Electric lamp and discharge devices – With optical device or special ray transmissive envelope – Polarizer or special ray transmission
Reexamination Certificate
1997-08-28
2001-07-31
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With optical device or special ray transmissive envelope
Polarizer or special ray transmission
C313S578000, C313S580000, C313S635000
Reexamination Certificate
active
06268685
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of Invention
This invention introduces techniques to improve the efficacy and color rendering of electric lamps. Our invention utilizes the advantageous properties of: (1) candoluminescent materials, (2) high temperature low thermal capacity insulating materials, (3) discriminative reflective filters, and (4) integration of items 1 through 3 into a cooperative, co-generating arrangement using non-precise energy concentrating shapes for the form of the discriminative reflective filter. A secondary aspect of this patent is an improved efficacy for linear polarized light.
B. Description of Related Art
Some prior art provides a candoluminescent coating for an incandescent filament. Other prior art replaces the metal tungsten incandescent filament with resistive carbon doped candoluminescent material filament that heats to luminescence when an electrical current is applied. The candoluminescent filaments are lower temperature visible light generating sources that generate light via luminescence rather then black body radiation as utilized in the prior art tungsten incandescent filament designs.
Some prior art in the tungsten incandescent filament designs improves efficacy by increasing the temperature of the tungsten incandescent filament. The tungsten filament shifts its output spectrum toward the visible as the temperature is increased in accordance with the physics of blackbody radiation rules. Increasing the tungsten filament temperature is achieved by making the filament thinner. Typical operating temperature of a 75-100 watt tungsten incandescent filament is approximately 2550° C.
Other efficacy improvements utilizing discriminative reflective filters are described in the prior art, and applied in cases where the geometry fits the stringent focusing requirements. These designs provide a reflective discriminative filter, which allows the desirable wavelengths to transmit through the filter. The reflected wasted energy is precisely focused onto the tungsten incandescent filament, which allows energy recycling and light regeneration. Nearly ninety percent of the energy is wasted to IR radiation in the conventional incandescent tungsten filament design; therefore, energy recycling using the discriminative filters offer potentially a great energy saving.
The reflective discriminative filter prior art describes improvements to the design in several areas. These include: (1) filter's transmission efficiency for the desirable wavelengths, (2) filter's reflection efficiency for the undesirable wavelengths, (3) filter temperature survivability and, (4) identification of optically accurate shapes for the reflective filter substrate such as ellipsoidal, spherical, cylindrical or lens shaped in order to accurately focus the reflected energy onto the small area provided by the incandescent filament. Pertinent prior art designs are identified and discussed in the next section.
1. Prior Art and Disadvantages
The Prior art discussion below is grouped into the categories of: candoluminescent electric lamp designs, candoluminescent material selection, low thermal capacity structures and reflective discriminative filter designs.
a) Prior Art for Candoluminescent Electric Lamps
Two patents suggest use of candoluminescent materials as a replacement for the metal tungsten filament.
Use of candoluminescent material as an incandescent light source is suggested as a porous coating material on an incandescent filament. U.S. Pat. No. 4,539,505, by Riseberg; Leslie A. and entitled “Candoluminescent Electric Lamp Source,” describes an electric lamp with a filament coated with candoluminescent material. The filament has a resistive core, which is heated electrically. Infrared radiation emitted by the resistive core is converted to visible light by a sheath of candoluminescent material surrounding the resistive core. The filament may be a sintered composition of carbon, ceric oxide and thorium dioxide.
U.S. Pat. No. 4,016,446 by Cadoff; Laurence H. entitled “Refractory-oxide-Based Incandescible Radiators and Method of Making” describes a design to make photo-luminescent semi-conductive element that replaces the tungsten incandescent filament in electric lamps. The filament includes a thin oxide coating, selected to improve the visible radiation emission by luminescence.
There are several design disadvantages of U.S. Pat. No. 4,539,505 and U.S. Pat. No. 4,539,505. (1) The coated incandescent filament design does not improve on usage of reflective filters to regenerate the wasted energy because the target filament remains a small target requiring accurate focusing of the reflected radiation. (2) If the temperature of the filament is too hot, thermal quenching occurs which causes the luminescent material to shift its output luminescence into infrared wavelength versus the desirable visible light. The filament then becomes a blackbody light generation unit, losing all advantages of the potential lower temperature luminescence phenomena. (3) The output spectrum of a luminescent coil is restricted to the wavelengths available from the luminescent material, and does not include the wavelength spectrum of a tungsten incandescent filament using blackbody radiation.
b) Prior Art Identifying Candoluminescent Materials
Several prior arts identify materials other than thorium and calcium oxide for use in gas lanterns. The disadvantage of these prior arts is restricting applicability to gas lanterns.
U.S. Pat. No. 4,532,073 by Cornu; Aime, et. al. entitled “Candoluminescent Material and its Preparation” identifies an alternative for the radioactive thorium oxide. The candoluminescent materials are a mixture formed into a netting of zirconium oxide, calcium oxide, aluminum oxide and/or magnesium oxide. It is prepared by impregnating a combustible textile with a solution of zirconium and calcium salts, optionally containing aluminum, iron, manganese, praseodymium and/or cerium salts and then subjecting the impregnated textile to a combustion process in order to eliminate the textile and transform the salts into oxides.
U.S. Pat. No. 5,124,286 by Edgar; John P. entitled “Incandescent Mantles” provides a mantle composed of zirconia, yttria, erbia and ceria. The mantle for incandescent gas lamps can be made of a substrate impregnated with a solution of oxides of zirconium, erbium, yttrium and cerium. This mantle produces light outputs and color comparable to that of thorium mantles.
c) Prior Art Identifying Low Thermal Capacity Structures
No prior art was identified that describes utilization of existing low thermal capacity insulators as a method to improve efficacy for electric lamps.
d) Prior Art Identifying Discriminative Filter Designs
Selected prior art designs that use discriminative reflective filters to transmit the desirable wavelengths, and reflect the undesirable wavelengths back to the incandescent filament in order to heat the filament and cause energy recycling are identified below.
U.S. Pat. No. 2,859,369 Williams et al. provides a method to selectively reflect back to the incandescent filament the infrared energy. This is accomplished by providing an infrared filter that selectively reflects the wasted infrared light back to the filament, and allows the visible light to transmit through the filter. A small filament is at the geometrical center of a spherical surface which is coated with the reflecting film. The reflecting film precisely reflects the infrared light back to the small incandescent filament, thus recycling the energy into visible light. The inside of the film is coated with a Raleigh scatterer which acts to selectively scatter the desirable visible component of the radiated light out of the lamp.
Follow-on prior art to U.S. Pat. No. 2,859,369 improved aspects of the original patent. Selected pertinent examples of the reflective filter design are identified and discussed below.
U.S. Pat. No. 4,366,407 Walsh, Peter titled “Incandescent Lamp with Selective Color Filter” uses a transparent heat mirror coating on the lamp envelope. The heat mirror transm
Chen Alan Ten-Lien
Stark Daniel Lee
Patel Ashok
Stark Daniel Lee
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