Omnidirectional light beacon with toroidal flash lamp

[57] ABSTRACT

A toroidal, gas filled arc discharge flash lamp encircles a reflector having a surface of revolution coaxial with the lamp and comprising the locus of normals to the bisectors of lines tangent to consistent loci on the toroidal lamp and of lines intersecting the axis at a constant angle. Light is reflected substantially uniformly nearly 360° around the reflector and concentrated around an angle somewhat above the horizontal.

Claim, 4 Drawing Figures

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PATENTEE DEC 31974

3,852,584

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RELATIVE INTENSITY

3,852 1

OMNIDIRECTIONAL LIGHT BEACON WITH TOROIDAL FLASH LAMP

BACKGROUND OF THE INVENTION

As disclosed in copending U.S. Pat. application Ser. 5 No. 212,190, filed Dec. 21, 1971, now Pat. No. 3,771,120 by Robert P. Bonazoli and Donald I. Coggins and erntitled Airport Runway Approach and Reference Lighting System and airport beacon unit may have both a directional gas discharge flash lamp and an omnidi- 10 rectional flash lamp. The directional lamp or a series of them are aimed in a relatively narrow beam toward and on the correct line of aircraft approaching a runway. The intensity of the lamp is governed by the duration of its discharge. The omnidirectional lamp radiating in ¹⁵all directions serves for earlier location of the runway, and also serves as a quench tube for terminating discharge of the directional lamp, thereby controlling the intensity of the directional lamp light emission.

The object of the present invention is to provide an ²⁰improved optical system for multidirectionally radiating light from the quench tube so as to produce a light intensity of nearly uniform magnitude in substantially all directions about a vertical axis, with maximum intensity at a preselected angle relative to the horizontal ²plane.

SUMMARY OF THE INVENTION

According to the invention a multidirectional light ₃₀comprisees a lamp of toroidal volume curved in a plane substantially around an axis normal to the plane, a reflector, and means to mount the lamp in fixed relation thereto, the reflector comprising a surface of revolution curved around the lamp axis and defined by a gen- ₃₅eratrix of the surface intersecting the lamp plane between the lamp and its axis and comprising the locus of normals to bisectors of the angle between two sets of lines, the first lines being tangent to consistent loci on the toroidal volume and the second lines intersecting 40 the axis at a constant angle such that the maximum intensity of reflected light is substantially uniform through, and concentrated around a selected angle relative to the lamp plane.

DRAWINGS

FIG. 1 is an isometric view of an omnidirectional light beacon according to the invention;

FIGS. 2 and 3 are optical diagrams of the beacon of FIG. 1.; and 50

FIG. 4 is a graph of light distribution from the beacons of FIGS. 2 and 3.

DESCRIPTION

FIG. 1 55

As shown in FIG. 1 an omnidirectional flash lamp system suitable for use in the previously described airport system or for other beacon use is mounted on a control cabinet 1. The beacon comprises a base 2 attaching a clear or tinted transparent cylindrical glass ⁶⁰enclosure 3 to the base 2. Mounted on the base 2 is a hollow metallic reflector 4 having top and bottom portions 6 and 7 separably joined at a central seam 8. A flash lamp 9 of toroidal volume encircles the reflector in the plane of the central seam and with the lamp axis coincident with the reflector axis A. Brackets 11 on the lower reflector portion 7 support the lamp, and a lamp ,584 holder 12 electrically interconnects the lamp terminals with a power supply within the control cabinet 1.

FIG. 2

The reflector 4 is a polished, surface of revolution about the axis A of a generatrix curve G defined as follows. A portion of the lamp 9 is shown in vertical section centered on the horizontal plane P and displaced outwardly a distance D from the axis of revolution and of the toroidal lamp volume. A first line T is drawn tangent to the inward surface of the toroidal volume of the lamp 9. A second line X intersecting the first line T at point 20 is drawn at the angle to the horizontal plane P at which the lowest light ray 21 is desired to radiate from the reflector. In an airport beacon system it is usually desirable for the lowermost ray 21 to issue horizontally, parallel with the ground, hence the line X is parallel, or at a zero degree angle to the plane P. Where, as shown in FIG. 3, it is desired that the lowermost ray 21* issue below the horizontal, the line X* is drawn at a corresponding angle x* to the horizontal. After drawing a bisector B of the angle between the first and second lines T and X, a line N normal (i.e., perpendicular) to the bisector B at the point P represents a reflecting increment on the generatrix G. Repetition of the development of the above described increment will trace the complete generatrix G. Successive first lines must be drawn consistently tangent to successively adjacent surfaces of the lamp volume. To construct a particular generatrix curve a point on the line P representing the horizontal plane is selected with regard to the cross sectional radius R of the lamp volume and to the radius of its torus which equals the displacement D of the torus from the vertical axis. For a lamp of sectional radius R=0.60 cm. and toroidal diameter D=5.O8 cm. a suitable value for the length of the first XI from the axis A to the generatrix G is 3.11 cm. Other suitable dimensions shown in FIG. 2 are S=9.54 cm., U=11.30 cm., W=7.76 cm. These three latter dimensions are selected with respect to the desired limits of the reflector size and the intensity of concentration of the emitted light close to the horizontal or ground plane. For greater concentration the extreme upper and lower edges of the reflector are at a greater distance D+S from the axis A than the lamp displacement D, so that one or both of the extreme edges overhang the lamp.

Having located one point on the generatrix curve a line T1 is drawn from the lamp volume, a bisecting line B drawn and a normal N to B drawn at the selected point as described above with respect to point 20. The generatrix curve is then completed graphically by connecting successive normal increments to the first normal increment in a known construction manner.

The above graphic description of the generatrix is summarized as follows:

The generatrix G is the locus of normals N to bisectors B of the angle between first lines T tangent to the toroidal lamp volume and second lines X intersecting the axis A of revolution at a constant angle x.

An equivalent description of a generatrix reflector may also be made mathematically in spherical coordinates p, g and r shown in FIG. 2 according to the equation below wherein p is the angle in the vertical plane, g the angle in the horizontal planes, r the variable radius, R the fixed radius of the toroidal lamp volume, D the displacement of the lamp volume center C from the vertex V of the reflector, and H a parameter dependent on reflector size:

3.852.584 (r²—2Dr cos p + D²-R²) ^1/2 —R tair'i^-lDr cos p + D²—R²)^1I2IR] + R tan^-1 [r sin p / (r² cos² p—2Dp cos p + D²)¹'²] —(r² cos² p - 2Dr cos p + D²)¹'² - 2//=0

As shown in FIG. 2 by way of example, the dimensions of the reflector in relation to the toroidal lamp may be as follows:

D — 5.08 cm.

R — 0.60 cm.

S — 9.54 cm.

U— 11.30 cm.

W — 7.76 cm.

Either of the above graphic or mathematical methods will generate a family of reflector curves, all of which satisfy the requirement that the lowermost ray issue from the reflector at the desired minimum angle with respect to the horizontal plane P. Moreover the reflectors so generated will concentrate the beam of rays within a relatively narrow vertical angle above the lowermost ray. Although rays on lines 21 consistently tangent to the inward surface of the lamp volume reflect at the desired minimum angle x, rays such as 22 or 23 in FIG. 2 emanating from outer surfaces of the toroidal volume will be reflected at an angle y above the horizontal. The angle, however is limited and substantially all concentrated near the horizontal as shown in FIG. 4.

FIG. 4

A beacon constructed with the above dimensions will distribute light with the specific distribution shown by the solid line curve I. At the below zero degrees above the horizontal the intensity of radiation is low and dropping sharply. Maximum intensity is at about 5° above horizontal, and above 5° drops off sharply, indicating the efficiency of the present reflector in concentrating light near the horizontal or other desired angle. Similarly the broken line curve I* shows a similar concentration of light at the slightly lower angle afforded by the reflector generated by the curve of FIG. 3.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.