Illumination – Light source and modifier – Including reflector
Patent
1993-12-08
1996-01-23
Lazarus, Ira S.
Illumination
Light source and modifier
Including reflector
362223, 362336, 362338, F21V 302
Patent
active
054869900
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates generally to lamp covers, and is particularly concerned with a lamp cover for a fluorescent lamp. Such lamp covers are known which are transparent or translucent and are appropriate for covering the lamp upward or downward.
The basic problem of such lamp covers is that the light-directing design of the lamp cover must be such that no disturbing shadows occur to the extent that light-impervious objects lie in the ray path and a certain light-directing effect is desired. In addition, the surface on one side of the lamp cover features a certain structure at least on one side.
Some known lamp covers have grooves that run longitudinally to the lamp cover, parallel to one another and at a reciprocal distance from each other, and that form a triangular structure (prism structure) in cross-section (profile). A disadvantage of this known lamp cover with prism structure is that it may bring about striation on illuminated surfaces and that shadowing elements located in the ray path may lead to undesired visibility, i.e. such elements may be readily seen from the outside. To the extent that one wishes to avoid such shadow formations, it is known to opalesce such lamp covers. The disadvantage however is that it produces relatively high diffusion losses. The related disadvantage is that the lamp cover continues to appear bright even from relatively flat angles of view, which is undesirable in many applications.
It also contradicts the appropriate norm.
In addition, such opal material also diffuses back into the lamp, which leads to efficiency losses.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve a lamp cover as described above that achieves a targeted ray expansion without diffusion losses with a kind of soft-focus effect but without using an opal structure.
According to the present invention, a lamp cover is provided which comprises a cover member having opposite inner and outer surfaces and a longitudinal axis, at least one surface having a wavelike structure which stretches perpendicularly to the longitudinal axis of the lamp cover and the number of wave trains is in the neighborhood of at least three, preferably ten and maximum a thousand per lamp width, and whereby the wave trains are constantly changing curves whereby these curves are either sine curves or constantly changing radius curves. Accordingly, the wavelike structure forms grooves which run longitudinally and parallel to the longitudinal axis of the fluorescent lamp.
In other words, essential characteristic of the present invention is that the structure in accordance with the invention achieves a sort of soft-focus effect, i.e. it produces a "ray expansion" which refers to the following.
Starting with a narrow beam of light that hits the structure (the term "narrow beam" refers to a curve in the polar diagram of intensity), the beam of light is expanded and widened in the same direction when shining through the structure without producing additional diffusion parts.
This is the essential advantage of the present invention in comparison to the prism structures mentioned earlier in that beam direction is in the foreground in the known prism structures and in that the diffusion portion is diffuse in the opal structures, i.e. a relatively big efficiency loss must be taken into the bargain. In other words, the incoming light beam has a different direction in prism structures as the outgoing light beam.
Important feature of the present invention is that barely translucent objects located in the beam of light are difficult to see from the outside as a result of the soft-focus effect in accordance with the invention, and that shadows and streaks that would occur on the illuminated surface are prevented.
Another significant advantage of the present invention is that the lamp cover in accordance with the invention is able to produce a targeted radiation (beam) in a very specific area so that when viewing the lamp cover from a flat angle it appears dark because there is no l
REFERENCES:
patent: 2334005 (1943-11-01), Hoeveler
patent: 2782297 (1957-02-01), Geissbuhler et al.
patent: 3431449 (1969-03-01), Hundley
patent: 3763369 (1973-10-01), Lewin
patent: 4825346 (1989-04-01), Schindler et al.
patent: 4930051 (1990-05-01), Golz
patent: 5040104 (1991-08-01), Huisingh et al.
patent: 5043856 (1991-08-01), Levin
Lazarus Ira S.
Sember Thomas M.
Zumtobel Licht GmbH
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