Light Beaming Reflector Lens Assembly

Abstract

Spotlighting and controlled beaming of illumination from an incandescent filament lamp is effected by use of a bulb having a lens tip envelope and a solid prismoidal body enclosing the bulb envelope. A curved, annular surface of the prismoidal body internally reflects all radiation emitted from the filament which emerges from a front lens surface except for the radiation that is directly transmitted through the lens tip of the envelope centrally projecting from the prismoidal body.

Description

This invention relates to light beaming lamps of the incandescent filament type.

Generally, the beaming of illumination originating from an incandescent filament lamp bulb, is produced by either a dioptic or a catadoptic effect involving the use of opaque reflectors spaced rearwardly of the bulb. In sealed beam headlights on automotive vehicles for example, the major light beam is created by a parabolic, aluminized reflector and various dioptic sections on the lens cover in order to control the light beam. In other types of lamp assemblies, a beaming effect is obtained by direct radiation from the lamp filament through the front lens while an opaque reflector is utilized to produce diffused, soft backlighting.

It is an important object of the present invention to provide an incandescent lamp assembly through which the beaming of illumination is controlled in an efficient and economical manner without reliance on any opaque reflectors.

In accordance with the present invention, a solid prismoidal body made of an optical plastic material is utilized to support or enclose an incandescent filament lamp bulb, the prismoidal body acting both as a reflector and a lens. The filament bulb envelope is provided in accordance with one embodiment of the invention with a lens tip portion and a thin cylindrical portion of constant thickness constituting the sole interface between the filament enclosure and the prismoidal body. The contours of the front lens surface of the prismoidal body and an internally reflective surface, control the beaming of the illumination.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

FIG. 1 is a perspective view illustrating a prismoidal body utilized in accordance with the present invention.

FIG. 2 is a side sectional view through a typical lamp assembly constructed in accordance with the present invention.

FIG. 3 is a front elevational view of the lamp assembly shown in FIG. 2.

Referring now to the drawings in detail, the lamp assembly generally referred to by reference numeral 10 in FIG. 2, includes a commercially available wedge type bulb generally denoted by reference numeral 12 that is inserted into a socket 14 so that electrical contact is made between the filament leads and a pair of electrical conductors 16 that extend from the socket. Electrical energy is thus conducted through an incandescent tungsten filament generally referred to by reference numeral 18, sealed within the bulb enclosure 20 in order to produce illumination at a predetermined point location 22 along an optical axis 24 that coincides with the longitudinal axis of the bulb 12.

In the illustrated embodiment, the bulb envelope generally referred to by reference numeral 26 includes a relatively thin cylindrical portion 28 of constant thickness and a tip portion 30 having a plano-convex lens curvature symmetrically aligned with the optical axis 24. Thus, radiation emitted from the tungsten filament 18 at the point source location 22, will be directly transmitted through the tip lens portion 30 for spotlighting purposes.

The bulb 12 is supported within a solid prismoidal body generally referred to by reference numeral 32 which in the illustrated embodiment of the invention, is made of a light transmissive plastic having an index of refraction that is different from that of the glass bulb envelope 26. Further, the body 32 is provided with a central, cylindrical bore 34 through which the bulb extends so that only the tip portion 30 projects forwardly from the body. The cylindrical portion 28 of the envelope constitutes the only interface between the prismoidal body 32 and the filament enclosure 20 so that radiation emitted at location 22 travels from the enclosure 20 through the material of the bulb envelope directly into the light transmitting medium of the prismoidal body.

When assembled with the lamp bulb, the prismoidal body 32 axially abuts the bulb socket 14 at one end of its cylindrical portion 36 that is arranged to be coaxial with the optical axis 24 of the lamp assembly. The cylindrical portion 36 is also located rearwardly of the location 22 from which light is emitted so that light will be internally reflected only along the annular, curved surface 38 on a radially enlarged forward portion 40 of the prismoidal body. The internally reflective surface 38 thus extends radially outwardly and forwardly from the cylindrical portion 36 to a radially outer rim 42. A front lens surface 44 extends radially inwardly from the rim 42 to the central bore 34 in surrounding relation to the projecting tip portion 30 of the bulb.

As diagrammatically shown in FIG. 2, a light ray 46 originating from the light emitting location 22, enters the prismoidal body and impinges on the internally reflective surface 38 at an incidence angle of 0 which is less than the critical angle so that the light ray is internally reflected and emerges from the front lens surface 44. Thus, the contours of the internally reflective surface 38 and the front lens surface 44 will control the beaming of the illumination.

The foregoing is considered as illutrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

What is claimed as new is as follows:

1. In combination with a bulb having an incandescent filament from which illumination is produced at a predetermined location and an enclosure for said filament formed by a transparent envelope provided with a tip portion spaced forwardly from said filament along an optical axis, a lamp assembly including a solid prismoidal body of light transmissive material having an opening extending therethrough, the outer surface of said bulb envelope being coextensive with the inner surface of said opening, said prismoidal body also having a front lens surface extending outwardly about said opening, said surface being spaced forwardly of the filament, and an internally reflective surface extending from the front lens surface rearwardly of the filament whereby beaming of the illumination emerging from the front lens surface is controlled by said internally reflective surface.

2. The combination of claim 1 wherein said tip portion of the bulb envelope has a lens curvature while the remainder of the envelope is of a constant thickness.

3. The combination of claim 1 wherein the lamp assembly further includes a socket for receiving a terminal end portion of the bulb and axially abutting the prismoidal body.

4. The combination of claim 1 wherein said prismoidal body is made of a light transmissive plastic.

5. The combination of claiim 1 wherein said internally reflective surface has a curvature establishing angles of incidence for radiation originating at said predetermined location that are less than the critical angle corresponding to the index of refraction of the solid prismoidal body, whereby beaming of illumination from the front lens surface is controlled by the curvatures of said surfaces.

6. In combination with a bulb having an incandescent filament from which illumination is produced at a predetermined location and an enclosure for said filament formed by a transparent envelope provided with a tip portion spaced forwardly from said filament along an optical axis, a lamp assembly including a solid prismoidal body of light transmissive material having an opening extending therethrough, the outer surface of said bulb envelope being coextensive with the inner surface of said opening, said prismoidal body also having a cylindrical portion spaced rearwardly of said predetermined location in coaxial relation to the optical axis, and a radially enlarged forward portion extending axially between the cylindrical portion and the tip portion of the envelope, said forward portion including a front lens surface spaced forwardly of the filament and an internally reflective surface extending rearwardly from the front lens surface to the cylindrical portion, said prismoidal body being made of separate material from the envelope and having a different index of refraction, the internally reflective surface of the radially enlarged portion of the body having a curvature establishing angles of incidence for radiation originating at said predetermined location that are less than the critical angle corresponding to said index of refraction of the body, whereby beaming of the illumination emerging from the front lens surface is controlled by the curvature of said surfaces.

7. The combination of claim 6 wherein the lamp assembly further includes a socket for receiving a terminal end portion of the bulb and axially abutting the cylindrical portion of the prismoidal body.

8. The combination of claim 6 wherein said tip portion of the bulb envelope has a lens curvature while the remainder of the envelope is of a relatively thinner and constant thickness.

9. The combination of claim 8 wherein the lamp assembly further includes a socket for receiving a terminal end portion of the bulb and axially abutting the cylindrical portion of the prismoidal body.