Patent Application
20140333192
The present application relates to lighting technology, and more particularly to non-cycling high pressure arc discharge lamps.
High pressure arc discharge lamps are useful in many applications, such as industrial installations, streets, tunnels, underpasses, car parks, courtyards, parks and gardens, buildings, monuments, and bridges, to name a few. Some particularly useful applications for high pressure arc discharge lamps are in areas where it is difficult to replace lamps, due to limited accessibility, such as streets and tunnels. High pressure arc discharge lamps can have a longer life than standard lamps and greater reliability than standard lamps making them the preferred lamp in many such applications.
A long life non-cycling high pressure arc discharge lamp configuration is disclosed. In some example embodiments, a high pressure arc discharge lamp is provided that electrically combines in parallel, two non-cycling high pressure sodium discharge arc tubes within one lamp envelope, with the arc tubes having elongated cylindrical shapes and being arranged lengthwise alongside each other in a parallel fashion such that the arc tubes at least partially or completely overlap with one another. A small space is provided between the arc tubes (e.g., uniform 1-50 mm space, for instance), such that they are close but don't physically touch one another. At least one of the arc tubes is configured with an ignition aid strip, such as cermet strip, located substantially lengthwise on the exterior surface of one or both arc tubes. In one particular embodiment, both arc tubes are configured with such an ignition aid strip, and the tubes are oriented such that their respective ignition aid strips are both facing outward with respect to one another. This has the effect of reducing the thermal load that the ignition aid of the non-operating arc tube is subjected during operation, which leads to sustained ignition performance. In another embodiment, one arc tube is a non-cycling high pressure sodium discharge arc tube having an ignition strip and a second arc tube is a low-pressure arc tube with no ignition strip. Numerous other lamp configurations will be apparent in light of this disclosure.
General Overview
As previously noted, high pressure arc discharge lamps can have a longer life than standard lamps and are useful in numerous applications. By extending re-lamp schedules, a number of benefits can be realized, including lower environmental impact, reduced maintenance costs, and increased safety (reducing re-lamp events reduces the opportunity for injury during re-lamp process). Typical high pressure arc tube lamp assemblies have life cycles of approximately forty-thousand hours and employ amalgam metallic sodium and mercury doses to prevent lamp cycling behavior. An even longer life lamp would be desirable, and particularly a lamp that provides fast start-up times for initial power applications and fast start-up times after a power interruption.
Thus, and in accordance with an embodiment of the present invention, a long life non-cycling high pressure arc tube lamp is disclosed. The lamp may be configured with, for example, dual high pressure sodium arc tubes having elongated cylindrical shapes electrically connected and physically arranged in parallel with a small gap therebetween. Each elongated cylindrical arc tube has an inward facing semicylinder portion and an outward facing semicylinder portion, wherein the inward facing semicylinder portions of the arc tubes face each other and the respective outward facing semicylinder portions are opposite-facing. In one particular such example embodiment, each of the arc tubes is configured with an ignition aid strip running lengthwise on the arc tube and disposed somewhere on the outward facing semicylinder portion of the respective arc tube. In this sense, the arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−90 degrees away from each other.
By combining two or more arc tubes in one lamp envelope, the lamp will effectively have double the life expectancy or more, depending on the arc tube configuration, as compared to a single arc tube construction. When one arc tube fails, any of the remaining arc tubes within the lamp envelope can then become the operative arc tube, given the nature of the electrically parallel configuration and arc tube turn-on characteristics (ignition performance), thereby extending the life of that particular lamp. In addition, having opposite-facing ignition strips as described herein can be used to further extend the life of the lamp by minimizing the thermal load during operation which leads to sustained ignition performance of any arc tube within that lamp envelope.
In alternative arrangements, the respective ignition aid strips need not be 180 degrees+/−90 degrees away from each other. However, in such configurations, the life of the lamp may generally be shorter than a configuration where the respective ignition aid strips are 180 degrees+/−90 degrees away from each other. It is believed that the thermal load management is improved in such a configuration, thereby allowing for longer lamp life. In more detail, during initial power up of a multiple arc tube lamp configuration as described herein, the arc tube with the lowest breakdown voltage lights first. A number of variables affect the breakdown voltage, such as contamination during arc tube assembly, resulting in higher breakdown voltages (such contamination being generally acceptable). Arc tubes having an ignition aid generally have lower breakdown voltages than arc tubes without. Cycled thermal exposure of the ignition aid, such as a cermet strip, on a non-operating arc tube, located with the non-operating arc tube cermet strip facing toward the operating arc tube, leads to conductivity changes in the ignition aid strip of the non-operating arc tube which leads to higher breakdown voltages for that arc tube. Thus, if the ignition aid strips face each other, breakdown voltages become higher over time. This thermal exposure can be minimized or otherwise reduced by locating the ignition aid such that it is facing away from the operating arc tube, as variously discussed herein, so as to achieve sustained lower breakdown voltages. In still other example embodiments, only one of the arc tubes within the lamp envelope is configured with an ignition aid strip. In one such specific example embodiment, the arc tube configured with the ignition aid strip is a non-cycling high pressure sodium discharge arc tube and the other arc tube can be, for example, a low-pressure arc tube.
The ignition aid strip can be implemented as typically done or using any suitable custom or proprietary process and materials. For instance, in some cases the ignition strip can be applied as a tungsten-containing paste (e.g., pure tungsten or a tungsten/alumina cermet) to the outside of the arc tube prior to sintering the arc tube to translucency. The arc tube can be any number of suitable materials such as polycrystalline alumina (PCA) or other suitable ceramic material. In some cases, the thermal expansion coefficient of the ignition aid material is closely matched to that of the arc tube so as to inhibit cracking of the strip (e.g., so that thermal expansion coefficients are within 10% of each other) For example, in one specific such example case, the ignition aids can be implemented with a conductive refractory metal nitride strip (e.g., titanium nitride or zirconium nitride) applied directly to the surface of a PCA arc tube. The metal nitride strip may be applied by any suitable means (e.g., aerosol spraying, ink pen, inkjet, or vapor deposition), and can then be sintered with the ceramic arc tube to bond it to the are tube surface. In some cases, the metal nitride ignition aid material can be mixed with a ceramic material (e.g., aluminum oxide or aluminum oxynitride).
As will be further appreciated in light of this disclosure, the techniques are particularly useful for non-cycling high pressure sodium lamp configurations. In one specific example non-cycling arc tube configuration, for instance, the arc tubes are filled with an amalgam of mercury and sodium at a suitable ratio along with xenon gas. In addition, a dual arc tube configuration can be used to perform fast re-strike during power interruption. For instance, in operation, only one arc tube is operating at a time. The second non-operating arc tube remains at a lower pressure allowing it to strike and warm-up quickly should a power interruption occur. After a power interruption event, the previously operating arc tube must cool down before starting again, but the second previously non-operating arc tube strikes and warms up almost immediately. Additionally, a lamp constructed with non-cycling arc tubes generally has a very low total mercury content making it TCLP-compliant (Toxicity Characteristics Leaching Procedure) and environmentally friendly. Numerous variations and configurations will be apparent in light of this disclosure.
In accordance with another example embodiment, multiple arc tube pairs are arranged within a given lamp envelope, wherein the pairs can be arranged in a collinear fashion. In such an embodiment, shadowing effects may be reduced by the collinear arrangement and the product life can be even further extended by having multiple arc tube pairs. In still another embodiment, alternative ignition aids can be used such as helical wires, non-linear capacitors, UV globottles, and other non-cermet based methods can be employed to minimize the thermal effects of a multiple arc tube assembly.
Lamp Architecture
In addition, this example embodiment includes an amalgam of metallic sodium and mercury 140 inside both arc tubes 100 and 105, so as to provide non-cycling high pressure sodium lamp. Each arc tube 100 and 105 of this example configuration includes an ignition aid strip 110 and 115, respectively, wherein each strip 110 and 115 runs lengthwise down its corresponding arc tube. In the embodiment shown, the arc tubes 100 and 105 are oriented so that ignition aid strips 110 and 115 face away from each other. Example orientations of the ignition strips will be discussed with further reference to
As can be further seen with respect to
As can be seen with respect to the example embodiment of
Note that the ignition aid strips 110 and 115 need not be located such that they are opposite-facing in a perfectly symmetrical fashion (e.g., such as the case where both strips are located at 180 degrees, or the case where one strip is located at 90 degrees and the other strip is located at 270 degrees). In a more general sense, the ignition aid strips can be located anywhere within the ignition aid location range, which happens to correspond to the outward facing semicylinder portion of each arc tube in this example case. Maximizing the distance of a given strip from the opposing arc tube can be beneficial, as will be appreciated in light of this disclosure. Further note that while straight ignition aid strips are shown, they may also be implemented in other shapes such as a sine wave shape, triangle wave shape, square wave shape, irregular line shape, or any other desired shape. The thickness of the ignition aid strip 110 and 115 may be uniform, but need not be, and may include any number of thickness variations and patterns along the length of the strip. Note in such alternative strip configurations, the strip may meander anywhere within the given ignition aid location range, such as from 180 degrees+/−90 degrees in a linear or non-linear fashion.
As can be seen with respect to the example embodiment of
Multiple Arc Tube Pairs
Comparative Data
As can be seen from
Numerous variations will be apparent in light of this disclosure. For instance, the example topologies depicted in
Numerous embodiments and configurations will be apparent in light of this disclosure. For example, one example embodiment provides a lamp. The lamp includes a first non-cycling high pressure arc tube having a first ignition aid, and a second arc tube electrically connected in parallel to the first arc tube. The lamp further includes a lamp envelope enveloping the first and second arc tubes. Each of the first and second arc tubes has an inward facing semicylinder portion and an outward facing semicylinder portion, wherein the inward facing semicylinder portions of the arc tubes face each other and the outward facing semicylinder portions are opposite-facing. In some cases, each of the first and second arc tubes is a non-cycling high pressure sodium arc tube. In one such case, the second arc tube is configured with a second ignition aid. In one such case, each of the first and second ignition aids is configured as an ignition aid strip running lengthwise down the corresponding arc tube. In one such case, each of the first and second ignition aid strips is disposed on the outward facing semicylinder portion of the corresponding arc tube. In another such case, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−90 degrees away from each other. In another such case, each of the first and second ignition aid strips is a cermet strip comprising tungsten. In some cases, the lamp further includes a frame electrically connected to the first and second arc tubes and enveloped by the envelope, a stem electrically connected to the first and second arc tubes and electrically connected to the frame, and a base electrically connected to the stem and operatively connected to the envelope. In some cases, the second arc tube is a low-pressure arc tube.
Another example embodiment of the present invention provides a high pressure discharge lamp. The lamp includes a first non-cycling high pressure sodium arc tube having a first ignition aid strip running lengthwise down the first arc tube, and a second non-cycling high pressure sodium arc tube having a second ignition aid strip running lengthwise down the second arc tube. The lamp further includes a lamp envelope enveloping the first and second arc tubes. Each of the first and second arc tubes has an inward facing semicylinder portion and an outward facing semicylinder portion, wherein the inward facing semicylinder portions of the arc tubes face each other and the outward facing semicylinder portions are opposite-facing. In addition, each of the first and second ignition aid strips is disposed on the outward facing semicylinder portion of the corresponding arc tube. In some embodiments, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−45 degrees away from each other. In some embodiments, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−35 degrees away from each other. In some embodiments, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−25 degrees away from each other. In some embodiments, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−15 degrees away from each other. In some embodiments, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−5 degrees away from each other. In some embodiments, the lamp includes a frame electrically connected to the first and second arc tubes and enveloped by the envelope, a stem electrically connected to the first and second arc tubes and electrically connected to the frame, and a base electrically connected to the stem and operatively connected to the envelope.
Another example embodiment of the present invention provides a lamp assembly method. The method includes providing a first non-cycling high pressure sodium arc tube having a first ignition aid strip running lengthwise down the first arc tube, and providing a second non-cycling high pressure sodium arc tube having a second ignition aid strip running lengthwise down the second arc tube. The method further includes providing a lamp envelope enveloping the first and second arc tubes. In some cases, each of the first and second arc tubes has an inward facing semicylinder portion and an outward facing semicylinder portion, wherein the inward facing semicylinder portions of the arc tubes face each other and the outward facing semicylinder portions are opposite-facing, and the method further includes orienting each of first and second arc tubes so that the first and second ignition aid strips are on the outward facing semicylinder portion of the corresponding arc tube. In some cases, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−90 degrees away from each other. In some cases, the first and second arc tubes are oriented such that their respective ignition aid strips are effectively 180 degrees+/−5 degrees away from each other.
The foregoing descriptions of the embodiments of the invention have been presented for the purposes of illustration and description and are not intended to be drawn to scale. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.
