Patent Publication Number: US-2015085498-A1

Title: Illuminating apparatus with large view angle

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to improvements in the viewing angle of light emitting diode (“LED”) lamps. More specifically, an LED light bulb provides a greater than 180° view angle through the combination of a globe or diffuser where the radius of curvature exceeds 180° prior to coupling with the LED light bulb housing, use of LEDs with enlarged view angles and placement of the LEDs along the periphery of the printed circuit board. 
     This application refers to products and publications, both of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     LEDs are highly energy-efficient light sources, which makes them more desirable than other types of light sources, for example, incandescent or fluorescent lighting. In addition, LED light bulbs have advantages of taking up a relatively small volume, having low power consumption, having a long service life and generating high light output. For these reasons, LED light bulbs are now replacing traditional light bulbs in many instance. 
     LED light bulbs come in many different configurations, which tend to be constrained because of the mounting and control requirements of the LEDs. Typically, LEDs are mounted on a printed circuit (“PC”) board that contains electrical connections for powering and/or controlling the LEDs. LED light bulbs also usually have a heat sink for dissipating heat generated by the LEDs and a housing for containing the components and connecting to the lamp cap or connector. The PC board, heat sink and housing are configured such that the PC board containing the LEDs is typically mounted level with where the globe connects to the housing. In this configuration, the PC board and housing block the view angle of the LEDs. In addition, light emitted by LEDs also tends to be fairly directional, that is, the emitted light tends to be projected primarily along the central vertical axis of the LED, which is typically an asymmetric axis of the LED bulb. Off the vertical axis, light intensity from the LEDs drop off often fairly dramatically. The result of these configurations is that most LED light bulbs can provide only a 180° total view angle. Accordingly, an LED bulb having increased view angle would be beneficial. 
     Therefore, it is with respect to these considerations and others that the present invention has been made. 
     SUMMARY OF THE INVENTION 
     In light of the above, there exists a need to further improve the art. 
     In one aspect of the invention, a LED lamp has a lamp base, a housing coupled to the lamp base, a printed circuit board coupled to the housing, where the printed circuit board has a circular peripheral edge, a plurality of LEDs mounted on the printed circuit board proximate the circular peripheral edge of the printed circuit board, with the plurality of LEDs having a view angle of over 120 degrees, a heat sink coupled to printed circuit board for dissipating heat generated by the plurality of LEDs, and a globe coupled to the housing, where the globe has a side cross sectional lighting surface that exceeds 180 degrees. 
     In another aspect of the invention, the lamp base has a live contact and a neutral contact for supplying electrical power to the LED lamp. 
     In another aspect of the invention, the globe can be made from plastic or glass. 
     In another aspect of the invention, the plurality of LEDs are approximately 3 millimeters from the circular peripheral edge of the printed circuit board. The plurality of light emitting diodes can have a typical viewing angle of 140 degrees. 
     In another aspect of fee Invention, the plurality of LEDs are disposed as dual concentric rings with an outer ring adjacent the circular peripheral edge of the printed circuit board and the inner ring disposed inward from and adjacent to the outer ring. 
     In yet another aspect of the invention, a method of illumination through an LED lamp having the steps of supplying electrical power to a plurality of LEDs through a lamp base, generating light through the plurality of LEDs, where the LEDs have a view angle of greater than 120 degrees and are mounted in a circle at a peripheral edge of a printed circuit board, dissipating heat generated by the LEDs through a heat sink coupled to the printed circuit board and transmitting light from the LEDs through a globe, the globe having a substantially spherical wall extending greater than 90 degrees from its vertical centerline. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The figures are for illustration purposes only and are not necessarily drawn to scale. However, the invention itself may best be understood by reference to the detailed description which follows when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a first exemplary embodiment of the present invention; 
         FIG. 2  is a top view of the first exemplary embodiment of the present invention; 
         FIG. 3  shows a side view of the first exemplary embodiment of the present invention; 
         FIG. 4  shows a graphical side view of the first exemplary embodiment, depicting the increased viewing angle of the LEDs; and 
         FIG. 5  is a graph of the light intensity distribution as a function of viewing angle for the first exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Various embodiments will now be described with reference to the accompanying drawings, which form a part of the description, and which show, by way of illustration, specific embodiments. However, this invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As described below, various embodiments of the invention may be readily combined without departing from the scope or spirit of the invention. 
     As shown in  FIG. 1 , LED lamp  100  is comprised of threaded lamp cap  102 , housing  104  and globe  106 . Threaded lamp cap  102  can be comprised of, for example, an Edison (e.g., E27, or E26) threaded configuration that has a connection button that couples the bottom of lamp cap  102  with contacts from an electrical power source, that is, a light socket. While lamp cap  102  is shown in the figures, the present invention is not limited to the disclosed embodiment and lamp cap  102  can be shaped in the form of a connector having any known configuration, for example, a double bayonet style mounting, a smooth shaped connector, . . . etc., for connection to any number of known wall or ceiling sockets. Housing  104  is attached to lamp cap  102  and encloses the electrical connections required for providing power to the LEDs within LED lamp  100 . Globe  106  performs, among other things, a light diffusing function by being made from transparent, frosted or other light transmissive/diffusive material. Globe  106  can be made of glass, plastic or other suitable material. Typically, the lower portion of globe  106  tapers inward to fit with the upper portion of housing  104 . 
     Proximate where housing  104  meets globe  106  is disposed LED PC board  108 . In one embodiment. LED PC board  108  is mounted on heat sink  110  which in turn can be thermally connected to either or both of housing  104  or globe  106 . Heat sink  110  is preferably made of a suitable heat conductive material, such as for example, copper, aluminum, alloys of copper or aluminum, steel, cast iron, plastics, thermoplastics and/or a combination thereof. The heat generated by the LEDs can be dissipated by heat sink  110  through housing  104  into the surrounding atmosphere. One of the advantages of providing an internal heat sink is that it makes the lamp appears and handles more like a traditional incandescent light bulb. 
     As shown in  FIG. 2 , LEDs  112  are mounted on LED PC board  108 . LEDs  112  typically are comprised of a series of arrays mounted equilaterally around the periphery of LED PC Board  108 . In one embodiment, LEDs  112  are mounted, approximately 2 to 3 mm from the edge of LED board  108 . In another embodiment, a second series of LED arrays can be mounted just inside the first series of arrays and offset so that the first and second series of LED arrays have the same center point with the second series of arrays being mounted in the spaces between the first series of LEDs. In one preferred embodiment, LEDs  112  have a viewing angle of 140°. An example of such an LED is the Cree XLamp XQ-B LED commercially available from Cree (see http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xqb). The relative luminous intensity (as a percentage) is close to 100% within approximately 30° of the vertical centerline. The relative luminous intensity drops thereafter to approximately 15% at an angle of approximately 90° from the vertical centerline. 
       FIG. 3  shows the position of LEDs  112  relative to the connection point between globe  106  and housing  104 . Globe center line A shows the approximate centerline diameter for the radius of curvature of globe  106 . As apparent globe-housing interlace  302  is located a distance d below globe centerline A. For this portion of globe  106  below globe centerline A, globe  106  curves inwardly. LEDs  112  are located approximately at globe-housing interface  302 . 
     The benefit of combining the inward curvature of globe  106  over distance d, placing LEDs  112  along the peripheral edge of LED PC board  108  and the use of LEDs with a large view angle is that the viewing angle for LED lamp  100  is greater than 180°. A graphical depiction of the increased viewing angle is shown in  FIG. 4 . Vertical centerline C for LED  100  is disposed on the longitudinal axis of the LED lamp. Globe centerline A is shown 90° from vertical centerline C. The increased viewing angle in this embodiment is shown as 27°. 
     The relative luminous intensity as a function of viewing angle for two representative embodiments of LED lamp  100  is shown in  FIG. 5  as curves  502  and  504 . At 0°, which corresponds with vertical centerline C, the relative luminous intensity is approximately 90%. As the angle from vertical centerline C increases, the relative luminous intensity decreases until it reaches approximately 65 percent at 90°. Past 90°, there is significant luminous intensity until it reaches less than approximately 50 percent at 117°. 
     Although specific embodiments have been described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present invention. For example, although a bulb-shaped lamp has been illustrated, the present invention can be applied to the construction of other configurations of an LED lighting fixture. The present invention can be used in any LED lamp configuration where an increased viewing angle is created through the use of a combination of an increase in THE size of the globe, an LED with a large view angle and placement of the LEDs close to the peripheral edge of the LED PC board. 
     Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications that reasonably and properly come within the scope of their contribution to the art.