Abstract:
A multiple LED based lighting device for commercial indoor or outdoor architectural applications is disclosed. The lighting device uses multiple LEDs which are arranged in a symmetrical array in order to combine their light output. The LEDs are supported in a fixed position and have a conical reflector to assist in focusing the light output. A heat sink is attached to the LEDs to allow for use of high power for greater light output. The multiple LEDs are mounted relative to an optic fiber which has a core and cladding material to retain light based on total internal reflection. The light output from the LEDs are cast on the optic fiber which may provide side lighting effects from the perimeter of the optic fiber or emit light from the opposite end of the optic fiber.

Description:
FIELD OF INVENTION 
     The present invention relates generally to the field of light emitting diodes. More specifically, the present invention is directed to a lighting device that uses the light from multiple LEDs focused on an optic fiber in order to create high output lighting. 
     BACKGROUND OF INVENTION 
     Light emitting diodes (LEDs) are well known solid state light sources. LEDs have many advantages over traditional lighting sources such as incandescent bulbs as they are cheaper to produce, more robust, and require less power. LEDs are especially desirable as they emit light with high power efficiency over specific colors in the spectrum. However, LEDs are not a focused light source and suffer from relatively low light output. The lack of focused light and low light output prevents application of LEDs to uses where high light intensity is desired. Further LEDs cannot be fabricated in different shapes for decorative purposes. Finally, the light output of LEDs cannot be intensified without an optical device to focus the light. 
     There are many commercial applications requiring high light output. For example, there is a great demand for outdoor and indoor decorative or architectural lighting. Neon lighting is presently used for such applications. Neon or fluorescent lighting uses a glass tube which is filled with neon gas. Such devices may be used for lighting but also for advertising and signs as the tubes may be fabricated into different shapes. Such tubes may have different colors or generate simple white light. The light intensity of a neon tube depends on the color generated. 
     However neon lighting suffers from a number of problems. Neon lights require a relatively large amount of electricity to offer resulting in greater costs for heavy use such as outdoor signs. Also, neon lights require periodic replacement and maintenance because such lights experience a significant drop off in output after continual use. Further, the maximum length of a neon tube is around seven feet which necessitates more units for large scale uses. All of these factors may create cost issues. Also, neon lights require a high voltage transformer which may create safety issues. Finally, neon lights do not allow for easy change of the light color output. 
     Another solution for outdoor applications is high intensity discharge (“HID”) lamps. HID lighting technology replaces the filament of the light bulb with a capsule of gas. The light is emitted from an arc discharge between two closely spaced electrodes hermetically sealed inside a small quartz glass tubular envelope capsule. To operate, they require ballasts, which supply proper voltage and control current. The amount of light produced is greater than a standard halogen bulb, while consuming less power, and more closely approximating the color temperature of natural daylight. Unfortunately, HID lighting has a short relative lifetime, requiring periodic replacement. Further, the HID lighting requires greater maintenance and repair. 
     Thus, there is a need for an LED based device which provides sufficient light intensity for high lighting applications. There is a further need for an LED based device which allows light output to be focused and directed. There is also a need for an LED based device which allows high light output from the end of an optic fiber. There is yet another need form an LED based device which allows bright side light effect. There is also a need for a low power, high reliability, lighting device suitable for commercial applications. 
     SUMMARY OF THE INVENTION 
     These needs and others may be met by the present invention, one example of which is a high output lighting device. The device has a support bracket having one end with a vertically extended arm and an opposing end with a lighting mounting bracket. An optic fiber having a receiving end and an emitting end supported by the vertically extended arm is provided. Multiple light emitting diodes are supported by the lighting mounting bracket and the multiple light emitting diodes are spaced at a fixed distance from the receiving end of the optic fiber and are angled to focus light output on the optic fiber. 
     Another example of the invention is a high output light emitting diode based lighting device. The lighting device has a support bracket having a flat bottom surface and two opposite first and second ends. A vertical support arm is attached to the first end of the support bracket. An optic fiber is attached to the vertical support arm, the optic fiber has a core material and a cladding material with a flat receiving end fixed in relation to the support bracket. A mounting arm is attached to the second end of the support bracket, the mounting arm includes multiple collars facing the receiving end of the optic fiber. A light emitting diode reflector assembly is attached to each of the multiple collars. The light emitting diode reflector assembly has a conical body having an open end mated with the collar, and an opposite closed end holding a light emitting diode. 
     It is to be understood that both the foregoing general description and the following detailed description are not limiting but are intended to provide further explanation of the invention claimed. The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawings serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and further aspects and advantages of the invention will be discussed more in detail hereinafter with reference to the disclosure of preferred embodiments, and in particular with reference to the appended Figures wherein: 
         FIG. 1  is a perspective view of a lighting device with multiple LEDs according to one example of the present invention; 
         FIG. 2  is a side view of the support bracket holding the LEDs of the lighting device shown in  FIG. 1 ; 
         FIG. 3  is front view of the support bracket holding the LEDs of the lighting device shown in  FIG. 1 ; 
         FIG. 4  is an exploded view of the lighting device with multiple LEDs shown in  FIG. 1 ; 
         FIG. 5  is a cutaway view of the lighting device in  FIG. 1  showing the path of the light rays emitted by the LEDs for a side light effect; 
         FIG. 6  is a view of the lighting device in  FIG. 1  showing the path of light rays emitted by the optic fiber for an end light effect; 
         FIG. 7  is a circuit diagram of the lighting device in  FIG. 1 ; 
         FIG. 8  is an alternate circuit diagram for the lighting device in  FIG. 1  used for different color output; and 
         FIG. 9  is a perspective view of an alternate embodiment of the present invention using a different number of LEDs. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the present invention is capable of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. 
       FIGS. 1–4  show a lighting device  10  that is one example of the present invention.  FIG. 1  is a perspective view,  FIG. 2  is a side view,  FIG. 3  is a front view and  FIG. 4  is an exploded view of the lighting device  10  which is a high output lighting device useable for indoor or outdoor architectural lighting. 
     The lighting device  10  has a support bracket  12  having a vertical arm  14  which supports an optic fiber  16 . The optic fiber  16  is shown in  FIGS. 1–4  as a linear rod shape. However, the optic fiber  16  may be formed or twisted in any variety of non-linear shapes. For example, the optic fiber  16  may be bent into the shape of a letter for a commercial application. In this example, the optic fiber  16  is manufactured by  3 M, although other optic fibers which allow for side or end light effects may be used. The optic fiber  16  is preferably plastic to be flexible and resistant to fatigue, elongation and vibration. The optic fiber  16  has a core material which is preferably polymethacrylate and a cladding material which has a lower refractive index than the core material. When light enters the optic fiber  16 , it is transported down the length of the fiber by total internal reflection between the core and cladding layers. 
     The support bracket  12  also includes an LED lighting support  18 . The LED lighting support  18  suspends LED reflector assemblies  20 ,  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36  in a symmetrical pattern. The LED reflector assemblies  20 – 36  are essentially identical components. Each LED reflector assembly  20 – 36  is held in a fixed position by the LED lighting support  18  to focus light output on the optic fiber  16 . 
     The LED support  18  includes a locking plate  38  which has a series of locking collars  40  each having a circular aperture  41 . The LED reflector assemblies  20 – 36  are inserted in the locking collars  40  through the circular apertures  41 . Each collar  40  is set at an angle on the plate  38  and a certain distance relative to the optic fiber  16  in order to focus light on the optic fiber  16 . 
     The LED reflector assembly  20  has a conical body  42  having an open front end  44  and a closed back end  46  holding a light emitting diode  48 . It is to be understood that the other LED reflector assemblies  22 – 36  are identical to the LED reflector assembly  20  and operate in the same manner. The open front end  44  of the conical body  42  has a pair of mounting tabs  50  and  52 . The mounting tabs  50  and  52  have mounting holes  54  and  56  which are used in conjunction with fastening devices such as a rivet or a screw to fix the conical body  42  in place relative to the collar  40  of the locking plate  38 . 
     The conical body  42  has a reflective interior surface  58  which is preferably coated with evaporated aluminum. The reflective interior surface  58  of the conical body  42  focuses the light emitted from the light emitting diode (LED)  48 . The LED  48  is any semi-conductor, solid state light source. In the preferred embodiment, the LED  48  is a Luxeon light emitting diode since it offers a lower thermal resistance. The LED  48  is mounted on the closed end  46  of the conical reflector  42  and may be coupled to a power source (not shown) via two electrical pins  60  and  62 . The closed end  46  of the conical reflector  42  is connected to a heat sink  70  which serves to dissipate the heat generated by the LED  48 . The heat sink  70  allows for the use of higher power and thus higher light intensity output LEDs. 
     The heat sink  70  includes a flat plate  72  which has a mounting collar  74  which is attached to the back end  46  of the conical reflector  42 . The flat plate  72  has a back surface  76  which has a series of protruding, vertical vanes  78  to assist in dissipation of heat. The heat sink  70  is typically made from a highly thermally conductive material such as die cast aluminum alloy to conduct and dissipate heat generated from the LED  48 . Of course other thermally conductive materials such as copper or thermally conductive plastic may be used to fabricate the heat sink  70 . It is to be understood that rather than having separate heat sinks such as heat sink  70  for each of the LED reflector assemblies  20 – 36 , a single heat sink could be thermally coupled to all of the LEDs  48  in the reflector assemblies  20 – 36 . 
     The components of the LED reflector assembly  20  may be better viewed with reference to LED reflector assembly  28  shown in exploded view in  FIG. 4 . The LED reflector  28  has identical element numbers as those assigned to LED reflector assembly  20  shown in  FIGS. 1–3 . 
     The LED support  18  has a tongue  80  which has a series of mounting holes  82 . The tongue  80  is joined to a triangular vertical arm  84  extending from the support bracket  12  via rivets or screws that are installed in the mounting holes  82 . The support bracket  12  also has a series of four feet  86 ,  88 ,  90  and  92  which extend outward and provide a flat surface to mount the support bracket  12  on a flat surface. Each of the feet  86 – 92  has a hole  94 ,  96 ,  98  and  100  respectively. The feet  86 – 92  may be bolted to a surface for mounting the lighting device  10  via the holes  94 – 100 . 
     The vertical arm  14  holds the optic fiber  16  at a fixed distance from the LED support  18 . The vertical arm  14  has a base  102  which is fixed to the surface plane of the support bracket  12 . The vertical arm  14  also has a mounting cradle  104  opposite the base  102 . The mounting cradle  104  has a channel  106  having a semi-circular shape to accommodate the optic fiber  16 . A locking bar  108  has an opposite semi-circular channel  110  to hold the optic fiber  16  in place. The locking bar  108  has two slots  112  and  114  which accommodate screws to hold the locking bar  108  on the mounting cradle  104 . 
     The optic fiber  16  has a body  126  and a receiving end  128  which receives the light from the LEDs mounted in the LED reflectors  20 – 36  and an emitting end  130 . The optic fiber  16  allows end light emission from the emitting end  130  or side light effect from the perimeter of the body  126 . 
     As shown in  FIG. 5 , light from the LEDs  48  in the LED reflector assemblies  20 – 36  may be directed toward the receiving end  108  and channeled through the body  126  of the optic fiber  16  for a bright side light effect. The LED reflector assemblies  20 – 36  are angled in order to maximize the amount of light output from the LEDs  48  transmitted to the optic fiber  16 . In addition, the conical body  42  is shaped such that the reflective surface  58  reflects incident light from the LEDs  48  to the optic fiber  16 . The basic shape of the conical body  42  is an ellipse according to the equation of x 2 /A+y 2 /B=1. The ellipse shape has two foci which enables light collection. The reflector  20  may also be a compound elliptical concentrator that also has two foci. 
     The combined light from the nine LEDs  48  allows sufficient intensity light output from the optic fiber  16  for different applications. In this case, the cladding material of the optic fiber  16  is translucent. When the light from the LEDs  48  is focused on receiving end  128 , it is scattered at the core/cladding interface and leaves the body  126  along the perimeter of the optic fiber  16 . The light emission appears visually uniform along the length of the optic fiber  16 . Since the light is directed by the optic fiber  16 , any shape may be formed by the body  126  and corresponding light will be emitted throughout the body  126 . 
     As shown in  FIG. 6 , light from the LEDs  48  may also be directed from the emitting end  130  of the optic fiber  16 . In this instance, a black jacket covers the cladding of the fiber and channels the light out of the emitting end  130 . This embodiment may be used for remote light applications like microscope lighting, endoscope lighting and machine vision. As described above, the lighting device  10  allows all of light emitted by the LEDs  48  to be focused on the optic fiber  16  for a combined high light output. 
       FIG. 7  is a circuit diagram of the electrical control for the LEDs  48  in the lighting device  10 . The circuit diagram includes a power source  140  which is a typical AC power source. The power source  140  is coupled to a power supply  142  which transforms the AC power from the power source  140  to a DC voltage. The power supply  142  supplies a sufficient voltage supply for the LEDs  48  which in this example are the same color. 
     Different colors may be used by changing the color of the exterior of the optic fiber  16 . Different colors may also be generated by providing different color LEDs. Additionally, other colors may be generated by having several different color LEDs and using the combination of the different colors to generate another color. For example, the LEDs in the lighting device  10  may be wired according to the circuit shown in  FIG. 8 .  FIG. 8  shows a power supply  150  which is coupled to a power source  152 . The power source  152  is coupled to a red set of LEDs  154 , a green set of LEDs  156  and a blue set of LEDs  158 . The combination of the sets of LEDs  154 ,  156  and  158  maybe used to generate different colors by varying the current to the LED outputs. 
       FIG. 9  shows a perspective view of a second alternate embodiment of a lighting device  200 . The lighting device  200  has a support bracket  202  which has one end holding an optic support arm  204  which holds an optic fiber  206 . The opposite end of the mounting bracket  202  includes an LED support arm  208 . The LED support arm  208  holds a series of fifteen LED reflector assemblies  210  which all contain light emitting diodes  212 . The LED assemblies  210  each have a conical reflecting surface  214  which focus light emitted by the LED  212  to the focal point of the optic fiber  206 . The LED  212  is also coupled to a heat sink  216  to dissipate heat generated by the LED  212 . 
     Similar to the previous example, light from the LEDs  212  are all focused by the angle of the respective LED reflectors  210  and the reflecting surfaces  214  to the optic fiber  206 . The light of all of the fifteen LEDs  212  are thus captured by the optic fiber  206  and emitted over the length of the optic fiber. 
     The lighting device  200  has fifteen LEDs which generate greater amounts of light than the nine LEDs in the lighting device described in  FIG. 1 . It is to be understood that different numbers of LEDs may be used in order to vary the intensity of the output. Additionally, light intensity may be varied by selectively powering certain LEDs in the array. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the method and system of the present invention without departing from the spirit or scope of the invention. Thus, the present invention is not limited by the foregoing descriptions but is intended to cover all modifications and variations that come within the scope of the spirit of the invention and the claims that follow.