Patent Application
20070120491
This section is intended to introduce the reader to various aspects of art that may be related to aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
High-intensity discharge (HID) lamps are often formed from a ceramic tubular body or arc tube that is sealed to one or more end structures. The end structures are often sealed to this ceramic tubular body using a single seal glass. Sealing usually involves heating the assembly of the ceramic tubular body, the end structures, and the seal glass to induce melting of the seal glass and reaction with the ceramic arc tube and the end structures to form a strong chemical and physical/mechanical bond. The ceramic tubular body and the end structures are often made of the same material, such as polycrystalline alumina (PCA). Thus, the single seal glass may have physical and mechanical properties matching those of all of the ceramic components, i.e., the ceramic arc tube and the ceramic end structures.
However, certain applications may require the use of different materials for the ceramic arc tube and the end structures. Unfortunately, various stresses may arise from the sealing process, the interface between the joined components, and the materials used for the different components. For example, the materials of the ceramic arc tube, the end structures, and the single seal glass may have different mechanical and physical properties. These properties generally include different coefficients of thermal expansion (CTE), which can lead to residual stresses and sealing cracks. These potential stresses and sealing cracks are particularly problematic for high-pressure lamps and operational conditions involving rapid cycling.
The geometry of the interface between the ceramic arc tube and the end structures also may attribute to the foregoing stresses. For example, the end structures are often shaped as a plug or a pocket, which interfaces both the flat and cylindrical surfaces of the ceramic arc tube. If the components have different coefficients of thermal expansion and elastic properties, then residual stresses arise because of the different strains that prevent relaxation of the materials to stress-free states. For example, in the case of the plug type end structure, if the plug has a lower coefficient of thermal expansion than the ceramic tubular body and seal glass, then compressive stresses arise in the plug region while tensile stresses arise in the ceramic arc tube.
In addition to the ceramic arc tube and end structures, high-intensity discharge lamps also include a variety of internal materials (e.g., gases) and electrode materials to create the desired high-intensity discharge for lighting. The particular internal materials disposed in the high-intensity discharge lamps can affect the sealing characteristics, the light characteristics, and the type of materials that may be workable for the lamp components and the seal glass. For example, certain internal materials, such as halides and metal halides, may be desirable for lighting characteristics, but they are corrosive to some of the ceramic and metallic components that comprise the tubular body and end structure.
Accordingly, a technique is needed to provide a lighting system, such as high-intensity discharge lamp, with improved sealing characteristics.
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
In accordance with a first aspect of the present invention, a lamp is provided with an arc envelope including a ceramic, an end member including a material different from the ceramic, and a compliant seal disposed between the end member and the arc envelope. The compliant seal includes a plurality of layers having different thermal expansion characteristics in an order of gradual change between the arc envelope and the end member.
In accordance with a second aspect of the present invention, a system is provided with a lamp including a ceramic arc envelope and a dosing tube coupled to the ceramic arc envelope via a compliant seal, wherein the compliant seal comprises a plurality of layers having different thermal expansion characteristics in an order of gradual change between the ceramic arc envelope and the dosing tube. The dosing tube has a material composition including a cermet, or a metal, or a combination thereof. The lamp also includes an electrode lead extending through the dosing tube to an arc electrode disposed inside the ceramic arc envelope, wherein the dosing tube is compressed and sealed about the electrode lead.
In accordance with a third aspect of the present invention, there is provided a method of operating a lamp. The method includes thermally expanding with different thermal expansion characteristics in a plurality of layers of material in a compliant seal between an arc envelope and an end member, wherein the arc envelope includes a ceramic and the end member includes a material different from the ceramic.
Various refinements of the features noted above exist in relation to the various aspects of the present invention. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present invention alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of the present invention without limitation to the claimed subject matter.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliant with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
In each of the following embodiments, one or more compliant seals may be disposed between various components of a lamp, wherein each compliant seal includes a plurality of concentric sleeves, adjacent rings, side-by-side sheets, or layers. The layers of the compliant seal generally include different thermal expansion characteristics, which gradually change from one layer to another between the adjacent components being sealed together. In other words, in the present application, the thermal expansion characteristics may be defined as different abilities to expand and/or contract in response to temperature changes. Moreover, the thermal expansion characteristics may be defined as material characteristics, geometrical characteristics, or combinations thereof. For example, the material characteristics may include the coefficient of thermal expansion, or the elastic modulus (i.e., Young's modulus), or other thermo-mechanical characteristics of the layers. In certain embodiments, the layers may have gradually changing (i.e., in steps) coefficients of thermal expansion within a range from 3×10−6/Kelvin to 12×10−6/Kelvin, or within a smaller range from 5×10−6/Kelvin to 9×10−6/Kelvin. By further example, the geometrical characteristics may include wall thickness, length, width, diameter, solidity or continuity (e.g., number of interruptions, spaces, slots, openings, grooves, channels, etc.), and so forth. In certain embodiments, the layers each may have an equal or different number, size, and configuration of expansion/contraction spaces. In each of the embodiments discussed in further detail below, the different layers of the compliant seals may have different thermal expansion characteristics based solely on material characteristics, or based solely on geometrical characteristics (e.g., spaces or slots), or based both on material and geometrical characteristics. These compliant seals are particularly useful in rapid cycling of lamps, where the temperatures change and cause expansion and contraction in the various components.
Turning now to the commonalities in
The concentric layers or sleeves 26, 28, 30, and 32 of the compliant seal 12 and the concentric layers or sleeves 38, 40, 42, and 44 of the compliant seal 14 generally include different thermal expansion characteristics, which gradually change from one layer/sleeve to another between the arc envelope 16 and the dosing tubes 18 and 20. Again, in the present application, the thermal expansion characteristics may be defined as different abilities to expand and/or contract in response to temperature changes. Moreover, the thermal expansion characteristics may be defined as material characteristics, geometrical characteristics, or combinations thereof. For example, the material characteristics may include the coefficient of thermal expansion, or the elastic modulus (i.e., Young's modulus), and so forth. In certain embodiments, the sleeves 26, 28, 30, and 32 and the sleeves 38, 40, 42, and 44 may have gradually changing (i.e., in steps) coefficients of thermal expansion within a range from 3×10−6 Kelvin to 12×10−6/Kelvin, or within a smaller range from 5×10−6/Kelvin to 9×10−6/Kelvin. By further example, the geometrical characteristics may include wall thickness, length, width, diameter, solidity or continuity (e.g., number of interruptions, spaces, slots, openings, grooves, channels, etc.) of the sleeves 26, 28, 30, and 32 and the sleeves 38, 40, 42, and 44. In certain embodiments, the sleeves 26, 28, 30, and 32 and the sleeves 38, 40, 42, and 44 each may have an equal or different number, size, and configuration of expansion/contraction spaces. Again, the different layers or sleeves of the compliant seals 12 and 14 may have different thermal expansion characteristics based solely on material characteristics (e.g., different cermets—e.g., alumina molybdenum cermets), or based solely on geometrical characteristics (e.g., spaces or slots), or based both on material and geometrical characteristics. In this manner, the compliant seals 12 and 14 improve the interface or compliance (e.g., thermal, mechanical, etc.) between the properties or behavior of the arc envelope 16 and the dosing tubes 18 and 20 during operation of the lamp assembly 10, and particularly during rapid cycling or thermal variations in the lamp assembly 10.
In the illustrated embodiment, the concentric layers or sleeves 26, 28, 30, and 32 of the compliant seal 12 include four different materials having different thermal expansion characteristics that provide a four stage gradual change between the thermal characteristics of a first material composition of the arc envelope 16 and the thermal characteristics of a second material composition of the dosing tube 18. For example, the concentric layer of sleeve 26 may have properties or thermal characteristics more closely matched with those of the arc envelope 16, while the concentric layer or sleeve 32 may have properties or thermal characteristics more closely matched with those of the dosing tube 18. In turn, the intermediate concentric layers or sleeves 28 and 30 may have properties or thermal characteristics in between those of the concentric layers or sleeves 26 and 32. In other words, each of the concentric layers or sleeves 26, 28, 30, and 32 of the compliant seal 12 provide an incremental change in the properties or thermal characteristics between the arc envelope 16 and the dosing tube 18, rather than a more abrupt change from the arc envelope 16 to a single sealing layer to the dosing tube 18. The concentric layers or sleeves 38, 40, 42, and 44 of the compliant seal 14 are also configured to provide a gradual or incremental change in the properties or thermal expansion characteristic from the arc envelope 16 to the dosing tube 20.
Regarding the material compositions of these components, in certain embodiments, the first material composition of the arc envelope 16 includes a variety of transparent ceramics and other materials, such as yttrium-aluminum-garnet, ytterbium-aluminum-garnet, or other lanthanide aluminum garnets, microgram polycrystalline alumina (μPCA), alumina or single crystal sapphire, yttria, spinel, ytterbia, or combinations thereof. Other embodiments of the arc envelope 16 are formed from conventional lamp materials, such as polycrystalline alumina (PCA). The second material composition of the dosing tubes 18 and 20 may include one or more metals (e.g., molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof), a cermet, or combinations thereof. For example, one exemplary molybdenum-rhenium alloy includes molybdenum and 44 percent by volume rhenium. Advantageously, certain embodiments of the dosing tubes 18 and 20 are formed of materials, e.g., molybdenum-rhenium alloys, that provide stability at high temperatures and pressures, stability against corrosive materials such as hot halide vapors, and ductility for cold welding the dosing tubes 18 and 20. An exemplary molybdenum-rhenium alloy includes about 35 to 55 percent weight of rhenium, or about 44 to 48 percent weight of rhenium.
Turning to the material composition of the compliant seals 12 and 14, the concentric layers or sleeves 26, 28, 30, and 32 of the compliant seal 12 and the concentric layers or sleeves 38, 40, 42, and 44 of the compliant seal 14 may include different ceramics (e.g., alumina, or yttrium-aluminum-garnet, i.e., YAG, or ceramic compositions based on rare earth oxides, alumina, and silica), or different cermets (e.g., alumina molybdenum cermets), or different combinations thereof. It should be noted that the material compositions described for any one of the compliant seals may be used for the other complaints seals disclosed herein. In certain embodiments, the layers or sleeves of the compliant seals 12 and 14 may be formed with the same material in different geometrical configurations, e.g., different degrees of continuity or interruptions (e.g., slots), as discussed in further detail below with reference to
The compliant seals 12 and 14 also may have a variety of lengths, thicknesses, diameters, or geometrical configurations in accordance with certain embodiments of the present technique. For example, the concentric layers or sleeves 26, 28, 30, and 32 of the compliant seal 12 and the concentric layers or sleeves 38, 40, 42, and 44 of the compliant seal 14 have incrementally greater lengths and incrementally smaller diameters from the arc envelope 16 to the dosing tubes 18 and 20. The thickness of the concentric layers or sleeves also may gradually increase, remain constant, or decrease from one layer or sleeve to another between the arc envelope 16 and the dosing tubes 18 and 20.
A few specific combinations of material compositions for the various parts of the embodiments of
Moreover, the set of thermal expansion slots 50 is circumferentially staggered relative to a set of thermal expansion slots 66 in the concentric layer or sleeve 28. As illustrated, the set of thermal expansion slots 66 is disposed on a rear or opposite circumferential portion 68 relative to the front 52 of the sleeve 26. Again, the set of thermal expansion slots 66 includes four axial slots 70, 72, 74, and 76, which are staggered one after another relative to top and bottom sides 78 and 80 of the sleeve 28.
The subsequent sleeve 30 has a configuration similar to the first sleeve 26. As illustrated, the sleeve 30 includes a set of thermal expansion slots 82 disposed along a front circumferential portion 84 of the sleeve 30, similar to the frontal arrangement of the sleeve 26. The set of thermal expansion slots 82 includes four axial slots 86, 88, 90, and 92, which are circumferentially staggered one after another between top and bottom sides 94 and 96 of the sleeve 30. In addition, in the illustrated embodiment, the axial slots 86, 88, 90, and 92 may be disposed in an axially opposite configuration as the axial slots 54, 56, 58, and 60 of the sleeve 26. In other words, the axial slots 86 and 90 extend into the sleeve 30 from the bottom side 96 rather than the top side 94, and the axial slots 88 and 92 extend into the sleeve 30 from the top side 94 rather than the bottom side 96.
Finally, the sleeve 32 has a set of thermal expansion slots 98 disposed in a similar configuration as the sleeve 28. As illustrated, the set of thermal expansion slots 98 is disposed on a rear circumferential portion 100 of the sleeve 32, which is opposite from the front circumferential portions 52 and 84 of the sleeves 26 and 30. The set of thermal expansion slots 98 includes four axial slots 102, 104, 106, and 108, which are circumferentially staggered one after another between top and bottom sides 110 and 112 of the sleeve 32. In the illustrated embodiment, the axial slots 102, 104, 106, and 108 are disposed in an axially opposite configuration relative to the axial slots 70, 72, 74, and 76 of the sleeve 28.
The circumferential staggering of the various sets of thermal expansion slots 50, 66, 82, and 98 ensures that the compliant seal 12 is sealed in the axial, radial, and circumferential directions between the arc envelope 16 and the dosing tube 18. The compliant seal 14 may have a similar configuration as the compliant seal 12 as illustrated in
Referring back to
In the illustrated embodiment, the arc electrode assemblies 114 and 116 are moved lengthwise along the interior of the dosing tubes 18 and 20 until the desired arc gap 138 is achieved between the arc tips 126 and 128. Upon reaching the desired arc gap 138, the arc electrode assemblies 114 and 116 are secured to the dosing tubes 18 and 20 by crimping intermediate portions 140 and 142 and laser welding outer end portions 144 and 146 of the dosing tubes 18 and 20 relative to the electrode lead assemblies 122 and 124, respectively. In certain embodiments, the dosing tubes 18 and 20 are crimped or mechanically compressed about the electrode lead assemblies 122 and 124 at other locations or at multiple locations along the dosing tubes 18 and 20. Moreover, one or more other forms of focused heating, such as induction heating, may be applied to seal the dosing tubes 18 and 20 to the electrode lead assemblies 122 and 124. The laser welding, crimping, induction heating, and other sealing techniques may be used alone or in combination with one another.
In certain embodiment, the dosing tubes 18 and 20 and the electrode lead assemblies 122 and 124 have material compositions to facilitate the forgoing crimping and laser welding techniques. For example, the dosing tubes 18 and 20 may include one or more metals (e.g., molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof), a cermet, or combinations thereof. Similarly, the wire overwraps 130 and 132 may include molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or combinations thereof. Finally, the mandrels or shanks 134 and 136 may include molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or combinations thereof. The ductile nature of these materials, e.g., a molybdenum-rhenium alloy, enables the dosing tubes 18 and 20 to be substantially compressed around the circumference of the electrode lead assemblies 122 and 124 at the intermediate portions 140 and 142, respectively. The other components of the arc electrode assemblies 114 and 116 also may include a variety of material compositions. For example, the arc electrodes 118 and 120 may have a material composition including tungsten, or molybdenum, or rhenium, or combinations thereof. The arc tips 126 and 128 may have a material composition including tungsten, or molybdenum, or rhenium, or combinations thereof.
Again, the arc envelope 16, the dosing tubes 18 and 20, the end plugs 148 and 150, and the layers or sleeves of the compliant seals 152 and 154 may have a variety of similar or different material compositions. In the illustrated embodiment of
For example, as discussed above, the illustrated arc envelope 16 has a material composition including a variety of transparent ceramics and other materials, such as yttrium-aluminum-garnet, ytterbium-aluminum-garnet, microgram polycrystalline alumina (μPCA), alumina or single crystal sapphire, yttria, spinel, ytterbia, or combinations thereof. Other embodiments of the arc envelope 16 are formed from conventional lamp materials, such as polycrystalline alumina (PCA). In contrast, the end plugs 148 and 150 have a nonceramic or different ceramic material composition, such as a cermet, a metal (e.g., molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof), or combinations thereof. The dosing tubes 18 and 20 also may include a material composition having thermal characteristics (e.g., coefficient of thermal expansion, elastic modulus, etc.) that are at least similar to those of the end plug 148 and 150. For example, the dosing tubes 18 and 20 may have a material composition including a cermet, or a metal (e.g., molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof), or combinations thereof. In one embodiment, the end plugs 148 and 150 are formed of a molybdenum rhenium alloy and the dosing tubes 18 and 20 are formed of the same or a different molybdenum rhenium alloy. In another embodiment, the end plugs 148 and 150 are formed of a molybdenum rhenium alloy and the dosing tubes 18 and 20 are formed of molybdenum. In a further embodiment, the end plugs 148 and 150 and the dosing tubes 18 and 20 are formed of molybdenum.
A specific combination of material compositions for the various parts is provided below as an example for the lamp assembly 10 of
In a similar manner, the compliant seals 176 and 178 provide a gradual change in properties or thermal expansion characteristics (e.g., coefficients of thermal expansion, elastic modulus, geometry or continuity—i.e., spaces or slots) in an axial direction between the arc envelope 16 and the end caps 180 and 182. Specifically, the illustrated compliant seal 176 includes a plurality of axially adjacent layers or rings 200, 202, 204, and 206, and the compliant seal 178 includes a plurality of axially adjacent layers or rings 208, 210, 212, and 214. The compliant seal 176 extends between a ring shaped end surface 216 of the arc envelope 16 and an interior ring shaped surface 218 of the end cap 180. Similarly, the compliant seal 178 extends between a ring shaped end surface 220 of the arc envelope 16 and an interior ring shaped surface 222 of the end cap 182.
Again, the compliant seals 172 and 174 accommodate differences in the properties or thermal expansion characteristics of the arc envelope 16 and the dosing tubes 18 and 20, while the compliant seals 176 and 178 accommodate differences in the properties or thermal expansion characteristics between the arc envelope 16 and the end caps 180 and 182. For example, the illustrated arc envelope 16 has a ceramic material composition, whereas the dosing tubes 18 and 20 and the end caps 180 and 182 have non-ceramic or other different types of ceramic compositions. Each of the compliant seals 172, 174, 176, and 178 includes four different materials having properties or thermal expansion characteristics (e.g., different coefficients of thermal expansion, elastic modulus, geometry or continuity—e.g., slots or spaces) that gradually change between the adjacent components, thereby reducing thermal stresses and potential stress crack development in the lamp assembly 10 between the various components.
The lamp assembly 10 as illustrated in
In a second specific embodiment, the arc envelope 16 has a material composition including alumina, the end caps 180 and 182 have a material composition including Mo-44Re, and the dosing tubes 18 and 20 have a material composition including Mo-44Re. In this second specific embodiment, the layers or sleeves 184/192, 186/194, 188/196, and 190/198 of the compliant seals 172 and 174 include alumina molybdenum cermets, e.g., alumina and 8 percent by volume molybdenum, alumina and 22 percent by volume molybdenum, alumina and 36 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum, in order from the arc envelope 16 to the dosing tubes 18 and 20. In addition, the layers or rings 200/208, 202/210, 204/212, and 206/214 of the compliant seals 176 and 178 have four different material compositions including alumina molybdenum cermets, e.g., alumina and 8 percent by volume molybdenum, alumina and 22 percent by volume molybdenum, alumina and 36 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum, in order from the arc envelope 16 to the end caps 180 and 182.
In a third specific embodiment, the arc envelope 16 has a material composition including alumina, the end caps 180 and 182 have a material composition including alumina, and the dosing tubes 18 and 20 have a material composition including Mo-44Re. In this third specific embodiment, the layers or sleeves 184/192, 186/194, 188/196, and 190/198 of the compliant seals 172 and 174 include alumina molybdenum cermets, e.g., alumina and 8 percent by volume molybdenum, alumina and 22 percent by volume molybdenum, alumina and 36 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum, in order from the arc envelope 16 to the dosing tubes 18 and 20. In addition, the layers or rings 200/208, 202/210, 204/212, and 206/214 of the compliant seals 176 and 178 have four different material compositions including dysprosia-alumina-silica seal rings, e.g., 74.5 wt % dysprosia-18.5 wt % alumina-7 wt % silica, 72 wt % dysprosia-16 wt % alumina-12 wt % silica, 69.5 wt % dysprosia-13.5 wt % alumina-17 wt % silica, and 67 wt % dysprosia-11 wt % alumina-22 wt % silica, in order from the arc envelope 16 to the end caps 180 and 182.
Similar to the embodiments of
As illustrated, the electrode assembly 310 includes the electrode lead 268 extending through and sealed with the end cap 254 via the compliant seal 264, an arc electrode 312 coupled to the electrode lead 268, and the arc tip 308 coupled to the arc electrode 312. Advantageously, in certain embodiments, the electrode lead 268 also may be moved lengthwise through the plurality of concentric layers or sleeves 282, 284, 286, and 288 of the compliant seal 264 to facilitate further control of the arc gap 304 between the arc tips 306 and 308 of the electrode assemblies 294 and 310, respectively.
Upon reaching the desires arc gap 304, the electrode assemblies 294 and 310 may be secured in place via one or more sealing and securing techniques. For example, the illustrated electrode lead assembly 298 is secured within the dosing tube 266 via a mechanically compressed or crimped portion 314 and a laser welded portion 316 between the electrode lead assembly 298 and the dosing tube 266. Alternatively, the electrode lead assembly 298 may be coupled to the dosing tube 266 via a variety of other focused heating or sealing techniques, such as induction heating, or resistance welding, or arc welding, or laser welding, or combinations thereof. Similarly, a laser or another focused heating technique may be directed onto the compliant seals 262 and 264 to bond the dosing tube 266 and the electrode lead 268 to the end caps 252 and 254, respectively.
In certain embodiments, the lamp assembly 250 as illustrated in
Alternatively, a laser or another focused heating technique may be directed toward the joints between the various components. For example, a laser or another focused heating technique may be directed toward the interface between the arc envelope 260 and each of the end caps 252 and 254 to create a bond with or without a seal material. For example, if the arc envelope 260 has a ceramic material composition and the end caps 252 and 254 have a ceramic or cermet composition, then the end caps 252 and 254 and the arc envelope 260 may be coupled together via diffusion bonding without an intermediate seal glass material. Alternatively, a compliant seal having a plurality of adjacent layers or rings may be disposed between the arc envelope 260 and the end caps 252 and 254 if the end caps 252 and 254 have a material composition significantly different from the arc envelope 260. For example, the arc envelope 260 may have a ceramic material composition, while the end caps 252 and 254 may have a material composition including a metal (e.g., molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof), or a cermet (e.g., an alumina molybdenum cermet), or combinations thereof.
Similarly, a laser or another focused heating technique may be applied to the compliant seals 262 and 264. In certain embodiments, the dosing tube 266 has a material composition including molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof. Similarly, the electrode lead 268 may have a material composition including molybdenum, or rhenium, or tungsten, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or niobium, or combinations thereof. In contrast, the end caps 252 and 254 may have a different material composition than the dosing tube 266 and the electrode lead 268. For example, the end caps 252 and 254 may have a material composition, such as a transparent ceramic (e.g., same or different than arc envelope 260), a cermet (e.g., an alumina molybdenum cermet), or combinations thereof. In some embodiments, the end caps 252 and 254 may be formed from a metal or alloy different from the dosing tube 266 and the electrode lead 268. However, in such an embodiment, compliant seals may be disposed between the end caps 252 and 254 and the ceramic arc envelope 260. Thus, the plurality of concentric layers or sleeves 270, 272, 274, and 276 of the compliant seal 262 and the plurality of concentric layers or sleeves 282, 284, 286, and 288 of the compliant seal 264 generally have different material compositions, which provide a gradual or incremental change in properties or thermal expansion characteristics between the properties or thermal characteristics of the end caps 252 and 254 and the dosing tube 266 and electrode lead 268, respectively. The laser or other focused heating technique may be directed onto these compliant seals 262 and 264 to seal the various components together without undesirably heating the remainder of the lamp assembly 250.
A variety of material compositions are possible within the scope of the illustrated embodiment. For example, if the dosing tube 266 and the electrode lead 268 have a molybdenum-rhenium material composition and the end caps 252 and 254 have a ceramic material composition (e.g., alumina), then the layers or sleeves of the compliant seals 262 and 264 may include alumina molybdenum cermets. For example, the layers or sleeves 270/282, 272/284, 274/286, and 276/288 may material compositions including alumina and 8 percent by volume molybdenum, alumina and 22 percent by volume molybdenum, alumina and 36 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum, respectively. In addition, as discussed with regard to the embodiments disclosed above, the arc electrodes 296 and 312 may have a material composition including tungsten or molybdenum, or rhenium, or combinations thereof. Similarly, the arc tips 306 and 308 may have a material composition including tungsten, or molybdenum, or rhenium, or combinations thereof. Finally, the electrode assembly 294 may be coupled and sealed to the dosing tube 266 after inserting a desired dosing substance within the lamp assembly 250. For example, a dose may be inserted through the dosing tube 266, and then the electrode lead assembly 298 may be inserted through the dosing tube 266 and secured and sealed via the compressed or crimped portion 314 and the laser welded portion 316. For example, the dose may include mercury, sodium, indium, thallium, scandium, halides of rare earth elements such as dysprosium, holmium, thulium, and inert gases such as krypton, argon or xenon, or combinations thereof.
In certain embodiments, the arc envelope 322 has a ceramic material composition, the end cap 324 has a cermet or ceramic material composition (e.g., alumina), the dosing tube 332 has a molybdenum-rhenium alloy composition, and the electrode leads 334 and 336 have a molybdenum-rhenium alloy composition. In this particular embodiment, the compliant seals 326, 328, and 330 may include layers or sleeves having a material composition including alumina and 8 percent by volume molybdenum, alumina and 22 percent by volume molybdenum, alumina and 36 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum in the order from the end cap 324 to the respective dosing tube 332 and electrode leads 334 and 336. However, the arc envelope 322, the end cap 324, the dosing tube 332, and the electrode leads 334 and 336 may have a variety of other material compositions as discussed in detail above.
In addition, the lamp assembly 320 includes arc electrodes 362 and 364 coupled to the electrode leads 334 and 336 within the cavity between the arc envelope 322 and the end cap 324. In the illustrated embodiment, the arc electrodes 362 and 364 are inwardly angled from the electrode leads 334 and 336 to set a desired arc gap 366 between arc tips 368 and 370 disposed on the arc electrodes 362 and 364, respectively. In addition, the arc electrodes 362 and 364 have a material composition including tungsten, or molybdenum, or rhenium, or combinations thereof. The arc tips 368 and 370 have a material composition including tungsten, or molybdenum, or rhenium, or combinations thereof.
The lamp assembly 320 may be constructed by positioning the end cap 324 against the arc envelope 322, inserting the dosing tube 332 and the compliant seal 326 through an opening in the end cap 324, inserting the electrode leads 334 and 336 and the respective compliant seals 328 and 330 through additional openings in the end cap 324, and heating the entire assembly within a furnace to bond the components to one another. Alternatively, a laser or another focused heating technique may be directed toward the specific interfaces between the various components to seal the components to one another. Subsequently, a dose may be inserted into the lamp assembly 320 via the dosing tube 332, which can be subsequently sealed via mechanical compression or crimped portion 372 and/or focused heating such as a laser weld 374. Again, the dose may include mercury, sodium, indium, thallium, scandium, halides of rare earth elements such as dysprosium, holmium, thulium, and inert gases such as krypton, argon or xenon, or combinations thereof.
In the illustrated embodiment, the arc envelope 382 has a ceramic material composition (e.g., alumina), whereas the dosing tube 386 has a nonceramic or different ceramic material composition. For example, the dosing tube 386 may have a material composition including tungsten, or molybdenum, or rhenium, or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or combinations thereof. In one specific embodiment, the dosing tube 386 is formed of a molybdenum and 44 percent by volume rhenium alloy. Accordingly, the plurality of layers or sleeves 388, 390, 392, 394, and 396 of the compliant seal 384 include a variety of different materials having different properties or thermal expansion characteristics that gradually change from the arc envelope 382 to the dosing tube 386. For example, the layers or sleeves 388, 390, 392, 394, and 396 may have material compositions including alumina and 10 percent by volume molybdenum, alumina and 20 percent by volume molybdenum, alumina and 30 percent by volume molybdenum, alumina and 40 percent by volume molybdenum, and alumina and 50 percent by volume molybdenum in order from the arc envelope 382 (e.g., alumina) toward the dosing tube 386 (e.g., molybdenum-rhenium).
In addition, the illustrated lamp 420 includes corrosion protective covers 452 and 454 disposed against leading annular edges 456 and 458 of the annular recesses 436 and 448 within the arc envelope 426, respectively. The corrosion protective covers 452 and 454 have a substantially conical geometry and a material composition including tungsten, or molybdenum, or rhenium, or alumina, or yttrium-aluminum-garnet (YAG), or a molybdenum-rhenium alloy, or a tungsten-rhenium alloy, or combinations thereof. Alternatively, the corrosion protective covers 452 and 454 may have a flat or disk shaped geometry. In certain embodiments having corrosive dose materials disposed inside the lamp 420, the corrosion protective covers 452 and 454 provide additional protection against corrosion of the concentric layers or sleeves of the compliant seals 422 and 424.
As illustrated in
In the illustrated embodiment, the dosing tubes 460 and 462 are coupled to the arc envelope 426 via the compliant seals 422 and 424, followed by insertion and sealing of the arc electrode assemblies 464 and 466 within the dosing tubes 460 and 462. For example, the lamp 420 including the arc envelope 426, the compliant seals 422 and 424, the corrosion protective covers 452 and 454, and the dosing tubes 460 and 462 may be placed inside of a furnace, wherein the components are collectively heated and sealed to one another prior to sealing the arc electrode assemblies 464 and 466 and inserting a dose material within the lamp 420. In alternative embodiments, a laser or another focused heating technique may be applied to the layers or sleeves of the compliant seals 422 and 424 and the corrosion protective covers 452 and 454 to bond these components with the dosing tubes 460 and 462 and the arc envelope 426. Subsequently, the arc electrode assembly 466 may be inserted through the dosing tube 462 to the desired position of the upper tip 470, and then the dosing tube 462 is compressed or crimped and laser welded about the electrode lead assembly 478 at portions 488 and 490. However, the arc electrode assembly 464 may remain separated from the dosing tube 460 until a desired dose material can be inserted into the lamp 420, as illustrated with reference to
While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
