Patent Grant
9892905
The present invention relates to lead-in wire assemblies for use in fused silica pinch seals and, more particularly to connection of an additional wire to the external portion of said assemblies.
Referring to prior art examples shown in
As shown in
The attachment/connection 932 in the outer lead assembly 934 between two generally round wires is difficult, especially because: they cannot be soldered due to high lamp operating temperature; and a mechanical/compression joint by itself (e.g., using a surrounding sleeve that is crushed around the overlapping ends) is not reliable due to cyclic thermal expansion and contraction of dissimilar metals and further due to surface oxidation developing over time. This connection is even more challenging because the wires are such different metals with different melting points, have different diameters (e.g., 1 mm solid vs. ˜1.5 mm twisted bundle), and different amounts of hardness/compressibility (stranded Ni is more easily deformed by compression, while solid Mo is relatively hard and non-compressible). Furthermore, the stranded wire has, for example, 19 strands that are twisted together like a cable, which makes resistance welding very difficult and inconsistent due to variable resistance between strands. Finally, as further detailed below, the connection 934 must be made after lamp sealing, so the outer pinch lead 116 will generally be oxidized so that it must be cleaned before a connection can be made.
The connection method that has been in use in the prior art is a combination of resistance spot welding of various portions of overlapping wire ends and a sleeve that is crimped around one or both of the overlapping wire ends. This prior art connection will be generically referenced herein as a “crimp connection” 932, even though welding is also typically involved. For example, the sleeve may be crimped around both wire ends to hold them together and the spot weld(s) are made simultaneously through all of the overlapping layers, or separately where the sleeve overlaps each wire. Or, for example, the sleeve may not surround the wires so that the spot welds can be made separately between each lead and the sleeve, thereby passing weld current through only one layer of the sleeve material. Before resistance welding, any oxidation must be cleaned off the wire surface(s), for example by brushing or sand blasting. The longitudinal positioning of the sleeved connection 934 is not precise enough to ensure adequate connection unless there is extra overlapping length (i.e., a larger target) in which the connection can be made. Therefor any solid wire 916 extending beyond the sleeve is usually trimmed off in an attempt to avoid potential interference with the socket clamp (see
Other techniques and method variations may be employed to establish the prior art electrical-mechanical connection designated herein as a crimp connection 932, however they all produce similar results as shown in
Also referring to
Importantly, in the prior art the stranded wire lead can only be added (to complete the lamp “base”) after the pinch seal is completed. This is because the prior art crimp connection 932 between the Mo outer pinch lead and the Ni stranded wire will not survive the extreme heating it would receive during the quartz pinch sealing process (quartz/fused silica “glass” requires the most intense heat of all lampmaking glass materials, e.g., 2,000 C versus around 1500 C for hard glass). As a result of the heating in atmosphere, the outer pinch lead 916 develops an oxide layer that must be removed (e.g., by sand blasting, brushing, etc.) before an acceptable weld connection can be made. Further complicating matters, the heating causes partial recrystallization of the Mo wire, making it somewhat brittle, therefor the crimp connection process must take care to avoid breaking the Mo wire. (The recrystallization may be controlled by using doped moly.)
There are many disadvantages and potential problems with this prior art “crimp connection”, including one or more of the following:
According to the invention a stranded outer lead wire assembly for a quartz pinch sealed lamp. The stranded outer lead wire assembly is a butt welded connection of a refractory metal outer pinch lead (e.g., molybdenum solid wire) and a stranded soft metal lead wire (e.g., nickel wire strands twisted together). The assembly is prefabricated and then welded to sealing foil to make a four part foliated lead wire assembly for pinch sealing in the quartz outer jacket. The foliated lead wire assembly and a quartz envelope lamp utilizing the stranded outer lead wire assembly are also claimed. The sealing machine is adapted to protect the stranded outer lead assembly with a water cooled sleeve. In an embodiment, the outer end of the stranded lead is fused to prevent fraying.
Other objects, features and advantages of the invention will become apparent in light of the following description thereof.
Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawing figures. The figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments.
Certain elements in selected ones of the drawings may be illustrated not-to-scale, for illustrative clarity. The cross-sectional views, if any, presented herein may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain background lines which would otherwise be visible in a true cross-sectional view, for illustrative clarity.
Elements of the figures can be numbered such that similar (including identical) elements may be referred to with similar numbers in a single drawing. For example, each of a plurality of elements collectively referred to as 199 may be referred to individually as 199a, 199b, 199c, etc. Or, related but modified elements may have the same number but are distinguished by primes. For example, 109, 109′, and 109″ are three different versions of an element 109 which are similar or related in some way but are separately referenced for the purpose of describing modifications to the parent element (109). Such relationships, if any, between similar elements in the same or different figures will become apparent throughout the specification, including, if applicable, in the claims and abstract.
The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein:
The following table is a glossary of terms and definitions, particularly listing drawing reference numbers or symbols and associated names of elements (features, aspects) of the invention(s) disclosed herein or of related elements in the prior art.
The invention(s) will now be described with reference to the drawings using the reference numbers and symbols listed in the above table.
A significant part of the present inventive concept is to replace the crimp connection 932 with a butt weld connection 102 as illustrated in
In addition to the greatly improved shape, as shown particularly in
An added advantage of the butt weld is that it is made before lamp sealing, for example by prefabricating an outer lead wire assembly 104 (stranded Ni leadwire 118 plus solid wire (e.g., Mo) outer pinch lead 116) as shown in the step of
An additional feature of the outer lead assembly 104 prefabrication is to create a fused end 108 (see
Prefabricating the entire (4-part) lead wire assembly 106 (using a butt welded connection 102) is much easier to do than the prior art crimp connection 930 because all of the (weld) connections can be made on a dedicated purpose machine in a controlled environment on a convenient schedule without having to hold a bulky sealed lamp 100 that may get in the way of the crimp and welding equipment. This is easier to automate thereby avoiding manual operations, and thereby reducing cost.
The butt weld equipment and process described here is an adaptation of a process previously used to make a butt weld connection between stranded Ni wire and a round solid tungsten lead wire (not Mo). The prior art lead wire assembly is distinguished by the use of round tungsten wire because it is for sealing in a hard glass stem. Tungsten has a thermal expansion coefficient that is suitable for such seals in “hard glass” so it is used without foil. It is important to note that hard glass sealing is accomplished at much lower temperatures (1500-1600 C) than for quartz glass sealing (approximately 2000 C), therefor the butt weld has never been previously suggested for use with quartz sealing lead wires. It was not obvious to try butt weld connected stranded nickel outer lead wire for quartz pinch seal leads because the general assumption has been that the nickel part of the butt weld would (obviously) soften/melt to fall apart, and/or would become too brittle as a result of the extreme heat of quartz pinch sealing being sufficient to affect the wire microstructure.
Thus the herein disclosed butt welded quartz pinch outer leadwire assembly 104, and the associated lampmaking process/method, is novel in that it is used as a lead wire for a quartz jacket 122 lamp 100 with a quartz pinch seal 124 that exposes the butt weld 102 and the stranded nickel lead wire 118 to much higher temperatures for a longer duration compared to hard glass sealing. Therefor it was not obvious that this would work, and experimentation and testing was needed to address the concerns about weld integrity after quartz pinch sealing. In particular, the quartz pinch operation has been adapted to protect the butt welded outer lead assembly 104 during sealing. Whereas the previous operation did not protect the exposed outer pinch lead 916, our inventive modifications to the pinch sealing machine add a water cooled sleeve that protectively encloses the assembly 104, i.e., the stranded lead 118, the weld connection 102 and an external portion of the outer pinch lead wire 116.
It may be noted that in our lamps, the wire we have labeled as “Mo” (molybdenum, a.k.a. “moly”), especially the outer pinch lead 116 is preferably lanthanated molybdenum (“ML wire”), which is Mo doped with lanthanum oxide LaO3 to increase its recrystallization temperature. (to preserve adequate ductility after being subjected to the extreme heating of the quartz pinch sealing process (˜2000 C). There are other doping agents for refractory metals known to have similar benefits, so the present disclosure is not specifically limited to lanthanated moly outer pinch lead 116, however that is a preferred (best known mode) embodiment of the outer pinch lead 116 that is butt welded to the stranded Ni lead wire 118. This is the material that we have tested so far and we know it works in terms of making an adequately flexible, non brittle outer leadwire assembly 104. We started with the ML wire because we have had a positive experience with its use for at least the sealing foil part of foliated leads in quartz pinch seals.
Prior art butt welded stranded Ni lead wire assemblies were designed to be sealed in hard glass which requires tungsten wire in order to seal properly (instead of foil or dumet). Recrystallization embrittlement is not as much a problem for this because hard glass only needs to be heated to about 1500-1600 C during its sealing process.
Regarding concerns about the effects of quartz pinch sealing temperature, we examined the structure and microstructure of the weld nugget before and after sealing with our adapted sealing machine.
a) that the “weld nugget” 102 is a tapered volume of melted Ni wire strands that flowed and fused over the unmelted end of the Mo wire.
b) that the weld structure is substantially unchanged by the heat from sealing the Mo wire in the quartz pinch. (This is helped by our use of lanthanated moly wire (“ML”) which resists and minimizes recrystallization embrittlement.)
In
Tensile tests were also conducted to determine if weld strength was affected. Since our butt weld tensile strength exceeded the ability of our test machine to measure it, we cannot determine differences, if any, before versus after sealing, however the tester did show that our butt weld connection was significantly stronger than the prior art crimp connection.
We concluded that our butt weld connection is better than the prior art connection in every way.
Although the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character—it being understood that the embodiments shown and described have been selected as representative examples including presently preferred embodiments plus others indicative of the nature of changes and modifications that come within the spirit of the invention(s) being disclosed and within the scope of invention(s) as claimed in this and any other applications that incorporate relevant portions of the present disclosure for support of those claims. Undoubtedly, other “variations” based on the teachings set forth herein will occur to one having ordinary skill in the art to which the present invention most nearly pertains, and such variations are intended to be within the scope of the present disclosure and of any claims to invention supported by said disclosure.
This application claims the benefit of U.S. Provisional Patent Application No. 62/262,768, filed Dec. 3, 2015, said application hereby incorporated in its entirety by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4061939 | Strok, Jr. | Dec 1977 | A |
| 5962960 | Regitz | Oct 1999 | A |
| 20050146257 | Trujillo | Jul 2005 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20170162376 A1 | Jun 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62262768 | Dec 2015 | US |
