US 3749968 A
A lighting system is disclosed utilizing an improved lamp including an exterior glass envelope which is affixed to a terminal fastener, and which contains an arc tube (for providing a high intensity discharge) as well as a filament (for use in a system furnishing auxiliary incandescent illumination). The arc tube incorporates starting and primary discharge electrodes. A limiting resistor is also contained in the envelope, serially connected with the starting electrode. As disclosed, the lamp is incorporated in a system such that the incandescent filament furnishes illumination indepdendent of the arc tube. For further control, a heat-operated switch may be incorporated.
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Description (OCR text may contain errors)
nited States atent [1 1 Jones et a].
[451 July 31,1973
[ INCANDESCENT-HIGII INTENSITY DISCHARGE LAMP LIGHTING SYSTEM  Assignee: Smoot-Holman Company,
 Filed: Nov. 30, 1971  Appl. No.: 203,189
Related US. Application Data  Continuation-impart of Ser. No. 148,375, June 1,
 11.8. CI 315/95, 313/198, 315/62  Int. Cl. 1105b 39/00  Field of Search 313/198, 184, 25; 315/62, 58, 95
 References Cited UNITED STATES PATENTS 3,445,719 5/1969 Thovret et al.t 315/49 3/1959 Macksoud 313/198 4/1948 Keiser et al 315/280 Primary Examiner-Nathan Kaufman Attorney-Charles E. Wills ABSTRACT A lighting system is disclosed utilizing an improved lamp including an exterior glass envelope which is affixed to a terminal fastener, and which contains an arc tube (for providing a high intensity discharge) as well as a filament (for use in a system furnishing auxiliary incandescent illumination). The are tube incorporates starting and primary discharge electrodes. A limiting resistor is also contained in the envelope, serially connected with the starting electrode. As disclosed, the lamp is incorporated in a system such that the incandescent filament furnishes illumination indepdendent of the arc tube. For further control, a heat-operated switch may be incorporated.
7 Claims, 3 Drawing Figures BACKGROUND AND SUMMARY OF THE INVENTION Y This is a continuation-in-part of currently pending U. S. Pat. Application Ser. No. 148,375, entitled Lighting System Utilizing High Intensity Discharge Lamps and filed June 1, 1971.
High intensity lamps, e.g. gaseous discharge lamps as mercury vapor units, have long been employed in view of their relatively high efficiency. However, such lamps have certain characteristics which present problems in certain applications. First, when gas discharge lamps are initially energized, a warming period of several minutes is required before any substantial illumination is provided. Second, if for any reason an operating high intensity discharge lamp is momentarily deenergized (as by a power failure) a recovery period is required before the lamp is again functionally operative. As a result of these characteristics of high intensity discharge lamps, it has been previously proposed to incorporate such lamps in combination with other lamps, e.g. incandescent or fluorescent units, in a system wherein operation of the two types of lamps is supplementary. Such a system is disclosed in the above-referenced parent case.
Although systems utilizing high intensity discharge lamps in combination with other units presently appear to be quite promising, certain difficulties have been dis covered. Specifically, for example, optimum operation of such systems requires rather precise selection of the separate incandescent and high intensity discharge units. Also, after designing and installing such a selection, there is always a danger of an inappropriate replacement which may cause substantial difficulty.
Another difficulty of prior systems relates to the inherent spaced-apart and independent nature of the gas discharge and incandescent lamps. For example, under certain circumstances it may be desirable to utilize the heat from one of the units in relationship to operation of the other. However, the physically separate nature of the units imposes restrictions in that regard.
Typically, high intensity discharge lamps include an arc tube which may, for example, contain an inert gas and a small amount of pure mercury. The arc tube may be made of fused quartz and may be contained within a glass-bulb envelope. In such a lamp, two primary discharge electrodes enter opposite ends of the arc tube and a small starting electrode is placed at one end of the tube and connected to the primary discharge electrode at the other end. A limiting resistor for the starting electrode may also be incorporated in the lamp and contained within the outer bulb or envelope. It may, therefore, be seen that high intensity discharge lamps are relatively expensive to manufacture and, accordingly, economies related thereto are quite significant.
In general, the present invention is based upon the discovery that a substantial improvement may be accomplished in high intensity discahrge lighting systems, by incorporating an incandescent filament within the enclosure of a high intensity discharge lamp. Specifically, economy, safety and improved operation are all afforded as a result of such structure. The incandescent filament may be appropriately designed to the components of the high intensity discharge lamp and the heat from the separate lamp components may be utilized, as
for starting the high intensity discharge under extremely cold conditions and for controlling the energization of the incandescent filament. In an operating system, the high intensity discharge lamp incorporates the incandescent filament, of somewhat critical size, to operate an approximately one-half the normal opencircuit voltage of the ballast secondary energizing the arc tube, so as to provide an output appropriate to the arc tube as well as the ballast configuration.
BRIEF DESCRIPTION OF THE DRAWING In the drawing, which constitutes a part of this specification, an exemplary embodiment exhibiting various objectives and features hereof is set forth, specifically:
FIG. 1 is a perspective and diagrammatic view of a lamp constructed in accordance with the present invention;
FIG. 2 is a circuit diagram of the lamp of FIG. 1 incorporated with an energizing circuit; and
FIG. 3 is a fragmentary view of the structure of FIG. 2, illustrating an alternative embodiment.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT Referring initially to FIG. 1, the exterior of the lamp or bulb is provided by a terminal base 10 and a glass envelope 12. The base 10 may be constructed in accordance with conventional techniques and incorporates an externally-threaded cylindrical section 14 which receives the envelope 12 in sealed relationship. In accordance with convention, the terminal base 10 functions not only as a mechanical fastener but additionally to provide electrical terminal contacts. Remote from the envelope 12, the section 14 terminates at an end defining a central tip contact 16 and concentric ring contact 18. The contacts 16 and 18 are physically and electrically isolated from each other and from the section 14.
The glass envelope 12 is evacuated and contains an arc tube 20 and an incandescent filament 22. The are tube 20 may be formed of fused quartz to define an interior space 24 in which a high intensity electrical discharge is established. The contents of the space 24 may vary; however, in an exemplary embodiment mercury is provided in an environment of argon gas. The space 24 is also penetrated by opposed primary discharge electrodes 26 and 28 and a smaller starting electrode 30. Each of the electrodes 26, 28 and 30 is sealed within the arc tube 20 as with a metal-to-glass seal.
The discharge electrode 26, in the arc tube 20, is connected to the pin contact 16 (base 10) and to the incandescent filament 22 through support wire 34. The discharge electrode 28 is connected through a wire 36 to the threaded contact section 14 of the base 10 and through a resistor 38 to the starting electrode 30. Finally, support wire 40 is connected between the contact 18 and the filament 22.
In the illustrative embodiment, the filament 22 consists of a single loop of incandescent wire supported at opposed locations by the wires 34 and 40 and which has a wattage of less than one eighth of the arc tube 20. Of course, numerous arrangements may be employed for supporting the incandescent filament 22 and a variety of different filaments might also be utilized as defined above. Consequently, emphasis is laid to the fact that the structure as disclosed in FIG. 1 is merely illustrative andmay be subjected to widespread variation, not only with regard to the interior contents of the envelope 12, but as to the configuration and nature of the entire structure as well.
For operation, the lamp as depicted in FIG. 1 is connected in an energizing circuit as illustratively represented in FIG. 2. Specifically, the lamp of FIG. 1 is represented schematically as lamp 44 in FIG. 2 in which component elements bear reference numerals similar to those identified above with reference to FIG. 1. The terminal contacts of the lamp 44 are designated 14a, 16a and 18a in association with the physical component elements l4, l6 and 18 as identified with reference to FIG. 1. I
The lamp 44 is energized with a standard or conventional ballast, by a source of alternating current that is to be applied across the terminals 46 (extreme left) through a ballast circuit or network 48 as generally indicated. The terminals 46 are connected through conductors 50 and 52 to the ends of a winding 54. A tap 56, located substantially at the center of the winding 54, is connected through a winding 58 and a capacitor 60 to the terminal 16a of the lamp 44. The lamp terminal 14a is returned to the winding 54 at a common point with the conductor 52. Another tap 64 on the winding 54 is connected directly to the lamp terminal 18a.
In the operation of the system as depicted in FIG. 2, with the initial application of alternating-current power across the terminals 46, a current is established through the winding 54 which constitutes an autotransformer with the inductively-coupled winding 58. Accordingly, a potential is developed through the capacitor 60 across the arc tube 20 and specifically between the discharge electrodes 26 and 28. As indicated, the starting electrode 30 is connected to the discharge electrode 28 through a resistor 38, therefore, an applied potential exists between the discharge electrode 26 and the start ing electrode 30. As a consequence, a glow discharge is established between the discharge electrode 26 and the starting electrode 30. For example, in one installation, an applied potential across the terminals 46 of 120 volts results in a potential across the electrodes 26 and 30 of approximately volts.
The glow discharge between the electrodes 26 and 30 ionizes gas within the arc tube while the resistor 38 limits the current to a few milliamperes. Gradually, as the glow discharge continues, the ionized gas, e.g. argon, within the arc tube 20 diffuses within the arc tube reducing the resistance between the primary discharge electrodes 26 and 28. When the resistance is sufficiently low, an arc strikes between the discharge electrodes 26 and 28, and the heat from the arc vaporizes the droplets of mercury establishing the high-intensity discharge to provide the desired light.
In the functioning mode (are operating), a substantial potential drop exists across the discharge electrodes 26 and 28, e.g. 135 volts in the example considered above. Of course, the potential across the discharge electrodes 26 and 28 will be even greater in the event of a power failure, for example, which extinguishes the are leaving conditions such that the glow discharge may not be established. That is, during recovery intervals when neither the arc nor the glow discharge is carrying current, the potential across the discharge electrodes 26 and 28 may approximate 240 volts using the exemplary values employed above.
From the above consideration, it may be seen that various voltage drops may appear across the discharge lamp or are tube 20 depending upon the state or mode, accommodated by the ballast network 48. In that regard, the autotransformer incorporating the winding 54 limits the flow of current and also affords an elevated potential to strike the arc in the arc tube 20. Generally, various configurations for ballast networks are well known in the prior art and are disclosed in the reference identified above.
The incandescent filament in the lamp 44 is referenced to a potential appearing at the tap 64 which is somewhat intermediate to the extreme potentials developed across the arc tube 20. For example, the tap 64 may provide a potential of approximately one-half the open circuit restrike voltage drop across the arc tube 20, e.g. volts. The provision of such a reference potential to the filament 22 (referenced to the potential of the discharge electrode 26) accomplishes an effective and efficient system in maintaining continuous illumination. That is, the system will effectively provide continuous illumination; however, at a reduced potential across the filament 22 when the arc tube 20 is operating to provide full illumination.
Pursuing the exemplary voltages considered to some extent above, during the initial starting or warmup interval for the arc tube 20, when the potential across the tube is some 10 volts, the potential across the filament 22 will be approximately 115 volts. Consequently, although the arc tube 20 is ineffective during such interval, the filament 22 is operating at an effective, fullpower level. After the arc is established in the arc tube 20, the potential across the tube 20 may raise to some volts, resulting in a drop in potential across the filament 22 of some 85 volts.
In some instances it may be desired to provide further control, whereby the filament is not continually energized. In that regard, a heat-operative switch 55 may be provided as illustrated in FIG. 3. Specifically, the switch 55 provides a closed circuit below predetermined temperatures; however, when the predetermined temperature is attained, the switch 55 opens. Accordingly, when the arc tube 20 is ignited, the heat therefrom is sufficient to raise and maintain the temperature to actuate the switch 55 thereby opening the cirucit through the filament 22 to inhibit any current therethrough.
In the event of a power failure or other cause extinguishing the are within the tube 20, a recovery period is initiated during which neither the arc discharge nor a glow discharge exists within the tube 20. During such an interval, some cooling will be necessary prior to reclosure of the switch 55 to energize the filament 22. However, design parameters may be provided to close the switch 55 well prior to the time when the arc is reestablished in the tube 20.
In view of the above, it may be seen that the lamp 44 is capable of providing a substantially continuous light source utilizing the benefits and efficiency of high intensity discharge lamps during stable operation supplemented by the reliability of incandescent lamps. The combination lamp affords economy as well as control parameters that may be employed for controlling elements, e.g. switch 55. Additionally, the lamp 44 is safe with regard to replacements in that the single unit avoids the necessity of balanced independent units. Various other features and advantages of the lamp 44 as well as the combination system will be apparent to those skilled in the art. Similarly, variations of the illustrative embodiment will be similarly apparent. Accordingly, the scope hereof is to be as set forth in the claims as follows.
What is claimed is:
1. A high-intensity lamp comprising: 5
are tube means defining a light-transmissive closure for supporting an illuminating gaseous discharge;
first and second discharge electrodes affixed in spaced-apart relationship within said are tube means;
a starting electrode means affixed in said arc tube means in glow-discharge relationship with one of said discharge electrodes for initiating an illuminating discharge between said discharge electrodes;
a light-transmissive envelope enclosing said are tube means;
connection means for providing first and second terminal contacts exterior of said envelope for connection to said electrodes;
an incandescent filament means affixed in said envelope and connected in cooperative relationship with one of said electrodes;
a third terminal contact external of said envelope,
connected to said incandescent filament means whereby said filament means is energized separately from said arc tube.
2. A high-intensity lamp according to claim 1 further including a resistance connected in series relationship with said starting electrode, and positioned inside said envelope means.
3. A high-intensity lamp according to claim 1 further including a heat-operated switch means positioned in heat-transfer relationship to said are tube means and connected in series relationship with said incandescent filament means.
4. A high-intensity lamp according to claim ll wherein said incandescent filament is of a wattage of less than one eighth of that of said discharge electrodes.
5. A high-intensity lamp according to claim I wherein one of said terminal contacts comprises a fastener terminal means.
6. A high-intensity lamp according to claim I wherein said are tube means enclosing said electrodes is composed of quartz.
7. A high-intensity lamp according to claim 1 incorporated in a system comprising:
a ballast circuit for connecting said gaseous discharge lamp to a source of power and limiting the flow of current therethrough;
means for providing a base level potential somewhat intermediate the extreme potential levels occurring across said discharge electrodes; and
means for connecting said incandescent resistance wire means to be energized by the potential devel oped across said discharge electrodes by said ballast circuit, referenced to said base level potential.
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