EP0160242A1

EP0160242A1 - Reflector lamp and lighting systems particularly suitable for architectural lighting

Info

Publication number: EP0160242A1
Application number: EP85104349A
Authority: EP
Inventors: Sriram Srikantia; Gilbert Henry Reiling
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1984-04-19
Filing date: 1985-04-10
Publication date: 1985-11-06
Also published as: CA1238936A; EP0160242B1; DE3568512D1; JPS60253140A

Abstract

An improved reflector lamp (10) particularly suitable for architectural lighting and having a color rendition substantially as that of incandescent type lamps is disclosed. The reflector lamp (10) has a compact light source (20) comprising a methal halide arc tube. Further disclosed is a lighting system having a plurality of the improved reflector lamps (10) arranged to provide overlapping beam patterns for highlighting the features of the exteriors of a building being illuminated.

Description

BACKGROUND OF THE INVENTION

This invention relates to the general field of lamps, more particularly, to an improved reflector lamp having a metal halide light source providing desired beam patterns, improved efficacy and increased life.
The continuing pursuit of improving the efficacy of lamps is of increasing importance due to the increasing cost of energy. One of the family of lamps in which the efficiency is desired to be improved is reflector lamps used for spotlighting, floodlighting, and architectural applications.
Reflector lamps having a desired beam pattern are disclosed in U.S. Reissue Patent 30,832 of F. F. LaGiusa, reissued December 22, 1981; U.S. Patents 4,420,801 of G.H. Reiling et al, and 4,420,800 of D. D. Van Horn; U. S. Patent Application Serial Numbers 377,754 of D. D. Van Horn et al, filed February 13, 1982 and 517,193, of Monoz et al, filed July 16, 1983; all of which are assigned to the same assignee as the present invention.
For such reflector lamps it is desired that the light output which is directed into a desired beam pattern be further increased. Also, the efficacy or lumens per watt of such reflector lamps are desired to be further improved.
Reflector lamps used for floodlighting, especially in architectural lighting applications, desire an intense compact light source so as to achieve an improved beam control or focusing ability. It is desired that the intensity of the light source for such reflector lamps for the architectural application be further increased. In architectural lighting, aesthetics are an important consideration. The obtainment of aesthetic effects is commonly accomplished by incandescent lighting.
Historically, the warm colors obtainable by incandescent lighting have been attractive for use for illumination of the the exteriors of certain types of stone, wooden and brick buildings. However, incandescent light sources are known to be relatively . inefficient devices and exterior architectural lighting utilizing incandescent devices had been reduced substantially especially since the public awareness of electrical energy shortage grew and the desire became apparent for the nation to conserve energy. The rapidly rising cost of electrical energy has also contributed to the reduction of exterior architectural lighting. It is desired to provide light sources more efficient than that of the incandescent source while still providing warm incandescent colors particularly beneficial to architectural lighting.
In certain forms of architectural lighting there is a desire to maintain a warm incandescent light color temperature which is particularly difficult to obtain for relatively high efficient lighting devices such as discharge lamps. The difficulty is primarily caused by the fact that increased wall temperatures of the arc tubes serving as the light source of the discharge lamps which lower the color temperature of the discharge lamps toward that of incandescent type color, result in a decreased anticipated life of the discharge lamp itself. The increased wall temperatures typically cause devitrification of fused silica walls of the arc tube which decrease the operating life of the arc tube. The present invention provides for a relatively high efficacy lighting device having an arc tube specially formulated to have a warm incandescent color without any major difficulty presented by increased wall temperatures.
The lighting sources for architectural lighting are desired to be small and compact and placed in a location where they cannot be seen. That is, the exterior of the building are desired to be illuminated with light sources which are to be hidden from view in order to not disturb the aesthetics of the surroundings of the buildings. It is desired that the size of the fixture housing the light source be small so that the placement of the fixture does not disturb the viewer or the environment. The present invention provides relatively small fixtures having contained therein the light source allowing location in such a manner as to preserve the aesthetics of the environment and inhibit unwanted distraction of the viewer.
A further consideration related to the arrangement of the light fixture is the desired beam pattern developed by the light source and the fixture. For architectural illumination, it is desired to mount the light source in the respective reflector unit in such a way that asymmetrical beam patterns are produced which allows for architectural illumination to overlap the beam patterns in order to maintain a smooth illuminance coverage as well as highlighting building features. Further, overlapping illumination allows that the loss of one lighting device does not leave a dark spot on the exterior of the building being illuminated. The present invention provides for such asymmetrical beam patterns. Further, the present invention provides relatively low wattage devices while still allowing architectural illumination having desired light levels for overlapping.
Still further, in reflector lamps used in floodlighting applications such as architectural lighting, a major contributor to the efficacy, beam pattern, and light intensity is the light source itself. If the overall efficiency of light source is increased, then such an increase improves the efficacy, beam pattern, and light intensity characteristics of reflector lamps.
In addition to the above consideration for reflector lamps, the present invention provides a fairly compact metal halide light source having an anticipated life intermediate between a compact light sources of the stage and studio lamps (100 to 500 hours) and the larger light sources for general illumination (15,000 hours). The light sources of the present invention allows its use in a compact reflector to develop narrow beam patterns, yet at the same time yielding a life suitable for architectural illumination.
Accordingly, objects of the present invention are to provide an improved reflector lamp particularly suitable for architectural lighting having: (1) improved beam control; (2) improved efficacy; (3) improved intensity; (4) a warm incandescent color; (5) a relatively long anticipated life; (6) a relatively small housing; and (7) capable of developing overlapping, smooth coverage and highlighting illumination.
These and other objects of the present invention will become more apparent by consideration of the following description of the invention.

SUMMARY OF THE INVENTION

In accordance with the present invention a reflector lamp particularly suitable for architectural lighting having improved beam control and a compact light source with improved efficacy and improved intensity is provided. The reflector lamp comprises a concave reflector, and a compact light source disposed therein. The compact light source comprises an arc tube containing an inert gas and a mercury vapor in the range of about 45 mg to about 65 mg effective to establish an A.C. operating voltage for the arc tube in the range from about 100 volts to about 150 volts. The arc tube further comprises a halide which develops a vapor during operation. The halide is selected from the group consisting of: (1) sodium iodide, scandium iodide, thorium iodide, cadmium iodide and mixtures thereof; (2) sodium iodide, scandium iodide, cadmium iodide, mixtures of the selected halide iodide, and the metal cadmium additive to the selected halide iodide and to the mixture of the halide iodides; and (3) the metal cadmium. In one embodiment the midsection of the arc tube is positioned near the focal point of the concave reflector and perpendicular to the axis of the concave reflector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a reflector lamp in accordance with the present invention.
FIG. 2 is a front view illustrating a reflector lamp of FIG. 1.
FIG. 3 illustrates the illumination of a portion of the exterior of a building by one or more reflector lamps of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a cross-sectional view of a reflector lamp 10 particularly suitable for architectural lighting and having a concave shape of a parabolic aluminized reflector (PAR) lamp of the commonly known type PAR 64.
The reflector lamp 10 has a concave reflector 12 preferably having a lens 14 mated at the front entrance of reflector 12 at a rim 16 along a plane 18. The primary purpose of lens 14 is to spread the reflected and directed light emitted by a compact light source 20 more effectively into a desired beam pattern. The lens 14 is placed to seal against the reflector rim 16 so as to protect and keep clean the reflective surfaces of the reflector 12. The sealing of the lens 14 to the rim 16 provides a clean environment for a suitable fill-gas, such as nitrogen, for which the compact light source may preferably operate within. The reflector 12 may be of a molded glass and its inner surfaces may be coated with aluminum, silver, dichroic heat-transmitting film, or other reflective material so as to provide spectral surfaces.
The opposite ends of the compact light source 20 are respectively connected to the inleads 22 and 24 of an extended mogul end prong 26 formed of a mica material, by means of inleads 28 and 30 of the light source 20. The reflective surfaces of the reflector 12 are preferably connected by appropriate means, such as a spot weld 32, which, in turn, is connected to a node 34 of serial arrangement of a capacitor Cl and diode Dl schematically shown in FIG. 1 and to be described hereinafter.
The compact light source 20 has a midsection 36 (shown in FIG. 2) which for one embodiment of'the present invention is positioned substantially at the focal point of the concave reflector 12 and perpendicular to the axis of the concave reflector 12. The compact light source 20 is shown in detail in FIG. 2 as a front view illustrating lamp 10.
The light source 20 is a double-ended arc tube comprised of a material selected from the group consisting of fused silica, mullite and alumina. The arc tube 20 designed to operate at 400 watts, has a length of about 70 mm, a width of about 18 mm and a thickness of about 1 mm.
The arc tube 20 has at opposite sealed ends a pair of main or primary discharge supporting electrodes 38 and 40. The primary electrode 38 is connected to the inlead 28 by means of an inlead 42 and a molybdenum foil portion 44. The primary discharge electrode 40 is connected to the inlead 30 by means of an inlead 46 and a molybdenum foil portion 48.
The arc tube 20 contains an inert gas, preferably argon, at a pressure in the range of about 20 torr to about 150 torr. The arc tube 20 further contains a mercury vapor in the range of 45 mg to 65 mg effective to establish an A.C. operating voltage for the arc tube in the range from about 100 volts to about 150 volts.
The arc tube 20 further comprises a halide which develops a vapor during operation. The halide is a selected group consisting of sodium iodide, scandium iodide, thorium iodide, cadmium iodide and mixtures of the selected halide iodide. The selected halide iodide and the selected halide iodide mixture may also include an excess metal such as cadmium. Still further, for one embodiment to be described, the halide is preferably selected as a compound sodium iodide including cadmium.
As discussed in the "Background" section above, it is desired to have a compact light source, such as arc tube 20, for architectural lighting that provides a warm incandescent light color temperature. As further discussed, the obtainment of an incandescent-like color for arc tube containing a metal halide, such as arc tube 20, usually requires undesired high wall temperatures of the arc tube, which, in turn, decreases the operating life of the arc tube and the lamp itself.
In the practice of the present invention the arc tube 20 provides an incandescent-like color without drastically elevating the wall temperatures of the arc tube which would lead to decreased life. This is primarily achieved by the particularly advantageous group of metal halides given above, including the compound sodium iodide, in combination with the use of cadmium which additionally lowers the color temperature nearer to incandescent. The metal halide and cadmium have typical respective percentage weight ratios of about 40 and about 1. The combination of these features not only achieves the desired color, but also increases the efficacy of the light source with only a relatively small reduction in the useful life.
Another factor of the present invention related to useful life of the lamp 10 is the A.C. operating voltage of the arc tube 20. This operating voltage is primarily determined by the amount of mercury contained in the arc tube 20. The desired operating voltage range is about 100 volts to about 150 volts. For this range the amount of mercury vapor contained in the arc tube 20, designed to operate at 400 watts, is in the range of about 45 mg to about 65 mg.
A further factor of the present invention which achieves the incandescent color of the arc tube with only a small reduction in its useful life, is the reduction of the sodium loss of the arc tube 20. High Intensity Discharge (HID) lamps, such as lamp 10 of FIG. 1, using sodium iodide as one of the constituents of the dose, such as arc tube 10 of FIG. 2, typically experiences a problem of diffusion of the sodium through the quartz envelope of the arc tube, particularly when large amounts of metallic surfaces are present near the arc tube such as shown in FIG. 2 for reflector 12. In our present invention this problem is substantially overcome by ensuring that the metal reflector 12 is electrically floating or is positively biased by the serial arrangement of the diode Dl and capacitor Cl connected in parallel with the arc tube as shown in FIG. 1. The serially arranged diode Dl and capacitor Cl having a typical value of .05 microfarads result in a substantial reduction of photoelectrons emitted from the reflective surfaces of reflector 12 which are one of the primary contributors to the sodium losses.of the arc tube 20. Experimental tests conducted in the practice of this invention showed a prevention of sodium loss which was sufficient to ensure a 2000 to 4000 anticipated life for the reflector lamp 10 of the present invention.
The lamp 10 embodying the arc tube 20 of the present invention provides an efficacy of 110 lumens per watt at a color corrected temperature (C.C.T.) of about 3500^*K which substantially lies on the black body curve. Further, the lamp 10 having the arc tube 20 operated at an A.C. voltage in the range of about 100 volts to about 150 volts provide relatively low wattage reflector lamp 10 in the range of about 80 to about 400 watts.
It should now be appreciated that the reflector lamp 10 of FIG. 1 having the improved compact light source 20 of FIG. 2 provides a warm incandescent color and a relatively long anticipated life. The relatively low wattage reflector lamp 10 comprising the compact light source 20 containing the filling and dimensions noted above, is particularly suitable for certain applications for architectural lighting related to the present-invention.
Typically in architectural lighting very high wattage lamps and associated large units are employed, which presents certain problems that are overcome by the present invention. For example, when these large units are used, it is ordinarily necessary to locate the bulky units some distance from the building being illuminated in order to avoid illuminating hot spots, which, in turn causes spillover of the illuminating light resulting in inefficient use of the light output of the high wattage lamps. With the compact lamp 10 disclosed in our invention having lower wattage light sources, such as in the 80 to 400 watt range, a number of the compact light sources housed in relatively small fixtures may be lodged close to the building being illuminated, which, in turn, improves the percentage of light from the compact light source of the present invention which is actually falling on the building being illuminated.
A further feature of the present invention which results in a particular advantage is the compact size of the reflector 12, having a configuration such as that of a PAR 64 reflector shown in FIGS. 1 and 2. The PAR 64 reflector lamp of FIGS. 1 and 2 is of a small compact size particularly when compared to the size of buildings illuminated by architectural lighting. That is, the fact that the light source 20 and the reflector 12 are arranged in one assembly 10, hermetically sealed from the deleterious elements of the atmosphere, allows the lamp 10 to be placed inconspicuously on low railings or parapets of the building being illuminated.
Another advantageous feature is the asymmetrical geometry of the metal halide light source 20 of the present invention. The asymmetrical geometry of the light source 20 forms a glowing arc which is longer than it is wide. This asymmetric geometry results in an elongated beam pattern transmitted by the reflector lamp 10 which is desirable for architectural lighting related to our invention. The elongated beam pattern of this invention, shown in Figure 3 as illuminating a portion of the exterior of a building, allows for aesthetic effects through overlapping and highlighting features of the building being illuminated.
FIG. 3 shows a portion 50 of the exterior of a building formed of limestone bricks 52 particularly suitable for the warm incandescent color of the architectural lighting of the present invention. The portion 50 shown in FIG. 3 is illuminated by a plurality of elongated, overlapping, smooth covering, highlighting, and contoured beam patterns 54A, 54_B, through 54_N transmitted from a plurality of lamps 10 inconspicuously lodged at the parapets of the building being illuminated.
The illuminating beam pattern 54A can be directed to the location of the portion 50 of the building desired to be illuminated, whereas, beam patterns 54B through 54_N can be directed to overlap beam pattern 54A so as to provide overlapping, highlighting, and contoured illumination of the building.
The advantages of using overlapping, contoured beam patterns are: (1) lamp to lamp color variations which are sometimes present in efficient metal halide sources tend to get smoothed out on the illuminated surface; (2) failure of a particular lamp is not prominently visible since it does not result in a dark area; (3) the lighting designer has great flexibility in contouring the illumination and highlighting particular features of the architecture for esthetic purposes.
It should now be appreciated that the reflector lamp 10 of the present invention having relatively small dimensions for suitable lodging in locations proximate to the building or on the building desired to be illuminated provides for overlapping, contouring and highlighting architectural features.
Still further, the practice of the present invention having the intense compact light source 20 having a relatively long anticipated life such as between 2000 to about 4000 hours may provide for indoor and outdoor floodlighting applications including sports lighting.

Claims

What we claim as new and desire to secure by Letters Patent of the United States is:
1. A reflector lamp particularly suitable for architectural lighting comprising a concave reflector having reflective surfaces, an arc tube rigidly supported in the concave reflector and having primary thermionic electrodes sealed in the opposite ends thereof, said arc tube further comprising;
an inert gas;

a mercury vapor in the range of about 45 mg to about 65 mg effective to establish an A.C. operating voltage for said arc tube in the range of from about 100 volts to about 150 volts; and,

a halide which develops a vapor during operation, said halide being selectable from the group consisting of (1) sodium iodide, scandium iodide, cadmium iodide and mixtures thereof, (2) sodium iodide, scandium iodide, cadmium iodide, mixtures of the selected halide iodide, and the metal cadmium additive to the selected halide iodide and to the mixture of the halide iodide, and (3) the metal cadmium.
2. A reflector lamp according to claim 1 wherein said arc tube is a double-ended type and has a length of about 70 mm, a width of about 18 mm and a thickness of about 1 mm.
3. A reflector lamp according to claim 1 wherein said metal halide is preferably a sodium iodide compound and the metal cadmium, said sodium iodide and said cadmium metal having respective weight ratios of about 40 to about 1.
4. A reflector lamp in accordance with claim 1 further comprising:
means for applying a positive potential to the reflective surfaces of said reflector comprising a serially arranged capacitor and diode, said capacitor having a value selected in the range from about .01 to about .1 microfarads.
5. A reflector lamp according to claim 1 wherein the midsection of said arc tube is positioned substantially at the focal point of said reflector and perpendicular to the axis of said reflector effective to provide an elongated beam pattern.
6. An illuminating lighting system comprising a plurality of reflector lamps according to claim 5 arranged effective to provide overlapping, elongated, and contoured beam patterns.