US 2194431 A
Description (OCR text may contain errors)
J. A. O'NEIL March 19, 1940.
REFLECTOR Filed Nov. 1'7} 1957 Inventor:
Patented Mar. 19, 1940 REFLECTOR James A. ONeil, Lynn, Mass., assignor to General Electric Company, a corporation of New York Application November 17, 1937, Serial No. 174,913
My invention relates to reflectors and more particularly to reflectors of the bowl type.
One object of my invention is to provide a reflector which will reflect light in a manner to 5 avoid overheating certain parts of a. lamp located within the reflector.
Another object of my invention is to provide a reflector which will reflect light in a manner to avoid striking certain parts of 'a lamp within the reflector and still maintain the symmetry of the reflected beam. 1
For a better understanding of my invention together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.
Luminaires oi the type used for highway illumination are provided with a high powered light source, more than one-half of the projected light from which is reflected and combined with the direct light from the source, into a beam having a width of 180 or less. In order to obtain the proper distribution of this reflected light, much 25 of the radiant energy is directed through the lamp, and consequently raises the temperature thereof above the normal operating temperature. In cases where the lamp is an incandescent filament lamp for example, this rise in temperature, if too great, may cause overheating of the supporting structure, or stem, for the incandescent filament thereby softening the glass, causing a displacement of the filament within the container and also causing a rapid deterioration of the seals between glass and metal so that the life of. the lamp is considerably reduced. It is therefore important; to distribute reflected light within the reflector so that the radiant reflected energy will not be directed into the center of the lamp, and at the same time will not materially afiect the beam formation. In view of the small space be tween the lamp bulb and the reflector, no attempt is made to deviate the reflected light enough to pass between the bulb and the reflector, but it.
zontal displacement is such that each panel will deviate the reflected beam from the projected radial beam by an angle suflicient to avoid striking the filament and its supporting structure, located at the axis of the reflector. The beams reflected by the individual panels are stacked radially about a cylindrical space concentric with the axis of the reflector, in the manner of the plates of an iris. The beams are thereby moved a minimum angular distance fromtheir normal radial direction and since each beam is moved the same angular distance and in the same direction there is substantially no cross reflection within the reflector.
A reflector embodying my invention is illusstrated in the accompanying drawing in which Fig. l is a front elevation, partly in section, of a street lighting luminaire; Fig. 2 is a fragmentary sectional view along lines 22 of the reobtained; Fig. 3 is a View similar to Fig. 2 of a section of the reflector taken along lines 33 of Fig. 1 together with a diagram of reflection.
Referring to the drawing in detail, Fig. 1 discloses a luminaire comprising a cap 3, a reflector 4, and a globe 5. The reflector 4 is attached to the cap 3 by suitable latches 6, and the globe 5 is attached to the reflector by a flange l which is spun over the beading on the edge of globe 5. Within the cap 3, a lamp socket 8 is supported by a bracket 9 and a conventional incandescent lamp I0 is mounted therein. The incandescent v flector of .Fig. 1, together with a diagram, illustrating the arrangement of the elements of the reflector whereby the desired light reflection is lamp I0 is provided with a glass stem II from which a lead-in wire l2 projects to the incandescent filament l3. The stem II is of the hollow glass tube type through which the lead I2 passes from the base of the lamp. The stem I I is closed at its end l4 to form the necessary vacuum tight seal between the glass and the metal of the supporting wire. The reflector is symmetrical about a vertical axis and is shaped to reflect light in vertical planes through the axis of the reflector along the lines illustrated by the dash and dot lines. Line I5, for example, indicates a ray of light projected from the center of the light source to the reflector at which sec- 4 tion 33 is taken, and is reflected as shown by line It in such direction that it passes just below the opposite edge of the reflector. Line I! illustrates a ray of light projected to and reflected from a point on the reflector, at which section 22 is taken, in the direction of line i8.
Bearing in mind that the lines 15 and I! represent radial rays, and that the reflected rays 16 and I 8 would also be radial in a conoidal reflector, it will be evident that the reflected energy is concentrated on the supporting structure within the lamp. This manner of distributing the light in vertical planes is fully described in Patent No. 2,110,018 issued March 1, 1938, to Halvorson, and assigned to the assignee of the present application. I
In order to avoid the reflection of this light energy through the stem H and the light source supported thereby onthe axis IQ of the reflector, the reflector 4 is divided into panels 20 which panels are each angularly displaced relatively to the normal circular cross section 2| of the reflector in the same direction and at the same angle in the manner illustrated in Figs. 2 and 3. The panels 20 are, in accordance with my invention, developed from a conoidal, or bowl-shaped, reflector which is given the desired contour or curvature. The surface is then divided into sections, or panels, by radial planes projected through the axis l9 and spaced at any desired angle. In the illustrated reflector the planes are spaced approximately 10, and each section or panel between a pair of radial planes is then moved about the trailing edge which is maintained at its curvature in the original surface. The arcuate distance which the section is turned about the trailing edge varies in proportion to the radial distance at which each element of the section is spaced from the axis of the conoid. At the lower edge of the reflector, in the present example, this distance is approximately and gradually increases to approximately at its upper end. Each panel therefore tends to assume the shape of a spiral. The leading edge of each panel is connected to the trailing edge of the following panel, which as above stated remains'in the original conoidal surface, by a surface 22 which is maintained as nearly as possible radial to the source in order to avoid any cross reflection therefrom, and its accompanying loss of efliciency.
Referring to Fig. 2 which illustrates a fragmentary section of the reflector 4 taken in a horizontal plane at the point indicated by lines 2-2, I have shown diagrammatically the reflectedrays from a single point on the surface of a section 20. The circle 23 indicates the circumference of the light source, the center of which only is considered in the diagrammatic portion of Fig. 1. It is obvious from Fig. 1 that the incandescent filament l3 supported in loops by the lead-in wire I I has a substantial dimension in a horizontal plane. Its dimension in a vertical plane is somewhat smaller. This vertical dimension affects only the distribution of the reflected light in vertical planes, and for the purposes of this present invention, need not be considered. In order to attain the objects of the present invention, however, the horizontal dimensions must be taken into consideration, and circle 23 being the circumference of the light source, is used to indicate the locus of points of tangency from which tangent light rays are projected from the source to the reflector. Line 24 is tangent to the circle 23 and indicates light projected to a point 25 on a section from one side or extremity of the light source, and line 26 is the tangent drawn to the other side of the circle 23 and indicates the direction of light projected from the. other side or extremity-of the light source, to the same point on the same panel 20. Line 21 is drawn from the center of the light source, which coincides with the axis IQ of the luminaire, to the point 23 onthe section 20 and line 23 indicates the reflected ray correspondingto the projected ray 23. The angular displacement of the section 20 relatively to the circular cross section 2| is equal to one-half of the angle between the projected ray 21 and its corresponding reflected ray 23. This angle is such that the reflection of the tangent ray 26 as indicated by line 28 is substantially parallel. In other words, the line 26 which is the light ray projected from one extremity of the light source is substantially normal to the section 20 in its displaced position. In accordance with the laws of reflection, the ray 24 is reflected along the line 30, and therefore all light projected from the source, defined by the circle 23 is projected to any point 25 on the sections 20 between the tangents 24 and 26, and is reflected between the lines 28 and 30, all of this light passing outside of the circle 23. The above explanation, of course, applies equally to every point on the reflector section in plane 2-2. The circle 3| is drawn to indicate the locus of tangents of reflected rays 29 and the circle 32 indicates the locus of tangents of reflected rays 30.
In Fig. 3, I have shown a section of the reflector at a shorter radial distance from the axis than in Fig. 2. The circumference of the light source is indicated by the circle 23. Tangent rays 35 and 36 are projected onto a point 31 on a section 20 and arerespectively reflected as rays 33 and 33. The circumference of the space which is to be kept free of reflected radiant energy is the same as at the plane at which section 2 2 was taken. In view of the shorter distance from the axis I9 therefore the angle of deviation is slightly increased so that each section 30 is gradually tilted at a larger angle as it approaches the axis of the reflector in order to clear the same diameter space around the axis.
From the foregoing description, it will be clear that the deviation of the light flux from the axis of the reflector is obtained with substantially no change in the formation of the beam. Each beam reflected by a section of the panel is deviated sumciently to avoid striking the filament or its supporting structure and is substantially parallel to the beam projected by anadjacent said reflector and at the focal point thereof, said reflector surrounding said light source and having a surface divided into panels each panel projecting light from said source across said reflector and outwardly of said reflector below the opposite edge thereof, said panels being angularly displaced relatively to the contour oi said reflector one edge thereof remaining in saidcontour. said displacement being such as to reflect light from said source at a horizontal angle to the radially projected light to create a space having a substantially uniform diameter about the axis, of said reflector which is free of reflected energy.
2. In a luminaire, the combination of a light source comprising a lamp provided with an incandescent filament supported by a structure within an evacuated container and a reflector, said reflector being conoidal having its axis coincident with the axis of said light source and being divided into panels by radial planes, said panels being angularly displaced relatively to said conoidal surface one edge thereof remaining in the said conoidal surface, said angular displacement increasing as the section approaches the axis of said reflector thereby creating a space of substantially uniform diameter about said reflector axis which is free of reflected energy.
3. In a luminaire the combination of a light source having a substantial diameter, a support therefor, a reflector surrounding said light source and support arranged to confine the light from said source to a beam of substantially 180 degrees, said reflector being divided into panels by radial planes projecting from said source and support, said panels being respectively displaced relatively to the curvature of said reflector at a horizontal angle about one edge which remains in the curvature of said reflector, the angle of displacement of the elements of said panels varying so that the light reflected by said panels creates a space about the said support which is free of reflected energy, said space having a diameter not less than the diameter of said light source.
4. In. a luminaire the combination of a light source, a support thereior, a conoidal reflector surrounding said source and support, said source and support being on the axis of said reflector and said reflector being divided into panels by radial planes projected through the axis of said source and support, said panels being arranged to project light from said source across said reflector and below the opposite edge thereof and being displaced about one edge respectively, and a radial surface connecting the opposite edge of said panel with the succeeding panel, each of said panels being displaced in the samedirection and at the same angle to create a space about said, support which is free of reflected energy.
5. In a luminaire the combination of a light source, a support therefor, a conoidal reflector surrounding the source and said support and divided into panels by radial planes projected through the axis of said source and support, said panels being shaped to project light across said reflector and below the opposite edge thereof and being respectively displaced about one edge and angularly displaced in the same direction to reflect light from said source at a distance from the axis thereof, whereby none of said reflected light will strike said support and said source, and radial surfaces connecting the ofl-set edges of adjacent panels.
JAMES A. ONElL.