US 3758770 A
Description (OCR text may contain errors)
Unite States atent 1 1 1111 3,758,770
Morasz Sept. 11, 1973  REFLECTOR HAVING RADIAL FLUTES 1,566,906 12/1925 Matisse et al 240/4136 1,841,917 1/1932 Schimpff 240/4136  lnvenm Walt" Gmmdenv Austra 2,035,215 3/1936 Bean 240/4136  Ass'ignee: U.S. Philips Corporation, New York,
' NY. Primary ExaminerSamuel S. Matthews  Filed, Dec 21 1971 Assistant ExaminerE. M. Bero Appl. No.: 210,408
Foreign Application Priority Data Att0rneyFrank R. Trifari  ABSTRACT A parabaloidal reflector adapted to receive an elongate light source along the axis of the reflector includes a number of fluted portions arranged in a repeated pattern over the surface of the reflector. The reflector achieves more uniform light reflection because adjacent fluted portions are concave or convex when viewed in cross-section and which merge in a geometrically discontinuous manner. The radius of curvature of the fluted portions in cross-section is the same from the widened open portion of the reflector to the narrowed tip.
3 Claims, 3 Drawing Figures Pmmmsm' 3.758.770
IN VEN TOR.
WALTER MORASZ BYM REFLECTOR HAVING RADIAL FLUTES The invention relates to a reflector for an elongate light source which is arranged therein axially with its longitudinal direction.
When such a reflector is provided with an elongate light source which is arranged therein axially, it provides a beam of light which has a large light intensity particularly in its central part.
In order to obtain a light beam having a uniform light distribution, the reflector could be provided with a number of radially extending flutes which contribute to aspreading of the reflected light beam. When, for reasons of manufacture, a constant radius of curvature is maintained in the cross-section of the flute, it is found that along a flute which, near the top of the reflector, is narrower than at the largest reflector circumference, the spreading is not constant which is also undesirable.
Instead of this, said flutes could be provided with a radius of curvature which is not constant so as to improve the constancy of the light spreading along the flute. However, this is particularly difficult to realize.
It is the object of the invention to provide a reflector which also comprises radial flutes and which on the one hand is simple to manufacture and on the otherhand has good light spreading properties.
For that purpose, the reflector according to the invention is characterized in that the reflecting inner surface of the reflector comprises a number of lightspreading flutes which extend in the radial direction of the reflector, merge into each other discontinuously, and are concave and convex relative to said reflector, the spreading capacity of each convex flute, calculated in a direction at right angles to the optical axis of the reflector, decreasing from a maximum in the-proximity of the side edges of the flute to a minimum at a location between the two edges, the spreading capacity of each concave flute increasing from a minimum .in the proximity of the edges of the flute to a maximum at a location between the edges, the maximum spreading capacity of the convex flutes decreasingin a direction from that the distribution of the reflected light is substantially uniform throughout the length of the unit constituted by two adjacent flutes.
According to'a preferred embodiment of the reflector according to the invention, each flute has a cross- The reflector shown in FIG. 1 is essentially formed as a paraboloid I; axially arranged in said reflector is an elongate filament 2 which is arranged in the focus F.
Said reflector comprises a number of radially extending convex and concave flutes 4 and 6 which have a cross-section (FIGS. 2 and 3) which is formed from arcs of circles having radii R and R The concave flute is formed from two parts. 6a and 6b. I
Each concave flute changes into a convex flute according to a discontinuous transition. Each flute forms part of a circular-cylindrical surface. This has for its resultthat the flute width decreases as the cross-section is nearer to the top 5 of the reflector.
The light rays reflected by the reflector are shown diagrammatically in FIG. 2.
The rays a incident on the convex flutes 4 are reflected in the opposite direction, while the rays b are reflected in a scattered manner according as the place of incidence approaches the point of intersection between a convex and a concave flute denoted by 7. The spreading capacity thus is maximum near said point of intersection 7.
The rays c incident on the concave flutes 6 are reflected in an analogous manner in an opposite direction, while the rays d are reflected in a more strongly spread manner between the center of the flute 6a, 6b. The spreading capacity thus is maximum near the edge At the area of the cross-section lIIlII, the convex flutes 4 are narrower and the cross-section comprises less strongly spreading parts, while in the concave flutes 6 the less strongly spreading parts are substantially lacking. As a result of this the spreading properties in two adjacent concave and convex flutes will become stronger or weaker towards the center calculated in the longitudinal direction of the flutes. This promotes a uniform reflection throughout the crosssection of the reflected light beam.
In the above example, each pair of adjacent flute is shown as a convex flute 4 and a concave flute consisting of two parts 6a and 6b. Of course, a convex flute consisting of a few parts and a single concave flute may be chosen for approximately the same uniform light reflection. Combination thereof may also be chosen.
What is claimed is: i
l. A reflector for an elongate light source comprisa contoured element being shaped in the form of a parabaloid having a closed tip portion at one end and a widened open portion at the other end, said element having a reflecting inner surface comprising a number of light-spreading flutes which extend along the radial contours of the element from the tip portion to the open portion, said flutes including convex and concave portions relative to the inner surface of the reflector, said convex and concave portions being arranged in a repeating pattern, adjacent flute portions merging in a geometrically discontinuous manner when viewed in crosssection, each convex flute portion having side edges where joinedwith adjacent flute portions and having a light spreading capacity which, when calculat'ed in a direction at right angles to the axis of i the parabaloidal reflector, decreases from a maximum in the proximity of the side edges of the convex flute portion to a minimum at a location between the two edges, each concave flute portion having side edges where joined with adjacent flute portions and having a light spreading capacity which, when calculated in a direction at right angles to the axis of the parabaloidal reflector, increases from a minimum in the proximity of the edges of the flute to a maximum at a location between the edges, the maximum light spreading capacity of the convex flute portions decreasing in a direction from the widened portion of the reflector toward the tip of the reflector, the minimum spreading capacity of the concave flute portions increasing in the direction from the tip to the widened open portion, said reflector adapted to receive an elongate light source arranged in the reflector along the axis of the parabaloid.
2. A reflector as in claim 1 wherein each convex flute portion is cojoined with a concave flute portion on either side edge and each concave portion is cojoined with a convex portion at one side edge and a concave portion at the other edge.
3. A reflector as claimed in claim 1 wherein each flute portion has the same radius of curvature when viewed in cross-section to the parabaloidal radius dimension of the flute portion at any place along the flute portion.