US3600570A

US3600570A - Low glare louver

Info

Publication number: US3600570A
Application number: US782557A
Authority: US
Inventors: Mizuo Okada
Original assignee: Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Chemical Corp
Priority date: 1967-12-11
Filing date: 1968-12-10
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17

Abstract

A low glare louver constructed of a grid of cells made of transparent material produces a low brightness ceiling by controlling the light from the light source. The opposite surfaces of each beam of the grid slope downwardly producing a thicker base for forming a multiprism lens or a cylindrical lens.

Description

llnited States Patent Mizuo Okada Kozagun, Japan Dec. 10, 1968 Aug. 17, 1971 Mitsubishi Rayon Company, Limited Tokyo, Japan Dec. 11, 1967, Dec. 25, 1967 Japan 42/103476 and 42/108002 inventor Appl. No. Filed Patented Assignee Priority LOW GLARE LOUVER 6 Claims, 13 Drawing Figs.

US. Cl 240/78 LD, 240/46.39, 240/l06.1

int. Cl F21s1/06 Field of Search 240/78 LD, 46.39,106,106.1

[56] References Cited UNITED STATES PATENTS 2,143,149 1/1939 Guth 240/78 LD-7 2,904,673 9/1959 Guth, Sr. 240/78 LD-7 2,927,994 3/1960 Guth, Sr. 240/78 LD-7 2,971,083 2/1961 Phillips et a1. 240/78 LD-7 2,996,609 8/1961 Wilson 240/78 LD-7 3,179,797 4/1965 Franck 240/78 LD-7 Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard M. Sheer Att0rneySughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT: A low glare louver constructed of a grid of cells made of transparent material produces a low brightness ceiling by controlling the light from the light source. The opposite surfaces of each beam of the grid slope downwardly producing a thicker base for forming a multiprism lens or a cylindrical lens.

l l l l PATENTED Aus I 71971 SHEEI 1 OF 4 o o f 3; a m

MIZUO 0KADA,|NVENTOR. BY L ZM M {W ATTORNEYS PATENTEflAusmsn 3 600 570 SHEET 3 or 4 I INVENTOR mzuo 0mm PATENTEBAusmsn 3600.570

SHEET 4 [1F 4 LIGHT msmmunou CURVE. HGI} SAMPLE LOUVER NoLSOURCEBRIGHTNESSOFTHELIGHTZOWxZLIGHTS.

msmucs 0=3oo mm INVENTOR MQIZUO OKADA BACKGROUND OF THE INVENTION The present invention relates to a louver by which the light rays from a light source are modified or controlled to lower the glare of the light. In particular the invention is directed to a low glare louver wherein a grid of cells made of transparent material is employed to lower the angle of incidence of the light transmitted from the light source.

' FIG. 7 is a cross-sectional view of the louver employing multiprism lens wherein the bottom surface is of a mat finish.

FIG. 8 is a cross-sectional view of a part of the louver employing a cylindrical lens wherein the bottom surface is mat finish;

FIG. 9 is a cross-sectional view of the louver in accordance with the present invention adapted for use on a lighting fix ture;

FIG. 10 is a sectional view of the louver with the lighting fix- In general, a louver is required to remove the glare effect of 10 take along the line in F 9;

a light source by refracting the light rays from the light source in a direction inclined at more than 30 from the ceiling face. This is desirable from the viewpoint of human engineering.

angle of the light at more than 30, for example the low brightness louver disclosed by US Pat No. 2,971,083, but the utilization of metallizing on the surface of the beam of the grid has proven to be a deficiency. Owing to the metallizing on the surface of the grid beam, the light intercepted by the beam FIG. 11 is an enlarged explanatory view of the cross section of the louver for explaining the formula (I hereinafter referred to;

FIG. 12 is a diagram showing the light distribution In accordance with the first embodiment of the present invention, and

FIG. 13 is a diagram showing the light distribution in ac cordance with the second embodiment of the present mven tion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, the louver in accordance with the present invention employs beams of grid made of transparent is reflected onto the ceiling and thereby partly absorbed. Thus material in the shape of cylindrical lens or multiprism Fens the brightness on the illuminated surface is lowered. And

moreover, metallizing the louver has proved to be expensive.

In other attempts to solve these problems in the prior art,

there has been provided a simple grid-shaped construction The beam of a grid employed in the present invention is preferred to be made of methyl methacrylate resin which has good transparency. although for example, inorganic glass, styrene resin or vinyl chloride resin could be emploved The made of opaque Synthetic resin This type of louver operates side surface 1 ofthe beam ofthe grid is required to form a cur at a disadvantage since the brightness on the illuminated surface is lowered due to absorption of the light by the louver itself.

SUMMARY OF THE INVENTION A grid of cells made of transparent material is utilized to lower the glare of the light in the louver in accordance with the present invention. In a luminair'e having a light source such as fluorescent or incandescent lamps, the light from the light source is refracted in limited directions to achieve the desired condition of illumination. The resulting brightness on the illuminated surface is both uniform and adequate. Since the grid of the louver is constructed of transparent material, the light from the light source is not absorbed by the louver and a high intensity level of brightness is obtained on the illuminated surface.

It is an object of the present invention to provide a low glare louver for producing a uniform brightness on the illuminated surface and lowering the glare of the light.

Another object of the present invention is to provide a low glare louver employing transparent material wherein the light from the light source is not unduly absorbed by the louver and high brightness is obtained on the illuminated surface.

A still further object of the present invention is to provide a low glare louver which is capable of spreading the light from the light source and producing a restful source of light for the eyes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an explanatory view showing the projected light range produced by the louver in accordance with the present invention;

FIG. 2 is a partial plan view of a louver employing the mulvature that will have the beam thinner at the upper portion thereof as shown in FIG. 3. Thus, the light from the llgh' source will be directed in a direction inclined at more than *0 with the ceiling face, the range of which is shown In Flt l and the light path of which is shown in FIGS. 4 and 5 We 'Iu merals shown in FIGS 4 and 5 denote the angle in which the light advances respectively through the louver In this case a natrium D-line of 5893 angstrom wavelength is used as the light with a louver made of methyl methacrylate resin The shape of the curve presented by the side surfaces of the beam of the grid is formed into a particular shape represented by the following formulas:

H=P -ltan 2(n1) sin 1/5 6 v3 R --1 Sm (,5 R 16 (2) 3 mm.H100 mm. (3)

wherein P is the pitch. H is the height of the beam R is a radius of curvature of the cylindrical lens or the circumscribed cylinder about the multiprism lens, and n is the index of refraction of the employed transparent material.

FIG. 11 explains the meaning of the formulae The light comes into the louver from the point D at the top of the beam having a pitch P, height H, radius of curvature R. and index of refraction n, it travels to the center E of the bottom of the adjacent beam through the center beam M which refracts the light ray. The light is inclined at 30 when it leaves the bottom surface of the beam of the louver. The path of the light and the curvature of the surface of the louver are formularized as follows:

Refraction at the portion M can be regarded as a refraction tiprism lens in accordance with an embodiment of the present at a pnsm havmg an angle wh'ch m comac wnh the invention;

FIG. 3 is an enlarged cross-sectional view of the louver in accordance with the present invention taken along the line A-A or B-B ofFIG. 2;

cylindrical lens at a point K on the surface thereof Since the triangle FGJ is similar to the triangle IGK, the angle GIK is equal to a (one-half of the angle of the prism) The distance KL is substantially equal to-P/ /5 since the prism FIGS. 4 and 5 are enlarged explanato y cross section views is thin Therefore: an equation Sin pump/W) obained of the louver showing the transmitting effect on the light rays from the light source;

FIG. 6 is a cross-sectional view of the louver employing cylindrical lens in accordance with the present invention;

with reference to the triangle IKL.

Thus, the following equation is obtained,

a=sina R The declination of a thin prism having a top angle of 2a is (n-l )Za, therefore, the declination at M becomes 1 P 2 n1 -sin' V3 R and the angle [3 becomes In order for the light which passes through the point E to pass through the point K shown in FIG. 11 the following condition is obtained:

B ZE -1 (i.)} H P tan B-P tan 2(n 1) sin B R which is written as follows LE) w/ R 16 That is, the top angle 2a is desired to be 17/8 or 22.5 or smaller.

As to the height H in the formula (I), there is a limitation since the louver is apt to be distorted or bent if too low, and apt to be too expensive due to the increase of the amount of the material if too high. Therefore, the height of the louver is required to be limited to the range indicated by the following formula from a practical viewpoint.

a=sin- 3mm.H100 mm. (3)

By designing a louver according to the above formulas, a small percent of the light from the light source will be directed in a direction included in the glare zone Z, (indicated with stippling in FIG. 1). But such a small degree of light will not fatigue the eyes but will rather produce a soft and calm illumination effect.

The bottom surface 2 of the beams of the grid employed in the louver can be mat finished while leaving the other surfaces mirror finished as shown in FIGS. 7 and 8. By providing this mat finish on the surface of the bottom of the louver in the multiprism or cylindrical lens shape, firstly, the light passing through the louver will be broadly dispersed and thus provides softer illumination effect and, secondly, the light passing through the louver will easily come out from the nadir of the louver walls because of edge-lighting effect and thus provides a high degree of efficiency.

Some embodiments in accordance with the present invention will be described hereinafter, but the invention is not to be considered limited to the following embodiments only.

EMBODIMENT 1 Methyl methacrylate resin is employed for the beam of the grid of the louver in which the radius of curvature R is 80 mm., and the pitch P is mm. The height H is calculated to 15.3

A louver having a cross section of pentagonal shape was molded into the wedge shape beam of a grid by injection molding. The louver had dimensions fitted to the above formula (width 300mm., length 660mm.).

When the above-described louver was adapted to a fluorescent lamp fixture as shown in FIGS. 9 and 10 (brightness of the lamp 20 w., the distance d mm. between the louver 3 and the two fluorescent lamps 4, 4), the light distribution was measured as illustrated in the curves of FIG. 12, wherein a solid line indicates the light distribution curve in a plane perpendicular to the axis of the lamp tube 4, broken line indicates the light distribution curve in a plane parallel to the lamp tube 4, and a dot-dash-line indicates the light distribution curve in a plane inclined at 45 with the lamp tube 4. Preferably, the distance d between the louver 3 and the lamps 4 is approximately the same as the distance between the lamps.

As shown in the light distribution curves, almost all the light from the light source is projected in the direction where the light range is inclined at more than 30 with respect to the horizontal plane. A small percent of the light falls out of the range, (inclined at 15 to 30 with the horizontal plane) and helps make the louver body appear soft, and gentle to the eyes.

By making the bottom surface of the louver mat finished (320 mesh) as shown in FIG. 7, the distribution of the light remains as good as the unmatted surface while producing a softer illumination effect.

EMBODIMENT ll Using the same material as employed in the first embodiment with a radius of curvature R of 100 mm., pitch P of 20 mm. and a height calculated as shown hereinafter, a louver having a cylindrical cross section was obtained by injection molding. (width 300mm. length 660mm.)

hll

When the louver made in accordance with the second embodiment was fitted to the fluorescent light fixture used in the first embodiment with distance d from the light tube to the louver being 300 mm., the light distribution was measured with the results shown in FIG. 13. Although the diagram of the light distribution curves are egg-shaped due to the deep troffer 5 (reflector box) the light distribution characteristics were almost the same as that of the first embodiment.

When the louver was molded by styrene resin (n=l .59) with the same mold piece, the light from the light source was slightly dispersed into a spectrum due to the higher index of refraction n in comparison with the methyl methacrylate resin, but the control of the light direction was better.

By matting the bottom surface of a louver made of methyl methacrylate resin by means of a sand paper of 0600, a softer louver was obtained.

The invention has been described in detail with particular reference to the above preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What I claim is:

1. In a luminaire having a light source, and a low glare louver made of transparent material disposed beneath said light source and comprised of beams forming a grid of cells, each of said beams being formed into a multiprism with the cross section of each beam being thinner in the upper portion closest to the light source and thickest at the nadir, said beams serving to gradually refract the light from the light source as it wherein P is a pitch of the grid of cells, H is the height of said beams, R is the radius of curvature of the circumscribed cylinder about said multiprism, and n is the index of refraction of said transparent material.

2. A low glare louver as defined in claim 1 wherein said multiprism lens is a cylindrical lens, and said R is the radius of curvature of said cylindrical lens.

3. A low glare louver as defined in claim 2 wherein only the bottom surface of said beams is mat finished.

4. A low glare louver as defined in claim 1 wherein only the bottom surface of said beams is mat finished.

5. A low glare louver as defined in claim 1 wherein said transparent material is a synthetic resin.

6. A low glare louver as defined in claim 5 wherein said resin is methyl methacrylate resin.

Claims

1. In a luminaire having a light source, and a low glare louver made of transparent material disposed beneath said light source and comprised of beams forming a grid of cells, each of said beams being formed into a multiprism with the cross section of each beam being thinner in the upper portion closest to the light source and thickest at the nadir, said beams serving to gradually refract the light from the light source as it passes through a plurality of said beams such that most of the light leaving said louver is inclined in a direction more than 30* from a horizontal plane, the dimension of said beams being given by the formulas wherein P is a pitch of the grid of cells, H is the height of said beams, R is the radius of curvature of the circumscribed cylinder about said multiprism, and n is the index of refraction of said transparent material.