Abstract:
A novel lighting assembly that incorporates a high brightness light emitting diode (LED) in a compact assembly for further integration into a lighting device is provided. The lighting head assembly of the present invention provides several novel aspects that are all closely integrated to provide a unique assembly for incorporating a high brightness LED into a lighting device. In particular, the head assembly utilizes a two part contact plunger wherein the inner portion of the plunger is electrically conductive and the outer portion of the plunger is non-conductive and includes an aperture therein. The aperture is sized to allow the smaller, positive battery contact to pass through and contact the inner portion while preventing the larger negative battery contact from reaching the inner portion. This configuration thereby prevents the device from activating if the battery is installed in the reverse polarity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is related to and claims priority from earlier filed provisional patent application No. 60/437,810, filed Jan. 3, 2003. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a new lighting head assembly for use in lighting devices such as commercial and residential lighting fixtures, flashlights and miniature flashlights. More particularly, the present invention relates to compact and efficient lighting head assemblies for use with lighting devices of the type employing a high brightness light emitting diode (LED) to provide a smooth uniform spotlight beam having sharp edges.  
           [0003]    Most commercially available lighting devices are designed to provide an on-axis, high intensity peak in their beam distribution as is typically found in flashlights with smooth reflectors or specialty architectural spotlights such as picture lights. In other words, most conventional lighting assemblies provide a central spot that is highly illuminated with a surrounding beam fall off region that varies from assembly to assembly. In general, these smooth reflector type assemblies simply re-image the light source into the far field of the device and create a poorly distributed, non-uniform illuminated field. Attempts to provide a more uniform beam distribution include the use of multi-faceted reflectors, however, the resulting beam pattern tends to be Gaussian with no sharp edge definition between the area illuminated by the beam and the surrounding non-illuminated area. In both the faceted and smooth reflector cases, the reflector generally tends to be parabolic in shape. While this shape reduces the direct re-imaging of the light source, this solution simply smears the image taken from the far field of the light source and projects that smeared image in the far field of the flashlight beam thereby still providing a non-uniform light image in the far field of the lighting device.  
           [0004]    Other prior art attempts to produce a focused light source include the provision of a standard convex lens with a relatively long convergence factor in front of an LED package. These devices also produce an unacceptable result as they capture the far field image from a plane projected in front of the LED package and simply enlarge the LED image and then reflects that image in a reversed pattern in the flashlight beam far field. If the beam pattern is carefully studied, an image of the emitter die, diode and reflector cup can easily be identified in the beam image.  
           [0005]    In most of the prior art assemblies, in order to provide even the marginally acceptable results using the assemblies described above, the lighting device needed a large reflector and a relatively large lens with a long focal length. These components dictated that the head of the light assembly have a large dimension as well. Further, because the LED lighting elements generate a great deal of heat, a heat dissipation path must be provided as well. In general, this heat dissipation path is simply provided in the form of creating a large volume of air space around the LED. All of these factors combined in the prior art to prevent the design of a compact lighting assembly that could incorporate a single high brightness LED.  
           [0006]    Finally, in order to manufacture a portable lighting assembly that is compact it is desirable to provide a lighting assembly that can be operated using a single conventional battery such as a conventional AA or AAA cell battery. However, in order for this type battery to activate the LED, step up circuitry must be provided to increase the 1.5 volt battery output to at least the threshold voltage required to illuminate the LED. The drawback is that this circuitry is extremely sensitive to reversed polarity. Therefore there is also a need for providing reliable polarity protection thereby preventing a user from accidentally activating the lighting assembly with a battery that has been installed in reverse orientation.  
           [0007]    Therefore, there is a need for a lighting device that produces a smooth, evenly distributed beam of light. In addition, there is a need for a lighting device that provides a high intensity beam of light that has a homogeneous illumination pattern. There is also a need for a high intensity flashlight beam that provides a uniform field of illumination and that has a sharp edge between the illuminated field and the non-illuminated field. There is a further need for a lighting head assembly that is compact and efficient in size while providing an integrated heat dissipation pathway. There is yet a further need for a compact lighting assembly that includes reliable and integrated polarity protection for the control circuitry therein.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    In this regard, the present invention provides a novel lighting assembly that incorporates a high brightness light emitting diode (LED) in a compact assembly for further integration into a lighting device. The lighting head assembly of the present invention provides several novel aspects that are all closely integrated in a single compact assembly to provide a solution to the drawbacks identified in the prior art. The lighting head assembly of the present invention is suitable for incorporation into any type of lighting device such as architectural lighting, accent lighting, task lighting and flashlights. The preferred embodiment shown and described in the disclosure of the present invention is designed for incorporation into a flashlight device. In this regard, the present invention will be described in the context of a flashlight assembly although the same concepts disclosed with respect to the preferred embodiment are also suitable for use in any type of lighting assembly.  
           [0009]    The central element of the assembly of the present invention is a tubular receiver sleeve that is configured to receive the lighting element in a manner that supports and aligns the lighting element along an optical axis. The receiver serves both to contain and to channel the light from the LED and direct it forwardly along the optical axis. To aid in channeling of the light, the reciever includes a narrowed tail section that entirely surrounds the side portions of the optical element of the LED. By providing a narrowed tail element that surrounds the LED, the receiver also provides an efficient structure for capturing the heat generated by the LED element and directing that heat away from the LED.  
           [0010]    In the preferred embodiment, the present invention utilizes a single high brightness lighting element such as an LED that is mounted onto a circuit board and placed into the tail of the receiver. When the LED is placed into the tail element of the receiver, the optical axis of the LED is automatically centered along the central axis of the receiver. In this manner the ability to further incorporate the assembly into lighting devices, such as flashlights, is greatly enhanced while providing the ability to utilize additional beam control elements in a precise and controlled manner. The end of the receiver opposite the tail element is configured to receive optical control elements such as a lens or an optical zoom assembly to capture the light output of the LED and project it into the far field of the device in a uniformly illuminated and carefully controlled beam.  
           [0011]    An additional feature that is incorporated into the receiver to facilitate the compact nature of the present assembly is the provision of an electrically conductive pathway for connecting one terminal of the battery to the LED driver circuitry. By using the receiver to provide this conductive pathway, the need for additional connections or wire bonds between the driver circuitry for the LED and the housing is eliminated. In this manner, the assembly process is streamlined and the precision of the finished device is greatly improved.  
           [0012]    In an effort to maintain the compact nature of the present invention, it is also desirable to drive the LED using a conventional single cell battery such as an AA or AAA type battery. As can be appreciated, this type battery is a 1.5 volt power source. Since typical LED&#39;s require 3.0 volts for operation, a step up circuit is provided in the LED driver circuitry. Step up circuits of this type are particularly sensitive and are susceptible to damage resulting from reversed polarity DC current. The present invention therefore also includes a novel construction for insuring that contact to the power source will only occur if the battery is installed in the proper orientation.  
           [0013]    Accordingly, one of the objects of the present invention is the provision of a compact lighting assembly that includes a high intensity light source such as an LED. Another object of the present invention is the provision of a lighting assembly that utilizes a receiver sleeve to position an LED along the optical axis of the lighting device thereby offering improved light capture and transfer. A further object of the present invention is the provision of a lighting assembly that utilizes a receiver sleeve to both center the LED light source along the optical axis of the assembly and act as a heat sink to transfer the heat generated by the LED away from the LED and the driver circuitry. Yet a further object of the present invention is to provide a compact LED lighting assembly that utilizes a receiver to center the LED, act as a heat sink for the LED and to provide an electrically conductive path from one terminal of the battery to the LED driver circuitry. An even further object of the present invention is the provision of a compact lighting assembly that includes integrated voltage polarity protection for the LED driver circuitry.  
           [0014]    Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:  
         [0016]    [0016]FIG. 1 is a perspective view of the preferred embodiment flashlight of the present invention;  
         [0017]    [0017]FIG. 2 is an exploded perspective view thereof;  
         [0018]    [0018]FIG. 3 is a cross-sectional view thereof as taken along line  3 - 3  of FIG. 1;  
         [0019]    [0019]FIG. 4 is an enlarged cross-sectional view thereof including only the lighting head components.  
         [0020]    [0020]FIG. 5 is a plan view showing the light beam pattern of a prior art lighting assembly; and  
         [0021]    [0021]FIG. 5 a  is a plan view showing the light beam pattern of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to the drawings, the lighting head assembly of the present invention is shown and illustrated in the form of a compact flashlight that is generally illustrated and indicated at  10  in FIGS.  1 - 5 . As stated above while the lighting head assembly is shown, for the purposes of the preferred embodiment, as being incorporated into a compact flashlight  10  assembly it can be appreciated by one skilled in the art that the present disclosure anticipated the lighting head being utilized in a variety of suitable assemblies. By way of example the head assembly of the present invention can be easily and efficiently incorporated into architectural lighting assemblies, general task lighting assemblies or automotive lighting assemblies and still remain within the spirit and scope of the present disclosure. As can be seen in FIG. 1 a flashlight  10  is shown that includes a tubular housing  12  with the lighting head assembly  14  of the present invention installed into one end thereof. The housing  12  is intended to receive the lighting head  14  at one end and to enclose a power source and a switch assembly to create a fully self contained lighting assembly such as a compact flashlight  10 . As will be more fully described below, the tubular housing  12 , in addition to enclosing the lighting head assembly  14 , also encloses a power source and switch mechanism in the tail portion for selective activation of the lighting assembly.  
         [0023]    Turning now to FIG. 2, an exploded perspective view showing all of the components of the flashlight  10  of the preferred embodiment is shown. The flashlight  10  generally includes three major sub-components, an outer housing  12  that encloses the power source  16 , the lighting head assembly  14  that is installed into one end of the outer housing  12  and an end cap assembly  18  that also includes the mechanism for selectively activating the flashlight  10 . In general terms, the flashlight  10  is shown to include a battery  16  that is installed into the outer housing  12  as the primary means for providing power to the lighting head assembly  14 . It should be appreciated that in place of the battery  16 , the lighting head assembly  14  could easily include a pair of electrically conductive leads (not shown) extending therefrom for connection to an alternate power source, such as a supply lead from a transformer or permanent building wiring. Further the end cap  18  assembly as will be more fully described below could be replaced with any type of switch as is known in the art.  
         [0024]    [0024]FIG. 3 is a cross-sectional view of the flashlight  10  fully assembled. By viewing FIGS. 2 and 3 in conjunction, it can be seen that the head assembly  14  is mounted into one end of the flashlight  10  housing  12 . The head assembly  14  includes a receiver sleeve  20  with an optical element  66  at one end thereof and a lighting element  30  mounted onto a circuit board  38  received into the end of the receiver sleeve  20  at the end opposite the optical element  66 . The central element of the head assembly  14  is the receiver sleeve  20 . The receiver sleeve  20  is a tubular element with rear wall  22  and a tail section  24  extending therefrom. The rear wall  22  of the receiver sleeve  20  includes an aperture  26  at the point where the tail section  24  joins the receiver sleeve  20 . The receiver sleeve  20  has a central axis  28  with the aperture  26  being formed to lie along the central axis  28 .  
         [0025]    The tail portion  24  of the receiver sleeve  20  has a diameter that is smaller than the overall diameter of the receiver sleeve  20 . Further, the tail portion  24  has a diameter that slightly larger than the outer diameter of the lighting element  30 . In this manner the lighting element  30  is received into the tail portion  24  and retained in a position that centers the lighting element  30  in the aperture  26  in the rear wall  22  of the receiver sleeve  20  and places the optical axis of the lighting element  30  into alignment with the central axis  28  of the receiver sleeve  20 .  
         [0026]    The lighting element  30  is preferably an LED although a conventional filament lamp or xenon lamp could also be used in the present invention. The LED  30  has an optical head portion  32  with two leads  34 ,  36  extending therefrom. The LED  30  is mounted onto a mounting board  38  wherein one of the contact leads  34  is in electrical communication with an electrical contact pad  40  formed on the top surface thereof. The electrical contact pad  40  is formed in concentric relation to the position where the lighting element  30  is mounted. As can be seen, when the lighting element  30  is received into the tail portion  24  of the receiver sleeve  20 , the tail portion  24  is in contact with the contact pad  40  formed on the top surface of the mounting board  38 . In this manner, an electrically conductive path is formed from the body of the receiver  20  through the tail piece  24 , into the contact pad  40  on the mounting board  38  and directly to one of the contact leads  34  of the lighting element  30 . This electrically conductive pathway facilitates electrical connection to the lighting element  30  on the mounting board  38  with out the need to include additional wire bonds or spring. Further, assembly steps where soldered connections need to be completed are eliminated. In this manner, the complexity of the assembly is greatly reduced while a more reliable and durable assembly is formed.  
         [0027]    This direct conductivity pathway between the lead  34  of the lighting element  30  and the receiver sleeve  20  also serves the secondary purpose by providing a thermally conductive pathway to dissipate heat from the lighting element  30 . As is well known in the art most of the heat generated by an LED device  30  is transmitted back through the contact leads  34 ,  36 . In the present invention this heat is conducted down the lead  34 , through the contact  40  on the mounting board  38  and transmitted into the receiver sleeve  20 . Since the receiver  20  has a large thermal mass, it serves as a heat sink for absorbing and further dissipating the heat generated by the lighting element  30 . Additionally, since the walls of the tail portion  24  of the receiver  20  are in close proximity to the optical portion  32  of the lighting element  30 , heat that is radiated by the lighting element  30  is also absorbed by the walls of the tail portion  24  and further dissipated by the receiver sleeve  20 . When the lighting head assembly  14  of the present invention is fully implemented by installing the assembly  14  into the housing  12 , the outer wall of the receiver sleeve  20  is in electrical and thermal contact with the inner surface of the outer housing  12 . In this manner, the housing  12  provides additional thermal mass for dissipation of the waste heat generated by the lighting element  30  while also extending the electrically conductive pathway for one contact of the power source  16  to be connected to the contact  40  on the top surface of the mounting board  38  and ultimately to the contact lead  34  of the lighting element  30 .  
         [0028]    The lighting head assembly  14  may also include driver and control circuitry  42  that is mounted onto the mounting board  38 . Preferably, the control circuitry  42  is electrically connected between the second contact lead  36  of the lighting element  30  and a contact pad  44  formed on the bottom surface of the mounting board  38 . The circuitry  42  is placed in contact with the second lead  36  and the bottom contact  44  so that it is not deposed along the thermal dissipation pathway that is provided between the lighting element  30  and the receiver sleeve  20 . Further the circuitry  42  is located on the mounting board  38  in a position that is outside of the tail portion  24  of the receiver sleeve  20 . In this manner, the circuitry  42  is shielded from damage that may result from being exposed to the heat generated by the lighting element  30 .  
         [0029]    A spring  46  is installed adjacent the bottom of the mounting board  38  and is in electrical communication with the contact pad  44  on the bottom surface thereof. The spring  46  provides an electrically conductive pathway to facilitate a connection with the second electrical contact of the power source  16 . The spring  46  engages a metallic contact cap  48  that is formed within an outer nonconductive plunger  50 . The plunger  50  includes an aperture  52  in the center of the bottom surface thereof. The aperture  52  is formed to have a dimension that allows the smaller contact end  54  of the power source  16  to pass through the aperture  52  and contact the contact cap  48  while preventing the larger contact end  56  of the power source  16  from reaching the contact cap  48  should the power source  16  be installed in reverse orientation. Specifically, the aperture  52  in the plunger  50  is sized to allow the smaller positive terminal  54  of an AAA, AA, C or D type battery  16  to extend through the aperture  52  and contact the contact cap  48  while preventing the negative terminal  56  from reaching the contact cap  48 . This polarity protection is necessary to protect the control circuitry  42  on the mounting board  38  from damage as a result of being exposed to reverse polarity. This is particularly necessary in applications where an LED lighting element  30  is used in conjunction with a single conventional cell battery  16  having a 1.5 volt supply voltage. Since the threshold voltage required for activation of an LED  30  is typically greater than the 1.5 volts available in an AA or AAA battery  16 , the control circuitry  42  must include a step up circuit. Since step up circuits are highly sensitive to damage resulting from reverse polarity, a permanent means for protecting the lighting head assembly  14  from having reverse polarity applied is necessary. In this manner the plunger  50  arrangement provides the necessary protection while also facilitating electrical connectivity with the second contact  44  on the mounting board  38 .  
         [0030]    The spring  46 , while providing spring force for the plunger  50  and contact cap  48  also urges the mounting board  38  forward against the end of the tail portion  24  of the receiver sleeve  20 . In this manner, the spring  46  serves to maintain the mounting board  38  and the electrical contact  40  on the top surface thereof tightly against the tail portion  24 . The forward pressure of the spring  46  is an important feature in the head assembly  14  because the mounting board  38  is formed to have a diameter that is smaller than the inner diameter of the outer housing  12 . This allows the mounting board  38  to float slightly in a laterally un-restrained manner during assembly as the lighting element  30  is inserted into the tail section  24  and the head assembly  14  is installed into the end of the outer housing  12 . When fully assembled, the slight degree of freedom of the mounting board  38  allows the lighting element  30  to be captured and centered in the aperture  26  of the receiver sleeve  20  and facilitates alignment of the entire assembly.  
         [0031]    To complete the flashlight assembly  10 , an end cap assembly  18  is provided to retain the battery  16  within the outer housing  12  and further provide a means for selectively activating the flashlight  10 . The cap  18  includes an actuator  58  with a contact plate  60  on the inner surface thereof. The actuator  58  is depressed by the user causing the contact plate  60  to form an electrical connection between the negative terminal  56  of the battery  16  and the end of the outer housing  12  thereby completing the electrical circuit and energizing the lighting element  30 . When the actuator  58  is released the spring  46  in the plunger  50  presses the battery  16 , contact plate  60  and actuator  58  rearwardly opening the circuit. Additionally, the end cap  18  can be fully tightened to retain the contact plate  60  into the closed position providing a constant “on” function.  
         [0032]    Finally, to create a waterproof assembly an assortment of gaskets and O-rings are also provided. As can be seen in FIG. 2, gaskets  62  are provided at the junction between the end cap  18  and the housing  12  as well as at the junction between the head assembly  14  and the housing  12 .  
         [0033]    Turning now to FIG. 4, another important and unique feature of the receiver sleeve  20  is illustrated. As was described above, the tail portion  24  of the receiver sleeve  20  captures the optical portion  32  of the lighting element  30  and centers it in the center of the aperture  26 . In this manner, the optical axis of the lighting element  30  is centered along the central axis  28  of the receiver sleeve  20 . The interior surfaces of the receiver sleeve  20  including the interior surface of the rear wall  22  and the interior wall of the tail portion  24  are all coated with a non reflective coating  64 . Preferably, the interior surfaces are coated with a flat black non-reflective coating  64 . When looking into the end of the receiver sleeve  20  with the lighting element  30  installed, it can be seen that a black non-reflective field is provided around the optical end  32  of the lighting element  30 . Light emitted from the lighting element  30  fully illuminates the aperture  26  area while a dark non-illuminated shoulder can be seen at back wall  22  of the receiver sleeve  20  adjacent the aperture  26 . This forms a high level of contrast between the illuminated aperture  26  and the non-illuminated back wall  22 . The use of the coating  64  is counter intuitive to the prior art type devices. In the present invention it prevents stray light from being redirected onto the face of the rear wall  22  and maintains the high level of contrast between the aperture  26  and the face of the adjacent rear wall  22 . An optical lens  66  is utilized to capture an undistorted image of the near field of the illuminated aperture  26 . Further the lens  66  captures a sharp, high contrast image of the edge of the aperture  26  providing a sharp beam cutoff. This circular image is transferred by the lens  66  into the far field of the lighting device while the coating  64  serves to prevent the smearing effect seen in the shiny reflector elements of the prior art.  
         [0034]    Turning to FIGS. 5 and 5 a , images from a prior art conventional LED flashlight using a standard piano convex lens and a conventional reflector (FIG. 5) and from a lighting head assembly  14  of the present invention (FIG. 5 a ) are shown adjacent to one another for comparison purposes. The image in FIG. 5 can be seen to have poor definition in the transition zone  68  between the illuminated  70  and non-illuminated field  72  areas and an uneven intensity of light can be seen over the entire plane of the illuminated field  70 . Areas of high intensity can be witnessed around the perimeter  74  of the illuminated field and in an annular ring  76  near the center of the field. In addition, a particularly high intensity area  78  of illumination can be seen in a square box at the center of the field and corresponds to the location of the emitter chip within the LED package  30 . In contrast, FIG. 5 a  shows an image from the present invention. Note that the illuminated field  80  has a uniform pattern of illumination across the entire plane, the image captured across the illuminated aperture  26  and the edge  82  between the illuminated  82  and non-illuminated  84  fields is clear and well defined providing high levels of contrast created by the sharp cut off edge of the aperture  26  and the non-illuminated back wall  22  of the receiver  20 .  
         [0035]    It can therefore be seen that the present invention provides a novel and compact lighting head assembly  14  that provides a high quality illumination while being efficient and easy to assemble. The lighting head assembly  14  includes a novel receiver sleeve  20  that serves to remove waste heat from the device, facilitate electrical connections and control the light output. Further, the lighting head assembly  14  is compact and easily modified to allow its incorporation into a variety of different lighting devices to provide a well defined, highly controlled, high intensity beam output thereby creating a useful and novel assembly. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit.  
         [0036]    While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.