Luminaire

Abstract

Luminaire for indoor industrial use has an optical assembly having a diameter substantially greater than its height and adapted to be mounted at a relatively low height above the floor. The optical assembly comprises a reflector with fluted concave upper portion and an outwardly flaring lower skirt portion to which a large diameter dish-shaped refractor is secured. The refractor has an annular side wall formed with horizontal rows of prisms which depress part of the incident light and reflect the remaining light rays upwardly toward the ceiling. The bottom panel of the refractor is formed with radial light dispersing flutes.

Description

The present invention relates to lighting fixtures, and particularly to luminaires of industrial indoor type.

It an object of the invention to provide a luminaire of the above type which spreads light over a large floor area when mounted at a relatively low height.

Another object of the invention is to provide a luminaire of the above type wherein the luminaire brightness or glare is minimized, especially in the zone between vertical angles of between about 45.degree. to 90.degree.. By "vertical angles" is meant the angle up from nadir defined by a light ray relative to the vertical axis of the light source.

Still another object of the invention is to provide a luminaire of the above type from which a portion of the light is directed toward the ceiling to minimize contrast.

A further object of the invention is to provide a luminaire of the above type which has a relatively low overall profile.

Other objects and advantages will become apparent from the following description and the appended claims.

With the above objects in view, the present invention in one of its aspects relates to a luminaire comprising, in combination, an optical assembly comprising a reflector having an upper portion and a lower downwardly flaring skirt portion defining an open bottom, and a generally dish-shaped refractor having an open top and a closed bottom, the reflector and refractor being connected to each other at their peripheries with the refractor arranged below and enclosing the bottom of the reflector, the optical assembly being substantially greater in overall diameter than in height, and a lamp mounted in the optical assembly, the refractor having a peripheral side wall formed with prisms for depressing light rays from the lamp downwardly toward the area to be illuminated by the luminaire.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view in elevation, partly broken away, of an industrial luminaire embodying the invention;

FIG. 2 is a top plan view of the refractor employed in the optical assembly of the FIG. 1 luminaire;

FIG. 3 is a bottom plan view of the main luminaire reflector of the optical assembly;

FIG. 4 shows a segment of the luminaire reflector as viewed along the line 4--4 in FIG. 1;

FIG. 5 is a somewhat schematic view of a vertical section of a portion of the luminaire optical assembly showing the path of light rays therein;

FIG. 6 is a view in vertical section of a portion of the refractor taken along the lines 6--6 in FIG. 2;

FIG. 7 is an enlarged detail view of the side wall prisms of the refractor; and

FIG. 8 is an enlarged cross-sectional view of a portion of the bottom panel of the refractor taken along the lines 8--8 of FIG. 6.

Referring now to the drawings, and particularly to FIG. 1, there is shown an industrial luminaire comprising a somewhat dome-shaped ballast housing 1 connected to and supported by a wire conduit 2, such as a metal pipe, and containing electrical operating components such as ballast transformer 3 and capacitor 4. Ballast housing 1 is formed with cooling fins 1a for radiating and dissipating heat generated therein by the electrical operating components. Suspended from ballast housing 1 below the open bottom thereof is optical assembly 5 comprising reflector 6 and refractor 7.

Reflector 6 is formed of a somewhat conical upper portion 6a open at its top and a lower outwardly flaring skirt portion 6b, with both reflector portions having reflecting flutes formed in the walls thereof, as seen in FIG. 3 wherein such flutes are shown only in one sector for the sake of simplicity. Refractor 7 is a shallow, somewhat dish-shaped transparent member having light control prisms 7a extending around the outer surface of its peripheral wall. In the optical assembly, as seen in FIG. 1, the lower rim of reflector skirt portion 6b mates with the upper flanged rim of refractor 7, and they are securely joined together in permanent sealed relation by suitable means, such as by forming the reflector rim into an annular channel 6c in which the annular flanged rim of refractor 7 is received and held.

Lamp 8 is arranged in optical assembly 5 with its base down and mounted in that position by bracket 10. Bracket 10 is generally V-shaped and secured at its upper arms to opposite upper portions of reflector 6. The apex of bracket 10 at its bottom is formed with a seat 10a in which lamp socket 9 with support bracket 9a is received and suitably secured. In such arrangement, lamp socket 9 is located closely adjacent the inner surface of the bottom panel of refractor 7, and lamp 8 extends upwardly in the optical assembly. The light center LC of lamp 8 is thus arranged in the proper position as shown in FIG. 1 relative to reflector 6 and refractor 7 to provide the desired light distribution.

Optical assembly 5 is detachably connected to ballast housing 1 by means of hinge 11 and latch 14 so as to permit the optical assembly to be swung down from ballast housing 1, thus providing access to the interior of the optical assembly. A separable electrical connection between the detachable parts is provided by electrical plug 16 secured to reflector 6 and electrical receptacle 17 secured to ballast housing 1 as shown in FIG. 1. These and other mechanical features are more fully disclosed in co-pending application of Judge et al, Ser. No. 123,685, filed Mar. 12, 1971, and assigned to the same assignee as the present invention.

In a typical luminaire constructed in accordance with the invention, the overall diameter of optical assembly 5 at the junction of reflector 6 and refractor 7 is about 31 inches, the overall height of the unit including ballast housing 1 and optical assembly 5 is about 21 inches, and the height of the optical assembly 5 is about 12 inches with the height of refractor 7 being only about 4 inches. Thus, the overall diameter of the optical assembly is substantially greater than the overall height of the entire unit and more than twice the height of the optical assembly. Because of the relatively large size of the refractor used in such a luminaire, it would usually be made of a synthetic plastic material such as an acrylic resin. Such a material is subject to discoloration if exposed to excessive heat due to close proximity to the lamp. By arranging lamp 8 with its base down, adequate spacing is provided between refractor 6 and the relatively hotter bulb portion of lamp 8 while still utilizing the space adjacent refractor 6 for the cooler lamp base and socket member 9. A further advantage in this arrangement is that the height of the ballast housing can be reduced since it need not accommodate the lamp socket, which in a base-up arrangement would have to be placed within the ballast housing so that the light center of lamp 8 can be correctly located at the proper optical position relative to the reflector flutes 6d and the refractor prisms 7a, as more fully disclosed herein. Such proper positioning of the light center of lamp 8 is necessary to provide the desired distribution of light on the floor to be lighted as well as to avoid undue glare from the luminaire. In addition, the relatively low profile of the luminaire thus achieved makes it feasible to use the luminaire in areas having relatively low ceilings.

As seen in the embodiment illustrated in FIG. 1, lamp 8 is arranged so that its light center LC is arranged somewhat above the bottom of upper reflector portion 6a. The latter reflector portion is relatively steeper in slope than reflector skirt portion 6b, and whereas the interior surface of reflector portion 6a is generally concave, reflector skirt portion 6b is straight in vertical section. As a result, as seen in FIG. 5, light rays from the light center LC of lamp 8 which are incident on upper portion 6a are reflected downwardly therefrom toward the opposite side of the luminaire, while light rays striking skirt portion 6b are reflected downwardly and outwardly therefrom toward the same side of the luminaire.

As seen in the generally horizontal section of reflector portion 6a shown in FIG. 4, flutes 6d have transversely convex inner reflecting surfaces so as to spread incident light rays in horizontal (i.e., lateral) directions. Similar flutes formed in skirt portion 6b similarly horizontally spread the light rays incident thereon.

Arranged at the open bottom of ballast housing 1 above the top opening of main reflector 6 (see FIG. 1) is accessory reflector 19 secured at its central portion to housing 1 by suitable means. As shown in FIG. 5, reflector 19 has a downwardly dished central portion 19a, a flat annular intermediate portion 19b extending substantially horizontally, and a downwardly sloping outer rim portion 19c. The light rays from lamp 8 striking central portion 19a are deflected therefrom downwardly and outwardly away from the lamp axis, intermediate portion 19b reflects light rays downwardly at smaller vertical angles than those reflected from portion 19a, and reflector rim portion 19c reflects light rays back toward the opposite side of the luminaire. Reflector rim portion 19c is preferably formed with flutes on its reflecting surface similar to those of main reflector 6 as shown in FIG. 4 to horizontally spread the incident light rays. In general, the light rays reflected from accessory reflector 19 as well as those reflected from main reflector portion 6a are directed downwardly through the bottom panel 7b of refractor 7. As seen in the plan view of FIG. 2, bottom panel 7b is formed on its inner surface with radially extending flutes 7e or the like, which serve (see FIG. 8) to disperse the light rays emanating therefrom so as to spread them over the area to be illuminated below the luminaire. Flutes 7e are transversely convex but are of substantially constant refractive power along their lengths, so that the emanating light rays are fanned out in varying vertical angles in circumferential direction without an appreciable change in vertical angle in radial directions as between a particular incident light ray and a corresponding emanating light ray.

As seen in FIG. 5, the light rays from lamp 8 which are reflected from reflector skirt portion 6b are incident on the prismatic side wall 7a of refractor 7, and a portion of direct light rays from lamp 8 are also incident thereon. Side wall 7a is formed on its outer surface with annular parallel rows of horizontal prisms, the rows from top to bottom being of decreasing diameter so as to be offset inwardly from one another as shown. Each prism (see FIG. 7) has a substantially horizontal reflecting surface 7c and a substantially vertical refracting surface 7d. By virtue of this structure and the arrangements described above, light rays incident on refractor wall 7a are in part refracted and depressed by vertical wall 7d of the prisms and in part are reflected by horizontal face 7c of the prisms so as to be directed upwardly and outwardly from the luminaire. As a result of this double-acting function of prisms 7a, a portion of the light is directed toward the ceiling to minimize contrast between the illumination of the floor and the ceiling, light rays are spread over a wide floor area even when the luminaire is mounted at a relatively low height, and the brightness (glare) from the luminaire in the zone of about 45.degree. to 90.degree. vertical angles is considerably reduced. Excessive brightness is also minimized due to the relatively large area of light emission from the large size refractor.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.

Claims

What we claim as new and desired to secure by Letters Patent of the United States is:

1. A luminaire comprising, in combination, an optical assembly comprising a reflector having an upper portion and a lower downwardly flaring skirt portion defining an open bottom, and a generally dish-shaped refractor having an open top and a closed bottom, said reflector and said refractor being connected to each other at their peripheries with said refractor arranged below and closing the bottom of said reflector, said optical assembly being substantially greater in overall diameter than in height, and a lamp mounted in said optical assembly and having a light center arranged above the bottom of said reflector, said refractor having a peripheral side wall formed on its outer surface with annular rows of prisms having substantially vertical refracting surfaces and substantially horizontal reflecting surfaces, said substantially vertical refracting surfaces depressing light rays incident thereon from said lamp downwardly from said optical assembly, and said substantially horizontal reflecting surfaces re-directing light rays incident thereon from said lamp upwardly from said optical assembly.

2. A luminaire as defined in claim 1, said refractor having a bottom panel formed with a plurality of elongated refracting portions radiating from the center of said bottom panel for circumferentially spreading light rays emanating from said panel.

3. A luminaire as defined in claim 2, said elongated radiating refracting portions comprising transversely convex flutes formed on the inner surface of said refractor panel.

4. A luminaire as defined in claim 3, said flutes being of substantially constant refractive power along their lengths.

5. A luminaire as defined in claim 1, a ballast housing arranged above and connected to said optical assembly for supporting the same, and an accessory reflector mounted at the bottom of said ballast housing above said upper reflector portion for reflecting light rays from said lamp downwardly through said refractor.

6. A luminaire as defined in claim 1, said reflector portions being formed with flutes for horizontally spreading light rays from said lamp.

7. A luminaire as defined in claim 1, the height of said reflector being about twice the height of said refractor.

8. A luminaire as defined in claim 7, the overall diameter of said optical assembly being at least twice its height.