Patent Grant
10074532
The present invention relates to arc discharge lamp ignition starting aids and, more particularly to starting aids comprising an antenna outside of the arc tube.
Generally speaking, high intensity discharge (HID) arc tubes need help starting an arc between electrodes at opposed ends because typical operating voltage levels are not high enough to initiate an arc. Historically the starting method has involved supplying high voltage spikes to the lamp lead-in wires during lamp startup. The spikes or pulses are generally provided by “ignitor” circuitry/components that are usually outside the lamp jacket, typically as part of the ballast, therefor the lamp supply wiring and lamp socket connectors must be able to deliver the maximum pulse voltage without arcing.
Adjusting HID lamp design factors to increase lamp performance can make the arc harder to start, and it has become very difficult to economically and safely supply starting voltage spikes any higher than they are now (e.g., ˜3 kV superimposed on the steady state lamp supply voltage).
It is known that ignition waveform requirements such as spike/pulse peak voltage can be decreased by using starting aids such as antennas and/or UV ionization sources. Conversely this means that starting aids can enable higher performance lamp designs that start more reliably at existing peak starting voltage. This is illustrated in
For example, in HID lamps the radiant output in desired spectrum bands (e.g., PAR radiation for horticultural lamps) can be improved in various ways by increasing the cold fill pressure of xenon gas, and/or by modifying other design factors such as the arc gap, etc., however such design changes raise the starting voltage requirement. High performance HID lamps have been pushing the envelope until they are limited by starting aid capabilities, therefor an improved starting aid is needed.
A known starting aid for arc tubes made with PCA (PolyCrystalline Alumina) such as in HPS (high pressure sodium) and CMH (ceramic metal halide) lamps, is called an “antenna”, which is a wire-like conductor extending longitudinally along the arc tube (usually outside of it) between the two electrodes. It is sufficient for the antenna to bridge the arc gap with antenna ends located radially outward (above or outside) of each of the two electrodes, and may include conductive rings around the tube that are electrically connected to each antenna end. As such, this is called a “passive antenna” because it is electrically floating and can be inductively charged by the AC voltage being applied across the nearby electrodes. A preferred implementation of this is where the conductors are applied (“printed”) on the outside arc tube wall and bonded by sintering.
As shown in
Thus recent design efforts have been directed to development of a starting aid that provides the benefits of an active antenna, but avoids its problems, thus allowing design changes to further improve performance without causing starting problems. For convenience in the present disclosure, where the improved starting aid is based on an antenna, we may call it a “semi-active antenna”.
U.S. Pat. No. 8,456,087 to Steere et al. and assigned to Koninklijke Philips Electronics N.V. (the Philips '087 patent) discloses a “High-Pressure Sodium Vapor Discharge Lamp With Hybrid Antenna” comprising an HID lamp arctube wherein a printed antenna is indirectly coupled to an electrode lead to produce a “hybrid antenna”. This is described with reference to drawings such as their FIG. 4D that is reproduced herein as
Thus the “hybrid antenna” appears to be Philips' implementation of an antenna wherein the printed antenna is indirectly (capacitively and/or resistively) coupled to an electrode lead by means of an electrical conductor that is connected to, and extends from, the printed antenna to the end of the arctube and continues around the end down toward the electrode lead.
It is an objective of the work disclosed herein to develop a novel form of antenna that enables improvement of HID arc tube performance while avoiding starting problems and/or other negative effects like those described above.
A starting aid for discharge lamp arc tubes that are characterized by a tubular arc tube body wall that longitudinally extends between first and second ends and surrounds an internal arc cavity wherein corresponding first and second electrodes in the arc cavity have corresponding first and second conductive feedthroughs that sealingly extend out through the first and second ends (typically through sealing end plugs, and electrically connected to corresponding first and second external arctube leads). According to the invention, the starting aid is an antenna being an elongated (e.g., wire-like) conductor extending longitudinally on the arc tube body wall between first and second antenna ends that are located radially outward of corresponding first and second electrodes; and an antenna coupling member comprising a conductive coupling member lead that is electrically connected to the first feedthrough (e.g., arctube lead), and extends to a coupling end located on the body wall near to the first antenna end and separated therefrom by a coupling gap of predetermined, non-zero gap dimension.
In an adjacent conductor type of coupling member the coupling gap is an air gap, the coupling member is on an outside surface of the body wall, and both the coupling end and the antenna end extend circumferentially around the arctube.
Other objects, features and advantages of the invention will become apparent in light of the following detailed description, drawings, and claims.
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 and aspects of the invention(s) disclosed herein.
The invention(s) will now be described with reference to the drawings using the reference numbers and symbols listed in the above table.
The present disclosure defines an HID arctube “semi-active” antenna as being an antenna-like starting aid that behaves like an active antenna during arc tube starting, but otherwise behaves like a passive one. In a crude way, this has been done previously by placing a bimetal switch in the connection between antenna and electrode lead, but this is relatively expensive, potentially unreliable, and is very difficult to place within the outer jacket of an HID lamp, especially those in a tubular jacket, e.g., a tubular double ended (DE) lamp. As described above, at least Philips has achieved the desired behavior with their “hybrid antenna” by indirectly coupling the antenna to an electrode lead, e.g., capacitively, or possibly through a high resistance link. When the high voltage, high frequency ignition pulses of an electronic ballast are applied to the supply side of the antenna coupling, a corresponding voltage may be induced on the antenna side, thereby providing a high voltage drop across the short gap between the distal electrode and the antenna above it. Once an arc starts, the high frequency/high voltage ignition pulses stop and, like all antenna types, the antenna has no effect on the arc because the high voltage gradient has been removed. Furthermore, like a passive antenna, the hybrid antenna (and our semi-active antenna) does not cause sodium migration because the indirect coupling doesn't charge the antenna sufficiently at normal steady state operating conditions.
In the present semi-active antenna 128 development, we have designed new forms of indirect coupling (e.g., members 130, 144) to an otherwise passive antenna embodiment (e.g., antenna conductors 124, 126), and have then proceeded to determine effective design limits such as dimensions (g, c) for a coupling gap 136, 150. In particular, we have devised configurations for an air gap 136 and for a dielectric gap 150.
Referring to
It is known that radiant output such as PAR output can be increased, for example, by raising the Xe fill pressure and/or other things, but arc tubes with a passive antenna cannot be reliably started if they have more than about 300-400 Torr cold fill pressure, as shown in the test results plotted in
The above test (
A test lamp arc tube was modified to test starting reliability for different test versions of our new type of semi-active antenna. The arc tube used for the tests was the 400 Torr version of the test lamp in the
Adjacent Conductor Type of Coupling Member (130)
A first type of our semi-active antenna starting aid 128, a standard passive antenna 124, preferably with a ring form of antenna end 126 is made what we call “semi-active” by adding a novel coupling member 130 indirectly connected (coupled) to the arc tube electrode 114 by a that couples one antenna end 126 to a conductive coupling end 134 (e.g., a band/ring) of a “coupling member” 128 that encircles the arc tube such that the antenna end (in this embodiment, the antenna end ring 126, although a simple end of the antenna wire 124 may work also) is spaced apart from an edge of the coupling end 134 by a uniform antenna coupling gap 136 of dimension ‘g’. This embodiment is presented in drawings shown by
The coupling ring may be, for example, a separate metal conductor assembled on a finished arc tube as a pre-form, or a length of material that is wrapped, clamped, and/or welded in place with a suitable electrical connection. It may be moly, tungsten, tantalum and the like. The antenna is preferably printed according to known processes. As shown in
The printed wire for the coupling connector 132 wraps around the arctube end 108 to enable electrical connection to the electrode by being pressed against metal frame parts that are welded to each other and to the electrode feedthrough 116. The figures show one or more of the connector 132 extension portions 132a, 132b, and 132c that may be printed on the arctube end 108, on the inner wall 106, and on the plug outer surface 113, respectively. This may mean that the printed connector must cross a gap that may have frit 111 fused in place to seal the plug 112 to the arc tube body 102. In the
Referring first to the coupling member 130f embodiment in
It also should be noted that the end 121 of the frame 120 (i.e., the edge of the hole cutout for the feedthrough) may be close, if not touching the feedthrough 116 and this could be used to establish electrical connection and/or mechanical leverage for applying pressure on the coupling conductor 132. Similarly, if the conductor extension 132c is applied on the plug outer face 113, then its end 133 might be able to directly contact the feedthrough.
In general mechanically forced contact between conductors is used to provide direct, low resistance electrical connection of the electrode (feedthrough/lead) to the coupling member components.
In tests of semi-active antenna prototype designs, we were able to achieve starting reliability comparable to that of an active antenna. Best results for coupling across a gap 136 dimension “g” of about 0.5 mm up to and including about 1.0 mm. Reliable starting was achieved for gaps in this range, as shown by the results in
In other words, an embodiment of the inventive semi-active antenna starting aid 128 was shown to enable 500 Torr gas filling in an HPS arctube with an arc length (144 mm) that would not start reliably with the existing passive antenna starting aid. Thus the present invention enables performance enhancements by increasing fill pressure, for example, without introducing degradation that active antennas cause.
Regarding other coupling air gap 136 dimensions “g” (for the adjacent conductor type of coupling member 130):
Layered Capacitor Type of Coupling Member (144)
Preliminary parameters are:
Further testing will determine optimum dimensions for overlapped areas and for dielectric thickness that determines the coupling gap. For example, may be a thickness of about 1 mm, although this will also depend upon the type of dielectric material being used.
Although this second coupling member type 144 is primarily presented as a layered capacitive coupling, our design is intended to include the possibility of a resistive coupling wherein the “dielectric band” would have a finite, predetermined electrical resistance.
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. 62/467,935 filed Mar. 7, 2017, said application hereby incorporated in its entirety by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6051927 | Graser | Apr 2000 | A |
| 20030193292 | Hecker | Oct 2003 | A1 |
| 20110115371 | Steere | May 2011 | A1 |
| 20180114688 | Qian | Apr 2018 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 62467935 | Mar 2017 | US |
