Abstract:
A flashlight assembly is provided that includes an LED, a battery and switch to selectively provide power to the LED, and an elongated light guide. The light guide is formed of solid, transparent material having a first end positioned immediately adjacent the front portion of the LED. A second end of the light guide is positioned remotely from the LED. The first end of the light guide receives light from the LED and the second end of the light guide emits light that passes through the light guide. A body is also included within which the various components are mounted.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to flashlights using light emitting diodes (LEDS) as the light source.  
       BACKGROUND OF THE INVENTION  
       [0002]     New high intensity LEDs have increased the light intensity and illumination of flashlights, while decreasing package size. The new high brightness LEDs use a more powerful chip to generate a much brighter light. Manufacturers are producing high brightness light emitting diode packages in a variety of forms. Originally these LEDs were directly substituted for standard incandescent bulbs. LEDs emit light from a plane rather than radiating omnidirectionally from an incandescent filament. The included angle of the light from an LED is much narrower than an incandescent bulb, but it is still not sufficiently narrow to form a beam, and the intensity of the light diminishes quickly with distance.  
         [0003]     Flashlights with incandescent bulbs have used parabolic reflectors to shape the light beam, and lenses to focus the beam. The conditioning of the emitted light was less complicated with incandescent bulbs, because the light source could be placed at the focal point of the parabolic reflector to get a focused beam. It is more difficult to get the apparent emitted light to appear at the focal point with a planar light source. LED flashlights have employed a number of methods in order to use reflecting surfaces and focus a beam. One method reflects the LED light from a second mirror at the focal point into the focusing mirror. Another method places the LED at the focal point on a support, but reverses the direction of the LED to emit the light toward the reflector. Yet another method uses a cylindrical reflector that directs the beam. Each of these methods increases the complexity, cost and weight of the flashlight, while absorbing a portion of the light.  
         [0004]     In all flashlights, the intensity of the light in the beam is not uniform across the beam. This results in lighter and darker areas in the illuminated field. Some flashlights also have a beam with an irregular shape.  
         [0005]     The optimal LED flashlight emits virtually all of the light from the LED into an optimally sized area with a fairly narrow angle. By so doing, light intensity and illumination are not diminished with distance from the viewer. The light should also be relatively uniform across the illuminated area. Small size and light weight are also important for flashlight design.  
       SUMMARY OF THE INVENTION  
       [0006]     A flashlight assembly is provided that includes an LED, a battery and switch to selectively provide power to the LED, and an elongated light guide. The light guide is formed of solid, transparent material having a first end positioned immediately adjacent the front portion of the LED. A second end of the light guide is positioned remotely from the LED. The first end of the light guide receives light from the LED and the second end of the light guide emits light that passes through the light guide. A body is also included within which the various components are mounted.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is an exploded, side elevation view of a first embodiment of the present invention.  
         [0008]      FIG. 2  is a side elevation sectional view of an LED housing of the embodiment of  FIG. 1 .  
         [0009]      FIG. 3  is a side elevation sectional view of a light guide and LED of the embodiment of  FIG. 1 .  
         [0010]      FIG. 4  is a side elevation sectional view of the embodiment of  FIG. 1 .  
         [0011]      FIG. 5  is an end elevation view of an lighting assembly of a second embodiment of the present invention showing three LEDs.  
         [0012]      FIG. 6  is a side elevation sectional view of the embodiment of  FIG. 5 .  
         [0013]      FIG. 7  is an end elevation view of a light guide of the embodiment of  FIG. 5 .  
         [0014]      FIG. 8  is a side perspective view of the light guide of the embodiment of  FIG. 5 .  
         [0015]      FIG. 9  is an exploded, side perspective view of the embodiment of  FIG. 5 .  
         [0016]      FIG. 10  is a side elevation sectional view of the embodiment of  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     A first embodiment of the present invention is shown best in  FIGS. 1 and 4 , and is generally identified with the numeral  10 . This preferred embodiment, commonly called a flashlight, typically includes a head housing  12 , a body  18  and an end cap  20 , each of which encloses internal components. Specifically, head housing  12  holds a lighting assembly  16  and a light guide  14 . The body holds a switch assembly  25  and a power source  22 . End cap  20  holds a spring  24 .  
         [0018]     As depicted in  FIG. 1 , lighting assembly  16  and elongated, substantially conical light guide  14  assemble into head housing  12 . The phrase “substantially conical” is intended to cover a perfectly conical shape as well as one that is somewhat rounded as shown in  FIG. 1 . Head housing  12  is typically tubular in configuration, and may include a retaining lip  13  on the front edge to retain the light guide. The head housing is normally internally threaded to receive lighting assembly  16 .  
         [0019]     As depicted in  FIG. 2 , a tubular LED housing  32  having a closed end is also provided. Lighting assembly  16  includes the LED, generally indicated at  27 , which includes an LED emitter  28  and an LED base  29 . LED emitter  28 , and the LED base  29 , are assembled to the closed end of LED housing  32 . LED base  29  has a first terminal  30  and a second terminal  31 . The first terminal is electrically isolated from LED housing  32  and is connected to spring  26 . Second LED terminal  31  is connected to LED housing  32 .  
         [0020]     As depicted in  FIG. 3 , light guide  14  may be manufactured from a single piece of material formed in the desired shape. The light guide  14  may be formed of a transparent, rigid material, with a high index of refraction such as glass, plexiglass or other polymer. As depicted in the same figure, light guide  14  generally includes an admitter face  43 , an emitter face  42 , a hole  40 , and a side wall  44 . Admitter face  43  typically includes three faces. The first face, which shall be referred to as an annular base  34 , is in the general configuration of an annular ring. In the depicted embodiment, annular base  34  contacts LED base  29  when annular base  34  is assembled to LED housing  32 . In alternate embodiments (not shown) annular base  34  may simply contact LED housing  32 , The second face shall be referred to as a protrusion  36  facing LED emitter  28 . The third face shall be referred to as an interior face  38 . Protrusion  36  and interior face  38  may be curved as shown to form hemispheres, but may have other shapes to form light admitting faces of different configurations. Side wall  44  may form a generally conical shape as shown in the preferred embodiment of  FIG. 3 . The sidewalls may also form parallel sides to form a generally cylindrical surface, as will be discussed and depicted below. Alternatively, it may be curved to form a generally parabolic surface (not shown).  
         [0021]     Light guide  14 , when assembled, is operatively coupled to LED  27 . Light guide  14  is designed to admit substantially all of the light from LED emitter  28 , and emit the light as a substantially collimated beam from emitter face  42  with relatively uniform brightness.  
         [0022]     A well known property of light guide  14  is that the light exiting the light guide at emitter face  42 , where the light guide is sufficient in length, will be relatively uniform in brightness. This relatively uniform brightness is due to the mixing within light guide  14  due to multiple reflections within the light guide.  
         [0023]     As depicted in  FIG. 3 , emitter face  42  normally has a hole  40  that is aligned along the longitudinal axis of light guide  14 . Hole  40  typically starts from emitter face  42  and extends into body  18  of light guide  14 .  
         [0024]      FIG. 4  illustrates the assembled flashlight  10  of  FIG. 1 . Emitter face  42  of light guide  14  is inserted into head housing  12 , and is seated against front lip  13  of head housing  12 . Lighting assembly  16  screws into head housing  12 . When lighting assembly  16  is screwed in, LED  27  is seated into admitter face  43  of light guide  14 . Light guide  14  is held between lip  13  and LED base  29 . In an alternate configuration (not shown), annular base  34  has an inside diameter larger than the LED base  29 . In this configuration annular base  34  abuts LED housing  32 , and LED  27  is seated into admitter face  43 .  
         [0025]     Head housing  12  typically screws onto body  18 . In the preferred embodiment shown in  FIG. 4 , body  18  typically contains switch assembly  25  and power source  22 . Switch assembly  25  has a first switch contact  49 , and a second switch contact  50 . First switch contact  49  presses against LED housing spring  26  on lighting assembly  16  when assembled. End cap  20  includes an end cap spring  24 . End cap  20  screws onto body  18 , and end cap spring  24  contacts power source  22 . The end cap spring compresses as the end cap is assembled to the body. The compression exerts an axial force, pressing first power source electrode  52  onto second switch contact  50 .  
         [0026]     In one configuration, as an example only, light guide  14  is manufactured for use in an LED flashlight  10 . Emitter face  42  of light guide  14  is normally about 25 mm in diameter. Admitter face  43  is typically 9 mm in diameter at the outside of annular base  34 , and 5.6 mm at the inside of the annular base. Protrusion  36  may be a hemisphere, with a base that is about 4 mm in diameter. The distance from emitter face  42  to admitter face  34  is typically 19.3 mm. The diameter of LED emitter face  28  is normally 5.5 mm. In the depicted embodiment the LED emitter face is 2.5 mm above LED base  29 , with the top of the hemisphere being 2.6 mm below annular base  34 . When assembled, this will typically provide a 0.1 mm clearance between the hemispheric protrusion  36  and LED emitter  28 . Hole  40  may be 11.2 mm deep and 5 mm in diameter. Light guide wall  44  forms a generally parabolic curve.  
         [0027]     LED housing  32 , body  18 , head  12  and end cap  20  are normally electrically conductive, forming an electrical path between second LED terminal  31 , and second power source electrode  54 . Alternatively, body  18  may be non conductive, and a separate conductor (not shown) may connect end cap spring  24  to end cap second LED terminal  31 . The path to first LED terminal  30  passes from first power source electrode  52  through switch assembly  25 , through LED housing spring  26 , to first LED terminal  30 . Power to the first LED terminal  30  can be interrupted by the functioning of switch assembly  25 , as controlled by switch button  48 . The switch button could alternatively take the form of a switch, or lever.  
         [0028]     Switch assembly  25  may be located in other positions, such as in end cap  20 . In this configuration the switch assembly would interrupt the current flow between spring  24  and end cap  20 . In this configuration, first power source electrode  52  would press against spring  26 , making electrical contact with first LED terminal  30  (again, not shown).  
       Embodiment of FIGS.  5 - 10   
       [0029]      FIGS. 5 through 110  illustrate a second embodiment of elongated light guide  114  and lighting assembly  116 . Because many of the components of this second embodiment  110  are similar to embodiment  10 , corresponding numerals will be used to designate corresponding parts. For example, light guide  14  will be designated with the numeral  114  and light assembly  16  will be designated with the numeral  116 . In this embodiment light guide  114  is generally cylindrical in configuration. It also includes a rounded end  162 , which may be convex or concave but in the depicted embodiment is concave. Lighting assembly  116  has three LEDs. First LED terminal  130  is attached to housing spring  126 , and is electrically isolated from LED housing  132 . Light guide  114  has three admitter faces  143 , corresponding to the positions of the LEDs in lighting assembly  116 . Light guide  114  and LEDs  127  in lighting assembly  116  are normally oriented in relation to rotation along the longitudinal axis of light guide  116 . There are many approaches for maintaining this orientation. One example of orienting the components is shown in  FIGS. 5 through 10 . In this example head housing  112 , light guide  114 , and LED housing  132  are keyed to maintain a rotational orientation between the three components along a light guide axis.  FIGS. 5 and 6  show an LED housing orienting tab  158 .  FIGS. 7 and 8  show a light guide orienting tab  158 . Light guide orienting tabs  156  and LED housing orienting tab  158  slide into head orienting slot  160 . The three annular bases  134  on the light guide abut the three LED bases  129 . All the light emitted by the three LEDs is admitted to the light guide. In an alternative configuration (not shown) annular base  134  has an inside diameter larger than the LED base  129 . In this configuration annular base  134  abuts LED housing  132 , and LED  127  is seated into admittor face  143 .  
         [0030]      FIG. 9  shows three LEDs  127  with orienting tabs  156  and  158 , and slot  160 . Head housing  112  is screwed onto body  118 . LED housing spring  126  is compressed as body  118  is assembled to the head housing  112 . LED housing spring  126  holds lighting assembly  116  firmly against light guide  114  as it is compressed.  
         [0031]     Power source  22  can be any of a number of devices that will supply the voltage required by the LED, and any supporting electronic components. It can be lead-acid batteries, lithium batteries, a kinetic energy storage device, or another source. Alternatively, the power source may even be in the form of a plug-in power source.  
         [0032]     Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention, except as it may be limited by the claims.  
         [0033]     Applicants regard the subject matter of their invention to include all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed examples is essential to all examples. The following claims define certain combinations and subcombinations which are regarded as novel and non-obvious. Other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such claims, whether they are different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of applicants&#39; invention.