BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a tungsten halogen aluimized reflector lamp wherein the lamp lens is a high efficiency optical lens having an inner surface which includes a predetermined pattern of surface features which provide a desired beam defining surface. The inner surface of the lens is processed by, for example, coating with a ceramic, such that the characteristic beam harshness of a typical tungsten halogen aluminized reflector lamp is eliminated without substantially reducing the lamp efficiency. A method of fabricating such a lamp is also described.

Description of the Prior Art

Two common applications in the field of lighting are spot lamps and flood lamps. Both involve a basic optical system which includes a reflector to concentrate the light output of the lamp, and a lens to focus or bend the light in the desired manner.

Presently, there are two major types of reflector/lens optical systems in use in these lamps, the first is known in the industry as an "R"-type lamp, and utilizes an integral reflector and lens manufactured by standard glass blowing techniques. Once formed, the portion of the interior of the bulb adjacent the base is

aluminized to form a reflector, and the forward or lens portion is frosted for better light dispersion. A standard incandescent coil is utilized as the light source. The beam of light produced by this "R" lamp is relatively inefficient, although the light is diffused to produce an esthetically pleasing soft and glare-free lamp. The second type of lamp is known as a PAR (Parabolic Aluminized Reflector) lamp, and is formed from separately pressed reflector and lens elements which are then flame-sealed or adhesively bonded together. Although incandescent filaments are still used in PAR lamps for some applications, a high efficiency tungsten halogen capsule is more commonly used as a light source today. Due to the accuracy of modern glass pressing techniques, a high degree of optical precision can be engineered into the PAR lamp, and when coupled with the high efficiency of a tungsten halogen capsule, substantial energy savings are realized over blown bulb • ⁱ R ^H -type lamps. Unfortunately, although the beam produced by this system is highly efficient, it is esthetically quite harsh, and the lens produces a "sparkle" with numerous glare points.

Prior attempts to soften the harshness of bright or efficient light sources have been quite varied, and have met with limited success. ^'

In U.S. Patent No. 4,315,186 to Hirano et al., which issued on February 9, 1982, a PAR lamp is provided having an incandescent filament as a light source. The lamp lens has an EC coating film on its inner surface, the film being prepared by adding minute amounts of antimony or tin, etc., to a metal halide such as tin or indium. This particular film permits transmission of visible lights therethrough and reflection of infrared rays.

In U.S. Patent No. 4,127,789 to Kostlin, et al., which issued on November 28, 1978, a heat reflective filter is disclosed for the face plate of a PAR lamp. The face plate is coated on its inner surface with an indium oxide layer which is covered with pyrolytic silicon oxide and doped with tin, resulting in a long life, light previous filter layer. As in the case regarding the '789 patent, the light source [as] a filament.

A method which has been used to diffuse the light from a halogen bulb has been to coat the bulb surface directly, as in U.S. Patent No. 4,721,877 to Kawakatsu et al., which issued on January 26, 1988. A porous light diffusive coating is applied over a standard reflective layer directly adjacent the quartz bulb surface. The coating is formed from a solidified metal oxide formed by evaporation with an occluded solvent.

Another example of direct bulb coating is disclosed in U.S. Patent No. 3,384,771 to Pomfrett, which issued on May 21, 1968. In this case, a high pressure mercury vapor arc tube is mounted within an integrally blown glass reflector/lens combination, and both the arc tube outer surface and lens inner surface are frosted to eliminate the problem of bright spots without resorting to heavy and costly frosting of the lens alone. A silica frost is sued on the lens, and sandblasting is used on the bulb.

An alternative technique is provided in U.S. Patent No. 2,838,705 to Hierholzer, Jr., et al., which issued on June 10, 1958. Color correction in an integrally blown bulb/reflector-type high-pressure mercury vapor lamp is achieved by coating the reflector surface with a

color-correcting phosphor. The lens portion of the lamp remains clear, although it may also be frosted or coated with silica.

In U.S. Patent No. Re 30,832 to LaGuisa, which reissued on December 22, 1981, a blown glass lamp integrally formed into a reflector/lamp face construction is provided. In one embodiment an ellipsoidal reflector is disclosed combined with a frosted lamp face.

Efforts have continued to produce a lamp combining the attributes of the typical tungsten halogen aluminized reflector lamp and the typical "R"-type lamp. However, to date the combination of lamp features which include both a high efficiency energy saving light source and the warmth of the more inefficient incandescent bulb remains elusive in the prior art.

The present invention represents an effort to achieve the esthetically pleasing soft beam of a conventional "R"-type lamp with the efficiency, precision and energy savings of a conventional tungsten halogen aluminized reflector lamp.

SUMMARY OF THE INVENTION

This invention achieves these and other results by providing a tungsten halogen aluminized reflector lamp, and method of fabricating such lamp, comprising an aluminized reflector sealed to a high efficiency optical lens to enclose a cavity. The reflector can be sealed to the lens in any manner known in the art. For example, a hermetic seal can be provided, an adhesive seal or bond can be provided, etc. The lens has an inner surface having a predetermined pattern of surface. features which provide a desired beam defining surface. A pair of

electrical conductors is sealed into and passes through the reflector. A tungsten halogen capsule is disposed within the cavity and is electrically connected to first ends of the electrical conductors. A lamp base is secured to an outer surface of the reflector and is electrically connected to opposite second ends of the electrical conductors.. Means is applied to the inner surface of the lens for substantially eliminating beam harshness without substantially reducing lamp efficiency.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a cross-sectional view of a tungsten halogen parabolic aluminized reflector lamp of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The embodiment of this invention which is illustrated in the drawing is particularly suited for achieving the objects of this invention. The drawing depicts one form, without limitation, of a tungsten halogen aluminized reflector lamp of the present invention. In particular, the drawing depicts a tungsten halogen parabolic aluminized reflector (PAR) lamp 2 which includes a conventional parabolic aluminized reflector 4 and a lens 6. It should be emphasized that the present invention is not limited to a PAR lamp, any tungsten halogen aluminized reflector lamp embodying the teachings herein being within the scope of the present invention. The reflector and the lens are formed by a conventional press-molding process and are hermetically sealed together by flame-sealing, adhesive bonding or any other method known in the art. A pair of electrical conductors such as conductors 8 and 10 are sealed into and pass through the reflector 4. One end of each conductor 8 and

10 is electrically coupled to a respective lead of a tungsten halogen capsule 12, and an opposite end of each conductor is electrically connected to a base 14, in a conventional manner. Additional circuitry typically provided in a conventional tungsten halogen lamp can be disposed within the cavity 16 formed by the reflector 4 and lens 6 but has been omitted from the drawing for the purpose of simplification, such circuitry being well known in the art.

In a conventional tungsten halogen PAR lamp, the lens 6 will be fabricated in accordance with a specified lens prescription. For example, the lens of a tungsten halogen PAR lamp for use as a spot light will have a different lens prescription than will a lens of a tungsten halogen PAR lamp for use as a flood light. The exact nature of such prescription-made lenses is well known in the art. Such lenses are referred to in the art as high efficiency optical lenses. In such lenses, a glass lens is typically press-molded such that its inner surface includes a predetermined pattern of structural features such as, without limitation, lenticules and stippling, which provide a desired beam defining surface, the exact configuration of which is determined by the prescription used. Examples of tungsten halogen PAR lamps having such high efficiency optical lenses include, without limitation, tungsten halogen GTE Sylvania CAPSYLITE PAR 30 flood lamps and spot lamps. CAPSYLITE is a trademark of GTE sylvania. The tungsten halogen lamps thus far described are well known in the art.

In the present invention, the inner surface 18 of lens 6 is further processed to reduce the harshness of the beam. The inner surface 18 is processed such that the beam of light exits the optical system with the required beam angle, center beam candle power, and

diffusivity or softness. It is desired that any loss in efficiency not be greater than 10%. In one embodiment, the inner surface 18 is provided with a translucent coating 20. In the embodiment of the drawing the coating is, without limitation, a ceramic.

One method used to coat the inner surface 18 with a ceramic coating 20 will now be discussed. First, a slurry is formed by mixing ceramic powder with water such that the slurry has a density of 1.8. Such ceramic ^' powder has a mesh size equal to U.S. No. 100. The ceramic slurry is then sprayed onto the inner surface 18 of the lens 6 for one second. The ceramic coating is then dried in a conventional oven for five minutes at 200 ^β C. This procedure allows for the substantial elimination of slurry puddles between the lens elements and assures that the slurry will not dry too slowly, causing an undesirable non-uniform coating, or too fast, causing undesirable bubbles resulting from boiling of the slurry. A lens processed in this manner will have a dried coating thickness in the range of 0.0020 to 0.0050 inches. Generally, the thickness of the coating at the peaks of the protuberances which extend from the inner lens surface will be at the lower end of this range and the thickness of the coating in the valleys relative to such protuberances will be at the high end of this range. This process provides a substantially uniform coating, the effect of which is to prevent light transmission irregularities. The surface tension of the slurry is such that all lenticules and other features of the lens inner surfaces are evenly covered.

In an alternative embodiment, rather than coating, the inner surface 18 can be processed by a vapor blast process. In particular, the inner surface 18 can be

impacted with a very fine and uniform grit. The grit is projected at a high velocity and is applied in a manner similar to a sandblast.

One method that can be used to vapor blast the inner surface 18 is to blast the inner surface with sand powder having a mesh size equal to U.S. No. 100. The inner surface 18 will be blasted with such grit for two seconds while the lens is being rotated at two revolutions per second. A longer blasting period will provide a less desirable denser surface configuration. A shorter blasting period will provide a lighter and often less uniform appearance.

It should be noted that it is not intended to limit the present invention to ceramic coating or vapor blasting of the inner surface of the high efficiency optical lens 6. Nor is it intended to limit the present invention to the foregoing procedures or parameters. For example, similar results might be obtainable by means of paint coatings, sandblasting, acid etching, other ceramic coatings, other vapor blasting procedures, and the like, but only to the extent that the usual beam harshness of the typical tungsten halogen aluminized reflector lamp is substantially eliminated without substantially reducing lamp efficiency.

Table 1 represents a comparison of conventional 75 watt R-type lamps, known in the industry and identified in Table 1 by the designation R30, with conventional 50 watt tungsten halogen GTE Sylvania CAPSYLITE PAR30 lamps, identified in Table 1 by the designation PAR30 (coated) , wherein the inner surface of the high efficiency optical lens of such conventional PAR 30 lamps was coated using the specific ceramic coating method discussed above. The lamps were compared by measuring center-beam candle power (CPCP) and beam angle

(BA) in spot lamp and flood lamp embodiments. The comparisons are noted below and represent the average of twenty lamps tested in each lamp category;

It will be apparent that the coatings on the tungsten halogen PAR30 lamp are such that the beam angles of 25" and 77° substantially match the beam angles of 26° and 80°, respectively, of the R30 lamp. The efficiency, and therefore energy savings, are also evident. It was also observed that the ceramic coated lens of the tungsten halogen PAR30 lamp softened the harsh appearance of the light produced by a conventional high efficiency optical tungsten halogen PAR30 lamp. Hence, it will be apparent that the present invention provides an improved lamp having the aesthetically pleasing soft beam of a conventional "R ^e type lamp with the efficiency, precision and energy savings of a conventional tungsten halogen aluminized reflector lamp.

The embodiments which have been described herein are but some of several which utilize this invention and are set forth here by way of illustration but not of limitation. It is apparent that many other embodiments which will be readily apparent to those skilled in the art may be made without departing materially from the spirit and scope of this invention.