US2732488A

US2732488A - wince

Info

Publication number: US2732488A
Authority: US
Publication date: 1956-01-24
Anticipated expiration: 1973-01-24

Description

DIRECT LIGHTING FIXTURES Filed Nov. 14, 1951 Tucrl.

2 Sheets-Sheet 1 INVENTOR V4IPA S. M/vca ATTORNEY Jan. 24, 1956 v. s. WINCE DIRECT LIGHTING FIXTURES 2 Sheets-Sheet 2 Filed NOV. 14, 1951 INVENTOR PEA/P4 S. M/VCE 6 2% M ATTORNEY United States Patent DIRECT LIGHTING FIXTURES Vearl S. Wince, Newark, Ohio, assignor to Holophane Company, Inc., New York, N. Y., a corporation of Delaware Application November 14, 1951, Serial No. 256,169

3 Claims. (Cl. 240-93) The present invention relates to direct lighting fixtures and more particularly to direct lighting fixtures for interior illumination and employing a reflector and refractor in association with a light source, the refractor acting on both direct and reflected light to alter the directions of the same.

For interior illumination from a number of units it is desirable to secure adequate spread of light to cover the working area with uniform illumination without an excessive number of units, or the requirement of excessive mounting heights, and that the light emitted from the units be confined to directions which avoid excessive glare.

Luminaires for these purposes have employed reflectors of spherical contour which return light through the lamp bulb, thereby introducing losses and scattering, or they have employed light transmitting closures shaped to present large areas of brightness in the field of view, or have employed reflectors whose distribution is too concentrated and have altered the distribution by using annular prisms with normally inactive, but light scattering surfaces.

According to the present invention, the light output of the reflector, particularly the part of the light which is close to the nadir, to avoid its passing through the lamp bulb is redirected by the refractor into wider angles from the nadir by prismatic action'characterized by the absence of losses and scattering by inactive surfaces. The prismatic light control elements for this reflected light may readily be incorporated in a flat plate of low projected area in the field of vision, and the plate may also be providedwith light diffusing elements at greater distances from the fixture axis for concealing the interior of the fixture from direct observation and for scattering to some extent the higher angle direct and reflected light.

In carrying out the redirection of the dominant reflected light, the prismatic elements employed by the present invention change the azimuthal direction of this reflected light, as well as direct light which naturally falls on them, approximately 90 in both directions all around the vertical axis of the luminaire, so that no matter in what direction one looks at the refracting plate, through which all the light is emitted, it has very uniform brightness over its entire area.

v.Other and further objects of the invention will appear as the description proceeds.

The accompanying drawings show, for purposes of illustrating the present invention, one embodiment in which the invention may take form, it being understood that the drawings are illustrative of the invention rather thanlimiting the same.

In the accompanying drawings:

Figure 1 is a vertical sectional view through the optical structure of the luminaire, showing the paths of the light Figure 2 is a top plan view of the closure plate;

Figures 3, 4 and are fragmentary sectional views on the lines 33; 4-4 and 5-5 of Figure 2; i I

Figure 6 is a diagrammatic perspective view illustrating the light control; and

, around into the plane of the paper as indicated at 51",'

Figure 7 illustrates the photometric curve obtained from the fixture.

In the drawings, the incandescent light source in the bulb B is indicated at S. It is within an annular specular reflector R, preferably made of prismatic glass of a profile which avoids sending reflected light back through the lamp bulb. It is preferably of elliptical profile with the other focus at 50' and in an annular locus. The top of the reflector is about 45 above the source and is of larger diameter than the lamp bulb. The mouth of the reflector is below the source close to the region where a further extension of the elliptical profile would become convergent. The reflector is closed by a relatively flat light transmitting cover T which has a small projected area in the line of vision. The particular form of reflector and cover shown, is one particularly well suited for vapor tight luminaires when provided with the proper mounting.

'The direct light rays such as 51, 52, 53, 54, intercepted by the specular reflector (preferably of prismatic glass), are indicated by relatively steep rays at 51', 52, 53', and relatively high-angled ray 54'. All miss the lamp bulb. If these rays were continued without deviation, they would intersect at 50', the other focus of the elliptical profile, and would proceed in the original direction with the dominant light output at very steep angles and in the original radial plane without deviation.

prisms and dilfusing flutes which change the direction of the light rays not only by varying the vertical angle of the rays with respect to the radial plane of the direct and reflected rays, but also by deviating them laterally from the radial plane. I

The bottom of plate T is smooth. The inner portion of the plate T is provided on its upper surface with a series of radial, relatively steep prisms 60, shown in more detail in Figure 3. These prisms act to deviate direct and reflected light out of the radial plane through the light source to the right and left in this figure as indicated by the

rays

61, 61. This action takes place all the way about the vertical axis x-x and the same rays are reproduced with the same reference characters in Figure 1.

Outside this region of relatively steep prisms there is preferably an annular region made up of radial prisms 62 of slightly less refracting power asindicated in Figure 4. These prisms act to deviate light from the radial plane through the light source to the right and left as indicated by the

rays

63, 63 in this figure. The same rays are re produced with the same reference characters in Figure 1. If desired, the steeper prisms 60 may be extended out through the entire area occupied by prisms 60 and. 62 or vice versa.

Outside the circular region occupied by the light fusing flutes 64 (see Figure 5), which act to spread the light as indicated at 66.

Not only is the reflected light reflected out of theradial plane by the radial prisms, but its vertical angle is also changed, as indicated by the corresponding rays, swung 52' and 53". The reflected light corresponding with the higher angle reflected rays 54 precedes without substanf tial change in its vertical angle as indicated at 54".

The direct rays such as 55 and 56 fall on the plate.

- Rays 55 falling on the portion'of the plate having the dif:

fusing flutes are transmitted without substantial change}: of vertical angle as indicated at 55" and are. spread about}, the same as the rays 66 of Figure 5. Direct rays, such, as 56, falling on the

radial prisms

60, 62 are deviated away r from the axis as indicated by the rays 56". These rays are likewise spread away from the radial plane in the same manner as the reflected rays above described.

The action which takes place in the luminaire is illusstrated in Figure 6. If it be assumed that the plane indicated by the converging line y-y and zz of this figure is the plane of Figure l and that there is no light transmitting plate, then reflected light rays passing through the annular region 70 would be in radial planes and would have the vertical angle determined by the reflector. Rays such as 72 at corresponding points around the vertical axis of the luminaire would fall on the working plane at points 72 in a circular path as indicated at 73. On account of the lateral deviation of the radial prisms in the plate '1 as above described, the rays through region 70, instead of having the direction indicated at 72, ar,e spread from the plane yy, z z, as indicated by the angle 74 to have the direction indicated by rays 75. These intersect the working plane at

points

76 and 77 on opposite sides of z-z, and the circle 78 indicates the region on which the rays 75 and like rays will fall. The vertical angle of the rays 72 against nadir N is indicated by the angle 79, while the vertical angle of the rays 76 against nadir is indicated by the angle 80. The action indicated In Figure 6 is typical of the action which takes place to a greater or less degree with respect to all the light transmitted through the prismatic and ribbed transmitting plate.

The radial ribs shown here provide a very eflicient optical means of dissolving the light from the reflector and reforming it into a new direction where, after crossing, it has a wider spread than the reflector alone would provide. A very narrow zone of these prismatic ribs accepts a very large proportion of the total light output and transmits it without loss such as occasioned by annular prismatic formations for similar purposes. They also eifec-v tively reduce the brightness of the plate in this annular region. The radial prisms are active over their entire n h As a result of the interposition of the light spreading prisms and flutes in the paths of the reflected and direct rays, all of the light escaping from the reflector is sent in new directions. After this light crosses the vertical axis xx of the luminaire below the luminaire, it is at greater angles from the nadir than the original reflected light so as to spread over a larger area, In this manner, it is possible to convert the distribution of reflected light from one which would normally require very high rnounb nst a s ib t n h h perm much ow r m unt ins h gh s and yet ma nta n s tisf ct y niform ty of llumin n o er th a ea li hte by a number i hese lum n r esh r he r fle or R is provided with an opaqusss er so that no light escapes horizontally from the reflector, the output o the lumin ir is ndic d y h p o omet ic curve 90 of Figure 7. It will be noted that this curve shows no light above about 55 above the nadir and that the light is well spread out over a region approximately 30 each side of the nadir, Owing to the small projected a o h r ns t n p a e and h relatively h er tical angle of the light transmitted through it, the luminaire. presents a relatively small area of brightness,

Since it is obvious that the invention may be embodied in other forms and constructions wtihin the scope of the claims, I wish it to be understood that the particular form shown is but one of these forms, and various modifications and changes being possible,I do not otherwise limit myself in any way with respect thfilflo.

hat is cla med is 1- A min i c pr s ng l mp ing substan tially point light source and enclosing bulb, a downwardly and outwardly flaring, annular, specular reflector about the source, the reflector being of substantially elliptical profile with feei at the source and in an annular region below the lamp such that the axes of the ellipses form a cone about the vertical axis, the top of the reflector being of greater diameter than the bulb and substantially above the horizontal through the source, and the mouth of the reflector being below the source and close to but above the region where the elliptical contour if continued would become convergent with respect to the vertical axis, whereby the highest angled direct light received is reflected substantially vertically downward outside the lamp bulb, the direct light above the high angled regions below the horizontal is concentrated into relatively sharply convergent beams at relatively steep angles above the lower foca egion and we a g ed dir ct. light is reflected at lower angles; and a substantially flat refractor disposed below the mo uth of the reflector and above the lower focal regions, the refractor having a relatively narrow annular zone of an inner diameter substantially that of the annular f c l re and o a idth o inter p t at y sharply n er nt refle ed b ams at aid s eep a l s. sai nnu r wa b n oc upi d y radia Prismstic ri s wh ch a o said re ec e ys t p ead the e h y om the co pondi a P n s so that the rays emitted from said ridged zone have, after cr ssing. a g a an l f pread from the e t c l x than the angles of Convergence of the corresponding re.- flectcd rays, the refractor having outside said zone of radial ridges a zone of relatively shallow diffusing flutes of less light spreading power for high angled reflected light than that of the radial ridges in the said annular zone, and an inner, circular, light-diffusing area for direct light only.

2. A luminaire having a concentrated light source, a downwardly and outwardly flaring annular, specular re: flector intercepting light in regions above and below the source and having a contour to focus reflected light with-. out crossing the reflector toward points in an annular re gion below the reflector and a light transmitting closure plate disposed between the reflector and said focal points and through which direct and reflected light passes, said plate having in the annular region where the dominant reflected light converges toward said points, light splitting prisms which spread the reflected light falling thereon in directions lateral of the radial plane through the same and substantially reduce the brightness of said region with respect to what it would be without such spreading.

3. A normally horizontal circular light controlling plate smooth on the bottom and adapted to receive downwardly divergent light from a source in the vertical axis of the plate and transmit the same downwardly, the peripheral portion of the plate being occupied by a series of radial light diffusing flutes of moderate light diffusing power to laterally spread and diffuse light into angles farther from the nadir than the incident light from the source, an

annular region of the plate inside the peripheral portion having radial light splitting prisms of greater retracting power than the maximum refracting power of the flutes and acting to deviate and laterally spread the transmitted light to a greater extent than the flutes, and an inner series of radial prisms similar to the first mentioned radial prisms but of still greater retracting power, the plate where it carries said flutes and prisms being substantially flat.

References Cited in the file of this patent UNITED STATES PATENTS