Illumination – Plural light sources – With modifier
Reexamination Certificate
1999-11-09
2001-01-09
Husar, Stephen (Department: 2875)
Illumination
Plural light sources
With modifier
C362S304000, C362S346000, C362S347000, C362S260000
Reexamination Certificate
active
06170962
ABSTRACT:
REFERENCES
1. U.S. Pat. No. 4,089,047 “Trifocal Mirror-Reflector” to Luderitz, May 9, 1978
2. U.S. Pat. No. 4,683,526 “Asymmetric Lamp” to Krogsrad and Jul. 28, 1987
3. U.S. Pat. No. 4,868,727 “Light Fixture With Integral Reflector and Socket Shield” to Ponds and Calloway, Sep. 19, 1989
4. U.S. Pat. No. 4,295,186 “Slit Illuminating Device” Sugiura, Muneharu; Sagara, Seiji, Oct. 13, 1981
5. U.S. Pat. No. 3,492,474 “Reflector With Compound Curvature Reflecting Surface” Yamaguchi, Seiichi; Hishinuma, Satoshi, Jan. 27, 1970
6. Illumination Engineer's Association Handbook
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is an article of manufacture and relates to reflectors, specifically, to a symmetrical reflector in the cross-sectional shape using two hyperbolas and fluorescent light fixtures utilizing such a reflector.
2. Description of Related Art
Other patents have taught how to use reflectors on light fixtures that have a cross-sectional shape generally hyperbolic, generally elliptic, or generally parabolic. For example, Reference 1 uses reflectors with elliptical cross-sections with the feature of one set of foci of the ellipses being coincident and with the other foci located at the ceiling level. These incandescent light fixtures use only reflected light with the embodiment designed such that all direct light coming from the light source is blocked. This patent would restrict the fixture to something small in diameter in order to meet the requirement of having one set of foci coincident. Having all direct light blocked seriously limits the efficiency of the lamp. A hyperbolic reflection surface is added to the lamp in another embodiment that is described, however, no diagram of the configuration is provided and the juxtaposition of the light source and the focus of the hyperbola is not taught.
Reference 2 claims a desk lamp with a reflector in the shape of a parabola formed from a series of triangular facets. This patent claims a method to approximately construct at reasonable cost, a curved reflection surface to improve the light delivery from the lamp.
Reference 3 claims a reflector, curvilinear in cross-sectional shape, and having tabs formed from part of the reflector surface for the purpose of socket protectors. The relative location of the light bulb to the reflector is not taught. Many other necessary features to define the embodiment of the reflector, such as the position of the light bulb relative to the focus of a conic section, is not taught. This embodiment utilizes a 300-watt light bulb, and therefore is not designed for energy savings but as a security lighting fixture.
Reference 4 is a lighting device having a plurality of linear surface mirrors, each partially surrounding a single light source. The reflector approximates an elliptical-shaped reflector. Its purpose is for use in a reproduction machine.
Reference 5 is a three-dimensional concavo-convex reflector for use as a headlamp on an automobile. At least part of the three-dimensional surface is formed having a hyperbolic curvature in the horizontal plane. It has a single light source. No attempt is made to provide energy savings.
Although there are a number of fluorescent light fixtures on the market, few seem to utilize the direct light and reflected light coming from the light source to full advantage. Reflection surfaces are painted milky white that has a medium reflectance. Some reflectors are being made on special order to retrofit existing light fixtures, reduce the number of fluorescent tubes, and thus improve the light efficiency and energy utilization. These retrofit reflectors are fabricated by bending them into rectangular facets thus approximating a parabola in cross-sectional shape. A highly reflective material, such as Silverlux by 3M Company applied to the surface of a thin aluminum sheet, is being used as the material for these reflectors. Since a parabolic reflector directs the light straight downward, the area of illumination between the rows of fixtures is lit only by direct light and receives very little of the reflected light. These installations tend to have a bright area under the fixture and a shadowy, dark area half way between fixtures. This non-uniform distribution of light is objectionable.
Generally, fluorescent light fixtures, which are designed to provide illumination for an area, should:
a. Provide an adequate level of illumination.
b. Uniformly illuminate the area.
c. Minimize the formation of shadows.
d. Provide light agreeable for human activity.
e. Minimize the use of energy while providing an adequate level of illumination.
None of the above mentioned embodiments meet all five of these criteria. Accordingly, there is a need for new, optimized, efficient fluorescent light fixtures that will provide uniform light patterns coupled with an adequate level of illumination, and providing substantial energy savings. They must be suitable for use in new building construction or retrofit to existing structures, for illumination of art works or advertising signs, and for use in homes, stores, and offices.
OBJECTS AND ADVANTAGES
Modern civilization has moved indoors and functions around the clock. Thus, there is a need for low cost lighting in buildings, offices, warehouses, barns, museums, homes, and where ever there is human activity. Electrical rates continue to slowly rise and, as a strategy to cope with these rate increases, conservation is one approach. Because much human activity takes place indoors under artificial light, the light level must be high enough so quality work can be conducted, sporting events well lit, and kitchen areas adequately lit for food preparation. Shadows produced by point sources of light are a nuisance. Similarly, uneven lighting in work areas creates eyestrain. Uneven lighting of advertising displays sacrifices impact. Light and dark areas on paintings or tapestries on exhibit in art museums detracts from the presentation of such artistic works.
Approximately 80% of what human beings learn comes through the sense of sight. Human beings see objects by reflected light. Therefore, it is important that human factors of illumination in a room, office, or other work place, be bright, have good color rendition, and exhibit a character and quality which is most pleasing and agreeable.
Accordingly, it is an object of this invention to provide an occupied area with fluorescent light fixtures which provide an adequate level of illumination while substantially saving energy compared to existing light fixtures. In addition, another object of this invention is to minimize or eliminate shadows and to provide an illuminated area that is lighted in a uniform manner. It is a further object of this invention to provide illumination to an area by light fixtures projecting light that has a most pleasing character and quality.
BRIEF SUMMARY OF THE INVENTION
The law of reflection is the essential physical principle upon which this invention is based. It states:
When an energy wave incident upon a flat or curved surface is reflected, the angles of incidence and of reflection are equal and lie in the same plane.
Various materials and types of surfaces reflect light at a different reflectance. A diffuse surface can reflect 10% to 60% of incident light while a specular surface can reflect 80% to 95% of the incident light. Since high efficiency is desired to achieve energy savings, the surface finish chosen for the reflector is specular. Polished aluminum, polished stainless steel, and a plastic laminate called Silverlux by 3M Company all qualify as possible candidates for reflector surfaces. Material selection for the reflector surface is not limited to this list of materials, others surely also qualify.
A second ingredient needed is the shape of the reflector. The classic shape used in the past for light fixtures with reflectors has been the parabola that is know to reflect the light downward. For this current invention, a hyperbola in a 2-dimensional shape is selected for the reflector. Reference 6 shows the general principle of the use of a hy
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