Luminaire Reflector

Abstract

An industrial luminaire has a dome-shaped reflector formed of vertically elongated facets arranged at angles to one another around the axis of the reflector, each facet having a convex reflecting surface, so that rays are not reflected back through the light source and are dispersed by each facet to overlap the illumination provided by other facets.

Description

The present invention relates to luminaires, and particularly to reflectors of luminaires such as those of industrial type for indoor lighting.

Luminaires of the above type conventionally employ dome or bell shaped reflectors in which a suitable light source, such as a gaseous discharge lamp, is mounted and which are often enclosed by a glass window covering the mouth of the reflector. Reflectors which have a smooth annular reflecting surface surrounding the lamp axis generally reflect the light rays so that they cross on the reflector axis in a concentrated region below the cover glass. As a result, a heated area is produced which causes thermal movement of floating dirt particles toward the cover glass on which they accumulate, thereby causing decreased light transmission through the glass and substantially reducing luminaire efficiency. While reflectors are known which are formed of a series of angularly arranged faceted reflecting surfaces or curved (fluted) reflecting surfaces which avoid the above problem to some extent, these reflectors have certain disadvantages. In the case of angularly arranged flat facets, each facet operates to illuminate a particular area of the floor below the luminaire, but in practice slight misalignment of the flat facets in manufacture of the reflector often results in a flat facet reflecting light to an area also covered by a nearby flat facet. As a result, some floor areas have more light than others, and the illumination provided by the luminaire does not have optimum uniformity. In the case of reflectors having a reflecting surface consisting of curved flutes, while the light rays reflected from the flutes are dispersed so that better uniformity of illumination is obtained, some light is reflected back from the flutes toward the light source, which may thereby be excessively heated, and toward the axis of the reflector to produce a heated region at the cross-over point, with the undesirable effects mentioned above.

It is an object of the invention to provide a luminaire reflector which overcomes the above disadvantages of known types of reflectors.

It is a particular object of the invention to provide a luminaire reflector which affords substantially uniform illumination, avoids overheating of the light source, and reduces the accumulation of dirt particles on the window closing the reflector.

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

With the above objects in view, the present invention relates to a luminaire reflector having a top and a bottom and formed by a wall extending about an axis and defining a bottom opening, the wall comprising a plurality of elongated reflecting facets arranged side by side about the axis and being at an angle to one another so as to form alternating ridges and grooves between adjacent facets, the facets having inwardly convex reflecting surfaces, whereby rays from a light source adapted to be positioned on the axis within the reflector are reflected by each convex facet in diverging paths through the space between the light source and the wall and outwardly through the bottom opening.

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 of an industrial luminaire having a reflector in which the invention may be embodied;

FIG. 2 is a bottom plan view of the FIG. 1 luminaire;

FIG. 3 is an enlarged view in elevation, partly broken away, of the luminaire reflector;

FIG. 4 is a bottom plan view of the FIG. 3 reflector;

FIG. 5 shows a segment of the luminaire reflector taken along the line 5--5 in FIG. 3 and including ray diagrams; and

FIG. 6 is a somewhat diagrammatic view of a segment of the luminaire reflector, similar to that of FIG. 5, showing a plurality of adjoining curved facets of the reflector and the radii and centers of curvature of the respective curved facets.

Referring now to the drawings, and particularly to FIG. 1, there is shown an industrial luminaire comprising a ballast housing 1 secured to a wire conduit 2 such as a metal pipe and having suspended from the bottom thereof an optical assembly 3. The latter assembly includes a dome-shaped faceted reflector 5, which is constructed in accordance with the invention, and in which is mounted a lamp 6, typically of gaseous discharge type, removably secured to a lampholder or socket 7 so as to extend into reflector 5 along the axis thereof. The open mouth at the bottom of reflector 5 is closed by a transparent window 8 (see FIG. 2) secured at one side to the reflector by hinge 9 and detachably secured to the reflector by clips 10 or the like at spaced points around the reflector rim.

As seen in FIGS. 3 and 4, reflector 5, which is typically made of aluminum, is formed of angularly related elongated facets extending from top to bottom of the reflector and arranged side by side symmetrically about the vertical axis A of reflector 5. Light rays emanating from lamp 6 are reflected by the inner surfaces of the reflector facets downwardly and outwardly through the mouth of reflector 5, such that the angle of the reflected rays relative to vertical axis A varies depending on the point of reflection from the reflector, as seen in FIG. 3.

In accordance with the invention, each of the reflector facets is formed with an inwardly convex surface so that the light incident thereon is dispersed sufficiently to illuminate the floor area also illuminated by the two nearby facets on opposite sides thereof which face in the same general direction. FIG. 5 shows a segment of the faceted reflector, and as shown therein, two adjoining facets 5a, 5b meet along their adjacent edges to form a ridge 5c and meet similar facets 5d, 5e at their opposite edges to form grooves 5f. Shown in solid lines are paths of light rays C coming from light source L and reflected from the curved reflecting faces of facets 5a, 5b. Shown in dashed lines adjacent facets 5a, 5b are the planes Fa, Fb in which those facets would lie if they were flat, and in correspondingly dashed lines are shown representative paths of light rays F as they would occur due to reflection from the faces of such flat facets. As will be seen, the rays reflected from the convex faces of facets 5a, 5b are dispersed laterally over a substantially wider range than the rays reflected from the flat facet surfaces. Hence, the illumination afforded by such curved facets overlaps the areas illuminated by those nearby facets on opposite sides which reflect the light toward the same general area, thus contributing to overall uniformity of illumination and compensating in substantial degree for any lack of precision in the alignment of the facets in the process of manufacture. It will further be evident that no light rays are reflected directly back to the light source, since the rays will be reflected on opposite sides of the lamp depending on which side of ridge 5c or groove 5f they strike. Moreover, the thus dispersed light rays passing through the space between the lamp and the reflector wall are directed away from the reflector axis and do not cross thereon. As a result, the formation of a heated area at the reflector axis and the undesirable effects of dirt accumulation on the reflector window 8 attendant thereon as explained above are entirely avoided. The floor area immediately below the luminaire is illuminated by direct light from the light source and by light reflected by the non-faceted annular surface 5' at the top of the reflector.

FIG. 6 is a somewhat diagrammatic view of a segment of the reflector similar to that shown in FIG. 5, showing adjoining convex facets 5a, 5b and 5g, 5h and the relative positions of the centers of curvature thereof. As will be seen, the center of curvature Ca of curved facet 5a (of radius Ra) and the center of curvature Cb of curved facet 5b (of radius Rb) are on opposite sides of line X, which represents the plane passing through the light source at the reflector axis (point L in FIG. 5) and ridge 5c marking the junction of facets 5a and 5b.

The degree of curvature of the convex surfaces of the reflecting surfaces may be selected to provide the desired angular dispersion of the reflected light. In general, it was found that for luminaires of the type illustrated where the diameter of the reflector rim is in the range of about 17 to about 22 inches, the radius of curvature of the convex facet surfaces will be in the range of about 2 to about 14 inches, with a radius of about 7 to 9 inches being optimum. The radius of curvature selected would also depend on the total angle of light intercepted by the particular facet. The larger the angle of intercepted light, the less the curvature needs to be; hence, relatively wide facets would have a relatively long radius of curvature, whereas relatively narrow facets would have a relatively short radius curvature.

For luminaire reflectors of the described type, the provision of facets with too small a radius of curvature, i.e., less than about 2 inches, would cause a substantial amount of light rays to undergo at least one additional reflection before passing out of the reflector. Such multiple reflections appreciably attenuate the light intensity and result in an undesirable loss of luminaire efficiency. Facets with a radius of curvature greater than about 14 inches do not provide sufficient dispersion of the light rays to provide the desired degree of overlapping illumination effects to result in optimum uniformity of illumination from the luminaire as a whole.

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 desire to secure by Letters Patent of the United States is:

1. A reflecting device comprising a dome-shaped reflector member having a top and a bottom and formed by a wall extending about an axis and defining a bottom opening, said wall comprising a plurality of elongated reflecting facets arranged side by side about said axis with adjacent facets being at an angle to one another so as to form alternating ridges and grooves between the adjoining sides of said facets, said facets having inwardly convex reflecting surfaces and the convex surfaces of adjacent ridge-forming facets having different centers of curvature, whereby rays from a light source adapted to be positioned on said axis within said reflector member are reflected by each convex facet in diverging paths through the space between the light source and said wall and outwardly through said bottom opening.

2. A reflecting device as defined in claim 1, the radii of curvature of each pair of facets adjacent a ridge formed thereby crossing a plane parallel to and containing said ridge and said axis.

3. A device as defined in claim 2, wherein said radii of curvature are in the range of about 2 to about 14 inches.

4. A luminaire comprising, in combination, a reflecting device as defined in claim 1, and a lamp mounted within said reflector member on said axis.

5. A luminaire as defined in claim 4, and a light transmitting window covering the bottom opening of said reflector member.

6. A luminaire comprising, in combination, a reflecting device as defined in claim 3, a lamp mounted within said reflector member on said axis, and a light transmitting window covering the bottom opening of said reflector member.