 and an arc discharge vessel 14 mounted within the envelope by mounting frame 16. The arc discharge vessel may be positioned within a shroud 20 which can also be supported by the mounting frame 16. Electrical energy is coupled to the arc discharge vessel 14 through a base 22, a lamp stem 24 and electrical leads 26 and 28. The arc discharge vessel contains a chemical fill or dose of materials to provide light when an arc is initiated therein, as is known. The shroud 20 comprises a cylindrical tube of light transmissive, heat resistant material such as quartz.
As noted, in this particular instance, the mounting frame 16 supports both the arc discharge vessel 14 and the shroud 20 within the lamp envelope 12. The mounting frame 16 includes a metal support rod 30 attached to lamp stem 24 by a strap 31. The support rod engages an inward projection 32 in the upper end of the lamp envelope 12. The support rod 30 in its central portion is parallel to a central axis of the arc discharge vessel 14 and shroud 20. The mounting means 16 further includes an upper clip 40 and a lower clip 42, which secure both arc discharge vessel 14 and shroud 20 to support rod 30. The clips 40 and 42 are attached to the support rod 30, preferably by welding.
Positioned in a sealed manner at press-seal ends 43 of the arc discharge vessel 14 are electrode assemblies 44 as shown in FIG. 2. Each electrode assembly 44 comprises an electrode 46 of a suitable material, such as tungsten, and may a have coil 48 attached to one end thereof, internally of the arc discharge vessel; a molybdenum sealing foil 50 attached to the other end of the electrode; and an in-lead 52 attached to the opposite end of the molybdenum sealing foil and extending externally of the arc discharge vessel for making electrical connection thereto. One of the in-leads 52 is connected to electrical lead 26 and one is connected to electrical lead 28.
The mounting assembly described above is exemplary and is not meant to limit the invention, many other mounting assembles being known and employed in arc discharge lamps.
Referring now with more particularity to FIG. 2, there is shown an arc discharge vessel 14 having sealed ends 43 containing electrode assemblies 44. The assemblies 44 comprise an in-lead, for example 52, a molybdenum foil 50 and an electrode 46 which can have a coil 48 affixed to the internal end thereof. Such electrode assemblies are common in quartz or fused silica arc discharge vessels.
Structure 60 for centering the arc is provided within the arc discharge vessel 14 and can comprise a tungsten wire annulus 62, which causes the arc (shown diagrammatically at 63) to remain centered even when the arc lamp 10 is operated horizontally.
As shown in FIG. 3, multiple centering structures 60 can be provided, preferably evenly spaced along the arc axis.
Referring now to FIG. 4 there is shown a “bulgy” ceramic arc discharge vessel 14a having capillary ends 61 containing electrodes 46 that are sealed in the ends 61 by frit, as is known. Positioned within the arc discharge vessel 14a there are three centering structures 60 in the form of annuli 62.
The centering structures 60 are equally applicable in cylindrical ceramic arc discharge vessels 14b, such as shown in FIG. 5.
The centering structures 60 can take many forms as shown in FIGS. 6-8 and 11-14.
Referring particularly to FIG. 6, the centering structure 60 comprises an annulus 62 provided with a number of mounting fingers 70 that contact the inner wall of the arc discharge vessel 14 or 14a.
An alternate embodiment of an annulus 62a is shown in FIG. 7 wherein tensioned fingers 72 are provided. The employment of tensioned fingers 72 is ideally suited to use within a ceramic arc discharge vessel when the annulus or annuli are positioned within the arc discharge vessel before sintering. Since the sintering operation causes some shrinkage of the arc discharge vessel the tensioned fingers 72 accommodate this shrinkage.
In addition to the annuli 62 and 62a, which can be circular in cross-section, the centering structure 60 can take the form of a “washer” 62b as shown in FIG. 8 wherein the cross-section would be rectangular.
Additional non-limiting variants are shown in FIGS. 11-13 wherein the centering structure 60 takes the form of an annulus 62c having a plurality of inwardly projecting fingers 73 (FIG. 11), an annulus 62d that can be stamped from sheet material and having a central aperture defined by a plurality of cusps 76 (FIG. 12), an annulus 62e that also can be stamped from sheet material and having an a central aperture defined by a plurality of semi-circles 78 (FIG. 13).
Various methods are possible for assembling the arc discharge vessels and arc centering structures. For example, one such method is shown in FIG. 9 wherein an arc discharge vessel blank 100 of quartz has a filling and exhaust tubulation 80. A centering structure 60 having a finger 70 attached is fed into an open end of the blank 100 until a terminus 74 of the finger 70 projects through the tubulation 80. The terminus 74 is bent in a substantially right angle to be held in position and the blank 100 is finished normally into an arc discharge vessel 14 by inserting electrode assemblies 44, forming the seals 43 and exhausting, filling and sealing the exhaust tubulation.
Alternatively, the tubulation 80 can be sealed about the finger 70 to absolutely maintain the centering structure 60 in its desired position and a separate exhaust and filling tubulation can be provided for those functions.
Still another method is shown in FIG. 10, which is applicable in the case of ceramic arc discharge vessels when only a single centering structure 60 is to be provided. Arc discharge vessels may be formed by molding two hemispherical halves 105, 106 having a ship lap joint 108 that is used to join the two halves. By providing a gap 110 between the halves a centering structure, for example, a washer-type 62b, can be sealed between the halves. Alternatively, the fingers 70 of a centering structure 60 in the form of an annulus 62 could be sealed within the gap 110.
Yet another method is illustrated in FIG. 14 wherein the centering structures 60 (one or more) could be fixed between a plurality of ceramic rods 112, for example, by having the terminal ends of fingers 70 wrapped about the rods. The latter method is ideally suited to arc discharge vessels having a cylindrical configuration.
In a specific example, a quartz arc discharge vessel having an inside diameter of 19.5 mm had two centering structures 60 (FIG. 3), comprised of two 7.7 mm outside diameter rings, made from 0.74 mm tungsten wire, placed 1.15 cm above and below the middle of the arc discharge vessel. Tungsten is preferred because its melting temperature is 3410° C.
During testing the arc is seen to constrict as it flows through the rings, raising their temperature to 2100 K.
In a second embodiment shown in FIG. 2 a single centering structure 60 was employed. The single centering structure had a 10 mm OD and was formed from tungsten wire having a 0.74 mm diameter. The single centering structure was centrally mounted within the arc discharge vessel and produced constriction in the arc. The structure temperature was 1860 K. The temperatures of the centering structures can be controlled by changing the diameters of the structures or the thickness of the materials from which they are made. For the arc discharge vessel 14 shown in FIG. 3 the centering structures were found to radiate approximately 10 watts of light each, with the color output being in the red portion of the spectrum.
In the examples illustrated above each arc discharge vessel had a filling of 33 torr argon, 50.7 mg mercury, 5.0 mg mercury iodide (HgI2), 0.5 mg scandium and 20.7 mg sodium iodide (NaI).
In addition to tungsten or tungsten doped with thoria, other high melting point metals such as molybdenum or tantalum or alloys thereof can be utilized. Also, the centering function can be achieved with use of high temperature resistant carbides, nitrides or other ceramics.
While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
Patent Application
20080054812
