US3047716A - Luminaire - Google Patents

Description

July 31, 1962 J oxn: ETAL 3,047,716

LUMINAIRE Filed Jan. 31, 1961 INVENTORS JbH/v P flax/E AND ITIEANKLIN M NEAL United States Patent Office 3,047,716 Patented July 31, 1962 3,047,716 LUMINAIRE John P. Hoxie and Franklin M. Neal, Corning, N.Y., assignors to Corning Glass Works, Corning, N.Y., a corporation of New York Filed Jan. 31, 1961, Ser. No. 86,208 2 Claims. (Cl. 2401.2)

The present invention relates to a luminaire which is adapted to be recessed substantially flush with a surface such as an airport runway and which is capable of emitting light at low angles of elevation above such surface.

It has generally been the practice to delineate airport runways at night by means of two rows of lights located one at each edge of the runway and projecting substantially thereabove. Recent conditions of increased air traffic have indicated the advisability of placing lights in the runway surface itself in order to render the runway more easily visible from the air.

In the construction of luminaires adapted for such use, it has been a problem to design units capable of directing light at low angles of elevation along an incoming flight path and at the same time sufficiently nearly flush with the runway surface so as to permit airplanes to taxi along the runway Without being subject to excessive vibration.

It has also been a problem to design a unit sufliciently compact to permit installation in presently existing runways with a minimum of excavation.

The luminaire of the present invention has among its objects the satisfaction of the above requirements.

In general, these objects are accomplished by the provision of a luminaire comprising a lens with a light source on the approach side of a lens, the lens including an entrance surface, a reflecting surface, and an exit surface, said luminaire being positioned so that the two first-mentioned surfaces are substantially beneath the level of the runway surface and the last-mentioned surface is only partially above the said level but completely exposed to view.

The construction of one embodiment of a luminaire according to the present invention may best be considered with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a lens and light source according to the present invention,

FIG. 2 is a sectional view taken along line 22 of FIG. 1,

FIG. 3 is a top view of one form of a luminaire adapted for seating in a cylindrical hold in a runway, and

FIG. 4 is a view taken through line 4-4 of FIG. 3.

The construction of the novel lens employed in the present luminaire is illustrated in FIGS. 1 and 2. Light from source 11 enters lens 12 through entrance surface 13, is reflected from reflecting surface 14, which is a coating of silver or any other reflecting substance, and emerges from exit surface 15.

In the illustrated embodiments, entrance surface 13 and exit surface 15 are plane surfaces, entrance surface 13 being vertical, and reflecting surface 14 is curved in both horizontal and vertical directions such that, when the light source is considered to be a point, the cumulative effect of the three surfaces is to collimate the emergent rays horizontally and to spread them vertically over angles of elevation above the horizontal varying continuously from 8 for those rays emerging near the bottom of exit surface 15 to 1 for those rays emerging near the top of that surface. These angles are illustrated in FIG. 2 by the angles b and a respectively. In other embodiments curved and plane surfaces may be interchanged.

In the illustrated embodiment light source 11 is in the form of a horizontal linear filament positioned parallel to entrance surface 13. A consequence of the finite horizontal length of the filament is that light emerging from the lens is spread over a few degrees in a horizontal plane, the spread depending upon the length of the filament and its distance from the lens. This small spread is desirable in order to render the signal visible from positions slightly off the sides of the runway. Variations in filament size and distance may be offset by Variations in the horizontal curvature of reflecting surface 14.

The effect of lens 12 on the vertical orientation of light rays originating at the center of filament 11 can be seen in FIG. 2. Rays 20 and 21 are refracted at entrance surface 13, are reflected from surface 14 and emerge at angles of elevation of 1 and 8 respectively after being refracted at exit surface 15. The lens is adapted to bend rays intermediate between rays 20 and 21 through angles varying between 1 and 8.

Lens 12 is recessed almost completely beneath the level of the surface of the runway. A convenient means for embedding the lens in a runway and at the same time insuring that most of the rays emitted from exit surface 15 are utilized is provided by mounting unit 25, illustrated in FIGS. 3 and 4. This unit comprises a cylinder having a height approximately equal to that of lens 12 and a diameter suflicient to permit inclusion of the lens and light source 11 in a cavity in the mounting unit. Lens 12 extends above the top surface of the mounting unit 25 only by an amount suflicient to present a substantial viewing surface at low elevations above the runway surface, which is substantially flush with the upper surface of the mounting unit when the unit is in position. It is unnecessary that all of exit surface 15 extend above the runway surface level since, as indicated in FIG. 2, those rays which are directed at low angles of elevation are emitted near the top of the exit surface, while the lower portion of said surface directs light at higher angles, at which angles obstruction from the rim of mounting unit 25 or the surface of the runway is less of a problem.

Light source 11 is positioned within the cavity of mounting unit 25 and on the approach side of lens 12, which side is the side from which a landing airplane approaches the luminaire. A transparent cover 26 may complete the enclosure of light source 11 and prevent the accumulation of deposits in the cavity.

It can be seen that only a small portion of the light emitted from source 11 is directed within the desired range. The efficiency of the device can be improved by placing a reflector behind the light source. It will also be observed that some light will enter the lens at angles outside the range between the angles of rays 20 and 21. These rays will emerge from the lens in various directions but the intensity in any given direction will be low.

It will be readily seen that the advantages of the present invention will accrue even though variations are made in the exact configuration of the luminaire. A cylindrical mounting unit has been chosen because of the ease with which circular holes may be formed in a runway. It is apparent that no arbitrary dimensions may be given to lens 12 and that various combinations of shapes of entrance, reflecting and exit surfaces within the spirit of the present invention will produce the desired pattern of emergent light.

The range of elevation of the emergent rays in the illustrated embodiment has been chosen to be between 1 and 8 since present conditions of air traflic indicate this range to be optimum. Under changed conditions, this range may be varied by changes in the configuration of lens 12 within the spirit of the invention. The exact configuration of lens 12 can easily be determined to satisfy varying requirements by those skilled in the art according to wellknown mathematical and optical laws.

Accordingly, it is intended that the present invention be limited only by the scope of the appended claims.

What is claimed is:

1. A luminaire for directing light through a range of low angles of elevation above a horizontal surface comprising .a light source located below the level of said horizontal surface and a lens extending from slightly above saidvhorizontal surface to a level silghtly below said light source, said lenscompr-ising an entrance surface located on the same side of said lens as said light source positioned to receive light rays therefrom, an exit surface located on the same side of said lens as said light source and at the top oftsaid lens and forming an acute angle with said horizontial surface when measured in the direction away from said light source, and a reflecting surface located at the 1 side of said lens opposite said light source, said reflecting surface being curved in both horizontal and vertical directions, said lens spreading light from said source vertically through angles of elevation above said horizontal surface varying continuously from a maximum for light emerging near the bottom ofi said exit surface to a minimum for light emerging near the top thereof.

2. A luminaire according to claim 1 wherein said refleeting surface substantially collimates horizontally the 10 light from said light source falling thereupon.

References Cited in the file of this patent FOREIGN PATENTS

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