Platform-based multiple foil high current electrode attachment for medium pressure quartz lamps

A medium pressure quartz lamp for arc discharge illumination, includes a quartz envelope having opposite electrode ends with an electrode unit sealably attached to each of the opposite electrode ends. Each of the electrode units includes an electrode rod extending into the envelope and a platform physically attached to the rod. The platform has a melting point of at least 1,000.degree. C. The electrode units also include at least one conductive, elongated metal foil which has a first end and a second end. The conductive elongated metal foil(s) are attached at their first end to the platform and attached at their second end to a terminal connector. Preferably, plural foils are utilized with a single platform attached to the electrode rod at their first ends and attached to a plurality of terminal connectors a their second ends. Present invention lamps, as a result of utilizing the conductor enhancing platform approximately doubles maximum operating current as compared to prior art lamps of otherwise similar configurations.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention involves medium pressure quartz lamps utilizing 
mercury and/or metal halide. More particularly, these lamps have very high 
maximum operating currents relative to similar prior art lamps, resulting 
from the inclusion of current enhancing platforms in the electrode units. 
2. Information Disclosure Statement 
The following patents represent the State of the Art for various vapor 
lamps. They do not teach or suggest the use of current enhancing 
platforms, nor are they necessarily directed to medium pressure lamps: 
U.S. Pat. No. 2,562,887 to N. C. Beese relates to a vapor lamp which 
comprises an envelope of glass resistant to caesium at temperatures 
between about 307.degree. and 325.degree. C. electrodes in and between. A 
discharge occurs upon the application of electrical energy. The envelope 
is generally cylindrical and has a diameter between 1 and 11/2 inches and 
a length between 4 and 6 inches. It also includes an ionizable medium in 
the envelope which consists of argon at a pressure between 5 and 30 
centimeters, admixed with between 0.2 and 0.5 gram of caesium. 
U.S. Pat. No. 2,749,461 to Frank J. Hierholzer, et al, relates to a lamp 
unit which includes a combination of an electric discharge device, an 
envelope enclosing the device and also has dome and neck portions. There 
is also an inwardly opening central pocket in the dome portion, a flare 
tube closing the neck portion, a frame holding the device in the envelope, 
the neck end of the frame being connected to the flare tube, transversely 
extending spring elements centering the frame in the neck portion. The 
device includes an annular portion connected to the dome end of the frame 
and a plurality of fingers extending from the annular portion, into and 
engaging the inner surface of the pocket, for centering purposes. The 
fingers are placed under compression upon the insertion of the discharge 
device in the outer envelope to enable longitudinal movement of the 
discharge device during operation due to expansion and contraction of the 
frame without deviation of the discharge device from its longitudinal axis 
in the outer envelope. 
U.S. Pat. No. 2,962,615 to Nicholas Anton, relates to a radiation detector 
tube of the type for detecting alpha, beta and gamma radiation which 
includes a gas tight envelope which has a hollow axially symmetrical 
conductive cathode, a radiation-permeable window sealed across one end of 
the cathode, an insulator sealed at the other end of the cathode, and an 
anode wire mounted in cantilever fashion and sealed to the insulator and 
extending coaxially within the cathode and terminating the adjacent 
window. The improvement which includes an anode support structure which 
has an insulating sleeve positioned along the anode wire adjacent to the 
unsupported end of the anode, and extending beyond the free tip of the 
anode, and a support member engaging the insulating sleeve and the cathode 
to hold the insulating sleeve in a fixed position to prevent the anode 
wire from vibrating. 
U.S. Pat. No. 3,211,941 to J. Sanden et al, relates to an electric 
incandescent lamp which includes a tubular envelope having a filament coil 
extending axially of the envelope. It also includes at least one support 
member supporting the filament from the envelope wall, the support member 
formed from a single wire length bent to form a retroverted mid-section 
having its bright portion engageable with the envelope wall and tow 
clamping legs extending from the mid-section. The legs have cooperating 
adjacent clamping portions thereof intermediate their lengths, at least 
one clamping portion being curved so that between then they embrace the 
filament coil and engage it at least at three points around its periphery. 
The clamping legs have their free ends beyond the clamping portions 
extending divergently away from the filament into engagement with the 
envelope wall. The clamping legs at their clamping portions crossing over 
at least one side of the filament cover. 
U.S. Pat. No. 3,250,941 to J. Wilson et al, relates to a compact source 
lamp which includes a vitreous envelope which has a tubular portion. There 
are pinch seals at opposite ends of the envelope through which extend 
inleads each which include a foil portion hermetically sealed through the 
pinch seal and a rod-like portion projecting into the envelope. There are 
electrodes which have their outer ends attached to the inner ends of the 
rod-like portions which define a short interelectrode gap. The foil 
portion is associated with at least one of the electrodes being 
insufficiently rigid to support the electrode vertically. At least one 
support member comprising a wire coiled around the one electrode at its 
outer end and having an expanded turn bearing against the wall of the 
vitreous envelope at the tubular portion. 
U.S. Pat. No. 3,497,752 to Carl L. Peterson, relates to a quartz halogen 
lamp having a connector coil at the end of a filament leg to physically 
support the filament and make an electrical connection to a lead-in wire. 
The coil encircles the lead-in wire and has two arms in an overlapping, 
compressive engagement which constricts the coil in its direction of 
winding and thereby clamps it on the wire. There is similar coil, that has 
arms which press against the lamp envelope, thereby supporting the 
interior end of the filament mount. 
U.S. Pat. No. 3,715,615 to Gordon R. Lavering, relates to an electrode 
support structure for use in a short arc lamp. The structure includes a 
ring having a plurality of flaps formed therein. Struts are attached to 
the electrode and to the flaps. These struts may be straight and may be 
abutted to the electrode. The flaps can bend to minimize the stresses 
created by the contraction and expansion of the struts relative to the 
ring during the temperature cycling of assembly and operation. 
U.S. Pat. No. 4,463,281 to Walter Tribel et al, relates to a high-pressure 
electric discharge lamp which includes a support part surrounding each 
electrode rod. Each electrode rod has a spring wound therearound and 
presses the respective support part toward an electrode mounted at the end 
of the respective electrode rods. This arrangement includes a part of an 
assembly which is then mounted into envelope necks which extend from 
respective opposite ends of a quartz glass envelope which defines the 
discharge space of the lamp. A narrowing area is defined at the transition 
of the envelope necks to the envelope. The supporting parts each have a 
rounded end resting against a respective inclined surface defined by the 
narrowings at the transitions between the envelope necks and the envelope. 
The springs resiliently bias the supporting parts against the inclined 
inner surfaced of the narrowings. Also disclosed is a method of 
manufacture of the above described high-pressure electric discharge lamp. 
U.S. Pat. No. 4,463,281 to Walter Triebel et al, relates to a high-pressure 
electric discharge lamp which includes a support part which surrounds each 
electrode rod, each electrode rod has a spring wound therearound and 
presses the respective support part toward an electrode mounted at the end 
of the respective electrode rods. This arrangement includes a part of an 
assembly which is then mounted into envelope necks which extend from 
respective opposite ends of a quartz glass envelope which defines the 
discharge space of the lamp. A narrowing area is defined at the transition 
of the envelope neck to the envelope. The supporting parts each have a 
rounded end resting against a respective inclined surface defined by the 
narrowings at the transition between the envelope necks and the envelope. 
The springs resiliently bias the supporting parts against the inclined 
inner surfaces of the narrowings. Also disclosed is a method of 
manufacture of the above described high-pressure electric discharge lamp. 
U.S. Pat. No. 4,559,472 to Walter Triebel et al, relates to a high-pressure 
discharge lamp having a glass enclosure defining a discharge space. 
Envelope portions extending away from the discharge space are provided 
with elongate electrode portions extending respectively through the 
envelope portions. These electrode portions carry respective electrode 
portions at their inner ends and the electrode portions are sealed 
hermetically to the respective envelope portions. In order to support the 
electrode portions within the envelope portions, respective support 
elements are fitted around the electrode portions in space relation to the 
envelope portions. Means including a respective resilient element engaging 
each support member, are provided to hold the support elements in their 
axial position around the respective electrode portions. The resilient 
elements are each held between the respective electrode and the inner 
surface of the respective support element to continuously urge the axially 
outer surface of the support element resiliently against the respective 
sealing means. 
UK Patent Application No. GB 2 106 312 A relates to a high pressure 
discharge lamp including a lamp envelope having a lamp bulb and at least 
one leg member attached to the bulb. An electrode shank within the leg 
member, carrying an electrode; a reinforcing abutment formed on the inside 
surface of the wall of the leg member; and a support clip arranged to 
resiliently engage the shank and the reinforcing abutment to form a 
resilient support for the shank within the leg member. 
U.S. Pat. No. 5,369,329 relates to a short arc discharge lamp having a 
quartz envelope with a bulb and a plurality of arms having a specified 
cross-section, and one or more electrode rods are supported within the 
lamp arms for specific alignment. Support elements for the electrode rods 
are made of high temperature metal and have a flat central portion with a 
central orifice of sufficient dimension to permit one of the electrode 
rods to pass into the central orifice, and have at least two legs, and 
preferably four legs, radially extending from the flat central portion. 
The legs have outer portions terminating with pods formed at substantially 
right angles to the flat central portion of the support element, the legs 
being of sufficient length to fit the envelope arms so as to contact an 
inside surface of the envelop arms with the pods. There is also provided 
means for securing the support elements within the envelope arms. 
Notwithstanding the prior art, the present invention is neither taught nor 
rendered obvious thereby. 
SUMMARY OF THE INVENTION 
A medium pressure quartz lamp for arc discharge illumination, includes a 
quartz envelope which has opposite electrode ends with an electrode unit 
sealably attached to each of the opposite electrode ends. Each of the 
electrode units include an electrode rod extending into the envelope and a 
platform physically attached to the rod. The platform has a melting point 
of at least 1,000.degree. C. The electrode units also include at least one 
conductive, elongated metal foil which has a first end and a second end. 
The conductive elongated metal foil(s) are attached at their first end to 
the platform and attached at their second end to a terminal connector. In 
one preferred embodiment, plural foils are utilized with a single platform 
attached to the electrode rod at their first ends and attached to a 
plurality of terminal connectors a their second ends. In another preferred 
embodiment plural foils are utilized with two platforms, a first platform 
connected to the electrode rod and second platform connected to the 
terminal connectors with the first end of the foils connected to the first 
platforms and the second end of the foils connected to the second 
platform. Present invention lamps, as a result of utilizing the conductor 
enhancing platform approximately doubles maximum operating current as 
compared to prior art lamps of otherwise similar configurations.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
In the present invention, medium pressure quartz lamps typically include 
electrode units at each end which contain electrode rods, foils and 
terminals. The metal foils are necessary to conduct from the terminal to 
the electrode rod within the lamp to achieve desired current levels for 
illumination. These medium pressure lamps are typically mercury vapor 
lamps and metal halide lamps and are used in such applications as ultra 
violet light curing, drying, printing and the like and are used in 
industries such as semiconductor manufacturing. FIG. 1 shows a side view 
of a typical prior art linear medium pressure gas vapor lamp 1. It 
includes the quartz bulb 3, electrode units shown generally as units 5 and 
7 and electrical connectors 9 and 11 which extend from each electrode unit 
5 and 7 respectively. This prior art medium pressure lamp dosed with an 
inert gas, could contain mercury vapor, metal halide or both. Typically, 
the lamp arc lengths (from electrode 13 to electrode 15) would be from as 
short as about 1 inch to as long as 180 inches or more. Power levels vary 
from about 100 to 1200 watts per inch of arc length. 
It has been discovered by the inventor herein that the maximum operating 
currents are governed in part, in these linear medium pressure lamps by 
the limitations of the weld connections between the electrode rods and the 
foils and at the use of a conductive platform between the foil and the 
electrode rod surprisingly, substantially increase the maximum operating 
current. Thus, FIGS. 2, 3 and 4 all illustrate prior art electrode units 
which achieve around 20 amps maximum operating current. 
FIG. 2 shows a cut side view of one end of a typical single foil mercury 
vapor lamp 20. Lamp 20 includes bulb or envelope 23, electrode rod 25, 
electrode unit 27, foil 21 and terminal connector 29. As can be seen, foil 
21 is welded directly to electrode rod 25 and directly to terminal 
connector 29. 
FIG. 3 illustrates a side view of a typical parallel dual foil lamp 30 
having bulb 31, electrode rod 33 contained within electrode unit 35 and 
with terminal connector 37. Foils 34 and 36 are both welded at one end to 
electrode rod 33 and at the other end to terminal connector 37, as shown. 
FIG. 4 shows a typical press sealed electrode lamp 40. This includes 
envelope 41, electrode rod 43, electrode unit 45, foil 47 and terminal 
connector 49. In the prior art lamps 20 and 30 shown on FIGS. 2 and 3, 
respectively, the foil connections are welded and contained within the 
electrode unit 27 and electrode unit 35, respectively, wherein they are 
sealed under vacuum to a solid piece of quartz in a cylindrical shape. 
Lamp 30 also contains a thin wafer of quartz between the two foils. In 
lamp 40 illustrated in FIG. 4, foil 47 is welded and press sealed into a 
solid quartz electrode unit 45. The FIG. 4 prior art electrode unit 45 is 
pressed and sealed to form a rectangular solid unit. Nonetheless, as 
illustrated in Table 1 below, maximum operating currents are relatively 
low and relatively similar for all of these prior art considerations. 
Referring now to FIG. 5, there is shown an exploded side oblique view of 
one preferred embodiment of a present invention lamp assembly electrode 
unit 50. In FIG. 5, there is shown a core element 51 (quartz glass), 
terminal connectors 53 and 55, electrode rod 57 and dual foils 59 and 61. 
The critical feature of the present invention involves the use of platform 
63. This is used for indirect connection of foils 59 and 61 to electrode 
rod 57, thus, maximum current capabilities have been discovered to be 
substantially increased by the use of a platform such as platform 63. 
FIG. 6 shows a side view of the elements shown in FIG. 5 but in an 
assembled state. Thus, identical elements are identically numbered. Foils 
59 and 61 have been welded to platform 63 and electrode rod 57 has been 
connected to platform 63 by insertion with force fitting and/or welding. 
Referring to FIG. 7 there is shown the same electrode unit 50 from FIGS. 5 
and 6 but in its fully assembled state. Here, in this partial side view, 
envelope 65 is shown with electrode unit 50 connected thereto and sealed 
therewith. Note that the unit 50 shown in FIG. 6 is now encased in a 
quartz glass sealed and pressed tube 67. It was found that the maximum 
operating current for the present invention device shown in FIG. 7 was 
about 100% greater than prior art results. 
The platform utilized in the present invention is preferably molybdenum, 
tungsten and any other metal with a melting point in excess of at least 
1000.degree. C. and preferably in excess of at least 1200.degree. C. In 
preferred embodiments, the foil is molybdenum and the electrode rod is 
tungsten. 
The platform, which is utilized to create a significant conductive surface 
area increase, may generally be a separate element and is preferably a 
separate element, such as shown in FIG. 5. It may be made of the same 
conductive material as the electrode rod or as the foil or may be made of 
a different material which is conductive and has a melting point of at 
least 1200.degree. C. and preferably at least 1400.degree. C., as 
mentioned. Additionally, the present invention should not be limited in 
shape as to the platform and core. While a round cross section is the 
simplest and may be the easiest to work with, other configurations such as 
square, rectangular oval, hexagonal and cross-sections may be used. 
FIG. 8 shows an alternative embodiment, element 80, useful in a present 
invention lamp. Thus, electrode rod 81 has a unistructurally formed shape 
which includes an enlarged end platform 83. This platform need not be 
round and, as illustrated in FIG. 9, element 80 could have a square 
configuration for platform 83. Further, platform 83 is shown in FIG. 9 to 
have foils 85, 87, 89 and 91 attached thereto. However, present invention 
platforms could be used for a single foil or any reasonable number of 
foils. 
FIG. 10 shows a side, oblique exploded view of a present invention 
electrode unit 100, and FIG. 11 shows a side assembled view thereof. This 
embodiment is similar to that which is shown in FIGS. 5, 6 and 7 except 
that two platforms are used instead of one, at opposite ends of the foils 
there is shown core 101, single terminal connector 103, foils 105 and 107, 
electrode rod 102 and platforms 109 and 111. 
The following Table 1 illustrates maximum operating currents achieved 
utilizing the present invention lamps verses the prior art: 
TABLE 1 
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LAMP MAX OPERATING CURRENT 
______________________________________ 
FIG. 2 prior art 18 amps 
FIG. 3 prior art 20 amps 
(dual foils) 
FIG. 4 prior art 22 amps 
(press sealed) 
FIG. 7 present invention 
40 amps 
Quadruple foil present invention 
50 amps 
______________________________________ 
As Table 1 illustrates the present invention achieves an increase of about 
100% maximum operating current over the prior art lamps. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore understood 
that within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described herein.