Edge-lit light assembly

Abstract: A lamp (10) for emanating light comprises a light source (16) and a lens (13,58,66) having an axis (A,B). The lens has a radially outward light entering surface (37,67) to introduce light from the light source (16) into the lens (13,58,66) in the form of an intra-lens beam (48,81). The light entering surface (37,67) is at a radially outward edge of the lens (13,58,66). The lens (13,58,66) also has an axially outward light exiting surface (51,84) and a lens back surface (42,65), which has reflective stepped faces (43,71) spaced apart by connecting faces (46,72). The reflective stepped faces (43,71) are arranged at an angle (47,73) to the lens axis (A,B) to intercept the intra-lens beam (48,81) and reflect a reflected beam (50,82) through the axially outward light exiting surface (51,84).

Description: TECHNICAL FIELD This invention relates to an efficient means of and device for collimating and distributing light introduced at the edge of a lens. One of a number of useful applications is in producing signal lights for automobiles. BACKGROUND OF THE INVENTION Lamps of the type used for signal lights typically are comprised of a light source, such as an incandescent bulb, a lens, and a reflector or collimating surface for directing the light toward the lens. Sometimes, more than one bulb is used. In some lamps, light-emitting diodes (LED's) are used instead of incandescent bulbs. LED's emit light in proportion to the forward current through the diode. LED's are low voltage devices that have a longer life than incandescent lamps. They respond quickly to changes in current. They produce a spectrum of light that is well defined and constrained. The light sources are typically few and positioned near the center of the reflector or lens. European Patent application EP 0 933 587 discloses a bar shaped light conductor having a light source at each edge of the conductor. It would be desirable to provide a lamp having multiple light sources at the edge of the lamp's lens. SUMMARY OF THE INVENTION The above objects as well as other objects not specifically enumerated are achieved by a lamp for emanating light comprising: a light source; and a lens having an axis, the lens comprising: a light entering surface to introduce light from the light source into the lens in the form of an intra-lens beam, the light entering surface being at an outward edge of the lens; an axially outward light exiting surface; and a lens back surface which is on the opposite side of the lens from said axially outward exiting light surface; characterized in that the lens comprises more than two spokes which extend radially from a central common point on said axis; said spokes having reflective stepped faces spaced apart by connecting faces, said stepped faces and connecting faces constituting said back lens surface wherein the reflective stepped faces are arranged at an angle to the lens axis to intercept the intra-lens beam and reflect a reflected beam through the axially outward light exiting surface . Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view of an edge-lit lamp according to the invention. Figure 2 is a more detailed plan view of an LED and radially outward end of a spoke. Figure 3 is a cross-sectional view of Figure 2 taken along line 3-3. Figure 4 is a plan view of an alternate embodiment of the lens of the lamp of Figure 1. DETAILED DESCRIPTION OF THE INVENTION As shown in Figures 1-3, a lamp 10 includes a lens 13 for emanating light. The lens 13 is preferably circular, but may be non-circular. Outward of the lens 13 is a series of light sources, such as LED's 16. The LED's 16 include a body 25 which supports an LED lens 28. The LED lens surface is preferably hyperbolic, thus having an apex 31. The LED's 16 are connected to a substrate 19, which provides an electrical connection to power the LED's 16. A bezel 22 attaches to and surrounds the substrate 19. The bezel 22 is preferably circular but can be of any suitable shape to position the LED's 16 with respect to the substrate 19 and lens 13. The bezel 22 attaches the lamp 10 to an object such as an automobile (not shown). A preferred embodiment of the lens 13 includes twelve radially extending spokes 34 although any number of spokes 34 can be used. For purposes of clarity, Figure 1 shows only three spokes 34. At the radially outward edge of the spokes 34 is a light entering surface 37. Radially inward to the light entering surface 37 of each spoke 34 is a lens back surface 42. The lens back surface 42 includes a series of reflective stepped faces 43 spaced apart by a series of connecting faces 46. The radial length of the connecting faces 46 may vary. The reflective stepped faces 43 and connecting faces 46 are preferably quadrilaterals, but can be of any suitable shape. A preferred embodiment of the spokes 34 includes seven reflective stepped faces 43 and six connecting faces 46. The reflective stepped faces 43 form an angle 47 with the lens axis "A" that is preferably within the range of from about 10 to about 60 degrees, more preferably about 30 degrees, as shown in Figure 3. The spokes 34 converge radially inwardly toward the center of the lens 13. Toward the center of the lens 13, the reflective stepped faces 43 are merged together to form a concentric reflective ring 49. The number of concentric reflective rings 49 will vary by the number and configuration of the spokes 34. In a similar fashion, at the center of the lens 13 the connecting faces 46 are merged together to form a concentric connecting ring 52. The presence of concentric connecting rings 52 is optimal, and if present the number of connecting rings 52 will vary by the number and configuration of the spokes 34. In a preferred embodiment, the spokes 34 converge to one or more concentric reflective rings 49 spaced apart by one or more concentric connecting rings 52. In a preferred embodiment a cone 55 is formed at the center of the lens 13. The spokes 34 also have two side surfaces 44 each. The side surfaces 44 are preferably approximately linear, but may be curved or may have any other suitable contour. The side surfaces 44 for any two adjacent spokes 34 define a preferably perpendicular floor 45 extending therebetween. The floor 45 is preferably wedge shaped, forming an inclusive angle of within the range of from about 5 to about 45 degrees. It should be understood that the inclusive angle will decrease in degrees as the number of spokes 34 in the lens 13 increases. The light entering surface 37 for the spokes 34 is preferably hyperbolic, thus having an apex 40, as shown in Figure 2. The apex 40 of the spokes 34 is positioned radially inward to the apex 31 of the LED lens 28. Preferably, the apex 40 of the spokes 34 contacts the apex 31 of the LED lens 28. In a preferred embodiment, the spokes 34 have a dedicated LED 16. The term "dedicated" means the light from a single LED 16 is projected into a single spoke 34, providing a one-to-one correspondence between each LED 16 and each spoke 34. As can be seen from Figure 3, the light entering the spoke 34 is in the form of an intra-lens beam 48, traveling radially inwardly. A portion of the intra-lens beam 48 strikes the first reflective stepped face 43 and is reflected out of the spoke 34 as a reflected beam 50 from the axially outward light exiting surface 51, which is on the opposite side of the lens 13 from the lens back surface 42. The axially outward light exiting surface 51 can be flat, curved, or any other suitable contour. Varying the contour of the axially outward light exiting surface 51 can vary the distribution of the reflected beam 50 along differing locations of the axially outward light exiting surface 51. The distribution of the reflected beam 50 along differing locations of the axially outward light exiting surface 51 can also be modified by changing the length of the reflective stepped faces 43 and the angle 47 of the faces 43. It should be understood that the lengths of the connecting faces 46 and reflective stepped faces 43 used in the lens 13 can vary. Connecting faces 46 are spaced apart along the lens axis "A" by a step height "X", as shown in Figure 3. At any given angle 47, as the length of the reflective stepped faces 43 increases, the step height "X" will increase. It should be understood that reflective stepped faces 43 of differing lengths can be used in the lens 13. Using reflective stepped faces 43 of differing lengths permits reflected beams 50 to vary in intensity at differing locations along the axially outward light exiting surface 51 radially from the perimeter of the lens 13 to the center of the lens 13. The lens 13 can also include reflective stepped faces 43 oriented at a number of different angles 47. Using angles 47 of differing values permits reflected beams 50 to vary in intensity at differing locations along the axially outward light exiting surface 51. At any given length of the reflective stepped faces 43, as angle 47 decreases, the step height "X" will increase. In operation, the reflective stepped faces 43 intercept the intra-lens beam 48 and reflect the reflected beam 50 through the axially outward light exiting surface 51. Figure 4 shows an alternate embodiment of the invention, in which a lens 58 includes a circumferential collar 61 provided for structural integrity. For purposes of clarity, only three spokes 34 are shown. The spokes 34 include the reflective stepped faces 43, the connecting faces 46, and the side surfaces 44 similar to those shown in Figure 1. In a preferred embodiment the circumferential collar's radially outward surface 60 includes one or more radially outwardly extending hyperbolic nodes 62 each having an apex 63. The hyperbolic nodes 62 are light entering surfaces, similar to the light entering surfaces 37 shown in Figure 1. Radially outward of the lens 58 is a series of light sources, such as LED's 16. In a preferred embodiment, the apices 63 of the hyperbolic nodes 62 contact the apices 31 of the lenses of the LED's 16. The lens of the invention is preferably manufactured from an optically clear medium. When manufacturing the lens, a material what will be optically clear when hardened can be injected into a mold and allowed to harden. A multi-part thermoset manufacturing molding method can also be used, wherein an epoxy resin is cured in a mold to form an optically clear solid. When using the multi-part thermoset manufacturing method, the epoxy resin must be mixed very well and stabilized. Failure to do so can result in cloudy and optically uneven and less optically efficient lenses. Injection-compression molding is yet another way the lens of the invention can be manufactured. Using this technique, a liquid is injected into an open mold. When the mold is shut, the portion of the mold covering the mold opening compresses the material inside and completes the mold. Using the injection-compression method allows for better cooling in the manufacturing process and produces less stress on the lens. The lens of the invention can be manufactured from clear polyurethane, which avoids uneven cooling, shrinking, sinking or pitting surfaces. The lens of the invention can also be manufactured from optically clear glass or any other optically clear substance. The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described without departing from the scope of the appended claims.

Claims: A lamp (10) for emanating light comprising: a light source (16); and a lens (13, 58) having an axis (A), the lens (13, 58) comprising: a light entering surface (37, 62) to introduce light from the light source (16) into the lens (13, 58) in the form of an intra-lens beam (48), the light entering surface (37, 62) being at an outward edge of the lens (13, 58); an axially outward light exiting surface (51); and a lens back surface (42) which is on the opposite side of the lens (13, 58) from said axially outward light exiting surface (51); characterized in that the lens (13, 58) comprises more than two spokes (34) which extend radially from a central common point on said axis (A); said spokes (34) having reflective stepped faces (43) spaced apart by connecting faces (46), said stepped faces (43) and connecting faces (46) constituting said back lens surface (42) wherein the reflective stepped faces (43) are arranged at an angle (47) to the lens axis (A) to intercept the intra-lens beam (48) and reflect a reflected beam (50) through the axially outward light exiting surface (51). A lamp (10) according to claim 1, further comprising approximately wedge-shaped floors (45) between spokes (34) in the lens (13, 58). A lamp (10) according to claim 1 or claim 2, wherein the spokes (34) have approximately linear side surfaces (44). A lamp (10) according to claim 1 or 2, wherein the spokes (34) have curved side surfaces (44). A lamp (10) according to any one of the preceding claims, wherein the angle (47) between the lens axis (A) and the reflective stepped faces (43) is within the range of from about 10 to about 60 degrees. A lamp (10) according to any one of the preceding claims, in which adjacent connecting faces (46) are spaced apart axially by step heights (X), and wherein the step heights (X) between some adjacent pairs of connecting faces (46) differ from the step heights (X) of other adjacent pairs of connecting faces (46). A lamp (10) according to any one of the preceding claims, wherein the axially outward light exiting surface (51) is curved. A lamp (10) according to any one of the preceding claims, wherein the length of the connecting faces (46) differs radially from the perimeter of the lens to the center of the lens (13, 58).

Inventors: SAYERS EDWIN M, TARNE JAMES D, SAYERS, EDWIN M., TARNE, JAMES D.
Applicants: VISTEON GLOBAL TECH INC, VISTEON GLOBAL TECHNOLOGIES, INC.
Application year: 2001
Main classification: F21V8
IPC codes: F21V8, F21V5, F21S8